Water absorption characteristics of fluorinated silicon oxide films deposited by electron cyclotron resonance plasma enhanced chemical vapor deposition using SiH4, SiF4 and O-2

Abstract

Fluorinated silicon oxide (SiOF) film having low dielectric constant is hygroscopic, a characteristic which leads to the increase in the dielectric constant by the formation of highly polar -OH bonds in the him. We prepared SiOF films by electron cyclotron resonance plasma enhanced chemical vapor deposition with precursors of SiH4, SiF4 and O-2, and investigated the water absorption characteristics of the films and the effect of hydrogen on the film stability. In addition to the unstable silicon fluoride bonds, the Si-O bonds around the free volumes were found to be the significant factor in absorbing moisture by observing the variations of the shoulder peaks in the Si-O stretching vibration bands. The SiOF films deposited with additional SiH4 exhibit a higher resistance to water absorption than the films not treated with additional SiH4. The reactive hydrogen atoms dissociated from SiH4 yield the films having stable silicon fluoride bonds by scavenging fluorines. Hydration of Si-O-Si bonds around free volumes is also suppressed since the generation of free volume is reduced as the excess fluorines are removed by hydrogen. (C) 2000 Elsevier Science S.A. All rights reserved.