You should be able to increase the etch rate if you have an ICP equipped
reactor. This will allow you to have a higher plasma density of monotomic
oxygen and it would be helpful to also have bias on your wafer electrode.
This will allow you to have some control over the directionality and shape of
the etch or removal. If you only want to remove it isotropically then having
a heated platen using only the ICP will work well. This is like a Matrix
system.  Bob Henderson