JP2022174714A - Multi-secondary electron beam alignment method, multi-secondary electron beam alignment apparatus, and electron beam inspection device - Google Patents

Abstract

PURPOSE: To provide a method for allowing alignment between multi-charged particle beams and a secondary electron detector.CONSTITUTION: A multi-secondary electron beam alignment method of an aspect of the present invention includes the steps of: scanning a plurality of first detection elements of a multi-detector arranged in a grid pattern with multi-secondary electron beams emitted from an object surface on a stage; detecting, by the multi-detector, a plurality of beams including corner beams located at the corners from the multi-secondary electron beams; calculating the positional relationship between the plurality of beams including the corner beams and a plurality of second detection elements, of the plurality of first detection elements, which detect the plurality of beams; calculating, based on the positional relationship, a shift amount for aligning the plurality of first detection elements to the multi-secondary electron beams; and moving the multi-detector relative to the multi-secondary electron beams by using the shift amount.SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for aligning multiple secondary electron beams, an alignment apparatus for multiple secondary electron beams, and an electron beam inspection apparatus, and irradiates a substrate with multiple primary electron beams to emit multiple electron beams emitted from the substrate. The present invention relates to a method of obtaining an image by detecting a secondary electron beam.

2. Description of the Related Art In recent years, as large-scale integrated circuits (LSIs) have become highly integrated and have large capacities, the circuit line width required for semiconductor elements has become increasingly narrow. In addition, the improvement of yield is essential for the manufacture of LSIs, which requires a great manufacturing cost. However, as typified by 1-gigabit-class DRAMs (random access memories), patterns forming LSIs are on the order of submicrons to nanometers. In recent years, as the dimensions of LSI patterns formed on semiconductor wafers have become finer, the dimensions that must be detected as pattern defects have become extremely small. Therefore, there is a need to improve the precision of a pattern inspection apparatus for inspecting defects in an ultrafine pattern transferred onto a semiconductor wafer. In addition, one of the major factors that lower the yield is the pattern defect of the mask used when exposing and transferring the ultra-fine pattern onto the semiconductor wafer by photolithography technology. Therefore, it is necessary to improve the precision of pattern inspection apparatuses for inspecting defects in transfer masks used in LSI manufacturing.

The inspection apparatus, for example, irradiates a substrate to be inspected with multiple beams using electron beams, detects secondary electrons corresponding to each beam emitted from the substrate to be inspected, and picks up a pattern image. Then, there is known a method of performing an inspection by comparing the captured measurement image with design data or a measurement image of the same pattern on the substrate. For example, "die to die inspection" that compares measurement image data obtained by imaging the same pattern at different locations on the same substrate, and design image data (reference image) based on pattern design data and compare it with a measurement image, which is the measurement data of the pattern captured. The captured image is sent to the comparison circuit as measurement data. After aligning the images, the comparison circuit compares the measurement data with the reference data according to an appropriate algorithm, and determines that there is a pattern defect if they do not match.

In a multi-beam inspection system, in a system in which the number of multi-beams and the number of elements of the secondary electron detector are the same, it is important to align the two. In particular, alignment with multiple secondary electron beams is important when a secondary electron detector is mounted on the device, either newly or as a replacement. For example, a technique is disclosed in which an aperture plate is placed between the final stage lens of the secondary optical system and the secondary electron detector, and the aperture plate is used to adjust the position of the secondary electron beam (for example, , see Patent Document 1).

JP 2014-026834 A

Accordingly, one aspect of the present invention provides a method capable of aligning a multi-charged particle beam and a secondary electron detector, and an apparatus capable of implementing such a method.

A method for aligning multiple secondary electron beams according to one aspect of the present invention includes:
scanning a plurality of first detection elements arranged in a grid pattern of a multi-detector with multiple secondary electron beams emitted from an object surface on the stage;
detecting a plurality of beams including a corner beam positioned at a corner among the multiple secondary electron beams with a multi-detector;
calculating a positional relationship between a plurality of beams including a corner beam and a plurality of second detection elements that detect the plurality of beams among the plurality of first detection elements;
calculating a shift amount for aligning the plurality of first detection elements with the multi-secondary electron beam based on the positional relationship;
moving the multi-detector relative to the multi-secondary electron beam using the shift amount;
characterized by comprising

calculating a rotation angle for aligning the plurality of first detection elements with the multi-secondary electron beam using the positional relationship and the rotation center coordinates of the multi-detector;
rotating the multiple detectors relative to the multiple secondary electron beams by a rotation angle;
It is preferable to further include

Alternatively, rotating the multi-detector through a first rotation angle;
scanning over the plurality of first detection elements with multiple secondary electron beams emitted from the surface of the sample in the rotated state;
detecting the plurality of beams, including the corner beam, with a multi-detector in the rotated state;
calculating the positional relationship between the plurality of beams including the corner beams and the plurality of second detection elements after rotation;
calculating rotation center coordinates of the multi-detector based on a first rotation angle by which the multi-detector is rotated and the positional relationship before and after the rotation;
calculating a second rotation angle for aligning the plurality of first detection elements with the multi-secondary electron beams using one of the positional relationships before and after rotation and the rotation center coordinates of the multi-detector;
rotating the multiple detectors relative to the multiple secondary electron beams by a second rotation angle;
It is preferable to further include

Also, when scanning with the multi-secondary electron beams, it is preferable to scan a scanning range that is four times or more the inter-beam pitch of the multi-secondary electron beams.

A multi-secondary electron beam alignment apparatus according to one aspect of the present invention includes:
a stage;
an electron optical system that irradiates an object surface on a stage with multiple primary electron beams;
A plurality of beams including a corner beam located at a corner among the multi-secondary electron beams emitted from the object surface by the irradiation of the multi-primary electron beams, having a plurality of first detection elements arranged in a grid pattern. a multi-detector for detecting
a secondary system deflector that scans a plurality of first detection elements with multiple secondary electron beams;
a positional relationship calculator that calculates a positional relationship between a plurality of beams including corner beams and a plurality of second detection elements that detect the plurality of beams among the plurality of first detection elements;
a shift amount calculation unit that calculates a shift amount for aligning the plurality of first detection elements with the multiple secondary charged particle beams based on the positional relationship;
a moving mechanism that moves the multi-detector relative to the multi-secondary electron beam using the shift amount;
characterized by comprising

An electron beam inspection apparatus according to one aspect of the present invention includes
a stage;
an electron optical system that irradiates an object surface on a stage with multiple primary electron beams;
A plurality of beams including a corner beam located at a corner among the multi-secondary electron beams emitted from the object surface by the irradiation of the multi-primary electron beams, having a plurality of first detection elements arranged in a grid pattern. a multi-detector for detecting
a secondary system deflector that scans a plurality of first detection elements with multiple secondary electron beams;
a positional relationship calculator that calculates a positional relationship between a plurality of beams including corner beams and a plurality of second detection elements that detect the plurality of beams among the plurality of first detection elements;
a shift amount calculation unit that calculates a shift amount for aligning the plurality of first detection elements with the multiple secondary charged particle beams based on the positional relationship;
a moving mechanism that moves the multi-detector relative to the multi-secondary electron beam using the shift amount;
a comparison unit that compares the secondary electron image of the substrate to be inspected placed on the stage with a predetermined image;
with
A secondary electron image is obtained by irradiating a substrate to be inspected on a stage with multiple primary electron beams and detecting the multiple secondary electron beams emitted from the substrate to be inspected by the irradiation of the multiple primary electron beams by a multi-detector. Characterized by being obtained by

According to one aspect of the present invention, it is possible to efficiently align the multiple secondary electron beams and the secondary electron detector.

1 is a configuration diagram showing the configuration of an inspection apparatus according to Embodiment 1; FIG. FIG. 2 is a conceptual diagram showing the configuration of a shaping aperture array substrate according to Embodiment 1; 3 is a diagram showing an example of an internal configuration of an alignment circuit according to Embodiment 1; FIG. FIG. 2 is a flow chart diagram showing an example of essential steps of an inspection method according to Embodiment 1; FIG. 2 is a diagram showing an example of a secondary electron beam array according to Embodiment 1; FIG. 4A and 4B are diagrams showing an example of an image captured by each detection element in Embodiment 1. FIG. FIG. 5 is a diagram showing an image of a corner portion among an example of images captured by each detection element according to Embodiment 1; 4 is a diagram showing an example of an image group of corner portions according to Embodiment 1. FIG. 4 is a diagram showing the relationship between a detection element D11 and positions of beams B11, B12, B21, and B22 in Embodiment 1. FIG. 4 is a diagram showing the relationship between a detection element D12 and positions of beams B11, B12, B21, and B22 in Embodiment 1. FIG. 4 is a diagram showing the relationship between a detection element D21 and positions of beams B11, B12, B21, and B22 in Embodiment 1. FIG. 4 is a diagram showing the relationship between a detection element D22 and positions of beams B11, B12, B21, and B22 in Embodiment 1. FIG. 4 is a diagram showing an example of the relationship between the position of each detection element and the position of each beam after synthesis in Embodiment 1. FIG. FIG. 4 is a diagram showing an example of overall positional relationship according to Embodiment 1; FIG. 4 is a diagram showing an example of coordinates of a plurality of detection elements of the multi-detector before and after rotation according to Embodiment 1; FIG. 4 is a diagram showing an arithmetic expression for calculating rotation center coordinates in Embodiment 1. FIG. FIG. 4 is a diagram for explaining a method of vector calculation of detection element coordinates in Embodiment 1; FIG. 4 is a diagram showing an arithmetic expression for calculating vector coefficients according to the first embodiment; FIG. FIG. 4 is a diagram for explaining a method of vector calculation of secondary electron beam coordinates in Embodiment 1; 4 is a diagram showing an arithmetic expression for calculating alignment angles in the first embodiment; FIG. 4 is a diagram showing an example of a plurality of chip regions formed on the semiconductor substrate according to Embodiment 1; FIG. 4 is a diagram for explaining inspection processing in the first embodiment; FIG. FIG. 2 is a configuration diagram showing an example of the internal configuration of a comparison circuit according to the first embodiment; FIG. FIG. 11 is a configuration diagram showing the configuration of an inspection apparatus according to Embodiment 2; FIG. 13 is a diagram showing an example of an internal configuration of an alignment circuit according to Embodiment 3; FIG. 11 is a flow chart diagram showing an example of main steps of an inspection method according to Embodiment 3; FIG. 12 is a configuration diagram showing the configuration of an inspection apparatus according to Embodiment 4; FIG. 13 is a diagram showing an example of an internal configuration of an alignment circuit according to Embodiment 4; FIG. 12 is a flow chart diagram showing an example of main steps of an inspection method according to Embodiment 4; FIG. 11 is a diagram for explaining a method of calculating a shape evaluation value in Embodiment 4; FIG. FIG. 12 is a diagram for explaining an example of a configuration of a distortion corrector and an example of an adjustment method according to Embodiment 4; FIG. 12 is a diagram for explaining another example of the configuration of the distortion corrector and another example of the adjustment method according to Embodiment 4;

In the following embodiments, an inspection apparatus using a multi-electron beam will be described as an example of a multi-secondary electron beam alignment apparatus. However, it is not limited to this. Any device may be used as long as it irradiates multiple primary electron beams and aligns the multiple secondary electron beams emitted from the substrate with the multiple detectors. For example, there is an image acquisition device that irradiates multiple primary electron beams and acquires an image using multiple secondary electron beams emitted from a substrate.

Embodiment 1.
FIG. 1 is a configuration diagram showing the configuration of an inspection apparatus according to Embodiment 1. FIG. In FIG. 1, an inspection apparatus 100 for inspecting a pattern formed on a substrate is an example of a multi-electron beam inspection apparatus. The inspection apparatus 100 has an image acquisition mechanism 150 and a control system circuit 160 . The image acquisition mechanism 150 includes an electron beam column 102 (electron lens barrel) and an inspection room 103 . Inside the electron beam column 102 are an electron gun 201, an electromagnetic lens 202, a shaping aperture array substrate 203, an electromagnetic lens 205, a batch blanking deflector 212, a limiting aperture substrate 213, an electromagnetic lens 206, an electromagnetic lens 207 (objective lens), Main deflector 208, sub-deflector 209, E×B separator 214 (beam separator), deflector 218, electromagnetic lens 224, deflector 226, detector stage 229, detector aperture array substrate 225, and multi-detector 222 are placed. Electron gun 201, electromagnetic lens 202, shaping aperture array substrate 203, electromagnetic lens 205, batch blanking deflector 212, limiting aperture substrate 213, electromagnetic lens 206, electromagnetic lens 207 (objective lens), main deflector 208, and sub-deflector The device 209 constitutes a primary electron optical system 151 (illumination optical system). Also, the electromagnetic lens 207, the E×B separator 214, the deflector 218, the electromagnetic lens 224, and the deflector 226 constitute a secondary electron optical system 152 (detection optical system). The multi-detector 222 is arranged on a detector stage 229 movable in the x, y directions and the rotation (θ) direction of the secondary coordinate system. The detector stage 229 has a rotary stage 227 and a secondary x, y stage 228 .

A stage 105 movable at least in the XY directions is arranged in the examination room 103 . A substrate 101 (sample) to be inspected is placed on the stage 105 . The substrate 101 includes an exposure mask substrate and a semiconductor substrate such as a silicon wafer. When the substrate 101 is a semiconductor substrate, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. When the substrate 101 is an exposure mask substrate, a chip pattern is formed on the exposure mask substrate. A chip pattern is composed of a plurality of figure patterns. A plurality of chip patterns (wafer dies) are formed on the semiconductor substrate by exposing and transferring the chip patterns formed on the mask substrate for exposure a plurality of times onto the semiconductor substrate. The following mainly describes the case where the substrate 101 is a semiconductor substrate. The substrate 101 is placed on the stage 105, for example, with the pattern formation surface facing upward. A mirror 216 is arranged on the stage 105 to reflect the laser beam for laser length measurement emitted from the laser length measurement system 122 arranged outside the inspection room 103 . A mark 111 is arranged on the stage 105 so as to be adjusted to the same height position as the surface of the substrate 101 . A cross pattern, for example, is formed as the mark 111 .

The multi-detector 222 is also connected to the detection circuit 106 outside the electron beam column 102 . The detection circuit 106 is connected to the chip pattern memory 123 .

The multi-detector 222 has a plurality of detection elements arranged in an array (grid). A plurality of openings are formed in the detector aperture array substrate 225 at the array pitch of the plurality of detection elements. A plurality of openings are formed circularly, for example. The center position of each opening is aligned with the center position of the corresponding detection element. Also, the size of the opening is formed smaller than the area size of the electron detection surface of the detection element.

In the control system circuit 160, a control computer 110 that controls the inspection apparatus 100 as a whole is connected via a bus 120 to a position circuit 107, a comparison circuit 108, a reference image generation circuit 112, a stage control circuit 114, a lens control circuit 124, a blanking It is connected to a control circuit 126 , a deflection control circuit 128 , a detector stage control circuit 130 , an E×B control circuit 133 , an alignment circuit 134 , a storage device 109 such as a magnetic disk device, a memory 118 and a printer 119 . The deflection control circuit 128 is also connected to DAC (digital-to-analog conversion) amplifiers 144 , 146 , 148 and 149 . The DAC amplifier 146 is connected to the main deflector 208 and the DAC amplifier 144 is connected to the sub deflector 209 . DAC amplifier 148 is connected to deflector 218 . DAC amplifier 149 is connected to deflector 226 .

Also, the chip pattern memory 123 is connected to the comparison circuit 108 and the alignment circuit 134 . Also, the stage 105 is driven by a drive mechanism 142 under the control of the stage control circuit 114 . In the drive mechanism 142, for example, a drive system such as a three-axis (XY-.theta.) motor that drives in the X, Y and .theta. It's becoming These X motor, Y motor, and θ motor (not shown) can be step motors, for example. The stage 105 can be moved in horizontal and rotational directions by motors on the XY and .theta. axes. The movement position of the stage 105 is measured by the laser length measurement system 122 and supplied to the position circuit 107 . The laser length measurement system 122 measures the position of the stage 105 based on the principle of laser interferometry by receiving reflected light from the mirror 216 . For the stage coordinate system, for example, the X direction, Y direction, and θ direction of the primary coordinate system are set with respect to a plane perpendicular to the optical axis of the multi primary electron beam 20 .

Detector stage 229 is driven by drive mechanism 132 under the control of detector stage control circuit 130 . In the drive mechanism 132, for example, a drive system such as a three-axis (xy-θ) motor that drives in the x, y, and θ directions in the stage coordinate system is configured. 228, the rotary stage 227 is movable in the .theta. The example of FIG. 1 shows the case where the x, y stage 228 is arranged on the rotating stage 227 . These x-motor, y-motor, and θ-motor (not shown) can be step motors, for example. The detector stage 229 can be moved in the horizontal and rotational directions by motors on the xy and θ axes. In the stage coordinate system, for example, the x direction, y direction, and θ direction of the secondary coordinate system are set with respect to a plane perpendicular to the optical axis of the multi-secondary electron beam 300 .

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 . E×B separator 214 is controlled by E×B control circuit 133 . The collective deflector 212 is an electrostatic deflector composed of two or more electrodes, and each electrode is controlled by the blanking control circuit 126 via a DAC amplifier (not shown). The sub-deflector 209 is an electrostatic deflector composed of four or more electrodes, and is controlled by the deflection control circuit 128 via the DAC amplifier 144 for each electrode. The main deflector 208 is an electrostatic deflector composed of four or more electrodes, and is controlled by the deflection control circuit 128 via the DAC amplifier 146 for each electrode. The deflector 218 is an electrostatic deflector composed of four or more electrodes, and is controlled by the deflection control circuit 128 via the DAC amplifier 148 for each electrode. The deflector 226 is an electrostatic deflector composed of four or more electrodes, and is controlled by the deflection control circuit 128 via the DAC amplifier 149 for each electrode.

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 (cathode) and an extraction electrode (anode) (not shown) in the electron gun 201, and another extraction electrode is applied. A group of electrons emitted from the cathode is accelerated by application of a (Wehnelt) voltage and heating of the cathode to a predetermined temperature, and is emitted as an electron beam 200 .

Here, FIG. 1 describes the configuration necessary for explaining the first embodiment. The inspection apparatus 100 may have other configurations that are normally required.

FIG. 2 is a conceptual diagram showing the configuration of the shaping aperture array substrate according to the first embodiment. In FIG. 2, the shaping aperture array substrate 203 has two-dimensional holes (openings) of horizontal (x direction) m ₁ rows x vertical (y direction) n ₁ stages (m ₁ and n ₁ are integers of 2 or more). ) 22 are formed at a predetermined arrangement pitch in the x and y directions. The example of FIG. 2 shows a case where 23×23 holes (openings) 22 are formed. Each hole 22 is formed in a rectangle having the same size and shape. Alternatively, they may be circular with the same outer diameter. Part of the electron beam 200 passes through each of the plurality of holes 22 to form the multiple primary electron beams 20 . Next, the operation of the image acquisition mechanism 150 when acquiring a secondary electron image will be described. The primary electron optical system 151 irradiates the substrate 101 with the multiple primary electron beams 20 . Specifically, it operates as follows.

An electron beam 200 emitted from an electron gun 201 (emission source) is refracted by an electromagnetic lens 202 to illuminate the entire shaped aperture array substrate 203 . A plurality of holes 22 (openings) are formed in the shaping aperture array substrate 203, as shown in FIG. The multiple primary electron beams 20 are formed by each part of the electron beam 200 irradiated to the positions of the plurality of holes 22 passing through the plurality of holes 22 of the shaped aperture array substrate 203 .

The formed multiple primary electron beams 20 are refracted by the electromagnetic lens 205 and the electromagnetic lens 206, respectively, and arranged on the intermediate image plane of each beam of the multiple primary electron beams 20 while repeating intermediate images and crossovers. It passes through E×B separator 214 to electromagnetic lens 207 (objective lens).

When the multiple primary electron beams 20 enter the electromagnetic lens 207 (objective lens), the electromagnetic lens 207 focuses the multiple primary electron beams 20 onto the substrate 101 . The multi-primary electron beams 20 focused (focused) on the substrate 101 (specimen) surface by the objective lens 207 are collectively deflected by the main deflector 208 and the sub-deflector 209, and the substrate 101 of each beam is deflected. Each irradiation position above is irradiated. When the entire multi-primary electron beam 20 is collectively deflected by the collective blanking deflector 212 , the position of the multi-primary electron beam 20 deviates from the center hole of the limiting aperture substrate 213 , and the multi-primary electron beam is deflected by the limiting aperture substrate 213 . The entire beam 20 is blocked. On the other hand, the multi-primary electron beams 20 not deflected by the collective blanking deflector 212 pass through the center hole of the limiting aperture substrate 213 as shown in FIG. Blanking control is performed by turning ON/OFF the batch blanking deflector 212, and ON/OFF of the beam is collectively controlled. Thus, the limiting aperture substrate 213 shields the multiple primary electron beams 20 that are deflected by the collective blanking deflector 212 to a beam-OFF state. The multiple primary electron beams 20 for image acquisition are formed by the group of beams that have passed through the limiting aperture substrate 213 and are formed from the time the beam is turned on until the beam is turned off.

When a desired position of the substrate 101 is irradiated with the multiple primary electron beams 20, each beam of the multiple primary electron beams 20 from the substrate 101 corresponds to the irradiation of the multiple primary electron beams 20. , a bundle of secondary electrons (multi secondary electron beam 300) including reflected electrons is emitted.

A multi-secondary electron beam 300 emitted from substrate 101 passes through electromagnetic lens 207 to E×B separator 214 . The E×B separator 214 has a plurality of magnetic poles of two or more poles using coils and a plurality of electrodes of two or more poles. For example, it has four magnetic poles (electromagnetic deflection coils) whose phases are shifted by 90° and four poles (electrostatic deflection electrodes) whose phases are similarly shifted by 90°. Then, for example, by setting two magnetic poles facing each other as an N pole and an S pole, a directional magnetic field is generated by the plurality of magnetic poles. Similarly, a directional electric field is generated by a plurality of such electrodes, for example, by applying potentials V of opposite signs to oppositely polarized electrodes. Specifically, the E×B separator 214 generates an electric field and a magnetic field in orthogonal directions on a plane orthogonal to the direction in which the central beam of the multi-primary electron beam 20 travels (orbit center axis). The electric field exerts a force in the same direction regardless of the electron's direction of travel. On the other hand, the magnetic field exerts a force according to Fleming's left-hand rule. Therefore, the direction of the force acting on the electrons can be changed depending on the electron penetration direction. In the multi-primary electron beam 20 entering the E×B separator 214 from above, the force due to the electric field and the force due to the magnetic field cancel each other out, and the multi-primary electron beam 20 travels straight downward. On the other hand, on the multi-secondary electron beam 300 entering the E×B separator 214 from below, both the force due to the electric field and the force due to the magnetic field act in the same direction, and the multi-secondary electron beam 300 is It is bent obliquely upward and separated from the trajectory of the multi primary electron beam 20 .

The multi-secondary electron beam 300 bent obliquely upward is further bent by the deflector 218 and projected onto the multi-detector 222 while being refracted by the electromagnetic lens 224 . Multi-detector 222 detects multi-secondary electron beams 300 projected through openings in detector aperture array substrate 225 . Each beam of the multi-primary electron beam 20 collides with a detection element corresponding to each secondary electron beam of the multi-secondary electron beam 300 on the detection surface of the multi-detector 222 to amplify the electrons and generate the secondary electron beams. Electronic image data is generated for each pixel. The intensity signal detected by the multi-detector 222 is output to the detection circuit 106 . Each primary electron beam is irradiated within a sub-irradiation area surrounded by the beam pitch in the x direction and the beam pitch in the y direction where the beam is positioned on the substrate 101, and scans the sub-irradiation area ( scanning).

Secondary electron images are obtained by irradiating the multiple primary electron beams 20 and multiplying the multiple secondary electron beams 300 emitted from the substrate 101 due to the irradiation of the multiple primary electron beams 20, as described above. Detected by the detector 222 . The detected multiple secondary electron beam 300 may contain backscattered electrons. Alternatively, reflected electrons may be separated while moving through the secondary electron optical system 152 and may not reach the multi-detector 222 . Secondary electron detection data (measurement image data: secondary electron image data: inspection image data) for each pixel in the individual irradiation region (sub-irradiation region) of each primary electron beam detected by the multi-detector 222 is , are output to the detection circuit 106 in the order of measurement. In the detection circuit 106 , the analog detection data is converted into digital data by an A/D converter (not shown) and stored in the chip pattern memory 123 . The obtained secondary electron image data (secondary electron image 1 data) is output to the comparison circuit 108 together with information indicating each position from the position circuit 107 .

In order to obtain an image within the sub-irradiation area of each primary electron beam, it is necessary to detect the secondary electron beam corresponding to each primary electron beam with the corresponding detection element of the multi-detector 222 . Therefore, in a system in which the number of the multi primary electron beams 20 and the number of detection elements of the multi detector 222 are the same, the multi secondary electron beams 300 corresponding to the multi primary electron beams 20 and the plurality of detection elements of the multi detector 222 is important.

3 is a diagram showing an example of an internal configuration of an alignment circuit according to Embodiment 1. FIG. In FIG. 3, the alignment circuit 134 includes a storage device 61 such as a magnetic disk device, a corner image extraction unit 62, a corner positional relationship calculation unit 64, an overall positional relationship identification unit 66, a rotation center calculation unit 68, a vector calculation unit A unit 70, a center-corresponding coordinate calculation unit 72, a shift amount calculation unit 74, a rotation angle calculation unit 76, a shift processing unit 78, and a rotation processing unit 79 are arranged.

A beam position calculator 80 , a combiner 82 , and a detection element coordinate calculator 84 are arranged in the corner portion positional relationship calculator 64 .

corner image extractor 62, corner positional relationship calculator 64 (beam position calculator 80, synthesizer 82, and detected element coordinate calculator 84), overall positional relationship identifier 66, rotation center calculator 68, vector calculator 70 , the center-corresponding coordinate calculation unit 72, the shift amount calculation unit 74, the rotation angle calculation unit 76, the shift processing unit 78, and the rotation processing unit 79 each include a processing circuit, and the processing circuit includes an electric Circuits, computers, processors, circuit boards, quantum circuits, or semiconductor devices are included. Also, each of the "-units" may use a common processing circuit (same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. corner image extractor 62, corner positional relationship calculator 64 (beam position calculator 80, synthesizer 82, and detected element coordinate calculator 84), overall positional relationship identifier 66, rotation center calculator 68, vector calculator 70 , the center-corresponding coordinate calculator 72, the shift amount calculator 74, the rotation angle calculator 76, the shift processor 78, and the rotation processor 79, necessary input data or calculated results are stored in a memory (not shown) each time. 118.

FIG. 4 is a flow chart showing an example of main steps of the inspection method according to the first embodiment. 4, the main steps of the inspection method in Embodiment 1 are a secondary beam scanning and image acquisition step (S104), a corner image extraction step (S106), a corner portion positional relationship calculation step (S108), Detector rotation step (S110), scanning and image acquisition step (S114), corner image extraction step (S116), corner portion positional relationship calculation step (S118), overall positional relationship specifying step (S120), rotation A center calculation step (S122), a vector calculation step (S124), a center-corresponding coordinate calculation step (S126), a shift amount calculation step (S128), a rotation angle calculation step (S130), and a shift step (S132). , a rotation step (S134) and an inspection processing step (S140).

The multi-electron beam alignment method according to Embodiment 1 includes, among these steps, a secondary beam scanning and image acquisition step (S104), a corner image extraction step (S106), and a corner portion positional relationship calculation step (S108). , a detector rotation step (S110), a scanning and image acquisition step (S114), a corner image extraction step (S116), a corner portion positional relationship calculation step (S118), and an overall positional relationship specifying step (S120). , a rotation center calculation step (S122), a vector calculation step (S124), a center corresponding coordinate calculation step (S126), a shift amount calculation step (S128), a rotation angle calculation step (S130), and a shift step (S132 ) and the rotation step (S134). Either the shift step (S132) or the rotation step (S134) may be performed first. Alternatively, they may be implemented at the same time. Similarly, it does not matter which of the shift amount calculation step (S128) and the rotation angle calculation step (S130) comes first. Alternatively, they may be implemented at the same time.

FIG. 5 is a diagram showing an example of a secondary electron beam array according to Embodiment 1. FIG. In the example of FIG. 5, for example, 5×5 multi-secondary electron beams 300 are shown. Here, even when looking at the image of the beam group near the center beam shown in FIG. On the other hand, from the image of the beam group at the four corners (for example, the 2×2 beam group at the upper left corner), the corner beams actually positioned at the corners can be identified. Therefore, it is possible to obtain the positional relationship of the beam group. If the positional relationship of the beam group with respect to the image is known, the positional relationship between the beam group and the detection element that captured the image can be obtained. Therefore, in Embodiment 1, the multiple secondary electron beams 300 and the multiple detection elements of the multiple detector 222 are aligned using the corner beam group. A specific description will be given below.

As the secondary beam scanning and image acquisition step ( S<b>104 ), the primary electron optical system 151 irradiates the object surface on the XY stage 105 with the multiple primary electron beams 20 . Specifically, it operates as follows. The image acquisition mechanism 150 irradiates the multi primary electron beam 20 onto the stationary stage 105 . At that time, the main deflector 208 and the sub-deflector 209 align the center of the multi-primary electron beam 20 with the trajectory central axis of the multi-primary electron beam. Even if it is not deflected, if it is positioned on the trajectory central axis of the multi primary electron beam 20, it may be without deflection. As a result, each primary electron beam is irradiated to the scanning center position of the scanning range of the respective primary electron beam. Here, an example of an object on the stage 105 that is the irradiation position is an evaluation substrate placed on the stage 105 . Alternatively, the mark 111 may be used. Alternatively, it may be the upper surface of the stage 105 .

The deflector 226 (secondary system deflector) uses the multi-secondary electron beams 300 emitted from the object surface by the irradiation of the multi-primary electron beams 20 to the plurality of detection elements (first detectors) of the multi-detector 222 . detection element). Specifically, it operates as follows. Multiple secondary electron beams 300 emitted from the object plane are projected onto the multiple detector 222 via the detector aperture array substrate 225 by the secondary electron optical system 152 . In this state, the deflector 226 scans the multi-secondary electron beam 300 in a preset secondary beam scanning range. The multi-detector 222 detects the multi-secondary electron beam 300 with a plurality of detection elements (first detection elements) arranged in a lattice. As a result, an aperture image of the detector aperture array substrate 225 is picked up by each detection element. The multi-detector 222 detects a plurality of beams including at least corner beams positioned at corners of the multi-secondary electron beam 300 .

Here, when the multiple secondary electron beams 300 are collectively scanned by the deflector 226, as shown in FIG. do. In FIG. 5, the solid line indicates a scanning range four times the inter-beam pitch P of the multiple secondary electron beams 300 . As a result, when the multi-secondary electron beam 300 is scanned, the 2×2 beams including the corner beams are formed within each scanning range of the 2×2 detection elements corresponding to the 2×2 beam group including the corner beams. Can contain groups.

FIG. 6 is a diagram showing an example of an image captured by each detection element according to Embodiment 1. FIG. The example of FIG. 6 shows an example of an aperture image captured by 5×5 detection elements D11 to D55 corresponding to 5×5 multi-secondary electron beams 300. In FIG. Each detection element picks up an image of a plurality of secondary electron beams that have passed over its own detection element by scanning the multiple secondary electron beams 300 . In practice, beams passing through the openings of the detector aperture array substrate 225 are detected. Therefore, each detection element detects a plurality of aperture images. Secondary electron detection data detected by each detection element is output to the detection circuit 106 in the order of measurement. In the detection circuit 106 , the analog detection data is converted into digital data by an A/D converter (not shown) and stored in the chip pattern memory 123 . The obtained secondary electron image data is output to the alignment circuit 134 . Within the registration circuit 134 , the secondary electronic image data (detected image) is stored in the storage device 61 .

As the corner image extraction step (S106), the corner image extraction unit 62 extracts the image group of the corner portion from the image group of all the detection elements.

FIG. 7 is a diagram showing an image of a corner portion among an example of an image captured by each detection element according to Embodiment 1. FIG. In the example of FIG. 7, as in FIG. 6, images captured by 5×5 detection elements D11 to D55 are shown. In FIG. 7, an image group of 2×2 detection elements D11, D12, D21, and D22 including the detection element D11 is given as one of the image groups of the corner portion. Similarly, one of the image groups of the corner portion is an image group of adjacent 2×2 detection elements D14, D15, D24, and D25 including the detection element D15. Similarly, an image group of 2×2 detection elements D41, D42, D51, and D52 including the detection element D51 is one of the image groups of the corner portion. Similarly, an image group of 2×2 detection elements D44, D45, D54, and D55 including the detection element D55 can be cited as one of the image groups of the corner portion.

Aperture images of adjacent 2×2 secondary electron beams including the corner beam corresponding to the detection element D11 are detected by the 2×2 detection elements D11, D12, D21, and D22 including the detection element D11. . Similarly, adjacent 2×2 detector elements D14, D15, D24, and D25 including the detector element D15 have aperture images of 2×2 secondary electron beams including the corner beam corresponding to the detector element D15. detected. Similarly, the 2×2 detector elements D41, D42, D51, and D52 including the detector element D51 have aperture images of adjacent 2×2 secondary electron beams including the corner beam corresponding to the detector element D51. detected. Similarly, the 2×2 detector elements D44, D45, D54, and D55 including the detector element D55 have aperture images of adjacent 2×2 secondary electron beams including the corner beam corresponding to the detector element D55. detected.

Here, for example, an image group of 2×2 detection elements D11, D12, D21, and D22 is extracted.

Here, it is possible that no corner beam exists in the image. A possible cause is that the beam pitch of the multi-secondary electron beam 300 is too wide. In that case, the beam pitch is adjusted, and the secondary beam scanning and image acquisition step (S104) is repeated.

In addition, there may be cases where images of two or more of the four corners cannot be obtained. A possible cause is that the beam axis of the multi-secondary electron beam 300 is largely deviated. In that case, the beam axis is adjusted, and the secondary beam scanning and image acquisition step (S104) is repeated.

In the corner positional relationship calculation step (S108), the corner positional relationship calculator 64 (positional relationship calculator) detects a plurality of beams including corner beams and a plurality of beams including corner beams among a plurality of detection elements. A positional relationship with a plurality of detection elements (second detection elements) is calculated. Specifically, it operates as follows.

The beam position calculator 80 calculates the positions of 2×2 beam groups including corner beams for each extracted image. If an image of a 2×2 beam group including a corner beam can be picked up, the corner beam can be identified from the positional relationship. For example, if there is no other adjacent beam within a predetermined range in the direction of the adjacent beam (eg, the x direction) and in the opposite direction (the −x direction), the direction of the other adjacent beam in the orthogonal direction (eg, the −x direction) A beam can be determined to be a corner beam if there is no other adjacent beam within a predetermined range in the y direction) and the opposite direction (y direction).

8A and 8B are diagrams illustrating an example of a corner portion image group according to Embodiment 1. FIG. The example of FIG. 8 shows an image group of 2×2 detection elements D11, D12, D21, and D22. For example, in the image of the detection element D11, an image centered on the position of the scan center (the center of the scan range) of the corresponding beam B11 is captured. Then, the corner beam B11 can be determined by the method described above. If the corner beam B11 is known, the relative position of the actually captured corner beam B11 from the scan center position of the beam B11 can be calculated. Further, if the corner beam B11 is known, the adjacent beams B12, B21 and B22 can be discriminated from the positional relationship of the multi-secondary electron beams 300. FIG. Therefore, each relative position of the beams B12, B21, and B22 from the position of the scanning center of the corner beam B11 (or the corner beam B11) can be calculated. The same is true for each image of the remaining detection elements D12, D21 and D22. As a result, the positions of the beams B11, B12, B21, and B22 from the position of the scan center of the corresponding beam (the center of each image) can be calculated for each image.

FIG. 9 is a diagram showing the relationship between the detection element D11 and the positions of the beams B11, B12, B21 and B22 in the first embodiment. FIG. 9 shows the positions of the beams B11, B12, B21, and B22 calculated from the image centered on the position of the detection element D11. If the positions of the multiple secondary electron beams 300 and the corresponding detection elements are aligned, the scanning centers of the beams and the corresponding detection elements are aligned. Therefore, each of the beams B11, B12, B21, and B22 detected in the detected image exists at a position obtained by vertically and horizontally inverting the vector from the center of the detected image to each beam when the detection element D11 is the center. . Therefore, as shown in FIG. 9, when the detection element D11 is the center, the corner beam B11 exists at the position indicated by the same vector length from the detection element D11 in the opposite direction of the vector from the detected image center to the corner beam B11. . Similarly, there is a corner beam B12 at a position indicated by the same vector length from detector element D11 in the opposite direction of the vector from the detected image center to beam B12. Similarly, there is a corner beam B21 at a position indicated by the same vector length from detector element D11 in the opposite direction of the vector from the detected image center to beam B21. Similarly, there is a corner beam B22 at a position indicated by the same vector length from detector element D11 in the opposite direction of the vector from the detected image center to beam B22.

FIG. 10 is a diagram showing the relationship between the detection element D12 and the positions of the beams B11, B12, B21 and B22 in the first embodiment. FIG. 10 shows the positions of the beams B11, B12, B21, and B22 calculated from the image centered on the position of the detection element D12. As in the case of FIG. 9, when the detection element D12 is the center, the corner beam B11 exists at the position indicated by the same vector length from the detection element D12 in the opposite direction of the vector from the detection image center to the corner beam B11. Similarly, beam B12 is located at the same vector length from detector element D12 in the opposite direction of the vector from the detected image center to beam B12. Similarly, there is a beam B21 at a position indicated by the same vector length from detector element D12 in the opposite direction of the vector from the detected image center to beam B21. Similarly, beam B22 is located at the same vector length from detector element D12 in the opposite direction of the vector from the detected image center to beam B22.

FIG. 11 is a diagram showing the relationship between the detection element D21 and the positions of the beams B11, B12, B21 and B22 in the first embodiment. FIG. 11 shows the positions of the beams B11, B12, B21, and B22 calculated from the image centered on the position of the detection element D21. As in the case of FIG. 9, when the detection element D21 is the center, the corner beam B11 exists at the position indicated by the same vector length from the detection element D21 in the opposite direction of the vector from the detection image center to the corner beam B11. Similarly, beam B12 is located at the same vector length from detector element D21 in the opposite direction of the vector from the detected image center to beam B12. Similarly, beam B21 exists at a position indicated by the same vector length from detector element D21 in the opposite direction of the vector from the detected image center to beam B21. Similarly, beam B22 is located at the same vector length from detector element D21 in the opposite direction of the vector from the detected image center to beam B22.

FIG. 12 is a diagram showing the relationship between the detection element D22 and the positions of the beams B11, B12, B21 and B22 in the first embodiment. FIG. 12 shows the positions of the beams B11, B12, B21, and B22 calculated from the image centered on the position of the detection element D22. As in the case of FIG. 9, when the detection element D22 is the center, the corner beam B11 exists at the position indicated by the same vector length from the detection element D22 in the opposite direction of the vector from the detection image center to the corner beam B11. Similarly, beam B12 is located at the same vector length from detector element D22 in the opposite direction of the vector from the detected image center to beam B12. Similarly, beam B21 exists at a position indicated by the same vector length from detector element D22 in the opposite direction of the vector from the detected image center to beam B21. Similarly, beam B22 is located at the same vector length from detector element D22 in the opposite direction of the vector from the detected image center to beam B22.

Next, the synthesizer 82 synthesizes the positional relationship of each beam with respect to each detection element calculated from the four images of the corner portion.

FIG. 13 is a diagram showing an example of the relationship between the position of each detection element after synthesis and the position of each beam according to the first embodiment. The same 2×2 beams B11, B12, B21, and B22 are used in any positional relationship. Therefore, the 2×2 beams B11, B12, B21, and B22 have the same positional relationship. Therefore, the positions of the detection elements are combined so that the positions of the 2×2 beams B11, B12, B21, and B22 including the corner beam B11 are aligned. In FIG. 13, the relationship between the positions of the detector elements D11, D12, D21, and D22 at the corners and the positions of the beams B11, B12, B21, and B22 in the coordinate system (secondary coordinate system) of the multi-secondary electron beam 300. is shown. The secondary coordinate system is a coordinate system centered on the central position of the multi-secondary electron beam 300 . Therefore, the coordinates of each secondary electron beam of the multiple secondary electron beams 300 can be specified in the secondary coordinate system. Therefore, the coordinates of the detection element in the secondary coordinate system can be specified if the positional relationship with each beam is known.

Also, the positional relationship is similarly calculated for other corner portions. Specifically, the relationship between the position of each detection element D14, D15, D24, D25 and the position of each beam B14, B15, B24, B25 is calculated. Similarly, the relationship between the position of each detection element D41, D42, D51, D52 and the position of each beam B41, B42, B51, B52 is calculated. Similarly, the relationship between the position of each detection element D44, D45, D54, D55 and the position of each beam B44, B45, B54, B55 is calculated.

As a detector rotation step (S110), detector stage control circuit 130 controls drive mechanism 132 to rotate rotation stage 227. FIG. Thereby, the rotation stage 227 rotates the multi-detector 222 by a preset rotation angle φ (first rotation angle).

As the secondary beam scanning and image acquisition step (S114), the image acquisition mechanism 150 irradiates the multi primary electron beam 20 onto the stage 105 in a stopped state. At that time, the main deflector 208 and the sub-deflector 209 align the center of the multi-primary electron beam 20 with the trajectory central axis of the multi-primary electron beam.

Then, the deflector 226 (secondary system deflector) causes the multi-secondary electron beams 300 emitted from the object surface in a state in which the multi-detector 222 has been rotated, to form a plurality of detection elements (secondary system deflector) of the multi-detector 222 . 1 detection element). After rotation, the multi-detector 222 detects the multi-secondary electron beam 300 with a plurality of detection elements (first detection elements) arranged in a lattice. As a result, an aperture image of the detector aperture array substrate 225 is picked up by each detection element. In other words, the multi-detector 222 detects multiple beams including the corner beams. The scanning method is the same as the secondary beam scanning and image acquisition step (S104).

In the corner image extraction step (S116), the corner image extraction unit 62 extracts the image group of the corner portion from the image group of all the detection elements detected after the multi-detector 222 is rotated. The extraction method is the same as the corner image extraction step (S106).

In the corner positional relationship calculation step (S118), the corner positional relationship calculation unit 64 detects a plurality of beams including the corner beam and a plurality of beams including the corner beam after the multi-detector 222 has rotated. A positional relationship with the element (second detection element) is calculated. The content of the corner portion positional relationship calculation step (S118) is the same as the corner portion positional relationship calculation step (S108).

As described above, the relationship between the positions of the detection elements D11, D12, D21 and D22 and the positions of the beams B11, B12, B21 and B22 after the multi-detector 222 is rotated is calculated. Similarly, the multi-detector 222 calculates the relationship between the position of each detection element D14, D15, D24, D25 and the position of each beam B14, B15, B24, B25 in the secondary coordinate system after rotation. Similarly, the multi-detector 222 calculates the relationship between the position of each detection element D41, D42, D51, D52 after rotation and the position of each beam B41, B42, B51, B52. Similarly, the multi-detector 222 calculates the relationship between the position of each detection element D44, D45, D54, D55 after rotation and the position of each beam B44, B45, B54, B55.

As the overall positional relationship specifying step (S120), the overall positional relationship specifying unit 66 specifies the overall positional relationship between the multi-secondary electron beam 300 and all the detection elements.

14 is a diagram showing an example of overall positional relationship according to Embodiment 1. FIG. Since the positional relationships of the four corners have been calculated, the positional relationships of the four corners are combined. Since the arrangement positional relationship and the arrangement pitch of the 5×5 detection elements D11 to D55 of the multi-detector 222 are known in advance, the 2×2 detection elements calculated at the individual corners are taken as one set. Four sets of corners are fitted to each alignment position. As a result, as shown in FIG. 14, the overall position of the 5×5 multiple secondary electron beams 300 can be specified with respect to the overall position of the 5×5 detection elements. Therefore, it is possible to identify the positional relationship of the 5×5 detection elements D11 to D55 in the secondary coordinate system.

15 is a diagram showing an example of coordinates of a plurality of detection elements of a multi-detector before and after rotation according to Embodiment 1. FIG. As shown in FIG. 15, the detection element D11 (D11') moves from coordinates (x1, y1) before rotation to coordinates (X1, Y1) after rotation about unknown rotation center coordinates (rx, ry). moving. Similarly, the detection element D12 (D12') moves from coordinates (x2, y2) before rotation to coordinates (X2, Y2) after rotation about unknown rotation center coordinates (rx, ry). .

As the rotation center calculation step (S122), the rotation center calculation unit 68 calculates the rotation angle φ (first rotation angle) obtained by rotating the multi-detector 222, a plurality of beams including the corner beam, and a plurality of detection beams before and after rotation. The rotation center coordinates of the multi-detector 222 are calculated based on the positional relationship with the elements. Specifically, as described above, the positional relationship between the 2×2 beams including the corner beams and the 2×2 detection elements before rotation corresponding to these beams has been calculated. Therefore, the detection element coordinate calculator 84 calculates the coordinates of the detection elements D11, D12, D21, and D22 in the secondary coordinate system from the positional relationship. Since the coordinates of each secondary electron beam can be defined by the secondary coordinate system, the coordinates of each detection element D11, D12, D21 and D22 can be calculated. Similarly, the positional relationship between the 2×2 beams including the corner beams and the rotated 2×2 detection elements corresponding to these beams has already been calculated. The position of the multi-secondary electron beam 300 in the secondary coordinate system does not change before and after the rotation of the multi-detector 222 . Therefore, the detection element coordinate calculator 84 calculates the coordinates of the detection elements D11, D12, D21, and D22 in the secondary coordinate system after the rotation of the multi-detector 222 based on the positional relationship of the multi-detector 222 after rotation. calculate. The positions before and after rotation of two or more of the 2×2 detection elements before and after rotation are used. Here, for example, the rotation angle φ obtained by rotating the multi-detector 222 and the coordinates (x1, y1), (x2 , y2), (X1, Y1), and (X2, Y2), the rotation center coordinates (rx, ry) of the multi-detector 222 are calculated.

16 is a diagram showing an arithmetic expression for calculating rotation center coordinates according to Embodiment 1. FIG. The rotation center coordinates (rx, ry) can be obtained from the relationship between the coordinates before and after rotation using equation (1). In equation (1), (x1, y1), (x2, y2), ..., (xn, yn) and (X1, Y1), (X2, Y2), ..., (Xn, Yn) , the coordinates of the detection element before and after rotation of n points are used, but n should be 2 or more. Also, in FIG. 16, the detection element is shown as PD. Note that the coordinates of 2×2 detection elements are known for each corner. Therefore, the calculation using the four coordinates of the detection element before and after the rotation can improve the accuracy more than the calculation using the coordinates of the detection element before and after the rotation of the two points. Furthermore, the coordinates of the 2×2 detection elements of the remaining three corners in the secondary coordinate system can be similarly calculated from the individual positional relationships. Alternatively, the coordinates of the 2×2 detection elements of the remaining three corners in the secondary coordinate system can be calculated from the overall positional relationship. Therefore, the coordinates of the detection elements before and after rotation of the 16 points of the four corners can be known. Calculation using 16 coordinates of the detection element before and after rotation can further improve the accuracy compared to calculation using 4 coordinates of the detection element before and after rotation.

In the above example, the operation when the relative rotation center position of the multi-detector 222 with respect to the plurality of detection elements D11 to D55 arranged on the detector stage 229 is unknown. When the relative rotation center positions for the plurality of detection elements D11 to D55 are known in advance, the detector rotation step (S110), the scanning and image acquisition step (S114), the corner image extraction step (S116), and the corner The positional relation calculation step (S118) and each step may be omitted. In such a case, in the rotation center calculation step (S122), the coordinates of the rotation center coordinates C1 can be calculated from the relative positional relationship from the already calculated coordinates of at least one of the plurality of detection elements D11 to D55 to the rotation center position. good.

As the vector calculation step (S124), the vector calculation unit 70 calculates, for example, a vector from the coordinates of the actual corner detection element to the rotation center coordinates C1 (rx, ry) among the 2×2 corner detection elements. is decomposed into two vectors from the coordinates of the actual corner detection element to the coordinates of the remaining two detection elements on the outer circumference side.

17A and 17B are diagrams for explaining a method of vector calculation of detection element coordinates according to Embodiment 1. FIG. A vector from the coordinates (x1, y1) of the detection element D11 of the actual corner detection element D11 before rotation and the two detection elements D12 and D21 on the outer circumference side before rotation to the rotation center coordinates (rx, ry) Let R1 be the vector Q1 from the coordinates (x1, y1) of the detection element D11 to the coordinates (x2, y2) of the detection element D12 and the vector Q1 from the coordinates (x1, y1) of the detection element D11 to the coordinates (x3, y3) of the detection element D21. vector P1 and . Vector R1 can be defined by the following equation (2) using vector P1 and vector Q1. In expression (2), the symbol (-) indicating a vector is omitted.
(2) R1=αP1+βQ1

18 is a diagram showing an arithmetic expression for calculating vector coefficients according to Embodiment 1. FIG. The unknown vector coefficients α and β can be obtained by Equation (3). Let vector P1=(Px, Py), vector Q1=(Qx, Qy), and vector R1=(Rx, Ry).

In the above example, the detection element D11 is used as the base point detection element, but the present invention is not limited to this. Any of the four detection elements D11, D15, D51 and D55 of the actual corners may be used for calculation. By using one of the four detection elements D11, D15, D51, D55 of the actual corner, vector operation can be performed using the positions of the 2×2 detection elements of such one corner. Alternatively, it is preferable to use the overall positional relationship as shown in FIG. If the overall positional relationship is used, the detection elements that serve as base points may be detection elements other than the four detection elements D11, D15, D51, and D55 of the actual corners. For example, detection element D22 can be used. In that case, for example, the positions of the two detection elements D42 and D24 can be used for vector calculation. The overall positional relationship in the secondary coordinate system has already been calculated. Therefore, the coordinates of each detection element can be obtained from the secondary coordinate system.

In the center-corresponding coordinate calculating step (S126), the center-corresponding coordinate calculating unit 72 calculates multiple secondary electron Corresponding coordinates C2 for beams B11, B21 and B12 are calculated.

FIG. 19 is a diagram for explaining a method of vector calculation of secondary electron beam coordinates in the first embodiment. In FIG. 19, the corresponding coordinate C2 is the synthesis of the two vectors when the two decomposed vectors αP2 and βQ2 are applied to the coordinates of the three secondary electron beams B11, B21 and B12 of the multi-secondary electron beams. Computed as vector coordinates. Specifically, the center-corresponding coordinate calculator 72 multiplies the vector P2 from the secondary electron beam B11 corresponding to the reference detection element D11 to the secondary electron beam B21 corresponding to the detection element D21 by the vector coefficient α. A resultant vector R2 of αP2 and βQ2 obtained by multiplying the vector Q2 from the secondary electron beam B11 corresponding to the detection element D11 to the secondary electron beam B12 corresponding to the detection element D12 by the vector coefficient β is calculated. Then, the center-corresponding coordinate calculator 72 calculates the coordinates of the combined vector R2 with the secondary electron beam B11 as the starting point as the corresponding coordinates C2.

In the shift amount calculation step (S128), the shift amount calculation unit 74 calculates, based on the positional relationship between the 2×2 beams including the corner beams and the 2×2 detection elements before rotation corresponding to these beams, A shift amount S for aligning the plurality of detection elements D11-D55 of the multi-detector 222 with the multi-secondary electron beams B11-B55 is calculated. For example, the shift amount S is calculated so that the positions of the 2×2 detection elements before rotation corresponding to these beams are aligned with the positions of the 2×2 beams including the corner beams. Specifically, if the shift amount S is calculated so as to minimize the positional deviation between the 2×2 beams including the corner beams and the 2×2 detection elements before rotation corresponding to these beams, good. This is particularly effective when there is no rotation error between the multiple detection elements of the multi-detector 222 and the multi-secondary electron beam 300 . Alternatively, the shift amount calculator 74 calculates, for example, the shift amount S (dx, dy) for shifting the rotation center coordinates C1 (rx, ry) to the corresponding coordinates C2 for the multi-secondary electron beam. This is particularly effective when there is a rotational error between the plurality of detection elements D11-D55 of the multi-detector 222 and the multi-secondary electron beams B11-B55.

As the rotation angle calculation step (S130), the rotation angle calculation unit 76 uses one of the above-described positional relationships before and after the rotation and the rotation center coordinate C1 of the multi-detector 222 to calculate the plurality of detection elements of the multi-detector 222 ( A rotation angle θ (second rotation angle) for aligning the first detection element) with the multi-secondary electron beam 300 is calculated. Specifically, the rotation angle calculator 76 calculates a plurality of A rotation angle θ (second rotation angle) for aligning the detection elements D11 to D55 with the multiple secondary electron beams B11 to B55 is calculated. Needless to say, when the coordinates before rotation are used, the angle of rotation from the state before rotation is used, and when the coordinates after rotation are used, the angle of rotation from the state after rotation is used.

FIG. 20 is a diagram showing an arithmetic expression for calculating alignment angles according to the first embodiment. The detected element coordinates (X, Y) after alignment are obtained by using the detected element coordinates (x, y) before alignment, the rotation center coordinates (rx, ry), and the unknown rotation angle θ. 20 can be defined as in Equation (4). By modifying the equation (4), the unknown rotation angle θ can be obtained. The detector element coordinates (X, Y) after alignment match the coordinates of the corresponding secondary electron beam.

In order to increase the accuracy of the rotation angle θ, it is preferable to obtain the unknown rotation angle θ using the coordinates (x1, y1) to (x4, y4) of the 2×2 detection elements of one corner. be. In order to further improve the accuracy, it is preferable to obtain the unknown rotation angle θ using the coordinates (x1, y1) to (x16, y16) of a total of 16 detection elements of the four corners.

As described above, the shift amount (dx, dy) and the rotation angle θ for alignment can be obtained.

In the shift step (S132), under the control of the shift processing unit 78, the x, y stage 228 (moving mechanism) uses the shift amount S to move the multi-detector 222 relative to the multi-secondary electron beam 300. move. Specifically, the multi-detector 222 is translated so as to shift the rotation center coordinate C1 to the corresponding coordinate C2. Here, the multi-detector 222 is mechanically moved.

As the rotation step (S134), the rotation stage 227 (rotation mechanism) rotates the multi-detector 222 at the rotation angle θ under the control of the rotation processing unit 79. FIG.

By the above operation, the plurality of detection elements D11 to D55 of the multi-detector 222 can be aligned with the multi-secondary electron beams B11 to B55.

As the inspection processing step (S140), the substrate 101 is inspected using the inspection apparatus 100 that has been aligned.

FIG. 21 is a diagram showing an example of a plurality of chip regions formed on the semiconductor substrate according to Embodiment 1. FIG. In FIG. 21, when the substrate 101 is a semiconductor substrate (wafer), a plurality of chips (wafer dies) 332 are formed in a two-dimensional array in an inspection area 330 of the semiconductor substrate (wafer). A mask pattern for one chip formed on a mask substrate for exposure is transferred to each chip 332 in a reduced size of, for example, 1/4 by an exposure device (stepper) (not shown). A mask pattern for one chip is generally composed of a plurality of figure patterns.

FIG. 22 is a diagram for explaining inspection processing according to the first embodiment. As shown in FIG. 22, the area of each chip 332 is divided into a plurality of stripe areas 32 with a predetermined width in the y direction, for example. The scanning operation by the image acquisition mechanism 150 is performed for each stripe region 32, for example. For example, while moving the stage 105 in the -x direction, the scanning operation of the stripe region 32 is relatively advanced 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 area 33 is performed by collective deflection of the entire multi-primary electron beam 20 by the main deflector 208 .

The example of FIG. 22 shows, for example, the case of the multi-primary electron beams 20 arranged in 5×5 rows. The irradiation area 34 that can be irradiated by one irradiation of the multi primary electron beams 20 is (the x direction obtained by multiplying the 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. size)×(the y-direction size obtained by multiplying the inter-beam pitch in the y-direction of the multi-primary electron beams 20 on the substrate 101 surface by the number of beams in the y-direction). The irradiation area 34 becomes the field of view of the multiple primary electron beams 20 . Each primary electron beam 8 constituting the multi-primary electron beam 20 is irradiated within a sub-irradiation region 29 surrounded by the beam-to-beam pitch in the x direction and the beam-to-beam pitch in the y direction where the beams are positioned. , scans (scanning operation) the inside of the sub-irradiation region 29 . Each primary electron beam 8 is in charge of one of sub-irradiation regions 29 different from each other. In each shot, each primary electron beam 10 irradiates the same position within the assigned sub-irradiation region 29 . Movement of the primary electron beam 10 within the sub-irradiation region 29 is performed by collective deflection of the entire multi-primary electron beam 20 by the sub-deflector 209 . Such an operation is repeated to sequentially irradiate one sub-irradiation region 29 with one primary electron beam 10 .

It is preferable to set the width of each stripe region 32 to the same size as the y-direction size of the irradiation region 34, or to a size narrower by the scan margin. The example of FIG. 22 shows the case where the irradiation area 34 has the same size as the rectangular area 33 . However, it is not limited to this. The irradiation area 34 may be smaller than the rectangular area 33 . Or it doesn't matter if it's big. Each of the primary electron beams 10 forming the multi-primary electron beam 20 is irradiated within the sub-irradiation region 29 where the beam is positioned, and scans (scans) the sub-irradiation region 29 . When the scanning of one sub-irradiation region 29 is completed, the main deflector 208 collectively deflects the entire multi-primary electron beam 20 to move the irradiation position to the adjacent rectangular region 33 within the same stripe region 32 . Such an operation is repeated to sequentially irradiate the inside of the stripe region 32 . After the scanning of one stripe region 32 is completed, the irradiation region 34 moves to the next stripe region 32 by moving the stage 105 and/or collectively deflecting the entire multi-primary electron beam 20 by the main deflector 208 . As described above, each sub-irradiation area 29 is scanned and a secondary electron image is acquired by irradiation with each primary electron beam 10 . A secondary electron image of the rectangular area 33 , a secondary electron image of the striped area 32 , or a secondary electron image of the chip 332 is constructed by combining the secondary electron images of the respective sub-irradiation areas 29 . Also, when actually performing image comparison, the sub-irradiation area 29 in each rectangular area 33 is further divided into a plurality of frame areas 30, and the frame image 31 of each frame area 30 is compared. The example of FIG. 22 shows a case where a sub-irradiation area 29 scanned by one primary electron beam 8 is divided into four frame areas 30 formed by, for example, dividing each into two in the x and y directions. .

Here, when the substrate 101 is irradiated with the multi primary electron beams 20 while the stage 105 is continuously moving, the main deflector 208 collectively deflects the irradiation position of the multi primary electron beams 20 so as to follow the movement of the stage 105 . A tracking operation is performed by Therefore, the emission positions of the multi-secondary electron beams 300 change every second with respect to the orbital central axis of the multi-primary electron beams 20 . Similarly, when scanning the sub-irradiation region 29, the emission position of each secondary electron beam changes within the sub-irradiation region 29 every second. The deflector 226 collectively deflects the multi-secondary electron beams 300 so that the secondary electron beams whose emission positions are changed in this way are irradiated in the corresponding detection regions of the multi-detector 222 .

As described above, the image acquisition mechanism 150 advances the scanning operation for each stripe region 32 . An image (secondary electron image) used for inspection is obtained by irradiating the substrate 101 to be inspected on the stage 105 with the multiple primary electron beams 20, and by irradiating the multiple primary electron beams 20, the substrate 101 emits multiple secondary electrons. It is obtained by detecting the beam 300 with the multi-detector 222 . The detected multiple secondary electron beam 300 may contain backscattered electrons. Alternatively, reflected electrons may be separated while moving through the secondary electron optical system 152 and may not reach the multi-detector 222 . 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. be. In the detection circuit 106 , the analog detection data is converted into digital data by an A/D converter (not shown) and stored in the chip pattern memory 123 . The obtained measured image data is transferred to the comparison circuit 108 together with information indicating each position from the position circuit 107 .

FIG. 23 is a configuration diagram showing an example of the internal configuration of the comparison circuit according to the first embodiment. 23, storage devices 50, 52, 56 such as magnetic disk devices, a frame image forming unit 54, an alignment unit 57, and a comparison unit 58 are arranged in the comparison circuit 108. FIG. Each of the frame image generator 54, alignment unit 57, and comparison unit 58 includes a processing circuit, which may be an electric circuit, computer, processor, circuit board, quantum circuit, or semiconductor. equipment, etc. are included. Also, each of the "-units" may use a common processing circuit (same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. Necessary input data or calculation results in the frame image creating section 54, the positioning section 57, and the comparing section 58 are stored in a memory (not shown) or the memory 118 each time.

The measured image data (beam image) transferred into the comparison circuit 108 is stored in the storage device 50 .

Then, the frame image creating unit 54 creates a frame image 31 for each of a plurality of frame areas 30 obtained by further dividing the image data of the sub-irradiation areas 29 acquired by the scanning operation of each primary electron beam 10. . Then, the frame area 30 is used as a unit area of the image to be inspected. It should be noted that each frame area 30 is preferably configured such that the margin areas overlap each other so that there is no missing image. The created frame image 31 is stored in the storage device 56 .

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 plurality of figure 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.

As described above, the figures defined in the design pattern data are, for example, rectangles and triangles as basic figures. The figure data defining the shape, size, position, etc. of each pattern figure is stored with information such as figure code, which is an identifier for distinguishing figure types.

When the design pattern data as such graphic data is input to the reference image generating circuit 112, it is developed into data for each graphic, and the graphic code, graphic dimensions, etc. indicating the graphic shape of the graphic data are interpreted. Then, it develops into binary or multi-valued design pattern image data as a pattern to be arranged in a grid of a predetermined quantization size as a unit, and outputs the data. In other words, the design data is read, and the occupancy rate of the figure in the design pattern is calculated for each square obtained by virtually dividing the inspection area into squares having a predetermined size as a unit, and n-bit occupancy rate data is obtained. Output. For example, it is preferable to set one square as one pixel. Assuming that one pixel has a resolution of 1/2 ⁸ (=1/256), a small area of 1/256 is allocated for the area of the figure arranged in the pixel, and the occupancy rate in the pixel is reduced. Calculate. Then, it becomes 8-bit occupancy rate data. Such squares (inspection pixels) may be aligned with the pixels of the measurement data.

Next, the reference image generation circuit 112 filters the design image data of the design pattern, which is image data of the figure, using a predetermined filter function. As a result, the design image data, which is image data on the design side in which the image intensity (gradation value) is a digital value, can be matched with the image generation characteristics obtained by the irradiation of the multi-primary electron beams 20 . Image data for each pixel of the created reference image is output to the comparison circuit 108 . The reference image data transferred into the comparison circuit 108 is stored in the storage device 52 .

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

Then, the comparison unit 58 compares the secondary electron image of the substrate 101 placed on the stage 105 with a predetermined image. Specifically, the comparison unit 58 compares the frame image 31 and the reference image pixel by pixel. A comparison unit 58 compares the two for each pixel according to a predetermined determination condition, and determines whether or not there is a defect such as a shape defect. For example, if the gradation value difference for each pixel is larger than the determination threshold value Th, it is determined as defective. Then, the comparison result is output. The comparison result may be output to the storage device 109 or memory 118, or output from the printer 119. FIG.

In the above example, the die-database inspection has been described, but the present invention is not limited to this. It may be a case where a die-to-die inspection is performed. When performing a die-to-die inspection, between a target frame image 31 (die 1) and a frame image 31 (die 2) in which the same pattern as the frame image 31 is formed (another example of a reference image) , the alignment and comparison processing described above may be performed.

As described above, according to Embodiment 1, it is possible to efficiently align the multiple secondary electron beams and the secondary electron detector.

Embodiment 2.
Embodiment 2 describes a configuration in which alignment is performed by moving the multi-secondary electron beam 300 instead of moving the multi-detector 222 . Points that are not particularly described below are the same as those in the first embodiment.

FIG. 24 is a configuration diagram showing the configuration of an inspection apparatus according to Embodiment 2. FIG. 24 is the same as FIG. 1 except that alignment coils 230 and 231 are added. Alignment coils 230 and 231 are placed, for example, on the secondary electron trajectory between deflector 218 and electromagnetic lens 224 . Alignment coils 230 and 231 are another example of a moving mechanism. Note that in FIG. 1, the x,y stage 228 or the detector stage 229 including the x,y stage 228 may be omitted.

In the second embodiment, in the shift step (S132), the shift amount is used to shift the trajectory of the multi-secondary electron beam 300, thereby moving the multi-detector 222 relative to the multi-secondary electron beam 300. move. Specifically, instead of the x, y stage 228 which is a part of the detector stage 229, alignment coils 230 and 231 are used to move the orbit center axis of the multi-secondary electron beam 300, so that the rotation center coordinates Translate so that C1 is shifted relative to the corresponding coordinate C2.

As described above, according to the second embodiment, it is possible to perform alignment without mechanically moving the multi-detector 222 in parallel. Although two alignment coils 230 and 231 are used in this embodiment, only one may be used. Also, in the rotating step (S134), instead of rotating stage 227, which is part of detector stage 229, a magnetic lens or an electromagnetic lens may be used to rotate the trajectory of multi-secondary electron beam 300. FIG.

Embodiment 3.
Embodiment 3 describes a configuration that takes into consideration the beam pitch. The configuration of the inspection apparatus 100 is the same as in FIG. Alternatively, it is similar to FIG. Points that are not particularly described below are the same as those in the first or second embodiment.

25 is a diagram showing an example of an internal configuration of an alignment circuit according to Embodiment 3. FIG. 25 is the same as FIG. 3 except that a beam pitch calculation unit 90, a determination unit 92, and a beam pitch adjustment processing unit 94 are added.

corner image extractor 62, corner positional relationship calculator 64 (beam position calculator 80, synthesizer 82, and detected element coordinate calculator 84), overall positional relationship identifier 66, rotation center calculator 68, vector calculator 70 , a center-corresponding coordinate calculator 72, a shift amount calculator 74, a rotation angle calculator 76, a shift processor 78, a rotation processor 79, a beam pitch calculator 90, a determination unit 92, and a beam pitch adjustment processor 94. "Part" includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, or the like. Also, each of the "-units" may use a common processing circuit (same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. corner image extractor 62, corner positional relationship calculator 64 (beam position calculator 80, synthesizer 82, and detected element coordinate calculator 84), overall positional relationship identifier 66, rotation center calculator 68, vector calculator 70 , center corresponding coordinate calculation unit 72, shift amount calculation unit 74, rotation angle calculation unit 76, shift processing unit 78, rotation processing unit 79, beam pitch calculation unit 90, determination unit 92, and beam pitch adjustment processing unit 94. Input data or calculated results are stored in a memory (not shown) or the memory 118 each time.

FIG. 26 is a flow chart showing an example of main steps of an inspection method according to the third embodiment. In FIG. 26, between the corner portion positional relationship calculation step (S108) and the detector rotation step (S110), a beam pitch calculation step (S109-1), a determination step (S109-2), and a beam pitch adjustment step (S109-3) and are the same as in FIG.

Alternatively, the beam A pitch calculation step (S109-1), a determination step (S109-2), and a beam pitch adjustment step (S109-3) may be added.

The contents of each step up to the corner portion positional relationship calculation step (S108) are the same as those in the first embodiment.

As the beam pitch calculation step (S109-1), the beam pitch calculator 90 specifies the positional relationship of one corner portion, and then calculates the beam pitch of the multi-secondary electron beam 300 based on the specified positional relationship. . The beam pitch is obtained by calculating the distance between two adjacent beams from the positions of the 2×2 beam group including the corner beams.

As the determination step (S109-2), the determination unit 92 determines whether the beam pitch P is within a predetermined range. If the beam pitch P is not within the predetermined range, the process proceeds to the beam pitch adjustment step (S109-3). If the beam pitch P is within the predetermined range, the process proceeds to the detector rotation step (S110).

The beam pitch adjustment processing unit 94 adjusts the beam pitch P as the beam pitch adjustment step (S109-3). Specifically, the beam pitch adjustment processing section 94 outputs a command for controlling the lens control circuit 124 . The lens control circuit 124 adjusts the beam pitch P by adjusting the magnification of the multi-secondary electron beam 300 by adjusting the electromagnetic lens 224 .

After adjusting the beam pitch, the process returns to the secondary beam scanning and image acquisition step (S104), and the steps from the secondary beam scanning and image acquisition step (S104) to the beam pitch adjustment step (S104) are repeated until the beam pitch P is within a predetermined range. Each step up to S109-3) is repeated. The contents of subsequent steps are the same as in the first embodiment. Therefore, the shift amount is calculated when the beam pitch is within a predetermined range.

As described above, in the third embodiment, when the beam pitch deviates from the design value after the coordinate extraction of the multi-detector 222, the pitch adjustment (magnification adjustment by the lens) is performed, and then the alignment flow proceeds. . This enables highly accurate alignment.

Embodiment 4.
In the fourth embodiment, a configuration that considers the beam distribution shape (beam array shape) of the multi-secondary electron beam 300 will be described. Points not particularly described below are the same as any one of the first to third embodiments.

FIG. 27 is a configuration diagram showing the configuration of an inspection apparatus according to Embodiment 4. FIG. 27 is the same as FIG. 1 except that a distortion corrector 232 and a distortion corrector control circuit 135 are added. The distortion corrector 232 is placed, for example, on the secondary electron trajectory between the deflector 218 and the electromagnetic lens 224 . Although the example of FIG. 27 shows a configuration in which a distortion corrector 232 is added to the configuration of FIG. 1, the configuration is not limited to this. For example, a configuration in which a distortion corrector 232 is added to FIG. 24 may be used.

In addition, the control computer 110 is connected via the bus 120 to the position circuit 107, the comparison circuit 108, the reference image generation circuit 112, the stage control circuit 114, the lens control circuit 124, the blanking control circuit 126, the deflection control circuit 128, the detector It is connected to a stage control circuit 130 , an E×B control circuit 133 , an alignment circuit 134 , a distortion corrector control circuit 135 , a storage device 109 , a memory 118 and a printer 119 . The distortion corrector 232 is controlled by a distortion corrector control circuit 135 .

FIG. 28 is a diagram showing an example of the internal configuration of an alignment circuit according to the fourth embodiment. 28 is the same as FIG. 3 except that a shape evaluation value calculation unit 95, a determination unit 96, and a distortion adjustment processing unit 97 are added.

corner image extractor 62, corner positional relationship calculator 64 (beam position calculator 80, synthesizer 82, and detected element coordinate calculator 84), overall positional relationship identifier 66, rotation center calculator 68, vector calculator 70 , the center-corresponding coordinate calculator 72, the shift amount calculator 74, the rotation angle calculator 76, the shift processor 78, the rotation processor 79, the shape evaluation value calculator 95, the determination unit 96, and the distortion adjustment processor 97. "Part" includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, or the like. Also, each of the "-units" may use a common processing circuit (same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. corner image extractor 62, corner positional relationship calculator 64 (beam position calculator 80, synthesizer 82, and detected element coordinate calculator 84), overall positional relationship identifier 66, rotation center calculator 68, vector calculator 70 , center-corresponding coordinate calculator 72 , shift amount calculator 74 , rotation angle calculator 76 , shift processor 78 , rotation processor 79 , shape evaluation value calculator 95 , determination unit 96 , and distortion adjustment processor 97 . Input data or calculated results are stored in a memory (not shown) or the memory 118 each time.

FIG. 29 is a flow chart showing an example of main steps of an inspection method according to the fourth embodiment. In FIG. 29, between the overall positional relationship identifying step (S120) and the rotation center calculating step (S122), a shape evaluation value calculating step (S121-1), a determining step (S121-2), and a distortion adjusting step (S121 -3) is the same as in FIG.

The contents of each step up to the overall positional relationship specifying step (S120) are the same as in the first embodiment.

As the shape evaluation value calculation step (S121-1), the beam distribution shape of the multi-secondary electron beam 300 is evaluated after specifying the overall positional relationship. Specifically, the shape evaluation value calculator 95 calculates the shape evaluation value Eval.

30A and 30B are diagrams for explaining a method of calculating a shape evaluation value according to the fourth embodiment. FIG. In the example of FIG. 30, for example, the positions of 3×3 multi-secondary electron beams 300 are shown. As shown in FIG. 30, from the position information of each beam, the length lk of the side connecting adjacent beams and the interior angle θk of four rectangles surrounded by the four sides are obtained. Then, the shape evaluation value calculator 95 calculates the shape evaluation value Eval using the length lk of each side and the interior angle θk of the rectangle using the formula shown in FIG.

As the determination step (S121-2), the determination unit 96 determines whether the beam distribution shape of the multi-secondary electron beam 300 is within a predetermined range. Specifically, it is determined whether the shape evaluation value Eval is within a predetermined range. If the shape evaluation value Eval is not within the predetermined range, the process proceeds to the distortion adjustment step (S121-3). If the shape evaluation value Eval is within the predetermined range, the process proceeds to the rotation center calculation step (S122).

As the distortion adjustment step (S121-3), the distortion adjustment processor 97 adjusts the beam distribution shape of the multi-secondary electron beam 300. FIG. Specifically, the distortion adjustment processing section 97 outputs a command for controlling the distortion corrector control circuit 135 . The distortion corrector control circuit 135 adjusts the beam distribution shape of the multi-secondary electron beam 300 by adjusting the excitation of the distortion corrector 232 .

31A and 31B are diagrams for explaining an example of a configuration of a distortion corrector and an example of an adjustment method according to Embodiment 4. FIG. In FIG. 31, the distortion corrector 232 is composed of, for example, eight magnetic poles indicated by C1 to C8. The eight magnetic poles are arranged to surround the multi-secondary electron beam 30 . In the example of FIG. 31, a state is shown in which C1, C2, C5 and C6 are magnetized toward the center side and C3, C4, C7 and C8 are magnetized to become N poles. In this case, a magnetic field is generated in the direction indicated by the solid line. As a result, the Lorentz force works in the direction of tension in the x direction, and the Lorentz force works in the direction of compression in the y direction. Therefore, the beam distribution shape is corrected to extend in the x direction and shrink in the y direction. Also, if the excitation directions of the eight magnetic poles are reversed, a magnetic field is generated in the direction indicated by the dotted line. As a result, the Lorentz force works in the direction of tension in the y direction, and the Lorentz force works in the direction of compression in the x direction. Therefore, the beam distribution shape is corrected to extend in the y direction and contract in the x direction.

32A and 32B are diagrams for explaining another example of the configuration of the distortion corrector and another example of the adjustment method according to Embodiment 4. FIG. In FIG. 32, the distortion corrector 232 is composed of, for example, eight magnetic poles indicated by C1 to C8, as in FIG. In the example of FIG. 32, a state is shown in which C1, C4, C5 and C8 are magnetized toward the center side and C2, C3, C6 and C7 are magnetized to become N poles. In this case, a magnetic field is generated in the direction indicated by the solid line. As a result, the Lorentz force works in the direction of tension in the direction of 135°-315° with respect to the x direction, and the Lorentz force works in the direction of compression in the direction of 45°-225°. Therefore, the beam distribution shape is corrected to extend in the direction of 135°-315° and contract in the direction of 45°-225°. Also, if the excitation directions of the eight magnetic poles are reversed, a magnetic field is generated in the direction indicated by the dotted line. As a result, the Lorentz force works in the direction of tension in the direction of 45°-225°, and the Lorentz force works in the direction of compression in the direction of 135°-315°. Therefore, the beam distribution shape is corrected to extend in the direction of 45°-225° and contract in the direction of 135°-315°.

After adjusting the beam distribution shape, the process returns to the secondary beam scanning and image acquisition step (S104), and the steps from the secondary beam scanning and image acquisition step (S104) to the distortion adjustment step (S104) are repeated until the beam distribution shape is within a predetermined range. Each step up to S121-3) is repeated. The contents of subsequent steps are the same as in the first embodiment. Therefore, the shift amount is calculated while the shape evaluation value is within a predetermined range.

As described above, in the fourth embodiment, when the beam distribution shape deviates from the design value after specifying the overall positional relationship, the alignment flow is advanced after performing distortion adjustment. This enables highly accurate alignment.

In the above description, a series of "-circuits" includes processing circuits, and the processing circuits include electric circuits, computers, processors, circuit boards, quantum circuits, semiconductor devices, and the like. Also, each "-circuit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. A program that causes a processor or the like to be executed may be recorded on a recording medium such as a magnetic disk device, magnetic tape device, FD, or ROM (Read Only Memory). For example, position circuit 107, comparison circuit 108, reference image generation circuit 112, stage control circuit 114, lens control circuit 124, blanking control circuit 126, deflection control circuit 128, detector stage control circuit 130, E×B control circuit 133 , and alignment circuitry 134 may comprise at least one processing circuitry as described above. For example, the processing within these circuits may be performed by the control computer 110 .

The embodiments have been described above with reference to specific examples. However, the invention is not limited to these specific examples. Although the example of FIG. 1 shows the case of forming the multiple primary electron beams 20 by the shaping aperture array substrate 203 from one beam irradiated from the electron gun 201 as one irradiation source, the present invention is limited to this. is not. A mode in which the multiple primary electron beams 20 are formed by irradiating primary electron beams from a plurality of irradiation sources may be employed.

In addition, descriptions of parts that are not directly necessary for the explanation of the present invention, such as the device configuration and control method, are omitted, but the required device configuration and control method can be appropriately selected and used.

In addition, all multi-secondary electron beam alignment methods, multi-secondary electron beam alignment devices, and electron beam inspection devices that have the elements of the present invention and can be appropriately modified in design by those skilled in the art are included in the present invention. Included in scope.

8 Primary electron beam 20 Multi primary electron beam 22 Hole 29 Sub-irradiation area 30 Frame area 31 Frame image 32 Stripe area 33 Rectangular area 34 Irradiation areas 50, 52, 56 Storage device 54 Frame image creation unit 57 Alignment unit 58 Comparison Section 62 corner image extraction section 64 corner positional relationship calculation section 66 overall positional relationship identification section 68 rotation center calculation section 70 vector calculation section 72 center corresponding coordinate calculation section 74 shift amount calculation section 76 rotation angle calculation section 78 shift processing section 79 rotation Processing unit 80 Beam position calculation unit 82 Synthesis unit 84 Detection element coordinate calculation unit 90 Beam pitch calculation unit 92 Judgment unit 94 Beam pitch adjustment processing unit 95 Shape evaluation value calculation unit 96 Judgment unit 97 Distortion adjustment processing unit 100 Inspection device 101 Substrate 102 Electron beam column 103 Inspection chamber 105 Stage 106 Detection circuit 107 Position circuit 108 Comparison circuit 109 Storage device 110 Control computer 111 Mark 112 Reference image creation circuit 114 Stage control circuit 117 Monitor 118 Memory 119 Printer 120 Bus 122 Laser length measurement system 123 Chip pattern Memory 124 Lens control circuit 126 Blanking control circuit 128 Deflection control circuit 130 Detector stage control circuit 132 Driving mechanism 133 E×B control circuit 134 Alignment circuit 135 Distortion corrector control circuit 142 Driving mechanism 144, 146, 148, 149 DAC Amplifier 150 Image Acquisition Mechanism 151 Primary Electron Optical System 152 Secondary Electron Optical System 160 Control System Circuit 201 Electron Gun 202 Electromagnetic Lens 203 Shaping Aperture Array Substrate 205, 206, 207, 224 Electromagnetic Lens 208 Main Deflector 209 Sub Deflector 212 collective blanking deflector 213 limiting aperture substrate 214 E×B separator 216 mirror 218 deflector 222 multi-detector 224 electromagnetic lens 225 detector aperture array substrate 226 deflector 227 rotary stage 228 x, y stage 229 detector stage 230, 231 alignment coil 232 distortion corrector 300 multi secondary electron beam 301 representative secondary electron beam 330 inspection region 332 chip

Claims (9)

scanning a plurality of first detection elements arranged in a grid pattern of a multi-detector with multiple secondary electron beams emitted from an object surface on the stage;
detecting a plurality of beams including a corner beam positioned at a corner among the multiple secondary electron beams with the multi-detector;
calculating a positional relationship between the plurality of beams including the corner beam and a plurality of second detection elements among the plurality of first detection elements that have detected the plurality of beams;
calculating a shift amount for aligning the plurality of first detection elements with the multi-secondary electron beam based on the positional relationship;
using the shift amount to move the multi-detector relative to the multi-secondary electron beam;
A method for aligning multiple secondary electron beams, comprising: calculating a rotation angle for aligning the plurality of first detection elements with the multi-secondary electron beam using the positional relationship and the rotation center coordinates of the multi-detector;
rotating the multi-detector relative to the multi-secondary electron beam at the rotation angle;
2. The method of aligning multiple secondary electron beams of claim 1, further comprising: rotating the multi-detector through a first rotation angle;
scanning the multiple secondary electron beams emitted from the sample surface over the plurality of first detection elements in the rotated state;
detecting the plurality of beams, including the corner beam, with the multi-detector in a post-rotation state;
calculating a positional relationship between the plurality of beams including the corner beam and the plurality of second detection elements after rotation;
calculating rotation center coordinates of the multi-detector based on the first rotation angle by which the multi-detector is rotated and the positional relationship before and after the rotation;
A second rotation angle for aligning the plurality of first detection elements with the multi-secondary electron beam is calculated using one of the positional relationships before and after rotation and the rotation center coordinates of the multi-detector. and
rotating the multi-detector relative to the multi-secondary electron beam by the second rotation angle;
2. The method of aligning multiple secondary electron beams of claim 1, further comprising: 4. The multi-secondary electron beam according to any one of claims 1 to 3, wherein when scanning with the multi-secondary electron beam, scanning is performed in a scanning range that is four times or more the inter-beam pitch of the multi-secondary electron beam. E-beam alignment method. 2. The method according to claim 1, wherein the shift amount is used to shift the trajectory of the multi-secondary electron beam, thereby moving the multi-detector relative to the multi-secondary electron beam. Alignment method for multiple secondary electron beams. calculating a beam pitch of the multiple secondary electron beams based on the positional relationship;
determining whether the beam pitch is within a predetermined range;
adjusting the beam pitch if the beam pitch is not within a predetermined range;
further comprising
2. The method of aligning multiple secondary electron beams according to claim 1, wherein the shift amount is calculated with the beam pitch within a predetermined range. calculating an overall positional relationship between the entire multi-secondary electron beam and the entire plurality of first detection elements;
calculating a shape evaluation value for evaluating a beam distribution shape of the multi-secondary electron beam based on the overall positional relationship;
a step of determining whether the shape evaluation value is within a predetermined range;
adjusting the beam distribution shape of the multi-secondary electron beam when the shape evaluation value is not within a predetermined range;
further comprising
2. The method of aligning multiple secondary electron beams according to claim 1, wherein the shift amount is calculated when the shape evaluation value is within a predetermined range. a stage;
an electron optical system for irradiating an object surface on the stage with multiple primary electron beams;
a plurality of first detection elements arranged in a lattice, including corner beams located at corners of the multi-secondary electron beams emitted from the object surface by the irradiation of the multi-primary electron beams; a multi-detector for detecting beams of
a secondary system deflector that scans the plurality of first detection elements with the multiple secondary electron beams;
a positional relationship calculator that calculates a positional relationship between the plurality of beams including the corner beam and a plurality of second detection elements among the plurality of first detection elements that have detected the plurality of beams;
a shift amount calculation unit that calculates, based on the positional relationship, a shift amount for aligning the plurality of first detection elements with the multiple secondary charged particle beams;
a movement mechanism for moving the multi-detector relative to the multi-secondary electron beam using the shift amount;
A multi-secondary electron beam alignment device comprising: a stage;
an electron optical system for irradiating an object surface on the stage with multiple primary electron beams;
a plurality of first detection elements arranged in a lattice, including corner beams located at corners of the multi-secondary electron beams emitted from the object surface by the irradiation of the multi-primary electron beams; a multi-detector for detecting beams of
a secondary system deflector that scans the plurality of first detection elements with the multiple secondary electron beams;
a positional relationship calculator that calculates a positional relationship between the plurality of beams including the corner beam and a plurality of second detection elements among the plurality of first detection elements that have detected the plurality of beams;
a shift amount calculation unit that calculates, based on the positional relationship, a shift amount for aligning the plurality of first detection elements with the multiple secondary charged particle beams;
a movement mechanism for moving the multi-detector relative to the multi-secondary electron beam using the shift amount;
a comparison unit that compares a secondary electron image of the substrate to be inspected placed on the stage with a predetermined image;
with
The secondary electron image is obtained by irradiating the substrate to be inspected on the stage with multiple primary electron beams, and performing the multiple detection of the multiple secondary electron beams emitted from the substrate to be inspected by the irradiation of the multiple primary electron beams. An electron beam inspection apparatus, characterized in that it is acquired by detecting a device.

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