Role of Cuprous Ion in Copper Electrodeposition Acceleration

We have previously reported that the cuprous ion concentration inside the via increases during the reverse portion of a periodic reverse pulse waveform. The void decreases and bottom-up via filling is achieved by increasing this reverse current during copper electrodeposition. Acceleration occurs at the via bottom by increasing the reverse current for cathodic polarization. J. R. White's work showed a low cuprous ion concentration during cathodic polarization without additives. During cathodic polarization, the current density is high for copper dissolution and nitrogen gas bubbling with bis-(3-sulfopropyl) disulfide (SPS) and chloride, using the through-mask electrode trench. We have measured the increases in cuprous ion production with SPS and chloride additives using a rotating ring disk electrode. Copper electrodeposition is accelerated with SPS and chloride. An acceleration complex forms, which is based on the cuprous ion; i.e., Cu(I)-thiolate, a high cuprous ion concentration is observed at the through-mask electrode trench bottom. From a mass transfer study, therefore, the Cu(I)-thiolate complex accumulates in the through-mask electrode trench bottom. The current density increases at the through-mask electrode trench bottom and bottom-up filling then occurs.