Structural development and electronic properties of hot filament low pressure chemical vapor deposited fluorocarbon polymer films

Abstract

Fluorocarbon polymer films in the poly(tetrafluoroethylene) (PTFE)-like structure are formed by a low-pressure chemical vapor deposition technique using the hot filament excitation of the gaseous C3F6O precursor. The filament and substrate temperatures were found to influence the structure of the deposited films. Infrared absorption and electron spectroscopy studies reveal that a PTFE-like (CF2)2n linear molecular chain structure evolves by an adsorption driven nucleation and CF2 polymerization process in the films deposited with low (450 °C) filament and high (70 °C) substrate temperatures. The films formed at a low substrate temperature (–165 °C) show a higher concentration of CF and C–CF bond defects and shorter (CF2)2n chains. A high (8–10 at.%) oxygen concentration in the films deposited at 600 °C filament temperature is attributed to the reaction of the (CF2)2n chains with COF and peroxyradicals arising from the dissociation of CF3C(O)F and affects the thermal stability of the films. Such reactions are not involved in the film growth at a low (450 °C) filament temperature. These films have much lower (<2 at.%) bonded oxygen content. The films having an ordered (CF2)2n chain structure formed at 70 °C are characterized by low leakage currents ∼7 × 10−11 A cm−2 at 0.1 MV cm−1 field. In comparison, high leakage currents ∼1 × 10−8 A cm−2 are observed for the films having a higher concentration of C–F and C–CF bonds.