Dear all,

I have some problems regarding to oxygen plasma etching of photoresists.

I'm trying to etch selectively and isotropically two different
photoresists: SU-8 2001 and PMGI SF13 of Microchem.

To perform the etching, i'm using a RIE equipment (ICP type) at high pressures
(200 mTorr) of oxygen, and low bias voltages (15 V).

Although the data sheet of PMGI says "High etch rate in oxygen
plasma",  and the SU8 is typically known as impossible to strip once
hard baked (the data sheet says "High chemical and plasma resistance"
), the best selectivity that i have obtained is 1:3.

I have tried with a long (about 16 hours)  hard bake of the SU8 on a
hot plate at 170 °C, without significant improvement.

Somebody have experience in this issues? What am i doing wrong? Where
can i find etch rates of photoresists?

Thanks in advance

Karim