Structural characterization of poly-Si Films crystallized by Ni Metal Induced Lateral Crystallization

The growth of the poly-Si films was studied by Transmission Electron Microscopy (TEM) after Ni Metal Induced Lateral Crystallization (Ni-MILC) of amorphous Si films at 413 degrees C. Significant differences in the morphology and the mode of growth of the films were observed, in comparison to films grown at temperatures above 500 degrees C. It was shown that at 413 degrees C the Solid Phase Crystallization (SPC), which acts in parallel with the Ni-MILC process at temperatures above 500 degrees C is suppressed. The suppression of SPC results in substantial change in the mode of growth. The poly-Si film grown at 413 degrees C consists of whiskers, which can be classified into two categories. Those growing fast along the < 111> direction, which were already observed in conventional Ni-MILC above 500 degrees C and whiskers grown along random crystallographic orientations having significantly slower growth rates. Because of the large difference in growth rates of the whiskers, significant orientation filtering due to growth-velocity competition is observed. The uniform poly-Si films consist of a mixture of fast < 111> type whiskers and slow ones, grown in other orientations, resulting in a tweed-like structure.