JPS62210654A - Semiconductor device - Google Patents

Abstract

PURPOSE:To obtain a device characterized by high moisture resisting reliability, excellent electric characteristics, high heat resisting reliability and less internal stress, by using an epoxy resin composition including specified components. CONSTITUTION:An epoxy resin composition used for sealing is composed of the following materials: epoxy resin; phenol resin; and remaining group heterocyclic-compound, in which both ends of a molecule chain have at least two second-class amino group in a molecule. The surface of a particle in a silica filler and the like is covered with a coating layer, whose main part is polydimethyl siloxane oligomer, in which the chain part of a molecule chain is coupled with nitrogen of a second-class amino group of any of the remaining end groups. Such filler and the like are used in the device. Thus, the highly reliable semiconductor device, in which internal stress is decreased and the amount of a hardening accelerator is largely decreased or made to be zero, is obtained.

Description

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

[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 (
Moreover, since 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. For this type of resin sealing,
Epoxy resin compositions have been used for a long time and have achieved good results. However, technological innovations in the semiconductor field have led to improvements in the degree of integration, as well as larger device sizes.
As interconnects become increasingly finer, packages tend to become smaller and thinner, and as a result, sealing materials are becoming more reliable (internal stress, moisture resistance, reliability, etc. of the resulting semiconductor devices).
Improvements in shock resistance, heat resistance, etc.) are desired. In particular, epoxy resin compositions used for semiconductor encapsulation consist of an epoxy resin, a phenol resin as a curing agent, and a curing accelerator (mainly tertiary amines) that accelerates the reaction between the two. Curing accelerators, which are tertiary amines, exist freely in cured epoxy resins and are easily mobile at high temperatures, significantly reducing the electrical properties (especially electrical insulation) and moisture resistance of cured epoxy resins. This deteriorates the electrical characteristics and moisture resistance reliability of the semiconductor device, and therefore improvements are desired.

[While the invention is trying to solve the problem]

As mentioned above, in conventional epoxy resin compositions for sealing, a considerably large amount of curing accelerator was present, leading to a decrease in electrical properties and moisture resistance. In the process of cooling from the curing temperature to room temperature, considerable internal stress is generated due to shrinkage, which causes problems such as damage to the semiconductor element and disconnection of wires. 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 amount of domains of such rubber particles in the epoxy resin matrix makes the fluidity of the epoxy resin composition There were also other drawbacks, such as a decrease in In addition, the curing accelerator present in a fairly large amount had an adverse effect on the electrical insulation properties of the cured epoxy resin as described above. In this way, conventional epoxy resin compositions for soil use are not only satisfactory in terms of mechanical properties, but also have limitations in the reliability of semiconductor devices using them, and the technological innovations described above have led to larger device sizes. It is strongly desired to improve the characteristics even further in order to be able to cope with the above problems.

In order to meet these demands, a proposal was made to coat silica, which is contained in a large amount in an epoxy resin composition for sealing, with synthetic rubber and to use this synthetic rubber-coated silica as a filler (Japanese Patent Application Laid-Open No. 1983-1981). -188418). According to this proposed method, the effect of reducing internal stress can be obtained by the synthetic rubber layer present at the interface between the silica and the matrix resin while suppressing the decrease in fluidity due to the use of synthetic rubber. However, this proposed method only has the effect of reducing internal stress, and does not improve the electrical properties caused by the curing accelerator. There were problems such as restrictions. That is, the synthetic rubber is attached to the outer periphery of the silica by the binder action of the silane coupling agent, and in order to create such a structure, the silane coupling agent must react with both the silica and the synthetic rubber. It is necessary to use a material having a functional group, and also to use a synthetic rubber having a functional group that reacts with the functional group of the silane coupling agent.

However, the above-mentioned raw materials belong to a relatively special category, and there are restrictions on the raw materials that can be used, and the production of synthetic rubber-coated silica using them is complicated. Moreover, the resulting synthetic rubber-coated silica contains the above-mentioned components and has the disadvantage that it cannot be applied to a wide range of epoxy resin compositions.

This invention was made in view of the above circumstances, and it is possible to reduce the internal stress in the epoxy resin composition used for resin sealing, and at the same time, to significantly reduce or eliminate the amount of curing accelerator, thereby achieving excellent results. The purpose is to provide a reliable semiconductor device.

[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) Both ends of the molecular chain are composed of residues of a heterocyclic compound having at least two secondary amino groups in the molecule, and the chain portion of the molecular chain is composed of residues of a heterocyclic compound having at least two secondary amino groups in the molecule, and the chain portion of the molecular chain is A silica filler whose particle surfaces are covered with a coating layer mainly composed of polydimethylsiloxane oligomers bonded to the nitrogen of secondary amino groups.

That is, this invention uses silica whose particle surface is coated with the M layer mainly composed of the polydimethylsiloxane oligomer as the C component, and this silica is coated with a binder like the synthetic rubber-coated silica described above. There is no need to bond the coating layer to the silica surface and therefore
It has a wide degree of freedom in selecting raw materials, is easy to manufacture, and does not contain a binder component, so it can be applied to a wide range of epoxy resin compositions. As a result, according to the present invention, there is no complication of the process when manufacturing semiconductor devices, and the use of the silica filler as component C not only reduces internal stress, but also significantly reduces the hardening accelerator. This can be reduced or eliminated, thereby significantly improving the reliability of semiconductor devices.

The epoxy resin composition used in this invention comprises an epoxy resin (component A), a phenol resin (component B), and a heterocyclic compound in which both ends of the molecular chain have at least two secondary amino groups in the molecule. Silica whose particle surface is covered with a coating layer mainly composed of polydimethylsiloxane oligomers, in which the chain portion of the molecular chain is bonded to the nitrogen of the secondary amino group of any of the terminal residues. filler(
It is obtained using component C), etc., and is usually in the form of a powder or a tablet formed by compressing it.

Note that the above-mentioned "oligomer" is used to include dimers.

The epoxy resin serving as the above A component is not particularly limited, and various epoxy resins conventionally used as encapsulating resins for semiconductor devices can be mentioned, such as Talesol 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. As a novolak type epoxy resin, usually epoxy ff1160~
250.1 and a softening point of 60 to 110°C is generally used as the cresol novolac type epoxy resin.

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 novolac, etc. are preferably used. These novolac resins have a softening point of 50 to 110°C and a hydroxyl equivalent of 70 to 150.
It is preferable to use one. Particularly, among the above novolac resins, use of cresol novolac brings about good results.

The C component is a silica filler covered with a coating layer mainly composed of a specific polydimethylsiloxane oligomer as described above, and the polydimethylsiloxane oligomer that is the main component of the coating layer has both ends of the molecular chain within the molecule. It is composed of a heterocyclic compound residue having at least two secondary amino groups, and the chain portion of the molecular chain is bonded to the nitrogen of any of the secondary amino groups of the terminal residue. It is of structure. Here, the term "mainly" is meant to include the case where the entire coating layer is composed mainly of polydimethylsiloxane oligomer.

As a specific example of the polydimethylsiloxane oligomer as described above, when the heterocyclic compound residue is, for example, a piperazine residue, it is schematically represented as shown in (a)2 below.

Examples of the heterocyclic compound residue having a secondary amino convexity as described above include, in addition to the piperazine residue described above, a pyrazolidine residue and an imidazolidine residue.

Polydimethylsiloxane oligomers as described above can be obtained by known methods. For example, ■ a reaction product of carboxypropyl-terminated disiloxane and aminoethylpiperazine (its chemical structure is as shown in formula (1) below) is prepared in advance, and this biperazine-terminated dimethylsiloxane dimer (formula (1) shown below) is prepared in advance. ) to form a piperazine-terminated polydimethylsiloxane oligomer (the chemical structure of which is expressed by the formula (see below)).
2) can be obtained. In addition, as another method, (1) First, a cyclic tetradimethylsiloxane is added to an epoxy-terminated dimethylsiloxane dimer (the chemical structure is as shown in formula (3) below), which is a reaction product of allyl glycidyl ether and metachlorosilane. An epoxy-terminated polydimethylsiloxane oligomer (the chemical structure of which is shown in formula (4) below) is synthesized by equilibration polymerization. next,
By reacting this oligomer with a large excess of piperazine, a piperazine-terminated polydimethylsiloxane oligomer (the chemical structure of which is as shown in formula (5) below) can be obtained. Naturally, contrary to method (2), the above epoxy-terminated dimethylsiloxane dimer (formula (3))
By reacting with a large excess of piperazine,
It is also possible to synthesize a piperazine-terminated dimethylsiloxane dimer and then obtain an oligomer by equilibration polymerization of cyclic tetradimethylsiloxane in the same manner as in method (2).

(Left below) Synthesis methods for these polydimethylsiloxane oligomers are described in many publications, but a representative example is Epoxy Resin Chemistry Volume 2, edited by R.S. Bauer. CS Symposium Series, ACS (1983) P21 = P54 (Ep
Oxy Re5in Chemistry II, 8C
3Symposium-5eries) and are explained in detail.

As mentioned above, both ends of the molecular chain are present within the molecule at least two times.
A special polydimethyl composed of heterocyclic compound residues having secondary amino groups, in which the chain part of the molecular chain is bonded to the nitrogen of any of the secondary amino groups of the terminal residues. The siloxane oligomer has a number average molecular weight of 30,000
It is preferably less than or equal to 2000, more preferably 2000.
It is 0 or less, and most preferably 15,000 or less.

Here, the number average molecular weight can be determined by quantifying the terminal secondary amine group per unit weight as follows. First, 5 g of a specimen is accurately weighed and dissolved in 30 g of isopropyl alcohol. Add 2-3 drops of bromophenol blue water/ethanol solution as an indicator and
．． Titrate with IN hydrochloric acid. The end point is the point where the system changes from blue-purple to yellow.

The silica whose particle surface is coated with the above polydimethylsiloxane oligomer is not particularly limited, and both crystalline silica (crystalline silica) and amorphous silica (fused silica) can be used. It is preferable that these silicas have an average particle size of 5 to 80 μm and do not contain large particles of 100 μm or more.

Silica can be coated with the specific polydimethylsiloxane oligomer by mixing the polydimethylsiloxane oligomer and silica using an organic solvent such as toluene as a medium, filtering the mixture, and then drying under reduced pressure. In this case, the polydimethylsiloxane oligomer has heterocyclic compound residues introduced at both ends of its molecular chain, which significantly improves its adhesion to the silica surface, and binders such as silane coupling agents. It adheres to the silica and coats the silica surface well without using any components.

In this invention, the fact that silica is coated with the polydimethylsiloxane oligomer can be clarified by the uneven distribution of the product in a benzene-water system (interaction ease discrimination method). That is, in this method, uncoated silica is normally unevenly distributed in the aqueous phase, but the coated silica of this invention is unevenly distributed in the benzene phase. This evaluation method has already been established by the present inventors [Tsunetaka Matsumoto et al., Collected Papers of the 7th Composite Materials Symposium, 2
61 (1974)).

In this way, introducing a heterocyclic compound to both ends of the molecular chain of polydimethylsiloxane oligomer significantly improves its adhesion, especially to the silica surface, and this phenomenon was discovered for the first time in the course of research by the present inventors. As a result, it has become possible to easily obtain polydimethylsiloxane oligomer-coated silica that can be applied to an extremely wide range of epoxy resin compositions and exhibits stress reduction effects and electrical property improvement effects. This is the biggest feature.

The coating layer mainly composed of polydimethylsiloxane oligomer that covers the surface of the silica exhibits a curing accelerating effect during the resin curing stage due to the action of heterocyclic compound residues at both ends of the molecular chain in the polydimethylsiloxane oligomer. The action of the polydimethylsiloxane portion exerts an effect of relieving internal stress at the stage after curing, thereby realizing a highly reliable semiconductor device. The polydimethylsiloxane oligomer has secondary amino groups at both ends of its molecular chain that easily react with epoxy groups, and the silicone compound has a high affinity for silica due to its structure. It exists firmly fixed at the interface between the epoxy resin and the matrix epoxy resin. Therefore, it does not move even at high temperatures, does not cause deterioration in the electrical characteristics of the cured epoxy resin due to the movement of the curing accelerator as in the conventional case, and ensures the reliability of the semiconductor device.

The coating layer of the silica particles is mainly composed of the polydimethylsiloxane oligomer, and in some cases, a peroxide may be used in combination with the polydimethylsiloxane oligomer.

Peroxides used with polydimethylsiloxane oligomers as described above include hensyl peroxide, p-chlorohensyl peroxide, 2,4-dichlorobenzoyl peroxide, oprylyl peroxide, lauroyl peroxide, acetyl peroxide, peroxide, cyclohexene peroxide, hydroxybutyl peroxide, tert-butyl perbenzoate, tert
-butyl peracetate, tert-butyl octoate, tert-butyl peroxyisobutyrate, di-tert-butyl perphthalate, and the like.

When the above-mentioned peroxide is used in combination with the above-mentioned polydimethylsiloxane oligomer, the above-mentioned polydimethylsiloxane oligomer attached to the silica particle surface is polymerized by the action of the peroxide, and the coating of the particle surface is quickly completed. will be obtained.

When peroxide and the polydimethylsiloxane oligomer are used together in this way, the amount of peroxide used is 0.02 to 0.02 to
Good results can be obtained by setting the proportion to 1 part by weight.

The above-mentioned special polydimethylsiloxane oligomer alone or a mixture of this and peroxide is 3 to 50% by weight in the epoxy resin composition (A+B) excluding filler components.
It is preferable to set it so that it is contained. That is,
This is because if the content is out of the above range, the reliability of the resulting semiconductor device tends to decrease.

Incidentally, in the epoxy resin composition used in the present invention, a curing accelerator may be used in addition to the above-mentioned components A to C, if necessary, but the amount used can be significantly reduced or completely eliminated. That is, the epoxy resin composition used in the present invention uses the specific polydimethylsiloxane oligomer as described above, so that the amount of the curing accelerator used is 0 relative to the total amount of the epoxy resin and phenol resin.
It can be suppressed to within the range of ~0.5%, thereby making it possible to significantly improve moisture resistance, electrical properties, etc.

Examples of the curing accelerator include the following tertiary amines.

Suitable examples include quaternary ammonium salts, imidazoles, and boron compounds, and these can be used alone or in combination.

Tertiary amine triethanolamine, tetramethylhexanediamine, triethylenediamine, dimethylaniline, dimethylaminoethanol, di-ethylaminoethanol,
2,4.6-1-lis(dimethylaminomethyl)phenol, N,N-dimethylpiperazine, pyridine, picoline, 1,8-diaza-bicyclo(5,4,0)undecene-7, benzyldimethylamine, 2-(Dimethylamine) Methylphenol quaternary ammonium salt Dodecyltrimethylammonium chloride, cetyltrimethylammonium chloride, benzyldimethyltetradecylammonium chloride, stearyltrimethylammonium chloride Imidazole 2-methylimidazole, 2-undecylimidazole, 2-ethylimidazole , 1-benzyl-2-methylimidazole, 1-cyanoethyl-2-undecylimidazole, boron compound, tetraphenylboron salts, such as triethyleneamine tetraphenylborate, N-methylmorpholine tetraphenylborate. In addition to the raw materials, inorganic fillers, antimony trioxide, 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 includes 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 can be produced, for example, as follows.

That is, components (A), (B), and (C) are blended together with appropriate amounts of other additives such as a pigment 2 coupling agent, etc., and the mixture is heated in 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 in the epoxy resin composition that relieves the internal stress generated at the filler/epoxy matrix interface, and also significantly reduces its electrical properties and moisture resistance. Because it does not contain a curing accelerator that causes curing or has a very low mff1, it has extremely excellent electrical properties and low stress properties.

〔Effect of the invention〕

The semiconductor device of the present invention is a special epoxy resin composition containing a silica filler whose particle surfaces are coated with a coating layer mainly composed of the specific polydimethylsiloxane oligomer, The plastic package is sealed using a material with no or significantly reduced amount of curing accelerator due to the curing accelerating effect of the siloxane oligomer, and also due to the internal stress relaxing effect of the polydimethylsiloxane oligomer in the sealing resin. However, unlike those made from conventional epoxy resin compositions, the internal stress is extremely low. Therefore, it has high moisture resistance reliability, electrical characteristics, and heat resistance reliability, and has low internal stress, making it extremely reliable. In particular, by sealing with the above-mentioned special epoxy resin composition, high reliability as described above can be obtained in large semiconductor devices with 8 pins or more, particularly 16 pins or more, or chips with long sides of 41 or more pins. This is a major feature. Furthermore, the silica filler uses special ingredients such as a special binder, can be applied to a wide range of epoxy resins, and is easy to manufacture, so special processes are added to the manufacturing of semiconductor devices. This is not necessary and does not complicate the manufacturing of semiconductor devices.

Next, examples will be described.

[Examples 1 to 6] First, six types of polydimethylsiloxane oligomers a to " shown in Table 1 were prepared. Then, a 30% by weight toluene solution of the polydimethylsiloxane oligomer and silica were mixed in a weight ratio of 2: 1, and both components were reacted and then filtered.Furthermore, the solvent was scattered by drying under reduced pressure, and the particle surface was coated with the polydimethylsiloxane oligomer by heating at 150°C for 2 hours. Silica a-r was obtained.The amount of the polydimethylsiloxane oligomer coated on the surface of the silica particles was determined from the amount of silica remaining after extracting the polydimethylsiloxane oligomer with toluene from the weighed coated silica (before heating) under reflux. .

(Left below) Next, using the coated silica obtained as above,
This and the raw materials shown in Table 2 below were blended and kneaded on a mixing roll machine at 100°C for 10 minutes to obtain a sheet composition. Here, the amount of coating silica added was adjusted based on the measured value of the coating amount of the polydimethylsiloxane oligomer described above so that the amount of silica alone added was 700 parts by weight. Then, the obtained sheet-like composition was pulverized to obtain the desired powdered epoxy resin composition.

As a reference example, a butadiene-acrylonitrile copolymer in which both ends of the molecular chain are carboxyl groups (manufactured by Ube Industries, Ltd., Hiker CT Polymer, CTBN 1)
300X8. Viscosity: 125,000 cps (27°C) 1 molecular weight: 3,500. A powdered epoxy resin composition was prepared in the same manner as in Examples 1 to 6 using acrylonitrile content: 17%, carboxyl group content: 2.37%.
As a conventional example, a powdered epoxy resin composition was prepared in the same manner as in Examples 1 to 6 using the raw materials shown in Table 2 below in the proportions shown in the same table.

A semiconductor device was obtained by molding a semiconductor element by transfer molding using the powdered epoxy resin composition obtained in the above Examples, Reference Examples, and Conventional Examples.

The semiconductor device obtained in this way was subjected to a 1000-hour reliability test (hereinafter referred to as "rPCBT test") using an internal stress 2 bending elastic modulus due to piezoresistance and a pressure cooker under voltage application conditions (hereinafter abbreviated as "rPCBT test") at -50°C for 15 minutes to 150 hours.
Temperature cycle test of 2000 times for 15 minutes at °C (rT
CT test (abbreviated as "CT test") was performed. The results are shown in Table 3 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 3, it can be seen that the actual height measurement has lower internal stress in the plastic package than the reference height measurement and the conventional example hole, has good electrical insulation, and has good moisture resistance and heat resistance reliability. I know it's expensive.

[Examples 7 to 12] First, six types of polydimethylsiloxane oligomers having a%f shown in Table 1 above were prepared. Then, a toluene solution containing 30% by weight of the polydimethylsiloxane oligomer and 1% by weight of peroxide (benzoyl peroxide) was mixed with silica at a weight ratio of 2:1, reacted, filtered, and dried under reduced pressure. By doing so, coated silica a%f whose particle surfaces were coated with the polydimethylsiloxane oligomer was obtained. In this case, 30 minutes was sufficient for the heating time at 150°C, and the time required to form the coating layer was shorter than in Examples 1 to 6. Using the coated silica obtained above, the raw materials shown in Table 4 below were blended and kneaded on a mixing roll machine at 100''C for 10 minutes to obtain a sheet-like composition.Then, the obtained sheet-like composition The composition was pulverized to obtain the desired powdered epoxy resin composition.

As a reference example, butadiene-acrylonitrile copolymer in which both ends of the molecular chain are carboxyl groups (manufactured by Ube Industries, Hiker CT Polymer, C"I'BN
1300X8. Viscosity: 125000cps (27°C)
1 molecule i1:3500. Acrylonitrile content: 17%
, carboxyl group content: 2°37%), and using this and the raw materials shown in Table 4 below in the proportions shown in the same table, Example 1
A powdered epoxy resin composition was prepared in the same manner as in steps 6 to 6. Further, as a conventional example, powdered epoxy resin compositions were prepared in the same manner as Examples 1 to 6 using the raw materials shown in Table 4 below in the proportions shown in the same table.

(Left below) A semiconductor device was obtained by molding a semiconductor element by transfer molding using the powdered epoxy resin compositions obtained in the above examples, reference examples, and conventional examples.

Example 1 Regarding the semiconductor device thus obtained
- Various tests were conducted in the same manner as in 6.

The results are shown in Table 5.

(Left below) From the results in Table 5, according to Examples 7 to 12, Example 1
It can be seen that excellent effects similar to those in Example 6 can be obtained. That is, the products of Examples 7 to 12 have lower internal stress in their plastic packages than the reference height measurement and conventional height measurement, have good electrical insulation properties, and have high moisture resistance and heat resistance 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), (B), and (C). (A) Epoxy resin. (B) Phenol resin. (C) both ends of the molecular chain are composed of heterocyclic compound residues having at least two secondary amino groups within the molecule;
A silica filler whose particle surface is coated with a coating layer mainly composed of a polydimethylsiloxane oligomer in which a chain portion of the molecular chain is bonded to the nitrogen of a secondary amino group of any of the terminal residues. (2) Claim 1, wherein the epoxy resin composition contains the curing accelerator in a proportion of 0.5% by weight or less based on the total amount of components (A) and (B). semiconductor devices.