A dual-axis MEMS capacitive inertial sensor with high-density proof mass

Abstract

This paper reports a novel dual-axis microelectromechanical systems (MEMS) capacitive inertial sensor that utilizes multi-layered electroplated gold. All the MEMS structures are made by gold electroplating that is used as a post complementary metal-oxide semiconductor (CMOS) process. Due to the high density of gold, the Brownian noise on the proof mass becomes lower than those made of other materials such as silicon in the same size. The single gold proof mass works as a dual-axis sensing electrode by utilizing both out-of-plane (Z axis) and in-plane (X axis) motions; the proof mass has been designed to be 660 μm × 660 μm in area with the thickness of 12 μm, and the actual Brownian noise in the proof mass has been measured to be 1.2 $${\upmu}{\text{G/}}\sqrt {\text{Hz}}$$μG/Hz (in Z axis) and 0.29 $${\upmu}{\text{G/}}\sqrt {\text{Hz}}$$μG/Hz (in X axis) at room temperature, where 1 G = 9.8 m/s2. The miniaturized dual-axis MEMS accelerometer can be implemented in integrated CMOS-MEMS accelerometers to detect a broad range of acceleration with sub-1G resolution on a single sensor chip.