The mechanism of an increase in electrical resistance in Al thin film induced by current stressing

A 10 mm × 2 mm × 500 nm Al thin film was stressed with electric current at 1.5–3.0 × 10⁵ A cm^− 2 for 1 h under an ambient atmosphere. Ex situ variations in the sheet resistance induced by current stressing were measured with a four-point probe. The critical current density for the resistance change was observed between 1.5 × 10⁵ and 2.0 × 10⁵ A cm^− 2. The electrical resistance reached a maximum increment of 5.47% at 2.5 × 10⁵ A cm^− 2. The lattice structure of the Al thin film was investigated with a high resolution transmission electron microscope to determine the fundamental effects of electric current stressing on the electrical property of the metal film. The high resolution lattice images incorporating a selected area fast Fourier transform indicated a large degree of lattice distortion and high dislocation density, up to 8.60 × 10¹⁶ m^− 2, in the metal film after current stressing at 3.0 × 10⁵ A cm^− 2. The dislocations are believed to have been generated by the impingement of electron wind. In situ synchrotron X-ray diffraction further evidenced a high degree of lattice strain, as great as 1.1% at 3.0 × 10⁵ A cm^− 2, as estimated from the low angle shifts in the diffraction peaks. The generation of dislocations and the lattice strain induced by current stressing were orientation-dependent, as determined by the d-spacing of the lattice orientation. The formation of a high dislocation density and the subsequent buildup of lattice strain caused to an increase in electrical resistance of the Al thin film.