HF vapour etching is isotropic, so etching square 10µm x 10µm holes 10µm
deep is not possible. What you would get is at best a 20µm circular hole.

I'm currently using this process to release fragile MEMS structures with
some success. It should be noted, that the only thing you need is a
container of 40% HF and a way to suspend your wafer above it (etch-side
down) in a fumehood- I use a PTFE/Teflon cylindrical shell with a
slightly smaller internal diameter than my wafer, which any workshop can
make. The etch rate is about 200nm/minute. We use 1.5µm AZ resist, but I
can't tell you if that's the best solution. It seems OK for 10µm etches
though.

// Morten

Daniel Drysdale wrote:
> Hi James, have you considered HF vapour etching? I know it is pretty useful
for SiO2 etching though I am unsure how your resist will react to the HF vapour.
There are a couple of companies that I know of that deal with this.. One based
at Livingston and also within Edinburgh University at their SMC building is
MEMSSTAR who do this kind of work. As I say, I am unsure of the reaction that
the vapour would have with the HF but its a possibility i guess.