Process quality control strategy for the Phase-2 Upgrade of the CMS Outer Tracker and High Granularity Calorimeter

Between 2025 and 2027, some essential components of the CMS (Compact Muon Solenoid) detector – most notably the tracker and the calorimeter endcap – will be upgraded to prepare for HL-LHC (High Luminosity Large Hadron Collider) conditions. The upgraded CMS Outer Tracker and parts of the new CMS High Granularity Calorimeter (HGCAL) will encompass over 50,000 new silicon sensors covering a total area of about 800m2. The sensor series production requires a dedicated strategy to monitor the quality and stability of the production process. The strategy is based on a test structure set that provides quick and easy access to critical process parameters. These include parameters not directly accessible on the sensors (e.g. oxide charge concentration and interface trap density) and parameters requiring potentially destructive measurements (e.g. dielectric strength). The set is implemented at least twice on each production wafer. It is divided into test structures for initial evaluation of the most relevant process parameters and structures for in-depth analysis. All structures can be contacted using a 20-needle probe card and an automated positioning stage. With this system, the initial analysis of one wafer is possible in about 30 min. In this paper, the CMS collaboration presents the quality assurance plan for the Phase-2 Upgrade with a focus on process quality control. We cover sensor process specifics, the layout of the test structure set that will be implemented in the production runs for the CMS Outer Tracker and HGCAL, and measurement results illustrating the functionality of the included test structures.