3-DIMENSIONAL MICROMACHINING OF SILICON PRESSURE SENSOR INTEGRATING RESONANT STRAIN-GAUGE ON DIAPHRAGM

A method of fabricating a novel pressure sensor is presented. The sensor has resonant strain gauges built into micro vacuum cavities on the surface of the diaphragm. The resonant strain gauge has a resonator the natural frequency of which is modulated by the strain in the diaphragm surface. The resonator and the vacuum cavity of the strain gauge are fabricated by a self-aligning selective epitaxial method and a hybrid selective etching method; a unique vacuum-sealing technique is used to make the vacuum cavity. © 1990.