Copper deep via superfilling by selective accelerator deactivation

Accelerator dominant bottom-up copper superfilling of TSVs was demonstrated. Because of the 100 times large dimensions compared to on-chip interconnections, strong inhibition on the top surface is needed and the superfilling of TSVs are generally achieved by addition of levelers in the plating bath. Recently, we reported that accelerator can be deactivated by reverse pulses and the deactivation needs solution agitation. It was expected that reverse pulses deactivate the acceleration selectively on the top surface and the acceleration around via bottoms was preserved and obvious bottom-up superfilling was demonstrated by three step plating process. Some levelers, such as PEI (Polyethyleneimin), is known to suppress the deposition strongly. We verified that PEI deactivated the accelerator and explored the use of PEI to deactivate the accelerator. In this study, we demonstrated that the bottom-up superfilling by the modified three step process in which a PEI bath was used instead of the reverse pulse proposed in our previous study.