Application of fluorinated amorphous carbon thin films for low dielectric constant interlayer dielectrics

Fluorinated amorphous carbon thin films (a-C:F) for use as low-dielectric-constant interlayer dielectrics are deposited by helicon-wave plasma-enhanced chemical vapor deposition using fluorocarbon compounds as a source material. The a-C:F films can be grown from C₄F₈ at a high deposition rate (above 400 nm/min) and they are thermally stable up to 350 °C. The addition of bias power to the substrate makes it possible to completely fill gaps in the wiring (space 0.35 μm, height 0.65 μm) with the a-C:F film. To protect the a-C:F film during further processing, a SiO₂ film is deposited to add mechanical strength and resistance to the oxygen plasma used to remove resist materials. The adhesion between the a-C:F and SiO₂ films is dramatically improved by inserting an adhesion promoter consisting of a-C:H and Si-rich SiO₂. By using the a-C:F and SiO₂ dielectrics and chemical mechanical polishing (CMP) process, globally planarized 3-level metallization is achieved. The a-C:F dielectric can reduce inter-line capacitance close to a half value as compared with the conventional SiO₂ dielectrics.