Comprehensive Investigation of Gate Oxide Instability in 4H-SiC MOSFETs and MOS Capacitors Under High Gate Bias Stress
Haonan Chen, Kanghua Yu, Jieqin Ding, Chengzhan Li, Jun Wang, Yuwei Wang
Abstract
In this article, gate oxide instability of 4H-SiC MOSFETs along with the n-type junction field effect transistor (JFET) and p-type channel capacitors fabricated under identical manufacturing process and thermal budget is simultaneously investigated under high gate bias stress. The degradation phenomena and the corresponding trapping mechanism of the three kinds of devices are comprehensively analyzed and compared with each other. Notably, the amount of charge injected into the gate oxide ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{s}{)}$ </tex-math></inline-formula> is used as a criterion to evaluate the shift of threshold voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {TH}}{)}$ </tex-math></inline-formula> and flat-band voltage ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {FB}}{)}$ </tex-math></inline-formula> during stress. The measured <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{\text {TH}}$ </tex-math></inline-formula> in 4H-SiC MOSFETs shows a strong linear relationship with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{s}$ </tex-math></inline-formula> , regardless of the value and polarity of the applied <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${E}_{\text {OX}}$ </tex-math></inline-formula> , whereas <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\Delta {V}_{\text {FB}}$ </tex-math></inline-formula> in capacitors is with a distinct behavior, demonstrating obvious saturation at high <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${Q}_{s}$ </tex-math></inline-formula> and a significant difference under various stress condition. All these results provide deeper insight into the study of gate oxide instability in 4H-SiC MOS devices.