JP2006071783A - Photosensitive resin composition and method for producing fine pattern using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a practically useful and alcohol-developable negative photosensitive resin composition having high transparency, a low dielectric constant, a low coefficient of thermal expansion, a high glass transition temperature and satisfactory toughness, and to provide a method for producing a fine pattern using the same. <P>SOLUTION: The photosensitive resin composition contains a polyimide precursor having a repeating unit represented by formula (1), a crosslinking agent, a crosslinking aid and a photopolymerization initiator. In the method for producing a fine pattern, the photosensitive resin composition is shaped into a film by casting and drying on a substrate, and this film is exposed through a photomask, developed with alcohol, glycol or monoalkyl ether of glycol, and subjected to dehydration ring closure by heating or with a cyclodehydrating reagent to form a polyimide film having a repeating unit represented by formula (2). <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a photosensitive resin composition and a method for producing a fine pattern using the same, and more specifically, a negative photosensitive material comprising a highly transparent polyimide precursor, a crosslinking agent, a crosslinking aid and a photopolymerization initiator. The composition, and after exposure to light, developed with alcohol, glycol, monoalkyl ethers of glycol and finely processed, and then obtained by imidization reaction, low dielectric constant, low thermal expansion coefficient, high glass transition temperature In addition, the present invention relates to a method for producing a practically useful polyimide film fine pattern having sufficient toughness.

Polyimide has not only excellent heat resistance but also chemical resistance, radiation resistance, electrical insulation, excellent mechanical properties, etc., so it can be used for flexible printed circuit boards, tape automation bonding substrates, and semiconductors. Currently, it is widely used in various electronic devices such as protective films for elements and interlayer insulating films for integrated circuits.
Polyimide generally has a high degree of polymerization obtained by equimolar reaction of an aromatic tetracarboxylic dianhydride such as pyromellitic anhydride and an aromatic diamine such as diaminodiphenyl ether in an aprotic polar organic solvent such as dimethylacetamide. The polyimide precursor is formed into a film and cured by heating.
However, in order to maintain the heat resistance of polyimide, in terms of molecular design, the skeleton structure must be rigid, and as a result, many polyimides are insoluble in organic solvents and do not melt above the glass transition temperature. Molding is usually not easy.
Therefore, generally, a method is used that uses a polyimide precursor that exhibits high solubility in an amide organic solvent. Specifically, a polyimide film is formed by applying an aprotic organic solvent solution of a polyimide precursor onto a metal substrate and drying, followed by heat dehydration ring-closing (imidization) reaction at 250 ° C. to 350 ° C.
Thermal stress generated in the process of cooling the polyimide / metal substrate laminate from the imidization temperature to room temperature (25 ° C.) often causes serious problems such as curling, film peeling and cracking. Recently, with the increasing density of electronic circuits, multilayer wiring boards have come to be used. However, even if film peeling or cracking does not occur, residual stress in the multilayer board significantly increases device reliability. Reduce.
The stress generated in the imidization process increases as the difference in coefficient of linear thermal expansion between the metal substrate and the polyimide film increases and as the imidization temperature increases.
One way to reduce thermal stress is to reduce the thermal expansion of polyimide. Most polyimides have a linear thermal expansion coefficient in the range of 50 to 90 ppm / K, which is much larger than the linear thermal expansion coefficient of 17 ppm / K for metal substrates, such as copper, so it is close to the value of copper, approximately 20 ppm / K or less. Research and development of the low thermal expansion polyimide shown is underway.
In general, it has been reported that lowering the thermal expansion of polyimide is a necessary condition that the main chain structure is linear and the internal rotation is constrained and rigid (see Non-Patent Document 1, for example).
As a practically low thermal expansion polyimide material, polyimide formed from 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride and paraphenylenediamine is best known. This polyimide film is known to exhibit a very low linear thermal expansion coefficient of 5 to 10 ppm / K depending on the film thickness and production conditions (see, for example, Non-Patent Document 2).
In recent years, increasing the calculation speed of microprocessors and shortening the rise time of clock signals have become important issues in the information processing and communication fields. To that end, the dielectric of polyimide films used as insulating films It is necessary to lower the rate. Also, for high-density wiring and a multilayer substrate for shortening the electrical wiring length, the lower the dielectric constant of the insulating film is advantageous in that the insulating layer can be made thinner.
In order to lower the dielectric constant of polyimide, it is effective to introduce a fluorine substituent into the skeleton (for example, see Non-Patent Document 3). For example, a fluorinated polyimide film obtained from 2,2-bis (3,4-carboxyphenyl) hexafluoropropanoic dianhydride and 2,2′-bis (trifluoromethyl) benzidine was estimated from the average refractive index. The dielectric constant is 2.65, which is a very low value (see, for example, Non-Patent Document 4).
In addition, replacing aromatic units with alicyclic units to reduce π electrons is an effective means for reducing the dielectric constant (see, for example, Non-Patent Document 5). For example, a non-aromatic polyimide film obtained from 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 4,4′-methylenebis (cyclohexylamine) has a dielectric constant estimated from an average refractive index of 2. 6 shows a very low value (see Non-Patent Document 6, for example).
However, a polyimide having a low dielectric constant (3.0 or less as a temporary target value) and a low thermal expansion coefficient (25 ppm / K or less as a temporary target value) at the same time and having solder heat resistance is obtained. This is not easy in terms of molecular design. Low dielectric constant polymer materials and inorganic materials other than polyimide are also being studied, but at present the required properties are not sufficiently satisfied in terms of dielectric constant, linear thermal expansion coefficient, heat resistance and toughness.
In general, when a fluorine substituent is introduced into the polyimide skeleton, the intermolecular interaction is weakened, and the spontaneous molecular orientation during imidation, which is a cause of low thermal expansion, tends to be disturbed. Further, excessive fluorination is disadvantageous in terms of cost. For example, total fluorine obtained from fluorinated acid dianhydride, 2,2-bis (3,4-carboxyphenyl) hexafluoropropanoic acid dianhydride and fluorinated diamine, 2,2'-bis (trifluoromethyl) benzidine As described above, the polyimide film exhibits a very low dielectric constant, but its linear thermal expansion coefficient is as extremely high as 64 ppm / K, and does not satisfy the low thermal expansion characteristics (see, for example, Non-Patent Document 4).
Also, the introduction of alicyclic structural units often causes a problem that the linearity and rigidity of the polyimide main chain skeleton are lowered and the linear thermal expansion coefficient is increased. For example, when a highly flexible alicyclic diamine such as 4,4′-methylenebis (cyclohexylamine) is used, the polymerization proceeds easily with various acid dianhydrides to produce a polyimide precursor with a high degree of polymerization. However, the polyimide film obtained by the ring closure reaction does not exhibit low thermal expansion characteristics.
A polyimide film obtained from 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 4,4′-methylenebis (cyclohexylamine) exhibits a low dielectric constant as described above, but its linear thermal expansion coefficient is 63 ppm / K is very high and does not show low thermal expansion characteristics.
On the other hand, when a rigid alicyclic diamine or trans-1,4-cyclohexanediamine is used in place of the flexible alicyclic diamine in order to develop low thermal expansion characteristics, strong salt formation occurs during polymerization of the polyimide precursor. Often, there is a problem that the polymerization reaction does not proceed.
For example, a polyimide composed of 1,2,3,4-cyclobutanetetracarboxylic dianhydride and trans-1,4-cyclohexanediamine has a rigid and relatively linear skeleton, so that it has a low heat resistance in addition to a low dielectric constant. Expected to exhibit expansion characteristics. In practice, however, it is difficult to polymerize the polyimide precursor for the above reasons.
In recent years, research and development of photosensitive polyimide (or its precursor), which greatly shortens the fine pattern formation process of polyimide film, has been actively conducted, but it has the low dielectric constant, low thermal expansion, and high glass transition temperature. If photosensitivity can be further imparted to the polyimide system, a material extremely useful in the industrial field can be provided.
Recently, in consideration of the environment, the importance of a positive photosensitive polyimide precursor for alkali development is increasing compared to a negative type in which development is performed with an organic solvent.
Dispersing a diazonaphthoquinone photosensitizer as a dissolution inhibitor in an alkali-soluble polyimide precursor (polyamide acid) film reduces the solubility in alkali, and the photosensitizer in the exposed area becomes hydrophilic indenecarboxylic acid. Because of the change, a difference in solubility occurs between the exposed portion and the unpassed rear portion, so that a positive fine pattern can be formed in principle. However, since polyamic acid is too soluble in an aqueous tetramethylammonium hydroxide solution generally used as an alkali developer for semiconductor resists, the effect of adding a dissolution inhibitor is insufficient, and in many cases a sharp pattern is formed. Is difficult. For this reason, since it is necessary to perform some chemical modification to the structure of the polyamic acid and to control the solubility in the aqueous alkali solution, the process is complicated.
On the other hand, in the case of a negative polyimide precursor, a technique is used in which an acryl group or a methacryl group is bonded to a carboxy group of a polyimide precursor, and is crosslinked by generation of a radical from a photopolymerization initiator to insolubilize an exposed portion in a solvent. In this case, a covalent bond such as an ester bond and a salt bond (ionic bond) between a carboxy group and a tertiary amine are known as the bonding mode. In the case of the salt bond type, the polyimide precursor and an acrylic group or methacryl group-containing tertiary amine need only be mixed in a solution, and the process is extremely simple.
In any case of the negative type, since the unexposed portion must be dissolved and removed with a solvent, a developer containing an amide organic solvent that dissolves the polyimide precursor well is usually used. For this reason, the negative photosensitive polyimide precursor still has a problem in that it places a burden on the environment in the development process.
Normally, polyimide precursors are insoluble in amide-based aprotic solvents such as N-methyl-2-pyrrolidone and N, N-dimethylacetamide, and alkaline aqueous solutions, but can be dissolved in monoalkyl ethers of alcohol, glycol and glycol. For example, it is possible to obtain a negative photosensitive polyimide precursor having a low environmental impact.
In the case of the positive type, a diazonaphthoquinone photosensitizer having strong absorption in the ultraviolet region is mixed in a large amount in the polyimide precursor film, so it is difficult to increase the thickness of the photosensitive layer and is usually about several microns. . On the other hand, in the negative type, the absorption intensity of the crosslinking agent, crosslinking aid, and photopolymerization initiator used for ultraviolet rays (for example, the wavelength of i-line of a high-pressure mercury lamp, 365 nm) is low, and the photosensitive layer can be thickened. .
For this reason, the transparency of the polyamic acid is also important. In the case of exposure with i-line, if the transmittance of the film at this wavelength is not sufficiently high, the irradiation light is shielded by the polyamic acid itself and it is difficult for the light to reach the photosensitive agent. In this case, the photoreaction of the photosensitizer is hindered and the pattern cannot be formed.

“Polymer”, 28, 1987, p. 2282-2288 “Macromolecules”, 29, 1996, p. 7897-7909 “Macromolecules”, 24, 1991, p. 5001-5005 “High Performance Polymers”, Volume 15, 2003, p. 47-64 “Macromolecules”, 32, 1999, p. 4933-4939 “Reactive and Functional Polymers”, Vol. 30, 1996, p. 61-69

  The present invention relates to a negative photosensitive resin composition comprising a highly transparent polyimide precursor, a crosslinking agent, a crosslinking auxiliary agent and a photopolymerization initiator, and alcohol, glycol or glycol after exposure to the negative photosensitive resin composition. This is a practically useful polyimide film that has a low dielectric constant, a low thermal expansion coefficient, a high glass transition temperature, and sufficient toughness. A method for manufacturing a pattern is provided.

In view of the above problems, as a result of intensive studies, polyimide precursors are polyimides of 1,2,3,4-cyclobutanetetracarboxylic dianhydride and 2,2′-bis (trifluoromethyl) benzidine. The precursor does not cause any salt formation which is a problem in the polymerization reaction, and can easily obtain a high molecular weight. Further, the polyimide film has a low dielectric constant (2.66) and a low thermal expansion coefficient (21 ppm / K). ) And a high glass transition temperature (356 ° C.) at the same time, and it has been found to be optimal as a material satisfying the required characteristics of the polyimide film. In the present invention, this polyimide precursor is used.
That is, this invention relates to the photosensitive resin composition formed by containing the polyimide precursor which has a repeating unit represented by Formula (1), a crosslinking agent, a crosslinking adjuvant, and a photoinitiator.

また本発明は、前記感光性樹脂組成物を有機溶媒溶液として基板上に流延・乾燥して製膜し、フォトマスクを介してこれを露光し、アルコール、グリコールまたはグリコールのモノアルキルエーテルで現像後、加熱あるいは脱水環化試薬を用いて脱水閉環して、式（２）で表される繰り返し単位を有するポリイミド膜とすることを特徴とする、微細パターンの製造方法に関する。

In the present invention, the photosensitive resin composition is cast as an organic solvent solution on a substrate, dried to form a film, exposed through a photomask, and developed with alcohol, glycol or a monoalkyl ether of glycol. Then, the present invention relates to a method for producing a fine pattern, characterized in that a polyimide film having a repeating unit represented by the formula (2) is formed by dehydration and ring closure using heating or a dehydrating cyclization reagent.

  The present invention uses a resin composition containing a highly transparent polyimide precursor, a crosslinking agent, a crosslinking auxiliary agent, and a photopolymerization initiator, so that it can be developed with the above-mentioned solvent having a low environmental load, and its cured film. Provides a fine pattern with low dielectric constant, low thermal expansion coefficient, and high glass transition temperature, and can be used for various electronic devices such as cover materials for flexible printed wiring boards, protective films for semiconductor elements and interlayer insulating films for integrated circuits. is there.

The present invention is described in detail below.
The polyimide precursor used by this invention can be obtained by superposing | polymerizing as follows. First, diamine component 2,2'-bis (trifluoromethyl) benzidine is dissolved in a well-dehydrated polymerization solvent, and equimolar 1,2,3,4-cyclobutanetetracarboxylic dianhydride is added to this solution. The product powder is gradually added, and the mixture is stirred at room temperature (25 ° C.) for 1 to 24 hours using a mechanical stirrer. In this case, the monomer concentration is preferably 5 to 40% by weight, more preferably 10 to 30% by weight.
Particularly in applications that require film toughness, it is preferable to increase the monomer concentration during polymerization in order to further increase the molecular weight of the polyimide precursor.
As a polymerization solvent, N, N-dimethylacetamide, N, N-diethylacetamide, N, N-dimethylformamide, N-methyl-2-pyrrolidone, hexamethylphosphoramide, dimethylsulfoxide, γ-butyrolactone, 1,3 -Protons such as dimethyl-2-imidazolidinone, 1,2-dimethoxyethane-bis (2-methoxyethyl) ether, terahydrofuran, 1,4-dioxane, picoline, pyridine, acetone, chloroform, toluene, xylene And protic solvents such as phenol, o-cresol, m-cresol, p-cresol, o-chlorophenol, m-chlorophenol, and p-chlorophenol can be used. These solvents may be used alone or in combination of two or more.

Other diamines may be used as long as the polymerization reactivity of the polyimide precursor according to the present invention, the transparency of the film, the solubility in a developer, the fine pattern processability, and the required characteristics of the polyimide film are not significantly impaired.
The aromatic diamine that can be used in addition to 2,2′-bis (trifluoromethyl) benzidine is not particularly limited, but p-phenylenediamine, m-phenylenediamine, 2,4-diaminotoluene, 2,5-diaminotoluene. 2,4-diaminoxylene, 2,4-diaminodurene, 4,4′-diaminodiphenylmethane, 4,4′-methylenebis (2-methylaniline), 4,4′-methylenebis (2-ethylaniline), 4 , 4'-methylenebis (2,6-dimethylaniline), 4,4'-methylenebis (2,6-diethylaniline), 4,4'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 3,3'- Diaminodiphenyl ether, 2,4′-diaminodiphenyl ether, 4,4′-diaminodiphenyl sulfone, 3, 3'-diaminodiphenylsulfone, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminobenzanilide, benzidine, 3,3'-dihydroxybenzidine, 3,3'-dimethoxybenzidine, o-tolidine, m-tolidine, 1,4-bis (4-aminophenoxy) benzene, 1,3-bis (4-aminophenoxy) benzene, 1,3-bis (3-aminophenoxy) benzene, 4,4 '-Bis (4-aminophenoxy) biphenyl, bis (4- (3-aminophenoxy) phenyl) sulfone, bis (4- (4-aminophenoxy) phenyl) sulfone, 2,2-bis (4- (4- Aminophenoxy) phenyl) propane, 2,2-bis (4- (4-aminophenoxy) phenyl) hexafluoropropa , 2,2-bis (4-aminophenyl) hexafluoropropane, p- terphenyl-phenylenediamine, and the like as examples. Two or more of these may be used in combination.

  Further, usable aliphatic diamines are not particularly limited, but trans-1,4-diaminocyclohexane, cis-1,4-diaminocyclohexane, 1,4-diaminocyclohexane (trans / cis mixture), 1,3- Diaminocyclohexane, isophoronediamine, 1,4-cyclohexanebis (methylamine), 2,5-bis (aminomethyl) bicyclo [2.2.1] heptane, 2,6-bis (aminomethyl) bicyclo [2.2 .1] Heptane, 3,8-bis (aminomethyl) tricyclo [5.2.1.0] decane, 1,3-diaminoadamantane, 4,4'-methylenebis (cyclohexylamine), 4,4'-methylenebis (2-methylcyclohexylamine), 4,4′-methylenebis (2-ethylcyclohexylamine), 4,4'-methylenebis (2,6-dimethylcyclohexylamine), 4,4'-methylenebis (2,6-diethylcyclohexylamine), 2,2-bis (4-aminocyclohexyl) propane, 2,2-bis (4-aminocyclohexyl) hexafluoropropane, 1,3-propanediamine, 1,4-tetramethylenediamine, 1,5-pentamethylenediamine, 1,6-hexamethylenediamine, 1,7-heptamethylenediamine, 1 , 8-octamethylenediamine, 1,9-nonamethylenediamine and the like. Two or more of these may be used in combination.

  Polymerization reactivity of the polyimide precursor according to the present invention, film transparency, solubility in developer, fine pattern processability and 1,2,3,4-cyclobutanetetracarboxylic as long as the required characteristics of the polyimide film are not significantly impaired. A part of the acid dianhydride component other than the acid dianhydride may be partially used. The tetracarboxylic dianhydride used for copolymerization is not particularly limited, but pyromellitic dianhydride, 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride, 3,3 ′, 4, 4′-benzophenone tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenyl ether tetracarboxylic dianhydride, 3,3 ′, 4,4′-biphenylsulfone tetracarboxylic dianhydride, 2 , 2′-bis (3,4-dicarboxyphenyl) hexafluoropropanoic dianhydride, 2,2′-bis (3,4-dicarboxyphenyl) propanoic dianhydride, 1,4,5,8 -Naphthalene tetracarboxylic dianhydride etc. are mentioned. These may be used alone or in combination of two or more as copolymerization components.

  In the obtained organic solvent solution of the polyimide precursor, the polyimide precursor is 100 parts by weight, and the crosslinking agent is preferably 1 to 100 parts by weight, more preferably 5 to 50 parts by weight, and a crosslinking aid is preferable with respect to the polymer. Is 0.5 to 50 parts by weight, more preferably 1 to 30 parts by weight, and the photopolymerization initiator is preferably added to and dissolved at 0.1 to 10 parts by weight, more preferably 1 to 7 parts by weight, It can be set as the photosensitive resin composition of the present invention. If the content of the crosslinking agent, crosslinking aid, and photopolymerization initiator is lower than the above concentration range, the photocrosslinking reaction does not occur sufficiently and the exposed area may not be completely eliminated. On the other hand, when the concentration is higher than the above range, a uniform and transparent cast film may not be obtained. This is coated on a substrate of copper, silicon, glass or the like using a spin coater or bar coater, and dried in warm air at 40 to 120 ° C. for 0.1 to 3 hours under light shielding to obtain a negative having a film thickness of 0.1 to 50 μm. Type photosensitive polyimide precursor film can be obtained.

  Although it does not specifically limit as a crosslinking agent which can be used, A vinyl group containing tertiary amine compound, such as methacrylic acid 2-dimethylaminoethyl ester and acrylic acid 2-dimethylaminoethyl ester, is mentioned as a preferable example. These may be used alone or in combination of two or more.

Although it does not specifically limit as a crosslinking adjuvant which can be used, Divinyl compounds, such as adipic acid divinyl ester, methacrylic acid vinyl ester, and acrylic acid vinyl ester, are mentioned as a preferable example. These may be used alone or in combination of two or more.
Since many of these commercially available vinyl group-containing compounds contain a polymerization inhibitor such as hydroquinone or p-methoxyphenol, the polymerization inhibitor should be removed by vacuum distillation or column separation before use. Is preferred.

  Although it does not specifically limit as a photoinitiator which can be used, 2-Benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1,2,2-dimethoxy-1,2-diphenylethane-1- Preferred examples include photo radical generators such as ON, 1-hydroxycyclohexyl phenyl ketone, and 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropan-1-one. These may be used alone or in combination of two or more.

The photosensitive resin composition film is irradiated with i-line of a high-pressure mercury lamp through a photomask at room temperature (25 ° C.) for 10 seconds to 1 hour, and alcohol, glycol, or monoalkyl ether of glycol is used for 10 seconds at room temperature. A clear negative pattern can be obtained by developing for 10 minutes and rinsing with pure water.
Examples of alcohols that can be used for development include primary alcohols such as methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, and 2-butanol.

Examples of glycols that can be used for development include ethylene glycol and propylene glycol. These may be used alone or in combination of two or more.
Examples of glycol monoalkyl ethers that can be used for development include ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. These may be used alone or in combination of two or more.

Heat-treating the fine pattern of the polyimide precursor formed on the substrate in air, in an inert gas atmosphere such as nitrogen or in vacuum, preferably at a temperature of 200 ° C. to 430 ° C., more preferably 250 ° C. to 400 ° C. A clear polyimide film pattern can be obtained.
Imidization can also be performed chemically using a dehydrating cyclization reagent. That is, a polyimide film is also obtained by a method in which a poly (amide acid-imide) copolymer film formed on a substrate is immersed in acetic anhydride containing a basic catalyst such as pyridine or triethylamine at room temperature for 1 minute to several hours. be able to.
In the obtained polyimide film, additives such as an oxidation stabilizer, a terminal blocking agent, a filler, a silane coupling agent, a photosensitizer, and a sensitizer may be mixed as necessary.

EXAMPLES The present invention will be specifically described below with reference to examples, but it should not be construed that the invention is limited thereto. In addition, the analytical value in each example was calculated | required with the following method.
<Intrinsic viscosity>
A 0.5 wt% polyimide precursor solution was measured at 30 ° C. using an Ostwald viscometer.
<Glass transition temperature (Tg)>
The dynamic viscoelasticity was measured from the loss peak at a frequency of 0.1 Hz and a heating rate of 5 ° C./min.
<5% weight loss temperature (Td ⁵ )>
The thermogravimetric change of the polyimide film was measured, and the temperature at which the weight was reduced by 5% was determined.
<Linear thermal expansion coefficient (CTE)>
The linear thermal expansion coefficient was determined as an average value in the range of 100 to 200 ° C. from the elongation of the test piece at a load of 0.5 g / film thickness of 1 μm and a heating rate of 5 ° C./min.
<Birefringence (Δn)>
The refractive index in the direction parallel to the polyimide film (nin) and the direction perpendicular to the polyimide film (nout) is measured with an Abbe refractometer (using a sodium lamp, wavelength 589 nm), and birefringence (Δn = nin−nout) is determined from the difference between these refractive indexes. )
<Dielectric constant>
Based on the average refractive index [nav = (2nin + nout) / 3] of the polyimide film, the dielectric constant (ε) at 1 MHz was calculated by the following formula.
ε = 1.1 × nav2

Example 1
In a closed reaction vessel equipped with a stirrer, 20 mmol (6.405 g) of 2,2′-bis (trifluoromethyl) benzidine was placed and dissolved in 16.68 g of N, N-dimethylacetamide sufficiently dehydrated with Molecular Sieves 4A. 20 mmol (3.922 g) of 1,2,3,4-cyclobutanetetracarboxylic dianhydride powder was gradually added. The mixture was stirred at room temperature (25 ° C.) for 24 hours to obtain a transparent, uniform and viscous polyimide precursor solution. The intrinsic viscosity of the polyimide precursor measured at 30 ° C. in N, N-dimethylacetamide was 1.56 dL / g. A polyimide precursor film (film thickness 20 μm) obtained by casting this polymerization solution on a glass substrate and drying at 60 ° C. for 2 hours has a cutoff wavelength of 299 nm and a wavelength of i-line (365 nm) of a high-pressure mercury lamp. The transmittance was 88%, indicating extremely high transparency.
Next, in the polyimide precursor solution, 1 equivalent (60.9% by weight) of 2-dimethylaminoethyl methacrylate as a crosslinking agent with respect to the carboxy group of the polyamic acid and 1/2 of adipic acid divinyl ester as a crosslinking aid are added. Equivalent (38.4 wt%), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) butanone-1 (1-7 wt%) as a photopolymerization initiator is mixed and dissolved uniformly. It was. This solution was cast on a glass substrate surface-treated with a silane coupling agent and dried in a hot air dryer at 60 ° C. for 2 hours to obtain a photosensitive film having a thickness of 10 to 20 μm. The absorbance at the i-line wavelength was 1.0 to 1.4. This was irradiated with i-line of an epi-illumination type high-pressure mercury lamp through an interference filter for 5 to 10 minutes through a photomask. The irradiation light intensity is approximately 3 mW / cm 2. After development with propylene glycol monomethyl ether at 25 ° C. for 1 to 5 minutes, rinsing with water was performed, and a clear pattern with a line width of 20 μm was obtained. This was subjected to thermal imidization at 330 ° C. for 2 hours under reduced pressure, and a clear polyimide film pattern having a line width of 20 μm was obtained. No pattern collapse due to imidization was observed. When development was performed using ethanol and an aqueous ethanol solution (50 to 75% by volume), a clear pattern having a line width of 20 μm was obtained in the same manner.

(Example 2)
The photosensitive resin composition film described in Example 1 was subjected to thermal imidization on a substrate at 330 ° C. for 2 hours in a vacuum to remove residual strain, and then removed from the substrate and further subjected to heat treatment at 335 ° C. for 1 hour. A transparent and tough polyimide film having a thickness of 10 μm was obtained. The physical properties of the polyimide film are as follows. The dielectric constant estimated from the average refractive index was 2.67, which was an extremely low dielectric constant. The linear thermal expansion coefficient was 18 ppm / K, which was a low linear thermal expansion coefficient comparable to that of a copper substrate. Judging from the birefringence value (Δn = 0.071), this is due to the fact that the polyimide chains are actually in-plane oriented to some extent. The glass transition point obtained from the dynamic viscoelasticity measurement was 352 ° C. Thus, the photosensitive resin composition (polyimide) film of the present invention satisfies a low dielectric constant, a low thermal expansion coefficient, and a high glass transition temperature. It was found that the decrease in storage modulus above the glass transition temperature was very small and there was almost no thermoplasticity. The 5% weight loss temperature was 459 ° C. in nitrogen and 450 ° C. in air, indicating a sufficiently high thermal stability. These physical properties of the polyimide film were almost the same as those of the polyimide film prepared without using a crosslinking agent, a crosslinking auxiliary agent, and a photopolymerization initiator. This is presumably because additives such as a crosslinking agent, a crosslinking auxiliary agent, a photopolymerization initiator and the like were almost volatilized out of the film during thermal imidization at a high temperature.

(Comparative Example 1)
A polyimide precursor was polymerized from trans-1,4-diaminocyclohexane and 3,3 ′, 4,4′-biphenyltetracarboxylic dianhydride. A polyimide film obtained by thermal imidization of this exhibited a low dielectric constant (3.15) and a low thermal expansion coefficient (10 ppm / K). However, the photosensitive polyimide precursor film produced according to the method described in Example 1 is soluble and developable in an organic solvent containing an amide aprotic solvent such as N-methylpyrrolidone or N, N-dimethylacetamide. However, it was insoluble in ethanol and propylene glycol monomethyl ether, and it was difficult to develop with an environmentally low load solvent.

Claims (5)

The photosensitive resin composition formed by containing the polyimide precursor which has a repeating unit represented by Formula (1), a crosslinking agent, a crosslinking adjuvant, and a photoinitiator.

The photosensitive resin composition according to claim 1, wherein the crosslinking agent is a tertiary amine compound having an acryloyl group or a methacryloyl group. The cross-linking agent is 1 to 100 parts by weight, the cross-linking auxiliary agent is 0.5 to 50 parts by weight and the photopolymerization initiator is 0.1 to 10 parts by weight with respect to 100 parts by weight of the polyimide precursor. 2. The photosensitive resin composition according to 2. The photosensitive resin composition according to claim 1 or 2, which is soluble in any one of alcohol, glycol, and monoalkyl ethers of glycol. A photosensitive resin composition according to any one of claims 1 to 4 is cast on a substrate and dried to form a film, which is exposed through a photomask, and alcohol, glycol or monoalkyl of glycol A method for producing a fine pattern, characterized in that after development with ether, a polyimide film having a repeating unit represented by formula (2) is obtained by heating or dehydrating and ring-closing using a dehydrating cyclization reagent.