JP2003203594A - Charged corpuscular beam device and sample image observing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To display a high-quality image on a remote control terminal arranged in a distant place. <P>SOLUTION: This charged corpuscular beam device has an image encoding means for compressing an image, and an image decoding means for decoding the image, and optimizes an encoding method and a decoding method according to a scanning speed and a scanning range of a charged corpuscular beam. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a charged particle beam device such as a scanning electron microscope, and more particularly to a charged particle beam device capable of displaying a high quality sample image on a remote control terminal installed at a remote place, And a method for observing a sample image by remotely controlling a charged particle beam device.

[0002]

2. Description of the Related Art A scanning electron microscope is a device that displays an image using secondary electrons and other signals generated from the sample by two-dimensionally scanning the sample by narrowing down the electron beam emitted from the electron source. This is a device for observing the fine structure of. recent years,
With the progress of miniaturization of semiconductor processes, it has become common to use a scanning electron microscope for quality control of semiconductors.
Scanning electron microscopes used for such purposes are often installed in a room called a clean room, which is equipped with equipment for minimizing dust. In order to maintain the cleanliness of the clean room, it is desirable to reduce the number of people entering the room, which is the source of dust. Therefore, there is a demand to remotely operate the scanning electron microscope installed in the clean room from the outside of the clean room.

In addition, a person different from the person who operates the scanning electron microscope requests the acquisition of an image, such as a device designer evaluating a photograph taken by a scanning electron microscope dedicated operator. May be evaluated. In that case, the operator tries to acquire an image of the sample position or condition instructed by the client, but the acquired image may be different from that requested by the client. Therefore, there is a demand for the client who is located in a remote place to confirm the sample position and conditions that the operator is trying to capture.
Conventionally, such a demand has been met by providing a dedicated cable for transmitting a video signal such as an NTSC signal to a display of a remote control terminal installed at a remote place.

On the other hand, a videophone and a videoconference system in which a moving image signal from a TV camera or the like is digitally compressed and transmitted using a digital line of about 64 [kilobits / second] have become widespread. Also, in recent years, it has become possible to transmit moving images on the Internet.
The devices connected to these public lines have standardized compression methods and screen formats for mutual communication.
One of the image transmission devices using such a standardization method is the "image transmission device" disclosed in Japanese Patent Laid-Open No. 302192/1990.
There is.

[0005]

When a cable for a video signal is installed from the scanning electron microscope to the display of a remote control terminal, there is a problem that when the cable becomes long, the amplitude and band of the signal are attenuated and the image quality is deteriorated. there were. It is possible to take countermeasures by installing a cable such as an optical fiber that has low attenuation, but if the distance is long, the facility cost will be high. Also, when transmitting with a general image transmission device such as a videophone or a video conference using a network or a digital telephone line, there is no limitation on the distance from the scanning electron microscope to the remote control terminal, but the transmission line communication There was a problem that high quality images could not be transmitted due to the limited amount. An object of the present invention is to provide a charged particle beam apparatus capable of displaying a high quality image on a remote control terminal installed at a remote place without installing expensive equipment.

[0006]

The above-mentioned object is to control a charged particle beam apparatus provided with an image encoding means for highly efficiently encoding image data and a transmission interface for transmitting the generated compressed image information to a transmission line. It is composed of a console and a remote control terminal equipped with an image decoding means for decoding compressed image information received from a transmission line to restore image data, and the image coding means includes an electron beam scanning speed, a scanning range, and an image. This is achieved by selecting an optimum method from different image coding methods according to the display method of (1) and performing high-efficiency coding. An image encoding means for compressing an image includes a subtracter, an orthogonal transformer,
When it is composed of a quantizer, a variable length encoder, an inverse quantizer, an inverse orthogonal transformer, and a frame memory, different image encoding schemes can be realized by changing the combination of each component. Further, when the image decoding means for restoring an image is composed of a variable length decoder, an inverse quantizer, an inverse orthogonal transformer, and a frame memory, a different decoding method is realized by combining the respective constituent elements. be able to.

That is, the charged particle beam apparatus according to the present invention comprises a charged particle source, a means for two-dimensionally scanning a charged particle beam emitted from the charged particle source on a sample, and a sample by irradiation with the charged particle beam. Detecting means for detecting a sample signal generated from the image sensor, an image memory for storing image data based on the output of the detecting means, an image data compressing means for compressing the image data stored in the image memory, and an image data compressing means for compressing the image data. In a charged particle beam device having a transmission interface for transmitting the compressed image data thus compressed to a transmission line, the image data compression means encodes the image data by a coding method having a high compression degree but a low image decompression degree. No. 1 image coding means, second image coding means for coding image data by a coding method having a low compression degree but a high image decompression degree, and a first image Characterized in that it comprises selecting means for selecting whether to use the second image encoding means or used Goka means.

It should be noted that the comparison of the degree of compression "high" or "low" is relative here, and the first image coding means is relatively relative to the second image coding means. An encoding method with a high degree of compression is used. Similarly, the level of the image restoration degree is also relative, and the image restoration degree of the first image coding means is relatively lower than the image restoration degree of the second image coding means. The selection means is the scanning speed of the charged particle beam,
The first image encoding means or the second image encoding means can be selected according to the scanning range of the charged particle beam scanning the sample or the image display system.

The image data compression means is a frame memory for storing image data for one frame, a means for reading out one block of image data from the image memory, and the image data and frame read out for each corresponding pixel in one block. A subtractor for outputting the difference data of the image data in the memory,
Orthogonal transformer that outputs the image data with the spatial resolution compressed by orthogonally transforming the difference data, the quantizer that divides the image data output by the orthogonal transformer using the quantization table, and the output from the quantizer The inverse quantizer that multiplies the generated image data by using the quantization table, the inverse orthogonal transformer that inversely orthogonally transforms the output of the inverse quantizer to generate reproduction difference data, and the output of the quantizer Selecting means for selecting whether to output the output of the inverse orthogonal transformer to the second output terminal or the output of the subtractor to the first and second output terminals, A variable-length encoder for converting fixed-length code data output from the first output terminal of the means into variable-length code data using the variable-length code table and outputting the variable-length code data to the transmission interface, and a second output terminal of the selecting means. The data output from A frame memory and the corresponding adder for adding the image data, the adder in the adding charged particle beam apparatus characterized in that it comprises a means for recording the corresponding pixel position of the frame memory the image data.

The charged particle beam apparatus of the present invention decodes compressed image data encoded by a transmission interface for receiving compressed image data from a transmission line and an encoding method having a high degree of compression but a low degree of image restoration. And a second image decoding unit that restores image data by decoding compressed image data that is encoded by an encoding method that has a low degree of compression but a high degree of image restoration. It is possible to further include a remote control terminal having an encoding unit and a selecting unit for selecting whether to use the first image decoding unit or the second image decoding unit.

The charged particle beam apparatus of the present invention also includes a transmission interface for receiving transmission data from a transmission line, and a variable length for converting the received variable length code data into fixed length code data using a variable length code table. Decoder, dequantizer that multiplies the fixed length coded data output from the variable length decoder using the quantization table, and inverse orthogonal transform the output of the dequantizer to reproduce difference data An inverse orthogonal transformer to be generated, a frame memory for storing one frame of image data, a selection means for selectively outputting the output of the variable length decoder or the output of the inverse orthogonal transformer, and the output from the selection means. And a means for recording the image data added by the adder at the corresponding pixel position in the frame memory. That.

The sample image observing method according to the present invention is a method of observing a sample image by remotely operating the charged particle beam device while observing the sample image transmitted from the charged particle beam device via a transmission line, Acquiring a sample image by TV scanning, encoding the acquired image data by an encoding method with a high compression degree but a low image restoration degree, and transmitting it, and a sample image obtained by decoding the transmitted encoded data The step of searching the observation field of view by the following, acquiring the sample image by reduce scan, encoding the acquired image data by the encoding method with low compression degree but high image decompression degree, and transmitting, the transmitted encoded data The step of performing focus adjustment by the sample image obtained by decoding the sample image and the sample image obtained by the slow scan, and the obtained image data has a low degree of compression. Characterized in that it comprises a step of recording a step of transmitting encoded by the image restitution high coding method, a sample image obtained by decoding the transmitted coded data.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below with reference to the drawings. Here, a scanning electron microscope will be described as an example. Further, in the following drawings, the same functional parts are designated by the same reference numerals, and duplicated description will be omitted.

FIG. 1 is a diagram showing a configuration example of a scanning electron microscope according to the present invention. This scanning electron microscope includes a scanning electron microscope main body 1, a control console 11, and a remote control terminal 2.
1, a control console 11 and a remote control terminal 2
1 are connected by a transmission line 19. The scanning electron microscope main body 1 is configured to include an electron source 2, a diaphragm 4, a deflection coil 5, an electron lens 6, a secondary electron detector 7, a sample stage 9, and the like. A control console 11 includes a deflection control circuit 13, an image. Memory 14, display device 15, operation panel 16, image coding means 17, transmission interface 18, control computer 1
Composed of two.

The electron beam 3 emitted from the electron source 2 is narrowed down by the diaphragm 4 and scan-deflected by the deflection coil 5. Deflection coil 5
Is the two-dimensional scanning signal 10 generated by the deflection control circuit 13.
2 is supplied. The electron lens 6 narrows the electron beam 3 so that the surface of the sample 8 mounted on the sample table 9 is focused.
When the sample 8 is irradiated with the electron beam 3, secondary electrons 10 are generated depending on the shape and material of the sample. The secondary electron detector 7 is
The generated secondary electrons 10 are detected, and a secondary electron detection signal 104 obtained by amplifying the signal is output to the image memory 14.

The image memory 14, as shown in FIG.
/ D converter 27, memory 28, address control circuit 29,
And a D / A converter 30. Analog detection signal 10 detected and amplified by the secondary electron detector 7.
4 is converted into digital data 111 by the A / D converter 27 and stored in the memory 28. Address control circuit 2
Reference numeral 9 generates an address 112 synchronized with the synchronization signal 103 of the scanning signal of the electron beam 3 and forms image data in the memory 28. Further, the address control circuit 29 generates an address signal 112 synchronized with the synchronizing signal of the video signal and reads the image data 113 from the memory 28. The D / A converter 30 converts the digital image data 113 into the analog video signal 105, and the display 15 displays the video signal 10.
The secondary electron image according to 5 is displayed.

The image coding means 17 compresses the image data stored in the image memory 14, and the transmission interface 18 sends the compressed image information to the transmission line 19.
The transmission line 19 is a general digital telephone line or network. Here, the transmission rate is 64 [Kbit /
Second] will be described when a digital telephone line of [second] is used as the transmission path.

The image data stored in the image memory 14 is updated by scanning the electron beam 3, but there are several types of scanning speed, scanning range, and display method of the electron beam of the scanning electron microscope. FIG. 3 is a diagram showing the scanning speed of the electron beam, the scanning range, and the update state of the image data in the image memory 14 according to the image display method. The types of electron beam scanning speed include TV scan and slow scan, the types of electron beam scanning range include standard mode and reduce mode, and the types of image display method such as dual mag mode and multi-screen mode. There is.

Television scanning at a scanning speed is 33 [millisecond], which is a frame rate equivalent to that of an NTSC video signal.
In the scanning for updating the image of 1 [frame], the quality of the secondary electron image obtained is not high, but the response is good, and it is used when searching for the observation position. Slow scan
This is scanning in which the scanning time for obtaining image data for one line is synchronized with the commercial power supply frequency. Since the irradiation time of the electron beam 3 for obtaining the image data of one pixel is longer than that in the television scan, the signal amount of the secondary electrons 10 is increased and a clear image can be obtained. With a commercial power frequency of 50 [Hz],
In the case of a slow scan of 20 [milliseconds], in which the scanning time for one line is equal to one cycle of the power supply frequency, if the image data is 640 [pixels] horizontally and 480 [pixels] vertically, the frame update time is 9.6 [seconds]. ] Becomes.

As a type of electron beam scanning range, there is a mode called a reduce mode in which only a part of the standard mode scanning range (480 × 640 pixels) is scanned. Although the slow scan in the reduce mode has a small display range, a clear image can be obtained and the frame speed can be increased as compared with the standard slow scan, so that the slow scan is used for focus adjustment. If the standard slow scan frame update time is 9.6 [seconds], the frame update time is about 0.6 [seconds] by limiting the number of pixels to 160 [pixels] horizontally and 120 [pixels] vertically. ] Becomes.

The types of image display methods include a method called dual mag mode in which images of different magnifications are simultaneously displayed on a screen divided into two, and a screen called multi-screen mode is divided into four areas or the like to divide a plurality of images. There is a method to display. When displaying such a plurality of images on a divided screen, it is sufficient to process only the data in the image memory of the part to be updated.

As described above, the image quality of image data varies depending on the scanning speed of the electron beam 3, the scanning range, and the image display system.
Frame rate and data amount are different. Therefore, by controlling the encoding method of the image encoding means 17 according to the scanning speed and the scanning range and optimizing the image information to be transmitted to the transmission path,
A high-quality scanning electron microscope image can be displayed on the remote control terminal 21.

FIG. 4 is a diagram showing a configuration example of the image encoding means 17. The image encoding means 17 of this example includes an image memory interface 31, a subtractor 32, an orthogonal transformer 33,
The quantizer 34, the switch 35, the variable length encoder 36, the inverse quantizer 37, the inverse orthogonal transformer 38, the adder 40, and the frame memory 41 are provided. If the size of one frame of an image to be transmitted is 640 [pixels] horizontally, 480 [pixels] vertically, and 8 [bits] of gradation, the size of image data of one frame is about 2.5 [megabits]. In order to transmit the image data in 33 [millisecond] which is the frame update time of the television scan without compression, a transmission rate of about 74 [megabit / sec] is required. However, since the transmission speed of the transmission line is 64 [kilobits / second], it is necessary to compress the image data to about 1/1000. On the other hand, in the image obtained by the television scan, the amount of secondary electrons 10 generated is small because the time for which the sample 8 is irradiated with the electron beam 3 is short.
It becomes a bad S / N image. Therefore, a filter is often applied to average the image data obtained by scanning one frame with the image data of the previous frame. in this case,
The updated image data has a high correlation with the image data before the update. Therefore, in order to highly efficiently encode the image data of the TV scan, an encoding method having a high degree of compression, which is also used in a videophone, is suitable.

FIGS. 5, 6 and 7 are diagrams showing the processing of the image coding means 17 at the time of television scanning. The image memory interface 31 of the image encoding means 17 reads out from the image memory 14 one block of image data 106 composed of 64 [pixels] horizontal 8 [pixels] and vertical 8 [pixels]. To handle color information in a videophone or the like, processing is performed by a macro block that is a combination of a luminance signal block and a color difference signal block. However, since there is no color information in a scanning electron microscope, one block is the processing unit. The subtractor 32 obtains the difference data 122 between the image data 121 and the prediction data 127 for each corresponding pixel in the block. Prediction data 1
Reference numeral 27 denotes image data stored in the frame memory 41, which is generated by decoding the image information of the frame coded and transmitted immediately before, in the same manner as the receiving side. Orthogonal transformer 3
3 produces | generates the image information 123 which compressed spatial resolution using orthogonal transformation, such as DCT (DISCRETE COSINE TRANSFORM). Equation 1 shows an arithmetic expression of DCT. Where f (i, j)
Is image data of coordinates (i, j) in one block (8 pixels × 8 pixels). The DCT coefficient of one block (8 × 8) is obtained from the image data of one block, and F (u, v) means the DCT coefficient of the coordinate (u, v). According to Equation 1, the DCT coefficient F (u, v) at each coordinate (u, v) is obtained from the image data f (i, j) at each coordinate (i, j).

[0025]

[Equation 1]

In the image information 123, low frequency components are gathered in the upper left part, and the whole image can be restored to some extent only by these components. The quantizer 34 divides the image information 123 according to the quantization table 128 to generate image information 124 having a higher degree of compression. Quantized image information 12
4 passes through the switch 35 and is input to the variable length encoder 36. The variable length encoder 36 reads the coefficients in a zigzag manner from the upper left portion where the low frequency components of the image information 124 are collected,
This is converted by a variable length code table 129 such as Huffman coding for converting data having a high appearance probability into a short code to generate variable length code data 107 with a higher degree of compression. In this example, 512 [bits] (8 [pixels] × 8 [pixels] × 8 [bits]) image data is highly compressed to about 1/17, which is 30 [bits]. In the case of an image of 30 [frames] with 4800 blocks in one screen and the appearance rate of effective blocks in which the coefficient is generated is 1/80, the transmission rate is approximately 54 [k bits / sec] (30 [bits) x 4800
[Block] x 30 [bits] ÷ 80) and 64 [k
[Bit / sec] transmission line.

Image information quantized by the quantizer 34
Is inversely quantized by the inverse quantizer 37 according to the quantization table 128. Further, the inverse orthogonal transformer 38 performs inverse orthogonal transformation (inverse DCT) according to Expression 2, and the reproduction difference data 125
To generate. Equation 2 shows an arithmetic expression of the inverse DCT. Image data f (i, j) of coordinates (i, j) in one block (8 pixels x 8 pixels)
j) is obtained from the DCT coefficient F (u, v) according to the equation 2.

[0028]

[Equation 2]

The switch 39 selects the signal on the side a, and the adder 40 selects the reproduction difference data 125 and the previous prediction data 127.
Is added to generate reproduction data 126. Playback data 1
26 is equal to the restored image data on the decoding side, and is used in the frame memory 4 for use in the encoding process of the next frame.
Store in 1. In this way, when the scanning speed is TV scanning, difference calculation between frames, orthogonal transformation, quantization,
An encoding method using variable-length encoding is applied to transmit image information with a high degree of compression corresponding to the transmission speed of the transmission path.

When the scanning speed of the electron beam 3 is slow scan, the irradiation time of the electron beam 3 to the sample 8 becomes long, so that the amount of secondary electrons 10 generated is large and the S / N of the obtained signal is large.
Will get better. Therefore, it is not necessary to apply a filter between frames. Further, since the update time of the image data becomes long, it is not necessary to increase the compression degree of the image information transmitted to the transmission path. Approximately 25 to transmit the image data of about 2.5 [megabits], which is the same as TV scan, without compressing it at the frame update time of slow scan 9.6 [seconds].
The transmission rate may be 6 [kilobits / second]. If the transmission rate of the transmission path is 64 [kilobits / second], the image data may be compressed to 1/4. Since the interframe coding method used in the case of television scanning processes in blocks of horizontal 8 [pixels] and vertical 8 [pixels], block distortion occurs in which the joints of blocks are discontinuous. easy. Further, due to a calculation error of DCT or quantization, the original image cannot be faithfully restored even if the compression degree is lowered,
The image becomes unclear. Therefore, in the case of slow scan, an encoding method that can faithfully restore the original image is used.

FIG. 8 and FIG. 9 are diagrams showing the processing performed by the image coding means 17 when the scanning speed of the electron beam 3 is slow scan. Here, the image data of 1 [pixel] is 1
[Pixel] An encoding method will be described in which it is possible to restore a complete original image on the receiving side although the compression degree is low by utilizing the fact that the probability of abrupt change from the previous image data is low. The image memory interface 31 of the image encoding means 17 is
Image data 106 from the image memory 14 in units of 1 [pixel]
Read out. The subtractor 32 reads out the image data 121
And the difference data 122 of the prediction data 127 one pixel before
Ask for. The prediction data 127 is generated by decoding the image information stored in the frame memory 41 up to immediately before 1 [pixel] and transmitted in the same manner as the receiving side.
The switches 35 and 39 select the signal on the b side and apply the difference data 122 to the variable length encoder 36 and the adder 40. The adder 40 adds the difference data 122 and the previous prediction data 127 to obtain the reproduction data 126. The reproduction data 126 is equal to the restored image data on the decoding side, and is used for the encoding process of the next pixel in the frame memory 41.
To store. The variable length encoder 36 uses the difference data 122.
To the variable length code 107.

As described above, when the scanning speed is slow scan, the difference calculation between pixels and the variable length coding
An encoding method capable of restoring a complete original image is applied to transmit image information. In this example, the image data of 512 [bits] (8 [pixels] × 8 [pixels] × 8 [bits]) is compressed to about 1/4, which is 120 [bits]. When the number of blocks in one screen is 4800 and the frame update time is 9.6 [seconds], the transmission rate is about 60 [k bits / second] (120 [bits] × 4800 [blocks] ÷
9.6 [seconds]), and transmission can be performed on a transmission path of 64 [k bits / second].

As shown in FIG. 10, the transmission interface 18 sets the frame start code 140, the coding code 141 indicating the type of coding method, and the kind of quantization table in the variable length code data 107 of the image according to the protocol of the transmission path. Quantization code 142 shown and block start position code 143 showing the position of the block are added and transmitted.

As shown in FIG. 1, the remote control terminal 21 is
A transmission interface 22, an image decoding means 23, a display 24, an operation panel 25, and a control computer 26 for controlling each component are provided. The transmission interface 22 receives the transmission data 108 from the transmission line 19, the image decoding means 23 restores the image data to generate a video signal,
The image is displayed on the display unit 24. The image decoding means 23,
As shown in FIG. 11, a variable length decoder 51, an inverse quantizer 52, an inverse orthogonal transformer 53, a switch 54, a frame memory 56, and a D / A converter 57 are provided.

When the transmission interface 22 detects the interframe coding by the television scan from the coding code at the head of the frame, the switch 54 of the decoding means 23 selects the signal on the side a. 12 and 13 are diagrams showing interframe decoding by television scanning. The variable length decoder 51 converts the transmitted variable length code 109 into a fixed length code 131 using the variable length code table 129. The inverse quantizer 52 performs inverse quantization using the quantization table 128. The inverse orthogonal transformer 53 performs inverse orthogonal transformation (inverse DCT) to generate reproduction difference data 133. This reproduction difference data 1
The reproduction data 135 of the previous frame is added to 33 by the adder 55 to obtain new reproduction data 134. D / A converter 5
7 converts the digital reproduction data 134 into an analog video signal, and the display 24 displays the reproduced image.

When the transmission interface 22 detects the pixel-by-pixel coding by the slow scan from the control information at the head of the frame, the switch 54 of the decoding means 23 selects the signal on the b side. FIG. 14 is a diagram showing decoding by slow scan. The variable length decoder 51 converts the transmitted variable length code 109 into a fixed length code 131 using the variable length code table 129. This fixed length code 13
The reproduction data 135 of the previous pixel is added to 1 by the adder 55,
Obtain new playback data 134. The D / A converter 57 converts the digital reproduction data 134 into an analog video signal, and the display 24 displays the reproduced image.

FIG. 15 shows the processing performed by the encoding means 17 when the scanning range is in the reduce mode. When the scanning range of the electron beam 3 is in the reduce mode, the address at which the image data of the image memory 14 is updated is known from the scanning range of the electron beam 3. Therefore, it suffices to read out the image data of only the updated portion and perform image coding. Image coding means 17
The image memory interface 31 reads the image data of the image memory 14 according to the scanning range and performs the image coding as described above. In the reduce mode, the amount of data is smaller than in the case of transmitting the entire data of the standard screen size. Therefore, the quantization amount of the quantization table 128 is reduced in order to improve the image quality.

FIG. 16 shows the processing performed by the encoding means 17 when the display system is the dual mag mode. The screen that is updated in dual mag mode is only one divided into the left and right, and the amount of data is smaller than when sending the entire data of the standard screen size.Therefore, the quantization table is used to improve the image quality. The quantization amount of 128 is reduced.

FIG. 17 shows the processing performed by the encoding means 17 when the display system is the multi-screen mode. The screen that is updated in the multi-screen mode is only one screen divided into four, and the amount of data is smaller than when transmitting the entire data of the standard screen size. The quantization amount of the conversion table 128 is reduced.

FIG. 18 shows a flowchart of a general operation of the scanning electron microscope. First, the sample is inserted into the sample chamber (S11), and an electron beam is irradiated by TV scanning (S1).
2), obtain a sample image. The observation field of view of the sample is searched for by using a TV scan whose screen is updated quickly (S13).
At this time, the image encoding means 17 of the control console 11
(See FIG. 4) selects the a-side signal by the switches 35 and 39, and the image decoding means 23 (see FIG. 11) of the remote control terminal 21 selects the a-side signal by the switch 54.

Once the observation field of view is determined, the reduce mode with a narrow range but good image quality is switched (S14), and adjustments such as focusing and electron beam astigmatism correction are performed (S1).
5). At this time, the image coding means 17 of the control console 11 selects the b side signal by the switches 35 and 39, and the image decoding means 23 of the remote control terminal 21 selects the b side signal by the switch 54.

When the adjustment is completed, the mode is switched to the slow scan in which the image quality of the entire surface is good (S16) and the image is taken (S1)
7). At this time, the image coding means 17 of the control console 11 selects the b side signal by the switches 35 and 39, and the image decoding means 23 of the remote control terminal 21 selects the b side signal by the switch 54.

After that, when observing another visual field, the procedure is returned to step 12 and the operation is repeated. When observing is finished, the procedure proceeds to step 18, and the sample is taken out from the sample chamber. In accordance with the operation of switching the scanning speed or the scanning range, the image coding means 17 switches the coding system to perform coding. The switching of the encoding method according to the switching of the scanning speed and the scanning range is performed by the control computer 12 detecting the operation on the operation panel 16 to detect the deflection control circuit 13 and the image memory 1.
This can be automatically performed by controlling the image coding means 17 at the same time as controlling the image coding means 4.

The image coding means 17 and the image decoding means 23 can be realized by an internal circuit of the LSI, and can be easily miniaturized and reduced in price. It can also be realized by software of the control computer. Although the transmission of the image data has been described in detail here, the remote operation can be performed by transmitting the operation information of the operation panel 25 of the remote operation terminal 21 to the control console 11 via the transmission path 19.

Although the scanning electron microscope for scanning the electron beam on the sample to acquire the secondary electron image has been described above, another charged particle beam device for scanning the charged particle beam on the sample to acquire the sample image. For example, a focused ion beam device that scans an ion beam to obtain an image, a device that scans an electron beam to obtain a backscattered electron image, a device that scans an electron beam or an ion beam to obtain an X-ray image, etc. The present invention can be similarly applied.

[0046]

As described above, according to the present invention, it is possible to display a high-quality scanning electron microscope image on a remote control terminal installed at a remote place without installing expensive equipment.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a scanning electron microscope.

FIG. 2 is a configuration example of an image memory.

FIG. 3 is a diagram showing an updated state of an image memory.

FIG. 4 is a configuration example of image encoding means.

FIG. 5 is a first processing example of the image decoding means.

FIG. 6 is a processing example 2 of the image decoding means.

FIG. 7 is a processing example 3 of the image decoding means.

FIG. 8 is a processing example 4 of the image decoding means.

FIG. 9 is a processing example 5 of the image decoding means.

FIG. 10 shows an example of transmission data.

FIG. 11 is a configuration example of image decoding means.

FIG. 12 is a first processing example of the image decoding means.

FIG. 13 is a second processing example of the image decoding means.

FIG. 14 is a processing example 3 of the image decoding means.

FIG. 15 is a processing example of the image encoding unit in the reduce mode.

FIG. 16 is a processing example of the image encoding means in the dual mag mode.

FIG. 17 is a processing example of the image encoding means in the multi-screen mode.

FIG. 18 is a flowchart of an operation procedure example.

[Explanation of symbols]

1: scanning electron microscope main body, 2: electron source, 3: electron beam,
4: stop, 5: deflection coil, 6: electron lens, 7: secondary electron detector, 8: sample, 9: sample stage, 10: secondary electron,
11: control console, 12: control computer, 1
3: deflection control circuit, 14: image memory, 15: display,
16: operation panel, 17: image encoding means, 18: transmission interface, 19: transmission line, 21: remote control terminal,
22: Transmission interface, 23: Image decoding means, 2
4: Display device, 25: Operation panel, 26: Control computer, 27: A / D converter, 28: Memory, 29: Address control circuit, 30: D / A converter, 31: Image memory interface, 32: Subtraction Vessel, 33: orthogonal transformer, 3
4: quantizer, 35: switch, 36: variable length encoder, 37: inverse quantizer, 38: inverse orthogonal transformer, 39: switch, 40: adder, 41: frame memory, 51:
Variable length decoder, 52: inverse quantizer, 53: inverse orthogonal transformer, 54: switch, 55: adder, 56: frame memory, 57: D / A converter, 101: control bus, 10
2: Two-dimensional deflection signal, 103: Scan signal synchronization signal, 1
04: secondary electron detection signal, 105: video signal, 10
6: image data, 107: variable-length code data, 108:
Transmission data, 109: variable length code data, 110: control bus, 111: digital data of secondary electron signal, 11
2: memory address signal, 113: image data, 12
1: image data, 122: difference data, 123: image information after orthogonal transformation, 124: image information after quantization, 12
5: reproduction difference data, 126: reproduction data, 127: prediction data, 128: quantization table, 129: variable length code table, 131: fixed length code, 132: image information after dequantization, 133: inverse orthogonal transform. Later image information, 13
4: reproduction data, 135: reproduction data, 140: frame start code, 141: coding method code, 142: quantization table code, 143: block start position code.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Daisuke Kanazawa             882 Ichige, Ichima, Hitachinaka City, Ibaraki Prefecture             Ceremony company Hitachi High Technologies Design and manufacturing             Headquarters Naka Operations F-term (reference) 4M106 AA01 CA38 DB05 DB30

Claims (8)

[Claims] 1. A charged particle source, means for two-dimensionally scanning a charged particle beam emitted from the charged particle source on a sample by finely narrowing it, and detecting a sample signal generated from the sample by irradiation of the charged particle beam. Detecting means, an image memory for storing image data based on the output of the detecting means, an image data compressing means for compressing the image data stored in the image memory, and a compressed image compressed by the image data compressing means. In a charged particle beam device having a transmission interface for transmitting data to a transmission line, the image data compression means encodes image data by an encoding method having a high degree of compression but a low degree of image restoration.
Image coding means, a second image coding means for coding image data by a coding method having a low degree of compression but a high degree of image restoration, and the first image coding means or the second image coding means. A charged particle beam device comprising: a selection unit that selects whether to use an image encoding unit. 2. The charged particle beam apparatus according to claim 1, wherein the selection unit selects the first image coding unit or the second image coding unit according to a scanning speed of the charged particle beam. A charged particle beam device characterized by the above. 3. The charged particle beam apparatus according to claim 1, wherein the selection unit is the first image encoding unit or the second image code according to a scanning range of the charged particle beam scanning a sample. A charged particle beam device, characterized in that a charging means is selected. 4. The charged particle beam apparatus according to claim 1, wherein the selecting means selects the first image coding means or the second image coding means in accordance with an image display system. Charged particle beam device. 5. The charged particle beam apparatus according to claim 1, wherein the image data compression unit includes a frame memory that stores image data for one frame, and a unit that reads out one block of image data from the image memory. A subtracter that outputs difference data between the read image data and the image data in the frame memory for each corresponding pixel in the one block, and outputs image data in which the difference data is orthogonally transformed and the spatial resolution is compressed. An orthogonal transformer, a quantizer that divides image data output from the orthogonal transformer using a quantization table, and a multiplication process that uses the quantization table to multiply the image data output from the quantizer. An inverse quantizer, an inverse orthogonal transformer that inversely orthogonally transforms the output of the inverse quantizer to generate reproduced difference data, and an output of the quantizer as a first output Selecting means for selecting whether to output the output of the inverse orthogonal transformer to the second output terminal or the output of the subtractor to the first and second output terminals, A variable-length encoder that converts fixed-length code data output from the first output terminal of the selecting means into variable-length code data using a variable-length code table and outputs the variable-length code data to the transmission interface; An adder for adding the data output from the second output terminal and the corresponding image data of the frame memory, and a means for recording the image data added by the adder at the corresponding pixel position of the frame memory. A charged particle beam device, comprising: 6. The charged particle beam apparatus according to claim 1, wherein a transmission interface for receiving compressed image data from a transmission path, and a compressed image encoded by an encoding method having a high degree of compression but a low degree of image restoration. A first image decoding means for decoding the data to restore the image data; and a first image decoding means for decoding the compressed image data encoded by an encoding method having a low compression degree but a high image restoration degree to restore the image data. Charged particle further comprising a remote control terminal having two image decoding means and a selection means for selecting whether to use the first image decoding means or the second image decoding means. Line device. 7. The charged particle beam apparatus according to claim 1, wherein a transmission interface for receiving transmission data from a transmission line and the received variable length code data are converted into fixed length code data using a variable length code table. A variable-length decoder, an inverse quantizer that multiplies fixed-length encoded data output from the variable-length decoder using a quantization table, and an inverse orthogonal transform of the output of the inverse quantizer. An inverse orthogonal transformer that generates reproduction difference data, a frame memory that stores one frame of image data, and a selection unit that selectively outputs the output of the variable length decoder or the output of the inverse orthogonal transformer. An adder for adding the data output from the selecting means and the corresponding image data of the frame memory, and the image data added by the adder for the corresponding image of the frame memory. A charged particle beam device further comprising a remote control terminal having a unit for recording at an elementary position. 8. A method of observing a sample image by remotely operating the charged particle beam device while observing the sample image transmitted from the charged particle beam device through a transmission path, wherein the sample image is acquired by television scanning. , A step of encoding and transmitting the acquired image data by an encoding method having a high degree of compression but a low degree of image decompression, and a step of searching an observation visual field by a sample image obtained by decoding the transmitted encoded data, Acquiring a sample image by reduce scan, encoding the acquired image data using an encoding method with low compression but high image restoration, and transmitting it, and a sample image obtained by decoding the transmitted encoded data The step of adjusting the focus by the method, and the encoding method in which the sample image is acquired by slow scan and the acquired image data has low compression but high image decompression. Thus a step of transmission by encoding a sample image observation method characterized by comprising the step of recording the sample image obtained by decoding the transmitted coded data.