Temperature-compensated CMOS-MEMS resonators via electrical stiffness frequency pulling
Journal
Journal of Micromechanics and Microengineering
Journal Volume
30
Journal Issue
1
Date Issued
2020
Author(s)
Abstract
Abstract A passively temperature-compensated micromechanical resonator based on an electrical stiffness frequency pulling technique was demonstrated. In particular, a 2.92 MHz free–free beam resonator achieved by a 0.35 µ m 2-poly-4-metal complementary metal-oxide semiconductor microelectromechanical systems (CMOS-MEMS) process platform yields a nearly zero first-order temperature coefficient of frequency (TCF 1 ), from −69.78 ppm °C −1 of an uncompensated version to +0.43 ppm °C −1 , and a 12× lower overall frequency drift from the uncompensated 5885 ppm to 496 ppm between 0 °C and 85 °C. The electrical stiffness compensation technique previously demonstrated on a CMOS-incompatible poly-Si surface micromachining process consumes no dc power consumption in contrast to other active methods. In this work, an improved design of the in-plane U -shaped compensating electrode allows not only the employment by a standard CMOS process but also layout-defined temperature dependency of the electrical stiffness via varying the length of the compensating electrode. A theoretical model predicts the thermally induced extension of the compensating electrode and further leads to an optimum electrode length which allows the use of only one voltage source for both compensation and polarization bias voltages. The measured results are compared with the analytical model prediction and discussion on the effects of process induced device parameter variations is presented.
Type
journal article