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.