Electrodeposition of Cobalt for Interconnect Applications

Electrodeposition of Cobalt for Interconnect Applications

Tyler W. Lyons, William D. Sides, Qiang Huang*

Department of Chemical and Biological Engineering, University of Alabama, Tuscaloosa, AL

*qhuang@eng.ua.edu

There is an urgent need to replace copper in state-of-the-art interconnects in semiconductor devices because copper resistivity increases exponentially with the decrease of dimension of features. This paper reports a study of electrodeposition of cobalt with two new additives, dimethylglyoxime and cyclohexane dioxime, aiming to form defect free cobalt interconnects. Cyclic voltammetry, chronopotentiometry with injection of additives, chronoamperometry with different agitation and additive concentrations as well as electrochemical impedance were carried out to characterize the behavior of additives. A quick strong suppression on Co deposition was observed upon the addition of both additives. While cobalt deposition was completely suppressed in presence of high rotation rate, the suppression effect disappeared in absence of agitation. A critical rotation rate was obtained, below which partial suppression was observed. A competition between the supply and adsorption of a suppressing intermediate species onto the electrode and the consumption of this intermediate by electrodeposition was hypothesized as the mechanism of partial suppression. Electrochemical impedance spectra suggested a strong inductance effect resulting from the perturbation of adsorption and desorption of the intermediate at rotation rates below the critical value. This was also consistent with the partial suppression effect and the hypothesized competition mechanism between the adsorption and consumption of an intermediate species.