Degradation mechanisms of Ta and Ta–Si diffusion barriers during thermal stressing

• Published in: Thin solid films Vol. 458; no. 1; pp. 237 - 245
• Main Authors: Hübner, R., Hecker, M., Mattern, N., Hoffmann, V., Wetzig, K., Wenger, Ch, Engelmann, H.-J., Wenzel, Ch, Zschech, E.
• Format: Journal Article
• Language: English
• Published: Lausanne Elsevier B.V 30.06.2004; Elsevier Science
• Subjects: Chemical interdiffusion; diffusion barriers; Cold working, work hardening; annealing, post-deformation annealing, quenching, tempering recovery, and crystallization; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Cu metallization; Diffusion barriers; Diffusion in solids; Exact sciences and technology; Glow discharge optical emission spectroscopy; Materials science; Physics; Transport properties of condensed matter (nonelectronic); Treatment of materials and its effects on microstructure and properties; X-Ray diffraction; Cu metallization; X-Ray diffraction; Glow discharge optical emission spectroscopy; Diffusion barriers; Amorphous material; Inorganic compounds; Metastable states; Polycrystals; XRD; Thermal stability; Thin films; Degradation; Reflection spectrum; Emission spectra; Thermal stresses; Glow discharges; Annealing; Transition element compounds; Binary compounds; X-ray spectra; Experimental study; Tantalum Silicides; Tantalum; Transmission electron microscopy; Transition elements
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/j.tsf.2003.11.313

The degradation mechanisms of 10 nm thick Ta and Ta 73Si 27 diffusion barriers deposited between Cu and SiO 2 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 T an=600 °C for t an=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 ( t an>1 h), microstructural changes occur within both barrier types. Whereas the amorphous Ta–Si layer starts to crystallize into Ta 5Si 3, 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 Ta 73Si 27 barrier shows an enhanced thermal stability compared to the pure Ta film.