The deposition and film properties of reactively sputtered titanium nitride

Abstract

Titanum nitride films were prepared by reactive d.c. magnetron sputtering from a titanium target in a working gas mixture of Ar + N 2. Film preparation was examined with respect to kinetics during reactive sputtering. Rutherford backscattering, Auger electron spectroscopy, transmission electron microscopy and electron diffraction were used to determine film composition, impurity levels and microstructure. The stoichiometric TiN films were found to possess a single-phase f.c.c. structure and demonstrated good diffusion barrier integrity in an Al/TiN/Si structure at temperatures below 550 °C. Interposition of a thin 60 Å titanium layer at the TiNSi interface yielded low contact resistance to p +- and n +-Si regions. The limitation of reactively sputtered TiN diffusion barrier layers was determined to be their effect on the electromigration of the overlying aluminum, an effect which has not previously been reported. The insertion of a TiN layer between the aluminum and the underlying SiO 2 shifted the electromigration failure mode from open- to short-circuit formation and reduced the median time to failure (MTF) by more than an order of magnitude. The MTF of the composite Al/TiN conductor was a factor of 5 less than that for a comparable Al/TiW conductor. Preliminary experimentation with layered Al/Ti conductors revealed the electromigration failure mode also to be short-circuit formation.