High aspect ratio through-silicon-via formation by using low-cost electroless-Ni as barrier and seed layers for 3D-LSI integration and packaging applications

A feasibility study has been carried out to find an alternative method to the laborious cum expensive physical vapor deposition (PVD)/atomic layer deposition for the deposition of barrier and seed metal layers inside the deep Si trenches with aspect ratio (AR) greater than 10, by using low-cost, highly-scalable, CMOS-compatible electroless (EL) plating method to plate Ni as (barrier cum) seed layer for the fabrication of sub-μm as well as 10 μm width copper through-silicon-vias (Cu-TSVs). Micro-structural data revealed that both sub-μm and 10 μm width TSVs with AR ranging from 12 to 17 were completely filled with Cu by using EL-Ni as a seed layer. Further, both scanning electron microscope and energy dispersive X-ray analyzes data confirms the conformal formation of EL-Ni all through TSV sidewall and TSV bottom, which is otherwise difficult to realize by the even sophisticated PVD tool. Therefore, the EL plating method appears to be a highly promising method for the conformal formation of barrier/seed layers inside the high AR TSVs for future three-dimensional integration and packaging applications.