A Dual-Axis Bulk Micromachined Resonant Accelerometer With Low Cross-Axis Sensitivity Fabricated With Masked–Maskless Etching

This paper presents the design, simulation, fabrication, and experiment of a dual-axis bulk micromachined resonant accelerometer. The resonant accelerometer consists of a proof mass, four crab-leg supporting beams, and four resonant beams. Resonant beams are located at the surface of a silicon chip in order to pattern resistors and metal lines. The gravity center of the proof mass basically lies within the neutral plane of crab-leg supporting beams to minimize the rotation of the proof mass under in-plane acceleration. The non-coplanar resonant beams and crab-leg supporting beams are formed simultaneously by masked-maskless wet etching in iodine-supersaturated KOH solution. The experimental results show that the cross-axis sensitivity of x-axis resonant beams under y -axis acceleration is 1.92% and that of y-axis resonant beams under x-axis acceleration is 1.55%.

I. Introduction

Accelerometers are used for a variety of motion sensing applications ranging from inertial navigation to vibration monitoring. There are different mechanisms to sense acceleration, such as piezoresistive, capacitive, piezoelectric, and resonant type. Among these accelerometers, resonant sensors have many advantages: wide dynamic range, quasi-digital nature of the output signal, and the inherent continuous self-test capability [1]. Generally, a resonant accelerometer consists of a proof mass, one or several supporting beams and resonators. When the proof mass is subjected to acceleration, resonators are stretched or compressed, resulting in resonant frequency shifts. The acceleration can be detected by measuring the frequency shift.