measures to support analysis of smaller regionsare needed. Since the analysis depth dependson the accelerating voltage of the electronbeam, the application of low accelerating volt-ages limits the characteristic-X-ray generationregion to a minute region near the specimensurface. However, the energies of the X-raysare less than those of the accelerated electrons;this causes a new problem: the use of analyticalX-ray lines is limited. This is particularly seri-ous for SEM-EDS that has low energy resolu-tion. The next section introduces the grazing-exit X-ray analysis method, which has the pos-sibility for improving the analysis region andmicro-volume analysis.Grazing-Exit X-ray AnalysisIn many cases, conventional EPMA orSEM-EDS detects characteristic X-rays with arelatively large take-off angle of 30 to 45°. Inparticular, an EDS detector is placed as near aspossible to the specimen so that the X-rays aremeasured with a larger solid angle. Thus, theanalysis depth extends to the order of microme-ters, as shown in Fig. 1 (a). Let me repeat thatmany specimens afford such a micrometer-order deep analysis, making EPMA a usefulmethod for localized analysis. However, if it isnecessary to obtain information on the regionfrom the surface to a depth of a few nanome-ters, conventional EPMA has difficulty in ana-lyzing this limited region. A method to breakthrough this obstacle is grazing-exit X-rayanalysis, which measures X-rays at very smalltake-off (grazing-exit) angles from the speci-men surface, as shown in Fig. 1 (b) [1-4]. Tolimit the solid angle, a slit is attached betweenthe specimen and the detector, actually, on thetop of the EDX detector. This instrument lay-out enables one to measure only characteristicX-rays emitted from the near-surface regions:that is, the X-rays emitted from the deepregions are not detected by the EDX detectordue to strong X-ray absorption in the specimenand refraction effects at the specimen surface(Fig. 2). Compared to conventional EPMA, theintensity of the detected X-rays is lower; how-ever, an important point for surface analysis isthe ratio of the signal intensity from the surfaceto that from the bulk. The grazing-exit analysis(Fig. 2) greatly enhances surface sensitivity inX-ray measurement. For the instrument config-uration needed for this grazing-exit analysis,refer to different papers [3, 5, 6].In this method, precise take-off (exit) anglecontrol is of crucial importance. To put it sim-ply, this is achieved by tilting the specimenstage in the direction of the X-ray detector [6].Another way of doing this is to move the X-raydetector or the specimen stage up and down [5,7]. For providing a slit, two pieces of metal areaffixed on the top of the EDX detector, or anaperture is placed between the specimen andthe detector. Therefore, a special device is notneeded and one can perform grazing-exit X-rayanalysis using a commercial EPMA or SEM-EDS.Application Examples ofGrazing-Exit X-ray Analysisto EPMASurface analysisFigure 3 shows the dependence of theanalysis depth on exit angle for characteristicX-rays (in this case, SiK from a silicon wafer)[1, 2]. It is shown that a certain critical angleexists, and that the analysis depth becomes asshallow as a few nanometers at angles belowthe critical angle. Thus, it is possible to performsurface analysis by setting the exit angle to thisrange of angles and by measuring the X-rays.Although it is not easy to precisely determinethe critical angle, when X-ray measurement ormapping measurement is carried out while thespecimen is tilted to decrease the exit angle, theintensity of characteristic X-rays changes at acertain angle, showing the transitional behaviorfrom bulk analysis to surface analysis. Figure 4shows an example of observation of the con-tamination on a specimen surface using thegrazing-exit X-ray analysis [8]. It is found thatthe contamination on the surface is wellobserved with high sensitivity at small exitangles, which was not realized at conventionallarge exit angles.Reduction of backgroundAn important point for observation andanalysis of trace components is signal-to-back-ground intensity ratio (S/B ratio), that is, theenhancement of the ratio of the signal intensityof characteristic X-rays to the backgroundGrazing-Exit Electron Probe Microanalysis(GE-EPMA)IntroductionElectron probe microanalysis (EPMA orSEM-EDS) is an indispensable analyticalmethod for materials development or variousinspections. The electron probe microanalyzer(EPMA), a general-purpose surface analyzer,allows observation of surface shapes of speci-mens using a finely focused electron beam. Itcan also perform qualitative and quantitativeanalysis of constituent elements in the speci-men by detecting characteristic X-rays emittedfrom the specimen irradiated with the electronbeam. The X-ray generation occurs in a regionmeasuring several micrometers deep in manycases, as will be explained later. Since this canbe regarded as a local region, the EPMA canoffer micro-area element (qualitative) analysis.In addition, various correction methods havebeen devised for quantitative analysis throughmany studies so far, making it possible for theEPMA to provide highly accurate quantitativeanalysis. Furthermore, improvements in analyt-ical software and the method of operating theEPMA have made it easy to use.On the other hand, the EPMA has severaldemerits: a) the specimen is susceptible todamage due to electron-beam irradiation, b) thespecimen has to be placed in vacuum, c) theanalysis region is of the order of micrometers(not nanometers), d) it is difficult to analyzemicro-volume specimens. To overcome demer-its a) and b), the low-vacuum SEM and theenvironmental SEM have been developed, andwith these developments, the application fieldsof the EPMA have broadened.As shown in Fig. 1 (a), since an electronbeam is scattered by a solid specimen, evenwhen the diameter of the electron beam irradi-ating the specimen surface is only several tensof nanometers, the characteristic X-rays emit-ted by the specimen come from a region sever-al micrometers in depth within the specimen.As miniaturization of semiconductor devicesand research on nano-science increasinglyadvance, analysis of a very minute region isincreasingly required. Thus, although several-micrometer-order analysis may meet users’needs depending on the type of specimens,Kouichi TsujiGraduate School of Engineering, Osaka City University, PRESTO, JSTSugimoto 3-3-138, Sumiyoshi-ku, Osaka558-8585,