Silicon sensor process quality control for the CMS phase-2 upgrade

The start of the High Luminosity Large Hadron Collider (HL-LHC) at the European Organization for Nuclear Research (CERN) scheduled for 2027 will herald a new era for high energy particle physics. The physics experiments located at the LHC will undergo a major upgrade between 2025 and 2027 to ready for the challenging conditions of the new high luminosity environment.As part of this upgrade, the CMS (Compact Muon Solenoid) experiment will see the complete replacement of the full silicon tracker and the calorimeter endcaps. Over 50 000 large-area, position-sensitive silicon sensors will be produced between 2020 and 2023 to be integrated into the CMS Outer Tracker and the new High Granularity Calorimeter (HGCAL).This thesis presents the CMS strategy to monitor the quality and stability of the sensor manufacturing process throughout production time. The process quality control procedure relies on tracking critical process parameters on test structures. The structures are manufactured on the same wafers as the sensors and, hence, share the same properties. They provide easy access to many process parameters, including parameters that are not directly accessible on sensors (e.g. oxide charge concentration and surface generation velocity) and parameters that require destructive measurements (e.g. dielectric breakdown voltage).The main part of this thesis establishes a set of test structures designed to allow automated assessment of a comprehensive set of process parameters. This test structure set constitutes the basis of CMS silicon sensor process quality control. It facilitates quick assessment of critical process parameters in about 30 minutes per wafer and provides the means for in-depth analysis in case of any irregularities detected. Measurements of the set utilize a 20-needle probe card and an automated positioning stage.The development process of the test structure set combined electrical measurements on individual test structures manufactured on prototype wafers by two different foundries and simulations of test structure response to the variation of different process parameters. Specific emphasis was put on investigating the capability of different test structures to access the same process parameters, aiming at providing complementary measurement methods within the finalized set.Measurements of the first instances of the set produced on CMS Outer Tracker production wafers and HGCAL prototype wafers have demonstrated the functionality of the set and the included test structures. The results serve to quantify process related differences of the wafer material for the CMS Outer Tracker and HGCAL. Based on these measurements, the shortcomings of the current design of the test structure set are identified and mitigation measures are proposed.The test structure set and the results presented in this thesis have served to standardize the process quality control procedure and to ensure cross-comparability between different test centers within the CMS silicon sensor working groups and over the full series production time. Together with direct electrical measurements of the manufactured sensors and irradiation tests, the presented process quality control procedure will ensure the quality of the silicon sensors integrated into the CMS Outer Tracker and HGCAL and, ultimately, will aid the search for new physics at the HL-LHC. (author)