Etch rate
measurements
Another application of the method is the
measurement of the etch rate during the plasma treatment of
different materials. In the figure above, is presented the variation
of the reflected intensity as a function of treatment time of
Polyethylene Terephthalate (PET) films from He-O2 plasma.
The refractive index of the material has the quite low value of 1.2
and this lead to the observation of broad maxima and sharp minima of
the reflected intensity. In addition, due to the low value of n1
the thickness of the layer that corresponds to the time that is
required for the appearance of two minimum has the quite high value
of 2150 Å.
The application of the Laser Reflectance Interferometry method for
the investigation of the effect of external plasma parameters on the
etch rate of PET from He discharges is presented in the figure
above. The application of the method in etch systems as in the case
of deposition systems gives the capability of quite large number of
etch rate measurements, thus reducing significantly the time
that is required for an optimization of a process.
