JPH0228604Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement of a sample cooling device incorporated into an electron microscope.

In an electron microscope, it is important to sufficiently vent the space surrounding the electron beam path. If the ventilation is insufficient and residual gas molecules such as water or hydrocarbons are present, electrons will be lost from the chemical reaction caused by the electron beam irradiation. Contaminants with poor conductivity are attached to the surface of the member around the wire path. This contamination phenomenon tends to become more pronounced as the temperature of the component decreases, so when observing an electron microscope image with a cooled sample, a sufficiently cooled fin should be placed near the sample. Measures such as reducing the amount of contaminants adhering to the sample by attaching gas molecules to the sample are essential.

FIG. 1 is a schematic diagram showing a so-called side-entry type electron microscope sample device in which a sample cooling device is incorporated and its surroundings. In the figure, 1 indicates the yoke of the objective lens, and 2 and 3 indicate upper and lower magnetic pole pieces for generating the lens magnetic field, respectively. A hole is bored in the side surface of the spacer 4 to accurately set the distance between the upper and lower magnetic pole pieces, and a rod-shaped member 5 is inserted through the hole from a direction perpendicular to the lens optical axis Z.
and the receiving member 6 passes through it. Rod-shaped member 5
A moving mechanism is incorporated in the portion 5a that penetrates the yoke 1 to move the member installed in the magnetic pole gap vertically, horizontally and horizontally using the tip T of the member installed in the magnetic pole gap as a fulcrum, and to expand and contract it in the direction of the receiving member 6. ing. An observation sample (not shown) is installed at a portion where the rod-shaped member 5 intersects with the optical axis Z.
Heat conduction rods (not shown) and mesh wires 7 provided inside
It is connected to a cooling tank 8 installed outside the vacuum via. An inner cooling trap 9 and an outer cooling trap 10 are placed in the vicinity of the magnetic pole piece with an insulator interposed therebetween, and each trap is connected to the cooling bath 8 by mesh wires 11 and 12. In this way, with conventional sample cooling devices, various parts must be installed in a narrow space, which not only makes it troublesome to install and remove the device, but also because the distance between the sample and the cooling trap is quite large. The drawback was that the cooling trap was not fully effective.

The purpose of the present invention is to solve these problems and enable a cooling member to be placed near the sample with a simple structure. A rod-shaped member 5 is inserted from a direction perpendicular to the optical axis, and the rod-shaped member has an outer cylinder extending along the rod-shaped member or a pair of parallel arms a1, a2, and the The sample stage 13 is placed between the two arms without contacting the two arms with the heat insulator 1.
5, and a heat conductive member 14 is attached to the gap between both arms along the rod-shaped member without contacting the arms, one end of the heat conductive member is connected to the sample stage, and the other end is connected to the sample stage. A cylindrical cap, which is connected to a cooling source and has a size that fits approximately inside both arms and covers both the sample stage and the heat conduction member, is heated so that it does not come in contact with both of them and neither of the arms. The cylindrical cap is attached to both arms via an insulator, and the cylindrical cap is connected to the cooling source via a heat conductive member so that the cylindrical cap is cooled to a temperature between the temperature of the sample stage and the temperature of both arms. The cylindrical cap is characterized in that an electron beam passage hole is provided in the cylindrical cap.

Compared to the conventional device shown in FIG. 1, the device of the present invention has a member functioning as a cooling trap inside the rod-shaped member 5, instead of providing an inner trap 9 and an outer trap 10, or in addition to these cooling means. A cross-sectional view along the axis A of the rod-shaped member is shown in FIG.
Fig. 3 shows a BB cross-sectional view in the figure.

In FIGS. 2 and 3, 5b is a rod-shaped member 5
The end portion on the electron beam optical axis Z side is shown. The rod-shaped member 5 has a pair of parallel arms a1 and a2 extending along the rod-shaped member 5. The sample stage 13 is attached to the setscrew 1 so that it is disposed between the arms a1 and a2 at the tip of the rod-shaped member 5 without contacting the arms.
5 to both arms a1 and a2. The set screw 15 is made of a highly thermally insulating material in order to prevent heat from flowing into the sample from both arms a1 and a2. The sample stage 13 is provided with a mechanism for placing a sample (not shown) around the electron beam passage hole 13a. A heat conducting member 14 is attached to both arms a1, a2 along rod-shaped member 5 in a gap between both arms a1, a2 without contacting both arms with set screws 15. The sample stage 13 and one end of the heat conduction rod 14 are connected via a thin copper plate 16. This thin plate 16 is for absorbing thermal expansion and contraction. The other end of the heat conduction rod 14 is connected to a cooling tank provided outside the vacuum.
The sample held in the sample holder 13 is cooled to a predetermined low temperature by the cooling tank. 17 is the sample stage 13
This is a cylindrical cap for covering both the heat conducting rod 14 and the heat conducting rod 14, and the cylindrical cap has a size that can fit approximately inside both arms. That is, it has a width narrower than the inner width W of both arms, and the width in the optical axis direction does not exceed the thickness T of both arms, or even if it does, it only slightly exceeds. This cylindrical cap 17 is attached to both arms a1 and a2 by set screws 15 so that it does not come into contact with both the sample stage 13 and the heat conduction rod 14, and also with the arms a1 and a2. Figure 4 is a three-dimensional view of the cylindrical cap, and the six holes 18 drilled on the side are the set screws 1.
5, and the two holes 19 bored above and below are for passing the electron beam. The open end 17b of the cylindrical cap 17 is connected to the heat conduction rod 14 by a flexible heat conduction member.

In the apparatus having the above-described structure, the sample stage 13 is attached to both arms a1, a2 via setscrews 15 made of heat insulators so that the sample stage 13 is not in contact with both arms a1, a2, In addition, the cylindrical cap 17 is attached to both arms a1 and a2 via setscrews 15 so that it does not contact both the sample stage 13 and the heat conduction rod 14, and also does not contact both arms. The arms a1, a2, the sample stage 13, and the cap 17 are sufficiently thermally insulated from each other. Furthermore, since the sample stage 13 is connected to the cooling tank via the heat conduction rod 14, the sample placed on the sample stage 13 is cooled to a temperature relatively close to the liquid nitrogen temperature. On the other hand, the open end 17b of the cylindrical cap 17 is connected to the heat conduction rod 14 by a flexible heat conduction member, and the radiant heat from the cylindrical cap 17 is transferred to the sample stage and the heat conduction rod. Because it is absorbed by 14,
Although the cylindrical cap 17 is not cooled as much as the sample,
It is cooled to a much lower temperature than both arms a1 and a2, which are close to room temperature. Therefore, while maintaining the function of the sample cooling device that cools the sample to an extremely low temperature, the cylindrical cap 17 plays the role of a cooling trap, and the cylindrical cap effectively removes contaminant particles that have flown into the empty space near the sample. Trapped.
In this case, the cylindrical trap functioning as a cooling trap is arranged inside both arms a1 and a2, so that the structure is simple and compact. Furthermore, compared to the conventional inner degradation trap 9 and outer cooling trap 10, the cylindrical trap is placed much closer to the sample, and the sample can be viewed from all directions (except for the direction in which the electron beam passes). Since it is covered, the effect of preventing sample contamination is extremely large.
Further, since the cylindrical cap 17 that covers the sample stage 13 from all directions also serves as a heat shield member, the cooling efficiency for the sample is improved.

It should be noted that the above-described embodiment is only one embodiment of the present invention, and may be modified and implemented.

For example, in the embodiment described above, the open end 17b of the cylindrical cap 17 is connected to the heat conductive rod 14 by a flexible heat conductive member.
In order to cool the cylindrical cap to a temperature between the temperature of the sample stage and the temperature of both arms, it may be directly connected to the deterioration tank by a flexible copper wire or the like.

As mentioned above, in the device of the present invention,
A sample stage 13 is attached to both arms via a thermal insulator 15 so that it can be placed between the two arms at the tip of the rod-shaped member without contacting the two arms, and the two arms are placed in the gap between the two arms along the rod-shaped member. A heat conductive member 14 is attached without contact with the sample stage, one end of the heat conductive member is connected to the sample stage, and the other end is connected to a cooling source, and the heat conductive member 14 is large enough to fit approximately inside both arms, and is connected to the sample stage and the heat conductive member. A cylindrical cap that covers both of the conductive members is attached to both arms via a thermal insulator so that it does not come in contact with both of them and with both of the arms, thereby providing a simple and compact contamination prevention mechanism. A specimen cooling device for an electron microscope is provided. In addition, the cylindrical trap is placed very close to the sample and covers the sample from all directions (except for the direction in which the electron beam passes).
The effect of preventing sample contamination is extremely large. Further, since the cylindrical cap that covers the sample stage from all directions also serves as a heat shield member, a sample cooling device for an electron microscope is provided that can improve the cooling efficiency for the sample.

[Brief explanation of the drawing]

Figure 1 is a schematic diagram showing a conventional sample cooling device;
4 through 4 are schematic diagrams for explaining essential parts of an apparatus according to an embodiment of the present invention. 1: Objective lens yoke, 2, 3: Magnetic pole piece, 4:
spacer, 5: rod-shaped member, a1, a2: arm, 6: receiving member, 7, 11, 12: mesh wire, 8:
Cooling tank, 9: Inner cooling trap, 10: Outer cooling trap, 13: Sample stage, 14: Heat conduction rod, 1
5: Set screw, 17: Cylindrical cap.

Claims (1)

[Scope of utility model registration request] A rod-shaped member 5 is inserted into a predetermined position in the gap between the magnetic pole pieces constituting the objective lens from a direction perpendicular to the optical axis of the lens. arm a1,
a2, and a sample stage 13 is attached to both arms via a thermal insulator 15 so as to be disposed between both arms at the tip of the rod-shaped member without contacting both arms, and A heat conductive member 14 is installed in the gap between the arms without contacting both arms,
A cylindrical cap having one end connected to the sample stage and the other end connected to a cooling source, and having a size that fits approximately inside both arms and covering both the sample stage and the heat conductive member, is connected to the sample stage and the heat conductive member. The cylindrical cap is attached to both arms via a thermal insulator so as to be in non-contact with both of them and with both arms, and the cylindrical cap is cooled to a temperature between the temperature of the sample stage and the temperature of both arms. 1. A sample cooling device for an electron microscope, characterized in that a cylindrical cap is connected to the cooling source via a heat conductive member, and an electron beam passage hole is provided in the cylindrical cap.