LAUSR

The etching process of monocrystalline silicon in potassium hydroxide solution with addition of Triton X-100 surfactant at different temperatures is studied. It is shown that decreasing the temperature lowers etch rates and improves surface morphology of Si (hkl) planes. Based on Arrhenius plots of etch rates, activation energies for Si (100) and (110) planes are determined. The obtained activation energies are lower than the ones for pure KOH solutions, reported in the literature. The possible explanation of this phenomenon, based on the temperature dependence of surfactant adsorption, is presented. Besides, it is established that the convex corners of microstructures etched at different temperatures are slightly curved, probably formed by planes vicinal to {221} plane. Furthermore, the {110} sidewalls inclined at 45° to Si (100) substrate are characterized by low surface roughness in a whole range of considered temperatures (60–90 °C). Thus, the {110} sidewalls could be used as MEMS micromirrors for reflecting light beam at an angle of 90°. It is indicated that the KOH solution containing Triton X-100 is of particular interest for fabrication of elongated mesa structures containing 45° micromirrors and waveguides concurrently.