(110) silicon etching for high aspect ratio comb structures

The characteristics of (110) silicon anisotropic bulk etching for fabrication of comb structure 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.%. The mechanism of beam reduction is also studied and modelled simply. Considering the etching characteristics, comb structure have been fabricated which are 8 μm wide, 150 μm high and separated by 7 μm gaps, using a comb mask pattern 10 μm wide with 5 μm gaps in 41 exact wt.% aqueous KOH solution at 65°C