Papers by Keyword: C/Si Ratio

Abstract: This study investigates the multifaceted relationships between key process parameters such as C/Si ratio, system pressure, temperature, and growth rate and their effects on nitrogen dopant incorporation in homoepitaxial layers on 4H-SiC substrates. We focus on understanding how these growth parameters influence the in situ nitrogen incorporation during chemical vapor deposition (CVD) of epitaxial layers on 150 mm commercially available SiC substrates. Through a carefully designed experimental framework, which explores the interactions between each parameter and the C/Si ratio, we have shed light on a refined approach for epitaxial growth. This approach may not only stabilize the nitrogen dopant concentration across the wafer but possibly also reduces the formation of epitaxial defects.

Abstract: The modified design using an air-pocket existing on inside of crucible has been proposed for the growth of 6-inch SiC single crystal. The actual growth has been performed for conventional, focus ring design and modified hot-zone designs under the same growth conditions and then three SiC crystals were systematically compared in terms of crystal quality. Since stacking faults and polytype inclusions, which could cause dislocation formation, were suppressed by the suitable C/Si ratio control, it was possible to grow SiC ingots with reduced defect density and excellent crystal quality with crucible structures proposed in this study.

Abstract: A modified process condition has been proposed for the growth of high-quality 6-inch 4H-SiC single crystal. Temperature gradient (dT[°C] = T_bottom-T_upper) was controlled by changing coil position in order to investigate the effect of the temperature gradient on the SiC crystal quality. SiC ingot surface and etch pit density (EPD) of etched SiC wafer were investigated according to different dT conditions at the initial stage of SiC crystal growth. The surface of SiC crystal ingots grown with different dT for 10h were observed by OM and etched SiC wafers were prepared from SiC crystal ingots after main growth step for 100h. Different dT conditions in the initial growth stage resulted in dramatically different surface images and the crystal quality evaluated by EPD.

Abstract: Boron (B) doping sources and crucible materials for stable, reproducible and high concentration B doping in fluorescent SiC (f-SiC) were investigated. When a Ta crucible was used with BN powder as a B doping source were used, B doping did not occur owing to too low C/Si ratio. On the other hand, when a C crucible and suitable Ta components inside the crucible were used, a high B concentration of 1.58 × 10¹⁹ cm^-3 was obtained, owing to the high C/Si ratio. The results indicate that a C crucible with optimal Ta components and BN powder are suitable for high concentration B doping.

Abstract: We investigated the run-to-run fluctuation in growth conditions of physical vapor transport growth of 4H-SiC boules through observations of surface morphology on the (000-1) facet of the boules. The boules, which were grown under the same macroscopic growth conditions, exhibited slightly different surface morphologies. This indicates that some microscopic growth parameters that influence the surface morphology fluctuate between growth runs. We have considered the C/Si ratio of the vapor sublimed from the source material as a major parameter and discussed the associated variations in the physical and surface properties of the grown crystals.

Abstract: In this study, we investigated the epitaxial surface defects resulting from the carbon-inclusion defects in 4H-SiC substrate. Most carbon-inclusion defects developed into one of three types of epitaxial surface defects under normal epitaxial growth conditions. Among them, we found a regular hexagonal pit by high-resolution microscopy, which we regarded as a large-pit defect, and which had an adverse impact on the reverse electrical characteristics of Schottky barrier diodes. Conversion of a carbon-inclusion defect to a large-pit defect or a triangular defect could be reduced by reducing the C/Si ratio.

Abstract: In this study, different parameters of 4H-SiC epitaxial growth were used to investigate the influence on surface pits density. It was found that the density of surface pits can be reduced significantly at lower C/Si ratio condition but doping uniformity became worse simultaneously. The background doping was higher than 2E15 cm^-3 when C/Si ratio was lower than 1.0. Influences of growth temperature and growth rate are also discussed. The lower surface pits density 4H-SiC epilayer with good uniformity (s/mean below 2%) can be realized during optimal condition.

Abstract: The large growth pits (LGPs) dependence of substrate quality, growth rate, and C/Si ratio have been discussed in the 4H-SiC epitaxial growth on 100 mm N-type 4H-SiC Si-face substrates misoriented by 4° toward [11-20] with a warm-wall planetary reactor. The formation and reduction of LGPs have been investigated by adjusting the growth process parameters. With the optimized process, the perfect surface morphology with lower LGPs density has been obtained on the high quality substrate.

Abstract: Application of dichlorosilane (DCS) in 4H-SiC epitaxial growth on 4° off-cut substrates has been studied. The effect of C/Si ratio and N₂ gas flow rate on epilayer properties is investigated in detail. It is found that the C/Si ratio has a significant influence on the growth rate, epilayer surface roughness (step-bunching), conversion of basal plane dislocations (BPDs), and generation of morphological defects and in-grown stacking faults. A wide range of doping concentration from p- to n+ can be controlled in DCS growth. High quality 4° off-cut SiC epilayers are achieved for C/Si=1.3 – 1.8. Addition of N₂ has no obvious influence on growth rate and defect densities. The BPD conversion greater than 99.8% is achieved independent of N doping without any pretreatment.

Abstract: We have investigated key factors for controlling the polytype and surface morphology of 4H-SiC homoepitaxial growth on less than 4^o off-axis substrates. In addition, we characterized the crystal quality and surface quality of the epitaxial layer of an entire 3-inch vicinal off angled substrate. The results suggested that the control of surface free energy, control of the vicinal off angle itself, and high temperature growth, is highly important in controlling the surface morphology and polytype stability of the epitaxial layer grown on a vicinal off angled substrate. We also obtained a high-quality epitaxial layer grown on a 3-inch vicinal off angle substrate, which was comparable to those on 4^o off-axis substrates.