A Study of Silicon based MEMS Capacitive Sensor for Absolute Pressure Measurement of a Specific Range

In this paper two MEMS capacitive pressure sensor of two diffident geometries are designed for measurement of absolute pressure. Both of these sensors are designed as parallel plates where one is movable and the other is fixed. The only difference with common parallel plate structure is that one of the movable plates is supported by four anchors with respect to the fixed plate. Here we have considered two such structures, one having square shaped parallel plates whereas the other having circular shaped. The area of the diaphragms for both the sensors are equal and will perform to sense absolute pressure variations for a very specific range. This specified range of absolute pressure is 10 KPa to 100 KPa for 5 micron thick diaphragm with 3600 micrometer area. Here silicon and silicon compound (like PolySi and SiC) are chosen for diaphragm material. In this paper various factors which play a critical role for measuring absolute pressure in the performance of a MEMS capacitive pressure sensor are discussed. Factors like length, radius, thickness, distance between two plates and shape and more above the selection of diaphragm materials are taken into consideration for the efficiency of the sensor. Mechanical, electromechanical as well as material studies were performed in the Finite Element Method based Multiphysics simulation platform. In this paper two same area different shape micro sensors are designed and their comparative study is analyzed with different silicon compound. This type of absolute pressure measuring sensor can be used for pulse rate measurement.