You may want to try high RPM dispense. When using a high rpm during dispense it
is important to dispense your resist as close to the wafer as possible.

-----Original Message-----
From: mems-talk-bounces+r-black1=ti.com@memsnet.org [mailto:mems-talk-
bounces+r-black1=ti.com@memsnet.org] On Behalf Of Gareth Jenkins
Sent: Thursday, December 20, 2012 10:27 PM
To: General MEMS discussion
Subject: Re: [mems-talk] Spin-coating of thick photoresist over existing
features

Perhaps try covering the wafer in the resist solvent before pouring the
resist? This may help fill the gaps.

On 21 December 2012 02:57, João Tiago dos Santos Fernandes <
jfernandes@inesc-mn.pt> 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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