Study of Ta(N,O) diffusion barrier stability: analytical and electrical characterization of low level Cu contamination in Si

Abstract

The diffusion barrier behaviour of 20 to 200 nm thin Ta(N,O) films in the Cu/Si contact system was evaluated by materials and transient ion drift analysis. Using high resolution transmission electron microscopy, grazing incidence X-ray diffractometry, Auger electron spectroscopy and secondary ion mass spectrometry depth profiling it was revealed that the as-deposited amorphous-like Ta(N,O) diffusion barriers tend to partially recrystallize after annealing at 1 h/500°C without any detectable diffusion and/or reaction of Cu and Si up to at least 1 h/600°C. By making use of the newly developed transient ion drift technique for trace element analysis down to 5 × 10 11 cm −3 of interstitially dissolved Cu in Si, an exponential decrease of the Cu concentration on the Ta(N,O) barrier thickness is observed.