Method of storing GaN substrate, stored substrate, and semiconductor device and method of its manufacture
Affords a method of storing GaN substrates from which semiconductor devices of favorable properties can be manufactured, the stored substrates, and semiconductor devices and methods of manufacturing the semiconductor devices. In the GaN substrate storing method, a GaN substrate ( 1 ) is stored in an atmosphere having an oxygen concentration of 18 vol. % or less, and/or a water-vapor concentration of 12 g/m 3 or less. Surface roughness Ra of a first principal face on, and roughness Ra of a second principal face on, the GaN substrate stored by the storing method are brought to no more than 20 nm and to no more than 20 μm, respectively. In addition, the GaN substrates are rendered such that the principal faces form an off-axis angle with the (0001) plane of from 0.05° to 2° in the <1 1 00> direction, and from 0° to 1° in the <11 2 0> direction.
1. A GaN-substrate storage system comprising:
a storage container internally establishing a sealed atmosphere containing either nitrogen gas or argon gas and being hermetic to oxygen and water vapor, said storage-container atmosphere therein for sealing a plurality of substrates and having a temperature from 5° C. to 60° C. and having an oxygen concentration of from 0.6 vol. % to 5 vol. % and/or a water-vapor concentration of from 1 g/m 3 to 17 g/m 3 ;
at least one device-formation-ready GaN substrate sealed inside said storage container, said GaN substrate defining first and second principal faces, and the first principal face having a surface roughness Ra of from 2 nm to 20 nm and the second principal face having a surface roughness Ra of from 2.4 μm to 20 μm, wherein an off-axis angle formed by the principal faces on said GaN substrate and its (0001) plane is between 0.05° and 2°, inclusive, in the <1 1 00> direction, and between 0° and 1°, inclusive, in the <11 2 0> direction; and
a storing device, storing said storage container, and equipped with a gas-introducing valve and, connected to said gas-introducing valve, an inert-gas introduction line, and equipped with a gas-exhaust valve and, connected to said gas-exhaust valve, a gas-exhaust line, said storing device therein for creating said storage-container atmosphere by enabling, via said gas-introducing valve and said inert-gas introduction line, the introduction into the storing device of an inert gas of from 0.6 vol. % to 5 vol. % oxygen concentration and from 1 g/m 3 to 17 g/m 3 water-vapor concentration, and by enabling, via said gas-exhaust valve and said gas-exhaust line, the exhaustion from the storing device of gas of more than 5 vol. % oxygen concentration and more than 17 g/m 3 water-vapor concentration.
2. A GaN-substrate storage system as set forth in claim 1 , wherein said storage container is made of aluminum.