Nam,
   We would use a jig of some sort.  I have tried to etch through using
a number of masking layers in the past, i.e. resists, metals, oxides.
They never seem to work.  As in one of the previous posts I would use a
teflon or peek jig. I think you can just buy them now so you will not
have to make your own.  I don't recall the vendor for such a product
though.

Good luck,
    Mike


>>> "Le Cao Hoai Nam"  08/27/06 3:46 AM >>>
Mike,

Thanks a lot for your prompt reply. Just one little question, how do
you
protect back side of the Si wafer when you etch for long time? If I am
not
wrong, from the etching set-up image, you etch the whole wafer, right?

Best regards,
Nam