Electrical and mechanical features of the platinum silicide-aluminum reaction

Abstract

The electrical and mechanical features of a thermally induced interaction between platinum silicide and aluminum have been investigated. It has been found that a diffusion-controlled reaction occurs between these two materials which results in conversion of platinum silicide to the intermetallic PtAl2. The activation energy for this process is found to be 0.77 eV. As platinum silicide Schottky diodes with aluminum contacts are sintered for increasing time periods, this reaction propagates to the platinum silicide-silicon interface and the effective barrier height of the metal-semiconductor junction is observed to drop sharply to a value below that of aluminum-silicon Schottky diodes. As longer sinter cycles are performed the effective barrier height rises to a value characteristic of aluminum-silicon contacts. This effect is shown to be a result of diffusion of aluminum through the reacted material and the formation of an essentially aluminum-silicon contact at the silicon substrate. The mechanical features of the platinum silicide-aluminum reaction observed on test devices are correlated with the electrical effects of this reaction noted on Schottky diodes.