Low-dielectric-constant-film deposition with various gases in a helicon plasma reactor

Low-dielectric-constant SiOF films are deposited using O-2/SiF4 and O-2/FSi (OC2H5)(3) mixtures in a helicon plasma reactor, and good quality films can be obtained without intentional heating or biasing of the substrate. Optic al emission spectroscopy (OES) is used to study the relation between the re lative densities of the radicals and the film properties. The OES data impl y that the source gases are highly dissociated above the RF power of 900 W where the helicon mode is generated. Consequently, the mechanism of helicon plasma chemical vapor deposition (CVD) is different from that of thermal C VD. In the case of thermal CVD, the source gases react chemically on the hi gh-temperature substrate and form films. However, in the case of helicon wa ve plasma CVD, the source gases are highly dissociated in the high-density plasma and many radicals are produced, that react on the substrate. SiOF fi lms are made in the case of O-2/SiF4 but CF/SiOF composite films are made i n the case of O-2/FSi(OC2H5)(3), where FSi(OC2H5)(3) is highly dissociated in plasma and C participates in the film formation. Films with a low dielec tric constant of below 3.0 can be made.