The influence of pixel cell layout on the timing performance of 3D sensors

This talk presents a detailed characterization of the timing performance of unirradiated 3D pixel sensors using the Two-Photon Absorption Transient Current Technique (TPA-TCT). The study focuses on understanding the spread in the Time-of-Arrival (ToA) caused by the intrinsic non-uniform electric and weighting fields in 3D architectures. Both square and hexagonal pixel layouts with 55 µm pitch were investigated using a femtosecond IR laser system at CERN. Depth-resolved ToA maps and voltage scans reveal significant spatial dependence of charge collection timing, with the square geometry exhibiting a smaller ToA spread (~75 ps) compared to the hexagonal one (~175 ps) at -20 V. Using pulse-pair analysis, time resolution values as low as 22 ps were extracted. These results underscore the importance of pixel geometry optimization and highlight the capability of TPA-TCT to provide high-resolution insight into 3D sensor timing behavior.