Low dielectric constant CF/SiOF composite film deposition in a helicon plasma reactor

Low dielectric constant CF/SiOF composite films are deposited using tri-eth oxy-fluorosilane (FTES) and O-2 mixture in a helicon plasma reactor without intentional healing or biasing the substrate. Optical emission spectroscop y (OES) is used to study the relation between the relative densities of the radicals and the film properties. The OES data imply that the FTES and O-2 gases are greatly dissociated above the RF power of 900 W. Consequently, t he deposition process of helicon plasma CVD where the source gases dissocia ted highly form CF/SiOF composite film is different from thermal CVD where the gases react chemically on the substrate and make the SiOF film. FTIR an d XPS spectra show that the film has Si-F, Si-O, and C-F bonds. The Si-F an d C-F bonds may lower the dielectric constant greatly. As the O-2/FTES rati o decreases, the fluorine concentration increases and the dielectric consta nt decreases. (C) 1999 Elsevier Science S.A. All rights reserved.