Effect of Rapid Thermal Annealing on the Superconductivity of ALD-Grown TiN thin films
Titanium nitride (TiN) is a promising superconducting material for scalable quantum technologies owing to its tunable kinetic inductance and compatibility with CMOS thin-film processing. However, the superconducting performance of atomic-layer-deposited TiN can be degraded by oxygen incorporation, off-stoichiometry, and crystallographic disorder. In this work, we investigate rapid thermal annealing (RTA) in high-purity nitrogen as a post-deposition strategy to improve polycrystalline TiN films grown by RF-biased plasma-enhanced atomic layer deposition. Grazing-incidence X-ray diffraction reveals reduced peak broadening, a smaller lattice parameter, and a stronger (111) preferred orientation with increasing annealing temperature. X-ray photoelectron spectroscopy depth profiling shows reduced oxygen-related bonding and a shift toward a Ti--N-dominated chemical environment after annealing. These structural and chemical changes result in a 25% increase in the superconducting transition temperature and a significant narrowing of the transition width. Annealing also reduced the sheet resistance and the estimated sheet kinetic inductance, increased the residual resistance ratio, and improved the magnetic-field tolerance. Together, the structural, chemical, and transport results are consistent with reduced material disorder and improved superconducting uniformity. Because RTA is a relatively low thermal budget and is a semiconductor fabrication compatible process, it offers a practical route to improve the quality of ALD-grown TiN for superconducting applications.