CMU MEMS Laboratory Publication Abstract


in Ph.D. Thesis, April 2002, Carnegie Mellon University, Pittsburgh, PA.
Temperature Control of CMOS Micromachined Sensors
H. Lakdawala
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 oC after temperature control.
© 2002 Carnegie Mellon University, Department of Electrical and Computer Engineering.
Full paper (PDF) (opens in new window).

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