In Situ Surface X-Ray Diffraction Studies of the Influence of the PEG-Cl-Complex on Homoepitaxial Electrodeposition on Cu(001)

Abstract

The influence of polyethylene glycol (PEG) on the atomic-scale interface structure and Cu growth behavior of Cu(001) in chloride-containing electrolyte was investigated by in situ surface X-ray diffraction. Studies in Cu-free solution unambiguously verify the presence of the ordered c(2 × 2) chloride adlayer in the presence of the polymer as well as reversible Cl adsorption/desorption and an order-disorder transition in the adlayer. The partially ordered chloride adlayer is found over a wider potential range as compared to PEG-free electrolyte, indicating stabilization of this adsorbate phase. Crystal truncation and superstructure rod measurements reveal that the polymer interacts more strongly with the partially c(2 × 2) Cl covered surface than with the close-packed c(2 × 2) adlayer at saturation coverage. In Cu-containing electrolyte layer-by-layer growth was observed at potentials ≤ −0.35 V vs. Ag/AgCl. The deposition rate was significantly reduced as compared to PEG-free electrolyte, providing clear evidence of inhibition on the atomic-scale. At more positive potentials a crossover to 3D growth and increasing surface roughness is found.

SEIRAS Study of Chloride-Mediated Polyether Adsorption on Cu

“…Recent literature exploring the structural specificity of such ν­(OH) assignments ascribes the blue shift to weakening of the hydrogen-bonding network as captured by coupling between stretching and bending overtones, Furthermore, beyond neutral water, the ν­(OH) bands also incorporate the Eigen (≈2800 cm –1 ) and Zundel (≈3200 cm –1 ) stretching modes of hydronium evident in Figure (and Figure S11). − , In the present work, the slow evolution of the 3000–3500 cm –1 spectral band, over 8 min, following Cl – addition is most likely correlated to coarsening of the freshly formed, ordered Cl – domains and mesoscopic step structure that impact long-range ordering in the adjacent hydration layer. − ,− Similar time-dependent microstructural effects on SEIRAS water spectra have been noted for sulfate adsorption on Au. , …”

“…In the presence of both additives, the halide layer is somewhat stabilized by the polymer as the order− disorder phase transition is shifted, −50 mV, to more negative potentials, as revealed by voltammetric and SXS studies. 19,29 From an application perspective, the link between the halide order−disorder phase transition, water structure, and polyether adsorption underlies the critical phenomena associated with breakdown of the polyether−Cl − suppressor layer that is central to bottom-up filling of Cu TSV. 5,17,18,25 Presently, there are numerous efforts underway to develop physically robust models of the associated dynamics.…”

“…Recently, LEED and X-ray surface scattering have been applied to examine Cl – adlayers on (111) and (100) Cu surfaces. − , Modeling scattering from a Cu(100) c (2 × 2) Cl – surface indicates the halide adlayer templates lateral ordering of the adjacent water and hydronium species. ,, For acid solutions, hydronium is thought to preferentially occupy hollow sites in the anionic layer, while the inner (anionic, Cl – ) and outer (cationic, H 3 O + ) components of the Helmholtz layer compete for water to form their respective solvation shells . Accordingly, the potential-dependent order–disorder phase transitions associated with halide adlayers provides a useful avenue to probe the connection between adsorbed anions and the neighboring water structure.…”

“…In the presence of polyethers, stepping to negative potentials results in some disruption of the polymer layer and corresponding alteration of the water modes. In the presence of both additives, the halide layer is somewhat stabilized by the polymer as the order–disorder phase transition is shifted, −50 mV, to more negative potentials, as revealed by voltammetric and SXS studies. , From an application perspective, the link between the halide order–disorder phase transition, water structure, and polyether adsorption underlies the critical phenomena associated with breakdown of the polyether–Cl – suppressor layer that is central to bottom-up filling of Cu TSV. ,,, Presently, there are numerous efforts underway to develop physically robust models of the associated dynamics. − ,,, What if any role cations, such as Cu 2+ or, more importantly, its hydrated form, play in suppressor film formation and operation remains to be resolved. Recent studies of specific ion effects on polymer aggregation, i.e., Hofmeister series, indicate that divalent, but not monovalent ions, affect the micellization and aggregation of poloxamers at higher temperatures .…”

Superconformal Copper Electrodeposition in Complexed Alkaline Electrolyte

“…[1][2][3][4][5][6][7] Superconformal filling processes relevant to the microelectronics industry is an area of active research, including surface studies, electrochemical measurements and feature filling assessments. [8][9][10][11][12][13][14][15] Alternative feature filling chemistries might, but need not, rely on a CEAC-based feature filling mechanism.…”