Hello Shane,
let me share my opinion on this:
- to clearly distinguish whether the problem you see is caused by poor
collimation or deep UV absorption is to check whether your structures have
negative profile (over 90 deg - DUV absorption) or positive (below 90 deg -
collimation issue).
For DUV filtering you have already received the recommendation, I would add
one more, just used SL glass as filter - I think you cannot get much light
below 350 through it. In one project I have seen even the profile change due
to i-line absorption - over 400 um high structures the bottom was few um
narrower than top. We solved by using h-line only but that needs a lot of
light to crosslink SU-8 (2 J/cm2 in that case)
For collimation - so called "front lens" is used, as was suggested - it
needs to be larger than your substrate size and I think you should place the
light source in the focal point of the lens and nowhere else. If the light
source is in focal point the light is focused by lens to infinity - so you
will achieve parallel light beams.
In order to increase the uniformity the fly-eye lens is used as well and to
maximize intensity the light is collected by elliptic mirror.
You can see the lamp house build up on brochures like this one:
http://www.itc.com.gr/console/pdf/14/MJB4.pdf page 4
BTW the angles calculated by Mike are not so severe in reality - once the
light enters SU8 it is refracted by Snell's law so the angles are much lower
in SU-8.
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
Disclaimer notice: The information contained in this message and any
attachments is intended only for the personal and confidential use of the
designated recipient(s) named above. If you are not the intended recipient
of this message you are hereby notified that any review, disseminitation,
distribution or copying of this message is strictly prohibited. If you have
received this message by error, please notify the sender immediately.
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On
Behalf Of SHANE GUO
Sent: Friday, December 06, 2013 07:25
To: [email protected]
Subject: [mems-talk] UV light source
Hi all,
We have a UV light source which is being used for exposing SU-8. It is not a
mask aligner with an advanced UV source but it still works for patterning
SU-8 features that are more than 100um wide with an aspect ratio of 0.5.
However, I found that the side walls are not very vertical for
narrow(smaller than 30um) and tall (over 200um) features.
I believe the UV light is the culprit, which is not very directional so the
side walls are tapered, especially for those tall and narrow features.
Does anyone know if there is a way to improve the directionality of the
light source?
Best
_______________________________________________
Hosted by the MEMS and Nanotechnology Exchange, the country's leading
provider of MEMS and Nanotechnology design and fabrication services.
Visit us at http://www.mems-exchange.org
Want to advertise to this community? See http://www.memsnet.org
To unsubscribe:
http://mail.mems-exchange.org/mailman/listinfo/mems-talk
_______________________________________________
Hosted by the MEMS and Nanotechnology Exchange, the country's leading
provider of MEMS and Nanotechnology design and fabrication services.
Visit us at http://www.mems-exchange.org
Want to advertise to this community? See http://www.memsnet.org
To unsubscribe:
http://mail.mems-exchange.org/mailman/listinfo/mems-talk
