>   1. After going through methods above, our results are still not good
enough to
>   be mirrors and v-grooves. We think the roughness may due to the
substrates (Si
>   wafer), there may be some defects inside. Therefore, please
recommand me some
>   wafer suplliers who can provide low defect wafers for MEMS bulk
micromachinig
>   purpose!!


I had very good experience with MEMC as a flexible, technologically
sound wafer supplier.  They have several types of wafers that may help
you with roughness after KOH etching, including low-oxygen wafers and
their special MDZ wafers that have a well-controlled denuded zone.  In
my experience, there does appear to be a link between crystal defects
(oxygen precipitates, stacking faults) and roughness after KOH etching.

Cheers,

Greg Mattiussi
Spectalis Corp.
greg@spectalis.com