Chemistry Reference
In-Depth Information
the surface is roughened first by mechanical grinding with sandpaper or by electro-
chemical polarization at a higher potential. A rough surface provides the sites with small
radius of curvature for the initial preferential dissolution because electrochemical reac-
tions on semiconductor surface are sensitive to surface curvature.
8
Different silicon
materials show different sensitivity toward scratches of different sizes and sharpness.
A certain amount of uniform dissolution may occur prior to and during the initi-
ation of pores. For example, as reported in one study, before the formation of the macro-
p-
Si(
pores on lowly doped 100) in anhydrous HF-MeCN solutions the entire surface
is etched forming (111) facets of about Pores then start to grow at the base of
these facets. Once macropores are developed the surface etch rate is greatly reduced,
by a factor of 4.
