|
Micromachined Fabry-Perot microcavity structures have been investigated for use as pressure sensors. For the application of pressure sensors, the devices are categorized based on the shape and location of the deflecting diaphragm. Discussed here are planar bottom, planar top, and corrugated top diaphragm Fabry-Perot microcavity structures. Output signal degradation as a function of pressure, referred to as the signal averaging effect, caused by the non-planar deflection of an edge-clamped diaphragm, is reduced using planar top diaphragm structures, as compared to planar bottom diaphragm structures. This is achieved by improving the flatness of the deflecting diaphragm in the optically sampled area of the planar top diaphragm structures by adjusting the ratio of the top diaphragm area to the bottom diaphragm area. Corrugation of the top diaphragm structure further enhances flat deflection. However, the corrugated structures induce a static deflection of the diaphragm due to localized internal stress generated by the asymmetry of the corrugation on the diaphragm, referred to as the zero- pressure offset effect. The existence and influence of these parasitic effects have been observed using real-time measurements of the diaphragm deflection.
|
