The effect of alcohol additives on etching characteristics in KOH solutions

Different alcohol additives to KOH solution have been studied. It was stated that the alcohols result in changing silicon etching anisotropy. The alcohols with one hydroxyl group exhibited similar effect as isopropyl alcohol. They caused strong reduction of etch rates of (h h 1) type planes, usually developing at the side-walls of etched convex figures. This was the reason of the reduction of convex corner undercut. The alcohols with more than one hydroxyl group did not influence the etching anisotropy and caused deterioration of surface finish. The connection of alcohol properties with (h h 1) etch rate reduction have been analysed. It has been stated that the advantageous effect of the alcohols from propanol and butanol groups is connected with their low surface tension. (C) 2002 Elsevier Science B.V. All rights reserved.