Design And Experiment For Enhancing The Sensitivity Of Piezoresistive Micro-Electromechanical Mechanical System (Mems) Cantilever By Introducing Stress Concentration Region (SCR)

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Date
2009-10
Authors
Sh Abdul Nasir, Sh Mohd Firdaus
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Abstract
The piezoresistive cantilever based MEMS (Micro-Electro-Mechanical System) sensors have been proven to be quite versatile devices in term of emerging applications from force/displacement sensing up to specific chemicallbiochemical detections. It is highly correlated with the stress that occurs as the cantilever deflects when a mass is applied and convert the sensed stress into voltage or current output. The challenge nowadays is to make the piezoresistive MEMS cantilever to be more sensitive so that it can detect smaller force or weight with high output value. There were three common approach that had been used by previous studies to enhance the MEMS device sensitivity; decreasing the device dimension, using low Young's modulus materials and by introducing stress concentration region (SCR). However most work in the previous studies involved only numerical investigation without fabrication. In this research, stress concentration region (SCR) approach has been selected to enhance the sensitivity of silicon based piezoresistive MEMS cantilever by using both simulation and experimental investigation. Four types of SCR geometry designs have been analyzed for stress distribution when a mass is applied to the cantilever by using ANSYS®. FEA results show that the rectangular SCR design has highest stress. Then length of rectangular SCR varied from lOOOlJm (AI) to SOOOlJm (AS) also has been studied for stress distribution along a selected path line. Due to fabrication process suitability, Piezoresistive MEMS cantilever with rectangular SCR A3 was selected for fabricated along with piezoresistive MEMS cantilever without SCR. From MultiSIMS® simulation, the sensitivity can be enhanced 2 times higher. Wheatstone bridge (WB) test for both fabricated cantilevers show that the sensitivity enhanced 1.97 times higher. The different between simulation and fabricated device testing sensitivity was 1.5%.
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Micro-Electro-Mechanical System sensors , have been proven to be quite versatile devices
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