JPS61190961A - Semiconductor device - Google Patents

Abstract

PURPOSE:To prevent the formation of cracks in a passivation layer by sealing a semiconductor element by using an epoxy resin composition containing epoxy resin, a phenolic novolak group curing agent and amorphous silica powder having specific sphericity. CONSTITUTION:A semiconductor element is sealed by using an epoxy resin composition containing epoxy resin, a phenolic novolak group curing agent, one molecule thereof has two or more of hydroxyl groups, and amorphous silica powder having the Wadel's sphericity, preferably, sphericity of 0.7-1.0. Epoxy resin having epoxy equivalent of 175-250 and the softening point of 60-130 deg.C can particularly be employed preferably as the epoxy resin. Novolak type epoxy resin is preferable as the form of the epoxy resin. The phenolic novolak group curing agent having the softening point of 60-120 deg.C can specially be used preferably as the curing agent. It means that a particle is close to a true sphere with an approach to 1.0 of the Wadel's sphericity. Sphericity of less than 0.5 results in the formation of a number of sharp projecting pieces, and is undesirable.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to so-called semiconductor devices such as ICs and LSIs, and its purpose is to manufacture semiconductor devices by sealing semiconductor elements using an epoxy resin composition using a transfer molding method. An object of the present invention is to provide a semiconductor device that can eliminate the drawback that cranks or the like enter the passivation layer of the semiconductor device during manufacturing, resulting in easy production of defective semiconductor devices.

[Prior Art] (Background of the Invention) Conventionally, semiconductor devices such as ICs and LSIs are generally manufactured by resin sealing using methods such as transfer molding. Because there is a large difference in the coefficient of thermal expansion between the element made of inorganic material and the encapsulating material, sudden temperature changes during or after molding can cause strain inside the resin encapsulation, causing cracks in the passivation layer of the semiconductor element. There was a problem with entering.

Semiconductor devices in which the passivation layer of the semiconductor element is cranked in this manner have poor moisture resistance, resulting in deteriorated electrical characteristics and become unreliable defective products.

In particular, when an epoxy resin composition is used as a resin material for sealing, molding is usually carried out at a high temperature of 150 to 185°C. The encapsulating resin undergoes relative heat shrinkage, and as a result, the semiconductor element encapsulated with such encapsulating resin (
In particular, the passivation layer that protects this semiconductor element has a cracker. This causes damage such as damage to semiconductor devices, which in turn causes damage to semiconductor devices, resulting in the production of defective semiconductor devices.

(Prior art) Conventionally, in order to eliminate the above-mentioned drawbacks, that is, to lower the coefficient of thermal expansion of the epoxy resin composition for sealing, in addition to this purpose, it has been used for the purpose of reducing the price as well as for general molding material resins. Epoxy resin compositions for sealing containing appropriate inorganic fillers are used for sealing semiconductor devices in order to improve molding operations by imparting thixotropy to the resin material.

The inorganic filler added to the encapsulating epoxy resin composition used for this purpose can provide excellent molding workability during the encapsulation work of semiconductor devices, but the inorganic filler does not have any harmful effects on the semiconductor element. It is necessary to satisfy at least two conditions that there are few impurities that give .

Conventionally, amorphous silica powder has been a typical material that satisfies this condition, and this powder is commonly used as an inorganic filler to be added to an epoxy resin composition for sealing.

(Disadvantages of the prior art) However, when an inorganic filler such as amorphous silica powder is added to an epoxy resin composition for sealing, the coefficient of thermal expansion of the epoxy resin composition for sealing becomes proportional to the amount added. On the other hand, if the amount of amorphous silica powder is too large, it will impair the good molding workability that is the original characteristic of amorphous silica powder, and the elastic modulus of the epoxy resin composition for sealing will decrease. There was a problem that the amount of

This problem can be solved by increasing the amount of amorphous silica powder added as the elastic modulus of the epoxy resin composition for sealing increases, since the stress strain is proportional to the product of the coefficient of thermal expansion and the modulus of elasticity. Even if the coefficient of thermal expansion of the epoxy resin composition could be reduced, it would not result in a reduction in stress strain.

In fact, semiconductor devices encapsulated with encapsulating epoxy resin compositions containing a large amount of amorphous silica powder have the disadvantage that they tend to end up with cracks in the passivation layer, resulting in defective products.

(Problems to be Solved by the Invention) In light of the above-mentioned conventional circumstances, the inventors have proposed that by adding amorphous silica powder, the coefficient of thermal expansion of the epoxy resin composition for sealing can be lowered and the relationship between the composition and the semiconductor element can be reduced. As a result of intensive research on an epoxy resin composition for a sealing layer that does not impair good molding workability and do not increase its elastic modulus even when the difference in thermal expansion coefficient is reduced and the amount of amorphous silica powder blended is increased, this result was obtained. This invention has been achieved.

(Solution Means) That is, the present invention consists of an epoxy resin, a phenol novolac curing agent having 2 (hard or more) hydroxyl groups in one molecule, and an amorphous silica powder having a Wardell sphericity of 0.5 to 1.0. By providing a semiconductor device characterized in that a semiconductor element is sealed using an epoxy resin composition for sealing containing It is an object of the present invention to provide a semiconductor device which can eliminate the drawback that cranks or the like enter the passivation layer of the semiconductor device even when the semiconductor device is manufactured using the same method, and as a result, the semiconductor device tends to be defective.

(Structure of the Invention) The epoxy resin used in this invention is -
Any compound having two or more epoxy groups in the molecule and a resin synthesized from epichlorohydrin, bisphenol A, or various novolaks may be used, such as an alicyclic epoxy resin or a resin that imparts a flame retardant function. Examples include epoxy resins into which halogen atoms such as bromine or chlorine are introduced.

Among such epoxy resins, epoxy resins having an epoxy equivalent of 175 to 250 and a softening point of 60 to 130° C. can be particularly preferably used in the present invention.

As for the form of the epoxy resin, novolac type epoxy resins such as phenol novolac epoxy resin and Talesol novolac epoxy resin are preferred.

The curing agent for such an epoxy resin used in this invention is a phenol novolac curing agent having two or more hydroxyl groups in one molecule (the normal upper limit is about 15), such as phenol novolak and Talesol Novolanc. is used.

The reason why the curing agent for epoxy resins in this invention is limited to phenol novolak-based curing agents having two or more hydroxyl groups in one molecule, such as phenol novolak and Talesol novolanc, is because they are known as curing agents for epoxy resins. With other amine curing agents and acid anhydride curing agents,
For example, the above-mentioned amine-based curing agents have general drawbacks such as toxicity and short life, and acid anhydride-based curing agents tend to have problems with moldability and are somewhat lacking in practicality as sealing materials. This is because both are undesirable.

Among such phenol novolac curing agents having two or more hydroxyl groups in one molecule, phenol novolak curing agents having a softening point of 60 to 120° C. can be particularly preferably used in the present invention.

The Wardell sphericity used in this invention is 0.5 to
Amorphous silica with a sphericity of 1.0 is defined as a sphericity of 0.5 to 1.0 in terms of Wardell's sphericity of the mechanically pulverized product obtained by mechanically pulverizing melted and solidified ingot-like amorphous silica. It refers to spherical amorphous silica with a sphericity of 0.7 to 1.0.

Here, Wardell's sphericity (see Chemical Engineering Handbook, published by Maruzen Co., Ltd.) means the sphericity of a particle as follows: (diameter of a circle equal to the projected area of the particle)/(diameter of the smallest circle circumscribing the projected image of the particle) ), and the closer this index is to 1.0, the closer the particle is to a perfect sphere.

The reason why the shape of the amorphous silica used in this invention is limited to a Wardell sphericity of 0.5 to 1.0 is that if the sphericity is less than 0.5, the amorphous silica powder has an irregular shape. This is because they often have sharp protrusions, which is undesirable.

Therefore, in the present invention, it is more desirable to use amorphous silica having a sphericity of 0.7 or more.

In this invention, there are 1 reasons why amorphous silica powder having irregularly shaped and sharp protrusions with a sphericity of 0.5 or less is not preferable.
．． When this amorphous silica powder having sharp protrusions is blended into an epoxy resin composition for sealing, a semiconductor device encapsulated with such an epoxy resin composition for sealing can be manufactured using an epoxy resin composition for sealing. The passivation layer that protects semiconductor elements is damaged by sharp protrusions of amorphous silica powder during thermal contraction of semiconductor devices. This is based on the inventors' experimental findings that the passivation layer is the cause of damage even when a semiconductor device is manufactured using the same method.

In this invention, it is preferable to blend the amorphous silica powder having such sphericity within the range of 50 to 85% by weight in the total composition. If it is less than this, it is difficult to impart thixotropic physical properties to the epoxy resin composition for sealing, which impairs workability and reduces costs, and furthermore, the effect of reducing stress and strain becomes insufficient, which is undesirable. be.

On the other hand, if the amount of amorphous silica powder exceeds 85% by weight, problems will arise in molding workability and the film-forming performance will also deteriorate, which is undesirable in either case.

The particle size of the amorphous silica powder having the above-mentioned sphericity used in this invention is preferably 149 μm or less, more preferably an average particle size of about 16 μm.

The reason for this is that if the particle size is larger than 149 μm, the filling properties during molding for sealing a semiconductor device using the sealing epoxy resin composition will be impaired.

In addition to the above-mentioned epoxy resin, curing agent, and amorphous silica powder, the encapsulating epoxy resin composition used in the semiconductor device according to the present invention can contain a commonly known internal mold release agent and curing accelerator.

Examples of the internal mold release agent include long chain carboxylic acids such as stearic acid and balmitic acid, metal salts of long chain carboxylic acids such as zinc stearate and calcium stearate, and waxes such as carnauba wax and montan wax.

In addition, in the present invention, various imidazoles, tertiary amines, phenols, organometallic compounds, catalytic curing agents such as boron trifluoride compounds, etc. may be used in combination with the curing agent as a curing accelerator.

In this invention, β-(3・4-
epoxycyclohexyl)ethyltrimethoxysilane,
surface treatment agents for fillers such as silane coupling agents such as r-glycidoxypropyltrimethoxysilane; flame retardants such as antimony oxide, halides, and phosphides;
Conventionally known additives such as various pigments may also be blended.

To prepare the encapsulating epoxy resin composition having the above composition used in the semiconductor device according to the present invention, it may be carried out according to a conventional method. It can be prepared by any method.

In order to obtain a semiconductor device according to the present invention using such a sealing epoxy resin composition, a semiconductor element may be sealed and prepared by a known method such as transfer molding.

(Examples and Test Examples) Next, the effects of the present invention will be explained more specifically by describing Examples and Comparative Examples of the present invention. Note that in the following, parts and % mean parts by weight and % by weight, respectively.

Example 1 Talesol novolak epoxy resin (epoxy equivalent weight 21
0, softening point 80°C) 100 parts, phenol novolac (
softening point 78°C) 50 parts, comethylimidazole 0.
7 parts, spherical amorphous silica powder (Wardell sphericity 0.
7 average particle size 16μ) 350 parts, silane cuff pulling agent A
-186 (trade name manufactured by Nippon Unicar Co., Ltd.) 1.8 parts, carnauba wax 6.0 parts, carbon blank 2.0 parts at 80 parts
The mixture was kneaded with a heated roll at ~90°C, cooled and pulverized to obtain an epoxy resin composition to be used in the semiconductor device according to the present invention.

Example 2 In Example 1, the spherical amorphous silica powder was
The procedure was exactly the same as in Example 1 except that 0 part was used.

Comparative Example 1 Instead of the spherical amorphous silica powder of Example 1, amorphous silica powder (Wardell's sphericity 0.4, average particle size 12
An epoxy resin composition was obtained in exactly the same manner as in Example 1 except that 350 parts of μ) were used.

Comparative Example 2 Example 1 except that 420 parts of amorphous silica powder (Wardell's sphericity 0.4 average particle size 12μ) was used in Comparative Example 1.
An epoxy resin composition was obtained in exactly the same manner.

Comparative Example 3 Example 1 except that 700 parts of amorphous silica powder (Wardell's sphericity 0.7 average particle size 12μ) was used in Comparative Example 1.
An epoxy resin composition was obtained in exactly the same manner.

Comparative Example 4 Example 1 except that 150 parts of amorphous silica powder (Wardell's sphericity 0.7 average particle size 12μ) was used in Comparative Example 1.
An epoxy resin composition was obtained in exactly the same manner.

Next, each epoxy resin composition was transfer molded at 175°C for 3 minutes.
Post-cure for 5 hours and heat from -65℃ to 150℃
Thermal shock tests were conducted 500 times to investigate passivation cracks in semiconductor devices.

The numerical values in Table 1 are the results of investigating the number of defective products out of 100 tested products.

As is clear from the above results, it can be seen that spherical amorphous silica powder is effective for passivation of semiconductor devices.

(Effects of the Invention) As detailed above, the semiconductor device according to the present invention combines an epoxy resin, a phenol novolak curing agent having two or more hydroxyl groups in one molecule, and a Wardell sphericity of 0.5 to 1.
．． Since this semiconductor device is characterized in that a semiconductor element is sealed using an epoxy resin composition for sealing containing amorphous silica powder having a sphericity of 0, this semiconductor device is manufactured using amorphous silica powder during manufacturing. It is possible to seal with a sealing resin that provides excellent molding workability due to the powder and is compatible with semiconductor elements in terms of electrical properties, and it is also possible to use amorphous silica powder in an epoxy resin composition for sealing. This amorphous silica powder has a spherical shape with a Wardell sphericity of 0.5 to 1.0 even when mixed in a large amount, so it can prevent cracks in the pansivation layer of semiconductor devices without impairing both of the above characteristics. This is a semiconductor device that has the effect of significantly reducing the

Claims (1)

[Claims] (1) A sealing epoxy containing an epoxy resin, a phenol novolac curing agent having two or more hydroxyl groups in one molecule, and an amorphous silica powder having a Wardell sphericity of 0.5 to 1.0. A semiconductor device characterized in that a semiconductor element is sealed using a resin composition.