加熱気化/ICP-MSにおけるパラジウムモディファイヤーの使用による検量線の直線性改善とシリコンウェハ表面超微量金属の定量

概要

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An electrothermal vaporization (ETV)/inductively coupled plasma mass spectrometry (ICP-MS) technique has been developed to determine the ultratrace metallic impurities of 10 elements (Na, Mg, Al, Cr, Mn, Fe, Ni, Cu, Zn, and Pb) in the natural oxide layer on a Si wafer. SiO_2 reacts to form SiF_6^<2-> with hydrofluoric acid in vapor-phase decomposition. The pyrolysis temperature (150℃) for eliminating SiF_6^<2-> was added to the ETV operating conditions, because the existence of ^<28>Si, ^<28>Si_2, and ^<28>SiO_2 due to SiF_6^<2-> influences the ion intensities of ^<27>Al, ^<56>Fe, and ^<60>Ni, respectively. Furthermore, adding 25ng of a palladium modifier improved the linearity of each calibration curve. As a result, it was possible to determine the 10 elements in concentration ranges of 20 (40)-10000pg ml^<-1>. The recovery percentages obtained by adding the mixed standard solution to the sample solution were 95-105%, showing that the ETV/ICP-MS measurements are accurate. The detection limit (3σ) was approximately 10^6 (Pb)-10^8 (Na) atoms cm^<-2> for a Si wafer with a diameter of 130mm. This method can be applied to the above wafer to determine the 10 metallic elements (10^9-10^11 atoms cm^<-2>).
2006-02-01