Plasma-enhanced atomic layer deposition of titanium nitride for superconducting devices

This study presents a comprehensive investigation into the exceptional superconducting attributes of titanium nitride (TiN) achieved through plasma-enhanced atomic layer deposition (PEALD) on both planar and three-dimensional (3D) structures. We introduced a substrate biasing cycle to densify the film and remove ligand residues, augmenting the film properties while minimizing impurities. While reactive-sputtered TiN films exhibit high quality, our technique can enable superior uniformity by consistently maintaining a desired sheet resistance (R□) > 95% across a 6-inch wafer—a critical aspect for fabricating extensive arrays of superconducting devices and optimizing wafer yield. Moreover, our films demonstrate exceptional similarity to conventional reactive-sputtered films, consistently reaching a critical temperature (Tc) of 4.35 K with a thickness of around 40 nm. This marks a notable achievement compared to previously reported ALD-based superconducting TiN. Using the same process as for planar films, we obtained Tc for aspect ratios (ARs) ranging from 2 to 40, observing a single transition in Tc of approximately 2 K for ARs between 2 and 10.5. We elucidate the mechanisms contributing to the limitations and degradation of superconducting properties over these aggressive 3D structures. Our results align with both current and next-generation superconducting technologies, meeting stringent criteria for thin-film constraints, large-scale deposition, conformality, 3D integration schemes, and yield optimization.