Electron beam observation method, electron beam observation apparatus, aperture diaphragm module for electron beam observation apparatus, and aperture diaphragm set for electron beam observation apparatus

Abstract

To allow an observation in accordance with an energy of an electron beam discharged from a sample.SOLUTION: An electron beam observation method using an electron beam observation device, comprises steps of: collecting a primary electron beam composed of a plurality of primary electrons and irradiating a plurality of places of a sample with the beam; detecting a secondary electron beam composed of a plurality of secondary electrons discharged from the sample which is irradiated with the primary electron beam, by a plurality of detectors; and acquiring a plurality of scanning images by using an electric signal obtained from the plurality of detectors by scanning the plurality of primary electron beams. The electron beam observation method further comprises steps of: specifying an energy of the secondary electron beam as an observation object; setting an aperture diaphragm having an annular opening corresponding to the specified energy of a plurality of aperture diaphragms having annular openings different in inner diameter and outer diameter, in the electron beam observation device; and detecting the secondary electron beam passing through the annular opening of the set aperture diaphragm by the detector.SELECTED DRAWING: Figure 1A

Description

[Technical Field]

[0001] The present invention relates to an electron beam observation method, an electron beam observation apparatus, an aperture diaphragm module for an electron beam observation apparatus, and an aperture diaphragm set for an electron beam observation apparatus. [Background technology]

[0002] Electron beam observation devices that irradiate a sample with an electron beam and observe the electron beam emitted from the sample are known (for example, see Patent Document 1). The energy distribution of the electron beam emitted from the sample depends on factors such as the shape, state, composition, chemical bond, and charged state of the sample surface. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2002-252259 Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to enable observation according to the energy of the electron beam emitted from the sample. [Means for solving the problem]

[0005] According to one aspect of the present invention, [1] 1. An electron beam observation method using an electron beam observation device, comprising: focusing a primary electron beam composed of a plurality of primary electrons and irradiating the primary electron beam onto a plurality of locations on a sample; detecting a secondary electron beam composed of a plurality of secondary electrons emitted from the sample irradiated with the primary electron beam using a plurality of detectors; and acquiring a plurality of scanned images using electrical signals obtained from the plurality of detectors by scanning the plurality of primary electron beams, Identify the energy of the secondary electron beam to be observed, installing an aperture stop having an annular opening corresponding to the specified energy among a plurality of aperture stops having annular openings with different inner and outer diameters in the electron beam observation device; There is provided an electron beam observation method in which the secondary electron beam that has passed through the annular aperture of the aperture stop is detected by the detector.

[0006] According to one aspect of the present invention, [2] 1. An electron beam observation method using an electron beam observation device, comprising: focusing a primary electron beam composed of a plurality of primary electrons and irradiating the primary electron beam onto a plurality of locations on a sample; detecting a secondary electron beam composed of a plurality of secondary electrons emitted from the sample irradiated with the primary electron beam using a plurality of detectors; and acquiring a plurality of scanned images using electrical signals obtained from the plurality of detectors by scanning the plurality of primary electron beams, installing one of a plurality of aperture stops, each having annular openings with different inner and outer diameters, in the electron beam observation apparatus; detecting the secondary electron beam passing through the annular aperture of the aperture stop with the detector; The present invention provides an electron beam observation method in which the above is performed while changing the aperture stop to be installed.

[0007] [3] In the electron beam observation method according to [1] or [2], It is desirable that, among the secondary electron beams, a secondary electron beam having an energy corresponding to the annular opening of the aperture stop that is provided passes mainly through the annular opening.

[0008] According to one aspect of the present invention, [4] a multi-beam optical system that focuses a primary electron beam composed of a plurality of primary electrons onto a sample placed on a stage and irradiates the sample at a plurality of locations; a projection optical system that detects, with a plurality of detectors, a secondary electron beam that is composed of a plurality of secondary electrons emitted from a sample irradiated with the primary electron beam; the projection optical system has a holder configured to accommodate one of a plurality of aperture stops, each having annular openings with different inner and outer diameters; An electron beam observation device is provided, in which the detector detects the secondary electron beam that has passed through the annular opening.

[0009] [5] In the electron beam observation apparatus according to [4], The projection optical system includes: a relay lens disposed between the detector and the stage; a field lens disposed between the detector and the relay lens; a projection lens disposed between the detector and the field lens; The holder is preferably disposed between the field lens and the projection lens.

[0010] [6] In the electron beam observation apparatus according to [4] or [5], It is desirable that, among the secondary electron beams, a secondary electron beam having an energy corresponding to the annular opening of the aperture stop that is provided passes mainly through the annular opening.

[0011] According to one aspect of the present invention, [7] A flat substrate; and a plurality of aperture stops provided on the base material, the aperture stops having annular openings with different inner and outer diameters from one another.

[0012] [8] [7] The aperture stop module according to [7], It is desirable that the inner diameter of the annular opening of one of the plurality of aperture stops is zero.

[0013] [9] [7] or [8], wherein the aperture stop module One of the plurality of aperture stops is the annular opening has a non-zero inner diameter; a circular inner member disposed inside the annular opening and having a diameter equal to the inner diameter; and a retaining member for retaining the inner member to the base material.

[0014]

[10] [7] to [9], wherein the aperture stop module is the plurality of aperture stops are arranged in a straight line, The aperture stop module preferably includes a drive mechanism for moving the substrate along the linear direction.

[0015] According to one aspect of the present invention,

[11] a multi-beam optical system that irradiates a sample placed on a stage with a primary electron beam composed of a plurality of primary electrons; a projection optical system that detects, with a detector, a secondary electron beam that is composed of a plurality of secondary electrons emitted from a sample irradiated with the primary electron beam; the projection optical system has an aperture stop module according to any one of [7] to

[10] , An electron beam observation device is provided, in which the detector detects the secondary electron beam that has passed through the annular opening.

[0016] According to one aspect of the present invention,

[12] A plurality of aperture stops are provided, There is provided an aperture stop set for an electron beam observation apparatus, in which each of the plurality of aperture stops has an annular opening with an inner diameter and an outer diameter different from each other.

[0017]

[13]

[12] The aperture diaphragm set according to It is desirable that the inner diameter of the annular opening of one of the plurality of aperture stops is zero.

[0018]

[14]

[12] or

[13] , wherein the aperture diaphragm set The plurality of aperture stops include: the annular opening has a non-zero inner diameter; a circular inner member disposed inside the annular opening and having a diameter equal to the inner diameter; an outer member provided outside the annular opening; and a retaining member for retaining the inner member to the outer member. [Effects of the Invention]

[0019] Observations can be made according to the energy of the electron beam emitted from the sample. [Brief explanation of the drawings]

[0020] [Figure 1A] FIG. 1 is a schematic diagram of an electron beam observation device. [Figure 1B] FIG. 2 is a schematic diagram of a detector 28. [Figure 1C] FIG. 1B is a schematic configuration diagram of an electron beam observation apparatus which is a modified example of FIG. 1A. [Figure 2A] FIG. 2 is a diagram schematically showing the dispersion range of a secondary electron beam having low energy at a cross section position of the aperture stop 26. [Figure 2B] FIG. 10 is a diagram showing a schematic view of the dispersion range of a secondary electron beam having a medium energy at a cross section position of the aperture stop 26. [Figure 2C] FIG. 2 is a diagram showing a schematic view of the dispersion range of a secondary electron beam having high energy at a cross section position of the aperture stop 26. [Figure 3A] FIG. 2 is a diagram schematically showing a low-energy aperture stop 261. [Figure 3B] FIG. 2 is a diagram schematically showing an aperture stop 261 for medium energy. [Figure 3C] FIG. 2 is a diagram schematically showing a high-energy aperture stop 261. [Figure 4] FIG. 2 is a schematic perspective view of an aperture stop module 3. [Figure 5] FIG. 1 is a schematic configuration diagram of an electron beam observation apparatus according to an embodiment. [Figure 6] 6 is a process diagram showing an example of an electron beam observation method using the electron beam observation apparatus of FIG. 5. [Figure 7] 6 is a process diagram showing another example of an electron beam observation method using the electron beam observation apparatus of FIG. 5. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

[0022] 1A is a schematic diagram of an electron beam observation apparatus, which is, for example, a scanning electron microscope (SEM), and includes a multi-beam optical system 1 (primary optical system) and a projection optical system 2 (secondary optical system).

[0023] The multi-beam optical system 1 focuses and irradiates a primary electron beam composed of multiple primary electrons onto multiple locations on a sample placed on a stage 16, and is composed of an electron source 11, a multi-beam generating mechanism 12, a transfer lens 13, a beam separator 14, an objective lens 15, a stage 16, a scan deflector 17, etc.

[0024] The electron beam emitted from the electron source 11 is appropriately accelerated by an accelerator (not shown) and expanded by a lens (not shown), and then enters the multi-beam generating mechanism 12. The multi-beam generating mechanism 12 has multiple apertures, and when the electron beam from the electron source 11 passes through these apertures, a primary electron beam consisting of multiple primary electrons is generated. The generated primary electron beams are individually focused by a transfer lens 13, a beam separator 14, and an objective lens 15, and are irradiated at multiple discrete points at equal intervals on a sample placed on a stage 16.

[0025] The primary electron beam is deflected by the scan deflector 17 so as to scan the sample two-dimensionally, thereby allowing the primary electron beam, which is emitted discretely, to be emitted evenly onto the sample.

[0026] The projection optical system 2 detects, with a detector 28, a secondary electron beam made up of multiple secondary electrons emitted from a sample irradiated with the primary electron beam, and is composed of an objective lens 15, a beam separator 14, a beam bender 21, a first relay lens 22, a second relay lens 23, a field lens 25, an aperture stop 26, a projection lens 27, and a detector 28. The objective lens 15 and the beam separator 14 are shared with the multi-beam optical system 1.

[0027] The secondary electron beam from the sample is focused by an objective lens 15. Then, the secondary electron beam is bent in a direction different from that of the multi-beam optical system 1 by a beam separator 14 that forms a superimposed field of an electric field and a magnetic field. The secondary electron beam is further bent by a beam bender 21.

[0028] The first relay lens 22 and the second relay lens 23 are adjusted so that the secondary electron beam is imaged at a fixed position and with a fixed size near the main surface of the field lens 25, regardless of the potential of the sample. By providing these first relay lens 22 and second relay lens 23, it is possible to accommodate a wide range of sample potentials.

[0029] The field lens 25 generates an electric field or a magnetic field to adjust the trajectory of the secondary electron beam so that the multiple secondary electrons constituting the secondary electron beam are closest to each other at the center of the optical axis near the position of the aperture stop 26. In other words, the aperture stop 26 is placed at a position where the multiple secondary electrons are closest to each other at the center of the optical axis.

[0030] The aperture stop 26 has an opening, and only the secondary electron beam that passes through the opening reaches the projection lens 27. This defines the aperture angle of the secondary electron beam.

[0031] The projection lens 27 forms an image of the secondary electron beam that has passed through the opening of the aperture stop 26 onto a detector 28 .

[0032] As shown in FIG. 1B, the detector 28 includes, for example, a scintillator 281, a light amplifier 282, an image sensor 283 (for example, a CMOS image sensor), a magnifying lens 284, and a half mirror 285.

[0033] Secondary electrons emitted from multiple locations on the sample form an image on a scintillator 281, and light corresponding to the number of secondary electron beams reaching the scintillator 281 is generated from the scintillator 281. Since the generated light is divergent, it is enlarged and projected using a magnifying lens 284 arranged in the optical path. Part of the light that passes through the magnifying lens 284 passes through a half mirror 285 and travels through a bundle of optical fibers to an optical amplifier 282, and part of the light is reflected by the half mirror 285 and travels to an image sensor 283. The former light is converted into an electrical signal by the amplifier 282, and a scanned image (SEM image) is formed with the number of beams corresponding to the number of secondary electron beams. The latter light forms an image on the image sensor 283, and an image of the secondary electron beam is obtained.

[0034] 1C is a schematic diagram of an electron beam observation apparatus that is a modified example of that shown in FIG. 1A. As shown in the figure, the first relay lens 22, the second relay lens 23, and the field lens 25 may be omitted from the electron beam observation apparatus of FIG. 1A. In this case, an aperture stop 26 is placed between a projection lens 27 and a detector 28. This is because it is important to place the aperture stop 26 at a position where the chief ray approaches closest to the optical axis.

[0035] 1A and 1C are merely examples. For example, the multi-beam optical system 1 may include multiple electron sources 11 arranged at specific intervals, in which case the multi-beam generating mechanism 12 may be omitted. The projection optical system 2 may also include only one relay lens. The beam bender 21 may also be omitted. However, it is desirable that the projection optical system 2 include at least one of relay lenses 22 and 23, a field lens 25, an aperture stop 26, and a projection lens 27, arranged in this order between the stage 16 and the detector 28.

[0036] Here, secondary electrons are emitted from the sample irradiated with multiple (e.g., several hundred) primary electron beams, and are accelerated by an accelerating electric field near the sample to form multiple (same number as the primary electron beams) secondary electron beams. The energy distribution of each secondary electron beam depends on factors such as the shape, state, composition, chemical bonds, and charging state of the sample surface.

[0037] There is also a demand for observing the secondary electron beam by focusing on a specific energy band, and for observing the difference in the energy distribution of the secondary electron beam at each position on the sample surface. One of the objects of the present invention is to meet these demands.

[0038] According to the study by the inventors, it has been found that the spread of the cross section of the secondary electron beam at the position of the aperture stop 26 increases as the energy of the secondary electron beam increases.

[0039] Figure 2A is a diagram schematically showing the dispersion range of a secondary electron beam having low energy at the cross section position of the aperture stop 26. Figure 2B is a diagram schematically showing the dispersion range of a secondary electron beam having medium energy at the cross section position of the aperture stop 26. Figure 2C is a diagram schematically showing the dispersion range of a secondary electron beam having high energy at the cross section position of the aperture stop 26. For simplicity, both diagrams depict the dispersion ranges of three electron beams out of multiple secondary electron beams, with each circle indicating the dispersion range of one secondary electron beam (however, the deviation from the optical axis has been exaggerated for ease of understanding).

[0040] As shown in Figure 2A, when the energy is low, the dispersion range of the secondary electron beam is small, whereas as shown in Figures 2B and 2C, the greater the energy, the greater the dispersion range of the secondary electron beam.

[0041] Therefore, one feature of this embodiment is that an aperture stop having an opening formed at a position corresponding to the energy is used to selectively allow a secondary electron beam having a desired energy to reach the detector 28.

[0042] 3A is a diagram schematically illustrating an aperture stop for observing a secondary electron beam having low energy (hereinafter referred to as "low-energy aperture stop 261"). Note that in FIG. 3A and in FIGS. 3B and 3C described below, for convenience, portions with holes (portions through which secondary electrons can pass) are depicted in black. This low-energy aperture stop 261 has a circular aperture 61 with a diameter r01 of, for example, 100 μm.

[0043] 1, when the low-energy aperture stop 261 is used, mainly the secondary electron beams having low energy pass through the circular aperture 61. Some secondary electron beams having medium or high energy pass through the circular aperture 61, but most of them move away from the center of the optical axis and are therefore blocked by the member 70 constituting the aperture stop 261 (the thickness near the aperture is, for example, 100 μm or less).

[0044] 3B is a schematic diagram of an aperture stop for observing a secondary electron beam having a medium energy (hereinafter referred to as "medium energy aperture stop 262"). The medium energy aperture stop 262 has an annular aperture 62 with an inner diameter ri2 of 150 μm and an outer diameter r02 of 200 μm, for example.

[0045] In other words, the medium energy aperture stop 262 has an inner member 72 provided inside the annular opening 62, an outer member 82 provided outside the annular opening 62, and a plurality of holding members 92 for holding the inner member 72 to the outer member 82.

[0046] The inner member 72 is in the shape of a disk (with a thickness of, for example, 100 μm or less) with a diameter equal to the inner diameter ri2 of the annular opening 62. The outer member 82 is a member (with a thickness of 100 μm or less near the opening) that has an opening with a diameter equal to the outer diameter r02 of the annular opening 62. The holding member 92 has a width d of about 30 to 50 μm, and one end is connected to the inner member 72 and the other end is connected to the outer member 82. It is sufficient for the holding member 92 to be able to hold the inner member 72 to the outer member 82, and for example, three or more holding members 92 are arranged at equal intervals. It can be said that the annular opening 62 is formed between the inner member 72 and the outer member 82.

[0047] 1, when the medium-energy aperture stop 262 is used, the secondary electron beam having mainly medium energy passes through the annular aperture 62. Although some of the secondary electron beam having high energy passes through the annular aperture 62, most of the secondary electron beam is blocked by the outer member 82 because it is far from the center of the optical axis. Although some of the secondary electron beam having low energy passes through the annular aperture 62, most of the secondary electron beam is blocked by the inner member 72 because it is near the center of the optical axis.

[0048] 3C is a diagram schematically showing an aperture stop for observing a secondary electron beam having high energy (hereinafter referred to as "high-energy aperture stop 263"). The high-energy aperture stop 263 has an annular opening 63 with an inner diameter ri3 of 300 μm and an outer diameter r03 of 400 μm, for example. Again, the high-energy aperture stop 263 may be composed of an inner member 73, an outer member 83, and a holding member 93.

[0049] 1, when the high-energy aperture stop 263 is used, the secondary electron beam having mainly high energy passes through the annular opening 63. Although some secondary electron beams having medium or low energy pass through the annular opening 63, most are blocked by the inner member 73 because they are near the center of the optical axis.

[0050] The circular aperture 61 of the low-energy aperture stop 261 in Fig. 3A can be considered to be an annular aperture 61 with an inner radius ri1 of 0. The multiple aperture stops 261-263 shown in Fig. 3A-3C can be said to have annular apertures 61-63 with different inner and outer diameters, respectively. Although three aperture stops 261-263 are shown in Fig. 3A-3C, an appropriate number of aperture stops can be used depending on the resolution of the energy to be observed.

[0051] 3A to 3C, an aperture diaphragm set for an electron beam observation apparatus is made up of a plurality of aperture diaphragms 261 to 263. Furthermore, as will be described below, an aperture diaphragm module 3 having a plurality of aperture diaphragms 261 to 263 may be used.

[0052] 4 is a schematic perspective view of the aperture diaphragm module 3. The aperture diaphragm module 3 includes a flat substrate 30 and a plurality of aperture diaphragms 31 to 33 provided on the substrate 30.

[0053] The substrate 65 is made of molybdenum with a film thickness of 0.1 mm, for example, and is coated with osmium on its surface. The aperture stops 31 to 33 may be similar to the low-energy aperture stop 261, the medium-energy aperture stop 262, and the high-energy aperture stop 263 described with reference to FIGS. 3A to 3C (they are depicted in a simplified form in FIG. 4). In this case, the holders of the medium-energy aperture stop 32 and the high-energy aperture stop 33 hold their inner members to the substrate 20. The substrate 30 may also be provided with a circular aperture 34 for normal observation.

[0054] The aperture diaphragm module 3 may have a cylinder rod 35 (drive mechanism). The aperture diaphragms 31 to 33 (and the circular aperture 34, if necessary) are arranged on a straight line. A control device (not shown) of the electron beam observation apparatus stores the positions (coordinates) of the aperture diaphragms 31 to 33. When a user selects a desired aperture diaphragm from an operation terminal, the control device controls the cylinder rod 35 so that the selected aperture diaphragm is positioned at the center of the optical axis. In response to this control, the cylinder rod 35 moves the substrate 30 in a direction along the straight line on which the aperture diaphragms 31 to 33 are arranged. When the aperture diaphragm module 3 is installed in the electron beam observation apparatus, the straight line is perpendicular to the optical axis of the projection optical system 2.

[0055] 5 is a schematic diagram of an electron beam observation apparatus according to one embodiment, which includes a holder 2A that is arranged at the position of aperture stop 26 in the electron beam observation apparatus of FIG. 1 and is configured to accommodate one of a plurality of aperture stops.

[0056] The aperture diaphragm to be installed may be any one of the aperture diaphragms 261 to 263 included in the aperture diaphragm set illustrated with reference to Figures 3A to 3C. In this case, the electron beam observation apparatus may be considered to be equipped with the aperture diaphragm set.

[0057] Alternatively, the electron beam observation apparatus may include an aperture stop module 3 having a plurality of aperture stops 31 to 33 as illustrated in Figure 4, and the aperture stop module 3 may be installed in the holder 2A so that one of the aperture stops 31 to 33 is positioned at the center of the optical axis.

[0058] Fig. 6 is a process diagram showing an example of an electron beam observation method using the electron beam observation apparatus of Fig. 5. This electron beam observation method is intended to observe a secondary electron beam having a certain energy.

[0059] First, the energy of the secondary electron beam to be observed is specified (step S1). This step can be performed by an observer.

[0060] Next, one of the aperture stops corresponding to the identified energy is installed in the electron beam observation apparatus (step S2). This step can also be performed by the observer.

[0061] For example, suppose the object of observation is a secondary beam with low energy. When an aperture diaphragm set is used, the low-energy aperture diaphragm 261 is installed in the holder 2A of the electron beam observation apparatus. When an aperture diaphragm module 3 is used, the cylinder rod 35 is controlled so that the low-energy aperture diaphragm 31 is positioned at the center of the optical axis.

[0062] Then, the secondary electron beam that has passed through the annular opening of the installed aperture stop is detected by detector 28 of the electron beam observation device (step S3). More specifically, the secondary electron beam having energy corresponding to the annular opening (inner and outer diameters) of the installed aperture stop mainly passes through the annular opening and is detected by detector 28.

[0063] As a result of the above, the observer can observe the secondary electron beam having the energy arbitrarily specified in step S1.

[0064] Fig. 7 is a process chart showing another example of an electron beam observation method using the electron beam observation apparatus of Fig. 5. This electron beam observation method is intended to observe the distribution of energy possessed by a secondary electron beam.

[0065] First, any one of the aperture stops is installed in the electron beam observation apparatus (step S11). This step can be performed by an observer.

[0066] As an example, when an aperture diaphragm set is used, the low-energy aperture diaphragm 261 is placed in the holder 2A of the electron beam observation apparatus. As another example, when an aperture diaphragm module 3 is used, the cylinder rod 35 is controlled so that the low-energy aperture diaphragm 31 is positioned at the center of the optical axis.

[0067] Then, the secondary electron beam that has passed through the annular opening of the installed aperture stop is detected by the detector 28 of the electron beam observation device (step S12).

[0068] The above steps S11 and S12 are carried out while changing the aperture stop to be installed (step S13).

[0069] For example, if the low-energy aperture stop 261 is installed in the first step S11, then the medium-energy aperture stop 262 is installed (step S11) and the secondary electron beam is detected (step S12). After that, the high-energy aperture stop 263 is installed (step S11) and the secondary electron beam is detected (step S12).

[0070] As a result, the observer can separately observe the secondary electron beam having low energy, the secondary electron beam having medium energy, and the secondary electron beam having high energy.

[0071] As described above, in this embodiment, a plurality of aperture stops having different inner and outer diameters are used, so that observation according to the energy of the electron beam emitted from the sample becomes possible.

[0072] The electron beam observation apparatus described in this embodiment can be applied to, for example, semiconductor inspection. In this case, an improvement in image contrast can be expected by observing using an aperture stop that selectively passes a specific energy band.

[0073] The electron beam observation apparatus described in this embodiment can also be applied to biological observation (3D imaging). In this case, since the high-energy band in the secondary electron energy distribution is likely to reflect the influence of elements, improvement in image contrast can be expected by cutting off electrons near the center of the optical axis during observation.

[0074] Based on the above description, a person skilled in the art may be able to conceive additional effects and various modifications of the present invention, but the aspects of the present invention are not limited to the individual embodiments described above. Various additions, modifications, and partial deletions are possible within the scope of the conceptual idea and spirit of the present invention, which is derived from the content defined in the claims and their equivalents.

[0075] For example, what is described in this specification as a single device (or component, the same applies hereinafter) (including what is depicted as a single device in the drawings) may be realized by multiple devices. Conversely, what is described in this specification as multiple devices (including what is depicted as multiple devices in the drawings) may be realized by a single device. Alternatively, some or all of the means or functions included in one device may be included in another device.

[0076] Furthermore, not all of the features described in this specification are essential requirements. In particular, features described in this specification but not included in the claims can be considered optional additional features.

[0077] It should be noted that the applicant is merely aware of the inventions disclosed in the documents listed in the "Prior Art Documents" section of this specification, and the present invention does not necessarily aim to solve the problems of the disclosed inventions. The problem that the present invention aims to solve should be determined by taking into consideration the entire specification. For example, if this specification states that a specific configuration achieves a certain effect, it can also be said that the present invention solves a problem that is the reverse of that effect. However, it is not necessarily intended that such a specific configuration be an essential requirement. [Explanation of symbols]

[0078] 1 Multi-beam optical system 11 Electron source 12 Multi-beam generation mechanism 13 Transfer lens 14 Beam separator 15 Objective Lens 16 stages 17 Scan deflector 2 Projection optical system 21 Beam Bender 22 First relay lens 23 Second relay lens 25 Field Lens 26 Aperture diaphragm 261 Low Energy Aperture Stop 262 Medium Energy Aperture Stop 263 High Energy Aperture Stop 27 Projection Lens 28 detectors 281 Scintillator 282 Optical Amplifier 283 Image Sensor 284 Magnifying Lens 285 Half Mirror 2A Holder 3 Aperture Stop Module 30 Base material 31 Low energy aperture stop 32 Medium energy aperture stop 33 High energy aperture stop 34 circular opening 35 Cylinder rod 50 Optical axis center 61 Circular Aperture 62,63 Annular opening 72,73 Inner member 82,83 Outer member 92,93 Retaining member

Claims

1. 1. An electron beam observation method using an electron beam observation device, comprising: focusing a primary electron beam composed of a plurality of primary electrons and irradiating the primary electron beam onto a plurality of locations on a sample; detecting a secondary electron beam composed of a plurality of secondary electrons emitted from the sample irradiated with the primary electron beam with a plurality of detectors; and acquiring a plurality of scanned images using electrical signals obtained from the plurality of detectors by scanning the plurality of primary electron beams, Identifying the energy of the secondary electron beam to be observed; installing, in the electron beam observation apparatus, an aperture stop having an annular opening with a larger outer diameter as the specified energy increases, among a plurality of aperture stops having annular openings with different inner and outer diameters; The secondary electron beam that has passed through the annular opening of the aperture stop is detected by the detector.

2. An electron beam observation method as described in claim 1, wherein the higher the specified energy, the larger the outer diameter and inner diameter of an annular opening is installed in the electron beam observation device.

3. 3. The electron beam observation method according to claim 1, wherein, of the secondary electron beams, a secondary electron beam having an energy corresponding to the annular opening of the aperture stop is mainly transmitted through the annular opening.

Images