Investigation of bottom-up electrodeposition filling for nanoscale through-silicon vias (TSVs)

The backside power delivery network (BSPDN), which connects backside metal wiring to frontside buried rails via through-silicon vias (TSVs) to reduce signal interference and improve efficiency, faces challenges in electrodeposition filling as TSV dimensions shrink to the nanoscale. At the nanoscale, the super filling of TSV via electrodeposition becomes increasingly constrained by the aspect ratio and diameter, leading to filling defects and low yield issues. This work introduces modules that integrate a four-step pre-wetting process with optimized additive selection for plating solutions. Using this process, we successfully fabricated an array of cobalt TSVs with an aspect ratio of 10:1 and an overall diameter of 1 μm (Electroplating cobalt filling with a diameter of 750 nm). Finite element simulation methods have confirmed the effectiveness of the four-step pre-wetting method. Additives containing paired amine (imine) groups can slow down the deposition kinetics during electroplating, altering the cobalt ion deposition rate on the cathode surface. The fabrication modules introduced in this work are essential for achieving void-free super filling in small-sized TSVs, especially at the nanoscale, where precise control over deposition dynamics is important to minimize defects.