JPH08291252A - Polyimide precursor varnish and electronic device using the same - Google Patents

Abstract

PURPOSE: To obtain the subject varnish having excellent viscosity stability and capable of increasing the concentrations of resins in spite of using water as a solvent by containing a polyimide precursor obtained from a polyamic acid, each a specific amine compound and an organic solvent. CONSTITUTION: (A) A polyamic acid of the formula (A and B are each an aromatic group or a fatty group; (n) is 17-2920) is reacted with (B) an amine compound selected from 2-dimethylaminoethanol, 2-diethylaminoethanol, 2- methylaminodiethanol, dimethyl-3-butanol, diethylamino-acetone, N- ethylaminodiethanol, N-methylaminoethanol, 2,2-aminodiethanol, 3-diethylamino-1- propanol and amino-cyclohexane and (C) an organic solvent selected from N,N- dimethylacetamide, N-methyl-2-pyrrolidone, dimethyl sulfoxide and N,N-DMF and the resultant polyimide precursor as a reaction product is added with water to obtain the objective varnish.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel polyimide precursor varnish, a polyimide obtained by imidizing the polyimide precursor varnish, and a polyimide suitable as an insulating layer for electronic devices such as multi-chip modules, thin film magnetic heads, and semiconductor devices, and the like. The present invention relates to an electronic device used for an insulating layer.

Polyimide is known as a resin having excellent heat resistance and chemical resistance, and is used as an interlayer insulator for electronic devices, a surface protective film, an alignment film for liquid crystal display elements, etc. ing. Generally, a polyimide is obtained by combining tetracarboxylic dianhydride or its derivative and diamine with N, N-dimethylacetamide (abbreviation: DAMc), N-methyl-
Polymerization is carried out in an organic solvent such as 2-pyrrolidone (abbreviation: NMP) to produce a polyamide precursor varnish, which is applied by spin coating or the like, and then imidized to obtain a polyimide. However, the polyamic acid varnish undergoes a large change in varnish viscosity even when stored at a low temperature (about 5 ° C.), and it is difficult to keep the quality of the alignment film, the insulating layer and the like constant. The cause of this viscosity change is in the literature (T.Miwa and S.Num.
ata: Polymer, 30, 898 (1989) and Hatsio Sugitani,
Yasuko Nakamura: Thermosetting resin: Vol.15, No.3 (199)
It is considered that amide exchange, hydrolysis and imidization proceed as described in 4)). Therefore, a polyimide precursor varnish having a high viscosity stability of the varnish even when stored at room temperature has been desired.

[0003]

2. Description of the Related Art To improve the viscosity stability of a polyimide precursor varnish, 1) increase the purity of the varnish and 2) store it at a very low temperature,
3) There are methods such as stable alkyl ester or silylation of a carboxyl group which is highly reactive among polyamic acids. However, since 1) has already been done, further purification is difficult. In 2), it is easy to absorb water because dew condensation occurs when putting it in and out of the storage. In 3), esterification and silylation are complicated in synthesis and could not be achieved by conventional techniques.

[0004]

An object of the present invention is to provide a polyimide precursor varnish having excellent varnish viscosity stability, a polyimide resin composition obtained by imidizing the varnish, and its use.

[0005]

[Means for Solving the Problems] Conventional DMAc and NMP
Polyamine acid varnish using amide, the addition of amine compounds and water accelerate the hydrolysis reaction and transamidation reaction, the molecular weight decreases (JAKreuz: J.Polym.Sci., Part
A, Polym. Chem., 28, 3787 (1990) and M. Hasegawa, Y. Shindo,
T.Sugiura, K.Horie, R.Yokota, and I.Mita: J.Polym.Sc
i., Part A, Polym. Chem., 29 , 1955 (1991))
Known by etc. Therefore, for the purpose of suppressing the hydrolysis reaction and the amide exchange reaction, the inventors examined various amine compounds having different basicities and various organic solvents, and found a polyimide precursor varnish excellent in the viscosity stability of the varnish which has never been obtained. It was

Since the polyimide precursor varnish of the present invention protects the functional groups of the polyamic acid with an amine compound and an organic solvent, the polyamic acid will not undergo a hydrolysis reaction or a transamidation reaction even if the varnish is prepared using water as the solvent. It won't happen. Therefore, the viscosity of the varnish changes little over time, and the storage stability is excellent. The reason is that the carboxyl group of polyamic acid and an amine compound form a salt, and the amide group of polyamic acid and an organic solvent form a complex. Therefore, despite the water-soluble varnish, carboxyls and amides are guarded, so that hydrolysis reaction or amide exchange reaction does not occur even in the presence of a large amount of water. The heat resistance and mechanical strength of the polyimide are almost the same as those of conventional polyimide precursor varnishes using conventional solvents.

In the present invention, it is represented by the following chemical formula 2.

[0008]

Embedded image

(Where A and B = aromatic group or aliphatic group, n
= 17-2920 is shown. ) And polyamic acid represented by 2-dimethylaminoethanol, 2-diethylaminoethanol, 2-methylaminodiethanol, dimethyl-
3-butanone, diethylamino-acetone, N-ethylaminodiethanol, N-methylaminoethanol,
2,2-aminodiethanol, 3-diethylamino-1
-A polyamic acid salt consisting of a reaction product with one or more amine compounds selected from propanol and amino-cyclohexane, and further DMAc, NMP, DMSO, D
A polyimide precursor varnish in which a polyimide precursor composed of a reaction product with one or more kinds of organic solvents selected from MF is dissolved in water.

To obtain the polyimide precursor varnish of the present invention, first, polyamic acid is indispensable. Polyamic acid varnish is available in the literature (CESroog, ALEndrey, SVAbramo, CEBe
rr, WM Edwards, KLOlioier, J. Polymer Sci., A-1,
No. 3,1375 (1965)), equimolar amounts of tetracarboxylic dianhydride and diamine are added to DMAc, N.
The method obtained by stirring polymerization in a solvent such as MP is most industrially suitable. The polyamic acid varnish obtained here was poured into water and stirred to remove polar solvents such as DMAc and NMP, and then dried to obtain a polyamic acid. This polyamic acid and the carboxyl group of the polyamic acid are from 0.6 to
A polyamic acid salt is prepared by reacting 1.0 equivalent of an amine compound, and 0.2 to 1.0 equivalent of an organic solvent is further added, and then water is added to form a polyimide precursor varnish having excellent viscosity stability. Created. The polyimide precursor varnish can be prepared by using two or more kinds of polyamic acid, an amine compound and an organic solvent.

The tetracarboxylic acid dianhydride required for the synthesis of polyamic acid is benzophenone-3,3 ', 4.
4'-tetracarboxylic dianhydride, diphenylsulfone-3,3 ', 4,4'-tetracarboxylic dianhydride,
2,2-bis (4-phthalic anhydride) propane. Oxy-bis (4-phthalic anhydride), 4,4 ′-(hexafluoroisopropylidene) phthalic acid dianhydride, 3,3 ′, 4
4'-biphenyltetracarboxylic dianhydride, 3,
3 ", 4,4" -p-terphenyltetracarboxylic dianhydride, diphenylether-3,3 ', 4,4'-tetracarboxylic dianhydride, pyromellitic dianhydride, trifluoromethylpyromellit Examples thereof include acid dianhydride and bis (trifluoromethyl) pyromellitic dianhydride.

On the other hand, diamines are o-tolidine, p-phenylenediamine, 2,4-diaminodiphenyl ether, 4,4'-diaminidiphenyl ether and 4,4 '.
-Diaminidiphenyl sulfone, 4,4'-diaminidiphenyl methane, 4,4'-diaminidiphenyl sulfide, 4,4 "-diaminoterphenyl, 4,4"-
Diaminodicyclylhexylmethane, 1,5-diaminonaphthalene, 4,4'-bis (p-aminophenoxy) biphenyl, 4,4'-bis (m-aminophenoxy) diphenyl sulfone, 2,2-bis (4 -(P-aminophenoxy) phenyl) propane, 3,3'-dimethyl-
4,4'-diaminodiphenylmethane, 2,7-diaminofluorene, acetoguanamine, 3,3'-dimethoxybenzidine, m-phenylenediamine, 2,2-bis (4- (p-aminophenoxyphenyl) hexafluoropropane, 2,6-diaminoanthraquinone, 1,4
-Diaminodurene, 2,6-aminotoluene, 2,5
-Diaminopyridine, 2,6-diaminopyridine, 2,
5-diaminotoluene, 2,3-diaminopyridine,
3,4-diaminopyridine, 4,4'-diaminobenzophenone, 4,4'-bis (p-aminophenoxy) diphenyl sulfone, benzoguanamine, 2,7-diaminonaphthalene, 3,4-diaminotoluene, m-xylenediamine , P-xylenediamine, 4,4'-dithiodianiline, o-phenylenediamine, 4,4'-methylenebis (2-methylcyclohexylamine) and the like.

The solvent used for polyamic acid synthesis is NMP,
There are DMF, DMAc (N, N-dimethylacetamide) and the like, and one kind or a mixture of two or more kinds may be used.

Since the molecular weight of polyamic acid is related to the strength of polyimide, the number average molecular weight (polystyrene conversion value) measured by GPC (gel permeation chromatography) is preferably 15,000 to 1,000,000. If it is 15,000 or less, the strength of the polyimide is insufficient, and if it is 1 million or more, the viscosity of the varnish becomes high, which is not preferable.

The amine compound which forms a salt with polyamic acid is 2
-Dimethylaminoethanol, 2-diethylaminoethanol, 2-methylaminodiethanol, dimethyl-3
-Butanone, diethylamino-acetone, N-ethylaminodiethanol, N-methylaminoethanol, 2,
2-aminodiethanol, 3-diethylamino-1-propanol, amino-cyclohexane and the like are available, but one kind or a mixture of two or more kinds may be used. These are preferably purified by distillation under a nitrogen atmosphere before use from the viewpoint of stability. In addition, the organic solvent that forms a complex with amide is NMP, D
There are MF, DMAc, etc., and one kind or a mixture of two or more kinds may be used.

The amount of the amine compound blended is preferably 0.6 to 1.1 equivalents, and particularly preferably 0.7 to 1.0 equivalents, relative to the carboxyl group of the polyamic acid. 0.6 equivalent or less and 1.
If it is 0 equivalent or more, the effect of protecting the carboxyl group is small.
The amount of the organic solvent blended is preferably 0.2 to 1.0 equivalent of the organic solvent with respect to the amide group of the polyamic acid, and particularly 0.3
~ 1.0 equivalents are preferred.

However, when a polyamic acid salt varnish is prepared using the amine shown below, solubility is low, varnish viscosity is extremely high, gel varnish is formed, storage stability of varnish viscosity is poor, and thermal imidization is performed. It is not preferable because it has a bad odor. Specifically, methylamine, ethylamine, propylamine, butylamine, pyridine, triethanolamine, diethanolamine, monoethanolamine, N-methylmorpholine, morpholine, piperazine, picoline, diethylenediamine, diethylamine,
2-diethylaminoethyl-methacrylate, 2-diethylaminoethyl-acrylate and the like.

The concentration of resin component (hereinafter represented by NV, unit =%) of the polyimide precursor varnish of the present invention is preferably 1 to 50 wt%. If it is 50 wt% or more, the viscosity of the varnish is remarkably increased, and there is a problem in workability. When it is 1 wt% or less, pinholes are easily generated in the obtained polyimide film, which is not preferable.

The polyimide precursor varnish of the present invention is excellent in solubility because there is no hydrogen bond in the molecular chain because the carboxyl group of the polyamic acid is protected. Therefore, NV can be increased. Therefore, it is excellent in the thick film of polyimide and the step coverage performance, that is, the flattening property.

[0020]

It is considered that the cause of the large decrease in viscosity of the polyamic acid varnish containing water is that the carboxyl or amide of the polyamic acid is attacked by water and has a low molecular weight. Therefore, since the carboxyl and amide of the polyamic acid are protected by the amine and the organic solvent by the polyimide precursor varnish of the present invention, the molecular weight does not change and the viscosity stability is excellent.

[0021]

EXAMPLES Before describing the present invention in detail with reference to Examples, first, a method for synthesizing a polyamic acid, a method for preparing a polyimide precursor varnish, and a method for producing a polyimide will be described.

(1) Polyamic acid Polyamide acid was synthesized by replacing a flask equipped with a thermometer, a nitrogen blowing tube, a calcium chloride tube, and a stirrer with nitrogen, and then stirring by adding 85 wt% of NMP as a reaction solvent and diamine. (In the examples and comparative examples, the polyamic acid was synthesized by NMP). After the diamine was completely dissolved, tetracarboxylic dianhydride was added. The compounding amount of the diamine and the tetracarboxylic dianhydride is 15 wt% in total, which is equimolar. Reaction temperature is room temperature, stirring speed is 100-200rp
went in m. After the reaction was started, the system that generated heat was water-cooled. The reaction time was 8 hours. Before that, when the varnish viscosity increased (molecular weight of polyamic acid increased) and it became entangled with the stirring bar (expression of Weisenberg hardening),
At that point the reaction was terminated. Further, a system having a varnish viscosity of 50 poise (at 25 ° C.) or less even after being reacted for 8 hours or more was further reacted for 1 day or more. Varnish viscosity after reaction is 5
Since the molecular weight is too high for those of 00 poise or more, 7
The polyamic acid was hydrolyzed by heating at 0 to 90 ° C., the molecular weight was lowered, and the varnish viscosity was adjusted to about 100 poise. Then put the varnish in water and stir it,
The polyamic acid was pulverized and the reaction solvent contained in the polyamic acid was extracted and removed. After separating by filtration, the pulverized polyamic acid is added again to warm water at 60 ° C., and while changing the warm water several times, 8
After washing for a period of time, the reaction solvent was completely removed from the polyamic acid. Use a vacuum dryer (40 ℃ / 0.1mmHg) for 3
Water was removed by drying for 6 hours to obtain dried polyamic acid.

(2) Preparation of Polyimide Precursor Varnish A predetermined amount of amine compound, organic solvent and water were added to dried polyamic acid and stirred for 5 hours to obtain a polyimide precursor varnish. Then, pressure filtration was performed using a 5 μm membrane filter to obtain a polyimide precursor varnish of the present invention.

(3) Preparation of Polyimide A varnish was spin-coated on a 4-inch silicon wafer and thermally imidized under the following conditions to obtain a polyimide. 50 ℃ / 3min + 100 ℃ / on a hot plate under nitrogen gas atmosphere
After heating for 3 minutes + 200 ° C./3 minutes + 350 ° C./3 minutes, it was cooled.

The names and abbreviations of the tetracarboxylic dianhydride, diamine and amine compounds used in the examples and comparative examples are shown below.

BPDA: 3,3 ', 4,4'-biphenyltetracarboxylic dianhydride, PMDA: pyromellitic dianhydride, BTDA: 3,3', 4,4'-benzophenonetetracarboxylic dianhydride ODPA: 3,3 ', 4,4'-diphenyloxytetracarboxylic dianhydride, DSDA: 3,3', 4,4'-diphenylsulfone tetracarboxylic dianhydride, PDA: 4-phenylenediamine , DAPP: 2,2-bis (4- (p-aminophenoxy) phenyl) propane, ODA: 4,4'-diaminodiphenyl ether, DMAEO: diethylaminoethanol, DEAPO: 3-diethylamino-1-propanol, DEABN: 1- Diethylamino-3-butanone, Table 1 shows the polyimide precursor crocodile made in each example. The composition of its properties.

[0027]

[Table 1]

The viscosity ratio of varnish was determined as follows. Clean the polyimide precursor varnish in a clean room (25
It was left for 30 days in (° C, 60% RH) and the viscosity ratio of the varnish was calculated from the following formula.

Varnish viscosity ratio = (viscosity of varnish left for 30 days / viscosity of initial varnish) The varnish viscosity is a rotational viscometer (manufactured by Tokyo Seimitsu Co., E
Type). Regarding the coefficient of thermal expansion of polyimide, a polyimide film (thickness 15 to 20 μm) was set in a thermophysical tester (TMA-3000 manufactured by Vacuum Riko Co., Ltd.), the temperature rising rate was 5 ° C./min, and the weight was applied per 1 μm of the film thickness. The elongation of the film was measured in tensile mode at 1 g. The coefficient of thermal expansion was calculated from the elongation rate of 100 to 200 ° C. in the elongation-temperature curve. Elongation at break is polyimide film (film thickness 15-
20 μm) cut into 10 mm x 70 mm is a Tensilon type tensile tester (CUT- manufactured by Orientec Co., Ltd.)
5T type), pulling speed 5 mm / min, measuring distance 20
It was measured in mm.

Example 1 As shown in Table 1, a polyamic acid was BPDA / ODA, a amine was DEABN, an organic solvent was NMP, and water was added to prepare a water-soluble polyimide precursor varnish of NV25 wt%. did. Table 1 shows the measurement results of the characteristics. As a result, an excellent value was shown, and particularly, the varnish viscosity ratio was 1.00, indicating excellent storage stability of the varnish. The α and breaking elongation also showed practically no problem.

[Examples 2 to 13] As shown in Table 1, in the same manner as in Example 1, a 25 wt% NV water-soluble polyimide precursor varnish was prepared from a polyamic acid, an amine compound, an organic solvent, and water, and various properties were measured. did. The results are also shown in Table 1. The varnish viscosity ratio was in the range of 0.99 to 1.04, and the viscosity stability of the varnish was extremely good. Other characteristics also showed practically sufficient values as in Example 1.

[Comparative Examples 1 to 3] The polyamic acids shown in Table 1 were measured. The solvent is NMP and NV 12%.
The viscosity ratio of the varnish was greatly increased to 1.36 to 2.05. The stability of the varnish viscosity is inferior to that in the examples. However, the elongation at break shows a large value.

Next, a method of manufacturing an electronic device using a polyimide composed of the polyimide precursor varnish of the present invention will be described.

FIG. 1 shows a cross-sectional view of the multi-layer wiring portion of the LSI. Aluminum wiring 3 is formed on the thermal oxide film 2 on the silicon wafer 1, and an insulating thin film of polyimide is formed on the interlayer insulating layer film of the wiring 3.

By forming the varnish of the present invention on the insulating thin film 4 by the spin coating method and heating and condensing it, the steps of the wiring 3 are alleviated and flattened, and a highly reliable wiring structure can be obtained. The same thing as the conventional polyimide precursor varnish using a polar solvent was obtained.

FIG. 2 shows a cross-sectional view of the thin film magnetic head. A lower magnetic body 6 and a geared alumina 7 are formed on the lower alumina 5. The first conductor coil 8 and the second conductor coil 10 are insulated by the interlayer insulating film 9. The upper magnetic body 11 is provided in the outermost layer. By forming the interlayer insulating film 9 by the spin coating method of the varnish of the present invention, the step difference of the interlayer insulating film 9 formed by the conductor coils 8 and 10 can be significantly reduced.

In the conventional method for forming an interlayer insulating layer, a thick coating is applied and then etching back is performed to process the film into a required film thickness. However, since the varnish of the present invention can have a high concentration, the amount of the etching back is conventional. It is less than half of that, and the manufacturing process can be shortened. An equivalent to a conventional polyimide precursor varnish using a solvent was obtained.

FIG. 3 shows a cross-sectional view of the multichip module. Copper wiring 14 is formed on the thermal oxide film 2 of the silicon wafer 1.
And a copper wiring 14 'is formed via the insulating thin film 4. A thin film electrode (Pb / Sn) 16 is provided on the copper wiring 14.
The solder ball electrode 17 is provided via the.

When the insulating film 4 is formed by using the polyimide obtained from the varnish of the present invention, the step of the insulating thin film caused by the copper wiring 14 can be flattened, so that a highly reliable wiring structure is provided.

As is clear from the examples and comparative examples, the polyimide precursor varnish of the present invention has excellent hydrolysis resistance and the like, and the varnish viscosity is extremely stable. Therefore, it is clear that high-quality insulating layers, protective films, and alignment films can be obtained.

[0041]

EFFECTS OF THE INVENTION The polyimide precursor varnish of the present invention is excellent in viscosity stability of varnish even though water is used as a solvent. Polyimide obtained from varnish can be used for a passivation film of a semiconductor device, a buffer coat film, an α-ray shielding film, a thin film magnetic head, a multi-chip module, an insulating layer of an LSI or the like.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a multilayer wiring portion of an LSI.

FIG. 2 is a sectional view of a thin film magnetic head.

FIG. 3 is a sectional view of a multi-chip module.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Silicon wafer, 2 ... Thermal oxide film, 3 ... Aluminum wiring, 4 ... Insulating thin film, 5 ... Lower alumina, 6 ... Lower magnetic body, 7 ... Gap alumina, 8 ... First conductor coil, 9 ...
Interlayer insulating film, 10 ... Second conductor coil, 11 ... Upper magnetic body, 14 ... Copper wiring, 16 ... Thin film electrode (Pb / Sn), 1
7 ... Solder ball electrode.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshinori Hirano 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Yasunari Maekawa 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi Ltd. Hitachi Research Laboratory

Claims (5)

[Claims] Claims: (However, A and B = aromatic group or aliphatic group, n = 17 to 29
20 is shown. ) Polyamic acid and 2-dimethylaminoethanol, 2-diethylaminoethanol, 2
-Methylaminodiethanol, dimethyl-3-butanone, diethylamino-acetone, N-ethylaminodiethanol, N-methylaminoethanol, 2,2-aminodiethanol, 3-diethylamino-1-propanol, amino-cyclohexane More than one type of amine compound and N, N-dimethylacetamide, N-
Methyl-2-pyrrolidone, dimethyl sulfoxide, N,
1. A polyimide precursor varnish comprising a polyimide precursor composed of a reaction product with one or more organic solvents selected from N-dimethylformamide and water. 2. The polyamic acid according to claim 1, an amine compound of 0.6 to 1.0 equivalent to the carboxyl group of the polyamic acid, and 0.2 to the amide group of the polyamic acid.
99 equivalent of polyimide precursor consisting of 1.0 equivalent of organic solvent
A polyimide precursor varnish comprising 50 wt% and 1 to 50 wt% of water as a solvent. 3. A polyimide resin composition obtained by heating and imidizing the polyimide precursor varnish according to claim 2. 4. An electrically insulating material comprising the polyimide precursor varnish according to claim 3. 5. An electronic device having an insulating layer formed of the electrically insulating material according to claim 4.