Quartz-based vibrating MEMS fabricated using a wafer-bonding process with sealed cavities

Here we present the results of a wafer-level approach allowing the collective fabrication of gyroscope sensors based on quartz vibrating MEMS. More specifically, we focus on suspended quartz tuning fork microstructures of a desired thickness over controlled depth cavities. This approach is based on the bonding and thinning of 4-inch z-cut quartz wafer on pre-structured silicon wafer. InfraRed (IR) inspection shows a large bonded area (>98%) while structural characterizations of the thinned quartz layer indicate a crystal quality and mechanical properties equivalent to quartz bulk material. The obtained gyroscope exhibits a quality factor (Q) around 12300 at 86.6 kHz very close to quartz theoretical thermoelastic limit. This Quartz-On-Silicon (QOS) technology open the way to a new generation of highly integrated quartz devices.