JPH0713163Y2 - Electron beam equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electron beam apparatus, and more particularly to an electron beam apparatus having an improved sample holder.

Taking a transmission electron microscope as an example of the electron beam apparatus,
An example of the structure is generally shown in FIG. This has an electron gun 3 and a focusing lens 5 built-in, an objective lens 9 provided with exciting coils 8 and 10 is arranged below the focusing lens 5, and an intermediate lens 11 and a projection lens 12 are further below the objective lens 9. It comprises a lens barrel 1 provided and an observation chamber 2 arranged below the lens barrel 1 and fixed to the lens barrel 1 and forming a hollow chamber 13 in which a projection screen 14 is arranged. A hollow hole 7 extending in the longitudinal direction is formed in the central portion of the lens barrel 1 along an axis (hereinafter referred to as an optical axis for convenience) 6 of an electron beam emitted from the electron gun 3. The objective lens 9 protrudes downward and is excited by the exciting coil 8, and the upper magnetic pole 16 protrudes upward.
It has a lower magnetic pole 17 which is symmetrically arranged downward at a predetermined interval from 16 and which is excited by the exciting coil 10. Between the upper magnetic pole 16 and the lower magnetic pole 17, a support protrusion 18 provided on the upper plate of the exciting coil 10, a sample moving stage 19 installed on the support protrusion 18 and movable in the horizontal direction, and a sample A sample holder mounted on the moving stage 19 and supporting the sample
A sample holder 20 consisting of 15 and 15 is provided.

The transmission electron microscope having such a configuration has been improved in performance year by year, and the resolution has been improved to a level at which the atomic structure of a solid sample is imaged, and is generally called a high performance electron microscope. There is. In this high-performance electron microscope, the aberration coefficient of the objective lens 9 is made extremely small, and the value is about 1 mm (millimeter) for both the spherical aberration coefficient Cs and the chromatic aberration coefficient Cc in the electron microscope whose electron beam acceleration voltage is 100 kV. is there.

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

δ = 0.65 Cs ^1/4 λ ^3/4 (1) where, δ: resolution (mm) Cs: spherical aberration coefficient of objective lens (mm) λ: wavelength of accelerating electron beam (mm).

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

However, in order to reduce the wavelength λ of the electron beam, the accelerating voltage of the electron beam has to be increased significantly, and in order to achieve this, the manufacturing cost may increase sharply.
Therefore, only one or two high-performance electron microscopes capable of producing an acceleration voltage of 1000 kV are produced worldwide every year. Therefore, in order to further improve the resolution of the electron microscope without being affected by economic problems, it is necessary to reduce the spherical aberration coefficient Cs based on the above equation (1). The best measure for reducing the spherical aberration is to reduce the distance between the upper and lower magnetic poles 16 and 17 of the objective lens 9 so that the distance between the sample on the sample holder 20 and the magnetic poles 16 and 17,
In other words, to shorten working distance. However, if such measures are taken, the following new problems will arise.

That is, the sample holder 15 which is one component of the sample holding device 20.
Means that the thickness in the optical axis direction is set to 2 mm or more at the minimum. This thickness is set so that the sample mesh and the sample are mounted and fixed on the sample holder 15, the sample tilting operation member is incorporated, and further, the vibration damping property is sufficient to obtain the resolution of the atomic image level. It is indispensable. Since the sample holder 15 is moved into and out of the magnetic pole gap from the lateral direction with respect to the optical axis 6 by the exchange rod (so-called side entry method), the magnetic pole gap of the objective lens 9 is 2 m.
It can't be less than m. Due to such circumstances, the minimum value of the magnetic pole gap has been set to about 2 mm in the past,
Measures to make it smaller than this were hardly considered. Therefore, the spherical aberration coefficient of the objective lens 9 has not been realized, though it is known that Cs <1 (mm) when the magnetic pole gap is 2 mm or less.

In addition, as one solution, the objective lens 9 magnetic pole gap is 2 m
There is a method in which the sample is taken in and out in the direction of the optical axis 6 through the hollow hole 7 of the upper magnetic pole 16 or the lower magnetic pole 17 between these magnetic poles (so-called top entry method). In this case, the hole diameter in the magnetic pole is At least 5 mm or more is practically necessary. For this reason, there arises a problem that the spherical aberration is increased as the hole diameter increases.

And such a problem occurs not only in the transmission type electron beam apparatus but also in the case where it is desired to improve the resolution in the scanning type electron beam apparatus.

The present invention has been made in order to eliminate such a conventional problem, and an object thereof is to sufficiently hold a sample mesh or a sample and to have a sufficient vibration damping property. An object of the present invention is to provide an electron beam apparatus equipped with a sample holding device that can be inserted into and pulled out from an objective lens magnetic pole gap of 2 mm or less.

The gist of the present invention is that in a sample holder, when a sample holder is loaded, the thickness of a predetermined area that crosses between the opposing apexes of the objective lens magnetic pole is formed thinner than the thickness of the other area, and the sample holder has a narrow objective lens magnetic pole. The point is that it can be easily inserted into and removed from the gap. In such a structure, a concave portion having a diameter sufficiently larger than the magnetic pole top surface diameter is formed in a portion of the sample holder corresponding to the magnetic pole of the objective lens, and the concave portion is substantially U-shaped and extends to the tip of the sample holder. Is formed, and a thin portion having a predetermined width dimension is formed from the tip of the sample holder to the concave portion. The thin portion has a thickness of, for example, about 0.4 to 0.5 mm, and the other portions have a thickness of 2 mm or more as in the conventional case. Since the thickness of the sample mesh is about 0.1 to 0.2 mm, the sample holder can be easily inserted and removed even when the size of the objective lens magnetic pole gap is set to be smaller than 2 mm. In addition, the reduction in strength or vibration isolation due to the provision of the thin portion is
By making the thickness of the portion other than the thin-walled portion large, it can be sufficiently compensated. The sample can be tilted by rotating the exchange rod for inserting and removing the sample holder. Further, an opening of a predetermined shape is provided in the sample holder, and a plate having the above-mentioned recessed portion is mounted in the opening so as to be rotatable in an inclined manner to form an inclined support, while the inclined support is positioned outside the objective lens magnetic pole gap. It is also possible to connect to the sample inclining member by means of which the inclining can be performed in a direction different from the inclining by the rotation of the exchange rod part. When the sample holder is used in a transmission electron beam device, a through hole is formed in the bottom of the recess,
A sample mesh is arranged in this through hole portion.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

2 to 6 are views showing a first embodiment of the present invention. This shows an application example to a transmission type electron beam apparatus, the sample holding device 30 of the electron beam apparatus according to this embodiment,
A support protrusion 18 attached to the upper plate of the exciting coil 10, a sample moving stage 31 installed horizontally on the support protrusion 18, and a sample holder 32 mounted on the sample moving stage 31 and supporting a sample. Consists of.

The support protrusions 18 are made of Teflon or another material having high wear resistance, and slidably support the sample moving stage 31.

The sample moving stage 31 has a stage main body 34 having an inner cavity 33 having a size capable of sufficiently containing the lower magnetic pole 17 of the objective lens 9 and having an inner cavity 33 extending in the vertical direction, and the stage main body 34 integrated with the stage main body 34. And the stage main body 34
And a support flange portion 35 that extends outward at the lower end of the and has its lower surface abutting the support protrusion 18. This sample moving stage 31
The side faces of the inner cavity 33 of the stage body 34 that face each other have a cross-sectional shape that gradually expands downward from the upper end of the stage body 34 and are substantially parallel to the direction intersecting the optical axis 6. Is formed with a pair of dovetail grooves 36. A spring 37 is interposed between one side surface of the support flange 35 and the inner side wall of the lens barrel 1, and a screw member 38 attached to the lens barrel 1 is provided on the side surface on the opposite side of the support flange 35. The sample moving stage 31 and the X drive rod 39 that moves the sample in one direction (for example, the X-axis direction) are in contact with each other by engaging and moving back and forth. The spring 37, the screw member 38, and the X drive rod 39 form an X movement mechanism. This X movement mechanism performs the same operation with an angular displacement of approximately 90 degrees in the plane Y
A moving mechanism is incorporated. This Y moving mechanism includes a spring 40 interposed between one side surface of the support flange 35 and the inner wall of the lens barrel 1, and a Y drive rod 42 whose tip abuts on the opposite side surface of the support flange 35. , A screw member 41 mounted on the lens barrel 1 and moving the Y drive rod forward and backward in the Y-axis direction. Although not shown in the figure, a sample tilting mechanism for tilting the sample moving stage 31 together with the sample holder 32 is also attached.

The sample holder 32 is composed of a plate-like body having a rectangular planar external structure and a trapezoidal front external structure (see FIG. 3) that gradually expands from the top surface to the bottom surface. A concave portion 43 is formed downward from the top surface in a substantially central portion of the sample holder 32, while a concave portion 44 is formed upward from the bottom surface.
A thin portion 45 is formed substantially at the center in the thickness direction, and a highly rigid frame portion 55 is formed at the peripheral portion. The recesses 43 and 44 are the sample holder 3
It is formed in a circular shape or other predetermined shape from the tip of 2 toward the depth direction, and has a diameter sufficiently larger than the top surface diameter of the upper or lower magnetic poles 16 and 17, respectively. That is, the recesses 43, 44 have a sufficiently large crossover dimension both in the width direction of the sample holder 32 and in the depth direction, and even if the tops of the upper and lower magnetic poles 16, 17 are inserted, the inner surfaces of the recesses 43, 44 are included. Never hit. Furthermore, a hole 46 having a stepped structure having a receiving portion 47 is formed in substantially the central portion of the recesses 43, 44, and the sample mesh 48 is placed on the receiving portion 47, and on the sample mesh 48. A ring 49 for holding the sample mesh 48 is installed. And the ring
A holding plate 50 having a through hole 51 and a screw insertion hole 52 is formed on the 49.
However, the through hole 51, the sample mesh 48, and the hole 46 are placed so that they are aligned with each other, and the set screw 54 is screwed into the screw hole 53 provided in the sample holder 32, so that the sample mesh 48 is inserted through the ring 49. Press and fix. Since the sample holder 32 has a trapezoidal front external structure, the dovetails 56 that fit into the dovetail grooves 36 are formed on both sides of the sample holder 32. A screw hole 57 is formed on the rear side surface of the sample holder 32. The screw hole 57 is slidably supported in a sample exchange chamber 60 mounted and fixed to the lens barrel 1 and has a screw at its tip. A sample exchange rod 58 having a portion 59 is adapted to be screwed in.

Further, the sample holder 32 has a thickness dimension of 2-3 mm (millimeter). And as an example, the thin part 45 is 0.4
The thickness is set to 0.5 mm, and a step of about 0.2 mm is provided from the upper surface of the thin portion 45 to the receiving portion 47. Sample mesh 48
Ring 49 has a thickness of 0.05-0.2 mm and a diameter of about 0.2 mm.
Is set to. Therefore, the sample mesh 48,
When the ring 49 is installed, the upper edge of the ring 49 is 0.05 to 0.2m.
Since it protrudes from the upper surface of the thin portion 45 by m, a pressing plate 50 is applied to this protruding portion to press and fix the sample mesh 48.
In FIG. 4, reference numeral 61 is a vacuum pump that evacuates the inside of the sample exchange chamber 60.

In the sample holding device 30 having such a structure, a sample holder (assuming a sample for observation is supported) 32
To set to the observation position, a sample exchange rod 58 is screwed into the sample holder 32, and the sample holder 32 is inserted from the side cylinder portion of the lens barrel 1 toward the magnetic pole gap in a direction orthogonal to the optical axis 6. Since the thin portion 45 is provided at the tip of the sample holder 32,
The thin-walled portion 4 is the portion that enters the magnetic pole gap of the sample holder 32.
5, and the total thickness of the sample mesh 48 and the sample loaded in the receiving part 47 is less than 1 mm. Therefore, the sample holder 32 can be sufficiently inserted into the magnetic pole gap set to the above-mentioned minimum size, whereby the center of the sample mesh 48 can be aligned with the optical axis. Then, when the sample holder 32 is inserted to a predetermined position, the dovetail portion 56 of the sample holder 32 fits into the dovetail groove 36 of the sample moving stage 31, and firmly supports the sample holder 32. In this state, if the X or Y moving mechanism is operated, the sample can be moved in a plane, and if the sample tilting mechanism is operated, the sample can be tilted.

Now, the hole diameter of the hollow hole 7 in the upper and lower magnetic poles 16 and 17 is 0.7 m.
m, the minimum magnetic pole gap dimension d is 1.3 mm, the magnetic pole top surface diameter is 2 mm, and the magnetic pole apex angle is 60 °. When observing the sample at an acceleration voltage of 100 kV, the spherical aberration coefficient Cs is about 0.3 mm. It was Further, in this state, the bright field image, the dark field image, and the electron diffraction image in which the objective diaphragm was driven were obtained with the same ease as in the conventional objective lens. 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. When changing the observation field of view of the sample, the sample moving stage 31 is horizontally moved by rotating the screw members 38 and 41. At this time, since the concave portion 43 is formed with a diameter (that is, a passing dimension) sufficiently larger than the diameter of the magnetic pole surface of the objective lens, the frame portion 55 moves the sample without interfering with the upper and lower magnetic poles 16 and 17. Can be made.

In this embodiment, the tip of the sample holder 32 is the thin portion 45. However, the tip side of the hole 46 may be completely cut off so that the thin portion starts from the hole 46.

The reason for forming the recesses 43, 44 in the sample holder 32 is that the thin wall portion 45 is provided so that the sample holder 32 can be inserted into a narrow magnetic pole gap without impairing the rigidity of the sample holder 32. Therefore, the recess may be formed only from the upper surface of the sample holder 32 or only from the lower surface of the sample holder 32.

Furthermore, in the above embodiment, the sample holding device 30 for inserting and holding the sample between the objective lens magnetic pole gears of the transmission electron beam device has been described, but the resolution is improved even in the scanning electron microscope. Therefore, the sample may be inserted into the magnetic pole gap of the objective lens. Even in such a case, the present invention can be effectively applied. 7th
The figure shows a sample holder 60 that can be applied to such a scanning electron beam apparatus. This sample holder 60 is different from the sample holder 32 in the first embodiment in that it does not have a hole for electron beam transmission and is not equipped with a member such as a sample mesh. The structure and technical aim are the same as those in the first embodiment.

As described above, according to the present invention, the sample holder is formed with the concave portion having a diameter sufficiently larger than the top surface diameter of the objective lens magnetic pole, and the concave portion is expanded to the tip portion of the sample holder and is substantially U-shaped. Since the sample holding device of the electron beam device is formed in the shape of a letter and the sample is placed in this recess, the sample can be smoothly inserted / removed, moved, and tilted even if the magnetic pole gap of the objective lens is set to be significantly small. As a result, the resolution of the electron beam apparatus can be improved. In addition, even when the sample is moved or tilted, the frame portion of the sample holder does not interfere with the magnetic pole of the objective lens, and various effects such as maximum sample movement and tilting can be obtained.

[Brief description of drawings]

FIG. 1 is a sectional view showing a general structure example of a conventional electron microscope, and FIG. 2 is a perspective view showing a sample holder used in an electron beam apparatus according to a first embodiment of the present invention. FIG. 3 is a sectional view showing a state where the sample holder in the first embodiment is installed in the objective lens magnetic pole gap, and FIG. 4 shows a state in which the sample holder according to the first embodiment is installed in the objective lens magnetic pole gap. 3 is a cross-sectional view taken along line IV-IV in FIG. 3, FIG. 5 is a cross-sectional view taken along line VV in FIG. 2, showing a mounting state of a sample mesh or the like on the sample holder according to the first embodiment. 5 is an enlarged view of a portion VI in FIG. 5 showing a fixed state of the sample mesh, and FIG. 7 is a perspective view showing a sample holder used in the electron beam apparatus according to the second embodiment of the present invention. 1 ... Lens barrel, 2 ... Observation room, 3 ... Electron gun, 5 ... Focusing lens, 6 ... Electron beam axis (optical axis), 8, 10 ... Excitation coil 9,25 ... Objective lens, 11 ... Intermediate lens, 12 ... Projection lens, 15 … Sample holder 16… Upper magnetic pole, 17… Lower magnetic pole 19, 31… Sample moving stage 20, 30… Sample holder, 32… Sample holder 43, 44… Recess, 58… Sample exchange rod

Continuation of the front page (56) References JP-A-58-26439 (JP, A) JP-A-56-22039 (JP, A) West German patent 958584 (DE, C)

Claims (7)

[Scope of utility model registration request] 1. An objective lens having an upper magnetic pole and a lower magnetic pole arranged at a predetermined distance from the upper magnetic pole,
A sample moving stage provided in the vicinity of the magnetic pole of the objective lens and a sample exchange rod from a direction intersecting the electron beam axis of the objective lens are inserted and installed on the sample moving stage without coming into contact with the both magnetic poles. In an electron beam apparatus provided with a sample holder for holding a sample, a concave portion having a diameter sufficiently larger than a top surface diameter of the objective lens magnetic pole is formed at a substantially central portion of the sample holder, and the concave portion is a sample. An electron beam apparatus having a substantially U-shape that extends to the tip of the holder. 2. An electron beam apparatus according to claim 1, wherein the recess is formed from the upper side of the sample holder to the lower side, and the sample is placed in the recess. 3. The electron beam apparatus according to claim 1, wherein the recess is formed from the lower side to the upper side of the sample holder. 4. The electron beam apparatus according to claim 1, wherein the recesses are formed from the upper side and the lower side of the sample holder. 5. The electron beam apparatus according to any one of claims 1 to 4, wherein a hole is formed so as to penetrate the bottom surface of the recess. 6. The electron beam apparatus according to claim 1, wherein the size of the magnetic pole gap of the objective lens is set to 2 mm or less. 7. The bottom of the recess is composed of a thin portion having a thickness of 1 mm or less, and a frame portion having a thickness dimension of 2 mm or more is formed in a portion other than the recess. Request for utility model registration No. 1
Item 7. The electron beam apparatus according to any one of Items 6 to 6.