Superconformal film growth is a key process in state-of-the-art Cu metallization of electronic devices. Superfilling of recessed surface features results from the competition between electrolyte additives that accelerate or inhibit Cu electroplating. In situ scanning tunneling microscopy is used to image the accelerating bis-͑3-sodiumsulfopropyl disulfide͒ ͑SPS͒-Cl − surfactant phase that is responsible for disrupting and preventing the formation of the inhibiting poly͑ethylene glycol͒-Cl − layer. Various aspects of competitive and coadsorption of Cl − and SPS on Cu͑100͒ were examined for industrially relevant additive concentrations. At potentials associated with superfilling, a saturated, c͑2 ϫ 2͒ Cl − ordered adlayer forms on the surface. When as-received SPS is added, individual SPS and ͑3-mercaptopropyl͒sulfonate ͑MPS͒ molecules are imaged as a mobile two-dimensional gas diffusing on the Cl − adlattice. The SPS-Cl − surfactant accounts for many aspects of the additive function previously observed and stipulated by the curvature enhanced accelerator model of superconformal film growth. SPS-derived species of differing mobility and tunneling contrast appear with exposure time. The lattice gas species are sensitive to the imaging conditions with tip-molecule interactions particularly evident at higher tunneling currents. At negative potentials, the c͑2 ϫ 2͒ Cl − adlayer is disrupted by an order-disorder transition, followed by desorption at more negative potentials. This allows direct access of SPS to the Cu metal whereupon irreversible sulfide formation occurs.In the past decade, Cu electrodeposition has become the dominant technology for fabricating interconnects for microelectronic devices over length scales ranging from those of damascene processing of submicrometer logic and memory circuitry to through silicon vias ͑TSVs͒ for chip stacking and circuit board metallization. 1 Central to the success of this technology is its ability to generate voidand seam-free bottom-up filling of trenches and vias by additive derived superconformal growth. 2 The desired bottom-up superconformal growth mode derives from a competition between rateaccelerating and rate-inhibiting two-dimensional ͑2D͒ phases for the available surface area within filling features. Area change is a key aspect that accompanies deposition on any nonplanar interface. 3,4 Feature filling behavior is well described by a mass balance construct known as the curvature enhanced adsorbate coverage ͑CEAC͒ model. 3,4 In this model, the coverage of the more strongly bound accelerator surface phase increases during area reduction accompanying deposition within recessed features, thereby giving rise to the bottom-up superfilling dynamic. For a prototypical acid CuSO 4 electrolyte, the suppressing or inhibiting phase involves coadsorption of chloride with polyether, whereas the accelerating phase derives from the combination of chloride with either a sulfonate-terminated disulfide or thiol. The most widely discussed additive system to date is chloride ͑Cl − ͒, ...

A model for copper electroplating of through-silicon vias (TSV) is proposed based on the suppressor adsorption/desorption mechanism, with special emphasis on the bottom-up filling of these structures. The proposed model is applicable for both 2-component (suppressor and accelerator) and 1-component (suppressor only) Cu plating chemistries. Numerical simulation was performed for the filling of 5 μm (diameter) × 40 μm (depth) vias. Simulated Cu profiles and the corresponding dependencies on additive concentration are confronted with existing experimental results.

The desorption / adsorption of suppressor additive during Cu electroplating plays a critical role in the void-free filling of recessed features such as through-silicon vias (TSVs) used in 3-dimensional integration. A stochastic model was proposed for Polyethylene Glycol (PEG) as a suppressor additive in Cu electroplating. Using the proposed model, a program capable of simulating transient processes such as cyclic voltammograms (CVs) was developed. The steep change of current density due to suppressor desorption, as well as the characteristic hysteresis, observed in the CVs was shown in simulation. The dependency of PEG desorption / adsorption on various factors, including the bath composition, scan rate and molecular weight, was simulated. The simulation results were confronted side-by-side with the corresponding experimental measurements. An overall good qualitative match was shown.