Anisotropic etching rates of single-crystal silicon for TMAH water solution as a function of crystallographic orientation

We evaluated orientation dependence in the etching rate of single-crystal s ilicon for tetramethyl-ammonium-hydroxide (TMAH) water solutions. Etching r ates for a number of crystallographic orientations were measured for a wide range of etching conditions, including TMAH concentrations of 10-25% and t emperatures of 70-90 degrees C. We found significantly different characteri stics from those for KOH water solutions. Firstly, different types of orien tation dependence in etching rate were found around (111) between TMAH and KOH. This means the bonding energy of the silicon crystal lattice is not a single factor that dominates orientation dependence, and there exist differ ent etching mechanisms for the two etchants. Secondly, effects of the circu lation of etchants on the etching rates were not negligible in TMAH in cont rast to KOH system. (C) 1999 Elsevier Science S.A. All rights reserved.