Silicon anisotropic etching in TMAH solutions containing alcohol and surfactant additives

Wet chemical etching of Si(1 0 0) and Si(1 1 0) wafers in TMAH solutions containing Triton X-100 and alcohol additives was studied in a wide range of alcohol concentrations. TMAH solutions containing butanol-2 and ternary solutions composed of TMAH + Triton + alcohol, used in the experiments, had not been investigated before. The phenomena associated with the presence of surfactant and alcohol additives in etching solutions were analyzed and the mechanism including co-solving of surfactant molecules in alcohol and interplay in the adsorbing mechanism was proposed. The influence of these phenomena on the etching rates and morphologies of Si(1 0 0) and Si(1 1 0) was discussed. The addition of alcohol, especially butanol-2, to a TMAH solution resulted in significant improvement of the etched surface finish. The roughness of Si(1 1 0) surfaces etched in TMAH + butanol solutions was superior to the roughness of the surfaces etched in TMAH + Triton. The best surface roughness parameters of Si(1 1 0) (Ra = 0.0322 μm and RMS = 0.0549 μm), measured with an optical profilometer on the area of 1.6 mm × 1.6 mm, were achieved after etching in a ternary solution of TMAH + Triton + butanol. This solution appears to be a good candidate in applications where high quality finish of etched surfaces is required on a substantially high area.