JPH0534769B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is an electron beam device that improves the sample holding device of an electron beam device so that the sample can be placed and tilted even in a narrow space between magnetic poles. Regarding equipment.

[Conventional technology]

Taking a transmission electron microscope as an example of a conventional electron beam device, an example of its structure is generally as shown in FIG. This has a built-in electron gun 3 and a focusing lens 5.
A microscope body 1 is provided with an objective lens 9 provided with excitation coils 8 and 10 below the objective lens, and an intermediate lens 11 and a projection lens 12 are provided below the objective lens 9. 1
It consists of an observation chamber 2 which forms a hollow chamber 13, which is fixed to the inside and has a projection screen 14 arranged therein. A hollow hole 7 is formed in the center of the microscope body 1 and extends in the longitudinal direction along an axis 6 of an electron beam emitted from an electron gun 3 (hereinafter referred to as an optical axis). The objective lens 9 includes an upper magnetic pole 16 that is excited by an excitation coil 8, and an upper magnetic pole 16 that is excited by an excitation coil 8.
A lower magnetic pole 17 is arranged downwardly at a predetermined interval and is excited by an excitation coil 10, and a sample holding device 20 is inserted between the upper magnetic pole 16 and the lower magnetic pole 17. Arranged so that it can be pulled out.

A transmission electron microscope with such a configuration is
Its performance has improved year by year, and its resolution has improved to the level where it can image the atomic structure of solid samples.
It is generally referred to as a high-performance electron microscope. In this high-performance electron microscope, the aberration coefficient of the objective lens 9 is minimized, and its value is the same as the spherical aberration coefficient in an electron microscope with an electron beam acceleration voltage of 100 kV.
C _S and chromatic aberration coefficient C _C are both 1 mm (millimeters)
That's about it.

By the way, the above-mentioned resolution, which plays an important role in determining the performance of an electron microscope, is theoretically expressed by the following equation.

δ＝0.65C _S ^1/4 λ ^3/4 ...(1) Here, δ: Resolution (mm) C _S : Spherical aberration coefficient of objective lens (mm) λ: Wavelength of accelerated electron beam (mm) .

As is clear from this equation, in order to obtain a fixed and more faithful atomic structure image, it is necessary to increase the accelerating voltage and shorten the wavelength λ of the electron beam, or to make the spherical aberration coefficient C _S smaller. . Currently, the highest resolution of an electron microscope is obtained at an accelerating voltage of 1000 kV (kilovolts), the wavelength of the electron beam at this time is λ = 8.7 × 10 ^-3 Å, and the spherical aberration is C _S = 2.
~3mm.

[Problem to be solved by the invention]

However, in order to reduce the wavelength λ of the electron beam,
The acceleration voltage of the electron beam must be significantly increased, and in order to achieve this, there is a risk that manufacturing costs will rise sharply. For this reason, only about one or two high-performance electron microscopes capable of generating an accelerating voltage of 1000 kV are produced worldwide each year. Therefore, in order to further improve the resolution of an electron microscope without being influenced by economical problems, it is necessary to reduce the spherical aberration C _S based on the above equation (1). The best measure to reduce spherical aberration is to use the upper and lower magnetic poles 16 of the objective lens 9,
17 to shorten the distance between the sample on the sample holding device 20 and the magnetic poles 16 and 17, that is, the working distance. However, when such measures are taken, the following new problems arise.

That is, the sample holding portion of the sample holding device 20 is set to have a minimum thickness of 2 mm or more in the optical axis direction. This thickness is essential for mounting and fixing the sample mesh on the sample holder, incorporating the sample tilting member, and providing sufficient vibration isolation to achieve resolution at the atomic image level. . Since the sample holding device 20 is moved in and out of the magnetic pole gap from the direction transverse to the optical axis 6 (so-called side entry method), it is impossible to reduce the magnetic pole gap of the objective lens 9 to less than 2 mm. Due to these circumstances, conventionally the minimum value of the magnetic pole gap has been set to approximately 2 mm, and little consideration has been given to measures to make it smaller than this. Therefore, objective lens 9
Regarding spherical aberration, it has been known that if the magnetic pole gap is set to 2 mm or less, C _S <1 (mm), but this has not been realized.

As one solution, the gap between the magnetic poles of the objective lens 9 is set to 2 mm or less, and the upper magnetic pole 16 is placed between the magnetic poles.
Alternatively, there is a method in which the sample is moved in and out in the direction of the optical axis 6 through the hollow hole 7 of the lower magnetic pole 17 (so-called top entry method), but in this case, the diameter of the hollow hole 7 in the magnetic pole must be at least 5 mm for practical purposes. It is. Therefore, a problem arises in that spherical aberration increases.

The present invention has been made with attention to such conventional problems, and its purpose is to have a sample holding part and a sample tilting member that can tilt the sample to the maximum extent within the distance between the objective lens magnetic poles of 2 mm or less. An object of the present invention is to provide an electron beam device equipped with a sample holding device.

[Means to solve the problem]

As a means for solving the above problems, the present invention has a configuration including a frustoconical upper magnetic pole and a frustoconical lower magnetic pole provided at a predetermined distance from the upper magnetic pole. and a sample holding device disposed between the magnetic poles of the objective lens, wherein the sample holding device includes a holding rod configured to be rotatable around an axis;
The frame body is integrally provided at the tip of the holding rod, has a storage opening in the center, has sufficient thickness to be vibration resistant, and is attached to the side wall of the electron beam device body at the tip of the frame. a sample holder having a contact part for rotatably abutting on the receiving part; and a sample holder arranged in the storage opening of the sample holder and tiltable about a direction perpendicular to the axis. It consists of an inclined support stand to be held, and a hole provided in the inclined support stand for inserting a sample mesh on which the sample is placed, and the inclined support stand is arranged such that the magnetic pole interferes with the inclination of the inclined support stand. In order to prevent this, the overall thickness including the sample and the sample mesh is made to be sufficiently thinner than the distance between the magnetic poles, at least in a region sufficiently wider than the top surface diameter of the magnetic poles.

[Effect]

Next, the operation of the present invention will be explained. The entire sample holding device can be tilted, and by tilting the tilting support base, it can be tilted in a second direction orthogonal to this, so that the sample placed on the sample mesh can be
It can be tilted in any direction. In addition, the abutment part provided at the tip of the sample holder, which has sufficient thickness to provide vibration resistance, makes contact with the receiving part on the side wall.
It can provide sufficient vibration isolation. moreover,
In order to prevent the magnetic poles from interfering with the inclination of the sample support stand, the overall thickness of the sample and sample mesh was made sufficiently thinner than the distance between the magnetic poles over an area sufficiently wider than the diameter of the top surface of the magnetic pole, so that the sample could be moved in two directions. The angle of inclination can be set over a wide range of angles.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

FIG. 3 is a diagram explaining the concept of the present invention, in which the sample holding device 20 includes an upper magnetic pole 16 and an upper magnetic pole 16.
The lower magnetic pole 17 is provided with a predetermined gap from the lower magnetic pole 17.
The sample holder 15 is provided within the magnetic pole gap of the objective lens 9, and the sample holder 15 has a sample holder 22. And the sample holding part 22 of the sample holder 15
A hole 2 having an opening sufficiently larger than the diameter of the top surface of the magnetic poles 16 and 17 of the objective lens is located approximately in the center of the objective lens.
3 is bored and a shelf 25 is provided that projects from the inner wall of the hole 23 inwardly, and a sample mesh 29 on which a sample is placed is arranged and fixed on the shelf 25.

In the above explanation, the shelf portion 25 is, for example, 0.5 mm
The thickness of the other parts is set to about 2 mm or more as before.
Since the thickness of the sample mesh is about 0.2 mm, the sample holder can be easily inserted and removed even if the objective lens magnetic pole gap is set smaller than 2 mm. Further, the reduction in strength or vibration damping properties due to the provision of the thin wall portion can be sufficiently compensated for by increasing the thickness of the portion other than the thin wall portion. The sample can be tilted by rotating the holding rod portion of the sample holding device. In addition, an opening of a predetermined shape is provided in the sample holder, and the plate with the above-mentioned hole is installed in this opening so as to be tiltable and rotatable to form an inclined support, and this inclined support is positioned outside the objective lens magnetic pole gap. It is also possible to connect the holding rod portion to the sample tilting member so that the holding rod portion can be tilted in a direction different from the tilting caused by rotation of the holding rod portion.

Hereinafter, the concept of the present invention will be explained in detail with reference to FIG. 29, and a mesh holding spring 32 that presses and fixes the sample mesh 29. The sample holder 15 includes a holding rod 21 rotatably supported on the side wall of the microscope main body 1.
and a sample holding section 22 that is integrally provided at the tip of the holding rod 21. The hole 23 provided approximately at the center of the sample holder 22 has an opening shaped into a circle or other predetermined shape with a diameter sufficiently larger than the diameter of the top surface of the magnetic pole, and is radially inward from the inner wall of the hole 23. A shelf portion 25 projecting toward the outside is provided at the bottom of the hole 23. Also, on the inner wall of hole 23,
A groove 26 is cut radially outward from the inner wall and extends in the circumferential direction, and an electron beam passage hole is formed in the center of the hole 23 .

The holding rod 21 of the sample holder 15 is made of a cylindrical rod so that it can rotate around its axis. On the other hand, the holding portion 22 is entirely made of a plate-like body having a thickness of 2 to 3 mm. This holding portion 22 is further formed with a cutout portion 37 cut out with a predetermined width dimension from the tip to the hole 23, and a thin wall portion 24 of about 0.5 mm is formed at the tip of the holding portion 22. Providing the thin portion 24 in this manner is convenient for inserting the sample holding device 20 into the magnetic pole gap of the objective lens 9.

At the rear ends of both sides of the notch 37, on the upper side of the groove 26, a locking part 2 protrudes radially inward from the opening edge of the hole 23 so as to cover the shelf 25.
7 and 28 are formed. Further, a recess 38 is cut into and approximately at the center of the tip of the thin portion 24 .

The sample mesh 29 includes a sample mounting section 31 having a mesh structure through which an electron beam can pass, and a support section 30 made of synthetic resin that supports this sample mounting section 31 from the outside.
The thickness is approximately 0.2 mm. This sample mesh 29 is placed on the shelf section 25 of the holding section 22 and installed by fitting its outer peripheral edge into the groove 26. A mesh holding spring 32 is inserted into the hole 23 from above the sample mesh 29, and its both ends are engaged with the locking parts 27 and 28 to fix it, and the sample mesh 29 is directed toward the shelf 25. Press down and secure.

For such a sample holding device, the objective lens 9 of the electron microscope has upper and lower magnetic poles 1 as shown in FIG.
6 and 17 are each formed in a relatively steep truncated conical structure with an opening angle of about 60 degrees, and the dimension d of the gap between the two magnetic poles is set to an extremely small size of 2 mm or less, for example, 1.3 to 1.5 mm. The outer magnetic pole 17 has an insertion hole 33 with a diameter of about 1.5 mm opened in a direction perpendicular to the optical axis 6 at a predetermined distance from the top surface of the magnetic pole. An objective diaphragm 35 fixed to the support rod 34 with a screw 36 is inserted.

With such a configuration, in this embodiment, the sample is placed on the sample mesh 29, and the sample holder 15 is inserted from the side cylinder part of the microscope main body 1 toward the magnetic pole gap in a direction perpendicular to the optical axis 6. . The portion of the sample holder 15 that enters the magnetic pole gap has a thickness of less than 1 mm including the sample mesh 29 loaded in the sample holder 22 and the sample. Therefore, the sample holder 15 can be fully inserted into the magnetic pole gap set to the above-mentioned extremely small size, and thereby the center of the sample mesh 29 can be aligned with the optical axis. As shown in FIG. 4, when the sample holder 15 reaches a predetermined position, the recess 38 provided at the tip of the sample holder 22 engages with a holder holder 39 fixed to the opposing side wall of the microscope body 1. , thus the sample holder 15 is supported.

Now, the hollow holes 7 in the upper and lower magnetic poles 16 and 17
When observing the sample at an accelerating voltage of 100 kV using an objective lens with a hole diameter of 0.7 mm, a minimum pole gap size d of 1.3 mm, a pole top surface diameter of 2 mm, and a pole top angle of 60 degrees, the spherical aberration coefficient C _S was approximately 0.3mm. Also,
In this state, a bright field image using the objective aperture,
Dark field images and electron diffraction images were obtained with the same ease as with conventional objective lenses. From this,
It can be seen that an atomic structure image with good resolution can be obtained without increasing the acceleration voltage of the electron beam. Note that the sample can be tilted by rotating the holding rod 21 about its axis. In particular, since the hole 23 is opened to have a sufficiently larger opening than the diameter of the objective lens magnetic pole surface, the thick part of the holding part 22 is connected to the upper and lower magnetic poles.
A sample tilt of about ±15° can be obtained without interfering with the angles 6 and 17.

FIGS. 5 and 6 are diagrams showing embodiments of the present invention. That is, the sample holder 15 has a rectangular storage opening 40 formed in the center of the sample holding part 22, and a pair of screw holes 41 facing each other on both sides thereof. A plate-shaped inclined support 43 having an external shape and dimensions that can be loosely fitted into the storage opening 40 is disposed inside the storage opening 40. It is rotatably supported by engaging with the receiving portions 45 provided on both sides. The inclined support base 43 is provided with a hole 23 having an opening sufficiently larger than the diameter of the top surface of the magnetic pole, and has a shelf 25 and a groove 26 similar to those in the first embodiment.
Further, a thin wall portion 24 having a notch portion 37 and a recess 38 is formed at the tip of the holding portion 22, and a thin wall portion of the notch portion 46 is formed on the inclined support base 43 so as to be continuous with the notch portion 37 and the thin wall portion 24, respectively. 44 are provided respectively. The structure and installation method of the sample mesh 29 and mesh presser spring 32 are as follows.
This is the same as in the first embodiment.

Because of this configuration, the sample holding device 20 according to this embodiment also has a portion of the sample holder 15 that enters the magnetic pole gap, which is 1 mm in total including the sample mesh 29 and the sample, as in the first embodiment.
It's just not thick enough. Therefore, this sample holder 15 can be inserted easily into the magnetic pole gap set to an extremely small size. In this embodiment, the sample holder 15 is
For example, by rotating the set screw 42, it is possible to perform an X-axis tilt, and on the other hand, by rotating the set screw 42, a Y-axis tilt, which is perpendicular to the X-axis, can be performed. Therefore, a greater variety of sample observations can be performed than in the first embodiment.

In the above embodiment, a holding device for inserting and holding a sample between the objective lens magnetic pole gap of a transmission electron microscope has been described. A sample may be inserted into the gap between the lens magnetic poles. Even in such a case, the present invention can be effectively applied. Furthermore, it is possible to apply not only to electron microscopes but also to other electron beam devices having similar functions.

〔Effect of the invention〕

As explained above, according to the present invention, the sample holding device of an electron beam apparatus includes a holding rod configured to be rotatable around an axis, and a holding rod that is integrally provided at the tip of the holding rod and stored in the center. It consists of a frame with an opening, vibration resistance, and a sufficient thickness, and has an abutting part at the tip of the frame for rotatably abutting on a receiving part provided on the side wall of the electron beam device main body. a sample holding section; a tilting support stand disposed within the storage opening of the sample holding section and held by the sample holding section so as to be tiltable about a direction perpendicular to the axis; and a sample mesh on which the sample is placed. a hole provided in the tilted support base for inserting a Since the overall thickness including the sample and the sample mesh in the area is configured to be sufficiently thinner than the distance between the magnetic poles, when the sample is tilted, the sample holding part of the sample holder and the tilting member do not interfere with the objective lens, and the sample mesh can be attached to the sample mesh. The mounted sample can be tilted to the maximum extent in two orthogonal directions, and the sample holder can have sufficient vibration-proofing properties.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a general structural example of a conventional electron microscope, and FIG. 2 is a perspective view showing the assembly of a sample support device of an electron beam apparatus according to an embodiment of the present invention.
FIG. 3 is a cross-sectional view showing the configuration of the invention and the sample holding device according to the embodiments inserted into the objective lens magnetic pole gap, and FIG. 4 is the sample holding device according to the above embodiment inserted into the objective lens magnetic pole gap. 5 is a perspective view showing the assembly of the sample support device of the electron beam apparatus according to the second embodiment of the present invention, and FIG. 6 is a plan view showing the sample support device in the second embodiment of the present invention FIG. 3 is a plan view showing a state in which the lens is inserted into a gap between magnetic poles. 9... Objective lens, 15... Sample holder, 16
... Upper magnetic pole, 17 ... Lower magnetic pole, 20 ... Sample holding device, 21 ... Holding rod, 22 ... Sample holding part, 23 ... Hole, 25 ... Shelf, 29 ... Sample mesh, 38 ... Recessed part (contact part), 39 ... Holder receiver (receiving part), 40 ... Storage opening, 43 ...
Inclined support platform.

Claims (1)

[Scope of Claims] 1. An objective lens having a frustoconical upper magnetic pole and a frustoconical lower magnetic pole provided at a predetermined distance from the upper magnetic pole, and a magnetic pole of the objective lens. In an electron beam apparatus, the sample holding device includes: a holding rod configured to be rotatable around an axis; and a holding rod that is integrally provided at the tip of the holding rod, It consists of a frame with a storage opening at the bottom and a sufficiently thick vibration-resistant frame, and the tip of the frame rotatably abuts against a receiving part provided on the side wall of the electron beam device main body. a sample holder having a sample holder; a tilted support stand disposed within the storage opening of the sample holder and held by the sample holder so as to be tiltable about a direction perpendicular to the axis, on which a sample is placed; a hole provided in the tilted support base for inserting a sample mesh to be sampled; An electron beam apparatus characterized in that the total thickness of the sample and the sample mesh in a sufficiently wide area is sufficiently thinner than the distance between the magnetic poles.