Polyvinylpyrrolidones (PVPs): Switchable Leveler Additives for Damascene Applications

The electroplating characteristics of polyvinylpyrrolidones (PVPs) have been studied by means of potential/time transients, secondary ion mass spectroscopy (SIMS depth profiling) and NMR methods. Our results identify the PVPs as a class of Cu plating additives whose mode of leveler action can be controlled (switched on/off) by the current density. At low current densities the PVPs show identical synergistic effects with chloride and similar antagonistic effects with SPS (bis-(sodium-sulfopropyl)-disulfide) as known from the PAGs (polyalkylene glycols). In particular the SPS loses its depolarizing capability at higher current densities. The dominance of non-specific interactions of the PVPs with the copper surface is identified as origin for the leveling capability of PVPs at these higher current densities. The transition from an antagonistic (no leveling) to a non-antagonistic (leveling) PVP/SPS interplay is demonstrated to be depending on the molecular weight of the PVPs.