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In this study, a polyethylene glycol-based organic additive, with quaternary ammonium cation functional groups linked to a naphthalene rings at both ends was synthesized, for through silicon via (TSV) filling. The synthesized additive strongly suppressed Cu electrodeposition under convection and successfully bifurcated the deposition surface of TSVs into active and passive regions, allowing defect-free TSV filling. However, there was a variation in TSV filling uniformity depending on the additive chain length. The chain length was adjusted using polyethylene glycol of various molecular weights as a starting material for the additive. The electrochemical investigation revealed that the chain length was related to the re-adsorption rate during Cu electrodeposition, which is critical in TSV filling. At the optimal chain length, uniform and defect-free bottom-up TSV filling was successfully achieved and TSV filling time was reduced to 500 s.

The effects of halide ions on the adsorption of polyethylene glycol (PEG) and through-silicon via (TSV) filling were investigated. Halide ions on a Cu surface assist the adsorption of PEG, and the suppression effect of PEG–halide ion layers increases in the order of Cl– < Br– < I−. For all halide ions, suppression breakdown and negative differential resistance were observed, suggesting that the three halide ions with PEG potentially induce Cu bottom-up filling. However, we confirmed that only Br− enables Cu bottom-up filling, whereas Cl– results in conformal deposition and I– cannot complete bottom-up filling due to the low Faradaic efficiency. The PEG-Br– provides sufficient suppression strength, facilitating the formation of passive–active regions and enabling defect-free Cu filling without an accelerator. This study indicates that the property of the suppression layer contributes significantly to Cu bottom-up filling based on a passive–active filling mechanism.

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