Epitaxial growth of 3C-SiC film by microwave plasma chemical vapor deposition in H2-CH4-SiH4 mixtures: Optical emission spectroscopy study

Abstract

Microwave (MW) plasma in silane-hydrogen and silane-hydrogen-methane mixtures is used effectively for chemical vapor deposition of Si, SiC, diamond, and SiC-diamond composite films; however, the properties of such plasma at pressures of the order of 100 Torr remain largely unexplored. Here we characterize the MW plasma (2.45 GHz) in SiH4 + H2 and SiH4 + СH4 + H2 mixtures (72 Torr) with silane content ranging from 0% to 5% in the process gas using high-resolution optical emission (OE) spectroscopy. Besides the OE lines of C2 dimer, Balmer series of excited atomic hydrogen (Hα, Hβ, Hγ, Hδ, and Hε), and CH radical, we observed atomic Si lines at 263, 288, and 391 nm and a relatively weak SiH emission. Gas temperature Tg of ≈3160 K is assessed from the rotational structure of the C2 dimer (Δν = 0, λ = 516.5 nm) emission band, and the absorbed microwave power density (MWPD) in the plasma fluctuates in the narrow range between 36 and 43 W/cm3 with a slight tendency to decrease with silane addition. The MWPD, intensity ratio Hα/Hβ of hydrogen Balmer series lines (related to excitation temperature Texc), and Si lines’ intensities in OE spectra as functions of SiH4 concentration in H2 and H2 + CH4 mixtures all show an extremum or a kink in slope near a special point at ≈0.5% SiH4. Finally, we produced a silicon carbide film of cubic polytype 3C-SiC on a (111) oriented Si substrate, which was characterized with Raman spectroscopy and x-ray diffraction, and its monocrystalline structure was confirmed.

In situ doping of epitaxial diamond with germanium by microwave plasma CVD in GeH4–CH4–H2 mixtures with optical emission spectroscopy monitoring

“…Note that, in contrast, for related H 2 + CH 4 + SiH 4 plasma, the intensities of C 2 (516nm) and H β and H γ lines are reported to monotonically increase with silane addition. 22,23 The spectral resolution of the spectrometer was high enough to resolve the rotational fine structure of Swan bands, and we were able to deduce the rotational temperature T rot from the analysis of the Swan band (Δ ν = 0) of the C 2 dimer with a head line of 516.5 nm. Assuming a thermal equilibrium between rotational levels, the emission was linked to the rotational temperature T rot through Boltzmann's relation, 23,28 and the T rot value was adopted as the gas temperature T g .…”

“…22,23 The spectral resolution of the spectrometer was high enough to resolve the rotational fine structure of Swan bands, and we were able to deduce the rotational temperature T rot from the analysis of the Swan band (Δ ν = 0) of the C 2 dimer with a head line of 516.5 nm. Assuming a thermal equilibrium between rotational levels, the emission was linked to the rotational temperature T rot through Boltzmann's relation, 23,28 and the T rot value was adopted as the gas temperature T g . The gas temperature T g is found to gradually decrease with the addition of GeH 4 from 2980 ± 150 K to 2690 ± 150 K (Fig.…”

“…The gas temperature was determined by measuring the rotational temperature of the Swan transitions for dimer C 2 emission at a 516 nm wavelength. 23,28…”

“…The approach is similar to CVD diamond doping with Si using silane SiH4 20 or tetramethylsilane (TMS) 21 precursors. While the microwave plasma chemistry in triple SiH 4 –CH 4 –H 2 mixtures has been the subject of studies in recent years using optical diagnostics, such as optical emission spectroscopy (OES), 6,22,23 the GeH 4 –CH 4 –H 2 system in MPCVD reactors with regard to parameters relevant to diamond deposition has remained experimentally unexplored by OES or other optical techniques.…”

Microporous poly- and monocrystalline diamond films produced from chemical vapor deposited diamond–germanium composites

“…44 However, the HPHT diamonds are limited in size and cannot be prepared in the form of thin films, so another technique for the synthesis of various diamond composites can be used instead – chemical vapor deposition (CVD). 45–47…”