Effect of Stirring on the Defect-Free Filling of Deep Through-Silicon Vias

Through-silicon-via (TSV) is an advanced 3D electronic integration technology. In order to achieve the defect-free filling of deep TSV, forced convection is commonly applied during TSV filling process. In this study, the interaction effect of forced convection and current density on deep TSV filling process is systemically investigated. The filling morphology of TSV electrodeposited with different stirring rate and different current density were observed by the scanning electron microscope (SEM). The phenomenon that forced convection reduces the TSV filling ratio at low current density but promotes the TSV filling ratio at high current density was discovered. Additionally, the influence of stirring rate on the TSV filling results was researched. In order to study the mechanism of forced convection at different current densities, electrochemical analysis and particle size measurement were carried out. The volt-ampere characteristic curves of the plating solution stirred at different speeds were analyzed. Furthermore, the effects of forced convection and current density on the crystal size of deposited copper were studied separately. Based on the experimental results, the mass transfer of additives and crystal nucleation of deposited copper were discussed to explain the interaction effect of forced convection and current density on deep TSV filling process.