Patent ID: 7678258

Claim:
A method of operating a plating bath comprising: providing a plating bath containing at least an accelerator; plating at least one metal on a substrate; measuring the bath concentration of at least one accelerator breakdown product (“void-formation marker, VFM”); measuring the bath concentration of said at least an accelerator; determining a VFM ratio at each of a plurality of time-points, wherein said VFM ratio is the concentration of said VFM divided by the concentration of said accelerator; counting, for each of said time-points, the number of voids in the metal plated on said substrate; determining a VFM threshold ratio as the highest VFM ratio at which no voids are observed; and maintaining said VFM ratio below said VFM threshold ratio by performing a bleed and feed of said plating bath to maintain said VFM ratio below said threshold VFM ratio.