JP2007149348A - Scanning electron microscope - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electron beam microscope device having a scan control capable of improving throughput of the device by shortening the substantial scanning time without changing image acquisition condition at the time of electron beam scanning. <P>SOLUTION: The phase difference between the phase when a scanning starting signal is supplied and the AC power supply phase wave is detected, and the scanning signal is supplied to a scanning deflector by shifting that portion of the phase difference detected from the power supply phase wave. Thereby, substantial scanning time is shortened and throughput of the device can be improved. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a scanning electron microscope, and more particularly to an apparatus that generates a scanning signal in synchronization with a power phase wave supplied from an AC power source.

  Conventionally, the imaging of an electron microscope apparatus is often performed in synchronization with the frequency of the power source used. This conventional example will be described with reference to FIG.

Conventional electron microscope devices and similar devices perform two-dimensional scanning on a sample to be observed by narrowing down an electron beam emitted from an electron source, and at this time secondary electron beam reflected electrons generated from the sample and others The digital signal is converted into a digital image and displayed to observe the microstructure and shape of the sample. An example of the configuration of the scanning electron microscope at this time is shown in FIG. When image acquisition is performed on the electron microscope main body 101, the information is transferred to the scan control unit 111 and the phase control unit 113 via the CPU 112 in response to a scan activation command from the operation personal computer (PC) or the control unit 109. Reportedly. The phase control unit 113 receives the scan activation command from the CPU 112 and the power supply phase wave (sin wave) from the AC power supply 110 supplied to the electron microscope main body 101, and detects and stores the phase of the power supply phase wave when the scan activation command is generated. Then, the detection phase is converted into a power phase wave. The selector 114 selects either the AC power supply 110 directly or the power supply phase wave converted by the phase control unit 113 as the power supply phase wave transmitted to the scanning control unit 111 by an operation from the CPU. In the scanning control unit 111, the power phase wave from the selector 114 and the CPU
Upon receipt of a scan activation command from 112, when a scan activation command is generated, a rising edge of a power phase wave or an arbitrary phase point is detected, and then an electron beam scanning synchronization signal is supplied to the electron microscope body 101, and at the same time A similar synchronization signal is supplied to the image preprocessing unit 104, the image memory 105, and the image processing unit 106. In the scanning electron microscope main body 101, an electron beam is generated from the electron source 115 by the electron beam scanning synchronization signal from the scanning control unit 111, and is irradiated onto the sample 116. At this time, the irradiation position of the electron beam is determined by changing the deflection coil 119 by a scanning synchronization signal (two-dimensional scanning signal) from the scanning control unit, and the electron beam scans the sample 116 two-dimensionally. When the sample 116 is irradiated with an electron beam, secondary electrons and reflected electrons are generated. The electron beam detector 102 detects the intensity of the secondary electrons and reflected electrons according to the shape and material of the sample 116 and amplifies them. To do. The amplified signal is converted into a digital image by the A / D converter 103, and the image pre-processing unit 104 performs an operation such as integration to improve the S / N of the image and temporarily stores it in the image memory 105. The image data once stored in the image memory 105 passes through the selector 107 and the D / A converter 108 in accordance with the synchronization signal of the scanning control unit 111, or is directly captured and sent to the PC or WS which is also a display device. The obtained image is displayed.

  At this time, the generation timing of the two-dimensional scanning of the electron beam is affected by the influence of the magnetic field by the AC power supply of the apparatus and the AC disturbance, so the scanning of the electron beam needs to be generated in synchronization with the frequency phase of the AC power supply. .

In this case, the scanning timing shown in FIG. The horizontal axis represents time, and the vertical axis represents AC power frequency phases 401 and 402 and scanning examples 403 and 404. 401 is a sin wave of an AC power source.
When the phase of the sin wave is 0 ° as a reference (other angles may be possible), the scanning of the electron beam was started from the reference of the next phase 0 ° at the start of scanning. Patent Documents 1 to 4 describe that the scanning timing is generated in synchronization with the AC power supply as described above.

JP 2003-203592 A Japanese Patent Laid-Open No. 10-97836 JP-A-63-80453 JP-A-10-092360

  In FIG. 4, 401 is a phase wave of the AC power supply, and the power supply frequency 405 is one cycle. A signal obtained by applying a torque to each phase of 180 ° is 402 (in this example, the phases are 0 ° and 180 °, but this is not the case). One example of scanning in this case is scanning I403. When scanning is activated at time (1), scanning I starts after waiting for the rise of 402, and in this case, scanning for two cycles of the power supply frequency is performed. Even if the activation is started immediately after the end of the scan, the next scan is similarly started after waiting for the rise of 402. In the example of the scan II 404, after the first scan is completed, the CPU 112 executes another operation (external process) and starts the operation again. At this time, even if the start timing is slightly exceeded due to the time of external processing other than the scan of the CPU, the start of the actual scan is delayed by one power supply synchronization only by exceeding the period of the rise timing 402.

  For this reason, since the substantial scanning time also changes in other controls, it is inevitable that the scanning timing depends on the AC power supply synchronization regardless of the scanning activation timing. Therefore, the actual scanning time is delayed and the apparatus throughput is reduced.

  As described in the prior art, the scanning timing of the electron beam is always synchronized with a constant frequency as shown in FIG. Therefore, there is a problem that a time lag occurs from the start of scanning to the actual start of scanning, and the maximum time reaches one cycle of the AC power source. For this reason, there is a problem that the accumulation of the time lag affects the apparatus throughput particularly in the operation of repeatedly starting and stopping the repeated scanning. Further, since the time lag is not constant, there is a problem that the throughput of the apparatus fluctuates each time depending on the operation and processing.

  SUMMARY OF THE INVENTION An object of the present invention is to realize and provide an electron beam microscope apparatus having scanning control capable of speeding up a substantial scanning time and improving the throughput of the apparatus without changing the image acquisition conditions at the time of electron beam scanning.

  In order to achieve the above object, in the present invention, the phase difference between the phase when the scan activation signal is supplied and the AC power supply phase wave is detected, and the detected phase difference is shifted from the power supply phase wave. It is proposed to supply a scanning signal to the scanning deflector.

  It is possible to shorten or make the time from the scan activation command to the actual start of scanning while keeping the scanning of the electron microscope unchanged in the influence of AC disturbance.

  Therefore, the scanning standby time from the scanning start command to the start of actual scanning becomes zero macroscopically, the substantial scanning time can be shortened, and the throughput of the apparatus can be improved.

An embodiment of the electron microscope and the similar apparatus of the present invention is shown below. An example of the structure and invention function of an electron microscope is shown in FIG. In FIG. 1, when acquiring an image with respect to the electron microscope main body 101, the information is transferred to the scan control unit 111 and the phase via the CPU 112 in response to a scan start command from the operation personal computer (PC) or the control unit 109. This is transmitted to the control unit 113. The phase control unit 113 receives the scan activation command from the CPU 112 and the power supply phase wave (sin wave) from the AC power supply 110 supplied to the electron microscope main body 101, and detects and stores the phase of the power supply phase wave when the scan activation command is generated. Then, the detection phase is converted into a power phase wave. The selector 114 selects either the AC power supply 110 directly or the power supply phase wave converted by the phase control unit 113 as the power supply phase wave transmitted to the scanning control unit 111 by an operation from the CPU. The scanning control unit 111 receives the power supply phase wave from the selector 114 and the scan activation command from the CPU 112, and when the scan activation command is generated, the rise of the power supply phase wave or an arbitrary phase point is detected before the electron microscope A synchronization signal for electron beam scanning is supplied to the main body 101, and at the same time, similar synchronization signals are supplied to the image preprocessing unit 104, the image memory 105, and the image processing unit 106. In the scanning electron microscope main body 101, an electron beam is generated from the electron source 115 by the electron beam scanning synchronization signal from the scanning control unit 111, and is irradiated onto the sample 116. At this time, the irradiation position of the electron beam is determined by changing the deflection coil 119 by a scanning synchronization signal (two-dimensional scanning signal) from the scanning control unit, and the electron beam scans the sample 116 two-dimensionally. When the sample 116 is irradiated with an electron beam, secondary electrons and reflected electrons are generated. The electron beam detector 102 detects the intensity of the secondary electrons and reflected electrons according to the shape and material of the sample 116 and amplifies them. To do. The amplified signal is converted into a digital image by the A / D converter 103, and the image pre-processing unit 104 performs an operation such as integration to improve the S / N of the image and temporarily stores it in the image memory 105. The image data once stored in the image memory 105 passes through the selector 107 and the D / A converter 108 in accordance with the synchronization signal of the scanning control unit 111, or is directly captured and sent to the PC or WS which is also a display device. The obtained image is displayed. At this time, it is also possible to pass through the image processing unit 106 by processing. This image processing can also be performed at an arbitrary location. In the present invention, parts that control the apparatus may be collectively referred to as a control apparatus.

Now, the operation of the scanning control unit 111 at this time will be described with reference to FIG. In the scan control unit 111, when the scan start command from the CPU 112 and the power supply phase wave from the AC power supply 110 are detected, the start / stop control unit 302 waits for the reference phase point of the power phase wave when detecting the scan start command. An operation start signal is sent to the pixel counter 303, the line counter 304, and the frame counter 305. The pixel counter 303 is synchronized with an external reference scanning clock,
The effective scanning time in the scanning horizontal direction (X direction) is counted according to the setting of the size and scanning time of the image of the two-dimensional scanning from the CPU 112. When the 1X direction ends, this is transmitted to the line counter 304, and the counter is Reset, start counting the pixel counter again, and repeat the same operation. Similarly, the line counter 304 counts the effective scanning time in the scanning vertical direction (Y direction) in synchronization with every 1X direction end signal from the pixel counter 303 in accordance with the setting from the CPU 112 in the pixel counter 303. When the direction is completed, this is transmitted to the frame counter 305, the counter is reset, the line counter is started again, and the same operation is repeated. The frame counter 305 operates similarly to the pixel counter 303 and the frame counter 304. These respective counter values are transmitted to the scanning synchronization signal generation unit 306, and the horizontal and vertical synchronization signals corresponding to the two-dimensional scanning and the number of repetitions of the two-dimensional scanning according to the counter value by the scanning synchronization signal generation unit 306. A synchronization signal for controlling the frame is generated and transmitted to the electron microscope main body 101, and at the same time, a synchronization signal added with a time delay of these synchronization signals is also sent to 104, 105, 106, and the like. That is, the scanning deflector is supplied by shifting the detected phase difference from the power supply phase wave.

  Accordingly, a series of operations from scanning of an electron beam to image acquisition and display can be performed by an activation command from the control unit 109.

The control of the phase control unit 113 at this time will be described with reference to FIG. FIG. 5 is a block diagram of the phase control unit 113. The phase counter 503 counts a clock having a certain arbitrary speed as a reference every time a power phase wave from the AC power source 110 is inputted. (The frequency of the clock is determined by the accuracy of the phase counter 503.) This phase counter continues to rotate as long as the power supply phase wave is received. This phase counter value is passed to the counter value storage unit 504 together with the scan activation command from the CPU 112, and the counter value storage unit 504 stores the phase counter value when the scan activation is detected. The stored counter value is sent to the coincidence detection unit 505, where it is compared with the phase counter value output from the phase counter 503 to detect the coincidence phase. This can be sent to the scanning controller 111 as a power phase wave whose phase has been converted by the phase converter 506.

  The specific operation of the phase control unit 113 at this time is shown in FIG. In FIG. 6, time is plotted on the horizontal axis, each operation item is plotted on the vertical axis, AC power supply synchronization signal 601, phase counter 602, storage counter value 603, detection signal 604, and internal power supply synchronization signal 605. The phase counter 602 is reset every time the AC power supply synchronization signal 601 changes. The phase counter 602 is counted up by an arbitrary clock. A detection signal 604 is generated at the point of coincidence with the stored counter value 603 by the counter value storage unit 504. In the case of FIG. 6, when the storage counter 603 is set to 8, a detection signal is generated every time the phase counter 602 becomes 8. By inverting the signal at each rising edge, an internal power supply synchronization signal 605 of the phase control unit 113, that is, a phase-controlled AC power supply phase synchronization signal is generated.

FIG. 7 shows a scanning time chart as an example of the operation at this time. Reference numeral 701 denotes a phase wave of the AC power supply, and the power supply frequency 705 is one cycle. There is a signal 702 in which this is torqued every 180 ° (in this example, the phases are 0 ° and 180 °, but this is not the case). One example of scanning in this case is scanning I of 703. When scanning activation (hereinafter abbreviated as activation) enters at timing (1), the phase control power phase wave 706 rises regardless of the power phase wave 702, and scanning I703 starts. In this case, the scanning is completed with two AC power source frequencies. The activation (2) was started immediately after the end of the scan. In this case as well, the phase control power phase wave 706 falls and rises regardless of the current operation, and the scan can be started again immediately after the activation. . Compared with the operation described with reference to FIG. 4, it can be seen that even when the same AC activation operation is performed, the time applied to the whole is shortened.

In this case, as compared with the conventional example, the actual scanning time is shortened by a maximum of N × AC power supply cycle by repeating the scanning N times.

  Next, an embodiment showing the effect of the present invention in the relationship between the scanning time and the AC power supply phase period will be described.

  In general, electron beam scanning in an electron microscope apparatus is often performed by raster scanning. An example of this is shown in FIG. In the example of FIG. 8, the scanning area is scanned from the upper left to the right in the horizontal direction. When one line scanning is completed, the scanning area returns to the left side and restarts from the lower side by one pixel in the vertical direction. I do. By repeating this, the entire scanning area is scanned.

  In raster scanning of such an electron microscope apparatus, when the scanning time is between 1/2 × 1 period and 1 period with respect to 1 AC power phase wave synchronization of the apparatus, that is, the examples described so far, This applies to the case of conforming to the scan time for TVs such as NTSC. FIG. 9 shows the relationship between the AC power source phase wave and scanning at this time. In FIG. 9, the horizontal axis represents time, and the vertical axis represents the AC power phase wave 901 and scanning example scan I902. The numbers in the scan I902 indicate the number of scan frames. FIG. 9 shows that the AC power supply phase is always the same at the same coordinate point (x, y) phase φ903 of each frame of the scan I902.

  In addition, even when one scanning time is short (less than 1/2 of the AC power supply period), it is possible to minimize the influence of the AC power supply by the same principle. An example of this case is shown in FIG. In FIG. 10, the horizontal axis indicates time, the vertical axis indicates AC power source phase wave 1001 and scanning example scan II 1002, and an arbitrary coordinate point (x, y) and phase φ1003. The numbers in Scan II 1002 indicate the number of scan frames. However, in this case, as one reason for shortening one scanning time, there is a case where the apparatus throughput is improved by shortening one scanning time, shortening the entire scanning time, and shortening the time required for imaging. However, in FIG. 10, since the next AC power supply start is awaited even after the completion of one scan, the power supply synchronization can substantially be performed only for one scan in one cycle, and the time effect is lost. In such a case, a configuration is adopted in which a plurality of frames can be scanned within the same AC power supply phase according to one scanning time. An example of this case is shown in FIG. In FIG. 11, the horizontal axis represents time, the vertical axis represents AC power phase wave 1101 and scanning example scan III 1102, arbitrary coordinate point (x, y) and phase φ 1103, coordinate point (x ′, y ′) and phase φ '1104 is shown. The numbers in scan III 1102 indicate the number of scan frames. The example of FIG. 11 is a case where one frame scanning time is ½ or less of the AC power supply phase period. At this time, the first frame of the scan III 1102 starts scanning in the same manner as in the previous embodiments, but the start of the second frame does not wait for the AC power supply, that is, ignores the AC power synchronization phase start point. Scan. Then, the third frame again waits for AC power supply synchronization. If this is repeated, the AC power phase positions of the odd and even frames are different, but the same coordinate point between the odd frames and the same coordinate point between the even frames are the same, and the AC power phase is the same, reducing the scanning time. In addition, the imaging influence of the AC power supply can be minimized.

  The same applies to the case where an arbitrary number of frames are included in one AC power supply synchronization (for example, in an imaging in which one scanning time is 5 ms and 2.5 ms, four frames and eight frames are included in one AC power supply cycle 20 ms).

  Hereinafter, as a specific application example when the present invention is incorporated in an apparatus, an embodiment in which the present invention is applied to an autofocus function during scanning in an electron microscope apparatus will be described.

FIG. 12 shows a time chart showing an example of autofocus scanning. In a general autofocus operation in an electron microscope, an image is acquired under a certain scanning condition, an autofocus operation is performed on the image, and the result is fed back to the scanning condition. The setting of the scanning condition is changed, and scanning is performed again under this condition. The operation of “scanning → autofocus → scanning condition change” is continuously performed, and when the autofocus calculation result enters a predetermined focus range (threshold), the scan is stopped and the autofocus is ended.

Now, an example of the time chart in FIG. 12 will be described. In FIG. 12, the horizontal axis indicates time, and one scale indicates one power supply synchronization. Here, the power supply frequency is 50 Hz. Therefore, one scale is T =
20 ms. The vertical axis represents each operation item, AC power frequency 1201, scanning condition setting 1202, scanning 1203, image transfer 1204, and autofocus calculation 1205. The unit of the numerical values in FIG. 12 is ms. First, as an initial setting, scanning condition setting 1206 is performed so that desired scanning can be performed. Thereafter, when a scanning start command 1207 is issued, scanning 1203 is started. In this example, scanning of 40 ms per frame is performed twice, the acquired images of 2 frames are integrated between the images, and the S / N is improved to obtain a completed captured image. At this time, the scan start command 1207 is issued immediately after power supply synchronization. In the conventional case, the scan start waits for the power supply synchronization start. Therefore, the actual scan start is delayed by a maximum of 20 ms power supply synchronization wait 1208 from the scan start command.

  After the start of scanning, scanning is finished 40 ms × 2 frames = 80 ms later. In order to transfer the completed acquired image to the memory in the image processing unit 106, image transfer 1204 is performed. Further, during this time, scanning end and start processing is performed, and the next scanning is subsequently started. In this case, the scanning start command 1210 is issued immediately after the next power supply synchronization after the end of the previous scanning. For this reason, as in the first scanning, the actual scanning is started after waiting for a maximum of 20 ms power supply synchronization waiting 1211.

  The scan acquired image transferred to the image processing unit 106 performs an autofocus calculation 1205. After the image processing unit transfer, the scan acquired image can be operated in parallel with the scan. This is reflected in the scanning control conditions.

These series of operations are repeated. If the scanning repetition time at this time is considered to be from the scanning start to the next scanning start,
Power supply synchronization wait + scan time + scan start command operation time (including transfer time)
And
20 ms + 40 ms × 2 (frame) +20 ms = 120 ms
Therefore, scanning and autofocus calculations are repeated at a cycle of 120 ms. Here, if 10 images are acquired during autofocus, a total time of 1286.4 ms is required as shown in the lower calculation in FIG.

  On the other hand, an example of autofocus when the present invention is applied will be described below. FIG. 13 shows a time chart when the present invention is applied to the autofocus example (FIG. 12) already described. 13 has the same functions and operations as those in FIG. 12, and the present invention is applied only to the scanning timing. Changing the intensity of the objective lens for autofocusing or adjusting the negative voltage applied to the sample (focus adjustment by adjusting the negative voltage) is performed between scans 1303. The function and operation are the same as in the autofocus example of FIG. In FIG. 13, the horizontal axis is time, and one scale is one power supply synchronization. Here, the power supply frequency is 50 Hz. Therefore, one scale is T = 20 ms. The vertical axis indicates each operation item, AC power frequency 1301, scanning condition setting 1302, scanning 1303, image transfer 1304, and autofocus calculation 1305. The unit of the numerical values in FIG. 13 is ms. Here, the difference from FIG. 12 and the difference in scanning processing time depending on whether or not the power supply synchronous phase control method is applied will be described.

  In FIG. 13, when a scan start command 1307 is issued, on a macro basis, an actual scan is started immediately after the command is issued, and the scan 1303 is finished 80 ms after the start. When the image transfer 1304 after the end of scanning is performed, the scanning end and start processes are performed, and a scanning start command 1309 is issued, the next scanning is started immediately after.

  At this time, the phase of power supply synchronization at a certain coordinate point in the image of the same scanning is exactly the same, and the influence of the magnetic field is uniform at the same coordinate point.

When the repetition time is obtained as in FIG.
Scan time + scan start command operation time (including transfer time)
And
40 ms x 2 frames + 13 ms = 93 ms
Therefore, scanning 1303, autofocus calculation 1305, and the like are repeated at a cycle of 93 ms. Here, as in FIG. 12, if autofocus converges in 10 images, the total time is 1014.4 ms, as shown in the lower calculation of FIG. 13, which is 264 ms compared to the conventional example of FIG. It turns out that time is shortened.

  As a result, when the present invention is applied to autofocus, the autofocus time can be shortened, which can contribute to an improvement in the throughput of the application apparatus (such as an electron microscope apparatus). Further, when it is determined that the focus evaluation value has reached a predetermined value as a result of the autofocus calculation, the subsequent scanning may be stopped.

  This effect becomes more effective as the number of scanning repetitions is larger, the number of integrations between scanning frames is smaller, and the number of autofocusing is larger.

  When the autofocus calculation is longer than the scanning repetition time, the calculation time becomes the rate-limiting condition. However, in recent years, the scanning time is often the rate-limiting condition in accordance with the recent increase in image processing.

  In this example, autofocus is taken as an example, but the same can be applied to other general image processing and the like.

As an example of a specific imaging sequence, an example of an image acquisition sequence in an electron microscope apparatus is shown in FIG. As shown in FIG. 14, this image processing sequence is largely imaged I
The operations are divided into 1401, imaging II 1402, imaging III 1403, processing I 1404, and processing II 1405. After the start of this sequence, imaging I1401 is performed, in which a mechanical operation such as stage movement 1406 of the electron microscope is performed and control is performed to move to a desired imaging position. Then, the autofocus 1407 described in the previous embodiment is performed to perform imaging focusing, and then scanning 1408 for imaging is performed to complete image acquisition. Of these, imaging
Since the II 1402 and the processing I 1404 and the imaging III 1403 and the processing II 1405 operate in parallel, the slower processing time becomes the rate limiting condition for the entire throughput.

  The acquired image is transferred 1409 after image transfer and image processing 1410 is performed (processing I1404) (for example, image processing by PC software and PC software), and in parallel with this, preparation for the next imaging is started. After completion of the imaging I1401, the imaging II1402 is started, the stage movement 1406 is performed in the same manner as the imaging I1401, the scanning 1408 is performed, and the image acquisition is performed.

  In the above sequence, the scan 1408 is repeated several times. In the case of the imaging I1401, as described above with the autofocus 1407, imaging is repeated until the focus converges, and finally one imaging for acquiring an image by actual scanning is performed, and the imaging I1401 ends. At this time, the present invention can be applied every time scanning is started, and the effect of improving the overall throughput can be exhibited every time imaging is performed. The same applies to the imaging II 1402 and the imaging III 1403.

  An example of processing time for the processing items of the image acquisition sequence at this time is shown in FIG. Conventionally, each stage movement does not change to 500 ms when the invention is applied. However, as described above, autofocus has a shortening effect of about 250 ms by repeating the imaging 10 times, and actual scanning (image acquisition) has a shortening effect of 20 ms each. is there. As a result, the total time shown in Table 1 for the entire image acquisition sequence is 5092 ms in the prior art, and 4488 ms when the invention is applied. This overall sequence has a shortening effect of 604 ms. It is possible to contribute to improvement.

The structure of the electron microscope to which the invention is applied. Configuration of a conventional electron microscope. Scan control. Scan timing. Phase control unit. Operation of the phase control unit. Scanning timing of the invention. Image of electron beam scanning. Relationship between AC power phase wave and scanning. Relationship between AC power supply phase wave and scanning (example when one scanning time is short). Relationship between AC power phase wave and scanning (an example in which one frame scanning time is 1/2 or less of AC power phase period). Conventional example of autofocus. Example of autofocus. An example of an image acquisition sequence. Comparison of time when image acquisition sequence and the present invention are applied.

Explanation of symbols

101 ... electron microscope main body, 102 ... electron beam detector, 103, 118 ... A / D converter,
DESCRIPTION OF SYMBOLS 104 ... Image pre-processing part, 105 ... Image memory, 106 ... Image processing part, 107, 114 ... Selector, 108 ... D / A converter, 109 ... Control part, 110 ... AC power supply, 111 ... Scan control part, 112 ... CPU, 113: phase control unit, 115: electron source, 116: sample, 117: deflection coil.

Claims (4)

An electron gun, a scanning deflector that scans the electron beam emitted from the electron gun, and a scanning signal to the scanning deflector in synchronization with a power phase wave supplied from an AC power source based on a scanning activation signal In a scanning electron microscope equipped with a control device to supply,
The control device detects a phase difference between the phase when the scanning activation signal is supplied and the power phase wave, and shifts the detected phase difference from the power phase wave to scan the scanning deflector. A scanning electron microscope characterized by supplying a signal. In claim 1,
When the scanning signal is shorter than half of one cycle of the power supply phase wave, the control device sends the scanning signal of two cycles to the scanning deflector during one cycle of the power supply phase wave. A scanning electron microscope characterized by being supplied. Scanning electron comprising: an electron gun; a scanning deflector that scans an electron beam emitted from the electron gun; a focus adjustment that performs focus adjustment of the electron beam; and a control device that supplies a scanning signal to the scanning deflector In the microscope,
The control device generates a scanning start signal during a plurality of scans for acquiring an image for focus adjustment of the electron beam, and supplies the scanning signal to the scanning deflector based on the scanning start signal. A scanning electron microscope. In claim 3,
The scanning electron microscope, wherein the control device sets a scanning start timing for acquiring a plurality of images for focus adjustment independently for each scanning for each image.

Images