JPH0259621B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for forming a polyimide layer with good adhesion on the surface of a substrate made of a silicon-containing material. BACKGROUND ART Conventionally, the use of heat-resistant polymers such as polyimide, polyamide-imide, and polyhydantoin, which have many excellent advantages such as heat resistance, electrical insulation, and mechanical strength, has been considered for semiconductor devices and the like. However, these layers made of heat-resistant polymers have a problem of poor adhesion to substrate surfaces such as silicon wafers and glass. For this reason, various proposals have been made to improve the adhesion of the heat-resistant polymer layer, one of which is to create a polyimide precursor using a polymerization reaction between an aromatic tetracarboxylic dianhydride and a diamino compound. There is a method of using diaminosiloxane as the diamino compound mentioned above when synthesizing the body. This method introduces Si-O-Si bonds derived from diaminosiloxane into the molecular skeleton, and these bonding parts form chemical bonds with silicon atoms in silicon-containing materials such as silicon wafers and glass. 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 the adhesion can be improved, the moisture resistance properties of the polyimide layer will be significantly impaired. There were flaws. Furthermore, excessive use of diaminosiloxane is not necessarily preferable in terms of heat resistance, electrical insulation, mechanical strength, etc. inherent to polyimide. Similarly, in the proposed method, there are polyimide precursors synthesized using an excessive amount 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 making a mixture with the body, but even in this case, the same problem as mentioned above occurs because the silicon content is large in the mixture, and since it is a mixture, it has poor adhesion, moisture resistance, and other general problems. Characteristics tended to vary between lots, making it difficult to obtain stable performance. From the above points of view, the present invention makes it possible to form a polyimide layer that has excellent adhesion and moisture resistance on the surface of a substrate made of a silicon-containing material, and that this polyimide layer has inherent heat resistance, electrical insulation, and mechanical properties. This discovery was made as a result of extensive research in order to obtain a siloxane-modified polyimide precursor that has high physical strength. That is, this invention provides the following general formula on the surface of a substrate made of a silicon-containing material. (R ₁ is a divalent organic group, R′ is a monovalent organic group,
n is an integer from 1 to 1000) and a diamine that does not contain a silicon atom in the molecule are polymerized simultaneously with an aromatic tetracarboxylic dianhydride,
The use ratio of the above diamino siloxane is in the range of 1 to 4 mol% of the total amount of the diamino compound, and the silicon content contained in the final reaction product is 0.5% by weight.
A polyimide layer with good adhesion is formed on the surface of a substrate made of a silicon-containing material, characterized by applying a siloxane-modified polyimide precursor obtained in the following manner and then subjecting it to high-temperature heat treatment to form a polyimide layer. It is related to the method. As described above, in this invention, the diaminosiloxane used to improve the adhesion of the polyimide layer is necessary and sufficient within the above specified range, and when used in such a proportion, the amount of moist heat in the polyimide precursor increases. Since the siloxane bonds that are easily broken by decomposition or acid or alkali are extremely small, the moisture resistance of the polyimide layer is not degraded, and polyimide's inherent heat resistance, electrical insulation, and mechanical strength are not impaired. I have found that there is nothing to worry about. 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 N−R ₂ −NH ₂ ………(2) (R ₂ is a divalent organic group not containing a silicon _atom ) These include aromatic diamines, aliphatic diamines, and alicyclic diamines represented by It may be the same as or different from R ₁ of . Particularly preferred 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'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfone, 4,4'-diaminodiphenylsulfide, benzidine, benzidine-3,3'-dicarboxylic acid, benzidine- 3,3'-disulfonic acid, benzidine-3-monocarboxylic acid, benzidine-3-
Examples include 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 diamine has the following general formula (3); (Ar is a tetravalent organic group) Typical examples are as follows. Namely, pyromellitic dianhydride, 3,3',4,4'-benzophenonetetracarboxylic dianhydride, 3,3',4,4'-biphenyltetracarboxylic dianhydride, 2,3・
3′・4′-biphenyltetracarboxylic dianhydride,
2.3.6.7-naphthalenetetracarboxylic dianhydride, 1.2.5.6-naphthalenetetracarboxylic dianhydride, 1.4.5.8-naphthalenetetracarboxylic dianhydride, 2. 2′-screw (3・4
-dicarboxyphenyl)propane dianhydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 3,4,9,10-perylenetetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)propane dianhydride, carboxyphenyl) 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,
Examples include 7,8-phenanthrenetetracarboxylic dianhydride. A particularly preferred aromatic tetracarboxylic dianhydride in 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 layer with excellent electrical properties as measured by the 2-atm pressure pressure test (hereinafter simply referred to as PCT), that is, extremely good moisture resistance properties, can be obtained. Of course, the moisture resistance can be improved even when other dianhydrides are used. In this invention, it is necessary to simultaneously polymerize the diaminosiloxane and the silicon-free diamine with the aromatic tetracarboxylic dianhydride. For example, it is not possible to polymerize both diamino compounds separately and then mix them together. , resulting in variations in adhesion and moisture resistance, making it impossible to stabilize quality. Further, as mentioned above, the diaminosiloxane used at this time is 1 to 4 mol%, preferably 3 to 3.5 mol%, of the total amount of the diamino compound, and is contained in the polyimide precursor that is the final reactant. The silicon atom content must be 0.5% by weight or less. If none of 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 diamine 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 a conventionally known method, and is generally carried out in the presence of an organic solvent in a nitrogen gas stream while limiting the temperature to usually 60°C or less, preferably 30°C or less, taking into account the polymerization heat generated. The reaction may be carried out until a high degree of polymerization is obtained. This degree of polymerization can be easily detected by examining the intrinsic viscosity [η] of the reactant. Examples of organic solvents include N-methyl-2-
Pyrrolidone, N・N'-dimethylacetamide,
Highly polar basic solvents such as 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. As shown in the following general formula (4), the polyimide precursor obtained by the present invention has a silicon-free diamine and a diaminosiloxane bonded to each other via an amide bond. The bonding units added to the anhydride have a random polymer structure, and are characterized by having a structure in which very few siloxane bonds are incorporated into the molecular chain of the 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) In the present invention, after applying the polyimide precursor to the surface of the base material made of a silicon-containing material,
By performing dehydration and cyclization through high-temperature heat treatment, it is possible to form a layer made of polyimide as represented by the general formula (5), which exhibits excellent adhesion to silicon wafers and glass. This polyimide layer has excellent moisture resistance, as well as good heat resistance, chemical resistance, mechanical properties, and excellent electrical insulation properties. It has the advantage that it can be effectively applied to various purposes. Note that in applications such as forming a polyimide layer on a semiconductor element, the polyimide forming material must be protected from being contaminated by ionic impurities. Care must be taken to avoid contamination from cationic impurities such as Na ⁺ , K ⁺ , Ca ²⁺ , and anionic impurities such as Cl ^-; Na ⁺ ions in particular have a negative impact on the electrical properties of semiconductors. effect. Therefore, during polymerization, both the raw material monomer and the solvent should be sufficiently purified by well-known methods before use. For example, with Na ⁺ ions
It is desirable that the amount is 5 PPM or less, preferably 1 PPM or less. Examples of this invention will be described below. In the following, the intrinsic viscosity [η] will be used as a parameter indicating the degree of polymerization (molecular weight) of the polyimide precursor.
This intrinsic viscosity was measured using N-methyl-2-pyrrolidone as a solvent at a temperature of 30±0.01℃ (in a constant temperature bath).
It was calculated according to the following formula. [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; Polyimide precursor (polymer) concentration (0.5 wt. %) Example 1 A 500 ml flask equipped with a stirrer, condenser, thermometer and nitrogen purging device was fixed on a water bath.
280.90 g of purified N-methyl-2-pyrrolidone, which had been dried over phosphorus pentoxide for one day and then distilled under reduced pressure, was added to the flask, and nitrogen was flushed into the flask. Next, using a 1 ml microsyringe, 0.87 g (0.0035 mol) of bis(3-aminopropyl)tetramethylenedisiloxane represented by the above formula A was added, followed by 19.3 g of 4,4'-diaminodiphenyl ether.
(0.0965 mol) and stirred until dissolved.
Next, 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 polyimide precursor obtained in this way is
The intrinsic viscosity was 1.67, and the silicon content was 0.397% by weight. A solution containing this precursor was spin-coated onto a silicon wafer and heated in a hot air dryer at 150°C for 1 hour, 200°C for 1 hour, and 250°C for 6 hours to form a polyimide layer. The infrared absorption spectrum of the polyimide layer formed in this way is 1780
Based on imide group formation at cm ^-1 and 1720 cm ^-1 >
Absorption of C=O was observed. The formed polyimide layer was strong and had good adhesion to the silicon wafer under normal conditions. It was also found that the adhesion was highly improved without peeling even after PCT treatment. Example 2 Example 1 except that 281.46 g of purified N-N'-dimethylacetamide was used as the solvent and 0.97 g (0.0035 mol) of bis(4-aminobutyl)tetramethyldisiloxane shown in (b) above was used as the diaminosiloxane. of polyimide precursor in the same way as
A 15% by weight solution was prepared. The intrinsic viscosity of the polyimide precursor at this time is 1.81
and the silicon content was 0.396% by weight. Example 1 using the above polyimide precursor solution
When a polyimide layer was formed on a silicon wafer under the same conditions as in Example 1, the toughness and adhesion of the layer were the same as in Example 1. Example 3 The amount of purified N-methyl-2-pyrrolidone used
A 15% by weight solution of the polyimide precursor was prepared in the same manner as in Example 1, except that 21.8 g (0.1 mol) of pyromellitic dianhydride was used as the aromatic tetracarboxylic dianhydride. The polyimide precursor thus obtained had an intrinsic viscosity of 1.65 and a silicon content of 0.469% by weight. A solution containing this precursor was spin coated in the same manner as in Example 1, and then dried in a hot air dryer at 150°C for 1 hour.
A polyimide layer was formed by heating at 200°C for 1 hour and at 300°C for 1 hour. The formed polyimide layer was strong, had good adhesion both under normal conditions and by PCT, and no peeling from the silicon wafer was observed. Example 4 The amount of purified N-methyl-2-pyrrolidone used
295.67 g, 32.2 g (0.1 mol) of 3,3',4,4'-benzophenonetetracarboxylic dianhydride as aromatic tetracarboxylic dianhydride, and 4,4' as silicon-free diamine. A 15% by weight solution of a polyimide precursor having an intrinsic viscosity of 1.38 and a silicon content of 0.377% by weight was prepared in the same manner as in Example 1, except that 19.107 g (0.0965 mol) of -diaminodiphenylmethane was used. Example 1 using the above polyimide precursor solution
When a polyimide layer was formed on a silicon wafer under the same conditions as in Example 1, the adhesion of the layer was the same as in Example 1, but the tensile strength after 6 months had decreased to 40% of the initial value. It was recognized that
Although it was found that the toughness of the film deteriorated over time, it was still strong enough to be used. Example 5 The amount of purified N-methyl-2-pyrrolidone used
259.36 g, 14.7 g (0.05 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 10.9 g (0.05 mol) of pyromellitic dianhydride as aromatic tetracarboxylic dianhydride. Polyimide precursor 15 was prepared in the same manner as in Example 1 except that
A wt% solution was made. The intrinsic viscosity of the obtained polyimide precursor is 1.52
And the silicon content was 0.430% by weight. Example 3 using the above polyimide precursor solution
When a polyimide layer was formed on a silicon wafer in the same manner as in Example 1, the toughness and adhesion of the layer were the same as in Example 1. Comparative Example 1 The amount of purified N-methyl-2-pyrrolidone used was
280.07 g, the amount of 4,4'-diaminodiphenyl ether used was 19.9 g (0.0995 mol), and the amount of bis(3-aminopropyl)tetramethyldisiloxane used was 0.1243 g (0.0005 mol). A 15% by weight solution of a polyimide precursor having an intrinsic viscosity of 2.37 and a silicon content of 0.057% by weight was prepared in the same manner as in Example 1. When a polyimide layer was formed on a silicon wafer using this solution under the same conditions as in Example 1, it did not peel off from the silicon wafer under normal conditions, but it peeled off easily with PCT. Comparative Example 2 The amount of purified N-methyl-2-pyrrolidone used was
281.86 g, the amount of 4,4'-diaminodiphenyl ether used was 18.6 g (0.093 mol), and the amount of bis(3-aminopropyl)tetramethyldisiloxane used was 1.7395 g (0.007 mol). A 15% by weight solution of the polyimide precursor was prepared in the same manner as in Example 1. The polyimide precursor thus obtained had an intrinsic viscosity of 0.80, and had a lower molecular weight than the polyimide precursor obtained in Example 1. Moreover, the silicon content of this precursor was 0.791% by weight. When a polyimide layer was formed on a silicon wafer using the polyimide precursor thus obtained under the same conditions as in Example 1, the toughness and adhesion of the layer were the same as in Example 1. . 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 3, and then both were mixed. A 15% 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. When a polyimide layer was formed on a silicon wafer using this solution under the same conditions as in Example 3,
The adhesion to the silicon wafer was inferior to that of Example 3, and the properties tended to vary and there were cases where PCT easily peeled off. Comparative example 4 The amount of purified N-methyl-2-pyrrolidone used
187.52 g, 21.8 g (0.1 mol) of pyromellitic dianhydride as the aromatic tetracarboxylic dianhydride, 10.42 g (0.0965 mol) of para-phenylene diamine as the silicon-free diamine, and bis(3 A 15% by weight solution of the polyimide precursor was prepared in the same manner as in Example 1, except that 0.87 g (0.0035 mol) of (aminopropyl)tetramethyldisiloxane was used. The intrinsic viscosity of this polyimide precursor was 1.58, and its silicon content was 0.594% by weight. When a polyimide layer was formed on a silicon wafer using the polyimide precursor solution obtained in this manner in the same manner as in Example 1, the adhesion of the layer was as follows.
It was the same. Next, the above Examples 1 to 5 and Comparative Examples 1 to 4
Each polyimide layer obtained in the above was tested for adhesion and electrical insulation under the same environmental conditions. The results were as shown in the following table.
The thickness of each polyimide layer is 50±5μ.
It has been adjusted to

【table】

[Table] As is clear from the above table, it can be seen that the polyimide layers according to Examples 1 to 5 of the present invention have excellent electrical properties and adhesion at high temperature and high humidity. In addition, in particular, Examples 1 and 2 in which 3,3',4,4'-biphenyltetracarboxylic dianhydride was used as the aromatic tetracarboxylic dianhydride,
It can also be seen that, compared to Examples 3 to 5 in which other dianhydrides were used, both of the above properties, especially the electrical properties at high temperature and high humidity, were much better. On the other hand, the polyimide layer formed in Comparative Example 1 was not inferior in electrical properties, but was inferior in adhesiveness to the silicon wafer. Furthermore, although the polyimide layers formed from Comparative Examples 2 and 4 do not have much of a problem with adhesion, they are inferior in electrical properties under high temperature and high humidity; for example, the polyimide layers formed from Comparative Example 2 are inferior to the polyimide layers formed from Example 1. In comparison, the volume resistivity is approximately 1/
The measurement result was 100. Comparative Example 3 is a polyimide layer formed from a mixed solution of a silicon-free polyimide precursor and a silicon-containing polyimide precursor, but in this case, even if the total silicon content is within the range of the present invention. It can be seen that good results were not obtained in terms of adhesion and electrical properties under high temperature and high humidity.

Claims (1)

[Claims] 1. The following general formula is applied to the surface of a substrate made of a silicon-containing material. (R ₁ is a divalent organic group, R′ is a monovalent organic group,
n is an integer from 1 to 1000) and a diamine that does not contain a silicon atom in the molecule are polymerized simultaneously with an aromatic tetracarboxylic dianhydride,
The use ratio of the above diamino siloxane is in the range of 1 to 4 mol% of the total amount of the diamino compound, and the silicon content contained in the final reaction product is 0.5% by weight.
A polyimide layer with good adhesion is formed on the surface of a substrate made of a silicon-containing material, characterized by applying a siloxane-modified polyimide precursor obtained in the following manner and then subjecting it to high-temperature heat treatment to form a polyimide layer. Method.