High quality NbTiN films fabrication and rapid thermal annealing investigation*

Abstract

NbTiN thin films are good candidates for applications including single-photon detector, kinetic inductance detector, hot electron bolometer, and superconducting quantum computing circuits because of their favorable characteristics, such as good superconducting properties and easy fabrication. In this work, we systematically investigated the growth of high-quality NbTiN films with different thicknesses on Si substrates by reactive DC-magnetron sputtering method. After optimizing the growth conditions, such as the gas pressure, Ar/N2 mixture ratio, and sputtering power, we obtained films with excellent superconducting properties. A high superconducting transition temperature of 15.5 K with narrow transition width of 0.03 K was obtained in a film of 300 nm thickness with surface roughness of less than 0.2 nm. In an ultra-thin film of 5 nm thick, we still obtained a transition temperature of 7.6 K. In addition, rapid thermal annealing (RTA) in atmosphere of nitrogen or nitrogen and hydrogen mixture was studied to improve the film quality. The results showed that T c and crystal size of the NbTiN films were remarkably increased by RTA. For ultrathin films, the annealing in N2/H2 mixture had better effect than that in pure N2. The T c of 10 nm films improved from 9.6 K to 10.3 K after RTA in N2/H2 mixture at 450 °C.

Vortex-glass transition and vortex pinning behavior in three-dimensional NbTiN epitaxial films

“…The superconducting transition temperature is 2.80 K for the ∼3.0-nm-thick film, and enhances to 14.07 K as the film thickness increases to ∼400 nm. In previous reports, similar thickness dependent behavior of T c was also observed in NbN [30,31] and TiN films [32] besides in NbTiN films [33,34]. In NbN epitaxial films, the reduction of T c with decreasing film thickness is ascribed to higher disorder level of the thinner film [31].…”

“…In NbN epitaxial films, the reduction of T c with decreasing film thickness is ascribed to higher disorder level of the thinner film [31]. For films with the same thickness, the T c value of our NbTiN film is less than that reported in [33,34], which could be related to the relative higher disorder level of our film.…”

Magnetic field robust high quality factor NbTiN superconducting microwave resonators

“…We attribute this to the highly textured growth of NbTiN induced by the removal of the native amorphous oxide layer. We note that only this NbTiN thin film exhibited crystalline reflexes in x-ray diffraction scans which can be attributed to a highly textured film with the (002) plane of the cubic phase oriented parallel to the substrate surface [35][36][37]. A study of the crystalline reflexes of this sample has been added to the supplemental material (SM) section I [38].…”

Properties of Nb x Ti(1−x)N thin films deposited on 300 mm silicon wafers for upscaling superconducting digital circuits

“…In addition, Nb x Ti (1−x) N has multiple advantages in processing and design including stability and scalability to small dimensions. Ti is a nitrogen getter, so Nb x Ti (1−x) N produces a low number of vacancies and high stability [15,16] even at higher temperatures [17,18] than those achieved in CMOS BEOL processes. In contrast to other superconducting nitrides, Nb x Ti (1−x) N exhibits a lower penetration depth, approximately 200-300 nm [19], and higher critical current density J c ≈ 100-140 mA µm −2 [20,21].…”