JPH0332778B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a resist material suitable for forming fine patterns used in the phosphor-free process in the production of high-density integrated circuits such as LSIs and VLSIs, or photomasks used in the production thereof, and more specifically, The present invention relates to a new negative resist material which has high sensitivity and high resolution, and which provides a resist film with excellent etching resistance after curing. As is well known, in recent years there has been an increasing demand for higher performance and higher integration of semiconductor integrated circuits and the like.
For this reason, lithography technology has replaced conventional photolithography using ultraviolet rays with ionizing radiation, which has a shorter wavelength and higher energy.
That is, efforts are being made to establish ultrafine pattern processing techniques using lithography using electron beams, soft X-rays, ion beams, and the like. On the other hand, in order to enable ultra-fine lithography technology by changing the radiation source, the resist material used must also have characteristics that correspond to such changes. Generally, resist materials used in ultrafine lithography using high-energy ionizing radiation are required to have the following properties. (b) High sensitivity to ionizing radiation. (b) Must have high resolution. (c) It is possible to form a homogeneous thin film. (d) Excellent dry etching resistance since dry etching is applied, which is essential for high-density, fine patterning. (e) Excellent developability. Conventionally, many types of ionizing radiation-sensitive resists have been developed to be used for the above-mentioned purposes. It is classified as a negative type, in which a crosslinking reaction occurs when irradiated with radiation, and the irradiated area becomes insolubilized. Among these, positive types generally have the drawbacks of a narrow range of developer suitability and weak dry etching resistance. On the other hand, many negative resists are superior to positive resists in these respects. Typical negative resists that have been developed since then include polyglycidyl methacrylate systems, glycidyl methacrylate-ethyl acrylate copolymer systems, and unsaturated carboxylic acid-methacrylate copolymer systems. However, these negative resists also have some practical drawbacks and are not necessarily satisfactory. For example, although a glycidyl methacrylate resist has high sensitivity, a large amount of scum occurs at the edges of the drawn pattern, resulting in a decrease in resolution, and in practice only a resolution of about 2.0 μm can be obtained. In addition, all of the above resists have low dry etching resistance (the film thickness decreases significantly during dry etching), and have the disadvantage that it is difficult to apply the dry etching process that is essential for creating high-density, fine patterns. ing. In view of the above-mentioned circumstances, an object of the present invention is to provide a new type of ionizing radiation-sensitive negative resist that is highly sensitive, has excellent dry etching resistance, and is capable of achieving high resolution. The present inventors have already developed one negative-tone resist sensitive to ionizing radiation for the above-mentioned purpose.
(Patent Application No. 161431). That is, this resist has the general formula (wherein R is at least one divalent organic group) consisting of a polyamide polymer or a copolymer with other monomers or a mixture with other polymers that are compatible with the same. It is characterized by: The resist of the present invention corresponds to a type of the above-mentioned resist, and is based on the knowledge that when R in the above formula is an organic group having a double bond in the side chain, a significant increase in sensitivity can be obtained. There is. That is,
The ionizing radiation-sensitive negative resist of the present invention is a polyamide polymer having a repeating unit represented by the above general formula (wherein R is a divalent organic group having a double bond in the side chain) or a polyamide polymer having a repeating unit represented by the above general formula (wherein R is a divalent organic group having a double bond in the side chain), or It is characterized by being composed of a polyamide copolymer having repeating units derived from other monomers or a mixture of this and other compatible polymers. The present invention will be explained in more detail below. In the following descriptions, "%" and "parts" indicate the composition.
are based on weight unless otherwise specified. The group R having a double bond in the side chain of the polyamide polymer represented by the above formula is, for example, one derived from an unsaturated dicarboxylic acid or a chloride thereof, and more specifically, for example,

【formula】

【formula】

【formula】

Preferred examples include unsaturated hydrocarbon groups having a double bond in the side chain, such as the formula: (where m is an integer of 1 to 20, and n is 0 or an integer of 1 to 20). When m and n exceed 20, the domain structure formed by the hydrophobic bonds between the groups R of each molecule becomes too large, and the reactivity of unsaturated dicarboxylic acids, etc. becomes poor, and the solubility of a suitable solvent for the resist becomes too large. Therefore, it is appropriate to limit the upper limits of m and n to 20 or less. The group R is not limited to one of the groups exemplified above, but can be two or more. That is, the polyamide polymer can apparently take on the structure of a copolymer. The above polyamide polymer can be produced by known methods. For example, the formula obtained by reduction of α-amino-ε-caprolactam as described in J. Polym. Sci 16 3035−3038 (1978) 3-amino-perhydroazepine (APA) with the formula ClOR ¹ OCl (R ¹ is -CO-R-CO-
) and a divalent acid chloride represented by
It can be obtained by an interfacial reaction or by condensation polymerization in a solution in the presence of an acid acceptor such as a base. In addition, for polyamide copolymers having other repeating units, a part of the divalent acid chloride having a double bond in the side chain is replaced with a part of the divalent acid chloride having no double bond in the side chain. Replace with or in addition to
It can be obtained by replacing part of APA with diamine and performing cocondensation polymerization. The molecular weight is 10,000 to 1,000,000 due to the above reaction.
Polyamide polymers (including copolymers) are obtained. The resist of the present invention is preferably made of the above-mentioned polyamide polymer alone, but if necessary, it can be used as a mixture with other polymers having good compatibility and solubility. Examples of such polymers include those made by reacting aliphatic polyamides such as 6-nylon and 6,6-nylon with epoxy compounds and making them soluble by grafting. When used as a mixture, the polyamide polymer having a perhydroazepine ring represented by the above formula is preferably used in an amount of 50% or more of the total amount with other polymers. Next, a method of performing lithography using the resist of the present invention will be described. First, the resist of the present invention is dissolved in a lower alcohol such as methanol or ethanol; chloroform, methyl cellosolve, etc. to prepare a resist solution of about 5 to 15% having a viscosity suitable for coating. Next, this resist solution is uniformly applied onto the semiconductor substrate or mask substrate to be processed by a conventional method such as a spinner coating method, and a prebaking process is performed to form a resist film with a thickness of about 0.1 to 2 μm. Prebake conditions depend on the type of solvent used, but in the case of lower alcohols, the temperature
A temperature of 70 to 90°C and a time of 20 to 40 minutes is suitable. Next, a desired part of the resist film is irradiated with ionizing radiation such as an electron beam or soft X-ray to draw a pattern according to a conventional method, and then treated with a developer to selectively remove unirradiated parts of the resist film. A resist pattern is formed by dissolving and removing the resist. As a developer,
Lower alcohols such as methanol and ethanol, or mixed solvents of these lower alcohols and benzene, chloroform, etc. are preferably used. On the substrate with the resist pattern after development,
After further performing post-baking treatment and scum removal treatment as necessary, etching is performed to form an etching pattern on the exposed portion of the substrate. Post-baking treatment is for example temperature 120-140℃, time 20
The scum removal process is performed for 1 to 2 minutes using oxygen plasma at a pressure of 0.9 to 1 Torr and an output of 100 W for 1 to 2 minutes.
I can do it. Although both wet etching and dry etching can be applied to etching, dry etching is more suitable for forming fine patterns for processing highly integrated semiconductor substrates, mask substrates, etc. As mentioned above, the crosslinked resist film of the present invention has excellent dry etching resistance, and is therefore particularly preferred in this respect. For example, a patterned film of the resist of the present invention is formed on a chrome mask substrate,
When dry-etching exposed chromium areas using a chlorine-based gas such as carbon tetrachloride, the film removal rate of the resist film is equivalent to that of a photoresist made of novolac-based phenolic resin, which has the best dry etching resistance. can get. In particular, polyamide copolymers in which a portion of the groups R are substituted with groups derived from terephthalic acid exhibit excellent dry etching properties. Further, the resist film of the present invention generally has excellent physical or mechanical properties. After etching, if the remaining resist pattern is removed by peeling etc., it can be removed as part of the lithography process.
The cycle ends. As described above, the present invention has particularly high sensitivity, high resolution, and excellent dry etching resistance, so it is suitable for manufacturing highly integrated semiconductor circuits or photomasks that require dry etching for fine patterning. A suitable and highly practical ionizing radiation sensitive negative resist is provided. EXAMPLES Hereinafter, the present invention will be explained in more detail with reference to Examples. Example 1 3-amino-berhydroazepine (APA)
13.6 g (0.12 mol) was dissolved in 600 cm ³ of an aqueous solution containing 0.24 mol sodium hydride, and this was added to a reactor together with 21.7 g (0.12 mol) of 2-methyleneglutaric acid chloride dissolved in 600 cm ³ of benzene. Get in,
Interfacial polymerization was carried out for 5 minutes by stirring at high speed while cooling the outside with ice. The generated precipitate is collected by filtration, dissolved in methanol, reprecipitated with a large amount of water,
By over-recovering, a polymer (APA-MGAC) represented by the following formula was obtained. ηsp/C at 30°C of a 0.1 g/10 c.c. concentration acid solution of the above polymer (where ηsp is the specific viscosity, C is the concentration [g/
cc]) is 44 cm ³ /g, and the molecular weight is estimated to be about 10,000. Dissolve the above polymer in methyl cellosorg,
A resist solution with a concentration of 6% was obtained by passing through a 0.2 μm filter. This resist solution was applied onto a chrome mask substrate by a spinner coating method and prebaked at 90° C. for 30 minutes to obtain a uniform resist film with a thickness of 6000 Å. Next, the beam diameter is
An electron beam of 0.25 μm and an energy of 10 KeV was irradiated.
After irradiating with varying exposure doses, immersion in methanol for 60 seconds to develop, and rinsing by immersing in a 1:1 mixture of water and isopropyl alcohol for 30 seconds, the remaining film rate is determined as the exposure dose. A sensitivity curve was obtained by plotting the exposure amount at which the residual film rate after development was 50%. The sensitivity of this resist is
It was 3.0×10 ^-6 coulombs/cm ² . Furthermore, using this resist, a resist film with a thickness of 6000 Å was obtained on a chromium mask substrate in the same manner as above, and an electron beam with a beam diameter of 0.5 μm and an acceleration voltage of 10 kV was used to deposit 3.0 × 10 ^-6 Coulombs/cm ³ on this. The pattern was drawn by irradiating with a dose of . Furthermore, this resist film was developed by treating it with methanol for 1 minute, and was washed with a 1:1 mixed solution of water and isopropyl alcohol for 30 seconds to form a resist pattern. Next, the substrate with the obtained resist pattern was post-baked at 140°C for 30 minutes, and then the pressure
Scum removal treatment was performed for 1 minute using oxygen plasma at 1 Torr and 100 W output. The exposed portion of the chromium film on this substrate was etched by reactive sputter etching using a 7:2 mixed gas of CCl ₄ and O ₂ at a pressure of 3×10 ⁻¹ Torr and an output of 300 W for 5 minutes. The film flaking rate of the resist pattern is 260 Å/min.
It showed sufficient dry etching resistance. After etching, the substrate was immersed in a stripping solution consisting of a sulfuric acid-hydrogen peroxide mixture at 70°C for 5 minutes, and the resist pattern was stripped off to obtain a photomask with a chrome pattern consisting of lines and spaces each 1 μm in size. . Example 2 The procedure of Example 1, except that in place of 21.7 g (0.12 mol) of 2-methyleneglutaric acid chloride, a mixture of 11 g (0.06 mol) of adipic acid chloride and 10.0 g (0.06 mol) of itaconic acid chloride is used. By repeating the process, a polymer corresponding to the formula below (APA-
IC-AC) was obtained with a yield of about 60%. (However, m and n indicate only the ratio of the number of units contained in the copolymer (that is, the composition ratio), and it is actually a random copolymer.) The obtained copolymer of concentrated sulfuric acid 0.1g/ ^10cm3 solution
The solution viscosity at 30° C. was 50 cm ³ /g, and the estimated molecular weight was about 12,000. The composition ratio m/n of the obtained copolymer was 5/5. The obtained polymer was dissolved in ethyl cellosolve acetate and passed through a 0.2 μm filter to obtain a resist solution with a concentration of 8%. Apply this resist solution to 3000 ml on top of the silicon oxide film.
It is coated by spin coating on a silicon wafer made by growing polysilicon with a thickness of 90 Å.
C. for 30 minutes to obtain a uniform resist film with a thickness of 5000 Å. Next, apply the beam diameter to this resist film.
0.25μm, energy 10KeV electron beam irradiation dose 5.0
A pattern was drawn by irradiating it at ×10 ⁻⁶ coulombs/cm ² . After drawing, it was developed by processing with methanol for 1 minute, and was washed with isopropyl alcohol for 30 seconds to form a resist pattern. Next, the silicon wafer on which the resist pattern was formed was post-baked at 140°C for 30 minutes, and then the scum was removed using plasma in the same manner as in Example 1, and then a gas containing 2% O ₂ mixed with CF ₄ was used. Dry etching was carried out in the same manner as in Example 1 under the conditions of 2 Torr and output of 300 W. After dry etching, the resist was removed by treating the substrate with oxygen plasma at 5 Torr and 300 W to obtain a polysilicon pattern in which lines with a width of 0.5 μm and gaps with a width of 0.5 μm were repeated in sequence. Example 3 21.7 g (0.12 mol) of 2-methyleneglutaric acid chloride was replaced with 12.2 g (0.06 mol) of terephthalic acid chloride.
mole) and 2-methyleneglutaric acid chloride 10.9g
By repeating the operation of Example 1 except for using a mixture with (0.06 mol), a polymer (APA-MGAC-TC) corresponding to the following formula was obtained with a yield of about 70%. (However ^, m and n have the same meanings as described in Example 2.)
The solution viscosity at °C was 70 cm ³ /g and the estimated molecular weight was about 15,000. The composition ratio m/n of the obtained copolymer was 3/7. An 8% methyl cellosolve solution of this copolymer was spin-coated onto a chrome substrate at a rotation speed of 2500 revolutions/min, and prebaked at 120°C for 30 minutes to obtain a uniform coating film with a thickness of 6000 Å. .
Next, various patterns were drawn on this coating using an electron beam with an energy of 10 KeV by changing the irradiation amount, and after drawing, the film was immersed in methanol for 60 seconds to be developed.
A resist pattern was obtained by rinsing by immersing in isopropyl alcohol for 30 seconds. In this example, the electron beam irradiation dose to achieve a residual film thickness of 50% is 4.5
It was ×10 ^-6 coulombs/cm ² . Next, using the above resist solution, a uniform coating film with a thickness of 4000 Å was created on the chromium substrate in the same manner as above, and then prebaked at 120°C for 30 minutes.
Next, drawing was performed using an electron beam with an energy of 10 KeV and a beam diameter of 0.5 μm, developed and rinsed in the same manner as above, and then post-baked at 140° C. for 30 minutes. The chromium substrate on which the resist pattern was formed in this way was exposed to CCl ₄ :O ₂ =3:
Dry etching was performed using gas No. 1 at 0.3 Torr and 300 W for 8 minutes to obtain a Cr pattern with a width of 1 μm. The resist of this example had a film reduction amount of 200 Å/min due to dry etching and had high plasma resistance. Other Examples and Comparative Examples Instead of methylene glutaric acid chloride as a starting material, approximately the same mole of trans-2
-Polymer obtained using butene-1,4-dicarboxylic acid chloride (APA-HC), trans-2-
A polymer obtained using a mixture of butene-1,4-dicarboxylic acid chloride and terephthalic acid chloride (APA-HC-TC), a polymer obtained using a mixture of methylene glutaric acid chloride and sebacic acid chloride (APA-MGAC) -SC), a polymer obtained using a mixture of methylene glutaric acid chloride and adipic acid chloride (APA-MGAC-AC)
The properties of these polymers are also shown in Table 1 along with the results of the measurements of the sensitivity (50% residual film rate) and γ value (50% residual film rate) of the polymers of Examples 1 to 3.

[Table] The methylene glutaric acid used in the above Examples and Comparative Examples was obtained by the following method. i.e. 60g methylene glutaric acid (MGA)
(0.42mol) and thionyl chloride 250g (2.1mol) in 500 g
cm ³ into an eggplant-shaped flask and refluxed at 60°C for 15 hours. After the reaction, unreacted thionyl chloride was removed, and then vacuum distillation was performed twice. A small amount of cuprous chloride, which is a radical inhibitor, was added during the first distillation. Methylene glutaric acid was obtained with a yield of 45% and its boiling point at 2 mmHg was 72-73°C.

Claims (1)

[Claims] 1. General formula (In the formula, R is a divalent organic group having a double bond in the side chain.) A polyamide polymer having a repeating unit represented by (wherein R is a divalent organic group having a double bond in the side chain) or a polyamide copolymer having a repeating unit derived from another monomer in addition to the above repeating unit. An ionizing radiation-sensitive negative resist characterized by being composed of a polymer or a mixture thereof with other polymers that are compatible with the resist.