Using SERS to Evaluate Additive Kinetics During Reverse Pulse Plating of Cu

Surface enhanced Raman spectroscopy (SERS) was used to evaluate the kinetics and relative surface amounts of additives during pulsed reverse plating of Cu. The amount of Cl⁻ relative to MPS was shown to increase as a result of the slow kinetics of Cl⁻ desorption relative to MPS desorption after the positive pulses. Kinetic Langmuir fits to SERS intensity data estimate the desorption rates of additives. Cl:MPS ratios confirm the increase in relative amounts of Cl⁻ after positive pulses. Additives in the plating baths were shown to affect the adsorption and desorption behaviors of the other additives. The relative amounts of additives at the Cu surface during Cu deposition can be tuned by the positive reverse pulses.