Reactive Magnetron Sputter Deposition of Superconducting Niobium Titanium Nitride Thin Films with Different Target Sizes

Reactive Magnetron Sputter Deposition of Superconducting Niobium Titanium Nitride Thin Films with Different Target Sizes

Bos, Boy Gustaaf Cornelis (Kavli institute of nanoscience Delft; Student TU Delft)
Thoen, David (TU Delft Tera-Hertz Sensing; TU Delft QN/van der Zant Lab; Kavli institute of nanoscience Delft)
Haalebos, E. A.F. (SRON Netherlands Institute for Space Research)
Gimbel, P. M.L. (Student TU Delft; Kavli institute of nanoscience Delft)
Klapwijk, T.M. (TU Delft QN/Klapwijk Lab; Kavli institute of nanoscience Delft)
Baselmans, J.J.A. (TU Delft Tera-Hertz Sensing; SRON Netherlands Institute for Space Research)
Endo, A. (TU Delft QN/Quantum Nanoscience; TU Delft Tera-Hertz Sensing; Kavli institute of nanoscience Delft)

QN/Quantum Nanoscience

2017-06-01

The superconducting critical temperature (T-\mathrm{c} > 15 K) of niobium titanium nitride (NbTiN) thin films allows for low-loss circuits up to 1.1 THz, enabling on-chip spectroscopy and multipixel imaging with advanced detectors. The drive for large-scale detector microchips is demanding NbTiN films with uniform properties over an increasingly larger area. This paper provides an experimental comparison between two reactive dc sputter systems with different target sizes: A small target (o100 mm) and a large target (127 mm × 444.5 mm). This paper focuses on maximizing the T-\mathrm{c} of the films and the accompanying I-V characteristics of the sputter plasma, and we find that both systems are capable of depositing films with T-\mathrm{c} > 15 K. The resulting film uniformity is presented in a second manuscript in this volume. We find that these films are deposited within the transition from metallic to compound sputtering, at the point where target nitridation most strongly depends on nitrogen flow. Key in the deposition optimization is to increase the system's pumping speed and gas flows to counteract the hysteretic effects induced by the target size. Using the I-V characteristics as a guide proves to be an effective way to optimize a reactive sputter system, for it can show whether the optimal deposition regime is hysteresis-free and accessible.

Optimization methods
reactive sputtering
submillimeter wave detectors
superconducting critical temperature
superconducting device fabrication
superconducting thin films

http://resolver.tudelft.nl/uuid:65c38474-ccc7-4211-9d2e-3621279cde2d

https://doi.org/10.1109/TASC.2016.2631939

1051-8223

IEEE Transactions on Applied Superconductivity, 27 (4)

Accepted Author Manuscript

Institutional Repository

journal article

© 2017 Boy Gustaaf Cornelis Bos, David Thoen, E. A.F. Haalebos, P. M.L. Gimbel, T.M. Klapwijk, J.J.A. Baselmans, A. Endo