Substrate composition effects on the interfacial fracture of tantalum nitride films

In this study we combined nanoscratch testing with a multilayer sapphire an d aluminum nitride single-substrate system to determine the effects of inte rface composition and structure on susceptibility to fracture of hard, thin tantalum nitride films, Nanoindentation tests showed that the elastic modu li of the tantalum nitride and aluminum nitride films, as well as the sapph ire substrate, were essentially equal at 400 GPa. On both portions of the s ubstrate, these tests also showed that near surface hardness was near 35 GP a. Nanoscratch tests triggered long blisters and circular spalls on both th e sapphire and aluminum nitride portions of the substrate. The blisters sho wed that the tantalum nitride film was subjected to a compressive residual stress of -6.7 GPa, The spalls showed that failure occurred along the tanta lum nitride film-substrate interface regardless of substrate composition. M ost importantly, the blisters and spalls showed that the mode I component o f the fracture energies was essentially equal on both substrate materials a t a value near 3.1 J/m(2), These energies are on the order of the energies for metallic bonding.