Novel Concept Design for Complementary Metal Oxide Semiconductor Capacitive $Z$-Direction Accelerometer

概要

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The purpose of this study is to provide a novel concept design for complementary metal oxide semiconductor (CMOS) capacitive $Z$-direction accelerometers. In this design, capacitance-sensing parallel plates and thin single-metal-layer springs are fabricated by chemical plasma etching. This plasma etching process utilizes a rough vacuum to shorten the mean free path of the reactive gases and increase lateral etching and undercut. Moreover, the thin single-metal-layer springs have the characteristic of a lower spring constant to increase the displacement of the proof mass. Thus, the sensitivity can be further improved. This study has established a post-CMOS chemical plasma etching process to release the accelerometer using sensing electrodes of the capacitance-sensing parallel plates. The $Z$-direction accelerometer has been fabricated by the standard CMOS 0.35 μm two-polycrystalline silicon four-metal (2P4M) process and a post-CMOS process of chemical plasma etching. The measurement results indicate that the sensitivity of the accelerometer is about 0.8 mV/g and the total noise floor is 4.2 μV/$\sqrt{\text{Hz}}$.
Published by the Japan Society of Applied Physics through the Institute of Pure and Applied Physicsの論文
2009-07-25