[labnetwork] PDMS in sputtering tool

[Mary Tang]

Hi Julia!

Great catching up with you at UGIM!

Just a few, quite possibly unrelated, comments about PDMS (which is one 
of my favorite materials...)  Most people use Sylgard 184. This is what 
is used in most literature references and it is handy because it 
self-cures.  At SNF, we recommend using Sylgard 182 because this does 
not self-cure (well, actually it eventually does, if you leave it long 
enough.)  There are several advantages:

1.  Spin coating.  Because it self-cures, the viscosity of 184 is said 
to double about every hour or so (to my recollection.)  The 
non-self-curing 182 allows for a more consistent/longer working time, if 
thickness control is an issue for your experiment.

2.  Even if you bake Sylgard 184 for the recommended time, it will 
continue curing.  For researchers who are doing microcontact printing or 
have other applications where small changes in elasticity, surface 
energy, etc. will matter, this could be very important.  I haven't 
experienced this myself, but was told by one of our research groups that 
their experimental results experienced a drift over the course of a 
month when they used 184, but that they had day-to-day consistency when 
using 182.

3.  The Sylgard 182 components come in jars.  I can use disposable 
syringes to extract and meter out exactly what I want, whereas the last 
time I purchased Sylgard 184, it came in a wacky, dual-syringe dispenser.

One other caveat about the Sylgard products:  these are potting agents, 
not precision-engineered materials.  There's a lot of batch to batch 
variability and limited shelf life -- and the main issue is variability 
in curing.  Even really old, out of date stuff will work great if all 
you want to do is to cast a structure.  But researchers requiring a 
higher degree of consistency should be aware that they will need to 
control for or account for this variability.

But getting back to your question about PDMS...  Whether 182 or 184 is 
used, it would be best to make sure it is thoroughly baked/cured before 
metal deposition.  It would also be good to make sure your researchers 
use fresh/non-expired material, or bake the living heck out of it if it 
is expired (though at $80/kg, there should be almost no excuse for 
keeping old stuff). Both 182 an 184 also have a high thermal expansion 
coefficient, so keeping deposition temperatures low is important to 
prevent buckling of the films.

Mary


-- 
Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
Paul G. Allen Bldg 141, Mail Code 4070
Stanford, CA  94305
(650)723-9980
mtang at stanford.edu
http://snf.stanford.edu



On 6/17/2016 3:21 PM, julia.aebersold at louisville.edu wrote:
> Greetings everyone!  I had a great time at UGIM and enjoyed seeing old 
> friends and making new acquaintances.  The University of Utah 
> hospitality was fantastic.  I do have some questions.
>
> 1.  We have had an aluminum adhesion issue with bubbling under the 
> deposited film.  We have had a user put their PDMS devices into our 
> sputtering tool and have been told that outgasing PDMS could be the 
> source of our bubbling underneath aluminum.  We do not see this 
> behavior with other metal depositions.  Do you ban PDMS from your 
> processing chambers?  Also, we will go ahead with decontamination 
> using sand blasting and solvent wipe downs, but do you recommend other 
> processes (i.e. chemical dips for parts that can be removed)?
>
> 2.  My second question revolves around organizational structure.  We 
> currently have a Faculty Director, Cleanroom Manager (me), 3 Engineers 
> and 1 Admin.  Structures and the number of people in facilties vary 
> immensely due to size of the facility, but I wanted to know how many 
> split their cleanroom manager position into a technical manager and 
> business operations manager.  The business operations manager would 
> primarily handle administrative tasks and rarely step foot into the 
> cleanroom.
>
> Cheers!
>
>
> Julia Aebersold, Ph.D.
>
> MNTC Cleanroom Manager
>
> University of Louisville
>
> 2210 South Brook Street
>
> Shumaker Research Building, Room 233
>
> Louisville, KY  40292
>
> (502) 852-1572
>
> http://louisville.edu/micronano/ <http://louisville.edu/micronano>
>
>
>
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