A Formation and Characteristics of the Fluorinated Amorphous Carbon Films with Low Dielectric Constant by HDPCVD

概要

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Fluorinated amorphous carbon(a-C:F) thin films were deposited on a p-type Si(100) substrate using carbon tetrafluoride(CF_4) and methane(CH_4) mixture gases by an High density plasma chemical vapor deposition(HDPCVD). High density CF_4/CH_4 plasma of about 10^<12> cm^<-3> is obtained at low pressure (200mTorr) with rf power above 700 W in the ICP source where the CF_4/CH_4 gases are greatly dissociated. Fourier transform infrared(FTIR) and X-ray photoelectron spectroscopy(XPS) spectra show that the film has C-F, C-F_2, C-F_3, C-CF_X and C-C bond. The C-F bond in the film may lower the dielectric constant greatly and the C-C crosslinked structure maintained the film's thermal stability. It is found that the C-F bonding configuration changes from a C-F bond to C-CF_X and C-F_3 bonds as a function of CF_4/CH_4 flow rate ratio. Therefore, the reduction mechanism of the dielectric constant can be obtained by the variation of the C-F_X bonding configuration as well as the incorporation of fluorine. The relative dielectric constant, leakage current density, and dielectric breakdown field strength of the film are about 2.4, 7×10^<-12> A/cm^2, and 12 MV/cm, respectively.
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2001-06-28