Correlation Between the V-I Characteristics of (0001) 4H-SiC PN Junctions Having Different Structural Features and Synch
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1069-D07-21
Correlation Between the V-I Characteristics of (0001) 4H-SiC PN Junctions Having Different Structural Features and Synchrotron X-ray Topography Ryoji Kosugi1, Toyokazu Sakata2, Yuuki Sakuma1, Tsutomu Yatsuo1, Hirofumi Matsuhata1, Hirotaka Yamaguchi1, Ichiro Nagai1, Kenji Fukuda1, Hajime Okumura1, and Kazuo Arai1 1 Energy Semiconductor Electronics Research Laboratory, National Institute of Advanced Industrial Science and Technology (AIST), AIST Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki, 305-8568, Japan 2 R&D Associations for Future Electron Devices, AIST Tsukuba Central 2, 1-1-1 Umezono, Tsukuba, Ibaraki, 305 -8568, Japan ABSTRACT We have fabricated 1.5kV class four pn-type junction TEGs (Test Element Groups) of TEG_A, B, C and D having different structural features on the same wafer. The TEG_A consists of one main pn junction as a simple pn diode, while the TEG_B, C and D have p-wells in an active area. In the TEG_D, it includes the n+ region within each p-wells as well. Comparing synchrotron white beam x-ray topography (SWBXT) images with the light emission images in TEG_A, it was suggested that only a small number of TSD (threading screw dislocation) brings fatal deterioration on the breakdown voltage (VBD), and the most of TSDs have less influence. The VBD and fabrication yields of TEG_C and D show a strong correlation with the activation annealing condition for the ion-implanted layer. INTRODUCTION In a practical use of the SiC power MOSFETs, a further reduction of the channel resistance, high stability under harsh environments, and also, high production yield of large area devices are indispensable. Pn diodes with the high current rating have been already reported with high yield [1]. Meanwhile, the production yield of large area SiC power MOSFETs have not been reported in detail. Basically, power MOSFETs utilize a pn junction in the blocking states just as the pn diodes. On the other hands, there are some structural differences between the pn diodes and power MOSFETs, such as p-well structure, gate oxide between adjacent p-wells and n+ source within each p-wells. This implies that there are some specific issues in power MOSFETs. Particularly, an activation annealing for the ion-implanted region becomes a critical process in the DiMOSFETs (Double-implanted MOSFETs), since it defines an activation ratio of the ion-implanted region and the surface condition before oxide/SiC interface formation. To clarify the difference between the simple pn diodes and DiMOSFETs under blocking states, we have fabricated four pn-type junction TEGs having different structural features. Those pn junctions are close to similar structure of DiMOSFETs step-by-step from simple pn diodes. Dependence of the V-I (voltage–current) characteristics on the each structural features was surveyed over the wafer. Two activation annealing conditions have been applied for the fabrication. Prior to the fabrication, we formed grid patterns over the wafer, and then performed the SWBXT measurements to obtain the crystal defects inf
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