JPS5849566Y2 - Electron microscope sample contamination prevention device - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a sample contamination prevention device for electron microscopes and the like.

It is thought that sample contamination in electron microscopes and the like occurs when organic gas molecules in residual gas near the sample are solidified by the electron beam and buried on the sample surface.

In order to prevent this sample contamination, it is effective to provide a so-called cooling trap that adsorbs organic gas near the sample with a cooling body.

Conventionally, as shown in FIG. 1, an apparatus has been used in which a cylindrical trap surrounds a sample.

In the figure, reference numeral 1 indicates an objective lens, and the objective lens is composed of upper and lower magnetic pole pieces integrated by an excitation coil 2, an inner cylinder yoke 3, an upper cover yoke 4, an outer cylinder yoke 5, and a non-magnetic spacer 8. It consists of 6 and 7.

Between the two magnetic poles is a sample holding rod 11a that passes through the outer cylinder yoke 5 and the spacer 8 from the outside.

11b is inserted, and the sample 10 is held at the tip of the holding rod 11a.

Reference numerals 12a and 12b indicate sample devices that are attached to the outer wall of the vacuum lens barrel, respectively, and perform sample position adjustment and sample exchange via holding members 11a and 11b.

A deflection member 14 molded with a deflection coil 13 for electron beam deflection is mounted on the upper part of the father magnetic pole piece 6, and a cylindrical cooling trap 16 is further installed above the deflection member 14 with a heat insulating material 15 interposed therebetween.

As shown in the figure, the lower part of the cooling trap 16 surrounds the sample 10 and is provided with holes for passing the electron beam and the holding members 11a and 11b. It is connected to a liquid nitrogen tank 18.

As a result, the residual gas molecules near the sample are removed from the low-temperature trap 1.
Since it is adsorbed on the surface of sample 6, electron beam irradiation removes sample 10.
The degree of sample contamination that occurs can be reduced.

Further, an objective lens diaphragm 19 is installed below the trap 16, and the diaphragm 19 is held by an diaphragm holding member (not shown) provided in a direction perpendicular to the plane of the paper and passes through the spacer 8 and the lens barrel wall. The aperture diameter is then changed from outside the vacuum.

However, the residual gas around the sample is mainly generated from the vacuum grease applied to the 01J gasket, which is a movable part used in many sample holders and objective lens diaphragm holders, so the conventional apparatus described above does not contaminate the sample. could not be sufficiently prevented.

The present invention has been made to solve these conventional drawbacks, and embodiments of the present invention will be described in detail below with reference to the drawings.

FIG. 2 shows an embodiment of the present invention, and the same numbers used in FIG. 1 represent the same components.

In this embodiment, in addition to the cylindrical trap 16 installed inside the upper magnetic pole 6, a second cylindrical trap 20 that surrounds the spacer 8 is used, and its upper end is connected to the thermal insulator 2.
1 to the yoke 4b.

The trap 20 has a hole for passing the sample holding member 11a, 11b through, and a thin cylindrical trap 20a, 20b for enclosing the holding member etc. is formed at the edge of the hole as shown in FIG. , 20c are provided.

These traps 20 and trap 20a. 20b, 20
C is connected to the cooling tank 18 via a flexible heat conductor 22.

This flexible thermal conductor 22 is passed through an exhaust hole 4c formed in the yoke 4.

In such a configuration, since heat is removed by the cooling tank 18, the trap 20 and the traps 20a, 20
b, 20c are kept at low temperature, but traps 20a, 2
By keeping 0b and 20c at a low temperature, it is possible to very efficiently adsorb the gas generated from the OIJ song cooker of the movable part of the sample holding device and the like and moving along the holding members 11a+11bs etc. to the sample chamber.

Moreover, since the trap 20 is kept at a low temperature, among these gases, the gases that move without being transmitted through the holding member can be effectively removed at a position close to the source of the gases.

Therefore, with the apparatus based on the present invention, it is possible to suppress the degree of sample contamination to an extremely low level even when a microscopic region on a sample is irradiated with a microscopic electron beam for a long period of time.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram showing a conventional sample contamination prevention device, FIG. 2 is a schematic diagram showing a sample contamination prevention device based on the present invention, and FIG. 3 is a schematic diagram showing essential parts of the device shown in FIG. 2. 3.4.4a, 5: Objective lens yoke, 6: Upper magnetic pole piece,
7: Lower magnetic pole piece, 8 Ni spacer-110: Sample, 19: Objective lens aperture, 16.20: Cooling trap, 18: Cooling tank.

Claims (1)

[Scope of utility model registration request] A spacer for generating an objective lens magnetic field, accurately maintaining the relative position between the upper and lower magnetic pole pieces, and integrating the upper and lower magnetic pole pieces, and a sample holding member for inserting the sample between the upper and lower magnetic pole pieces. , a first cooling member inserted from above the upper magnetic pole piece to cool the sample, a cylindrical second cooling member disposed so as to surround the outside of the spacer, and penetrating the first cooling member. A sample contamination prevention device for an electron microscope, comprising a third cylindrical cooling member provided so as to surround the sample holding member that moves.