XPS characterization of the interface between low dielectric constant amorphous fluoropolymer film and evaporation-deposited aluminum

The interaction of low dielectric constant amorphous fluoropolymer (AF) film with evaporation-deposited aluminum has been investigated via high-resolution X-ray photoelectron spectroscopy (XPS). For the sake of gaining the interface of the Al/AF sample, the partial aluminum has been removed by Ar ion etching. In situ XPS measurements show that Al fluoride, COAl and Al carbide are formed at the interface between aluminum and AF. The formation of Al fluoride results mainly from a reaction between Al atom and F free radicals due to the breakage of one CF bond in CF3 groups, meanwhile, this also leads to an increase in CF2 groups. After annealing, the relative content of CF bonds at the interface decreases remarkably, and the relative concentrations of COAl and AlC complexes increase evidently. However, the relative percentage of Al fluoride decreases, indicating that Al fluoride has higher fluidity than the COAl and AlC complexes against annealing. Moreover, the relative percentages of the elements at the interface show that the annealing causes a little diffusion of Al into the AF film. Possible reaction mechanisms of Al with AF are also discussed.