Hello Nagare,

There is no specific process to make the PMMA "more resistant" for =
etching. If you are using it as an etch mask you have to be sure your =
PMMA is thick enough and doesn't get washed away during the etch process =
(and make sure you hard bake it beforehand). The optimization for this =
process depends on your specific case. How big are the features you need =
to etch? Which is their aspect ratio? You basically have to consider =
that nonometer scale features require high resolution (thus a thinner =
resist layer, << 400nm), whereas micron scale feature can be patterned =
on thicker resist (> 500nm). The trade off you are going to face here is =
that a thicker resist layer offers more resistance to the etching, =
although is unpractical if you need high resolution.=20
Also, when dealing with etching it could be useful to switch to ZEP, as =
it has a much improved resistance to etching (although potentially lower =
resolution and a bit more difficult processing).

Regards,

R.

-----Messaggio originale-----
Da: mems-talk-bounces@memsnet.org per conto di Nagare Gajanan Nagare
Inviato: dom 04/05/2008 20.24
A: mems-talk@memsnet.org
Oggetto: [mems-talk] PMMA as a mask for RIE-SixNx
=20
What should be the tretament for PMMA to use it as a mask for RIE of =
SixNx
with CHF3 and CF4 gass.

Nagare Gajanan D