Performance evaluation method of electromagnetic lens of electron microscope and computer equipment

Abstract

The invention provides a performance evaluation method of an electromagnetic lens of an electron microscope and computer equipment. The performance evaluation method of the electromagnetic lens of the electron microscope comprises the following steps: acquiring multiple groups of magnetic field data of the electromagnetic lens; fitting the multiple groups of magnetic field data to obtain a fitting function; fourier transform is carried out on the fitting function to obtain a multi-pole field amplitude irrelevant to the off-axis distance; and evaluating the performance of the electromagnetic lens based on the multi-pole field amplitude. According to the scheme, subsequent data processing is carried out by adopting the fitting function instead of finite discrete data points, so that errors are reduced, the accuracy of the data is improved, and errors in evaluating the performance of the electromagnetic lens are reduced; and off-axis distance decoupling is realized, and the stability of a judgment index is ensured.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and in particular to a method and computer device for evaluating the performance of an electromagnetic lens for an electron microscope. Background Technology

[0002] The rapid development of science and technology has enabled people to explore the microscopic world more deeply, and observation tools have been upgraded from the naked eye to microscopes. However, the resolution of optical microscopes is significantly dependent on wavelength. The advent of electron microscopes has led to the rapid development of fields such as semiconductor manufacturing processes, materials science, and life sciences. Its main uses include detecting wafer defects, measuring wafer feature dimensions, and analyzing the microstructure and composition of samples. The resolution of general electron microscopes is generally between 0.1-100 nm. Two main modules contribute significantly to this resolution: the electron beam filament module and the electromagnetic lens module. Electron beam filaments include tungsten filaments, lanthanum hexaboride filaments, Schottky emission, and cold field emission. The electromagnetic lens module is mainly the objective lens. It uses a permalloy material to make a magnetic yoke that contains a current-carrying coil. It generates a rotationally symmetrical magnetic field within a limited range to focus the high-speed electron beam, causing the focused electron beam to bombard the sample surface, thereby generating signal electrons. The signal electrons are collected and modulated into a grayscale image.

[0003] Electromagnetic lenses, including condenser lenses, objective lenses, and projection lenses, generally require high manufacturing precision, especially objective lenses. They typically require a pole piece roundness of 0.0001D, where D is the pole piece aperture size, which is very challenging for machining metal materials. Furthermore, the inhomogeneity of the material's microscopic regions disrupts the rotational symmetry of the magnetic field, increasing aberrations and resulting in decreased resolution of the electron microscope, failing to meet usage requirements. Additionally, the assembly and debugging cycle for electron microscopes is lengthy, typically 90 to 120 days. If, after all modules are assembled, images are acquired on the testing machine and found to be of poor image quality due to substandard objective lens performance or large alignment errors, replacing the objective lens module or reassembling the alignment is necessary—a very time-consuming and labor-intensive process. If the performance of electromagnetic lenses could be tested and evaluated before assembly into the module, it would significantly improve work efficiency, provide feedback on the electromagnetic lens manufacturing process, facilitate process improvement, and enhance module quality control. However, currently, testing and evaluating the performance of electromagnetic lenses faces significant difficulties, and the accuracy of the evaluation results cannot be guaranteed. Summary of the Invention

[0004] One objective of this invention is to improve the accuracy of test data and reduce errors in evaluating the performance of electromagnetic lenses.

[0005] A further objective of this invention is to achieve decoupling from off-axis distance, thereby ensuring the stability of the judgment index.

[0006] Specifically, the present invention provides a method for evaluating the performance of an electromagnetic lens for an electron microscope, comprising: acquiring multiple sets of magnetic field data of the electromagnetic lens; fitting the multiple sets of magnetic field data to obtain a fitting function; performing a Fourier transform on the fitting function to obtain a multipole field amplitude independent of off-axis distance; and evaluating the performance of the electromagnetic lens based on the multipole field amplitude.

[0007] Optionally, the steps for obtaining multiple sets of magnetic field data of the electromagnetic lens include: measuring multiple sets of magnetic field data using a gaussmeter probe, wherein the testing accuracy of the gaussmeter probe is greater than or equal to 0.1uT.

[0008] Optionally, the step of obtaining multiple sets of magnetic field data using a gaussmeter probe includes: using the gaussmeter probe at different distances from the axis of the electromagnetic lens on the same horizontal plane to measure magnetic field data at multiple locations on the same horizontal plane as a set, wherein the number of multiple locations is greater than or equal to 3; and using the gaussmeter probe to perform a measurement at preset intervals along the axial direction to obtain multiple sets of magnetic field data on multiple horizontal planes.

[0009] Optionally, the electromagnetic lens is placed on a turntable, with the axis of the electromagnetic lens coinciding with the rotation axis of the turntable. The gaussmeter probe is configured to perform data measurement at a position at a set distance from the axis as the turntable drives the electromagnetic lens to rotate at a constant speed.

[0010] Optionally, the step of evaluating the performance of an electromagnetic lens based on the multipole field amplitude includes: comparing the multipole field amplitude with a plurality of preset threshold ranges, each threshold range corresponding to an evaluation level characterizing the performance of the electromagnetic lens; and determining the performance evaluation level of the electromagnetic lens based on the comparison results.

[0011] Optionally, the multipole field amplitude includes positive diode field amplitude, oblique diode field amplitude, positive tetrapole field amplitude, and oblique tetrapole field amplitude.

[0012] Optionally, the step of fitting multiple sets of magnetic field data includes: fitting multiple sets of magnetic field data using a polynomial, wherein the polynomial is any one of Legendre polynomial, Chebyshev polynomial, or Hermitian polynomial.

[0013] Optionally, after obtaining the fitting function, the method further includes: calculating and outputting the error term corresponding to the fitting function, and performing a Fourier transform on the fitting function if the error term meets a preset threshold.

[0014] Optionally, the electromagnetic lens includes any one of a condenser lens, an objective lens, and a projection lens.

[0015] According to another aspect of the present invention, a computer device is also provided, including a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor executes the computer program to implement the performance evaluation method of the electromagnetic lens of the electron microscope as described above.

[0016] The present invention provides a method for evaluating the performance of an electromagnetic lens in an electron microscope. This method involves acquiring multiple sets of magnetic field data for the electromagnetic lens, fitting these data sets to obtain a fitting function, performing a Fourier transform on the fitting function to obtain a multipole field amplitude independent of off-axis distance, and evaluating the performance of the electromagnetic lens based on the multipole field amplitude. The method uses the fitting function instead of finite discrete data points for subsequent data processing, thereby reducing errors, improving data accuracy, and minimizing the error in evaluating the performance of the electromagnetic lens.

[0017] Furthermore, the performance evaluation method for the electromagnetic lens of the electron microscope of the present invention utilizes a gaussmeter probe at different distances from the axis of the electromagnetic lens on the same horizontal plane to measure magnetic field data at multiple locations on the same horizontal plane as a set. Then, the gaussmeter probe is used to perform measurements at preset intervals along the axis to obtain multiple sets of magnetic field data on multiple horizontal planes. By avoiding the position on the central axis of the positioning pole piece, the off-axis distance and on-axis field function are indirectly obtained by using multi-point measurement. After obtaining the fitting function, the error term corresponding to the fitting function is calculated and output. If the error term meets the preset threshold, the fitting function is subjected to Fourier transform. The fitting accuracy is understood through the error term. By deriving a quantity independent of the off-axis distance through the Fourier transform of the fitting function, the off-axis distance is decoupled, thereby ensuring the stability of the judgment index.

[0018] The above and other objects, advantages and features of the present invention will become more apparent to those skilled in the art from the following detailed description of specific embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0019] The following sections will describe some specific embodiments of the invention in detail by way of example and not limitation, with reference to the accompanying drawings. The same reference numerals in the drawings denote the same or similar parts or portions. Those skilled in the art should understand that these drawings are not necessarily drawn to scale. In the drawings: Figure 1 This is a schematic diagram of measuring the magnetic field data of an electromagnetic lens in the prior art; Figure 2 This is a schematic diagram of the SEM tube in a method for evaluating the performance of an electromagnetic lens of an electron microscope according to an embodiment of the present invention. Figure 3 This is a schematic diagram of the pole shoe ellipse in a method for evaluating the performance of an electromagnetic lens of an electron microscope according to an embodiment of the present invention. Figure 4This is a schematic diagram showing the tilt of the pole piece relative to the optical axis in a performance evaluation method for the electromagnetic lens of an electron microscope according to an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating a method for evaluating the performance of an electromagnetic lens in an electron microscope according to an embodiment of the present invention, in which the pole piece is not properly aligned. Figure 6 This is a schematic diagram of a method for evaluating the performance of an electromagnetic lens of an electron microscope according to an embodiment of the present invention; Figure 7 This is a schematic diagram of measuring the magnetic field data of an electromagnetic lens using a gaussmeter probe in a performance evaluation method for an electromagnetic lens of an electron microscope according to an embodiment of the present invention. Figure 8 yes Figure 7 Enlarged view of region A in the middle; Figure 9 This is a schematic diagram of the electromagnetic lens being placed on a turntable in a method for evaluating the performance of an electromagnetic lens in an electron microscope according to an embodiment of the present invention. Figure 10 This is a schematic diagram of a computer program product according to an embodiment of the present invention; Figure 11 This is a schematic diagram of a computer-readable storage medium according to an embodiment of the present invention; and Figure 12 This is a schematic diagram of a computer device according to an embodiment of the present invention. Detailed Implementation

[0020] Figure 1 This is a schematic diagram illustrating the measurement of magnetic field data from an electromagnetic lens in existing technology. (Example) Figure 1 As shown, in existing technologies, on-axis and off-axis magnetic field data near the pole shoe 103 of the electromagnetic lens 102 are typically collected using a gaussmeter probe 101 for analysis. This data is then compared with the field distribution calculated by numerical simulation software to verify the consistency between the simulated and measured data and the fluctuations in the measured field function. However, this method has some easily overlooked problems: First, the magnetic field measured by the gaussmeter probe 101 may not be the on-axis magnetic field, and it is difficult to provide an error estimate; second, the measured data is only discrete data, and direct data processing, due to the small data volume, introduces random errors, affecting the accuracy of the final result; third, simply comparing the field distribution does not effectively utilize the collected data.

[0021] Because when the gaussmeter probe 101 is positioned near the pole piece 103 of the electromagnetic lens 102, it cannot be guaranteed to be centered on the pole piece hole. Generally, during testing, the center point of this pole piece hole needs to be used as a reference for lateral and longitudinal movement. The main reasons for the inaccurate positioning are: the gaussmeter probe 101 is a long, straight rod, and its shape inherently has a certain degree of tilt, making it difficult to find a positioning reference surface from its shape; the Hall sensor chip of the gaussmeter probe 101 may not be on the central axis of the gaussmeter probe 101 during packaging, further increasing the difficulty of accurate positioning; and the tools used for positioning and adjustment have limited precision, making it impossible to obtain satisfactory accuracy, such as a positioning accuracy of around 5µm. The actual field distribution function is a continuous function in space, and each position of the field coverage in space has a corresponding value. Directly processing the measured finite discrete field values ​​makes it difficult to control errors. Due to the above reasons, in-depth exploration of data processing methods has not been conducted, resulting in a large amount of test data that has not been effectively analyzed and summarized.

[0022] Figure 2 This is a schematic diagram of the SEM tube in a method for evaluating the performance of an electromagnetic lens in an electron microscope according to an embodiment of the present invention. The scanning electron microscope (SEM) tube generally includes: a cathode 201, an anode 202, an anode aperture 203, a condenser lens 204 (CL), a condenser coil 205, an objective aperture 206, a detector 207, an objective lens 208 (OL), a second deflector 209, a lower objective pole piece 210, the sample being observed 211, an objective coil 212, a first deflector 213, an electron beam 214, and signal electrons 215. The objective aperture 206 generally has multiple apertures, and the signal electrons 215 may be secondary electrons (SE), backscattered electrons (BSE), or other electrons.

[0023] The working principle of SEM is as follows: the cathode 201 emits an electron beam 214, which, after acceleration, passes through the anode aperture 203. The condenser lens 204 adjusts the electron beam current or half-angle. After passing through the objective aperture 206, it undergoes grid scanning via the first deflector 213 and the second deflector 209. Under the action of the objective lens 208, it is focused into a nanometer-scale beam spot, which bombards the observed sample 211. Electrons interact with the observed sample 211, generating a large number of signal electrons 215, which are received by the detector 207. Finally, after processing, the signal is modulated into an image with a certain contrast. This embodiment mainly focuses on the analysis and diagnosis of the performance of the electromagnetic lenses, such as the condenser lens 204 and the objective lens 208.

[0024] In one specific embodiment, the electromagnetic lens includes any one of a condenser lens 204, an objective lens 208, and a projection lens. When the rotational symmetry of the electromagnetic lens pole piece cannot be satisfied, some aberrations will be introduced. There are three main reasons for the violation of rotational symmetry: first, the pole piece is elliptical; second, the pole piece is tilted relative to the optical axis; and third, the pole piece is not properly aligned.

[0025] Figure 3 This is a schematic diagram of the pole shoe ellipse in a method for evaluating the performance of an electromagnetic lens of an electron microscope according to an embodiment of the present invention. Figure 4 This is a schematic diagram illustrating the tilt of the pole piece relative to the optical axis in a performance evaluation method for the electromagnetic lens of an electron microscope according to an embodiment of the present invention. Figure 5 This is a schematic diagram illustrating a method for evaluating the performance of an electromagnetic lens in an electron microscope according to an embodiment of the present invention, in which the pole piece is not properly aligned.

[0026] like Figure 3 As shown, when the pole shoe is elliptical, the expression for the magnetic field strength introduced by the ellipse is: .like Figure 4 As shown, the expression for the magnetic field strength introduced when the pole piece is tilted relative to the optical axis is: .like Figure 5 As shown, the expression for the magnetic field strength introduced when the pole shoes are not properly aligned is: Among them, H r H represents the magnetic field strength in the radial direction of the electromagnetic lens, i.e., the r-direction, measured in A / m. z The magnetic field strength is in the direction of the electromagnetic lens axis, i.e., the z-direction, and is expressed in A / m.

[0027] Because the field functions introduced by the violation of rotational symmetry are all trigonometric functions, this embodiment considers using the Fourier transform method to extract the field functions separately. This allows for quantitative evaluation of the electromagnetic lens's performance, enabling offline performance testing of the electromagnetic lens. This ensures that all modules assembled on the equipment meet performance standards, greatly improving work efficiency. At the same time, it leaves valuable analysis and testing data, facilitating future product upgrades and iterations, and benefiting the optimization of subsequent processing techniques.

[0028] This embodiment provides a method for evaluating the performance of electromagnetic lenses in an electron microscope. Figure 6 This is a schematic diagram of a method for evaluating the performance of an electromagnetic lens in an electron microscope according to an embodiment of the present invention. Figure 7 This is a schematic diagram of the gaussmeter probe 301 measuring the magnetic field data of the electromagnetic lens in a performance evaluation method for the electromagnetic lens of an electron microscope according to an embodiment of the present invention. Figure 8 yes Figure 7 Enlarged diagram of region A in the middle. Figure 9 This is a schematic diagram of the electromagnetic lens being placed on a turntable in a method for evaluating the performance of an electromagnetic lens in an electron microscope according to an embodiment of the present invention. Figure 6 As shown, the performance evaluation method for the electromagnetic lens of the electron microscope in this embodiment generally includes: Step S602: Obtain multiple sets of magnetic field data from the electromagnetic lens 302; Step S604: Fit multiple sets of magnetic field data to obtain a fitting function; Step S606: Perform a Fourier transform on the fitted function to obtain the multipole field amplitude that is independent of off-axis distance; Step S608: Evaluate the performance of electromagnetic lens 302 based on multi-field amplitude.

[0029] In the above steps, step S602, obtaining multiple sets of magnetic field data from the electromagnetic lens 302, may specifically include: measuring multiple sets of magnetic field data using a gaussmeter probe 301, wherein the testing accuracy of the gaussmeter probe 301 is greater than or equal to 0.1 μT. In a specific embodiment, the step of measuring multiple sets of magnetic field data using the gaussmeter probe 301 may include: measuring magnetic field data at multiple locations on the same horizontal plane at different distances from the axis 303 of the electromagnetic lens 302 using the gaussmeter probe 301, wherein the number of multiple locations is greater than or equal to 3; and measuring once at preset intervals along the axial direction using the gaussmeter probe 301 to obtain multiple sets of magnetic field data on multiple horizontal planes.

[0030] In one specific embodiment, the electromagnetic lens 302 is placed on the turntable 304, and the axis 303 of the electromagnetic lens 302 coincides with the rotation axis of the turntable 304. The gaussmeter probe 301 is configured to perform data measurement at a position at a set distance from the axis 303 during the process of the turntable 304 driving the electromagnetic lens 302 to rotate at a constant speed.

[0031] In a preferred embodiment, the gaussmeter probe 301 can be a 3D gaussmeter probe, which can be used to measure the magnetic induction intensity B(z) in the z-direction of the electromagnetic lens 302 axis. Furthermore, the 3D gaussmeter probe can also be temperature compensated. Fluxgates offer high measurement accuracy, typically reaching the nT level, but their measurement range is limited, generally <1mT. Therefore, they cannot measure the magnetic field generated by the electromagnetic lens 302, although they can test weak magnetic fields. The method of this embodiment can then be used to evaluate the magnetic field.

[0032] In one specific embodiment, the gaussmeter probe 301 can be fixed on a support (not shown in the figure) with precisely adjustable vertical displacement. In actual operation, the electromagnetic lens 302 can be placed on the turntable 304 of the cylindricity meter. The axis 303 of the electromagnetic lens 302 coincides with the rotation axis of the turntable 304. During the uniform rotation of the turntable 304, the gaussmeter probe 301 collects magnetic field data at a distance r from the axis 303 of the electromagnetic lens 302, obtaining the test data for the first position on this horizontal plane. Then, based on this, the gaussmeter probe 301 is moved horizontally by ∆r1 and ∆r2, and the above operation is repeated to collect data to obtain a set of magnetic field data on this horizontal plane. It should be noted that the distance r is an unknown quantity; it can only be determined that it is close to the axis 303, but its specific value cannot be known, therefore it is an unknown quantity. ∆r1 and ∆r2 are pre-selected, for example, 0.5mm, 1.5mm, etc., as long as they are not equal. After completing a set of magnetic field data measurements, the gaussmeter probe 301 can measure the next set of data at intervals of ∆z along the axial direction. ∆z can be adjusted according to the movement accuracy of the test equipment, and can generally reach 0.01mm or even smaller.

[0033] Step S604, fitting multiple sets of magnetic field data, may specifically include: fitting multiple sets of magnetic field data using a polynomial, wherein the polynomial is any one of Legendre polynomial, Chebyshev polynomial, or Hermitian polynomial. After obtaining the fitting function in step S604, the process may further include: calculating and outputting the error term corresponding to the fitting function, and performing a Fourier transform on the fitting function if the error term meets a preset threshold. The multipole field amplitudes in step S606 include positive diode field amplitudes, oblique diode field amplitudes, positive quadrupole field amplitudes, and oblique quadrupole field amplitudes.

[0034] For the rotationally symmetric electromagnetic lens 302, its on-axis magnetic scalar potential is φ(r, θ, z), and its field function is B. z (r, z). Since the influence of higher-order terms is relatively weak, they are generally not considered; we only consider the squared term of r. Equation ⑥ can be used to calculate the specific data for r. After calculating r, the obtained B... z (r, θ, z) or B z (r+∆r1, θ, z) or B z (r+∆r², θ, z) is fitted using a polynomial, and the derivation process follows B. z Taking (r, θ, z) as an example, three polynomials are available for fitting: Legendre polynomials, Chebyshev polynomials, and Hermitian polynomials. All three polynomials can achieve satisfactory fitting accuracy. After obtaining the fitted function, a Fourier transform is performed on the fitted function to obtain the multipole field amplitudes independent of off-axis distance: positive diode field amplitude B1(z), oblique diode field amplitude D1(z), positive tetrapole field amplitude B2(z), and oblique tetrapole field amplitude D2(z). Other multipole fields can be obtained using a similar method. This derivation focuses on the amplitudes of the diode and tetrapole fields for intuitive understanding, as these two components have a significant impact on the performance of the electromagnetic lens 302, while the other components account for a very small proportion.

[0035] The amplitudes of the positive diode field B1(z), the oblique diode field D1(z), the positive tetrapole field B2(z), and the oblique tetrapole field D2(z) are indicators that can be used to quantitatively quantify the diode and tetrapole fields, and are independent of off-axis distance. In a preferred embodiment, step S608, which evaluates the performance of the electromagnetic lens 302 based on the multipole field amplitude, may specifically include: comparing the multipole field amplitude with multiple preset threshold ranges, each threshold range corresponding to an evaluation level characterizing the performance of the electromagnetic lens 302; and determining the performance evaluation level of the electromagnetic lens 302 based on the comparison results.

[0036] For example, for electromagnetic lenses that meet the usage requirements on the machine, their corresponding B1(z), D1(z), B2(z), and D2(z) are tested as the first reference values; for electromagnetic lenses that do not meet the usage requirements on the machine, their corresponding B1(z), D1(z), B2(z), and D2(z) are tested as the second reference values, where the first reference value is less than the second reference value. Subsequent routine measurements can refer to the first and second reference values ​​to quantitatively evaluate the performance of the electromagnetic lens. If the measured multipole field amplitude is less than or equal to the first reference value, it can be rated as Grade A; if the measured multipole field amplitude is greater than the first reference value but less than the second reference value, it can be rated as Grade B; if the measured multipole field amplitude is greater than or equal to the second reference value, it can be rated as Grade C, where Grade A, Grade B, and Grade C represent decreasing performance of the electromagnetic lens in that order. It should be noted that the specific number and division of the above performance evaluation levels are only examples and are not intended to limit the invention. In other embodiments, settings can be made according to actual conditions.

[0037] In a preferred embodiment, the performance evaluation method for the electromagnetic lens of the electron microscope in this embodiment also includes a signal acquisition system for accurately acquiring magnetic field data measured by the gaussmeter probe 301. A memory is used to store the acquired magnetic field data; generally, a standard computer is sufficient for this purpose. Furthermore, a linear constant current source can be included to power the electromagnetic lens; typically, 50V-2A is sufficient for most designs.

[0038] The turntable 304 can be a turntable for a high-precision cylindricity meter or other high-precision turntables. The axis 303 of the electromagnetic lens is aligned with the rotation axis of the turntable 304. During testing, the turntable 304 rotates at a constant speed while the gaussmeter probe 301 remains stationary. Data is collected during the rotation of the turntable 304. The signal acquisition rate is selected based on the resolution of the gaussmeter probe 301 and the rotational speed of the turntable 304. Generally, the data acquisition rate ranges from 1 data point to 500 data points / second. Too fast an acquisition speed will affect the accuracy of the acquired data, while too slow a speed will affect efficiency. The gaussmeter probe 301 can be fixed on a device capable of precise three-dimensional movement, typically implemented using a high-precision slide table or a stepper motor or linear motor. It should be noted that both the gaussmeter probe 301 and the turntable 304 are high-precision devices.

[0039] The performance evaluation method for electromagnetic lenses in an electron microscope, as described in this embodiment, can analyze and diagnose the performance of electromagnetic lenses, select high-quality electromagnetic lenses for assembly into the equipment, and improve product stability and imaging quality. It also strengthens quality control of key modules, reducing machine differences between devices. Simultaneously, it accumulates test data, providing a reference for future design of novel electromagnetic lenses.

[0040] It is important to emphasize that positioning a high-precision gaussmeter probe at the center of the electromagnetic lens's pole piece aperture using high-precision alignment methods or equipment is quite difficult and requires expensive equipment. While directly evaluating the electromagnetic lens's performance by establishing a correlation between its performance and the image quality obtained using an electron microscope on a standard sample is the most direct approach, image quality involves numerous module and assembly process parameters, making it difficult to quickly establish a clear and direct causal relationship with the electromagnetic lens.

[0041] This embodiment only tests the magnetic field of a single module, the electromagnetic lens, to determine whether the module's performance is superior or inferior. During the field function fitting process, three polynomials can be chosen. From a numerical analysis perspective, these three are essentially equivalent and can be substituted for each other. Alternatively, the acquired field function can be directly subjected to a Fourier transform.

[0042] More than three measurement positions can be used in the r direction. In this embodiment, three measurement positions are used for derivation in order to clearly illustrate the principle. In actual measurement, more than three measurement positions can be used. After calculating the final evaluation parameters separately, the average value is then calculated, which can further reduce the error.

[0043] To clearly illustrate the principle, this embodiment uses a general field function term. For electron microscope systems with high precision requirements, such as achieving a resolution within 1 nm, it is advisable to consider taking more terms in the field function calculation. However, taking more terms means adding more measurement positions in the r-direction, requiring the calculation of additional variables. This leads to reduced work efficiency and increased detection difficulty.

[0044] This embodiment also provides a computer program product, a computer-readable storage medium, and a computer device. Figure 10 This is a schematic diagram of a computer program product 500 according to an embodiment of the present invention. Figure 11 This is a schematic diagram of a computer-readable storage medium 300 according to an embodiment of the present invention. Figure 12 This is a schematic diagram of a computer device 400 according to an embodiment of the present invention.

[0045] Computer program product 500 includes computer program 310, which, when executed by processor 410, implements the performance evaluation method for the electromagnetic lens of any of the aforementioned electron microscopes. Computer-readable storage medium 300 stores the aforementioned computer program 310 thereon, which, when executed by processor 410, implements the performance evaluation method for the electromagnetic lens of any of the aforementioned electron microscopes. Computer device 400 may include memory 420, processor 410, and computer program 310 stored in memory 420 and running on processor 410, wherein, when processor 410 executes computer program 310, it implements the performance evaluation method for the electromagnetic lens of any of the aforementioned electron microscopes.

[0046] The computer program 310 used to perform the operations of the present invention may be assembly instructions, instruction set architecture (ISA) instructions, machine instructions, machine-related instructions, microcode, firmware instructions, status setting data, integrated circuit configuration data, or source code or object code written in any combination of one or more programming languages ​​and procedural programming languages.

[0047] Computer program 310 may execute entirely on the user's computer, partially on the user's computer, as a standalone software package, partially on the user's computer and partially on a remote computer, or entirely on a remote computer or server. In the latter case, the remote computer may be connected to the user's computer via any type of network, including a local area network (LAN) or a wide area network (WAN), or may be connected to an external computer (e.g., via the Internet using an Internet service provider).

[0048] In some embodiments, in order to perform aspects of the present invention, electronic circuits including, for example, programmable logic circuits, field-programmable gate arrays (FPGAs) or programmable logic arrays (PLAs) can execute computer-readable program instructions to personalize the electronic circuits by utilizing state information of computer-readable program instructions.

[0049] For the purposes of this embodiment, computer program product 500 is a related product containing computer program 310. For the purposes of this embodiment, computer-readable storage medium 300 is a tangible device capable of holding and storing computer program 310, and can be any device capable of containing, storing, communicating, propagating or transmitting computer program 310 for use by or in conjunction with an instruction execution system, apparatus or device.

[0050] More specific examples (a non-exhaustive list) of computer-readable storage media 300 include the following: portable computer disks, hard disks, random access memory (RAM), read-only memory (ROM), erasable programmable read-only memory (EPROM or flash memory), static random access memory (SRAM), portable optical disc read-only memory (CD-ROM), digital multifunction disc (DVD), memory sticks, floppy disks, mechanical encoding devices, and any suitable combination of the foregoing.

[0051] It should be noted that the logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as a sequenced list of executable instructions for implementing logical functions, and can be specifically implemented in any machine-readable storage medium for use by, or in conjunction with, instruction execution systems, apparatuses or devices (such as computer-based systems, processor-based systems or other systems that can fetch and execute instructions from, or instruction execution systems, apparatuses or devices).

[0052] It should be understood that various parts of the present invention can be implemented using hardware, software, firmware, or a combination thereof. In the above embodiments, multiple steps or methods can be implemented using software or firmware stored in memory and executed by a suitable instruction execution system.

[0053] Computer device 400 can be, for example, a server, desktop computer, laptop computer, tablet computer, or smartphone. In some examples, computer device 400 can be a cloud computing node. Computer device 400 can be described in the general context of computer system executable instructions (such as program modules) executed by a computer system. Typically, program modules can include routines, programs, object programs, components, logic, data structures, etc., that perform specific tasks or implement specific abstract data types. Computer device 400 can be implemented in a distributed cloud computing environment where tasks are performed by remote processing devices linked through a communication network. In a distributed cloud computing environment, program modules can reside on local or remote computing system storage media, including storage devices.

[0054] Computer device 400 may include a processor 410 adapted to execute stored instructions and a memory 420 that provides temporary storage space for the operation of instructions during operation. The processor 410 may be a single-core processor, a multi-core processor, a computing cluster, or any other configuration. The memory 420 may include random access memory (RAM), read-only memory, flash memory, or any other suitable storage system.

[0055] The processor 410 can be connected via a system interconnect (e.g., PCI, PCI-Express, etc.) to an I / O interface (input / output interface) suitable for connecting the computer device 400 to one or more I / O devices (input / output devices). I / O devices may include, for example, a keyboard and indicating devices, where indicating devices may include a touchpad or touchscreen, etc. I / O devices may be built into the computer device 400 or may be external devices connected to the computing device.

[0056] The processor 410 may also be linked via a system interconnect to a display interface suitable for connecting the computer device 400 to a display device. The display device may include a display screen as a built-in component of the computer device 400. The display device may also include an external computer monitor, television, or projector connected to the computer device 400. Furthermore, a network interface controller (NIC) may be adapted to connect the computer device 400 to a network via a system interconnect. In some embodiments, the NIC may use any suitable interface or protocol (such as an Internet Minicomputer System Interface) to transmit data. The network may be a cellular network, a radio network, a wide area network (WAN), a local area network (LAN), or the Internet, etc. Remote devices may connect to the computing device via the network.

[0057] Therefore, those skilled in the art should recognize that although numerous exemplary embodiments of the present invention have been shown and described in detail herein, many other variations or modifications conforming to the principles of the present invention can be directly determined or derived from the disclosure of the present invention without departing from the spirit and scope of the invention. Thus, the scope of the present invention should be understood and construed as covering all such other variations or modifications.

Claims

1. A method for evaluating the performance of an electromagnetic lens in an electron microscope, comprising: Acquire multiple sets of magnetic field data from the electromagnetic lens; The multiple sets of magnetic field data are fitted to obtain a fitting function; Performing a Fourier transform on the fitted function yields the multipole field amplitude, which is independent of off-axis distance. as well as The performance of the electromagnetic lens is evaluated based on the multipole field amplitude.

2. The method according to claim 1, wherein the step of acquiring multiple sets of magnetic field data of the electromagnetic lens includes: The multiple sets of magnetic field data were obtained by measuring with a gaussmeter probe, and The testing accuracy of the gaussmeter probe is greater than or equal to 0.1uT.

3. The method according to claim 2, wherein the step of obtaining the multiple sets of magnetic field data by measuring with a gaussmeter probe includes: Using the gaussmeter probe at different distances from the axis of the electromagnetic lens on the same horizontal plane, the magnetic field data at multiple locations on the same horizontal plane are measured as a group, wherein the number of such multiple locations is greater than or equal to 3; and The gaussmeter probe is used to perform measurements at preset intervals along the axis to obtain multiple sets of magnetic field data on multiple horizontal planes.

4. The method according to claim 3, wherein, The electromagnetic lens is placed on a turntable, and the axis of the electromagnetic lens coincides with the axis of rotation of the turntable. The gaussmeter probe is configured to perform data measurements at a predetermined distance from the axis as the turntable drives the electromagnetic lens to rotate at a constant speed.

5. The method of claim 1, wherein the step of evaluating the performance of the electromagnetic lens based on the multipole field amplitude comprises: The amplitude of the multipole field is compared with a plurality of preset threshold ranges, each threshold range corresponding to an evaluation level characterizing the performance of the electromagnetic lens; as well as The performance evaluation level of the electromagnetic lens is determined based on the comparison results.

6. The method according to claim 1, wherein, The multipole field amplitude includes positive diode field amplitude, oblique diode field amplitude, positive tetrapole field amplitude, and oblique tetrapole field amplitude.

7. The method according to claim 1, wherein the step of fitting the plurality of sets of magnetic field data includes: A polynomial was used to fit the multiple sets of magnetic field data, and The polynomial is any one of Legendre polynomials, Chebyshev polynomials, or Hermitian polynomials.

8. The method of claim 1, further comprising, after the step of obtaining the fitting function: Calculate and output the error term corresponding to the fitted function, and If the error term meets a preset threshold, perform a Fourier transform on the fitted function.

9. The method according to claim 1, wherein, The electromagnetic lens includes any one of a condenser lens, an objective lens, and a projection lens.

10. A computer device comprising a memory, a processor, and a computer program stored in the memory and running on the processor, wherein the processor, when executing the computer program, implements the performance evaluation method for the electromagnetic lens of an electron microscope according to any one of claims 1 to 9.

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