You may use other gas, such as SF6/O2 mixture and try to reduce the
ratio of O2 flow.

Regards,

Xu Zhu
-----Original Message-----
From: Ravi Gupta [mailto:[email protected]]
Sent: Tuesday, July 13, 2004 6:52 PM
To: [email protected]; [email protected]
Subject: [mems-talk] RIE PMMA/Si

Hi All,
I need to etch Si with a PMMA mask in RIE using a CH4/O2 mixture.
But as per the literature I found that the selectivity of Si:PMMA is 1:3

which would surely be a problem.

Does anyone has any suggestions on how to increase the selectivity or
use of
other polymers as resist? Is Polystyrene a good alternative?

Thanks,

Ravi Gupta.