Hi everybody,

I m working on micromachining of Si (100) substrate using KOH and the
problem I have to face is to achieve smooth (mirror-like) 111 surface
for V-shapped grooves. For the moment, we obtain 111 surfaces with
scratches and vortex-like holes.
We think that our substrate is well oriented because we use a
pre-etching process.
Our reflections deal with :
1) Si substrate: do you know suppliers who have excellent
cristallographic quality and impurity free substrates (suppliers
dedicated for MEMS) ?
2) KOH etching rate : is increased etching rate makes 111 surfaces
smoother ? Which temperature must we try ?
3) What s the best concentration for KOH bath ?
4) Our etch mask is thermally grown SiO2 (1050°). Is there problems
whith thermally growm SiO2 during etching ? Is there impurity diffusion,
or dislacation creation during oxidation which can explain our scratches
and vortex-like holes ? Is there any advantage to use SiO2 / Si3N4
deposited by-layer?

And have you got others informations, explanations, experiences on this
problem ? May be some publications ?

Thanks a lot !