Electromigration Resistance Measurements of Multilayered Interconnections by Short Test Lines

Abstract

The electromigration performance of Al/W bilayered interconnections was investigated. The cumulative failure plots deviate from the usual two-parameter log-normal distribution for some test conditions, and incubation time is needed as a third parameter to fit the plots to an ideal curve. The incubation time can be found more easily as the gradient of the cumulative failure density plot becomes smaller. Shortening the sample line length is effective in decreasing the gradient of the plot. Decreasing the damaged point density in interconnections has the same effect as shortening the test line length. In interconnections having a low damaged point density, the reliability will be limited by weak points within a few of the test lines, even though the average lifetime is improved. The incubation time is necessary as another parameter to evaluate the reliability of such interconnections accurately.