V. Shogun et al., EMISSION ACTINOMETRIC INVESTIGATIONS OF ATOMIC-HYDROGEN AND CH RADICALS IN PLASMA-ENHANCED CHEMICAL-VAPOR-DEPOSITION PROCESSES OF HEXAMETHYLDISILOXANE, Surface & coatings technology, 98(1-3), 1998, pp. 1382-1386
Spectral investigations were carried out in a plasma-enhanced chemical
vapour deposition (PECVD) process using hexamethyldisiloxane (HMDSO)
thin film deposition. The experiments were performed in a closed react
or with r.f. plasma generation in the pressure range of 20-40 Pa and p
ower range of 10-20 W. It is shown that the emission lines of atomic h
ydrogen (486 nm) and CH radicals (431 nm) are the most informative lin
es from the point of view of the process dynamic control, because hydr
ogen is the final product of the discharge and CII is an indicator for
the last intermediate products (CxHy) of the process obtained. Other
species (Si and O) are built in the deposited coating. The excitation
energy of the hydrogen lines (approximate to 12 eV) permit the use of
the argon emission line at 750 nm as an actinometer (approximate to 11
eV). A problem for using actinometry is the large difference of the e
xciting level of the CH band (approximate to 3 eV). That is why in the
following article is shown as only a first approximation for characte
rising this PECVD process. By adding argon (up to 10%) the process dyn
amic was controlled in the hydrogen and CH radicals concentration meas
urement mode. The measurement was realised by using spectral signals m
easured at 5-8 (peak and its background) different wavelengths in the
quasi parallel mode of an acoustooptical spectrometer. The measured cu
rves of the relative H and CH concentrations demonstrate the CH accumu
lation due to plasma chemical conversion of HMDSO during the first two
stages of the process duration. The final stage of the process is cha
racterised by the dissociation of CH radicals, which results in a sync
hronous increase of the hydrogen signal and decrease of the CH radical
s signal causing the existence of free carbon, which appears as carbon
enriched coverage on reactor walls. (C) 1998 Elsevier Science S.A.