This research was carried out in order to develop the ultra-precision polishing technology of the single crystal diamond substrate. This substrate is expected to apply to a substrate for the next-generation semiconductor element used under specific environment. In this polishing process, after the carbon atoms are excited up to band gap energy of diamond by the photon energy, and the carbon atom will be finally oxidized. The oxidized carbon layer could be removed as CO or CO_2 during this polishing. As a result of evaluation of diamond (100) and diamond (111) polished surface by WYKO (interferometer microscope) and photon microscope, the high polishing rate and the good surface roughness (Ra:0.3nm) were confirmed.
