Aperture array with integrated current measurement

Abstract

Systems and methods for measuring beam current in a multi-beam device are disclosed. The multi-beam device may include a charged particle source configured to generate a primary charged particle beam, and an aperture array. The aperture array may include a plurality of apertures configured to form a plurality of beamlets from the primary charged particle beam; and a detector including a circuit system for detecting a current of at least a portion of the primary charged particle beam radiating the aperture array. The method for measuring beam current may include radiating the primary charged particle beam onto the aperture array and detecting a current of at least a portion of the primary charged particle beam.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to EP application 19166009.1, filed on March 28, 2019, which is incorporated herein by reference in its entirety. Technical Field

[0003] The embodiments provided herein disclose a multi-beam apparatus, and more particularly, a multi-beam electron microscope including an aperture array with integrated beam current measurement capability. Background Art

[0004] During the manufacture of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured according to design and are free of defects. Inspection systems utilizing optical microscopes or charged particle (e.g., electron) beam microscopes, such as scanning electron microscopes (SEMs), can be employed. As the physical dimensions of IC components continue to shrink, the accuracy and yield of defect detection become more important. Although brighter electron sources can be used to increase throughput and resolution; however, the stability of the electron source may be compromised, resulting in an inspection tool that is insufficient for its intended purpose.

[0005] Therefore, related art systems face limitations when, for example, determining the stability of an electron source at high beam currents.Further improvements in the art are needed. Summary of the Invention

[0006] Various embodiments of the present disclosure may provide systems and methods for measuring beam current in a multi-beam device. In one aspect, the present disclosure relates to a multi-beam device. The multi-beam device may include a charged particle source configured to generate a primary charged particle beam, and an aperture array. The aperture array may include a plurality of apertures configured to form a plurality of beamlets from the primary charged particle beam; and a detector including circuitry for detecting a current of at least a portion of the primary charged particle beam radiating the aperture array.

[0007] The detector may include circuitry for accumulating charge of at least a portion of the primary charged particle beam and measuring current based on the accumulated charge. The circuitry may be configured to monitor the current of at least a portion of the primary charged particle beam. The current of at least a portion of the primary charged particle beam may be used to determine the total current of the primary charged particle beam.

[0008] The detector may include a circuit system for further detecting a change in the position or size of a portion of the primary charged particle beam. The detector may include a plurality of current detectors configured to detect a change in at least one of the plurality of parameters of the primary charged particle beam. The plurality of parameters may include beam position, beam diameter, beam current, beam current density, or the uniformity of beam current density. Each current detector in the plurality of current detectors may be associated with at least one aperture of the aperture array and may be arranged on the aperture array. The current detector may include a Faraday cup, a diode, a diode array, a scintillator, or a photomultiplier tube.

[0009] In another aspect, the present disclosure relates to a multi-beam apparatus comprising a charged particle source configured to generate a primary charged particle beam. The apparatus may include a first aperture array comprising a plurality of first apertures and configured to form a plurality of beamlets from the primary charged particle beam; and a second aperture array. The second aperture array may include a plurality of second apertures and a plurality of current detectors, wherein each current detector in the plurality of current detectors is associated with at least one aperture in the plurality of second apertures and includes circuitry for detecting a current flowing through a corresponding beamlet in the plurality of beamlets radiating the second aperture array.

[0010] The first aperture array may include a current limiting aperture array, which is arranged between the charged particle source and the second aperture array. Each of the multiple current detectors may include a circuit system for accumulating the charge of at least a portion of the corresponding sub-beam of the multiple sub-beams and measuring the current based on the accumulated charge. Each of the multiple current detectors may include a circuit system for monitoring the current of the corresponding sub-beam and detecting at least one change in the position or size of the corresponding sub-beam. Each of the multiple current detectors may include a circuit system for detecting a change in at least one parameter of a plurality of parameters of the corresponding sub-beam, the plurality of parameters including one of the following: sub-beam position, sub-beam diameter, sub-beam current, sub-beam current density, or uniformity of sub-beam current density. Each of the multiple current detectors may be a Faraday cup, a diode, a diode array, a scintillator, or a photomultiplier tube.

[0011] In yet another aspect, the present disclosure relates to a multi-beam apparatus comprising a charged particle source configured to generate a primary charged particle beam; a first aperture array comprising a plurality of first apertures configured to form a plurality of beamlets from the primary charged particle beam; and a first current detector comprising a circuit system for detecting a current radiating at least a portion of the primary charged particle beam radiating the first aperture array. The multi-beam apparatus may include a second aperture array comprising a plurality of second apertures, wherein each aperture of the plurality of second apertures is configured to receive at least a portion of a corresponding beamlet of the plurality of beamlets.

[0012] The first current detector may include circuitry to accumulate charge of at least a portion of the primary charged particle beam and measure current based on the accumulated charge.The second aperture array may include a second current detector associated with at least one aperture of the plurality of second apertures.

[0013] In yet another aspect, the present disclosure relates to a method for measuring beam current in a multi-beam device. The method may include radiating a primary charged particle beam onto an aperture array and detecting a current of at least a portion of the primary charged particle beam. The method may include adjusting at least one beam parameter from a plurality of beam parameters based on the detected current using a control circuit. The method may also include accumulating a charge of at least a portion of the primary charged particle beam and measuring the beam current based on the accumulated charge.

[0014] The method may further include monitoring a beam current of at least a portion of the primary charged particle beam and detecting a change in at least one of a plurality of parameters of the portion of the primary charged particle beam. The plurality of parameters may include at least one of the following: beam position, beam diameter, beam current, beam current density, or uniformity of beam current density. The method may further include determining a total current of the primary charged particle beam based on the measured current of at least a portion of the primary charged particle beam. The detector may include a plurality of current detectors, and each of the plurality of current detectors is associated with at least one aperture of the aperture array.

[0015] In yet another aspect, the present disclosure relates to a non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a multi-beam device to cause the multi-beam device to perform a method for measuring beam current in the multi-beam device. The method may include controlling the illumination of a primary charged particle beam on an aperture array, and determining a current of the primary charged particle beam based on a current of at least a portion of the primary charged particle beam detected by a detector.

[0016] A set of instructions executable by one or more processors of the multi-beam device may cause the multi-beam device to activate a detector to accumulate charge of at least a portion of the primary charged particle beam and measure a current of at least a portion of the primary charged particle beam based on the accumulated charge. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system according to an embodiment of the present disclosure.

[0018] Figure 2 It is a diagram illustrating an embodiment of the present disclosure that can be used as Figure 1 A schematic diagram of an exemplary electron beam tool that is part of an exemplary electron beam inspection system.

[0019] Figure 3 is a schematic diagram illustrating an exemplary arrangement of an aperture array in a multi-beam device according to an embodiment of the present disclosure.

[0020] Figure 4 It is a diagram illustrating an embodiment of the present disclosure that can be used as Figure 1 A block diagram of an exemplary multi-beam apparatus that is part of an exemplary electron beam inspection system.

[0021] 5A to 5D is a schematic diagram illustrating an exemplary configuration of an aperture array of a multi-beam device including an integrated beam current detector according to an embodiment of the present disclosure.

[0022] Figure 6 is a flow chart illustrating an exemplary method of measuring beam current in a multi-beam apparatus according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which, unless otherwise indicated, the same numbers in different figures represent the same or similar elements. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations. Instead, they are merely examples of apparatus and methods consistent with various aspects related to the disclosed embodiments as described in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, the present disclosure is not limited thereto. Similarly, other types of charged particle beams may be applied. Furthermore, other imaging systems such as optical imaging, light detection, X-ray detection, etc. may be used.

[0024] Increasing the computing power of electronic devices while reducing the physical size of the devices can be achieved by significantly increasing the packaging density of circuit components such as transistors, capacitors, diodes, etc. on integrated circuit (IC) chips. For example, in a smartphone, an IC chip (which is the size of a fingernail) may contain more than 2 billion transistors, each of which is less than 1 / 1000 the size of a human hair. Not surprisingly, semiconductor IC manufacturing is a complex process with hundreds of individual steps. Even an error in a single step can greatly affect the operation of the final product. Even a "fatal defect" can cause equipment failure. The goal of the manufacturing process is to increase the overall yield of the process. For example, in order to achieve a 75% yield for a 50-step process, the yield of each individual step must be greater than 99.4%, and if the yield of a single step is 95%, the yield of the entire process drops to 7%.

[0025] As geometries shrink and the IC chip industry migrates to three-dimensional (3D) architectures such as NAND gates, FinFETs, and advanced dynamic random access memory (DRAM), finding defects becomes increasingly challenging and expensive at each lower node. While IC chip manufacturing facilities require high process yields, it is also critical to maintain high wafer throughput, which is defined as the number of wafers processed per hour. High process yields, as well as high wafer throughput, are impacted by the presence of defects, especially when operator intervention is involved. Therefore, detecting and identifying micron- and nanometer-sized defects by inspection tools such as SEMs is critical to maintaining high yields and high throughput at a low cost.

[0026] Semiconductor chips are fabricated in extremely clean and controlled environments with very low levels of contaminants such as dust, airborne particles, aerosol particles, and chemical vapors. More specifically, semiconductor cleanrooms are required to maintain controlled contamination levels, specified by the number of particles of a specified size per cubic foot. A typical chip manufacturing cleanroom contains between 1 and 10 particles per cubic foot of air, each less than 5 μm in diameter. By comparison, ambient air outside in a typical urban environment contains approximately 1.25 billion particles per cubic foot, each with an average diameter of approximately 200 μm. A speck of dust as small as 1 μm on a wafer in processing can span thousands of transistors on a chip, potentially rendering the entire chip unusable. In some cases, a speck of dust on the reticle or photomask used to create repetitive patterns on the wafer can cause physical or electrical defects to reappear. For example, one or more metal lines connecting transistors in a single chip might overlap or become undesirably connected through a dust particle, resulting in a short circuit across the entire chip.

[0027] It is becoming increasingly important to ensure that wafers can be observed, inspected, and imaged with high accuracy and resolution while maintaining high throughput (e.g., defined as the number of wafers processed per hour). To increase throughput, some inspection tools may use multiple beams to simultaneously form multiple probe spots on a sample surface. As an example, an inspection tool may generate a primary beam that is split into multiple beamlets (e.g., "beamlets") that can then each be scanned over the sample surface, as in a multi-beam inspection system or a multi-charged particle beam device.

[0028] In order to maintain high throughput when enhancing resolution in many charged particle beam devices such as multi-beam SEM, it is desirable that primary beam has high current density or high brightness so that a plurality of beamlets have as many electrons as possible.The current density of primary beam (for example, electron beam) can be defined as the number of electrons (or electric charge) per unit area of ​​per unit time beam.Although current density may be an important beam parameter, because electrons leave electron source and the angular distribution of electrons in the beam with a certain range of divergence angle may be an important beam parameter, so under the background of electron microscope, beam brightness may be more relevant.Therefore, beam brightness can be defined as the current density per unit solid angle (expressed in steradian) of primary source.

[0029] For example, a high-brightness electron beam can be generated by increasing the voltage between the anode and cathode (typically an electron source). However, subjecting the primary electron source to high voltage for an extended period of time may affect the durability and stability of the electron source. Instability in the primary electron source may affect not only the performance of the source, but also the generated primary electron beam. For example, the primary electron beam may exhibit time-dependent variations in emission current, variations in the position of the primary beam relative to other components of the inspection system, variations in beam size, variations in the total current of the beam, variations in the uniformity of the current density of the beam, etc., which may reduce the overall efficiency and throughput of the inspection system.

[0030] In a multi-beam SEM system, a primary electron beam is split into multiple beamlets, and each of the multiple beamlets can generate a probe spot on the sample surface. The interaction of the electrons of the beamlet with the sample generates a signal containing information associated with the probe spot on the sample. The generated signal is then processed to create an image representing the probed sample area, enabling the user to visually analyze the sample and any defects on it. An unstable primary electron beam from an unstable electron source can cause the generated beamlet current to be non-uniform, thereby affecting image quality. In IC chip manufacturing facilities, visual inspection tools such as multi-beam SEMs are often relied upon for wafer inspection and defect analysis. Therefore, any compromise in image quality may hinder the user's ability to analyze and inspect the wafer and may affect overall throughput.

[0031] Because image quality can be affected by several factors, including but not limited to an unstable primary electron beam, an unstable primary electron source, an uncalibrated detection system, misaligned optics in the SEM column, sample contamination, mechanical vibrations, thermal interference, and acoustic interference, determining the cause of image quality degradation during wafer inspection is very challenging. Any or all of these sources of imaging defects may affect the overall resolution and throughput of the inspection system. Some aspects of the present disclosure provide for measuring the beam current (or beamlet current) at the aperture array to detect and monitor instabilities in the primary electron source or primary electron beam while scanning the primary electron beam for wafer inspection. The measurement information can also be used to determine the source of the instability and adjust the primary electron source, primary electron beam, or related components of the inspection system accordingly.

[0032] In one aspect of the present disclosure, a multi-beam apparatus including a beam current detector can be used to measure the current of a primary beam or beamlet. The beam current detector can be disposed on an aperture array irradiated by the primary electron beam or beamlet. The beam current detector can include circuitry for measuring the current of the primary electron beam by accumulating charge of at least a portion of the primary electron beam and measuring the current of the portion of the primary electron beam.

[0033] For the sake of clarity, the relative sizes of the components in the drawings may be exaggerated. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and only the differences with respect to the various embodiments are described.

[0034] As used herein, unless expressly stated otherwise, the term "or" encompasses all possible combinations, unless impractical. For example, if it is stated that a component may include A or B, then unless expressly stated otherwise or impractical, the component may include A or B or A and B. As a second example, if it is stated that a component may include A, B, or C, then unless expressly stated otherwise or impractical, the component may include A or B or C, or A and B, or A and C, or B and C, or A and B and C.

[0035] Now refer to Figure 1 ,Should Figure 1 An exemplary electron beam inspection (EBI) system 100 is illustrated in accordance with an embodiment of the present disclosure. Figure 1 As shown, the charged particle beam inspection system 100 includes a main chamber 10, a load / lock chamber 20, an electron beam tool 100, and an equipment front end module (EFEM) 30. The electron beam tool 100 is located in the main chamber 10.

[0036] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include one or more additional load ports. The first load port 30a and the second load port 30b receive front-opening unification units (FOUPs) containing wafers to be inspected (e.g., semiconductor wafers or wafers made of other materials) or samples to be inspected (wafers and samples may be collectively referred to as "wafers" hereinafter). One or more robotic arms (not shown) in the EFEM 30 transfer the wafers to the load / lock chamber 20.

[0037] The load / lock chamber 20 is connected to a load / lock vacuum pump system (not shown), which removes gas molecules from the load / lock chamber 20 to reach a first pressure lower than atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) transport the wafer from the load / lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown), which removes gas molecules from the main chamber 10 to reach a second pressure lower than the first pressure. After reaching the second pressure, the wafer is inspected by the electron beam tool 100.

[0038] The controller 40 is electronically connected to the electron beam tool 100 and may also be electronically connected to other components. The controller 40 may be a computer configured to perform various controls of the EBI system 1. Figure 1 1. The controller 40 is shown outside of the structure including the main chamber 10, the load / lock chamber 20, and the EFEM 30, but it will be appreciated that the controller 40 may be part of the structure.

[0039] While the present disclosure provides an example of a main chamber 100 housing an electron beam inspection tool, it should be noted that aspects of the present disclosure in its broadest sense are not limited to chambers housing electron beam inspection tools. Rather, it should be appreciated that the aforementioned principles may also be applied to other tools.

[0040] Now refer to Figure 2 ,Should Figure 2 is a diagram illustrating an embodiment of the present disclosure including Figure 1 Schematic diagram of an exemplary electron beam tool as part of an exemplary charged particle beam inspection system. The electron beam tool 100 (also referred to herein as apparatus 100) includes an electron source 101, a gun aperture plate 171 having a gun aperture 103, a focusing lens 110, a source conversion unit 120, a primary projection system 130, a sample stage ( Figure 2), a secondary optical system 150, and an electronic detection device 140. The primary projection optical system 130 may include an objective lens 131. The electronic detection device 140 may include a plurality of detection elements 140_1, 140_2, and 140_3. The beam splitter 160 and the deflection scanning unit 132 may be placed within the primary projection optical system 130. It should be understood that other known components of the apparatus 100 may be added or omitted as appropriate.

[0041] The electron source 101, the gun aperture plate 171, the converging lens 110, the source conversion unit 120, the beam splitter 160, the deflection scanning unit 132, and the primary projection optical system 130 may be aligned with the primary optical axis 100_1 of the apparatus 100. The secondary optical system 150 and the electron detection device 140 may be aligned with the secondary optical axis 150_1 of the apparatus 100.

[0042] The electron source 101 may include a cathode, an extractor, or an anode, wherein primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 102 having crosses (virtual or real) 101s. The primary electron beam 102 may be considered to be emitted from the crosses 101s.

[0043] The source conversion unit 120 may include an image forming element array ( Figure 2 ). The image forming element array may include a plurality of micro-deflectors or micro-lenses to form a plurality of parallel images (virtual or real) of the crosses 101s with the plurality of beamlets of the primary electron beam 102. Figure 2 Three sub-bundles 102_1 , 102_2 , and 102_3 are shown as an example, and it should be appreciated that the source conversion unit 120 can handle any number of sub-bundles.

[0044] The converging lens 110 can focus the primary electron beam 102. The currents of the sub-beams 102_1, 102_2, and 102_3 downstream of the source conversion unit 120 can be varied by adjusting the focusing power of the converging lens 110 or by changing the radial size of the corresponding beam-limiting apertures within the beam-limiting aperture array. The objective lens 131 can focus the sub-beams 102_1, 102_2, and 102_3 onto the sample 190 for inspection and form three probe spots 102_1s, 102_2s, and 102_3s on the surface of the sample 190. The gun aperture plate 171 can block unused peripheral electrons of the primary electron beam 102 to reduce Coulomb interaction effects. The Coulomb interaction effect can increase the size of each of the probe spots 102_1s, 102_2s, and 102_3s, thereby degrading inspection resolution.

[0045] The beam splitter 160 may be a Wien filter type beam splitter comprising an electrostatic deflector generating an electrostatic dipole field E1 and a magnetic dipole field B1 (both at Figure 2 (Not shown in the figure). If applied, the electrostatic dipole field E1 exerts a force on the electrons of beamlets 102_1, 102_2, and 102_3 that is equal in magnitude and opposite in direction to the force exerted on the electrons by the magnetic dipole field B1. As a result, beamlets 102_1, 102_2, and 102_3 can pass straight through beam splitter 160 at zero deflection angle.

[0046] The deflection scanning unit 132 can deflect the beamlets 102_1, 102_2, and 102_3 to scan the probe spots 102_1s, 102_2s, and 102_3s over three small scanning areas in a section of the surface of the sample 190. In response to the incidence of the beamlets 102_1, 102_2, and 102_3 at the probe spots 102_1s, 102_2s, and 102_3s, three secondary electron beams 102_1se, 102_2se, and 102_3se can be emitted from the sample 190. Each of the secondary electron beams 102_1se, 102_2s, and 102_3s can include electrons having an energy distribution including secondary electrons (energy ≤ 50 eV) and backscattered electrons (energy between 50 eV and the landing energy of the beamlets 102_1, 102_2, and 102_3). The beam splitter 160 can direct the secondary electron beams 102_1se, 102_2se, and 102_3se to the secondary optical system 150. The secondary optical system 150 can focus the secondary electron beams 102_1se, 102_2se, and 102_3se onto the detection elements 140_1, 140_2, and 140_3 of the electron detection device 140. The detection elements 140_1, 140_2, and 140_3 can detect the corresponding secondary electron beams 102_1se, 102_2se, and 102_3se and generate corresponding signals for constructing an image of the corresponding scanning area of ​​the sample 190.

[0047] Now refer to Figure 3 ,Should Figure 3 FIG illustrates an exemplary arrangement of aperture arrays in a multi-beam device 300 according to an embodiment of the present disclosure. It should be appreciated that the multi-beam device 300 may be substantially similar to Figure 2 The electron beam tool 100 of the multi-beam device 300 may include a primary electron source 301, a primary electron beam 302, a current limiting aperture array 305, a focusing lens 310, and a beam limiting aperture array 320. Each of the components of the multi-beam device 300 may be aligned with the primary optical axis 300_1.

[0048] The primary electron source 301 and the primary electron beam 302 of the multi-beam device 300 are substantially similar to Figure 2 The electron source 101 and primary electron beam 102 of the electron beam tool 100 are shown. In some embodiments, the primary electron source 301 may include, for example, a tungsten filament, a lanthanum hexaboride (LaB6) cathode, cerium hexaboride (CeB6), tungsten / zirconium oxide (W / ZrO2), or the like. The electron source may generate electrons by thermionic emission from a heated source or by electric field-induced emission from a cathode. Other suitable electron emission or electron generation methods may also be employed.

[0049] The primary electron beam 302 may include electrons having high kinetic energy due to a high accelerating electric field to drive the electrons toward a sample (not shown). The kinetic energy of the electrons may be in the range of 0.2 keV to 40 keV or higher, which is determined by the extraction voltage, the accelerating voltage, the beam-modifying lens, etc. In some embodiments, the primary electron beam 302 may have an optical axis (not shown) along which the primary electron beam 302 travels toward the sample. The optical axis of the primary electron beam 302 may be aligned with the primary optical axis 300_1.

[0050] The multi-beam device 300 may include a current-confined aperture array 305 having a plurality of apertures 303 to form a plurality of beamlets. Figure 3 Three beamlets 302_1, 302_2, and 302_3 are shown as an example, but it should be appreciated that the current-confining aperture array 305 can include any number of apertures 303 and form any number of beamlets, as appropriate. The cross-section of the apertures 303 of the current-confining aperture array 305 can be, for example, circular, rectangular, elliptical, or a combination thereof. The current-confining aperture array 305 can be positioned along the primary optical axis 300_1 between the primary electron source 301 and the converging lens 310. The current-confining aperture array 305 can be placed at a fixed, predetermined distance away from the primary electron source 301.

[0051] In some embodiments, the current-confining aperture array 305 may include a uniform aperture matrix, e.g., each aperture 303 of the current-confining aperture array 305 may be uniform in cross-section, shape, or size. In some embodiments, the current-confining aperture array 305 may include a non-uniform aperture matrix, comprising apertures that are non-uniform in cross-section, shape, or size. In some embodiments, the apertures 303 may be arranged in a linear, circular, rectangular, spiral, zigzag, serpentine, triangular pattern, or a combination thereof. It should be appreciated that the apertures of the current-confining aperture array 305 may be randomly arranged across the array. Other suitable arrangements and configurations of the apertures may also be used.

[0052] In some embodiments, the current confining aperture array 305 may include metal, ceramic, plastic, alloy, composite material, semiconductor, or any suitable material that is compatible with a vacuum and can be processed to form the apertures 303. The apertures 303 of the current confining aperture array 305 may be fabricated using photolithography, embossing, ultra-precision laser machining, injection molding, mechanical drilling, micro-electromechanical systems (MEMS)-based technology, or any other suitable technology.

[0053] In some embodiments, the multi-beam device 300 may include an aperture plate (not shown), such as Figure 2 The gun aperture plate 171 may be configured to block unused peripheral electrons of the primary electron beam 102 to reduce Coulomb interaction effects, which may enlarge the size of the probe spot on the sample surface, thereby reducing detection resolution, etc.

[0054] In some embodiments, the multi-beam device 300 can include a current-limiting aperture array 305 and an aperture plate. The aperture plate can be placed between the primary electron source 301 and the current-limiting aperture array 305. The aperture plate can be placed at a predetermined distance from the primary electron source 301 so that the plane of the aperture plate is perpendicular to the primary optical axis 300_1. The position of the aperture plate can be fixed or adjustable based on the beam current requirements.

[0055] The current limiting aperture array 305 may be configured to reduce the primary beam current by dividing the primary electron beam 302 into beamlets 302_1, 302_2, and 302_3. The associated beamlet current of each of the beamlets 302_1, 302_2, and 302_3 may be lower than the primary beam current of the primary electron beam 302. As used herein, the associated beamlet current refers to a current determined by the number of time intervals of electrons forming the beamlets.

[0056] Return Reference Figure 3 , the converging lens 310 of the multi-beam device 300 is substantially similar to Figure 2 The converging lens 110 of the electron beam tool 100 is shown. The converging lens 310 can be configured to collimate the sub-beams 302_1, 302_2, and 302_3. The electron beam from the source is inherently divergent, and an uncollimated electron beam may generate an undesirably large probe spot, resulting in poor resolution of the acquired image. For example, in Figure 3 In FIG. 3 , one or more beamlets such as 302_1 may be divergent after passing through an aperture plate (not shown) or current limiting aperture array 305 and may have to be collimated by a converging lens 310 into a plurality of relatively parallel beamlets.

[0057] The multi-beam device 300 may include a beam-limiting aperture array 320. Beamlets 302_1, 302_2, and 302_3 may be directed to the beam-limiting aperture array 320 after passing through the converging lens 310. The beam-limiting aperture array 320 may include a plurality of apertures 323 configured to receive the beamlets and allow at least a portion of the beamlets to pass through. In some embodiments, each aperture in the plurality of apertures 323 may be aligned to receive a collimated beamlet (e.g., beamlet 302_1) from the converging lens 310.

[0058] The beam-limiting aperture array 320 may include a matrix of apertures 323 arranged in a rectangular, circular, triangular, square, serpentine, or spiral pattern. In some embodiments, the apertures 323 may be randomly arranged across the beam-limiting aperture array 320. The apertures 323 of the beam-limiting aperture array 320 may have a uniform cross-section, shape, or size.

[0059] Now refer to Figure 4 ,Should Figure 4 The embodiment of the present disclosure is shown as follows Figure 1 1. An exemplary multi-beam apparatus 400 is shown as part of the exemplary electron beam inspection system 100 of FIG. The multi-beam apparatus 400 may include a primary electron source 401, a primary electron beam 402, a current limiting aperture array 405 having a plurality of apertures 403, a current detector 404, a converging lens 410, a beam limiting aperture array 420, an objective lens 431, a beam control circuit 440, a current measurement circuit 450, a lens control circuit 460, a stage control circuit 470, a controller 480, and a sample 490 disposed on a stage 495. In some embodiments, one or more of the beam control circuit 440, the current measurement circuit 450, the lens control circuit 460, the stage control circuit 470, and the controller 480 may be Figure 1 is part of the controller 40. Each aperture of the plurality of apertures 403 is configured to generate a beamlet (eg, 402_1, 402_2, 402_3) and a corresponding probe spot (eg, 402_1S, 402_2S, 402_3S) on the sample 490.

[0060] It should be appreciated that primary electron source 401, primary electron beam 402, and converging lens 410 are similar or substantially similar to primary electron source 301, primary electron beam 302, and converging lens 310, respectively. Current confining aperture array 405 may include a plurality of apertures 403 that are substantially similar to apertures 303 or current confining aperture array 305.

[0061] The current limiting aperture array 405 may include a current detector 404 configured to measure the current of the primary electron beam 402. In some embodiments, the current detector 404 may include a Faraday cup, a diode, a diode array, or a scintillator. It should be appreciated that other current detection devices and techniques may also be employed.

[0062] In some embodiments, the multi-beam device 400 may include a current detector 404 disposed on the current limiting aperture array 405. The current detector 404 may be placed on the current limiting aperture array 405 such that at least a portion 402 of the incident primary electron beam covers the entire current detector 404. Charge (e.g., electrons) of the portion of the incident primary electron beam 402 incident on the current detector 404 may be accumulated over a predetermined time. The current of the portion of the primary electron beam 402 incident on the current detector 404 may be measured using a current measurement circuit 450 based on the accumulated charge. For example, for a continuous beam of charged particles such as electrons, a measured current of 1 nA (1×10 -9 The current of 100 amperes corresponds to about 6.25 billion electrons incident on the current detector 404 per second, assuming that the charge of the electron is 1.6×10 -19 coulomb.

[0063] In some embodiments, the current measurement circuit 450 can be electrically connected to the current detector 404 and a controller 480 configured to control the current measurement circuit 450. The current measurement circuit 450 can include a timing control unit, a measurement circuit, a sample-and-hold circuit, an analog-to-digital converter circuit, and other related components for signal processing and communication with other elements of the multi-beam device 400. The controller 480 can include a central processing unit including a computer, a server, a microprocessor, a processor, or an integrated circuit. In some embodiments, the controller 480 can be Figure 1 A portion of the controller 40 or substantially similar to Figure 1 Controller 40.

[0064] The total current or current density of the primary electron beam 402 may be determined based on the measured current or current density of the portion of the beam that is incident on the current detector 404. For example, the current density of the primary electron beam 402 may be determined based on the measured current of the portion of the beam and the area of ​​the current detector exposed to the primary electron beam 402.

[0065] In some embodiments, the current detector 404 can be configured to monitor the beam current or beam current density over an extended period of time to determine changes in beam parameters, including but not limited to beam current, beam current density, the position of the beam with respect to the current-limiting aperture array 405, the size of the beam, and the uniformity of the current density. For example, if the current detector 404 is placed near the edge of the diameter of the primary electron beam 402 incident on the current-limiting aperture array 405, a small shift in the position of the beam such that the current detector 404 is not completely covered by the primary electron beam 402 may result in a decrease in the amount of charge detected, thereby causing the measured current to be smaller.

[0066] In a conventional multi-beam SEM such as the multi-beam device 400, the primary electron beam 402 may comprise a conical diverging beam having a circular cross-section, and the current limiting aperture array 405 may comprise a square aperture array. In such a configuration, it may be desirable to employ more than one current detector 404. For example, placing current detectors (e.g., current detectors 404) along each side of the square aperture array and within the boundaries formed by the periphery of the primary electron beam 402 incident on the current limiting aperture array 405 may enable detection of beam drift along the X-direction and the Y-direction. In the context of the present disclosure, "drift" of a beam may refer to a finite and continuous change in a beam parameter over time relative to an expected initial value of the parameter. For example, drift may refer to a change in the beam parameter relative to the primary optical axis (e.g., Figure 3 The controller 480 may be configured to detect and determine drift in beam parameters based on information from the current measurement circuit 450, such as changes in the X and Y coordinates of the beam position measured along the primary optical axis 300-1, or changes in the size of the beam cone diameter along a plane perpendicular to the primary optical axis. When detecting and determining drift in beam parameters based on information from the current measurement circuit 450, the controller 480 may facilitate repositioning or shaping the primary electron beam 402 by adjusting source settings via the beam control circuit 440, adjusting lens settings via the lens control circuit 460, or adjusting beam targeting via the stage control circuit 470. It will be appreciated that other control mechanisms may also be employed as appropriate.

[0067] Figure 4The beam control circuit 440 shown can be configured to control the primary electron beam 402. Controlling the primary electron beam can include, but is not limited to, controlling the extraction voltage, controlling the acceleration voltage, controlling the beam deflection voltage, etc. In some embodiments, the beam control circuit 440 can control the primary electron beam 402 based on feedback from the current measurement circuit 450 through the controller 480. For example, the current measurement circuit 480 can determine changes in the beam current density incident on the aperture array 405 and generate a signal. The controller 480 can use a signal processing circuit (not shown) to process the input signal and generate an output signal based on the input signal. The output signal can be communicated to the beam control circuit 440 to adjust the beam current density of the primary electron beam 402 based on the signal.

[0068] Figure 4 The measurement circuit 450 shown can be configured to measure the current of the primary electron beam 402 or the sub-beams 402_1, 402_2, and 402_3. The measurement circuit 450 can be electrically connected to one or more current detectors 404 disposed on the current limiting aperture array 405. In some embodiments, the measurement circuit 450 can be electrically connected to the current detectors 404 and a current detector disposed on a beam limiting aperture array (not shown). The measurement circuit 450 can include electrical leads connected to the current detectors 404 (e.g., a Faraday cup), a current measuring instrument such as an ammeter, or a voltmeter, or an oscilloscope that displays the voltage generated across a resistor from the conductive leads to ground. In some embodiments, the measurement circuit 450 can exchange information with the controller 480.

[0069] In some embodiments, current measurement circuit 450 may include a switching device configured to control current detector 404. The switching device may control current detector 404 to collect charge based on a programmed schedule. For example, the switching device may be configured to operate current detector 404 at a 50% duty cycle in detection mode. However, in monitoring mode, current detector 404 may operate at a 100% duty cycle. Duty cycle refers to the fraction of a period during which a signal or system is active. A current detector, such as a Faraday cup, may be activated or deactivated by applying a voltage signal to attract or repel electrons.

[0070] Figure 4The lens control circuit 460 shown can be configured to control the converging lens 410 or the objective lens 431. The lens control circuit 460 can exchange information with the controller 480. In some embodiments, the converging lens 410 or the objective lens 431 or both can be adjusted based on information from the controller 480. For example, the lens control circuit 460 can adjust the focus or focus intensity of the converging lens to ensure that the beamlets are collimated. In some embodiments, the lens focusing circuit 450 can include a storage module, such as a local memory, to store information related to lens adjustments and lens positions. The controller 480 can include a global memory configured to store information from the beam control circuit 440, the measurement circuit 450, the lens control circuit 460, or the stage control circuit 470.

[0071] Figure 4 The stage control circuit 470 shown can be configured to control the movement of the stage 495 on which the sample 490 is securely placed. The stage control circuit 470 can include a signal processing unit configured to receive stage position information from a position sensor and process the stage position information to generate a signal for moving the stage 495 based on the received position information. In some embodiments, the position of the stage 495 can be adjusted based on the position of the probe spot 402_1S, 402_2S, or 402_3S. The stage control circuit 470 can exchange information with the controller 480. In some embodiments, the position of the stage 495 can be adjusted by the stage control circuit 470 to compensate for changes in beam parameters.

[0072] In some embodiments, the primary optical axis 400_1 of the multi-beam device can be aligned with the geometric center of the current-limiting aperture array 405. One or more current detectors 404 can be placed at or near the geometric center of the current-limiting aperture array 405 to obtain information related to the primary electron source 401. In some embodiments, information obtained from the current detector 404 placed at or near the center of the current-limiting aperture array 405 can be combined with information obtained from current detectors 404 placed elsewhere on the current-limiting aperture array 405 to determine the cause of drift. For example, a map of the electron density within the primary electron beam 402 across a plane (e.g., the plane of the current-limiting aperture array 405 on which the primary electron beam 402 is incident and on which the current detectors 404 are disposed) can be generated to determine an electron density gradient on the XY axis or an electron density distribution within the plane, thereby enabling a user to correct for drift while inspecting a wafer.

[0073] The beam-limiting aperture array 420 may include a plurality of apertures 423 configured to receive the beamlets 402_1, 402_2, and 402_3 and to limit the number of electrons that pass through the objective lens 431 to form corresponding probe spots 402_1S, 402_2S, and 402_3S on the sample 490. In some embodiments, the beam-limiting aperture array 420 may include a plurality of current detectors 404 (not shown) disposed thereon. The beam-limiting aperture array 420 may include a current detector 404 associated with each of the apertures 423. Alternatively, each current detector 404 may be associated with more than one aperture 423. For example, if the beam-limiting aperture array 420 includes two apertures 423 separated by a substrate of the beam-limiting aperture array 420, such that a single beamlet (e.g., beamlet 402_3) completely irradiates a portion of the beam-limiting aperture array 420 that includes the two apertures, the portion including the substrate that separates the two apertures, and if the current detector 404 is placed within the portion of the substrate that separates the apertures 423.

[0074] In some embodiments, in addition to the current-limiting aperture array 405, the multi-beam device 400 may include an aperture plate (e.g., Figure 2 1) and the beam limiting aperture array 420. One or more current detectors 404 may also be used on the aperture plate, the beam limiting aperture array 420, and the current limiting aperture array 405. In this configuration, beam parameters such as beam position, beam current density, beam current density uniformity, etc. may be monitored at multiple locations along the path of the beamlets 402_1, 402_2, and 402_3 or the primary electron beam 402 in the SEM column to determine the cause of drift and allow the user to correct for the drift during wafer inspection.

[0075] In some embodiments, the current detector 404 may include one or more micromachined Faraday cups fabricated using MEMS-based device fabrication techniques. A current detector such as a Faraday cup may include a conductive cylindrical charge receiver cup coaxially enclosed within a grounded outer housing. The gap between the inner cup and the outer housing may be filled with a dielectric or insulator, including but not limited to polymers, air, ceramic, etc. The Faraday cup may also include a suppressor grid on the front to repel stray electrons and also to prevent backscattering of ions or charges collected in the cup. A coaxial connector, such as a metal wire, may be electrically connected to the inner cup to form a measurement circuit. Some of the advantages of using a Faraday cup for charge or electron detection may include, but are not limited to, high accuracy, independence from the energy and mass of the charge being analyzed, scalability, manufacturability, ease of operation, compatibility with a wide range of vacuum levels, and simple data analysis.

[0076] Now refer to Figure 5A ,Should Figure 5A FIG. 5 illustrates an exemplary configuration of a current limiting aperture array 505 including a plurality of apertures 503 and a current detector 504 according to an embodiment of the present disclosure. Figure 5A Four current sensors 504-1, 504-2, 504-3, and 504-4 are shown, but more or fewer current sensors may be used. The current limiting aperture array 505 is substantially similar to Figure 4 Current limiting aperture array 405. As shown, Figure 5A A virtual boundary 515 is shown depicting the periphery of the incident primary electron beam 402 on the current confining aperture array 505, encompassing the square aperture array 503 and one or more current detectors 504 positioned along the edges of the virtual boundary 515 but within the confined area represented by the virtual boundary 515. In some embodiments, the current detectors 504 may be located anywhere on the current confining aperture array 505 within the confined area represented by the virtual boundary 515, such that no current detector prevents charged particles from passing through the aperture array 503.

[0077] In some embodiments, a current detector (e.g., Figure 5A 504-1, 504-2, 504-3, or 504-4) can be associated with at least one aperture of the current-restricting aperture array 505. For example, if the current-restricting aperture array 505 includes n number of apertures, the number of current detectors can be nm, where m is a positive integer and m<n. In some embodiments, two or more current detectors can be associated with an aperture of the current-restricting aperture array 505. For example, if the current-restricting aperture array 505 includes n number of apertures, the number of current detectors can be n+m, where m is a positive integer. In some embodiments, each aperture of the current-restricting aperture array 505 can be associated with a current detector 504. In this configuration, the number of apertures is equal to the number of current detectors.

[0078] Now refer to Figure 5B ,Should Figure 5B An exemplary configuration of a current confining aperture array 505 is illustrated, wherein the geometric center of the current confining aperture array 505 is aligned with the primary optical axis 500_1 (similar to Figure 3 The primary optical axis 300_1 and Figure 4 In this configuration, the current detector 504C can be positioned close to the central aperture 503. Alternatively, one or more peripheral current detectors 504 may be employed.

[0079] In some embodiments, each aperture 503 of the current limiting aperture array 505 may have an associated current detector 504 positioned adjacent to the aperture. In this configuration, each current detector 504 may generate a current that is Figure 4 The information generated can be stored in Figure 4 The current measurement circuit 450 or local memory within the controller 480. For example, the information can be used to generate a map of the electron density within the primary electron beam 402 to determine the cause of the drift.

[0080] In some embodiments, the total beam current may be determined based on the collected total beam current or the average beam current detected by the current detectors (eg, 504-1, 504-2, 504-3, and 504-4). Figure 5C As shown, the Figure 5C An exemplary configuration of current-limiting aperture array 505 is illustrated, with virtual boundary 515C representing a cross-section of primary electron beam 402 incident on current-limiting aperture array 505 shifted along the x-axis such that a portion of current detector 504-2 is not exposed to primary electron beam 402. The amount of beam current collected by the detector can vary based on the portion of the beam incident on the current detector. For example, the number of charged particles collected by current detector 504-2 can be smaller than the number of charged particles collected by one of current detectors 504-1, 504-3, and 504-4. Consequently, the total beam current collected can be smaller, indicating drift of primary electron beam 402. In some embodiments, each current detector 504 can be configured to generate information related to the number of charged particles collected. In such a configuration, the amount and direction of beam drift can be determined based on the information received from each current detector.

[0081] Now refer to Figure 5D ,Should Figure 5D An exemplary configuration of a current limiting aperture array 505 is shown, wherein Figure 5A Compared to the diameter of the primary electron beam 402 represented by the virtual boundary 515 shown, the diameter of the primary electron beam 402 represented by the virtual boundary 515D is smaller so that a portion of the one or more current detectors 504 is not exposed to the electrons of the primary electron beam 402. In some embodiments, as shown in FIG. Figure 5DAs shown, the primary electron beam 402, represented by virtual boundary 515D, may not be incident in its entirety on one or more apertures 503, resulting in a change in the probe spot size and shape. The amount of beam current collected by current detector 504 can indicate a change in the beam size incident on current-limiting aperture array 505. Therefore, the change in beam size can be determined based on information related to the number of charged particles collected by each current detector 504.

[0082] Although not shown, it will be appreciated that in some embodiments, the primary electron beam 402 incident on the current confining aperture array 505 represented by virtual boundary 515D may be large enough to expose all of the apertures 503 , but may only expose a portion of one or more current detectors 504 .

[0083] Figure 6 In a multi-beam device (eg, Figure 3 The present invention provides a process flow chart of an exemplary method for measuring beam current in a multi-beam device 300. The method for measuring beam current may include generating a primary charged particle beam, such as an electron beam from a primary charged particle source, radiating the primary charged particle beam onto an aperture array, and detecting a current of the primary charged particle beam incident on the aperture array.

[0084] In step 610, a primary charged particle beam (e.g., Figure 3 The primary electron beam 302) can be irradiated at an aperture array (e.g., Figure 3 The primary charged particle beam may be provided by a primary charged particle source (e.g., Figure 3 The primary electron source 301 is generated by a multi-beam device. In some embodiments, the multi-beam device may include a gun aperture plate disposed between the primary charged particle source and the current-limiting aperture array. The gun aperture plate may be configured to adjust the beam current or beam current density by blocking peripheral electrons of the primary electron beam, thereby generating an electron beam with higher current density uniformity.

[0085] The current confining aperture array may include a plurality of apertures (e.g., Figure 3 The current-limiting aperture array can be configured to block peripheral electrons and off-axis beam electrons of the primary electron beam to reduce Coulomb interaction effects. Coulomb interaction effects can enlarge the size of each probe spot in the probe spot, thereby reducing detection resolution.

[0086] In some embodiments, the current-confining aperture array may include an aperture matrix. Each aperture in the matrix may be uniform in size, shape, or cross-section. The apertures may be arranged in a rectangular, square, or circular matrix. Other arrangements of apertures are also possible.

[0087] In step 620, a detector including circuitry (e.g., Figure 4 The current detector 404 can be configured to detect a current of at least a portion of the primary electron beam. The total current of the primary electron beam can be determined based on the detected current of the portion of the beam incident on the detector. In some embodiments, the detector can include a single current detector disposed on the current-limiting aperture array. Information related to the beam current or beam current density can be obtained based on the current detected by the single current detector.

[0088] In some embodiments, as 5A to 5D As shown, the detector may include a plurality of current detectors (eg, Figure 5A 515 ). A plurality of current detectors 504 are provided on the current-confining aperture array. For example, one or more current detectors 504 can be positioned along an edge of a virtual boundary 515, but within the confined area represented by the virtual boundary 515. In some embodiments, the current detectors 504 can be positioned anywhere on the current-confining aperture array 505 within the confined area represented by the virtual boundary 515, such that no single current detector prevents charged particles from passing through the aperture array 503. In this configuration, beam position and beam cone diameter can be determined in addition to beam current or beam current density. In some embodiments, a current detector can be placed adjacent to each aperture of the current-confining aperture array. In this configuration, the uniformity of the beam current density can be determined based on information obtained from each current detector.

[0089] The current detector can be electrically connected to a current measurement circuit (e.g., Figure 4 Each of the current sensors may include electrical leads connected to an electrical measuring device, such as, but not limited to, an ammeter, a voltmeter, an oscilloscope, or the like. The current sensors may include a Faraday cup, a diode, a diode array, or a scintillator. Other current sensing methods may also be used.

[0090] In step 630, the detector may be configured to accumulate charge of at least a portion of the primary electron beam incident on the detector. Charge, such as electrons of the primary electron beam, may be collected in the detector for a predetermined time. The current detector may be controlled by a switching device in the current measurement circuit.

[0091] In detection mode, the switching device may activate the current sensor to operate at a 50% duty cycle or a 75% duty cycle. However, in monitoring mode, the current sensor may operate at a 100% duty cycle. A 100% duty cycle refers to continuous operation of the current sensor.

[0092] In step 640, the beam current or beamlet current can be measured based on the accumulated charge. The current detector may be exposed to a portion of the primary electron beam and, therefore, may only accumulate charge in the portion of the beam incident thereon. The total beam current or current density can be determined based on the measured current representing the accumulated charge of the portion of the electron beam, the area of ​​the beam incident on the current detector, the exposure time, and the type of charge of the primary charged particle beam.

[0093] In step 650, (for example, using Figure 4 After the current measurement circuit 450 of the beam current is measured, the parameters of the beam can be adjusted. Figure 4 , the controller 480 can be configured to send a signal to the beam control circuit 440 to control the primary electron beam 402. Controlling the primary electron beam 402 can include adjusting one or more beam parameters based on the measured beam current. The beam parameters can be adjusted by, for example, controlling an extraction voltage, controlling an acceleration voltage, controlling a beam deflection voltage, etc. For example, when it is determined that the beam is not large enough to adequately cover all apertures of the current-limiting aperture array 505, the beam current of the primary electron beam 402 can be increased to expand the size and thus cover all apertures with the incident primary electron beam 402. In some embodiments, the primary electron beam 402 can be adjusted based on the measured beam current to offset the determined drift, for example, by deflecting the primary electron beam so that all apertures can receive sufficient current and be covered by the incident primary beam.

[0094] In some embodiments, the current detector can be configured to monitor multiple beam parameters including, but not limited to, beam position, beam diameter, beam current, beam current density, or beam current density uniformity. 5A to 5D As shown, placing one or more current detectors on the current-limiting aperture array can allow the beam position to be determined based on the amount of beam current collected by the current detectors. For example, if the beam is shifted in one direction, the total number of electrons, and therefore the current collected, may change based on the amount and direction of the shift, allowing the user to determine the beam position, beam current, and beam current density. Figure 5D As illustrated, the beam position may be determined based on the amount of charge collected by the peripheral current detectors.

[0095] The embodiments may be further described using the following terms:

[0096] 1. A multi-beam device comprising:

[0097] a charged particle source configured to generate a primary charged particle beam; and

[0098] Aperture array, including:

[0099] A plurality of apertures are configured to form a plurality of beamlets from a primary charged particle beam; and a detector including circuitry to detect current of at least a portion of the primary charged particle beam radiating the array of apertures.

[0100] 2. The apparatus of clause 1, wherein the detector comprises circuitry to accumulate charge of at least a portion of the primary charged-particle beam and to measure the current based on the accumulated charge.

[0101] 3. Apparatus according to any of clauses 1 and 2, wherein the detector comprises circuitry to monitor the current of at least a portion of the primary charged-particle beam.

[0102] 4. The apparatus of clause 3, wherein the detector comprises circuitry to detect at least one of a change in position or a change in size of at least a portion of the primary charged-particle beam.

[0103] 5. Apparatus according to any of clauses 1 to 4, wherein the current of at least a portion of the primary charged-particle beam is used to determine the total current of the primary charged-particle beam.

[0104] 6. Apparatus according to any of clauses 1 to 5, wherein the detector comprises a plurality of current detectors configured to detect a change in at least one of a plurality of parameters of the primary charged-particle beam.

[0105] 7. The apparatus of clause 6, wherein the plurality of parameters comprises at least one of: beam position, beam diameter, beam current, beam current density, or uniformity of beam current density.

[0106] 8. The apparatus of any of clauses 6 and 7, wherein each current detector of the plurality of current detectors is associated with at least one aperture of the aperture array.

[0107] 9. The apparatus of any of clauses 6 to 8, wherein each current detector of the plurality of current detectors is disposed on an array of apertures.

[0108] 10. The apparatus of any one of clauses 1 to 9, wherein the detector comprises a Faraday cup, a diode, a diode array, or a scintillator.

[0109] 11. A multi-beam device comprising:

[0110] a charged particle source configured to generate a primary charged particle beam;

[0111] a first aperture array comprising a plurality of first apertures and configured to form a plurality of beamlets from the primary charged particle beam; and

[0112] A second aperture array comprising:

[0113] a plurality of second apertures; and

[0114] A plurality of current detectors, wherein each current detector of the plurality of current detectors is associated with at least one aperture of the plurality of second apertures and includes circuitry to detect current of a corresponding beamlet of the plurality of beamlets radiating the second aperture array.

[0115] 12. The apparatus of clause 11, wherein the first aperture array is disposed between the charged particle source and the second aperture array.

[0116] 13. The apparatus of any of clauses 11 and 12, wherein the first aperture array comprises a current confining aperture array.

[0117] 14. Apparatus according to any of clauses 11 to 13, wherein each current detector of the plurality of current detectors comprises circuitry to accumulate charge of at least a portion of a corresponding beamlet of the plurality of beamlets and to measure current based on the accumulated charge.

[0118] 15. Apparatus according to any of clauses 11 to 14, wherein each current detector of the plurality of current detectors comprises circuitry to monitor the current of a corresponding beamlet.

[0119] 16. The apparatus of clause 15, wherein each current detector of the plurality of current detectors comprises circuitry to detect at least one of a change in a position or a size of a corresponding beamlet.

[0120] 17. Apparatus according to any of clauses 11 to 16, wherein each current detector of the plurality of current detectors comprises circuitry to detect a change in at least one of a plurality of parameters of the corresponding beamlet.

[0121] 18. The apparatus of clause 17, wherein the plurality of parameters comprises one of: beamlet position, beamlet diameter, beamlet current, beamlet current density, or uniformity of beamlet current density.

[0122] 19. The apparatus of any of clauses 11 to 18, wherein each current detector of the plurality of current detectors comprises a Faraday cup, a diode, a diode array, or a scintillator.

[0123] 20. A multi-beam device comprising:

[0124] a charged particle source configured to generate a primary charged particle beam;

[0125] A first aperture array comprising:

[0126] a plurality of first apertures configured to form a plurality of beamlets from a primary charged particle beam; and

[0127] a first current detector comprising circuitry for detecting a current of at least a portion of the primary charged particle beam irradiating the first aperture array; and

[0128] The second aperture array includes a plurality of second apertures, wherein each aperture of the plurality of second apertures is configured to receive at least a portion of a corresponding beamlet of the plurality of beamlets.

[0129] 21. The apparatus of clause 20, wherein the first current detector comprises circuitry to accumulate charge of at least a portion of the primary charged-particle beam and to measure the current based on the accumulated charge.

[0130] 22. The apparatus of any of clauses 20 and 21, wherein the second aperture array comprises a second current detector associated with at least one aperture of the second plurality of apertures.

[0131] 23. The apparatus of clause 22, wherein the second current detector comprises circuitry to accumulate charge of at least a portion of a corresponding beamlet of the plurality of beamlets and to measure the current based on the accumulated charge.

[0132] 24. Apparatus according to any of clauses 20 to 23, wherein the first current detector comprises circuitry to detect a change in at least one of a plurality of parameters of the primary charged-particle beam.

[0133] 25. Apparatus according to any of clauses 22 to 24, wherein the second current detector comprises circuitry to detect a change in at least one of a plurality of parameters of the corresponding beamlet.

[0134] 26. The apparatus of clause 24, wherein the plurality of parameters of the primary charged particle beam comprises one of: beam position, beam diameter, beam current, beam current density, or uniformity of beam current density.

[0135] 27. The apparatus of clause 25, wherein the plurality of parameters corresponding to the beamlets comprises one of: beamlet position, beamlet diameter, beamlet current, beamlet current density, or uniformity of beamlet current density.

[0136] 28. The apparatus of any of clauses 20 to 27, wherein the first current detector comprises a Faraday cup, a diode, a diode array, or a scintillator.

[0137] 29. The apparatus of any of clauses 22 to 28, wherein the second current detector comprises a Faraday cup, a diode, a diode array, or a scintillator.

[0138] 30. The device of any of clauses 20 to 29, wherein the first aperture array comprises a plurality of current detectors.

[0139] 31. A method for measuring beam current in a multi-beam device, the method comprising:

[0140] radiating a primary charged particle beam onto an aperture array;

[0141] detecting a current of at least a portion of the primary charged particle beam using a detector located on the aperture array; and

[0142] At least one beam parameter of a plurality of beam parameters is adjusted based on the detected current.

[0143] 32. The method of clause 30, further comprising accumulating charge of at least a portion of the primary charged-particle beam and measuring the beam current based on the accumulated charge.

[0144] 33. The method of any of clauses 30 and 31, further comprising monitoring a beam current of at least a portion of the primary charged-particle beam.

[0145] 34. The method of any of clauses 30 to 32, further comprising detecting a change in at least one of a plurality of parameters of a portion of the primary charged-particle beam.

[0146] 35. The method of clause 33, wherein the plurality of parameters comprises at least one of: beam position, beam diameter, beam current, beam current density, or uniformity of beam current density.

[0147] 36. The method of any of clauses 30 to 34, further comprising determining a total current of the primary charged-particle beam based on a measured current of at least a portion of the primary charged-particle beam.

[0148] 37. A method according to any of clauses 30 to 35, wherein the detector comprises a plurality of current detectors, and each current detector of the plurality of current detectors is associated with at least one aperture of the aperture array.

[0149] 38. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a multi-beam apparatus to cause the multi-beam apparatus to perform a method for measuring beam current in the multi-beam apparatus, the method comprising:

[0150] controlling the impingement of the primary charged particle beam on the aperture array; and

[0151] The current of the primary charged particle beam is determined based on the current of at least a portion of the primary charged particle beam detected by the detector.

[0152] 39. The non-transitory computer-readable medium of clause 37, wherein the set of instructions executable by one or more processors of the multi-beam apparatus causes the multi-beam apparatus to further perform:

[0153] activating a detector to accumulate charge of at least a portion of the primary charged particle beam;

[0154] measuring a current of at least a portion of the primary charged particle beam based on the accumulated charge; and

[0155] At least one beam parameter of a plurality of beam parameters is adjusted based on the measured current.

[0156] A non-transitory computer readable medium may be provided that stores information for use with a controller (e.g., Figure 1 A processor of the controller 40 executes instructions for image inspection, image acquisition, stage positioning, beam focusing, electric field adjustment, beam bending, etc. Common forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid-state drives, magnetic tape or any other magnetic data storage medium, compact disk read-only memory (CD-ROM), any other optical data storage medium, any physical medium with a pattern of holes, random access memory (RAM), programmable read-only memory (PROM) and erasable programmable read-only memory (EPROM), FLASH-EPROM or any other flash memory, non-volatile random access memory (NVRAM), cache, registers, any other memory chip or cartridge, and networked versions thereof.

[0157] It should be understood that the embodiments of the present disclosure are not limited to the exact configurations described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope thereof. The present disclosure has been described in conjunction with various embodiments, and other embodiments of the present invention will be apparent to those skilled in the art in view of the specification and practice of the invention disclosed herein. The description and embodiments are to be considered as exemplary only, with the true scope and spirit of the invention being indicated by the appended claims.

[0158] The above description is intended to be illustrative, and not restrictive. It will therefore be apparent to those skilled in the art that modifications may be made from the description without departing from the scope of the claims set forth herein.

Claims

1. A multi-beam device, comprising: a charged particle source configured to generate a primary charged particle beam; as well as Aperture arrays, including: a plurality of apertures configured to form a plurality of beamlets from the primary charged particle beam; and a detector coupled to the circuit system and configured to detect a current of at least a portion of the primary charged particle beam irradiating the aperture array, wherein the detector is disposed on a beam entrance side of the aperture array with respect to the primary charged particle beam; Wherein the detector is coupled to circuitry to detect at least one of a change in position or size of the at least a portion of the primary charged particle beam. 2 . The apparatus of claim 1 , wherein the detector comprises circuitry to accumulate charge of the at least a portion of the primary charged particle beam and to measure the current based on the accumulated charge.

3. The apparatus of claim 1, wherein the detector is coupled to circuitry for monitoring the current of the at least a portion of the primary charged-particle beam. 4 . The apparatus of claim 1 , wherein the current of the at least a portion of the primary charged-particle beam is used to determine a total current of the primary charged-particle beam. 5 . The apparatus of claim 1 , wherein the detector comprises a plurality of current detectors configured to detect a change in at least one of a plurality of parameters of the primary charged particle beam. 6 . The apparatus of claim 5 , wherein the plurality of parameters comprises at least one of: beam position, beam diameter, beam current, beam current density, or uniformity of the beam current density.

7. The apparatus of claim 5, wherein each current detector of the plurality of current detectors is associated with at least one aperture of the aperture array.

8. The apparatus of claim 5, wherein each current detector of the plurality of current detectors is disposed on the aperture array.

9. The apparatus of claim 1, wherein the detector comprises a Faraday cup, a diode, a diode array, or a scintillator.

10. A method for measuring beam current in a multi-beam device, the method comprising: radiating a primary charged particle beam onto an aperture array; detecting a current of at least a portion of the primary charged particle beam using a detector located on a beam entrance side of the aperture array; as well as adjusting at least one beam parameter of a plurality of beam parameters based on the detected current; Wherein the detector is coupled to circuitry to detect at least one of a change in position or size of the at least a portion of the primary charged particle beam.

11. The method according to claim 10, further comprising: Charge of the at least a portion of the primary charged-particle beam is accumulated, and the beam current is measured based on the accumulated charge.

12. The method according to claim 10, further comprising: The beam current of the at least a portion of the primary charged-particle beam is monitored.

13. The method according to claim 10, further comprising: A change in at least one of a plurality of parameters of the portion of the primary charged-particle beam is detected.

14. The method of claim 10, wherein the detector comprises a plurality of current detectors, and wherein each current detector of the plurality of current detectors is associated with at least one aperture of the array of apertures.

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