JPS6177243A - Scanning electron microscope enabling surface analysis - Google Patents

Abstract

PURPOSE:To enable the image for a desired area of the sample having an arbitrary shape to be analyzed with high accuracy by installing both a means for obtaining and storing X and Y address groups with signals which are adjacent to a specified address in a binary signal and a means for scanning electron rays over the sample surface in accordance with the stored X and Y address groups. CONSTITUTION:An operation part 23 is controlled to set a switch 8 to a comparator 19. At the same time, a reference power supply 20 is properly operated to regulate its reference signal level. As the result, a binary signal is generated from the comparator 19 and a binary image free of images of signals of at most a given level is displayed on a cathode-ray tube 10. Then, a desired area of the displayed image is specified by operating a light pen 24. All X and Y addresses for the specified image area are stored and then supplied to electron ray deflectors 4x and 5y through D-A converters 15x and 15y multiplying-factor controllers 16x and 16y respectively. Only a desired area of the sample 4 to be analyzed is scanned and X-rays generated during the scanning are detected by a detector 11 and then analyzed by an analyzer 12.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a scanning electron microscope that can easily and accurately set only the area of a sample to be analyzed.

[Prior art 1] In a scanning electron microscope, a focused electron beam is irradiated onto a sample, the electron beam is scanned two-dimensionally over a desired area, and then secondary electron beams and reflected electrons scattered from the sample are scanned. By detecting this and introducing it as a brightness signal into a cathode ray tube synchronized with the scanning of the electron beam, an image of the surface of the sample is obtained. Such scanning electron microscopes are used not only to observe the morphology of samples, but also to perform qualitative and quantitative analysis of the substances that make up the sample using X-rays, etc. for specific sample parts in the image, especially when observing mineral samples such as metals. 1) Cases often occur where it is desired to have a row <r. Therefore, many of the scanning electron microscopes currently on the market are equipped with an X-ray analyzer, and are capable of performing area analysis of a specific point on a sample or a desired region of the sample.

[Problems to be Solved by the Invention] However, in the conventional area analysis, a desired rectangular portion is provided in the displayed sample image, and analysis is performed on that rectangular portion. Even though it is desired to analyze only a small part of a sample with a specific shape, the peripheral part is also scanned, so unnecessary information from the surrounding area is injected, which poses a problem in terms of analysis accuracy.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a scanning electron microscope capable of carrying out a surface analysis of a sample portion having an arbitrary desired shape with high accuracy, in addition to the conventional analysis method described above.

[Means for Solving the Problem] In order to achieve the above object, the present invention scans a desired region on the specimen two-dimensionally with a focused electron beam, detects the information signal 17 emitted from the specimen, and performs the test. means for obtaining another scanned image; means for performing binarization on a desired level of the discrimination information signal obtained by scanning the electron beam and displaying the binarized image; and means for displaying the binarized image. means for selecting a desired image part in the area and specifying an arbitrary point thereof; means for determining and storing a group of X and Y addresses adjacent to the address of the specified point and where a moon signal exists; The present invention is characterized by a scanning electron microscope equipped with a device that scans an electron beam over a specimen based on a group of Y addresses and analyzes the specimen surface in that region.

[Operation 1 of the Invention] In the present invention, first, a trial scanned image is displayed on a cathode ray tube, and a trial information signal constituting the image is converted into a binary signal using a desired value as a boundary. Next, the signal is introduced into a cathode ray tube to display a binarized image, and a desired sample portion in the binarized image is selected and an arbitrary point thereof is addressed. Next, if there is a signal adjacent to the specified address,
- select the addresses and store the address group.

Then, when the stored address group is rearranged in scanning order and supplied as an electron beam deflection signal, only the selected sample portion is scanned by the electron beam, and only this portion is subjected to X-ray analysis.

"Example] Embodiments of the present invention will be described below based on the drawings.

FIG. 1 is a block diagram of one embodiment of the present invention, and numeral 1 indicates an electron gun that generates and emits an electron beam. The electron beam from the electron gun is narrowly focused by a focusing lens 2 and an objective lens 3, and is irradiated onto a sample 4. There are X and Y deflectors 5X and 5y between the focusing lens 2 and the objective lens 3,
The electron beam is scanned two-dimensionally on the sample by receiving a scanning signal from a power source, which will be described later. After being irradiated with the electron beam, the sample 4 scatters and generates secondary electron beams, foul electron beams, X-rays, etc. Among them, for example, a secondary electron beam is detected by a detector 6, a preamplifier 7, a changeover switch 8,
The signal is supplied as a brightness modulation signal to the grid of a cathode ray tube 10 via an amplifier 9. Further, the X-rays are detected by the detector 11, and the detection output is sent to the X-ray analyzer 12, where wavelength analysis of the characteristic X-rays is performed, and qualitative and constant volume analysis of the sample is performed. Although not shown, the analysis results are supplied to and displayed on a well-known display device or recording device. Instead of this X-ray analyzer, it is also possible to perform a trial analysis using a similar analyzer such as an Auger electron analyzer or an ion analyzer.

13 is a clock pulse generator, and a clock signal from the generator is supplied to a counter 14X for horizontal (Y direction) deflection and counted. Further, the reset 1 signal of the counter is supplied to a deflection counter 14y (vertically in the Y direction), and one pulse is supplied every time one horizontal scan count is completed. Karan 1 of both J Unta
The values are converted into Jz real analog values by D-Δ converters 15x and i5y, and the output signals, that is, X and Y scanning signals, are sent to the electron beam deflector 5x via magnification adjusters i5x and 16V.
, 5y, and scans the electron beam two-dimensionally. Also, a part of the output signal from the D-A converter is sent to an amplifier 17x,
17y to the electron beam deflector 18x, i of the cathode ray tube 10.
sy, and the electron beam that irradiates the sample and the electron beam of the cathode ray tube are scanned synchronously. Therefore, if the scanning signal is supplied to each deflector while the secondary electron signal from the detector 6 is supplied to the grid of the cathode ray tube, a sample image based on the secondary electron signal will be displayed on the screen of the cathode ray tube 10. is played.

A part of the output of the detector 6 is also supplied to a comparator 19, and its signal is compared with a reference signal from a reference power source 20, and the comparison is made only when the signal is at a higher (or lower) level than the reference signal. The detector emits a signal and binarizes the detection multiplier. This binarized signal is appropriately converted and sent to the memory 21. Both counters 14X are stored in the memory.
, 14y are sending X and Y address signals, and the binarized signal is stored at the address specified by both addresses. Furthermore, the signal binarized by one of the comparators is supplied to the other terminal of the selector switch 8, and when the switch is switched to the comparator side, the binarized image is displayed on the cathode ray tube. will be displayed. Reference numeral 22 denotes a control device, which has an operation section 23 and a light pen 24, and the control device controls the memory 2 by control signals from the operation section and the light pen.
1. Supply control signals to the changeover switch 8 and other parts to control them.

The operation of the above drawing apparatus will be explained with reference to FIGS. 2 and 3. FIG. 2 shows the relationship between the sample surface and its electron beam scanning, and FIG. 3 shows an image on a cathode ray tube corresponding to FIG. However, although the sample surface diagram in FIG. 2 is actually much smaller than that in FIG. 3, it is shown in the same size here to improve correspondence between the two ministries. (a> The figure shows the specimen observation mode, and the changeover switch 8 is connected to the detector 6 side by a command from the control device 22 (the state shown in Figure 1). Trials 1 to 4 are two-dimensional When scanned,
The sample image is displayed as is on the cathode ray tube. From this state, the operator controls the operating section 23, switches the switch 8 to the one comparator side, and at the same time appropriately operates the reference power source 20 to adjust the level of the reference signal. As a result, a binarized signal is generated from the comparator, and a binarized image in which images of signals below a certain level are cut out is displayed on the cathode ray tube as shown in FIG. 3(b). The binarized signal is also supplied to the memory 21, and the signal is stored only in the memory area at the address corresponding to the image displayed in FIG. 3(b). While observing this binarized image, the operator operates the light pen 24 to select and designate a desired image portion (sample portion) therein. When the light pen is operated, a mark (→- mark) is generated on the cathode ray tube, and this mark moves with the movement of the light pen and can be erased by specifying a desired image area. In this state, the control device successively selects all addresses adjacent to the specified mark address and in which signals are stored, and stores the address group in another area of the memory.

That is, all the X and Y addresses for the image portion designated by the + mark in FIG. 3(0) are stored. Next, when data other than the address selected above is erased from the memory where the original binarized image is stored, the image area specified with the light pen as shown in Figure 3(d) is only is displayed. When this state is reached, the data of the selected and separately stored address group is rearranged in the order of operation and sent to the electron beam deflector 5x via the DA converters 15X, i5y and the magnification adjusters 16x, 16y.

Supply to 5y. As a result, as shown in FIG. 2(e), only the portion of the sample 4 to be analyzed is scanned, and the X-rays generated at that time are detected by the detector 11 and analyzed by the analyzer 12. In other words, the sample surface analysis of only the part of the sample that the operator has focused on is achieved. Note that it is not always necessary to display the sample portion under analysis as shown in FIG. 3(e).

FIG. 4 shows another embodiment, in which the same reference numerals as in FIG. 1 indicate similar components. In this embodiment, an all-log scanning power supply is used in place of the digital scanning power supply of the embodiment of FIG. 25 is a normal X, Y sawtooth wave oscillator, and the X direction scanning signal from this oscillator is supplied to a magnification adjuster 16x and an amplifier 17x via a switch 26x, and sent to both deflectors 5x and 18X. Further, the Y-direction scanning signal is supplied to the magnification adjuster 16y and the amplifier 17y via the switch 26y, and sent to each of the deflectors 5y and 18y. The sawtooth wave signals in the x and Y directions are A-D, respectively.
Converters 27x, 27yk: Converted into Jζ re-digital signals and supplied to the memory 21 as address signals.

28x and 28y are D-A converters, which sequentially D-A convert the address group of the desired image portion stored in the memory 21, send it to switches 26x and 26y, and supply it to the deflectors 5X and 51V through the switch. By this, Figure 2(e)
It is used to perform sample scanning.

The signal from the detector 6 is sent to the memory 21 via two A-D converters.
and the A-D converter 27X.

The data is stored in the designated area using the signal of 27y as the address.

Further, the signal stored in the memory is converted into an analog value by a D-Δ converter 30 and supplied to the other terminal of the switch 8. Therefore, when the switch 8 is connected to the memory side, an image based on the signals stored in the memory 21 is displayed. In addition to the light pen 24 and the operating section 23, the control device 22 is provided with a level adjuster 31 for binarizing the stored signal, and by operating the level adjuster, the signal is temporarily stored in the memory. The image signal is replaced with a bright and dark binary signal. Therefore, the image on the cathode ray tube after this binarization is completed becomes an image as shown in FIG. 3(b).

The subsequent operations are the same as in Figure 1, but select the desired image part while moving the mark with the light pen, and when you specify the desired part, if there is a binary signal at the address adjacent to that address, the Store a group of addresses in a separate area of memory. After this time, the data stored in the memory is not rewritten by the signal from the detector 6. When the scanning signals from the A-D converters 27X and 27y match the selected address, the stored binary signal is transferred to the D-A
The grid of the cathode ray tube 10 is supplied via a converter 30. As a result, the image shown in FIG. 3(d) is displayed. Next, the control device 22 switches the switches 26x and 26y, and the memory 2
The address BY of the selected image portion stored separately in the D-Δ converter 28x, 2sy, switch 26x, 2 is read out.
6y, magnification adjuster 16X, deflector 5x via 16V,
! Supply to 5y. Figure 3(d) selected as a result of this
Only the sample portion corresponding to the image portion of is scanned as shown in FIG. 2(e). Then, a surface analysis is performed regarding the trial 1'31 portion.

Note that the above is an example of the present invention, and various changes can be made in implementation. For example, although a light pen is used to select the image portion to be analyzed, the present invention is not limited to this, and any other device such as a touch pen or cursor can be used. Further, although a secondary electron image is used to observe the sample image, it goes without saying that a reflected electron image, a transmitted electron image, etc. can also be used. Furthermore, the normal sample image and the binarized image may be displayed on separate cathode ray tubes.

[Effects] With the above configuration, it becomes possible to perform area analysis of the desired sample part, and as there is no contamination of information from areas other than the specified area as in the past, extremely accurate analysis is possible. It becomes possible.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIGS. 2 and 3 are explanatory diagrams of the apparatus shown in FIG. 1, and FIG. 4 is a block diagram showing another embodiment of the present invention. be. 1: Electron gun 3: Objective lens 4: Sample 5X, 5V: Deflector 6: Detector
8: Selector switch 10: Cathode ray tube 11: X
Line detector 12: Analyzer 13: Clock pulse oscillator 14x, 14y: Counter 15x, 15y: D-A converter 16X, 16V: Magnification adjuster

Claims (1)

[Claims] A means for two-dimensionally scanning a desired area on a sample with a focused electron beam, detecting an information signal obtained from the sample at that time and introducing it into a display device to obtain a scanned image of the sample; means for performing binarization at a desired level of the sample information signal and displaying the binarized image;
means for selecting a desired image portion in the binarized image and specifying an arbitrary point thereof; means for determining and storing a group of X and Y addresses adjacent to the address of the specified point and where signals exist; What is claimed is: 1. A scanning electron microscope capable of area analysis, comprising: a device for scanning an electron beam over a sample based on a group of X and Y addresses, and analyzing the area of the sample.