Direct quantitative analysis of phthalate esters as micro-contaminants in cleanroom air and wafer surfaces by auto-thermal desorption--gas chromatography--mass spectrometry.
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 microg 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 microg m(-3)) was nearly four times higher than that in the cleanroom environment (0.12 microg 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.
Kang
Yuhao
Y
Institute of Environmental Engineering, National Chiao-Tung University, 75 Po-Ai Street, Hsinchu, Taiwan.
Den
Walter
W
Bai
Hsunling
H
Ko
Fu-Hsiang
FH
D000393:Air Pollutants / Q000032:analysis*; D004952:Esters / Q000032:analysis*; D008401:Gas Chromatography-Mass Spectrometry / Q000379:methods*; D010795:Phthalic Acids / Q000737:chemistry*; D012680:Sensitivity and Specificity; D014874:Water Pollutants, Chemical / Q000032:analysis*
D000393:Air Pollutants; D004952:Esters; D010795:Phthalic Acids; D014874:Water Pollutants, Chemical