Group,
I am interested in wet etching sputtered copper on a semiconductor
wafer.
I realize that I'm not talking boards here, but I'm hoping that someone
can
give me some insight to the problems that I'm facing.
Using traditional positive photoresists for semiconductor manufacturing,
I
am getting a very large undercut of my copper features.  Features are
4-8
mils in x,y and anywhere from a few thousand angstroms to 1 um thick.
Unfortunately, the amount of undercut is 10-20 times the feature
thickness.
 (I would expect 1x the feature thickness)  I believe the problem is the
interface between the copper and the resist.  When I use a metal mask
(say
Al), no appreciable undercut is observed.  Also, the undercut seems to
be
independent of etch solution.  Right now I am using a dilute
sulfuric/peroxide mixture.
In the pcb world, I assume copper is etched with photoresist masks.  The
question is, is the photoresist a different chemistry to improve the
adhesion/interface between the polymer and the copper?  If so, what
photoresists exist out there?  And finally, is there a version that can
be
applied by SPIN coating (i.e. semiconductor process)?
Any insight would be greatly appreciated!
Jeff

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