Patent Publication Number: US-11651936-B2

Title: Charged particle beam apparatus

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2020-208387 filed Dec. 16, 2020, 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 
     In a charged particle beam apparatus, such as a transmission electron microscope, a specimen is loaded into a specimen chamber and observed and analyzed. In such charged particle beam apparatuses, a charged particle beam apparatus, that includes a transporting mechanism to transport a specimen between the specimen chamber and the specimen exchange chamber, is known. 
     For example, JP-A-2015-88237 discloses a charged particle beam apparatus equipped with a transporting mechanism that transports a cartridge, in which a specimen is fixed, between a specimen exchange chamber and a specimen chamber. The transporting mechanism transfers the cartridge to a specimen holder disposed in the specimen chamber. 
     If there is a temperature difference between the transporting mechanism and the specimen holder when the transporting mechanism transfers a specimen to the specimen holder, a position of the transporting mechanism and a position of the specimen holder are misaligned when a specimen is transferred. For example, when the temperature of the transporting mechanism is lower than the temperature of the specimen holder, a member constituting the transporting mechanism contracts more than a member constituting the specimen holder, and this causes the misalignment. 
     If the misalignment occurs like this, the specimen holder and the transporting mechanism may rub against each other, or the specimen holder and the cartridge may rub against each other. Because of this, metal particles may scatter in the specimen chamber. Further, the transporting mechanism and the specimen holder may deteriorate. Furthermore, the cartridge may not be transported normally, and the cartridge may drop into a lens barrel, or damage the transporting mechanism or the specimen holder. 
     SUMMARY OF THE INVENTION 
     According to an aspect of the invention, there is provided a charged particle beam apparatus including: 
     a specimen chamber; 
     a specimen holder that is disposed in the specimen chamber; 
     a specimen exchange chamber that is connected to the specimen chamber; 
     a transporting mechanism that transports a specimen between the specimen chamber and the specimen exchange chamber; 
     a first temperature sensor that measures a temperature of the specimen holder; 
     a second temperature sensor that measures a temperature of the transporting mechanism; and 
     a control unit that controls the transporting mechanism, 
     the control unit performing processing of: 
     calculating a temperature difference between the specimen holder and the transporting mechanism based on information on the temperature of the specimen holder measured by the first temperature sensor and information on the temperature of the transporting mechanism measured by the second temperature sensor when the control unit has received an instruction to transport a specimen; 
     determining whether or not the temperature difference is a threshold or more; and 
     stopping transportation of a specimen when the control unit has determined that the temperature difference is the threshold or more. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1    is a diagram illustrating a configuration of an electron microscope according to an embodiment of the invention. 
         FIG.  2    is a diagram illustrating a configuration of a second transporting mechanism. 
         FIG.  3    is a diagram illustrating a configuration of a control unit. 
         FIG.  4    is a flow chart illustrating an example of a transporting processing. 
         FIG.  5    is a diagram illustrating a state where a second transporting mechanism is transporting a cartridge from a specimen exchange chamber to a specimen chamber. 
         FIG.  6    is a diagram illustrating a state where a second transporting mechanism is transporting a cartridge from a specimen exchange chamber to a specimen chamber. 
         FIG.  7    is a diagram illustrating a state where a second transporting mechanism is transporting a cartridge from a specimen exchange chamber to a specimen chamber. 
         FIG.  8    is a diagram illustrating a state where positions of a specimen holder and a second transporting mechanism are misaligned when a cartridge is transferred. 
         FIG.  9    is a diagram illustrating an electron microscope according to a modification. 
     
    
    
     DESCRIPTION OF THE INVENTION 
     A charged particle beam apparatus according to an embodiment of the invention, includes: 
     a specimen chamber; 
     a specimen holder that is disposed in the specimen chamber; 
     a specimen exchange chamber that is connected to the specimen chamber; 
     a transporting mechanism that transports a specimen between the specimen chamber and the specimen exchange chamber; 
     a first temperature sensor that measures a temperature of the specimen holder; 
     a second temperature sensor that measures a temperature of the transporting mechanism; and 
     a control unit that controls the transporting mechanism, 
     the control unit performing processing of: 
     calculating a temperature difference between the specimen holder and the transporting mechanism based on information on the temperature of the specimen holder measured by the first temperature sensor and information on the temperature of the transporting mechanism measured by the second temperature sensor when the control unit has received an instruction to transport a specimen; 
     determining whether or not the temperature difference is a threshold or more; and 
     stopping transportation of a specimen when the control unit has determined that the temperature difference is the threshold or more. 
     In this charged particle beam apparatus, transportation of a specimen is stopped if there is a temperature difference between the specimen holder and the transporting mechanism, hence it can be prevented that the specimen holder and the transporting mechanism rub against each other or the specimen holder and the specimen rub against each other by the misalignment of the specimen holder and the transporting mechanism when a specimen is transferred. 
     Preferred embodiments of the invention will be 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. Further, all of the components described in the following embodiments are not necessarily essential requirements of the invention. 
     In the following, a transmission electron microscope, that performs observation and analysis of a specimen by emitting an electron beam onto the specimen, will be described as an example of the charged particle beam apparatus according to the invention, but the charged particle beam apparatus according to the invention may be an apparatus that performs observation and analysis of a specimen by emitting a charged particle beam other than an electron beam, such as an ion beam. 
     1. Electron Microscope 
     First an electron microscope, which is an embodiment of the invention, will be described with reference to the drawings.  FIG.  1    is a diagram illustrating a configuration of an electron microscope  100  according to an embodiment of the invention. 
     The electron microscope  100  is a transmission electron microscope (cryo-electron microscope) that can load and observe a specimen in a frozen state. With the electron microscope  100 , a specimen can be observed at a liquid nitrogen temperature, for example. 
     As illustrated in  FIG.  1   , the electron microscope  100  includes a specimen container  10 , a specimen chamber  20 , a specimen holder  24 , a specimen stage  26 , a first cooling mechanism  28 , a specimen exchange chamber  30 , a gate valve  40 , an evacuation device  50 , a specimen storage  60 , a second cooling mechanism  70 , a first transporting mechanism  80 , a second transporting mechanism  90 , and a control unit  102 . 
     The specimen container  10  is a container to transport a cooled specimen. The specimen container  10  can contain a magazine  4  in which a plurality of cartridges  2  is installed. In each cartridge  2 , a specimen is fixed. 
     Specimens may be contained directly in the specimen container  10  without using the cartridge  2  or magazine  4 . 
     The specimen container  10  can be connected to the specimen exchange chamber  30 . As illustrated in  FIG.  1   , the specimen container  10  is connected to the specimen exchange chamber  30  in the state where the gate valve  40  is closed. The specimen container  10  is connected to the specimen exchange chamber  30  via a connecting member  42 . 
     The specimen container  10  is evacuated by the evacuation device  50  in the state where the gate valve  40  is closed. Therefore an increase of pressure (deterioration of degree of vacuum) in the specimen exchange chamber  30  can be prevented, even if the gate valve  40  is opened. Therefore in the electron microscope  100 , the magazine  4  can be loaded from the specimen container  10  to the specimen exchange chamber  30  while maintaining the specimen exchange chamber  30  in the vacuum state. 
     The specimen chamber  20  includes a space inside a lens barrel  22 . In the lens barrel  22 , an electron source, an irradiation optical system to irradiate a specimen with an electron beam emitted from the electron source, and an imaging system to form a transmission electron microscope image by the electron beam transmitted through a specimen are arranged, (these composing elements are not illustrated in  FIG.  1   ). The electron microscope  100  also includes a detector to detect an image formed by the imaging system, a detector to detect an X-ray emitted from a specimen, and the like (these composing elements are not illustrated in  FIG.  1   ). 
     The specimen holder  24  is disposed in the specimen chamber  20 . The specimen holder  24  is installed in the specimen stage  26 . The specimen held by the specimen holder  24  is positioned by the specimen stage  26 . In the specimen chamber  20 , a specimen is irradiated with the electron beam. The specimen chamber  20  is evacuated by an evacuation device (not illustrated). Thereby the specimen chamber  20  is maintained in a vacuum state. 
     The specimen holder  24  is a holder that can cool a specimen. The specimen holder  24  includes the first cooling mechanism  28  to cool a specimen. For example, the first cooling mechanism  28  includes a tank to store liquid nitrogen, which is a refrigerant. Thereby a specimen can be cooled down to the liquid nitrogen temperature in the specimen holder  24 . 
     The specimen exchange chamber  30  is connected to the specimen chamber  20 . A gate valve  32  is disposed between the specimen exchange chamber  30  and the specimen chamber  20 . The gate valve  32  is a valve that is used as a vacuum partition between the specimen exchange chamber  30  and the specimen chamber  20 . 
     The specimen exchange chamber  30  is evacuated by the evacuation device  50 . Thereby the specimen exchange chamber  30  is maintained in a vacuum state. 
     The specimen container  10  is connected to the specimen exchange chamber  30 . In the case of the example in  FIG.  1   , the specimen container  10  is connected to the specimen exchange chamber  30  via a connecting member  42 . The connecting member  42  is connected to the specimen exchange chamber  30 . An O-ring  44  is attached to the end face of the connecting member  42 , so that the space between the specimen container  10  and the connecting member  42  is sealed by the O-ring  44 . 
     The evacuation device  50  evacuates the specimen container  10  via an exhaust pipe  52 . A solenoid valve  54  is disposed in the exhaust pipe  52 . The evacuation device  50  evacuates the specimen container  10  in a state where the specimen container  10  is connected to the specimen exchange chamber  30  and the gate valve  40  is closed, whereby the specimen container  10  can be in a vacuum state. 
     The evacuation device  50  also evacuates the specimen exchange chamber  30 . The evacuation device  50  evacuates the specimen exchange chamber  30  via an exhaust pipe  56 . A solenoid valve  58  is disposed in the exhaust pipe  56 . 
     The specimen storage  60  is disposed in the specimen exchange chamber  30 . The specimen storage  60  is a place to store specimens. The specimen storage  60  can hold a plurality of specimens. In the case of the example of  FIG.  1   , the specimen storage  60  holds a plurality of cartridges  2  in which specimens are fixed respectively. 
     The specimen storage  60  is cooled by the second cooling mechanism  70 . Therefore a specimen can be stored in the cooled state. The specimen storage  60  is formed by a material having high thermal conductivity, for example. 
     The second cooling mechanism  70  cools the specimen storage  60 . The second cooling mechanism  70  includes a tank  72  that stores the refrigerant (e.g. liquid nitrogen tank that stores liquid nitrogen), and a thermally conductive member  74   a  that thermally connects the tank  72  and the specimen storage  60 , for example. The specimen storage  60  can be cooled, since the tank  72  and the specimen storage  60  are thermally connected by the thermally conductive member  74   a.    
     The second cooling mechanism  70  also cools the first transporting mechanism  80  and the second transporting mechanism  90 . The second cooling mechanism  70  includes a thermally conductive member  74   b  that thermally connects the tank  72  and the first transporting mechanism  80 , and a thermally conductive member  74   c  that thermally connects the tank  72  and the second transporting mechanism  90 . The thermally conductive members  74   a ,  74   b  and  74   c  are copper wires, for example. 
     The tank that stores the refrigerant of the first cooling mechanism  28  and the tank  72  may be integrated as a common tank, although this is not illustrated. In other words, the specimen holder  24 , the specimen storage  60 , the first transporting mechanism  80  and the second transporting mechanism  90  may be cooled using this one tank. 
     The first transporting mechanism  80  transports a specimen between the specimen container  10  and the specimen exchange chamber  30 . Here the first transporting mechanism  80  transports a specimen by transporting the magazine  4 . The first transporting mechanism  80  holds the magazine  4  in the specimen container  10 , and transports the held magazine  4  from the specimen container  10  to the specimen exchange chamber  30 . The first transporting mechanism  80  can also transport the magazine  4  from the specimen exchange chamber  30  into the specimen container  10 . 
     The first transporting mechanism  80  is cooled by the second cooling mechanism  70 . Therefore it can be prevented that the temperature of the magazine  4  rises while the magazine  4  is being transported by the first transporting mechanism  80 . 
     The second transporting mechanism  90  transports a specimen between the specimen exchange chamber  30  and the specimen chamber  20 . Here the second transporting mechanism  90  transports a specimen by transporting the cartridge  2 . 
     Specifically, in the specimen exchange chamber  30 , the second transporting mechanism  90  removes the cartridge  2  from the magazine  4  held by the first transporting mechanism  80 , and transfers the cartridge  2  to the specimen holder  24  disposed in the specimen chamber  20 . The second transporting mechanism  90  also removes the cartridge  2  from the specimen holder  24 , and installs the cartridge  2  in the magazine  4  held by the first transporting mechanism  80  in the specimen exchange chamber  30 . 
     Further, in the specimen exchange chamber  30 , the second transporting mechanism  90  removes the cartridge  2  from the specimen storage  60  and transfers the cartridge  2  to the specimen holder  24  disposed in the specimen chamber  20 . Furthermore, the second transporting mechanism  90  removes the cartridge  2  from the specimen holder  24  disposed in the specimen chamber  20 , and installs the cartridge  2  in the specimen storage  60 . 
     Furthermore, in the specimen exchange chamber  30 , the second transporting mechanism  90  transports a specimen between the magazine  4  held by the first transporting mechanism  80  and the specimen storage  60 . Specifically, in the specimen exchange chamber  30 , the second transporting mechanism  90  removes the cartridge  2  from the magazine  4  held by the first transporting mechanism  80 , and installs the cartridge  2  in the specimen storage  60 . The second transporting mechanism  90  also removes the cartridge  2  from the specimen storage  60 , and installs the cartridge  2  in the magazine  4  held by the first transporting mechanism  80 . 
     The second transporting mechanism  90  is cooled by the second cooling mechanism  70 . Therefore it can be prevented that the temperature of the cartridge  2  rises while the cartridge  2  is being transported by the second transporting mechanism  90 . 
     The control unit  102  controls each composing element constituting the electron microscope  100 . For example, in the later mentioned transporting processing, the control unit  102  controls the specimen holder  24 , the gate valve  32  and the second transporting mechanism  90 . 
     2. Configuration of Second Transporting Device 
       FIG.  2    is a diagram illustrating a configuration of the second transporting mechanism  90 . 
     As illustrated in  FIG.  2   , the second transporting mechanism  90  includes a chuck device  92  and a transporting rod  94 . The chuck device  92  is a device to hold the cartridge  2 . The chuck device  92  is disposed at the front end of the transporting rod  94 . The transporting rod  94  supports the chuck device  92 . The second transporting mechanism  90  includes a moving device (not illustrated) that moves the transporting rod  94 . The cartridge  2  that is held by the chuck device  92  can be moved by moving the transporting rod  94  using the moving device. 
     The chuck device  92  and the transporting rod  94  are cooled by the second cooling mechanism  70 . 
     As illustrated in  FIG.  2   , the electron microscope  100  includes a first temperature sensor  110 , a second temperature sensor  112 , a temperature monitor  114 , and a control circuit  120 . 
     The first temperature sensor  110  measures the temperature of the specimen holder  24 . The first temperature sensor  110  is a silicon diode, for example. The first temperature sensor  110  is installed in the specimen holder  24 . 
     The second temperature sensor  112  measures the temperature of the second transporting mechanism  90 . The second temperature sensor  112  is a silicon diode, for example. The second temperature sensor  112  measures the temperature of the chuck device  92 , for example. The second temperature sensor  112  may measure the temperature of the transporting rod  94 . 
     The temperature monitor  114  acquires information on the temperature of the specimen holder  24  and information on the temperature of the second transporting mechanism  90 . The temperature monitor  114  acquires the information on the temperature of the specimen holder  24  based on the output signal of the first temperature sensor  110 , and acquires the information on the temperature of the second transporting mechanism  90  based on an output signal of the second temperature sensor  112 . The temperature monitor  114  has information on the current temperature of the specimen holder  24 , and information on the current temperature of the second transporting mechanism  90 . 
     The control circuit  120  is a circuit to operate the second transporting mechanism  90 , the specimen holder  24  and the gate valve  32 . The control circuit  120  receives a control signal from the control unit  102 , and operates the second transporting mechanism  90 , the specimen holder  24 , and the gate valve  32  based on this control signal. 
     3. Configuration of Control Unit 
       FIG.  3    is a diagram illustrating a configuration of the control unit  102 . 
     As illustrated in  FIG.  3   , the control unit  102  includes a processing unit  210 , an operation unit  220 , a display unit  230 , and a storage unit  240 . 
     The operation unit  220  is for the user to input operation information, and outputs the inputted operation information to the processing unit  210 . The functions of the operation unit  220  can be implemented by such hardware as a keyboard, mouse, buttons, touch panel and touch pad. 
     The display unit  230  displays an image generated by the processing unit  210 . The functions of the display unit  230  can be implemented by a liquid crystal display (LCD), a cathode ray tube (CRT), a touch panel which also functions as an operation unit  220 , or the like. A graphical user interface (GUI) to control the electron microscope  100  is displayed on the display unit  230 . 
     The storage unit  240  stores programs and various data to cause a computer to function as each composing element of the processing unit  210 . The storage unit  240  also functions as a work area of the processing unit  210 . The functions of the storage unit  240  can be implemented by a hard disk, a random access memory (RAM), or the like. 
     The processing unit  210  performs processing to transport the cartridge  2  and the magazine  4 . The functions of the processing unit  210  can be implemented by hardware, such as various processors (e.g. central processing unit (CPU)). The processing unit  210  includes a temperature information acquiring unit  212 , a transporting instruction receiving unit  214 , a temperature difference calculating unit  216 , a transporting control unit  218 , and a notification unit  219 . 
     The temperature information acquiring unit  212  acquires, from the temperature monitor  114 , information on the temperature of the specimen holder  24  measured by the first temperature sensor  110 , and information on the temperature of the second transporting mechanism  90  measured by the second temperature sensor  112 . 
     The temperature information acquiring unit  212  requests the information on the temperature of the specimen holder  24  and the information on the temperature of the second transporting mechanism  90 , to the temperature monitor  114  at predetermined time intervals. Responding to the request from the control unit  102 , the temperature monitor  114  transfers the information on the temperature of the specimen holder  24  and the information on the temperature of the second transporting mechanism  90  to the temperature information acquiring unit  212 . 
     The transporting instruction receiving unit  214  receives an instruction to transport a specimen (transporting instruction). For example, when the transporting button of the GUI displayed on the display unit  230  has been pressed, the transporting instruction receiving unit  214  determines that the user instructed to transport a specimen, and receives the transporting instruction. 
     When the transporting instruction has been received, the temperature difference calculating unit  216  calculates the temperature difference between the specimen holder  24  and the second transporting mechanism  90  based on the information on the temperature of the specimen holder  24  measured by the first temperature sensor  110  and the information on the temperature of the second transporting mechanism  90  measured by the second temperature sensor  112 . 
     The transporting control unit  218  controls the first transporting mechanism  80  and the second transporting mechanism  90 . The transporting control unit  218  also controls the specimen holder  24 . 
     Further, the transporting control unit  218  determines whether or not the temperature difference between the specimen holder  24  and the second transporting mechanism  90  is a threshold or more. 
     The threshold has been stored in the storage unit  240  in advance. For example, the threshold is set to a value of a temperature difference or less, with which misalignment does not occur between the second transporting mechanism  90  and the specimen holder  24  when the cartridge  2  is transferred between the second transporting mechanism  90  and the specimen holder  24 . For example, an optimum threshold can be determined by repeatedly transferring the cartridge  2  between the second transporting mechanism  90  and the specimen holder  24  at a different temperature difference setting. The threshold is set to 30° C., for example. The threshold can be changed when necessary. 
     When the transporting control unit  218  has determined that the temperature difference between the specimen holder  24  and the second transporting mechanism  90  is lower than the threshold, the transporting control unit  218  transfers the cartridge  2  from the specimen exchange chamber  30  to the specimen chamber  20 . In a case where the cartridge  2  is in the specimen chamber  20 , the transporting control unit  218  may transport the cartridge  2  from the specimen chamber  20  to the specimen exchange chamber  30 , if the transporting control unit  218  has determined that the temperature difference between the specimen holder  24  and the second transporting mechanism  90  is smaller than the threshold. 
     When the transporting control unit  218  has determined that the temperature difference between the specimen holder  24  and the second transporting mechanism  90  is the threshold or more, the transporting control unit  218  stops the transporting of the cartridge  2 . 
     When the transporting control unit  218  has determined that the temperature difference between the specimen holder  24  and the second transporting mechanism  90  is the threshold or more, the notification unit  219  notifies alarm information. The alarm information is a message indicating that the transporting is stopped since the temperature difference between the specimen holder  24  and the second transporting mechanism  90  is large, for example. The notification unit  219  causes the display unit  230  to display such a message. The notification by the notification unit  219  is not limited to the display of a message, but may be notification by sound using a buzzer, for example, or may be notification by light using a lamp, for example. 
     4. Operation 
     An operation of the electron microscope  100  will be described next. Here an operation when the second transporting mechanism  90  transports the cartridge  2  from the specimen exchange chamber  30  to the specimen chamber  20  will be described. 
     In the electron microscope  100 , the cartridge  2  can be automatically transported from the specimen exchange chamber  30  to the specimen chamber  20 . Also in the electron microscope  100 , the control unit  102  performs the transporting processing to transport the cartridge  2  from the specimen exchange chamber  30  to the specimen chamber  20 , whereby the cartridge  2  can be transported from the specimen exchange chamber  30  to the specimen chamber  20 . 
       FIG.  4    is a flow chart illustrating an example of the transporting processing by the control unit  102 . 
     The temperature information acquiring unit  212  acquires information on the temperature of the specimen holder  24 , which was measured by the first temperature sensor  110 , from the temperature monitor  114  (S 100 ). Then the temperature information acquiring unit  212  acquires information on the temperature of the second transporting mechanism  90 , which was measured by the second temperature sensor  112 , from the temperature monitor  114  (S 102 ). 
     The temperature information acquiring unit  212  may acquire information on the temperature of the specimen holder  24  after acquiring the information on the temperature of the second transporting mechanism  90 . The temperature information acquiring unit  212  may simultaneously acquire both the information on the temperature of the specimen holder  24  and the information on the temperature of the second transporting mechanism  90 . 
     The transporting instruction receiving unit  214  determines whether or not the user performed the transporting instruction (S 104 ). 
     When the transporting instruction receiving unit  214  has determined that the transporting instruction was not performed (No in S 104 ), the processing returns to S 100 , and the processing of acquiring the information on the temperature of the specimen holder  24  (S 100 ) and the processing of acquiring the information on the temperature of the second transporting mechanism  90  (S 102 ) are performed. The temperature information acquiring unit  212  repeats the processing step S 100  and the processing step S 102  until it is determined that the transporting instruction was received. 
     When the transporting instruction receiving unit  214  has determined that the transporting instruction was performed (Yes in S 104 ), that is, when the transporting instruction receiving unit  214  has received the transporting instruction, the temperature difference calculating unit  216  calculates the temperature difference between the specimen holder  24  and the second transporting mechanism  90  based on the information on the temperature of the specimen holder  24  measured by the first temperature sensor  110 , and the information on the temperature of the second transporting mechanism  90  measured by the second temperature sensor  112  (S 106 ). 
     The transporting control unit  218  determines whether or not the temperature difference calculated by the temperature difference calculating unit  216  is the threshold or more (S 108 ). 
     When the transporting control unit  218  has determined that the temperature difference is lower than the threshold (No in S 108 ). The transporting control unit  218  causes the second transporting mechanism  90  to transport the cartridge  2  from the specimen exchange chamber  30  to the specimen chamber  20  (S 110 ). 
       FIG.  5    to  FIG.  7    are diagrams illustrating a state where the second transporting mechanism  90  is transporting the cartridge  2  from the specimen exchange chamber  30  to the specimen chamber  20 . 
     The transporting control unit  218  sends a control signal to the control circuit  120  to transport the cartridge  2  to the specimen chamber  20 . 
     When a control signal is sent to the control circuit  120  in a state where the second transporting mechanism  90  is holding the cartridge  2  in the specimen exchange chamber  30 , as illustrated in  FIG.  2   , the gate valve  32  opens, as illustrated in  FIG.  5   , and the second transporting mechanism  90  moves the transporting rod  94  so as to transport the cartridge  2  to the specimen chamber  20 . Then as illustrated in  FIG.  6   , the second transporting mechanism  90  transfers the cartridge  2  held by the chuck device  92  to the specimen holder  24  in the specimen chamber  20 . After transferring the cartridge  2  to the specimen holder  24 , the second transporting mechanism  90  retracts the chuck device  92  into the specimen exchange chamber  30 , as illustrated in  FIG.  7   . Then the gate valve  32  is closed, and the electron microscope  100  enters a state where a specimen can be observed. 
     When the transporting control unit  218  has determined that the temperature difference is the threshold or more (Yes in S 108 ), the transporting control unit  218  stops transporting the cartridge  2  (S 112 ). The transporting control unit  218  causes the second transporting mechanism  90  to maintain the state where the cartridge  2  is in the specimen exchange chamber  30 , as illustrated in  FIG.  2   , for example. 
     Then the notification unit  219  notifies the alarm information (S 114 ). 
     The control unit  102  ends the transporting processing after processing step S 110  or the processing step S 114 . 
     In the above description, the second transporting mechanism  90  transports the cartridge  2  from the specimen exchange chamber  30  to the specimen chamber  20 , but the control unit  102  also performs the same processing in a case where the second transporting mechanism  90  transports the cartridge  2  from the specimen chamber  20  to the specimen exchange chamber  30 . 
     5. Functional Effect 
     In the electron microscope  100 , when the control unit  102  has received an instruction to transport a specimen, the control unit  102  performs processing of: calculating the temperature difference between the specimen holder  24  and the second transporting mechanism  90 ; determining whether or not this temperature difference is a threshold or more; and stopping transportation of a specimen if it has been determined that this temperature difference is the threshold or more, based on information on the temperature of the specimen holder  24  measured by the first temperature sensor  110  and information on the temperature of the second transporting mechanism  90  measured by the second temperature sensor  112 . 
     Therefore in the electron microscope  100 , transportation of a specimen is stopped when there is a temperature difference, hence it can be prevented that the specimen holder  24  and the second transporting mechanism  90  rub against each other, or that the specimen holder  24  and the cartridge  2  rub against each other due to the positioning misalignment of the specimen holder  24  and the second transporting mechanism  90  when a specimen is transferred. 
       FIG.  8    is a diagram illustrating a state where the positions of the specimen holder  24  and the second transporting mechanism  90  are misaligned when the cartridge  2  is transferred. 
     In the case of the example in  FIG.  8   , the height of the specimen holder  24  and the height of the second transporting mechanism  90  are not aligned. When such a misalignment occurs, the specimen holder  24  and the cartridge  2  may rub against each other, or the specimen holder  24  and the second transporting mechanism  90  may rub against each other, and metal particles and the like may scatter. If such metal particles adhere to a specimen, a specimen image cannot be observed accurately. Furthermore, if the specimen holder  24  and the cartridge  2  rub against each other, or if the specimen holder  24  and the second transporting mechanism  90  rub against each other, the specimen holder  24  and the second transporting mechanism  90  deteriorate. And in some cases a specimen may be damaged. 
     In the case of the example in  FIG.  8   , the height of the specimen holder  24  and the height of the second transporting mechanism  90  are not aligned, but a similar problem occurs when the horizontal positions of the specimen holder  24  and the second transporting mechanism  90  are not aligned. 
     In the electron microscope  100 , transportation of a specimen is stopped when there is a temperature difference, therefore the above mentioned problem does not occur. 
     In the electron microscope  100 , the control unit  102  performs processing of notifying the alarm information when the control unit  102  has determined that the temperature difference is the threshold or more. Therefore in the electron microscope  100 , the user can recognize that the specimen holder  24  and the second transporting mechanism  90  have a temperature difference. 
     The electron microscope  100  includes the first cooling mechanism  28  that cools the specimen holder  24 , and the second cooling mechanism  70  that cools the second transporting mechanism  90 . Therefore in the electron microscope  100 , a specimen at low temperature can be observed. Further, in the electron microscope  100 , a temperature difference is generated between the specimen holder  24  and the second transporting mechanism  90  when the liquid nitrogen in the first cooling mechanism  28  or in the second cooling mechanism  70  vaporizes and no longer exists. However, in the electron microscope  100 , transportation of a specimen is stopped when there is a temperature difference, as mentioned above, hence it can be prevented that the specimen holder  24  and the second transporting mechanism  90  rub against each other, or that the specimen holder  24  and the cartridge  2  rub against each other, even in the case where the liquid nitrogen in the first cooling mechanism  28  or the second cooling mechanism  70  vaporizes and no longer exists. 
     6. Modification 
     The invention is not limited to the above mentioned embodiment, but various modifications are possible within the scope of the spirit of the invention. 
     6.1. Modification 1 
     In the above embodiment, the case where the electron microscope  100  is a cryo-electron microscope was described, but the changed particle beam apparatus according to the invention is not limited to the cryo-electron microscope, but may be a transmission electron microscope for observing a specimen at room temperature. 
       FIG.  9    is a diagram illustrating a configuration of an electron microscope  200  according to a modification. 
     As illustrated in  FIG.  9   , the electron microscope  200  does not include the first cooling mechanism  28  to cool the specimen holder  24 , and the second cooling mechanism  70  to cool the first transporting mechanism  80  and the second transporting mechanism  90 . 
     Here bakeout is performed in the electron microscope  200  in order to maintain the inside of the lens barrel  22  in the high vacuum state. “Bakeout” refers to an operation to forcibly discharge gas occluded in the inner wall of the lens barrel  22  by heating the inner wall of the lens barrel  22  in the vacuum state using a baking device (not illustrated). After performing bakeout, the amount of gas to be discharged later can be reduced. 
     When bakeout of the lens barrel  22  is performed in the electron microscope  200  like this, a temperature difference is generated between the specimen holder  24  and the second transporting mechanism  90 . In the electron microscope  200 , just like the electron microscope  100 , transportation of a specimen is stopped when there is a temperature difference. Therefore a similar functional effect as in the electron microscope  100  can be implemented in the electron microscope  200 . 
     6.2. Modification 2 
     In the embodiment described above, the charged particle beam apparatus according to the invention is the transmission electron microscope, but the charged particle beam apparatus according to the invention is not limited to the transmission electron microscope. The charged particle beam apparatus according to the invention may be a scanning transmission electron microscope (STEM), a scanning electron microscope (SEM), an electron probe microanalyser (EPMA), a focused ion beam apparatus (FIB), an electron beam exposure apparatus, or the like. 
     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 that are the same in function, method, and results, or configurations that are the same in objective and effects, for example. The invention also includes configurations in which non-essential elements described in the embodiments are replaced by other elements. 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.