Micro-morphology of single crystalline silicon surfaces during anisotropicwet chemical etching in KOH: velocity source forests

For silicon etched in KOH the micro-morphology of any surface, no matter th e crystallographic orientation, is defined by some sort of persistent corru gations. As a matter of principle, the occurrence of these corrugations is incompatible with the classical kinematic wave theory for the evolution of crystal shapes. Either the re-entrant or the protruding edges or vertices a re stabilized by some mechanism that is not accounted for in the microscopi c etch rate function, i.e. are velocity sources. Exact Si{1 1 1 } surfaces are dominated by etch pits caused by edge dislocations corresponding to oxy gen-induced stacking faults. Exact Si{1 0 0} surfaces are dominated by circ ular indentations, probably owing to fast etching of accumulations of point defects. On exact and vicinal Si{1 0 0}, also pyramidal protrusions are fo und, which, we hypothesize, are formed and stabilized by silicate particles adhering to the surface. Exact and vicinal Si{1 1 0} surfaces are dominate d by a zigzag pattern at low KOH concentration and a hillock pattern at hig h KOH concentration, which, we hypothesize, are also the result of the pres ence of silicate particles, created during etching, on the surface. Vicinal Si{1 0 0} and Si{1 1 1} surfaces, finally, are dominated by step bunching patterns, probably owing to time-dependent impurity adsorption. (C) 2001 El sevier Science B.V. All rights reserved.