Research On The Correlation Between Charge Carriers Trapping Near The SiC-SiO₂ Interface And 1/f Noise In 4H-SiC MOSFETs

SiC power metal-oxide-semiconductor field-effect transistors?MOSFETs? with low on-resistance, high-speed switching and excellent gate insulating characteristics, can significantly reduce the power consumption and help to achieve the advantages of miniaturization. They have excellent potentials for power electronics, aircraft electronics and high temperature applications, mainly used for power switching and auxiliary power. But the reliability problems common in SiC power MOSFETs may threaten device performances, which are mainly caused by gate oxide issues and large amounts of SiC-Si O₂ interface states. In order to promote the commercialization application of SiC power MOSFETs, it is much important to focus on device reliability and the reproducibility of device design. As the first step, we need to find an efficient reliability characterization tool. With the advantages of sensitivity and non-destructive, noise method has been a powerful tool in researching device quality and reliability. The 1/f noise features in SiC MOSFETs are closely associated with the capture and emission of charge carriers by traps at, or near, the SiC-Si O₂ interface. So this paper will analysis the correlation between the 1/f noise and trap issues for 4H-SiC power MOSFETs.In this paper, main defect traps issues in SiC MOSFETs were summarized at first, including their microscopic structures and their impacts on device performances. Both electrical and noise methods used for characterization of SiC-Si O₂ interface were introduced. Then the 1/f noise number fluctuation model for SiC MOSFETs was deduced in this paper, which indicates that the noise spectral density?S? is a function of trap density?D t?E t??.Finally, in the experimental study of this article, both electrical I-V characteristics measurements and low-frequency noise measurements were performed for the N-channel enhancement-type 4H-SiC power MOSFETs.Continuous measurements of transfer characteristic increased device threshold voltage, which could be attributed to the accumulation of negative trap charges in these devices. Noise measurements were carried out when devices were operated in strong inversion in their linear regimes. At room temperature it was found that, for all of the device samples, S Vd were proportional to V d?/?V g-V T??. V d-dependences of S Vd were basically consistent with those in the Si MOSFETs,while V g-dependencies of S Vd were quite different from those in the Si MOSFETs. It is evident that these large amounts of SiC-Si O₂ interface traps lead to these differences between Si- and 4H-SiC- MOSFETs. Moreover, special differences in the V g-dependencies of S Vd for two types of 4H-SiC MOSFETs may imply something else.After calculating the standardized 1/f noise value K, it was found that for one type of devices with lower on-resistance and higher transconductance, K increased as V g did. The K at a given V g is determined by the D t?E t?, V g-dependencies of K implies that D t tends to increase as E t approaches the 4H-SiC conduction band edge, which is consistent with the general ideas. But for another type of devices with higher on-resistance and lower transconductance, K decreased as V g increased in the strong inversion region. As this type of devices generally have larger amounts of interface states, the V g-dependencies of K may be related to the assisted tunneling through the SiC-Si O₂ interface states, and the weakening of mobility fluctuation as V g increases.