Abstract
The variations in the degradation of electrical characteristics resulting from different device structures for trench-gate SiC metal-oxide-semiconductor field effect transistors (MOSFETs) are investigated in this work. Two types of the most advanced commercial trench products, which are the asymmetric trench SiC MOSFET and the double-trench SiC MOSFET, are chosen as the targeted devices. The discrepant degradation trends caused by the repetitive avalanche stress are monitored. For the double-trench device, the conduction characteristic improves while the gate-drain capacitance (Cgd) increases seriously. It is because positive charges are injected into the bottom gate oxide during the avalanche process, which are driven by the high oxide electronic field (Eox) and the high impact ionization rate (I.I.) there. Meanwhile, for the asymmetric trench SiC MOSFET, the I–V curve under the high gate bias condition and the Cgd remain relatively stable, while the trench bottom is well protected by the deep P+ well. However, it’s threshold voltage (Vth) decreases more obviously when compared with that of the double-trench device and the inclined channel suffers from more serious stress than the vertical channel. Positive charges are more easily injected into the inclined channel. The phenomena and the corresponding mechanisms are analyzed and proved by experiments and technology computer-aided design (TCAD) simulations.
Highlights
With etching, oxidation, and other critical processing technologies becoming more and more mature, SiC metal-oxide-semiconductor field effect transistors (MOSFETs) are gradually applied to power electronic fields to replace traditional silicon power devices [1–4].Numerous SiC MOSFET products have been pushed into the market [5–7]
For the sidewall and the bottom of a trench gate, which suffer from higher electric fields during practical applications, trench-gate SiC MOSFETs are faced with more serious reliability issues when compared with planar-gate devices [11,12]
Was set from to was connected in series with an inductor gs At this time, the SiC MOSFET is under the avalanche state
Summary
Oxidation, and other critical processing technologies becoming more and more mature, SiC metal-oxide-semiconductor field effect transistors (MOSFETs) are gradually applied to power electronic fields to replace traditional silicon power devices [1–4]. Most of the existing articles only report the failure or the degradation mechanism of one single trench-gate device [15–22]. The avalanche stress, which applies load current (Iload) are investigated in detail. It is found thatand afterleads to obvious degradation or even damage, is chosen as the targeted stress It isoffound that after enduring enduring repetitive avalanche stress, the static and dynamic characteristics the two repetitive avalanche stress, the static and dynamic characteristics of the trench-gate devices exhibit different degradation trends. ProvedWith by analyzing physical the dominant mechanism is found and proved by analyzing the physical characteristics of characteristics of both the devices under avalanche state.
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