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

Abstract

Formation of fluorocarbon polymer films with a linear (CF 2–CF 2) 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–F 2 asymmetric and symmetric stretches, rock at 518 cm −1 and wag at 637 cm −1 indicate formation of linearly organized CF 2 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, CF 3, 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 O 2 in fluorocarbon films is chemically bonded as C–O and F 2C O with relative ratio depending on the film growth temperature. Both O 2 and OH are the result of additional reaction pathways involving the species generated from fragmentation of CF 3C(O)F. Molecular structure of fluorocarbon polymer films involving these species are discussed which are in conformity with the XPS and IR absorption data.