Emission Spectroscopy, Mass Spectrometry, and Kinetics in CH[sub 4]–CO[sub 2] Plasmas Used for Diamond Deposition

Abstract

Diamond deposition in microwave CH 4 -CO 2 plasmas depends on various parameters that change the nature and the concentration of the various species in the plasma. In this work emphasis was put on the effect exerted by changes in the power density injected in the plasma. These changes were obtained by varying both the microwave power and the pressure. The ro-vibrational temperature and then the kinetic temperature of the heavy species were determined by emission spectroscopy. Variations induced in the nature and the concentration of both stable species ͑H 2 , CH 4 , CO, CO 2 , . . . ͒ and radicals ͑H, OH, CH 3 , C 3 H 3 , C 3 H 5 , ...͒ were derived from analyses performed with a mass spectrometer associated to a molecular beam sampling technique. Modeling based on various reactor configurations showed that the kinetics in the plasma is principally controlled by the gas temperature at the highest power density, whereas reactions with electrons are needed to initiate the mechanism at low power densities. The comparison of computed and experimental concentration profiles also shows that the influence of the residence time is of capital importance when CH 4 /CO 2 plasmas are used for diamond deposition. This parameter allows explaining the correlation between the experimental conditions and the etching/deposition domains.

Experimental and kinetic studies of C–H–O plasmas for polycrystalline and nano-smooth diamond deposition

“…In the 500-800 W range and a pressure of 10 Torr, at low power density, the CO bands were clearly observed by OES whatever the inlet composition [2]. These spectra were simulated as reported previously [2] in order to determine both rotational and vibrational temperatures of the CO molecules as a function of all experimental parameters.…”

“…These spectra were simulated as reported previously [2] in order to determine both rotational and vibrational temperatures of the CO molecules as a function of all experimental parameters. No significant variation was observed as a function of neither the total flow rate nor the inlet composition.…”

“…The measurements were carried out at about 2 cm above the substrate through a 25 × 6 mm 2 aperture in the waveguide. The device allowed collection of the light on an optical fiber that transmitted the signal to the entrance slit of the spectrometer, as detailed in [2]. N e was measured by MI with a reactor which was especially modified.…”