Dear all:

MEMS is not my major but I need to do a simple process.
Recently, I have worked SiO2 etching using a PMMA etch mask(100nm thickness).
My goal is to etch SiO2 about 400A depth.(There should be PMMA alive for the
lift-off process)
About 300nm is the width of lines written by e-beam lithography.

In wet etching with 25:1 HF, I failed to get some good results.
(PMMA was peeled off at around 120 seconds, and the etch depth is less than 100A
during this time)
Does anyone who use my condition in wet etching?

We have a Oxford Etcher(plasmalab 80+).
The 100nm-PMMA is nearly wiped-out in my conditions:
CF4(40sccm) + O2(5sccm) under 50mtorr, 50W for 90 seconds.
Now, I can use some other gases, Ar, SF6, and CHF3.
Is there someone who try to other conditions?

Could you please give your invaluable comments to me?

Thanks in advance.

Sungjun / Graduate Student.