We have problems regarding reactive ion etching with freon
(CF_4) of thick (1-5um) SiO_2 layers. We use an old PLASMA
THERM PD 2480 Plasma Etch System 1984.
Problem: Even after very long etching times we observe high aspect
ratio "needles" and residues at the substrate (diamond) surface.
Our process parameters are: 400W, 45mTorr, 45 SCCM CF_4
We use an Al mask for etching.

Thanks in advance
Mario