Degradation Under Low Drain Bias Induced by Heavy Ion in SiC MOSFETs

The safe operating area (SOA) for the drain bias of silicon carbide (SiC) metal oxide semiconductor field effect transistors (MOSFETs) in space applications has been limited due to the single-event effects (SEEs) induced by heavy-ion irradiation. At a drain bias lower than 5% of the rated voltage, SiC MOSFETs are typically considered to be in the charge collection region, which usually does not cause destructive damage. However, in this article, the degradation induced by heavy ions at drain biases below 50 V for 1200 V SiC MOSFETs has been observed. During irradiation, the drain leakage current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} {_{\text {DSS}}}$ </tex-math></inline-formula>) continuously increased with the accumulated dose. Meanwhile, the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} {_{\text {DSS}}}$ </tex-math></inline-formula> degradation showed a correlation between the drain bias and the cell topology of SiC MOSFETs. After irradiation, unacceptable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} {_{\text {DSS}}}$ </tex-math></inline-formula> degradation was still observed, but it recovered by about 40% after a month of room-temperature annealing. <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} {_{\text {DSS}}}$ </tex-math></inline-formula> also returned to its preirradiation level under negative gate bias, suggesting that the increase in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} {_{\text {DSS}}}$ </tex-math></inline-formula> could be associated with a leakage current path through the channel region, resulting from defects within the oxide or at the SiO2/SiC interface, likely introduced by the microdose effect. The gate leakage current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} {_{\text {GSS}}}$ </tex-math></inline-formula>) was tested within the temperature range of 25 °C–250 °C to investigate the temperature impact for gate oxide latent damage activation. As the drain bias increased during irradiation, <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I} {_{\text {GSS}}}$ </tex-math></inline-formula> also increased significantly at higher temperatures, suggesting that latent damage within the gate oxide had been formed during irradiation.