Isotropic plasma-thermal atomic layer etching of superconducting TiN films using sequential exposures of molecular oxygen and SF$_6/$H$_2$ plasma

Azmain A. Hossain; Haozhe Wang; David S. Catherall; Martin Leung; Harm C. M. Knoops; James R. Renzas; Austin J. Minnich

doi:10.1116/6.0002965

paper

Isotropic plasma-thermal atomic layer etching of superconducting TiN films using sequential exposures of molecular oxygen and SF $_{6} /$ H $_{2}$ plasma

arXiv:2307.02821 · doi:10.1116/6.0002965

Abstract

Microwave loss in superconducting titanium nitride (TiN) films is attributed to two-level systems in various interfaces arising in part from oxidation and microfabrication-induced damage. Atomic layer etching (ALE) is an emerging subtractive fabrication method which is capable of etching with Angstrom-scale etch depth control and potentially less damage. However, while ALE processes for TiN have been reported, they either employ HF vapor, incurring practical complications; or the etch rate lacks the desired control. Further, the superconducting characteristics of the etched films have not been characterized. Here, we report an isotropic plasma-thermal TiN ALE process consisting of sequential exposures to molecular oxygen and an SF $_{6}$ /H $_{2}$ plasma. For certain ratios of SF $_{6}$ :H $_{2}$ flow rates, we observe selective etching of TiO $_{2}$ over TiN, enabling self-limiting etching within a cycle. Etch rates were measured to vary from 1.1 Å/cycle at 150 $^{\circ}$ C to 3.2 Å/cycle at 350 $^{\circ}$ C using ex-situ ellipsometry. We demonstrate that the superconducting critical temperature of the etched film does not decrease beyond that expected from the decrease in film thickness, highlighting the low-damage nature of the process. These findings have relevance for applications of TiN in microwave kinetic inductance detectors and superconducting qubits.

17 pages, 7 figures

Isotropic plasma-thermal atomic layer etching of superconducting TiN films using sequential exposures of molecular oxygen and SF $_{6} /$ H $_{2}$ plasma

Abstract

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Isotropic plasma-thermal atomic layer etching of superconducting TiN films using sequential exposures of molecular oxygen and SF6​/H2​ plasma

Abstract

References in corpus (5)

Cited by in corpus (2)

Isotropic plasma-thermal atomic layer etching of superconducting TiN films using sequential exposures of molecular oxygen and SF $_{6} /$ H $_{2}$ plasma