Brominated chemistry for chemical vapor deposition of electronic grade SiC
In short: We present a direct comparison between chlorinated and brominated chemistry for chemical vapor deposition (CVD) of SiC. Addition of chlorine to the gas mixture reduces the time needed for growth of SiC layers for electronic devices by a factor ten. Addition of Cl enables formation of molecules with Si-Cl bonds which are stronger than Si-Si bonds preventing formation of silicon clusters. By using either HCl or HBr gas as additive we show that brominated chemistry leads to the same high material quality and control of material properties as chlorinated chemistry.
For the last, approximately ten years, addition of the element chlorine (Cl) to the gas mixture in chemical vapor deposition (CVD) of silicon carbide (SiC) has been studied as it has been shown to reduce the time needed for growth of epitaxial SiC layers for electronic devices by a factor ten. Chlorinated chemistry has also paved the way for synthesis of very thick epitaxial SiC layers in short deposition time and novel crystal growth processes for SiC. This since the addition of Cl enables formation of molecules with Si-Cl bonds which are stronger than Si-Si bonds thus preventing silicon clusters from forming in the CVD process. The Semiconductor Materials division has been pioneering the field of chlorinated SiC CVD and recently summarized the field in a review paper [H. Pedersen et al., Chemical Reviews 112, 2434 (2012)].
Given the often very similar chemistry for the halogens (F, Cl, Br and I) and the fact that also the Si-Br bond is stronger than the Si-Si bond, brominated chemistry could also be interesting for SiC CVD. In the literature there is only one previous paper on brominated chemistry for SiC CVD [T. H. Kunstmann et al., Chem. Mater., 1675 (1995)] but then SiC is grown on silicon at significantly lower temperatures. None the less, this paper suggests that Br could be a better choice than Cl as additive.
We can now, for the first time, present a direct comparison between chlorinated and brominated CVD chemistry for CVD of SiC layers on SiC substrates. This was done by using either HCl or HBr gas as additive in the CVD process. We show that brominated chemistry leads to the same high material quality and control of material properties during growth of SiC as chlorinated chemistry and that the growth rate is on average 10 % higher for a brominated chemistry compared to chlorinated chemistry. Brominated and chlorinated SiC CVD also show very similar gas phase chemistries in thermochemical modelling. This study thus argues that brominated chemistry is a strong alternative for SiC CVD since the deposition rate can be increased with preserved material quality. The thermochemical modelling also suggest that the currently used chemical mechanism for halogenated SiC CVD might need to be revised. Our study has recently been published in the highly regarded journal Chemistry of Materials.
Details of the research are described in Chem. Mater., 27, 793 (2015)
- Swedish Energy Agency.
- Swedish Foundation for Strategic Research (SFF).
- Swedish Research Council (VR),
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Last updated: 02/13/15