Comparative analysis of proton collision effects in silicon on insulator MOSFETs using steady-state and transient responses

Abstract

Proton irradiation degrades MOSFETs through multiple, spatially distinct mechanisms, yet separating the dominant damage sites remains challenging. This work presents a region-resolved electrical study of proton-irradiated partially depleted silicon-on-insulator (PDSOI) nMOSFETs, focusing on degradation at the Si/SiO 2 interface states, body- source/drain junctions, and the gate insulator (GI). Devices were irradiated with 15 and 100 MeV protons at fluences of 10 12 and 10 13 p/cm², corresponding to estimated total ionizing doses of approximately 0.43 and 4.3 Mrad at 15 MeV and 0.10 and 1.0 Mrad at 100 MeV, respectively, and were characterized using electrical measurements. In the transfer characteristics, increased subthreshold swing and mobility degradation, together with a positive threshold-voltage shift and enhanced hysteresis, indicate substantial trap generation. Interface trap density extracted from the subthreshold region increases systematically across the tested combinations of proton energy and fluence, enabling quantitative tracking of interface damage. Importantly, the kink behavior in output characteristics is strongly suppressed after irradiation, consistent with reduced floating-body dynamics. Junction analysis–via parasitic diode I-V and laser-assisted body-current transients–reveals increased SRH recombination, reduced carrier lifetime, and elevated defect density in the depletion region. GI degradation is further supported by prolonged current transients under on-state bias, indicative of slow oxide-trap filling. Across the tested conditions, 15 MeV protons induce stronger electrical degradation than 100 MeV, consistent with their higher linear energy transfer (LET) and more effective energy deposition within the active device regions. These findings provide a measurement-based comparative picture of proton-induced degradation in PDSOI MOSFETs under representative proton energy conditions (15 and 100 MeV), offering qualitative physical insights into radiation-induced degradation pathways in SOI devices.