Potassium hydroxide (KOH) creates anisotropic silicon etch profiles that follow the natural crystal orientation of the wafer. Because KOH etches silicon at different rates along crystal planes, engineers can form well-defined cavities, V-grooves, and angled sidewalls with excellent dimensional control. That makes KOH a frequent choice when a design calls for deep cavities, suspended membranes, or precisely defined structural features, with consistent etch rates and smooth silicon surfaces across the wafer. LPCVD silicon nitride often serves as the etch mask for KOH processing. Patterned nitride protects selected regions of the wafer while exposed silicon etches along crystallographic planes, producing predictable sidewall angles and complex device geometries with high precision. KOH etches with crystal-plane precision. Exposed silicon etches along the (111) planes at 54.74°, forming self-terminating V-grooves or timed flat-bottom cavities beneath a patterned LPCVD silicon nitride mask.
