Study of Direct Copper Electroplating on Ruthenium Seed Layer for Nano-TSVs Processes on 300mm Wafers

The copper filling capability of nano-through silicon vias (nano-TSVs) with an alternative ruthenium (Ru) seed layer on 300mm wafer was thoroughly examined. We studied the effects of current densities, anode current distribution, and periodic pulse current waveform on the nucleation mechanism of direct copper electrochemical plating (ECP) on Ru, as well as its impact on nano-TSVs filling performance. By employing periodic pulse current, void-free filling is achieved with an 80% reduction in processing time. Furthermore, the “terminal effect” typically encountered when plating on a resistive substrate was effectively mitigated by optimizing the anode current distribution.