ATOMIC RESOLUTION STUDY OF THE STRUCTURE AND INTERFACE OF ALUMINUM FILMS DEPOSITED EPITAXIALLY ON SILICON BY IONIZED CLUSTER BEAM METHOD

Aluminum films with unusual properties have been deposited on silicon substrates at room temperature by ionized cluster beam (ICB). As demonstrated in previous studies, these films have high thermal stability, are resistant to electromigration and provide good step coverage. The structure of the films and the interface were investigated by atomic resolution electron microscopy. In the A1 (111)/Si(111) case, the interface is flat and no transition layer was observed. No interface damage due to energetic ion bombardment could be seen. By annealing at 400 °C, small angle grain boundaries vanished and the film became an almost perfect single crystal. In the case of Si(100) substrates, films have Al(110) bicrystal form with curved grain boundaries separating Al(110) structures rotated 90°. Again, no transition layer and no trace of ion-bombarded damage at the A1 (110)/Si (100) interface could be seen. By in situ annealing during transmission electron microscopy (TEM) observation, it was found that the movement of the bicrystal grain boundaries occurs at temperatures above 500 °C and a considerable number of bicrystal grains are absorbed into the neighboring bicrystal grain. Then the films become a large grain bicrystal. © 1990, American Vacuum Society. All rights reserved.