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
****************************************************************************