One-dimensional-motion and pressure hybrid sensor fabricated and process-level-packaged with CMOS back-end-of-line processes

One-dimensional movable structures (motion sensors) made from a metal silicide (WSi) core were successfully encapsulated inside a cavity in an interlayer dielectric (SiO₂) covered by another metallic layer. The latter half of the fabrication process is the same as to that for the pressure sensor that we previously reported [1]; thus, both sensors can be fabricated simultaneously. As is the case with our previously reported pressure sensor, the fabrication processes are compatible with CMOS back-end-of-lines (BEOL) processes (carried out below 400degC). The motion sensor can thus be fabricated directly above integrated circuits (ICs). The fabricated sensors were electrically tested, and the measured pull-in voltage was in good agreement with the design value.