Stress in Al, AlSiCu, and AlVPd films on oxidized Si substrates

Electromigration and stress migration in Al metallization are major reliability issues for advanced ICʹs. Recently it has been shown that, compared to AlSiCu alloy films, alloys containing Si, V and Pd combine excellent plasma etchability with good corrosion resistance, while a high resistance against electromigration is maintained [1]. It is commonly accepted that the resistance against stress migration, i.e. the creep strength, of Al can be improved by addition of alloying elements in combination with appropriate heat treatments (e.g. precipitation hardening). We present data on the influence of alloying elements on the behaviour of stress as a function of temperature for a number of Al-alloy films. Pure mono- and polycrystalline Al, AlSi(1.0 at%)Cu(1.0 at%) and AlV(0.1 at%)Pd(0.1 at%) films were studied. The sputter conditions, the film thickness and the annealing conditions were similar to reliability tests described in the literature. These films are subjected to thermal cycles from 50 to 425°C in a vacuum furnace, while the stress behaviour was measured by means of wafer curvature measurements.