Dear all,

I was hoping someone out there has some experience of the edge bead removal
(EBR) of conventional positive photoresists from silicon/silicon oxide
wafers.

I've recently commissioned the automated EBR on our Karl Suss RC8 spinner
but I've done some profiling and discovered that although the EBR reduces
the width of the edge bead, it actually increases the peak heights.

Without EBR the photoresist ends up with a 2mm wide edge bead of up to 1.6um
in height (for a spun film of thickness of 660nm).

With EBR, a new bead is created at the new edge of the photoresist where the
solvent hits.  This is only 1.2mm wide but has a thinner peak of up to 3.5um
high!  These peaks are only ~100um wide.

Should edge bead removal normally create a highly vertical edge or is it
normal for new peaks to be introduced?  Will the new thinner peaks have less
of an effect on high resolution hard contact lithography or is edge bead
removal not going to help at all unless I get a perfect vertical edge
without additional peaks?

About my process:  I am spinning the wafer at 1250RPM whilst the solvent
(acetone) is dispensed at pressure by an automated arm through a syringe.
1250RPM is the maximum speed the system will allow and high speeds are
recommended to prevent backside contamination.

Many thanks for any comments in advance,

Bob Ibbotson
Heriot-Watt University