Effects of Addition of Heavy Rare-Earth Elements on the Structures and Resistivities of Al Thin Films for TFT - LCD Interconnects

The addition of Ho or Er to Al thin films markedly suppresses the grain growth at high temperature (350 °C – 450 °C). However, different from the effect of adding elements of Y, La, Pr, Nd, Sm, Gd, and Dy, thermal defects of hillocks or whiskers start to appear on the film surface after annealing at 300 °C ( though depending on the content of added elements). It has been revealed that small amounts of metallic compounds of Al3RE (RE = Ho and Er) have been segregated in a supersaturated solid solution of the Al phase after annealing at 300 °C, and that a large amount of added impurities still remained in the Al matrix. The resistivity of Al1−xREx alloy thin films (RE = Ho or Er, x = 2 – 7 atomic %) was 5 – 7 μΩcm after annealing at 450 °C.