RBTIBD Deposition and Characterization of NbTiN Superconducting Thin Films

This study investigates the deposition and characterization of NbTiN superconducting thin films using Reactive Biased Target Ion Beam Deposition (RBTIBD). The primary objective was to understand the effects of deposition parameters. The main variables were target bias, pulse frequency, duty cycle, cathode current, substrate temperature and reactive gas flow. The material properties investigated were stress, roughness, resistivity, lattice parameters, and superconducting transition temperature (Tc). The parameters were systematically varied, and the resulting films analyzed using Grazing Incidence X-Ray Diffraction (GI-XRD), Atomic Force Microscopy (AFM), wafer deflection stress measurements, four-point probe resistivity measurements, and superconducting transition temperature.
The findings reveal the increasing target bias leads to lower stress but higher roughness, with an optimal point around -1100V. Higher pulse frequencies resulted in smoother films and lower resistivity, with an optimal frequency around 71.43KHz. Duty cycle variations showed that lower values, (1µs-2µs), minimized resistivity while giving lower stress and higher Tc’s. Cathode currents around 8A-9A produced films with optimal stress-resistivity balance. Elevated temperatures (300°C) and DC bias sputtering mode, improved film uniformity and reduced stress while increasing Tc. Optimal Nitrogen flow of 3sccm yielded the best superconducting transition temperatures.
These results provide a framework for the reproducible deposition of customizable NbTiN films deposited in this RBTIBD system.

School of Engineering and Applied Science

Master of Science in Electrical Engineering

Technical Advisor: Arthur Lichtenberger

STS Advisor: Arthur Lichtenberger

Technical Team Members: Arthur Lichtenberger, Michael Cyberey, Robert Weikle, N. Scott Barker, Chris Moore