Plasma-enhanced chemical vapor deposition growth of fluorinated amorphous carbon thin films using C4F8 and Si2H6/He for low-dielectric-constant intermetallic-layer dielectrics

The Si2H6/He gas mixture was used for growing fluorinated amorphous carbon thin films (a-C:F) for low-dielectric-constant intermetallic-layer dielectrics by plasma-enhanced chemical vapor deposition (PECVD) with C4F8, which has a lower fluorine/carbon ratio than CF4. Si2H6 captures excessive fluorine ions and carries C4F8 to the substrate. It is also much safer than other carrier gases such as H,) or CH4. To characterize and improve film properties, we changed conditions such as deposition temperature and ambient pressure, and we measured the growth rate, Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and C-V characteristics. At a low temperature, the film properties were very poor, although the growth rate was very high. On the other hand, the growth rate was low at a high temperature. The growth rate increased with deposition pressure. The XPS result showed that the carbon peaks shifted to a higher energy level due to a carbon-fluorine combination, and the FT-IR results showed a bonding between C-F and C-F-2. The dielectric constants of the samples were in the range of 1.5-5 and the sample with a constant of 2.18 showed relatively good thermal characteristics.