JP2023043500A - Charged particle beam device and image acquisition method - Google Patents

Abstract

To provide a charged particle beam device which can acquire an image that allows various information on a sample to be easily obtained.SOLUTION: A charged particle beam device according to the present invention comprises: an optical system for scanning a sample with a charged particle beam; an energy filter which selects a signal emitted from the sample with the energy; a detector which detects the signal selected by the energy filter; and a control unit which controls the energy filter. The control unit performs processing of acquiring an image of an observation area by scanning the observation area of the sample with the charged particle beam. In the processing of acquiring an image, a selection condition of the energy filter is the first selection condition when a first area in the observation area is scanned with the charged particle beam, and the selection condition of the energy filter is a second selection condition different from the first selection condition when a second area in the observation area is scanned with the charged particle beam.SELECTED DRAWING: Figure 6

Description

The present invention relates to a charged particle beam device and an image acquisition method.

A scanning electron microscope scans a sample with an electron probe formed by narrowing an electron beam, and acquires an image of the sample by detecting secondary electrons and reflected electrons emitted from the sample.

Secondary electrons are electrons that are excited from the atoms that make up the sample by inelastic scattering of electrons within the sample. Backscattered electrons are backscattered electrons in the process of scattering when the sample is irradiated, and have higher energy than secondary electrons. Therefore, the secondary electron image obtained by detecting the secondary electrons has a contrast that reflects the unevenness of the sample surface, and the backscattered electron image obtained by detecting the backscattered electrons reflects the difference in composition. good contrast is obtained.

In a scanning electron microscope with an energy filter, electrons are energy sorted by the energy filter and the sorted electrons can be detected by a detector. Therefore, images with various characteristics can be acquired with one detector.

For example, Patent Document 1 discloses a scanning electron microscope equipped with an energy filter for separating secondary electrons and backscattered electrons.

JP 2006-054094 A

As described above, the secondary electron image provides a contrast that reflects the unevenness of the sample surface, and the backscattered electron image provides a contrast that reflects the difference in composition. Therefore, acquiring both a secondary electron image and a backscattered electron image and comparing the two images is important in obtaining information about the sample.

One aspect of the charged particle beam device according to the present invention is
an optical system for scanning a sample with a charged particle beam;
an energy filter that sorts the signals emitted from the sample by energy;
a detector that detects the signal filtered by the energy filter;
a control unit that causes the optical system to scan an observation area of the sample with the charged particle beam to obtain an image of the observation area;
including
The observation area includes a first area and a second area,
The control unit
when the first region is scanned with the charged particle beam, the selection condition of the energy filter is set as the first selection condition;
When scanning the second area with the charged particle beam, the selection condition of the energy filter is set to a second selection condition different from the first selection condition.

In such a charged particle beam device, the image of the second area in the image of the observation area is obtained by detecting electrons with energy different from that of the image of the first area, so various information about the specimen can be easily obtained. can be obtained.

One aspect of the image acquisition method according to the present invention includes:
an optical system for scanning a sample with a charged particle beam;
an energy filter that sorts the signals emitted from the sample by energy;
a detector that detects the signal filtered by the energy filter;
An image acquisition method in a charged particle beam device comprising
scanning an observation region of the sample with the charged particle beam to obtain an image of the observation region;
The observation area includes a first area and a second area,
In the step of acquiring the image,
when the first region is scanned with the charged particle beam, the selection condition of the energy filter is set as the first selection condition;
When scanning the second area with the charged particle beam, the selection condition of the energy filter is set to a second selection condition different from the first selection condition.

In such an image acquisition method, since the image of the second region in the image of the observation region is obtained by detecting electrons with energy different from that of the image of the first region, various information about the sample can be easily obtained. Obtainable.

The figure which shows the structure of the scanning electron microscope which concerns on one Embodiment of this invention. The sample image when the voltage applied to the energy filter is set to V=+300 V and electrons are detected using the first detector. A sample image when the voltage applied to the energy filter is set to −1000 V and electrons are detected using the first detector. FIG. 4 is a diagram for explaining an image acquisition method in a scanning electron microscope; Enlarged view of the second region. A sample image obtained by changing the applied voltage of the energy filter in a part of the observation area. 4 is a flowchart showing an example of image acquisition processing of the control unit; FIG. 10 is a diagram showing first to N-th images obtained by detecting electrons with different energies; 4 is a flowchart showing an example of image acquisition processing of the control unit; FIG. 10 is a diagram showing display examples of the first image to the Nth image; 4 is a flowchart showing an example of image acquisition processing of the control unit;

Preferred embodiments of the present invention will be described in detail below with reference to the drawings. It should be noted that the embodiments described below do not unduly limit the scope of the invention described in the claims. Moreover, not all the configurations described below are essential constituent elements of the present invention.

Further, hereinafter, a scanning electron microscope that observes a sample by irradiating an electron beam will be described as an example of the charged particle beam device according to the present invention. It may be an apparatus that observes a sample by irradiating it with a charged particle beam (ion or the like).

1. Scanning Electron Microscope First, a scanning electron microscope according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing the configuration of a scanning electron microscope 100 according to one embodiment of the invention.

The scanning electron microscope 100 is an apparatus that scans a sample S with an electron probe, detects secondary electrons and reflected electrons emitted from the sample S, and acquires an image of the sample.

The scanning electron microscope 100 includes an electron gun 10, an optical system 20, a sample stage 30, a first detector 40, a second detector 42, an energy filter 50, a control section 60, an operation section 70, A display unit 72 and a storage unit 74 are included.

The electron gun 10 emits electron beams. The electron gun 10, for example, accelerates electrons emitted from the cathode at the anode and emits an electron beam.

The optical system 20 narrows the electron beam emitted from the electron gun 10 to form an electron probe, and scans the sample S with the electron probe. Optical system 20 includes condenser lens 22 , objective lens 24 , and scanning coil 26 .

A condenser lens 22 converges the electron beam emitted from the electron gun 10 . The diameter of the electron probe and probe current can be controlled by the condenser lens 22 . The objective lens 24 converges the electron beam on the sample S to form an electron probe. The scanning coil 26 two-dimensionally deflects the electron beam. An electron probe is formed by narrowing the electron beam with the condenser lens 22 and the objective lens 24 , and the sample S can be scanned with the electron probe by deflecting the electron beam with the scanning coil 26 .

Although not shown, the optical system 20 includes an astigmatism correction device for correcting astigmatism. Also, the optical system 20 may include lenses other than the condenser lens 22, the objective lens 24, and the scanning coil 26, and optical elements such as a diaphragm.

The first detector 40 is arranged above the objective lens 24 . A first detector 40 is positioned between the energy filter 50 and the condenser lens 22 .

A second detector 42 is arranged above the objective lens 24 . A second detector 42 is positioned between the energy filter 50 and the objective lens 24 .

In the scanning electron microscope 100, electrons emitted from the sample S are sucked into the objective lens 24 by the stray magnetic field of the objective lens 24, constrained by the magnetic field of the objective lens 24, and guided upward along the optical axis. Therefore, the first detector 40 and the second detector 42 are arranged above the objective lens 24 . The first detector 40 and the second detector 42 detect electrons emitted from the sample S. FIG.

An energy filter 50 is positioned between the first detector 40 and the second detector 42 . The energy filter 50 selects electrons emitted from the sample S by energy. The energy filter 50 can, for example, transmit or block only secondary electrons having a specific energy or only reflected electrons. The energy filter 50 is composed of a plurality of electrodes. The energy filter 50 can sort electrons incident on the first detector 40 and electrons incident on the second detector 42 according to the applied voltage.

The operation unit 70 is used by a user to input operation information, and outputs the input operation information to the control unit 60 . The functions of the operation unit 70 can be implemented by input devices such as a keyboard, mouse, buttons, touch panel, and touch pad.

The display unit 72 displays images generated by the control unit 60 . The display unit 72 displays an image acquired by the scanning electron microscope 100 and a GUI (Graphical User Interface). The function of the display unit 72 can be realized by an LCD, a CRT, a touch panel that also functions as the operation unit 70, or the like.

The storage unit 74 stores programs and various data for performing various controls. The storage unit 74 also functions as a work area for the control unit 60 . The function of the storage unit 74 can be realized by a hard disk, RAM (Random Access Memory), or the like.

A controller 60 controls the electron gun 10 , optical system 20 , sample stage 30 , first detector 40 , second detector 42 and energy filter 50 .

The control unit 60 controls a high-voltage power supply 110 that supplies acceleration voltage to the electron gun 10 . Thereby, the acceleration voltage for accelerating electrons can be controlled. The controller 60 controls the condenser lens 22 via the condenser lens control circuit 122 .

The controller 60 controls the scan coil 26 via the scan coil control circuit 126 . The scanning coil control circuit 126 , for example, generates scanning signals and supplies the scanning signals to the scanning coils 26 . Thereby, the sample S can be scanned by the electron probe. The control unit 60 also synchronizes the detection signal output from the first detector 40 with the scanning signal to obtain a sample image. Similarly, the controller 60 synchronizes the detection signal output from the second detector 42 with the scanning signal to obtain a sample image.

The control section 60 controls the objective lens 24 via the objective lens control circuit 124 . This allows focus to be controlled.

The controller 60 controls the energy filter 50 via the energy filter control circuit 150 . The energy filter control circuit 150 controls the voltage applied to the energy filter 50 based on the control signal including information on the applied voltage from the control section 60 .

The functions of the control unit 60 can be realized by executing a program by a processor such as a CPU (Central Processing Unit).

2. Operation 2.1. First Operation Example (1) Image Acquisition Method In the scanning electron microscope 100, electrons detected by the first detector 40 can be sorted by energy by changing the sorting conditions of the energy filter 50. FIG. By changing the voltage applied to the energy filter 50, the sorting conditions can be changed.

FIG. 2 is a sample image when electrons are detected using the first detector 40 with the voltage applied to the energy filter 50 set to V=+300V. FIG. 3 is an image of a sample when electrons are detected using the first detector 40 with the voltage applied to the energy filter 50 set to −1000V. The sample S was a foreign substance on a nickel mesh, and the incident voltage was set at 1 kV.

When the applied voltage of the energy filter 50 is set to +300 V, mainly secondary electrons enter the first detector 40 . Therefore, in the sample image shown in FIG. 2, the contrast mainly reflecting the unevenness of the sample S is obtained. On the other hand, when the voltage applied to the energy filter 50 is set to −1000 V, mainly reflected electrons enter the first detector 40 . Therefore, in the sample image shown in FIG. 3, the contrast mainly reflecting the composition is obtained.

In the scanning electron microscope 100, when scanning the observation area of the sample S with the electron probe to acquire an image of the observation area, the voltage applied to the energy filter 50 can be changed in the area specified by the user.

FIG. 4 is a diagram for explaining an image acquisition method in the scanning electron microscope 100. FIG. Arrows shown in FIG. 4 indicate trajectories of the electron probe on the sample S. FIG. FIG. 4 shows an X-axis and a Y-axis as two axes orthogonal to each other.

As shown in FIG. 4, in the scanning electron microscope 100, an observation area A of the sample S is raster-scanned by an electron probe. That is, the observation area A is scanned by repeatedly moving the electron probe in the X direction to draw the scanning line L in the X direction and moving the position of drawing the scanning line L in the Y direction.

For example, the user designates the second area A2 in which the voltage applied to the energy filter 50 is changed from within the observation area A via the operation unit 70 . As a result, the observation area A is divided into a first area A1 excluding the specified second area A2 and a second area A2. Here, the second area A2 is surrounded by the first area A1.

In this case, when scanning the first area A1 with the electron probe, the selection condition of the energy filter 50 is set as the first selection condition, and when scanning the second area A2 with the electron probe, the selection condition of the energy filter 50 is set as the first selection condition. A second sorting condition different from the first sorting condition is used. That is, when the electron probe scans the first area A1, the voltage applied to the energy filter 50 is the first voltage, and when the electron probe scans the second area A2, the voltage applied to the energy filter 50 is the first voltage. are different second voltages. As a result, in the image I2 of the observation area A, the image of the second area A2 can be an image obtained by electrons of energy different from that of the image of the first area A1. Therefore, different characteristics of the sample S are emphasized in the area B1 corresponding to the first area A1 and the area B2 corresponding to the second area A2 of the image I2.

When the voltage applied to the energy filter 50 is changed, optical conditions such as electron beam axis, focus, astigmatism, and brightness are shifted. Therefore, in the scanning electron microscope 100, the optical system 20 is set to the first optical condition when the electron probe scans the first area A1, and the optical system 20 is set to the first optical condition when the electron probe scans the second area A2. A second optical condition different from the condition is set. That is, when the electron probe scans the first area A1, the voltage applied to the energy filter 50 is set to the first voltage, and the optical conditions of the optical system 20 are set to the first optical conditions. When the electron probe scans the second area A2, the voltage applied to the energy filter 50 is set to the second voltage, and the optical conditions of the optical system 20 are set to the second optical conditions.

Here, the optical conditions include electron beam axis conditions, focus conditions, astigmatism conditions, and brightness conditions. The first optical condition is an optical condition in which the electron beam axis, focus, astigmatism, brightness, etc. are adjusted when the voltage applied to the energy filter 50 is the first voltage. The second optical condition is an optical condition in which the electron beam axis, focus, astigmatism, brightness, etc. are adjusted when the voltage applied to the energy filter 50 is the second voltage.

Information on the voltage applied to the energy filter 50 and information on the optical conditions are pre-stored in the storage unit 74 . Information on the voltage applied to the energy filter 50 and the optical conditions of the optical system 20 are associated and stored in the storage unit 74 .

Adjustments for electron beam axis, focus, astigmatism, and brightness can be made using the automatic adjustment function. Therefore, the optical conditions according to the voltage applied to the energy filter 50 are
It can be obtained using the automatic adjustment function. For example, a first voltage is applied to the energy filter 50 and the optical system 20 is adjusted using the automatic axis adjustment function, automatic focusing (autofocus) function, automatic astigmatism correction function, and automatic contrast brightness adjustment function. As a result, information on the first optical condition can be obtained.

FIG. 5 is an enlarged view of the second area A2.

The scanning line L straddles the first area A1 and the second area A2. When the electron probe moves from the first area A1 to the second area A2, the voltage applied to the energy filter 50 and the optical conditions of the optical system 20 are changed.

For example, when the electron probe moves from the measurement point P1 in the first area A1 to the measurement point P2 in the second area A2 adjacent to the measurement point P1 on the same scanning line L, scanning of the observation area A by the electron probe stops. , the voltage applied to the energy filter 50 is changed from the first voltage to the second voltage, and the optical condition of the optical system 20 is changed from the first optical condition to the second optical condition.

When the electron probe moves from the measurement point P3 in the second area A2 to the measurement point P4 in the first area A1 adjacent to the measurement point P3, scanning of the observation area A by the electron probe stops, and the voltage applied to the energy filter 50 is reduced to the first area. The second voltage is changed to the first voltage, and the optical condition of the optical system 20 is changed from the second optical condition to the first optical condition.

Thus, in the scanning electron microscope 100, when the electron probe moves from the first area A1 to the second area A2 and when the electron probe moves from the second area A2 to the first area A1, the energy filter 50 A process of changing the applied voltage and a process of changing the optical conditions of the optical system 20 are performed.

FIG. 6 shows sample images acquired by changing the voltage applied to the energy filter 50 in a partial region within the observation region.

The area within the frame shown in FIG. 6 is an image mainly obtained by detecting secondary electrons, and the contrast mainly reflecting the composition is obtained. The area outside the frame is an image obtained mainly by detecting backscattered electrons, and a contrast mainly reflecting the unevenness of the sample S is obtained. In this way, an image with contrast reflecting the composition of the sample S is obtained in a part of the image in which the contrast reflecting the unevenness of the sample S is obtained. can be obtained.

(2) Processing FIG. 7 is a flow chart showing an example of image acquisition processing of the control unit 60 .

The control unit 60 determines whether or not the user has issued an instruction to start shooting (S100). A GUI is displayed on the display unit 72, and the user operates the GUI via the operation unit 70 to specify the observation area A, specify the second area A2, instruct the start of imaging, and set the applied voltage. etc. The control unit 60 determines that the user has issued an instruction to start shooting when the user presses the shooting start button after specifying the observation area A and the second area A2 on the GUI.

When the control unit 60 determines that the user has issued an instruction to start shooting (Yes in S100), the control unit 60 applies the first voltage to the energy filter 50 (S102). By applying the first voltage to the energy filter 50, secondary electrons are sorted out in the energy filter 50, for example.

The control unit 60 reads information about the applied voltage set by the user from the table stored in the storage unit 74, and controls the energy filter control circuit 150 so that the set applied voltage is applied to the energy filter 50. The table stores, for example, the voltage applied to the energy filter 50 and the energy band of electrons detected by the first detector 40 when the applied voltage is applied to the energy filter 50 in association with each other.

Next, the controller 60 adjusts the optical system 20 (S104). The controller 60 adjusts the optical system 20 using an automatic axis adjustment function, an automatic focusing function, an automatic astigmatism correction function, and an automatic contrast brightness adjustment function. Then, the control unit 60 stores the optical conditions (first optical conditions) of the optical system 20 after automatic adjustment in the storage unit 74 . The storage unit 74 stores in advance the information of the optical conditions when the first voltage is applied to the energy filter 50, and the control unit 60 reads out the optical conditions and controls the optical system 20. may

By performing processing S102 and processing S104 by the control unit 60, the first voltage is applied to the energy filter 50, and the optical condition of the optical system 20 becomes the first optical condition.

The controller 60 causes the optical system 20 to start scanning the observation area A with the electronic probe (S106). As a result, raster scanning of the observation area A shown in FIG. 4 is started.

When the electron probe starts scanning the observation area A, electrons are emitted from the sample S, the energy of the emitted electrons is selected by the energy filter 50, and the selected secondary electrons are detected by the first detector 40. be. The control unit 60 causes the storage unit 74 to store the electron detection result (electron intensity) in the first detector 40 and the position information of the electron probe based on the scanning signal.

When the electron probe starts scanning the observation area A, the controller 60 determines whether or not to change the voltage applied to the energy filter 50 (S108). The control unit 60 determines to change the applied voltage when the electron probe moves from the first area A1 to the second area A2 or when the electron probe moves from the second area A2 to the first area A1.

When the controller 60 determines not to change the applied voltage (No in S108), it determines whether or not the entire observation area A has been scanned (S110).

If the control unit 60 determines that the entire observation area A has not been scanned (No in S110), the control unit 60 continues scanning the observation area A with the electronic probe.

When the control unit 60 determines that the electron probe moves from the measurement point P1 to the measurement point P2 to change the applied voltage (Yes in S108), the control unit 60 stops scanning the observation area A by the electron probe at the measurement point P2, and the energy A second voltage is applied to the filter 50 (S102). By applying the second voltage to the energy filter 50, for example, the energy filter 50 sorts out reflected electrons.

Next, the control unit 60 adjusts the optical system 20 using the automatic axis adjustment function, automatic focusing function, automatic astigmatism correction function, and automatic contrast brightness adjustment function (S104). Then, the control unit 60 stores the optical conditions (second optical conditions) of the optical system 20 after automatic adjustment in the storage unit 74 .

By the control unit 60 performing processing S102 and processing S104, the second voltage is applied to the energy filter 50, and the optical condition of the optical system 20 becomes the second optical condition.

The controller 60 causes the optical system 20 to resume scanning the observation area A with the electronic probe (S106). Thereby, scanning of the second area A2 is started.

The control unit 60 repeats processing S102, processing S104, processing S106, processing S108, and processing S110 until the entire observation area A is scanned, and scans the observation area A with the electronic probe. Note that after the first optical condition and the second optical condition are stored in the storage unit 74, in the process S104, the first optical condition and the second optical condition stored in the storage unit 74 are adjusted without using the automatic adjustment function. is used to adjust the optical system 20 .

When the control unit 60 determines that the entire observation area A has been scanned (Yes in S110), the image acquisition process ends. As a result, an image I2 shown in FIG. 4 can be obtained. The control unit 60 causes the display unit 72 to display the acquired image I2.

2.2. Second Operation Example (1) Image Acquisition Method The scanning electron microscope 100 can automatically acquire a plurality of images obtained by detecting electrons with different energies by changing the voltage applied to the energy filter 50 .

FIG. 8 is a diagram showing the first image I2-1 to the N-th image I2-N obtained by detecting electrons with different energies. However, N is an integer of 2 or more.

As shown in FIG. 8, the scanning electron microscope 100 can automatically acquire the first image I2-1 to the Nth image I2-N. The first image I2-1 to the N-th image I2-N are, for example, images obtained by gradually increasing the voltage applied to the energy filter 50. FIG. That is, the voltage applied to the energy filter 50 when acquiring the second image I2-2 is higher than the voltage applied to the energy filter 50 when acquiring the first image I2-1, and the third image I2-3 is acquired. The voltage applied to the energy filter 50 at this time is greater than the voltage applied to the energy filter 50 when the second image I2-2 was acquired.

The voltage applied to the energy filter 50 when acquiring each image can be arbitrarily set. For example, the control unit 60 may determine the applied voltage when acquiring each image from the range of the applied voltage and the number N of image acquisitions.

Since the scanning electron microscope 100 can automatically acquire the first image I2-1 to the N-th image I2-N, for example, it is possible to easily determine the applied voltage for obtaining an image with desired characteristics.

(2) Processing FIG. 9 is a flow chart showing an example of image acquisition processing of the control unit 60 .

The control unit 60 determines whether or not the user has given an instruction to start shooting (S200). A GUI is displayed on the display unit 72, and by operating the GUI via the operation unit 70, the user can specify the observation area A, instruct the start of imaging, set the applied voltage, and the like. The control unit 60 determines that the user has issued an instruction to start imaging when the imaging start button is pressed after the operation of setting the observation area A and the applied voltage of the energy filter 50 in each image on the GUI. Here, it is assumed that the voltage applied to the energy filter 50 when acquiring the Mth image (M is a number from 1 to N) is set to the Mth voltage.

When the control unit 60 determines that the user has issued an instruction to start shooting (Yes in S200), the control unit 60 applies the first voltage to the energy filter 50 (S202). The control unit 60 reads the first voltage, which is information about the applied voltage when acquiring the first image I2-1, from the storage unit 74, and controls the energy filter control circuit so that the first voltage is applied to the energy filter 50. control 150;

Next, the controller 60 adjusts the optical system 20 (S204). The controller 60 adjusts the optical system 20 using an automatic axis adjustment function, an automatic focusing function, an automatic astigmatism correction function, and an automatic contrast brightness adjustment function. The storage unit 74 stores in advance the information of the first optical condition, which is the optical condition when the first voltage is applied to the energy filter 50, and the control unit 60 stores the information of the first optical condition. It may be read out to control the optical system 20 .

Next, the control unit 60 causes the optical system 20 to scan the observation area A with the electronic probe to acquire the first image I2-1 (S206). The control unit 60 causes the storage unit 74 to store the acquired image data of the first image I2-1. After acquiring the first image I2-1, the control unit 60 determines whether or not the Nth image I2-N has been acquired, that is, whether or not M=N (S208).

When the control unit 60 determines that M is not equal to N (No in S208), it sets M=M+1, returns to the process S202, applies the second voltage to the energy filter 50 (S202), The condition is set to the second optical condition (S204), and the second image is acquired (S206).

The control unit 60 repeats processing S202, processing S204, processing S206, and processing S208 until it is determined that M=N.

When determining that M=N (Yes in S210), the control unit 60 ends the image acquisition process. As a result, the first image I2-1 to the Nth image I2-N shown in FIG. 8 can be obtained.

3. Effect In the scanning electron microscope 100, the control unit 60 causes the optical system 20 to scan the observation area A of the sample S with the electron probe, acquires an image of the observation area A, and scans the first area A1 with the electron probe. When scanning the second area A2 with the electron probe, the selection condition of the energy filter 50 is the second selection condition different from the first selection condition. condition.

Therefore, in the scanning electron microscope 100, the image of the second area A2 in the image of the observation area is obtained with electrons of energy different from that of the image of the first area A1. Obtainable. For example, as shown in FIG. 6, information on the unevenness of the sample S and information on the composition of the sample S can be obtained in one image.

For example, when acquiring both a secondary electron image and a backscattered electron image and comparing the contrast of the two images, both the secondary electron image and the backscattered electron image must be acquired, which takes time. end up On the other hand, in the scanning electron microscope 100, one image includes a secondary electron image and a backscattered electron image, so the measurement time can be shortened. Furthermore, since a single image includes a secondary electron image and a backscattered electron image, comparison is easier than in the case of acquiring a secondary electron image and a backscattered electron image and comparing the two images.

In the scanning electron microscope 100, one detector (the first detector 40) can detect electrons of different energies and acquire an image. , the equipment cost can be reduced.

In the scanning electron microscope 100, the controller 60 sets the optical condition of the optical system 20 to the first optical condition when scanning the first area A1 with the electron probe, and scans the second area A2 with the electron probe. When there is, the optical condition of the optical system 20 is set to the second optical condition different from the first optical condition. Here, when the voltage applied to the energy filter 50 is switched, the optical conditions such as the electron beam axis, focus, astigmatism, and brightness are shifted. When the control unit 60 scans the first area A1 with the electronic probe, the optical condition of the optical system 20 is the first optical condition, and when the electronic probe scans the second area A2, the optical system By setting the optical condition of 20 as the second optical condition, it is possible to reduce the deviation of the optical condition even if the applied voltage is switched.

In the scanning electron microscope 100, the controller 60 causes the optical system 20 to raster scan the observation area A. FIG. Raster scanning is performed by repeatedly drawing scanning lines L in the X direction with an electronic probe and moving the position at which the scanning lines L are drawn in the Y direction perpendicular to the X direction. It straddles the area A1 and the second area A2. Thus, in the scanning electron microscope 100, by raster scanning the observation area A, an image of the first area A1 and an image of the second area A2 can be obtained.

4. Modification 4.1. First Modification In the embodiment described above, the voltage applied to the energy filter 50 and the energy band of electrons detected by the first detector 40 when the applied voltage is applied to the energy filter 50 are associated and stored. A table was used to determine the applied voltage. On the other hand, using a polynomial that shows the relationship between the applied voltage of the energy filter 50 and the energy band of electrons detected by the first detector 40 when the applied voltage is applied to the energy filter 50, the applied Voltage may be determined.

4.2. Second Modification FIG. 10 is a diagram showing a display example of the first image I2-1 to the Nth image I2-N.

In the above-described second operation example, the control unit 60 may list the first image I2-1 to the Nth image I2-N on the display unit 72 as shown in FIG. At this time, the control unit 60 may display the applied voltage of the energy filter 50 when each image is acquired on the display unit 72 . As a result, even if the applied voltage for obtaining an image with desired characteristics is unknown, the user can see the first image I2-1 to the N-th image I2-N displayed in a list and find the optimum applied voltage. can be determined.

4.3. Third Modification As shown in FIG. 4, the controller 60 causes the optical system 20 to raster scan the observation area A. FIG. At this time, the control unit 60 sets the scanning speed of the electron probe to the first speed when scanning the first area A1 with the electron probe, and sets the scanning speed of the electron probe to the first speed when scanning the second area A2 with the electron probe. Let the scanning speed of the probe be a second speed different from the first speed.

When the voltage applied to the energy filter 50 is changed, the amount of signal obtained also changes. Therefore, the control unit 60 controls the scanning speed when scanning the first area A1 and the scanning speed when scanning the second area A2 so that the amount of signal per unit area is equal between the first area A1 and the second area A2. to control the scanning speed of

For example, when the user sets the scanning speed when scanning the first area A1 to the first speed, the control unit 60 monitors the signal amount in the first area A1 and the signal amount in the second area A2, Based on the amount of signal in the first area A1 and the amount of signal in the second area A2, the second speed, which is the scanning speed when scanning the second area A2, is determined. As a result, the signal amount per unit area can be made equal between the first area A1 and the second area A2.

Further, the control unit 60 may determine the second scanning speed based on the signal amount at the measurement point P1 in the first area A1 and the signal amount at the measurement point P2 in the second area A2 shown in FIG. . As a result, the signal amount per unit area can be made equal between the first area A1 and the second area A2.

The user may set the scanning speed for scanning the first area A1 and the scanning speed for scanning the second area A2 to arbitrary speeds.

4.4. Fourth Modification As described above, when the electron probe moves from the first area A1 to the second area A2 and when the electron probe moves from the second area A2 to the first area A1, the control unit 60 The voltage applied to the energy filter 50 is changed. Here, when the voltage applied to the energy filter 50 is changed, it may take time until the voltage applied to the energy filter 50 is stabilized at the set voltage. Therefore, after changing the voltage applied to the energy filter 50, the controller 60 stops scanning the observation area A with the electron probe for a predetermined time. The control unit 60 restarts the scanning of the observation area A after stopping the scanning of the observation area A for a predetermined time. This allows the energy filter 50 to operate stably.

For example, the control unit 60 stops scanning the observation area A with the electron probe at the measurement point P2 of the second area A2 shown in FIG. After changing the voltage applied to the energy filter 50, the controller 60 stops scanning the observation area A for a predetermined time. After a predetermined time has elapsed, the control unit 60 resumes scanning the observation area A from the measurement point P2.

4.5. Fifth Modification As described above, the controller 60 sets the voltage applied to the energy filter 50 to the first voltage when scanning the first area A1 with the electron probe, and sets the voltage applied to the energy filter 50 to the first voltage when scanning the second area A2 with the electron probe. The voltage applied to the energy filter 50 was the second voltage. Further, the control unit 60 sets the acceleration voltage to the first acceleration voltage when scanning the first area A1 with the electron probe, and sets the acceleration voltage to a second acceleration voltage different from the first acceleration voltage when scanning the second area A2 with the electron probe. 2 accelerating voltage. Information on different depths of the sample S can be obtained by changing the acceleration voltage.

FIG. 11 is a flowchart showing an example of image acquisition processing of the control unit 60. As shown in FIG.

The image acquisition process shown in FIG. 11 differs from the image processing method shown in FIG. 7 in that the process S103 of applying an acceleration voltage is performed after the process S102 of applying a voltage to the energy filter 50 . Differences from the image processing method shown in FIG. 7 will be described below, and descriptions of the same points will be omitted.

After step S102 of applying voltage to the energy filter 50, the control unit 60 controls the high-voltage power supply 110 so that a predetermined acceleration voltage is applied to the electron gun 10 (S103). The control unit 60 sets the acceleration voltage to the first acceleration voltage when scanning the first area A1 with the electron probe, and sets the acceleration voltage to the second acceleration voltage when scanning the second area A2 with the electron probe. voltage.

In the scanning electron microscope 100, in the image acquisition process, the controller 60 sets the acceleration voltage to the first acceleration voltage when the electron probe is scanning the first area A1, and scans the second area A2 with the electron probe. When there is, the acceleration voltage is set to a second acceleration voltage different from the first acceleration voltage. Therefore, in the scanning electron microscope 100, since images with different information in the depth direction are displayed in one image, the information in the depth direction of the sample S can be easily obtained.

4.6. Sixth Modification As described above, in the scanning electron microscope 100, when the electron probe moves from the first area A1 to the second area A2 and when the electron probe moves from the second area A2 to the first area A1, , the scanning of the electron probe is stopped in order to change the applied voltage of the energy filter 50 . Therefore, for example, the update speed of the image displayed on the display unit 72 is slower than when the voltage applied to the energy filter 50 is not changed in the second area A2.

Therefore, the image of the observation area A displayed on the display unit 72 remains the previous image until the observation area A is scanned and the image is updated. The image of the observation area A may be updated for each area where the sample S is scanned by the electron probe, or the entire image may be updated after the entire observation area A is scanned.

4.7. Seventh Modification In the above embodiment, the observation area A includes two areas (the first area A1 and the second area A2) in which images are obtained under different conditions of applied voltages to the energy filter 50. As described above, three or more areas in which images are obtained under different conditions of applied voltages to the energy filter 50 may be provided in the observation area A. FIG. Accordingly, various information on the sample S can be obtained.

It should be noted that the above-described embodiments and modifications are examples, and the present invention is not limited to these. For example, each embodiment and each modification can be combined as appropriate.

The present invention is not limited to the above-described embodiments, and various modifications are possible. For example, the present invention includes configurations that are substantially the same as the configurations described in the embodiments. "Substantially the same configuration" means, for example, a configuration having the same function, method, and result, or a configuration having the same purpose and effect. Moreover, the present invention includes configurations in which non-essential portions of the configurations described in the embodiments are replaced. In addition, the present invention includes a configuration that achieves the same effects or achieves the same purpose as the configurations described in the embodiments. In addition, the present invention includes configurations obtained by adding known techniques to the configurations described in the embodiments.

DESCRIPTION OF SYMBOLS 10... Electron gun, 20... Optical system, 22... Condenser lens, 24... Objective lens, 26... Scanning coil, 30... Sample stage, 40... First detector, 42... Second detector, 50... Energy filter, 60 100 Scanning electron microscope 110 High voltage power supply 122 Condenser lens control circuit 124 Objective lens control circuit 126 Scanning coil control circuit , 150 energy filter control circuit

Claims (9)

an optical system for scanning a sample with a charged particle beam;
an energy filter that sorts the signals emitted from the sample by energy;
a detector that detects the signal filtered by the energy filter;
a control unit that causes the optical system to scan an observation area of the sample with the charged particle beam to obtain an image of the observation area;
including
The observation area includes a first area and a second area,
The control unit
when the first region is scanned with the charged particle beam, the selection condition of the energy filter is set as the first selection condition;
A charged particle beam device, wherein the selection condition of the energy filter is set to a second selection condition different from the first selection condition when the second region is scanned with the charged particle beam. In claim 1,
The control unit
when the first region is scanned with the charged particle beam, the optical condition of the optical system is set to the first optical condition;
A charged particle beam apparatus, wherein the optical condition of the optical system is set to a second optical condition different from the first optical condition when scanning the second region with the charged particle beam. In claim 1 or 2,
The control unit
when the first region is scanned with the charged particle beam, the scanning speed of the charged particle beam is set to a first speed;
A charged particle beam device, wherein a scanning speed of the charged particle beam is set to a second speed different from the first speed when the second region is scanned with the charged particle beam. In any one of claims 1 to 3,
The control unit
When scanning the first region with the charged particle beam, the acceleration voltage is set to the first acceleration voltage,
A charged particle beam device, wherein an acceleration voltage is set to a second acceleration voltage different from the first acceleration voltage when scanning the second region with the charged particle beam. In any one of claims 1 to 4,
The charged particle beam apparatus, wherein the controller causes the optical system to stop scanning the observation region with the charged particle beam for a predetermined time when switching from the first selection condition to the second selection condition. In any one of claims 1 to 5,
The charged particle beam device, wherein the second region is surrounded by the first region. In any one of claims 1 to 6,
The control unit causes the optical system to raster scan the observation area,
The raster scan is performed by repeatedly drawing a scanning line in a first direction with the charged particle beam and moving the position of drawing the scanning line in a second direction perpendicular to the first direction,
The charged particle beam device, wherein the scanning line straddles the first area and the second area. In any one of claims 1 to 7,
A charged particle beam apparatus, comprising an operation unit for designating the second area in the observation area. an optical system for scanning a sample with a charged particle beam;
an energy filter that sorts the signals emitted from the sample by energy;
a detector that detects the signal filtered by the energy filter;
An image acquisition method in a charged particle beam device comprising
scanning an observation region of the sample with the charged particle beam to obtain an image of the observation region;
The observation area includes a first area and a second area,
In the step of acquiring the image,
when the first region is scanned with the charged particle beam, the selection condition of the energy filter is set as the first selection condition;
The image acquiring method, wherein the selection condition of the energy filter is set to a second selection condition different from the first selection condition when the second region is scanned with the charged particle beam.

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