Selective Copper Electrodeposition for Redistribution Layer by Varying Concentration and Agitation of Janus Green B

Abstract

A fine-pitch redistribution layer (RDL) for high-performance devices in a fan-out wafer-level package (FOWLP) is required in semiconductor packaging technology. The damascene process for fine-pitch RDL has been studied for several years, which has been introduced to overcome the etching problems. Although surface planarization for removing overburden is necessary for the damascene process in RDL, it adds high cost to the FOWLP process. Selective Cu electrodeposition is a method used to prevent overburden. Janus Green B (JGB) is utilized as a leveler in Cu electrodeposition and has properties that depend on concentration and agitation. These properties affected the Cu deposition rate according to the pattern position. Thus, the electrochemical properties of JGB were investigated based on the concentration of JGB and agitation. Furthermore, the effect of JGB on the crystalline structure of the Cu film was examined. Additionally, changes in the growth behavior of the Cu nuclei caused by JGB were observed during the initial stage of chronoamperometry. Based on these results, selective Cu electrodeposition was successfully performed on the patterned substrate using the difference in the concentration of JGB and agitation.