Automatic calibration method for electron beam quantity detection equipment

Abstract

The invention discloses an automatic calibration method for electron beam quantity detection equipment, which realizes one-key high-precision automatic calibration through a preset software process and algorithm based on image recognition, calibration closed loop and mutual verification evaluation, and meets the use scene requirements of different electron beam machines.

Description

Technical Field

[0001] This invention belongs to the field of high-end manufacturing technology, specifically, it relates to an automatic calibration method for electron beam quantity detection equipment. Background Technology

[0002] Electron beam metrology equipment is an indispensable key metrology and inspection tool in high-end manufacturing, especially in semiconductor chip manufacturing. It is a high-precision instrument that uses a focused electron beam as a "probe" to scan the sample surface. By detecting various signals generated by the interaction between electrons and the sample (such as secondary electrons and backscattered electrons), it quantitatively measures the microstructure, size, composition, and electrical properties of the sample and inspects for defects. Its core working principle is based on scanning electron microscopy (SEM) technology, and more advanced functions have been developed on this basis. In a vacuum environment, an electron gun (usually thermal field emission or Schottky emission) emits electrons. The emitted electrons are focused by a series of electromagnetic lenses into an extremely fine electron probe (the beam spot diameter can reach the nanometer scale). Then, a scanning coil controls the electron beam to perform a grating scan on the sample surface. When the high-energy electron beam bombards the sample surface, it excites various signals. The detector receives these signals, converts them into electrical signals, amplifies them, and synchronizes them with the position signal of the scanning system, ultimately forming a high-resolution grayscale image on a computer screen. Electron beam metrology equipment is the cornerstone supporting the development of advanced processes and the improvement of yield. During the R&D phase, electron beams are used for the development and characterization of new processes and materials. In mass production, they enable process control, real-time monitoring of die and overlay accuracy, and timely adjustment of process parameters. When yield issues arise, electron beams are the "ultimate tool" for physical failure analysis, locating and classifying specific defects, and also detecting potential electrical defects.

[0003] Traditional electron beam metrology calibration methods typically present a series of sequential steps, but it is essentially a multi-step, multi-parameter iterative and coupled process. A typical procedure includes: beam alignment, astigmatism correction, focus correction, scan field distortion correction, and beam intensity calibration. However, this single-step sequential approach faces several serious problems, which are also the main bottlenecks of current calibration technology: Parameter coupling issues. Parameters in electro-optical systems are highly coupled. For example, adjusting the scan field distortion (a deflection parameter) may slightly affect the beam spot shape (a lens parameter), thereby disrupting previously completed focusing and astigmatism corrections. In a serial workflow, a later step may invalidate the calibration results of a previous step.

[0004] There is a lack of a globally optimal solution. Serial calibration is like "blind men touching an elephant," where each step seeks only the optimality of a single parameter (local optimum), but cannot guarantee that the entire system is in the best state (global optimum) when all parameters are combined.

[0005] Inefficient. Due to parameter coupling, multiple rounds of repeated calibration may be required to obtain a barely usable result, which is very time-consuming.

[0006] It relies heavily on operator experience. When automated processes fail to achieve satisfactory results, they depend heavily on the intuition and experience of senior engineers for manual fine-tuning, resulting in low repeatability and standardization. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide an automatic calibration method for electron beam quantity detection equipment.

[0008] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: an automatic calibration method for an electron beam quantity detection device. Step 1: Calibration begins. First, switch to OM mode, transfer the product, identify two points on the same line using the image recognition tool, and transfer the sheet in sequence using the aligner for correction. Establish a precise sample coordinate system, providing an accurate and unified spatial reference for all subsequent electron beam calibration steps. This eliminates systematic errors introduced by sample placement deviations and stage movement errors, and is the foundation for achieving high-precision and repeatable calibration.

[0009] Step 2: Re-input the product with the pattern. The image recognition will move the two points on the same line to the center respectively, and perform OM coordinate system calibration and OM center calibration. Step 3: Based on product size and image recognition, find the edges of the three size points, move to the center of the image, and calculate the origin of the wafer coordinate system; Step 4: Based on image recognition, move the electric aperture in the X and Y directions at the set step size to find the position of the light spot and locate the coordinate position of the standard and Faraday cup calibration. Step 5: Switch to SEM mode, turn off other power drives, remove the motorized variable aperture, and keep only three electromagnetic lenses, namely the first-stage condenser coil, the second-stage condenser coil, and the objective lens coil. The swing coil current is used to check the mechanical alignment of the electromagnetic lenses and detector based on the image spot, so that the maximum spot is centered, while concentric scaling and brightness changes are performed. Step 6: Insert the motorized variable aperture, search for the aperture position, center the aperture spot, and check the beam spot center position and brightness distribution histogram through image recognition to ensure that the image changes concentrically when the first-stage condenser coil is swung, the image is centered without shift when the second-stage condenser coil is swung, and the image is concentrically scaled when the objective lens coil is swung. Step 7: Beam calibration. Under the current current of the first-stage condenser coil, move to the Faraday cup sample stage coordinate position, read the current beam current value in real time, and then move left and right at the current coordinate position to find the position of maximum beam current and save it as Faraday cup coordinates. Subsequently, according to the configuration file, gradually change the current value of the first-stage condenser coil, record the beam current value, plot the calibration curve and save it. Based on the beam current set by the current quantity detection, issue the corresponding first-stage condenser coil 4 current. By automatically searching for the aperture position and "swinging" the lens current, the physical alignment of the electron beam with the aperture, lens, and detector is verified and ensured. This directly reduces astigmatism and distortion, which is a prerequisite for obtaining high-quality images; By automatically scanning the CL1 current and measuring the beam current, precise beam current control was established, ensuring that the required beam current intensity can be obtained quickly and accurately in different application scenarios.

[0010] Step 8: Perform detector brightness and contrast algorithms, optimize detector gain and signal ratio distribution, and adjust sampling parameters. Find the best image parameters through image resolution and pixel distribution histogram; optimize signal reception to make image features easiest to identify and process.

[0011] Step 9: In a small field of view, the focusing, astigmatism correction, and magnetic deflection algorithms are executed alternately to find the parameters that produce the clearest image quality. At this point, the image is clear, without trailing or elongation, and without image wobbling. This is the core step in solving the parameter coupling problem. It is no longer executed sequentially, but rather "alternatingly," meaning that the system iteratively optimizes these highly coupled parameters, ultimately finding a combination of parameters that makes the overall image clearest, thus approximating the global optimum.

[0012] Step 10: In a large field of view, detector shadows often occur due to the central aperture of the lower detector. By dynamically adjusting the detector's scaling parameters, signals that miss the central aperture of the lower detector are deflected to the upper detector for supplementary collection. The signals from the upper and lower detectors are combined, and the detector shadows are identified through image recognition. An appropriate electromagnetic field deflection direction is selected until the SEM image is uniform and the pixel distribution histogram is close to a normal distribution. This solves the image shadow problem in a large field of view, improves the image uniformity and signal-to-noise ratio, and lays the foundation for accurate measurement in a large field of view.

[0013] Step 11: After the automatic centering and optimization of the SEM image is completed, at the standard sample position, the OM-SEM coordinate difference is corrected based on the OM and SEM images with the same pattern by image feature recognition; the coordinate system of optical positioning and electron beam measurement is unified, and seamless connection and accurate positioning between the two modes are realized.

[0014] Step 12: At the feature pattern, perform pixel size calibration. At the same time, by offsetting the image, generate calibration coefficients in the X and Y directions of the image, perform orthogonality correction of the deflection system, and save the configuration. (Pixel size, deflection gain, orthogonality calibration) directly calibrates the measurement "ruler" to ensure that the pixel size and geometry (such as orthogonality) of the image are accurate at different positions and magnifications.

[0015] Step 13: Select Z Level positions at different heights, and automatically calibrate the height-focus and image scaling factors based on the pattern on the wafer; establish an automatic correlation model between sample height and focusing current and image scaling factor, so that the system can automatically track and maintain optimal focus and dimensional accuracy when measuring at different heights, which greatly improves the ease of use and measurement efficiency of the equipment.

[0016] Step 14: Finally, the repeatability and stability of the automatic verification measurement are tested on the wafer, and a complete calibration report is generated.

[0017] Automated repeatability and stability tests are used to quantitatively evaluate the overall effectiveness of the calibration and generate a standard report. This provides objective evidence of calibration quality and reduces the subjectivity of human judgment.

[0018] Furthermore, step 4 specifically includes: Automatic calibration of the motorized aperture verifies the mechanical alignment of the primary condenser coil, the secondary condenser coil, and the objective lens coil through the large-aperture APT1. Then, switching to the small-aperture APT2, the system automatically searches to center the beam spot. When the primary condenser coil is oscillated, the image exhibits concentric brightness changes; when the secondary condenser coil is oscillated, the image remains centered without shift; and when the objective lens coil is oscillated, the image scales concentrically. After successful image verification, beam calibration is performed, fitting the beam current Ip and the primary condenser coil current curves. Subsequently, after focusing, astigmatism correction, magnetic deflection alignment, and automatic brightness and contrast adjustments, the deflection gain, linearity, and orthogonality are evaluated. Finally, selecting different Z-level positions based on the pattern on the product, the height-focus and image scaling factors are automatically calibrated.

[0019] Furthermore, in step 5, in the switching mode, the electron beam gate and electron gun valve are switched on and off, the current of the first-stage condenser coil is set, and the CL1-Ip curve is obtained. Then, SEM image algorithms are used to adjust brightness and contrast, focus, astigmatism, magnetic deflection alignment, and automatic pixel size calibration. The SEM image algorithms include: Z-Level height automatic calibration records data including X and Y coordinates, Z-Level height, focus current (OLFine), and current pixel size (P). (X, Y, Z, OLFine, P) Record the position information of two different patterns. (X0, Y0, Z0, OLFine0, P0) & (X1, Y1, Z1, OLFine1, P1) Focus on automatic tracking: Focusing coefficient Kf = (OLFine1 - OLFine0) / (Z1 - Z0), OLfine=Kf*(Z-Z0)+OLfine0=Kf*Z+(OLfine0-Kf*Z0)=Kf*Z+Bf (slope and intercept). Automatic pixel size tracking: Pixel size factor Kp=(P1-P0) / (Z1-Z0), P = Kp*(Z-Z0) + P0 = Kp*Z + (P0-Kp*Z0) = Kp*Z + Bp (slope and intercept).

[0020] Furthermore, the deflection system correction in step 12, the image offset step, includes: The system includes a scanning voltage of 2Vscan for the field of view, a reserved voltage of 2Voffset for electron beam offset, a DC bias voltage of 2Vdc, and a nonlinear voltage range. The maximum linear range includes the scanning voltage of the field of view, the electron beam offset voltage, and the DC bias voltage. The pixel size is determined by the intensity of the deflection excitation signal. Calibration is achieved by establishing a correspondence between deflection gain and pixel size, judging linearity through fitting, and performing reverse lookup through interpolation. The electron beam is offset to different positions using the reserved scanning offset voltage Voffset. The moving distance is calculated through image recognition, and the pixel sizes in the X and Y directions are calculated separately. Their proportions and angles are compared to evaluate orthogonality.

[0021] A computer-readable medium having a computer program stored thereon, which, when executed by a processor, implements the steps of an automatic calibration method for an electron beam quantity detection device.

[0022] Compared with the prior art, the advantages of the present invention include: (1) The present invention provides an automatic calibration method for an electron beam quantity detection device, which is based on image recognition and calibration closed loop, and verifies and evaluates each other. Through preset software process and algorithm, it realizes one-click high-precision automatic calibration to meet the needs of different electron beam equipment usage scenarios. (2) The automatic calibration method for electron beam measurement equipment provided by this invention enables one-click execution of the entire process, from wafer alignment, optical path alignment, image optimization to dimensional calibration. This greatly shortens the calibration time and solves the problem of low efficiency in traditional methods. At the same time, it minimizes the reliance on the operator's personal experience and intuition, making the calibration results highly repeatable and standardized, and enabling different equipment and different operators to obtain stable and consistent performance. (3) The automatic calibration method for electron beam quantity detection equipment provided by this invention ensures that the equipment is in optimal working condition through refined automatic management of the entire chain, from mechanical alignment and beam current control to image optimization and size calibration. For example... Figure 12 and 13 As shown, the calibrated SEM images show significant improvements in resolution, contrast, and geometric fidelity (orthogonality), thus directly supporting the core mission of the metrology equipment—to provide high-precision metrology and reliable defect detection results. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 This is a schematic diagram of an existing electron beam quantity detection device. Figure 2 This is a flowchart of the automatic calibration method for the direct electron beam quantity detection device in this invention; Figure 3 This is a diagram showing the deflection scanning waveform distribution of the automatic calibration method for the direct electron beam quantity detection device in this invention. Figure 4 This is a flowchart of the automatic alignment process of the electric aperture in the automatic calibration method of the electron beam quantity detection device in this invention. Figure 5 This is a flowchart of the automatic calibration process for the Faraday cup beam in the automatic calibration method for the electron beam quantity detection device of the present invention. Figure 6 This is a flowchart of the automatic calibration process for EM images in the automatic calibration method for electron beam quantity detection equipment of the present invention. Figure 7 This is a SEM image of the automatic alignment of the motorized aperture in the automatic calibration method of the direct electron beam quantity detection device in this invention. Figure 8 This is a Faraday cup beam calibration curve of the automatic calibration method for the electron beam quantity detection equipment in this invention; Figure 9 This is a gain calibration diagram of the deflection system in the automatic calibration method for the direct electron beam quantity detection device of the present invention; Figure 10 This is a calibration diagram showing the linearity and orthogonality of the deflection system in the automatic calibration method for the direct electron beam quantity detection device of the present invention. Figure 11 These are focusing and tracking diagrams at different Z-heights in the automatic calibration method of the electron beam quantity detection device of this invention. Figure 12 This is a SEM image of the automatic calibration method for the direct electron beam quantity detection device in this invention before calibration; Figure 13 This is a calibrated SEM image of the automatic calibration method for electron beam quantity detection equipment in this invention.

[0025] Figure label: 1. Electron source; 2. Electron beam; 3. Anode; 4. First-stage condenser coil; 5. Motorized variable aperture; 6. Second-stage condenser coil; 7. Astigmatism correction coil; 8. Magnetic deflection coil; 9. Detector; 10. Linear filter; 11. Lower detector; 12. Deflection system; 13. Objective lens coil; 14. Z-level sensor; 15. Optical camera; 16. Wafer; 17. Scattered signal. Detailed Implementation

[0026] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The technical solution, its implementation process, and principles will be further explained below with reference to the accompanying drawings and specific implementation examples in the embodiments of this application.

[0027] It should be noted that the embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention. The described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, the present invention covers any substitutions, modifications, equivalent methods and solutions made on the spirit, principles and scope of the present invention as defined by the claims. All other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0028] In the description of this application, the terms "first," "second," "third," and similar words do not indicate any order, quantity, or importance, but are merely used to distinguish different components. Similarly, the terms "a" or "one," and similar words, do not indicate a quantity limitation, but rather indicate the presence of at least one. The terms "comprising" or "including," and similar words, mean that the elements or objects preceding "comprising" or "including" encompass the elements or objects listed following "comprising" or "including," and their equivalents, but do not exclude other elements or objects. The terms "connected" or "linked," and similar words, are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect.

[0029] In the description of this application, the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are used solely for the convenience of describing this application and for simplification, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application. Furthermore, when using positional terms such as "both sides," "outer side," and "upper and lower," it should be understood that they are used only for ease of understanding and description, taking into account that the structure may be oriented to other positions.

[0030] In the description of this application, unless otherwise expressly specified and limited, the technical or scientific terms used shall have the ordinary meaning understood by a person with ordinary skills in the art to which this application pertains. Terms such as “installation,” “connection,” and “joining” shall be interpreted broadly, for example, as fixed connection, detachable connection, mating connection, or integral connection. For a person skilled in the art, the specific meaning of the above terms in this application can be understood according to the specific circumstances.

[0031] The present invention aims to introduce and explain the structural composition and the cooperation relationship between the components of an automatic calibration method for an electron beam quantity detection device. Unless otherwise specified, the dimensions, materials and manufacturing processes of the components in the automatic calibration method for an electron beam quantity detection device in the present invention can be selected according to specific circumstances, and no special limitations or explanations are given here.

[0032] Furthermore, to provide the public with a better understanding of the present invention, certain specific details are described in detail in the following description of the invention. However, those skilled in the art will fully understand the invention even without these detailed descriptions.

[0033] Electron beam metrology equipment is a high-precision instrument that uses a focused electron beam as a "probe" to scan the sample surface. By detecting various signals generated by the interaction between electrons and the sample (such as secondary electrons and backscattered electrons), it quantitatively measures the sample's microstructure, size, composition, and electrical properties, and inspects for defects. The working principle of existing electron beam metrology equipment is as follows: Figure 1 As shown: In a high vacuum environment, electron source 1 (Schottky thermal field electron source) emits electron beam 2, which is confined by anode 3, and then focused by first-stage condenser coil 4 (Condense Lens 1, CL1) to determine the beam size entering the motorized variable aperture 5 (Move Aperture). Simultaneously, the motorized variable aperture 5 adjusts the electron beam spot size and beam intensity by selecting different apertures. The small vertical spot electron beam then passes through second-stage condenser coil 6 (Condense Lens 2, CL2) for beam angle adjustment. Simultaneously, the electron beam undergoes astigmatism correction by stigmator 7 to round the beam spot, and is deflected by magnetic deflector 8. The electron beam then undergoes line-by-line scanning by deflector system 12, and finally, the electron beam is focused onto the surface of wafer 16 by objective lens coil 13 (Object Lens, OL), exciting secondary electrons and backscattered signals 17. Secondary electron signal 17 enters the microscope tube and is received by the lower detector 11 (Low Detector), entering the image channel to generate a lower detector SEM image. Secondary electrons and backscattered signals leaking from the central aperture of the lower detector 11 are deflected by a linear filter 10 (such as a Wien filter) based on a combination of electric and magnetic fields to the upper detector 9 (such as a High Detector), entering the image channel to generate an upper detector SEM image. In optical microscope (OM) mode, the wafer surface pattern is acquired by the optical camera 15 for optical correction and inspection alignment. In both OM and SEM modes, the wafer height is acquired by 14 and fed back to the OL coil current for focusing.

[0034] Example 1 Please see Figures 1-13 An automatic calibration method for an electron beam quantity detection device, comprising: Step 1: Click "Start Calibration". The system will automatically switch to OM mode and transfer the patterned wafer 16. The image will identify two points on the same line and automatically correct the transfer angle to ensure the orthogonal orientation of wafer 16. The automatic correction of the transmission angle includes the automatic deflection system correction, which includes: The field of view (FOV) includes a scanning voltage of 2Vscan, a reserved voltage of 2Voffset for electron beam deflection, a DC bias voltage of 2Vdc, and a nonlinear voltage range. The maximum linear range encompasses the FOV scanning voltage, electron beam deflection voltage, and DC bias voltage. Pixel size is determined by the intensity of the deflection excitation signal. Calibration establishes a series of relationships between deflection gain and pixel size. Linearity is determined through fitting, and inverse lookup is performed through interpolation. By using the reserved scanning offset voltage Voffset, the electron beam is deflected to different positions. Image recognition calculates the movement distance, and the pixel sizes in the X and Y directions are calculated separately. Comparing their proportions and angles allows for the evaluation of orthogonality.

[0035] Step 2: Re-input the patterned wafer 16. Image recognition moves two points on the same line to the center respectively, automatically correcting the angles of the wafer coordinate system and the sample stage coordinate system to ensure wafer movement accuracy. Step 3: Based on wafer size and image recognition, automatically find the edges of three points on the wafer, move them to the center of the image, and calculate the origin of the wafer coordinate system.

[0036] Step 4: Based on image recognition, the electric aperture is automatically moved in the X and Y directions at a set step size to find the spot position and automatically locate the coordinate position of the standard sample and Faraday cup for automatic calibration.

[0037] Specifically, it includes: The automatic calibration of the motorized aperture verifies the mechanical alignment of the electromagnetic lenses (first-stage condenser coil 4, second-stage condenser coil 6, and objective lens coil 13) through the large-aperture APT1. Then, it switches to the small-aperture APT2, automatically searching to center the beam spot. When the first-stage condenser coil 4 is moved, the image shows concentric brightness changes; when the second-stage condenser coil 6 is moved, the image remains centered without shift; and when the objective lens coil 13 is moved, the image scales concentrically. After the image is deemed acceptable, beam current calibration is performed, fitting the beam current Ip and the current curve of the first-stage condenser coil 4, as shown below. Figure 8 As shown. Subsequently, after autofocus, autoassay correction, auto magnetic deflection alignment, and auto brightness / contrast, the deflection gain, linearity, and orthogonality were evaluated, as shown. Figure 9 and 10 As shown. Then, by selecting Z Level positions at different heights, the height-focus and image scaling factors are automatically calibrated based on the pattern on the wafer.

[0038] In automatic switching mode, the electron beam gate and electron gun valve are switched on and off, and the current of a series of first-stage condenser lens coils 4 is set to obtain the CL1-Ip curve.

[0039] Then, using SEM image algorithms, automatic brightness and contrast, automatic focus, automatic astigmatism correction, automatic magnetic deflection alignment, and automatic pixel size calibration are performed. Automatic focus, automatic astigmatism correction, automatic magnetic deflection alignment, automatic brightness and contrast, and automatic pixel size calibration all utilize image recognition, high-order filtering, Fourier transform, and pixel distribution histogram analysis to find the optimal image parameters.

[0040] The SEM image algorithms include: Z-Level automatic calibration records data including X and Y coordinates, Z-Level height, focus current (OLFine), and current pixel size (P). (X, Y, Z, OLFine, P) Record the position information of two different patterns. (X0, Y0, Z0, OLFine0, P0) & (X1, Y1, Z1, OLFine1, P1) Focus on automatic tracking: Focusing coefficient Kf = (OLFine1 - OLFine0) / (Z1 - Z0), OLfine = Kf*(Z-Z0) + OLfine0 = Kf*Z + (OLfine0 - Kf*Z0) = Kf*Z + Bf (slope and intercept) Automatic pixel size tracking: Pixel size factor Kp=(P1-P0) / (Z1-Z0), P = Kp*(Z-Z0) + P0 = Kp*Z + (P0-Kp*Z0) = Kp*Z + Bp (slope and intercept).

[0041] Step 5: Switch to SEM mode, turn off other power drives, remove the motorized variable aperture 5, and keep only three electromagnetic lenses, the first-stage condenser coil 4, the second-stage condenser coil 6, and the objective lens coil 13. Adjust the swing coil current and automatically check the mechanical alignment of the electromagnetic lenses and detectors based on the image spot to ensure that the maximum spot is centered, concentrically scaled, and changes in brightness.

[0042] Step 6: Insert the motorized variable aperture 5, automatically search for the aperture position, ensure that the aperture spot is centered, and automatically check the beam spot center position and brightness distribution histogram through image recognition to ensure that the image changes concentrically when the first-stage condenser coil 4 is swung, the image is centered without offset when the second-stage condenser coil 6 is swung, and the image is concentrically scaled when the objective lens coil 13 is swung.

[0043] Step 7: Automatic beam calibration. Under the current current of the first-stage condenser coil 4, move to the Faraday cup sample stage coordinate position, read the current beam current value in real time, and then move left and right from the current coordinate position to find the position of maximum beam current, automatically saving it as the Faraday cup coordinates. Subsequently, according to the configuration file, gradually change the current value of the first-stage condenser coil 4, record the beam current value, plot the calibration curve and save it automatically. Based on the beam current set by the current quantity detection, automatically send the corresponding current of the first-stage condenser coil 4.

[0044] Step 8: Automatically perform detector brightness and contrast (Auto Brightnes and Auto Contrast) algorithms to optimize detector gain and signal ratio distribution, while automatically adjusting sampling parameters and finding the optimal image parameters through image resolution and pixel distribution histogram.

[0045] Step 9: In a small field of view, the automatic focus, automatic stig, and automatic magnetic deflector algorithms are executed alternately to find the parameters that produce the clearest image quality. At this point, the image is clear, the graphic is not elongated or trailed, and the image is not wobbly. Step 10: Under a large field of view, detector shadows usually occur due to the central hole of the lower detector 11. By dynamically adjusting the scaling parameters of the upper detector 9, the signals that missed the central hole of the lower detector 11 are deflected to the upper detector 9 for supplementary collection. The signals from the upper and lower detectors are combined, and the detector shadows are identified by image recognition. The appropriate electromagnetic field deflection direction is automatically selected until the SEM image is uniform and the pixel distribution histogram is close to a normal distribution.

[0046] Step 11: After the SEM image is automatically centered and optimized, at the standard sample location, the OM-SEM coordinate difference is automatically corrected based on the OM and SEM images with the same pattern through image feature recognition.

[0047] Step 12: At the feature pattern, pixel size calibration is automatically performed. At the same time, by offsetting the image, calibration coefficients in the X and Y directions of the image are generated to perform automatic orthogonality (proportion and angle) correction of the deflection system, and the configuration is automatically saved.

[0048] The automatic calibration of the motorized aperture verifies the mechanical alignment of the electromagnetic lenses (first-stage condenser coil 4, second-stage condenser coil 6, and objective lens coil 13) through the large-aperture APT1. Then, it switches to the small-aperture APT2, automatically searching to center the beam spot. When the first-stage condenser coil 4 is moved, the image shows concentric brightness changes; when the second-stage condenser coil 6 is moved, the image remains centered without shift; and when the objective lens coil 13 is moved, the image scales concentrically. After the image is deemed acceptable, beam current calibration is performed, fitting the beam current Ip and the current curve of the first-stage condenser coil 4, as shown below. Figure 8 As shown. Subsequently, after autofocus, autoassay correction, auto magnetic deflection alignment, and auto brightness / contrast, the deflection gain, linearity, and orthogonality were evaluated, as shown. Figure 9 and 10 As shown. Then, by selecting Z Level positions at different heights, the height-focus and image scaling factors are automatically calibrated based on the pattern on the wafer.

[0049] Step 13: Select Z Level positions at different heights and automatically calibrate the height-focus and image scaling factors based on the pattern on the wafer.

[0050] Step 14: Finally, the repeatability and stability of the automatic verification measurement are performed on the wafer, and a complete calibration report is generated.

[0051] For example, such as Figure 7 As shown, the automatic calibration of the motorized aperture verifies the mechanical alignment of the electromagnetic lens (first-stage condenser coil 4, second-stage condenser coil 6, and objective lens coil 13) through the large-aperture APT1. Then, it switches to the small-aperture APT2, automatically searching to center the beam spot. When the first-stage condenser coil 4 is oscillated, the image exhibits concentric brightness changes; when the second-stage condenser coil 6 is oscillated, the image remains centered without shift; and when the objective lens coil 13 is oscillated, the image scales concentrically. After the image is deemed acceptable, beam current calibration is performed, fitting the beam current Ip and the current curve of the first-stage condenser coil 4, as shown... Figure 8 As shown. Subsequently, after autofocus, autoassay correction, auto magnetic deflection alignment, and auto brightness / contrast, the deflection gain, linearity, and orthogonality were evaluated, as shown. Figure 9 and 10 As shown. Then, by selecting Z-Level positions at different heights, the height-focus and image scaling factors are automatically calibrated based on the pattern on the wafer, as follows. Figure 11 As shown. Figure 12 and 13 The results show SEM images before and after calibration, with significant improvements in resolution and orthogonality. The entire process is automated with a single click, involving iterative verification of the SEM images before and after calibration.

[0052] A computer-readable medium having a computer program stored thereon, which, when executed by a processor, implements the steps of an automatic calibration method for an electron beam quantity detection device.

[0053] It should be understood that the above embodiments are only for illustrating the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. It should not be considered that the specific implementation of the present invention is limited to these descriptions. For those skilled in the art, several simple deductions or substitutions can be made without departing from the concept of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the protection scope of the present invention.

Claims

1. An automatic calibration method for an electron beam quantity detection device, characterized in that: Step 1: First, switch to OM mode, transfer the product, identify two points on the same line in the image, and transfer the image for correction. Step 2: Re-input the product with the pattern. The image recognition will move the two points on the same line to the center respectively, and perform OM coordinate system calibration and OM center calibration. Step 3: Based on product dimensions and image recognition, find the edges of the three dimensions, move them to the center of the image, and calculate the origin of the product coordinate system; Step 4: Based on image recognition, move the electric aperture in the X and Y directions at the set step size to find the position of the light spot and locate the coordinate position of the standard and Faraday cup calibration. Step 5: Switch to SEM mode, turn off other power drives, remove the motorized variable aperture, retain the three electromagnetic lenses, swing the coil current, check the mechanical alignment of the electromagnetic lenses and detector based on the image spot, center the maximum spot, and simultaneously perform concentric scaling and brightness changes. Step 6: Insert the motorized variable aperture, search for the aperture position, center the aperture spot, and check the center position of the beam spot and the histogram of brightness and darkness distribution through image recognition; Step 7: Beam calibration; Step 8: Perform detector brightness and contrast algorithms, optimize detector gain and signal ratio distribution, and adjust sampling parameters to find the optimal image parameters through image resolution and pixel distribution histogram. Step 9: In a small field of view, use focusing, astigmatism correction, and magnetic deflection algorithms alternately to find the parameters that produce the clearest image quality. Step 10: Under a large field of view, by dynamically adjusting the scale parameters of the detector, the signal that missed the center hole of the lower detector is deflected to the upper detector for supplementary collection. The signals from the upper and lower detectors are combined, and the detector shadow is identified by image recognition. The appropriate electromagnetic field deflection direction is selected until the SEM image is uniform and the pixel distribution histogram is close to a normal distribution. Step 11: After the automatic centering and optimization of the SEM image is completed, at the standard sample position, the OM-SEM coordinate difference is corrected based on the OM and SEM images with the same pattern by image feature recognition. Step 12: At the feature pattern, perform pixel size calibration, and at the same time, generate calibration coefficients in the X and Y directions of the image by offsetting the image, perform orthogonality correction of the deflection system, and save the configuration. Step 13: Select Z Level positions at different heights, and automatically calibrate the height-focus and image scaling factors based on the pattern on the product.

2. The automatic calibration method for an electron beam quantity detection device according to claim 1, characterized in that: It also includes step 14, verifying the repeatability and stability of quantitative tests on the product, and generating a complete set of calibration reports.

3. The automatic calibration method for an electron beam quantity detection device according to claim 1, characterized in that: Step 4 specifically includes: Automatic calibration of the motorized aperture verifies the mechanical alignment of the primary condenser coil, the secondary condenser coil, and the objective lens coil through the large-aperture APT1. Then, switching to the small-aperture APT2, the system automatically searches to center the beam spot. When the primary condenser coil is oscillated, the image exhibits concentric brightness changes; when the secondary condenser coil is oscillated, the image remains centered without shift; and when the objective lens coil is oscillated, the image scales concentrically. After successful image verification, beam calibration is performed, fitting the beam current Ip and the primary condenser coil current curves. Subsequently, after focusing, astigmatism correction, magnetic deflection alignment, and automatic brightness and contrast adjustments, the deflection gain, linearity, and orthogonality are evaluated. Finally, selecting different Z-level positions based on the pattern on the product, the height-focus and image scaling factors are automatically calibrated.

4. The automatic calibration method for an electron beam quantity detection device according to claim 1, characterized in that: In step 5, the three electromagnetic lenses, namely the first-stage condenser coil, the second-stage condenser coil, and the objective lens coil, are switched on and off in the switching mode, and the current of the first-stage condenser coil is set to obtain the CL1-Ip curve. Then, SEM image algorithms are used to adjust brightness and contrast, focus, astigmatism, magnetic deflection alignment, and automatic pixel size calibration.

5. The automatic calibration method for an electron beam quantity detection device according to claim 4, characterized in that: The SEM image algorithm includes: Z-Level height automatic calibration records data including X and Y coordinates, Z-Level height, focus current (OLFine), and current pixel size (P). (X, Y, Z, OLFine, P) Record the position information of two different patterns. (X0, Y0, Z0, OLFine0, P0) & (X1, Y1, Z1, OLFine1, P1) Focus on automatic tracking: Focusing coefficient Kf = (OLFine1 - OLFine0) / (Z1 - Z0), OLfine=Kf*(Z-Z0)+OLfine0=Kf*Z+(OLfine0-Kf*Z0)=Kf*Z+Bf (slope and intercept). Automatic pixel size tracking: Pixel size factor Kp=(P1-P0) / (Z1-Z0), P = Kp*(Z-Z0) + P0 = Kp*Z + (P0-Kp*Z0) = Kp*Z + Bp (slope and intercept).

6. The automatic calibration method for an electron beam quantity detection device according to claim 1, characterized in that: Step 7, beam calibration specifically includes: checking the beam spot center position and brightness distribution histogram, ensuring that the image changes concentrically when the first-stage condenser lens coil is oscillating, the image is centered without offset when the second-stage condenser lens coil is oscillating, and the image is concentrically scaled when the objective lens coil is oscillating.

7. An automatic calibration method for an electron beam quantity detection device according to any one of claims 1-6, characterized in that: Under the current of the first-stage condenser coil, move to the coordinate position of the Faraday cup sample stage, read the current beam current value in real time, and then move left and right at the current coordinate position to find the position of maximum beam current and save it as the Faraday cup coordinates; then, according to the configuration file, gradually change the current value of the first-stage condenser coil, record the beam current value, draw the calibration curve and save it; based on the beam current set by the current quantity detection, issue the corresponding first-stage condenser coil current.

8. The automatic calibration method for an electron beam quantity detection device according to claim 1, characterized in that: The deflection system correction in step 12, the image offset step, includes: The system includes a scanning voltage of 2Vscan for the field of view, a reserved voltage of 2Voffset for electron beam offset, a DC bias voltage of 2Vdc, and a nonlinear voltage range. The maximum linear range includes the scanning voltage of the field of view, the electron beam offset voltage, and the DC bias voltage. The pixel size is determined by the intensity of the deflection excitation signal. Calibration is achieved by establishing a correspondence between deflection gain and pixel size, judging linearity through fitting, and performing reverse lookup through interpolation. The electron beam is offset to different positions using the reserved scanning offset voltage Voffset. The moving distance is calculated through image recognition, and the pixel sizes in the X and Y directions are calculated separately. Their proportions and angles are compared to evaluate orthogonality.

9. A computer-readable medium having a computer program stored thereon, characterized in that: When the program is executed by the processor, it implements the steps of the method as described in any one of claims 1-8.

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