Jitendra and Sonia,

The cracking issue with all SU-8 resists is linked to the cross-link density and
the effect of the developing solvent....This can be overcome by optimising the
exposure dose for your particular process and the substrate you are going
over...It is well known that exposures on Copper can require up to 2X the
exposure dose for Silicon...I would recommend using an exposure matrix to get
the correct dose...

If after all of the optimisation work has beed completed the cracks are still
evident just perform a post develop bake/hard bake/ cure at 150C for 1-3 minutes
and all of the cracks will disappear or anneal away...

As a note all SU-8/SU-8 2000 users a revised data sheet and updated processing
guidelines will be published soon....The data contained in the new sheets is up
to date and contains much more processing information for these type of
issues....For specific processing problems please contact Mark Shaw at
MicroChem....

Mark Shaw
Sales and Technical Support Manager
Epoxy Business Unit
MicroChem Corp.

Email: mshaw@microchem.com
Tel: 617-407-9490 (cell)
Tel: 617-965-5511 ext 308 (desk)


   1. RE: SU-8  2050 Cracking (GARCIA BLANCO Sonia)


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Message: 1
Date: Fri, 21 Oct 2005 13:10:34 -0400
From: GARCIA BLANCO Sonia 
Subject: RE: [mems-talk] SU-8  2050 Cracking
To: 'General MEMS discussion' 
Message-ID: <12EDAD956333D8118C830007E9086704042159A4@mozart.ino.ca>
Content-Type: text/plain;       charset="iso-8859-1"

Hi Patel,

I had the same problem with another thick resist. In my case I was overexposing
the resist and that is why it was cracking.

Hope this helps!

Sonia.

-----Message d'origine-----
De : PATEL JITENDRA [mailto:jpatel@ENGR.UARK.EDU] Envoyé : Thursday, October 20,
2005 5:05 PM À : mems-talk@memsnet.org Objet : [mems-talk] SU-8 2050 Cracking


I am working with SU-8, 2050, photoresist. I am trying to create 30 micron
diameter vias using SU-8 for copper posts. After expose and develop I notice
that I see cracks around the edge of the vias. Has anyone come accross this
problem? if so, what was the solution. Thanks for your help.
Jitendra Patel

p.s. I am following the processing step as recommend by MicroChem. This is my
process Clean wafer, Baked, Sputter Ti/Cu/Ti, apply omnicoat, baked, apply SU-8
2050, soft bake, expose using 365nm UV light source, Post expose bake, let it
sit overnight, Develop SU-8 using SU-8 developer, Develop omnicoat using de-
scum.