Probing single electrons across 300 mm spin qubit wafers

TL;DR

This paper demonstrates a high-throughput cryogenic testing process for 300 mm silicon spin qubit wafers, enabling rapid device characterization, process optimization, and analysis of single-electron behavior at scale.

Contribution

It introduces a novel cryogenic wafer probing method for large-scale spin qubit testing, improving yield and reducing process variation in quantum device fabrication.

Findings

High-yield fabrication process with low disorder levels

Automated measurement of single-electron operating points

Low variation in electron transition voltages across wafers

Abstract

Building a fault-tolerant quantum computer will require vast numbers of physical qubits. For qubit technologies based on solid state electronic devices, integrating millions of qubits in a single processor will require device fabrication to reach a scale comparable to that of the modern CMOS industry. Equally importantly, the scale of cryogenic device testing must keep pace to enable efficient device screening and to improve statistical metrics like qubit yield and voltage variation. Spin qubits based on electrons in Si have shown impressive control fidelities but have historically been challenged by yield and process variation. Here we present a testing process using a cryogenic 300 mm wafer prober to collect high-volume data on the performance of hundreds of industry-manufactured spin qubit devices at 1.6 K. This testing method provides fast feedback to enable optimization of the CMOS-compatible fabrication process, leading to high yield and low process variation. Using this system, we automate measurements of the operating point of spin qubits and probe the transitions of single electrons across full wafers. We analyze the random variation in single-electron operating voltages and find that the optimized fabrication process leads to low levels of disorder at the 300 mm scale. Together these results demonstrate the advances that can be achieved through the application of CMOS industry techniques to the fabrication and measurement of spin qubit devices.