Effect of cetyl-trimethyl-ammonium-bromide (CTAB) and bis (3-sulfopropyl) disulfide (SPS) on the through-silicon-via (TSV) copper filling

Through silicon via (TSV) is a key structure of three-dimensional (3-D) IC integration. However, the fabrication of TSV still faces the challenge of void-free copper filling. In this study, a new suppressor cetyl trimethyl ammonium bromide (CTAB) with a low molecular weight is used as a suppressor for the TSV copper filling. The effect of various CTAB concentrations on the TSV filing ratio are studied. It is observed that low concentrations of CTAB (0.1 g/L) can inhibit the copper deposition. However, this does not occur at higher concentrations (0.5 g/L). Possible inhibitor mechanisms of CTAB at different concentrations were proposed. As only CTAB cannot fill the TSV completely, bis (3-sulfopropyl) disulfide (SPS) was added to increase the deposition rate at the bottom of the TSV. Finally, a TSV filling ratio prediction model based on LSV curves is established to enhance the filling ratio, and consequently, optimized concentrations of CTAB and SPS were found to realize a complete TSV filling. [Display omitted] •The effect concentration of cetyl-trimethyl-ammonium-bromide (CTAB).•High concentration, viscosity and micelles are not conducive to TSV filling.•The defect size could be reduced at a moderate concentration of accelerator.•Concentration optimization by using a TSV filling ratio prediction model.•Void-free filling was achieved with a two-additives system.