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The range of polishing-induced subsurface damage remaining in a commercially available production grade 4H-SiC (0001) epi-ready substrate was evaluated by the observation from the (-1100) cleavage plane using two kinds of highly strain-sensitive characterization methods. Firstly, the analysis using electron backscattered diffraction (EBSD) with a submicron spatial resolution was conducted on the exposed cross sectional plane. Then, for the further quantitative evaluation excluding the influence of roughness or contamination of the cleavage plane, a synchrotron X-ray micro-diffraction experiment was carried out. The range of the subsurface damage evaluated in those experiments was ensured by confirming none of additional strain inserted at the cleavage, as compared with the damage-free substrate prepared by high temperature thermal etching. As a result, the depth of the residual strained region below polishing-induced scratches at the surface was estimated to be in the range of a few microns, which is much deeper than the previously reported value of 100 nm by cross-sectional transmission electron microscopy. It suggests a potential of EBSD for the conventional tool to characterize even a small amount of strain in SiC single crystal.

Mechanism of surface roughening caused by the polishing induced subsurface damage on 4o off-cut 4H-SiC (0001) substrate during thermal etching, CVD epitaxial growth, and the subsequent high temperature annealing was investigated in the wide temperature range of 1000-1800°C. Different from the previous study based on a macroscopic characterization by optical microscopy, microscopic characterization based on a scanning electron microscopy (SEM) was employed in this study. By utilizing the SEM operated under various conditions, disordered step arrangements as well as stacking faults and dislocations were imaged. The obtained results revealed that the SFs cause the fluctuation in the step kinetics, resulting in the step bunching formation during the thermal process.

The orientation of growth sectors of highly B doped p+ high pressure and high temperature (HPHT) substrates were investigated by high angular resolution electron backscatter diffraction (HR-EBSD). The lattice rotation mapping images of the areas across the 〈111〉 growth sector boundaries were measured. The crystal orientation was found to be inclined approximately 0.03°for [001] to [-1-10], compared with the [-1-11] growth sector area at a given location. Other orientation inclinations were observed such as 0.02°for [001] to [110] and 0.025°for [001] to [1-10]. The same phenomena were confirmed for the other two crystals. Conventionally, it has been recognized that a HPHT-grown crystal is a perfect single crystal, however, our results indicate that "twin boundaries" are formed between the growth sectors for p+ HPHT substrates. To meet the requirements for the power device wafer specifications, the establishment of growth technology is desirable in the near future.

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