Etch rates of (100), (111) and (110) single-crystal silicon in TMAH measured in situ by laser reflectance interferometry

Abstract

Laser reflectance interferometry has been used to measure in situ etch rates of (100), (110) and (111) single-crystal silicon planes in 5–35 wt.% tetramethyl ammonium hydroxide (TMAH) solutions. The laser reflectance method was seen to give very accurate etch rates for samples that developed a surface roughness lower than 100 nm during the experiments. The etch rate of (100) and (111) was found to decrease with increasing etchant concentration, while the highest and lowest etch rates of (110) were observed for the 25 and 15 wt.% solutions, respectively. Activation energies were calculated as 0.54–0.59 eV for the 20–35 wt.% solutions, about 0.54 eV for the 25–35 wt.% solutions and 0.50–0.54 eV for the 25–35 wt.% solutions for the (100), (111) and (110) crystal orientation, respectively.