JPH0452589B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a scanning modulation type observation display device, in particular, to a scanning modulation type observation display device, in particular, to rapidly modulate the scanning position, diameter, wavelength, etc. of a probe irradiated onto a specimen to be observed. This invention relates to a scanning modulation type observation and display device that extracts and displays characteristics of a sample to be observed based on signals obtained from the .

(Technical Background and Problems) Conventionally, scanning electron microscopes and the like sequentially scan an observed sample using an electron beam probe focused to a minute diameter, and collect signals obtained from the observed sample, for example, 2
By performing brightness, amplitude modulation, etc. in synchronization with the scanning signal using signals such as secondary electrons, Auger electrons, reflected electrons, X-rays, and light, a desired image can be displayed on the display. ing.

Some types of scanning microscopes, such as scanning Auger microscopes, can modulate the electron beam density by making the shape of the electron beam probe that irradiates the observed sample the same in order to improve the S/N of images. It is being done. By performing the density modulation, the Auger electrons detected from the sample to be observed become a signal that changes in an alternating current manner, the alternating current signal is amplified, and after the amplification, phase detection is performed to obtain an image signal.
Therefore, it is possible to obtain an image signal with a high S/N, especially with reduced drift.

However, the electron current density modulation of the electron beam probe is performed to facilitate amplification, obtain a high S/N, etc., and is not used to extract features related to the observed sample. Conventionally, in order to extract the image information required for a specimen to be observed, the image signal is once stored in a memory or the like, and the stored image information is subjected to image processing by a computer.
I was getting it. This poses a problem in that image processing cannot be performed in real time, and the configuration for performing image processing becomes complicated.

(Object and Structure of the Invention) An object of the present invention is to solve the above-mentioned problems, and to quickly modulate the scanning position, diameter, wavelength, etc. of the probe when irradiating the sample to be observed with the probe. detect a signal with modulation from the sample to be observed, extract an unmodulated image signal and a modulated image signal from the detected signal, and display a desired image on a display etc. based on both image signals. By doing so, the objective is to obtain an image in which features of the observed sample are extracted using a simple configuration and image processing. Therefore, the scan modulation type observation display device of the present invention is a scan modulation type observation display device that displays the state of the sample to be observed by scanning the sample to be observed with charged particles formed in a probe shape, ultrasonic waves, or light waves. In the apparatus, there is provided a main scanning section that scans the sample to be observed with the probe, and a main scanning section that scans the sample to be observed using the probe; a modulation section that modulates at a high speed compared to a scanning speed; a signal detection section that detects a signal obtained by irradiating the sample to be observed with the probe; and a signal detection section that detects the signal based on a reference signal from the modulation section. a signal demodulation unit that extracts a non-modulated signal and a modulated signal from the signal detected by the signal demodulation unit; and a signal demodulation unit that extracts a non-modulated signal and a modulated signal from the signal detected by the signal demodulation unit; The present invention is characterized in that it includes an image signal generation section that generates a signal, and observes and displays the state of the sample to be observed based on the image signal generated by the image signal generation section.

(Example of the invention) The present invention will be explained in detail below based on the drawings.

FIG. 1 is a configuration diagram of one embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams illustrating an application example using the configuration of one embodiment of the present invention shown in FIG. 1.

In the figure, 1 is a sample to be observed, 2 is an electron gun, 2-1 is an electron source, 2-2 is a Wehnelt tube, 2-3 is an anode, 3 is a focusing lens, 4 is a main scanning coil, and 5 is a scintillation detection 6 is an amplifier, 7 is a demodulation circuit, 8 is a video amplifier, 9 is a display, 10
11 is a scanning electron microscope control section, 11 is a focus modulation coil, 12 is a sub-deflection section, 13 is a high-speed waveform generator, and 14 is a master oscillator.

FIG. 1 shows the configuration of one embodiment of the present invention, in which the position irradiated by the electron beam probe or the diameter of the electron beam probe is changed when scanning a sample 1 to be observed using a scanning electron microscope. Give an example.

First, image observation will be explained. Reference numeral 2 in the figure is an electron gun for emitting electron beam probes. The electron gun 2 is composed of an electron source 2-1, a Wehnelt tube 2-2, and an anode 2-3. Generally, the electron source 2-1 is connected to the anode 2-3.
A negative voltage (~25 KV) is applied from a high-voltage power supply not shown, and a negative bias voltage (~several hundred V) is applied to the Wehnelt tube 2-2 with respect to the filament, which is the electron source 2-1. ing. By employing this configuration, an electron beam probe having a minute cross-sectional area is emitted from the electron gun 2 downward in the drawing.

3 is a focusing lens for irradiating the sample 1 to be observed with the electron beam probe emitted from the electron gun in a reduced form.

Reference numeral 4 in the figure is a main scanning coil for scanning (X, Y) the electron beam probe irradiated onto the observed sample 1 by the converging lens 3.

In the figure, reference numeral 5 denotes a scintillation detector, which is used to detect and amplify secondary electrons generated when the electron beam probe irradiates the sample 1 to be observed. A high positive voltage (~several hundred V) is applied to the tip of the scintillation detector 5, and the secondary electrons generated from the observed sample 1 are pulled, focused, and accelerated. By colliding with the tip of the scintillation detector 5, the light is converted into light. The image signal converted into light is further photoelectrically converted and amplified by a photomultiplier or the like, and converted into an electric signal.

In the figure, 6 is an amplifier that converts the impedance of the signal detected by the scintillation detector 5 and adjusts the voltage level of the signal to prevent noise from entering when the image signal is sent to the next stage. This is to facilitate signal processing.

Reference numeral 7 in the figure is a demodulation circuit, which is used to demodulate an image signal when the electron beam probe irradiating the observed sample 1 is modulated, as will be described later.

Reference numeral 8 in the figure is a video amplifier, which is used to amplify the image signal that has undergone various signal processing in order to display the image signal.

Reference numeral 9 in the figure is a display for converting the image signal supplied from the video amplifier 8 into a video format that can be observed by humans.

In the figure, 10 is a scanning electron microscope control section,
It is used to perform various controls.

The operation when observing the sample 1 to be observed using the scanning electron microscope employing the above configuration will be briefly described.

The electron beam probe emitted from the electron gun 2 finely adjusts the magnitude of the DC current supplied to the focusing lens 3 by rotating a predetermined knob in the scanning electron microscope control unit 10, thereby detecting the sample to be observed. An image is formed on the surface of 1 in the form of a minute spot (several thousand to several tens of angstroms). Then, the minute spots are sequentially scanned by supplying sawtooth wave currents for scanning to the main scanning coils 4 (X, Y), respectively, thereby performing surface scanning.

The secondary electrons emitted from the observed sample 1 irradiated by the electron beam probe are detected, image width, and signal processing is performed,
The signal is supplied to, for example, a brightness modulation terminal of the display 9. A current synchronized with the sawtooth wave supplied to the main scanning coil 4 is supplied to the display 9, and a bright and dark image (secondary electron image) corresponding to the amount of secondary electrons emitted from the observed sample 1 is displayed. is obtained. The display magnification of the image is inversely proportional to the magnitude of the sawtooth wave current supplied to the main scanning coil 4; for example, when the current is decreased, the magnification increases, and when the current is increased, the magnification decreases.

Next, a configuration in which the electron beam probe irradiated onto the observed sample 1 is modulated at high speed will be described.

In the figure, reference numeral 11 denotes a focus modulation coil for rapidly modulating the diameter of the electron beam probe irradiated onto the sample 1 to be observed.

12 in the figure is a sub-deflector, and the main scanning coil 4
This is for scanning randomly at high speed, centering on the position of the electron beam probe irradiated onto the sample 1 to be observed, which is determined by the current supplied to the sample.

In the figure, 13 is a high-speed waveform generator for driving the focus modulation coil 11 and/or the sub-deflector 12 with a predetermined scanning signal at a higher speed than scanning by the main scanning coil 4. It is.

In the figure, 14 is a master oscillator. The focus modulation coil 1 is controlled by the high speed waveform generator 13.
1 and the sub-deflector 12 are driven by an extremely high frequency, it is not necessary to synchronize them. It is synchronized to an integral multiple of the horizontal scanning frequency.

The operation when the diameter of the electron beam probe irradiated onto the sample to be observed 1 is modulated at high speed will be explained using FIG.

In FIG. 2A, by finely adjusting the current flowing through the focusing lens 3, the electron beam probe is brought into focus on the sample 1 to be observed.
Then, the electron beam probe is modulated into the non-focus state shown in the drawing based on the current supplied from the high-speed waveform generator 13 to the focus modulation coil 11. In this way, by supplying or not supplying the rectangular wave current to the focus modulation coil 11, it is possible to arbitrarily select a focused point or a non-focused point.
The degree of defocusing can be set to any value suitable for extracting desired features of the observed sample 1 by changing the magnitude of the current supplied to the focus modulation coil 11. Secondary electrons emitted from the irradiated area in the focused or out-of-focus state are detected by the scintillation detector 5 as an image signal corresponding to, for example, one pixel.

FIG. 2B shows a modulation waveform signal, which is the waveform of the current supplied to the focus modulation coil 11. Amplitude value I ₀ of the modulated waveform signal consisting of the rectangular wave
As mentioned above, is the current value that determines the degree of defocus shown in FIG. be.

In Figure 2B, the output signal from the scintillation detector 5 is shown at the non-observation sample 1 with the electron beam probe diameter corresponding to each waveform of the modulated waveform signal.
This shows a signal obtained by amplifying the secondary electrons emitted when scanning. In the signal, "+" indicates addition integral,
This shows a state in which signals in a focused state are added by an integrating circuit having a predetermined time constant provided in the demodulation circuit 7. “-” indicates source calculation integral. The time constant of the integrating circuit is set to a value corresponding to the resolution in the horizontal scanning direction.

In this way, by performing addition integration or subtraction integration in synchronization with the current supplied to the focus modulation coil 11 by the demodulation circuit 7, the image signal in the out-of-focus state can be obtained from the image signal in the in-focus state shown in FIG. The image signal, that is, the so-called background signal is subtracted, and the unique signal that occurs only in the in-focus state is extracted in an emphasized form. The extracted image signal is displayed on the display 9 as described above. Further, it can also be stored in an image memory or the like not shown, if necessary.

The case where so-called "weighting" is performed by reducing the modulation time ratio will be explained using FIG.

In the out-of-focus state shown in FIG. 3A, the focus modulation coil 1
The magnitude of the rectangular wave current supplied to the circuit 1 is adjusted, and the time for supplying the current is shortened.

The modulated waveform signal shown in FIG. 3B shows the case where the modulation time is set to a duty of 50% or less. I in the figure. can be set arbitrarily.

The output signals of the scintillation detectors in FIG. 3B are signals obtained by imaging the secondary electrons detected by the scintillation detectors 5 in correspondence with the modulated waveform signals. By performing addition integration ("+" in the figure) or subtraction integration ("-" in the figure) of the amplified signal, a locally emphasized signal as shown by diagonal lines in Figure 3D is extracted, and the A waveform as shown in FIG. 3E can be obtained. That is, when the state is in the in-focus state (out-of-focus state as shown in FIG. 3A), a scintillation detector output signal in the "+"("-") state in FIG. 3B is obtained. One horizontal scan is shown as a solid line (dotted line) in FIG. 3C. By adding and integrating the signals and subtracting and integrating the signals, the third
A waveform is obtained by extracting the shaded part in Figure D.
A signal as shown in FIG. 3E is obtained. At this time, the dotted line 9 shown in FIG. 3D corresponds to a signal obtained by subtracting and integrating the signal shown by the dotted line 8 shown in FIG. 3C, and the duty of the modulated waveform signal shown in FIG. 3B is adjusted. This is because the amount of subtraction becomes too large,
This was done to avoid the formation of donut-shaped signals. As a result, it becomes possible to obtain the same result as equivalently reducing the electron beam diameter. In this way, by appropriately setting the "weighting" and "defocus amount" when subtracting and integrating the signal in the out-of-focus state from the signal in the in-focus state, so-called two-dimensional convolution can be easily performed. This can be done with a suitable device configuration.

Further, although the case where the observed sample 1 is irradiated with an electron beam probe has been described, the present invention is not limited to this, and the observed sample 1 may be irradiated with an ultrasonic wave, light wave, etc. probe. can also be done in the same way.

Furthermore, in the embodiments shown in FIGS. 2 and 3, the diameter of the electron beam probe irradiated onto the observed sample 1 was modulated to be large; however, the present invention is not limited to this; High-speed random scanning may be performed near the focused point and used in place of the non-focused signal shown in the figure to extract features from the non-observation sample 1.

Note that all electron beam paths must be kept in a vacuum. This is because the mean free path of an electron beam is extremely short in the atmosphere, and the beam is attenuated or scattered.

(Effects of the Invention) As explained above, according to the present invention, when scanning a sample to be observed with a probe, the scanning position, diameter, wavelength, etc. of the probe are rapidly modulated to remove the sample from the sample to be observed. Detects signals with modulation,
An unmodulated image signal and a modulated image signal are extracted from the detection signal, and a desired image is displayed on a display etc. based on both image signals. An image with extracted features can be obtained.
In particular, by weighting when obtaining a desired image based on both image signals, so-called two-dimensional convolution can be performed extremely quickly with a simple configuration. 2 like this
As a result of realizing dimensional convolution, it becomes possible to perform image background correction processing, Laplacian processing, resolution improvement processing, etc. in real time, which were conventionally achieved by offline methods, and has great practical significance.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of one embodiment of the present invention, and FIGS. 2 and 3 are explanatory diagrams illustrating an application example using the configuration of one embodiment of the present invention shown in FIG. 1. In the figure, 1 is a sample to be observed, 2 is an electron gun, 2-1 is an electron source, 2-2 is a Wehnelt tube, 2-3 is an anode, 3 is a focusing lens, 4 is a main scanning coil, and 5 is a scintillation detection 6 is an amplifier, 7 is a demodulation circuit, 8 is a video amplifier, 9 is a display, 10
11 is a scanning electron microscope control section, 11 is a focus modulation coil, 12 is a sub-deflection section, 13 is a high-speed waveform generator, and 14 is a master oscillator.

Claims (1)

[Claims] 1. In a scanning modulation type observation display device that displays the state of the observed sample by scanning the observed sample with probe-shaped charged particles, ultrasonic waves, or light waves, the observed sample is scanned by the probe. A main scanning section that scans, and at least one of the position, diameter, or wavelength of the probe when the main scanning section sequentially scans using a probe.
A modulation section that compares the scanning speed and modulates the sample to a high speed, a signal detection section that detects a signal obtained by irradiating the probe to the sample to be observed, and a signal detection section that detects a signal obtained by irradiating the sample to be observed with the probe; a signal demodulation unit that extracts a non-modulated signal and a modulated signal from the signal detected by the signal detection unit; and a signal demodulation unit that extracts a non-modulated signal and a modulated signal from the signal detected by the signal detection unit, and and an image signal generation section that generates a predetermined image signal, and the state of the observed sample is observed and displayed based on the image signal generated by the image signal generation section. Display device.