Plasma-Enhanced Atomic Layer Deposition of Superconducting TiN films*

To reduce dependency on error correction in quantum computation, this study aims to investigate the decoherence that originates from the impurities within the superconducting qubit material itself, specifically Titanium Nitride (TiN). Since TiN is attractive for its long coherence times and plasma-enhanced atomic layer deposition (PEALD) provides incomparable homogeneity and thickness control, optimizing PEALD TiN film fabrication for higher superconducting transition temperature Tc, lower impurity concentration, and increased crystallinity is crucial to making replicable and reliable qubits. This begins with tuning the fabrication parameters, such as titanium precursor pulse time and post deposition cooling time, across varying film thicknesses, then placing those films inside a cooled dilution fridge and recording their Tc and other electrical properties. In this work, we present our experimental study of PEALD TiN film where the parameters mentioned above were analyzed for increased film quality. We also show the measurement results of testing TiN films of various thicknesses in the dilution fridge and their corresponding Tc values. Furthermore, we recorded how the effects of the fabrication parameter variations manifested in different characterization tools across different film thicknesses, from spectroscopic ellipsometry (Woollam) to X-ray diffraction analysis (XRD).