Papers by Author: Olof Kordina

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Authors: Anant K. Agarwal, Sei Hyung Ryu, Ranbir Singh, Olof Kordina, John W. Palmour
Authors: Milan Yazdanfar, Stefano Leone, Henrik Pedersen, Olof Kordina, Anne Henry, Erik Janzén
Abstract: Epitaxial growth of 4H-SiC on 8º off-axis substrates has been performed under different condition during the temperature ramp up in order to study the effect on the carrot defect. The study was done in a hot wall chemical vapor deposition reactor using the single molecule precursor methyltrichlorosilane (MTS). During the temperature ramp up, a small flow of HCl or C2H4 was added to the H2 ambient to study different surface etching conditions. The best result was obtained when HCl was added from 1175 to 1520 °C during the ramp up to growth temperature (1575 °C).
Authors: Ivan G. Ivanov, Ulf Lindefelt, Anne Henry, T. Egilsson, Olof Kordina, Erik Janzén
Authors: Anne Henry, Stefano Leone, Franziska Christine Beyer, Sven Andersson, Olof Kordina, Erik Janzén
Abstract: A chloride-based chemical-vapor-deposition (CVD) process has been successfully used to grow very high quality 3C-SiC epitaxial layers on on-axis α-SiC substrates. An accurate process parameters study was performed testing the effect of temperature, in situ surface preparation, precursor ratios, nitrogen addition, and substrate polytype and polarity. The 3C layers deposited showed to be largely single-domain material of very high purity and of excellent electrical characteristics. A growth rate of up to 10 µm/h and a low background doping enable deposition of epitaxial layers suitable for MOSFET devices.
Authors: Stefano Leone, Anne Henry, Olof Kordina, Erik Janzén
Abstract: Chloride-based growth on on-axis SiC substrates has been studied at higher temperature than typical CVD conditions. The use of chlorinated precursors allows to grow homo-polytypic layers and to achieve high growth rates for thick layers deposition. In this study a vertical reactor with the gas flow inlet at the bottom has been used to grow layers up to 1.5 mm thick. Thanks to the addition of hydrogen chloride (HCl) to the standard precursors mixture, growth rates up to 300 μm/h have been achieved at a process temperature lower than 1900 °C. Very pure layers, micropipe free, and with a low background doping have been grown on 4H and 6H-SiC carbon and silicon-face, respectively, on-axis 3” diameter substrates. The results obtained indicates that this process has the potential to become a novel bulk growth technique at lower temperature than usual, which could give several advantages.
Authors: Stefano Leone, Yuan Chih Lin, Franziska Christine Beyer, Sven Andersson, Henrik Pedersen, Olof Kordina, Anne Henry, Erik Janzén
Abstract: The epitaxial growth at 100 µm/h on on-axis 4H-SiC substrates is demonstrated in this study. Chloride-based CVD, which has been shown to be a reliable process to grow SiC epitaxial layers at rates above 100 µm/h on off-cut substrates, was combined with silane in-situ etching. A proper tuning of C/Si and Cl/Si ratios and the combination of different chlorinated precursors resulted in the homoepitaxial growth of 4H-SiC on Si-face substrates at high rates. Methyltrichlorosilane, added with silane, ethylene and hydrogen chloride were employed as precursors to perform epitaxial growths resulting in very low background doping concentration and high quality material, which could be employed for power devices structure on basal-plane-dislocation-free epitaxial layers.
Authors: Stefano Leone, Henrik Pedersen, Franziska Christine Beyer, Sven Andersson, Olof Kordina, Anne Henry, Andrea Canino, Francesco La Via, Erik Janzén
Abstract: A review of recently achieved results with the chloride-based CVD on 8° and 4° off axis and nominally on-axis 4H-SiC wafers is done to clarify the epitaxial growth mechanisms on different off-angle substrates. The process conditions selected for each off-axis angle become even more difficult when running at growth rates of 100 µm/h or more. A fine-tuning of process parameters mainly temperature, C/Si ratio and in situ surface preparation is necessary for each off-angle. Some trends related to the surface properties and the effective C/Si ratio existing on the surface prior to and during the epitaxial growth can be observed.
Authors: Nguyen Tien Son, Alexsandre Ellison, Mike F. MacMillan, Olof Kordina, W.M. Chen, Bo Monemar, Erik Janzén
Authors: I.D. Booker, Jawad ul Hassan, Anders Hallén, Einar Ö. Sveinbjörnsson, Olof Kordina, Peder Bergman
Abstract: We compare two methods for post-growth improvement of bulk carrier lifetime in 4H-SiC: dry oxidations and implantations with either 12C or 14N, followed by high temperature anneals in Ar atmosphere. Application of these techniques to samples cut from the same wafer/epilayer yields 2- to 11-fold lifetime increases, with the implantation/annealing technique shown to give greater maximum lifetimes. The maximum lifetimes reached are ~5μs after 12C implantation at 600°C and annealing in Ar for 180 minutes at 1500°C. Higher temperatures give decreased lifetimes, a result which differs from reports in literature.
Authors: Anne Henry, Stefano Leone, Sven Andersson, Olof Kordina, Erik Janzén
Abstract: A chloride-based CVD process has been studied in concentrated growth conditions. A systematic study of different carrier flows and pressures has been done in order to get good quality epilayers on 8° off and on-axis substrates while using very low carrier flows. Hydrogen chloride (HCl) was added to the standard gas mixture to keep a high growth rate and to get homo-polytypic growth on on-axis substrates. The carrier flow was reduced down to one order of magnitude less than under typical growth condition. By lowering the process pressure it was possible to reduce precursor depletion along the susceptor which improved the thickness uniformity to below 2% variation (σ/mean) over a 2” diameter wafer.
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