JPS63142839A - Semiconductor device - Google Patents

Abstract

PURPOSE:To cope with the increase of an element in size and the miniaturization of wirings by adding an inorganic powder filler covered on the surface with a polymer of low molecules having a substance for performing internal stress reducing effect, phenol resin and vinyl group to an epoxy resin composition used for resin-sealing. CONSTITUTION:Phenol resin is operated as an epoxy resin hardener, and is adapted for preferably mixing epoxy group in the epoxy resin and hydroxide group in the phenol resin at equivalent ratio of 0.8-1.2. An inorganic powder filler covered on the surface with a polymer of low molecules having vinyl group is covered on the surface with the filler, such as silica, alumina, calcium carbonate, aluminum nitride, beryllium oxide, etc. The quantity of the polymer of the low molecules having the vinyl group is preferably 3-30% with respect to the epoxy resin composition from which the filler content is removed. The sealing of a semiconductor element using such epoxy resin composition is not limited, but formed by known molding method, such as a normal transfer molding, etc.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a highly reliable semiconductor device.

[Conventional technology]

Conventionally, semiconductor elements such as transistors, ICs, and LSIs
It used to be sealed with a ceramic package and made into a semiconductor device, but recently, from the viewpoint of cost and mass production,
Resin sealing using plastic packages has become mainstream. Epoxy resins have conventionally been used for this type of resin sealing, and have achieved good results. However, due to technological innovation in the semiconductor field, the degree of integration has increased, element sizes have become larger, and interconnects have become finer, and packages are also becoming smaller and thinner. There is a demand for further improvement in reliability (humidity resistance reliability, shock resistance reliability, heat resistance reliability, etc. of the obtained semiconductor device). In particular, internal stress caused by shrinkage of the epoxy resin composition due to cooling from the curing temperature to room temperature reduces the reliability of the epoxy resin composition, so reducing the internal stress is important.

[Problem that the invention seeks to solve]

As mentioned above, conventional epoxy resin compositions for sealing generate considerable internal stress during the process of cooling from the curing temperature to room temperature, which can cause damage to semiconductor elements, disconnection, etc. was causing problems. In order to reduce this internal stress, addition of rubber particles, modification with liquid elastomers, etc. have been carried out, but the presence of a large number of domains of such rubber particles in the epoxy resin matrix causes the epoxy resin composition to become There were also drawbacks such as reduced liquidity. For this reason, the optical characteristics are not entirely satisfactory, and there are limits to the reliability of semiconductor devices using them. , it is strongly desired to improve the characteristics even further.

This invention was made in view of the above circumstances, and provides a highly reliable semiconductor device by adding a substance that has an effect of reducing internal stress to an epoxy resin composition used for resin sealing. Its purpose is to

[Means for solving problems]

In order to achieve the above object, the semiconductor device of the present invention includes:
The structure is such that a semiconductor element is sealed using an epoxy resin composition containing the following components (A), (B), and (C).

(A) Epoxy resin.

(B) Phenol resin.

(C) An inorganic powder filler whose surface is coated with a low molecular weight polymer having vinyl groups.

The epoxy resin composition used in this invention consists of an epoxy resin (component A), a phenol resin (component B), and an inorganic powder filler (component C) whose surface is coated with a low-molecular polymer having a vinyl group. ), and is usually in powder form or tablet form.

Such an epoxy resin composition can be used as a plastic package with excellent low stress properties, especially by using the above-mentioned component C, and a highly reliable semiconductor device can be realized.

The epoxy resin serving as component A is not particularly limited, and examples include various epoxy resins conventionally used as encapsulating resins for semiconductor devices, such as cresol novolac type, phenol novolac type, and bisphenol A type. . Among these resins, it is preferable to use one that has a melting point above room temperature and is in the form of a solid or highly viscous solution at room temperature. Novolac type epoxy resin usually has an epoxy equivalent of 160
~250. Those having a softening point of 50 to 130°C are used, and particularly cresol novolac type epoxy resins have a softening point of 1tso to 210°C per epoxy. Those having a softening point of 60 to 110°C are generally used.

The phenolic resin of component B used together with the epoxy resin acts as a curing agent for the epoxy resin, and phenol novolak, cresol novolac, etc. are preferably used. These novolac resins have a softening point of 50 to 110°C and a hydroxyl equivalent of lOO to 13
It is preferable to use 0. Particularly, among the novolac resins mentioned above, use of Talesol novolac brings about good results.

The blending ratio of the epoxy resin as component A and the phenol resin as component B in the epoxy resin composition is such that the equivalent ratio of the epoxy group in the epoxy resin to the hydroxyl group in the phenol resin is 0.8 to 1. .2. The closer this equivalence ratio is to 1, the better the results.

The C component is an inorganic powder filler whose surface is coated with a low molecular weight polymer having vinyl groups. That is,
Silica, alumina, silicon nitride.

silicon carbide, zirconia, titanium white, talc, clay,
An inorganic powder filler such as calcium carbonate, aluminum nitride, or beryllium oxide is surface-coated with a low-molecular polymer having a vinyl group. The above-mentioned polymer of a low molecular weight substance having a vinyl group is a homopolymer obtained by polymerizing only a low molecular weight substance having one vinyl group, a low molecular weight substance having one vinyl group, and a low molecular weight substance having two vinyl groups. A copolymer with a compound having one vinyl group and a copolymer with one vinyl group
It is a copolymer of a low molecular weight substance with other functional groups,
One of these polymers is used to coat the surface of the inorganic powder filler. In some cases, the above two or three types of polymers may be used in combination. Examples of methods for coating the surface of an inorganic powder filler with the above polymer include the following two methods. Method (2) is a method in which a catalyst having polymerization initiating ability is attached to the surface of inorganic powder filler particles such as silica particles, and the surface is coated by polymerizing the above-mentioned low molecular weight substance having a vinyl group in this state. . Method (2) involves first polymerizing a low-molecular substance having a vinyl group to form a polymer, dissolving this in a solvent, etc., immersing an inorganic powder filler such as silica particles in the solution, and then drying. This is a method of surface coating.

To explain the method (2) above in more detail, a catalyst having polymerization initiation ability is dissolved in an organic solvent such as toluene, and an inorganic powder filler such as silica particles is added to this solution and mixed, followed by suction filtration. The obtained inorganic powder filler is placed under reduced pressure to scatter the remaining organic solvent, thereby producing an inorganic powder filler with the catalyst attached to the particle surface. Next, this is mixed with a low molecular weight substance having a vinyl group and polymerized by heating. The surface-coated inorganic powder filler obtained in this manner undergoes polymerization on the particle surface, so that the coating state is uniform and the internal stress is more effectively reduced. Method (2) is a method in which a low-molecular substance having a vinyl group is polymerized in advance in the presence of a catalyst, etc. that has polymerization initiation ability, and this is dissolved in a solvent, etc., and coated with an inorganic powder filler. It is. For example, when coating silica particles with polybutyl acrylate,
Toluene solution of butyl polyacrylate (about 1% by weight)
Silica particles are added to and dispersed, and then methanol is added to adsorb polybutyl acrylate onto the surface of the silica particles. In this case, methanol corresponds to the non-solvent for polybutyl acrylate. Further, it is preferable to treat the surface of the silica particles used for coating with a silane coupling agent in advance, since this will result in a better coating state. As such a silane coupling agent, general-purpose silane coupling agents such as epoxy silane and vinyl silane can be used.

Examples of catalysts having polymerization initiating ability used in methods (1) and (2) above include the following.

(Peroxide) Benzoyl peroxide, p-chlorobenzoyl peroxide, 2,4-dichlorobenzoyl peroxide, obrylyl peroxide, lauroyl peroxide, acetyl peroxide, cyclohexene peroxide, hydroxyhebutyl peroxide, tert- Butyl perbenzoate, tert-butyl peracetate, tert
tert-butyl octoate, tert-butyl peroxyisobutyrate, di-tert-butyl perphthalate, potassium persulfate, ammonium persulfate.

(Compound having a diazo group) 2.2''-azobis(2,4-dimethylvaleronitrile), 2,2°-azobis(isobutyronitrile), 4.
4'-azobis-4-cyanopentanoic acid, 2
．． 2'-azobis(2-amidinopropane) hydrochloride, 4
．． 4′-azobis-4-cyanovaleric acid, 2.2
° -azobis(2-methylvaleronitrile), 2.2
″-azobis(2,4-dimethylvalonitrile), 2,
2”-azobis(2-methylcapronitrile), 2.
2'-azobis(2,3,3-trimethylvaleronitrile), 2-phenylazo-2,4-dimethyl-4-methoxyvaleronitrile, 2-cyano-2=propylazoformamide, 1. lo -azobiscyclohexane-1-
Carbonitrile, 1,1"-azobis(cyclohexane-carbonitrile), ■, bi-azobis(cyclopentane-carbonitrile), 1,1°-azobis(cyclooctane-carbonitrile), 2,2'-azobis(
2゜4-dimethyl-4-methoxyvaleronitrile), 2
．． 2'-azobis(2,4-dimethyl-4-ethoxyvaleronitrile), 2,2'-azobis(2,4-dimethyl-4-n-butoxyvaleronitrile), 2.2''
-Azobis(2,4-dimethyl-4-benzyloxyvaleronitrile), 2,2゛-Azobis(2-nitropropane), 2.2"-Azobis(2-thiocyanato-propane), 2.2°- Azobis(2-thiophenylpropane), 2,2'-azobis(2-benzthiazole-
2″-thiopropane), 2.2″-azobis(2-methoxycarbonylpropane), 2.2′-azobis(2-
phenylpropionitrile), 2.2”-azobis(2
-methyl-3-chlorophenylpropionitrile), 1
．． 1°-azobis(1,1°-diphenylmethane), trans-3°5-diphenyl-1-pyrazoline, 1. l
” -azobis(1-cyclo-1-p-chlorophenylethane).

The catalysts exemplified above may be used alone or in combination.

In addition, the low-molecular substances having a vinyl group used for surface coating include: (1) a low-molecular substance having one vinyl group, (2) a low-molecular substance having two vinyl groups, and (1) a low-molecular substance having one vinyl group and another functional group. There are three types of low molecular weight substances that have groups. When only ① is used, the surface of the inorganic powder filler is coated with a homopolymer, and when ① and ③ are used,
The surface of the inorganic powder filler is coated with both copolymers. Similarly, when (1) and (2) are used together, the surface of the inorganic powder filler is coated with the copolymer of both.

Examples of the low molecular weight substances having one vinyl group include acrylic acid esters and alkyl groups that are methyl groups.

Ethyl group, n-propyl group, linear or branched butyl group, amyl, hexyl, octyl, cyclohexyl,
Those consisting of phenyl, 2-ethylhexyl groups, etc. Methacrylic acid esters: linear or branched alkyl groups having 1 to 12 carbon atoms, such as methyl, propyl, butyl, isobutyl, hexyl, cyclohexyl, isohexyl, octyl, dodecyl groups , octadecyl group, phenyl group, undecyl group, etc. Typical examples include octadecyl methacrylate,
Examples include hydroxyethyl methacrylate and 2-ethylhexyl methacrylate.

Vinyl esters: vinyl acetate, vinyl propionate,
Examples include vinyl butyrad. Vinyl ethers:
Examples include alkyl vinyl ethers, and preferred examples of the alkyl group include methyl, ethyl, propyl, butyl, amyl, hexyl, and the like. Vinyl cyanide: Methacrylic nitrile, maleic dinitrile, vinylidene dianiide, etc. can be mentioned. Vinylmaleimides: (meth)acrylamide, acrylic-substituted (meth)acrylamide, etc., and representative examples include:
Examples include N-methylacrylamide and N,N-dimethylacrylamide. Dienes: Isoprene, chloroprene, butadiene, etc. Other monomers include acrylonitrile, methacrylonitrile, vinylcarbazole, vinyl formal, vinylpyrrolidone,
0-vinylbenzyl alcohol, styrene, o-, m-
3p-methylstyrene, 2,4-dimethylstyrene, 2
, 5-dimethylstyrene, 3,4-dimethylstyrene,
p-tert-butylstyrene, p-phenylstyrene, p-phenoxystyrene, p-chlorostyrene, 2,
Examples include 5-dichlorostyrene, α-methylstyrene, and α-vinylnaphthalene. The above monomers may be used alone or in combination of two or more.

In addition, examples of low molecular weight substances having two vinyl groups include divinylbenzene, monoethylene glycol dimethacrylate,
Tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, trimethylolpropane trimethacrylate, 1,6-hexanediol dimethacrylate, bisphenol A1 dimethacrylate, diethylene glycol acrylate, tetraethylene glycol diacrylate, neo diacrylate Examples include pentyl glycol, 1,5-bentanediol diacrylate, 1,6-hexanediol diacrylate, and trimethylolpropane triacrylate. These may be used alone or in combination without any problem.

Further, examples of low molecular weight substances having one vinyl group and other functional groups include the following.

(Low molecular compound with epoxy group) Glycidyl methacrylate, glycidyl acrylate, etc.

(Low molecular weight substances with carboxyl groups) Acrylic acid, methacrylic acid, α-chloroacrylic acid, α
-bromoacrylic acid, α-cyanoacrylic f11. W
, hydromaleic acid, α-chloromaleic acid.

Dichloromaleic anhydride, itaconic acid, etc.

(Low molecular weight substances having hydroxyl groups) Hydroxyethyl methacrylate, hydroxyethyl acrylate, etc.

These may be used alone or in combination of two or more.

Note that the above-exemplified low-molecular substances having a vinyl group are usually composed of monomers, but in some cases, dimers may be used, and oligomers may also be used.

The amount of the low-molecular-weight polymer having vinyl groups in the inorganic powder filler whose surface is coated with the low-molecular-weight polymer having vinyl groups obtained as described above is The amount is preferably 3 to 30% based on the epoxy resin composition (A+B).

That is, if the content is out of the above range, the reliability of the resulting semiconductor device tends to decrease.

In addition, in the epoxy resin composition used in this invention, a curing accelerator may be used in addition to the above-mentioned components A to C, if necessary. Suitable examples of the curing accelerator include the following tertiary amines, quaternary ammonium salts, imidazoles, and boron compounds, which may be used alone or in combination.

Tertiary amine triethanolamine, tetramethylhexanediamine, triethylenediamine, dimethylaniline, dimethylaminoethanol, diethylaminoethanol, 2.4
．． 6-tris(dimethylaminomethyl)phenol, N
, N'-dimethylpiperazine, pyridine, picoline, 1
,8-diaza-bicyclo(5,4,0)undecene-7
, benzyldimethylamine, 2-(dimethylamino)methylphenol quaternary ammonium salt dodecyltrimethylammonium chloride, cetyltrimethylammonium chloride, benzyldimethyltetradecylammonium chloride, stearyltrimethylammonium chloride imidazoles 2-methylimidazole, 2-undecylimidazole , 2-ethylimidazole, 1-benzyl-2-methylimidazole, l-cyanoethyl-2-undecylimidazole, boron compounds, tetraphenylboron salts, such as triethyleneaminetetraphenylborate, N-methylmorpholinetetraphenylborate, and optionally Accordingly, in addition to the above raw materials, inorganic fillers, antimony trioxide, flame retardants such as phosphorus compounds, and pigments can be used.

The epoxy resin composition used in this invention can be produced, for example, as follows.

That is, the above components (A), (B), and (C) are blended together with appropriate amounts of pigments, coupling agents, etc., and the mixture is kneaded in a heated state using a kneading machine such as a mixing roll machine. The desired epoxy resin composition can be obtained through a series of steps of melt-mixing, cooling to room temperature, pulverizing by known means, and, if necessary, tableting.

Sealing of a semiconductor element using such an epoxy resin composition is not particularly limited, and can be performed by a known molding method such as ordinary transfer molding.

The semiconductor device obtained in this way has a substance (component C) that relieves internal stress generated at the filler-epoxy matrix interface in the above-mentioned engineered boxy resin composition, and has excellent thermal shock resistance and moisture resistance. It becomes extremely superior in quality.

〔Effect of the invention〕

The semiconductor device of the present invention is encapsulated using a special epoxy resin composition containing an inorganic powder filler whose surface is coated with the above-mentioned low-molecular-weight polymer having a vinyl group. Due to the internal stress-relaxing effect of the surface-coated inorganic powder filler inside, the sealed plastic package has extremely low internal stress, unlike those made of conventional epoxy resin compositions. Therefore, it has high moisture resistance, high heat resistance reliability, low internal stress, and extremely high reliability. In particular, by sealing with the above-mentioned special epoxy resin composition, the above-mentioned high reliability can be obtained in large semiconductor devices with 8 or more pins, especially 16 or more pins, or a chip with a long side of 4 cranes or more. This is a major feature.

Next, the present invention will be explained based on examples.

[Examples 1 to 12] First, the peroxide catalyst shown in Table 1 below was made into a 1% toluene solution, and silica particles (average particle size 80 μm) as an inorganic powder filler were added and mixed to this toluene solution. After that, it was suction filtered and air-dried.

Then, 1 kg of the obtained silica was mixed with 200 g of a low molecular weight monomer having a vinyl group such as butyl acrylate as shown in Table 1, and polymerized for 2 hours with stirring at 80°C until the surface became polymerized. Coalescence coated silica particles were created. The amount of polymer coating on the surface of the silica particles was determined by ash content measurement.

(Left below) Next, using the coated silica obtained as above,
This, an 0-cresol novolac type epoxy resin, a phenol novolac type resin, and the raw materials shown in Table 2 are blended in the proportions shown in the same table, and kneaded on a mixing roll machine at 100°C for 10 minutes to form a sheet composition. Obtained. Next, this sheet-like composition was pulverized to obtain the desired powdered epoxy resin composition.

(Space below) C Examples 13 to 16] First, silica particles similar to those used in Example 1 (average particle size 80 μIII) were immersed in a 1% solution of epoxytrimethoxysilane (silane coupling agent) and filtered by suction. It was then air-dried. The surfaces of these silica particles have been made hydrophobic with a silane coupling agent. Next, 1 kg of the surface-treated silica particles were immersed in a 1% polymer solution (toluene solution) 3β of butyl polyacrylate shown in Table 3, stirred for 1 hour, and then methanol 11 was added and filtered with suction. Dry under reduced pressure to obtain three types of coated silica [phases]
~0 was created.

(Left below) Next, the coated silica [phase] ~@
This and each raw material were blended in the proportions shown in Table 4, and powdered epoxy resin compositions were obtained in the same manner as in Examples 1 to 12.

(Left below) [Comparative Examples 1 and 2] As a polybutadiene-acrylonitrile copolymer in which both terminal groups are carboxyl groups, H
YCARCT polymer (CTBN 1300X8. Viscosity: 125000cps (27℃) 1 molecule ft13
500. Powdered epoxy resin compositions were obtained in the same manner as Examples 1 to 16 according to the compositions shown in Table 5 using acrylonitrile content i of 17% and carboxyl group content 2.37%.

[Conventional example]

According to Table 5 below, each raw material was blended and Examples 1 to 1 were prepared.
A powdered epoxy resin composition was obtained in the same manner as in Example 6.

A semiconductor device was obtained by molding a semiconductor element by transfer molding using the powdered epoxy resin composition obtained in the above Examples, Comparative Examples, and Conventional Examples. The semiconductor device thus obtained was subjected to internal stress 1 bending elastic modulus due to piezoresistance, reliability test for 1000 hours using a pressure cooker under voltage application (hereinafter abbreviated as rPCBT test), -50°C for 15 minutes.
Measurements such as a temperature cycle test (hereinafter abbreviated as rTCT test) of 2000 times at 150° C. for 15 minutes were performed. The results are shown in Table 6 below. Note that the glass transition temperature (T
g) indicates the temperature at which the peak of tan δ of viscoelastic properties occurs.

(Left below) From the results in Table 6, it can be seen that the plastic package of the implemented product has lower internal stress, better electrical insulation, and better moisture resistance and heat resistance than the comparative height measurement and conventional height measurement products. It can be seen that the

Claims (3)

[Claims] (1) A semiconductor device in which a semiconductor element is sealed using an epoxy resin composition containing the following components (A), (B), and (C). (A) Epoxy resin. (B) Phenol resin. (C) An inorganic powder filler whose surface is coated with a low molecular weight polymer having vinyl groups. (2) Claim 1, wherein the polymer of a low molecular weight substance having a vinyl group is a copolymer of a low molecular weight substance having one vinyl group and a low molecular weight substance having two vinyl groups. semiconductor devices. (3) A patent claim in which the polymer of a low molecular weight substance having a vinyl group is a copolymer of a low molecular weight substance having one vinyl group and a low molecular weight substance having one vinyl group and another functional group. The semiconductor device according to item 1.