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1– 16 For on-chip damascene interconnects as well as blind via PCB metallization, organic additive combinations are often used in either two (suppressor-accelerator) or three (suppressor-accelerator-leveler) component combinations. Central to this and other manufacturing applications is void-free electrodeposition of Cu in high-aspect ratio features, accomplished using electrolyte additives that selectively inhibit and accelerate the deposition rate to enable superconformal or bottom-up filling of recessed surface features. Significant research efforts and commercial resources have focused on development of efficient processes for fabricating electronic circuitry that range in length-scale from sub-10 nm transistor interconnects to millimeter-scale wiring in printed circuit boards (PCBs). Microelectrodes constrain or frustrate the otherwise random bifurcation process giving rise to predictable morphologies unattainable on macroscale electrodes. The difference between potentiodynamic and galvanodynamic responses reflects the convolution of S-NDR critical behavior with the respective control-loop load lines. In contrast, galvanodynamic experiments in more concentrated Cl − solutions reveal spatially selective suppressor breakdown with deposition initially localized to the microelectrode center followed by outward expansion as applied current is increased. For potentiodynamic conditions, adlayer breakdown propagates rapidly from the center of the microelectrode surface although the final deposit profile is non-uniform due to enhanced transport to the disk perimeter. The impact of electrode shape change on simulations of electroanalytical experiments is quantified in comparison to a stationary interface approximation. Simulations involving co-adsorption of the suppressor-halide adlayer and its subsequent breakdown capture the positive feedback and negative differential resistance (S-NDR) evident in electroanalytical measurements as well as important aspects of electrode shape evolution.
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Optical imaging during cyclic voltammetry and galvanodynamic measurements reveal hysteresis, overpotential inversions, and the morphological evolution accompanying breakdown of the polyether-chloride inhibition layer. Copper electrodeposition from a CuSO 4-H 2SO 4 electrolyte containing a polyether suppressor and (0 to 100) μmol L −1 Cl − is examined using a 25 μm diameter microdisk electrode.