<title>Anisotropic etching of (111)-oriented silicon and applications</title>

Abstract

Anisotropic etching characteristics of (111)-oriented silicon in alkaline solutions was studied. Through a spoke pattern, it was found that (110) planes have the highest etching rate rather than high-index ones such as (211) or (331). With a round open, the final emergent periphery is hexagonal. The six sidewalls are defined by other (111) facets from its crystal geometry with three inclining angles of 70.5 degrees and another three declining angles of 109.5 degrees. The etched bottom surface morphology was also investigated by SEM pictures observation. Results show that aqueous KOH solution results in smooth surface due to its higher etching rate of residual oxide existed in the silicon, while the other etchants such as hydrazine (N2H4) and tetramethyl ammonium hydroxide (TMAH) induce seriously wavy roughness. As an application example, floating single-crystal silicon (c-Si) structures were fabricated with some potential functions as thermopile, silicon bolometer, mass flow transducer and other force microsensors.© (1998) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.