Fabrication and Initial Characterization of 600 V 4H-SiC RESURF-type JFETs
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Fabrication and Initial Characterization of 600 V 4H-SiC RESURF-type JFETs Satoshi Hatsukawa, Michitomo Iiyama, Kazuhiro Fujikawa and Atsushi Ito Device Technologies Center, Sumitomo Electric Industries, Ltd., 1-1-3, Shimaya, Konohana-ku, Osaka, 554-0024, Japan ABSTRACT A RESURF-type JFET is a suitable structure as a lateral switching device with a breakdown voltage of above 600 V for an inverter module which drives motors of an electric or hybrid automobile. In this study, 600 V RESURF-type JFETs were fabricated to investigate the operation and characteristics. The drift region between the drain and the source areas has a double RESURF structure to reduce the on-resistance. At first, small devices were fabricated. The width and length of the channel are 200 µm and 10 µm, respectively. The distance between the drain and the gate areas, which is the drift length, is 15 µm. The saturation current normally-off device is about 0.6 mA at a gate voltage of 3 V. The specific on-resistance is about 160mΩcm2. The maximum breakdown voltage is 720 V. Next, large ones were fabricated. The width of the channel is 80 mm. The saturation current normally-on device is about 0.5 A at a gate voltage of 2 V. The specific on-resistance is about 200mΩcm2. The maximum breakdown voltage is 250 V. INTRODUCTION An integrated circuit module with SiC switching device is promising, because of low loss and high temperature operation, especially in an electric or hybrid automobile. A lateral switching device is suitable for the module from the point of view of system integration. The breakdown voltage is devices with normally-off operation will be preferred to be above 600 V for an inverter module which drives automobile’s motors. Switching devices with normally-off operation will be preferred. In spite of recent progress, SiC-MOSFETs still suffer from low channel mobility and oxide reliability. Therefore, SiC RESURF-type JFET is a suitable structure as a lateral switching device with a breakdown voltage of above 600 V [1]. In this paper, the fabrication and characteristics 600 V RESURF-type JFETs are described and discussed. EXPERIMENTAL DETAILS Device fabrication Figures 1 and 2 show the schematic view and the top view of the fabricated device, respectively. The drift region between the drain and the source areas has double RESURF structure. Compared with a single RESURF structure, a double RESURF structure prevents field concentration on the edge of the source and the gate areas. Thus, it can realize devices with high breakdown voltage and low on resistance. The structure is designed based on the theory or the super-junction structure [2] and breakdown electric field of 4H-SiC [3]. At first, small devices were fabricated. The width and the length of the channel are 200 µm
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and 10 µm, respectively. The channel thickness is about 0.1 µm, which is smaller than the thickness of the depletion region produced by the built-in potential in the channel, so that the devices are normally-off. The distance between the drain and the gate a
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