Micro-morphology of single crystalline silicon surfaces during anisotropic wet chemical etching in KOH and TMAH

An optical microscopy study is presented of the micromorphology of silicon surfaces etched in KOH and TMAH, using large hemispherical specimen on which all possible surface orientations are present. Many of the features found on the silicon surfaces can be correlated with features of the etch rate as a function of surface orientation. The topics that are treated include: triangular and hexagonal shaped etch pits on Si{1 1 1}, spherical depressions and the occurrence of pyramidal protrusions on Si{1 0 0}, the occurrence of staircase or zigzag structures on Si{1 1 0} and the morphology of the transition regions between these three main silicon surfaces. Nowhere on any of the etched silicon hemispheres microscopically smooth surfaces can be observed.