Abstract:
Provided are a device and a method allowing a crystal orientation to be adjusted with adequate throughput and high precision to observe a sample, regardless of the type of the sample or the crystal orientation. In the present invention, the method comprises: setting a fitting circular pattern ( 26 ) displayed overlaid so that a main spot ( 23 ) is positioned on the circumference thereof, on the basis of the diffraction spot brightness distribution in an electron diffraction pattern ( 22   b ) displayed on a display unit ( 13 ); setting a vector ( 28 ) displayed with the starting point at the center position ( 27 ) of the displayed circular pattern ( 26 ), and the end point at the location of the main spot ( 23 ) positioned on the circumference of the circular pattern ( 26 ); and adjusting the crystal orientation on the basis of the orientation and the magnitude of the displayed vector ( 28 ).

Description:
CROSS REFERENCE TO PRIOR APPLICATIONS 
     This application is a U.S. National Phase application under 35 U.S.C. §371 of International Application No. PCT/JP2015/066424, filed on Jun. 8, 2015, which claims benefit of priority to Japanese Application No. 2014- 139273, filed on Jul. 7, 2014. The International Application was published in Japanese on Jan. 14, 2016 as WO 2016/006375 A1 under PCT Article 21(2). The contents of the above applications are hereby incorporated by reference. 
     TECHNICAL FIELD 
     The present invention relates to an electron microscope; and particularly relates to a transmission electron microscope with which it is possible to form, observe, and record a scanning and transmitting electron image and an electron beam diffraction pattern. 
     BACKGROUND ART 
     An electron beam diffraction pattern is used for adjusting the crystal orientation of a sample using a transmission electron microscope. Adjusting the electron beam incidence direction and the direction of the crystal axis makes it possible to acquire atomic column information and identify the crystal. In addition, when ascertaining the structure of polycrystalline particles in the vicinity of an interface, it is possible to accurately obtain the particle boundary width or the like by setting a crystalline particle boundary and an electron beam axis in parallel. For example, when evaluating the structure of a semiconductor device, in order to accurately measure the length of structural object which is laminated on a Si substrate, the crystal orientation of the Si substrate is adjusted and the sample is tilted such that electron beams are incident thereto in parallel with the substrate surface. 
     While the adjustment of the crystal orientation is an essential technique when using a crystalline sample, expertise is required in order to accurately adjust the crystal orientation while observing the electron beam diffraction pattern. 
     Here, the crystalline sample refers to a sample of which apart or all has an ordering. Examples of samples include single crystals, polycrystals which are complexes of a plurality of fine crystals, or quasicrystals. In addition, compounds which are formed of a single element or a plurality of elements may also be included in the crystalline sample. 
     In PTL 1, regarding the adjustment of the crystal orientation, electron beam diffraction pattern data which is acquired for each tilting angle of the sample is stored in advance, a distribution of spots of the electron beam diffraction pattern is fitted in a circle based on the stored data, and the sample is automatically tilted such that the radius of the circle is minimized. In addition, for a plurality of electron beam diffraction patterns, a trajectory of a central coordinate of an approximate circle which is determined for each pattern is approximated to a primary function, and a sample tilting angle which is able to obtain an intersection on a primary function straight line at the shortest distance between the primary function straight line and a direct spot central coordinate is determined and set as the optimum tilting angle. 
     CITATION LIST 
     Patent Literature 
     PTL 1: JP-A-2010-212067 
     SUMMARY OF INVENTION 
     Technical Problem 
     However, in the method described in PTL 1, the throughput decreases since it is necessary to store data of an electron diffraction pattern which corresponds to a plurality of different sample tilting angles in advance and a long time is necessary to obtain a crystal zone axis (one crystal axis in common to the collection of surfaces which are referred to as the crystal zone). 
     In consideration of the problems described above, the present invention has an object of providing an apparatus and a method allowing a crystal orientation to be adjusted with adequate throughput and high precision to observe a sample, regardless of the type of the sample or the crystal orientation, even by non-experts. 
     Solution to Problem 
     As an aspect for solving the problem described above, in the present invention, the adjustment of the crystal orientation of the sample includes setting a fitting circular pattern displayed overlaid so that a main spot is positioned on the circumference thereof, on the basis of the diffraction spot brightness distribution in an electron beam diffraction pattern; setting a vector displayed with the starting point at the center position of the displayed circular pattern, and the endpoint at the location of the main spot positioned on the circumference of the circular pattern; and controlling the operation of the sample stage based on the orientation and magnitude of the displayed vector. 
     Advantageous Effects of Invention 
     The present invention allows a crystal orientation to be adjusted with adequate throughput and high precision to observe a sample, regardless of the type of the sample or the crystal orientation, even by non-experts. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a basic configuration diagram of an electron microscope according to the present embodiment. 
         FIG. 2  is a light path diagram of a transmission electron microscope when observing an electron beam diffraction pattern according to the present embodiment. 
         FIGS. 3A and 3B  are diagrams which show a relationship between a crystalline sample, electron beams, and an electron beam diffraction pattern according to the present embodiment. 
         FIGS. 4A to 4E  are diagrams which illustrate a method for adjusting a crystal orientation according to a first embodiment. 
         FIG. 5  is a graph which shows an example of rectangular coordinates for determining a tilting direction and angle of the sample according to the present embodiment. 
         FIG. 6  is a flowchart which shows steps of adjusting the crystal orientation according to the first embodiment. 
         FIGS. 7A to 7E  are diagrams which illustrate a method for adjusting a crystal orientation according to a second embodiment. 
         FIGS. 8A to 8D  are diagrams which illustrate a method for adjusting a crystal orientation according to a third embodiment. 
         FIGS. 9A to 9D  are diagrams which show an example of transmitted electron images and electron beam diffraction patterns before and after adjusting the crystal orientation. 
         FIGS. 10A and 10B  are diagrams which illustrate a method for adjusting a crystal orientation according to a fourth embodiment. 
         FIG. 11  is a diagram which illustrates a main configuration of a main body control unit which relates to a process of adjusting the crystal orientation according to the present embodiment. 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     First Embodiment 
     Description will be given below of embodiments of the present invention using the diagrams. Here, description may be omitted by giving the same reference numerals to each of the same configuration parts throughout in each diagram. 
     Apparatus Configuration 
       FIG. 1  shows the basic configuration of an electron microscope  1  according to the present embodiment. A column of the electron microscope  1  is mainly formed by an electron gun  2 , a condenser lens  3 , an object lens  4 , an intermediate lens  5 , and a projection lens  6 . 
     A sample  8  is mounted on a sample holder  7  and the sample holder  7  is introduced through a sample stage  32  which is provided on a side surface of the microscope column of the electron microscope  1  to an inner portion. The movement and tilt of the sample  8  are controlled by a sample fine movement driving mechanism  9  which is connected to the sample stage  32 . 
     A condenser movable aperture  16  for converging electron beams  15  with which the sample  8  is irradiated is arranged on the upper portion of the object lens  4 . A diffraction pattern is formed on a back focal plane of the object lens  4 , an object movable aperture  17  is provided on the same surface, and a selected area aperture  18  is provided on an image surface. Each of the movable apertures is connected to an aperture driving control unit  19  and able to move in a horizontal direction and the operation thereof is controlled by the aperture driving control unit  19  so as to be adjusted to the observation target and taken in and out on the optical axis. 
     A fluorescent screen  10  is arranged below the projection lens  6  and a camera  11  is mounted under the fluorescent screen  10 . The camera  11  is connected to a monitor  13  and an image analysis apparatus  14  via the camera control unit  12 . 
     Each lens of the condenser lens  3 , the objective lens  4 , the intermediate lens  5 , and the projection lens  6  is connected to a lens power source  20 . 
     The electron beams  15  which are emitted from the electron gun  2  are brought together by the condenser lens  3  and the condenser movable aperture  16  and the sample  8  is irradiated therewith. The electron beams  15  which are transmitted through the sample  8  are imaged by the objective lens  4  and the image thereof is enlarged by the intermediate lens  5  and the projection lens  6  to be projected on the fluorescent screen  10 . When the fluorescent screen  10  is moved so as to be shifted from the optical axis, the image is projected on the camera  11  and a transmitted image or an electron beam diffraction pattern  22  is displayed on the monitor  13  and recorded on the image analysis apparatus  14 . 
     A main body control unit  21  is connected to the sample fine movement driving mechanism  9 , the camera control unit  12 , the aperture driving control unit  19 , and the lens power source  20  and sends and receives control signals for controlling the entire apparatus. The sample fine movement driving mechanism  9  is formed by a sample moving mechanism  9   a  which moves the sample  8  and a sample tilting mechanism  9   b  which tilts the sample  8 . The configuration of the control system shown in  FIG. 1  is merely an example and modified examples of the control unit, communication wiring, or the like are included in the scope of the electron microscope of the present embodiment as long as the functions which are intended in the present embodiment are satisfied. For example, in  FIG. 1 , the main body control unit  21  is connected to each of the constituent unit and controls the entire apparatus; however, it is also possible to form the invention so as to be provided with an independent control unit for each constituent unit. 
     &lt;Configuration of Main Control Unit&gt; 
       FIG. 11  is a diagram which, in the configuration included in the main body control unit  21 , mainly illustrates constituent unit which relate to adjusting the crystal orientation according to the present embodiment which will be described below. The constituent unit which relate to adjusting the crystal orientation are mainly a main spot setting unit  34 , a pattern setting unit  35 , a vector setting unit  36 , a vector information acquiring unit, a calculation unit  38 , a sample fine movement driving mechanism instruction unit  39 , and an observation mode switching unit  40 . Here, the main body control unit  21  includes various types of constituent unit other than the constituent unit described above. 
     The main spot setting unit  34  sets a position of the main spot  23  in the electron beam diffraction pattern  22  which is projected on the fluorescent screen  10  or the camera  11  which will be described below. A marker  25  is displayed at the position of the set main spot  23 . Here, the setting of the main spot  23  is either able to be selected by an operator or to be automatically determined by an apparatus as will be described below. 
     The pattern setting unit  35  sets a circular pattern  26  or an circular arced pattern  33  such that the main spot  23  of the electron beam diffraction pattern  22   b  is positioned on the circumference. In addition, by using the pattern setting unit  35 , it is possible to change the shape and size of the circular pattern  26  and the circular arced pattern  33  set based on the brightness distribution of the electron beam diffraction pattern  22   b.    
     After completing the setting of the circular pattern  26  and the circular arced pattern  33 , the vector setting unit  36  sets a vector V which has a central point (or a virtual coordinate point of a central point) which will be described below as a starting point and the position of the main spot  23  as the origin. 
     The vector information acquiring unit  37  acquires information on the orientation and magnitude of the set vector V and determines the tilting direction and the tilting angle of the sample  8  based thereon. 
     The sample fine movement driving mechanism instruction unit  39  controls an operation of the sample tilting mechanism  9   b  of the sample fine movement driving mechanism  9  based on the tilting direction and the tilting angle of the sample  8  determined by the calculation unit  38 . 
     The observation mode switching unit  40  is able to change the observation mode of the electron microscope  1  between an image observation mode and an observation mode of the electron beam diffraction pattern  22 . 
     &lt;Optical Path Diagram&gt; 
       FIG. 2  shows an optical path diagram of the transmission electron microscope  1  when observing the electron beam diffraction pattern  22  according to the present embodiment. The present diagram shows a state when the fluorescent screen  10  is moved to be separated from the optical axis; however, it is also possible to arrange the fluorescent screen  10  on the upper unit of the camera  11 . The sample  8  is irradiated with the electron beams  15  in parallel. In a case where the sample  8  is a crystalline sample, the electron beams  15  includes electron beams  15   a  which move straight forward without being diffracted by the crystal and electron beams  15   b  which are diffracted, and the electron beams  15   b  which are diffracted at the same angle are gathered at one point on the back focal plane of the object lens  4  and form an electron beam diffraction pattern  22   a  on the back focal plane. 
     The electron beams  15  which form these electron beam diffraction patterns  22   a  further form an image on an image plane of the object lens  4 . The selected area aperture  18  is arranged on the image plane and a region in which an image of the electron beam diffraction pattern  22  is observed is adjusted according to the opening angle of the selected area aperture  18 . 
     When observing the electron beam diffraction pattern  22   a,  the intermediate lens  5  is focused on the electron beam diffraction pattern  22   a  which is formed at the back focal plane of the object lens  4 , enlarged by the intermediate lens  5  and the projection lens  6 , and projected by the fluorescent screen  10  or the camera  11 , and the electron beam diffraction pattern  22   b  after the projection is obtained. In addition, in the image observation mode, the intermediate lens  5  is focused on the image which is imaged on the image plane, enlarged by the intermediate lens  5  and the projection lens  6 , and projected by the fluorescent screen  10  or the camera  11 . 
     At this time, the entire field of view is observed by taking the selected area aperture  18  out from the microscope column. In addition, by arranging the selected area aperture  18  in the microscope column and adjusting the divergence angle, the electron beam diffraction pattern  22   a  which is formed in the field of view which corresponds to the divergence angle in the sample  8  is observed. 
       FIGS. 3A and 3B  show the relationship between the crystalline sample  8 , the electron beams  15 , and the electron beam diffraction pattern  22   a  according to the present embodiment.  FIG. 3A  is a state where the electron beams  15  are incident in parallel with respect to a crystal axis  8   a  on a crystal plane of the sample  8  and  FIG. 3B  is a state where the electron beams  15  are incident at an angle of θ from a crystal zone axis with respect to the crystal axis  8   a  on the crystal-plane of the sample  8 . Here, the state where the electron beams  15  are incident in parallel with respect to the crystal axis  8   a  on the crystal plane of the sample  8  in  FIG. 3A  is referred to as a state of being incident on the crystal zone axis. From  FIG. 3A , a relationship between a diffraction angle θ of the electron beams  15  which are incident to the crystalline sample  8 , a distance R from the main spot  23  to a diffraction spot  24 , and a camera length L is represented by
 
R=L tan θ to Lθ.   [Formula 1]
 
Here, since L is determined using the crystalline sample  8  which is already known, it is possible to determine the distance R on the plane on which the electron beam diffraction pattern  22   a  is formed and the angle θ at which the electron beams  15  are incident with respect to the crystal axis  8   a  on the crystal plane of the sample  8  using Formula (1) by measuring the distance R on the diffraction pattern  22 .
 
       FIG. 3B  is a case where the sample  8  is tilted at an angle of θ and, as shown in the present diagram, it is understood that it is necessary to tilt the sample  8  at an angle of θ in order to make the electron beams  15  incident in parallel with the crystal axis  8   a , that is, incident on the crystal zone axis. 
       FIGS. 9A to 9D  are diagrams which show an example of the transmitted electron image and the electron beam diffraction pattern before and after adjusting the crystal orientation.  FIGS. 9A and 9C  show a transmitted electron image of which a part of a structure of a Si device is enlarged and  FIGS. 9B and 9D  show the electron beam diffraction pattern  22   b  which corresponds to the crystal orientation of a Si substrate  29  of  FIGS. 9A and 9C  respectively. It is understood from the results of the electron beam diffraction pattern  22   b  which are shown in  FIG. 9B  that the electron beams  15  are incident while shifted from the crystal axis of the Si substrate  29  in  FIG. 9A . On the other hand, it is understood from the results of the electron beam diffraction pattern  22  which are shown in  FIG. 9D  that the electron beams  15  in  FIG. 9C  is in a state of being incident on the crystal axis with respect to the Si substrate  29 . When comparing each transmitting electron image of  FIGS. 9A and 9C , it is understood that an interface of the Si substrate  29  in  FIG. 9C  is sharper compared to that in  FIG. 9A  and that an edge (an arrow portion in the diagram)  31  of a gate electrode  30  which is formed thereon is also sharper. This shows that each of the interfaces is in parallel with respect to the incident electron beams  15  and it is understood that it is necessary for the relationship between the incident electron beams  15  and the sample  8  to be in a state of being incident on the crystal zone axis as shown in  FIG. 9C , for example, in order to accurately evaluate the thickness of a gate oxide film between the gate electrode  30  and the Si substrate  29 . According to the present embodiment, it is possible to measure the length of the material structural object quickly and accurately since it is possible to easily obtain the conditions of being incident on the crystal zone axis under which it is possible to obtain the transmitted electron image which is shown in  FIG. 9C . 
       FIGS. 4A to 4E  are diagrams which illustrate a method for a process of adjusting the crystal orientation according to the first embodiment. 
     Firstly, the electron beam diffraction pattern  22  is displayed on the monitor  13 . When the operator selects, for example, the main spot (direct beams)  23  of the electron beam diffraction pattern  22   b  after being projected on the fluorescent screen  10  or the camera  11  which is displayed on the monitor  13  by a clicking operation or the like using a mouse, the marker  25  is displayed (a) and the position is set as the origin 0 (0, 0) and X and Y rectangular coordinates which are adjusted to the tilting direction α and β of the sample  8  are obtained (b). Here, an example of displaying the X and Y rectangular coordinates is shown; however, in practice, it is also possible to carry out the process by storing the acquired X and Y rectangular coordinates without displaying them on the monitor  13 . 
     At this time, in a case where the strengths of the main spot  23  and the adjacent diffraction spot are approximately the same, it is difficult to select the main spot  23 . In this case, it is possible to determine a position which matches a spot which is stored in advance as the main spot by moving the sample stage  32  to a place at which the sample  8  is not present for the time being, storing the positional information of the illuminated spot, and subsequently moving the sample stage  32  so as to display the electron beam diffraction pattern  22   b  on the sample  8  after being projected on the fluorescent screen  10  or the camera  11 . By doing so, it is possible to select the position of the main spot  23  correctly even in a case where a diffraction spot with approximately the same strength is present at an adjacent position. Here, description is given of a case where the operator selects the position of the main spot  23  in the example described above; however, it is also possible to automatically select the position of the main spot  23  which is stored in advance by the method described above according to the instruction of the main body control unit  21 . 
     Next, when the monitor  13  is clicked, the circular pattern  26  is displayed overlaid so that a main spot  23  of the electron beam diffraction pattern  22   b  is positioned on the circumference thereof (Step  606 ). At this time, the operator is able to adjust the size of the circular pattern  26  by adjusting the brightness distribution of the electron beam diffraction pattern  22   b.    
     Here, a second marker  27  is displayed in the center of the circular pattern  26 , a coordinate P (x, y) at the position of the second marker  27  on the X and Y rectangular coordinates is stored, and a vector  28  is displayed from the point P to the point 0 (d). 
     The information of the positions of each of the coordinates of 0 (0, 0) and P (x, y) on the X and Y rectangular coordinates and the information of the size and direction of the vector  28  are sent to the vector information acquiring unit  37  of the main body control unit  21 . 
     Here, as will be described below using  FIG. 5 , the tilting direction of the sample  8  from the direction of the vector  28  is determined by the calculation unit  38  of the main body control unit  21  and the tilt angle of the sample  8  of the α and β axes is determined using Formula (1) from the size R of the vector  28 , that is, from the difference x of the α coordinate and the difference y of the β coordinate. 
     Based on the determined tilting direction and tilting angle of the sample  8 , the main body control unit  21  controls the sample tilting mechanism  9   b  of the sample fine movement driving mechanism  9  and tilts the sample  8 . 
     Here, when P (x, y) matches 0 (0, 0), the electron beams  15  are incident on the crystal zone axis. In addition, switching to the image observation mode, when tilting the sample  8 , makes it possible to confirm the size of the field of view which is limited by the selected area aperture  18 . Even in a case where a field of view movement occurs due to the tilting of the sample  8 , it is possible to prevent the field of view from being lost when tilting the sample  8  by adjusting the fine movement of the sample or the like by operating the sample moving mechanism  9   a  of the sample fine movement driving mechanism  9  either by manual operation of the operator or by automatic operation of the main body control unit  21 . In the method of correcting positional shifting by determining the adjustment amount of the field of view movement based on the relationship between the tilting angle and the amount of positional shifting which are acquired in advance or based on a correction calculation formula, there are cases where it is not possible to adjust to the actual position of the sample  8  depending on the reproducibility or precision of the sample stage; however, it is possible to execute reliable correction of the positional shifting by adjusting the field of view movement in real time when observing the image in the image observation mode in this manner. 
       FIG. 5  is a graph which shows the X and Y rectangular coordinates which are used for obtaining the tilting direction and tilting angle of the sample  8  according to the present embodiment. The horizontal axis is an X axis which corresponds to the α axis of the sample tilting axis, the vertical axis is a Y axis which corresponds to the β axis of the sample tilting axis, and the position of the main spot  23  of the electron beam diffraction pattern  22  is set to be the origin 0 (0, 0). In addition, the central point of the circular pattern  26  which is displayed overlaid by adjusting to the brightness distribution of the electron beam diffraction pattern  22  is set to be P (x, y). The tilting angle and direction of the sample  8  are calculated from the vector  28  from the point P to the point 0. In this case, the α component of the tilting angle is α′=−x/L from Formula (1) and the β component is β′=−y/L. 
       FIG. 6  is a flowchart which shows operation steps of adjusting the crystal orientation according to the first embodiment. 
     Firstly, the magnification is set (Step  601 ). At this time, it is desirable to set the magnification to an appropriate level or less in order to make tracking easy even when the field of view moves when tilting the sample  8 . 
     Next, in order to determine the restricted field of view, the field of view on the sample  8  for adjusting the crystal orientation is determined using the sample moving mechanism  9   a  and the sample tilting mechanism  9   b  of the sample fine movement driving mechanism  9  (Step  602 ). 
     After that, the selected area aperture  18  is inserted using the aperture driving mechanism  19  with respect to the sample  8  on which the crystal orientation adjustment is performed (Step  603 ). 
     Here, the observation mode of the electron beam diffraction pattern  22  is turned on (Step  604 ). Due to this, the lens power source  20  of the intermediate lens  5  and the projection lens  6  is controlled from the main body control unit  21  so that the intermediate lens  5  is focused on the electron beam diffraction pattern  22   a  which is formed at the back focal plane of the objective lens  4 , the electron beam diffraction pattern  22  is enlarged and projected on the fluorescent screen  10  or the camera  11  by the intermediate lens  5  and the projection lens  6 . Due to this, the electron beam diffraction pattern  22   b  after being projected on the fluorescent screen  10  or the camera  11  is obtained. Due to the control of the main body control unit  21 , the electron beam diffraction pattern  22   b  which is projected on the fluorescent screen  10  or the camera  11  is displayed on the monitor  13  via the camera control unit  12 . 
     Next, by the operator selecting the main spot (direct beams)  23  of the electron beam diffraction pattern  22   b  which is displayed on the monitor  13  by a clicking operation or the like via an input apparatus such as a mouse, the position of the main spot  23  is displayed by the main spot setting unit  34  of the main body control unit  21  (Step  605 ). 
     At this time, it is difficult to select the main spot  23  in a case where the strengths of the main spot  23  and the adjacent diffraction spot are approximately the same. In this case, it is possible to determine a position which matches a position stored in advance as the main spot  23  by moving the sample stage  32  to a place in which the sample  8  is not present for the time being, storing the positional information of the illuminated spot, and subsequently moving the sample stage  32  so as to display the electron beam diffraction pattern  22  on the sample  8 . By doing so, it is possible to select the main spot  23  correctly even in a case where a diffraction spot with approximately the same strength is present at an adjacent position. Here, description is given of a case where the operator selects the main spot in the example described above; however, it is also possible to automatically select the main spot according to the instruction of the main body control unit  21 . 
     Next, by clicking on the monitor  13 , the circular pattern  26  is displayed overlaid so that a main spot  23  is positioned on the circumference thereof via the pattern setting unit  35  of the main body control unit  21  (Step  606 ). At this time, it is possible to adjust the size of the circular pattern  26  to match the brightness distribution of the electron beam diffraction pattern  22   b . Here, the pattern setting unit  35  of the main body control unit  21  is able to display the circular pattern  26  so as to be arranged in the brightness distribution of the diffraction spot of the electron beam diffraction pattern  22   b.    
     Due to this, the circular pattern  26  and the central point (the starting point of the vector) P (x, y) are determined and a vector V 28  which connects the central point P (x, y) of the circular pattern  26  and the origin (the end point of the vector) 0 (0, 0) which is the position of the main spot  23  is displayed. 
     Next, when the monitor  13  is clicked, the sample  8  is tilted in correspondence with the orientation and magnitude (length) of the vector  28  (Step  607 ). Here, since the information of the position of each of the coordinates of 0 (0, 0) and P (x, y) on the X and Y rectangular coordinates and the information of the size and direction of the vector  28  are sent to the vector information acquiring unit  37  of the main body control unit  21  and the tilting direction and tilt angle of the sample  8  are determined by the calculation unit  38 , the sample  8  is tilted via the sample fine movement driving mechanism instruction portion  39  based on the determined results. 
     At the same time as the tilting of the sample  8  starts, the electron microscope  1  is changed to the image observation mode by the observation mode switching unit  40  of the main body control unit  21  and the image when tilting the sample  8  is displayed on the monitor  13 . At this time, even in a case where a field of view movement occurs due to the tilting of the sample  8 , it is possible to prevent the field of view from being lost when tilting the sample  8  by adjusting the fine movement of the sample or the like by operating the sample moving mechanism  9   a  of the sample fine movement driving mechanism  9  either by manual operation of the operator or the automatic operation of the main body control unit  21 . In the method of correcting positional shifting by determining the adjustment amount of the field of view movement based on the relationship between the tilting angle and the amount of positional shifting which are acquired in advance or based on a correction calculation formula, there are cases where it is not possible to adjust to the actual position of the sample  8  depending on the reproducibility or precision of the sample stage; however, it is possible to execute reliable correction of the positional shifting by adjusting the field of view movement in real time when observing the image in the image observation mode in this manner. In addition, apart from the adjustment of fine movement of the sample, it is also possible to adjust the field of view movement by changing the irradiation region of the electron beams  15  by controlling a tilting device which is not shown in the diagram. 
     When the operation of tilting the sample  8  is completed, the mode is changed to the observation mode of the electron beam diffraction pattern  22   b  by the observation mode switching unit  40  of the main body control unit  21 , and the electron beam diffraction pattern  22   b  is displayed on the monitor  13  (Step  608 ). 
     Next, the results of adjusting the crystal orientation of the displayed electron beam diffraction pattern  22  are confirmed (Step  609 ). Here, in a case where shifting remains between the central point P (x, y) of the circular pattern  26  and the origin 0 (0, 0) which is the position of the main spot  23  of the electron beam diffraction pattern  22   b , the operations from Step  608  to Step  609  are further repeated. 
     When the center of the circular pattern  26  and the main spot  23  of the electron beam diffraction pattern  22   b  are overlaid, the crystal orientation adjustment is finished, the image observation mode is turned on, and the observation and length measurement of the sample  8  are performed (Step  610 ). 
     Here, in Step  607  described above, when carrying out correction in a case where a field of view movement occurs when tilting the sample  8 , it is desirable for the correction to handle the switching to the image mode. At this time, in a case where, for example, the selected area aperture  18  is small and it is difficult to confirm the movement only with the field of view which is included in the aperture, the entire field of view is displayed by taking out the selected area aperture  18  in synchronization with the switching to the image mode, and, after correcting the field of view movement, the aperture driving mechanism  19  may be driven such that the selected area aperture  18  is introduced again when switching to the observation mode of the electron beam diffraction pattern  22   b . In addition, in a case where a field of view movement does not occur when tilting the sample  8 , it is possible to omit the switching to the image mode. 
     (Second Embodiment) 
       FIGS. 7A to 7E  are diagrams which illustrate the operation of adjusting the crystal orientation according to the present embodiment. 
     Circular Pattern 
     In the example in  FIGS. 4A to 4E  described above in the first embodiment, description is given of the method of fitting the brightness distribution of the diffraction pattern  22  and the size of the circular pattern  26 . However, in a case where the crystal orientation is greatly shifted from the incident crystal zone axis when starting the observation of the diffraction pattern  22 , there are times when fitting using the circular pattern  26  is difficult by the method described above. 
     Thus, in the second embodiment, the main spot  23  is firstly assigned as the origin 0 (0, 0) by a cursor  25  (a) and subsequently displayed overlaid such that the circumference of the displayed circular pattern  26  always passes through the main spot  23 , that is, the cursor  25 , in the diffraction spots of the electron beam diffraction pattern  22   b , that is, a region in which there is a large amount of brightness distribution (b). At this time, it is possible to set the crystal orientation to be incident on the crystal zone axis by determining the tilt angle of the sample  8  based on the vector  28  which connects the marker  27  which is displayed as the central point P (x, y) of the circular pattern  26  and the main spot  23 , that is, the marker  25 , displaying the above as the circular pattern  26  again, repeating the same operations (c, d), and eventually matching the coordinates of the central point P (x, y) of the circular pattern  26  and the origin 0 (0, 0) which is the main spot  23 . According to the method described above, it is necessary to repeat the operation of tilting the sample  8  a plurality of times; however, even when the crystal orientation is greatly shifted from being incident on the crystal zone axis when starting the observation, it is possible to easily adjust the crystal orientation. 
     (Third Embodiment) 
       FIG. 8  is a diagram which shows a method of adjusting the crystal orientation according to the third embodiment. In the present embodiment, description will be given of a method for performing fitting using a circular arced pattern (a part of the circumference)  33  instead of the circular pattern  26  described above. 
     In a case where the crystal orientation is greatly shifted from being incident on the crystal zone axis when starting the observation of the electron beam diffraction pattern  22   b , an option marker  25  is firstly displayed with the main spot  23  as the origin 0 (0, 0) (a). Next, the circular arced pattern  33  is displayed so as to pass through the origin 0 (0, 0) which is the main spot  23 , that is, the marker  25 , and fit in the brightness distribution of the electron beam diffraction pattern  22   b  (b). Optional coordinates (x1, y1) and (x2, y2) of two points on the fitted circular arced pattern  33  are displayed and recorded (c). The fitted circular arced pattern  33  is a part of the circumference of the circular pattern  26  and it is possible to determine the virtual coordinate point P (a, b) of the central point of the circular pattern  26  by the simultaneous equations (2-1, 2-2, and 2-3) below when the virtual radius of the circular pattern  26  is r.
 
 a   2   +b   2   =r   2   Equation 2-1
 
( x   1 −1) 2 +( y   1   −b ) 2   =r   2   Equation 2-2
 
( x   2   −a ) 2 +( y   2   −b ) 2   =r   2   Equation 2-3
 
     The vector  28  from the virtual coordinate point P (a, b) of the central point to the origin 0 (0, 0), that is, the marker  25 , is obtained from the results which are determined from the equations described above and it is possible to carry out adjustment so as to be incident on the crystal zone axis (d) by determining the amount of tilting and the direction of the corresponding sample  8 , tilting the sample  8  by the sample tilting mechanism  9   b  of the sample fine movement driving mechanism  9 , and adjusting the crystal orientation. 
     According to the present embodiment, even in a case where the incidence of the electron beams  15  is greatly shifted from the crystal zone axis and fitting using the circular pattern  26  is difficult, it is possible to adjust the crystal orientation by obtaining the virtual coordinate point of the central point using the circular arced pattern  33 . 
     (Fourth Embodiment) 
       FIG. 10  are diagrams which illustrate an operation according to the fourth embodiment.  FIG. 10A  shows the electron beam diffraction pattern  22   b  in a case where the crystal orientation is shifted from the crystal zone axis with respect to the incident axis of the electron beams  15  and  FIG. 10B  shows the electron beam diffraction pattern  22   b  in a state where the crystal orientation matches the crystal zone axis with respect to the incident axis of the electron beams  15 , that is, in a state of being incident on the crystal zone axis. In the present embodiment, the circumference of the circular pattern  26  which is fitted in the diffraction spot is displayed not as a line but a marker in a semi-transparent strip form with an optional width. Due to this, even when displayed as overlapping on the diffraction spot, it is possible to confirm the position of the diffraction spot. Therefore, compared to the embodiments described above, it is possible to perform the fitting to the diffraction spot more easily. 
     REFERENCE SIGNS LIST 
     
         
           1  ELECTRON MICROSCOPE 
           2  ELECTRON GUN 
           3  CONDENSER LENS 
           4  OBJECTIVE LENS 
           5  INTERMEDIATE LENS 
           6  PROJECTION LENS 
           7  SAMPLE HOLDER 
           8  SAMPLE 
           8  CRYSTAL AXIS 
           9  SAMPLE FINE MOVEMENT DRIVING MECHANISM 
           9   a  SAMPLE MOVING MECHANISM 
           9   b  SAMPLE TILTING MECHANISM 
           10  FLUORESCENT SCREEN 
           11  CAMERA 
           12  CAMERA CONTROL PORTION 
           13  MONITOR 
           14  IMAGE ANALYSIS PORTION 
           15  ELECTRON BEAM 
           16  CONDENSER MOVABLE APERTURE 
           17  OBJECTIVE MOVABLE APERTURE 
           18  SELECTED AREA APERTURE 
           19  APERTURE DRIVING CONTROL MECHANISM 
           20  LENS POWER (SOURCE) 
           21  MAIN BODY CONTROL UNIT 
           22   a  ELECTRON BEAM DIFFRACTION PATTERN 
           22   b  ELECTRON BEAM DIFFRACTION PATTERN AFTER PROJECTION TO FLUORESCENT SCREEN OR CAMERA 
           23  MAIN SPOT 
           24  DIFFRACTION SPOT 
           25  MARKER 
           26  CIRCULAR PATTERN 
           27  MARKER 
           28  VECTOR 
           29  Si SUBSTRATE 
           30  GATE ELECTRODE 
           31  GATE ELECTRODE EDGE 
           32  SAMPLE STAGE 
           33  CIRCULAR ARCED PATTERN (PART OF CIRCUMFERENCE) 
           34  MAIN SPOT SETTING UNIT 
           35  PATTERN SETTING UNIT 
           36  VECTOR SETTING UNIT 
           37  VECTOR INFORMATION ACQUIRING UNIT 
           38  CALCULATION UNIT 
           39  SAMPLE FINE MOVEMENT DRIVING MECHANISM INSTRUCTION UNIT 
           40  OBSERVATION MODE SWITCHING UNIT