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Microwave loss in superconducting 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. Furthermore, 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 ° C to 3.2 Å/cycle at 350 ° 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. [ABSTRACT FROM AUTHOR]

We report the isotropic plasma atomic layer etching (ALE) of aluminum nitride using sequential exposures of SF6 plasma and trimethylaluminum [Al(CH3)3]. ALE was observed at temperatures greater than 200 ° C, with a maximum etch rate of 1.9 Å/cycle observed at 300 ° C as measured using ex situ ellipsometry. After ALE, the etched surface was found to contain a lower concentration of oxygen compared to the original surface and exhibited a ∼ 35 % decrease in surface roughness. These findings have relevance for applications of AlN in nonlinear photonics and wide bandgap semiconductor devices. [ABSTRACT FROM AUTHOR]