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 400°C). 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.