Temperature control of CMOS micromachined sensors

In this paper, we describe a methodology for temperature stabilization of CMOS micromachined sensors. Temperature stabilization of a z-axis accelerometer, fabricated in a 0.5 /spl mu/m Agilent CMOS process is demonstrated. The accelerometer motion is sensed by a vertical comb drive designed by controlling the rotor and stator curvature. The polysilicon layer of the CMOS process has been utilized for heating the device structure to a constant temperature, that is higher than the maximum ambient operating temperature. The capacitance detection circuits have temperature independent gain. The D.C. bias stability of the accelerometer improved from 1.9 G//spl deg/C, to 42 mG//spl deg/C, and the sensitivity stability improved from 60% to 18% over a temperature of 70/spl deg/C after temperature control.