Aluminum Josephson Junction Formation on 200mm Wafers Using Different Oxidation Techniques

This work focuses on the manufacturing of Al/AlOx/Al Josephson junctions (JJs), which are essential components of many quantum circuits. Two processes were studied to understand the oxidation of the aluminum surface. Static oxidation was performed by removing native AlOx in a cluster system with Ar-ion beam milling and controlling the final tunneling oxide by applying a specific O2 pressure in the chamber. Controlled plasma oxidation was performed by removing native AlOx with a H2 plasma followed by a defined reoxidation with an oxygen plasma. The resulting oxides had thicknesses up to 10 nm and their electrical properties were analyzed on wafer level, providing insight into the structure and composition of the aluminum oxides and their applicability for Qubits. This work is crucial for reliable industrial manufacturing on full-scale 200 mm wafers with a very high uniformity level.