Hi there,

I am using some high melting point polymer (PES Phenylene-ehter-sulfone) to
replace the bottom layer MMA in e-beam patterning. (follow the article but
not exactly same process, Dubos et al. J.Vac.Sci.Techno.B 18(1), 122, 2000)

The problem for the PES right now is when doing wet etching using DMSO
(Dimethyl sulfoxide) as described by Dubos2000, there are some cracks appear
on the PES surface which was not reported in the original article. It is
somehow similar to what happened before when I used Chlorobenzene to harden
the top surface layer of Photoresist to achieve larger undercut (which now
mostly replaced by two layer LOL technique). I am now trying to use IPA
diluted DMSO. But it seems after dilution it can not etch effectively.

The thickness of PES is around several hundred nanometers. When it is
thinner, ~70nm, no cracks.

Are there some any general reasons that explain why polymer cracks?

Btw I search and found something might be related:
http://mail.mems-exchange.org/pipermail/mems-talk/2003-March/009665.html

Also I am curious why in the article they choose NMP as solvent and DMSO as
etchant.
When I called Aldrich tech support staff they told me Aniline and Dimethyl
acetamide will are better solvent.

Jian

 Department of Physics and Astronomy
 Rutgers, the State University of New Jersey