Effect of annealing ambient on the self-formation mechanism of diffusion barrier layers used in Cu(Ti) interconnects

S. Tsukimoto, T. Kabe, K. Ito, M. Murakami

Research output: Contribution to journalArticlepeer-review

47 Citations (Scopus)

Abstract

Copper (titanium) [Cu(Ti)] films with low titanium (Ti) concentration were found to form thin Ti-rich barrier layers at the film/substrate interfaces after annealing, which is referred to as self-formation of the barrier layers. This Cu(Ti) alloy was one of the best candidates for interconnect materials used in next-generation ultra-large-scale integrated (ULSI) devices that require both very thin barrier layers and low-resistance interconnects. In the present paper, in order to investigate the influences of annealing ambient on resistivity and microstructure of the Cu alloys, the Cu(7.3at.%Ti) films were prepared on the SiO 2 substrates and annealed at 500°C in ultra-high vacuum (UHV) or argon (Ar) with a small amount of impurity oxygen. After annealing the film at 500°C in UHV, the resistivity was not reduced below 16 μΩ-cm. Intermetallic compounds of Cu 4Ti were observed to form in the films and believed to cause the high resistivity. However, after subsequently annealing in Ar, these compounds were found to decompose to form surface TiO x and interfacial barrier layers, and the resistivity was reduced to 3.0 μΩ-cm. The present experiment suggested that oxygen reactive to titanium during annealing played an important role for both self-formation of the interfacial barrier layers and reduction of the interconnect resistivity.

Original languageEnglish
Pages (from-to)258-265
Number of pages8
JournalJournal of Electronic Materials
Volume36
Issue number3
DOIs
Publication statusPublished - 2007 Mar
Externally publishedYes

Keywords

  • Annealing ambient
  • Barrier metal layer
  • Cu-Ti alloy
  • Impurity oxygen
  • Interconnect
  • Self-formation

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Electrical and Electronic Engineering
  • Materials Chemistry

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