Speaker
Description
The CMS detector at the CERN Large Hadron Collider is undergoing major upgrades for the High-Luminosity LHC (HL-LHC), including the replacement of its endcap calorimeters with the High Granularity Calorimeter (HGCAL). The electromagnetic section (CE-E) and the high-radiation regions of the hadronic section (CE-H) will employ radiation-tolerant, fast-response silicon pad sensors, collectively covering a surface area of approximately 620 m². These sensors must maintain stable performance under the extreme particle fluences expected throughout the HL-LHC lifetime. Ensuring their reliability and consistency has required a comprehensive silicon quality control (SQC) program that monitors the electrical and mechanical robustness of the sensors across the entire production chain.
From early 2023 to mid-2025, the manufacturer Hamamatsu Photonics K.K. completed the production of nearly 25,000 8-inch p-type wafers with multiple sensor designs and thicknesses. This large-scale production included per-cell leakage current (IV) and capacitance (CV) measurements as well as mechanical inspections performed both at the vendor and during subsequent acceptance stages in multiple CMS institutes. The resulting dataset—both from Hamamatsu and by SQC efforts at CERN—enabled detailed monitoring of process stability, early identification of systematic effects, and quick feedback to the manufacturer.
In this talk, we present an overview of the QC workflow developed for HGCAL, including automated handling of vendor data, validation of electrical measurements, and cross-checking of wafer-level characteristics using CMS SQC results. We summarize key observations from the production campaign, such as thickness-dependent trends, recurring spatial patterns in leakage current, delivery-to-delivery variations, and correlations between mechanical features and electrical response. These findings provided essential input during the production phase and contributed to progressive improvements in sensor quality.
Beyond supporting HGCAL construction, the methodologies and insights gained from this large-volume testing campaign offer valuable guidance for future silicon detector projects facing similar challenges in scale, radiation hardness, and long-term reliability.