I.A. Shah,
A.J.J. Koekkoek, W.J.P. van Enckevort, E. Vlieg
Influence of
additives on alkaline etching of silicon (111)
Cryst. Growth Des. 9 (2009) 4315-4323
Abstract:
Apart from temperature and alkaline
concentration, the surface morphology of silicon surfaces after wet
chemical etching is also profoundly influenced by the presence of
additives in the etchant solution. In this study, the influence of
several organic (aprotic, protic, and ionic) additives on the density
and shape of etch pits on etched Si-(111) surfaces is investigated
using optical microscopy and the Lichtfigur technique. For all the
additives used, the number density of the pits increases by 1−3 orders
of magnitude. The triangularity of the pit shape, expressed by a
dimensionless number, Rab, increases substantially as well. These
alterations are attributed to local desolvation of reaction products by
the organic additives in a thin “surfactant” layer in the vicinity of
the silicon surface. Chemisorption of additive molecules does not play
a role in this process.