Leveling with Step Potential in Damascene Cu Electrodeposition

Abstract

Organic leveler-free leveling, issued in damascene Cu electrodeposition for uniform Cu patterning by the chemical mechanical polishing process, was investigated using a potentiostatic step function. A perfectly leveled Cu surface was obtained with applying a positive step potential. The distribution of locally adsorbed bis 3–sulfopropyl disulfide SPS , which was the main cause of the formation of topographic variation on the wafer surface, was modified by the use of a positive step potential. The redistribution of adsorbed SPS was a result of desorption of SPS through the dissolution occurring during the step time. Desorbed SPS was then readsorbed uniformly on the Cu surface after a step time, resulting in a flat Cu surface. Electrochemical linear sweep voltammetry and chronoamperometry analyses revealed a decrease in current, which meant the desorption of SPS on Cu surface was caused by the dissolution of Cu. By varying the step potential and step time, it was confirmed that at least 6 nm of the Cu layer should be dissolved for effective desorption of SPS and successful leveling.