Hello,

We are making devices that involve the bonding of two centimeter-scale chips
and the subsequent removal of oxide from in between them. Since all the
etchant must come in from the sides, we're having problems with getting rid
of all the oxide. In between the two chips are 2 um pillars that effectively
serve as spacers, so our geometry, from top to bottom, is basically a top
chip, a 2 um air gap, an oxide layer on the bottom chip that we want
removed, and the rest of the bottom chip. Does anyone have experience in
etching oxide in places where HF might have trouble getting to?

Thanks a bunch!
Patrick Lu