Chao.,

The first thing happens.,because the effective current
density varies.may be you have to insulate your anode
(similar to the EFAB method ) or increase
your Anode cathode distance (may be 10 - 15 cm).So
that the current density variation will not much
affect your different holes.

The third one is to try for pulse (AC deposition)
which will dissolve more of the material (from more CD
regions).SO you will get more uniform coatings.

This should solve ur second and third problems.

Just reduce your current density or the amount of
current. This will give a good control over
plating.But may be you have to do electroplating for
longer hrs.

All the best for your results.

regards
Bala



--- [email protected] wrote:

> 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?