Temperature control of CMOS micromachined sensors.

摘要

An understanding of residual stress, in the various layers of the CMOS process is important for design of sensors. A simulation methodology based on experimentally extracted material properties was developed in the course of this work. The differences in stress gradient with temperature are exploited to design a novel IR imager pixel. The IR imager can achieve a NEDT of 6mK.; A methodology for the design of a temperature stabilization scheme for CMOS micromachined sensors is presented in this work. Temperature stabilization of a z-axis accelerometer, fabricated in a 0.5 μm 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 1.7 G/°C, to 42 mG/°C, and the sensitivity stability improved from 60% to 18% over a temperature range of 70°C after temperature control.