Correction method and correction device

Abstract

Provided is a correction method capable of reducing defocus in an image caused by variations in height of a semiconductor pattern by image processing performed after imaging.　This correction method for correcting an image includes: acquiring a target image 801 in which a semiconductor pattern having a plurality of areas the height of which varies step-wisely is imaged; storing a plurality of correction coefficients C1 and the like for correcting the respective areas of the acquired target image 801; and correcting the respective areas of the target image 801 using the stored plurality of correction coefficients C1 and the like.

Description

[Technical field]

[0001] The present disclosure relates to a correction method and a correction apparatus for correcting a target image obtained by capturing an image of a semiconductor pattern. [Background technology]

[0002] Charged particle beam devices such as scanning electron microscopes (SEM) are suitable for measuring and observing semiconductor patterns formed on semiconductor wafers, which are becoming increasingly miniaturized. Electron beam observation devices such as scanning electron microscopes accelerate electrons emitted from an electron source, and then focus and irradiate the surface of a sample using electrostatic or electromagnetic lenses. These electrons are called primary electrons. When the primary electrons enter the sample, secondary electrons (low-energy electrons are sometimes called secondary electrons, and high-energy electrons are sometimes called reflected electrons) are emitted from the sample. By detecting these secondary electrons while deflecting and scanning the electron beam, a scanned image of the fine pattern or composition distribution on the sample can be obtained. To obtain a scanned image with good resolution, the electrostatic or electromagnetic lens is controlled to adjust the focus according to the height of the sample and the charged state of the sample surface so that the diameter of the electron beam irradiated on the pattern is minimized. A method is generally known in which multiple images are taken by varying the focal position, and the focal position at which the sharpness of the image is maximized is selected. However, when an electron beam is irradiated at the observation target position for focusing, the damage to the target area caused by the electron beam becomes a problem. Furthermore, if focusing is performed for each observation target, throughput decreases.

[0003] Patent Document 1 proposes a method of setting an adjustment region around a target region and determining the optical conditions of the target region based on the optical conditions of the optical system in the adjustment region. Patent Document 2 also proposes a method of creating a height map by measuring and storing the height of the sample in advance with a height sensor, and comparing the height map during imaging to shorten the focusing time. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] JP 2019-160464 A [Patent Document 2] JP 2009-259878 A Summary of the Invention [Problem to be solved by the invention]

[0005] The above-mentioned Patent Documents 1 and 2 do not disclose a focusing method for a semiconductor pattern whose height changes stepwise. When imaging a semiconductor pattern whose height changes stepwise, if the focus is set at a certain height, the pattern at other heights will not be in focus, resulting in out-of-focus of the captured image.

[0006] In order to eliminate the defocus, it is possible to take multiple images by focusing on each height of the semiconductor pattern and then synthesize the images in a later stage. However, since the irradiation area overlaps during the synthesis, there are concerns that the imaging target may be damaged or electrostatically charged. Furthermore, the throughput is reduced by taking and synthesizing multiple images.

[0007] The present disclosure provides a technique capable of reducing image defocus caused by differences in height of semiconductor patterns through image processing after capture. [Means for solving the problem]

[0008] In order to solve the above problem, the correction method disclosed herein includes acquiring a target image of a semiconductor pattern having a plurality of regions whose heights change stepwise, storing a plurality of image correction values ​​for correcting each region of the target image, and correcting each region of the target image using the stored image correction values. Effect of the Invention

[0009] According to the present disclosure, it is possible to reduce image out-of-focus blur caused by differences in height of semiconductor patterns by image processing after capture.

[0010] Problems, configurations and effects other than those described above will become apparent from the following description of the embodiments. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram showing a schematic configuration of a scanning electron microscope according to a first embodiment. [Diagram 2] 1A and 1B are diagrams showing cross-sectional views of a semiconductor pattern and images of the semiconductor pattern. [Diagram 3] 10 is a flowchart showing a procedure for calculating a correction coefficient. [Figure 4] FIG. 13 is a diagram for explaining a window function. [Diagram 5] FIG. 11 is a diagram for explaining a procedure for calculating a correction coefficient. [Figure 6] FIG. 11 is a diagram for explaining a procedure for calculating a correction coefficient. [Figure 7] 10 is a flowchart showing a procedure for correcting an image by applying a calculated correction coefficient. [Figure 8] 11A to 11C are diagrams for explaining a procedure for correcting an image by applying a calculated correction coefficient. [Figure 9] FIG. 13 is a diagram showing an example of an environment setting screen displayed on the display device in a procedure for calculating a correction coefficient. [Figure 10] FIG. 13 is a diagram showing an example of an environment setting screen displayed on the display device in a procedure for correcting an image. [Figure 11] 10 is a flowchart showing a procedure for calculating a correction coefficient according to a second embodiment. [Figure 12] 13 is a flowchart showing a procedure for correcting an image by applying a correction coefficient calculated by another device according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] The embodiments of the present disclosure will be described in detail with reference to the drawings. In the following embodiments, the components (including element steps, etc.) are not necessarily essential unless otherwise specified or considered to be obviously essential in principle.

[0013] Preferred embodiments of the present disclosure will be described below with reference to the drawings. In the embodiments, a scanning electron microscope will be described as an example, but the present disclosure can also be applied to electron beam observation devices other than a scanning electron microscope. Example 1 1 is a diagram showing a schematic configuration of a scanning electron microscope according to Example 1. The configuration of the scanning electron microscope will be described with reference to FIG.

[0014] <Scanning Electron Microscope 1> The scanning electron microscope 1 includes an electron source 101 , a modified illumination aperture 103 , a detector 104 , a scanning deflection deflector 105 , an objective lens 106 , a stage 107 , a control device 109 , a system control unit 110 , and an input / output unit 115 .

[0015] In the downstream direction of the electron beam 102 output from the electron source 101, a modified illumination aperture 103, a detector 104, a scanning deflection deflector 105, and an objective lens 106 are arranged. Furthermore, the electron optical system has an aligner (not shown) and an aberration corrector (not shown) for adjusting a central axis (optical axis) 117 of the primary beam. The objective lens 106 in the first embodiment is an electromagnetic lens that controls the focus by an excitation current, but may be an electrostatic lens or a combination of an electromagnetic lens and an electrostatic lens. The stage 107 is configured to move with a sample 108 (e.g., a semiconductor wafer) placed thereon. A control device 109 is communicably connected to each of the electron source 101, the detector 104, the scanning deflection deflector 105, the objective lens 106, and the stage 107. A system control unit 110 is communicably connected to the control device 109.

[0016] In this embodiment, the detector 104 is disposed upstream of the objective lens 106 and the scanning deflector 105, but the order of arrangement is not limited to that shown in Fig. 1. An aligner (not shown) for correcting the optical axis 117 of the electron beam 102 is disposed between the electron source 101 and the objective lens 106. The aligner corrects the central axis of the electron beam 102 when the central axis is misaligned with respect to the aperture or the electron optical system.

[0017] The electron beam 102 output from the electron source 101 is focused by the objective lens 106 and converged on the sample 108 so that the beam diameter is extremely small. The scanning deflector 105 is controlled by the control device 109 so that the electron beam 102 scans a predetermined area of ​​the sample 108. The electron beam 102 that reaches the surface of the sample 108 interacts with the material near the surface. As a result, secondary electrons such as reflected electrons, secondary electrons, and Auger electrons are generated from the sample 108. In this embodiment, an electron microscope image is displayed using a signal of the secondary electrons 116. The secondary electrons 116 generated from the position where the electron beam 102 reaches the sample 108 are detected by the detector 104. The signal processing of the secondary electrons 116 detected by the detector 104 is performed in synchronization with a scanning signal sent from the control device 109 to the scanning deflector 105, thereby forming an SEM image. This makes it possible to observe the sample 108.

[0018] Needless to say, components other than the control system and the circuit system are arranged in a vacuum chamber and operate in a vacuum-evacuated chamber. In addition, the scanning electron microscope 1 includes a wafer transfer system that places a sample 108 such as a semiconductor wafer on a stage 107 from outside the vacuum.

[0019] <System Control Unit 110> The system control unit 110 is a correction device that corrects a target image obtained by capturing an image of a semiconductor pattern having a plurality of regions whose heights change stepwise. This correction device may be on-premise or cloud-based. The system control unit 110 includes a storage device 111, a processor 112, an input / output interface unit (hereinafter abbreviated as I / F unit) 113, and a memory 114. An input / output unit 115 including an output device such as a display device and an input device such as a keyboard and a mouse is communicatively connected to the I / F unit 113. The input / output unit 115 may be a touch panel in which the input device and the output device are integrated.

[0020] The processor 112 is, for example, a central processing unit (CPU), a digital signal processor (DSP), or an application specific integrated circuit (ASIC). The processor 112 deploys a program stored in the storage device 111 in an executable manner in a working area of ​​the memory 114. The memory 114 stores programs executed by the processor 112, data processed by the processor, and the like. The memory 114 is, for example, a flash memory, a random access memory (RAM), or a read only memory (ROM). The storage device 111 stores various programs and various data. The storage device 111 stores, for example, an operating system (OS), various programs, various tables, and the like. The storage device 111 is, for example, a silicon disk including a non-volatile semiconductor memory (flash memory, erasable programmable ROM (EPROM)), a solid state drive device, a hard disk drive (HDD, Hard Disk Drive) device, and the like.

[0021] The processor 112 loads the control program 120, the image processing program 121, etc. stored in the storage device 111 in an executable manner in the memory 114. The processor 112 then executes the control program 120 and the image processing program 121, and WaferThe image processing program 121 controls the control device 109 and the like and processes images related to defect inspection and dimensional measurement. The storage device 111 also stores a plurality of image correction values ​​for correcting areas of the target image having different heights. The image correction values ​​are, for example, correction coefficients described below. The image correction values ​​may be a table, a function, a mathematical formula, a mathematical model, a trained model, or a DB. The image processing program 121 is a program for processing SEM images.

[0022] <Control device 109> The control device 109 includes a storage device, a processor, an I / F unit, and a memory, similar to the above-described system control unit 110. The storage device (not shown) of the control device 109 stores a program for moving the stage 107, a program for controlling the focus of the objective lens 106, and the like. The processor (not shown) of the control device 109 loads the program stored in the storage device into a memory (not shown) and executes it. The I / F unit (not shown) of the control device 109 is connected to the system control unit 110, the electron source 101, the modified illumination aperture 103, the detector 104, the scanning deflection deflector 105, the objective lens 106, and the stage 107 so as to be able to communicate with them.

[0023] <Method of correcting microscope images> Hereinafter, a method for correcting a microscope image (image) of a semiconductor pattern having a plurality of regions whose heights change stepwise will be described. Since the height of a semiconductor pattern varies depending on the position, the image is not in focus at all positions. Therefore, a correction method and device for correcting an image using an image correction value determined in advance for each region with a different height will be described.

[0024] FIG. 2 is a diagram showing a cross-sectional view of a semiconductor pattern and an image of the semiconductor pattern. The semiconductor pattern 201 shown in FIG. 2 has a plurality of regions whose height changes stepwise. The image 202 shown in FIG. 2 is an image captured by scanning the semiconductor pattern 201 of FIG. 2 from above the figure with an electron beam. When the electron beam is irradiated on the portion of the semiconductor pattern 201 whose height changes stepwise, the corners of the semiconductor pattern 201 generate many secondary electrons. For this reason, the image 202 appears as a white band 203 that is brighter than other regions. When the focus is on a region of any height of the semiconductor pattern 201, the region of a different height is not in focus, and the image 202 becomes out of focus. That is, when the image 202 is captured by focusing on one white band, the other white bands of different heights become out of focus.

[0025] Therefore, in the first embodiment, in the image 202, each region having a different height is corrected by image processing so that each region has the same frequency characteristic as that in the case of the in-focus point. The correction method in the first embodiment is roughly divided into a procedure of calculating a correction coefficient and a procedure of correcting an image by applying the calculated correction coefficient.

[0026] <Procedure for calculating correction coefficient> First, the procedure for calculating the correction coefficient will be described with reference to the flowchart in Fig. 3. When correcting an image (target image) of a semiconductor pattern having a plurality of regions whose heights change stepwise, a correction coefficient is calculated for each region whose height differs. Each step in Fig. 3 is executed by a system control unit 110, which is a computer system.

[0027] 3, a procedure for calculating a correction coefficient for correcting an image of an Nth stage (any integer) of a semiconductor pattern having regions of different heights will be described. First, a reference semiconductor pattern is imaged at an arbitrary focal position, and the system control unit 110 acquires one or more images (reference images) (S301). In addition, in a procedure for correcting an image by applying a calculated correction coefficient, which will be described later, the semiconductor pattern is imaged at the same position as this arbitrary focal position.

[0028] Next, the system control unit 110 detects the position of the white band in the image acquired in S301 (S302). The position of the white band can be detected by acquiring a luminance profile of the image, detecting the peak position of the profile, and taking the Nth peak position as the Nth stage white band position. The method of detecting the position of the white band is not limited to this. Note that in this embodiment, an example of detecting the position of the white band as the position of the semiconductor pattern will be described, but the position of the semiconductor pattern is not limited to the position of the white band as long as the position of the semiconductor pattern, such as the position of the edge or contour of the semiconductor pattern, can be detected.

[0029] Next, the system control unit 110 applies a window function Wn centered on the position of the Nth white band (S303). Here, the window function Wn will be described with reference to FIG. 4. In the first embodiment, a Tukey window is used as an example of the window function, but the window function may be another window function such as a rectangular window or a Gaussian window. The window function Wn in FIG. 4 is a function in which the area other than the area centered on the position of the Nth white band is 0. The amplitude of this function is normalized in the range from 0 to 1. By applying the window function Wn to an image, it is possible to create an image in which the area centered on the position of the Nth white band is extracted.

[0030] Next, the system control unit 110 converts the image extracted by the window function Wn into an image in frequency space by, for example, Fourier transforming it, and obtains the frequency characteristic (reference frequency characteristic) An from this image (S304).

[0031] Furthermore, the system control unit 110 changes the focal position and executes the processes of S305 to S308 in the same manner as S301 to S304. Specifically, the system control unit 110 focuses on the Nth stage, captures the reference semiconductor pattern, and acquires one or more images (focused images) (S305). Next, the system control unit 110 detects the position of the white band in the image acquired in S305 (S306). Next, the system control unit 110 applies a window function Wn to the image captured by focusing on the Nth stage, centered on the position of the white band in the Nth stage (S307). Next, the system control unit 110 converts the image extracted by the window function Wn into an image in frequency space by, for example, Fourier transforming it, and acquires the frequency characteristic Bn from this image (S308).

[0032] A correction coefficient Cn for correcting an image centered on the position of the Nth white band is calculated by the following formula (S309). Correction coefficient Cn = Frequency characteristic Bn / Frequency characteristic An (Formula 1) The correction coefficient Cn is calculated for each pixel of an image obtained by converting an image into a frequency space, and the correction coefficient Cn is calculated for each of a plurality of regions having different heights.

[0033] Next, a method of calculating a plurality of correction coefficients for each of a plurality of regions having different heights will be described with reference to Figs. 5 and 6. Here, a method of calculating four correction coefficients C1 to C4 for each of four regions will be described. Needless to say, the number of regions is not limited to four. First, the scanning electron microscope 1 captures an image of a reference semiconductor pattern at an arbitrary focal position, and acquires one or more images (reference images) 501. The system control unit 110 detects the positions of white bands 502a to 502e in the acquired image 501. Then, the system control unit 110 applies each of Tukey windows W1 to W4 to the image 501, centered on the positions of the white bands 502a to 502d, to acquire images 503a to 503d.

[0034] Then, system control unit 110 converts images 503a to 503d into images in frequency space by performing a Fourier transform or the like, and acquires frequency characteristics (reference frequency characteristics) A1 to A4 from these images.

[0035] 6, the scanning electron microscope 1 focuses on the positions of the first to fourth stages and captures the reference semiconductor pattern to obtain images (focused images) 601a to 601d. Next, the system control unit 110 detects the positions of the white bands in each of the images 601a to 601d. Then, the system control unit 110 applies window functions (Tukey window) W1 to W4 to each of the images 601a to 601d, centered on the positions of the white bands in the first to fourth stages.

[0036] Next, the system control unit 110 converts each of the images 602a to 602d extracted by the window functions (Tukey window) W1 to W4 into an image in frequency space by, for example, Fourier transforming, and acquires frequency characteristics B1 to B4 from these images.

[0037] Then, the system control unit 110 calculates the correction coefficients C1=B1 / A1, C2=B2 / A2, C3=B3 / A3, and C4=B4 / A4 based on the above-mentioned (Equation 1).

[0038] <Procedure for applying the calculated correction coefficient to correct the image> Next, a procedure for correcting an image by applying the calculated correction coefficient will be described with reference to the flowchart of Fig. 7. Each step in Fig. 7 is executed by a system control unit 110, which is a computer system. Fig. 7 describes a procedure for correcting an image of the Nth stage (any integer) of a semiconductor pattern having regions of different heights. The correction executed in this procedure is a correction related to the focus adjustment of a microscope that captures the target image.

[0039] An image of an object (semiconductor pattern) is captured at a predetermined focal position, and the system control unit 110 acquires one or more images (object images) (S701). This predetermined focal position is the same focal position as when the image was acquired in S301 of FIG. 3. Next, the system control unit 110 detects the position of the white band in the object image acquired in S701 (S702). Next, the system control unit 110 applies a window function Wn centered on the position of the Nth white band (S703). By applying the window function Wn to the image, it is possible to create an image in which an area centered on the position of the Nth white band is extracted.

[0040] Next, the system control unit 110 converts the image extracted by the window function Wn into an image in frequency space by, for example, Fourier transform (S704). Then, the system control unit 110 multiplies each pixel of the image in frequency space by a correction coefficient Cn (=frequency characteristic Bn / frequency characteristic An) calculated in the procedure for calculating the correction coefficient (S705). Next, the system control unit 110 converts the image in frequency space multiplied by the correction coefficient Cn back into an image in real space by a method such as two-dimensional inverse Fourier transform (S706).

[0041] Furthermore, the system control unit 110 applies a window function Xn to the image acquired in S701 (S707). The window function Xn is calculated by the following formula. Window function Xn=1.0-window function Wn (Equation 2)

[0042] Here, the window function Xn will be described with reference to Fig. 4. The window function Xn in Fig. 4 is a function in which the area centered on the position of the Nth white band is 0. The amplitude of this function is normalized in the range from 0 to 1. By applying the window function Xn to an image, it is possible to create an image in which the area other than the area centered on the position of the Nth white band is extracted.

[0043] The system control unit 110 synthesizes the image acquired in S706 and the image acquired in S707 (S708). Synthesizing means adding each pixel of the two images. By synthesizing the two images, an image after the Nth stage of correction is output (S709). Since this corrected image is an image in which correction has been applied only to an area centered on the position of the Nth stage white band, when performing multiple stages of correction, each process in the flowchart of FIG. 7 must be repeated multiple times.

[0044] Next, a method for outputting a composite image will be described with reference to Fig. 8. Here, a method for correcting the first-stage image will be described. First, the scanning electron microscope 1 captures an image of an object (semiconductor pattern) at a predetermined focal position, and acquires one or more images (object images) 801. The system control unit 110 detects the positions of white bands 802a to 802e in the acquired image 801. Then, the system control unit 110 applies a window function (Tukey window) W1 to the image 801, centered on the position of the white band 802a, to acquire an image 803a.

[0045] Then, the system control unit 110 converts the image 803a into an image 804a in frequency space by performing a Fourier transform or the like. The system control unit 110 then multiplies each pixel of the image 804a in frequency space by a correction coefficient C1 (=frequency characteristic B1 / frequency characteristic A1). Next, the system control unit 110 converts the image 804a in frequency space multiplied by the correction coefficient C1 back into an image 805a in real space by a method such as a two-dimensional inverse Fourier transform.

[0046] Furthermore, the system control unit 110 acquires an image 806a by applying a window function (Tukey window) X1 to the image 801. Then, the system control unit 110 synthesizes the image 805a in the real space with the image 806a to acquire a corrected image 807a.

[0047] <GUI(Graphical User Interface)> 9 and 10 show an example of a GUI (Graphical User Interface) for performing environment setting in the embodiment 1. Fig. 9 is a diagram showing an example of an environment setting screen 900 displayed on the display device of the input / output unit 115 in the procedure for calculating the correction coefficient described above.

[0048] The environment setting screen 900 includes a text box 901 for inputting the number of regions with different heights, a button 902 for capturing an image at an arbitrary focal position, and a button 903 for capturing an image of a reference semiconductor pattern by changing the focal position by the number inputted in the text box 901. The environment setting screen 900 also includes a file storage unit 904 for storing the calculated correction coefficients in a file with an arbitrary name.

[0049] 10 is a diagram showing an example of an environment setting screen 1000 output to the display device of the input / output unit 115 in the procedure for correcting an image by applying the above-mentioned calculated correction coefficients. The environment setting screen 1000 includes a switch 1001 for setting whether or not to correct a captured image by turning it ON or OFF in the figure, and a file selection section 1002 for selecting a file in which the correction coefficients are recorded. In the file selection section 1002, it is possible to select a file saved by the file saving section 904.

[0050] <Effects of Example 1> In the first embodiment, a plurality of correction coefficients C1 to Cn are stored for correcting each of a plurality of regions of an image (target image) 801. This makes it possible to reduce the out-of-focus blur of the (target image) 801 caused by differences in height of the semiconductor patterns by image processing after capturing the image.

[0051] In addition, in the first embodiment, each region of the image (target image) 801 can be corrected with each of a plurality of correction coefficients. Therefore, the image (target image) 801 needs to be captured only once. Therefore, it is not necessary to irradiate the semiconductor pattern with the electron beam many times, and therefore damage to the semiconductor pattern and the influence of charging can be reduced.

[0052] Furthermore, as described above, imaging of the semiconductor pattern only needs to be done once, and therefore throughput is improved compared to the case where imaging is done multiple times in accordance with the height of the semiconductor pattern.

[0053] Furthermore, in the first embodiment, the correction of each area of ​​the image (target image) 801 is a correction related to the focus adjustment of the scanning electron microscope 1, so that the out-of-focus blur can be reduced by image processing after capturing.

[0054] In the first embodiment, a plurality of correction coefficients C1 to Cn can be calculated for each focal position based on the image (reference image) 501 and a plurality of images (focused images) 601a to 601n captured with different focal positions. This allows each region of the image (target image) 801 to be corrected with the correction coefficients C1 to Cn appropriate for each region, thereby making it possible to obtain an image with reduced focus blur.

[0055] In addition, in the first embodiment, by calculating the frequency characteristics of the image (reference image) 501 and the images (focused images) 601a-n by Fourier transform, it is possible to easily obtain a plurality of correction coefficients for correcting each area of ​​the image (target image) 801.

[0056] Furthermore, in the first embodiment, since the image 805a in real space can be acquired by the inverse Fourier transform, the observer can observe the image 805a in real space of the semiconductor pattern.

[0057] Furthermore, in the first embodiment, by using the white bands 502a to 502e of the image (reference image) 501, the white bands of the images (focused images) 601a to 601n, and window functions W1 to Wn that extract areas centered on these white bands, it is possible to calculate correction coefficients C1 to Cn that reduce the focus blur in each of the areas centered on these white bands.

[0058] Furthermore, in the first embodiment, by using the correction coefficients C1 to Cn, each of the multiple regions of the image (target image) 801 can be corrected individually.

[0059] Furthermore, in the first embodiment, the number of areas with different heights can be input on the environment setting screen 900. This allows each area of ​​the image (target image) 801 to be corrected by the number designated by the user.

[0060] Example 2 The frequency characteristics for calculating the correction coefficient can be obtained from a single image, but in order to reduce the influence of value variations due to noise, etc., the frequency characteristics may be calculated from multiple images captured under the same conditions. For example, the frequency characteristics of multiple images captured under the same conditions may be averaged, and the correction coefficient may be calculated using the average value. In the second embodiment, with reference to FIG. 11, an example of calculating the correction coefficient from the average of the frequencies of multiple images captured under the same conditions will be described. Each step in FIG. 11 is executed by a system control unit 110, which is a computer system.

[0061] As shown in Fig. 11, system control unit 110 repeats the processes of S1101 to S1104 M times. Since the processes of S1101 to S1104 are the same as the processes of S301 to S304 in Fig. 3, the description thereof will be omitted. Then, system control unit 110 averages the M frequency characteristics An to obtain average frequency characteristic AAn (S1109).

[0062] Furthermore, system control unit 110 repeats the processes of S1105 to S1108 L times. Since the processes of S1105 to S1108 are the same as the processes of S305 to S308 in Fig. 3, the description thereof will be omitted. System control unit 110 then averages the L frequency characteristics Bn to obtain an average frequency characteristic ABn (S1110).

[0063] A correction coefficient ACn for correcting an image centered on the position of the Nth white band is calculated by the following formula (S1111). Correction coefficient ACn = Frequency characteristic ABn / Frequency characteristic AAn (Equation 3) The correction coefficient is calculated for each pixel of an image converted into a frequency space.

[0064] The above M and L are each an integer equal to or greater than 1, and M and L may be different values ​​or may be the same value. The average of the frequency characteristics means the average of the amplitude characteristics at each frequency.

[0065] <Effects of Example 2> In the second embodiment, even if noise or variation occurs when capturing the image (reference image) 501 or the images (focused images) 601a to 601d, the influence of the noise or variation can be reduced by using the average of the frequency characteristics. Other effects are the same as those in the first embodiment, and therefore the description thereof will be omitted.

[0066] Example 3 In the first embodiment, an example is described in which a procedure for calculating a correction coefficient and a procedure for correcting an image by applying the calculated correction coefficient are executed by one device. In the third embodiment, an example is described in which a plurality of devices are operated and a correction coefficient acquired by one device is applied to an image captured by another device.

[0067] The procedure for calculating the correction coefficients is the same as that in Fig. 3 and Fig. 11, and therefore will be omitted. The procedure for applying the correction coefficients to correct the image in each device is the same as that in Fig. 7, and therefore will be omitted. When there are N regions with different heights, N correction coefficients are obtained and image correction is applied N times. 12 The explanation will be omitted here. An electron beam observation apparatus (hereinafter, "electron beam observation apparatus" will be referred to as "apparatus") A transforms an image IA captured by the apparatus A into frequency space (S1201), multiplies the image in frequency space by a correction coefficient CA calculated by the apparatus A (S1202), and converts it into an image in real space (S1203). This obtains a correction result image CIA. On the other hand, an apparatus B transforms an image IB captured by the apparatus B into frequency space (S1204), multiplies the image in frequency space by a correction coefficient CA calculated by the apparatus A (S1205), and converts it into an image in real space (S1206). This obtains a correction result image CIB.

[0068] <Effects of Example 3> By using the correction coefficient CA calculated by device A for the image captured by device B, the corrected image CIB becomes closer to the frequency characteristics of the image captured by device A. In other words, the image becomes closer to the image captured by device A, and it becomes possible to reduce the machine difference between device A and device B. Other effects are similar to those of the first and second embodiments, and therefore the description thereof will be omitted.

[0069] The present disclosure is not limited to the above-mentioned embodiments, and includes various modified examples. The above-mentioned embodiments have been described in detail to clearly explain the present disclosure, and are not necessarily limited to those having all of the configurations described. In addition, it is also possible to replace a part of the configuration of one embodiment with the configuration of another embodiment, and it is also possible to add the configuration of another embodiment to the configuration of one embodiment. In addition, it is also possible to add, delete, or replace a part of the configuration of each embodiment with another configuration.

[0070] In the first to third embodiments, examples have been described in which the system control unit 110 executes each of the steps in Figures 3, 7, 11, and 12. However, the control device 109 may execute each of the above steps, or the system control unit 110 and the control device 109 may share the role of executing each of the above steps. [Explanation of symbols]

[0071] 1...scanning electron microscope, 101...electron source, 102...electron beam, 103...modified illumination aperture, 104...detector, 105...scanning deflection deflector, 106...objective lens, 107...stage, 108...sample, 109...control device, 110...system control unit, 111...storage device, 112...processor, 113...input / output interface unit, 114...memory, 115...input / output unit, 116...secondary electrons, 117...optical axis, 120...control program, 121...image processing program, 201...semiconductor pattern, 202...image, 501...reference image, 502a to 502e...white band, 503 a to 503d... images with window function applied, 601a to 601d... in-focus images, 602a to 602d... images with window function applied, 801... image of an object captured at a specified focal position, 802a to 802e... white band, 803a... image with window function applied, 804a... image in frequency space, 805a... image in real space, 806a... image with window function applied, 807a... image after correction, 900... environment setting screen, 901... text box, 902... button, 903... button, 904... file saving section, 1000... environment setting screen, 1001... switch, 1002... file selection section

Claims

1. Acquiring a reference image by imaging a reference semiconductor pattern at an arbitrary focal position; acquiring a first in-focus image by imaging the reference semiconductor pattern with a focus set at a first position, and acquiring a second in-focus image by imaging the reference semiconductor pattern with a focus set at a second position different from the first position; Acquiring a target image by imaging a semiconductor pattern having a plurality of regions whose heights change stepwise; storing a plurality of image correction values ​​for correcting each region of the target image; and correcting each region of the target image using the stored plurality of image correction values; a correction method characterized in that the plurality of image correction values ​​include a first correction coefficient calculated based on the reference image and the first focused image, and a second correction coefficient calculated based on the reference image and the second focused image.

2. 2. The correction method according to claim 1, wherein the correction of each region of the target image is a correction related to focus adjustment of a microscope that captures the target image.

3. performing a Fourier transform on the reference image to obtain a reference frequency characteristic; and and performing a Fourier transform on each of the first focused image and the second focused image to obtain a first frequency characteristic and a second frequency characteristic, 2. The correction method according to claim 1, wherein the first correction coefficient is a correction coefficient calculated based on the reference frequency characteristic and the first frequency characteristic, and the second correction coefficient is a correction coefficient calculated based on the reference frequency characteristic and the second frequency characteristic.

4. performing a Fourier transform on the target image to obtain an image in frequency space; applying the first correction factor or the second correction factor to each region of the image in frequency space; and 4. The method of claim 3, further comprising: performing an inverse Fourier transform on each of the first image in the frequency space to which the first correction coefficient has been applied and the second image in the frequency space to which the second correction coefficient has been applied to obtain an image in real space.

5. Detecting positions of a first pattern and a second pattern in the reference image; applying a first window function to an area of ​​the reference image that includes the location of the first pattern, and applying a second window function to an area of ​​the reference image that includes the location of the second pattern; acquiring a first in-focus image by imaging the reference semiconductor pattern while focusing on an area corresponding to the position of the first pattern, and acquiring a second in-focus image by imaging the reference semiconductor pattern while focusing on an area corresponding to the position of the second pattern; Detecting a position of a pattern in the first focused image and detecting a position of a pattern in the second focused image; and applying the first window function to an area including a position of a pattern corresponding to the first pattern in the first focused image, and applying the second window function to an area including a position of a pattern corresponding to the second pattern in the second focused image; 2. The correction method according to claim 1, wherein the image correction value includes a first correction coefficient calculated based on the reference image to which the first window function has been applied and the first focused image to which the first window function has been applied, and a second correction coefficient calculated based on the reference image to which the second window function has been applied and the second focused image to which the second window function has been applied.

6. locating a third pattern corresponding to the first pattern in the target image, and detecting a fourth pattern corresponding to the second pattern in the target image; and applying the first window function to an area of ​​the target image that includes the position of the third pattern, and applying the second window function to an area of ​​the target image that includes the position of the fourth pattern; 6. The correction method according to claim 5, wherein the correcting step includes correcting the target image to which the first window function has been applied using the first correction coefficient, and correcting the target image to which the second window function has been applied using the second correction coefficient.

7. 2. The method of claim 1, further comprising displaying an environment setting screen for specifying a number of the plurality of image correction values.

8. Obtaining a plurality of reference images by imaging a reference semiconductor pattern a plurality of times at an arbitrary focal position; acquiring a plurality of first in-focus images by imaging the reference semiconductor pattern a plurality of times while focusing on a first position, and acquiring a plurality of second in-focus images by imaging the reference semiconductor pattern a plurality of times while focusing on a second position different from the first position; Acquiring a target image by imaging a semiconductor pattern having a plurality of regions whose heights change stepwise; storing a plurality of image correction values ​​for correcting each region of the target image; and correcting each region of the target image using the stored plurality of image correction values; a correction method characterized in that the plurality of image correction values ​​include a first correction coefficient calculated based on the plurality of reference images and the plurality of first focused images, and a second correction coefficient calculated based on the plurality of reference images and the plurality of second focused images.

9. 2. The correction method according to claim 1, wherein the plurality of image correction values ​​are image correction values ​​calculated based on an image of the reference semiconductor pattern captured by an apparatus different from an apparatus that captured the target image.

10. A computer system including a processor and a memory, The computer system includes: A reference image is obtained by capturing an image of a reference semiconductor pattern at an arbitrary focal position; acquiring a first in-focus image by imaging the reference semiconductor pattern with a focus set at a first position, and acquiring a second in-focus image by imaging the reference semiconductor pattern with a focus set at a second position different from the first position; Acquire a target image of a semiconductor pattern having a plurality of regions whose heights change stepwise; storing a plurality of image correction values ​​for correcting each region of the target image; correcting each region of the target image using the stored plurality of image correction values; a correction device characterized in that the plurality of image correction values ​​include a first correction coefficient calculated based on the reference image and the first focused image, and a second correction coefficient calculated based on the reference image and the second focused image.

11. 11. The correction device according to claim 10, wherein the correction of each area of ​​the target image is a correction related to focus adjustment of a microscope that captures the target image.

12. The computer system includes: Fourier transform the reference image to obtain a reference frequency characteristic; performing a Fourier transform on each of the first focused image and the second focused image to obtain a first frequency characteristic and a second frequency characteristic; 11. The correction device according to claim 10, wherein the first correction coefficient is a correction coefficient calculated based on the reference frequency characteristic and the first frequency characteristic, and the second correction coefficient is a correction coefficient calculated based on the reference frequency characteristic and the second frequency characteristic.

13. The computer system includes: Fourier transform the target image to obtain an image in frequency space; applying the first correction coefficient or the second correction coefficient to each region of the image in the frequency space; The correction device according to claim 12, further comprising an inverse Fourier transform of each of the first image in the frequency space to which the first correction coefficient has been applied and the second image in the frequency space to which the second correction coefficient has been applied to obtain an image in real space.

14. The computer system includes: Detecting the positions of a first pattern and a second pattern in the reference image; applying a first window function to an area of ​​the reference image that includes the position of the first pattern, and applying a second window function to an area of ​​the reference image that includes the position of the second pattern; acquiring a first focused image by imaging the reference semiconductor pattern while focusing on an area corresponding to the position of the first pattern, and acquiring a second focused image by imaging the reference semiconductor pattern while focusing on an area corresponding to the position of the second pattern; Detecting a position of a pattern in the first focused image, and detecting a position of a pattern in the second focused image; applying the first window function to an area including a position of a pattern corresponding to the first pattern in the first focused image, and applying the second window function to an area including a position of a pattern corresponding to the second pattern in the second focused image; 11. The correction device according to claim 10, wherein the image correction value includes a first correction coefficient calculated based on the reference image to which the first window function has been applied and the first focused image to which the first window function has been applied, and a second correction coefficient calculated based on the reference image to which the second window function has been applied and the second focused image to which the second window function has been applied.

15. The computer system includes: Detecting a position of a third pattern corresponding to the first pattern in the target image, and detecting a fourth pattern corresponding to the second pattern in the target image; applying the first window function to an area of ​​the target image including the position of the third pattern, and applying the second window function to an area of ​​the target image including the position of the fourth pattern; 15. The correction device according to claim 14, wherein the target image to which the first window function has been applied is corrected using the first correction coefficient, and the target image to which the second window function has been applied is corrected using the second correction coefficient.

16. The computer system includes:

11. The correction device according to claim 10, further comprising: a configuration screen for specifying the number of the plurality of image correction values.

17. A computer system including a processor and a memory, The computer system includes: A plurality of reference images are obtained by capturing an image of a reference semiconductor pattern a plurality of times at an arbitrary focal position; Obtaining a plurality of first in-focus images by imaging the reference semiconductor pattern a plurality of times while focusing on a first position, and obtaining a plurality of second in-focus images by imaging the reference semiconductor pattern a plurality of times while focusing on a second position different from the first position; Acquire a target image of a semiconductor pattern having a plurality of regions whose heights change stepwise; storing a plurality of image correction values ​​for correcting each region of the target image; correcting each region of the target image using the stored plurality of image correction values; a correction device characterized in that the plurality of image correction values ​​include a first correction coefficient calculated based on the plurality of reference images and the plurality of first focused images, and a second correction coefficient calculated based on the plurality of reference images and the plurality of second focused images.

18. The correction device according to claim 10, wherein the plurality of image correction values ​​are image correction values ​​calculated based on an image of the reference semiconductor pattern captured by an apparatus different from an apparatus that captured the target image.

19. The position of the first pattern is any one of an edge, a contour line, and a white band of the first pattern, 6. The method according to claim 5, wherein the position of the second pattern is any one of an edge, a contour line, and a white band of the second pattern.

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