Effect of decamethylcyclopentasiloxane and trifluoromethane electron cyclotron resonance plasmas on F–SiCOH low dielectric constant film deposition

Abstract

The characteristics of decamethylcyclopentasiloxane (DMCPS) and trifluoromethane (CHF3) electron cyclotron resonance plasmas for depositing F–SiCOH low dielectric constant films were investigated by quadrupole mass spectrometry and optical emission spectroscopy. The radicals in the plasma come from the dissociation of DMCPS and CHF3 molecules and the recombination of active radicals. The DMCPS dissociation produced the Si-related and CH-related radicals, including the SiOC2H5, SiOCH3, SiCH3, SiO, Si, O, CH3, CH2, CH, C, and H radicals, by breaking the Si–O fivefold ring and Si–O chain and by removing hydrocarbon groups from Si atoms. The CHF3 dissociation produced the F-related radicals, including the CHF2, CF3, and F radicals. The recombination of active radicals produced the HF, C2H2, C2H3, C2H4, C2H5, C2, H2, SiH2, SiF3, SiF2, and SiF radicals. The Si-related and CH-related radicals led to the deposition of SiCOH films; however, the F-related radicals led not only to the deposition of F–SiCOH films but also to the etching of SiCOH films by the reactions between F and Si atoms in the plasma and at the surface of as-deposited films simultaneously. The competition between film deposition and etching led to an n-type dependence of the deposition rate on CHF3/DMCPS flow rate ratio, the drastic composition change, and the structural evolution from SiCOH to Si-doping COF and further to COF films.