JPH0259619B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming an interlayer insulating film of a semiconductor element. Conventionally, interlayer insulating films for semiconductor devices are made using CVD.
(Chemical Vapor Deposition) method etc.
The use of silicon dioxide has been considered, but its application to semiconductors has been delayed because thin silicon dioxide films have drawbacks such as being prone to cracks and having many pinholes. In recent years, heat-resistant polymers, particularly polyimide, have been attracting attention in this field as a new material to replace the above-mentioned silicon dioxide film.
In other words, this heat-resistant polymer has sufficient heat resistance to withstand wire bonding, and also has many excellent advantages such as excellent electrical insulation, low stress distortion, and mechanical strength, and when made into a thick film. However, it is an organic material that is attracting attention because it does not cause cracks and has minimal pinholes. In this way, heat-resistant polymers, mainly polyimide, are being considered as interlayer insulating films for various semiconductor devices. It has the drawbacks of poor adhesiveness and difficulty in adhesion, and as a result, the reliability of semiconductor devices has not been satisfactory. For this reason, various proposals have been made to improve the adhesion of the above-mentioned heat-resistant polymers, and one of them is to create a polyimide precursor using a polymerization reaction between an aromatic tetracarboxylic dianhydride and a diamino compound. When synthesizing, there is a method of using diaminosiloxane as the above diamino compound. This method introduces Si-O-Si bonds derived from diaminosiloxane into the molecular skeleton, and this bond creates a chemical bond between the silicon atoms of the silicon-containing material that makes up silicon wafers, etc. The purpose is to improve adhesion by using these as active sites for adhesion to silicon-containing materials. However, in the above proposed method, diaminosiloxane is used in a considerable proportion of the diamino compound or as all of the diamino compound, so even if it is possible to improve the adhesion, the moisture resistance of the interlayer insulating film made of polyimide is poor. There is a problem that greatly impairs the characteristics. Moreover, excessive use of diaminosiloxane is not necessarily preferable in terms of heat resistance, electrical insulation, mechanical strength, etc. inherent to polyimide. Furthermore, in the proposed method, there are polyimide precursors synthesized using an excess of diaminosiloxane, and polyimide precursors synthesized without using diaminosiloxane at all, that is, using diamines that do not contain silicon atoms in the molecule. There is also a method of forming a mixture of these, but even in this case, not only does the same problem as mentioned above arise due to the large silicon content in the mixture, but also the adhesion, moisture resistance, and other general characteristics are poor because it is a mixture. It was easy to vary between lots, and stable performance could not be obtained. On the other hand, this type of siloxane-modified polyimide precursor is desired to be a high molecular weight material with high intrinsic viscosity in view of heat resistance and other general properties, but in this case, the However, there is a problem in that the viscosity of the solution becomes high and a practical solids concentration cannot be obtained. For example, the feed concentration during the synthesis of polyimide precursors is generally set to be at least 5 to 15% by weight for economical reasons, but even with such a low feed concentration, spin In order to obtain a solution viscosity suitable for coating, dipping or brushing, considerable further dilution is required after the polymerization reaction. Such a dilution operation causes variations in solution viscosity between manufacturing lots and complicates the coating process, and also causes repellency and uneven thickness in the formed coating film due to a significant decrease in solid content concentration. This results in an adverse effect on the performance of the interlayer insulating film made of polyimide. In view of the above, the present invention provides an interlayer insulating film made of polyimide that exhibits a viscosity that allows coating in a highly concentrated state, has excellent adhesion to the element surface, and has good moisture resistance. This discovery was made as a result of extensive research in order to obtain a siloxane-modified polyimide precursor that possesses inherent heat resistance, electrical insulation, and mechanical strength. That is, this invention provides the following general formula in an inert solvent; (R ₁ is a divalent organic group, R′ is a monovalent organic group,
n is an integer from 1 to 1000) A diamino compound consisting of a diamino siloxane represented by the formula (n is an integer from 1 to 1000) and a diamine that does not contain a silicon atom in the molecule is combined with an aromatic tetracarboxylic dianhydride, and the diamino siloxane is the total amount of the diamino compound. 1 to 4
By conducting a polymerization reaction at a ratio of mol%,
A solution of a siloxane-modified polyimide precursor with a silicon content of 0.5% by weight or less was obtained, and this solution was heated at 40 to 80°C.
interlayer insulation of a semiconductor element, characterized in that the intrinsic viscosity of the precursor is lowered by heating and aging in a wafer, and then this solution is applied onto a semiconductor element, and then subjected to high temperature heat treatment to form an interlayer insulation film made of polyimide. This relates to a film forming method. As described above, in this invention, the specific range of diaminosiloxane used to improve the adhesion of the interlayer insulating film made of polyimide is necessary and sufficient. Since the siloxane bonding portion that is easily broken by wet thermal decomposition or acid or alkali is extremely small, the moisture resistance of the polyimide insulating film is not deteriorated.
It has also been found that there is no fear of impairing polyimide's inherent heat resistance, electrical insulation, mechanical strength, etc. On the other hand, the siloxane-modified polyimide precursor synthesized using diaminosiloxane in the above-mentioned proportion has the same drawback as conventional precursors in that it has a high solution viscosity. However, according to the present invention, when the polyimide precursor solution after the polymerization reaction is further heated and aged at a specific temperature, its intrinsic viscosity decreases due to molecular cleavage or rearrangement of the precursor, and the polyimide precursor solution is not diluted with a solvent after that. It is possible to obtain a solution viscosity that can be coated with a polyimide insulating film, and when a solution of high concentration and low viscosity is obtained by this method, it not only has excellent adhesion and moisture resistance properties as a polyimide insulating film achieved by the above method. about,
It has been found that it has almost no adverse effect on heat resistance, mechanical strength, electrical insulation, etc. In the diaminosiloxane represented by the general formula (1) in this invention, two R ₁ and each R' in the formula may be the same or different,
A wide variety of conventionally known methods are included. Typical examples are as follows. The diamine that does not contain a silicon atom in its molecule (hereinafter simply referred to as silicon-free diamine) used in this invention has the following general formula (2); H ₂ NR ₂ −NH ₂ ...(2) ( R ₂ is a divalent organic group that does not contain a silicon atom) _. It may be the same as or different from R ₁ . Particularly suitable are aromatic diamines, representative examples of which include metaphenylenediamine, paraphenylenediamine, 4.
4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl ether, 2,2'-bis(4-aminophenyl)propane, 3,3'-diaminodiphenyl sulfone, 4,4'-diaminodiphenyl sulfone , 4,4'-diaminodiphenyl sulfide,
Benzidine, benzidine-3,3'-dicarboxylic acid, benzidine-3,3'-disulfonic acid, benzidine-3-monocarboxylic acid, benzidine-3-monosulfonic acid, 3,3'-dimethoxy-benzidine, para-bis (4-aminophenoxy)benzene, meta-bis(4-aminophenoxy)benzene, metaxylylenediamine, paraxylylenediamine, and the like. In this invention, the aromatic tetracarboxylic dianhydride to be polymerized and reacted with the diamino compound consisting of the above diaminosiloxane and silicon-free diamino has the following general formula (3); (Ar is a tetravalent organic group) Typical examples include pyromellitic dianhydride, 3.
3', 4, 4'-benzophenonetetracarboxylic dianhydride, 3, 3', 4, 4'-biphenyltetracarboxylic dianhydride, 2, 3, 3', 4'-biphenyl tetra Carboxylic dianhydride, 2, 3, 6, 7-naphthalenetetracarboxylic dianhydride, 1, 2, 5,
6-naphthalenetetracarboxylic dianhydride, 1.
4,5,8-naphthalenetetracarboxylic dianhydride, 2,2'-bis(3,4-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride , 3・4・9・
10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, 2,2'-bis(2,3-dicarboxyphenyl)propane dianhydride, 1,1 '-Bis (2・3
-dicarboxyphenyl)ethane dianhydride, benzene-1,2,3,4-tetracarboxylic dianhydride, 2,3,6,7-anthracenetetracarboxylic dianhydride, 1,2,7, Examples include 8-phenanthrenetetracarboxylic dianhydride. A particularly suitable aromatic tetracarboxylic dianhydride for this invention is 3,3',4,4'-biphenyltetracarboxylic dianhydride. When this dianhydride is used, under a high temperature and high humidity atmosphere, for example, 121℃,
A polyimide with excellent electrical properties as determined by the 2-atm pressure pressure test (hereinafter simply referred to as PCT), that is, extremely good moisture resistance properties, can be obtained, and its performance as an interlayer insulating film can be greatly improved. . Of course, the moisture resistance can be improved even when other dianhydrides are used. In this invention, it is necessary to simultaneously polymerize the above-mentioned diaminosiloxane and silicon-free diamino with aromatic tetracarboxylic dianhydride. For example, in a method in which both diamino compounds are polymerized separately and then mixed, This causes variations in adhesion and moisture resistance, making it impossible to stabilize quality. As mentioned above, the diaminosiloxane used in this polymerization reaction is 1 to 4 mol%, preferably 3 to 3.5 mol% of the total amount of the diamino compound,
Further, the amount used must be determined so that the silicon content contained in the obtained siloxane-modified polyimide precursor is 0.5% by weight or less. Unless these quantitative relationships are satisfied, it becomes difficult to achieve both adhesion and moisture resistance. The ratio of the diamino compound consisting of diaminosiloxane and silicon-free diamino to the aromatic tetracarboxylic dianhydride is usually equimolar, but one may be slightly increased if necessary. The polymerization reaction may be carried out according to conventionally known methods, generally in the presence of an inert solvent and in a stream of nitrogen gas, while taking into consideration the polymerization heat generation and generally limiting the temperature to below 40°C, particularly preferably below 30°C. The reaction may be carried out until a predetermined degree of polymerization is obtained. Note that polyimide used as an interlayer insulating film of a semiconductor element must be prevented from being contaminated by ionic impurities. Care must be taken to avoid contamination from cationic impurities such as Na ⁺ , K ² , Ca ²⁺ and anionic impurities such as Cl ^-. In particular, Na ⁺ ions can cause damage to the interlayer insulation film made of polyimide. Adversely affects electrical properties. Therefore, during polymerization, both the raw material monomer and the solvent should be sufficiently purified by well-known methods before use. For example, it is desirable that the concentration of Na ⁺ ions is 5 PPM or less, preferably 1 PPM or less. Examples of inert solvents used in such polymerization reactions include N-methyl-2-pyrrolidone,
Highly polar basic solvents such as N.N'-dimethylacetamide, N.N'-dimethylformamide, N.N'-dimethylsulfoxide, and hexamethylphosphoramide are used. All of these types of solvents are highly hygroscopic, and absorbed water causes a decrease in molecular weight during polymerization and storage stability, so it is recommended to thoroughly dehydrate with a dehydrating agent before use. . Moreover, general-purpose solvents such as toluene, xylene, benzonitrile, benzene, and phenol can also be used together with these solvents. However, the amount used should be within a range that does not reduce the solubility of the polyimide precursor produced. The degree of polymerization of the siloxane-modified polyimide precursor synthesized by the above method can be easily detected by examining the intrinsic viscosity [η] of the reactant. It is desirable that the polymerization degree is high. This is because if it is lower than this, good results will not be obtained in terms of heat resistance and other general properties. The intrinsic viscosity [η] described in this specification is
It means the value calculated according to the following formula using N-methyl-2-pyrrolidone as a solvent at a measurement temperature of 30±0.01°C (static bath). [η] = ln (t/to)/c t; Falling time To of the polymer solution measured with an Ubbelohde viscometer; Falling time c of the solvent measured in the same manner as above; Polymer concentration (assumed to be 0.5% by weight) In the invention, subsequent to the above polymerization reaction step, heat aging is carried out in the same reaction vessel in a nitrogen stream by raising the temperature to 40 to 80°C, preferably 50 to 60°C. By this heat aging, the siloxane-modified polyimide precursor having a high degree of polymerization obtained in the above-mentioned polymerization reaction undergoes appropriate molecular cleavage or rearrangement, thereby reducing the molecular weight. The degree of molecular weight reduction is determined by the relationship between solution viscosity and polyimide properties, and it is generally preferable to set the intrinsic viscosity to 0.3 to 0.7. As a guide, the solution viscosity is about 1,000 to 20,000 centipoise at a solution concentration of 25% by weight. If the above-mentioned intrinsic viscosity becomes too low, the film forming ability in the final stage will be poor, and the insulation properties, heat resistance and other properties will be impaired when the interlayer insulation film is formed. The reason why the heat aging temperature was set at 40 to 80℃ is that at temperatures exceeding 80℃, especially at temperatures above 100℃, crosslinking reactions proceed and there is a risk of gelation. This is because sufficient effects cannot be obtained and the aging time becomes long, impairing workability. Even if the siloxane-modified polyimide precursor as the final product obtained in this way has a lower degree of polymerization, it is still a silicon-free diamine as shown in the following general formula (4). The bonding unit of and diaminosiloxane added to aromatic tetracarboxylic dianhydride via an amide bond is
It has a random polymer structure, and is characterized by having a structure in which very few siloxane bonds are incorporated into the molecular chain of this polyimide precursor. (R ₁ , R ₂ , R', n and Ar are as described above, l
and m are both positive integers, m/l+m=0.01
~0.04) (R ₁ , R ₂ , R', Ar, n, l, and m are as described above.) Such a siloxane-modified polyimide precursor has a low solution viscosity, and for example, when the charging concentration in the polymerization reaction step is 20 to 25 Even when the weight is % or higher, even if it is not diluted after the heat aging process,
It has a viscosity suitable for spin coating, dipping or brushing. In this invention, the above precursor solution is coated on an element such as a silicon wafer by the above coating method, and then subjected to high temperature heat treatment, dehydrated and cyclized, thereby achieving excellent adhesion to the silicon wafer etc. It is possible to form an interlayer insulating film made of polyimide as shown by the above general formula (5) showing the properties. This polyimide insulating film has excellent moisture resistance, as well as its inherent good heat resistance.
It has chemical resistance, mechanical properties, and excellent electrical insulation properties, and exhibits excellent performance as an interlayer insulating film for semiconductor devices. EXAMPLES Below, examples of the present invention will be described in more detail. Example 1 A 500 ml flask equipped with a stirrer, condenser, thermometer and nitrogen purging device was fixed on a water bath.
N・N'-dimethylformamide 148.71, which was dried over calcium hydride for a day and night, and then distilled after purging with nitrogen.
g was added into the above flask, nitrogen was poured into the flask, and a polymerization reaction was carried out in the following manner. First, 1 ml of microsiridine was added to bis(3
-aminopropyl)tetramethyldisiloxane (diaminosiloxane of formula A above) 0.87g
(0.0035 mol) and then 19.3 g (0.0965 mol) of 4,4'-diaminodipheniether were added and stirred until dissolved. Thereafter, 29.4 g (0.1 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride was gradually added. The reaction system was stirred while maintaining the temperature below 30°C until a clear viscous solution was obtained. The 25% by weight solution of the siloxane-modified polyimide precursor obtained in this way has a viscosity (hereinafter the same) measured with a BH type viscometer at 25°C that is at least the measurement upper limit (2,000,000 centipoise), and the intrinsic viscosity of the precursor was 1.67, and the silicon content was 0.397% by weight. Next, in the heating and aging process, the water bath was removed and replaced with a hot water bath, and the same reaction vessel was heated and stirred at 55±5°C, heated and aged in a nitrogen stream for 6 hours, and then continued for another 28 hours, for a total of 34 hours. By heating and aging, the molecular weight was reduced to an intrinsic viscosity of 0.42 and a solution viscosity of 4400 centipoise. This precursor solution was spin-coated onto a silicon wafer, heated to 150°C for 1 hour in a hot air dryer, and then heated to 200°C for 1 hour.
A heat treatment was performed at 250° C. for 6 hours to form an interlayer insulating film made of tough polyimide. The infrared absorption spectrum of this polyimide insulating film is 1780 cm ^-1
and >C= based on imide group formation at 1720 cm ^-1
Absorption of O was observed. In addition, in the above spin coating, 2 to 3 g of the precursor solution is applied at a rotation speed of 3500 rpm.
I did it by dripping method. Example 2 The amount of purified N/N'-dimethylformamide used was 125.91 g, and pyromellitic dianhydride was 21.8 g (0.1 mol) as aromatic tetracarboxylic dianhydride.
The polymerization reaction was carried out in the same manner as in Example 1 except that the silicon content was 0.469% by weight and the intrinsic viscosity was
1.65, a 25% by weight solution of a high molecular weight siloxane-modified polyimide precursor with a solution viscosity of 2,000,000 centipoise or more was obtained. Next, as a heating aging step, the above precursor solution was heated and aged for 24 hours at 55 ± 5°C in the same manner as in Example 1 to lower the molecular weight until the intrinsic viscosity was 0.38 and the solution viscosity was 2200 centipoise. did. Example 1 This precursor solution was applied onto a silicon wafer.
Spin coat in the same manner as above and dry in a hot air dryer at 150℃.
An interlayer insulating film made of tough polyimide was formed by heat treatment at 200°C for 1 hour, 200°C for 1 hour, and 300°C for 1 hour. Example 3 The amount of purified N/N'-dimethylformamide used was 156.53 g, and 32.2 g of 3,3',4,4'-benzophenonetetracarboxylic dianhydride was used as aromatic tetracarboxylic dianhydride ( The polymerization reaction was carried out in the same manner as in Example 1, except that 19.107 g (0.0965 mol) of 4,4'-diaminodiphenylmethane was used as the silicon-free diamine, and the silicon content was 0.377 wt. A 25% by weight solution of a high molecular weight siloxane modified polyimide precursor with a % intrinsic viscosity of 1.38 and a solution viscosity of 1700000 centipoise was obtained. Next, as a heat aging step, the above precursor solution was heated at 55±5°C in the same manner as in Example 1.
By heating and aging for 15 hours, the intrinsic viscosity is 0.45.
The molecular weight was lowered to a solution viscosity of 2300 centipoise. Example 1 This precursor solution was applied onto a silicon wafer.
After spin coating in the same manner as above, heat treatment was performed to form an interlayer insulating film made of polyimide. This insulating film has a tensile strength of 40% of its initial value after 6 months.
However, it had sufficient toughness to be used as an interlayer insulating film. Comparative Example 1 The amount of purified N・N'-dimethylformamide used was 148.27 g, the amount of 4,4'-diaminophenyl ether used was 19.9 g (0.0995 mol), and the amount of bis(3-aminopropyl)tetramethyldisiloxane used was 148.27 g. A polymerization reaction was carried out in the same manner as in Example 1, except that the amount used was 0.1243 g (0.0005 mol), and the silicon content was 0.057% by weight, the intrinsic viscosity was 2.37, and the solution viscosity was
A 25% by weight solution of a siloxane-modified polyimide precursor with a high molecular weight of 2,000,000 centipoise was obtained. Next, as a heating aging step, the above precursor solution was heated and aged in the same manner as in Example 1 to lower the molecular weight until the intrinsic viscosity was 0.41 and the solution viscosity was 2700 centipoise. This precursor solution was spin-coated onto a silicon wafer in the same manner as in Example 1, and then heat-treated to form an interlayer insulating film made of polyimide. Comparative Example 2 The amount of purified N/N'-dimethylformamide used was 149.22 g, the amount of 4,4'-diaminophenyl ether used was 18.6 g (0.093 mol), and the amount of bis(3-aminopropyl)tetramethyldisiloxane used was 149.22 g. A polymerization reaction was carried out in the same manner as in Example 1, except that the amount used was 1.7395 g (0.007 mol), and the silicon content was reduced.
0.791% by weight, intrinsic viscosity 0.80, solution viscosity
A 25% by weight solution of 50000 centipoise siloxane modified polyimide precursor was obtained. Next, as a heat aging step, the above precursor solution was heated and aged in the same manner as in Example 1 to reduce the molecular weight until the intrinsic viscosity was 0.45 and the solution viscosity was 5100 centipoise. This precursor solution was spin-coated onto a silicon wafer in the same manner as in Example 1, and then heat-treated to form an interlayer insulating film made of polyimide. Comparative Example 3 Bis(3-aminopropyl)tetramethyldisiloxane and 4,4'-diaminodiphenyl ether were polymerized separately with pyromellitic dianhydride in the same proportions as in Example 2, and then both were mixed. A 25% by weight solution of the polyimide precursor mixture was obtained.
The intrinsic viscosity of the polyimide precursor obtained from diaminosiloxane was 0.63, and the intrinsic viscosity of the polyimide precursor obtained from silicon-free diamine was 2.00. The silicon content in the polyimide precursor mixture was 0.469% by weight, and the solution viscosity was above the upper limit of measurement (2,000,000 centipoise). Next, the above solution was further heated and aged in the same manner as in Example 1, so that the intrinsic viscosity was reduced.
The molecular weight was lowered to 0.53, and the solution viscosity was 4100 centipoise. This precursor solution was spin-coated in the same manner as in Example 2, and then heat-treated in the same manner to form an interlayer insulating film made of polyimide. Comparative Example 4 The amount of purified N/N'-dimethylformamide used was 99.27 g, and the amount of pyromellitic dianhydride used was 21.8 g (0.1 g) as the aromatic tetracarboxylic dianhydride.
Example 1 except that 10.42 g (0.0965 mol) of para-phenylenediamine was used as the silicon-free diamine and 0.87 g (0.0035 mol) of bis(3-aminopropyl)tetramethyldisiloxane was used as the diaminosiloxane. A polymerization reaction was carried out in the same manner as above, and the silicon content was 0.594% by weight and the intrinsic viscosity was
1.58, a 25% by weight solution of the siloxane modified polyimide precursor was obtained with a solution viscosity of 1800000 centipoise. Next, as a heat-ripening step, the above precursor solution was heat-ripened in the same manner as in Example 1 to lower the molecular weight until the intrinsic viscosity was 0.39 and the solution viscosity was 1900 centipoise. This precursor solution was spin-coated onto a silicon wafer in the same manner as in Example 1, and then heat-treated to form an interlayer insulating film made of polyimide. Next, the above Examples 1 to 3 and Comparative Examples 1 to 4
The polyimide insulating film obtained was tested for adhesion and electrical insulation under the same environmental conditions. Furthermore, the coatability (state of the coating film) by spin coating when forming the polyimide insulating film was visually observed. These results were as shown in the following table. In addition, "B" in Examples 1 to 3 is the result of each example, and "A" is the high molecular weight obtained in the polymerization reaction step by omitting the heat aging step in each example for reference. , are test results when an interlayer insulating film made of polyimide was formed by diluting a highly viscous siloxane-modified polyimide precursor solution with a solvent to the extent that it could be coated.

[Table] As is clear from the above table, the present invention has excellent coating properties on the surface of devices such as silicon wafers, can overcome defects caused by coating film defects such as cracks and pinholes, and has excellent adhesion and It is possible to form an interlayer insulating film made of polyimide that has excellent heat resistance, low stress properties, mechanical strength, and moisture resistance.
It can be seen that this contributes to stable supply of semiconductor devices and improved reliability. In addition, in this invention, 3.
It is also clear that the effect is particularly remarkable in Example 1, which uses 3', 4, 4'-biphenyltetracarboxylic dianhydride. On the other hand, unlike this invention, in the case where heat treatment is not performed after the polymerization reaction ("A" in each example), the coating properties are poor, and the amount of diaminosiloxane used is small (Comparative Example 1) On the other hand, when the amount used is large (Comparative Examples 2 and 4), the adhesion is impaired or the moisture resistance is deteriorated, and even if the amount of diaminosiloxane used is within the range of this invention, diaminosiloxane and silicon-free diamine It can also be seen that when a method of separately reacting these with an aromatic tetracarboxylic dianhydride (Comparative Example 3), good results were not obtained in terms of adhesion, moisture resistance, etc. In addition, as another experiment, a siloxane-modified polyimide precursor having an intrinsic viscosity of 0.75 and a solution viscosity of 30,000 centipoise was prepared by changing the heat treatment time in the heat aging step in Example 1 to 6 hours, and using this, a polyimide precursor made of polyimide was prepared in the same manner as above. When an interlayer insulating film was formed, the properties of the coating film upon spin coating were improved to some extent, but some thickness unevenness was observed, and the coating properties were inferior to that of Example 1. On the other hand, when a siloxane-modified polyimide precursor with an intrinsic viscosity of 0.28 and a solution viscosity of 600 centipoise was prepared by heating for 60 hours, and an interlayer insulating film made of polyimide was formed using this, the molecular weight was too low. As a result, microcracks occur in the insulating film, the dielectric breakdown voltage decreases, and the performance as an interlayer insulating film of a semiconductor element cannot be achieved.

Claims (1)

[Claims] 1. In an inert solvent, the following general formula; (R ₁ is a divalent organic group, R′ is a monovalent organic group,
n is an integer from 1 to 1000) A diamino compound consisting of a diamino siloxane represented by the formula (n is an integer from 1 to 1000) and a diamine that does not contain a silicon atom in the molecule is combined with an aromatic tetracarboxylic dianhydride, and the diamino siloxane is the total amount of the diamino compound. 1 to 4
By conducting a polymerization reaction at a ratio of mol%,
A solution of a siloxane-modified polyimide precursor with a silicon content of 0.5% by weight or less was obtained, and this solution was heated at 40 to 80°C.
interlayer insulation of a semiconductor element, characterized in that the intrinsic viscosity of the precursor is lowered by heating and aging in a wafer, and then this solution is applied onto a semiconductor element, and then subjected to high temperature heat treatment to form an interlayer insulation film made of polyimide. Film formation method.