JPS6184025A - Formation of film on surface of semiconductor element - Google Patents

Abstract

PURPOSE:To obtain a polyimide thick film in a simple manner by a method wherein a diamino compound, consisting of the prescribed components A and B, and aromatic tetracarboxylic acid ester is dissolved into a solvent, the solvent is heated up, the heated solvent is coated on the surface of a semiconductor element and it is heated up again. CONSTITUTION:The equimolar amounts of diamino compound, consisting of 99-80mol% of component A of aromatic tetranucleus body diamine indicated by formula I and 1-20mol% of component B of diaminosiloxane indicated by formula B, and 3.3'.4.4'-biphenyl tetracarboxylic acid ester are dissolved into an insoluble solvent and a low molecular weight polymer solution, containing the imid-ring having the density of solid part of 20wt% or more at the viscosity of 100cps/25+ or -1 deg. is formed by heating the above-mentioned solution. This solution is coated on the surface of a substrate, the film forming component is hardened by heating and formed into a polyimide film. According to this method, a thick polyimide film can be formed on the surface of an element without performing a complicated coating work.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for forming a polyimide insulating film on the surface of a semiconductor element, such as the exposed surface of a PN junction of a semiconductor element.

[Background technology]

Conventionally, polyimide silicon, that is, siloxane-modified polyimide, which has excellent moisture resistance and adhesion, has been used as a junction protective film for a P-N junction of a semiconductor element or a passivation film on the surface of a semiconductor element. However, some high-voltage, large-current semiconductor devices, especially high-voltage diodes, are made of square chip-shaped semiconductor devices, and as a junction protective film for this P-N junction, a conventional siloxane-modified polyamic acid solution obtained by heat curing is used. If a polyimide film is used, the film thickness at the edge of the square chip may become too thin, resulting in discharge, resulting in a lower product yield and a problem in improving the initial good product rate. That is, in a normally used silicon diode of the mesa type semiconductor element type having a curved cylindrical shape as shown in FIG. The semiconductor element 4 is the lead wire 1a.

1b with solder, and these are sealed with a molding material 2 such as epoxy resin. The surface of the semiconductor element 4 is
A portion of the lead wire is covered with a polyimide film 6. However, when the semiconductor element 4 is a rectangular chip as shown in FIG. 2, the polyimide film 6 becomes very thin at the four corner edges, which may cause discharge and cause a significant increase in leakage current in the reverse direction. This was caused by the low solid content concentration, which is the concentration of polyimide forming components, of the siloxane-modified polyamic acid, which is a coating solution for forming a polyimide film.

Generally, a coating solution used for forming a polyimide insulating film is composed of a polyamic acid or a derivative thereof dissolved in an inert solvent. However, since the above polymer has a high molecular weight, the concentration of the polymer that can be dissolved in practical use is generally 5 to 30% by weight, and furthermore, when applying to the above diode etc., the application process such as brush painting or dispensing method is required. To improve its properties, it is further diluted with a solvent to lower the solution viscosity, typically from 50 to 130 centipoise (cps). However, the polymer concentration at this viscosity is usually 2
As a result, the edge portion of the square chip becomes extremely thin. In order to improve edge coverage, attempts have been made to thicken the edges by applying them multiple times, but this method increases the number of steps and reduces workability. In order to achieve sufficient edge coverage with at least one coating, the coating solution needs to be a highly concentrated solution with a high solid content concentration. Furthermore, the difference in level at the adhesive part of the semiconductor element to the lead wire is 10
It is also necessary to be able to form a transparent and tough film even if the thickness is 0 μm or more and the maximum film thickness is 100 μm or more. FIG. 4 is a cross-sectional view of one embodiment of a high voltage transistor, which is a discrete semiconductor. That is, a power transistor element 11 is fixed on a plating copper frame 8 with a heat sink, and is bonded to a lead frame with an aluminum wire 9, and on the surface of this element is formed a conventional polyamide acid or its derivative. polyimide protective film 1
2 are provided, and these are molded with a molding material 1 such as epoxy resin.
It is sealed with 0. This polyimide protective film 12 is mainly used for the purpose of improving the moisture resistance of the half body, and is usually made of 5 to 20
Sufficient characteristics are exhibited with a film thickness of approximately μm, but the bonding portion of the aluminum wire 9 (on the element surface) often has a thickness of 100 μm or more due to the surface tension of the coating solution. In some cases, the polyimide film did not become a transparent film but turned into powder. This is due to the fact that conventional polyamic acid coating solutions lack the ability to form thick films. In the powdered polyimide film, the dielectric withstand voltage is significantly lowered, causing an increase in leakage current and a decrease in the withstand voltage. Further, a similar problem has occurred on the side surface of a semiconductor element having a thickness of 300 μm or more.

[Purpose of the invention]

The present invention was made in view of the above circumstances, and an object of the present invention is to provide a method for forming a film on the surface of a semiconductor element, by which a thick polyimide film can be formed without performing complicated coating operations.

[Disclosure of the invention]

In order to achieve the above object, the method of forming a film on the surface of a semiconductor element of the present invention includes the steps of preparing a semiconductor element whose surface is coated with a solution for forming a polyimide film, and forming a film in the solution for forming a polyimide film. A method for forming a film on the surface of a semiconductor element, comprising a step of heating and curing a forming component to form a polyimide film. u
As f&, 99 to 80 mol% of the following A component and B
An imide ring-containing low molecular weight polymer solution obtained by dissolving equimolar or approximately equimolar diamino compound and aromatic tetracarboxylic acid ester consisting of 1 to 20 mol% of components in an inert solvent and heating the solution is used. Take composition.

A: (al) Aromatic 4 represented by the following general formula (1)
Nuclear diamine (bl) A diamine consisting of a diamine that does not contain a silicon atom in the molecule other than the above (al and B components).

However, the mutual molar ratio of (al and (bl) is 100:O~
It is 70:30.

B: Diaminosiloxane represented by the following general formula (2) That is, this invention uses an aromatic tetranuclear diamine represented by the general formula (1) that has an affinity for organic solvents, and a diaminosiloxane that has high adhesiveness to the surface of a semiconductor element. By using diaminosiloxane of the general formula (2) above in combination, these diamines and esters, which are slightly less reactive than aromatic tetracarboxylic dianhydrides, which are sensitive to diamines, are inactivated. By dissolving it in a solvent and subjecting it to heat treatment, it is possible to obtain a molecular weight substance 2 that has a significantly lower molecular weight than polyamic acid and has extremely good solubility despite having an imide ring.
00,000 or less, containing an imide ring (polyimide in which all the condensed parts are imidized, polymers or oligomers with a polyimide-polyamic acid structure in which the remainder is imidized with some unclosed parts), and used for forming polyimide films. This makes it possible to increase the concentration of the solution and form a thick polyimide film on the surface of a semiconductor element.

The semiconductor element surface to be treated with the imide ring-containing low molecular weight polymer solution (polyimide film forming solution) is as follows:
Usually refers to the exposed surface of the P-N junction. However, this also includes a case where a glass passivation film or the like is formed on this exposed surface.

This imide ring-containing low molecular weight polymer solution has the above formula (11
Aromatic tetranuclear diamine (A component) represented by the above formula (
Constructed using diaminosiloxane (component B) represented by 2). Suitable aromatic tetranuclear diamines include 2,2-bis(4-(4-aminophenoxy)phenyl)propane.Other preferred representative examples include 2,2-bis[3-methyl -4-(4-aminophenoxy)phenyl]propane, 2,2-bis[3-
Chloro-4-(4-aminophenoxy)phenyl]propane, 1.1-bis(4-(4-aminophenoxy)phenyl)ethane, 1.1-bis[3-methyl-4・-(
4-aminophenoxy)phenylcomethane, 1,1-bis[3-chloro-4-(4-aminophenoxy)phenyl]ethane, 1,1-bis[3,5-dimethyl-4-(
4-Aminophenoxy)phenyl]ethane, bisC4-
(4-aminophenoxy)phenylcomethane, bis[3
-Methyl-4-(4-aminophenoxy)phenylcomethane, bis[3-chloro-4-(4-aminophenoxy)phenyl]ethane, bis[3,5-dimethyl-4-(
Examples include 4-aminophenoxy)phenylcomethane.

Note that up to 30 mol% of the aromatic tetranuclear diamine represented by the above general formula (1) can be a conventional diamine that does not contain a silicon atom in its molecule as part of the A component. Use beyond this point must be stopped because the ability of the resulting polyimide film-forming solution (hereinafter abbreviated as "film-forming solution") to form a thick film will be impaired. Examples of such conventional diamines include mononuclear diamines such as metaphenylenediamine and paraphenylenediamine;
．． 4′-diaminodiphenylmethane, 4,4″-diaminodiphenyl ether, 2.2″-bis(4-aminophenyl)propane, 3.3″-diaminodiphenylsulfone, 4,4′-diaminodiphenylsulfone,
4. Dinuclear diamines such as 4'-diaminodiphenylsulfide, benzidine, benzidine-3°3'-disulfonic acid, benzidine-3-monosulfonic acid, benzidine-3-monocarboxylic acid, and 3°3'-dimethoxybenzidine , 4-4″-diamino-p-terphenyl, 1°4-bis(m-aminophenoxy)benzene, 1.4-
Bis(p-aminophenoxy)benzene, 1.4-bis(m-aminosulfonyl)benzene, 1.4-bis(p
-aminophenylsulfonyl)benzene, 1,4-bis(m-aminophenylthioether)benzene, 1,4
- trinuclear diamine such as bis(p-aminophenylthioether)benzene, 4.4' -diaminodiphenyl ether-3-carbonamide, 3.4' -diaminodiphenyl ether-4-carbonamide, 3,4' -
Diaminocarbonamide compounds such as diaminodiphenyl ether-3'-carbonamide, 3.3'-diaminodiphenyl ether-4-carbonamide, 4.4
″-(4-aminophenoxy)diphenylsulfone,
Included in general formula (1) such as 4.4°-(3-aminophenoxy)diphenylsulfone, 4.4′-(4-7minophenoxy)diphenylsulfide, 4.4′-(4-aminophenoxy)biphenyl, etc. Examples include aliphatic diamines such as tetranuclear diamines, hexamethylene diamine, and heptamethylene diamine, and alicyclic diamines such as 1,4-diaminocyclohexane, isophorone diamine, and 4,4'-diaminodicyclohexylmethane.

The diaminosiloxane (component B) represented by the above general formula (2) is used as an adhesion improver in order to improve the adhesion of the produced polyimide film to the semiconductor element.

However, if a large amount is used, the heat resistance etc. of the produced polyimide film will be impaired, so the amount used needs to be set at 1 to 20 mol% of the total diamino compound. The preferred amount is 1 to 4 mol%. In other words, if the amount of diamino-siloxane used exceeds 20 mol%, the heat resistance and moisture resistance of the resulting polyimide film will decrease, and if it is less than 1 mol%, the adhesion to the semiconductor element will become poor. be. Representative examples of such diaminosiloxanes are as follows.

CH,CH3 CH, C)! .

C) 13 CH:I Cb Hs Cb It 5 CHz CH3 CbHs OCH3CbHs In this invention, an aromatic tetracarboxylic acid ester is used as the acid to be reacted with the diamino compound consisting of the A component and the B component. As such an aromatic tetracarboxylic acid ester, one having a molecular weight of about 200 to 700 is usually used. This type of ester is e.g.
Aromatic tetracarboxylic dianhydride and m having 4 or less carbon atoms
It is made by reacting with alcohol. Examples of such alcohols include methanol, ethanol, n-
Examples include propatool, 5ec-propatool, n-butanol, see-butanol, and tert-butanol. Among these alcohols,
Methanol, ethanol, n-propertool.

It is preferable to use 5ec-butanol, and methanol and ethanol are most preferable. Representative examples of aromatic tetracarboxylic dianhydrides to be reacted with the above-mentioned alcohol include pyromellitic dianhydride,
3,3',4.4''-benzophenonetetracarboxylic dianhydride, 3,3',4.4''-biphenyltetracarboxylic dianhydride, 2,3.3',4'-biphenyltetracarboxylic acid 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)propanihydride, bis(3,4-dicarboxyphenyl)sulfone dianhydride, 3,4,9.10-perylene Tetracarboxylic dianhydride, bis(3,4-dicarboxyphenyl)ether dianhydride, 2,2°-(2,3-dicarboxyphenyl)propanihydride, ■, 1'-bis(2,3- dicarboxyphenyl)ethane dianhydride, benzene-1,
2,3,4-tetracarboxylic dianhydride, 2.3.6.
7-anthracenetetracarboxylic dianhydride, 1,2,
7.8-phenanthrenetetracarboxylic dianhydride is mentioned.

Esterification was performed by adding an excess amount of alcohol to the aromatic tetracarboxylic dianhydride to a reaction vessel, heating to reflux at the boiling point of the alcohol, and reacting at least one alcohol with one anhydride group. This can be carried out by using a polyester having a structure of aromatic tetracarboxylic acid diester or higher, and distilling off excess alcohol after the reaction is completed.

Among the above aromatic tetracarboxylic acid esters, particularly preferred are 3,3'',4.4'-biphenyltetracarboxylic acid dimethyl ester and 3.3'',4.4
'-biphenyltetracarboxylic acid diethyl ester. These suitable esters usually do not have an acid anhydride group, and when these aromatic tetracarboxylic acid esters are used, the thickest polyimide film can be formed, and the formed polyimide film has the same properties as a polyimide film with the same structure obtained via polyamic acid. Of course, it is possible to form a thick film even when dianhydride esters other than the above-mentioned esters are used, but it is preferable to take measures such as relaxing the heating conditions.

In this invention, first, a film-forming liquid is manufactured using the above raw materials, for example, in the following manner. That is, A component 99 centered on aromatic tetranuclear diamine represented by formula (1)
~20 mol% and a diamino compound having a composition of 1 to 20 mol% of component B consisting of diaminosiloxane represented by formula (2) and an aromatic tetracarboxylic acid ester in an equimolar or approximately equimolar inert solvent. , after dissolving at room temperature or a temperature below 70°C to make a homogeneous transparent solution, 80-2
The mixture is heated to 00°C to proceed with polycondensation by dealcoholization reaction. As a result, the desired film-forming liquid is obtained. The film forming solution obtained in this way has a low molecular weight imide ring-containing polymer, and furthermore, aromatic tetranuclear diamine with high solvent affinity is introduced into the polymer, so that polyimide formation is possible. The component polymer described above can be dissolved at a high concentration. The solid content concentration (the above-mentioned polymer concentration), which is the concentration of the polyimide-forming component in this film-forming solution, can vary depending on the application, but as a guide, the solution viscosity of the coating solution is 100 cps (at 25 ± 0.1 °C). ) is preferably adjusted so that the solid content concentration is 20% by weight or more.

Note that the heat treatment of the inert solvent solution is preferably performed at a temperature of 80 to 200°C as described above. By heating under the above temperature conditions, the molecular weight is 2100~
A polymer containing an imide ring and having a low molecular weight of 200,000 is obtained. Here, the above molecular weight is based on polystyrene? J substance and expansion? Each section shows the weight average molecular weight determined by gel permeation chromatography using tetrahydrofuran. In addition, depending on the type of ester group in the aromatic tetracarboxylic acid ester, the reaction rate of the dealcoholization reaction is sometimes fast (as a result, the molecular weight of the polymer containing an imide ring is not only 200,000 but also higher than that). Insolubilization in an inert solvent may also occur. In such a case, it can be dealt with by conducting the reaction at a low temperature, etc.

Further, the above-mentioned inert solvent that dissolves the aromatic tetracarboxylic acid ester and diamino compound refers to an organic solvent that does not react with the above-mentioned ester and diamino compound and is capable of dissolving the produced low molecular weight polymer. Examples of such inert solvents include N-methyl-2-pyrrolidone, N,N"-dimethylformamide, N,N'-
Examples include highly polar basic solvents such as dimethylacetamide, N,N'-dimethylsulfoxide, and hexamethylphosphoramide. Of course, other solvents such as tetrahydrofuran, acetophenone, cyclohexanone, triethylene glycol dimethyl ether, and dioxane can also be used. Moreover, these solvents can also be used in combination with general-purpose solvents such as toluene, xylene, benzonitrile, benzene, and phenol. but,
The amount used must be controlled within a range that does not reduce the solubility of the produced polymer.

Next, using the film forming liquid obtained as above,
A polyimide film is formed on the surface of a semiconductor element as follows. That is, the film forming liquid is applied to the surface of the semiconductor element. In this case, the film forming liquid is usually applied not only to the element surface but also to the vicinity thereof. Since this film-forming liquid is a highly concentrated liquid, a thick coating layer can be formed by applying it twice. Next, add this to 200-350
Heat to ℃. As a result, the low molecular weight polymer in the film forming solution is polymerized and converted into polyimide, forming a thick polyimide film. It should be noted that the film-forming solution may occasionally contain unreacted monomers, but these unreacted monomers are converted into low-molecular-weight polymers ( (polymer and oligomer), so there is no need to specifically remove it. The polyimide film formed on the surface of the semiconductor element as described above is
Polyimide has good heat resistance, chemical resistance, mechanical properties, and excellent electrical insulation properties. Therefore, it can be applied to various conventionally known uses.

The above film forming liquid is also useful as a binder for pastes in which various fillers are dispersed, since it is excellent in not only thick film forming properties but also moldability. That is, it can be used as a binder for a heat-resistant conductive paste made by dispersing conductive fillers such as silver powder, gold powder, palladium powder, etc. for chip bonding, electrodes of electronic components, etc. Furthermore, by dispersing organic or inorganic fillers containing uranium or thorium of 5 ppb or less, it can also be used as a screen printing paste for preventing soft errors.

〔Effect of the invention〕

As described above, the present invention uses the aromatic tetranuclear diamine of the general formula (1) and the diaminosiloxane of the general formula (2) together, and allows these diamines to react with an aromatic tetracarboxylic acid ester. Since the high concentration imide ring-containing low molecular weight polymer solution prepared by is used as a solution for forming a polyimide film, a thick polyimide film can be formed on the surface of a semiconductor element by one application of this solution and heat treatment. It becomes like this. Therefore, there is no need to apply the solution many times as in the past. In other words, even for conventional prismatic chip-shaped semiconductor devices, which required multiple coatings to form a thin film on the edges of the prismatic areas, it is possible to achieve a sufficient film thickness on the edges with just one coating. You will be able to finish it. Furthermore, it becomes possible to easily form a polyimide film thicker than 100 μm, which was impossible to achieve with conventional polyamic acid solutions because of the powdering phenomenon.

In particular, in this invention, the diamine and aromatic tetracarboxylic acid ester are not dissolved as they are and used as a solution for forming a polyimide film, but are used after a considerable reaction. During the heat treatment, almost no alcohol is liberated from the aromatic tetracarboxylic acid ester. Therefore, an excellent effect is obtained in that the polyimide film does not have micropores that occur when free alcohol escapes into the atmosphere. As described above, according to the present invention, 10 coats can be coated on a semiconductor device in - times of coating.
A transparent polyimide insulating film with a thickness of 0 μm or more can be formed. Therefore, in addition to protective films for diodes and transistors, the present invention is useful for forming protective films for cyclers and integrated circuits such as ICs and LSIs that require thick films. In particular, VLS
The α-ray shielding film of the memory cell of I is usually 20 to 70
A film thickness of micrometers is required, and in order to achieve this thickness, conventionally a large amount of a coating solution made of polyamic acid or its derivatives was applied using a spinner method or potting method, but in order to prevent the polyimide film from turning into powder, This required sophisticated and complicated processes such as strictly controlling the amount of coating and managing coating accuracy. However, according to the present invention, it is possible to form a film with a predetermined thickness in just one coating time, which eliminates the need for the above-mentioned sophisticated and complicated processes, simplifying the overall process and making the work easier. It becomes possible to realize simplification.

Further, the present invention can be applied to liquid crystal alignment films of liquid crystal cells made of glass substrates including transparent electrodes, laminates, and various insulating films.

Next, examples will be described.

In addition, in the following examples, solution viscosity and solid content concentration were measured as follows.

(1) Total viscosity Measurement was performed using an E-type rotational viscometer at 25±0.1°C.

(2) Solid content concentration Where, W,; Weight of Petri dish (g) W2: Weight of sample and Petri dish (g) w,: Weight of sample and Petri dish after drying at 150°C for 60 minutes and further at 200°C for 60 minutes. Weight (g) [Example 1] In a flask equipped with a stirrer, a cooling tube and a thermometer,
29.4 g (0.1 mol) of 3.3',4.4°-biphenyltetracarboxylic dianhydride and 160 g of methanol (
5 mol) was added thereto, and the mixture was heated under reflux at 64 to 65° C. for 6 hours until the reaction system became transparent. Thereafter, excess methanol was distilled off, and the methanol residue was further completely distilled off under reduced pressure. The obtained esterified product has an acid value of 311 and an IR
From the spectrum, it was confirmed that it was 3.3', 4.4'-biphenyltetracarboxylic acid dimethyl ester. Next, 3, 3', 4.4 obtained in this way
'-Biphenyltetracarboxylic acid dimethyl ester 35
．． 8 g (0.1 mol) and 39.57 g of 2,2-bis(4-(4-aminophenoxy)phenyl)propane.
(0,0965 mol) and bis(3-aminopropyl)tetramethyldisiloxane 0,87 g (0,003
5 mol) and N-methyl-2- and Loliton 69.8 g
The solution was stirred at 40° C. for 2 hours to obtain a transparent solution, and then stirred at 80° C. for 20 hours to obtain a transparent viscous solution (film-forming liquid). The film forming liquid thus obtained has a solid content concentration of 50.3% and a solution viscosity of 4000%.
It was cps.

Next, the above film-forming solution was poured into water, the resulting reprecipitated polymer was dried under reduced pressure, and then an infrared absorption spectrum was measured. A characteristic absorption band of C=O appeared. From this result, it was confirmed that the above polymer contained an imide ring.

[Example 2] Into the same reaction vessel as in Example 1, 29.4 g of 3.3',4.4''-biphenyltetracarboxylic dianhydride (0,1
mol) and 300 g (5 mol) of n-propatool,
The mixture was heated to reflux at 97° C. for 4 hours until the reaction system became transparent. After that, excess n-propertool was distilled off, and 3.3'
4.4°-Biphenyltetracarboxylic acid di-n-propyl ester was synthesized. Then, the obtained 3, 3″, 4.
To 41.4 g of 4''-biphenyltetracarboxylic acid di-n-propyl ester, 38.95 g of 2,2-bis[4°(4-aminophenoxy)phenyl]propane (0,0
95 mol) and 1.24 g (0,005 mol) of bis(3-aminopropyl)tetramethyldisiloxane and N-
After adding 81.6 g of methyl-2-pyrrolidone and stirring at 60°C for 2 hours, the mixture was stirred at 105°C for 2 hours, and then stirred at 150°C for 2 hours.
The mixture was stirred at ℃ for 1 hour to prepare the desired film-forming solution.

The solid content concentration of the obtained film-forming liquid was 50.5%, and the solution viscosity was 4900 cps.

Next, the film-forming solution obtained as described above was poured into water, and the resulting reprecipitated polymer was dried under reduced pressure, and then an infrared absorption spectrum was measured.As shown in FIG.
Characteristic absorption bands of <>C=O based on imide groups appeared at 780 cm-' and 1720c111-'. From this, it was confirmed that the above polymer was a polymer containing an imide ring.

[Example 3] Instead of 3.3', 4.4'-biphenyltetracarboxylic dianhydride, the same mole of 3.3', 4.4''-benzophenonetetracarboxylic dianhydride was used. A film forming solution having a solid content concentration of 50.0% and a solution viscosity of 1800 cps was prepared in the same manner as in Example 1 except for this.

Next, the film-forming solution obtained as described above was poured into water, and the resulting reprecipitated polymer was dried under reduced pressure, and then an infrared absorption spectrum was measured. As shown in FIG.
A characteristic absorption band of <>C═O based on the imide group was observed in 780an-' and 1720C1ll-', and it was confirmed that they were polymers containing imide rings.

[Example 4] Instead of 41.0 g (0.1 mol) of 2.2-bis(4-(4-aminophenoxy)phenyl)propane, 2.2
-33.62 g (0,082 mol) of bis[4-(4-aminophenoxy)phenyl]propane and 4.47 g (0,082 mol) of bis(3-aminopropyl)tetramethyldisiloxane (
0,018 mol) was used. Other than that, the same procedure as in Example 1 was carried out, with a solid content concentration of 50.0% and a solution viscosity of 1300 c.
A ps film forming solution was obtained.

Next, the film-forming solution obtained as described above was poured into water, and the resulting reprecipitated polymer was dried under reduced pressure, and then an infrared absorption spectrum was measured.As shown in FIG.
Characteristic absorption bands of <>C═O based on imide groups were observed at 780an-' and 1720cm-', confirming that the polymer contained imide rings.

[Comparative Example 1] Aromatic tetracarboxylic dianhydride was not esterified and used as it was. That is, 29.4 g (0.1 mol) of 3,3',4,4'-biphenyltetracarboxylic dianhydride and 2,2-bis(4-
(4-aminophenokidine phenyl)propane 39.
57 g (0,0965 mol) and 0.87 g (0,00 mol) of bis(3-aminopropyl)tetramethyldisiloxane
35 mol) and N-methyl-2-pyrrolidone 279,4
g and stirred while maintaining the temperature at 30° C. or lower (particularly at or near room temperature). As a result, the polymerization reaction proceeds quickly and the viscosity of the reaction system increases, resulting in a solid content concentration of 19.9% and a solution viscosity of 2,000,000 cp.
A polyamic acid solution of s or more was obtained. Next, add this to 60
Heat and age the solution at 3000 cp while keeping it at ℃.
The solution was then diluted with N-methyl-2-pyrrolidone to a solution viscosity of 105 cps. The solid content concentration of this polyamic acid solution was 10.5%.

[Comparative Example 2] In a reaction vessel similar to Example 1, 3 obtained in Example 1,
3", 4,4'-biphenyltetracarboxylic acid dimethyl ester 35.8 g (0,1 mol) and 4,4'-diaminodiphenyl ether 19.3 g (0,0965 mol)
and 0.87 g (0,0035 mol) of bis(3-aminopropyl)tetramethyldisiloxane in N-methyl-2
- Added to 49.6 g of pyrrolidone and stirred at 40'C for 2 hours to completely dissolve, followed by stirring at 80'C for 20 hours to form a clear viscous solution. This polymer solution had a solid content concentration of 49.8% and a solution viscosity of 2000 cps.

Next, the coating solutions obtained in Examples 1 to 4 and Comparative Examples 1 to 2 were brushed onto the P-N junction surface of a high-voltage silicon diode having a square chip shape, including a part of the lead frame. After coating, drying and curing, the semiconductor device was sealed with a resin molding material. Table 1 shows its drying, curing conditions, initial characteristics (forward voltage, good product rate, reverse withstand voltage good product rate, number of good products out of 100 samples), and 121 The measurement results of the reverse leakage current yield rate after steam pressure Kutsuker test (abbreviated as PCT) at ℃ and 2 atm are shown.

(Left below) When the polyimide forming coating solution prepared in Examples 1 to 4 is used, the edges of the rectangular shape can also be covered thickly with a polyimide film, as shown in FIG. This can be prevented and the initial good product rate can be improved. Further, as shown in FIG. 5, similar effects were observed when the solution obtained in the above example was applied as an insulating film of a high voltage transistor. In addition, the above Examples 1 to 4
The coating solutions obtained in Comparative Examples 1 and 2 were sequentially diluted with the solvents constituting the solution, and the viscosity (25
(measured at ±1°C) and graphed it as shown in Figure 10. Straight line a corresponds to Example 1. b is Example 2. c is Example 3. d
indicates that of Example 4, and straight line e indicates that of Comparative Example 1. f indicates that of Comparative Example 2. As is clear from FIG. 10, it can be seen that the solutions of Examples have significantly higher solid content concentrations than those of Comparative Examples. Although Comparative Example 2 has a high solid content concentration, the resulting polyimide film becomes opaque and cannot be put to practical use.

[Brief explanation of drawings]

1(A) and 2(A) are longitudinal cross-sectional views of an example of a conventional semiconductor device, FIG. 1(B) and FIG. 2(B) are cross-sectional views thereof, and FIG. 4 is a conventional semiconductor device. FIG. 3(A) is an explanatory diagram of an example of a semiconductor device manufactured using the method of the present invention, FIG. 3(B) is a cross-sectional view thereof, and FIG. The figure is a longitudinal cross-sectional view of another example of a semiconductor device similarly manufactured using the method of the present invention, Figures 6 to 9 are infrared absorption spectra of polyimide obtained in Examples, and Figure 10 is a coating It is a solid content concentration-solution viscosity diagram of a solution. Patent Applicant Nitto Electric Industry Co., Ltd. Agent Patent Attorney Yukihiko Nishifuji 6. Contents of the amendment Procedural amendment (self-initiated February 18, 1985, published in 1985, Shōmo 205253 No. 2, Title of the invention Method for forming a film on the surface of a semiconductor device 3, Person who makes a gong (with a cow) Related Patent Applicant Address: 1-1-2, Noriyoshi, Sueichi, and Ina (396) Hiyorihi 1, Fukuyani, Yu, Hijikata, 3rd Department, 4, Agent's Specification (1) Specification, page 18, line 19 eyes, "99-20 mol%
, j is corrected to "99 to 80 mol%."

Claims (3)

[Claims] (1) A semiconductor element surface comprising the steps of preparing a semiconductor element whose surface is coated with a polyimide film-forming solution, and heating and curing film-forming components in the polyimide film-forming solution to form a polyimide film. A method for forming a film on a polyimide film, in which a diamino compound consisting of 99 to 80 mol% of component A and 1 to 20 mol% of component B and an aromatic tetracarboxylic acid ester are mixed in an inert solvent as the polyimide film forming solution. 1. A method for forming a film on the surface of a semiconductor device, the method comprising using a solution of a low molecular weight polymer containing an imide ring obtained by dissolving the imide ring-containing low molecular weight polymer in equimolar or approximately equimolar amounts in a liquid and heat-treating the solution. A: (a) Aromatic tetranuclear diamine represented by the general formula (1) below▲There are mathematical formulas, chemical formulas, tables, etc.▼……(1) [In formula (1), R_1 and R_2 are hydrogen , a C1-C4 alkyl group, or CF_3, which may be the same or different from each other. R_3, R_4, R_5, R_6
are hydrogen, halogen, or an alkyl group having 1 to 4 carbon atoms, and may be the same or different. (b) A diamine that does not contain a silicon atom in its molecule other than the components (a) and B above. However, the mutual molar ratio of (a) and (b) is 100:0 ~
It is 70:30. B: Diaminosiloxane represented by the general formula (2) below ▲ Numerical formulas, chemical formulas, tables, etc. are available ▼ ...... (2) [In formula (2), R_7 is a divalent organic group, and R_8 is a monovalent organic group. It is an organic group, and n is an integer of 1 to 1000. ] (2) Aromatic tetracarboxylic acid ester is 3,3′,
The method for forming a film on the surface of a semiconductor device according to claim 1, wherein the film is formed of 4,4'-biphenyltetracarboxylic acid ester. (3) The imide ring-containing low molecular weight polymer solution is set such that the solid content concentration is 20% by weight or more when the solution viscosity is adjusted to 100 cps (25±1°C) The method for forming a film on the surface of a semiconductor element according to item 1 or 2.