THE MICROSTRUCTURAL STABILITY OF AL(CU) LINES DURING ELECTROMIGRATION

We have used transmission electron microscopy to examine in detail how microstructural changes take place in aluminum/copper lines adjacent to tungsten contacts during electromigration testing. Observations made on aluminum-4% copper lines show that significant changes in the grain structure surrounding precipitates occur during testing even under conditions where grain growth is not normally observed in the lines. Grain coarsening and precipitate growth produced by the applied current result in the formation of new diffusion blocking structures in the lines which are likely to significantly influence their time to failure. (C) 1995 American Institute of Physics.