Interface stability and microstructure of an ultrathin α-Ta/graded Ta(N)/TaN multilayer diffusion barrier

• Published in: Microelectronic engineering 2012-10, Vol.98, p.80-84
• Main Authors: Liu, C.H., Liu, W., Wang, Y.H., Wang, Y., An, Z., Song, Z.X., Xu, K.W.
• Format: Article
• Language: English
• Subjects: Annealing; Applied sciences; Cold working, work hardening; annealing, quenching, tempering, recovery, and recrystallization; textures; Condensed matter: structure, mechanical and thermal properties; Cross-disciplinary physics: materials science; rheology; Deposition by sputtering; Diffusion barrier; Exact sciences and technology; Heat treatment; Interface stability; Interface structure and roughness; Materials science; Metals. Metallurgy; Methods of deposition of films and coatings; film growth and epitaxy; Phase structure; Physics; Production techniques; Solid surfaces and solid-solid interfaces; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Treatment of materials and its effects on microstructure and properties; XTEM
• ISSN: 0167-9317; 1873-5568
• DOI: 10.1016/j.mee.2012.05.054

An ultrathin α-Ta (5nm)/graded Ta(N) (1.5nm)/TaN (2.5nm) multilayer film covered by Cu film was deposited on the Si substrate using reactive magnetron sputtering in N2/Ar ambient. The film stacks of Cu/α-Ta/graded Ta(N)/TaN/Si were then annealed in a vacuum chamber at 400–700°C for 1h. X-ray diffraction (XRD), scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM), and energy-dispersive spectrometer (EDS) line scans were employed to investigate the microstructure evolution and the diffusion behavior of the film stacks. The results show that the α-Ta/graded Ta(N)/TaN multilayer film as a diffusion barrier had sufficient interface stability, which was attributed to a relative stable amorphous layer forming at the interface of Cu and α-Ta layer, to prevent Cu atom diffusion at elevated temperatures up to 700°C. The relationship between the interface stability and the microstructure of the multilayer barrier were also constructed. [Display omitted] ► An ultrathin α-Ta/graded Ta(N)/TaN multilayer film was prepared. ► The reliability of Ta/TaN film is sensitive to variation of Ta phase structure. ► An amorphous interlayer can improve the properties of the diffusion barrier. ► The α-Ta/graded Ta(N)/TaN multilayer could block Cu diffusion at 700°C. An ultrathin α-Ta (5nm)/graded Ta(N) (1.5nm)/TaN (2.5nm) multilayer film coated with Cu film was deposited on the Si substrate using reactive magnetron sputtering in N2/Ar ambient. The film stacks of Cu/α-Ta/graded Ta(N)/TaN/Si were then annealed in a vacuum chamber at 400–700°C for 1h. X-ray diffraction (XRD), scanning electron microscopy (SEM), cross-sectional transmission electron microscopy (XTEM), and energy-dispersive spectrometer (EDS) line scans were employed to investigate the microstructure evolution and the diffusion behavior of the film stacks, respectively. The results show that the α-Ta/graded Ta(N)/TaN multilayer film as a diffusion barrier had sufficient interface stability, which could be attributed to a relative stable amorphous layer forming at the interface of Cu and α-Ta layer, to prevent Cu atom diffusion at elevated temperatures up to 700°C. The relationship between the interface stability and the microstructure of the multilayer barrier were also investigated.