ELECTRON BEAM APPLICATION DEVICE

Abstract

Electron beam application device comprising: a sample stage (101) on which a sample (20) is to be arranged, an electron-optical system comprising an objective lens (102) for generating an electronic image by electrons emitted from the sample (20) and whose optical axis (109, 305, 315, 503) is perpendicular to a sample holding surface of the sample stage (101), and a camera (108) that generates the electronic image, wherein the electron-optical system comprises: a mirror aberration corrector (106) arranged perpendicular to the optical axis (109, 305, 315, 503), several magnetic field sectors (104, 301, 302, 501) through which the path of the electrons passing through the objective lens (102) is directed away from the optical axis (109, 305, 315, 503). is deflected so that the electrons fall onto the mirror aberration corrector (106), and the path of the electrons emitted by the mirror aberration corrector (106) to the optical axis (109, 305, 315,503), and a doublet lens (105) is arranged between adjacent magnetic field sectors (104, 301, 302, 501) along the path of the electrons, wherein the several magnetic field sectors (104, 301, 302, 501) have the same deflection angle at which the path of the electrons is deflected, and the doublet lens (105) is arranged such that its object plane or image plane is the median plane (508) of the adjacent magnetic field sectors (104, 301, 302, 501) along the path of the electrons.

Description

Technical field The present invention relates to an electron beam application device. Technical background A photoelectron emission microscope (PEEM) is a device for generating an image using photoelectrons emitted when the surface of a sample is irradiated with ultraviolet light or X-rays (excitation light), whereby a photoelectron image can be obtained that shows the surface structure of the sample in high contrast. PTL 1 discloses the construction of a cathode lens microscope (the PEEM is an example of this) with an aberration correction function, and PTL 2 discloses the construction of a PEEM equipped with a mirror aberration corrector. List of citations Patent literature PTL 1: JP 2009 - 528 668 APTL 2: JP 2020 - 85 873 A Further examples of conventional electron beam instruments are disclosed in US 8 334 508 B1 , DE 101 07 910 A1 , US 2007 / 0 200 062 A1 , US 8 729 466 B1 and in the article by K. Grzelakowski et al. “A flange-on type low energy electron microscope”, Review of Scientific Instruments 67 (1996), pages 742 - 747 . Summary of the invention Technical problem To inspect patterns formed on the surface of a semiconductor wafer, both light-based optical inspection devices and electron-beam-based scanning electron microscope (SEM) inspection devices have been widely used. The size of observable structures on a sample (a semiconductor wafer) differs between optical and SEM inspection devices. Optical inspection devices can perform pattern inspections quickly over a wide inspection area, but detection becomes increasingly difficult as the defects become finer. SEM inspection devices, on the other hand, have the advantage of being able to detect finer defects, although their field of view is narrow, and their throughput for pattern inspection over a wide inspection area is reduced. The inventors have investigated an inspection device (PEEM inspection device) for detecting pattern defects in a photoelectron image formed by the PEEM, as an inspection device in which both the throughput of optical inspection devices and the defect detection resolution of SEM inspection devices can be obtained. For the use of the PEEM inspection device on a semiconductor manufacturing line, it is desirable that the PEEM inspection device, similar to the inspection devices currently used in semiconductor manufacturing lines, has a horizontal wafer table on which a sample (a semiconductor wafer) is arranged horizontally, and an electron-optical system installed in an upright column perpendicular to a wafer holding surface of the horizontal wafer table, and that the handling of semiconductor wafers is aligned with other devices of the semiconductor manufacturing line.In the prior art PEEM or low-energy electron microscope (LEEM), which has the same projection image generation system as the PEEM, it is assumed that the analysis of small sample pieces can be performed, the limitations due to sample handling on the sample stage are reduced, and the stage can be freely positioned. For example, in PTL 1, the path from the sample to a field-of-view screen, onto which an image is projected, is bent at a right angle by a prism arrangement. Accordingly, the electron-optical system from PTL 1 is not suitable for an inspection device used in a semiconductor manufacturing line. On the other hand, PTL 2 discloses a photoelectron emission microscope in which an electron-optical system, which includes the mirror aberration corrector, is arranged perpendicular to a sample plane.In the PTL 2 configuration, however, the electron beams are pulsed by intermittent reflection to create a linear optical path in the aberration correction unit. This necessitates advanced control techniques for the pulsed electron beams to perform highly accurate aberration correction, and it reduces the number of electrons reaching the imaging system per unit time. Consequently, the time required to obtain a clear photoelectron image increases, and the throughput decreases. Solution to the problem An electron beam application device according to an embodiment of the invention comprises a sample stage on which a sample is to be arranged, an electron-optical system comprising an objective lens for generating an electronic image by electrons emitted from the sample and whose optical axis is perpendicular to a sample holding surface of the sample stage, and a camera that generates the electronic image.The electron-optical system comprises the following: a mirror aberration corrector arranged perpendicular to the optical axis, several magnetic field sectors by which the path of the electrons passing through the objective lens is deflected from the optical axis so that the electrons fall onto the mirror aberration corrector, and the path of the electrons emitted by the mirror aberration corrector is returned to the optical axis, and a doublet lens arranged between adjacent magnetic field sectors along the path of the electrons, wherein the several magnetic field sectors have the same deflection angle at which the path of the electrons is deflected, and the doublet lens is arranged such that its object plane or image plane are the median planes of the adjacent magnetic field sectors along the path of the electrons. Beneficial effect A projection electron beam application device suitable for use in a semiconductor manufacturing line is provided. Other problems and novel features will become clear from the descriptions in this patent specification and the accompanying drawings. Brief description of the drawings Figure 1 shows a configuration example of an electron beam application device, Figure 2A shows a diagram illustrating the control of the path of an electron beam by a magnetic field sector, Figure 2B shows a diagram illustrating the control of the path of the electron beam by the magnetic field sector, Figure 3A shows a diagram illustrating a basic principle of canceling a deflection aberration caused by the magnetic field sector, Figure 3B shows a doublet lens, Figure 4 shows a configuration example (a modification) of an electron beam application device, Figure 5 shows a diagram of a configuration of the magnetic field sector, Figure 6 shows an example of a pole piece, Figure 7A shows an example of the pole piece, Figure 7B shows an example of the pole piece, and Figure 8 shows an example of the pole piece. Description of embodiments Fig. 1 shows a configuration example of an electron beam application device according to the present embodiment. Fig. 1 shows a PEEM in which an image (photoelectron image) is obtained by photoelectrons generated by emitting excitation light 10, such as ultraviolet light or X-rays, to the surface of a wafer (a sample) 20. The main configuration of a device body 114 comprises a sample stage 101 on which the wafer 20 to be inspected is arranged, a camera 108 for generating the photoelectron image, and an electron-optical system for projecting the photoelectron image onto the camera 108. A sample holding surface of the sample stage 101 is adjusted so that it is horizontal to the floor surface on which the device body 114 is installed.The camera 108 can directly capture and image electrons (photoelectrons) or be equipped with a scintillator to convert the electrons into light and capture the light for image generation. The main body of the device 114 (including the sample stage 101, the camera 108, and the electron-optical system) is connected to a control device 112. The control device 112 controls the main body of the device 114 in response to a command entered by a user via a graphical user interface (GUI) device 111 and performs image processing on the photoelectron image captured by the camera 108. The control device 112 has a storage unit 113 which stores control parameters of the main body of the device 114 and the photoelectron image. An optical axis 109, which is the center of the electron beam path in the electron-optical system shown in Fig. 1, is perpendicular to the sample holder surface of the sample stage 101. Accordingly, the electron-optical system and the camera 108 can be integrated into an upright column, and the handling of the wafer 20 can be aligned with other devices used in a semiconductor manufacturing line. The electron-optical system is described as divided into three sections A to C. If the sample holder surface of the sample stage 101 is defined as the XY plane and a direction perpendicular to the XY plane is defined as the Z direction, the optical axis 109 extends from the incident position of the excitation light 10 with respect to the wafer 20 in the Z direction. In section A, an objective lens 102 generates a photoelectron image. In Fig. 1, an axial beam is shown as axial beam 110a before it strikes the mirror aberration corrector 106, and a field beam is shown as field beam 110b before it strikes the mirror aberration corrector 106. The lens 103 is an auxiliary objective lens that aligns the field beam 110b parallel to the optical axis 109. The photoelectron image is magnified by the objective lens 102 from a distance between the axial beam 110a and the field beam 110b on the wafer 20 to a distance between the axial beam 110a and the field beam 110b (indicated by an arrow) in the magnetic field sector 104a. In Section B, the chromatic aberration and spherical aberration of the photoelectron image are corrected. The mirror aberration corrector 106 is used to correct the chromatic and spherical aberration of the photoelectron image. The mirror aberration corrector 106 has several electrodes and reflects a path near the electrodes by means of a voltage applied to its last stage. The spherical and chromatic aberration can be corrected by controlling the voltage applied to the electrodes. The mirror aberration corrector 106 is similar, for example, to the electronic mirror disclosed in PTL 1, and a known configuration can be used. The mirror aberration corrector 106 is arranged orthogonally to the optical axis 109.Accordingly, the magnetic field sectors 104a to 104c in Section B are used to control the path of the photoelectrons so that it deviates from the optical axis 109, the photoelectrons fall onto the mirror aberration corrector 106, and the path of the photoelectrons emitted by the mirror aberration corrector 106 is guided back to the optical axis 109. In Fig. 1, an axial beam after emission from the mirror aberration corrector 106 is shown as axial beam 110c, and a field beam after emission from the mirror aberration corrector 106 is shown as field beam 110d. The magnetic field sector 104a is arranged such that its center is located at a position where the axial beam 110a and the optical axis 109 intersect. Similarly, the magnetic field sector 104c is arranged so that its center is located at a position where the axial beam 110c and the optical axis 109 intersect.In section B, a photoelectron image (indicated by an arrow in magnetic field sector 104c) is obtained in which chromatic aberration and spherical aberration are corrected. The magnifications (1x) of the photoelectron images at the input (magnetic field sector 104a) and output (magnetic field sector 104c) of section B are not changed. In section C, the aberration-corrected photoelectron image is magnified and projected onto the imaging surface of the camera 108 through a projection lens 107. Regarding the path of the electron beam (the photoelectrons) in the magnetic field sectors, it should be noted that Fig. 1, for the sake of clarity, shows that the electron beam moves linearly and is refracted at an angle at a certain point, but that the electron beam is actually slightly curved. The same applies to the following drawings. The control of the photoelectron (electron beam) path in section B is described with reference to Figures 2A and 2B. In section B, the electron beam's path must be diffracted by 90° (π / 2) with respect to the optical axis 109 to cause the electron beam to fall on the mirror aberration corrector, and then diffracted again by 90° (π / 2) in the direction of travel of the electron beam to cause the electron beam emitted (reflected) by the mirror aberration corrector to travel again along the optical axis 109. The magnetic field sectors 104 are used to change the direction of travel of the electron beam, and they generate a deflection aberration depending on the direction of deflection.Accordingly, in the present embodiment, the electron beam deflected in the first magnetic field sector falls onto a second magnetic field sector, the electron beam is deflected in the second magnetic field sector, and the deflection aberration generated in the first magnetic field sector is canceled out. Therefore, the absolute values ​​of the magnitudes of the deflection aberration generated in the first magnetic field sector and in the second magnetic field sector must be equal, so that the deflection angle of the first magnetic field sector and the deflection angle of the second magnetic field sector must be equal. It is necessary to cancel the deflection aberration of a path from the optical axis 109 to the point of incidence on the mirror aberration corrector and the deflection aberration of a path from the emission point of the mirror aberration corrector to the optical axis 109. Accordingly, an even number of magnetic field sectors are required before and after the point of incidence of the electron beam on the mirror aberration corrector, and the magnetic field sector located immediately in front of the mirror aberration corrector (magnetic field sector 104b in Fig. 1) is used both before and after the point of incidence of the electron beam on the mirror aberration corrector. The electron-optical system in section B (corresponding to Fig. 2A) in Fig. 1 is shown with a configuration in which the number of magnetic field sectors is minimized, resulting in a total of three magnetic field sectors, each with a deflection angle of π / 4. The configuration of the magnetic field sectors controlling the path of the electron beam in section B is shown in a generalized form in Fig. 2B. Magnetic field sectors are arranged at diffraction points in Fig. 2B. If the number of magnetic field sectors in section B is π / 4, the deflection angle of the magnetic field sector in this case is A, where S and A are expressed by the following equations: Here, N is a natural number. Fig. 2A corresponds to a case N = 1, and Fig. 2B corresponds to a case N = 2. As N increases, the number of magnetic field sectors increases, but the deflection aberration caused by the magnetic field sectors can be reduced, so that the path of the electron beam can be controlled more precisely. The deflection aberration generated in the first magnetic field sector can be eliminated by sandwich-shaped arrangement of a doublet lens 105 between the first magnetic field sector and the second magnetic field sector. First, the doublet lens is described with reference to Fig. 3B. The doublet lens has two lenses, namely 313 and 314. If the focal lengths of lenses 313 and 314 are F1 and F2 respectively, the distance between the object plane and lens 313 is F1, the distance between lens 313 and lens 314 is (F1 + F2), and the distance between lens 314 and a negative image plane is F2. A field ray 317 falling parallel to the optical axis 315 from the object plane onto the lens 313 crosses the optical axis at a position whose distance from the lens 313 is F1 and whose distance from the lens 314 is F2, and the field ray 317 is again parallel to the optical axis 315 after passing through the lens 314. An axial ray 316, which passes through the optical axis 315 at the object plane, passes through the optical axis 315 at the image plane.This is demonstrated by a feature in which the directions of travel of the axial beam 316 and the field beam 317 are reversed before and after incident on the double lens with respect to the optical axis 315. With this feature, the deflection aberration generated in the first magnetic field sector is canceled out in the second magnetic field sector. Because lenses 313 and 314 have the same magnification in the doublet lens used according to the present embodiment, focal length F1 = focal length F2. In a case where lenses 313 and 314 are magnetic field lenses, the rotation of the electron beam path is eliminated by reversing the direction of the current flowing through the coil. Fig. 3A schematically shows the paths of electron beams passing through a doublet lens having a first magnetic field sector 301, a second magnetic field sector 302, and lenses 303 and 304 arranged between the magnetic field sectors 301 and 302. The first magnetic field sector 301 is located at the object plane of the doublet lens, and the second magnetic field sector 302 is located at the image plane of the doublet lens. In reality, the paths of the electron beams are deflected by the magnetic field sectors, although this is simplified in Fig. 3A, where the paths of the electron beams are shown to be straight. Arrows shown in the first magnetic field sector 301 and the second magnetic field sector 302 indicate the direction and magnitude of the deflection. As described above, the direction and magnitude of the deflection of the first magnetic field sector 301 and the second magnetic field sector 302 are the same. As described with reference to Fig. 1, the axial beam of photoelectrons (electron beam) intersects the optical axis at the center of the magnetic field sectors. Accordingly, the center of the magnetic field sectors lies in the object plane and the image plane of the doublet lens, so that, as shown in Fig. 3A, if no deflection aberration occurs, the axial beam 306 intersects the optical axis 305 at the center of the first magnetic field sector 301 and again at the center of the second magnetic field sector 302. The field beam 307 falls on the lens 303 in a path parallel to the optical axis 305 and is emitted by the lens 304 in a path parallel to the optical axis 305. As a result of the deflection aberration generated in the first magnetic field sector 301, the axial beam 306 is transformed into a deflected axial beam 308 and the field beam 307 is transformed into a deflection field beam 309. In this example, when viewed in the plane of the paper, the axial deflection beam 308 and the deflection field beam 309 fall below the axial beam 306 and the field beam 307, respectively, onto the lens 303. As described with reference to Fig. 3B, because the paths of the electron beams are reversed with respect to the optical axis before and after incident on the doublet lens, in a case where the second magnetic field sector 302 does not produce a deflection aberration, the deflected axial beam 308 and the deflection field beam 309, which pass through the second magnetic field sector 302, fall above the axial beam 306 and the field beam 307, respectively, when viewed in the plane of the paper.Because the second magnetic field sector 302 generates the same deflection aberration as the first magnetic field sector 301, the deflected axial beam 308 and the deflection field beam 309, which pass through the second magnetic field sector 302, are returned to the axial beam 306 and the field beam 307, respectively. This means that the deflection aberration has been eliminated. In a case where it is difficult to establish a correlation between the distance from the first magnetic field sector 301 to the second magnetic field sector 302 and the focal lengths of the lenses 303 and 304 forming the doublet lens using a single-stage doublet lens, doublet lenses with odd numbers of stages can be arranged between the magnetic field sectors. If the number of lenses arranged between adjacent magnetic field sectors is L, then L can accordingly be expressed by the following equation: Here, M is a natural number. In Fig. 1, both a doublet lens 105a arranged between magnetic field sector 104a and magnetic field sector 104b, and a doublet lens 105b arranged between magnetic field sector 104b and magnetic field sector 104c, are examples (L = 2) of the single-stage doublet lens. The number of stages of the doublet lens can be different for each position between the magnetic field sectors. Fig. 4 shows a modification of the main body of the device 114. In this modification, magnetic field sectors can be temporarily switched off when high resolution is not required or when the main body of the device needs to be adjusted. The configuration is essentially the same as that shown in Fig. 1, except that a lens group 401 is arranged between the magnetic field sector 104a closest to a sample and the magnetic field sector 104c closest to a camera. In an aberration correction OFF mode, the axial beam 110a and the field beam 110b travel in a straight path without being deflected by the magnetic field sector 104 because the magnetic field sectors 104a to 104c are switched off without any current flowing through them. The lens group 401 projects a central area 402 of the magnetic field sector 104a onto a central area 403 of the magnetic field sector 104c at a magnification of 1.By using a simple magnification projection, the magnification of the electron-optical systems can be made constant, independent of the on / off state of the magnetic field sectors (aberration correction ON mode / aberration correction OFF mode). Accordingly, the offset from the axis when the axial beam and the field beam pass through the projection lens 107 can be the same regardless of the aberration correction ON / off mode, so that the aberration produced by the projection lens 107, the path selection based on an aperture, and the sensitivity of the adjustment device can also be adjusted. For example, the lens group 401, which projects with a simple magnification, can be implemented by designing the lens group 401 with a single- or multi-stage doublet lens and ensuring that the focal lengths of the lenses in the lens group 401 are equal. A configuration of the magnetic field sector used according to the present embodiment is described. Fig. 5 shows a magnetic field sector 501 viewed from an X-direction. The XYZ directions are the same as those in Fig. 1, and the direction in which the electron beam is deflected by the magnetic field sector 501 lies in an XZ plane. The optical axis 503, which is the center of the electron beam's path, is also shown. The magnetic field sector 501 has two planar pole pieces 502a and 502b, which are opposite each other across the intervening optical axis 503. The pole pieces 502a and 502b are arranged parallel to the XZ plane. The pole pieces 502a and 502b have the same shape. Fig. 6 shows the pole piece 502a viewed from the optical axis in the Y-direction. Fig. 6 shows an example of a magnetic field sector with a circular planar shape. The pole piece 502 is made of a magnetic material of the iron type. A groove 505 concentric to the pole piece 502 is formed, the inner side of which is referred to as the main pole piece 504 and the outer side as the shielding magnetic pole 506. A coil is wound around the groove 505, and by controlling the direction and magnitude of the current flowing through the opposing pole piece coils, a uniform magnetic field B0 is generated between the main pole piece 504 of pole piece 502a and the main pole piece 504 of pole piece 502b. The magnetic field B0 terminates at the shielding magnetic pole 506, and no magnetic field is present outside the magnetic field sector. An electron beam is deflected in the X-direction by the Lorentz force. An electron beam incidence plane 507a and an electron beam emission plane 507b of the magnetic field sector are perpendicular to the optical axis. The deflection angle A of the magnetic field sector according to the present embodiment is π / 4N[rad] (N = 1 in Fig. 6), as described above, and the electron beam emission plane 507b is defined according to the deflection angle A of the magnetic field sector. A median plane 508 has the intersection line between the electron beam incidence plane 507a and the electron beam emission plane 507b and the center of the pole piece 502a. The distance within the main pole piece, the groove spacing, and the distance of the shielding magnetic pole of the optical axis 503 are equal about the median plane 508, and the path of the electron beam is symmetrical with the median plane 508 as its starting point. As shown in Fig. 3A, the deflection aberrations generated in the magnetic field sectors cancel each other out with the median plane 508 as its boundary, because the axial electron beam intersects the optical axis at the center of the magnetic field sector. The planar shape of the magnetic field sector cannot be circular, and the same effect can be obtained by maintaining the conditions described in Fig. 6 regarding symmetry and verticality. Examples of such a case are shown in Figs. 7A and 7B. The dotted lines in each of Figs. 7A and 7B show the shape (corresponding to Fig. 6) when the planar shape of the pole piece is circular, which can deflect the same electron beam. Accordingly, the arrangement of the main pole piece 504, the groove 505, and the shielding magnetic pole 506 on the optical axis 503 is the same as in Fig. 6, and furthermore, the electron beam incidence plane 507a and the electron beam emission plane 507b are end faces of the pole piece 502 in both structures from Fig. 7A and Fig. 7B, which is why the structures from Fig. 7A and Fig. 7B are superior to those in Fig. 7A in that a deflection aberration is less likely to occur.The structure shown in Figure 6 is advantageous. Figure 7B shows a structure in which a structural section, through which the electron beam does not pass, is further cut out from the structure in Figure 7A, which has the advantage that the space of the column in which the electron-optical system is installed can be used effectively. Fig. 8 shows another configuration example of the magnetic field sector. Because the Lorentz force does not act on the electron beam traveling parallel to the magnetic field B0, the electron beam is essentially focused only in the deflection direction within the magnetic field sector. In this way, the electron beam is in a state in which strong astigmatism is generated. Fig. 8 shows a configuration that modifies the generation of astigmatism due to the magnetic field sector. A boundary field (magnetic field) near the groove 505 of the pole piece has a magnetic field component horizontal to the deflection direction of the electron beam and can therefore act in a direction perpendicular to the deflection direction of the electron beam. Therefore, in the magnetic field sector of Fig. 8, the generation of astigmatism is prevented by using the boundary field. Because in the electron-optical system shown in Fig. 1 the electron beam falls twice onto and is emitted from the magnetic field sector 104b, which is closest to the mirror aberration corrector 106, very precise control of the electron beam is required. Accordingly, Fig. 8 shows a pole piece in which an astigmatism prevention device has been added to the pole piece shown in Fig. 7B. To make the relationship with the magnetic field sector 104b in Fig. 1 easier to understand, the pole piece in Fig. 7B has been rotated 90° to the left and is shown in Fig. 8. In the configuration shown in Fig. 8, a main pole piece is subdivided into three main pole pieces 601 to 603 by grooves. An intermediate plane 604a is an intermediate plane with respect to an electron beam incidence plane 507a1 and an electron beam emission plane 507b1, and an intermediate plane 604b is an intermediate plane with respect to an electron beam incidence plane 507a2 (equal to the electron beam emission plane 507b1) and an electron beam emission plane 507b2. The grooves 505d1 and 505d2, which separate the main pole pieces, are formed parallel to the intermediate planes 604a and 604b. In this example, the same current flows in the coils of the first and third main pole pieces, so that the magnetic field B1 generated by the first main pole piece 601 becomes equal to the magnetic field B3 generated by the third main pole piece 603. A different current flows in a coil of the second main pole piece 602, so that the magnetic field B2 generated by the second main pole piece 602 is opposite to the magnetic field B1 (B3). As long as the optical axis 503, which passes through the corresponding electron beam incidence and emission planes, is kept symmetrical with respect to the intermediate plane 604a or the intermediate plane 604b, the magnetic fields B1 (B3) and B2 can be freely chosen. In the example from Fig. 8, the magnetic field B2 is inverted with respect to the magnetic fields B1 and B3, so that a path is formed in which the optical axis bulges outwards.If all currents flowing through the first to third main pole pieces are equal, the paths of the deflected electron beams are the same, as with the pole piece in Fig. 7B. Because the edge magnetic field received when the electron beam passes through the grooves 505 (including the grooves 505d separating the main pole piece) changes depending on the combination of magnetic fields B1 to B3, a combination of magnetic fields B1 to B3 can be chosen that minimizes the strength of the generated astigmatism. Fig. 8 shows an example where the main pole piece is divided into three parts, and the main pole piece can be further divided into an even greater number of parts.Because it is difficult to wind the coil along a recessed main pole piece in terms of assembly, the first main pole piece 601 or the second main pole piece 602 is divided into an upper and a lower part, coils are wound for the parts and the same current flows through the coils, thus achieving the same effects. Although the invention has been described above with reference to the embodiments, it is not limited to the content described above. Although a PEEM has been described as an example in the present embodiment, the electron-optical system according to the present embodiment can, for example, also be applied to a LEEM with a similar electron-optical system. Reference symbol list 10 Excitation light 20 Wafer (sample) 101 Sample stage 102 Objective lens 103 Auxiliary objective lens 104 Magnetic field sector 105 Doublet lens 106 Mirror aberration corrector 107 Projection lens 108 Camera 109 Optical axis 110a, 110c Axial beam 110b, 110d Field beam 111 GUI device 112 Control device 113 Storage device 114 Device main body 301, 302: Magnetic field sector 303, 304, 313, 314 Lens 305, 315 Optical axis 306, 308, 316 Axial beam 307, 309, 317 Field beam 401 Lens group 402, 403 Central area 501 Magnetic field sector 502 Pole piece 503 optical axis 504 main pole piece 505 groove 506 shielding magnet pole 507a electron beam incidence plane 507b electron beam emission plane 508 intermediate plane 601 first main pole piece 602 second main pole piece 603 third main pole piece 604 intermediate plane

Claims

Electron beam application device comprising: a sample stage (101) on which a sample (20) is to be arranged, an electron-optical system comprising an objective lens (102) for generating an electronic image by electrons emitted from the sample (20) and whose optical axis (109, 305, 315, 503) is perpendicular to a sample holding surface of the sample stage (101), and a camera (108) that generates the electronic image, wherein the electron-optical system comprises: a mirror aberration corrector (106) arranged perpendicular to the optical axis (109, 305, 315, 503), several magnetic field sectors (104, 301, 302, 501) through which the path of the electrons passing through the objective lens (102) is directed away from the optical axis (109, 305, 315, 503). is deflected so that the electrons fall onto the mirror aberration corrector (106), and the path of the electrons emitted by the mirror aberration corrector (106) to the optical axis (109, 305, 315,503), and a doublet lens (105) is arranged between adjacent magnetic field sectors (104, 301, 302, 501) along the path of the electrons, wherein the several magnetic field sectors (104, 301, 302, 501) have the same deflection angle at which the path of the electrons is deflected, and the doublet lens (105) is arranged such that its object plane or image plane is the median plane (508) of the adjacent magnetic field sectors (104, 301, 302, 501) along the path of the electrons. Electron beam application device according to claim 1, wherein if the number of magnetic field sectors (104, 301, 302, 501) in the electron-optical system is S and the deflection angles of the multiple magnetic field sectors (104, 301, 302, 501) are A, S and A are expressed by the following equations: S = 4 N − 1 A = π / 4 N [ rad ] where N is a natural number. Electron beam application device according to claim 1, wherein the median plane (508) of the magnetic field sector (501) has the intersection line between an electron beam incidence plane (507a) and an electron beam emission plane (507b) of the magnetic field sector (501) and the center of the magnetic field sector (501). Electron beam application device according to claim 1, wherein the doublet lens (105) is arranged with odd-numbered steps between adjacent magnetic field sectors (104) along the path of the electrons. Electron beam application device according to claim 1, wherein the multiple magnetic field sectors include a first and a second magnetic field sector (301, 302) whose centers are arranged on the optical axis (305), the center of the first magnetic field sector (301) is located at the intersection between an axial beam (306, 308) of electrons passing through the objective lens (102) and the optical axis (305), and the center of the second magnetic field sector (302) is located at the intersection between an axial beam (306, 308) of electrons emitted from the mirror aberration corrector (106) and the optical axis (305). Electron beam application device according to claim 5, wherein the electron-optical system comprises: an auxiliary objective lens (103) by which a field beam (317) of the electrons passing through the objective lens (102) is aligned between the objective lens (102) and the first magnetic field sector (104) parallel to the optical axis (305), and a projection lens (107) which magnifies an electronic image that is aberration-corrected by the mirror aberration corrector (106) and projects it onto the image-generating surface of the camera (108). Electron beam application device according to claim 5, wherein the doublet lens (105) is arranged with one or more stages between the first and the second magnetic field sector (301, 302) and the multiple magnetic field sectors (301, 302) can be switched off. Electron beam application device according to claim 7, wherein an electronic image is formed on the second magnetic field sector (302) at the same magnification as an electron image formed on the first magnetic field sector (301), regardless of whether the multiple magnetic field sectors (301, 302) are switched on or off. Electron beam application device according to claim 1, wherein the magnetic field sectors (501) have opposing planar pole pieces (502, 504), the optical axis (503) being sandwiched between them, the pole piece (502, 504) being divided by a first groove (505, 505d1) into a main pole piece (504) and a shielding magnetic pole (506), the first groove (505, 505d1) surrounding the main pole piece (504) and a coil generating a magnetic field in the magnetic field sector (501) being arranged in the first groove (505, 505d1). Electron beam application device according to claim 9, wherein the planar shape of the pole piece (502, 504) is a circular shape and the first groove (505, 505d1) is formed concentrically with the pole piece (502, 504). Electron beam application device according to claim 9, wherein a first end surface of the pole piece (502, 504) is an electron beam incidence plane (507a) of the magnetic field sector (501), a second end surface of the pole piece (502, 504) is an electron beam emission plane (507b) of the magnetic field sector (501), and the arrangement of the main pole piece (504), the first groove (505, 505d1) and the shielding magnetic pole (506) is the same on the optical axis (503) from the electron beam incidence plane (507a) to the center and on the optical axis (503) from the center to the electron beam emission plane (507b) in the magnetic field sector (501). Electron beam application device according to claim 9, wherein a second groove (505d2) is formed to further subdivide the main pole piece (504) into several main pole pieces (601-603), a coil generating a magnetic field in the magnetic field sector (501) is arranged in both the first (505d1) and the second groove (505d2), and the second groove (505d2) is formed parallel to the central plane (508) of the magnetic field sector (501). Electron beam application device according to claim 12, wherein a different magnetic field is generated for each of the several subdivided main pole pieces (601-603). Electron beam application device according to claim 12, wherein the median plane (508) of the magnetic field sector (501) has the intersection line between an electron beam incidence plane (507a) and an electron beam emission plane (507b) of the magnetic field sector (501) and the center of the magnetic field sector (501). Electron beam application device according to claim 1, wherein the sample holding surface of the sample table (101) is adjusted horizontally to the floor surface on which the electron beam application device is installed.

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