Hello Diane,



Some ideas:

1) do you have transparent layers under your SU-8? Glass substarte, thick
oxide, ... -  the footing can be caused by back reflection from layers
underneath. It will be worse close to larger structures

2) are you sure that it is no caused by diffraction from the mask - do you
have good contact or controlled proximity during exposure? What is your mask
aligner?

3) Is your SU-8 sufficiently cross-linked? Sometimes what can happen is that
if your resist is not cross-linked enough, you are slowly dissolving some of
it during development step and during rinsing and drying you deposit the
residues along the structures. If you compare the thickness of your layer
before and after development and do not see significant thickness loss you
can discriminate this.





With best regards,



Daniel







Daniel Figura



smartfabgroupT Company



process consulting . data processing . fab software



Phone: +421 944 45 26 86



E-mail: [email protected], Web: www.smartfabgroup.com







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-----Original Message-----
From: [email protected]
[mailto:[email protected]] On
Behalf Of Diane Atkinson
Sent: Thursday, September 13, 2012 14:04
To: [email protected]
Subject: [mems-talk] Issues with footing in thin SU8



Hello,

       I am trying to process 4um of SU8 3005,and am having issues with the
footing at the bottom of my pattern, I t is about 1-1.5 microns. I have
tried several things and nothing seem to fix this problem, I am about to try
CEM, but am wondering if there is an alternative way to prevent this ,maybe
reduce the PEB ?  Thank you



Also,I tried to send this once but I am not sure if it went so I am
resending-

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