A Study on the Seed Step-Coverage Enhancement Process (SSEP) of through Silicon Via (TSV) Using Electrophoretic Deposition (EPD) of Pd/PVP Colloids

The seed step-coverage enhancement process (SSEP) using Pd/PVP (Polyvinylpyrrolidone) colloids were investigated for the filling of through silicon via (TSV) without void. TEM analysis showed that the Pd nano-particles were well dispersed in aqueous colloidal solution with average diameter of 5.67 nm. These Pd nano-particles were uniformly deposited on the substrate of Si/SiO₂/Ti wafer by electrophoresis with high frequency alternating current (AC). After electroless Cu deposition on the substrate treated with Pd/PVP colloids, the adhesive property between deposited Cu layer and substrate was evaluated. As a result of that, the Cu deposit showed superior adhesion property in comparison with that on treated substrate by the existing Pd ion catalyst. Finally, by implementing the SSEP using Pd/PVP colloids in TSV, we achieved 700% improvement of step coverage of Cu seed layer compared to PVD process, resulting in void-free fillng in high aspect ratio TSV.