POST-SPUTTERING IONIZATION SECONDARY ION MASS SPECTROMETRY : GLOW DISCHARGE MASS SPECTROMETRY (GDMS) AND SECONDARY NEUTRALS MASS SPECTROMETRY (SNMS)

Research output: Conference Papers (RGC: 31A, 31B, 32, 33)32_Refereed conference paper (no ISBN/ISSN)peer-review

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Original languageEnglish
Number of pages8
Publication statusPublished - 1985
Externally publishedYes

Abstract

Secondary Ion Mass Spectrometry (SIMS) is at present one of the most sensitive analytical methods and has found wide applications in various fields of microelectronics, geology, metallurgy and biology. However, quantitative analysis by SIMS has been hampered by extreme variations in sputtered ion yields of different elements and for the same element in different materials (so-called matrix effects). Recently, commercial instrumentation has been introduced to incorporate two post-sputtering ionization techniques which minimize these matrix effects by decoupling the sputtering and ionization processes. The first technique (Glow Discharge Mass Spectrometry) utilizes inert gas ions (e.g. argon) generated in a d.c. plasma to sputter atoms from the surface of a cathode composed of the material to be studied into the ambient plasma. The sputtered atoms, predominantly neutral, are then ionized in the plasma by Penning and electron impact ionization. The ion yields are relatively uniform, and GDMS thus provides quantitative survey analyses ranging from matrix to ultra trace concentrations (sub ppba). The second technique (Secondary Neutrals Mass Spectrometry) uses either low energy plasma ions or an independent focussed ion beam to sputter atoms into the overlying low pressure hf plasma. The sputtered neutral atoms are then ionized by electron impact in the plasma. Besides the basic principles, the general instrumental features and general applications will be presented.

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