Variable-energy Positron Study of Nanopore Structure in Hydrocarbon-Siliconoxide Hybrid PECVD Films

Nanopore formation upon heat treatment of hydrocarbon-siliconoxide hybrid films was investigated by means of the variable-energy positron annihilation gamma- ray and lifetime techniques. The films were prepared using plasma enhanced chemical vapor deposition (PECVD), and nanoscopic pores in the films were developed through the decomposition of a sacrificial hydrocarbonous porogen by annealing the films at temperatures up to 600 degrees C. As a result of the positron annihilation gamma-ray measurements, the line-shape S parameter increases with increasing annealing temperature from 150 degrees C to 400 degrees C, while it reduces with further increasing temperature. This suggests that more positronium annihilate with carbonous elements remaining on the wall of pores formed at temperatures up to 400 degrees C. The lifetime measurements revealed the nanopore sizes in the range from 0.2 nm(3) to 2.0 nm(3). With increasing the pore size the film refractive index reduced from 1.44 to 1.29. The variable-energy positron techniques were demonstrated to be useful to examine the nanoporosity evolution for porous PECVD films. (c) 2012 The Authors Published by Elsevier B.V. Selection and/or peer-review under responsibility of Organizing Committee.