Grain growth, agglomeration and interfacial reaction of copper interconnects

• Published in: Thin solid films Vol. 420; pp. 398 - 402
• Main Authors: Yang, Ching-Yu, Jeng, J.S, Chen, J.S
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 02.12.2002
• Subjects: Agglomeration; Copper interconnect; Diffusion; TaN; TaN; Agglomeration; Diffusion; Copper interconnect
• ISSN: 0040-6090; 1879-2731
• DOI: 10.1016/S0040-6090(02)00810-6

In this work, Cu(50 nm)/Ta(10 nm, or no Ta)/TaN(50 nm)/Ta(10 nm) metallization layers were deposited onto Si or SiO 2/Si substrates by magnetron sputtering. Samples were subsequently annealed at various temperatures ranging from 400 to 800 °C in vacuum. The sheet resistance, crystalline microstructure, and surface morphology were investigated by four-point probe, θ–2θ X-ray diffraction, and scanning electron microscopy. Experimental results reveal that Cu films exhibit (111) preferred orientation on Ta but show both (111) and (200) textures on TaN. After annealing, copper films agglomerate on TaN but remain continuous on Ta. However, the Ta layer interposed between Cu and TaN dilutes the nitrogen concentration of the barrier so that reaction between Cu and Si occurs in the Cu/Ta/TaN/Ta/Si system after annealing at 800 °C and Cu 3Si forms. In contrast, the Cu/TaN/Ta/Si system shows agglomeration but no reaction up to 800 °C. Upon annealing, Cu/TaN/Ta and Cu/Ta/TaN/Ta stacks on a SiO 2/Si substrate exhibit similar crystal structural and morphological evolution to their parallel samples on a Si substrate, except that no Cu–Si reaction is observed for the Cu/Ta/TaN/Ta/SiO 2/Si system after annealing at 800 °C. Grain growth behavior of Cu films deposited on different multilayer structures is also discussed.