Garrett is correct, to a point.

AZ9260 can be spun to thicker layers, with 25-30 µm being possible in a single
pass using fairly standard techniques (using pretty low spin-speeds), allowing
greater thicknesses in multiple coats.  I have also demonstrated that it is
possible to coat AZ9260 to a thickness of 105 µm in a single pass, but in this
case the process takes fairly specialized techniques (my apologies, I have been
forbidden to share these in general, but I felt it is still important to
communicate the possibility), and is probably coating system specific (in this
case, and EVG150).

The trade-off is that the process becomes somewhat environment sensitive, and
edge beads become pretty severe.

Best Regards,
Chad Brubaker

EV Group
invent * innovate * implement
Senior Process Technology Engineer - Direct: +1 (480) 305 2414, Main: +1 (480)
305 2400 Fax: +1 (480) 305 2401
Cell: +1 (602) 321 6071
E-Mail: C.Brubaker@EVGroup.com, Web: www.EVGroup.com

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org] On
Behalf Of Oakes Garrett
Sent: Friday, January 23, 2009 11:23 AM
To: mazzolari@fe.infn.it; General MEMS discussion
Subject: Re: [mems-talk] Thick AZ-9260

Andrea,

By default, AZ9260 is a resist designed for a 6.0 - 8.0 µm coating thickness
when spun between 3000 and 4000 rpm.  One can increase the thickness of a single
pass coating by decreasing the casting rotational velocity but this will come at
the expense of thickness control.  Film thickness of 50 µm might require coating
the resist four times or more!

The best solution is to look for a resist which is designed for the needed
thickness at 3000 rpm.  You can look at the XT and nXT resists from AZ-EM.  They
have materials designed for the thickness range you desire and can be coated in
only one or two passes.

Best Regards,
Garrett Oakes