JP4840045B2 - Method for forming polyimide pattern, article, and suspension for hard disk - Google Patents

Description

  The present invention relates to a method for forming a polyimide pattern that does not use an organic solvent in a patterning step, and a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member having a polyimide pattern manufactured by using the method. It relates to any article, in particular a suspension for hard disk drives.

With the rapid development of semiconductor technology, semiconductor packages have become smaller, more pins, fine pitches, and miniaturized electronic components, and have entered the era of so-called high-density packaging. Along with this, printed wiring boards are also being made thinner and thinner from single-sided wiring to double-sided wiring (Non-Patent Document 1).
In addition, the pattern forming method for forming such wiring / circuits is to form a wiring by etching a metal on a substrate having a layer structure of metal-insulating layer-metal with an acidic solution such as ferric chloride. In order to establish electrical continuity between layers, the insulating layer is removed in a desired shape in a dry state such as a laser or a wet state such as hydrazine (Patent Document 1). A method of forming an insulating layer in a desired shape using polyimide (Patent Document 2) and then forming a wiring by plating in the gap (Preliminary Collection of the 7th Research Discussion Meeting of the Japan Institute of Electronics Packaging) has been performed. .
Electrical products, especially personal computers, are affected by lower prices, and the price of components and parts that use these products is drastically decreasing, and how to make products at low cost is a very big issue.

Currently, the production volume of personal computers is growing rapidly due to the spread of the Internet, etc. The hard disk incorporated in it is also a component called a suspension that supports the head that reads magnetism as the production volume also increases. However, the main product is changing from a wired suspension that connects copper (distribution) wires to stainless steel springs to what is called a wireless suspension in which copper wiring is formed directly on stainless steel springs to accommodate downsizing. is there.
Such a wireless suspension has a structure in which polyimide is applied as an insulating layer on a stainless steel base material, and copper wiring is further formed thereon. In recent years, since higher reliability has been demanded, a wiring protective layer is often provided with polyimide or the like so as to cover the copper wiring.

Since this is a member to which fine vibration is applied because the disk is scanned at a high speed, the adhesion strength between the layers is very important, and strict specifications are required. In addition, since the hard disk is a device for recording information, high reliability is required for reading and writing data, and the specifications are strict against the adhesion strength of wiring, dust such as dust generated from the suspension, and outgas.
In general, a suspension uses a stainless steel layer, a low-expansion insulating layer having the same thermal expansion coefficient as that of the conductor layer, and a wiring protective layer in order to prevent the substrate from warping. Furthermore, management of the hygroscopic expansion coefficient of the insulating layer and the wiring protective layer is also required in order to prevent warping due to environmental changes such as humidity.

The method of forming the polyimide pattern of the insulating layer formed on the stainless steel includes a method using a photosensitive polyimide (Patent Document 3) and a method of etching a polyimide layer formed on the entire surface of the stainless steel with plasma or a chemical solution (Patent Document 4). ) Are disclosed. The above-described method can also be used for a polyimide pattern used as a wiring protective layer.
The method using photosensitive polyimide has the advantage that the process is short and simple, but the polyimide pattern to be formed contains decomposition residues of the photosensitive agent, so that there is a problem that they are released as gas during heating. is there. Furthermore, there is a problem that it is difficult to achieve both of imparting photosensitivity and desired physical properties.
The method of etching a polyimide layer formed on the entire surface of stainless steel with plasma and forming a pattern has the advantage of being able to cope with a relatively wide range of compositions of polyimide, but the etching rate is very low and etching takes time. Therefore, there is a problem that productivity is not good.
The method of etching with a chemical solution has a high etching rate and very high productivity, but has a problem that the molecular structure of the polyimide that can be etched is limited and the range of selection of the composition is small.

  Furthermore, a hole for conducting conduction between layers of a multilayer board is usually drilled with a laser, and it is die-cut into a desired shape with a mold, and an electron using polyimide such as a flexible printed board or multilayer board as an insulating layer Components can also be manufactured using similar polyimide patterning techniques.

JP-A-6-164084 JP-A-4-168441 JP-A-10-12983 JP 2002-240194 A JP-A-6-275511 Iwata, Haraen, “Electronic Materials”, 1996, 35 (10), p. 53.

As a polyimide patterning method that has been used for a long time, it is based on the fact that the polyimide precursor polyamic acid is soluble in a basic aqueous solution. After forming a conductive material (resist) film, exposing to a desired pattern and developing with a basic aqueous solution, the positive photoresist and the polyamic acid film are simultaneously patterned, and then the positive photoresist is converted into acetic acid. A technique is disclosed in which a polyimide pattern is obtained by peeling with an organic solvent such as n-butyl to obtain a polyamic acid pattern and then imidizing (Patent Document 5).
Since this method can obtain a pattern formed only of polyimide that does not contain a photosensitizer, the polyimide pattern obtained by this method is highly reliable and does not generate outgas.

However, there has been a problem that an organic solvent is required for stripping the positive photoresist. In general, the basic aqueous solution or the like cannot be used in the peeling step of peeling the positive photoresist because the polyamic acid itself is soluble in the basic aqueous solution. Therefore, there has been a situation that the positive photoresist must be peeled off using an organic solvent that does not dissolve the polyamic acid but dissolves the unexposed positive photoresist.
Such a stripping process using a non-polar water-insoluble organic solvent is not only a heavy burden on the natural environment, but also a major obstacle to practical use due to safety measures for workers and waste liquid treatment costs. .
In Patent Literature 5, a positive photoresist is subjected to pattern exposure, developed simultaneously with a polyamic acid coating film, and then heated by a hot plate or oven at 50 ° C. to 90 ° C. for about 30 seconds to 20 minutes. However, in order to improve the releasability of the positive photoresist, the residual solvent in the positive photoresist film is made uniform.

  The present invention has been accomplished in view of the above circumstances, and a method for forming a polyimide pattern that does not contain a photosensitizer without using a water-insoluble organic solvent in a patterning step, and a method for producing the same. It is an object of the present invention to provide an electronic component having a polyimide pattern formed, particularly a suspension for a hard disk drive.

In order to solve the above problems, the present invention provides the following steps (A) to (G):
(A) forming a polyimide precursor layer on the substrate;
(B) forming a positive photoresist layer on the polyimide precursor layer;
(C) a pattern exposure step for selectively exposing the positive photoresist layer;
(D) a development step of selectively removing and patterning the underlying polyimide precursor layer after or simultaneously with the development of the positive photoresist layer;
(E) an overall exposure process for exposing the entire surface of the patterned positive photoresist layer;
(F) a step of reducing solubility in a basic aqueous solution or a water-soluble basic substance by at least partially imidizing the patterned polyimide precursor layer;
(G) A method of forming a polyimide pattern comprising: a peeling step of peeling the patterned positive photoresist layer with a basic aqueous solution or a water-soluble basic substance.

  According to the present invention, (E) an overall exposure step of exposing the entire surface of the patterned positive photoresist layer, and (F) at least partially imidizing the patterned polyimide precursor layer. The step of reducing the solubility in a basic aqueous solution or a water-soluble basic substance is used to peel the patterned positive photoresist layer with a basic aqueous solution or a water-soluble basic substance. A polyimide pattern that does not contain a photosensitizer can be formed without using a water-insoluble organic solvent in the patterning step.

  In the method for forming a polyimide pattern according to the present invention, it is preferable that the method further comprises (H) a step of polyimidizing the patterned polyimide precursor layer. In the step (F), the polyimide precursor can be converted into a polyimide, but when the polyimide precursor is completely converted into a polyimide in the step (F), a photoresist layer as an upper layer of the polyimide precursor is formed. Since it is often deteriorated by a relatively strong stimulus for making it into a polyimide and difficult to peel off, it is usually preferable to have a step of completely polyimideizing the positive photoresist after peeling.

  In the method for forming a polyimide pattern according to the present invention, it is preferable that a compound that promotes imidization is contained in the polyimide precursor layer in the step (A). When the polyimide precursor layer in the step (A) contains a compound that promotes imidization, the basic aqueous solution or water-soluble basic substance of the patterned polyimide precursor layer (F) In the process of lowering the solubility of the polyimide precursor layer, the action of the compound that promotes imidization makes it possible to cause the imidization reaction by a milder stimulus such as lower temperature heating for a shorter time, and the dissolution of the polyimide precursor layer It becomes possible to reduce the property. Accordingly, it is possible to suppress deterioration of the photoresist layer, which is the upper layer of the polyimide precursor, and to easily solve problems such as difficulty in peeling the photoresist layer.

  In the method for forming a polyimide pattern according to the present invention, it is preferable that the compound that promotes imidization is an amine from the viewpoint of catalytic ability for the imidization reaction and further from the viewpoint of corrosion resistance to the metal layer.

  In the method for forming a polyimide pattern according to the present invention, the amine is preferably an aliphatic amine from the viewpoint of high catalytic effect on the imidization reaction.

  In the polyimide pattern forming method according to the present invention, in the polyimide precursor layer in the step (A), 0.1 to 40 parts by weight of a compound that promotes imidization with respect to 100 parts by weight of the polyimide precursor. It is preferably contained. When the amount is less than 0.1 part by weight, a sufficient catalytic effect cannot be obtained. When the amount exceeds 40 parts by weight, amine tends to remain in the polyimide after imidation, and the physical properties of the polyimide may deteriorate.

  In the method for forming a polyimide pattern according to the present invention, the linear thermal expansion coefficient of the obtained polyimide pattern is 1 ppm / ° C. to 40 ppm / ° C., and the flatness of the finally obtained electronic component, particularly a hard disk drive suspension. Is preferable from the viewpoint of improving the image quality. When the polyimide pattern is laminated with a metal used as a conductor layer or the like, the warpage of the substrate is reduced and the flatness is improved as the linear thermal expansion coefficient is closer to the metal.

  In the polyimide pattern forming method according to the present invention, the resulting polyimide pattern has a hygroscopic expansion coefficient of 1 ppm /% RH to 40 ppm /% RH. It is preferable from the viewpoint that the property can be improved. When the hygroscopic expansion coefficient of the polyimide pattern is large, the substrate may be warped with an increase in humidity due to a difference in expansion coefficient with a metal whose hygroscopic expansion coefficient is almost zero.

  In the method for forming a polyimide pattern according to the present invention, the basic aqueous solution in the steps (F) and (G) is preferably a tetramethylammonium hydroxide aqueous solution from the viewpoint of availability and cost.

  In the method for forming a polyimide pattern according to the present invention, the tetramethylammonium hydroxide concentration in the tetramethylammonium hydroxide aqueous solution is 0.1% by weight to 70% by weight. It is preferable from the point of easiness.

  In the method for forming a polyimide pattern according to the present invention, in the step (F), before the resist is peeled off, the substrate on which the patterned positive photoresist layer and the patterned polyimide precursor layer are formed is heated. It is a heating step, and the heating temperature is 100 ° C. to 250 ° C. while an imidization reaction sufficient to create poor solubility of the polyimide precursor layer in a basic aqueous solution or a water-soluble basic substance is performed. From the viewpoint of preventing the deterioration of the positive type photoresist.

An article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, and an optical member according to the present invention has a polyimide pattern formed by using the polyimide pattern forming method according to the present invention.
An article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member according to the present invention has a polyimide pattern formed by using the polyimide pattern forming method according to the present invention. Since it has a polyimide pattern that does not contain an agent, there is no outgas generation, and the moisture absorption linear expansion coefficient and linear thermal expansion coefficient can be lowered, so that problems such as warping of the substrate do not occur and the reliability is high. . Furthermore, it has a feature that it can be manufactured at low cost because it can be processed with an aqueous liquid with a low waste liquid processing cost by using a less expensive polyimide precursor and a positive resist.

  In the article according to the present invention, as one embodiment, it is mentioned that the polyimide pattern is formed on stainless steel or stainless steel subjected to surface treatment. For example, in the hard disk drive suspension according to the present invention, the polyimide pattern is usually formed on stainless steel or a stainless steel pattern subjected to surface treatment. The thickness of the stainless steel used here or the surface-treated stainless steel is preferably 50 μm to 1 μm from the viewpoint of followability to the magnetic disk.

The suspension for a hard disk according to the present invention has a polyimide pattern formed by using the method for forming a polyimide pattern according to the present invention.
The hard disk suspension according to the present invention has a polyimide pattern that is formed by using the polyimide pattern forming method according to the present invention, and thus has a polyimide pattern that does not contain a photosensitive agent. Since the linear expansion coefficient and the linear thermal expansion coefficient can be lowered, problems such as warpage do not occur and the reliability is high.

As described above, according to the method for forming a polyimide pattern of the present invention, a polyimide pattern that does not contain a photosensitizer can be formed without using a water-insoluble organic solvent in the patterning step. Furthermore, since it is possible to form a pattern without being restricted by the chemical structure of the polyimide precursor, polyimide precursors having a wide variety of chemical structures can be used. You can choose.
According to the present invention, the positive photoresist can be peeled off with a basic aqueous solution or a water-soluble basic substance without using a water-insoluble organic solvent. In addition to being usable as it is, it can reduce the load on the natural environment and solve problems faced in practical use such as worker safety measures and waste liquid treatment costs.
According to the method for forming a polyimide pattern of the present invention, a polyimide pattern that does not contain a photosensitizer can be formed. Therefore, the obtained polyimide pattern has no outgassing and has a hygroscopic linear expansion coefficient and a linear thermal expansion coefficient. Function as an element imparting heat resistance, insulation and dimensional stability as a permanent film, for example, electronic components such as suspensions for hard disks, semiconductor devices, optical circuits, optical circuit components, or Suitable for forming any article of optical member.

  An electronic component such as a hard disk suspension, a semiconductor device, an optical circuit, an optical circuit component, or an optical member according to the present invention includes a photosensitive agent formed by the polyimide pattern forming method according to the present invention. Because there is no polyimide pattern, no outgas is generated, and the hygroscopic expansion coefficient and linear thermal expansion coefficient can be lowered, so there is no problem such as warpage or product malfunction, and the reliability is high. .

The present invention will be described in detail below.
In the present invention, the light used for exposure includes not only electromagnetic waves having wavelengths in the visible and non-visible regions, but also particle beams such as electron beams, and radiation or ionizing radiation that collectively refers to electromagnetic waves and particle beams. It is.
The present invention relates to a polyimide pattern forming method, an article, and a suspension for a hard disk drive. Hereinafter, a polyimide pattern forming method, an article, and a hard disk drive suspension will be described in order.

I. First, a method for forming a polyimide pattern according to the present invention will be described. The method for forming a polyimide pattern of the present invention includes the following steps (A) to (G):
(A) forming a polyimide precursor layer on the substrate;
(B) forming a positive photoresist layer on the polyimide precursor layer;
(C) a pattern exposure step for selectively exposing the positive photoresist layer;
(D) a development step of selectively removing and patterning the underlying polyimide precursor layer after or simultaneously with the development of the positive photoresist layer;
(E) an overall exposure process for exposing the entire surface of the patterned positive photoresist layer;
(F) a solubility lowering step for reducing solubility in a basic aqueous solution or a water-soluble basic substance by at least partially imidizing the patterned polyimide precursor layer;
(G) It has a peeling process which peels the patterned positive photoresist layer with a basic aqueous solution or a water-soluble basic substance.

  According to the present invention, (E) an overall exposure step of exposing the entire surface of the patterned positive photoresist layer, and (F) at least partially imidizing the patterned polyimide precursor layer. The step of reducing the solubility in a basic aqueous solution or a water-soluble basic substance is used to form the patterned positive photoresist layer into a basic aqueous solution or a water-soluble basic substance (hereinafter referred to as a base). Polyimide that does not contain a photosensitive agent without using a water-insoluble organic solvent in the patterning step, and may be peeled off by a basic aqueous solution or a water-soluble basic substance. A pattern can be formed. The polyimide pattern of the present invention is a two-dimensional pattern formed of polyimide having a certain thickness.

The method of forming a polyimide pattern using a polyimide precursor having no photosensitivity and a positive type photoresist does not include a photosensitizer in the polyimide pattern in the final product because the polyimide precursor does not include a photosensitizer. Since a pattern formed only of polyimide can be obtained, outgas is not generated, and the hygroscopic coefficient of linear expansion and the coefficient of linear thermal expansion can be lowered, which has the advantages of high reliability. However, in the conventional method of forming a polyimide pattern using a polyimide precursor layer having no photosensitivity and a positive photoresist, the positive photoresist is stripped using a water-insoluble organic solvent. Not only is the load on the natural environment high, but it has become a major obstacle to practical use due to the safety measures of workers and waste liquid treatment costs.
In this regard, according to the present invention, by using the (E) whole surface exposure step and the (F) solubility lowering step in combination, a positive type photo can be obtained with a basic solution without using a water-insoluble organic solvent. The resist can be stripped, existing equipment used in other processes can be used as it is, the load on the natural environment is reduced, and there are problems of practical use such as worker safety measures and waste liquid treatment costs. While solving, a highly reliable polyimide pattern can be obtained.

In the present invention, the positive photoresist is peeled off with a basic solution without using a water-insoluble organic solvent by using a combination of the (E) whole surface exposure step and the (F) solubility lowering step. This is possible for the following reasons.
That is, since the exposed portion of the positive photoresist becomes basic-soluble, the entire surface of the patterned positive photoresist layer can be exposed again to be peeled off by the basic solution. However, since the patterned polyimide precursor layer is also dissolved in the basic solution, a polyimide pattern cannot be obtained if it is attempted to peel off with the basic solution as it is.
Therefore, after the (C) pattern exposure step and (D) development step, (G) the entire surface is exposed in a state before the positive photoresist peeling step, so that the positive photoresist is soluble in a basic solution. (E) The entire surface exposure step to change to the above situation and, for example, moderate heating to lower the solubility in the basic solution by at least partially imidizing the polyimide precursor layer (F) By combining with the solubility lowering step, the positive photoresist patterned with the basic solution can be subsequently peeled off, so that only the positive photoresist can be peeled off.

  Such a polyimide pattern forming method of the present invention will be specifically described with reference to the drawings. FIG. 1 is a process diagram showing an example of a method for forming a polyimide pattern of the present invention. As shown in FIG. 1A, first, the step (A) for forming the polyimide precursor layer 2 on the substrate 1 is performed. Next, as shown in FIG. 1B, the step (B) for forming the positive photoresist layer 3 on the polyimide precursor layer 2 is performed. Next, as shown in FIG. 1C, the pattern exposure step (C) is performed in which the positive photoresist layer 3 is selectively exposed 5 through, for example, a mask 4. As a result, only the exposed portion of the positive photoresist layer 3 changes so as to be dissolved in the basic solution. Next, as shown in FIG. 1 (D), after or simultaneously with the development of the exposed portion of the positive photoresist layer 3, the polyimide precursor layer below the exposed portion of the positive photoresist layer 3 is developed. Only the portion 2 is selectively removed, and the development step (D) is performed to obtain a patterned positive photoresist layer 3 ′ and a patterned polyimide precursor layer 2 ′. Next, as shown in FIG. 1 (E), the above-mentioned (E) whole surface exposure step of exposing 5 the whole surface of the patterned positive photoresist layer 3 'is performed. As a result, the patterned positive photoresist layer 3 ′ becomes a positive photoresist layer 3 ″ changed so as to be dissolved in the basic solution. Next, as shown in FIG. By applying a stimulus 6 such as heating to at least partially imidize the patterned polyimide precursor layer 2 ′, the solubility in a basic aqueous solution or a water-soluble basic substance is reduced ( F) A solubility lowering step is performed, whereby the patterned polyimide precursor layer 2 ′ becomes a polyimide precursor layer 2 ″ having reduced solubility in a basic solution. Depending on the combination of the polyimide precursor layer 2 ′ and the stimulus 6, the polyimide precursor layer 2 ″ whose solubility in a basic solution is reduced may be a completely polyimide-immobilized polyimide layer. As shown in G), the above-described (G) stripping step of stripping the patterned positive photoresist layer 3 ″ changed so as to be dissolved in the basic solution with the basic solution is performed. Thereby, a two-dimensional pattern of the polyimide precursor layer 2 ″ is obtained.

  As described above, in the step (F), the polyimide precursor layer 2 ″ may be a completely polyimideized polyimide layer. Usually, however, (H) the patterned polyimide precursor layer 2 is further added. And a step of polyimidizing (not shown). Thereby, a two-dimensional pattern formed of polyimide is obtained.

The (E) whole surface exposure step may be performed before the (F) solubility lowering step as described above, or may be performed after the (F) solubility lowering step. When the (E) whole surface exposure step is performed before the (F) solubility reduction step, the photosensitive component of the positive photoresist is less deteriorated by heating and is peeled off with a lower concentration basic solution. There are features that can be done. On the other hand, when the (E) whole surface exposure step is performed after the (F) solubility lowering step, there is a feature that peeling unevenness is hardly formed on the polyimide precursor layer.
Hereinafter, the method for forming a polyimide pattern of the present invention will be described step by step.

<(A) Polyimide precursor layer forming step>
In this invention, it has a process (A) which forms a polyimide precursor layer on a board | substrate first.
Examples of the method for forming the polyimide precursor layer on the substrate include, but are not particularly limited to, a method of applying a polyimide precursor layer forming coating solution on the substrate and drying to form a coating film.

As a substrate for forming a polyimide pattern, it can be used without particular limitation as long as it is appropriately selected according to the purpose. For example, a metal such as an alloy such as stainless steel, copper, aluminum, copper alloy, a silicon wafer or a silicon wafer. A semiconductor device having a circuit or element formed thereon, a resin such as polyimide or epoxy resin, or a fiber or particle such as glass, carbon, or aramid resin mixed with such a resin, or copper or Examples are those in which wiring is formed of aluminum or the like.
These substrates are subjected to surface treatments such as chemical treatments such as plating, sputtering, and silane coupling treatment, and physical treatments such as sandblasting for the purpose of improving adhesion, improving reliability, and preventing migration. Also good.

The polyimide precursor used in the present invention is appropriately selected according to the purpose of use of the obtained polyimide pattern, and can be used without any particular limitation. In the step (D), simultaneously with the development of the portion of the positive photoresist layer 3, only the portion of the polyimide precursor layer 2 under the exposed portion of the positive photoresist layer 3 is selectively removed. In view of the above, those which are soluble in a basic solution such as a basic aqueous solution or a water-soluble basic substance are preferable, and examples of a material suitably used include polyamic acid. Specific examples of polyimide precursors that are soluble in basic solutions include those in which a phenol residue is introduced into the carboxyl group of a polyamic acid by an ester bond or the like, a partially imidized polyamic acid, and the like. It is done.
Polyamic acid is not only soluble in a basic solution but also obtained by simply mixing acid dianhydride and diamine in the solution, so it can be synthesized in a single-step reaction, easy to synthesize and at low cost. It is preferable because it is available.

  In addition, for polyamic acid, for applications where the heat resistance and dimensional stability requirements of the finally obtained polyimide are severe, the part derived from acid dianhydride has an aromatic structure, and the part derived from diamine A precursor of wholly aromatic polyimide containing an aromatic structure is preferable. Therefore, the structure derived from the diamine component is also preferably a structure derived from an aromatic diamine.

  Here, the wholly aromatic polyimide precursor is a polyimide precursor obtained by copolymerization of an aromatic acid component and an aromatic amine component, or polymerization of an aromatic acid / amino component, and a derivative thereof. The aromatic acid component is a compound in which all four acid groups forming the polyimide skeleton are substituted on the aromatic ring, and the aromatic amine component is the two amino groups forming the polyimide skeleton. Both are compounds substituted on the aromatic ring, and the aromatic acid / amino component is a compound in which both the acid group and amino group forming the polyimide skeleton are substituted on the aromatic ring. However, as is clear from the specific examples of raw materials described later, it is not necessary for all acid groups or amino groups to be present on the same aromatic ring.

  As a method for producing the polyamic acid of the present invention, a conventionally known method can be applied. For example, (1) a method of synthesizing a polyamic acid as a precursor from an acid dianhydride and a diamine; (2) an ester acid synthesized by reacting an acid dianhydride with a monovalent alcohol, an amino compound, an epoxy compound, or the like. And a method in which a compound obtained by reacting a diamino compound or its derivative with a carboxylic acid of an amic acid monomer and an acid dianhydride are further reacted to synthesize a polyamic acid partially having a functional group introduced. Although it is mentioned, it is not limited to this.

  Examples of the acid dianhydride applicable to the polyamic acid of the present invention include ethylene tetracarboxylic dianhydride, butane tetracarboxylic dianhydride, cyclobutane tetracarboxylic dianhydride, and cyclopentane tetracarboxylic dianhydride. Pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 2,2 ′, 3,3′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4 , 4′-biphenyltetracarboxylic dianhydride, 2,2 ′, 3,3′-biphenyltetracarboxylic dianhydride, 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, 2, 2-bis (3,4-dicarboxyphenyl) propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) propane dianhydride, bis (3,4-dicarboxy) Phenyl) ether dianhydride, bis (3,4-dicarboxyphenyl) sulfone dianhydride, 1,1-bis (2,3-dicarboxyphenyl) ethane dianhydride, bis (2,3-dicarboxyphenyl) ) Methane dianhydride, bis (3,4-dicarboxyphenyl) methane dianhydride, 2,2-bis (3,4-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoro Propane dianhydride, 2,2-bis (2,3-dicarboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride, 1,3-bis [(3,4- Dicarboxy) benzoyl] benzene dianhydride, 1,4-bis [(3,4-dicarboxy) benzoyl] benzene dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) Phenoxy] phenyl} propane Anhydride,

2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} propane dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride Bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, 4,4′-bis [4- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, 4,4′-bis [3- (1,2-dicarboxy) phenoxy] biphenyl dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis { 4- [3- (1,2-dicarboxy) phenoxy] phenyl} ketone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfone dianhydride, bis {4- [3- (1,2-dicarbo Cis) phenoxy] phenyl} sulfone dianhydride, bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} sulfide dianhydride, bis {4- [3- (1,2-dicarboxy) Phenoxy] phenyl} sulfide dianhydride, 2,2-bis {4- [4- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-hexafulpropane dianhydride 2,2-bis {4- [3- (1,2-dicarboxy) phenoxy] phenyl} -1,1,1,3,3,3-propane dianhydride, 2,3,6,7 -Naphthalene tetracarboxylic dianhydride, 1,4,5,8-naphthalene tetracarboxylic dianhydride, 1,2,5,6-naphthalene tetracarboxylic dianhydride, 1,2,3,4-benzene Tetracarboxylic dianhydride, 3,4,9, 0 Bae Li Ren dianhydride, 2,3,6,7-anthracene tetracarboxylic dianhydride, 1,2,7,8-phenanthrene tetracarboxylic acid dianhydride, and the like. These may be used alone or in combination of two or more. And as a particularly preferred tetracarboxylic dianhydride, pyromellitic dianhydride, 3,3 ′, 4,4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyltetra Carboxylic dianhydride, 2,2 ′, 6,6′-biphenyltetracarboxylic dianhydride, bis (3,4-dicarboxyphenyl) ether dianhydride, 2,2-bis (3,4-di Carboxyphenyl) -1,1,1,3,3,3-hexafluoropropane dianhydride.

When an acid dianhydride into which fluorine is introduced or an acid dianhydride having an alicyclic skeleton is used as the acid dianhydride to be used in combination, the transparency of the polyimide precursor is improved. Also, rigid acid dianhydrides such as pyromellitic acid anhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, etc. When used, the linear thermal expansion coefficient of the finally obtained polyimide becomes small.

  On the other hand, the amine component can also be used alone or in combination of two or more diamines. The diamine component used is not limited, but p-phenylenediamine, m-phenylenediamine, o-phenylenediamine, 3,3′-diaminodiphenyl ether, 3,4′-diaminodiphenyl ether, 4,4′-diamino. Diphenyl ether, 3,3′-diaminodiphenyl sulfide, 3,4′-diaminodiphenyl sulfide, 4,4′-diaminodiphenyl sulfide, 3,3′-diaminodiphenyl sulfone, 3,4′-diaminodiphenyl sulfone, 4,4 '-Diaminodiphenylsulfone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzophenone, 3,4'-diaminobenzophenone, 3,3'-diaminodiphenylmethane, 4,4'-diaminodiphenylmethane, 3,4' -Diaminodiph Nylmethane, 2,2-di (3-aminophenyl) propane, 2,2-di (4-aminophenyl) propane, 2- (3-aminophenyl) -2- (4-aminophenyl) propane, 2,2 -Di (3-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 2,2-di (4-aminophenyl) -1,1,1,3,3,3-hexa Fluoropropane, 2- (3-aminophenyl) -2- (4-aminophenyl) -1,1,1,3,3,3-hexafluoropropane, 1,1-di (3-aminophenyl) -1 -Phenylethane, 1,1-di (4-aminophenyl) -1-phenylethane, 1- (3-aminophenyl) -1- (4-aminophenyl) -1-phenylethane, 1,3-bis ( 3-Aminophenoxy) benzene, 1,3 Bis (4-aminophenoxy) benzene, 1,4-bis (3-aminophenoxy) benzene, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminobenzoyl) benzene, 1, 3-bis (4-aminobenzoyl) benzene, 1,4-bis (3-aminobenzoyl) benzene, 1,4-bis (4-aminobenzoyl) benzene, 1,3-bis (3-amino-α, α -Dimethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dimethylbenzyl) benzene, 1,4-bis (3-amino-α, α-dimethylbenzyl) benzene, 1,4-bis ( 4-amino-α, α-dimethylbenzyl) benzene, 1,3-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,3-bis (4-amino-α, α-dito Trifluoromethylbenzyl) benzene, 1,4-bis (3-amino-α, α-ditrifluoromethylbenzyl) benzene, 1,4-bis (4-amino-α, α-ditrifluoromethylbenzyl) benzene, 2 , 6-bis (3-aminophenoxy) benzonitrile, 2,6-bis (3-aminophenoxy) pyridine, 4,4′-bis (3-aminophenoxy) biphenyl, 4,4′-bis (4-amino) Phenoxy) biphenyl, bis [4- (3-aminophenoxy) phenyl] ketone, bis [4- (4-aminophenoxy) phenyl] ketone, bis [4- (3-aminophenoxy) phenyl] sulfide, bis [4- (4-aminophenoxy) phenyl] sulfide,

Bis [4- (3-aminophenoxy) phenyl] sulfone, bis [4- (4-aminophenoxy) phenyl] sulfone, bis [4- (3-aminophenoxy) phenyl] ether, bis [4- (4-amino) Phenoxy) phenyl] ether, 2,2-bis [4- (3-aminophenoxy) phenyl] propane, 2,2-bis [4- (4-aminophenoxy) phenyl] propane, 2,2-bis [3- (3-Aminophenoxy) phenyl] -1,1,1,3,3,3-hexafluoropropane, 2,2-bis [4- (4-aminophenoxy) phenyl] -1,1,1,3 3,3-hexafluoropropane, 1,3-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (4-aminophenoxy) benzoyl] ben 1,4-bis [4- (3-aminophenoxy) benzoyl] benzene, 1,4-bis [4- (4-aminophenoxy) benzoyl] benzene, 1,3-bis [4- (3-amino Phenoxy) -α, α-dimethylbenzyl] benzene, 1,3-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 1,4-bis [4- (3-aminophenoxy) -Α, α-dimethylbenzyl] benzene, 1,4-bis [4- (4-aminophenoxy) -α, α-dimethylbenzyl] benzene, 4,4'-bis [4- (4-aminophenoxy) benzoyl ] Diphenyl ether, 4,4′-bis [4- (4-amino-α, α-dimethylbenzyl) phenoxy] benzophenone, 4,4′-bis [4- (4-amino-α, α-dimethylbenzen) ) Phenoxy] diphenylsulfone, 4,4′-bis [4- (4-aminophenoxy) phenoxy] diphenylsulfone, 3,3′-diamino-4,4′-diphenoxybenzophenone, 3,3′-diamino-4 , 4′-Dibiphenoxybenzophenone, 3,3′-diamino-4-phenoxybenzophenone, 3,3′-diamino-4-biphenoxybenzophenone, 6,6′-bis (3-aminophenoxy) -3,3 3 ′, 3′-tetramethyl-1,1′-spirobiindane, 6,6′-bis (4-aminophenoxy) -3,3,3 ′, 3′-tetramethyl-1,1′-spirobiindane, , 3-bis (3-aminopropyl) tetramethyldisiloxane, 1,3-bis (4-aminobutyl) tetramethyldisiloxane, α, ω-bis ( -Aminopropyl) polydimethylsiloxane, α, ω-bis (3-aminobutyl) polydimethylsiloxane, bis (aminomethyl) ether, bis (2-aminoethyl) ether, bis (3-aminopropyl) ether, bis ( 2-aminomethoxy) ethyl] ether, bis [2- (2-aminoethoxy) ethyl] ether, bis [2- (3-aminoprotoxy) ethyl] ether,

1,2-bis (aminomethoxy) ethane, 1,2-bis (2-aminoethoxy) ethane, 1,2-bis [2- (aminomethoxy) ethoxy] ethane, 1,2-bis [2- (2 -Aminoethoxy) ethoxy] ethane, ethylene glycol bis (3-aminopropyl) ether, diethylene glycol bis (3-aminopropyl) ether, triethylene glycol bis (3-aminopropyl) ether, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, 1,5-diaminopentane, 1,6-diaminohexane, 1,7-diaminoheptane, 1,8-diaminooctane, 1,9-diaminononane, 1,10-diaminodecane, 1, 11-diaminoundecane, 1,12-diaminododecane, 1,2-diaminocyclohex 1,3-diaminocyclohexane, 1,4-diaminocyclohexane, 1,2-di (2-aminoethyl) cyclohexane, 1,3-di (2-aminoethyl) cyclohexane, 1,4-di (2- Aminoethyl) cyclohexane, bis (4-aminocyclohexyl) methane, 2,6-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,5-bis (aminomethyl) bicyclo [2.2. 1] A diamine obtained by substituting some or all of the hydrogen atoms on the aromatic ring of the above diamine with a substituent selected from a fluoro group, a methyl group, a methoxy group, a trifluoromethyl group, or a trifluoromethoxy group. Can be used.

  Furthermore, depending on the purpose, any one or two or more of the ethynyl group, benzocyclobuten-4′-yl group, vinyl group, allyl group, cyano group, isocyanate group, and isopropenyl group serving as a crosslinking point, Even if it introduce | transduces into some or all of the hydrogen atoms on the aromatic ring of diamine as a substituent, it can be used.

  The diamine can be selected depending on the desired physical properties. If a rigid diamine such as p-phenylenediamine is used, the finally obtained polyimide has a low expansion coefficient. Rigid diamines include p-phenylenediamine, m-phenylenediamine, 1,4-diaminonaphthalene, 1,5-diaminonaphthalene, 2, 6 as diamines in which two amino groups are bonded to the same aromatic ring. -Diaminonaphthalene, 2,7-diaminonaphthalene, 1,4-diaminoanthracene and the like can be mentioned.

Further, diamines in which two or more aromatic rings are bonded by a single bond, and two or more amino groups are bonded to separate aromatic rings directly or as part of a substituent can be mentioned. Specific examples include benzidine and the like.
Furthermore, in the above diamine, a diamine having a substituent at a position where the amino group on the benzene ring is not substituted and which does not participate in the bond with another benzene ring can also be used. These substituents are monovalent organic groups, but they may be bonded to each other.
Specific examples include 2,2′-dimethyl-4,4′-diaminobiphenyl, 2,2′-ditrifluoromethyl-4,4′-diaminobiphenyl, 3,3′-dichloro-4,4′-diamino. Biphenyl, 3,3′-dimethoxy-4,4′-diaminobiphenyl, 3,3′-dimethyl-4,4′-diaminobiphenyl and the like can be mentioned.

  When the finally obtained polyimide is used as an optical waveguide or an optical circuit component, the transmittance for electromagnetic waves having a wavelength of 1 μm or more can be improved by introducing fluorine as a substituent of the aromatic ring.

On the other hand, when a diamine having a siloxane skeleton such as 1,3-bis (3-aminopropyl) tetramethyldisiloxane is used as the diamine, the elastic modulus of the finally obtained polyimide is lowered and the glass transition temperature is lowered. be able to.
Here, the selected diamine is preferably an aromatic diamine from the viewpoint of heat resistance. However, depending on the desired physical properties, the diamine may be an aliphatic diamine or siloxane within a range not exceeding 60 mol%, preferably not exceeding 40 mol%. Non-aromatic diamines such as diamines may be used.

The polyimide precursor used in the present invention preferably has solubility in a basic solution as described above, and specifically, 0.1 wt% of the coating film formed on the substrate at 25 ° C. The dissolution rate with respect to an aqueous solution of tetramethylammonium hydroxide (TMAH) is preferably 100 kg / sec or more. The dissolution rate is more preferably 500 kg / sec or more. Furthermore, the dissolution rate in a 2.38% by weight tetramethylammonium hydroxide aqueous solution, which is a more commonly used developer, is preferably 100 kg / sec or more, and more preferably 500 kg / sec or more. . When the dissolution rate according to the above definition is less than 100 Å / sec, the development time is delayed, workability and productivity are deteriorated, and it is difficult to obtain a solubility contrast between the exposed and unexposed areas.
As a specific procedure for measuring the dissolution rate, a polymer precursor coating film formed on a substrate such as an alkali-free glass was heated to 25 ° C. and stirred with a developer (in this case, 0.1%). The difference between the initial film thickness and the film thickness measured after being immersed in a weight% TMAH aqueous solution or 2.38 wt% TMAH aqueous solution for a certain period of time, rinsed with distilled water and dried The amount of film reduction divided by the time immersed in the developer is the dissolution rate per unit time at 25 ° C.

The weight average molecular weight of the polyimide precursor is preferably in the range of 3,000 to 1,000,000, more preferably in the range of 5,000 to 500,000, although it depends on the application. More preferably, it is in the range of 3,000 to 500,000. When the weight average molecular weight is less than 3,000, it is difficult to obtain sufficient strength when a coating film or film is used. In addition, the strength of the film is reduced when heat treatment is performed to obtain polyimide. On the other hand, when the weight average molecular weight exceeds 1,000,000, the viscosity increases and the solubility decreases, so that it is difficult to obtain a coating film or film having a smooth surface and a uniform film thickness.
The molecular weight used here is a molecular weight obtained by a known method, and is exemplified by a value in terms of polystyrene by gel permeation chromatography (GPC). In this case, the molecular weight of the polyimide precursor itself may be used, or the molecular weight after chemical imidization treatment with acetic anhydride or the like may be used.

  (A) It is preferable to contain the compound which accelerates | stimulates imidation in the polyimide precursor layer in a process. The compound that promotes imidization refers to a compound having a catalytic action that promotes the polyimide formation reaction of the polyimide precursor. When the polyimide precursor layer in the step (A) contains a compound that promotes imidization, the basic aqueous solution or water-soluble basic of the patterned polyimide precursor layer described later (F). In the step of reducing the solubility in a substance, it is possible to reduce the solubility of the polyimide precursor layer in a basic aqueous solution or a water-soluble basic substance by a milder stimulus by the action of a compound that promotes imidization. . Therefore, it is possible to prevent deterioration of the photoresist layer, which is an upper layer of the polyimide precursor, and to easily solve problems such as difficulty in peeling the photoresist layer.

Examples of the compound that promotes imidization contained in the polyimide precursor layer include basic substances. Among them, amines that are organic substances are preferable because of their high catalytic ability.
Among them, aliphatic amines are particularly preferable because they have a high catalytic effect on the imidation reaction of the polyimide precursor regardless of the series. The aliphatic amine refers to a compound in which a hydrogen atom of ammonia is substituted with a hydrocarbon group, and all the bonds extending from a carbon atom having a bond with nitrogen of the hydrocarbon group are single bonds. The hydrocarbon group may be linear, branched or cyclic, and may have a substituent or a hetero bond in the structure. These include primary amines such as n-butylamine, benzylamine, amylamine, hexylamine and octylamine, secondary amines such as diethylamine, dipropylamine, diisopropylamine, dibutylamine and dimethylpiperidine, ethylenediamine , Propylenediamine, trimethylenediamine, triethylenediamine (1,4-diazabicyclo [2.2.2] octane), alkylenediamines such as tetramethylenediamine, pentamethylenediamine and hexamethylenediamine, triamines such as diethylenetriamine, and other tetramines Compounds and amines such as benzylamine are exemplified, but are not particularly limited as long as the effects of the present invention can be achieved.

  In the polyimide precursor layer in the step (A), the compound for promoting imidization with respect to 100 parts by weight of the polyimide precursor is 0.1 to 40 parts by weight, and further 0.5 to 30 parts by weight. It is preferably contained. When the compound that promotes imidization is less than 0.1 part by weight based on 100 parts by weight of the polyimide precursor, the effect of promoting the imidization reaction is insufficient. On the other hand, when the compound that promotes imidization with respect to 100 parts by weight of the polyimide precursor exceeds 40 parts by weight, the compound that promotes imidization tends to remain in the polyimide after imidation, and the physical properties of the polyimide are May decrease.

  The compound that promotes imidization contained in the polyimide precursor layer in the step (A) is preferably used from the viewpoint of reliability so as not to remain in the finally obtained polyimide pattern. Therefore, the compound that promotes imidization is preferably decomposed or volatilized in the step of imidization. Specifically, the compound that promotes imidization has a temperature (5% weight reduction temperature) when it is reduced by 5% from the initial weight by heating (25% to 350 ° C), preferably 25 ° C to 250 ° C. It is preferable that the temperature is 0 ° C. because the compound that promotes imidization can be decomposed or volatilized by heating so that it does not remain in the polyimide after imidization.

  In the polyimide precursor layer in the step (A) of the present invention, various organic or inorganic low molecules or polymers are added to impart processing characteristics and various functionalities unless the effects of the present invention are impaired. You may mix | blend a compound. For example, dyes, surfactants, leveling agents, plasticizers, fine particles and the like can be used. The fine particles include organic fine particles such as polystyrene and polytetrafluoroethylene, inorganic fine particles such as colloidal silica, carbon, and layered silicate, and these may have a porous or hollow structure. The function or form includes pigments, fillers, fibers, and the like.

  The coating liquid in the case where the polyimide precursor layer is formed by applying a polyimide precursor layer forming coating liquid on the substrate and drying to form a coating film, the polyimide precursor as an essential component, and the like. Are mixed and dissolved in a solvent to prepare. The solvent is not particularly limited as long as the polyimide precursor is an essential component and is a good solvent for other components. For example, N-methyl-2-pyrrolidinone, dimethylacetamide, dimethylformamide, γ-butyrolactone can be used. , Γ-valerolactone, dimethyl sulfoxide and the like.

  As a coating method, a known method such as dip coating, spin coating, die coating, roll coating, slit coating or the like can be used as appropriate.

  The drying method for removing the solvent from the film coated with the coating liquid includes heating, and a known apparatus / method such as an oven or a hot plate can be used. The heating temperature is preferably in the range of 80 ° C to 140 ° C.

  The thickness of the polyimide precursor layer is appropriately selected depending on the use of the obtained polyimide pattern and is not particularly limited, but is usually formed to be 0.5 μm to 100 μm.

<(B) Step of forming a positive photoresist layer on the polyimide precursor layer>
As a method of forming a positive photoresist layer on the polyimide precursor layer, a positive photoresist layer forming coating solution is applied on the polyimide precursor layer formed in the step (A) and dried. And a method of forming a coating film is not particularly limited. A film obtained by forming a positive photoresist layer into a film shape, such as a dry film resist, may be bonded onto the substrate.

  The positive type photoresist is a material whose solubility in the developer is changed from insoluble or hardly soluble to soluble when irradiated with electromagnetic waves such as ultraviolet rays. In the present invention, the positive photoresist is peeled off by the basic aqueous solution or the water-soluble basic substance in the step (G) as described above. A material whose solubility in a basic substance is changed from insoluble / slightly soluble to soluble is used. The positive photoresist used in the present invention is typically a mixture of a cresol-novolak polymer and a naphthoquinonediazide derivative as shown below, but is not limited thereto.

(1) A polycondensation product of phenol, m-cresol and formalin.
(2) A formalin polycondensation product of phenol and p-tert-butylphenol.
(3) A formalin condensation polymerization product of phenol and p-methoxyphenol.
(4) A formalin polycondensation product of phenol and p-butoxyphenol.
(5) A formalin condensation polymerization product of m-cresol and p-tert-butylphenol.
(6) A formalin condensation polymer of p-propylphenol and p-ethoxyphenol.
(7) A formalin condensation polymer of p-methoxyphenol and p-ethoxyphenol.
(8) A polycondensation product of m-cresol and formalin.
(9) A polycondensation product of phenol, p-phenylphenol and formaldehyde.
(10) A polycondensation product of m-cresol, p-ethoxyphenol and formaldehyde.
(11) A polycondensation product of phenol cardanol and formaldehyde.
The positive photoresist used in the present invention is preferably one that can be developed with a basic solution.

When the positive photoresist coating solution is applied on the polyimide precursor layer and dried to form a coating film to form a positive photoresist layer, the coating solution is a cresol-novolak-based coating. In addition to the components that form a positive photoresist such as a molecule and a naphthoquinonediazide derivative, other components are appropriately blended and dissolved in a solvent. Care should be taken in selecting the solvent. That is, it is necessary to select a solvent that does not dissolve the underlying polyimide precursor layer. Specifically, it is necessary to select a solvent that does not dissolve 3.0% by weight or more of the polyimide precursor as a lower layer with respect to the solvent.
As a coating method, the same method as mentioned in the step (A) can be used.

  The drying temperature after coating is preferably 60 ° C to 120 ° C, more preferably 70 ° C to 100 ° C. If it is less than 60 ° C., the solvent does not volatilize sufficiently and remains in the film or takes time for drying, which is not preferable. If it exceeds 120 ° C., the photosensitive agent and additives in the positive photoresist are gradually decomposed, which is not preferable.

  On the other hand, as a laminating method for laminating a dry film resist on a polyimide precursor layer, a known laminating method such as a roll press or a surface press can be used.

  The thickness of the positive photoresist layer is not particularly limited, but is usually formed to be 0.5 μm to 100 μm.

<(C) Pattern exposure process>
In the step (C), the positive photoresist layer is selectively exposed. As a result, only the exposed portion of the positive photoresist layer changes so as to be dissolved in the basic solution.
Examples of the selective exposure method include a projection exposure method through a mask. The exposure method and exposure apparatus used in the exposure process are not particularly limited, and may be contact exposure or indirect exposure, and any known means such as a stepper, scanner, aligner, contact printer, laser, and electron beam drawing can be used. .

<(D) Development step>
In the step (D), after or simultaneously with the development of the portion of the positive photoresist layer 3 exposed in the step (C), the polyimide precursor layer under the exposed portion of the positive photoresist layer 3 Only the portion 2 is selectively removed to obtain a patterned positive photoresist layer 3 ′ and a patterned polyimide precursor layer 2 ′.

The development of the positive photoresist layer is preferably carried out under the recommended conditions using a developer corresponding to the positive photoresist used, and is not particularly limited.
However, as described above, from the viewpoint of waste disposal, development with a basic aqueous solution is preferable as in the later-described (G) peeling step. In particular, development with an aqueous organic alkali solution is preferred, and among them, an aqueous tetramethylammonium hydroxide solution is preferred. The concentration is preferably between 0.01% and 70% by weight. If it is less than 0.01% by weight, the exposed portion of the positive photoresist is poorly soluble and cannot be developed well. If it exceeds 70% by weight, the unexposed area will swell and it will be difficult to obtain the desired pattern.

The developing method may be a dip method, a spray method, or a submerged spray method, and is not particularly limited.
When the polyimide precursor layer under the positive photoresist is dissolved in the developer used at this time, the positive photoresist layer and the polyimide precursor layer can be selectively removed at the same time and patterned. Therefore, the process can be reduced. Also in this sense, development of a positive photoresist with an inorganic or organic alkaline aqueous solution is effective after using a polyimide precursor soluble in a basic aqueous solution.

  If the polyimide precursor does not dissolve in the positive photoresist developer, use a liquid that does not dissolve the resulting positive photoresist pattern but dissolves the polyimide precursor after the development of the positive photoresist. Pattern formation of the polyimide precursor film is performed. In that case, the difference between the dissolution rate of the positive photoresist pattern and the dissolution rate of the polyimide precursor with respect to the solution used for forming the pattern of the polyimide precursor is 50 times or more, and the larger the polyimide precursor is better.

<(E) Whole surface exposure process>
In the step (D), the entire surface of the positive photoresist layer patterned in the development step (D) is exposed.
The exposure method in the overall exposure process for the positive photoresist is not particularly limited, and a known technique can be used. However, it is preferable to use a conveyor type exposure apparatus because productivity is improved. When exposure is performed using a high-pressure mercury lamp, the exposure is preferably performed at a wavelength of 365 nm in the order of 10 mJ / cm ^{2 to} 50 J / cm ² . If it is less than 10 mJ / cm ² , peeling with a basic solution does not work well, and if it exceeds 50 J / cm ² , the process time becomes long and the productivity may decrease.

<(F) Solubility reduction step>
In the step (F), the solubility in a basic aqueous solution or a water-soluble basic substance is lowered by at least partially imidizing the polyimide precursor layer patterned in the development step (D). The basic aqueous solution or the water-soluble basic substance will be described in detail in the next step (G).
By reducing the solubility of the patterned polyimide precursor layer in the basic solution, the solubility of the patterned polyimide precursor layer in the basic solution can be improved between the positive photoresist layer that can be dissolved in the upper basic solution. It is possible to make a difference, and it becomes possible to peel only the upper positive photoresist layer with a basic solution. The difference in solubility with respect to the basic solution is that the dissolution rate of the positive photoresist pattern after performing the step (F) with respect to the basic solution used is the polyimide precursor after performing the step (F). The dissolution rate of the body pattern is preferably 10 times or more, more preferably 30 times or more. More specifically, for example, the dissolution rate of the polyimide precursor pattern after the step (F) in the 0.1 wt% tetramethylammonium hydroxide (TMAH) aqueous solution at 25 ° C. is less than 1000 kg / sec. Further, the dissolution rate in a 2.38 wt% tetramethylammonium hydroxide (TMAH) aqueous solution at 25 ° C. is preferably less than 1000 kg / sec.

  A polyimide precursor that is soluble in a basic aqueous solution or a water-soluble basic substance is preferably used because of the advantages in the above-described steps, but even such an alkali-soluble polyimide precursor is converted into a polyimide. The solubility of the polyimide precursor in a basic aqueous solution or a water-soluble basic substance is lowered. Therefore, in the present invention, as a method for reducing the solubility of the polyimide precursor layer in a basic aqueous solution or water-soluble basic substance, the upper positive photoresist is applied to a certain basic aqueous solution or water-soluble basic substance. The polyimide precursor layer is at least partially imidized to such an extent that the layer dissolves but does not dissolve the polyimide precursor layer. In addition, partial imidation means that the imidization reaction of the polyimide precursor in the polyimide precursor layer does not proceed completely, and the portion imidized in the molecular chain of the polyimide precursor is imidized. It means that there are no parts.

The imidation ratio in the polyimide precursor layer is appropriately adjusted depending on the solubility of the polyimide precursor used in the basic solution and is not particularly limited, but is usually 1% or more, and further 5% or more. It is preferable. The imidation rate here is about the polyimide precursor as a raw material used at the said (A) process in an infrared absorption spectrum (For example, measured using the Fourier transform type infrared spectrophotometer FT-IR610 by JASCO Corporation). , When the peak area of the carbonyl group peak of the amide bond derived from the precursor (usually around 1663 cm ⁻¹ ) is 1, the amount of decrease in the peak area in the heating process is calculated in terms of the imidization rate. . The state of the polyimide precursor layer in the step (A) is 0% imidation, and the imidation rate is 100% when the peak completely disappears. From the viewpoint of reducing the solubility of the polyimide precursor pattern in a basic solution, the polyimide reaction may be performed until the imidization rate reaches 100%. The type photoresist layer may deteriorate and become difficult to dissolve in a basic solution. In this case, it is preferable to partially imidize the polyimide precursor layer appropriately so that a difference in solubility in a basic solution can be made between the positive photoresist layer. In addition, when using the polyimide precursor partially imidized from the beginning, the imidation rate is calculated by setting the initial value to 0%.

As a method for partially imidizing the polyimide precursor layer, for example, moderate heating can be mentioned. The process of partially imidizing by heating can be performed by an oven, a hot plate, a conveyor-type infrared furnace, or the like. The temperature condition in this case can be appropriately selected according to the polyimide precursor used, but is usually in the range of 100 ° C to 250 ° C, preferably in the range of 140 ° C to 200 ° C. When a compound that promotes imidization is contained in the polyimide precursor layer in the step (A), the solubility can be lowered by performing imidization at a lower temperature, and the temperature condition is 120 ° C. It can select in the range of -200 degreeC. If the temperature is less than 100 ° C., the imidization reaction sufficient to create poor solubility in a basic aqueous solution or a water-soluble basic substance cannot be performed. It is easy to deteriorate and may be difficult to dissolve in a basic solution.
In addition, the heating temperature of the heating conditions in this invention says the temperature of the location where what is heated is in contact.

The heating and holding time at the heating temperature needs to be appropriately set depending on the heating temperature and the heating method, but is preferably 1 second to 120 minutes, and preferably 5 seconds to 30 minutes. If the heating and holding time is too short, the effect of heating is difficult to be exhibited, and the polyamic acid is likely to dissolve in the liquid used for peeling the positive photoresist, which is the next step. Sex is reduced.
Further, the heating step is preferably performed in an inert atmosphere from the viewpoint of suppressing deterioration of the positive resist. Specific examples of the inert atmosphere in this case include reduced pressure, nitrogen atmosphere, and rare gas atmosphere such as argon and helium.

  Depending on the combination of the polyimide precursor to be used and the positive photoresist, imidization may be carried out completely when the imidization reaction is carried out in the (F) solubility reduction step. In this case, the polyimide-forming step after the (H) positive photoresist peeling described later can be omitted.

<(G) peeling step>
In the step (G), the patterned positive photoresist layer that can be dissolved in the basic solution in the (E) overall exposure step is peeled off with a basic aqueous solution or a water-soluble basic substance.
In the present invention, in order to reduce the load on the natural environment and solve practical problems such as worker safety measures and waste liquid treatment costs, a basic aqueous solution or a water-soluble solution is used without using a water-insoluble organic solvent. The positive photoresist is peeled off with a basic substance. Since peeling is performed with a basic aqueous solution or a water-soluble basic substance, there is an advantage that the equipment used in the development step (D) can be used as it is. Further, the substrate rinsing and cleaning steps after peeling can be performed with water or an aqueous solution.

  As the basic solution, the polyimide precursor pattern after the step (F) has low solubility, but it is necessary to appropriately select and use a solution having high solubility with respect to the positive photoresist pattern. As a guideline for selecting such a basic solution, the dissolution rate of the positive photoresist pattern after the step (F) is the dissolution rate of the polyimide precursor pattern after the step (F). And a basic solution having a dissolution rate of 10 times or more, more preferably 100 times or more.

  Among the basic solutions used in the present invention, examples of the basic aqueous solution include inorganic or organic alkaline aqueous solutions, and organic alkaline aqueous solutions are particularly preferable from the viewpoint of waste liquid treatment. Examples of the basic aqueous solution include tetramethylammonium hydroxide (TMAH) aqueous solution, potassium hydroxide aqueous solution, water having a concentration of 0.01% by weight to 70% by weight, preferably 0.05% by weight to 10% by weight. Examples thereof include an aqueous solution of sodium oxide, an aqueous solution of magnesium hydroxide, an aqueous solution of calcium hydroxide, an aqueous solution of sodium hydrogen carbonate, an aqueous solution of primary, secondary, and tertiary amines, and an aqueous solution of hydroxide ions and ammonium ions.

Of the basic solutions used in the present invention, the water-soluble basic substance means an organic compound having a water-soluble pH greater than 7, specifically, a primary, secondary, tertiary amine, or A quaternary amine (ammonium compound) is mentioned. The water solubility of the water-soluble basic substance of the present invention means that an aqueous solution can be obtained at a concentration of 1% by weight or more and 90% by weight or less at 25 ° C., preferably an aqueous solution having a concentration of 5% by weight or more and 60% by weight or less. Means what can be obtained.
In order to peel off a positive photoresist pattern whose solubility has been greatly lowered by heat treatment, peeling with the above water-soluble basic substance is preferable. Specifically, primary to quaternary amines that are liquid at any temperature between 0 ° C. and 100 ° C. are used, and primary to quaternary aliphatic amines are preferred. Since aliphatic amines are generally highly basic, they are more excellent in peelability.
These primary to quaternary amines may have a substituent, and an aliphatic amine having a hydroxyl group is particularly effective for peeling. Specific examples include ethanolamine, N, N, -dimethylethanolamine, propanolamine, and triethanolamine, but are not particularly limited.

<(H) Polyimideization process>
In step (G), (H) the patterned polyimide precursor layer 2 ″ is polyimideized.
Before imidizing the patterned polyimide precursor layer 2 ″, it may be washed with distilled water or warm water as necessary.

Examples of the imidization method include a method of heating, a method of contacting with a catalyst, a method of heating after being immersed in a catalyst solution, and the like.
In the case of imidization by heating, it is preferable to perform heat treatment at a temperature between 150 ° C. and 400 ° C., preferably at a temperature between 200 ° C. and 370 ° C. for 1 minute to 300 minutes. A known method can be used. Further, this heating step is preferably performed in an inert atmosphere when the substrate contains a metal that is easily oxidized from the viewpoint of preventing oxidation of the metal. Specific examples of the inert atmosphere in this case include reduced pressure, nitrogen atmosphere, and rare gas atmosphere such as argon and helium.

The polyimide pattern thus obtained has a 5% weight loss temperature measured in nitrogen of preferably 250 ° C. or higher, more preferably 300 ° C. or higher. In particular, when used in applications such as electronic parts that pass through the solder reflow process, if the 5% weight loss temperature is 300 ° C. or less, defects such as bubbles occur due to the decomposition gas generated in the solder reflow process. There is a fear.
Here, the 5% weight reduction temperature is the time when the weight of the sample is reduced by 5% from the initial weight when the weight loss is measured using a thermogravimetric analyzer (in other words, the sample weight becomes 95% of the initial weight). Temperature). Similarly, the 10% weight reduction temperature is a temperature at which the sample weight is reduced by 10% from the initial weight.

The polyimide pattern thus obtained preferably has a linear thermal expansion coefficient of 1 ppm / ° C. to 40 ppm / ° C. from the viewpoint of dimensional stability. In particular, when a film is formed on a metal such as copper or stainless steel in a manufacturing process for electronic parts or the like, it is more preferably 1 ppm / ° C. to 20 / ° C. from the viewpoint of adhesion and warpage of the substrate. Here, since the linear thermal expansion coefficient of the polyimide pattern in the present invention can be regarded as an equivalent value regardless of the size of the pattern, if the polyimide pattern itself cannot be measured due to the size of the pattern, A polyimide film for evaluating linear thermal expansion coefficient that has undergone a similar pattern forming process may be prepared and evaluated using the polyimide precursor that is used. In addition, the linear thermal expansion coefficient in this invention can be calculated | required with a thermomechanical analyzer (TMA). Using a thermomechanical analyzer (for example, Thermo Plus TMA8310 (manufactured by Rigaku Corporation), the heating rate is 10 ° C./min, and the tensile load is 1 g / 25,000 μm ² so that the weight per cross-sectional area of the evaluation sample is the same. .

  The polyimide pattern thus obtained preferably has a hygroscopic expansion coefficient of 1 ppm /% RH to 40 ppm /% RH from the viewpoint of dimensional stability. In particular, it is more preferably 1 ppm /% RH to 20 ppm /% RH from the viewpoint of adhesion and warpage of the substrate in the manufacturing process of electronic parts and the like. Here, since the hygroscopic expansion coefficient of the polyimide pattern in the present invention can be regarded as an equivalent value regardless of the size of the pattern, when the polyimide pattern itself cannot be measured due to the size of the pattern, it is used for the polyimide pattern. A polyimide film for evaluating hygroscopic expansion coefficient that has undergone the same pattern forming process may be prepared and evaluated using the polyimide precursor that has been prepared. In addition, the hygroscopic expansion coefficient in the present invention refers to an average change rate (displacement / initial length) of the material length per 1% Rh when the humidity is changed from 30% Rh to 70% Rh at 25 ° C.

II. Articles such as suspension for hard disk The article according to the present invention is an article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member, and uses the method for forming a polyimide pattern according to the present invention. It has a polyimide pattern formed.
The suspension for a hard disk according to the present invention has a polyimide pattern formed by using the method for forming a polyimide pattern according to the present invention.
Since an article such as an electronic component such as a hard disk suspension according to the present invention has a polyimide pattern formed by using the polyimide pattern forming method according to the present invention, it has a polyimide pattern that does not contain a photosensitive agent. Therefore, the hygroscopic coefficient of linear expansion and the coefficient of linear thermal expansion can be lowered, so that problems such as warping do not occur and the reliability is high.

  The article according to the present invention having a polyimide pattern formed by using the polyimide pattern forming method according to the present invention is any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member, There is no particular limitation. For example, a semiconductor device having a polyimide pattern in an insulating layer of a flexible printed board, a wiring protective layer, an insulating layer of a semiconductor mounting board, a wiring protective layer, an insulating layer of a semiconductor device, a surface protective film, etc. is exemplified. In addition to electronic components such as hard disk suspensions and chip scale package substrates, optical circuit components such as waveguides and cladding layers of optical circuit components can be used.

An electronic component which is one of the articles according to the present invention will be specifically described with reference to the hard disk suspension according to the present invention. The hard disk suspension according to the present invention is a component that supports a magnetic head of a hard disk drive.
FIG. 2 is a schematic cross-sectional view of an example of a hard disk suspension according to the present invention.
As shown in FIG. 2, the suspension for a hard disk according to the present invention includes a metal substrate 10 serving as a spring, and a polyimide pattern formed on the metal substrate 10 using the polyimide pattern forming method according to the present invention. An insulating layer 20, a copper wiring layer 30 provided on the insulating layer 20, and a wiring protective layer in which the copper wiring layer 30 is a polyimide pattern formed by using the polyimide pattern forming method according to the present invention. The structure is covered by 40.

In the above example, both the insulating layer 20 and the wiring protective layer 40 are polyimide patterns formed by using the polyimide pattern forming method according to the present invention. Only the kana may be a polyimide pattern formed by using the polyimide pattern forming method according to the present invention. As the wiring protective layer 40, an acrylic resin can also be used.
As the metal substrate 10, a metal foil having spring-like elasticity such as stainless steel or stainless steel subjected to surface treatment is usually used. When the thickness of the metal substrate 10 used is 20 μm or less, especially 50 μm to 1 μm, the followability to the magnetic disk is improved and combined with the polyimide pattern formed using the polyimide pattern forming method according to the present invention. When used, warpage can be further reduced and flatness can be improved.

  If the polyimide pattern used in the suspension for a hard disk according to the present invention satisfies the characteristics required for the polyimide pattern formed by using the polyimide pattern forming method according to the present invention, a suspension exhibiting good characteristics can be obtained.

General examples of manufacturing the suspension include the following. First, a polyimide pattern is formed in a desired shape on a stainless steel foil (20 μm) as the metal substrate 10 using the polyimide pattern forming method according to the present invention, and a substrate provided with the insulating layer 20 is obtained. Next, a seed layer such as copper or nickel is formed on the entire surface of the obtained substrate by sputtering. Thereto, a negative resist solution is applied or a negative dry film resist is laminated, and a negative resist layer is formed on the substrate. Thereafter, exposure and development are performed, and an opening is provided only at a site where a copper wiring is to be formed.
Next, after copper plating is performed on the opening in the shape of the wiring, the resist is peeled off. Thereafter, the back surface of the substrate is masked, and the copper wiring and the surface layer of the seed layer are etched using a dilute hydrochloric acid aqueous solution or the like. Here, when the portion where the seed layer is exposed is completely removed, the substrate on which the independent copper wiring layer 30 is formed is obtained. Next, on the board | substrate with which the said copper wiring layer was formed, a polyimide pattern is formed in a desired shape using the polyimide pattern formation method which concerns on this invention, and the wiring protective layer 40 is formed.

  The present invention is not limited to the above embodiment. The above-described embodiment is an exemplification, and the present invention has any configuration that has substantially the same configuration as the technical idea described in the claims of the present invention and that exhibits the same effects. Are included in the technical scope.

Hereinafter, the present invention will be specifically described with reference to examples.
(Production Example 1)
4.20 g (6 mmol) of 4,4′-diaminodiphenyl ether was put into a 50 ml three-necked flask, dissolved in 5 ml of dehydrated N-methyl-2-pyrrolidone (NMP), and cooled in an ice bath under a nitrogen stream. While stirring. Pyromellitic dianhydride 1.31 g (6 mmol) was added little by little, and after the addition was completed, the mixture was stirred in an ice bath for 5 hours, and the solution was reprecipitated with dehydrated diethyl ether. The product was dried at room temperature under reduced pressure for 17 hours to obtain 2.11 g (polyimide precursor 1) of a white solid.

Example 1
A 20 wt% dimethylacetamide solution of the polyimide precursor 1 obtained in Production Example 1 is bar-coated on SUS304 (manufactured by Nippon Steel Corporation) with a thickness of 20 μm, and is applied so as to be 18 ± 2 μm after drying. Then, it was dried at 80 ° C. for 30 minutes in a hot air circulating oven. Thereafter, the positive photoresist OFPR-800LB (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is dried and then bar-coated to 10 ± 2 μm, dried in a hot air drying oven at 80 ° C. for 20 minutes, and then on the polyimide precursor layer. A substrate on which a positive photoresist layer was formed was prepared.

Next, using a manual exposure apparatus (MA-1200, manufactured by Dainippon Screen Co., Ltd.), exposure is performed at 950 mJ / cm ² (i-line conversion) through a photomask on which a desired pattern is drawn, and 2.38 wt%. The positive photoresist layer and the polyimide precursor layer were developed simultaneously using a conveyor type spray developing device using a tetramethylammonium hydroxide (TMAH) aqueous solution (liquid temperature 27 ° C.), and then rinsed with distilled water. And dried with warm air to obtain a pattern in which a positive photoresist layer and a polyimide precursor layer were laminated.

The substrate on which the pattern obtained by laminating the positive photoresist layer and the polyimide precursor layer obtained by the above method was formed on the entire surface without using a mask, using an apparatus similar to that used for pattern exposure. The film was exposed at an exposure amount of / cm ² , and then heated at 160 ° C. for 10 minutes in a hot air circulating oven.
The sample was treated with a 2.38 wt% TMAH aqueous solution, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Then, it heat-processed for 350 minutes at 350 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

(Example 2)
A substrate on which a pattern obtained by laminating a positive photoresist layer and a polyimide precursor layer formed in the same manner as in Example 1 was formed on the entire surface without using a mask, using an apparatus similar to that used for pattern exposure. It exposed with the exposure amount of 1 J / cm < ² > in conversion, and heated with the hot-air circulation type oven at 200 degreeC for 10 minutes.
The sample was treated with ethanolamine, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Then, it heat-processed for 350 minutes at 350 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

(Example 3)
A substrate on which a pattern obtained by laminating a positive photoresist layer and a polyimide precursor layer obtained in the same manner as in Example 1 was heated at 200 ° C. for 10 minutes in a hot air circulation oven, and then pattern exposure and Using the same apparatus, the whole surface was exposed with an exposure amount of 1 J / cm ^{2 in} terms of i-line without using a mask.
The sample was treated with ethanolamine, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Then, it heat-processed for 350 minutes at 350 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

Example 4
Instead of the 20 wt% dimethylacetamide solution of the polyimide precursor 1 used in Example 1, a solution (resin composition) in which dimethylpiperidine was added so that the addition amount was 5 wt% with respect to the weight of the polyimide precursor 1 A substrate having a polyimide precursor layer and a positive photoresist layer formed on the polyimide precursor layer was prepared in the same manner as in Example 1 except that 1) was used. Further, in the same manner as in Example 1, a pattern in which a positive photoresist layer and a polyimide precursor layer were laminated was obtained.

The substrate on which the pattern obtained by laminating the positive photoresist layer and the polyimide precursor layer obtained as described above was formed on the entire surface using a device similar to that used for pattern exposure without using a mask. The film was exposed at an exposure amount of / cm ² and heated in a hot air circulation oven at 150 ° C. for 10 minutes.
The sample was treated with a 2.38 wt% TMAH aqueous solution, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Then, it heat-processed for 60 minutes at 300 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

(Example 5)
A substrate on which a pattern obtained by laminating a positive photoresist layer and a polyimide precursor layer obtained in the same manner as in Example 4 was formed on the entire surface without using a mask using an apparatus similar to that used for pattern exposure. Exposure was performed at an exposure amount of 1 J / cm ^{2 in} terms of conversion, and heating was performed at 180 ° C. for 10 minutes in a hot air circulating oven.
The sample was treated with ethanolamine, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Then, it heat-processed for 60 minutes at 300 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

(Example 6)
A substrate on which a pattern obtained by laminating a positive photoresist layer and a polyimide precursor layer obtained in the same manner as in Example 4 was heated at 180 ° C. for 10 minutes in a hot air circulation oven, and then pattern exposure and Using the same apparatus, the whole surface was exposed with an exposure amount of 1 J / cm ^{2 in} terms of i-line without using a mask.
The sample was treated with ethanolamine, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Then, it heat-processed for 60 minutes at 300 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

(Example 7)
Instead of dimethylpiperidine used in Example 4, a solution in which 1,4-diazabicyclo [2,2,2] octane was added so that the amount added was 5% by weight with respect to the weight of polyimide precursor 1 was obtained. A substrate having a polyimide pattern formed on a SUS foil was prepared in the same manner as in Example 4 except for the (resin composition 2) used, and a good polyimide pattern was obtained under the same conditions.

(Example 8)
A substrate on which a pattern obtained by laminating a positive photoresist layer and a polyimide precursor layer obtained in the same manner as in Example 7 was formed on the entire surface without using a mask, using an apparatus similar to that used for pattern exposure. Exposure was performed at an exposure amount of 1 J / cm ^{2 in} terms of conversion, and heating was performed at 180 ° C. for 10 minutes in a hot air circulating oven.
The sample was treated with ethanolamine, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Then, it heat-processed for 60 minutes at 300 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

Example 9
A substrate on which a pattern obtained by laminating a positive photoresist layer and a polyimide precursor layer obtained in the same manner as in Example 7 was heated at 180 ° C. for 10 minutes in a hot air circulation oven, and then pattern exposure and Using the same apparatus, the whole surface was exposed with an exposure amount of 1 J / cm ^{2 in} terms of i-line without using a mask.
The sample was treated with ethanolamine, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Then, it heat-processed for 60 minutes at 300 degreeC under nitrogen stream, and obtained the board | substrate with which the polyimide pattern was formed on SUS foil.

  About Examples 4-9, the temperature which carries out the imidation reaction for changing the solubility of a polyimide precursor may be reduced by adding the basic substance which is a compound which accelerates | stimulates imidation to a polyimide precursor. Therefore, in the step of reducing the solubility of the polyimide precursor layer in the basic solution, the heat treatment temperature can be lowered, and damage to the substrate or the like can be minimized.

<Test example; thermosetting temperature>
The polyimide precursor 1 and the resin composition 1 were each spin-coated on a chromium-plated glass plate to a final film thickness of 2 μm and dried on a hot plate at 100 ° C. for 2 minutes. The infrared spectroscopic spectrum of this coating film was measured using IR-610 manufactured by JASCO Corporation and HOTPLATE EC-1200 manufactured by ASONE Co., Ltd. while heating from room temperature at 5 ° C./min to 350 ° C.
The spectrum derived from the precursor disappeared with heating, and a peak derived from polyimide generated by heating appeared. In order to confirm the progress of imidization, when the peak area of 1663 cm ⁻¹ derived from the precursor before the measurement was set to 1, the amount of decrease in the peak area in the heating process was converted into the imidation rate and plotted. (The state before measurement was 0% imidation, and the time when the peak completely disappeared was taken as 100% imidation.)
The result is as shown in FIG. It was found that the resin composition 1 had a decrease in the precursor at a lower temperature than the polyimide precursor 1 due to the effect of the amine addition.

(Example 10: suspension for hard disk)
SUS304 HTA foil made of Nippon Steel with a thickness of 20 μm—a laminate made of copper alloy foil (NK-120) made of Japan Energy with a thickness of 10 μm polyimide—with a ferric chloride solution using a metal working resist. The Cu surface was etched into the desired shape. Laminate an alkali development type dry film resist for polyimide layer etching on the substrate obtained by stripping the resist, expose it to UV light through a mask of the desired shape, and dry the film with a 1% by weight Na ₂ CO ₃ aqueous solution. The resist was developed. Thereafter, the polyimide layer was etched, and the dry film resist was peeled off with a 3 wt% NaOH aqueous solution. In this way, the insulating layer was wet etched into a desired shape, and a polyimide patterned into the desired shape as an insulating layer was sandwiched on the foil to obtain a substrate on which copper wiring was formed.
On the substrate, (resin composition 1) obtained in Example 4 was bar-coated, dried and coated to 18 ± 2 μm, and dried in a hot air circulation oven at 80 ° C. for 30 minutes. Thereafter, the positive photoresist OFPR-800LB (manufactured by Tokyo Ohka Kogyo Co., Ltd.) is dried and then bar-coated to 10 ± 2 μm, dried in a hot air drying oven at 80 ° C. for 20 minutes, and then on the polyimide precursor layer. A substrate on which a positive photoresist layer was formed was prepared.
Next, using a manual exposure apparatus (MA-1200, manufactured by Dainippon Screen Co., Ltd.), exposure is performed at 950 mJ / cm ² (i-line conversion) through a photomask on which a desired pattern is drawn, and 2.38 wt%. The positive photoresist layer and the polyimide precursor layer were developed simultaneously using a conveyor type spray developing apparatus using an aqueous tetramethylammonium hydroxide (TMAH) solution (liquid temperature 27 ° C.), and then rinsed with distilled water. And dried with warm air to obtain a pattern in which a positive photoresist layer and a polyimide precursor layer were laminated.

The substrate on which the pattern obtained by laminating the positive photoresist layer and the polyimide precursor layer obtained by the above method was formed on the entire surface without using a mask, using an apparatus similar to that used for pattern exposure. The film was exposed at an exposure amount of / cm ² , and then heated at 160 ° C. for 10 minutes in a hot air circulating oven.
The sample was treated with a 2.38 wt% TMAH aqueous solution, rinsed with distilled water, and only the positive photoresist pattern was peeled off. Thereafter, heat treatment was performed at 350 ° C. for 60 minutes in a nitrogen stream to obtain a substrate on which a polyimide pattern was formed as a wiring protective layer.
Thereafter, the SUS foil was etched into a desired shape with a ferric chloride solution using a metal working resist to obtain a hard disk suspension.

It is process drawing which shows an example of the formation method of the polyimide pattern which concerns on this invention. It is a typical sectional view of an example of a suspension for hard disks concerning the present invention. It is a graph which shows the relationship between the thermosetting temperature in the polyimide precursor 1 and the said resin composition 1, and the imidation ratio of a polyimide precursor.

Claims (15)

The following steps (A) to (G);
(A) forming a polyimide precursor layer on the substrate;
(B) forming a positive photoresist layer on the polyimide precursor layer;
(C) a pattern exposure step for selectively exposing the positive photoresist layer;
(D) a development step of selectively removing and patterning the underlying polyimide precursor layer after or simultaneously with the development of the positive photoresist layer;
(E) an overall exposure process for exposing the entire surface of the patterned positive photoresist layer;
(F) a step of reducing solubility in a basic aqueous solution or a water-soluble basic substance by at least partially imidizing the patterned polyimide precursor layer;
(G) A method for forming a polyimide pattern comprising: a peeling step of peeling the patterned positive photoresist layer with a basic aqueous solution or a water-soluble basic substance.   The method for forming a polyimide pattern according to claim 1, further comprising (H) a step of polyimidizing the patterned polyimide precursor layer.   The formation method of the polyimide pattern of Claim 1 or 2 which contains the compound which accelerates | stimulates imidation in the said polyimide precursor layer in the said (A) process.   The method for forming a polyimide pattern according to claim 3, wherein the compound that promotes imidization is an amine.   The method for forming a polyimide pattern according to claim 4, wherein the amine is an aliphatic amine.   The said polyimide precursor layer in the said (A) process WHEREIN: The compound which accelerates | stimulates imidation with respect to 100 weight part of polyimide precursors contains 0.1 to 40 weight part. A method for forming a polyimide pattern according to claim 1.   The formation method of the polyimide pattern in any one of Claims 1 thru | or 6 whose linear thermal expansion coefficient of the obtained polyimide pattern is 1 ppm / degrees C-40 ppm / degrees C.   The method for forming a polyimide pattern according to any one of claims 1 to 7, wherein the resultant polyimide pattern has a hygroscopic expansion coefficient of 1 ppm /% RH to 40 ppm /% RH.   The method for forming a polyimide pattern according to any one of claims 1 to 8, wherein the basic aqueous solution in the steps (F) and (G) is a tetramethylammonium hydroxide aqueous solution.   The method for forming a polyimide pattern according to claim 9, wherein the tetramethylammonium hydroxide concentration in the tetramethylammonium hydroxide aqueous solution is 0.1 wt% to 70 wt%.   The step (F) is a heating step before resist peeling for heating the substrate on which the patterned positive photoresist layer and the patterned polyimide precursor layer are formed, and the heating temperature is 100 ° C. to The formation method of the polyimide pattern in any one of Claims 1 thru | or 10 which is 250 degreeC.   An article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member having a polyimide pattern formed by using the polyimide pattern forming method according to any one of claims 1 to 11.   The article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, and an optical member according to claim 12, wherein the polyimide pattern is formed on stainless steel or surface-treated stainless steel.   The article of any one of a semiconductor device, an electronic component, an optical circuit, an optical circuit component, or an optical member according to claim 13, wherein the stainless steel or the surface-treated stainless steel has a thickness of 1 μm to 50 μm.   A suspension for a hard disk having a polyimide pattern formed by using the method for forming a polyimide pattern according to any one of claims 1 to 11.

Images