An optical lithography defect detection method and system based on orbital angular momentum

Abstract

The application belongs to the technical field of photolithography detection, and specifically discloses a photolithography defect detection method and system based on orbital angular momentum. According to the application, an OAM light beam is used to replace a Gaussian light beam for illumination, and the defect position is determined by analyzing the far-field asymmetric signal generated along the scanning path. Since the far-field asymmetric signal caused by the defect under the illumination of the OAM light beam is more obvious, the signal-to-noise ratio can be improved by 5.57 times at most, and the sensitivity of defect detection is significantly improved. According to the application, the OAM light beam is used for illumination, the scanning step is an integer multiple of the minimum period of the sample pattern in the scanning direction, and the left and right and the upper and lower asymmetric information of these specific scanning points is comprehensively used to determine the coordinate position of the defect, so that more available information is provided and the false detection rate is reduced. The difference between the diffraction images corresponding to the adjacent scanning points of the sample with defects is processed, and the diffraction image difference of the sample without defects is not needed, so that the position error is small in actual implementation, and the sample pattern does not need to be symmetrical, and the applicability is stronger.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of photolithography detection, and more particularly, to a photolithography defect detection method and system based on orbital angular momentum. BACKGROUND

[0002] In the field of nanostructure defect detection, especially the defect detection of photolithography substrates, masks and wafers, visible light or deep ultraviolet light is usually used for defect inspection. For technology nodes below 10 nm, extreme ultraviolet (EUV) or electron beam illumination has been used. At present, the production of integrated circuit (IC) devices and related equipment has been increasing year by year, and people hope that the detection equipment can detect intermediate products such as masks and wafers with high precision requirements non-destructively and at high speed, and at the same time, the positioning and classification of defects and accuracy are also put forward with higher and higher requirements. Optical far-field detection technology has the advantages of simple and reliable system, breaking through the limitation of imaging elements and high throughput. Among them, the coherent Fourier scattering method (CFS) usually uses a coherent laser with a planar amplitude of Gaussian distribution to irradiate the sample to be tested, and uses a COMS, QD or other detector to obtain the diffraction field intensity information in reciprocal space. However, as the critical dimension of IC structure continues to decrease, the size of the defects required to be detected has been pushed to the sub-deep wavelength scale. Limited by Rayleigh scattering, the scattering information caused by defects is gradually overwhelmed by noise, resulting in a significant decrease in signal-to-noise ratio and a decrease in defect detection sensitivity. The traditional coherent scattering measurement method gradually encounters technical bottlenecks.

[0003] In recent years, traditional optical detection combined with various new technologies has provided more possibilities for the field of defect detection. Among them, the detection method based on orbital angular momentum (Orbital Angular Momentum, OAM) has gradually attracted people's attention. OAM beam is a new type of structured beam with special phase distribution, which is different from polarized beam and Gaussian beam. OAM beam has a special spiral wave front, and it is this spiral phase wave front that carries a specific orbital angular momentum. It has been partially applied in optical sensing enhancement and high-bandwidth communication. Using OAM beam for optical detection is similar to a special illumination configuration applied to bright field defect detection. Although it is still limited by Rayleigh scattering, due to its special spiral phase, it can cause greater frequency shift of the defect scattering field in reciprocal space. The light intensity distribution after differential processing can produce greater asymmetry, thereby improving the signal-to-noise ratio of detection. Overall, defect detection based on OAM beam illumination is a very promising technology.

[0004] In 2021, BIN WANG et al. proposed a defect detection strategy using OAM beams as probes in coherent Fourier scattering measurement. As long as the pattern structure has reflection symmetry, the OAM-based CFS will be unique because it does not rely on the reference to the pre-constructed database. However, this method is based on differential processing with a defect-free sample. In the actual detection process, under the condition of a large number of scanning points, the large cumulative error is easy to cause the pattern in the probe to be difficult to align, and the displacement table needs to have high position accuracy. In the model-free method, the sample pattern needs to have a certain symmetry, and the universality is not high. SUMMARY

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

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

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

[0008] S2. Transfer the near-field distribution function to the reciprocal space by a far-field propagation model to obtain the far-field diffraction intensity distribution function of the defect-containing 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 up-down 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 up-down asymmetric matrix of the current scanning point to obtain the up-down asymmetric information of the current scanning point;

[0012] S6. Move the probe center to the next scanning point by a scanning step, wherein the scanning step 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 up-down asymmetric information of all scanning points on the scanning path are obtained;

[0014] S8. Synthesizing two kinds of asymmetric information of all scanning points to obtain the lithographic defect detection result.

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

[0016]

[0017] S defect (ξ,η)=S(ξ,η)+D(ξ,η)

[0018]

[0019] wherein, represents the near-field distribution function, P(λ,q) represents the OAM beam with a spiral phase, S defect (η,η) represents a sample containing defects, S(η,η) represents the complex refractive index of the sample pattern, D(ξ,η) represents the complex refractive index of the defects 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 angle, and q represents the topological charge number of the OAM beam.

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

[0021]

[0022] wherein, 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] wherein, Ψ 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 up-down asymmetric matrix of the second-order difference image of the current scanning point are specifically as follows:

[0027]

[0028] wherein, represents a left-right asymmetric matrix, represents an up-down asymmetric matrix, Ψ n (-x, y) represents a difference matrix Ψ n (x, y) represents a horizontal flip matrix of Ψ n (x, -y) represents a difference matrix Ψ n (x, y) represents a vertical flip matrix of Ψ n (x, y) represents a 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 a photolithography defect detection result, specifically as follows:

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

[0031] Preferably, before defect positioning, the left-right asymmetric information and the up-down asymmetric information of all scanning points are normalized respectively.

[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 suitable for defect detection of photolithography substrates, masks, wafers and intermediate products.

[0034] To achieve the above-mentioned purposes, in a second aspect, the present application provides a photolithography 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 realize the photolithography defect detection method of the first aspect.

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

[0038] (1) Compared with the defect detection method using traditional Gaussian beam illumination, the application provides an optical lithography defect detection method and system based on orbital angular momentum, uses an OAM beam to replace the traditional Gaussian beam illumination, determines the defect position by analyzing the far-field asymmetric signal generated along the scanning path, and since the far-field asymmetric signal caused by the defect under the OAM beam illumination is more obvious, the signal-to-noise ratio can be improved by 5.57 times at most, and the sensitivity of defect detection is significantly improved; the application uses OAM beam illumination, the scanning step is an integer multiple of the minimum period of the sample pattern in the scanning direction, and the left and right and upper and lower two kinds of asymmetric information of these specific scanning points are comprehensively determined to determine the coordinate position of the defect, more information is available, and the false detection rate is reduced. The positioning accuracy is further improved under the double positioning of the two kinds of asymmetric information.

[0039] (2) Compared with the existing defect detection method based on OAM beam illumination, the application provides an optical lithography defect detection method and system based on orbital angular momentum, which differentiates the diffraction images corresponding to adjacent scanning points of the sample containing defects, without the need for diffraction image differentiation with a sample without defects, so that the position error is small in actual implementation, and the sample pattern does not need to have symmetry, and the applicability is stronger. BRIEF DESCRIPTION OF DRAWINGS

[0040] Figure 1 is a flowchart of an optical lithography defect detection method based on orbital angular momentum provided by an embodiment of the application.

[0041] Figure 2 is a schematic diagram of a sample containing defects used in the simulation process provided by an embodiment of the application.

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

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

[0044] Figure 5 is a schematic diagram of the motion trajectory of a scanned sample provided by an embodiment of the application.

[0045] Figure 6 is a schematic diagram of two kinds of asymmetric signals of OAM beam illumination and Gaussian beam illumination provided by an embodiment of the application, wherein (a) is upper and lower asymmetry, and (b) is left and 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 7FIG. 1 is a contrast diagram of up-down asymmetry signals caused by defects detected by using OAM beams and Gaussian beams under different bias distances s provided by an embodiment 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] In all the drawings, the same reference signs are used to denote the same elements or structures, wherein:

[0048] 1-He-Ne laser, 2-attenuation plate, 3-adjustable diaphragm, 4-reflection mirror, 5-beam expander, 6-adjustable diaphragm, 7-space light modulator, 8-beam splitting prism, 9-focusing lens, 10-mask sample, 11-camera. DETAILED DESCRIPTION

[0049] In order to make the objects, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and should not be used to limit the present application.

[0050] The term "and / or" used herein is a description of an association relationship between associated objects, which means that there can be three relationships, for example, A and / or B can mean that A exists alone, A and B exist together, and B exists alone. The symbol " / " in this paper represents the relationship of or, for example, A / B represents A or B.

[0051] The terms "first" and "second" and the like in the description and claims herein are used to distinguish different objects, and are not used to describe a specific order of the objects. For example, the first response message and the second response message are used to distinguish different response messages, and are not used to describe a specific order of the response messages.

[0052] In the embodiments of the present application, the words "exemplary" or "for example" are used to mean serving as an example, instance, or illustration. Any embodiment or design presented as "exemplary" or "for example" in the embodiments of the present application should not be interpreted as being more preferred or advantageous than other embodiments or design solutions. Rather, the use of "exemplary" or "for example" is intended to present concepts in a concrete manner.

[0053] In the description of the embodiments of the present application, unless otherwise specified, "a plurality of" means two or more, for example, a plurality of processing units means two or more processing units, and the like; a plurality of elements means two or more elements, and the like.

[0054] Next, the technical solutions provided in the embodiments of this application will be described.

[0055] like Figure 1 As shown, this application provides a photolithographic defect detection method based on orbital angular momentum. This method is applied to a coherent Fourier scattering detection optical system and includes:

[0056] Step S1: Set the sample pattern. In this embodiment, the sample pattern is set as a periodic pattern composed of a pair of nanolines. Each nanoline is 2μm long and 200nm wide, with a spacing of 100nm between the two lines, serving as the defect-free pattern S(ξ,η). Then, a defect pattern D(ξ,η) is added to the sample, which is a square pattern with both length and width of 100nm. The mask pattern and the defect pattern are expressed as complex transmittance or reflectance functions. The expression for the sample with defects is as follows, and the pattern is shown in the figure. Figure 2 As 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 defects on the sample.

[0059] Step S2: Set the OAM structured light as the input to 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 helical azimuth angle.

[0062] In simulation, this function can be used as the system input. For hardware implementation, 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, indicating that the beam rotates clockwise one revolution within one wavelength of its propagation range.

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

[0064] The coherent linearly polarized light outputted by the helium-neon laser stably passes through the attenuator 2, the adjustable diaphragm 3 and the mirror 4 in turn, passes through the beam expander 5 and the adjustable diaphragm 6 to adjust the incident light beam to a suitable power and beam diameter. The adjusted light beam continues to be divided into two light beams after passing through the beam splitter prism 8, one of which is not needed when detecting and does not need to be reflected back to the main light path; the other light beam is normally incident on the spatial light modulator 7 for wavefront modulation and then reflected back in the original path. The light beam after wavefront modulation is again divided into two light beams after passing through the beam splitter, one of which returns to the original path and has no effect on the detection light path; the other light beam converges to the mask sample 10 after passing through the focusing lens 9, and the outgoing wave after the focusing light beam interacts with the sample continues to propagate to the camera 11.

[0065] The system parameters are input, the wavelength of the incident light of the system is 543 nm, the transmission distance of diffraction is 50 mm, and the spot size is 20 μm. According to the Fraunhofer approximation condition:

[0066]

[0067] The calculation result of the right side of the formula is 1.16 μm by substituting the system parameters, and the beam propagation distance is much larger than the value, so the Fraunhofer diffraction can be used for calculation.

[0068] Step S3: Calculate the near-field electric field distribution of the OAM light beam after acting on the sample containing defects The calculation method is as follows:

[0069]

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

[0071]

[0072] Wherein, represents the Fourier transform operation. In this embodiment, the far-field propagation model is the Fraunhofer propagation model, and other far-field propagation models such as the Fresnel propagation model, the angular spectrum propagation model, etc. can also be used. For Fraunhofer diffraction, the Fourier transform of the near-field electric field distribution function is strictly multiplied by But for diffraction Figure 1 Generally, only the relative intensity distribution is concerned, that is, the square of the amplitude, and this term does not affect the relative intensity distribution, so it is omitted.

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

[0074] The present application has strict regulations for the step length of scanning. The moving step length is set as an integer multiple of the minimum period length in the direction, so as to ensure that the relative position of the pattern in the probe does not change when the sample and the probe interact each time, and only the relative position of the defect changes, so as to ensure that the detected asymmetric signal is completely caused by the change of the defect position.

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

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

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

[0078] Step S7: Obtain the up-down asymmetric matrix and the left-right asymmetric matrix

[0079] Using the simulation method or actually using the CMOS detector to receive the light intensity signal will obtain the discretized light intensity information, which is finally embodied in the form of a matrix. The asymmetric matrix solving method is as follows:

[0080]

[0081] It should be noted that the left-right asymmetric matrix is solved, that is, the difference matrix Ψ n (x, y) is subtracted from its horizontal flip matrix Ψ n (-x, y); the up-down asymmetric matrix is solved, that is, the difference matrix Ψ n (x, y) is subtracted from its vertical flip matrix Ψ n (x, -y).

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

[0083] Step S9: Analyze the two kinds of asymmetric signals respectively.

[0084] 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 have a small jump; when the defect is close to the center position, the up-down asymmetric signal will have five consecutive positive-negative peak jumps, showing a total of five adjacent peak values with opposite signs, and the left-right asymmetric signal will have four consecutive positive-negative peak jumps, showing a total of four adjacent peak values with opposite signs.

[0085] Figure 4 is a schematic diagram of a beam wavefront carrying orbital angular momentum, q represents the topological charge number, and its sign represents the spiral direction. When the sign is positive, it rotates counterclockwise along the optical axis, and when the sign is negative, it rotates clockwise. The size represents the number of revolutions of the wavefront around the optical axis within one wavelength of propagation distance. The OAM beam used in this embodiment is 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 application.

[0086] Figure 5 is a schematic diagram of the moving path of the illumination spot on the sample to be measured. In the figure, the horizontal axis is defined as the x-axis and the vertical axis is defined as the y-axis, and the y-axis direction is taken as the scanning direction. The circular dashed line represents the illumination probe, and d is the scanning step, which is defined as an integer multiple of the minimum period τ of the sample pattern in the scanning direction, i.e. d = kτ, k = 1, 2, 3… To ensure that there are enough feature points to draw the feature curve, the relationship between the probe diameter D and the scanning step d should at least ensure that s represents the offset distance of the probe center position from the defect center position in the direction perpendicular to the scanning direction. In order to demonstrate the advantages of using OAM beams compared to traditional Gaussian beams for detecting sample defects, a number of comparative simulation experiments were conducted, with the scanning step fixed at 700 nm (k = 1).

[0087] Figure 6 (a) and (b) in the middle are the up-down and left-right asymmetric signals obtained by passing the defect center position through the center of the probe (offset s = 0) along the scanning path. The system parameters are an incident light wavelength λ = 543 nm, a diffraction transmission distance z = 50 mm, and a spot diameter D = 20 μm. The scanning method is one-dimensional scanning along the y direction (from top to bottom). In this case, the OAM beam in the up-down asymmetric signal has five consecutive peaks with opposite signs, and the highest peak signal strength is 0.92 times that of the Gaussian beam. The OAM beam in the left-right asymmetric signal also has four consecutive peaks with opposite signs, while the Gaussian beam shows no signal.

[0088] In the actual detection process, the defect position has randomness, so the defect center position will always have a certain bias s on the path of the probe center movement, so the second group of simulation experiments are carried out, and the up-down asymmetric signals of s=0nm, 100nm, 300nm and 1000nm are compared, and the scanning results of the OAM light beam and the Gaussian light beam are shown in Figs. Figure 7 The peak intensity of the up-down asymmetric signal using the OAM light beam is 0.92 times, 2.87 times, 5.57 times and 2.23 times of that of the Gaussian light beam, respectively. It can be seen that in the case of bias between the defect position and the scanning path (which is also the general case), the defect signal detected using the OAM light beam is more obvious.

[0089] The up-down asymmetric curve can also locate the defect position, and the position of the 20th scanning point in the 40 scanning points is set as the position of the defect in the center of the probe, and the coordinate point corresponding to the middle peak value in the up-down asymmetric signal is the defect coordinate. It should be noted that in the second-order difference, the first scanning point and the last scanning point are omitted due to lack of data, so the defect position corresponds to the position of the 19th scanning point, Figure 7 The position corresponding to the middle peak value in Figs. (a), (b), (c) and (d) is the actual defect position. For the left-right asymmetric curve, it can be used to assist in locating the defect position, which is embodied in the higher absolute value of the middle two peak values.

[0090] It can be understood that the detailed function implementation of each unit / module can be referred to the description in the foregoing method embodiments, which will not be repeated here.

[0091] It should be understood that the above device is used to execute the method in the above embodiments, and the corresponding program modules in the device have similar implementation principles and technical effects to those described in the above method. The working process of the device can be referred to the corresponding process in the above method, which will not be repeated here.

[0092] Based on the method in the above embodiments, the embodiment of the present application provides a computer readable storage medium, which stores a computer program, when the computer program runs on the processor, so that the processor executes the method in the above embodiments.

[0093] Based on the method in the above embodiments, the embodiment of the present application provides a computer program product, when the computer program product runs on the processor, so that the processor executes the method in the above embodiments.

[0094] It can be understood that the processor in the embodiments of the present application can be a central processing unit (CPU), and can also be 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 in the form of 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 a random access memory (RAM), a flash memory, a read-only memory (ROM), a programmable read-only memory (PROM), an erasable PROM (EPROM), an electrically EPROM (EEPROM), a register, a hard disk, a mobile hard disk, a CD-ROM or any other form of storage medium well known in the art. An exemplary storage medium is coupled to the 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 an integral part of the processor. The processor and the storage medium can be located in an ASIC.

[0096] In the above embodiments, all or part of the embodiments can be implemented by software, hardware, firmware or any combination thereof. When implemented by software, all or part of the embodiments can be implemented 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, all or part of the processes or functions described in the embodiments of the present application are generated. The computer can be a general purpose computer, a special purpose computer, a computer network, or other programmable apparatus. The computer instructions can be stored in or transmitted by a computer readable storage medium. The computer instructions can be transmitted from one website, computer, server or data center to another website, computer, server or data center through a wired (such as coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (such as infrared, wireless, microwave, etc.) manner. The computer readable storage medium can be any available medium accessible by a computer or a data storage device such as a server, data center, etc. integrated with one or more available media sets. The available media can be a magnetic medium (such as a floppy disk, a hard disk, a magnetic tape), an optical medium (such as a DVD), or a semiconductor medium (such as a solid state disk (SSD)), etc.

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

[0098] Those skilled in the art easily understand that the above only describes the preferred embodiments of the present application and is not used to limit the present application. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application should be included in the protection scope of the present application.

Claims

1. A method for detecting a lithographic defect based on orbital angular momentum, characterized in that, The photolithography defect detection method is applied to a coherent Fourier scattering detection system, and comprises the following steps: S1. calculating a near-field distribution function after an illumination probe and a sample containing defects interact, wherein the illumination probe is an OAM light beam, and the sample containing defects is a superposition of a sample pattern and a defect pattern; S2. transmitting the near-field distribution function to reciprocal space through a far-field propagation model to obtain a far-field diffraction intensity distribution function of the sample containing defects; S3. performing 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. calculating a left-right asymmetry matrix and an up-down asymmetry matrix of the second-order difference image of the current scanning point; S5. summing all elements of the left-right asymmetry matrix of the current scanning point to obtain left-right asymmetry information of the current scanning point, and summing all elements of the up-down asymmetry matrix of the current scanning point to obtain up-down asymmetry information of the current scanning point; S6. moving the probe center to the next scanning point by a scanning step, wherein the scanning step is an integer multiple of the minimum period of the sample pattern in the scanning direction; S7. repeating the above operations until the left-right asymmetry information and the up-down asymmetry information of all scanning points on the scanning path are obtained; S8. synthesizing the two kinds of asymmetry information of all scanning points to obtain a photolithography defect detection result; The near-field distribution function is specifically as follows: wherein, represents a near-field distribution function, represents an OAM beam with a helical phase, represents a sample with defects, represents a complex refractive index of a sample pattern, represents a complex refractive index of a defect on a sample, represents a coordinate in a sample coordinate system, represents an amplitude, represents a light source wavelength, represents a beam propagation distance from a sample plane to a diffraction plane, represents a helical azimuthal angle, represents a topological charge of an OAM beam.

2. The method of photolithography defect detection of claim 1, wherein, The far field diffraction intensity distribution function of the sample containing defects In detail as follows: wherein denotes a Fourier transform operation, denotes a coordinate in the diffraction plane coordinate system.

3. The method of photolithography defect detection of claim 1, wherein, The second-order difference image of the current scanning point is specifically as follows: wherein, represents a second-order difference image corresponding to the scanning point in the scanning path, represents a second-order difference image corresponding to the scanning point in the scanning path, represents a coordinate in a diffraction plane coordinate system.

4. The method of photolithography defect detection of claim 1, wherein, The left-right asymmetry matrix and the up-down asymmetry matrix of the second-order difference image of the current scanning point are specifically as follows: wherein, denotes a left-right asymmetric matrix, denotes an up-down asymmetric matrix, denotes a difference matrix a horizontal flipping matrix of the difference matrix, denotes a difference matrix a vertical flipping matrix of the difference matrix, denotes a second-order difference image corresponding to the th scanning point in the scanning path, denotes a coordinate in the diffraction plane coordinate system.

5. The method of photolithography defect detection of claim 1, wherein, The synthesis of the two kinds of asymmetry information of all scanning points to obtain a photolithography defect detection result is specifically as follows: Taking the scanning points along the scanning direction as the horizontal axis and the asymmetry information of the scanning points as the vertical axis, if one kind of asymmetry information appears four consecutive positive and negative peak value jumps, and the other kind of asymmetry information appears five consecutive positive and negative peak value jumps, the scanning point position corresponding to the highest peak value in the middle is determined as the defect position along the scanning direction.

6. The method of photolithography defect detection of claim 5, wherein, Before defect positioning, the left-right asymmetry information and the up-down asymmetry information of all scanning points are normalized respectively.

7. The method of photolithography defect detection of claim 1, wherein, The illumination probe diameter And the scan step length Satisfy the following condition: .

8. The method of detecting photolithography defects according to any one of claims 1 to 7, wherein, The photolithography defect detection method is suitable for defect detection of photolithography substrates, masks, wafers and intermediate products.

9. An orbital angular momentum based lithography defect detection system, characterized in that, The system comprises 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 realize the photolithography defect detection method in any one of claims 1 to 8.

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