Ameya,

Spray coating a thin, conformal film of photoresist might be the first
step to solving your problem.  Using this technique, one can eliminate
the problems encountered when spinning resist across topography.
Percent (non-)uniformity can also be decreased to roughly 10%.

Please feel free to contact me directly if you have any further
questions.

Best Regards,

Garrett Oakes

EV Group
invent * innovate * implement
Director of Technology North America - Direct: +1 (480) 305 2443, Main:
+1 (480) 305 2400 Fax: +1 (480) 305 2401
Cell: +1 (480) 516 6724
E-Mail: G.Oakes@EVGroup.com, Web: www.EVGroup.com


-----Original Message-----
From: ameya g [mailto:ameya.g@gmail.com]
Sent: Tuesday, November 10, 2009 1:04 AM
To: General MEMS discussion
Subject: [mems-talk] Photolithography on a rough surface

Hello everyone,

I need some advice regarding photolithography on a patterened surface.
I have a 4 inch Si wafer that has 30 um deep and 20 um wide trenches all
over the wafer. This uneven topography makes it difficult to uniformly
spin
and develop the photoresist (AZ3312 and AZ4330). Extensive fringing is
visible due to the non-uniform film and the measured thickness varies
from 0.1 um to 4 um. The problem is compounded by the fact that my
smallest linewidth is 1 um.

Has anyone faced a similar issue before? Is there any polymer I could
use to fill and level the trenches? Any advice on how to attain a
uniform
film on such a heavily patterened wafer will be greatly appreaciated.

Thank you,
-Ameya