Wafer-level quartz dry etching technology

Wafer-level quartz dry etching technology has been developed, which enables deep reactive ion etching (DRIE) for through-etch of ≥120-μm-thick crystal quartz wafers and an X-cut quartz DRIE. Our DRIE process employs direct wafer bonding of crystal quartz and silicon wafer by means of surface active bonding at room temperature and epoxy-based negative tone, i-line photoresist for the mask of the dry etching. Etching gases and DRIE parameters are optimized from the points of etching rate, mask selectivity, the angle of the sidewall and micro-loading effect. X-cut tuning fork resonator having folded arms has been fabricated by the wafer-level quartz dry etching technology.