A study on the plasma parameters and characteristics of carbon-doped silicon-oxide films by using MTMS/O-2 and He plasmas

Abstract

Carbon-doped silicon-oxide films with a low dielectric constant were deposited on p-type Si(100) substrates by using ultraviolet source-assisted plasma-enhanced chemical-vapor deposition with a methyltrimethoxysilane (MTMS:CH3Si(OCH3)(3)) precursor and oxygen gases. The deposition rate of the SiOC(-H) film with ultraviolet irradiation was 10 to 15 % higher than it was without ultraviolet irradiation. The lowest dielectric constant observed was 2.3 +/- 0.11 for a flow rate ratio of 100 % with ultraviolet irradiation. When the bulk plasma is illuminated with ultraviolet light, the carbon ions and other radicals are increased, and some of the Si-O-C open-linked bonds change into cage-linked bonds in which C atoms are incorporated in the Si-O-C bonding structure. The UV illumination of the bulk plasma with the precursor + O-2 + He mixture caused a dissociation of ions that are more reactive and an increase in the number of radicals, such as Si-*, -CH3*, CHn+, O-2(*), O-2(-), etc. The large increase in the number of radicals is due to inelastic scattering of electrons with excited precursors.