Abstract
The usefulness of titanium nitride thin films deposited under different sputter deposition conditions as a diffusion barrier in silicon-to-aluminum contacts was examined. In particular, the effect of oxygen in the barrier film was investigated. The films were r.f. sputter deposited from a titanium target in an Ar-N 2 or Ar-N 2-O 2 gas mixture under varying conditions of applied d.c. substrate bias voltage. The variations in film oxygen content, resistivity, film stress and deposition rate are presented as functions of nitrogen and oxygen partial pressures, and applied substrate bias. The diffusion barrier properties of dark brown films (B films) deposited under no-bias conditions, bright golden films (G films) deposited under proper substrate bias, and oxygen-containing golden films (Ox films) were tested by Rutherford backscattering spectrometry and optical measurements at temperatures of 450–600°C. Cross-bridge Kelvin resistor contact resistance structures were formed on the sapphire wafers for electrical characterization of these films. It was found that the G films are much better diffusion barriers than our B films, and show very low contact resistance in an Al/TiN/Ti/Si metallization scheme. Addition of oxygen in the G films increases the contact resistance, but at the same time decreases the failure rate of the contacts during heat-treatment cycles.
Published Version
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