Publications Details

Bottom-Up Copper Filling of Millimeter Size Through Silicon Vias

Hollowell, Andrew E.; Josell, Daniel; Menk, Lyle A.; Blain, Matthew G.; Moffat, Thomas P.

This work demonstrates void-free Cu filling of millimeter size Through Silicon Vias (mm-TSV) in an acid copper sulfate electrolyte using a combination of a polyoxamine suppressor and chloride, analogous to previous work filling TSV that were an order of magnitude smaller in size. For high chloride concentration (i.e., 1 mmol/L) bottom-up deposition is demonstrated with the growth front being convex in shape. Instabilities in filling profile arise as the growth front approaches the freesurface due to non-uniform coupling with electrolyte hydrodynamics Filling is negatively impacted by large lithography-induced reentrant notches that increase the via cross section at the bottom. In contrast, deposition from low chloride electrolytes, proceeds with a passive-active transition on the via sidewalls. For a given applied potential the location of the transition is fixed in time and the growth front is concave in nature reflecting the gradient in chloride surface coverage. Application of a suitable potential wave form enables the location of the sidewall transition to be advanced thereby giving rise to void-free filling of the TSV.