The Reliability Improvement of Cu Interconnection by the Control of Crystallized α‐Ta/TaN_x  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 ofα- andβ-phases with amorphous-like structure. Increasing the N concentration of amorphous TaN underlayer successfully leads upper Ta film to form pureα-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 crystallizedα-Ta and TaN with high N concentration efficiently reduces the KRc and improves the EM resistance of Cu interconnection structure.

Enhancing Interconnect Reliability and Performance by Converting Tantalum to 2D Layered Tantalum Sulfide at Low Temperature

“…Liner Properties: Ta has been used as the "liner layer" to provide good Cu adhesion enabling survival after multiple damascene process steps [1][2][3] . However, it is also well known that the inelastic scattering at the Ta/Cu interface 25,26 can increase Cu resistivity, especially when Cu wire dimensions are extremely scaled.…”

“…Otherwise, Cu ions/atoms will drift/diffuse through the inter-metal dielectric (IMD) that separates two distinct interconnects, resulting in circuit shorting. Conventionally, tantalum nitride (TaN) has been adopted as the diffusion barrier owing to its superior capability of blocking Cu diffusion 1,2 . However, the adhesion of Cu to TaN is not ideal.…”

MoS2 for Enhanced Electrical Performance of Ultrathin Copper Films

“…However, when the thickness of Cu films decreases, reaching about the electron mean free path in copper, which is ∼40 nm at room temperature, the electrical resistivity increases significantly due to increased electron scattering at the film surfaces − and grain boundaries. , This size effect impacts the time delay in interconnects severely and represents a major challenge. , Although pristine atomically smooth Cu surfaces show partially specular scattering, , there are many factors such as oxidation in ambient environment , or the coating with a secondary material that can readily lead to diffusive surface scattering. Indeed, TaN/Ta bilayers have been used to encapsulate Cu interconnects in damascene structures as the diffusion barrier and liner layer to block Cu diffusion and provide good Cu adhesion . However, it is well known that inelastic scattering at the Ta/Cu interface can increase Cu resistivity due to wave function penetration.…”

Analysis of the composition of tantalum nitride in CMOS metallization trenches using parallel angle‐resolved XPS

“…Several publications describe a change from high resistive tetragonal β-Ta to low resistive body-centered cubic α-Ta with increasing nitrogen content in the TaN interlayer. [5][6][7] For future technology nodes, it is therefore important to develop analysis methods that can be used to quantify current and future materials in small structures. In this paper, we show that parallel angle-resolved X-ray photoelectron spectroscopy (pAR-XPS) as a non-…”

“…Furthermore, it influences the crystallinity of the Ta layer deposited on top of it. Several publications describe a change from high resistive tetragonal β ‐Ta to low resistive body‐centered cubic α ‐Ta with increasing nitrogen content in the TaN interlayer 5–7 …”