Anisotropic Bulk Etching of (110) Silicon with High Aspect Ratio

Abstract

The characteristics of (110) silicon anisotropic bulk etching are studied with varied temperature and concentration of aqueous KOH solution. The etch rates of (110) and (111) planes increase with increasing temperature but decrease with increasing concentration. The maximum etch rate ratio is above 150 at 45 exact wt.% and 60°C of aqueous KOH solution. Surface roughness varies greatly with concentration, and the minimum roughness is observed in an aqueous KOH solution of 41 exact wt.%. In 41 exact wt.% aqueous KOH solution at 65°C, comb structure have been fabricated which are 8μm wide, 150μm high and separated by 7μm gaps, using a comb mask pattern 10μm wide with 5μm gaps.