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

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Abstract
Contact reaction and Schottky barrier heights on Si were studied using Ti‐W alloys of increasing W concentration (Ti, Ti8W2, Ti4W6, 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 W7/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.