Electronics materials, activation analysis

Activation analysis electronics materials, 294-305 measurement procedure, 300-303... 

The most frequently applied analytical methods used for characterizing bulk and layered systems (wafers and layers for microelectronics see the example in the schematic on the right-hand side) are summarized in Figure 9.4. Besides mass spectrometric techniques there are a multitude of alternative powerful analytical techniques for characterizing such multi-layered systems. The analytical methods used for determining trace and ultratrace elements in, for example, high purity materials for microelectronic applications include AAS (atomic absorption spectrometry), XRF (X-ray fluorescence analysis), ICP-OES (optical emission spectroscopy with inductively coupled plasma), NAA (neutron activation analysis) and others. For the characterization of layered systems or for the determination of surface contamination, XPS (X-ray photon electron spectroscopy), SEM-EDX (secondary electron microscopy combined with energy disperse X-ray analysis) and... 

Moreover the energies of these ( -partides (electrons) are known to be 1.39 MeV and that of the gamma-rays 1.38 MeV so that the measnned values of these magnitudes are characteristic of substances containing sodium. (Measurement of the y-radiadon is the usual procedure.) At least 70 of the elements can be activated in this way, by the capture of thermal neutrons, i.e.. by neutron activation analysis. An activation analysis follows a procedure similar to that shown ill Fig. 2. In almost all analyses, the sample materials are not treated before the bombardment, but are placed directly into the bombardment capsule or container. The length of the bombardment interval is usually determined by the half-life of the radionuclide used for the element of interest and the flux of nuclear particles. 

A multifaceted characterization effort to stndy these materials as a function of thermal treatment has been undertaken. The techniques include BET surface area measurements. X-ray diffraction, chemisorption, scanning and high-resolution transmission electron microscopy, analytical electron microscopy, neutron activation analysis, atomic absorption spectroscopy, FTIR and isotopic tracer studies. The details of catalyst preparation have been previously... 

Since that time the development of large, high-resolution gamma-ray detectors has made NAA less dependent on radiochemistry and transformed it into a high-precision spectroscopic technique. There are many references in the literature to the characterization of electronics materials by NAA and other nuclear methods (3, 5,6,7). Several excellent textbooks on activation analysis are available (8,9,10), to which the reader is referred for more complete discussion of the matters outlined in the present summary. 

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