Hi,

        I would add some inputs here. I don't know if Cr can be etched in
highly concentrated HF or not. If it is merely lifted off from the
substrate, you should see a lot of Cr flakes in the HF bath. Even your
features are in mm scale, undiluted 49% HF can still etch SiO2 very fast.
Another thing you may have overlooked is wet etchant has tendency in
penetrating the interface between the masking material and the underlying
material being etched, due to surface tension.  If you dilute your HF with
NH4F, it should solve your problem. Besides, your SiO2 layer is thin, you
probably don't need concentrated HF. You are welcome to contact me if you
have questions.


Yours sincerely,

Isaac Chan

Ph.D. Candidate
Dept. Electrical & Computer Engineering
University of Waterloo
200 University Ave. W
Waterloo, Ontario, Canada
N2L 3G1
Tel: (519) 888-4567, ext. 6014
Fax: (519) 746-6321
iwchan@venus.uwaterloo.ca
http://www.ece.uwaterloo.ca/~a-sidic


On Mon, 10 Nov 2003, Yilei Zhang wrote:

> Hi all,
> I just finished one experiment and found that the chrome layer (300nm)
> disappeared in HF (49%) in one minute. Is that because that chrome doesnot
> adhere well to the silicon substrate?
>
> Another possible source may be the 300nm SiO2 layer between Chrome and Si
> substrate in certain area. But the feature (in mm scale) should be large
> enough to avoid lift off caused by undercutting.
>
> Any other reason? Thanks.
>
> Regards,
> Yilei Zhang
>
>
>
>
>
>
>
>
>
>
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