1. Introduction

[49] Berthold A., Laugere F., Schellevis H., de Boer C. R., Laros M., Guijt R. M., Sarro P.

sis Device with Integrated Contactless Conductivity Detection, Electrophoresis 2002;

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Silicon Carbide (SiC) is regarded as a promising candidate for electronic devices used in harsh radiation environments (Rad-hard devices) such as in space, accelerator facilities and nuclear power plants [1-5]. In order to apply SiC to such rad-hard devices, we have to know the radiation response of the characteristics of SiC devices, because semiconductor devices show destructive and non-destructive malfunctions and/or degradation their characteristics due to irradiation. For radiation effects on semiconductor devices, three major effects, Single Event Effects (SEEs), Total Ionizing Dose (TID) effect, and Displacement Damage Dose (DDD) effects are known.

When charged particles such as heavy ions are irradiated into semiconductors, dense charge (electron-hole pairs) is generated in semiconductors along to the ion track. The malfunctions of electronic devices such as LSIs and power devices caused by charge generated by charged particles are called SEEs. The SEEs occur even by only one particle incidence, and there are both nondestructive (soft errors) and destructive (hard errors) SEE failures [6-8f^z\$!z/+"0z!.¥ rors arise if the amount of charge collected by devices is large enough to reverse or flip the 0z/00!z+"zz)!)+.5z!((\_z.!#%/0!.\_z(0\$\_z+.z"(%,w"(+,^z%\*!z0\$!z/+"0z!..+./z.!z\*+0z !/0.1¥ tive, the function of semiconductor devices can be recovered by writing new data to the bit and/or resetting of devices. For example, the Single Event Upset (SEU) and the Multiple Bit Upset (MBU) in a Static Random Access Memory (SRAM) and a Dynamic Random Access Memory (DRAM), the Single Event Functional Interrupt (SEFI) in Field Programmable Gate Array (FPGA) or DRAM control circuitry are known as the soft errors. Recently, the Single

© 2013 Ohshima et al.; licensee InTech. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. © 2013 Ohshima et al.; licensee InTech. This is a paper distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Event Transient (SET) arises as a serious issue for analog electronics and digital logic cells. \*z#!\*!.(\_z0\$!z/z%\*z\*(+#z!(!0.+\*%/z.!z.!"!..! z0+z/z/\_z\* z0\$+/!z%\*z %#%0(z+)¥ binatorial logic are referred to as DSETs. In contrast, the Single Event Latch-up (SEL), the Single Event Burnout (SEB), and the Single Event Gate Rupture (SEGR) in power electronic devices are known as the hard errors.

Electron-hole pairs are induced in insulator layers of Metal-Insulator-Semiconductor (MIS) structure devices, such as Metal-Oxide-Semiconductor (MOS) devices by irradiation, and as a result, charge trapped in insulator (oxide) and/or traps near the interface between oxide and semiconductor (interface traps) are generated. Since such charge trapped in insulator and interface traps act give harmful influence to transport properties of semiconductors, the electrical characteristics of MIS devices are degraded by their generation [9, 10f^z+.z!4)¥ ple, the shift of threshold voltage (*V* T) and the decrease in the channel mobility (µchdz.!z+¥ served in MOS field effect transistors (FETs). This radiation effect is called the TID effect, \* z%\*z#!\*!.(\_z0\$!z2(1!z+"z0\$!z z!""!0/z#. 1((5z%\*.!/!/z3%0\$z%\*.!/%\*#z +/!z+"z. %¥ 0%+\*/z !1/!z 0\$!z )+1\*0z +"z . %0%+\*w%\* 1! z \$.#!z %\*z %\*/1(0+.z \* z %\*0!."!z 0.,/z %\*¥ creases with increasing dose.

Figure 1. Change in the subthreshold region of *I*<sup>D</sup> –*V*G curves (subthreshold curves) for n-channel 6H-SiC MOSFETs by gamma-ray irradiation. The bias of 12 V was applied to drain during measurements. The "+" mark on the each line

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3\$+.0!.z\* z%\*+'1.zeLf\_z0\$!z !\*/%05z+"z\$.#!z0.,,! z%\*z#0!z+4% !zc*N*OX) \* z%\*0!."!z0.,/zc*N*ITdz#!\*!.0! z5z%.. %0%+\*z\*z!z!/0%)0! z".+)z0\$!z/\$%"0z+"z/10\$.!/¥ hold curves using a following analysis. Since charge trapped in gate oxide does not respond to bias applied to gate, the entire subthreshold curve is simply shifted by the generation of \$.#!z0.,,! z%\*z#0!z+4% !^z\*z0\$!z+0\$!.z\$\* \_z/%\*!z0\$!z\$.#!z/00!z+"z%\*0!."!z0.,/z !¥ pends on Fermi level (thus, the value of the bias applied to gate oxide), the subthereshold curve is stretched by the generation of interface traps. This behavior can be expressed as

where *V*T\_z*V*OX and *V*IT are the shift of the threshold voltage by irradiation, the voltage shifts due to the generation of oxide-trapped charge and interface traps, respectively. Also, since the charge state of interface traps is assumed to be neutral at midgap state, at which Fermi level corresponds to the intrinsic Fermi level, the shift of the midgap voltage (*V*MID)

Since the subthreshold curve between *V*MID and *V*<sup>T</sup> is stretched by the generation of interface

due to irradiation is caused by oxide-trapped charge. Thus,

*VV V* T OX IT (1)

Radiation Response of Silicon Carbide Diodes and Transistors

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381

*V V* MID OX (2)

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0.,/\_z*V*IT is determined as

When energetic particles are irradiated into semiconductor crystals, atoms at lattice sites are scattered into non-lattice sites (knock-on effects). As a result, vacancies and interstitials are created in semiconductor crystals. This is the origin of the DDD effect. However, in reality, 0\$!z/0.101.!z+"z.!/% 1(z !"!0/z%/z\*+0z/+z/%),(!z\* zz3% !z2.%!05z+"z !"!0/z/1\$z/z %2¥ \*%!/\_z2\*5z(1/0!./\_z\* z2\*5w%),1.%05z+),(!4!/z!4%/0/z%\*z.5/0(/z!1/!z#!\*!.¥ ated vacancies and interstitials thermally diffuse and finally they become stable defects. In general, such defects act as scattering/recombination centers to free carriers, and as a result, the electrical characteristics of semiconductors devices are degraded. In the case of the DDD !""!0\_z/%)%(.z0+z0\$!z z!""!0\_z0\$!z !#. 0%+\*z+"z0\$!z\$.0!.%/0%/z+"z/!)%+\* 10+.z !2%¥ ces becomes larger with increasing fluence of radiation. The degradation of the electrical performance of solar cells installed in space satellites is known as one of the examples of the DDD effect [11-14].

 \*z0\$%/z\$,0!.\_z0\$!z!""!0/z+"z. %0%+\*z+\*z0\$!z!(!0.%(z\$.0!.%/0%/z+"z%z !2%!/z.!z !¥ scribed from the point of view of the TID effect and the SEEs.
