Highly Efficient Damage-Free Correction of Thickness Distribution of Quartz Crystal Wafers by Atmospheric Pressure Plasma Etching

A new finishing method was developed to correct the thickness distribution of a quartz crystal wafer by the numerically controlled scanning of a localized atmospheric pressure plasma. The thickness uniformity level of a commercially available AT-cut quartz crystal wafer was improved to less than 50 nm without any subsurface damage by applying one correction process. Furthermore, applying a pulse-modulated plasma markedly decreased the correction time of the thickness distribution without breaking the quartz crystal wafer by thermal stress.