I once etched 4 micron thick thermal oxide with 49 %
HF using PR as a etch mask. In my sample there was a
metal layer (Cr) underneath PR. Nothing happened to my
PR in HF for 5-6 minutes. 6:1 buffer was once used,
and PR was ok for over 1 hour.
Soojin
UNC-CH
--- [email protected] wrote:
> > I want to mask HF etching with photoresist. Just
> now,
> > somebody suggest me that
> > for the same thickness of oxide I will etch. The
> photoresist
> > could stand
> > buffered HF, but for concentrated HF, it will not.
> Is it
> > exactly the case?
> > Could I be able to find some reference?
>
> Stronger HF solutions tend to peel the photoresist
> off,
> rather than etching it (indeed, I have sometimes
> measured an increase
> in photoresist thickness after HF-base etches due to
> absorption).
>
> Concentrated HF (49% by weight) that has been
> diluted more than about 3:1 by volume
> by H2O or NH4F (40% by weight), to make for example
> 10:1 HF or 5:1 BHF,
> can be used with photoresist for at least a few
> minutes.
>
>       --Kirt Williams Agilent Technologies
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