JPH01215760A - Production of aluminum nitride sintered form - Google Patents

Abstract

PURPOSE:To obtain the title sintered form improved in density, thermal conductivity, and thermal, electrical and mechanical properties, by forming a mixed powder comprising AlN powder and a specific additive followed by calcination in a non-oxidative atmosphere. CONSTITUTION:Firstly, a mixed powder is prepared by mixing (A) AlN powder with a purity of >=98% and average particle size of <=10mum and (B) as the additive, a blend of (i) 0.05-17wt.% of Y2O3 and (ii) 0.05-13wt.% of an alkaline earth metal fluoride (e.g., CaF2). Thence, this mixed powder is formed and calcined in a non-oxidative atmosphere at 1,500-2,000 deg.C, thus obtaining the objective AlN sintered form with a thermal conductivity of >=140W/mk (at room temperature).

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to a method for manufacturing an aluminum nitride sintered body.

[Conventional technology]

In recent years, due to rapid technological innovation in the semiconductor industry, IC.

Large-scale integrated circuits such as L'S■ are highly integrated.

As power output has been increased, the amount of heat generated per unit area of silicon devices has increased significantly. Therefore, a problem has begun to occur that prevents the normal operation of the silicon element due to the heat generated by the energizing operation of the silicon element. Accordingly, insulating substrate materials with good thermal conductivity are required.

Conventionally, alumina sintered bodies have been most commonly used as insulating substrate materials. However, recently, alumina substrates cannot be said to be satisfactory in terms of heat dissipation, and there has been a growing demand for the development of insulating substrate materials with even better heat dissipation (thermal conductivity). Such an insulating substrate material has good thermal conductivity (high thermal conductivity) and electrical insulation of 62. It is required to have properties such as a coefficient of thermal expansion close to that of a silicon single crystal and high mechanical strength.

By the way, aluminum nitride, which is known to have good thermal conductivity, has a coefficient of thermal expansion of about 4.3X 10-'
/℃ (average value from room temperature to 400℃), which is smaller than that of alumina sintered body, which is approximately 7X10"/℃, and is close to that of silicon elements, which has a thermal expansion coefficient of 3.5 to 4.OX 10"/℃. .

It also has a mechanical strength of about 50 Kq/mm' in terms of bending strength, which is higher than that of alumina sintered body, which is 20-30 Kg/mm', and is a material with excellent electrical insulation properties.

Conventionally, aluminum nitride (1!N) sintered bodies are obtained by molding and sintering aluminum nitride powder, but since aluminum nitride is a difficult-to-sinter substance, it is difficult to obtain a dense sintered body. is difficult.

Up to now, attempts have been made to obtain a dense aluminum nitride sintered body by adding a sintering aid and using pressureless sintering or hot pressing. P of the Proceedings of the 1981 Ceramics Association
A method for producing an aluminum nitride sintered body is shown in which 2O3 is added with IJium oxide (Y20□) as a sintering aid. According to this method, the thermal conductivity is 100W/m
An aluminum nitride sintered body of k (room temperature) was obtained.

[Problem to be solved by the invention]

However, with the recent development of integrated circuit technology, there is a demand for heat dissipation substrate materials having even higher thermal conductivity.

An object of the present invention is to provide a method for producing an aluminum nitride sintered body having high thermal conductivity and other useful properties.

[Means to solve the problem]

The method for producing an aluminum nitride sintered body of the present invention involves molding a mixed powder containing aluminum nitride powder and at least one kind of fluoride of yttrium oxide and an alkaline earth metal as additives, and then converting the powder into a non-oxidizing interfacial fluoride. Strontium and barium fluoride are preferred.

The amount of yttrium oxide added is 0.05 to 17.

The total amount of alkaline earth metal fluoride added is 0.05
~13% by weight is preferred.

First, aluminum nitride has a high purity, preferably 98% or higher, but 95-98%
It is also possible to use a medium-sized one. The average particle size is preferably 10 μm or less, preferably 2 μm or less.

It is necessary to add both yttrium hydroxide and at least one alkaline earth metal fluoride as additives. That is, by using a suitable amount of yttrium oxide and an alkaline earth metal fluoride in combination, the thermal conductivity can be significantly increased. Examples of alkaline earth metal fluorides include calcium fluoride and strontium heptadide.

Barium fluoride is preferred. 0% yttrium oxide
．． By setting the total amount of fluoride of 05 to 17 F# and alkaline earth metal to 0.05 to 13% by weight, the thermal conductivity becomes 140 W/mk (room temperature) or more, which makes it superior to conventional aluminum nitride sintered bodies. A larger value is obtained.

When the amount of yttrium oxide added is less than 0.05% by weight, the thermal conductivity is less than 140 (w/mk), which is less effective;
If the weight is higher than i%, there will be many different phases, so the thermal conductivity will be 140 (
W/mk) or less. When the total amount of alkaline earth fluorides is less than 0.05 weight, the thermal conductivity is t4o (W
/mk) or less, the effect is small, and if it is 13 fold tts or more, there are many different phases, so the thermal conductivity becomes small at 140 (W/mk).

For the above reasons, the amount of IJium added (IJ oxide) is 0,
The total amount of alkaline earth fluorides is preferably 0.05% to 13% by weight.

Next, sintering requires high temperature sintering in a non-oxidizing atmosphere. If sintered in an oxidizing atmosphere, aluminum nitride will be oxidized and a dense sintered body will not be obtained. Nitrogen gas is used as a non-oxidizing atmosphere.

Helium gas, argon gas, -carbon oxide gas.

Vacuum atmosphere can be used, especially nitrogen gas.

Argon gas, helium gas, and vacuum atmosphere are convenient and preferred. Sintering is carried out at 1500-2000 °C, especially at 16
00 to 2000°C is effective, but is not particularly limited to this temperature range. Further, the sintering may be performed by a pressureless sintering method or a pressure sintering method. As the pressure sintering method, either the hot press method (-axis processing sintering method) or the HIP method (hot isostatic pressing sintering method) is possible.

〔Example〕

Example 1 Y2O in aluminum nitride powder with an average particle size of 2 μm.

and CaF2 were added, and then this mixed powder was made into a compact by applying a pressure of 2 tons/Cm at room temperature.
An aluminum nitride sintered body was produced by sintering at normal pressure for 0 hours. The thermal conductivity of this aluminum nitride sintered body at room temperature is shown in FIG. According to the present invention, the thermal conductivity at room temperature is 140
An aluminum nitride sintered body with high thermal conductivity of W/mk or more was obtained. The coefficient of thermal expansion is approximately 4. :(xlo-'/°C, bending strength was approximately 2.6 tons 2♂ or more.

Example 2 YzOx and CaF2. SrF2. One or two types of BaF2 were added, and then a pressure of 2 tons/- was applied to this mixed powder at room temperature to form a compact. Table 1 shows the relative density and thermal conductivity at room temperature of the aluminum nitride sintered body, which was sintered in a sintering furnace at 2000°C under nitrogen gas atmosphere for 10 hours under normal pressure. According to the present invention, the thermal conductivity at room temperature is 1
An aluminum nitride sintered body with high thermal conductivity of 40 W/mk or more was obtained. The coefficient of thermal expansion is approximately 4.3 x 10 = /'C,
The bending strength was approximately 2.6 tons/d.

Table 1 [Effects of the Invention] The aluminum nitride sintered body produced by the production method of the present invention has high density, excellent thermal conductivity, and thermal properties. Temperature properties 1 Since the mechanical properties are also good, crucibles are used in addition to being used as heat dissipation materials in the semiconductor industry.

It has many industrial advantages, such as being able to be used as a high-temperature material for vapor deposition containers, heat-resistant jigs, high-temperature members, and the like.

[Brief explanation of the drawing]

FIG. 1 is a characteristic diagram showing the relationship between thermal conductivity at room temperature and composition of an aluminum nitride sintered body produced according to the present invention. Agent: Patent Attorney Shindai Uchihara fTI! J Mu f2 (Higashie)

Claims (1)

[Claims] Production of an aluminum nitride sintered body, which is characterized in that a mixed powder is formed by blending aluminum nitride powder with yttrium oxide and at least one kind of alkaline earth metal fluoride as an additive, and then fired in a non-oxidizing atmosphere. Method.