Controlling fluorine concentration of fluorinated amorphous carbon thin films for low dielectric constant interlayer dielectrics

Control of the fluorine to carbon (F/C) ratio of fluorinated amorphous carbon (a-C:F) thin films by changing the deposition pressure is investigated. Decreasing the deposition pressure increases the dissociation of the source fluorocarbon material in the plasma, causing a decrease in the F/C ratio of the deposited film. There is a tradeoff relationship between the dielectric constant and the thermal stability. Both the thermal stability and the dielectric constant of the a-C:F films are increased as the F/C ratio is decreased. Thus, the tradeoff relationship between them can be optimized by the pressure during deposition.