Electromigration studies of large- and fine-grain aluminum films showed that fine-grain films were characterized by a mixed orientation and a grain size of ≈2 μ, and that large-grain films had a highly preferred 98% 〈111〉 orientation and a grain size of ≈8 μ. Stripes fabricated from the large-grained films had a consistently longer life, higher activation energy, and lower standard deviation of the life distribution than stripes fabricated from fine-grained films. These results are interpreted in terms of the nature of flux divergences in the two films. Calculations give the magnitude of vacancy supersaturations at various structural divergences present in the films studied.

Experiments have been undertaken to determine the length and width dependence of electromigration-induced failure time in aluminum thin-film conductors. A statistical model is presented and compared to the experimental data. The significance of the experimental data and the statistical model are discussed in terms of randomly distributed structural defects which produce flux divergences during electromigration.

A statistical metallurgical model of the random structural defects which cause electromigration failure in aluminum thin-film conductors is presented. The model relates time-to-failure to the various divergences which may be present in the conductor. Structural divergences due to differences in grain size, grain-boundary mobility, and grain-boundary orientation with respect to the electric field vector E lim →, are considered. The statistical distributions of divergences due to these attributes are empirically determined. A computer is then used to simulate both the structure of a thin-film conductor and its time-to-failure. The simulation model is used to predict the dependence of conductor reliability on such microscopic design features as grain size distribution, conductor length, and conductor width. The curves produced by computer simulation are then compared with those derived from experimental data.

A study of the damage introduced into tungsten by fast neutrons using field ion microscopy, is described. This consisted of examining the type of damage as reflected in the vacancy content of the material and the removal of the vacancy content after various annealing treatments. Evidence is presented which shows that vacancies are removed from tungsten in stage IV. The observations also indicate the presencc of depleted zones in the irradiated tungsten. Das Strahlungsdamage durch schnclle h'cutronen in Wolfram wird mit dem Feld-Ionenmikroskop untersucht. Dabei wird gefunden, daD sich der Typ des Damage im Liickengehalt des Materials widerspiegelt und deS sich die Liicken durch verschiedene Temperungsbehandlungen beseitigen lassen. Es wird der Hinweis gegcben, dal) die Liicken aus Wolfram im Zushnd IV entfernt werden. Die Untersuchungen zeigen aul3erdem die Anwcsenheit von Verarmungsgebieten im bestrahlten Wolfram. _ _~ l ) This work was performed under the auspices of the United States Atomic Energy Commission.

No abstract