Papers by Keyword: C Face

Abstract: We studied interface defects of C-face 4H-SiC metal-oxide-semiconductor field-effect transistors (MOSFETs) by means of electrically-detected-magnetic-resonance (EDMR) spectroscopy. EDMR measurements were carried out on opposite types of C-face MOSFETs, which were prepared by dry oxidation and wet oxidation, and we found EDMR signals of interface defects from both the MOSFETs. Judging from their spectroscopic features, the interface signals of the two MOSFETs are assigned to be the same type, and we call them “C-face defects.” The density of C-face defects was found to be larger in the dry-oxide MOSFETs than in the wet-oxide MOSFETs. It is also revealed that part of C-face defects in wet-oxide MOSFETs are coupled with hydrogen atoms.

Abstract: This paper presents an investigation of the morphological and structural properties of graphene (Gr) grown on SiC(000-1) by thermal treatments at high temperatures (from 1850 to 1950 °C) in Ar at atmospheric pressure. Atomic force microscopy and micro-Raman spectroscopy showed that the grown Gr films are laterally inhomogeneous in the number of layers, and that regions with different stacking-type (coupled or decoupled Gr films) can coexist in the same sample. Scanning transmission electron microscopy and electron energy loss spectroscopy shoed that a nm-thick C-Si-O amorphous layer is present at the interface between Gr and SiC. Basing on these structural results, the mechanisms of Gr growth on the C-face of SiC under these annealing conditions and the role of this disordered layer in the suppression of epitaxy between Gr and the substrate have been discussed.

Abstract: We investigated the 4H-SiC C-face MOS interface properties around valence-band, and fabricated 4H-SiC C-face p-channel MOSFETs for the first time. For C-face p-channel MOSFETs, relatively low-temperature wet-gate-oxidation was preferable. Post-deposition-annealing for contact metal was found to degrade the C-face MOS interface around valence-band. Low-temperature (800°C) PDA in hydrogen including ambient was effective to some extent in order to suppress the degradation owing annealing. We obtained C-face p-channel MOSFET with normal FET operation by utilizing 900°C wet-gate-oxidation and 800°C PDA in He-H2 forming gas ambient.

Abstract: The sloped sidewall angle in 4H-SiC mesa structure could be controlled by a thermal etching at 900oC in chlorine (Cl2) based ambience. 4H-SiC C face with 8o off substrate was used. The SiO2 layers for the etching mask were formed by a deposited SiO2 layer or a thermally oxidized layer. Thermal etching was carried out at Cl2 ambience at 900oC for 15 minutes. The surface morphologies of the mesa structures were observed with the scanning electron microscope (SEM) and atomic force microscope (AFM). The sloped angles at the mesa sidewalls using deposited SiO2 mask and thermal SiO2 mask were about 23o and 60o, respectively. These results mean that the angle of sloped sidewall can change by mask fabrication method.

Abstract: We have investigated the morphology and doping characteristics of 4H-SiC epilayers grown on 13o-22o off-axis (0001) substrates by horizontal hot-wall CVD. Step bunching is not observed on 18o off-axis substrates as well as on other substrates with large off-angles. The rms roughness is a minimum (as small as 0.10 nm) on 18o off-axis (0001). Under C-rich condition (C/Si >1.0), the donor concentration increases by increasing the off-angle, when the off-angle is larger than 15o. This trend in doping characteristic is enhanced in CVD growth at 1450-1500oC. At a high temperature of 1600oC, however, the off-angle dependence of donor concentration is significantly reduced. Epitaxial growth on 4H-SiC(000-1) with large off-angles is also reported.

Abstract: 4H-SiC layers have been homoepitaxially grown on 4°off-axis (0001) and (000-1) under various conditions by horizontal hot-wall CVD. We have investigated surface morphology and background doping concentration of the epi-layers on 4°off-axis substrates. Surface morphology grown on the (0001) Si-face showed strong step bunching under C-rich conditions. On the other hand, smooth surface morphology on the (000-1) C-face could be grown in the wide C/Si ratio range at 1600 °C. Site-competition behavior is clearly observed under low-pressure growth conditions on 4°off-axis (000-1) C-face, leading to a lowest doping concentration of 4.4x1014 cm-3.

Abstract: 4H-SiC layers have been homoepitaxially grown on off-axis 4H-SiC(000-1) under various conditions by horizontal hot-wall CVD. Improvement of surface morphology and reduction of background doping concentration have been achieved. Surface morphology grown on the (000-1) C face strongly depends on the C/Si ratio at 1500 °C, and hillock-like surface defects can be eliminate by increasing growth temperature to 1600 °C. Site-competition behavior is clearly observed under low-pressure growth conditions even on the (000-1) C face. The lowest doping concentration has been determined to be 6.0x1014 cm-3. A trial of high-speed growth on the (000-1) C face and deep level analysis are also discussed.