[labnetwork] How do you handle PDMS in a cleanroom environment?

[Matt Moneck]

Hi Leif,

 

We get a lot of requests for PDMS in our lab, and we do allow users to
process PDMS coated wafers/chips as well as cured PDMS molds.  However, we
have a lot of restrictions in place in order to mitigate the same concerns
that you highlighted in your post.  Our PDMS users are basically classified
into two categories:  thin-film and thick-film.  The thin-film users are
generally working with PDMS in the range of several microns or less.  We
allow spin-coating of these films in the cleanroom, but the users are
restricted to a specific spinner and a specific hot plate.  The thick-film
users are working with hundreds of microns or even millimeters of PDMS.  At
the moment, we do not allow coating of such thick films in the cleanroom, as
we found that it was simply too messy.  They must coat and cure their
samples outside the cleanroom.  

 

Fully cured PDMS samples are allowed in certain process equipment, but
again, we had to restrict users to a specific subset of tools, as we have
seen and are continually concerned about contamination.  These films do
outgas, so users are restricted to one of two sputtering systems for
deposition.  Samples are typically placed on carrier wafers to avoid contact
with the substrate table.  In addition, we limit the range of sputtering
powers that users can run in an attempt to mitigate heat at the sample.  So
far, we have not had any vacuum issues or problems with other standard films
in these tools.  We also have an RIE dedicated to “dirty” processes.  Users
are allowed to etch PDMS in this tool, but it does leave residue in the
chamber that must be cleaned from time to time.  In addition, users are
restricted to a specific profilometer, as we found that even fully cured
PDMS was contaminating the stylus in our other systems.  

 

Uncured PDMS is not allowed in any of our tools, and heating of PDMS in any
vacuum system is not allowed.  

 

Hope this helps.

 

Best Regards,

 

Matt

 

-- 
Matthew T. Moneck, Ph.D.
Executive Manager, Carnegie Mellon Nanofabrication Facility
Electrical and Computer Engineering | Carnegie Mellon University
5000 Forbes Ave., Pittsburgh, PA 15213-3890
T: 412.268.5430
F: 412.268.3497
www.ece.cmu.edu <http://www.ece.cmu.edu> 
nanofab.ece.cmu.edu

 

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu]
On Behalf Of Leif Johansen
Sent: Wednesday, November 25, 2015 3:58 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] How do you handle PDMS in a cleanroom environment?

 

Dear Lab Network, 

 

I have a dilemma. Polydimethylsiloxane (PDMS) is a promising material for
soft lithography, and a lot of our users have a strong wish to process this
material in our lab – especially for making nanoimprint stamps . However,
before being cured, PDMS is basically a silicone oil, and all our front end
engineers (plasma chambers, lithography etc. ) are really scared about this
substance ending up in their equipment. Our back end engineers (especially
the wire bonding engineer) is also strongly opposed to the introduction of
PDMS into the back end lab. 

 

Are there any experience out there in the community on how to handle PDMS in
a cleanroom environment?

 

Best regards, 

Leif

 


Leif S. Johansen 


Head of Operations


DTU Danchip 


  


Technical University of Denmark




Danchip 


Ørsteds Plads, Byg. 347 


2800  Lyngby 


Direct +45 45255713 

Mobile +45 25348992


lesjo at danchip.dtu.dk <mailto:lesjo at danchip.dtu.dk>  


www.danchip.dtu.dk/ <http://www.danchip.dtu.dk/>  

 

 

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