Overhung electrostatic microgripper

A monolithic microgripper unit suitable for mounting on a micropositioner has been designed and fabricated by a combination of surface and bulk micromachining. The unit consists of a silicon die (7*5 mm), a 1.5-mm-long support cantilever made from p/sup +/-substrate material and protruding from the die, and a 400- mu m-long polysilicon microgripper attached at the end of the support cantilever. The microgripper is electrostatically driven by flexible, interdigitated comb pairs. The microgripper has significantly smaller feature sizes than previously reported surface- and bulk-micromachined structures. Problems addressed successfully in the microgripper fabrication include the protection of surface-micromachined fine structures during etching and rinsing. Embedding the polysilicon structures in PSG (phosphosilicate glass) film during etching in EPW, introducing break lines to the PSG membrane, and partial blocking of liquid flow during final PSG etching and rinsing in DI water have been the keys to a successful fabrication sequence.<>