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Quantum bits, or qubits, are an example of coherent circuits envisioned fornext-generation computers and detectors. A robust superconducting qubit with acoherent lifetime of $O$(100 $\mu$s) is the transmon: a Josephson junctionfunctioning as a non-linear inductor shunted with a capacitor to form ananharmonic oscillator. In a complex device with many such transmons, precisecontrol over each qubit frequency is often required, and thus variations of thejunction area and tunnel barrier thickness must be sufficiently minimized toachieve optimal performance while avoiding spectral overlap between neighboringcircuits. Simply transplanting our recipe optimized for single, stand-alonedevices to wafer-scale (producing 64, 1x1 cm dies from a 150 mm wafer)initially resulted in global drifts in room-temperature tunneling resistance of$\pm$ 30%. Inferring a critical current $I_{\rm c}$ variation from thisresistance distribution, we present an optimized process developed from asystematic 38 wafer study that results in $<$ 3.5% relative standard deviation(RSD) in critical current ($\equiv \sigma_{I_{\rm c}}/\left\langle I_{\rm c}\right\rangle$) for 3000 Josephson junctions (both single-junctions andasymmetric SQUIDs) across an area of 49 cm$^2$. Looking within a 1x1 cm movingwindow across the substrate gives an estimate of the variation characteristicof a given qubit chip. Our best process, utilizing ultrasonically assisteddevelopment, uniform ashing, and dynamic oxidation has shown $\sigma_{I_{\rmc}}/\left\langle I_{\rm c} \right\rangle$ = 1.8% within 1x1 cm, on average,with a few 1x1 cm areas having $\sigma_{I_{\rm c}}/\left\langle I_{\rm c}\right\rangle$ $<$ 1.0% (equivalent to $\sigma_{f}/\left\langle f\right\rangle$ $<$ 0.5%). Such stability would drastically improve the yield ofmulti-junction chips with strict critical current requirements.

Improving wafer-scale Josephson junction resistance variation in superconducting quantum coherent circuits