Indentation fracture and continuous nanoscratch testing were used in this study to determine the effects of compressive residual stresses on the fracture of thin sputter-deposited tantalum nitride films. Some films were tested in the as-deposited condition while others were vacuum annealed at 300°C. The only discernible change in structure was a surface rearrangement of atoms into parallel arrays of striations on the vacuum annealed samples revealing a high compressive residual stress state after deposition. Comparison of results and application of mechanics-based models showed that these stresses had a strong effect on the fracture of the as-deposited films. The models also provided a good measure of the residual stress levels and interfacial strain energy release rates.
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The authors thank C. Rood from Sandia National Laboratories, Livermore, CA and J. Nelson from the Univesity of Minnesota for their technical support. We especially thank J. Hoehn and D. Bahr of the University of Minnesota and M. De Boer from Sandia National Laboratories, Albuquerque, NM for their many helpful technical discussions. NRM, RQH, DPN and JEA gratefully acknowledge the support of the U.S. DOE through Contract DE-AC04-94AL85000. SV and WWG gratefully acknowledge the support of the Center for Interfacial Engineering at the University of Minnesota under grant NSF/CDR-8721551. WWG also acknowledges support of the U.S. DOE through Contract DE-FG02-96ER45574.