Chemistry Reference
In-Depth Information
8.2.4.1.2.2 Plasma Polymerization of Fluorocarbons
Plasmas in fluorocarbon gases show special features:
•
Plasmapolymerization of fluorocarbons leads to thin films with distin-
guished properties concerning the very low surface energy and, therefore,
important properties for special applications.
•
Fluorocarbon plasmas are suitable for thin film coating but also for plasma
etching in dependence on the nature of admixture to the fluorocarbon
feed gas.
•
The discharge in fluorocarbon feed gas shows, due to the electron affinity, a
high concentration of negative ions.
Monomers for coating processes are
•
Perfluoralkane such as CF
4
,C
2
F
6
,C
3
F
8
, and C
4
F
10
•
Perfluoralkene such as C
2
F
4
,C
3
F
6
, and C
4
F
8
•
Fluorohydrocarbons such as CHF
3
A compilation of data of electron interactions (excitation, dissociation, ionization,
attachment, drift and diffusion coefficients) with such plasma processing gases is
given by Christophorou and Olthoff [323]. An example is presented in Figure 8.49.
Here partial ionization cross sections (suggested values) for the generation of
fragment ions of CF
4
and the dissociation cross section for the formation of
F
1
CF
3
+
CF
2
+
0.1
C
+
F
+
CF
+
0.01
1E-3
10
20
30
40
50
60
70
80
90
Electron energy eV
FIGURE 8.49
Partial ionization cross sections (suggested values) for the formation of frag-
ment ions and of dissociation cross section of
F
atom formation by dissociative ionization and
dissociationinneutralfragments[324]independenceonelectronenergy.(FromChristophorou,
L.G. and Olthoff, J.K.,
Fundamental Electron Interactions with Plasma Processing Gases
,
Kluwer Academic/Plenuim Publishers, New York, 2004.)
