Dear MEMs enthusiasts,
        I have a friend, based in The Netherlands, who is using Chrome as a
hardmask (limited to this) for dry etching
deep 'silicon dioxide'. He is using, as far as I am aware, Fluorine based
chemistry of only ..F4 at 50mTorr
in 'Bright Mode' (ICP mode).

He has found that the chrome begins to erode substantially once the Chrome
is broken through into the oxide.

I think it could be due to Cr2O3 or CrO3 formation from oxygen, liberated
during the oxide etch?

Without having to embark on a 2K Factorial DOE, any suggestions as to how he
could improve on the Oxide to Chrome selectivity?

Perhaps, increasing  pressure to reduce Chrome etchrate?


suggestions or known effects from experience  would be appreciated.

Best Regards,

Philip Lau





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