Titanium-tungsten contacts to Si: The effects of alloying on Schottky contact and on silicide formation

Contact reaction and Schottky barrier heights on Si were studied using Ti-W alloys of increasing W concentration (Ti, Ti₈W₂, Ti ₄W₆, Ti₂W₈) in order to determine the effect of alloy composition on Schottky contact behavior. Glancing angle x-ray diffraction, Rutherford backscattering spectroscopy, and scanning electron microscopy were used to analyze the contact reaction. Schottky barrier heights were determined from the I-V behavior of circular diodes. Four-point probe measurements were used to compute the film electrical resistivity. Our experiments show that the addition of small amounts of W has raised the formation temperature of Ti silicides and maintained a low barrier height (∼0.55 eV) Schottky contact on n-type Si up to 550 °C. A bilayer shallow contact metallurgy Si/Ti₈W₂/Ti₃ W ₇/Al which provides a low barrier metal contact to n-type Si as well as an effective diffusion barrier between Al and Si is proposed as a result of this study.