Effects of alcoholic moderators on anisotropic etching of silicon in aqueous potassium hydroxide solutions

The etching rates on the Si-(1 0 0) and Si-(1 1 0) planes at various temperatures and concentrations of a KOH/alcoholic moderator (glycerol, ethylene glycerol, 1,2-propanediol, 1,3-propanediol, isopropanol (IPA), or 1,5-pentanediol) were measured. In addition, the sequential development of holes through a circle mask of the Si (10 0) with various etchants and times was observed by using scanning electronic microscopy (SEM). The effect of the added alcoholic moderators to the KOH solution was more pronounced on the etching of the Si (110) plane, especially with the addition of IPA and 1,5-pentanediol. The addition of 1,5-pentanediol to the KOH solution resulted in an improvement in the etching anisotropy as well as in a smoother etched Si (10 0) surface than with the addition of IPA to the KOH solution. The other advantage of using KOH/1,5-pentanediol as etchant was that it could be used at higher temperatures (more than 80degreesC); where the IPA had an evaporation problem. (C) 2004 Elsevier B.V. All rights reserved.