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The dislocation behavior during bulk crystal growth on the 4H-SiC (000-1) C-face using the solution method was investigated. A 2 inch wafer with a 4° off angle was fabricated from a bulk crystal grown by the TSSG method, and the dislocations in the crystal were evaluated using synchrotron X-ray topography and TEM observation. From the topograph images, it was found that the TSD density remarkably decreased as the growth progressed. Furthermore, the TEM observation suggested that TSD decreases as the threading dislocations convert to in-plane defects toward the center of the crystal. Conventionally, it was considered that conversion of threading dislocations hardly occurs in solution growth on the C-face. However, it is thought that this phenomenon was not observable because the conversion efficiency is remarkably low. We speculate that dislocations may be transformed by suddenly making macrosteps during bulk growth.

This study reports our newly developed technology for SiC solution growth. In particular, we succeed in completely suppressing solvent inclusions, which have been a serious technological problem peculiar to the solution growth method. Then, we fabricate two-inch-diameter 4° off-axis SiC wafers without solvent inclusions. Moreover, we performed their crystal defects evaluation. It was found that our wafers were low resistance n-type 4H-SiC and contain almost no basal plane dislocation. As a result, the superior quality of our solution-grown crystal was confirmed.

To determine the mechanism of 4H-SiC replication during solution growth on a concave surface, SiC growth on a 2-in.-diameter 4H-SiC (0001) seed and on 0.5-in. square seeds of different planes was ...

To develop a long-term and stable growth technology for the solution growth of silicon carbide (SiC), the use of the newly fabricated SiC/C gradient crucible was studied. The fabrication of the SiC/C gradient structure was achieved by a two-step heat treatment, and a SiC/C structure with a high SiC areal ratio of more than 50% was obtained by Si infiltration into the porous graphite. Then, the top-seeded solution growth was performed using the fabricated SiC/C gradient crucible that revealed the suppression of the compositional change of the solution during the growth in comparison to the growth using a graphite crucible, which is the general method for the SiC solution growth. Furthermore, the SiC growth behaviors and crystal qualities were maintained when the SiC/C gradient crucible was used instead of the graphite crucible. The use of such a high-purity SiC/C gradient crucible was thus found to be effective in achieving crystal growth with less compositional change, which would enable long-term growth while maintaining a stable growth interface.

Solution growth using a Si–Cr-based solvent is a promising process to produce high quality 4H–SiC single crystal. Computational fluid dynamics simulation is an effective method to estimate and control the temperature and fluid flow in the process, although simulations are presently performed using the physical properties of liquid silicon due to the lack of data for properties of the alloy solvent. In the present work, the density, surface tension, and viscosity of liquid Si–18, 40, and 50 mol% Cr alloys were measured by electrostatic levitation. Computational fluid dynamics simulation was carried out using the measured melt properties and compared with those of liquid silicon. Simulation of the Si–40 mol%Cr solvent predicted a larger fluid velocity and smaller temperature distribution in solution than those of the pure silicon solvent.

A long-term growth of high-quality 4H-SiC single crystals by a top-seeded solution growth method using a Si–Cr-based melt was investigated. A new growth technique called “solution growth on concave surface” (SGCS) was developed to help prevent solvent inclusions. The concave shape of the growth surface was achieved by controlling the meniscus height, which enhances the step provision from the periphery to the center. In contrast, under the growth surface, the solution flows from the center to the periphery through convection by inductive heating. The opposite directions of the step flow and solution flow during solution growth create a smooth surface without solvent inclusions. SGCS was used to successfully grow a 1-in. diameter 4H-SiC crystal with a thickness of 30 mm, which is the thickest reported for a solution growth technique, and 1.7-in. diameter high-quality wafers without solvent inclusions were obtained. Schottky barrier diodes were fabricated on 4H-SiC substrates grown by SGCS, which demonstrat...

Solution growth of SiC is currently regarded as a promising process to produce high-quality SiC crystals. To date, Si–Cr, Si–Ti, and Fe–Si solvents have been used for rapid solution growth of SiC. However, optimization of the solvent system and composition is still needed to maximize the growth rate of high-quality SiC crystals. In this paper, to clarify the features of respective solvents from the viewpoint of the solubility of carbon, the C–Cr–Si, C–Ti–Si, and C–Fe–Si systems were evaluated by thermodynamic analysis. Phase relations in the respective ternary systems were investigated by the calculation of phase diagrams method. In addition, the solubility of carbon in Si–Cr, Si–Ti, and Fe–Si alloys at saturation with SiC was measured and its consistency with the estimated results was examined. Correlation of the experimental growth rate of SiC using Si–Cr, Si–Ti, and Fe–Si solvents was analyzed in terms of the supersaturation of carbon in each solution evaluated from the estimated temperature dependence of carbon solubility. Rate determining step for solution growth was presumed to be mass transfer in the liquid phase.

The top-seeded solution growth of 4H-SiC at three inches in diameter has been investigated using Si–Ti alloy as a solvent. A perforated graphite disk called “immersion guide” (IG) was positioned in the solution in order to control solution flow. The morphological instability was improved and growth rate was significantly increased using the IG compared with conventional growth without the IG. Numerical fluid flow analysis with coupled heat and mass transportation was performed as well to understand convection and growth behavior. The origins of these improvements in the growth performance are discussed based on the numerical results. By controlling solution flow, we could successfully grow a three-inch-diameter 4H-SiC with 4-mm thickness.

We performed top-seeded solution growth of 4H-SiC for obtaining longer length crystal. Si-Cr and Si-Ti melts were used as solvents. Meniscus formation technique was applied to the present study. Special attention was paid to improve the process stability during long-term growth. One of major technological problems in the solution growth is that the precipitation of polycrystalline SiC which hiders the stable single crystal growth. Another problem is the fluctuation of supersaturation at the growth interface during the growth. Through the optimization of growth process conditions, we have successfully grown 4H-SiC single crystals up to 14 mm long with three-inch-diameter, and evaluated their crystalline quality.

In this study, we have investigated the rate-limiting process of 4H-SiC solution growth using Si-Cr based melt, and have tried high-speed growth. It is revealed that the rate-limiting process of SiC growth under our experimental condition is interface kinetics, which can be controlled by such factors as temperature and supersaturation of carbon. By enhancing the interface kinetics, SiC crystal has been grown at a high rate of 2 mm/h. The FWHM values of X-ray rocking curves and threading dislocation density of the grown crystals are almost the same as those of seed crystal. Possibility of high-speed and high-quality growth of 4H-SiC has been indicated.

4H-SiC single crystal with 3-inch diameter was grown by top seeded solution growth (TSSG) technique. We used a new convection control member called “Immersion Guide (IG)” which causes the high and homogenous fluid flow in the solution. As a result, we achieved relatively high growth rate and morphological stability

Crystallinity of 4H-SiC bulk crystal obtained by solution growth technique was characterized mainly by KOH etching of the off-ground and serially ground specimen. Marked reduction of basal plane dislocation, threading edge and screw dislocations during the growth of on-axis crystal was confirmed. Cross-sectional TEM observation revealed the rapid reduction behavior of threading dislocations microscopically. AFM observation of as-grown morphology showed that screw dislocation dipoles is related to the reduction of threading screw dislocations and single domain formation, which is essential for establishing the high crystallinity.

We have grown high-quality long cylindrical (12 mm thick) 4H-SiC bulk crystals by the meniscus formation technique, which was first applied for the solution growth of bulk SiC. It enabled long-term growth by suppressing parasitic reactions such as polycrystal precipitation around the seed crystal. In addition, we could control the growth angle from −22° to 61° by adjusting the meniscus height. The thickness of the grown cylindrical crystals was 12 mm, which is the largest reported until now, and corresponded to a growth rate of 0.6 mm/h. Smooth morphology growth was maintained on the (000-1) C-face. In cross-sectional transmission optical microscopy images, few solvent inclusions and voids were observed. XRD measurements revealed that the FWHM values of the grown crystals were almost the same as those of the seed crystal.

High-speed solution growth using Si-Cr based melt has been performed on on-axis 4H-SiC(0001) at a high temperature of about 2000°C. The maximum growth rate for one-hour growth reaches to 1120 m/h, while the typical growth rate of growth for 2h is about 500 m/h. A large crystal that is about 25 mm in diameter and 1650 m in thickness can be obtained by growth for 5h. The crystal quality is confirmed to be homogeneous by X-ray diffraction and X-ray topography, because FWHM is less than 30 arcsec. Etch pit density of the threading dislocations in the grown crystal is 103-104 cm-2, and that of basal plane dislocation is 2×102-3×103 cm-2. Resistivity of the crystals grown by the solution growth is comparable to those of crystals grown by physical vapor transport technique.