Dear all,

I try to do isotropic etching in quartz (fused silica, to be more
precise) with HF. It has been very hard to mask, but recently I
succeeded with the masking step. But then the profiles where quite
different than suspected.

The mask patterns are either straight lines or circular holes. I had
expected the profiles to be similar to that of HNA etching in silicon,
rounded pits that (in the case of the circular holes) expand as ever
larger half spheres around the etch hole. But instead of this I see
almost totally straight sidewalls and flat bottom.

Can this be due to lack of agitation? When you lack agitation in HNA
silicon etching you will get a flat bottom, but always somewhat
rounded sidewalls.

Can it be a material issue? Is there perhaps a very specific material
requirement for isotropic quartz etching that I have missed?

regards,

Sven