Hi Jobert,

Why don't you try a single step process with C4F8/SF6 about 1:1
(50sccm?) and low pressure (10mT??).
Etch rate will be slower than BOSCH. But it would work with your
application with a little process tuning.
Sidewall should be VERY smooth with no scalloping whatsoever.
Let me know how it goes. You can email me directly if you wish to know
more detail.... I can try to help
You. Which chamber do you have? Plasma therm? STS? Or Applied DPS-DT?


ShuTing



Graduate Student
UCLA EE Department
Email:  shuting@icsl.ucla.edu



-----Original Message-----
From: mems-talk-bounces+shuting=ucla.edu@memsnet.org
[mailto:mems-talk-bounces+shuting=ucla.edu@memsnet.org] On Behalf Of
Jobert van Eisden
Sent: Monday, October 27, 2003 4:05 PM
To: 'mems-talk@memsnet.org'
Subject: [mems-talk] Anisotropic c-Si RIE


Dear all,

We are trying to etch vias (3-10 um) to a depth of 5 um with sidewall
roughness under 30 nm. The mask we use is 1 um thermal oxide. I would
like to ask you all if there is any way the Bosch process can be
adapted, or if there is a gas chemistry we can use to do a RIE process
that gives us these smooth sidewalls. There should be little or no mask
undercut.

We have tried running a Bosch like recipe using very little ICP power
and short cycles, which gave us too much sidewall roughness. The
available chemistries are CHF3, CF4, O2 and N2 on the dieletrics chamber
and SF6, C4F8, O2 and Ar on the Bosch chamber.

I would very much appreciate ideas and suggestions.

Regards,

Jobert van Eisden
Graduate student
SUNY Albany

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