Patent Document

TECHNICAL FIELD 
       [0001]    The present invention relates to a charged particle beam apparatus ta can be used for measurement. 
       BACKGROUND ART 
       [0002]    A scanning electron microscope as a mode of a charged particle beam apparatus is an apparatus that converges a primary charged particle beam accelerated and emitted from a charged particle source using an electromagnetic lens and detects a secondary signal obtained from a sample when the surface of the sample is irradiated with the primary charged particle beam by electromagnetic deflection while scanning to convert the secondary signal into an image. The scanning electron microscope using an electron source as a charged particle source is widely known as a representative apparatus in this mode and fine shapes can be observed by converging a primary electron beam diminutively and so is used for dimensional measurement and the like of fine circuit patterns in a semiconductor manufacturing process. 
         [0003]    The secondary signal obtained when the sample is irradiated with a primary electron beam is a signal having various levels of energy such as secondary electrons and reflected electrons. By selecting and detecting energy of the secondary signal, an image having desired information can be acquired. In an optical system in which a secondary signal travels onto an optical path of primary electrons and a detector to detect the secondary signal is arranged outside an axis of the optical path of primary electrons, it is necessary to deflect the secondary signal without deflecting the primary electron beam. 
         [0004]    As a means for implementing this, an apparatus using a Wien filter as a deflecting means of the secondary signal is described in PTL 1. In PTL 1, correcting changes of a curvature of field due to changes of a deflection angle of a primary electron beam by a magnetic pole of an objective lens and causing deflection color aberration using an E×B separator is described. 
         [0005]    Also, an apparatus that suppresses a curvature of field as geometric aberration and astigmatism is described in PTL 2. In PTL 2, correcting a curvature of field and astigmatism caused by a Wien filter operating as a deflection color aberration correcting element inside the deflection color aberration correcting element is described. 
       CITATION LIST 
     Patent Literature 
       [0000]    
       
         PTL 1: JP 2003-187733 A 
         PTL 2: WO 2012/050018 A 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0008]    Incidentally, when a Wien filter is used as a deflector of a secondary signal in a detector and energy of a secondary signal is switched for detection, it is necessary to switch the action of the Wien filter. At this point, the amount of aberration of a primary electron beam such as a curvature of field and astigmatism caused by the Wien filter changes and thus, a focal position on a sample also changes. Particularly when energy of the secondary signal to be detected is switched significantly, a change of the focal position manifests itself. Further, when energy of the secondary signal to be detected is switched, if defocusing is corrected by a means of correcting the focal position on the sample, deflection sensitivity of the primary electron beam is affected, posing a problem that an error of display dimensions of an acquired image occurs. 
         [0009]    In the above Citation List, defocusing and deflection sensitivity deviations caused by switching energy of the secondary signal deflected by the Wien filter are not assumed. Thus, in PTL 1, the Wien filter acts as a portion of the deflector that deflects primary electrons and the effect is limited to correcting defocusing by linking an electrostatic lens arranged on the sample side from the primary electron deflector. In PTL 2, the Wien filter is not used as a deflector of the secondary signal. 
         [0010]    An object of the present invention is to provide a charged particle beam apparatus capable of correcting defocusing and astigmatism caused when operating conditions of a Wien filter acting as a deflector of a secondary signal are changed and holding display dimensions of an acquired image in a constant state. 
       Solution to Problem 
       [0011]    To achieve the above object, one representative charged particle beam apparatus of the present invention is provided with a Wien filter arranged between a lens arranged on a side of a sample of 2-stage lenses to converge a charged particle beam and a detector and further, a processor that controls the Wien filter and a lens arranged on the side of the charged particle source of the 2-stage lenses in linkage. 
         [0012]    For example, a configuration described in CLAIMS is adopted. The present application includes a plurality of means for solving the above problem and an example thereof is provided as: a charged particle beam apparatus including a charged particle source; 2-stage lenses for converging a primary charged particle beam emitted from the charged particle source on a sample, wherein a first lens arranged on a side of the charged particle source and a second lens arranged on a side of the sample are included; a deflector that specifies an irradiation position of the primary charged particle beam on the sample; a detector arranged between the 2-stage lenses to detect a secondary charged particle signal generated by the sample being irradiated with the primary charged particle beam from the sample; a first Wien filter arranged between the detector and the second lens to deflect the secondary charged particle signal; and a processor that controls the first Wien filter and the first lens in linkage. 
       Advantageous Effects of Invention 
       [0013]    According to the present invention, defocusing and astigmatism caused when operating conditions of a Wien filter acting as a deflector of a secondary signal are changed can be corrected and display dimensions of an acquired image can be held in a constant state. 
         [0014]    Further features related to the present invention will be apparent from the description of this specification and appended diagrams. Other problems, configurations, and effects than those described above will be apparent from the description of examples described below. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0015]      FIG. 1  is an overall configuration diagram of a charged particle beam apparatus (scanning electron microscope) according to Example 1. 
           [0016]      FIG. 2  is a schematic diagram illustrating a trajectory of secondary electrons passing through a Wien filter according to Example 1. 
           [0017]      FIG. 3  is a schematic diagram illustrating gang control of the Wien filter according to Example 1 and a condensing lens. 
           [0018]      FIG. 4  is a diagram showing a configuration example of an image acquisition condition setting GUI screen according to Example 1. 
           [0019]      FIG. 5  is an overall configuration diagram of the charged particle beam apparatus (scanning electron microscope) according to Example 2. 
           [0020]      FIG. 6  is an overall configuration diagram of the charged particle beam apparatus (scanning electron microscope) according to Example 3. 
           [0021]      FIG. 7  is an overall configuration diagram of the charged particle beam apparatus (scanning electron microscope) according to Example 4. 
           [0022]      FIG. 8  is an overall configuration diagram of the charged particle beam apparatus (scanning electron microscope) according to Example 5. 
           [0023]      FIG. 9  is a diagram showing a configuration example of the image acquisition condition setting GUI screen according to Example 5. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0024]    Hereinafter, the examples of the present invention will be described with reference to the appended drawings. The appended drawings shows concrete examples conforming to the principle of the present invention, but these examples are intended for a better understanding of the present invention and are never used for a restrictive interpretation of the present invention. 
         [0025]    As a sample observation apparatus, a charged particle beam apparatus that scans a primary charged particle beam (typically, electrons) emitted from a charged particle source on the surface of a sample to detect a signal of secondary charged particles generated secondarily is known. The present invention can be applied to charged particle beam apparatuses in general. Representative examples of the charged particle beam apparatus include a scanning electron microscope (SEM). 
       Example 1 
       [0026]    Example 1 will be described using  FIGS. 1 to 4 .  FIG. 1  is an overall configuration diagram of a scanning electron microscope as a form of a charged particle beam apparatus according to the present example. 
         [0027]    The scanning electron microscope includes an electron-optical lens barrel  91 , a power unit  92  to supply an operating voltage/driving current to various components of the electron-optical lens barrel  91 , a processor  93  that centrally controls a whole system, a storage device  94  attached to the processor  93 , and an input/output apparatus  95 . The input/output apparatus  95  includes an input apparatus such as a mouse or a keyboard and an output apparatus such as a display (display unit). 
         [0028]    The electron-optical lens barrel  91  includes an electron source  1 , an observation sample  2 , a detector  5 , a current limiting diaphragm  6 , an objective lens  11 , a condensing lens  12 , a Wien filter for secondary signal deflection  23 , and a 2-stage scanning deflector  30 . The detector  5  is arranged between 2-stage lenses (the objective lens  11 , the condensing lens  12 ). The Wien filter for secondary signal deflection  23  is constructed of an electrostatic deflector  21  and an electromagnetic deflector  22 . The 2-stage scanning deflector  30  is constructed of an upper scanning deflector  31  and a lower scanning deflector  32 . 
         [0029]    A primary electron beam  3  emitted from the electron source  1  successively passes through the condensing lens  12  and the objective lens  11  before being converged on the observation sample  2  as a microscopic spot for irradiation. In the meantime, the primary electron beam  3  on the observation sample  2  is two-dimensionally scanned by the 2-stage scanning deflector  30  constructed of the upper scanning deflector  31  and the lower scanning deflector  32 . 
         [0030]    A secondary signal  4  such as secondary electrons and reflected electrons emitted from the observation sample  2  due to irradiation with the primary electron beam  3  is detected by the detector  5  positioned between the 2-stage lenses (the objective lens  11 , the condensing lens  12 ). The signal detected by the detector  5  is sent to the processor  93 . Image processing is performed by the processor  93  based on input information and a two-dimensional image corresponding to the irradiation position of the primary electron beam  3  scanned two-dimensionally is displayed in a display or the like of the input/output apparatus  95 . 
         [0031]    The Wien filter for secondary signal deflection  23  is arranged on the side of the observation sample  2  from the detector  5 . The Wien filter for secondary signal deflection  23  is arranged between the detector  5  and the objective lens  11  to deflect secondary electrons and reflected electrons in the direction of the detector  5 . The Wien filter for secondary signal deflection  23  can deflect secondary electrons and reflected electrons in the direction of the detector  5  without deflecting the primary electron beam  3  by orthogonalizing an electric field of the electrostatic deflector  21  and a magnetic field of the electromagnetic deflector  22 . Here, the operating condition of the Wien filter that does not deflect the primary electron beam  3  is called the Wien condition. Unless there are exceptional circumstances, the Wien filter described in the present example is used under the condition of not deflecting the primary electron beam  3 . 
         [0032]    The power unit  92  is a collection of control power supply of each component of the electron-optical lens barrel  91 . The power unit  92  is controlled by the processor  93 . The power unit  92  includes a voltage source  51  that controls an applied voltage to the electron source  1 , a voltage source  53  that controls an applied voltage to the electrostatic deflector  21 , a current source  52  that controls a current applied to the condensing lens  12 , a current source  57  that controls a current applied to the objective lens  11 , a current source  54  that controls a current applied to a coil of the electromagnetic deflector  22 , and current sources  55 ,  56  that control a current applied to the upper scanning deflector  31  and the lower scanning deflector  32  respectively. If the upper scanning deflector  31  and the lower scanning deflector  32  are electrostatic deflectors, a voltage source may be included instead of the current sources  55 ,  56 . 
         [0033]      FIG. 2  shows details of trajectories of secondary electrons or reflected electrons passing through a Wien filter for secondary signal deflection. In the Wien filter for secondary signal deflection  23 , the voltage source  53  of the electrostatic deflector  21  and the current source  54  of the electromagnetic deflector  22  are driven such that the Wien condition is fulfilled. Secondary electrons and reflected electrons  4  advancing into the Wien filter for secondary signal deflection  23  are separated into secondary electrons  7  of low energy and reflected electrons  8  of high energy and the secondary electrons  7  enter the detector  5 . If the reflected electrons  8  should enter the detector  5 , outputs of the voltage source  53  and the current source  54  are changed such that the reflected electrons  8  change to a trajectory of reflected electrons  10  indicated by a broken line while the Wien condition is fulfilled. At this point, the secondary electrons  7  change to a trajectory of secondary electrons  9  indicated by a broken line. By switching outputs of the voltage source  53  and the current source  54  as described above, energy of a secondary signal to be detected can be selected. 
         [0034]      FIG. 3  schematically shows details of a configuration in which the Wien filter for secondary signal deflection  23  and the condensing lens  12  are controlled in linkage. The processor  93  calculates the action (indicated value to the current source  52 ) of the condensing lens  12  from a deflection amount of a secondary electron signal of the Wien filter for secondary signal deflection  23  so that the Wien filter for secondary signal deflection  23  and the condensing lens  12  are controlled in linkage. 
         [0035]    The processor  93  includes a drive current calculator  71  of the condensing lens  12 , a drive current calculator  72  of the condensing lens  12  linked with the Wien filter for secondary signal deflection  23 , an applied voltage calculator  73  of the electrostatic deflector  21  constituting the Wien filter for secondary signal deflection  23 , and a drive current calculator  74  of the electromagnetic deflector  22  constituting the Wien filter for secondary signal deflection  23 . 
         [0036]    When an indicated value  41  of the condensing lens focused position and an indicated value  42  of primary electron energy are input into the drive current calculator  71  of the condensing lens  12 , the drive current calculator  71  outputs an indicated value of the current source  52  of the condensing lens  12 . Accordingly, the condensing lens  12  operates and the primary electron beam  3  converges on a position of the indicated value  41  of the condensing lens focused position. The condensing lens focused position is normally set to between the objective lens  11  and the condensing lens  12 . 
         [0037]    When an indicated value  43  of detected electron energy is input into the applied voltage calculator  73  of the electrostatic deflector  21 , the applied voltage calculator  73  outputs an indicated value of the voltage source  53  of the electrostatic deflector  21 . Further, when the indicated value  43  of detected electron energy and the indicated value  42  of primary electron energy are input into the drive current calculator  74  of the electromagnetic deflector  22 , the drive current calculator  74  outputs an indicated value of the current source  54  of the electromagnetic deflector  22  in such a way that the Wien condition is satisfied. Accordingly, the Wien filter for secondary signal deflection  23  operates and a secondary signal is deflected. At the same time, the focal position of the primary electron beam  3  on the observation sample  2  is shifted. If the focal position shift on the observation sample  2  is ΔF 1  and the reduction ratio of the objective lens  11  is M, a correction amount ΔF 2  of an object surface position of the objective lens  11  needed to correct ΔF 1  is converted by the following formula: 
         [0000]      Δ F 2=Δ F 1/ M   2   [Math 1]
 
         [0038]    ΔF 2  can be set by the condensing lens  12  and thus, ΔF 1  can be corrected by the condensing lens  12 . 
         [0039]    The amount of change of the current value input into the current source  52  of the condensing lens  12  can be calculated by the drive current calculator  72  of the condensing lens  12  linked with the Wien filter for secondary signal deflection  23 . The indicated value  41  of the condensing lens focused position, the indicated value  42  of primary electron energy, and the indicated value  43  of detected electron energy are input into the drive current calculator  72 . Instead of the indicated value  43  of detected electron energy, an output value of the applied voltage calculator  73  of the electrostatic deflector  21  may be input into the drive current calculator  72 . 
         [0040]    If the indicated value  41  of the condensing lens focused position is set, a distance L 1  between the condensing lens focused position and an action position of the Wien filter for secondary signal deflection  23  is obtained. When the electrostatic deflector  21  of the Wien filter for secondary signal deflection  23  is operated alone, a deflection amount X 1  of the primary electron beam  3  in a position L 1  away from the Wien filter for secondary signal deflection  23  is shown by the following formula: 
         [0000]        X 1= s 1· L 1· V 1  [Math 2]
 
         [0041]    s 1  is deflection sensitivity of the electrostatic deflector  21  and V 1  is an operating voltage of the electrostatic deflector  21 . V 1  is determined if the indicated value  43  of detected electron energy is set. If X 1  as an action of the Wien filter on the primary electron beam  3  is used, ΔF 2  is given by the following formula: 
         [0000]      Δ F 2= k 1· X 1 2   =k 1·( s 1· L 1· V 1) 2   [Math 3]
 
         [0042]    k 1  is a coefficient used to convert the action of the Wien filter for secondary signal deflection  23  into a focal position shift and a value obtained by a calculator simulation or apparatus adjustments. The amount of change (correction value) needed to change the condensing lens focused position by ΔF 2  by the condensing lens  12  and input into the current source  52  is calculated from the value obtained by adding ΔF 2  to the indicated value  41  of the condensing lens focused position and the indicated value  42  of primary electron energy and is the output value of the drive current calculator  72 . 
         [0043]    The processor  93  inputs a value obtained by adding the output value of the drive current calculator  71  and the output value of the drive current calculator  72  into the current source  52 . When the added value of the output value of the drive current calculator  71  and the output value of the drive current calculator  72  is input into the current source  52 , a focal position shift of the primary electron beam  3  generated by an operation of the Wien filter for secondary signal deflection  23  on the observation sample  2  can be corrected by the condensing lens  12  in linkage with the Wien filter for secondary signal deflection  23 . 
         [0044]    While the correction value is calculated by the drive current calculator  72  in the above example, the correction value may be input into the current source  52  by a different method. For example, the correction value corresponding to the indicated value  41  of the condensing lens focused position, the indicated value  42  of primary electron energy, and the indicated value  43  of detected electron energy may be defined in a table in advance and stored in the storage device  94 . When the indicated value  41  of the condensing lens focused position, the indicated value  42  of primary electron energy, and the indicated value  43  of detected electron energy are input into the drive current calculator  72 , the drive current calculator  72  may output the correction value by referring to the table. 
         [0045]      FIG. 4  shows a configuration example of a GUI screen to set the aforementioned condensing lens focused position, primary electron energy, detected electron energy and the like and also to display a scanning electron microscope image obtained during settings. 
         [0046]    A GUI screen  101  is displayed on the input/output apparatus  95 . The GUI screen  101  includes an image display unit  102 , a button  103  to set the optics mode, a button  104  to set the irradiation voltage of the primary electron beam  3  to the observation sample  2 , a button  105  to set the detector mode, a button  106  to set the imaging magnification of an image displayed in the image display unit  102 , a scroll bar  107  to set an excitation condition of the objective lens  11  and a display unit  108  of the excitation condition of the objective lens  11 , a button  109  to execute auto-focus of the objective lens  11 , buttons  110  to indicate an operation of a scanning deflector, a button  111  to store an image displayed in the image display unit  102  in the storage device  94 , and a button  112  to measure the dimension of an observation object on an image displayed in the image display unit  102 . 
         [0047]    The setting of the button  106  may be FOV (Field Of View) of an image displayed in the image display unit  102 . The optics mode set by the button  103  is used to set a beam aperture angle of the primary electron beam  3  on the observation sample  2  and the control range of a probe current and when the optics mode is set, the focused position of the condensing lens  12  is determined. When the acceleration voltage (Vacc) is set by the button  104 , the primary electron energy is determined (that is, the indicated value  42 =Vacc of the primary electron energy). When the detector mode is set by the button  105 , detected electron energy to be detected by the detector  5  is determined. For example, when the detector mode is set by the button  105 , as described with reference to  FIG. 3 , energy of a secondary signal to be detected can be selected. 
         [0048]    Effects of the present example will be described. According to the configuration in the present example, even if a secondary signal to be deflected by a Wien filter is deflected by any deflection amount, deflection sensitivity of the primary electron beam  3  (primary charged particle beam) by a deflector can be held in a constant state. Thus, the operation on the GUI screen  101  in  FIG. 4  is as described below. 
         [0049]    If, after an image is displayed in the image display unit  102  by operating the button  110 , the button  112  is operated, two cursors  113  appear. The dimension of an observation object is measured by moving the two cursors  113 . The pitch line of a line pattern formed from equidistant pitches is desired for dimensional measurement, but the pattern is not limited to the line pattern and any pattern such as a hole pattern capable of measurement may be used. The measurement value at this point is displayed in a dimensional measurement value display unit  114 . 
         [0050]    Then, after the detector mode is switched by operating the button  105 , the image is re-displayed in the image display unit  102  by operating the button  110 . Here, the action of the Wien filter for secondary signal deflection  23  is changed by scanning of the button  105  and a focal position shift of the primary electron beam  3  on the observation sample  2  caused at this point is corrected by the operation described with reference to  FIG. 3 . As a result, a clear image without defocusing is displayed in the image display unit  102  without resetting the scroll bar  107  or operating the button  109  while the display value in the display unit  108  of the excitation condition of the objective lens  11  is held. 
         [0051]    Then, when the dimension of the same location as the observation location before operating the button  105  is measured by operating the button  112 , the dimension value displayed in the dimensional measurement value display unit  114  matches the dimension value obtained before operating the button  105  when variations within measurement accuracy are allowed for. In the present example, when the operating condition of the Wien filter  23  is changed, defocusing and astigmatism caused thereby can be corrected synchronously. With the above operation, an image can also be obtained when the operating condition of the Wien filter  23  is changed without varying the imaging magnification of the image in the image display unit  102 . 
         [0052]    In the past, when the operating condition of the Wien filter is changed, it is necessary to reset the excitation condition of the objective lens or the like and thus, the imaging magnification of an image varies and display dimensions of an acquired image cannot be held in a constant state. According to the configuration in the present example, by contrast, when the operating condition of the Wien filter  23  acting as a deflector of a secondary signal is changed, defocusing and astigmatism are corrected by the condensing lens  12  linked with the Wien filter for secondary signal deflection  23  so that display dimensions of an acquired image can be held in a constant state. 
       Example 2 
       [0053]    Example 2 will be described using  FIG. 5 . Unless there are exceptional circumstances, matter described in Example 1 and not described in the present example can also be applied to the present example. 
         [0054]      FIG. 5  is an overall configuration diagram of the scanning electron microscope as a form of the charged particle beam apparatus according to the present example. The present example is different from Example 1 in that a Wien filter for chromatic aberration correction  26  is mounted for the purpose of correcting deflection color aberration generated in the Wien filter for secondary signal deflection  23 . Incidentally, the same signs as those in  FIG. 1  indicate the same components. 
         [0055]    The Wien filter for chromatic aberration correction  26  is arranged on the side of the electron source  1  from the Wien filter for secondary signal deflection  23 . More specifically, the Wien filter for chromatic aberration correction  26  is arranged between the condensing lens  12  and the current limiting diaphragm  6 . The Wien filter for chromatic aberration correction  26  is constructed of an electrostatic deflector  24  and an electromagnetic deflector  25 . 
         [0056]    In the Wien filter for chromatic aberration correction  26 , a voltage source  58  of the electrostatic deflector  24  and a current source  59  of the electromagnetic deflector  25  are driven such that the Wien condition is fulfilled. If the indicated value  41  of the condensing lens focused position is set, a distance L 2  between the condensing lens focused position and an action position of the Wien filter for chromatic aberration correction  26  is obtained simultaneously with L 1 . When the electrostatic deflector  24  of the Wien filter for chromatic aberration correction  26  is operated alone, a deflection amount X 2  of the primary electron beam  3  in a position L 2  away from the Wien filter for chromatic aberration correction  26  is shown by the following formula: 
         [0000]        X 2= s 2· L 2· V 2  [Math 4]
 
         [0057]    s 2  is deflection sensitivity of the electrostatic deflector  24  and V 2  is an operating voltage of the electrostatic deflector  24 . Deflection color aberration D 1  generated in the Wien filter for secondary signal deflection  23  and deflection color aberration D 2  generated in the Wien filter for chromatic aberration correction  26  are given by the following formulas: 
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         [0058]    c 1  is a deflection color aberration coefficient of the electrostatic deflector  21 , c 2  is a deflection color aberration coefficient of the electromagnetic deflector  22 , c 3  is a deflection color aberration coefficient of the electrostatic deflector  24 , c 4  is a deflection color aberration coefficient of the electromagnetic deflector  25 , V 0  is primary electron energy emitted from the electron source  1 , ΔV 0  is chromatic dispersion of primary electrons emitted from the electron source  1 . The coefficients c 1  to c 4  are values obtained in advance. The Wien filter for chromatic aberration correction  26  is operated in such a way that deflection color aberration generated in the Wien filter for secondary signal deflection  23  is canceled and so the following relationship holds: 
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         [0059]    The positive/negative sign of V 2  is the same as that of V 1  when the condensing lens focused position is between the Wien filter for secondary signal deflection  23  and the Wien filter for chromatic aberration correction  26  and otherwise, the inverted sign of that of V 1 . When controlled under this condition, the correction amount ΔF 2  of an object surface position of the objective lens  11  needed to correct a focal position shift on the observation sample  2  caused by operations of the Wien filter for secondary signal deflection  23  and the Wien filter for chromatic aberration correction  26  is converted by the following formula: 
         [0000]    
       
         
           
             
               
                 
                   
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         [0060]    k 2  is a coefficient used to convert the action of the Wien filter for chromatic aberration correction  26  into a focal position shift and a value obtained by a calculator simulation or apparatus adjustments. Accordingly, the correction amount of the object surface position increased by an operation of the Wien filter for chromatic aberration correction  26  is determined by the distance L 1  between the condensing lens focused position and the action position of the Wien filter for secondary signal deflection  23  and the indicated value  43  of detected electron energy. Thus, if, as described in Example 1, the condensing lens focused position is changed by ΔF 2 , a focal position shift on the observation sample  2  caused by operations of the Wien filter for secondary signal deflection  23  and the Wien filter for chromatic aberration correction  26  can be corrected. Therefore, the drive current calculator  72  may calculate a value obtained by correcting the condensing lens focused position by the above ΔF 2  using the same configuration as that described with reference to  FIG. 3 . 
         [0061]    With the above configuration, the processor  93  controls the Wien filter for secondary signal deflection  23 , the Wien filter for chromatic aberration correction  26 , and the condensing lens  12  arranged on the electron source  1  side in linkage. As a result, an image can also be obtained when the operating conditions of the Wien filters  23 ,  26  are changed without varying the imaging magnification of the display image. 
       Example 3 
       [0062]    Example 3 will be described using  FIG. 6 . Unless there are exceptional circumstances, matter described in Example 1 or Example 2 and not described in the present example can also be applied to the present example. 
         [0063]      FIG. 6  is an overall configuration diagram of the scanning electron microscope as a form of the charged particle beam apparatus according to the present example. Incidentally, the same signs as those in  FIG. 5  indicate the same components. In the present example, when compared with Example 2, a condensing lens  13  is added to the electron source  1  side from the condensing lens  12 . The present example is configured to be a able to independently set a beam aperture angle of the primary electron beam  3  and the control range of a probe current by independently controlling the two condensing lenses  12 ,  13 . 
         [0064]    Also, a portion of a magnetic path of the objective lens  11  is electrically separated by an insulator  14 . The objective lens  11  can also be made to act as an electrostatic lens by applying a voltage to a pole piece  15  and at the same time, can apply a voltage to the observation sample  2 . In the present example, high resolution can be achieved by optimizing these setting voltages. A current source  60  is connected to the condensing lens  13  and a voltage source  61  and a voltage source  62  are connected to the pole piece  15  and the observation sample  2  respectively. 
         [0065]    In the present example, an irradiation voltage Vacc applied to the observation sample  2  of the primary electron beam  3  is given by the following formula if the voltage applied to the observation sample  2  is Vr: 
         [0000]        Vacc=V 0− Vr   [Math 9]
 
         [0066]    Also in Example 3, a correction can be made by the same configuration as that described with reference to FIG.  3 . In the present example, the irradiation voltage set by using the button  104  inside the GUI screen  101  in  FIG. 4  becomes Vacc. The primary electron energy passing through each of the Wien filters  23 ,  26  is V 0 . Therefore, the value (Vacc+Vr) obtained by adding Vr to Vacc set by the button  104  is input into the drive current calculator  72  as the indicated value  42  of the primary electron energy. 
         [0067]    A secondary signal obtains energy for Vr when emitted from the observation sample  2  and thus, the value (E 1 +Vr) obtained by adding the voltage Vr applied to the observation sample  2  to energy E 1  of the secondary signal immediately before being emitted from the observation sample  2  is input into the drive current calculator  72  as the indicated value  43  of detected electron energy. 
         [0068]    The condensing lens  13  is added in the present example and the condensing lens focused position can be changed by controlling the condensing lens  13 . Thus, the indicated value  41  of the condensing lens focused position can be changed by being linked with the control of the condensing lens  13 . 
         [0069]    A focal position shift on the observation sample  2  caused by the operation of each Wien filter may be corrected, like in Example 2, by a lens on the electron source  1  side from the scanning deflectors  31 ,  32 . If the operating condition of a Wien filter is changed in the present example, a correction may be made by the condensing lens  12  or the condensing lens  13 . Thus, when a correction is made by the condensing lens  12 , the same configuration as that described with reference to  FIG. 3  may be used. When a correction is made by the condensing lens  13 , a value obtained by adding an output value of the drive current calculator  72  and a output value of a drive current calculator (not shown) for the condensing lens  13  may be input into the current source  60 . 
         [0070]    In the present example, the processor  93  controls the Wien filter for secondary signal deflection  23 , the Wien filter for chromatic aberration correction  26 , and the condensing lenses  12 ,  13  arranged on the electron source  1  side in linkage. An image can also be obtained when the operating condition of each Wien filter is changed without varying the imaging magnification of the display image by making a correction using the condensing lens  12  or the condensing lens  13 . 
         [0071]    Incidentally, the distribution of energy of a secondary signal immediately before being emitted from the observation sample  2  is known and can be obtained in advance. The relationship between each detector mode that can be changed by the button  105  inside the GUI screen  101  in  FIG. 4  and the value of the energy E 1  of a secondary signal immediately before being emitted from the observation sample  2  may be stored in the storage device  94  in advance. Thus, when the detector mode is changed by operating the button  105  inside the GUI screen  101 , after switched to the value of E 1  corresponding to the detector mode, the value (E 1 +Vr) obtained by adding the voltage Vr applied to the observation sample  2  to the value of E 1  after switched is input into the drive current calculator  72  as the indicated value  43  of the detected electron energy. Accordingly, an image can be obtained when the operating condition of a Wien filter is changed without varying the imaging magnification of the display image. 
       Example 4 
       [0072]    Example 4 will be described using  FIG. 7 . Unless there are exceptional circumstances, matter described in any one of Examples 1 to 3 and not described in the present example can also be applied to the present example. 
         [0073]      FIG. 7  is an overall configuration diagram of the scanning electron microscope as a form of the charged particle beam apparatus according to the present example. Incidentally, the same signs as those in  FIG. 6  indicate the same components. When compared with Example 3, a 2-stage scrolling deflector  35  operating for the purpose of moving a position deflected by the 2-stage scanning deflector  30  by beam deflection, a Wien filter  29  operating in linkage with the 2-stage scrolling deflector  35 , and an electrostatic lens  16 . The 2-stage scrolling deflector  35  is constructed of an upper scrolling deflector  33  and a lower scrolling deflector  34 . The Wien filter  29  is constructed of an electrostatic deflector  27  and an electromagnetic deflector  28 . 
         [0074]    A current source  65  is connected to the upper scrolling deflector  33 , a current source  66  is connected to the lower scrolling deflector  34 , a voltage source  63  is connected to the electrostatic deflector  27 , a current source  64  is connected to the electromagnetic deflector  28 , and a voltage source  67  is connected to the electrostatic lens  16 . If the upper scrolling deflector  33  and the lower scrolling deflector  34  are electrostatic deflectors, a voltage source may be connected instead of the current sources  65 ,  66 . 
         [0075]    The secondary signal  4  generated from the observation sample  2  is subject to the action of deflection by a deflection field of the upper scrolling deflector  33  and the lower scrolling deflector  34 . Due the deflection, the secondary signal  4  passes through a position deviating from the axis center in the position of the Wien filter for secondary signal deflection  23 . The Wien filter  29  deflects the secondary signal  4  such that the secondary signal  4  passes through the axis center in the position of the Wien filter for secondary signal deflection  23  in linkage with the operations of the upper scrolling deflector  33  and the lower scrolling deflector  34 . At this point, the focal position of the primary electron beam  3  on the observation sample  2  is shifted in accordance with an operation amount of the Wien filter  29  and so the focal position shift is corrected by the lens on the electron source  1  side from the 2-stage scrolling deflector  35 . The focal position shift may be corrected by the condensing lens  12  or the condensing lens  13 , but the correction of the focal position shift linked with the 2-stage scrolling deflector  35  needs a high-speed operation and so is desired to be made by the electrostatic lens  16  in the present example. 
         [0076]    The processor  93  calculates an action of the condensing lens  12  and an action of the electrostatic lens  16  from a deflection amount of a secondary electron signal of the Wien filter for secondary signal deflection  23  and a deflection amount of a secondary electron signal of the Wien filter  29  to control the Wien filter for secondary signal deflection  23 , the Wien filter for chromatic aberration correction  26 , the Wien filter  29 , the condensing lens  12 , and the electrostatic lens  16  in linkage. 
         [0077]    If the distance between the condensing lens focused position and the action position of the Wien filter  29  is L 3 , the deflection amount of the primary electron beam  3  in a position L 3  away from the Wien filter  29  when the electrostatic deflector  27  of the Wien filter  29  is operated alone is X 3 , deflection sensitivity of the electrostatic deflector  27  is s 3 , and the operating voltage of the electrostatic deflector  27  is V 3 , the correction amount ΔF 2  of an object surface position of the objective lens  11  needed to correct a focal position shift on the observation sample  2  caused by the operation of each Wien filter is converted by the following formula: 
         [0000]    
       
         
           
             
               
                 
                   
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                     10 
                   
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         [0078]    k 3  is a coefficient used to convert the action of the Wien filter  29  into a focal position shift and a value obtained by a calculator simulation or apparatus adjustments. Of these terms, the third term added when compared with Math 8 is corrected by the electrostatic lens  16 . Though not depicted in  FIG. 7 , the present function can be implemented by providing an arithmetic unit that controls the Wien filter  29  and the electrostatic lens  16  in linkage inside the processor  93 . As an example, the distance L 3  between the condensing lens focused position and the action position of the Wien filter  29 , the deflection sensitivity s 3  of the electrostatic deflector  27 , and the operating voltage V 3  of the electrostatic deflector  27  are input into the arithmetic unit as input values. The arithmetic unit determines the value of the third term in Math 10 from these input values. The arithmetic unit may input the value corrected by the determined third term into the voltage source  67  for the electrostatic lens  16 . 
         [0079]    In the present example, an example in which only the third term of Math 10 is corrected by the electrostatic lens  16  is described, but a similar effect can also be obtained by correcting all terms of Math 10 by the electrostatic lens  16 . The processor  93  controls the Wien filter for secondary signal deflection  23 , the Wien filter for chromatic aberration correction  26 , the Wien filter  29 , and the electrostatic lens  16  in linkage. In this case, the value obtained by adding the third term to the value of Math 8 calculated by the drive current calculator  72  may be input into the voltage source  67  for the electrostatic lens  16  as a correction value. 
         [0080]    In the present example, an image can also be obtained when the operating condition of the Wien filter  29  is changed without varying the imaging magnification of the display image. 
       Example 5 
       [0081]    Example 5 will be described using  FIGS. 8 and 9 . Unless there are exceptional circumstances, matter described in any one of Examples 1 to 4 and not described in the present example can also be applied to the present example. 
         [0082]      FIG. 8  is an overall configuration diagram of the scanning electron microscope as a form of the charged particle beam apparatus according to the present example. Incidentally, the same signs as those in  FIG. 7  indicate the same components. When compared with Example 4, an astigmatic corrector  36  is added. The current source  68  is connected to the astigmatic corrector  36 . 
         [0083]    Astigmatism caused by a Wien filter being operated can be described as a function of the operation amount of the Wien filter  29  operating in linkage with the Wien filter for secondary signal deflection  23  and the 2-stage scrolling deflector  35 . Thus, astigmatism caused by the operation of each of the Wien filter for chromatic aberration correction  26  and the Wien filter  29  operating in linkage with the Wien filter for secondary signal deflection  23  and the Wien filter for secondary signal deflection  23  can automatically be corrected by controlling the astigmatic corrector  36  in linkage with the operation amount of each Wien filter. 
         [0084]    Though not depicted in  FIG. 8 , the present function can be implemented by providing an arithmetic unit that controls the Wien filter for secondary signal deflection  23  and the astigmatic corrector  36  in linkage and an arithmetic unit that controls the Wien filter  29  and the astigmatic corrector  36  in linkage inside the processor  93 . 
         [0085]    These arithmetic units input a correction value of astigmatism calculated based on the above function into the astigmatic corrector  36  when the detector mode (the button  105  in  FIG. 9 ) is switched. Therefore, when the operating conditions of the Wien filters are changed, astigmatism caused by the operation of a Wien filter can automatically be corrected by controlling the Wien filter for secondary signal deflection  23 , the Wien filter  29 , and the astigmatic corrector  36  in linkage. 
         [0086]      FIG. 9  shows a configuration example of the GUI screen in the present example. When compared with GUI in  FIG. 4  described in Example 1, a scroll bar  115  to set the condition for an X-direction astigmatic corrector, a scroll bar  116  to set the condition for a Y-direction astigmatic corrector, a display unit  117  of setting values of the X-direction astigmatic corrector, a display unit  118  of setting values of the Y-direction astigmatic corrector, and a button  119  to automatically make an astigmatic correction are added. 
         [0087]    When the detector mode is switched by the button  105 , setting conditions of the astigmatic corrector  36  automatically change in accordance with a change of the operating condition of a Wien filter. In the present example, the display of the display unit  117  of setting values of the X-direction astigmatic corrector and the display unit  118  of setting values of the Y-direction astigmatic corrector is automatically updated by correction values calculated by the above arithmetic units. That is, when the detector mode is switched by the button  105 , the display of the display unit  117  of setting values of the X-direction astigmatic corrector and the display unit  118  of setting values of the Y-direction astigmatic corrector is updated without operating the scroll bar  115 , the scroll bar  116 , and the button  119 . When only the same operation is performed by the button  105 , the amount of change of numbers displayed in the display unit  117  and the display unit  118  is always constant. As a result, an image can also be obtained when the operating conditions of the Wien filters are changed without varying the imaging magnification of the display image. 
         [0088]    The present invention is not limited to the examples described above and includes various modifications. The above examples have been described in detail to describe the present invention so as to be understood more easily and all components described above are not necessarily included. A portion of components of some example may be replaced with components of other examples. Also, components of other examples may be added to components of some example. Also, additions, deletions, or substitutions of other components may be made for a portion of components of each example. 
         [0089]    Each calculator of the processor  93  and the like may be implemented by software in which a processor interprets and executes programs implementing each function. Information of programs, tables, files and the like to implement each function can be placed in a storage device such as a memory, a hard disk, and SSD (Solid State Drive) or a storage medium such as an IC card, an SD card, and DVD. Also, each calculator of the processor  93  described above and the like may be implemented by hardware by designing a portion or the whole thereof as an integrated circuit. 
         [0090]    Control lines and information lines in drawings considered to be necessary for description are shown and all control lines and information lines are not necessarily shown from a product viewpoint. All components may be mutually connected. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           1  electron source 
           2  observation sample 
           3  primary electron beam 
           4  secondary signal 
           5  detector 
           6  current limiting diaphragm 
           7  secondary electron 
           8  reflected electron 
           9  secondary electron 
           10  reflected electron 
           11  objective lens 
           12  condensing lens 
           13  condensing lens 
           14  insulator 
           15  pole piece 
           16  electrostatic lens 
           21  electrostatic deflector 
           22  electromagnetic deflector 
           23  Wien filter for secondary signal deflection 
           24  electrostatic deflector 
           26  electromagnetic deflector 
           26  Wien filter for chromatic aberration correction 
           27  electrostatic deflector 
           28  electromagnetic deflector 
           29  Wien filter 
           31  upper scanning deflector 
           32  lower scanning deflector 
           33  upper scrolling deflector 
           34  lower scrolling deflector 
           36  astigmatic corrector 
           41  indicated value of the condensing lens focused position 
           42  indicated value of primary electron energy 
           43  indicated value of detected electron energy 
           51  voltage source 
           52  current source 
           53  voltage source 
           54  current source 
           55  current source 
           56  current source 
           57  current source 
           58  voltage source 
           59  current source 
           60  current source 
           61  voltage source 
           62  voltage source 
           63  voltage source 
           64  current source 
           65  current source 
           66  current source 
           67  voltage source 
           68  current source 
           71  drive current calculator of the condensing lens 
           72  drive current calculator of the condensing lens linked with the Wien filter 
           73  applied voltage calculator of the electrostatic deflector 
           74  drive current calculator of the electromagnetic deflector 
           91  electron-optical lens barrel 
           92  power unit 
           93  processor 
           94  storage device 
           95  input/output apparatus 
           101  GUI screen 
           102  image display unit 
           103  button 
           104  button 
           105  button 
           106  button 
           107  scroll bar 
           108  display unit of objective lens excitation conditions 
           109  button 
           110  button 
           111  button 
           112  button 
           113  cursor 
           114  dimensional measurement value display unit 
           115  scroll bar 
           116  scroll bar 
           117  display unit 
           118  display unit 
           119  button

Technology Category: 5