Ultrathin TaN Damascene Nanowire Structures on 300-mm Si Wafers for Quantum Applications

Abstract

We report on the development and characterization of superconducting damascene tantalum nitride (TaN) nanowires, 100 nm–3 μm wide, with TaN thicknesses varying from 5 to 35 nm, using 193-nm optical lithography and chemical mechanical planarization among other 300-mm wafer-scale processes. The TaN film composition chosen for nanowire fabrication was informed by a detailed study of unpatterned TaN films with varying nitrogen to tantalum ratios, formed by reactive sputtering. We also discuss the influence of encapsulation by copper and disordered atomic layer deposited TaN on the critical current of superconducting nanowires. Superconducting critical current density (measured at 12 mK) ranges from 0.12 to 0.85 MA/cm2 depending on nanowire width and film thickness. The potential of ultrathin TaN nanowires at 300-mm scale is discussed in the context of applications such as on-chip integration for readout of superconducting qubits, in single-photon detection for quantum computing, as well as in large single-photon detecting focal plane arrays for cosmology in a broader range of wavelengths.

Keywords

• Damascene nanowires
• quantum applications
• superconducting nanowires
• ultrathin tantalum nitride (TaN) films
• 300 mm Si substrates