Hello Yahong,
Is this film insulating or conductive? HF solutions typically contain high
quantities of metal impurities, which can be deposited by photoelectric
reactions on the silicon underlying the target oxide layer. Perhaps this is what
is happening to your devices? It
would be consistent with the successful removal by piranha etch.
Try covering your sample with a darkened beaker during the etch to see if this
solves the problem. You may find it useful to use a lower concentration HF
etchant when doing this, so that the time the sample is uncovered during
insertion and removal is a small
percentage of the etch time.
Good luck!
-Craig McGray
Dartmouth College
[email protected] wrote:
> 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