Abstract: In this paper, an overview of the SiC bulk growth processes is given with a special focus on the most recent results related to growth and modeling. In addition, even if SiC growth is a very old topic and that it is now considered as an « industrial development problem », we will show that there are still many open questions of both fundamental and technological importance related to its crystal growth. Process chemistry and surface mechanisms will be more specifically discussed.
Abstract: In this paper, we present our new setup and technique for obtaining a real-time 3-D volume shape of the SiC crystal using X-ray computed tomography (CT). Hence, it is possible to determine in-situ the shape of the growth interface with high precision at growth temperatures above 2000 °C in a conventional 3" physical vapor transport (PVT) growth system. We show that the size and shape of a facet can be monitored at different stages during growth and furthermore the crystals face boundary can be determined with high precision throughout the whole growth process.
Abstract: We report on polytype destabilization during bulk crystal growth of Silicon Carbide by seeded sublimation method. Polytype transitions are experimentally obtained and a thermodynamic analysis using classical 2D nucleation theory is used towards the understanding of the experimental results. Whether it is a thin lamella or an inclusion, it is found that the polytype transitions systematically occur on the (0001) facet. This suggests that the polytype switch takes place through classical 2D nucleation at the facet. We will show that two criteria must be fulfilled for the occurrence of a foreign polytype: i) minimization of nucleation energy and ii) presence of a facet. This is directly depending on the crystal shape (convex or concave) and its evolution with growth time.
Abstract: We have developed RAF (Repeated a-face) growth method which is high quality bulk crystal growth technology [1, 2]. A block crystal more than 150 mm square size was produced by the RAF growth method. Since c-face growth crystal was produced on the seed obtained from the block crystal, high quality 150mm 4H-SiC wafer was achieved. This paper reports the results of the quality evaluation.
Abstract: Two kinds of SiC powder having a different impurity contents and particle size were prepared by carbothermal reduction under different conditions from traditional process for controlling the purity of product. SiC single crystal was grown in the RF heating PVT machine at the temperature above 2,100 °C. After crystal growth, boule was cut to wafers in 1mm thickness and fine polished using diamond abrasive slurry. The impurity in the powder and wafer was analyzed using glow discharged mass spectroscopy (GDMS). Major impurities in the SiC wafer were aluminum, boron, iron and titanium which were accorded in the SiC powder and these impurities were decreasing in proportional to those in the powder. However, behavior of each elemental impurity was different from each other during the crystal growth. In case of boron was increased after crystal growth while aluminum decreased. In case of titanium and boron were higher in the wafer than in the powder. It can be explained to other impurity source such as graphite crucible and insulation felt.
Abstract: The present research was focused to extensively investigate the effect of TaC-coated crucible on the SiC crystal growth and then compare the difference of various properties between SiC crystals grown in conventional graphite crucible and TaC-coated crucible. The bulk growth was conducted around 2200°C of the growth temperature and 40 mbar of an argon atmosphere for the growth pressure. The better crystalline quality was obtained from the crystal grown in TaC-coated crucible. The SiC crystal grown in the TaC-coated crucible exhibited superior characteristics than SiC crystal grown in the conventional crucible in terms of the crystal quality and defect density. Furthermore, nitrogen incorporation in SiC crystal grown in the TaC-coated crucible was definitely decreased.
Abstract: Graphite crucible in seeded sublimation growth of Silicon Carbide (SiC) single crystal does not only act as a container but also as an additional carbon source. The modeling of the growth process integrated with the etching phenomenon caused by the interaction between vapor species and the graphite crucible is shown to be able to predict the shape of the crystal front during the growth. The additional fluxes produced at the graphite part are delivered to the growing crystal mainly at the crystal periphery. The results obtained from the modeling are in good agreement with the experimental ones.
Abstract: The numerical modeling of the SiC bulk growth process by physical vapor transport has been established as the essential tool for the process development, especially for understanding and predicting the favorable growth conditions. An accurate computation of mass transfers is strongly dependent on the equilibrium partial pressure calculations. In this paper, we compare the relative impact of the different thermodynamic databases available on the full PVT process modeling. We found that whatever the database used, the trends regarding growth rate calculation, crystal shape, Si/C ratio are correctly described and none of the database would bring about unacceptable errors from the process development point of view even if some discrepancies in the absolute values could be obtained.
Abstract: Under specific and reproducible conditions we observed that the top bilayer of a spiral step can detach from the remaining bunched step. This dissociated bilayer is located in the middle of a terrace. In this work we detail the parameters for which the spiral step dissociation appears. Furthermore the possible origins of this effect and the reasons why the dissociated step is located in the center of a terrace are discussed.