The deposition of SiOF film with low dielectric constant in a helicon plasma source

Abstract

SiOF films deposited by a helicon wave plasma chemical vapor deposition method has been characterized using Fourier transform infrared spectroscopy and ellipsometry. High density plasma of ≳1012 cm−3 can be obtained on a substrate at low pressure (<10 mTorr) with rf power ≳400 W with a helicon plasma source. A gas mixture of SiF4, O2, and Ar was used to deposit SiOF films on 5 in. Si(100) wafers not intentionally heated. Optical emission spectroscopy was used to study the relation between the relative densities of the radicals and the deposition mechanism. It was found that the addition of Ar gas to the SiF4/O2 mixture greatly increased the F concentration in the SiOF film. Discharge conditions such as gas composition, sheath potential, and the relative densities of the radicals affect the properties of the film. The dielectric constant of the SiOF film deposited using the helicon plasma source was 3.1, a value lower than that of the oxide film by other methods. © 1996 American Institute of Physics.