Correlation between Filled Via and Produced Cuprous Ion Concentration by Reverse Current Waveform

To enable low power consumption and the access speed increase, three dimensional packaging of semiconductor chips has been proposed. In particular, a high-aspect ratio through silicon via (TSV) allows short chip to chip interconnection. In this study, we studied the role of produced cuprous ion in via filling by changing periodic reverse pulse current waveform. 4 μm diameter and aspect ratio of 7.5 via TSV has filled. The perfect via filling was achieved within 25 minutes with the increasing irev/|ion| ratios of periodic reverse pulse current waveform. In addition, we evaluated produced cuprous ion concentration during electrodeposition by using rotating ring disk electrode (RRDE). From the electrochemical measurement by RRDE, cuprous ion concentration on the reactive surface was markedly increasing with the increasing irev/|ion| ratios. At irev/|ion| ratio of large (irev/|ion| = 6.0), a large amount of cuprous ion concentration produces during copper dissolution by reverse current and cuprous ion remain at via bottom. High cuprous ion concentration at via bottom accelerates deposition at via bottom and achieve bottom up filling.