TCAD Simulations and Test Beam Characterization of MAPS for Future Lepton Colliders

Abstract

Monolithic active pixel sensors (MAPS) produced in a 65 nm CMOS imaging technology are being investigated for applications in particle physics. The MAPS design has a small collection electrode with an input capacitance of ~fF, granting a high signal-to-noise ratio and low power consumption. Additionally, compared to previously studied technologies, the 65 nm CMOS imaging technology reduces material budget and improves the readout logic density. Given these features, this technology is employed in the TANGERINE project to develop the next generation of silicon pixel sensors. The sensor design targets temporal and spatial resolutions compatible with the requirements for a vertex detector at future lepton colliders. By fulfilling these requirements, the detector is also suitable as a telescope plane for the DESY-II Test Beam facility. Simulations and test-beam characterization of technology demonstrators have been carried out in close collaboration with the CERN EP R&D program and the ALICE ITS3 upgrade. TCAD device simulations and Monte Carlo simulations have been used to study detector sensing characteristics and predict its performance parameters. This work presents a technology-independent simulation approach that uses generic doping profiles for TCAD simulations. The results agree qualitatively with previous studies, providing a preliminary validation of the simulation approach. Prototypes of a 65 nm CMOS MAPS with a small collection electrode have been characterized in laboratory and test-beam facilities by studying performance parameters such as cluster size, charge collection, spatial resolution, and detection efficiency. This work presents the test beam results for different sensor designs and bias configurations. The results are consistent with studies of the previous technologies, proving the scalability of sensor designs from 180 nm to 65 nm technology and offering perspectives on the necessary compromises to accomplish the ultimate detector goals. Finally, Monte Carlo simulations using TCAD electric fields generated in this thesis have produced performance parameters comparable to experimental data. The comparisons demonstrate that the simulation approach is progressing in the right direction. Discrepancies between the two highlight the need to perform studies on the substrate and epitaxial layer doping concentration to allow for accurate predictions of the detector sensing properties. This thesis showcases MAPS in a 65 nm CMOS imaging technology as a promising candidate for a vertex detector at future lepton colliders and provides valuable insight for refining the simulation approach.