I would suggest the following course of action:

50 grams / Liter PMMA in xylene, or cyclohexanol. PLace in clean sealed bottle.
Sonicate until the PMMA pellets have dissolved completely (approx. 3 hours).
Remove solution from US bath and allow to stand overnight. This removes
cavitation bubbles within the solution. Place clean Si substrate on spin coater
vacuum chuck, set rotation for approx. 10000rpm. Deposit solution using pipette,
being careful to load substrate completely to the edges. Initiate the rotation.
Spin for about 60 seconds, remove and bake film at 60 degrees celsius for 1
hour.

10000rpm should give you approximately 100nm thickness, especially at 50g per
liter polymer solution concentration.
You will need to measure the thickness using a stylus profilometer. For thicker
films, prism coupling (mode line spectroscopy) is most accurate. I would suggest
that you spin several films, from the same stock solution at various speeds and
have them all measured. A graph of thickness vs. spin speed should allow
interpolation (extrapolation) for specific film parameters.

Regards,

K. Cazzini (Ph.D)
Senior Scientist
Alcon Laboratories Inc.
>
> From: "Matthias Kruse" 
> Date: 2002/01/24 Thu AM 10:52:08 EST
> To: [email protected]
> Subject: [mems-talk] Thin PMMA layer
>
> Hello!
>
> I need an thin layer of PMMA on silicon. Round about 50-100 nm.
> Does anybody have an idea?
>
> Thanx a lot
>
>
> **********************************
> Dipl.-Chem. Matthias Kruse
> Institut fuer Anorganische Chemie
> Fachbereich 8
> Universitaet Essen
> Universitaetsstr. 5-7
> 45117 Essen
>
> Tel.  +49 (0)201 183-4515
> Fax.  +49 (0)201 183-4195
> email [email protected]
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