Hey Colleagues,

Recently, I observed residue after etching doped oxide by HF.  Two kinds of
films:

1. PSG deposited by LPCVD.  This film is used as the sacrificial layer.
After etching by HF (49%), a blanket-sheet-like residue stays on the sample
surface.  This can be removed by Piranha but Piranha is not good for my
device at this point.

2. Phosphorous doped LTO.  This film also leaves residue on the sample
surface after etched by HF.  This residue is not like a blanket.  There are
some spots sticking on pattern edges.

Did anybody come across the same problem?  Any help is highly appreciated.
Thanks.

Yahong

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