WO1996031897A1

WO1996031897A1 - Electron microscope

Info

Publication number: WO1996031897A1
Application number: PCT/JP1995/000689
Authority: WO
Inventors: Takafumi Yotsuji; Hiroyuki Kobayashi
Original assignee: Hitachi, Ltd.; Hitachi Instruments Engineering Co., Ltd.
Priority date: 1995-04-07
Filing date: 1995-04-07
Publication date: 1996-10-10

Abstract

Images related to the appearance and shape of a sample (5) are displayed by automatically moving a sample stage (4) mounted with a sample (5) by an amount of movement determined in accordance with the magnification of an electron microscope, inputting the intensity of electron beam impinging on the fluorescent screen (7), converting the intensity into arbitrary luminance or color tone data, and, displaying the luminance or color tone data on a CRT monitor in units of an arbitrary number of picture elements. The image of the sample (5) can be observed in a wide visual field without requiring any special device, and therefore, the working efficiency of the electron microscope is remarkably improved.

Description

Specification

Electron microscope technology

The present invention relates to an electron microscope, and more particularly to an electron microscope suitable for observing the appearance, shape, and the like of a sample in a wide field of view. Background art

When observing a sample with an electron microscope, for example, in a transmission electron microscope, the sample is set on a sample mesh, and the sample mesh is mounted on a sample stage. For this purpose, the sample stage is moved in advance to determine where the desired sample is located on the sample mesh, and is searched on a fluorescent screen for observation or on a CRT monitor with an expensive TV camera attached, and then the desired sample is observed. Perform a new analysis. In recent years, there has been a method disclosed in Japanese Patent Application Laid-Open No. 1-21844, for example, which has improved the efficiency of sample retrieval. However, where the sample mesh is, in what shape the sample exists, a fluorescent plate for observation, or a CRT monitor is used. It could not be confirmed without constant monitoring.

Scanning electron microscopes, on the other hand, have a permanent CRT monitor that displays secondary electron images, making image observation relatively easy.However, it is necessary to specify the shape of a large sample and the observation points within it. Is not easy. For this reason, for example, Japanese Patent Publication No. 4-74824 proposes a method of obtaining a wide-field image by combining a plurality of secondary electron images. However, this required complicated processing. Disclosure of the invention An object of the present invention is to provide an electron microscope capable of easily observing the appearance and shape of a sample with a wide field of view. In particular, even with a transmission electron microscope, the above-mentioned object can be achieved without the need for an expensive TV camera, and a transmission image can be created and stored, and a position search using the image can be performed. Where you do it.

In order to achieve such an object, the present invention provides a method that enables the electron beam irradiation area on the sample to be switched over a wide range by moving or deflecting the sample table, and also to adjust the electron beam irradiation area of the sample caused by the electron beam irradiation. Measure electrons from the area, for example transmitted or secondary electrons. By converting the brightness or color tone according to the amount of electrons in each area measured in this way and displaying the converted brightness or color tone corresponding to the irradiation area of the sample, a wide range of The appearance and shape of the sample can be displayed on one screen.

Such features of the present invention, particularly in relation to a transmission electron microscope, use a CRT monitor for the display device, a sample fine movement device for moving the sample stage, and an electron dosimeter for measuring the electron dose transmitted through the sample. An example of searching the sample shape and sample position at an arbitrary magnification is as follows. First, the magnification of the electron microscope image is determined, and a sample shape search execution instruction is issued.The sample stage automatically moves to the sample shape search start position, and the electron microscope image of the sample mounted on the sample stage is displayed on the fluorescent screen. Form an image. At this time, the intensity of the electron dose on the fluorescent screen detected by the electron dosimeter is taken in, converted into arbitrary brightness and color tone data, and corresponded to the coordinate position of the sample table obtained from the sample fine movement device, and the CRT monitor is used. It is displayed in an arbitrary number of pixels. Subsequently, the sample stage is moved by a movement amount that is linked to the magnification of the electron microscope so that the next field of view is imaged on the fluorescent screen, and the converted electron dose data is similarly displayed on the CRT monitor. The image showing the shape of the sample is displayed on the CRT monitor by sequentially repeating the display on the CRT monitor. By the way, when the composition of the sample is uniform, the intensity of the electron dose obtained from the electron dosimeter is inversely proportional to the thickness of the sample.Therefore, the brightness or color tone of the sample image displayed on the CRT monitor is the thickness of the sample. It indicates the relative value of the height. By automating these operations and means under CPU control, the efficiency of sample shape search is dramatically improved. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a configuration diagram of a transmission electron microscope showing one embodiment of the present invention.

FIG. 2 is a flowchart showing an example of a sample shape automatic search program built in the CPU of FIG.

Fig. 3 is a configuration diagram showing a specific example of the electron beam transmission area and brightness data conversion in Fig. 1.

Figure 4 is a three-dimensional display showing the shape of the sample.

FIG. 5 is a configuration diagram of a transmission electron microscope showing an embodiment using an electric visual field moving means.

FIG. 6 is a configuration diagram of a scanning electron microscope according to another embodiment of the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, an embodiment of the present invention will be described in detail with reference to an example in which the present invention is applied to a particularly effective transmission electron microscope. Note that, in this embodiment, an example will be described in which the electron beam irradiation area switching device is configured by a sample table and a sample fine movement device, and the electron measurement device is configured by an electron dosimetry device using a fluorescent plate. Of course, it is not limited to these.

FIG. 1 is a configuration diagram of a transmission electron microscope showing one embodiment of the present invention. Transparent The electron microscope 1 emits the electron beam 2 from the electron gun 1, converges on the irradiation lens 3, and irradiates the sample 5 mounted on the sample stage 4. The electron beam 2 transmitted through the sample 5 is enlarged by the imaging lens 6 and forms an electron microscope image on the fluorescent screen 7. The sample stage 4 is driven by a sample fine movement device 8, and the magnification of the electron microscope image is controlled by a magnification control device 9. The intensity of the electron dose from the fluorescent screen 7 is obtained from the electron dosimeter 10. The CPU 11 is connected to a sample fine movement device 8, a magnification control device 9, an electron dosimeter 10 and a CRT monitor 12. The sample fine-movement device 8 drives the sample stage 4 by combining two axes of the X-axis direction and the Y-axis direction, and sets the movement coordinates in the X-axis direction and the Y-axis direction according to CPI 11 to move the sample stage 4 It can be moved, and when the movement of the sample stage 4 is completed, the CPU 11 is instructed to complete the movement. When receiving the movement completion instruction from the sample fine movement device 8, the CPU 11 takes in the intensity of the electron dose on the fluorescent screen 7 detected by the electron dosimeter 10 and converts it into brightness or color tone data to convert it into a CRT monitor 1 2 To be displayed. The shape of the sample 5 can be displayed on the CRT monitor 12 by sequentially repeating the movement of the sample table 4, the capture of the electron dose intensity, the brightness conversion, and the display. These series of sample shape searches are executed via the CPU 11 based on the flowchart of the sample shape automatic search program shown in FIG.

Next, the sample shape automatic search program will be described in detail with reference to Figs. When the sample shape automatic search program starts, the sample shape search range specification A 2, sample shape search magnification specification A 3, brightness or color tone specification A 4, CRT display pixel number specification A 5 are requested, and the operator follows the request message. Make the settings in order. Sample shape search range specification A2 is a search range specification for sample 5 in the X and Y directions, and two coordinates are specified by diagonal coordinates within a range of ± 100.0 0.0 μππι. Sample shape search magnification specification A3 is electron microscope for shape search Specify the magnification of the mirror. The specified magnification can be obtained by setting the excitation conditions of the irradiation lens 3 and the imaging lens 6 from the magnification controller 9 via the CPU 11. Since the designated magnification is the magnification of the electron microscope image on the fluorescent screen 7, the amount of movement with respect to the sample 5 must be calculated. That is, by moving the sample stage 4 by a moving amount linked to the magnification, the electron dose transmitted through the entire sample 5 is received on the fluorescent screen 7 and can be obtained as the intensity of the electron dose via the electron dosimeter 10. . FIG. 3 is a configuration diagram showing the correspondence between the electron beam transmission area of the sample 5a and the data converted into the luminance to be displayed on the CRT monitor 12a. P 0 (X 0, Y 0) is the coordinate of the sample shape search start point, and P n (Xn, Y η) is the coordinate of the sample shape search end point, which coincides with the diagonal coordinates of the sample shape search range. Δχ and Ay are the amounts of movement of the sample 5a in the X and Y axis directions linked to the magnification. In the present example, the amount of movement corresponding to 15 cm on the fluorescent plate was set in consideration of the overlap of the electron microscope images. Also, a case will be described in which the luminance of the CRT monitor 12a in units of pixels is displayed in 256 gradations (gray scale), but the present invention is not limited to 256 gradations. As for the color tone specification, a gradation is provided for each of R (red), G (green), and B (blue). When the sample shape search magnification is Mag, Δχ and Δy are obtained by the following equations.

Δ X = 0.15 / Mag

… (Number 1)

Δ y = 0.15 / Mag

Sample 5a moves to PO (X 0, YO), PI (XI, Y l), P 2 (X 2, Y 2) in order of sample shape search end point P n (Xn, Υη) . The route of the movement is not particularly limited.

Brightness or hue designation A4 is read via the electron dosimeter 10 Specifies the level for converting the intensity of the electron dose into luminance information. Normally, when pixels are displayed in gray scale, black points are displayed when the luminance data is zero, and white points when the luminance data is 256. The minimum value of the electron dose transmitted through sample 5a is specified by the luminance data near 256 of 256 gradations, and the maximum value of the electron dose is similarly calculated by the luminance data of 256 gradations near 256. By specifying, the brightness data proportional to the transmitted electron dose can be easily calculated. To search the sample shape in detail, the intensity distribution of 256 gradations can be displayed by associating the intensity of an arbitrary electron dose with zero or 256 in the luminance data.

CRT display pixel number specification A5 specifies that the sample shape search coordinates of sample 5a correspond to the number of CRT pixels, and arbitrarily specifies from 1 X 1 pixel to the unit of 10 X〗 0 pixel. When changing the magnification for performing the sample shape search while keeping the sample shape search range constant, the lower the magnification, the smaller the number of sample shape searches, and the higher the magnification, the greater the number of sample shape searches. Therefore, when the magnification is low, the unit of the number of pixels is increased, and the unit of the number of pixels is displayed with the same luminance data, so that the enlarged display can be performed on the CRT monitor 12a. When the magnification is high, the unit of the number of pixels is reduced, the intensity of the electron dose obtained from the corresponding sample shape search coordinates is averaged, and the unit of the number of pixels is displayed, thereby reducing the display on the CRT monitor 12a. It can be performed. The accuracy of the sample shape display is improved by searching the sample shape at a high magnification and performing a reduced display on the CRT monitor 12a. In this embodiment, a specific example of a 3 × 3 pixel unit is shown. In the case of a reduced display, a means 15 for averaging the electron dose intensity obtained from the corresponding sample shape search coordinates is required, but the enlarged display is performed. In this case, the averaging means 15 is unnecessary.

When the above specification is completed, the sample shape automatic search program 8 is moved to move the sample 5a to the shape search start position coordinate P 0 (X 0, Y 0) (corresponding to the processing of A 6 in the flow chart). When the movement of the sample 5a to the shape search position coordinates is completed, a movement completion instruction is issued from the sample fine movement device 8 to the CPU 11, and the intensity of the electron dose from the fluorescent screen 7a is measured via the electron dosimeter 10a. And converts it into the luminance data described above. Further, the same number of pixels as the pixel number unit 14 specified by the CRT display pixel number specification A 5 are set to the same luminance data, and the display is performed from the upper left of the CRT monitor 12 a. (Corresponds to the processing of A7 and A8 in the flow chart.) Then, the sample fine movement device 8 is driven, and the sample 5a is moved to the next shape search position coordinate P1 (XI, Y1). Execute the process repeatedly. When the brightness data of the sample displayed on the CRT monitor 1 2a becomes P n (Xn, Y η), the sample shape automatic search program ends and the CR Τ monitor 1 2a displays the sample 5 within the search range. The shape of a is displayed in gray scale. It is extremely easy to store the displayed grayscale on the hard disk or the floppy disk via the CPU 11 or to redisplay the stored image.

In addition, if the composition of the sample to be searched is uniform, the intensity of the electron dose transmitted through the sample is inversely proportional to the thickness of the sample. In other words, the electron dose intensity decreases as the sample thickness increases. Therefore, by executing the sample shape automatic search program, it is possible to confirm the difference in sample thickness with the grayscale image displayed on the CRT 12a. Further, by setting the luminance data of the image displayed on the CRT 12a as the relative thickness of the sample, the thickness of the sample can be relatively measured.

In addition, three-dimensional display can be performed by displaying the electron dose intensity in the vertical direction, the sample shape search coordinate X in the horizontal direction, and the sample shape search coordinate Y in the depth direction on the CRT monitor 12 (Fig. 4). ). In the above description, the driving means of the sample stage on which the sample is mounted can be replaced with the electric visual field moving means 8a using the deflection coil 16 shown in FIG.

According to the present embodiment, the shape of a sample can be searched by an unmanned state with a simple operation, which is extremely suitable for automating sample shape search and improving the work efficiency of an electron microscope.

FIG. 6 shows an example of the configuration when the present invention is applied to a scanning electron microscope. In the figure, the electron beam 2 converged by the converging lens 17 is deflected and scanned by the deflection coil 18 and is scanned on the sample 5 via the objective lens 19. One scan image is obtained by setting and scanning the set area once. Therefore, as in the embodiment shown in FIG. 1, the sample stage 4 is driven by the sample fine movement device 8 every time one area is scanned, and the sample irradiation area is switched by repeating this operation sequentially. The amount of secondary electrons in each area is detected by the secondary electron detector 21 and converted into brightness or color tone data corresponding to the amount of electrons in each area by the CPU 11 as in the embodiment of FIG. Each scanning area of the sample 5 is displayed on the display device 12 in a form represented by one luminance or color tone. Therefore, a wide visual field image of the whole or part of the appearance and shape of the sample 5 can be easily observed. Industrial applicability

According to the present invention, it is possible to propose a new microscope image capable of observing the external appearance and shape of a sample in a wide field of view without being restricted by a conventional fluorescent plate for observation and without requiring a TV camera or the like. In particular, the working efficiency of a transmission electron microscope can be dramatically improved.

Claims

The scope of the claims

1. In an electron microscope equipped with an electron gun, a sample stage on which a sample is mounted, and an electron lens for irradiating an electron beam from the electron gun toward the sample, an electron beam irradiation area on the sample is adjusted. An electron beam irradiation area switching device for sequentially switching, an electron measurement device for measuring electrons from each region of the sample caused by the electron beam irradiation, and a device for converting the brightness or color tone according to the measured amount of electrons. An electron microscope, comprising: a display device for displaying the converted luminance or color tone in association with an irradiation area on the sample.

2. In claim 1, the electron beam irradiation region switching device is characterized in that the electron beam irradiation region is moved by a predetermined region in conjunction with a set magnification of the electron microscope. electronic microscope.

3. In an electron microscope including an electron mirror, a sample stage on which a sample is mounted, and an irradiation lens for irradiating the sample with the electron beam from the electron gun, an electron beam irradiation area on the sample is adjusted. An electron beam irradiation area switching device for sequentially switching, an electron beam measuring device for measuring an electron beam transmitted through the sample, a device for converting the brightness or color tone according to the measured amount of electrons, and irradiation of the sample A display device for displaying the converted luminance or color tone in association with the region.

4. The electron microscope according to claim 3, wherein the electron beam irradiation area switching device is constituted by a sample stage driving device that moves a sample with respect to the position of the irradiated electron beam.

5. The electron microscope according to claim 3, wherein the electron beam irradiation area switching device includes an electron beam deflector for moving a position of an electron beam to be irradiated on the sample.

6. In Claim 3, the electron beam irradiation area switching device is configured to An electron microscope, wherein an electron beam irradiation area on the sample is moved in conjunction with a setting magnification of the microscope.

7. The method according to claim 3, further comprising: an imaging lens that expands the electron beam transmitted through the sample on a fluorescent plate. ♦ The electron beam measurement device measures an electron dose formed on the fluorescent plate. An electron microscope characterized by being configured to measure.

8. In claim 3, in the display device, the coordinate position of the sample is made to correspond to a coordinate plane in the X-axis direction and the Y-axis direction of the display device, and the conversion is performed in conjunction with an irradiation area on the sample. An electron microscope characterized in that a plurality of regions of the sample are simultaneously displayed by sequentially displaying the brightness or color tone.

9. The display device according to claim 3, wherein the display device causes the coordinate position of the sample to correspond to a coordinate plane in the X-axis direction and the Y-axis direction of the display device. An electron microscope characterized in that the intensity of an electron beam measured by a beam measuring device is displayed in three dimensions.

10. An electron microscope including an electron beam, a sample stage on which a sample is mounted, and an irradiation lens for irradiating the sample with the electron beam from the electron gun. An electron beam irradiation area switching device for sequentially switching, an electron beam measurement device for measuring an electron beam transmitted through the sample, and an electron beam transmitted through the sample as the relative amount of the thickness of the sample. An electron microscope, comprising: a display device for displaying an image corresponding to an irradiation area.

11. An electron microscope including an electron gun, a sample stage on which a sample is mounted, a deflector that scans an electron beam from the electron gun toward the sample, and an objective lens. Electron beam scanning area that switches areas sequentially A switching device, a secondary electron measuring device for measuring secondary electrons from the sample, a device for converting to a brightness or color tone corresponding to the amount of the measured secondary electrons, and corresponding to an irradiation area on the sample. Further, an electron microscope comprising: a display device for displaying the converted luminance or color tone.