Hi All

                 I am trying to transfer the pattern over 500nm thick layer of
SiO2 thermally grown over a planar Si wafer using RIE. The minimum feature size
is 1um. Right now we have CF4 gas with us. I am looking for best RIE parameters
to obtain anisotropic etching of SiO2 (500nm). i.e. RIE power gas flow rate mask
thickness and vaccuum etc. I am using PMMA as the hard mask. Has anyone tried it
before. If so please share me the details. Any suggestions will be appreciated
well. Thanks in advance.

Renil