Multiple electron beam irradiation device and multiple electron beam irradiation method

Abstract

A multiple electron beam irradiation device of one embodiment of the present invention is characterized by being provided with: an emission source for emitting an electron beam in a direction of divergence; a shaping aperture array substrate in which a plurality of first openings are formed, and which forms multiple electron beams moving in the direction of divergence by causing portions of respective electron beams moving in the direction of divergence to pass through the plurality of first openings; a multiple-stage lens array of three or more stages, which includes a plurality of lens arrays of two or more stages, having a quadrupole or higher-order multipole in which lenses are each arranged on the trajectory of an assigned beam of the multiple electron beams, which forms multiple electron beams with which the electron beams have substantially parallel central trajectories due to deflection of the multiple electron beams moving in the direction of divergence, and which also performs magnification correction and focal length correction in two orthogonal directions; and an angle-limiting aperture array substrate in which a plurality of second openings are formed, and which limits a divergence angle or convergence angle of each of the electron beams by causing the multiple electron beams having passed through the multiple-stage lens array to pass through the plurality of second openings.

Description

Multi-electron beam irradiation device and multi-electron beam irradiation method

[0001] This application claims priority from JP2023-125751 (application number) filed in Japan on August 1, 2023. The entire contents of JP2023-125751 are incorporated herein by reference.

[0002] One aspect of the present invention relates to a multi-electron beam irradiation apparatus and a multi-electron beam irradiation method, for example, to an apparatus for correcting variations in the shape of the multi-electron beams and variations in the convergence angle at an intermediate image plane position of an electron source image of the multi-electron beams caused by aberrations or the like.

[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, a substrate to be inspected is scanned with multiple primary electron beams using electron beams, multiple secondary electron beams emitted from the substrate to be inspected are separated from the trajectories of the multiple primary electron beams, and the multiple secondary electron beams are detected by a detector to capture a pattern image.

[0005] Here, it is desirable that the multiple primary electron beams have the same shape, size, and focusing angle on the specimen surface. However, there is a problem in that these vary due to aberrations caused by electromagnetic lenses and the like along the way. Therefore, it is desirable to reduce the variations in shape and focusing angle of the multiple electron beams on the specimen surface. In addition to achieving the same shape, it is also desirable to further reduce the variation in size, if possible. Therefore, it is desirable to adjust the intermediate image plane position of each beam and the shape and focusing angle at the intermediate image plane position so as to cancel out the variations in shape and focusing angle caused by the influence of the electron optical system.

[0006] Here, it is disclosed that a two-stage stigmator is used to refract the entire multi-beams at once, thereby correcting both astigmatism and linear distortion (see, for example, Patent Document 1).

[0007] Japanese Patent Application Laid-Open No. 2022-159159

[0008] Therefore, one aspect of the present invention provides an apparatus and method that can reduce variations in at least the shape and convergence angle or adjust the distribution of at least the shape and convergence angle at an intermediate image plane position of multiple electron beams.

[0009] A multi-electron beam irradiation device according to one aspect of the present invention comprises: an emission source that emits electron beams in divergent directions; a shaping aperture array substrate having a plurality of first openings formed therein, in which a portion of each of the electron beams traveling in the divergent directions passes through the plurality of first openings, thereby forming multi-electron beams traveling in the divergent directions; a multi-stage lens array having three or more stages, each of which includes a plurality of lens arrays having two or more stages, each lens having a multipole element of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that it is responsible for, and which deflects the multi-electron beams traveling in the divergent directions to form multi-electron beams whose central trajectories are approximately parallel to each other, and which also performs magnification correction and focal length correction in two orthogonal directions; and an angle-limiting aperture array substrate having a plurality of second openings formed therein, in which the multi-electron beams that have passed through the multi-stage lens array pass through the plurality of second openings, thereby limiting the divergence angle or the convergence angle of each electron beam.

[0010] Another aspect of the present invention provides a multi-electron beam irradiation device comprising: an emission source that emits electron beams in divergent directions; a shaping aperture array substrate having a plurality of first openings formed therein, whereby a portion of each of the electron beams traveling in the divergent directions passes through the plurality of first openings, thereby forming a multi-electron beam traveling in the divergent directions; a deflector array that deflects the multi-electron beams traveling in the divergent directions to form a multi-electron beam with approximately parallel central trajectories of each electron beam; a multi-stage lens array having three or more stages, including a plurality of lens arrays having two or more stages, each lens having a multipole element of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that it is responsible for; and an angle-limiting aperture array substrate having a plurality of second openings formed therein, whereby the multi-electron beams that have passed through the multi-stage lens array pass through the plurality of second openings, thereby limiting the divergence angle or convergence angle of each electron beam.

[0011] Another aspect of the present invention is a multi-electron beam irradiation device comprising: an emission source that emits electron beams in divergent directions; a shaping aperture array substrate having a plurality of first openings formed therein, in which a portion of each of the electron beams traveling in the divergent direction passes through the plurality of first openings to form a multi-electron beam and limit the divergence angle or convergence angle of each electron beam; and a multi-stage lens array having three or more stages, each of which includes a plurality of lens arrays having two or more stages, each lens having a multipole element of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that it is responsible for, and which deflects the multi-electron beam traveling in the divergent direction to form a multi-electron beam in which the central trajectories of each electron beam are approximately parallel, and which performs magnification correction and focal length correction in two orthogonal directions.

[0012] Another aspect of the multi-electron beam irradiation device of the present invention is characterized by comprising: an emission source that emits electron beams in divergent directions; a shaping aperture array substrate in which a plurality of first openings are formed, and in which a portion of each of the electron beams traveling in the divergent directions passes through the plurality of first openings to form a multi-electron beam and limit the divergence angle or convergence angle of each electron beam; a deflector array that deflects the multi-electron beams traveling in the divergent directions to form a multi-electron beam in which the central trajectories of each electron beam are approximately parallel; and a multi-stage lens array of three or more stages that performs magnification correction and focal length correction in two orthogonal directions, including a plurality of lens arrays of two or more stages, each having a multipole element of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that it is responsible for.

[0013] A multi-electron beam irradiation method according to one aspect of the present invention includes: emitting electron beams from an emission source in divergent directions; using a shaping aperture array substrate having a plurality of first openings, a multi-electron beam is formed by causing each portion of the electron beam traveling in the divergent direction to pass through the plurality of first openings; using a multi-stage lens array having three or more stages including a plurality of lens arrays having two or more stages, each lens having a multipole element of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that it is responsible for, to deflect the multi-electron beam traveling in the divergent direction to form a multi-electron beam with central trajectories of each electron beam being approximately parallel, and performing magnification correction and focal length correction in two orthogonal directions; and using an angle-limiting aperture array substrate having a plurality of second openings, the multi-electron beam that has passed through the multi-stage lens array passes through the plurality of second openings, thereby limiting the divergence angle or convergence angle of each electron beam.

[0014] Another aspect of the multi-electron beam irradiation method of the present invention is characterized in that it includes: emitting electron beams from an emission source in divergent directions; using a shaping aperture array substrate having a plurality of first openings, a portion of each of the electron beams traveling in the divergent directions passes through the plurality of first openings to form a multi-electron beam; deflecting the multi-electron beams traveling in the divergent directions to form a multi-electron beam with each electron beam having a substantially parallel central trajectory; performing magnification correction and focal length correction in two orthogonal directions using a multi-stage lens array of three or more stages including a plurality of lens arrays of two or more stages, each lens having a multipole element of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that it is responsible for; and using an angle-limiting aperture array substrate having a plurality of second openings, the multi-electron beams that have passed through the multi-stage lens array pass through the plurality of second openings to limit the divergence angle or the convergence angle of each electron beam.

[0015] Another aspect of the multi-electron beam irradiation method of the present invention is characterized in that it includes: emitting electron beams in divergent directions from an emission source; using a shaped aperture array substrate having a plurality of first openings, each portion of the electron beam traveling in the divergent direction passes through the plurality of first openings to form a multi-electron beam, and limiting the divergence angle or convergence angle of each electron beam; and using a multi-stage lens array of three or more stages including a plurality of lens arrays of two or more stages, each lens having a multipole element of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that it is responsible for, to deflect the multi-electron beam traveling in the divergent direction to form a multi-electron beam with central trajectories of each electron beam approximately parallel, and performing magnification correction and focal length correction in two orthogonal directions.

[0016] Another aspect of the multi-electron beam irradiation method of the present invention is characterized in that it includes: emitting electron beams in divergent directions from an emission source; using a shaping aperture array substrate having a plurality of first openings, each portion of the electron beam traveling in the divergent direction passes through the plurality of first openings to form a multi-electron beam, and limiting the divergence angle or convergence angle of each electron beam; deflecting the multi-electron beam traveling in the divergent direction to form a multi-electron beam in which the central trajectories of each electron beam are approximately parallel; and performing magnification correction and focal length correction in two orthogonal directions using a multi-stage lens array of three or more stages including a plurality of lens arrays of two or more stages, each lens having a multipole element of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that it is responsible for.

[0017] According to one aspect of the present invention, the intermediate image plane position of the multiple electron beams can be adjusted, and further, variations in at least the shape and the convergence angle can be reduced at the intermediate image plane position.

[0018] 1 is a configuration diagram showing the configuration of a pattern inspection device in embodiment 1. FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate in embodiment 1. FIG. 3 is a diagram showing an example of a plurality of chip regions formed on a semiconductor substrate in embodiment 1. FIG. 4 is a diagram for explaining image acquisition processing in embodiment 1. FIG. 5 is a diagram showing an example of the configuration from a radiation source to an intermediate image plane position of a multi-primary electron beam in comparative example 1 of embodiment 1. FIG. 6 is a diagram showing an example of the configuration of a two-stage multipole lens in comparative example 2 of embodiment 1. FIG. 7 is a diagram showing an example of the configuration of a three-stage multipole lens in embodiment 1. FIG. 8 is a diagram showing an example of the configuration of a multipole lens array in embodiment 1. FIG. 9 is a diagram showing an example of the range in which a three-stage multipole lens in embodiment 1 can be adjusted. FIG. 10 is a diagram showing an example of the configuration of a two-stage multipole lens and a one-stage circular lens in embodiment 1. FIG. 11 is a diagram showing an example of the configuration of a circular lens array in embodiment 1. FIG. 12 is a diagram showing an example of the range in which a combination of a two-stage multipole lens and a one-stage circular lens in embodiment 1 can be adjusted. FIG. 13 is a diagram showing an example of the configuration of a three-stage multipole lens and a one-stage circular lens in embodiment 1. FIG. 1 is a diagram showing an example of an adjustable range for a combination of a three-stage multipole lens and a one-stage circular lens in embodiment 1. FIG. 2 is a diagram showing an example of a configuration of a two-stage multipole lens and a two-stage circular lens in embodiment 1. FIG. 3 is a diagram showing an example of a configuration of a four-stage multipole lens in embodiment 1. FIG. 4 is a diagram showing an example of a configuration of an angle-limiting aperture array in comparative example 3 of embodiment 1. FIG. 5 is a diagram showing an example of a configuration of a beam dimension limiting aperture array in comparative example 3 of embodiment 1. FIG. 6 is a diagram for explaining the function of an angle-limiting aperture array substrate in embodiment 1. FIG. 7 is a diagram showing an example of each configuration from an electron source to an intermediate image plane after astigmatism correction in modified example 1 of embodiment 1. FIG. 8 is a diagram showing an example of each configuration from an electron source to an intermediate image plane after astigmatism correction in modified example 2 of embodiment 1. FIG. 9 is a diagram showing an example of each configuration from an electron source to an intermediate image plane after astigmatism correction in modified example 3 of embodiment 1.Fig. 1 is a diagram showing an example of the configuration of an inspection device in embodiment 2. Fig. 2 is a diagram showing an example of a beam shaped by a shaping aperture array substrate in embodiment 2. Fig. 3 is a diagram showing another example of the configuration of a three-stage multipole lens in each embodiment. Fig. 4 is a diagram showing an example of the arrangement of multipole lenses in each embodiment.

[0019] 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.

[0020] [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, a shaping aperture array substrate 203, a multi-stage lens array 210, an angle limiting aperture array substrate 211, a condenser lens 205 (post-condenser lens), 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.

[0021] The primary electron optical system 151 (illumination optical system) is composed of the electron gun 201, the shaping aperture array substrate 203, the multistage lens array 210, the angle limiting aperture array substrate 211, the condenser 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.

[0022] The multi-detector 222 has a plurality of detection elements arranged in an array (grid).

[0023] The multi-stage lens array 210 is composed of three or more stages of lens arrays, including two or more stages of multiple lens arrays (multipole lens arrays), each of which has a quadrupole or higher multipole arranged on the trajectory of the beam it is responsible for among the multi-primary electron beams 20.

[0024] The angle limiting aperture array substrate 211 has a plurality of passage holes (second openings) formed at positions where the multiple primary electron beams 20 pass through.

[0025] 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.

[0026] 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.

[0027] 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-stage lens array 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 .

[0028] 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.

[0029] The condenser lens 205 , the electromagnetic lens 206 , the electromagnetic lens 207 , and the electromagnetic lens 224 are controlled by the lens control circuit 124 .

[0030] The multi-lens array 210 is controlled by a multi-lens array control circuit 130 .

[0031] 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.

[0032] 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.

[0033] The E×B separator 214 is controlled by the E×B separator control circuit 132 .

[0034] 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.

[0035] 1 shows the configuration necessary for explaining the first embodiment. The inspection device 100 may also include other configurations that are normally required.

[0036] 2 is a conceptual diagram showing the configuration of the shaping aperture array substrate in the embodiment 1. In FIG. 2, the shaping aperture array substrate 203 has a two-dimensional lateral (x direction) m １ Columns x columns (y direction) n １ Step (m １ , n １ The shaping aperture array substrate 203 has holes (apertures) 22 (where n is an integer of 2 or more) formed at a predetermined arrangement pitch in the x and y directions. The example in FIG. 2 shows a case where 5 × 5 holes (apertures) 22 are formed. Each hole 22 is formed as a circle with the same outer diameter. Alternatively, they may be rectangular 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.

[0037] The image acquisition mechanism 150 uses multiple electron beams to acquire an image of the graphic pattern to be inspected from the substrate 101 on which the graphic pattern is formed. The operation of the image acquisition mechanism 150 in the inspection device 100 will be described below.

[0038] An electron gun 201 (an example of an emission source) emits an electron beam 200 in diverging directions. The emitted electron beam can be approximated as being emitted from a region near the tip of the cathode, which is the electron emission source of the electron gun 201. This region is called, for example, a virtual light source or virtual electron source. An image obtained downstream from the electron gun by projecting this virtual light source or virtual electron source through a lens is called an electron source image. The electron beam 200 emitted from the electron gun 201 and traveling in diverging directions illuminates the entire shaping aperture array substrate 203. As shown in FIG. 2 , a plurality of holes 22 (first openings) are formed in the shaping aperture array substrate 203, and the electron beam 200 illuminates an area including 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 each of the plurality of holes 22 in the shaping aperture array substrate 203, thereby forming multiple primary electron beams 20. For simplicity, Fig. 1 shows an example in which the shaping aperture array substrate 203 is placed immediately after the electron gun 201. However, if necessary, a lens group consisting of one or more stages of lenses may be placed between the electron gun 201 and the shaping aperture array substrate 203. The size of the electron source image can also be adjusted by adjusting the focal length of each lens that makes up the lens group. The lenses that make up the lens group include either or both of electromagnetic lenses and electrostatic lenses.

[0039] The formed multiple primary electron beams 20 proceeding in divergent directions are deflected by the first lens array of the multi-stage lens array 210 by forming a dipole field to form multiple electron beams with approximately parallel central trajectories of each electron beam (hereinafter referred to as approximately parallel multiple primary electron beams 20), and are refracted by forming a quadrupole field to correct variations in the shape (and size) of each beam at the image plane 19 (intermediate image plane). Forming approximately parallel beams by the first lens array of the multi-stage lens array 210 allows the multiple primary electron beams 20 to proceed substantially parallel to each other. This makes it easier to align the positions of multiple openings in the lens array downstream of the multi-stage lens array 210 and / or the positions of multiple openings in the angle-limiting aperture array substrate 211 with the passing positions of the multiple primary electron beams 20. In other words, errors in the formation positions of openings in each component through which the multiple primary electron beams 20 pass can be eliminated or reduced.

[0040] The angle-limiting aperture array substrate 211 limits the divergence angle or convergence angle of each electron beam of the multi-primary electron beams 20 that have passed through the multistage lens array 210, thereby correcting variations in the convergence angle at the image plane 19 (intermediate image plane) position. The image plane 19 (intermediate image plane) position is determined so that the position of the electron source image after passing through the downstream optical system coincides with the surface of the substrate 101. This makes it possible to eliminate the influence of the field curvature of the downstream optical system. In an axially symmetric optical system, the image plane 19 (intermediate image plane) position is made more downstream for electron beams farther from the central axis in order to correct the field curvature aberration in the downstream optical system.

[0041] The multi-primary electron beams 20 that have passed through the angle-limiting aperture array substrate 211 are refracted by the condenser lens 205, and form an intermediate image of the electron source image and a crossover. Here, the crossover refers to the beam distribution at a position where the centers of the aberration-free trajectories of the multi-primary electron beams 20 converge at one point. The positions of the angle-limiting aperture array substrate 211 and the condenser lens 205 may be reversed. In such a case, the multi-primary electron beams 20 that have passed through the multistage lens array 210 are refracted by the condenser lens 205, and form an intermediate image and a crossover after passing through the angle-limiting aperture array substrate 211.

[0042] The multi-primary electron beams 20 that have passed through the condenser lens 205 are refracted by an electromagnetic lens 206 to further form an intermediate image, and proceed to an E×B separator 214 that is disposed at the height of the intermediate image plane (image plane conjugate position: I.I.P.) of the electron source image of each beam of the multi-primary electron beams 20. The multi-primary electron beams 20 then pass through the E×B separator 214 and proceed to an electromagnetic lens 207. Furthermore, by disposing a limiting aperture substrate 213 with limited passage holes near the crossover position of the multi-primary electron beams 20, scattered beams can be blocked. Furthermore, by deflecting the entire multi-primary electron beams 20 collectively with a collective deflector 212 and blocking the entire multi-primary electron beams 20 with the limiting aperture substrate 213, the entire multi-primary electron beams 20 can be blanked.

[0043] 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.

[0044] The multi-primary electron beams 20, which have been 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.

[0045] 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.

[0046] 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 .

[0047] The E×B separator 214 separates the multiple secondary electron beams 300 from the orbit of the multiple primary electron beams 20 .

[0048] The EXB separator 214 has two or more magnetic poles (electromagnetic deflection poles) 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 function 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 separating 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.

[0049] 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.

[0050] 3 is a diagram showing an example of a plurality of chip regions formed on a semiconductor substrate in the first embodiment. In the example of FIG. 3, a case where the substrate 101 is a semiconductor wafer is shown as an example. A plurality of chips (wafer dies) 332 are formed in a two-dimensional array in an inspection region 330 of the substrate 101. A mask pattern for one chip formed on an exposure mask substrate is transferred onto each chip 332 by an exposure device (stepper) (not shown), reduced to, for example, 1 / 4.

[0051] 4 is a diagram for explaining the image acquisition process in embodiment 1. As shown in Fig. 4, the area of ​​each chip 332 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 mask substrate, a pattern formation area (inspection area) formed on the mask is divided into a plurality of stripe areas 32 with a predetermined width in the y direction, for example.

[0052] 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).

[0053] The example of FIG. 4 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 is 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 within 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 mutually different sub-irradiation areas 29. Each primary electron beam 10 irradiates the same position within the assigned sub-irradiation area 29. The two-stage deflectors 208 and 209 deflect the multi-primary electron beams 20 collectively, thereby scanning the surface of the substrate 101 on which the pattern is formed with the multi-primary electron beams 20. In other words, the movement of the primary electron beam 10 within the sub-irradiation region 29 is achieved by collective deflection of the entire multi-primary electron beams 20 by the two-stage deflectors 208 and 209. By repeating this operation, one primary electron beam 10 is sequentially irradiated within one sub-irradiation region 29.

[0054] 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 in FIG. 4 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.

[0055] 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.

[0056] 5 is a diagram showing an example of the configuration from the radiation source to the intermediate image plane position of the multiple primary electron beams in Comparative Example 1 of Embodiment 1. In Comparative Example 1 of Embodiment 1, an electron beam emitted from an electron gun 301 serving as a radiation source is refracted by a condenser lens 302 into a substantially parallel beam and proceeds to a shaping aperture array substrate 303. Then, multiple primary electron beams are formed by portions of the electron beam passing through a plurality of holes in the shaping aperture array substrate 303. The formed multiple primary electron beams pass through an electrostatic lens array 310 and are refracted by a condenser lens 305 to form an intermediate image and a crossover of the electron source image.

[0057] Here, aberrations such as field curvature occur due to the reduction optical system further downstream of the optical system shown in Figure 5. This can cause deviations in the image positions of the electron source images on the sample surface at the object plane 313 of each beam. Therefore, it is desirable to shift the intermediate image planes of the peripheral beams downstream (e.g., to intermediate image plane position 319b) from the intermediate image plane position 319a of the central beam depending on the distance from the axis to compensate for the field curvature caused by the downstream reduction optical system. Therefore, in Comparative Example 1, an electrostatic lens array 310 is provided to correct the position of the intermediate image plane of each beam.

[0058] However, astigmatism occurs in the condenser lenses 302 and 305. This causes variations in the size of the beam images in the x and y directions at the intermediate image plane positions 319a and 319b. For example, even if the central beam has a nearly circular shape, the peripheral beams have a flattened shape.

[0059] Furthermore, in order to obtain the desired brightness for each beam, it is desirable to limit the divergence angle. However, for example, the divergence angle of the peripheral beams becomes larger than that of the central beam, which tends to cause variations in the convergence angles of the multiple primary electron beams at the intermediate image positions 319 a and 319 b.

[0060] As described above, it is desirable for the multiple primary electron beams to have the same shape, size, and focusing angle on the specimen surface. However, there is a problem in that these variations occur due to aberrations caused by condenser lenses and the like along the way. Therefore, it is desirable to reduce the variations in shape and focusing angle at the intermediate image plane position of each beam of the multiple electron beams, which is used to correct the field curvature of the downstream reduction optical system. In addition to achieving the same shape, it is also desirable to further reduce the size variations, if possible. It is difficult to correct these variations using the electrostatic lens array 310 of Comparative Example 1.

[0061] FIG. 6 is a diagram showing an example of the configuration of a two-stage multipole lens in Comparative Example 2 of Embodiment 1. Comparative Example 2 in FIG. 6 shows the lens action of two-stage multipole lenses 40-1 and 40-2 for one primary electron beam in a two-stage multipole lens array 40 corresponding to multiple primary electron beams 20. The two-stage multipole lenses 40-1 and 40-2 (quadrupole tablet lenses) are composed of multipoles with four or more poles and form a quadrupole field. Therefore, when each multipole lens 40-1 and 40-2 produces a lens action in the focusing direction in the x direction, it also produces a lens action in the diverging direction in the y direction. Alternatively, when each multipole lens 40-1 and 40-2 produces a lens action in the focusing direction in the y direction, it also produces a lens action in the diverging direction in the x direction. For ease of understanding, the following description will ignore the difference in image plane position for correcting the field curvature caused by the downstream reduction optical system, and will assume that the image is formed on the same image plane 19.

[0062] In Comparative Example 2 of FIG. 6 , the primary electron beam emitted from the object plane 11 is refracted by the first-stage multipole lens 40-1 in the x direction, for example, in the converging direction, and conversely in the y direction, in the diverging direction. Subsequently, the second-stage multipole lens 40-2 refracts the primary electron beam in the x direction, for example, in the diverging direction, and conversely in the y direction, in the converging direction, and forms an image (an intermediate image) on the image plane 19 (intermediate image plane position). However, since the two-stage multipole lenses 40-1 and 40-2 (quadrupole tablet lenses) have two degrees of freedom, if the positions of the object plane 11 and the image plane 19 are determined with the positions of the multipole lenses 40-1 and 40-2 fixed, the magnifications in the x direction and the y direction are determined. It should be noted that the magnifications in the x direction and the y direction can be reversed. Therefore, it is difficult to image the peripheral beams and the central beam isotropically with magnifications in both the x and y directions on the same image plane 19. In other words, with the two-stage multipole lenses 40-1, 40-2 (quadrupole tablet lenses), it is difficult to reduce the variation in the shape of each beam at the intermediate image plane position of each beam. Furthermore, as will be explained below, even when the focusing effect due to deflection is taken into consideration, there is no freedom in the magnification in the x direction or the magnification in the y direction.

[0063] Therefore, in the first embodiment, a three- or more-stage multi-stage lens array including two or more stages of multiple lens arrays (multipole lens arrays) having quadrupole or higher multipoles is used to correct the magnification anisotropy in two orthogonal directions for each beam and to correct the image plane position of the electron source image. This corrects the beam-specific shape variations at the intermediate image plane position of each beam. In the first embodiment, no condenser lens is disposed between the object plane 11 and the first-stage multipole lens 40-1. Meanwhile, as will be described later, for example, the first-stage multipole lens deflects the multiple primary electron beams 20, each of which has a diverging central axis, to form multiple primary electron beams 20 whose trajectory central axes are approximately parallel. In this case, deflection aberrations cause anisotropy in the divergence of each electron beam. The focusing action of the deflection field and the actions of the quadrupole lens and circular lens are approximated by a thin lens. This allows the focusing / divergence action of each element to be expressed by a matrix. This will be described in detail below.

[0064] Fig. 7 is a diagram showing an example of the configuration of a three-stage multipole lens in embodiment 1. Fig. 7 shows a case where a three-stage multipole lens array is used as the three or more stage multipole lens array 210. Fig. 7 shows the lens action of three-stage multipole lenses 40-1, 40-2, and 40-3 for one primary electron beam in the three-stage multipole lens array 40 corresponding to the multiple primary electron beams 20. The three-stage multipole lenses 40-1, 40-2, and 40-3 are made up of multipoles with quadrupoles or more and form a quadrupole field.

[0065] Furthermore, in the first embodiment, as described above, no condenser lens is disposed between the object plane 11 and the first-stage multipole lens 40-1. Therefore, the orbital central axes of each beam of the formed multi primary electron beams 20 travel in the diverging direction. Therefore, for example, in the first-stage multipole lens 40-1, a dipole field is formed in addition to the quadrupole field described above. In the dipole field, potentials with reversed positive and negative polarities are applied to the opposing electrodes of the multipole. Both the quadrupole field and the dipole field can be configured in parallel. Then, as shown in FIG. 1 , the dipole field deflects the multi primary electron beams 20, whose orbital central axes travel in the diverging direction, into substantially parallel multi primary electron beams 20. In other words, for example, the first-stage multipole lens 40-1 functions as a deflector array in addition to its original function of forming a quadrupole field. When an electron beam is deflected, a focusing effect proportional to the square of the curvature of the deflection field and the deviation from the central orbit acts parallel to the plane containing the deflection orbit. This anisotropic focusing effect generates deflection aberrations. When a deflection field and a quadrupole field are superimposed, both the focusing effect of the deflection field and the focusing / divergence effect of the quadrupole field act.

[0066] 7, the first-stage multipole lens 40-1 is disposed at a distance ηd from the object plane 11. The third-stage multipole lenses 40-1, 40-2, and 40-3 are disposed at a distance d from each other. The image plane 19 is located at a distance λd from the third-stage multipole lens 40-3.

[0067] FIG. 8 is a diagram showing an example of the configuration of a multipole lens array according to the first embodiment. In FIG. 8 , each multipole lens array 40 is configured with three electrode substrates, for example, an upper electrode substrate 12, a middle electrode substrate 14, and a lower electrode substrate 18. A plurality of passage holes 17 are formed in the three electrode substrates, through which the multiple primary electron beams 20 pass. At least the surfaces of the upper electrode substrate 12 and the lower electrode substrate 18 are made of a conductive material, and a ground potential (GND) is applied. A plurality of electrodes 16 are disposed in the plurality of passage holes 17 in the middle electrode substrate 14, each of which forms a quadrupole or higher multipole element surrounding the passage hole 17. In other words, in the multipole lens array 40, each lens has a quadrupole or higher multipole element. The substrate body of the middle electrode substrate 14 is insulated from each electrode. Here, it is preferable that the multipole elements at each position are arranged so that, for example, the phases of the eight electrodes are equally spaced relative to the electrodes arranged on a line extending radially from the center of the central beam passage hole 17. However, this is not a limitation. For example, the multipole elements at each position may be arranged so that, for example, the phases of the eight electrodes are equally spaced relative to the electrodes arranged in the x-direction or y-direction. Furthermore, electrostatic multipoles may be used as the multipoles. Alternatively, magnetic multipoles may be used as the multipoles. Furthermore, the multiple electrodes 16 may be arranged on either the top or back surface of the middle electrode substrate 14. In the example of FIG. 8, eight electrodes 16a to 16h are arranged on the top surface of the middle electrode substrate 14. An independent control potential is applied to each of the eight electrodes 16a to 16h. Therefore, a maximum of eight independent potentials equal to the number of beams times eight poles can be applied. This allows the focal length of each multipole lens in a single multipole lens array to be independently controlled. Therefore, it is possible to perform correction appropriate for each electron beam that constitutes the multi-electron beam. Here, the quadrupole lens acts as a convex lens in one direction and a concave lens in the orthogonal direction, and a positive focal length fq is defined, where the focal length of the convex lens is defined as fq and the focal length of the concave lens is defined as -fq.

[0068] In the example of Figure 7, the primary electron beam emitted from the object plane 11 travels through three stages of multipole lenses 40-1, 40-2, and 40-3. The primary electron beam, whose central axis orbit travels in a diverging direction, is deflected by, for example, the first-stage multipole lens 40-1 so that it becomes an approximately parallel beam whose central axis orbit is approximately parallel to the central axis (optical axis) of the orbit of the central beam of the multiple primary electron beams 20. The approximately parallel primary electron beam is then refracted by the first-stage multipole lens 40-1 in, for example, a converging direction in the x direction, and conversely in a diverging direction in the y direction. Subsequently, by the second-stage multipole lens 40-2, the primary electron beam is refracted in, for example, a diverging direction in the x direction, and conversely in a converging direction in the y direction. Next, the third stage multipole lens 40-3 refracts the light in the x direction, for example, in a converging direction, and in the y direction, conversely, in a diverging direction, so that the light is focused (forms an intermediate image) on the image plane 19 (intermediate image plane position).

[0069] The three-stage multipole lenses 40-1, 40-2, and 40-3 allow for magnification correction and focal length correction in two orthogonal directions. Because there are three degrees of freedom, even if the positions of the object plane 11 and the image plane 19 are determined with the positions of the multipole lenses 40-1, 40-2, and 40-3 fixed, the remaining one degree of freedom can be used to correct the magnification anisotropy between the magnification in the x direction and the magnification in the y direction. In other words, it is possible to correct the shape variations of each beam after aligning each beam with the desired image plane 19.

[0070] It is preferable to correct the distribution of the electron source image array to be corrected so that the distribution on the surface of the substrate 101 has a desired value. In other words, it is preferable to correct the distribution so that the distortion aberration of the downstream optical system is corrected. This can be achieved by using a multipole lens as a deflector. And / or, it is preferable to determine the imaging positions in the x and y directions of the electron source images of each beam of the multiple primary electron beams 20 so that the imaging positions of each beam on the surface of the substrate 101 coincide. In other words, it is preferable to correct the positions so that the astigmatism and field curvature of the downstream optical system are corrected.

[0071] 9 is a diagram showing an example of the adjustable range of the three-stage multipole lens in embodiment 1. In the example of FIG. 9, the vertical axis indicates the absolute value of the magnification in the y direction, and the horizontal axis indicates the absolute value of the magnification in the x direction. Also shown is a simulation result when the coefficient λ of the distance λd to the image plane position is set to a predetermined value λ1. Since the remaining degree of freedom is 1, only the magnification ratio can be corrected, and when the coefficient λ is fixed, the obtained magnification is the magnification indicated by the point on the curve of the graph surrounded by the dotted line. The obtained magnification ratio has an upper and lower limit depending on the coefficient λ.

[0072] FIG. 10 is a diagram showing an example of a configuration of a two-stage multipole lens and a single-stage circular lens in the first embodiment. FIG. 10 shows a case where a two-stage multipole lens array 40 and a single-stage circular lens array 42 are used as a three-stage or more multistage lens array. FIG. 10 shows the lens action of the two-stage multipole lenses 40-1 and 40-2 for one primary electron beam of the two-stage multipole lens array 40 and the single-stage circular lens array 42 corresponding to the multiple primary electron beams 20, and the single-stage circular lens 42-1. The two-stage multipole lenses 40-1 and 40-2 are composed of multipoles with quadrupoles or more and form a quadrupole field. Furthermore, for example, the first-stage multipole lens 40-1 further forms a dipole field.

[0073] The first-stage multipole lens 40-1 is disposed at a distance ηd from the object plane 11. The second-stage multipole lenses 40-1 and 40-2 are disposed at a distance d. The first-stage circular lens 42-1 is disposed at a distance d from the second-stage multipole lens 40-2. The image plane 19 is located at a distance λd from the first-stage circular lens 42-1.

[0074] FIG. 11 is a diagram showing an example of the configuration of a circular lens array according to the first embodiment. In FIG. 10 , the circular lens array 42 is composed of three electrode substrates: an upper electrode substrate 62, a middle electrode substrate 64, and a lower electrode substrate 66. The three electrode substrates have a plurality of passage holes 67 formed therein for the multiple primary electron beams 20 to pass through. At least the surfaces of the upper electrode substrate 62 and the lower electrode substrate 66 are made of a conductive material, and a ground potential (GND) is applied to them. A ring-shaped electrode 66 is disposed in each of the plurality of passage holes 67 in the middle electrode substrate 64, surrounding the passage hole 67. In the circular lens array 42, each lens applies a uniform force from the periphery to the electron beams passing through it. The substrate body of the middle electrode substrate 64 is insulated from the electrode 66. The electrode 66 may be disposed on either the top or back surface of the middle electrode substrate 64. A control potential is applied to the electrode 66. Therefore, a maximum of one pole times the number of beams can be applied, which allows the focal length of each circular lens to be controlled independently. This allows for correction appropriate for each electron beam constituting the multi-electron beam.

[0075] In the example of FIG. 10 , the primary electron beam emitted from the object plane 11 travels through two-stage multipole lenses 40-1 and 40-2. The primary electron beam, whose central axis orbit travels in a diverging direction, is deflected by, for example, the first-stage multipole lens 40-1 so that it becomes an approximately parallel beam whose central axis orbit is approximately parallel to the central axis (optical axis) of the orbit of the central beam of the multiple primary electron beams 20. The approximately parallel primary electron beam is then further refracted by the first-stage multipole lens 40-1, for example, in a converging direction in the x direction, and conversely, in a diverging direction in the y direction. Next, the second-stage multipole lens 40-2 refracts the primary electron beam in the diverging direction in the x direction, and conversely, in a converging direction in the y direction. Next, the first-stage circular lens 42-1 refracts the primary electron beam in the converging direction in both the x and y directions, and forms an image (an intermediate image) on the image plane 19 (intermediate image plane position).

[0076] By using two-stage multipole lenses 40-1 and 40-2 and a single-stage circular lens 42-1, magnification correction and focal length correction are performed in two orthogonal directions. Because there are three degrees of freedom, even if the two-stage multipole lenses 40-1 and 40-2 and the single-stage circular lens 42-1 are fixed in position and the magnification anisotropy of the position of the object plane 11 and the magnification in the x direction and the magnification in the y direction are corrected by the two-stage multipole lenses 40-1 and 40-2, the position of the image plane 19 can be adjusted by the remaining one degree of freedom of the circular lens 42-1. In other words, it is possible to adjust the shape variation of each beam after aligning each beam with the desired image plane 19.

[0077] FIG. 12 is a diagram showing an example of the adjustable range of the combination of a two-stage multipole lens and a single-stage circular lens according to the first embodiment. In the example of FIG. 12, the vertical axis indicates the absolute value of the magnification in the y direction, and the horizontal axis indicates the absolute value of the magnification in the x direction. Also shown is a simulation result when the coefficient η of the distance ηd to the object plane position is set to a predetermined value η1. In the example of FIG. 12, the coefficient λ of the distance λd to the image plane position is calculated for three different values ​​λ1, λ2, and λ3. Since the remaining degree of freedom is one, the magnification distributions obtained for each image plane 19 are all curved. Since only positive values ​​are allowed for the focal length of the circular lens 42-1, it is difficult to achieve a condition in which the focal length of the circular lens 42-1 is negative or zero. Therefore, when the coefficients η and λ are fixed, the obtained magnification is the magnification indicated by the point on the curve of the graph obtained with the set coefficients η and λ.

[0078] 13 is a diagram showing an example of a configuration of a three-stage multipole lens and a single-stage circular lens in the first embodiment. FIG. 13 shows a case where a three-stage multipole lens array 40 (first lens array) and a single-stage circular lens array 42 (second lens array) are used as a three-stage or more multistage lens array 210. In other words, the multistage lens array has a plurality of three-stage multipole lens arrays 40, each having a quadrupole or higher multipole element, and a single-stage circular lens array 42, in which each lens exerts a uniform force from the periphery on the electron beam passing through it. FIG. 13 shows the lens action of the three-stage multipole lens array 40 corresponding to the multiple primary electron beams 20 and the three-stage multipole lenses 40-1, 40-2, and 40-3 for one primary electron beam of the single-stage circular lens array 42, as well as the lens action of the single-stage circular lens 42-1. The three stages of multipole lenses 40-1, 40-2, and 40-3 are made up of multipoles with quadrupoles or more and form a quadrupole field. For example, the first stage of multipole lens 40-1 also forms a dipole field.

[0079] The first-stage multipole lens 40-1 is disposed at a distance ηd from the object plane 11. The three-stage multipole lenses 40-1, 40-2, and 40-3 are disposed at a distance d. The first-stage circular lens 42-1 is disposed at a distance d from the third-stage multipole lens 40-3. The image plane 19 is located at a distance λd from the first-stage circular lens 42-1.

[0080] In the example of FIG. 13 , the primary electron beam emitted from the object plane 11 travels through three stages of multipole lenses 40-1, 40-2, and 40-3. The primary electron beam, whose central axis orbit travels in a diverging direction, is deflected by, for example, the first-stage multipole lens 40-1 so that it becomes an approximately parallel beam whose central axis orbit is approximately parallel to the central axis (optical axis) of the orbit of the central beam of the multi primary electron beam 20. The approximately parallel primary electron beam is then refracted by the first-stage multipole lens 40-1, for example, in the converging direction in the x direction, and conversely, in the diverging direction in the y direction. Subsequently, by the second-stage multipole lens 40-2, the primary electron beam is refracted by, for example, the diverging direction in the x direction, and conversely, in the converging direction in the y direction. Subsequently, by the third-stage multipole lens 40-3, the primary electron beam is refracted by, for example, the converging direction in the x direction, and conversely, in the diverging direction in the y direction. Subsequently, the light is refracted in the converging direction in both the x and y directions by the first-stage circular lens 42-1, and is imaged (forms an intermediate image) on the image plane 19 (intermediate image plane position).

[0081] By combining three stages of multipole lenses 40-1, 40-2, and 40-3 with a single stage of circular lens 42-1, magnification correction in two orthogonal directions and focal length correction are performed. Because there are four degrees of freedom, it is possible to correct the magnification anisotropy between the position of the object plane 11, the position of the image plane 19, the magnification in the x direction, and the magnification in the y direction while the positions of the three stages of multipole lenses 40-1, 40-2, and 40-3 and the single stage of circular lens 42-1 are fixed. In other words, it is possible to correct the shape variations of each beam after aligning each beam with the desired image plane 19. Furthermore, because there are four degrees of freedom, there are even fewer restrictions than in the example described above.

[0082] In addition, among the combinations of three-stage multipole lenses 40-1, 40-2, and 40-3 and one-stage circular lens 42-1, it is also preferable to use the three-stage multipole lenses 40-1, 40-2, and 40-3 to align each beam with the desired image plane 19 under the conditions described in Figure 7, and then correct the shape variations for each beam, and use the one-stage circular lens 42-1 to correct the size variations for each beam on the image plane 19.

[0083] 14 is a diagram showing an example of an adjustable range for a combination of a three-stage multipole lens and a single-stage circular lens in embodiment 1. In the example of FIG. 14, the vertical axis indicates the absolute value of magnification in the x direction, and the horizontal axis indicates the absolute value of magnification in the y direction. This shows that magnification can be achieved over a wide range, except when magx = 0 and magy = 0.

[0084] FIG. 15 is a diagram showing an example of a configuration of a two-stage multipole lens and a two-stage circular lens according to the first embodiment. FIG. 15 shows a case where a two-stage multipole lens array 40 (first lens array) and a two-stage circular lens array 42 (second lens array) are used as a three-stage or more multistage lens array 210. In other words, the multistage lens array has two stages of a plurality of multipole lens arrays 40, each having a quadrupole or more multipole element, and a two-stage circular lens array 42, each of which applies a uniform force from the periphery to an electron beam passing through the lens. FIG. 16 shows the lens action of the two-stage multipole lenses 40-1 and 40-2 for one primary electron beam of the two-stage multipole lens array 40 and the two-stage circular lens array 42 corresponding to the multiple primary electron beams 20, and the lens action of the two-stage circular lenses 42-1 and 42-2. The two-stage multipole lenses 40-1 and 40-2 are made up of multipoles with quadrupoles or more and form a quadrupole field. Furthermore, for example, the first-stage multipole lens 40-1 further forms a dipole field.

[0085] Furthermore, the first-stage multipole lens 40-1 is disposed at a distance ηd from the object plane 11. The second-stage multipole lenses 40-1 and 40-2 are disposed at a distance d apart. The first-stage circular lens 42-1 is disposed at a distance d from the second-stage multipole lens 40-2. The second-stage circular lenses 42-1 and 42-2 are disposed at a distance d apart. The image plane 19 is located at a distance λd from the second-stage circular lens 42-2.

[0086] In the example of FIG. 16 , the primary electron beam emitted from the object plane 11 travels through two-stage multipole lenses 40-1 and 40-22. The primary electron beam, whose central axis orbit travels in a diverging direction, is deflected by, for example, the first-stage multipole lens 40-1 so that it becomes an approximately parallel beam whose central axis orbit is approximately parallel to the central axis (optical axis) of the orbit of the central beam of the multi-primary electron beams 20. The approximately parallel primary electron beam is then refracted by the first-stage multipole lens 40-1, for example, in a converging direction in the x direction, and conversely, in a diverging direction in the y direction. Subsequently, the second-stage multipole lens 40-2 refracts the primary electron beam, for example, in a diverging direction in the x direction, and conversely, in a converging direction in the y direction. The primary electron beam then forms an intermediate image plane 1, and is then refracted by the first-stage circular lens 42-1 in the converging direction in both the x and y directions. Subsequently, the second-stage circular lens 42-1 refracts the light in the converging direction in both the x and y directions, and focuses the light (an intermediate image) on the image plane 19 (intermediate image plane 2). While Fig. 15 shows the case where the intermediate image 1 is a real image, the intermediate image 1 may be either a real image or a virtual image.

[0087] The combination of two-stage multipole lenses 40-1 and 40-2 and two-stage circular lenses 42-1 and 42-2 allows for magnification correction in two orthogonal directions and focal length correction. Because there are four degrees of freedom, the two-stage multipole lenses 40-1 and 40-2 (quadrupole tablets) can correct the position of the object plane 11 and the magnification anisotropy in the x and y directions. While the position of the intermediate image plane 1 cannot be set arbitrarily, the subsequent two-stage circular lenses 42-1 and 42-2 (circular lens tablets) can correct the position of the image plane 19 (intermediate image plane 2) and the size of the electron source image on the image plane 19. In other words, each beam can be aligned with the desired image plane 19, and then the variations in shape and size of each beam can be corrected. However, when correcting the size of the electron source image, the intermediate image plane 1 must not overlap with the center position of either of the two-stage circular lenses 42-1 and 42-2.

[0088] FIG. 16 is a diagram showing an example of the configuration of a four-stage multipole lens in the first embodiment. FIG. 16 shows a case where a four-stage multipole lens array 40 is used as the three-stage or more multipole lens array 210. In other words, the multipole lens array has four stages of a plurality of multipole lens arrays 40, each lens having a quadrupole or higher multipole element. FIG. 16 shows the lens action of four-stage multipole lenses 40-1, 40-2, 40-3, and 40-4 for one primary electron beam in the four-stage multipole lens array 40 corresponding to the multiple primary electron beams 20. The four-stage multipole lenses 40-1, 40-2, 40-3, and 40-4 are composed of quadrupole or higher multipoles and form a quadrupole field. Furthermore, for example, the first-stage multipole lens 40-1 further forms a dipole field.

[0089] The first-stage multipole lens 40-1 is disposed at a distance ηd from the object plane 11. The two upstream multipole lenses 40-1 and 40-2 are disposed at a distance d. The third-stage multipole lens 40-3 is disposed at a distance d from the second-stage multipole lens 40-2. The two downstream multipole lenses 40-3 and 40-4 are disposed at a distance d. The image plane 19 is located at a distance λd from the fourth-stage multipole lens 40-4.

[0090] In the example of FIG. 16 , the primary electron beam emitted from the object plane 11 travels through four stages of multipole lenses 40-1, 40-2, 40-3, and 40-4. The primary electron beam, whose central axis orbit travels in a diverging direction, is deflected by, for example, the first-stage multipole lens 40-1 so that it becomes an approximately parallel beam whose central axis orbit is approximately parallel to the central axis (optical axis) of the orbit of the central beam of the multi-primary electron beams 20. The approximately parallel primary electron beam is then refracted by the first-stage multipole lens 40-1, for example, in a converging direction in the x direction, and conversely, in a diverging direction in the y direction. Subsequently, by the second-stage multipole lens 40-2, the primary electron beam is refracted by, for example, the diverging direction in the x direction, and conversely, in a converging direction in the y direction. Subsequently, by the third-stage multipole lens 40-3, the primary electron beam is refracted by, for example, the converging direction in the x direction, and conversely, in a diverging direction in the y direction. Next, the fourth-stage multipole lens 40-4 refracts the light in the x direction, for example, in a diverging direction, and in the y direction, conversely, in a converging direction, so that the light is focused (forms an intermediate image) on the image plane 19 (intermediate image plane 2).

[0091] By using four-stage multipole lenses 40-1, 40-2, 40-3, and 40-4, magnification correction and focal length correction can be performed in two orthogonal directions. Since there are four degrees of freedom, the degree of freedom is even greater than in the case of three-stage multipole lenses 40-1, 40-2, and 40-3. The four-stage multipole lenses 40-1, 40-2, 40-3, and 40-4 can correct the position of the object plane 11, the position of the image plane 19, and the magnification anisotropy in the x- and y-directions. Furthermore, the size of the electron source image on the image plane 19 can be corrected. In other words, it is possible to correct variations in the shape and size of each beam after aligning each beam with the desired image plane 19.

[0092] When a multipole lens array 40 having five or more stages is used as a multistage lens array 210 having three or more stages, each beam can be aligned with the desired image plane 19 with even fewer restrictions than when a four-stage multipole lens array 40 is used, and variations in the shape and size of each beam can be corrected.

[0093] As described above, the shaped multiple primary electron beams 20 are aligned with the desired intermediate image plane position for each beam by the multistage lens array 210, and then the variations in shape (and size) for each beam are corrected. The multiple primary electron beams 20 that have passed through the multistage lens array 210 proceed to the angle-limiting aperture array substrate 211. Next, the variations in the focusing angle are corrected.

[0094] FIG. 17 is a diagram showing an example of the configuration of an angle-limiting aperture array in Comparative Example 3 of Embodiment 1. FIG. 18 is a diagram showing an example of the configuration of a beam-size-limiting aperture array in Comparative Example 3 of Embodiment 1. In Comparative Example 3, as shown in FIG. 18 , for example, at the position of the image plane 19, corresponding beams of the multi-primary electron beams 20 are passed through a plurality of passage holes in a beam-size-limiting aperture array substrate 341. This limits the size of each beam and shapes the beam. Furthermore, by providing an angle-limiting aperture substrate 311 downstream as shown in FIG. 17 , it is possible, in principle, to control both the beam size and the beam divergence angle. However, if there is a mismatch between the pitch of the multi-primary electron beams 20 and the pitch of the plurality of passage holes, as shown in FIG. 18 , some passage holes may form a beam with a partial beam shape, while other passage holes may block the entire beam, resulting in no beam shaping. Another problem is that passage holes on the order of sub-micron are prone to clogging with contaminants.

[0095] On the other hand, in the first embodiment, the beam shape (and beam size) is corrected by the multi-stage lens array 210, and then the divergence angle or convergence angle of each electron beam is limited by the angle-limiting aperture array substrate 211. In the angle-limiting aperture array substrate 211, a plurality of passage holes (second openings) are formed at positions where the multiple primary electron beams 20 pass through.

[0096] FIG. 19 is a diagram illustrating the function of the angle-limiting aperture array substrate in the first embodiment. In FIG. 19, the upper diagram shows a case where angle limitation is performed downstream of the multistage lens array 210. The lower diagram of FIG. 19 shows a case where angle limitation is performed upstream of the multistage lens array 210, for example, by a shaping aperture array substrate. The larger the convergence angle of each beam on the substrate 101 surface, the larger the beam current can be obtained. However, a larger convergence angle increases aberrations. Therefore, it is desirable to determine the convergence angle so that a large beam current can be obtained within the desired dimensional range on the sample surface. For this reason, the angle-limiting aperture substrate 211 is used to limit the convergence angle. Furthermore, since the image magnification and the angular magnification are inversely proportional in the paraxial approximation, forming images with different magnifications in the x and y directions results in different convergence angles in each direction on the substrate 101 surface for electron beams that had an isotropic angular distribution upon incidence on the optical system. To address this issue, the convergence angle can be adjusted by providing an angle-limiting aperture to align the convergence angle-dependent aberrations. FIG. 19 shows an example. When imaging with different magnifications in the x and y directions, the convergence angle becomes large at trajectories with small magnifications. Therefore, the convergence angle is limited by the angle-limiting aperture substrate 211. As shown in the upper diagram of Figure 19 , by placing the angle-limiting aperture substrate 211 close to the lens, the effect on the beam distribution at the imaging position can be suppressed. Alternatively, as shown in the lower diagram of Figure 19 , the angular distribution at the time of incidence on the optical system can be modified by using the shaping aperture array substrate 203, which serves as both a shaping aperture and an angle-limiting aperture (to be described later). It is desirable to determine the shape of the angle-limiting aperture substrate 211 so that an isotropic convergence angle distribution is obtained for each beam on the sample surface.

[0097] Specifically, the angle-limiting aperture array substrate 211 is disposed at a position away from the image plane 19 on the upstream side. In the example of FIG. 1 , for example, the angle-limiting aperture array substrate 211 is disposed between the multistage lens array 210 and the condenser lens 205. However, the present invention is not limited to this. The angle-limiting aperture array substrate 211 may be disposed between the condenser lens 205 and the image plane 19. In other words, the angle-limiting aperture array substrate 211 may be disposed at a position before the multiple primary electron beams 20 reach the image plane 19 after being refracted in the focusing direction. Since the divergence angle or focusing angle is limited when each beam has a wide beam diameter before forming the intermediate image plane, the diameter size of the multiple passage holes of the limiting aperture array 211 can be made sufficiently larger than the beam size at the image plane position. Therefore, blockage due to contamination or the like can be suppressed or reduced. The angle-limiting aperture array substrate 211 limits the divergence angle or focusing angle of each electron beam by allowing the multiple primary electron beams 20, which have passed through the multistage lens array 210, to pass through the multiple passage holes. If each beam is diverging, the angle of divergence can be limited, and if each beam is focusing, the angle of focusing can be limited. This makes it possible to correct variations in the convergence angle for each beam at the position of the image plane 19.

[0098] FIG. 20 is a diagram showing an example of the configuration from the electron source to the intermediate image plane after magnification correction and focal length correction in two orthogonal directions in a first modification of the first embodiment. In the first modification of the first embodiment, as shown in FIG. 20 , a multipole lens array 40 is arranged at the final stage of a multistage lens array 210, and deflects the multiple primary electron beams 20 in the focusing direction instead of the condenser lens 205. The multipole lens array 40, instead of the condenser lens 205, functions as a deflector array that deflects the multiple primary electron beams 20 passing through the multistage lens array 210 in the focusing direction. In this case, the multipole lens array 40, instead of the condenser lens 205, generates a dipole field to focus each primary electron beam to a single point. In other words, potentials with reversed positive and negative polarities are applied to the opposing electrodes of the multipole element. As a result, the primary electron beam passing through the multipole element is deflected in the direction of the positive potential of the electric field formed. In order to correct for variations in the shape (and size) of the electron source image at the image plane 19, the multipole lens array in the multistage lens array 210 has each multipole forming a quadrupole field, but the dipole field and quadrupole field can be applied in parallel.

[0099] Alternatively, it is also preferable to separately arrange a multipole lens array 40 downstream of the multistage lens array 210. It is sufficient to make each multipole of the multipole lens array 40 generate only a dipole field. In such a case, the multipole lens array 40 instead of the condenser lens 205 functions as a deflector array that deflects the multi primary electron beams 20 that have passed through the multistage lens array 210 in the focusing direction.

[0100] 20, the angle limiting aperture array substrate 211 is disposed on the trajectory of the multi-primary electron beams 20 after they have been refracted in the convergence direction. The other configurations are the same as those in FIG.

[0101] 21 is a diagram showing an example of the configuration from the electron source to the intermediate image plane after magnification correction and focal length correction in two orthogonal directions in Modification 2 of Embodiment 1. In Modification 2 of Embodiment 1, as shown in FIG. 21 , a multipole lens array 40 is arranged downstream of an angle-limiting aperture array substrate 211 to deflect the multi-primary electron beams 20 in the focusing direction instead of the condenser lens 205. The other configuration is the same as that shown in FIG. 1. The multipole lens array 40 instead of the condenser lens 205 functions as a deflector array that deflects the multi-primary electron beams 20 that have passed through the multistage lens array 210 in the focusing direction. In this case as well, it is sufficient to make each multipole of the multipole lens array 40 generate only a dipole field.

[0102] 22 is a diagram showing an example of the configuration from the electron source to the intermediate image plane after magnification correction and focal length correction in two orthogonal directions in a third modification of the first embodiment. In the above example, the first-stage multipole lens array 40 of the multistage lens array 210 forms multiple primary electron beams 20, each of which has a substantially parallel central axis of orbit. However, this is not limitative. In the third modification of the first embodiment, as shown in the example of FIG. 22 , a multipole lens array 40 is disposed between the shaping aperture array substrate 203 and the multistage lens array 210, in addition to the multistage lens array 210. The multipole lens array 40 forms multiple primary electron beams 20, each of which has a substantially parallel central axis of orbit. In this case, the multipole lens array 40 functions as a deflector array.

[0103] In the above example, the multipole lens arrays 40 of two or more stages of the multistage lens array 210 are configured by electrostatic multipole lens arrays configured by electrostatic multipoles, or by magnetic multipole lens arrays configured by magnetic multipoles, or by a combination of an electrostatic multipole lens array configured by electrostatic multipoles and a magnetic multipole lens array configured by magnetic multipoles.

[0104] As described above, variations in the shape and focusing angle of each beam can be reduced at the desired image plane 19 (intermediate image plane) of each beam by using a three or more stage lens array including a two or more stage multipole lens array 40 and the angle-limiting aperture array substrate 211. Furthermore, by using a four or more stage lens array, variations in the size of each beam can be corrected at the desired image plane 19 (intermediate image plane) of each beam.

[0105] FIG. 23 is a flowchart illustrating an example of the main steps of the method for adjusting a multistage lens array according to the first embodiment. First, the lenses of the entire inspection apparatus 100, including the multistage lens array 210, are driven under initial conditions determined by simulation or past measurement experience (S102). Then, the beam array shape at different focal positions is measured (S104). From the measurement results, the residual astigmatism, field curvature, beam size, and focusing half angle are determined (S106). Then, it is determined whether the obtained results satisfy the desired conditions (S108). If the obtained results do not satisfy the desired conditions, lens conditions capable of correcting the astigmatism, field curvature, and magnification are determined (S110). If the obtained results satisfy the desired conditions, the adjustment is completed, and the inspection process proceeds. The lens conditions are changed to the determined conditions (S112). Then, the process returns to S104, and steps S104 to S112 are repeated until the obtained results satisfy the desired conditions.

[0106] After adjusting the lenses of the entire inspection device 100 including the multistage lens array 210 as described above, the inspection device 100 inspects the substrate 101 .

[0107] In the scanning process, the image acquisition mechanism 150 scans the object (here, the substrate 101) with the multi-primary electron beams 20. 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.

[0108] FIG. 24 is a configuration diagram showing an example of the configuration of a comparison circuit in embodiment 1. In FIG. 24 , 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 "unit" 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 electric 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.

[0109] 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.

[0110] The measurement image data (beam image) transferred to the comparison circuit 108 is stored in the storage device 50 .

[0111] 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.

[0112] 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.

[0113] 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.

[0114] 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.

[0115] 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.

[0116] 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.

[0117] 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.

[0118] 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 measurement image of the device itself.

[0119] As described above, according to the first embodiment, it is possible to reduce variations in at least the shape and the convergence angle at the intermediate image plane position of the multiple electron beams.

[0120] [Embodiment 2] In the first embodiment, the angle-limiting aperture array substrate 211 is disposed downstream of the multi-stage lens array 210, but the method of angle limitation is not limited to this. In the second embodiment, a configuration will be described in which angle limitation is also performed when shaping the multiple primary electron beams 20.

[0121] Fig. 25 is a diagram showing an example of the configuration of an inspection device in embodiment 2. Fig. 25 is the same as Fig. 1 except that the angle-limiting aperture array substrate 211 is omitted. Points other than those particularly described below may be the same as embodiment 1.

[0122] In the second embodiment, the shaping aperture array substrate 203 forms multiple primary electron beams 20 and limits the divergence angle or convergence angle of each primary electron beam, thereby making it possible to omit the angle-limiting aperture array substrate 211 at the subsequent stage.

[0123] Here, as mentioned above, the multiple primary electron beams 20 may have astigmatism, so when the beam is shaped by the shaping aperture array substrate 203, the beam shape due to such astigmatism may be corrected.

[0124] FIG. 26 shows an example of a beam shaped by the shaping aperture array substrate in the second embodiment. For example, when forming an image with a magnification of 1 in the x direction and 0.5 in the y direction, the angular magnification of the multistage lens array 210 is set to 1 in the x direction and 2 in the y direction. To align the focusing angle on the image plane 19 side equivalent to an opening with a diameter of 2r formed on the angle-limiting aperture array substrate 211, the focusing angle on the shaping side is limited to x direction:y direction = 1:0.5. To achieve this, the opening on the shaping aperture array substrate 203 is set to an ellipse with a major axis:minor axis ratio of 2:1. Note that the size may vary depending on the position. When determining the dimensions of the aperture, it is practical to assume that the angular distribution of the electron beam passing through the multistage lens array 210 is the desired one, trace the trajectory in reverse by simulation to determine the distribution at the shaping aperture array position, and then determine the shape of the aperture to provide that distribution. Alternatively, the marks 111 may be provided at different heights, and the beam convergence angle may be determined from the dependence of the beam distribution obtained by irradiating the marks 111 with an electron beam on the height of the marks 111, and may be determined so as to obtain a desired distribution.

[0125] As described above, according to the second embodiment, it is possible to shape the beam and limit the angle, thereby correcting variations in the focusing angle on the image plane 19. Note that, like the first embodiment, the multistage lens array 210 can correct variations in the shape (and size) of the electron source image on the image plane 19.

[0126] 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. Furthermore, each "circuit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. The program that runs the processor may be recorded on a recording medium such as a magnetic disk drive, a magnetic tape drive, a floppy disk, or a ROM (read-only memory). For example, the position circuit 107, the comparison circuit 108, and the reference image creation circuit 112 may be composed of at least one of the processing circuits described above. In this description, it is assumed that the absolute value of the focal length of the quadrupole lens or circular lens used can take any value other than zero. In practice, there are limitations on the focal length that can be achieved due to physical limitations such as discharge in the case of electrostatic lenses and magnetic pole saturation in the case of magnetic lenses. Furthermore, the quadrupole component of a condenser lens is also subject to limitations due to the desired magnification and lens arrangement. It is recommended that these limitations be taken into account when optimizing the device design.

[0127] Although the embodiments have been described above with reference to specific examples, the present invention is not limited to these specific examples.

[0128] 27 is a diagram showing another example of the configuration of a three-stage multipole lens in each embodiment. For example, in the above explanation, the position of the intermediate image plane is adjusted to be the same in the x direction and the y direction, but as shown in FIG. 27, it is also possible to adjust the position to be different so as to cancel astigmatism in the downstream optical system.

[0129] FIG. 28 shows an example of the arrangement of multipole lenses in each embodiment. While the focal length of each lens constituting the lens array can be controlled independently, if the condition for the independence of the adjustment range is relaxed, the lenses constituting the lens array can be divided into at least two or more groups, with independent focal lengths between different groups and a common focal length within the same group. For example, when the distribution of field curvature and astigmatism is axially symmetric, as shown in FIG. 28 , the phase of the rotational direction of the electrodes of the multipole lens can be changed depending on the direction from the central axis, and the lenses can be divided into two or more groups according to radial distance. A common power supply can be used to apply potential to corresponding electrodes within the same group so that the focal lengths are equal, thereby reducing the number of power supplies. In the example shown, the power supply for electrodes assigned the same number can be shared. Furthermore, when only a quadrupole field is generated, a common power supply can be used by applying the same potential to opposing electrodes, such as electrodes 1 and 5. Circular lenses can also be divided into groups according to radial distance so that the focal lengths are equal within the same group, thereby sharing a power supply.

[0130] 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.

[0131] In addition, all other multi-electron beam irradiation devices and multi-electron beam irradiation methods 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.

[0132] The present invention relates to a multi-electron beam irradiation apparatus and a multi-electron beam irradiation method, which can be used, for example, in an apparatus for correcting variations in the shape of the multi-electron beams and variations in the convergence angle at an intermediate image plane position of an electron source image of the multi-electron beams caused by aberrations or the like.

[0133] 10 Primary electron beam 11 Object plane 12 Upper electrode substrate 14 Middle electrode substrate 16 Electrode 17 Passage hole 18 Lower electrode substrate 19 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 Multipole lens array 40-1, 40-2, 40-3, 40-4 Multipole lens 42 Circular lens array 42-1, 42-2 Circular lens 50, 52, 56 Storage device 54 Frame image creation unit 57 Alignment unit 58 Comparison unit 62 Upper electrode substrate 64 Middle electrode substrate 66 Electrode 67 Passage hole 18 Lower electrode substrate 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-stage lens array 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 Condenser lens 203 Shaping aperture array substrate 206, 207 Electromagnetic lens 208 Deflector 209 Deflector 210 Multi-stage lens array 211 Angle limiting aperture array substrate 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 301 Electron gun 302, 305 Condenser lens 303 Shaping aperture array substrate 310 Electrostatic lens array 313 Object plane 319 Image plane 330 Inspection area 332 Chip 341 Beam size limiting aperture array substrate

Claims

1. A multi-electron beam irradiation device comprising: an emission source which emits an electron beam in a diverging direction; a shaping aperture array substrate having a plurality of first openings formed therein, and in which a portion of each of the electron beams traveling in the diverging direction passes through the plurality of first openings to form a multi-electron beam traveling in the diverging direction; a multi-stage lens array having three or more stages, each of which includes a plurality of lens arrays having two or more stages of multipoles with quadrupoles or more arranged on the trajectory of a beam of the multi-electron beam which it is responsible for, and which deflects the multi-electron beam traveling in the diverging direction to form a multi-electron beam whose central trajectories of each electron beam are approximately parallel, and which performs magnification correction and focal length correction in two orthogonal directions; and an angle-limiting aperture array substrate having a plurality of second openings formed therein, and in which the multi-electron beams which have passed through the multi-stage lens array pass through the plurality of second openings to limit the divergence angle or convergence angle of each electron beam.

2. The multi-electron beam irradiation device according to claim 1, characterized in that the multi-stage lens array comprises: a first lens array having two stages, each of which has a multipole element of quadrupole or more; and a second lens array having two stages, each of which exerts a force uniformly from the periphery on the electron beam passing through it.

3. The multi-electron beam irradiation device according to claim 1, characterized in that the multi-stage lens array comprises: a first lens array having three stages, each lens having a multipole element of quadrupole or more; and a second lens array having one stage, each lens of which exerts a uniform force from all around on the electron beam passing through it.

4. A multi-electron beam irradiation device according to claim 1, characterized in that the multi-stage lens array has a plurality of lens arrays of four or more stages, each lens having a multipole element of quadrupole or more.

5. A multi-electron beam irradiation apparatus according to claim 1, further comprising a condenser lens for refracting the multi-electron beams having passed through the multi-stage lens array in a focusing direction.

6. A multi-electron beam irradiation apparatus according to claim 1, further comprising a deflector array for deflecting the multi-electron beams having passed through the multi-stage lens array in a focusing direction.

7. A multi-electron beam irradiation apparatus according to claim 1, characterized in that an electrostatic multipole element is used as the multipole element.

8. A multi-electron beam irradiation apparatus according to claim 1, characterized in that a magnetic multipole is used as the multipole.

9. A multi-electron beam irradiation device as described in claim 1, characterized in that the two or more stages of multiple lens arrays having the multipoles are composed of a combination of an electrostatic multipole lens array composed of electrostatic multipoles and a magnetic multipole lens array composed of magnetic multipoles.

10. A multi-electron beam irradiation device comprising: an emission source which emits an electron beam in a diverging direction; a shaping aperture array substrate in which a plurality of first openings are formed, and in which a portion of each of the electron beams traveling in the diverging direction passes through the plurality of first openings, thereby forming a multi-electron beam traveling in the diverging direction; a deflector array which deflects the multi-electron beam traveling in the diverging direction to form a multi-electron beam with each electron beam having a central trajectory that is approximately parallel; a multi-stage lens array having three or more stages including a plurality of lens arrays having two or more stages, each lens having a quadrupole or higher multipole arranged on the trajectory of a beam it is responsible for among the multi-electron beams; and an angle-limiting aperture array substrate in which a plurality of second openings are formed, and in which the multi-electron beams which have passed through the multi-stage lens array pass through the plurality of second openings, thereby limiting the divergence angle or convergence angle of each electron beam.

11. The multi-electron beam irradiation device as described in claim 10, characterized in that the multi-stage lens array comprises: a two-stage plurality of first lens arrays, each lens having a quadrupole or higher multipole; and a two-stage plurality of second lens arrays, each lens exerting a uniform force from all around on the electron beam passing through it.

12. The multi-electron beam irradiation device according to claim 10, characterized in that the multi-stage lens array comprises: a plurality of first lens arrays in three stages, each lens having a quadrupole or higher multipole; and a second lens array in one stage, each lens of which exerts a uniform force from all around on the electron beam passing through it.

13. A multi-electron beam irradiation device comprising: an emission source which emits an electron beam in a diverging direction; a shaped aperture array substrate in which a plurality of first openings are formed, and in which a portion of each of the electron beams traveling in the diverging direction passes through the plurality of first openings to form a multi-electron beam and limit the divergence angle or convergence angle of each electron beam; and a multi-stage lens array of three or more stages, each of which includes a plurality of lens arrays of two or more stages, each of which has a multipole element of quadrupole or more arranged on the trajectory of a beam it is responsible for among the multi-electron beams, and which deflects the multi-electron beam traveling in the diverging direction to form a multi-electron beam whose central trajectories are approximately parallel, and which performs magnification correction and focal length correction in two orthogonal directions.

14. A multi-electron beam irradiation device as described in claim 13, characterized in that the multi-stage lens array comprises: a two-stage plurality of first lens arrays, each lens having a quadrupole or higher multipole; and a two-stage plurality of second lens arrays, each lens exerting a uniform force from all around on the electron beam passing through it.

15. A multi-electron beam irradiation device as described in claim 13, characterized in that the multi-stage lens array comprises: three stages of a plurality of first lens arrays, each lens having a quadrupole or higher multipole; and one stage of a second lens array, each lens of which exerts a uniform force from all around on the electron beam passing through it.

16. A multi-electron beam irradiation device comprising: an emission source which emits an electron beam in a diverging direction; a shaped aperture array substrate in which a plurality of first openings are formed, and in which a portion of each of the electron beams proceeding in the diverging direction passes through the plurality of first openings to form a multi-electron beam and limit the divergence angle or convergence angle of each electron beam; a deflector array which deflects the multi-electron beams proceeding in the diverging direction to form a multi-electron beam in which the central trajectories of each electron beam are approximately parallel; and a multi-stage lens array of three or more stages which performs magnification correction and focal length correction in two orthogonal directions, including a plurality of lens arrays of two or more stages each having a multipole of four or more arranged on the trajectory of a beam it is responsible for among the multi-electron beams.

17. A multi-electron beam irradiation method comprising: emitting an electron beam in a diverging direction from an emission source; using a shaped aperture array substrate having a plurality of first openings, a portion of each of the electron beams traveling in the diverging direction passes through the plurality of first openings to form a multi-electron beam; using a multi-stage lens array having three or more stages including a plurality of lens arrays having two or more stages each having a quadrupole or higher multipole element arranged on the trajectory of a beam of the multi-electron beam that it is responsible for, deflecting the multi-electron beam traveling in the diverging direction to form a multi-electron beam whose central trajectories are approximately parallel, and performing magnification correction and focal length correction in two orthogonal directions; and using an angle-limiting aperture array substrate having a plurality of second openings, the multi-electron beam that has passed through the multi-stage lens array passes through the plurality of second openings to limit the divergence angle or convergence angle of each electron beam.

18. A multi-electron beam irradiation method comprising: emitting an electron beam in a diverging direction from an emission source; using a shaped aperture array substrate having a plurality of first openings, a portion of each of the electron beams traveling in the diverging direction passes through the plurality of first openings to form a multi-electron beam; deflecting the multi-electron beam traveling in the diverging direction to form a multi-electron beam with each electron beam having a substantially parallel central trajectory; performing magnification correction and focal length correction in two orthogonal directions using a multi-stage lens array of three or more stages including a plurality of lens arrays of two or more stages having multipoles of quadrupole or higher arranged on the trajectory of a beam of the multi-electron beam that each lens is responsible for; and using an angle-limiting aperture array substrate having a plurality of second openings, limiting the divergence angle or convergence angle of each electron beam by passing the multi-stage lens array through the plurality of second openings.

19. A multi-electron beam irradiation method comprising: emitting an electron beam in a diverging direction from an emission source; using a shaped aperture array substrate having a plurality of first openings, a portion of each of the electron beams traveling in the diverging direction passes through the plurality of first openings to form a multi-electron beam and limit the divergence angle or convergence angle of each electron beam; and using a multi-stage lens array of three or more stages including a plurality of lens arrays of two or more stages having multipoles of quadrupole or higher arranged on the trajectory of a beam it is responsible for among the multi-electron beams, deflecting the multi-electron beam traveling in the diverging direction to form a multi-electron beam with central trajectories of each electron beam approximately parallel, and performing magnification correction and focal length correction in two orthogonal directions.

20. A multi-electron beam irradiation method comprising: emitting an electron beam in a diverging direction from an emission source; using a shaped aperture array substrate having a plurality of first openings, a portion of each of the electron beams traveling in the diverging direction passes through the plurality of first openings to form a multi-electron beam and limiting the divergence angle or convergence angle of each electron beam; deflecting the multi-electron beam traveling in the diverging direction to form a multi-electron beam with each electron beam having a central trajectory that is approximately parallel; and performing magnification correction and focal length correction in two orthogonal directions using a multi-stage lens array of three or more stages including a plurality of lens arrays of two or more stages having multipoles of four or more elements arranged on the trajectory of a beam of the multi-electron beam that it is responsible for.

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