Hi,

> If I remember correctly the spin coaters used in clean rooms first spin up the wafer and then dispense the liquid

That did the job. I still think that the RPM is quite low because the fan is too weak, and I might later switch to the power drill to improve that, but applying the liquid only after the motor is spinning is definitely very important.

> You need to dispense liquid in middle of wafer as liquid will online move outwards.

Obviously :)

> I guess, you're experiencing problems because you didn't apply a primer first.

I only did a test, spinning oil onto a coin. I guess that the primer helps with wetting and/or sticking to the wafer surface, which wasn't (yet) a problem in my test. Anyway, good to know!

Greetings,
Martin


On Wed, Apr 28, 2021 at 5:06 PM David Lanzendörfer <leviathan@libresilicon.com> wrote:
Exactly.
First you've gotta spin up the wafer, and then you've gotta dispense it
kind of towards the center, but it's not so critical.
I guess, you're experiencing problems because you didn't apply a
primer first.
https://www.3mdeutschland.de/3M/de_DE/unternehmen-de/produkte/~/3M-Silan-Glas-Primer-Transparent-1-L-Flasche/?N=5002385+3294237313&rt=rud

Cheers
-lev

On Wednesday, April 28, 2021 12:24:57 PM WEST Staf Verhaegen wrote:
> On wo, 2021-04-28 at 11:23 +0200, Martin Geisse wrote:
> > Hi,
> >
> > - spin coating
> >
> > I finally tried to build a makeshift spin coater the way Sam Zeloof
> > did, by mounting a plastic can on top of a CPU fan (actually a case
> > fan from another device I had lying around). I can't say this is the
> > way to go... the fan is way too weak to spin the can at a meaningful
> > speed. It is also very hard to center the can exactly, so it wobbles
> > a lot and that probably reduces the speed even more. Mounting a die
> > without a container would allow the fan to spin faster, but would
> > likely clog the fan with chemicals in no time. I'll next try my
> > original idea, to mount the can to an axle that I'll stick into a
> > power drill.
> >
> > One thing I did find out is that the coating liquid should be evenly
> > applied before spinning. It will NOT spread to the whole surface by
> > itself, but rather run to a single direction in a concentrated
> > stream, probably due to surface tension.
>
> If I remember correctly the spin coaters used in clean rooms first spin
> up the wafer and then dispense the liquid. You need to dispense liquid
> in middle of wafer as liquid will online move outwards.
>
> greets,
> Staf.



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