JPH0859832A - Water-soluble polyamic acid salt and polyimide precursor varnish, polyimide and its use - Google Patents

Abstract

(57) [Abstract] [PROBLEMS] To provide a polyimide precursor varnish containing water, which is preferable for the global environment, as a solvent, a novel polyamic acid salt used in the production thereof, and an electrically insulating polyimide resin composition obtained therefrom. [Structure] General formula (Formula 1), (In the formula, A and B are aromatic groups, n is 17 to 2920), and 2-methylaminodiethanol, dimethyl-3-butanone, and diethylamino-
Acetone, N-ethylaminodiethanol, N-methylaminoethanol, 2,2-aminodiethanol, 3-
Water-soluble polyamic acid salt consisting of a reaction product with one or more amine derivatives selected from diethylamino-1-propanol and amino-cyclohexane, and 1 to 60 wt% of the amidate salt, and 99 to 40 wt% of water as a solvent. An odorless water-soluble polyimide precursor varnish consisting of

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a novel water-soluble polyamic acid salt, an odorless water-soluble polyimide precursor varnish which is environmentally friendly, and a multi-chip module, a thin film magnetic head and a semiconductor device obtained by imidizing the varnish. And a polyimide suitable as an insulating layer of an electronic device, and an electronic device using the polyimide as an insulating layer.

[0002]

2. Description of the Related Art Polyimide is known as a resin having excellent heat resistance and chemical resistance, and its usage amount is increasing. In general, polyimide includes tetracarboxylic dianhydride or its derivative and diamine, N, N-dimethylacetamide (abbreviation: DAMc), N-methyl-2-pyrrolidone (abbreviation: NMP), N, N-dimethylformamide (abbreviation: It is obtained by reacting in a polar solvent such as DMF) to produce a high molecular weight polyamic acid varnish, which is applied by spin coating or the like and then thermally imidized. However, about 85 wt% or more of the polar solvent contained in the varnish applied during thermal imidization is vaporized and released into the atmosphere. At present, when the amount of use is increasing, it is not preferable to use a polar solvent for the polyimide precursor varnish from the viewpoint of the global environment, and improvement thereof has been demanded.

The following representative polyimide varnishes that do not use a polar solvent are known. A polyimide precursor varnish consisting of a polyamic acid salt and water as a solvent is described in T. Yamashita, H. Higuchi, K. Horie, and
I.Mita, Proceedinds of the International Symposium
on "Polymers for Microelectronics-Science and Tec
hnology- "(PME '89), Tokyo, Japan, October 29 to N
ovember 2, (1989). This is to make water soluble by making a polyamic acid salt from a carboxyl group of a polyamic acid and an amine. Although a water-soluble polyimide precursor varnish is obtained by this method, the amine used, triethylamine, is known as a liquid having an extremely strong ammonia odor. Therefore, the above-mentioned water-soluble varnish is not preferable in working environment and cannot be put into practical use because triethylamine evaporates and a strong bad odor is generated during compounding or coating, particularly during thermal imidization.

Japanese Patent Publication No. 3-15659 discloses that
Method for producing water-soluble resin by making polyamic acid salt from polyamic acid, which is a product of 1,2,3,5-tricarboxy-pentylacetic acid or its anhydride and diamine, and ammonia or an organic base compound to make it water-soluble Is listed. When using ammonia, odor and toxicity become problems. On the other hand, the organic base compound has a problem that the varnish viscosity is lowered due to hydrolysis of the organic base compound due to addition of amine and hydrolysis due to addition of amine, resulting in cleavage of the main chain. When the varnish viscosity decreases, the mechanical strength of the polyimide decreases. In other words, in order to put the water-soluble polyimide precursor varnish into practical use by the polyamic acid salt method, there have been problems of low poisoning, deodorization and storage stability of the varnish.

[0005]

Therefore, the present invention solves the above-mentioned problems of the prior art, and is an odorless water-soluble polyimide precursor varnish which is excellent in mechanical strength and storage stability of varnish and is preferable from the global environment. Another object of the present invention is to provide a novel polyamic acid salt for obtaining the same, a polyimide resin composition imidized with the same, and uses thereof.

[0006]

In order to solve the above-mentioned problems, the present invention uses the general formula (Formula 1),

Embedded image (In the formula, A and B are aromatic groups, n is 17 to 2920), and 2-methylaminodiethanol, dimethyl-3-butanone, and diethylamino-
Acetone, N-ethylaminodiethanol, N-methylaminoethanol, 2,2-aminodiethanol, 3-
It is a water-soluble polyamic acid salt comprising a reaction product with one or more amine compounds selected from diethylamino-1-propanol and amino-cyclohexane.

In the present invention, the water-soluble polyamic acid salt is contained in an amount of 1 to 60% by weight, and the solvent water is contained in an amount of 99 to 40% by weight.
An odorless water-soluble polyimide precursor varnish consisting of Further, in order to solve the above other problems, in the present invention, the odorless water-soluble polyimide precursor varnish is a polyimide resin composition obtained by heat imidization, the polyimide resin composition is an electrical insulation It can be preferably used as a material and can form an insulating layer of an electronic device.

Next, the present invention will be described in detail. First, a method for producing the polyamic acid of Chemical formula 1 for obtaining the polyamic acid salt will be described. Polyamic acid is available in Polymer Sci., A-1,3, 1375.
The method obtained by stirring and polymerizing equimolar amounts of tetracarboxylic dianhydride and diamine in a polar solvent such as DMAc or NMP as described in (1965) is most suitable for industrialization. The polyamic acid 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 was reacted with 0.5 to 2 times the molar amount of amine in water to form a polyamic acid salt, thereby preparing an odorless water-soluble polyimide precursor varnish. An odorless water-soluble polyimide precursor varnish can be obtained by using two or more polyamic acids.

The tetracarboxylic acid dianhydride necessary 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, as the diamine, o-tolidine,
p-phenylenediamine, 2,4-diaminodiphenyl ether, 4,4'-diaminodiphenyl ether,
4,4'-diaminodiphenyl sulfone, 4,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfide, 4,4'-diaminoterphenyl,
4,4 "-diaminodicyclohexylmethane, 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-phenylenedimine, 2,
2-bis (4- (p-aminophenoxyphenyl) hexafluoropropane, 2,6-diaminoanthraquinone, 1,4-diaminodurene, 2,6-aminotoluene, 2,5-diaminopyridine, 2,6-diamino Pyridine, 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
-Xylylenediamine, p-Xylenediamine, 4,4 '
-Dithiodianiline, o-phenylenediamine, 4,
4'-methylenebis (2-methylcyclohexylamine) and the like.

The polar solvent used for polyamic acid synthesis includes NMP, DMF, DMAc 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 15,000 to 10,000.
00 is preferable. If it is 15,000 or less, the strength of the polyimide is insufficient, and if it is 1,000,000 or more, the viscosity of the varnish becomes high, which is not preferable.

As amine compounds for forming salts with polyamic acid, 2-methylaminodiethanol and dimethyl-3-
Butanone, diethylamino-acetone, N-ethylaminodiethanol, N-methylaminoethanol, 2,2
-Aminodiethanol, 3-diethylamino-1-propanol, and amino-cyclohexane, 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.

When a water-soluble polyimide precursor varnish is prepared using any of the following amines other than those mentioned above, it is not preferable because the solubility is low, the varnish viscosity is high, the storage stability of the varnish viscosity is poor, and the bad odor is severe. These amines include methylamine, ethylamine, propylamine,
Butylamine, pyridine, triethanolamine, diethanolamine, monoethanolamine, N-methylmorpholine, morpholine, piperazine, picoline, diethylenediamine, diethylamine, 2-diethylaminoethyl-methacrylate and the like. The varnish concentration (resin concentration) of the polyimide precursor varnish of the present invention is 60 to 1 wt.
% Is preferred. If it is 60 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.

These polyimide precursor varnishes of the present invention were spin-coated to obtain polyimide under the following heating conditions in a hot air dryer under a nitrogen gas atmosphere. Start heating from room temperature (heating rate 2 ° C / min) 50 ° C / 30 minutes, then 100 ° C / 3
After 0 minutes, 200 ° C./30 minutes, 350 ° C./30 minutes, it was cooled. Further, since the polyamic acid salt of the present invention has excellent solubility, it is possible to increase the concentration of varnish. Therefore, the step coverage, that is, the flattening property is excellent.

[0015]

The odorless water-soluble polyimide precursor varnish obtained from the polyamito acid salt of the present invention is water and is harmless even if a large amount of the solvent is released into the air during thermal imidization. Excellent in storage stability with little change in varnish viscosity over time. Therefore, in the polyimide precursor varnish which is preferable in the global environment, the polyimide shows the same value as that of the polyimide precursor varnish which has been used up to now using the co-polar solvent having heat resistance and mechanical strength.

[0016]

EXAMPLES The present invention will be described in detail below with reference to examples. Example 1 (1) Synthesis of Polyamic Acid After synthesizing polyamic acid, a flask equipped with a thermometer, a nitrogen blowing tube, a calcium chloride tube, and a stirrer was replaced with nitrogen, and then 85 wt% of NMP as a reaction solvent and diamine were added. Charge and stir (in Examples and Comparative Examples, polyamic acid was synthesized by NMP). After the diamine has completely dissolved,
Tetracarboxylic dianhydride was added. The compounding amount of the diamine and the tetracarboxylic dianhydride is 15 wt% in total, which is equimolar.

The reaction temperature is room temperature, and the stirring speed is 100 to 20.
It was performed at 0 rpm. Water was cooled in the system that generated heat after the reaction started. The reaction time was 8 hours. Before that, when the viscosity of the varnish was increased (the molecular weight of the polyamic acid was increased) and the state became entangled with the stirring bar (expression of Weisenberg hardening), the reaction was terminated at that time. 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. A varnish having a viscosity of 500 Poise or higher after the reaction has an excessively large molecular weight, and therefore is heated to 70 to 90 ° C. to cause a hydrolysis reaction of the polyamic acid to reduce the molecular weight to make the varnish viscosity 100.
It was adjusted to about Poise.

After that, the varnish is poured into water and stirred forcibly,
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. This was dried in a vacuum dryer (40 ° C./0.1 mmHg) for 36 hours to remove water, and dried polyamic acid was obtained.

(2) Preparation of Polyimide Precursor Varnish To the dried polyamic acid, the amine compound of the present invention and water as a solvent were added and stirred for 5 hours to obtain a polyamic acid salt aqueous solution. 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 The above-mentioned varnish was spin-coated on a 4-inch silicon wafer and thermally imidized under the above conditions to obtain a polyimide.

The thermal decomposition temperature, thermal expansion coefficient (α), elongation at break, etc. were measured from this film. Next, those measuring methods are shown. Varnish viscosity It was measured at room temperature (25 ° C) using a rotational viscometer (Tokyo Seimitsu Co., Ltd., E type). Thermal Expansion Coefficient of Polyimide A polyimide film (film thickness 15 to 20 μm) is set in a thermophysical tester (manufactured by Vacuum Riko Co., Ltd., TMA-3000 type), and pulled at a temperature rising rate of 5 ° C./min and a load of 1 g per film thickness 1 μm. The elongation of the film was measured in the mode. The coefficient of thermal expansion was calculated from the elongation rate of 100 to 200 ° C. in the elongation-temperature curve.

Thermal Decomposition Temperature of Polyimide A polyimide film is thermobalanced (manufactured by Vacuum Riko Co., Ltd., TGD-
3000 type), water contained in polyimide,
After removing the condensation water due to the ring closure of the unreacted polyamic acid, the weight change when heated at a heating rate of 5 ° C./min was measured, and the temperature when the weight loss rate reached 3% was defined as the thermal decomposition temperature. did. Breaking Elongation of Polyimide Film A polyimide film having a width of 10 mm and a length of 70 mm was pulled by an autograph (manufactured by Shimadzu Corporation, DSS-5000 type) to measure its strength. The pulling speed is 5 mm / min and the measuring distance is 40 mm.

Storage stability A polyimide precursor varnish was cleaned in a clean room (25 ° C, 6
It was allowed to stand in 0% RH) and the storage stability was evaluated from the change in the viscosity of the varnish. The goal was to change the viscosity of the varnish within ± 20% when left for 1 month. Table 1 shows the viscosity and varnish concentration of the polyimide precursor varnish produced in the examples, and the characteristics of the polyimide obtained by thermally imidizing the varnish. In Table 1,
No. A to L are examples of the present invention, and for comparison, examples other than the present invention are No. Shown as a to d. In Tables 2 and 3, the tetracarboxylic dianhydride, diamine, used in Table 1,
The names and abbreviations of amines are shown.

[0023]

[Table 1]

[0024]

[Table 2]

[0025]

[Table 3]

In Table 1, No. As K and L, those obtained by mixing equimolar amounts of two types of polyamic acid were used. As shown in Table 1, those of the present invention show excellent values, and particularly, the varnish storage stability is excellent when the change in varnish viscosity is within ± 20%. No odor was felt during synthesis or thermal imidization. Further, the varnish having a varnish concentration of 40 wt% also increased the varnish viscosity, but had good storage stability and other properties,
The odor was also the same as that of the varnish having a concentration of 20 wt%.

On the other hand, for comparison, No. 3 using triethylamine (B-1) as the amine compound was used. In the case of a, the characteristics were the same as those of the present invention, but the viscosity of the varnish was drastically lowered, the storage stability was poor, and the odor was so bad that mass production in the factory was impossible. No. 2 using 2-diethylaminoethyl methacrylate (B-2) as the amine compound. In b and c, it did not completely dissolve and did not become a varnish. Further, No. using diethanolamine (B-3). In the case of d, the properties were equivalent to those of the present invention, but the varnish viscosity increased greatly and the storage stability was poor.

Example 2 Next, a method of manufacturing an electronic device using a polyimide composed of the odorless water-soluble polyimide precursor varnish of the present invention will be described. FIG. 1 shows a schematic cross-sectional view of a multilayer wiring portion of an LSI. Aluminum wiring 3 is formed on the thermal oxide film 2 on the silicon wafer 1.
The polyimide insulating thin film 4 is formed on the interlayer insulating film of the wiring 3. The varnish of the present invention is formed on the wiring thin film 4 by a spin coating method, and is heated and condensed so that the step of the wiring 3 is alleviated and flattened.
A highly reliable wiring structure can be obtained. The same thing as the conventional polyimide precursor varnish using a polar solvent was obtained.

Embodiment 3 FIG. 2 shows a schematic sectional view of a thin film magnetic head. A lower magnetic body 6 and a gap alumina 7 are formed on the lower alumina 5. First conductor coil 8 and second conductor coil 1
0 is insulated by the interlayer insulating film 9. The upper magnetic body 11 is provided in the outermost layer. By forming the above-mentioned 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 of forming an interlayer insulating layer, a thick coating is applied and then etch back is performed to process the film into a required film thickness. Therefore, the manufacturing process can be shortened. The same thing as the conventional polyimide precursor varnish using a polar solvent was obtained.

Example 4 FIG. 3 shows a schematic sectional view of a multichip module. Copper wirings 14 are formed on the thermal oxide film 2 of the silicon wafer 1, and copper wirings 14 ′ are formed via the insulating thin film 4. A copper ball 14 is provided with a solder ball (BLM: Ball Limiting Metallizati) via a thin film electrode (Pb / Sn) 16.
on) electrode 17 is provided. When the insulating film 4 is formed using the polyimide obtained from the varnish of the present invention, the copper wiring 1
Since the step of the insulating thin film caused by 4 can be flattened, a highly reliable wiring structure is provided. As is clear from the above examples, the odorless water-soluble polyimide precursor varnish of the present invention is excellent in hydrolysis resistance, and it is clear that the polyimide obtained by thermal imidization is excellent in heat resistance and mechanical strength. .

[0031]

The odorless, water-soluble polyimide precursor varnish obtained from the novel water-soluble polyamic acid salt of the present invention uses water as a solvent, so that an environment-friendly and excellent polyimide can be easily obtained. . It has excellent storage stability.
The above-mentioned polyimide can be used for a passivation film of a semiconductor element, a buffer coat film, an α-ray shielding film, a thin film magnetic head, a multichip module, an insulating layer of an LSI or the like.

[Brief description of drawings]

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

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

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

[Explanation of symbols]

1 ... Silicon wafer, 2 ... Thermal oxide film, 3 ... Aluminum wiring, 4 ... Insulating thin film, 5 ... Lower alumina, 6 ... Lower magnetic material, 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) Takao Miwa Inventor Takao Miwa 7-1, 1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi, Ltd. Hitachi Research Laboratory (72) Inventor Akio Takahashi 7-chome, Omika-cho, Hitachi-shi, Ibaraki No. 1 Hitachi Ltd. Hitachi Research Laboratory (72) Inventor Kazuyuki Horie 7-3-1 Hongo, Bunkyo-ku, Tokyo (72) Inventor Shun Yamashita 7-3-1 Hongo, Bunkyo-ku, Tokyo

Claims (5)

[Claims] 1. A general formula (Formula 1), (In the formula, A and B are aromatic groups, n is 17 to 2920), and 2-methylaminodiethanol, dimethyl-3-butanone, and diethylamino-
Acetone, N-ethylaminodiethanol, N-methylaminoethanol, 2,2-aminodiethanol, 3-
A water-soluble polyamic acid salt comprising a reaction product with one or more amine compounds selected from diethylamino-1-propanol and amino-cyclohexane. 2. An odorless water-soluble polyimide precursor varnish comprising 1 to 60 wt% of the water-soluble polyamic acid salt according to claim 1 and 99 to 40 wt% of water as a solvent. 3. A polyimide resin composition obtained by heating and imidizing the odorless water-soluble polyimide precursor varnish according to claim 2. 4. An electrical insulating material comprising the polyimide resin composition according to claim 3. 5. An electronic device having an insulating layer formed of the electrically insulating material according to claim 4.