Hi
References are missing, please send the mail again.
Kim


On Mon, 20 Apr 2009 Prem Pal wrote :
>Dear Kim
>
>As Andrea suggested you can use HNA for making the circular grooves. In wet
etchants, it is not possible to etches circular masking shapes (or other shapes)
with vertical sidewalls due to crystallographic limitation of silicon. If the
sidewalls is not a issue, you can use surfactant (NC-200, PEG, Triton-X-100)
added 25 TMAH in order to etch any shapes of masking pattern with negligible
undercutting at the rounded and sharp corners, curved and <100> edges. Recently
some studies of TMAH+surfactant have been published  for the fabrication of new
shapes of structures. Some of the references are given below: