High temperature smart-cut SOI pressure sensor

摘要

Piezoresistive pressure sensors based on SMART CUT (R) SOI wafer have been developed, which can be used in extreme high temperature environments. It has been demonstrated that the resistance value of a heavily doped thin film (similar to 0.34 mu m) resistor increases monotonically with temperature up to 600 degrees C. This is much higher than the maximum temperature of 330 degrees C normally shown in bulk silicon resistors. An analytical model is developed to explain how to extend the maximum operating temperature range based on doping effects and minority-carrier exclusion effects. 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 0.5-25 psi and -55 to 300 degrees C and the latter is calibrated across the range of 16-600 psi and -55 to 500 degrees C. 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 500 degrees C indicates that the single crystal silicon diaphragm is capable of operating at very high temperature without creep or plastic deformation.