Performance and Design Validation of CMS Phase-2 Pixel Modules

Abstract

In view of the High Luminosity LHC, the current CMS tracking detector will have to be replaced during Long Shutdown 3 to cope with the higher radiation environment and to withstand an increased data rate. To prepare for the so-called CMS Phase-2 upgrade, multiple studies were carried out to characterize the pixel module design and its performance with a particular focus on the Quality Control (QC) and Assurance. For this purpose, different aspects were put together to establish a module full-performance test procedure, and novel techniques became part of the module design validation process for the full-size readout chip (CROCv1). Based on the results collected on CROCv1 prototype modules and according to the module selection criteria the community agreed on, some changes were introduced in the module design to improve the performance. This resulted in multiple prototype versions, including the production of the definitive chip (CROCv2). This study presents the quality control test flow performed, both for the dual and quad-chip module designs, on a big sample of CROCv1 prototypes and on several Kick-off and CROCv2 pre-production modules. In particular, the validation process includes measurements of the readout chip powering, sensor IV bias and open bump bonds identification. Thermal stress tests in extended temperature ranges were performed only on a subset of pixel modules to ensure the integrity of the sensor and to provide quick feedback on the quality of the bump bond connectivity after harsh temperature cycles.