JPS62253621A - Polyimide resin - Google Patents

Abstract

PURPOSE:To obtain a polyimide resin suitable as semiconductor element, module base, etc., having low thermal expansion, improved hydrolytic resistance, heat resistance and processing properties of wet etching, obtained by reacting a specific diamine with a tetracarboxylic acid. CONSTITUTION:(A) A tetracarboxylic acid containing >=25mol% pyromellitic acid and (B) a diamine (e.g. p-phenylenediamine, etc.) shown by formula I, II, or III (R is alkyl; n and m are 0-4) are dissolved in a solvent (e.g. N- methylpyrrolidone, etc.) and reacted at 0-200 deg.C to give polyamic acid varnish. The varnish is processed into a film, coated, heated, dried and imidated to give the aimed resin.

Description

[Detailed Description of the Invention] [Industrial Field of Application] The present invention has low thermal expansion and excellent properties such as hydrolysis resistance and heat resistance. Semiconductor elements, module substrates,
The present invention relates to polyimide resins useful for flexible printed circuit boards and the like, and particularly to polyimide resins with excellent wet etching processability.

[Conventional technology]

Conventional polyimides are obtained from diamino compounds and tetracarboxylic acids or derivatives thereof (for example,
6-10999). This polyimide has excellent heat resistance and mechanical properties, and is known to be useful for space equipment, semiconductor parts, and the like. Furthermore, it has been discovered that polyimide, which has a certain special chemical structure, has an extremely small coefficient of thermal expansion that would be unimaginable under the conventional wisdom of organic materials (for example, Japanese Patent Application No. 139438/1983; Publication No. 59-180549).

[Problem that the invention seeks to solve]

However, this type of low thermal expansion polyimide has a problem in that it cannot be processed by wet etching, which is important for application to semiconductor products and the like.

On the other hand, even with these polyimides, wet etching is possible when the imidization reaction is not completed, but the wet etching speed when the imidization reaction is not completed changes significantly due to slight variations in the imidization rate, etc. Therefore, there is a problem that it cannot be used practically.

SUMMARY OF THE INVENTION In order to solve these problems, it is an object of the present invention to provide a wet-etchable polyimide resin.

[Means and effects for solving the problems] The present inventors measured the wet etching rate and thermal expansion coefficient of polyimides having various chemical structures, and proposed a material that satisfies both.

As a result, it was found that a certain combination of polyimides satisfied both of the above characteristics.

The present invention was made based on this knowledge, and provides a polyimide resin comprising a copolymer of a diamine unit and a tetracarboxylic acid component, wherein the diamine unit is a copolymer of a tetracarboxylic acid component.

[R is an alkyl group, rh and m are integers of 0 or more and 4 or less] A polyimide resin characterized by being at least one member of the group consisting of the following, and being the tetracarboxylic acid unit.

The diamine unit used in the structure of the present invention is as follows:
For example, P-phenylenediamine, 2,5-diaminotoluene, 2,6-diaminodurene.

2,5-diamino-1,3,4-)-limethylbenzene or diaminodurene. In terms of heat resistance, P-phenylenediamine is the best.

In addition, those used as pyromellitic acid units include:
This halide in addition to pyromellitic acid.

There are anhydrides and esters.

Another tetracarboxylic acid unit contained in the polyimide resin according to the present invention is 3.3'.

4.4'-biphenyltetracarboxylic acid derivatives, 3.
3',4,4'-benzophenonetetracarboxylic acid derivatives and the like can be used. but.

If something other than these pyromellitic acids is used, the thermal expansion coefficient will be 3.3' or a pyromellitic acid derivative.

4.It is larger than when using a 4'-biphenyltetracarboxylic acid derivative. Furthermore, if the proportion of the pyromellitic acid derivative is too large, the hydrolysis resistance will be significantly reduced and the material will also become mechanically brittle.

Therefore, as the tetracarboxylic acid component, it is desirable to use a pyromellitic acid derivative and a 3.3',4,4'-biphenyltetracarboxylic acid derivative together, and the ratio thereof is 25:75 to 75:25 mol%, respectively. The range of questions is good. When the pyromellitic acid derivative is less than 25 mol%, the wet etching rate hardly changes;
Beyond that, it speeds up rapidly. Furthermore, if the amount of the pyromellitic acid derivative exceeds 75 mol%, the hydrolysis resistance and mechanical strength will rapidly deteriorate.

In the above polyimide resin according to the present invention, other diamines and other additives may be added to the extent that the basic physical properties are not impaired. In some cases, it is preferable to introduce a diamine skeleton with soft bonds. Such diamines include m-phenylenediamine, 2,4-diaminotoluene, diaminodiphenyl ether, diaminobenzophenone, diaminodiphenylmethane, diaminosulfide, diaminodiphenylsulfone, 2.2-
Dianilinopropane, 1,4-bis(aminophenoxy)benzene, 4,4'-bis(aminophenoxy)biphenyl, 4,4'-bis(aminophenoxy)diphenyl ether, 4゜4'-bis(aminophenoxy)diphenyl Sulfone, 2,2-bis((aminophenoxy)
phenyl)propane, 2,2-bis((amitubuenoxy)phenyl)hexafluoropropane, and the like. However, since the addition of these diamines increases the coefficient of thermal expansion, the amount added needs to be at most 40% by weight of the diamine units of the polyimide resin.

Furthermore, the polyimide resin according to the present invention has excellent adhesion to aluminum, alumina, etc., but has difficulty adhering to silicon, silica, etc.

Therefore, as measures to improve adhesion, there are methods such as copolymerizing diaminosiloxane such as bis(aminopropyl)tetramethyldisiloxane, mixing a silane coupling agent, and pre-coating aluminum heptanoethyl acetoacetate on the substrate in advance. Examples include a method of treating with an aluminum chelate compound such as diisopropylate or a surface treatment agent such as aminopropyltrimethoxysilane.

The method for synthesizing the polyimide resin according to the present invention is almost the same as that for conventional polyimides. Namely, N-methylpyrrolidone (NMP), N,N-dimethylformamide (DMF), N,N-dimethylacetamide (DM
Ac), dimethyl sulfoxide (DMSO), sulfolane, γ-butyrolactone, cresol, phenol, halogenated phenol, acetophenone, cyclohexanone, dioxane, tetrahydrofuran, etc. at a temperature of 0 to 200°C. It can be reacted at a relatively low temperature to form a polyamic acid varnish, coated with a 1 m film, and then heated to dry and imidize at the same time. The completion temperature of the imidization reaction is 76 or higher for the obtained polyimide.

〔Example〕

Next, specific examples of the present invention and comparative examples with conventional polyimide resins will be described.

In each Example and Comparative Example, the diamine units and tetracarboxylic acid (anhydride) units were changed, polyimide resins were synthesized using the synthesis method described below, and the wet etching rate and coefficient of thermal expansion were determined for each polyimide resin on each side. It was measured. The results are shown in Table 1.

, 2,5-DATO is 2,5-diaminotolue, D
DM is 4,4'-silaminodiphenyl meta is 4,4'terphenyldiamine 2-bis(4-(4-aminophenoxy)phenyl)]
Propane is shown respectively.

In addition, in the tetracarboxylic acid anhydride unit in Table 1, P
MDA represents pyromellitic anhydride and 4-(4-aminophenoxy)phenylcob.

In addition, in the tetracarboxylic acid anhydride unit in Table 1, P
MDA represents pyromellitic anhydride, and BTDA represents benzophenone-3,4,3', 4'.

[Examples 1 to 3. Comparative Examples 1 to 21] A 4-tube flask equipped with a thermometer, a stirrer, a reflux condenser, and a nitrogen inlet was charged with the amount of diamine shown in Table 1, and 850 g of N-methyl-2-pyrrolidone (NMP) was added.
Then, the flask was immersed in a water bath at 0 to 50°C, and the tetracarboxylic dianhydride was added while suppressing the heat generation.

After the tetracarboxylic dianhydride was dissolved, the water bath was removed and the reaction was continued for about 5 hours at around room temperature to obtain the polyamic acid varnish shown in Table 1. If the varnish viscosity becomes very high, 80 to 85
The mixture was heated and stirred at ℃.

The etching rate of polyimide obtained by heating these polyamic acids was measured as follows.

That is, approximately 4,000 people's 5i
A 0.5% toluene solution of aluminum chelate (aluminum monoethyl acetate bisbrobylate) was applied onto the silicon wafer on which the NS film was formed, and the solution was incubated in air for 30 minutes.
After baking at 50℃ for 30 minutes, it was diluted to a viscosity of 2.
A polyamic acid varnish with around 0 poise was spin-coded and applied to a thickness of approximately 5 μm, and after heating at 100°C for 30 minutes and 200°C in nitrogen for 30 minutes, a polyimide film was coated under each final vectoring condition shown in the table. Obtained. In the polyimide obtained under these conditions, almost 100% of the imidization reaction progressed.

Next, 0MR83 (negative photoresist) manufactured by Tokyo Ohka was spin-coded to a thickness of 3 μm, prebaked at 80° C. for 30 minutes, exposed with a mask aligner, and immersed in a prescribed developer and rinse solution to form a pattern. , and 15 more
Post-baked for 30 minutes at 0°C. The pattern is 5 loaves x 10
It is an island-like pattern of m.

This sample was immersed in an etching solution containing hydrazine hydride and ethylenediamine in a ratio of 7:3.

Etching was performed at 30°C for a predetermined time. After washing with water, the photoresist was removed by immersing it in Tokyo Ohka Photoresist Remover 8502 at 100° C. for 10 minutes. After washing well with methanol.

After baking at 350°C, the etching depth was measured.

The etching speed was determined from the relationship between etching time and etching depth. Depending on the type of polyimide, the relationship between the two was not linear, and there were some that had an induction period.

The time required to etch 5 μm was determined and expressed as an average value.

Moreover, the thermal expansion coefficient of polyimide was measured as follows. Apply it evenly on a glass plate using an applicator, dry it at 80 to 100°C for 0.5 to 3 hours to form a film, peel it off from the glass plate, fix it on an iron frame, and heat it at 200°C for 30 minutes. An imide film was prepared under the final baking conditions shown in the table. The ffl thickness was 30 to 50 μm. After setting this in a thermomechanical testing machine, it was heated again in a vacuum to the final baking temperature shown in the table for 5 minutes, and then removed to room temperature to remove drying and residual stress. 5℃/w
Dimensional changes were measured while heating under conditions of in.

The measurement results of the wet etching speed and thermal expansion coefficient of various polyimides are shown in Table 1 above. From the results, it is found that the etching speed is 0.2 μm/1 lin or more from a practical point of view and the thermal expansion coefficient is also a practical point. From 2.0X10-
It can be seen that there are very few cases of 1IK-1 or less. In the case of Example 1, the thermal expansion coefficient could not be measured because the film was very brittle, but it is clear from the copolymerization data described below that the thermal expansion coefficient was extremely small.

[Examples 4-14. Comparative Examples 22 to 24] Polyimide acid copolymers were synthesized using the same synthesis method as described above, changing the blending ratio of diamine and tetracarboxylic acid as shown in Table 2. The etching rate and thermal expansion coefficient were measured by the same method. Furthermore, the moisture resistance (hydrolysis resistance) of these polyimide films, polyimide/polyimide, and polyimide 1
The adhesion between SiOx was measured by leaving it in water vapor at 120° C. and 2 atm. The evaluation was carried out by scratching the v1 film (1 μm x 2) in the shape of a base plate, leaving it in high-temperature steam for a predetermined period of time, and then peeling it off with a strong adhesive tape (Nitto Denko Layer). When the polyimide film deteriorates due to hydrolysis, the area around the cut end of the base grain becomes brittle and adheres to the adhesive tape. Moreover, when the adhesion of the interface decreases, each hole of the substrate adheres to the adhesive tape. The results are shown in Table 2. As is clear from Table 2, as the reaction ratio of PMDA in the tetracarboxylic acid component increases, the etching rate increases, but the adhesiveness and hydrolysis resistance of the polyimide-polyimide interface significantly decrease. Ru. It is also understood that when the diamine component is copolymerized with a material having a large coefficient of thermal expansion such as DDE, up to about 40 mol % can be tolerated.

〔Effect of the invention〕

As explained above, the polyimide resin according to the present invention allows wet etching.

Therefore, in the conventional etching of polyimide resin, only the dry etching method for ultrafine processing of VLSI etc. could be used, but the polyimide resin according to the present invention can use the wet etching method, and can be applied to a wider range of applications. can.

Claims (1)

[Claims] 1. In a polyimide resin consisting of a copolymer of diamine units and tetracarboxylic acid units, the diamine units have ▲ mathematical formulas, chemical formulas, tables, etc. ▼ [R is an alkyl group, n and m are Indicates an integer between 0 and 4. ] A polyimide resin which is at least one member of the group consisting of pyromellitic acid units, and 25 mol% or more of the tetracarboxylic acid units are pyromellitic acid units. 2. The polyimide resin according to claim 1, wherein the tetracarboxylic acid units are pyromellitic acid units and 3, 3', 4, 4' biphenyltetracarboxylic units. 3. The pyromellitic acid unit and 3,3',4,4'-
The ratio with biphenyltetracarboxylic acid units is 25:75
A polyimide resin characterized in that the content is in the range of 75:25 mol%.