Electric Characterization of Thin Silicon Sensors for Beam Monitoring in Advanced Radiotherapy Techniques

The INFN projects FRIDA and MIRO aim to optimize and test segmented thin silicon sensors for real-time monitoring of clinical beams, particularly under the conditions required by emerging radiotherapy techniques such as Ultra-High Dose Rate and Spatially Fractionated Radiotherapy. This study presents the electric characterization of thin PIN silicon sensors, segmented into pads, with active thicknesses ranging from 15 µm to 45 µm. Current-voltage (I-V) and capacitance-voltage (C-V) measurements were conducted at room temperature, revealing breakdown and full depletion voltages, as well as variations in doping concentration and active thickness. The results showed that the sensors demonstrate consistent behavior across a broad voltage range. The C-V measurements indicated a correlation between variations in full depletion voltage and bulk doping concentration. Doping profile analysis revealed discrepancies of up to 12% between nominal and actual active thicknesses. These findings underscore the importance of static characterization in ensuring sensor accuracy and operational reliability.