Chlorinated chemical vapor deposition (CVD) chemistry for growth of homoepitaxial layers of silicon carbide (SiC) has paved the way for very thick epitaxial layers in short deposition time as well as novel crystal growth processes for SiC. Here, we explore the possibility to use a brominated chemistry for SiC CVD by using HBr as additive to the standard SiC CVD precursors. We find that brominated chemistry leads to the same high material quality and control of material properties during deposition 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 modeling. This study thus argues that brominated chemistry is a strong alternative for SiC CVD because the deposition rate can be increased with preserved material quality. The thermochemical modeling also suggest that the currently used chemical mechanism for halogenated SiC CVD might need to be revised.

By carefully controlling the surface chemistry of the chemical vapor deposition process for silicon carbide (SiC), 100 lm thick epitaxial layers with excellent morphology were grown on 4 off-axis SiC substrates at growth rates exceeding 100 lm/h. In order to reduce the formation of step bunching and structural defects, mainly triangular defects, the effect of varying parameters such as growth temperature, C/Si ratio, Cl/Si ratio, Si/H 2 ratio, and in situ pre-growth surface etching time are studied. It was found that an in-situ pre growth etch at growth temperature and pressure using 0.6% HCl in hydrogen for 12 min reduced the structural defects by etching preferentially on surface damages of the substrate surface. By then applying a slightly lower growth temperature of 1575 C, a C/Si ratio of 0.8, and a Cl/Si ratio of 5, 100 lm thick, step-bunch free epitaxial layer with a minimum triangular defect density and excellent morphology could be grown, thus enabling SiC power device structures to be grown on 4 off axis SiC substrates. V C 2013 AIP Publishing LLC.

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Abstract: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.

Chemical vapor deposition of silicon carbide with a chloride-based chemistry can be done using several different silicon and carbon precursors. Here, we present a comparative study of SiCl 4 , SiHCl 3 , SiH 4 +HCl, C 3 H 8 , C 2 H 4 and CH 4 in an attempt to find the optimal precursor combination. We find that while the chlorinated silanes SiCl 4 and especially SiHCl 3 give higher growth rate than natural silane and HCl, SiH 4 +HCl gives better morphology at C/Si around 1 and SiCl 4 gives the best morphology at low C/Si. Our study shows no effect on doping incorporation with precursor chemistry. We suggest that these results can be explained by the number of reaction steps in the gas phase chemical reaction mechanisms for producing SiCl 2 , which is the most important Si species, and by formation of organosilicons in the gas phase. As carbon precursor, C 3 H 8 or C 2 H 4 are more or less equal in performance with a slight advantage for C 3 H 8 , CH 4 is however not a carbon precursor that should be used unless extraordinary growth conditions are For the last, approximately ten years, chloride-based chemistry has been studied for chemical vapor deposition (CVD) of electronic grade SiC.1 The addition of Cl to the gas mixture circumvents condensation of silicon droplets above the substrate since the stronger Si-Cl bond (400 kJ/mol or 4.15 eV) 2 prevents Si-Si bonds (226 kJ/mol or 2.34 eV) 2 to form. This allows a higher precursor concentration in the CVD gas mixture which enables higher growth rates of epitaxial SiC layers; growth rates exceeding 100 μm/h are common, compared to the 5-10 μm/h usually obtained for the standard, non-chlorinated chemistry based on silane (SiH 4 ) and small hydrocarbons like ethylene (C 2 H 4 ) or propane (C 3 H 8 ). Cl-based CVD chemistry is therefore seen as an enabler of SiC power device technology 1 , where approximately 100 μm thick, low doped (10 14 cm −3 ), epitaxial layers are required for devices capable of blocking voltages on the order of 10 kV.Addition of Cl can be done either through the addition of HCl to the standard precursors, by using a chlorinated silane molecule (SiH x Cl y ) instead of SiH 4 , by using a chlorinated hydrocarbon (CH x Cl y ) instead of C 3 H 8 /C 2 H 4 or by using a single molecule (SiH x C y Cl z ). All these approaches have been reported to be successful and capable of growth rates exceeding 100 μm/h. 1 However, the optimal precursor for Clbased CVD of SiC is still not identified, despite ten years of research on Cl-based CVD chemistry. The single molecule approach has been successful, 3 but the inherent locked C/Si ratio hinders an efficient control of the doping incorporation 4 in SiC. Thermochemical studies suggests that the use of CH x Cl y is not likely an optimal route since the C-Cl bond is found to break, allowing Si-Cl bonds to form.5 Thus the CH x Cl y approach is probably a chemical detour. There have been attempts to compare data from various groups 1,6 but these comparisons are hampered by the fact that the data are acquired in differ...