Compositions: ceramic – Ceramic compositions – Refractory
Patent
1996-09-04
1998-06-09
Bell, Mark L.
Compositions: ceramic
Ceramic compositions
Refractory
501 985, 501 32, 264 65, C04B 35581
Patent
active
057633444
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to an aluminum nitride sintered body used as electronics parts such as semiconductor substrates and the like and structural components and a method of manufacturing the aluminum nitride sintered body, and more specifically, to an aluminum nitride sintered body provided with a high thermal conductivity intrinsic to the aluminum nitride (AlN) sintered body as well as high density or minuteness equal to or greater than that of conventional AlN sintered body and further improved corrosion resistance and a method of manufacturing the aluminum nitride sintered body.
BACKGROUND ART DISCLOSURE
Ceramic sintered bodies which are excellent in various characteristics such as strength, heat resistance, corrosion resistance, wear resistance, lightness and the like as compared with conventional metal materials have been widely used as machines parts, functional parts, structural members and ornament materials such as semiconductor substrates, electronic equipment materials, engine parts, high speed cutting tool materials, nozzles, bearings and the like which are used under severe conditions of temperature, stress and wear which cannot be endured by the conventional metal material.
In particular, since an aluminum nitride (AlN) sintered body is an insulator having a high thermal (heat) conductivity and has a coefficient of thermal expansion near to that of silicon (Si), it finds an enlarged field of application as radiation plates and substrates of highly-integrated semiconductor devices.
Conventionally, the above aluminum nitride sintered body is generally made in large quantities by the following method. That is, a mixed material is prepared in such a manner that aluminum nitride material powder is added with sintering assistants, an organic binder and when necessary with various additives, solvent and a dispersing agent and the thus obtained mixed material is molded to a thin or sheet-shaped molded body by a doctor blade method or a slurry casting method or pressed to a thick or large molded body. Next, the thus obtained molded body is degreased by being heated in air or a nitrogen gas atmosphere to remove a hydrocarbon component and the like used as the organic binder. Then, the decreased molded body is densely sintered by being heated to a high temperature of about 1700.degree. to 1900.degree. C. in a non-oxidizing atmosphere such as a nitrogen gas or the like and formed to the aluminum nitride sintered body.
In the manufacturing method described above, when ultra-fine material powder having an average grain size of about 0.5 .mu.m or less is used as the material AlN powder, a considerably dense and fine sintered body can be obtained even if the AlN powder is used independently. However, a lot of impurities such as oxygen etc. adhered on the surface and the like of the material powder are dissolved in AlN crystal lattices or create composite oxides such as an Al--O--N compound and the like which prevent the transmission of lattice vibration when sintering is carried out, with a result that the AlN sintered body not using a sintering assistant has a relatively low thermal conductivity (heat transfer coefficient).
On the other hand, when AlN powder having an average grain size of 1 .mu.m or more is used as the material powder, since the sintering property of the material powder is not good when it is used independently, it is difficult to obtain a dense and minute sintered body by a method other than a hot-pressing method when no assistant agent is added, thus the above AlN powder has a drawback that mass-productivity is low. Thus, when it is intended to effectively make a sintered body by an ordinary pressure sintering method, it is a generally employed practice to add rare earth oxides and the like such as yttrium oxide (Y.sub.2 O.sub.3) etc.
It is contemplated that these sintering assistants form liquid phases by being reacted with impurity oxides and Al.sub.2 O.sub.3 contained in the AlN material powder to thereby make the sintered body dense and minute as well as f
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Bell Mark L.
Kabushiki Kaisha Toshiba
Troilo Louis M.
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