JP3406182B2 - Transmission electron microscope and sample observation method using the same - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sample observing method using a transmission electron microscope, and more particularly to a sample observing method and a transmission electron microscope suitable for preventing damage of a visual field to be photographed and recorded by an electron beam.

[0002]

2. Description of the Related Art In observing a sample with a transmission electron microscope, if the sample is apt to be damaged by electron beam irradiation, the amount of electron beam irradiation to the sample is reduced or the sample is thermally damaged by electron beam irradiation. Measures such as cooling the sample have been taken for the purpose of reducing the temperature. However, damage due to electron beam irradiation in the process of searching for a sample to be photographed cannot be prevented unless the irradiation amount of the electron beam is reduced as much as possible and the irradiation amount is limited to a level at which almost no observation is possible. Especially when observing light-sensitive materials, the nature of the sample is inherently sensitive to the electron beam, so without irradiating the electron beam until shooting, blindly irradiating the electron beam The method is to shoot without adjusting them, but in this case most of them are out of focus, and only the images that cannot be used can be taken.

Regarding prevention of damage to a sample due to electron beam irradiation,
Japanese Unexamined Patent Publication No. 59-103256 discloses a method of reducing the damage caused by an electron beam by designating the focusing timing when focusing the scanning electron microscope. Japanese Unexamined Patent Publication No. 1-151146 describes a method of observing a sample with a scanning electron microscope equipped with a sample position control device without causing a large damage to the sample. Further, Japanese Patent Laid-Open No. 4-269613 discloses a method for focusing a charged beam, in which the focal length of an objective lens at a measurement point is stored and the focusing accuracy at a measurement point in the vicinity thereof is improved. ing.

[0004]

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention
In Japanese Patent No. 103256 and Japanese Patent Laid-Open No. 1-151146, since the position of the sample is confirmed by irradiating the electron beam in advance, no means for preventing electron beam damage during that period is taken. . Further, in Japanese Patent Laid-Open No. 4-269613, means for observing a sample that is easily damaged by electron beam irradiation and means for controlling the electron microscope main body by stored information are provided for focusing at an observation position. Not not. An object of the present invention is to provide a transmission electron microscope capable of preventing the field of view to be photographed and observed from being damaged by electron beam irradiation.

[0005]

In the present invention, a field of view for focusing is provided separately from the field of view for photographing, and the field of view for focusing is set so that it is always a field of view that has been irradiated. The above-mentioned object is achieved by preventing the damage of the sample in the field of view due to. That is, by always focusing at the irradiated position, it is possible to avoid irradiating an unirradiated visual field for focusing. At the same time, by automatically recording and saving the amount of focus change and astigmatism correction amount of the field of view for focusing, and reproducing the same conditions as necessary,
To enable automatic control of transmission electron microscope conditions.

That is, the first step of moving the sample stage loaded with the sample to search the field of view, and after determining the imaging field of view, the electron beam deflecting means deflects the electron beam to a position different from the imaging field of view to focus. In a sample observation method using a transmission electron microscope including a second step of performing alignment, the electron beam deflecting means is controlled so that the deflection direction of the electron beam in the second step is always the irradiated direction on the sample. It is characterized by

If there is no suitable sample for focusing at the position where the electron beam is deflected in the second step, the electron beam is deflected in order to find a sample for focusing with reference to the deflected position. To do. Then, the observation condition for focusing is automatically recorded by linking with the coordinate position on the sample of the imaging visual field. The recorded observation conditions are read at the time of focusing of the next photographing field of view, and the observation conditions obtained by extrapolating using the coordinate position at the time of recording and the current coordinate position are used to control the electron microscope body. By using it, the number of operations for focusing can be reduced, and the time required for focusing can be shortened. The observation conditions for focusing the sample image are specifically the acceleration voltage, the bias voltage, the exciting current of each lens, the exposure amount, and the like.

Further, according to the present invention, an electron beam generating means, an electron beam deflecting means for deflecting an electron beam generated from the electron beam generating means, a sample stage for loading a sample, and a sample stage control for driving the sample stage. And a control device for controlling the electron beam deflecting means and the sample stage control means,
In a transmission electron microscope having a function of deflecting an electron beam to a position different from a photographing visual field when performing a field-of-view search, in a transmission electron microscope, the control device controls the sample stage control means by the sample stage control means at the time of focusing. Based on the movement information, the electron beam deflecting means is controlled so that the electron beam deflecting direction is the irradiated direction on the sample.

The control device has a function of controlling the electron beam deflecting means so that the electron beam is deflected in a predetermined pattern on the basis of the deflected position, and the electron beam is deflected from the photographing field to a position where the electron beam is deflected. When there is no suitable sample for focusing, the electron beam can be deflected again based on the deflected position to search for the sample for focusing.

The control device also has a function of automatically recording the observation condition for focusing on the recording device by linking it with the coordinate position on the sample of the photographing field, and reading out the recorded observation condition to display the electronic condition. It is preferable to have a function of controlling the microscope body. The observation conditions for focusing the sample image are specifically the acceleration voltage, the bias voltage, the exciting current of each lens, the exposure amount, and the like.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a schematic diagram showing an example of a transmission electron microscope according to the present invention. The electron beam 3 emitted from the electron gun 2 of the electron microscope body 1 is converged by the irradiation lens 4 and irradiated on the sample 5 on the sample stage 9. The electron beam 3 transmitted through the sample 5 is magnified by the objective lens 6 and the magnifying lens 7. The electron beam 3 magnified by the magnifying lens 7 is projected on the fluorescent plate 8. The conditions such as bias voltage, beam current, and exposure conditions at the time of observation and imaging are set by the voltage control device 11, the irradiation lens control device 12,
It is input to the control device 18 connected to the objective lens control device 14, the magnifying lens control device 16, and the exposure amount detection device 17. The control device 18 includes an input device 19 and a recording device 20.
Are connected.

The position of the sample stage 9 is controlled by the sample stage controller 10. Sample stage controller 1
0 is under the control of the control device 18, and the storage device 20 connected to the control device 18 stores the coordinates of the sample moved by the stage control device 10, that is, the history of the sample movement. Further, the mirror body 1 is provided with an upper deflection coil 21 and a lower deflection coil 22 for deflecting the electron beam 3. These bias coils 21 and 22 are controlled by the upper deflection coil control device 13 and the lower deflection coil control device 15 under the control of the control device 18.

Next, an example of a procedure for photographing the sample 5 on the sample stage 9 will be described with reference to the flowchart of FIG. The sample stage 9 is controlled by the sample stage controller 10.
Move to find the field of view (step 1). When the photographing field of view is found, the input device 19 instructs the control device 18. Then, the electron beam 3 is deflected by the upper deflection coil 21 into the field of view for focusing based on the deflection amount which is input to the upper deflection coil control device 13 in advance (step 2).

Observation conditions such as the irradiation area of the electron beam on the sample and the irradiation amount of the electron beam in the field of view for focusing are input to the control device 18 in advance via the respective control devices, and the upper deflection coil control is performed. These conditions are reproduced on the electron microscope in synchronization with the deflection of the electron beam 3 by the device 13. Further, the information on the direction of the visual field movement up to that time is input to the control device 18 via the sample stage control device 10, and the control device 18 determines the deflection direction of the electron beam 3 based on the information on the visual field movement. The upper deflection coil control device 13 is controlled so that the field of view on the sample already irradiated with the electron beam is obtained.

Subsequently, focusing and astigmatism correction are performed in the field of view for focusing (step 3). The focus change amount and the astigmatism correction amount at this time are input to the control device 18 through the objective lens control device 14 and the astigmatism correction device in synchronization with the information of the XY coordinates of the focusing field, and stored. It is stored in the device 20 (step 4). When the focusing is completed, the lower deflection coil 22 deflects the electron beam 3 into the field of view for photographing (step 5), and the exposure is started (step 6). The exposure conditions are recorded in advance in the storage device 20 connected to the control device 18 via the exposure detection device 17, and are adjusted so that the proper exposure conditions can be reproduced in synchronization with the start of exposure.

When the photographing of the first photographing field of view is completed as described above, subsequently, the second photographing field of view is searched for,
The same is taken. When photographing the second field of view, focusing and astigmatism correction can be performed by extrapolation based on the amount of focus change and the amount of astigmatism correction at the time of photographing the first field of view described above. To do so. That is, the condition extrapolated from the focus change amount and the astigmatism correction amount during the first visual field imaging to the second imaging visual field is instructed by the control device 18 by the objective lens control device 14 and the astigmatism. The correction device is set, and with that as the initial state, focusing and astigmatism correction are performed in the field of view for focusing the second imaging field of view.

A method of deflecting the electron beam 3 by the deflection coils 21 and 22 will be described with reference to FIG. The sample stage 9 is moved by moving the sample stage 9 by the sample stage controller 10.
If the desired field of view (position A) can be found while observing the upper sample 5, electron beam deflection is instructed by a key switch or the like attached to the outside. Then, the electron beam 3 is deflected by the upper deflection coil 21 and moved to the field of view (position A ′ or position A ″) for focusing. The objective lens controller 14 controls the objective lens 6 to complete focusing. Then, the lower deflection coil 22 deflects the electron beam 3 to the photographing visual field position A. The deflection amount of the electron beam 3 can be set by the upper deflection coil control device 13 and the lower deflection coil control device 15. .

FIG. 4 shows how the electron beam moves on the sample surface. When the sample stage 9 on which the sample 5 is mounted is moved in the XY coordinate directions by the sample stage control device 10, the observation sample is projected onto the fluorescent plate 8 together with the mesh holding the sample 5. As shown by the arrow in the drawing, when the sample stage 9 is moved in accordance with the XY coordinates and the observation is performed and the visual field to be photographed (photographing visual field position A) is found, the electron beam 3 is immediately focused by the upper deflection coil 21. Of the field of view (position A ').

The control unit 18 deflects the upper portion of the position based on the movement history information of the sample stage 9 input from the sample stage control unit 10 so that the position A'will always be in the direction in which the electron beam 3 has been irradiated. The coil controller 13 is instructed to control the deflection direction of the electron beam 3. Usually, it is preferable that the deflection direction is the direction in which the electron beam irradiation is performed immediately before the electron beam irradiation is performed on the photographing visual field position A. In synchronization with this, each visual field position is controlled by the controller 1 via the sample stage controller 10.
8 is automatically entered. When the focusing is completed in the field of view (position A ′) for focusing, the start of photographing is instructed by an externally attached key switch or the like. Then,
By the lower deflection coil controller 15, the photographing visual field position A
The electron beam 3 is swung back to and the image is taken.

If no suitable sample for focusing is found in the field of view (position A ') deflected from the photographing visual field position A, an externally mounted key switch or the like is operated. Thus, the control device 18 commands the electron beam control device to deflect the electron beam in accordance with a predetermined pattern with reference to the position A ', and searches for a field of view for focusing.

FIG. 5 is a diagram for explaining an example of the electron beam deflection pattern with reference to the position A '. In the figure, the broken line shows the movement of the visual field due to the movement of the sample stage, and the solid line shows the deflection pattern of the electron beam. 5A is a pattern in which the position A ′ is traced in the opposite direction along the direction of movement of the sample by the sample stage, and FIG. 5B is a pattern in which the electron beam is spirally scanned around the position A ′. 5C shows a pattern for scanning on a circle having a constant radius centered on the position A ', and FIG. 5D shows a pattern for scanning in a zigzag pattern from the position A'in the direction opposite to the direction of sample movement. Besides, any pattern can be set.

[0022]

As described above, according to the present invention, focusing for photographing a sample image can be always performed in the irradiated visual field.
It is possible to prevent the sample from being damaged by the electron beam. In addition, it becomes possible to record and save the amount of focus change and astigmatism correction amount in the field of view for focusing on the recording device and reproduce it on the electron microscope main body as needed. The number and time can be shortened.

[Brief description of drawings]

FIG. 1 is a schematic view showing an example of a transmission electron microscope according to the present invention.

FIG. 2 is a flowchart showing an example of an operation procedure until shooting.

FIG. 3 is a diagram illustrating details of a method of deflecting an electron beam by a deflection coil.

FIG. 4 is a diagram for explaining a moving state of an electron beam on a sample surface.

FIG. 5 is a diagram illustrating a deflection pattern for searching a sample for focusing.

[Explanation of symbols]

1 ... Electron microscope mirror body, 2 ... Electron gun, 3 ... Electron beam, 4 ... Irradiation lens, 5 ... Sample, 6 ... Objective lens, 7 ... Magnifying lens, 8 ... Fluorescent plate, 9 ... Sample stage, 10 ... Sample stage control Device, 11 ... Voltage control device, 12 ... Irradiation lens control device, 13 ... Upper deflection coil control device, 14 ... Objective lens control device, 15 ... Lower deflection coil control device, 16 ...
Magnifying lens control device, 17 ... Exposure amount detection device, 18 ... Control device, 19 ... Input device, 20 ... Recording device, 21 ... Upper deflection coil, 22 ... Lower deflection coil

Front page continued (72) Inventor Isao Nagaoki 882 Ichige, Ichige, Hitachinaka City, Ibaraki Prefecture, Hitachi Ltd., Measuring Instruments Division (56) References JP-A-55-43714 (JP, A) JP-A-56-130066 (JP, A) Actual Kaihei 1-124654 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H01J 37/21 H01J 37/147 H01J 37/26 H01J 37/153

Claims (8)

(57) [Claims] 1. A first step in which a sample stage loaded with a sample is moved to search a field of view, and an electron beam deflecting means deflects an electron beam to a position different from the imaging field of view after determining an imaging field of view. A sample observation method using a transmission electron microscope, comprising: a second step of performing focusing; in the second step , movement history information of the sample stage.
Sample observation method using a transmission electron microscope, wherein a deflection direction of the electron beam for controlling the electron beam deflecting means such that the irradiated field of view direction <br/> direction on specimen based. 2. The method for observing a sample by a transmission electron microscope according to claim 1, wherein when there is no suitable sample for focusing at a position where the electron beam is deflected in the second step, the deflection is performed. A method for observing a sample by a transmission electron microscope, which comprises deflecting an electron beam to search for a sample for focusing based on a position. 3. The method for observing a sample with a transmission electron microscope according to claim 1, wherein the first position is linked to a coordinate position on the sample in the imaging field of view .
A method for observing a sample by a transmission electron microscope, which automatically records the observation condition for focusing determined in step 2 . 4. The method for observing a sample with a transmission electron microscope according to claim 3, wherein the recorded observation conditions are read out, and the coordinates at the time of recording are read.
The observation conditions obtained by extrapolation using the position and the current coordinate position
A method for observing a sample by a transmission electron microscope, which comprises controlling an electron microscope main body as an initial condition . 5. An electron beam generating means, an electron beam deflecting means for deflecting an electron beam generated from the electron beam generating means, a sample stage for loading a sample, and a sample stage control means for driving the sample stage, A transmission electron microscope including a control device for controlling the electron beam deflecting means and the sample stage control means, and having a function of deflecting an electron beam to a position different from a photographing visual field to perform focusing when performing a visual field search. In the above, a storage means for storing the movement history of the sample stage is provided.
At the time of the focusing, the control device stores the memory.
Based on the movement history information of the sample stage stored in the means, the electron beam deflecting means is controlled so that the deflection direction of the electron beam becomes the direction of the irradiated field on the sample. Characteristic transmission electron microscope. 6. The transmission electron microscope according to claim 5, wherein the control device controls the electron beam deflecting means so that the electron beam is deflected in a predetermined pattern with reference to the deflected position. A transmission electron microscope having a function of: 7. The transmission electron microscope according to claim 5, wherein the control device links a coordinate position of the photographing field of view on a sample and determines a focus determined at a position different from the photographing field of view. A transmission electron microscope having a function of automatically recording observation conditions for alignment. 8. The transmission electron microscope according to claim 7, wherein the controller reads the recorded observation conditions,
Using the coordinate position at the time of recording the observation conditions and the current coordinate position
The observation conditions obtained by extrapolation to the initial condition Te a transmission electron microscope and having a function of controlling the electron microscope body.