Repetitive Short-Circuit Tests on SiC VMOS Devices

Abstract

SiC MOSFET are now commercially available and show promising performances when considering static losses, commutations and long term reliability. The devices may face short-circuit conditions and knowing their capibility in terms of critical time and repetitive fault is mandatory before integration in commercial systems. This paper presents the short-circuit performances for two families of commercial devices in terms of critical energy, time and repetitve SC stress. It shows that both devices show similar critical time but very different behavior when stressed under repetitive SC pulses. These results demonstrate that SiC MOSFET reliability under repetitive short-circuit pulses strongly depends on the pulse length and device provider. This information will be crucial to design the system in order to limit the SC length depending on the application requirements.

A Structural Based Thermal Model Description for Vertical SiC Power MOSFETs under Fault Conditions

“…The first diagram shows an increase of the gate leakage current which flows into the gate right before the device is turned off. This is an indication of degrading gate oxide due to high temperature and high electric field [21][22][23]. After a number of SC pulses, with the pulse duration of 17 s from Figure 15(a), the gate oxide is partially breaking through at Figure 15(b) leading to a continuous current flowing into the gate in the on-state; this can be seen in the voltage difference between the driver-output voltage ST and the gate-source voltage GS .…”

“…In order to have higher carrier mobility in the channel, the gate voltage (electrical field strength) for 2nd-generation SiC MOSFETs was chosen higher than for conventional IGBTs. This high level of inversion together with a thinner oxide layer OX results in a rather high electric field in the gate oxide ⃗ OX [21,22]. This is imposing a lot of stress for the gate oxide especially at high temperatures, like in short-circuit mode.…”

“…As a result, even if the device is not failing during a short circuit, the gate oxide will be damaged substantially due to a temperature increase in the space charge region right below the gate, thus reducing the number ,OX of sustainable short circuits. In the literature [4,[21][22][23], it is shown that the longer the duration of the short-circuit pulse is, the lower the number of accomplishable short circuits and thus the lifetime of the gate oxide will be.…”

Measurement and analysis of SiC-MOSFET threshold voltage shift

“…Thanks to its superior electrical properties compared to Silicon, SiC is a promising material for high voltage and high temperature devices. However there are still a lot of reliability issues that remain to be understood such as oxide degradation [1], threshold voltage instability [2], [3] and short-circuit behaviours [4], [5] and [6]. Some of these key points are crucial to develop reliable power devices for industrial applications [7].…”

Robustness study of 1700 V 45 mΩ SiC MOSFETs

“…However, the current state-of-the-art of this technology is not yet fully mature. There are still a lot of reliability issues that remain to be understood such as oxide degradation [2], threshold voltage instability [3], [4] and short-circuit behaviours [5], [6] and [7]. Industrial people are worried about some future power applications.…”