JPS61215264A - Aluminum nitride sintered body and manufacture - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION (1) Background of the Invention Technical Field The present invention relates to an aluminum nitride sintered body and a method for manufacturing the same.

Prior art and its problems Traditionally, sintered alumina has been used as an insulating substrate material for integrated circuits. However, alumina substrates have poor thermal conductivity and a higher coefficient of thermal expansion than silicon, so
It has many drawbacks, including poor adhesion to large silicon chips.

Instead, use beryllium oxide.

Although its thermal conductivity is more than 10 times that of alumina, this material is toxic and expensive, making it difficult to supply.

SiC substrates have also been developed, but they are disadvantageous in terms of cost because they use hot pressing during sintering, and have a high dielectric constant, and since SIC is originally a semiconductor, they have low dielectric strength. There is a problem.

Therefore, 9AiN sintered bodies using aluminum nitride (AfLN), which has high thermal conductivity and high resistance, are attracting attention. This material also has the advantage of having a coefficient of thermal expansion close to that of silicon and a low dielectric constant.

However, in order to take full advantage of these advantages, A! L
The N sintered body is required to be dense and have a low oxygen content.

However, since the sinterability of the A-type N powder alone, which has a low oxygen content, is not good, it is necessary to use a sintering aid.

Up to now, several proposals have been made regarding this sintering aid.

For example, aluminum oxide (see A203) is added to IIN powder.
) or Ittria (Y203) is added and pressureless sintering or hot pressing is performed.

A! A method of adding calcium oxide (Cao), barium oxide (Bad), and strontium oxide (SrO) to LN powder and sintering it under normal pressure (Japanese Patent Application No. 74166/1982).

A method of adding boron nitride (BN) to AILN powder and sintering or hot pressing in a non-oxidizing atmosphere (Japanese Patent Application No. 58-32073).

A method of adding a mixed powder containing at least one powder selected from compounds including Cab, Bad, and SrO to AILN powder and hot pressing in a non-oxidizing atmosphere (
(Japanese Patent Application No. 59-50077).

Among these, the method of adding oxides.

It is insufficient in terms of thermal conductivity.

On the other hand, the method of adding BN provides an AJIN sintered body with higher thermal conductivity than the others, and is also said to be better than the others in terms of compactness.

However, all of the conventional AILN sintered bodies produced as described above tend to have uneven firing, so much so that a white pattern on one surface can be observed with the naked eye. There will be a lot of variation in values.

Therefore, in order to improve these points, it is desired to develop an AiN sintered body using a new sintering aid.

■ Purpose of the Invention The purpose of the present invention is to have a material that has no uneven firing, is dense, has high thermal conductivity and electrical resistance, has suitable performance as an electrically insulating substrate material, is easy to mold and sinter, and is inexpensive. An object of the present invention is to provide an aluminum nitride sintered body and a method for manufacturing the same.

■Disclosure of the Invention Such an object is achieved by the following first and second inventions. In other words, the first invention is a method of adding rare earth elements and oxygen-free rare earth elements to aluminum nitride as a sintering aid. This is an aluminum nitride sintered body characterized by being formed by adding and firing a mixture of one or more of the elemental compounds and boron nitride.

Further, the second invention provides a method for adding and mixing powder consisting of boron nitride and one or more of a rare earth element and a compound of a rare earth element not containing oxygen as a sintering aid to aluminum nitride powder. , a method for producing an aluminum nitride sintered body, characterized by forming and firing in a non-oxidizing atmosphere.

■Specific structure of the invention Hereinafter, a specific configuration of the present invention will be explained in detail.

The aluminum nitride sintered body of the present invention contains aluminum nitride (A9.N) powder, one or more of rare earth elements and rare earth element compounds that do not contain S as sintering aids, and boron nitride (BN). ).

Rare earth elements include Sc, Y, La, and Ce.

Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, H
o, Er, Tm, Yb, Lu, etc., among which Y
, La, Ce, Pr, and Nd are preferred.

As rare earth element compounds that do not contain oxygen, halides, hydrides, sulfides, borides, carbides, thiocyanides, nitrides, etc. are preferable, and specific examples include YF3゜LaF3, CeF3, PrF3, Nd.
F3.

YBa, YB2.5N3. LaH, 5N3゜Y233
, La2 S3 , YCl3 , YBr3, YI3.
Examples include YBe, among others YB6, LaF3.5
cH2-3, CeB6.

YF3 and the like are preferred.

The ARN powder is preferably pulverized, and preferably has an average particle size of 0.1 to 10 um, particularly 0.5 to 6 pm.

The average particle diameter of the sintering aid is 1 to 44I in the case of rare earth elements.
Lm, especially 5 to 10 ILm, in the case of compounds of rare earth elements that do not contain oxygen, 0.1 to 44 gm, especially 0.5 to 3 IL
m, 0.1 to 44 JLm for BN, especially 0.5 to 3
Preferably it is 4 m.

The total amount of these sintering aids added is 0.01 to 10% by weight based on AfLN.

In particular, it is preferably 1 to 3% by weight.

If the amount added is less than 0.01% by weight, a dense sintered body cannot be obtained, and if it is more than 10% by weight, as in the case of less than 0.01% by weight, a dense sintered body cannot be obtained by normal pressure firing. That's because there isn't.

In addition, 111 or more of rare earth elements and rare earth element compounds that do not contain oxygen are 0.1-
It is preferable to add boron nitride at a rate of 10 wt%, preferably 0.5 to 3 wt%, and boron nitride at a rate of 0.1 to 3 wt%, preferably 1 to 2 wt%.

The reason why it is added in such a ratio is that the former is effective as a sintering aid for densification of A-N, while the latter alone does not have a large effect as a sintering aid in normal pressure firing. ,
This is because the combination with the former increases the contribution to thermal conductivity and electrical resistance.

Unlike conventional sintering aids such as alkaline earth metal oxides and ittria, these sintering aids do not contain oxygen and do not produce impurities such as oxygen that inhibit thermal conductivity. It is considered difficult.

A! LN sintered body is 1 normal A! The above-mentioned sintering aid powder is added and mixed with the LN powder, pressure molded at room temperature, and the molded body is sintered by the pressureless sintering method in a non-oxidizing atmosphere, and then left to cool. It will be done.

The pressure during pressure molding is approximately 500 to 2000 kg/C 2.

The non-oxidizing atmosphere during sintering includes an inert gas such as N2, Ar, He, etc., N2. GO1 Various hydrocarbons, etc., or a mixed atmosphere of these.

Furthermore, various atmospheres such as a vacuum may be used.The purpose of creating a non-oxidizing atmosphere is to prevent oxidation of the surface of the pulverized AIH.

In this case, the non-oxidizing atmosphere is preferably one containing nitrogen, with 50% or more nitrogen, Ar, He
An inert gas such as may be mixed.

The atmospheric pressure may be atmospheric pressure, but it is usually in a nitrogen stream.

The temperature during sintering is 160.0 to 1900°C, preferably 1
A temperature of 750 to 1800°C is effective.

If the temperature is lower than 1600℃, it will not be sufficiently densified even if fired for a long time, and if the temperature is higher than 1900℃, AIN
volatilization is observed, and if the temperature is higher than 1800°C, the oxygen content is AJ2. This is because it easily forms a solid solution in N and becomes a cause of phonon scattering, that is, a decrease in thermal conductivity.

Sintering time is usually 0.5 to 2 hours, especially 175
At 0°C, the heating time is preferably about 1 hour.

In the case of sintering, a hot press method may be used by applying a pressure of about 100 to 300 kg/C.

The AiN sintered body obtained in this way has no uneven firing and has an A rating of A at room temperature. It has a density that is 90% or more of the theoretical density of LN, an electrical resistivity of 1012Ωc11 or more, and a thermal conductivity of 80w/IIIK or more at room temperature. Further, the coefficient of thermal expansion is about 5×10″6.

The electrical resistivity is the same as the conventional A9. For N sintered bodies, the value is 10 to 2.
There is a variation of 0%, but in the case of the present invention, there is no uneven baking, so the variation is only about 1%.

V. Specific Effects of the Invention According to the present invention, a mixture of one or more of rare earth elements and compounds of rare earth elements not containing oxygen and boron nitride is used as a sintering aid, and this is used as a sintering aid for aluminum nitride. This is because after adding 0.01 to 10% by weight to powder and mixing it, it is made into a molded body, and this molded body is fired in a non-oxidizing atmosphere.

An aluminum nitride sintered body with high thermal conductivity and electrical resistance and no uneven firing can be obtained.

In addition, it is dense, has high thermal conductivity and electrical insulation, and has no uneven heating, so it has good adhesion and no variation in electrical resistivity, making it suitable for electrical insulation substrates used in integrated circuits and other It has suitable performance as a material for heat dissipation substrates.

Furthermore, since the pressureless sintering method is applied during sintering, the manufacturing method is easy and advantageous in terms of cost.

(2) Specific Examples of the Invention Hereinafter, specific examples of the present invention will be shown, and the effects of the present invention will be explained in further detail.

Example: AIN powder with an average particle size of 31Lm was added with an average particle size of 10I
Sintering aid powder Lm was added and mixed as shown in Table 1. This mixture is then weighed at room temperature at approximately 1000 kg/
A pressure of cm2 was applied to form a compact.

Thereafter, the temperature of the molded body was raised to 1750°C in a N2 stream,
After holding at 1750°C for 1 hour.

It was left to cool.

In this way, the AiN sintered body shown in Table 1 (sample 101
'-108) was produced.

For comparison, we also added calcium carbonate (Ca) to the sintering aid.
Samples 101 to 108 were prepared in the same manner as Samples 101 to 108, except that CO3) was used at 1.0% by weight based on the AmonN powder.

This is designated as sample 201.

Using Ittria (Y203) as a sintering aid, AIIN
Sample 101~ except that 1.0% by weight was added to the powder
Sample 301 was prepared in the same manner as Sample 108.

Furthermore, sample 4 was prepared by adding 3% by weight of BN to AIN.
Set it to 01.

Samples 101-108, 201, 301 and 40 above
Table 1 shows the characteristics of No. 1.

Measurement of properties is as follows.

(1) Density and relative density The measured density and its relative value to the theoretical density were determined.

(2) Electrical resistivity and its variation Baked Ag paste on the front and back surfaces of a sample with a thickness of 30 m and 21 layers to form electrodes, and at 23°C and 50% relative humidity.
0 samples were measured and the range between the maximum and minimum values was determined.

(3) Thermal conductivity of the sample (2) was measured at room temperature without silver paste attached.

(4) Uneven grilling area The area of baking unevenness where white deposits were formed was calculated.

From Table 1, it can be seen that the AILN sintered body of the present invention has high thermal conductivity and high electrical resistivity. It can also be seen that there is little unevenness in baking, and as a result, there is little variation in the electrical resistivity value. Moreover, it has good density and is found to have suitable performance as an electrically insulating substrate material.

Note that sample 401 had a low density and did not exhibit practically satisfactory characteristics.

From the above, the effects of the present invention are clear.

When the AIN sintered body of the present invention was applied to an electrically insulating substrate of a semiconductor power module, it showed good resistance to heat cycles.

Furthermore, effects similar to those shown in Table 1 were obtained even with mixtures of BN and compounds of these elements that do not contain other transition elements or oxygen. Furthermore, in the auxiliary agent of the present invention, the same effect was obtained even when a transition element and a compound of these elements not containing oxygen were added in combination.

Claims (8)

[Claims] (1) Nitriding characterized by being made by adding a mixture of boron nitride and one or more of rare earth elements and compounds of rare earth elements not containing oxygen as a sintering aid to aluminum nitride and firing the mixture. Aluminum sintered body. (2) According to claim 1, wherein aluminum nitride and the above-mentioned sintering aid are mixed in powder form, and the above-mentioned sintering aid is added in an amount of 0.01 to 10% by weight based on the aluminum nitride. The described aluminum nitride sintered body. (3) The aluminum nitride sintered body according to claim 1 or 2, wherein the firing is performed in a non-oxidizing atmosphere. (4) The aluminum nitride sintered body according to any one of claims 1 to 3, which has a thermal conductivity of 80 W/m·K or more. (5) Claim 1 in which the relative density is 90% or more
The aluminum nitride sintered body according to any one of items 1 to 4. (6) The aluminum nitride sintered body according to any one of claims 1 to 5, which has a volume resistivity of 10^1^2 Ωcm or more. (7) After adding and mixing powder consisting of boron nitride and one or more of rare earth elements and oxygen-free rare earth element compounds as a sintering aid to aluminum nitride powder, molding and non-oxidizing 1. A method for producing an aluminum nitride sintered body, the method comprising firing in a neutral atmosphere. (8) Claim 7 in which the non-oxidizing atmosphere contains nitrogen
A method for producing an aluminum nitride sintered body as described in 2.