JPH0226813A - Purification of aluminum nitride powder - Google Patents

Abstract

PURPOSE:To obtain aluminum nitride powder low oxygen content by placing aluminum nitride powder in a vessel made of carbon and by heat-treating at a high temp. in an inert gas contg. nitrogen. CONSTITUTION:The aluminum nitride powder is placed in the vessel made of carbon and heat-treated at 1200-1800 deg.C in nitrogen or the inert gas contg. nitrogen. As raw aluminum nitride powder, one having about 0.05-1mum mean particle size obtd. by the observation with a scanning electron microscope and about 0.7-3.0wt.% oxygen content, is pref. As the inert gas above-mentioned, helium, neon, argon, etc., are exemplified. The filling density of aluminum nitride powder in the vessel made of carbon is preferably about 0.05-0.8g/cc.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a novel method for purifying aluminum nitride powder.

(Prior art) Aluminum nitride powder (^ff1N) is theoretically 30
It has a high thermal conductivity of more than 0 W/m, comparable to beryllum oxide (Bed), and has excellent electrical properties such as insulation and dielectricity, making it a semiconductor that is becoming more powerful and highly integrated. It is attracting a lot of attention as an insulating heat dissipation substrate material.

Incidentally, although AfN theoretically has a high thermal conductivity, one of the major factors that influences the thermal conductivity of the obtained sintered body is electroceramics (Vol. 17 1).
As shown in January issue (1986) P, 33-P, 40), this is the amount of oxygen impurities in the AfN powder raw material.

Conventionally, attempts have been made to reduce the oxygen content in AZN powder by sufficiently carrying out the HelN production reaction, but the oxygen content in AffiN powder still varies depending on the synthesis method of Al2N powder. Although it varies, it was around 1% by weight or more.

As a method for treating Al2N powder to reduce the oxygen content, Japanese Patent Application Laid-open No. 71576/1983 describes a method in which a granular mixture of AIN and carbonaceous additives such as free carbon, carbon-containing organic substances, and mixtures thereof is heated with argon. , nitrogen, and mixtures thereof. According to this method, a granular mixture consisting of AfN powder and carbonaceous additive must be formed, and the carbonaceous additive must be added accurately, and if a large amount is added, the amount of residual carbon after heat treatment will be reduced. To increase.

(Problems to be solved by the present invention) The problems to be solved by the present invention are
The present invention provides a method for purifying IN powder to obtain IN powder.

(Means for Solving the Problem) As a result of intensive research into the above-mentioned problems, the present inventors found that Af
We have discovered a method for purifying fiN powder.

That is, in the present invention, AfN powder is stored in a carbon container and heated to 1200 to
This is an AfN powder purification method characterized by heat treatment at 1800°C.

More specifically, Ai! used in the present invention! Regarding the N powder, there are no particular limitations on the average particle size, oxygen content, and specific surface area, but it is suitable that the average particle size determined by scanning electron microscopy is 0.05 to lum. Furthermore, 0.1 to 0.8 μm, and even 0
．． A thickness of 2 to 0.6 μm is preferable. In addition, the average particle size determined by centrifugal sedimentation is preferably 0.5 to 3 μm, more preferably 0.5 to 1.5 μm, and even 0.6 to 1 μm.
．． Preferably, the thickness is 0 μm. For oxygen content, 0
．． 7 to 3.0% by weight, more preferably 0.8 to 2.0% by weight, and even more preferably 0.8 to 1.5% by weight.

The specific surface area is preferably 1 ryf/g or more, more preferably 2 rrf/g or more, and even more preferably 3 rrf/g or more.

The above AfN powder is placed in a carbon container and heat-treated. It is desirable that the carbon container used be as pure as possible, but if it is of low purity, it should be heat-treated in chlorine gas. It is preferable to use The shape of the carbon container is not particularly limited.

The AffN powder is placed in a carbon container and then heat-treated in an atmosphere of nitrogen or an inert gas containing nitrogen. In this case, the inert gas is helium,
Neon and argon. Heating temperature is 1200-180
0°C, preferably 1300 to 1600°C, more preferably 1350 to 1550°C.

At temperatures exceeding the claimed range, although a reduction in oxygen content is observed, sintering of the particles progresses and large agglomerates begin to form, which is not preferable. Further, at a temperature lower than the claimed range, the effect of reducing oxygen content is small, which is not preferable. The gas flow rate is not particularly limited as it varies depending on the amount of AfN powder to be heat treated or the structure of the furnace used for the heat treatment, but if possible, oxygen reduction will be easier if the flow rate is large.

In addition, regarding the state in which AfN powder is stored in a carbon container, if it is packed too densely, it may be difficult to reduce the oxygen content, so the packing density is 0.05 to 0.
．． 8 g/cc is desirable, and more preferably 0.10 to 0.6
0g/cc, or even 0.15-0.50g/cc
is desirable.

The oxygen content of the IN powder obtained by the present invention is reduced to about 1/6 from 273 of the oxygen content of untreated Aj2N powder, but it is usually easier to reduce the oxygen content to about 1/2 to 1/4. .

AI obtained by adding a suitable sintering aid to the Aj2N powder obtained by the treatment according to the present invention and sintering it! , N sintered bodies exhibit higher thermal conductivity compared to Aj2N sintered bodies obtained from untreated IRON powder.

〔Example〕

Next, an example of the present invention was carried out as follows.

The average particle size determined by the centrifugal sedimentation method of the ^2N powder described in the Examples was determined using Particle Size Distribution Micro Photosizer 5 manufactured by Seishin Enterprise Co., Ltd.
The particles were measured by centrifugal sedimentation using KA-5000 and isobutyl alcohol as a solvent, and the 50% by weight diameter was defined as the average particle diameter.

SEM (scanning electron microscope) observation was performed using a Hitachi S-650 scanning electron microscope.

The average particle diameter X determined by SEM observation is calculated from the following formula by measuring the particle diameters Xi of n particles visible within a unit field of view.

In the present invention, the average particle size was determined by measuring the particle size of about 300 particles.

The specific surface area of the AIN powder was determined by the BET method using nitrogen gas adsorption.

The oxygen content in AffiN powder is TC-1 manufactured by LECO.
The analysis was carried out using a Model 36 analyzer.

Analysis of metal impurities in AfN powder is conducted by Nippon Jarrell Co., Ltd.
Emission spectrometer ICAP-575Ma manufactured by Ash ■
I went with rkI [.

The thermal conductivity of the AIN sintered body was measured using a laser flash method thermal constant measuring device TC-3000 manufactured by Shinku Riko Co., Ltd.

Example 1 Average particle size determined by centrifugal sedimentation method is 1.5 μm, average particle size determined by 58M observation is 0.56 μm, and specific surface area is 3
．． 6 rrf/g, an oxygen content of 0.95% by weight, and an amount of metal impurities of 0.03% by weight.
00 mm carbon crucible. Place the carbon crucible in an electric furnace and set the nitrogen gas flow rate to 542/min.
The samples were treated under the conditions shown in Table 1. The results are shown in Table 1.

Example 2 Average particle size by centrifugal sedimentation method is 0.87 μs, 58M
An A2N powder with an average particle diameter of 0.28 μm, a specific surface area of 6.9 rd/g, an oxygen content of 1.21% by weight, and a metal impurity content of 0.08% by weight, determined by observation, was prepared with an inner diameter of 1
The carbon crucible was filled in a carbon crucible with a diameter of 0.00 m, and the carbon crucible was placed in an electric furnace and treated under the conditions shown in Table 1 with a nitrogen gas flow rate of 51/min. The results are shown in Table 1.

Example 3 Average particle size by centrifugal sedimentation method is 0.80 tIm, 58
Aj2N powder with an average particle size of 0.15 μm determined by M observation, an oxygen content of 2.30% by weight, and a metal impurity amount of 0.05% by weight was filled into a carbon crucible with an inner diameter of 100 mm, and the carbon crucible was into an electric furnace and add 1 liter of nitrogen gas.
027mln and processed under the conditions shown in Table 1. The results are shown in Table 1.

Comparative Example The AfN powder used in Example 1 was treated in the same manner as in Example 1 except for the treatment conditions shown in Table 1. The results are shown in Table 1.

(The following is a blank space) Table 1 (Effects of the Invention) As explained above, the method for refining aluminum nitride powder of the present invention is a method that can easily reduce the oxygen content of A1N powder. AlN powder whose oxygen content has been reduced by this method is similar to conventional AI! , compared to N powder, the amount of sintering aid added can be reduced, and the obtained sintered body exhibits high thermal conductivity.

Therefore, the present invention is effective as a method for purifying raw material powder for ^fN sintered bodies that will be used in a wide range of electronic materials including large-scale integrated circuit boards that will require very strong thermal properties.

Patent applicant: Asahi Kasei Industries, Ltd.

Claims (1)

[Claims] Aluminum nitride powder is stored in a carbon container and heated to 1200 to 180 in nitrogen or an inert gas containing nitrogen.
A method for refining aluminum nitride powder, characterized by heat treatment at 0°C