III-1. Atomic & Solid State Physics (Ion)

RIKEN Accel. Prog. Rep. 54 (2021)

RIKEN Accel. Prog. Rep. 54 (2021)

Single-event eﬀects in SiC planar and trench power MOSFETs
M. Iwata,∗1 E. Mizuta,∗1 M. Takahashi,∗1 and H. Shindou∗1
Wide-bandgap semiconductors such as silicon carbide(SiC) have been attracting attention as materials forhigh-eﬃciency semiconductor devices. The adoption ofSiC power modules has recently progressed in the ﬁeldof railways and automobiles. In the aerospace industry,
the use of SiC devices requires the eﬀects of radiation
to be clariﬁed and these issues to be overcome. In thispaper, we report the results of radiation tests for SiC
power metal-oxide-semiconductor ﬁeld-eﬀect transistors(MOSFETs).
Two types of commercial n-channel SiC power MOSFETs were used in this experiment, as shown in Fig. 1.
The maximum rating for the drain-source breakdown
voltage of these devices is 1200 V. Test samples wereirradiated with 136 Xe ions of 638 MeV perpendicularly
at the device surface at room temperature in air using
RIKEN RILAC2 in combination with the RIKEN Ring
Cyclotron (RRC). During irradiation, the gate voltage,
VGS , was set to 0 V. The drain bias voltage, VDS , wasinitialized at 100 V and increased in 20 V steps. The
total ﬂuence at each VDS was 3.0 × 105 ions/cm2 .
Figure 2 shows the current transition of IDS duringirradiation up to VDS = 160 V. The leakage current of
the planar-type sample started to increase gradually at
VDS = 140 V, as shown in Fig. 2(a). This behavior isquite diﬀerent from that usually observed during heavyion irradiation on Si power MOSFETs, where the leakage current abruptly increases by single-event burn-out.
The tendency of gradual increase on the planar sample
is analogous to the failure modes of SiC Schottky barrier diodes.1) On the other hand, the leakage current of
the trench-type sample increased rapidly at the beginning of irradiation, as shown in Fig. 2(b). In Si trench
MOSFETs, a degradation mechanism related to a microdose eﬀect due to heavy-ion irradiation was reported,2)and we assume that the same eﬀect is caused in the SiC

Fig. 1. Cross-sectional structure of the test devices.
∗1Fig. 2. Result of current monitoring during irradiation.

Fig. 3. Result of current monitoring before and after irradiation.

trench-type sample. The trench structure enables the irradiated ions to pass through the gate oxide along theentire length of the channel and generate electron-holepairs. Trapped holes might exist in the gate oxide because the hole diﬀusion velocity is less than that of electrons, and they might introduce a large leakage current
path immediately after the start of irradiation.
Figure 3 shows the I-V curves of the drain leakage
current before and after irradiation. The degradation byirradiation seemed worse in the trench-type sample thanin the planar sample.
Because the planar-type SiC MOSFETs did not show
the microdose eﬀect and its leakage current after irradiation was less than that of the trench-type sample, theplanar gate structure can be considered suitable for usein space.
References

Research and Development Directorate, Japan Aerospace Exploration Agency

1) S. Kuboyama et al., IEEE Trans. Nucl. Sci. 53, 6 (2006).
2) J. A. Felix et al., IEEE Trans. Nucl. Sci. 54, 6 (2007).

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