Silicon Carbide and Related Materials 2004

Volumes 483-485

doi: 10.4028/www.scientific.net/MSF.483-485

Paper Title Page

Authors: Michel Pons, Elisabeth Blanquet, Jean Marc Dedulle, M. Ucar, Peter J. Wellmann, Örjan Danielsson, Pierre Ferret, Lea Di Cioccio, Francis Baillet, Didier Chaussende, Roland Madar
Abstract: Modeling and simulation of the SiC growth process is sufficiently mature to be used as a training tool for engineers as well as a decision making tool, e.g. when building new process equipment or up-scaling old ones. It is possible to simulate accurately temperature and deposition distributions, as well as doping. The key of success would be the combined use of simulation, experiments and characterization in a "daily interaction". The main limitation in SiC growth modeling is the accurate knowledge of physical, thermal, radiative, chemical and electrical data for the different components of the reactor. This is the weakest link in developing completely predictive models. In addition, the link between the thermochemical history of the grown material and its structure and defects still needs further development and input of experimental data.
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Authors: Thomas Anderson, Donovan L. Barrett, J. Chen, Ejiro Emorhokpor, A. Gupta, R.H. Hopkins, Andrew E. Souzis, C.D. Tanner, Murugesu Yoganathan, Ilya Zwieback, Wolfgang J. Choyke, Robert P. Devaty, Fei Yan
Abstract: Semi-insulating 6H SiC substrates, 2”, 3” and 100mm in diameter, and n+ 4H SiC substrates, 2” and 3” in diameter, are grown at II-VI using the Advanced Physical Vapor Transport (APVT) technique [1]. The process utilizes high-purity SiC source and employs special measures aimed at the reduction of background contamination. Semi-insulating properties are achieved by precise vanadium compensation, which yields substrates with stable and uniform electrical resistivity reaching ~ 1011 Ω-cm and higher. Conductive n+ 4H SiC crystals with the spatially uniform resistivity of 0.02 W-cm are grown using nitrogen doping. Crystal quality of the substrates, their electrical properties and low temperature photoluminescence are discussed.
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Authors: Kazuhiko Kusunoki, Kazuhito Kamei, Y. Ueda, S. Naga, Y. Ito, Mitsuhiro Hasebe, Toru Ujihara, Kazuo Nakajima
Abstract: The growth of 6H-SiC crystal from Si-Ti-C ternary solution was conducted under the temperature gradient and the crystalline quality evaluations of the grown crystals were carried out. 6H-SiC(0001) on-axis pvt-grown crystal was used as a seed crystal. Micropipes in the seed crystal were terminated during the solution growth and 28mm􀊷28mm self-standing micropipe-free SiC crystals were obtained. The quality of the grown crystals was investigated by SIMS, high-resolution x-ray diffraction and molten KOH etching. The content of residual impurities in the SiC were very low. The X-ray 􀐢-rocking curves of the solution grown SiC showed single peak with high peak intensity ,while that of the seed crystal showed several peaks due to the misoriented domains. Moreover, it was found that the number of etch-pit in the grown crystal is much less than that in the seed crystal and it decreases with the increase of the growth thickness. These results indicate that the crystalline quality of grown crystal was significantly improved during the solution growth.
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Authors: Soo Hyung Seo, Joon Suk Song, Myung Hwan Oh, Yen Zen Wang
Abstract: We examined the formation of poly-crystals and polytypes under the point of view applying various powder phases. 6H-SiC single crystal was easily grown by using the green (α-SiC) powder, while the poly-crystals were generated when β-SiC powder was utilized. The method of mixed β-SiC and carbon powder and of graphite pipe inserted in β-SiC powder were applied to overcome the generation of poly-crystals, respectively. It was confirmed that the occurrence of poly-crystals in 6H-SiC crystal was successfully suppressed by C-rich environment.
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Authors: Eugene Y. Tupitsyn, Arul Arjunan, Robert T. Bondokov, Robert M. Kennedy, Tangali S. Sudarshan
Abstract: 4H-SiC crystals were grown using the seeded sublimation technique (modified Lely technique) in the temperature range of 1950-2200°C. The nucleation of 4H-SiC on 6HSiC has been optimized and 4H-SiC crystals of 1cm thickness were grown using 6H-SiC seeds. a-face and c-face wafers obtained from the grown boules were characterized by KOH etching, X-ray diffraction, and Raman scattering studies. Complete polytypic homogeneity of 4H SiC was obtained during growth and it was found that the 6H to 4H transition occurs in three ways: 1) without a transition layer, 2) with thick 6H-SiC layer growth, and 3) with traces of 3C SiC inclusions. The crown regions of the grown crystals exhibit an X-ray rocking curve width of 21 arcsecs.
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Authors: Peter J. Wellmann, Thomas L. Straubinger, Patrick Desperrier, Ralf Müller, Ulrike Künecke, Sakwe Aloysius Sakwe, Holger Schmitt, Albrecht Winnacker, Elisabeth Blanquet, Jean Marc Dedulle, Michel Pons
Abstract: We review the development of a modified physical vapor transport (M-PVT) growth technique for the preparation of SiC single crystals which makes use of an additional gas pipe into the growth cell. While the gas phase composition is basically fixed in conventional physical vapor transport (PVT) growth by crucible design and temperature field, the gas inlet of the MPVT configuration allows the direct tuning of the gas phase composition for improved growth conditions. The phrase "additional" means that only small amounts of extra gases are supplied in order to fine-tune the gas phase composition. We discuss the experimental implementation of the extra gas pipe and present numerical simulations of temperature field and mass transport in the new growth configuration. The potential of the growth technique will be outlined by showing the improvements achieved for p-type doping of 4H-SiC with aluminum, i.e. [Al]=9⋅1019cm-3 and ρ<0.2Ωcm, and n-type doping of SiC with phosphorous, i.e. [P]=7.8⋅1017cm-3.
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Authors: Ralf Müller, Ulrike Künecke, Roland Weingärtner, Holger Schmitt, Patrick Desperrier, Peter J. Wellmann
Abstract: Several highly aluminum doped SiC bulk crystals were grown with a modified PVT (MPVT) method. To facilitate 4H-SiC formation, growth was conducted on the C-face. The samples were investigated using Hall measurements in the Van-der-Pauw geometry. Lowest room temperature values for specific resistivities were 0.09 Ωcm for 6H-SiC and 0.2 Ωcm for 4H-SiC, which are to our knowledge the lowest values yet reported in literature. Thus, resistivity values of < 0.2 Ωcm, which are required for substrates in high power device applications, could be demonstrated for 4HSiC. Remarkably, in very highly doped samples the type of conduction could not be determined by Hall measurements.
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Authors: Thomas Anderson, Donovan L. Barrett, J. Chen, Ejiro Emorhokpor, A. Gupta, R.H. Hopkins, Andrew E. Souzis, C.D. Tanner, Murugesu Yoganathan, Ilya Zwieback
Abstract: II-VI has developed an Advanced PVT (APVT) process for the growth of nominally undoped (vanadium-free) semi-insulating 2” and 3” diameter 6H-SiC crystals with room temperature resistivity up to 1010 W·cm. The process utilizes high-purity SiC source and employs special measures aimed at the reduction of the impurity background. The APVT-grown material demonstrates concentrations of B and N reduced to about 2·1015cm-3. Wafer resistivity has been studied and correlated with Schottky barrier capacitance, yielding the density of deep compensating centers in 6H-SiC in the low 1015 cm-3 range for both ntype and p-type material. The nearly equal density of deep donors and deep acceptors ndicates that the centers responsible for the intrinsic compensation can be amphoteric. TheEPR density of spins from free carbon vacancies is about 1014 cm-3. It is also hypothesized that impurity-vacancy complexes can be present in the undoped material and participate in compensation.
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