Picosecond Time Stamping in Fully-Monolithic Highly-Granular Silicon Pixel Detector

This thesis presents the development and characterization of monolithic silicon detectors with precise time resolution developer in the context of the MONOLITH project. Three generations of prototypes were fabricated using SiGe BiCMOS technology, using hexagonal pixels with a pitch of \SI{100}{\um} and innovative sensor designs to achieve outstanding efficiency and timing performance while addressing power consumption and radiation tolerance challenges. The first proof-of-concept PicoAD prototype, featuring a double-junction gain layer, demonstrated a detection efficiency of \SI{99.9}{\percent} and a time resolution of \SI{17.3}{\ps} across the full pixel area at a power density of \SI{2.7}{\watt/\cm\squared}. Performance remained excellent down to \SI{0.4}{\watt/\cm\squared}, proving the viability of the continuous gain layer for efficient, low-power monolithic detectors. A second prototype, produced without a gain layer, confirmed the potential of SiGe HBT front-end electronics. Tested with a \SI{120}{\GeV}/c pion beam, it achieved a \SI{20}{\ps} time resolution at \SI{0.9}{\watt/\cm\squared}, with minimal dependence on hit position. After proton irradiation up to \num{1e16}~n$_{\mathrm{eq}}$/cm$^{2}$, a detection efficiency above \SI{99.6}{\percent} and time resolutions below \SI{50}{\ps} were maintained by adjusting bias voltages. Measurements with a femtosecond laser helped disentangle the various contributions to the time resolutions, supported by a dedicated Garfield++ simulation framework that successfully reproduced experimental results. A third prototype, combining the second-generation ASIC with a PicoAD-like gain layer, achieved detection efficiencies up to \SI{99.99}{\percent} and time resolutions of \SI{12.1}{\ps} at \SI{2.6}{\watt/\cm\squared}. Remarkably, at power densities below \SI{1}{\watt/\cm\squared}, time resolutions of approximately \SI{18}{\ps} were obtained, confirming the suitability of these devices for large-area applications like 4D trackers. SiGe BiCMOS-based monolithic pixel detectors demonstrated scalability, radiation tolerance, and performance, establishing this technology as a promising solution for future collider experiments and high-precision timing applications, from particle physics to LiDAR. Integration with a low-gain avalanche may further enhance time resolution towards the picosecond time stamping.