Timing performance of the first CMOS-LGADs for the future ALICE 3 Time-of-Flight detector

This work presents the experimental characterization of the first-generation of monolithic CMOS-LGAD sensors developed for the future ALICE 3 Time-of-Flight detector. Three sensors with different gain and five devices irradiated up to 10¹⁴ neq/cm² were characterized and compared. The study combines laboratory measurements, including IV characterization and laser-based jitter analysis, with a test beam campaign at CERN PS using 10 GeV charged particles to evaluate timing performance as a function of gain, irradiation fluence and temperature. Laser measurements were used to evaluate the intrinsic jitter contribution, demonstrating the crucial role of internal gain in reducing time uncertainty through enhanced signal amplitude and slew rate. The best intrinsic jitter achieved under optimized operating conditions reached 22 ps. Test beam results show that the non-irradiated device achieves time resolutions below 80 ps at room temperature. At the fluence level expected the inner ALICE 3 TOF region (10¹³ neq/cm²) a timing resolution of approximately 75 ps is maintained at 20° C indicating minimal performance degradation until the end of this detector operation. Increasing irradiation fluence up to 10¹⁴ neq/cm² leads to a systematic degradation of the time resolution, primarily due to gain layer acceptor removal and increased leakage current. Sensor's cooling effectively mitigates radiation-induced degradation: at the highest fluence, operation at -10° C improves the timing resolution by more than 20 ps compared to ambient temperature. Overall, these results show that monolithic CMOS-LGAD sensors provide competitive timing performance together with the advantage of full CMOS integration, confirming the robustness of the layout and supporting the development of thinner, higher-gain sensors aimed at achieving the 20 ps timing target for the ALICE 3 upgrade.