Surface micromachined multi-layer moving gate field effect transistor (MOGFET) pressure switch with integrated vacuum sealed cavity

Abstract

A microelectromechanical pressure switch with electronic switching using a moving gate field effect transistor (MOGFET) has been designed and fabricated. The MOGFET is designed to replace the metal to metal contact switches which are susceptible to arcing, micro-welding, and deformation of the contacts. Sufficient pressure hysteresis is achieved by the electrostatic force between the moving gate and the substrate. The threshold pressures and the pressure hysteresis are adjustable electrically. The spring-capacitor model is presented to explain pull-in and pull-out conditions which are critical for stable switching operations. A vacuum cavity is formed during fabrication process and provides the reference vacuum pressure without an extra vacuum package. The fabricated devices have various switching pressure ranges from 12 psia to 500 psia. The measured switching channel resistance values are approximately 11.8 K/spl Omega/ for a channel W/L ratio of 21 and 2.4 K/spl Omega/ for a W/L ratio of 51 at the gate voltage of 12 V.