Influence of Ta/Si atomic ratio on the interdiffusion between Ta–Si–N and Cu at elevated temperature

Abstract

Ta–Si–N thin films with comparable N content but different Ta/Si ratios (Ta57Si5N38, Ta53Si11N36, and Ta29Si32N39) were prepared by cosputtering from Ta and Si targets, in an Ar+N2 atmosphere. All as-deposited Ta–Si–N films exhibit the amorphouslike (nanocrystalline) structure. The Ta–Si–N films were then applied as diffusion barriers in a Cu–SiO2 metallization system. After annealing at 800 °C for 30 min, the Ta57Si5N38 barrier crystallizes into Ta2N phase but the other two systems exhibit minuscule diffraction peaks. However, the Cu/Ta53Si11N36 couple shows almost no interdiffusion while the interdiffusion is apparent for Cu/Ta57Si5N38 and Cu/Ta29Si32N39 systems. Cu/Ta–Si–N interdiffusion is evidently not related to the crystallization of Ta–Si–N. The Cu/Ta–Si–N interdiffusion behavior is discussed on the basis of the Ta atom mobility and the atomic density of Ta–Si–N of various Ta/Si ratios.