Elemental coverage

Survey capability with ppm detection limits, not affected by surface charging effects complete elemental coverage survey microanalysis of contaminated areas, chemical failure analysis... 

The electron probe X-ray microanalyzer provides extraordinary power for measuring the elemental composition of solid matter with pm lateral spatial resolution. The spatial resolution, limited by the spread of the beam within the specimen, permits pg samples to be measured selectively, with elemental coverage from boron to the actinides. By incorporating the imaging capability of the SEM, the electron probe X-ray microanalyzer combines morphological and compositional information. 

Molecular ion mass interferences are not as prevalent for the simpler matrices, as is clear from the mass spectrum obtained for the Pechiney 11630 A1 standard sample by electron-gas SNMSd (Figure 4). For metals like high-purity Al, the use of the quadrupole mass spectrometer can be quite satisfiictory. The dopant elements are present in this standard at the level of several tens of ppm and are quite evident in the mass spectrum. While the detection limit on the order of one ppm is comparable to that obtained from optical techniques, the elemental coverage by SNMS is much more comprehensive. 

Because GDMS can provide ultratrace analysis with total elemental coverage, the technique fills a unique analytical niche, supplanting Spark-Source Mass Spectrometry (SSMS) by supplying the same analysis with an order-of-magnitude better accuracy and orders-of-magnitude improvement in detection limits. GDMS analy-... 

Qualification of 5N-7N pure metals, since GDMS provides fiill elemental coverage to ultratrace levels... 

Almost complete elemental coverage (>70 metallic/nonmetallic elements) more limited for simultaneous ICP-AES... 

No spectral or matrix interferences Complete, simultaneous elemental coverage Isotope analysis capability... 

Elemental coverage Large Large Large Large... 

Almost complete elemental coverage (isotopic fingerprinting)... 

Subsequent studies of Zn chalcogenide deposition, using the TLEC, involved coulometric stripping of deposits to characterize elemental coverages/cycle as a function of cycle conditions, specifically deposition potentials and solution compositions. Those experiments proved tedious, each cycle requiring about 12 steps (Fig. 12), but worthwhile. Figure 13 displays stripping curves for deposits of ZnTe, ZnSe, and ZnS, each formed from four EC ALE cycles. The same trend in Zn stability observed in the deposition scans (Fig. 11) is seen in Fig. 13 i.e., Zn is easier to strip from... 

Elemental mass spectrometry has undergone a major expansion in the past 15-20 years. Many new a, elopments in sample introduction systems, ionization sources, and mass analyzers have been realized. A vast array of hybrid combinations of these has resulted from specific analytical needs such as improved detection limits, precision, accuracy, elemental coverage, ease of use, throughput, and sample size. As can be seen from most of the other chapters in this volume, however, the mass analyzers used to date have primarily been magnetic sector and quadrupole mass spectrometers. Ion trapping devices, be they quadrupole ion (Paul) [1] traps or Fourier transform ion cyclotron resonance (Penning) traps, have been used quite sparingly and most work to date has concentrated on proof of principal experiments rather that actual applications. 

Atomic absorption spectrometry (AAS) is a technique of particular utility in the determination of trace elements in petroleum feedstuffs and products [1, 2], It combines the virtues of simplicity, sensitivity, wide elemental coverage and relatively low cost. 

Glow-discharge-atomic emission techniques (GD-AE) for solid analysis are instru-mentally simpler and more inexpensive than GD-MS [200], Major trade-offs, however, include poorer limits of detection and reduced elemental coverage. Although compact commercial GD-AE instruments were popular in Europe during the 1980s, their use in the USA remained modest until the 1990s. 

Neutron activation is a major contributer to modern elemental analysis. In a recent compilation of 11,000 published analyses of 75 environmental and biological Standard Reference Materials issued by the National Bureau of Standards (NBS), over half the analyses reported were performed by NAA (11). A considerable part of contemporary trace-element geochemistry is reliant on INAA, largely because of the method s high sensitivity, broad elemental coverage, and the ease of analysis of large numbers of small samples with a modest investment of time (12). 

The role of Spark Source Mass Spectrography (SSMS) as a high sensitivity trace element analytical method is discussed. The unparalleled combination of sensitivity and complete element coverage makes SSMS especially suitable for the analysis of liquid and solid materials involved in semiconductor processing. Sample requirements are discussed. The application of SSMS to semiconductor materials, process reagents, dopants, and metals, is Illustrated. Advantages and disadvantages of the technique as well as sensitivity and accuracy are discussed. 

The first SSMS Instrument was reported by Dempster ( 2) in 1946. Hannay of Bell Laboratories was responsible for the first applications to semiconductor materials (3,4) in the mid 50 s. The technique was so promising that commercial instrumentation became available in 1960. The attractive features of the technique were complete element coverage (all elements on the periodic table could be detected) and excellent sensitivity (to 1 part per billion atomic). The two major applications of SSMS at that time were semiconductor and nuclear reactor materials — both new technologies and both enctremely impurity sensitive. The biggest disadvantage of the technique, although not clearly realized at the time, was lack of quantitation. 

An X-ray diffraction (XRD) pattern of one of the early deposits is shown in Figure 4b. A small peak for In is evident in the unannealed deposits. However, elemental coverage data from electron probe microanalysis (EPMA) indicated that the deposit was rich in arsenic, not In. Evidently, the excess As is not crystalline, so that it does not show up in XRD, while the In is crystalline, and does show up. The extent of the In peaks in the XRD and the amount of excess As. from EPMA, are a function of the cycle used, and optimization of the cycle is ongoing. 

Obviously, SS-MS is not suited for elemental analysis of small sample amounts, but SS-MS offers a high dynamic range making it very powerful for multiple element analysis including those present at trace level in alloys, ores, and similar samples. SS-MS also offers wide element coverage, an extensive concentration range and analysis of solids without dissolution. 

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