JP7386619B2 - Electron beam inspection method and electron beam inspection device - Google Patents

Description

The present invention relates to an electron beam inspection method and an electron beam inspection apparatus. For example, the present invention relates to an inspection apparatus and an inspection method thereof that perform inspection using a secondary electron image of a pattern emitted by irradiating multiple beams of electron beams.

In recent years, as large-scale integrated circuits (LSIs) have become more highly integrated and have larger capacities, the circuit line width required for semiconductor devices has become increasingly narrower. Improving yield is essential for manufacturing LSIs, which require a large manufacturing cost. However, the patterns constituting LSIs are becoming on the order of 10 nanometers or less, and the dimensions that must be detected as pattern defects have also become extremely small. Therefore, there is a need for higher precision pattern inspection equipment that inspects defects in ultrafine patterns transferred onto semiconductor wafers. Another major factor that reduces yield is pattern defects in masks used when exposing and transferring ultra-fine patterns onto semiconductor wafers using photolithography. Therefore, there is a need for higher precision pattern inspection equipment that inspects defects in transfer masks used in LSI manufacturing.

As a defect inspection method, inspection is performed by comparing a measurement image taken of a pattern formed on a substrate such as a semiconductor wafer or lithography mask with design data or a measurement image taken of the same pattern on the substrate. method is known. For example, pattern inspection methods include "die to die inspection," which compares measurement image data obtained by capturing images of the same pattern at different locations on the same substrate, and design image inspection based on pattern design data. There is a "die to database inspection" in which data (reference image) is generated and compared with a measurement image that is measurement data obtained by capturing a pattern. The captured image is sent to the comparison circuit as measurement data. After aligning the images, the comparison circuit compares the measurement data and reference data according to an appropriate algorithm, and if they do not match, it is determined that there is a pattern defect.

The above-mentioned pattern inspection apparatus includes a device that irradiates a substrate to be inspected with a laser beam and captures a transmitted or reflected image thereof, as well as a device that scans the substrate to be inspected with a primary electron beam. Progress is also being made in the development of inspection devices that acquire pattern images by detecting secondary electrons emitted from a substrate to be inspected upon irradiation with a secondary electron beam. In order to detect the edge position of a pattern on a sample with high precision, in electron beam inspection, the outline of the pattern in the image is extracted rather than comparing pixel values, and the distance from the outline of the reference image is used as a judgment index. (For example, see Patent Document 1). An image obtained by irradiating an electron beam contains more noise than an image obtained by irradiating a laser beam. Therefore, in the process of extracting such a contour line, a process is performed to reduce the influence of noise. Therefore, there was a problem that the amount of calculation processing increased. Furthermore, when the pattern density is high or when the pattern becomes complicated, the amount of calculation processing becomes enormous. Furthermore, since the electron beam inspection apparatus needs to scan with a beam narrowed to a few nanometers, the total number of pixels becomes extremely large, which also results in an enormous amount of calculation processing. Furthermore, because the image resolution is high, it is required to detect finer defects than with conventional inspection equipment, which makes the contour extraction process and distance calculation method complicated, resulting in an increase in the amount of calculation processing. It becomes. Therefore, it is desirable to be able to perform the inspection using calculation processing with as little processing amount as possible.

Japanese Patent Application Publication No. 2018-151202

Further, it is assumed that such calculation processing uses an algorithm suitable for calculation by a computer such as a CPU. Therefore, it is difficult to implement hardware such as FPGA (field-programmable gate array).

Accordingly, one aspect of the present invention provides an inspection method and an inspection apparatus that can reduce the processing amount of contour line inspection in electron beam inspection.

An electron beam inspection method according to one embodiment of the present invention includes:
A secondary electron image of the substrate is obtained by irradiating a substrate on which a graphic pattern is formed with a primary electron beam and detecting secondary electrons emitted from the substrate due to the irradiation with the primary electron beam. process and
The secondary electron image is divided into a grid, and the brightness value of each pixel is defined.A group of adjacent first grids among a plurality of first grids that serve as the intersection point of the division and the center of the target pixel. For each first rectangular area surrounded by calculating a first area of the region;
Using a reference image for comparison with the secondary electron image, the reference image is divided into a grid with the same size as the secondary electron image, and the brightness value of each pixel is defined. The luminance defined by the second grid group within a second rectangular area surrounded by the second grid group at a position corresponding to the first grid group among the plurality of second grids that are the centers of pixels. calculating a second area of a second region where the brightness value interpolated by the value is larger than the reference brightness value;
a step of comparing the first area and the second area for each first rectangular area;
It is characterized by having the following.

Furthermore, when inspecting the edge position of a figure pattern placed within the first rectangular area, if the difference between the first area and the second area is not within a predetermined range, the edge position It is preferable to determine that there is a defect in.

In addition, when inspecting the line width of a figure pattern placed within the first rectangular area, the difference between the first area and second area at one edge, which is the basis of the line width, and the other edge It is preferable to determine that a line width defect exists if the difference between the first area and the second area is not within a predetermined range.

Further, it is preferable that the first grid group is composed of 2×2 first grid groups in a coordinate system in two orthogonal directions.

An electron beam inspection apparatus according to one embodiment of the present invention includes:
A secondary electron image of the substrate is obtained by irradiating a substrate on which a graphic pattern is formed with a primary electron beam and detecting secondary electrons emitted from the substrate due to the irradiation with the primary electron beam. a secondary electron image acquisition mechanism;
The secondary electron image is divided into a grid, and the brightness value of each pixel is defined.A group of adjacent first grids among a plurality of first grids that serve as the intersection point of the division and the center of the target pixel. For each first rectangular area surrounded by a first area calculation unit that calculates a first area of the region;
Using a reference image for comparison with the secondary electron image, the reference image is divided into a grid with the same size as the secondary electron image, and the brightness value of each pixel is defined. The luminance defined by the second grid group within a second rectangular area surrounded by the second grid group at a position corresponding to the first grid group among the plurality of second grids that are the centers of pixels. a second area calculation unit that calculates a second area of a second region where the brightness value interpolated by the value is larger than the reference brightness value;
a comparison unit that compares a first area and a second area for each first rectangular area;
Equipped with
When inspecting the position of an edge of a graphic pattern arranged within the first rectangular area, if the difference between the first area and the second area is not within a predetermined range, the edge It is characterized in that it is determined that a defect exists at the position.

According to one aspect of the present invention, the processing amount of contour line inspection can be reduced in electron beam inspection.

1 is a configuration diagram showing an example of the configuration of a pattern inspection device in Embodiment 1. FIG. 2 is a conceptual diagram showing the configuration of a molded aperture array substrate in Embodiment 1. FIG. 3 is a diagram showing an example of a plurality of chip regions formed on a semiconductor substrate in Embodiment 1. FIG. FIG. 3 is a diagram for explaining a multi-beam scanning operation in the first embodiment. FIG. 3 is a flowchart showing main steps of the inspection method in the first embodiment. FIG. 2 is a configuration diagram showing an example of a configuration inside a comparison circuit in Embodiment 1. FIG. 3 is a diagram for explaining a pixel group and a grid area in Embodiment 1. FIG. FIG. 3 is a diagram for explaining rotation of a grid area in the first embodiment. FIG. 3 is a diagram for explaining brightness contour lines and sub-regions in the first embodiment. FIG. 3 is a diagram showing an example of a difference area in the first embodiment. FIG. 3 is a diagram for explaining a modification of the calculation area of the first embodiment. FIG. 3 is a diagram for explaining an example of an edge search method in the first embodiment. FIG. 3 is a diagram for explaining an example of a paired edge search method in the first embodiment. FIG. 3 is a diagram for explaining line width inspection of a graphic pattern in the first embodiment.

In the following embodiments, an inspection apparatus that acquires images using a multi-beam consisting of a plurality of electron beams will be described, but the present invention is not limited to this. An inspection device that acquires an image using a single electron beam may also be used.

Embodiment 1.
FIG. 1 is a configuration diagram showing an example of the configuration of a pattern inspection apparatus according to the first embodiment. In FIG. 1, an inspection apparatus 100 that inspects a pattern formed on a substrate is an example of a multi-electron beam inspection apparatus. The inspection device 100 includes an image acquisition mechanism 150 (secondary electronic image acquisition mechanism) and a control system circuit 160. The image acquisition mechanism 150 includes an electron beam column 102 (electron lens barrel) and an examination chamber 103. Inside the electron beam column 102, an electron gun 201, an electromagnetic lens 202, a shaped aperture array substrate 203, an electromagnetic lens 205, a bulk blanking deflector 212, a limiting aperture substrate 213, an electromagnetic lens 206, an electromagnetic lens 207 (objective lens), A main deflector 208, a sub-deflector 209, a beam separator 214, a deflector 218, an electromagnetic lens 224, an electromagnetic lens 226, and a multi-detector 222 are arranged. In the example of FIG. 1, an electron gun 201, an electromagnetic lens 202, a molded aperture array substrate 203, an electromagnetic lens 205, a collective blanking deflector 212, a limiting aperture substrate 213, an electromagnetic lens 206, an electromagnetic lens 207 (objective lens), a main deflection The deflector 208 and the sub-deflector 209 constitute a primary electron optical system that irradiates the substrate 101 with multiple primary electron beams. The beam separator 214, the deflector 218, the electromagnetic lens 224, and the electromagnetic lens 226 constitute a secondary electron optical system that irradiates the multiple detector 222 with multiple secondary electron beams.

A stage 105 movable at least in the X and Y directions is arranged within the examination room 103. A substrate 101 (sample) to be inspected is placed on the stage 105 . The substrate 101 includes an exposure mask substrate and a semiconductor substrate such as a silicon wafer. When the substrate 101 is a semiconductor substrate, a plurality of chip patterns (wafer die) 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. A plurality of chip patterns (wafer die) are formed on the semiconductor substrate by exposing and transferring the chip pattern formed on the exposure mask substrate a plurality of times onto the semiconductor substrate. The case where the substrate 101 is a semiconductor substrate will be mainly described below. For example, the substrate 101 is placed on the stage 105 with the pattern formation surface facing upward. Further, a mirror 216 is arranged on the stage 105 to reflect a laser beam for laser length measurement irradiated from a laser length measurement system 122 arranged outside the examination room 103. Multi-detector 222 is connected to detection circuit 106 external to electron beam column 102.

In the control system circuit 160, a control computer 110 that controls the entire inspection apparatus 100 controls a position circuit 107, a comparison circuit 108, a reference image creation circuit 112, a stage control circuit 114, a lens control circuit 124, and a blanking circuit via a bus 120. It is connected to a control circuit 126, a deflection control circuit 128, a storage device 109 such as a magnetic disk device, a monitor 117, and a memory 118. The deflection control circuit 128 is also connected to DAC (digital-to-analog conversion) amplifiers 144, 146, and 148. DAC amplifier 146 is connected to main deflector 208 , and DAC amplifier 144 is connected to sub-deflector 209 . DAC amplifier 148 is connected to deflector 218.

Further, the detection circuit 106 is connected to the chip pattern memory 123. Chip pattern memory 123 is connected to comparison circuit 108. Further, the stage 105 is driven by a drive mechanism 142 under the control of a stage control circuit 114. The drive mechanism 142 includes, for example, a drive system such as a 3-axis (X-Y-θ) motor that drives in the X direction, Y direction, and θ direction in the stage coordinate system, so that the stage 105 can move in the XYθ directions. It has become. For these X motors, Y motors, and θ motors (not shown), for example, stepping motors can be used. The stage 105 is movable in the horizontal direction and rotational direction by motors for each of the XYθ axes. The moving position of the stage 105 is then measured by the laser length measurement system 122 and supplied to the position circuit 107. The laser length measurement system 122 measures the position of the stage 105 using the principle of laser interferometry by receiving the reflected light from the mirror 216. In the stage coordinate system, for example, the X direction, Y direction, and θ direction are set with respect to a plane perpendicular to the optical axis (electron orbit center axis) of the multi-primary electron beam.

The electromagnetic lens 202, the electromagnetic lens 205, the electromagnetic lens 206, the electromagnetic lens 207 (objective lens), the electromagnetic lens 224, the electromagnetic lens 226, and the beam separator 214 are controlled by the lens control circuit 124. The collective blanking deflector 212 is composed of two or more electrodes, and each electrode is controlled by the blanking control circuit 126 via a DAC amplifier (not shown). The sub-deflector 209 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 144. The main deflector 208 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 146. The deflector 218 is composed of four or more electrodes, and each electrode is controlled by the deflection control circuit 128 via the DAC amplifier 148.

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

Here, FIG. 1 shows a configuration necessary for explaining the first embodiment. The inspection apparatus 100 may normally include other necessary configurations.

FIG. 2 is a conceptual diagram showing the configuration of the molded aperture array substrate in the first embodiment. In FIG. 2, the molded aperture array substrate 203 has a two-dimensional horizontal (x direction) m ₁ column x vertical (y direction) n ₁ stage (m ₁ , n ₁ is an integer of 2 or more, and the other is an integer of 2 or more; Holes (openings) 22 (an integer of 1 or more) are formed at a predetermined array pitch in the x and y directions. The example in FIG. 2 shows a case where 23×23 holes (openings) 22 are formed. Ideally, each hole 22 is formed in a rectangular shape with the same size and shape. Alternatively, they may ideally be circular with the same outer diameter. When a portion of the electron beam 200 passes through each of these plurality of holes 22, m ₁ ×n _one (=N) multi-primary electron beams 20 are formed.

Next, the operation of the image acquisition mechanism 150 in the inspection apparatus 100 will be explained.

An electron beam 200 emitted from an electron gun 201 (emission source) is refracted by an electromagnetic lens 202 and illuminates the entire shaped aperture array substrate 203. As shown in FIG. 2, a plurality of holes 22 (openings) are formed in the shaped aperture array substrate 203, and the electron beam 200 illuminates a region including all the plurality of holes 22. A multi-primary electron beam 20 is formed by each part of the electron beam 200 irradiated to the positions of the plurality of holes 22 passing through the plurality of holes 22 of the shaped aperture array substrate 203.

The formed multi-primary electron beam 20 is refracted by an electromagnetic lens 205 and an electromagnetic lens 206, and is placed at the crossover position of each beam of the multi-primary electron beam 20 while repeating intermediate images and crossovers. The beam passes through a beam separator 214 and advances to an electromagnetic lens 207 (objective lens). Then, the electromagnetic lens 207 focuses the multi-primary electron beam 20 onto the substrate 101. The multi-primary electron beams 20 focused on the substrate 101 (sample) surface by the objective lens 207 are collectively deflected by the main deflector 208 and the sub-deflector 209, and the Each irradiation position on 101 is irradiated. Note that when the entire multi-primary electron beam 20 is deflected all at once by the collective blanking deflector 212, it is displaced from the center hole of the limiting aperture substrate 213 and is shielded by the limiting aperture substrate 213. On the other hand, the multi-primary electron beam 20 that has not been deflected by the collective blanking deflector 212 passes through the center hole of the limited aperture substrate 213, as shown in FIG. Blanking control is performed by turning ON/OFF the collective blanking deflector 212, and ON/OFF of the beam is collectively controlled. In this way, the limited aperture substrate 213 shields the multi-primary electron beam 20 that has been deflected by the collective blanking deflector 212 so as to turn the beam OFF. Then, a multi-primary electron beam 20 for inspection (for image acquisition) is formed by a group of beams that have passed through the limiting aperture substrate 213 and are formed from when the beam is turned on until when the beam is turned off.

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

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

Here, the beam separator 214 generates an electric field and a magnetic field in orthogonal directions on a plane perpendicular to the direction in which the central beam of the multi-primary electron beam 20 travels (electron orbit center axis). The electric field exerts a force in the same direction regardless of the direction in which the electrons travel. On the other hand, a magnetic field exerts a force according to Fleming's left-hand rule. Therefore, the direction of the force acting on the electrons can be changed depending on the direction in which the electrons enter. For the multi-primary electron beam 20 entering the beam separator 214 from above, the force due to the electric field and the force due to the magnetic field cancel each other out, and the multi-primary electron beam 20 travels straight downward. On the other hand, the force due to the electric field and the force due to the magnetic field act in the same direction on the multiple secondary electron beam 300 that enters the beam separator 214 from below, and the multiple secondary electron beam 300 is directed diagonally upward. It is bent and separated from the multi-primary electron beam 20.

The multi-secondary electron beam 300 that is bent diagonally upward and separated from the multi-primary electron beam 20 is further bent by a deflector 218 and projected onto a multi-detector 222 while being refracted by electromagnetic lenses 224 and 226. Ru. The multiple detector 222 detects the projected multiple secondary electron beams 300. The reflected electrons and secondary electrons may be projected onto the multi-detector 222, or the reflected electrons may diverge midway and the remaining secondary electrons may be projected onto the multi-detector 222. Multi-detector 222 has a two-dimensional sensor. Then, each secondary electron of the multi-secondary electron beam 300 collides with a corresponding region of the two-dimensional sensor to generate electrons, thereby generating secondary electron image data for each pixel. In other words, the multi-detector 222 has a detection sensor for each primary electron beam i (for 23×23 multi-primary electron beams 20, i=1 to 529) of the multi-primary electron beams 20. Placed. Then, a corresponding secondary electron beam emitted by irradiation with each primary electron beam i is detected. Therefore, each detection sensor of the plurality of detection sensors of the multi-detector 222 detects the intensity signal of the image secondary electron beam resulting from the irradiation of the primary electron beam 10i for which it is responsible. The intensity signal detected by the multi-detector 222 is output to the detection circuit 106.

FIG. 3 is a diagram illustrating an example of a plurality of chip regions formed on a semiconductor substrate in the first embodiment. In FIG. 3, when the substrate 101 is a semiconductor substrate (wafer), a plurality of chips (wafer die) 332 are formed in a two-dimensional array in an inspection area 330 of the semiconductor substrate (wafer). A mask pattern for one chip formed on an exposure mask substrate is transferred to each chip 332 by reducing the size to, for example, 1/4 by an exposure device (not shown) (stepper, scanner, etc.). The area of each chip 332 is divided, for example, into a plurality of stripe areas 32 with a predetermined width in the y direction. The scanning operation by the image acquisition mechanism 150 is performed for each stripe area 32, for example. For example, while moving the stage 105 in the −x direction, the scanning operation of the stripe region 32 is relatively progressed in the x direction. Each stripe area 32 is divided into a plurality of rectangular areas 33 in the longitudinal direction. The movement of the beam to the target rectangular region 33 is performed by deflecting the entire multi-primary electron beam 20 at once by the main deflector 208.

FIG. 4 is a diagram for explaining the multi-beam scanning operation in the first embodiment. The example in FIG. 4 shows the case of a 5×5 array of multi-primary electron beams 20. The irradiation area 34 that can be irradiated by one irradiation with the multi-primary electron beam 20 is (x-direction calculated by multiplying the inter-beam pitch in the x-direction of the multi-primary electron beams 20 on the surface of the substrate 101 by the number of beams in the x-direction). size)×(y-direction size obtained by multiplying the inter-beam pitch in the y-direction of the multi-primary electron beams 20 on the surface of the substrate 101 by the number of beams in the y-direction). It is preferable that the width of each stripe area 32 is set to be the same as the y-direction size of the irradiation area 34, or to a size narrower by the scan margin. The examples in FIGS. 3 and 4 show a case where the irradiation area 34 has the same size as the rectangular area 33. However, it is not limited to this. The irradiation area 34 may be smaller than the rectangular area 33. Or it doesn't matter if it's big. Each beam of the multi-primary electron beam 20 is irradiated into a sub-irradiation area 29 surrounded by the inter-beam pitch in the x direction and the inter-beam pitch in the y direction, where its own beam is located, and the sub-irradiation area 29 is Scan inside (scanning operation). Each primary electron beam 10 constituting the multi-primary electron beam 20 is responsible for one of the different sub-irradiation areas 29. Then, during each shot, each primary electron beam 10 irradiates the same position within the assigned sub-irradiation area 29. Movement of the primary electron beam 10 within the sub-irradiation area 29 is performed by deflecting the entire multi-primary electron beam 20 at once by the sub-deflector 209. This operation is repeated to sequentially irradiate one sub-irradiation area 29 with one primary electron beam 10. When scanning of one sub-irradiation area 29 is completed, the entire multi-primary electron beam 20 is collectively deflected by the main deflector 208, so that the irradiation position moves to an adjacent rectangular area 33 within the same stripe area 32. This operation is repeated to sequentially irradiate the inside of the stripe area 32. When scanning of one stripe area 32 is completed, the irradiation position is moved to the next stripe area 32 by moving the stage 105 and/or deflecting the entire multi-primary electron beam 20 at once by the main deflector 208. As described above, a secondary electron image is obtained for each sub-irradiation area 29 by irradiation with each primary electron beam 10i. By combining these secondary electron images for each sub-irradiation area 29, a secondary electron image of the rectangular area 33, a secondary electron image of the striped area 32, or a secondary electron image of the chip 332 is constructed.

As shown in FIG. 4, each sub-irradiation area 29 is divided into a plurality of rectangular frame areas 30, and a secondary electron image (image to be inspected) of each frame area 30 is used for inspection. The example in FIG. 4 shows a case where one sub-irradiation area 29 is divided into, for example, four frame areas 30. However, the number of divisions is not limited to four. It does not matter if it is divided into other numbers.

Note that it is also preferable that, for example, a plurality of chips 332 lined up in the x direction are grouped into the same group, and each group is divided into a plurality of stripe regions 32 with a predetermined width in the y direction, for example. Furthermore, the movement between the stripe regions 32 is not limited to each chip 332, and it is also suitable to move each group.

Here, when the multi-primary electron beam 20 is irradiated onto the substrate 101 while the stage 105 is continuously moving, the main deflector 208 deflects the multi-primary electron beam 20 at once so that the irradiation position follows the movement of the stage 105. Tracking operation is performed by Therefore, the emission position of the multiple secondary electron beams 300 changes every moment with respect to the orbit center axis of the multiple primary electron beams 20. Similarly, when scanning the sub-irradiation area 29, the emission position of each secondary electron beam changes momentarily within the sub-irradiation area 29. The deflector 218 collectively deflects the multiple secondary electron beams 300 so that each of the secondary electron beams whose emission positions have changed in this way is irradiated into the corresponding detection area of the multiple detector 222.

Here, an image obtained by irradiating an electron beam contains more noise than an image obtained by irradiating a laser beam. For example, it contains 10 times more noise. Therefore, in the image obtained by the multi-detector 222, noise components are reduced according to a predetermined model function, for example, using surrounding pixels for each pixel. Thereafter, the outline of the graphic pattern is determined from the noise-reduced image. Therefore, there was a problem that the amount of calculation processing increased. In particular, when the pattern density is high or when the pattern becomes complicated, the amount of calculation processing becomes enormous. Furthermore, since the electron beam inspection apparatus needs to scan with a beam narrowed to a few nanometers, the total number of pixels becomes extremely large, which also results in an enormous amount of calculation processing. Furthermore, because the image resolution is high, it is required to detect finer defects than with conventional inspection equipment, which makes the contour extraction process and distance calculation method complicated, resulting in an increase in the amount of calculation processing. It becomes. Therefore, in Embodiment 1, instead of determining a specific contour line, the brightness values are set in advance within a rectangular area in which the brightness values of surrounding pixels are defined at the four corners of the image to be inspected and the reference image. By calculating the area of a small area from which the value contour lines are separated and calculating the difference between the obtained areas, the deviation of the contour line within the rectangular area is inspected.

FIG. 5 is a flowchart showing the main steps of the inspection method in the first embodiment. In FIG. 5, the inspection method in the first embodiment includes a secondary electron image acquisition step (S102), a reference image creation step (S110), a pixel selection step (S120), a grid area rotation step (S122), A series of steps are performed: a sub-region area calculation step (S124), a pixel selection step (S130), a grid region rotation step (S132), a sub-region area calculation step (S134), and a comparison step (S140). do. When performing edge position inspection, the comparison step (S140) includes an area difference calculation step (S142) and a determination step (S144) as internal steps. Alternatively, when inspecting the line width of a graphic pattern, the comparison step (S140) includes an area difference calculation step (S142), a paired edge search step (S145), a difference calculation step (S146), and a determination step as internal steps. (S148). Alternatively, when both edge position inspection and graphic pattern line width inspection are performed, the comparison step (S140) includes an area difference calculation step (S142), a determination step (S144), and a paired edge search step (S140) as internal steps. S145), a difference calculation step (S146), and a determination step (S148) are performed.

As the secondary electron image acquisition step (S102), the image acquisition mechanism 150 irradiates the substrate 101 on which the graphic pattern is formed with the multi-primary electron beam 20, and the substrate By detecting the multiple secondary electron beams 300 emitted from the substrate 101, a secondary electron image of the substrate 101 is acquired. As described above, reflected electrons and secondary electrons may be projected onto the multi-detector 222, or reflected electrons may diverge on the way and remaining secondary electrons (multiple secondary electron beam 300) may be projected onto the multi-detector 222. It's okay to be.

As described above, the image is acquired by irradiating the multiple primary electron beams 20 and detecting the multiple secondary electron beams 300 emitted from the substrate 101 due to the irradiation of the multiple primary electron beams 20 using the multiple detector 222. Detect with. The detection data of secondary electrons for each pixel in each sub-irradiation area 29 detected by the multi-detector 222 (measurement image data: secondary electron image data: image data to be inspected) is output to the detection circuit 106 in the order of measurement. Ru. 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. The obtained measurement image data is then transferred to the comparison circuit 108 together with information indicating each position from the position circuit 107. It is transferred to the comparison circuit 108.

In the reference image creation step (S110), the reference image creation circuit 112 (reference image creation unit) creates a frame image (secondary Create a reference image at the position corresponding to the electronic image). Specifically, it operates as follows. First, 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 multivalued image data.

As mentioned above, the shapes defined in the design pattern data are basic shapes such as rectangles and triangles, and include the coordinates (x, y) at the reference position of the shape, the length of the sides, the rectangle, triangle, etc. Graphic data is stored that defines the shape, size, position, etc. of each pattern graphic using information such as a graphic code serving as an identifier for distinguishing the graphic type.

When design pattern data serving as such graphic data is input to the reference image creation circuit 112, it is developed into data for each graphic, and the graphic code, graphic dimensions, etc. indicating the graphic shape of the graphic data are interpreted. Then, it is expanded into binary or multivalued design pattern image data as a pattern arranged in a grid with a grid of a predetermined quantization size as a unit, and output. In other words, read the design data, calculate the occupancy rate occupied by the figure in the design pattern for each square created by virtually dividing the inspection area into squares with predetermined dimensions as units, and calculate the n-bit occupancy data. Output. For example, it is preferable to set one square as one pixel. If one pixel has a resolution of ^1/28 (=1/256), a small area of 1/256 is allocated for the area of the figure placed within the pixel, and the occupancy rate within the pixel is calculated. calculate. This results in 8-bit occupancy data. Such squares (inspection pixels) may be aligned with pixels of measurement data.

Next, the reference image creation circuit 112 performs filter processing on the design image data of the design pattern, which is the image data of the figure, using a predetermined filter function. Thereby, the design image data, which is image data on the design side in which the image intensity (gradation value) is a digital value, can be matched to the image generation characteristics obtained by irradiation with the multi-primary electron beam 20. The image data for each pixel of the created reference image is output to the comparison circuit 108.

FIG. 6 is a configuration diagram showing an example of the internal configuration of the comparison circuit in the first embodiment. In FIG. 6, the comparison circuit 108 includes storage devices 50 and 52 such as magnetic disk devices, pixel selection sections 60 and 61, grid area rotation sections 62 and 63, sub-area area calculation sections 64 and 65, and comparison processing sections. 66 is placed. When performing an edge position inspection, an area difference calculation section 67 and a determination section 68 are arranged within the comparison processing section 66 . Alternatively, when inspecting the line width of a graphic pattern, the comparison processing section 66 includes an area difference calculation section 67, a pair edge search section 69, a difference calculation section 70, and a determination section 72. When performing both edge position inspection and graphic pattern line width inspection, the comparison processing section 66 includes an area difference calculation section 67, a determination section 68, a paired edge search section 69, a difference calculation section 70, and a determination section 72. Placed.

In FIG. 6, pixel selection units 60 and 61, grid area rotation units 62 and 63, sub-area area calculation units 64 and 65, and comparison processing unit 66 (area difference calculation unit 67, determination unit 68, pair edge search unit 69, difference Each "unit" such as the calculation unit 70 and the determination unit 72) includes a processing circuit, and the processing circuit includes an electric circuit, a computer, a processor, a circuit board, a quantum circuit, a semiconductor device, or the like. Further, each "~ section" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. Pixel selection units 60 and 61, grid area rotation units 62 and 63, sub-area area calculation units 64 and 65, and comparison processing unit 66 (area difference calculation unit 67, determination unit 68, pair edge search unit 69, difference calculation unit 70, Input data or calculated results required in the determination unit 72) are stored in a memory (not shown) or in the memory 118 each time.

The measurement data input into the comparison circuit 108 is stored in the storage device 50 as a frame image (image to be inspected) of each frame area 30. The reference image data input into the comparison circuit 108 is stored in the storage device 52.

As the pixel selection step (S120), the pixel selection unit 60 selects, for each pixel of the frame image, surrounding pixels forming a 2×2 pixel group, for example, based on the pixel.

FIG. 7 is a diagram for explaining pixel groups and grid areas in the first embodiment. In FIG. 7, the frame image of each frame region 30 is composed of a plurality of mesh-like pixels 36. Each pixel 36 is set in a rectangular area centered on each grid 37 of a plurality of grids 37 (first grid) that are intersection points when each frame image (secondary electron image) is divided into a grid. It is preferable that each pixel 36 is set to a size comparable to the diameter size of each beam of the multi-primary electron beam 20, for example. A brightness value is defined for each grid 37 as the pixel value of the pixel where the grid is located. The brightness value is defined by a gradation value depending on the resolution of the pixel. For example, the brightness value is defined as 256 gradations from 0 to 255. As shown in FIG. 7, a rectangular grid area 38 (rectangular area ) is set. Therefore, the size of the grid area 38 is the same as the size of the pixel 36 in the example of FIG. In other words, brightness values are defined in each of the grids 37 at the four corners of the rectangular grid area 38. The grid 37 group is composed of 2×2 grid groups in a two-direction coordinate system of orthogonal x and y directions. Adjacent grid 37 groups and grid areas 38 are configured each time the target pixel changes. Therefore, the frame area 30 is completely filled with a plurality of grid areas 38 except for half a pixel at the end.

As the grid area rotation step (S122), the grid area rotation unit 62 rotates the grid area 38 for each grid area 38 so that the grid 37 where the maximum brightness value is defined becomes the origin position (for example, the lower left corner). Rotate.

FIG. 8 is a diagram for explaining rotation of the grid area in the first embodiment. In the example of FIG. 8A, the brightness value of the lower left grid 37 of the grid area 38 is 100, the brightness value of the upper left grid 37 is 250, the brightness value of the lower right grid 37 is 0, and the brightness value of the upper right grid 37 is 0. A case where the brightness value is 100 is shown. When the origin position is set to the lower left, the brightness value of the upper left grid 37 indicates the maximum value, so the grid area 38 is rotated 90 degrees counterclockwise so that the brightness value of the upper left grid 37 becomes the origin position. let As a result, as shown in FIG. 8B, the brightness value of the lower left grid 37 of the grid area 38 is 250, the brightness value of the upper left grid 37 is 100, the brightness value of the lower right grid 37 is 100, and the brightness value of the lower right grid 37 is 100, and the brightness value of the lower right grid 37 is 100. The brightness value of the grid 37 can be set to 0. When the maximum brightness is defined in a plurality of grids, the grid 37 may be rotated so that one of the grids 37 becomes the origin position. Thereby, in the x, y coordinate system, a grid area 38 can be defined with the grid 37 of maximum brightness as the origin.

As the sub-region area calculation step (S124), the sub-region area calculation unit 64 (first area calculation unit) divides the frame image (secondary electron image) into a grid pattern, and defines the luminance value of each pixel 36. For each grid area 38 surrounded by adjacent grid 37 groups among the plurality of grids 37, a brightness value interpolated with the brightness value defined for the grid 37 group within the grid area 38 is a preset reference brightness value. The area (first area) of a sub-region (first region) larger than the sub-region (first area) is calculated. The brightness value at each position within the grid area 38 is a value linearly interpolated by the brightness values of the grid 37 at the four corners.

FIG. 9 is a diagram for explaining brightness contour lines and sub-regions in the first embodiment. FIG. 9A shows one grid area 38 within the frame image. FIG. 9B shows a grid area 48 at a corresponding position in the reference image at the same position as the frame image. The edge of the graphic pattern in the frame image exists in the middle of the rise of the brightness value or at the peak position. Therefore, a reference brightness value that determines the edge of the graphic pattern is set in advance. Then, a brightness contour line 41 (y=f(x)) of the reference brightness value z within the grid area 38 is calculated. The brightness contour line 41 of the reference brightness value has coefficients a, b, c, Using d, it can be defined by the following equations (1-1) to (1-5). Here, the coordinates of A to D are (0,0), (1,0), (0,1), (1,1).

Therefore, the area of the sub-region 40 larger than the reference luminance value within the grid region 38 can be determined by integrating the luminance contour line y=f(x) of the reference luminance value z. Therefore, the area S of the sub-region 40 can be defined by the following equations (2-1) and (2-2).

In the pixel selection step (S130), the pixel selection unit 61 selects a reference image corresponding to the target frame image that is the same as, for example, a 2×2 pixel group selected for the frame image in the pixel selection step (S120). For example, surrounding pixels constituting a 2×2 pixel group at the position are selected. Therefore, a rectangular grid area 48 surrounded by 2x2 adjacent grids 47 in the reference image is set, which corresponds to a rectangular grid area 38 surrounded by 2x2 adjacent grids 37 in the frame image.

As the grid area rotation step (S132), the grid area rotation unit 63 rotates the grid area 48 for each grid area 48 so that the grid 47 where the maximum brightness value is defined becomes the origin position (for example, the lower left corner). Rotate.

As the sub-region area calculation step (S134), the sub-region area calculation unit 65 (second area calculation unit) divides the reference image into a grid with the same size as the frame image, and defines the brightness value of each pixel. Among the plurality of grids 47 (second grids), the luminance value defined in the grid 47 group is interpolated within a rectangular grid area 48 (rectangular area) surrounded by the grid 47 group at a position corresponding to the grid 37 group. The area S' (second area) of the sub-region 42 (second area) whose brightness value is larger than the reference brightness value is calculated. The brightness contour lines 43 (y=f(x)) of the reference brightness value z in the grid area 48 of the reference image shown in FIG. 9(b) are located at the lower left, lower right, upper left, and upper right of the four corners of the grid area 48. The above equations (1-1) to (1-5) can be calculated using coefficients a, b, c, and d defined using the luminance values A, B, C, and D shown in this order. Furthermore, the area S' of the sub-region 42 larger than the standard brightness value in the grid area 48 of the reference image can be obtained by integrating the brightness contour line 43 (y=f(x)) of the standard brightness value z. can. Therefore, the area S' of the sub-region 42 can be determined by replacing S in equation (2) with S'.

As a comparison step (S140), the comparison processing section 66 (comparison section) compares the area S (first area) and the area S' (second area) for each grid area 38. Specifically, it operates as follows. First, a case in which edge position inspection is performed will be described.

As the area difference calculation step (S142), the area difference calculation unit 67 calculates the difference ΔS between the area S of the sub-region 40 of the grid area 38 and the area S' of the sub-region 42 of the grid area 48 for each grid area 38. do. Specifically, a value (SS') obtained by subtracting the area S' from the area S is calculated.

FIG. 10 is a diagram illustrating an example of a difference area in the first embodiment. FIG. 10 shows a difference region 44 between the sub-region 40 of the grid region 38 in FIG. 9(a) and the sub-region 42 of the grid region 48 in FIG. 9(b). In other words, it shows the area surrounded by the brightness contour line 41 in the grid area 38 of the frame image, the brightness contour line 43 in the grid area 48 of the reference image, and the frame of the grid area 38. Although the example in FIG. 10 shows a case where there is one difference area 44, the present invention is not limited to this. If there are two or more pairs of brightness contour lines 41 in the grid area 38 of the frame image and brightness contour lines 43 in the grid area 48 of the reference image, the same number of difference areas 44 will also exist. In the first embodiment, the edge position shift is evaluated based on the area of the difference region 44.

In the determination step (S144), the determination unit 68 determines whether the difference value ΔS between the area S and the area S' is a predetermined value when inspecting the edge position on one side of the graphic pattern arranged in the grid area 38 (48). If it is not within the range, it is determined that a defect exists at the edge position. Specifically, if the absolute value of the difference value ΔS between the area S and the area S' is larger than the threshold Th, in other words, if the following equation (3) is not satisfied, there is a defect in the grid area 38. Determine that it exists.

Note that for the grid area 38 (48) in which the brightness contour line 41 of the reference brightness value does not exist, it is assumed that the contour line of the graphic pattern does not exist in the grid area 38 (48), and the steps after the sub-area area calculation step (S124) are performed. It is also preferable to exclude it from the calculation processing target. Of course, it may also be used as a target for calculation processing. In such a case, for the grid area 38 (48) where the outline of the graphic pattern does not exist, the difference ΔS will normally be zero because the difference area 44 does not exist.

As described above, in the first embodiment, when inspecting the edge position of a graphic pattern, each pixel is surrounded by a brightness contour line interpolated using surrounding pixels and a frame of the grid area 38 (48). By calculating the area difference value, the presence or absence of defects can be inspected. In this manner, in the first embodiment, inspection can be performed by simply performing one integral calculation and one differential calculation. Therefore, the amount of processing required to remove noise can be reduced, and the processing required to extract the outline of each image and the distance between the contours between images can be eliminated, and the amount of processing can be significantly reduced. .

FIG. 11 is a diagram for explaining a modification of the calculation area of the first embodiment. As shown in FIG. 11, the brightness contour line 41 of the frame image and the brightness contour line 43 of the reference image may not be located within one grid area 38 (48). Therefore, instead of calculating using one grid area 38 (48), for example, the brightness values of nine grids 37 (47) at the four corners of the 2 x 2 grid area 38 (48) are used to calculate the brightness values of the 2 x 2 grid area 38 (48). It is also preferable to calculate the brightness contour line 41 and the brightness contour line 43 by interpolating the brightness values at each position within 38 (48).

Next, the case of inspecting the line width of a graphic pattern will be described. The contents of the area difference calculation step (S142) are as described above. Although it is possible to evaluate the positional deviation of one edge passing through the grid area 38 (48) using only the area ΔS of the difference area 44 in each grid area 38 (48), the line width cannot be determined. Therefore, it is necessary to search for the other edge that is a pair of such one edge.

As the paired edge searching step (S145), the paired edge searching unit 69 first searches for at least one edge (end) of the graphic pattern for each frame area.

FIG. 12 is a diagram for explaining an example of an edge search method in the first embodiment. In the example of FIG. 12, for each frame area 30, the edge of the graphic pattern 12 in the frame image is searched for using the frame image of the frame area 30. In the example of FIG. 12, a rising point where the luminance value of each pixel increases in order is searched from the edge of the frame image (for example, the left edge) toward the opposite edge (for example, the right edge), in other words, in the x direction. do. Then, for example, it is determined that the edge point of the graphic pattern is located at a position indicating the midpoint of the luminance value from the beginning of the rising edge to the upper limit peak. One of the edges of the graphic pattern can be constructed by connecting a plurality of edge points obtained by repeatedly performing the same operation pixel by pixel from the top to the bottom of the edge (for example, the left edge) of the frame image. Since the number of graphic patterns 12 located within one frame area 30 is not limited to one, one edge of a plurality of graphic patterns within the same frame image can be searched for by performing a similar operation. Further, a similar operation is performed in the y direction.

Next, the paired edge search unit 69 searches for the other edge that is paired with the obtained one edge. Specifically, it operates as follows.

FIG. 13 is a diagram for explaining an example of a paired edge search method in the first embodiment. The paired edge search unit 69 searches for the shortest edge from a point (edge point) on one edge 11a of the graphic pattern. In the example of FIG. 13, the search circle is expanded around the edge point. Then, the edge 11b closest to the edge point is searched as a paired edge. In order to find a pair edge, a falling point where the luminance value of each pixel decreases in order is searched for. Then, for example, the other edge 11b of the graphic pattern is determined to be an edge point located at a position indicating the midpoint of the luminance value from the beginning of the fall to the lower limit peak. By performing the same operation on multiple edge points on one edge 11a of the same graphic pattern and connecting the other multiple edge points obtained as a result of searching in the same direction, one edge 11a of the graphic pattern and The other edge 11b serving as a pair can be configured. Furthermore, since rising edges and falling edges appear alternately, both searches can be performed simultaneously during scanning in the same direction. As a result, the edge point on the other edge 11b of the graphic pattern 12 that is closest to each edge point on the one edge 11a of the graphic pattern 12 can be found. Once the two edge points forming a pair on both edges are determined, a grid area 38 including the edge points is determined.

As the difference calculation step (S146), the difference calculation unit 70 calculates, for each grid area 38, the difference ΔS1 between the area S at one edge and the area S' of the graphic pattern on which the line width is based, and the area at the other edge. The difference value (ΔS1-ΔS2) between S and the area S' is calculated. At this time, the distance (for example, in pixel units) between the edge 11a and the edge 11b is determined, and if the distance is not within a predetermined range, the difference value is not calculated.

FIG. 14 is a diagram for explaining line width inspection of a graphic pattern in the first embodiment. In the example of FIG. 14, the brightness contour 41a of the grid area 38a in the frame image including one edge point on one edge 11a of the graphic pattern 12, the brightness contour 43a of the grid area 48a in the reference image, and the brightness contour 43a of the grid area 38a ( A difference area 44a surrounded by a frame 48a) is shown. The brightness contour line 41a corresponds to one edge 11a of the graphic pattern 12 in the frame image. The brightness contour line 43a corresponds to one edge 13a of the graphic pattern 12 in the reference image. In the example of FIG. 14, the brightness contour 41b of the grid area 38b in the frame image including the pair of edge points on the other edge 11b of the graphic pattern 12, the brightness contour 43b of the grid area 48b in the reference image, and the grid A difference area 44b surrounded by a frame of area 38b (48b) is shown. The brightness contour line 41b corresponds to the other edge 11b of the graphic pattern 12 in the frame image. The brightness contour line 43b corresponds to the other edge 13b of the graphic pattern 12 in the reference image. In other words, in the example of FIG. 14, the difference area 44a in the grid area 38a (48a) including one edge point on one edge 11a of the graphic pattern 12 and the pair on the other edge 11b of the same graphic pattern 12 An example of the difference area 44b in the grid area 38b (48b) including edge points is shown. In the first embodiment, the deviation in the line width L of the graphic pattern is evaluated based on the difference value between the difference ΔS1, which is the area of the difference region 44a, and the difference ΔS2, which is the area of the difference region 44b.

In the determination step (S148), when inspecting the line width of the graphic pattern arranged in the grid area 38 (48), the determination unit 71 determines the area S and area S at one edge, which is the basis of the line width L. If the difference value ΔS1 between the two edges and the difference value ΔS2 between the area S and the area S' at the other edge are not within a predetermined range, it is determined that a line width defect exists. Specifically, if the absolute value of the difference value (ΔS1-ΔS2) between the difference value ΔS1 and the difference value ΔS2 is larger than the threshold Th', in other words, if the following formula (4) is not satisfied, the corresponding It is determined that a line width defect of the graphic pattern exists in the grid area 38 .

Note that for the grid area 38 (48) where the brightness contour line 41 of the reference brightness value does not exist, as described above, the sub-area area calculation is performed on the assumption that there is no outline of the graphic pattern in the grid area 38 (48). It is also suitable to exclude it from the calculation processing targets after step (S124).

As described above, in the first embodiment, when inspecting the line width of a graphic pattern, each pixel is surrounded by a luminance contour line interpolated using surrounding pixels and a frame of the grid area 38 (48). The presence or absence of a defect can be inspected by calculating the difference in area difference values between paired pixels. In this manner, in the first embodiment, inspection can be performed by simply performing one integral calculation, one calculation of the difference, and one calculation of the difference between these differences. Therefore, the amount of processing required to remove noise can be reduced, and the processing required to extract the outline of each image and the distance between the contours between images can be eliminated, and the amount of processing can be significantly reduced. .

When both edge position inspection and graphic pattern line width inspection are performed, the comparison step (S140) includes the above-mentioned area difference calculation step (S142), determination step (S144), and paired edge search step (S140) as internal steps. S145), a difference value addition step (S146), and a determination step (S148) may be performed.

In the above example, a case was explained in which a die database check was performed, but the present invention is not limited to this. The image to be inspected may be one for die-to-die inspection. A case of performing a die-to-die inspection will be explained.

The frame image of the die 2 in which the same pattern as the frame image of the target die 1 is formed is used as the above-mentioned reference image to carry out each step after the pixel selection step (S130). In other words, the same steps may be carried out by replacing the frame image with the frame image of die 1 and the reference image with the frame image of die 2.

As described above, according to the first embodiment, the processing amount of contour line inspection can be reduced in electron beam inspection.

In the above description, a 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, each "circuit" may use a common processing circuit (the same processing circuit). Alternatively, different processing circuits (separate processing circuits) may be used. A program for executing a processor or the like may be recorded on a recording medium such as a magnetic disk device, a magnetic tape device, an FD, or a ROM (read only memory). For example, the position circuit 107, the comparison circuit 108, the reference image creation circuit 112, the stage control circuit 114, the lens control circuit 124, the blanking control circuit 126, and the deflection control circuit 128 are configured with at least one processing circuit described above. Also good.

The embodiments have been described above with reference to specific examples. However, the present invention is not limited to these specific examples. The example in FIG. 1 shows a case where a multi-primary electron beam 20 is formed by a shaping aperture array substrate 203 from one beam irradiated from an electron gun 201 serving as one irradiation source, but the present invention is not limited to this. isn't it. An embodiment may be adopted in which the multi-primary electron beam 20 is formed by irradiating primary electron beams from a plurality of irradiation sources, respectively.

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

In addition, all electron beam inspection methods and electron beam inspection apparatuses that include the elements of the present invention and whose designs can be modified as appropriate by those skilled in the art are included within the scope of the present invention.

10 Primary electron beams 11, 13 Edge 12 Graphic pattern 20 Multi-primary electron beam 22 Hole 29 Sub-irradiation area 30 Frame area 32 Stripe area 33 Rectangular area 34 Irradiation area 36 Pixel 37, 47 Grid 38, 48 Grid area 40, 42 Sub-regions 41, 43 Brightness contours 44 Difference regions 50, 52 Storage devices 60, 61 Pixel selection sections 62, 63 Grid region rotation sections 64, 65 Sub-region area calculation section 66 Comparison processing section 67 Area difference calculation section 68 Judgment section 69 Pair edge Search section 70 Difference calculation section 72 Judgment section 100 Inspection device 101 Board 102 Electron beam column 103 Inspection chamber 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 120 Bus 122 Laser length measurement system 123 Chip pattern memory 124 Lens control circuit 126 Blanking control circuit 128 Deflection control circuit 142 Drive mechanism 144, 146, 148 DAC amplifier 150 Image acquisition mechanism 160 Control system circuit 201 Electron gun 202 Electromagnetic lens 203 Shaped aperture array substrate 205, 206, 207, 224, 226 Electromagnetic lens 208 Main deflector 209 Sub-deflector 212 Collective blanking deflector 213 Limiting aperture substrate 214 Beam separator 216 Mirror 218 Deflector 222 Multi-detector 300 Multi-secondary electron Beam 330 Inspection area 332 Chip

Claims (4)

A secondary electron image of the substrate is obtained by irradiating a substrate on which a graphic pattern is formed with a primary electron beam and detecting secondary electrons emitted from the substrate due to the irradiation of the primary electron beam. a step of obtaining
The secondary electron image is divided into a lattice, and the brightness value of each pixel is defined , and adjacent first grids among the plurality of first grids serve as the intersection point of the division and the center of the target pixel. For each first rectangular area surrounded by a group, a first rectangular area in which a brightness value interpolated with the brightness value defined in the first grid group is larger than a preset reference brightness value within the first rectangular area. a step of calculating a first area of one region;
Using a reference image for comparison with the secondary electron image, the reference image is divided into a grid with the same size as the secondary electron image, and the brightness value of each pixel is defined at the intersection point of the division. The second grid group within a second rectangular area surrounded by the second grid group at a position corresponding to the first grid group among the plurality of second grids that are the center of the target pixel. calculating a second area of a second region where the brightness value interpolated with the brightness value defined by is larger than the reference brightness value;
Comparing the first area and the second area for each first rectangular area;
Equipped with
When inspecting the position of an edge of a graphic pattern arranged within the first rectangular area, if the difference between the first area and the second area is not within a predetermined range, the edge An electron beam inspection method characterized by determining that a defect exists at a position. When inspecting the line width of a figure pattern arranged in the first rectangular area, the difference between the first area and the second area at one edge, which is the basis of the line width, and the other Claim: 1. If the difference between the first area and the second area at the edge is not within a predetermined range, it is determined that the line width defect exists. 1. The electron beam inspection method according to 1. 3. The electron beam inspection method according to claim 1, wherein the first grid group is composed of 2×2 first grid groups in a coordinate system in two orthogonal directions. A secondary electron image of the substrate is obtained by irradiating a substrate on which a graphic pattern is formed with a primary electron beam and detecting secondary electrons emitted from the substrate due to the irradiation of the primary electron beam. a secondary electron image acquisition mechanism that acquires
The secondary electron image is divided into a lattice, and the brightness value of each pixel is defined , and adjacent first grids among the plurality of first grids serve as the intersection point of the division and the center of the target pixel. For each first rectangular area surrounded by a group, a first rectangular area in which a brightness value interpolated with the brightness value defined in the first grid group is larger than a preset reference brightness value within the first rectangular area. a first area calculation unit that calculates a first area of one area;
Using a reference image for comparison with the secondary electron image, the reference image is divided into a grid with the same size as the secondary electron image, and the brightness value of each pixel is defined at the intersection point of the division. The second grid group within a second rectangular area surrounded by the second grid group at a position corresponding to the first grid group among the plurality of second grids that are the center of the target pixel. a second area calculation unit that calculates a second area of a second region where the brightness value interpolated by the brightness value defined by is larger than the reference brightness value;
a comparison unit that compares the first area and the second area for each first rectangular area;
Equipped with
When inspecting the position of an edge of a graphic pattern arranged within the first rectangular area, if the difference between the first area and the second area is not within a predetermined range, the edge An electron beam inspection device characterized by determining that a defect exists at a position.

Images