Texture control and electromigration performance in Al-based and Cu-based layered interconnects

Texture control of Al and Cu by underlying refractory metal is discussed. AI texture can be controlled with underlayer metals like as Ti and TiN which have the same atomic arrangement within 3% misfits to Al. Cu texture can be also controlled by underlayer TiN in spite of a large difference in inter-atomic distance of Cu and TiN. Since the epitaxial growth of TiN on Cu is observed, it is suggested that epitaxial growth may occur at the early stage of Cu deposition on TiN. The electromigration performance was evaluated in double level interconnects with W-stud via. It is confirmed that highly < 111 > textured Al and Cu have high electromigration resistance. Both the diffusion of Cu in Al-Cu and Al drift are suppressed in < 111 > textured A-ahoy interconnects, and Cu drift is also suppressed in Cu damascene lines formed on < 111 > textured TiN. Grain boundary diffusion and the interfacial diffusion would be suppressed in highly textured metals with underlayer and it is speculated that interfacial diffusion is more important in Cu damascene lines.