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The mechanical behaviour of silicon diaphragms for micromachined capacitive pressure sensor

Research output: Contribution to journalJournal articlepeer-review

Published
<mark>Journal publication date</mark>2008
<mark>Journal</mark>Advances in Science and Technology
Volume54
Number of pages6
Pages (from-to)422-427
Publication StatusPublished
<mark>Original language</mark>English

Abstract

Single crystal silicon diaphragms are widely used as pressure sensitive elements in micromachined pressure sensors. When designing such a sensor it is usual to assume that the silicon is an isotropic material and the average elastic constants are used. However, the mechanical properties of single crystal silicon are orthotropic, and this has an important effect on the mechanical behaviour of silicon diaphragms under pressure. In this work, the deflections of orthotropic silicon circular diaphragms which are orientated against the (100) and the (110) planes are presented. It is found that by assuming silicon is isotropic material, the maximum stress is underestimated by 9.4% for (110) orientated silicon diaphragms, while the maximum stress is underestimated by 8% for (100) orientated silicon diaphragms. Therefore, when a silicon diaphragm is used in a MEMS sensor, the orthotropic properties should be taken into account for accuracy. Finally, the performance of a capacitive sensor is predicted by using finite element method.