Solid State Phenomena Vol. 362

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: We compared the evolution of three different SiC sources during standard PVT growth runs. The evolution of the growing crystal and the morphological changes in the SiC source were visualized using in-situ X-ray visualization. Computer simulation was used to calculate the temperature field distributions. It is found that the densification and shrinkage of the SiC source material during the growth process can affect the growth conditions in such a way that the convexity of the growth interface is increased in an unfavorable manner. While unfavorable growth conditions can be related to thermal properties due to less favorable SiC powder evolution, predicting such behavior is a rather complex task that still relies on the support of experimental methods.

Abstract: This study substantiates the epigraphene formation theory on SiC, presenting it as freestanding graphene during thermal decomposition epitaxy. It was found that cool down process is responsible for the formation of the graphene buffer layer. Additionally the capping capabilities of the buffer layer have been evaluated using Raman spectroscopy and AFM measurements.

Abstract: The memory effect of Al doping in 3C-SiC prevents sharp interfaces between layers of different doping levels and can lead to unintentional doping of subsequent epilayers and even growth runs. Introducing HCl into the growth phase of 3C-SiC reduces the Al incorporation but has a significant impact on Al dopant decay rates and background levels within the chamber, resulting in far sharper doping profiles. The impact of relatively high flow rates of HCl is low within a chlorine-based growth system giving fine control over its influence on the growth process and memory effect.

Abstract: The total ionising dose (TID) reliability of a phosphorous pentoxide (P₂O₅) treated SiO₂ (silicon dioxide) layer is compared for the first time to other industrially relevant oxides formed on 4H-silicon carbide (SiC). Metal-oxide-semiconductor capacitors (MOSCAPs) are characterised before and after irradiation to ascertain changes in flat band voltage shift, leakage current, and dielectric breakdown (BV). Secondary ion mass spectrometry (SIMS) profiling reveals a significant phosphorus concentration near the SiO₂/SiC interface, which led to improved TID resistance. The P₂O₅ treated oxide had the lowest leakage current at high voltage bias due to the high-temperature (1,000°C) anneal, though it had a significantly negative flat band voltage due to the high concentration of deposited phosphorus atoms. The thermal and P₂O₅ oxides demonstrated a TID resistance, suffering only minor shifts in flat band voltage, while the P₂O₅ oxide suffered the smallest decrease in its BV and the smallest leakage current rise, post-irradiation.

Abstract: During crystal growth processes, growth sectors are formed due to growth along different crystallographic directions. Although the crystal structure in the different growth sectors is unchanged, strain induced topography contrast is observed by synchrotron X-ray topography. In this study, synchrotron monochromatic beam X-ray topography (SMBXT), synchrotron X-ray plane wave topography (SXPWT), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and secondary ion mass spectrometry (SIMS) are used to characterize growth sectors in gallium nitride (GaN) substrate wafers grown by patterned hydride vapor phase epitaxy (HVPE). The SMBXT images reveal the boundaries of {0001} and {1122} type growth sectors. Strain maps generated from SXPWT shows that the out-of-plane strains in different growth sectors have a difference of the order of 10^-5. SEM images from SE2 signal shows no contrast of growth sector boundaries while images from Robinson detector (RBSD) show different growth sectors as different grey scale contrast, indicating a strain effect. SIMS analysis shows that the different oxygen impurity levels in the growth sectors, which is the origin of the strain. A formation mechanism of growth sectors in patterned HVPE grown GaN wafers is proposed.

Abstract: Recent advances in SiC MOSFET technology allow significant reduction of on-state resistance of the active transistor cell, increasing thus relative contribution of the drift region comprised typically from epitaxial layer or stack thereof. Tight process control of thickness and doping of epitaxial layers is therefore gaining increasing importance. This paper summarizes some key factors and features of four state-of-the-art SiC epitaxial platforms and their impact on achievable epi parameters and wafer throughput.