JP2006164617A - Sample replacement mechanism of electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a sample replacement mechanism capable of preventing damage of a sample-stage support part cooled down to an extremely low temperature at a replacement operation of a sample cooled. <P>SOLUTION: A conveyance grip 12 an operator operates at the time of sample replacement and a block 13 moving in piece with the sample replacement mechanism 8 are coupled by a spring 15 and a slider capable of moving only in one direction. After a sample holder 4 comes into contact with a sample stage 2, the spring begins to get extended, and a contact face between the sample holder 4 and the sample stage 2 receives an adhesive pressure by the spring 15. If a spring 15 with an appropriate spring constant is selected, and a stopper 10 is set to come into contact with a stopper rest part 11 within a range of a maximum allowable added pressure of a heat insulating material, the heat insulating material 3 can be prevented from damage. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a sample exchange mechanism such as an electron microscope, and more particularly to a sample exchange mechanism in a sample cooling apparatus that cools a sample such as a biological sample or a polymer material that is easily damaged by electron beam irradiation to a cryogenic temperature.

  When observing a sample with a charged particle beam apparatus such as an electron microscope, if a sample such as a biological sample or a polymer material is irradiated with an electron beam or the like, the structure of the sample may be destroyed and the sample in a normal state may not be observed. In this case, if the sample is cooled to a very low temperature, it becomes difficult to break even if the sample is irradiated with an electron beam or the like, and a normal sample can be observed. A sample cooling device for cooling a sample for such a purpose is disclosed in, for example, Japanese Patent Application Laid-Open No. 2000-285844. Japanese Patent Application Laid-Open No. 2002-334677 discloses an example of a sample exchange device that allows an operator unfamiliar with the device to exchange a sample in a short time when replacing a cooled sample.

  The prior art will be briefly described by taking the sample cooling apparatus and sample exchange apparatus of the cryogenic electron microscope described in the above disclosed example as an example. FIG. 1 shows a cross section of a lens barrel, a sample cooling device, and a sample exchange mechanism. In FIG. 1, a sample stage 2 and an objective lens 20 are provided inside a lens barrel 1. The sample stage 2 is cooled to the vicinity of the liquid helium temperature (4.2 K) by the liquid helium supplied from the liquid helium tank 23 through the capillary 22 to the refrigerant reservoir 21, so that it is supported by the heat insulating material 3 with a small heat inflow. ing. The refrigerant reservoir 21 and the liquid helium tank 23 are surrounded by a cooling member 25 that is cooled by liquid nitrogen in the liquid nitrogen tank 24 to prevent temperature rise.

FIG. 1 shows a state before the sample holder 4 is mounted on the sample stage 2. A sample 5 is placed at the tip of the sample holder 4, and the sample holder 4 is precooled by a cooling block 6 cooled by liquid nitrogen.
When the operator manually attaches the sample holder 4 to the sample stage 2, the operator grasps the transport grip 12 (transport base) and moves the transport arm 9 of the sample transport mechanism 8 operating integrally with the transport grip 12 to the guide rail 7. Is inserted into the lens barrel 1 along the line. The transport grip 12 is provided with a stopper 10 and a stopper receiving portion 11 for limiting the amount of insertion of the sample transport mechanism 8.

  FIG. 2 shows a state in which the sample holder 4 is transported to the sample stage 2 and the contact surface between the sample holder 4 and the sample stage 2 is pressed. When the mounting of the sample holder 4 is completed, the sample holder 4 is separated by a sample holder attaching / detaching mechanism (not shown), and the cooling block 6 and the transport arm 9 are returned to the positions before the sample replacement. When extracting the sample holder 4 from the sample stage 2, the cooling block 6 and the transfer arm 9 are inserted into the lens barrel 1 again, the sample holder 4 is gripped, and the sample holder 4 is pulled out to the position shown in FIG.

JP 2000-285844 A JP 2002-334777 A

  As described above, when the sample holder 4 is mounted on the sample stage 2, the stopper 10 for limiting the insertion amount of the transfer arm 9 is provided. The stopper 10 is attached to the stopper holder 11 after the outer peripheral surface of the sample holder 4 comes into contact with the inner peripheral surface of the sample stage 2 and the transport arm is slightly inserted. It is set to stop. Accordingly, in a state where the stopper is in contact with the stopper receiving portion 11, the sample stage 2 is pushed downward by a set amount by the sample holder 4. The mounting position of the stopper 10 must be adjusted so that the pushing amount is set within a range where the heat insulating material 3 can be bent.

  The reason for setting the pushing amount of the sample stage 2 by the sample holder 4 is as follows. The contact surfaces of the sample holder 4 and the sample stage 2 have the same surface shape so that they are as close as possible. This is because when the contact surface is not sufficiently familiar (the contact area is small), it is impossible to observe a high-resolution electron microscope image due to the influence of vibration. In order for both contact surfaces to be in close contact with each other, it is necessary not only to place the sample holder 4 on the sample stage 2 but also to apply a certain amount of pressure.

  Further, immediately after the sample holder 4 is transported to the sample stage 2, there is a problem that the amount of heat shrinkage is different because there is a temperature difference between the two. Since both have the same contact surface shape at the same temperature (usually room temperature), the contact surface does not blend in just by pressing immediately after conveyance. For this reason, after several tens of seconds to several minutes after the transfer, the sample holder 4 is pushed several times through the transfer arm 9 of the sample transfer mechanism 8 so that the contact surface with the sample stage 2 is brought into close contact again. Whether or not the contact state between the two is good is determined by taking a high-resolution image with a resolution of about 0.2 nm and confirming the presence or absence of the influence of vibration.

As described above, in order to finally bring the contact surface between the sample holder 4 and the sample stage 2 into contact with each other by pressing, it is necessary to adjust the position of the stopper 10 and set the pushing amount. However, since it is necessary to minimize the amount of heat flowing into the sample stage 2 that is cooled to near the liquid helium temperature, it is extremely difficult to increase the mechanical strength of the heat insulating material 3 that supports the sample stage 2. .
Within the allowable range in which damage to the heat insulating material 3 can be prevented, the amount of pushing that is set by adjusting the position of the stopper 10 is extremely small, and varies depending on individual differences between the sample cooling device and the sample changing device. Therefore, it is extremely sensuous to appropriately adjust the required push-in amount without excess or deficiency, and it is not easy for a skilled worker. In addition, since the amount of push-in may change due to secular change or the like, there is a possibility that readjustment may be necessary, so there is always a possibility of damaging the heat insulating material 3 supporting the sample stage 2.

  The present invention solves these problems, and can perform assembly adjustment without damaging the sample stage support member without relying on the sense of a skilled person, and can be used without requiring readjustment with respect to secular change. The purpose is to provide a sample exchange mechanism.

In order to solve the above problems, the present invention provides:
A sample exchange mechanism in a sample cooling device mounted on a charged particle beam device,
A sample stage that is adiabatically supported from the surroundings and can be cooled to a cryogenic temperature, a sample stage support thermal insulator that supports the sample stage while preventing heat from flowing into the sample stage, a sample holder that mounts the cooled sample, and the tip at the tip A sample transport mechanism mounted with a sample holder, a stopper for limiting the amount of insertion of the sample transport mechanism after the sample holder contacts the sample stage, and the sample transport mechanism being inserted by contacting the stopper. In the sample cooling device provided with a stopper receiving part for stopping,
A block that moves integrally with the sample transport mechanism, a transport base that applies a force from the atmosphere side to move the sample holder when the sample holder is mounted on the sample stage, and the block and the transport base are integrated. A slider that connects the block and the transport base so as to enable relative movement only in a direction, and a spring that connects the block and the transport base are provided.
Further, according to the present invention, when the sample holder is mounted on the sample stage by operating the transfer base, the block and the transfer base are positioned relative to each other by the spring until the sample holder contacts the sample stage. Kept unchanged,
After the sample holder contacts the sample stage, a pressing force is applied to the contact surface between the sample holder and the sample stage by the spring force of the spring until the stopper comes into contact with the stopper receiving portion. Features.
Further, the present invention sets the position where the stopper contacts the stopper receiving portion so that the maximum value of the pressing force does not exceed the range of allowable additional pressure for preventing damage to the sample stage supporting heat insulating material. The insertion of the sample transport mechanism is stopped to prevent breakage of the heat insulating material for supporting the sample stage.
According to the present invention, in the apparatus in which the operator manually changes the sample, the transfer base is a transfer grip that the operator can hold to move the sample holder during the sample change operation.
The present invention also includes a detection switch for detecting the insertion end position of the sample transport mechanism and a drive unit for driving the transport base by an actuator, and drives the sample holder replacement unit via the transport base. Thus, the sample is automatically exchanged.

  After the sample holder comes into contact with the sample stage, a pressing force is applied to the contact surface between the sample holder and the sample stage by the spring force of the spring, and the maximum value of the pressing force is the heat insulating material for supporting the sample stage. In order not to exceed the range of the allowable additional pressure for preventing damage, the position where the stopper contacts the stopper receiving portion is set and the insertion of the sample transport mechanism is stopped. No need for sensuous and difficult adjustments when deciding. Therefore, it is possible to prevent the sample stage support heat insulating material from being damaged both when the operator manually changes the sample and when the operator automatically changes the sample using an actuator or the like.

  In addition, even if the push amount to be set due to secular change or the like changes slightly, it is no longer necessary to readjust the mounting position of the stopper, so without always worrying about damage to the sample stage support heat insulating material, Since the sample holder can be securely attached to the sample stage and mounted, it is possible to ensure an environment for obtaining a high-resolution electron microscope image even in the observation of a cryogenic sample.

  Next, the embodiment of the present invention will be described with reference to an example incorporated in a cryogenic electron microscope. First, the case where the operator manually changes the sample will be described with reference to FIGS. 3 and 4, the configuration on the lens barrel 1 side with the transport arm 9 interposed therebetween is the same as the configuration described in the prior art of FIG. 1, and a description thereof will be omitted to avoid duplication.

  The side of the sample transport mechanism 8 across the transport arm 9 is a component according to the present invention. The block 13 is configured to move integrally with the sample transport mechanism 8, and the transport grip 12 is connected to the block 13 by a spring 15. Further, the block 13 and the transport grip 12 are connected by a slider 14 so that the block 13 and the transport grip 12 can be relatively moved in only one direction. A stopper 10 is incorporated in the block 13. Here, the transport grip 12 refers to the transport base. However, when the operator manually changes the sample, it is necessary to easily grip the transport base. Therefore, in FIGS. 3 and 4, the transport grip 12 is used. Represent as

  The operation of the present invention will be described together with a sample exchange operation performed manually by an operator. In FIG. 3, the sample holder 4 with the sample 5 placed on the tip contacts the cooling block 6 and is precooled to near the liquid nitrogen temperature. By inserting the transfer arm 9 of the sample transfer mechanism 8 into the lens barrel 1, the sample holder 4 is transferred to the sample stage 2 along the guide rail 7. At this time, the operator holds the transport grip 12 and operates so that the sample holder 4 is transported to the sample stage 2. Since the sample transport mechanism 8 and the block 13 are configured to move integrally, and the transport grip 12 is connected to the block 13 and the spring 15, the block 13 and the block 13 are moved until the sample holder 4 contacts the sample stage 2. The transport grip 12 is held by a spring 15 so that the relative position does not change.

  In FIG. 4, since the block 13 and the transport grip 12 can be moved relative to each other by the slider 14, the spring 15 starts to extend after the sample holder 4 comes into contact with the sample stage 2, and the transport arm 9 is inserted several mm. By the way, the stopper 10 comes into contact with the stopper receiving portion 11 and the insertion operation is stopped. After the sample holder 4 comes into contact with the sample stage 2, a pressing force by a spring force acts on the contact surface between the sample holder and the sample stage. The set pressure range (spring force) of the overrun portion of several mm can be limited by selecting a spring having a suitable spring constant. Further, the variation in the pressing force to be set which varies depending on the individual difference between the sample holder 4 and the sample stage 2 can be individually coped with by selecting the spring 15. Ascertain the maximum allowable applied pressure so that the heat insulating material 3 supporting the sample stage is not damaged, and the spring force acting on the contact surface between the sample holder and the sample stage is within the allowable range of the heat insulating material 3. The mounting position of the stopper 10 is set.

  When the mounting of the sample holder 4 to the sample stage 2 is completed, the cooling block 6 is once separated from the sample holder 4. After several tens of seconds to several minutes, when the sample holder 4 is cooled to the vicinity of the liquid helium temperature similar to that of the sample stage 2, the sample holder 4 is pressed again so as to be in close contact with the sample stage 2 via the transfer arm 9. . At this time, the pressing force applied to the sample stage is a force by a spring force. Even if the stopper 10 is pressed until it comes into contact with the stopper receiving portion 11, the pressing force applied to the contact surface between the sample holder 4 and the sample stage 2 is adiabatic. The material 3 stays within the range of the maximum allowable applied pressure so as not to break.

  FIG. 5 shows an embodiment in which the sample is automatically exchanged by driving the transport base 16 by the actuator 19 of the drive unit 18. The detection switch 17 is a switch for detecting the insertion end position of the sample transport mechanism. The sample exchange operation is performed by moving the transport base 16 with the actuator 19. After the sample holder 4 comes into contact with the sample stage 2, the slider 15 that can move only in one direction is provided, so that the spring 15 begins to extend, and when the transport arm 9 is inserted several mm, the detection switch 17 Operates and the insertion operation stops. There is a time lag until a stop signal is output to the actuator 19 and the insertion operation of the transfer arm 9 actually stops. However, immediately after the detection switch 17 is operated, the stopper 10 comes into contact with the stopper receiving portion 11 and the insertion operation is stopped. Further, the insertion amount of the transfer arm 9 overrun by the time lag is absorbed by the relative movement of the block 13 and the transfer base 16 due to the provision of the slider 14.

  That is, the stopper 10 in the conventional sample exchange mechanism has a role of directly determining the force with which the sample holder presses the sample stage, depending on the mounting position. However, in the present invention, the force with which the sample holder presses the sample stage is determined by the spring force of the spring connecting the conveyance grip 12 and the block 13, so the setting position of the stopper 10 is set to the maximum pressing force by the spring force. It only serves as a safety valve for limiting the pressure and preventing the heat insulating material 3 from being damaged.

  Therefore, according to the present invention, the maximum allowable additional pressure for preventing the heat insulating material 3 supporting the sample stage from being damaged is grasped, and a spring having an appropriate spring constant is selected. It is possible to take a wide tolerance range.

The figure which shows the example of the sample cooling device mounted in the cryogenic electron microscope and the conventional sample exchange device (a state where the sample holder is not attached to the sample stage). The figure which shows the example of the sample cooling device mounted in the cryogenic electron microscope, and the conventional sample exchange device (The state which conveyed the sample holder to the sample stage manually, and applied the surface pressure after contact). The figure which shows the example of the sample cooling device mounted in the cryogenic electron microscope, and the sample replacement | exchange apparatus of this invention (a sample holder is a state with the sample stage unattached). The figure which shows the example of the sample cooling device mounted in the cryogenic electron microscope and the sample exchange device of this invention (The state which conveyed the sample holder to the sample stage manually, and applied the surface pressure after contact). The figure which shows the example of the sample cooling device mounted in the cryogenic electron microscope, and the sample exchange apparatus of this invention (The state which conveyed the sample holder to the sample stage with the drive unit, and applied the surface pressure after contact).

Explanation of symbols

(Those that perform the same or similar operations are denoted by a common reference.)
EB: Electron beam 1: Lens tube 14: Slider 2: Sample stage 15: Spring 3: Heat insulating material 16: Transfer base 4: Sample holder 17: Detection switch 5: Sample 18: Drive unit 6: Cooling block 19: Actuator 7: Guide rail 20: Objective lens 8: Sample transport mechanism 21: Refrigerant reservoir 9: Transport arm 22: Capillary
10: Stopper 23: Liquid helium tank
11: Stopper receiving part 24: Liquid nitrogen tank
12: Transport grip 25: Cooling member
13: Block

Claims (5)

A sample exchange mechanism in a sample cooling device mounted on a charged particle beam device,
A sample stage that is adiabatically supported from the surroundings and can be cooled to a cryogenic temperature, a sample stage support thermal insulator that supports the sample stage while preventing heat from flowing into the sample stage, a sample holder that mounts the cooled sample, and the tip at the tip A sample transport mechanism mounted with a sample holder, a stopper for limiting the amount of insertion of the sample transport mechanism after the sample holder contacts the sample stage, and the sample transport mechanism being inserted by contacting the stopper. In the sample cooling device provided with a stopper receiving part for stopping,
A block that moves integrally with the sample transport mechanism, a transport base that applies a force from the atmosphere side to move the sample holder when the sample holder is mounted on the sample stage, and the block and the transport base are integrated. A sample exchanging mechanism comprising: a slider connecting the block and the transport base so as to enable relative movement only in a direction; and a spring connecting the block and the transport base. . When the transport base is operated and the sample holder is mounted on the sample stage, the relative position of the block and the transport base is held by the spring until the sample holder contacts the sample stage. And
After the sample holder contacts the sample stage, a pressing force is applied to the contact surface between the sample holder and the sample stage by the spring force of the spring until the stopper comes into contact with the stopper receiving portion. The sample exchanging mechanism according to claim 1, wherein: The sample transport mechanism is configured by setting a position where the stopper abuts the stopper receiving portion so that the maximum value of the pressing force does not exceed a range of allowable additional pressure for preventing damage to the sample stage supporting heat insulating material. 3. The sample exchange mechanism according to claim 1, wherein the sample stage support heat insulating material is prevented from being damaged by stopping insertion of the sample stage. 3. The apparatus for manually exchanging a sample by an operator, wherein the conveyance base is a conveyance grip that can be grasped by an operator and move a sample holder during a sample exchange operation. 4. The sample exchange mechanism according to 3. A detection switch for detecting the insertion end position of the sample transport mechanism and a drive unit for driving the transport base by an actuator, and exchanging the sample by driving the sample holder replacement part via the transport base 4. The sample exchange device according to claim 1, wherein the sample exchange device is automatically performed.

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