Model Friction Studies of Chemical Mechanical Planarization Using a Pin-on-Disk Tribometer
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A pin-on-disk attachment for a commercial rheometer was used as a model system for chemical–mechanical planarization. The system enables real-time measurements of friction and the pin height changes as a function of velocity and load. We found the pin-on-disk tribology geometry was able to achieve a range of down pressures relevant to CMP processes (24.5 kPa at Fn = 1.5 N). It was possible to measure changes in the pin height, or gap, on the order of 1 µm during the test, which was useful to determine the amount of wear on the polishing pad and whether the system moves into hydrodynamic lubrication. The pad conditioning, or break-in process with water using a stainless steel disk with embedded diamond teeth, was conducted right before the tribology test, as in CMP processes, to give a consistent texture and remove surface impurities. Control studies of pure water at various pH’s showed the friction coefficient data and gap changes between the pad and the silicon wafer vary with the pH and ionic strength of the solution. CMP polishing was also studied with commercial slurries, pads and silicon wafers, showing that COF and pad wear can be measured reliably in the tribometer and compares well to measurements made on a 200 mm CMP commercial polisher for both water and the slurry. Overall, the pin-on-disk attachment was found to provide good insights of the tribology of a full CMP system.
KeywordsCMP Tribology Water CMP pad CMP slurry
The authors are grateful to John McCormick, Doran Bennett, Michael Mills, and Naresh Penta for numerous discussions about CMP process friction, and providing historical CMP polishing data. We thank Tim Mace and Jianxin Ma for confocal microscopy of samples. We thank Marty DeGroot, Jim Alexander, and Bob Auger for research support, as well as The Dow Chemical Company and the DuPont Electronics and Imaging business.
- 1.Li, Y. (ed.): Microelectronic Applications of Chemical Mechanical Planarization. Wiley Interscience, New York (2008)Google Scholar
- 2.Gitis, N., Mudhivarthi, R.: Tribometrology of CMP process. In: Li, Y. (ed.) Microelectronic Applications of Chemical Mechanical Planarization, pp. 81–122. Wiley Interscience, New York (2008)Google Scholar
- 36.Reddy, K.-A., Lawing, A.S., Koons, G.S., Guo, Y., Zhendong, L.: CMP pad asperity wear dependence on the morphology and concentration of the abrasive particles in the polishing slurries. Proceedings of 2010 International Conference on Planarization/CMP Technology, Phoenix, AZ, p. 168. American Vacuum Society, Phoenix, AZ (2010)Google Scholar