Patent Publication Number: US-2022230835-A1

Title: Electron Gun and Charged Particle Beam Device Equipped With Electron Gun

Description:
TECHNICAL FIELD 
     The present invention relates to an electron gun and a charged particle beam device including the electron gun, and particularly, can be suitably used for an electron gun including a diaphragm on an extraction electrode. 
     BACKGROUND ART 
     In a charged particle beam device such as a scanning electron microscope (SEM), for example, a Schottky type or electric field emission type electron gun is used in order to stably extract a high-luminance current with a narrow energy width. Generally, an electron gun includes an extraction electrode that generates a strong electric field in order to extract electrons to a tip of an electron source, and the extraction electrode includes a diaphragm for limiting electrons passing through the extraction electrode. 
     US-A-2010/0320942 (PTL 1) discloses a technique for providing a recess on a surface of the extraction electrode of the electron gun. 
     JP-A-2013-45525 (PTL 2) discloses a technique in which the extraction electrode of the electron gun includes a two-stage diaphragm and surfaces thereof are coated with carbon. 
     JP-A-2008-117662 (PTL 3) discloses a technique of suppressing an angle of the electron beam passing through the diaphragm to a predetermined range by providing a two-stage diaphragm on the extraction electrode of the electron gun. 
     WO-A-2008/120412 (PTL 4) discloses a technique in which a permanent magnet is arranged in an electron accelerating portion of the electron gun, and the electron beam emitted from the electron source is converged by a magnetic field from the permanent magnet. 
     CITATION LIST 
     Patent Literature 
     
         
         PTL 1: US-A-2010/0320942 
         PTL 2: JP-A-2013-45525 
         PTL 3: JP-A-2008-117662 
         PTL 4: WO-A-2008/120412 
       
    
     SUMMARY OF INVENTION 
     Technical Problem 
     An electron beam emitted from an electron source of an electron gun is accelerated by an acceleration electrode and irradiates a sample to be inspected through an electron lens such as a focusing lens, an objective lens, and the like. In this case, for example, in a scanning electron microscope, secondary electrons generated when the electron beam collides with the sample are detected, and the structure of the sample is observed and analyzed. 
     At this time, a bright region called flare may sometimes occur around the observed main spot. Then, the flare causes problems such as a decrease in the S/N ratio of the observation image and a decrease in the resolution. As one of the causes of the flare, a case is considered where the secondary electrons generated inside the electron gun are mixed in the electron beam emitted from the electron source. Therefore, for the electron gun, a technique is desired, which is capable of suppressing mixing of secondary electrons into the electron beam, and for a charged particle beam device, a technique for suppressing generation of the flare as much as possible is required. 
     Other issues and novel features will become apparent from the description of the present specification and the accompanying drawings. 
     Solution to Problem 
     The outline of a certain representative example of the embodiments disclosed in the present application will be briefly described below. 
     An electron gun according to an embodiment includes an electron source, an extraction electrode for extracting an electron beam from the electron source, and an acceleration electrode for accelerating the extracted electron beam. Here, the extraction electrode includes a diaphragm for allowing a part of the electron beam to pass through, a first shield positioned above the diaphragm apart from the diaphragm, and a second shield positioned below the diaphragm apart from the diaphragm. Further, the diaphragm includes a first opening having a first opening diameter, the first shield includes a second opening having a second opening diameter greater than the first opening diameter, and the second shield includes a third opening having a third opening diameter greater than the first opening diameter. 
     Advantageous Effects of Invention 
     According to an embodiment, it is possible to provide an electron gun in which mixing of the secondary electrons is suppressed. In addition, the accuracy of the observation image obtained by the charged particle beam device including such an electron gun can be improved. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a cross-sectional view illustrating an electron gun according to a first embodiment. 
         FIG. 2  is a perspective view illustrating a peripheral structure of a diaphragm provided on an extraction electrode according to the first embodiment. 
         FIG. 3  is a schematic view illustrating a charged particle beam device according to the first embodiment. 
         FIG. 4  is an enlarged cross-sectional view illustrating a main part of an electron gun in a study example. 
         FIG. 5  is an enlarged cross-sectional view illustrating a main part of an electron gun according to the first embodiment. 
         FIG. 6  is an enlarged cross-sectional view illustrating a main part of the electron gun according to the first embodiment. 
         FIG. 7  is an enlarged cross-sectional view illustrating a main part of the electron gun according to the first embodiment. 
         FIG. 8  is an enlarged cross-sectional view illustrating a main part of an electron gun according to a modification. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Hereinbelow, embodiments will be described in detail with reference to the drawings. In all the drawings for illustrating the embodiments, the members having the same functions are designated by the same reference numerals, and the repeated description thereof will be omitted. Further, in the following embodiments, the description of the same or similar components is not repeated in principle except when it is particularly necessary. 
     Further, in the drawings used in the embodiment, hatching may be omitted even in the cross-sectional view in order to make the drawings easier to see. 
     First Embodiment 
     An electron gun EG according to a first embodiment will be described below with reference to  FIGS. 1 and 2 . In this example, the electron gun EG is a Schottky type electron gun, for example. 
     For example, the electron gun EG includes an electron source  1  formed of a tungsten single crystal, a filament  7  welded to the electron source  1 , a zirconium oxide layer  8  coated on the electron source  1 , and a suppressor electrode  9  provided around the electron source  1 . The filament  7  is provided to heat the electron source  1 , and the suppressor electrode  9  is provided to suppress thermionic electrons generated from the filament  7 . 
     Further, the electron gun EG includes an extraction electrode  2  for generating a strong electric field in order to extract electrons from the electron source  1 , and an acceleration electrode  3  for accelerating the extracted electrons to a predetermined energy. 
     The extraction electrode  2  includes a diaphragm  4  for limiting an incident angle of an electron beam E 1  (primary electron, electron beam) and allowing a part of the electron beam E 1  to pass through, a shield  5  (electric field shielding plate) positioned above the diaphragm  4 , and a shield  6  (electric field shielding plate) positioned below the diaphragm  4 . The diaphragm  4  and the shield  5  are separated from each other by a sufficient distance, and the diaphragm  4  and the shield  6  are separated from each other by a sufficient distance. 
     Further, each of the diaphragm  4 , the shield  5 , and the shield  6  is formed of a conductive material and of a material having high heat resistance. Such materials are metals and mainly include molybdenum (Mo), tantalum (Ta) or tungsten (W), for example. Further, the materials also include the above metals coated on their surfaces with platinum-palladium, carbon or the like. 
       FIG. 2  is a partial perspective view illustrating in enlargement the peripheries of the diaphragm  4 , the shield  5 , and the shield  6  provided on the extraction electrode  2 . 
     The diaphragm  4  includes an opening OP 4 , and a part of the electron beam E 1  emitted from the electron source  1  is passed through the inside of the opening OP 4 . The shield  5  and the shield  6  include an opening OP 5  and an opening OP 6 , respectively, and the opening diameter of each of the opening OP 5  and the opening OP 6  is greater than the opening diameter of the opening OP 4 . Note that although each of the openings OP 4  to OP 6  is illustrated as a semicircular shape in  FIG. 2 , these are actually in circular shapes centered on an optical axis OA. 
     In the first embodiment, the main features of the electron gun EG include the shield  5  provided above the diaphragm  4  and the shield  6  provided below the diaphragm  4 , and the shapes of the same, and such features will be described in detail below by comparison with the study examples. 
     The basic operation of the electron gun EG in  FIG. 1  will be described below. 
     A tip of the electron source  1  is sharply etched, and a negative potential V 0  with respect to the ground potential is applied to the electron source  1 . While a negative voltage Vs is applied to the suppressor electrode  9 , when currents are flowed through the filament  7  from a current source If, the filament  7  is heated, and the zirconium oxide layer  8  coated on the electron source  1  is diffused toward the tip of the electron source  1 . At this time, when a positive voltage V 1  is applied to the extraction electrode  2 , the electric field near the tip of the electron source  1  is increased, and the electron beam E 1  is emitted from the crystal plane of the electron source  1  toward the extraction electrode  2  due to the Schottky effect. Most of the electron beam E 1  emitted from the electron source  1  is shielded by the extraction electrode  2  including the diaphragm  4 , the shield  5 , and the shield  6 , but a part of the electron beam E 1  is passed through the diaphragm  4  (the opening OP 4 ). The electron beam E 1  passed through the diaphragm  4  is accelerated by the acceleration electrode  3  and emitted from the electron gun EG. 
     The same voltage is applied to each of the diaphragm  4 , the shield  5 , and the shield  6  provided on the extraction electrode  2 , and the positive voltage V 1  is applied as in the extraction electrode  2 . 
       FIG. 3  is a schematic view illustrating a charged particle beam device  100  including the electron gun EG described with reference to  FIGS. 1 and 2 . In addition, in the first embodiment, the charged particle beam device  100  is a scanning electron microscope (SEM), for example. 
     As illustrated in  FIG. 3 , the charged particle beam device  100  includes the electron gun EG, an electron lens  10 , a deflection coil  11 , a stage  12 , and a detector  14 . Actually, these are included in one housing, and this housing also includes a control circuit and the like for controlling each configuration, although illustrations thereof are omitted herein. 
     To observe a sample  13  to be inspected, the sample  13  is mounted on the stage  12 . The electron beam E 1  emitted from the electron gun EG is reduced to a specific magnification by the electron lens  10  and focused as an electron spot on the sample  13 . The electron lens  10  is an electromagnet having a coil, and the electromagnetic field generated from the electron lens  10  serves as a lens that exerts a focusing action on the electron beam E 1 . Further, the electron beam E 1  is scanned over a desired position in the sample  13  by the deflection coil  11 . 
     For example, the detector  14  is a secondary electron detector, and detects secondary electrons E 2  that are generated from the sample  13  when the electron beam E 1  collides with the sample  13 . An SEM image can be obtained by displaying the amount of the detected secondary electrons E 2  as brightness on an image processing device or the like electrically connected to the detector  14 . 
     Note that, in addition to the detector  14  described above, the charged particle beam device  100  may include a backscattered electron detector for detecting backscattered electrons, an X-ray detector for detecting the spectrum of X-rays generated from the sample  13  and performing elemental analysis of the sample  13 , and the like. 
     &lt;Structure of Extraction Electrode  2  of Electron Gun in Study Example and Problems Thereof&gt; 
       FIG. 4  is an enlarged cross-sectional view illustrating a main part of an electron gun in the study example, illustrating the structure of the extraction electrode  2 . Further,  FIG. 4  also illustrates the equipotential lines and secondary electrons E 3  generated around the extraction electrode  2 . 
     The electron gun and the extraction electrode  2  in the study example have substantially the same structure as the electron gun EG and the extraction electrode  2  in the first embodiment, but are different from the first embodiment in that the shield  5  and the shield  6  are not provided above and below the diaphragm  4 . 
     Most of the electron beam E 1  that does not pass through the opening OP 4  of the diaphragm  4  collides with the diaphragm  4  and is absorbed by the diaphragm  4 . However, as illustrated in  FIG. 4 , some of such electron beams E 1  generate the secondary electrons E 3  at the time of collision. While there is a large number of secondary electrons E 3  actually generated, only one secondary electron E 3  is illustrated herein as an example. 
     In the vicinity of the opening OP 4  of the diaphragm  4 , a part of the electric field formed between the extraction electrode  2  and the acceleration electrode  3  slightly protrudes from the lower side toward the upper side of the opening OP 4 . Due to this protruding electric field, the secondary electrons E 3  generated in the vicinity of the opening OP 4  receive a force in the direction of passing through the diaphragm  4  (to lower side of the opening OP 4 ), further are accelerated by the acceleration electrode  3 , are mixed with the electron beam E 1 , and are emitted from the electron gun EG. 
     The secondary electrons E 3  emitted from the electron gun EG have lower energy than the electron beam E 1  which is the primary electron (main beam) directly emitted from the electron source  1 , but are observed as a flare in the charged particle beam device  100 . As described above, the flare causes a decrease in the S/N ratio and a decrease in the resolution of the observation image in the charged particle beam device  100 . 
     &lt;Main Features of Electron Gun EG in First Embodiment&gt; 
     The electron gun EG in the first embodiment is one devised in order to suppress the problem of the study example described above.  FIG. 5  corresponds to the same region as that of  FIG. 4 , and illustrates the structure of the extraction electrode  2  in the first embodiment. 
     As illustrated in  FIG. 5 , in the first embodiment, the shield  5  is provided above the diaphragm  4 . When the electron beam E 1  collides with the shield  5  or the extraction electrode  2 , secondary electrons E 4  are generated, and when the electron beam E 1  collides with the diaphragm  4 , secondary electrons E 5  are generated. Further, since the opening diameter of the opening OP 6  is smaller than the opening diameter of the opening OP 4 , the electron beam E 1  does not collide with the shield  6 . That is, secondary electrons are not generated from the shield  6 . 
     In this case, in the vicinity of the opening OP 5  of the shield  5 , a part of the electric field formed between the electron gun EG and the extraction electrode  2  slightly protrudes downward toward the lower side in the opening OP 5 . Further, in the vicinity of the opening OP 6  of the shield  6 , a part of the electric field formed between the acceleration electrode  3  and the extraction electrode  2  slightly protrudes upward toward the upper side in the opening OP 6 . 
     However, since the diaphragm  4  is separated from the shield  5  and the shield  6  at sufficient distance, the peripheries of the diaphragm  4  and the opening OP 4  are in an electric field-free state, and at least the inside of the opening OP 4  has no electric field. Therefore, as illustrated in  FIG. 5 , most of the low-energy secondary electrons E 4  is not passed through the opening OP 5  and easily absorbed by the surface of the shield  5  or the extraction electrode  2 . In this case, a part of the secondary electrons E 4  may sometimes be passed through the opening OP 5  and headed toward the diaphragm  4 . However, since the opening diameter of the opening OP 4  is smaller than the opening diameter of the opening OP 5 , the secondary electrons E 4  are blocked by the diaphragm  4  and hardly pass through the opening OP 4  of the diaphragm  4 . 
     Further, for the secondary electrons E 5  generated in the diaphragm  4 , since there is no electric field around the diaphragm  4  and the opening OP 4 , the secondary electrons E 5  are easily absorbed by the surface of the diaphragm  4 . As illustrated in  FIG. 1  and the like, the high-energy electron beam E 1  is passed through the opening OP 4  toward the acceleration electrode  3  side and emitted from the electron gun EG. 
     As described above, since mixing of the secondary electrons E 4  and E 5  generated in the shield  5  and the diaphragm  4  and the electron beam E 1  which is the main beam is suppressed, the occurrence of flare during observation using the charged particle beam device  100  is reduced. 
     Hereinafter, the relative relationship between the shapes of the diaphragm  4 , the shield  5 , and the shield  6  included in the extraction electrode  2  will be described with reference to  FIGS. 6 and 7 . Regarding the structures of the diaphragm  4 , the shield  5 , and the shield  6 , reference is also made to the  FIG. 2  described above. 
     Further, in other words, the side of the diaphragm  4  in the opening OP 4 , the side of the shield  5  in the opening OP 5 , and the side of the shield  6  in the opening OP 6  are the ends of the diaphragm  4 , the shield  5 , and the shield  6  in the cross-sectional view. Therefore, in the following description, each side may be described as an end of the diaphragm  4 , an end of the shield  5 , and an end of the shield  6 . 
     As illustrated in  FIG. 6 , an opening diameter D 5  of the opening OP 5  is greater than an opening diameter D 4  of the opening OP 4 . Further, in a plan view, the opening OP 4  overlaps with the opening OP 5  and is included in the opening OP 5 . In other words, the end of the shield  5  is positioned closer to the extraction electrode  2  than the end of the diaphragm  4 . In other words, the end of the shield  5  is positioned farther from the optical axis OA than the end of the diaphragm  4 . This is because the electron beam E 1  is blocked by the shield  5  before the electron beam E 1  reaches the diaphragm  4  when the opening diameter D 5  is smaller than the opening diameter D 4 . Basically, the passage of the electron beam E 1  in the first embodiment is controlled by the shape of the diaphragm  4 , rather than by the shape of the shield  5 . 
     Further, a distance L 45  between the shield  5  and the diaphragm  4  is the same as the opening diameter D 5  of the opening OP 5  or greater than the opening diameter D 5 . Further, a distance L 46  between the shield  6  and the diaphragm  4  is the same as an opening diameter D 6  of the opening OP 6  or greater than the opening diameter D 6 . By increasing the distance L 45  and the distance L 46 , the periphery of the diaphragm  4  is less likely to be affected by the electric fields from the shield  5  and the shield  6 , and is likely to be in an electric field-free state. Further, since the aspect ratio defined by “the distance L 45 /the opening diameter D 5 ” increases, it is difficult for the secondary electrons E 4  generated in the vicinity of the shield  5  to reach the diaphragm  4 . 
     The opening diameter D 6  of the opening OP 6  is greater than the opening diameter D 4  of the opening OP 4 . Further, in a plan view, the opening OP 4  overlaps with the opening OP 6  and is included in the opening OP 6 . In other words, the end of the shield  6  is positioned closer to the extraction electrode  2  than the end of the diaphragm  4 . In other words, the end of the shield  6  is positioned farther from the optical axis OA than the end of the diaphragm  4 . This is because when the opening diameter D 6  is the same as the opening diameter D 4  or smaller than the opening diameter D 4 , the electron beam E 1  passed through the diaphragm  4  is blocked by the shield  6 . This will be described in more detail with reference to  FIG. 7 . 
     The electron beam region EA illustrated in  FIG. 7  represents a region in which a part of the electron beam E 1  emitted from the electron source  1  is passed through the opening OP 4  of the diaphragm  4 . In  FIG. 7 , the electron beam region EA is a region surrounded by the lines connecting the tip of the electron source  1  and the sides of the diaphragm  4  in the opening OP 4 , and virtual extension lines VEL below the opening OP 4 . When drawing the lines connecting the tip of the electron source and the sides of the diaphragm  4  in the opening OP 4 , the virtual extension lines VEL may be extended from these lines to the shield  6  side, and are represented by broken lines. 
     Below the opening OP 4 , the electron beam E 1  has a strong tendency to be focused inside (to the optical axis side) the virtual extension lines VEL, so that there is no or few electron beams E 1  passed outside the virtual extension lines VEL. 
     In this case, the shape of the opening OP 6  of the shield  6  needs to be considered so as not to block the electron beam region EA. Therefore, the end of the shield  6  is preferably positioned outside the virtual extension lines VEL and is preferably positioned closer to the extraction electrode  2  than the virtual extension lines VEL. In other words, the opening diameter D 6  of the opening OP 6  is adjusted such that the virtual extension lines VEL do not come into contact with the shield  6  and are extended through the inside of the opening OP 6 . 
     Further, the opening diameter D 5  and the opening diameter D 6  are individually determined mainly by the strength of the electric field between the electron beam E 1  and the extraction electrode  2  and the strength of the electric field between the acceleration electrode  3  and the extraction electrode  2 , respectively. Therefore, the opening diameter D 5  and the opening diameter D 6  may have the same length or may have different lengths from each other. For the same reason, the distance L 45  and the distance L 46  may have the same length or may have different lengths from each other. 
     Meanwhile, the opening diameter D 6  has restrictions on the virtual extension lines VEL as described with reference to  FIG. 7 , but the opening diameter D 5  does not have such restrictions. 
     Therefore, in order to reduce the secondary electrons E 4  generated in the vicinity of the shield  5  and suppress flare caused by the secondary electrons E 4  more efficiently, the opening diameter D 5  may be configured to be smaller than the opening diameter D 6 . 
     As described above, by using the electron gun EG of the first embodiment, it is possible to suppress mixing of the secondary electrons E 4  and E 5  into the electron beam E 1 . Further, when the electron gun EG is used in the charged particle beam device  100 , since mixing of the secondary electrons E 4  and E 5  is suppressed, the occurrence of flare is reduced, and problems such as a decrease in the S/N ratio of the observation image, a decrease in resolution, and the like are suppressed. That is, the accuracy of the observation image obtained by the charged particle beam device  100  can be improved. 
     (Modification) 
     A modification of the first embodiment will be described below with reference to  FIG. 8 . In the electron gun EG according to the modification, the structure other than the extraction electrode  2  is the same as that in the first embodiment. 
     In the first embodiment, the extraction electrode  2  includes one shield  5  and one shield  6 , but in the modification, the extraction electrode  2  includes a plurality of shields  5  and a plurality of shields  6 . In  FIG. 8 , as an example of the plurality of shields  5  and the plurality of shields  6 , it is illustrated that two shields  5   a  and  5   b  are provided above the diaphragm  4 , and two shields  6   a  and  6   b  are provided below the diaphragm  4 . 
     The shield  5   b  is positioned above the diaphragm  4  apart from the diaphragm  4 , and the shield  5   a  is positioned above the shield  5   b  apart from the shield  5   b . In addition, the shield  6   a  is positioned below the diaphragm  4  apart from the diaphragm  4 , and the shield  6   b  is positioned above the shield  6   a  apart from the shield  6   a.    
     The same voltage is applied to the shields  5   a  and  5   b  and the shields  6   a  and  6   b , respectively, and the positive voltage V 1  illustrated in  FIG. 1  is applied thereto in the same manner as the extraction electrode  2  and the diaphragm  4 . In addition, the distance L 45  and the distance L 46  described in  FIG. 6  are applied to the respective distances between the shield  5   b  and the shield  6   a  closest to the diaphragm  4  and the diaphragm  4 . 
     Further, the opening diameter D 5  is applied to the respective opening diameters of openings OP 5   a  and OP 5   b  of the shields  5   a  and  5   b  in the same manner as the opening OP 5  of the shield  5 , and the opening diameter D 6  is applied to the respective opening diameters of openings OP 6   a  and OP 6   b  of the shields  6   a  and  6   b  in the same manner as the opening OP 6  of the shield  6 . 
     Further, respective ends of the shields  6   a  and  6   b  are preferably positioned outside the virtual extension lines VEL and are preferably positioned closer to the extraction electrode  2  than the virtual extension lines VEL for the same reason as described in  FIG. 7 . That is, the opening diameter D 6  of the openings OP 6   a  and OP 6   b  is adjusted such that the virtual extension lines VEL are extended through the inside of each of the openings OP 6   a  and OP 6   b.    
     As described above, when the extraction electrode  2  includes the plurality of shields  5   a  and  5   b  and the plurality of shields  6   a  and  6   b , mixing of the secondary electrons E 4  and E 5  into the electron beam E 1  can also be suppressed. Further, when the electron gun EG according to the modification is used in the charged particle beam device  100 , problems such as a decrease in the S/N ratio of the observation image, a decrease in resolution, and the like are also suppressed. 
     The number of each of the shield  5  and the shield  6  is not limited to two such as the shields  5   a  and  5   b  and the shields  6   a  and  6   b , and may be three or more. Further, the number of shields  5  and the number of shields  6  may be different from each other. 
     Although the present invention has been specifically described above based on the embodiments for carrying out the present invention, the present invention is not limited to the embodiments described above and can be variously modified without departing from the gist thereof. 
     For example, in the embodiments described above, the Schottky type electron gun EG has been described, but the technique disclosed in the embodiments described above can also be applied to the electric field emission type electron gun. 
     Further, in the embodiments described above, the scanning electron microscope (SEM) has been described as an example of the charged particle beam device  100  including the electron gun EG, but the technique disclosed in the embodiment described above can also be applied to a scanning transmission electron microscope (STEM) or a transmission electron microscope (TEM). 
     Further, the idea of the electron gun EG disclosed in the embodiments described above is not limited to the technique of emitting an electron beam, and can be applied to a technique of emitting an ion beam such as a focused ion beam (FIB) device, for example. That is, the electron source  1  can be used as an ion source, the electron gun EG can be used as an ion gun, and the charged particle beam device  100  can be used as an FIB device. In that case, when the ion beam (primary ion) is passed through the diaphragm  4 , most of the ion beam collides with the shield  5  or the diaphragm  4 , and secondary ions are generated, but it is possible to suppress mixing of the secondary ions into the ion beam by the same technical idea as in the embodiments described above. Therefore, in the FIB device, the occurrence of flare can be suppressed. 
     Further, the electron gun EG disclosed in the embodiments described above is not limited to an inspection device for obtaining an observation image, and can be applied to a wide range of technical fields as a mechanism for simply emitting an electron beam or an ion beam. 
     REFERENCE SIGNS LIST 
     
         
         
           
               1 : electron source 
               2 : extraction electrode 
               3 : acceleration electrode 
               4 : diaphragm 
               5 ,  5   a ,  5   b : shield (electric field shielding plate) 
               6 ,  6   a ,  6   b : shield (electric field shielding plate) 
               7 : filament 
               8 : zirconium oxide layer 
               9 : suppressor electrode 
               10 : electron lens 
               11 : deflection coil 
               12 : stage 
               13 : sample 
               14 : detector 
               100 : charged particle beam device 
             D 4  to D 6 : opening diameter 
             E 1 : electron beam (primary electron, electron beam) 
             E 2 -E 5 : secondary electron 
             EA: electron beam region 
             EG: electron gun 
             If: current source 
             L 45 , L 46 : distance 
             OA: optical axis 
             OP 4 : opening 
             OP 5 , OP 5   a , OP 5   b : opening 
             OP 6 , OP 6   a , OP 6   b : opening