Capacitive Single Crystal Silicon Touch-Mode Pressure Sensor

摘要

A capacitive, touch-mode pressure sensor has been developed. The sensor element is formed entirely from single crystal silicon, giving it good linearity with exceptional stability over time, temperature and pressure cycles. The sensor is produced using a low-cost, high volume fabrication process. The sensor diaphragm deflects in proportion to absolute pressure, resulting in a quasi-linear change in capacitance between the diaphragm and the substrate. The key to the linearity of this device is the touch-mode operation, in which the diaphragm makes physical contact with the oxide on the substrate during normal operation. The device is suited for both wire-bonded and flip-chip applications. The sensor is designed to measure pressures from 100 to 800 kPa absolute over a -40°C to 125°C temperature range. Typical device sensitivity in this range is 0.05pF/kPa +/-3%. Temperature Coefficient of Offset(TCO) over the full temperature range is less than 120ppm/°C and a Temperature Coefficient of Sensitivity(TCS) less than 200ppm/°C. Finite Element Analysis (FEA) modeling and actual characterization results have shown that other ranges and sensitivities may be obtained with simple changes to the device geometry.