You didn't really give any details, but I will guess
that you are doing some kind of plasma processing
prior to your electroplating step.  Either you are
forming your trenches through plasma etching or you
are using a plasma step to help with wetting prior to
plating.

In the words of our former president, Bill Clinton, "I
feel your pain".

My co workers comment was "Welcome to the Wacky World
of Plasma Processing"

If you could provide more details about your process
perhaps I and the rest of the group could give you
some suggestions on ways of reducing this effect.

We struggle with this problem where I work and I'm
sure other folks do as well.  If there's any thin film
head people on this group I'd like it if they would
weigh in on this issue as well.  Rumor has it that
they know more about electroplating than anybody else
in the semiconductor industry.

Regards,

Mike Jolley
Yahoo! Tax Center - online filing with TurboTax
http://taxes.yahoo.com/