Wafer-scale uniformity improvement of Dolan-bridge Josephson junction by shadow evaporation bias correction

• Main Authors: Moskaleva, Daria A, Korshakov, Nikita D, Moskalev, Dmitry O, Solovyova, Anastasiya A, Matanin, Alexey R, Malevannaya, Elizaveta I, Smirnov, Nikita S, Teleganov, Maksim I, Panfilov, Yuri V, Rodionov, Ilya A
• Format: Journal Article
• Language: English
• Published: 04-03-2024
• Subjects: Physics - Quantum Physics
• DOI: 10.48550/arxiv.2403.01894

One of the practical limitations of solid-state superconducting quantum
processors technology is frequency crowding due to low qubits fabrication
reproducibility. Josephson junction 100 nm-scale nonlinear inductance of the
qubits still suffers from Dolan-bridge shadow evaporation process. Here, we
report on a robust wafer-scale Al/AlOx/Al Dolan-bridge Josephson junction (JJ)
process using preliminary shadow evaporation bias resist mask correction and
comprehensive oxidation optimization. We introduce topology correction model
for two-layer resist mask biasing at a wafer-scale, which takes into account an
evaporation source geometry. It results in Josephson junction area variation
coefficient improvement down to 1.1% for the critical dimensions from 130x170
nm2 to 130x670 nm2 over 70x70 mm2 (49 cm2) wafer working area. Next, we
investigate JJ oxidation process (oxidation method, pressure and time) and its
impact on a room temperature resistance reproducibility. Finally, we combine
both shadow evaporation bias correction and oxidation best practices for 4-inch
wafers improving room temperature resistance variation coefficient down to
6.0/5.2/4.1% for 0.025 {\mu}m2 JJ area and 4.0/3.4/2.3% for 0.090 {\mu}m2 JJ
area for 49/25/16 cm2 wafer working area correspondingly. The proposed model
and oxidation method can be useful for robust wafer-scale superconducting
quantum processors fabrication.