Structural and Electrical Properties of Tantalum Films Sputtered in Oxygen-Argon Mixtures

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Abstract
The dependence of the structural and electrical properties of sputtered tantalum films on the rate at which oxygen is leaked into the system has been investigated. The films were deposited on glass and polycrystalline alumina substrates and both structural and electrical measurements were made on the same samples. While some films deposited in argon contained both the body‐centered‐cubic and tetragonal β phases of tantalum, those deposited in the presence of oxygen consisted of the β phase. Increasing oxygen content of the films caused an expansion of the tetragonal lattice and changed the preferred grain orientation from (200) to (202). Increases in the oxygen content from 10 to 50 at.% decreased the film density by 2 g/cm3, increased the resistivity ρ from 200 to 5000 μΩ cm, and decreased Δρ/ΔT from 0 to −3.5 μΩ cm/°C. While the activation energy for conduction was small, it increased with the changing orientation of the β‐Ta. This may indicate that ρ is due to the semiconducting nature of β‐Ta and that the band structure of β‐Ta is anisotropic.