A case study of a change in migration behaviour of a transferred AlCu metallization

The work presented here shows a change in migration behaviour of a transferred AlCu metallization system. Different failure mechanisms in metallization are known. Migration effects like electro-, thermo- and stress migration are the main failure mechanisms in a metallization. This study shows the detection and exploration of a significant change in the migration mechanism of a wide lines of a top level interconnect of a standard metallization. The study demonstrates the differences of the transferred metallization system and the influence for the degradation behaviour and reliability. Based on a comparison of test results of accelerated metallization tests, failure analysis and the process simulation to get the values and divergences of mechanical stress for this interconnect it was possible to explain the difference in migration behaviour.