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The High-Luminosity Large Hadron Collider (HL-LHC) upgrade, scheduled to start at the end of 2026, will increase the collision luminosity by a factor of 7.5 and raise the average vertex density along the z-axis to 1.5 vertices per millimeter. This will impose extremely demanding requirements on detector radiation tolerance and tracking performance. As the core component of the HGTD timing detector, the LGAD silicon sensor can achieve a time resolution of 50 ps thanks to its thin multiplication layer structure. The sensor adopts a 15 x 15 pixel-array design, with a single-pixel size of 1.3 x 1.3 mm2, and is read out through bump bonding to the dedicated ALTIROC front-end chip. Its performance directly determines the overall performance of the HGTD detector.
This report will focus on the mass production and quality-control procedure of LGAD sensors. Each wafer contains main detector sensors and dedicated quality-control test structures. The Institute of Microelectronics of the Chinese Academy of Sciences performs probe-card tests for each sensor, and the sensors are classified into four categories, A, B1, B2, and C, according to the current-voltage criteria defined by the HGTD Sensors group. IHEP performs sampling inspections of Class A sensors using probe-based per-pixel measurements. CERN and USP measure key parameters of QC-TS at multiple wafer locations, including gain-layer depletion voltage and coupling capacitance. JSI evaluates the radiation tolerance of the QC-TS through irradiation tests.
At present, the IV/CV performance of Class A sensors and QC-TS structures from the pre-production batch satisfies the acceptance criteria. The yield of Class A sensors reaches 42.08%. Some B1 and B2 sensors also satisfy the requirements after probe-based testing, effectively improving the overall wafer yield. The final mass production covering five batches is progressing steadily according to schedule. In addition, considering that sensors will face an ultra-high radiation-dose environment above 2.5 x 1015 neq/cm2 after the future LHC upgrade, this report will also introduce neutron-irradiation test results of LGAD sensors with different epitaxial-layer thicknesses. Based on beta-test analysis, these studies provide technical guidance and selection criteria for optimizing next-generation LGAD devices with higher radiation tolerance.
| 请选择分会 | 粒子物理实验技术 |
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