Poly-Si Based Two-Axis Differential Capacitive-Sensing Accelerometer

• Published in: IEEE sensors journal Vol. 12; no. 12; pp. 3301 - 3308
• Main Authors: Chun-Kai Chan, Sung-Cheng Lo, Yu-Che Huang, Mingching Wu, Ming-Yung Wang, Weileun Fang
• Format: Journal Article
• Language: English
• Published: IEEE 01.12.2012
• Subjects: Acceleration; Accelerometer; Accelerometers; Capacitance; capacitive sensing; Electrodes; gimbal-spring; inertial sensors; Micromachining; pendulum proof-mass; poly silicon; Sensors; Silicon
• ISSN: 1530-437X; 1558-1748
• DOI: 10.1109/JSEN.2012.2215313

This paper reports the design and implementation of a two-axis capacitive-type accelerometer using well-known two poly-Si processes. The accelerometer design consists of a pendulum proof-mass (bulk Si), a gimbal-spring (poly-Si film), and vertical-comb sensing electrodes. This design has three merits: 1) pendulum proof-mass to produce torque by in-plane acceleration; 2) high-aspect-ratio-micromachined (HARM) gimbal-springs enable the detection of two-axis accelerations; and 3) vertical-combs of different vertical positions enable the differential sensing electrodes design to detect the angular motion. In short, this paper exploits the vertical-comb electrodes for differential capacitive sensing to detect the two-axis in-plane accelerations. Measurement results show that the sensitivities (nonlinearity) of etch direction are 17.87 mV/G (2.65%) of X-axis, and 16.54 mV/G (2.71%) of Y-axis in the excitation range of 0.6~2 G. Due to the HARM gimbal-spring design, the cross axis sensitivity introduced by the Z-axis excitation is less than 0.3% for both X-axis and Y-axis sensing. However, the cross-axis error between the X-axis and the Y-axis sensing elements still need to be improved.