JPH01130458A - Distortion correcting device for scanning electron microscope image - Google Patents

Abstract

PURPOSE:To eliminate influence of deflection distortion by simple constitution and enable accurate observation of scanning image by storing the scanning image once in a memory, reading, and displaying, and meantime converting the address of the scanning image through an address converting means. CONSTITUTION:A ROM 3 accommodate various processing programs or an address converting map for distortion correction, while a RAM 2 accommodate primarily a scanning image obtained by a scanning electron microscope 6 or uses is as an operating region for implementation of various programs. An A/D converter 4 converts video signal (scanning image signal) obtained from a sensor of the scanning electron microscope 6 into digital signals, while an I/O device 5 takes in horizontal synch. signals and vertical synch. signals. When the scanning image is accommodated into the RAM 2, or when read out of it to be displayed on a cathode-ray tube 9, the distortion is corrected by performing address conversion with the address converting map. Thereby accurate scanning image can be displayed on a CRT, screen using simple constitution to serve for observation.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention is directed to a method of distortion of a scanning electron microscope image that can eliminate the influence of electron beam deflection distortion on a scanning electron microscope image and display an accurate scanned image of a sample. This invention relates to a correction device.

[Advanced technology]

FIG. 6 is a diagram showing an outline of the configuration of a signal processing system of a scanning electron microscope, in which 21 is a filament, 22 is a Wehnelt electrode, 23 is an accelerating electrode, 24 is an accelerating power source, 25 is an objective lens, 27 is a converging lens, 28 29 is a deflection coil, 29 is a sample, 30 is a secondary electron detector, 31 is a computer, 32 is a first memory, 33 is a second memory, 34 is a ROM writer, 35 is a scanning signal generation circuit, and 36 is a magnification setting circuit,
37 is an adder circuit, 38 is an amplifier circuit, 39 is a cathode ray tube (C
RT).

In a scanning electron microscope, as shown in FIG. 6, an electron beam is generated by a filament 21, accelerated by an accelerating electrode 23, and then narrowly focused onto a sample 29 by an objective lens 25. Further, the electron beam is deflected by a deflection coil 28 using a scanning signal, and the electron beam irradiation position on the sample 29 is two-dimensionally scanned. A scanning signal generated by a scanning signal generation circuit 35 is amplified and supplied to the deflection coil 28 according to a designated magnification through a magnification setting circuit 36 . The blanking signal from the scanning signal generation circuit 35 is supplied to the amplifier circuit 38 to blank only the CRT. When the sample 29 is irradiated and scanned with the finely focused electron beam in this manner, secondary electrons are generated from the sample 29 and detected by the detector 30. After this detection signal is amplified by the amplifier 38, the cathode ray tube 39
is supplied as a brightness modulation signal to the scanning signal generation circuit 35.
A secondary electron scanned image of the sample is displayed on the tube surface.

In this way, in a scanning electron microscope, an electron beam is narrowly focused onto a sample and scanned two-dimensionally, and the secondary electrons generated as a result of the electron beam irradiation are detected and used to detect the secondary electrons that are generated by the electron beam on the sample. A secondary electron image of the sample is observed by supplying it to a cathode ray tube in synchronization with scanning.

[Problem that the invention seeks to solve]

However, when observing a secondary electron image using a scanning electron microscope with the above configuration, for example, when scanning a rectangular area on a sample indicated by a solid line in FIG. 7 with an electron beam, due to the well-known deflection distortion of the electron beam, In reality, a distorted area as shown by the dotted line is scanned, and there is a problem in that an accurate rectangular area cannot be scanned. Such deflection distortion of a scanned image includes orthogonal distortion and peripheral distortion, of which the orthogonal distortion is fixed regardless of the magnification of both the irradiation system and the CRT. Furthermore, peripheral distortion is fixed in a CRT, but distortion in the irradiation system becomes worse as the magnification is lowered.

Therefore, the applicant of the present invention previously proposed a scanning electron microscope for correcting such distortion (Japanese Patent Application No. Sho 6l-z97987). In this proposal, as shown in FIG.
2, the computer 31 calculates the correction amount, and the adder 37 adds it to the scanning signal. Furthermore, the amount of deviation in orthogonality specific to each device is stored in the second memory 33, and the computer 31 similarly calculates the amount of correction, which is added to the scanning signal by the adder 37.

However, the above proposal corrects distortion by directly manipulating the deflection signal, and cannot perform detailed image correction.

The present invention solves the above-mentioned problems, and the scanning electronic i
! ] The object of the present invention is to provide a microscopic image distortion correction device.

Means for Solving Problem C] To this end, the scanning electron microscope image distortion correction device of the present invention has the following features:
A scanning electron microscope that displays a scanned image of a sample on a cathode ray tube by narrowly converging an electron beam onto the sample and scanning it two-dimensionally, comprising a memory for storing the scanned image of the sample and means for converting the address of the scanned image. , the address of the scanned image is converted through address conversion means while the scanned image is once stored in a memory, read out, and displayed.

[Effect]

In the scanning electron microscope image distortion correction device of the present invention, after a scanned image of a sample is stored in a memory, the scanned image is read out and displayed on a cathode ray tube, and in the process of storing and reading out the scanned image in the memory, address conversion is performed. Since the address of the scanned image is converted through the map, the distortion of the scanned image can be accurately corrected by preparing an address conversion map that also corrects the distortion of the scanning system and display system.

〔Example〕

Examples will be described below with reference to the drawings.

FIG. 1 is a diagram showing an embodiment of a scanning electron microscope image distortion correction device according to the present invention, FIG. 2 is a diagram for explaining the distortion of a scanned image and a memory area for storing raw data, and FIG. is a diagram for explaining an example of distortion correction processing performed when reading memory,
FIG. 4 is a diagram for explaining an example of distortion correction processing performed when storing in memory, and FIG. 5 is a diagram for explaining an example of processing when only orthogonal distortion is corrected.

In Figure 1, 1 is the CPU, 2 is the RAM, and 3 is the ROM.
, 4 is an A/D converter, 5 is an I10 device, 6 is a scanning electron microscope, 7 is a horizontal synchronization signal generation circuit, 8 is a vertical synchronization signal generation circuit, 9 is a CRT, 10 is a video RAM, and 11 is a bus. .

The ROM 3 stores various processing programs and address conversion maps for distortion correction, and the RAM 2 is used to temporarily store scanned images obtained from the scanning electron microscope 6 and as a work area for executing various programs. It is something to do. The A/D converter 4 converts a video signal (scanning image signal) obtained from the detector of the scanning electron microscope 6 into a digital signal, and the I10 device 5 takes in a horizontal synchronization signal and a vertical synchronization signal. It is something.

Next, the operation will be explained. First, an electron beam is scanned by the scanning electron microscope 6 in synchronization with the horizontal synchronization signal and vertical synchronization signal generated by the horizontal synchronization signal generation circuit 7 and the vertical synchronization signal generation circuit 8, and secondary electrons emitted from the sample are detected. Then, the video signal is converted into a digital signal by the A7Dgi converter 4 and stored in the RAM 2. The memory address at this time is generated based on the horizontal synchronization signal and vertical synchronization signal taken in through the I10 device 5. Once this scanned image is stored in RAM2, this RAM2 is then sequentially accessed to read out the scanned image and store it in the video RAM.
By writing to l0, the scanned image is displayed on the CRT 9. The present invention corrects distortion by converting addresses using an address conversion map when storing such a scanned image in the RAM 2 or reading it from the RAM 2 and displaying it on the CRT 9.

Distortion usually includes peripheral distortion and orthogonal distortion, as shown in FIG. As shown in FIG. 2, raw data that is distorted with respect to the rectangular display data range has protruding areas, especially in the partitions.

Therefore, in order to perform the distortion correction process after once storing the raw data in the RAM 2, it is necessary to make the memory area for storing the raw data larger than the rectangular display data range (dotted line). Then, an address conversion map as shown in FIG. 3 ta+ is prepared, and when raw data is read from the RAM 2 and displayed on the CRTIO, the read line is address converted according to the distortion and image data is output.

The address conversion map is the distortion H2 shown in the same figure (bl).
(2) For certain raw data, memory addresses corresponding to each readout line on the CRT display screen are stored. Therefore, when reading the display data of the first line, A1. A
Z,...,B1.・・・・・・、C、、・・・
The raw data of the same figure (bl) stored in the memory address of . . . may be read out and output as image data for display.

In addition, when performing distortion correction processing when storing raw data in the RAM 2, when reading the raw data, set the memory address where it is stored at 3.-43 shown in Figure 4 (al).
．． ', 3. ja,' according to the distortion. For example, the microscope scanning position (E○S) and the CRT scanning position (CR
T) is shifted as shown in the same figure (bl),
The distortion is corrected by converting (x, y)→(X-X+,)'Y+) so that the image data at the microscope scanning position matches the memory address on the CRT display. As a result, the data is
Stored in a rectangular display data range.

Generally, peripheral distortion appears prominently at low magnifications, but orthogonal distortion appears regardless of the magnification, so correction of orthogonal distortion is absolutely necessary. Therefore, if peripheral distortion is ignored, the configuration for distortion correction can be implemented quite easily.

For example, if only the orthogonal distortion as shown in Fig.
2, the access clock is shifted for each line as shown in FC+ in the same figure with respect to the display line shown in the same figure (bl).This distortion data should be stored in advance. is the ROM 3. Since the horizontal synchronization signal and the memory address can be made to correspond to each other by a clock, the corrected image data as shown in FIG.
By displaying the image on the screen, a distortion-corrected scanned image of secondary electrons can be observed. If correction is to be made when displaying on the CRTIO, the access start may be shifted for each line and output according to the diagram (C1).

〔Effect of the invention〕

As is clear from the above description, according to the present invention, when an address conversion map is prepared and the image data of a scanned image is stored in a memory, or read out from the memory and displayed, the address conversion map is used to convert the address. Since the conversion is performed, an accurate scanned image can be displayed and observed on a CRT screen with a simple configuration.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing an embodiment of a scanning electron microscope image distortion correction device according to the present invention, FIG. 2 is a diagram for explaining the distortion of a scanned image and a memory area for storing raw data, and FIG. is a diagram for explaining an example of distortion correction processing performed when reading memory,
Fig. 4 is a diagram for explaining an example of distortion correction processing performed when storing in memory, Fig. 5 is a diagram for explaining an example of processing when only orthogonal distortion is corrected, and Fig. 6 is a diagram for explaining an example of processing for correcting only orthogonal distortion. FIG. 7 is a diagram showing an outline of the configuration of the signal processing system, and is a diagram showing an example of deflection distortion of an electron beam. ■...CPU, 2...RAM, 3...ROM, 4
... A/D converter, 5... Bow 10 device, 6... Scanning electron microscope, 7... Horizontal synchronization signal generation circuit, 8...
Vertical synchronization signal generation circuit, 9...CRT, 10...Video RAM, 11...Bagen. Applicant JEOL Technics Co., Ltd. Agent Patent Attorney Ryukichi Abe (3 others) Figure 1 Figure 2 Figure 3 (n) Figure 5 (α) Eyes, 5tcrt Figure 6 Figure 7 figure

Claims (1)

[Claims] (1) In a scanning electron microscope that displays a scanned image of a sample on a cathode ray tube by narrowly converging an electron beam onto the sample and scanning it two-dimensionally, a memory that stores the scanned image of the sample;
and an address conversion means for a scanned image, and converts the address of the scanned image through the address conversion means while the scanned image is once stored in a memory, read out, and displayed.