C. Barholmhansen et al., OPTICAL-EMISSION SPECTROSCOPY DURING GROWTH OF DIAMOND-LIKE CARBON FROM A METHANE PLASMA, DIAMOND AND RELATED MATERIALS, 3(4-6), 1994, pp. 564-568
The influence of the CH4 flow rate on the emission intensity of the CH
radical has been investigated by optical emission spectroscopy in the
190-315 nm and 378-503 mm wave bands. Emission intensities of two neu
tral carbon lines at 193.0 nm and 247.9 nm were observed to have a sim
ilar dependence on process parameters as the intensity of the CH 430.9
nm emission line. For a given r.f. power a critical value of the CH4
flow rate is observed. For flow rates lower than this critical value t
he dynamic equilibrium between C(x)H(y) and hydrogen is shifted toward
s higher hydrogen partial pressures. Thin films of diamond-like carbon
deposited at such low flow rates were measured to have a lower densit
y than those grown at higher flow rates. The intensities of the CH 430
.8 nm and the Hgamma lines were studied at pressures from 1 to 30 Pa,
and only at the lowest values was a significant pressure dependence fo
und. The deposition rate and the intensity of the CH 430.9 nm emission
line is found to scale with the effective current defined as the rati
o between the applied r.f. power and the negative self-bias.