Method for forming thin silicon membrane or beam

Abstract

A method is disclosed for forming thin, suspended membranes of epitaxial silicon material. Silicon oxide strips having a predetermined thickness are first formed on a silicon substrate. The gap, or spacing, between adjaceant beams is preferably less than or equal to about 1.4 times the thickness of the silicon oxide strip. The underlying silicon substrate is exposed within these gaps in the silicon oxide layer, thereby the gaps provide a seed hole for subsequent epitaxial growth from the silicon substrate. Epitaxial silicon is grown through the seed holes and then allowed to grow laterally over the silicon oxide strips to form a continuous layer of epitaxial silicon over the silicon oxide strips. The backside of the silicon substrate, or surface opposite the surface having the silicon oxide strips, is then masked to delineate the desired diaphragm and microbridge pattern. The silicon is etched conventionally from the backside. Etching is substantially terminated automatically by the presence of the silicon oxide strips. The thin, single crystal silicon membranes are suitable for use as diaphragms and microbridges in a microaccelerometers or pressure sensor.