SEM image oxygen

Abstract

Disclosed herein is a method of reducing sample charging effects in a scanning electron microscope (SEM) image, the method including obtaining a first SEM image from a first electron beam scan, where a parameter is a first quantity, obtaining a second SEM image from a second electron beam scan, where the parameter is a second quantity different from the first quantity, and generating a sample charging effect reduced image based on a convolution equation including a representation of the first SEM image, a representation of the second SEM image, a first point spread function corresponding to the first SEM image, and a second point spread function corresponding to the second SEM image.

Description

[Technical Field]

[0001] Cross-reference of related applications

[0001] This application claims priority to European Patent Application No. 21163831.7, filed on 19 March 2021, which is incorporated herein by reference in its entirety.

[0002]

[0002] The description herein relates to the field of image enhancement, and more particularly to scanning electron microscope (SEM) image enhancement. [Background technology]

[0003]

[0003] In the manufacturing process of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured according to the design and free from defects. Inspection systems using charged particle (e.g., electron) beam microscopes or optical microscopes, such as scanning electron microscopes (SEMs), may be used. As the physical size of IC components continues to shrink and their structures continue to become more complex, the accuracy and throughput of defect detection and inspection are becoming increasingly important.

[0004]

[0004] However, when inspecting electrically insulating materials, the quality of SEM images is usually degraded by SEM-induced charging artifacts. A known technique used in SEM imaging to reduce SEM-induced charging artifacts is to average multiple SEM images obtained using different scanning directions. However, further improvements in the art are desired. [Overview of the project]

[0005]

[0005] According to a first aspect of the present invention, a method is provided for reducing the sample charging effect in a scanning electron microscope (SEM) image, the method comprising: acquiring a first SEM image from a first electron beam scan in which a parameter is a first amount; acquiring a second SEM image from a second electron beam scan in which a parameter is a second amount different from the first amount; and generating a sample charging effect-reduced image based on a convolution equation including a representation of the first SEM image, a representation of the second SEM image, a first point image distribution function corresponding to the first SEM image, and a second point image distribution function corresponding to the second SEM image.

[0006]

[0006] A second aspect of the present invention provides a method for reducing the sample charging effect in a scanning electron microscope (SEM) image, the method comprising: acquiring a first SEM image from an electron beam scan where a parameter is a first quantity; acquiring a second SEM image from another electron beam scan where the parameter is a second quantity different from the first quantity; and generating a sample charging effect-reduced image based on first and second convolution equations, wherein the first convolution equation includes a representation of the first scanning electron microscope image and a first charged point image distribution function corresponding to the first scanning electron microscope image; and the second convolution equation includes a representation of the second scanning electron microscope image and a second charged point image distribution function corresponding to the second scanning electron microscope image.

[0007]

[0007] A third aspect of the present invention provides a method for reducing the sample charging effect in a scanning electron microscope (SEM) image, the method comprising: acquiring a first SEM image from a first electron beam scan in which a parameter is a first quantity; acquiring a second SEM image from a second electron beam scan in which a parameter is a second quantity different from the first quantity; acquiring a point image distribution function from the first and second SEM images using a convolution equation; and generating a sample charging effect reduction image based on a convolution equation that includes a representation of the first SEM image, a representation of the second SEM image, and the acquired point image distribution function.

[0008]

[0008] According to a fourth aspect of the present invention, there is provided a method including obtaining a first SEM image from a first electron beam scan in which a certain parameter is a first amount, obtaining a second SEM image from a second electron beam scan in which the parameter is a second amount different from the first amount, and generating an image based on a convolution equation including a representation of the first SEM image, a representation of the second SEM image, a first point spread function corresponding to the first SEM image, and a second point spread function associated with the first point spread function according to a difference in sample charging effects between the first electron beam scan and the second electron beam scan.

[0009]

[0009] Other advantages of embodiments of the present disclosure will become apparent from reading the following description in conjunction with the accompanying drawings. The accompanying drawings illustrate specific embodiments of the present invention by way of explanation and example.

Brief Description of the Drawings

[0010] [Figure 1]

[0010] It is a schematic diagram showing an exemplary electron beam inspection (EBI) system consistent with embodiments of the present disclosure. [Figure 2]

[0011] It is a schematic diagram showing an exemplary electron beam tool consistent with embodiments of the present disclosure that can be part of the exemplary electron beam inspection system of FIG. 1. [Figure 3]

[0012] It is a diagram showing an exemplary process of charging effects caused by SEM consistent with embodiments of the present disclosure. [Figure 4]

[0013] It is a flowchart of a method for generating an SEM image consistent with embodiments of the present disclosure. [Figure 5]

[0014] It is a flowchart of a method for generating an SEM image consistent with embodiments of the present disclosure. [Figure 6a]

[0015] It is a diagram showing an emphasized SEM image consistent with embodiments of the present disclosure. [Figure 6b]

[0016] This figure shows a waveform associated with a first scan line associated with an SEM image, consistent with embodiments of the present disclosure. [Figure 6c]

[0017] This figure shows a waveform associated with a second scan line associated with an SEM image, consistent with embodiments of the present disclosure. [Figure 7a]

[0018] This figure shows a first point image distribution function consistent with the embodiments of the present disclosure. [Figure 7b]

[0019] This figure shows a second point image distribution function consistent with the embodiments of the present disclosure. [Modes for carrying out the invention]

[0011]

[0020] Herein, exemplary embodiments are described in detail. Examples of embodiments are shown in the accompanying drawings. The following description refers to the accompanying drawings, and the same numbers in different drawings represent identical or similar elements unless otherwise noted. The embodiments described in the following description of exemplary embodiments are not representative of all embodiments. Rather, they are merely examples of apparatus and methods consistent with the aspects relating to the disclosed embodiments enumerated in the accompanying claims. For example, some embodiments are described in the context of utilizing electron beams, but this disclosure is not limited in that way. Other types of charged particle beams may be applied similarly. Furthermore, other imaging systems, such as optical imaging, photodetection, and X-ray detection, may be used.

[0012]

[0021] Electronic devices consist of circuits formed on a silicon substrate. Multiple circuits can be formed together on the same silicon substrate; this is called an integrated circuit (IC). The size of these circuits has been dramatically reduced, allowing more circuits to fit on a single substrate. For example, a smartphone IC chip can be as small as a thumbnail and contain over 2 billion transistors, each smaller than 1 / 1000th the thickness of a human hair. Manufacturing these extremely small ICs is a complex, time-consuming, and costly process, often involving hundreds of individual steps. An error in just one step can result in a defect in the finished IC, rendering it unusable. Therefore, one of the goals of the manufacturing process is to avoid such defects and maximize the number of functional ICs produced, i.e., to improve the overall process yield.

[0013]

[0022] One factor in improving yield is monitoring the chip manufacturing process to ensure that a sufficient number of functional integrated circuits are produced. One way to monitor the manufacturing process is to inspect the chip circuit structure at various stages of its formation. Inspection can be performed using a scanning electron microscope (SEM). Using an SEM, these very small structures can be imaged, essentially taking a "photograph" of the structure. This image can be used to verify whether the structure was formed properly and in the correct location. If a defect is found in the structure, the process can be adjusted to reduce the likelihood of the defect recurring. To satisfy the requirements of IC manufacturers, it may be desirable to increase the throughput of the defect detection and inspection process.

[0014]

[0023] However, structural errors shown in SEM images can be either "true" or "false." For example, when an SEM images a structure, distortion may appear in the image, making it seem as if the structure is deformed or placed in the wrong position, even though there are actually no errors in the structure's configuration or arrangement. This distortion can be caused by the accumulation and alteration of electric charge on the wafer structure after it interacts with electrons introduced during the scanning phase. Consequently, the SEM may no longer produce an image that accurately represents the structure.

[0015]

[0024] This disclosure, in particular, describes methods and systems for generating SEM images with reduced distortion. Thus, SEM images generated by the methods disclosed herein can be more faithful to the original structure, resulting in more accurate inspection of ICs and eliminating the wasted time due to false errors. In one example, two (or more) images acquired under different conditions, e.g., different scanning directions, are used. Using these two images and knowledge of the effects of the different conditions used to generate them, a more accurate image can be mathematically calculated.

[0016]

[0025] Now, refer to Figure 1. Figure 1 shows an exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. The EBI system 100 may be used for imaging. As shown in Figure 1, the EBI system 100 may include a main chamber 101, a load / lock chamber 102, an electron beam tool 104, and an instrument front-end module (EFEM) 106. The electron beam tool 104 is located within the main chamber 101. While the description and drawings relate to electron beams, it should be understood that the embodiments are not intended to limit the present disclosure to specific charged particles.

[0017]

[0026] The EFEM106 may include a first loading port 106a and a second loading port 106b. The EFEM106 may include one or more additional loading ports. The first loading port 106a and the second loading port 106b receive a wafer FOUP (front opening unified pod), which contains a wafer to be inspected (e.g., a semiconductor wafer or a wafer made of other materials) or a sample (the wafer and sample may be used interchangeably).

[0018]

[0027] One or more robotic arms (not shown) within the EFEM 106 may transport the wafer to the load / lock chamber 102. The load / lock chamber 102 is connected to a load / lock vacuum pump system (not shown) that removes gas molecules from within the load / lock chamber 102 until a first pressure lower than atmospheric pressure is reached. After the first pressure is reached, one or more robotic arms (not shown) may transport the wafer from the load / lock chamber 102 to the main chamber 101. The main chamber 101 is connected to a main chamber vacuum pump system (not shown) that removes gas molecules from within the main chamber 101 until a second pressure lower than the first pressure is reached. After the second pressure is reached, the wafer is subjected to inspection by an electron beam tool 104. The electron beam tool 104 may be a single-beam system or a multi-beam system.

[0019]

[0028] The controller 109 is electronically connected to the electron beam tool 104 and may also be electronically connected to other components. The controller 109 may be a computer configured to perform various controls of the EBI system 100. The controller 109 may also include processing circuits configured to perform various signal and image processing functions. In Figure 1, the controller 109 is shown as being outside the structure including the main chamber 101, the load / lock chamber 102, and the EFEM 106, but it should be understood that the controller 109 may be part of this structure.

[0020]

[0029] Depending on the embodiment, the controller 109 may include one or more processors (not shown). A processor may be a general-purpose or dedicated electronic device capable of manipulating or processing information. For example, a processor may include any number of central processing units (i.e., CPUs), graphics processing units (i.e., GPUs), optical processors, programmable logic controllers, microcontrollers, microprocessors, digital signal processors, intellectual property (IP) cores, programmable logic arrays (PLAs), programmable array logic (PALs), generic array logic (GALs), complex programmable logic devices (CPLDs), field-programmable gate arrays (FPGAs), system-on-a-chip (SoCs), application-specific integrated circuits (ASICs), and any type of circuitry capable of data processing. A processor may also be a virtual processor, including one or more processors distributed across multiple machines or devices connected via a network.

[0021]

[0030] Depending on the embodiment, the controller 109 may further include one or more memories (not shown). The memories may be general-purpose or dedicated electronic devices capable of storing code and data accessible by the processor (e.g., via a bus). For example, the memories may include any number of random access memories (RAM), read-only memories (ROM), optical disks, magnetic disks, hard drives, solid-state drives, flash drives, security digital (SD) cards, memory sticks, compact flash (CF) cards, or any type of storage device in any combination. The code may include an operating system (OS) and one or more application programs (i.e., “apps”) for a particular task. The memories may also be virtual memories, including one or more memories distributed across multiple machines or devices connected via a network.

[0022]

[0031] Now, refer to Figure 2. Figure 2 shows an exemplary imaging system 200 according to an embodiment of the present disclosure. The electron beam tool 104 in Figure 2 may be configured for use in an EBI system 100. The electron beam tool 104 may be a single-beam or multi-beam device. As shown in Figure 2, the electron beam tool 104 may include a motorized sample stage 201 and a wafer holder 202 supported by the motorized sample stage 201, which holds a wafer 203 to be inspected. The electron beam tool 104 may further include an objective lens assembly 204, an electron detector 206 (including electron sensor surfaces 206a and 206b), an objective aperture 208, a focusing lens 210, a beam limiting aperture 212, a gun aperture 214, an anode 216, and a cathode 218. In some embodiments, the objective lens assembly 204 may include an improved SORIL (swing objective retarding immersion lens), which includes a pole piece 204a, a control electrode 204b, a deflector 204c, and an excitation coil 204d.

[0023]

[0032] By applying an accelerating voltage between the anode 216 and the cathode 218, a primary electron beam 220 is emitted from the cathode 218. The primary electron beam 220 passes through a gun aperture 214 and a beam limiting aperture 212, both of which may determine the size of the electron beam before it enters the focusing lens 210 located below the beam limiting aperture 212. The focusing lens 210 focuses the beam before the primary electron beam 220 enters the objective aperture 208, setting the size of the electron beam before it enters the objective lens assembly 204. A deflector 204c deflects the primary electron beam 220 to facilitate beam scanning on the wafer. For example, in a scanning process, the deflector 204c may be controlled to sequentially deflect the primary electron beam 220 to different positions on the upper surface of the wafer 203 at different time points to provide data for reconstructing images of different parts of the wafer 203. Furthermore, the deflector 204c may also be controlled to deflect the primary electron beam 220 to different sides of the wafer 203 at specific locations at different time points, providing data for reconstructing a stereo image of the wafer structure at those locations. In addition, depending on the embodiment, the anode 216 and cathode 218 may generate multiple primary electron beams 220, and the electron beam tool 104 may include multiple deflectors 204c to project these multiple primary electron beams 220 simultaneously onto different parts / sides of the wafer, providing data for reconstructing images of different parts of the wafer 203.

[0024]

[0033] The excitation coil 204d and the pole piece 204a generate a magnetic field that starts at one end of the pole piece 204a and ends at the other end. The portion of the wafer 203 scanned by the primary electron beam 220 may be immersed in this magnetic field or may be electrically charged to generate an electric field. This electric field reduces the energy at which the primary electron beam 220 collides near the surface of the wafer 203 before it strikes the wafer 203. The control electrode 204b is electrically isolated from the pole piece 204a and controls the electric field on the wafer 203 to prevent micro-arching of the wafer 203 and ensure proper beam focusing.

[0025]

[0034] Upon receiving the primary electron beam 220, a secondary electron beam 222 may be emitted from a portion of the wafer 203. The secondary electron beam 222 may form beam spots on the sensor surfaces 206a and 206b of the electron detector 206. The electron detector 206 may generate a signal (e.g., voltage, current, etc.) representing the intensity of the beam spots and provide this signal to the image processing system 250. The intensity of the secondary electron beam 222 and the resulting beam spots may vary depending on the external or internal structure of the wafer 203. Furthermore, as discussed above, the primary electron beam 220 may be projected onto various positions on the upper surface of the wafer, or onto various sides of the wafer at specific positions, to generate secondary electron beams 222 (and resulting beam spots) of different intensities. Thus, by mapping the intensity of the beam spots to the positions on the wafer 203, the processing system may reconstruct an image that reflects the internal or surface structure of the wafer 203.

[0026]

[0035] The imaging system 200 may be used to inspect a wafer 203 on a sample stage 201 and includes an electron beam tool 104, as discussed above. The imaging system 200 may also include an image processing system 250, which includes an image acquirer 260, storage 270, and a controller 109. The image acquirer 260 may include one or more processors. For example, the image acquirer 260 may include a computer, server, mainframe host, terminal, personal computer, any kind of portable computing device, etc., or a combination thereof. The image acquirer 260 may be connected to the detector 206 of the electron beam tool 104 via a medium such as a conductor, fiber optic cable, portable storage medium, IR, Bluetooth, the internet, a wireless network, wireless radio, or a combination thereof. The image acquirer 260 may receive a signal from the detector 206 and construct an image. Thus, the image acquirer 260 may acquire an image of the wafer 203. The image acquirer 260 may also perform various post-processing functions, such as contour generation and overlaying indicators onto the acquired image. The image acquirer 260 may also perform adjustments to the brightness and contrast of the acquired image. The storage 270 may be a storage medium such as a hard disk, cloud storage, random access memory (RAM), or other types of computer-readable memory. The storage 270 may be coupled with the image acquirer 260 and may be used to store the raw image data scanned as the source image and the post-processed image. The image acquirer 260 and the storage 270 may be connected to the controller 109. Depending on the embodiment, the image acquirer 260, the storage 270, and the controller 109 may be integrated together as a single control unit.

[0027]

[0036] In some embodiments, the image acquisition device 260 may acquire one or more images of a sample based on an imaging signal received from the detector 206. The imaging signal may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image containing multiple imaging areas. This single image may be stored in the storage 270. This single image may be a source image that is divided into multiple regions. Each of these regions may contain one imaging area containing features of the wafer 203.

[0028]

[0037] In some embodiments, the SEM image may be an individual SEM image generated by a single scan of the primary electron beam 220 on the wafer 203 along a single scanning direction. In some embodiments, the SEM image may be a plurality of SEM images, each of which is a first average SEM image generated by averaging a plurality of SEM images generated by a single scan of the primary electron beam 220 on the wafer 203 along the same scanning direction. Embodiments of the present disclosure are not limited to any particular SEM image generated by any particular method, and the disclosed methods and systems may highlight SEM images including, but not limited to, the examples herein.

[0029]

[0038] A challenge in defect detection is artifacts introduced by inspection tools (e.g., SEM). These artifacts are not due to actual defects in the final product. Artifacts can distort or degrade the image quality of the object being inspected, leading to difficulties or inaccuracies in defect detection. For example, when inspecting electrically insulating materials using an SEM, the quality of the SEM image is typically reduced by charging artifacts caused by the SEM.

[0030]

[0039] Referring now to Figure 3, Figure 3 shows an exemplary process of a charging effect caused by a SEM, consistent with embodiments of the present disclosure. The SEM generates a primary electron beam (e.g., primary electron beam 220 in Figure 2) for inspection. In Figure 3, electrons from the primary electron beam 302 are projected onto the surface of a sample 304. The sample 304 may be an insulating material such as a nonconductive resist or a silicon dioxide layer. The electrons from the primary electron beam 302 may penetrate the surface of the insulating sample 304 to a certain depth and interact with particles of the insulating sample 304 within an interaction volume 306. Some electrons from the primary electron beam 302 may interact elastically with particles within the interaction volume 306 (e.g., in the form of elastic scattering or elastic collision), or they may be reflected or bounced off the surface of the sample 304. In elastic interactions, the total kinetic energy of the interacting objects (e.g., electrons in the primary electron beam 302 and particles in the sample 304) is conserved, and the kinetic energy of the interacting objects is not converted into other forms of energy (e.g., heat, electromagnetic energy, etc.). Such reflected electrons produced from elastic interactions are sometimes called backscattered electrons (BSEs), such as BSE308 in Figure 3. Some electrons in the primary electron beam 302 may interact inelastically with particles within the interaction volume 306 (e.g., in the form of inelastic scattering or inelastic collisions). In inelastic interactions, the total kinetic energy of the interacting objects is not conserved, and some or all of the kinetic energy of the interacting objects is converted into other forms of energy. For example, through inelastic interactions, the kinetic energy of some electrons in the primary electron beam 302 may cause electron excitation and transitions of atoms in the particles. Such inelastic interactions may also produce electrons that exit the surface of the sample 304, which are sometimes called secondary electrons (SEs), such as SE310 in Figure 3. The production or emission rate of BSE and SE depends, in particular, for example, on the energy of the electrons in the primary electron beam 302 and the material being tested. The energy of the electrons in the primary electron beam 302 may be partially provided by an accelerating voltage (for example, the accelerating voltage between the anode 216 and cathode 218 in Figure 2).The amounts of BSE and SE may be greater than or less than (or even equal to) the electrons injected by the primary electron beam 302. Due to the imbalance between incoming and outgoing electrons, charge (e.g., positive or negative charge) may accumulate on the surface of sample 304. Excess charge may accumulate locally on or near the surface of sample 304, which is sometimes called the SEM-induced charging effect.

[0031]

[0040] Typically, insulating materials (e.g., many types of resists) can become positively charged because the outgoing electrons (e.g., BSE or SE) usually exceed the incoming electrons of the SEM's primary electron beam, causing the excess positive charge to accumulate on or near the surface of the insulating material. Figure 3 shows a case where the SEM-induced charging effect occurs and positive charge accumulates on the surface of the insulating sample 304. The positive charge may be physically modeled as holes 312. In Figure 3, electrons from the primary electron beam 302 injected into the interaction volume 306 may also diffuse into adjacent volumes of the interaction volume 306, which may be called diffuse electrons, such as diffuse charges 314. The diffuse electrons may recombine with positive charges (e.g., holes) in the sample 304, such as recombination pairs 316. The diffusion and recombination of charges may affect the distribution of holes 312. Hall 312 can cause problems, for example, by pulling BSE and SE back to the surface of sample 304, increasing the landing energy of electrons in the primary electron beam 302, causing electrons in the primary electron beam 302 to deviate from their intended landing sites, or by interfering with the electric field between the surface of the insulating sample 304 and the electron detectors of BSE and SE, such as the electron detector 206 in Figure 2.

[0032]

[0041] SEM-induced charging can attenuate and distort the SEM signal received by the electron detector, which can further distort the acquired SEM image. Furthermore, because sample 304 is nonconductive, positive charge may accumulate along the path of the primary electron beam 302 as it scans the surface of sample 304. Such accumulation of positive charge can increase or complicate distortion in the acquired SEM image. Such distortion caused by the SEM-induced charging effect is sometimes called SEM-induced charging artifact. Since the charge accumulates primarily along the path of the primary electron beam 302, SEM-induced charging artifacts may occur primarily along the scanning direction. SEM-induced charging artifacts can cause errors in estimating the geometric size of the fabricated structure or lead to misidentification of defects during inspection.

[0033]

[0042] Refer to Figure 4. The flowchart in this figure illustrates a method for generating SEM images according to embodiments of the present disclosure. This method uses diversity techniques, such as phase diversity techniques or directional diversity techniques, to infer SEM-induced charging artifacts from image data. This method uses two or more acquired SEM images. One of the SEM images is an SEM image acquired using the techniques described above, which may be affected by unknown SEM-induced charging artifacts. Then, one or more additional SEM images are acquired while varying this unknown SEM-induced charging artifact in a known manner. For example, the parameters of the SEM electron beam scanning may be changed. Then, an enhanced SEM image with reduced SEM-induced charging artifacts may be generated.

[0034]

[0043] The method according to the embodiment may be particularly advantageous near the feature edges of the object being imaged. The method according to the embodiment may be particularly advantageous near feature edges parallel to the scanning direction.

[0035]

[0044] In step 402, a first SEM electron beam scan is performed on one or more features of the object to be imaged (e.g., a wafer or sample). Thus, a first SEM image may be acquired.

[0036]

[0045] The first SEM electron beam scan is performed using a set of parameters having a first set of values. The set of parameters includes beam characteristics and scanning characteristics. Beam characteristics may include, for example, the beam current and beam profile of the electron beam. Scanning characteristics may include, for example, the scanning direction and scanning speed of the electron beam scan.

[0037]

[0046] In step 404, a second SEM electron beam scan is performed on one or more features of the object to be imaged. Thus, a second SEM image may be acquired.

[0038]

[0047] A second SEM electron beam scan is performed using a set of parameters having a second set of values. The second set of predetermined values ​​differs from the first set of values ​​in that one of the parameters in the set of parameters is different, i.e., one of the SEM electron beam scanning characteristics is modified. In one embodiment, the second electron beam scan is performed using beam characteristics different from the corresponding beam characteristics of the first electron beam scan. In another embodiment, the second electron beam scan is performed using scanning characteristics different from the corresponding scanning characteristics of the first electron beam scan. In one embodiment, the two scans are performed in different scanning directions. In one embodiment, the two scans are performed at different scanning speeds. In one embodiment, the two scans are performed at different beam currents. In one embodiment, the two scans are performed with different beam profiles.

[0039]

[0048] In one embodiment, the same single electron beam may be used to acquire both the first and second SEM images. In an alternative embodiment, the electron beam used to acquire the first SEM image may be identical to the electron beam used to acquire the second SEM image. In yet another embodiment, the electron beam used to acquire the first SEM image may be sufficiently similar to the electron beam used to acquire the second SEM image. Sufficiently similar electron beams may be used if, for example, differences in electron beam characteristics do not substantially affect the acquired image, apart from differences introduced by modified beam characteristics. For example, a multi-beam SEM may be used to acquire SEM images. In this case, one of the electron beams in the multi-beam system may be used to acquire the first SEM image, and a different electron beam in the multi-beam system may be used to acquire the second SEM image.

[0040]

[0049] In one embodiment, the same feature may be scanned by the first and second scans. In an alternative embodiment, if the first set of features is sufficiently similar to the second set of features, the first scan may scan one set of features and the second scan may scan the corresponding second set of features. For example, the first row of holes may be scanned in a first direction, and the second row of holes may be scanned in a second direction. If the holes are sufficiently similar (which may be the case for high-precision manufacturing equipment such as a lithography system), an enhanced SEM image can be obtained according to the embodiment. In such a configuration, throughput may be improved because each row of holes is scanned only once.

[0041]

[0050] This disclosure is not limited to imaging any particular feature type. The example described above focused on imaging contact holes, which is only one of many possible features to which this method can be used. Other possible features include, but are not limited to, line-and-space, pillar, tip-to-tip features, and tip-to-line-to-tip features.

[0042]

[0051] In step 406, an enhanced SEM image is generated from the acquired first and second SEM images. The generated SEM image may have reduced effects from SEM-induced charging artifacts.

[0043]

[0052] Here, we will explain how to generate enhanced SEM images from the first and second SEM images.

[0044]

[0053] The first SEM image may be described by the following equation. I A (x) = (I true *PSF A )(x) (1) However, I A (x) shows the first acquired SEM image as a function of position x, true This shows the true ground image (which we are trying to obtain), PSF A represents the point image distribution function of the first SEM image (called the first point image distribution function), and * represents the convolution operator defined by the following equation.

number

[0045]

[0054] The point image distribution function may be described as the degree of influence of SEM-induced charging artifacts on the SEM image. In the absence of SEM-induced charging artifacts, the point image distribution function may be described by the Dirac delta function. More generally, the point image distribution function may be described as the impulse response of the imaging system. Therefore, the point image distribution function is related to the "blurring" of the imaging system.

[0046]

[0055] The second SEM image may similarly be described by the following equation. I B (x) = (I true*PSF B )(x) (3) However, I B (x) represents the acquired second SEM image, and PSF B represents the point spread function of the second SEM image (referred to as the second point spread function).

[0047]

[0056] Therefore, a system including two equations (Equation 1 and Equation 3) and three unknowns (I true , PSF A , and PSF B ) may describe the relationship between the true ground image and the acquired first and second SEM images.

[0048]

[0057] Furthermore, the point spread function PSF A of the first image may be related to the point spread function PSF B of the second image. These two point spread functions may be related based on the (known) change in the electron beam scanning parameter values between the first electron beam scanning and the second electron beam scanning. This will be considered in more detail in relation to FIG. 7.

[0049]

[0058] Therefore, a system of equations including two equations and two unknowns is obtained. By solving these two equations simultaneously, an enhanced SEM image may be generated.

[0050]

[0059] The system of equations may be solved by any suitable known method. The solutions may include analytical solutions and numerical solutions. In some embodiments, these two equations are solved computationally.

[0051]

[0060] Here, refer to FIG. 5. The flowchart of this figure shows a method for generating an SEM image according to an embodiment of the present disclosure. This flowchart particularly shows a preferred embodiment in which the above-described system of equations is solved in two steps by first obtaining the point spread function and then generating the enhanced SEM image.

[0052]

[0061] In step 502, the first SEM image is acquired, for example, as described in relation to step 402 in Figure 4.

[0053]

[0062] In step 504, a second SEM image is acquired, for example, as described in relation to step 404 in Figure 4.

[0054]

[0063] In step 506, one of the first and second point image distribution functions is obtained. The obtained point image distribution function is obtained by solving the two simultaneous equations 1 and 2 outlined above. Once one of the first and second point image distribution functions is obtained, the other may be obtained by the relationship between the first and second point image distribution functions.

[0055]

[0064] The point image distribution function may also be obtained by solving a system of two linear equations for each pixel.

[0056]

[0065] Alternatively, the point image distribution function may be obtained by parameterizing the point image distribution function using a parameterized model. This may significantly reduce the complexity, cost, and / or time of the computation. In one embodiment, the point image distribution function may be described by a parameterized model given by the following equation: PSF(x) = εδ(x) - ae -γx sin(bx+c)θ(x) (4) However, ε, a, γ, b, and c are the optimization or fitting parameters to be determined, δ(x) is the Dirac / Kronecker delta function, and θ(x) is the Heaviside step function.

[0057]

[0066] In another embodiment, the point image distribution function may be described by a 2D parameterized model given by the following equation.

number

[0058]

[0067] This disclosure is not limited to the examples of parameterized models described above, and any appropriate parameterized model may be used to obtain the point image distribution function.

[0059]

[0068] The two equations, 1 and 3, can be solved simultaneously for the two unknowns. These equations may also be solved by an optimization method that can formulate a cost function as the squared difference between the acquired SEM image and the true ground SEM image. The squared difference may be formulated as follows: L = Σ x [I A (x)-(I true *PSF A )(x)] 2 +[I B (x)-(I true *PSF B )(x)] 2 (6)

[0060]

[0069] Next, any suitable optimization method, for example, I that yields a local or global minimum of the scalar cost factor L, is used. true And optimization methods that repeatedly find PSF may use this cost function. In the embodiment, the cost function first has an unknown I true The point image distribution function may be solved by removing the element.

[0061]

[0070] As another example, the scalar cost factor L may be the absolute difference instead of the squared difference.

[0062]

[0071] In embodiments where measurement noise reduces the likelihood of obtaining accurate values ​​for the point image distribution function and the true ground image, the formulation of the cost function may be extended to include a so-called regularization term or antecedent term. In this case, the process of solving the system of equations may become more robust to the noise problem.

[0063]

[0072] In step 508, the acquired point image distribution function is used to generate an enhanced SEM image. The generated SEM image may have reduced effects from SEM-induced charging artifacts.

[0064]

[0073] Using the acquired point image distribution function along with the first and second SEM images, an enhanced SEM image may be generated from a system of equations.

[0065]

[0074] Enhanced SEM images may be generated from a system of simultaneous equations using any suitable known method.

[0066]

[0075] In one embodiment, the enhanced SEM image is generated by using the Fourier transform. The Fourier transform may be, but is not limited to, the Fast Fourier Transform.

[0067]

[0076] In one embodiment, after obtaining the point image distribution function, an enhanced SEM image may be generated using the following formula.

number

[0068]

[0077] In the embodiment, the true ground image may alternatively be generated by again using the optimization method. For example, the true ground image may be generated by using the cost function of Equation 6. Since the point image distribution function may already be obtained, the only unknown in the cost function is the true ground image. As with obtaining the point image distribution function, the cost function may be defined as any suitable cost function, for example, as a difference of squares as in Equation 6, or as an absolute difference. A regularization term or antecedent term may be introduced to improve accuracy or stability in the presence of noise.

[0069]

[0078] Now, refer to Figure 6. Figure 6 shows an exemplary enhanced SEM image according to an embodiment. Figure 6(a) shows a simulated mock SEM image of a contact hole. This mock SEM image has a first scan line 602 and a second scan line 604. The first scan line 602 intersects one or more edges of the feature. The second scan line 604 is located near and parallel to one edge of the feature.

[0070]

[0079] Figure 6(b) shows the waveform of the SEM image at the first scan line 602. Figure 6(b) shows the waveform of the enhanced SEM image generated using the first simulated SEM image and a second simulated SEM image obtained through simulation in the opposite scanning direction along the first scan line 602. Figure 6(b) further compares the enhanced SEM image generated by the embodiment with a simulated true ground SEM image, a simulated SEM image without any enhancement technique, and an SEM image generated by averaging the first and second simulated SEM images.

[0071]

[0080] Compared to an unenhanced SEM image, the embodiment may be found to provide an enhanced SEM image that is much closer to a ground truth image, at least in certain areas.

[0072]

[0081] Figure 6(c) shows the waveform of the SEM image at the second scan line 604. Figure 6(c) shows the waveform of the enhanced SEM image generated using the first simulated SEM image and the second simulated SEM image obtained through simulation in the opposite scanning direction along the second scan line 604. Figure 6(c) further compares the enhanced SEM image generated by the embodiment with a simulated true ground SEM image, a simulated SEM image without any enhancement technique, and an SEM image generated by averaging the first and second simulated SEM images.

[0073]

[0082] The embodiment may prove particularly advantageous when the SEM electron scanning beam moves parallel to the feature edge. As discussed in the Background section, a known technique for reducing SEM-induced charging artifacts is to acquire multiple SEM images using different scanning directions and average them. The embodiment provides a significant improvement compared to the averaging technique, particularly when the SEM electron beam scan moves along the feature edge. This is because it is known that the SEM signal decreases when the scanning beam moves parallel to the feature edge. Therefore, if two SEM images are acquired using opposite scanning directions, averaging those two SEM images will not yield an improved image, because the artifacts are equally present in both the forward and reverse scanning directions.

[0074]

[0083] Therefore, the enhanced SEM images produced by the embodiment may have reduced effects of SEM-induced charging artifacts compared to other known SEM image enhancement techniques. The embodiment may also provide a significant improvement compared to an unenhanced SEM image. The enhanced SEM image produced by the embodiment may be identical to the ground truth image.

[0075]

[0084] The embodiment offers further advantages over conventional known techniques. When the SEM electron scanning beam moves parallel to the feature edge, a decrease in the SEM signal can cause problems in contouring the feature in the SEM image. Thus, "missing contours" may be present. The embodiment provides an enhanced SEM image with improved sharpness of the feature edge, thus preventing "missing contours."

[0076]

[0085] Here, we refer to an exemplary embodiment in which the first and second scans are performed in opposite scanning directions.

[0077]

[0086] In this case, the equations representing the first and second SEM images may be described by the following equations. I x,-x (x) = (I true *PSF x,-x )(x) (6) However, the subscript x is used to indicate scanning in the positive x direction, and the subscript -x is used to indicate scanning in the negative x direction.

[0078]

[0087] The first and second point image distribution functions may be related based on the known difference in SEM-induced charging artifacts resulting from two opposite scanning directions. As mentioned above, SEM-induced charging artifacts exist primarily along the scanning direction of the SEM electron beam scan. Therefore, if the scanning direction is changed, the principal axis of the SEM-induced charging artifacts is also changed. Furthermore, the point image distribution function is related to the SEM-induced charging artifacts. Thus, the point image distribution function is related to the scanning direction. In the example where the second scanning direction is opposite to the first scanning direction, the second scanning direction is a mirror image of the first scanning direction in a plane orthogonal to the first scanning direction. Similarly, the second point image distribution function is a mirror image of the first point image distribution function in a plane orthogonal to the axis representing the direction parallel to the first scanning direction. In other words, the second point image distribution function is a reflected version of the first point image distribution function.

[0079]

[0088] This can be seen in Figure 7, which shows how the first and second point image distribution functions relate in this example with opposite scanning directions. Figure 7(a) shows the first point image distribution function. Figure 7(b) shows the second point image distribution function.

[0080]

[0089] By using this relationship between the first point image distribution function and the second point image distribution function in a system of simultaneous equations, enhanced SEM images may be generated by any of the above methods for solving the system of equations.

[0081]

[0090] Here, we refer to an exemplary embodiment in which the first and second scans are performed in different scanning directions that are not necessarily opposite.

[0082]

[0091] The first and second scanning directions may be appropriate scanning directions depending on the geometry of the feature of interest.

[0083]

[0092] In this case, the first and second point image distribution functions may be related to each other in a manner similar to the previous example in the opposite scanning direction, but in a more general manner.

[0084]

[0093] Furthermore, the first and second point image distribution functions may be related based on the known difference in SEM-induced charging artifacts resulting from two opposite scanning directions. As mentioned above, SEM-induced charging artifacts are mainly present along the scanning direction of the SEM electron beam scan, and the point image distribution function is related to SEM-induced charging artifacts. Therefore, the point image distribution function is related to the scanning direction.

[0085]

[0094] The first and second scanning directions may be considered as vectors indicating those directions. In cases where the second scanning direction is different from the first scanning direction, the second scanning direction vector may be considered as a rotation of the first scanning direction vector by a certain amount of rotation in the plane containing the first and second scanning direction vectors (i.e., in other words, a rotation around an axis orthogonal to both the first and second scanning direction vectors). Accordingly, the second point image distribution function is obtained by rotating the first point image distribution function by that amount around an axis representing the directions orthogonal to the first and second scanning directions.

[0086]

[0095] For example, in a 3D geometry represented by orthogonal x, y, and z axes, where the first and second scanning direction vectors lie in the xy-plane, the second scanning direction vector is obtained by rotating the first scanning direction vector by an amount around the z axis. Similarly, the second point image distribution function is obtained by rotating the first point image distribution function by the same amount around the z axis.

[0087]

[0096] By using this relationship between the first point image distribution function and the second point image distribution function in a system of simultaneous equations, enhanced SEM images may be generated by any of the above methods for solving the system of equations.

[0088]

[0097] Here, we refer to an exemplary embodiment in which an electron beam scanning parameter other than the scanning direction is changed between the first scan and the second scan. The electron beam scanning parameter to be changed may include the scanning speed, beam current, or beam profile.

[0089]

[0098] In an example where the scanning speed is changed between two SEM images, the first and second point distribution functions may be related based on the known difference in SEM-induced charging artifacts resulting from the two different scanning speeds. Changing the scanning speed results in an enlarged or reduced version of the point distribution function. In other words, the point distribution function is scaled by an amount resulting from the known change in scanning speed.

[0090]

[0099] In an example where the beam profile is changed between two SEM images, the beam profile may be changed, for example, by changing the lens intensity so that the beam can become out of focus. In this case, the first and second point image distribution functions may be related based on the known difference in SEM-induced charging artifacts resulting from the out-of-focus (or other change in the beam profile). Changing the beam focus leads to an expansion of the isotropy of the point image distribution function. This is similar to the phase diversity technique used in optical systems.

[0091]

[0100] In an example where the beam current changes between two SEM images, the lower beam current may be small enough not to cause significant SEM-induced charging artifacts. The higher beam current may then be large enough to be substantially affected by SEM-induced charging artifacts. In this case, equations 1 and 3 may be expressed as follows: I A (x=I true (x)+n A (x) (8) I B (x) = (I true *PSF B )(x)+n B (x) (9) However, n A (x) and n B (x) is the noise in each SEM image. Noise n in Equation 9 B The contribution of (x) (i.e., the measurement at the higher beam current) is the noise n in Equation 8. A It may be negligibly small compared to the contribution of (x) (i.e., the measurement at the lower beam current).

[0092]

[0101] Therefore, there are two equations, each with two unknowns, and in the solution, these unknowns can be found (I true and PSF B ). Additional noise term n A (x) and n B(x) may be handled automatically in the optimization method by using an appropriate parameterization model of the point image distribution function, for example, a parameterization model that does not overfit the solution with noise, or by including an additional regularization term or antecedent term in the optimization method. Both of these modifications to the optimization method have been previously described.

[0093]

[0102] Even if noise is present in the first and second SEM images, the embodiment can generate enhanced SEM images.

[0094]

[0103] When processing noisy SEM images, noise reduction techniques may be used. When processing noisy SEM images, the method for solving the system of equations according to the embodiment may be modified to include appropriate regularization options. For example, the method for solving the system of equations according to the embodiment may be modified to include the squared norm |I| of the unknown true ground image in the optimization cost function. true | 2 , the full variation of the unknown true ground image |∇I true | or may include any other suitable techniques known in the field of image processing or optimization, such as non-local means and elastic nets.

[0095]

[0104] Embodiments include the use of additional SEM images in addition to the first and second SEM images. Thus, the enhanced SEM images may be further improved. In the enhanced SEM images, the effects of SEM-induced charging artifacts may be further reduced. The additional SEM images may be obtained by scanning with further modified electron beam scanning parameters. For example, one or more additional SEM images obtained using one or more additional scanning directions may be used. In one embodiment, each of the additional SEM images has modifications that differ from all the other SEM images.

[0096]

[0105] The relative dimensions of components in the drawings may be exaggerated for clarity. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and only the differences relating to individual embodiments are described.

[0097]

[0106] As used herein, unless otherwise specified, the term “or” includes all possible combinations unless they are impossible to achieve. For example, if it is stated that a component may include A or B, then unless otherwise specified or impossible to achieve, this component may include A, or B, or A and B. As a second example, if it is stated that a component may include A, B, or C, then unless otherwise specified or impossible to achieve, this component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0098]

[0107] A non-temporary computer-readable medium may be provided, which stores instructions for the controller's processor to perform tasks such as image inspection, image acquisition, operation of a charged particle source, adjustment of the electrical excitation of a stigmeter, adjustment of the electron landing energy, adjustment of the objective lens excitation, adjustment of the position and orientation of the secondary electron detector, control of the stage movement, excitation of a beam separator, application of a scanning deflection voltage to a beam deflector, reception and processing of data related to signal information from the electron detector, setting up electrostatic elements, detection of signal electrons, adjustment of the control electrode potential, adjustment of the voltage applied to the electron source, extractor electrode, and sample, etc. Common forms of non-temporary media include, for example, floppy disks, flexible disks, hard disks, solid-state drives, magnetic tapes, or any other magnetic data storage media, CD-ROMs (Compact Disc Read Only Memory), any other optical data storage media, any physical media with a hole pattern, RAM (Random Access Memory), PROMs (Programmable Read Only Memory), EPROMs (Erasable Programmable Read Only Memory), FLASH-EPROMs, or any other flash memory, NVRAMs (Non-Volatile Random Access Memory), caches, registers, any other memory chips or cartridges, and network versions thereof.

[0099]

[0108] Embodiments may be further described using the following clauses. 1. A method for reducing the sample charging effect in scanning electron microscope (SEM) images, Acquiring a first SEM image from a first electron beam scan where a certain parameter is a first quantity, This involves acquiring a second SEM image from a second electron beam scan where this parameter is a second quantity different from the first quantity, A method comprising generating a sample charge effect reduction image based on a convolution equation including a representation of a first SEM image, a representation of a second SEM image, a first point image distribution function corresponding to the first SEM image, and a second point image distribution function corresponding to the second SEM image. 2. The method according to Clause 1, wherein the step of generating a sample charge effect reduction image includes relating a first point image distribution function to a second point image distribution function according to the difference in sample charge effect between a first electron beam scan and a second electron beam scan. 3. The method according to clause 1 or 2, wherein the step of generating a sample charge effect reduction image includes obtaining one or both of the first and second point image distribution functions from the first and second SEM images using a convolution equation. 4. The method according to Clause 3, wherein the step of obtaining one or both of the first and second point image distribution functions includes expressing the point image distribution function in a parameterized form. 5. The method according to clause 3 or 4, wherein the step of generating a sample charge effect reduction image includes generating a sample charge effect reduction image using the acquired point image distribution function. 6. The method described in any one of the preceding clauses, wherein the parameter is the scanning direction. 7. The method according to Clause 6, wherein the first quantity is in the first direction and the second quantity is in the second direction opposite to the first direction. 8. The method according to clause 7, wherein the second point image distribution function is a mirror image of the first point image distribution function with respect to a plane orthogonal to the axis representing the direction parallel to the first direction. 9. The parameter is the scanning speed, as described in any one of clauses 1 to 5. 10. The parameter is the electron beam current, as described in any one of clauses 1 to 5. 11. A sample charge effect reduction image is generated according to one or more equations that include one or more Fourier transform operations, as described in any one of the preceding clauses. 12. The method according to any one of the preceding clauses, further comprising obtaining one or more additional SEM images from an additional set of electron beam scans, wherein the parameters of each scan among the additional set of electron beam scans are different from the first and second amounts. 13. This method further, The first electron beam scan is performed using a scanning electron microscope, The method of any one of the preceding clauses, comprising performing a second electron beam scan using a scanning electron microscope. 14. A computer program product that includes a non-temporary computer-readable medium on which instructions are recorded, wherein, when executed by a computer, the instructions perform the actions described in any one of the preceding clauses. 15. A system, A scanning electron microscope (SEM) configured to generate images by scanning using an electron beam, A non-temporary, machine-readable medium for storing instructions, which, when executed by the processor, communicates to the processor in cooperation with the SEM. Acquiring a first SEM image from a first electron beam scan where a certain parameter is a first quantity. This involves acquiring a second SEM image from a second electron beam scan where this parameter is a second quantity different from the first quantity, and, A system including a non-temporary machine-readable medium that causes the system to perform an operation including generating a sample charge effect reduction image based on a convolution equation including a representation of a first SEM image, a representation of a second SEM image, a first point image distribution function corresponding to the first SEM image, and a second point image distribution function corresponding to the second SEM image. 16. A method for reducing the sample charging effect in scanning electron microscope (SEM) images, Acquiring a first SEM image from an electron beam scan where a certain parameter is a first quantity, This involves obtaining a second SEM image from another electron beam scan where this parameter is a second quantity different from the first quantity, This includes generating a sample charge effect reduction image based on first and second convolution equations, The first convolution equation is: Representation of the first scanning electron microscope image, and It includes a first charged point image distribution function corresponding to a first scanning electron microscope image, The second convolution equation is: Representation of the second scanning electron microscope image, and A method comprising a second charged point image distribution function corresponding to a second scanning electron microscope image. 17. The method according to Clause 16, wherein the step of generating a sample charge effect reduction image includes relating a first point image distribution function to a second point image distribution function according to the difference in sample charge effect between a first electron beam scan and a second electron beam scan. 18. The method according to clause 16 or 17, wherein the step of generating a sample charge effect reduction image includes obtaining one or both of the first and second point image distribution functions from the first and second SEM images using a convolution equation. 19. The method according to Clause 18, wherein the step of obtaining one or both of the first and second point image distribution functions includes expressing the point image distribution function in a parameterized form. 20. The method according to clause 18 or 19, wherein the step of generating a sample charge effect reduction image comprises generating a sample charge effect reduction image using the acquired point image distribution function. 21. The parameter is the scanning direction, as described in any one of clauses 16 to 20. 22. The method according to Clause 21, wherein the first quantity is in the first direction and the second quantity is in the second direction opposite to the first direction. 23. The method according to clause 22, wherein the second point image distribution function is a mirror image of the first point image distribution function with respect to a plane orthogonal to the axis representing the direction parallel to the first direction. 24. The parameter is the scanning speed, as described in any one of clauses 16 to 20. 25. The parameter is the electron beam current, as described in any one of the provisions 16-20. 26. A sample charge effect reduction image is generated according to one or more equations that include one or more Fourier transform operations, as described in any one of clauses 16 to 25. 27. The method according to any one of the provisions of 16 to 26, further comprising obtaining one or more additional SEM images from an additional set of electron beam scans, wherein the parameters of each scan among the additional set of electron beam scans are different from the first and second amounts. 28. This method further, The first electron beam scan is performed using a scanning electron microscope, The method according to any one of the clauses 16 to 27, comprising performing a second electron beam scan using a scanning electron microscope. 29. A computer program product that includes a non-temporary computer-readable medium on which instructions are recorded, wherein, when executed by a computer, the instructions carry out the method described in Clause 16. 30. It is a system, A scanning electron microscope (SEM) configured to generate images by scanning using an electron beam, A non-temporary, machine-readable medium for storing instructions, which, when executed by the processor, communicates to the processor in cooperation with the SEM. Acquiring a first SEM image from an electron beam scan where a certain parameter is a first quantity. This involves acquiring a second SEM image from another electron beam scan where this parameter is a second quantity different from the first quantity, and also, The system performs an operation that includes generating a sample charging effect reduction image based on the first and second convolution equations. The first convolution equation is: Representation of the first scanning electron microscope image, and It includes a first charged point image distribution function corresponding to a first scanning electron microscope image, The second convolution equation is: Representation of the second scanning electron microscope image, and A system comprising a non-temporary machine-readable medium, including a second charged point image distribution function corresponding to a second scanning electron microscope image. 31. A method for reducing the sample charging effect in scanning electron microscope (SEM) images, Acquiring a first SEM image from a first electron beam scan where a certain parameter is a first quantity, This involves acquiring a second SEM image from a second electron beam scan where this parameter is a second quantity different from the first quantity, Obtaining the point distribution function from the first and second SEM images using the convolution equation, A method comprising generating a sample charge effect reduction image based on a convolution equation including a representation of a first SEM image, a representation of a second SEM image, and an acquired point image distribution function. 32. The method according to Clause 31, wherein the step of obtaining a point image distribution function includes relating the first point image distribution function to the second point image distribution function according to the difference in sample charging effects between the first electron beam scan and the second electron beam scan. 33. The method according to clause 31 or 32, wherein the step of obtaining the point image distribution function includes expressing the point image distribution function in a parameterized form. 34. The parameter is the scanning direction, as described in any one of the clauses 31 to 33. 35. The method according to Clause 34, wherein the first quantity is in the first direction and the second quantity is in the second direction opposite to the first direction. 36. The parameter is the scanning speed, as described in any one of clauses 31 to 33. 37. The parameter is the electron beam current, as described in any one of the provisions 31 to 33. 38. The method according to any one of clauses 31 to 37, wherein the sample charge effect reduction image is generated according to one or more equations that include one or more Fourier transform operations. 39. The method according to any one of the provisions of 31 to 38, further comprising obtaining one or more additional SEM images from an additional set of electron beam scans, wherein the parameters of each scan among the additional set of electron beam scans are different from the first and second amounts. 40. This method further, The first electron beam scan is performed using a scanning electron microscope, The method according to any one of clauses 31 to 39, comprising performing a second electron beam scan using a scanning electron microscope. 41. A computer program product comprising a non-temporary computer-readable medium on which instructions are recorded, wherein, when executed by a computer, the instructions perform the method described in Clause 31. 42. A system, A scanning electron microscope (SEM) configured to generate images by scanning using an electron beam, A non-temporary, machine-readable medium for storing instructions, which, when executed by the processor, communicates to the processor in cooperation with the SEM. Acquiring a first SEM image from a first electron beam scan where a certain parameter is a first quantity. This involves acquiring a second SEM image from a second electron beam scan where this parameter is a second quantity different from the first quantity. Obtain the point distribution function from the first and second SEM images using the convolution equation. A system including a non-temporary machine-readable medium that causes the system to perform an operation including generating a sample charge effect reduction image based on a convolution equation including a representation of a first SEM image, a representation of a second SEM image, and an acquired point image distribution function. 43. Method Acquiring a first SEM image from a first electron beam scan where a certain parameter is a first quantity, This involves acquiring a second SEM image from a second electron beam scan where this parameter is a second quantity different from the first quantity, A method comprising generating an image based on a convolution equation including a representation of a first SEM image, a representation of a second SEM image, a first point image distribution function corresponding to the first SEM image, and a second point image distribution function related to the first point image distribution function according to the difference in sample charging effect between a first electron beam scan and a second electron beam scan. 44. The method according to clause 43, wherein the generated image is an image with reduced sample charging effect. 45. The method according to clause 43 or 44, wherein the step of generating a sample charge effect reduction image includes obtaining one or both of the first and second point image distribution functions from the first and second SEM images using a convolution equation. 46. ​​The method according to Clause 45, wherein the step of obtaining one or both of the first and second point image distribution functions includes expressing the point image distribution function in a parameterized form. 47. The method according to clause 45 or 46, wherein the step of generating a sample charge effect reduction image includes generating a sample charge effect reduction image using an acquired point image distribution function. 48. The parameter is the scanning direction, as described in any one of the clauses 43 to 47. 49. The method according to Clause 48, wherein the first quantity is in the first direction and the second quantity is in the second direction opposite to the first direction. 50. The method according to clause 49, wherein the second point image distribution function is a mirror image of the first point image distribution function with respect to a plane orthogonal to the axis representing the direction parallel to the first direction. 51. The parameter is the scanning speed, as described in any one of the clauses 43 to 47. 52. The parameter is the electron beam current, as described in any one of the provisions 43 to 47. 53. A sample charge effect reduction image is generated according to one or more equations that include one or more Fourier transform operations, as described in any one of clauses 43 to 52. 54. The method according to any one of the provisions of 43 to 53, further comprising obtaining one or more additional SEM images from an additional set of electron beam scans, wherein the parameters of each scan among the additional set of electron beam scans are different from the first and second amounts. 55. This method further, The first electron beam scan is performed using a scanning electron microscope, The method according to any one of the clauses 43 to 53, comprising performing a second electron beam scan using a scanning electron microscope. 56. A computer program product comprising a non-temporary computer-readable medium on which instructions are recorded, wherein, when executed by a computer, the instructions perform the actions described in Clause 43. 57. It is a system, A scanning electron microscope (SEM) configured to generate images by scanning using an electron beam, A non-temporary, machine-readable medium for storing instructions, which, when executed by the processor, communicates to the processor in cooperation with the SEM. Acquiring a first SEM image from a first electron beam scan where a certain parameter is a first quantity. This involves acquiring a second SEM image from a second electron beam scan where this parameter is a second quantity different from the first quantity, and, A system including a non-temporary machine-readable medium that causes the system to perform an operation including generating an image based on a convolution equation including a representation of a first SEM image, a representation of a second SEM image, a first point image distribution function corresponding to the first SEM image, and a second point image distribution function related to the first point image distribution function according to the difference in sample charging effect between a first electron beam scan and a second electron beam scan.

[0100]

[0109] It should be understood that the embodiments of this disclosure are not strictly limited to the configurations described above and shown in the accompanying drawings, and that various modifications and changes may be made without departing from the scope of this disclosure. Although various embodiments of this disclosure have been described in relation to this disclosure, other embodiments will be obvious to those skilled in the art from considering the provisions and practices of the invention disclosed herein. This specification and examples are to be considered merely examples, and the true scope and spirit of the invention are intended to be shown by the following claims.

[0101]

[0110] The above description is illustrative and not limiting. Therefore, it will be apparent to those skilled in the art that modifications may be made as described below without departing from the claims.

Claims

1. A computer program product comprising a non-temporary computer-readable medium on which instructions are recorded, wherein the instructions, when executed by a computer, A step of acquiring a first SEM image from a first electron beam scan in which a certain parameter is a first quantity, The steps include acquiring a second SEM image from a second electron beam scan in which the parameter is a second amount different from the first amount, A computer program product that performs a method comprising the steps of generating a sample charge effect reduction image based on a convolution equation including a representation of a first SEM image, a representation of a second SEM image, a first point image distribution function corresponding to the first SEM image, and a second point image distribution function corresponding to the second SEM image.

2. The computer program product according to claim 1, wherein the step of generating the sample charging effect reduction image includes relating the first point image distribution function to the second point image distribution function according to the difference in sample charging effect between the first electron beam scan and the second electron beam scan.

3. The computer program product according to claim 1, wherein the step of generating the sample charge effect reduction image comprises obtaining one or both of the first and second point image distribution functions from the first and second SEM images using the convolution equation.

4. The computer program product according to claim 3, wherein the step of obtaining one or both of the first and second point image distribution functions includes expressing the point image distribution function in a parameterized form.

5. The computer program product according to claim 3, wherein the step of generating the sample charge effect reduction image includes generating the sample charge effect reduction image using the acquired point image distribution function.

6. The computer program product according to claim 1, wherein the parameter is the scanning direction.

7. The computer program product according to claim 6, wherein the first quantity is in a first direction, and the second quantity is in a second direction opposite to the first direction.

8. The computer program product according to claim 7, wherein the second point image distribution function is a mirror image of the first point image distribution function with respect to a plane orthogonal to an axis representing a direction parallel to the first direction.

9. The computer program product according to claim 1, wherein the parameter is the scanning speed.

10. The computer program product according to claim 1, wherein the parameter is electron beam current.

11. The computer program product according to claim 1, wherein the sample electrostatic effect reduction image is generated according to one or more equations including one or more Fourier transform operations.

12. The computer program product according to claim 1, further comprising obtaining one or more additional SEM images from the additional electron beam scans, wherein the parameters of each scan among the additional electron beam scans are different from the first and second amounts.

13. The aforementioned method further, Performing the first electron beam scan using a scanning electron microscope, The computer program product according to claim 1, comprising performing the second electron beam scan using the scanning electron microscope.

14. It is a system, A scanning electron microscope (SEM) configured to scan and generate images using an electron beam, A non-temporary machine-readable medium for storing instructions, wherein, when an instruction is executed by a processor, the processor, in cooperation with the SEM, Acquiring a first SEM image from a first electron beam scan where a certain parameter is a first quantity. Acquiring a second SEM image from a second electron beam scan in which the parameter is a second amount different from the first amount, and A system including a non-temporary machine-readable medium that performs an operation including generating a sample charging effect reduction image based on a convolution equation including a representation of the first SEM image, a representation of the second SEM image, a first point image distribution function corresponding to the first SEM image, and a second point image distribution function corresponding to the second SEM image.

15. A method for reducing the sample charging effect in scanning electron microscope (SEM) images, Acquiring a first SEM image from a first electron beam scan where a certain parameter is a first quantity, A second SEM image is obtained from a second electron beam scan in which the parameter is a second amount different from the first amount, A method comprising generating a sample charging effect reduction image based on a convolution equation that includes a representation of the first SEM image, a representation of the second SEM image, a first point image distribution function corresponding to the first SEM image, and a second point image distribution function corresponding to the second SEM image.

Images