Multi-electron beam image acquisition apparatus and multi-electron beam image acquisition method

Abstract

The amount of swing-back deflection on the trajectory of the multiple secondary electron beams is made zero or small.SOLUTION: A multi-electron beam image acquisition apparatus includes a beam separator 214 that separates multiple secondary electron beams from trajectories of multiple primary electron beams, a multi-detector 222 that individually detects the multiple secondary electron beams, and a plurality of stages of first deflectors 209,208 that are disposed on a common trajectory of the multiple primary electron beams and the multiple secondary electron beams and dynamically deflect the multiple primary electron beams. When the multiple primary electron beams are deflected by the plurality of stages of first deflectors 209,208, the deflection intensity ratio and the deflection direction difference of the plurality of stages of first deflectors 209,208 are set so that the position variation of the multiple secondary electron beams, which are emitted from the substrate and pass through the plurality of stages of first deflectors, on the detection surface of the multi-detector is equal to or less than a threshold value.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a multi-electron beam image acquisition device and a multi-electron beam image acquisition method, and more particularly to an image acquisition technique for a multi-beam inspection device that performs pattern inspection using secondary electron images resulting from irradiation with multiple primary electron beams. [Background technology]

[0002] In recent years, with the increasing integration and capacity of large-scale integrated circuits (LSIs), the circuit line width required for semiconductor elements has 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, there is a need for highly accurate pattern inspection equipment that can inspect defects in ultra-fine patterns transferred onto semiconductor wafers.

[0003] Inspection equipment, for example, irradiates a substrate under inspection with multiple electron beams and detects secondary electrons corresponding to each beam emitted from the substrate to capture a pattern image. A known inspection method then compares the captured measurement image with design data or a measurement image of the same pattern on the substrate. Examples include "die-to-die inspection," which compares measurement image data captured of the same pattern at different locations on the same substrate, and "die-to-database inspection," which generates design image data (reference image) based on the design data for the pattern design and compares it with a measurement image of the pattern, which serves as measurement data. The captured image is sent to a comparison circuit as measurement data. After aligning the images, the comparison circuit compares the measurement data with the reference data using an appropriate algorithm. If there is a mismatch, it is determined that a pattern defect exists.

[0004] When an inspection image is acquired using a multiple electron beam, a deflector scans the sample surface with the multiple primary electron beams. The multiple secondary electron beams emitted from the sample surface are then individually detected by a multiple detector. In this case, the irradiation position of the multiple primary electron beams on the sample surface changes constantly due to the scanning, and the position of the emitted multiple secondary electron beams also changes constantly. In contrast, the position of the multiple detector is fixed. Therefore, to ensure that the position of the emitted multiple secondary electron beams remains constant on the detection surface of the multiple detector, a secondary deflector is placed on the trajectory of the multiple secondary electron beams after they are separated from the common trajectory of the multiple primary electron beams and the multiple secondary electron beams. This secondary deflector is used to deflect back the multiple secondary electron beams whose position has shifted due to the deflection of the multiple primary electron beams. When the positional deviation (positional fluctuation) of the multiple secondary electron beams on the detection plane due to the deflection of the multiple primary electron beams is large, aberrations occur due to the deflection field for deflecting the multiple secondary electron beams back and the focusing field by the lens, resulting in a deterioration in the distribution of the multiple secondary electron beams on the detection plane. As a result, problems such as a decrease in the secondary electron collection efficiency of the multi-detector and / or an increase in crosstalk occur. Therefore, in order to reduce such aberrations, it is desirable to minimize the amount of deflection for deflecting the multiple secondary electron beams back. This problem is not limited to inspection devices, but can occur in all devices that acquire images using multiple electron beams.

[0005] Here, it is disclosed that when a sample is scanned with an electron beam using a scanning coil, the positional change of the transmitted electron beam is offset by deflecting the transmitted electron beam that has passed through the sample back using a deflection coil (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Laid-Open No. 2006-196236 Summary of the Invention [Problem to be solved by the invention]

[0007] One aspect of the present invention provides an apparatus and method capable of reducing the amount of deflection of multiple secondary electron beams, which are separated from the common orbit with multiple primary electron beams, to zero or to a small amount on the orbit. [Means for solving the problem]

[0008] A multi-beam image acquisition device according to one aspect of the present invention includes: a stage on which a substrate is placed; a plurality of lenses for imaging the multiple primary electron beams onto a substrate using the multiple primary electron beams; a separator that separates the multiple secondary electron beams emitted as a result of irradiation of the substrate with the multiple primary electron beams from the orbit of the multiple primary electron beams; a multi-detector for individually detecting the multi-secondary electron beams separated from the orbit of the multi-primary electron beams; a multi-stage first deflector arranged on a common trajectory of the multiple primary electron beams and the multiple secondary electron beams, and configured to dynamically deflect the multiple primary electron beams; Equipped with a deflection intensity ratio and a deflection direction difference of the first deflectors of the multiple stages are set so that a positional variation on a detection surface of the multi-detector of the multi-secondary electron beams emitted from the substrate and passing through the first deflectors of the multiple stages becomes equal to or less than a threshold value when the multi-primary electron beams are deflected by the first deflectors of the multiple stages with a retarding potential applied to the substrate; It is characterized by:

[0009] Also, a second deflector for statically deflecting the multi-secondary electron beams is disposed on the orbit of the multi-secondary electron beams separated from the orbit of the multi-primary electron beams and at a position conjugate with the detection surface of the detector. Furthermore, the plurality of lenses are adjusted to achieve both imaging of the multiple primary electron beams onto the surface position of the substrate and imaging of the multiple secondary electron beams onto intermediate positions within the second deflector; This is preferable.

[0010] The multi-detector has a plurality of detection elements that individually detect the multiple secondary electron beams, The plurality of detection elements have limited apertures through which corresponding secondary electron beams of the multiple secondary electron beams can pass, At least one of a deflection intensity ratio and a deflection direction difference of the first deflectors in the multiple stages is set so that the amount of positional variation of the multiple secondary electron beams on the detection surface of the multi-detector is equal to or less than the shortest distance from the center of the aperture surface of each detection element to the edge of the aperture surface. This is preferable.

[0011] It is also preferable to further comprise a third deflector that is arranged on the orbit of the multiple secondary electron beams separated from the orbit of the multiple primary electron beams and that is capable of dynamically deflecting the multiple secondary electron beams.

[0012] A multi-beam image acquisition method according to one aspect of the present invention includes: imaging the multiple primary electron beams onto a substrate placed on a stage using a plurality of lenses; separating multiple secondary electron beams emitted as a result of irradiation of the substrate with the multiple primary electron beams from the orbit of the multiple primary electron beams; using a multi-detector to individually detect the multiple secondary electron beams separated from the orbits of the multiple primary electron beams; dynamically deflecting the multiple primary electron beams using a multi-stage first deflector arranged on a common trajectory of the multiple primary electron beams and the multiple secondary electron beams; Equipped with a deflection intensity ratio and a deflection direction difference of the first deflectors of the multiple stages are set so that a positional variation on a detection surface of the multi-detector of the multi-secondary electron beams emitted from the substrate and passing through the first deflectors of the multiple stages becomes equal to or less than a threshold value when the multi-primary electron beams are deflected by the first deflectors of the multiple stages with a retarding potential applied to the substrate; It is characterized by: [Effects of the Invention]

[0013] According to one aspect of the present invention, the amount of deflection of the multiple secondary electron beams separated from the common orbit with the multiple primary electron beams on their orbits can be reduced to zero or small, thereby suppressing crosstalk and improving the secondary electron collection efficiency of the multi-detector. [Brief explanation of the drawings]

[0014] [Figure 1] FIG. 1 is a configuration diagram showing a configuration of a pattern inspection device according to a first embodiment. [Figure 2] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate according to the first embodiment. [Figure 3] FIG. 2 is a cross-sectional view showing an example of the configuration of a multi-detector according to the first embodiment. [Figure 4] FIG. 3 is a diagram showing an example of the trajectories of multiple secondary electron beams in the first embodiment. [Figure 5] FIG. 3 is a diagram showing an example of the trajectories of multiple primary electron beams in the first embodiment. [Figure 6] FIG. 10 is a diagram showing an example of trajectories of multiple secondary electron beams in a second comparative example of the first embodiment. [Figure 7] FIG. 10 is a diagram showing another example of the trajectories of multiple secondary electron beams in Comparative Example 2 of the first embodiment. [Figure 8] FIG. 10 is a diagram showing another example of the trajectories of multiple secondary electron beams in Comparative Example 2 of the first embodiment. [Figure 9]1 shows an example of the trajectory of a central secondary electron beam among multiple secondary electron beams and an example of an outline of the device in the first embodiment. [Figure 10] FIG. 3 is a diagram showing an example of the trajectories of multiple secondary electron beams in the first embodiment. [Figure 11] 3 is a block diagram showing an example of the internal configuration of a deflection condition acquisition circuit according to the first embodiment. FIG. [Figure 12] FIG. 3 is a flowchart showing an example of main steps of the inspection method according to the first embodiment. [Figure 13] FIG. 10 is a flowchart showing another example of the main steps of the inspection method according to the first embodiment. [Figure 14] FIG. 4 is a diagram for explaining combinations of deflection conditions in the first embodiment. [Figure 15] FIG. 4 is a diagram showing an example of the sensitivity of multiple secondary electron beams to the magnitude of the deflection amount of multiple primary electron beams in the first embodiment. [Figure 16] FIG. 4 is a diagram for explaining a threshold value for the position fluctuation of multiple secondary electron beams in the first embodiment. [Figure 17] 10 shows another example of the trajectory of the central secondary electron beam among the multiple secondary electron beams and another example of the outline of the device in the first embodiment. [Figure 18] 10 shows another example of the trajectory of the central secondary electron beam among the multiple secondary electron beams and another example of the outline of the device in the first embodiment. [Figure 19] FIG. 10 is a diagram showing an example of positions of multiple secondary electron beams on a detection surface in a first comparative example of the first embodiment. [Figure 20] FIG. 4 is a diagram showing an example of the positions of multiple secondary electron beams on a detection surface in the first embodiment. [Figure 21] FIG. 2 is a diagram for explaining an image acquisition process according to the first embodiment. [Figure 22] FIG. 2 is a configuration diagram showing an example of the configuration inside a comparison circuit according to the first embodiment. [Figure 23] FIG. 10 is a diagram showing an example of a configuration of a multi-stage deflector in a modification of the first embodiment. [Figure 24] FIG. 10 is a flowchart showing an example of main steps of a writing method according to a modified example of the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] In the following embodiments, a multi-electron beam inspection device will be described as an example of a multi-electron beam image acquisition device. However, the image acquisition device is not limited to an inspection device, and may be any device that acquires images using multiple beams.

[0016] Embodiment 1 Fig. 1 is a configuration diagram showing the configuration of a pattern inspection apparatus according to the 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 includes an image acquisition mechanism 150 and a control circuit 160. 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 is arranged with an electron gun 201, an illumination lens 202, a shaping aperture array substrate 203, an electromagnetic lens 205, a collective deflector 212, a limiting aperture substrate 213, an electromagnetic lens 206, an electromagnetic lens 217, a deflector 208, a deflector 209, an electromagnetic lens 207, a beam separator 214 (an example of a separator), a deflector 218, a deflector 226, an electromagnetic lens 224, and a multi-detector 222.

[0017] The electron gun 201, the electromagnetic lens 202, the shaping aperture array substrate 203, the electromagnetic lens 205, the collective deflector 212, the limiting aperture substrate 213, the electromagnetic lens 206, the electromagnetic lens 217 (pre-objective lens), the deflector 209, the deflector 208, and the electromagnetic lens 207 (objective lens) constitute a primary electron optical system 151. The electromagnetic lens 207 (objective lens), the deflector 208, the deflector 209, the electromagnetic lens 217 (pre-objective lens), the beam separator 214, the deflector 218, the deflector 226, and the electromagnetic lens 224 constitute a secondary electron optical system 152.

[0018] The electromagnetic lens 217 (pre-objective lens), the deflector 209, the deflector 208, and the electromagnetic lens 207 (objective lens) are arranged on the common orbit of the primary electron orbit and the secondary electron orbit. In the example of FIG. 1, the electromagnetic lens 217 (pre-objective lens), the deflector 209, the deflector 208, and the electromagnetic lens 207 (objective lens) are arranged between the beam separator 214 and the substrate 101.

[0019] 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, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. When the substrate 101 is an exposure mask substrate, a chip pattern is formed on the exposure mask substrate. The chip pattern is composed of a plurality of graphic patterns. The chip patterns formed on the exposure mask substrate are transferred onto the semiconductor substrate by exposure multiple times, thereby forming a plurality of chip patterns (wafer dies) on the semiconductor substrate. The following description will mainly focus on the case where the substrate 101 is an exposure mask substrate. The substrate 101 is placed on the stage 105, for example, with the pattern-forming surface facing upward. For example, it is supported at three points by three support rods (not shown). Also, on the stage 105, a mirror 216 is arranged to reflect a laser beam for laser length measurement irradiated from a laser length measurement system 122 arranged outside the inspection room 103.

[0020] Furthermore, the multi-detector 222 is connected to a detection circuit 106 outside the electron beam column 102. The detection circuit 106 is connected to a chip pattern memory 123.

[0021] 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 retarding control circuit 130, a separator control circuit 132, a deflection condition acquisition circuit 134, 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 conversion) amplifiers 144, 146, and 149. The DAC amplifier 146 is connected to a deflector 208, and the DAC amplifier 144 is connected to the deflector 209. The DAC amplifier 149 is connected to a deflector 226. The deflection control circuit 128 is also connected to a DC power supply 148. The DC power supply 148 is connected to a deflector 218 (bender).

[0022] 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 a stage control circuit 114. The drive mechanism 142 is configured with a drive system, such as a three-axis (XY-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 of 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 a 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 multiple primary electron beams 20.

[0023] The electromagnetic lenses 202, 205, 206, 217, 207, 224, and beam separator 214 are controlled by a lens control circuit 124. The collective deflector 212 is composed of two or more electrodes, and is controlled by the blanking control circuit 126 via a DAC amplifier (not shown) for each electrode. The deflector 209 is composed of four or more electrodes, and is controlled by the deflection control circuit 128 via a DAC amplifier 144 for each electrode. The deflector 208 is composed of four or more electrodes, and is controlled by the deflection control circuit 128 via a DAC amplifier 146 for each electrode. The deflector 226 is composed of four or more electrodes, and is controlled by the deflection control circuit 128 via a DAC amplifier 149 for each electrode.

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

[0025] The beam separator 214 is controlled by a separator control circuit 132. It is preferable to use, for example, an E×B separator as the beam separator 214. Alternatively, it is also preferable to use, for example, an electromagnetic prism as the beam separator 214. The example in Fig. 1 shows a case where, for example, an E×B separator is used as the beam separator 214.

[0026] The retarding control circuit 130 applies a desired retarding potential to the substrate 101 to adjust the energy of the multiple primary electron beams 20 irradiated onto the substrate 101. For example, a negative potential is applied to the substrate 101.

[0027] 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 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.

[0028] 1 shows the configuration necessary for explaining the first embodiment. The inspection device 100 may also be provided with other configurations that are normally required.

[0029] FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate in the first embodiment. In FIG. 2, shaping aperture array substrate 203 has two-dimensional holes (apertures) 22 formed in m1 columns (x direction) by n1 rows (y direction) (m1 and n1 are integers of 2 or more) at a predetermined arrangement pitch in the x and y directions. The example in FIG. 2 shows a case where 23 × 23 holes (apertures) 22 are formed. Each hole 22 is formed as a rectangle of the same size and shape. Alternatively, they may be circles of the same outer diameter. Portions of electron beam 200 pass through these multiple holes 22, thereby forming multiple primary electron beams 20. Shaping aperture array substrate 203 is an example of a multi-beam forming mechanism that forms multiple primary electron beams.

[0030] 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.

[0031] An electron gun 201 (an example of an emission source) emits an electron beam 200 in a diverging direction. The electron beam 200 emitted from the electron gun 201 is refracted in a converging direction by an electromagnetic lens 202, and illuminates the entire shaping aperture array substrate 203. As shown in FIG. 2 , a plurality of holes 22 (openings) are formed in the shaping aperture array substrate 203, and the electron beam 200 illuminates an area that includes all of the plurality of holes 22. Portions of the electron beam 200 irradiated onto the positions of the plurality of holes 22 pass through the respective holes 22 of the shaping aperture array substrate 203, thereby forming multiple primary electron beams 20.

[0032] The formed multi-primary electron beams 20 are refracted by electromagnetic lenses 205 and 206, respectively, and proceed to a beam separator 214 arranged at an intermediate image plane (image plane conjugate position) of each beam of the multi-primary electron beams 20 while repeating intermediate images and crossovers. Then, the beam separator 214 passes through and proceeds to an electromagnetic lens 217. Also, by arranging 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. Also, by deflecting the entire multi-primary electron beams 20 collectively by 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.

[0033] When the multiple primary electron beams 20 are incident on the electromagnetic lenses 217, 207, the multiple primary electron beams 20 are imaged on the substrate 101 by the electromagnetic lenses 217, 207. In other words, the multiple electromagnetic lenses 217, 207 use the multiple primary electron beams 20 to image the multiple primary electron beams 20 on the substrate 101. The multiple primary electron beams 20 focused on the surface of the substrate 101 (sample) by the multiple electromagnetic lenses 217, 207 are deflected collectively by the deflectors 208 and 209, and each beam is irradiated onto its respective irradiation position on the substrate 101. In this way, the primary electron optical system 151 irradiates the surface of the substrate 101 with the multiple primary electron beams.

[0034] When the multi-primary electron beams 20 are irradiated onto a desired position on the substrate 101, a bundle of secondary electrons (multi-secondary electron beams 300) including reflected electrons corresponding to each beam of the multi-primary electron beams 20 is emitted from the substrate 101 due to the irradiation of the multi-primary electron beams 20.

[0035] The multiple secondary electron beams 300 emitted from the substrate 101 pass through the electromagnetic lenses 217 and 207 and proceed to the beam separator 214 .

[0036] Here, the E×B separator, which is an example of the beam separator 214, has two or more magnetic poles using coils and two or more electrodes. These magnetic poles generate a directional magnetic field. Similarly, the electrodes generate a directional electric field. Specifically, the E×B separator generates electric and magnetic fields in orthogonal directions on a plane perpendicular to the direction of travel of the central beam of the multiple primary electron beams 20 (the central axis of the orbit). The electric field exerts a force in the same direction regardless of the direction of electron travel. In contrast, 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 entry of the electrons. For the multiple beams 20 entering the E×B separator from above, the force due to the electric field and the force due to the magnetic field cancel each other out, causing the multiple primary electron beams 20 to travel straight downward. In contrast, the multi-secondary electron beams 300 entering the E×B separator from below are subjected to both the electric field force and the magnetic field force in the same direction, causing the multi-secondary electron beams 300 to be statically bent obliquely upward and separated from the orbit of the multi-primary electron beams 20.

[0037] 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 separated from the multi primary electron beams 20 proceed to the deflector 218 (second deflector). The deflector 218 is disposed on the trajectory of the multi secondary electron beams 300 separated from the trajectory of the multi primary electron beams 20, at a position conjugate with the detection surface of the multi-detector 222. Specifically, the deflector 218 is disposed so that an intermediate position (for example, a middle position) within the deflector 218 is conjugate with the detection surface of the multi-detector 222. The multi secondary electron beams 300 are then statically deflected by the deflector 218, and are thereby further bent. The multiple secondary electron beams 300 statically deflected by the deflector 218 are projected onto the multi-detector 222 while being refracted in the focusing direction by an electromagnetic lens 224 at a position away from the trajectory of the multiple primary electron beams 20. The multi-detector 222 (multi-secondary electron beam detector) individually detects the refracted and projected multiple secondary electron beams 300.

[0038] FIG. 3 is a cross-sectional view showing an example of the configuration of the multi-detector according to the first embodiment. In FIG. 3, the multi-detector 222 includes a plurality of detecting elements 60 (60a, 60b, 60c) (e.g., diode-type two-dimensional sensors) arranged in element holders 62 (62a, 62b, 62c), respectively, and a detector aperture array substrate 428 on which a plurality of openings 41 (41a, 41b, 41c) serving as aperture surfaces of the detecting elements 60 are formed. The detecting elements 60 individually detect the multiple secondary electron beams. Each element holder 62 and the detector aperture array substrate 428 are supported by a support base 429. The example in FIG. 3 shows an example of an x-direction cross section in the case where, for example, 3 × 3 multiple secondary electron beams are detected. Each opening 41 is arranged upstream of the detection surface of the corresponding detecting element 60. Therefore, the multiple detecting elements 60 have limited aperture surfaces through which the corresponding secondary electron beams of the multiple secondary electron beams 300 can pass. In other words, each opening 41 becomes the opening surface of the corresponding detection element 60 and limits the secondary electron beam incident on the detection element 60. The opening diameter of each opening 41 is formed to be equal to or smaller than the diameter size of the detection surface of the detection element 60. Preferably, the opening diameter is formed to be smaller than the diameter size of the detection surface of the detection element 60.

[0039] Each beam of the multiple secondary electron beams 300 collides with a corresponding detection element 60 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.

[0040] FIG. 4 is a diagram showing an example of the trajectories of multiple secondary electron beams in the first embodiment. FIG. 5 is a diagram showing an example of the trajectories of the multiple primary electron beams in the first embodiment. The example in Fig. 4 shows the trajectory of the central secondary electron beam 301 of the multiple secondary electron beams 300. The example in Fig. 5 shows the trajectory of the central primary electron beam 21 of the multiple primary electron beams 20. In the first embodiment, as shown in Fig. 5, the multiple primary electron beams 20 spread after passing through the beam separator 214 arranged at a position conjugate to the image plane, and although their trajectories are slightly changed by the electromagnetic lens 217, they continue to spread toward the electromagnetic lens 207, and their trajectories are bent in the focusing direction by the electromagnetic lens 207 to form an image on the surface of the substrate 101. Under conditions in which such primary electron beams form an image on the surface of the beam separator 214 and the electromagnetic lens 207 focuses the multiple primary electron beams 20 on the substrate 101, as shown in Fig. 4, although the trajectory of the secondary electron beam 301 is bent in the focusing direction by the electromagnetic lens 207 (objective lens), an intermediate image plane 600 (image point) is formed at a position just before it reaches the beam separator 214.

[0041] In the first embodiment, the trajectories of the multiple secondary electron beams are bent in the converging direction by the electromagnetic lens 207 (objective lens) to form an intermediate image plane 600 (image point), and the trajectories of the multiple secondary electron beams that have become diverging are bent in the converging direction by the electromagnetic lens 217. At this time, the electromagnetic lens 217 forms an intermediate image plane 601 (image point) for the multiple secondary electron beams 300 at an intermediate position (e.g., an intermediate position) in the deflector 218. In other words, the electromagnetic lenses 207, 217 (multiple lenses) are adjusted to achieve both the imaging of the multiple primary electron beams 20 on the surface position of the substrate 101 and the imaging of the multiple secondary electron beams 300 at an intermediate position (e.g., an intermediate position) in the deflector 218. The intermediate position of the arc-shaped central axis from the entrance to the exit of the deflector 218 corresponds to the deflection fulcrum of the deflector 218. As a result, as shown in FIG. 4, the beam diameter of the secondary electron beam 301 can be reduced at the position of the deflection fulcrum formed midway within the deflector 218. This makes it possible to suppress aberrations occurring in the deflector 218. Therefore, the beam diameter can be narrowed on the detection surface of the multi-detector 222 by the lens action of the electromagnetic lens 224 after passing through the deflector 218, and each secondary electron beam can be imaged on the detection surface of the multi-detector 222 in a separated state. In other words, crosstalk can be suppressed or reduced. As a result, each secondary electron beam can be detected individually. Therefore, the deflection fulcrum of the deflector 218 is conjugate with the surface of the substrate 101 and the detection surface of the multi-detector 222.

[0042] It is preferable that the deflector 218 (bender) has a cross section formed in an arc shape when divided by a plane including the central axis of the secondary electron orbit. However, this is not a limitation. The cross section formed in a rectangular shape when divided by a plane including the central axis of the secondary electron orbit may also be formed. In the first embodiment, the position of the exact midpoint of the length of the central axis within the deflector 218 through which the central secondary electron beam 301 passes is set as the deflection fulcrum (or deflection center).

[0043] Here, in order to obtain a pattern image on the substrate 101, it is necessary to scan the substrate 101 with the multiple primary electron beams 20 by dynamic beam deflection using deflectors 208 and 209 (multiple-stage first deflectors). Therefore, the emission positions of the multiple secondary electron beams 300 emitted from the substrate 101 change every moment. Furthermore, when scanning is performed while the stage 105 is moving, tracking control is performed by the deflectors 208 and 209 so that the multiple primary electron beams 20 follow the movement of the stage 105. In such a case, too, the emission positions of the multiple secondary electron beams 300 emitted from the substrate 101 change every moment. Furthermore, the emitted multiple secondary electron beams 300 also pass through the deflectors 208 and 209 from the opposite direction to the multiple primary electron beams 20, and are therefore subjected to dynamic beam deflection by the deflectors 208 and 209.

[0044] On the other hand, because the position of the multi-detector 222 is fixed, in this state the multiple secondary electron beams 300 will not be incident on the desired detection elements. Therefore, it is necessary to keep the position of the multiple secondary electron beams 300, whose emission position changes moment by moment due to scanning of the multiple primary electron beams 20, fixed on the detection surface (specifically, the aperture surface) of the multi-detector 222. For this reason, in the past, dynamic deflection was performed by a deflector placed on the trajectory of the multiple secondary electron beams 300 after they were separated from the trajectory of the multiple primary electron beams 20. This offsets the positional fluctuation of the multiple secondary electron beams 300 caused by scanning of the multiple primary electron beams 20, etc.

[0045] However, if the amount of deflection of this back deflection is large, aberration occurs due to the deflection field of the deflector and the subsequent electromagnetic lens 224, which causes a problem of deterioration of the beam distribution on the detection surface of the multi-detector 222. This can result in a decrease in the collection efficiency of secondary electrons and an increase in crosstalk. Therefore, it is necessary to reduce this dynamic amount of back deflection, preferably to zero.

[0046] FIG. 6 is a diagram showing an example of trajectories of multiple secondary electron beams in Comparative Example 2 of the first embodiment. FIG. 7 is a diagram showing another example of the trajectories of multiple secondary electron beams in Comparative Example 2 of the first embodiment. FIG. 8 is a diagram showing another example of the trajectories of multiple secondary electron beams in Comparative Example 2 of the first embodiment. Figures 6 to 8 show simulation results of the trajectories of the multi-secondary electron beams when two-stage deflectors, a first deflector and a second deflector, are arranged on the common trajectory of the multi-primary electron beams and the multi-secondary electron beams, and the deflection amount of the multi-primary electron beams is changed by interlocking the two-stage deflectors. Figures 6 to 8 show cases where the deflection amount of the multi-primary electron beams is increased in order. Comparative Example 2 shows a case where the deflection amount is changed without considering the deflection intensity ratio of the two-stage deflectors. As shown in Figures 6 to 8, it can be seen that changing the deflection amount also changes the amount of positional fluctuation on the detection plane of the multi-secondary electron beams. The examples in Figures 6 to 8 show cases where the amount of positional fluctuation on the detection plane of the multi-secondary electron beams increases as the deflection amount increases.

[0047] Therefore, in the first embodiment, a multi-stage deflector is used to reduce the amount of positional fluctuation of the multiple secondary electron beams while scanning with the multiple primary electron beams.

[0048] FIG. 9 shows an example of the trajectory of the central secondary electron beam 301 of the multiple secondary electron beams 300 and an example of an outline of the device according to the first embodiment. FIG. 10 is a diagram showing an example of the trajectory of the multiple secondary electron beams according to the first embodiment. The example in FIG. 10 shows the result of scanning the primary electron beam over a distance D on the surface of the substrate 101 using a two-stage deflector consisting of a first deflector and a second deflector. By adjusting the deflection intensity ratio of the two-stage deflectors 209 and 208 consisting of the first deflector and the second deflector, the amount of positional fluctuation of the multiple secondary electron beams on the detection surface can be reduced to zero, as shown in FIG. 10. By maintaining the deflection intensity ratio of the two-stage deflectors 209 and 208, the amount of positional fluctuation of the multiple secondary electron beams on the detection surface can be reduced to zero, as shown in FIG. 10, regardless of the deflection amount of the primary electron beam. A method for acquiring such deflection conditions will be specifically described below.

[0049] Fig. 11 is a block diagram showing an example of the internal configuration of the deflection condition acquisition circuit according to Embodiment 1. In Fig. 11, deflection condition acquisition circuit 134 includes a deflection intensity setting unit 64, a deflection direction setting unit 65, a deflection intensity ratio setting unit 66, a deflection direction difference setting unit 68, a determination unit 69, and a deflection condition setting unit 70. Each of the "units" such as the deflection intensity setting unit 64, the deflection direction setting unit 65, the deflection intensity ratio setting unit 66, the deflection direction difference setting unit 68, the determination unit 69, and the deflection condition setting unit 70 includes a processing circuit, and the processing circuit 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), or may use different processing circuits (separate processing circuits). Necessary input data or calculated results for the deflection intensity setting unit 64, the deflection direction setting unit 65, the deflection intensity ratio setting unit 66, the deflection direction difference setting unit 68, the determination unit 69, and the deflection condition setting unit 70 are stored in a memory (not shown) or in the memory 118 each time.

[0050] Fig. 12 is a flowchart showing an example of main steps of the inspection method according to Embodiment 1. In Fig. 12, the inspection method according to Embodiment 1 carries out a series of steps including a deflection direction difference setting step (S102), a deflection intensity ratio setting step (S104), a scanning step (S106), a determination step (S110), a deflection condition setting step (S112), an image acquisition step (S120), and a comparison step (S122).

[0051] In the deflection direction difference setting step (S102), the deflection direction setting unit 65 sets the deflection direction θ1 of the deflector 209 and the deflection direction θ2 of the deflector 208. This determines the deflection direction difference Δθ (=θ1−θ2) between the two stages of deflectors 209 and 208.

[0052] In the deflection intensity ratio setting step (S104), the deflection intensity ratio setting unit 66 sets a deflection intensity ratio E1 / E2 between the deflection intensity E1 of the deflector 209 and the deflection intensity E2 of the deflector 208. In the case of an electrostatic deflector, the deflection intensity of the deflector is determined by the potential applied to the deflector. Therefore, the deflection intensity ratio E1 / E2 can be defined as the ratio V1 / V2 of the potential V1 applied to the deflector 209 and the potential V2 applied to the deflector 208. Hereinafter, this will be referred to as the deflection intensity ratio V1 / V2. Hereinafter, the potential V1 applied to the deflector 209 refers to a potential applied in the deflection direction θ1 by combining the potentials applied to the multiple electrodes (e.g., octopoles) constituting the deflector 209. Similarly, the potential V2 applied to the deflector 208 refers to a potential applied in the deflection direction θ2 by combining the potentials applied to the multiple electrodes (e.g., octopoles) constituting the deflector 208. In the deflection field, the same potential with the opposite sign is applied to the opposing electrodes.

[0053] In the scanning step (S106), the substrate 101 is scanned with the multi-primary electron beam 20 by two-stage deflectors 209, 208 to acquire an image on the substrate 101. Alternatively, a stage surface set at the same height as the substrate 101 surface or a mark on the stage may be scanned. Alternatively, scanning an evaluation substrate is also preferable. When scanning the substrate 101, evaluation substrate, or mark, it is preferable to scan an area without a pattern or an area with a solid pattern. As will be described later, in order to check changes in brightness of the area during scanning, it is desirable to scan an area without a pattern or a solid area where the amount of secondary electron beam generated is the same. At this time, with the deflection directions θ1 and θ2 fixed, the deflection intensity setting unit 64 variably changes the potentials V1 and V2 while maintaining the deflection intensity ratio V1 / V2 to change the deflection amount, thereby scanning the substrate 101, the evaluation substrate, the stage, or the mark with the multi-primary electron beam 20. In this manner, the two-stage deflectors 209 and 208 are driven in conjunction with each other. Here, the deflection directions of the two-stage deflectors 209 and 208 are fixed in the set states. Therefore, the multi-primary electron beam 20 is deflected in a fixed direction determined by the set deflection direction difference Δθ (= θ1 - θ2). By variably changing the potentials V1 and V2 while maintaining the deflection intensity ratio V1 / V2, the substrate 101, the stage, or the mark with the multi-primary electron beam 20 is scanned in that direction. Then, multiple secondary electron beams 300 emitted from the substrate 101, the evaluation substrate, the stage, or the mark are detected by the multi-detector 222. At this time, no deflection is performed by the deflector 226 on the secondary beam orbit.

[0054] In the determination step (S110), the determination unit 69 determines whether the brightness of the secondary electron image obtained by the multi-detector 222 is constant during the scanning of the multi-primary electron beams 20. If the brightness is constant, the process proceeds to the image acquisition step (S120). If the brightness is not constant, or if an image cannot be obtained at all, the process returns to the deflection intensity ratio setting step (S104), and while varying the deflection intensity ratio, the steps from the deflection intensity ratio setting step (S104) to the determination step (S110) are repeated until the brightness becomes constant.

[0055] If the brightness is constant during scanning, the multiple secondary electron beams 300 can be detected by the corresponding detection elements of the multi-detector 222, regardless of the deflection amount of the multiple primary electron beams 20. This means that the positional fluctuation of the multiple secondary electron beams 300 on the detection surface can be suppressed to below the threshold. Such a deflection intensity ratio V1 / V2 becomes a deflection condition that can suppress the positional fluctuation of the multiple secondary electron beams 300 on the detection surface to below the threshold under the condition of the set deflection direction difference Δθ.

[0056] In an actual inspection process, when acquiring a pattern image of the substrate 101, the deflection direction θ1 of the deflector 209 and the deflection direction θ2 of the deflector 208 are determined so as to be the desired deflection direction (for example, the y direction) while maintaining the set deflection direction difference Δθ. Then, when scanning the substrate 101, the deflection amount can be changed by variably changing the deflection intensity E1 (deflection potential V1) of the deflector 209 and the deflection intensity E2 (deflection potential V2) of the deflector 208 while maintaining the obtained deflection intensity ratio V1 / V2.

[0057] The method for acquiring the deflection conditions is not limited to this.

[0058] Fig. 13 is a flowchart showing another example of the main steps of the inspection method according to Embodiment 1. In Fig. 13, the inspection method according to Embodiment 1 carries out a series of steps including a deflection intensity ratio setting step (S103), a deflection direction difference setting step (S105), a scanning step (S106), a determination step (S110), a deflection condition setting step (S112), an image acquisition step (S120), and a comparison step (S122).

[0059] In the deflection intensity setting step (S103), the deflection intensity setting unit 64 sets a deflection intensity E1 of the deflector 209 and a deflection intensity E2 of the deflector 208. Specifically, the deflection intensity setting unit 64 sets a deflection potential V1 of the deflector 209 and a deflection potential V2 of the deflector 208. Thus, a deflection intensity ratio V1 / V2 is determined.

[0060] In the deflection direction difference setting step (S105), the deflection direction difference setting unit 68 sets the deflection direction difference Δθ (=θ1−θ2) between the deflection direction θ1 of the deflector 209 and the deflection direction θ2 of the deflector 208.

[0061] In the scanning step (S106), as described above, the substrate 101, the evaluation substrate, the stage, or the mark is scanned with the multi-primary electron beam 20 by the two-stage deflectors 209, 208, and an image on the substrate 101 is acquired. At this time, with the deflection potential V1 of the deflector 209 and the deflection potential V2 of the deflector 208 fixed, the deflection direction setting unit 65 variably changes the deflection directions θ1 and θ2 while maintaining the deflection direction difference Δθ, thereby scanning the substrate 101, the evaluation substrate, the stage, the mark, or the like with the multiple primary electron beams 20.

[0062] In the determination step (S110), the determination unit 69 determines whether the brightness of the secondary electron image obtained by the multi-detector 222 is constant during the scanning of the multi-primary electron beams 20. If the brightness is constant, the process proceeds to the image acquisition step (S120). If the brightness is not constant, or if an image cannot be obtained at all, the process returns to the deflection direction difference setting step (S105), and while varying the deflection direction difference, the steps from the deflection direction difference setting step (S105) to the determination step (S110) are repeated until the brightness becomes constant.

[0063] If the brightness is constant during scanning, the multiple secondary electron beams 300 can be detected by the corresponding detection elements of the multi-detector 222, regardless of the deflection direction of the multiple primary electron beams 20. This means that the positional fluctuation of the multiple secondary electron beams 300 on the detection surface can be suppressed to below the threshold. This deflection direction difference Δθ becomes a deflection condition that can suppress the positional fluctuation of the multiple secondary electron beams 300 on the detection surface to below the threshold under the condition of the set deflection intensity ratio V1 / V2.

[0064] In an actual inspection process, when acquiring a pattern image of the substrate 101, the deflection direction θ1 of the deflector 209 and the deflection direction θ2 of the deflector 208 can be determined so as to achieve a desired deflection direction (for example, the y direction) while maintaining the obtained deflection direction difference Δθ. Then, when scanning the substrate 101, the deflection amount can be changed by variably changing the deflection intensity E1 (deflection potential V1) of the deflector 209 and the deflection intensity E2 (deflection potential V2) of the deflector 208 while maintaining the set deflection intensity ratio V1 / V2.

[0065] FIG. 14 is a diagram illustrating combinations of deflection conditions in the first embodiment. In FIG. 14, the vertical axis represents the deflection intensity ratio V1 / V2, and the horizontal axis represents the deflection direction difference Δθ. If the deflection intensity ratio V1 / V2 changes, the deflection direction difference Δθ, which can suppress the positional fluctuation of the multiple secondary electron beams 300 on the detection surface to a threshold value or less, changes. Conversely, if the deflection direction difference Δθ changes, the deflection intensity ratio V1 / V2, which can suppress the positional fluctuation of the multiple secondary electron beams 300 on the detection surface to a threshold value or less, changes. Therefore, there are many combinations of the deflection intensity ratio V1 / V2 and the deflection direction difference Δθ that can suppress the positional fluctuation of the multiple secondary electron beams 300 on the detection surface to a threshold value or less. A desired combination can be used from these multiple combinations.

[0066] 15 is a diagram showing an example of the sensitivity of the multi secondary electron beams to the magnitude of the deflection amount of the multi primary electron beams in Embodiment 1. If the positional fluctuation of the multi secondary electron beams 300 can be reduced to zero when the multi primary electron beams 20 have a certain deflection amount, the positional fluctuation of the multi secondary electron beams 300 can be reduced to zero even if the magnitude of the deflection amount of the multi primary electron beams 20 is changed.

[0067] FIG. 16 is a diagram illustrating a threshold value for the positional fluctuation of the multiple secondary electron beams in the first embodiment. FIG. 16 shows how one secondary electron beam 301 of the multiple secondary electron beams 300 is incident on the aperture 41 of the corresponding detection element 60. The positional fluctuation of the secondary electron beam 301 on the detection surface can be detected by the detection element 60 if it is equal to or less than half the aperture diameter d of the aperture 41 (aperture surface). Therefore, it is sufficient to suppress the positional fluctuation of the multiple secondary electron beams 300 to equal to or less than half the aperture diameter (threshold) of the aperture surface. Strictly speaking, if the positional fluctuation of the secondary electron beam 301 on the detection surface is d / 2, half of the beam will protrude from the aperture 41. However, if such a slight deviation occurs, fine adjustment can be performed using the deflector 226. While the example in FIG. 16 shows a circular aperture 41, the present invention is not limited to this. For example, the aperture 41 may be rectangular. In this case, half of the aperture diameter d is preferably set to, for example, half the distance between two opposing sides. Therefore, it is sufficient to suppress the positional fluctuation of the multiple secondary electron beams 300 to the shortest distance (threshold) or less from the center of the opening 41 (opening surface) to the end (edge) of the opening 41.

[0068] In the deflection condition setting step (S112), the deflection condition setting unit 70 sets the deflection intensity ratio V1 / V2 and the deflection direction difference Δθ of the deflectors 209, 208 in the deflection control circuit 128 so that the positional fluctuation of the multi-secondary electron beam 300, which is emitted from the substrate 101 and passes through the deflectors 208, 209, on the detection surface of the multi-detector 222 is equal to or less than a threshold value Th when the multi-primary electron beam 20 is deflected by the deflectors 209, 208 with a retarding potential applied to the substrate 101. Specifically, the deflection intensity ratio V1 / V2 and the deflection direction difference Δθ of the deflectors 209, 208 are set in the deflection control circuit 128 so that the amount of positional fluctuation of the multi-secondary electron beam 300 on the detection surface of the multi-detector 222 is equal to or less than the shortest distance from the center of the aperture surface of each detection element 60 to the end (edge) of the aperture 41. For example, the deflection intensity ratio V1 / V2 and the deflection direction difference Δθ of the deflectors 209, 208 are set in the deflection control circuit 128 so that they are equal to or less than half the aperture diameter d of the aperture surface of each detection element 60. More preferably, the deflection intensity ratio V1 / V2 and the deflection direction difference Δθ of the deflectors 209, 208 are set in the deflection control circuit 128 so that the positional fluctuation of the multi-secondary electron beams 300 on the detection surface of the multi-detector 222 becomes zero.

[0069] As described above, deflection of the multi primary electron beams 20 by the deflectors 209, 208 can eliminate or significantly reduce the positional fluctuation of the multi secondary electron beams 300 on the detection surface when the substrate 101 is dynamically scanned with the multi primary electron beams 20. For example, if the positional fluctuation of the multi secondary electron beams 300 cannot be reduced to zero, it is preferable to perform necessary back deflection by the deflector 226 as a fine adjustment. Even in this case, the amount of back deflection by the deflector 226 can be significantly reduced compared to the conventional case. The deflector 226 that deflects the multi secondary electron beams 300 is driven in conjunction with the deflectors 209, 208 that deflect the multi primary electron beams 20.

[0070] FIG. 17 shows another example of the trajectory of the central secondary electron beam 301 of the multiple secondary electron beams 300 and another example of the outline of the apparatus according to the first embodiment. 18 shows another example of the trajectory of the central secondary electron beam 301 of the multiple secondary electron beams 300 and another example of the outline of the device in the first embodiment. FIGS. 17 and 18 show a deflector 226 (an example of a third deflector). In the example of FIG. 17, the deflector 226 (an example of a third deflector) is disposed on the trajectory of the multiple secondary electron beams 300 between the beam separator 214 and the multi-detector 222. More preferably, the deflector 226 is disposed between the deflector 218 and the electromagnetic lens 224, or, as shown in the example of FIG. 18, between the beam separator 214 and the deflector 218. This allows the multiple secondary electron beams 300 to be incident on the electromagnetic lens 224 at a fixed position after being deflected back. Therefore, even if aberration occurs in the electromagnetic lens 224, it can be reduced.

[0071] Note that if the positional fluctuation of the multiple secondary electron beams 300 on the detection surface can be reduced to zero by adjusting the deflection conditions of the deflectors 209 and 208, in other words, if the positional fluctuation of the multiple secondary electron beams 300 can be reduced to zero, the deflector 226 may be omitted.

[0072] FIG. 19 is a diagram showing an example of positions of multiple secondary electron beams on a detection surface in Comparative Example 1 of the first embodiment. Fig. 20 is a diagram showing an example of the positions of the multiple secondary electron beams on the detection surface in embodiment 1. In comparative example 1, since the amount of return deflection of the multiple secondary electron beams is large, aberrations cause the positions of the secondary electron beams to shift and cause them to protrude from the aperture surfaces (openings 41) of the corresponding detection elements, as shown in Fig. 19. In contrast, in embodiment 1, the amount of return deflection of the multiple secondary electron beams can be set to zero or significantly reduced, so that the aberrations that occur are suppressed or reduced, and each secondary electron beam can be incident on the aperture surface (openings 41) of the corresponding detection element, as shown in Fig. 20.

[0073] As described above, the deflection conditions of the primary deflector are adjusted, and then the inspection process for the substrate to be inspected is carried out.

[0074] As an image acquisition step (S120), the image acquisition mechanism 150 acquires secondary electron images of multiple graphic patterns formed on the substrate 101 by scanning the substrate 101 with the multi-primary electron beam 20 using deflectors 209, 208 whose deflection conditions are set.

[0075] FIG. 21 is a diagram for explaining the image acquisition process in the first embodiment. As shown in FIG. 21, the inspection area 330 of the substrate 101 is divided into a plurality of stripe areas 32 with a predetermined width in the y direction, for example. The scanning operation by the image acquisition mechanism 150 is performed, for example, for each stripe area 32. For example, while moving the stage 105 in the -x direction, the scanning operation of the stripe area 32 proceeds relatively in the x direction. Each stripe area 32 is divided into a plurality of rectangular areas 33 in the longitudinal direction. The beam is moved to the target rectangular area 33 by collective deflection of the entire multi-primary electron beam 20 by the deflectors 209 and 208.

[0076] The example in FIG. 21 shows, for example, a case of 5×5 arrays of multi-primary electron beams 20. An irradiation area 34 that can be irradiated by one irradiation of the multi-primary electron beams 20 is defined as (x-direction size obtained by multiplying the inter-beam pitch in the x-direction of the multi-primary electron beams 20 on the surface of the substrate 101 by the number of beams in the x-direction) × (y-direction size obtained by multiplying the inter-beam pitch in the y-direction of the multi-primary electron beams 20 on the surface of the substrate 101 by the number of beams in the y-direction). The irradiation area 34 becomes the field of view of the multi-primary electron beams 20. Each primary electron beam 10 constituting the multi-primary electron beam 20 is irradiated into a sub-irradiation area 29 surrounded by the inter-beam pitch in the x-direction and the inter-beam pitch in the y-direction where the beam itself 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 its assigned sub-irradiation region 29. The deflectors 209, 208 collectively deflect the multiple primary electron beams 20, thereby scanning the surface of the substrate 101 on which the pattern is formed with the multiple primary electron beams 20. In other words, the movement of the primary electron beam 10 within the sub-irradiation region 29 is achieved by the collective deflection of the entire multiple primary electron beams 20 by the deflectors 209, 208. By repeating this operation, one primary electron beam 10 is sequentially irradiated within one sub-irradiation region 29.

[0077] 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. 21 , 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 multiple primary electron beams 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 deflectors 209 and 208 collectively deflect the entire multiple primary electron beams 20, moving the irradiation position to an adjacent rectangular region 33 in the same stripe region 32. This operation is repeated to sequentially irradiate the stripe region 32. After scanning one stripe region 32, the irradiation region 34 moves to the next stripe region 32 by moving the stage 105 and / or by simultaneously deflecting the entire multi-primary electron beam 20 using the deflectors 209 and 208. As described above, scanning and secondary electron images are acquired 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 multiple frame regions 30, and frame images 31, which serve as measurement images for each frame region 30, are compared. The example in FIG. 21 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.

[0078] Here, 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 by the deflectors 209 and 208 so that the irradiation positions of the multiple primary electron beams 20 follow the movement of the stage 105.

[0079] As described above, the image acquisition mechanism 150 performs a scanning operation for each stripe region 32. As described above, the multi-primary electron beams 20 are irradiated, and the multi-secondary electron beams 300 emitted from the substrate 101 due to the irradiation of the multi-primary electron beams 20 form an intermediate image plane in the deflector 218, are deflected by the deflector 218, and are then detected by the multi-detector 222. 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. Then, a secondary electron image is acquired based on the signal of the detected multi-secondary electron beams 300. Specifically, the secondary electron detection data (measurement image data: secondary electron image data: inspection image data) for each pixel in each sub-irradiation region 29 detected by the multi-detector 222 is output to the detection circuit 106 in the order of measurement. In 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 obtained measurement image data is then transferred to the comparison circuit 108 together with information indicating each position from the position circuit 107.

[0080] 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 graphic patterns formed on the substrate 101. Specifically, it operates as follows: First, the design pattern data is read from the storage device 109 through the control computer 110, and each graphic pattern defined in the read design pattern data is converted into binary or multi-value image data.

[0081] As described above, the figures defined in the design pattern data are based on, for example, rectangles or triangles, 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 to distinguish between different types of figures such as rectangles or triangles.

[0082] When the design pattern data that becomes 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. Then, 1 / 2 is assigned to one pixel. 8 If a pixel has a resolution of (=1 / 256), a small area of ​​1 / 256 is allocated to 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. This grid (inspection pixel) can be aligned with the pixel of the measurement data.

[0083] Next, the reference image creation circuit 112 performs filtering on the design image data of the design pattern, which is image data of the graphic, using a predetermined filter function. This allows the design image data, which is image data on the design side with image intensity (grayscale value) as a digital value, to be matched 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.

[0084] In the comparison step (S122), the comparison circuit 108 compares the inspection image with the reference image. Specifically, the operation is as follows.

[0085] FIG. 22 is a configuration diagram showing an example of the configuration within the comparison circuit in the first embodiment. In FIG. 22, comparison circuit 108 includes storage devices 50, 52, and 56, such as a magnetic disk device, a frame image creation unit 54, an alignment unit 57, and a comparison unit 58. Each "unit" such as frame image creation unit 54, alignment unit 57, and comparison unit 58 includes a processing circuit, and this processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each "unit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. Input data or calculation results required for frame image creation unit 54, alignment unit 57, and comparison unit 58 are stored in a memory (not shown) or memory 118 each time.

[0086] The measurement image data (stripe image) transferred into the comparison circuit 108 is stored in the storage device 50. The reference image data transferred into the comparison circuit 108 is stored in the storage device 52.

[0087] The frame image creation unit 54 then creates a frame image 31 for each of a plurality of frame areas 30 obtained by further dividing the data of the stripe image acquired by the scanning operation of each primary electron beam 10. The frame areas 30 are then used as unit areas of the image to be inspected. Preferably, the frame areas 30 are configured so that their margin areas overlap each other to ensure that no image is missing. The created frame images 31 are stored in the storage device 56.

[0088] 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 can be performed using the least squares method.

[0089] The comparison unit 58 then compares at least a portion of the acquired secondary electron image with a predetermined image. Here, frame images obtained by further dividing the image of the sub-irradiation region 29 acquired for each beam are used. The comparison unit 58 then compares the frame image 31 with the reference image pixel by pixel. The comparison unit 58 compares the two pixel by pixel according to predetermined judgment conditions and determines 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 determined 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.

[0090] In the above example, die-to-database inspection has been described, but the present invention is not limited to this. Die-to-die inspection may also be performed. When performing die-to-die inspection, the above-described alignment and comparison process may be performed between the target frame image 31 (die 1) and a frame image 31 (die 2) (another example of a reference image) on which the same pattern as that of the frame image 31 is formed.

[0091] As described above, according to the first embodiment, the amount of deflection of the multiple secondary electron beams separated from the common orbit with the multiple primary electron beams can be reduced to zero or small, thereby suppressing crosstalk and improving the secondary electron collection efficiency in each detection element of the multi-detector.

[0092] FIG. 23 is a diagram showing an example of a configuration of a multi-stage deflector in a modification of the first embodiment. In the above example, the case where the multi-primary electron beams are dynamically deflected by the two-stage deflectors 209 and 208 has been described, but the present invention is not limited to this. As shown in FIG. 23, the multi-primary electron beams may be dynamically deflected by three-stage deflectors 209, 208, and 211 (another example of the multi-stage first deflector). Alternatively, four or more stages of deflectors may be used. In the example of FIG. 23, the deflector 211 is disposed after the deflector 208, but the present invention is not limited to this. The deflector 211 may be disposed between the deflector 209 and the deflector 208. The three-stage deflectors 209, 208, and 211 are driven in conjunction with each other. For example, aberration in the primary system may cause the positional fluctuation of the multi-primary electron beams 20 to become small, which may result in excessively large potentials V1 and V2 used in the two-stage deflectors 209 and 208. Increasing the number of deflectors can increase the degree of freedom in the potential setting range.

[0093] Fig. 24 is a flowchart showing an example of main steps of the writing method according to the modified example of Embodiment 1. Fig. 24 is the same as Fig. 12 except that a determination step (S111) is placed between the determination step (S110) and the deflection condition setting step (S112).

[0094] In the deflection direction difference setting step (S102), the deflection direction setting unit 65 sets the deflection direction θ1 of the deflector 209, the deflection direction θ2 of the deflector 208, and the deflection direction θ3 of the deflector 211. This determines the deflection direction difference Δθ (=θ1-θ2-θ3) between the three stages of deflectors 209, 208, and 211.

[0095] In the deflection intensity ratio setting step (S104), the deflection intensity ratio setting unit 66 sets a deflection intensity ratio E1:E2:E3 between the deflection intensity E1 of the deflector 209, the deflection intensity E2 of the deflector 208, and the deflection intensity E3 of the deflector 211. In the case of an electrostatic deflector, the deflection intensity of the deflector is determined by the potential applied to the deflector. Therefore, the deflection intensity ratio E1:E2:E3 can be defined as the ratio V1:V2:V3 between the potential V1 applied to the deflector 209, the potential V2 applied to the deflector 208, and the potential V3 applied to the deflector 211.

[0096] In the scanning step (S106), the substrate 101 is scanned with the multi-primary electron beam 20 by three stages of deflectors 209, 208, and 211 to acquire an image on the substrate 101. Alternatively, a stage surface set at the same height as the surface of the substrate 101 or a mark on the stage may be scanned. Alternatively, scanning an evaluation substrate is also suitable. At this time, with the deflection directions θ1, θ2, θ3 fixed, the deflection intensity setting unit 64 variably changes the potentials V1, V2, V3 while maintaining the deflection intensity ratio V1:V2:V3, thereby changing the amount of deflection, thereby scanning the substrate 101, evaluation substrate, stage, mark, etc. with the multi-primary electron beams 20. Therefore, the multi-primary electron beams 20 are deflected in a fixed direction determined by the set deflection direction difference Δθ (=θ1-θ2-θ3). Then, multiple secondary electron beams 300 emitted from the substrate 101, the evaluation substrate, the stage, or the mark are detected by the multi-detector 222. At this time, no deflection is performed by the deflector 226 on the secondary beam orbit.

[0097] In the determination step (S110), the determination unit 69 determines whether the brightness of the secondary electron image obtained by the multi-detector 222 is constant during the scanning of the multi-primary electron beams 20. If the brightness is constant, the process proceeds to the determination step (S111). If the brightness is not constant, or if no image can be obtained at all, the process returns to the deflection intensity ratio setting step (S104), and while varying the deflection intensity ratio, the steps from the deflection intensity ratio setting step (S104) to the determination step (S110) are repeated until the brightness becomes constant.

[0098] In the determination step (S111), the control computer 110 determines whether the deflection aberration of the multiple primary electron beams 20 is equal to or less than a threshold value Th2. If the deflection aberration of the multiple primary electron beams 20 is equal to or less than the threshold value Th2, the process proceeds to a deflection condition setting step (S112). If the deflection aberration of the multiple primary electron beams 20 is not equal to or less than the threshold value Th2, the process returns to the deflection intensity ratio setting step (S104), and while varying the deflection intensity ratio V1:V2:V3, the process repeats the steps from the deflection intensity ratio setting step (S104) to the determination step (S111) until the deflection aberration becomes equal to or greater than the threshold value Th2.

[0099] In the deflection condition setting step (S112), the deflection condition setting unit 70 sets the deflection intensity ratio V1:V2:V3 and the deflection direction difference Δθ of the deflectors 209, 208, and 211 in the deflection control circuit 128 so that the deflection sensitivity of the multiple secondary electron beams 300 emitted from the substrate 101 and passing through the deflectors 208, 209, and 211 on the detection surface of the multi-detector 222 is equal to or less than the threshold value Th when the multiple primary electron beams 20 are deflected by the deflectors 209, 208, and 211 with a retarding potential applied to the substrate 101. More preferably, the deflection intensity ratio V1:V2:V3 and the deflection direction difference Δθ of the deflectors 209, 208, and 211 are set in the deflection control circuit 128 so that the positional fluctuation of the multiple secondary electron beams 300 on the detection surface of the multi-detector 222 is zero.

[0100] The image acquisition step (S120) and the comparison step (S122) are the same as those described above.

[0101] 24, the case where the deflection intensity ratio V1:V2:V3 of the deflectors 209, 208, and 211 is made variable while the deflection direction difference Δθ is fixed, and the positional fluctuation of the multiple secondary electron beams 300 is adjusted to be equal to or less than the threshold value has been described, but the present invention is not limited to this. As with the adjustment method using two-stage deflectors described above, it is also preferable to make the deflection direction difference Δθ (=θ1-θ2-θ3) of the deflectors 209, 208, and 211 variable while the deflection intensity ratio V1:V2:V3 is fixed, and the positional fluctuation of the multiple secondary electron beams 300 is adjusted to be equal to or less than the threshold value.

[0102] By using three or more stages of deflectors, it is possible to reduce the deterioration of position fluctuations due to aberrations in the primary system, and therefore to prevent the potentials V1, V2, V3, etc. used in the three or more stages of deflectors 209, 208, 211 from becoming too large.

[0103] In the above description, a series of "circuits" includes processing circuits, which may include electrical circuits, computers, processors, circuit boards, quantum circuits, or semiconductor devices. Each "circuit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. A program for executing a processor or the like may be recorded on a recording medium such as a magnetic disk drive, a magnetic tape drive, a FD, or a ROM (read-only memory). For example, the position circuit 107, the comparison circuit 108, and the reference image creation circuit 112 may be configured with at least one of the processing circuits described above.

[0104] Although the embodiments have been described above with reference to specific examples, the present invention is not limited to these specific examples.

[0105] 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.

[0106] In addition, all other multi-electron beam image acquisition devices and multi-electron beam image acquisition methods that include the elements of the present invention and that can be appropriately modified by those skilled in the art are included within the scope of the present invention. [Explanation of symbols]

[0107] 10 Primary electron beam 20 Multi-primary electron beam 21 Primary electron beam 22 holes 29 Sub-irradiation area 30 Frame Area 31 frame images 32 stripe area 33 Rectangular area 34 Irradiation area 41 Opening 50,52,56 storage device 54 Frame image creation section 57 Alignment section 58 Comparison Section 60 Detector element 62 Element holder 64 Deflection strength setting section 65 Deflection direction setting section 66 Deflection intensity ratio setting section 68 Deflection direction difference setting section 69 Judgment section 70 Deflection condition setting section 100 Inspection equipment 101 Substrate 102 Electron Beam Column 103 Examination Room 106 Detection circuit 107 Position circuit 108 Comparison circuit 109 Storage device 110 Control computer 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 Retarding control circuit 132 Separator control circuit 134 Deflection condition acquisition circuit 142 Stage drive mechanism 150 Image acquisition mechanism 151 Primary electron optical system 152 Secondary electron optical system 160 Control Circuits 200 electron beam 201 Electron Gun 202, 205, 207, 217 Magnetic lenses 203 Shaped Aperture Array Substrate 208 Deflector 209 Deflector 211 Deflector 212 Bulk deflector 213 Limiting Aperture Substrate 214 Beam Separator 216 Mirror 217 Electromagnetic Lens 218 Deflector 222 Multi-detector 224 Projection Lens 226 Deflector 300 Multi-Secondary Electron Beam 301 Secondary Electron Beam 332 Drawing area 428 Detector aperture board 429 Support stand 600 intermediate image plane

Claims

1. a stage on which a substrate is placed; a plurality of lenses for imaging the multiple primary electron beams onto the substrate using the multiple primary electron beams; a separator that separates multiple secondary electron beams emitted as a result of irradiation of the substrate with the multiple primary electron beams from the orbit of the multiple primary electron beams; a multi-detector for individually detecting the multiple secondary electron beams separated from the orbits of the multiple primary electron beams; a multi-stage first deflector arranged on a common trajectory of the multiple primary electron beams and the multiple secondary electron beams, and configured to dynamically deflect the multiple primary electron beams; Equipped with a deflection intensity ratio and a deflection direction difference of the first deflectors of the multiple stages are set so that a positional variation on a detection surface of the multi-detector of the multi-secondary electron beams emitted from the substrate and passing through the first deflectors of the multiple stages becomes equal to or less than a threshold value when the multi-primary electron beams are deflected by the first deflectors of the multiple stages with a retarding potential applied to the substrate; A multi-electron beam image acquisition device characterized by:

2. a second deflector that statically deflects the multiple secondary electron beams, the second deflector being disposed on the orbit of the multiple secondary electron beams separated from the orbit of the multiple primary electron beams and at a position conjugate with a detection surface of the detector; Furthermore, the plurality of lenses are adjusted to achieve both imaging of the multiple primary electron beams onto a surface position of the substrate and imaging of the multiple secondary electron beams onto an intermediate position within the second deflector.

2. The multi-electron beam image acquisition device according to claim 1.

3. the multi-detector has a plurality of detection elements that individually detect the multiple secondary electron beams, the plurality of detection elements have limited aperture surfaces through which corresponding secondary electron beams of the multiple secondary electron beams can pass; at least one of a deflection intensity ratio and a deflection direction difference of the first deflectors of the plurality of stages is set so that a positional fluctuation amount of the multi-secondary electron beam on a detection surface of the multi-detector is equal to or less than a shortest distance from a center of the aperture surface of each detection element to an end of the aperture surface; 3. A multi-electron beam image acquisition device according to claim 1 or 2.

4. 3. The multi-electron beam image acquisition device according to claim 2, further comprising a third deflector arranged on the orbit of the multi-secondary electron beams separated from the orbit of the multi-primary electron beams, and capable of dynamically deflecting the multi-secondary electron beams.

5. imaging the multiple primary electron beams onto a substrate placed on a stage using a plurality of lenses; separating multiple secondary electron beams emitted as a result of irradiation of the substrate with the multiple primary electron beams from the orbits of the multiple primary electron beams; using a multi-detector to individually detect the multiple secondary electron beams separated from the orbits of the multiple primary electron beams; dynamically deflecting the multiple primary electron beams using a multi-stage first deflector arranged on a common trajectory of the multiple primary electron beams and the multiple secondary electron beams; Equipped with a deflection intensity ratio and a deflection direction difference of the first deflectors of the multiple stages are set so that a positional variation on a detection surface of the multi-detector of the multi-secondary electron beams emitted from the substrate and passing through the first deflectors of the multiple stages becomes equal to or less than a threshold value when the multi-primary electron beams are deflected by the first deflectors of the multiple stages with a retarding potential applied to the substrate; A multi-electron beam image acquisition method.

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