Effects of Acetic Acid, Tartaric Acid and Pb UPD on Cu Electrodeposition in Sub-Micron Trenches

Abstract

The effects of acetic acid, tartaric acid, and Pb-mediated underpotential deposition (UPD) on the filling characteristics of copper electrodeposition in sub-micron trenches were studied. In the absence of other electrolyte additives, potentiostatic and galvanostatic depositions from electrolytes containing organic acids were capable of producing dense filling in sub-micron trenches due to higher deposition rates at the trench bottoms compared to the side-walls and adjacent surfaces surrounding the recessed features. The mechanism for dense filling of trenches from depositions in the organic acid containing electrolytes did not appear to match previously identified mechanisms for superfilling associated with surfactant effects. Instead, the differential deposition rates across the trench profile were attributed to textural and/or structural differences in the copper seed layer as the copper deposition rates were enhanced at both the bottom and adjacent surfaces surrounding the trenches, or sidewalls of the trench depending on the organic acid species present in the electrolyte. The organic acids induced conformal and smooth depositions improving with increasing overpotential. Pb mediated UPD yielded smooth, conformal films relative to non-mediated deposition under otherwise identical conditions. The density of the UPD mediated films was best at higher Pb coverage during Cu deposition.

Survey of P-Block Metal Additives for Superconformal Cu Deposition in an Alkaline Electrolyte

“…[29][30][31][32][33][34][35] Likewise, Bi 3+ as well as Pb 2+ and Tl + , for that matter, are all well-known accelerators of Au deposition 36 in sulfite (and cyanide) electrolytes that have been shown to yield superconformal feature filling, 37,38 with Pb 2+ additions being more effective for trench filling and Tl + additions generating bright surfaces. In moderately acidic complexing Cu electrolytes, Pb 2+ has been reported to yield indications of superconformal feature filling, 39 albeit as a modest suppressor. Accordingly, a limited survey of the impact of Tl + and Pb 2+ on Cu deposition was also performed.…”