MECHANICAL STRENGTH AND MICROSTRUCTURE OF OXYGEN ION-IMPLANTED AL FILMS

The influence of finely dispersed, stable particles on the mechanical strength and microstructure of Al films on Si substrates has been studied. Aluminum oxide particles were produced in Al films by oxygen ion implantation, and the grain size was increased by a laser reflow treatment. Transmission electron microscopy (TEM) was employed to observe the oxide particles and the grain structure in the films after subsequent annealing, and the wafer curvature technique was used to study the deformation properties of the films as a function of temperature. Significant particle strengthening was obtained in the coarse-grained films in tension as well as in compression. In the as-deposited and ion-implanted films a very fine grain size of only 0.35 mu m is stabilized after annealing which causes considerable softening of the film in compression at higher temperature because of the enhancement of grain boundary and volume diffusion controlled relaxation mechanisms. However, in tension at low temperature these films show high stresses comparable to those of the laser reflowed and ion-implanted films. The results are discussed in the light of TEM observations.