Change search
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf
Fluorinated SiC CVD
Linköping University, Department of Physics, Chemistry and Biology, Semiconductor Materials. Linköping University, Faculty of Science & Engineering.
2017 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

For the emerging semiconductor material silicon carbide (SiC) used in high power devices, chemical vapor deposition (CVD) is the most prominent method to create the electrically active SiC epitaxial layers in the device. The process of growing such epitaxial layers is to use a hydrocarbon and silane diluted in hydrogen flow through a hot chamber where chemical reactions take place in such manner that Si and C finally deposit on the surface creating epitaxial SiC. The addition of chlorine (Cl) to the process has been thoroughly investigated due to its ability to reduce homogeneous nucleation in the gas phase attributed to the stronger Si-Cl bond compared to the Si-Si bond. In this thesis the fluorinated chemistry has been investigated, since the Si-F bond is even stronger than the Si-Cl bond and the fluorinated chemistry for SiC CVD has remained poorly understood.

Using SiF4 as Si precursor in growth experiments combined with thermal equilibrium calculations of gas phase composition and quantum chemical computations of the surface chemistry first the silicon chemistry in the CVD process has been probed. It is shown that while growth rates on the order of 35 µm/h can be achieved with a fluorinated chemistry, the deposition chemistry is very sensitive to the mass flows of the precursors and not as robust as the chlorinated CVD chemistry which routinely yields 100 µm/h over wide conditions. By using the position for the onset of epitaxial growth along the gas flow direction as a new measurable, together with modeling, it is conclude that SiF is the main Si growth species with SiHF as a minor Si species contributing to growth.

The carbon chemistry in a fluorinated SiC CVD process has been probed by a similar approach. Here it is found that the slow kinetics of the SiF4 molecule needs to be matched by a carbon precursor with comparable slow kinetics. It is shown that methane is a suitable carbon precursor in combination with SiF4.

Before a fluorinated CVD chemistry can be adopted in device processing, the effect of fluorine on the dopant incorporation must be understood since dopant incorporation is of paramount importance in semiconductor manufacturing. Dopant incorporation studies for n-type doping with N using N2 and p-type doping with Al using TMAl in fluorinated CVD of homoepitaxial SiC are presented. It is found to be possible to control the doping in SiC epitaxial layers when using a fluorinated CVD chemistry for both n- and p-type material using the C/Si ratio as in standard SiC CVD. However, large area doping uniformity seems to be a challenge for a fluorinated CVD chemistry, most likely due to the very strong Si-F and Al-F bonds. It is found that no additional optically or electrically active defects are created due to the use of fluorine in the CVD process.

Finally, the fluorinated chemistry is compared to the chlorinated and brominated chemistries for SiC CVD and an overall model for halogen addition to SiC CVD is presented.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2017. , p. 42
Series
Linköping Studies in Science and Technology. Dissertations, ISSN 0345-7524 ; 1826
National Category
Condensed Matter Physics
Identifiers
URN: urn:nbn:se:liu:diva-133832DOI: 10.3384/diss.diva-133832ISBN: 9789176855911 (print)OAI: oai:DiVA.org:liu-133832DiVA, id: diva2:1064141
Public defence
2017-02-24, Planck, Linköpings universitet, Linköping, 09:15 (English)
Opponent
Supervisors
Available from: 2017-01-30 Created: 2017-01-11 Last updated: 2017-02-09Bibliographically approved
List of papers
1. Silicon Chemistry in Fluorinated Chemical Vapor Deposition of Silicon Carbide
Open this publication in new window or tab >>Silicon Chemistry in Fluorinated Chemical Vapor Deposition of Silicon Carbide
Show others...
2017 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 121, no 5, p. 2711-2720Article in journal (Refereed) Published
Abstract [en]

The use of chlorinated chemical vapor deposition (CVD) chemistry for growth of homoepitaxial layers of silicon carbide (SiC) has diminished the problem of homogenous gas phase nucleation, mainly the formation of Si droplets, in CVD of SiC by replacing Si-Si bonds with stronger Si-Cl bonds. Employing the even stronger Si-F bond could potentially lead to an even more efficient CVD chemistry, however, fluorinated chemistry is very poorly understood for SiC CVD. Here, we present studies of the poorly understood fluorinated CVD chemistry for homoepitaxial SiC layers using SiF4 as Si precursor. We use a combination of experimental growth studies, thermal equilibrium calculations of gas phase composition and quantum chemical computations (i.e. hybrid density functional theory) of the surface chemistry to probe the silicon chemistry in the CVD process. We show that while growth rates on the order of 35 µm/h can be achieved with a fluorinated chemistry, the deposition chemistry is very sensitive to the mass flows of the precursors and not as robust as the chlorinated CVD chemistry which routinely yields 100 µm/h over wide conditions. By using the position for the onset of epitaxial growth along the gas flow direction as a measurable, together with modeling, we conclude that SiF is the main Si growth species with SiHF as a minor Si species contributing to growth.

Place, publisher, year, edition, pages
Washington: American Chemical Society (ACS), 2017
National Category
Chemical Process Engineering Inorganic Chemistry Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:liu:diva-134247 (URN)10.1021/acs.jpcc.6b10849 (DOI)000394080900026 ()
Note

Funding agencies: Knut & Alice Wallenberg Foundation (KAW) project "Isotopic Control for Ultimate Material Properties"; Swedish Foundation for Strategic Research project "SiC - the Material for Energy-Saving Power Electronics" [EM11-0034]; Advanced Functional Materials (AFM)

Available from: 2017-01-30 Created: 2017-01-30 Last updated: 2017-11-29Bibliographically approved

Open Access in DiVA

fulltext(763 kB)88 downloads
File information
File name FULLTEXT01.pdfFile size 763 kBChecksum SHA-512
66368db9c33cb2b630893682bb9e6e4e0b45a41317a5063a5bd86c95a49e65858835f970be608fbcf392ba98b65ae3a2a2b9432af0e4bb91de54a733809ea357
Type fulltextMimetype application/pdf
omslag(142 kB)8 downloads
File information
File name COVER01.pdfFile size 142 kBChecksum SHA-512
9d642f683f22d7c7886139cf4c36aa4da5b57b0dd1c2b4246fc3e91aafb21f031e3650eb70a6c07870e7f6ad14d71370fa9679b703ce23a0ee8b7c8c954677a3
Type coverMimetype application/pdf

Other links

Publisher's full text

Search in DiVA

By author/editor
Stenberg, Pontus
By organisation
Semiconductor MaterialsFaculty of Science & Engineering
Condensed Matter Physics

Search outside of DiVA

GoogleGoogle Scholar
Total: 88 downloads
The number of downloads is the sum of all downloads of full texts. It may include eg previous versions that are now no longer available

doi
isbn
urn-nbn

Altmetric score

doi
isbn
urn-nbn
Total: 751 hits
CiteExportLink to record
Permanent link

Direct link
Cite
Citation style
  • apa
  • ieee
  • modern-language-association-8th-edition
  • vancouver
  • Other style
More styles
Language
  • de-DE
  • en-GB
  • en-US
  • fi-FI
  • nn-NO
  • nn-NB
  • sv-SE
  • Other locale
More languages
Output format
  • html
  • text
  • asciidoc
  • rtf