Extreme fast filling of conical shape through-silicon vias in 3 minutes and additive optimization

Abstract

Through-silicon via (TSV) technology has been quickly improved, however, there are challenges in reducing electrodeposition time. In this research, new conical TSVs, 3μm diameter and 27μm depth (3×27μm), were made. The flow pattern of the electrolyte inside a conical TSV and a cylindrical TSV is simulated with a TSV chip attached on a rotating disk electrode (RDE) rotating at 1000rpm in the electrolyte. The flow pattern inside conical TSVs confirmed advantages of the conical shape over the cylindrical shape. The conical shape forms deeper vortexes and shows higher velocities at the same depth than the cylindrical shape. A character of electrolyte bases on anodic area charge was used to optimize electrolyte bath composition for the extreme fast filling. Without additives, the anodic area charge at 1000rpm was larger than that at 10rpm, however, the reverse obtained in the presence of additives. D-optimal designs for quantitative multilevel of additives were applied to create an experiment plan. The result confirmed a strong effect of Cl− concentration and interactions of Cl− with polyethylene glycol (PEG) and bis-(3-sodiumsulfopropyl)-disulfide (SPS) with sulfonated diallyl dimethyl ammonium chloride copolymer (SDDACC) which bring to anodic area charge at 1000rpm was smaller than that at 10rpm. In an optimal concentration of SDDACC, the 3×27μm conical TSV was filled within 3minutes. A new additive acceleration mechanism was proposed from the accumulation of Cu(I) thiolate inside vortexes.