Marcel:

In theory, all you'll need for the passivation step is a continuous film
but in practice a few tens to hundreds of nm may be required.  Typical
deposition rates in DRIE-specific reactors could be 200-500nm/min using
C4F8.  I don't think that you will get this with CHF3 with your RIE
system so you might need to run a few tests to determine the deposition
rates that can be achieved in your system.

It might be easier to do a few deposition experiments with blanket
wafers.  You might also run the wafers for five to ten minutes so that
you get enough deposit to measure.  You can get a reasonable
approximation of the thickness of the deposit using an interferometer
with parameters for measuring PR thickness.

One possible explanation for not seeing any deposition is that your bias
power setting is too high so you may need to reduce the bias power.

If you cannot get deposition on blanket wafers then it is not likely
that you will deposit on patterned wafers.  You can reuse the wafers by
stripping in an oxygen plasma.

Robert

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of
Marcel Spurny
Sent: Wednesday, August 04, 2010 10:03 AM
To: General MEMS discussion
Subject: Re: [mems-talk] DRIE with SF6 and CHF3

Hi,

I just tried to etch with SF6 and a polymerization step with CHF3. With
SF6 I get up to 1.6um/min etchrate.

But I could not see a polymer film after the CHF3 step. How thick can I
expect the polymer layer to be?

Cheers,
Marcel