Abstract:
A beam source of an inspection apparatus discharges a beam, and a stage system holds a specimen and moves in at least one direction. A primary optical system directs the beam to the specimen, and a secondary optical system guides a secondary beam coming from the specimen. A sensor outputs an electric signal of the specimen image from the secondary beam, an image processor generates image information of the specimen by processing the electric signal output by the sensor, and a host computer generates an inspection timing signal for controlling the sensor to transfer the image information at a preset data transfer rate.

Description:
BACKGROUND OF THE INVENTION  
       [0001]     1. Field of Invention  
         [0002]     The present invention relates to an electron beam apparatus for irradiating a specimen to be inspected with an electron beam, and an inspection apparatus and inspection-method for inspecting the specimen by the use of this electron beam apparatus.  
         [0003]     2. Related Background Art  
         [0004]     As is generally known, an electron beam apparatus for irradiating the specimen with an electron beam is equipped with an electron gun and electron optical system (electron lenses, etc.). In the electron beam apparatus, the electron beam discharged from the electron gun is applied on the specimen surface via the electron-optical system.  
         [0005]     For an example of the equipment incorporating this electron beam apparatus, a description will be made on a scanning electron microscope (SEM) and electron beam inspection apparatus (EB inspection apparatus). By the way, to the SEM and EB inspection apparatus, a mechanism for detecting secondary electrons generated from the specimen by irradiating a specimen with an electron beam and creating a specimen image is incorporated.  
         [0006]     To acquire the specimen image in SEM, the specimen is held stationary and the specimen surface is two-dimensionally scanned with the electron beam squeezed in the form of spot (spot beam). Consequently, SEM is popularly used for observing a comparatively small region (defect portion, etc.) of the specimen surface. The inspection of the whole specimen surface by SEM is not realistic due to its slow throughput.  
         [0007]     As against this, the EB inspection apparatus has been under development in recent years in order to satisfy the requirements of inspecting a comparatively wide area or the whole area of the specimen surface.  
         [0008]     For example, in the Japanese Patent Application Laid-Open(JP-A) No. 7-249393 or in the Japanese Patent Application Laid-Open(JP-A) No. 10-197462, there are disclosed EB inspection apparatus in which by scanning the specimen surface with the electron beam shaped in the form of a rectangle (rectangle beam) while the stage is being continuously moved, the specimen image is obtained.  
         [0009]     In addition, in the Japanese Patent Application Laid-Open(JP-A) No. 10-294345, there is disclosed an EB inspection apparatus which acquires the specimen image by continuously moving the stage in one direction and allowing the spot beam to scan the specimen surface in the direction crossing at right angles the one direction mentioned above.  
         [0010]     In these EB inspection apparatus, since the specimen image is acquired while the stage is being moved, the specimen image is able to be taken in continuously from a comparatively wide area or the whole area of the specimen surface. Consequently, the EB inspection apparatus is able to inspect the specimen surface at an incomparably higher speed than that of the whole surface inspection by SEM.  
         [0011]     In addition, in the above-mentioned EB inspection apparatus, the inspection speed is able to be increased as much as the stage moving speed is increased.  
       SUMMARY OF THE INVENTION  
       [0012]     Now, in the conventional EB inspection apparatus mentioned above, simply increasing the stage moving speed lowers the total current volume of electron beam irradiated over the specimen (hereinafter called the “dosage”) and the specimen image is degraded. In order to prevent this image degradation, the current volume of the electron beam discharged from the electron gun must be increased as much as the stage moving speed is increased. In this way, the high-speed inspection in the conventional EB inspection apparatus has been carried out by continuously irradiating the specimen surface with the large-current electron beam while the stage is being continuously moved at a high speed. However, even during the high-speed inspection, the stage may be stopped or the moving speed may be decreased for some reason. If this kind of stage stop or speed reduction should occur during the high-speed inspection, the large-current electron beam continued to strike against the same place or the vicinity of the specimen surface, and the dosage rapidly increases at the relevant place.  
         [0013]     On the other hand, there is a limit of acceptable dosage for the specimen, and if the electron beam continues to be irradiated to the level exceeding the allowable range of the dosage, contamination or charge-up occurs in the specimen, or for the worst, the specimen may be destroyed.  
         [0014]     This kind of problem occurs even when the scanning by the spot beam is stopped or decelerated in the EB inspection apparatus disclosed in the Japanese Patent Application Laid-open(JP-A) No. 10-294345.  
         [0015]     It is an object of the present invention to provide an electron beam apparatus, inspection apparatus, and inspection method that can prevent a rapid increase of dosage caused by stop or deceleration of the relative move and can protect the specimen when the specimen is irradiated with the electron beam while the specimen and the electron beam are being relatively moved.  
         [0016]     An electron beam apparatus according to the present invention is an electron beam apparatus for irradiating a specimen to be inspected with the electron beam comprising an electron beam outputting means for outputting the electron beam, a measuring means for measuring the dosage of electron beam irradiated per unit area of the specimen, a storage section for storing the predetermined dosage per unit area for the specimen, a detection means for detecting over exposure of the electron beam when the dosage per unit are a measured by the measuring means is greater than the dosage per unit area stored in the storage section, and a control means for controlling the electron beam outputting means to reduce the dosage per unit area of the electron beam than the dosage per unit area stored in the storage section, when the over exposure of electron beam is detected by the detection means.  
         [0017]     When the dosage of electron beam irradiated per unit area of the specimen is measured by the measuring means and the measured dosage is detected to be larger than the dosage stored in advance in the storage section in this way, the electron beam outputting means is controlled to reduce the dosage than that stored in the storage section. By this, when the specimen is irradiated with the electron beam while the electron beam irradiating position and the specimen position are relatively moved, the dosage of the electron beam to be applied to the specimen is able to be held to a predetermined dosage range stored in the storage section.  
         [0018]     In addition, in the electron beam apparatus, the control means desirably controls to make the dosage of electron beam per unit area smaller than the dosage per unit area stored in the storage section when the over exposure of electron beam is detected over a specified time.  
         [0019]     In the electron beam apparatus, the control means controls the electron beam outputting means in such a manner to make the dosage per unit area of the electron beam applied to the specimen smaller than the dosage per unit area stored in the storage section by expanding the irradiation range of the electron beam.  
         [0020]     Furthermore, the electron beam apparatus may further comprise a stage for placing the specimen and a moving means for moving the stage, and may be characterized in that the measuring means measures the dosage per unit area in accordance with the output current volume of electron beam and the moving speed of the stage moved by the moving means.  
         [0021]     Because the irradiation current volume of the electron beam applied to the specimen placed on a stage has a specified relation with the output current volume of the electron beam, the dosage per unit area is able to be measured in accordance with the output current volume of the electron beam and the stage moving speed.  
         [0022]     In the electron beam apparatus, the measuring means may be measure the dosage per unit area in accordance with the secondary beam volume generated from the specimen.  
         [0023]     Because the volume of the secondary beam generated from the specimen is defined in accordance with the volume of the electron beam impinging on the specimen, the dosage is able to be measured by the volume of the secondary beam.  
         [0024]     The electron beam apparatus according to the present invention comprises an electron beam output means for outputting the electron beam, a stage irradiated with the electron beam outputted by the electron beam outputting means, a moving means for moving the stage, a storage section for storing the stage moving speed predetermined in accordance with the specimen and the output current volume of the electron beam, a detection means for detecting over exposure of the electron beam when the moving speed of the stage moved by the moving means is smaller than the moving speed stored in the storage section, and a control means for controlling the electron beam outputting means to prevent the stage from being irradiated with the electron beam when the over exposure of electron beam is detected by the detection means.  
         [0025]     In this way, when the stage moving speed by the moving means is compared with the predetermined moving speed stored in the storage section and if the actual stage moving speed is smaller than the moving speed stored in the storage section, the over exposure of electron beam is detected. And when the over exposure of electron beam is detected, the control means controls the electron beam not to be applied to the stage, thereby quickly detecting the over exposure of the electron beam and stopping the electron beam from being irradiated over the stage.  
         [0026]     The electron beam apparatus according to the present invention is an electron beam apparatus for irradiating the specimen to be inspected with the electron beam, and comprises an electron beam outputting means for outputting the electron beam, a storage section for storing the output current volume of the electron beam and the volume of the secondary beam predetermined in accordance with the specimen and the output current volume of the electron beam, a detection means for detecting the over exposure of the electron beam when the volume of the secondary beam generated from the specimen is greater than the volume of the secondary beam stored in the storage section, and a control means for controlling the electron beam outputting means to prevent the stage from being irradiated with the electron beam when the over exposure of the electron beam is detected by the detection means.  
         [0027]     The volume of the secondary beam generated from the specimen in this way is compared with the volume of the secondary beam stored in the storage section, and when the volume of the generated secondary beam is greater than the volume of the secondary beam stored in the storage section, the over exposure of the electron beam is detected. And when the over exposure of the electron beam is detected, the control means controls the electron beam from being applied to the stage, thereby quickly detecting the over exposure of the electron beam and preventing the electron beam from being applied to the stage.  
         [0028]     The inspection apparatus according to the present invention comprises the electron beam apparatus and an image acquisition means for acquiring the image information of the specimen in accordance with the secondary beam generated from the specimen.  
         [0029]     By configuring an inspection apparatus equipped with an electron beam apparatus, it is possible to prevent the condition in which the specimen to be inspected is destroyed by over exposure of the electron beam.  
         [0030]     In addition, in the inspection apparatus, the measuring means may be intended to measure the dosage on the basis of the output current volume of the electron beam and the contrast ratio of the image information acquired by the image acquisition means.  
         [0031]     Because the contrast ratio of the image information formed on the basis of the secondary beam is determined by the dosage of the electron beam impinged in the specimen, the dosage can be measured by the contrast ratio of the image information.  
         [0032]     In addition, the inspection apparatus according to the present invention is an inspection apparatus for inspecting the specimen by irradiating the specimen to be inspected with the electron beam, comprises an electron beam outputting means for outputting the electron beam and irradiating the specimen with the electron beam, a storage section for storing the contrast ratio predetermined on the basis of the specimen and the output current volume of the electron beam, a detection means for detecting the over exposure of the electron beam when the contrast ratio of the image information acquired by the image acquisition means is greater than the contrast ratio stored in the storage section, and a control means for controlling the electron beam outputting means to prevent the electron beam from being applied to the specimen.  
         [0033]     In this way, the contrast ratio of the image information based on the secondary beam generated from the specimen is compared with the contrast ratio of the image information predetermined and stored in the storage section, and when the contrast ratio of the image information based on the secondary beam actually generated is greater than the contrast ratio of the image information stored in the storage section, the over exposure of the electron beam is detected. And when the over exposure of the electron beam is detected, the control means controls the electron beam from being applied to the specimen to quickly detect the over exposure of the electron beam and stops electron beam from being applied to the specimen.  
         [0034]     The inspection method according to the present invention is an inspection method for inspecting the specimen by irradiating the specimen to be inspected with the electron beam and comprises an electron beam irradiation step for outputting the electron beam and irradiating the specimen with the electron beam, an image acquisition step for acquiring the image information of the specimen based on the secondary beam generated from the specimen, a measuring step for measuring the dosage of the electron beam irradiated per unit area of the specimen, a detection step for detecting the over exposure of the electron beam when the dosage per unit area measured in the measuring step is greater than the dosage per unit area predetermined for the specimen, and a control step for controlling the electron beam outputting means in such a manner that the dosage per unit area of the electron beam is made smaller than the dosage per unit area stored in the storage section when the over exposure of the electron beam is detected in the detection step.  
         [0035]     The dosage of the electron beam irradiated per unit area of the specimen is measured in this way, and the measured dosage and the dosage stored in the storage section predetermined are compared to detect the over exposure of the electron beam. And because the dosage is brought to be reduced when the over exposure of the electron beam is detected, it is possible to prevent the condition in which the specimen to be inspected is not destroyed by the electron beam.  
         [0036]     The inspection method according to the present invention is an inspection method for inspecting the specimen by irradiating the specimen to be inspected with the electron beam, and comprises an electron beam irradiating step for outputting the electron beam to irradiate the specimen with the electron beam, an image acquisition step for acquiring the image information of the specimen based on the secondary beam generated from the specimen, a stage moving step for moving the stage with the specimen placed, and a detection step for detecting the over exposure of the electron beam when the moving speed of the stage moved in the stage moving step is smaller than the stage moving speed predetermined in accordance with the specimen and the output current volume of the electron beam, and a control step for controlling the electron beam to prevent the stage from being irradiated with the electron beam when the stage is detected to be overexposed with the electron beam in the detection step.  
         [0037]     In this way, when the stage moving speed is compared with the moving speed predetermined and stored in the storage section and the moving speed of the actual stage is smaller than the moving speed stored in the storage section, the over exposure of the electron beam is detected. And when the over exposure of the electron beam is detected, control is made to prevent the stage from being irradiated with the electron beam in the control step. With this contrivance, the over exposure of the electron beam is quickly detected and it is able to stop the stage from being irradiated with the electron beam.  
         [0038]     The present invention will be more fully understood from the detailed description given hereinbelow and the accompanying drawings, which are given by way of illustration only and are not to be considered as limiting the present invention.  
         [0039]     Further scope of applicability of the present invention will become apparent from the detailed description given herein after. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will be apparent to those skilled in the art from this detailed description. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0040]      FIG. 1  is a drawing showing the overall configuration of the EB inspection apparatus  10  according to the present embodiment;  
         [0041]      FIG. 2  is a drawing showing the configuration of the primary optical system  23 ;  
         [0042]      FIG. 3  is a drawing showing the configuration of the primary polarizer  24  and the secondary polarizer  38 ;  
         [0043]      FIG. 4  is a drawing showing trajectories of the primary beam and the secondary beam;  
         [0044]      FIG. 5  is a drawing explaining the irradiation region  21 A of the primary beam;  
         [0045]      FIG. 6  is a drawing explaining the deflection of the primary beam by the primary polarizer  24 ;  
         [0046]      FIG. 7  is a drawing explaining the deflection of the primary beam by the secondary polarizer  38 ;  
         [0047]      FIG. 8A  is a drawing explaining the move of the specimen image  45 A by the secondary polarizer  38 ;  
         [0048]      FIG. 8B  is a drawing explaining the move of the specimen image  45 A by the secondary polarizer  38 ;  
         [0049]      FIG. 8C  is a drawing explaining the move of the specimen image  45 A by the secondary polarizer  38 ;  
         [0050]      FIG. 9A  is a drawing explaining the move of the specimen image  45 A by the stage  28 ;  
         [0051]      FIG. 9B  is a drawing explaining the move of the specimen image  45 A by the stage  28 ;  
         [0052]      FIG. 9C  is a drawing explaining the move of the specimen image  45 A by the stage  28 ;  
         [0053]      FIG. 10  is a drawing explaining the TDI sensor  45 ;  
         [0054]      FIG. 1A  is a flow chart explaining the specimen protection mechanism;  
         [0055]      FIG. 11B  is a flow chart explaining the specimen protection mechanism;  
         [0056]      FIG. 12  is a drawing showing the other example of the EB inspection apparatus according to the present embodiment; and  
         [0057]      FIG. 13  is a drawing showing another example of the EB inspection apparatus according to the present embodiment. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0058]     Referring now to the drawings, preferable embodiments according to the present invention will be described in detail hereinafter. In explaining the drawings, the like reference characters are assigned to like or corresponding parts throughout, and redundant explanation will be omitted.  
         [0059]      FIG. 1  is a drawing showing the EB inspection apparatus  10  that incorporates the electron beam apparatus according to the present embodiment. The EB inspection apparatus  10  has a capability to acquire the image of the specimen placed on the stage  28 , and it is able to change over the operation mode for acquiring the specimen image with the stage  28  stopped (hereinafter called the “observation mode”) to the operation mode for acquiring the specimen image at a high-speed with the stage  28  moved (herein after called the “inspection mode”). The EB inspection apparatus  10  is characterized in a mechanism  50  incorporated for protecting the specimen on the stage  28  (hereinafter called the “specimen protection mechanism”) when the operation in the inspection mode becomes a condition in which the specimen is irradiated with the electron beam in excess for some reason. The specimen protection mechanism  50  will be described later.  
         [0060]     The EB inspection apparatus  10  is equipped with the primary column  11 , secondary column  12 , and the chamber  13  as illustrated in  FIG. 1 . The primary column  11  is mounted aslant to the side surface of the secondary column  12 . To the lower part of the secondary column  12 , the chamber  13  is installed. These primary column  11 , secondary column  12 , and chamber  13  are evacuated by a turbo pump of the vacuum evacuation system not illustrated, and the vacuum condition inside is maintained.  
         [0061]     Now, the description will be made on the configuration of the primary column  11 , secondary column  12 , and chamber  13 , respectively.  
         [0062]     Inside the primary column  11 , an electron gun  21  is arranged. The electron gun  21  accelerates and converges the thermion discharged from the cathode, and releases the electron beam. For the cathode of the electron gun  21 , lanthanum hexaborite (LaB6) that is generally a rectangle cathode and can take out a large current is used. To the electron gun  21 , an electron gun control unit  22  for controlling the acceleration voltage Vac of the electron gun  21  and on-off controlling the power-supply of the electron gun  21  are connected. Furthermore, a gun alignment mechanism or gun aligner not illustrated for adjusting the position of the electron gun  21  are also mounted.  
         [0063]     On the optical axis of the electron beam discharged from the electron gun  21  (hereinafter called the “primary beam B 1 ”), the primary optical system  23  formed in three stages, a primary polarizer  24 , and an aperture  25  are arranged. Each stage of the primary optical system  23  consists of electrostatic quadrupole (or octupole) lenses (or electromagnetic lenses) of asymmetry rotation axis. For example, in the case of the electrostatic lens in which each of the primary optical system  23  consists of four cylindrical rods 1-4 as shown in  FIG. 2 , the cylindrical rods which are opposite to each other (1 and 3, 2 and 4) are set to the equivalent potential, and are provided with opposite voltage characteristics (+Vq to 1 and 3, −Vq to 2 and 4). With this configuration, same as the so-called cylindrical lens, the primary beam B 1  is able to be focused or diverged. Consequently, according to this primary optical system  23 , the lens voltage of each electrostatic lens is optimized and the cross section D of the primary beam B 1  is able to be shaped into an optional form (rectangular or elliptical) without losing the discharged electrons.  FIG. 2  shows the case in which the cross section of the primary beam B 1  is rectangle. The lens voltage of each stage of the primary optical system  23  is controlled by the primary column control unit  26  (see  FIG. 1 ) connected to the primary optical system  23 .  
         [0064]     The primary polarizer  24  is formed by a electrostatic polarizer or electromagnetic polarizer. For example, when the primary polarizer  24  is an electrostatic polarizer consisting of four independent electrodes  5  to  8  as shown in  FIG. 3 , varying the voltage applied to the electrodes  6 ,  8  which are located opposite to each other along the X-axis can deviate the trajectory of the primary beam B 1  in the X direction. In addition, varying the voltage applied to the electrodes  5 ,  7  which are located opposite to each other along the Y-axis can deviate the trajectory of the primary beam B 1  in the Y direction. The voltage applied to each electrode of the primary polarizer  24  is controlled by the primary polarizer control unit  27  connected to the primary polarizer  24 .  
         [0065]     The electron gun control unit  22 , primary column control unit  26 , and primary polarizer control unit  27  are connected to the host computer  14 .  
         [0066]     Now, the description will be made on the chamber  13 . Inside the chamber  13 , a stage  28  on which the specimen  15  is placed and at the same time which is movable to X and Y directions is installed. To the stage  28 , the specified retarding voltage Vr (later discussed) is applied. To the stage  28 , a stage control unit  29  is connected. The stage control unit  29  drives the stage  28  in the X and Y directions and at the same time, reads the X, Y position of the stage  28  by the use of a laser interferometer (the data rate is, for example, 10 Hz), and outputs the XY position signal to the host computer  14 . The stage control unit  29  detects the moving speed of the stage  28  based on the XY positions read and outputs the speed signal to the host computer  14 .  
         [0067]     Next description will be made on the secondary column  12 . Inside the secondary column  12 , a cathode lens  31 , numerical aperture  32 , Wien filter  33 , second lens  34 , field aperture  35 , third lens  36 , fourth lens  37 , secondary polarizer  38 , and detector  39  are arranged on the optical axis of the secondary beam B 2  (later discussed) generated from the specimen  15 .  
         [0068]     The cathode lens  31  consists of three electrodes  31   a ,  31   b ,  31   c  as shown, for example, in  FIG. 4 . In this event, to the first electrode  31   a  and the second electrode  31   b  from below the cathode lens  31  (on the specimen  15  side), a specified voltage is applied, and the third electrode  31   c  is set to a zero potential  
         [0069]     The numerical aperture  32  corresponds to the opening throttle, and determines the opening angle of the cathode lens  31 . The numerical aperture  32  is a thin film plate made of metal (Mo, etc.) with a round opening section formed, and the opening section is arranged to become a focus position of the cathode lens  31 . Consequently, the numerical aperture  32  and the cathode lens  31  form a telecentric electron optical system. The numerical aperture  32  plays a function to impede the unwanted electron beam that scatters in the EB inspection apparatus  10  from reaching the specimen  15  in order to prevent contamination of the specimen  15 . In addition, the numerical aperture  32  plays a role to suppress the lens aberration of the second lens  34  to fourth lens  37  on the latter stages for the secondary beam B 2  (later discussed).  
         [0070]     The Wien filter  33  is a polarizer that works as an electromagnetic prism, which is capable for allowing the charged particle (for example, secondary beam B 2 ) only that satisfies the Wien conditions (E=vB, where v denotes the velocity of the charged particle, E the electric field, B the magnetic field, and E ⊥B) to go straight and bending the trajectories of other charged particles (for example, primary beam B 1 ).  
         [0071]     The second lens  34 , third lens  36 , and fourth lens  37  are all symmetrical rotation axis type lenses called unipotential electrostatic lenses or Einzel lens, and consist of three electrodes, respectively. Each lens generally controls the lens actions by holding the two electrodes on the outside to a zero potential and varying the voltage applied to the center electrode sandwiched in between two electrodes.  
         [0072]     The field aperture  35  is disposed between the second lens  34  and the third lens  36 , and restricts the field of view to a required range as in the case of the field stop of the optical microscope. The field aperture  35  intercepts the unwanted secondary beam B 2  together with the third lens  36  and the fourth lens  37  on the latter stage and prevents charge-up and contamination of the detector  39 .  
         [0073]     Each voltage of the cathode lens  31 , second lens  34 , third lens  36 , and fourth lens  37  as well as the electromagnetic field applied to the Wien filter  33  are controlled by the secondary column control unit  41  connected to the secondary column  12 .  
         [0074]     The secondary polarizer  38  is a biaxially polarizable electrostatic polarizer comprising four independent electrodes  5  to  8  as with the primary polarizer  24  (see  FIG. 3 ) described above. In this case, varying the voltage-applied to electrodes  6 ,  8  can deviate the trajectory of the secondary beam B 2  in the X direction. In addition, varying the voltage applied to electrodes  5 ,  7  can deviate the trajectory of the secondary beam B 2  in the Y direction. The voltage applied to each electrode of the secondary polarizer  38  is controlled by the secondary polarizer control unit  42  connected to the secondary polarizer  38 .  
         [0075]     The detector  39  comprises an MCP (micro channel plate)  43  for accelerating and multiplying electrons, a fluorescent plate  44  for converting an electron image to an optical image, and TDI (time delay and integration) array CCD sensor (hereinafter called the “TDI sensor”)  45  for picking up the optical image. Between the fluorescent plate  44  and the TDI sensor  45 , an optical relay lens  47  is installed, which contracts the optical image on the fluorescent plate  44  to about ⅓ and projects on the image pick-up surface of the TDI sensor  45 .  
         [0076]     Between the fluorescent plate  44  and the optical relay lens  47 , a view port  48  is disposed as a transmission window for transmitting the optical image. With this view port  48 , the inside of the detector  39  is divided into a vacuum chamber  9   a  and an atmospheric chamber  9   b.    
         [0077]     Now, the image pick-up surface of the TDI sensor  45  comprises a plurality of light-receiving pixels arranged two-dimensionally. To the TDI sensor  45 , an image processing unit  46  is connected. The secondary polarizer control unit  42 , secondary column control unit  41 , and image processing unit  46  are connected to the host computer  14 . To the host computer  14 , CRT  16  is connected.  
         [0078]     Next discussion will be made on the host computer  14  connected to each control unit. The host computer  14  comprises a control section  52  for controlling each control unit and the interface section  51  for connecting the control section  52  to each control unit. The control section  52  is also capable for acquiring control information from each control unit. In addition, the host computer  14  has an dosage measuring section  54  for measuring the dosage applied to the specimen in conformity to the control information, a storage section  55  for storing the dosage prescribed for each specimen in memory, and an over exposure detection section  53  for detecting the over exposure of electron beam on the basis of the dosage measured by the dosage measuring section  54  and the dosage stored in the storage section  55 . The specimen protection mechanism  50  comprises a control section  52  that is possessed by the host computer  14 , a dosage measuring section  54 , storage section  55 , and over exposure detection section  53 .  
         [0079]     Now, the trajectory, etc. of the primary beam B 1  and the secondary beam B 2  in the EB inspection apparatus  10  (see  FIG. 1 ) according to the present embodiment will be explained successively.  
         [0080]     The primary beam B 1  is discharged in a current volume corresponding to the acceleration voltage Vac of the electron gun  21 . Now, the current volume of the primary beam B 1  discharged from the electron gun  21  is hereinafter called the “outgoing current volume Ia.” The primary beam B 1  from the electron gun  21  passes and reaches the primary polarizer  24  while being subject to the lens actions of the primary optical system  23 . When no voltage is applied to electrodes  5  to  8  (see  FIG. 3 ) of the primary polarizer, the polarizing action of the primary polarizer  24  does not reach the primary beam B 1 , and the primary beam B 1  passes the primary polarizer  24  and the aperture  25  successively and impinges aslant on the center section of Wien filter  33 .  
         [0081]     The primary beam B 1  incident on the Wien filter  33  has the trajectory bent by the polarizing action of the Wien filter  33 , and reaches the opening section of the numerical aperture  32 . At this place, the primary beam B 1  forms image at the opening section of the numerical aperture by the setting of the lens voltage of the primary optical system  23  (see  FIG. 4 ). The specimen surface  15   a  is irradiated with the primary beam B 1  which formed image at the opening section of the numerical aperture  32  via the cathode lens  31 .  
         [0082]     Since the numerical aperture  32  and the cathode lens  31  compose a telecentric electron optical system, as described above, the primary beam B 1  that has passed the cathode lens  31  becomes a parallel beam. As a result, the primary beam B 1  is applied perpendicularly and uniformly to the specimen surface  15   a . That is, the Kohler illumination of the optical microscope is achieved.  
         [0083]     To the stage  28  on which the specimen  15  is placed, the retarding voltage Vr is applied, and between the electrode  31   a  of the cathode lens  31  and the specimen  15 , a electric field negative to the primary beam B 1  is formed. Consequently, the primary beam B 1  that has passed the cathode lens  31  is decelerated before it reaches the specimen surface  15   a.    
         [0084]     Now, the current volume of the primary beam B 1  applied to the specimen surface  15   a  (hereinafter called the “irradiated current volume Ib”) is far reduced as compared with the outgoing current volume Ia. Here, because the corresponding relation between the irradiated current volume Ib and the outgoing current volume Ia is known, and the corresponding relation between the outgoing current volume Ia and the acceleration voltage Vac of the electron gun  21  is known, the corresponding relation between the irradiated current volume Ib and the acceleration voltage Vac becomes known. Consequently, in the electron gun control unit  22 , the irradiated current volume Ib of the primary beam B 1  is able to be set to a required value by controlling the acceleration voltage Vac of the electron gun  21 . The information concerning the setting of the irradiated current volume Ib is outputted from the electron gun control unit  22  to the host computer  14 .  
         [0085]     By the way, the irradiated current volume Ib is set to different values at the time of observation mode later discussed and at the inspection mode, as shown in Table 1.  
                                         TABLE 1                                   OBSERVATION   INSPECTION           MODE   MODE                                    IRRADIATED CURRENT   62.5   250       VOLUME IB OF PRIMARY       BEAM (NA)                  
 
         [0086]     On the other hand, the profile of the irradiated region  21 A (see  FIG. 4 ) of the primary beam B 1  in the specimen surface  15   a  is shaped into an optional profile (rectangular or elliptical) by controlling the lens voltage of the primary optical system  23 .  FIG. 5  shows an example when the irradiated region  21 A is rectangular. In this way, in the EB inspection apparatus  10  according to the present embodiment, the specimen  15  located inside the rectangular irradiated region  21 A is uniformly irradiated with their radiated current volume Ib by the use of the primary beam B 1  adjusted as described above.  
         [0087]     Now, the dosage Do when the stage  28  is stopped (for example, in the observation mode) is given by the following equation (1) assuming that S denotes the area of the irradiated region  21 A and T denotes the irradiation time of the primary beam B 1 . That is, the dosage Do increases in proportion to the irradiated current volume Ib and the irradiation time T. 
 
 Do∝Ib×T/S   (1) 
 
         [0088]     The dosage Dv when the stage  28  is being moved (for example, in the inspection mode) is given by the following equation (2) when the moving speed V (≠0) of the stage  28  is used. That is, the dosage Dv increases in inverse proportion to the moving velocity V of the stage. 
 
 Dv∝Ib×V/S   (2) 
 
         [0089]     However, for the specimen  15 , there is a limit of dosage which the specimen  15  can accept, and if the primary beam B 1  is irradiated exceeding this allowable range of dosage, contamination or charge-up occurs in the specimen  15  or for the worst, the specimen  15  may be destroyed.  
         [0090]     Consequently, the data concerning the allowable dosage range of the specimen  15  is predetermined for kinds of the specimen  15  and stored in memory in the storage section  55  of the host computer  14 . The data concerning the allowable range of this dosage is utilized by the specimen protection mechanism  50 .  
         [0091]     The XY position of the irradiated region  21 A (see  FIG. 5 ) of the primary beam B 1  can be moved on the specimen surface  15   a  by controlling the voltage applied to the primary polarizer  24  and deviating the trajectory of the primary beam B 1  (see  FIG. 6 ).  
         [0092]     It is also possible to greatly deviate the trajectory of the primary beam B 1  by controlling the voltage applied to the primary polarizer  24  and preventing the primary beam B 1  from passing the opening section of the aperture  25 . The voltage applied to the primary polarizer  24  in this event is called the “blanking voltage.” 
         [0093]     When the specimen  15  is irradiated with the primary beam B 1 , the secondary beam B 2  comprising at least 1 kind of the secondary electron, reflected electron, or backscattered electron is generated from the specimen in the irradiated region  21 A. This secondary beam B 2  has the two-dimensional image information of the irradiated region  21 A. Because the primary beam B 1  is applied perpendicularly with respect to the specimen surface  15 A as described above, the secondary beam B 2  has a clear image free of shades. Now, because the retarding voltage Vr is applied to the stage  28  on which the specimen  15  is held, the electric field positive to the secondary beam B 2  is formed between the specimen  15  and the electrode  31   a  of the cathode lens  31 . Consequently, the secondary beam B 2  generated from the specimen  15  is accelerated towards the cathode lens  31 .  
         [0094]     And the secondary beam B 2  is subject to the focusing action by the cathode lens  31  and passes the numerical aperture  32  and at the same time goes straight as it is without being subject to polarization action of the Wien filter  33 , and forms image at the opening section of the field aperture  3  via the second lens  34 . In this way, it is possible to suppress the generation of the lens aberration by forming the first image of the secondary beam B 2  generated from the specimen  15  by joint efforts of the cathode lens  31  and the second lens  34 .  
         [0095]     By the way, varying the electromagnetic field applied to the Wien filter  33  can select the electron (for example, secondary electron, reflected electron, or backscattered electron) with a specific energy band only from the secondary beam B 2  and allow it to pass.  
         [0096]     The secondary beam B 2  that has passed the field aperture  35  repeats focusing and divergence by the third lens  36  and the fourth lens  37  located in the latter stage and forms image again on the detection surface of the detector  39  after it passes the polarizer  38 . The number of image formations in this event may be one time each (a total of two times) by the third lens  36  and the fourth lens  37  or may be once as a result of cooperation with the third lens  36  and the fourth lens  37 . In either case, the intermediate image of the irradiated region  21 A obtained at the opening section of the field aperture  35  is enlarged and projected on the detection surface of the detector  39  via the third lens  36  and the fourth lens  37 .  
         [0097]     Furthermore, the secondary beam B 2  which formed image again on the detection surface of the detector  39  is accelerated and multiplied when it passes MCP 43  in the detector  39  and converted into light by the fluorescent plate  44 . And the light from the fluorescent plate  44  forms image on the image pickup surface of the TDI sensor  45  via the optical relay lens  47 . That is, the two dimensional image of the irradiated region  21 A enlarged and projected on the detection surface of the detector  39  is converted into the optical image in the fluorescent plate  44  and is projected on the image pick-up surface of the TDI sensor  45  via the optical relay lens  47 . The image of the irradiated region  21 A which is projected on the image pickup surface of this TDI sensor  45  is hereinafter called the “specimen image  45 A.” 
         [0098]     The projection position of the specimen image  45 A is able to be moved on the image pickup surface of the TDI sensor  45  as shown in  FIG. 8A  to  8 C by controlling the voltage applied to the secondary polarizer  38  and deviating (see  FIG. 7 ) the trajectory of the secondary beam B 2 .  
         [0099]     Now, the corresponding relation between the projection position of the specimen image  45 A and the voltage applied to the secondary polarizer  38  is known. Consequently, in the secondary polarizer control unit  42 , it is possible to project the specimen image  45 A to a specified position of the image pickup surface of the TDI sensor  45  or move the specimen image  45 A at a specified velocity. The move of the specimen image  45 A by the secondary polarizer  38  in this way is utilized in the observation mode later discussed.  
         [0100]     Furthermore, the projection position of the specimen image  45 A is able to be moved on the image pickup surface of the TDI sensor  45  as shown in  FIG. 9A  to  9 C by varying the position of the specimen  15  with respect to the irradiated region  21 A (see  FIG. 5 ).  
         [0101]     In this event, in the stage control unit  29 , it is possible to project the specimen image  45 A on the specified position of the image pickup surface of the TDI sensor  45  or move the specimen image  45 A at a specified velocity by controlling the XY position and moving velocity of the stage  28 . Movement of the specimen image  45 A effected by such a stage  28  is utilized in an inspection mode described later.  
         [0102]     Now, the specimen image  45 A projected on the image pickup surface of the TDI sensor  45  is converted to signal charge of a plurality of each light-receiving pixel (see  FIG. 10 ) that compose the image pickup surface of the TDI sensor  45 . And the signal charge of each light receiving pixel is transferred successively in the vertical direction and in the horizontal direction in accordance with the driving pulse imputed from the image processing unit  46 , and is outputted to the image processing unit  46 .  
         [0103]     The rate when the signal charge is horizontally transferred or vertically transferred is set to different values in the observation mode and in the inspection mode later discussed, respectively as shown in Table 2.  
                                         TABLE 2                                   OBSERVATION   INSPECTION           MODE   MODE                                    EFFECTIVE DATA TRANSFER   2.29E+07   9.15E+07       RATE (HZ/PIX)       LINE RATE (HZ/LINE   11175   44700                  
 
         [0104]     The vertical transfer of signal charge takes place for every horizontal line  45 - 1  to  45 -N in synchronism with the move of the specimen image  45 A ( FIG. 8A-8C  or  FIG. 9A-9C ). Consequently, the signal charges accumulated in each of the horizontal lines  45 - 1  to  45 -N of the TDI sensor  45  are integrated every time the signal charge is transferred in the horizontal line adjacent to the vertical direction.  
         [0105]     The image processing unit  46  A/D converts the output signal from the TDI sensor  45 , stores in the VRAM inside, and generates and outputs the image information of the specimen  15  to the host computer  14 . The host computer  14  displays the image on CRT  16  in conformity to the image information outputted from the image processing unit  46 .  
         [0106]     Now, the actions of the EB inspection apparatus  10  configured as above will be described. For the actions of the EB inspection apparatus, there are an observation mode for acquiring the image of the specimen  15  with the stage  28  stopped and an inspection mode for acquiring the image of the specimen  15  at a high speed with the stage moved. In either mode, in the EB inspection apparatus  10 , the size at the specimen  15  corresponding to one light receiving pixel of the TDI sensor  45  is adjusted to become 0.1 μm.  
         [0107]     First of all, the observation mode will be described.  
         [0108]     In the observation mode, the stage control unit  29  drives the stage  28  in XY directions and positions the region desired to observe (for example, region including a defect portion) in the specimen  15  to the inside of the irradiated region  21 A of the primary beam B 1 . After positioning, the stage  28  is stopped. The electron gun control unit  22  controls the acceleration voltage Vac of the electron gun  21  and sets the irradiated current volume Ib of the primary beam B 1  to 62.5 nA (see Table 0.1).  
         [0109]     Furthermore, the image processing unit  46  supplies the driving pulse to the TDI sensor  45  in conformity to the observation timing signal from the host computer  14 . As a result, the signal charge of the specimen image  45 A converted by each light receiving pixel of the TDI sensor  45  is transferred successively at an effective data transfer rate of 2.29E+07 Hz/pix and line rate of 11175 Hz/line (see Table 2).  
         [0110]     On the other hand, the secondary polarizer control unit  42  controls the voltage applied to the secondary polarizer  38  in conformity to the observation timing signal from the host computer  14 . As a result, the specimen image  45 A projected on the image pick-up surface of the TDI sensor  45  moves in the vertical direction at a specified velocity according to the line rate (11175 Hz/line) ( FIG. 8A-8C ). As described above, by synchronizing the move of the specimen image  45 A in the TDI sensor  45  with the vertical transfer of the signal charge, the signal charge of the specimen image  45 A is integrated and outputted to the image processing unit  46  (specimen image). According to this observation mode, the image of the region desired to observe (for example, a region including a defect portion) in the specimen  15  is able to be constantly displayed on CRT  16 . Furthermore, according to this observation mode, by picking up the image of the specified test pattern, various adjustments are able to be carried out, including focus adjustment of the primary optical system  23  and secondary optical system ( 31 - 37 ), aberration adjustment, brightness adjustment in the detector  39 , etc.  
         [0111]     Now, the description will be made on the action for acquiring the specimen image in the inspection mode. In the inspection mode, the electron gun control unit  22  controls the acceleration voltage Vac of the electron gun  21  and sets the irradiated current volume Ib of the primary beam B 1  to 250 nA (see Table 1). The image processing unit  46  supplies the driving pulse to the TDI sensor  45  in conformity to the inspection timing signal form the host computer  14 . As a result, the signal charge of the specimen image  45 A converted by each light receiving pixel of the TDI sensor  45  is transferred successively at an effective data transfer rate of 9.15E+07 Hz/pix and line rate of 44700 Hz/line (see Table 2).  
         [0112]     On the other hand, the stage control unit  29  moves the stage  28  at a high speed in conformity to the inspection timing signal from the host computer  14 . As a result, the specimen image  45 A projected on the image pick-up surface of the TDI sensor  45  moves in the vertical direction at a specified velocity according to the line rate (44700 Hz/line) ( FIG. 9A-9C ). As described above, by synchronizing the move of the specimen image  45 A in the TDI sensor  45  with the vertical transfer of the signal charge, the signal charge of the specimen image  45 A is integrated and outputted to the image processing unit  46  (specimen image).  
         [0113]     According to this inspection mode, because the image pickup action is executed while the stage  28  is being moved at a high speed, it is possible to take in the specimen image continuously and in a short time from a comparatively wide range or the whole of the specimen surface  15   a . Because the stage  28  is moved at a high speed, there is a possibility to cause minor displacement (1 μm or less) of the specimen image  45 A arising from speed variation or mechanical vibration of the stage  28 , but the displacement of the specimen image  45 A is able to be compensated for by supplying the position compensation voltage to the secondary polarizer  36 . When the acquisition of the specimen image in the inspection mode completes, the host computer  14  can specify the defect position of the specimen  15  by executing template matching, etc. for the image information.  
         [0114]     Next discussion will be made on the features of the EB inspection apparatus  10  according to the present embodiment.  
         [0115]     In the inspection mode of the EB inspection apparatus  10  mentioned above, in order to increase the inspection speed, the moving velocity of the stage  28  was accelerated and at the same time the transfer rate (see Table 2) of the signal charge in the TDI sensor  45  was also set to a faster value. And the irradiation current volume IB (see Table 1) of the primary beam B 1  was set to a stronger value as much as the moving velocity and the transfer rate were increased. That is, the inspection mode above is to carry out a high-speed inspection by continuously irradiating the specimen surface  15   a  with a large-current beam, while the stage is being moved continuously and at a high velocity. Consequently, if the stage  28  should stop or the moving velocity should decrease for some reason during the high-speed inspection, the large current beam is continuously applied to the same place or the vicinity of the specimen surface, and the dosage rapidly increases (see Eqs. (1) and (2) above).  
         [0116]     However, there is a limit to the acceptable dosage for the specimen  15 , and if the primary beam B 1  is irradiated exceeding this allowable range of dosage, contamination or charge up are caused in the specimen  15  or for the worst, the specimen  15  may be destroyed. Therefore, the EB inspection apparatus  10  according to the present embodiment has a specimen protection mechanism incorporated to protect the specimen  15 .  
         [0117]     Referring now to flow charts shown in  FIGS. 11A and 11B , the action of the specimen protection mechanism  50  incorporated in the EB inspection apparatus  10  will be described.  
         [0118]     The host computer  14  acquires the predetermined dosage data for the specimen  15  to be inspected when it receives a command of inspection mode to be entered from the outside (S 10 ), acquires the predetermined dosage data from the stored section  55  for the specimen  15  (S 11 ), and temporarily accumulated in the over exposure detection section  53 .  
         [0119]     Then, the host computer  14  acquires the signal concerning the moving velocity of the stage  28  entered from the stage control unit  29  to the control section  52  via the interface section  51 . The control section  52  transmits the entered signal to the dosage measurement section  54 . The dosage measurement section  54  calculates the dosage Dv of the electron beam actually applied to the specimen  15  (S 12 ) in conformity to the transmitted moving speed V, the irradiated current volume Ib of the primary beam B 1 , and the area S of the irradiated region  21 A (see Eq. (2)).  
         [0120]     Next, the over exposure detection section  53  of the host computer  14  judges whether the specimen is excessively irradiated with the electron beam by comparing the dosage data acquired from the storage section  55  with the actual dosage Dv calculated by the dosage measuring section  54  (S 13 ). And if the dosage Dv measured by the dosage measuring section  54  is greater than the dosage stored in the storage section  55 , the over exposure of electron beam is detected. And when the over exposure of electron beam is detected, the control section  52  of the host computer  14  outputs a notice of over exposure of the electron beam to the primary polarizer control unit  27  (S 14 ). On the other hand, if the actual dosage Dv is smaller than the dosage acquired from the storage section  55 , the host computer returns to the stage where the signal concerning the moving velocity V of the stage  28  is acquired (S 12 ). Consequently, as long as the actual dosage Dv is smaller than the allowable range data, the specimen image acquiring action continuously takes place in the inspection mode mentioned above.  
         [0121]     When the primary polarizer control unit  27  receives the notice of over exposure of electron beams from the host computer  14  (S 21 ), it applies blanking voltage to the primary polarizer  24  and greatly polarizes the trajectory of the primary beam B 1  as shown in  FIG. 6 , and prevents electron beams from passing the opening section of the aperture  25  (S 22 ). As a result, the specimen  15  is not irradiated with the large-current primary beam B 1 . Consequently, the worst condition such as generation of contamination or charge-up in the specimen  15  or destruction of the specimen  15  can be avoided.  
         [0122]     In the above-mentioned embodiment, the host computer is configured to contain the dosage measuring section  54  and the over exposure detection section  53 , but as shown in  FIG. 12 , the stage control unit may be configured to contain the dosage measuring section  62  and the over exposure detection section  63 . And the dosage data predetermined by the specimen to be inspected is acquired from the host computer  14  in advance and developed in the memory  64 . In addition, the over exposure detection section  63  is connected in series to the primary polarizer control unit  27 . In this kind of configuration, the over exposure of electron beams is able to be quickly detected by comparing the dosage Dv of the electron beam measured by the dosage measuring section  62  with the dosage data developed in the memory  64 , and if over exposure of electron beams is detected, it is notified to the primary polarizer control unit  27  and blanking of electron beams is able to be carried out quickly.  
         [0123]     In the above-mentioned embodiment, a description was made on an example to outputting the notice of over exposure from the host computer  14  to the primary polarizer control unit  27  and blanking the primary beam B 1  by the primary polarizer  24 , but the present invention shall not be limited to this configuration. For example, the notice of over exposure of electron beams from the host computer  14  is outputted to the electron gun control unit  22  and the electron discharge of the electron gun  21  may be stopped by turning off the power supply of he electron gun  21 . If a driving mechanism that moves the position of the aperture  25  in the surface-intersecting the trajectory of the primary beam B 1  is disposed, the notice of the over exposure of electron beams is outputted to this driving mechanism to move the aperture  25 , and the trajectory of the primary beam B 1  may be intercepted by the plate section (place other than the opening section) to carry out blanking of the primary beam B 1 . Needless to say, a shutter mechanism dedicated for intercepting the trajectory of the primary beam B 1  may be installed. If a polarizer other than the primary polarizer  24  or apertures other than the aperture  25  is located in the trajectory of the primary beam B 1 , blanking control similar to the above-mentioned may be carried out using these other a polarizer and apertures.  
         [0124]     Furthermore, in the above-mentioned embodiment, discussion was made on an example in which the primary beam B 1  is completely intercepted by the notice of over exposure of electron beams from the host computer  14  and the specimen  15  is prevented from being irradiated with the primary beam B 1 , but the irradiation of the primary beam B 1  may be controlled and the current density of the primary beam B 1  (=irradiating current volume Ib/(area S of the irradiated region  21 A)) may be reduced to prevent rapid increase of the dosage.  
         [0125]     Specifically, there is a method for using a primary polarizer, deflecting the trajectory of the primary beam B 1  at high velocity and in a wide range, and to prevent the irradiated region  21 A from staying in the same place on the specimen surface  15   a . In addition, a method to increase the area S of the irradiated region  21 A by expanding the cross section of the primary beam B 1  by the use of the primary optical system  23  can lower the current density of the primary beam B 1  and can prevent rapid increase of the dosage (corresponds to claim  3 ). Furthermore, similarly, an increase of the dosage is able to be prevented by a method for controlling the acceleration voltage Vac of the electron gun and lower the outgoing current volume Ia of the primary beam B 1 .  
         [0126]     In the above-mentioned embodiment, an example for calculating the actual dosage Dv was discussed in conformity to the moving speed of the stage  28  detected by the stage control unit  29 , but the present invention shall not be limited to this configuration. For example, because as the dosage of the specimen  15  increases, the amount of the secondary beam B 2  generated from the specimen  15  increases, the actual dosage Dv is also be able to be detected by detecting the generation volume of secondary beam B 2  and making the best of the corresponding relation between the secondary beam B 2  generation volume and the dosage of specimen  15  (corresponds to claim  5 ). By the way, the generation volume of secondary beam B 2  can be detected by disposing the detection coil around the trajectory of the secondary beam B 2  as shown in  FIG. 13  and connecting to the secondary beam B 2  measuring unit for measuring the volume of the secondary beam B 2  by the current outputted from the detection coil. Because to the fluorescent plate  44  composing the detector  39 , a specified voltage is applied and current flows by collisions of the secondary beam B 2 , it is possible to detect the generation volume of the secondary beam B 2  in conformity to the current that flows this fluorescent plate  44 .  
         [0127]     In addition, because as the dosage of the specimen  15  increases, the specimen image becomes brighter and the contrast ratio lowers, it is also possible to detect the actual dosage Dv by detecting the contrast ratio of the specimen image and at the same time by utilizing the corresponding relation between this contrast ratio and the material  15  (corresponds to claim  9 ). By the way, the detection of the contrast ratio of the specimen image is enabled by comparing the mean value of the concentration of each light receiving pixel stored in memory in the image processing unit  42  with the threshold value of the predetermined concentration.  
         [0128]     In the above-mentioned embodiment, the description was made on an example in which the allowable range data of the dosage of the specimen  15  is stored in the storage section  55  of the host computer  14  and the allowable range data is compared with the actual dosage Dv to judge whether the over exposure of electron beams has occurred or not in the inspection mode, but the present invention shall not be limited to this configuration. For example, the allowable range data of the moving velocity of the stage  28  is calculated in advance in conformity to the allowable range data of the dosage of the specimen  15  and this allowable range data of the moving velocity may be stored in the storage section  55  of the host computer  14 . In such event, the over exposure of the electron beam in the inspection mode is able to be detected by comparing the allowable range data of the moving velocity of the stage  28  with the actual moving velocity of the stage  28  (corresponds to claim  6 ). Similarly, the allowable range data of the secondary beam B 2  is calculated in advance in conformity to the allowable range data of the dosage of the specimen  15 , and this allowable range data of the generation volume of the secondary beam B 2  may be stored in the storage section  55  of the host computer  14 . In such event, the over exposure of the electron beam in the inspection mode is able to be detected by comparing the allowable range data of the generation volume of the secondary beam B 2  with the actual generation volume of the secondary beam B 2  (corresponds to claim  7 ). Furthermore, the allowable range data of the contrast ratio of image information is calculated in advance in conformity to the allowable range data of the dosage of the specimen  15 , and this allowable range data of the contrast ratio of image information may be stored in the storage section  55  of the host computer  14 . In such event, the over exposure of the electron beam in the inspection mode is able to be detected by comparing the allowable range data of the contrast ratio of image information with the actual contrast ratio of image information (corresponds to claim  10 ).  
         [0129]     In the above-mentioned embodiment, discussion was made on an example in which the primary beam B 1  is not polarized while the specimen image is being acquired in the inspection mode (irradiated region  21 A is not moved), but the present invention is applicable even when the specimen image is acquired while the primary beam B 1  is polarized (irradiated region  21 A is being moved). Furthermore, in the above-mentioned embodiment, an inspection apparatus using the primary beam B 1  shaped in a plane form was taken for an example, but the present invention is able to be applied when inspection is carried out using the primary beam B 1  squeezed in the spot form.  
         [0130]     That is, the present invention can be applied to any of the configurations including SEM, in which the specimen image is acquired while the primary beam B 1  is moved relative to the specimen. In the above-mentioned embodiment, an example for joining the electron optical system of the primary column  11  (primary optical system  23 ) to the electron optical system of the secondary column (second lens, etc.) with the Wien filter  33 , but the inspection method of the present invention is able to applied to the case in which they are configured separately.  
         [0131]     Because according to the electron beam apparatus related to the present invention, when the specimen is irradiated with the electron beam while the specimen and the electron beam are relatively moved, the rapid increase of the dosage caused by the stop of the relative move or decreased speed can be prevented and the specimen can be protected, as described above, the reliability to the high-speed processing (in particular, high-speed inspection) using the large-current beam can be improved.  
         [0132]     From the invention thus described, it will be obvious that the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.