Superconducting TiN Films Sputtered over a Large Range of Substrate DC Bias

TL;DR

This study explores how varying substrate bias during sputtering affects the structural, compositional, and superconducting properties of TiN films, demonstrating potential for reproducible low-temperature superconducting devices.

Contribution

It provides a comprehensive analysis of the influence of RF bias on TiN film properties, highlighting the relationship between bias, crystallinity, impurity levels, and superconducting performance.

Findings

Higher bias yields cubic TiN with (200) orientation

Films show low oxygen impurity levels and uniform resistivity

Coplanar resonators demonstrate high kinetic inductance and quality factor

Abstract

We have investigated properties of superconducting titanium nitride (TiN) films that were sputtered over a large range of RF-induced DC bias voltage applied to the substrate. Films grown with the largest bias voltages contained cubic TiN phases with a large fraction of the (200) crystalline growth orientation. These films also contained the smallest concentrations of oxygen impurities, resulting in stoichiometric TiN. Over the range of bias, variations of the stress from slightly tensile to highly compressive were measured and correlated to crystallinity of the (200) growth. The films exhibited highly uniform thickness and resistivity, and show the potential for yielding reproducible low-temperature devices. Finally, coplanar resonators fabricated with the films exhibited high kinetic inductance and quality factor, where the latter was obtained in part from temperature-dependent frequency shifts.