Thermal annealing effects on total-ionizing-dose radiation hardness in HfO2 /SiC MOS structures

Abstract Thermal annealing is a critical step in fabricating hafnium oxide/silicon carbide (HfO 2 /SiC) metal-oxide-semiconductor (MOS) devices. However, its effect on total ionizing dose (TID) radiation hardness remains unclear. We find that for the unannealed Sample A, γ -ray irradiation (300 krad(Si)) produces a positive flat-band voltage shift (V fb ) of 1.76 V. Compared with Sample A, the annealed Sample B (975 ℃ rapid thermal annealing, RTA) shows a reduction in the interface trap density ( D it ) at the HfO 2 /SiC interface from 1.01 × 10 13 cm -2 ·eV -1 to 3.67 × 10 12 cm -2 ·eV -1 , and an increase in the breakdown field strength of the MOS capacitor from 5.28 MV/cm to 6.91 MV/cm. However, Sample B suffers from adverse effects after irradiation, such as a negative V fb shift, a reduction in barrier height ( φ b ), and a degradation of the breakdown field (1.98 MV/cm). Therefore, we propose a pre-annealing step at 550 ℃ for 30 minutes (Sample C) prior to the RTA. This pre-annealing converts the negative V fb shift caused by TID effects into a positive V fb shift. Furthermore, the D it of this sample drops to 1.61 × 10 12 cm -2 ·eV -1 after irradiation, while φ b increases from 0.42 eV to 1.18 eV. XPS depth profiling reveals irradiation-induced redistribution of Hf-O coordination and the emergence of an O-Hf-C interfacial component, which we interpret as consistent with oxygen-mediated defect reordering. These findings reveal how thermal annealing influences the TID radiation response of HfO 2 dielectrics and provide critical guidance for the development of radiation-tolerant HfO 2 /SiC devices intended for extreme-environment applications.