Direct quantitative analysis of phthalate esters as micro-contaminants in cleanroom air and wafer surfaces by auto-thermal desorption-gas chromatography-mass spectrometry

Yuhao Kang, Walter Den*, Hsun-Ling Bai, Fu-Hsiang Ko

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

38 Scopus citations

Abstract

This study established an analytical method for the trace analyses of two phthalate esters, including diethyl phthalate (DEP) and di-n-butyl phthalate (DBP), known as the major constituents of cleanroom micro-contamination detrimental to the reliability of semiconductor devices. Using thermal desorption coupled with a GC-MS system, standard tubes were prepared by delivering liquid standards pre-vaporized by a quasi-vaporizer into Tenax GR tubes for calibration. This method was capable of achieving detection limits of 0.05 μg m-3 for 0.1 m3 air samples and 0.03 ng cm -2 for 150-mm wafer surface density. Actual samples collected from a semiconductor cleanroom showed that the concentration of DBP in a polypropylene wafer box (0.45 μg m-3) was nearly four times higher than that in the cleanroom environment (0.12 μg m-3). The surface contamination of DBP was 0.67 ng cm-2 for a wafer stored in the wafer box for 24 h. Furthermore, among the three types of heat-resistant O-ring materials tested, Kalrez® was found to be particularly suitable for high-temperature processes in semiconductor cleanrooms due to their low emissions of organic vapors. This analytical procedure should serve as an effective monitoring method for the organic micro-contamination in cleanroom environments.

Original languageEnglish
Pages (from-to)137-145
Number of pages9
JournalJournal of Chromatography A
Volume1070
Issue number1-2
DOIs
StatePublished - 8 Apr 2005

Keywords

  • Airborne molecular contaminants
  • Cleanroom
  • GC-MS
  • Phthalate esters
  • Surface desorption
  • Wafer contamination

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