A bulk silicon dissolved wafer process for microelectromechanical systems

The authors describe a single-sided bulk silicon dissolved wafer process that has been used to fabricate several different micromechanical devices. It involves the simultaneous processing of glass and silicon wafers, which are eventually bonded together electrostatically before being etched to leave heavily boron-doped devices attached to a glass substrate. The process requires a minimum of three masks: two for the silicon wafers to define the microstructures, and one for the glass wafers to define the interconnect and lead transfer to these devices. Overhanging features can be fabricated without any additional masking steps. The authors also describe the measurements of three kinds of laterally driven comb structures fabricated for application in a scanning thermal profilometer. They comprise shuttle masses supported by 200- mu m long beams, and mounted with probes that extend 250 mu m past the edge of the die. Devices with beam thicknesses of 3.7 mu m and 6.4 mu m yield measured resonant frequencies between 32 and 46 kHz, and peak-to-peak displacements exceeding 18 mu m.<>