High temperature smart-cut SOI pressure sensor

Piezoresistive pressure sensors based on SMART CUT® 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 (∼0.34 μm) resistor increases monotonically with temperature up to 600 °C. This is much higher than the maximum temperature of 330 °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 °C and the latter is calibrated across the range of 16–600 psi and −55 to 500 °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 °C indicates that the single crystal silicon diaphragm is capable of operating at very high temperature without creep or plastic deformation.