Impact of Total Ionizing Dose Effects on the Threshold Voltage Hysteresis of SiC MOSFETs

This work investigates the effects of total ionizing dose (TID) irradiation bias, temperature, dose, and post-irradiation annealing on the threshold voltage hysteresis of silicon carbide (SiC) MOSFETs. The research reveals that the TID effect decreases the threshold voltage hysteresis, which is proportional to the accumulation of radiation-induced charges in the gate oxide. The reduction in threshold voltage hysteresis is unrelated to the change of the interface-trapped charges. However, it is mainly caused by the reduction of the nonequilibrium interface trapped charge energy range (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {E}_{\text {VTH}}$ </tex-math></inline-formula>). The radiation-induced charges can exacerbate the hole emission process of the donor interface traps during the up-sweep process, which causes an upward shift of the lower boundary of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {E}_{\text {VTH}}$ </tex-math></inline-formula>. The slight shift of the Fermi energy level during the down-sweep process leads to no significant change in the upper boundary of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {E}_{\text {VTH}}$ </tex-math></inline-formula>. Eventually, the TID effect causes a reduction in the threshold voltage hysteresis. The changes in the occupation probability of the donor and acceptor interface traps during the scanning of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} _{\text {DS}}$ </tex-math></inline-formula>–<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V} _{\text {GS}}$ </tex-math></inline-formula> curves were extracted by TCAD simulation. The results showed that the inconsistent changes in the occupation probability of the donor interface traps in the up-sweep and down-sweep curves cause a reduction of the threshold voltage hysteresis. The analysis was further verified using different voltage sweep ranges in the experiment.