Hi

We use wet etching for sacrificial etching of oxide
followed by supercritical CO2 drying.
For the wet etch, we use a solution of 2 Buffered HF:1
glycerol because of exposed Al contact pads. Following
the etch, we rinse the sample in glycerol, DI water
and then IPA. However, we observed during the methanol
rinse, some form of crystals are formed on the surface
of the sample, which stay even after drying.
Sometimes, a little longer etch helps to get rid of
some of it, but not all.
I wanted to ask if anyone else has observed the same
and has some solution for it.
Also, we think it is because of glycerol residues
which is difficult to rinse away. Has anyone worked
with a lower glycerol concentration, and does it
shield the Al pads well?
Also, we were consdiering removing these crystals by a
O2 plasma etch. Is that recommended? Please suggest.

Thanks,
Anshu Mehta.

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