Wet chemical etching of silicon {1 1 1}: Etch pit analysis by the Lichtfigur method

The Lichtfigur method is introduced to determine the average pit morphology of etched silicon surfaces. It is an effective method in surface analysis complementary to optical microscopy. The surface morphology of silicon {1 1 1} after wet chemical etching in aqueous KOH solution has been investigated by this technique. The morphology does not change significantly in pure KOH solutions as a function of time. In solutions containing additive isopropanol, however, the etch pits evolve from circular to triangular, with a final shape that depends on the isopropanol concentration. It has been experimentally proven that the IPA additive does not participate in the etching reaction and no etching occurs in the absence of water, which implies that OH− only serves as a catalyst.