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The 4H-SiC material offers high thermal conductivity, very low dark currents, high saturation velocity, high breakdown voltage, and possible advantages in radiation hardness. These intrinsic properties make it well-suited for high-radiation environments. Moreover, recent advances in SiC power electronic devices and substrate fabrication have enabled the production of high-quality, thick, low-doped epi wafers for SiC detectors. However, SiC radiation damage is only partially modelled in Technology CAD (TCAD), which is the standard design tool for semiconductor particle detectors. Although a bulk radiation model for 4H-SiC has been recently proposed [1], there is still no modelling scheme for surface radiation damage at the 4H-SiC-SiO2 interface.
This contribution presents the properties of the SiO2 layer and the 4H-SiC-SiO2 interface, studied using MOS capacitors fabricated by CNM (Barcelona, Spain) on high-resistivity n-type 4H-SiC. Measurements were performed both before and after X-ray irradiation at doses ranging from 50 krad to 10 Mrad. High-frequency (HF) and quasi-static (QS) C–V characteristics were analysed using the High-Low method [2] to extract the oxide charge density (NOX) and the interface trap density (DIT). These measured parameters, NOX and DIT, were implemented in TCAD to build a surface radiation-damage model for the 4H-SiC–SiO2 interface. The impact of annealing at 80°C on oxide and interface trap charges was also investigated.
[1] P. Gaggl et al., “TCAD modeling of radiation-induced defects in 4H-SiC diodes”, NIMA 1070 (2025) 170015. https://doi.org/10.1016/j.nima.2024.170015
[2] E. H. Nicollian and J. R. Brews, MOS (metal Oxide Semiconductor) Physics and technology, John Wiley and Sons, pp. 319-356, 1982