JP2021197264A - Multi-secondary electron beam position acquisition device and multi-secondary electron beam position acquisition method - Google Patents

Abstract

To provide a device capable of grasping the position of each beam of a multi-beam on the detection surface of a detector.SOLUTION: A multi-secondary electron beam position acquisition device includes a multi-detector with multiple detection elements arranged in a grid pattern to detect a multi-secondary electron beam, a beam selection unit 60 that selects secondary electron beams that reach the multi-detector one by one, a possible position calculation unit 61 that calculates the possible position of the selected secondary electron beam on a grid-like region surface using a detection intensity signal from the detection element that has detected the selected secondary electron beam, an index value calculation unit 66 that calculates the index value to evaluate the positional relationship of the multiple possible positions that make up the combination for each of the multiple combinations that use one possible position of each secondary electron beam of some multiple secondary electron beams, and a beam position specifying unit 71 that specifies the position of each secondary electron beam on the basis of the calculated index value.SELECTED DRAWING: Figure 4

Description

The present invention relates to a multi-secondary electron beam position acquisition device and a multi-secondary electron beam position acquisition method.

In recent years, with the increasing integration and capacity of large-scale integrated circuits (LSIs), the circuit line width required for semiconductor devices has become narrower and narrower. Further, improvement of the yield is indispensable for manufacturing LSI, which requires a large manufacturing cost. However, as typified by 1-gigabit class DRAM (random access memory), the patterns constituting the LSI are on the order of submicrons to nanometers. In recent years, with the miniaturization of LSI pattern dimensions formed on semiconductor wafers, the dimensions that must be detected as pattern defects have become extremely small. Therefore, it is necessary to improve the accuracy of the pattern inspection device for inspecting the defects of the ultrafine pattern transferred on the semiconductor wafer. In addition, one of the major factors that reduce the yield is a pattern defect of a mask used when exposing and transferring an ultrafine pattern on a semiconductor wafer by photolithography technology. Therefore, it is necessary to improve the accuracy of the pattern inspection device for inspecting defects of the transfer mask used in LSI manufacturing.

In the inspection device, for example, a multi-beam using an electron beam is irradiated to the inspection target substrate, secondary electrons corresponding to each beam emitted from the inspection target substrate are detected, and a pattern image is captured. Then, a method of performing an inspection by comparing the captured measurement image with the design data or the measurement image obtained by capturing the same pattern on the substrate is known. For example, "die-to-die" inspection, which compares measurement image data obtained by capturing the same pattern at different locations on the same substrate, and design image data (reference image) based on pattern-designed design data. There is a "die-to-database (die-database) inspection" that generates a data and compares it with a measurement image that is measurement data obtained by imaging a pattern. The captured image is sent to the comparison circuit as measurement data. In the comparison circuit, after the images are aligned with each other, the measurement data and the reference data are compared according to an appropriate algorithm, and if they do not match, it is determined that there is a pattern defect.

In a multi-beam inspection device, it is important to align the multi-beam with each detection element of the multi-detector. For that purpose, it is important to grasp the position of each beam of the multi-beam on the detection surface as a premise. In particular, it is important to grasp the position of each beam of the multi-beam on the detection surface when the secondary electron detector is mounted on the device as a new or exchanged one. Here, a method of dividing a pixel of a detector into three regions and specifying a beam position in the pixel is disclosed (see, for example, Patent Document 1). If the number of detection elements is tripled, the number of output signals also increases accordingly, which increases the scale of the circuit that processes the signals.

U.S. Pat. No. 10,338,013

Therefore, one aspect of the present invention provides a device and a method capable of grasping the position of each beam of the multi-beam on the detection surface of the detector.

The multi-secondary electron beam position acquisition device according to one aspect of the present invention is
A multi-detector having a plurality of detection elements arranged in a grid pattern for detecting a multi-secondary electron beam, and a multi-detector.
A beam selection unit that selects the secondary electron beams that reach the multi-detector one by one from the multi-secondary electron beams.
For each selected secondary electron beam, the secondary electron beam is arranged in a grid pattern in which a plurality of detection elements are arranged by using the detection intensity signal from at least one detection element that detected the secondary electron beam. A possible position calculation unit that calculates at least one possible position on the area surface, and a possible position calculation unit.
A plurality of possible existences constituting the combination for each combination of a plurality of combinations using one possible position of each secondary electron beam of at least a part of the plurality of secondary electron beams in the multi-secondary electron beam. The index value calculation unit that calculates the index value that evaluates the positional relationship of the positions, and the index value calculation unit.
A position specifying part that specifies the position of each secondary electron beam based on the calculated index value,
It is characterized by being equipped with.

In addition, as index values, for each combination, the lengths of a plurality of sides generated by connecting the adjacent possible positions of a plurality of possible positions constituting the combination, and the distance between two connected sides among the plurality of sides. It is preferable to use a value calculated from an equation using each internal angle of.

Further, it is preferable that the position of each secondary electron beam is specified based on the combination in which the deviation of the lengths of the plurality of sides is smaller than that of other combinations and the deviation between each internal angle and the right angle is small. ..

The multi-secondary electron beam position acquisition device of another aspect of the present invention is
A multi-detector having a plurality of detection elements arranged in a grid pattern for detecting a multi-secondary electron beam, and a multi-detector.
A beam selection unit that selects the secondary electron beams that reach the multi-detector one by one from the multi-secondary electron beams.
A lens that controls the focal position of the selected secondary electron beam,
With the focal position of the multi-secondary electron beam controlled so that each secondary electron beam is detected by three or more detection elements, three or more secondary electron beams are detected for each secondary electron beam. A position specifying part that specifies the position of each secondary electron beam using the detection intensity signal from the detection element,
It is characterized by being equipped with.

The method for acquiring the position of the multi-secondary electron beam according to one aspect of the present invention is
A step of selecting one secondary electron beam that reaches the multi-detector having a plurality of detection elements arranged in a grid pattern for detecting the multi-secondary electron beam from the multi-secondary electron beams.
For each selected secondary electron beam, the secondary electron beam is arranged in a grid pattern in which a plurality of detection elements are arranged by using the detection intensity signal from at least one detection element that detected the secondary electron beam. A step of calculating at least one possible position on the area plane and
A plurality of possible existences constituting the combination for each combination of a plurality of combinations using one possible position of each secondary electron beam of at least a part of the plurality of secondary electron beams in the multi-secondary electron beam. The process of calculating the index value to evaluate the positional relationship of the positions and
The process of identifying and outputting the position of each secondary electron beam based on the calculated index value, and
It is characterized by being equipped with.

The method for acquiring the position of the multi-secondary electron beam according to another aspect of the present invention is as follows.
A step of selecting one secondary electron beam that reaches the multi-detector having a plurality of detection elements arranged in a grid pattern for detecting the multi-secondary electron beam from the multi-secondary electron beams.
A step of controlling the focal position of the multi-secondary electron beam so that each selected secondary electron beam is detected by three or more detection elements.
With the focal position of the multi-secondary electron beam controlled so that each secondary electron beam is detected by three or more detection elements, three or more secondary electron beams are detected for each secondary electron beam. The process of identifying and outputting the position of each secondary electron beam using the detection intensity signal from the detection element, and
It is characterized by being equipped with.

According to one aspect of the present invention, the position of each beam of the multi-beam on the detection surface of the detector can be acquired.

It is a block diagram which shows the structure of the inspection apparatus in Embodiment 1. FIG. It is a conceptual diagram which shows the structure of the molded aperture array substrate in Embodiment 1. FIG. It is a figure which shows an example of the positional relationship between a multi-secondary electron beam and a plurality of detection elements of a multi-detector in the stage before alignment in Embodiment 1. FIG. It is a figure which shows an example of the internal structure of the beam position search circuit in Embodiment 1. FIG. It is a flowchart which shows an example of the main part process of the inspection method in Embodiment 1. FIG. It is a figure for demonstrating the method of beam selection in Embodiment 1. FIG. It is a figure which shows an example of the existence | existence range of each beam in Embodiment 1. FIG. It is a figure which shows an example of the possible position of each beam in Embodiment 1. FIG. It is a figure which shows an example of the combination by the existence position of each beam in Embodiment 1. FIG. It is a figure which shows an example of the specified beam position in Embodiment 1. FIG. It is a figure for demonstrating another connection method between possible positions of each beam using the correct position of a beam in Embodiment 1. FIG. It is a figure for demonstrating still another connection method in Embodiment 1. FIG. It is a figure for demonstrating still another connection method in Embodiment 1. FIG. It is a figure for demonstrating the connection method which is the modification of FIG. 9 and has different measurement angles. It is a figure which shows an example of the positional relationship between the multi-secondary electron beam and the number of multi-secondary electron beams and the same number of detection elements in the modification 1 of Embodiment 1. FIG. It is a figure which shows an example of the existence | present position of each beam in the modification 1 of Embodiment 1. FIG. It is a figure which shows an example of the existence | present position of each beam in the modification 2 of Embodiment 1. FIG. It is a figure which shows an example of the position of each specified beam in the modification 2 of Embodiment 1. FIG. It is a figure which shows an example of the detection method of each beam in the modification 3 of Embodiment 1. FIG. It is a figure which shows an example of the plurality of chip regions formed on the semiconductor substrate in Embodiment 1. FIG. It is a figure for demonstrating the inspection process in Embodiment 1. FIG. It is a block diagram which shows an example of the structure in the comparison circuit in Embodiment 1. FIG. It is a figure which shows an example of the internal structure of the beam position search circuit in Embodiment 2. It is a flowchart which shows an example of the main part process of the inspection method in Embodiment 2. It is a figure which shows an example of the irradiation position of each beam in Embodiment 2. FIG. It is a figure which shows an example of the method of specifying a beam position in Embodiment 2. FIG.

Hereinafter, in the embodiment, an electron beam will be described as an example of the charged particle beam. However, it is not limited to this. For example, it may be an ion beam or the like. Further, as an example of the multi-beam position acquisition device and / or the multi-beam image acquisition device, an inspection device using the multi-beam will be described. However, it is not limited to this. The multi-beam image acquisition device may be any device that acquires an image using a secondary electron detector corresponding to the multi-beam. The multi-beam position acquisition device is not limited to the case of acquiring the position of the secondary electron beam, but may be the case of acquiring the position of the primary electron beam.

Embodiment 1.
FIG. 1 is a configuration diagram showing a configuration of an inspection device according to the first embodiment. In FIG. 1, the inspection device 100 for inspecting a pattern formed on a substrate is an example of a multi-electron beam inspection device. The inspection device 100 includes 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 examination room 103. In the electron beam column 102, an electron gun 201, an electromagnetic lens 202, a molded aperture array substrate 203, a beam selection aperture substrate 232, a drive mechanism 234, an electromagnetic lens 205, a batch blanking deflector 212, a limiting aperture substrate 213, and an electromagnetic lens. 206, electromagnetic lens 207 (objective lens), main deflector 208, sub-deflector 209, beam separator 214, deflector 218, electromagnetic lens 224, alignment coils 225 and 226, detector stage 229 and multi-detector 222 are arranged. ing. Electron optics 201, electromagnetic lens 202, molded aperture array substrate 203, electromagnetic lens 205, batch blanking deflector 212, limiting aperture substrate 213, beam selection aperture substrate 232, electromagnetic lens 206, electromagnetic lens 207 (objective lens), main deflection The primary electron optics system 151 is composed of the device 208 and the sub-deflector 209. Further, the secondary electron optical system 152 is composed of the electromagnetic lens 207, the beam separator 214, the deflector 218, the electromagnetic lens 224, and the alignment coils 225 and 226. The multi-detector 222 is arranged on the detector stage 229 which can move in the x, y direction and the rotation (θ) direction of the secondary coordinate system. The detector stage 229 has a rotary stage 227 and a secondary system x, y stage 228.

In the examination room 103, a stage 105 that can move at least in the XY direction is arranged. A substrate 101 (sample) to be inspected is arranged on the stage 105. The substrate 101 includes a mask substrate for exposure and a semiconductor substrate such as a silicon wafer. When the substrate 101 is a semiconductor substrate, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. When the substrate 101 is an exposure mask substrate, a chip pattern is formed on the exposure mask substrate. The chip pattern is composed of a plurality of graphic patterns. By exposing and transferring the chip pattern formed on the exposure mask substrate to the semiconductor substrate a plurality of times, a plurality of chip patterns (wafer dies) are formed on the semiconductor substrate. Hereinafter, the case where the substrate 101 is a semiconductor substrate will be mainly described. The substrate 101 is arranged on the stage 105, for example, with the pattern forming surface facing upward. Further, on the stage 105, a mirror 216 that reflects the laser beam for laser length measurement emitted from the laser length measuring system 122 arranged outside the examination room 103 is arranged.

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

In the control system circuit 160, the control computer 110 that controls the entire inspection device 100 uses the position circuit 107, the comparison circuit 108, the reference image creation circuit 112, the stage control circuit 114, the lens control circuit 124, and the blanking via the bus 120. It is connected to a control circuit 126, a deflection control circuit 128, a detector stage control circuit 130, a beam position search circuit 134, a beam selection aperture control circuit 136, a storage device 109 such as a magnetic disk device, a memory 118, and a printer 119. Further, the deflection control circuit 128 is connected to a DAC (digital-to-analog conversion) amplifier 144, 146, 148. The DAC amplifier 146 is connected to the main deflector 208, and the DAC amplifier 144 is connected to the sub-deflector 209. The DAC amplifier 148 is connected to the deflector 218.

Further, the chip pattern memory 123 is connected to the comparison circuit 108 and the beam position search circuit 134. Further, the stage 105 is driven by the 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−θ) motor that drives in the X direction, the Y direction, and the θ direction in the stage coordinate system is configured, and the stage 105 can be moved in the XYθ direction. It has become. As these X motors, Y motors, and θ motors (not shown), for example, step motors can be used. The stage 105 can be moved in the horizontal direction and the rotational direction by the motor of each axis of XYθ. Then, the moving position of the stage 105 is measured by the laser length measuring system 122 and supplied to the position circuit 107. The laser length measuring system 122 measures the position of the stage 105 by the principle of the laser interferometry method by receiving the reflected light from the mirror 216. In the stage coordinate system, for example, the X direction, the Y direction, and the θ direction of the primary coordinate system are set with respect to the plane orthogonal to the optical axis of the multi-primary electron beam 20.

The detector stage 229 is driven by the drive mechanism 132 under the control of the 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 direction, the y direction, and the θ direction in the stage coordinate system is configured, and the x, y stage is configured in the x, y direction. In 228, the rotary stage 227 can be moved by the θ method. The example of FIG. 1 shows a case where the x and y stages 228 are arranged on the rotary stage 227. As these x motors, y motors, and θ motors (not shown), for example, step motors can be used. The detector stage 229 can be moved in the horizontal direction and the rotational direction by the motor of each axis of xyθ. In the stage coordinate system, for example, the x direction, the y direction, and the θ direction of the secondary coordinate system are set with respect to the plane orthogonal 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 (objective lens), the electromagnetic lens 224, the alignment coils 226, 227, and the beam separator 214 are controlled by the lens control circuit 124. Further, the batch blanking deflector 212 is composed of electrodes having two or more poles, and is controlled by a blanking control circuit 126 via a DAC amplifier (not shown) for each electrode. The sub-deflector 209 is composed of electrodes having four or more poles, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 144. The main deflector 208 is composed of electrodes having four or more poles, and each electrode is controlled by a deflection control circuit 128 via a DAC amplifier 146. The deflector 218 is composed of electrodes having four or more poles, and each electrode is controlled by a deflection control circuit 128 via a DAC amplifier 148.

The beam selection aperture substrate 232 is driven by the drive mechanism 234, and the drive mechanism 234 is controlled by the beam selection aperture control circuit 136.

A high-voltage power supply circuit (not shown) is connected to the electron gun 201, and another extraction electrode is applied along with the application of an acceleration voltage from the high-voltage power supply circuit between the filament (cathode) and the extraction electrode (anode) in the electron gun 201 (not shown). By applying a voltage of (Wenert) and heating the cathode at a predetermined temperature, a group of electrons emitted from the cathode is accelerated and emitted as an electron beam 200.

Here, FIG. 1 describes a configuration necessary for explaining the first embodiment. The inspection apparatus 100 may usually have other necessary configurations.

FIG. 2 is a conceptual diagram showing the configuration of the molded aperture array substrate according to the first embodiment. In FIG. 2, the molded aperture array substrate 203 has _{holes (openings) of two-dimensional horizontal (x direction) m 1} row × vertical (y direction) n ₁ step (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. In the example of FIG. 2, a case where a hole (opening) 22 of 23 × 23 is formed is shown. Each hole 22 is formed by a rectangle having the same size and shape. Alternatively, it may be a circle having the same outer diameter. A part of the electron beam 200 passes through each of these plurality of holes 22, so that the multi-primary electron beam 20 is formed. Next, the operation of the image acquisition mechanism 150 in the case of acquiring a secondary electronic image will be described. The primary electron optical system 151 irradiates the substrate 101 with the multi-primary electron beam 20. Specifically, it operates as follows.

The electron beam 200 emitted from the electron gun 201 (emission source) is refracted by the electromagnetic lens 202 to illuminate the entire molded aperture array substrate 203. As shown in FIG. 2, a plurality of holes 22 (openings) are formed in the molded aperture array substrate 203, and the electron beam 200 illuminates a region including all the plurality of holes 22. Each part of the electron beam 200 irradiated to the positions of the plurality of holes 22 passes through the plurality of holes 22 of the molded aperture array substrate 203, respectively, thereby forming the multi-primary electron beam 20.

The formed multi-primary electron beam 20 is refracted by the electromagnetic lens 205 and the electromagnetic lens 206, respectively, and the intermediate image plane (image plane) of each beam of the multi-primary electron beam 20 is repeated while repeating the intermediate image and the crossover. Conjugated position: Passes through the beam separator 214 arranged at IP) and proceeds to the electromagnetic lens 207 (objective lens).

When the multi-primary electron beam 20 is incident on the electromagnetic lens 207 (objective lens), the electromagnetic lens 207 focuses the multi-primary electron beam 20 on the substrate 101. The multi-primary electron beam 20 focused (focused) on the surface of the substrate 101 (sample) by the objective lens 207 is collectively deflected by the main deflector 208 and the sub-deflector 209, and the substrate 101 of each beam is applied. Each of the above irradiation positions is irradiated. When the entire multi-primary electron beam 20 is collectively deflected by the batch blanking deflector 212, the position is displaced from the central hole of the limiting aperture substrate 213, and the multi-primary electrons are displaced by the limiting aperture substrate 213. The entire beam 20 is shielded. On the other hand, the multi-primary electron beam 20 not deflected by the batch blanking deflector 212 passes through the central hole of the limiting aperture substrate 213 as shown in FIG. By turning ON / OFF of the batch blanking deflector 212, blanking control is performed, and ON / OFF of the beam is collectively controlled. In this way, the limiting aperture substrate 213 shields the multi-primary electron beam 20 deflected so that the beam is turned off by the batch blanking deflector 212. Then, the multi-primary electron beam 20 for image acquisition is formed by the beam group that has passed through the limiting aperture substrate 213 formed from the time when the beam is turned on to the time when the beam is turned off.

When the multi-primary electron beam 20 is irradiated to a desired position of the substrate 101, it corresponds to each beam of the multi-primary electron beam 20 from the substrate 101 due to the irradiation of the multi-primary electron beam 20. , A bundle of secondary electrons including backscattered electrons (multi-secondary electron beam 300) is emitted.

The multi-secondary electron beam 300 emitted from the substrate 101 passes through the electromagnetic lens 207 and advances to the beam separator 214.

Here, the beam separator 214 generates an electric field and a magnetic field in a direction orthogonal to each other on a plane orthogonal to the direction (orbital center axis) in which the central beam of the multi-primary electron beam 20 travels. The electric field exerts a force in the same direction regardless of the traveling direction of the electron. 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 electron can be changed depending on the intrusion direction of the electron. The force due to the electric field and the force due to the magnetic field cancel each other out in the multi-primary electron beam 20 that enters the beam separator 214 from above, and the multi-primary electron beam 20 travels straight downward. On the other hand, in the multi-secondary electron beam 300 that invades the beam 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 obliquely upward. Can be bent.

The multi-secondary electron beam 300 bent diagonally upward is further bent by the deflector 218 and projected onto the multi-detector 222 while being refracted by the electromagnetic lens 224. The multi-detector 222 detects the projected multi-secondary electron beam 300. The multi-detector 222 has a plurality of detection elements (detection sensors). Then, each beam of the multi-primary electron beam 20 collides with the 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 and generate electrons. Secondary electron image data is generated for each pixel. The intensity signal detected by the multi-detector 222 is output to the detection circuit 106. Each primary electron beam is irradiated into a sub-irradiation region surrounded by an inter-beam pitch in the x direction and an inter-beam pitch in the y direction in which its own beam is located on the substrate 101, and scans the sub-irradiation region ( Scan operation).

As described above, the secondary electron image is obtained by irradiating the multi-primary electron beam 20 with the multi-secondary electrons including backscattered electrons emitted from the substrate 101 due to the irradiation of the multi-primary electron beam 20. The beam 300 is detected by the multi-detector 222. The reflected electrons may diverge before reaching the multi-detector 222 and may not reach the multi-detector 222. The detection data (measured image data: secondary electron image data: inspected image data) of the secondary electrons for each pixel in the individual irradiation region (sub-irradiation region) of each primary electron beam detected by the multi-detector 222 is , It is output to the detection circuit 106 in the order of measurement. In the detection circuit 106, analog detection data is converted into digital data by an A / D converter (not shown) and stored in the chip pattern memory 123. Then, the obtained secondary electronic image data (data of the secondary electronic image 1) is output to the comparison circuit 108 together with the information indicating each position from the position circuit 107.

In order to obtain an image in the sub-irradiation region 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, it is important to align the multi-primary electron beam 20 with each detection element of the multi-detector 222. For that purpose, it is important to grasp the position of each beam of the multi-beam on the detection surface as a premise. In particular, it is important to grasp the position of each beam of the multi-beam on the detection surface when the secondary electron detector is mounted on the device as a new or exchanged one.

FIG. 3 is a diagram showing an example of the positional relationship between the multi-secondary electron beam and the plurality of detection elements of the multi-detector at the stage before the alignment in the first embodiment. In the example of FIG. 3, for example, a case where a 3 × 3 multi-secondary electron beam 300 (10a to 10i) is detected by, for example, 5 × 5 detection elements 223 arranged in a grid pattern is shown. The example of FIG. 3 shows a case where the detection elements 223 are arranged one square extra around the detection elements arranged in the same number and in the same arrangement as the multi-secondary electron beams 300 arranged in the array. There is. When the multi-detector 222 is newly mounted on the inspection device 100 or as a replacement, the position of each secondary electron beam 10 of the multi-secondary electron beam 300 on the detection surface is unknown. Since each detection element 223 simply detects the incident secondary electrons, it is difficult to distinguish between the two or more beams when two or more beams are simultaneously incident on the same square (detection element 223). Therefore, it is difficult to obtain an image of the substrate 101 as it is. Therefore, in the first embodiment, the positions of the secondary electron beams 10 are measured.

FIG. 4 is a diagram showing an example of the internal configuration of the beam position search circuit according to the first embodiment. In FIG. 4, in the beam position search circuit 134, a storage device 68 such as a magnetic disk device, a beam selection unit 60, an existence possible position calculation unit 61, a determination unit 62, a combination setting unit 63, a side length calculation unit 64, The internal angle calculation unit 65, the index value calculation unit 66, the determination unit 67, the determination unit 69, and the beam position specifying unit 71 are arranged. Beam selection unit 60, possible position calculation unit 61, determination unit 62, combination setting unit 63, side length calculation unit 64, internal angle calculation unit 65, index value calculation unit 66, determination unit 67, determination unit 69, and beam position. Each "-part" such as the specific part 71 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, and the like. Further, a common processing circuit (same processing circuit) may be used for each “~ part”. Alternatively, different processing circuits (separate processing circuits) may be used. Beam selection unit 60, possible position calculation unit 61, determination unit 62, combination setting unit 63, side length calculation unit 64, internal angle calculation unit 65, index value calculation unit 66, determination unit 67, determination unit 69, and beam position. The necessary input data or the calculated result in the specific unit 71 is stored in a memory (not shown) or a memory 118 each time.

FIG. 5 is a flowchart showing an example of a main step of the inspection method according to the first embodiment. In FIG. 5, the main steps of the inspection method according to the first embodiment are a beam selection step (S102), a beam detection step (S104), a possible position calculation step (S106), and a determination step (S108). The combination setting process (S110), the side / inside angle calculation process (S116), the index value calculation process (S118), the determination process (S120), the minimum index value storage process (S122), and the determination process (S124). , A series of steps of a beam position specifying step (S126), a detector position adjusting step (S128), and an inspection processing step (S130) are carried out.

As a beam selection step (S102), the beam selection unit 60 selects one secondary electron beam 10 reaching the multi-detector 222 from the multi-secondary electron beam 300. For example, the secondary electron beam 10a is selected. First, the corresponding primary electron beam from the multi-primary electron beam 20 is passed so that only the selected secondary electron beam 10a is emitted from the surface of the substrate 101.

FIG. 6 is a diagram for explaining a method of beam selection in the first embodiment. In FIG. 6, the small opening 13 is formed in a size that allows one primary electron beam to pass through. The large aperture 11 is formed to a size that allows the entire multi-primary electron beam 20 to pass through. Under the control of the beam selection aperture control circuit 136, the drive mechanism 234 horizontally moves the beam selection aperture substrate 232 to form a small aperture in the orbit of one of the multi-primary electron beams 20. By aligning the positions of 13, the single primary electron beam is selectively passed.

As a beam detection step (S104), the multi-detector 222 detects only the selected secondary electron beam 10a. Specifically, the primary electron beam focused on one beam that has passed through the beam selection aperture substrate 232 is applied to the substrate 101 and emits the corresponding secondary electron beam. The emitted secondary electron beam is separated from the primary electron beam by the beam separator 214, and is detected by the multi-detector 222 via the deflector 218 and the electromagnetic lens 224.

In the existence possible position calculation step (S106), the existence possible position calculation unit 61 uses the detection intensity signal from at least one detection element that detected the secondary electron beam for each secondary electron beam 10. The secondary electron beam calculates at least one possible position on the grid-like region surface where the plurality of detection elements 223 are arranged.

FIG. 7 is a diagram showing an example of the existence range of each beam in the first embodiment. In FIG. 7, for example, the secondary electron beam 10a is detected by two detection elements 223 arranged in the x direction. Therefore, it can be seen that the secondary electron beam 10a straddles the two detection elements 223 arranged in the x direction. In such a case, the position of the center of gravity of the secondary electron beam 10a in the x direction is calculated by calculating the ratio of the detection intensities detected by the two detection elements 223. However, the position of the center of gravity of the secondary electron beam 10a in the y direction is undecided. Therefore, it can be seen that the position of the center of gravity of the secondary electron beam 10a exists on a straight line extending in the y direction at the obtained position in the x direction. In the example of FIG. 7, a straight line extending in the y direction at the x position in the detection element 223 on the left side, which is slightly displaced in the −x direction from the boundary between the two detection elements 223 arranged in the x direction, is the center of gravity of the secondary electron beam 10a. It can be seen that the existence range is 15a.

FIG. 8 is a diagram showing an example of possible positions of each beam in the first embodiment. In the first embodiment, a plurality of grids are arranged in the existence range 15 with a predetermined resolution. In the example of FIG. 8, since the possible range 15a of the center of gravity of the secondary electron beam 10a is a straight line extending in the y direction at a certain x position, a plurality (for example, 4) arranged in an array in the y direction on the straight line extending in the y direction. The grid 40a of one) is arranged. The existence possible position calculation unit 61 calculates the positions of the plurality of grids 40a as possible positions of the secondary electron beam 10a.

As a determination step (S108), the determination unit 62 determines whether or not the possible positions for all the beams have been calculated. If there are still beams for which the possible positions have not been calculated, the process returns to the beam selection step (S102), and the determination step is performed from the beam selection step (S102) until the possible positions for all the beams are calculated. Each step up to (S108) is repeated.

Thereby, in the example of FIG. 7, for example, the secondary electron beam 10b is detected by one detection element 223. Therefore, it can be seen that the secondary electron beam 10b is housed in one detection element 223. Therefore, in the example of FIG. 7, it can be seen that the rectangular region of the one detection element 223 is the existence range 15b of the center of gravity of the secondary electron beam 10b. Therefore, in the example of FIG. 8, since the possible existence range 15b of the center of gravity of the secondary electron beam 10b is a rectangular region of a certain detection element 223, a plurality of arrays are arranged in the rectangular region of the detection element 223 in the x and y directions. (For example, 4 × 4 = 16) grids 40b are arranged. The existence possible position calculation unit 61 calculates the positions of the plurality of grids 40b as possible positions of the secondary electron beam 10b.

Similarly, in the example of FIG. 7, for example, the secondary electron beam 10c is detected by two detection elements 223 arranged in the y direction. Therefore, it can be seen that the secondary electron beam 10c straddles the two detection elements 223 arranged in the y direction. In such a case, the position of the center of gravity of the secondary electron beam 10c in the y direction is calculated by calculating the ratio of the detection intensities detected by the two detection elements 223. However, the position of the center of gravity of the secondary electron beam 10c in the x direction is undecided. Therefore, it can be seen that the position of the center of gravity of the secondary electron beam 10c exists on a straight line extending in the x direction at the obtained position in the y direction. In the example of FIG. 7, a straight line extending in the x direction at the y position in the upper detection element 223, which is slightly displaced in the + y direction from the boundary between the two detection elements 223 arranged in the y direction, is the presence of the center of gravity of the secondary electron beam 10c. It can be seen that the possible range is 15c. Therefore, in the example of FIG. 8, since the possible range 15c of the center of gravity of the secondary electron beam 10c is a straight line extending in the x direction at a certain y position, a plurality of array arrangements are arranged in the x direction on the straight line extending in the x direction. For example, four) grids 40c are arranged. The existence possible position calculation unit 61 calculates the positions of the plurality of grids 40c as possible positions of the secondary electron beam 10c.

Similarly, in the example of FIG. 7, for example, the secondary electron beam 10d is detected by two detection elements 223 arranged in the x direction. Therefore, it can be seen that the secondary electron beam 10d straddles the two detection elements 223 arranged in the x direction. In such a case, the position of the center of gravity of the secondary electron beam 10d in the x direction is calculated by calculating the ratio of the detection intensities detected by the two detection elements 223. However, the position of the center of gravity of the secondary electron beam 10d in the y direction is undecided. In the example of FIG. 7, a straight line extending in the y direction at the x position in the detection element 223 on the right side, which is slightly displaced in the + x direction from the boundary between the two detection elements 223 arranged in the x direction, is the presence of the center of gravity of the secondary electron beam 10d. It can be seen that the possible range is 15d. Therefore, in the example of FIG. 8, since the possible range 15d of the center of gravity of the secondary electron beam 10d is a straight line extending in the y direction at a certain x position, a plurality of arrays are arranged in the y direction on the straight line extending in the y direction. For example, four) grids 40d are arranged. The existence possible position calculation unit 61 calculates the positions of the plurality of grids 40d as the possible positions of the secondary electron beam 10d.

Similarly, in the example of FIG. 7, for example, the secondary electron beam 10e is detected by two detection elements 223 arranged in the x direction. Therefore, the position of the center of gravity of the secondary electron beam 10e in the x direction is calculated by calculating the ratio of the detection intensities detected by the two detection elements 223. However, the position of the center of gravity of the secondary electron beam 10e in the y direction is undecided. In the example of FIG. 7, a straight line extending in the y direction at the x position in the detection element 223 on the right side, which is offset in the + x direction from the boundary between the two detection elements 223 arranged in the x direction, can have the center of gravity of the secondary electron beam 10e. It can be seen that the range is 15e. Therefore, in the example of FIG. 8, the existence possible position calculation unit 61 has the secondary electron beam 10e at the positions of a plurality of (for example, four) grids 40e arranged in an array in the y direction on the straight line extending in the y direction. Calculated as a possible position.

Similarly, in the example of FIG. 7, for example, the secondary electron beam 10f is detected by four detection elements 223 arranged in 2 × 2 in the x and y directions. Therefore, by calculating the ratio of the detection intensities detected by the four detection elements 223, the positions of the center of gravity of the secondary electron beam 10f in the x and y directions are calculated at one point. In the example of FIG. 7, one point in the detection element 223 on the upper right side, which is slightly displaced in the + x, + y directions from the center position of the four detection elements 223 arranged in 2 × 2, is the center of gravity of the secondary electron beam 10f. It can be seen that the possible range of existence is 15f. Alternatively, the calculation of the center of gravity position (xc, yc) may be performed using the equations (2-1) and (2-2) described later. Therefore, in the example of FIG. 8, the existence possible position calculation unit 61 calculates the position of the grid 40f arranged at such one point as the existence possible position of the secondary electron beam 10f.

Similarly, in the example of FIG. 7, for example, the secondary electron beam 10 g is detected by one detection element 223. Therefore, it can be seen that the secondary electron beam 10 g is contained in one detection element 223. Therefore, in the example of FIG. 7, it can be seen that the rectangular region of the one detection element 223 is the existence range 15g of the center of gravity of the secondary electron beam 10g. Therefore, in the example of FIG. 8, the existence possible position calculation unit 61 determines the positions of a plurality of (for example, 4 × 4 = 16) grids 40g arranged in an array in the x and y directions in the rectangular region of the detection element 223. It is calculated as the position where the secondary electron beam 10 g can exist.

Similarly, in the example of FIG. 7, for example, the secondary electron beam 10h is detected by one detection element 223. Therefore, in the example of FIG. 7, it can be seen that the rectangular region of the one detection element 223 is the existence range 15h of the center of gravity of the secondary electron beam 10h. Therefore, in the example of FIG. 8, the existence possible position calculation unit 61 determines the positions of a plurality of (for example, 4 × 4 = 16) grids 40h arrayed in the x and y directions in the rectangular region of the detection element 223. It is calculated as the position where the secondary electron beam 10h can exist.

Similarly, in the example of FIG. 7, for example, the secondary electron beam 10i is detected by two detection elements 223 arranged in the y direction. Therefore, it can be seen that the secondary electron beam 10i straddles the two detection elements 223 arranged in the y direction. Therefore, in the example of FIG. 7, a straight line extending in the x direction at the y position in the upper detection element 223, which is slightly displaced in the + y direction from the boundary between the two detection elements 223 arranged in the y direction from the ratio of the detection intensities, is secondary. It can be seen that the possible range of the center of gravity of the electron beam 10i is 15i. Therefore, in the example of FIG. 8, the existence possible position calculation unit 61 is arranged in an array in the x direction on a straight line extending in the x direction at the y position in the detected upper detection element 223 (for example, four). The position of the grid 40i is calculated as the possible position of the secondary electron beam 10i.

As described above, at least one possible position of each secondary electron beam 10 can be acquired.

As a combination setting step (S110), the combination setting unit 63 uses a plurality of combinations using one possible position of each secondary electron beam of at least a part of the plurality of secondary electron beams in the multi-secondary electron beam. Set one of them. Here, for example, one of a plurality of combinations using one possible position of each secondary electron beam of all the secondary electron beams is set. The number of combinations exists as many as the number obtained by multiplying the number of possible positions of each secondary electron beam 10. For example, in the example of FIG. 8, there are 4,194,304 (= 4 × 16 × 4 × 4 × 4 × 1 × 16 × 16 × 4) combinations. Here, one of them, a combination composed of one possible position (○ part) on the left side and the upper side, respectively, is shown.

As a side / internal angle calculation step (S116), the side length calculation unit 64 connects the lengths of a plurality of sides generated by connecting adjacent possible positions of a plurality of possible positions constituting the set combination. Is calculated. Then, the internal angle calculation unit 65 calculates each internal angle θ between two connected sides among the plurality of sides.

FIG. 9 is a diagram showing an example of a combination of beams according to possible positions in the first embodiment. In the example of FIG. 9, as shown in FIG. 8, a combination composed of one possible position (○ part) on the left side and the upper side is shown. _{As shown in FIG. 9, sides l 1 to l 12} are generated by connecting adjacent possible positions of a plurality of possible positions (grids 40a to 40i) constituting the set combination. Further, by the side _l 1 _{to l 12} is generated, there is the inner angle theta ₁ through? ₁₆ between the two sides leading out of the sides of the side _l 1 _{to l 12.} The side length calculation unit 64 calculates the lengths of the sides l _{1 to l 12} . Then, the internal angle calculation unit 65 calculates the internal _{angles θ 1 to θ 16} between the two connected _{sides of the plurality of sides l 1 to l 12} .

As the index value calculation step (S118), the index value calculation unit 66 uses one possible position of each secondary electron beam of at least a part of the plurality of secondary electron beams in the multi-secondary electron beam 300. For each combination of the plurality of combinations, the index value E for evaluating the positional relationship of the plurality of possible positions constituting the combination is calculated. The 3 × 3 multi-secondary electron beams 300 are arranged in an array at the same pitch in the x and y directions. Therefore, ideally, the length of each side is the same, and each internal angle is a right angle. Therefore, in the first embodiment, as index values, the lengths of a plurality of sides generated by connecting the adjacent possible positions of the plurality of possible positions constituting the combination and the plurality of sides are used as index values. Of these, the value calculated from the formula using each internal angle between the two connected sides is used. Here, the index value E is an index as to whether or not the deviation between the lengths of the plurality of sides is small and the deviation between each internal angle and the right angle is small. Index value E is the length of each side _l 1 _{to l 12,} the average value _{l ave} length of each side, with the internal angle theta ₁ through? _16, it can be defined by the following equation (1). In the example of FIG. 9, m = 12, n = 16, and θ _std = 90 degrees.

As a determination step (S120), the determination unit 67 determines whether or not the calculated index value E is less than the currently stored minimum index value. When the index value is calculated first, it is determined that the calculated index value E is less than the minimum index value. Alternatively, it is preferable to set a sufficiently large value as the initial value.

When the calculated index value E is determined to be less than the minimum index value in the minimum index value storage step (S122), the control computer 110 stores the calculated index value E in the storage device 68.

As a determination step (S124), the determination unit 69 determines whether or not all combinations have been completed. If there are still remaining combinations, the process returns to the combination setting step (S110), and each step from the combination setting step (S110) to the determination step (S124) is repeated until all the combinations are completed.

The beam position specifying step (S126) and the beam position specifying unit 71 specify the position of each secondary electron beam based on the calculated index value E. The beam position specifying unit 71 specifies the position of each secondary electron beam based on the combination in which the deviation in the lengths of the plurality of sides is small and the deviation between each internal angle and the right angle is small as compared with other combinations. To. Specifically, the possible positions (positions of the grids 40a to 40i) of each beam constituting the combination having the smallest index value E are specified as the positions of the respective secondary electron beams 10. The information on the position of each of the identified secondary electron beams 10 is output to the detector stage control circuit 130.

FIG. 10 is a diagram showing an example of the specified beam position in the first embodiment. FIG. 10 shows the specified positions 42a to 42i. This result could be estimated at almost the correct position. Instead of the multi-detector 222, an electron beam detection image sensor (Electron Detection Image Sensor, hereinafter referred to as EDIS) (hereinafter referred to as EDIS) is attached, and the position of the multi-secondary electron beam 300 is detected by EDIS, which is ± 89 μm. I was able to identify it with accuracy. By doubling the resolution of the grid 40 to be arranged, it was possible to specify with an accuracy of ± 34 μm.

In calculating the index value E, in the above example, as shown in FIG. 9, the possible positions are connected so that the internal angles formed by the straight lines are all right angles when the adjacent possible positions are connected by a straight line. However, other connection methods are also conceivable.

FIG. 11 is a diagram for explaining another connection method between possible positions of each beam using the correct position of the beam in the first embodiment. In the example of FIG. 11, the two points are connected between the positions where the beams can exist adjacent to each other in the diagonal direction (45 degrees) with respect to the arrangement in the x-direction and the y-direction of each beam. At this time, all the line segments have the same length, and the formed internal angle (θ) should be 90 degrees, so that the index value E can be calculated by the equation (1). In this case, m = n = 8 and θ _std = 90 degrees in the equation (1).

FIG. 12 is a diagram for explaining still another connection method in the first embodiment. At each possible position, a line segment is formed between the possible positions and the other possible positions that have been moved by 2 in the x direction and 1 in the y direction, or 1 in the x direction and 2 in the y direction. In this example as well, all the line segments should have the same length, and the formed internal angle (θ) should be 53.1 degrees (= 2 × tan ^-1 (1/2)). The index value E can be calculated by the equation (1), and m = n = 8 and θ _std = 53.1 degrees. The central beam position is obtained by interpolation calculation from the other beam positions after the other beam positions are calculated. For example, the centers of gravity of the other eight beam positions can be assigned.

FIG. 13 is a diagram for explaining still another connection method in the first embodiment. As shown in FIG. 13, it is possible to connect between possible positions on the outer circumference and form a line segment in the diagonal direction. In this case, the length of the line segment is two types and the internal angle is also two types, and the index value E can be calculated by the equation (2). In the example of FIG. 13, m = 8, n = 8, θ _std = 45 degrees, p = 4, q = 4, φ _std = 90 degrees.

FIG. 14 is a diagram for explaining a connection method having different measurement angles, which is a modification of FIG. 9. As shown in FIG. 14, six angles, which should have an angle of 180 degrees, are used in the calculation of the evaluation value E. In this example, equation (1) can be applied, with m = 12, n = 6, and θ _std = 180 degrees. As described above, in the four evaluation value setting examples, the number of measured lines and angles can be reduced, which can contribute to shortening the calculation time. These are just examples of the setting method, and it is possible to determine the line segment and the angle to be evaluated by combining them. Further, since the calculation amount increases as the number of beams increases, it is possible to reduce the calculation amount by, for example, thinning out the number of beams for specifying the position every other beam, every two beams, and the like. In this case, the position of the thinned beam can be obtained by interpolation calculation from the specified beam position in the surroundings. For example, it can be calculated by assigning the positions of the center of gravity of a plurality of specified beams in the surrounding area.

Further, in the above example, it is necessary to calculate the equation (1) or the equation (2) for 4,194,304 combinations in order to specify the beam existing position, which is a huge amount of calculation. The following methods can be used to alleviate this. When calculating the internal angle in FIG. 9, the difference from the right angle is obtained at the same time. For example, when Δθ = | 90 ° −θ ₁ | and Δθ is larger than the preset difference threshold (Δθ _thr ; for example, 5 °), this combination is judged to be inappropriate and the subsequent calculation is stopped. Then move to the next combination. That, | 90 ° -.theta.1 | if a> [Delta] [theta] _thr is calculated is terminated only at .theta.1, other calculations _{(l 1 ~l 12, θ 2} ~θ 16) is omitted, and becomes. By determining the validity of the combination at an early stage in this way, it is possible to realize a significant reduction in the amount of calculation.

In the above-mentioned example, the case where the number of detection elements 223 larger than the number of multi-secondary electron beams is used has been described, but the case where the same number of detection elements 223 as the number of multi-secondary electron beams is used can also be applied.

FIG. 15 is a diagram showing an example of the positional relationship between the number of multi-secondary electron beams and the number of multi-secondary electron beams and the same number of detection elements in the first modification of the first embodiment. In the example of FIG. 15, for example, a case where a 3 × 3 multi-secondary electron beam 300 (10a to 10i) is detected by 3 × 3 detection elements 223 arranged in a grid pattern is shown. In FIG. 15, since the secondary electron beams 10a, 10c, and 10d protrude from the 3 × 3 detection elements 223, it is difficult to specify the positions as they are. Therefore, in the first modification of the first embodiment, a threshold value is set for the output value Dout of the detection element 223, and a rough beam position is determined.

In the existence possible position calculation step (S106), the existence possible position calculation unit 61 compares the detection intensity signal from at least one detection element that detected the secondary electron beam with the threshold value for each secondary electron beam 10. do. As the threshold value, the threshold value Thr1 for the existence of the beam and the threshold value Thr2 for determining whether or not the beam fits in one detection element are used. It is preferable to use the minimum detection value (for example, one gradation) as the threshold value Thr1. As the threshold value Thr2, it is preferable to use a value obtained by subtracting the deviation value σ of the standard deviation from the output average value when the detection element detects the entire beam in advance by an experiment or the like. This makes it possible to obtain the minimum value of variation.

In the example of FIG. 15, the case where the output value Dout of each of the detection elements 223 that detected the secondary electron beams 10a, 10c, and 10d is Thr1 <Dout <Thr2 is shown. In such a case, it is determined that the secondary electron beams 10a, 10c, and 10d straddle the outer peripheral boundary of the detected detection element 223, respectively.

In the example of FIG. 15, the case where the output value Dout of each of the detection elements 223 that detected the secondary electron beams 10b, 10g, and 10h is Thr2 <Dout is shown. In such a case, it is determined that the secondary electron beams 10b, 10g, and 10h are contained in the detected detection element 223, respectively.

The secondary electron beam 10i is detected by two detection elements 223 having an outer peripheral boundary, but when the sum of the output values Dout1 and Dout2 of the two detection elements 223 is larger than Thr2, the secondary electron beam 10i is contained in the two detection elements 223. Judge that it exists across.

The secondary electron beams 10e and 10f can be determined in the same manner as the possible positions of the secondary electron beams 10e and 10f in the first embodiment described above.

FIG. 16 is a diagram showing an example of possible positions of each beam in the first modification of the first embodiment. As for the secondary electron beams 10a, 10c, and 10d determined to straddle the outer peripheral side boundary of the detection element 223, as shown in FIG. 16, the outer peripheral side boundary position and the outer and inner sides of the boundary are along the boundary, respectively. , Arrange a plurality of grids 40. Since the secondary electron beam 10a has boundaries on the left side and the upper side, a plurality of grids 40a are arranged along both boundaries. As for the secondary electron beam 10c, as shown in FIG. 16, since there is a boundary on the upper side, a plurality of grids 40c are arranged along the upper boundary. As for the secondary electron beam 10d, as shown in FIG. 16, since the boundary exists on the left side, a plurality of grids 40d are arranged along the boundary on the left side. The other secondary electron beams 10b, 10e, 10f, 10g, 10h, 10i correspond to the possible positions of the secondary electron beams 10b, 10e, 10f, 10g, 10h, 10i in the above-described first embodiment. A plurality of grids 40b, 40e, 40g, 40h, 40i, and one grid 40f are arranged. The existence possible position calculation unit 61 calculates the position of the grid 40 as the existence possible position for each secondary electron beam. Then, similarly, by carrying out each step in the same manner, the position of each secondary electron beam 10 is specified.

FIG. 17 is a diagram showing an example of possible positions of each beam in the second modification of the first embodiment. In the second modification, the combination is set by using only the information of the beams contained in the detection element 223 having the same number of multi-secondary electron beams without straddling the boundary on the outer peripheral side, and the index value E is set for each combination. Calculate. Then, the possible positions (positions of the grids 40b, 40e to 40i) of the beams constituting the combination having the smallest index value E are specified as the positions of the secondary electron beams 10b, 10e to 10i, respectively.

FIG. 18 is a diagram showing an example of the position of each specified beam in the second modification of the first embodiment. FIG. 18 shows the identified positions 42b, 42e to 42i. The positions of the remaining secondary electron beams 10a, 10c, and 10d may be obtained by linear interpolation from the specified positions 42b, 42e to 42i.

FIG. 19 is a diagram showing an example of a method for detecting each beam in the modified example 3 of the first embodiment. In the third modification, the secondary electron beams 10a, 10c, and 10d that are determined to straddle the outer peripheral boundary are detected again by shifting the beam positions using the alignment coils 225 and 226. When the secondary electron beams 10a and 10d are detected, by shifting the beam in the x direction by the size of one detection alignment as shown in FIG. 19A, the secondary electron beams 10a and 10d can be detected without straddling the outer peripheral boundary. When the secondary electron beam 10c is detected, as shown in FIG. 19B, the beam is shifted in the −y direction by the size of one detection alignment, so that the secondary electron beam 10c can be detected without straddling the outer peripheral boundary. By returning the shift amount after calculating the possible position 40 (or the possible range 15), the possible position 40 can be calculated for the beam straddling the outer peripheral boundary. The contents of each subsequent step are the same as those described above.

As described above, if any of the methods of Modifications 1 to 3 is carried out, the position of each secondary electron beam 10 can be specified even when the same number of detection elements 223 as the number of multi-secondary electron beams are used. The information on the position of each of the identified secondary electron beams 10 is output to the detector stage control circuit 130.

As the detector position adjusting step (S128), the x and y stages 228 are moved by the drive mechanism 132 under the control of the detector stage control circuit 130, and the rotary stage 227 is rotated to rotate each secondary electron beam 10. The position of the multi-detector 222 is adjusted so that the detection element corresponding to the position of is arranged.

As an inspection processing step (S130), the substrate 101 is inspected using the aligned inspection apparatus 100.

FIG. 20 is a diagram showing an example of a plurality of chip regions formed on the semiconductor substrate according to the first embodiment. In FIG. 20, when the substrate 101 is a semiconductor substrate (wafer), a plurality of chips (wafer dies) 332 are formed in a two-dimensional array in the inspection region 330 of the semiconductor substrate (wafer). A mask pattern for one chip formed on an exposure mask substrate is transferred to each chip 332 by being reduced to, for example, 1/4 by an exposure device (stepper) (not shown). The mask pattern for one chip is generally composed of a plurality of graphic patterns.

FIG. 21 is a diagram for explaining the inspection process according to the first embodiment. As shown in FIG. 21, the region of each chip 332 is divided into a plurality of stripe regions 32 with a predetermined width, for example, in the y direction. The scanning operation by the image acquisition mechanism 150 is performed, for example, for each stripe region 32. For example, while moving the stage 105 in the −x direction, the scanning operation of the stripe region 32 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 rectangular region 33 of interest is performed by batch deflection of the entire multi-primary electron beam 20 by the main deflector 208.

In the example of FIG. 21, for example, the case of a multi-primary electron beam 20 having 5 × 5 rows is shown. The irradiation region 34 that can be irradiated by one irradiation of the multi-primary electron beam 20 is (the x-direction obtained by multiplying the x-direction beam-to-beam pitch of the multi-primary electron beam 20 on the substrate 101 surface by the number of beams in the x-direction. Size) × (size in the y direction obtained by multiplying the pitch between beams of the multi-primary electron beam 20 in the y direction on the surface of the substrate 101 by the number of beams in the y direction). The irradiation region 34 becomes the field of view of the multi-primary electron beam 20. Then, each of the primary electron beams 8 constituting the multi-primary electron beam 20 is irradiated into the 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 in which the own beam is located. , Scan (scan operation) in the sub-irradiation area 29. Each primary electron beam 8 is responsible for any of the different sub-irradiation regions 29. Then, at each shot, each primary electron beam 8 irradiates the same position in the responsible sub-irradiation region 29. The movement of the primary electron beam 8 in the sub-irradiation region 29 is performed by collective deflection of the entire multi-primary electron beam 20 by the sub-deflector 209. This operation is repeated to sequentially irradiate the inside of one sub-irradiation region 29 with one primary electron beam 8.

It is preferable that the width of each stripe region 32 is set to the same size as the y-direction size of the irradiation region 34 or to be narrowed by the scan margin. In the example of FIG. 21, the case where the irradiation area 34 has the same size as the rectangular area 33 is shown. However, it is not limited to this. The irradiation area 34 may be smaller than the rectangular area 33. Or it may be large. Then, each primary electron beam 8 constituting the multi-primary electron beam 20 is irradiated into the sub-irradiation region 29 in which its own beam is located, and scans (scans) the inside of the sub-irradiation region 29. Then, when the scan of one sub-irradiation region 29 is completed, the irradiation position is moved to the adjacent rectangular region 33 in the same stripe region 32 by the collective deflection of the entire multi-primary electron beam 20 by the main deflector 208. This operation is repeated to irradiate the inside of the stripe region 32 in order. After scanning one stripe region 32 is complete, the irradiation region 34 moves to the next stripe region 32 by moving the stage 105 and / or batch deflection of the entire multi-primary electron beam 20 by the main deflector 208. As described above, by irradiating each of the primary electron beams 8, the scanning operation and the acquisition of the secondary electron image are performed for each sub-irradiation region 29. By combining these secondary electronic images for each sub-irradiation region 29, a secondary electronic image of the rectangular region 33, a secondary electronic image of the striped region 32, or a secondary electronic image of the chip 332 is configured. Further, when actually performing image comparison, the sub-irradiation region 29 in each rectangular region 33 is further divided into a plurality of frame regions 30, and the frame image 31 for each frame region 30 is compared. The example of FIG. 21 shows a case where the sub-irradiation region 29 scanned by one primary electron beam 8 is divided into four frame regions 30 formed by dividing the sub-irradiation region 29 into two in the x and y directions, for example. ..

Here, when the substrate 101 is irradiated with the multi-primary electron beam 20 while the stage 105 continuously moves, the main deflector 208 collectively deflects the irradiation position of the multi-primary electron beam 20 so as to follow the movement of the stage 105. Tracking operation is performed by. Therefore, the emission position of the multi-secondary electron beam 300 changes momentarily with respect to the orbital central axis of the multi-primary electron beam 20. Similarly, when scanning in the sub-irradiation region 29, the emission position of each secondary electron beam changes momentarily in the sub-irradiation region 29. The deflector 218 collectively deflects the multi-secondary electron beam 300 so that each secondary electron beam whose emission position has changed is irradiated into the corresponding detection region of the multi-detector 222.

As described above, the image acquisition mechanism 150 promotes the scanning operation for each stripe region 32. As described above, the multi-secondary electron beam 300 emitted from the substrate 101 due to the irradiation of the multi-primary electron beam 20 by irradiating the multi-primary electron beam 20 is detected by the multi-detector 222. .. The detected multi-secondary electron beam 300 may contain backscattered electrons. Alternatively, the backscattered electrons may be separated while moving through the secondary electron optical system 152 and may not reach the multi-detector 222. The secondary electron detection data (measured image data: secondary electron image data: inspected image data) for each pixel in each sub-irradiation region 29 detected by the multi-detector 222 is output to the detection circuit 106 in the order of measurement. To. In the detection circuit 106, analog detection data is converted into digital data by an A / D converter (not shown) and stored in the chip pattern memory 123. Then, the obtained measurement image data is transferred to the comparison circuit 108 together with the information indicating each position from the position circuit 107.

FIG. 22 is a configuration diagram showing an example of the configuration in the comparison circuit according to the first embodiment. In FIG. 22, storage devices 50, 52, 56 such as a magnetic disk device, a frame image creation unit 54, an alignment unit 57, and a comparison unit 58 are arranged in the comparison circuit 108. Each "-part" such as the frame image creation unit 54, the alignment unit 57, and the comparison unit 58 includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor. Equipment etc. are included. Further, a common processing circuit (same processing circuit) may be used for each “~ part”. Alternatively, different processing circuits (separate processing circuits) may be used. The input data or the calculated result required in the frame image creation unit 54, the alignment unit 57, and the comparison unit 58 are stored in a memory (not shown) or a 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 creation unit 54 creates a frame image 31 for each frame region 30 of a plurality of frame regions 30 by further dividing the image data of the sub-irradiation region 29 acquired by the scanning operation of each primary electron beam 8. .. Then, the frame area 30 is used as a unit area of the image to be inspected. It is preferable that the frame regions 30 are configured so that the margin regions overlap each other so that the image is not omitted. 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 region 30 based on the design data that is the source of the plurality of graphic patterns formed on the substrate 101. Specifically, it operates as follows. First, the design pattern data is read from the storage device 109 through the control computer 110, and each graphic pattern defined in the read design pattern data is converted into binary or multi-valued image data.

As described above, the figure defined in the design pattern data is, for example, a basic figure of a rectangle or a triangle, for example, the coordinates (x, y) at the reference position of the figure, the length of the side, the rectangle, the triangle, or the like. Graphical data that defines the shape, size, position, etc. of each pattern graphic is stored in information such as a graphic code that serves as an identifier that distinguishes the graphic types of.

When the design pattern data to be the graphic data is input to the reference image creation circuit 112, the data is expanded to the data for each graphic, and the graphic code indicating the graphic shape of the graphic data, the graphic dimension, and the like are interpreted. Then, it is developed into binary or multi-valued design pattern image data as a pattern arranged in the squares having a grid of predetermined quantized dimensions as a unit and output. In other words, the design data is read, the occupancy rate of the figure in the design pattern is calculated for each cell created by virtually dividing the inspection area into cells with a predetermined dimension as a unit, and the n-bit occupancy rate data is obtained. Output. For example, it is preferable to set one cell as one pixel. Then, when to have a resolution of 1/2 8 ^{(= 1/256)} to 1 pixel, the occupancy rate of the pixel allocated the small area region amount corresponding 1/256 of figures are arranged in a pixel Calculate. Then, it becomes 8-bit occupancy rate data. Such squares (inspection pixels) may be matched with the pixels of the measurement data.

Next, the reference image creation circuit 112 filters the design image data of the design pattern, which is the image data of the figure, by using a predetermined filter function. Thereby, the design image data in which the image intensity (shade value) is the image data on the design side of the digital value can be matched with the image generation characteristics obtained by the irradiation of the multi-primary electron beam 20. The 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 to be 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 pixels. For example, the alignment may be performed by the method of least squares.

Then, the comparison unit 58 compares the frame image 31 and the reference image for each pixel. The comparison unit 58 compares the two for each pixel according to a predetermined determination condition, and determines the presence or absence of a defect such as a shape defect. For example, if the difference in gradation value for each pixel is larger than the determination threshold value Th, it is determined to be a defect. Then, the comparison result is output. The comparison result may be output to the storage device 109 or the memory 118, or may be output from the printer 119.

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

As described above, according to the first embodiment, the position of each beam of the multi-beam on the detection surface of the multi-detector 222 can be acquired.

Embodiment 2.
In the first embodiment, a configuration in which at least one possible position is calculated and the position of each beam is specified from the index value for each combination has been described, but the present invention is not limited to this. In the second embodiment, a configuration for directly specifying the position of each beam instead of specifying the position of each beam from the index value for each combination will be described. The configuration of the inspection device 100 in the second embodiment is the same as that in FIG. Further, the contents other than the points particularly described below are the same as those in the first embodiment.

FIG. 23 is a diagram showing an example of the internal configuration of the beam position search circuit according to the second embodiment. In FIG. 23, a beam selection unit 60, a determination unit 62, and a beam position specifying unit 70 are arranged in the beam position search circuit 134. Each "-part" such as the beam selection unit 60, the determination unit 62, and the beam position specifying unit 70 includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, or a semiconductor. Equipment etc. are included. Further, a common processing circuit (same processing circuit) may be used for each “~ part”. Alternatively, different processing circuits (separate processing circuits) may be used. The input data or the calculated result required in the beam selection unit 60, the determination unit 62, and the beam position specifying unit 70 are stored in a memory (not shown) or a memory 118 each time.

FIG. 24 is a flowchart showing an example of a main step of the inspection method according to the second embodiment. In FIG. 24, the main steps of the inspection method according to the second embodiment are a beam selection step (S102), a focus adjustment step (S103), a beam detection step (S104), a beam position specifying step (S107), and the like. A series of steps of a determination step (S108), a detector position adjustment step (S128), and an inspection processing step (S130) are carried out.

The content of the beam selection step (S102) is the same as that of the first embodiment. The primary electron beam focused on one beam that has passed through the beam selection aperture substrate 232 is applied to the substrate 101 and emits the corresponding secondary electron beam. The emitted secondary electron beam is separated from the primary electron beam by the beam separator 214, and travels to the multi-detector 222 via the deflector 218 and the electromagnetic lens 224.

As the focus adjustment step (S103), the electromagnetic lens 224 controls the focal position of the multi-secondary electron beam 20 under the control of the lens control circuit 124. Specifically, the focal position of the multi-secondary electron beam 20 is shifted and blurred. Then, the focal position of the multi-secondary electron beam 20 is controlled so that the selected secondary electron beam (for example, the secondary electron beam 10a is detected by three or more detection elements 223).

FIG. 25 is a diagram showing an example of the irradiation position of each beam in the second embodiment. In the second embodiment, the focal position is adjusted so that each secondary electron beam 10 is incident on the plurality of detection elements 223 by intentionally blurring the focal point.

As a result, in the example of FIG. 8, for example, the secondary electron beam 10a straddling the two detection elements 223 arranged in the x direction is defocused so that the secondary electron beam 10a on the detection surface is defocused. The secondary electron beam 44a having an increased beam size is incident on four detection elements 223 arranged in 2 × 2 in the x and y directions.

In the beam detection step (S104), the focal position of the multi-secondary electron beam 20 is controlled so that each secondary electron beam of the multi-secondary electron beam 20 is detected by three or more detection elements 223. The detector 222 detects the secondary electron beam for each secondary electron beam.

In the beam position specifying step (S107), the beam position specifying unit 70 is in a state where the focal position of the multi-secondary electron beam 20 is controlled so that each secondary electron beam is detected by three or more detection elements. For each secondary electron beam, the position (position of the center of gravity) of each secondary electron beam is specified by using the detection intensity signals from the three or more detection elements 223 that detected the secondary electron beam.

FIG. 26 is a diagram showing an example of how to specify the beam position in the second embodiment. In the example of FIG. 26, a case is shown in which the calculation is performed including the detection intensity of one detection element around the three or more detection elements 223 detected. Specifically, in the example of FIG. 26, the calculation is performed using the 4 × 4 detection element 223 including one detection element around the 2 × 2 detection element 223. Of the 4 × 4 detection elements 223, the detection element 223 in the upper left corner is used as the coordinates (x1, y1), and the coordinates of x = 1 to n and y = 1 to m are defined. _{Using the output D hk of the} detection intensity detected by each detection element 223 and the positions x _hk and y _hk , the position of the center of gravity (xc, yc) of each secondary electron beam 10 is calculated by the following equation (3-1). It is defined in (3-2).

In the example of FIG. 8, one point in the detection element 223 on the upper left side, which is displaced in the −x, + y direction from the center position of the four detection elements 223 arranged in 2 × 2, is the center of gravity of the secondary electron beam 10a. You can see that it is a position.

As a determination step (S108), the determination unit 62 determines whether or not all the beam positions have been specified. If there is still a beam whose beam position has not been specified, the process returns to the beam selection step (S102), and the beam selection step (S102) to the determination step (S108) until the beam positions are specified for all the beams. ) Is repeated.

Therefore, for each of the other secondary electron beams 10b to 10i, the larger secondary electron beams 44b to 44i are incident on the adjacent three or more detection elements 223 by increasing the beam size. Then, the positions of the secondary electron beams 10b to 10i are specified by using the detection intensity signals from the three or more detection elements 223. The information on the position of each of the identified secondary electron beams 10 is output to the detector stage control circuit 130.

In the above example, the case where the number of detection elements 223 is larger than the number of the multi-secondary electron beams 20 has been described, but the case where the same number of detection elements 223 as the number of the multi-secondary electron beams 20 are used can also be applied. .. In FIG. 25, for example, the positions of the three secondary electron beams 10e, 10f, and 10h that can be detected without straddling the outer peripheral boundary even if the beam size is expanded are specified, and the rest are as in the case described with reference to FIG. The secondary electron beams may be obtained by linear interpolation from the positions of the three secondary electron beams 10e, 10f, and 10h from which the secondary electron beams can be specified. Alternatively, for example, for a beam that straddles the outer peripheral boundary when the beam size is increased, the method described with FIGS. 19 (a) and 19 (b) is used to straddle the outer peripheral boundary even if the beam size is increased. If the position is shifted in the x and y directions to the position where there is no such position, the position is calculated, and then the shift amount is returned, the position can be calculated even for the beam straddling the outer peripheral boundary.

The contents of each step of the detector position adjusting step (S128) and the inspection processing step (S130) are the same as those in the first embodiment.

As described above, according to the second embodiment, the position of each beam of the multi-beam on the detection surface of the multi-detector 222 can be acquired without specifying the position of each beam from the index value for each combination.

In the above description, the series of "~ circuits" 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, and the like. Further, a common processing circuit (same processing circuit) may be used for each “~ circuit”. Alternatively, different processing circuits (separate processing circuits) may be used. The program for executing the processor or the like may be recorded on a recording medium such as a magnetic disk device, a magnetic tape device, an FD, or a ROM (read-only memory). For example, position position circuit 107, comparison circuit 108, reference image creation circuit 112, stage control circuit 114, lens control circuit 124, blanking control circuit 126, deflection control circuit 128, detector stage control circuit 130, beam position search circuit 134. , And the beam selection aperture control circuit 136 may be configured by at least one processing circuit described above. For example, the processing in these circuits may be carried out by the control computer 110.

The embodiment has been described above with reference to specific examples. However, the present invention is not limited to these specific examples. The example of FIG. 1 shows a case where a multi-primary electron beam 20 is formed by a molded aperture array substrate 203 from a single beam emitted from an electron gun 201 as one irradiation source, but the present invention is limited to this. is not it. A mode may be used in which the multi-primary electron beam 20 is formed by irradiating each of the primary electron beams from a plurality of irradiation sources.

Further, although the description of parts not directly required for the description of the present invention such as the device configuration and the control method is omitted, the required device configuration and the control method can be appropriately selected and used.

In addition, all multi-charged particle beam alignment methods and multi-charged particle beam inspection devices that include the elements of the present invention and can be appropriately redesigned by those skilled in the art are included in the scope of the present invention.

10 Primary electron beam 11 Large opening 13 Small opening 20 Multi-primary electron beam 22 Hole 29 Sub-irradiation area 30 Frame area 31 Frame image 32 Stripe area 33 Rectangular area 34 Irradiation area 50, 52, 56 Storage device 54 Frame image creation unit 57 Alignment unit 58 Comparison unit 60 Beam selection unit 61 Possible position calculation unit 62 Judgment unit 63 Combination setting unit 64 Side length calculation unit 65 Internal angle calculation unit 66 Index value calculation unit 67 Judgment unit 68 Storage device 69 Judgment unit 70, 71 Beam position identification unit 100 Inspection device 101 Board 102 Electron beam column 103 Inspection room 105 Stage 106 Detection circuit 107 Position circuit 108 Comparison circuit 109 Storage device 110 Control computer 112 Reference image creation circuit 114 Stage control circuit 117 Monitor 118 Memory 119 Printer 120 Bus 122 Laser length measurement system 123 Chip pattern memory 124 Lens control circuit 126 Blanking control circuit 128 Deflection control circuit 130 Detector stage control circuit 132 Drive mechanism 134 Beam position search circuit 136 Beam selection aperture control circuit 142 Drive mechanism 144, 146 148 DAC amplifier 150 Image acquisition mechanism 151 Primary electro-optical system 152 Secondary electro-optical system 160 Control system circuit 201 Electron gun 202 Electron lens 203 Molded aperture array substrate 205, 206, 207, 224,226 Electromagnetic lens 208 Main deflector 209 Sub-deflector 212 Bulk blanking deflector 213 Limited aperture substrate 214 Beam separator 216 Mirror 218 Deflector 222 Multi-detector 225, 226 Alignment coil 227 Rotating stage 228 x, y Stage 229 Detector stage 232 Beam selection aperture board 234 Drive mechanism 300 Multi-secondary electron beam 330 Inspection area 332 Chip

Claims (6)

A multi-detector having a plurality of detection elements arranged in a grid pattern for detecting a multi-secondary electron beam, and a multi-detector.
A beam selection unit that selects one secondary electron beam that reaches the multi-detector from the multi-secondary electron beams.
For each selected secondary electron beam, the secondary electron beam has a grid pattern in which the plurality of detection elements are arranged by using the detection intensity signal from at least one detection element that detected the secondary electron beam. A possible position calculation unit that calculates at least one possible position that may exist in the area plane of
A plurality of existences constituting the combination for each combination of a plurality of combinations using one possible position of each secondary electron beam of at least a part of the plurality of secondary electron beams in the multi-secondary electron beam. An index value calculation unit that calculates an index value that evaluates the positional relationship of possible positions, and an index value calculation unit.
A position specifying part that specifies the position of each secondary electron beam based on the calculated index value,
A multi-secondary electron beam position acquisition device characterized by being equipped with. As the index value, for each of the combinations, the lengths of the plurality of sides generated by connecting the adjacent possible positions of the plurality of possible positions constituting the combination and the two connected sides of the plurality of sides are connected. The multi-secondary electron beam position acquisition device according to claim 1, wherein a value calculated from an equation using each internal angle between the two is used. The feature is that the position of each secondary electron beam is specified based on the combination in which the deviation in the lengths of the plurality of sides is small as compared with other combinations and the deviation between each internal angle and the right angle is small. 2. The multi-secondary electron beam position acquisition device according to claim 2. A multi-detector having a plurality of detection elements arranged in a grid pattern for detecting a multi-secondary electron beam, and a multi-detector.
A beam selection unit that selects one secondary electron beam that reaches the multi-detector from the multi-secondary electron beams.
A lens that controls the focal position of the selected secondary electron beam,
The third electron beam was detected for each secondary electron beam in a state where the focal position of the multi-secondary electron beam was controlled so that each secondary electron beam was detected by three or more detection elements. Using the detection intensity signal from the above detection elements, the position identification unit that specifies the position of each secondary electron beam and the position identification unit.
A multi-secondary electron beam position acquisition device characterized by being equipped with. A step of selecting one secondary electron beam that reaches the multi-detector having a plurality of detection elements arranged in a grid pattern for detecting the multi-secondary electron beam from the multi-secondary electron beams.
For each selected secondary electron beam, the secondary electron beam has a grid pattern in which the plurality of detection elements are arranged by using the detection intensity signal from at least one detection element that detected the secondary electron beam. The process of calculating at least one possible position on the area plane of
A plurality of existences constituting the combination for each combination of a plurality of combinations using one possible position of each secondary electron beam of at least a part of the plurality of secondary electron beams in the multi-secondary electron beam. The process of calculating the index value to evaluate the positional relationship of possible positions and
The process of identifying and outputting the position of each secondary electron beam based on the calculated index value, and
A method for acquiring the position of a multi-secondary electron beam, which is characterized by being equipped with. A step of selecting one secondary electron beam that reaches the multi-detector having a plurality of detection elements arranged in a grid pattern for detecting the multi-secondary electron beam from the multi-secondary electron beams.
A step of controlling the focal position of the multi-secondary electron beam so that each selected secondary electron beam is detected by three or more detection elements.
The third electron beam was detected for each secondary electron beam in a state where the focal position of the multi-secondary electron beam was controlled so that each secondary electron beam was detected by three or more detection elements. The process of identifying and outputting the position of each secondary electron beam using the detection intensity signal from the above detection element, and
A method for acquiring the position of a multi-secondary electron beam, which is characterized by being equipped with.

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