4/22/2003 9:00:06 AM, [email protected] wrote:

>  From:   Vishwanath Somashekar 
>
>  Subject:[mems-talk] Reg: Spin coating of Su-8 2025
>  Date:   Mon, 21 Apr 2003 22:32:50 -0500 (CDT)
>  To:     [email protected]
>
>  Hi,
>  I am a grad student at Iowa State and have been involved very recently with
>   the
>  fabrication of channels for experiments in microfluidics. I take a 100mm
>  silicon wafer, clean it with ethyl alcohol and then rinse with water and
>  prebake it for some time. Then, I put the wafer on the spin coating machine.
>
>  The diameter of the chuck on which this wafer rests is slightly smaller than
>
>  that of wafer. so I am not able to place the wafer such that the center of
>   the
>  wafer and the center of the chuck match. As a result of this, when i run the
>
>  spin coating, I can see kinda wobbling movement at low speed which tends to
>  vanish at high speed. The way i dispose of the resist is take a syringe and
>  measure about 4ml of SU-8 2025 and dipense off at the center. Then I ramp at
>
>  100rpm/sec for like 5 sec and then will ramp to the desired rpm based on the
>
>  thickness of the coating required. The problems that I am faced with are
>  1) after the spin coating, I see like streaks of su-8 strecthing from the
>  center and the coating is not uniform and its kinda wavy and sometimes, the
>  coating is not on the entire surface.
>  2) we also use su-8 2100 which is really viscous and when we spin coat, it
>  coating is really pathetic. Can you suggest me some technique to improve. As
>   I
>  am new to this fabrication, I might not have described my problem
>   technically.
>  I apologize for that.
>
>  Thanks very much in advance.
>
>  vishwa
>
>
>  Vishwanath Somashekar
>  3219, Ross Rd.,
>  Ames
>  IA 50014
>  Ph: 515-292-1766(Res)
>
>  ****************************************************************************
>                A little learning is a dangerous thing:
>              Drink deep, or taste not the Pierian Spring
>  ****************************************************************************

Hi Vishwanath,

from my experience with spin coating a high viscosity glue (24Pa*s) I recommand
you
to use much more resist volume. Just pour a realy large amount of resist on the
waver.
You star pattern should vanish. Then you can try to reduce the resist volume.
I usually spin coat with 500rpm for 20s and ramp up to 5000rpm for 40s.

Hope I could help you.

Michael

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Michael Vosseler
University of California Los Angeles
Mechanical & Aerospace Engineering Department
letters: 48-121 Engineering IV
packages: 18-111 Engineering IV
420 Westwood Plaza
Los Angeles, CA 90095
USA
(310) 825 1350 (Voice & FAX)
mailto:[email protected]
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