JPH01111705A - Production of aluminum nitride powder - Google Patents

Abstract

PURPOSE:To obtain the above particulate powder, by removing water from an aq. soln. contg. 3 kinds of specified compd. and thereafter, by calcining in a non-oxidative atmosphere contg. N2. CONSTITUTION:The aq. soln. contg. components (A), (B) and (C) is obtd. by adding powdered aluminum alkoxide of preferably C10 or lower fatty alcohol (e.g., aluminum isopropylate) (B) and urea (C) to an aq. soln. contg. tetraalkylammonium hydroxide preferably having C10 or lower alkyl group (e.g., tetramethylammonium hydroxide) (A). Then, the water is removed from the aq. soln. by evaporating, drying, etc., to obtain mixed particulate powder uniformly mixed with the components in the molecular order. Further, the particulate powder is calcined at >=600 deg.C, preferably 900-1,600 deg.C, in the non- oxidative atmosphere contg. N2 and thereafter, as occasion demands, treated by heating at 600-700 deg.C in an oxidative atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention relates to a method for producing aluminum nitride powder suitable for producing highly thermally conductive substrates.

[Background technology]

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 these, aluminum nitride ceramic substrates are being put into practical use because they are particularly excellent in terms of thermal conductivity, thermal expansion, electrical insulation, and the like.

However, this aluminum nitride ceramic substrate has the drawback of being expensive. The reason for this high price is
In particular, aluminum nitride powder, which is a raw material, is expensive and sintering requires high temperatures.

Conventionally, aluminum nitride powder has been produced by direct nitriding of aluminum or carbon reduction of alumina, but for example, it is difficult to obtain aluminum nitride powder with high purity and small particle size using the direct nitriding method of aluminum. However, in the carbon reduction method of alumina, there were problems such as the high temperature required for the reaction and the high cost of raw materials.

As an improvement to the carbon reduction method for alumina, a method has been proposed in which the aluminum source is mixed in a solution state. could not be improved.

Regarding the prior art, for example, Japanese Patent Publication No. 61-26
There are disclosures in JP-A No. 485 and JP-A-61-83606.

[Purpose of the invention]

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for producing aluminum nitride powder that can obtain fine-grained aluminum nitride powder with high purity.

[Disclosure of the invention]

This invention involves preparing an aqueous solution containing an aluminum alkoxide, a tetraalkylammonium hydroxide, and urea, mixing these in an aqueous state, and calcining the mixture prepared from this aqueous solution in a non-oxidizing atmosphere containing nitrogen. The method is characterized in that aluminum nitride powder is obtained.

The present invention will be explained in detail below according to the steps shown as a specific example.

■ Mix aluminum alkoxide, tetraalkylammonium hydroxide and urea as an aqueous solution. In this case, it is desirable to add aluminum alkoxide in powder form to an aqueous solution of tetraalkylammonium hydroxide to form an aqueous solution. Urea may be mixed in advance as an aqueous solution, or may be added in powder form to an aqueous solution containing tetraalkylammonium hydroxide. In short, there is no restriction on the order of dissolution. In the aqueous solution thus obtained, each component is homogeneously mixed on a molecular order.

Examples of aluminum alkoxides include aluminum methylate, aluminum ethylate, aluminum propylate, aluminum isopropylate, etc. with a carbon number of 1.
Although an aliphatic alcohol of 0 or less is desirable, this is not intended to be particularly limiting.

The tetraalkylammonium hydroxide is not particularly limited, but one having an alkyl group having 10 or less carbon atoms is preferred. For example, tetramethylammonium hydroxide, tetraethylammonium hydroxide, tetrapropylammonium hydroxide, etc. are used. Those having a lower alkyl group are more preferred.

(2) From the mixed aqueous solution, a mixed fine powder in which the components are homogeneously mixed on a molecular order is obtained by evaporation, drying, etc. A suitable drying temperature is 100 to 200°C.

(2) The mixture is fired in a non-oxidizing atmosphere containing nitrogen to obtain aluminum nitride powder. Since the mixture has a nitrogen source in the mixture, a reducing atmosphere is locally formed to promote the nitriding reaction from within the mixture, and aluminum nitride is rapidly formed.

As the non-oxidizing atmosphere, nitrogen or the like is used, more preferably ammonia or the like. Note that it is free to include an inert gas or the like in addition to the gas serving as the nitrogen source.

The firing temperature is suitably 600°C or higher, more preferably 900 to 1600°C.

Although carbon may remain even after the above firing,
This can be removed by heat treatment in an oxidizing atmosphere at 600 to 700° C. after forming aluminum nitride.

In the method of the present invention, it is mixed in a solution state and contains urea as a nitrogen source, so that the nitriding reaction of aluminum proceeds more smoothly during the calcination reaction. It is characterized by the ability to synthesize aluminum nitride powder with extremely high Therefore, when firing a substrate or the like, it is possible to obtain aluminum nitride that has an extremely small amount of residual carbon and is easy to sinter. Note that, according to this method, aluminum nitride or an aluminum nitride substrate can be obtained at low cost.

(Examples 1 to 5) As aluminum alkoxides, aluminum isopropylate and aluminum ethylate were used.

Tetramethylammonium hydroxide was used as the tetraalkylammonium hydroxide. First, a 15% by weight aqueous solution of tetramethylammonium hydroxide was prepared, and an amount equivalent to 15% by weight of aluminum isopropylate or aluminum ethylate was dissolved in this aqueous solution. In addition to this, the first
A mixed aqueous solution was prepared by dissolving the predetermined amount of urea listed in the table.

The resulting mixture was fired in nitrogen (N2) gas at a predetermined temperature for a predetermined time to synthesize aluminum nitride powder. The results are shown in Table 1.

[Hereafter, blank space] By mixing 3% by weight of Y2O3 as a sintering aid with the aluminum nitride powder obtained in Examples 1 to 5 above, and baking it in a nitrogen atmosphere at 1650 ° C. for 3 hours after molding, A sintered aluminum nitride ceramic having a density of 98% or more was obtained.

It goes without saying that the method for producing aluminum nitride powder according to the present invention is not limited to the above embodiments. In the examples, an example was shown in which a carbon-containing compound and a nitrogen-containing compound were used, but a water-soluble compound containing both carbon and nitrogen may be used instead.

Normally, when aluminum nitride is sintered, rare earth metal oxides such as yttrium oxide and alkaline earth metal oxides such as calcium oxide are added as sintering aids to improve sinterability. If yttrium chloride, calcium nitrate, etc. are simultaneously added to the mixed aqueous solution when preparing the aqueous solution, there is an advantage that aluminum nitride powder in which the sintering aid is uniformly dispersed can be obtained.

[Effects of the Invention] The present invention is characterized in that after preparing an aqueous solution containing aluminum alkoxide, tetraalkylammonium hydroxide, and urea, water is removed and the solution is calcined in a non-oxidizing atmosphere containing nitrogen. Therefore, highly pure and fine-grained aluminum nitride can be obtained.

Patent applicant Matsushita Electric Works Co., Ltd.

Claims (1)

[Claims] (1) A method for producing aluminum nitride powder, which comprises preparing an aqueous solution containing aluminum alkoxide, tetraalkylammonium hydroxide, and urea, removing water, and firing in a non-oxidizing atmosphere containing nitrogen. .