[labnetwork] Blisters on PMMA resists

[Mark Giulio Chiappa]

Hi Shiva,

I agree it's probably a thermal issue. When we had the same issue we experimented with PMMA from different batches, baking times and temps as well as thermally conductive mounts (mung etc) to no avail. Interestingly we solved the issue by increasing the deposition rate.

So it seems there is no definite answer I suppose it is dependant in the distance between source an substrate. I don't remember how much we experimented with wait times but that sounds like a good idea.

Kind regards
Mark.

Sent from my iPhone

On 6 Apr 2017, at 18:23, Price, Aimee <price.798 at osu.edu<mailto:price.798 at osu.edu>> wrote:

Hi Shiva,
I believe we've had a thread on this subject in the last year or so.  Can someone remind me how to find the old/archived threads (or do we just look in our email history)?

Past that, we have had this several different times on a couple different evaporators, almost always with Ti/Au or Ni/Au ...  Assuming we've baked the PMMA sufficiently it appears to be heating, though we've tried thermal dots alongside and not found very high temps.  Our solution has been to slow the deposition rate and put a "wait" step in during thick Au, Ni, sometimes Pt steps.  The rate we use is 1-2A/s in most cases and the wait times vary but are usually halfway through the Au step.

Lastly, we have a lot of people working with piezoelectric materials and this happens sometimes with those.  That's a separate topic.  I'm assuming you are working with more "standard" semiconductor substrates and the issue is caused by the metal/PMMA not the substrate itself?

Feel free to reach out to me off-line at price.798 at osu.edu<mailto:price.798 at osu.edu> if you want more details.  We did a lot of work with this at two different times, about 3 years ago and 10 years ago.  We even had students travel back to UlUC to use their evaporator when we were diagnosing this issue the first time.

Best of luck.

Aimee

From: labnetwork-bounces at mtl.mit.edu<mailto:labnetwork-bounces at mtl.mit.edu> [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Shivakumar Bhaskaran
Sent: Wednesday, April 05, 2017 10:03 PM
To: LabNet (labnetwork at mtl.mit.edu<mailto:labnetwork at mtl.mit.edu>)
Subject: [labnetwork] Blisters on PMMA resists

Hi All,

We are getting blisters or metal film peeling off when depositing metals (Ti/Au/Al) on PMMA resists using EBeam Evaporation.

Did anyone had this issue in your EBeam Evaporation tool. If so how did you fix this?

-thanks
-Shiva

SNSF
http://snsf.stanford.edu/

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