Effects of fluorination of carbon film and annealing conditions on side leakage current and current breakdown time of SiO₂/graphene/Cu/Ti/SiO₂/Si specimens

Efforts are made to grow a few-layer graphene film over copper micro-interconnects to reduce the electrical resistance and improve the impediment of current breakdown. The annealing conditions for successful graphene growth and the effective method for the minimization of side leakage current between adjacent copper wires become the challenges for the targets. Copper micro-interconnects deposited on an Si wafer substrate with a SiO₂ as the top dielectric layer are prepared using lithography with an ultrathin carbon film between the copper wire and SiO₂ layer. The annealing conditions in the process of converting carbon into graphene are set with consideration of the preservation of copper wires and enhancement of the intensity of the Raman signal of graphene. Carbon films between adjacent copper microwires are converted into CF_x by fluorination to impede side leakage current from the interconnects. A sufficiently low chamber vacuum pressure and large hydrogen flow rate can increase graphene intensity and thus impede the side leakage current effectively. Specimens with few-layer graphene have a higher voltage and a longer time needed for current breakdown. In tests without current breakdown, the thermal diffusion intensity of copper ions into SiO₂ layer and the electrical resistance of the specimen with few-layer graphene are greatly reduced indeed.