Controlling Ta phase in Ta/TaN bilayer by surface pre-treatment on TaN

Jung Chih Tsao, Chuan-Pu Liu, Ying Lang Wang, Yu Sheng Wang, Ke Wei Chen

Research output: Contribution to journalArticlepeer-review

14 Citations (Scopus)

Abstract

Beyond 0.13 μm feature size, a bilayer of Ta/TaN is commonly used as a metal barrier and adhesive layer for copper multilevel interconnections. However, for the Ta films, cubic α-phase is preferred due to the lower resistivity, whereas high-resistive tetragonal β-phase should be avoided but easily formed by sputtering. Here, we demonstrate that the Ta overlayer phase can be effectively controlled by resputtering TaN surface using Ar prior to Ta growth. Upon surface treatment for enough time, α-phase forms instead of β-Ta. The intriguing phase change is attributed to the decrease of TaN lattice constant toward the surface, which renders a better lattice-matched template for α-Ta. From Auger depth profile, resputtering causes nitrogen deficiency in the surface layer of TaN to become TaN0.1, leading to about 1.9% lattice mismatch. The mechanism for the phase change of the Ta overlayer was further verified by examining phase evolution of Ta deposited on various materials with different structure and lattice constants including W, TaNx (x<1) and Ti.

Original languageEnglish
Pages (from-to)501-504
Number of pages4
JournalJournal of Physics and Chemistry of Solids
Volume69
Issue number2-3
DOIs
Publication statusPublished - 2008 Feb 1

All Science Journal Classification (ASJC) codes

  • Chemistry(all)
  • Materials Science(all)
  • Condensed Matter Physics

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