Poly-SiC capacitive pressure sensors made by wafer bonding

SiC is an attractive material for harsh environment micromachined transducers due to its outstanding electrical, mechanical and chemical properties. In this paper, we report on the successful fabrication of SiC-based capacitive pressure sensors made from low-stress, heavily-doped polycrystalline 3C-SiC (poly-SiC) films. The low stress films enable the use of conventional vacuum wafer bonding techniques to realize diaphragm-based sensors that incorporate sealed vacuum cavities. Sensors with diaphragms ranging from 200 mum to 1 mm in diameter were successfully fabricated by wafer bonding. The sensors operate as touch-mode devices and exhibit a linear response between 17.0 and 25.3 PSI at 400degC, which was the maximum operating temperature of the setup