ABSTRACT
Stress migration is caused by the mechanical stress experienced by the metal lines versus the electron currents that cause electromigration. The drivers of the stress migration mechanism described can be separated into environmental and material factors. The models that describe the impact of all material factors on stress migration are, as with electromigration, typically expressed in terms that cannot be directly measured or related to failure distributions, and are hence of limited practical use. The environmental factors, temperature and thermal cycling, are controlled by the component design and the application environment, and for a given silicon process technology, are the only variables that can be controlled. By deriving the electromigration failure distributions on test structures that are sensitive to stress effects, the stress migration impact on reliability is encompassed within the electromigration distributions. As with electromigration, stress migration can be managed by controlling the material factors or the environmental factors, or both.
