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On the use of methane as a carbon precursor in Chemical Vapor Deposition of silicon carbide
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
Linköping University, Department of Physics, Chemistry and Biology, Chemistry. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-7171-5383
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.ORCID iD: 0000-0002-6175-1815
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
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2014 (English)In: Journal of Crystal Growth, ISSN 0022-0248, E-ISSN 1873-5002, Vol. 390, 24-29 p.Article in journal (Refereed) Published
Abstract [en]

It is generally considered that methane is not a suitable carbon precursor for growth of silicon carbide (SiC) epitaxial layers by Chemical Vapor Deposition (CVD) since its use renders epitaxial layers with very high surface roughness. In this work we demonstrate that in fact SiC epitaxial layers with high-quality morphology can be grown using methane. It is shown that a key factor in obtaining high-quality material is tuning the C/Si ratio of the process gas mixture to a region where the growth is limited neither by carbon nor by silicon supplies. From the growth characteristics presented here, we argue that the reactivity of methane with the SiC surface is much higher than generally assumed in SiC CVD modeling today.

Place, publisher, year, edition, pages
Elsevier, 2014. Vol. 390, 24-29 p.
Keyword [en]
Chloride-based; Al CVD; BL Methane; Silicon carbide; SiC
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-107126DOI: 10.1016/j.jcrysgro.2013.12.033ISI: 000335770000005OAI: oai:DiVA.org:liu-107126DiVA: diva2:722008
Available from: 2014-06-05 Created: 2014-06-05 Last updated: 2017-12-05Bibliographically approved
In thesis
1. Precursors and defect control for halogenated CVD of thick SiC epitaxial layers
Open this publication in new window or tab >>Precursors and defect control for halogenated CVD of thick SiC epitaxial layers
2014 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Silicon carbide (SiC) is a very hard semiconductor material with wide band gap, high breakdown electric field strength, high thermal conductivity and high saturation electron drift velocity making it a promising material for high frequency and high power devices. The performance of electrical devices is strongly dependent on the quality, doping level and thickness of the grown epitaxial layers. The SiC epitaxial layers are usually grown by chemical vapor deposition (CVD), using silane (SiH4) and light hydrocarbons (C2H4 or C3H8) as precursors, diluted in a massive flow of hydrogen (H2), at growth temperatures and pressures of 1500-1600 °C and 100-300 mbar, respectively. A Silicon Carbide (SiC) device with a high breakdown voltage (> 10 kV) requires thick (> 100 μm) and low doped (1014cm-3) epitaxial layers. The typical growth rate is usually 5-10 μm/h, rendering very long growth times which result in a high cost for the final device. It is hard to increase the growth rate without running into problems with homogeneous gas phase nucleation, which badly affects the surface morphology and the usefulness of the epitaxial layers for devices. This problem can be avoided by lowering the growth pressure and/or increasing the carrier gas flow (H2) to minimize the homogeneous gas phase nucleation or by increasing the growth temperature to evaporate the silicon droplets. On the other hand introducing chlorine into the gas mixture, by adding HCl or using some chlorinated silicon precursor, such as trichlorosilane (SiHCl3) or tetrachlorosilane (SiCl4), or by methyltrichlorosilane (CH3SiCl3) as a single molecule will prevent nucleation in the gas phase. In this thesis a detailed study of the chloride-based processes and an investigation of a bromide-based CVD process is made using a horizontal hot wall reactor. Focus has been mainly on the study of various precursor molecules but also the effect of process parameters on the growth of thick epitaxial layers (100-200 μm). In paper 1 the growth of SiC epitaxial layers on 4° off-axis substrates manifesting very good morphology when using methane (CH4) as carbon precursor is demonstrated. A comparative study of SiCl4, SiHCl3, SiH4+HCl, C3H8, C2H4 and CH4 in an attempt to find the optimal precursor combination is presented in Paper 2 for growth of 4H-SiC epitaxial layers on 4° off-axis substrates with very good morphology. Paper 3 presents a direct comparison between chloride-based and bromide-based CVD chemistries for growth of SiC epitaxial layers using SiH4 and C2H4 as Si- respectively C-precursors with HCl or HBr as growth additives. The influence of temperature ramp up conditions on the carrot defect density on 8° off-axis 4H-SiC epitaxial layers using the single molecule precursor methyltrichlorosilane (MTS) as growth precursor is studied in Paper 4. In paper 5 growth of about 200 μm thick epitaxial layers with very good morphology at growth rates exceeding 100 μm/h using SiCl4+C2H4 and SiH4+HCl+C2H4 precursor approaches is reported. The effect of growth conditions on dislocation density by decorating the dislocations using KOH etching is reported in Paper 6. In Paper 7 the effect of varying parameters such as growth  temperature, C/Si ratio, Cl/Si ratio, Si/H2 ratio and in situ pre-growth surface etching time are studied in order to reduce the formation of step bunching and structural defects, mainly triangular defects for growth of about 100 μm thick epitaxial layers on 4° off-axis substrates with very good morphology at growth rates up to 115 μm/h.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2014. 61 p.
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1625
National Category
Physical Sciences Chemical Sciences
Identifiers
urn:nbn:se:liu:diva-111076 (URN)10.3384/diss.diva-111076 (DOI)978-91-7519-213-0 (ISBN)
Public defence
2014-10-31, Plank, Fysikhuset, Campus Valla, Linköpings universitet, Linköping, 10:15 (English)
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Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2015-03-11Bibliographically approved

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