JPS5956452A - Composition for protecting semiconductor element - Google Patents

Abstract

PURPOSE:To provide the titled compsn. which gives a coating film having excellent heat resistance and adhesion, by blending an org. solvent and a filler contg. small quantities of U and Th with a solvent-soluble polyimide contg. a specified tetracarboxylic acid component and a silicon diamine component. CONSTITUTION:A tetracarboxylic acid dianhydride (A) contg. 41-59mol% of 3,3',4,4'-diphenyltetracarboxylic acid dianhydride and 59-41mol% of 3,3',4,4'- benzophenonetetracarboxylic acid dianhydride and a diamine (B) contg. 0.1- 10mol% of silicon diamine of the formula (wherein R1 is methylene, phenylene; R2 is methyl, phenyl; X is O, phenylene; n is 1, 3, 4) and optionally less than 30mol% of toluenediamine, are subjected to a polycondensation reaction by dehydration. An org. solvent and a filler contg. U and Th in a quantity of not more than 5ppb in total, such as synthetic silica, is blended with the resulting solvent-soluble polyimide to obtain the titled compsn.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a resin composition that is coated onto a semiconductor device to protect the device.

Traditionally, semiconductor devices have often been encapsulated with resin materials such as epoxy resins or ceramic materials, but these materials contain impurities such as uranium and thorium of several ppm. The above impurities emit alpha rays, which cause malfunctions (hereinafter referred to as soft errors) of memory devices and the like.

In recent years, as a measure to prevent such soft errors, semiconductor elements have been coated and protected with polyimide resin, which has an alpha ray shielding effect and has excellent heat resistance and electrical properties, and then encapsulated with the above-mentioned sealing material. A method has been proposed. Here, since the above-mentioned polyimide resin itself is difficult to dissolve in an organic solvent, it is generally dissolved in an organic solvent in the form of its precursor polyamic acid, and after coating this on a semiconductor element, By heating and curing (imidization), it becomes a polyimide resin that covers and protects the above-mentioned element.

However, this method has the disadvantage that the heat treatment to convert polyamic acid into polyimide requires a high temperature and a long time, and it is also necessary to apply the polyamic acid solution at a considerably low resin concentration to form semiconductor devices. There were major problems in workability for forming the protective film, such as pinholes being likely to occur in the film unless the film was made considerably thinner by spin coating the entire silicon wafer. If this film formation work is insufficient, the adhesion to the semiconductor element will be poor, and problems will likely arise in terms of electrolytic corrosion under high temperature or high humidity conditions.

From the above-mentioned viewpoints, this invention has a pin that has a high resin concentration and can be coated thickly by means such as screen printing, and has excellent heat resistance and adhesion by short-time heat treatment at a low temperature after coating. It is possible to form a hole-less polyimide protective film, which greatly improves the workability for forming the protective film and the resistance to electrolytic corrosion under high temperature or high humidity.In addition, this protective film has thermal shock resistance and inherent prevention of installation errors. The object of the present invention is to provide a composition for protecting semiconductor elements that has excellent functionality.

By the way, the applicant has already heated a specific tetracarboxylic dianhydride and a specific diamine to perform a dehydration polycondensation reaction consisting of an amidation reaction and a subsequent imidization reaction. We succeeded in forming a polyimide film with excellent adhesion to silicon-containing materials easily by heat treatment at low temperature for a short time and obtaining a solvent-soluble polyimide.

In the subsequent research, this invention dissolved the solvent-soluble polyimide obtained as described above in an organic solvent,
Further, a resin composition containing a filler having a very low content of uranium and thorium can be used to meet the above-mentioned purpose, especially in various solutions of polyimide precursors such as polyamic acid according to the above-mentioned proposal. This was done based on the knowledge that this protective composition is extremely suitable for preventing soft errors in semiconductor devices, which have no defects at all.

That is, this invention relates to 3,3,4,4-diphenyltetracarboxylic dianhydride (hereinafter simply referred to as s-BPDA) and 3,3,4,4-benzophenonetetracarboxylic dianhydride (hereinafter simply referred to as s-BPDA). The proportion of 5-BPDA in the total amount of both components is 41~
Tetracarboxylic dianhydride containing 59 mol% BTDA at a mixing ratio of 59 to 41 mol% and the following general formula; R2 is a methyl group, phenyl group or substituted phenyl group, X is an oxygen atom, phenylene group is a substituted phenylene group, n is an integer of 1 when R1 is a phenylene group or a substituted phenylene group, and 3 or 4 when it is a methylene group ] A solvent-soluble polyimide obtained by dehydration polycondensation with a diamine containing at least 0.1 to 10 mol% of a silicone diamine represented by the formula and which may contain toluene diamine in a proportion of less than 30 mol%. The present invention relates to a composition for protecting a semiconductor device, characterized in that a filler having a total content of uranium and thorium of 5 ppb or less is blended together with an organic solvent.

As described above, in the present invention, a specific proportion of silicone-based diamine represented by the above general formula is an essential component, a mixed diamine which may contain a specific amount of toluenediamine among other diamines, and a specific proportion of 5- The gist is that a filler with an extremely low content of uranium and thorium is kneaded into an organic solvent solution of a solvent-soluble polyimide obtained by dehydration polycondensation with a tetracarboxylic dianhydride consisting of BPDA and BTDA. According to this method, the resin can be easily coated thickly on the semiconductor chip by means such as screen printing with a high resin concentration, and after this coating, the organic solvent can be removed by heat treatment at a low temperature for a short time. Since a pinhole-free polyimide protective film with excellent adhesion and heat resistance can be formed, workability for forming the protective film and electrolytic corrosion resistance under high humidity or high temperature can be greatly improved.

Furthermore, the protective film thus formed has excellent thermal shock resistance due to the filler it contains, and this type of filler contains almost no uranium or thorium. Therefore, it does not interfere with the original purpose of the protective film, which is to prevent soft errors, and when various sealing materials such as epoxy resin are applied on top of this protective film, the α-ray shielding effect can be fully demonstrated. , greatly contributes to the reliability of the memory device.

The tetracarboxylic acid component used in this invention is
A mixed system of 5-BPDA and BTDA, where the proportion of 5-BPDA in the total amount of both components is 41 to 59 mol%.
, the proportion of BTDA is 59 to 41 mol%, and by using both dianhydrides in the above specific ratio, toluene diamine is less than 30 mol% (even 0) as a diamine component other than silicone diamine. Polyimides soluble in organic solvents can also be obtained using various diamines.

In addition to such tetracarboxylic dianhydride, 25
If it is a mol% powder drop, other tetracarboxylic acid components, such as 2,3,3,4-diphenyltetracarboxylic dianhydride (hereinafter simply referred to as a-BPDA), pyromellitic dianhydride (hereinafter simply referred to as PMDA and when), 3.3.4.
4-') phenyl ether tetracarboxylic dianhydride,
2,3,6,7-naphthalenetetracarboxylic dianhydride, 1,4,5,8-naphthalenetetracarboxylic dianhydride, etc. can be used. All of these tetracarboxylic acid components must be dianhydrides, and other tetracarboxylic acids themselves or their esters may have poor reactivity with the diamine component, or may produce non-Mercury alcohols as by-products. Removal of the by-products therein becomes troublesome and does not give good results to the formation of high molecular weight polyimide.

The diamine component used in this invention includes at least a silicon-based diamine represented by the above general formula, and various types of diamines, including less than 30 mol% of toluenediamine such as 2,4-toluenediamine and 2,6-toluenediamine. Diamines can be used, especially 4.4
- Diaminodiphenylmethane, 4,4-diaminodiphenyl ether, 3,3-diaminodiphenylmethane, para-phenylenediamine, meta-phenylenediamine, bendisibenzidine, 4,4-diaminodiphenylsulfone, 4,4-diaminodiphenyl sulfide, 3,3 −
Diaminodiphenyl sulfone, 3,3-diaminodiphenyl sulfide, 4,4-diaminodiphenylpropane-2,2.3,3-diaminodiphenylpropane-2.
Aromatic diamines such as No. 2 are preferred.

Specific examples of silicon-based diamines include those having the structural formula shown below, and the proportion used is 0.1 to 10 mol%, preferably 2 to 7 mol%. be. By using such a proportion, it is possible to produce a polyimide that is soluble in organic solvents and has excellent adhesion to semiconductor elements and heat resistance.

<Specific example of silicone-based diamine> GO+ a(3C1(3CH3a)) In the dehydration polycondensation reaction in this invention, the above tetracarboxylic dianhydride and diamine component are mixed in approximately equal moles (one or the other is in excess). ] and heating both components in a phenolic solvent to 80 to 200°C, usually 2 to 10
This is accomplished by a time reaction. This reaction is
A dehydration polycondensation reaction consisting of an amidation reaction and a subsequent imidization reaction is carried out, and the water produced as a by-product during the above imidization reaction is removed by distillation out of the reaction system.

Removal of water increases the reaction rate and results in the production of high molecular weight polyimides.

Phenolic solvents were selected because they are compatible with water (thus making it easy to distill off by-product water, are economical, and are easy to volatilize during film formation).Polar solvents such as pyrrolidone is unsuitable for this reaction from the above point of view. As the phenolic solvent, metacresol, para-cresol, xylenol, phenol, and mixed solvents thereof are used. A preferred method is to use an aromatic solvent such as toluene in combination to facilitate distillation of water.

The raw materials for polymerization consisting of the above organic solvents, the above tetracarboxylic dianhydride and diamine components may contain cationic impurities such as Na, K, Ca, etc. and anionic impurities such as C/. When you are there,
When the resulting polyimide solution is applied to a semiconductor device, there is a risk that the electrical characteristics and moisture resistance of the device will deteriorate. Therefore, each of the above raw materials should be sufficiently purified in advance by a well-known method before use. For example, it is desirable that the Na ion content be 5 PPm or less, preferably I PPm or less.

The polymerization reaction product thus obtained was almost completely imidized and had a concentration of 0.5 FI in N-methyl-2-pyrrolidone.
Intrinsic viscosity [η
) is a high molecular weight polyimide in the range of about 0.3 to 3.0.

The composition for protecting semiconductor elements of the present invention is obtained by kneading a filler with a total content of uranium and thorium of J5 ppb or less into the organic solvent solution of the solvent-soluble polyimide obtained as described above, For the purpose of surface treatment of the filler and improving its adhesion to the semiconductor element, various optional components such as a silane coupling agent and polysiloxane may be added as necessary for this crosstalk.

The above-mentioned filler used in this invention may be inorganic or organic. Typical examples of inorganic fillers include synthetic silica obtained by oxidizing purified silicon tetrachloride with oxygen smoke in the gas phase or oxidizing with plasma, and synthetic silica obtained by gelling silicic acid. Can be mentioned.

Typical examples of organic fillers include finely pulverized polyimide resins that have been heat-cured. In addition to powders made of resins, powders made of polyimide, isoindolo, and quinazolinedione resins obtained by reacting diaminocarbonamide with diamine and tetracarboxylic dianhydride or its derivatives are included, as well as powders made of resins. . As the diamine, diaminocarbonamide and tetracarboxylic dianhydride or derivatives thereof used in the above, any conventionally known diamines can be used, but aromatic ones are particularly preferred.

The inorganic filler and the organic filler are not particularly limited to those on the upper side (as long as the total content of uranium and thorium is 5 ppb or less, particularly preferably 2 ppb or less, conventionally known fillers can be used. The particle size of these various fillers is generally 30
The thickness is preferably 15 μm or less, preferably 15 μm or less. The amount used is usually 50 to 75% by volume, preferably 55 to 70% by volume of the solid bone in the entire composition.

In the present invention, as the organic solvent for dissolving the solvent-soluble polyimide, the phenolic solvent used in synthesizing the polyimide can be used as is, and if necessary, the same type of organic solvent or naphtha, xylene and It may be diluted with a mixed solvent containing a general-purpose solvent such as cellosolve. If necessary, after synthesizing the polyimide, precipitate it in acetone or methanol, filter and dry it to purify it, and then use cresol or other phenolic additives, N-methyl-2-pyrrolidone, N/N-dimethylacetamide, N,N- -dimethylformamide, to
N-diethylformamide, dimethyl sulfoxide,
It may be dissolved in various organic solvents such as hexamethylphosphoramide, tetramethylene sulfone, and 2-ethoxyethyl acetate 11. The amount of solvent is preferably such that the solid content concentration of the composition is about 20 to 50% by volume.

The composition for protecting a semiconductor device of the present invention prepared in this manner is coated onto a semiconductor device by means such as screen printing, and then heated to a temperature such as 180 to 250° C. that the organic solvent can volatilize. By heat-treating for 1 to 3 hours, a polyimide protective film having excellent adhesion, heat resistance, thermal shock resistance, and α-ray shielding prevention function can be obtained.

EXAMPLES Below, examples of the present invention will be described in more detail. In addition, the intrinsic viscosity below refers to N-methyl-2-
Means the value measured at 30°C at a concentration of 057/100- in pyrrolidone.

Example I S-BPDA 14.7! i! (0.05 mol),
BTDA15, IPCo, 05 mol), 4,4'-diaminodiphenyl ether 19.41i' (0,097 mol), and bis(3-aminopropyl)tetramethyldisiloxane represented by the above structural formula A 0.74 P C0
,003 mol), 154 g of meta- and para-mixed cresol
The mixture was added to 20 g of xylene, and the temperature was raised to 180° C. in 1 hour while stirring.

During the temperature rise, the reaction system temporarily solidified, but as it was further heated, it became a homogeneous solution at around 100°C.

Further, when the temperature of the reaction system reached 100 to 120°C, a dehydration reaction occurred and an imidization reaction began to proceed. The by-produced water was distilled out of the reaction system by azeotroping with xylene while flowing nitrogen gas. In this way, a transparent and viscous solution was obtained by heating and reacting at 170 to 180° C. for 8 hours.

This solution had a solid content concentration (measured by heating at 200° C. for 2 hours) of 26.5% by weight and an intrinsic viscosity of 0.82.

Also, after applying this solution on a glass plate, 80℃
When the infrared absorption spectrum was measured for the film obtained by heating and drying for 2 hours under 0.5 wan HP, it was found that 17
Absorption of <>C=O based on imide groups was clearly observed at 80 cm and 1720 cm.

Next, add uranium to 35 g of this solution (resin content: 10 g).
Synthetic silica powder with a total thorium content of 5 ppb or less (obtained by gas phase reaction of silica tetrachloride,
Specific gravity 2,2. 24.05' of particles having a maximum particle size of 30 μm were added and thoroughly kneaded with a three-roll mill to obtain a composition for protecting semiconductor devices of the present invention.

Examples 2 to 7 6 was carried out in the same manner as in Example 1, except that the raw materials for polymerization shown in Table 1 below were used and the reaction conditions were set as shown in the same manner.
A seed polyimide solution was obtained. The solid content concentration and intrinsic viscosity of each solution were as shown in the table. Each solution was formed into a film according to Example 1, and its infrared absorption spectrum was measured.
780 cm-'' Absorption at ()C=0 based on the niimide group was clearly observed.

Next, polyimide powder was added as a filler to each solution in a small proportion as shown in Table 1, and the mixture was thoroughly mixed using a three-roll roll to obtain a composition for protecting a semiconductor element of the present invention. The polyimide fine powder used in each example was obtained by finely pulverizing polyimide resin with a jet mill, and contained uranium,
Total thorium content is 2PPb or less, maximum particle size is 2
5 gn, and the average particle size is 10 μm.

Comparative Example I 1 mol of PMDA and 1 mol of 4,4-diaminodiphenyl ether in N-methylol-2-pyrrolidone at about 80°C
The mixture was stirred while being maintained at a temperature below (particularly at or near room temperature). As a result, the reaction proceeded rapidly, and the viscosity of the reaction system gradually increased, yielding a polyamic acid having an intrinsic viscosity of 0.7.

Next, 75 g of the same polyimide fine powder as in the example was added to 30.35' of this polyamic acid solution (resin concentration 165% by weight), thoroughly kneaded with three rolls, and then
-Rotational viscosity 2.00 when diluted with methyl-2-pyrrolidone
A composition for protecting a semiconductor element having a zero poise was obtained.

Comparative Example 2 PMDAQ, 5 mol and BTDAo, 5 mol were used as the tetracarboxylic dianhydride, and 4 mol was used as the diamine.
・4-diaminodiphenyl ether 0.6 mol and diaminodiphenyl ether carbonamide have an intrinsic viscosity of 1
．． A polyimide precursor of No. 8 was synthesized. Next, this precursor solution (resin concentration 12.5% by weight) 40! Synthetic silica powder 14I as in Example 1 was added to i' (5 g of resin).
i, and three or more rolls of each of the compositions of Examples 1 to 7 and Comparative Example 1.2 were coated on a model electrolytic erodible element having Al wiring. After heat treating each piece at 200°C for 120 minutes, they were assembled and molded into a 16-pin DIP, and this molded product was subjected to a 400-hour pressure tester at 142°C, 5 atm, and 9'596 RH. I did this. The results were as shown in Table 2 below. In addition, the above test caused the oven to fail due to corrosion of the Al wiring, and the test AI! The defective wiring rate for 40 wirings was investigated.

As is clear from the upper table of Table 2, the protective composition of the present invention can form a polyimide protective film with extremely excellent adhesion by applying heat treatment at a low temperature for a short time on a semiconductor element. I understand that there is something.

In addition, other tests have shown that the protective film formed by the above method has excellent heat resistance and thermal shock resistance, and has good electrical insulation properties because it has no pinholes. When this process was carried out, it was found that the original α-ray shielding effect was sufficiently exhibited.

Patent applicant: Nitto Electric Industry Co., Ltd. 40

Claims (1)

[Claims] (1) 3,3,4,4-diphenyltetracarboxylic dianhydride and 3,3',4,4'-benzophenonetetracarboxylic dianhydride, the former being 41 to 5% of the total amount of both components.
Tetracarboxylic dianhydride containing 9 mol% of the latter at a mixing ratio of 59 to 41 mol%, and the following general formula;
R1 is a methylene group, a phenylene group or a substituted phenylene group, k2 is a methyl group, a phenyl group or a substituted phenyl group, X is an oxygen atom, a phenylene group or a substituted phenylene group, n is 1 when R1 is a phenylene group or a substituted phenylene group , an integer of 3 or 4 in the case of a methylene group] and a diamine containing 0.1 to 10 mol% of silicone-based diamine, which may contain toluenediamine at a ratio of less than 30 mol%. Uranium and organic solvent are added to the solvent-soluble polyimide obtained by polycondensation.
1. A composition for protecting a semiconductor device, comprising a filler having a total thorium content of 5 ppb or less.