Electrochemical etching in HF solution for silicon micromachining

Electrochemical etching of silicon in hydrofluoric acid (HF) solution is employed as a micromachining technique. It is demonstrated that the commonly accepted geometric constraints on the shape of electrochemically etched silicon structures can be significantly relaxed. Several new structures etched on the same n-doped silicon wafer are reported. The fabricated structures include wall arrays, hole arrays, meander-shaped structures, spiral-like walls, microtubes, micropillars, microtips and more. A simple model for the electrochemical etch process, which describes the effect of the dimension of the initial seed, the current density, and also the KOH etching time of the initial pattern on the final geometries, is detailed.