Effect of Reverse Pulse on Additives Adsorption and Copper Filling for Through Silicon Via

Abstract

In order to develop the suitable Cu electrolyte for TSV filling using period pulse reverse (PPR) electroplating, the operating mechanism of reverse pulse on the adsorption of additives within TSV was systematically investigated. Whether the promotion or reduction of the adsorption of polyethylene glycol (PEG), bis (sodiumsulfopropyl) disulfide (SPS) and Janus Green B (JGB) by reverse pulse was determined by the charge of the formed complex of this additive with Cu+ and Cl−. The charge of formed complex was dependent on the Cl− concentration. The reverse pulse had no significant effect on the adsorption of single JGB. In comparison, the composite JGB-PEG inhibitor could be repelled by reverse pulse at the microvia bottom. For the composite PEG-SPS or PEG-JGB-SPS, since the preferentially adsorbed Cu+-Cl−-PEG dense layer could effectively block the transportation of Cl−, few sites of Cl− were left for the SPS adsorption and then mainly formed positively charged SPS-Cu+, which accounted for the detachment of SPS by anodic pulse current at microvia entrance in the presence of PEG. Based on the change of the additives coverage surface by reverse pulse, the microvia filling performances in PPR plating compared to those in DC plating could be well explained.