hi

The copper might be contaminated/oxidized from prior
processing. Try dipping your wafer for 30 seconds in
10% Sulfuric Acid prior to etching. It will greatly
increase your etching uniformity.

regards,
adnan merhaba


--- Lahpai Nang Htoi  wrote:
> Hi,
>
> I have an issue with Cu UBM wet-etching. I use
> Nitric acid together with acetic acid and hydrogen
> peroxide. Although my over etching time is long
> enough (50 to 80%) to clear all un-masked Cu, round
> shape Cu residue is left behind.
> Does anyone know what causes this kind of residue?
> Any idea or suggestion will be greatly appreciated.
>
> Thanks & brgds,
> Nang Htoi
>
>
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