Variable-energy positron lifetime study of silicon-oxide films plasma deposited from hexamethyldisiloxane and oxygen mixtures

Abstract

Mixtures of hexamethyldisiloxane [HMDSiO, (CH3)3SiOSi(CH3)3] and oxygen are plasma polymerized at different oxygen pressures (P = 1.3–11.4 Pa) and a fixed monomer pressure (Pm = 2.6 Pa). The discharge power is kept at 100 W throughout the work. Nanometer-size holes in the deposited films are characterized by variable-energy positron annihilation lifetime spectroscopy (PALS). Additional information on the film composition and structure is obtained by X-ray photoelectron spectroscopy and IR absorption spectroscopy. The ortho-positronium lifetime τ3 and intensity I3 increase with the P up to 6.2 Pa and then decrease with the P. PALS measurements after annealing at 400°C show that films prepared at high oxygen pressure have a less stable structure than a film deposited at a lower oxygen pressure. These results are discussed in comparison with plasma deposition of pure HMDSiO, as are the possible effects of oxygen radicals on the film structure. © 2000 John Wiley & Sons, Inc. J Appl Polym Sci 79: 974–980, 2001