Abstract
A monolithic composite MEMS sensor with sandwich structure is designed, simulated, fabricated and characterized. It consists of a rectangular diaphragm piezoresistive pressure sensor and a double-cantilever-mass piezoresistive accelerometer. The professional MEMS software, Intellisuite 8.5, is used to simulate the performances of the composite sensor. The composite sensor is fabricated on a (100)—silicon wafer by using MEMS bulk-micromachining and anodic bonding technology. One-step wet anisotropic etching process on the backside of the wafer can form the main backside shape of the composite sensor including the mass of accelerometer and the pressure sensing diaphragm. The glass-silicon-glass sandwich structure is formed with α-Si (amorphous silicon)-glass anodic bonding on the top surface of the wafer and Si-glass anodic bonding at the bottom. The fabricated composite sensor is measured, resulting in 33.0 μV/V kPa sensitivity for the 450 kPa-ranged pressure sensor, as well as, 11.2 μV/V g sensitivity for the 125 g-ranged accelerometer. The die size of the composite sensor chip is 2.5 mm × 2.5 mm × 1.4 mm. The measured results show that the composite sensor is appropriate for the application fields such as automobile, aerospace and environment monitoring.
Highlights
With the development of silicon micromachining technology, silicon pressure sensors (Crescini et al 2003; Suja et al.2015; Kulwant singh et al 2014; Santosh Kumar and Pant 2015) and accelerometers (Liu et al 2014; Ravi Sankar and Lahiri 2009; Ravi Sankar et al 2012; Manuel Engesser et al 2009) have been well developed and widely used in industrial and commercial applications
This study aims at developing a novel monolithic composite MEMS sensor
Glass is bonded with the low pressure chemical vapor deposition (LPCVD) α-Si layer in front side of wafer and with the silicon substrate in back side, respectively, to form sandwich structure
Summary
With the development of silicon micromachining technology, silicon pressure sensors The composite sensor integrated a piezoresistive pressure sensor and a piezoresistive accelerometer on one chip. It has a sandwich structure and is fabricated using bulk-micromachining process (Chen et al 2009) and anodic wafer bonding technology (Liu et al 2011; San et al 2013). Anodic bonding technology is used to seal the pressure-reference cavity for the pressure sensor and form the vacuum chamber for free motivation of accelerometer’s cantilever-mass. Glass is bonded with the low pressure chemical vapor deposition (LPCVD) α-Si (amorphous silicon) layer in front side of wafer and with the silicon substrate in back side, respectively, to form sandwich structure. Around bonding areas in front side of wafer, trenches are designed and fabricated to ensure the electrical conduction between the LPCVD α-Si layer and the silicon substrate, which can protect the piezoresistors from p–n junction break-down during anodic bonding process in front side of wafer
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