Film thickness effects on the fracture of tantalum nitride on aluminum nitride thin film systems

In this study, nanoindentation and nanoscratch testing were combined with t ransmission electron microscopy to establish the relationship between struc ture, properties, and fracture resistance of thin tantalum nitride resistor films on aluminum nitride substrates. The films were sputter-deposited to thicknesses of 160, 440, and 500 nm. Nanoindentation was used to determine mechanical properties while nanoscratch tests were used to measure interfac ial fracture energies. These tests showed that the measured elastic moduli of all films were independent of indenter depth and approximately equal to the value measured for the aluminum nitride substrates, They also showed th at measured hardness values increased with film thickness. More importantly , the fracture energies measured in indentation fracture and nanoscratch te sts were essentially equal and independent of film thickness. These results showed that tantalum nitride films and aluminum nitride substrates behaved in an inherently brittle manner. They further showed that fracture was loc alized along the interface suggesting that adhesion was controlled by the n ature of bonding across the interface plane. (C) 1998 Elsevier Science Ltd. All rights reserved.