Effect of Electroplated Gold Film on the Performance of a Piezoresistive Accelerometer with Stress Concentrated Tiny Beams

Background/Objective: In the recent times, piezoresistive accelerometers have been extensively explored with the primary focus on the optimization of its sensitivity and measurement bandwidth. In this paper, the design of an in-plane deflection mode accelerometer sensor has been devised with selective deposition of gold metal on the top and both the sides of the proof mass. Methods/Statistical Analysis: The micromachined silicon accelerometer constitutes of stress concentrated tiny piezoresistor beams and a central cantilever beam to support the proof mass. In order to improve the electromechanical response of the sensor, selective deposition of the gold metal layer was performed on the top and both the sides of the proof mass. The design and modeling of the sensor has been performed utilizing a Finite Element Model (FEM) software simulation tool IntelliSuite®. Findings: Compared to the conventional designs reported in the literature, accelerometer sensors with stress concentrated tiny beams and gold layer selectively deposited on the proof mass have shown an improvement in the electrical sensitivity and the FOM (product of the sensitivity and square of the resonant frequency). Simulation results demonstrate that the accelerometer structure with gold layer atop of the proof mass has a better sensitivity and FOM than the conventional design without gold by 28.26% and 27.43% respectively. Similarly, the accelerometer structure with gold on both sides of the proof mass has shown an improvement in the sensitivity by 57.82% and the Figure Of Merit (FOM) by 29.70% compared to the structure without gold layer. Conclusion/Improvements: It has been demonstrated that the performance metrics of piezoresistive accelerometer sensors with stress concentrated tiny beams can further be improved by selective deposition of metal gold layer on the proof mass of the accelerometer structure.