Pulsed plasma-enhanced chemical vapor deposition from CH2F2, C2H2F4, and CHClF2

Abstract

Pulsed plasma enhanced chemical vapor deposition films have been grown from 1,1,2,2-C2H2F4, CH2F2, and CHClF2. C 1s x-ray photoelectron spectroscopy indicates a prevalence of C¯–CF species in the films from C2H2F4 and CH2F2, whereas CF2 species dominate the films from CHClF2. The CFx species distributions for the films are largely controlled by the competition between CF2-producing and HF elimination reactions in the pulsed plasmas. Dominance by HF elimination produces films with high C¯–CF and CF concentrations (e.g., CH2F2), whereas dominance by CF2-producing reactions leads to films with higher CF2 concentrations (e.g., CHClF2). The % CF3 in the film is lowest for the precursor having the lowest F:H ratio, CH2F2. Little or no hydrogen was detected in the deposited films. Pulsed plasma films from all three precursors gave dielectric constants of 2.4, with loss tangents on the order of 10−2. Dielectric measurements of pulsed plasma films from hexafluoropropylene oxide gave a dielectric constant of 2.0±0.1 with a loss tangent of 0.009.