JP2000195457A - Scanning microscope - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a scan microscope capable of obtaining a uniformly vivid picture in a visual field even if sever projecting and recessed parts exist on a specimen. SOLUTION: A focusing position (focus point position) of a primary electron beam EB irradiated onto a specimen 2 can be changed by controlling lens power of a focus control lens 15 by a variable focus position controller 16. The lens power changes in synchronization with a scan controller 8, and is fixed to a constant value for every frame integrated on the frame buffer of a picture integrator 9. Since a detected signal obtained at each lens power is integrated for every picture element, if a picture is displayed on a cathode ray tube 10 based on the integrated signal, a focused picture can be observed within a visual field for observation even if projecting and recessed parts remarkably exist on the specimen.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a scanning microscope which scans a focused electron beam or ion beam on a sample and detects a signal of secondary electrons or the like obtained from the sample to obtain a scanned image. About.

[0002]

2. Description of the Related Art A scanning microscope focuses a primary electron beam or a primary ion beam emitted from an electron gun or an ion gun on a sample surface using an electron lens, and scans the focused primary electron beam or the primary ion beam. And
An image signal is obtained by detecting secondary electrons emitted from the sample surface. Hereinafter, a scanning electron microscope will be described as an example.

FIG. 1 shows a system configuration of a conventional scanning electron microscope, and 1 is an objective lens. Objective lens 1
Focuses the primary electron beam EB generated from an electron gun (not shown) and accelerated on the sample 2 finely. The exciting coil of the objective lens 1 is supplied with an exciting current from the objective lens controller 3, and the lens strength of the objective lens 1 is controlled by adjusting the amount of the exciting current.

The scanning coils 4 and 5 are arranged along the optical axis of the primary electron beam EB.
Is supplied from the scanning controller 6 with a signal for deflecting the primary electron beam EB. The intensity of deflection of the primary electron beam EB by the scanning coils 4 and 5 is determined by the amount of current flowing through each scanning coil.
It is controlled in the Y direction.

As a result, a predetermined area on the sample 2 is two-dimensionally scanned by the primary electron beam. Secondary electrons e generated by irradiating the sample 2 with the primary electron beam are taken out upward by being constrained by the magnetic field of the objective lens 1, and the secondary electrons e arranged at a position away from the optical axis of the primary electron beam EB. The voltage is applied to the front surface of the detector 7 and is drawn in the direction of the detector 7, and is detected by the detector 7.

The detection signal from the detector 7 is amplified by a signal amplifier 8, converted into a digital signal by an AD converter in the signal amplifier 8, and then supplied to an image integrator 9. The signal supplied to the image integrator 9 is integrated on the frame buffer, and an image from which white noise has been removed by the image integration is displayed on the cathode ray tube 10.

In the above-described configuration, the primary electron beam EB generated and accelerated from the electron gun is narrowly focused on the sample 2 by the condenser lens (not shown) and the objective lens 1. Further, the primary electron beam EB is two-dimensionally scanned in a predetermined area on the sample 2 by the scanning coils 4 and 5.

A secondary electron e generated by irradiating the sample 2 with a primary electron beam is detected by a secondary electron detector 7, and a detection signal of the detector 7 is sent to an image integrator 9 via a signal amplifier 8. Supplied. In the image integrator 9, the integration process is performed for each pixel, and the noise component is significantly reduced. The image signal in which the noise component has been reduced is supplied to the cathode ray tube 10, and a scanned secondary electron image with an improved SN ratio is displayed on the cathode ray tube 10.

Here, the focal position of the primary electron beam EB can be adjusted by changing the lens strength of the objective lens 1, and the amount of current supplied to the scanning coils 4 and 5 can be adjusted. The display magnification of the image on the cathode ray tube 10 can be changed by changing the two-dimensional scanning area of the primary electron beam on the sample.

[0010]

Next, the difference in the secondary electron image depending on the focal position of the primary electron beam EB in the above-mentioned scanning electron microscope will be described with reference to FIGS. In this description, a semiconductor sample in which a pattern is formed on a wafer substrate as the sample 2 will be described as an example.

FIG. 2 shows a cross section of the semiconductor sample 2. Substrate 1
1, a pattern 12 is formed. The height of the pattern 12 is about several μm, and there is a problem that a secondary electron image changes depending on where the primary electron beam EB is focused on the pattern 12.

FIG. 2A shows a case where the primary electron beam EB is focused on the bottom portion 13 of the pattern 12, and the primary electron beam is not focused on the top portion 14 of the pattern 12.
In the secondary electron image formed in this case, as shown in FIG. 3A, the bottom 13 of the pattern 12 can be clearly observed, and the top 14 of the pattern 12 is blurred.

FIG. 2B shows the case where the primary electron beam EB is focused on the pattern top 14 and the pattern bottom 1
In 3, the primary electron beam is not focused. in this case,
In the formed secondary electron image, as shown in FIG. 3B, the top 14 of the pattern 12 can be clearly observed, and the bottom 13 of the pattern is blurred.

As described above, when the height of the pattern on the sample 2 is high, there is a problem that the secondary electron image changes depending on where the primary electron beam EB is focused on the pattern. That is, in the case of a sample having severe irregularities, a clear portion and an unclear portion occur in the field of the secondary electron image due to the difference in the focal position of the primary electron beam. Such a phenomenon is caused by the fact that the resolution of the scanning electron microscope has increased, the opening angle of the primary electron beam has increased, and the depth of focus has decreased.

The present invention has been made in view of the above points, and an object of the present invention is to provide a scanning microscope capable of uniformly obtaining a clear image in a field of view even for a sample having severe irregularities. To be realized.

[0016]

According to a first aspect of the present invention, a scanning microscope scans a primary beam two-dimensionally on a sample, and detects a signal obtained by irradiating the sample with the primary beam. A detector, means for changing the focal position of the primary beam in accordance with the unevenness of the sample surface, an image integrator for integrating and processing detection signals based on different focal positions of the primary beam, and storing in the image integrator Display means for displaying an image based on the received signal.

In the first invention, the focal position of the primary beam irradiated on the sample is changed in accordance with the height of a pattern or the like formed on the sample surface, and a detection signal based on the different focal positions of the primary beam is generated. The images are integrated, and an image is displayed based on the integrated signals, so that an image focused on almost the entire area within the observation visual field is obtained.

According to a second aspect of the present invention, in the scanning microscope according to the first aspect, the means for changing the focal position of the primary beam is a focal position control lens arranged near the objective lens, and the lens intensity of the focal position control lens is changed. Is the primary beam 2
It is characterized in that it can be changed in synchronization with dimensional scanning.

The scanning microscope according to the third invention is the scanning microscope according to the first invention, wherein the means for changing the focal position of the primary beam is an objective lens, and the lens intensity of the objective lens changes in synchronization with the two-dimensional scanning of the primary beam. It is characterized by being let.

The scanning microscope according to the fourth invention comprises
The invention according to the third aspect is characterized in that the primary beam is an electron beam. The scanning microscope according to the fifth invention is
In the first to third inventions, the primary beam is an ion beam.

According to a sixth aspect of the present invention, in the scanning microscope according to the first aspect, the focal position of the primary beam is set to a constant value during the vertical scanning of the primary beam. Seventh
The scanning microscope according to the invention of the invention of
Scanning means for dimensional scanning, a detector for detecting a signal obtained by irradiating the sample with the primary beam, and means for changing the focal position of the primary beam according to the height of the uneven structure on the sample surface An image integrator for integrating and detecting detection signals based on different focal positions of the primary beam, display means for displaying an image based on the signal stored in the image integrator, and different focal positions of the primary beam And a detecting means for detecting a focus position range corresponding to the unevenness of the sample based on a result of the integration for each frame.

In the seventh invention, detection signals based on different focal positions of the primary beam are integrated for each frame, and a focal position range corresponding to the unevenness of the sample is detected based on the integrated result, and irradiated onto the sample. The focal position of the primary beam is changed according to the detected focal position range, the detection signals based on the different focal positions of the primary beam are integrated, an image is displayed based on the integrated signal, and the An in-focus image is obtained over almost the entire area.

A scanning microscope according to an eighth aspect of the present invention provides a scanning means for two-dimensionally scanning a primary beam on a sample, a detector for detecting a signal obtained by irradiating the sample with the primary beam, Means for changing the focal position of the primary beam according to the tilt angle and the height of the uneven structure on the sample surface; an image integrator for integrating and storing detection signals based on two-dimensional scanning of the sample; and an image integrator Display means for displaying an image based on the signal stored in the scanning microscope.

In the eighth invention, the focal position of the primary beam irradiated on the sample is changed according to the inclination angle of the sample and the height of a pattern or the like formed on the sample surface, and the two-dimensional beam on the sample is changed. A detection signal based on the scanning is integrated, an image is displayed based on the integrated signal, and an in-focus image is obtained over almost the entire area within the observation visual field.

[0025]

Embodiments of the present invention will be described below in detail with reference to the drawings. FIG. 4 shows an example of a scanning electron microscope system according to the present invention, and the same or similar components as those in the conventional system of FIG. 1 are denoted by the same reference numerals.

In FIG. 4, reference numeral 1 denotes an objective lens. The objective lens 1 narrowly focuses the accelerated primary electron beam EB generated from an electron gun (not shown) on the sample 2. The exciting coil of the objective lens 1 is supplied with an exciting current from the objective lens controller 3, and the lens strength of the objective lens 1 is controlled by adjusting the amount of the exciting current.

The scanning coils 4 and 5 are arranged along the optical axis of the primary electron beam EB.
Is supplied from the scanning controller 6 with a signal for deflecting the primary electron beam EB. The intensity of deflection of the primary electron beam EB by the scanning coils 4 and 5 is determined by the amount of current flowing through each scanning coil.
It is controlled in the Y direction.

As a result, a predetermined area on the sample 2 is two-dimensionally scanned by the primary electron beam. Secondary electrons e generated by irradiating the sample 2 with the primary electron beam are taken out upward by being constrained by the magnetic field of the objective lens 1, and the secondary electrons e arranged at a position away from the optical axis of the primary electron beam EB. The voltage is applied to the front surface of the detector 7 and is drawn in the direction of the detector 7, and is detected by the detector 7.

The detection signal of the detector 7 is amplified by a signal amplifier 8, converted into a digital signal by an AD converter in the signal amplifier 8, and supplied to an image integrator 9. The signal supplied to the image integrator 9 is integrated on the frame buffer, and an image from which white noise has been removed by the image integration is displayed on the cathode ray tube 10.

A focus control lens 15 for finely adjusting the focus position of the primary electron beam EB is provided near the objective lens 2.
Is arranged. It is desirable that an air-core coil be used for the focus control lens 15 in order to increase the response speed. The intensity of the focus control lens 15 is controlled by a variable focus position controller 16.

The exciting current from the variable focus position controller 16 to the focus control lens 15 is controlled by a signal from the focus position data storage 17. Also, the variable focus position controller 1
The excitation current from 6 is configured to change in synchronization with the scanning signal of the primary electron beam EB from the scanning controller 8.

Reference numeral 18 denotes a focus position detector. The focus position detector 18 synchronizes with the scanning controller 8 based on an image signal from the image integrator 9 and, for example, detects the top of a pattern formed on the sample 2 and The focus position of the primary electron beam at the bottom is detected. The focus position of the primary electron beam EB corresponds to the value of the excitation current supplied to the focus control lens 15 when the top of the pattern is focused and when the bottom is focused. The operation of such a configuration will now be described.

In the above configuration, the accelerated primary electron beam EB generated from the electron gun is narrowly focused on the sample 2 by the condenser lens (not shown) and the objective lens 1. Further, the primary electron beam EB is two-dimensionally scanned in a predetermined area on the sample 2 by the scanning coils 4 and 5.

Secondary electrons e generated by the irradiation of the sample 2 with the primary electron beam are detected by a secondary electron detector 7, and a detection signal of the detector 7 is sent to an image integrator 9 via a signal amplifier 8. Supplied. In the image integrator 9, the integration process is performed for each pixel, and the noise component is significantly reduced. The image signal in which the noise component has been reduced is supplied to the cathode ray tube 10, and a scanned secondary electron image with an improved SN ratio is displayed on the cathode ray tube 10.

Here, the focus position (focal position) of the primary electron beam EB irradiated on the sample 2 is determined by the focus control lens 15.
Is controlled by the variable focus position controller 16 to change the lens intensity. Focus control lens 15
The relationship between the intensity of the primary electron beam and the focusing position of the primary electron beam is known in advance as shown in FIG.

FIG. 6A shows a vertical scanning amplitude waveform S controlled by the scanning controller 8, and FIG.
Indicates a focus position control curve F controlled by the variable focus position controller 16 in synchronization with each frame of vertical scanning. The focus position (focus position) control curve F is converted into data and stored in the focus position data storage 17. The procedure for creating the stored data will be described later. The top and bottom in FIGS. 5 and 6B correspond to the top and bottom 13 of the pattern 12 shown in FIG.

The focusing position control curve F changes in synchronization with the scanning controller 8 as described above, and the focal position (focusing position) is changed for each frame in which the image is integrated on the frame buffer of the image integrator 9. It is fixed at a constant value. When the number of image integration in the image integrator 9 is Na times, FIG. 7 shows a change curve M of the focusing position, that is, the lens strength of the focus control lens 15 according to the number of integration.

The focus position change curve M is stored in the focus position data storage 17 and controls where the focused image is formed in the pattern formed on the irregularities according to the sample 2 to be observed. be able to.

The focusing position change curve M shown in FIG.
Is to obtain an image in which the primary electron beam is simultaneously focused at each position between the top portion 14 and the bottom portion 13 of the pattern 12 on the sample 2, and to obtain an image in which the top portion 14 and the bottom portion 13 are focused.
This is an example in which the number of integrations in the focused state is set to be relatively large at the position of FIG.

In this case, even when observing a pattern of a semiconductor sample having a height of several μm, as shown in FIG.
Even if the focusing position of the primary electron beam is different between the top 14 and the bottom 13 of the second pattern 2, it is possible to obtain an image in a uniformly focused state without a focus shift over the entire pattern 12 on the image. it can. By changing the shape of the focusing position control curve stored in the focusing position data storage 17, the image quality of the image finally obtained according to the sample can be arbitrarily changed.

FIGS. 9A and 9B show various examples of the focusing position control curve M. FIG. 9A shows a case where the focus is placed on the center of the pattern 12, and FIG.
9C shows a case where the focus is placed on the bottom 13 of the pattern 12, and FIG. 9C shows a case where the focus is placed on the top 14 of the pattern 12.

Each of the cases shown in FIGS. 9A to 9C corresponds to a case where the focus is focused on a substantially specific position in the height direction of the sample. This shows that an image focused on a specific height position can be obtained similarly.

Next, the operation of the focus position detector 18 will be described. The focus position detector 18 synchronizes with the scanning controller 8 to output the top 1 of the pattern 12 on the sample 2 from the image integrator 9.
4 and the focus position at the bottom 13 are detected. FIG.
(A) is a focus position detector 18 which is the top 14 of the pattern 12.
5 shows a change in the lens strength of the focus control lens 15 when the focus position between the focus control lens 15 and the bottom 13 is detected.

Synchronous with the image capture of one frame, FIG.
As shown in FIG. 0 (a), the lens strength is changed from the lower search limit to the upper search limit. Then, when the signal of each frame obtained at that time is image-integrated, as shown in FIG.
It becomes stronger with b and Ft. This indicates that the primary electron beam is focused on the sample in this section, and the focal position due to the lens intensity at the time of Fb is shifted to the bottom 1 of the pattern 12.
3, and the focal position based on the lens strength at the time of Ft is the position of the top 14 of the pattern 12.

In this way, the variable focus position controller 16
Prior to the image integration using, the focal position detector 18 detects the focal positions of the top portion 14 and the bottom portion 13 of the pattern 12 and, based on the relationship between the lens intensity and the focal position shown in FIG. The determined top and bottom lens strengths can be set. The focus position control curve M stored in the focus position data storage 17 can be displayed on the cathode ray tube 10, and the operator looks at the curve M while watching the curve displayed on the screen of the cathode ray tube 10. Can be easily corrected.

In the above-described embodiment, the sample is positioned horizontally, but the present invention can be applied to the case where the sample is observed in an inclined state. FIG.
Shows a main part of the scanning electron microscope which can tilt the sample at a large angle. The same or similar components as those of the first embodiment shown in FIG.
A detailed description thereof will be omitted.

In FIG. 11, when the sample 2 is tilted at a large angle, the difference between the focal positions at the top and bottom of the pattern formed on the sample 2 at low magnification is several tens of μm, and all positions within the same visual field are observed. However, there is a problem that an in-focus image cannot be obtained.

Even when such a sample is tilted greatly,
Although not shown in FIG. 11, the focus control lens 15 includes a variable focus position controller 16, a focus position data storage 17, and a focus position detector 18 similar to those shown in FIG. By performing the same operation as that described in the embodiment, it is possible to acquire images in focus at all positions in the same visual field.

FIG. 12A shows a vertical scanning amplitude waveform S supplied from the scanning controller 8 to the scanning coils 4 and 5. FIG. 12B shows a focus position control curve F of a variable focus position controller 16 for controlling the intensity of the focus control lens 15.
Is shown. The start point and the end point indicate the highest and lowest focus positions in the same field of view based on the tilt angle of the sample.

As shown in FIG. 12B, by changing the focusing position control curve F in synchronization with the image integration of one frame, even if the sample is inclined, the focal point can be adjusted at all positions in the same visual field. A perfect image is obtained. This operation is called dynamic focus and is known. The focusing position control curve F is stored in the focusing position data storage 17, and its contents can be easily modified.

FIG. 13 shows the sample 2 tilted.
The pattern 12 is on the substrate 11 and the top 14 of the pattern
And the bottom 13 have different focal positions. In such a case, as shown in FIG. 14, the focusing position control curve M is a curve that focuses on the pattern top portion 14 and the pattern bottom portion 13, so that the degree of inclination of the sample depends on the sample. Accordingly, it is possible to obtain an image without defocus in the field of view according to the above.

Although the embodiments of the present invention have been described above, the present invention is not limited to these embodiments, and various modifications can be made. For example, although the embodiment has been described by taking a scanning electron microscope as an example, the present invention can be applied to a scanning microscope that scans a sample two-dimensionally with an ion beam.

Although a secondary electron image is obtained by detecting a secondary electron, the present invention can be applied to a case where a scanned image is displayed by detecting a reflected electron or a reflected ion. it can. Furthermore, a focal position control lens is arranged near the objective lens, and the focal position of the primary beam is changed by this control lens. However, although there is a problem in response speed, the focal position is changed by the objective lens itself. You may let it.

[0054]

According to the first aspect of the present invention, the focal position of the primary beam irradiated on the sample is changed in accordance with the height of a pattern or the like formed on the sample surface, and the primary beam is detected based on the different focal positions. Since the signal is integrated and the image is displayed based on the integrated signal, an in-focus image can be obtained over almost the entire visual field even if there are significant irregularities on the sample surface. be able to.

In the scanning microscope according to the second invention, in the first invention, the means for changing the focal position of the primary beam is a focal position control lens arranged near the objective lens, and the lens intensity of the focal position control lens is changed. Is the primary beam 2
It is characterized in that it can be changed in synchronization with dimensional scanning, so that the response speed can be increased and the focal position of the primary beam can be changed, and an in-focus image can be obtained almost in the entire observation field. it can.

In the scanning microscope according to the third invention, in the first invention, the means for changing the focal position of the primary beam is an objective lens, and the lens intensity of the objective lens changes in synchronization with the two-dimensional scanning of the primary beam. And an effect equivalent to that of the first invention is obtained.

The scanning microscope according to the fourth invention comprises
According to the third aspect, the primary beam is an electron beam, and the same effect as that of the first aspect can be obtained. The scanning microscope according to the fifth invention is characterized in that, in the first to third inventions, the primary beam is an ion beam, and an effect equivalent to that of the first invention is obtained.

A scanning microscope according to a sixth aspect of the present invention is the scanning microscope according to the first aspect, wherein the focal position of the primary beam is set to a constant value during the vertical scanning of the primary beam.
The same effect as that of the invention is obtained.

In the seventh invention, detection signals based on different focal positions of the primary beam are integrated for each frame, and a focus position range corresponding to the unevenness of the sample is detected based on the integration result, and the sample is irradiated onto the sample. Since the focal position of the primary beam is changed according to the detected focal position range, the detection signals based on the different focal positions of the primary beam are integrated, and an image is displayed based on the integrated signal. An in-focus image can be obtained over almost the entire area within the observation field.

In the eighth invention, the focal position of the primary beam irradiated on the sample is changed according to the inclination angle of the sample and the height of a pattern or the like formed on the sample surface, and the two-dimensional beam on the sample is changed. Since the detection signal based on the scanning is integrated and the image is displayed based on the integrated signal, even if the sample is inclined and there is a conspicuous unevenness on the surface of the sample, it can be viewed within the observation field of view. , A focused image can be obtained over almost the entire area of the image.

[Brief description of the drawings]

FIG. 1 is a diagram showing a system configuration of a conventional scanning electron microscope.

FIG. 2 is a diagram illustrating a cross section of a sample in which a pattern is formed on a surface and a state of focusing of an electron beam.

FIG. 3 is a diagram showing a displayed pattern image.

FIG. 4 is a diagram showing a system configuration of a scanning electron microscope according to the present invention.

FIG. 5 is a diagram illustrating a relationship between a lens intensity and a focal position of an electron beam.

FIG. 6 is a diagram showing a vertical scanning amplitude waveform of an electron beam and a focal position of the electron beam for each frame.

FIG. 7 is a diagram showing a relationship between the number of times of integration of an image and a focus position of an electron beam.

FIG. 8 is a diagram showing an example of a sample image displayed based on the present invention.

FIG. 9 is a diagram illustrating various focusing position control curves.

FIG. 10 is a diagram showing a change in a focal position of an electron beam and a change in detection signal strength when the lens strength is changed.

FIG. 11 is a diagram showing an embodiment in a case where a sample is observed while being tilted.

FIG. 12 is a diagram showing a vertical scanning amplitude waveform and a change curve of a focal position of an electron beam.

FIG. 13 is a diagram showing a state of a sample tilted.

FIG. 14 is a diagram showing a vertical scanning amplitude waveform and a change curve of a focal position of an electron beam.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Objective lens 2 Sample 3 Objective lens controller 4,5 Scan coil 6 Scan controller 7 Secondary electron detector 8 Signal amplifier 9 Image integrator 10 Cathode ray tube 15 Focus control lens 16 Variable focus position controller 17 Data storage 18 Focus position detector

Claims (8)

[Claims] A scanning means for two-dimensionally scanning a primary beam on a sample; a detector for detecting a signal obtained by irradiating the sample with the primary beam; Means for changing the focal position of the primary beam in accordance with the image, an image integrator for integrating and detecting detection signals based on different focal positions of the primary beam, and displaying an image based on the signal stored in the image integrator A scanning microscope provided with a display unit that performs the operation. The means for changing the focal position of the primary beam is a focal position control lens disposed near the objective lens, and the lens intensity of the focal position control lens is changed in synchronization with the two-dimensional scanning of the primary beam. The scanning microscope according to claim 1, 3. The scanning microscope according to claim 1, wherein the means for changing the focal position of the primary beam is an objective lens, and the lens strength of the objective lens is changed in synchronization with the two-dimensional scanning of the primary beam. 4. The method according to claim 1, wherein the primary beam is an electron beam.
Scanning microscope according to any one of claims 1 to 3. 5. The scanning microscope according to claim 1, wherein the primary beam is an ion beam. 6. The scanning microscope according to claim 1, wherein the focal position of the primary beam is a constant value during the vertical scanning of the primary beam. 7. A scanning means for two-dimensionally scanning a primary beam on a sample, a detector for detecting a signal obtained by irradiating the primary beam to the sample, and a detector for detecting a signal obtained by irradiating the sample with a primary structure. Means for changing the focal position of the primary beam in accordance with the image, an image integrator for integrating and detecting detection signals based on different focal positions of the primary beam, and displaying an image based on the signal stored in the image integrator A scanning microscope, comprising: display means for performing detection; and detection means for integrating detection signals based on different focal positions of the primary beam for each frame, and detecting a focal position range corresponding to unevenness of the sample based on the integration result. 8. A scanning means for two-dimensionally scanning a primary beam on a sample, a detector for detecting a signal obtained by irradiating the sample with the primary beam, an inclination angle of the sample and an uneven structure on the surface of the sample. Means for changing the focal position of the primary beam according to the height of the object, an image integrator for accumulating and storing a detection signal based on the two-dimensional scanning of the sample, and a signal stored in the image integrator. A scanning microscope comprising a display unit for displaying an image.