New copper seed-layer enhancement process metrology for advanced dual-damascene interconnects

The extendibility of the physical vapor deposition (PVD), seed-layer deposition process for future devices needs to be enhanced with electrochemical techniques. Developing analytical techniques for the plating bath is a particular challenge because bath ingredients are often proprietary and difficult to ascertain. The feasibility of using an ion chromatography for an electrochemical copper, seed-layer enhancement (SLE) process metrology is studied. It is shown that the ion-chromatography method can be used to precisely determine the composition dynamics in a copper SLE plating bath. The bath concentration dynamics are found to be significant in influencing the electroplated Cu film properties, i.e., the resistivity and surface roughness. An excellent correlation exists between the ion chromatograms and the electroplated Cu film properties, suggesting that the ion-chromatography method is a powerful method.