Paolo:

Yes, we do have oxygen in the receipt and I also found it was said that
oxygen will avoid the formation of the polymer layer. I am not sure whether
the polymer layer is the reason that sio2 cannot be etched with HF after
RIE. Maybe it is fluorinated silicon? And if it is caused by "sputtered"
polymer, it should be removed by pure o2 etching, and I will do it and let
you know the result.

Regards,

Yilei Zhang
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From: Paolo Tassini [mailto:paolo.tassini@portici.enea.it]
Subject: Re: [mems-talk] residues on RIE etched sio2

Yilei, are you sure about your etching gas?

O2 is mixed with CF4 to avoid the formation of
the polymer layer (O2 reacts with C).
How much power do you use, for RIE?
Is it possible that the polymer layer already presents
on the sample could be "sputtered" away and deposit
all over the oxide?
You can do a pure O2 etching before extracting the sample
from the RIE system.

Or try to exchange the power connection
to the electrodes of the system, if you can:
the sample connected to ground and the other electrode to power,
then go with lower power and longer time than RIE:
it is only a chemical etching without ions mechanical bombardment.