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International Research Journal of Engineering and Technology (IRJET) e-ISSN: 2395-0056 Volume: 11 Issue: 05 | May 2024

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p-ISSN: 2395-0072

A Review of MEMS based Capacitive Pressure Sensor Uday Singh1, Kamalesh Singh2, Dr. Vikas Nehra3, Dr. Kusum Dalal4 1B.Tech Student, Department of Electronics and Communication Engineering, Deenbandhu Chhotu Ram University

of Science and Technology (DCRUST), Murthal, Sonipat, Haryana, India

2Scientist/ Engineer ‘SD’, Semi-Conductor Laboratory, S.A.S Nagar, Punjab, India

3Assistant Professor, Department of Electronics and Communication Engineering, DCRUST, Murthal, Sonipat,

Haryana, India

4Assistant Professor, Department of Electronics and Communication Engineering, DCRUST, Murthal, Sonipat,

Haryana, India ---------------------------------------------------------------------***-------------------------------------------------------------------

Abstract: This paper presents a review of the capacitive

applications. The current pressure sensors are being used in the pressure range from a few Pascals to mega Pascals. The sensors are to being used in the temperature ranges between – 25 oC to 125 oC and advancements are being made to operate the sensors above 600 oC. Among the various pressure sensors, piezoresistive and capacitive sensors are widely used. Piezoresistive pressure sensors provide high sensitivity, and they have linear operation for a wide range of pressure. Capacitive pressure sensors are preferred as they provide high sensitivity and the change due to temperature is very small. MEMS pressure sensors include a flexible diaphragm that deforms on the application of pressure, and this deformation is converted to an electrical signal, generally voltage or digital signals. Bulk micromachining is generally used to create the silicon membrane in the pressure sensors. Piezoresistors are patterned across the diaphragm. The sensor is generally designed and packaged so that the topside of the diaphragm is exposed to the environment for the application of pressure. (Balavalad et al., 2015) The change in pressure forces a deformation of the diaphragm; this deformation results in a change in resistance of the piezoresistors and, in turn, a change in voltage by on-chip electronics (Wheatstone bridge). Capacitive sensors consist of a fixed electrode and a movable electrode, The movable electrode displaces under the applied pressure, which results in a change in capacitance. The change in capacitance depicts the applied pressure.

pressure sensor. Firstly, the different types of sensors available are compared. For applications requiring high sensitivity and very low effects due to temperature, the capacitive sensor is preferred. Various methods to change the capacitance are also compared, which leads to the conclusion that the method involving changing the distance between the plates has the highest sensitivity. The different diaphragms available are also compared in this paper. The result of the comparison shows that the square diaphragm is most suitable. Further study shows that the diaphragm with a bossed structure has the highest sensitivity and the lowest nonlinearity. After the structural analysis, the pull-in effect phenomenon present during anodic bonding is also studied. The analysis of the pull-in effect showed that the dimension of the sensor should be chosen such that the electrodes do not stick during the anodic bonding. Different capacitive sensing schemes are also shown in this paper. The parasitic capacitances and the noise are major factors limiting the performance of the sensor. So the sources and methods to mitigate such effects are also presented. The ASICs available for the conversion of the capacitance to voltage or digital output are compared based on different parameters. Key words: Capacitive pressure sensor, sensitivity, nonlinearity, bossed diaphragm, pull-in effect, differential structure, capacitance to voltage circuit

1. INTRODUCTION

This paper aims to provide a review of the technological advancements in pressure sensor technology. The main focus of this paper is the capacitive pressure sensor, the advancements in its structure, and various factors affecting its design.

MEMS stands for microelectromechanical systems. MEMS technology combines microelectronics and mechanical systems. MEMS sensors and actuators are used in almost every modern system. MEMS sensors have accommodated a major part of the sensor market in recent years and are fast developing with new capabilities. The MEMS pressure sensors are being used in various areas like biomedical, defence, automobile, consumer products, industries, and many more civilian and domestic applications. MEMS pressure sensors claim 72% of revenue, medical electronics at 12%, industry segments at 10%, and the rest 6%, split between consumer electronics and military/aerospace

Impact Factor value: 8.226

2. Evolution of the mems pressure sensor 2.1 Strain Gauge Sensors The first developed pressure sensors was a metal strain gauge. This sensor is still being widely used in the mechanical transducers used in the industries. These

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