JAEA-Review-2010-065.pdf:15.99MB - 日本原子力研究開発機構

Total Ionizing Dose Tolerance of SiC
Buried Gate Static Induction Transistors up to 10 MGy
S. Onoda a) , Y. Tanaka b) , A. Takatsuka b) , T. Yatsuo b) and T. Ohshima a)
a) Environment and Industrial Materials Research Division, QuBS, JAEA,
b) National Institute of Advanced Industrial Science and Technology
Silicon Carbide (SiC) is regarded as one of the candidate
materials for devices with radiation hardness, owing to its
superior radiation resistance as well as excellent physical
1)
properties and chemical stability. Ohshima et al. reported
that the electrical properties for 6H-SiC Metal-Oxide Field
Effect Transistors (MOSFETs) with steam-annealed gate
oxide did not degrade by gamma-ray irradiation at 200 kGy
in spite that H2-annealed ones showed the degradation above
40 kGy. These results suggest that the ionizing radiation
response of MOSFETs is strongly affected by their
fabrication processes especially gate oxidation. Instead of
SiC MOSFETs, in this study, the Total Ionizing Dose (TID)
effects on SiC Buried Gate Static Induction Transistors
Change in On-voltage ( V )
Change in Breakdown-voltage ( V )
1-07
6
5
4
3
2
1
0
-1
-2
0 2 4 6 8 10
100
0
-100
-200
-300
Absorbed Dose ( MGy )
-400
Si IGBT
-500 Si MOSFET
SiC-SIT
-600
0 2 4 6 8 10
Absorbed Dose ( MGy )
Si IGBT
Si MOSFET
SiC-SIT
Fig. 1 Change in on-voltage of SiC-SIT, Si MOSFET,
and Si IGBT after gamma-ray irradiation up to the
absorbed dose of 10 MGy.
Fig. 2 Change in breakdown voltage of SiC-SIT, Si
MOSFET, and Si IGBT after gamma-ray irradiation
up to the absorbed dose of 10 MGy.
JAEA-Review 2010-065
- 11 -
(SiC-BGSITs) involving no silicon dioxide are evaluated up
to the absorbed dose of 10 MGy(SiO 2). For comparative
purpose, we also evaluated the TID effects on commercial
Si-MOSFET (17N80C3) and Si-IGBT (5J301).
The SiC-BGSITs are developed by AIST 2, 3) for the
evaluation of radiation hardness. All devices including
both SiC and Si transistors were mounted in TO220
packages. The gamma-ray irradiation from 60 Co source in
JAEA was performed at the dose rate of 8.8 kGy(SiO 2)/h up
to the total dose of 10 MGy. During the gamma-ray
irradiation, the devices were floating. After each
irradiation, the on-state, the threshold, and the blocking
characteristics of each device were measured. The on-state
characteristics were measured at the gate voltage (V G) of
+15 V for Si-IGBT and Si-MOSFET and that of +2.5 V for
SiC-BGSIT. The on-voltage (V on) was defined as the drain
voltage (V D) at the drain current (I D) of 10 A. The
threshold voltage (V th) was derived from I D-V G
characteristic measured at V D of +0.3 V. The blocking
characteristics were measured at V G of 0 V for Si-IGBT and
Si-MOSFET and that of -10 V for SiC-BGSIT.
Figure 1 and 2 show the change in on- and breakdown
voltage as a function of gamma-ray absorbed dose. The
V on of Si-IGBT degraded excessively at the early stage of
the irradiation (>~0.1 MGy(SiO 2)) due to the bulk damage
produced by Compton electrons. Although not shown here
the V th of Si-MOSFET is very sensitive against the radiation.
The blocking characteristics of Si-MOSFET degraded
significantly against the radiation as shown in Fig. 2. The
reduction in V on of Si-IGBT and the degradation of blocking
characteristics of Si-MOSFET are very serious problems to
use these devices for the application under high radiation
environment. On the other hand, we successfully
confirmed that SiC-BGSIT has very high radiation hardness
and can operate stably under harsh environment.
References
1) T. Ohshima et al., Mater. Sci. Forum 1093 (2002)
389-393.
2) Y. Tanaka et al., Mater. Sci. Forum 1219 (2006)
527-529.
3) Y. Tanaka et al., IEEE Elect. Dev. Lett. 908 (2006) 27.
Acknowledgement
This study was carried out under the Strategic Promotion
Program for Basic Nuclear Research by the Ministry of
Education, Culture, Sports, Science and Technology of
Japan.