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 SiF₄/(SiF₄+Ar) partial pressure and annealing temperature. The absorption bands were assigned: 1,015 cm⁻¹ (SiF₄ stretching), 965 cm⁻¹ (Si–F₃ stretching), 920 cm⁻¹ (Si–F₂ stretching), 870 cm⁻¹ ((Si–F₂)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 (SiF₄ bending), and 300 cm⁻¹ (Si LA mode). SiF₄ molecules incorporated into a-Si: F films are observed in samples prepared with high SiF₄ partial pressures, but in samples prepared lower SiF₄ partial pressures dangling bonds seem to be saturated by fluorine atoms. The transition from Si–F, Si–F₂, and Si–F₃ groups to SiF₄ 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.