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

RIKEN Accel. Prog. Rep. 50 (2017)

Investigation of non-catastrophic failure mode observed in SiC diodes
H. Shindou,*1Power devices are widely used for the power handlingportion of the electronic devices for space systems as wellas ground-based commercial devices. In our previous study,
we investigated the fatal destruction mode called
single-event effects (SEEs) in the SiC schottky barrier diode(SiC-SBD) and SiC metal-oxide-semiconductor field-effecttransistor (SiC-MOSFET). SiC is expected to be a candidate
material the next-generation semiconductor devices. It isapplicable to high-voltage and high-temperatureapplications because of its inherent wide energy band gap.
In addition, SiC is suitable for use in ultra-high frequency
applications.
However, experimental date on SiC properties forradiation are rare. If we elucidate the mechanism of SEEs, itwill be an innovative achievement.
In our previous study, 3 regions were revealed in thefailure mode of SiC diodes as shown in Fig. 1. Region 1 is a
non-destructive region, and collected charge is reproducibly
measured with no damage. In region 2, there is a permanent
increase in leakage current. We define the permanent
damage region, region 2 in Fig. 1, as a non-catastrophic
failure region. Further, region 3 in Fig. 1 is defined as a
catastrophic failure region in which a single event burnout(SEB) occures. SEB is a failure mechanism caused by alarge current arising from the irradiation of heavy ion. In aprevious study, it was reported that the failure mode of SiC
diodes is due to local heating.1) By irradiating heavy ions,high density electron-hole pairs and many defects (traps)
are generated along its track. The resulting current flow
contributes to local heating, and carriers are generated bytrap-assisted tunneling. However, little is known about
which factors the mechanism is depends on, its structure,applied voltage, and energy and fluences of ions.
Thus, in this experiment, to evaluate the difference ofstructures of SiC diodes and the effect of fluence, 4 types ofcommercial SiC-SBDs were prepared. Table 1 lists theelectrical characteristic of the samples. The test sample wasirradiated with a Kr-ion beam with an energy of 2304 MeV
using the RIKEN RILAC+RRC. The total fluence was set
to 2.5×104 or 3×105 ions/cm2 at the chip surface. The
reverse voltage, VR, was increased with an interval of 20 V.
The result of this experiment is presented Fig. 2. It shows
the leakage current of all test samples. Solid lines show thatthe total fluence at each VR is 2.5×104 ions/cm2 and dashedlines show that it is 3×105 ions/cm2 at each VR. We defined
the device as broken when the leakage current deviatedfrom the rated current. It can be seen that the leakage
current increases permanently with increasing reverse

S. Kuboyama䠆1 and K. Suzuki䠆1voltage. Finally, for example, the leakage current of
SiC-SBD C deviated from its rated current at 400 V. Theleakage current of SiC-SBD D deviated at 460 V.
Moreover, Fig. 2 shows that there are some effects ofdifference of radiation fluence. The leakage current
increases with increasing fluence. These results correspondwith the previous experimental results. Generated
electron-hole pairs tended to increase with increasingradiation fluence. A greater number of electron-hole pairscauses greater damage to devices. Finally, the leakage
current at 3×105 ions/cm2 is greater than that at 2.5×104
ions/cm2.
In this experiment, non-catastrophic failure is observed inall samples. However, for use in space, it is important toclarify the long-term reliability of SiC diodes in region 2,and additional careful experiments are required in thefuture.

Fig. 1. Characteristic regions observed by heavy ion
irradiations on SiC Schottky diodes.
Table 1. Test sample
SiC-SBD A

SiC-SBD B

SiC-SBD C

SiC-SBD D

VBR1200 V

600 V

1200 V

1200 VIR

200 uA

100 uA

400 uA

200 uA

DiodeType

Schottky Barier

1e-02
Solid line: 2.5 104 [p/cm2]
Dashed line: 3 105 [p/cm2]

1e-03
1e-04
1e-05

IR [A]

Y. Nakada,䠆1 E. Mizuta,*1

SiC-SBD A

1e-06

SiC-SBD B

1e-07

SiC-SBD C

1e-08

SiC-SBD D

1e-09
0100

200300400500600

VR [V]

Fig. 2. Leakage current of SiC diodes.
Reference䠆1Japan Aerospace Exploration Agency

1) S. Kuboyama et al., IEEE Trans., vol. 53, No. 6, 2006.

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