A bulk silicon dissolved wafer process for microelectromechanical devices

A single-sided bulk silicon dissolved wafer process that has been used to fabricate several different micromechanical structures is described. It involves the simultaneous processing of a glass wafer and a silicon wafer, which are eventually bonded together electrostatically. The silicon wafer is then dissolved to leave heavily boron doped devices attached to the glass substrate. Overhanging features can be fabricated without additional masking steps. It is also possible to fabricate elements with thickness-to-width aspect ratios in excess of 10:1. Measurements of various kinds of laterally driven comb structures processed in this manner, some of which are intended for application in a scanning thermal profilometer, are described. They comprise shuttle masses supported by beams that are 160-360 μm long, 1-3 μm wide, and 3-10 μm thick. Some of the shuttles are mounted with probes that overhang the edge of the die by 250 μm. Resonant frequencies from 18 to 100 kHz and peak-to-peak displacements up to 18 μm have been measured