Failure temperature of amorphous Cu-Ta alloys as diffusion barriers in Al-Si contacts

Abstract

Self-supporting films of amorphous Cu20Ta80 alloys have a crystallization temperature as high as 800 °C, yet they fail as diffusion barriers in aluminum-silicon contacts at much lower temperature because of compound formation. On Si(100) the a-Cu20Ta80 films react above the temperature at which TaSi2 forms (650 °C). In contact with aluminum, Al3Ta starts to form at 500 °C, which is also the failure temperature of a-Cu20T80 as diffusion barrier between Al and Si(100). The reaction characteristics of the barrier constituents with the surrounding elements as well as the crystallization temperature determine the thermal stability of amorphous alloy diffusion barriers.