The side wall angle depends primarily on 2 factors.  1) The angle of
collimation, no your light source is not 100% collimated.  2) The light
is now unfortunately bent as it enters the resist.  This is a function
of the refractive index of the resist.  Experience with hundreds of
image reversal tests for lift off, leads us to expect angles from +22
degrees with normal exposure and develop.  Reversal and flood exposure
gives any angle from +22 to -22 dependent upon the level of flood
exposure.

Bill Moffat, CEO
Yield Engineering Systems, Inc.
203-A Lawrence Drive, Livermore, CA  94551-5152
(925) 373-8353

www.yieldengineering.com

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of preetha jothimuthu
Sent: Wednesday, May 14, 2008 12:20 PM
To: mems-talk@memsnet.org
Subject: [mems-talk] sidewall angle of photoresist

Hi All,

Can anyone tell me the relation between the sidewall angle and the
distance between the mask and the substrate for proximity exposure of a
positive photoresist.