Pure Al thin film protective layer to prevent stress migration in Al wiring for thin-film transistors

The anti-stress migration property of layered structure aluminum (Al) thin films overcoated with pure Al was investigated for application of such films as interconnect materials in large arrays of high-resolution thin-film transistor liquid crystal displays (TFT-LCDs). It was found that no hillock or whisker generation occurred in a pure Al thin film with a sputter-deposited fine-grained polycrystalline pure Al layer after exposure to mechanical and 300°C thermal stresses. Atomic force microscopy (AFM) and cross-sectional transmission electron microscopy (TEM) analyses revealed the morphology of the layered structure thin film and the mechanism for the prevention of stress migration in the film.