Hi Joao,
One technique that might work is to heat up the sample sitting on the chuck with
a heat gun, then very quickly spin coat the resist. As the sample cools down. It
will suck in the resist into the crevices. Of course this might introduce other
issues downstream, but give it a shot. I'd be interested in how it works for
you. I've tried it on a thinner Futurexx resist with success in the past.

Felix

Sent from my iPhone

Felix Lu, Ph.D.
Applied Quantum Technologies
Durham, NC 27707



On Dec 20, 2012, at 10:57 AM, João Tiago dos Santos Fernandes  wrote:

> Hi everyone,
>
> I'm currently using AZ 40XT thick photoresist to make a 20-30 µm thin film
over a Si sample with ~30 µm high SU-8 features.
>
> The problem I am facing is the following: when I pour the AZ on top of the
sample, tiny air-bubbles are created in areas where SU-8 features are small
(small wells, gaps, etc) - I'm guessing that this happens because the AZ is very
viscous and isn't able to fill those spaces and traps air. When I spin coat,
those tiny air bubbles are spread across the sample, compromising the process.
>
> Is there any way to get the air bubbles out of the way without compromising
the final film thickness? I tried low rpm for a couple of minutes, with no
success.
>
> Thank you so much,
>
> -----------------------------
> João Tiago dos Santos Fernandes
>
> INESC Microsistemas e Nanotecnologias (INESC MN)
> Rua Alves Redol, 9
> 1000-029 Lisboa
> Portugal
>
> Tel: +351 213100237
> Email: jfernandes@inesc-mn.pt
> URL: www.inesc-mn.pt
>
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