Has anyone tried using PMMA as a mask when etching SiO2? I need to etch 10 nm of SiO2 with 100 nm of PMMA as the mask layer. However, when I use the mrc with O2 and freon 23, the PMMA does not survive. Ideally, I would like an anisotropic etch, but if necessary, I would accept a wet process that undercuts slightly. Thanks, Scott Andrews