Thank you to Sangeeth and Gabriel, I found out the problem was with the DI water
bath after development. I changed it to a 10s IPA rinse and all of my issues
were fixed.

Kyle


On Nov 11, 2014, at 22:49, sangeeth kallatt  wrote:

> Hi Kyle,
> I think PMMA is underdeveloped in these images. You may want to try out few
> things.
>
>   1. Make sure that you are exposing PMMA with required dose. If you are
>   using 100kV, apply 800uC or more.
>   2. PMMA A6 would be really thick. It requires more time to develop in
>   1:3 solution
>   3. Pre-bake for more time. say, 5 min on hot plate.
>
> If these things are not working, then you can suspect PMMA/developer. I
> don't think PMMA can redeposit after development.
>
> Regards,
>
> Sangeeth
>
> On Fri, Nov 7, 2014 at 3:49 AM, Kyle Godin  wrote:
>
>> Hello. This fall I have been having trouble with my PMMA EBL processing.
>> After development, the patterns are filled in randomly and also there are
>> waves of PMMA deposited with macroscale features in-plane. I believe the
>> issue is developed PMMA redepositing everywhere. I found some hints online
>> about PMMA redepositing or scumming, but nothing to suggest a solution for
>> me. I cannot figure out why this is happening as my process has been the
>> same for two years and never had this issue until recently. Please see two
>> photos:
>>
>>
>> https://www.dropbox.com/s/rpmuv6heh9zfauj/ebl%20scum%20image%20width%201mm.jp
g?dl=0
>>
>> https://www.dropbox.com/s/wl3jgpo3tc66d5b/ebl%20scum%20image%20width%202mm.jp
g?dl=0
>>
>> I tried getting new resist from the main bottle, used different resists,
>> inspected the resist optically before exposure and there is no thickness
>> variation, have tried “developing” unexposed resist and optically
>> everything looked fine.
>>
>> Process:
>> SiO2 on Si, thickness 90nm or 300nm or 1um.
>> PMMA 950 A4 or 950 A6.
>> Spin 3k 30s, bake 180C hot plate for 60s.
>> Sometimes I expose right away, sometimes the chips rest overnight - same
>> results.
>> Exposure is with a Jeol6300 at 2nA.
>> Development is MIBK:IPA 1:3 for 55s.
>> Then dunk in a large bath of DI water to quench development.
>>
>> Thanks,
>> Kyle Godin
>> kgodin@stevens.edu
>>
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>
>
>
> --
>
>
>
>
> *Sangeeth KCenter for Nano Science and Engineering (CeNSE)Department of
> Electrical Communication EngineeringIndian Institute of ScienceBangalore-12*
> _______________________________________________
> Hosted by the MEMS and Nanotechnology Exchange, the country's leading
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