The Annealing Behavior of Si–F Bonding Structure of Amorphous Si–F Films

Abstract

The infrared transmittance and reflectance spectra of amorphous fluorinated silicon films (a-Si: F) have been measured as a function of a ratio of SiF 4 /(SiF 4 +Ar) partial pressure and annealing temperature. The absorption bands were assigned: 1,015 cm -1 (SiF 4 stretching), 965 cm -1 (Si–F 3 stretching), 920 cm -1 (Si–F 2 stretching), 870 cm -1 ((Si–F 2 ) 2 stretching), 825 cm -1 (Si–F stretching), 600 cm -1 (Si–C stretching or Si 2LA mode), 515 cm -1 (Si TO mode), 380 cm -1 (SiF 4 bending), and 300 cm -1 (Si LA mode). SiF 4 molecules incorporated into a-Si: F films are observed in samples prepared with high SiF 4 partial pressures, but in samples prepared lower SiF 4 partial pressures dangling bonds seem to be saturated by fluorine atoms. The transition from Si–F, Si–F 2 , and Si–F 3 groups to SiF 4 molecules occurs above annealing temperatures (600°C). The total fluorine content is constant until crystallization, and a-Si: F films are found to be more stable than a-Si: H films.