Electrochemical Atomic Layer Deposition Of Metals For Applications In Semiconductor Interconnect Metallization

Author : Kailash Venkatraman
Publisher :
ISBN 13 :
Total Pages : 165 pages
Book Rating : 4.:/5 (114 download)

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Download or read book Electrochemical Atomic Layer Deposition of Metals for Applications in Semiconductor Interconnect Metallization written by Kailash Venkatraman and published by . This book was released on 2019 with total page 165 pages. Available in PDF, EPUB and Kindle. Book excerpt: High-performance microprocessors and memory devices require miniaturized copper (Cu) interconnects that carry electrical signals to circuit elements such as transistors. Conventionally, these nanoscale Cu interconnects are fabricated using electrodeposition; however, with the continued scaling of the interconnects below 10 nm, electrodeposition does not allow the requisite atomic-scale control over the interconnect fabrication process. As a result, future interconnect fabrication will require novel materials fabrication techniques. Vapor-phase atomic layer deposition (ALD) is a promising alternative to replace the conventional electrodeposition approach; however, a major drawback of the vapor-phase Cu ALD process is that it uses metalorganic precursors which are highly unstable, undergo decomposition and thus introduce contaminants in the metal deposit. To address such critical issues, we pursue here the development of an electrochemical atomic layer deposition (e-ALD) process which utilizes benign liquid-phase precursors in combination with electrode potential manipulation for the deposition of atomic-scale metal films. In the present work, a novel electrochemical atomic layer deposition process for copper (Cu) and cobalt (Co) is developed. The process is mediated by zinc underpotential deposition (Znupd) which serves as a sacrificial adlayer. Zn underpotential deposition is studied using cyclic voltammetry and quartz crystal microbalance. Chronoamperometry studies on a rotating disk electrode provide insights into the diffusion-reaction properties of the Znupd process. A general strategy for e-ALD is developed which involves deposition of a sacrificial monolayer of Zn via underpotential deposition followed by its spontaneous redox replacement (SLRR) by the desired noble metal (Cu or Co). UPD+SLRR cycles are repeated to build multi-layered metal deposits with controlled thickness in the sub-nm range and minimal surface roughness amplification. Layer-by-layer growth mode of Cu e-ALD is experimentally confirmed using quartz crystal microgravimetry and anodic stripping coulometry. Through considerations of the unsteady-state diffusional transport of species and the time-dependent surface redox reactions, a semi-analytical e-ALD process model is developed. The developed model provides quantitative information about the e-ALD growth rate and the deposit surface roughness as a function of various e-ALD process parameters, i.e., electrolyte composition and deposition time. Model predictions are compared to experimental measurements of the growth rate and deposit roughness. Furthermore, electroless Cu e-ALD process is developed in which the sacrificial Znupd step can be facilitated without applying an external potential to the substrate. This allows e-ALD to be used when the substrate is highly-resistive or contains electrically-isolated micro-patterned features.