Properties of PEG, PPG and Their Copolymers: Influence on Copper Filling of Damascene Interconnects

Abstract

Common open-source suppressors for copper filling of damascene interconnects include polyethylene glycol (PEG), polypropylene glycol (PPG), or a copolymer structure of both. Differences in the structure of these suppressors generate variations in polarization strength, surface adsorption rate, and SPS displacement rate. These properties were measured by electrochemical transient analysis and coupled with the results of time-evolved partial fill plating experiments on 32 nm and 45 nm node features to determine the effect of electrochemical property variations on the gap-fill characteristics. The high polarization strength of PPG, along with its greater dependence on concentration was found to greatly increase the bottom-up growth rate during copper filling, while the improved resistance to accelerator displacement of PEG resulted in better sidewall protection. Both these gap-fill characteristics were evident when PEG and PPG were combined together as a homopolymer mixture or in copolymer structures, although the overall influence was dependent on the size and configuration of each component. These data sets provided a more fundamental understanding of PEG, PPG and their different configurations role in the metallization of damascene interconnects. The relative gap-fill performance can also be inferred to screen new suppressor candidates and reduce the quantity of plating experiments by comparison of the electrochemical properties.