Thermal chemical vapor deposition of fluorocarbon polymer thin films in a hot filament reactor

Formation of fluorocarbon polymer films with a linear (CF₂-CF₂)_n molecular structure similar to polytetrafluoroethylene, PTFE is described by a hot filament chemical vapor deposition method. Growth process is analyzed by infrared absorption and C(1s), O(1s) and F(1s) core level electron spectroscopy of films deposited at −5 and +70 °C. Absorption doublet at 1220 and 1160 cm⁻¹ assigned to C-F₂ asymmetric and symmetric stretches, rock at 518 cm⁻¹ and wag at 637 cm⁻¹ indicate formation of linearly organized CF₂ groups with minimum hindrance to molecular vibration modes in CVD grown films. Absorption bands at 1660 and 3389 cm⁻¹ show O and OH groups in the films which diminish on annealing. The C(1s) components, CF₃, CF and C-CF bonding show branching, cross-liking and defects sites which increase as substrate temperature is increased. The O(1s) line analysis shows O₂ in fluorocarbon films is chemically bonded as C-O and F₂CO with relative ratio depending on the film growth temperature. Both O₂ and OH are the result of additional reaction pathways involving the species generated from fragmentation of CF₃C(O)F. Molecular structure of fluorocarbon polymer films involving these species are discussed which are in conformity with the XPS and IR absorption data.