Patent Publication Number: US-2022223370-A1

Title: Sample Holder and Charged Particle Beam System

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority to Japanese Patent Application No. 2021-002165, filed Jan. 8, 2021, the disclosure of which is hereby incorporated by reference in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to a sample holder and a charged particle beam system. 
     2. Description of the Related Art 
     In the field of charged particle beam systems including transmission electron microscopes, it is known to use an automated transport device for automatically conveying a cartridge, which holds a sample therein, into a sample chamber. 
     For example, JP-A-2015-88237 discloses a charged particle beam system equipped with a transport rod for carrying a cartridge between a sample exchange chamber and a sample chamber. The sample chamber is a space between the top and bottom polepieces constituting an objective lens. The transport rod carries the cartridge into the sample chamber through the gap between the top and bottom polepieces. 
     Where a crystalline sample such as a semiconductor material is observed, it is customary to align the crystallographic orientation to the direction of an incident electron beam. Therefore, the cartridge for observation of the crystalline sample has a tilt mechanism for tilting a sample stage. 
     When the cartridge is conveyed into the sample chamber while the sample stage of the cartridge is tilted, there is the danger that the sample stage will collide against any other member of the charged particle beam system, thus damaging the stage. The gap between the top and bottom polepieces is as narrow as on the order of millimeters, for example. Therefore, if the tilt angle of the sample stage of the cartridge is large, the sample stage will touch the polepieces when the cartridge is passed through the gap between the top and bottom polepieces. 
     SUMMARY OF THE INVENTION 
     One aspect of the sample holder associated with the present invention is for use in a charged particle beam system and comprises: a cartridge having a sample stage for holding a sample therein; and a holder base having a mounting portion to which the cartridge can be mounted. The cartridge has: a tilt mechanism for tilting the sample stage; and a lock lever which, when the cartridge has been detached from the mounting portion, makes contact with the sample stage and limits tilt of the sample stage. 
     With this sample holder, when the cartridge is transported, it is possible to limit tilt of the sample stage and so collision of the sample stage with any other member of the charged particle beam system can be prevented. 
     One aspect of the charged particle beam system associated with the present invention includes the sample holder described just above. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIGS. 1 and 2  are schematic plan views of a sample holder associated with one embodiment of the present invention, showing different states. 
         FIG. 3  is a diagram illustrating the operation of a lock lever. 
         FIGS. 4 and 5  are diagrams illustrating different operational states of a tilt mechanism. 
         FIGS. 6 and 7  are diagrams illustrating the configuration of an electron microscope including the sample holder of  FIGS. 1 and 2 . 
     
    
    
     DESCRIPTION OF THE INVENTION 
     The preferred embodiments of the present invention are hereinafter described in detail with reference to the accompanying drawings. It is to be understood that the embodiments provided below are not intended to unduly restrict the contents of the present invention delineated by the claims and that not all the configurations set forth below are the essential constituent components of the invention. 
     1. Sample Holder 
     A sample holder associated with one embodiment of the present invention is first described by referring to  FIGS. 1 and 2 , which are schematic plan views of the sample holder,  100 . The sample holder  100  is for use in a transmission electron microscope and includes a holder base  110  and a cartridge  150 , as shown. The holder base  110  has a shaft portion  102 , a mounting portion  112 , a block  120 , and another block  122 .  FIG. 1  shows a state in which the cartridge  150  has been detached from the mounting portion  112  of the holder base  110 .  FIG. 2  shows a state in which the cartridge  150  has been mounted to the mounting portion  112  of the holder base  110 . 
     The shaft portion  102  is a rodlike member and constitutes a hand grip of the sample holder  100 . An O-ring  104  is mounted on the shaft portion  102 . In particular, the shaft portion  102  has an outer surface provided with a groove in which the O-ring  104  is mounted. When the sample holder  100  is inserted into an electron microscope, the sample chamber can be made airtight by the O-ring  104 . The shaft portion  102  has a grip portion (not shown) at its rear end to permit a user to grip the sample holder  100 . 
     The mounting portion  112  is formed at the front end of the shaft portion  102  and designed such that the cartridge  150  can be mounted thereto. The mounting portion  112  has a cartridge placement surface  114  on which the cartridge  150  is to be placed. Furthermore, the mounting portion  112  has a leaf spring  116  that presses the cartridge  150 , which is placed on the placement surface  114 , against the blocks  120  and  122  by means of the leaf spring  116 , thus securing the cartridge  150 . 
     The blocks  120  and  122  are members which make contact with the cartridge  150  when the cartridge  150  is placed on the cartridge placement surface  114 . When the cartridge  150  is mounted to the mounting portion  112 , the blocks  120  and  122  operate to guide the cartridge  150 . 
     The holder base  110  has a shaft  130  permitting operation of a tilt mechanism  170  for the cartridge  150 . The shaft  130  is coupled to a drive source such as an electric motor via a feed screw (not shown) mounted inside the shaft portion  102 . 
     As shown in  FIG. 1 , the cartridge  150  is mounted to the mounting portion  112  from a direction C at an angle to the center axis L of the shaft portion  102 . In particular, the cartridge  150  is inserted into the mounting portion  112  by moving the cartridge  150  in the oblique direction C while the mounting portion  112  is at rest. Thus, the cartridge  150  is attached to the mounting portion  112 . 
     No restriction is imposed on the method of mounting the cartridge  150  to the mounting portion  112 . That is, the configuration of the mounting portion  112  is not restricted to the foregoing example. Rather, the mounting portion  112  may be so configured that the cartridge  150  can be detachably mounted thereto. 
     The cartridge  150  operates to hold a sample, and has a frame  152 , a sample stage  160 , the aforementioned tilt mechanism  170 , and a lock lever  180 . The sample stage  160  holds the sample therein. The sample stage  160  is provided with a through hole over which the sample is secured. The sample is secured on the sample stage  160  using a C-ring or a leaf spring, for example. 
     The sample stage  160  is coupled to the frame  152  of the cartridge  150  by a shaft member (not shown), the frame  152  being a framelike member. The sample stage  160  is supported by the shaft member so as to be rotatable about an axis A. Therefore, the sample stage  160  can tilt or rotate about the axis A that is a tilted axis. When the cartridge  150  is mounted to the mounting portion  112 , the axis A is orthogonal to the center axis L of the shaft portion  102  of the holder base  110 . 
     The tilt mechanism  170  has a tilt arm  172  and a tilt lever  174 . The tilt arm  172  is connected to the sample stage  160  and also to the tilt lever  174 . When the cartridge  150  has been mounted to the mounting portion  112 , the front end of the shaft  130  is in contact with the tilt lever  174 . As the shaft  130  stretches and compresses, the tilt lever  174  rotates, and the sample stage  160  connected to the tilt arm  172  tilts around the axis A (see  FIG. 5 ). 
     After the cartridge  150  has been detached from the mounting portion  112 , the lock lever  180  limits tilt of the sample stage  160 . The lock lever  180  is in the form of the letter “L”, for example, and has a first rodlike member  181  and a second rodlike member  182  which extend mutually perpendicular directions from a shaft member  184 . The lock lever  180  can rotate about its axis of rotation, i.e., the shaft member  184 . 
     A resilient member  186  is in contact with the second rodlike member  182 . One end of the resilient member  186  is in contact with the second rodlike member  182 , while the other end is secured to the frame  152 . The resilient member  186  is a leaf spring, for example. In the example shown in  FIGS. 1 and 2 , the resilient member  186  biases the lock lever  180  to rotate it in a counterclockwise direction. 
     When the cartridge  150  has been detached from the mounting portion  112  as shown in  FIG. 1 , the lock lever  180  touches the sample stage  160  and limits its tilt. When the cartridge  150  has been mounted to the mounting portion  112 , the lock lever  18  is away from the sample stage  160  as shown in  FIG. 2 , thus permitting tilting of the sample stage  160 . 
     2. Operation 
     2.1. Mounting of Cartridge 
     2.1.1. Operation of Lock Lever 
     The operation of the lock lever  180  when the cartridge  150  is mounted to the mounting portion  112  of the holder base  110  is first described by referring to  FIG. 3 , which illustrates the operation of the lock lever  180 . 
     When the cartridge  150  has been detached from the mounting portion  112  as shown in  FIG. 1 , the lock lever  180  is in contact with the sample stage  160  and limits tilt of the sample stage  160 . Specifically, the second rodlike member  182  is biased by the resilient member  186 , and the first rodlike member  181  makes contact with the sample stage  160 . In the example of  FIG. 1 , the first rodlike member  181  is located under the sample stage  160 . Consequently, the sample stage  160  is limited from tilting and is held horizontally. 
     The cartridge  150  is made to plunge into the mounting portion  112  while the sample stage  160  is retained horizontally by the lock lever  180 . In particular, the cartridge  150  is moved in the direction C at an angle to the center axis L of the shaft portion  102 . The cartridge  150  slides on the cartridge placement surface  114  of the mounting portion  112  in the oblique direction C. 
     Because the sample stage  160  is retained horizontally at this time, if the cartridge  150  is made to plunge into the mounting portion  112 , the stage  160  collides neither against the frame  113  of the mounting portion  112  nor against the cartridge placement surface  114 . 
     As shown in  FIG. 3 , the cartridge  150  passes between the blocks  120  and  122  and moves in the oblique direction C while guided by these blocks  120 ,  122 . 
     If the cartridge  150  is moved in the oblique direction C, the second rodlike member  182  comes into contact with the block  120 . If the cartridge  150  is moved in the oblique direction C further, the lock lever  180  rotates in the clockwise direction about the shaft member  184  because the second rodlike member  182  is in contact with the block  120 . This moves the first rodlike member  181  away from the sample stage  160 . As a result, tilt of the sample stage  160  is no longer limited, whereby the sample stage  160  is made tiltable. 
     If the cartridge  150  is moved in the oblique direction C still further, the cartridge  150  is secured to the mounting portion  112  as shown in  FIG. 2 . Under this condition, the first rodlike member  181  is away from the sample stage  160  and thus the stage  160  is tiltable. The limitation on the tilt of the sample stage  160  by the lock lever  180  is relieved by moving the cartridge  150  in the oblique direction C in this way. The cartridge  150  can be mounted to the mounting portion  112 . Because of the process steps described so far, the cartridge  150  can be mounted to the mounting portion  112 . 
     2.1.2. Operation of Tilt Mechanism 
     The operation of the tilt mechanism  170  when the cartridge  150  is mounted to the mounting portion  112  is next described by referring to  FIGS. 4 and 5 , which illustrate the operation of the tilt mechanism  170 . Before the second rodlike member  182  strikes the block  120 , the first rodlike member  181  is in contact with the sample stage  160  which in turn is maintained horizontally as shown in  FIG. 4 . At this time, the shaft  130  is not in contact with the tilt lever  174 . 
       FIG. 5  shows a state in which the cartridge  150  has been moved further in the oblique direction C from the state of  FIG. 4 . As shown in  FIG. 5 , simultaneously with contact of the second rodlike member  182  with the block  120 , the tilt lever  174  touches the shaft  130 . In consequence, the shaft  130  pushes the tilt lever  174 , so that the lever  174  rotates and tilts the sample stage  160 . In the example of  FIG. 5 , the tilt lever  174  has a protrusion  175  which is in contact with a ball  132  at the front end of the shaft  130 . 
     Because the tilt lever  174  touches the shaft  130  and tilts the sample stage  160  in this way, when the lock lever  180  is rotated and the sample stage  160  is made tiltable, the lock lever  180  (first rodlike member  181 ) does not come in contact with the sample stage  160 . That is, when the lock lever  180  is moved to relieve the limitation on tilt of the sample stage  160 , the lock lever  180  does not touch the sample stage  160 . Consequently, biting frictional engagement between the lock lever  180  and the sample stage  160  can be prevented. 
     2.2. Detachment of Cartridge 
     2.2.1. Operation of Lock Lever 
     When the cartridge  150  is detached from the mounting portion  112 , the lock lever  180  is caused to perform an operation reverse to the operation performed when the cartridge  150  is mounted to the mounting portion  112 . In particular, the cartridge  150  is moved in a direction opposite to the oblique direction C from the state of  FIG. 2  in which the cartridge  150  is mounted to the mounting portion  112 . This moves the second rodlike member  182  away from the block  120 . Therefore, the lock lever  180  is biased by the resilient member  186  to rotate in the counterclockwise direction, resulting in contact of the first rodlike member  181  with the sample stage  160  as shown in  FIG. 2 . As a result, tilt of the sample stage  160  is limited, and the sample stage  160  is held horizontally. 
     If the cartridge  150  is moved further in the direction opposite to the oblique direction C, the cartridge  150  is detached from the mounting portion  112  while the sample stage  160  is retained horizontally as shown in  FIG. 1 . 
     2.2.2. Operation of Tilt Mechanism 
     When the cartridge  150  is detached from the mounting portion  112 , the tilt mechanism  170  performs an operation reverse to that done when the cartridge  150  is mounted to the mounting portion  112 . Specifically, in the state of  FIG. 5  where the cartridge  150  is mounted to the mounting portion  112 , the cartridge  150  is moved in the direction opposite to the oblique direction C. Consequently, the lock lever  180  rotates in the counterclockwise direction. At this time, the tilt lever  174  is in contact with the shaft  130 , and the sample stage  160  is tilted. Therefore, the lock lever  180  can move to below the sample stage  160  without touching the sample stage  160 . 
     If the cartridge  150  is moved in the direction opposite to the oblique direction C, the shaft  130  and the tilt lever  174  move away from each other as shown in  FIG. 4 , thus making the sample stage  160  horizontal. As a result, the sample stage  160  makes contact with the lock lever  180  (first rodlike member  181 ), limiting tilt of the sample stage  160 . 
     3. Functions and Effects 
     The sample holder  100  includes: the cartridge  150  having the sample stage  160  for holding a sample therein; and the holder base  110  having the mounting portion  112  to which the cartridge  150  can be mounted. The cartridge  150  has: the tilt mechanism  170  for tilting the sample stage  160 ; and the lock lever  180  which, when the cartridge  150  has been detached from the mounting portion  112 , makes contact with the sample stage  160  and limits tilt of the sample stage  160 . 
     Therefore, when the cartridge  150  is transported, the sample holder  100  can limit tilt of the sample stage  160 . Otherwise, the sample stage  160  may tilt and collide with other members of the electron microscope such as the polepieces and the frame  152  of the mounting portion  112 . Hence, damage to the sample stage  160  can be prevented. 
     The sample holder  100  includes the resilient member  186  connected to the lock lever  180 . When the cartridge  150  has been detached from the mounting portion  112 , the lock lever  180  is biased into contact with the sample stage  160  by the resilient member  186 . When the cartridge  150  has been mounted to the mounting portion  112 , the lock lever  180  strikes on the block  120  of the mounting portion  112  and separates from the sample stage  160 . Therefore, when the cartridge  150  has been detached from the mounting portion  112 , the sample holder  100  touches the sample stage  160  and can limit its tilt. When the cartridge  150  has been mounted to the mounting portion  112 , the sample holder  100  moves away from the sample stage  160  and permits tilting of the sample stage  160 . 
     In the sample holder  100 , the tilt mechanism  170  has the tilt arm  172  and the tilt lever  174  which are connected to the sample stage  160  and the tilt arm  172 , respectively. The holder base  110  has the shaft  130  that comes into contact with the tilt lever  174  when the cartridge  150  has been mounted to the mounting portion  112 . The tilt lever  174  comes into contact with the shaft  130  and causes tilting of the sample stage  160 , whereby the sample stage  160  and the lock lever  180  move away from each other. 
     Therefore, in the sample holder  100 , when the lock lever  180  rotates, it does not touch the sample stage  160 . This prevents biting frictional engagement between the lock lever  180  and the sample stage  160 . 
     4. Electron Microscope 
     4.1. Configuration of the Electron Microscope 
     An electron microscope including the sample holder  100  is next described.  FIGS. 6 and 7  illustrate the configuration of the electron microscope, generally indicated by reference numeral  1 , including the sample holder  100 .  FIG. 6  is a cross-sectional view taken on line VI-VI of  FIG. 7 . In  FIG. 7 , for the sake of convenience, only the sample holder  100 , a second transport rod  50 , and an electron optical column  12  are shown. 
     As shown in  FIG. 6 , the electron microscope  1  includes a sample chamber  10 , a sample exchange chamber  20 , a transport device  30 , vacuum pumping equipment  60 , a controller  70 , and the sample holder  100 . The electron microscope  1  is a transmission electron microscope, for example. 
     The sample chamber  10  is a space inside the electron optical column  12 . An electron source for emitting an electron beam, an illumination optical system, and an imaging system (none of which are shown) are housed in the electron optical column  12 . The electron beam emitted from the electron source is directed at a sample by the illumination optical system. The imaging system creates a focused TEM image from the electron beam transmitted through the sample. The electron microscope  1  is also equipped with a detector for detecting the image focused by the imaging system and a detector for detecting X-rays released from the sample in a manner not illustrated. 
     The sample chamber  10  is a space between the top and bottom polepieces of an objective lens (not shown). The sample chamber  10  is evacuated to a vacuum by the vacuum pumping equipment. The mounting portion  112  of the holder base  110  is disposed in the sample chamber  10 . The sample held in the sample holder  100  is irradiated with the electron beam within the sample chamber  10 . 
     The sample holder  100  is placed in position by a goniometer stage  14 , which can tilt the sample by rotating about the center axis L of the shaft portion  102  of the sample holder  100 . Furthermore, the holder can tilt the sample by rotating the sample stage  160  about the axis A. In this way, in the electron microscope  1 , the sample can be tilted relative to the two mutually perpendicular axes. 
     The sample exchange chamber  20  is connected into the sample chamber  10 . A partition valve  22  is mounted between the sample exchange chamber  20  and the sample chamber  10 . 
     A sample container  2  can be attached and detached to and from a connective member  26  that is mounted in the sample exchange chamber  20 . Another partition valve  24  is mounted between the sample exchange chamber  20  and the sample container  2 . A magazine  4  in which a plurality of cartridges  150  are loaded can be received in the sample container  2 . The sample exchange chamber  20  and the sample container  2  can be evacuated by the vacuum pumping equipment  60 . 
     The transport device  30  has a first transport rod  40  and the second transport rod  50 . The first transport rod  40  transports the cartridges  150  between the sample container  2  and the sample exchange chamber  20 . In this example, the first transport rod  40  transports the cartridges  150  by carrying the magazine  4 . The first transport rod  40  grips the magazine  4  at its front end and moves the gripped magazine  4  upwardly, thus transporting the magazine  4  from the sample container  2  to the sample exchange chamber  20 . 
     The second transport rod  50  carries each cartridge  150  between the sample exchange chamber  20  and the sample chamber  10 . In particular, the second transport rod  50  extracts one cartridge  150  from the magazine  4  gripped by the first transport rod  40 . The second transport rod  50  transports the extracted cartridge  150  from the sample exchange chamber  20  into the sample chamber  10  and mounts the cartridge to the mounting portion  112 . 
     As shown in  FIG. 7 , the second transport rod  50  mounts the cartridge  150  to the mounting portion  112  by moving the cartridge  150  in the oblique direction C relative to the center axis L of the sample holder  100 . 
     The vacuum pumping equipment  60  evacuates the sample container  2  to a vacuum via an exhaust tube  62 . A solenoid valve  64  is mounted in the exhaust tube  62 . The vacuum pumping equipment  60  also evacuates the sample exchange chamber  20  to a vacuum via an exhaust tube  66 . A solenoid valve  68  is mounted in the exhaust tube  66 . 
     The controller  70  controls the partition valves  22 ,  24 , transport device  30 , and solenoid valves  64 ,  68 . The controller  70  includes a CPU (central processing unit) and storage devices such as a RAM (random access memory) and a ROM (read only memory). The controller  70  performs various kinds of control operations by executing programs stored in the storage devices with the CPU. 
     4.2. Operation 
     4.2.1. Mounting of Cartridge 
     In the electron microscope  1 , the cartridge  150  loaded in the sample container  2  can be automatically transported into the sample chamber  10  and mounted to the mounting portion  112 . 
     The cartridge  150  loaded in the magazine  4  is received in the sample container  2 . The sample container  2  containing the cartridge  150  is mounted to the connective member  26 . At this time, the partition valve  24  is closed. The user enters an instruction to the controller  70  to introduce the cartridge  150 . 
     Upon receiving the instruction for introducing the cartridge  150 , the controller  70  opens the solenoid valve  64  and evacuates the interior of the sample container  2  to a vacuum. When the interior of the sample container  2  becomes below a given pressure, the controller  70  opens the partition valve  24 . 
     The magazine  4  in the sample container  2  is gripped by the first transport rod  40  and transported into the sample exchange chamber  20  under control of the controller  70 . Then, the partition valve  24  is closed while the partition valve  22  is opened also under control of the controller  70 . 
     The specified cartridge  150  is gripped by the second transport rod  50  from within the magazine  4  gripped by the first transport rod  40  and is transported into the sample chamber  10  through the gap between the top and bottom polepieces of the objective lens also under control of the controller  70 . 
     The cartridge  150  is moved in the oblique direction C by the second transport rod  50  and attached to the mounting portion  112  under control of the controller  70 . At this time, the lock lever  180  and the tilt mechanism  170  operate as described in the “2.1. Mounting of Cartridge”. 
     After the cartridge  150  is mounted to the mounting portion  112 , the second transport rod  50  is returned into the sample exchange chamber  20  and the partition valve  22  is closed under control of the controller  70 . 
     As a result of the processing steps described thus far, the cartridge  150  can be mounted to the mounting portion  112 . Consequently, the sample held in the cartridge  150  can be observed with the electron microscope  1 . 
     4.2.2. Detachment of Cartridge 
     In the electron microscope  1 , the cartridge  150  can be automatically taken out from the mounting portion  112  and carried into the sample exchange chamber  20 . The partition valve  22  is opened and the second transport rod  50  is moved into the sample chamber  10  under control of the controller  70 . The cartridge  150  mounted to the mounting portion  112  is gripped by the second transport rod  50  and moved in a direction opposite to the oblique direction C also under control of the controller  70 . Consequently, the cartridge  150  is removed from the mounting portion  112 . At this time, the lock lever  180  and the tilt mechanism  170  operate as described in “2.2. Detachment of Cartridge”. 
     The controller  70  causes the second transport rod  50  to carry the cartridge  150  into the sample exchange chamber  20  through the gap between the top and bottom polepieces of the objective lens. The controller  70  then closes the partition valve  22  after the transportation of the cartridge  150  into the sample exchange chamber  20 . Then, the cartridge  150  is loaded by the second transport rod  50  into the magazine  4  gripped by the first transport rod  40  under control of the controller  70 . Because of the processing steps described so far, the cartridge  150  can be taken out from the mounting portion  112 . 
     5. Modified Embodiments 
     In the foregoing embodiment, the charged particle beam system associated with the present invention has been described in which an electron microscope for observing or analyzing a sample using an electron beam is taken as an example. The charged particle beam system associated with the present invention may also be an instrument for making an observation or analysis using a charged particle beam other than an electron beam such as an ion beam. For example, the charged particle beam system associated with the present invention may be a scanning transmission electron microscope, a scanning electron microscope, an Auger electron spectrometer, a focused ion beam system, or the like. 
     It is to be understood that the present invention is not restricted to the above embodiment and modifications thereof and that the invention can be practiced in further modified forms. For example, the present invention embraces configurations substantially identical (e.g., in function, method and results or in purpose and advantageous effects) to the configurations described in the above embodiment. Furthermore, the present invention embraces configurations similar to the configurations described in the above embodiment except that nonessential portions have been replaced. In addition, the present invention embraces configurations identical in advantageous effects or purpose to the configurations described in the above embodiment. Further, the present invention embraces configurations similar to the configurations described in the above embodiment except that a well-known technique is added.