Materials Science Forum Vols. 645-648

Abstract: The stable long time growth with the use of Si -C-Ti ternary solution was realized　by improving the thermal condition during the growth. We have succeeded in obtaining a maximum 10 mm thick bulk 6H-SiC crystal, which is the largest bulk crystal ever obtained by the solution growth technique. The obtained crystal was free of cracks and exhibited a homogeneous light green color. The crystallinity of the grown crystal was characterized by X-ray rocking curve measurements using (0006) reflection and by the molten KOH etching. The mapping of the full width at half maximum (FWHM) revealed the average FWHM around 30 arc seconds and the minimal FWHM under 16 arc seconds. The etch pit density (EPD) was typically in the range between 104 and 105 cm-2, which was comparable to that of the crystal seed.

Abstract: The present research was focused to produce 2 inch wafers from small rectangular seeds and to investigate the quality of non-polar SiC substrates grown by a conventional PVT method. The non-polar SiC seeds were prepared by cutting along <0001> direction of 6H-SiC crystal grown on (0001) basal plane. As SiC ingot grows, many defects in connected region were gradually diminished. While the full width at half maximum (FWHM) values of m-plane SiC substrate measured along a-direction and c-direction were 60 arcsec and 70 arcsec, respectively, and the FWHM values of a-plane SiC substrate measured along m-direction and c-direction were 27 arcsec and 31 arcsec respectively. The stacking faults lying in the basal plane can be detected by molten KOH etching as linear etch pits extending along <0001> on the (11-20) surface and the carrier concentration was observed by Raman spectrum.

Abstract: To improve the purity of SiC and the yield of high purity SiC in the conventional Acheson Process, the behaviour of metal oxide impurities (Al2O3, CaO, Fe2O3 and MgO) with/without addition of sodium chloride (NaCl) is studied with the help of FactSageTM from a thermodynamic point of view. Equilibrium phases and compositions during evaporation and gas deposition are examined in the system of SiO2 + 3C. The calculation results are compared with industrial observations and published data. Purifying mechanism is clarified for the first time since the invention of the Acheson Process in 1891.

Abstract: We attempted the vapor–liquid–solid (VLS) growth of SiC film in Si-Li solution using gaseous CH4 as a carbon source at 900 oC. A 100-m-thick liquid-phase epitaxy (LPE) layer was obtained on a 4H-SiC (0001) substrate under CH4 pressure of 0.9 MPa. X-ray diffraction (XRD) and a high-resolution transmission electron microscope (HR-TEM) measurement showed that the LPE layer was single-phase 2H-SiC. We concluded that VLS growth in Si-Li solution using gaseous CH4 as a carbon source is useful for growing single-phase 2H-SiC.

Abstract: The objective of this review is to set the present state of the art of 3C-SiC crystalline growth by emphasizing the new and promising trends related to this polytype elaboration. The need of high quality 3C seed is showed to be more important than for other polytypes, in order to avoid β→ transformation during high temperature bulk growth. The effect of various parameters, such as supersaturation, gas phase composition, strain or impurities, is discussed. Recent results obtained using vapour-liquid-solid mechanism and continuous feed vapour phase transport are bringing new insight on 3C-SiC stability and setting new standards of material quality.

Abstract: The control of the nucleation step is a critical issue for a future development of 3C-SiC bulk growth. The possibility to get very high quality 3C-SiC single crystal through self-nucleation on graphite was already demonstrated but the large number of nuclei limits the growth of only one crystal. In this study, we have investigated different configurations that help improving the nucleation step. For that, the “necking” stage, well established in Bridgman or Czochralski growth processes, has been successfully applied to the growth of 3C-SiC with the CF-PVT technique. This has allowed getting only one 3C-SiC crystal. The enlarged parts, after having passed the neck, are of high structural quality.

Abstract: We report in this work, the solution growth of heavily p-type doped 3C-SiC and 6H-SiC. Description of the 3C and 6H-SiC crystals in terms of defects and resistivity are presented and discussed with respect to growth conditions such as temperature, Al content in the melt and seed polarity. Crystals and thick layers are investigated by means of TEM, NDIC microscopy and Raman.

Abstract: The Continuous Feed-Physical Vapor Transport Technique (CF-PVT) was optimized by considering the heating, thermal insulation and the geometry of growth cavity. The effects of seeds on the surface morphology of the grown layer have been discussed. We successfully grew 3C-SiC bulk with a diameter of 7.0 mm and 3.3 mm in height with a high growth rate of 0.8 mm/h by the CF-PVT technique.

Abstract: Despite outstanding properties, the development of 3C-SiC electronics is still suffering from the lack of bulk 3C-SiC substrates. Up to now, there is no real seed and optimized growth processes for this material. We address in this work the bulk growth of 3C-SiC by a two-step-liquid phase approach. By coupling experiments with global process simulation, we address the problems that must be overcome to consider the solution growth technique as a possible approach for the growth of bulk 3C-SiC.

Abstract: In this study, we carried out a sol-gel processing to synthesize two types of phenol resin and TEOS sol with fluoric acid as the catalysts, and fabricated the β-SiC powder by carbothermal reduction of the obtained precursor gels. The gels were observed to be cross linked between TEOS and phenol resins by FT-IR and TG-DTA. After pyrolyzed at 1000oC in Ar to obtain the precursor, to confirm the phase transition and morphologies by XRD, and SEM were measured. Finally, the light green colored SiC powder was obtained after carbothermal reduction process up to 1800oC. The residual condensed SiO(v) phase and free carbons as a role of impurities for final products using the solid type phenol resin was observed in the surface of powder by BSE.