Surface micromachined pressure sensors with integrated CMOS read-out electronics

In this paper a single chip pressure and temperature sensor system with on chip electronics is presented. The capacitive pressure sensor is fabricated using a CMOS process with additional surface micromachining steps to form the membranes. The membrane dimensions have been optimized for a pressure range of 2, 3.5, 10 and 35 bars, respectively. The temperature sensor shows a straight linear output signal in a temperature range of 0 to 70 xC. For the signal processing switched capacitor circuits are used. The sensor signals are converted to a pulse width modulated output signal. The silicon chip has an active area of 3.5 mmü. Between 0 and 80 xC a temperature dependence of the pressure signal of less than 200 ppm/xC reffering to full scale was found.