Bottom-up Cu Filling of through-Silicon-Via(TSV) with Single Additive

Abstract

Downscaling of the Cu interconnection was one of core technologies to enhance the performance of semiconductor devices. However, the shrinkage of Cu interconnection will face the limitation due to the physical limitation of Si based semiconductor device. In order to maintain the development in semiconductor device, the 3D interconnection is emerged, and the through-Si-via(TSV) interconnection is noticed. Large integration, high efficiency and high performance could be realized by composing the 3D integrated circuit with TSV. Furthermore, hetero interconnection between the logic and memory was possible by accepting the TSV technology. The TSV filling process which plating the Cu in the TSV by electrodeposition was one of core process in TSV process due to high cost and difficulty. During the TSV filling process, bottom-up Cu filling which the Cu filled from the bottom of via to the top, should be occurred for avoiding the void formation and decreasing the processing time. In other to achieve the bottom-up filling, various additives were added in the electrolyte. The suppressor inhibited the deposition rate of Cu at the top surface and the sidewall of TSV. The accelerator promoted deposition rate of Cu at the undermost bottom of TSV. Theoretically, the bottom-up filling of TSV was initiated by suppression breakdown at the bottom of TSV.1-3 Simultaneous detachment of suppressor by high potential due to ion depletion at TSV bottom leads focus of current at bottom of TSV. Therefore, bottom-up TSV filling could be achieved by only using the suppressor. Moreover, it was reported that accelerator substitute the suppressor at the sidewall and disturbed the bottom-up filling.3 In this research, the characteristics of suppressor were systematically investigated to achieve the bottom-up Cu filling of TSV with only using the suppressor. The influence of suppressor concentration on the Cu electrodeposition was investigated by observing the CV curves and morphology of Cu deposit. The influence of suppressor concentration and current density on the bottom-up TSV filling had also been observed. Interesting changes in bottom-up TSV filling by changing experimental conditions were delicately analyzed. Finally, the bottom-up TSV filling was achieved with only using the suppressor. This leaded the perfect and fast void free filling of 60 μm deep TSV within 1000 seconds.