A BAROMETRIC PRESSURE SENSOR WITHINTEGRATED REFERENCE PRESSURE CONTROL USING LOCALIZED CVD

摘要

This paper reports a barometric pressure sensor withintegrated reference pressure control. The device was packaged ina cavity, which was created using anodic bonding andsubsequently vacuum sealed using localized CVD (ChemicalVapor Deposition) at near ambient temperature. A post-packagingpressure control system, which consisted of in-cavity pressuremonitoring and pressure control units, was incorporated with thebarometric pressure sensors. The sensor modules, with embeddedcomb resonators and gettering heaters, were fabricated using adouble-polysilicon dissolved-wafer process. The wafers wereanodically bonded, thinned, and then released in EDP. LocalizedCVD was then used to seal the cavity and to react away theresidual gas within it using the getters to create the desiredreference pressure, as measured using the in-cavity resonators.This implementation required very little extra design space, andonly one additional mask compared to the sensor alone. Processimprovements have reduced the sealing time and power by a factorof four compared to that previously reported [1]. Sensors capableof resolving 25mTorr pressure changes with a sensitivity of~60fF/Torr were obtained.