> What is the size of your wafer and what size is your chuck?

This is a good point.  The wafer should be larger than the chuck at
least by a few cm (assuming 6" wafer). If the wafer is smaller than
the chuck (I've seen this done), you will get contamination on the
backside.

If this is for research purpose, simply cleaning off the backside of
the wafer (before softbake, esp if contact bake) with acetone should
be fine.

If this is for production - you really do need a coater with backside
wash capability.

dbp

On 9/20/07, Seth Burtner  wrote:
> Hello Edward,
>
> Does your spin coater have backside rinsing capability?  Also, the
> exhaust during spin can actually create more problems as this
> dramatically increases turbulence in the spinner environment.  One more
> thing to increase uniformity of the coating is a solvent rich
> environment which can be achieved by a cup rinse during spin or if you
> can not do this pour solvent bath in the spinner bowl.  This can be the
> primary solvent of your resist.