Hi,

I need some help with Copper electroplating.

I have 30 micron wide and 60 micron deep trenches in silicon and I need
to electroplate copper into the whole trench. However, after a certain
duration of plating, my trench gets closed off and I get voids in them.
The best I've been able to get is a ratio of 2 in the thickness
uniformity. That is 12 microns on each sidewall and 6 microns at the
bottom.

I do not use any mask for now. The copper is plated onto the whole
wafer.
I have tried many plating schemes such as pulse plating and reverse
pulse plating with pulse periods of 12 to 13 ms.
I have not tried DC plating however, because I thought it would not
work.
I have a seed layer that is deposited by sputtering and my estimate is
that it is 5000 A thick so I believe the seed layer is not very
resistive.
I am using organic additives called PCM+ from the company LeaRonal.

The plating bath has a magnetic stirrer.

The solution is mixed as:
CuSO4: 75 g/L
H2SO4: 184 g/L
PCM: .005 L/L
HCl: .166 ml/L

I chanced upon a solution to an electroplating problem by Eric Sanjuan
on this website, and I'm hoping someone can help me.
Also, how often would one need to make new baths.I mean in terms of
Thanking you,
Sajid