Carbon content control of silicon oxycarbide film with methane containing plasma

Abstract

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.

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“…For the passivating tunnel junction (TJ), PH3 was added to the precursor gases to obtain n + SiCx. Subsequently, a thin oxide layer was formed on the n + layer using CH4 plasma treatment in the same PECVD system, [17,18,19] followed by deposition of a p + SiC layer using trimethyl boron (TMB). To crystallize the layers and to activate their dopants, they were subjected to a thermal treatment.…”

“…(7) CH4 plasma treatment: In the case of co-annealing samples, this CH4 plasma treatment showed remarkable effects on iVOC and ρC, as samples with treatment have much higher iVOC than samples without treatment. The effect of CH4 plasma treatment on Si wafers has been studied by Song et al [17] and Kim et al, [18] showing that an oxide layer is formed by CH4 plasma treatment on a Si surface, with the composition of SiOC. Based on this, it was assumed that CH4 plasma treatment between depositions of n + and p + SiC layers would form an in-situ grown SiOC layer at the interface.…”