4H-SiC(0001), (000 " 1 1), and (11 " 2 20) have been directly oxidized by N 2 O at 1300 C, and metal-oxide-semiconductor (MOS) interfaces have been characterized. The interface state density has been significantly reduced by N 2 O oxidation on any face, compared to conventional wet O 2 oxidation at 1150 C. Planar n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) fabricated on 4H-SiC(0001), (000 " 1 1) and (11 " 2 20) faces have shown effective channel mobilities of 26, 43, and 78 cm 2 /Vs, respectively. Secondary ion mass spectrometry analyses have revealed a clear pileup of nitrogen atoms near the MOS interface. The thickness of the interfacial transition layer can be decreased by N 2 O oxidation. The crystal face dependence of the interface structure is discussed. A simple consideration of chemistry indicates that NO, generated from the decomposition of N 2 O, may be a more efficient oxidant of carbon than O 2 .
In this paper, a fundamental investigation on shortchannel effects (SCEs) in 4H-SiC MOSFETs is given. Planar MOS-FETs with various channel lengths have been fabricated on p-type 4H-SiC (0001), (000 1) and (11 20) faces. In the fabricated MOS-FETs, SCEs such as punchthrough behavior, decrease of threshold voltage, deterioration of subthreshold characteristics, and saturation of transconductance occur by reducing channel length. The critical channel lengths below which SCEs occur are analyzed as a function of p-body doping and oxide thickness by using device simulation. The critical channel lengths obtained from the device simulation is in good agreement with the empirical relationship for Si MOSFETs. The critical channel lengths in the fabricated SiC MOSFETs are slightly longer than simulation results. The dependence of crystal face orientations on SCEs is hardly observed. Impacts of interface charge on the appearance of SCEs are discussed.
Planar n-channel MOSFETs have been fabricated on , ( 0001) and (000-1) faces by using oxidation in N 2 O ambient. The relationship between the MOSFET performance and the acceptor concentration (7×10 15 -2×10 17 cm -3 ) of epilayers has been investigated. MOSFETs have shown a high effective channel mobility of 70 cm 2 /Vs at a 2×10 16 cm -3 doping, and 54 cm 2 /Vs at 2×10 17 cm -3 . Short-channel effects have been also investigated.
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