| US 7,338,555 B2 | ||
| Highly crystalline aluminum nitride multi-layered substrate and production process thereof | ||
| Hiroyuki Fukuyama, Yokohama (Japan); Wataru Nakao, Kawasaki (Japan); Shinya Kusunoki, Kawasaki (Japan); Kazuya Takada, Shunan (Japan); and Akira Hakomori, Shunan (Japan) | ||
| Assigned to Tokuyama Corporation, Tojuyama-shi (Japan); and The Circle for the Promotion of Science and Engineering, Tokyo (Japan) | ||
| Filed on Sep. 10, 2004, as Appl. No. 10/937,344. | ||
| Claims priority of application No. 2003-320836 (JP), filed on Sep. 12, 2003. | ||
| Prior Publication US 2005/0059257 A1, Mar. 17, 2005 | ||
| Int. Cl. C30B 25/00 (2006.01) | ||
| U.S. Cl. 117—84 [117/952] | 3 Claims |
| 1. A process for producing a highly crystalline aluminum nitride multi-layered substrate by nitriding a single-crystal α-alumina
substrate in the presence of carbon, nitrogen and carbon monoxide to form a crystalline aluminum oxynitride layer and a highly
crystalline aluminum nitride film as an outermost layer directly on the crystalline aluminum oxynitride layer, said highly
crystalline aluminum nitride film as an outermost layer having a film surface smoothness in terms of Ra and RMS of 100 nm
or less, wherein nitriding is carried out under reaction conditions which satisfy the following conditions a to d:
a: the equilibrium partial pressure of Al2O(g) in the reaction formula (1) is 5×10−4 bar or less:
Al2O3(s)+2C(s)=Al2O(g)+2CO(g) (1)
b: the equilibrium partial pressure of Al2O(g) in the reaction formula (2) is 5×10−6 bar or less:
2AlN(s)+CO(g)=Al2O(g)+C(s)+N2(g) (2)
c: the reaction formula (3) proceeds to the right side:
 d: the reaction temperature is 1,630° C. (1,903K) or higher and lower than 1,700° C. (1,973K).
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