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Modeling Irradiation-Induced Degradation for 4H-SiC Power MOSFETs | IEEE Journals & Magazine | IEEE Xplore

Modeling Irradiation-Induced Degradation for 4H-SiC Power MOSFETs


Abstract:

In this article, we proposed a comprehensive model for predicting the degradation of SiC MOSFETs after gamma-ray irradiation. It is experimentally founded that SiC MOSFET...Show More

Abstract:

In this article, we proposed a comprehensive model for predicting the degradation of SiC MOSFETs after gamma-ray irradiation. It is experimentally founded that SiC MOSFETs exhibit different degradation behaviors under gate bias (i.e., {V}_{\text {GS}} =15 V and {V}_{\text {DS}} = 0 V) and drain bias (i.e., {V}_{\text {GS}} = 0 V and {V}_{\text {DS}} =400 V) in terms of threshold voltage ( {V}_{\text {TH}} ) and ON-resistance ( {R}_{\text {ds}, \text{ON}} ). TCAD simulation shows that gate bias causes a high electric field in gate oxide above the MOS channel region, while drain bias generates relatively lower electric field in gate oxide around near-channel region. The differences in electric field under gate bias and drain bias lead to different hole yields and charge accumulation in gate oxide, which is the underlying physical mechanism for their different degradation behaviors. {V}_{\text {TH}} is chosen as the parameter to quantify the accumulated charges in gate oxide and further predict irradiation-induced degradation. The relationship between the variation of threshold voltage ( {\Delta} {V}_{\text {TH}} ) and the total ionizing doses (TIDs) under both gate and drain bias is formulated and validated. Comparison among measured data, TCAD simulation, and model prediction shows that the maximum prediction error is lower than 0.08 V, which proves the rationale and accuracy of the proposed degradation model. In addition, the two submodels for gate bias and drain bias are unified as one according to the time dependence effect (TDE) for TID irradiation. The proposed model could be useful to predict the degradation and/or lifetime of SiC MOSFETs in irradiation environments.
Published in: IEEE Transactions on Electron Devices ( Volume: 70, Issue: 3, March 2023)
Page(s): 1176 - 1180
Date of Publication: 09 January 2023

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I. Introduction

Due to the superior material and device properties, SiC MOSFETs have become one of the most promising power switches for high-performance power electronic systems [1], [2], [3]. Nowadays, SiC MOSFETs not only have already been widely adopted in electric vehicles (EVs) and photovoltaic inverters but also are increasingly gaining attention from the aerospace industry [4]. However, irradiation reliability is still in the way of adopting them in space applications because the incident irradiation could gradually degrade the power devices’ electrical parameters or even destroy them instantaneously. Total ionizing dose (TID) effect is one of the most important types of space irradiation, and extensive research concerned with the irradiation effect on SiC MOSFETs has been reported so far. For example, Akturk et al. [5] experimentally verified that even those unhardened commercial SiC MOSFETs have an irradiation resistance of >100 krad. Many individual studies have also been conducted to explore the mechanisms of the irradiation-induced degradation in MOS structure in detail, and a common understanding that the accumulation of positive charges and interface traps in gate oxide causes the degradation has been achieved [6], [7], [8], [9]. Based on the fundamental understanding, Nicole [10] quantitively modeled the TID reliability effect in SiO2 layers, and Sanchez et al. [11] proposed a physics-based model incorporating TID and aging effect for MOS technologies by calculating surface potential to capture the charge contribution. Though these physical models further help understand the basic mechanisms, they are hardly suitable for predicting the degradation and/or lifetime of SiC MOSFETs after irradiation. In addition, it should be noted that almost all reported irradiation experiments focused on gate bias conditions, and seldom investigation under drain bias condition has been reported yet. Consequently, there is lacking a comprehensive model that can predict irradiation-induced degradation of SiC MOSFETs for switching-mode applications, which hinders the adoption of SiC MOSFETs into practical space applications.

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