JP2654376B2 - Epoxy resin composition for encapsulation and resin-encapsulated semiconductor device using the same - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a sealing epoxy resin composition and a resin-sealed semiconductor device using the same.

[0002]

2. Description of the Related Art Resin-sealed semiconductor devices are used to protect semiconductor elements such as integrated circuits (ICs), large-scale integrated circuits (LSIs), transistors, and diodes from the external atmosphere and mechanical shock. It is formed by sealing with a thermosetting resin.

Conventionally, as a semiconductor element sealing technique, hermetic sealing using metal, ceramics, or the like has been adopted. However, recently, resin sealing has prevailed because of its economical advantage. ing.

As such a resin for semiconductor encapsulation, an epoxy resin composition for low-pressure molding, which can be used in a low-pressure transfer molding method suitable for mass production, is generally widely used. However, a conventional resin-encapsulated semiconductor device obtained by transfer molding an epoxy resin composition comprising an epoxy resin, a novolak-type phenol resin curing agent, an imidazole oxidation accelerator, and the like has the following disadvantages. . That is, (1) corrosion and deterioration of aluminum electrodes and the like due to poor moisture resistance, (2) poor electrical characteristics at high temperatures, and particularly, a decrease in the function of the semiconductor element due to an increase in leak current; It is. If (1) is described, the resin-encapsulated semiconductor device may be used or stored in a high-temperature and high-humidity atmosphere.
Reliability must be guaranteed even under such conditions. As a reliability evaluation test for quality assurance of moisture resistance, an accelerated evaluation method of exposing to saturated steam at 85 ° C. or 120 ° C. is performed. Recently, an evaluation test of a bias application type in which a voltage is applied to further improve the acceleration is also being performed.

However, in a resin-sealed semiconductor device using an epoxy resin composition, since the sealing resin has a hygroscopic property, moisture is transferred from an external atmosphere via the sealing resin layer or between the sealing resin and the lead frame. Penetrates through the interface of the semiconductor device and reaches the surface of the semiconductor element. As a result of the action of the moisture and the impurities present in the sealing resin, the resin-sealed type semiconductor device generates defects due to corrosion of aluminum electrodes, wirings and the like. Further, when a bias voltage is applied, defects due to corrosion of aluminum electrodes and wirings occur particularly frequently due to the electrochemical action.

[0008] Next, (2) will be described. Since the resin-encapsulated semiconductor device is sometimes used under high temperature conditions,
Reliability must be guaranteed under such conditions. As an evaluation test therefor, an accelerated test in which a bias voltage is applied at 80 ° C. to 150 ° C. to evaluate reliability is generally used.

In such a test, for example, a device having a MOS structure in which the semiconductor surface is sensitive to external charges or a device having a PN junction to which a reverse bias is applied is a defect that occurs particularly frequently. There is an increasing phenomenon. It is considered that this phenomenon occurs when an electric field acts on the sealing resin layer in contact with the surface of the element to which the voltage is applied.

The conventional resin-encapsulated semiconductor device has the above-mentioned drawbacks, and therefore has been required to be improved.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to remedy such disadvantages of the conventional resin-encapsulated semiconductor device, and to provide a highly reliable sealing device having excellent moisture resistance and high-temperature electrical characteristics. An object of the present invention is to provide an epoxy resin composition for stopping and a resin-sealed semiconductor device using the same.

[0010]

The inventors of the present invention have conducted intensive studies to achieve the above object, and as a result, the following epoxy resin composition has been used as a resin for encapsulating a semiconductor device. It has been found that the resin-encapsulated semiconductor device has excellent characteristics as compared with the resin composition, and that a resin-encapsulated semiconductor device having excellent moisture resistance and high-temperature electrical characteristics can be obtained by using the resin composition.

That is, the present invention is a sealing resin composition comprising (a) an epoxy resin, (b) a phenol aralkyl resin, (c) a novolak type phenol resin, and (d) an organic phosphine compound.

The present invention also provides a resin-sealed semiconductor device in which a semiconductor device is sealed with a cured product of an epoxy resin composition, wherein the epoxy resin composition comprises: (a) an epoxy resin; and (b) a phenol aralkyl resin. A resin-encapsulated semiconductor device comprising: c) a novolak-type phenol resin; and (d) an organic phosphine compound.

The epoxy resin used in the present invention is generally known and is not particularly limited. For example, glycidyl ether type epoxy resin such as bisphenol A type epoxy resin, phenol novolak type epoxy resin, cresol novolak type epoxy resin, glycidyl ester type epoxy resin, glycidylamine type epoxy resin, linear aliphatic epoxy resin, alicyclic epoxy resin, An epoxy resin having two or more epoxy groups in one molecule, such as a heterocyclic epoxy resin and a halogenated epoxy resin, may be used. These epoxy resins may be used alone or in a mixture of two or more.

The more preferred epoxy resin used in the present invention is a novolak epoxy resin having an epoxy equivalent of 170 to 300, such as a phenol novolak epoxy resin, a cresol novolap epoxy resin, a halogenated phenol novolak epoxy resin, and the like. It is. These epoxy resins preferably have a chlorine ion content of 10 ppm or less and a hydrolyzable chlorine content of 0.1% by weight or less. The reason for this is that if chlorine ions exceeding 10 ppm or hydrolyzing chlorine exceeding 0.1% by weight are contained, the aluminum electrode of the sealed semiconductor element is easily corroded.

The phenol aralkyl resin used as a curing agent for the epoxy resin in the present invention is represented by the general formula [I]
Can be indicated by

[0016]

Embedded image Here, n is an integer of 1 or more. The phenol aralkyl resin can be generally obtained by condensing phenol and α, α′-dimethoxyparaxylene by a Friedel-Crafts reaction. In addition, since it is marketed under the trade name of Xyloc, it can be easily obtained. In the above formula [I], a preferable value of n or a preferable average value of n is n = 2 to 20.

The mixing ratio of the epoxy resin to the phenol aralkyl resin is preferably such that the number of phenolic hydroxyl groups of the phenol aralkyl resin is 0.5 to 1.5 per one epoxy group of the epoxy resin. . If the ratio is out of the above range, the characteristic tends to deteriorate.

In the present invention, examples of the novolak type phenol resin used together with the phenol aralkyl resin as a curing agent for the epoxy resin include phenol novolak resin, cresol novolak resin, tert-butylphenol novolak resin, and nonylphenol novolak resin. For example, phenol,
Cresol, xylenol, hydroquinone, resorcin, catechol, bisphenol A, bisphenol F
Such phenols and aldehydes can be obtained by condensation. The softening point of such a novolak-type phenol resin is preferably in the range of 60 to 120 ° C., and the content of the water-soluble phenol resin component at room temperature is preferably 3% or less.

The compounding ratio of the novolak type phenol resin is such that the total number of phenolic hydroxyl groups of the phenol aralkyl resin and the novolak type phenol resin is 0.5 to 1.5 with respect to the number of epoxy groups of the epoxy resin. It is preferable to mix them. If the ratio is out of the above range, the characteristic tends to deteriorate. The mixing ratio of phenol aralkyl resin and novolak type phenol resin is
It is desirable that the novolak-type phenol resin is blended in an amount of 0.01 to 100 parts by weight per 1 part by weight of the phenol aralkyl resin. If the amount is less than 0.01 part by weight, the effect of the addition of the novolak type phenol resin is hardly recognized, and if it is 100 parts by weight or more, the effect of the phenol aralkyl resin is reduced. In order to effectively mix the phenol aralkyl resin and the novolak type phenol resin, a molten mixture of both may be prepared in advance and used.

These phenol aralkyl resins and novolak type phenol resins can be used in combination with other curing agents. Examples of such other curing agents include phenol compounds having two or more phenolic hydroxyl groups in one molecule, acid anhydrides and amine compounds, and the like.
What is known as a curing agent for epoxy resin can be used. Among them, phenol compounds having two or more phenolic hydroxyl groups in one molecule are preferable.

Examples of the phenol compound having two or more phenolic hydroxyl groups in one molecule include a resol type phenol resin, polyhydroxystyrene, tris (hydroxyphenyl) methane, tetrakis (hydroxyphenyl) ethane, bisphenol A, bisphenol F and the like. Is mentioned.

On the other hand, in the present invention, by using an organic phosphine compound as a curing accelerator, the moisture resistance of the resin-encapsulated semiconductor device is improved as compared with the case where a conventional curing accelerator such as imidazole or amine is used. High temperature electrical properties can be significantly improved.

The organic phosphine compound used in the present invention includes a compound represented by the formula [II]:

[0024]

Embedded image A third phosphine compound wherein R _{1 to} R ₃ are all organic groups, a second phosphine compound wherein only R ₃ is hydrogen,
There is a first phosphine compound in which both R ₂ and R ₃ are hydrogen. Specific examples include triphenylphosphine, tributylphosphine, tricyclohexylphosphine, methyldiphenylphosphine, butylphenylphosphine, diphenylphosphine, phenylphosphine, octylphosphine, and the like. R ₁ may be an organic group containing an organic phosphine. For example, 1,2-bis (diphenylphosphino) ethane, bis (diphenylphosphino)
Such as methane. Among them, aryl phosphines are preferable, and triaryl phosphines such as triphenyl phosphine are particularly preferable. These organic phosphine compounds may be used alone or in a mixture of two or more.

The amount of the organic phosphine compound to be added is generally 0.03% of the resin component (epoxy resin and curing agent).
A range of from 0.01 to 20% by weight, but particularly preferred properties are obtained in a range of from 0.01 to 5% by weight. By setting the amount of the organic phosphine compound in this range, an epoxy resin composition for sealing having excellent properties can be obtained. When the amount is less than 0.001% by weight, the effect of the addition is hardly recognized, and there is a disadvantage that the curing of the epoxy resin composition requires a long time, and when it exceeds 20% by weight, the quality is adversely affected.

The epoxy resin composition according to the present invention may optionally contain an inorganic filler.
In particular, in the case of transfer molding semiconductor elements such as integrated circuits and transistors, it is preferable to incorporate an inorganic filler. One of the reasons is to improve the moldability. Another is to reduce the difference in the coefficient of thermal expansion between the sealing resin such as elements, bonding wires, lead frames, etc. This is to reduce defects that occur due to a large difference in thermal expansion coefficient such as breakage.

The inorganic filler used in the present invention includes quartz glass powder, crystalline silica powder, glass fiber, talc, alumina powder, calcium silicate powder,
Among them are calcium carbonate powder, barium sulfate powder, magnesium powder and the like. Of these, quartz glass powder and crystalline silica powder are most preferable in terms of high purity and low coefficient of thermal expansion. The amount of the inorganic filler varies depending on the type of the epoxy resin, the curing agent and the inorganic filler. For example, when used in transfer molding, the weight ratio is 1.5 times the total amount of the epoxy resin and the curing agent. It may be about 4 times. Regarding the particle size distribution of the inorganic filler, the formability can be improved by combining coarse particles and fine particles to make the distribution uniform.

The epoxy resin composition according to the present invention may be used, if necessary, for example, with a release agent such as natural waxes, synthetic waxes, metal salts of linear fatty acids, acid amides, esters or paraffins, chlorination. A flame retardant such as paraffin, bromotoluene, hexabromobenzene, antimony trioxide, a coloring agent such as carbon black, a silane coupling agent, etc. may be appropriately added and blended in an amount of about 0.01 to 10% by weight.

As a general method for preparing the epoxy resin composition according to the present invention as a molding material, a raw material composition selected in a predetermined composition ratio is sufficiently mixed by, for example, a mixer, and then melt-mixed by a hot roll. An epoxy resin molding material can be easily obtained by adding a treatment or a mixing treatment using a kneader or the like.

The resin-encapsulated semiconductor device of the present invention can be easily manufactured by encapsulating the semiconductor device using the epoxy resin composition or the molding material. The most common sealing method is a low-pressure transfer molding method, but sealing by injection molding, compression molding, casting or the like is also possible. As a special sealing method, a method of coating a semiconductor surface using a solvent-type or non-solvent-type composition or a local sealing application as a so-called junction coating can be used. It can also be used as a resin composition for die bonding.

The epoxy resin composition or the molding material is cured by heating at the time of sealing, and finally, a resin-sealed semiconductor device sealed with the cured product of the composition or the molding material is obtained. it can. In curing, it is desirable to heat to 150 ° C. or higher.

The semiconductor device in the present invention is an integrated circuit, a large-scale integrated circuit, a transistor, a thyristor, a diode and the like, and is not particularly limited.

[0033]

Next, synthesis examples of the present invention will be described. Synthesis Example 1 A phenol aralkyl resin having a hydroxyl equivalent of 174 and a phenol novolak resin having a hydroxyl equivalent of 104 were mixed in an amount of 100 parts by weight, respectively, and heated to 160 ° C. to obtain a molten mixture. This was cooled and pulverized to obtain a raw material of the epoxy resin composition.

Next, an embodiment of the present invention will be described. Examples 1 to 4 Cresol novolak type epoxy resin having an epoxy equivalent of 220 (epoxy resin A), brominated epoxy novolak resin having an epoxy equivalent of 290 (epoxy resin B), a phenol aralkyl resin having a hydroxyl equivalent of 174, and a hydroxyl equivalent of 104 as phenolic compound A A phenol novolak resin, a melt mixture of Synthesis Example 1, triphenylphosphine,
Table 1 shows 2-methylimidazole, dimethylaminomethylphenol, tetraphenylphosphonium / tetraphenylborate, quartz glass powder, antimony trioxide, carnauba wax, carbon black, and a silane coupling agent (γ-glycidoxypropyltrimethoxysilane). The composition (parts by weight) shown in the above is selected, and each composition is mixed by a mixer and kneaded by a heating roll,
Nine types of transfer molding materials including a comparative example were prepared.

[0035]

[Table 1] The MOS integrated circuit was resin-sealed by transfer molding using the molding material thus obtained. Sealing is performed by molding the molding material heated to 90 ° C with a high frequency
Molding was performed at 2 ° C. for 2 minutes, and after-curing was performed at 200 ° C. for 8 hours. The following test was conducted for each of the 100 resin-sealed semiconductor devices. (1) Moisture resistance test (bias PCT) was conducted by applying 10 V in water vapor at 120 ° C. and 2 atm to check for disconnection failure due to corrosion of aluminum wiring. Table 2 shows the results. (2) Offset gate MOS in oven at 100 ° C
A test (MOS-BT test) for applying a drain voltage of 5 V and an offset gate voltage of 5 V to the FET circuit to check for a leak current failure due to deterioration of electrical characteristics is performed. And the results are shown in Table 3.

[0036]

[Table 2]

[0037]

[Table 3] Example 5 A compound represented by the following formula (epoxy resin C) as an epoxy resin,

[0038]

Embedded image (However, n = 2, epoxy equivalent: 160) As a phenol compound, a novolak-type phenol resin (phenol compound B,
A composition having the composition (parts by weight) shown in Table 4 was prepared using the same raw materials as in Examples 1 to 4 except that the hydroxyl equivalent 120) was used.

[0039]

[Table 4] Using these compositions, an evaluation test of a resin-encapsulated semiconductor device was performed in the same manner as in Examples 1 to 4. The results are shown in Tables 5 and 6.

[0040]

[Table 5]

[0041]

[Table 6]

[0042]

As is apparent from the above-mentioned objects, outlines and examples of the present invention, a resin-sealed semiconductor device obtained by encapsulating a semiconductor using the epoxy resin composition of the present invention has a bias. The PCT is excellent in moisture resistance as shown by extremely low corrosion breakage of the aluminum wiring due to moisture in the PCT, and is excellent in high-temperature electrical characteristics in the MOS-BT test as shown by extremely low leakage current. Therefore, a highly reliable resin-encapsulated semiconductor device can be obtained by the present invention.

Claims (2)

(57) [Claims] 1. An epoxy resin composition for sealing, comprising (a) an epoxy resin, (b) a phenol aralkyl resin, (c) a novolak type phenol resin, and (d) an organic phosphine compound. 2. A resin-encapsulated semiconductor device in which a semiconductor device is encapsulated with a cured product of an epoxy resin composition, wherein the epoxy resin composition comprises: (a) an epoxy resin; (b) a phenol aralkyl resin; A resin-encapsulated semiconductor device comprising a novolak-type phenol resin and (d) an organic phosphine compound.