Enhanced thermal stability of TA-based thin diffusion barriers by ion implantation (original) (raw)

Vacuum

Abstract

ABSTRACT The efficiency as a diffusion barrier of RF-magnetron sputtered Ta-layers modified by ion implantation has been studied using Auger electron spectroscopy and X-ray diffraction. Two systems were prepared: 50 nm Ta/500 nm Cu/50 nm Ta on SiO2 and 200 nm Cu/50 nm Ta on SiO2. The samples were annealed at temperatures from 600°C to 850°C in a vacuum of 2×10−4 Pa. The thermal stability was determined by interdiffusion of Cu into the diffusion barrier. The as-deposited Ta barriers are polycrystalline. After annealing at 600°C for 1 h interdifusion of Cu is observed for the non-implanted barrier. Ion implantation of nitrogen into the Ta layer leads to a nanocrystalline or amorphous-like structure with an important improvement of the barrier effect. The nitrogen-implanted 50 nm Ta barrier on Cu is stable up to 750°C for 1 h. Ta layers between the Cu and SiO2 exhibit even higher thermal stability. The Cu/Ta/SiO2 system shows beginning of copper diffusion and a strong interdiffusion between Ta and SiO2 after annealing at 800°C without implantation. The implanted Ta-barriers in this system are still effective after annealing at 850°C for 3 h.

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