JPH0587468B2 - - Google Patents

Description

[Detailed description of the invention]

[Industrial Application Field] The present invention relates to a method for producing a highly thermally conductive aluminum nitride sintered body. [Conventional technology] The rapid development of technology in the field of electronics has not only led to the miniaturization of semiconductor devices, but also
It has become possible to achieve higher output and higher integration at the same time. Additionally, research is also being conducted on methods for high-density packaging of semiconductor devices on a single substrate. Examples include power diodes, power transistors, semiconductor lasers, LSIs, and even VLSIs. 2. Description of the Related Art Semiconductor devices that have higher output, higher integration, or higher density packaging have a problem in that the amount of heat generated per unit area or unit volume increases. Currently, the heat generated by semiconductor devices is dissipated by using materials with good thermal conductivity such as diamond, cubic boron nitride, beryllium oxide, and insulating silicon carbide as part of the heat sink or package material. ing. However, the above-mentioned materials with good thermal conductivity are not necessarily sufficient from the viewpoint of safety, cost required for manufacturing, absolute value of production, etc. For the practical application of semiconductor devices that generate a large amount of heat, there is a need for high thermal conductivity materials that are low cost and can be supplied in large quantities. [Problems to be Solved by the Invention] Therefore, the present inventors focused on aluminum nitride as a highly thermally conductive material that is low cost and available in large quantities. Aluminum nitride as a material was thought to have a thermal conductivity nearly eight times that of saphire due to its crystal structure, but the measured value was 50W/mk.
It was only moderate. The thermal conductivity of the aluminum nitride sintered body is about 1/6 of the theoretical value (320W/mk). This is thought to be caused by the effects of grain boundaries, impurities, or lattice defects. In particular, the presence of oxygen in aluminum nitride crystal grains has a large effect on the decrease in thermal conductivity. One method to solve this problem is to add various compounds such as oxides and fluorides of group A elements, perform sintering, and trap oxygen mainly present on the powder surface with additives (especially 1978
-Refer to Publication No. 55377). However, this method is still insufficient, and the thermal conductivity is
Currently, only sintered bodies of about 100W/mk have been obtained. The object of the present invention is to obtain an aluminum nitride sintered body having a thermal conductivity exceeding 100 W/mk. [Means for Solving the Problems] The present invention was made as a result of studies to produce aluminum nitride with higher conductivity at a lower cost.
Aluminum nitride powder with an oxygen content of 1.0% by weight or less, a metal impurity content of 0.2% by weight or less, and a powder specific surface area of 1m ² /g or more, and an alkoxide compound of an element in Group A of the Periodic Table in terms of oxide. This is a method for producing an aluminum nitride sintered body having a thermal conductivity of 100 W/mk or more, which is characterized by adding and mixing 0.01 to 20% by weight of aluminum nitride, followed by sintering in a non-oxidizing atmosphere at 1500 to 2200°C. Here, group a elements are Be, Mg, Ca, Sr, Ba,
At least one of Ra. The aluminum nitride powder used in the present invention is preferably fine particles with as high purity as possible, with a specific surface area of 1 m ² /g, metal impurities of 0.2% by weight or less,
Use one with an oxygen content of 1.0% by weight or less. High-purity AIN powder heat-treated under nitrogen gas at 1600°C or higher is particularly desirable. The group a alkoxide compound as an additive is
It is expressed as M (OR) _o , where M is a group a element,
R is an alkyl group. The alkoxide compound is dissolved in alcohol or used in powder form. The amount of alkoxide added is converted to group a oxide,
0.01-20% by weight. This is because if it is less than 0.01 weight percent, it is difficult to obtain a dense sintered body, and if it exceeds 20 weight percent, the thermal conductivity of AIN is significantly reduced. The difference between the case of adding known oxides, fluorides, etc. of Group A elements and the case of adding them as alkoxide compounds is that, although the reason is not clear, the alkoxide compound disperses uniformly and helps sintering with a small amount. Acts as an agent and further AIN
It is also thought that the carbon in the alkoxide acts on deoxidation. The obtained mixture is molded by conventional methods such as dry pressing, doctor blade, extrusion, etc.
Sintered and densified at 1500-2200℃ in a non-oxidizing atmosphere. [Example] Example 1 High-purity aluminum nitride powder with an oxygen content of 1.0 weight percent (specific surface area 4 m ² /g, metal impurities 0.19 weight percent) was added with Ca ethoxide of 30 weight percent or less in terms of oxide in Table 1 The mixture was added in the proportions shown in ethanol, mixed in a ball mill for 10 hours, hydrolyzed, dried,
Sintered in a nitrogen stream at ℃. Table 1 shows the relative density and thermal conductivity of the obtained sintered body. In addition, No. 8 in Table 1
~10 are comparative examples.

【table】

[Table] Example 2 High purity aluminum nitride powder with an oxygen content of 0.5% by weight (specific surface area 2 m ² /g, metal impurities
A sintered body similar to that in Example 1 was obtained by adding 2 weight percent (calculated as oxide) of Mg, Ba, and Sr ethoxides to 0.10 weight percent (0.10 weight percent). All sintered bodies achieved relative density of 98% or higher and thermal conductivity of 150W/mk or higher. Example 3 High purity aluminum nitride powder with an oxygen content of 0.5% by weight (specific surface area 2 m ² /g, metal impurities
A sintered body was obtained under the same conditions as in Example 1 by adding Ca methoxide and Ca butoxide corresponding to 2 weight percent of CaO in terms of oxide. All sintered bodies have a relative density of 97
% or more, and the thermal conductivity was 150W/mk or more. [Effects of the Invention] As explained above, the present invention produces highly thermally conductive aluminum nitride sintered material by adding an alkoxide compound of group A of the periodic table to high-purity aluminum nitride powder and sintering it. You get a body. This aluminum nitride sintered body is used for IC substrates, heat sinks,
It has excellent performance as a structural material and is highly practical.

Claims (1)

[Claims] 1 Oxygen content is 1.0% by weight or less and metal impurity content is 0.2% by weight or less,
After adding and mixing aluminum nitride powder with a powder specific surface area of 1 m ² /g or more and an alkoxide compound of an element of group A of the periodic table in an amount of 0.01 to 20 percent by weight in terms of oxide, the mixture was heated in a non-oxidizing atmosphere at 1500 to 2200°C. Thermal conductivity is 100w/characterized by sintering.
A method for producing an aluminum nitride sintered body having a size of m.k or more.