SPS ͑bis-͑3-sulfopropyl͒ disulfide͒ is an essential electrolyte additive used in the fabrication of copper interconnects by electrodeposition. In electroplating baths, the disulfide component of SPS may be cleaved to form the thiol analog, MPS ͑3-mercaptopropyl sulfonate͒, by either homogenous interactions with the Cu͑I͒ reaction intermediate or by dissociative adsorption onto the copper surface. However, mechanistic studies into the role of these additives in copper electrodeposition are presently constrained by limited knowledge of the purity of commercially available SPS and MPS. This report details the use of ion chromatography ͑IC͒ and electrospray ionization mass spectrometry to characterize aqueous solutions of commercial SPS and MPS source materials. Sulfate ͑2.0%͒ and propane disulfonic acid ͑0.9%͒ ͑PDS͒ were determined to be the principal impurities in SPS ͑96.3% estimated purity, mass fraction͒. IC fractionation was used to purify and isolate SPS for surface and electroanalytical studies. Stability of SPS, MPS, and PDS in the presence of O 2 and Cu͑II͒ was also examined. No degradation of SPS or PDS in aqueous solution was observed over a 3-month period. Solutions of MPS were metastable to O 2 saturation, but the addition of Cu͑II͒ resulted in formation of SPS by dimerization as well as parasitic PDS generation.State-of-the-art Cu wiring for microelectronic circuitry is fabricated by electrochemical deposition. 1,2 The electroplating process requires the use of a specific combination of additives in an acidic Cu͑II͒ plating bath to enable void-free filling of recessed surface features such as trenches and vias. Commercial additive packages comprised at least three species: Cl − , an accelerator such as bis-͑3-sulfopropyl͒ disulfide ͑SPS͒, and a polyether-based suppressor such as polyethylene glycol ͑PEG͒ or a related block or branched copolymer. 3,4 Chloride is a required coadsorbate for the formation of the inhibiting PEG layer as well as the subsequent formation of the SPS-derived accelerating surface phase. Feature filling involves a competition between SPS and the polyether for Cl − -saturated Cu surface sites. 2,3 As the local surface area decreases, such as within a filling trench, the more tightly bound SPS-derived adsorbates remain on the surface while the polyether suppressor is displaced into the electrolyte. This displacement results in an accelerated rate of Cu deposition on the SPS-enriched concave surface segments, leading to bottom-up superconformal filling. Several quantitative descriptions of feature filling based on the curvature enhanced accelerator coverage ͑CEAC͒ mechanism are available. 2-6 Nevertheless, much remains unknown about the physical and chemical nature of the SPS-derived accelerator surface phase.A recent scanning tunneling microscope ͑STM͒ study of SPS adsorption on a Cl − saturated Cu͑100͒ surface revealed a plurality of lattice gas species diffusing on top of, or within, the Cl − adlayer. 7 In addition to the dimer-like SPS species, smaller molecules suggestive of th...

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State of the art manufacturing of semiconductor devices involves electrodeposition of copper for device wiring and more recently for through-silicon-vias (TSVs). The process depends on the use of electrolyte additives that affect the local deposition rate thereby resulting in superconformal, or bottom–up “superfilling” of trenches and vias. In the case of Damascene processing of submicron features the deposition process is explained by the recently developed curvature enhanced accelerator coverage (CEAC) mechanism. The model stipulates that 1.) the growth velocity is proportional to the local accelerator, or catalyst, surface coverage and 2.) the catalyst remains segregated at the metal/electrolyte interface during copper deposition. For growth on non-planar geometries this leads to enrichment of the catalyst on advancing concave surfaces and dilution on advancing convex sections; thereby giving rise to bottom-up superfilling of recessed surface features such as trenches and vias. In the case of larger features other avenues for feature filling become available that will be outlined in some detail. Despite the success of these superconformal growth processes much remains to be known concerning the detailed molecular nature of the competitive co-adsorption processes involved in both the suppression and acceleration of the metal deposition reaction. The application of in situ surface science tools such as in situ STM and SEIRAS towards a better understanding of the additive interactions will also be detailed. The interaction between adsorbed anions, polyether suppressors, sulfonate terminated thiol/disulfide accelerator additves and water at the growing interface reveal the critical role of hydrophobic/hydrophilic interactions in controlling the growth velocity during metal deposition. The talk will conclude with an overview of the current understanding of additive adsorption, consumption and/or deactivation dynamics relevant to superfilling and microstructural evolution in both Damascene and TSV Cu processing.