Sub-μg Ultra-Low-Noise MEMS Accelerometers Based on CMOS-Compatible Piezoelectric AlN Thin Films

Abstract

Piezoelectric accelerometers based on aluminum nitride thin films offer a number of advantages in microelectromechanical systems such as high signal-to-noise ratio, low dielectric loss, low power requirements and CMOS process compatibility. This paper reports the state-of-the-art piezoelectric accelerometer design with an emphasis on maximizing the sensitivity per area. The accelerometers have a novel sensing structure to increase the sensitivity without increasing the sensing area using the approach of stress concentrations. Furthermore, the sensing structure is designed to have low off-axis sensitivity and to be reliable with symmetric balanced bars between sensing beams. Experimental results confirm the significantly improved sensitivity of the accelerometers obtained with the new sensing structures. The tested charge sensitivity is 5.2pC/g and the measured total noise floor of sensor plus interface electronics is as low as 670ng/√Hz.