Compositions: ceramic – Ceramic compositions – Refractory
Patent
1996-09-18
1998-06-16
Bell, Mark L.
Compositions: ceramic
Ceramic compositions
Refractory
501 983, 264 65, C04B 35581, F27B 904, F27D 700
Patent
active
057670285
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an aluminum nitride sintered body for use as a semiconductor board (substrate) or the like and a method of manufacturing the same, and more particularly to an aluminum nitride sintered body and a method of manufacturing the same capable of significantly improving strength and fracture toughness and exhibiting excellent radiation characteristics while maintaining thermal conductivity peculiar to aluminum nitride.
BACKGROUND ART
A ceramic sintered body having a variety of excellent characteristics, such as strength, heat resistance, corrosion resistance, wear resistance and light weight and the like, as compared with the conventional metal materials has been widely used in a mechanical part, functional part, structural material and decorative material for forming a semiconductor board, electronic equipment material, engine part, material for a high-speed cutting tool, nozzle, bearing or the like that is used in severe temperature, stress and wear conditions under which conventional metal materials cannot be used satisfactorily.
Since an aluminum nitride (AlN) sintered body is an insulating body having excellent thermal conductivity and a thermal expansion coefficient near that of silicon (Si), it has been further widely used as a heat radiation plate or a substrate of a highly-integrated semiconductor apparatus.
The aluminum nitride sintered body has been usually mass-produced by the following manufacturing method. That is, a sintering agent, an organic binder and, if necessary, any of various additives, a solvent and a dispersant are added to a raw material powder of aluminum nitride. The obtained raw material powder mixture is, by a doctor blade method or a slip casting method, molded into a thin-plate shape or sheet-shape molded body or is press-molded into a thick-plate or a large-size molded body. Then, the thus obtained molded body is, in the air or nitrogen atmosphere, heated and dewaxed so that carbon hydride component and the like used as the organic binder is removed from the molded body and is dewaxed. The dewaxed molded body is, in nitrogen atmosphere or the like, heated to high temperature so as to be densified and sintered so that an aluminum nitride sintered body is formed.
In a case where very fine raw material powder having an average grain size of about 0.5 .mu.m or less is used as the raw material AlN powder in the foregoing manufacturing method, a considerably fine sintered body can be obtained even if the AlN powder is used solely. However, a large quantity of impurities, such as oxygen is, in the sintering period, solid-dissolved in AlN crystal lattices or a composite oxide, such as Al--O--N, which hinders the propagation of the oscillations of the lattices, is generated, thus causing the AlN sintered body using no sintering agent to have a relatively low thermal conductivity.
In the case where AlN powder having an average grain size of 1 .mu.m or larger is used as the raw material powder, sole use of the raw material powder cannot realize satisfactory sintering characteristics. Therefore, it is difficult to obtain a sintered body having high density if no sintering agent is added, except the hot pressing method. In this case, a problem arises in that the mass-productivity is unsatisfactory. Accordingly, a sintered body has been usually and efficiently manufactured by a normal-pressure sintering method in such a way that the sintered body is densified and solid dissolving of impure oxygen in the raw material AlN powder into AlN crystal grains is prevented by adding a rare-earth oxide, such as a yttrium oxide (Y.sub.2 O.sub.3) or an alkali-earth metal oxide, such as a potassium oxide, as a sintering agent.
It is considered that each of the foregoing sintering agents reacts with impure oxygen and Al.sub.2 O.sub.3 and thus forms a liquid phase so that the sintered body is densified or fined. Moreover, the sintering agent fixes impure oxygen as a boundary grain phase and also realizes high thermal conductivity.
However, the conventional m
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Komatsu Michiyasu
Shirai Takao
Bell Mark L.
Kabushiki Kaisha Toshiba
Troilo Louis M.
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