Electromagnetic lens and multi-electron beam irradiation device

Abstract

An electromagnetic lens according to one aspect of the present invention is characterized by comprising a first magnetic pole which is formed of a magnetic body, has a plurality of first openings formed therein through which multiple electron beams pass, is connected to an inner peripheral wall or an upper wall on the upstream side in the traveling direction of the multiple electron beams in a gap of the inner peripheral wall, and is disposed so as to close a space inside the inner peripheral wall, and a second magnetic pole which is formed of a magnetic body, has a plurality of second openings through which the multiple electron beams pass, is connected to the inner peripheral wall or a lower wall on the downstream side in the traveling direction of the multiple electron beams in the gap of the inner peripheral wall, and is disposed so as to close the space inside the inner peripheral wall, wherein the plurality of first openings and / or the plurality of second openings are formed with a plurality of different diameter sizes so that the lens action becomes smaller from the center toward the outer peripheral side.

Description

Electromagnetic lens and multi-electron beam irradiation device

[0001] This application claims priority from JP2023-145592 (application number) filed in Japan on September 7, 2023. The entire contents of JP2023-145592 are incorporated herein by reference.

[0002] One aspect of the present invention relates to an electromagnetic lens and a multi-electron beam irradiation device, for example, an electromagnetic lens mounted in a multi-beam inspection device that performs pattern inspection using a secondary electron image resulting from irradiation with multiple primary electron beams.

[0003] In recent years, with the increasing integration and capacity of large-scale integrated circuits (LSIs), the circuit line widths required for semiconductor elements have become increasingly narrow. Furthermore, improving yield is essential for the manufacture of LSIs, which incur significant manufacturing costs. However, as exemplified by 1-gigabit-class DRAMs (Dynamic Random Access Memory), the patterns that make up LSIs are now on the order of submicrons to nanometers. As the dimensions of LSI patterns formed on semiconductor wafers have become increasingly miniaturized in recent years, the dimensions that must be detected as pattern defects have also become extremely small. Therefore, high-precision image capture is necessary to inspect defects in ultra-fine patterns transferred onto semiconductor wafers.

[0004] In the inspection device, for example, multiple primary electron beams using electron beams are focused on the substrate to be inspected, and the substrate to be inspected is scanned with the multiple primary electron beams, and multiple secondary electron beams emitted from the substrate to be inspected are separated from the trajectories of the multiple primary electron beams.The separated multiple secondary electron beams are then guided to a detector, and the detector detects the multiple secondary electron beams to capture a pattern image.

[0005] When the substrate to be inspected is irradiated with multiple primary electron beams, there is a problem in that the electromagnetic lens that forms the image generates a field curvature aberration.

[0006] Here, a technique has been disclosed in which a multi-axis electron lens is used to independently converge a plurality of electron beams and adjust the focal points of the electron beams so that the lens intensities are approximately equal (see, for example, Patent Document 1).

[0007] Republished No. 01 / 075949

[0008] Therefore, one aspect of the present invention provides an electromagnetic lens and device capable of correcting the field curvature aberration occurring in multiple primary electron beams.

[0009] An electromagnetic lens according to one aspect of the present invention comprises: a coil; a pole piece formed of a magnetic material, having an upper wall upstream in the direction of propagation of multiple electron beams passing therethrough, a lower wall downstream in the direction of propagation of the multiple electron beams, an outer peripheral wall, and an inner peripheral wall having a gap formed in the circumferential direction, the pole piece surrounding the coil with the upper wall, lower wall, outer peripheral wall, and inner peripheral wall; a first magnetic pole formed of a magnetic material, having a plurality of first openings through which the multiple electron beams pass, connected to the inner peripheral wall or the upper wall on the upstream side of the gap in the inner peripheral wall in the direction of propagation of the multiple electron beams, and arranged to close a space inside the inner peripheral wall; and a second magnetic pole formed of a magnetic material, having a plurality of second openings through which the multiple electron beams pass, connected to the inner peripheral wall or the lower wall on the downstream side of the gap in the inner peripheral wall in the direction of propagation of the multiple electron beams, and arranged to close a space inside the inner peripheral wall. At least one of the plurality of first openings and the plurality of second openings is formed with a plurality of different diameter sizes so that the lens action decreases from the center toward the outer periphery.

[0010] A multi-electron beam irradiation device according to one aspect of the present invention comprises: a coil; a pole piece formed of a magnetic material, having an upper wall upstream in the direction of propagation of the multi-electron beams passing therethrough, a lower wall downstream in the direction of propagation of the multi-electron beams, an outer peripheral wall, and an inner peripheral wall having a gap formed in the circumferential direction, the pole piece surrounding the coil with the upper wall, lower wall, outer peripheral wall, and inner peripheral wall; a first magnetic pole formed of a magnetic material, having a plurality of first openings through which the multi-electron beams pass, connected to the inner peripheral wall or the upper wall on the upstream side of the gap in the inner peripheral wall in the direction of propagation of the multi-electron beams, and arranged to close a space inside the inner peripheral wall; and a second magnetic pole formed of a magnetic material, having a plurality of second openings through which the multi-electron beams pass, connected to the inner peripheral wall or the lower wall on the downstream side of the gap in the inner peripheral wall in the direction of propagation of the multi-electron beams, and arranged to close a space inside the inner peripheral wall. At least one of the plurality of first openings and the plurality of second openings comprises an electromagnetic lens formed with a plurality of different diameter sizes so that the lens action decreases from the center toward the outer periphery, and a stage on which a sample to be irradiated with the multi-electron beams that have passed through the electromagnetic lens is placed.

[0011] According to one aspect of the present invention, it is possible to correct field curvature aberration occurring in multiple primary electron beams.

[0012] 1 is a configuration diagram showing the configuration of a pattern inspection device according to the first embodiment. FIG. 2 is a cross-sectional view showing an example of the configuration of a multi-axis electromagnetic lens according to the first embodiment. FIG. 3 is a top view showing an example of the configuration of a shaping aperture array substrate of the multi-axis electromagnetic lens according to the first embodiment. FIG. 4 is a top view showing an example of the configuration of an upper magnetic pole and a lower magnetic pole of the multi-axis electromagnetic lens according to the first embodiment. FIG. 5 is a diagram showing an example of the relationship between the field curvature height and the number of beam columns according to the first embodiment. FIG. 6 is a diagram showing an example of the relationship between the focus height and the opening diameter size of the passage hole according to the first embodiment. FIG. 7 is a top view showing another example of the passage hole of the upper magnetic pole of the multi-axis electromagnetic lens according to the first embodiment. FIG. 8 is a top view showing another example of the passage hole of the lower magnetic pole of the multi-axis electromagnetic lens according to the first embodiment. FIG. 9 is a diagram showing an example of the beam size of multi-primary electron beams on a substrate surface in a comparative example of the first embodiment. FIG. 10 is a diagram showing an example of the beam size of multi-primary electron beams on a substrate surface according to the first embodiment. FIG. 11 is a cross-sectional view showing a part of the configuration of a multi-axis electromagnetic lens according to a first modification of the first embodiment. FIG. 12 is a cross-sectional view showing a part of the configuration of a multi-axis electromagnetic lens according to a second modification of the first embodiment. FIG. 13 is a diagram for explaining an example of a method of acquiring an image according to the first embodiment. 1 is a configuration diagram showing an example of the configuration inside a comparison circuit according to Embodiment 1. FIG. 2 is a cross-sectional view showing an example of the configuration of a multi-axis electromagnetic lens according to Embodiment 2.

[0013] In the following embodiments, a multi-electron beam inspection apparatus will be described as an example of a multi-electron beam irradiation apparatus. However, the multi-electron beam irradiation apparatus is not limited to an inspection apparatus, and may be, for example, a drawing apparatus or the like.

[0014] [First Embodiment] Fig. 1 is a configuration diagram showing the configuration of a pattern inspection apparatus according to a first embodiment. In Fig. 1, an inspection apparatus 100 that inspects a pattern formed on a substrate is an example of a multi-electron beam inspection apparatus. The inspection apparatus 100 is an example of a multi-electron beam irradiation apparatus. The inspection apparatus 100 is an example of a multi-electron beam image acquisition apparatus. The inspection apparatus 100 includes an image acquisition mechanism 150 and a control system circuit 160 (control unit). The image acquisition mechanism 150 includes an electron beam column 102 (electron lens barrel), an inspection chamber 103, a detection circuit 106, a chip pattern memory 123, a stage driving mechanism 142, and a laser length measurement system 122. The electron beam column 102 contains an electron gun 201, an electromagnetic lens 202, a multi-axis electromagnetic lens 210, an electromagnetic lens 205, a collective deflector 212, a limiting aperture substrate 213, an electromagnetic lens 206, an E×B separator 214 (separator), an electromagnetic lens 207 (objective lens), deflectors 208 and 209, a deflector 218, deflectors 225 and 226, an electromagnetic lens 224, and a multi-detector 222.

[0015] The primary electron optical system 151 (illumination optical system) is composed of the electron gun 201, the electromagnetic lens 202, the multi-axis electromagnetic lens 210 (electromagnetic lens), the electromagnetic lens 205, the collective deflector 212, the limiting aperture substrate 213, the electromagnetic lens 206, the E×B separator 214 (separator), the electromagnetic lens 207, and the deflectors 208 and 209. The secondary electron optical system 152 (detection optical system) is composed of the electromagnetic lens 207, the E×B separator 214, the deflector 218, the deflectors 225 and 226, and the electromagnetic lens 224.

[0016] The multi-detector 222 has a plurality of detection elements arranged in an array (grid).

[0017] A stage 105 movable at least in the X and Y directions is disposed within the inspection chamber 103. A substrate 101 (sample) to be inspected is disposed on the stage 105. The substrate 101 includes an exposure mask substrate and a semiconductor substrate such as a silicon wafer. When the substrate 101 is a semiconductor substrate, multiple chip patterns (wafer dies) are formed on the semiconductor substrate. When the substrate 101 is an exposure mask substrate, multiple chip patterns are formed on the exposure mask substrate. The chip patterns are composed of multiple graphic patterns. The chip patterns formed on the exposure mask substrate are transferred onto the semiconductor substrate multiple times by exposure, thereby forming multiple chip patterns (wafer dies) on the semiconductor substrate. The substrate 101 is disposed on the stage 105, for example, with its pattern-forming surface facing upward. A mirror 216 is disposed on the stage 105 to reflect laser light for laser measurement irradiated from a laser measurement system 122 disposed outside the inspection chamber 103. A mark 111 is disposed on the stage 105 at the same height as the surface of the substrate 101. The mark 111 has, for example, a cross pattern formed thereon.

[0018] Furthermore, the multi-detector 222 is connected to a detection circuit 106 outside the electron beam column 102. The detection circuit 106 is connected to a chip pattern memory 123.

[0019] In the control system circuit 160, a control computer 110 that controls the entire inspection apparatus 100 is connected via a bus 120 to a position circuit 107, a comparison circuit 108, a reference image creation circuit 112, a stage control circuit 114, a lens control circuit 124, a blanking control circuit 126, a deflection control circuit 128, a multi-axis electromagnetic lens control circuit 130, an E×B separator control circuit 132, a storage device 109 such as a magnetic disk drive, a monitor 117, a memory 118, and a printer 119. The deflection control circuit 128 is also connected to DAC (digital-to-analog converter) amplifiers 144, 146, 147, and 149, and a DC power supply 148. The DAC amplifier 146 is connected to a deflector 208, and the DAC amplifier 144 is connected to the deflector 209. The DC power supply 148 is connected to a deflector 218. The DAC amplifier 147 is connected to a deflector 225. The DAC amplifier 149 is connected to the deflector 226 .

[0020] The chip pattern memory 123 is also connected to the comparison circuit 108. The stage 105 is driven by a drive mechanism 142 under the control of the stage control circuit 114. The drive mechanism 142 is configured with a drive system, such as a three-axis (X-Y-θ) motor that drives the stage 105 in the X, Y, and θ directions of a stage coordinate system, thereby enabling the stage 105 to move in the X, Y, and θ directions. These X, Y, and θ motors (not shown) can be, for example, step motors. The stage 105 can move horizontally and in rotational directions by the motors for the X, Y, and θ axes. The movement position of the stage 105 is measured by a laser length measurement system 122 and supplied to the position circuit 107. The laser length measurement system 122 measures the position of the stage 105 based on the principle of laser interferometry by receiving light reflected from a mirror 216. In the stage coordinate system, for example, the X, Y, and θ directions of the primary coordinate system are set relative to a plane perpendicular to the optical axis of the multi-primary electron beams 20.

[0021] The electromagnetic lens 202 , the electromagnetic lens 205 , the electromagnetic lens 206 , the electromagnetic lens 207 , and the electromagnetic lens 224 are controlled by the lens control circuit 124 .

[0022] Furthermore, the multi-axis electromagnetic lens 210 is controlled by a multi-axis electromagnetic lens control circuit 130 .

[0023] The collective deflector 212 is composed of two or more electrodes and is controlled by the blanking control circuit 126 for each electrode via a DAC amplifier (not shown). The deflector 209 is composed of four or more electrodes and is controlled by the deflection control circuit 128 for each electrode via a DAC amplifier 144. The deflector 208 is composed of four or more electrodes and is controlled by the deflection control circuit 128 for each electrode via a DAC amplifier 146. The deflector 225 is composed of four or more electrodes and is controlled by the deflection control circuit 128 for each electrode via a DAC amplifier 147. The deflector 226 is composed of four or more electrodes and is controlled by the deflection control circuit 128 for each electrode via a DAC amplifier 149.

[0024] The deflector 218 (bender) is configured, for example, in the shape of a cylinder curved in an arc by a plurality of electrodes having four or more poles, and each electrode is controlled by the deflection control circuit 128 via the DC power supply 148. Alternatively, the deflector 218 may be configured to be configured by a plurality of flat electrodes having four or more poles, and each electrode may be controlled by the deflection control circuit 128 via the DC power supply 148.

[0025] The E×B separator 214 is controlled by the E×B separator control circuit 132 .

[0026] A high-voltage power supply circuit (not shown) is connected to the electron gun 201, and an acceleration voltage is applied from the high-voltage power supply circuit between a filament (not shown) and an extraction electrode (not shown) inside the electron gun 201. In addition, a voltage is applied to a predetermined extraction electrode (Wehnelt) and the cathode is heated to a predetermined temperature, whereby a group of electrons emitted from the cathode are accelerated and emitted as an electron beam 200.

[0027] 1 shows the configuration necessary for explaining the first embodiment. The inspection device 100 may also include other configurations that are normally required.

[0028] FIG. 2 is a cross-sectional view showing an example of the configuration of the multi-axis electromagnetic lens according to the first embodiment. FIG. 3 is a top view showing an example of the configuration of a shaping aperture array substrate of the multi-axis electromagnetic lens according to the first embodiment. FIG. 4 is a top view showing an example of the configuration of an upper magnetic pole and a lower magnetic pole of the multi-axis electromagnetic lens according to the first embodiment. In FIG. 2, the multi-axis electromagnetic lens 210 has a coil 40, a pole piece 42 (also referred to as a yoke), an upper magnetic pole 44, and a lower magnetic pole 46. The multi-axis electromagnetic lens 210 also has a shaping aperture array substrate 203. The pole piece 42, the upper magnetic pole 44, and the lower magnetic pole 46 may be formed integrally or separately.

[0029] 2 and 3, the shaping aperture array substrate 203 has a two-dimensional horizontal (x direction) m １ Column x vertical (y direction) n １ Step (m １ , n １ 2 and 3 show a case where, for example, 5 × 5 holes (openings) 22 are formed. Each hole 22 is formed in a circular shape with the same dimensions. Alternatively, each hole 22 may be formed in a rectangular shape with the same dimensions. Multiple primary electron beams 20 are formed by portions of the electron beam 200 passing through these multiple holes 22. The shaping aperture array substrate 203 is an example of a multi-beam forming mechanism that forms multiple primary electron beams 20. The shaping aperture array substrate 203 is arranged on the upper magnetic pole 44. The shaping aperture array substrate 203 is formed of a non-magnetic material.

[0030] The coil 40 is arranged in an annular shape to surround the passage area of ​​the electron beam 200 and the multiple primary electron beams 20. The pole piece 42 is formed of a magnetic material. The pole piece 42 has an upper wall 12, a lower wall 14, an outer peripheral wall 16, and an inner peripheral wall 18 with a gap G formed in the circumferential direction. The upper wall 12 and the lower wall 14 are formed in the shape of concentric disks with an opening at the center. The outer peripheral wall 16 and the inner peripheral wall 18 are formed in the shape of concentric cylinders with different diameters. However, the inner peripheral wall 18 is divided into, for example, an upper portion and a lower portion by the gap G. The distance between the upper wall 12 and the lower wall 14 is set to a size that allows the coil 40 to be sandwiched between the upper wall 12 and the lower wall 14. The distance between the outer peripheral wall 16 and the inner peripheral wall 18 is set to a size that allows the coil 40 to be sandwiched between the outer peripheral wall 16 and the inner peripheral wall 18. The pole piece 42 surrounds the coil 40 with the upper wall 12 , the lower wall 14 , the outer peripheral wall 16 and the inner peripheral wall 18 .

[0031] The upper magnetic pole 44 (first magnetic pole) is made of a magnetic material. As shown in FIG. 4 , the upper magnetic pole 44 has a plurality of passage holes 47 (first openings) formed therein, through which the multiple primary electron beams 20 pass. The examples of FIGS. 2 and 4 show a case in which, for example, 5×5 passage holes 47 are formed in accordance with the arrangement of the holes 22 in the shaping aperture array substrate 203. The multiple passage holes 47 are formed with a diameter size larger than that of the holes 22 in the shaping aperture array substrate 203. As shown in FIG. 2 , the upper magnetic pole 44 is connected to the inner circumferential wall 18 on the upstream side of the gap G in the inner circumferential wall 18 in the traveling direction of the multiple primary electron beams 20, and is disposed so as to block the space inside the inner circumferential wall 18.

[0032] The lower magnetic pole 46 (second magnetic pole) is made of a magnetic material. As shown in FIG. 4 , the lower magnetic pole 46 has a plurality of passage holes 48 (second openings) formed therein, through which the multiple primary electron beams 20 pass. The examples of FIGS. 2 and 4 show a case in which, for example, 5×5 passage holes 48 are formed in accordance with the arrangement of the holes 22 in the shaping aperture array substrate 203. The multiple passage holes 48 are formed with a diameter size larger than that of the holes 22 in the shaping aperture array substrate 203. As shown in FIG. 2 , the lower magnetic pole 46 is connected to the inner circumferential wall 18 downstream of the gap G in the inner circumferential wall 18 in the traveling direction of the multiple primary electron beams 20, and is disposed so as to block the space inside the inner circumferential wall 18.

[0033] The plurality of passage holes 47 in the upper magnetic pole 44 and the plurality of passage holes 48 in the lower magnetic pole 46 are formed in accordance with the plurality of orbital axes that are the traveling directions of the multiple primary electron beams 20. In the example of Fig. 4, the upper magnetic pole 44 and the lower magnetic pole 46 are formed with coaxial openings having the same diameter size, through which the same beams of the multiple primary electron beams 20 pass.

[0034] By exciting the coil 40 (by passing a current through the coil 40), individual magnetic fields are formed between the plurality of passage holes 47 and the plurality of passage holes 48 on the same orbital axis. As a result, a lens action acts individually on the primary electron beams passing through the passage holes 47, 48 on each axis, and the passing primary electron beams are individually focused.

[0035] The image acquisition mechanism 150 irradiates the substrate 101 on which a graphic pattern is formed with the multiple primary electron beams 20. Then, it acquires an inspection image of the graphic pattern from the substrate 101. The operation of the image acquisition mechanism 150 in the inspection device 100 will be described below.

[0036] An electron gun 201 (an example of an emission source) emits an electron beam 200 in a diverging direction. The electron beam 200 emitted from the electron gun 201 and traveling in the diverging direction is refracted by an electromagnetic lens 202 in a converging direction so as to become a substantially parallel beam. The substantially parallel electron beam 200 then travels to a multi-axis electromagnetic lens 210 and illuminates the entire shaping aperture array substrate 203. As shown in FIG. 3 , a plurality of holes 22 are formed in the shaping aperture array substrate 203, and the electron beam 200 illuminates an area that includes all of the plurality of holes 22. Portions of the electron beam 200 irradiated at the positions of the plurality of holes 22 pass through the plurality of holes 22 in the shaping aperture array substrate 203, thereby forming multiple primary electron beams 20.

[0037] The formed multiple primary electron beams 20 are individually refracted by a multi-axis electromagnetic lens 210, and the intermediate image plane positions are individually corrected.

[0038] The multi-primary electron beam 20 that has passed through the multi-axis electromagnetic lens 210 is refracted by the electromagnetic lenses 205 and 206 to form a crossover and an intermediate image, and then proceeds to an E×B separator 214 that is disposed at the height of the intermediate image plane (image plane conjugate position) of the electron source image of each beam of the multi-primary electron beam 20. The multi-primary electron beam 20 then passes through the E×B separator 214 and proceeds to the electromagnetic lens 207. Furthermore, by disposing a limiting aperture substrate 213 with a limited passage hole near the crossover position of the multi-primary electron beam 20, scattered beams can be blocked. Furthermore, by deflecting the entire multi-primary electron beam 20 collectively with the collective deflector 212 and blocking the entire multi-primary electron beam 20 with the limiting aperture substrate 213, the entire multi-primary electron beam 20 can be blanked.

[0039] When the multiple primary electron beams 20 are incident on the electromagnetic lens 207, the electromagnetic lens 207 forms an image of the multiple primary electron beams 20 on the substrate 101. In other words, the electromagnetic lens 207 irradiates the substrate 101 with the multiple primary electron beams 20.

[0040] The multi-primary electron beams 20, which are focused (focused) on the surface of the substrate 101 (sample) by the electromagnetic lens 207, are deflected collectively by the deflectors 208 and 209, and each beam is irradiated onto a respective irradiation position on the substrate 101. In this way, the primary electron optical system 151 illuminates the substrate 101 with the multi-primary electron beams 20. In other words, the substrate 101 is irradiated with the multi-primary electron beams 20 that have passed through the multi-axis electromagnetic lens 210.

[0041] When a desired position on the substrate 101 is irradiated with the multi-primary electron beams 20, a bundle of secondary electrons including reflected electrons (multi-secondary electron beams 300) is emitted from the substrate 101 due to the irradiation of the multi-primary electron beams 20. A secondary electron beam corresponding to each beam of the multi-primary electron beams 20 is emitted.

[0042] The multiple secondary electron beams 300 emitted from the substrate 101 pass through the electromagnetic lens 207 and proceed to the E×B separator 214 .

[0043] The E×B separator 214 separates the multiple secondary electron beams 300 from the orbit of the multiple primary electron beams 20 .

[0044] The EXB separator 214 has two or more magnetic poles (electromagnetic deflection coils) using coils and two or more electrodes (electrostatic deflection electrodes). For example, two opposing magnetic poles and two opposing electrodes shifted in phase by 90° are arranged. The arrangement is not limited to this. For example, a structure in which the electrodes also serve as magnetic poles may be arranged, with four or eight electrodes / magnetic poles. The EXB separator 214 deflects the multiple secondary electron beams 300 to produce a separation effect. The EXB separator 214 generates a directional magnetic field using multiple magnetic poles. Similarly, it generates a directional electric field using multiple electrodes. Specifically, the EXB separator 214 generates an electric field E and a magnetic field B in perpendicular directions on a plane perpendicular to the direction in which the central beam of the multiple primary electron beams 20 travels (the central axis of the orbit). The electric field exerts a force in the same direction regardless of the direction of electron travel. On the other hand, the magnetic field exerts a force according to Fleming's left-hand rule. Therefore, the direction of the force acting on the electrons can be changed depending on the direction of electron travel. The force FE due to the electric field and the force FB due to the magnetic field cancel each other out on the multi-primary electron beams 20 entering the E×B separator 214 from above, causing the multi-primary electron beams 20 to travel straight downward. On the other hand, the force FE due to the electric field and the force FB due to the magnetic field act in the same direction on the multi-secondary electron beams 300 entering the E×B separator 214 from below, causing the multi-secondary electron beams 300 to bend obliquely upward by being deflected in a predetermined direction, and to separate from the trajectory of the multi-primary electron beams 20.

[0045] The multi-secondary electron beams 300, which have been bent obliquely upward and separated from the multi-primary electron beams 20, are guided to the multi-detector 222 by the secondary electron optical system 152. Specifically, the multi-secondary electron beams 300, which have been separated from the multi-primary electron beams 20, are deflected by the deflector 218, whereby they are further bent, and proceed to the electromagnetic lens 224. The multi-secondary electron beams 300 are then projected onto the multi-detector 222 while being refracted in the focusing direction by the electromagnetic lens 224 at a position away from the trajectories of the multi-primary electron beams 20. The multi-detector 222 (multi-secondary electron beam detector) detects the multi-secondary electron beams 300 which have been separated from the trajectories of the multi-primary electron beams 20. In other words, the multi-detector 222 detects the refracted and projected multi-secondary electron beams 300. The multi-detector 222 has a plurality of detection elements (for example, a diode-type two-dimensional sensor, not shown). Each beam of the multi primary electron beams 20 collides with a detection element corresponding to each secondary electron beam of the multi secondary electron beams 300 on the detection surface of the multi detector 222, generating electrons and generating secondary electron image data for each pixel. The intensity signal detected by the multi detector 222 is output to the detection circuit 106.

[0046] Here, when the multiple primary electron beams 20 are refracted by the multiple electromagnetic lenses 205, 206, and 207, aberrations such as field curvature occur. In particular, the electromagnetic lens 207, which functions as an objective lens, generates field curvature aberrations when the multiple primary electron beams 20 are imaged on the surface of the substrate 101. When field curvature occurs, the size of each beam on the substrate 101 varies. Therefore, in the first embodiment, as shown in FIG. 2 , a multi-axis electromagnetic lens 210 is used to shift the intermediate image plane of the peripheral beams downstream from the intermediate image plane position of the central beam according to the distance from the axis so as to compensate for the field curvature occurring in the downstream reduction optical system. In other words, the intermediate image plane 19 of the multiple primary electron beams 20 is formed by adjusting the intermediate image plane position of each beam by the multi-axis electromagnetic lens 210 so that the focal positions of the field-curved multiple primary electron beams 20 occurring on the substrate 101 have the same positional relationship as a position flipped upside down.

[0047] In order to adjust the intermediate image plane position of each beam, it is necessary to set the lens strength (magnetic field strength) acting on each beam, which is generated by the multi-axis electromagnetic lens 210, to a different strength.

[0048] Therefore, in the first embodiment, at least one of the multiple through holes 47 in the upper magnetic pole 44 and the multiple through holes 48 in the lower magnetic pole 46 is formed with a plurality of different diameter sizes so that the lens effect decreases from the center toward the outer periphery. Specifically, the diameter sizes of the through holes 47, 48 vary symmetrically with respect to the central axis. In other words, the through holes 47, 48 whose orbital axes are located on the same concentric circle are formed with the same size. For example, as shown in FIG. 4 , the diameter sizes of the through holes 47, 48 on the outer periphery are made larger than those of the through holes 47, 48 on the central side. The diameter sizes of the through holes 47, 48 whose orbital axes are located on the outermost concentric circle are made larger. By increasing the diameter size, the strength of the magnetic field acting on the passing beam can be reduced compared to when the diameter size is smaller. This allows the focal length of the beam on the outer periphery to be longer than the focal length of the beam on the central side. This allows the field curvature occurring on the substrate 101 to be corrected.

[0049] 5 is a diagram showing an example of the relationship between the height of field curvature and the number of beam rows in embodiment 1. In FIG. 5, the vertical axis represents the height of field curvature relative to the height position of the central beam, and the horizontal axis represents the number of beam rows. As shown in FIG. 5, it can be seen that the greater the number of beam rows, the higher the height of field curvature relative to the height position of the central beam.

[0050] FIG. 6 is a diagram showing an example of the relationship between the focus height and the aperture diameter size of the passage hole in the first embodiment. In FIG. 6, the vertical axis represents the focus height, and the horizontal axis represents the aperture diameter size of the passage hole. As shown in FIG. 6, the larger the aperture diameter size of the passage holes 47 and 48, the longer the focal length of the passing beam in the −z direction, and the lower the height of the focus position (intermediate image plane position). In other words, the larger the aperture diameter size of the passage holes 47 and 48, the lower the strength of the magnetic field acting on the passing beam.

[0051] 4 shows a case where the plurality of through holes 47 in the upper magnetic pole 44 and the plurality of through holes 48 in the lower magnetic pole 46 are formed with the same diameter size for the through holes of the same orbital axis, but this is not limitative. In the first embodiment, it is also preferable that the upper magnetic pole 44 and the lower magnetic pole 46 are formed with through holes of different diameter sizes for the coaxial through holes through which the same beam of the multiple primary electron beams 20 passes.

[0052] 7 is a top view showing another example of the through holes of the upper magnetic pole of the multi-axis electromagnetic lens in embodiment 1. FIG. 8 is a top view showing another example of the through holes of the lower magnetic pole of the multi-axis electromagnetic lens in embodiment 1. As shown in the examples of FIGS. 7 and 8 , for example, with respect to the plurality of through holes 47 of the upper magnetic pole 44, the diameter size of the through holes 47 on the outer periphery is made larger than that of the through holes 47 on the central side, as in FIG. 4 . On the other hand, the plurality of through holes 48 of the lower magnetic pole 46 are formed with the same diameter size. In this way, if the focal position of the multi-primary electron beams 20 can be sufficiently adjusted simply by changing the diameter size of the plurality of through holes 47 of the upper magnetic pole 44, the diameter size of the plurality of through holes 48 of the lower magnetic pole 46 may be the same.

[0053] 7 and 8, for example, the plurality of through holes 47 in the upper magnetic pole 44 may be formed to have the same diameter size, and the plurality of through holes 48 in the lower magnetic pole 46 may have a larger diameter size on the outer periphery than the plurality of through holes 48 in the center, as in Fig. 4. If the focal position of the multi-primary electron beams 20 can be sufficiently adjusted only by changing the diameter size of the plurality of through holes 48 in the lower magnetic pole 46, the diameter size of the plurality of through holes 47 in the upper magnetic pole 44 may be the same.

[0054] Alternatively, for the multiple through holes 47 in the upper magnetic pole 44, the diameter of the through holes 47 on the outer periphery is made larger than that of the through holes 47 on the central side, as in Fig. 4. Also, for the multiple through holes 48 in the lower magnetic pole 46, the diameter of the through holes 48 on the outer periphery is made larger than that of the through holes 48 on the central side, as in Fig. 4. However, it is also preferable to make the diameter of the coaxial through holes smaller or larger than that of the multiple through holes 47 in the upper magnetic pole 44.

[0055] 9 is a diagram showing an example of the beam size of the multiple primary electron beams on the substrate surface in a comparative example of the first embodiment. FIG. 10 is a diagram showing an example of the beam size of the multiple primary electron beams on the substrate surface in the first embodiment. In the comparative example, an example of the size of each beam irradiated onto the substrate 101 in a configuration in which the multi-axis electromagnetic lens 210 is not arranged is shown. As shown in FIG. 9 , in the comparative example, the field curvature aberration is not corrected by the multi-axis electromagnetic lens 210, so the beam size becomes larger toward the outer periphery. In contrast, in the first embodiment, the field curvature aberration is corrected by the multi-axis electromagnetic lens 210, so that multiple primary electron beams 20 of approximately the same size can be formed on the substrate 101 as shown in FIG.

[0056] In the above example, the gap G is formed at the center of the inner circumferential wall 18 in the height direction, but the present invention is not limited to this.

[0057] Fig. 11 is a cross-sectional view showing a part of the configuration of the multi-axis electromagnetic lens in Modification 1 of Embodiment 1. The example of Fig. 11 shows a case where the gap G is formed at the upper end of the inner circumferential wall 18 in the height direction. Fig. 11 also shows the coil 40 and the pole piece 42 on the left side of the cross section of the multi-axis electromagnetic lens 210. The other configurations are the same as those in Figs. 2 to 4. When the gap G is formed at the upper end of the inner circumferential wall 18 in the height direction, the upper magnetic pole 44 may be connected to the upper wall 12 upstream of the gap G of the inner circumferential wall 18 in the traveling direction of the multi-primary electron beams 20.

[0058] Fig. 12 is a cross-sectional view showing a part of the configuration of the multi-axis electromagnetic lens in Modification 2 of Embodiment 1. The example of Fig. 12 shows a case where the gap G is formed at the lower end in the height direction of the inner circumferential wall 18. Fig. 12 shows the coil 40 and the pole piece 42 on the left side of the cross section of the multi-axis electromagnetic lens 210. The other configurations are the same as those in Figs. 2 to 4. When the gap G is formed at the lower end in the height direction of the inner circumferential wall 18, the lower magnetic pole 46 may be connected to the lower wall 14 downstream of the gap G of the inner circumferential wall 18 in the traveling direction of the multi-primary electron beams 20.

[0059] 13 is a diagram for explaining an example of a method of acquiring an image in the first embodiment. The example in FIG. 13 shows a case where the substrate 101 is an exposure mask substrate. The inspection area 330 of the substrate 101 is divided into a plurality of stripe areas 32 with a predetermined width in the y direction, for example. If the substrate 101 is a semiconductor substrate, each chip area (inspection area) of a plurality of chip areas formed on the wafer is divided into a plurality of stripe areas 32 with a predetermined width in the y direction, for example.

[0060] The scanning operation by the image acquisition mechanism 150 is performed, for example, for each stripe region 32. For example, while moving the stage 105 in the -x direction, the scanning operation of the stripe region 32 proceeds relatively in the x direction. Each stripe region 32 is divided into a plurality of rectangular regions 33 in the longitudinal direction. The movement of the beam to the target rectangular region 33 is performed by collective deflection of the entire multi-primary electron beam 20 by two-stage deflectors 208 and 209 (electrostatic deflectors).

[0061] The example of FIG. 13 shows, for example, a case of 5×5 arrays of multi-primary electron beams 20. An irradiation area 34 that can be irradiated by one irradiation of the multi-primary electron beams 20 is defined as (x-direction size obtained by multiplying the inter-beam pitch in the x-direction of the multi-primary electron beams 20 on the surface of the substrate 101 by the number of beams in the x-direction) × (y-direction size obtained by multiplying the inter-beam pitch in the y-direction of the multi-primary electron beams 20 on the surface of the substrate 101 by the number of beams in the y-direction). The irradiation area 34 becomes the field of view of the multi-primary electron beams 20. Each primary electron beam 10 constituting the multi-primary electron beam 20 is irradiated into a sub-irradiation area 29 surrounded by the inter-beam pitch in the x-direction and the inter-beam pitch in the y-direction where the beam is located, and scans (performs a scanning operation) within the sub-irradiation area 29. Each primary electron beam 10 is responsible for one of the different sub-irradiation areas 29. Each primary electron beam 10 irradiates the same position within the assigned sub-irradiation region 29. The two-stage deflectors 208, 209 collectively deflect the multiple primary electron beams 20, thereby scanning the surface of the substrate 101 on which the pattern is formed with the multiple primary electron beams 20. In other words, the movement of the primary electron beams 10 within the sub-irradiation region 29 is achieved by the collective deflection of the entire multiple primary electron beams 20 by the two-stage deflectors 208, 209. By repeating this operation, one primary electron beam 10 is sequentially irradiated within one sub-irradiation region 29.

[0062] The width of each stripe region 32 is preferably set to the same size as the irradiation region 34 in the y direction or narrower by a scan margin. In the example of FIG. 4 , the irradiation region 34 is shown to be the same size as the rectangular region 33. However, this is not limiting. The irradiation region 34 may be smaller or larger than the rectangular region 33. Each primary electron beam 10 constituting the multi-primary electron beam 20 is irradiated into the sub-irradiation region 29 in which it is located, and scans (scans) the sub-irradiation region 29. After scanning one sub-irradiation region 29, the irradiation position is moved to an adjacent rectangular region 33 in the same stripe region 32 by collective deflection of the entire multi-primary electron beam 20 by the two-stage deflectors 208 and 209. This operation is repeated to sequentially irradiate the stripe region 32. After scanning one stripe region 32 is completed, the irradiation region 34 moves to the next stripe region 32 by moving the stage 105 and / or collectively deflecting the entire multi-primary electron beam 20 using the two-stage deflectors 208 and 209. As described above, scanning operations and secondary electron images are performed for each sub-irradiation region 29 by irradiating each primary electron beam 10. By combining the secondary electron images for each sub-irradiation region 29, a secondary electron image of the rectangular region 33, a secondary electron image of the stripe region 32, or a secondary electron image of the chip 332 is constructed. In actual image comparison, the sub-irradiation region 29 within each rectangular region 33 is further divided into a plurality of frame regions 30, and frame images 31 serving as measurement images for each frame region 30 are compared. The example of FIG. 13 shows a case where the sub-irradiation region 29 scanned by one primary electron beam 10 is divided into four frame regions 30, for example, by dividing the sub-irradiation region 29 into two in each of the x and y directions.

[0063] Furthermore, when the substrate 101 is irradiated with the multiple primary electron beams 20 while the stage 105 is continuously moving, a tracking operation is performed by collective deflection using the two-stage deflectors 208 and 209 so that the irradiation positions of the multiple primary electron beams 20 follow the movement of the stage 105. Therefore, the emission positions of the multiple secondary electron beams 300 change from moment to moment relative to the central axis of the orbit of the multiple primary electron beams 20. Similarly, when scanning the sub-irradiation region 29, the emission positions of each secondary electron beam change from moment to moment within the sub-irradiation region 29. For example, the two-stage deflectors 225 and 226 collectively deflect the multiple secondary electron beams 300 so that each secondary electron beam whose emission position has changed in this way is irradiated into the corresponding detection region of the multi-detector 222. In other words, the deflectors 225 and 226 fix the position of the multi secondary electron beams 300 on the detection surface of the multi-detector 222, which changes due to scanning using the multi primary electron beams 20, by deflecting the multi secondary electron beams back. This allows each secondary electron beam to be detected by the corresponding detection element of the multi-detector 222. The deflectors 225 and 226 are not limited to two-stage deflectors, and may be configured as a single-stage deflector.

[0064] Next, the inspection process will be described.

[0065] In the scanning process, the image acquisition mechanism 150 scans the object (here, the substrate 101) with the multi-primary electron beams 20 as described above. Here, the image acquisition mechanism 150 scans the stripe region 32 with the multi-primary electron beams 20 for each stripe region 32. As described above, the primary electron optical system 151 irradiates the object (here, the substrate 101) with the multi-primary electron beams 20. The multi-secondary electron beams 300 emitted as a result of the irradiation of the substrate 101 with the multi-primary electron beams 20 are guided to the multi-detector 222 (detector array) by the secondary electron optical system 152. The guided multi-secondary electron beams 300 are then detected by the multi-detector 222 (detector array). The detected multi-secondary electron beams 300 may include reflected electrons. Alternatively, the reflected electrons may diverge while moving through the secondary electron optical system and not reach the multi-detector 222. A secondary electron image is acquired based on the signals of the detected multi-secondary electron beams 300. Specifically, secondary electron detection data (measurement image data: secondary electron image data: inspection image data) for each pixel in each sub-irradiation area 29 detected by the multi-detector 222 is output to the detection circuit 106 in the order of measurement. Within the detection circuit 106, an A / D converter (not shown) converts the analog detection data into digital data, which is stored in the chip pattern memory 123. The acquired measurement image data is then transferred to the comparison circuit 108 together with information indicating each position from the position circuit 107.

[0066] FIG. 14 is a block diagram showing an example of the configuration of a comparison circuit according to the first embodiment. In FIG. 14 , the comparison circuit 108 includes storage devices 50, 52, and 56, such as magnetic disk devices, a frame image creation unit 54, an alignment unit 57, and a comparison unit 58. Each of the "units" (such as the frame image creation unit 54, the alignment unit 57, and the comparison unit 58) includes a processing circuit, which may include an electrical circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. The "units" may share a common processing circuit (the same processing circuit). Alternatively, they may use different processing circuits (separate processing circuits). The input data or calculation results required for the frame image creation unit 54, the alignment unit 57, and the comparison unit 58 are stored in a memory (not shown) or in memory 118.

[0067] In the comparison step, the comparison circuit 108 compares the acquired secondary electron image with a predetermined reference image. Specifically, for example, the operation is as follows.

[0068] The measurement image data (beam image) transferred to the comparison circuit 108 is stored in the storage device 50 .

[0069] The frame image creation unit 54 then creates a frame image 31 for each of a plurality of frame regions 30 obtained by further dividing the image data of the sub-irradiation regions 29 acquired by the scanning operation of each primary electron beam. The frame regions 30 are then used as unit regions of the image to be inspected. It is preferable that the frame regions 30 are configured so that their margins overlap each other to prevent any missing parts of the image. The created frame images 31 are stored in the storage device 56.

[0070] On the other hand, the reference image creation circuit 112 creates a reference image corresponding to the frame image 31 for each frame area 30 based on the design data that is the basis of the multiple figure patterns formed on the substrate 101. Specifically, it operates as follows: First, it reads out the design pattern data from the storage device 109 through the control computer 110, and converts each figure pattern defined in the read design pattern data into binary or multi-value image data.

[0071] As described above, the figures defined in the design pattern data are, for example, rectangles or triangles as basic figures, and the figure data stored defines the shape, size, position, etc. of each pattern figure using information such as the coordinates (x, y) at the reference position of the figure, the length of the sides, and a figure code that serves as an identifier for distinguishing the type of figure, such as a rectangle or a triangle.

[0072] When the design pattern data that constitutes such graphic data is input to the reference image creation circuit 112, it is expanded into data for each graphic, and the graphic code and graphic dimensions that indicate the graphic shape of the graphic data are interpreted.Then, it is expanded into binary or multi-valued design pattern image data as a pattern to be arranged in a grid with a predetermined quantized dimension as a unit, and output.In other words, the design data is read, the inspection area is virtually divided into grids with a predetermined dimension as a unit, and the occupancy rate of the graphic in the design pattern is calculated for each grid, and n-bit occupancy data is output.For example, it is preferable to set one grid as one pixel.And, 1 / 2 for one pixel. ８ If a resolution of (= 1 / 256) is to be given, a small area of ​​1 / 256 is allocated for the area of ​​the figure placed within the pixel, and the occupancy rate within the pixel is calculated. This results in 8-bit occupancy data. The grid (inspection pixel) can be aligned with the pixel of the measurement data.

[0073] Next, the reference image creation circuit 112 applies filtering to the design image data of the design pattern, which is image data of the graphic, using a predetermined filter function. This makes it possible to match the design image data, which is image data on the design side with image intensity (grayscale value) in digital values, with the image generation characteristics obtained by irradiation with the multiple primary electron beams 20. The image data for each pixel of the created reference image is output to the comparison circuit 108. The reference image data transferred to the comparison circuit 108 is stored in the storage device 52.

[0074] Next, the alignment unit 57 reads out the frame image 31 to be the image to be inspected and the reference image corresponding to the frame image 31, and aligns the two images in units of sub-pixels, which are smaller than pixels. For example, the alignment may be performed using the least squares method.

[0075] The comparison unit 58 then compares the secondary electron image of the substrate 101 placed on the stage 105 with a predetermined image. Specifically, the comparison unit 58 compares the frame image 31 with the reference image for each pixel. The comparison unit 58 compares the two for each pixel in accordance with predetermined judgment conditions, and judges whether or not there is a defect, such as a shape defect. For example, if the difference in gradation value for each pixel is greater than the judgment threshold value Th, it is judged to be a defect. The comparison result is then output. The comparison result may be output to the storage device 109 or memory 118, or may be output from the printer 119.

[0076] In addition to the die-to-database inspection described above, it is also suitable to perform die-to-die inspection, which compares measurement image data obtained by capturing images of the same pattern at different locations on the same substrate. Alternatively, inspection may be performed using only the own measurement image.

[0077] As described above, according to the first embodiment, the field curvature aberration occurring in the multiple primary electron beams 20 can be corrected.

[0078] [Embodiment 2] The configuration of the inspection device 100 in embodiment 2 is the same as that shown in Fig. 1, except for the internal configuration of the multi-axis electromagnetic lens 210. Furthermore, the contents other than those specifically described below are the same as those of embodiment 1.

[0079] Fig. 15 is a cross-sectional view showing an example of the configuration of the multi-axis electromagnetic lens in embodiment 2. Fig. 15 is the same as Fig. 2 except that a plurality of correction coils 49 are arranged between the upper magnetic pole 44 and the lower magnetic pole 46. In addition, an example of the configuration of the shaping aperture array substrate of the multi-axis electromagnetic lens in embodiment 2 is the same as Fig. 3. A top view showing an example of the configuration of the upper magnetic pole and the lower magnetic pole of the multi-axis electromagnetic lens in embodiment 2 is the same as Fig. 4.

[0080] Each correction coil 49 individually corrects a corresponding beam among the multiple primary electron beams 20. Each correction coil 49 is formed, for example, on the outer peripheral surface of a non-magnetic cylinder having an inner diameter equal to the diameter of the passage hole on the same axis as the upper magnetic pole 44 and the lower magnetic pole 46. Each correction coil 49 corrects the focal position that could not be adjusted by the size of each passage hole, by the lens effect of the magnetic field that it forms.

[0081] The correction coils also allow for more accurate correction of field curvature.

[0082] In the above description, a series of "circuits" includes processing circuits, which may include electrical circuits, computers, processors, circuit boards, quantum circuits, or semiconductor devices. Each "circuit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. The program for executing the processors may be recorded on a recording medium such as a magnetic disk drive, a magnetic tape drive, a FD, or a ROM (read-only memory). For example, the position circuit 107, the comparison circuit 108, and the reference image creation circuit 112 may each be configured with at least one of the processing circuits described above.

[0083] Although the embodiments have been described above with reference to specific examples, the present invention is not limited to these specific examples.

[0084] Furthermore, although descriptions of the device configuration, control method, and other parts not directly necessary for explaining the present invention have been omitted, the required device configuration and control method can be appropriately selected and used.

[0085] In addition, all electromagnetic lenses and multi-electron beam irradiation devices that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included in the scope of the present invention.

[0086] The present invention relates to an electromagnetic lens and a multi-electron beam irradiation device, and can be used, for example, in an electromagnetic lens mounted in a multi-beam inspection device that performs pattern inspection using a secondary electron image generated by irradiation with multiple primary electron beams.

[0087] 10 Primary electron beam 12 Upper wall 14 Lower wall 16 Outer peripheral wall 18 Inner peripheral wall 19 Intermediate image plane 20 Multi-primary electron beam 22 Hole 29 Sub-irradiation area 30 Frame area 31 Frame image 32 Stripe area 33 Rectangular area 34 Irradiation area 40 Coil 42 Pole piece 44 Upper magnetic pole 46 Lower magnetic pole 47, 48 Passage hole 49 Correction coil 50, 52, 56 Storage device 54 Frame image creation unit 57 Alignment unit 58 Comparison unit 100 Inspection device 101 Substrate 102 Electron beam column 103 Inspection chamber 105 Stage 106 Detection circuit 107 Position circuit 108 Comparison circuit 109 Storage device 110 Control computer 111 Mark 112 Reference image creation circuit 114 Stage control circuit 117 Monitor 118 Memory 119 Printer 120 Bus 122 Laser length measurement system 123 Chip pattern memory 124 Lens control circuit 126 Blanking control circuit 128 Deflection control circuit 130 Multi-axis electromagnetic lens control circuit 132 E×B separator control circuit 142 Stage drive mechanism 144, 146, 147, 148, 149 DAC amplifier 150 Image acquisition mechanism 151 Primary electron optical system 152 Secondary electron optical system 160 Control system circuit 200 Electron beam 201 Electron gun 202, 205 Electromagnetic lens 203 Shaping aperture array substrate 206, 207 Electromagnetic lens 208 Deflector 209 Deflector 210 Multi-axis electromagnetic lens 212 Collective deflector 213 Limiting aperture substrate 214 E×B separator 216 Mirror 218 Deflector 222 Multi-detector 224 Electromagnetic lens 225, 226 Deflector 300 Multi-secondary electron beam

Claims

1. A coil; a pole piece formed of a magnetic material and having an upper wall upstream in the direction of propagation of multiple electron beams passing therethrough, a lower wall downstream in the direction of propagation of the multiple electron beams, an outer wall, and an inner wall with a gap formed in the circumferential direction, the pole piece surrounding the coil with the upper wall, lower wall, outer wall, and inner wall; a first magnetic pole formed of a magnetic material and having a plurality of first openings through which the multiple electron beams pass, connected to the inner wall or the upper wall on the upstream side of the gap in the inner wall in the direction of propagation of the multiple electron beams, and arranged to close the space inside the inner wall; and a second magnetic pole formed of a magnetic material and having a plurality of second openings through which the multiple electron beams pass, connected to the inner wall or the lower wall on the downstream side of the gap in the inner wall in the direction of propagation of the multiple electron beams, and arranged to close the space inside the inner wall, An electromagnetic lens, characterized in that at least one of the plurality of first openings and the plurality of second openings is formed with a plurality of different diameter sizes so that a lens action decreases from the center toward the outer periphery.

2. An electromagnetic lens according to claim 1, wherein said diameter size varies symmetrically about a central axis.

3. An electromagnetic lens as described in claim 1, characterized in that the first magnetic pole and the second magnetic pole are formed with coaxial openings through which the same beams of the multiple electron beams pass, the openings having different diameter sizes.

4. The electromagnetic lens according to claim 1, further comprising a plurality of correction coils disposed between said first magnetic pole and said second magnetic pole for individually correcting corresponding beams of said multiple electron beams.

5. An electromagnetic lens according to claim 1, further comprising a shaping aperture array substrate disposed on said first magnetic pole, which is irradiated with an electron beam and forms multiple electron beams.

6. The electromagnetic lens according to claim 5, characterized in that a plurality of third openings for forming the multiple electron beams are formed in the shaping aperture array substrate, and the plurality of first openings in the first magnetic pole are formed with a diameter size larger than the plurality of third openings in the shaping aperture array substrate.

7. The electromagnetic lens according to claim 5, characterized in that a plurality of third openings for forming the multiple electron beams are formed in the shaping aperture array substrate, and the plurality of second openings in the second magnetic pole are formed with a diameter size larger than the plurality of third openings in the shaping aperture array substrate.

8. An electromagnetic lens as described in claim 1, characterized in that the first magnetic pole and the second magnetic pole are provided with coaxial openings having the same diameter size through which the same beams of the multiple electron beams pass.

9. The electromagnetic lens according to claim 1, wherein said pole piece, said first magnetic pole and said second magnetic pole are integrally formed.

10. A coil; a pole piece formed of a magnetic material and having an upper wall upstream in the direction of propagation of multiple electron beams passing therethrough, a lower wall downstream in the direction of propagation of the multiple electron beams, an outer wall, and an inner wall with a gap formed in the circumferential direction, the pole piece surrounding the coil with the upper wall, lower wall, outer wall, and inner wall; a first magnetic pole formed of a magnetic material and having a plurality of first openings through which the multiple electron beams pass, connected to the inner wall or the upper wall on the upstream side of the gap in the inner wall in the direction of propagation of the multiple electron beams, and arranged to close the space inside the inner wall; and a second magnetic pole formed of a magnetic material and having a plurality of second openings through which the multiple electron beams pass, connected to the inner wall or the lower wall on the downstream side of the gap in the inner wall in the direction of propagation of the multiple electron beams, and arranged to close the space inside the inner wall, a stage for supporting a sample to be irradiated with the multiple electron beams that have passed through the electromagnetic lens, the sample being formed with a plurality of different diameter sizes so that the lens action of at least one of the plurality of first openings and the plurality of second openings becomes smaller from the center to the outer periphery.

Images