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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