SiOF film deposition using FSi(OC2H5)(3) gas in a helicon plasma source

Abstract

SiOF film deposited using FSi(OC2H5)(3) (known as FTES) and O-2 mixture in a helicon plasma source is characterized with various plasma conditions. High density O-2/FTES/Ar plasma above 10(12) cm(-3) is obtained at low pressure (<3 mTorr) with rf power above 900 W in the helicon plasma source. The plasma parameters such as electron density with the various rf power, the magnetic field strength, and the pressure are measured. A gas mixture of FTES and O-2 is used to deposit SiOF film on 5 in. Si(100) wafers without intentional heating or biasing the substrate. Optical emission spectroscopy (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 at the helicon mode, which-is launched above threshold plasma density. Thus, the SiOF film deposited in the helicon reactor contains C-F bonds which are not sound in the SiOF film made by thermal chemical vapor deposition, where the FTES and O-2 react chemically on the substrate. Fourier transform infrared and X-ray photoelectron spectroscopy spectra show that the film has Si-F, Si-O, and C-F bonds. The Si-F and C-F bonds may lower the dielectric constant greatly. As O-2/FTES ratio decreases, the fluorine concentration increases and the dielectric constant decreases.