All,

I am currently attempting to electroplate Ni onto a seed layer of 200A Cr /
1000A Cu into thick PR (SPR 220-7) patterned spots on a silicon wafer, but I
am having problems with the resulting Ni layer.  The layer has been plating
non-uniformly (which I would expect for narrower and wider regions because
of the enhancement of current density for narrower regions), and the layer
looks "spongy" and blackish under a scope post-plating.  It should be noted
that the plating parameters are within spec using the optimal ASF current
density, the optimal temperature, the optimal pH, the optimal anode,
agitation, etc.

One suggestion that I received was to do a quick O2 plasma de-scum, and then
a quick dip in BOE to remove the native oxide layer.  However, my thoughts
are that the presence of hydrocarbons on the seed layer would contaminate
the layer's electrical characteristics (which is a moot point for my
reserach), and the presence of copper's native oxide layer would impede the
growth of the layer and not change the overall characteristics of the layer
(making it blackish or spongy).

Hence, my questions are the following:

First, is it really absolutely critical to perform the aforementioned plasma
and BOE steps for my plating process, or is it just an industry standard for
preventative measures?  If it is critical, please explain why.

Second, has anyone observed this kind of behavior when plating Ni into thick
PR channels, and if so, what causes it and how do I correct my process to
prevent this to attain a smooth, matte gray, relatively uniform layer?

Thanks in advance!