SILICON PRESSURE SENSOR WITH INTEGRATED CMOS SIGNAL-CONDITIONING CIRCUIT AND COMPENSATION OF TEMPERATURE-COEFFICIENT

A silicon pressure sensor designed for automotive applications with on-chip signal conditioning is presented. The micromechanical processing steps are added to a standard 3-mu-m CMOS process. The membrane is etched in (100)-oriented Si by anisotropic etching with an electrochemical etch stop. Thickness control with tolerances of less than 0.5-mu-m is readily achieved. A complete CMOS evaluation circuit is integrated on the same device. The signal of the piezoresistive Wheatstone bridge is processed by an instrumentation amplifier with temperature-dependent amplification for on-chip compensation of the sensitivity variation with temperature. Moreover, the sensitivity variation itself, the offset and the offset variation with temperature are compensated. On-chip trimming is provided for the adjustment of these terms in the full automotive temperature range from -40-degrees-C to + 125-degrees-C.