A negative sloped side wall is essential  Using image reversal the flood
exposure controls the side wall angle from a +22 degrees through
vertical to -22 degrees or slope back.  Using this for example Cray
Research when they produced chips for the Cray super computer had a
number of image reversal systems and were producing 0.1 Micron metal
lines.  Other customers use the vertical side walls for plate up and
produce 30 Micron thick copper with vertical walls inside 40 micron
vertical wall trenches.

Bill Moffat, CEO
Yield Engineering Systems, Inc.
2185 Oakland Rd., San Jose, CA  95131
(408) 954-8353