Electron beam image acquisition device and electron beam image acquisition method

Abstract

To provide a device capable of correcting color aberration which occurs in a deflection field of a secondary electron beam.SOLUTION: An electron beam image acquisition device comprises: a stage 105 on which a specimen is placed; a primary electron optical system 151; an E×B separator 214; two or more stages of deflectors 218 and 219; and a multi-detector 222. Using independent two orbits xa and xb satisfying an equation that a sum of a product with a value T depending on a rank-1 dispersion orbit of color aberration of a secondary electron beam, which is deflected by a deflection field formed from the separator and the two or more stages of deflectors, and the deflection field and twice differentiations of the dispersion orbit is zero, the deflection field of the separator and the deflection field of each of the two or more stages of deflectors are set in such a manner that a value obtained by integrating a product of a quantity D proportional to the deflection field and the orbit xa with a range of the deflection field is zero and simultaneously that a value obtained by integrating a product of the quantity D proportional to the deflection field and the orbit xb with the range of the deflection field is zero.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to an electron beam image acquisition device and an electron beam image acquisition method, and more particularly to 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 typified by 1-gigabit-class DRAMs (random access memories), the patterns that make up LSIs are now on the order of submicrons to nanometers. As the dimensions of LSI patterns formed on semiconductor wafers have become increasingly miniaturized in recent years, the dimensions that must be detected as pattern defects have also become extremely small. Therefore, high-precision image capture is necessary to inspect defects in ultra-fine patterns transferred onto semiconductor wafers.

[0003] In an inspection device, for example, multiple primary electron beams using electron beams are focused on the substrate to be inspected, and the substrate to be inspected is scanned with the multiple primary electron beams, and multiple secondary electron beams emitted from the substrate to be inspected are separated from the trajectory of the multiple primary electron beams.The separated multiple secondary electron beams are then guided to a detector, which detects the multiple secondary electron beams and captures a pattern image.

[0004] However, when deflecting the secondary electron beam, the higher the energy of the secondary electrons, the lower the deflection sensitivity, which causes a problem of rank 1 chromatic aberration, where the trajectories of the secondary electron beam passing through the deflector are separated depending on the energy differences of the secondary electrons in the beam. Such divergent trajectories cause the secondary electron beam detected by the detector to become blurred.

[0005] To address this issue, a technique has been disclosed in which the chromatic aberration of the electron beam is reduced to zero at a single point determined by two-stage deflection (see, for example, Patent Document 1). However, with this technique, the dispersion trajectory deviates from the central axis of the electron beam trajectory (so-called optical axis) at other points.

[0006] Also disclosed is a technique for correcting deflection chromatic aberration of a primary electron beam by arranging three stages of deflectors so as to satisfy an equation using the inter-deflector distances D5, 6, and 7 of the three stages of deflectors and the deflection angles α, β, and γ (see, for example, Patent Document 2). Patent Document 2 also discloses a technique for correcting axial chromatic aberration of a secondary electron beam using four stages of quadrupole lenses. However, this technique does not adequately address deflection chromatic aberration of a secondary electron beam. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Japanese Patent Application Publication No. 59-083336 [Patent Document 2] Japanese Patent Application Laid-Open No. 2006-221870 Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, one aspect of the present invention provides an apparatus capable of correcting chromatic aberration occurring in the deflection field of a secondary electron beam. [Means for solving the problem]

[0009] An electron beam image acquisition apparatus according to one aspect of the present invention includes: a stage on which a sample is placed; a primary electron optical system that irradiates a sample with a primary electron beam; a separator that is disposed on the trajectory of the primary electron beam and statically deflects a secondary electron beam emitted from the sample by irradiation with the primary electron beam to separate the trajectory of the secondary electron beam from the trajectory of the primary electron beam; a deflector having two or more stages for statically deflecting a secondary electron beam separated from the orbit of the primary electron beam; a detector for detecting the secondary electron beam that has passed through the separator and the two or more stages of deflectors; Equipped with The deflection field of the separator and the deflection fields of each of the deflectors of the two or more stages of deflectors are set so that, using two independent trajectories xa and xb that satisfy an equation in which the sum of the product of the dispersion trajectory due to rank 1 chromatic aberration of the secondary electron beam deflected by the deflection field formed by the separator and the deflection field and a value T depending on the deflection field and the second derivative of the dispersion trajectory is zero, the value obtained by integrating the product of the quantity D proportional to the deflection field and the trajectory xa over the range of the deflection field becomes zero, and at the same time, the value obtained by integrating the product of the quantity D proportional to the deflection field and the trajectory xb over the range of the deflection field becomes zero. It is characterized by:

[0010] It is also preferable to further provide a slit for limiting the energy of the secondary electron beam, which is arranged within a predetermined range from the position where the deviation between the dispersion trajectory of the secondary electron beam due to rank 1 chromatic aberration and the trajectory of secondary electrons having a preset reference energy becomes maximum while the secondary electron beam passes through the deflection field.

[0011] Also, the slit is preferably positioned at a crossover position of the secondary electron beam within the deflection field.

[0012] Alternatively, it is preferable to further include a quadrupole lens disposed between any of the deflectors in a deflector group made up of a separator and two or more stages of deflectors.

[0013] Alternatively, it is preferable that at least one deflector in a deflector group made up of a separator and two or more stages of deflectors not only forms a deflection field but also forms a quadrupole field by superimposing it on the deflection field.

[0014] An electron beam image acquisition method according to one aspect of the present invention includes: irradiating a sample mounted on a stage with a primary electron beam; a step of statically deflecting a secondary electron beam emitted from the sample by irradiation with the primary electron beam using a separator arranged on the orbit of the primary electron beam, thereby separating the orbit of the secondary electron beam from the orbit of the primary electron beam; Statically deflecting a secondary electron beam separated from the orbit of the primary electron beam using a deflector of two or more stages; detecting the secondary electron beam that has passed through the separator and the two or more stages of deflectors using a detector; a step of setting the deflection field of the separator and the deflection field of each deflector of the two or more stages of deflectors so that the value obtained by integrating the product of the quantity D proportional to the deflection field and the trajectory xa over the range of the deflection field by the trajectory xa becomes zero and at the same time the value obtained by integrating the product of the quantity D proportional to the deflection field and the trajectory xb over the range of the deflection field becomes zero, using two independent trajectories xa and xb that satisfy an equation in which the sum of the product of the dispersion trajectory due to rank 1 chromatic aberration of the secondary electron beam deflected by the deflection field formed by the separator and the two or more stages of deflectors and a value T depending on the deflection field and a second derivative of the dispersion trajectory becomes zero; The present invention is characterized by the following.

[0015] Another aspect of the present invention is an electron beam image acquisition apparatus, a stage on which a sample is placed; a primary electron optical system that irradiates a sample with a primary electron beam; a separator that is disposed on the trajectory of the primary electron beam and statically deflects a secondary electron beam emitted from the sample by irradiation with the primary electron beam to separate the trajectory of the secondary electron beam from the trajectory of the primary electron beam; a deflector having two or more stages for statically deflecting a secondary electron beam separated from the orbit of the primary electron beam; a detector for detecting the secondary electron beam that has passed through the separator and the two or more stages of deflectors; Equipped with the deflection field of the separator and the deflection fields of each of the deflectors of the two or more stages are set so that the deviation between the dispersion trajectory of the secondary electron beam due to rank 1 chromatic aberration, which occurs in the deflection field formed by the separator and the two or more stages of deflectors, and the trajectory of the secondary electrons having a preset reference energy falls within a predetermined range downstream of the final stage deflector of the two or more stages of deflectors; It is characterized by: [Effects of the Invention]

[0016] According to one aspect of the present invention, chromatic aberration occurring in the deflection field of the secondary electron beam can be corrected. [Brief explanation of the drawings]

[0017] [Figure 1] FIG. 1 is a configuration diagram showing a configuration of a pattern inspection device according to a first embodiment. [Figure 2] 1 is a top view showing an example of the configuration of a shaping aperture array substrate according to the first embodiment. FIG. [Figure 3] FIG. 3 is a diagram showing an example of a deflection trajectory of a secondary electron beam in the first embodiment. [Figure 4] FIG. 10 is a diagram showing an example of a deflection trajectory and a dispersion trajectory by two-stage deflection in a comparative example of the first embodiment. [Figure 5] FIG. 3 is a diagram showing an example of the trajectory of a secondary electron beam passing through a static deflection field formed by three stages of deflector groups in the first embodiment. [Figure 6] 1 is a block diagram showing an example of the internal configuration of a simulation device according to a first embodiment. [Figure 7A] FIG. 3 is a flowchart showing an example of some of the main steps of the inspection method according to the first embodiment. [Figure 7B] 10 is a flowchart showing an example of the remaining main steps of the inspection method according to the first embodiment. FIG. [Figure 8] 3A and 3B are diagrams illustrating an example of a target trajectory and an example of an electric field according to the first embodiment. [Figure 9A] FIG. 3 is a diagram showing an example of a deflection trajectory in the first embodiment. [Figure 9B] FIG. 3 is a diagram showing an example of the relationship between a deflected orbit and a dispersed orbit in the first embodiment. [Figure 10] FIG. 10 is a diagram showing an example of the relationship between deflected orbits and dispersed orbits in the first modification of the first embodiment. [Figure 11] FIG. 10 is a diagram showing an example of a configuration of a slit in a first modification of the first embodiment. [Figure 12] FIG. 10 is a diagram showing an example of a trajectory of a secondary electron beam passing through a static deflection field formed by three stages of deflector groups in the second modification of the first embodiment. [Figure 13] FIG. 10 is a diagram showing an example of a deflection orbit in the relationship between a deflection orbit and a dispersion orbit in Modification 2 of Embodiment 1. [Figure 14] FIG. 10 is a diagram showing an example of a dispersed orbit in the relationship between a deflected orbit and a dispersed orbit in Modification 2 of Embodiment 1. [Figure 15A] FIG. 10 is a diagram showing an example of a deflection field and a quadrupole field formed in a deflector in the third modification of the first embodiment. [Figure 15B] FIG. 10 is a diagram showing an example of a deflection orbit in the relationship between a deflection orbit and a dispersion orbit in a third modification of the first embodiment. [Figure 15C] FIG. 11 is a diagram showing an example of a dispersed orbit in the relationship between a deflected orbit and a dispersed orbit in a third modification of the first embodiment. [Figure 16] FIG. 13 is a diagram showing an example of a trajectory of a secondary electron beam passing through a static deflection field formed by four stages of deflector groups in the fourth modification of the first embodiment. [Figure 17A] FIG. 13 is a diagram showing an example of a deflection orbit in the relationship between a deflection orbit and a dispersion orbit in a fourth modification of the first embodiment. [Figure 17B] FIG. 13 is a diagram showing an example of a dispersed orbit in the relationship between a deflected orbit and a dispersed orbit in a fourth modification of the first embodiment. [Figure 18] FIG. 2 is a diagram for explaining an example of a method for acquiring an image in the first embodiment. [Figure 19] FIG. 2 is a configuration diagram showing an example of the configuration inside a comparison circuit according to the first embodiment. [Figure 20]FIG. 10 is a diagram showing an example of the configuration of an image acquisition mechanism of an inspection device according to a second embodiment. [Figure 21] FIG. 10 is a diagram showing an example of a dispersion trajectory in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0018] In the following embodiments, a case where multiple beams are used as electron beams will be described. However, the electron beam is not limited to multiple beams, and may be a single beam. Furthermore, a multi-electron beam inspection device will be described as an example of an electron beam image acquisition device. However, the electron beam image acquisition device is not limited to an inspection device, and may be, for example, a scanning electron microscope (SEM) or the like.

[0019] Embodiment 1 FIG. 1 is a configuration diagram showing the configuration of a pattern inspection apparatus in embodiment 1. In FIG. 1, an inspection apparatus 100 that inspects a pattern formed on a substrate is an example of a multi-electron beam inspection apparatus. The inspection apparatus 100 is an example of an electron beam image acquisition apparatus. The inspection apparatus 100 is an example of a multi-electron beam image acquisition apparatus. The inspection apparatus 100 includes an image acquisition mechanism 150 and a control system circuit 160 (control unit). The image acquisition mechanism 150 includes an electron beam column 102 (electron lens barrel), an inspection chamber 103, a detection circuit 106, a chip pattern memory 123, a stage driving mechanism 142, and a laser length measurement system 122. The electron beam column 102 includes an electron gun 201, an electromagnetic 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 E×B separator 214 (separator), an electromagnetic lens 207 (objective lens), deflectors 208 and 209, a group of deflectors 217 with two or more stages, a deflector 226, an electromagnetic lens 224, and a multi-detector 222.

[0020] 1, the deflector group 217 is shown to be configured with two stages of deflectors, for example, a deflector 218 (first bender) and a deflector 219 (second bender). Either electrostatic deflectors or electromagnetic deflectors may be used as the deflector group 217. Below, for example, a case where an electrostatic deflector is used will be described.

[0021] The primary electron optical system 151 (illumination optical system) is configured by the electron gun 201, the electromagnetic lens 202, the electromagnetic lens 205, the collective deflector 212, the limiting aperture substrate 213, the electromagnetic lens 206, the E×B separator 214 (separator), the electromagnetic lens 207, and the deflectors 208 and 209. The secondary electron optical system 152 (detection optical system) is configured by the electromagnetic lens 207, the E×B separator 214, the deflector group 217, the deflector 226, and the electromagnetic lens 224.

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

[0023] 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. If the substrate 101 is a semiconductor substrate, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. If 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 substrate 101 is disposed on the stage 105, for example, with its pattern-forming surface facing upward. Also disposed on the stage 105 is a mirror 216 that reflects laser light for laser measurement irradiated from a laser measurement system 122 disposed outside the inspection chamber 103. Also disposed on the stage 105 is a mark 111 disposed at the same height as the surface of the substrate 101. The mark 111 has, for example, a cross pattern formed thereon.

[0024] 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.

[0025] 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 chromatic aberration correction circuit 130, an E×B separator control circuit 132, a storage device 109 such as a magnetic disk drive, a monitor 117, a memory 118, and a printer 119. The deflection control circuit 128 is also connected to DAC (digital-to-analog conversion) amplifiers 144, 146, and 147 and DC power supplies 148 and 149. The DAC amplifier 146 is connected to a deflector 208, and the DAC amplifier 144 is connected to the deflector 209. The DC power supply 148 is connected to a deflector 218. The DC power supply 149 is connected to the deflector 219. The DAC amplifier 147 is connected to a deflector 226.

[0026] 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.

[0027] The electromagnetic lens 202 , the electromagnetic lens 205 , the electromagnetic lens 206 , the electromagnetic lens 207 , and the electromagnetic lens 224 are controlled by the lens control circuit 124 .

[0028] The collective deflector 212 is composed of two or more electrodes, and is controlled by the blanking control circuit 126 for each electrode via a DAC amplifier (not shown). The deflector 209 is composed of four or more electrodes, and is controlled by the deflection control circuit 128 for each electrode via a DAC amplifier 144. The deflector 208 is composed of four or more electrodes, and is controlled by the deflection control circuit 128 for each electrode via a DAC amplifier 146. The deflector 226 is composed of four or more electrodes, and is controlled by the deflection control circuit 128 for each electrode via a DAC amplifier 147.

[0029] The deflector 218 (first bender) is configured, for example, by a plurality of electrodes having four or more poles and in the shape of a cylinder bent in an arc, and each electrode is controlled by the deflection control circuit 128 via a DC power supply 148. The deflector 219 (second bender) is configured, for example, by a plurality of electrodes having four or more poles and in the shape of a cylinder bent in an arc, and each electrode is controlled by the deflection control circuit 128 via a DC power supply 149. Alternatively, the deflector 218 (219) may be configured by a plurality of flat electrodes having four or more poles and controlled by the deflection control circuit 128 via a DC power supply 148 (149) for each electrode.

[0030] The E×B separator 214 is controlled by the E×B separator control circuit 132 .

[0031] 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.

[0032] 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.

[0033] FIG. 2 is a top view showing an example of the configuration of the shaping aperture array substrate according to the first embodiment. In FIG. 2, holes (apertures) 22 are formed in a two-dimensional array of m1 columns (x direction) by n1 rows (y direction) (m1 and n1 are integers of 2 or greater) on the shaping aperture array substrate 203 at a predetermined arrangement pitch in the x and y directions. The example in FIG. 2 shows, for example, a case where 5 × 5 holes (apertures) 22 are formed. All the holes 22 are formed in a circular shape with the same dimensions. Alternatively, all the holes 22 may be formed in a rectangular shape with the same dimensions. Portions of the electron beam 200 pass through these 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.

[0034] The image acquisition mechanism 150 irradiates the substrate 101 on which a graphic pattern is formed with the multiple primary electron beams 20. Then, an inspection image of the graphic pattern is acquired from the substrate 101. The operation of the image acquisition mechanism 150 in the inspection device 100 will be described below.

[0035] An electron gun 201 (an example of an emission source) emits an electron beam 200 in a diverging direction. The electron beam 200 emitted from the electron gun 201 and traveling in a diverging direction is refracted in a converging direction by an electromagnetic lens 202. The electron beam 200 then illuminates the entire shaping aperture array substrate 203. As shown in FIG. 2 , a plurality of holes 22 are formed in the shaping aperture array substrate 203, and the electron beam 200 illuminates an area that includes all of the plurality of holes 22. Portions of the electron beam 200 irradiated 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.

[0036] The formed multiple primary electron beams 20 are refracted by electromagnetic lenses 205 and 206 to form a crossover and an intermediate image, and proceed to an E×B separator 214 that is located at the height of the intermediate image plane (image plane conjugate position) of the electron source image of each beam of the multiple primary electron beams 20. Then, the multiple primary electron beams 20 pass through the E×B separator 214 and proceed to an electromagnetic lens 207. Moreover, scattered beams can be shielded by arranging a limiting aperture substrate 213 with limited passage holes near the crossover position of the multiple primary electron beams 20. Moreover, the entire multiple primary electron beams 20 can be blanked by collectively deflecting the entire multiple primary electron beams 20 using the collective deflector 212 and shielding the entire multiple primary electron beams 20 with the limiting aperture substrate 213.

[0037] When the multiple primary electron beams 20 are incident on the electromagnetic lens 207, the electromagnetic lens 207 forms an image of the multiple primary electron beams 20 on the substrate 101. In other words, the electromagnetic lens 207 irradiates the substrate 101 with the multiple primary electron beams 20.

[0038] The multi-primary electron beams 20, which are 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 way, the primary electron optical system 151 illuminates the substrate 101 with the multi-primary electron beams 20. At this time, the multi-primary electron beams 20 are decelerated to a predetermined energy by a decelerating electric field applied between an electrode (not shown) and the substrate.

[0039] When a desired position on the substrate 101 is irradiated with the multiple primary electron beams 20, a bundle 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.

[0040] The multiple secondary electron beams 300 emitted from the substrate 101 are accelerated by a decelerating electric field relative to the primary electron beam, pass through the electromagnetic lens 207, and proceed to the E×B separator 214. The increase in energy of the secondary electrons due to acceleration is, for example, Edec. Secondary electrons emitted with initial energy of approximately 0 have an energy of Edec after being accelerated. Therefore, the minimum energy of the secondary electrons after acceleration can be taken as Edec.

[0041] The E×B separator 214 separates the trajectories of the multiple secondary electron beams 300 from the trajectories of the multiple primary electron beams 20 .

[0042] The E×B separator 214 has two or more magnetic poles (electromagnetic deflection coils) using coils and two or more electrodes (electrostatic deflection electrodes). For example, two opposing magnetic poles and two opposing electrodes shifted in phase by 90° may be arranged. The arrangement is not limited to this. For example, electrodes may also function as magnetic poles, and four or eight electrodes / magnetic poles may be arranged. The E×B separator 214 deflects the multiple secondary electron beams 300 to generate a separation effect. The E×B separator 214 generates a directional magnetic field using multiple magnetic poles. Similarly, it generates a directional electric field using multiple electrodes. Specifically, the E×B separator 214 generates an electric field E and a magnetic field B in orthogonal directions on a plane orthogonal to the direction of travel of the central beam (the orbital central axis) of the multiple primary electron beams 20. An electric field exerts a force in the same direction regardless of the direction of electron travel. In contrast, a 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 F E due to the electric field and the force F B due to the magnetic field cancel each other out on 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 F E due to the electric field and the force F B 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 bent obliquely upward by being statically deflected in a predetermined direction, and are separated from the trajectory of the multi primary electron beams 20.

[0043] The multi secondary electron beams 300, which have been bent obliquely upward and separated from the multi primary electron beams 20, are guided to the multi-detector 222 by the secondary electron optical system 152. Specifically, the multi secondary electron beams 300, which have been separated from the multi primary electron beams 20, are statically deflected by a group of deflectors 217 having two or more stages, whereby they are further bent, and proceed to the electromagnetic lens 224. The multi secondary electron beams 300 are then projected onto the multi-detector 222 while being refracted in the focusing direction by the electromagnetic lens 224 at a position away from the trajectories of the multi primary electron beams 20. The multi-detector 222 (multi-secondary electron beam detector) detects the multi secondary electron beams 300 which have been separated from the trajectories of the multi primary electron beams 20. In other words, the multi-detector 222 detects the refracted and projected multi secondary electron beams 300. The multi-detector 222 has a plurality of detection elements (for example, a diode-type two-dimensional sensor, not shown). Each beam of the multi primary electron beams 20 collides with a detection element corresponding to each secondary electron beam of the multi secondary electron beams 300 on the detection surface of the multi detector 222, generating electrons and generating secondary electron image data for each pixel. The intensity signal detected by the multi detector 222 is output to the detection circuit 106.

[0044] Furthermore, in order to acquire an image of the pattern on the substrate 101, it is necessary to scan the substrate 101 with the multiple primary electron beams 20. Such scanning is achieved, for example, by dynamically deflecting the multiple primary electron beams 20 using deflectors 208 and 209. Therefore, the positions of the secondary electron beams emitted from the substrate 101 irradiated with each primary electron beam change constantly. Furthermore, when the stage 105 is scanned while continuously moving, the multiple primary electron beams 20 are dynamically deflected by the deflectors 208 and 209 to follow the movement of the stage 105 in order to maintain the irradiation position of the multiple primary electron beams 20 at a desired position. This is called trunking control. Meanwhile, the position of each emitted secondary electron beam changes constantly by the amount of stage movement. Therefore, if this continues, each secondary electron beam will not be able to reach the corresponding detection element of the multi-detector 222. Therefore, the deflector 226 keeps the multi-secondary electron beams 300 stationary by dynamically performing scanning with the multi-primary electron beams 20 and deflection by trunking control to reverse the deflection so that each secondary electron beam can reach the corresponding detection element of the multi-detector 222.

[0045] As described above, in the first embodiment, the E×B separator 214 deflects the secondary electron beam by static beam deflection, and the deflector group 217 further deflects the secondary electron beam by static beam deflection. Here, "static" means a state in which the beam is not touched once certain conditions are determined. Therefore, static beam deflection is a deflection in which a determined deflection field state is maintained while the inspection apparatus 100 is in operation.

[0046] FIG. 3 is a diagram showing an example of a deflection trajectory of a secondary electron beam in the first embodiment. When deflecting a secondary electron beam, the higher the energy of the secondary electrons, the lower the deflection sensitivity. This causes a problem in that the trajectory of the secondary electron beam passing through the deflector has rank 1 chromatic aberration (deflection chromatic aberration), which has a dispersed trajectory that separates depending on the energy of the secondary electrons in the beam. This causes the secondary electron beam detected by the detector to become blurred. In the example of FIG. 3, with respect to the trajectory (deflection trajectory, central axis trajectory) (so-called optical axis) of electrons with energy less than the reference energy E0, the trajectory is more deflected than the central axis trajectory after deflection (an example of a dispersed trajectory). Conversely, the trajectory of electrons with energy greater than the reference energy E0 is more deflected than the central axis trajectory after deflection (another example of a dispersed trajectory).

[0047] FIG. 4 is a diagram showing an example of a deflection trajectory and a dispersion trajectory by two-stage deflection in a comparative example of the first embodiment. In the comparative example, the chromatic aberration of the electron beam is reduced to zero at a point determined by two-stage deflection. However, with this technology, the dispersion trajectory deviates from the central axis trajectory (so-called optical axis) of the electron beam at other points, as shown by wkx in FIG. 4. Therefore, deflection chromatic aberration may occur on the detection surface of the detector. Xaxis in FIG. 4 is the X coordinate of the central axis trajectory in a fixed coordinate system, and the definition of Xaxis will be described later.

[0048] Therefore, in the first embodiment, the dispersion trajectory of the secondary electron beam caused by the rank 1 chromatic aberration caused by statically deflecting the secondary electron beam is made to coincide with the central axis trajectory of the secondary electron beam after passing through the final stage deflector, or the deviation of the dispersion trajectory from the central axis trajectory is kept within a desired range. To achieve this, in the first embodiment, the deflection field of a total of three or more stages of deflector groups, including the E×B separator 214 that statically deflects the secondary electron beam and the two or more stages of deflector groups 217, is controlled. This will be explained in detail below.

[0049] Here, we use a right-handed orthogonal curvilinear coordinate system to describe the trajectory. Distance s is the length measured from the object surface along the reference trajectory. The z-axis is taken as the direction of travel of the reference trajectory. We consider the case where the reference trajectory is on a plane. At a point s away from the object surface, the unit direction vector (0,0,1) is defined as being parallel to the tangent to the reference trajectory at that point, distance s, and positive in the direction of travel of the electron. (1,0,0) is taken as being perpendicular to the reference trajectory and parallel to the curvature vector. (0,1,0) is defined as (0,0,1) × (1,0,0) (× is the cross product of the vectors). When a point is expressed as (x,y,s) or (x(s),y(s)), that point refers to the position of the point on the reference trajectory at distance s from the object surface, with x in the (1,0,0) direction and y in the (0,1,0) direction. When it is not necessary to specify the distance s from the object surface, the third coordinate may be omitted and it may be expressed simply as (x, y). When the optical axis is used as the reference trajectory, these expressions are used for the coordinates on the optical axis. In a region where the trajectory is linear, the direction of (1, 0, 0) from the object surface until deflection begins is made to coincide with (1, 0, 0) determined by the curvature vector first defined downstream. Furthermore, the direction of (1, 0, 0) after deflection ends is made to coincide with (1, 0, 0) defined at the closest upstream position. In this invention, the central axis trajectory (the so-called optical axis) is taken as the reference trajectory.

[0050] First, when an electron is emitted from a position (xo, yo) on the object plane (s=0) at an emission angle (xo', yo') with an energy shifted by κ·E0 from the reference energy E0, the deviation of the electron's trajectory from the reference trajectory at a distance s from the object plane is defined as (Xdev(s), Ydev(s)). Then, the following equation (1-1) is defined as a complex expression, where I is the imaginary unit.

[0051]

number

[0052] Furthermore, assuming that x0, y0, x0', y0', and κ are infinitesimal quantities and Σ is the sum when n1,...,n4, and l are expanded from 0 to infinity, when equation (1-1) is expanded as in equation (1-2), the rank r is defined by equation (1-3). Among the trajectories given by equation (1-4), those that satisfy Wab(0) = 0 and Wab'(0) = 0 are called rank 1 chromatic aberration dispersion trajectories or rank 1 dispersion trajectories. Here, when s = si indicates the irradiation surface, A(0,0,0,0,1,si)·κ gives rank 1 chromatic aberration. An example of rank 1 chromatic aberration is deflection chromatic aberration, in which the trajectory splits when the secondary electrons are deflected by a deflector depending on their energy, as shown in Figure 3. When deflection chromatic aberration occurs, the central axis trajectory of secondary electrons having a preset reference energy E0 (the trajectory on which electrons having the reference energy E0 that coincide in position and direction with the trajectory at a certain point remain and move, the so-called optical axis) does not coincide with the dispersed trajectories of secondary electrons having other energies. As the reference energy E0, it is preferable to preset, for example, the energy at the center of gravity of the energy distribution of secondary electrons, or the minimum value Edec of the energy distribution of secondary electrons.

[0053] Next, we will explain the theory behind how the dispersion trajectory is made to coincide with the central axial trajectory (the so-called optical axis) after passing through the deflection field. We will consider a case where there is no acceleration / deceleration and no magnetic field components parallel to the central axial trajectory. We will assume that the deflection electric field exists in the x direction and the deflection magnetic field exists in the y direction. We will approximate that the axis of the quadrupole field coincides with the central axial trajectory. Regarding the quadrupole field, we will assume that the quadrupole electric field is symmetric with respect to the xz plane, and the quadrupole magnetic field is antisymmetric. Here, if the central axis trajectory (the so-called optical axis) after deflection by the deflector is taken as the deflection trajectory, the deflection trajectory exists within a plane, and as mentioned above, the z-axis is taken along the optical axis in the plane containing the deflection trajectory, and the x-axis is taken perpendicular to the z-axis within the plane. The deflection field generated by the deflector is assumed to exist between Zf1 and Zf2 shown in the following equation (2-1). Zs and Ze are the coordinates of the start and end points when calculating the trajectory.

[0054]

number

[0055] Note that the velocity of secondary electrons in the optical axis direction is assumed to be constant in the region where the deflection field exists. In this case, the rank 1 dispersed trajectory xc can be defined by equation (2-2). (2-2) is called the paraxial trajectory equation that secondary electrons follow. xc″ indicates the state where xc is differentiated twice with respect to Z. However, xc(Zs) = 0 and xc(Zs)' = 0. xc(Zs)′ indicates the state where xc(Zs) is differentiated once with respect to Z. If κ = 0, xc(Zs) = 0, and xc(Zs)′ = 0, then xc(z) = 0 satisfies (2-2). In other words, when an electron with a certain energy departs from the central axis (the so-called optical axis) parallel to the central axis (the so-called optical axis), its trajectory is always on the optical axis. Furthermore, the real number T represents a quantity that depends on the deflection field (deflection electric field Ex and / or deflection magnetic field By), or a quantity that depends on the deflection field (deflection electric field Ex and / or deflection magnetic field By), and the quadrupole electric field EQ and quadrupole magnetic field BQ. The real number T is defined by equation (2-3). F is a function. The deflection field (deflection electric field Ex and / or deflection magnetic field By), and the quadrupole fields EQ and BQ change with position Z, so the real number T changes with position Z. In regions where only a uniform deflection field exists, T consists of quadratic terms of Ex and By and takes a positive value. The second term on the left side of (2-2) indicates that a focusing force acts on the deviation of the trajectory from the optical axis. The real number D is a quantity that depends on the deflection fields Ex and By. The quadrupole field also includes the quadrupole field experienced by electrons when their orbits pass obliquely relative to the pole tips of the deflection magnetic field. The trajectory calculations used in the following explanation include the quadrupole field associated with the deflection magnetic field when the orbit passes obliquely through the E×B separator. In addition, in this explanation, the deflection electric field is assumed to be one created by a deflector with infinite width in the y direction. For example, by using an octupole and providing an appropriate potential distribution, such a deflection electric field can be realized with a good approximation near the center. The quantity D is a linear function of the deflection field (deflecting electric field Ex and / or deflecting magnetic field By) and is defined by equation (2-4). F and G also depend on the energy. Furthermore, κ represents the ratio (κ=ΔV / V0) between the voltage V0 corresponding to the reference energy E0 and the voltage deviation ΔV corresponding to the deviation of energy from the reference energy E0.

[0056] Here, let xa and xb be two independent orbits that satisfy the condition κ=0, i.e., (2-2) when the right-hand side = 0. In other words, xa and xb are independent solutions to the following paraxial orbit equation (3-1) followed by electrons with the same specified energy. Now, if we consider a deflection field, for example, a deflection electric field Ex, T is proportional to Ex^2. On the other hand, the deflection angle is approximately proportional to the amount obtained by integrating Ex. Therefore, even if the deflection angle is the same, xa and xb will take different forms for deflectors of different lengths. The same is true for deflection magnetic fields. The dispersion trajectory xc is defined as shown in equation (3-2) using coefficient functions α(z) and β(z) and two trajectories xa and xb. In other words, two independent trajectories xa and xb are used, such that the sum of the product of the dispersion trajectory xc of rank 1 of the chromatic aberration of the secondary electron beam deflected by the deflection field and the value T that depends on the deflection field and the second derivative of the dispersion trajectory xc is zero.

[0057]

number

[0058] Outside the deflector, that is, when z≧Zf2 and both α(z) and β(z) are simultaneously 0, the dispersion trajectory xc coincides with the central axis trajectory (so-called optical axis) of the secondary electron beam. The condition for this to be met is that the two trajectories xa and xb simultaneously satisfy the following equation (4-1), which shows that the product of the quantity D proportional to the deflection field and the trajectory xa is zero when integrated over the range of the deflection field, and equation (4-2), which shows that the product of the quantity D proportional to the deflection field and the trajectory xb is zero when integrated over the range of the deflection field. Here, the upper limits of the integral are Ze and Zs instead of Zf1 and Zf2, including the region where no field exists (D = 0). In this case, the dispersion trajectory xc on the outer downstream side of the deflection field satisfies equation (4-3). This means that it coincides with the central axis trajectory (optical axis).

[0059]

number

[0060] For the two trajectories xa and xb, for example, trajectories that satisfy the following equations (5-1) and (5-2) can be selected at a position Zs that is sufficiently upstream of the incidence point of the deflection field and can be considered to have no electric or magnetic field. Note that the orbitals that satisfy equation (3-1) are not limited to orbitals xa and xb that satisfy (5-1) and (5-2), but can be expressed as a linear combination of orbitals xa and xb that satisfy (5-1) and (5-2). This makes it possible to create orbitals whose values ​​and slopes at z = Zs are different from those of (5-1) and (5-2).

[0061]

number

[0062] In the first embodiment, based on this theory, the deflection field of a total of three or more stages of deflector groups, including the E×B separator 214 that statically deflects the secondary electron beam and the two or more stages of deflector groups 217, is calculated.

[0063] FIG. 5 is a diagram showing an example of the trajectory of a secondary electron beam passing through a static deflection field formed by a three-stage deflector group in the first embodiment. In FIG. 5, the three-stage deflector group includes the E×B separator 214, the deflector 218, and the deflector 219. In the example of FIG. 5, one secondary electron beam 301 is shown as a representative of the multiple secondary electron beams 300. For example, this may be the central beam of the multiple secondary electron beams 300. The z-axis indicates the direction along the central axial trajectory (optical axis) of the secondary electron beam. In the example of FIG. 5, the direction of the central axial trajectory (optical axis) of the secondary electron beam emitted from the substrate 101 and heading toward the E×B separator 214 is shown as the z-axis. Therefore, after deflection by each deflector, the direction of the z-axis changes along the central axial trajectory (optical axis).

[0064] 5, the secondary electron beam 301 is bent diagonally upward to the right on the page by static deflection by the E×B separator 214. Thereafter, the secondary electron beam 301 is bent further diagonally upward to the right on the page by static deflection by the deflector 218. Thereafter, the secondary electron beam 301 is bent in the opposite direction to the deflector 218 by static deflection by the deflector 219. After passing through the final-stage deflector 219, the secondary electron beam 301 follows a trajectory that proceeds in a straight line toward the multi-detector 222 unless dynamic deflection is performed.

[0065] 6 is a block diagram showing an example of the internal configuration of the simulation apparatus according to the first embodiment. In FIG. 6, the simulation apparatus 600 includes a memory 61, a storage device 63 such as a magnetic disk device, a target trajectory setting unit 60, an electric field (magnetic field) setting unit 62, a T calculation unit 66, a D calculation unit 68, a trajectory xa, xb calculation unit 70, a distributed trajectory calculation unit 72, a determination unit 74, a deflector shape determination unit 76, and a voltage determination unit 78. Each of the "units" such as the target trajectory setting unit 60, the electric field (magnetic field) setting unit 62, the T calculation unit 66, the D calculation unit 68, the trajectory xa, xb calculation unit 70, the distributed trajectory calculation unit 72, the determination unit 74, the deflector shape determination unit 76, and the voltage determination unit 78 includes a processing circuit, and the processing circuit may include an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, or the like. Furthermore, each of the "units" may share 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 target trajectory setting unit 60, electric field (magnetic field) setting unit 62, T calculation unit 66, D calculation unit 68, trajectory xa, xb calculation unit 70, distributed trajectory calculation unit 72, judgment unit 74, deflector shape determination unit 76, and voltage determination unit 78 are stored in memory 61 each time. The simulation device 600 is arranged outside the inspection device 100. Alternatively, it may be arranged inside the inspection device 100. For example, each function of the simulation device 600 may be arranged in the chromatic aberration correction circuit 130.

[0066] FIG. 7A is a flowchart illustrating an example of some of the main steps of the inspection method according to the first embodiment. FIG. 7B is a flowchart showing an example of the remaining main steps of the inspection method according to the first embodiment. 7A and 7B, the inspection method in embodiment 1 carries out a series of steps including a target trajectory setting step (S102), an electric field (magnetic field) setting step (S104), a T and D calculation step (S106), an independent trajectory xa and xb calculation step (S108), a distributed trajectory calculation step (S110), a judgment step (S112), a shape, arrangement position and voltage determination step of each deflector (S120), a manufacturing and arrangement step of each deflector (S124), a voltage setting step of each deflector (S130), an image acquisition step (S140), and a comparison step (S150).

[0067] Of the above-mentioned steps, the simulation device 600 performs the following: a target trajectory setting step (S102), an electric field (magnetic field) setting step (S104), a T, D calculation step (S106), an independent trajectory xa, xb calculation step (S108), a deflection trajectory calculation step (S110), a judgment step (S112), and a shape, arrangement position, and voltage determination step (S120) of each deflector.

[0068] In the first embodiment, the dispersion trajectory of the secondary electron beam caused by rank 1 chromatic aberration due to static deflection of the secondary electron beam is made to coincide with the optical axis (central axis trajectory) of the secondary electron beam after passing through the final-stage deflector, or the deviation of the dispersion trajectory from the optical axis of the secondary electron beam is kept within a desired range. To achieve this objective, first, using the simulation device 600, the shape, arrangement position, and deflection voltage of each of the three or more stages of deflectors, including the E×B separator 214 that statically deflects the secondary electron beam and the two or more stages of deflector group 217, which satisfies this objective, are obtained by simulation.

[0069] In the target trajectory setting step (S102), the target trajectory setting unit 60 sets a target trajectory, which is a deflection trajectory to be generated by each of three or more stages of deflectors, including the E×B separator 214 and the two or more stages of deflector group 217, arranged in the inspection device 100. For example, the target trajectory is set as a deflection trajectory from a position Zs, shown in FIG. 5, sufficiently upstream of the incident point on the E×B separator 214, where it is assumed that there are no electric or magnetic fields, to a position Ze, sufficiently downstream after passing through the final deflector, where it is assumed that there are no electric or magnetic fields. In the example of FIG. 5, a deflection trajectory is assumed to be generated by a total of three stages of deflectors, including the E×B separator 214 and two stages of deflectors 218 and 219. Note that if there is no dynamic beam deflection, the non-deflected trajectory (optical axis) not affected by the deflectors from position Ze to the multi-detector 222 will be a straight trajectory.

[0070] In the electric field (magnetic field) setting step (S104), the electric field (magnetic field) setting unit 62 sets an electric field or / and a magnetic field on the set target trajectory.

[0071] FIG. 8 is a diagram showing an example of a target trajectory and an example of an electric field in the first embodiment. The example in FIG. 8 shows a case where an electric field and / or magnetic field for deflecting the trajectory is set on the target trajectory using a total of three stages of deflectors, including the E×B separator 214 and two stages of deflectors 218 and 219. In FIG. 8, the range (length) and strength of the electric field are set at each position. The position where the electric field etc. is set is the point where the trajectory bends in the set target trajectory. For example, the center (center of gravity) of the electric field is set at the center of the point where the trajectory bends. The deflection field (deflection electric field Ex and / or deflection magnetic field By) is determined by the range (length) and strength of the electric field (or magnetic field).

[0072] In the T and D calculation step (S106), the T calculation unit 66 calculates a real number T, which is a quantity that depends on the set deflection field (deflection electric field Ex and / or deflection magnetic field By), or a quantity that depends on the deflection field (deflection electric field Ex and / or deflection magnetic field By) and the quadrupole field EQ. The real number T can be calculated using equation (2-3). For example, when the deflector group 217 is composed of only deflectors, the function F that determines the real number T is expressed as a quadratic polynomial with the deflection field Ex and the magnetic field By as variables. Alternatively, when the deflector group 217 further includes quadrupole lenses, the function F is expressed as a sum of a quadratic polynomial of the deflection field Ex and the magnetic field By and a polynomial with the quadrupole field EQ as a linear variable. When electrostatic deflectors are used as the deflector group 217, the deflection field generated by the deflector group 217 is formed by the deflection electric field Ex. When an electromagnetic deflector is used as the deflector group 217, the deflection field generated by the deflector group 217 is formed by a deflection magnetic field By. Since both an electric field and a magnetic field are generated in the E×B separator 214, the deflection field is formed by a deflection electric field Ex and a deflection magnetic field By. In the E×B separator 214, the deflection electric field Ex and the deflection magnetic field By determine the direction in which the primary electron beam travels through the E×B separator 214.

[0073] The D calculation unit 68 calculates the quantity D proportional to the deflection field (deflection electric field Ex and / or deflection magnetic field By). The quantity D can be obtained, for example, by equation (2-4).

[0074] In the independent trajectory xa, xb calculation step (S108), the trajectory xa, xb calculation unit 70 calculates two independent trajectories xa, xb such that the sum of the product of a rank 1 dispersion trajectory xc of the secondary electron beam deflected by the deflection field and a value T that depends on the deflection field and the second derivative of the dispersion trajectory xc is zero. The independent trajectories xa, xb are calculated to satisfy equation (3-1) as described above. Furthermore, the relationship between the independent trajectories xa, xb and the dispersion trajectory xc satisfies equation (3-2).

[0075] In the dispersed trajectory calculation step (S110), the dispersed trajectory calculation unit 72 calculates dispersed trajectory Xc using the calculated independent trajectories xa and xb. The dispersed trajectory xc is calculated so as to satisfy equation (3-2). Note that functions α(z) and β(z) are set so as to satisfy equation (2-2) using dispersed trajectory xc.

[0076] In the determination step (S112), the determination unit 74 uses two independent trajectories xa and xb to determine whether the product of the quantity D proportional to the deflection field and the trajectory xa, integrated over the range of the deflection field (Zs≦Z≦Ze), is zero, and the product of the quantity D proportional to the deflection field and the trajectory xb, integrated over the range of the deflection field, is zero. In other words, the determination unit 74 determines whether the two trajectories xa and xb simultaneously satisfy both equations (4-1) and (4-2). If the two trajectories xa and xb simultaneously satisfy both equations (4-1) and (4-2), the process proceeds to the step (S120) of determining the shape, placement position, and voltage of each deflector. If the two orbits xa and xb do not simultaneously satisfy the formula (4-1) and the formula (4-2), the process returns to the electric field (magnetic field) setting step (S104), and the steps from the electric field (magnetic field) setting step (S104) to the determination step (S112) are repeated while changing the electric field (magnetic field) settings until the two orbits xa and xb simultaneously satisfy the formula (4-1) and the formula (4-2).

[0077] In addition, even if the number of times the independent trajectories xa and xb have been determined reaches a preset number of calculations m, if the two trajectories xa and xb do not simultaneously satisfy the formula (4-1) and the formula (4-2), the process may return to the target trajectory setting unit (S102) to change the setting of the target trajectory, and each step from the target trajectory setting unit (S102) to the determination step (S112) may be repeated while changing the setting of the target trajectory.

[0078] In the step (S120) of determining the shape, position, and voltage of each deflector, the deflector shape determination unit 76 determines the shape and position of each deflector capable of generating an electric field and / or a magnetic field under the condition that the two trajectories xa and xb simultaneously satisfy Equation (4-1) and Equation (4-2). The shape of each deflector is determined based on the range (length) and strength of the electric field and / or the magnetic field. For example, the length of each electrode, the shape of the electrode, the distance between opposing electrodes, etc. are determined. The shape of the electrode may be a columnar shape in which the electron path inside the deflector is linear, or it may be an arcuate cylindrical shape in which the electron path inside the deflector follows an arcuate trajectory. When manufacturing an arcuate deflector, the shape information includes, for example, the curvature of the electron trajectory. Furthermore, the voltage determination unit 78 determines deflection voltages V1, V2, and V3 of each deflector capable of generating an electric field and / or a magnetic field under these conditions. A deflection voltage V1 is applied to the E×B separator 214. Deflection voltages V2 and V3 are applied to the deflectors 218 and 219. V1 is a collective term for the deflection voltages applied to the electrode group of the E×B separator 214. V2 is a collective term for the deflection voltages applied to the electrode group of the deflector 218. V3 is a collective term for the deflection voltages applied to the electrode group of the deflector 219. Information on the determined shape, arrangement position, and voltage of each deflector is stored in the storage device 63 and output to the outside. Information on the determined voltage of each deflector is input to the inspection device 100 and then to the chromatic aberration correction circuit 130.

[0079] As a result of the above, it is possible to obtain one solution (here, the shape, arrangement position, and deflection voltages V1, V2, V3 of each deflector) that can correct the dispersed trajectory of rank 1 of the multi-two electron beam 300. Since there may be more than one solution, it is possible to return to the target trajectory setting unit (S102) or the electric field (magnetic field) setting step (S104) and search for another solution.

[0080] In the manufacturing and arranging step (S124) of each deflector, each deflector is manufactured according to the determined shape and arrangement position of each deflector. Then, each manufactured deflector is arranged in the inspection apparatus 100.

[0081] In the voltage setting step (S130) for each deflector, the chromatic aberration correction circuit 130 sets a deflection potential V1 to be applied to the E×B separator 214 in the E×B separator control circuit 132. The E×B separator also generates a magnetic field corresponding to the deflection voltage V1 so that the primary electron beam travels in a straight line. The chromatic aberration correction circuit 130 also sets deflection voltages V2 and V3 to be applied to the deflectors 218 and 219 in the deflection control circuit 130.

[0082] As a result, the deviation of the dispersion trajectory xc from the trajectory of the reference energy E0 can be kept to zero or within a predetermined range on the downstream side (the multi-detector 222 side) of the range of the deflection field (Zs≦Z≦Ze). In other words, the deflection fields of the E×B separator 214 and the deflectors of the two or more stages 218 and 219 are set so that the deviation between the dispersion trajectory xc of rank 1 of the secondary electron beam generated in the deflection field formed by the E×B separator 214 and the two or more stages of deflectors 218 and 219 and the central axis trajectory (deflection trajectory, optical axis) of the secondary electrons having a preset reference energy E0 falls within a predetermined range downstream of the final stage deflector 219 of the two or more stages of deflectors 218 and 219.

[0083] Furthermore, if the deflection trajectory deviates from the target trajectory due to manufacturing errors, or if V1, V2, and V3 are changed to bring the deflection trajectory closer to the target trajectory, the rank 1 dispersion trajectory may deviate from the optical axis downstream of the deflector group. In this case, if the change in V1, V2, and V3 is small, fine adjustments are made so that the direction of the deflection trajectory faces the desired direction under conditions where the deviation of the dispersion trajectory is small. Furthermore, if there are four or more stages of deflectors, the direction and position of the deflection trajectory can be finely adjusted. For efficient fine adjustments, it is recommended to create a parameter list in advance by calculating examples of deviations in the deflection trajectory and dispersion trajectory in response to deviations in the deflection field conditions, and then make adjustments based on this list.

[0084] On the other hand, as a method for expanding the adjustment range, the deflection electrodes of deflectors 218 and 219 are configured, for example, so that the electrodes are divided into three in the beam propagation direction, and the bore diameters of the electrodes at both ends (the distance between the opposing electrodes) are made variable. If the chromatic aberration of rank 1 exceeds the allowable range when the deflection voltages V1, V2, and V3 are set so that the deflection trajectory approaches the target trajectory, the bore diameters of the electrodes at both ends are changed to change the deflection electric field distribution, V2 and V3 are adjusted to correct the deflection trajectory so that it falls within the allowable range, and the chromatic aberration of rank 1 is then measured. By repeating this loop, the chromatic aberration of rank 1 can be brought within the allowable range for the desired deflection trajectory.

[0085] One method for measuring rank 1 chromatic aberration is to use one central beam (central primary beam) of a multi-beam system. Place an aperture below the beam separator (on the sample side) through which the central primary beam and the center of the secondary electron beam pass and further reduce the spread of the secondary electron beam. Then, place a detector (e.g., a fluorescent screen, not shown) for measuring the beam shape downstream of the deflector 219 (on the multi-detector 222 side) to measure the beam blur due to chromatic aberration. In this case, if the detector can measure at two separate locations along the trajectory, the deflection trajectory can be accurately measured. To perform this measurement, for example, two movable fluorescent screens can be installed at separate locations perpendicular to the trajectory of the secondary electron beam, allowing for switching between the fluorescent screens used for measurement. Alternatively, the fluorescent screen can be designed to be movable parallel to the trajectory, allowing for measurements at different locations along the trajectory.

[0086] FIG. 9A is a diagram showing an example of a deflection trajectory in the first embodiment. Here, the deflection trajectory is assumed to be a straight line at the starting point. The horizontal axis is taken in the direction along the initial straight line trajectory, and this is referred to as the Z axis. Now, it is assumed that the deflection trajectory is within a plane, and the X axis is taken perpendicular to the Z axis within this plane. The X and Z axes provide a fixed coordinate system. Furthermore, the deflection trajectory is within the XZ plane. The origin of the XZ coordinates is taken as the starting point of the trajectory calculation. The trajectory (deflection trajectory) of an electron that initially departs in the positive direction of the Z axis (towards the right in the figure) is deflected in the negative direction of the X axis (downward in the figure). The X coordinate of a point on the deflection trajectory is represented as the X axis. FIG. 9B is a diagram showing an example of the relationship between the deflection trajectory and the dispersion trajectory in the first embodiment. In FIG. 9B, the X axis is shown on the left side of the vertical axis. The dispersion trajectory is shown on the right side of the vertical axis. The horizontal axis represents the distance along the central axis trajectory (optical axis). As described above, by setting the deflection fields of each deflector so that the two trajectories xa and xb simultaneously satisfy Equation (4-1) and Equation (4-2), the dispersion trajectory can be made zero downstream of the deflector 219. Specifically, the dispersion trajectory xc generated by the deflection by the E×B separator 214 gradually increases, reaches a maximum value, and then gradually decreases, and can be made zero downstream of the deflector 219. The dispersion trajectory becomes zero at a position where the deflection field is sufficiently weak, for example, at least γ times the inter-electrode distance (γ≧5) away from the outlet of the final deflector 219 in the three-stage deflector group including the E×B separator 214. The example in Figure 9B shows a case where the dispersion trajectory Xc is already zero near the exit of the deflector 219. After that, there is no static deflector on the trajectory up to the multi-detector 222, so the beam follows a straight trajectory (non-deflected trajectory) that is not statically deflected, as shown in Figure 5. Therefore, deflection chromatic aberration can be corrected.

[0087] FIG. 10 shows an example of the relationship between the deflection trajectory and the dispersion trajectory in Modification 1 of Embodiment 1. In FIG. 10, the left side of the vertical axis shows the dispersion trajectory xc, and the trajectory Xmulti, which is proportional to the deviation in the x-direction of the central trajectory of the beams other than the central beam when the central beam of the multiple beams constituting the multibeam is arranged so that it passes through the optical axis. In the example of FIG. 10, it is assumed that the image plane of the multibeam is located at the left end of the graph, and furthermore, the deviation in the x-direction of the central trajectory of each beam of the multibeam from the optical axis is proportional to Xmulti. These conditions are determined by the optical system upstream of the deflector group. Xmulti is expressed as a linear combination of xa and xb. Similarly, if the trajectory proportional to the deviation in the y-direction of the central trajectory of the multibeam is Ymulti, Ymulti is expressed as a linear combination of ya and yb. Xaxis is shown on the right side of the vertical axis. The horizontal axis indicates the distance along the central axis trajectory (optical axis). The example of FIG. 10 shows a case where the deflector group 217 is composed of three stages of deflectors 218, 223, and 219. Therefore, chromatic aberration is corrected using a four-stage deflector group including the E×B separator 214. As shown in FIG. 10, by setting the deflection fields of each deflector (e.g., the shape and position of the deflector, and the deflection voltages V1, V2, V3, and V4) so ​​that the two trajectories xa and xb simultaneously satisfy the formulas (4-1) and (4-2), the dispersion trajectory can be made zero downstream of the deflector 219. Specifically, the dispersion trajectory xc generated by the deflection by the E×B separator 214 gradually increases, reaches a maximum value, and then gradually decreases, and can be made zero downstream of the deflector 219. The deflection voltage V4 is a collective term for the voltages applied to each electrode of the deflector 223.

[0088] It is also preferable to place a slit 225 for limiting the energy of the secondary electron beam within a predetermined range from the position where the deviation between the rank 1 dispersion trajectory xc of the secondary electron beam and the central axis trajectory (optical axis) of the secondary electrons having a preset reference energy E0 is maximum while the secondary electron beam is passing through the deflection field.

[0089] Fig. 11 is a diagram showing an example of the configuration of a slit in Modification 1 of Embodiment 1. In Fig. 11, slit 225 has, for example, a rectangular opening 11 formed in a plane perpendicular to the central axis trajectory (Z axis) that is narrowed in the direction of energy dispersion (here, the x direction). This makes it possible to perform energy filtering. Therefore, it is possible to reduce chromatic aberration that may occur due to the lens in the linear trajectory after passing through final-stage deflector 219. It is more preferable to position the slit 225 at a position where the multiple secondary electron beams 300 in the deflection field form a crossover in the x direction. Here, the crossover in the x direction refers to the position where the deviation of the center of the paraxial trajectory of the multiple beams from the optical axis in the x direction is zero. To achieve this, the deflection trajectory should be adjusted so that the maximum value of the dispersion trajectory xc is located near the position where the multiple secondary electron beams 300 form the crossover in the x direction. This allows filtering of the energy in the dispersion direction for each beam of the multiple secondary electron beams 300 using a single aperture 11. The example in Figure 10 shows a case where the multiple beams take an trajectory (given by a constant x multiply) in which the multiple beams diverge from the starting point of the trajectory. Xbeam = 0, i.e., a crossover in the x direction, is formed near the position where the deviation of xc is maximum. By doing this, multiple beams close to the reference energy E0 can pass through the slit even when a slit is placed.

[0090] Alternatively, when the deflector group 217 is made up of two stages of deflectors 218 and 219, the deflector 218 may be divided into two stages at an intermediate position, for example, and a slit 225 may be disposed between them.

[0091] FIG. 12 is a diagram showing an example of a trajectory of a secondary electron beam passing through a static deflection field formed by a three-stage deflector group in Modification 2 of Embodiment 1. In FIG. 12, the three-stage deflector group includes an E×B separator 214, a deflector 218, and a deflector 219. In the example of FIG. 12, one secondary electron beam 301 representing the multiple secondary electron beams 300 is shown. For example, the central beam of the multiple secondary electron beams 300 is shown. The z-axis indicates the direction along the central axis trajectory (optical axis) of the secondary electron beam. In the example of FIG. 12, a quadrupole lens 232 is disposed between any of the deflectors in the deflector group formed by the E×B separator 214 and two or more stages of deflectors 218 and 219. At least one quadrupole lens is disposed. In the example of FIG. 12, the quadrupole lens 232 is disposed between the deflector 218 and the deflector 219. By providing at least one quadrupole lens 232, the deviation of the trajectory can be finely adjusted. Therefore, for example, each of the multiple quadrupole lenses 231, 232, and 233 may be disposed near one of the deflectors in a deflector group composed of the E×B separator 214 and two or more stages of deflectors 218 and 219. The example in FIG. 12 shows a case in which the quadrupole lens 231 is disposed between the E×B separator 214 and the deflector 218, the quadrupole lens 232 is disposed between the deflector 218 and the deflector 219, and the quadrupole lens 233 is disposed near the outlet of the deflector 219. In other words, one quadrupole lens may be disposed for each deflector. Furthermore, if the electromagnetic field distribution of the deflector group deviates slightly from the design value, the rank 1 dispersion trajectory may deviate from the optical axis in the designed deflection trajectory. In such cases, the strength and orientation of two or more stages of quadrupole lenses placed between the deflectors, for example, two stages of quadrupole lenses 231 and 232 placed between three-stage deflectors, can be adjusted to make the rank 1 dispersion trajectory coincide with the optical axis downstream of the deflector group. Any deviation from the design value of the independent trajectories that occurs in this case can be corrected by placing multiple quadrupole lenses downstream of the deflector group. The quadrupole lenses 231, 232, and 233 are controlled by the chromatic aberration correction circuit 130.

[0092] FIG. 13 is a diagram showing an example of a deflection orbit in the relationship between the deflection orbit and the dispersion orbit in the second modification of the first embodiment. Fig. 14 is a diagram showing an example of a dispersed orbit in the relationship between the deflection orbit and the dispersed orbit in Modification 2 of Embodiment 1. In Fig. 13, the vertical axis represents the X axis. As described above, the X axis represents one plane of the deflection orbit. The horizontal axis represents the distance along the deflection orbit (central axis orbit, optical axis). In Fig. 14, the left side of the vertical axis represents the independent orbits xa and xb in the x direction and the independent orbits ya and yb in the y direction, and the right side of the vertical axis represents the dispersed orbit xc. The horizontal axis represents the distance along the deflection orbit (central axis orbit, optical axis). The examples in Figures 13 and 14 show a three-stage deflector group consisting of an ExB separator 214 and deflectors 218 and 219, with quadrupole lenses 231, 232, and 233 positioned near each deflector. By setting the deflection fields (e.g., shape, placement position, and voltages V1, V2, and V3) of each deflector so that the two trajectories xa and xb simultaneously satisfy Equation (4-1) and Equation (4-2), the dispersion trajectory can be reduced to zero downstream of the deflector 219. Furthermore, by matching the independent trajectories xa and ya and the independent trajectories xb and yb, chromatic aberration-free deflection and a focusing function equivalent to a circular lens are achieved. Furthermore, if the dispersion trajectory deviates from the optical axis under the design conditions due to manufacturing errors or the like, the strength and orientation of the quadrupole lenses 231 and 232 can be adjusted to align the dispersion trajectory with the optical axis. The deviation between the x- and y-orbits that occurs at this time can be corrected by providing multiple quadrupole lenses downstream.

[0093] 15A is a diagram showing an example of a deflection field and a quadrupole field formed in a deflector in Modification 3 of Embodiment 1. In the example of FIG. 12, a quadrupole lens 232 and the like are arranged separately from each deflector, but this is not limiting. At least one deflector in a deflector group consisting of an E×B separator 214 and two or more stages of deflectors 218 and 219 may form a deflection field and further form a quadrupole field by superimposing it on the deflection field. For example, for a deflector consisting of eight electrodes (or magnetic poles), a deflection field that deflects secondary electrons in the -x direction is formed, and a quadrupole field that pulls the secondary electrons in the x direction and compresses them in the y direction is superimposed.

[0094] FIG. 15B is a diagram showing an example of a deflection orbit in the relationship between the deflection orbit and the dispersion orbit in Modification 3 of Embodiment 1. In FIG. 15C is a diagram showing an example of a dispersion trajectory in the relationship between the deflection trajectory and the dispersion trajectory in Modification 3 of Embodiment 1. In Fig. 15B, the vertical axis represents the X axis, and the horizontal axis represents the distance along the deflection trajectory (central axis trajectory, optical axis). Figure 15B shows the X axis when a quadrupole field is generated simultaneously with a deflection field in the E×B separator 214 and two or more stages of deflectors 218 and 219. In Figure 15C, the left side of the vertical axis shows independent trajectories xa and xb in the x direction and independent trajectories ya and yb in the y direction, and the right side of the vertical axis shows a dispersed trajectory xc. Each horizontal axis represents the distance along the deflection trajectory (central axis trajectory, optical axis). In the E×B separator, an electrostatic quadrupole field and an electromagnetic quadrupole field are superimposed on the primary electron beam so that the forces due to the electrostatic quadrupole field and the electromagnetic quadrupole field cancel each other out. In this case, the secondary electron beam travels in the opposite direction to the primary electron beam, so a force due to the quadrupole field acts on the secondary electron beam.

[0095] FIG. 16 shows an example of the trajectory of a secondary electron beam passing through a static deflection field formed by a four-stage deflector group in Modification 4 of Embodiment 1. In FIG. 16, the four-stage deflector group includes an E×B separator 214 and deflectors 218, 223, and 219. In the example of FIG. 16, one secondary electron beam 301 representing the multiple secondary electron beams 300 is shown. For example, the central beam of the multiple secondary electron beams 300 may be used. The z-axis indicates the direction along the central axial trajectory (optical axis) of the secondary electron beam. In the example of FIG. 16, a quadrupole lens 232 is disposed between any of the deflectors in the deflector group formed by the E×B separator 214 and the three-stage deflectors 218, 223, and 219. At least one quadrupole lens is disposed. In the example of FIG. 17, the quadrupole lens 232 is disposed between the deflector 218 and the deflector 223. By providing at least one quadrupole lens 232, the deviation of the trajectory can be finely adjusted. Therefore, for example, each of the multiple quadrupole lenses 231, 232, 233, and 234 may be disposed near one of the deflectors in a deflector group consisting of the E×B separator 214 and three stages of deflectors 218, 223, and 219. The example of FIG. 16 shows a case in which the quadrupole lens 231 is disposed between the E×B separator 214 and the deflector 218, the quadrupole lens 232 is disposed between the deflector 218 and the deflector 223, the quadrupole lens 233 is disposed between the deflector 223 and the deflector 219, and the quadrupole lens 234 is disposed near the outlet of the deflector 219. In other words, one quadrupole lens may be disposed for each deflector.

[0096] FIG. 17A is a diagram showing an example of a deflection orbit in the relationship between the deflection orbit and the dispersion orbit in the fourth modification of the first embodiment. Fig. 17B is a diagram showing an example of a dispersed trajectory in the relationship between the deflection trajectory and the dispersed trajectory in Modification 4 of Embodiment 1. In Fig. 17A, the vertical axis represents Xaxis. The horizontal axis represents the distance along the deflection trajectory (central axis trajectory, optical axis). In Fig. 17B, the left side of the vertical axis represents the independent trajectory xa in the x direction, the independent trajectory ya in the y direction, and the trajectories Xmulti and Ymulti proportional to the deviations of the multi-beam central trajectory in the x and y directions, respectively, and the right side of the vertical axis represents the dispersed trajectory xc. The horizontal axis represents the distance along the deflection trajectory (central axis trajectory, optical axis). 17A and 17B show a case where a four-stage deflector group including an E×B separator 214 and deflectors 218, 223, and 219 is arranged, as shown in FIG. 16, and quadrupole lenses 231, 232, 233, and 234 are arranged near each deflector. The quadrupole lens 234 is arranged near the outlet of the deflector 223. By setting the deflection voltages V1, V2, V3, and V4 of each deflector so that the two trajectories xa and xb simultaneously satisfy Equation (4-1) and Equation (4-2), the dispersion trajectory can be made zero downstream of the deflector 219. In the example of Figure 17, the deviation of the trajectory of the center of the multi-beam from the optical axis in the x direction (given by a constant x Xmulti) is zero at the position where the dispersion trajectory xc is approximately maximum, approximately halfway between the deflector and the quadrupole lens, i.e., a crossover in the x direction is formed. As a result, even when a slit 225 as shown in FIG. 11 is placed at the crossover position in the x direction, most of the beams close to the reference energy E0 can pass through the slit 225.

[0097] It has been confirmed that even under conditions that do not satisfy the equation using the inter-deflector distances D5, 6, and 7 and deflection angles α, β, and γ of the three stages of deflectors in Patent Document 2, the technique of Embodiment 1 may be able to make the dispersion trajectory zero downstream of the final stage deflector 219. Therefore, according to Embodiment 1, chromatic aberration may be corrected even for a group of deflectors with a combination of deflection angles that was difficult to achieve in the past.

[0098] Next, the inspection process will be described.

[0099] In the image acquisition step (S140), the image acquisition mechanism 150 scans the substrate 101 with the multiple primary electron beams 20.

[0100] Fig. 18 is a diagram for explaining an example of a method of acquiring an image in the first embodiment. In the example of Fig. 18, a case where the substrate 101 is a mask substrate for exposure is shown as an example. The inspection area 330 of the substrate 101 is divided into a plurality of stripe areas 32 with a predetermined width in the y direction, for example. If the substrate 101 is a semiconductor substrate, each chip area (inspection area) of a plurality of chip areas formed on the wafer is divided into a plurality of stripe areas 32 with a predetermined width in the y direction, for example.

[0101] 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).

[0102] 18 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 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 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 (performs a scanning operation) within the sub-irradiation region 29. Each primary electron beam 10 is assigned to a different sub-irradiation region 29. Each primary electron beam 10 irradiates the same position within the assigned sub-irradiation region 29. The two-stage deflectors 208 and 209 collectively deflect the multi-primary electron beams 20, thereby scanning the surface of the substrate 101 on which the pattern is formed with the multi-primary electron beams 20. In other words, the movement of the primary electron beams 10 within the sub-irradiation region 29 is achieved by the collective deflection of the entire multi-primary electron beams 20 by the two-stage deflectors 208 and 209. This operation is repeated, and one primary electron beam 10 is used to sequentially irradiate one sub-irradiation region 29.

[0103] 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. 18, 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 irradiation position is moved to an 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. After scanning one stripe region 32, the irradiation region 34 moves to the next stripe region 32 by moving the stage 105 and / or simultaneously deflecting the entire multi-primary electron beam 20 using the two-stage deflectors 208, 209. 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. 13 shows a case where the sub-irradiation region 29 scanned by one primary electron beam 10 is divided into four frame regions 30, for example, by dividing the sub-irradiation region 29 into two in each of the x and y directions.

[0104] Furthermore, when the substrate 101 is irradiated with the multiple primary electron beams 20 while the stage 105 is continuously moving, a tracking operation is performed by the two-stage deflectors 208, 209 through dynamic collective deflection 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 moment by moment with respect to the central axis of the trajectory 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 moment by moment within the sub-irradiation region 29. The deflector 226 dynamically deflects the multiple secondary electron beams 300 moment by moment so that each secondary electron beam with its emission position changed is irradiated within the corresponding detection region of the multi-detector 222. In other words, the deflector 226 fixes the position of the multiple secondary electron beams 300 on the detection surface of the multi-detector 222, which dynamically changes due to scanning with the multiple primary electron beams 20, by deflecting the multiple secondary electron beams back. This allows each secondary electron beam to be detected by a corresponding detection element of the multi-detector 222. The deflector 226 is not limited to a single-stage deflector, and may be configured with two or more stages of deflectors.

[0105] As described above, the image acquisition mechanism 150 scans the stripe region 32 with the multi-primary electron beam 20 for each stripe region 32. The multi-secondary electron beams 300 emitted as a result of irradiation of the substrate 101 with the multi-primary electron beams 20 are guided to the multi-detector 222 (detector array) by the secondary electron optical system 152. The guided multi-secondary electron beams 300 are then detected by the multi-detector 222 (detector array). The detected multi-secondary electron beams 300 may include reflected electrons. Alternatively, the reflected electrons may diverge while moving through the secondary electron optical system and not reach the multi-detector 222. A secondary electron image is then 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.

[0106] FIG. 19 is a configuration diagram showing an example of the configuration within a comparison circuit in the first embodiment. In FIG. 19, 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 may include 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.

[0107] In the comparison step (S150), the comparison circuit 108 compares the acquired secondary electron image with a predetermined reference image. Specifically, for example, the operation is as follows.

[0108] The measurement image data (beam image) transferred to the comparison circuit 108 is stored in the storage device 50.

[0109] The frame image creation unit 54 then creates a frame image 31 for each of a plurality of frame regions 30 obtained by further dividing the image data of the sub-irradiation regions 29 acquired by the scanning operation of each primary electron beam. The frame regions 30 are then used as unit regions of the image to be inspected. Preferably, the frame regions 30 are configured so that their marginal regions overlap each other to ensure that no image is missing. The created frame images 31 are stored in the storage device 56.

[0110] 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.

[0111] 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.

[0112] 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.

[0113] Next, the reference image creation circuit 112 applies filtering to the design image data of the design pattern, which is image data of the graphic, using a predetermined filter function. This 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. The reference image data transferred to the comparison circuit 108 is stored in the storage device 52.

[0114] 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.

[0115] The comparison unit 58 then compares the secondary electron image of the substrate 101 placed on the stage 105 with a predetermined image. Specifically, the comparison unit 58 compares the frame image 31 with the reference image for each pixel. The comparison unit 58 compares the two for each pixel according to predetermined judgment conditions, and judges whether or not there is a defect, such as a shape defect. For example, if the difference in gradation value for each pixel is greater than the judgment threshold value Th, it is judged to be a defect. The comparison result is then output. The comparison result may be output to the storage device 109 or memory 118, or may be output from the printer 119.

[0116] In addition to the die-to-database inspection described above, it is also suitable to perform die-to-die inspection, in which measurement image data of the same pattern captured at different locations on the same substrate are compared. Alternatively, inspection may be performed using only the own measurement image.

[0117] As described above, according to the first embodiment, it is possible to correct the chromatic aberration that occurs in the deflection field of the secondary electron beam.

[0118] Embodiment 2 In the first embodiment, the configuration in which the trajectories of the multiple secondary electron beams 300 are separated from the trajectories of the multiple primary electron beams 20 by the E×B separator 214 has been described, but the present invention is not limited to this. In the second embodiment, a configuration in which separation is performed by an electromagnetic prism will be described.

[0119] Fig. 20 is a diagram showing an example of the configuration of an image acquisition mechanism of an inspection apparatus in embodiment 2. In Fig. 20, inspection apparatus 400 includes an electron gun 401, an electromagnetic lens 402, a shaping aperture array substrate 403, an electromagnetic lens 405, an electromagnetic prism 414 (another example of a separator), an electromagnetic lens 407 (objective lens), a deflector 408, a secondary electron beam accelerator 409, two or more stages of deflectors 418 and 419, quadrupole lenses 431, 432, and 433, an electromagnetic lens 424, a deflector 426, and a multi-detector 422. In Fig. 20, the control system circuitry is not shown. The operation of inspection apparatus 400 will be described.

[0120] 20 shows a case where one quadrupole lens is placed near each of three or more stages of deflectors composed of electromagnetic prism 414 and two or more stages of deflectors 418 and 419, but one, more than one, or all of quadrupole lenses 431, 432, and 433 may be omitted. Also, while Fig. 20 shows an example in which the trajectories of secondary electrons passing through the right end face and the left end face of electromagnetic prism 414 are perpendicular to each other, it is also possible to determine the angle of the prism end face so that the trajectories pass at an angle, and to cause a converging force or a diverging force to act in the direction perpendicular to the paper surface.

[0121] An electron gun 401 (an example of an emission source) emits an electron beam 500 in a diverging direction. The electron beam 500 emitted from the electron gun 401 and traveling in a diverging direction is refracted by an electromagnetic lens 402 into a converging direction. The electron beam 500 then illuminates the entire shaping aperture array substrate 403. As in FIG. 2 , a plurality of holes 22 are formed in the shaping aperture array substrate 403, and the electron beam 420 illuminates an area that includes all of the plurality of holes 22. Portions of the electron beam 500 irradiated onto the positions of the plurality of holes 22 pass through the respective holes 22 of the shaping aperture array substrate 403, thereby forming multiple primary electron beams 502.

[0122] The formed multi-primary electron beams 502 are refracted by the electromagnetic lens 405 to form a crossover and an intermediate image, and proceed to the electromagnetic prism 414. Then, they pass through the E×B separator 214 and proceed to the electromagnetic lens 407.

[0123] The electromagnetic lens 407 images the multiple primary electron beams 502 onto the substrate 501 .

[0124] The multiple primary electron beams 502 are focused on the surface of the substrate 501 (sample) by the electromagnetic lens 407, and are deflected collectively by the deflector 408, and each beam is irradiated onto the respective irradiation positions on the substrate 501.

[0125] When a desired position on the substrate 501 is irradiated with the multiple primary electron beams 502, a bundle of secondary electrons (multiple secondary electron beams 504) including reflected electrons is emitted from the substrate 501 due to the irradiation of the multiple primary electron beams 502.

[0126] Multiple secondary electron beams 504 emitted from the substrate 501 pass through an electromagnetic lens 407 and proceed to an electromagnetic prism 414 .

[0127] The electromagnetic prism 414 separates the trajectories of the multiple secondary electron beams 504 from the trajectories of the multiple primary electron beams 502 by an electromagnetic prism action. The multiple secondary electron beams 504 are bent obliquely upward by being statically deflected in a predetermined direction, and are separated from the trajectories of the multiple primary electron beams 502.

[0128] The multiple secondary electron beams 504, which have been bent obliquely upward and separated from the multiple primary electron beams 502, are further bent by static deflection by two or more stages of deflectors 418 and 419, and proceed to an electromagnetic lens 424. The multiple secondary electron beams 504 are then projected onto a multi-detector 422 while being refracted in the focusing direction by the electromagnetic lens 424. The multi-detector 422 is formed in the same manner as the multi-detector 222.

[0129] Furthermore, to acquire an image of the pattern on the substrate 501, the deflector 408 dynamically deflects the beam to scan the substrate 101 with the multiple primary electron beams 502. The stage 415 also moves continuously while scanning. Therefore, the deflector 408 performs tracking control by dynamic beam deflection so as to follow the movement of the stage 415. Furthermore, the position of each emitted secondary electron beam changes from moment to moment by the amount of scanning and by the amount of stage movement. Therefore, the deflector 426 keeps the multiple secondary electron beams 504 stationary by dynamically performing scanning with the multiple primary electron beams 502 and deflection by trunking control to reverse the deflection so that each secondary electron beam can reach the corresponding detection element of the multi-detector 422.

[0130] Fig. 21 is a diagram showing an example of a dispersion trajectory in the second embodiment. In Fig. 21, the deflection trajectory (central axis trajectory, optical axis) is omitted. In Fig. 21, the left side of the vertical axis shows the independent trajectory xa in the x direction and the independent trajectory ya in the y direction, as well as the trajectories Xmulti and Ymulti proportional to the deviations of the multi-beam central trajectory in the x and y directions, respectively, and the right side of the vertical axis shows the dispersion trajectory xc. The horizontal axis shows the distance along the deflection trajectory (central axis trajectory, optical axis). 21 shows a case where a four-stage deflector group consisting of an electromagnetic prism 414 and deflectors 418, 423, and 419 is arranged, with quadrupole lenses 431, 432, and 433 arranged between each deflector. By setting the deflection voltages V1, V2, V3, and V4 of each deflector so that the two trajectories xa and xb simultaneously satisfy equations (4-1) and (4-2), the dispersion trajectory can be made zero downstream of the deflector 419. Furthermore, Xmulti=0 is established at the position where the dispersion trajectory xc is approximately at its maximum.

[0131] As described above, even when the electromagnetic prism 414 is used instead of the E×B separator 214, deflection chromatic aberration can be corrected in the same manner.

[0132] 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.

[0133] Although the embodiments have been described above with reference to specific examples, the present invention is not limited to these specific examples.

[0134] 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.

[0135] In addition, all electron beam image acquisition devices and 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]

[0136] 10 Primary electron beam 11 Opening 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 50,52,56 storage device 54 Frame image creation section 57 Alignment section 58 Comparison Section 60 Target trajectory setting section 61 memory 62 Electric field (magnetic field) setting section 63 Storage device 66 T calculation section 68 D calculation section 70 Trajectory xa,xb calculation part 72 Dispersion trajectory calculation section 74 Judgment section 76 Deflector shape determining section 78 Voltage determination unit 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 marks 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 225 Slit 126 Blanking control circuit 128 Deflection control circuit 130 Chromatic aberration correction circuit 132 E×B separator control circuit 142 Stage drive mechanism 144,146,147 DAC amplifier 148,149 DC power supply 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 Electromagnetic lenses 203 Shaped Aperture Array Substrate 206,207 Electromagnetic lenses 208 Deflector 209 Deflector 212 Bulk deflector 213 Limiting Aperture Substrate 214 E×B separator 216 Mirror 217 Deflector group 218,219 Deflector 222 Multi-detector 224 Electromagnetic Lens 226 Deflector 227,228,229 Deflector 231,232,233 Quadrupole Lens 300 Multi-Secondary Electron Beam 400 Inspection Equipment 401 Electron Gun 402 Electromagnetic Lens 403 Shaped Aperture Array Substrate 405 Electromagnetic Lens 407 Electromagnetic Lens 408 Deflector 409 Secondary Electron Beam Accelerator 414 Electromagnetic Prism 418,419 Deflector 422 Multi-Detector 424 Electromagnetic Lens 426 Deflector 431,432,433 Quadrupole Lens 500 primary electron beam 502 Multi-primary electron beam 504 Multi-Secondary Electron Beam 600 Simulation Device

Claims

1. a stage on which a sample is placed; a primary electron optical system for irradiating the sample with a primary electron beam; a separator that is disposed on the trajectory of the primary electron beam and statically deflects a secondary electron beam emitted from the sample by irradiation with the primary electron beam to separate the trajectory of the secondary electron beam from the trajectory of the primary electron beam; a deflector having two or more stages for statically deflecting the secondary electron beam separated from the orbit of the primary electron beam; a detector that detects the secondary electron beam that has passed through the separator and the two or more stages of deflectors; Equipped with using two independent trajectories xa and xb that satisfy an equation in which the sum of the product of a dispersion trajectory of rank 1 of chromatic aberration of the secondary electron beam deflected by a deflection field formed by the separator and the two or more stages of deflectors and a value T depending on the deflection field and a second derivative of the dispersion trajectory becomes zero, the deflection field of the separator and the fields of each of the two or more stages of deflectors are set so that the value obtained by integrating the product of the quantity D proportional to the deflection field and the trajectory xa over the range of the deflection field becomes zero, and at the same time, the value obtained by integrating the product of the quantity D proportional to the deflection field and the trajectory xb over the range of the deflection field becomes zero; Electron beam image acquisition device characterized by:

2. 2. The electron beam image acquisition device according to claim 1, further comprising a slit for limiting the energy of the secondary electron beam, the slit being arranged within a predetermined range from a position where the deviation between the rank 1 dispersion trajectory due to chromatic aberration of the secondary electron beam and the trajectory of secondary electrons having a preset reference energy becomes maximum while the secondary electron beam passes through the deflection field.

3. 3. The electron beam image acquisition device according to claim 2, wherein the slit is disposed at a crossover position of the secondary electron beam within the deflection field.

4. 4. The electron beam image acquisition device according to claim 1, further comprising a quadrupole lens disposed between any of the deflectors in the group of deflectors formed by the separator and the two or more stages of deflectors.

5. An electron beam image acquisition device according to any one of claims 1 to 3, characterized in that at least one deflector of a group of deflectors consisting of the separator and the two or more stages of deflectors forms a deflection field and further forms a quadrupole field by superimposing it on the deflection field.

6. irradiating a sample mounted on a stage with a primary electron beam; a step of statically deflecting a secondary electron beam emitted from the sample by irradiation with the primary electron beam using a separator arranged on the orbit of the primary electron beam, thereby separating the orbit of the secondary electron beam from the orbit of the primary electron beam; statically deflecting the secondary electron beam separated from the orbit of the primary electron beam using a deflector of two or more stages; detecting the secondary electron beam that has passed through the separator and the two or more stages of deflectors using the detector; a step of setting the deflection field of the separator and the deflection fields of each of the deflectors of the two or more stages using two independent trajectories xa and xb that satisfy an equation in which the sum of the product of a dispersion trajectory of rank 1 of chromatic aberration of the secondary electron beam deflected by the deflection field formed by the separator and the two or more stages of deflectors and a value T depending on the deflection field and a second derivative of the dispersion trajectory becomes zero, so that the value obtained by integrating the product of the quantity D proportional to the deflection field and the trajectory xa over the range of the deflection field becomes zero, and at the same time, the value obtained by integrating the product of the quantity D proportional to the deflection field and the trajectory xb over the range of the deflection field becomes zero; 1. An electron beam image acquisition method comprising:

7. a stage on which a sample is placed; a primary electron optical system for irradiating the sample with a primary electron beam; a separator that is disposed on the trajectory of the primary electron beam and statically deflects a secondary electron beam emitted from the sample by irradiation with the primary electron beam to separate the trajectory of the secondary electron beam from the trajectory of the primary electron beam; a deflector having two or more stages for statically deflecting the secondary electron beam separated from the orbit of the primary electron beam; a detector that detects the secondary electron beam that has passed through the separator and the two or more stages of deflectors; Equipped with the deflection field of the separator and the deflection fields of the deflectors of the two or more stages are set so that a deviation between a rank 1 dispersion trajectory due to chromatic aberration of the secondary electron beam generated in the deflection field formed by the separator and the two or more stages of deflectors and a trajectory of a secondary electron having a preset reference energy falls within a predetermined range downstream of a final stage deflector among the two or more stages of deflectors. Electron beam image acquisition device characterized by:

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