Photoetching defect detection method and system based on orbital angular momentum

Abstract

The invention belongs to the technical field of photoetching detection, and particularly discloses a photoetching defect detection method and system based on orbital angular momentum. According to the method, the OAM light beam is used for replacing the Gaussian light beam for illumination, the defect position is determined by analyzing the far-field asymmetric signal generated along the scanning path, and the far-field asymmetric signal caused by the defect under the irradiation of the OAM light beam is more obvious, so that the signal-to-noise ratio can be increased by 5.57 times at most, and the sensitivity of defect detection is remarkably improved; according to the method, OAM light beam illumination is used, the scanning step length is the integral multiple of the minimum period of the sample pattern in the scanning direction, the left-right asymmetric information and the up-down asymmetric information of the specific scanning points are synthesized, the coordinate position of the defect is determined, more available information is achieved, and the false detection rate is reduced. Diffraction processing is carried out on the diffraction images corresponding to the adjacent scanning points of the defect-containing sample, diffraction image difference between the defect-containing sample and a defect-free sample is not needed, the position error is small in the actual implementation process, symmetry is not needed for the sample pattern, and the applicability is higher.

Description

Technical Field

[0001] The present application belongs to the field of photolithography detection technology, and more specifically, relates to a photolithography defect detection method and system based on orbital angular momentum. Background Art

[0002] In the field of defect detection of nanostructures, especially defect detection of lithography substrates, masks and wafers, visible light or deep ultraviolet light is usually used for defect inspection. For technology nodes below 10nm, extreme ultraviolet light (EUV) or electron beam illumination has been used. At present, the output of integrated circuit (IC) devices and related equipment has been increasing year by year. People hope that the detection equipment can perform non-destructive and high-speed detection of intermediate products with high precision requirements such as masks and wafers. At the same time, higher and higher requirements are also put forward for the positioning, classification and accuracy of defects. Optical far-field detection technology has the advantages of simple and reliable system, ability to break through the limitations of imaging elements and high throughput. Among them, coherent Fourier scattering (CFS) usually uses coherent laser with a plane amplitude of Gaussian distribution to illuminate the sample to be tested, and uses detectors such as COMS and QD to obtain the diffraction field intensity information in the reciprocal space. However, as the critical dimensions of IC structures continue to decrease, the size of defects to be detected has been pushed to the sub-deep wavelength scale. Affected by Rayleigh scattering, the scattering information caused by defects is gradually submerged by noise, resulting in a significant decrease in the signal-to-noise ratio and a decrease in the sensitivity of defect detection. Traditional coherent scattering measurement methods are gradually encountering technical bottlenecks.

[0003] In recent years, the combination of traditional optical detection and a variety of new technologies has provided more possibilities in the field of defect detection. Among them, the detection method based on orbital angular momentum (OAM) has gradually attracted people's attention. OAM beam is a new type of structural beam with a special phase distribution. Different from polarized beams and Gaussian beams, OAM beams have special spiral wavefronts. It is this spiral phase wavefront that carries a specific orbital angular momentum. It has been partially applied in optical sensing enhancement and high-bandwidth communications. The use of OAM beams for optical detection is similar to a special illumination configuration used for bright field defect detection. Although it is still limited by Rayleigh scattering, due to its special spiral phase, the defect scattering field can undergo a larger frequency shift in reciprocal space, and the light intensity distribution after differential processing can produce greater asymmetry, thereby improving the signal-to-noise ratio of detection. In general, defect detection based on OAM beam illumination is a very promising technology.

[0004] BIN WANG et al. proposed a defect detection strategy in 2021, using OAM beams as probes in coherent Fourier scattering measurements. As long as the pattern structure has reflection symmetry, OAM-based CFS will be unique because it does not rely on reference to a pre-built database. However, this method is based on differential processing with defect-free samples. In the case of more scanning points during the actual detection process, the large cumulative error can easily lead to difficulty in aligning the pattern in the probe, requiring the translation stage to have a high position accuracy. In the model-free method, the sample pattern needs to have a certain symmetry, and the universality is not high. Summary of the invention

[0005] In view of the defects of the prior art, the purpose of this application is to propose a lithography defect detection method and system based on orbital angular momentum, aiming to solve the problems of low signal-to-noise ratio, low sensitivity and low accuracy of the existing defect detection methods.

[0006] To achieve the above objectives, in a first aspect, the present application provides a lithography defect detection method based on orbital angular momentum, wherein the lithography defect detection method is applied to a coherent Fourier scattering detection system, comprising:

[0007] S1. Calculate the near-field distribution function after the illumination probe interacts with the defective sample, wherein the illumination probe is an OAM beam, and the defective sample is a superposition of a sample pattern and a defect pattern;

[0008] S2. Through the far-field propagation model, the near-field distribution function is transferred to the reciprocal space to obtain the far-field diffraction intensity distribution function of the defective sample;

[0009] S3. Perform a second-order difference operation on the far-field diffraction intensity distribution function of the current scanning point to obtain a second-order difference image of the current scanning point;

[0010] S4. Calculate the left-right asymmetric matrix and the top-bottom asymmetric matrix of the second-order difference image of the current scanning point;

[0011] S5. Sum all elements of the left-right asymmetric matrix of the current scanning point to obtain the left-right asymmetric information of the current scanning point, and sum all elements of the upper-lower asymmetric matrix of the current scanning point to obtain the upper-lower asymmetric information of the current scanning point;

[0012] S6. moving the probe center to the next scanning point according to the scanning step length, wherein the scanning step length is an integer multiple of the minimum period of the sample pattern in the scanning direction;

[0013] S7. Repeat the above operation until the left-right asymmetric information and the top-bottom asymmetric information of all scanning points on the scanning path are obtained;

[0014] S8. Combining the two asymmetric information of all scanning points, the photolithography defect detection result is obtained.

[0015] Preferably, the near-field distribution function is as follows:

[0016]

[0017] S defect (ξ,η)=S(ξ,η)+D(ξ,η)

[0018]

[0019] in, represents the near-field distribution function, P(λ,q) represents the OAM beam with a spiral phase, S defect (η,η) represents a defective sample, S(η,η) represents the complex refractive index of the sample pattern, D(ξ,η) represents the complex refractive index of the defect on the sample, (ξ,η) represents the coordinates in the sample coordinate system, A0 represents the amplitude, λ represents the wavelength of the light source, z represents the beam propagation distance from the sample plane to the diffraction plane, θ represents the spiral azimuth, and q represents the topological charge of the OAM beam.

[0020] Preferably, the far-field diffraction intensity distribution function of the defective sample is as follows:

[0021]

[0022] in, represents the Fourier transform operation, represents the near-field distribution function, (ξ,η) represents the coordinates in the sample coordinate system, and (x,y) represents the coordinates in the diffraction plane coordinate system.

[0023] Preferably, the second-order difference image of the current scanning point is specifically as follows:

[0024] Ψ n (x,y)=Φ n-1 (x,y)-2Φ n (x,y)+Φ n+1 (x,y)

[0025] Among them, n (x, y) represents the second-order difference image corresponding to the nth scanning point in the scanning path, Φ n (x, y) represents the far-field intensity distribution function corresponding to the nth scanning point in the scanning path, and (x, y) represents the coordinates in the diffraction plane coordinate system.

[0026] Preferably, the left-right asymmetric matrix and the top-bottom asymmetric matrix of the second-order difference image of the current scanning point are specifically as follows:

[0027]

[0028] in, represents a left-right asymmetric matrix, represents an upper and lower asymmetric matrix, Ψ n (-x,y) represents the difference matrix Ψ n The horizontal flip matrix of (x,y), Ψ n (x,-y) represents the difference matrix Ψ n The vertical flip matrix of (x,y), Ψ n (x, y) represents the second-order difference image corresponding to the nth scanning point in the scanning path.

[0029] Preferably, the two asymmetric information of all scanning points are integrated to obtain the photolithography defect detection result, which is specifically as follows:

[0030] With the scanning point along the scanning direction as the horizontal axis and the asymmetric information of the scanning point as the vertical axis, if one asymmetric information has four consecutive positive and negative peak jumps, and the other asymmetric information has five consecutive positive and negative peak jumps, the scanning point position corresponding to the highest peak in the middle is determined as the defect position along the scanning direction.

[0031] Preferably, before defect positioning, normalization processing is performed on left-right asymmetric information and top-bottom asymmetric information of all scanning points.

[0032] Preferably, the illumination probe diameter D and the scanning step length d satisfy the following conditions:

[0033] Preferably, the photolithography defect detection method is applicable to defect detection of photolithography substrates, masks, wafers and intermediate products.

[0034] To achieve the above-mentioned purpose, in a second aspect, the present application provides a lithography defect detection system based on orbital angular momentum, comprising at least one processor and at least one memory;

[0035] The at least one memory is used to store computer instructions;

[0036] The at least one processor is used to execute at least part of the computer instructions to implement the lithography defect detection method described in the first aspect.

[0037] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the prior art:

[0038] (1) Compared with the traditional defect detection method using Gaussian beam illumination, this application proposes a lithography defect detection method and system based on orbital angular momentum, using OAM beam to replace the traditional Gaussian beam illumination, and determining the defect position by analyzing the far-field asymmetric signal generated along the scanning path. Since the far-field asymmetric signal caused by the defect is more obvious under the OAM beam illumination, the signal-to-noise ratio can be increased by up to 5.57 times, significantly improving the sensitivity of defect detection; this application uses OAM beam illumination, and the scanning step length is an integer multiple of the minimum period of the sample pattern in the scanning direction. The left-right and up-down asymmetric information of these specific scanning points is combined to determine the coordinate position of the defect, which has more available information and reduces the false detection rate. The dual positioning of the two asymmetric information also further improves the positioning accuracy.

[0039] (2) Compared with the existing defect detection method based on OAM beam illumination, the present application proposes a lithography defect detection method and system based on orbital angular momentum. By performing differential processing on the diffraction images corresponding to adjacent scanning points of the defective sample, there is no need to perform diffraction image differentiation with the defect-free sample. Therefore, the position error is small in actual implementation, and there is no need for symmetry requirements on the sample pattern, which makes it more applicable. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Figure 1 This is a flow chart of a lithography defect detection method based on orbital angular momentum provided in an embodiment of the present application.

[0041] Figure 2 It is a schematic diagram of a defective sample used in the simulation process provided in the embodiment of the present application.

[0042] Figure 3 It is a schematic diagram of a coherent Fourier scattering detection optical system provided in an embodiment of the present application.

[0043] Figure 4 It is a schematic diagram of a light beam wavefront with orbital angular momentum provided in an embodiment of the present application.

[0044] Figure 5 It is a schematic diagram of the motion trajectory of the scanning sample provided in the embodiment of the present application.

[0045] Figure 6 It is a schematic diagram of two asymmetric signals of OAM beam illumination and Gaussian beam illumination provided in the embodiments of the present application, wherein (a) is up-down asymmetry, (b) is left-right asymmetry, the horizontal axis is the number of scanning points along the scanning direction, and the vertical axis is the normalized signal intensity.

[0046] Figure 7This is a comparison diagram of the upper and lower asymmetric signals caused by defects detected using OAM beam illumination and Gaussian beam illumination at different offset distances s provided in the embodiments of the present application, wherein (a) corresponds to a bias distance of 0 nm, (b) corresponds to a bias distance of 100 nm, (c) corresponds to a bias distance of 300 nm, and (d) corresponds to a bias distance of 1000 nm. The horizontal axis is the number of scanning points along the scanning direction, and the vertical axis is the normalized signal intensity.

[0047] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0048] 1- He-Ne laser, 2- Attenuation plate, 3- Adjustable aperture, 4- Reflector, 5- Beam expander, 6- Adjustable aperture, 7- Spatial light modulator, 8- Beam splitter prism, 9- Focusing lens, 10- Mask sample, 11- Camera. DETAILED DESCRIPTION

[0049] In order to make the purpose, technical solution and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0050] The term "and / or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and / or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol " / " in this article indicates that the associated objects are in an or relationship, for example, A / B means A or B.

[0051] The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of the objects. For example, a first response message and a second response message are used to distinguish different response messages rather than to describe a specific order of the response messages.

[0052] In the embodiments of the present application, words such as "exemplary" or "for example" are used to indicate examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or more advantageous than other embodiments or designs. Specifically, the use of words such as "exemplary" or "for example" is intended to present related concepts in a specific way.

[0053] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two. For example, multiple processing units refer to two or more processing units, etc.; multiple elements refer to two or more elements, etc.

[0054] Next, the technical solutions provided in the embodiments of the present application are introduced.

[0055] like Figure 1 As shown, the present application provides a method for detecting lithography defects based on orbital angular momentum, which is applied to a coherent Fourier scattering detection optical system, comprising:

[0056] Step S1: Set the sample pattern. In the embodiment of the present application, the sample pattern is set to a periodic pattern consisting of a pair of nanowires. Each nanowire is 2 μm long and 200 nm wide, with a spacing of 100 nm between the two lines. This is used as a defect-free pattern S(ξ,η). A defect pattern D(ξ,η) is then added to the sample, which is a square pattern with a length and width of 100 nm. The mask pattern and the defect pattern are expressed as complex transmittance or reflectance functions. The expression of the defective sample is as follows: Figure 2 shown.

[0057] S defect (ξ,η)=S(ξ,η)+D(ξ,η)

[0058] Where S(ξ,η) is the complex refractive index of the sample pattern, and D(ξ,η) is the complex refractive index of the defect on the sample.

[0059] Step S2: Set the OAM structured light as the input of the coherent Fourier scattering detection optical system. The wavefront function of the OAM beam is as follows:

[0060]

[0061] Where A0 is the amplitude, λ is the wavelength of the light source, z is the beam propagation distance from the sample plane to the diffraction plane, and θ is the spiral azimuth.

[0062] In simulation, this function can be used as the input of the system. For hardware practice, a liquid crystal spatial light modulator (LC-SLM) can be used to adjust the topological charge q of the OAM beam. In this embodiment, the q value of the OAM beam is set to +1, which means that the beam rotates clockwise for one circle within the propagation range of one wavelength.

[0063] In this embodiment, the coherent Fourier scattering detection optical system is a transmission-based mask defect detection system. Figure 3 As shown, the mask defect detection system is configured in sequence as follows: a helium-neon laser 1, an attenuation plate 2, an adjustable aperture 3, a reflector 4, a beam expander 5, an adjustable aperture 6, a spatial light modulator 7, a beam splitter prism 8, a focusing lens 9, a mask sample 10 and a camera 11.

[0064] The stable coherent linear polarization output by the helium-neon laser passes through the attenuation plate 2, the adjustable aperture 3 and the reflector 4 in sequence, and then passes through the beam expander 5 and the adjustable aperture 6 to adjust the incident light beam to the appropriate power and beam diameter. The adjusted light beam continues to pass through the beam splitter prism 8 and is divided into two light beams. One light beam is not needed for detection and does not need to be reflected back to the main light path; the other light beam is incident on the spatial light modulator 7 for wavefront modulation and then reflected back along the original path. The wavefront modulated light beam passes through the beam splitter again and is divided into two light beams. One light beam returns along the original path and has no effect on the detection light path; one light beam converges to the mask sample 10 after passing through the focusing lens 9, and the outgoing wave after the focused light beam interacts with the sample to be tested continues to propagate forward to the camera 11.

[0065] Input system parameters, the system incident light wavelength is 543nm, the diffraction transmission distance is 50mm, the spot size is 20μm, and the Fraunhofer approximation conditions are:

[0066]

[0067] Substituting the system parameters into the equation, the result on the right side is 1.16 μm. The beam propagation distance is much greater than this value, so Fraunhofer diffraction can be used for calculation.

[0068] Step S3: Calculate the near-field electric field distribution after the OAM beam acts on the defective sample The calculation is as follows:

[0069]

[0070] Step S4: Use the far-field propagation model to propagate the near-field electric field distribution to the reciprocal space to obtain the far-field diffraction image Φ(x,y), which is calculated as follows:

[0071]

[0072] in, In this embodiment, the far-field propagation model is the Fraunhofer propagation model. Other far-field propagation models may also be used, such as the Fresnel propagation model, the angular spectrum propagation model, etc. For Fraunhofer diffraction, strictly speaking, after the near-field electric field distribution function is Fourier transformed, it is necessary to multiply it by But for diffraction Figure 1 Generally, we only care about the relative intensity distribution, that is, the square of the amplitude. This item does not affect the relative intensity distribution, so it is ignored.

[0073] Step S5: Move the illumination probe along the scanning direction by a step length, and repeat steps S3 and S4 until all scanning points are traversed.

[0074] This application has strict regulations on the scanning step length, and the moving step length is set to an integer multiple of the minimum period length along that direction, thereby ensuring that each time the sample and probe interaction is calculated, the relative position of the pattern in the probe does not change, only the relative position of the defect changes, to ensure that the detected asymmetric signal is entirely caused by the change in the defect position.

[0075] Step S6: Perform a second-order difference operation on the far-field diffraction intensity distribution function of all scanning points to obtain a corresponding second-order difference image. The second-order difference operation is defined as follows:

[0076] Ψ n (x, y) = Φ n-1 (x, y)-2Φ n (x,y)+Φ n+1 (x, y)

[0077] Among them, Φ n Represents the far-field intensity distribution function corresponding to the nth scanning point in the scanning path.

[0078] Step S7: Obtain an upper and lower asymmetric matrix for each coordinate point and the left-right asymmetric matrix

[0079] Using simulation methods or actually using CMOS and other detectors to receive light intensity signals will obtain discrete light intensity information, which is ultimately reflected in the form of a matrix. The asymmetric matrix solution is as follows:

[0080]

[0081] It should be noted that the left-right asymmetric matrix is ​​solved, that is, the obtained difference matrix Ψ n (x,y) and its horizontal flip matrix Ψ n (-x, y) subtracted; solve the upper and lower asymmetric matrix, that is, the difference matrix Ψ n (x,y) and its vertical flip matrix Ψ n (x,-y) subtract.

[0082] Step S8: Sum the elements of the two asymmetric matrices respectively as the asymmetric information ∑Ψ of the scanning position L-R and ∑Ψ T-B .

[0083] Step S9: Analyze the two asymmetric signals separately.

[0084] Here, it is assumed that the horizontal direction is the x-axis and the vertical direction is the y-axis. When scanning along the y-direction, if the defect just enters the scanning probe range, both asymmetric signals will show a slight jump; when the defect is close to the center position, the up-down asymmetric signal will show five consecutive positive-negative peak jumps of negative-positive-negative-positive-negative, which is manifested as a total of five peaks with opposite signs of adjacent peaks, and the left-right asymmetric signal will show four consecutive positive-negative peak jumps of negative-positive-negative-positive, which is manifested as a total of four peaks with opposite signs of adjacent peaks.

[0085] Figure 4 : is a schematic diagram of a beam wavefront carrying orbital angular momentum, q represents the topological charge, its sign represents the spiral direction, when the sign is positive, it rotates counterclockwise along the optical axis, when the sign is negative, it rotates clockwise, and its magnitude represents the number of revolutions of the wavefront around the optical axis within the propagation distance of one wavelength. This embodiment uses an OAM beam with q=+1. In addition, when q=0, there is no spiral wavefront, which is equivalent to using a Gaussian beam for illumination, as a comparison with the embodiment of the invention.

[0086] Figure 5 It is a schematic diagram of the moving path of the illumination spot on the sample to be tested. In the figure, the horizontal axis is defined as the x-axis, the vertical axis is defined as the y-axis, and the y-axis direction is defined as the scanning direction. The circular dotted line represents the illumination probe, and d is the scanning step length, which is defined as an integer multiple of the minimum period τ of the sample pattern in the scanning direction, that is, d = kτ, k = 1, 2, 3... In order to ensure that there are enough feature points to draw the feature curve, the relationship between the probe diameter D and the scanning step length d should at least ensure s represents the offset distance between the center of the probe and the center of the defect perpendicular to the scanning direction. In order to reflect the advantages of using OAM beams over the traditional method of using Gaussian beams to detect sample defects, multiple sets of comparative simulation experiments were carried out, and the scanning step size was fixed at 700nm (k was 1).

[0087] Figure 6 (a) and (b) are the cases where the probe passes through the exact center of the defect center (bias s=0), and the up-down and left-right asymmetric signals of the second-order difference diagram along the scanning path are obtained. The system parameters are the incident light wavelength λ=543nm, the diffraction transmission distance z=50mm, and the spot diameter D=20μm. The scanning mode is a one-dimensional scan along the y direction (from top to bottom). In this case, the OAM beam has five consecutive peaks of opposite signs in the up-down asymmetric signal, and the highest peak signal intensity is 0.92 times that of the Gaussian beam. The OAM beam also has four consecutive peaks of opposite signs in the left-right asymmetry, while the Gaussian beam shows no signal.

[0088] In the actual detection process, the defect position is random, so there will always be a certain offset s in the defect center position on the path where the probe center moves. Therefore, the second set of simulation experiments were conducted to compare the up and down asymmetric signals of s = 0nm, 100nm, 300nm, and 1000nm. The scanning results using OAM beam and Gaussian beam are shown as follows: Figure 7 As shown in (a), (b), (c), and (d). The peak intensities of the upper and lower asymmetric signals using the OAM beam are 0.92, 2.87, 5.57, and 2.23 times that of the Gaussian beam, respectively. It can be seen that when there is an offset between the defect position and the scanning path (usually the general case), the defect signal detected using the OAM beam is more obvious.

[0089] The upper and lower asymmetric curve can also locate the defect position. The position of the 20th scanning point among the 40 scanning points is set as the position of the defect in the center of the probe. The coordinate point corresponding to the middle peak in the upper and lower asymmetric signal is the defect coordinate. It should be noted that when performing the second-order difference, the first and last scanning points are omitted due to lack of data, so the defect position corresponds to the position of the 19th scanning point. Figure 7 The positions corresponding to the middle peaks of (a), (b), (c), and (d) are the actual defect locations. For left-right asymmetric curves, they can be used to assist in locating the defect location, which is reflected by the higher absolute value of the two middle peaks.

[0090] It can be understood that the detailed functional implementation of each of the above-mentioned units / modules can be found in the introduction of the aforementioned method embodiment, and will not be repeated here.

[0091] It should be understood that the above-mentioned device is used to execute the method in the above-mentioned embodiment. The implementation principle and technical effect of the corresponding program module in the device are similar to those described in the above-mentioned method. The working process of the device can refer to the corresponding process in the above-mentioned method, which will not be repeated here.

[0092] Based on the method in the above embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0093] Based on the method in the above embodiment, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method in the above embodiment.

[0094] It is understandable that the processor in the embodiment of the present application can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application specific integrated circuits (ASIC), field programmable gate arrays (FPGA) or other programmable logic devices, transistor logic devices, hardware components or any combination thereof. The general-purpose processor can be a microprocessor or any conventional processor.

[0095] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, and the software modules can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to a processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can be located in an ASIC.

[0096] In the above embodiments, it can be implemented in whole or in part by software, hardware, firmware or any combination thereof. When implemented using software, it can be implemented in whole or in part in the form of a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, the process or function described in the embodiment of the present application is generated in whole or in part. The computer may be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions may be stored in a computer-readable storage medium or transmitted through the computer-readable storage medium. The computer instructions may be transmitted from a website site, a computer, a server or a data center to another website site, a computer, a server or a data center by wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium may be any available medium that a computer can access or a data storage device such as a server or a data center that includes one or more available media integrated. The available medium may be a magnetic medium (e.g., a floppy disk, a hard disk, a tape), an optical medium (e.g., a DVD), or a semiconductor medium (e.g., a solid state disk (SSD)), etc.

[0097] It should be understood that the various numerical numbers involved in the embodiments of the present application are only used for the convenience of description and are not used to limit the scope of the embodiments of the present application.

[0098] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application shall be included in the scope of protection of the present application.

Claims

1. A method for detecting lithography defects based on orbital angular momentum, characterized in that: The photolithography defect detection method is applied to a coherent Fourier scattering detection system, comprising: S1. Calculate the near-field distribution function after the illumination probe interacts with the defective sample, wherein the illumination probe is an OAM beam, and the defective sample is a superposition of a sample pattern and a defect pattern; S2. Through the far-field propagation model, the near-field distribution function is transferred to the reciprocal space to obtain the far-field diffraction intensity distribution function of the defective sample; S3. Perform a second-order difference operation on the far-field diffraction intensity distribution function of the current scanning point to obtain a second-order difference image of the current scanning point; S4. Calculate the left-right asymmetric matrix and the top-bottom asymmetric matrix of the second-order difference image of the current scanning point; S5. Sum all elements of the left-right asymmetric matrix of the current scanning point to obtain the left-right asymmetric information of the current scanning point, and sum all elements of the upper-lower asymmetric matrix of the current scanning point to obtain the upper-lower asymmetric information of the current scanning point; S6. moving the probe center to the next scanning point according to the scanning step length, wherein the scanning step length is an integer multiple of the minimum period of the sample pattern in the scanning direction; S7. Repeat the above operation until the left-right asymmetric information and the top-bottom asymmetric information of all scanning points on the scanning path are obtained; S8. Combining the two asymmetric information of all scanning points, the photolithography defect detection result is obtained.

2. The photolithography defect detection method according to claim 1, characterized in that: The near field distribution function is as follows: S defect (ξ,η)=S(ξ,η)+D(ξ,η) in, represents the near-field distribution function, P(λ,q) represents the OAM beam with a spiral phase, S defect (ξ,η) represents a defective sample, S(ξ,η) represents the complex refractive index of the sample pattern, D(ξ,η) represents the complex refractive index of the defect on the sample, (ξ,η) represents the coordinates in the sample coordinate system, A0 represents the amplitude, λ represents the wavelength of the light source, z represents the beam propagation distance from the sample plane to the diffraction plane, θ represents the spiral azimuth, and q represents the topological charge of the OAM beam.

3. The photolithography defect detection method according to claim 1, characterized in that: The far-field diffraction intensity distribution function Φ(x,y) of the defective sample is as follows: in, represents the Fourier transform operation, represents the near-field distribution function, (ξ,η) represents the coordinates in the sample coordinate system, and (x,y) represents the coordinates in the diffraction plane coordinate system.

4. The photolithography defect detection method according to claim 1, characterized in that: The second-order difference image of the current scanning point is as follows: Ψ n (x,y)=Φ n-1 (x,y)-2Φ n (x,y)+Φ n+1 (x,y) Among them, n (x, y) represents the second-order difference image corresponding to the nth scanning point in the scanning path, Φ n (x, y) represents the far-field intensity distribution function corresponding to the nth scanning point in the scanning path, and (x, y) represents the coordinates in the diffraction plane coordinate system.

5. The photolithography defect detection method according to claim 1, characterized in that: The left-right asymmetric matrix and the top-bottom asymmetric matrix of the second-order difference image of the current scanning point are specifically as follows: in, represents a left-right asymmetric matrix, represents an upper and lower asymmetric matrix, Ψ n (-x,y) represents the difference matrix Ψ n The horizontal flip matrix of (x,y), Ψ n (x,-y) represents the difference matrix Ψ n The vertical flip matrix of (x,y), Ψ n (x, y) represents the second-order difference image corresponding to the nth scanning point in the scanning path.

6. The photolithography defect detection method according to claim 1, characterized in that: The two asymmetric information of all scanning points are integrated to obtain the lithography defect detection result, which is as follows: With the scanning point along the scanning direction as the horizontal axis and the asymmetric information of the scanning point as the vertical axis, if one asymmetric information has four consecutive positive and negative peak jumps, and the other asymmetric information has five consecutive positive and negative peak jumps, the scanning point position corresponding to the highest peak in the middle is determined as the defect position along the scanning direction.

7. The photolithography defect detection method according to claim 6, characterized in that: Before defect location, the left-right asymmetric information and the top-bottom asymmetric information of all scanning points are normalized.

8. The photolithography defect detection method according to claim 1, characterized in that: The illumination probe diameter D and the scanning step length d satisfy the following conditions:

9. The photolithography defect detection method according to any one of claims 1 to 8, characterized in that: The photolithography defect detection method is suitable for defect detection of photolithography substrates, masks, wafers and intermediate products.

10. A lithography defect detection system based on orbital angular momentum, characterized in that: comprising at least one processor and at least one memory; The at least one memory is used to store computer instructions; The at least one processor is used to execute at least part of the computer instructions to implement the lithography defect detection method according to any one of claims 1 to 9.

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