JP7668766B2 - Composition for forming protective film against alkaline hydrogen peroxide solution, substrate for manufacturing semiconductor device, method for forming protective film, and method for forming pattern - Google Patents

Description

The present invention relates to a protective film-forming composition that provides a protective film that is resistant to wet etching solutions used in the manufacturing process of a semiconductor device, a substrate for manufacturing a semiconductor device that uses the composition, a method for forming a protective film, and a method for forming a pattern using a multilayer resist method.

Conventionally, the high integration and high speed of semiconductor devices have been achieved by miniaturizing the pattern dimensions by shortening the wavelength of the light source in the general-purpose lithography technology (photolithography) using light exposure. In order to form such fine circuit patterns on a semiconductor device substrate (substrate to be processed), a method is used in which the substrate to be processed is processed by dry etching using a photoresist film on which a pattern is usually formed as an etching mask. However, in reality, there is no dry etching method that can achieve perfect etching selectivity between the photoresist film and the substrate to be processed, so in recent years, substrate processing using the multilayer resist method has become common. In this method, an intermediate film with a different etching selectivity from the photoresist film (hereinafter referred to as the resist upper layer film) is interposed between the resist upper layer film and the substrate to be processed, and after obtaining a pattern on the resist upper layer film, the pattern is transferred to the intermediate film by dry etching using the resist upper layer film pattern as a dry etching mask, and the pattern is further transferred to the substrate to be processed by dry etching using the intermediate film as a dry etching mask.

One of the multilayer resist methods is the three-layer resist method, which can be performed using a general resist composition used in the single-layer resist method. In this method, an organic underlayer film (hereinafter referred to as organic film) is formed on a substrate to be processed by applying and baking an organic underlayer film material made of an organic resin-containing composition, and a silicon-containing film (hereinafter referred to as silicon intermediate film) is formed on the organic underlayer film by applying and baking a resist intermediate film material made of a silicon-containing resin-containing composition on the organic underlayer film, and a general organic photoresist film (hereinafter referred to as resist upper layer film) is formed on the organic underlayer film. After patterning the resist upper layer film, dry etching with fluorine-based gas plasma is performed, and the organic resist upper layer film can have a good etching selectivity relative to the silicon intermediate film, so the resist upper layer film pattern can be transferred to the silicon intermediate film. According to this method, even if a resist upper layer film that does not have a sufficient film thickness to directly process the substrate to be processed or a resist upper layer film that does not have sufficient dry etching resistance to process the substrate to be processed is used, the silicon intermediate film usually has a film thickness equal to or less than that of the resist upper layer film, so the pattern can be easily transferred to the silicon intermediate film. Next, by using the silicon intermediate film with the transferred pattern as a dry etching mask to transfer the pattern to the organic underlayer film by dry etching with oxygen- or hydrogen-based gas plasma, the pattern can be transferred to an organic underlayer film that has sufficient dry etching resistance for processing the substrate. This pattern-transferred organic underlayer film pattern can be transferred to the substrate by dry etching using fluorine- or chlorine-based gases.

On the other hand, miniaturization in the manufacturing process of semiconductor devices is approaching the essential limit due to the wavelength of the light source for photolithography. Therefore, in recent years, high integration of semiconductor devices without relying on miniaturization has been considered, and as one of the methods, semiconductor devices with complex structures such as multi-gate structures have been considered, and some have already been put to practical use. When such a structure is formed by the multi-layer resist method, it is possible to apply an organic film material that can fill micropatterns such as holes, trenches, and fins formed on the substrate to be processed with a film without gaps, or fill steps, dense pattern areas, and areas without patterns with a film to achieve planarization. By forming a flat organic lower layer surface on a stepped substrate using such an organic film material, it is possible to suppress the film thickness fluctuation of the silicon intermediate film and resist upper layer film formed thereon, and to suppress the focal tolerance of photolithography and the reduction in margins in the subsequent processing process of the substrate to be processed. This makes it possible to manufacture semiconductor devices with a high yield. On the other hand, in the single-layer resist method, in order to fill in the steps and patterns on the substrate to be processed, the thickness of the top resist film must be thick, which can lead to pattern collapse after exposure and development, and deterioration of the pattern shape due to reflection from the substrate during exposure. This narrows the tolerance for pattern formation during exposure, making it difficult to manufacture semiconductor devices with a high yield.

Since it is necessary to form a pattern with a high aspect ratio by processing the organic film material by dry etching, the organic film is required to have not only the above-mentioned filling and planarization performance, but also high dry etching resistance. Furthermore, since high dry etching resistance is required for the silicon intermediate film on the organic film, an inorganic hard mask formed by CVD or ALD method, which has a higher dry etching resistance than the silicon intermediate film formed by spin coating, is often selected as the silicon intermediate film. Since the temperature when forming this hard mask is usually 300°C or higher, the organic film is also required to have high heat resistance to withstand these. In addition, peeling from the substrate may occur when forming an inorganic hard mask by CVD or ALD method, so adhesion to the processed substrate is also required. It is important for organic film materials with excellent process tolerance to have these properties.

Furthermore, as a method for increasing the speed of next-generation semiconductor devices, the application of precision materials such as new materials with high electron mobility using, for example, strained silicon or gallium arsenide, and ultra-thin polysilicon controlled in angstrom units is also being considered. However, in a substrate to be processed using such new precision materials, the material is corroded by oxygen in the air under the conditions for forming a planarization film using the organic underlayer film material described above, for example, under film formation conditions in air at 300° C. or higher, and the semiconductor device cannot achieve the performance as designed for high speed operation, and there is a possibility that a yield sufficient for industrial production cannot be achieved. Therefore, in order to avoid a decrease in yield due to corrosion of the substrate by air under such high-temperature conditions, an organic underlayer film material that can be formed in an inert gas is expected. Furthermore, there are cases where substrate processing by wet etching using chemicals is required, and in such cases, the organic underlayer film that serves as the processing mask is also required to be resistant to wet etching solutions.

Here, the background of the desire for a material compatible with the wet etching process in relation to the multilayer resist method will be described in detail. In order to improve the performance of semiconductor devices, state-of-the-art semiconductor devices use technologies such as three-dimensional transistors and through-wiring. In the patterning process used to form structures within such semiconductor devices, patterning using the above-mentioned multilayer resist method is also performed. In such patterning, after pattern formation, a process of removing the silicon intermediate film without damaging the pattern may be required. If this removal is insufficient, that is, if the wafer is sent to the next manufacturing process while the object to be cleaned remains, the device manufacturing yield will certainly decrease. Thus, with the miniaturization of elements, the cleanliness required for the cleaning process has been increasing. However, in many cases, the main constituent element of the conventional silicon intermediate film and the main constituent element of the semiconductor device substrate are both silicon, and even if an attempt is made to selectively remove the silicon intermediate film by dry etching, the constituent components are similar, making it difficult to suppress damage to the semiconductor device substrate. This problem cannot be solved even by performing wet etching using a normal hydrofluoric acid-based stripping solution. Therefore, it is possible to use an alkaline hydrogen peroxide solution called SC1 (Standard Clean-1), which is commonly used in semiconductor manufacturing processes, as a wet etching solution that does not damage the semiconductor device substrate. In this case, the organic underlayer film must be resistant to alkaline hydrogen peroxide.

In addition, a process is being considered in which an organic underlayer film is used as an etching mask to wet etch a substrate such as titanium nitride using alkaline hydrogen peroxide. In this case, too, the organic underlayer film must be resistant to alkaline hydrogen peroxide.

As described above, there is a demand for an organic underlayer film material for semiconductor device manufacturing that has heat resistance of 300°C or more even in an oxygen-free inert gas, high-level filling/planarization properties, and adhesion to the substrate, as well as high compatibility with wet etching processes (i.e., resistance to alkaline hydrogen peroxide), and a pattern formation method using the same.

Patent Document 1 and other publications have proposed protective films with good alkaline hydrogen peroxide resistance. However, although this material has resistance to alkaline hydrogen peroxide, there are problems with the planarization performance on uneven substrates and the high heat resistance when forming a hard mask on the protective film by CVD, ALD, or other methods.

In addition, examples of compounds having an imide structure as shown in the present invention include compounds having an imide structure as described in Patent Documents 2 to 6, resins having a polyimide structure as described in Patent Documents 7 to 9, and Patent Document 10, which uses a compound having a bismaleimide structure. There is no description of the resistance of these materials to alkaline hydrogen peroxide, and the resistance of resins having a polyimide structure to alkaline hydrogen peroxide is not known.

WO2017-191767 WO2019-146378 JP 2020-177225 A JP 2021-091841 A JP 2021-130763 A JP 2021-152639 A JP 2013-137334 A JP 2010-122297 A JP 2020-193325 A WO2018-212116

The present invention has been made in consideration of the above circumstances, and aims to provide a protective film-forming composition using a polymer containing imide groups that can be cured not only in air but also under film-forming conditions in an inert gas, and that can form a protective film that is excellent in heat resistance, filling and flattening properties of a pattern formed on a substrate, as well as good adhesion to the substrate and excellent resistance to alkaline hydrogen peroxide water, and a substrate for manufacturing semiconductor devices, a method for forming a protective film, and a method for forming a pattern that use the material.

（式中、Ｗ_１は１種類以上のフッ素原子又は水酸基を含んでいてもよい４価の有機基であり、Ｗ_２は１種類以上のフッ素原子又は水酸基を含んでいてもよい２価の有機基であり、かつＷ_１とＷ_２のうち少なくとも一方は１つ以上のフッ素原子を含み、Ｗ_１とＷ_２のうち少なくとも一方は１つ以上の水酸基を含む。）

（式中、Ｗ_３は１種類以上のフッ素原子を含んでいてもよい４価の有機基であり、Ｗ_４は１種類以上のフッ素原子を含んでいてもよい２価の有機基であり、かつＷ_３とＷ_４のうち少なくとも一方は１つ以上のフッ素原子を含む。）

（式中、Ｗ_５は１種類以上の水酸基を含んでいてもよい４価の有機基であり、Ｗ_６は１種類以上の水酸基を含んでいてもよい２価の有機基であり、かつＷ_５とＷ_６のうち少なくとも一方は１つ以上の水酸基を含む。）

（式中、Ｒ_１は下記式（１Ｄ）で示される基のいずれかであり、２種以上のＲ_１を組み合わせて用いてもよい。）

In order to solve the above problems, the present invention provides
(A) a polymer having a fluorine atom and a hydroxyl group represented by any one of the following (I) and (II), or a mixture of a polymer having a fluorine atom and a polymer having a hydroxyl group represented by the following (III):
(I) A polymer having a repeating unit containing at least one fluorine atom and one hydroxyl group, represented by the following general formula (1A), and having a terminal group represented by any one of the following general formulas (1B) and (1C):
(II) A polymer having a repeating unit containing at least one fluorine atom, represented by the following general formula (2A), and a repeating unit containing at least one hydroxyl group, represented by the following general formula (3A), in which a terminal group is a group represented by any one of the following general formulas (1B) and (1C):
(III) Provided is a mixture of a polymer having a repeating unit containing at least one fluorine atom, represented by the following general formula (2A), and a terminal group represented by any one of the following general formulas (1B) and (1C), and a polymer having a repeating unit containing at least one hydroxyl group, represented by the following general formula (3A), and a terminal group represented by any one of the following general formulas (1B) and (1C), and (B) a protective film-forming composition for alkaline hydrogen peroxide, which contains an organic solvent.

(In the formula, _W1 is a tetravalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, _W2 is a divalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, and at least one of _W1 and _W2 contains one or more fluorine atoms and at least one of _W1 and _W2 contains one or more hydroxyl groups.)

(In the formula, _W3 is a tetravalent organic group which may contain one or more types of fluorine atoms, _W4 is a divalent organic group which may contain one or more types of fluorine atoms, and at least one of _W3 and _W4 contains one or more fluorine atoms.)

(In the formula, _W5 is a tetravalent organic group which may contain one or more types of hydroxyl groups, _W6 is a divalent organic group which may contain one or more types of hydroxyl groups, and at least one of _W5 and _W6 contains one or more hydroxyl groups.)

(In the formula, R ₁ is any of the groups represented by the following formula (1D), and two or more types of R ₁ may be used in combination.)

Such a protective film-forming composition is cured under film-forming conditions not only in air but also in an inert gas due to the action of the terminal crosslinking group. In addition, since the main chain is composed of a polyimide skeleton, a protective film having high heat resistance, good adhesion to the substrate, and high embedding/flattening properties can be formed, and since fluorine atoms and hydroxyl groups are present in the polymer containing the imide group, the protective film-forming composition can form a protective film having excellent alkaline hydrogen peroxide resistance. In addition, by combining one or more of _W1 and _W2 , _W3 and _W4 , or _W5 and _W6 with the above-mentioned organic groups, the thermal fluidity, heat resistance, and adhesion can be improved.

It is also preferred that _W2 in the general formula (1A) contains at least one fluorine atom and one hydroxyl group.

Having such a partial structure in the main chain is preferable from the viewpoint of achieving both adhesion and excellent resistance to alkaline hydrogen peroxide solution.

Moreover, _W2 in the general formula (1A) is preferably a group represented by the following general formula (1E).

Having such a partial structure in the main chain is preferable from the viewpoints of heat resistance, flatness, adhesion, and even alkaline hydrogen peroxide resistance.

Moreover, W ₁ in the general formula (1A) is preferably any one of groups represented by the following general formula (1F).

Having such a partial structure in the main chain is preferable from the viewpoints of heat resistance, flatness, and resistance to alkaline hydrogen peroxide solution.

（式中、Ｗ_７は４価の有機基であり、Ｗ_８は２価の有機基である。）

（式中、Ｒ_２は炭素数１～１０の１価の有機基を表し、ｎ１は０または１の整数を表し、ｎ２およびｎ３は、１≦ｎ２≦６および０≦ｎ３≦６であり、かつ、１≦ｎ２＋ｎ３≦６の関係を満たす。） Furthermore, it is preferable that the component (A') contains a polymer (IV) having a repeating unit represented by the following general formula (4A) and a terminal group represented by the following general formula (2C):

(In the formula, _W7 is a tetravalent organic group, and _W8 is a divalent organic group.)

(In the formula, _R2 represents a monovalent organic group having 1 to 10 carbon atoms, n1 represents an integer of 0 or 1, and n2 and n3 satisfy the relationship of 1≦n2≦6 and 0≦n3≦6, and 1≦n2+n3≦6.)

It is preferable to contain a polymer (IV) having a hydroxyl group at the end group from the viewpoint of resistance to alkaline hydrogen peroxide solution.

It is also preferable that the weight average molecular weight of the (A) component is 1,000 to 10,000.

A protective film-forming composition containing polymer (A) with such a Mw range can suppress outgassing during baking without impairing solubility in organic solvents.

It is also preferable that the (B) component is a mixture of one or more organic solvents having a boiling point of less than 180°C and one or more organic solvents having a boiling point of 180°C or higher.

In such a protective film-forming composition, the addition of a high-boiling point solvent to the polymer (A) provides the film with thermal fluidity, resulting in a protective film-forming composition that has both high-level filling and planarizing properties.

It is also preferable that the protective film-forming composition further contains one or more of (C) an acid generator, (D) a surfactant, (E) a crosslinking agent, and (F) a plasticizer.

A protective film-forming composition containing such components can be a protective film-forming composition with superior coatability or filling/planarization properties.

It is also preferable that the protective film-forming composition provides a protective film that is resistant to ammonia-containing hydrogen peroxide solution.

Furthermore, it is preferable that the protective film forming composition is such that when a silicon substrate on which the protective film is formed is immersed in 1.0 mass % hydrogen peroxide solution containing 0.5 mass % ammonia at 70°C for 5 minutes, peeling of the protective film is not observed.

Such a protective film-forming composition has sufficient resistance to alkaline hydrogen peroxide, which increases the options for processable substrates and silicon intermediate films that can be removed by wet etching.

The present invention also provides a substrate for manufacturing a semiconductor device, which has a protective film formed on the substrate by curing the above-mentioned protective film-forming composition.

A protective film formed from the cured protective film-forming composition of the present invention has both high filling and planarization properties, resulting in a protective film that is free of microvoids caused by poor filling or unevenness on the protective film surface caused by insufficient planarity. Substrates for manufacturing semiconductor devices that are planarized with such a protective film have a wide process margin during patterning, making it possible to manufacture semiconductor devices with a high yield.

The present invention also provides a method for forming a protective film that is applied in the manufacturing process of a semiconductor device, which comprises spin-coating the above-mentioned protective film-forming composition on a substrate to be processed, and then subjecting the substrate to which the protective film-forming composition has been applied to a heat treatment in an inert gas atmosphere at a temperature of 50°C or higher and 600°C or lower for a period of 10 to 7200 seconds to obtain a cured film.

The present invention also provides a method for forming a protective film that is applied in the manufacturing process of a semiconductor device, which comprises spin-coating the above-mentioned protective film-forming composition on a substrate to be processed, heat-treating the substrate to which the protective film-forming composition has been applied in air at a temperature of 50°C or higher and 250°C or lower for 5 to 600 seconds to form a coating film, and then heat-treating the substrate in an inert gas atmosphere at a temperature of 200°C or higher and 600°C or lower for 10 to 7200 seconds to obtain a cured film.

The protective film formed by the method of the present invention and applied in the manufacturing process of a semiconductor device has high heat resistance and advanced filling/planarization properties, and its use in the manufacturing process of a semiconductor device improves the yield of the semiconductor device.

At this time, it is preferable that the oxygen concentration in the inert gas be 1% or less.

The protective film-forming composition of the present invention can be sufficiently cured without generating sublimates even when heated in such an inert gas atmosphere, and can form a protective film that has excellent adhesion to the substrate.

It is also preferable to use a substrate having a structure or step with a height of 30 nm or more as the substrate to be processed.

The protective film forming method of the present invention is particularly useful for forming a flat protective film on such a substrate.

The present invention also provides a method for forming a pattern on a workpiece substrate, comprising the steps of:
(I-1) A step of forming a protective film on a substrate to be processed using the protective film-forming composition;
(I-2) forming a silicon-containing resist intermediate film on the protective film using a silicon-containing resist intermediate film material;
(I-3) forming a resist upper layer film on the silicon-containing resist intermediate film using a photoresist composition;
(I-4) a step of forming a circuit pattern on the resist upper layer film;
(I-5) a step of transferring a pattern to the silicon-containing resist intermediate film by etching using the resist upper layer film on which the pattern has been formed as a mask;
(I-6) a step of transferring a pattern to the protective film by etching using the silicon-containing resist intermediate film to which the pattern has been transferred as a mask; and (I-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
The present invention provides a pattern forming method comprising the steps of:

Further, the present invention provides a method for forming a pattern on a workpiece substrate, comprising the steps of:
(II-1) forming a protective film on a substrate to be processed using the protective film-forming composition;
(II-2) forming a silicon-containing resist intermediate film on the protective film using a silicon-containing resist intermediate film material;
(II-3) forming an organic anti-reflective coating on the silicon-containing resist intermediate film;
(II-4) forming a resist upper layer film on the organic antireflective film using a photoresist composition to form a four-layer film structure, and forming a circuit pattern on the resist upper layer film;
(II-5) a step of transferring a pattern to the organic antireflective film and the silicon-containing resist intermediate film by etching using the resist upper layer film on which the pattern has been formed as a mask;
(II-6) a step of transferring a pattern to the protective film by etching using the silicon-containing resist intermediate film to which the pattern has been transferred as a mask; and (II-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
The present invention provides a pattern forming method comprising the steps of:

The present invention also provides a method for forming a pattern on a workpiece substrate, comprising the steps of:
(III-1) forming a protective film on a substrate to be processed using the protective film-forming composition;
(III-2) forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a titanium oxide film, and a titanium nitride film on the protective film;
(III-3) forming a resist top layer film on the inorganic hard mask using a photoresist composition;
(III-4) forming a circuit pattern on the resist upper layer film;
(III-5) a step of transferring a pattern to the inorganic hard mask by etching using the resist top layer film on which the pattern has been formed as a mask;
(III-6) a step of transferring a pattern to the protective film by etching using the inorganic hard mask to which the pattern has been transferred as a mask; and (III-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
The present invention provides a pattern forming method comprising the steps of:

The present invention also provides a method for forming a pattern on a workpiece substrate, comprising the steps of:
(IV-1) forming a protective film on a substrate to be processed using the protective film-forming composition;
(IV-2) forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a titanium oxide film, and a titanium nitride film on the protective film;
(IV-3) forming an organic anti-reflective coating on the inorganic hard mask;
(IV-4) forming a resist upper layer film on the organic antireflective film using a photoresist composition to form a four-layer film structure, and forming a circuit pattern on the resist upper layer film;
(IV-5) a step of transferring a pattern to the organic anti-reflective film and the inorganic hard mask by etching using the resist top layer film on which the pattern has been formed as a mask;
(IV-6) a step of transferring a pattern to the protective film by etching using the inorganic hard mask to which the pattern has been transferred as a mask; and (IV-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
The present invention provides a pattern forming method comprising the steps of:

The protective film-forming composition of the present invention can be suitably used in various pattern formation methods, such as a three-layer resist process using a silicon-containing resist intermediate film or an inorganic hard mask, and in addition to these, a four-layer resist process using an organic anti-reflective film. If a circuit pattern is formed using such a pattern formation method of the present invention in the manufacturing process of a semiconductor device, the semiconductor device can be manufactured with a high yield. Furthermore, as described above, the protective film formed using the protective film-forming composition of the present invention has good resistance to alkaline hydrogen peroxide water, and therefore can also be applied to a wet etching process using alkaline hydrogen peroxide water.

It is also preferable that the inorganic hard mask is formed by CVD or ALD.

In the pattern formation method of the present invention, for example, an inorganic hard mask can be formed in this manner.

In addition, the present invention can be a pattern formation method that further includes a step of removing the silicon-containing resist intermediate film to which the pattern has been transferred by wet etching using alkaline hydrogen peroxide after the step (I-6) or (II-6).

The protective film formed using the protective film-forming composition of the present invention has good resistance to alkaline hydrogen peroxide, so that the silicon-containing resist intermediate film can be removed by wet etching using alkaline hydrogen peroxide as described above.

In addition, in the present invention, in the step (I-7), step (II-7), step (III-7), or step (IV-7), the pattern forming method can include a step of transferring the pattern to the substrate to be processed by wet etching using alkaline hydrogen peroxide solution, using the protective film to which the pattern has been transferred as a mask.

The protective film formed using the protective film-forming composition of the present invention has good resistance to alkaline hydrogen peroxide, so that a pattern can be transferred to a substrate to be processed by wet etching using alkaline hydrogen peroxide as described above.

In addition, in the present invention, the pattern forming method may include a step of performing ion implantation using the protective film to which the pattern has been transferred as a mask in step (I-7), step (II-7), step (III-7), or step (IV-7) to pattern the substrate to be processed.

This type of pattern formation method is particularly suitable for ion implantation processing of substrates with uneven surfaces.

In this case, after the step of patterning the substrate to be processed by the ion implantation, a step of removing the silicon-containing resist intermediate film to which the pattern has been transferred by wet etching using alkaline hydrogen peroxide may be further included.

The protective film formed using the protective film-forming composition of the present invention has good resistance to alkaline hydrogen peroxide, so that the silicon-containing resist intermediate film after pattern processing by ion implantation can be removed by wet etching using alkaline hydrogen peroxide as described above.

In addition, in forming the circuit pattern, it is preferable to form the circuit pattern by lithography using light having a wavelength of 10 nm or more and 300 nm or less, direct drawing with an electron beam, nanoimprinting, or a combination of these.

In addition, in forming the circuit pattern, it is preferable to develop the circuit pattern using an alkaline developer or an organic solvent.

In the pattern formation method of the present invention, such circuit pattern forming means and developing means can be suitably used.

The substrate to be processed is preferably a semiconductor device substrate, or a semiconductor device substrate having a metal film, a metal carbide film, a metal oxide film, a metal nitride film, a metal oxide carbide film, or a metal oxide nitride film formed thereon.

In this case, it is preferable to use a substrate containing silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, silver, gold, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, cobalt, manganese, molybdenum, or an alloy thereof as the substrate to be processed.

The pattern formation method of the present invention makes it possible to form a pattern by processing a substrate to be processed as described above.

As described above, the protective film forming composition of the present invention can form a cured film without generating by-products even when formed in an inert gas that prevents corrosion of the substrate, and is useful for forming a protective film having both high filling and planarization properties. In addition, the protective film forming composition of the present invention is a material for forming a protective film that has filling/planarization properties and also has various properties such as heat resistance, etching resistance, adhesion, and alkaline hydrogen peroxide resistance. Therefore, it is extremely useful as a protective film material in multilayer resist methods such as a two-layer resist method, a three-layer resist method using a silicon-containing intermediate film, and a four-layer resist method using a silicon-containing intermediate film and an organic anti-reflective film, or as a planarization material for manufacturing semiconductor devices. In addition, the protective film formed from the protective film forming composition of the present invention has excellent heat resistance, so that even when a CVD hard mask is formed on the protective film, there is no film thickness variation due to thermal decomposition, and it is suitable for pattern formation. Furthermore, it is extremely useful for pattern formation methods using a wet etching processing process.

FIG. 4 is an explanatory diagram of flattening characteristics in the present invention. 1 is an explanatory diagram of an example of a pattern forming method using a three-layer resist method according to the present invention. FIG. 2 is an explanatory diagram of a method for evaluating embedding characteristics in an embodiment. FIG. 4 is an explanatory diagram of a method for evaluating flattening characteristics in an embodiment.

In order to prevent corrosion of the substrate, there was a demand for the development of a protective film-forming composition that can form a protective film that does not generate by-products even under film-forming conditions in an inert gas, for example at 300°C or higher, has excellent filling and planarizing properties for patterns formed on a substrate, and also has good resistance to dry etching during substrate processing. In addition, even when a CVD hard mask is formed on the protective film, there is no change in the thickness of the protective film due to thermal decomposition, and is highly compatible with wet etching processes (i.e., resistance to alkaline hydrogen peroxide).

The present inventors have further conducted intensive research and have discovered that a polyimide structure having at least one fluorine atom and one hydroxyl group represented by the above general formula (1A) in its main skeleton and a polyimide structure represented by the above general formulas (1B) and (1C) _The present inventors have found that by using, in a protective film-forming composition, a polymer having, as an end group, a group having a triple bond as a thermosetting group, as represented by the general formula (1), a polymer having, in its main skeleton, a polyimide structure containing at least one fluorine atom, as represented by the general formula (2A), and a polyimide structure containing at least one hydroxyl group, as represented by the general formula (3A), and having an end group as represented by the general formula (1B) or (1C), or a mixture of a polymer having, in its main skeleton, a polyimide structure represented by the general formula (2A) and having an end group as represented by the general formula (1B) or (1C), and a polymer having, in its main skeleton, a polyimide structure represented by the general formula (3A) and having an end group as represented by the general formula (1B) or (1C), the protective film-forming composition has thermosetting properties equivalent to those of conventional underlayer film materials not only in air but also in an inert gas, and has excellent thermal fluidity and therefore has advanced filling/planarization properties.

The inventors also found that the protective film-forming composition has high heat resistance and good adhesion to the substrate, without any change in coating thickness due to thermal decomposition, even when forming a CVD hard mask. Furthermore, they found that by examining a mixture of the polymers shown in (I) and (II) and the polymer shown in (III), a protective film-forming composition having excellent resistance to alkaline hydrogen peroxide water can be obtained, thus completing the present invention.

（式中、Ｗ_１は１種類以上のフッ素原子又は水酸基を含んでいてもよい４価の有機基であり、Ｗ_２は１種類以上のフッ素原子又は水酸基を含んでいてもよい２価の有機基であり、かつＷ_１とＷ_２のうち少なくとも一方は１つ以上のフッ素原子を含み、Ｗ_１とＷ_２のうち少なくとも一方は１つ以上の水酸基を含む。）

（式中、Ｗ_３は１種類以上のフッ素原子を含んでいてもよい４価の有機基であり、Ｗ_４は１種類以上のフッ素原子を含んでいてもよい２価の有機基であり、かつＷ_３とＷ_４のうち少なくとも一方は１つ以上のフッ素原子を含む。）

（式中、Ｗ_５は１種類以上の水酸基を含んでいてもよい４価の有機基であり、Ｗ_６は１種類以上の水酸基を含んでいてもよい２価の有機基であり、かつＷ_５とＷ_６のうち少なくとも一方は１つ以上の水酸基を含む。）

（式中、Ｒ_１は下記式（１Ｄ）で示される基のいずれかであり、２種以上のＲ_１を組み合わせて用いてもよい。）

That is, the present invention provides: (A) a polymer having a fluorine atom and a hydroxyl group represented by any one of the following (I) and (II), or a mixture of a polymer having a fluorine atom represented by the following (III) and a polymer having a hydroxyl group; (I) a polymer having a repeating unit represented by the following general formula (1A) containing at least one fluorine atom and a hydroxyl group, the end group of which is a group represented by the following general formula (1B) or (1C); (II) a polymer having a repeating unit represented by the following general formula (2A) containing at least one fluorine atom and a repeating unit represented by the following general formula (3A) containing at least one hydroxyl group: (III) a polymer having a repeating unit containing at least one fluorine atom, as represented by the following general formula (2A), and having a terminal group represented by the following general formula (1B) or (1C), and a polymer having a repeating unit containing at least one hydroxyl group, as represented by the following general formula (3A), and having a terminal group represented by the following general formula (1B) or (1C), and (B) a protective film-forming composition for alkaline hydrogen peroxide containing an organic solvent.

(In the formula, _W1 is a tetravalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, _W2 is a divalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, and at least one of _W1 and _W2 contains one or more fluorine atoms and at least one of _W1 and _W2 contains one or more hydroxyl groups.)

(In the formula, _W3 is a tetravalent organic group which may contain one or more types of fluorine atoms, _W4 is a divalent organic group which may contain one or more types of fluorine atoms, and at least one of _W3 and _W4 contains one or more fluorine atoms.)

(In the formula, _W5 is a tetravalent organic group which may contain one or more types of hydroxyl groups, _W6 is a divalent organic group which may contain one or more types of hydroxyl groups, and at least one of _W5 and _W6 contains one or more hydroxyl groups.)

(In the formula, R ₁ is any of the groups represented by the following formula (1D), and two or more types of R ₁ may be used in combination.)

The present invention is described in detail below, but is not limited to these.

<Component (A)>
The component (A) in the present invention is either the following polymer (I) or polymer (II), or a mixture of polymers (III).

（式中、Ｗ_１は１種類以上のフッ素原子又は水酸基を含んでいてもよい４価の有機基であり、Ｗ_２は１種類以上のフッ素原子又は水酸基を含んでいてもよい２価の有機基であり、かつＷ_１とＷ_２のうち少なくとも一方は１つ以上のフッ素原子を含み、Ｗ_１とＷ_２のうち少なくとも一方は１つ以上の水酸基を含む。）

（式中、Ｒ_１は下記式（１Ｄ）で示される基のいずれかであり、２種以上のＲ_１を組み合わせて用いてもよい。）

Polymer (I)
The polymer for forming a protective film used in the protective film-forming composition of the present invention is a polymer (polymer (I)) having a repeating unit containing at least one fluorine atom and one hydroxyl group, as represented by the following general formula (1A), and having an end group represented by either of the following general formulas (1B) and (1C).

(In the formula, _W1 is a tetravalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, _W2 is a divalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, and at least one of _W1 and _W2 contains one or more fluorine atoms and at least one of _W1 and _W2 contains one or more hydroxyl groups.)

(In the formula, R ₁ is any of the groups represented by the following formula (1D), and two or more types of R ₁ may be used in combination.)

By forming the polyimide structure in advance as in (1A), (1B), and (1C) above, the elimination reaction such as dehydration that occurs as a by-product when the precursor of the polyimide compound such as polyamic acid is thermally cyclized is eliminated, and the film shrink is suppressed and the flatness of the protective film is not impaired. In addition, by forming a stable imide structure in advance, the decomposition due to the equilibrium reaction of the polyimide compound precursor such as polyamic acid can be suppressed, and the storage stability is also superior. In addition, the polyimide structure contributes to improving adhesion to the substrate as well as imparting heat resistance. The improved adhesion prevents film peeling when an inorganic hard mask using the CVD method or the ALD method is formed directly on the protective film, making it possible to form a protective film with excellent process tolerance. Furthermore, the presence of fluorine atoms and hydroxyl groups in the main skeleton of the polyimide structure shown in (1A) above also contributes to improving resistance to alkaline hydrogen peroxide water. This is thought to be because fluorine atoms provide the protective film with water repellency against alkaline hydrogen peroxide, while hydroxyl groups provide improved adhesion between the protective film and the substrate being processed. This inhibits peeling during wet etching using alkaline hydrogen peroxide, resulting in good resistance to alkaline hydrogen peroxide.

_R1 in the above formula (1D) functions as a thermal crosslinking group, and is preferably an ethynyl group or an ethynylphenyl group in terms of curability, heat resistance, and ease of raw material availability.

Examples of _W1 in the above general formula include the following structural formulas, which may have a substituent on the aromatic ring. Examples of the substituent include a hydroxyl group, a trifluoromethyl group, an alkyl group having 1 to 10 carbon atoms, an alkynyl group or alkenyl group having 3 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkynyloxy group or alkenyloxy group having 3 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a nitro group, a halogen group, a nitrile group, an alkoxycarbonyl group having 1 to 10 carbon atoms, and an alkanoyloxy group having 1 to 10 carbon atoms.

Examples of _W2 in the above general formula include the following structural formulas, and these may have a substituent on the aromatic ring. Examples of the substituent include a hydroxyl group, a trifluoromethyl group, an alkyl group having 1 to 10 carbon atoms, an alkynyl group or alkenyl group having 3 to 10 carbon atoms, an alkyloxy group having 1 to 10 carbon atoms, an alkynyloxy group or alkenyloxy group having 3 to 10 carbon atoms, an aryl group having 6 to 10 carbon atoms, a thiol group, a nitro group, a halogen group, a nitrile group, a sulfonic acid group, an alkoxycarbonyl group having 1 to 10 carbon atoms, and an alkanoyloxy group having 1 to 10 carbon atoms.

By using one or more types of _W1 and _W2 as a combination of organic groups as described above, it is possible to improve thermal fluidity, heat resistance, and adhesion. _W1 and _W2 may each be one type, or a combination of two or more types. However, from the viewpoint of resistance to alkaline hydrogen peroxide water, the selected _W1 and _W2 must contain at least one or more fluorine atoms and hydroxyl groups. That is, at least one of _W1 and _W2 contains one or more fluorine atoms, and at least one of _W1 and _W2 contains one or more hydroxyl groups.

Furthermore, the polymer (I) used in the protective film-forming composition of the present invention preferably contains at least one fluorine atom and one hydroxyl group in _W2 in the general formula (1A).

Having such a partial structure in the main chain is preferable from the viewpoint of achieving both adhesion and excellent resistance to alkaline hydrogen peroxide solution.

Furthermore, in the polymer (I) used in the protective film-forming composition of the present invention, _W2 in the general formula (1A) is preferably a group represented by the following general formula (1E).

The hexafluoroisopropylidene group suppresses aggregation between imide groups by introducing flexibility into the main chain, making it possible to achieve both high-level embedding/flattening properties and heat resistance. Furthermore, since the above general formula (1E) simultaneously contains a hexafluoroisopropylidene group and a hydroxyl group, the hexafluoroisopropylidene group efficiently exerts the effect of water repellency of the protective film against alkaline hydrogen peroxide solution, and the hydroxyl group efficiently exerts the effect of improving adhesion between the protective film and the substrate to be processed, making it particularly preferable from the viewpoint of alkaline hydrogen peroxide solution resistance.

Furthermore, in the polymer used in the protective film-forming composition of the present invention, W ₁ in the general formula (1A) is preferably a group represented by the following general formula (1F).

The hexafluoroisopropylidene group suppresses aggregation between imide groups by introducing flexibility into the main chain, making it possible to achieve both high-level filling/planarization properties and heat resistance. Furthermore, the hexafluoroisopropylidene group can improve water repellency to alkaline hydrogen peroxide solution, so it is also preferable from the viewpoint of resistance to alkaline hydrogen peroxide solution. Among the above, a structure having a hexafluoroisopropylidene group and an ether bond as a linking group of the main chain is particularly preferable. The ether bond functions as a flexible linking group and can impart thermal fluidity and solvent solubility, making it possible to achieve both high-level filling/planarization properties and heat resistance.

Furthermore, the Mw (weight average molecular weight) of the above polymer (I) is preferably 1000 to 10000, more preferably 1000 to 8000, and even more preferably 1500 to 5000. In the present invention, the weight average molecular weight can be the polystyrene-equivalent weight average molecular weight (Mw) determined by gel permeation chromatography (GPC) using tetrahydrofuran as an eluent.

With such a molecular weight, solubility in organic solvents can be ensured and the generation of sublimates during baking can be suppressed. In addition, the polymer of component (A) (polymer for forming a protective film) has good thermal fluidity, so that when it is incorporated into a protective film-forming composition, not only can it effectively embed the microstructures formed on the substrate, but it can also form a protective film that flattens the entire substrate.

（式中、Ｗ_３は１種類以上のフッ素原子を含んでいてもよい４価の有機基であり、Ｗ_４は１種類以上のフッ素原子を含んでいてもよい２価の有機基であり、かつＷ_３とＷ_４のうち少なくとも一方は１つ以上のフッ素原子を含む。）

（式中、Ｗ_５は１種類以上の水酸基を含んでいてもよい４価の有機基であり、Ｗ_６は１種類以上の水酸基を含んでいてもよい２価の有機基であり、かつＷ_５とＷ_６のうち少なくとも一方は１つ以上の水酸基を含む。）

（式中、Ｒ_１は下記式（１Ｄ）で示される基のいずれかであり、２種以上のＲ_１を組み合わせて用いてもよい。）

Polymer (II)
The polymer (A) having a fluorine atom and a hydroxyl group may also be a polymer (polymer (II)) having a repeating unit containing at least one fluorine atom, represented by the following general formula (2A), and a repeating unit containing at least one hydroxyl group, represented by the following general formula (3A), and having a terminal group represented by any one of the following general formulas (1B) and (1C):

(In the formula, _W3 is a tetravalent organic group which may contain one or more types of fluorine atoms, _W4 is a divalent organic group which may contain one or more types of fluorine atoms, and at least one of _W3 and _W4 contains one or more fluorine atoms.)

(In the formula, _W5 is a tetravalent organic group which may contain one or more types of hydroxyl groups, _W6 is a divalent organic group which may contain one or more types of hydroxyl groups, and at least one of _W5 and _W6 contains one or more hydroxyl groups.)

(In the formula, R ₁ is any of the groups represented by the following formula (1D), and two or more types of R ₁ may be used in combination.)

The polymer (A) used in the present invention contributes to improving resistance to alkaline hydrogen peroxide by having fluorine atoms and hydroxyl groups in the main skeleton of the polyimide structure. Therefore, the polymer (A) is not limited to the polymer (I) having both fluorine atoms and hydroxyl groups in one repeating unit, but may be a copolymer (polymer (II)) of a repeating unit having only fluorine atoms and a repeating unit having only hydroxyl groups. Like the polymer (I), the polymer (II) also provides good filling/planarization properties, heat resistance, adhesion, and resistance to alkaline hydrogen peroxide.

In the repeating unit containing at least one or more fluorine atoms represented by the above general formula (2A), _W3 is not particularly limited as long as it is a tetravalent organic group that may contain one or more types of fluorine atoms, but for example, it can be a group that does not contain a hydroxyl group among the above-mentioned specific examples of _W1 . _W4 is not particularly limited as long as it is a divalent organic group that may contain one or more types of fluorine atoms, but for example, it can be a group that does not contain a hydroxyl group among the above-mentioned specific examples of _W2 . However, at least one of _W3 and _W4 contains one or more fluorine atoms.

In the repeating unit containing at least one hydroxyl group represented by the above general formula (3A), _W5 is not particularly limited as long as it is a tetravalent organic group that may contain one or more types of hydroxyl groups, but for example, it can be a group that does not contain a fluorine atom among the specific examples of _W1 . _W6 is not particularly limited as long as it is a divalent organic group that may contain one or more types of hydroxyl groups, but for example, it can be a group that does not contain a fluorine atom among the specific examples of _W2 . However, at least one of _W5 and _W6 contains one or more hydroxyl groups.

The end group structure and weight average molecular weight of polymer (II) are as described for polymer (I).

Polymer Mixture (III)
Furthermore, the component (A) of the present invention may be a copolymer (polymer (II)) of a repeating unit represented by the general formula (2A) and a repeating unit represented by the general formula (3A), or a mixture (polymer mixture (III)) of a polymer having a repeating unit represented by the general formula (2A) and a polymer having a repeating unit represented by the general formula (3A) (polymer (III-1)).

Polymer (III-1) is a polymer having a repeating unit containing at least one fluorine atom, as shown in the above general formula (2A), and an end group represented by either of the general formulas (1B) and (1C). In polymer (III-1), the repeating unit represented by the above general formula (2A), the structure of the end group represented by either of the general formulas (1B) and (1C), and the weight average molecular weight are as explained in the section on polymer (II).

Polymer (III-2) is a polymer having repeating units containing at least one hydroxyl group, as shown in the above general formula (3A), and having a terminal group represented by either of the general formulas (1B) and (1C). In polymer (III-2), the repeating units represented by the above general formula (3A), the structure of the terminal group represented by either of the general formulas (1B) and (1C), and the weight average molecular weight are as explained in the section on polymer (II).

In the present invention, the component (A) does not necessarily have to contain both the fluorine atom and the hydroxyl group in the main skeleton of the polyimide structure in the same polymer. Even if the fluorine atom in the main skeleton of the polyimide structure and the hydroxyl group in the main skeleton of the polyimide structure are contained in separate polymers, the alkaline hydrogen peroxide resistance can be improved in the same way. Therefore, like the polymers (I) and (II), the polymer mixture (III) also provides good filling/planarization properties, heat resistance, adhesion, and alkaline hydrogen peroxide resistance.

[(A) Method for producing polymer]
The method for producing the polymer of component (A) will be described taking polymer (I) as an example, but polymer (II), polymer (III-1), and polymer (III-2) can also be produced by the same method.

As a means for obtaining the polymer used in the protective film-forming composition of the present invention, either one of the diamines and tetracarboxylic anhydrides shown below is charged in excess to obtain a polyamic acid intermediate (STEP 1) having an amino group or a carboxylic anhydride active end at the end. Thereafter, a polyimide precursor (STEP 2) is synthesized using a phthalic anhydride derivative or an aniline derivative having R ₁ as a substituent as an end-capping agent, and then thermal or chemical imidization (STEP 3) is performed to synthesize the polymer of component (A). The diamine compound or tetracarboxylic anhydride used in synthesizing the polyamic acid compound in STEP 1, and the phthalic anhydride derivative or aniline derivative used for end-capping in STEP 2 can be used alone or in combination of two or more kinds. These can be appropriately selected and combined according to the required properties. W ₁ , W ₂ , and R ₁ in the following formula are the same as above.

(Excess diamine condition)

(Excess tetracarboxylic acid condition)

The synthesis of the polyamic acid intermediate shown in STEP 1 can usually be carried out in an organic solvent at room temperature or under cooling or heating as necessary. Solvents that can be used include alcohols such as methanol, ethanol, isopropyl alcohol, butanol, ethylene glycol, propylene glycol, diethylene glycol, glycerol, ethylene glycol monomethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether; ethers such as diethyl ether, dibutyl ether, diethylene glycol diethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, and 1,4-dioxane; chlorine-based solvents such as methylene chloride, chloroform, dichloroethane, and trichloroethylene; and hexafluorophenyl ether. Examples of the solvent include hydrocarbons such as benzene, heptane, benzene, toluene, xylene, and cumene; nitriles such as acetonitrile; ketones such as acetone, ethyl methyl ketone, isobutyl methyl ketone, and cyclohexanone; esters such as methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol methyl ether acetate, and γ-butyrolactone; and aprotic polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethylsulfoxide, N,N-dimethylformamide, and hexamethylphosphoric triamide. These can be used alone or in combination of two or more.

In these syntheses, a base catalyst can be used as necessary. Examples of base catalysts include inorganic base compounds such as sodium bicarbonate, sodium carbonate, potassium carbonate, calcium carbonate, cesium carbonate, sodium hydroxide, potassium hydroxide, sodium hydride, and potassium phosphate, and organic bases such as triethylamine, diisopropylethylamine, N,N-dimethylaniline, pyridine, and 4-dimethylaminopyridine. These may be used alone or in combination of two or more.

The reaction method includes a method of charging the diamine compound and the tetracarboxylic anhydride in a solvent all at once, a method of dropping the diamine compound and the tetracarboxylic anhydride dispersed or dissolved separately or mixed together, and a method of dropping one of the diamine compound and the tetracarboxylic anhydride dispersed or dissolved in a solvent and then dropping the other. In addition, when multiple types of diamine compounds and tetracarboxylic anhydrides are charged, they may be mixed and reacted in advance, or they can be reacted individually and sequentially. When a catalyst is used, the diamine compound or the tetracarboxylic anhydride are charged in a lump, and the catalyst is dispersed or dissolved in advance and then dropped. It is possible to adjust the charging ratio of the diamine compound and the tetracarboxylic anhydride to any ratio so that the Mw range of the desired range is obtained. For example, when an aniline derivative is used as the end-capping agent in the next step, the tetracarboxylic anhydride is used in excess relative to the diamine compound, and when phthalic anhydride is used as the end-capping agent, the diamine compound is used in excess relative to the tetracarboxylic anhydride to synthesize a polyamide intermediate. The resulting polyamic acid intermediate reaction solution can be continued to the terminal blocking reaction in STEP 2, but it can also be diluted with an organic solvent to remove unreacted raw materials, catalysts, etc. that are present in the system as a reaction intermediate, and then crystallized with a separation wash or poor solvent to be recovered as a powder.

In the terminal blocking step of STEP 2, the reaction solution of the polyamic acid intermediate (if recovered as a powder, it is first dissolved) is reacted with a terminal blocking agent. The reaction solvent and reaction catalyst can be the same as those for the polyamic acid intermediate of STEP 1. The reaction method can be the same as that of STEP 1, except that the substrate is a polyamic acid intermediate and an aniline derivative or phthalic anhydride is used as the terminal blocking agent instead of a diamine compound and a tetracarboxylic acid anhydride. The reaction solution of the obtained polyimide precursor can be continued to the imidization reaction of STEP 3, but it can also be diluted with an organic solvent to remove unreacted raw materials, catalysts, etc. present in the system as a reaction intermediate, and then crystallized with a poor solvent and recovered as a powder.

The imidization step shown in STEP 3 can be carried out by thermal or chemical imidization. These methods can be selected appropriately depending on the thermal stability of the crosslinking group of the target imide compound and the reactivity of the introduced substituent with the reagent used during chemical imidization.

When thermal imidization is performed, a solvent capable of forming an azeotropic mixture with water is added to the reaction liquid of the polyamic acid obtained in STEP 2 (if it is recovered as a powder, it is dissolved in a soluble solvent beforehand), and the mixture is heated to 100°C to 250°C. The imidization is performed by a dehydration ring-closing reaction while removing the water that is produced.

Examples of solvents that can form an azeotropic mixture with water include esters such as γ-butyrolactone, polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethylsulfoxide, and N,N-dimethylformamide, and non-polar solvents such as benzene, toluene, xylene, and mesitylene. It is preferable to use these solvents alone or in combination and heat them to distill off the water produced by ring closure from the system while dehydrating.

When chemical imidization is performed, the reaction liquid of the polyimide precursor obtained in STEP 2 (if it is recovered as a powder, it is dissolved in a soluble solvent beforehand) is added with a base catalyst and an acid anhydride or the like as a dehydrating agent, and the mixture is heated to perform imidization.

Examples of base catalysts used in chemical imidization include pyridine, triethylamine, trimethylamine, tributylamine, and trioctylamine. Among these, pyridine is preferred because it has an appropriate basicity for promoting the reaction. Examples of dehydrating agents include acetic anhydride, trimellitic anhydride, pyromellitic anhydride, trifluoroacetic anhydride, polyphosphoric acid, phosphorus pentoxide, phosphorus pentachloride, and thionyl chloride. From the viewpoint of purification after the reaction, acetic anhydride is preferred. In addition, the base catalyst and dehydrating agent may be used alone or in combination of two or more types. The imidization rate can be appropriately controlled by adjusting the amount of catalyst, amount of dehydrating agent, reaction temperature, and reaction time according to the required performance of the target compound.

The solvent used in this case is not particularly limited as long as it is inert to the above reaction, but examples include ethers such as diethylene glycol diethyl ether, diethylene glycol dimethyl ether, tetrahydrofuran, 1,4-dioxane, etc.; chlorine-based solvents such as methylene chloride, chloroform, dichloroethane, trichloroethylene, etc.; hydrocarbons such as hexane, heptane, benzene, toluene, xylene, cumene, etc.; nitriles such as acetonitrile, etc.; ketones such as acetone, ethyl methyl ketone, isobutyl methyl ketone, cyclohexanone, etc.; esters such as methyl acetate, ethyl acetate, n-butyl acetate, propylene glycol methyl ether acetate, γ-butyrolactone, etc.; aprotic polar solvents such as N-methyl-2-pyrrolidone, N,N-dimethylacetamide, dimethylsulfoxide, N,N-dimethylformamide, hexamethylphosphoric triamide, etc., which can be used alone or in combination.

After the reaction is complete, the composition may be used as is as a protective film-forming composition, but it may also be diluted with an organic solvent to remove unreacted raw materials, catalysts, etc. present in the system, and then recovered by separation and washing.

The organic solvent used for the separation washing is not particularly limited as long as it can dissolve the compound and separate into two layers when mixed with water, but examples of the organic solvent include hydrocarbons such as hexane, heptane, benzene, toluene, and xylene, esters such as ethyl acetate, n-butyl acetate, and propylene glycol methyl ether acetate, ketones such as methyl ethyl ketone, methyl amyl ketone, cyclohexanone, and methyl isobutyl ketone, ethers such as diethyl ether, diisopropyl ether, methyl-tert-butyl ether, and ethylcyclopentyl methyl ether, chlorine-based solvents such as methylene chloride, chloroform, dichloroethane, and trichloroethylene, and mixtures thereof. The washing water used in this case is usually what is called deionized water or ultrapure water. The number of washings may be one or more times, but since washing ten or more times does not necessarily provide the same effect as washing, it is preferable to wash the material one to five times.

In order to remove unreacted raw materials or acidic components from the system during separation washing, washing may be performed with a basic aqueous solution. Specific examples of bases include alkali metal hydroxides, alkali metal carbonates, alkaline earth metal hydroxides, alkaline earth metal carbonates, ammonia, and organic ammonium.

Furthermore, in order to remove unreacted raw materials, metal impurities or base components from the system during separation washing, washing with an acidic aqueous solution may be performed. Specific examples of acids include inorganic acids such as hydrochloric acid, hydrobromic acid, sulfuric acid, nitric acid, phosphoric acid and heteropolyacids, and organic acids such as oxalic acid, fumaric acid, maleic acid, trifluoroacetic acid, methanesulfonic acid, benzenesulfonic acid, p-toluenesulfonic acid and trifluoromethanesulfonic acid.

Either the above-mentioned separation washing with a basic aqueous solution or an acidic aqueous solution may be performed, or a combination of the two may be performed. From the viewpoint of removing metal impurities, it is preferable to perform the separation washing in the order of a basic aqueous solution and then an acidic aqueous solution.

After the above-mentioned separation washing with the basic aqueous solution or acidic aqueous solution, washing with neutral water may be performed subsequently. Washing may be performed at least once, but preferably 1 to 5 times. As the neutral water, the above-mentioned deionized water or ultrapure water may be used. Washing may be performed at least once, but if the number of times is too few, the basic and acidic components may not be removed. Washing 10 times or more does not necessarily provide the effect of washing alone, so 1 to 5 times is preferable.

Furthermore, the reaction product after the separation operation can be recovered as a powder by concentrating the solvent to dryness or crystallizing it under reduced or normal pressure, but it can also be left in a solution state of a moderate concentration to improve operability when preparing the protective film-forming composition. The concentration in this case is preferably 0.1 to 50% by mass, and more preferably 0.5 to 30% by mass. At such a concentration, the viscosity is unlikely to increase, preventing a loss of operability, and the amount of solvent is not excessive, making it economical.

The solvent used in this case is not particularly limited as long as it can dissolve the reaction product (polymer of component (A)). Specific examples include ketones such as cyclohexanone and methyl-2-amyl ketone; alcohols such as 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethyl ether, ethylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether, and diethylene glycol dimethyl ether; and esters such as propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate, methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate, tert-butyl propionate, and propylene glycol mono-tert-butyl ether acetate. These can be used alone or in combination of two or more.

In the synthesis of the above polyimide, it is possible to combine diamine compounds constituting the main chain of the polymer, tetracarboxylic anhydride derivatives, phthalic acid derivatives used for terminal blocking, and aniline derivatives according to the required performance. Specifically, it is possible to introduce substituents that contribute to improving solvent solubility, adhesion, and filling/planarization properties, substituents that contribute to etching resistance and film-forming properties, and substituents that contribute to alkaline hydrogen peroxide resistance, etc., according to the desired required performance. Protective film-forming compositions using these polymers are able to achieve a high level of both filling/planarization properties, heat resistance, and alkaline hydrogen peroxide resistance.

As described above, the polymer of component (A) provides a protective film-forming composition that has heat resistance of 400°C or higher, high-level filling/planarization properties, and alkaline hydrogen peroxide resistance.

In the present invention, the planarization characteristic refers to the ability to planarize the surface of a substrate. For example, as shown in FIG. 1, the protective film-forming composition of the present invention can reduce a 100 nm step in the substrate 1 to 30 nm or less by applying the protective film-forming composition 3' onto the substrate 1 and heating it to form a protective film 3. The step shape shown in FIG. 1 shows a typical example of the step shape in a substrate for manufacturing a semiconductor device, and the step shape of a substrate that can be planarized by the protective film-forming composition of the present invention is not limited to this.

<Protective film forming composition>
The present invention provides a protective film-forming composition for alkaline hydrogen peroxide solution, which contains (A) the above-mentioned polymer or polymer mixture, and (B) an organic solvent. In the protective film-forming composition of the present invention, the above-mentioned component (A) can be used alone or in combination of two or more.

The organic solvent that can be used in the protective film-forming composition of the present invention is not particularly limited as long as it dissolves the components contained in the above-mentioned base polymer, and the materials such as the acid generator, crosslinking agent, and other additives described below. Specifically, solvents with a boiling point of less than 180°C, such as those described in paragraphs (0091) to (0092) of JP-A-2007-199653, can be used. Among them, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, 2-heptanone, cyclopentanone, cyclohexanone, and mixtures of two or more of these are preferably used. The amount of the organic solvent is preferably 200 to 10,000 parts by mass, more preferably 300 to 5,000 parts by mass, per 100 parts by mass of component (A).

Such a protective film-forming composition can be applied by spin coating, and because it contains the above-mentioned component (A), it is a protective film-forming composition that has heat resistance of 400°C or higher, high-level filling/planarization properties, and alkaline hydrogen peroxide resistance.

Furthermore, in the protective film-forming composition of the present invention, it is also possible to add a high-boiling point solvent having a boiling point of 180°C or higher to the above-mentioned solvents having a boiling point of less than 180°C as an organic solvent (a mixture of a solvent having a boiling point of less than 180°C and a solvent having a boiling point of 180°C or higher). The high-boiling organic solvent is not particularly limited as long as it can dissolve component (A), and may be any of hydrocarbons, alcohols, ketones, esters, ethers, chlorinated solvents, etc., but specific examples include 1-octanol, 2-ethylhexanol, 1-nonanol, 1-decanol, 1-undecanol, ethylene glycol, 1,2-propylene glycol, 1,3-butylene glycol, 2,4-pentanediol, 2-methyl-2,4-pentanediol, 2,5-hexanediol, 2,4-heptanediol, 2-ethyl-1,3-hexanediol, diethylene glycol, dipropylene glycol, triethylene glycol, tripropylene glycol, glycerin, n-nonyl acetate, and ethylene glycol monohexyl ether. , ethylene glycol mono-2-ethylhexyl ether, ethylene glycol monophenyl ether, ethylene glycol monobenzyl ether, diethylene glycol monoethyl ether, diethylene glycol monoisopropyl ether, diethylene glycol mono-n-butyl ether, diethylene glycol monoisobutyl ether, diethylene glycol monohexyl ether, diethylene glycol monophenyl ether, diethylene glycol monobenzyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, diethylene glycol butyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol monomethyl ether, triethylene glycol ethylene glycol mono-n-butyl ether, triethylene glycol butyl methyl ether, triethylene glycol diacetate, tetraethylene glycol dimethyl ether, dipropylene glycol monomethyl ether, dipropylene glycol mono-n-propyl ether, dipropylene glycol mono-n-butyl ether, tripropylene glycol dimethyl ether, tripropylene glycol monomethyl ether, tripropylene glycol mono-n-propyl ether, tripropylene glycol mono-n-butyl ether, ethylene glycol monoethyl ether acetate, ethylene glycol monobutyl ether acetate, diethylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether Examples of the diethyl ether acetate include diethylene glycol monobutyl ether acetate, triacetin, propylene glycol diacetate, dipropylene glycol monomethyl ether acetate, dipropylene glycol methyl-n-propyl ether, dipropylene glycol methyl ether acetate, 1,4-butanediol diacetate, 1,3-butylene glycol diacetate, 1,6-hexanediol diacetate, triethylene glycol diacetate, γ-butyrolactone, dihexyl malonate, diethyl succinate, dipropyl succinate, dibutyl succinate, dihexyl succinate, dimethyl adipate, diethyl adipate, and dibutyl adipate. These may be used alone or in combination.

The boiling point of the high-boiling solvent may be appropriately selected according to the temperature at which the protective film-forming composition is heat-treated. The boiling point of the high-boiling solvent to be added is preferably 180°C to 300°C, and more preferably 200°C to 300°C. With such a boiling point, there is no risk of the solvent volatilizing too quickly during baking (heat treatment) due to a boiling point that is too low, and sufficient thermal fluidity can be obtained. In addition, with such a boiling point, the solvent is so high that it does not remain in the film after baking without volatilizing, and there is no risk of adversely affecting the film properties such as etching resistance.

When using the above-mentioned high boiling point solvent, the blending amount of the high boiling point solvent is preferably 1 to 30 parts by mass per 100 parts by mass of the solvent with a boiling point of less than 180°C. With such a blending amount, there is no risk of the blending amount being too small to impart sufficient thermal fluidity during baking, or the blending amount being too large to remain in the film and lead to deterioration of the film properties such as etching resistance.

In such a protective film-forming composition, the addition of a high-boiling point solvent to the above-mentioned component (A) gives it thermal fluidity, resulting in a protective film-forming composition that has both higher filling and planarizing properties.

（式中、Ｗ_７は４価の有機基であり、Ｗ_８は２価の有機基である。）

（式中、Ｒ_２は炭素数１～１０の１価の有機基を表し、ｎ１は０または１の整数を表し、ｎ２およびｎ３は、１≦ｎ２≦６および０≦ｎ３≦６であり、かつ、１≦ｎ２＋ｎ３≦６の関係を満たす。） <Component (A')>
Polymer (IV)
The composition for forming a protective film of the present invention may further contain, as component (A'), a polymer (IV) having a repeating unit represented by the following general formula (4A) and having a terminal group represented by the following general formula (2C), in addition to the above-mentioned component (A).

(In the formula, _W7 is a tetravalent organic group, and _W8 is a divalent organic group.)

(In the formula, _R2 represents a monovalent organic group having 1 to 10 carbon atoms, n1 represents an integer of 0 or 1, and n2 and n3 satisfy the relationship of 1≦n2≦6 and 0≦n3≦6, and 1≦n2+n3≦6.)

The amount of polymer (IV) is preferably 1 to 30 parts by mass, and more preferably 1 to 10 parts by mass, per 100 parts by mass of component (A). With such an amount, the terminal hydroxyl groups improve adhesion to the substrate without deteriorating heat resistance, and resistance to alkaline hydrogen peroxide can be improved.

The substituent represented by _OR2 can be appropriately selected according to the intended use, such as an alkyloxy group for imparting fluidity, an alkenyl or alkynyloxy group for imparting curability under an inert gas, etc. By having a substituent represented by _OR2 , it is possible to exhibit appropriate solvent solubility and, after curing, to exhibit excellent solvent resistance and heat resistance.

Furthermore, the Mw (weight average molecular weight) of the above polymer (IV) is preferably 1000 to 10000, more preferably 1000 to 8000, and even more preferably 1500 to 5000. In the present invention, the weight average molecular weight can be the polystyrene-equivalent weight average molecular weight (Mw) determined by gel permeation chromatography (GPC) using tetrahydrofuran as an eluent.

In the above general formula (4A), specific examples of _W7 include those mentioned above as specific examples of _W1 .

In the above general formula (4A), specific examples of _W8 are those mentioned above as specific examples of _W2 .

Examples of the terminal group represented by the above general formula (2C) include the following structural formulas.

The polymer (IV) can also be produced by a method similar to the method for producing the polymer (A) described above.

In the protective film-forming composition of the present invention, an acid generator (C) can be added to further accelerate the curing reaction. There are acid generators that generate acid by thermal decomposition and those that generate acid by light irradiation, and either can be added. Specifically, the materials described in paragraphs (0061) to (0085) of JP-A-2007-199653 can be added, but are not limited to these.

The above acid generators can be used alone or in combination of two or more. When an acid generator is added, the amount added is preferably 0.05 to 50 parts, more preferably 0.1 to 10 parts, per 100 parts of component (A).

A surfactant (D) can be added to the protective film-forming composition of the present invention in order to improve the coatability in spin coating. For example, the surfactants described in (0142) to (0147) of JP 2009-269953 A can be used. When a surfactant is added, the amount added is preferably 0.01 to 10 parts by mass, more preferably 0.05 to 5 parts by mass, per 100 parts by mass of component (A).

In addition, a crosslinking agent (E) can be added to the protective film-forming composition of the present invention in order to enhance the curability and further suppress intermixing with the upper layer film. There are no particular limitations on the crosslinking agent, and a wide variety of known crosslinking agents can be used. Examples include melamine-based crosslinking agents, glycoluril-based crosslinking agents, benzoguanamine-based crosslinking agents, urea-based crosslinking agents, β-hydroxyalkylamide-based crosslinking agents, isocyanurate-based crosslinking agents, aziridine-based crosslinking agents, oxazoline-based crosslinking agents, and epoxy-based crosslinking agents.

Specific examples of melamine-based crosslinking agents include hexamethoxymethylated melamine, hexabutoxymethylated melamine, alkoxy- and/or hydroxy-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of glycoluril-based crosslinking agents include tetramethoxymethylated glycoluril, tetrabutoxymethylated glycoluril, alkoxy- and/or hydroxy-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of benzoguanamine-based crosslinking agents include tetramethoxymethylated benzoguanamine, tetrabutoxymethylated benzoguanamine, alkoxy- and/or hydroxy-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of urea-based crosslinking agents include dimethoxymethylated dimethoxyethyleneurea, alkoxy- and/or hydroxy-substituted derivatives thereof, and partial self-condensates thereof. Specific examples of β-hydroxyalkylamide-based crosslinking agents include N,N,N',N'-tetra(2-hydroxyethyl)adipic acid amide. Specific examples of the isocyanurate crosslinking agent include triglycidyl isocyanurate and triallyl isocyanurate.Specific examples of the aziridine crosslinking agent include 4,4'-bis(ethyleneiminocarbonylamino)diphenylmethane and 2,2-bishydroxymethylbutanol-tris[3-(1-aziridinyl)propionate]. Specific examples of the oxazoline crosslinking agent include 2,2'-isopropylidenebis(4-benzyl-2-oxazoline), 2,2'-isopropylidenebis(4-phenyl-2-oxazoline), 2,2'-methylenebis4,5-diphenyl-2-oxazoline, 2,2'-methylenebis-4-phenyl-2-oxazoline, 2,2'-methylenebis-4-tertbutyl-2-oxazoline, 2,2'-bis(2-oxazoline), 1,3-phenylenebis(2-oxazoline), 1,4-phenylenebis(2-oxazoline), and 2-isopropenyloxazoline copolymer. Specific examples of epoxy crosslinking agents include diglycidyl ether, ethylene glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, 1,4-cyclohexanedimethanol diglycidyl ether, poly(glycidyl methacrylate), trimethylolethane triglycidyl ether, trimethylolpropane triglycidyl ether, and pentaerythritol tetraglycidyl ether. When a crosslinking agent is added, the amount added is preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass, per 100 parts by mass of component (A).

In addition, a plasticizer (F) can be added to the protective film-forming composition of the present invention in order to further improve the planarization/filling properties. The plasticizer is not particularly limited, and various known plasticizers can be widely used. Examples include low molecular weight compounds such as phthalates, adipic esters, phosphates, trimellitates, and citrates, and polymers such as polyethers, polyesters, and polyacetal polymers described in JP-A-2013-253227. When a plasticizer is added, the amount of the plasticizer is preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass, per 100 parts by mass of component (A).

In addition, in the protective film-forming composition of the present invention, as an additive for imparting filling/flattening properties in the same manner as a plasticizer, for example, a liquid additive having a polyethylene glycol or polypropylene glycol structure, or a thermally decomposable polymer having a weight loss rate of 40% or more between 30°C and 250°C and a weight average molecular weight of 300 to 200,000 is preferably used. This thermally decomposable polymer preferably contains a repeating unit having an acetal structure represented by the following general formula (DP1) or (DP1a). When the above liquid additive or thermally decomposable polymer is added, the amount added is preferably 1 to 100 parts by mass, more preferably 5 to 50 parts by mass, per 100 parts by mass of component (A).

（式中、Ｒ_６は水素原子又は置換されていてもよい炭素数１～３０の飽和もしくは不飽和の一価有機基である。Ｙ_１は炭素数２～３０の飽和又は不飽和の二価有機基である。）

(In the formula, _R6 is a hydrogen atom or an optionally substituted saturated or unsaturated monovalent organic group having 1 to 30 carbon atoms. _Y1 is a saturated or unsaturated divalent organic group having 2 to 30 carbon atoms.)

（式中、Ｒ_６ａは炭素数１～４のアルキル基である。Ｙ^ａは炭素数４～１０の飽和又は不飽和の二価炭化水素基であり、エーテル結合を有していてもよい。ｎは平均繰り返し単位数を表し、３～５００である。）

(In the formula, R _6a is an alkyl group having 1 to 4 carbon atoms. ^{Y a} is a saturated or unsaturated divalent hydrocarbon group having 4 to 10 carbon atoms, which may have an ether bond. n represents the average number of repeating units and is 3 to 500.)

The protective film-forming composition of the present invention preferably provides a protective film that is resistant to an ammonia-containing hydrogen peroxide solution. Such a protective film-forming composition can form a protective film that has good resistance to alkaline hydrogen peroxide solution, and can therefore be applied to a wet etching process that uses alkaline hydrogen peroxide solution.

Alkaline hydrogen peroxide is commonly used for cleaning semiconductor wafers. In particular, a mixture of 5 parts by mass of deionized water, 1 part by mass of 29% ammonia water, and 1 part by mass of 30% hydrogen peroxide is called SC1 (Standard Clean-1) and is a standard chemical solution for cleaning and removing organic impurities and fine particles from the wafer surface. In addition, alkaline hydrogen peroxide can be used to strip or etch some metals and metal compounds as well as silicon-containing resist intermediate films designed for wet stripping. The composition of the alkaline hydrogen peroxide used in these processes is not particularly limited, but is typically a mixture of deionized water, hydrogen peroxide, and ammonia. In this case, the concentration of hydrogen peroxide is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass, and the concentration of ammonia is preferably 0.1 to 10% by mass, more preferably 0.2 to 5% by mass. The processing temperature is preferably 0 to 90°C, more preferably 20 to 80°C.

Here, the alkaline hydrogen peroxide resistance test of the protective film will be described. First, a protective film-forming composition is formed into a film of approximately 100 nm thickness on a silicon wafer cut into 3 cm squares according to the film formation conditions described below. This wafer piece is immersed in 1.0 mass % hydrogen peroxide containing 0.5 mass % ammonia at 70°C for 5 minutes, and then rinsed with deionized water, after which the protective film can be visually inspected for peeling off from the wafer. If part or all of the protective film peels off, exposing the silicon wafer surface, the protective film used in the test is judged to have insufficient alkaline hydrogen peroxide resistance.

That is, it is preferable that the protective film formed from the protective film-forming composition of the present invention is one in which peeling of the protective film is not observed when a silicon substrate on which the protective film is formed is immersed in 1.0 mass % hydrogen peroxide solution containing 0.5 mass % ammonia at 70°C for 5 minutes.

As described above, the protective film-forming composition of the present invention is a protective film-forming composition that has heat resistance of 400° C. or more, high filling/planarization properties, and alkaline hydrogen peroxide resistance. Therefore, the protective film-forming composition of the present invention is extremely useful as a protective film-forming composition for multi-layer resist methods such as a two-layer resist method, a three-layer resist method using a silicon-containing resist intermediate film or a silicon-containing inorganic hard mask, and a four-layer resist method using a silicon-containing resist intermediate film or a silicon-containing inorganic hard mask and an organic anti-reflective film. In addition, the protective film-forming composition of the present invention does not generate by-products even when formed in an inert gas, and has excellent filling/planarization properties, so it can be suitably used as a planarization material in semiconductor device manufacturing processes other than the multi-layer resist method. Furthermore, it is extremely useful for pattern formation methods using a wet etching process.

<Substrate for manufacturing semiconductor device>
The present invention also provides a substrate for manufacturing a semiconductor device, which comprises a substrate having a protective film formed thereon by curing the above-mentioned protective film-forming composition.

A protective film formed from the cured protective film-forming composition of the present invention has both high filling/planarization properties, resulting in a protective film that is free of microvoids due to poor filling or unevenness on the protective film surface due to insufficient flatness. Substrates for manufacturing semiconductor devices that are planarized with such a protective film have a wide process margin during patterning, making it possible to manufacture semiconductor devices with a high yield. Furthermore, the protective film has resistance to alkaline hydrogen peroxide water, making it highly compatible with wet etching processes.

<Protective Film Forming Method>
The heating film formation process for forming the protective film can be performed by one-stage baking, two-stage baking, or multi-stage baking of three or more stages, but one-stage baking or two-stage baking is economically preferable. Film formation by one-stage baking is performed, for example, at a temperature of 100°C to 600°C in the range of 5 to 3600 seconds, but preferably at a temperature of 150°C to 500°C in the range of 10 to 7200 seconds. By performing heat treatment under such conditions, flattening due to thermal flow and crosslinking reaction can be promoted. In the multilayer resist method, a coating type silicon intermediate film or a CVD hard mask may be formed on the obtained film. When a coating type silicon intermediate film is applied, it is preferable to form the film at a temperature higher than the temperature at which the silicon intermediate film is formed. Usually, the silicon intermediate film is formed at a temperature of 100°C to 400°C, preferably 150°C to 350°C. If the protective film is formed at a temperature higher than this temperature, dissolution of the protective film by the composition for forming a silicon intermediate film can be prevented, and a protective film that does not mix with the composition can be formed.

When using a CVD hard mask, it is preferable to form the protective film at a temperature higher than the temperature at which the CVD hard mask is formed. Examples of temperatures at which the CVD hard mask is formed include temperatures of 150°C or higher and 500°C or lower.

On the other hand, in the case of film formation by two-stage baking, the upper limit of the treatment temperature in air is, for example, 300°C or less, preferably 250°C or less, in the range of 10 to 600 seconds, in consideration of the influence of corrosion of the substrate by oxygen in the air, in the first stage of baking. The second stage of baking is preferably performed at a temperature higher than the first stage of baking, 600°C or less, preferably 500°C or less, in the range of 10 to 7200 seconds. In the multilayer resist method, a coating type silicon intermediate film or a CVD hard mask may be formed on the obtained film. When a coating type silicon intermediate film is applied, it is preferable to form the film at a temperature higher than the temperature at which the silicon intermediate film is formed. Usually, the silicon intermediate film is formed at a temperature of 100°C or more and 400°C or less, preferably 150°C or more and 350°C or less. If the protective film is formed at a temperature higher than this temperature, it is possible to prevent the protective film from being dissolved by the composition for forming the silicon intermediate film, and to form a protective film that does not mix with the composition.

When applying a CVD hard mask with two-stage baking, it is preferable to form the protective film at a temperature higher than the temperature at which the CVD hard mask is formed. Examples of temperatures at which the CVD hard mask is formed include temperatures of 150°C or higher and 500°C or lower.

The present invention also provides a method for forming a protective film used in the manufacturing process of a semiconductor device, which forms a hardened film by heat treating the substrate to be processed in an atmosphere with an oxygen concentration of 1% or less to prevent corrosion of the substrate to be processed.

In this method for forming a protective film, for example, the protective film-forming composition of the present invention described above is first spin-coated onto a substrate to be processed. After spin-coating, in a two-stage bake, the composition is first baked in air at 300°C or less, and then the second stage baked in an atmosphere with an oxygen concentration of 1% or less. In the case of a one-stage bake, the first stage bake in air may be skipped. Examples of the atmosphere during baking include inert gases such as nitrogen, argon, and helium. With the protective film-forming composition of the present invention, even when fired in such an inert gas atmosphere, a sufficiently hardened protective film can be formed without generating sublimates.

In addition, the method for forming a protective film of the present invention can be used with a substrate to be processed that has structures or steps with a height of 30 nm or more. As described above, the protective film-forming composition of the present invention has excellent filling/planarization properties, so that even if the substrate to be processed has structures or steps (unevenness) with a height of 30 nm or more, a flat cured film can be formed. In other words, the method for forming a protective film of the present invention is particularly useful when forming a flat protective film on such a substrate to be processed.

The thickness of the protective film formed can be selected appropriately, but is preferably 30 to 20,000 nm, and more preferably 50 to 15,000 nm.

The above-mentioned method for forming a protective film can be applied to both the formation of a protective film for pattern formation using the protective film-forming composition of the present invention and the formation of a protective film for a planarization film.

The present invention provides a method for forming a protective film that is applied in the manufacturing process of a semiconductor device, which comprises spin-coating the above-mentioned protective film-forming composition on a substrate to be processed, and then subjecting the substrate to which the protective film-forming composition has been applied to a heat treatment in an inert gas atmosphere at a temperature of 50°C or higher and 600°C or lower for a period of 10 to 7200 seconds to obtain a cured film.

The present invention further provides a method for forming a protective film that is applied in the manufacturing process of a semiconductor device, which comprises spin-coating the above-mentioned protective film-forming composition on a substrate to be processed, heat-treating the substrate to which the protective film-forming composition has been applied in air at a temperature of 50°C or higher and 250°C or lower for 5 to 600 seconds, preferably 10 to 600 seconds, to form a coating film, and then heat-treating the substrate in an inert gas atmosphere at a temperature of 200°C or higher and 600°C or lower, preferably 250°C or higher, for 10 to 7200 seconds to obtain a cured film.

The protective film formed by the method of the present invention and applied in the manufacturing process of a semiconductor device has high heat resistance and advanced filling/planarization properties, and its use in the manufacturing process of a semiconductor device improves the yield of the semiconductor device.

In this method for forming a protective film, first, the protective film-forming composition of the present invention described above is spin-coated onto the substrate to be processed. By using the spin-coating method, good embedding properties can be obtained. After spin-coating, baking (heat treatment) is performed to promote flattening by thermal flow and crosslinking reaction. This baking can evaporate the solvent in the protective film-forming composition, so mixing can be prevented even when a resist top layer film or a silicon-containing resist intermediate film is formed on the protective film.

<Pattern Formation Method>
[Three-layer resist method using silicon-containing resist intermediate film]
The present invention also provides a method for forming a pattern on a substrate to be processed, comprising the steps of:
(I-1) A step of forming a protective film on a substrate to be processed using the protective film-forming composition;
(I-2) forming a silicon-containing resist intermediate film on the protective film using a silicon-containing resist intermediate film material;
(I-3) forming a resist upper layer film on the silicon-containing resist intermediate film using a photoresist composition;
(I-4) a step of forming a circuit pattern on the resist upper layer film;
(I-5) a step of transferring a pattern to the silicon-containing resist intermediate film by etching using the resist upper layer film on which the pattern has been formed as a mask;
(I-6) a step of transferring a pattern to the protective film by etching using the silicon-containing resist intermediate film to which the pattern has been transferred as a mask; and (I-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
The present invention provides a pattern forming method comprising the steps of:

As the substrate to be processed, it is preferable to use a semiconductor device substrate, or a semiconductor device substrate having any one of a metal film, a metal carbide film, a metal oxide film, a metal nitride film, a metal oxide carbide film, and a metal oxide nitride film formed thereon. More specifically, although not limited to, substrates such as Si, α-Si, p-Si, SiO ₂ , SiN, SiON, W, TiN, Al, etc., and substrates having the above-mentioned metal films formed thereon as a layer to be processed, etc., can be used.

As the processed layer, various low-k films and their stopper films such as Si, SiO ₂ , SiON, SiN, p-Si, α-Si, W, W-Si, Al, Cu, and Al-Si are used, and can be formed to a thickness of usually 50 to 10,000 nm, particularly 100 to 5,000 nm. When forming the processed layer, the substrate and the processed layer are made of different materials.

The metal constituting the substrate to be processed is preferably silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, silver, gold, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, cobalt, manganese, molybdenum, or an alloy thereof.

It is also preferable to use a substrate to be processed that has a structure or step with a height of 30 nm or more.

When forming a protective film on a substrate to be processed using the protective film-forming composition of the present invention, the above-described protective film-forming method of the present invention may be applied.

Next, a resist intermediate film (silicon-containing resist intermediate film) is formed on the protective film using a resist intermediate film material containing silicon atoms. As the silicon-containing resist intermediate film material, a polysiloxane-based intermediate film material is preferable. By imparting an anti-reflection effect to the silicon-containing resist intermediate film, reflection can be suppressed. In particular, for 193 nm exposure, if a material containing many aromatic groups and having high etching selectivity with the substrate is used as the protective film forming composition, the k value becomes high and the substrate reflection becomes high, but by imparting absorption to the silicon-containing resist intermediate film so that the k value becomes appropriate, it is possible to suppress reflection and make the substrate reflection 0.5% or less. As a silicon-containing resist intermediate film with an anti-reflection effect, anthracene is preferably used for 248 nm and 157 nm exposure, and polysiloxane that has a phenyl group or a light-absorbing group having a silicon-silicon bond in a pendant structure or polysiloxane structure for 193 nm exposure and crosslinks with acid or heat is preferably used.

Next, a resist upper layer film is formed on the silicon-containing resist intermediate film using a resist upper layer film material consisting of a photoresist composition. The resist upper layer film material may be either positive or negative, and the same as a commonly used photoresist composition can be used. After spin-coating the resist upper layer film material, it is preferable to perform pre-baking at 60 to 180°C for 10 to 300 seconds. Thereafter, exposure is performed according to a conventional method, and further post-exposure baking (PEB) and development are performed to obtain a resist upper layer film pattern. The thickness of the resist upper layer film is not particularly limited, but is preferably 30 to 500 nm, and more preferably 50 to 400 nm.

Next, a circuit pattern (resist upper layer film pattern) is formed on the resist upper layer film. In forming the circuit pattern, it is preferable to form the circuit pattern by lithography using light having a wavelength of 10 nm or more and 300 nm or less, direct drawing with an electron beam, nanoimprinting, or a combination of these.

Examples of the exposure light include high-energy rays having a wavelength of 300 nm or less, specifically far ultraviolet rays, KrF excimer laser light (248 nm), ArF excimer laser light (193 nm), _F2 laser light (157 nm), _Kr2 laser light (146 nm), _Ar2 laser light (126 nm), soft X-rays (EUV) of 3 to 20 nm, electron beams (EB), ion beams, X-rays, and the like.

In addition, when forming a circuit pattern, it is preferable to develop the circuit pattern using an alkaline developer or an organic solvent.

Next, the pattern is transferred to the silicon-containing resist intermediate film by etching using the resist top layer film on which the circuit pattern has been formed as a mask. The etching of the silicon-containing resist intermediate film, which is performed using the resist top layer film pattern as a mask, is preferably performed using a fluorocarbon gas. In this way, a silicon-containing resist intermediate film pattern is formed.

Next, the pattern is transferred to the protective film by etching using the silicon-containing resist intermediate film with the transferred pattern as a mask. Since the silicon-containing resist intermediate film exhibits higher etching resistance to oxygen gas or hydrogen gas than organic materials, it is preferable to use an etching gas mainly composed of oxygen gas or hydrogen gas to etch the protective film using the silicon-containing resist intermediate film pattern as a mask. This allows the protective film pattern to be formed.

Next, a pattern is formed on the substrate to be processed using the protective film to which the pattern has been transferred as a mask. For example, the protective film to which the pattern has been transferred is used as a mask to transfer the pattern to the substrate to be processed by etching. The next etching of the substrate to be processed (layer to be processed) can be performed by a conventional method. For example, if the substrate to be processed is a SiO ₂ , SiN, or silica-based low dielectric constant insulating film, etching is performed mainly with fluorocarbon gas, and if it is p-Si, Al, or W, etching is performed mainly with chlorine or bromine gas. When the substrate is processed by etching with fluorocarbon gas, the silicon-containing resist intermediate film pattern is peeled off at the same time as the substrate is processed. On the other hand, when the substrate is processed by etching with chlorine or bromine gas, it is necessary to separately perform dry etching stripping with fluorocarbon gas after the substrate is processed in order to strip the silicon-containing resist intermediate film pattern.

The protective film obtained using the protective film-forming composition of the present invention can have excellent etching resistance when etching the substrate to be processed as described above.

[Four-layer resist method using silicon-containing resist intermediate film and organic anti-reflective film]
Further, the present invention provides a method for forming a pattern on a workpiece substrate, comprising the steps of:
(II-1) forming a protective film on a substrate to be processed using the protective film-forming composition;
(II-2) forming a silicon-containing resist intermediate film on the protective film using a silicon-containing resist intermediate film material;
(II-3) forming an organic anti-reflective coating on the silicon-containing resist intermediate film;
(II-4) forming a resist upper layer film on the organic antireflective film using a photoresist composition to form a four-layer film structure, and forming a circuit pattern on the resist upper layer film;
(II-5) a step of transferring a pattern to the organic antireflective film and the silicon-containing resist intermediate film by etching using the resist upper layer film on which the pattern has been formed as a mask;
(II-6) a step of transferring a pattern to the protective film by etching using the silicon-containing resist intermediate film to which the pattern has been transferred as a mask; and (II-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
The present invention provides a pattern forming method comprising the steps of:

This method can be carried out in the same manner as the three-layer resist method using the silicon-containing resist intermediate film described above, except that an organic antireflective coating (BARC) is formed between the silicon-containing resist intermediate film and the resist top layer film.

The organic anti-reflective coating can be formed by spin coating using known organic anti-reflective coating materials.

[Three-layer resist method using an inorganic hard mask]
The present invention also provides a method for forming a pattern on a substrate to be processed, comprising the steps of:
(III-1) forming a protective film on a substrate to be processed using the protective film-forming composition;
(III-2) forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a titanium oxide film, and a titanium nitride film on the protective film;
(III-3) forming a resist top layer film on the inorganic hard mask using a photoresist composition;
(III-4) forming a circuit pattern on the resist upper layer film;
(III-5) a step of transferring a pattern to the inorganic hard mask by etching using the resist top layer film on which the pattern has been formed as a mask;
(III-6) a step of transferring a pattern to the protective film by etching using the inorganic hard mask to which the pattern has been transferred as a mask; and (III-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
The present invention provides a pattern forming method comprising the steps of:

This method can be carried out in the same manner as the three-layer resist method using the silicon-containing resist intermediate film described above, except that an inorganic hard mask is formed on the protective film instead of the silicon-containing resist intermediate film.

The inorganic hard mask selected from silicon oxide film, silicon nitride film, and silicon oxide nitride film (SiON film) can be formed by CVD method, ALD method, etc. Methods for forming silicon nitride film are described in, for example, JP 2002-334869 A and WO 2004/066377 A. The thickness of the inorganic hard mask is preferably 5 to 200 nm, more preferably 10 to 100 nm. As the inorganic hard mask, a SiON film, which has a high effect as an anti-reflection film, is most preferably used. Since the substrate temperature when forming the SiON film is 300 to 500°C, the underlayer film needs to withstand temperatures of 300 to 500°C. The protective film formed using the protective film forming composition of the present invention has high heat resistance and can withstand high temperatures of 300°C to 500°C, so it is possible to combine an inorganic hard mask formed by CVD method or ALD method with a protective film formed by spin coating method.

[Four-layer resist method using inorganic hard mask and organic anti-reflective coating]
The present invention also provides a method for forming a pattern on a workpiece substrate, comprising the steps of:
(IV-1) forming a protective film on a substrate to be processed using the protective film-forming composition;
(IV-2) forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a titanium oxide film, and a titanium nitride film on the protective film;
(IV-3) forming an organic anti-reflective coating on the inorganic hard mask;
(IV-4) forming a resist upper layer film on the organic antireflective film using a photoresist composition to form a four-layer film structure, and forming a circuit pattern on the resist upper layer film;
(IV-5) a step of transferring a pattern to the organic anti-reflective film and the inorganic hard mask by etching using the resist top layer film on which the pattern has been formed as a mask;
(IV-6) a step of transferring a pattern to the protective film by etching using the inorganic hard mask to which the pattern has been transferred as a mask; and (IV-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
The present invention provides a pattern forming method comprising the steps of:

This method can be carried out in the same manner as the three-layer resist method using the inorganic hard mask described above, except that an organic anti-reflective coating (BARC) is formed between the inorganic hard mask and the resist top layer.

In particular, when a SiON film is used as an inorganic hard mask, the two-layer anti-reflection film of the SiON film and the BARC makes it possible to suppress reflections even in immersion exposure with a high NA exceeding 1.0. Another advantage of forming the BARC is that it has the effect of reducing the tailing of the resist top layer pattern directly above the SiON film.

Here, an example of a pattern forming method using the three-layer resist method of the present invention is shown in Figures 2(A) to (F). In the case of the three-layer resist method, as shown in Figure 2(A), a protective film 3 is formed on a workpiece layer 2 formed on a substrate 1 using the protective film forming composition of the present invention, and then a silicon-containing resist intermediate film 4 is formed on the protective film 3, and a resist upper layer film 5 is formed thereon. Next, as shown in Figure 2(B), the exposed portion 6 of the resist upper layer film 5 is exposed and PEB (post-exposure bake) is performed. Next, as shown in Figure 2(C), development is performed to form a resist upper layer film pattern 5a. Next, as shown in Figure 2(D), the silicon-containing resist intermediate film 4 is dry-etched using a fluorocarbon gas using the resist upper layer film pattern 5a as a mask to form a silicon-containing resist intermediate film pattern 4a. Next, as shown in Figure 2(E), after removing the resist upper layer film pattern 5a, the protective film 3 is oxygen plasma etched using the silicon-containing resist intermediate film pattern 4a as a mask to form a protective film pattern 3a. Furthermore, as shown in FIG. 2(F), after removing the silicon-containing resist intermediate film pattern 4a, the processing layer 2 is etched using the protective film pattern 3a as a mask to form a pattern 2a.

When forming an inorganic hard mask, the silicon-containing resist intermediate film 4 can be changed to an inorganic hard mask, and when forming a BARC, the BARC can be formed between the silicon-containing resist intermediate film 4 and the resist top layer film 5. Etching of the BARC can be performed consecutively prior to etching of the silicon-containing resist intermediate film 4, or etching of only the BARC can be performed and then etching of the silicon-containing resist intermediate film 4 can be performed by changing the etching device, etc.

(Special processing)
Furthermore, application of the pattern formation method of the present invention makes it possible to establish various special processing processes in addition to the above-mentioned general processing processes, and is therefore of great industrial value.

(First aspect)
First, as described above, dry etching stripping is generally essential for stripping the silicon-containing resist intermediate film, but in the pattern formation method of the present invention, since the protective film has resistance to alkaline hydrogen peroxide, wet stripping of only the silicon-containing resist intermediate film using alkaline hydrogen peroxide is also an option. That is, in the pattern formation method using the three-layer resist process of the present invention, after the above step (I-6) or step (II-6), a step of removing the silicon-containing resist intermediate film to which the pattern has been transferred by wet etching using alkaline hydrogen peroxide may be added.

(Second Aspect)
Furthermore, when the substrate to be processed is made of W, TiN, etc., wet etching of the substrate with alkaline hydrogen peroxide solution may be an option if the pattern formation method of the present invention is applied. That is, in the pattern formation method using the three-layer or four-layer resist process of the present invention, the etching method in the above step (I-7), step (II-7), step (III-7), or step (IV-7) may be a step of transferring a pattern to the substrate to be processed by wet etching using alkaline hydrogen peroxide solution, using the protective film to which the pattern has been transferred as a mask.

In one example of such a process, a protective film is first formed on the substrate to be processed, and then a silicon-containing resist intermediate film is formed on top of the protective film, if necessary, followed by a resist top film. The resist top film is then patterned by a conventional method, and the pattern is then transferred to the protective film by etching. Finally, the substrate to be processed can be patterned by wet etching using the protective film as a mask.

(Third Aspect)
In the pattern formation method using the three-layer or four-layer resist process of the present invention, the above-mentioned step (I-7), step (II-7), step (III-7), or step (IV-7) may be a step of patterning the workpiece substrate by ion implantation using the protective film to which the pattern has been transferred as a mask. In this case, after the step of patterning the workpiece substrate by ion implantation, a step of removing the silicon-containing resist intermediate film to which the pattern has been transferred by wet etching using an alkaline hydrogen peroxide solution may be added.

The pattern formation method of the present invention is also suitable for processing substrates with structures or steps with heights of 30 nm or more. An example of such a process is described below.

First, a protective film is formed on the stepped substrate to fill and planarize it, and if necessary, a silicon-containing resist intermediate film is formed, followed by a resist top film. Next, the resist top film is patterned by a conventional method, and the pattern is then transferred to the protective film by etching. Next, the substrate can be patterned by ion implantation using the protective film as a mask. The remaining silicon-containing resist intermediate film can be peeled off by a method selected from dry etching and wet etching, if necessary. Finally, the protective film can be removed by dry etching.

As described above, the pattern formation method of the present invention makes it possible to form fine patterns on a substrate to be processed with high precision using a multi-layer resist method.

The present invention will be explained in more detail below with reference to synthesis examples, comparative synthesis examples, working examples, and comparative examples, but the present invention is not limited to these. Note that the molecular weight and dispersity were determined by determining the weight average molecular weight (Mw) and number average molecular weight (Mn) in terms of polystyrene by gel permeation chromatography (GPC) using tetrahydrofuran as an eluent, and the dispersity (Mw/Mn).

Synthesis Example Synthesis of Polymer for Protective Film-Forming Composition, and Polymer Having Hydroxyl Group at Terminal Group The polymer (or polymer mixture) (A1) to (A9) for the protective film-forming composition, and the polymer (A10) to (A12) having a hydroxyl group at the terminal group were synthesized using the following tetracarboxylic acid anhydrides (B1) to (B5), diamine compounds (C1) to (C8), aniline derivatives serving as end-capping agents, and phthalic anhydride derivatives (D1) to (D10).

Tetracarboxylic acid anhydrides:

Diamine compounds:

End-capping agent:

[Synthesis Example 1] Synthesis of polymer (A1) 17.77 g of tetracarboxylic anhydride (B1), 10.65 g of diamine compound (C1) were added with 120 g of NMP (N-methyl-2-pyrrolidone), and the mixture was reacted for 3 hours at an internal temperature of 40°C under a nitrogen atmosphere. 3.15 g of end-capping agent (D1) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40°C to obtain a polyimide precursor solution. 150 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180°C from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, 400 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 100 g of a 3% aqueous nitric acid solution, and then washed six times with 100 g of pure water, and the organic layer was dried under reduced pressure. 100 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 400 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 300 g of diisopropyl ether, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (A1). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ａ１）：Ｍｗ＝３７５０、Ｍｗ／Ｍｎ＝１．６６

(A1): Mw=3750, Mw/Mn=1.66

[Synthesis Example 2] Synthesis of polymer (A2) 90 g of NMP (N-methyl-2-pyrrolidone) was added to 15.61 g of tetracarboxylic anhydride (B2), 2.51 g of diamine compound (C2) and 1.94 g of diamine compound (C3), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 5.80 g of end-capping agent (D2) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 120 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180 ° C. from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 300 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 75 g of a 3% aqueous nitric acid solution, and then further washed six times with 75 g of pure water, and the organic layer was dried under reduced pressure. The residue was added with 75 g of THF (tetrahydrofuran) to obtain a homogeneous solution, and then crystallized with 300 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 200 g of diisopropyl ether, and collected. The collected crystals were dried in a vacuum at 70° C. to obtain a polymer (A2). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the following results were obtained.

（Ａ２）：Ｍｗ＝２４８０、Ｍｗ／Ｍｎ＝１．４２

(A2): Mw=2480, Mw/Mn=1.42

[Synthesis Example 3] Synthesis of polymer (A3) 90 g of NMP (N-methyl-2-pyrrolidone) was added to 19.28 g of tetracarboxylic anhydride (B3), 1.92 g of diamine compound (C4) and 1.30 g of diamine compound (C5), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 4.22 g of end-capping agent (D3) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 120 g of o-xylene was added to the obtained reaction solution, and the mixture was reacted for 9 hours at an internal temperature of 180 ° C. while removing the water generated from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 300 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 75 g of 3% aqueous nitric acid solution, and then further washed six times with 75 g of pure water, and the organic layer was dried under reduced pressure. The residue was added with 75 g of THF (tetrahydrofuran) to obtain a homogeneous solution, and then crystallized with 300 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 200 g of diisopropyl ether, and collected. The collected crystals were dried in a vacuum at 70° C. to obtain a polymer (A3). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the following results were obtained.

（Ａ３）：Ｍｗ＝２１８０、Ｍｗ／Ｍｎ＝１．２８

(A3): Mw=2180, Mw/Mn=1.28

Synthesis Example 4 Synthesis of Polymer Mixture (A4) The polymers (A4-1) and (A4-2) used in the polymer mixture (A4) were each synthesized as follows.

[Synthesis Example 4-1] Synthesis of polymer (A4-1) 60 g of NMP (N-methyl-2-pyrrolidone) was added to 6.36 g of tetracarboxylic anhydride (B4) and 3.84 g of diamine compound (C6), and the mixture was reacted for 3 hours at an internal temperature of 40°C under a nitrogen atmosphere. 2.34 g of end-capping agent (D4) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40°C to obtain a polyimide precursor solution. 80 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180°C from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 200 g of methyl isobutyl ketone was added. The organic layer was washed twice with 50 g of a 3% aqueous nitric acid solution, and then washed six times with 50 g of pure water, and the organic layer was dried under reduced pressure. 50 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 200 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 150 g of diisopropyl ether, and collected. The collected crystals were dried in a vacuum at 70° C. to obtain a polymer (A4-1). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ａ４－１）：Ｍｗ＝２３１０、Ｍｗ／Ｍｎ＝１．４５

(A4-1): Mw=2310, Mw/Mn=1.45

[Synthesis Example 4-2] Synthesis of polymer (A4-2) 60 g of NMP (N-methyl-2-pyrrolidone) was added to 6.36 g of tetracarboxylic anhydride (B4) and 2.58 g of diamine compound (C3), and the mixture was reacted for 3 hours at an internal temperature of 40° C. under a nitrogen atmosphere. 2.34 g of end-capping agent (D4) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40° C. to obtain a polyimide precursor solution. 80 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180° C. from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 200 g of methyl isobutyl ketone was added. The organic layer was washed twice with 50 g of a 3% aqueous nitric acid solution, and then washed six times with 50 g of pure water, and the organic layer was dried under reduced pressure. 50 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 200 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 150 g of diisopropyl ether, and collected. The collected crystals were dried in a vacuum at 70° C. to obtain a polymer (A4-2). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ａ４－２）：Ｍｗ＝２１９０、Ｍｗ／Ｍｎ＝１．４３

(A4-2): Mw=2190, Mw/Mn=1.43

[Synthesis Example 5] Synthesis of polymer (A5) 45 g of NMP (N-methyl-2-pyrrolidone) was added to 9.64 g of tetracarboxylic anhydride (B3) and 2.20 g of diamine compound (C7), and the mixture was reacted for 3 hours at an internal temperature of 40°C under a nitrogen atmosphere. 3.48 g of end-capping agent (D2) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40°C to obtain a polyimide precursor solution. 60 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180°C from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 150 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 40 g of a 3% aqueous nitric acid solution, and then further washed six times with 40 g of pure water, and the organic layer was dried under reduced pressure. 40 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 150 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 120 g of diisopropyl ether, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (A5). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ａ５）：Ｍｗ＝２２３０、Ｍｗ／Ｍｎ＝１．２２

(A5): Mw=2230, Mw/Mn=1.22

[Synthesis Example 6] Synthesis of polymer (A6) 100 g of NMP (N-methyl-2-pyrrolidone) was added to 10.88 g of tetracarboxylic anhydride (B1) and 12.82 g of diamine compound (C7), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 1.95 g of terminal blocking agent (D5) and 2.61 g of terminal blocking agent (D6) were added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 130 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180 ° C. from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 350 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 90 g of 3% aqueous nitric acid solution, and then further washed six times with 90 g of pure water, and the organic layer was dried under reduced pressure. The residue was added with 90 g of THF (tetrahydrofuran) to obtain a homogeneous solution, and then crystallized with 350 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 250 g of diisopropyl ether, and collected. The collected crystals were dried in a vacuum at 70° C. to obtain a polymer (A6). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the following results were obtained.

（Ａ６）：Ｍｗ＝３９５０、Ｍｗ／Ｍｎ＝１．７０

(A6): Mw=3950, Mw/Mn=1.70

[Synthesis Example 7] Synthesis of polymer (A7) 15.71 g of tetracarboxylic anhydride (B5), 3.66 g of diamine compound (C7) were added with 75 g of NMP (N-methyl-2-pyrrolidone), and the mixture was reacted for 3 hours at an internal temperature of 40°C under a nitrogen atmosphere. 3.51 g of end-capping agent (D3) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40°C to obtain a polyimide precursor solution. 90 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180°C from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 250 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 60 g of a 3% aqueous nitric acid solution, and then further washed six times with 60 g of pure water, and the organic layer was dried under reduced pressure. 60 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 250 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 180 g of diisopropyl ether, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (A7). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ａ７）：Ｍｗ＝１９５０、Ｍｗ／Ｍｎ＝１．２１

(A7): Mw=1950, Mw/Mn=1.21

[Synthesis Example 8] Synthesis of polymer (A8) 75 g of NMP (N-methyl-2-pyrrolidone) was added to 7.86 g of tetracarboxylic anhydride (B5), 9.07 g of diamine compound (C8) and 2.75 g of diamine compound (C7), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 4.30 g of end-capping agent (D7) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 90 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180 ° C. from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 250 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 60 g of a 3% aqueous nitric acid solution, and then further washed six times with 60 g of pure water, and the organic layer was dried under reduced pressure. The residue was added with 60 g of THF (tetrahydrofuran) to obtain a homogeneous solution, and then crystallized with 250 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 180 g of diisopropyl ether, and collected. The collected crystals were dried in a vacuum at 70° C. to obtain a polymer (A8). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the following results were obtained.

（Ａ８）：Ｍｗ＝２５６０、Ｍｗ／Ｍｎ＝１．４１

(A8): Mw=2560, Mw/Mn=1.41

[Synthesis Example 9] Synthesis of polymer (A9) 40 g of NMP (N-methyl-2-pyrrolidone) was added to 7.54 g of tetracarboxylic anhydride (B5), 0.80 g of diamine compound (C2) and 0.88 g of diamine compound (C7), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 1.69 g of end-capping agent (D4) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 45 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180 ° C. from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 120 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 30 g of a 3% aqueous nitric acid solution, and then further washed six times with 30 g of pure water, and the organic layer was dried under reduced pressure. The residue was added with 30 g of THF (tetrahydrofuran) to obtain a homogeneous solution, and then crystallized with 120 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 90 g of diisopropyl ether, and collected. The collected crystals were dried in a vacuum at 70° C. to obtain a polymer (A9). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the following results were obtained.

（Ａ９）：Ｍｗ＝２０１０、Ｍｗ／Ｍｎ＝１．２９

(A9): Mw=2010, Mw/Mn=1.29

[Synthesis Example 10] Synthesis of polymer (A10) 75 g of NMP (N-methyl-2-pyrrolidone) was added to 16.07 g of tetracarboxylic anhydride (B3) and 3.34 g of diamine compound (C2), and the mixture was reacted for 3 hours at an internal temperature of 40°C under a nitrogen atmosphere. 3.27 g of end-capping agent (D8) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40°C to obtain a polyimide precursor solution. 90 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180°C from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 250 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 60 g of a 3% aqueous nitric acid solution, and then further washed six times with 60 g of pure water, and the organic layer was dried under reduced pressure. 60 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 250 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 180 g of diisopropyl ether, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (A10). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ａ１０）：Ｍｗ＝１９７０、Ｍｗ／Ｍｎ＝１．２４

(A10): Mw=1970, Mw/Mn=1.24

[Synthesis Example 11] Synthesis of polymer (A11) 75 g of NMP (N-methyl-2-pyrrolidone) was added to 16.07 g of tetracarboxylic anhydride (B3) and 3.66 g of diamine compound (C7), and the mixture was reacted for 3 hours at an internal temperature of 40°C under a nitrogen atmosphere. 4.17 g of end-capping agent (D9) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40°C to obtain a polyimide precursor solution. 90 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180°C from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 250 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 60 g of a 3% aqueous nitric acid solution, and then further washed six times with 60 g of pure water, and the organic layer was dried under reduced pressure. 60 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 250 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 180 g of diisopropyl ether, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (A11). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ａ１１）：Ｍｗ＝２０１０、Ｍｗ／Ｍｎ＝１．２３

(A11): Mw=2010, Mw/Mn=1.23

[Synthesis Example 12] Synthesis of polymer (A12) 75 g of NMP (N-methyl-2-pyrrolidone) was added to 15.71 g of tetracarboxylic anhydride (B5) and 5.18 g of diamine compound (C8), and the mixture was reacted for 3 hours at an internal temperature of 40°C under a nitrogen atmosphere. 4.78 g of end-capping agent (D10) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40°C to obtain a polyimide precursor solution. 90 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180°C from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 250 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 60 g of a 3% aqueous nitric acid solution, and then washed six times with 60 g of pure water, and the organic layer was dried under reduced pressure. 60 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 250 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 180 g of diisopropyl ether, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (A12). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ａ１２）：Ｍｗ＝２１００、Ｍｗ／Ｍｎ＝１．２５

(A12): Mw=2100, Mw/Mn=1.25

Comparative polymers (R1) to (R9) were synthesized using the compounds (E1) to (E10) shown below, as well as the above-mentioned tetracarboxylic acid anhydrides (B1), (B3), and (B5), diamine compounds (C1), (C7), and (C8), and end-capping agents (D3), (D6), and (D7). For (E10), a 60:40 mixture of isomers was used.

[Synthesis Example 13] Synthesis of polymer (R1) 120 g of NMP (N-methyl-2-pyrrolidone) was added to 7.11 g of tetracarboxylic anhydride (B1) and 14.65 g of diamine compound (C7), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 7.11 g of (E1) was added as an end-capping agent to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 150 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180 ° C. from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, 400 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 100 g of a 3% aqueous nitric acid solution, and then washed six times with 100 g of pure water, and the organic layer was dried under reduced pressure. 100 g of THF (tetrahydrofuran) was added to the residue to make a uniform solution, and then crystallized with 400 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 300 g of diisopropyl ether, and collected. The collected crystals were vacuum dried at 70° C. to obtain a polymer (R1). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ｒ１）：Ｍｗ＝２２５０、Ｍｗ／Ｍｎ＝１．３２

(R1): Mw=2250, Mw/Mn=1.32

[Synthesis Example 14] Synthesis of polymer (R2) 90 g of NMP (N-methyl-2-pyrrolidone) was added to 13.33 g of tetracarboxylic anhydride (B1) and 4.40 g of diamine compound (C7), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 3.35 g of (E2) was added as an end-capping agent to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 120 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180 ° C. from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 300 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 75 g of a 3% aqueous nitric acid solution, and then washed six times with 75 g of pure water, and the organic layer was dried under reduced pressure. 75 g of THF (tetrahydrofuran) was added to the residue to obtain a homogeneous solution, and then crystallized with 300 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 200 g of diisopropyl ether, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (R2). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the following results were obtained.

（Ｒ２）：Ｍｗ＝２１４０、Ｍｗ／Ｍｎ＝１．２９

(R2): Mw=2140, Mw/Mn=1.29

[Synthesis Example 15] Synthesis of polymer (R3) 120 g of NMP (N-methyl-2-pyrrolidone) was added to 12.57 g of tetracarboxylic anhydride (B5) and 14.65 g of diamine compound (C7), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 3.92 g of (E3) was added as an end-capping agent to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 150 g of o-xylene was added to the obtained reaction solution, and the reaction was carried out for 9 hours while removing the water generated at an internal temperature of 180 ° C. from the system to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, 400 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 100 g of a 3% aqueous nitric acid solution, and then further washed six times with 100 g of pure water, and the organic layer was dried under reduced pressure. 100 g of THF (tetrahydrofuran) was added to the residue to obtain a uniform solution, and then crystallized with 400 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 300 g of diisopropyl ether, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (R3). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ｒ３）：Ｍｗ＝２３６０、Ｍｗ／Ｍｎ＝１．３６

(R3): Mw=2360, Mw/Mn=1.36

[Synthesis Example 16] Synthesis of polymer (R4) 150 g of N-methylpyrrolidone was added to 30.00 g of tetracarboxylic anhydride (B1), and the mixture was made into a homogeneous solution at an internal temperature of 40° C. under a nitrogen atmosphere. Then, 14.74 g of amine compound (E4) was added and reacted at an internal temperature of 40° C. for 3 hours to obtain an amic acid solution. 200 g of o-xylene was added to the obtained amic acid solution, and the mixture was reacted for 9 hours at an internal temperature of 150° C. while removing the low boiling point products and water produced from the system to perform dehydration imidization. After the reaction was completed, the mixture was cooled to room temperature and crystallized in 1000 g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 500 g of diisopropyl ether, and collected. The collected crystals were dried in a vacuum at 70° C. to obtain an imide compound (R4').

Next, 15.00 g of the obtained imide compound (R4'), 1.36 g of the aldehyde compound (E5), and 60 g of 2-methoxy-1-propanol were made into a homogeneous solution at an internal temperature of 80°C under a nitrogen atmosphere, and then 1.5 g of a 20% solution of paratoluenesulfonic acid in 2-methoxy-1-propanol was slowly added and stirred at an internal temperature of 110°C for 8 hours. After cooling to room temperature, 200 g of methyl isobutyl ketone was added, and the organic layer was washed five times with 50 g of pure water, and then the organic layer was dried under reduced pressure. 50 g of THF was added to the residue, and the polymer was reprecipitated with 200 g of hexane. The precipitated polymer was separated by filtration and dried under reduced pressure to obtain polymer (R4). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the following results were obtained.

（Ｒ４）：Ｍｗ＝２８２０、Ｍｗ／Ｍｎ＝１．７２

(R4): Mw=2820, Mw/Mn=1.72

[Synthesis Example 17] Synthesis of polymer (R5) 120 g of NMP (N-methyl-2-pyrrolidone) was added to 15.55 g of tetracarboxylic anhydride (B1) and 14.62 g of diamine compound (E6), and the reaction was carried out for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 5.16 g of end-capping agent (D7) was added to the obtained polyamic acid intermediate solution, and the reaction was carried out for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 4.00 g of pyridine was added to the obtained reaction solution, and 12.25 g of acetic anhydride was slowly dropped, and then the reaction was carried out for 4 hours at an internal temperature of 60 ° C. to carry out imidization. After the reaction was completed, the mixture was cooled to room temperature, and 400 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 100 g of a 3% aqueous nitric acid solution, and then further washed six times with 100 g of pure water, and the organic layer was dried under reduced pressure. 100 g of THF (tetrahydrofuran) was added to the residue to make a uniform solution, and then crystallized with 400 g of methanol. The precipitated crystals were separated by filtration, washed twice with 300 g of methanol, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (R5). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ｒ５）：Ｍｗ＝４３２０、Ｍｗ／Ｍｎ＝１．７２

(R5): Mw=4320, Mw/Mn=1.72

[Synthesis Example 18] Synthesis of polymer (R6) 70 g of NMP (N-methyl-2-pyrrolidone) was added to 13.33 g of tetracarboxylic anhydride (B1) and 7.32 g of diamine compound (E7), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 2.11 g of end-capping agent (D3) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 2.37 g of pyridine was added to the obtained reaction solution, and 7.35 g of acetic anhydride was slowly dropped, and the mixture was reacted for 4 hours at an internal temperature of 60 ° C. to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 240 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 60 g of a 3% aqueous nitric acid solution, and then washed six times with 60 g of pure water, and the organic layer was dried under reduced pressure. 60 g of THF (tetrahydrofuran) was added to the residue to make a uniform solution, and then crystallized with 240 g of methanol. The precipitated crystals were separated by filtration, washed twice with 240 g of methanol, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (R6). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ｒ６）：Ｍｗ＝３７８０、Ｍｗ／Ｍｎ＝１．６７

(R6): Mw=3780, Mw/Mn=1.67

[Synthesis Example 19] Synthesis of polymer (R7) 70 g of NMP (N-methyl-2-pyrrolidone) was added to 7.71 g of tetracarboxylic anhydride (B3) and 15.55 g of diamine compound (C8), and the mixture was reacted for 3 hours at an internal temperature of 40 ° C. under a nitrogen atmosphere. 6.20 g of end-capping agent (D7) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40 ° C. to obtain a polyimide precursor solution. 2.37 g of pyridine was added to the obtained reaction solution, and 7.35 g of acetic anhydride was slowly dropped, and the mixture was reacted for 4 hours at an internal temperature of 60 ° C. to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 240 g of methyl isobutyl ketone was added, and the organic layer was washed twice with 60 g of a 3% aqueous nitric acid solution, and then washed six times with 60 g of pure water, and the organic layer was dried under reduced pressure. 60 g of THF (tetrahydrofuran) was added to the residue to make a uniform solution, and then crystallized with 240 g of methanol. The precipitated crystals were separated by filtration, washed twice with 240 g of methanol, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (R7). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ｒ７）：Ｍｗ＝２４２０、Ｍｗ／Ｍｎ＝１．２６

(R7): Mw=2420, Mw/Mn=1.26

[Synthesis Example 20] Synthesis of polymer (R8) 18.34g of tetracarboxylic anhydride (E8), 8.30g of diamine compound (C8) were added with 100g of NMP (N-methyl-2-pyrrolidone), and the mixture was reacted for 3 hours at an internal temperature of 40°C under a nitrogen atmosphere. 5.62g of end-capping agent (D3) was added to the obtained polyamic acid intermediate solution, and the mixture was reacted for another 3 hours at an internal temperature of 40°C to obtain a polyimide precursor solution. 3.16g of pyridine was added to the obtained reaction solution, and 9.80g of acetic anhydride was slowly added dropwise, and the mixture was reacted for 4 hours at an internal temperature of 60°C to perform imidization. After the reaction was completed, the mixture was cooled to room temperature, and 320g of methyl isobutyl ketone was added, and the organic layer was washed twice with 80g of a 3% aqueous nitric acid solution, and then washed six times with 80g of pure water, and the organic layer was dried under reduced pressure. 80g of THF (tetrahydrofuran) was added to the residue to make a uniform solution, and then crystallized with 320g of methanol. The precipitated crystals were separated by filtration, washed twice with 240 g of methanol, and collected. The collected crystals were dried in vacuum at 70° C. to obtain a polymer (R8). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ｒ８）：Ｍｗ＝２２４０、Ｍｗ／Ｍｎ＝１．２７

(R8): Mw=2240, Mw/Mn=1.27

[Synthesis Example 21] Synthesis of polymer (R9) 50g of THF was added to 6.32g of compound (E9), and a homogeneous solution was prepared in an ice bath under a nitrogen atmosphere. 4.00g of diamine compound (E10) and 3.34g of triethylamine, which had been dissolved in 20g of NMP in advance, were slowly dropped, and the reaction was carried out at room temperature for 1 hour. 14.28g of compound (C1) and 100g of NMP were further added to the reaction solution, and the reaction was carried out at an internal temperature of 40°C for 3 hours, after which 11.18g of end-capping agent (D6) was added to obtain a polyimide precursor. 150g of o-xylene was added to the reaction solution obtained, and the reaction was carried out for 9 hours while removing the low boiling point products and water produced at an internal temperature of 180°C from the system, to carry out imidization. After the reaction was completed, the mixture was cooled to room temperature and crystallized in 600g of diisopropyl ether. The precipitated crystals were separated by filtration, washed twice with 200g of diisopropyl ether, and collected. The recovered crystals were dried in a vacuum at 70° C. to obtain (R9). The weight average molecular weight (Mw) and dispersity (Mw/Mn) were determined by GPC, and the results were as follows.

（Ｒ９）：Ｍｗ＝２９３０、Ｍｗ／Ｍｎ＝１．４２

(R9): Mw=2930, Mw/Mn=1.42

Preparation of protective film-forming compositions (UDL-1 to 22, Comparative UDL-1 to 9) The above polymers (A1) to (A12) and (R1) to (R9) and high boiling point solvents (S1) 1,6-diacetoxyhexane: boiling point 260° C., (S2) γ-butyrolactone: boiling point 204° C., and (S3) tripropylene glycol monomethyl ether: boiling point 242° C. were used. Propylene glycol monomethyl ether acetate (PGMEA) containing 0.1% by mass of FC-4430 (manufactured by Sumitomo 3M Limited) and cyclohexanone (CyHO) were used to dissolve the components in the proportions shown in Table 1, and then filtered through a 0.1 μm fluororesin filter to prepare protective film-forming compositions (UDL-1 to 22, Comparative UDL-1 to 9).

Example 1 Solvent resistance measurement (Examples 1-1 to 1-22, Comparative Examples 1-1 to 1-9)
The protective film-forming compositions (UDL-1 to 22, Comparative UDL-1 to 9) prepared above were applied onto silicon substrates, baked at 450°C for 60 seconds under a nitrogen flow with an oxygen concentration controlled to 0.2% or less, the film thickness was measured, PGMEA solvent was dispensed thereon, left for 30 seconds, spin-dried, and baked at 100°C for 60 seconds to evaporate the PGMEA, the film thickness was measured, and the difference in film thickness before and after the PGMEA treatment was determined. The results are shown in Table 2.

As shown in Table 2, the protective film-forming compositions of the present invention (Examples 1-1 to 1-22) had a residual film rate of 99% or more after PGMEA treatment, and it was found that a crosslinking reaction occurred even in a nitrogen atmosphere, resulting in sufficient solvent resistance. In contrast, in Comparative Examples 1-1, 1-2, and 1-4, which used polyimide without a crosslinking group, the residual film rate after PGMEA treatment was about 70%, and sufficient solvent resistance was not achieved. These results show that _R1 introduced as a substituent effectively functions as a thermal crosslinking group.

Example 2 Evaluation of heat resistance characteristics (Examples 2-1 to 2-22, Comparative Examples 2-1 to 2-9)
The above protective film-forming compositions (UDL-1 to 22, Comparative UDL-1 to 9) were each applied onto a silicon substrate and baked in air at 180° C. for 60 seconds to form a coating film of 200 nm, and the film thickness A was measured. This substrate was further baked for an additional 10 minutes at 450° C. in a nitrogen stream controlled to an oxygen concentration of 0.2% or less, and the film thickness B was measured. These results are shown in Table 3.

As shown in Table 3, the protective film-forming composition of the present invention (Examples 2-1 to 2-22) shows a film thickness reduction of less than 1% even after baking at 450°C, and the protective film-forming composition of the present invention maintains the film thickness before high-temperature baking even after baking at 450°C, and is found to have high heat resistance. In contrast, when compared with Comparative Examples 2-1, 2-2, and 2-4 using polyimide without a crosslinking group, it is found that the protective film-forming composition of the present invention forms a dense film by thermal crosslinking due to the terminal crosslinking group R ₁ , and a film having excellent heat resistance is formed. In addition, in Comparative Example 2-3 having a bismaleimide structure as a crosslinking group, solvent resistance is expressed by thermal crosslinking under the conditions of Example 1, but it is found that sufficient heat resistance is not expressed by thermal crosslinking due to the bismaleimide structure under the conditions of long-term high-temperature treatment such as Example 2.

Example 3: Evaluation of filling characteristics (Examples 3-1 to 3-22, Comparative Examples 3-1 to 3-9)
As shown in FIG. 3, the above protective film-forming compositions (UDL-1 to 22, Comparative UDL-1 to 9) were applied onto a SiO ₂ wafer substrate having a dense hole pattern (hole diameter 0.16 μm, hole depth 0.50 μm, distance between the centers of two adjacent holes 0.32 μm), and baked for 60 seconds at 450° C. under a nitrogen gas flow with an oxygen concentration controlled to 0.2% or less using a hot plate to form a protective film 8. The substrate used was a base substrate 7 (SiO ₂ wafer substrate) having a dense hole pattern as shown in FIG. 3 (G) (overhead view) and (H) (cross-sectional view). The cross-sectional shape of each of the obtained wafer substrates was observed using a scanning electron microscope (SEM) to confirm whether or not there were voids (air gaps) inside the holes and the holes were filled with the protective film. The results are shown in Table 4. When a protective film-forming composition with poor filling properties was used, voids were generated inside the holes in this evaluation. When a protective film-forming composition having good filling properties is used, the protective film fills the inside of the hole without leaving any voids, as shown in FIG. 3(I) in this evaluation.

As shown in Table 4, it was confirmed that the protective film-forming composition of the present invention (Examples 3-1 to 3-22) was capable of filling the hole pattern without generating voids and had good filling properties. On the other hand, in Comparative Examples 3-1 to 3-4, it was confirmed that voids were generated and the filling properties were poor. From this result, it can be seen that the protective film-forming composition of the present invention ensures heat resistance through the thermosetting reaction and improves the filling properties. On the other hand, in Comparative Examples 3-1 to 3-4, even though Comparative UDL-3 exhibits solvent resistance, voids were generated due to insufficient heat resistance, and good filling properties were not obtained.

Example 4: Evaluation of planarization characteristics (Examples 4-1 to 4-22, Comparative Examples 4-1 to 4-9)
Each of the protective film-forming compositions (UDL-1 to 22, comparative UDL-1 to 9) was applied onto a base substrate 9 (SiO ₂ wafer substrate) having a giant isolated trench pattern (FIG. 4(J), trench width 10 μm, trench depth 0.10 μm), and baked for 60 seconds at 450 ° C. under a nitrogen flow with an oxygen concentration controlled to 0.2% or less. The step (delta 10 in FIG. 4(K)) between the trench portion and the non-trench portion of the protective film 10 was observed using an atomic force microscope (AFM) NX10 manufactured by Park Systems. The results are shown in Table 5. In this evaluation, the smaller the step, the better the planarization characteristics. In this evaluation, a trench pattern with a depth of 0.10 μm was planarized using a protective film-forming composition with a normal film thickness of about 0.2 μm, and the evaluation conditions were strict in order to evaluate the superiority or inferiority of the planarization characteristics.

As shown in Table 5, the protective film forming composition of the present invention (Examples 4-1 to 4-22) was confirmed to have a smaller step between the trench portion and the non-trench portion of the protective film and to have excellent planarization characteristics compared to Comparative Examples 4-1 to 4-4. Comparative Example 4-3 had poor heat resistance as shown in the heat resistance evaluation results of Example 2, and therefore the film thickness loss caused by high-temperature baking was large, emphasizing the difference in film thickness between the upper and lower portions of the step, and thus worsening the planarization, resulting in the above-mentioned results. Comparative Examples 4-1, 4-2, and 4-4 also used non-crosslinked polyimide, so the impact of film loss due to high-temperature treatment was large, resulting in poor planarization. In addition, when Examples 4-11 to 4-13, 4-20 to 4-22 in which a high-boiling point solvent was added were compared with Examples 4-3, 4-5, 4-7, and 4-17 to 4-19 in which no high-boiling point solvent was added, it was found that the addition of a high-boiling point solvent improved the planarization.

Example 5: Evaluation of alkaline hydrogen peroxide resistance (Examples 5-1 to 5-22, Comparative Examples 5-1 to 5-9)
The above protective film forming compositions (UDL-1 to 22, Comparative UDL-1 to 9) were each applied onto a silicon wafer substrate on which a 300 nm SiO ₂ film had been formed, and baked for 60 seconds at 450 ° C. under a nitrogen stream in which the oxygen concentration was controlled to 0.2% or less, to form a protective film (resist underlayer film) with a thickness of 200 nm. The wafer was then cut into 2 cm widths, and the wafer pieces were immersed in 1.0 mass % hydrogen peroxide solution containing 0.5 mass % ammonia at 70 ° C. for 5 minutes, rinsed with deionized water, and dried, and then visually inspected for peeling of the protective film from the wafer. If a part or all of the protective film peels off and the silicon wafer surface is exposed, the protective film used in the test is judged to have insufficient resistance to alkaline hydrogen peroxide solution. These evaluation results are shown in Table 6.

As shown in Table 6, no peeling of the protective film was observed in any of the protective film-forming compositions of the present invention (Examples 5-1 to 5-22). On the other hand, peeling of the protective film was observed in Comparative Examples 5-1 to 5-9, even though heat resistance and solvent resistance were ensured. This shows that polyimide compounds in which fluorine atoms and hydroxyl groups coexist, such as those of the present invention, have excellent alkaline hydrogen peroxide resistance. Furthermore, it was found that adding a polyimide containing a hydroxyl group at the terminal group also results in excellent alkaline hydrogen peroxide resistance.

Example 6 Pattern formation test (Examples 6-1 to 6-22, Comparative Examples 6-1 to 6-9)
The above protective film forming compositions (UDL-1 to 22, comparative UDL-1 to 9) were each applied onto a silicon wafer substrate on which a 300 nm SiO ₂ film had been formed, and baked for 60 seconds at 450 ° C. under a nitrogen stream in which the oxygen concentration was controlled to 0.2% or less to form a protective film (resist underlayer film) with a thickness of 200 nm. A CVD-SiON hard mask was formed thereon, and an organic anti-reflective film material (ARC-29A: manufactured by Nissan Chemical Co., Ltd.) was further applied thereon and baked at 210 ° C. for 60 seconds to form an organic anti-reflective film with a thickness of 80 nm, and a single layer resist for ArF of the resist upper layer film material was applied thereon and baked at 105 ° C. for 60 seconds to form a photoresist film with a thickness of 100 nm. A liquid immersion protective film material (TC-1) was applied onto the photoresist film and baked at 90 ° C. for 60 seconds to form a protective film with a thickness of 50 nm.

The resist top layer material (ArF single layer resist) was prepared by dissolving the polymer (RP1), acid generator (PAG1), and basic compound (Amine1) in a solvent containing 0.1 mass% FC-430 (Sumitomo 3M Limited) in the proportions shown in Table 7, and filtering through a 0.1 μm fluororesin filter.

The polymer (RP1), acid generator (PAG1), and basic compound (Amine1) used in the resist top layer material (ArF single layer resist) are shown below.

The immersion protective film material (TC-1) was prepared by dissolving the protective film polymer (PP1) in an organic solvent in the ratio shown in Table 8 and filtering through a 0.1 μm fluororesin filter.

The polymer (PP1) used in the immersion protective film material (TC-1) is shown below.

Then, the film was exposed using an ArF immersion exposure system (Nikon Corporation; NSR-S610C, NA 1.30, σ 0.98/0.65, 35-degree dipole s-polarized illumination, 6% halftone phase shift mask), baked at 100°C for 60 seconds (PEB), and developed for 30 seconds with a 2.38% by weight aqueous solution of tetramethylammonium hydroxide (TMAH), yielding a 55 nm 1:1 positive line and space pattern.

Next, the organic anti-reflective film and the CVD-SiON hard mask were dry-etched using a Telium etching system manufactured by Tokyo Electron Co., Ltd., with the resist pattern as a mask to form a hard mask pattern, and the protective film was etched using the obtained hard mask pattern as a mask to form a protective film pattern. The etching conditions were as shown below.

Conditions for transferring the resist pattern to the SiON hard mask.
Chamber pressure 10.0 Pa
RF power 1,500W
_CF4 gas flow rate: 75 sccm
_O2 gas flow rate: 15 sccm
Time 15 seconds

Conditions for transferring the hard mask pattern to the protective film.
Chamber pressure: 2.0 Pa
RF power 500W
Ar gas flow rate: 75 sccm
_O2 gas flow rate: 45 sccm
Time 120 seconds

The formation of the protective film pattern was confirmed by observing the wafer after the protective film etching with a top-down SEM view. The wafer was then cut into 2 cm widths, and the wafer pieces were immersed in 1.0% by mass hydrogen peroxide solution containing 0.5% by mass ammonia at 70°C for 5 minutes, rinsed with deionized water, and dried. The protective film pattern was then observed using an optical microscope to evaluate whether it had peeled off. The evaluation results are shown in Table 9.

As shown in Table 9, the results of the protective film forming composition of the present invention (Examples 6-1 to 6-22) confirmed that in all cases, the resist upper layer film pattern was transferred well to the protective film, and the protective film forming composition of the present invention is suitable for use in microfabrication by the multilayer resist method. Furthermore, it was also confirmed that the formed protective film pattern had good resistance to alkaline hydrogen peroxide water. In Comparative Example 6-3, the heat resistance was insufficient, but a pattern could be formed. Furthermore, in Comparative Examples 6-1, 6-2, and 6-4, the heat resistance and solvent resistance were insufficient, but a pattern could be formed. On the other hand, in Comparative Examples 6-1 to 6-9, even though heat resistance and solvent resistance were ensured, peeling was observed in the formed protective film pattern. Therefore, the protective film forming composition and pattern forming method of the present invention are particularly useful in enabling the manufacture of semiconductor devices by microfabrication that combines chemical etching using alkaline hydrogen peroxide water or the like with the multilayer resist method.

Example 7 Pattern formation test (Examples 7-1 to 7-22, Comparative Examples 7-1 to 7-9)
The above protective film forming compositions (UDL-1 to 22, Comparative UDL-1 to 9) were each applied onto a _SiO2 wafer substrate having a trench pattern (trench width 10 μm, trench depth 0.10 μm) and baked at 450° C. for 60 seconds under a nitrogen flow with an oxygen concentration controlled to 0.2% or less. A coating film was formed in the same manner as in Example 6, and patterning and dry etching were performed to form a protective film pattern. Furthermore, the obtained protective film pattern was used as a mask to perform etching of the _SiO2 film. The etching conditions are as shown below.

Conditions for transferring the protective film pattern to the _SiO2 film.
Chamber pressure: 2.0 Pa
RF power 2,200W
_C5F12 gas flow rate _{20sccm
C2F6 gas} flow rate 10 sccm
Ar gas flow rate: 300 sccm
_O2 gas flow rate: 60 sccm
Time 90 seconds

The results of observing the cross section of the pattern using an electron microscope (S-4700) manufactured by Hitachi, Ltd. are shown in Table 10.

As shown in Table 10, in the results of the protective film-forming composition of the present invention (Examples 7-1 to 7-22), in all cases the resist top layer film pattern was successfully transferred to the substrate, confirming that the protective film-forming composition of the present invention is suitable for use in microfabrication using the multilayer resist method. On the other hand, in Comparative Examples 7-1 to 7-4, even though heat resistance and solvent resistance were ensured, pattern collapse occurred during pattern processing due to poor pattern embedding, and ultimately a good pattern could not be obtained.

From the above, the protective film-forming composition of the present invention has heat resistance of 400°C or more even under an oxygen-free inert gas, and has high filling/planarization properties, making it extremely useful as a protective film-forming composition for use in a multilayer resist method. Furthermore, the pattern formation method of the present invention using this composition can form fine patterns with high precision even when the workpiece is a substrate with steps, making it suitable for use in a multilayer resist process for fine patterning in the manufacture of semiconductor devices. In particular, it can be applied to a multilayer resist process including wet etching processing, making it extremely useful industrially.

This specification includes the following inventions:

（式中、Ｗ_１は１種類以上のフッ素原子又は水酸基を含んでいてもよい４価の有機基であり、Ｗ_２は１種類以上のフッ素原子又は水酸基を含んでいてもよい２価の有機基であり、かつＷ_１とＷ_２のうち少なくとも一方は１つ以上のフッ素原子を含み、Ｗ_１とＷ_２のうち少なくとも一方は１つ以上の水酸基を含む。）

（式中、Ｗ_３は１種類以上のフッ素原子を含んでいてもよい４価の有機基であり、Ｗ_４は１種類以上のフッ素原子を含んでいてもよい２価の有機基であり、かつＷ_３とＷ_４のうち少なくとも一方は１つ以上のフッ素原子を含む。）

（式中、Ｗ_５は１種類以上の水酸基を含んでいてもよい４価の有機基であり、Ｗ_６は１種類以上の水酸基を含んでいてもよい２価の有機基であり、かつＷ_５とＷ_６のうち少なくとも一方は１つ以上の水酸基を含む。）

（式中、Ｒ_１は下記式（１Ｄ）で示される基のいずれかであり、２種以上のＲ_１を組み合わせて用いてもよい。）

[1]: (A) a polymer having a fluorine atom and a hydroxyl group represented by any one of the following (I) and (II), or a mixture of a polymer having a fluorine atom represented by the following (III) and a polymer having a hydroxyl group; (I) a polymer having a repeating unit having at least one or more fluorine atoms and a hydroxyl group represented by the following general formula (1A), the end group being a group represented by any one of the following general formulas (1B) and (1C); (II) a polymer having a repeating unit having at least one or more fluorine atoms represented by the following general formula (2A) and a repeating unit having at least one or more hydroxyl groups represented by the following general formula (3A): and (III) a mixture of a polymer having a repeating unit containing at least one fluorine atom, represented by the following general formula (2A), and a terminal group being one of the groups represented by the following general formula (1B) or (1C), and a polymer having a repeating unit containing at least one hydroxyl group, represented by the following general formula (3A), and a terminal group being one of the groups represented by the following general formula (1B) or (1C), and (B) an organic solvent.

(In the formula, _W1 is a tetravalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, _W2 is a divalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, and at least one of _W1 and _W2 contains one or more fluorine atoms and at least one of _W1 and _W2 contains one or more hydroxyl groups.)

(In the formula, _W3 is a tetravalent organic group which may contain one or more types of fluorine atoms, _W4 is a divalent organic group which may contain one or more types of fluorine atoms, and at least one of _W3 and _W4 contains one or more fluorine atoms.)

(In the formula, _W5 is a tetravalent organic group which may contain one or more types of hydroxyl groups, _W6 is a divalent organic group which may contain one or more types of hydroxyl groups, and at least one of _W5 and _W6 contains one or more hydroxyl groups.)

(In the formula, R ₁ is any of the groups represented by the following formula (1D), and two or more types of R ₁ may be used in combination.)

[2]: A protective film-forming composition for alkaline hydrogen peroxide according to the above [1], characterized in that _W2 in the general formula (1A) contains at least one fluorine atom and one hydroxyl group.

[3]: A protective film-forming composition for alkaline hydrogen peroxide according to the above [1] or [2], characterized in that _W2 in the general formula (1A) is a group represented by the following general formula (1E).

[4]: A protective film-forming composition for alkaline hydrogen peroxide according to the above [1], [2], or [3], characterized in that W ₁ in the general formula (1A) is any one of groups represented by the following general formula (1F).

（式中、Ｗ_７は４価の有機基であり、Ｗ_８は２価の有機基である。）

（式中、Ｒ_２は炭素数１～１０の１価の有機基を表し、ｎ１は０または１の整数を表し、ｎ２およびｎ３は、１≦ｎ２≦６および０≦ｎ３≦６であり、かつ、１≦ｎ２＋ｎ３≦６の関係を満たす。） [5]: The protective film-forming composition for alkaline hydrogen peroxide according to the above [1], [2], [3], or [4], further comprising, as component (A'), a polymer (IV) having a repeating unit represented by the following general formula (4A) and an end group represented by the following general formula (2C).

(In the formula, _W7 is a tetravalent organic group, and _W8 is a divalent organic group.)

(In the formula, _R2 represents a monovalent organic group having 1 to 10 carbon atoms, n1 represents an integer of 0 or 1, and n2 and n3 satisfy the relationship of 1≦n2≦6 and 0≦n3≦6, and 1≦n2+n3≦6.)

[6]: A protective film-forming composition for alkaline hydrogen peroxide according to [1], [2], [3], [4], or [5], characterized in that the weight average molecular weight of the component (A) is 1,000 to 10,000.

[7]: A protective film-forming composition for alkaline hydrogen peroxide according to [1], [2], [3], [4], [5], or [6], characterized in that the (B) component is a mixture of one or more organic solvents having a boiling point of less than 180°C and one or more organic solvents having a boiling point of 180°C or higher.

[8]: A protective film-forming composition for alkaline hydrogen peroxide solution according to [1], [2], [3], [4], [5], [6], or [7], characterized in that the protective film-forming composition further contains one or more of (C) an acid generator, (D) a surfactant, (E) a crosslinking agent, and (F) a plasticizer.

[9]: A protective film-forming composition for alkaline hydrogen peroxide solution according to [1], [2], [3], [4], [5], [6], [7], or [8], characterized in that the protective film-forming composition provides a protective film that is resistant to ammonia-containing hydrogen peroxide solution.

[10]: A protective film-forming composition for alkaline hydrogen peroxide solution as described in [9] above, characterized in that when a silicon substrate on which the protective film is formed is immersed in 1.0 mass % hydrogen peroxide solution containing 0.5 mass % ammonia at 70°C for 5 minutes, no peeling of the protective film is observed.

[11]: A substrate for manufacturing a semiconductor device, characterized in that a protective film is formed on the substrate by curing the protective film-forming composition described in [1], [2], [3], [4], [5], [6], [7], [8], [9], or [10].

[12]: A method for forming a protective film used in the manufacturing process of a semiconductor device, comprising spin-coating a protective film-forming composition according to any one of [1], [2], [3], [4], [5], [6], [7], [8], [9], and [10] above onto a substrate to be processed, and subjecting the substrate to which the protective film-forming composition has been applied to a heat treatment in an inert gas atmosphere at a temperature of 50°C or higher and 600°C or lower for a period of 10 to 7200 seconds to obtain a cured film.

[13]: A method for forming a protective film used in the manufacturing process of a semiconductor device, comprising spin-coating a protective film-forming composition according to [1], [2], [3], [4], [5], [6], [7], [8], [9], or [10] on a substrate to be processed, heat-treating the substrate to which the protective film-forming composition has been applied in air at a temperature of 50°C or higher and 250°C or lower for 5 to 600 seconds to form a coating film, and subsequently heat-treating the substrate in an inert gas atmosphere at a temperature of 200°C or higher and 600°C or lower for 10 to 7200 seconds to obtain a cured film.

[14]: The method for forming a protective film according to [12] or [13] above, characterized in that the oxygen concentration in the inert gas is 1% or less.

[15]: The method for forming a protective film according to [12], [13], or [14] above, characterized in that the processed substrate has a structure or step having a height of 30 nm or more.

[16]: A method for forming a pattern on a workpiece substrate, comprising: (I-1) forming a protective film on a workpiece substrate using the protective film-forming composition described in [1], [2], [3], [4], [5], [6], [7], [8], [9], or [10]; (I-2) forming a silicon-containing resist intermediate film on the protective film using a silicon-containing resist intermediate film material; (I-3) forming a resist upper layer film on the silicon-containing resist intermediate film using a photoresist composition; (I-4) forming a circuit pattern on the resist upper layer film; (I-5) transferring a pattern to the silicon-containing resist intermediate film by etching using the resist upper layer film on which the pattern is formed as a mask; (I-6) transferring a pattern to the protective film by etching using the silicon-containing resist intermediate film on which the pattern is transferred as a mask; and (I-7) forming a pattern on the workpiece substrate using the protective film on which the pattern is transferred as a mask. The pattern forming method is characterized by comprising the steps of:

[17]: A method for forming a pattern on a workpiece substrate, comprising: (II-1) forming a protective film on a workpiece substrate using the protective film-forming composition described in [1], [2], [3], [4], [5], [6], [7], [8], [9], or [10]; (II-2) forming a silicon-containing resist intermediate film on the protective film using a silicon-containing resist intermediate film material; (II-3) forming an organic anti-reflective film on the silicon-containing resist intermediate film; and (II-4) forming a photoresist composition on the organic anti-reflective film. A pattern forming method characterized by comprising the steps of forming a resist top layer film to form a four-layer film structure, forming a circuit pattern on the resist top layer film, (II-5) using the resist top layer film on which the pattern has been formed as a mask to transfer the pattern to the organic anti-reflective film and the silicon-containing resist intermediate film by etching, (II-6) using the silicon-containing resist intermediate film on which the pattern has been transferred as a mask to transfer the pattern to the protective film by etching, and (II-7) using the protective film on which the pattern has been transferred as a mask to form a pattern on the processed substrate.

[18]: A method for forming a pattern on a substrate to be processed, comprising: (III-1) forming a protective film on the substrate to be processed using the protective film-forming composition described in [1], [2], [3], [4], [5], [6], [7], [8], [9], or [10]; (III-2) forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, a silicon oxide nitride film, a titanium oxide film, and a titanium nitride film on the protective film; and (III-3) forming a photoresist composition on the inorganic hard mask. A pattern forming method comprising the steps of: forming a resist top layer film; (III-4) forming a circuit pattern on the resist top layer film; (III-5) using the resist top layer film on which the pattern has been formed as a mask to transfer the pattern to the inorganic hard mask by etching; (III-6) using the inorganic hard mask on which the pattern has been transferred as a mask to transfer the pattern to the protective film by etching; and (III-7) forming a pattern on the processed substrate by using the protective film on which the pattern has been transferred as a mask.

[19]: A method for forming a pattern on a substrate to be processed, comprising: (IV-1) forming a protective film on a substrate to be processed using the protective film-forming composition described in [1], [2], [3], [4], [5], [6], [7], [8], [9], or [10]; (IV-2) forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, a silicon oxide nitride film, a titanium oxide film, and a titanium nitride film on the protective film; (IV-3) forming an organic anti-reflective film on the inorganic hard mask; (IV-4) forming a photoresist on the organic anti-reflective film. A pattern forming method comprising the steps of: forming a resist top layer film using a resist composition to form a four-layer film structure; forming a circuit pattern on the resist top layer film; (IV-5) using the resist top layer film on which the pattern has been formed as a mask to transfer the pattern to the organic antireflective film and the inorganic hard mask by etching; (IV-6) using the inorganic hard mask on which the pattern has been transferred as a mask to transfer the pattern to the protective film by etching; and (IV-7) using the protective film on which the pattern has been transferred as a mask to form a pattern on the substrate to be processed.

[20]: The pattern formation method according to [18] or [19] above, characterized in that the inorganic hard mask is formed by a CVD method or an ALD method.

[21]: The pattern forming method according to [16] or [17] above, further comprising, after step (I-6) or step (II-6), a step of removing the silicon-containing resist intermediate film to which the pattern has been transferred by wet etching using an alkaline hydrogen peroxide solution.

[22]: The pattern forming method according to [16], [17], [18], [19], or [20], characterized in that in the step (I-7), step (II-7), step (III-7), or step (IV-7), a step of transferring a pattern to the substrate to be processed by wet etching using an alkaline hydrogen peroxide solution, using the protective film to which the pattern has been transferred, as a mask.

[23]: The pattern forming method according to [16], [17], [18], [19], or [20], characterized in that in the step (I-7), step (II-7), step (III-7), or step (IV-7), a step of patterning the substrate to be processed by ion implantation using the protective film to which the pattern has been transferred as a mask is included.

[24]: The pattern forming method according to [23] above, further comprising a step of removing the silicon-containing resist intermediate film to which the pattern has been transferred by wet etching using an alkaline hydrogen peroxide solution, after the step of patterning the substrate to be processed by the ion implantation.

[25]: The pattern forming method according to [16], [17], [18], [19], [20], [21], [22], [23], or [24], characterized in that in forming the circuit pattern, the circuit pattern is formed by lithography using light having a wavelength of 10 nm or more and 300 nm or less, direct drawing with an electron beam, nanoimprinting, or a combination thereof.

[26]: The pattern forming method according to [16], [17], [18], [19], [20], [21], [22], [23], [24], or [25], characterized in that in forming the circuit pattern, the circuit pattern is developed using an alkaline developer or an organic solvent.

[27]: The pattern forming method according to [16], [17], [18], [19], [20], [21], [22], [23], [24], [25], or [26], characterized in that the processed substrate is a semiconductor device substrate, or a semiconductor device substrate on which a metal film, a metal carbide film, a metal oxide film, a metal nitride film, a metal oxide carbide film, or a metal oxide nitride film is formed.

[28]: The pattern formation method described in [27] above, characterized in that the substrate to be processed contains silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, silver, gold, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, cobalt, manganese, molybdenum, or an alloy thereof.

The present invention is not limited to the above-described embodiments. The above-described embodiments are merely examples, and anything that has substantially the same configuration as the technical idea described in the claims of the present invention and provides similar effects is included within the technical scope of the present invention.

1... substrate, 2... layer to be processed, 2a... pattern (pattern to be formed on the layer to be processed),
3... protective film, 3'... protective film-forming composition, 3a... protective film pattern,
4...silicon-containing resist intermediate film, 4a...silicon-containing resist intermediate film pattern,
5: resist upper layer film, 5a: resist upper layer film pattern, 6: exposed portion,
7... base substrate having a dense hole pattern; 8... protective film;
9... Underlying substrate having a giant isolated trench pattern; 10... Protective film;
delta10 . . . Step between the trench portion and the non-trench portion of the protective film 10.

Claims (28)

(A) a polymer having a fluorine atom and a hydroxyl group represented by any one of the following (I) and (II), or a mixture of a polymer having a fluorine atom and a polymer having a hydroxyl group represented by the following (III):
(I) A polymer having a repeating unit containing at least one fluorine atom and one hydroxyl group, represented by the following general formula (1A), and having a terminal group represented by any one of the following general formulas (1B) and (1C):
(II) A polymer having a repeating unit containing at least one fluorine atom, represented by the following general formula (2A), and a repeating unit containing at least one hydroxyl group, represented by the following general formula (3A), in which a terminal group is a group represented by any one of the following general formulas (1B) and (1C):
(III) A protective film-forming composition for alkaline hydrogen peroxide, characterized in that it contains a mixture of a polymer having a repeating unit containing at least one fluorine atom, represented by the following general formula (2A), and an end group being a group represented by any one of the following general formulas (1B) and (1C), and a polymer having a repeating unit containing at least one hydroxyl group, represented by the following general formula (3A), and an end group being a group represented by any one of the following general formulas (1B) and (1C), and (B) an organic solvent.

(In the formula, _W1 is a tetravalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, _W2 is a divalent organic group which may contain one or more types of fluorine atoms or hydroxyl groups, and at least one of _W1 and _W2 contains one or more fluorine atoms and at least one of _W1 and _W2 contains one or more hydroxyl groups.)

(In the formula, _W3 is a tetravalent organic group which may contain one or more types of fluorine atoms, _W4 is a divalent organic group which may contain one or more types of fluorine atoms, and at least one of _W3 and _W4 contains one or more fluorine atoms.)

(In the formula, _W5 is a tetravalent organic group which may contain one or more types of hydroxyl groups, _W6 is a divalent organic group which may contain one or more types of hydroxyl groups, and at least one of _W5 and _W6 contains one or more hydroxyl groups.)

(In the formula, R ₁ is any of the groups represented by the following formula (1D), and two or more types of R ₁ may be used in combination.)

2. The composition for forming a protective film against alkaline hydrogen peroxide according to claim 1, wherein _W2 in the general formula (1A) contains at least one fluorine atom and one hydroxyl group. 3. The composition for forming a protective film against alkaline hydrogen peroxide according to claim 2, wherein _W2 in the general formula (1A) is a group represented by the following general formula (1E):

A protective film-forming composition for alkaline hydrogen peroxide solution according to any one of claims 1 to 3, characterized in that W ₁ in the general formula (1A) is any one of the groups represented by the following general formula (1F):

A protective film-forming composition for alkaline hydrogen peroxide solution according to any one of claims 1 to 3, characterized in that it further contains, as component (A'), a polymer (IV) having a repeating unit represented by the following general formula (4A) and having an end group represented by the following general formula (2C).

(In the formula, _W7 is a tetravalent organic group, and _W8 is a divalent organic group.)

(In the formula, _R2 represents a monovalent organic group having 1 to 10 carbon atoms, n1 represents an integer of 0 or 1, and n2 and n3 satisfy the relationship of 1≦n2≦6 and 0≦n3≦6, and 1≦n2+n3≦6.) The protective film-forming composition for alkaline hydrogen peroxide solution according to any one of claims 1 to 3, characterized in that the weight average molecular weight of component (A) is 1,000 to 10,000. The protective film-forming composition for alkaline hydrogen peroxide solution according to any one of claims 1 to 3, characterized in that the (B) component is a mixture of one or more organic solvents having a boiling point of less than 180°C and one or more organic solvents having a boiling point of 180°C or higher. The protective film-forming composition for alkaline hydrogen peroxide solution according to any one of claims 1 to 3, characterized in that the protective film-forming composition further contains one or more of (C) an acid generator, (D) a surfactant, (E) a crosslinking agent, and (F) a plasticizer. The protective film-forming composition for alkaline hydrogen peroxide solution according to any one of claims 1 to 3, characterized in that the protective film-forming composition provides a protective film that is resistant to ammonia-containing hydrogen peroxide solution. The protective film-forming composition for alkaline hydrogen peroxide according to claim 9, characterized in that when a silicon substrate on which the protective film is formed is immersed in 1.0 mass % hydrogen peroxide containing 0.5 mass % ammonia at 70°C for 5 minutes, no peeling of the protective film is observed. A substrate for manufacturing a semiconductor device, characterized in that a protective film formed on the substrate is formed by curing the protective film-forming composition according to any one of claims 1 to 3. A method for forming a protective film used in the manufacturing process of a semiconductor device, comprising spin-coating the protective film-forming composition according to claim 1 onto a substrate to be processed, and subjecting the substrate to which the protective film-forming composition has been applied to a heat treatment in an inert gas atmosphere at a temperature of 50°C or higher and 600°C or lower for a period of 10 to 7200 seconds to obtain a cured film. A method for forming a protective film used in the manufacturing process of a semiconductor device, comprising spin-coating the protective film-forming composition according to claim 1 onto a substrate to be processed, heat-treating the substrate to which the protective film-forming composition has been applied in air at a temperature of 50°C or higher and 250°C or lower for 5 to 600 seconds to form a coating film, and subsequently heat-treating the substrate in an inert gas atmosphere at a temperature of 200°C or higher and 600°C or lower for 10 to 7200 seconds to obtain a cured film. The method for forming a protective film according to claim 12 or 13, characterized in that the oxygen concentration in the inert gas is 1% or less. The method for forming a protective film according to claim 12 or 13, characterized in that the substrate to be processed has a structure or step having a height of 30 nm or more. A method for forming a pattern on a workpiece substrate, comprising the steps of:
(I-1) A step of forming a protective film on a substrate to be processed using the protective film-forming composition according to claim 1;
(I-2) forming a silicon-containing resist intermediate film on the protective film using a silicon-containing resist intermediate film material;
(I-3) forming a resist upper layer film on the silicon-containing resist intermediate film using a photoresist composition;
(I-4) a step of forming a circuit pattern on the resist upper layer film;
(I-5) a step of transferring a pattern to the silicon-containing resist intermediate film by etching using the resist upper layer film on which the pattern has been formed as a mask;
(I-6) a step of transferring a pattern to the protective film by etching using the silicon-containing resist intermediate film to which the pattern has been transferred as a mask; and (I-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
A pattern forming method comprising the steps of: A method for forming a pattern on a workpiece substrate, comprising the steps of:
(II-1) A step of forming a protective film on a substrate to be processed using the protective film-forming composition according to claim 1;
(II-2) forming a silicon-containing resist intermediate film on the protective film using a silicon-containing resist intermediate film material;
(II-3) forming an organic anti-reflective coating on the silicon-containing resist intermediate film;
(II-4) forming a resist upper layer film on the organic antireflective film using a photoresist composition to form a four-layer film structure, and forming a circuit pattern on the resist upper layer film;
(II-5) a step of transferring a pattern to the organic antireflective film and the silicon-containing resist intermediate film by etching using the resist upper layer film on which the pattern has been formed as a mask;
(II-6) a step of transferring a pattern to the protective film by etching using the silicon-containing resist intermediate film to which the pattern has been transferred as a mask; and (II-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
A pattern forming method comprising the steps of: A method for forming a pattern on a workpiece substrate, comprising the steps of:
(III-1) A step of forming a protective film on a substrate to be processed using the protective film-forming composition according to claim 1;
(III-2) forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a titanium oxide film, and a titanium nitride film on the protective film;
(III-3) forming a resist top layer film on the inorganic hard mask using a photoresist composition;
(III-4) forming a circuit pattern on the resist upper layer film;
(III-5) a step of transferring a pattern to the inorganic hard mask by etching using the resist top layer film on which the pattern has been formed as a mask;
(III-6) a step of transferring a pattern to the protective film by etching using the inorganic hard mask to which the pattern has been transferred as a mask; and (III-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
A pattern forming method comprising the steps of: A method for forming a pattern on a workpiece substrate, comprising the steps of:
(IV-1) A step of forming a protective film on a substrate to be processed using the protective film-forming composition according to claim 1;
(IV-2) forming an inorganic hard mask selected from a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a titanium oxide film, and a titanium nitride film on the protective film;
(IV-3) forming an organic anti-reflective coating on the inorganic hard mask;
(IV-4) forming a resist upper layer film on the organic antireflective film using a photoresist composition to form a four-layer film structure, and forming a circuit pattern on the resist upper layer film;
(IV-5) a step of transferring a pattern to the organic anti-reflective film and the inorganic hard mask by etching using the resist top layer film on which the pattern has been formed as a mask;
(IV-6) a step of transferring a pattern to the protective film by etching using the inorganic hard mask to which the pattern has been transferred as a mask; and (IV-7) a step of forming a pattern on the substrate to be processed using the protective film to which the pattern has been transferred as a mask.
A pattern forming method comprising the steps of: The pattern formation method according to claim 18 or 19, characterized in that the inorganic hard mask is formed by a CVD method or an ALD method. The pattern forming method according to claim 16 or 17, further comprising, after step (I-6) or step (II-6), a step of removing the silicon-containing resist intermediate film to which the pattern has been transferred by wet etching using an alkaline hydrogen peroxide solution. The pattern forming method according to any one of claims 16 to 19, characterized in that in the step (I-7), step (II-7), step (III-7), or step (IV-7), a step of transferring the pattern to the substrate to be processed by wet etching using alkaline hydrogen peroxide solution, using the protective film to which the pattern has been transferred, as a mask, is included. The pattern forming method according to any one of claims 16 to 19, characterized in that in step (I-7), step (II-7), step (III-7), or step (IV-7), a step of patterning the substrate to be processed by ion implantation using the protective film to which the pattern has been transferred as a mask is included. The pattern forming method according to claim 23, further comprising a step of removing the silicon-containing resist intermediate film to which the pattern has been transferred by wet etching using an alkaline hydrogen peroxide solution, after the step of patterning the substrate to be processed by the ion implantation. The pattern forming method according to any one of claims 16 to 19, characterized in that the circuit pattern is formed by lithography using light having a wavelength of 10 nm or more and 300 nm or less, direct drawing with an electron beam, nanoimprinting, or a combination thereof. The pattern forming method according to any one of claims 16 to 19, characterized in that in forming the circuit pattern, the circuit pattern is developed using an alkaline developer or an organic solvent. The pattern forming method according to any one of claims 16 to 19, characterized in that the substrate to be processed is a semiconductor device substrate, or a semiconductor device substrate having a metal film, a metal carbide film, a metal oxide film, a metal nitride film, a metal oxide carbide film, or a metal oxide nitride film formed thereon. The pattern formation method according to claim 27, characterized in that the substrate to be processed contains silicon, titanium, tungsten, hafnium, zirconium, chromium, germanium, copper, silver, gold, aluminum, indium, gallium, arsenic, palladium, iron, tantalum, iridium, cobalt, manganese, molybdenum, or an alloy thereof.

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