(Invited) Understanding of Growth Kinetics of Thermal Oxides on 4H-SiC (0001) for Control of MOS Characteristics

Control of thermal oxidation conditions is inevitable to achieve a high-quality MOS interface on SiC substrates. We investigated the kinetics and thermodynamics of 4H-SiC oxidation for nanometer-thick SiO2/SiC system, to find out thermodynamically preferred conditions for a smooth elimination of carbon byproduct from the interface. A linear regime of thermal oxidation of 4H-SiC (0001) was clearly observed with a high activation energy corresponding to direct CO ejection from the interface. Based on our understanding of oxidation kinetics, we found that nearly-ideal MOS characteristics with reduced interface state density ~1011 cm-2eV-1 or less, were achievable on 4H-SiC (0001) only by dry oxidation processes.

Source:IOPscience

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Epitaxial Deposition of SiC onto 4H SiC using a Hollow Cathode

Thin films of SiC were deposited using DC, RF and pulsed sputtering of a hollow cathode. The majority of the films were deposited using RF sputtering at temperatures ranging from 610 to 858 degrees C. Initial films were deposited onto Si substrates in order to determine deposition rates, film uniformity, and film composition. The introduction of a rotating substrate holder greatly improved the film thickness and composition uniformity. The samples were characterized using X-ray diffraction (XRD), Raman spectroscopy, optical absorption, and infrared ellipsometry. The initial films were polycrystalline in nature independent of the substrate used for deposition. The 4H/3C polytype ratio increases strongly for elevated substrate temperatures for the films which were grown homo-epitaxially on 4H SiC. This observation suggests a new avenue for homo-epitaxial growth of SiC onto 4H SiC and rapid hollow cathode sputtering is envisioned for the growth of single crystal films of 4H SiC for future device applications.

Source:IOPscience

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Characterization of 4H-SiC Homoepitaxial Films on Porous 4H-SiC from Bis(trimethylsilyl)methane Precursor

4H-SiC homoepitaxial films were grown on 8° off-axis porous 4H-SiC (0001) faces in the temperature range of  by chemical vapor deposition from bis(trimethylsilyl)methane (BTMSM) precursor. The activation energy for growth was 5.6 kcal/mol, indicating that the film growth is dominated by the diffusion-limited mechanism. Triangular stacking faults were incorporated in the SiC thin film grown at low temperature of 1280°C due to the formation of 3C-SiC polytype. Moreover, super-screw dislocations appeared seriously in the SiC film grown below 1320°C. Clean and featureless morphology was observed in the SiC film grown below 25 standard cubic centimeters per minute (sccm)  carrier gas flow rate of BTMSM at 1380°C while 3C-SiC polytype with double positioning boundaries grew at 30 sccm flow rate of BTMSM. The dislocation density of the epi layer was strongly influenced by the growth temperature and flow rate of BTMSM. Double axis crystal X-ray diffraction and optical microscopy analysis revealed that the dislocation density decreased at the higher growth temperature and lower flow rate of BTMSM. The full width at half maximum of the rocking curve of the film grown at optimized condition was 7.6 arcsec and the sharp free exciton and Al bound exciton lines appear in the epi layer, which indicates that the 4H-SiC film was of very high quality. © 2003 The Electrochemical Society. All rights reserved.

Source:IOPscience

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