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.

1. Y. Kanda, A graphical representation of the piezoresistance coefficients in silicon,IEEE Transactions on Electron Devices ED-29 (1982) 64–70. R. Nicole, "Title of paper with only first word capitalized," J. Name Stand. Abbrev. , in press.
2. Y. Yorozu, M. Hirano, K. Oka, and Y. Tagawa, "Electron spectroscopy studies on magneto-optical media and plastic substrate interface," IEEE Transl. J. Magn. Japan, vol. 2, pp. 740–741, August 1987 [Digests 9th Annual Conf. Magnetics Japan, p. 301, 1982].
3. Y. Kanda, A graphical representation of the piezoresistance coefficients in silicon,IEEE Transactions on Electron Devices ED-29 (1982) 64–70.
4. J. -S. Park, Y. B. Gianchandani, A servo-controlled capacitive pressure sensor using a capped-cylinder structure microfabricated by a three-mask process, Journal of Microelectromechanical Systems 12 (2003) 209–220.
5. K. Kasten, J. Amelung, W. Mokwa, CMOS-compatible capacitive high temperature pressure sensors, Sensors and Actuators 85 (2000) 147–152.
6. C. Kolle,W. Scherr, D. Hammerschmidt, G. Pichler,M. Motz, B. Schaffer, B. Forster, U. Ausserlechner, Ultra low-power monolithically integrated capacitive pressure sensor for tirepressuremonitoring, in: Proceedings of IEEE Sensors, Vienna, Austria, 24–27 October 2004, 2004, pp. 244–247.
7. M. Habibi, E. Lueder, T. Kallfass, D. Horst, A surface micromachined capacitive absolute pressure sensor array on a glass substrate, Sensors and Actuators A 46–47 (1995) 125–128.
8. U. Paschen, M. Leineweber, J. Amelung, M. Schmidt, G. Zimmer, A novel tactile sensor system for heavy-load applications based on an integrated capacitive pressure sensor, Sensors and Actuators A 68 (1998) 294–298.
9. W. H. Ko,Q. Wang, Touchmode capacitive pressure sensor, Sensors andActuators 75 (1999) 242–251.
10. P. Dimitropoulos, C. Kachris, D. Karampatzakis, G. Stamoulis, A new SOI monolithic capacitive sensor for absolute and differential pressure measurements, Sensors and Actuators A 123–124 (2005) 36–43.
11. S. T. Moe, K. Schjølberg-Henriksen, D. T. Wand, E. Lund, J. Nysæther, L. Furuberg,M. Visser, T. Fallet, R. W. Bernstein, Capacitive differential pressure sensors for harsh environments, Sensors and Actuators A 83 (2000) 30–33.
12. R. Puers, Capacitive sensors: when and howto use them, Sensors and Actuators A 37–38 (1993) 93–105.
13. A. V. Chavan, K. D. Wise, Batch-processed vacuum-sealed capacitive pressure sensors, Journal of Microelectromechanical Systems 4 (10) (2001) 580–588.
14. B. Puers, E. Peeters, A. van den Bossche,W. Sansen, A capacitive pressure sensor with low impedance output and active suppression of parasitic effects, Sensors and Actuators A 21–23 (1990) 108–114.
15. W. C. Young and R. G. Budynas "Roark's formulas for stress and strain" by (Mc Graw Hill)
16. Tai Ran Hsu "Mems and Microsystems" Tata McGraw-Hill 2002.

Capacitive Pressure Sensor Mems Finite Element Method (fem) Si Polysi Sic Absolute Pressure