Epitaxial Growth of SiC on Non-Typical Orientations and MOS Interfaces
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Epitaxial Growth of SiC on Non-Typical Orientations and MOS Interfaces Hiroyuki Matsunami, Tsunenobu Kimoto and Hiroshi Yano Department of Electronic Science and Engineering, Kyoto University Yoshidahonmachi, Sakyo, Kyoto 606-8501, Japan
ABSTRACT High-quality 4H-SiC has been epitaxially grown on 4H-SiC(11 2 0) substrates by chemical vapor deposition. The physical properties of epilayers and MOS interfaces on both (11 2 0) and off-axis (0001) substrates are elucidated. An unintentionally doped 4H-SiC epilayer on (11 2 0) 14 -3 12 shows a donor concentration of 1x10 cm with a total trap concentration as low as 3.8x10 -3 cm . Inversion-type planar MOSFETs fabricated on 4H-SiC(11 2 0) exhibit a high channel 2 -2.2 mobility of 96 cm /Vs. The channel mobility decreases according to the T dependence above 200K, indicating reduced Coulomb scattering and/or electron trapping. The superior MOS interface on (11 2 0) originates from the much lower interface state density near the conduction band edge. INTRODUCTION Although the outstanding potential of silicon carbide (SiC) has been demonstrated in various prototype devices projected for high-power, high-frequency, and high-temperature electronics, micropipes and a low MOS channel mobility have been severe obstacles to realize low-loss and high-voltage SiC MOSFETs. Micropipes, hollow cores associated with super screw dislocations running along the c-axis () direction, cause premature breakdown in high-voltage SiC devices [1]. Recently, Takahashi and Ohtani have succeeded to produce “micropipe-free” SiC wafers by sublimation growth on (1 1 00) and (11 2 0) seed crystals [2]. These SiC (1 1 00) and (11 2 0) wafers with the surface orientation parallel to the c-axis have much potential to develop large-area SiC devices, leading to an increased current (or power) handling capability. Although it has been reported that SiC homoepitaxial growth on (11 2 0) is more successful than that on (1 1 00) [3-5], the quality of (11 2 0) epilayers and doping control have not been fully investigated. 4H-SiC has been regarded as the most promising SiC polytype, owing to its higher bulk mobility and smaller anisotropy. However, inversion-type MOSFETs fabricated on off-axis 4H-SiC(0001) wafers generally show an unacceptably low channel mobility, typically below 10 2 cm /Vs, severely limiting the on-resistance of SiC power MOSFETs [6-8]. In 1999, the authors have found that the channel mobility of 4H-SiC MOSFETs can be remarkably improved by utilizing (11 2 0), instead of conventional off-axis (0001) [9]. In this paper, the authors describe successful 4H-SiC homoepitaxy on (11 2 0) and the inversion-type MOSFET performance processed on SiC (11 2 0) and off-axis (0001) substrates. The origin of the high channel mobility on (11 2 0) substrates is discussed based on the temperature dependence of MOSFET performance and capacitance-voltage (C-V) H3.4.1
measurements.
EPITAXIAL GROWTH OF 4H-SiC ON (1120) SUBSTRATES
B
C
B
Undoped 4H-SiC SiH4=0.30sccm
-3
A
Donor Concentration (cm )
Homoepitaxi
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