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The modified hot-zone design, consisting of a new design and new materials for the backside of SiC seed holder was adopted for reducing stress in grown SiC crystal ingot and for reducing the warpage of 6-inch SiC wafer. Crucible lid on the backside of SiC seed holder was designed to be movable during the growth process. Based on the warp value and mapping measurement of FWHM (Full width at half maximum) value in X-ray rocking curve, the crystal quality of SiC crystals grown with new hot-zone design was observed to be better than conventional design.

6-inch 4H-SiC crystal ingot was successfully separated from a seed holder by the contraction enhancement of adhesive. The resin used as an adhesive with 10~30% in contraction ratio during the cooling was selected. The crack between seed holder and grown SiC crystal was observed to be formed after the cooling procedure and the crystal was easily separated from the seed holder without any machining process for the separation. The warp value and the rocking curve value of SiC crystal grown with modified adhesive was observed to be smaller than those of SiC crystal with conventional method.

6H-SiC single crystal was grown with simple modification in PVT process to investigate the aspect of resistivity change in crystal. The modified process consisted of a new initial step to get rid of impurities in the growth cell before the main growth of SiC crystal. The new step in the modified process was designed to consist of higher temperature than the growth temperature for sublimation of impurities. SiC crystal grown with using 2 times of impurities sublimation process (ISP) step exhibited lower variation of resistivity value on whole wafer than SiC grown using with 1 time. With implementation of new modified step in growth process, SiC single crystal with resistivity value above 103Ωcm could be obtained by simple PVT process and conventional low-purity SiC source material.

The present research was focused to investigate various process parameters influenced on the large 4H-SiC crystal growth on a 6H-SiC seed by PVT method. The crucible diameter along horizontal axial direction and inserted graphite ring was modified to change the growth parameter like the temperature gradient. In the initial stage of growth, foreign polytypes such as 6H/4H were observed on 6H-SiC seed, indicating the growth temperature to be unstable on crystal surface. However, from the middle of growth step, 4H-SiC was successfully formed in the ingot with the modification of growth pressure and a SIMS analysis confirmed the high doping concentration in grown 4H-SiC crystal.

Extensive study of various process parameters to influence on the growth of 4H-SiC crystal has been carried out using the transformation of the 6H-SiC seed by a PVT method. The axial temperature gradients were increased throughout increasing the crucible length along growth direction in order to enhance the growth rate and transformed crystal yield. The N2/Ar gas ratio used during the crystal growth related with carrier concentration/mobility of grown crystal. In the initial stage of growth, foreign polytypes such as 6H/15R were observed on 6H-SiC seed crystal but 4H crystals were entirely grown after the process optimization. While the typical absorption spectrum of SiC seed crystal indicated that the SiC polytype was the 6H-SiC with fundamental absorption energy of about 3.02eV, absorption spectrum of grown SiC crystal exhibited 4H-SiC with fundamental absorption energy of about 3.26eV. The entirely transformed SiC region exhibited lower micropipe density than 6H/4H transition region.

The single crystal ingots by using a sublimation technique were grown on 6H-SiC dual-seed crystals with opposite face polarities and then SiC crystal wafers sliced from the SiC ingot were systematically investigated to find out the polarity dependence of the crystal quality. The growth rate of the SiC crystal grown in this study was about 0.2mm/hr. N-type 2’’ SiC crystals exhibiting the 4H- and 6H-SiC polytype were successfully fabricated on C-face and Si-face, respectively. The incorporation of nitrogen donors in the SiC crystals grown on the C-face seed crystal was exhibited to be higher than in SiC crystals grown on a Si-face crystal. When the SiC crystal ingot proceeded to grow, the SiC crystal region grown on the C-face seed crystal was enlarged compared to the SiC crystal region on the Si-face seed crystal.