JPS62147749A - Semiconductor device - Google Patents

Abstract

PURPOSE:To improve the moisture resistance and the thermal impact resistance of a semiconductor device by using silicone compound particles including epoxy resin, phenol resin and peroxide as a core, and sealing a semiconductor element with epoxy resin composition containing fine particles of the structure that the outer periphery is covered with resin shell. CONSTITUTION:An epoxy resin composition is formed in a core of epoxy resin, phenol resin and further silicon compound particles including peroxide, and obtained by using fine particles of the structure that the outer periphery is covered with a resin shell. Preferable result is obtained when using the resin which exhibits solid or high viscosity solutionlike at room temperature with melting point exceeding room temperature of resins. The phenol resin acts as epoxy resin curing agent, and preferably employs phenol novolac, cresol novolac. The core of the fine particles used as dispersive phase is formed of peroxide and silicone compound, and the peroxide is solid by crosslinking the silicone compound normally of liquid. Thus, moisture resistance and thermal impact resistance can be improved.

Description

[Detailed Description of the Invention] [Field of Industrial Application] This invention relates to a semiconductor device encapsulated with a encapsulating resin composition that has low internal stress and excellent moisture resistance reliability and thermal shock resistance. .

[Conventional technology]

Semiconductor elements such as transistors, ICs, and LSIs are usually sealed with ceramic packages, plastic packages, or the like to form semiconductor devices. The above-mentioned ceramic package has heat resistance in the constituent material itself,
It also has excellent moisture permeability, so it is resistant to temperature and humidity, and because it is a hollow package, it has high mechanical strength and can be sealed with high reliability. However, since the constituent materials are relatively expensive and the mass productivity is poor, resin sealing using the above-mentioned plastic package has recently become mainstream. Epoxy resin compositions 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 interconnections have become finer. However, while packages have become smaller and thinner, there has been a trend toward smaller and thinner packages. Reliability (internal stress of semiconductor devices obtained)

There is a demand for improvements in moisture resistance reliability, shock resistance reliability, heat resistance reliability, etc. In particular, the thermal stress generated between the semiconductor element and the encapsulating material causes damage to the package, and has a significant impact on the moisture resistance and thermal shock resistance of the semiconductor device. Reducing this has become an important issue.

Therefore, various attempts have been made to reduce the stress of epoxy resins used in sealing materials, and currently the mainstream method is to add rubbers such as urethane rubber and butadiene rubber.

In other words, by taking advantage of the fact that rubber and epoxy resin are not very compatible, the cured resin has a so-called "sea product" structure in which rubber particles are precipitated and dispersed in the continuous phase of epoxy resin. , attempts to absorb and relieve thermal stress with rubber particles while maintaining the high heat resistance of epoxy resin.

[Problems to be Solved by the Invention] However, when the rubber particles are dispersed in the epoxy resin as described above, some of the rubber particle components may be dissolved in the epoxy resin that is the continuous phase. When the rubber particle component is dissolved in the epoxy resin in this way, the dispersion of the rubber neck particles becomes incomplete, resulting in disadvantages such as a decrease in the strength of the final cured resin of the epoxy resin composition for sealing. was occurring. Therefore, there is a demand for the development of an epoxy resin composition for sealing in which rubber particles are completely dispersed in the epoxy resin as a continuous phase, that is, in which the dispersed phase has an independent "sea-island" structure. , we still haven't gotten enough.

This invention was made in view of the above circumstances, and it is possible to completely eliminate a portion of the rubber particles from dissolving into the epoxy resin, which is the continuous phase, in the epoxy resin composition used for resin sealing. The purpose of the present invention is to provide a highly reliable semiconductor device that prevents deterioration of physical properties such as mechanical strength of a cured product, has low internal stress, and has excellent moisture resistance and thermal shock resistance.

[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) to (C).

(A) Epoxy resin.

(B) Phenol resin.

(C) Fine particles having a structure in which a silicone compound particle containing peroxide is used as a core body and the outer periphery of the core body is covered with a resin shell body.

That is, in order to completely eliminate the partial dissolution of rubber particles into epoxy resin, the present inventors have conducted intensive research on the types and forms of rubber particles, and have found that We use a silicone compound that has better heat deterioration resistance than conventional urethane rubber, butadiene rubber, etc., and we also crosslink the silicone compound by impregnating this silicone compound with peroxide. When the outer periphery of the particles is coated with resin, the silicone compound particles are completely dispersed without dissolving in the epoxy resin during mixing and dispersion with the epoxy resin, forming the "sea-island" structure, and the resulting epoxy resin. The present invention was achieved by discovering that the strength of the cured product does not decrease.

The epoxy resin composition used in this invention uses an epoxy resin (component A) and a phenol resin (component B), and further has a core made of silicone compound particles containing peroxide, the outer periphery of which is covered with a resin shell. It is obtained using structured fine particles (component C), and is usually in the form of a tablet made from a powder.

The epoxy resin serving as the component A is not particularly limited, and various epoxy resins conventionally used as sealing resins for semiconductor devices, such as cresol novolac type, phenol novolac type, and bisphenol A type, can be mentioned. 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. Phenol novolac type epoxy resin usually has an epoxy equivalent of 1
60-250. A cresol novolac type epoxy resin having a softening point of 50 to 130°C is used, and an epoxy equivalent of 180 to 210. 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, talesol novolak, etc. are preferably used.

These novolak resins preferably have a softening point of 50 to 110° C. and a dihydroxyl equivalent of 70 to 150. Particularly, among the above novolac resins, use of cresol novolac brings about good results.

The fine particles of component C used as the dispersed phase in this invention consist of a core and a shell covering the core.

The core is made of peroxide and a silicone compound, and the peroxide plays a role in crosslinking the normally liquid silicone compound to make it solid.

The above peroxides include benzoyl peroxide, p~
Dichlorobenzoyl peroxide 2.4-dichlorobenzoyl peroxide, oprylyl peroxide, lauroyl peroxide, acetyl peroxide, cyclohexene peroxide, hydroxyhebutyl peroxide,
tert-butyl perbenzoate, tert-butyl peracetate, tert-butyl octoate, t
ert-butyl peroxyisobutyrate, tert
Examples include t-butyl perphthalate.

Further, as the silicone compound, for example, liquid polydimethylsiloxane having a methyl group, a carboxyl group, an amino group, or an epoxy group at both ends of the molecular chain can be used. These silicone compounds are commercially available as aqueous emulsions using water as a dispersion medium.

Then, the silicone compound becomes core particles containing peroxide in an aqueous medium by a preparation method described later, and each particle is coated with a resin and used. The particles of the silicone compound have a particle size of 0.05 to 10 μm.
A thickness of 0.05 to 5 μm is particularly preferred.

Examples of the resin for the shell covering the silicone compound particles include those obtained by polymerizing an unsaturated monomer having one unsaturated double bond. Examples of the unsaturated monomers include methyl methacrylate, acrylonitrile,
Methacrylonitrile, vinylcarbazole, vinyl formal, vinylpyrrolidone, 0-vinylbenzyl alcohol, styrene, o +, m-, p-methylstyrene, 224-dimethylstyrene, 2,5-dimethylstyrene, 3,4-dimethylstyrene , p-tert-butylstyrene, p-phenylstyrene, p-phenylstyrene, p-chlorostyrene, 2,5-dichlorostyrene, α-methylstyrene, α-vinylnaphthalene, and the like. These may be used alone or in combination of two or more.

Further, the shell is formed by copolymerizing the unsaturated monomer having one unsaturated double bond and the unsaturated monomer having two or more unsaturated double bonds on the outer periphery of the silicone compound particles. You may also do so.

Examples of the unsaturated monomers having two or more unsaturated double bonds include divinylbenzene, monoethylene glycol dimethacrylate, diethylene glycol dimethacrylate, tetraethylene glycol dimethacrylate, neopentyl glycol dimethacrylate, and trimethacrylate. trimethylolpropane diacrylate, 1.6-hexanediol dimethacrylate, bisphenol A dimethacrylate, diethylene glycol acrylate, tetraethylene glycol diacrylate, neopentyl glycol diacrylate, 1.5-bentanediol diacrylate, diacrylic acid 1. 6
-hexanediol, trimethylolpropane triacrylate, etc. These may also be used alone or in combination of two or more.

Such monomers having two or more unsaturated double bonds in one molecule include 0, Good results are obtained when it is used in proportions of 5 to 50% by weight. That is, addition within this range further enhances the effect of reducing thermal stress.

Among such unsaturated monomers, those that form polymers with a glass transition temperature of 70°C or higher are particularly suitable, and those that have relatively high hydrophilicity and high affinity with epoxy resins are particularly suitable. Methyl methacrylate (molecular weight 100, glass transition temperature 105°C) is most preferred. Note that the glass transition temperature of the (meth)acrylic ester resin defined here is measured with a differential calorimeter or the like, and refers to a value known for each (meth)acrylic ester resin.

For example, the following method can be used to prepare the fine particles that are component C used in the present invention using the peroxide, the silicone compound aqueous emulsion, and the monomer for forming shell resin. That is, a monomer for forming a shell resin is added dropwise over time or all at once to an aqueous emulsion of a silicone compound, polymerized on the surface of the silicone compound particles serving as the core, and formed into a resin film to cover the silicone compound particles. let Next, an organic solvent in which peroxide is dissolved is added and stirring is started to form two phases, an aqueous phase and an organic phase.
A peroxide-containing organic solvent is absorbed into silicone compound liquid particles coated with a resin film through the resin film. Then, the organic solvent in the silicone compound particles is removed by vacuum distillation using an evaporator or the like, and the silicone compound containing peroxide is further dried at room temperature to 50°C to scatter water. This is a method of obtaining fine particles having a core particle and a resin shell formed around its outer periphery.

The organic solvent for dissolving the peroxide may be any solvent, but in order to prevent peroxide from diffusing into water, the following organic solvents having relatively low solubility in water are preferred. That is,
hexane, ethylbenzene, p-xylene, toluene,
Hydrocarbons such as benzene, halogenated hydrocarbons such as tetracarbon, trichloroethylene, dichloromethane, n
-, iso -, 5ec-amyl alcohol, n-, s
Alcohols such as ec-butanol and cyclohexanol, phenols such as m-cresol, ethers such as diethyl ether, diisobutyl ketone, methyl isobutyl ketone, and methyl isopropyl ketone.

Ketones such as methyl-n-propyl ketone and cyclohexanone, n-,1so-butyl acetate, n-9iso-amyl acetate, n-,1so-probyl acetate.

Examples include esters such as ethyl acetate, methyl acetate, and ethyl propionate.

In addition, when polymerizing the monomer for forming the shell resin in an aqueous medium,
Various water-soluble or oil-soluble polymerization initiators that are normally used in aqueous polymerization are used. Such polymerization initiators include potassium persulfate, ammonium persulfate, 4.4゛
Examples include -azobis-4-cyanovaleric acid, 2,2'-azobis(2-amidinopropane) hydrochloride, and the like.

Furthermore, when preparing the above-mentioned fine particles, drying of the fine particles,
In order to achieve good powderization and prevent mutual fusion of particles to complete powderization, the proportion of resin used for shell formation is 5 to 50% by weight (hereinafter abbreviated as "%") based on the entire fine particles. It is preferable that

That is, if it is less than 5%, the shell body will not be sufficiently formed and the dispersibility of the fine particles in the epoxy resin will be poor, and if it exceeds 50%, the thermal stress absorption ability of the fine particles for the epoxy resin will not function sufficiently. This is because it is not desirable.

In addition, in the step of preparing the fine particles of component C, the silicone compound liquid particles absorb the peroxide-containing organic solvent by stirring and come into contact with the peroxide, and due to the action of this peroxide, a slight crosslinking reaction occurs. occurs. Then, when the mixture is mixed with the A component and B component and compressed into a tablet, the crosslinking reaction further proceeds, and the core of the fine particles, which is the C component, gradually solidifies. Finally, when a semiconductor element is resin-sealed with an epoxy resin composition containing these A-C components, a crosslinking reaction progresses further, and the core body has a silicone skeleton and is made of peroxide. The result is a crosslinked rubbery solid. This is a major feature of this invention.

The fine particles of component C thus obtained have a structure in which the core is a silicone compound containing peroxide and a resin shell is formed around the core.

The epoxy resin composition used in this invention includes the above A
-C component is contained, and if necessary, various conventionally used curing accelerators are also contained. 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-) lis(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 Imidazole 2-methylimidazol, 2-undecylimidazole, 2-ethylimidazole, 1- Benzyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, boron compound, tetraphenylboron salts, such as triethyleneaminetetraphenylborate, N-methylmorpholinetetraphenylborate, and, if necessary, in addition to the above raw materials. , inorganic fillers, antimony dioxide, flame retardants such as phosphorus compounds, pigments, and coupling agents such as silane coupling agents can be used. The inorganic filler is not particularly limited, and may include commonly used quartz glass powder, talc, and silica powder.

Alumina powder or the like is appropriately used.

The epoxy resin composition used in this invention has an epoxy resin as a continuous phase and fine particles of component C as a dispersed phase, and can be produced, for example, as follows. That is, first, 3 to 120 parts, particularly preferably 5 parts, of fine particles are added to 100 parts by weight (hereinafter abbreviated as "parts") of the epoxy resin.
The fine particles were mixed with epoxy resin powder at a ratio of ~60 parts and thoroughly stirred, and then a phenol resin as a curing agent was added.

By adding a curing accelerator, filler, etc. and heating and kneading, the fine particles can be completely dispersed in the epoxy resin continuous phase to produce a resin composition for encapsulating semiconductor devices. The reason why the blending ratio of fine particles as a dispersed phase to the epoxy resin as a continuous phase is limited to the above ratio is as follows.
If it is less than 3 parts, the effect of reducing thermal stress is insufficient;
This is because if the amount exceeds 20 parts, the epoxy resin becomes a discontinuous phase, which is not preferable.

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

The semiconductor device obtained in this manner is made of the cured epoxy resin composition and has a structure in which silicone compound particles are the core and the outer periphery thereof is covered with a resin shell, and the fine particles are the dispersed phase and the epoxy resin is the continuous phase. Because the semiconductor element is encapsulated by the structure, the resin encapsulation itself has high strength, and the resin encapsulation has low internal stress and is highly reliable with excellent moisture resistance and thermal shock resistance. A stop has been put in place.

Note that when a cross section of a cured resin composition from which the filler component has been removed is observed using a scanning electron microscope, this dispersion state is recognized as a so-called "sea-island" structure in which the fine particles are present in the form of islands.

〔Effect of the invention〕

The semiconductor device of the present invention uses a special epoxy resin composition containing silicone compound particles having a special structure, the outer periphery of which is covered with a resin shell, and which is cross-linked with peroxide to become a solid. The sealed plastic package is different from conventional epoxy resin compositions, so it has low internal stress, high moisture resistance reliability, electrical characteristics, and heat resistance reliability, making it extremely reliable. It's expensive. That is, the above-mentioned epoxy resin composition does not contain the silicone compound particles as they are, but rather contains them in a state in which the outer periphery is covered with a resin shell and is crosslinked with peroxide to become a solid. Therefore, when sealing with resin,
Dissolution of the silicone compound particles into the epoxy resin that is the continuous phase is suppressed, and a so-called "sea-island" structure is formed in which the silicone compound particles are completely dispersed in the epoxy resin that is the continuous phase. As a result, the silicone compound particles existing in the island-like front exhibit their properties to the fullest, which not only provides sufficient thermal stress absorption and relaxation effects, but also reduces stress caused by the dissolution of the silicone compound particles. The strength of the cured resin body itself does not decrease, and a cured body with good characteristics can always be obtained. As a result, the semiconductor device of the present invention has high reliability as described above. be. 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 pins or more, especially 16 pins or more, or a chip with a long side of 41 m or more. This is a major feature.

Next, examples will be described together with comparative examples.

First, water and an aqueous emulsion of silicone compound particles were added to a reaction vessel equipped with a stirrer, a thermometer, and a cooling tube, the reaction system atmosphere was maintained at 70°C, and nitrogen gas was further introduced into the reaction vessel. . Next, an unsaturated monomer component for forming a resin layer was added into the reaction vessel, and polymerization was carried out at 70° C. for 3 hours to obtain a dispersed emulsion of fine particles in which the surface of the silicone compound particles was covered with a resin shell. The formulation of each component is shown in Table 1 below. Then, a 1% toluene solution of benzoyl peroxide was added in the amount shown in Table 1 to the obtained dispersed emulsion, and the mixture was stirred at 50° C. for about 3 hours. It was confirmed that even when this was left for 30 minutes, it did not separate into an aqueous phase and a toluene phase, and the toluene phase was completely absorbed by the silicone compound particles. Then, toluene was distilled off by vacuum distillation using an evaporator.

This emulsion was dried in a ventilation dryer at about 50°C for 24 hours to obtain 10 types of fine particle powders (a-j).

A transparent film is obtained by coating a portion of the aqueous emulsion of silicone compound particles on a glass plate and drying it at room temperature.On the other hand, an unsaturated monomer component for forming a resin shell is added to the emulsion. The emulsion obtained by carrying out the polymerization reaction was dried in the same manner as above to obtain a white powder. From this, it can be seen that the fine particles obtained through the polymerization reaction have a structure in which the core is a silicone compound particle and the outer periphery of the core is covered with a resin shell.

(The following is a blank space) In addition, in order to produce a comparative example product, fine particles k were obtained in the same manner as above without adding the toluene solution of benzoyl peroxide. The types and amounts of the silicone compound emulsion and the raw materials for forming the resin shell were the same as those for fine particles j.

[Examples 1 to 16. Comparative Example] After mixing the fine particle powder obtained as described above and epoxy resin powder in the proportions shown in Table 2 below, the phenol resin as a curing agent and other additives were mixed in the proportions shown in the same table. The mixture was added in a mixing roll machine and kneaded at 100° C. for 10 minutes to obtain a sheet composition. Next, this sheet-like composition was pulverized to obtain the desired powdered epoxy resin composition.

(Left below) *1 Epoxy equivalent: 19Q, softening point -8 (*2 Phenol equivalent: 130. Softening point: 8 [Conventional Example 1.2] Using the raw materials shown in Table 3 below, these raw materials were mixed. Powdered epoxy resin compositions were obtained in the same manner as in Examples 1 to 16 using the sheet composition obtained by kneading with a roll machine for 10 minutes.

*1. *2: A semi-0°C conductor device was obtained by molding a semiconductor element by transfer molding using the powdered epoxy resin composition obtained in the above Examples and Conventional Examples as shown in Table 2. Regarding the semiconductor device obtained in this way, internal stress 1 bending elastic modulus due to piezoresistance, 1000 hour reliability test using a pressure cooker under voltage application state (hereinafter referred to as rPCBT test), -5
Measurements such as a temperature cycle test (hereinafter abbreviated as rTCT test) of 2000 times from 0° C. 15 minutes to 150° C. 15 minutes were performed. The results are shown in Table 4 below. Note that the glass transition temperature (Tg) is the temperature at which the peak of Tan δ, which is a viscoelastic property, is reached.

(Left below) From the results in Table 4, it can be seen that each product according to the present invention has a higher defective rate in the PCBT test than the comparative height measurement and the conventional product.
It can be seen that the crack occurrence rate in the CT test is almost 0, and the internal stress is also low, so it has excellent moisture resistance and thermal shock resistance, and has high reliability.

Claims (2)

[Claims] (1) A semiconductor device in which a semiconductor element is sealed using an epoxy resin composition containing the following components (A) to (C). (A) Epoxy resin. (B) Phenol resin. (C) Fine particles having a structure in which a silicone compound particle containing peroxide is used as a core body and the outer periphery of the core body is covered with a resin shell body. (2) The semiconductor device according to claim 1, wherein the resin forming the shell is a resin having a glass transition temperature of 70° C. or higher.