Research On MEMS Piezoresistive Accelerometer With Sandwich Structure

MEMS(micro-electromechanical systems) piezoresistive accelerometer is widely used nowadays, from portable electronic consumer products to the aerospace field. It has advantages of small volume, low cost, high precision, good reliability and batch manufacturing, etc. Therefore, the research of the MEMS piezoresistive accelerometer has important theoretical significance and application value.This paper presents a MEMS piezoresistive accelerometer with sandwich structure. The sensor adopts a wafer level packaging manufacturing technology based on anodic bonding, it has a glass-silicon-glass sandwich structure. Silicon is anodic bonded with glass on the top surface of the device, and the bonding process adopt silicon-amorphous silicon-glass anodic bonding on the bottom. An amorphous silicon layer is deposited to conduct the bonding current to the trenches, protecting the electrical properties of the device. The sensor is fabricated using bulk micromachining process, etching of the acceleration mass makes full use of the undercutting in KOH convex corner compensation etching process. A cone-like mass structure is shaped after etching, although this kind of design lose some sensor sensitivity, it greatly reduces the size of the device.Firstly, this paper introduces several kinds of MEMS piezoresistive accelerometer, the working principle of the MEMS piezoresistive accelerometer is analyzed, the sensor structure is designed to meet the design index of sensor. Simulations of the sensor are conducted based on IntelliSuite.Secondly, the etching mask layout is optimized through simulations of etching process and experiments, the derived mass has a cone-like structure.Thirdly, process flow and layout of the MEMS piezoresistive accelerometer is designed, the process parameters are determined, and some problems of the process are analyzed and resolved.Finally, a series of tests are conducted, including stress testing, pressure testing, linearity, sensitivity and stability testing. The sensor chip has a size of 2500 μm×1450 μm×1380 μm, sensitivity of 11.2 μV/V?g, nonlinearity of 1.28%?FS, the test results show that the sensor has good performance, and the design of the sensor and the process is feasible.