The next generation of superconducting quantum devices requires both 3D integration and reduced loss. While early devices in the field have been mainly made with Nb and Al, these materials have lossy surface oxides. They are incompatible with conformal deposition techniques required for superconducting through silicon vias. Superconducting nitrides have emerged as a compelling alternative due to their potential for reduced surface oxide-induced loss and compatibility with conformal deposition techniques such as Atomic Layer Deposition (ALD). While TiN has been thoroughly studied with sputtering and CVD, little work has been published with ALD or promising alternative nitrides such as NbN, NbTiN, and TaN.

In this work, we have developed a process for the fabrication of superconducting resonators and superconducting through silicon vias using NbN deposited with plasma-enhanced ALD. We report Tc, measured internal quality factors, and our novel ALD-based approach to superconducting TSV fabrication. Our results clearly demonstrate that ALD superconducting nitrides are promising and practical alternatives for next-generation 3D integrated low-loss superconducting quantum devices.
*We acknowledge funding from Innovate UK ISCF Quantum Technologies, NPL and EPSRC iCASE.

Keywords: Qubit, vertical integration, Through silicon via