A mirror-polished obverse surface and a roughened reverse surface of the conventional
GaN wafers have been discriminated by difference of roughness on the surfaces with
human eyesight. The difference of the surfaces is rather ambiguous. Cracks/breaks
and distortion of the wafers have been likely to occur because the roughness of
the reverse surface is apt to bring fine particles.
To discern an obverse from a reverse without making use of the difference of
the
surface roughness, the present invention provides an obverse/reverse discriminative
rectangular nitride semiconductor wafer having a longer slanting edge and a shorter
slanting edge at obversely-clockwise neighboring corners, or having an asymmetric
slanting edge at a corner, or having asymmetrically bevelled parts or having discriminating
characters marked by laser. The present invention can make the reverse surface
mirror-polished and smooth, so that particles on the reverse surface and distortion,
cracks or breaks of the wafer decrease.
