JP2003064162A - Epoxy resin composition and semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an epoxy resin composition for sealing a semiconductor having excellent adhesion to a polyimide resin on the surface of a semiconductor element. SOLUTION: This epoxy resin composition for sealing the semiconductor consists essentially of (A) an epoxy resin containing 40-80 wt.% of a biphenyl type epoxy resin and 20-60 wt.% of an amorphous dicyclopentadiene-modified phenol type epoxy resin having <=60 deg.C softening point, (B) a phenol resin containing 60-90 wt.% of a phenolaralkyl resin and 10-40 wt.% of a modified novolak type phenol resin prepared by condensing phenol with cresols through an aldehyde in the presence of an acidic catalyst, (C) a curing accelerator and (D) an inorganic filler. The epoxy resin composition is characterized in that the equivalent ratio (total number of epoxy groups/total number of phenolic hydroxy groups) is 1.05-1.50 and the amount of the inorganic filler (D) is 85-93 wt.%.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an epoxy resin composition for semiconductor encapsulation having excellent adhesion to a polyimide resin on the surface of a semiconductor element and a semiconductor device having excellent solder crack resistance.

[0002]

2. Description of the Related Art In the market trend of miniaturization, weight reduction, and high performance of electronic devices, semiconductor elements are becoming highly integrated year by year.
Further, as surface mounting of semiconductor devices is promoted, demands for epoxy resin compositions used for sealing semiconductor elements are becoming more and more severe. Particularly in the current situation where surface mounting of semiconductor devices is becoming common, the absorbed semiconductor device is exposed to high temperature during solder reflow processing, and peels off at the interface between the semiconductor element or lead frame and the cured product of the epoxy resin composition. Occurs, resulting in cracks in the cured product and other defects that greatly impair the reliability of the semiconductor device, and prevention of these defects, that is, improvement of solder crack resistance is a major issue. To solve these problems, improvement of the epoxy resin used in the epoxy resin composition for encapsulation of semiconductor elements such as IC and LSI and the phenol resin as a curing agent has been made to improve the characteristics against the above problems. . Furthermore, for problems that cannot be solved by the encapsulating material, measures are taken by changing the shape of the lead frame, especially the shape of the island that is bonded to the semiconductor element, and the LOC (lead-on-chip) structure, window
The pad frame corresponds to this.

In recent years, as part of the elimination of environmentally hazardous substances,
Replacement of lead-free solder is under way. Since solder containing no lead has a higher melting point than conventional solder, the solder reflow temperature during surface mounting is about 20 ° C. higher than that of the conventional solder, and 260 ° C. is required. By changing the solder reflow temperature to accommodate lead-free solder, even in window / pad frames, peeling occurs at the interface between the cured product of the epoxy resin composition and the semiconductor element / pad, or at the interface between the semiconductor element and the resin paste for semiconductors. The problem of cracking of the semiconductor device due to the peeling of the semiconductor has arisen. A particular problem is that the semiconductor element is coated with a polyimide resin at the interface between the cured product of the epoxy resin composition and the semiconductor element. In semiconductor memories with higher integration, circuit miniaturization, and larger semiconductor elements, the aluminum circuit slides due to curing shrinkage of the epoxy resin composition and thermal shock during the soldering process, inorganic passivation film (oxidation on the surface of the semiconductor element In order to avoid the problem of cracking of silicon or the like), the surface of the semiconductor element is coated with a polyimide resin. Regarding the water absorption rate of the material constituting the semiconductor device, the polyimide resin is about 1%, and the epoxy resin composition and the resin pace for the semiconductor are approximately 0.
The polyimide resin shows the highest water absorption at 2 to 0.3%. During a high temperature process such as a solder reflow temperature of 260 ° C., water absorption significantly lowers the adhesion strength and causes interfacial peeling. However, the most peeling occurs at the interface between the cured epoxy resin composition and the polyimide resin in which more water is present. Easier to do. Therefore, an epoxy resin composition having good solder crack resistance, which improves the adhesion to a polyimide resin at high temperature and enhances the adhesion to a structure having a fine structure or a heterogeneous interface by imparting fluidity, is required. Has been done. Furthermore, in the semiconductor device for memory, LOC structure, non-L
Although a thin semiconductor device having an OC structure or a non-LOC window pad structure is applied, an epoxy resin composition for semiconductor encapsulation that can be commonly used for all structures is required in terms of manufacturing process control, inventory control, and cost. ing.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides an epoxy resin composition for semiconductor encapsulation which is excellent in adhesion to a polyimide resin on the surface of a semiconductor element, and particularly a LOC structure for memory.
A thin semiconductor device having a non-LOC structure and a non-LOC window pad structure, which is excellent in solder crack resistance, is provided.

[0005]

The present invention provides [1] (A)
An epoxy resin containing 40 to 80% by weight of the epoxy resin represented by the general formula (1) and 20 to 60% by weight of a non-crystalline epoxy resin having a softening point of 60 ° C. or less, (B) represented by the general formula (2). 60-90% by weight of phenolic resin,
A modified novolac type phenolic resin obtained by condensing phenol and cresols via an aldehyde in the presence of an acid catalyst 1
Phenol resin containing 0 to 40% by weight, (C) curing accelerator and (D) inorganic filler as essential components, equivalent ratio (total number of epoxy groups / total phenolic hydroxyl group) = 1.05 to 1.5
0 and the inorganic filler is 85 to 93% by weight, the epoxy resin composition for semiconductor encapsulation,

[0006]

[Chemical 3] (R1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms and may be the same or different.)

[0007]

[Chemical 4] (N is an average value and is an integer of 1 to 6)

[2] A semiconductor device comprising a semiconductor element encapsulated with the epoxy resin composition as described in the item [1].

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION The epoxy resin used in the present invention is
An epoxy resin containing 40 to 80% by weight of the epoxy resin represented by the general formula (1) and 20 to 60% by weight of a non-crystalline epoxy resin having a softening point of 60 ° C. or lower is essential. The biphenyl type epoxy resin represented by the general formula (1) has a low viscosity when melted, and thus provides excellent fluidity and wettability.
However, the biphenyl type epoxy resin represented by the general formula (1) has low viscosity when melted, but has poor crystallinity because it is crystalline. The meltability can be improved by using it together with a non-crystalline epoxy resin having a softening point of 60 ° C. or lower.

A non-crystalline epoxy resin having a softening point of 60 ° C. or less has a very good melting property, and when used in combination with the biphenyl type epoxy resin represented by the general formula (1), it melts the crystalline epoxy. Gives an accelerating effect. If the softening point exceeds 60 ° C., the effect of promoting the melting of the non-crystalline epoxy resin decreases, and the melt viscosity of itself increases,
The fluidity of the epoxy resin composition is reduced. Softening point is 60
The melt viscosity of the non-crystalline epoxy resin having a temperature of ℃ or less is higher than that of the biphenyl-type epoxy resin represented by the general formula (1), and it is favorable when used in combination with the biphenyl-type epoxy resin represented by the general formula (1). Excellent fluidity and wettability can be obtained. The softening point of the epoxy resin was measured according to the ring and ball method of JIS K7234.

An epoxy resin of the general formula (1) is used in an amount of 40-80.
Wt%, the best meltability by setting the amorphous epoxy resin having a softening point of 60 ° C. or less to 20 to 60% by weight,
It is possible to obtain an epoxy resin composition having low viscosity and excellent fluidity and wettability. If the epoxy resin of the general formula (1) is less than 40% by weight, the melt viscosity of the epoxy resin composition is high and good flowability and wettability cannot be obtained. 80
If it exceeds 5% by weight, the crystalline epoxy may not be completely melted, so that good fluidity and wettability cannot be obtained. If the fluidity and wettability are poor, a structure having a step, such as an LOC structure, may not have sufficient adhesiveness with a different type interface, or a thin semiconductor device cannot be filled. Other epoxy resins may be used in combination as long as the characteristics of the epoxy resin used in the present invention are not impaired.

The phenolic resin represented by the general formula (2) used in the present invention has a paraxylylene skeleton, and the cured product of the epoxy resin composition using the phenolic resin represented by the general formula (2) is hydrophobic. It has a low water absorption rate due to its structure, and a low cross-linking density, so it has a low elastic modulus in the high temperature region above the glass transition temperature, reducing thermal stress during soldering of surface mounting. It has a feature that it is excellent in adhesion to metals such as lead frames and semiconductor elements. Further, the paraxylylene bond between the phenyl groups has a feature that the heat resistance is less deteriorated although the crosslink density is low.

The modified novolac type phenol resin obtained by condensing the phenol (c) and the cresols (d) used in the present invention through an aldehyde in the presence of an acid catalyst is a good curability of the phenol resin and a low water absorption of the cresol resin. The characteristics that combine both are expressed. The molar ratio (c: d) of c and d in the modified novolac type phenol resin is 2: 8 to 8 :.
2 is preferred. This is because when the proportion of phenol is high, the curability and strength are improved, but the water absorption resistance is reduced,
This is because when the proportion of cresols is high, the water absorption resistance is improved but the curability and strength are reduced. As cresols, there are three kinds of isomers of orthocresol, para-cresol and meta-cresol, and these may be used alone or in combination of two or more kinds, but orthocresol is easily available as an industrial product. Is preferred. The aldehyde source used for the synthesis is not particularly limited, but formaldehyde (formalin) or paraformaldehyde is preferable because it is industrially mass-produced and inexpensive. As a method for synthesizing the modified novolac type phenolic resin of the present invention, for example, orthocresol and formaldehyde (formalin) are reacted in the presence of an acid catalyst, and then phenol and formaldehyde (formalin) are added to obtain a condensation reaction. There is also a method, a method of adding formaldehyde (formalin) to orthocresol and phenol, conducting a condensation reaction in the presence of an acid catalyst, and removing unreacted substances to obtain a solid resin. The molar ratio (c: d) in the phenol resin is 2: 8 to 8: 2
If so, the synthesis method is not particularly limited.

The weight average molecular weight of the modified novolac type phenol resin used in the present invention is preferably 2000 or less. This is because by setting the weight average molecular weight to 2000 or less, the viscosity at the time of heating and melting can be suppressed to a low level, and the inorganic material can be highly filled. The modified novolac type phenolic resin of the present invention has a lower viscosity, excellent flow characteristics, and good curability, as compared with a low water-absorbing phenol aralkyl resin, and an epoxy resin of higher quality. A composition can be obtained. On the other hand, low stress and low water absorption are inferior to phenol aralkyl resin. The weight average molecular weight in the present invention is GPC (Gel Permeation
Chromatography) is the value obtained by converting to polystyrene. That is, Tosoh Corp. GPC column (G
1000H x L: 1 line, G2000H x L: 2 lines, G3
000H × L: 1 present) using a flow rate of 1.0 cm ^3/60
Sec., Tetrahydrofuran as the eluting solvent, column temperature 4
The value was measured by using a differential refractometer as a detector under the condition of 0 ° C., and calculated in terms of polystyrene.

60 to 90% by weight of a phenol aralkyl resin represented by the general formula (2) and 10 to 40% by weight of a modified novolac type phenol resin obtained by condensing phenol and orthocresols via an aldehyde in the presence of an acid catalyst. When used in combination, the best balance among low water absorption, low stress, low viscosity, and curability is obtained, and an epoxy resin composition having excellent adhesion and solder crack resistance can be obtained. The phenol aralkyl resin represented by the general formula (2) is 60
If the amount of the modified novolac-type phenol resin, which is less than 40% by weight, of phenol and orthocresols condensed with an aldehyde in the presence of an acid catalyst, exceeds 40% by weight, low water absorption and low stress will be reduced, and the epoxy resin composition Adhesion and solder crack resistance are reduced. When the modified novolac type phenolic resin obtained by condensing phenol and orthocresols via an aldehyde in the presence of an acid catalyst is less than 10% by weight, low viscosity and curability are deteriorated, and the adhesiveness of the epoxy resin composition,
Solder crack resistance is reduced. Other phenol resins may be used in combination as long as the characteristics of the phenol resin used in the present invention are not impaired.

In the present invention, the polyimide resin present on the surface of the semiconductor element targeted for adhesion has a surface treated with plasma, so that the C—N bond in the imide ring is preferentially cleaved, resulting in a carboxyl group or an amino group. A functional group such as a group has been introduced. Therefore, by setting the equivalent ratio of the total epoxy resin to the total phenolic resin to be 1.05 to 1.50, the epoxy resin that does not contribute to the crosslinked structure is compatible with the functional groups such as carboxy groups and amino groups on the polyimide resin surface. Alternatively, it reacts and gives excellent adhesion. The equivalent ratio referred to in the present invention refers to the ratio of the number of epoxy groups in the epoxy resin / the number of phenolic hydroxyl groups in the phenol resin. Further, by setting the equivalent ratio to 1.05 to 1.50, the epoxy resin that does not contribute to the crosslinked structure imparts fluidity, and not only the polyimide resin but also the wettability with different kinds of interfaces such as metals is enhanced. Give effect. Equivalence ratio is 1.50
If it exceeds, a sufficient crosslinked structure cannot be obtained, so that the curability is greatly reduced, and a problem occurs in solder crack resistance. On the other hand, if the equivalent ratio is less than 1.05, the amount of epoxy resin that does not contribute to the cross-linking structure becomes extremely small, so that the wettability to the polyimide resin surface on the semiconductor element, which becomes large, becomes poor, and sufficient adhesion is obtained. It is not preferable because it cannot be done.

The curing accelerator (C) used in the present invention may be any one as long as it accelerates the reaction between the epoxy resin and the phenolic hydroxyl group, and those generally used for sealing materials can be widely used. For example, 1,8-diazabicyclo (5,4,0) undecene-7, triphenylphosphine, tetraphenylphosphonium tetraphenylborate, 2-methylimidazole and the like may be used alone or in combination. The inorganic filler (D) used in the present invention includes fused silica, spherical silica, crystalline silica, secondary agglomerated silica,
Examples thereof include porous silica, secondary agglomerated silica, silica obtained by pulverizing porous silica, and alumina, and fused silica is particularly preferable. 8 inorganic fillers for all epoxy resin compositions
It is essential to be 5 to 93% by weight. If it is less than 85% by weight, the strength of the cured product of the epoxy resin composition is insufficient,
Further, since the proportion of the resin component is increased, the water absorption rate is increased and the solder crack resistance is deteriorated. If it exceeds 93% by weight, the viscosity at the time of melting becomes high and the fluidity is lowered, so that it becomes impossible to mold a thin semiconductor device for memory.

The epoxy resin composition of the present invention comprises (A)-
(D) is an essential component, but if necessary, a silane coupling agent, a red phosphorus flame retardant, a brominated epoxy resin, a flame retardant such as antimony oxide, carbon black,
Coloring agents such as red iron oxide, low-stress additives such as silicone oil and rubber, and various additives such as release agents may be appropriately blended. In order to produce the epoxy resin composition of the present invention, components (A) to (D) and other additives are sufficiently homogeneously mixed with a mixer or the like, and then melt-mixed with a hot roll or a kneader, and after cooling. It can be obtained by crushing. The epoxy resin composition of the present invention may be used to seal electronic components such as semiconductors and to manufacture semiconductor devices by curing and molding by conventional molding methods such as transfer molding, compression molding, and injection molding.

Examples 1 to 5 The present invention will be shown below by examples. The components of the epoxy resin composition used in the examples are as follows. The blending ratio is shown in Table 1. The mixing ratio of each component is parts by weight. -Epoxy resin A: Biphenyl type epoxy resin represented by formula (3) (epoxy equivalent 190, melting point 105 ° C) -Epoxy resin B: Orthocresol novolac type epoxy resin (softening point 55 ° C, epoxy equivalent 196) -Epoxy resin C : Epoxy resin represented by the formula (4) (softening point 53 ° C, epoxy equivalent 244) -Phenol resin A: Phenol aralkyl resin represented by the formula (2) (softening point 75 ° C, hydroxyl equivalent 174) -Phenol resin B: Modified novolac type phenol resin obtained by condensing phenol and orthocresol at a molar ratio (5: 5) through an aldehyde in the presence of an acid catalyst (hydroxyl group equivalent 113, weight average molecular weight 910). Phenol resin C: phenol and orthocresol Condensation via aldehyde in the presence of acid catalyst in a molar ratio (7.5: 2.5) Modified novolac type phenol resin (hydroxyl group equivalent weight 108, weight average molecular weight 900) -Fused silica: Average particle size 20um-Red phosphorus flame retardant: Red phosphorus surface is coated with aluminum hydroxide, and then the surface is phenol resin The content of red phosphorus is 94% by weight, the average particle size is 4.5 μm, and the maximum particle size is 11 μm. 1,8-diazabicyclo (5,4,0) undecene-
7 (hereinafter referred to as DBU) -Silane coupling agent-Carnauba wax-Carbon black The above components are blended according to the prescription of Table 1, mixed with a mixer at room temperature, and kneaded with a twin roll at 50 to 130 ° C. Then, it was cooled and pulverized to obtain a molding material, which was tableted to obtain an epoxy resin composition for semiconductor encapsulation. This epoxy resin composition was molded using a low-pressure transfer molding machine (molding condition: 175 ° C., 6.9 MPa, 120 seconds), and the obtained molded product was post-cured at 175 ° C. for 8 hours and evaluated. The results are shown in Table 1.

[0020]

[Chemical 5]

[0021]

[Chemical 6]

<Evaluation method> Spiral flow: A mold for spiral flow measurement conforming to EMMI-1-66 was used and the mold temperature was 175 ° C.
The injection pressure was 6.9 MPa and the curing time was 2 minutes. The spiral flow is a fluidity parameter, and the larger the value, the better the fluidity. Unit: cm. × Solder crack resistance, peeling rate: The package used is 50
pTSOP (LOC structure, package size: 21 x 1
0x1.0mm, 42 alloy lead frame, chip size: 8.8x18.8x0.35mm), 44pTS
OP normal structure (non-LOC structure, package size: 18
× 10 × 1.0 mm, 42 alloy lead frame, island size: 5.0 × 8.5 mm, chip size:
4.5 × 8.0 × 0.35 mm), 44p TSOP window frame structure (non-LOC structure, package size: 18 × 10 × 1.0 mm, 42 alloy lead frame, island size / window size: 5.0 ×)
8.5 mm / 2.0 × 5.0 mm, chip size: 4.
5 x 8.0 x 0.35 mm) total 3 types. A semiconductor element having a polyimide resin film on the surface is LOC, non-LOC2
, A total of three types of TSOP type lead frames (42 alloy material, inner lead tips coated with silver plating), and then 175 ° C., 9.8 MPa, using the resin composition.
It was cured in 1 minute to obtain a molded product, which was post-cured at 175 ° C. for 8 hours to obtain a sample. Five packages were obtained for each material. This package was placed in a constant temperature and humidity chamber at 85 ° C. and 60% for 168 hours and then subjected to IR reflow treatment at 260 ° C. The package after processing is observed with a microscope and the rate of occurrence of external cracks [(number of cracked packages) /
(Total number of packages) × 100] was determined. Units%. The polyimide resin film on the surface of the semiconductor element inside the package after the treatment and the peeling on the back surface of the lead frame pad were observed with an ultrasonic flaw detector, and the ratio of the peeled area between the chip and the resin composition was measured. Peeling rate ((peeling area) / (chip area) x 100)%
Displayed in.

Comparative Examples 1 to 8 Compounds were blended according to the formulation shown in Table 2, epoxy resin compositions were obtained in the same manner as in Examples, and evaluated in the same manner as in Examples. Each component of the epoxy resin composition used in the comparative example is as follows. Epoxy resin D: Orthocresol novolac type epoxy resin (softening point 65 ° C., epoxy equivalent 200) Epoxy resin E: epoxy resin represented by the formula (4) (softening point 71 ° C., epoxy equivalent 248)

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

According to the present invention, a polyimide resin on the surface of a semiconductor device, an epoxy resin composition for semiconductor encapsulation excellent in adhesion to a metal lead frame, and a LOC for a memory.
Various thin semiconductor devices such as a structure, a non-LOC structure, and a non-LOC window pad structure have excellent solder crack resistance.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H01L 23/31 F term (reference) 4J002 CC054 CC074 CD00X CD04W CE003 DE147 DJ007 DJ017 EU076 EU116 EW016 EW176 EY016 FD017 FD156 GJ02 GQ05 4J036 AA01 AA05 AD07 DA02 DA05 DC41 DD07 FA02 FA05 FB06 FB08 GA04 JA07 4M109 AA01 BA01 CA21 EA06 EB03 EB04 EB12 EC05 EC09

Claims (2)

[Claims] 1. (A) An epoxy resin containing 40 to 80% by weight of the epoxy resin represented by the general formula (1) and 20 to 60% by weight of an amorphous epoxy resin having a softening point of 60 ° C. or lower, (B) ) The phenolic resin represented by the general formula (2) is added to 6
Phenolic resin containing 0 to 90% by weight, 10 to 40% by weight of a modified novolac type phenolic resin obtained by condensing phenol and cresols via aldehyde in the presence of an acid catalyst,
Equivalent ratio (total number of epoxy groups / total phenolic hydroxyl groups) with (C) curing accelerator and (D) inorganic filler as essential components
= 1.05 to 1.50 and the inorganic filler is 85 to 93
An epoxy resin composition for semiconductor encapsulation, characterized in that the content is wt%. [Chemical 1] (R1 represents a hydrogen atom or an alkyl group having 1 to 4 carbon atoms and may be the same or different from each other.) (N is an average value and is an integer of 1 to 6) 2. A semiconductor device obtained by encapsulating a semiconductor element using the epoxy resin composition according to claim 1.