Low resistivity Al–RE (RE=La, Pr, and Nd) alloy thin films with high thermal stability for thin‐film‐transistor interconnects

The addition of light rare‐earth (RE) metal elements (La, Pr, and Nd) to Al thin films with about 2–7 at. % markedly decreases the grain size of the Al matrix more than 50% compared with those of pure Al. Such addition largely suppresses growth of thermal defects of hillocks and whiskers at high temperatures (350–450 °C). A large number of fine metallic compounds of Al11RE3 and/or Al3RE (RE=La, Pr, and Nd) were segregated in an Al matrix, mostly at grain boundaries, after annealing at 350 °C. The resistivities of the films after annealing at the above temperatures show low values of less than 6 μΩ cm compared with those of current thin‐film‐transistor liquid‐crystal displays gate electrode materials (more than about 15 μΩ cm), without the salient formation of hillocks or whiskers on the surfaces.