Journal
JOURNAL OF CHROMATOGRAPHY A
Volume 1070, Issue 1-2, Pages 137-145Publisher
ELSEVIER
DOI: 10.1016/j.chroma.2005.02.055
Keywords
airborne molecular contaminants; phthalate esters; GC-MS; cleanroom; wafer contamination; surface desorption
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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 mu g m(-3) for 0.1 m(3) 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 mu g m(-3)) was nearly four times higher than that in the cleanroom environment (0.12 mu g 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((R)) 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. (c) 2005 Elsevier B.V. All rights reserved.
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