RF plasma etching of a polyimide film with oxygen mixed with nitrogen trifluoride - Polyimides and Other High Temperature Polymers - page 412

ylic anhydride, diamine and benzene) and fluorine and oxygen radicals were cal-
culated.
Figures 7 and 8 show the cleavage schemes of imide ring due to fluorine and
oxygen radicals, respectively. As the enthalpies of the fluorine radical reactions
are negative, a fluorine radical can easily cleave the imide ring. An oxygen radical
can also cleave the imide ring, but this cleavage reaction hardly takes place, be-
cause the enthalpy of the formation of the intermediate compound is positive.
The reactions of fluorine radical with a benzene ring are shown in Fig. 9. The
benzene ring is considered to be easily fluorinated by fluorine radicals. The hy-
drogen in the benzene ring is pulled out by the fluorine radical. The reaction en-
thalpies of the fluorination of diphenylether were also calculated and are shown in
Figure 7. Cleavage scheme of imide ring by fluorine. Reaction enthalpies are shown: [kJ/mol].
Figure 8. Cleavage scheme of imide ring by oxygen. Reaction enthalpies are shown: [kJ/mol].
Figure 9. Reactions of fluorine with benzene ring. Reaction enthalpies are shown: [kJ/mol].