JPH02220339A - Scanning transmission type electron microscope - Google Patents

Abstract

PURPOSE:To permit simultaneous display of a diffraction image and a scanning transmission image with diffraction image picture elements assumed to be Xi, Yj by providing a means for indicating a specific area, a means for storing signal values associated with picture elements within a specified portion, and a means for displaying an associated scanning transmission image based on stored values. CONSTITUTION:The diffraction image of a specimen 5 over an image pickup tube 8 is stored in memories 12, 13. In response to a signal from a read area designation signal generation circuit 20, a read/erase control signal generation circuit 22 carries out addressing. If the picture elements for a diffraction image in a display means 16 are Xi, Yj (i=1-m, j=1-n), only the addresses of picture elements enclosed by a bright line according to a signal from an area designation circuit 19 are stored at associated addresses in memory 14 together with a signal from a scanning signal generator 9 via an integrating circuit 21. The picture elements Xu, Yv (1<=u<=m, 1<=v<=n) stored in the memory 14 can be read out for display via a read control signal from a display unit 17 to obtain a dark-field image. A light-field passing image can be obtained by moving a bright line via a manipulation section 18 to enclose the O-order diffraction spot.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a scanning transmission electron microscope capable of simultaneously displaying a diffraction image based on an electron beam transmitted through a sample and a scanning transmission image.

[Prior art] A scanning transmission electron microscope scans a sample two-dimensionally,
By detecting the electron beam transmitted through the sample during this scanning and displaying the sample image based on this detection signal, a scanning transmission electron microscope image of the sample is displayed. At this time, if the transmitted electron beam (0th order) that is not diffracted by the sample is selectively detected among the electron beams that have transmitted through the sample, and the sample image is displayed based on that, the scanning transmission image can be converted into a so-called bright field image. If only the electron beam (other than 0th order) that forms an image and is diffracted by the sample, e.g., the electron beam responsible for the 1st order diffraction spot, is detected, the image becomes a so-called dark field image.

Conventionally, when attempting to observe the scanning transmission image, a scintillator having an optical transmission path to the photomultiplier is inserted into the upper part of the fluorescent screen, and this scintillator is connected to a zero-order transmitted electron beam or a non-zero-order transmitted electron beam. I try to place it at the projection position of the line.

Alternatively, a scintillator such as the one described above is placed under the fluorescent screen, the screen is flipped up, and a deflection coil is used to irradiate the scintillator with a zero-order transmitted electron beam or a non-zero-order transmitted electron beam for detection. I am trying to do this.

[Problems to be Solved by the Invention] Therefore, conventionally, when attempting to observe a transmission scanning image, an electron beam diffraction image cannot be observed.

Furthermore, it was not possible to observe a bright-field image and a dark-field image at the same time.

The present invention solves these conventional drawbacks and provides a scanning transmission electron microscope that can select and observe a scanning transmission image corresponding to an arbitrary diffraction spot while observing an electron beam diffraction pattern. The purpose is

[Means for Solving the Problems] Therefore, the present invention provides a means for focusing and irradiating an electron beam onto a sample, a means for two-dimensionally scanning the sample with the electron beam, and a means for irradiating the sample with the electron beam. A lens system for forming a diffraction image of the transmitted electron beam, an imaging device disposed on the imaging surface, and a display means for displaying the diffraction image based on a signal from the imaging device. In a scanning transmission electron microscope, the pixels constituting the diffraction image displayed on the display means are (Xi, Yj) (where n is a certain value)
i = 1, 2, ..., ■ j-1, 2, ... n), means for indicating a specific region of the displayed diffraction image, and all u+V For each set of values, the electron beam scanning over the sample has a pixel (Xu,
Yv) (where 1≦u≦m and ■≦V≦n) is irradiated, and the signal values of the pixels included in the designated area are integrated to calculate the signal value of the pixel (Xu).

Yv); and means for displaying a scanning transmission image corresponding to a specific region of the diffraction image based on the stored signal of each pixel. It is a feature.

[Example] Embodiments of the present invention will be described in detail below based on the drawings.

FIG. 1 is a diagram illustrating an example of a device for carrying out the present invention, FIG. 2 is a diagram illustrating output signals from each circuit shown in FIG. 1, and FIG. FIG. 7 is a diagram illustrating a display example on a second display device.

In FIG. 1, 1 is an electron gun, 2 is an electron beam, 3 is a scanning coil, 4 is an irradiation lens, 5 is a sample, 6 is an objective lens, and 7
8 is a projection lens, and 8 is an image pickup tube.

9 is a first scanning signal generator, and the first scanning signal generator 9 generates a horizontal scanning step signal and a vertical scanning step signal (not shown) as shown in FIG. 2(a). This scanning signal is sent to the scanning coil 3. The scanning signal from the first scanning signal generator 9 is transmitted to the second scanning signal generator 9. The data is sent to the read/write controllers 13a and 14a of the third image memory 13.14.

Further, the scanning signal from the first scanning signal generator 9 is sent to the second scanning signal generator 10 and the read/erase control signal generation circuit 22. The second scanning signal generator 10 generates a vertical scanning signal as shown in FIG. 2(b) and a horizontal scanning signal obtained by frequency-dividing this signal based on the supplied scanning signal. The scanning signal from the second scanning signal generator 10 is sent to the image pickup tube 8 and also to the read/write control section 12a of the first image memory 12. 11 is an AD converter, and the output signal of the AD converter 11 is sent to second and third image memories 13 and 14. The image signal from the first image memory 12 is sent to a first image display device 16 via an adder circuit 15.

In order to control the read address of the first image memory 12,
A scanning signal is sent from the first image display device 16 to the read/write control section 12a of the first image memory 12. 1
Reference numeral 8 denotes an area specifying operation unit for specifying a specific area on the display screen of the first image display device 16. Reference numeral 19 denotes an area display signal generation circuit, and the area display signal generation circuit 19 displays an image on the screen of the first image display device 16 in response to an instruction from the area instruction operation unit 18 based on a signal from the area instruction operation unit 18. A signal is generated to display a bright line having a corresponding position and size. FIG. 3(a) shows an example of bright lines displayed on such a screen. Reference numeral 20 denotes a readout area instruction signal generation circuit, and the readout area instruction signal generation circuit 20 generates only the signals of pixels included in the area surrounded by the bright line based on the signal from the area instruction operation unit 18 in the second image. memory 1
3 is sent to the read/write control section 13a of the second image memory 13. 2
1 is an integration circuit for integrating the signals sent from the second image memory 13, and the signal from the integration circuit 21 is integrated into the third image memory 13.
The image data can be sent to the image memory 14 of. Further, the read/erase control signal generating circuit 22 generates a signal as shown in FIG. 2(c) based on the scanning signal from the first scanning signal generator 9.
The read/write control section 1 of the second image memory 13 generates a read scanning signal (actually a digital signal) shown in FIG.
3a, and also generates an erase signal shown in FIG. 2(d) and sends it to the read/write controller 13a.

In such a configuration, the first scanning signal generator 9 generates the scanning signal shown in FIG. 2(a) to scan the sample 5 with the electron beam 2. At this time, a diffraction pattern of the electron beam diffracted by the sample 5 is projected onto the image pickup tube 8, and if the electron beam 2 is irradiated parallel to the sample 5, this pattern will be reflected on the tube surface regardless of the scanning of the electron beam 2. It is projected upward without moving.

Therefore, the second scanning signal generator 1o generates the scanning signal shown in FIG. 2(b) to scan the image pickup tube 8, and
The image signal obtained from the image pickup tube 8 is converted into a digital signal by the AD converter 11, and then sent to the second and third image memories 12.
13. In the first image memory 12, when image signals for a predetermined frame are supplied from the image pickup tube 8, the integration of image signals is stopped by a control circuit (not shown). Immediately after this stop, the image signal is read out from the first image memory based on a readout control signal from the first image display device 16, and based on this read signal, the first display device 16 A diffraction pattern as shown in FIG. 3(a) is displayed. Therefore, the position and size of the bright line are adjusted based on the signal from the area display signal generation circuit 19 by operating the area instruction operation section 18, and the third
As shown in Figure (a), the bright line surrounds one of the first-order diffraction spots. At this time, the readout area instruction signal generation circuit 20 sends a readout area instruction signal corresponding to the area surrounded by the bright line to the read/write control section 13a of the second image memory 13. Second image memory 1
3, an image signal is sent in synchronization with the scanning signal from the second scanning signal generator 10. Therefore, immediately after each vertical scanning signal shown in FIG. 2(b) ends, the second image memory 13 stores a diffraction pattern image with a brightness corresponding to the electron beam irradiation point at that time. .

The signal corresponding to this stored diffraction pattern image is
The signal from the read/erase control signal generating circuit 22 shown in FIG. Reading of addresses other than those specified by the signal is prevented from being read.

That is, the pixels constituting the diffraction image displayed on the first display means are (xt, Yj) (However, if m and n are given certain values, 1=1.2.-, s j-1,2, -n), only signals at addresses corresponding to pixels included in the area surrounded by the bright line are read out and sent to the integration circuit 21. The integration circuit 21 integrates the signals of each pixel sent to it, and the signal from the integration circuit 21 is addressed by the signal from the first scanning signal generator 9, that is, the signal in the third image memory 14. It is stored at the address corresponding to the electron beam irradiation point on the sample. Every time the reading of the signal from the second image memory 13 is completed based on the signal shown in FIG. 2(c), the stored contents of the second image memory 13 are subject to the read/erase control shown in FIG. 2(d). It is erased by an erase signal from the signal generation circuit 22. In this way, for each set of U and V values, the electron beam 2 scanning the sample corresponds to a pixel (Xu, Yv) (where 1≦U≦layer and 1≦v≦n) When a point is being irradiated, the pixel signals within the specified area are integrated and this integrated value signal is stored in the address corresponding to the pixel (Xu, Yv) in the third image memory 14. Therefore, the electron beam 2 hits the sample 5 at 1
At the stage when frame scanning is completed, image signals for one screen are stored in the third image memory 14.

Therefore, if the second display device 17 generates a readout control signal to read out the image signal stored in the third image memory 14 and displays the sample image based on this readout signal, the second On the screen of the display device 17, there is a screen shown in FIG.
) A scanned transmission dark-field image is displayed.

This scanning transmitted image is a dark field image, but if you wish to display a bright field image, operate the area designation operation unit 18 to move the brightness fjIL so that the bright line becomes L in FIG. 3(a). surround the 0th order diffraction spot as shown in . In this way, the transmission scanning image is displayed based on the integrated value of the signals of the pixels surrounded by the bright line L', so that the second image display device 17 displays a bright field image. In this way, while observing the electron beam diffraction image, it becomes possible to select and observe a scanning transmission image corresponding to an arbitrary diffraction spot.

The embodiment described above is only one embodiment of the present invention, and the present invention can be implemented with various modifications.

For example, in the above embodiment, a square bright line was used to indicate a specific area of the diffraction pattern displayed on the image display device, but two circular bright lines as shown in FIG. 3(C) were used. Alternatively, a transmission scanned image may be displayed based on the signal of the pixel in the area surrounded by these two bright lines.

Further, the area may be indicated using a curved line using a mouse or the like, or may be indicated using a light bend or the like.

Furthermore, the designated areas may be identified by different colors instead of using bright lines.

Furthermore, as shown in FIG. 4, not only the first region of the diffraction image but also the second region can be simultaneously indicated by the bright lines Ll and L2, etc., and the electron beam is directed to each pixel (Xu
, Yv), the signals of the pixels included in the second area are integrated to calculate the pixel (
Xu, Yv), for example, by specifying the 0th-order diffraction spot area with the bright line L1 and specifying the second diffraction spot with the bright line L2, the diffraction pattern and It is also possible to simultaneously display a transmission scanning bright field image and a transmission scanning dark field image.

Further, the signal integrated by the integration circuit 21 is transmitted to one of the image pickup tubes.
The signal was obtained by frame scanning, but the signal for several frames was integrated for each pixel in the second image memory.
The integration circuit 21 may perform integration based on this integrated image signal.

Furthermore, by making the first image memory also serve as the second image memory, it is also possible to carry out the process without using the first image memory.

In addition, by directly connecting the image pickup tube to the display device, it determines in real time whether the signals sequentially sent from the image pickup tube correspond to pixels included in the specified area, and integrates only the signals of the included pixels. By leading to a circuit, not only the first image memory but also the second image memory can be omitted.

In addition, although an image pickup tube was used as a two-dimensional image detection means,
Other detection means such as a CCD element may also be used.

Also, without using the first display device and the second display device, it is possible to display a diffraction pattern and a scanning transmission image on one display device by dividing the screen, or to display a transmission scanning bright field image on one display device. The image and the transmission scanning dark-field image may also be displayed.

Furthermore, although the above-described embodiments are implemented by configuring each circuit in hardware, replaceable functions may also be implemented by replacing them with software.

[Effect of the invention] As is clear from the above explanation, the present invention has the following effects:
The pixels constituting the diffraction image displayed on the display means are (Xi,
Yj) (However, if n is a certain value, 1=1.
2. -, s j-1, 2, -n), means for indicating a specific region of the displayed diffraction image, and for each set of all U and V values, The signal value of the pixel included in the designated area when the electron beam scanning the sample is irradiated to a point corresponding to the pixel (XLl, YV) (15u Ss and l≦V≦n). The present invention includes means for integrating the signal value and storing it as a signal value corresponding to the pixel, and means for displaying a scanning transmission image corresponding to a specific area of the diffraction image based on the stored value. , a scanning transmission electron microscope is provided that allows one to select and observe a scanning transmission image corresponding to an arbitrary diffraction spot while observing an electron beam diffraction image.

[Brief explanation of the drawing]

FIG. 1 is a diagram illustrating an example of a device for carrying out the present invention, FIG. 2 is a diagram illustrating output signals from each circuit shown in FIG. 1, and FIG. FIG. 4 is a diagram illustrating a display example in the second display device, and FIG. 4 is a diagram illustrating a display screen in another embodiment. 1: Electron gun 2: Electron beam 3: Scanning coil 4: Irradiation lens 5: Sample
6: Objective lens 7: Projection lens 8: Image pickup tube 9.10: Scanning signal generator 11: AD converter 12.13.14: Image memory 12a, 13a, 14a: Read/write controller 15:
Addition circuit 16, 17: Image display device 18: Area instruction signal operation section 9: Area display signal generation circuit 20: Readout area instruction signal generation circuit 21: Integration circuit 22: Read/erase control signal generation circuit, L-, LL
, L2: Bright line (Figure 2, Figure 4 (cL) Figure 3, CG) (b)

Claims (1)

[Claims] means for focusing and irradiating an electron beam onto a sample; means for two-dimensionally scanning the sample with the electron beam; and a lens for forming a diffraction image of the electron beam transmitted through the sample. In a scanning transmission electron microscope, the scanning transmission electron microscope is equipped with a display system for displaying the diffraction image based on a signal from the imaging device, an imaging device disposed on the imaging surface, and a display device for displaying the diffraction image based on a signal from the imaging device. The pixels that make up the diffraction image are (Xi, Yj) (however, if m and n are certain values, i=1, 2,..., m
j = 1, 2, ... n), means for indicating a specific region of the displayed diffraction image;
For each set of values of u and v, the electron beam scanning the sample has a pixel (Xu, Yv) (where 1≦u≦m
and 1≦v≦n) in order to integrate the signal values of pixels included in the designated area when the point corresponding to 1≦v≦n is irradiated and store the resultant signal value as a signal value corresponding to the pixel (Xu, Yv). and means for displaying a scanning transmission image corresponding to a specific region of the diffraction image based on the stored signals of each pixel.