Using a triblock copolymer as a single additive in high aspect ratio through silicon via (TSV) copper filling

Through silicon via (TSV) is a promising interconnect technology in three-dimensional (3D) integration which has large packing density, improves efficiency and consumes less energy. Since the optimization process of multi-additives system is complicated to achieve void-free TSV copper filling, the use of a single additive become a new trend. In this paper, the using of a triblock copolymer ethylene oxide (EO) - propylene oxide (PO) - ethylene oxide (EO) as a single additive in TSV copper electrodeposition was investigated. High and low concentration of EPE (0.02 g/L and 0.002 g/L) were used for the filling experiment at different current densities. It was found that low concentration EPE had stronger inhibition ability, and achieved "V shape" filling at 0.3 ASD (A/dm2). However, EPE of high concentration would form micelles in electrolyte, resulting in the decrease of inhibition ability. We proposed a mechanism for the different EPE concentrations to explan the phenomenon. In addition, the effect of ultrasonic agitation on EPE filling performance was investigated. With the ultrasonic agitation, bottom-up filling can be achieved at 0.02 g/L, and filling rates can be increased at 0.002 g/L. This can be attributed to the cavitation of the ultrasound which can promote the mass transfer and clean the activated electrode.