Patent Publication Number: US-3881108-A

Title: Ion microprobe analyzer

Description:
United States Patent Kondo et al.  
 [ 1 Apr. 29, 1975 ION MICROPROBE ANALYZER Primary Examiner lames W. Lawrence [75] Inventors: Toshio Kondo, Sagamihara; Hifumi Assistant c&#39; chlirch Tamura, Hachiojiq both of Japan Attorney, Agent, or F1rmCra1g &amp; Antonelli [73] Assignee: Hitachi, Ltd., Tokyo. Japan [57] ABSTRACT [22] Filed: Oct. 26, 1973 An ion microprobe analyzer adapted for use in effect 1 pp 409970 ing the solid analysis of a specimen in the depth direction thereof in such a manner that the specimen is [30] Foreign Application priority Data scanned by a primary ion beam for etching to derive O t 0 977 J I 47 07951 therefrom information on the specimen such as c charged particle beams or electromagnetic waves in an attempt to analyze the surface of the specimen in gggi succession with the progress of the etching, wherein 6 3 the etching of the specimen is effected by scanning the le 0 earc primary ion beam over an area larger than and inclusive of a region to be analyzed and the information generated from the specimen surface only when the [56] References cued primary ion beam passes through the region to be ana- UNITED STATES PATENTS lyzed which is preset is detected, thereby making free 3.502.870 3/1970 Fujiyasu 250/310 from influences from the side wall of a hole produced 3.600.573 8/1971 wata 250/286 on the specimen by the etching to improve the preci sion of analysis in the depth direction of the specimen.  
 . mura r v 22 Claims, 21 Drawing Figures ION SOURCE 4A1? 5 L 5 ION ACCELERN&#39;ING POWER SUPPLY :7 E 5 &#34;-E l 311 a I I 7 i I l 1 POWER P NE 9 SUPPLY 6 SLPPLY l3]? RATOR IfiLg; COMHA- W l3 3 RATOR PATENTEU APRZQ I975 SHEET 1 BF 8 FIG .I PRIOR ART ION FIG-2 PRIOR ART lg m 3 7 6 w 4:5 Dn Ill w E s. aubwo P w 4 V 9 4 m 2 RU z EEP 7 ma w l m IJENTEE APR 2 9 i975 SHEET 2 BF 8 6 DISTANCE 225E828 Y 25m 29 FIG.5PRIORART P:&#39;- TENTF.UAPR29I975 V 91,108.  
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  ION SOURCE &#34;I ION ACCELERN&#39;I POWER SUPPLY Pmgmgnmzsms 3.681.108  
 SHEET 5 OF 8 Fl G l6 ION ELECTRO- DETECTOR METER F&#39;LTER r1 tl 1::  
 POWER SUPPLY L EL t4 t2 I \23 Fl G l7 l2 A {26 ION PULSE SCALER DETECTOR AMPLIFIER PATENTEDAPRZMQYS 3. 881 1 O8 SHEET 8 OF 8 FIG. 2|  
  ION SOURCE l 2 4w: 1 ION S E5 Y a 33 33 SUPPLY :{WT  
 l EiEl 7/72 n- Haw l x POWER 27 6 SUPPLY 3 5 |4; COMPA- |3 RATOR 4 1 COMPA= LOG&#34;: 3&#39; RATOR C|RCU|T COMPA-. il RATOR 4&#34;: COMPA- RATOR AMPLIFIER PULSE GATE PNPUFIER CIRCUIT ION MICROPROBE ANALYZER FIELD OF THE INVENTION The present invention relates to an ion microprobe analyzer, and more particularly to an ion microprobe analyzer for effecting the solid analysis on the surface of a solid in the depth direction thereof through etching with the aid of ion sputtering.  
 BRIEF DESCRIPTION OF THE DRAWING FIG. I is a schematic view of explaining of principle of a conventional ion microprobe analyzer.  
  FIG. 2 is a graph of concentration distribution of an ion beam which is adjusted to have a uniform concentration by electrostatic lenses in the device shown in FIG. 1.  
  FIG. 3 is a cross-sectional view of a specimen which it etched with an ion beam having the concentration distribution of FIG. 2.  
  FIG. 4 is a graph showing concentration distributions of an ion beam wider focussed and an ion beam narrower focussed by means of the electrostatic lens to generate an ion beam having strong intensity.  
  FIG. 5 is a view showing a relation between the ion beams and the section of the specimen taken in etching the specimen with the ion beam having the concentration distribution as shown in FIG. 4.  
  FIG. 6 is a view showing a pair of deflecting elec trodes for moving that point on the surface of the specimen on which the ion beam is radiated.  
  FIG. 7 is a graph showing voltage waveforms applied to the deflecting electrodes shown in FIG. 6, respectively.  
  FIG. 8 is a view showing a locus of the point on the surface of the specimen on which the ion beam is radiated when the ion beam is deflected by the voltage having the waveform shown in FIG. 7.  
  FIG. 9 is a graph showing the sensitivity of a mass spectrometer used in an ion microprobe analyzer in terms of a position thereof from which the secondary ions are generated.  
  FIG. 10 is a cross-sectional view showing the specimen which is etched by moving the point on which the ion beam is radiated as shown in FIG. 8.  
  FIG. 11 is a schematic view showing one embodiment of an ion microprobe analyzer according to the present invention.  
  FIG. 12 is a view showing the locus of the point on which the ion beam is radiated in connection with the range of analysis, the point being moved to etch the specimen by means of the device according to the present invention.  
  FIG. 13 is a graph showing a relation between a voltage for deflecting the ion beam radiated on the specimen in the device according to the present invention, a reference voltage applied to a comparator, and a signal voltage for controlling a gate relative to secondary ions or a gate relative to an output signal from a secondary ion detector.  
  FIG. 14 is a view showing one example of a gate for permitting or interrupting the passage of the secondary ions.  
  FIG. 15 is a block diagram showing an embodiment of a gate for connecting or disconnecting a signal from the secondary ion detector.  
  FIG. 16 is a block diagram showing another embodiment of a gate for connecting or disconnecting the signal from the secondary ion detector.  
  FIG. 17 is a block diagram showing an embodiment of a gate for connecting or disconnecting a signal from a counting ion detector.  
  FIG. 18 is a view showing one example of an image on a cathode-ray tube representative of a portion of specimen analyzed in the depth direction thereof during a time when the surface of the specimen is etched by the ion microprobe analyzer according to the present invention.  
  FIG. 19 is a schematic view showing an embodiment of an ion microprobe analyzer according to the present invention by which the image as shown in FIG. 18 is obtained.  
  FIG. 20 is a schematic view showing another embodiment of an ion microprobe analyzer according to the present invention in which X-rays generated from the surface of the specimen due to radiation of the primary ions are employed for analysis.  
  FIG. 21 is a schematic view showing a further embodiment of an ion microprobe analyzer according to the present invention in which light generated from the surface of the specimen due to radiation of the primary ions is employed for analysis.  
 DESCRIPTION OF THE PRIOR ART An ion microprobe analyzer has features of being capable of analysis of the thin surface layer of a specimen and capable of measurement of a concentration distribution of a specific ion, that is, an element of the specimen in the depth direction thereof. The analysis of the thin surface layer is a merit not possessed by the other like devices, and is profitably put into practical use at present. Such an ion microprobe analyzer is used to analyze iron and steel materials, semiconductor materials, surface treating materials, insulator materials, surface pollution, organic materials, and so forth.  
  FIG. I shows a schematic view of a conventional ion microprobe analyzer. Ions generated from an ion source 1 are extracted for acceleration due to an electric field established between an extracting electrode 3 and the ion source 1 to which a high voltage is applied by an ion accelerating power supply 2. The thus extracted ion beam is focussed on the surface of a specimen 6 by two electrostatic lenses 5 and 5&#39; to which suitable voltages are applied through voltage dividers 4 and 4. A diaphragm 7 is provided to cause the ion beam to be directed only toward the central portion of the electrostatic lens 5&#39;. That position on the specimen surface on which the ion beam is to be radiated is roughly set by providing the specimen with great movement and then set by adjustingthe voltage applied to an ion beam deflecting electrode 8 by a power supply 9. Secondary ions generated upon irradiation of the ions on the specimen are separated from each other in accordance with a mass-to-charge ratio by a double focussing mass spectrometer including an electrostatic cylinder 10 and a magnetic sector 11 and are then detected by an ion detector provided with a secondary electron multiplier 12. In this arrangement, the analysis of the specimen in the depth direction thereof is effected in such a way that only the condenser lens nearer to the ion source of the electrostatic l&#39;enses is provided with a converging function and the periphery of the ion beam is cut off by means of a diaphragm of a suitable diameter for irradiation on the surface of the specimen to provide an ion beam having a substantially uniform concentration. In FIG. 2 there is shown a radial distribution of the ion beam concentration over the surface of the specimen in such an arrangement.  
  The etching of the specimen with such an ion beam causes the specimen to be etched substantially as flat in section as shown in FIG. 3, thus permitting the analysis of the specimen in the depth direction thereof. However, at the periphery of the ion beam there remain portions subjected to no etching; nevertheless the etching to the specimen is progressed, these portions inducing disadvantageous errors in the analysis of the bottom portion subjected to the etching. Further it is difficult to obtain great current by the use of the ion beam which has the uniform concentration.  
  On the other hand, the adjustment of the two electrostatic lenses permits the ion beam to be charged so that the radial distribution of the ion beam concentration may be provided as shown by curves A and B in FIG. 4. It is, accordingly, proposed that the ion beam is increased in diameter to etch the specimen with the ion beam, the concentration of which is distributed in the radial direction as represented by the curve B of FIG. 4 until the specimen is etched to a predetermined depth. The specimen is then analyzed with a narrower focussed ion beam of a small diameter represented by the curve A of FIG. 4 with the result of the analysis of only a portion corresponding to the center of the wider ion beam of a large diameter where the substantially flat etching is effected, thus removing influences resulting from the periphery of the ion beam upon the etching. In FIG. 5 there are shown conditions where the wider ion beam B first etches the specimen and the narrower ion beam A then analyzes the central portion thereof. which is etched to a predetermined depth.  
  This method has the drawback of inducing the errors in the analysis of the specimen in the depth direction thereof because any small central portion to be analysed is not made completely flat even if the ion beam is made wide. Further, it is disadvantageous in that the errors are also brought into the result of analysis when attention must be paid to an etching speed in the analysis because the specimen is being etched even during the analysis under the condition of the small diameter of the ion beam.  
 SUMMARY OF THE INVENTION An object of the present invention is to provide an ion microprobe analyzer which has a remarkably enhanced precision of analysis of a specimen in the depth direction thereof.  
  Another object of the present invention is to provide an ion microprobe analyzer which is capable of effecting uniform etching in any position on the surface of a specimen and which is capable of accurate measurement of a concentration distribution in the depth direction with respect to some element of the specimen to be analyzed.  
  The present inventors have tried to effect the etching by scanning an ion beam in an attempt to eliminate the non-uniform etching in the conventional methods. More specifically, it has been found that the movement of the ion beam on the surface of the specimen 6 causes the current due to the radiated ions to be made uniform in terms of time average and the uniform etching can be effected irrespective of the position on the surface of the specimen even if the uniform distribution of current density of the ion beam is not always provided as shown in FIG. 2 in etching the surface of the specimen to be analyzed with the ion beam.  
  In FIG. 6 there is shown a portion of a particular device embodying the above-mentioned fact. The ion beam for irradiating the specimen is scanned on the surface of the specimen in directions of X and Y as shown in FIG. 8 by applying voltages V, and V varying with a time t as shown in FIG. 7 to deflecting electrodes 8 and 8&#39;, respectively, in response to energization of a power supply 9. In this case, the surface of the specimen undergoes the uniform etching as shown in section in FIG. 10 except for the periphery thereof. On the other hand, the use of the double focussing mass spectrometer for separating the secondary ions in accordance with mass as shown in FIG. 1 permits any secondary ions to be detected no longer in the case where the portion of the surface of the specimen from which the secondary ions are generated due to the radiation of the ions are caused to be spaced away from the designed center at which the sensitivity of the double focussing mass spectrometer becomes at maximum. If, accordingly, an analyzing method is employed in which the ion beam is scanned for etching with a width sufficiently greater than a region over which the secondary ions are detected in the double focussing mass spectrometer, then no secondary ions generated from portions near to the surface of the specimen is permitted to be detected because of a little progress of the etching at the periphery of the specimen even if the etching is progressed to analyse the deep portion of the specimen. Thus, the drawback of the two earlier-mentioned methods can be removed. However, difficulty is encountered in the analysis using the herein described method under the condition where the concentration distribution in the depth direction with respect to the element of the specimen to be analyzed depends on the position thereof and its range is small.  
  The reason is that the element of secondary ions emitted from peripheral side walls of the region etched by scanning the ion beam is mixed with the secondary ions emitted from the region to be scanned. This fact can not be avoided even if the region to be scanned is limited. As a result, the concentration distribution in the depth direction with respect to the element of the specimen to be analyzed depends upon the position, and thus no measurement is permitted as the distribution in the depth direction of the particular narrow region to which attention is paid.  
  The present invention provides a further improvement of this method, and is intended to effect the etching of the specimen by scanning a primary ion beam over a range greater than that including the region to be analyzed and the secondary ion beam generated from the surface of the specimen is caused to reach the detector only when the primary ion beam passes through the region to be analyzed which is preset, thereby removing influences resulting from the side of a hole produced on the specimen due to the etching for improvement in the precision of analysis in the depth direction. The selection of the secondary ion beam is provided by means for setting the region to be analyzed, comparator means for comparing a signal from the setting means with a scanning signal of the primary ion beam, and control means for controlling means for analyzing the secondary ions and an output from a detector in response to the result from the comparator means.  
  The above description has been made of the method in which the specimen is analyzed using the secondary ions generated from the specimen, but the method is also applicable in quite the same manner as above to an ion microprobe analyzer provided with means for analyzing and detecting information from the specimen such as charged particles, light of X-rays other than the secondary ions generated from the specimen upon the radiation of the primary ions thereon.  
  Understanding of the present invention will be facilitated by referring to the following detailed description thereof.  
 DESCRIPTION OF PREFERRED EMBODIMENTS FIG. 11 shows one embodiment of an ion microprobe analyzer according to the present invention, comprising an ion source 1, an ion accelerating power supply 2, an extracting electrode 3, voltage dividers 4 and 4&#39;, electrostatic lenses 5 and 5&#39;, a specimen 6, a diaphragm 7, a deflecting electrode 8, a power supply 9 for the deflecting electrode 8, an electrostatic cylinder 10, a magnetic sector 11, an ion detector 12, potentiometers 13, 13&#39;. 13&#34; and 13&#34;, comparators 14, 14, 14 and 14&#34;, a logic circuit and an electric field power supply 16.  
  In the device, voltages having the waveforms as shown in (A) and (B) of FIG. 13 are applied to the deflecting electrodes 8 through the power supply 9 in order to move the ion beam on the surface of the specimen so that the locus of the ion beam on the surface of the specimen may be represented by a solid line in FIG. 12. According to the present invention, if an output of analysis is caused to be recorded or displayed only when the ion beam exists in a region not including the periphery of the range over which the ion beam moves,  
 for example, in a region A shown in FIG. 12, then analysis errors in the depth direction are prevented from occurring which are derived from the influences from the peripheral portion etched by the ion beam and which form the drawbacks of the conventional devices. Further, the optional selection of the area and position of the region A as shown in FIG. 12 makes possible the analysis in which the concentration distribution in the depth direction with respect to the element of the specimen to be analyzed depends on the position thereof.  
  In order to put the above-mentioned facts into practice, a signal voltage (shown in (C) of FIG. 13) is caused to be generated by comparators 14, 14&#39;, 14&#34; and 14&#34;, and the logic circuit 15 only when the ion beam exists in the region A in view of the fact that the voltages V, and V (their waveforms being shown in (A) and (B) of FIG. 13) applied to a pair of electrodes for deflecting the ion beam are related to V, V, V and V V V when the ion beam exists, for example, in the region A. In this case, voltages corresponding to V V V and V set by the potentiometers I3, 13, 13 and 13&#34; and the voltages applied to the deflecting electrodes are assumed to meet the above-mentioned inequality. The double focussing mass spectrometer is adapted to provide a voltage to its electrostatic cylinder by means of the power supply 16 in response to the signal voltage so that the secondary ions are permitted to pass therethrough, thus permitting the secondary ions to be detected which are generated when the ion beam exists in the region A of FIG.  
 12. If the time constant of the ion detector in the mass spectrometer is chosen to be sufficiently greater than the time taken for the ion beam to scan all over the surface of the specimen, then the surface of the specimen is etched by repeating the scanning of the specimen to analyze the region having a predetermined area and position in the depth direction.  
  To alter the set values of the potentiometers 13, 13&#39;, 13&#34; and 13 permits the area and position of the region to be analyzed to be set optionally.  
  In the above-mentioned embodiment of the present invention, the double focussing mass spectrometer used to obtain the analysis output of the secondary ions generated by the ion beam scanning the surface of the specimen has its field voltage controlled so as to pro vide a function corresponding to a gate for the secondary ions at a path along which the secondary ions reach the ion detector. Other methods for providing the same function as above may be proposed, and FIG. 14 shows one of them in which deflecting electrodes 18 are provided at a suitable position selected from an ion track of the mass spectrometer, for example, at a position between a collector slit 17 and an ion detector 12 as shown in FIG. 14. The deflecting electrodes 18 receive the voltage from the power supply 19 to deflect the secondary ions so that no secondary ions may reach the ion detector, thus causing the interruption of the secondary ions. In this case, the power supply 19 generating the voltage applied to the deflecting electrode 18 is so controlled that an output voltage therefrom becomes zero with the aid of the device such as the logic circuit 15 only when the ion beam for irradiating the specimen exists in the region to be analyzed which is previously set, and a voltage is produced therefrom which is great enough to deflect and interrupt the secondary ions when the ion beam exists in the other fields.  
  In the following, in connection with FIGS. 15 to 17 the description will be made of embodiments of another method which has above been mentioned as an example of the method in which only the output of analysis of the secondary ions which are generated at the previously set field is detected by scanning the ion beam over the surface of the specimen.  
  In an embodiment shown in FIG. 15, reference numeral 12 designates an ion detector such as a secondary electron multiplier, numeral 20 an electrometer, numeral 21 an analog switch, and numeral 22 a filter. Output current from the secondary electron multiplier 12 is converted to a voltage by the electrometer 20. The output voltage is measured by a recorder through the analog switch 21 effective to be opened or closed in response to an external control signal so that the voltage may be transmitted only when the ion beam exists in the region to be analyzed which is preset on the surface of the specimen, and through the filter 22 for reducing pulsation of the signal voltage from the secondary ions passing therethrough in response to the opening of the analog switch.  
  In an embodiment as shown in FIG. 16, reference numeral l2 designates an ion detector such as a secondary electron multiplier, numeral 20 an electrometer, numeral 22 an filter and numeral 23 a power supply for the secondary electron multiplier 12. In this embodiment, the detection of the secondary ions is effected by the secondary electron multiplier 12, the power supply 23 with the voltage in response to the control signal generated when the ion beam exists in the region to be analyzed which is preset on the surface of the specimen, the electrometer and the filter 22. In the present embodiment, the selective detection of the secondary ions generated only when the ion beam exists in the region to be analyzed which is preset on the surface of the specimen is effected by a gate function connecting or disconnecting the voltage applied to the secondary electron multiplier.  
  FIG. 17 shows an embodiment in which a counting ion detector is employed. In the Figure, reference numeral 12 designates ion detector such as a secondary electron multiplier, numeral 24 a pulse amplifier, numeral 25 a gate circuit and numeral 26 a sealer. In this case, output current from the secondary electron multiplier 12 is transmitted to a wide-band pulse amplifier 24.  
  Thus, each ion incoming on the secondary electron multiplier is converted to a pulse voltage per one ion particle. The pulse voltage appears at the output terminal of the wide-band pulse amplifier 24, and is transmitted to the scaler 26 through the gate circuit 25 operable in response to the control signal generated when the ion beam exists in the region to be analyzed which is preset on the surface of the specimen. Thus the pulse voltage due to the secondary ions generated only when the ion beam exists in the region to be analyzed which is preset on the surface of the specimen is permitted to pass through the gate circuit and to be measured by the sealer.  
  FIG. 19 shows a still further embodiment of an ion microprobe analyzer, provided with the following function other than those described above. In other words, a device for viewing the surface of the specimen is provided which includes a cathode-ray tube in which an electron beam is deflected in synchronism with the scanning of the ion beam on the surface of the specimen and is subjected to a brightness modulation in dependence on the generation of the charged particles generated due to the radiation of the ion beam thereon. An image projected on the cathode-ray tube is added with the image of the region which is to be analyzed in the depth direction and which has any area and position, the region being made much lighter or darker as shown in A of FIG. 18 to display the boundary of the region.  
  In FIG. 19 there are shown an electrometer 20, an analog switch 21, a filter 22, a secondary electron multiplier 27, a switch 28, an amplifier 29, and a cathoderay tube 30. The other portions are similar to those shown in FIG. 11.  
  The switch 28 selects either of an output signal from the secondary electron multiplier 27 for sensing a positive or negative ion or electron generated when the ions are radiated on the surface of the specimen, or an output signal from the secondary electron multiplier 12 for sensing ions having a particular mass-to-charge ratio and separated in accordance with mass by the mass spectrometer. The output signal is adapted to provide the brightness modulation to the cathode-ray tube through the amplifier 29 the gain of which is controlled by the output from the gate circuit 15. Further, the electron beam in the cathode-ray tube is adapted to be scanned in synchronism with the scanning of the ion beam on the surface of the specimen thereby to permit one to view the conditions on the surface thereof.  
 The level of the output signal from the amplifier herein used is adapted to vary with the control signal generated when the ion beam exists in the region to be analyzed which is preset on the surface of the specimen, and is superimposed on the image on the surface of the specimen as mentioned earlier to distinctly display the region to be analyzed which is preset.  
  Further, it is to be noted that in the embodiment of FIG. 11 a magnetizing power supply (not shown) may be controlled by the output from the logic circuit 15 and that the mass spectrometer used in the present invention is not restricted to that of a double focussing type.  
  FIG. 20 is a schematic view showing a still further embodiment of an ion microprobe analyzer according to the present invention in which X-rays generated due to the radiation of the primary ions are employed. In the Figure there are shown an X-ray spectroscopic crystal 31 (the details of an X-ray spectrometer being omitted) and an X-ray detector 32, for example, various kinds of counters. The other portions are the same as those of FIGS. 21 and 17. In this device, characteristic X-rays generated from the specimen 6 undergo a spectroscopic analysis by means of the spectroscopic crystal 31 and then converted to an electric pulse signal corresponding to the number of quantum of the X-rays by the X-rays detector 32. No X-rays generated from the peripheral side wall of the etched region of the specimen are detected to thus improve the reduction in a resolving power in the direction of the depth because the pulse due to the X-rays from the region of the specimen other than that to be analyzed is prevented by the gate 25 from passing therethrough in the same manner as in FIG. 17.  
  FIG. 21 is a schematic view showing a still further embodiment of an ion microprobe analyzer according to the present invention in which light generated from the specimen upon the radiation of the primary ions thereon is employed. In the Figure, there are shown a spectrometer 33 and a photo detector 34 connected thereto, for example, a photo-electro multiplier, which detects the light as pulse current in dependence on the intensity of light according to a photo counting method. The other portions are the same as those of FIGS. 21 and 17. In this device, the light generated from the specimen 6 undergoes the spectroscopic analysis by means of the spectrometer 33 and then converted to an electric pulse signal corresponding to the number of light quanta. The pulse due to the light from the region of the specimen other than that to be analyzed is prevented by the gate 25 from passing therethrough in the same manner as in FIG. 17, so that the same effects as those obtained in the previous embodiments are obtained.  
  The above embodiments has been described by way of the ion microprobe analyzer including the individual analyzers for analyzing the secondary ions, X-rays, light or the like, but it will be apparent that a plurality of those analyzers may be provided.  
  While the invention has been described by reference to particular embodiments thereof, it will be understood that numerous and further modifications may be made by those skilled in the art without actually departing from the invention. We, therefore, aim in the appended claims to cover all such equivalent variations as come within the true sprite and scope of the foregoing disclosure.  
 We claim:  
  1. An ion microprobe analyzer comprising means for generating a primary ion beam, means for focusing the generated primary ion beam on a specimen, means for etching the specimen by scanning the focussed primary ion beam over an area larger than and inclusive of a region to be analyzed on the specimen, at least one means for analyzing information generated from the specimen upon radiation of the primary ion beam thereon, means for detecting an analysis result from said analyzing means, means for setting the region to be analyzed on the specimen, means for comparing an output from said scanning means with an output from said setting means, and means for controlling an output from said analyzing means in response to an output from said comparing means, whereby only information derived from the region to be analyzed on the surface etched by the scanning of the primary ion beam is permitted to be detected to thereby permit accurate measurement of the concentration distribution of an element of the specimen in the depth direction thereof.  
  2. An ion microprobe analyzer as set forth in claim 1, further comprising means for detecting information generated by the scanning of said scanning means, means for displaying a result from said information detecting means, and means for simultaneously displaying information from the region to be analyzed on the specimen on said displaying means.  
  3. An ion microprobe analyzer as set forth in claim 1, wherein said setting means comprises a potentiometer.  
  4. An ion microprobe analyzer as set forth in claim 1, wherein said analyzing means comprises a mass spectrometer for analyzing secondary ions from the speci&#39; men.  
  5. An ion microprobe analyzer as set forth in claim 4, wherein said controlling means comprises means for altering a voltage to an electric field of said mass spec trometer.  
  6. An ion microprobe analyzer as set forth in claim 4, wherein said controlling means comprises means for altering the intensity of a magnetic field of said mass spectrometer.  
  7. An ion microprobe analyzer as set forth in claim 4, wherein said controlling means comprises means provided between the specimen and said detecting means for deflecting the secondary ions from the specimen.  
  8. An ion microprobe analyzer as set forth in claim 7, wherein said analyzing means comprises an electric field device and a magnetic field device and said deflecting means is provided between said devices.  
  9. An ion microprobe analyzer as set forth in claim 6, wherein said analyzing means comprises an X-ray spectrometer and said detecting means comprises an X-ray detector.  
  10. An ion microprobe analyzer comprising means for generating a primary ion beam, means for focussing the generated primary ion beam on a specimen, means for etching the specimen by scanning the focussed primary ion beam over an area larger than and inclusive ofa region to be analyzed on the specimen, at least one means for analyzing information generated from the specimen upon radiation of the primary ion beam thereon, means for detecting an analysis result from said analyzing means, means for setting the region to be analyzed on the specimen, means for comparing an output from said scanning means with an output from said setting means, and means for controlling an output from said detecting means in response to an output from said comparing means, whereby only information derived from the region to be analyzed on the surface etched by the scanning of the primary ion beam is permitted to be detected to thereby permit accurate measurement of the concentration distribution of an element of the specimen in the depth direction thereof.  
  11. An ion microprobe analyzer as set forth in claim 10, further comprising means for detecting information generated by the scanning of said scanning means, means for displaying&#39;a result from said information detecting means, and means for simultaneously displaying information from the region to be analyzed on the specimen on said displaying means.  
  12. An ion microprobe analyzer as set forth in claim 10, wherein said setting means comprises a potentiometer.  
  13. An ion microprobe analyzer as set forth in claim 7, wherein said detecting means is provided between said mass spectrometer and said deflecting means.  
  14. An ion microprobe analyzer as set forth in claim 10, wherein said analyzing means comprises a photospectrometer and said detecting means comprises a photo-detector.  
  15. An ion microprobe analyzer as set forth in claim 10, wherein said analyzing means comprises a mass spectrometer for analyzing secondary ions from the specimen.  
  16. An ion microprobe analyzer as set forth in claim 15, wherein said detecting means comprises an electron multiplier and said controlling means comprises a switch for connecting and disconnecting an output from said electron multiplier.  
  17. An ion microprobe analyzer as set forth in claim 15, wherein said detecting means comprises an electron multiplier and said controlling means comprises means for controlling a voltage applied to said electron multiplier.  
  18. An ion microprobe analyzer as set forth in claim 15, wherein said detecting means comprises a counting ion detector.  
  19. An ion microprobe analyzer comprising means for generating a primary ion beam, means for scanning the generated primary ion beam over an area larger than and inclusive of a region to be analyzed on the specimen and for etching the scanned area, at least one means for analyzing information generated from the specimen upon radiation of the primary ion beam thereon, means for detecting an analysis result from said analyzing means, means for setting the region to be analyzed on the specimen, means for comparing an output from said scanning means with an output from said setting means, and means for controlling an output from said analyzing means in response to an output from said comparing means, whereby only information derived from the region to be analyzed on the surface etched by the scanning of the primary ion beam is permitted to be detected to thereby permit accurate measurement of the concentration distribution of an element of the specimen in the depth direction thereof.  
  20. An ion microprobe analyzer comprising means for generating a primary ion beam, means for focussing the generated primary ion beam on a specimen, means for scanning the focussed primary ion beam over an area larger than and inclusive of a region to be analyzed on the specimen and for etching the scanned area, at least one means for analyzing information which are generated from the specimen upon radiation of the primary ion beam thereon, means for detecting an analysis result from said analyzing means, means for setting the region to be analyzed on the specimen, means for comparing an output from said scanning means with an output from said setting means, and means for controlling an output from said detecting means in response to an output from said comparing means, whereby only information derived from the region to be analyzed on the surface etched by the scanning of the primary ion beam is permitted to be detected to thereby permit accurate measurement of the concentration distribution of an element of the specimen in the depth direction thereof.  
  21. A method of analysis by use of an ion microprobe analyzer comprising the steps of generating a primary ion beam, focussing the generated primary ion beam on a specimen, etching the specimen by scanning the focussed primary ion beam over an area larger than and inclusive of a region to be analyzed on the specimen, analyzing information generated from the specimen upon radiation of the primary ion beam thereon, detecting an analysis result from said analyzing, detecting the region being scanned on the specimen, comparing the region being scanned with the region to be analyzed, controlling said analyzing in response to the result of said comparing to inhibit said analyzing when the region on said specimen being scanned is outside the region to be analyzed, whereby only information derived from the region to be analyzed on the surface etched by the scanning of the primary ion beam is permitted to be detected to thereby permit accurate measurement of the concentration distribution of an element of the specimen in the depth direction thereof.  
  22. A method of analysis by use of an ion microprobe analyzer comprising the steps of generating a primary ion beam, focussing the generated primary ion beam on a specimen, etching the specimen by scanning the focussed primary ion beam over an area larger than and inclusive of a region to be analyzed on the specimen, analyzing by analyzing means information which are generated from the specimen upon radiation of the primary ion beam thereon, detecting an analysis result from said analyzing means, setting by setting means the region to be analyzed on the specimen, comparing by comparing means an output from said scanning means with an output from said setting means, and controlling an output from said detecting means in response to an output from said comparing means, whereby only information derived from the region to be analyzed on the surface etched by the scanning of the primary ion beam is permitted to be detected to thereby permit accurate measurement of the concentration distribution of an element of the specimen in the depth direction