R. Navya Sri ¹, S. Vetrivel ¹, Ribu Mathew ¹, A. Ravi Sankar ¹

Affiliations
1 School of Electronics Engineering (SENSE), VIT University, Chennai - 600 127, Tamil Nadu, IN

Abstract

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.

Keywords

Accelerometer Sensor, Electroplated Gold, In-plane Deflection, Piezoresistive Read Out, Resonant Frequency, Sensitivity

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P. A. Ajeesh ¹, Ribu Mathew ¹, A. Ravi Sankar ¹

Affiliations
1 School of Electronics Engineering (SENSE), VIT Chennai Campus, VIT University, Chennai-600 127, Tamil Nadu, IN

Abstract

Background/Objective: Thermally actuated dog-bone actuators with an in-plane extensional mode of operation and integrated piezoresistive sensing have found versatile applications especially in realizing miniaturized precision oscillators. In this paper, we present a systematic investigation on the impact of dimensional scaling of the resonator structure and the surface doping concentration of the piezoresistor on the performance of a joules heating driven thermal actuator. Methods/Statistical Analysis: To enhance the performance, the dependence of the in-plane resonant frequency and piezoresistive sensing mechanism on the electrical and mechanical design parameters of the actuator has been investigated. Especially, an in-depth analysis of the effect of the dimensional scaling and the surface doping concentration of the piezoresistor on the electromechanical response of the actuator were performed. The resonator structure and the joules heating induced actuation mechanism were efficiently modeled using a Finite Element Model (FEM) software simulation tool IntelliSuite®. Findings: Here, we devise a modified version of the thermally actuated dog-bone resonator with enhanced performance compared to the traditional designs reported in the literature. The simulation results show that the modified version of the thermally actuated resonator with an additional central beam depicts an improved in-plane extensional mode of resonant frequency by a factor of 2.55. It has been shown that the surface doping concentration of the piezoresistor plays a crucial role in determining the resonant frequency and the equivalent electrical signal by directly influencing the rate of heat generation by varying the drive current of the actuator. In addition, it has been also demonstrated that the doping concentration also plays an important role in determining the resultant magnitude of ΔR/R of the thermally driven actuator. Conclusion/Improvements: It has been demonstrated that the performance of the thermally actuated resonators improve with dimensional scaling. Moreover, the performance metrics of the thermally driven resonator with piezoresistive readout has been shown to have a strong dependence on the surface doping concentration of the piezoresistor.

Keywords

Dog-bone Actuator, Piezoresistive Readout, Surface Doping Concentration, Thermal Actuation

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