Abstract
In this paper, a monolithic tri-axis piezoresistive high-shock accelerometer has been proposed that has been single-sided fabricated in a single (111)-silicon wafer. A single-cantilever structure and two dual-cantilever structures are designed and micromachined in one (111)-silicon chip to detect Z-axis and X-/Y-axis high-shock accelerations, respectively. Unlike the previous tri-axis sensors where the X-/Y-axis structure was different from the Z-axis one, the herein used similar cantilever sensing structures for tri-axis sensing facilitates design of uniform performance among the three elements for different sensing axes and simplifies micro-fabrication for the multi-axis sensing structure. Attributed to the tri-axis sensors formed by using the single-wafer single-sided fabrication process, the sensor is mechanically robust enough to endure the harsh high-g shocking environment and can be compatibly batch-fabricated in standard semiconductor foundries. After the single-sided process to form the sensor, the untouched chip backside facilitates simple and reliable die-bond packaging. The high-shock testing results of the fabricated sensor show linear sensing outputs along X-/Y-axis and Z-axis, with the sensitivities (under DC 5 V supply) as about 0.80–0.88 μV/g and 1.36 μV/g, respectively. Being advantageous in single-chip compact integration of the tri-axis accelerometers, the proposed monolithic tri-axis sensors are promising to be embedded into detection micro-systems for high-shock measurement applications.
Highlights
MEMS inertial sensors can be widely used in the automobile industry and consumer electronics [1], among which high-shock sensors, i.e., high-g accelerometers with the measure range as tens of thousands of gravities, are essential to access and analyze structure destruction, rapture, and the collision process [2]
Most of the previously reported cantilever high-shock sensing structures were fabricated with double-sided processes like the work in [4] where wet anisotropic etching from wafer backside creates difficulties in precise control of the deep etching depth
The subsequent wafer-to-wafer bonding process introduces mismatching at the bonding interface, and degrades the robustness of the sensor when it works in harsh high-shock detections
Summary
MEMS (microelectromechanical systems) inertial sensors can be widely used in the automobile industry and consumer electronics [1], among which high-shock sensors, i.e., high-g accelerometers with the measure range as tens of thousands of gravities, are essential to access and analyze structure destruction, rapture, and the collision process [2]. Most of the previously reported cantilever high-shock sensing structures were fabricated with double-sided processes like the work in [4] where wet anisotropic etching from wafer backside creates difficulties in precise control of the deep etching depth. A single-wafer single-side micromachined high-g sensor was proposed and developed for single-axis high-shock detection [5]. It is highly demanded to develop new micromachining techniques to form identical-shaped sensing structure, e.g., the same cantilever structures, for the monolithically integrated tri-axis sensor. Tri-axis multi-cantilever high-shock accelerometers are eventually designed into monolithic integration and the fabrication is still performed from the single-side (front-side) of a single (111) wafer by developing a dual-step trench-etching based micromachining method. The design, fabrication, and testing of the single-chip integrated tri-axis sensor will be detailed in following sections
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