SUBSTRATE FOR FILM GROWTH OF GROUP III NITRIDES, METHOD OF MANUFACTURING THE SAME, AND SEMICONDUCTOR DEVICE USING THE SAME
A substrate for film growth of group III nitride, a method of manufacturing the same, and a semiconductor device using the same are provided which can make an AlN thin film relatively thin without cloudiness, as well as cracks and pits are reduced in a group III nitride thin film layer constituting the device grown thereon. A substrate 10 for film growth of group III nitride is constituted which includes a substrate material 11 and an AlN thin film 12 formed on said substrate as a buffer layer, and a semiconductor device comprising group III nitride thin film is formed thereon, and the AlN thin film is formed at plural steps at least one of which changes film growth conditions during the film growth.
1 . A substrate for film growth of group III nitride, including a substrate material, and AlN system thin film formed on said substrate material as a buffer layer, characterized in that:
a semiconductor device comprising group III nitride thin film is formed thereon,
said AlN system thin film is formed at plural steps at least one of which changes film growth conditions during film growth, and
its pit density is 2×10 8 cm 2 or less.
2 . The substrate for film growth of group III nitride as set forth in claim 1 , characterized in that the parameters of said film growth condition change are a growth temperature, a pressure, or source gases flow rates and its flow rate ratio, and a timing of change of growth conditions.
3 . The substrate for film growth of group III nitride as set forth in claim 1 , characterized in that said substrate material is either a sapphire substrate, a SiC substrate or a Si substrate.
4 . The substrate for film growth of group III nitride as set forth in claim 3 , characterized in that the surface of said substrate is treated for making nitride.
5 . The substrate for film growth of group III nitride as set forth in claim 1 , characterized in that said AlN system thin film is formed by changing film growth conditions non-stepwise at least in a part of film growth time.
6 . The substrate for film growth of group III nitride as set forth in claim 1 , characterized in that said AlN system thin film is AlN thin film.
7 . A method of manufacturing a substrate for film growth of group III nitride to grow a semiconductor device comprising a group III nitride thin film thereon by forming AlN system thin film on a substrate as a buffer layer, characterized in that:
said AlN system thin film is formed at plural steps at least one of which changes film growth conditions during film growth.
8 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that the parameters of said film growth condition change are a growth temperature, a pressure, or gases flow rates and its flow rate ratio, and a timing of change of growth conditions.
9 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that said substrate is either a sapphire substrate, a SiC substrate, or a Si substrate.
10 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 9 , characterized in that the surface of said substrate is treated for making nitride.
11 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that said AlN system thin film is formed by changing film growth conditions non-stepwise at least in a part of film growth time.
12 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that the film growth temperature, among said film growth conditions, is changed as gradually higher at each step.
13 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that the film growth time, among said film growth conditions, is changed as gradually longer at each step.
14 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that V/III ratio, among said film growth conditions, is changed as gradually smaller at each step.
15 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that film growth of AlN system thin film is temporarily interrupted during said film growth condition change.
16 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that film growth of AlN system thin film is continuously conducted uninterrupted during said film growth condition change.
17 . The method of manufacturing a substrate for film growth of group III nitride as set forth in claim 7 , characterized in that said AlN system thin film is AlN thin film.
18 . A semiconductor device, characterized in that:
it is constituted by using a substrate for film growth of group III nitride including a substrate material, and AlN system thin film formed on said substrate material as a buffer layer, characterized in that a semiconductor device comprising group III nitride thin film is formed thereon; said AlN system thin film is formed at plural steps at least one of which changes film growth conditions during film growth, and its pit density is 2×10 8 cm 2 or less, or
by using a substrate for film growth of group III nitride manufactured by growing a semiconductor device comprising a group III nitride thin film thereon by forming AlN system thin film on a substrate as a buffer layer, characterized in that said AlN system thin film is formed at plural steps at least one of which changes film growth conditions during film growth, and
by forming a thin film of device structure of a semiconductor device on said substrate for film growth of group III nitride.
19 . The semiconductor device as set forth in claim 18 , characterized in that said device structure of a semiconductor device is a semiconductor light emitting device such as a light emitting diode and a laser diode.
20 . The semiconductor device as set forth in claim 18 , characterized in that said device structure of a semiconductor device is an electronic device such as an FET.