Analysis of failure mechanisms in electrically stressed Au nanowires

An analysis of polycrystalline Au thin film interconnects of widths ranging from 850 to 25 nm, and lengths ranging from 1.0 mu m to 20 nm which have b een electrically stressed to the point of failure is presented. For the lon ger wires (widths 60-850 nm), the failure current density is typically foun d to be 10(12) A m(-2), essentially independent of the wire width, and then rapidly approaching zero for thinner wires. For the wider wires, failure o ccurs at the end towards the negative electrode; for narrow wires, failure tends to occur towards the center of the wire, as observed using scanning e lectron microscopy and atomic force microscopy. The mean time to failure fo r fixed current density is seen to decrease with decreasing wire width. The failure current density for a given wire width increases as the length dec reases. An analysis of the temperature profile based on calculations of a s imple model is presented which shows that this width-dependent behavior of narrow lines is not anticipated from the assumption of a homogeneous line s ubject to thermally-assisted electromigration alone. (C) 1999 American Inst itute of Physics. [S0021-8979(99)00815-4].