JPH02275766A - Production of sintered aluminum nitride - Google Patents

Abstract

PURPOSE:To obtain a sintered AIN having high density and high thermal conductivity and useful as a substrate of a large-scale integrated high-power semiconductor by adding Y powder as a sintering assistant to AIN powder, forming the mixture and calcining in a non-oxidizing atmosphere. CONSTITUTION:The objective sintered AIN can be produced by mixing 100 pts.wt. of powder composed mainly of AIN with 0.05 to 5 pts.wt. of a sintering assistant consisting of Y powder preferably covered with a Y2O3 layer having a thickness of <=10nm, forming the mixture and calcining at 1400 to 2000 deg.C in a non-oxidizing atmosphere. The covering of the Y powder with Y2O3 is effective in preventing the deterioration of Y with oxygen, moisture, etc., in air and improving the handleability of the powder.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for manufacturing an aluminum nitride sintered body, and in particular, a method for manufacturing an aluminum nitride sintered body with high density and high thermal conductivity, which is in high industrial demand. Regarding.

[Prior Art I] Aluminum nitride sintered bodies have high thermal conductivity and high insulation properties, and are attracting attention as substrate materials for highly integrated, high-output semiconductors.

Desirable properties of the sintered body as a substrate material include: ■High insulation resistance.

■High thermal conductivity.

■High strength.

That is the condition.

However, if aluminum nitride powder is molded and fired without adding a sintering aid, sintering will be insufficient and impurities such as oxygen will not be completely removed. It was impossible to obtain.

For this reason, yttrium oxide is generally used as a sintering aid (for example, JP-A-49-111909), and although it has been somewhat effective, it has been desired to improve the above characteristics.

[Problems to be Solved by the Invention] In view of the above-mentioned prior art, the present invention seeks to provide a manufacturing method capable of improving the characteristics of an aluminum nitride sintered body.

[Means for Solving the Problems 1] The present inventors have arrived at the present invention as a result of various studies in order to solve the above problems by developing a method for manufacturing aluminum nitride sintered bodies with excellent properties. In the present invention, 1 part by weight of aluminum nitride powder as the main component is mixed with 0.05 to 5 parts by weight of yttrium powder as a sintering aid, and after the mixture is molded, the molded body is placed in a non-oxidizing atmosphere. 1400 inside
A method for producing an aluminum nitride sintered body characterized by firing at ~2000°C, in which yttrium powder is used as yttrium powder.
Yttrium powder whose surface is covered with a yttrium oxide layer having a thickness of 10 nm or more can be used.

[Effect J There are no particular restrictions on the manufacturing method or purity of the aluminum nitride powder, which is the main component, but in order to obtain a high sintered body density, it is preferable that the powder be as fine as possible and have a uniform particle size. In order to obtain conductivity, it is preferable to use a material with a low amount of oxygen and metal impurities.

The manufacturing method and purity of the yttrium powder to be mixed as a sintering aid are not particularly limited, but it is preferable that it be as fine and uniform in particle size as possible so that it can be evenly mixed with the main component, aluminum nitride powder. It is preferable to use a lower one.

The mechanism of action of yttrium as a sintering aid is not clear, but yttrium combines with oxygen contained as an impurity in aluminum nitride to form a Y2O3-Aff203-based liquid phase, resulting in the mechanism of liquid phase sintering. It is assumed that yttrium promotes sintering, and thus, since yttrium does not carry oxygen, the amount of oxygen in the sintered body is significantly reduced compared to yttrium oxide, which improves the thermal conductivity of the sintered body. The mixture of yttrium 6 powder that is considered to be obtained is
．． 05 to 5 parts by weight. If it is less than 0.05 parts by weight, the effect is insufficient, and even if it exceeds 5 parts by weight, the effect will not be improved. Mix and cross-wire thoroughly using At this time, a suitable dispersant may be added if necessary. The slurry obtained in this way has
Add appropriate amount of binder and mold into desired shape.

As a molding method, a doctor blade method is often used when manufacturing a substrate, but other pressing methods, roll coating methods, etc. can also be used.

After the molded body is dried, the binder is decomposed and volatilized by heating (degreasing process).

Firing is generally performed at 1400°C to 2°C in a non-oxidizing atmosphere that does not contain molecular oxygen, such as nitrogen, ammonia, or argon.
It is carried out in the range of 000°C. When fired in an oxidizing atmosphere, Aε
N decomposes into oxides, and if the firing temperature is less than 1,400°C, sintering is insufficient, and if it exceeds 2,000°C, the evaporation of AεN becomes intense, resulting in a significant decrease in the density of the sintered body.

The present invention uses yttrium powder with a surface thickness of 10 nm.
Yttrium powder covered with a layer of yttrium oxide with a thickness of m or more can be used.

Since yttrium is highly active and easily reacts with oxygen and water vapor to change into hydroxide, etc., its handling properties can be improved by covering it with a layer of yttrium oxide, which is stable in the atmosphere.

If the thickness of the yttrium layer is less than lonm, the above effect will be insufficient, and the upper limit is not particularly limited, but it is better to be as thin as possible in order to suppress the oxygen band concentration of the yttrium powder.

[Example 1 Example 1 100 parts by weight of ARN powder with an average particle size of 1 μm was mixed with yttrium powder with an average particle size of 0.3 μm produced by the in-gas evaporation method as a sintering aid for mixing shown in Table 1. The mixture was charged into a ball mill together with trichlorethylene, thoroughly mixed and crushed, and then polyvinyl butyral resin was added as a binder to prepare a slurry. Using this slurry, a green sheet was created using the doctor blade method, and the size was 65 x 65 mm.
The corners were punched to obtain a green molded body. The atmosphere so far was N2.

The green molded body was degreased in N2 at 700°C for 3 hours, and then fired at 1800°C for 3 hours under normal pressure in N2 atmosphere to obtain a sintered plate.

Regarding the obtained sintered plate, appearance, relative density, thermal conductivity,
Characteristics generally required for insulating substrates, such as insulation resistance and surface roughness, were measured. The results are shown in Table 1.

Among the characteristics, the relative density was determined by calculating the density of the sintered body using the Archimedes method, divided by the true density, and expressed as a percentage. Thermal conductivity was measured using a laser flash method, insulation resistance was measured using an insulation meter, and surface roughness (Ra) was measured using a stylus type surface roughness meter.

Example 2 The yttrium powder used in Example 1 was treated with dry oxygen.
Heated in argon mixed gas.

The surface was covered with a layer of yttrium oxide with a thickness of about 50 nm. This yttrium powder was mixed as a sintering aid in the specified amount shown in Table 2, and the average particle size was 1 tLm, and the process was carried out in the atmosphere until a green molded body was obtained.
A sintered plate was created using the same method as in Example 1, and its appearance,
Relative density, thermal conductivity, insulation resistance, and surface roughness were measured, and the results are shown in Table 2.

Comparative Example A sintered plate was prepared in the same manner as in Example 1, except that yttrium oxide powder with an average particle size of 0.8 μm was used as a sintering aid, and its appearance, relative density, thermal conductivity, and insulation were evaluated. The resistance and surface roughness were measured and the results are shown in Table 3.

[Effects of the invention j] By using yttrium in addition to yttrium oxide as a sintering aid, the thermal conductivity of the sintered body can be significantly improved without impairing other properties, and By covering the yttrium powder with a yttrium oxide layer, the handling properties of the yttrium powder could be improved without impairing the properties of the sintered body.

Distributor: Kawasaki Steel Co., Ltd.

Claims (1)

[Claims] 1. 100 parts by weight of aluminum nitride powder as the main component, and 0.05 to 0.05 parts by weight of yttrium powder as a sintering aid.
A method for producing an aluminum nitride sintered body, which comprises mixing 5 parts by weight of the mixture, molding the mixture, and then firing the molded body at 1400 to 2000°C in a non-oxidizing atmosphere. 2. The method for producing an aluminum nitride sintered body according to claim 1, wherein the yttrium powder is a yttrium powder whose surface is covered with a yttrium oxide layer having a thickness of 10 nm or more.