Dear all,

I have some questions about copper electroplating. I hope somebody with similar
experience can help me.

I have some via holes in my su-8 layer (with bottom gold layer as seed) and I
need to do copper electroplating to fill these holes. The sizes of these holes
are 30um-100um in diameter and 75um deep. After plating, I always find

1)deposition rate in larger via holes is faster, which means larger via holes
are always over plated when smaller ones are just about done.

2)inside each via hole, the deposition on the side wall is easier(or faster?) so
that when plating is done, the top of the copper post is not flat. Instead, it's
more lile a volcano.

3) it's hard to control the plating thickness - in my case, I need exactly 75um
thick copper.

Anybody has any idea what I can do to solve these problems? How I can get
uniform and flat plating (with good thickness control) through the whole
sample?

Thanks in advance!

Chao