International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395 -0056
Volume: 04 Issue: 02 | Feb -2017
p-ISSN: 2395-0072
www.irjet.net
Finite Element Analysis of MEMS based Piezoresistive Diamond Thin Film Cantilever Pressure Sensor Harini Mathur1, Vimal Agarwal2, Kanchan Sengar3 Dept. of ECE, JECRC University, Jaipur, Rajasthan, India Professor, Dean Academics, Apex Institute of Technology, Jaipur, Rajasthan, India 3 Assistant Professor, Dept. of ECE Engineering, JECRC University, Jaipur, Rajasthan, India
2Associate
1Scholar,
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Abstract - MEMS (Micro-Electro-Mechanical Systems)
technology is an emerging technology, now-a-days, which consists of both electrical and mechanical components integrated on the same chip. The main objective of this paper is to design and simulate the cantilever based pressure sensor using MEMS technology. Performance parameters such as stress, deflection and sensitivity has been studied and compared for the cantilever using different materials i.e. diamond and poly-silicon. Ultrananocrystalline diamond (UNCD) technology may be used for producing diamond thin film (DTF). Four piezoresistors of p-type silicon are incorporated on the sensor in wheat stone bridge configuration. The stress is being induced in the structure, on the application of external pressure, which changes the electrical resistance of the piezoresistor. The output voltage is then calculated from the change in resistance. The simulated results depicts that cantilever designed with DTF gives sensitivity of 6.92 × 10-10mΩ/kPa which is higher as compared to the cantilever designed with poly-silicon. The simulation is done using software COMSOL Multiphysics 4.4. Key Words: MEMS pressure sensor, cantilever, stress, deflection, sensitivity, UNCD, DTF.
1.INTRODUCTION Micro Electro Mechanical System (MEMS) pressure sensors play a vital role in both industrial as well as commercial sector. A pressure sensor is a device which is used to measure pressure, acts as a transducer generating a signal as a function of the pressure [1]. The study of micro-cantilevers is one of the most important application of the MEMS technology. Nallathambi [2] discussed design which uses finite element analysis to simulate the geometrical specifications for poly silicon placed piezoresistive micro cantilevers sensor. The displacements and the variation of the change in the resistance to the original resistance of the cantilevers were also examined. Abdul-Aziz Yousif Ahmed et al. [3] analyzed the existing commercial sensing technology which shows that micro cantilever sensors must satisfy the variable properties such as better sensitivity, cheaper cost, smaller in size and reliability.
sensitivity of the sensor depends upon the various parameters such as shape and size of the cantilever, material of cantilever, placement of the piezoresistors etc. The parameter taken in the respective simulation is the selection of the material. In the first simulation, cantilever is designed using polysilicon as a material. The stress, resistance and the sensitivity is calculated. In the second simulation, cantilever is designed using diamond thin film (DTF) as a material on the silicon base. Similarly stress, resistance and sensitivity is determined. The results of both the studies are then compared. The simulation is done using COMSOL Multiphysics 4.4. The final results show that the cantilever designed with DTF gives higher sensitivity as compared to cantilever designed with poly-silicon.
2. MEMS PIEZORESISTIVE SENSORS 2.1 Piezo Resistive Effect The piezo-resistive effect can be defined as the variation of the change in electrical resistance to the original resistance on the application of force to the resistor. It is expressed by the given equation 1, (1) where
G = Gauge Factor ΔR = Change in Resistance R = Original Resistance ς = Stress Induced The resistance R of a resistor of length L, width W, thickness t and the resistivity , is expressed by the relation, (2) where
ρ = Resistivity of the Material L = Length W = Width and t = Thickness
The main objective of this paper is to design a cantilever based pressure sensor with higher sensitivity. The © 2017, IRJET
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