Development of Novel Pixel CMOS Sensors Optimised for Time Resolution

The upgrade to the High Luminosity LHC in the years 2025 to 2027 brings challenging requirements for tracking detectors in terms of spatial resolution, time resolution, radiation hardness, as well as material budget and power consumption. Dedicated R&D activities are necessary to meet these difficult requirements. The main scope of this thesis is the development of a simulation framework using 3D-TCAD simulations combined with high statistics Monte Carlo simulations for the design and optimisation of silicon pixel sensors, specifically the so-called Monolithic Active Pixel Sensors (MAPS). The performance of these sensors depends on many parameters, such as the pixel geometry, the reverse bias voltage, the epitaxial layer geometry, substrate thickness as well as doping concentrations. Using Sentaurus TCAD and Garfield++, I developed a simulation framework that calculates the sensor response based on first principles using the sensor geometry, thedopingconcentrations, andthefulldynamicsofthechargecarriersinthesensor as input. I showed that dynamic weighting fields are not necessary to simulate the response of small collection electrode MAPS. I benchmarked the simulation framework using experimental data from MAPS sensors that allowed me to gain a detailed understanding of all the performance parameters, some of which are very difficult to quantify in measurements. Using this simulation framework I then went on to design novel pixel elements in a 65 nm CMOS process. Many different pixel geometries were investigated and optimised for position and time resolution. A set of these sensors was implemented in a test wafer and the characterisation of these sensors is currently ongoing.