[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/spl deg/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 /spl mu/m wide, 150 /spl mu/m high and separated by 7 /spl mu/m gaps, using a comb mask pattern 10 /spl mu/m wide with 5 /spl mu/m gaps in 41 exact wt.% aqueous KOH solution at 65/spl deg/C.