High temperature high accuracy piezoresistive pressure sensor based on smart-cut soi

Piezeoresistive pressure sensors based on SMART CUTreg SOI wafer have been developed, which can be used in extreme high temperature environments. It is demonstrated that the minority-carrier exclusion effect in ultra thin film (~0.34 mum) Smart-cut SOI enables resistance values to increase monotonically with temperature up to 600degC which is much higher than the maximum temperature of 330degC normally shown in bulk silicon resistors. Two types of packaging have been developed for different applications; one is for low pressure, high accuracy application, the other is for high pressure, high temperature application. The former is fully characterized across the range of 0.5 psi to 25 psi and -55degC to 300degC and the latter is calibrated across the range of 16 to 600 psi and -55degC to 500degC. A digitized curve fitting technique is used to calibrate the sensors by use of on-chip temperature signals. After curve fitting, the accuracy is < 0.05% F.S. for the first type of the pressure sensor and < 0.25% F.S. for the second type of the pressure sensor. A very low pressure hysteresis (< 0.1% FS) at 500degC indicates that the single crystal silicon diaphragm is capable of operating at very high temperature without creep or plastic deformation.