JPH0765775A - Detector of charged-corpuscular beam device - Google Patents

Abstract

PURPOSE:To obtain an image having a three-dimemsional feeling including the uneven surface of a sample, by grasping a reflected electron near the electron beam so as to obtain a good quality of composition image of the sample surface, in the case of a sample having a plain surface, while grasping the reflected electron discharged from the periphery of a reflected electron detector so as to obtain an image having a three-dimensional feeling including the uneven surface of the sample, in the case of a normal sample having an uneven surface. CONSTITUTION:A detector 10 of a charged corpuscular beam device is formed of at least two or more circular plate bodies 12 to 14, and at least two or more detecting elements 11 are provided to each circular plate body 12 to 14. And each detecting element 11 has an independent signal amplifier 20, and the output from the signal amplifier 20 is fed to a signal adder and a signal subtructor, and the signal added or subtracted by the adder or the subtractor is output to an image displayed means selectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a detector of a charged particle beam apparatus having a backscattered electron detector for effectively detecting backscattered electrons in an electron beam apparatus such as an electron microscope.

[0002]

2. Description of the Related Art A conventional scanning electron microscope equipped with a backscattered electron detector is shown in FIG. A backscattered electron detector 3 is provided between the sample 1 and the objective lens 2.
Is arranged, the electron beam 4 is two-dimensionally scanned and irradiated on the plane of the sample 1, and the backscattered electrons obtained from the sample 1 are detected by the backscattered electron detector 3 arranged above the sample 1, The sample image is displayed using the detection signal.

The backscattered electron detector 3 in this case has a disk shape as shown in FIG. 5, and has a hole 5 having a diameter of about 3 mm at the center thereof for passing an electron beam for irradiating the sample. Around the periphery, semiconductor detection elements 3a, 3b, etc., which are divided into two as shown in FIG. 5A or divided into four as shown in FIG. Detects electrons. The detection elements divided into a plurality of parts are connected to independent signal amplifiers 6, respectively, and by adding or subtracting the respective signals, the result is switched by the selection switch 7 and displayed as image information.

The semiconductor detecting elements 3a, 3b ... Of the backscattered electron detector 3 cannot be made larger than a certain size due to the restrictions in manufacturing the elements, and if the shape is large, the response speed is lowered. Because it comes, its size is limited,
A diameter of 20 mm to 25 mm is a general size.

Consider backscattered electrons that can be detected using such a backscattered electron detector 3. As shown in FIG.
The half-vertical angle of the cone formed by the electron beam irradiation point 8 of the sample 1 and the hole 5 of the backscattered electron detector 3 with the distance d between the sample 1 and the detection elements 3a, 3b. Is θ ₁ and the half apex angle of the cone formed by the electron beam irradiation point 8 of the sample 1 and the outer periphery of the backscattered electron detector 3 is θ ₂ , the reflection emitted from the electron beam irradiation point 8 of the sample 1 Electron backscattered electron detector 3
The area detected by is an inverted conical area whose angle with the irradiation electron beam 4 is designated by the angle (θ ₂ −θ ₁ ).
That is, the inside of the angle θ _{1 and} the outside of the angle θ ₂ are the backscattered electron detector 3
This is an area that cannot be detected by.

The area specified by the angle (θ ₂ −θ ₁ ) is
It is changed by increasing or decreasing the distance d between the sample 1 and the detecting elements 3a, 3b .... That is, when the distance d is reduced, the angle θ ₂ formed on the outer peripheral portion of the backscattered electron detector 3 increases, but at the same time, the angle θ ₁ also increases and the signal electrons near the irradiation electron beam 4 are lost. . On the other hand, when the distance d is increased, the angle θ ₁ is decreased and the detection amount of the signal electrons near the irradiation electron beam 4 is increased, but the angle θ ₂ is also decreased, and therefore the detection amount of the signal electrons scattered at a large angle is increased. Will be drastically reduced.

As a characteristic of the backscattered electrons generated when the sample is irradiated with the electron beam, the generation efficiency of the backscattered electrons largely depends on the composition (atomic number) of the sample. The radiation direction distribution of the reflected electrons changes depending on the incident angle of the irradiation electron beam with respect to the sample surface, and has the maximum value in the direction of specular reflection of the incident angle. As a result, when a flatly polished sample is irradiated with an electron beam, the backscattered electron emission rate greatly changes depending on the composition (atomic number) of the sample, but since the sample is flat, the area close to the irradiated electron beam 6 is large and the angle d ₁ in FIG. 6 is increased to decrease the angle θ ₁ , so that many reflected electrons in a region close to the irradiation electron beam can be detected. If the number of backscattered electrons detected in this way increases, it becomes easier to specify the composition of the sample, and a large change in the signal amount occurs due to the difference in the elemental components, and a high-quality composition image of the sample surface, that is, an element formed with an image contrast. A distribution image of components can be obtained.

However, in the case of a general sample whose surface has severe irregularities, the radiation direction distribution of reflected electrons changes depending on the incident angle, and the maximum value of the distribution occurs in the specular reflection direction of the incident angle. In the electron emission direction, due to the unevenness of the sample surface, the emission angle of the backscattered electrons increases to a region close to the angle θ ₂ of the outer periphery of the backscattered electron detector 3 or a region exceeding θ ₂ to detect backscattered electrons. The number of reflected electrons that do not enter the container 3 increases. Then, theta ₁ by increasing the distance d, under the conditions of the composition image priority theta ₂ Decrease the elemental analysis, the reflected electrons to the region beyond the region or angle theta ₂ closer to the corner theta _2, the sample surface irregularity Since it has information, it is not possible to obtain information including unevenness of the sample, that is, a stereoscopic image, and only an image with a reduced stereoscopic effect can be obtained.

[0009]

Therefore, conventionally, as shown in FIG. 7, the backscattered electron detector 3 is moved in a plane orthogonal to the irradiation electron beam 4 to capture backscattered electrons in an area exceeding the angle θ _2. The means to do was adopted. However, even if the backscattered electron detector is moved in a plane, since it can move only in a linear direction, it can move only in a fixed direction, and a detection element divided into ½ or ¼ is used. Therefore, even if they are moved in the radial direction, it is difficult to capture the backscattered electrons exceeding the angle θ ₂ in all the regions diverging in the direction of 360 °, which is not suitable for obtaining a stereoscopic image. It was enough.

The present invention has been made by paying attention to such a conventional problem as described above, and the half apex angle θ ₁ of the cone formed by the electron beam irradiation point and the hole of the backscattered electron detector is set to a small angle. In the case of a sample flattened by capturing backscattered electrons in the vicinity, a high-quality composition image of the sample surface is obtained, and
Provided is a detector for a charged particle beam device capable of capturing a three-dimensional image by trapping backscattered electrons diverging to the outer periphery of the backscattered electron detector when the sample surface has irregularities. The purpose is to

[0011]

As a means for solving the above-mentioned problems, the present invention has a constitution in which a sample is scanned with a charged particle beam, and reflected electrons generated from the sample in association with the scanning are generated. In a charged particle beam device that detects a backscattered electron detector and displays a sample image based on an output signal of the backscattered electron detector, the detector comprises at least two or more annular plate members each having a concentric circle with a different radius. And each annular plate member has at least two or more detection elements.

Further, each of the detection elements has an independent signal amplifier, and an output from the signal amplifier is connected to a signal adder and a signal subtractor, and added or subtracted by the signal adder and the signal subtractor. The signal is selectively output to the image display means.

[0013]

The detector of the charged particle beam device is formed by at least two or more annular plate members each having concentric circles with different radii, and each annular plate member has at least two or more detection elements. The area of the backscattered electrons captured by the instrument expands, the distance between the sample and the backscattered electron detector is increased, and the half-vertical angle of the cone formed by the electron beam irradiation point of the sample and the hole of the backscattered electron detector To make it possible to detect backscattered electrons in the region close to the irradiation electron beam, and to increase the area that can be covered by the backscattered electron detector. It is possible to obtain information including the unevenness of, that is, a stereoscopic image, and an image having a stereoscopic effect can be obtained.

Further, each of the detection elements has an independent signal amplifier, and the output from the signal amplifier is connected to a signal adder and a signal subtractor, and added or subtracted by the signal adder and the signal subtractor. Since the signal is selectively output to the image display means, a clearer atomic number contrast (composition image) and unevenness contrast (unevenness image) can be obtained.

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the drawings.
As in the case of FIG. 4, in the charged particle beam device, the sample 1
A backscattered electron detector is arranged between the objective lens 2 and the objective lens 2, the electron beam 4 is two-dimensionally scanned / irradiated on the plane of the sample 1, and the backscattered electrons obtained from the sample 1 along with the scanning / irradiation. To
Detected by a backscattered electron detector arranged above the sample 1,
The sample image is displayed based on the output signal of the backscattered electron detector. This point is the same as in the prior art, and the same members are denoted by the same reference numerals.

FIG. 1 is a block diagram of the present invention, and FIG. 1A shows a plan view of the backscattered electron detector 10 as seen from directly below,
The detection element 11 of the backscattered electron detector 10 is formed by three annular plate bodies 12, 13, 14 which are concentric circles having different radii. The innermost annular plate body 12 is divided into two in the circumferential direction to form the detection elements 12a and 12b, and the outer annular plate body 13 is divided into four in the circumferential direction.
The detection elements 13a, 13b, 13c, 1 are divided into individual pieces.
It is 3d. The outermost annular plate 14 is divided into eight pieces in the circumferential direction, and the detection elements 14a, 14b, ...
… It has been 14 hours.

At the center of the innermost annular plate body 12, there is formed a through hole 15 for the irradiation charged particle beam to pass through, and its diameter is about 3 mm. FIG. 1B is a side view showing the positional relationship between the entire detection element 11 of the backscattered electron detector 10 and the sample 1. Here, when the distance d between the sample 1 and the detection element 11 is set to a constant value, the half-vertical angle of the cone formed by the charged particle beam irradiation point 8 of the sample 1 and the through hole 15 of the annular plate 12 Is θ ₁ , and the half apex angles of the cone formed by the charged particle beam irradiation point 8 of the sample 1 and the outer peripheral portions of the annular plate bodies 12, 13, 14 are θ ₂ , θ ₃ , and θ ₄ , respectively. The detection element 11 has a structure in which it is attached onto the substrate 16, and the hole 15 of the innermost annular plate body 12 is also formed in the central portion of the substrate 16.
A hole 17 corresponding to is formed.

Then, the distance d between the sample 1 and the detection element 11 is increased to decrease the angle θ ₁ formed by the through hole 15 so that the backscattered electrons in the region close to the irradiation electron beam can be detected, and the flatness can be obtained. Even if a high quality composition image of the sample surface is obtained, the angles θ ₃ and θ ₄ have large values, so that the area that can be covered by the entire detection element 11 of the backscattered electron detector 10 increases, and backscattered electrons that cannot be detected are detected. The number of is reduced. Therefore, even in the case of a general sample having a rough surface, the information including the unevenness of the sample, that is, the stereoscopic image can be obtained, and an image having a stereoscopic effect can be obtained.

Further, as shown in FIG. 2, each of the detection elements 12a, 12b ... 13a, ... 14h has an independent signal amplifier 20 and is amplified. Here, the innermost circular plate member 12 is the first track, the outer circular plate member 13 is the second track, and the outermost circular plate member 14 is the second track.
Will be referred to as the third track.

In the first track, the detecting element 12
The signals from a and 12b are amplified by the respective signal amplifiers 20, but the detection elements of the first track do not add at the moment. In the second track, the detecting elements 13a ... 1
The signal from 3d is amplified by each signal amplifier 20, the output is input to the adders 22 and 22 'and added, and the output is added together with the signals from the detection elements 12a and 12b to the adder 23,
23 '. In the third track, the signals from the detection elements 14a ...
The output is input to the adders 21 and 21 'for addition, and the outputs from the adders 23 and 23' are added together with the adder 2
Input in 4, 24 '.

The detection information of the left and right semicircular first and second tracks on the drawing, which are input to the adders 23 and 23 ', are input to the subtractor 33, and the first and second tracks are input. Information on the detection difference between the left and right blocks on the track is output, and the left and right semi-circular first track, second track, and third track on the drawing which are input to the adders 24 and 24 'are detected. The information is input to the subtractor 34, and the information on the detection difference between the left and right blocks on the first track, the second track, and the third track is output.

Further, in the first track, the signals from the detection elements 12a and 12b are amplified by the respective signal amplifiers 20, and the outputs are input to the adder 25 and the subtractor 28, respectively, and in the second track, the detection elements are detected. 13a ... 13d
The signal from is amplified by each signal amplifier 20 and added by the adder 2
2, 22 'are added, and the respective outputs are input to the adder 26 and the subtractor 29, respectively. Further, in the third track, the signals from the detection elements 14a ... 14h are amplified by the signal amplifiers 20 and added by the adders 22 and 22 ', and the outputs are input to the adder 27 and the subtractor 30, respectively. To do.

As the outputs from the adders 25, 26 and 27, the detection information from the detection elements arranged in the respective loops of the first track, the second track and the third track is obtained, and the subtractors 28, 29, As the output from 30, the first
Information on the detection difference between the left and right semicircular blocks on the track, the second track, and the third track can be obtained. Then, the outputs from the adders 25 and 26 are input to the adder 31, and as the output of the adder 31, the detection information from the detection elements arranged in the annular shape of the total of the first track and the second track is obtained, The outputs of the adder 31 and the adder 27 are input to the adder 32, and the output of the adder 32 is the total of the first track, the second track, and the third track from the detection elements arranged in a ring. Detection information is obtained.

The detection information of each track of the annular shape is selected from the signals from the adders 25, 26 and 27 by the signal selection switch 35 and displayed on the CRT 40 as an image. As the detection information of the output sum of the two tracks, the signal from the adder 31 is selected by the signal selection switch 35 and displayed as an image. Furthermore, the first
The detection information of the output sum of the track, the second track, and the third track is displayed by displaying the image from the signal from the adder 32 by the signal selection switch 35, and the composition image of the sample can be obtained by these image displays. it can.

Further, the output difference of the detection information of the left and right semi-circular blocks on each of the first track, the second track and the third track, the signals from the subtracters 28, 29 and 30 are changed to the signal selection switch 35. Selected by CRT
The output difference of the detection information in the left and right semi-circular blocks in which the first track and the second track are combined is displayed on the image 40, and the signal from the subtractor 33 is selected by the signal selection switch 35 to display the image. To be done. Furthermore, combining the first track, the second track, and the third track,
The output difference of the detection information in the left and right semicircular blocks is
The signal from the subtractor 34 is selected by the signal selection switch 35 and displayed as an image, and the contrast of the unevenness of the sample (unevenness image) can be obtained by these image displays.

Further, the information about the sample brought by the reflected electrons depends on the angle (scattering angle) α formed by the irradiation electron beam and the emission direction of the reflected electrons. When α is small, there is a lot of information on the composition of the element, and α is If it is large, it gives a lot of information about the surface roughness of the sample. Therefore, when the backscattered electron detector and the auxiliary circuit having the above-described configuration are provided, the backscattered electron detector is used for each track, and thus the backscattered electron signal can be selectively used according to the scattering angle α. .

That is, when only the first track is used, an image can be obtained only by backscattered electrons having a small scattering angle, and a high-quality composition image can be obtained. When only the second track is used, an image having composition information and stereoscopic information can be obtained by the reflected electrons having a medium scattering angle. When only the third track is used, an image by backscattered electrons with a large scattering angle is obtained, composition information is suppressed,
A display rich in three-dimensional information can be obtained. Further, it becomes possible to selectively observe a high-quality image having a large amount of information by using a plurality of tracks at the same time.

Further, with the above configuration, it is possible to use the optimum size of the element which does not deteriorate the element performance and the response speed. Further, there is an advantage that the detection area of the detection element can be increased by electrically adding the signals, and at the same time, the reduction of the response speed due to the increase of the detection area can be prevented.

In addition, by performing subtraction processing on the detection signal, it is possible to display unevenness, and it is also possible to display unevenness image for each track, all elements, or only a plurality of specific tracks. Further, as an application, it is possible to further add the uneven image signal obtained by subtracting the outputs of the left and right elements of the first track and the stereoscopic image signal obtained by adding the second or the third or the second and the third. , A large three-dimensional structure image on the sample surface,
It is also possible to emphasize fine irregularities and superimpose them.

The feature of the present invention is that it is not necessary to move the position of the backscattered electron detector to obtain a stereoscopic image,
The position of the detector is fixed, and the composition image to the stereoscopic image can be easily observed only by switching the signal selection switch.

In the above embodiment, the case where the number of annular plate members is three has been described, but the number of annular plate members is not limited to three,
As shown in FIG. 3, if there are two or more tracks, the first track 3
It is needless to say that the first track, the second track 32, the third track 33, ..., The n-th track N, etc. may be provided and any number of two, four or more may be provided. The example is not limited to the one divided into 2, 4, and 8 from the inside, and any division may be used.

[0032]

As described above, according to the present invention, the detector of the charged particle beam device is formed by at least two or more annular plate members each having a concentric circle with a different radius, and each annular plate. Since the body has at least two detection elements, the flatly polished sample captures the backscattered electrons in the vicinity of the electron beam to obtain a high-quality composition image of the sample surface,
In other words, the difference in the signal component occurs due to the difference in the elemental component, and the distribution image of the elemental component formed by the image contrast due to this can be obtained. It is possible to capture the backscattered electrons diverging to the outer peripheral part of the
That is, there is an effect that a stereoscopic image can be obtained and an image having a stereoscopic effect can be obtained.

[Brief description of drawings]

FIG. 1 (a) is a plan view of a backscattered electron detector as seen from directly below, and FIG. 1 (b) is a side view showing the positional relationship between the entire detection element of the backscattered electron detector and a sample.

FIG. 2 is a circuit diagram of a detection element of the backscattered electron detector of the present invention to which an amplifier, an adder / subtractor and the like and an image display means are added.

FIG. 3 is a plan view of a backscattered electron detector according to another embodiment of the present invention.

FIG. 4 is a side view of a sample and a backscattered electron detector of a conventional charged particle beam apparatus including a backscattered electron detector.

5A and 5B are circuit diagrams of a conventional detection element of a backscattered electron detector and a device connected to the detection element. FIG. 5A shows a case where the element is divided into two, and FIG. 5B shows a case where the element is divided into four. Is.

FIG. 6 is a side view showing a conventional positional relationship between a backscattered electron detector and a sample.

FIG. 7A is a side view and FIG. 7B is a plan view when a detection element of a conventional backscattered electron detector is moved in a plane orthogonal to a charged particle beam.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 sample 10 backscattered electron detector 11 detection element 12, 13, 14 annular plate body 20 signal amplifier 21, 21 ', 22, 22', 23, 23 ', 24, 2
4 ', 25,26,27,31,32 signal adder 28,29,30,33,34 signal subtractor 40 CRT (image display means)

Claims (2)

[Claims] 1. A sample is scanned with a charged particle beam, backscattered electrons generated from the sample in association with the scanning are detected by a backscattered electron detector, and a sample image is displayed based on an output signal of the backscattered electron detector. In the charged particle beam device, the detector is formed of at least two or more annular plate bodies formed of concentric circles having different radii, and each annular ring plate body has at least two or more detection elements. And a detector of the charged particle beam device. 2. The detection element according to claim 1, wherein each of the detection elements has an independent signal amplifier, and the output from the signal amplifier is connected to a signal adder and a signal subtractor, and the signal adder and the signal subtractor are used. The added or subtracted signal is
A detector of a charged particle beam device, which is selectively output to an image display means.