JPH03159048A - Electron microscope - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to an electron microscope, and particularly to its sample moving mechanism.

[Conventional technology]

Positioning of a sample in an electron microscope is performed by moving a sample holder (generally referred to as a stage, holder, etc.) in at least two directions, the X-axis and the Y-axis. Specifically, for example, a mechanism such as a return spring that presses the sample holder in one direction, and a moving mechanism that applies a pressing force in the opposite direction to the force of the return spring are used. That is, the movement mechanism and the return spring work together to move the sample holder forward or backward to perform fine movement adjustment of the sample. Note that instead of the return spring, a pressure difference between the outside and outside of the sample chamber may be used to apply a return force to the sample holder.

In addition, as a sample moving mechanism, a screw rod or the like that converts mechanical rotational motion into linear reciprocating motion is used, and this is operated by human power from the outside.

Incidentally, one of the factors that influences the resolution and image quality of an electron microscope is the influence of vibration, drift, and the like.

That is, the sample holder of an electron microscope is structurally susceptible to vibrations, which causes problems in specifying the field of view for observation, taking photographs, and the like. Drift also includes thermal drift caused by thermal effects such as heat generation on the same side of the lens coil,
There is mechanical drift (including irregular movements such as backlash and meandering) resulting from the mechanical inertia of the sample moving mechanism.

Of these, thermal drift is stabilized after a certain period of time has elapsed after the sample is inserted into the observation position by cooling the lens coil and the like with water to maintain thermal equilibrium. On the other hand, mechanical drift occurs each time the specimen moving mechanism is moved (fine movement > rp adjustment) and the observation field of view is changed, so waiting for a period of time until the specimen becomes stable significantly impairs the efficiency of microscopy.

As a conventional drift countermeasure, for example, Japanese Patent Application Laid-Open No. 51-1
As disclosed in Japanese Patent No. 34555, etc., there is a method that corrects the ia field of view by detecting the amount of drift of the sample image with a fluorescent plate and deflecting the electron beam in the opposite direction to the direction of the drift.

In addition, as a countermeasure against vibration etc.,
After moving the sample, as disclosed in Publication No. 8 and the like.

Techniques have been proposed in which the sample moving mechanism is locked using a locking mechanism that utilizes the internal and external pressures of the sample chamber.

[Problem to be solved by the invention]

By the way, among the conventional techniques mentioned above, even if a means for correcting the amount of drift of the sample image by deflecting the electron beam is adopted, this alone does not provide sufficient consideration for vibration resistance, and if external vibrations are applied to the sample holding part. , the observation field changes,
This will interfere with drift correction and electron microscopic photography.

Such problems occur particularly in a high resolution range of nm. Therefore, it is necessary to wait until the sample comes to a complete standstill, which takes a relatively long time.

Furthermore, external vibrations are likely to be applied while taking photos.
Therefore, when taking photos, it is best to do it at a quiet night, etc.
I'm having trouble finding countermeasures.

Furthermore, even if a means for locking the specimen movement mechanism is adopted after the specimen has been moved, the specimen must be mechanically moved to select the observation field before locking. For example, in a high-magnification, high-resolution area such as a transmission electron microscope, the observation field of view becomes narrow, which increases the number of mechanical fine movements of the sample using the moving mechanism.

Mechanical drift occurs each time the adjustment is made, so a
It took a lot of time and effort to select a case field.

The present invention has been made in view of the above points, and its purpose is to improve the vibration and mechanical drift that have conventionally been problems in electron microscopes, especially in high magnification and high resolution areas. The purpose is to enable selection of a highly accurate observation field of view with simple operations.

[Means to solve the problem]

The present invention is configured as follows to achieve the above object.

That is, one aspect of the present invention is a sample moving mechanism in an electron microscope that uses an electric linear actuator as a drive source to move a sample holder in at least two directions, an X-axis and a Y-axis, within a sample chamber.

an electric locking mechanism that applies a mechanical fixing force (lock) to the sample moving mechanism; and an image shift deflection that electrically moves the observation field of the sample by deflecting the electron beam focused by the electron lens. an electric signal related to sample movement to the linear actuator of the sample movement mechanism by operation, and a signal to capture the operating state of the sample movement mechanism, or an electric signal related to locking and unlocking to the locking mechanism by operation; and a control system that provides an electrical signal related to movement of the observation field to the deflector.

[Effect]

With this configuration, since the sample moving mechanism and its locking mechanism are electrically operated, these mechanisms and the image shift deflector are all electrically controlled by the control system.

In other words, when finely adjusting the sample in the X-axis and Y-axis directions, an electric signal related to the movement of the sample is sent from the control system to the linear actuator of the sample movement mechanism by operating the adjustment operation part (for example, a knob, etc.). Given. As a result, the linear actuator is driven and controlled, and the sample in the sample holding section is moved to the target position within the sample chamber.

When the sample reaches the target position and the moving mechanism is stopped, the control system sends a locking command signal to the locking mechanism, and the sample moving mechanism and thus the sample are mechanically locked. This locking operation improves the vibration resistance of the sample.

Then, if you operate the image shift operation part after locking,
The deflector is current controlled by electrical signals from the control system, the electron beam passing through the sample is deflected according to the manipulated variable, the sample image at observation position n is electrically moved, and the desired ma field of view is selected. Ru.

In this way, in the present invention, the selection of the wtrA field of view is performed electrically on the premise that the sample moving mechanism is locked, so the selection of the observation field of view is not hindered by external vibrations, etc. Since this is performed by electrical movement, mechanical drift does not occur during visual field selection, and highly accurate visual field selection can be performed in a short time and with simple operations. In addition, image blurring caused by photographing is also prevented.

According to the present invention, high magnification, high resolution areas (e.g. 10
I! It also enables observation and electron microscopic photography.

〔Example〕

An embodiment of the present invention will be described with reference to the drawings.

Fig. 1 is a system configuration diagram of an electron microscope that is an embodiment of the present invention, Fig. 2 is an explanatory diagram showing a specific example of a sample moving mechanism used in the above embodiment, and Fig. 3 is a line A-A in Fig. 2. A cross-sectional view is shown.

The electron microscope shown in FIG. 1 is a transmission type electron microscope, and an electron beam 2 emitted by electron #1iil is focused by an irradiation lens system 3 and irradiates a sample 4.

The electron beam 2 that has passed through the sample 4 is magnified by an imaging lens system 5 and displayed as an image on a fluorescent plate 6 for observation.

A deflection coil (deflector) 15 is arranged between the set position of the sample 4 and the imaging lens system 5 for moving and selecting the observation field of the sample. That is, the deflection coil 15 is incorporated into the magnetic path, electromagnetically deflects the electron beam 2 that has passed through the sample 4, and electrically moves the sample image projected onto the fluorescent plate 6.

The sample moving mechanism 7 is composed of a moving body 7A, a sample holding section 19 provided at the tip thereof, a motor 8° linear actuator 9 as a driving source, and the like. The sample holder 19 holds the sample 4.
is placed.

The linear actuator 9 converts the rotation of the motor 8 into linear motion and transmits it to the moving body 7A.

In the drawing, only one linear actuator 9 and one motor 8 are shown, but in reality, this is a linear actuator and motor for moving in the X-axis direction, and a linear actuator and motor for moving in the Y-axis direction. What is composed of an actuator and a motor is shown in a unified manner.

The sample 4 placed on the sample holder 19 is moved along the X-axis, Y-axis, and
It is movable in two axial directions, and by combining the X and Y axes, it is possible to observe the entire range of the sample 4 on a two-dimensional plane.

A rotary encoder 10 that shares the rotation axis of the motor 8 is connected to the motor 8 , and output pulses from the rotary encoder 10 are input to a microprocessor 11 .

The microprocessor 11 serves as a control system for the electron microscope, and in addition to controlling the drive of the motor 8 via the motor drive circuit 12, it also controls the operation of a lock mechanism 14 and controls the flow of the deflection coil 15, which will be described later.

The microprocessor 11 includes the rotary encoder 1
In addition to inputting signals from 0, there is also an operation unit for moving the sample (e.g., a knob with a rotary encoder, etc.)
Operation signal from 13, operation unit for shifting the image (
Input the operation signal from 16 (operation knob with rotary encoder, etc.). Note that the operation section 13 for moving the sample is 1
Although only one is shown in the drawing, there are actually an operating section for X-axis movement and an operating section for Y-axis movement.

Next, the operation of this embodiment will be explained.

When the operation unit 13 is rotated, a number of pulses (operation command signal) proportional to the amount of rotation of an encoder provided on the operation unit is output, and the microprocessor 11 uses an electric signal corresponding to this number of pulses to output the signal via the motor drive circuit 1512. motor 8
to drive and control.

The rotation of the motor 8 is converted into linear motion by the linear actuator 9 and transmitted to the moving body 7A, and the sample 4 is moved.

Monitoring of the movement of the sample 4 corresponding to the number of pulses output from the operating section 13 is performed by the microprocessor 11 counting output pulses from the rotary encoder 10 on the motor side.

The above is the mechanical sample movement, and when the rotation operation of the operation unit 13 stops, the microprocessor 11 detects this and
Generates a lock command signal.

In response to this lock command signal, the locking mechanism 14 fixes the movable body 7A in an immovable state, and the sample 4 is kept stationary.

In this case, if the target object of the observation image projected onto the fluorescent plate 6 is not projected at the center of the fluorescent plate 6, or when searching so that the desired arA field of view is at the position of the fluorescent plate 6, the following steps should be taken: The image movement adjustment is performed as follows.

Assuming that the movable body 7A is in a locked state, when the operation section 16 for image shifting is rotated, the number of pulses output from the operation section 16 is counted by the microprocessor 11.
A current value corresponding to this number of pulses is output to the DA converter 17, and a coil current flows through the deflection coil 15 via the amplifier 18.

In this way, by electromagnetically deflecting the electron beam passing through the imaging lens system 5 and electrically moving the R holy image, fine adjustments can be made so that the desired Wt holy image is placed in the center of the fluorescent plate 6, or The observation field is selected.

It has been confirmed that electrical image movement using such a deflection coil 15 can achieve a magnification of about 5μ while completely suppressing mechanical vibrations applied to the sample, and a magnification of 1,000,000 times is achieved. When observing on a fluorescent plate, the range that can be observed on the fluorescent plate is about 200 mmφ, so a field of view that is 25 times larger can be selected without causing mechanical drift.

In this embodiment, the drive circuit 12 of the motor 8 is set to be switched off (cut off) when the image shift operation section 16 is rotating. Therefore, even if the operation section 13 for the movement mechanism is accidentally rotated while the operation section 16 is being operated, the microprocessor 11 will not drive the motor 8;
The mobile body 7A is.

The sample 4 is stably stopped while being fixed by the lock mechanism 14.

Further, when the operating section 13 is operated while the operating section 16 is in the non-operating state, the locking mechanism 14 is in an off (unlocked) state, and when the operating section 13 is in the non-operating state, the locking mechanism 14 is in the off (unlocked) state. Machine 4! The operating mode of J14 is set by the microprocessor 11 so that it is on (locked operating state). Therefore, if the operation section 13 is operated again after the operation of the operation section 16 is stopped, the lock mechanism 14 is unlocked by the microprocessor 11, and the movement of the movable body 7A is resumed.

Here, specific examples of the sample moving mechanism 7 and the locking mechanism 14 will be described in detail with reference to FIGS. 2 and 3.

Reference numeral 20 denotes a sample chamber of the electron microscope, which is surrounded by a side wall 20A and kept in a vacuum.

A cylindrical receiving fitting 21 penetrates the inside and outside of the side wall 20A and is fixed to the side wall 20A through an O-ring so as to keep the sample chamber 20 airtight. An inner tube 22 is rotatably fitted into the inner periphery of the receiving fitting 21 on the outside side of the sample chamber.

The inner cylinder 22 includes a motor and a worm (not shown).

It rotates via a worm gear or the like, and positioning in the direction of rotation is variably performed.

This positioning of the inner tube 22 in the rotational direction is for changing the wtr% inclination angle of the sample holder 19 supported by the inner tube 22 and thus the sample position.

A movable body 7A is inserted into the interior 22A of the inner cylinder 22 and the interior 21A of the receiving fitting 21 while being supported by a guide 26. A hole 33 is provided in the center of the movable body 7A in the axial direction, and a sample holder (hereinafter referred to as a holder) 19 is inserted into the hole 33 so as to be slidable in the axial direction while maintaining airtightness. .

The tip of the holder 19 protrudes into the sample chamber 20, and the sample 4 is placed on this tip. The tip of the holder 19 is stopped by a receiver 23 arranged coaxially with the holder 19 within the sample chamber 20 . The holder 19 is
This kind of distribution W! Due to the IW construction, due to the difference between the atmospheric pressure outside the sample chamber 20 and the vacuum pressure inside the sample chamber 20, the pressure on the sample chamber 20 side (
A returning force is applied in the left direction in FIG. 2), and a moving force is applied in the opposite direction to the returning force via the receiver 23 by a linear actuator (not shown) (actuator for moving in the Y-axis direction). It is.

A spherical body 24 is integrally formed at the tip of the movable body 7A, and is supported by a concave spherical surface 25 disposed inside the tip of the receiving fitting 21.
The movable body 7A uses this sphere 24 as a fulcrum to move the inside of the receiving fitting 2.
LA and the inside of the inner cylinder 22A are designed to be able to swing in the X-axis direction while maintaining airtightness using O-rings.

This swinging motion in the X-axis direction is performed from the receiving bracket 21 to the inner cylinder 22
The motor 8, linear actuator 9,
Return spring 28. This is done by the cooperative operation of push pins 29 and the like.

That is, while the push bottle 29 is urged by the return spring 28, its tip abuts on one side of the moving body 7A, and on the other hand, the tip of the linear actuator 9 abuts on the other side of the moving body 7A. In this way, the bin 29 and the linear actuator 9 are arranged to face each other in the X-axis direction. Then, the linear actuator 9 is moved forward by the rotation of the motor 8 against the force of the return spring 28, or the linear actuator 9 is moved backward by the reverse rotation of the motor 8, and by this and the force of the return spring 28, the moving body 7A and therefore holder 19
swings in the X-axis direction, and the sample 4 is positioned in the X-axis direction.

The return spring 28 and push pin 29 are mounted inside a holder 30 screwed into the inner cylinder 22.

Next, the lock mechanism 14 will be explained.

As shown in FIG. 3, the locking mechanism 14 has planar portions a and b partially formed on the upper and lower surfaces of the moving body 7A.

It is composed of a guide 26 that supports the movable body 7A, a motor 14 mounted on a receiving metal fitting 21 and an inner cylinder 22, a linear actuator 14B, a push pin 14C1, a spring 32, and the like.

The guide 26 is fixed to a part of the inner circumference of the inner cylinder 22.

The upper surface of the guide 26 has a flat portion a of the movable body 7A.

A plane parallel to b is formed, and the lower plane of the movable body 7A is supported in surface contact with the upper surface of the guide 26.

The linear actuator 1413, push pin 14G, spring 32, etc. are mounted inside the holder 31. Push bottle 14C
receives the force of the spring 32, and its tip (lower end) contacts the upper plane portion a of the movable body 7A.

The linear actuator 14B is arranged above the push bin 14G, and when the motor 14A is in the off state,
Push bottle 14G and a small gap (for example, about 0.5 mm)
is maintained.

According to such a lock mechanism 14, when the motor 14A is off, the force of the linear actuator 14B is not applied to the push pin 14C.

Since the push bottle 14C comes into contact with only the spring force, the moving body 7
A moves smoothly in the X-axis direction when controlling the drive of the linear actuator 9 for movement.

Furthermore, when the sample movement operation is stopped, a lock command signal is generated and the motor 14A is activated, and the linear actuator 14B presses the push bottle 14C, so that the movable body 7A is pressed against the guide 26 and moved. body 7Δ
movement is prevented.

In addition, the push bottle 1 by the linear actuator 14I3
The pressing force to 4G is kept constant by controlling the current flowing through the motor 14A.

In other words, when the linear actuator 14B cannot move straight, the motor 14A is overloaded and an excessive current flows. By detecting this current amount, the motor current amount is controlled to be maintained at an appropriate state and the push Keep pressure constant.

According to this embodiment, when the sample is positioned, the movable body 7Δ of the moving mechanism 7 is automatically locked, and the sample image is electrically moved and adjusted based on this lock. The movement 2 selection of the observation field of view can be performed quickly and with high precision without causing mechanical drift. Therefore, it is possible to observe and photograph a sample image with high resolution without any problem, not only at night. Furthermore, it is even more effective if used in a field emission transmission electron microscope that performs elemental analysis in a 1 nm analysis range using a field emission electron gun that has a brightness 1000 times higher than that of a thermionic electron gun.

Further, in this embodiment, the deflection coil 15 is
When selecting the field of view a using , even if the operating section for the moving mechanism is operated by mistake, the moving mechanism can be kept in a non-operating state and the reliability of the operation can be maintained.

Further, since sample movement, locking, and selection of the riR observation field can all be electrically controlled by simple operations, operability can be improved.

In the above embodiment, the motor 14A and the linear actuator 14B are used as the drive source for the lock mechanism 14, but a linear actuator using an electromagnetic solenoid may be used instead.

Further, although the locking device 4i114 detects the operating state of the sample moving mechanism 7 and automatically controls it, it is also possible to give a lock command and a lock release command by external operation.

〔Effect of the invention〕

As described above, according to the present invention, it is possible to improve vibration and mechanical drift, which have been problems in the past.

In addition, the selection of the observation field can be performed with simple operations in a short time and with high precision, and in particular, it is possible to observe and photograph sample images in high magnification and high resolution areas such as transmission electron microscopes.
It can be done without any problem.

[Brief explanation of the drawing]

FIG. 1 is a system configuration diagram of an electron N-microscope which is an embodiment of the present invention, FIG. 2 is an explanatory diagram showing a specific example of a sample moving mechanism used in the above embodiment, and FIG. 3 is an A-- It is an A-line sectional view. 1... Electron gun, 2... Electron beam, 4... Sample,
6... Fluorescent plate, 7... Sample moving mechanism, 7A... Moving body, 8... Motor, 9... Linear actuator, 11... Control means, 12... Motor drive circuit, 1
3... Operating unit for moving mechanism, 14... Lock mechanism, 1
5... Deflector (deflection coil), 16... Operation section for deflection coil, 19... Sample holding section.

Claims (1)

[Scope of Claims] 1. In an electron microscope, a sample moving mechanism that uses an electric linear actuator as a drive source to move a sample holder in at least two directions, an X-axis and a Y-axis, within a sample chamber; and the sample moving mechanism. An electric locking mechanism that applies a mechanical fixing force (lock) to the sample, an image shift deflector that deflects the electron beam focused by the electron lens, and electrically moves the observation field of the sample. An electric signal related to sample movement is applied to the linear actuator of the sample movement mechanism, an electric signal related to locking and unlocking is applied to the locking mechanism by a signal or operation that captures the operating state of the sample movement mechanism, and an electric signal related to locking and unlocking is applied to the deflector by the operation. An electron microscope characterized by comprising: a control system that provides an electric signal related to movement of an observation field of view. 2. In the first aspect, when the movement of the sample moving mechanism stops, the control system detects this and automatically sends a lock signal to the locking mechanism, and also controls the movement of the sample moving mechanism. The electron microscope is configured to automatically send an unlock command signal to the lock mechanism when the command signal is output. 3. The electronic device according to claim 1 or 2, wherein the drive circuit of the sample moving mechanism is automatically shut off when the image shifting deflector is being operated. microscope.