A Novel Trapezoidal ScAlN/AlN-Based MEMS Piezoelectric Accelerometer

Abstract

This paper presents a ScAlN/AlN-based MEMS piezoelectric accelerometer using the trapezoidal with corners (TWC) shaped cantilevers. The composite Sc <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.2</sub> Al <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">0.8</sub> N/AlN piezoelectric film is deposited on a silicon-on-insulator (SOI) substrate to improve the sensitivity of the piezoelectric accelerometer. The theoretical and FEM model is established to analyze the relationship between the cantilever stiffness and the piezoelectric parameters on the sensitivity and resonance frequency. The fabricated accelerometer includes a trapezoidal part, a rectangular part, and a silicon proof mass. The experimental results show that the sensitivity, minimum detectable signal (MDS), resolution, and resonant frequency of the proposed TWC shaped accelerometer are 7.95 mV/g, 1 mg, 1 mg, and 1290 Hz, respectively. The manufactured accelerometer exhibits good linearity up to 2 g (non-linearity<0.087%). Moreover, the TWC and Sc components increase the electric output by about 36% compared with the traditional trapezoidal accelerometer. At room temperature ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${T}=300$ </tex-math></inline-formula> K), the thermal noise of the fabricated accelerometer is lower than 94.7 nV/ <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\surd $ </tex-math></inline-formula> Hz. Meanwhile, the charge amplifier circuit noise is about <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.97~\mu \text{V}/\surd $ </tex-math></inline-formula> Hz. The proposed TWC accelerometer is sensitive and suitable to sense vibration acceleration in low-frequency scenarios.