Highly stable carbon-doped Cu films on barrierless Si

Electrical resistivities and thermal stabilities of carbon-doped Cu films on silicon have been investigated. The films were prepared by magnetron sputtering using a Cu–C alloy target. After annealing at 400 °C for 1 h, the resistivity maintains a low level at 2.7 μΩ-cm and no Cu–Si reaction is detected in the film by X-ray diffraction (XRD) and transmission electron microscopy (TEM) observations. According to the secondary ion mass spectroscopy (SIMS) results, carbon is enriched near the interfacial region of Cu(C)/Si, and is considered responsible for the growth of an amorphous Cu(C)/Si interlayer that inhibits the Cu–Si inter-diffusion. Fine Cu grains, less than 100 nm, were present in the Cu(C) films after long-term and high-temperature annealings. The effect of C shows a combination of forming a self-passivated interface barrier layer and maintaining a fine-grained structure of Cu. A low current leakage measured on this Cu(C) film also provides further evidence for the carbon-induced diffusion barrier interlayer performance.