The Reliability Improvement of Cu Interconnection by the Control of Crystallized α‐Ta/TaN_<i>x</i>  Diffusion Barrier

Abstract

Ta/TaN bilayers have been deposited by a commercial self‐ionized plasma (SIP) system. The microstructures of Ta/TaN bilayers have been systematically characterized by X‐ray diffraction patterns and cross‐sectional transmission electron microscopy. TaN films deposited by SIP system are amorphous. The crystalline behavior of Ta film can be controlled by the N concentration of underlying TaN film. On amorphous TaN film with low N concentration, overdeposited Ta film is the mixture of α ‐ and β ‐phases with amorphous‐like structure. Increasing the N concentration of amorphous TaN underlayer successfully leads upper Ta film to form pure α ‐phase. For the practical application, the electrical property and reliability of Cu interconnection structure have been investigated by utilizing various types of Ta/TaN diffusion barrier. The diffusion barrier fabricated by the combination of crystallized α ‐Ta and TaN with high N concentration efficiently reduces the KRc and improves the EM resistance of Cu interconnection structure.