Gas-Phase Modeling of Chlorine-Based Chemical Vapor Deposition of Silicon Carbide

Abstract

Kinetic calculations of the chemical phenomena occurring in the epitaxial growth of silicon carbide are performed in this study. The main process parameters analyzed are precursor types, growth temperature, Cl/Si ratio, and precursors' concentration. The analysis of the gas-phase reactions resulted in a model which could explain most of the already reported experimental results, performed in horizontal hot-wall reactors. The effect of using different carbon or silicon precursors is discussed, by comparing the gas-phase composition and the resulting C/Si ratio inside the hot reaction chamber. Chlorinated molecules with three chlorine atoms seem to be the most efficient and resulting in a uniform C/Si ratio along the susceptor coordinate. Further complexity in the process derives from the use of low temperatures, which affects not only the gas-phase composition but also the risk of gas-phase nucleation. The Cl/Si ratio is demonstrated to be crucial not only for the prevention of silicon clusters but also for the uniformity of the gas-phase composition.

On the use of methane as a carbon precursor in Chemical Vapor Deposition of silicon carbide

“…This is a further indication that the growth chemistries for the two hydrocarbons are different. Ethylene is commonly considered to decompose predominantly to acetylene (C 2 H 2 ) in the gas phase [5]. If we assume that the low reactivity of methane in the gas-phase leads to decomposition of only a fraction of the molecules to CH 3 , then the dominant species responsible for growth in the methane and ethylene case will be methane and acetylene, respectively.…”

“…The thickness of the grown epitaxial layers was measured by FT-IR reflectance and the morphology of the epitaxial layers was studied using optical microscope with Nomarski differential interference contrast and in greater detail using atomic force microscopy (AFM) 5 in tapping mode on a 20 × 20 µm 2 surface at the center of the substrate and at two different areas close to the periphery, about 2 mm from the edge. The surface roughness of the samples was quantified by the root mean square (RMS) value of the height variations over the scanned area by AFM.…”

“…The introduction of chloride-based growth chemistry in SiC CVD has enabled considerably higher growth rates of epitaxial SiC layers [4] owing to the different gas phase [5] and surface chemistry [6] initiated by the presence of chlorine, and has also made a high temperature chlorinated SiC bulk growth process possible [7]. In the process proposed by Fanton et al [7]., where high temperatures of around 2000 °C are used, methane has proven to be the best carbon precursor yielding a more stable process with less formation of solid carbon in the gas inlet.…”

Bulk and epitaxial growth of silicon carbide

“…These precursors do not decompose below 800°C (cf. 400°C for SiH4) and start to form SiClx (mainly x = 2) above about 1000°C in a H2 ambient [203]. CH3Cl [204] and SiCH3Cl3 [205,206] have also been used successfully for fast epitaxy of SiC.…”

Epitaxial Growth of Silicon Carbide

“…These precursors do not decompose below 800 ∘ C (cf. 400 ∘ C for SiH 4 ) and start to form SiCl x (mainly x = 2) above about 1000 ∘ C in a H 2 ambient [182]. CH 3 Cl [183] and SiCH 3 Cl 3 [184,185] have also been used successfully for fast epitaxy of SiC.…”