Thermal decomposition mechanisms of tungsten nitride CVD precursors on Cu(1 1 1)

Yaw Wen Yang*, Jin Bao Wu, Jelin Wang, Yi Feng Lin, Hsin-Tien Chiu

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

16 Scopus citations

Abstract

Chemisorption and thermal decomposition of metallorganic chemical vapor deposition precursors, (t-BuN) 2W(NHBu-t) 2, bis(tert-butylimido)bis(tert-butylamido)tungsten (BTBTT) and (t-BuN) 2W(NEt 2) 2, bis(tert-butylimido) bis(diethylamido)tungsten (BTBDT), on Cu(1 1 1) have been investigated by means of thermal desorption spectroscopy (TDS) and synchrotron-based X-ray photoelectron spectroscopy (SR-XPS) under ultrahigh vacuum conditions. The precursors remain intact upon chemisorption on Cu(1 1 1) at 100 K, and at 300 K both precursors decompose readily via the characteristic hydride abstraction/elimination pathways to produce two stable surface intermediates for each precursor. For BTBTT, one species is W(=NBu-t) 3 and the other is proposed to be a bridged amido complex, [(t-BuN) 2W(μ-NBu-t)] 2. In comparison, a W-imine complex and a W-N-C metallacycle are two intermediates produced from BTBDT. Annealing toward 800 K further decomposes the intermediates and the detectable desorption species are completely derived from the ligands. The desorption products from BTBTT include t-butylamine generated from α-H abstraction, isobutylene from γ-H elimination, acetonitrile from β-methyl elimination, and molecular hydrogen. In addition to these desorption species, BTBDT produces hydrogen cyanide and imine (EtN = CHMe) via β-H elimination, not possible with BTBTT due to the absence of β-H in the ligands. Eventually, tungsten nitrides incorporating oxygen atoms and a small amount of graphitic carbons are formed and the stoichiometry is approximated as WN 1.5O 0.1. Oxygen incorporation, driven by a large oxide formation enthalpy, is sensitively dependent on the moisture exposure in UHV environment.

Original languageEnglish
Pages (from-to)743-754
Number of pages12
JournalSurface Science
Volume600
Issue number3
DOIs
StatePublished - 1 Feb 2006

Keywords

  • Chemical vapor deposition
  • Copper
  • Surface chemical reaction
  • Synchrotron radiation photoelectron spectroscopy
  • Thermal desorption spectroscopy
  • Tungsten nitrides

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