Semiconductor applications high purity materials

In principle, the applications of ICP-MS resemble those listed for OES. This technique however is required for samples containing sub-part per billion concentrations of elements. Quantitative information of nonmetals such as P, S, I, B, Br can be obtained. Since atomic mass spectra are much simpler and easier to interpret compared to optical emission spectra, ICP-MS affords superior resolution in the determination of rare earth elements. It is widely used for the control of high-purity materials in semiconductor and electronics industries. The applications also cover the analysis of clinical samples, the use of stable isotopes for metabolic studies, and the determination of radioactive and transuranic elements. In addition to outstanding analytical features for one or a few elements, this technique provides quantitative information on more than 70 elements present from low part-per-trillion to part-per-million concentration range in a single run and within less than 3 min (after sample preparation and calibration). Comprehensive reviews on ICP-MS applications in total element determinations are available. " ... 

Microflow or low-flow nebulizers, which were described in greater detail in Chapter 3, are being used more and more for routine applications. The most common ones used in ICP-MS are based on the microconcentric design, which operate at sample flows of 20-500 pL/min. Besides being ideal for small sample volumes, the major benefit of microconcentric nebulizers is that they are more efficient and produce smaller droplets than a conventional nebulizer. In addition, many microflow nebulizers use chemically inert plastic capillaries, which makes them well suited for the analysis of highly corrosive chemicals. This kind of flexibility has made low-flow nebulizers very popular, particularly in the semiconductor industry, where it is essential to analyze high-purity materials using a sample introduction system that is free of contamination." ... 

There has been considerable interest in the determination of ions at trace levels as, for example, in applications need high-purity water as in semiconductor processing and the determination of trace anions in amine treated waters. For this investigation, we will define "trace" as determinations at or below 1 pg/1 (ppb) levels. The Semiconductor Equipment and Materials International (SEMI) recommended the use of IC for tracking trace ionic contaminants from 0.025 to 0.5 pg/1 [18]. In addition, the Electric Power Research Institute (EPRI) has established IC as the analytical technique for determining of trace level concentrations of sodium, chloride and sulfate down to 0.25 pg/1 in power plant water [19]. 

Neutron activation is not a widely used method (Fig. 17.8). Some of its applications include characterisation of materials (e.g. high purity metals, semiconductors), the study of the distribution of chemical elements within fossils, ultra-trace analysis in archaeology and geology, and the study of volcanoes. 

For the experimenter in the laboratory, not only do materials have to be chosen on the basis of their corrosion-resistance, but also for their effect on ozone decay. Some metals (e. g. silver) or metal seals enhance ozone decay considerably. This can be especially detrimental in drinking water and high purity water (semiconductor) ozone applications, causing contamination of the water as well as additional ozone consumption. Moreover, the latter will cause trouble with a precise balance on the ozone consumption, especially in experiments on micropollutant removal during drinking water ozonation. With view to system cleanliness in laboratory experiments, use of PVC is only advisable in waste water treatment, whereas quartz glass is very appropriate for most laboratory purposes. 

The technique has been widely applied to analyses for lighter elements such as carbon, oxygen, sulphur, nitrogen and boron in high purity metals and semiconductor materials 86-88,90-92) Neutron activation techniques for these elements do not provide sufficient sensitivity for many applications. In addition, the high neutron capture cross sections of many metals prevent the use of neutron activation techniques in the determination of trace impurities in the high purity metal matrix. 

In comparison with traditional inorganic semiconductors, semiconducting polymers cannot be considered materials with ultra-high purity. As a result, although many device concepts have been demonstrated using semiconducting polymers as the active materials, there has been considerable skepticism that these novel semiconductors could be used in commercial applications. 

A large number of semiconductors, used in various technologies and in pure and applied research, are known, and most of them are grown artificially. It is difficult to grow intrinsic semiconductors because FA contamination affects the crystal growth moreover, except for very special uses1, there are not many applications for truly intrinsic materials. The purest available crystals thus contain residual impurity atoms or more complex centres. Some of the residual impurities are not electrically active and they cannot be detected by electrical methods, and hence, the term intrinsic cannot be taken as a synonym for high purity. 

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