X-ray absorption spectroscopy on copper trace impurities on silicon wafers

Andy Singh*, Katharina Baur, Sean Brennan, Takayuki Homma, Nobuhiro Kubo, Piero Pianetta

*Corresponding author for this work

Research output: Contribution to journalConference articlepeer-review

9 Citations (Scopus)


Trace metal contamination during wet cleaning processes on silicon wafer surfaces is a detrimental effect that impairs device performance and yield. Determining the chemical state of deposited impurities helps in understanding how silicon surfaces interact with chemical species in cleaning solutions. However, since impurity concentrations of interest to the semiconductor industry are so low, conventional techniques such as x-ray photoelectron spectroscopy cannot be applied. Nonetheless, chemical information on trace levels of contaminants can be determined with x-ray absorption near edge spectroscopy (XANES) in a grazing incidence geometry. In this study, silicon samples were dipped in ultra pure water (UPW) and 2% hydrofluoric (HF) solutions with copper concentrations of 5 and 1000 ppb, respectively. These samples were then analyzed using XANES in fluorescence yield mode to determine the oxidation state of deposited copper contaminants. It was found that copper impurities on the silicon surface from HF solution were metal in character while copper impurities deposited from the spiked UPW solution were deposited as an oxide. These results show that XANES can provide information on the chemical state of trace impurities even at surface concentrations below a few thousandths of a monolayer.

Original languageEnglish
Pages (from-to)23-28
Number of pages6
JournalMaterials Research Society Symposium - Proceedings
Publication statusPublished - 2002
EventSilicon Materials - Processing, Characterization and Reliability - San Francisco, CA, United States
Duration: 2002 Apr 12002 Apr 5

ASJC Scopus subject areas

  • Materials Science(all)
  • Condensed Matter Physics
  • Mechanics of Materials
  • Mechanical Engineering


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