Current Transport Mechanism for Heavy-Ion Degraded SiC MOSFETs

Abstract

High sensitivity of SiC power MOSFETs has been observed under heavy ion irradiation, leading to permanent increase of drain and gate leakage currents. Electrical postirradiation analysis confirmed the degradation of the gate oxide and the blocking capability of the devices. At low drain bias, the leakage path forms between drain and gate, while at higher bias the heavy ion induced leakage path is mostly from drain to source. An electrical model is proposed to explain the current transport mechanism for heavy-ion degraded SiC power MOSFETs.

Heavy-Ion Microbeam Studies of Single-Event Leakage Current Mechanism in SiC VD-MOSFETs

“…These different areas for ion-induced drain leakage response are illustrated in Fig. 6, where the three regions discussed in [9] are updated with the new considerations. At low bias voltages, the ion-induced charge is collected with a similar multiplication mechanism as in Si MOSFETs and no permanent damage is observed in the device.…”

“…Unfortunately, this was noticed only afterward and the run was not repeated. For the irradiations performed at V DS irr < 350 V, as discussed in [9] and as mentioned earlier, the leakage current path is from the drain to the gate, that is, I D ≈ I G . For V DS irr > 350 V, instead, the leakage paths are divided between the drain-gate and drain-source path.…”

“…However, like their silicon counterparts, SiC power devices (MOSFETs and diodes) are sensitive to single-event effects (SEEs). In particular, a unique SEE signature is observed in SiC power devices under heavy-ion irradiation [6]- [9]. For power MOSFETs, single ions can cause permanent degradation that leads to a gradual increased leakage in both drain and gate currents with increasing heavy-ion fluence.…”

“…The heavy-ion-induced degradation in SiC MOSFETs was previously studied in [9]. It was observed that the gate area is the most vulnerable part within the MOSFET structure.…”

“…Also, the leakage current path and the gate and drain degradation rates were observed to be independent of the prior degradation. Based on the experimental results, an electrical equivalent circuit model was proposed in [9] to explain the current transport in the degraded SiC vertical double-diffused power (VD)-MOSFETs.…”