HIGH-PRESSURE HIGH-TEMPERATURE BULK-TYPE PIEZORESISTIVE PRESSURE SENSOR

A silicon-based bulk-type pressure sensor capable of measuring pressure up to 200 MPa at temperature up to 175 o C is realized and characterized. Hydrostatic pressure acting on the sensor is converted to anisotropic biaxial compression inside an encapsulated vacuum cavity, and measured using two pairs of piezoresistors oriented to optimally utilize the anisotropy of silicon piezoresistance on (110)-oriented substrate. It is also possible to realize the sensor on a conventional (001)-oriented substrate, with the stress-symmetry broken by reducing the biaxial stress field on one pair of the piezoresistors to a uniaxial stress field.