JPH02199008A - Production of aluminum nitride powder and sintered aluminum nitride compact - Google Patents

Abstract

PURPOSE:To rapidly obtain high-purity and fine particulate readily sinterable AlN powder at a low cost by sintering a mixture of an Al-containing compound with beta-alanine in a nonoxidizing atmosphere containing N2. CONSTITUTION:An Al-containing compound, such as Al(NO3)3 or AlCl3, is homogeneously mixed with beta-alanine in a state of an aqueous solution and dried to remove moisture and afford a mixture. The drying temperature in this case is, e.g. within the range of 70-200 deg.C, more preferably about 100-200 deg.C. The above- mentioned mixture is then calcined at >=900 deg.C, preferably about 1200-1800 deg.C in a nonoxidizing atmosphere, such as Ar, containing N2, to afford the objective AlN powder. The afore-mentioned AlN powder in a state of an added sintering assistant, such as Y2O3, is then sintered at >=1200 deg.C, preferably about 1400-2000 deg.C in the same nonoxidizing atmosphere as that described above to afford a sintered AlN compact.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for producing aluminum nitride powder for producing, for example, a highly thermally conductive (insulating) substrate; ) A method for producing an aluminum nitride sintered body suitable for use as a substrate.

[Conventional technology and problems]

BACKGROUND OF THE INVENTION As semiconductor devices such as ICs have become more highly integrated and have more power, electrical insulating materials with good heat dissipation properties have become required. In response to this demand, various highly thermally conductive substrates have been proposed. Among them, aluminum nitride ceramic substrates in particular are being put into practical use because they are excellent in terms of thermal conductivity, thermal expansion, electrical insulation, and the like.

This aluminum nitride ceramic substrate is a sintered body obtained using aluminum powder. The aluminum nitride powder used here is manufactured by direct nitriding of aluminum, carbon reduction of alumina, etc.
In the direct nitriding method of aluminum, it is difficult to obtain powder with high purity and small particle size, and in the carbon reduction method of alumina, there are problems such as the reaction requires high temperature and the cost of raw materials is high. As an improvement to the carbon reduction method of alumina,
A method of reducing an aluminum source with a carbon-containing compound has been proposed, but it cannot be said to be sufficient in terms of reduction efficiency.

[Problem to be solved by the invention]

In view of these circumstances, the first objective of the present invention is to provide a method that can inexpensively obtain highly pure, fine-grained, easily sinterable aluminum nitride powder. A second object of the present invention is to provide a method for obtaining an aluminum nitride sintered body simply and inexpensively.

[Means to solve the problem]

In order to solve the first problem, in the method for producing aluminum nitride powder according to claim 1, a mixture of an aluminum-containing compound and β-alanine is fired in a non-oxidizing atmosphere containing nitrogen.

In order to solve the second problem, in the method for producing an aluminum nitride sintered body according to claim 2, a molded body of a predetermined shape made of a mixture of an aluminum-containing compound and β-alanine is heated in a non-oxidizing atmosphere containing nitrogen. I try to bake it underneath.

As for the mixture of an aluminum-containing compound and β-alanine used in both production methods of the present invention, for example, as in the invention according to claim 3, the aluminum-containing compound is a water-soluble compound, and this and β-alanine are mixed in an aqueous solution. Examples include those obtained by uniformly mixing with water and then removing water.

The aluminum-containing compound used in the production method of the present invention includes at least one of an aluminum polynuclear complex and an aluminum alkoxide.

In the method for producing an aluminum nitride sintered body according to the present invention, for example, as in the fifth aspect of the invention, the molded body may contain a sintering aid and then be fired.

This will be explained in more detail below.

The aluminum-containing compound is a source of aluminum, which is the main component of aluminum nitride. Therefore, as long as it is a compound containing aluminum, it is not particularly limited, and examples thereof include aluminum nitrate, aluminum chloride, aluminum sulfate, aluminum hydroxide, aluminum lactate, alumina, aluminum polynuclear complex, aluminum alkoxide, and the like.

Examples of the aluminum polynuclear complex include basic aluminum chloride, basic aluminum lactate, and basic aluminum nitrate.

As the aluminum alkoxide, aliphatic alkoxides having 10 or less carbon atoms such as aluminum methoxide, aluminum ethoxide, aluminum propoxide, and aluminum butoxide can be suitably used. Used alone or in combination.

β-alanine functions to remove the oxygen element contained in the aluminum-containing compound in the form of co, co, in the aluminum nitride production reaction in the firing process.

The aluminum-containing compound is a water-soluble compound, and after uniformly mixing it with β-alanine in an aqueous solution state, it is dried to remove water (thereby obtaining a mixture, the drying temperature is, for example, 70 to 200 ° C. , even 100-20
A range of about 0°C is appropriate.

In the case of powder production, the mixture obtained by drying is in a powder state or in a bulk state. If it is in a bulk state, it is fired as it is or after it is pulverized. When the aluminum nitride powder is fired in the bulk state, the aluminum nitride powder is usually in such a clump-like state that it easily crumbles at the stage of firing.

Also in the case of producing a sintered body, the mixture obtained by drying is in a powder state or a bulk state. In the production of sintered bodies, the mixture is formed into a molded body of a predetermined shape, but if the mixture obtained by drying is in bulk form, it is preferable to first crush and powder it before molding. , it may also be molded in bulk form.

The molding method may be, for example, a pressure molding method using a mold, but is not particularly determined as long as it does not cause undesirable deterioration of components or flow holes.

Examples of the sintering aid contained in the compact include salts and oxides of alkaline earth or rare earth elements. Specific examples include indium nitrate, indium chloride, basic yttrium acetate, yttrium oxide, calcium nitrate, calcium chloride, calcium oxide, etc., but are not limited thereto. The content of the sintering aid is preferably about 3 to 10% by weight based on the aluminum.The timing of adding the sintering aid is at the stage of the aqueous solution when the aluminum-containing compound and β-alanine are mixed, or It may be in any stage such as a powder stage after drying an aqueous solution, and is not particularly limited.

Furthermore, in the method for producing aluminum nitride powder, calcium salts, yttrium salts, or salts of lanthanide group elements, etc., are also added to the mixture in order to promote nitriding and facilitate carbon removal. You may also do so.

As the non-oxidizing atmosphere, an atmosphere of argon containing nitrogen, carbon monoxide containing nitrogen, nitrogen, ammonia, or the like is used. In the method for producing aluminum nitride powder, the firing temperature is 900°C or higher, preferably 12°C.
00-1800°C, and in the method for producing an aluminum nitride sintered body, 1200°C or higher, preferably,
The temperature is about 1400 to 2000°C. In addition, when removing residual carbon in the powder or sintered body, for example, after nitriding,
Further heat treatment is performed in an oxidizing atmosphere at about 700°C.

[For production]

As in the method for producing aluminum nitride powder according to the present invention, when an aluminum-containing compound, such as an aluminum polynuclear complex or a mixture of aluminum alkoxide and β-alanine, is fired in a non-oxidizing atmosphere containing nitrogen,
Even if the firing temperature is not high, aluminum nitride powder with high purity (nitridation rate) and sufficiently small particle size can be obtained at low cost. Powder with a small particle size is easily sintered when producing a highly thermally conductive insulating substrate.

In the method for producing an aluminum nitride sintered body according to the present invention, a molded body of a predetermined shape made of an aluminum-containing compound, such as an aluminum polynuclear complex or a mixture of aluminum alkoxide and β-alanine, is heated in a non-oxidizing atmosphere containing nitrogen. By firing the aluminum nitride sintered body, an aluminum nitride sintered body with high purity (nitridation rate), denseness, and good thermal conductivity can be easily obtained without going through a complicated powder process.

Since β-alanine is a nitrogen-containing compound, the mixture also has a nitrogen source, so a local reducing atmosphere is formed to promote the nitriding reaction from within the mixture, and aluminum nitride is rapidly formed.

The aluminum-containing compound is a water-soluble compound, and after uniformly mixing it with β-alanine in an aqueous solution state, the mixture obtained by removing water is a mixture of the aluminum-containing compound and β-alanine on a molecular order. As a result, a more pure and homogeneous powder or sintered body can be obtained.

〔Example〕

Hereinafter, specific examples will be described.

First, an example of a method for producing aluminum nitride powder will be described.

Example 1 - An aqueous solution was prepared by mixing 0.89 parts by weight of β-alanine with 1 part by weight of basic aluminum chloride. In addition, basic aluminum chloride has an aluminum content of 50% by weight in terms of Alyes, and a basicity of 84.
% was used.

Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid was pulverized and calcined in a nitrogen atmosphere (non-oxidizing atmosphere) at 1550°C for 8 hours, and then heated at 700°C.
A heat treatment was performed for 1 hour in an air atmosphere (oxidizing atmosphere) at a temperature of .degree. C. to obtain aluminum nitride powder.

Example 2 - An aqueous solution was prepared by mixing 0.65 parts by weight of β-alanine with 1 part by weight of basic aluminum lactate. The basic aluminum lactate used had an aluminum content of 37% by weight in terms of Al*Os and a lactic acid content of 56%.

Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid material was pulverized and calcined in a nitrogen atmosphere at 1550°C for 8 hours, and then heat-treated at a temperature of 700°C in an air atmosphere for 1 hour to obtain aluminum nitride powder.

Example 3 - 1 part by weight of aluminum triisopropoxide (aluminum triisoprofoquinide), 0.44 β-alanine
Parts of ffi were added to 2.97 parts by weight of a 15% aqueous solution of tetramethylammonium hydroxide, and after stirring at room temperature for 1 hour, the solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid was pulverized and calcined in a nitrogen atmosphere at 1550°C for 8 hours, and then at a temperature of 700°C.
Heat treatment was performed for 1 hour in an air atmosphere to obtain aluminum nitride powder.

Example 4 1 part by weight of alumina powder with a purity of 99.9% and an average particle size of 0.4μ was added to an aqueous solution in which 1.75 parts by weight of β-alanine was dissolved, and after stirring at room temperature for 10 minutes, This solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid material was pulverized and calcined in a nitrogen atmosphere at 1600°C for 8 hours, and then heat-treated at 700°C in an air atmosphere for 1 hour to obtain aluminum nitride powder.

Comparative Example 1 An aqueous solution was prepared by mixing 1 part by weight of basic aluminum chloride used in Example 1 with 0.70 part by weight of hexamethylenetetramine.

Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid material was pulverized and calcined in a nitrogen atmosphere at 1600°C for 8 hours, and then heat-treated at 700°C in an air atmosphere for 1 hour to obtain aluminum nitride powder.

- Comparative Example 2 - Carbon black (Mitsubishi Kasei ■ 940
10B) 0.50 parts by weight was suspended and stirred at room temperature for 30 minutes. Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid was pulverized and
It was fired in a nitrogen atmosphere at 0° C. for 8 hours, and then heat-treated at a temperature of 700° C. in an air atmosphere for 1 hour to obtain aluminum nitride powder.

Examples 1 to 6 and Comparative Example 1.
The nitridation rate (purity) and average particle size of the aluminum nitride powder of No. 2 were measured. The results are shown in Table 1.

Table 1 The aluminum nitride powders of Examples 1 to 4 have high purity as shown in Table 1. The aluminum nitride powder of Comparative Example 1.2 has very poor purity. Even if the firing temperature is not very high, the powders of the examples have a very high nitridation rate. Of course, as shown in Table 1, the powders of the examples are fine particles with small particle sizes, and it goes without saying that they have excellent sinterability.

In addition, when the powders of Examples 1 to 4 and Comparative Example 1.2 were analyzed by X-ray, it was found that the powders of Examples had no unnitrided residual Al.
Almost no peak indicating the presence of t Os was detected, but on the other hand, in each powder of the comparative example, unnitrided residual Al s
A peak indicating the presence of Os was clearly detected, confirming that the purity of the powder of the comparative example was insufficient.

Next, an example of the method for manufacturing an aluminum nitride sintered body according to the present invention will be described.

Example A - An aqueous solution was prepared by mixing 0.79 parts by weight of β-alanine with 1 part by weight of basic aluminum chloride. The basic aluminum chloride used had an aluminum content of 50% by weight in terms of Al*O* and a basicity of 84%.

Next, this aqueous solution was evaporated to dryness at a drying temperature of 70°C. The obtained solid material was first pulverized, and then made into a disk-shaped body with a diameter of 25 mm and a thickness of 3 mm using a mold, and then baked in a nitrogen atmosphere at 1900 ° C. for 8 hours. An aluminum nitride sintered body was obtained.

Example B - An aqueous solution containing 0.79 parts by weight of β-alanine and 0.068 parts by weight of yttrium nitrate hexahydrate based on the basic aluminum chloride content used in Example A. was created. Next, this aqueous solution was evaporated to dryness at a drying temperature of 80°C. The obtained solid material was first pulverized, then formed into a disc-shaped molded product with a diameter of 25 tm and a thickness of 3 fins using a molding die, and then fired in a nitrogen atmosphere at 1850°C for 4 hours to nitride it. An aluminum sintered body was obtained.

Example C - 0.58 parts by weight of β-alanine and 0.0 parts by weight of yttrium nitrate hexahydrate per 1 part by weight of basic aluminum lactate
An aqueous solution was prepared by mixing 5 parts by weight. In addition, basic aluminum lactate has an aluminum content of A
The lactic acid content was 37% by weight in terms of ltos, and the lactic acid content was 56%. Next, this aqueous solution was evaporated to dryness at a drying temperature of 80°C. The obtained solid material was first pulverized, and then made into a disk-shaped body with a diameter of 25 mm and a thickness of 3 mm using a molding die, and then fired in a nitrogen atmosphere at 1850 ° C. for 4 hours. An aluminum nitride sintered body was obtained.

Example D - 1 part by weight of aluminum triisopropoxide, 0.40 β-alanine
0.033 ft parts by weight of yttrium nitrate hexahydrate, 15 parts by weight of tetramethylammonium hydroxide
% aqueous solution and stirred for 1 hour at room temperature, the solution was evaporated to dryness at a drying temperature of 80°C.

After pulverizing the obtained solid, a molded body was obtained in the same manner as in Example A, and then fired at a temperature of 1850° C. in a nitrogen atmosphere for 4 hours to obtain an aluminum nitride sintered body.

Example E - 0.21 parts by weight of β-alanine and 0.21 parts by weight of yttrium nitrate hexahydrate per 1 part by weight of aluminum nitrate nonahydrate.
An aqueous solution was prepared by mixing the mixture to a volume of 0.019 parts.

Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. The obtained solid was pulverized and a molded body was obtained in the same manner as in Example A, and then fired at a temperature of 1850° C. in a nitrogen atmosphere for 4 hours to obtain an aluminum nitride sintered body.

- Comparative Example A - An aqueous solution was prepared by mixing 1 part by weight of basic aluminum chloride with 0.47 parts by weight of hexamethylenetetramine. The basic aluminum chloride used had an aluminum content of 9 of 50% by weight in terms of A1.08 and a basicity of 84%. Next, this aqueous solution was evaporated to dryness at a drying temperature of 120°C. After crushing the obtained solid, it was molded into a mold with a diameter of 25 mm.
Tsuru, made into a disk-shaped molded product with a thickness of 3 cranes, then heated to 1000℃
The aluminum nitride sintered body was obtained by firing in a nitrogen atmosphere for 8 hours.

The density and thermal conductivity of the aluminum nitride sintered bodies of Examples A to E and Comparative Example A thus obtained were measured.

The measurement results are shown in Table 2.

As shown in Table 2, the aluminum nitride sintered bodies of Examples A to E are dense sintered bodies with higher densities than those of Comparative Example A. It is conductivity. When the sintered bodies of Examples A-H were subjected to X-ray analysis, almost no peak indicating the presence of unnitrided residual AI, 0, was detected, but when the sintered bodies of Comparative Example A were analyzed by X-rays. , a peak indicating the presence of unnitrided residual A 1 *O* was clearly detected.

(Effects of the Invention) As described above, in the method for producing aluminium nitride powder according to the present invention, powder with high purity and small particle size can be obtained quickly and inexpensively even though the firing temperature is low. , an excellent high thermal conductivity (insulating) substrate can be obtained easily and inexpensively.

Further, in the method for producing an aluminum nitride sintered body according to the present invention, a dense and highly thermally conductive sintered body can be directly produced without going through the state of aluminum nitride powder. Therefore, an excellent high thermal conductivity (insulating) substrate can be obtained easily and inexpensively.

In both of these production methods, when the mixture is obtained by uniformly mixing an aluminum-containing compound and β-alanine in an aqueous solution state and then removing water, the aluminum-containing compound and β-alanine are sufficiently mixed. This allows the powder and sintered body to be mixed with each other, making it possible to obtain more pure and homogeneous powders and sintered bodies.

Agent: Patent Attorney Takehiko Matsumoto October 6, 1999

Claims (1)

[Claims] 1. A method for producing aluminum nitride powder, which comprises firing a mixture of an aluminum-containing compound and β-alanine in a non-oxidizing atmosphere containing nitrogen. 2. A method for producing an aluminum nitride sintered body, in which a molded body of a predetermined shape made of a mixture of an aluminum-containing compound and β-alanine is fired in a non-oxidizing atmosphere containing nitrogen. 3. The aluminum-containing compound is a water-soluble compound, and after uniformly mixing this and β-alanine in an aqueous solution state,
The method for producing aluminum nitride powder or aluminum nitride sintered body according to claim 1 or 2, wherein the mixture is obtained by removing moisture. 4. The method for producing aluminum nitride powder or aluminum nitride sintered body according to any one of claims 1 to 3, wherein the aluminum-containing compound is at least one of an aluminum polynuclear complex and an aluminum alkoxide. 5. The method for producing an aluminum nitride sintered body according to any one of claims 2 to 4, wherein the molded body contains a sintering aid.