Patent Publication Number: US-2022216033-A1

Title: Charged Particle Beam Apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-001502 filed Jan. 7, 2021, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention relates to a charged particle beam apparatus. 
     Description of Related Art 
     An energy-dispersive X-ray spectrometer is known as an elemental analyzer to be installed in a scanning electron microscope or a transmission electron microscope. 
     When an X-ray generated on a specimen is detected in an electron microscope including an energy-dispersive X-ray spectrometer, an X-ray detector is disposed near the specimen. Such an energy-dispersive X-ray spectrometer is disclosed in JP-A-2016-72005. 
     In an electron microscope, a specimen stage has a tilt mechanism for tilting a specimen. For example, when a crystalline specimen is observed at a high magnification in a transmission electron microscope, the specimen is tilted to observe a crystal lattice, and a specific crystal orientation is adjusted to the incident direction of an electron beam. 
     However, when the specimen is tilted, an X-ray generated on the specimen may be blocked by a member disposed near the specimen of a specimen holder or the like, allowing the X-ray to reach only a part of the detection surface of an X-ray detector. This reduces the detection solid angle of the X-ray detector, resulting in low detection efficiency. The detection efficiency means the ratio of X-rays detected to be signals with respect to X-rays emitted from a specimen. 
     In an electron microscope, the determination of the detection solid angle of a detector enables a measurement in an optimum state with high detection efficiency. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, there is provided a charged particle beam apparatus including: 
     a tilt mechanism that tilts a specimen; 
     a detector that detects an electromagnetic wave emitted from the specimen; 
     a table storage unit that stores a table in which tilt angle information on the tilt angle of the specimen and detection solid-angle information on the detection solid angle of the detector are associated with each other; 
     a tilt control unit that controls the tilt mechanism; and 
     a detection-solid-angle information acquisition unit that acquires the tilt angle information from the tilt control unit and acquires the detection solid-angle information with reference to the table. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a configuration of an electron microscope according to the first embodiment. 
         FIG. 2  is a diagram for describing an X-ray detector. 
         FIG. 3  is a diagram for describing a positional relationship between an X-ray detector and a specimen. 
         FIG. 4  illustrates a configuration of a detector control unit. 
         FIG. 5  illustrates a table in which tilt angle information and detection solid-angle information are associated with each other. 
         FIG. 6  schematically illustrates an analysis screen. 
         FIG. 7  is a flowchart illustrating an example of display processing. 
         FIG. 8  schematically illustrates a modification of an analysis screen. 
         FIG. 9  schematically illustrates a modification of an analysis screen. 
         FIG. 10  is a diagram illustrating a modification of a detector control unit. 
         FIG. 11  is a flowchart illustrating an example of processing for setting a measurement time. 
         FIG. 12  is a diagram illustrating a modification of a detector control unit. 
         FIG. 13  is a flowchart illustrating an example of processing for setting a detection solid angle. 
         FIG. 14  is a diagram illustrating a modification of a detector control unit. 
         FIG. 15  illustrates an example of a notification by a notification unit. 
         FIG. 16  is a flowchart illustrating an example of processing for a notification. 
         FIG. 17  is a diagram illustrating a modification of a detector control unit. 
         FIG. 18  illustrates a configuration of an electron microscope according to the second embodiment. 
         FIG. 19  illustrates a configuration of an electron microscope according to the second embodiment. 
         FIG. 20  is a diagram for describing a positional relationship between a first X-ray detector and a specimen and a positional relationship between a second X-ray detector and a specimen. 
         FIG. 21  is a diagram illustrating a configuration of a detector control unit. 
         FIG. 22  illustrates a table in which tilt angle information and detection solid-angle information in a second X-ray detector are associated with each other. 
         FIG. 23  schematically illustrates an analysis screen. 
         FIG. 24  schematically illustrates an analysis screen. 
         FIG. 25  schematically illustrates an analysis screen. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     According to an embodiment of the invention, there is provided a charged particle beam apparatus including: 
     a tilt mechanism that tilts a specimen; 
     a detector that detects an electromagnetic wave emitted from the specimen; 
     a table storage unit that stores a table in which tilt angle information on the tilt angle of the specimen and detection solid-angle information on the detection solid angle of the detector are associated with each other; 
     a tilt control unit that controls the tilt mechanism; and 
     a detection-solid-angle information acquisition unit that acquires the tilt angle information from the tilt control unit and acquires the detection solid-angle information with reference to the table. 
     In such a charged particle beam apparatus, the detection-solid-angle information acquisition unit acquires the detection solid-angle information from the tilt angle information with reference to the table, thereby easily determining the detection solid angle. 
     Preferred embodiments of the invention are specifically described in detail below with reference to the drawings. It is noted that the following embodiments do not unduly limit the scope of the invention as stated in the claims. In addition, all of the components described in the following embodiments are not necessarily essential requirements of the invention. 
     In the following example, a charged particle beam apparatus according to the embodiments of the invention is a transmission electron microscope that generates X-rays by emitting electron beams to a specimen. The charged particle beam apparatus according to the invention may be an apparatus that generates X-rays by emitting charged particle beams (e.g., ion beams) other than electron beams to a specimen. Alternatively, the charged particle beam apparatus according to the invention may be an apparatus that generates electromagnetic waves (e.g., cathode luminescence) other than X-rays by emitting electron beams to a specimen. 
     1. First Embodiment 
     1.1. Electron Microscope 
     An electron microscope according to a first embodiment will be first described below with reference to the accompanying drawings.  FIG. 1  illustrates the configuration of an electron microscope  100  according to the first embodiment. For convenience,  FIG. 1  illustrates X axis, Y axis, and Z axis as three axes orthogonal to one another. 
     The electron microscope  100  includes an electron source  10 , illumination-system lenses  11 , a specimen holder  12 , a specimen stage  14 , an objective lens  15 , an intermediate lens  16 , a projector lens  17 , an imaging device  18 , an X-ray detector  20 , a tilt control unit  30 , and a detector control unit  40 . The electron microscope  100  is a transmission electron microscope. 
     The electron source  10  generates electron beams. The electron source  10  is an electron gun for accelerating electrons, which are emitted from a cathode, at an anode and emitting electron beams. 
     The illumination-system lenses  11  are lenses for focusing an electron beam generated by the electron source  10  and irradiating a specimen S with the electron beam. 
     The specimen holder  12  holds the specimen S. The specimen holder  12  can be attached to the specimen stage  14 . The specimen stage  14  positions the specimen S held by the specimen holder  12 . In the illustrated example, the specimen stage  14  is a side-entry stage that inserts the specimen S from the side of the pole piece of the objective lens  15 . 
     The electron microscope  100  includes a tilt mechanism  13  for tilting the specimen S. The tilt mechanism  13  includes an X tilt mechanism for tilting the specimen S in X direction and a Y tilt mechanism for tilting the specimen S in Y direction. Specifically, the specimen stage  14  includes an X tilt mechanism for tilting the specimen S in X direction. Furthermore, the specimen holder  12  includes a Y tilt mechanism for tilting the specimen S in Y direction. In this way, the specimen S can be tilted in two directions (X direction and Y direction) orthogonal to each other in the electron microscope  100 . The configuration of the tilt mechanism  13  is not particularly limited. 
     The objective lens  15  is a first-stage lens for forming a transmission-electron-microscope image (TEM image) with an electron beam having passed through the specimen S. The objective lens  15  has a pole piece, which is not illustrated. A magnetic field is generated between the upper pole of the pole piece and the lower pole of the pole piece and focuses an electron beam. 
     The intermediate lens  16  and the projector lens  17  further enlarge the TEM image formed by the objective lens  15  and form the enlarged image on the imaging device  18 . The objective lens  15 , the intermediate lens  16 , and the projector lens  17  constitute an image-forming system in the electron microscope  100 . 
     The imaging device  18  captures the TEM image formed by the image-forming system. The imaging device  18  is a digital camera, for example, a CCD (Charge Coupled Device) camera or a CMOS (Complementary MOS) camera. 
     The X-ray detector  20  detects a characteristic X-ray that is emitted from the specimen S by irradiating the specimen S with an electron beam. The X-ray detector  20  can be, for example, a silicon drift detector (SDD) or a Si (Li) detector. The X-ray detector  20  is disposed near the specimen S when an X-ray is detected. 
     The tilt control unit  30  controls the tilt mechanism  13 . The tilt control unit  30  controls the X tilt mechanism of the specimen stage  14  and the Y tilt mechanism of the specimen holder  12 . For example, the tilt control unit  30  controls the tilt mechanism  13  to perform processing for tilting the specimen S. The tilt control unit  30  includes an input receiving unit for receiving an input of tilt angle information on the tilt angle of the specimen S. The tilt angle of the specimen S is the angle of specimen S with respect to a horizontal plane. The functions of the input receiving unit can be implemented by, for example, a keyboard, a mouse, a button, a touch panel, and a touch pad. 
     The tilt control unit  30  sends the tilt angle information on the tilt angle of the specimen S to the detector control unit  40 . The tilt control unit  30  sends the tilt angle information to the detector control unit  40 , so that the tilt angle information can be shared by the tilt control unit  30  and the detector control unit  40 . 
     The tilt angle information includes information on the tilt angle of the specimen S in X direction and information on the tilt angle of the specimen S in Y direction. The tilt angle information is information for specifying the tilt angle of the specimen S. 
     The tilt control unit  30  includes, for example, a central processing unit (CPU) and storage devices (random access memory (RAM) and read only memory (ROM)). In the tilt control unit  30 , programs stored in the storage device are executed by hardware such as a CPU, so that various kinds of calculation and various kinds of control are performed. 
     The detector control unit  40  controls the X-ray detector  20 . Moreover, the detector control unit  40  generates analysis data based on an X-ray detection result in the X-ray detector  20 . The analysis data includes spectrum data and mapping data. 
       FIG. 2  is a diagram for describing the X-ray detector  20 . 
     When an X-ray enters the X-ray detector  20 , a charge is generated according to the energy of the X-ray in the X-ray detector  20 . The charge is converted into a voltage by a field-effect transistor in the X-ray detector  20 . A signal (pulse signal) outputted from the X-ray detector  20  is amplified by a proportional amplifier  22  and is counted for each peak value by a multichannel pulse height analyzer  24 . The detector control unit  40  generates, based on the number of pulses for each peak value, spectrum data on spectrums indicated by X-ray energy plotted on the horizontal axis and the number of X-ray counts (intensity) plotted on the vertical axis. 
       FIG. 3  is a diagram for describing a positional relationship between the X-ray detector  20  and the specimen S. 
     As illustrated in  FIG. 3 , in the electron microscope  100 , the X-ray detector  20  is disposed on the side of the specimen S when an X-ray generated on the specimen S is detected. In the illustrated example, the X-ray detector  20  is disposed in −X direction when viewed from the specimen S. As described above, the electron microscope  100  includes the tilt mechanism  13  capable of tilting the specimen S. In the illustrated example, the specimen S is tilted in X direction by using the X tilt mechanism. 
     In this configuration, when the specimen S is tilted, an X-ray emitted from the specimen S may be blocked by a member disposed near the specimen S. In the example of  FIG. 3 , the X-ray emitted from the specimen S is partially blocked by the specimen holder  12 . Hence, the X-ray enters only a part of a detection surface  21  of the X-ray detector  20 . This reduces the detection solid angle of the X-ray detector  20 . In this case, the detection solid angle means a solid angle from the incident point of an electron beam on the specimen S to the detection surface  21  of the X-ray detector  20 . The detection solid angle can be increased with the effective detection area of the detection surface  21 . The larger the detection solid angle, the higher the detection efficiency. 
       FIG. 4  illustrates a configuration of the detector control unit  40 . 
     As illustrated in  FIG. 4 , the detector control unit  40  includes a processing unit  410 , an operation unit  420 , a display unit  430 , and a storage unit  440 . 
     The operation unit  420  is provided for a user input of operation information. The inputted operation information is outputted to the processing unit  410 . The functions of the operation unit  420  can be implemented by hardware such as a keyboard, a mouse, a button, a touch panel, and a touch pad. 
     The display unit  430  displays an image generated by the processing unit  410 . The functions of the display unit  430  can be implemented by, for example, liquid crystal display (LCD), a cathode ray tube (CRT), and a touch panel also acting as the operation unit  420 . 
     The storage unit  440  stores programs and various kinds of data that are provided for causing a computer to act as the units of the processing unit  410 . The storage unit  440  also acts as a work area of the processing unit  410 . The functions of the storage unit  440  can be implemented by, for example, a hard disk and RAM. 
     The processing unit  410  controls the X-ray detector  20 . The functions of the processing unit  410  can be implemented by executing programs by means of hardware including various processors (e.g., a CPU). The processing unit  410  includes a detection-solid-angle information acquisition unit  412 , an analysis-data generation unit  414 , and a display control unit  416 . 
     The detection-solid-angle information acquisition unit  412  acquires tilt angle information from the tilt control unit  30  and acquires detection solid-angle information with reference to a table in which the tilt angle information and the detection solid-angle information are associated with each other. 
       FIG. 5  illustrates a table T2 in which the tilt angle information and the detection solid-angle information are associated with each other. 
     The horizontal axis of the table T2 in  FIG. 5  indicates tilt angle information (TiltX) in X direction while the vertical axis indicates tilt angle information (TiltY) in Y direction. In the illustrated example, TiltX denotes the tilt angle [° ] of the specimen S in X direction and TiltY denotes the tilt angle [° ] of the specimen S in Y direction. Coordinates (TiltX,TiltY)=(0,0) indicate that the specimen S has a tilt angle of 0° in X direction and a tilt angle of 0° in Y direction. In other words, the coordinates (TiltX,TiltY)=(0,0) indicate that the specimen S is horizontal. 
     At coordinates (TiltX,TiltY) of the table T2, detection solid-angle information corresponding to tilt angle information expressed by the coordinates is stored. 
     For example, a tilt angle of A[° ] in X direction and a tilt angle of B[° ] in Y direction can be expressed as coordinates (TiltX,TiltY)=(A,B). At coordinates (A,B) of the table T2, C[sr] is stored as detection solid-angle information. Thus, the detection solid-angle information C[sr] can be acquired from the tilt angle information (A,B) with reference to the table T2. 
     In the table T2 of  FIG. 5 , hatching is performed at coordinates where a ratio Ω/Ω max  is at least 80% and coordinates where a ratio Ω/Ω max  is 40% or less where Ω is a detection solid angle, and Ω max  is a maximum detection solid angle obtained by the X-ray detector  20 . 
     The table T2 can be created by, for example, generating the model of the electron microscope  100  with three-dimensional CAD and calculating a detection solid angle by using the model. A detection solid angle is calculated for each of tilt angles that can be formed by the X tilt mechanism and the Y tilt mechanism, so that the table T2 can be created. 
     The table T2, C[sr] is stored in the storage unit  440 . In other words, the storage unit  440  acts as a table storage unit where the table T2 is stored. 
     The analysis-data generation unit  414  generates analysis data based on an X-ray detection result in the X-ray detector  20 . The analysis-data generation unit  414  generates, for example, spectrum data and mapping data. The mapping data includes element mapping data about the distribution of elements on the specimen and spectrum mapping data in which a position and a spectrum on the specimen are associated with each other. 
     The analysis-data generation unit  414  stores the generated analysis data in the storage unit  440 . At this point, the analysis-data generation unit  414  stores the analysis data in association with measurement conditions. The measurement conditions include the detection solid-angle information. The analysis-data generation unit  414  acquires the detection solid-angle information from the detection-solid-angle information acquisition unit  412  and stores the acquired detection solid-angle information in the storage unit  440  in association with the analysis data. 
     The storage unit  440  acts as an analysis-data storage unit which stores measurement condition information in association with the analysis data. 
     In the electron microscope  100 , the single storage device acts as the analysis-data storage unit and the table storage unit. The analysis-data storage unit and the table storage unit may be implemented by different storage devices. 
     The display control unit  416  causes the display unit  430  to display an image based on the detection solid-angle information. The image based on the detection solid-angle information includes numbers, symbols, figures, and graphs. Moreover, the display control unit  416  causes the display unit  430  to display an image based on the analysis data. The image based on the analysis data includes spectrums and maps. 
       FIG. 6  schematically illustrates an analysis screen  2 . 
     The display control unit  416  causes the display unit  430  to display the analysis screen  2 . The analysis screen  2  includes an analysis-result display area  4  and a detection solid-angle display area  6 . In the analysis-result display area  4 , an image based on the analysis data is displayed. In the illustrated example, a spectrum is displayed as an image based on the analysis data. In the detection solid-angle display area  6 , an image based on the detection solid-angle information is displayed. In the illustrated example, a numeric value indicating a detection solid angle is displayed as an image based on the detection solid-angle information. As illustrated in  FIG. 6 , an image displayed based on the detection solid-angle information on the display unit  430  enables a user to easily determine a detection solid angle. 
     1.2. Operation 
     The operations of the electron microscope  100  will be described below. In the electron microscope  100 , the detection solid angle changes in response to a change of the tilt angle of the specimen S. Thus, when the tilt angle of the specimen S is changed, an image for indicating a detection solid angle corresponding to the changed tilt angle is displayed on the display unit  430  in the electron microscope  100 . The display processing that causes the display unit  430  to display an image for indicating a detection solid angle will be described below. 
       FIG. 7  is a flowchart illustrating an example of display processing in the electron microscope  100 . 
     In the electron microscope  100 , when a user operates the input receiving unit of the tilt control unit  30  to input the tilt angle information on the specimen S, the input receiving unit receives the tilt angle information (Yes at S 100 ). 
     The tilt control unit  30  controls the tilt mechanism  13  based on the inputted tilt angle information (S 102 ). The tilt control unit  30  acquires tilt angle information in X direction (TiltX) and tilt angle information in Y direction (TiltY) from the tilt angle information, operates the X tilt mechanism based on the tilt angle information in X direction, and operates the Y tilt mechanism based on the tilt angle information in Y direction. Thus, the tilt angle of the specimen S reaches a tilt angle corresponding to the inputted tilt angle information. 
     The tilt control unit  30  then sends the tilt angle information to the detector control unit  40  (S 104 ). Thus, the tilt angle information on the current tilt angle of the specimen S can be shared in the tilt control unit  30  and the detector control unit  40 . The tilt angle information may be sent before the control of the tilt mechanism  13  (S 102 ) or concurrently with the control of the tilt mechanism  13  (S 102 ). 
     The detection-solid-angle information acquisition unit  412  acquires tilt angle information from the tilt control unit  30  and acquires detection solid-angle information with reference to the table T2 (S 106 ). 
     The analysis-data generation unit  414  determines whether the user has provided an instruction to start measurement (start instruction) (S 108 ). For example, when a start instruction is inputted from the operation unit  420 , it is determined that the start instruction has been provided. 
     If it is determined that the start instruction has been provided (Yes at S 108 ), the analysis-data generation unit  414  generates analysis data based on an X-ray detection result in the X-ray detector  20  (S 110 ). As illustrated in  FIG. 6 , the display control unit  416  causes the display unit  430  to display an image based on the analysis data and an image based on the detection solid-angle information (S 112 ). Thus, as illustrated in  FIG. 6 , the display unit  430  displays an image indicating the analysis data and an image indicating the detection solid angle of the X-ray detector  20  during measurement. 
     The analysis-data generation unit  414  stores the detection solid-angle information in the storage unit  440  in association with the analysis data (S 114 ). 
     If it is determined that a start instruction has not been provided (No at S 108 ), the display control unit  416  causes the display unit  430  to display an image based on the detection solid-angle information (S 116 ). Thus, the display unit  430  displays an image indicating the current detection solid angle of the X-ray detector  20 . After processing S 114  or processing S 116 , the electron microscope  100  terminates the display processing. 
     1.3. Operation/Working-Effect 
     The electron microscope  100  includes the storage unit  440  that stores the table T2 in which the tilt angle information on the tilt angle of the specimen S and the detection solid-angle information on the detection solid angle of the X-ray detector  20  are associated with each other, the tilt control unit  30  for controlling the tilt mechanism  13 , and the detection-solid-angle information acquisition unit  412  that acquires the tilt angle information from the tilt control unit  30  and acquires the detection solid-angle information with reference to the table T2. As described above, in the electron microscope  100 , the detection-solid-angle information acquisition unit  412  acquires the detection solid-angle information from the tilt angle information with reference to the table T2, thereby easily determining the detection solid angle. 
     In the electron microscope  100 , the analysis-data generation unit  414  acquires the detection solid-angle information from the detection-solid-angle information acquisition unit  412  and stores the acquired detection solid-angle information in the storage unit  440  in association with the analysis data. In this way, in the electron microscope  100 , the detection solid-angle information is stored in the storage unit  440  in association with the analysis data, enabling analysis in consideration of the detection solid angle. For example, in the case of a quantitative analysis with an acquired spectrum, a detection solid angle can be taken into consideration. This can increase the quantitative accuracy. 
     The electron microscope  100  includes the display control unit  416  that causes the display unit  430  to display an image based on the detection solid-angle information. Thus, the electron microscope  100  allows the user to easily determine the detection solid angle. Hence, even in the case of analyses on multiple specimens S, detection solid angles can be analyzed under the same conditions in the electron microscope  100 . 
     1.4. Modification 
     A modification of the electron microscope according to the first embodiment will be described below. Differences from the example of the electron microscope  100  will be described below and an explanation of similar points is omitted. 
     1.4.1. First Modification 
       FIGS. 8 and 9  schematically illustrate a modification of the analysis screen  2 . 
     In the foregoing embodiment, as illustrated in  FIG. 6 , a numeric value indicating a detection solid angle in the detection solid-angle display area  6  is displayed as an image based on the detection solid-angle information. An image based on the detection solid-angle information is not limited thereto. 
     For example, as illustrated in  FIG. 8 , the image based on the detection solid angle may indicate a detection solid angle as a ratio Ω/Ω max  (hereinafter may be simply referred to as “ratio Ω/Ω max  to a maximum detection solid angle”) of a detection solid angle Ω to a maximum detection solid angle Ω max  obtained by the X-ray detector  20 . In this case, detection solid-angle information recorded at the coordinates of the table T2 in  FIG. 5  may be a ratio Ω/Ω max  to a maximum detection solid angle. 
     For example, as illustrated in  FIG. 9 , the image based on the detection solid angle may indicate a ratio Ω/Ω max  to a maximum detection solid angle as a figure or a graph. In the illustrated example, only an area of a circle is filled according to the ratio Ω/Ω max  to the maximum detection solid angle, thereby indicating the ratio Ω/Ω max  to the maximum detection solid angle. 
     Furthermore, as an image based on the detection solid-angle information, an area actually irradiated with an X-ray and an area not irradiated with an X-ray may be displayed on a schematic image of the detection surface  21 . These areas are not illustrated. This can visually identify an area actually irradiated with an X-ray on the detection surface  21 . 
     1.4.2. Second Modification 
     In a second modification, the electron microscope  100  sets a measurement time based on a detection solid angle such that a signal amount is kept constant in each measurement even when the detection solid angle is changed.  FIG. 10  illustrates a modification of the detector control unit  40 . 
     As illustrated in  FIG. 10 , in the second modification, the processing unit  410  of the detector control unit  40  includes a measurement time setting unit  417 . 
     The measurement time setting unit  417  sets a measurement time based on a detection solid-angle information. A measurement time is a time for detecting an X-ray by the X-ray detector  20  in each measurement. 
     The measurement time setting unit  417  sets a measurement time based on detection solid-angle information such that a signal amount (X-ray dosage) detected by the X-ray detector  20  is kept constant in each measurement even when multiple measurements are conducted at different detection solid angles. 
     For example, when a ratio Ω/Ω max  to a maximum detection solid angle is 100%, the measurement time setting unit  417  sets the measurement time at 2×t seconds in response to a change of the ratio Ω/Ω max  to the maximum detection solid angle to 50% with a measurement time set at t seconds. This can keep a constant signal amount. 
     For example, when a ratio Ω/Ω max  to a maximum detection solid angle is 50%, the measurement time setting unit  417  sets the measurement time at t/2 seconds in response to a change of the ratio Ω/Ω max  to the maximum detection solid angle to 100% with a measurement time set at t seconds. This can keep a constant signal amount. 
       FIG. 11  is a flowchart illustrating an example of processing for setting a measurement time in the electron microscope  100 . 
     In the electron microscope  100 , when a user operates the operation unit  420  of the detector control unit  40  to input measurement time information for setting a measurement time, the operation unit  420  receives the measurement time information (Yes at S 200 ). When receiving the measurement time information, the operation unit  420  sends the measurement time information to the processing unit  410 . In this way, the operation unit  420  acts as an input receiving unit for receiving the measurement time information. 
     The measurement time setting unit  417  acquires the measurement time information from the operation unit  420  and sets a measurement time based on the acquired measurement time information (S 202 ). 
     The tilt control unit  30  then sends tilt angle information to the detector control unit  40  (S 204 ). Thus, current tilt angle information on the specimen S can be shared in the tilt control unit  30  and the detector control unit  40 . The tilt angle information may be sent before the setting of a measurement time (S 202 ) or concurrently with the setting of a measurement time (S 202 ). 
     The detection-solid-angle information acquisition unit  412  acquires the tilt angle information from the tilt control unit  30  and acquires detection solid-angle information with reference to the table T2 (S 206 ). 
     The measurement time setting unit  417  determines whether a detection solid angle has been changed, based on detection solid-angle information (S 208 ). If the measurement time setting unit  417  determines that a detection solid angle is not changed (No at S 208 ), the process returns to processing S 204 , and then the processing S 204  for sending the tilt angle information by the tilt control unit  30  and the processing S 206  for acquiring the tilt solid-angle information by the detection-solid-angle information acquisition unit  412  are performed. The measurement time setting unit  417  then determines whether a detection solid angle has been changed (S 208 ). In this way, the measurement time setting unit  417  monitors a detection solid angle. 
     If the measurement time setting unit  417  determines that a detection solid angle has been changed (Yes at S 208 ), a measurement time is set based on detection solid-angle information (S 210 ). 
     For example, when a ratio to a maximum detection solid angle has changed from 100% to 50%, the measurement time setting unit  417  changes a measurement time from t seconds to  2   x  seconds. For example, when a ratio to a maximum detection solid angle has changed from 50% to 100%, the measurement time setting unit  417  changes a measurement time from t seconds to t/2 seconds. After the processing S 210 , the electron microscope  100  terminates the processing for setting a measurement time. 
     In the second modification, the electron microscope  100  includes the measurement time setting unit  417  that sets a measurement time for detecting an X-ray by the X-ray detector  20 . The measurement time setting unit  417  sets a measurement time based on the detection solid-angle information. Thus, the electron microscope  100  can set uniform conditions for a signal amount detected by the X-ray detector  20  in each measurement even when multiple measurements are conducted at different detection solid angles. 
     1.4.3. Third Modification 
     In a third modification, when a user inputs desired detection solid-angle information via the operation unit  420 , the electron microscope  100  tilts the specimen S to a desired detection solid angle.  FIG. 12  illustrates a modification of the detector control unit  40 . 
     As illustrated in  FIG. 12 , in the third modification, the processing unit  410  of the detector control unit  40  includes a tilt-angle information acquisition unit  418 . 
     When the user inputs detection solid-angle information via the operation unit  420 , the operation unit  420  receives the detection solid-angle information and sends the information to the processing unit  410 . In this way, the operation unit  420  acts as an input receiving unit for receiving the detection solid-angle information. 
     The tilt-angle information acquisition unit  418  acquires the detection solid-angle information from the operation unit  420  and acquires tilt angle information with reference to the table T2. For example, if C[sr] is inputted as detection solid-angle information, the tilt-angle information acquisition unit  418  searches the table T2 for coordinates where C[sr] is stored. In the table T2 of  FIG. 5 , C[sr] is stored at coordinates (TiltX,TiltY)=(A,B). Thus, the tilt-angle information acquisition unit  418  acquires a tilt angle of A[° ] in X direction and a tilt angle of B[° ] in Y direction as tilt angle information. 
     The tilt-angle information acquisition unit  418  sends the acquired tilt angle information to the tilt control unit  30 . The tilt control unit  30  controls the tilt mechanism  13  based on the tilt angle information. Hence, the user can perform a measurement at a desired detection solid angle. 
       FIG. 13  is a flowchart illustrating an example of processing for setting a detection solid angle in the electron microscope  100 . 
     In the electron microscope  100 , when the user operates the operation unit  420  of the detector control unit  40  to input detection solid-angle information, the operation unit  420  receives the detection solid-angle information (Yes at S 300 ). The operation unit  420  sends the detection solid-angle information to the processing unit  410 . 
     The tilt-angle information acquisition unit  418  acquires the detection solid-angle information from the operation unit  420  and acquires tilt angle information with reference to the table T2 (S 302 ). The tilt-angle information acquisition unit  418  sends the acquired tilt angle information to the tilt control unit  30  (S 304 ). 
     The tilt control unit  30  controls the tilt mechanism  13  based on the tilt angle information (S 306 ). Thus, the specimen S tilts, and the detection solid angle of the X-ray detector  20  reaches a detection solid angle corresponding to the inputted detection solid-angle information. After the processing S 306 , the electron microscope  100  terminates the processing for setting a detection solid angle. 
     In the third modification, the electron microscope  100  includes the operation unit  420  acting as an input receiving unit for receiving the input of the detection solid-angle information, and the tilt-angle information acquisition unit  418  that acquires the detection solid-angle information from the input receiving unit and acquires tilt angle information with reference to the table T2. The tilt control unit  30  controls the tilt mechanism  13  based on the tilt angle information. Thus, the electron microscope  100  can operate the tilt control unit  30  with a desired detection solid angle. This can automatically set the detection solid angle of the X-ray detector  20  to a desired detection solid angle in the electron microscope  100 . 
     1.4.4. Fourth Modification 
     In a fourth modification, the electron microscope  100  notifies warning information when a detection solid angle is small.  FIG. 14  illustrates a modification of the detector control unit  40 . 
     As illustrated in  FIG. 14 , in the fourth modification, the processing unit  410  of the detector control unit  40  includes a notification unit  419 . 
       FIG. 15  illustrates an example of a notification by the notification unit  419 . 
     The notification unit  419  notifies warning information when a detection solid angle is smaller than a preset threshold. As indicated in  FIG. 15 , a notification by the notification unit  419  is a message  8  for warning of a small detection solid angle. A notification by the notification unit  419  is not limited to the display of the message  8 . For example, the notification may be a notification with a beeper sound or a notification with lamplight. 
       FIG. 16  is a flowchart illustrating an example of processing for a notification in the electron microscope  100 . 
     In the electron microscope  100 , when a user operates the input receiving unit of the tilt control unit  30  to input tilt angle information on the specimen S, the input receiving unit receives the tilt angle information (Yes at S 400 ). The input receiving unit outputs the tilt angle information to the tilt control unit  30 . 
     The tilt control unit  30  controls the tilt mechanism  13  based on the inputted tilt angle information (S 402 ). The tilt control unit  30  sends the tilt angle information to the detector control unit  40  (S 404 ). 
     The detection-solid-angle information acquisition unit  412  acquires the tilt angle information from the tilt control unit  30  and acquires detection solid-angle information with reference to the table T2 (S 406 ). 
     The notification unit  419  determines whether a detection solid angle indicated by the detection solid-angle information acquired by the detection-solid-angle information acquisition unit  412  is smaller than the preset threshold (S 408 ). If it is determined that the detection solid angle indicated by the detection solid-angle information is smaller than the threshold (Yes at S 408 ), the notification unit  419  notifies warning information (S 410 ). 
     If it is determined that the detection solid angle is not smaller than the threshold (No at S 408 ) or after the processing S 410 , the electron microscope  100  terminates the notification. 
     In the fourth modification, the electron microscope  100  includes the notification unit  419 , allowing a user to easily determine that a detection solid angle is small. 
     1.4.5. Fifth Modification 
       FIG. 17  illustrates a modification of the detector control unit  40 . 
     The specimen holder  12  appears in various forms according to the purpose of observation or analysis. The relationship between tilt angle information and detection solid angle information changes depending upon the shape of the tip of the specimen holder  12 . 
     In the fifth modification, the electron microscope  100  includes a first specimen holder and a second specimen holder as the specimen holder  12 . The first specimen holder and the second specimen holder have tips in different shapes. 
     Moreover, the storage unit  440  stores a table T2 (an example of a first table) and a table T4 (an example of a second table). In the table T2, tilt angle information and detection solid-angle information in the first specimen holder are associated with each other. In the table T4, tilt angle information and detection solid-angle information in the second specimen holder are associated with each other. 
     When receiving information for specifying the kind of specimen holder, the detection-solid-angle information acquisition unit  412  determines whether to use the table T2 or the table T4 based on the information. 
     For example, the information for specifying the kind of specimen holder is inputted by a user via the operation unit  420 , so that the information for specifying the kind of specimen holder is sent from the operation unit  420  to the processing unit  410 . The information for specifying the kind of specimen holder may be acquired by reception by the detection-solid-angle information acquisition unit  412 , the information being outputted from the first specimen holder and the second specimen holder. 
     In the foregoing description, the electron microscope  100  includes two kinds of specimen holder  12 . The electron microscope  100  may include three or more kinds of specimen holder  12 . In this case, the number of tables stored in the storage unit  440  increases with the number of kinds of specimen holder  12 . 
     2. Second Embodiment 
     2.1. Electron Microscope 
     An electron microscope according to a second embodiment will be described below with reference to the accompanying drawings.  FIGS. 18 and 19  illustrate configurations of an electron microscope  200  according to the second embodiment. 
     In the electron microscope  200  according to the second embodiment, members having the same functions as the components of the electron microscope  100  according to the first embodiment are indicated by the same reference numerals, and a detailed explanation thereof is omitted. 
     The electron microscope  100  includes the single X-ray detector  20  as illustrated in  FIGS. 1 and 2 , whereas the electron microscope  200  includes a second X-ray detector  220  in addition to an X-ray detector  20  (hereinafter also referred to as “first X-ray detector  20 ”) as illustrated in  FIGS. 18 and 19 . In other words, the electron microscope  200  includes two X-ray detectors. 
     As illustrated in  FIG. 19 , when viewed from a specimen S, the first X-ray detector  20  is disposed in −X direction, whereas the second X-ray detector  220  is disposed in +Y direction. 
     When an X-ray enters the first X-ray detector  20 , a charge is generated according to the energy of the X-ray in the first X-ray detector  20 . The charge is converted into a voltage by a field-effect transistor in the X-ray detector  20 . A signal (pulse signal) outputted from the first X-ray detector  20  is amplified by a proportional amplifier  22 . 
     When an X-ray enters the second X-ray detector  220 , a charge is generated according to the energy of the X-ray in the second X-ray detector  220 . The charge is converted into a voltage by a field-effect transistor in the second X-ray detector  220 . A signal (pulse signal) outputted from the second X-ray detector  220  is amplified by a proportional amplifier  222 . 
     A pulse signal outputted from the first X-ray detector  20  and a pulse signal outputted from the second X-ray detector  220  are counted for each peak value by a multichannel pulse height analyzer  24 . The detector control unit  40  generates, based on the number of pulses for each peak value, data on spectrums (spectrum data) indicated by X-ray energy plotted on the horizontal axis and the number of X-ray counts (intensity) plotted on the vertical axis. 
     The electron microscope  200  includes the first X-ray detector  20  and the second X-ray detector  220 , thereby improving the detection efficiency. 
       FIG. 20  is a diagram for describing a positional relationship between the first X-ray detector  20  and the specimen S and a positional relationship between the second X-ray detector  220  and the specimen S. 
     As illustrated in  FIG. 20 , in the electron microscope  200 , the first X-ray detector  20  and the second X-ray detector  220  are disposed on the side of the specimen S when an X-ray generated on the specimen S is detected. 
     In this configuration, the first X-ray detector  20  and the second X-ray detector  220  are disposed at different positions. In the illustrated example, the detection surface  21  of the first X-ray detector  20  is directed in +X direction while a detection surface  221  of the second X-ray detector  220  is directed in −Y direction. The specimen S tilts in +X direction. Thus, even if the tilt angle of the specimen S remains the same, the detection solid angle of the first X-ray detector  20  and the detection solid angle of the second X-ray detector  220  are different from each other. For this reason, the relationship between a tilt angle and a detection solid angle in the first X-ray detector  20  and the relationship between a tilt angle and a detection solid angle in the second X-ray detector  220  are different from each other. 
       FIG. 21  is a diagram illustrating a configuration of the detector control unit  40 . 
     As described above, the relationship between a tilt angle and a detection solid angle in the first X-ray detector  20  and the relationship between a tilt angle and a detection solid angle in the second X-ray detector  220  are different from each other. Thus, a storage unit  440  stores a table T2 (an example of a third table) in which tilt angle information and detection solid-angle information are associated with each other in the first X-ray detector  20  and a table T6 (an example of a fourth table) in which tilt angle information and detection solid-angle information are associated with each other in the second X-ray detector  220 . 
     The detection-solid-angle information acquisition unit  412  refers to the table T2 when acquiring the detection solid-angle information in the first X-ray detector  20  from the tilt angle information. Furthermore, the detection-solid-angle information acquisition unit  412  refers to the table T6 when acquiring the detection solid-angle information in the second X-ray detector  220  from the tilt angle information. 
     If the electron microscope  200  includes two kinds of specimen holder, the storage unit  440  stores four tables, which are not illustrated. 
       FIG. 22  illustrates the table T6 in which tilt angle information and detection solid-angle information in the second X-ray detector  220  are associated with each other. 
     As indicated in  FIG. 22 , the table T6 is different from the table T2 in  FIG. 5 . The table T6 is created by the same method as the table T2. 
     A display control unit  416  causes a display unit  430  to display an image based on the detection solid-angle information of the first X-ray detector  20  and an image based on the detection solid-angle information of the second X-ray detector  220 . 
       FIGS. 23 to 25  each schematically illustrate an analysis screen  2 . 
     As illustrated in  FIG. 23 , the detection solid angle of the first X-ray detector  20 , the detection solid angle of the second X-ray detector  220 , and the sum of the detection solid angle of the first X-ray detector  20  and the detection solid angle of the second X-ray detector  220  may be displayed in a detection solid-angle display area  6 . 
     As illustrated in  FIG. 24 , a ratio Ω/Ω max  to a maximum detection solid angle in the first X-ray detector  20 , a ratio Ω/Ω max  to a maximum detection solid angle in the second X-ray detector  220 , and the mean value of the ratio Ω/Ω max  to the maximum detection solid angle in the first X-ray detector  20  and the ratio Ω/Ω max  to the maximum detection solid angle in the second X-ray detector  220  may be displayed in the detection solid-angle display area  6 . 
     As illustrated in  FIG. 25 , a ratio Ω/Ω max  to a maximum detection solid angle in the first X-ray detector  20  and a ratio Ω/Ω max  to a maximum detection solid angle in the second X-ray detector  220  may be displayed as figures or graphs in the detection solid-angle display area  6 . 
     2.2. Operation 
     The display processing in the electron microscope  200  is different from the display processing in the electron microscope  100  in  FIG. 7  in that in processing S 106 , the electron microscope  200  refers to the table T2 when acquiring the detection solid-angle information of the first X-ray detector  20  and refers to the table T6 when acquiring the detection solid-angle information of the second X-ray detector  220 . Other processing is similar to the display processing in the electron microscope  100  illustrated in  FIG. 7 , and an explanation thereof is omitted. 
     2.3. Operation/Working-Effect 
     In the electron microscope  200 , the table T2 and the table T6 are stored in the storage unit  440 . Thus, in the electron microscope  200 , the detection solid angle of the first X-ray detector  20  and the detection solid angle of the second X-ray detector  220  can be easily determined. 
     2.4. Modification 
     The second to fifth modifications of the first embodiment are also applicable to the second embodiment. 
     3. Others 
     The invention is not limited to the foregoing embodiments and can be modified in various ways within the scope of the invention. 
     For example, in the first embodiment and the second embodiment, the specimen is irradiated with an electron beam to generate an X-ray on the specimen. A charged particle beam apparatus according to the invention may generate an X-ray on a specimen by emitting a charged particle beam (e.g., an ion beam) other than an electron beam. 
     The charged particle beam apparatus according to the invention may include a detector for detecting electromagnetic waves other than X-rays. For example, the charged particle beam apparatus according to the invention may include a detector for detecting light (cathode luminescence) generated by irradiating a specimen with an electron beam. 
     The charged particle beam apparatus according to the invention may be, for example, a scanning transmission electron microscope (STEM), a scanning electron microscope (SEM), an electron probe microanalyzer (EPMA), a focused ion beam system (FIB), or a cathode luminescence microscope. 
     The above-described embodiments and modifications are examples and the invention is not limited thereto. For example, the embodiments and the modifications may be combined appropriately. 
     The invention is not limited to the above-described embodiments, and various modifications can be made. For example, the invention includes configurations that are substantially the same as the configurations described in the embodiments. Substantially same configurations means configurations having the same functions, methods and results, or configurations having the same objectives and effects as those of the configurations described in the embodiments, for example. The invention also includes configurations in which non-essential components described in the embodiments are replaced by other components. The invention also includes configurations having the same effects as those of the configurations described in the embodiments, or configurations capable of achieving the same objectives as those of the configurations described in the embodiments. The invention further includes configurations obtained by adding known art to the configurations described in the embodiments. 
     Some embodiments of the invention have been described in detail above, but a person skilled in the art will readily appreciate that various modifications can be made from the embodiments without materially departing from the novel teachings and effects of the invention. Accordingly, all such modifications are assumed to be included in the scope of the invention.