1. Field of the Invention
This invention relates to a nitride semiconductor substrate and a method of fabricating the nitride semiconductor substrate. In particular, this invention relates to a nitride semiconductor substrate with a chamfered edge portion and a method of fabricating the nitride semiconductor substrate.
2. Description of the Related Art
In a Si substrate, a GaAs substrate etc. as a semiconductor substrate used for fabricating an electronic device etc., the shape recognition and the localization of the substrate are conducted by image processing upon the transport during the device fabrication process, or upon the appearance inspection during the device fabrication process and the shipping. The shape recognition and the localization of the substrate are frequently conduced by irradiating the substrate with visible light or infrared light and detecting light reflected by the substrate.
As a conventional nitride semiconductor substrate, a gallium nitride (GaN) semiconductor substrate is known which is formed circular in its top view and has an edge portion with a surface roughness (Ra) of 10 nm to 5 μm (e.g., see JP-A-2004-319951).
The nitride semiconductor substrate as described in JP-A-2004-319951 is formed such that the edge portion is smoothened so as to reduce the incidence of cracks and to enhance the fabrication yield of an electronic device in the electronic device fabrication process using the nitride semiconductor substrate.
However, since the nitride semiconductor substrate as described in JP-A-2004-319951 is transparent to (i.e., not reflective to) visible light and infrared light, it is impossible to achieve the shape recognition and the localization of the substrate by directly applying to the nitride semiconductor substrate the shape recognition method and the localization method used for a Si substrate, a GaAs substrate etc.