Surface-micromachined piezoelectric pressure sensors

Surface-micromachined piezoelectric pressure sensors fabricated on deformable polysilicon membranes are described. The process is completely compatible with CMOS technology because it uses conventional fabrication techniques, materials, and chemicals. Integrating microsensors and circuitry on a single chip reduces power consumption and allows localization of information processing operations to be carried out over a small area. Previously reported pressure/acoustic microsensors have been fabricated using bulk-machining techniques and/or hybrid sealing techniques. Bulk machining severely limits device density and weakens the mechanical integrity of the wafer. Front-to-backside alignment unnecessarily complicates the process while silicon etchants such as KOH and EDP (or EPW) can potentially lower the yield of working circuits on the wafer. Hybrid bonding and sealing techniques often require prolonged high-temperature processing steps after the formation of circuits.<>