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Effect of process parameters on dislocation density in thick 4H-SiC epitaxial layers grown by chloride-based CVD on 4 degrees off-axis substrates
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.
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, The Institute of Technology.
2014 (English)In: SILICON CARBIDE AND RELATED MATERIALS 2013, PTS 1 AND 2, Trans Tech Publications , 2014, Vol. 778-780, 159-162 p.Conference paper, Published paper (Refereed)
Abstract [en]

The effect of process parameters such as growth temperature, C/Si ratio, etching time, and Si/H2 ratio on dislocation density was investigated by performing KOH etching on 100 mu m thick epitaxial layers grown on 4 degrees off axis 4H-SiC substrates at various growth conditions by a chemical vapor deposition (CVD) process using a chloride-based chemistry to achieve growth rates exceeding 100 mu m/h. We observe that the growth temperature and the growth rate have no significant influence on the dislocation density in the grown epitaxial layers. A low C/Si ratio increases the density of threading screw dislocations (TSD) markedly. The basal plane dislocation (BPD) density was reduced by using a proper in-situ etch prior to growth.

Place, publisher, year, edition, pages
Trans Tech Publications , 2014. Vol. 778-780, 159-162 p.
Series
Materials Science Forum, ISSN 1662-9752 ; 778-780
Keyword [en]
Silicon Carbide; SiC; CVD; Dislocation; 4 degrees off-axis substrates; Epitaxial layers
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:liu:diva-108191DOI: 10.4028/www.scientific.net/MSF.778-780.159ISI: 000336634100037OAI: oai:DiVA.org:liu-108191DiVA: diva2:729509
Conference
The International Conference on Silicon Carbide and Related Materials, September 29-October 4, 2013, Phoenix Seagaia Resort, Miyazaki, Japan
Available from: 2014-06-26 Created: 2014-06-26 Last updated: 2015-03-11
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)
Opponent
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Available from: 2014-10-07 Created: 2014-10-07 Last updated: 2015-03-11Bibliographically approved

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Yazdanfar, MilanPedersen, HenrikKordina, OlleJanzén, Erik

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