Development of high-efficient damage-free figuring process using open-air type atmospheric pressure plasma

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A chemical finishing process using open-air type atmospheric pressure plasma is proposed to correct the ununiformity in thickness of the quartz wafer. In this process, free figuring without mask pattern can be realized by numerically controlled scanning of the localized removal area. The thickness uniformity of commercially available quartz wafer is improved from 123nm to 15nm only by one correction process without any subsurface damage. Furthermore, a novel polishing technique named plasma-assisted polishing was proposed for the finishing of silicon carbide material. The irradiation of helium-based water vapor plasma efficiently oxidized the surface of single-crystal 4H-SiC (0001), and a result of nanoindentation test revealed that the hardness of SiC decreased by one order of magnitude compared with the unprocessed surface. Plasma-assisted polishing using CeO_2 abrasive enabled us to improve the surface roughness of commercially available SiC wafer without introducing crystallographical subsurface damage, and a scratch-free atomically flat surface with an rms roughness of 0.1nm level was obtained.