Analysis of unstable leakage current in ATLAS18 Strip Sensors after long-term tests

Le résumé fourni par la source

With the upgrade of the LHC to the High-Luminosity LHC (HL-LHC), the ATLAS Inner Detector will be replaced with the new all-silicon ATLAS Inner Tracker (ITk) to maintain tracking performance in a high-occupancy environment and to cope with the increase in the integrated radiation dose. Comprising an active area of 165 m 2 , the outer four layers in the barrel and six disks in the end-cap region will host strip modules, built with single-sided micro-strip sensors and glued-on hybrids carrying the front-end electronics necessary for readout. Before being shipped out for module building, a total of 24010 ATLAS18 n + -in-p strip sensors, of which 17888 sensors are to be installed in the experiment, were tested at different institutes in the collaboration. The main sensors were tested for mechanical and electrical compliance with technical specifications, the quality control (QC), while technological parameters were verified on test structures from the same wafers before and after irradiation, the quality assurance (QA). Reverse-bias leakage current measurements of every sensor, together with leakage current stability measurements on a sample basis, are an important part of QC procedure. During these measurements, a recurring pattern of performance degradation and recovery in leakage current and sensor breakdown after long-term testing has been observed for a subset of sensors. A comprehensive analysis of those changes observed during sensor QC is presented. Mitigation and recovery procedures, such as ionizing guns, exposure to UV light and sensor baking, developed by the ITk strip sensor community and applied at different QC sites are also discussed, including their impact on sensor performance.

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