End-point detection of copper super-filling in small features under a potentiostatic mode of operation

Copper filling of small features using a potential-controlled technique in electrolytic bath containing organic additives in a selected potential range is shown to be highly beneficial. End-points filling detection in features with width of less than 150 nm are observed in the current–time profile. This behavior is obtained once potential is applied in a selected potential range, capable of providing efficient copper deposition suppression on flat wafer surface sites. Thus, achieving a controlled feature filling with a clear end-point of copper super-filling with minimum copper overburden is feasible in a potentiostatic operation mode. Copper filling rate depends primarily on the selected potential value and the feature dimension characteristics (aspect ratio). Selective copper filling during potentiostatic deposition is favorable (over galvanostatic deposition) in high aspect ratio patterned wafers. Illustrations of i–t curve profiles during copper super-filling of complex wafer patterns in a potentiostatic mode are presented.