Carbon content control of silicon oxycarbide film with methane containing plasma

Deposition of silicon oxycarbide (SiCOH) thin films by remote plasma atomic layer deposition was performed. In the experiment, the recipe was composed by adjusting the ratio of Ar and CH4 plasmas to control the carbon content in the SiCOH thin film. Octamethyl cyclotetrasiloxane was used as a precursor during the deposition process at 200, 300, and 400 °C. Ar plasma was used as an activant and CH4 plasma was used as a reactant. Plasma and deposition temperatures cause a significant impact on the physical and electrical properties of the film. When CH4 plasma was used during the deposition process, the film contained carbon and exhibited a low dielectric constant. In addition, when CH4 plasma is used as a reactant, Si–C bonds in the thin film form pores and lower ionic polarization to lower the dielectric constant. Fourier-transform infrared spectroscopy data indicate that the higher the ratio of CH4 plasma, the more the cage structure in the thin film. The cage structure contributes to lowering the dielectric constant of the thin film. The film deposited with Ar plasma has the dielectric constant of 3.2 and the film deposited with CH4 plasma has the dielectric constant of 2.6. In both plasma conditions, the dielectric constant was lower than the SiO2 film with the dielectric constant of 3.9. On the other hand, x-ray photoelectron spectroscopy analysis showed that SiO1–C3 and SiC4 bonds appeared in the film deposited with CH4 plasma, which did not appear in the film deposited with Ar plasma. These bonds affected the physical and electrical properties of the thin film.