Coulomb diamond analysis for wafer-level characterization of Si qubit devices

Silicon spin qubits are among the most promising candidates for scalable quantum computing because of their long coherence times and compatibility with CMOS fabrication technology. However, achieving uniform charge properties across devices remains a key challenge. To address this, wafer-level statistical characterization of quantum dots is essential for identifying high-quality devices and providing feedback for process optimization.

In this work, we present an automated method to measure Coulomb diamonds and extract key parameters such as the lever arm and charging energy. The methodology is developed and tested using a cryogenic wafer prober, where two challenges must be addressed: (i) reduced sensitivity and increased setup noise resulting from fast acquisition needed to ensure high measurement throughput, and (ii) blurred features caused by the relatively high electron temperature (compared to dilution refrigerators), which makes it difficult to determine the boundaries of the blockade region. Moreover, since many devices are tested, the methodology must be robust to disorder. Using the proposed approach, we gain insights into fabrication variability and the underlying physical mechanisms influencing the performance of qubit devices.