H. Kersten et al., INVESTIGATIONS ON PLASMA-ASSISTED SURFACE CLEANING OF ALUMINUM IN AN OXYGEN GLOW-DISCHARGE, Contributions to Plasma Physics, 34(4), 1994, pp. 563-574
Aluminum plates which are contaminated with hydrocarbon containing com
pounds (oil, grease) were treated in an Ar-, O2- and Ar/O2-plasma gene
rated by a dc-discharge. Besides a variation of the macroscopic discha
rge parameters (power, pressure) also different modes (anomalous glow
regime, hollow cathode regime) have been studied. In most cases the co
ntaminated substrates served as cathodes of an anomalous glow discharg
e where the combined influence of chemically reactive radicals and ene
rgetic ions was very effective. During the plasma process the discharg
e was monitored by means of power variation and optical emission spect
roscopy. The spectral line intensities of several species (etchants an
d products) have been measured as functions of the process duration. S
imultaneously the removal of the contamination layers was observed by
means of in-situ ellipsometry. The temporal change of the ellipsometri
c parameters PSI and DELTA during the cleaning process was taken as a
measure for the state of the surface. The combination of spectroscopic
and ellipsometric measurements which indicate the progress of the pla
sma treatment gave interesting results on the mechanisms at the surfac
e. In addition. surface analysis was used to assess the quality of the
substrates treated.