Damage-free improvement of thickness uniformity of quartz crystal wafer by plasma chemical vaporization machining

The thickness uniformity of an quartz crystal wafer is an essential requirement for improving the productivity of a quartz resonator because it prevents frequency adjustment after dicing the wafer. In this paper, chemical finishing utilizing a localized atmospheric pressure plasma is proposed to correct the thickness deviation of a quartz crystal wafer. In this process, free figuring without mask patterning can be realized by the numerically controlled scanning of a localized removal area. The thickness uniformity of a commercially available quartz wafer is improved from 250 to 50 nm only by one correction without subsurface damage.