Papers by Keyword: Step Bunching

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Authors: Kazutoshi Kojima, Sachiko Ito, Junji Senzaki, Hajime Okumura
Abstract: We have carried out detailed investigations of 4H-SiC homoepitaxial growth on vicinal off-angled Si-face substrates. We found that the surface morphology of the substrate just after in-situ H2 etching was also affected by the value of the vicinal-off angle. Growth conditions consisting of a low C/Si ratio and a low growth temperature were effective in suppressing macro step bunching at the grown epilayer surface. We also demonstrated epitaxial growth without step bunching on a 2-inch 4H-SiC Si-face substrate with a vicinal off angle of 0.79o. Ni Schottky barrier diodes fabricated on an as-grown epilayer had a blocking voltage above 1000V and a leakage current of less than 5x10-7A/cm2. We also investigated the propagation of basal plane dislocation from the vicinal off angled substrate into the epitaxial layer.
Authors: Christopher L. Frewin, Camilla Coletti, Christian Riedl, Ulrich Starke, Stephen E. Saddow
Abstract: A comprehensive study on the hydrogen etching of numerous SiC polytype surfaces and orientations has been performed in a hot wall CVD reactor under both atmospheric and low pressure conditions. The polytypes studied were 4H and 6H-SiC as well as 3C-SiC grown on Si substrates. For the hexagonal polytypes the wafer surface orientation was both on- and off-axis, i.e. C and Si face. The investigation includes the influence of the prior surface polishing method on the required etching process parameters. 3C-SiC was also studied grown in both the (100) and (111) orientations. After etching, the samples were analyzed via atomic force microscopy (AFM) to determine the surface morphology and the height of the steps formed. For all cases the process conditions necessary to realize a well-ordered surface consisting of unit cell and sub-unit cell height steps were determined. The results of these experiments are summarized and samples of the corresponding AFM analysis presented.
Authors: Dong Hee Yeon, Pil Ryung Cha, Jong Kyu Yoon
Authors: Hiroyuki Matsunami
Authors: Massimo Camarda, Judith Woerle, Véronique Soulière, Gabriel Ferro, Hans Sigg, Ulrike Grossner, Jens Gobrecht
Abstract: In this study, we compare the electrical properties of MOS capacitors fabricated on different surface morphologies. Comparing a standard, low-roughness (<1nm), surface with one with a roughness of ~40nm, characterized by big macrosteps and large terraces. We compared the two surfaces for different thermal oxide thicknesses, ranging from dOx = 3.6 nm to dOx = 32 nm. The extracted interface state traps (Dit) shows a small, but systematic, decrease of ~10-15 % for the samples with macrosteps.
Authors: Mikael Syväjärvi, Rositza Yakimova, T. Iakimov, Erik Janzén
Authors: Kazutoshi Kojima, Hajime Okumura, Kazuo Arai
Abstract: We have carried out detailed investigations on the influence of the growth conditions and the wafer off angle on the surface morphology of low off angle homoepitaxial growth. We found triangular features to be also serious problems on a 4 degree off 4H-SiC Si-face epitaxial layer surface. The control of the C/Si ratio by controlling the SiH4 flow rate is effective in suppressing the triangular features on 4 degree off Si-face homoepitaxial layer. As regards epitaxial growth on a vicinal off-axis substrate, the small off angle difference of a tenth part of a degree has an influence on the surface morphology of the epitaxial layer. This tendency depends on the face polarity and a C-face can be obtained that has a specular surface with a lower vicinal off angle than a Si-face. By controlling this off angle, a specular surface morphology without a bunched step structure could be obtained on a vicinal off angle 4H-SiC Si-face.
Authors: Ming Hung Weng, Fabrizio Roccaforte, Filippo Giannazzo, Salvatore di Franco, Corrado Bongiorno, Edoardo Zanetti, Alfonso Ruggiero, Mario Saggio, Vito Raineri
Abstract: This paper reports a detailed study of the electrical activation and the surface morphology of 4H-SiC implanted with different doping ions (P for n-type doping and Al for p-type doping) and annealed at high temperature (1650–1700 °C) under different surface conditions (with or without a graphite capping layer). The combined use of atomic force microscopy (AFM), transmission electron microscopy (TEM), and scanning capacitance microscopy (SCM) allowed to clarify the crucial role played by the implant damage both in evolution of 4H-SiC surface roughness and in the electrical activation of dopants after annealing. The high density of broken bonds by the implant makes surface atoms highly mobile and a peculiar step bunching on the surface is formed during high temperature annealing. This roughness can be minimized by using a capping layer. Furthermore, residual lattice defects or precipitates were found in high dose implanted layers even after high temperature annealing. Those defects adversely affect the electrical activation, especially in the case of Al implantation. Finally, the electrical properties of Ni and Ti/Al alloy contacts on n-type and p-type implanted regions of 4H-SiC were studied. Ohmic behavior was observed for contacts on the P implanted area, whilst high resistivity was obtained in the Al implanted layer. Results showed a correlation of the electrical behavior of contacts with surface morphology, electrical activation and structural defects in ion-implanted, particularly, Al doped layer of 4H-SiC.
Authors: N. Bécourt, J.C. Ferrer, F. Peiró, A. Cornet, J.R. Morante, P. Gorostiza, G. Halkias, K. Michelakis, A. Georgakilas
Authors: Didier Chaussende, Lucile Parent-Bert, Yun Ji Shin, Thierry Ouisse, Takeshi Yoshikawa
Abstract: Using a sessile drop method, investigation of the surface reconstruction of a Si-face, 4°off (0001) 4H-SiC surface in contact with pure silicon or Al-Si alloys has been carried out in the 1600-1800°C temperature range. In pure silicon and at 1600°C, the surface evolves with a two stage process: i) a fast step-bunching leading to parallel macrosteps and ii) a slower step leading equilibrium morphology, composed of (0001), (10-1n) and (01-1n) facets. Increasing the temperature to 1800°C or adding a few percents of aluminium drastically enhance the first stage, but strongly reduce the second one.
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