Quantification issues of trace metals on silicon oxide and nitride films by VPD-ICP-MS and VPD-GF-AAS

Quantification issues of trace metals analysis on silicon oxide and nitride films by using VPD-ICP-MS and VPD-GF-AAS

Surface and Interface Analysis 2008, 40, 60-66
Ming-Peng Yeh, Casey Hsien, Cheng-Sung Huang, Ter-Chuan Lin

Abstract: Vapor phase decomposition (VPD) is a pretreatment technique for collecting trace metal contaminants on the surface of a Si wafer. Such trace metals can be identified and quantified by inductively coupled plasma mass spectrometry (ICP-MS) or graphite furnace atomic absorption spectroscopy (GF-AAS). However, the analytical results can be influenced by the Si-matrix in the VPD samples. This article discusses the approaches to eliminate the interference caused by Si-matrix. When the thickness of oxide film on wafer surface is less than 100 Å, the quantification results of ICP-MS analysis will not be affected by Si-matrix in the VPD samples. Except this, the Si-matrix must be removed before analysis. An improved heating pretreatment approach has been adopted successfully to eliminate the Si-matrix. For GF-AAS analysis, the Si-matrix will influence the sodium and aluminum analyses. Adding HNO3 to the graphite furnace tubing after sample injection could also eliminate the interference caused by the Si-matrix. The method detection limits (MDLs) of VPD-GF-AAS and VPD-ICP-MS range from 0.04 to 0.55 × 10¹⁰ atoms cm^-2 and 0.05 to 1.73 × 10⁹ atoms cm^-2, respectively.

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