Abstract
The degradation mechanisms of 10 nm thick Ta and Ta73Si27 diffusion barriers deposited between Cu and SiO2 are compared by means of X-ray reflectometry, glancing angle X-ray diffraction, glow discharge optical emission spectroscopy depth profiling and transmission electron microscopy analysis. Annealing the samples at Tan=600 °C for tan=1 h results in a diffusion of Ta atoms through the Cu capping layer to the sample surface, particularly in the case of the pure Ta barrier. During longer heat treatment (tan>1 h), microstructural changes occur within both barrier types. Whereas the amorphous Ta–Si layer starts to crystallize into Ta5Si3, the initially grown metastable β-Ta of the pure Ta film transforms into the equilibrium α-Ta phase. Analyzing the diffusion rate of Cu atoms into the substrate, the Ta73Si27 barrier shows an enhanced thermal stability compared to the pure Ta film.
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