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

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.