In the semiconductor metallization process, the superior gap-fill capability of copper ͑Cu͒ electroplating is mainly due to external additives, such as bis-͑3-sodiumsulfopropyl disulfide͒ ͑SPS͒, which is used as an accelerator. This study demonstrates that the byproducts of SPS induced Cu defects after a chemical-mechanical-polishing ͑CMP͒ process. In conventional cyclic-voltammetric-stripping analysis, the byproducts generated from organic additives are very difficult to quantify. In this study, the authors used mass-spectrum analysis to quantify SPS byproducts and found that the SPS byproduct, 1,3-propanedisulfonic acid, correlated with the formation of Cu defects because it influenced the properties of electroplated Cu films and the chemical corrosion rate, then induced defects after the CMP process.

In this article, electrochemical impedance spectroscopy is used to characterize the mechanism of galvanic corrosion between copper ͑Cu͒ seeds and tantalum nitride ͑TaN x ͒ barriers deposited with different N 2 flow rates. By way of software simulating with EIS data, an equivalent circuit is built up to explain the corrosion behavior of the TaN x films' relation to the Cu seeds in an acidic chemical-mechanical-polishing slurry. The equivalent circuit can respond to changes in resistance and capacitance elements of the Cu-TaN x electrochemical system. It is found that the charge-transfer resistance of the TaN x galvanic corrosion increases with the N 2 flow rate, whereas the resistance of a tantalum-oxide layer is opposite because increasing the N content of the TaN x films inhibits corrosion and oxidation of the Ta metals. The result is consistent with our previous investigation that the galvanic corrosion of the TaN x films to the Cu seeds is retarded by the N element ͓C.

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In semiconductor copper ͑Cu͒ metallization, external organic additives including bis͑3-sodiumsulfopropyl disulfide͒ ͑SPS͒ and polyalkylene glycols ͑PAG͒ are necessary and widely used to improve the gap-fill capability of Cu electroplating for high-aspectratio features. In this study, the interaction of SPS and PAG ͑SPS-PAG͒ in the electrolytes was investigated. The results not only show the antisuppression effects of SPS in the presence of PAG, but also indicate the competitive adsorption between SPS and PAG. The proposed mechanism is that when SPS-PAG are added to a plating bath, the Cu-electroplating rate is influenced by competing adsorptions of SPS-PAG and SPS, which disperses PAG species far away from the Cu surface to enhance electroplating rates. The elements ͑charge-transfer resistance, adsorption-layer resistance, and inductance͒ of the equivalent circuit simulated using the electrochemistry-impedance spectroscopy data also demonstrate the behavior of SPS-PAG competing reactions.

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