Abstract
For decades, Ta/TaN has been the industry standard for a diffusion barrier against Cu in interconnect metallisation. The continuous miniaturisation of transistors and interconnects into the nanoscale are pushing conventional materials to their physical limits and creating the need to replace them. Binary metallic systems, such as Ru-W, have attracted considerable attention as possible replacements due to a combination of electrical and diffusion barrier properties and the capability of direct Cu electroplating. The process of Cu electrodeposition on Ru-W is of fundamental importance in order to create thin, continuous, and adherent films for advanced interconnect metallisation. This work investigates the effects of the current density and application method on the electro-crystallisation behaviour of Cu. The film structure, morphology, and chemical composition were assessed by digital microscopy, atomic force microscopy, scanning and transmission electron microscopies, energy-dispersive X-ray spectroscopy, and X-ray diffraction. The results show that it was possible to form a thin Cu film on Ru-W with interfacial continuity for current densities higher than 5 mA·cm−2; however, the substrate regions around large Cu particles remained uncovered. Pulse-reverse current application appears to be more beneficial than direct current as it decreased the average Cu particle size.
Highlights
Increasing miniaturisation, well described by the famous Moore’s law, has made supercomputing-multitasking devices able to be downscaled for decades
Ru is chemically inert and stable, contrasting with its counterparts, such as Co, which is prone to dissolution during conventional acidic electroplating, requiring electrolyte modification to be used in seedless diffusion barrier systems [11,12]
The nucleation and growth of EP-Cu on Ru-W thin films are conditioned by the chemical composition of the substrate, namely the Ru/W ratio [25]
Summary
Increasing miniaturisation, well described by the famous Moore’s law, has made supercomputing-multitasking devices able to be downscaled for decades. Advanced interconnects require liners that are effective diffusion barriers, display low resistivity, and allow direct (seedless) Cu electroplating. Ru is chemically inert and stable, contrasting with its counterparts, such as Co, which is prone to dissolution during conventional acidic electroplating, requiring electrolyte modification to be used in seedless diffusion barrier systems [11,12]. The development of submicron-thick electroplated (EP) Cu films directly on diffusion barrier layers is of particular interest for advanced interconnect metallisation. Understanding how Cu electro-crystallises on Ru-W is essential to evaluate its eligibility as a substitute of Ta/TaN Such knowledge is essential to develop strategies to tackle the challenges/issues emerged by electroplating Cu on a substrate that is more complex than the conventional Cu(seed)/Ta/TaN. This work focuses on the formation and growth of EP-Cu on equimolar Ru-W using a conventional acidic electroplating electrolyte
Sign-in/Register to view highlights & summary 
Published Version (
Free)
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
