[labnetwork] Photomask sticks to SU8

[Demis D. John]

To add to this - once SU8 has been fully cured, it is very difficult to
remove and doesn’t appear to dissolve in most solvents.  Hence why you need
to use piranha in this case.  SU8 on your mask plate will have been exposed
many times and possibly is very old (perhaps similar to curing).

-- Demis (contact info <https://wiki.nanotech.ucsb.edu/wiki/Demis_D._John>)
*Reminder*: The NanoFab has a publications policy
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On Fri, Feb 13, 2026 at 16:46 Robert Nidetz <nidetz at umich.edu> wrote:

> Definitely try the developer first. If it has not been cross linked by the
> exposure then it will clean up easy. But if it’s been exposed, you’ll need
> piranha solution.
>
> To prevent sticking in the future, make sure your tweezers cannot leave an
> impression after the soft bake once the wafer has cooled to room
> temperature. If they leave an impression, you’ll need to soft bake more.
>
> Good luck!
>
> Robert Nidetz, PhD (he/him/his)
> University of Michigan
> LNF User Liaison and Domain Expert
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>
> On Thu, Feb 12, 2026 at 7:36 PM Phillip Bauer <
> Phillip.Bauer at formfactor.com> wrote:
>
>> Hello
>>
>> I am somewhat new to SU-8 working with Positive resists throughout my
>> career. I agree with data sheets are just guideline, for processing.  I saw
>> a note from another University to run a 65 deg post bake after the 95 deg
>> soft bake.  My question is about mask cleaning.  Is Sulfuric/Peroxide
>> (Piranha ~ 60-90C) really needed.  I would think the PGMEA or PGMEA/Acetone
>> followed by IPA would be an effective clean.  Just wanted to poll the
>> audience.
>>
>>
>>
>> <https://www.google.com/maps/search/4350+Innovation+Drive+%0D%0A+%0D%0AFarmers+Branch,+Texas+75244?entry=gmail&source=g>
>>
>> *Thank you,*
>> *Phillip Bauer *
>>
>> Principal Photolithography Process Engineer
>> 4350 Innovation Drive
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>>
>> <https://www.google.com/maps/search/4350+Innovation+Drive+%0D%0A+%0D%0AFarmers+Branch,+Texas+75244?entry=gmail&source=g>
>>
>> *phillip.bauer at formfactor.com <phillip.bauer at formfactor.com>*
>>
>> M: 682 521 0874
>>
>>
>>
>>
>>
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