INFLUENCE OF FORMATION AND DECOMPOSITION OF SOLID-SOLUTION ON RESISTIVITY AND HILLOCK SUPPRESSION IN SPUTTERED AL-TA THIN-FILMS

The effects of Ta addition on the resistivity and hillock suppression were studied in Al-Ta sputtering films in comparison with Al-Cu alloy films. Ta was dissolved in the Al matrix of the as-deposited films. The metastable AlTa solid solution was decomposed into Al3Ta during annealing at more than 573 K. As the Ta content increased, the resistivity of the as-deposited films was increased, and the hillock density after annealing was remarkably reduced due to the increase of hillock formation temperature. The resistivity reduced after annealing due to decomposition of the metastable solid solution. Resistivity and hillock suppression in the Al-Ta alloy films had stronger dependence on the content than the Al-Cu alloy films. It is probable that the dependence is attributed to the electric interaction between Ta and Al, and the suppression of the Al diffusion by the dissolved Ta.