The Crystal Structure of Silicon
Since TMAH is an anisotropic etchant, the structure etched in TMAH are usually
formed by several special planes of silicon. In order to get a good understanding
of TMAH etching, we should first know the crystal structure of silicon.
The crystal structure of silicon is that of the diamond type with lattice constant
a = 5.43A˙
. The structure is face centered cubic(FCC) but with two atoms in the
unit cell. The following figure shows the atom lattice of silicon and some facets of
the silicon crystal.