CMOS-Compatible Ultrathin Superconducting NbN Thin Films Deposited by Reactive Ion Sputtering on 300 mm Si Wafer

TL;DR

This paper demonstrates the successful large-scale deposition of ultrathin, high-quality superconducting NbN films on 300 mm silicon wafers using reactive ion sputtering, with enhanced superconducting properties enabled by an AlN buffer layer.

Contribution

It introduces a scalable method for producing uniform, high-performance NbN superconducting films on standard CMOS wafers with improved critical temperature and magnetic field properties.

Findings

Achieved uniform ultrathin NbN films on 300 mm wafers.

Enhanced superconducting critical temperature with AlN buffer.

Increased upper critical magnetic field (Hc2) with AlN buffer.

Abstract

We report a milestone in achieving large-scale, ultrathin (~5 nm) superconducting NbN thin films on 300 mm Si wafers using a high-volume manufacturing (HVM) industrial physical vapor deposition (PVD) system. The NbN thin films possess remarkable structural uniformity and consistently high superconducting quality across the entire 300 mm Si wafer, by incorporating an AlN buffer layer. High-resolution X-ray diffraction and transmission electron microscopy analyses unveiled enhanced crystallinity of (111)-oriented {\delta}-phase NbN with the AlN buffer layer. Notably, NbN films deposited on AlN-buffered Si substrates exhibited a significantly elevated superconducting critical temperature (~2 K higher for the 10 nm NbN) and a higher upper critical magnetic field or Hc2 (34.06 T boost in Hc2 for the 50 nm NbN) in comparison with those without AlN. These findings present a promising pathway for the integration of quantum-grade superconducting NbN films with the existing 300 mm CMOS Si platform for quantum information applications.