Preparation of low leakage current fluorine-doped silicon-oxycarbide by PECVD Original Research Article

A new dielectric barrier film using fluorine-doped silicon-oxycarbide (SiCOF) for 65 nm multilevel interconnect in very large scale integration (VLSI) has been fabricated. The film is deposited by the addition of silane fluoride (SiF4) to tetramethylsilane (4MS) and in carbon dioxide (CO2) plasma enhanced chemical vapor deposition (PECVD) system. The refractive index and dielectric constant decreased with SiF4 flow rate. The fluorine content in the SiCOF film measured by X-ray photoelectron spectroscopy (XPS) increased with SiF4 flow rate. Si–F bonds were formed in the film and detected by Fourier-transform infrared spectroscopy (FTIR) and XPS. The peak positions of Si–O and Si–C stretching mode shifted to a higher wave with an increase in fluorine concentration. The SiCOF film exhibited an F content of 10.7 at% and a relative dielectric constant of 4.03 at a SiF4 flow rate of 1200 sccm. The leakage current density of SiCOF is 10 times lower than that of fluorine-free SiCO film. Therefore, SiCOF is a good candidate for a dielectric barrier for processes under 65 nm with a back end of line requirement.