Ph.d. degree
Centro Nacional de Microelectrónica (IMB-CNM, CSIC), Spain, 2020

Javier Fernández Tejero

Supervisor: Miguel Ullán Comes, Celeste Fleta Corral

Design and Optimization of Advanced Silicon Strip Detectors for High Energy Physics Experiments

Keywords:

• Si microstrip and pad detectors
• Radiation-hard detectors
• Particle tracking detectors (Solid-state detectors)
• Large detector systems for particle and astroparticle physics

Abstract:

The European Organization for Nuclear Research (CERN) is currently implementing a major upgrade of the 27-kilometre Large Hadron Collider (LHC), with the aim to expand the physics reach, increasing the luminosity and triggering the consequent multiplication of interactions per bunch crossing. The new High-Luminosity LHC (HL-LHC) operational conditions will have a direct impact in the silicon tracking sensors of the main detectors, the ATLAS and CMS experiments, causing a large increase of detector occupancy and radiation damage. This PhD thesis investigates the design and optimization of a new generation of silicon strip detectors able to withstand the severe operational conditions expected for the HL-LHC upgrade. Firstly, the study tackles the development of the silicon strip detectors from a layout design point of view. Basic device elements are presented and its design is discussed based on performance considerations. A new python-based Automatic Layout Generation Tool (ALGT) is presented, with the aim to address the need for large area prototypes of strip detectors at the R&D stages of the ATLAS Inner-Tracker (ITk) upgrade. The ALGT is used to design a large area strip sensor prototype, several miniature sensors and diodes. These devices are generated, and arranged in a full 6-inch wafer layout design, for the participation of Infineon Technologies AG in the ATLAS ITk strip sensor Market Survey. In addition, layout designs of a wide range of microelectronic test structures with different applications are presented. A set of test structures for the development of strip technologies is proposed, along with a test chip able to cover all the routine tests planned for the Quality Assurance (QA) works during the ATLAS strip sensor production. On the other hand, in order to improve the readout connection, several designs of Embedded Pitch Adaptors (EPA) are also proposed to minimize the possible drawbacks associated to the introduction of a second metal layer on the sensor structure. An extensive characterization is performed in the frame of the ATLAS ITk strip sensor Market Survey. Devices fabricated by the candidate foundries, Infineon Technologies AG and Hamamatsu Photonics K.K., are evaluated before and after proton, neutron and gamma irradiations, up to fluences expected at the end of the HL-LHC lifetime. Test structures and QA test chips designed are also characterized, with the objective to validate its design, expand the technology evaluation and provide reference values for the ATLAS production tests. Additional studies and developments are presented with application in High Energy Physics (HEP) experiments in general. Hot topics, such as the humidity sensitivity of large area sensors or the effectiveness of the punch-through protection in a beam-loss scenario, are extensively investigated. A complete study of the new EPA structures proposed, and results of the first strip sensors fabricated in 6-inch wafers at Centro Nacional de Microelectronica (IMB-CNM), are also shown. The layout designs and characterizations presented, contribute to define the final design of the ATLAS strip sensors for the HL-LHC upgrade, and the additional investigations reveal conclusions of general interest that can lay the foundation for future developments.