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

Abstract

PURPOSE: To provide a device capable of reducing one of variations in a shape and variations in a size, and variations in a focusing angle of multi-electron beams on a sample surface.CONSTITUTION: A multi-electron beam irradiation device according to one aspect of the present invention includes: an electron gun 201 that emits an electron beam in a divergence direction; a first condenser lens 202 that deflects the electron beam traveling in the divergence direction in a focusing direction to form substantially parallel beams; a shaping aperture array substrate 203 in which a plurality of first openings is formed and a portion of each of the electron beams that have become the substantially parallel beams passes through the plurality of first openings, to thereby form multi-electron beams; and a multi-stage lens array 210 comprising a plurality of lens arrays of two or more stages in which each lens has a multipole of at least a quadrupole disposed on a trajectory of an associated beam among the multi-electron beams.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a multiple electron beam irradiation apparatus and a multiple electron beam irradiation method, and more particularly to an apparatus for correcting the variation in the shape of multiple electron beams and the variation in the convergence angle at the intermediate image plane position of an electron source image of the multiple electron beams caused by aberration or the like. [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 the yield is essential for the manufacture of LSIs, which incur huge manufacturing costs. However, as typified by 1-gigabit-class DRAMs (random access memories), the patterns that make up LSIs are on the order of submicrons to nanometers. In recent years, with the miniaturization of LSI pattern dimensions formed on semiconductor wafers, the dimensions that must be detected as pattern defects have also become extremely small. Therefore, in order to inspect defects in ultra-fine patterns transferred onto semiconductor wafers, it is necessary to capture high-precision images.

[0003] In the inspection device, for example, a multi-primary electron beam using an electron beam is used to scan the substrate to be inspected, and the multi-secondary electron beams emitted from the substrate to be inspected are separated from the trajectory of the multi-primary electron beam.Then, the multi-secondary electron beams are detected by a detector to capture a pattern image.

[0004] Here, it is desirable for the multiple primary electron beams to have the same shape, size, and focusing angle on the sample surface. However, there is a problem in that variations in these occur due to the field curvature aberration and astigmatism caused by electromagnetic lenses and the like along the way. It is desirable to reduce these variations even as much as possible.

[0005] Here, it is disclosed that a two-stage stigmator is used to refract the entire multi-beams collectively, thereby correcting both the astigmatism and the linear distortion (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0006] [Patent Document 1] JP 2022-159159 A Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, one aspect of the present invention provides an apparatus and method capable of correcting astigmatism of multiple electron beams on a sample surface and reducing the variation in focal position, and further provides an apparatus and method capable of reducing the variation in focusing angle. [Means for solving the problem]

[0008] A multi-electron beam irradiation apparatus according to one aspect of the present invention includes: an emission source that emits an electron beam in divergent directions; a first condenser lens that refracts the electron beam traveling in a diverging direction into a converging direction to form a substantially parallel beam; a shaping aperture array substrate in which a plurality of first openings are formed, and in which a portion of the electron beam that has become a substantially parallel beam passes through the plurality of first openings to form a multi-electron beam; a two-stage multipole lens array, each lens having a quadrupole or higher multipole arranged on the trajectory of a beam it is responsible for among the multiple electron beams; The present invention is characterized by comprising:

[0009] It is preferable that the device further comprises an angle-limiting aperture array substrate having a plurality of second openings formed therein, the multi-electron beams having passed through the two-stage multipole lens array passing through the plurality of second openings to limit the divergence angle or convergence angle of each electron beam.

[0010] Alternatively, the shaping aperture array substrate preferably forms multiple electron beams while limiting the divergence or convergence angle of each electron beam.

[0011] Moreover, it is preferable that one of the two-stage multipole lens arrays generates a dipole field so that each beam of the multiple electron beams becomes a parallel beam.

[0012] Alternatively, it is preferable to further include a multipole lens array disposed between the shaping aperture array substrate and the two-stage multipole lens array, which generates a dipole field so that each beam of the multiple electron beams becomes a parallel beam.

[0013] It is also preferable to further comprise a second condenser lens for refracting the multi-electron beams that have passed through the two-stage multipole lens array in a focusing direction.

[0014] Moreover, it is preferable to use an electrostatic multipole element as the multipole element.

[0015] Alternatively, it is preferable to use a magnetic multipole element as the multipole element.

[0016] Alternatively, the two-stage multipole lens array may be It is preferable that the lens array is configured by combining an electrostatic multipole lens array constituted by electrostatic multipoles and a magnetic multipole lens array constituted by magnetic multipoles.

[0017] It is also preferable to further include a deflector array that deflects the multi-electron beams that have passed through the two-stage multipole lens array in a focusing direction.

[0018] A multi-electron beam irradiation method according to one aspect of the present invention includes the steps of: emitting an electron beam from an emission source in divergent directions; using a first condenser lens to refract the electron beam traveling in a diverging direction into a converging direction to form a substantially parallel beam; forming a multi-electron beam by allowing each part of the electron beam, which has become a substantially parallel beam, to pass through the first openings by using a shaping aperture array substrate having a plurality of first openings; correcting the position of the electron source image in two orthogonal directions for each beam by using a two-stage multipole lens array, each lens having a multipole element of quadrupole or more arranged on the trajectory of a beam in charge of the multiple electron beams; The present invention is characterized by comprising:

[0019] It is also preferable to further include a step of limiting the divergence angle or the convergence angle of each electron beam by using an angle-limiting aperture array substrate on which a plurality of second openings are formed, so that the multi-electron beam that has passed through the two-stage multipole lens array passes through the plurality of second openings.

[0020] Alternatively, the step of forming multiple electron beams preferably includes forming multiple electron beams and limiting the divergence angle or convergence angle of each electron beam. Effect of the Invention

[0021] According to one aspect of the present invention, it is possible to correct the astigmatism of multiple electron beams on a sample surface and reduce the variation in the focal position. Furthermore, it is possible to reduce the variation in the focusing angle. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a configuration diagram showing a configuration of a pattern inspection device according to a first embodiment. [Diagram 2] 2 is a conceptual diagram showing a configuration of a shaping aperture array substrate in the first embodiment. FIG. [Diagram 3] 1 is a diagram showing an example of a plurality of chip regions formed on a semiconductor substrate in the first embodiment. [Figure 4] FIG. 4 is a diagram for explaining an image acquisition process in the first embodiment. [Diagram 5]FIG. 13 is a diagram showing an example of a configuration from a radiation source to an intermediate image plane position of multiple primary electron beams in a first comparative example of the first embodiment. [Figure 6] FIG. 13 is a diagram showing an example of a method of correction by a one-stage stigmator in Comparative Example 2 of the first embodiment. [Figure 7] 5A and 5B are diagrams showing an example of a method for isotropic astigmatism correction using a two-stage multipole lens in the first embodiment. [Figure 8] FIG. 2 is a diagram showing an example of the configuration of a multipole lens array in the first embodiment. [Figure 9] 6A and 6B are diagrams showing another example of a method for isotropic astigmatism correction using a two-stage multipole lens in the first embodiment. [Figure 10] 13 is a diagram showing another example of a method for forming an image plane at an arbitrary position using a two-stage multipole lens in the first embodiment. FIG. [Figure 11] FIG. 2 is a diagram showing an example of a configuration in which two stages of multipole lenses are arranged when the object surfaces do not coincide in the first embodiment. [Figure 12] 11 is a diagram showing an example of the range of magnification adjustment when the object surfaces do not match in the first embodiment. FIG. [Figure 13] 1A is a diagram showing an example of a configuration in which two stages of multipole lenses are arranged in the case where the image plane is shifted in the x and y directions in the first embodiment. FIG. [Figure 14] 6A to 6C are diagrams showing an example of the range of magnification adjustment when the image plane is shifted in the x and y directions in the first embodiment. [Figure 15] 5 is a diagram showing an example of a range of focal lengths when an image plane is shifted in the x and y directions in the first embodiment. FIG. [Figure 16] 4A to 4C are diagrams for explaining the action of the angle limiting aperture array in the first embodiment. [Figure 17] FIG. 13 is a diagram showing an example of each configuration from an electron source to an intermediate image plane after astigmatism correction in a first modification of the first embodiment. [Figure 18] FIG. 13 is a diagram showing an example of each configuration from an electron source to an intermediate image plane after astigmatism correction in Modification 2 of Embodiment 1. [Figure 19]FIG. 13 is a diagram showing an example of each configuration from an electron source to an intermediate image surface after astigmatism correction in a third modification of the first embodiment. [Figure 20] 4 is a flow chart showing an example of main steps of a method for adjusting the multistage lens array in the first embodiment. FIG. [Figure 21] 4 is a configuration diagram showing an example of the internal configuration of a comparison circuit according to the first embodiment. FIG. [Figure 22] FIG. 11 is a diagram showing an example of the configuration of an inspection device according to a second embodiment. [Figure 23] FIG. 11 is a diagram showing an example of a beam shaped by a shaping aperture array substrate in the second embodiment. [Figure 24] 3A to 3C are diagrams illustrating examples of arrangement of multipole lenses in each embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] In the following, in the embodiment, 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.

[0024] Embodiment 1 FIG. 1 is a configuration diagram showing the configuration of a pattern inspection apparatus in the first embodiment. In FIG. 1, an inspection apparatus 100 for inspecting 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. Arranged within the electron beam column 102 are an electron gun 201, a condenser lens 202 (first condenser lens) (pre-condenser lens), a shaping aperture array substrate 203, a multi-stage lens array 210, an angle limiting aperture array substrate 211, a condenser lens 205 (second condenser lens) (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.

[0025] The primary electron optical system 151 (illumination optical system) is configured by the electron gun 201, the condenser lens 202, the shaping aperture array substrate 203, the multi-stage 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 configured by the electromagnetic lens 207, the E×B separator 214, the deflector 218, the deflectors 225 and 226, and the electromagnetic lens 224.

[0026] The multi-detector 222 has a plurality of detection elements arranged in an array (grid).

[0027] The multi-stage lens array 210 is configured by a two-stage multipole lens array (plurality of lens arrays), in which each lens has a multipole element of quadrupole or more arranged on the trajectory of a beam of the multiple primary electron beams 20 that it is responsible for.

[0028] In the angle limiting aperture array substrate 211, a plurality of passing holes (second openings) are formed at positions where the multiple primary electron beams 20 pass through.

[0029] In the inspection chamber 103, a stage 105 movable at least in the XY direction is arranged. On the stage 105, a substrate 101 (sample) to be inspected is arranged. 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 figure patterns. The chip pattern formed on the exposure mask substrate is exposed and transferred onto the semiconductor substrate a plurality of times, thereby forming a plurality of chip patterns (wafer dies) on the semiconductor substrate. The substrate 101 is arranged on the stage 105, for example, with the pattern forming surface facing upward. In addition, on the stage 105, a mirror 216 is arranged to reflect a laser beam for laser measurement irradiated from a laser measurement system 122 arranged outside the inspection chamber 103. In addition, on the stage 105, a mark 111 arranged at the same height position as the substrate 101 surface is arranged. The mark 111 has, for example, a cross pattern formed thereon.

[0030] In addition, 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.

[0031] In the control system circuit 160, a control computer 110 that controls the entire inspection apparatus 100 is connected 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 device, a monitor 117, a memory 118, and a printer 119 via a bus 120. The deflection control circuit 128 is also connected to DAC (digital-to-analog conversion) 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 a 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 a deflector 226.

[0032] The chip pattern memory 123 is connected to the comparison circuit 108. The stage 105 is driven by a driving mechanism 142 under the control of the stage control circuit 114. The driving mechanism 142 is configured with a driving system such as a three-axis (XY-θ) motor that drives in the X, Y, and θ directions in the stage coordinate system, and the stage 105 can be moved 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 be moved in the horizontal and rotational directions by the motors of the X, Y, and θ axes. The moving 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 by receiving the reflected light from the mirror 216 based on the principle of laser interference. For example, the X, Y, and θ directions of the primary coordinate system are set for the stage coordinate system with respect to a plane perpendicular to the optical axis of the multi-primary electron beams 20.

[0033] The condenser lens 202 , 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 .

[0034] Moreover, the multi-stage lens array 210 is controlled by a multi-stage lens array control circuit 130 .

[0035] Moreover, 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 225 is composed of four or more electrodes, and is controlled by the deflection control circuit 128 via a DAC amplifier 147 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.

[0036] The deflector 218 (bender) is configured, for example, in a cylindrical shape 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.

[0037] The E×B separator 214 is controlled by the E×B separator control circuit 132 .

[0038] A high-voltage power supply circuit (not shown) is connected to the electron gun 201, and an acceleration voltage from the high-voltage power supply circuit is applied between a filament (not shown) and an extraction electrode (not shown) in the electron gun 201. A predetermined voltage is applied to the 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.

[0039] 1 shows the configuration necessary for explaining the embodiment 1. The inspection device 100 may also include other configurations that are normally required.

[0040] FIG. 2 is a conceptual diagram showing the configuration of the shaping aperture array substrate in the first embodiment. In FIG. 2, the shaping aperture array substrate 203 has two-dimensional holes (apertures) 22 of m1 horizontal (x direction) columns × n1 vertical (y direction) rows (m1 and n1 are integers of 2 or more) formed at a predetermined arrangement pitch in the x and y directions. The example of 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, it may be a rectangle with the same size and shape. A part of the electron beam 200 passes through each of the multiple holes 22, thereby forming multiple primary electron beams 20. The shaping aperture array substrate 203 is an example of a multi-beam forming mechanism that forms multiple primary electron beams 20.

[0041] The image acquiring mechanism 150 acquires an inspection image of the geometric pattern from the substrate 101 on which the geometric pattern is formed, using multiple electron beams. The operation of the image acquiring mechanism 150 in the inspection device 100 will be described below.

[0042] An electron gun 201 (an example of an emission source) emits an electron beam 200 in a diverging direction. The emitted electron beam can be considered to be emitted from a virtual electron source 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 a virtual electron source. An image obtained downstream of the electron gun by projecting the image through the lens of this virtual light source or virtual electron source is called an electron source image. The electron beam 200 emitted from the electron gun 201 and proceeding in a diverging direction is subjected to a focusing force by a condenser lens 202. An electromagnetic lens or an electrostatic lens is used as the condenser lens 202. Then, the electron beam 200, which has become a substantially parallel beam, illuminates the entire shaping aperture array substrate 203. For simplicity, an example is shown here in which a single-stage condenser lens 202 is placed immediately after the electron gun 201. If necessary, the single-stage condenser lens 202 may be a lens group composed of multiple stages of lenses. The size of the electron source image can also be adjusted by adjusting the focal length of each lens constituting the lens group. The lenses constituting the lens group include either or both of electromagnetic lenses and electrostatic lenses. The structure of the electron gun also includes a structure including an electrode group that further accelerates and focuses electrons emitted from the cathode after they are extracted by an extraction electrode. 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. Each part of the electron beam 200 irradiated to the position of the plurality of holes 22 passes through each of the plurality of holes 22 in the shaping aperture array substrate 203, thereby forming multiple primary electron beams 20. By forming a substantially parallel beam by the condenser lens 202, the multiple primary electron beams 20 can travel substantially parallel to each other. This makes it easier to align the positions of the multiple openings of the downstream multistage lens array 210 and / or the multiple openings of the angle limiting aperture array substrate 211 with the passing positions of the multiple primary electron beams 20. In other words, it is possible to eliminate or reduce errors in the formation positions of the openings of each component through which the multiple primary electron beams 20 pass.

[0043] The formed multiple primary electron beams 20 are refracted by a multistage lens array 210, and the positions of the electron source images in two orthogonal directions for each beam are corrected. The divergence angle or convergence angle of each electron beam of the multiple primary electron beams 20 that have passed through the multistage lens array 210 is limited by an angle-limiting aperture array substrate 211, thereby correcting the variation 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 sample surface. This makes it possible to eliminate the effect of the field curvature of the downstream optical system.

[0044] The multiple primary electron beams 20 that have passed through the angle limiting aperture array substrate 211 are refracted by the condenser lens 205 to form an intermediate image of the electron source image and a crossover. Here, the crossover refers to a beam distribution at a position where the centers of the aberration-free trajectories of the multiple primary electron beams 20 converge to one point. The positions of the angle limiting aperture array substrate 211 and the condenser lens 205 may be reversed. In this case, the multi-primary electron beams 20 that have passed through the multi-stage 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.

[0045] The multi-primary electron beam 20 that has passed through the condenser lens 205 is refracted by the electromagnetic lens 206 to further form an intermediate image, and proceeds to an E×B separator 214 disposed at the height position of an intermediate image plane (image plane conjugate position: IIP) of the electron source image of each beam of the multi-primary electron beam 20. Then, the multi-primary electron beam 20 passes through the E×B separator 214 and proceeds to an electromagnetic lens 207. Also, by disposing a limiting aperture substrate 213 with a limited passing hole near the crossover position of the multi-primary electron beam 20, it is possible to block scattered beams. Also, by deflecting the entire multi-primary electron beam 20 collectively by the collective deflector 212 and blocking the entire multi-primary electron beam 20 with the limiting aperture substrate 213, it is possible to blank the entire multi-primary electron beam 20.

[0046] When the multiple primary electron beams 20 are incident on the electromagnetic lens 207, the electromagnetic lens 207 images the multiple primary electron beams 20 onto the substrate 101. In other words, the electromagnetic lens 207 irradiates the substrate 101 with the multiple primary electron beams 20.

[0047] The multiple primary electron beams 20 focused on the surface of the substrate 101 (sample) by the electromagnetic lens 207 are deflected collectively by the deflector 208 and the deflector 209, and each beam is irradiated onto a respective irradiation position on the substrate 101. In this manner, the primary electron optical system 151 illuminates the substrate 101 with the multiple primary electron beams 20.

[0048] When a desired position on the substrate 101 is irradiated with the multiple primary electron beams 20, a bunch of secondary electrons including reflected electrons (multiple secondary electron beams 300) is emitted from the substrate 101 due to the irradiation of the multiple primary electron beams 20. A secondary electron beam corresponding to each beam of the multiple primary electron beams 20 is emitted.

[0049] The multiple secondary electron beams 300 emitted from the substrate 101 pass through an electromagnetic lens 207 and proceed to an E×B separator 214 .

[0050] The E×B separator 214 separates the multiple secondary electron beams 300 from the trajectory of the multiple primary electron beams 20 .

[0051] The E×B separator 214 has two or more magnetic poles (electromagnetic deflection magnetic poles) using coils, and two or more electrodes (electrostatic deflection electrodes). For example, two opposing magnetic poles and two opposing electrodes with a phase shift of 90° are arranged. The arrangement is not limited to this. For example, a structure in which the electrodes also serve as magnetic poles can be arranged with four or eight electrodes / magnetic poles. The E×B separator 214 deflects the multi-secondary electron beams 300 to generate a separation action. The E×B separator 214 generates a directional magnetic field by using multiple magnetic poles. Similarly, a directional electric field is generated by using multiple electrodes. Specifically, the E×B separator 214 generates an electric field E and a magnetic field B in a direction perpendicular to the direction in which the central beam of the multi-primary electron beams 20 advances (the central axis of the orbit). The electric field exerts a force in the same direction regardless of the direction of advance of the electrons. 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 traveling direction of the electrons. The force FE due to the electric field and the force FB due to the magnetic field cancel each other out for the multi primary electron beams 20 entering the E×B separator 214 from above, and the multi primary electron beams 20 travel straight downward. In contrast, 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, and the multi secondary electron beams 300 are deflected in a predetermined direction and bent obliquely upward, and separated from the trajectory of the multi primary electron beams 20.

[0052] The multi secondary electron beams 300 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 are deflected by the deflector 218, and are further bent, and proceed to the electromagnetic lens 224. Then, the multi secondary electron beams 300 are projected onto the multi detector 222 while being refracted in the focusing direction by the electromagnetic lens 224 at a position away from the orbit of the multi primary electron beams 20. The multi detector 222 (multi secondary electron beam detector) detects the multi secondary electron beams 300 separated from the orbit 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). Then, 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 to generate electrons, and secondary electron image data is generated for each pixel. The intensity signal detected by the multi detector 222 is output to the detection circuit 106.

[0053] 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 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 inspection region 330 of 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) at a reduced size of, for example, 1 / 4.

[0054] Fig. 4 is a diagram for explaining the image acquisition process in the first embodiment. 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. When 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.

[0055] 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, 209 (electrostatic deflectors).

[0056] 4 shows, for example, a case of 5×5 arrays of multi primary electron beams 20. An irradiation area 34 that can be irradiated with one irradiation of the multi primary electron beam 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 substrate 101 surface 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 substrate 101 surface 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. Then, each primary electron beam 10 constituting the multi-primary electron beam 20 is irradiated into a sub-irradiation region 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 (scans) the sub-irradiation region 29. Each primary electron beam 10 is assigned to one of the different sub-irradiation regions 29. Then, each primary electron beam 10 irradiates the same position in the assigned sub-irradiation region 29. The two-stage deflectors 208 and 209 collectively deflect the multi-primary electron beam 20, thereby scanning the multi-primary electron beam 20 over the surface of the substrate 101 on which the pattern is formed. In other words, the movement of the primary electron beam 10 in the sub-irradiation region 29 is performed by collective deflection of the entire multi-primary electron beam 20 by the two-stage deflectors 208 and 209. By repeating such an operation, one sub-irradiation region 29 is sequentially irradiated with one primary electron beam 10.

[0057] The width of each stripe region 32 is preferably set to the same size as the y-direction size of the irradiation region 34 or a size narrower by the scan margin. In the example of FIG. 4, the irradiation region 34 is the same size as the rectangular region 33. However, this is not limited to this. The irradiation region 34 may be smaller than the rectangular region 33. Alternatively, it may be larger than the rectangular region 33. Then, each primary electron beam 10 constituting the multiple primary electron beams 20 is irradiated into the sub-irradiation region 29 in which the beam is located, and scans (scans) the sub-irradiation region 29. Then, when the scanning of one sub-irradiation region 29 is completed, the irradiation position moves to the adjacent rectangular region 33 in the same stripe region 32 by collective deflection of the entire multiple primary electron beams 20 by the two-stage deflectors 208 and 209. This operation is repeated to sequentially irradiate the stripe region 32. When scanning of one stripe region 32 is completed, the irradiation region 34 moves to the next stripe region 32 by moving the stage 105 or / and deflecting the entire multi-primary electron beam 20 by the two-stage deflectors 208, 209. As described above, scanning operation and acquisition of secondary electron images are performed for each sub-irradiation region 29 by irradiation of each primary electron beam 10. By combining the secondary electron images for each of these sub-irradiation regions 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 formed. In addition, when actually performing image comparison, the sub-irradiation region 29 in each rectangular region 33 is further divided into a plurality of frame regions 30, and frame images 31 that are measurement images for each frame region 30 are compared. The example of 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 formed by dividing it into two in the x and y directions, for example.

[0058] Furthermore, when the substrate 101 is irradiated with the multiple primary electron beams 20 while the stage 105 is moving continuously, a tracking operation is performed by collective deflection by the two-stage deflectors 208 and 209 so that the irradiation position of the multiple primary electron beams 20 follows the movement of the stage 105. Therefore, the emission position of the multiple secondary electron beams 300 changes from moment to moment with respect to the central axis of the orbit of the multiple primary electron beams 20. Similarly, when scanning within the sub-irradiation region 29, the emission position of each secondary electron beam changes 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 within 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 with a single-stage deflector.

[0059] 5 is a diagram showing an example of a configuration from a radiation source to an intermediate image plane position of multiple primary electron beams in Comparative Example 1 of the first embodiment. In Comparative Example 1 of the first embodiment, an electron beam emitted from an electron gun 301 serving as a radiation source is refracted into a substantially parallel beam by a condenser lens 302 and proceeds to a shaping aperture array substrate 303. Then, multiple primary electron beams are formed by each part 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.

[0060] Here, aberrations such as curvature of field occur due to the reduction optical system further downstream of the optical system shown in FIG. 5. This may cause a shift in the image formation position on the specimen surface of the electron source image on the object plane 311 of each beam. If the image formation position on the specimen surface shifts, the size of each beam on the specimen surface varies. Therefore, it is desirable to shift the intermediate image plane of the peripheral beams downstream (for example, intermediate image plane position 319b) from the intermediate image plane position 319a of the central beam according to the distance from the axis so as to compensate for the curvature of field occurring in the reduction optical system downstream. Therefore, in Comparative Example 1, an electrostatic lens array 310 is arranged to correct the position of the intermediate image plane of each beam.

[0061] However, astigmatism occurs in the condenser lenses 302 and 305 and the downstream optical system. This causes a shift in the image plane position in the x and y directions. This shift is larger for the peripheral beams. Therefore, there is a variation in the size in the x and y directions of each beam image at the intermediate image plane positions 319a and 319b when it is assumed that there is no astigmatism. For example, even if the central beam has a nearly circular shape, the peripheral beams have a flattened shape.

[0062] As described above, it is desirable for the multiple primary electron beams to form an image on the sample surface without astigmatism for all beams. However, there is a problem in that the image plane position varies due to astigmatism and field curvature caused by lenses such as a condenser lens along the way. Therefore, it is desirable to correct these variations at the intermediate image plane positions of each beam of the multiple electron beams. However, it is difficult to correct astigmatism with the electrostatic lens array 310 of Comparative Example 1.

[0063] FIG. 6 is a diagram showing an example of a method of correction by a one-stage stigmator in Comparative Example 2 of the first embodiment. In FIG. 6, the limit of correction by a one-stage stigmator (multipole lens 40-1) for one beam is described. In the one-stage stigmator, when astigmatism occurs in the object surface in the x orbit and the y orbit, a virtual object surface 11 that coincides in the x and y directions can be formed, and the image surface position can be coincident in the x and y directions. However, the image surface position after correction is determined by the distance kxd from the object surface to the stigmator in the x direction and the distance kyd from the object surface to the stigmator in the y direction. Therefore, it is difficult to match the image surface to an arbitrary position. Note that, when the condenser lens 202 generates astigmatism, it can be considered that a virtual quadrupole lens exists at the position of the condenser lens 202, but the degree of freedom does not increase because the focal length of this virtual quadrupole lens is fixed. Therefore, the above situation does not change.

[0064] Therefore, in the first embodiment, the positions of the electron source images in two directions orthogonal to each other for each beam are individually corrected using a multistage lens array 210 consisting of two stages of a plurality of multipole lens arrays each having a multipole element with a quadrupole or more. In order to explain the effects of the invention, in each embodiment including this embodiment, an approximation is made that the effect of astigmatism in the condenser lens 202 for the beam to be described is further focused in the x direction in addition to the effect of obtaining a parallel beam. This effect is obtained by placing a quadrupole lens at the position of the condenser lens 202 and adjusting the conditions of the focal length of the condenser lens 202 and the focal length of this quadrupole lens. In addition, a thin lens approximation is made for the quadrupole lens and the condenser lens 202. As a result, the action of each lens can be expressed by a matrix. A specific explanation will be given below.

[0065] FIG. 7 is a diagram showing an example of a method of isotropic astigmatism correction using a two-stage multipole lens in the first embodiment. The trajectories in the x and y directions are not strict, but are used to show the effect of each lens. FIG. 7 shows a case where a two-stage multipole lens array is used as the multistage lens array 210. FIG. 7 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 the multiple primary electron beams 20. The two-stage multipole lenses 40-1 and 40-2 are composed of multipoles with a quadrupole or more and form a quadrupole field. FIG. 7 shows an example of a diverging trajectory of an electron beam emitted from an object surface. In embodiment 1, the primary electron beam emitted from the object surface is refracted by the pre-condenser lens 202 to become an approximately parallel beam that is approximately parallel to the central axis of the orbit (optical axis) of the central beam of the multiple primary electron beams 20, and proceeds to two-stage multipole lenses 40-1 and 40-2.

[0066] FIG. 8 is a diagram showing an example of the configuration of the multipole lens array in the first embodiment. In FIG. 8, each multipole lens array 40 is composed of 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 for the passage of the multi primary electron beams 20 are formed in the three electrode substrates. 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 to them. In the plurality of passage holes 17 in the middle electrode substrate 14, a plurality of electrodes 16 are arranged as multipoles of quadrupole or more surrounding the passage holes 17 for each passage hole 17. In other words, in the multipole lens array 40, each lens has a multipole of quadrupole or more. 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 such that the phases of, for example, eight electrodes are equally spaced with respect to the electrodes arranged on a straight line extending radially from the center of the central beam passage hole 17. However, this is not limited to this. For example, the multipole elements at each position may be arranged such that the phases of, for example, eight electrodes are equally spaced with respect to the electrodes arranged in the x direction or y direction. Furthermore, an electrostatic multipole element is used as the multipole element, or a magnetic multipole element may be used as the multipole element. Furthermore, the electrodes 16 may be disposed on either the upper surface or the rear surface of the middle-stage electrode substrate 14. In the example of Fig. 8, eight electrodes 16a-16h are disposed on the upper surface of the middle-stage electrode substrate 14. An independent control potential is applied to each of the eight electrodes 16a-16h. Therefore, a maximum of the number of independent potentials applied is equal to the number of beams x 8 poles. This allows the focal length of each multipole lens in one multipole lens array to be controlled independently. Therefore, it is possible to perform correction appropriate for each electron beam that composes the multi-electron beam. Here, the quadrupole lens acts as a convex lens in one direction and a concave lens in the perpendicular direction, but a positive focal length fq is defined, and the focal length of the convex lens is defined as fq, and the focal length of the concave lens is defined as -fq.

[0067] The example of FIG. 7 shows a case where the object plane is misaligned between the x and y trajectories. In the example of FIG. 7, the primary electron beam having astigmatism emitted from the object plane in the x and y directions proceeds to two multipole lenses 40-1 and 40-2. Then, the primary electron beam is refracted, for example, in the diverging direction in the x direction by the first multipole lens 40-1, and is refracted in the converging direction in the y direction conversely. Then, the primary electron beam is refracted, for example, in the converging direction in the x direction by the second multipole lens 40-2, and is refracted in the diverging direction in the y direction conversely. As a result, when the object plane is misaligned between the x and y trajectories, the trajectory in the x direction and the trajectory in the y direction can be aligned with the trajectory from the virtual object plane 11 that is aligned in the x and y directions. Here, the position of the object plane 11 is determined so that the image plane formed by the downstream optical system is aligned with the position of the sample plane.

[0068] This makes it possible to correct the curvature of field while correcting the astigmatism.

[0069] This makes it possible to match the intermediate image plane positions in the x and y directions to desired positions while correcting astigmatism. As described above, by arranging the two-stage multipole lens array 40, the astigmatism and the field curvature aberration can be corrected for the multiple primary electron beams 20 individually.

[0070] FIG. 9 is a diagram showing an example of a method for isotropic astigmatism correction using a two-stage multipole lens according to the first embodiment. FIG. 10 is a diagram showing another example of a method for forming an image plane at an arbitrary position using the two-stage multipole lens according to the first embodiment. 9 and 10 show a case where a two-stage multipole lens array is used as the multistage lens array 210. In FIG. 9 and FIG. 10, the lens action of two-stage multipole lenses 40-1 and 40-2 for one primary electron beam of the two-stage multipole lens array 40 corresponding to the multi-primary electron beam 20 is shown. The two-stage multipole lenses 40-1 and 40-2 are composed of multipoles having quadrupoles or more and form a quadrupole field. FIG. 9 and FIG. 10 show an example of a focused trajectory of an electron beam. In the first embodiment, the primary electron beam emitted from the object surface is refracted by the front condenser lens 202 so as to become a substantially parallel beam substantially parallel to the trajectory central axis (optical axis) of the central beam of the multi-primary electron beam 20, and proceeds to the two-stage multipole lenses 40-1 and 40-2.

[0071] In the examples of Figs. 9 and 10, if the primary electron beam on the convergent trajectory is not corrected by the two-stage multipole lenses 40-1 and 40-2, the image plane in the x direction and the image plane in the y direction are shifted from each other. However, the primary electron beam on the convergent trajectory is refracted, for example, in the diverging direction in the x direction by the first-stage multipole lens 40-1, and is refracted in the converging direction in the y direction. Then, the primary electron beam on the convergent trajectory is refracted, for example, in the converging direction in the x direction and is refracted in the diverging direction in the y direction by the second-stage multipole lens 40-2. As a result, when the object surface is shifted between the x orbit and the y orbit, the image surface 19 can be formed at any position where the x and y directions coincide with each other while correcting the astigmatism. Similarly, when the object surface is coincident between the x orbit and the y orbit, the image surface 19 can be formed at any position where the x and y directions coincide with each other while correcting the astigmatism.

[0072] As described above, by arranging the two-stage multipole lens array 40, the image plane positions coincident with each other in the x and y directions for the multiple primary electron beams 20 can be adjusted to any position. 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 coincide with each other on the surface of the substrate 101. In other words, it is preferable to correct the positions so that the image curvature of the downstream optical system is corrected.

[0073] FIG. 11 is a diagram showing an example of a configuration in which two stages of multipole lenses are arranged in the case where there is astigmatism in the condenser lens in the first embodiment and one electron beam is incident on a focused trajectory in the x direction and a parallel trajectory in the y direction. FIG. 12 is a diagram showing an example of the range of magnification adjustment according to the first embodiment. The example in Fig. 11 shows a case where astigmatism occurs in a condenser lens. In Fig. 11, in multistage lens array 210 in embodiment 1, first stage multipole lens 40-1 is disposed at a position that is a distance ηd from object plane 11 and a distance ηd from the object plane in the y direction (and the Y object plane). Second stage multipole lenses 40-1 and 40-2 are disposed with a distance d between them. The image plane 19 is located at a distance λd from second stage multipole lens 40-2.

[0074] FIG. 13 is a diagram showing an example of a configuration in which two stages of multipole lenses are arranged in the case where the image planes are shifted in the x and y directions in the first embodiment. FIG. 14 is a diagram showing an example of the range of magnification adjustment when the image plane is shifted in the x and y directions in the first embodiment. FIG. 15 is a diagram showing an example of the range of focal lengths when the image plane is shifted in the x and y directions in the first embodiment. The example in Fig. 14 shows a case where the image planes in the x and y directions are shifted. In Fig. 14, in the multistage lens array 210 in the first embodiment, 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 position at a distance λx from the second stage multipole lens 40-2 is the x-direction image plane 19, and the position at a distance λy is the y-direction image plane 19b.

[0075] As described above, for the shaped multi-primary electron beams 20, the image plane positions of the electron source images in two orthogonal directions for each beam are individually corrected by the multistage lens array 210. This makes it possible to individually correct the variation in the image formation position on the sample surface for each beam at the intermediate image plane position of each beam (the variation in size for each beam on the sample surface). In other words, by arranging the two-stage multipole lens array 40, although magnification anisotropy occurs in the x and y directions, as long as the coefficient λ is within a predetermined range, an image with astigmatism correction can be formed at any position. The multi-primary electron beams 20 that have passed through the multi-stage lens array 210 proceed to an angle limiting aperture array substrate 211. Next, the variation in the focusing angle is corrected.

[0076] Fig. 16 is a diagram for explaining the function of the angle-limiting aperture array substrate of embodiment 1. In Fig. 16, the upper diagram shows a case where the angle is limited on the downstream side of the multistage lens array 210. The lower diagram of Fig. 16 shows a case where the angle is limited on the upstream side 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, but on the other hand, the larger the convergence angle, the greater the aberration. Therefore, it is desirable to determine the convergence angle so that the beam current can be obtained in a desired dimensional range on the substrate 101 surface. For this purpose, the convergence angle is limited by using the angle limiting aperture substrate 211. However, since the image magnification and the angular magnification are inversely proportional in the paraxial approximation, when imaging is performed with different magnifications in the x and y directions, the convergence angles in each direction on the sample surface of the electron beam, which had an isotropic angular distribution when entering the optical system, will differ. Therefore, the convergence angle can be adjusted by providing the angle limiting aperture substrate 211 in order to align the aberrations that depend on the convergence angle. An example is shown in FIG. 16. When imaging is performed with different magnifications in the x and y directions, the convergence angle becomes large in an orbit with a small magnification. Therefore, the convergence angle is limited by the angle limiting aperture. By arranging the angle limiting aperture near the lens, the effect on the beam distribution at the imaging position can be suppressed. Alternatively, the angle limiting aperture can be used to deform the angular distribution when entering the optical system. It is desirable to determine the shape of the angle limiting aperture so that an isotropic convergence angle distribution is obtained for each beam on the sample surface.

[0077] 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, it is disposed between the multi-stage lens array 210 and the condenser lens 205. However, it is not limited to this. It may be disposed between the condenser lens 205 and the image plane 19. In other words, it may be disposed at a position before the multi-primary electron beams 20 reach the position of the image plane 19 after being refracted in the focusing direction. Since the divergence angle or the focusing angle is limited in a state where the beam diameter of each beam is wide before forming the intermediate image plane, the diameter size of the multiple passing 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 convergence angle of each electron beam by passing the multi-primary electron beam 20, which has passed through the multi-stage lens array 210, through a plurality of passage holes. If each beam is diverging, the divergence angle can be limited, and if each beam is converging, the convergence angle can be limited. This makes it possible to correct the variation in the convergence angle for each beam at the position of the image plane 19.

[0078] FIG. 17 is a diagram showing an example of each configuration from the electron source to the intermediate image surface after astigmatism correction in the first modification of the first embodiment. In the first modification of the first embodiment, as shown in FIG. 17, a multipole lens array 40 is separately arranged downstream of the multistage lens array 210 to deflect the multi-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 multi-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 so as to focus each primary electron beam to one point. In other words, a potential with a reversed positive and negative sign is applied to the electrodes facing the multipole. As a result, the primary electron beam passing through the multipole is deflected in the direction of the positive potential of the electric field formed. In order to correct variations in the shape (and size) of the electron source image on 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 the quadrupole field can be made to act in parallel.

[0079] 17, the angle limiting aperture array substrate 211 is disposed on the trajectory of the multiple primary electron beams 20 after they are refracted in the focusing direction. The other configurations are the same as those in FIG.

[0080] Fig. 18 is a diagram showing an example of each configuration from the electron source to the intermediate image surface after astigmatism correction in the second modification of the first embodiment. In the second modification of the first embodiment, as shown in Fig. 18, 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 configurations are the same as those 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.

[0081] FIG. 19 is a diagram showing an example of each configuration from the electron source to the intermediate image surface after astigmatism correction in the third modification of the first embodiment. In the first embodiment, a substantially parallel beam is formed using the condenser lens 202, but the parallelism may deviate from the allowable degree. Therefore, in the third modification of the first embodiment, as shown in FIG. 19, for example, the first-stage multipole lens array 40 of the multistage lens array 210 is used to deflect at least one primary electron beam of the multi-primary electron beam 20 to a substantially parallel beam. Therefore, for example, the first-stage multipole lens array 40 also functions as a deflector array in parallel with the above-mentioned original function. The dipole field and the quadrupole field can be made to act in parallel. However, the multipole lens array functioning as a deflector array is not limited to the first stage. One multipole lens array of the multistage lens array 210 may generate a dipole field so that each beam of the multi-primary electron beam 20 becomes a parallel beam.

[0082] Alternatively, it is also preferable to separately dispose a multipole lens array 40 between the shaping aperture array substrate 203 and the multistage lens array 210. The multipole lens array 40 disposed separately from the multistage lens array 210 generates a dipole field so that each beam of the multi primary electron beams 20 becomes a parallel beam. In this case, the multipole lens array 40 functions as a deflector array.

[0083] In the above example, the two-stage multipole lens array 40 constituting the multistage lens array 210 is composed of an electrostatic multipole lens array composed of electrostatic multipoles, or a magnetic multipole lens array composed of magnetic multipoles, or a combination of an electrostatic multipole lens array composed of electrostatic multipoles and a magnetic multipole lens array composed of magnetic multipoles.

[0084] As described above, the two-stage multipole lens array 40 and the angle-limiting aperture array substrate 211 can reduce the variation in the shape of each beam and the variation in the focusing angle. Alternatively, the variation in the position of the image plane 19 (intermediate image plane) of each beam and the variation in the focusing angle can be reduced.

[0085] FIG. 20 is a flow chart illustrating an example of main steps of the method for adjusting the multistage lens array according to the first embodiment. First, the lenses of the entire inspection apparatus 100 including the multi-stage lens array 210 are driven under initial conditions obtained from simulation or past measurement experience (S102). Then, the beam array shapes at different focal positions are measured (S104). From the above measurement results, the residual astigmatism, the field curvature, the beam size, and the focusing half angle are obtained (S106). Then, it is determined whether the obtained result satisfies the desired conditions (S108). If the obtained result does not satisfy the desired conditions, the lens conditions capable of correcting the astigmatism and the variation in the image plane position are obtained (S110). If the obtained result satisfies the desired conditions, the adjustment is completed and the process proceeds to the inspection process. The lens conditions are changed to the obtained ones (S112). Then, the process returns to S104, and steps S104 to S112 are repeated until the obtained results satisfy the desired conditions.

[0086] After the lenses of the entire inspection apparatus 100 including the multistage lens array 210 have been adjusted as described above, the inspection apparatus 100 inspects the substrate 101 .

[0087] 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 substrate 101 being irradiated with the multi-primary electron beams 20 are guided to the multi-detector 222 (detector array) by the secondary electron optical system 152. Then, the guided multi-secondary electron beams 300 are 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 may not reach the multi-detector 222. Then. A secondary electron image is obtained based on the detected signal of the multi-secondary electron beam 300. Specifically, secondary electron detection data (measurement image data: secondary electron image data: inspected 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, the analog detection data is converted to digital data by an A / D converter (not shown) and 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.

[0088] FIG. 21 is a configuration diagram showing an example of the configuration in the comparison circuit in the first embodiment. In FIG. 21, the comparison circuit 108 includes storage devices 50, 52, 56 such as a magnetic disk device, a frame image creation unit 54, a positioning unit 57, and a comparison unit 58. Each "unit" such as the frame image creation unit 54, the positioning unit 57, and the comparison unit 58 includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. In addition, 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 the frame image creation unit 54, the positioning unit 57, and the comparison unit 58 are stored in a memory (not shown) or memory 118 each time.

[0089] 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.

[0090] The measured image data (beam image) transferred to the comparison circuit 108 is stored in the storage device 50.

[0091] Then, the frame image creation unit 54 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 region 29 acquired by the scanning operation of each primary electron beam. The frame regions 30 are used as unit regions of the inspection image. It is preferable that each frame region 30 is configured so that the margin regions overlap each other to prevent any missing image. The created frame images 31 are stored in the storage device 56.

[0092] 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, it reads out the design pattern data from the storage device 109 through the control computer 110, and converts each graphic pattern defined in the read out design pattern data into binary or multi-value image data.

[0093] As described above, the figures defined in the design pattern data are based on basic figures such as rectangles and 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 the type of figure, such as a rectangle or triangle.

[0094] 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 indicating the graphic shape of the graphic data, the graphic dimensions, etc. are interpreted. The circuit then expands the data into binary or multi-value design pattern image data as a pattern to be placed within a grid having a predetermined quantized dimension as a unit, and outputs the data. In other words, the design data is read, the inspection area is virtually divided into grids having a predetermined dimension as a unit, 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 pixel is assigned to one pixel. 8 If the resolution is to be 1 / 256, a small area of ​​1 / 256 is allocated for the area of ​​the figure placed in 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 pixels of the measurement data.

[0095] Next, the reference image creation circuit 112 applies a filter process 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) being a digital value, to 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.

[0096] 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 smaller than pixels. For example, the alignment may be performed using the least squares method.

[0097] Then, the comparison unit 58 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 according to a predetermined judgment condition, and judges the presence or absence of a defect such as a shape defect. For example, if the gradation value difference for each pixel is greater than the judgment threshold value Th, it is judged to be a defect. Then, the comparison result is output. The comparison result may be output to the storage device 109 or memory 118, or may be output from the printer 119.

[0098] In addition to the above-mentioned die-to-database inspection, it is also preferable to perform a die-to-die inspection in which measurement image data obtained by capturing the same pattern at different locations on the same substrate are compared. Alternatively, inspection may be performed using only the own measurement image.

[0099] As described above, according to the first embodiment, it is possible to reduce either the variation in shape or size of the multiple electron beams on the sample surface, and the variation in the focusing angle.

[0100] 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 limiting the angle is not limited to this. In the second embodiment, a configuration in which angle limiting is also performed when forming the multiple primary electron beams 20 will be described.

[0101] Fig. 22 is a diagram showing an example of the configuration of an inspection device in embodiment 2. Fig. 22 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.

[0102] 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.

[0103] Here, the formed multiple primary electron beams 20 may have astigmatism as described above. Therefore, when the beam is shaped by the shaping aperture array substrate 203, the beam shape due to such astigmatism may be corrected.

[0104] 23 is a diagram showing an example of a beam shaped by the shaping aperture array substrate in embodiment 2. For example, when forming an image with a magnification of 1 in the x direction and a magnification of 0.5 in the y direction, the angular magnification of the multistage lens array 210 is 1 in the x direction and 2 in the y direction. In order to make the convergence angle equivalent to that of an opening of diameter 2r formed on the angle limiting aperture array substrate 211 so as to align the convergence angle on the image surface 19 side, the convergence angle on the shaping side is limited to x direction:y direction=1:0.5. For this purpose, the opening of the shaping aperture array substrate 203 is an ellipse with major axis: minor axis=2:1. The size may vary depending on the position. When determining the size of the aperture, it is practical to assume that the angular distribution of the electron beam that has passed through the multi-stage lens array 210 is the desired one, trace the trajectory in reverse by simulation to obtain the distribution at the shaping aperture array position, and determine the shape of the aperture so as to give that distribution. Alternatively, it is also possible to set the marks 111 at different heights, obtain the beam convergence angle from the height dependency of the marks 111 of the beam distribution obtained by irradiating the electron beam, and determine it so as to obtain the desired distribution.

[0105] As described above, according to the second embodiment, the angle can be limited as well as the beam shaping. This makes it possible to correct the variation in the focusing angle on the image plane 19. Note that, like the first embodiment, the multistage lens array 210 can correct the variation in the shape of the electron source image on the image plane 19 or the variation in the image plane position (variation in size on the sample plane).

[0106] In the above description, a series of "circuits" includes a processing circuit, which may include an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor device. Each "circuit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. The program for executing the processor may be recorded on a recording medium such as a magnetic disk device, a magnetic tape device, 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 composed of at least one of the above-mentioned processing circuits. 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 0. In practice, there is a limit to the focal length that can be realized due to physical limitations such as discharge in the case of an electrostatic lens and saturation of the magnetic pole in the case of a magnetic field lens. In addition, there are limitations to the quadrupole component of a condenser lens due to the desired magnification and lens arrangement. It is advisable to perform optimization in device design taking these limitations into consideration.

[0107] Although the embodiments have been described above with reference to specific examples, the present invention is not limited to these specific examples. For example, in this explanation, the intermediate image plane is adjusted so that its position is the same in the x and y directions, but it can also be adjusted to a different position so as to cancel astigmatism in the downstream optical system, as shown in Fig. 13. Also, although it has been described that the focal length of each lens constituting the lens array can be controlled independently, when the condition for the independence of the adjustment range is relaxed, it is also possible to divide the lenses constituting the lens array into at least two or more groups, and to set the focal length independent between different groups and the focal length common within the same group.

[0108] FIG. 24 is a diagram showing an example of the arrangement of multipole lenses in each embodiment. For example, when the distribution of field curvature and astigmatism is axially symmetric, as shown in Figure 24, the number of power supplies can be reduced by changing the phase of the rotational direction of the electrodes of the multipole lens depending on the direction from the central axis, dividing the lenses into two or more groups according to the radial distance, and sharing a power supply that applies a potential to corresponding electrodes within the same group so that the focal lengths are equal. In the example of Figure 24, the power supply can be shared for electrodes given the same number. Furthermore, when only a quadrupole field is generated, it is possible to share a power supply by applying the same potential to opposing electrodes, such as electrodes 1 and 5.

[0109] Further, although the description of the device configuration, control method, and other parts not directly necessary for the explanation of the present invention have been omitted, the required device configuration and control method can be appropriately selected and used.

[0110] 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. [Explanation of symbols]

[0111] 10 Primary electron beam 11 Object surface 12 Upper electrode substrate 14 Middle electrode board 16 electrodes 17 Passing hole 18 Lower electrode board 19 Image plane 20 Multi-primary electron beam 22 holes 29 Sub-irradiation area 30 Frame Area 31 Frame Images 32 Stripe Area 33 Rectangular area 34 Irradiation area 40 Multipole Lens Array 40-1,40-2 Multipole Lens 50,52,56 storage device 54 Frame image creation section 57 Alignment section 58 Comparison section 62 Upper electrode substrate 64 Middle electrode board 66 electrodes 67 Passing hole 18 Lower electrode board 100 Inspection Equipment 101 Substrate 102 Electron Beam Column 103 Examination Room 105 Stages 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 Amplifiers 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 Condenser lens 203 Shaped aperture array substrate 206,207 Electromagnetic Lenses 208 Deflector 209 Deflector 210 Multi-stage lens array 211 Angle limiting aperture array substrate 212 Bulk 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 Shaped aperture array substrate 310 Electrostatic Lens Array 311 Object surface 319 Image plane 330 Inspection Area 332 Chips 341 Beam size limiting aperture array substrate

Claims

1. an emission source that emits an electron beam in divergent directions; a first condenser lens that refracts the electron beam traveling in a diverging direction into a converging direction to form a substantially parallel beam; a shaping aperture array substrate in which a plurality of first openings are formed, and in which a portion of the electron beam that has become the substantially parallel beam passes through the plurality of first openings to form a multi-electron beam; a two-stage multipole lens array, each lens having a multipole element of quadrupole or more arranged on a trajectory of a beam to be handled among the multiple electron beams; A multi-electron beam irradiation device comprising:

2. 2. The multi-electron beam irradiation device according to claim 1, further comprising an angle-limiting aperture array substrate having a plurality of second openings formed therein, the angle-limiting aperture array substrate limiting the divergence angle or convergence angle of each electron beam by the multi-electron beam passing through the two-stage multipole lens array passing through the plurality of second openings.

3. 2. The multi-electron beam irradiation device according to claim 1, wherein the shaping aperture array substrate forms the multiple electron beams and limits the divergence angle or convergence angle of each electron beam.

4. 2. The multi-electron beam irradiation apparatus according to claim 1, wherein one of the two-stage multipole lens arrays generates a dipole field so that each beam of the multiple electron beams becomes a parallel beam.

5. The multi-electron beam irradiation device according to claim 1, further comprising a multipole lens array disposed between the shaped aperture array substrate and the two-stage multipole lens array, for generating a dipole field so that each beam of the multi-electron beam becomes a parallel beam.

6. 2. The multi-electron beam irradiation apparatus according to claim 1, further comprising a second condenser lens for refracting the multi-electron beams having passed through the two-stage multipole lens array in a focusing direction.

7. 2. The multi-electron beam irradiation apparatus according to claim 1, wherein an electrostatic multipole element is used as the multipole element.

8. 2. The multi-electron beam irradiation apparatus according to claim 1, wherein a magnetic multipole is used as the multipole.

9. The two-stage multipole lens array includes:

2. The multi-electron beam irradiation device according to claim 1, comprising a combination of an electrostatic multipole lens array constituted by electrostatic multipoles and a magnetic multipole lens array constituted by magnetic multipoles.

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

11. emitting an electron beam from an emission source in divergent directions; using a first condenser lens to refract the electron beam traveling in a diverging direction into a converging direction to form a substantially parallel beam; forming a multi-electron beam by passing each part of the electron beam, which has become the substantially parallel beam, through the first openings by using a shaping aperture array substrate having a plurality of first openings; correcting the position of an electron source image in two directions orthogonal to each other for each beam by using a two-stage multipole lens array, each lens having a multipole element of quadrupole or more arranged on a trajectory of a beam in charge of the multiple electron beams; A multi-electron beam irradiation method comprising:

12. 12. The multi-electron beam irradiation method according to claim 11, further comprising a step of limiting the divergence angle or the convergence angle of each electron beam by using an angle-limiting aperture array substrate on which a plurality of second openings are formed, so that the multi-electron beams that have passed through the two-stage multipole lens array pass through the plurality of second openings.

13. 12. The method for irradiating multiple electron beams according to claim 11, wherein the step of forming multiple electron beams includes forming the multiple electron beams and limiting a divergence angle or a convergence angle of each electron beam.

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