Sulfur-Containing Additives for Mitigating Cu Protrusion in Through Silicon via (TSV)

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Since the introduction of through silicon via (TSV) technology, Cu electrodeposition methods for defect-free and fast TSV filling have been investigated, such as by using various organic additives or controlling deposition conditions. However, there are few studies on regulating Cu protrusion of TSV, which may occur in subsequent semiconductor processes and strongly influences the reliability of Cu TSV. In this study, we used 2-mercapto-5-benzimidazole sulfonic acid (2M5S) and thiourea (TU) as separate additives during TSV filling to mitigate Cu protrusion. The electrochemical behavior of 2M5S and TU showed that they interacted strongly with iodide ions (leveler) to promote or suppress Cu electrodeposition, respectively. The uniformity of TSV filling was also influenced by the additives. During Cu electrodeposition, these additives were incorporated into the Cu matrix to induce the pinning effect and mitigate Cu protrusion. The degree of Cu protrusion was effectively reduced by 84.9% and 69.2% with 2M5S and TU, respectively, when compared to the absence of these additives.