A laboratory scale plating cell was built that provided reproducible bottom-up fill results for the electrochemical deposition of copper in damascene features. Several techniques used in the full wafer plating tool were incorporated into the setup to accurately control the process conditions. These techniques included but were not limited to a voltage controlled `hot-entry' step, a custom coupon holder to allow sample rotation, a secondary thief electrode and an automatic entry system. The results of qualification experiments are presented to demonstrate that precise control was realized along with repeatable partial fill plating results. The qualified setup was then used to perform time-evolved partial fill plating experiments using several different structural configurations of open-source suppressors to investigate their affect on the gap-fill characteristics.
Common open-source suppressors used for copper filling of damascene interconnects include polyethylene glycol (PEG), polypropylene glycol (PPG), or a copolymer structure of both. Differences in the configuration and 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 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 mixture of separate homopolymers 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. These data can also be used to infer the relative gap-fill performance to screen new suppressor candidates and reduce the quantity of plating experiments by comparison of the electrochemical properties.
|Commitee:||LaBella, Vincent, Lloyd, James, Witt, Christian, van Eisden, Jobert|
|School:||State University of New York at Albany|
|Department:||Nanoscale Science and Engineering-Nanoscale Engineering|
|School Location:||United States -- New York|
|Source:||DAI-B 74/10(E), Dissertation Abstracts International|
|Subjects:||Polymer chemistry, Chemical engineering, Electrical engineering, Nanotechnology|
|Keywords:||Copper, Damascene, Electrochemical deposition, Polyethylene glycol, Suppressor, Tri-block copolymer|
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