Novel fabrication and characterization method of Fabry–Perot microcavity pressure sensors

Abstract

Micromachined Fabry–Perot microcavity structures have been investigated for use as pressure sensors. A combination of the bulk and the surface micromachining techniques with sacrificial layer processes has been adapted as a fabrication method. Output signal degradation as a function of pressure, `signal averaging effect', is observed. This is one of the primary obstacle in improving the device performance due to the bowing nature of the clamped diaphragm during deflection. This parasitic signal averaging effect is reduced by maximizing the ratio of the area of the deflecting top diaphragm to the area of the stationary bottom diaphragm, and consequently by enhancing the flatness of the deflecting diaphragm within the optically sampled area. The deflection behavior of the moving diaphragm is evaluated experimentally by a real-time, three-dimensional imaging method of a confocal scanning laser microscopy and theoretically by the analytical modeling of a planar, circular diaphragm.