MICROSTRUCTURAL EFFECTS ON THE 1/F-ALPHA NOISE OF THIN ALUMINUM BASED FILMS

The 1/f(alpha) noise was measured on a variety of Al-based thin metal films with widely varying microstructure using an ac bridge technique. The magnitude of the current noise in response to a small, non-destructive ac signal was found to vary several orders of magnitude between 0.01 and 10 Hz and was correlated to the microstructural differences of the films. These differences have a strong effect on film lifetimes as measured in an accelerated electromigration test. Variation in microstructure was accomplished by different deposition temperatures and annealing parameters, and verified using TEM micrographs. Following fabrication, the current noise magnitude was measured and found to be sensitive to film width and grain size. The use of this technique to discriminate differences in film microstructure is discussed along with the correlations between excess noise and the quality of the thin film as a metallic interconnection.