Multiple charged particle beam device

Abstract

To provide systems and methods of mitigating Coulomb effect in a multi-beam apparatus.SOLUTION: The multi-beam apparatus may include a charged-particle source configured to generate a primary charged-particle beam along a primary optical axis, a first aperture array comprising a first plurality of apertures having shapes and configured to generate a plurality of primary beamlets derived from the primary charged-particle beam, a condenser lens comprising a plane adjustable along the primary optical axis, and a second aperture array comprising a second plurality of apertures configured to generate probing beamlets corresponding to the plurality of beamlets, where each of the probing beamlets comprises a portion of charged particles of a corresponding primary beamlet based at least on a position of the plane of the condenser lens and a characteristic of the second aperture array.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application Ser. No. 62 / 853,670, filed May 28, 2019, and U.S. patent application Ser. No. 62 / 984,760, filed March 3, 2020, which are incorporated by reference in their entireties herein.

[0002]

[0002] Embodiments provided in this specification disclose a multi-beam device, and more specifically, a multi-beam charged particle microscope including an aperture array having apertures configured to accommodate variations in beam current and beam position and to mitigate the Coulomb effect. [Background technology]

[0003]

[0003] In the manufacturing process 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 size of IC components continues to shrink, accuracy and yield in defect detection become more important. Although multiple electron beams can be used to increase throughput, limitations in the variation of probe current limit the imaging resolution desired for reliable defect detection and analysis, making inspection tools unsuitable for their desired purpose. Summary of the Invention

[0004]

[0004] In one aspect of the present disclosure, a charged particle beam device is disclosed. The charged particle beam device includes a charged particle source configured to generate a primary charged particle beam along a main optical axis, a first aperture array including a first number of apertures configured to generate a number of primary beamlets from the primary charged particle beam, a focusing lens including a plane adjustable along the main optical axis, and a second aperture array including a second number of apertures configured to generate a number of probing beamlets. Each of the number of probing beamlets includes a portion of the charged particles of a corresponding primary beamlet, and the portion of the charged particles is determined based at least on a position of the plane of the focusing lens and a characteristic of the second aperture array.

[0005]

[0005] The first aperture array may include a pre-beamlet forming aperture array disposed between the charged particle source and the focusing lens. The first aperture array may include an on-axis aperture configured to generate an on-axis beamlet, which is incident on an on-axis aperture of the second aperture array. The first aperture array may further include an off-axis aperture configured to generate an off-axis beamlet, which is incident on a corresponding off-axis aperture of the second aperture array. The off-axis aperture of the first aperture array may include an elongated aperture with rounded ends and a tapered width. The off-axis aperture of the first aperture array may include an elongated aperture with rounded ends and a tapered width and may have a curved shape. The off-axis aperture may be oriented to have a narrower width toward the primary optical axis.

[0006]

[0006] The focusing lens may be configured such that a portion of the off-axis beamlets form corresponding probing beamlets of the multiple probing beamlets. The focusing lens may be configured such that a portion of the off-axis beamlets form corresponding probing beamlets of the multiple probing beamlets. The second multiple apertures may be configured to determine a size and a shape of the multiple probing beamlets. The characteristics of the second aperture array may include at least one of a size, a shape, and an arrangement of the second multiple apertures. The focusing lens may include an electrostatic, electromagnetic, or electromagnetic composite lens.

[0007]

[0007] The first multiple apertures may include multiple off-axis apertures. The multiple off-axis apertures may include an aperture having a first off-axis aperture overlapping with a second off-axis aperture, the first off-axis aperture enabling the second aperture array to generate a first off-axis probing beamlet, and the second off-axis aperture enabling the second aperture array to generate a second off-axis probing beamlet. Each of the multiple off-axis apertures of the first aperture array may be separated by a substrate material of the first aperture array. The on-axis apertures of the first aperture array may be substantially circular, and the area of ​​the on-axis apertures of the first aperture array is substantially similar to the area of ​​the off-axis apertures.

[0008]

[0008] In another aspect of the present disclosure, a first aperture array of a charged particle beam device is disclosed. The first aperture array may include a first multiple apertures configured to generate multiple primary beamlets from a primary charged particle beam. A portion of the charged particles of each primary beamlet of the multiple primary beamlets forms a corresponding probing beamlet of the multiple probing beamlets, the portion of the charged particles being determined based at least on a position of a plane of a focusing lens and a characteristic of a second aperture array, and the second aperture array is configured to generate the multiple probing beamlets.

[0009]

[0009] In yet another aspect of the present disclosure, a method of observing a sample using a multi-beam device is disclosed. The method may include: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from the primary charged particle beam using a first aperture array; generating a number of probing beamlets corresponding to the number of primary beamlets using a second aperture array; adjusting a position of a plane of a focusing lens along a main optical axis relative to the first and second aperture arrays; and generating a number of probe spots incident on a surface of the sample from the number of probing beamlets, each of the number of probing beamlets including a portion of the charged particles of a corresponding primary beamlet of the number of primary beamlets, the portion of the charged particles being determined based at least on a position of the plane of the focusing lens and a characteristic of the second aperture array.

[0010]

[0010] By adjusting the position of the plane of the focusing lens, the characteristics of the probing beamlet, including the current of the probing beamlet, can be modified. Generating the multiple primary beamlets can include generating an on-axis beamlet and an off-axis beamlet. The method can further include using the focusing lens to make a portion of the off-axis beamlet form a corresponding probing beamlet of the multiple probing beamlets.

[0011]

[0011] In yet another aspect of the present disclosure, a non-transitory computer readable medium is disclosed that stores a set of instructions executable by one or more processors of a multi-beam device having a first and a second aperture array. The set of instructions can cause the multi-beam device to perform a method of observing a sample using the multi-beam device. The method can include activating a charged particle source to generate a primary charged particle beam, and adjusting a position of a plane of a collection lens along a main optical axis relative to the first and second aperture arrays, the first aperture array being configured to generate a number of primary beamlets from the primary charged particle beam using a first number of apertures, a portion of the charged particles of each primary beamlet of the number of primary beamlets forms a corresponding probing beamlet, the portion of the charged particles being determined based at least on a position of the plane of the collection lens and a characteristic of the second aperture array.

[0012]

[0012] In yet another aspect of the present disclosure, a charged particle beam device is disclosed. The charged particle beam device includes a charged particle source configured to generate a primary charged particle beam along a main optical axis, a first aperture array including a plurality of aperture sets configured to form a number of primary beamlets from the primary charged particle beam, a focusing lens arranged in a plane perpendicular to the main optical axis, and a second aperture array including a number of apertures configured to generate a number of probing beamlets. Each probing beamlet of the number of probing beamlets is associated with an aperture set of the first aperture array, and the apertures of the aperture set forming the probing beamlet are determined based at least on a characteristic of the focusing lens.

[0013]

[0013] The first aperture array may include a pre-beamlet forming aperture array disposed between the charged particle source and the focusing lens. The first aperture array may further include an on-axis aperture configured to generate an on-axis primary beamlet, the on-axis primary beamlet being incident on the on-axis aperture of the second aperture array. The on-axis aperture of the first aperture array may be substantially circular. The first aperture array may include a plurality of off-axis aperture sets configured to generate a number of off-axis primary beamlets, the off-axis primary beamlets being incident on corresponding off-axis apertures of the second aperture array.

[0014]

[0014] Each set of the multiple off-axis aperture sets may include apertures arranged along a curved path. Each set of the multiple off-axis aperture sets may include at least two apertures having different sizes. Each set of the multiple off-axis aperture sets may include apertures sized to determine a current of a corresponding primary beamlet. Each set of the multiple off-axis aperture sets may include apertures having a uniform pitch. Each set of the multiple off-axis aperture sets may include apertures having a non-uniform pitch. The multiple off-axis aperture sets may include apertures having a circular, rectangular, elliptical or polygonal cross section.

[0015]

[0015] The focusing lens may be configured such that each primary beamlet of the multiple primary beamlets forms a corresponding probing beamlet of the multiple probing beamlets. The focusing lens may include an electrostatic, electromagnetic or electromagnetic composite lens. The second aperture array may include a beam-limiting aperture array disposed between the focusing lens and the objective lens. The second multiple apertures may be configured to determine the size and shape of the multiple probing beamlets.

[0016]

[0016] In yet another aspect of the present disclosure, a first aperture array of a charged particle beam device is disclosed. The first aperture array may include a plurality of aperture sets configured to form a number of primary beamlets from a primary charged particle beam. Each probing beamlet of the number of probing beamlets is associated with a respective set of the plurality of aperture sets of the first aperture array, and the aperture of the aperture set forming the probing beamlet is determined based at least on a characteristic of a focusing lens.

[0017]

[0017] In yet another aspect of the present disclosure, a method of observing a sample using a multi-beam device is disclosed. The method may include activating a charged particle source to generate a primary charged particle beam, generating a number of primary beamlets from the primary charged particle beam using a first aperture array, adjusting a position of a plane of a focusing lens along a main optical axis relative to the first and second aperture arrays, and generating a number of probe spots incident on a surface of the sample from the number of probing beamlets. Each probing beamlet of the number of probing beamlets may be associated with an aperture set of the first aperture array, and the apertures of the aperture set forming the probing beamlet are determined based at least on a characteristic of the focusing lens.

[0018]

[0018] By adjusting the position of the plane of the focusing lens, the characteristics of the probing beamlet can be modified. By adjusting the position of the plane of the focusing lens, the current of the probing beamlet can be modified. Generating the multiple primary beamlets can include generating on-axis primary beamlets and off-axis primary beamlets.

[0019]

[0019] The method of observing a sample using a multi-beam device may further include using a focusing lens to cause the off-axis primary beamlet to form a corresponding probing beamlet of the multiple probing beamlets.

[0020]

[0020] In yet another aspect of the present disclosure, a non-transitory computer readable medium is disclosed that stores a set of instructions executable by one or more processors of a multi-beam device having a first and a second aperture array. The set of instructions can cause the multi-beam device to perform a method of observing a sample using the multi-beam device. The method may include activating a charged particle source to generate a primary charged particle beam, and adjusting a position of a plane of a collection lens along a main optical axis relative to the first aperture array and the second aperture array, the first aperture array being configured to generate a number of primary beamlets from the primary charged particle beam using a number of aperture sets, each primary beamlet of the number of primary beamlets forming a corresponding probing beamlet, and an aperture of the aperture set forming the probing beamlet is determined based at least on a characteristic of the collection lens.

[0021]

[0021] In yet another aspect of the present disclosure, a charged particle beam device is disclosed. The device may include a first aperture array including a first number of apertures configured to form a number of primary beamlets from a primary charged particle beam. Each aperture of the first number of apertures may include a first aperture plate configured to be at a first voltage and a second aperture plate configured to be at a second voltage different from the first voltage to generate an electric field that enables adjustment of the path of the charged particles of the primary charged particle beam. The device may further include a third aperture plate configured to be at a third voltage substantially similar to the first voltage. The apparatus may further include a focusing lens including a plane adjustable along the main optical axis, and a second aperture array including a second multiple apertures configured to generate a multiple probing beamlets, each of the multiple probing beamlets including a portion of the charged particles of a corresponding primary beamlet, the portion of the charged particles being based at least on a position of the plane of the focusing lens and a characteristic of the second aperture array.

[0022]

[0022] The first and third voltages may include reference voltages. The second aperture plate may include a charged particle beam deflector configured to adjust the path of the charged particle in response to electrical activation. The charged particle beam deflector may include a monopole deflector or a multipole deflector. The electrical activation of the second aperture plate may include a voltage signal being applied to generate an electric field. The path of the charged particle is adjusted based on a characteristic of the voltage signal applied to the second aperture plate. The characteristic of the voltage signal may include a polarity or an amplitude. Each aperture of the first multiple apertures may include a first aperture of the first aperture plate, a second aperture of the second aperture plate, and a third aperture of the third aperture plate, the second aperture plate being disposed between the first aperture plate and the third aperture plate, and the geometric centers of the first, second, and third apertures are aligned. The first and second apertures may be of different sizes, and the first and third apertures may be of substantially similar sizes.

[0023]

[0023] The third aperture plate can be configured to block a portion of the charged particles that exit the second aperture. The first aperture array can include a pre-beamlet forming aperture array disposed between the charged particle source and the collection lens. The first aperture array can include an on-axis aperture configured to generate an on-axis beamlet, the on-axis beamlet being incident on the on-axis aperture of the second aperture array. The first aperture array can include an off-axis aperture configured to generate an off-axis beamlet, the off-axis beamlet being incident on a corresponding off-axis aperture of the second aperture array. The off-axis aperture of the first aperture array can include an elongated aperture with rounded ends and a tapered width. The off-axis aperture of the first aperture array can include an elongated aperture with rounded ends and a tapered width and have a curved shape. The off-axis aperture can be oriented to taper in width towards the primary optical axis.

[0024]

[0024] The focusing lens may be configured such that a portion of the off-axis beamlets form corresponding probing beamlets of the multiple probing beamlets. The focusing lens may be configured such that a portion of the off-axis beamlets form corresponding probing beamlets of the multiple probing beamlets. The second multiple apertures may be configured to determine a size and a shape of the multiple probing beamlets. The characteristics of the second aperture array may include at least one of a size, a shape, and an arrangement of the second multiple apertures. The focusing lens may include an electrostatic, an electromagnetic, or an electromagnetic composite lens.

[0025]

[0025] The first multiple apertures may include multiple off-axis apertures. The multiple off-axis apertures may include an aperture having a first off-axis aperture overlapping with a second off-axis aperture, the first off-axis aperture enables the second aperture array to generate a first off-axis probing beamlet, and the second off-axis aperture enables the second aperture array to generate a second off-axis probing beamlet. Each of the multiple off-axis apertures of the first aperture array may be separated by a substrate material of the first aperture array. The on-axis apertures of the first aperture array may be substantially circular, and the area of ​​the on-axis apertures of the first aperture array is substantially similar to the area of ​​the off-axis apertures.

[0026]

[0026] In yet another aspect of the present disclosure, a method of observing a sample using a charged particle beam device is disclosed. The method may include: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from the primary charged particle beam using a first aperture plate and a second aperture plate of a first aperture array, the first aperture plate operating at a first voltage and the second aperture plate operating at a second voltage different from the first voltage to adjust the path of the charged particles exiting the first aperture plate; generating a number of probing beamlets corresponding to the number of primary beamlets using the second aperture array; and generating a number of probe spots from the number of probing beamlets incident on a surface of the sample. The method may further include operating a third aperture plate at a third voltage substantially similar to the first voltage, the first and third voltages comprising a reference voltage. The method may further include adjusting a path of the charged particles by electrically activating a second aperture plate, where the electrical activation of the second aperture plate includes applying a voltage signal to generate an electric field. The method may further include adjusting a position of a plane of a collector lens along a primary optical axis relative to the first and second aperture arrays, where adjusting the position of the plane of the collector lens modifies characteristics of the multiple probing beamlets, where adjusting the position of the plane of the collector lens modifies a current of the multiple probing beamlets, and where generating the multiple primary beamlets includes generating on-axis beamlets and off-axis beamlets. The method may further include using the collector lens to cause a portion of the off-axis beamlets to form corresponding probing beamlets of the multiple probing beamlets.

[0027]

[0027] In yet another aspect of the present disclosure, a non-transitory computer readable medium is disclosed that stores a set of instructions executable by one or more processors of a multi-beam device having a first and a second aperture array. The set of instructions can cause the multi-beam device to perform a method of observing a sample using the multi-beam device. The method can include activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from the primary charged particle beam using a first, a second and a third aperture plate of the first aperture array, where the first and the third aperture plates operate substantially at a first voltage and the second aperture plate operates at a second voltage different from the first voltage to adjust the path of the charged particles exiting the first aperture plate; generating a number of probing beamlets corresponding to the number of primary beamlets using the second aperture array; and generating a number of probe spots from the number of probing beamlets that are incident on a surface of the sample.

[0028]

[0028] In yet another aspect of the present disclosure, a charged particle beam device is disclosed. The device may include a first aperture array including a first multiple aperture configured to form a multiple primary beamlet from a primary charged particle beam. Each aperture of the first multiple aperture may include a first aperture plate configured to be at a first voltage, a second aperture plate configured to be at a second voltage different from the first voltage to generate an electric field between the first aperture plate and the second aperture plate, and a second aperture array configured to generate a probing beamlet from the corresponding primary beamlet, the beam current of the probing beamlet being adjustable. The electric field between the first aperture plate and the second aperture plate may be substantially fixed, and the beam current is discretely adjusted based on the size of each aperture of the first multiple aperture of the first aperture array. The electric field between the first aperture plate and the second aperture plate can be adjustable, and the beam current is adjusted based on the electric field between the first aperture plate and the second aperture plate.

[0029]

[0029] In yet another aspect of the present disclosure, a method of observing a sample using a charged particle beam device is disclosed. The method may include: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from the primary charged particle beam using a first aperture plate and a second aperture plate of a first aperture array, where the first aperture plate operates at a first voltage and the second aperture plate operates at a second voltage different from the first voltage to adjust the path of the charged particles leaving the first aperture plate; generating probing beamlets from corresponding primary beamlets using the second aperture array, where the beam current of the probing beamlets is adjustable; and generating probe spots from the probing beamlets that are incident on a surface of the sample. The method may further include adjusting a path of the charged particles, where adjusting the path includes deflecting the charged particles based on an electric field formed between the first aperture plate and the second aperture plate. The electric field between the first aperture plate and the second aperture plate may be substantially fixed, and adjusting the beam current of the probing beamlet is based on a size of an aperture of the first aperture array. The electric field between the first aperture plate and the second aperture plate may be adjustable, and adjusting the beam current of the probing beamlet includes adjusting the electric field between the first aperture plate and the second aperture plate. Deflecting the charged particles may be caused by electrically activating the second aperture plate by applying a voltage signal to generate the electric field. The method may further include operating the third aperture plate with a third voltage substantially similar to the first voltage, where the first and third voltages include reference voltages.

[0030]

[0030] In yet another aspect of the present disclosure, a non-transitory computer readable medium is disclosed that stores a set of instructions executable by one or more processors of a multi-beam device having first and second aperture arrays, the set of instructions causing the multi-beam device to perform a method. The method may include activating a charged particle source to generate a primary charged particle beam, generating a number of primary beamlets from the primary charged particle beam using a first aperture plate and a second aperture plate of the first aperture array, where the first aperture plate operates at a first voltage and the second aperture plate operates at a second voltage different from the first voltage to adjust the path of the charged particles exiting the first aperture plate, generating probing beamlets from corresponding primary beamlets using the second aperture array, where a beam current of the probing beamlets is adjustable, and generating probe spots from the probing beamlets that are incident on a surface of a sample.

[0031]

[0031] In yet another aspect of the present disclosure, a charged particle beam device is disclosed. The device may include a pre-beamlet forming aperture set configured to form a number of primary beamlets from a primary charged particle beam, and a beam limiting aperture configured to form a probing beamlet from the corresponding primary beamlet, where the beam current of the probing beamlet is determined based on a characteristic of the aperture of the pre-beamlet forming aperture set forming the primary beamlet. The characteristic of the aperture of the pre-beamlet forming aperture set may include a size, a shape, or a location of the aperture. The beam current of the probing beamlet can be discretely adjusted based on the size of the aperture of the pre-beamlet forming aperture set. The device may include a first array of the number of pre-beamlet forming aperture sets, and a second array of the number of beam limiting apertures arranged downstream of the first array along a main optical axis of the primary charged particle beam. The apertures of the pre-beamlet forming aperture set forming the probing beamlet may be determined based at least on a characteristic of the collector lens, the characteristic of the collector lens may include a position of a plane of the collector lens along the main optical axis. A change in the position of the plane of the collector lens may be configured to affect the beam current of the probing beamlet. The collector lens may be configured to affect the beam current of the probing beamlet by directing a portion of the primary charged particle beam to pass through a different aperture of the pre-beamlet forming aperture set. The collector lens located at a first position of the plane may be configured for a first portion of the primary charged particle beam to pass through a first aperture of the pre-beamlet forming aperture set to form a first primary beamlet, and the collector lens located at a second position of the plane may be configured for a second portion of the primary charged particle beam to pass through a second aperture of the pre-beamlet forming aperture set to form a second primary beamlet.

[0032]

[0032] The first array may include an on-axis aperture configured to generate an on-axis primary beamlet, which is incident on an on-axis aperture of the second array, and the pre-beamlet forming aperture set may include a number of off-axis pre-beamlet forming apertures configured to generate an off-axis primary beamlet, which is incident on a corresponding off-axis beam limiting aperture of the second array. Each of the off-axis pre-beamlet forming apertures may be separated by a substrate material of the first array. The number of off-axis pre-beamlet forming apertures may be arranged along a curved path. The number of off-axis pre-beamlet forming apertures may include at least two apertures having different sizes. The number of off-axis pre-beamlet forming apertures may be sized to determine the beam current of the generated primary beamlet upon passing through each aperture of the number of off-axis pre-beamlet forming apertures. Each aperture of the multiple off-axis pre-beamlet forming apertures may have a uniform pitch or a non-uniform pitch.

[0033]

[0033] Other advantages of the embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0033] In the following description, by way of illustration and example, certain embodiments of the invention are set forth. [Brief description of the drawings]

[0034] [Figure 1] FIG. 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system consistent with an embodiment of the present disclosure. [Diagram 2]

[0035] 2 is a schematic diagram illustrating an example electron beam tool that may be part of the example electron beam inspection system of FIG. 1 consistent with an embodiment of the present disclosure. [Diagram 3]

[0036] 1 is a schematic diagram illustrating an example configuration of an adjustable focusing lens of a multi-beam device consistent with an embodiment of the present disclosure. [Figure 4A]

[0037] 4 is a schematic diagram illustrating an example charged particle beam profile with varying probe current at an aperture array of the multi-beam apparatus of FIG. 3 consistent with an embodiment of the present disclosure. [Figure 4B] FIG. 4 is a schematic diagram illustrating an example charged particle beam profile with varying probe current at the aperture array of the multi-beam apparatus of FIG. 3 consistent with an embodiment of the present disclosure. [Figure 4C] FIG. 4 is a schematic diagram illustrating an example charged particle beam profile with varying probe current at the aperture array of the multi-beam apparatus of FIG. 3 consistent with an embodiment of the present disclosure. [Figure 5A]

[0038] 4 is a schematic diagram illustrating an example charged particle beam profile with varying probe current at an aperture array of the multi-beam apparatus of FIG. 3 consistent with an embodiment of the present disclosure. [Figure 5B] FIG. 4 is a schematic diagram illustrating an example charged particle beam profile with varying probe current at the aperture array of the multi-beam apparatus of FIG. 3 consistent with an embodiment of the present disclosure. [Figure 5C] FIG. 4 is a schematic diagram illustrating an example charged particle beam profile with varying probe current at the aperture array of the multi-beam apparatus of FIG. 3 consistent with an embodiment of the present disclosure. [Figure 6A]

[0039] 1 is a schematic diagram illustrating an exemplary arrangement of elongated apertures in an aperture array consistent with an embodiment of the present disclosure. FIG. [Figure 6B]

[0039] FIG. 1 is a schematic diagram showing an exemplary arrangement of elongated apertures in an aperture array consistent with an embodiment of the present disclosure. [Figure 7A]

[0040] 1 is a schematic diagram illustrating an exemplary curved aperture of an aperture array consistent with an embodiment of the present disclosure. [Figure 7B] FIG. 1 is a schematic diagram illustrating an exemplary curved aperture of an aperture array consistent with an embodiment of the present disclosure. [Figure 8A]

[0041] 1 is a schematic diagram illustrating an example arrangement of apertures in an aperture array of a multi-beam device consistent with an embodiment of the present disclosure. [Figure 8B]

[0041] FIG. 1 is a schematic diagram showing an exemplary arrangement of apertures in an aperture array of a multi-beam device consistent with an embodiment of the present disclosure. [Figure 9]

[0042] 4 is a schematic diagram illustrating an example arrangement of apertures of a beam-limiting aperture array of the multi-beam device of FIG. 3, consistent with an embodiment of the present disclosure. [Figure 10]

[0043] 1 is a schematic diagram illustrating an example projection of partially overlapping apertures of an aperture array of a multi-beam device consistent with an embodiment of the present disclosure. [Figure 11A]

[0044] 11 is a schematic diagram illustrating an example arrangement of merge apertures of the aperture array of FIG. 10 consistent with an embodiment of the present disclosure. [Figure 11B]

[0045] 11 illustrates an exemplary arrangement of apertures in the aperture array of FIG. 10, consistent with an embodiment of the present disclosure. [Figure 11C]

[0046] 11C shows the relationship between spot size and beam current of the beamlets formed by the aperture of FIG. 11B, consistent with an embodiment of the present disclosure. [Figure 11D]

[0047] 11 illustrates an exemplary arrangement of apertures in the aperture array of FIG. 10, consistent with an embodiment of the present disclosure. [Figure 11E]

[0048] 1 illustrates a close-up view of an example aperture of an active aperture array, consistent with an embodiment of the present disclosure. [Figure 11F]

[0049] 11E shows a cross-sectional view of the example aperture of FIG. 11E, consistent with an embodiment of the present disclosure. [Figure 12]

[0050] 1 is a process flow diagram depicting an exemplary method of observing a sample using a multi-beam inspection tool consistent with an embodiment of the present disclosure. [Figure 13]

[0051] 1 is a process flow diagram depicting an exemplary method of observing a sample using a multi-beam inspection tool consistent with an embodiment of the present disclosure. [Figure 14]

[0052] 1 is a process flow diagram depicting an exemplary method of observing a sample using a multi-beam inspection tool consistent with an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0035]

[0053] 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 the same numbers in different drawings represent the same or similar elements unless otherwise stated. The implementations described in the following description of exemplary embodiments do not represent all implementations. Instead, the implementations are merely examples of apparatuses and methods consistent with aspects related to the disclosed embodiments, as described in the appended claims. For example, although some embodiments are described in the context of utilizing an electron beam, the disclosure is not so limited. Other types of charged particle beams can be applied as well. Moreover, other imaging systems can be used, such as optical imaging, photo detection, x-ray detection, and the like.

[0036]

[0054] Electronic devices are built with circuits formed on a piece of silicon called a substrate. Many circuits can be formed together on the same piece of silicon and are called integrated circuits, or ICs. The size of these circuits has decreased dramatically, so that many more can fit on a substrate. For example, an IC chip in a smartphone is only about the size of a thumbnail, yet it can contain over 2 billion transistors, each less than 1 / 1000 the size of a human hair.

[0037]

[0055] Creating these tiny ICs is a time-consuming, complex, and expensive process that often involves hundreds of individual steps. An error in even one step can introduce defects into the finished IC, rendering it useless. Thus, one of the goals of a manufacturing process is to avoid such defects in order to maximize the number of functioning ICs produced by the process, i.e., to increase the overall yield of the process.

[0038]

[0056] One factor in improving yield is monitoring the chip creation process to ensure that it produces a sufficient number of functioning integrated circuits. One way to monitor the process is to inspect the chip circuit structures at various stages of their formation. Inspection can be done using a scanning electron microscope (SEM). An SEM can be used to image these extremely small structures, in effect taking a "picture" of the structure. The image can be used to determine if the structure was formed correctly, and if it was formed in the correct location. If the structure is defective, the process can be adjusted to make it less likely that the defect will reoccur.

[0039]

[0057] Although multiple charged particle beam imaging systems such as multi-beam SEMs can be useful in increasing wafer inspection throughput, the imaging resolution of multi-beam SEMs can be negatively affected by Coulomb interaction effects. To achieve high throughput, it is desirable for the beam to contain as many electrons as possible. However, due to repulsive Coulomb interactions between electrons, it is difficult to confine a large number of electrons within a very small volume. Moreover, these interactions can widen the beam and change the flight direction of the electrons. As a result, the probe spot becomes larger, thus negatively impacting the overall resolution of the SEM. Therefore, it is desirable to mitigate the Coulomb interaction effects in order to maintain the high resolution of multi-beam SEMs.

[0040]

[0058] To mitigate Coulomb interaction effects, an aperture array can be placed near the electron source to eliminate peripheral electrons or split the primary electron beam into multiple beamlets. However, adjusting the probing beam current to adjust the resolution can alter the beam path through the aperture array. One of several problems that can be encountered is that the apertures of the aperture array may not be configurable to allow the passage of beams of various sizes and positions while maintaining a small enough area to mitigate Coulomb interaction effects.

[0041]

[0059] Moreover, because imaging resolution can be adversely affected by Coulomb interaction effects, it may be desirable to maintain uniformity of the total area of ​​the apertures, despite non-uniform shapes of those apertures, to accommodate variations in the probing beam current. Variations in Coulomb interaction effects between apertures in an aperture array can result in non-uniform resolution of areas within the same image, affecting, for example, a user's ability to detect and identify defects.

[0042]

[0060] In conventional SEMs and multi-beam SEMs, the size of the probing electron beam or probe spot size can determine the imaging resolution. For example, a large probe spot with a high beam current can result in low resolution, and a small probe spot with a low beam current can result in better resolution. The low imaging resolution from a large beam spot size can be partially attributed to enhanced Coulomb interaction effects in high current beams.

[0043]

[0061] A large range of beam currents may be desirable for performing various operations during wafer inspection in a multi-beam SEM tool. For example, a high current beam may be used to perform low resolution macroscopic inspection of large areas on the wafer, and a low current and high resolution scan may be desirable to perform thorough defect investigation at the microscopic or nanoscopic level. One of several ways to generate a large range of beam currents from a single electron source in a multi-beam SEM may include increasing the size or length of the aperture through which the electrons may pass. However, multiple large apertures may not only increase Coulomb interaction effects, but may also negatively affect the mechanical integrity of the aperture array. Therefore, it may be desirable to have an imaging tool, such as a multi-beam SEM, that can provide a large range of beam currents while reducing Coulomb interaction effects and maintaining the mechanical integrity of the aperture array.

[0044]

[0062] In some embodiments of the present disclosure, the multi-beam device may include an aperture array including multiple elongated apertures having tapered widths and configured to generate multiple beamlets associated with the primary charged particle beam. The device may also include a focusing lens on an adjustable plane along the primary optical axis, and a second aperture array including multiple apertures configured to generate probing beamlets. The shape of the first multiple apertures is based on the path of the corresponding beamlet associated with an adjustable probe current of the probing beamlet, the adjustability of the focusing lens plane, and the characteristics of the second aperture array (such as the size, shape, and positioning of the apertures).

[0045]

[0063] In some embodiments of the present disclosure, a multi-beam device may include a first aperture array including a number of aperture sets configured to form a number of primary beamlets from a primary charged particle beam. The device may also include a second aperture array including a number of apertures configured to generate a number of probing beamlets. The probing beamlets may be associated with an aperture set, and the apertures of the aperture sets that form the probing beamlets may be determined based at least on a characteristic of the focusing lens.

[0046]

[0064] In the drawings, the relative dimensions of the components may be exaggerated for clarity. Within the following description of the drawings, the same or similar reference numbers refer to the same or similar components or entities and only describe the differences for the individual embodiments. As used herein, unless specifically stated otherwise, the term "or" encompasses all possible combinations unless impracticable. For example, if it is stated that a component may include A or B, the component may include A or B, or A and B, unless specifically stated otherwise or impracticable. As a second example, if it is stated that a component may include A, B, or C, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A, B, and C, unless specifically stated otherwise or impracticable.

[0047]

[0065] Reference is now made to Figure 1, which illustrates an exemplary electron beam inspection (EBI) system 100 consistent with embodiments of the present disclosure. As shown in Figure 1, the charged particle beam inspection system 100 includes a main chamber 10, a load-lock chamber 20, an electron beam tool 40, and a front-end equipment module (EFEM) 30. The electron beam tool 40 is located within the main chamber 10. Although the description and drawings are directed to an electron beam, it is understood that the embodiments are not used to limit the present disclosure to any particular charged particle.

[0048]

[0066] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional load ports. The first load port 30a and the second load port 30b receive wafer front-opening integrated pods (FOUPs) containing wafers (e.g., semiconductor wafers or wafers made of other materials) or samples to be inspected (hereinafter, wafers and samples are collectively referred to as "wafers"). One or more robotic arms (not shown) of the EFEM 30 transfer the wafers to the load-lock chamber 20.

[0049]

[0067] The load-lock chamber 20 is connected to a load / lock vacuum pumping system (not shown) that removes gas molecules in the load-lock chamber 20 to reach a first pressure below atmospheric pressure. After the first pressure is reached, one or more robot arms (not shown) transfer the wafer from the load-lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pumping system (not shown) that removes gas molecules in the main chamber 10 to reach a second pressure below the first pressure. After the second pressure is reached, the wafer is inspected by the electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single beam inspection tool. In other embodiments, the electron beam tool 40 may include a multi-beam inspection tool.

[0050]

[0068] The controller 50 may be electronically connected to the electron beam tool 40 and may also be electronically connected to other components. The controller 50 may be a computer configured to perform various controls of the charged particle beam inspection system 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. In FIG. 1, the controller 50 is shown as being external to the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, but it is understood that the controller 50 may also be part of the structure.

[0051]

[0069] It should be noted that while the present disclosure provides an example of a main chamber 10 housing an electron beam inspection system, aspects of the present disclosure, in its broadest sense, are not limited to chambers housing an electron beam inspection system, rather, it is understood that the principles described above may be applied to other chambers as well.

[0052]

[0070] Referring now to FIG. 2, FIG. 2 shows a schematic diagram illustrating an exemplary electron beam tool 40 that may be part of the exemplary charged particle beam inspection system 100 of FIG. 1 consistent with an embodiment of the present disclosure. The electron beam tool 40 (also referred to herein as the apparatus 40) includes an electron source 101, a gun aperture plate 171 having a gun aperture 103, a condenser lens 110, a source conversion unit 120, a primary projection optics 130, a sample stage (not shown in FIG. 2), a secondary optics 150, and an electron detection device 140. The primary projection optics 130 may include an objective lens 131. The electron detection device 140 may include multiple detection elements 140_1, 140_2, 140_3. The beam separator 160 and the deflection scanning unit 132 may be disposed within the primary projection optics 130. It may be understood that other commonly known components of the apparatus 40 may be appropriately added / omitted as necessary.

[0053]

[0071] The electron source 101, the gun aperture plate 171, the condenser lens 110, the source conversion unit 120, the beam separator 160, the deflection scanning unit 132 and the primary projection optics 130 may be aligned with a main optical axis 100_1 of the apparatus 100. The secondary optics 150 and the electron detection device 140 may be aligned with a secondary optical axis 150_1 of the apparatus 40.

[0054]

[0072] The electron source 101 may include a cathode, extractor, or anode, and primary electrons may be emitted from the cathode and then extracted or accelerated to form a primary electron beam 102 that forms a crossover (virtual or real image) 101s. The primary electron beam 102 may be visualized as emitting from the crossover 101s.

[0055]

[0073] The source conversion unit 120 may include an image forming element array (not shown in FIG. 2), an aberration compensator array (not shown), a beam limiting aperture array (not shown), and a pre-bent micro-deflector array (not shown). The image forming element array may include multiple micro-deflectors or micro-lenses to form multiple parallel images (virtual or real images) of the crossover 101s with multiple beamlets of the primary electron beam 102. FIG. 2 shows three beamlets 102_1, 102_2, 102_3 as an example, it being understood that the source conversion unit 120 can handle any number of beamlets.

[0056]

[0074] The condenser lens 110 is configured to focus the primary electron beam 102. The current of the beamlets 102_1, 102_2, 102_3 downstream of the source transformation unit 120 can be varied by adjusting the focusing power of the condenser lens 110 or by changing the radial size of the corresponding beam-limiting aperture in the beam-limiting aperture array. The current can be changed by changing both the radial size of the beam-limiting aperture and the focusing power of the condenser lens 110. The condenser lens 110 can be an adjustable condenser lens that can be configured to move the position of its first principle plane. The adjustable condenser lens can be configured to be magnetic, whereby the off-axis beamlets 102_2 and 102_3 are irradiated to the source transformation unit 120 with a rotation angle. The rotation angle can be changed together with the focusing power or the position of the first principle plane of the adjustable condenser lens. Accordingly, the focusing lens 110 may be an anti-rotation focusing lens that can be configured to keep the rotation angle unchanged while changing the focusing power of the focusing lens 110. In some embodiments, the focusing lens 110 may be an adjustable anti-rotation focusing lens that does not change the rotation angle when changing the focusing power and the position of the first principal plane of the focusing lens 110.

[0057]

[0075] The objective lens 131 can be configured to focus the beamlets 102_1, 102_2, 102_3 onto the sample 190 for inspection, forming three probe spots 102_1s, 102_2s, 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, which can enlarge the size of each of the probe spots 102_1s, 102_2s, 102_3s and thus degrade the inspection resolution.

[0058]

[0076] The beam separator 160 may be a Wien filter type beam separator that includes an electrostatic deflector that generates an electrostatic dipole field E1 and a magnetic dipole field B1 (both not shown in FIG. 2). When these fields are applied, the force exerted on the electrons of the beamlets 102_1, 102_2, 102_3 by the electrostatic dipole field E1 is equal in magnitude and opposite in direction to the force exerted on the electrons by the magnetic dipole field B1. Thus, the beamlets 102_1, 102_2, 102_3 can pass straight through the beam separator 160 with zero deflection angle.

[0059]

[0077] The deflection scanning unit 132 can deflect the beamlets 102_1, 102_2, 102_3 to scan the probe spots 102_1s, 102_2s, 102_3s over three small scanning areas of a section of the surface of the sample 190. In response to the beamlets 102_1, 102_2, 102_3 being incident on the probe spots 102_1s, 102_2s, 102_3s, three secondary electron beams 102_1se, 102_2se, 102_3se can be emitted from the sample 190. Each of the secondary electron beams 102_1se, 102_2se, 102_3se can include electrons with distributed energies, including secondary electrons (energy ≦50 eV) and backscattered electrons (energy between 50 eV and the landing energy of the beamlets 102_1, 102_2, 102_3). The beam separator 160 can direct the secondary electron beams 102_1se, 102_2se, 102_3se towards the secondary optical system 150. The secondary optical system 150 can focus the secondary electron beams 102_1se, 102_2se, 102_3se onto the detection elements 140_1, 140_2, 140_3 of the electron detection device 140. The detection elements 140_1, 140_2, 140_3 can detect the corresponding secondary electron beams 102_1se, 102_2se, 102_3se and generate corresponding signals that are used to construct an image of a corresponding scanned area of ​​the sample 190.

[0060]

[0078] In some embodiments, the controller 50 may include an image processing system, which includes an image acquirer (not shown) and storage (not shown). The image acquirer may include one or more processors. For example, the image acquirer may include a computer, a server, a mainframe host, a terminal, a personal computer, any type of mobile computing device, and the like, or a combination thereof. The image acquirer may be communicatively coupled to the electronic detection device 140 of the apparatus 40 through a medium such as electrical conductors, fiber optic cables, portable storage media, IR, Bluetooth, the Internet, a wireless network, a wireless radio, or a combination thereof, among others. In some embodiments, the image acquirer may receive signals from the electronic detection device 140 and construct an image. Thus, the image acquirer may acquire an image of the sample 190. The image acquirer may also perform various post-processing functions such as generating contours, superimposing indicators on the acquired image, and the like. The image acquirer may be configured to perform adjustments such as brightness and contrast of the acquired image. In some embodiments, the storage may be a storage medium such as a hard disk, a flash drive, cloud storage, random access memory (RAM), other types of computer readable memory, and the like. The storage may be coupled with the image acquirer and may be used to store raw scanned image data as original images or to store post-processed images.

[0061]

[0079] In some embodiments, the image acquirer can acquire one or more images of the sample based on the imaging signal received from the electronic detection device 140. The imaging signal can correspond to a scanning operation to perform charged particle imaging. The acquired image can be a single image including multiple imaging areas. The single image can be stored in the storage. The single image can be an original image that can be divided into multiple regions. Each of the regions can include an imaging area that includes a feature of the sample 190. The acquired image can include multiple images of a single imaging area of ​​the sample 190 sampled multiple times over a time series. The multiple images can be stored in the storage. In some embodiments, the controller 50 can be configured to perform an image processing step using multiple images of the same location of the sample 190.

[0062]

[0080] In some embodiments, the controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain a distribution of detected secondary electrons. The electron distribution data collected during the detection time window, in combination with the corresponding scan path data of each of the primary beamlets 102_1, 102_2, 102_3 incident on the wafer surface, may be used to reconstruct an image of the wafer structure under inspection. The reconstructed image may be used to reveal various features of the internal or external structure of the sample 190, and thus, any defects that may be present in the wafer.

[0063]

[0081] In some embodiments, the controller 50 can control a motorized stage (not shown) to move the sample 190 during inspection. In some embodiments, the controller 50 can cause the motorized stage to move the sample 190 continuously at a constant speed in one direction. In other embodiments, the controller 50 can cause the motorized stage to vary the speed at which the sample 190 moves over time depending on the step of the scanning process. In some embodiments, the controller 50 can adjust the configuration of the primary projection system 130 or the secondary projection system 150 based on the images of the secondary electron beams 102_1se, 102_2se, 102_3se.

[0064]

[0082] 2 illustrates that the electron beam tool 40 uses three primary electron beams, it is understood that the electron beam tool 40 can use two or more primary electron beams, and the present disclosure does not limit the number of primary electron beams used in the apparatus 40.

[0065]

[0083] 3, which is a schematic diagram of a multi-beam apparatus 300 illustrating an exemplary configuration of an adjustable focusing lens 110 consistent with embodiments of the present disclosure. It is understood that the multi-beam apparatus 300 may be part of a charged particle beam inspection system (e.g., the electron beam inspection system 100 of FIG. 1).

[0066]

[0084] The multi-beam device 300 may include an electron source 101, a pre-beamlet forming aperture mechanism 172, a condenser lens 110, an objective lens 131, and a source conversion unit 120, which may include a beam limiting aperture array 121 and an image forming element array 122. In some embodiments, the electron source 101 may be configured to emit primary electrons and form a primary electron beam 102. In some embodiments, a gun aperture plate (not shown) may be configured to block electrons on the periphery of the primary electron beam 102 to reduce the Coulomb effect. In some embodiments, the pre-beamlet forming aperture mechanism 172 further removes electrons on the periphery of the primary electron beam 102 to reduce the Coulomb effect. After passing through the pre-beamlet forming aperture mechanism 172, the primary electron beam 102 may be reduced to three primary electron beamlets 102_1, 102_2, 102_3 (or any other number of beamlets). The electron source 101 , the gun aperture plate 171 , the pre-beamlet forming aperture mechanism 172 and the condenser lens 110 may be aligned with the main optical axis 100_1 of the multi-beam electron beam tool 300 .

[0067]

[0085] In some embodiments, the source conversion unit 120 can be provided with a beam-limiting aperture array 121 and an image forming element array 122. The beam-limiting aperture array 121 can include beam-limiting apertures 121_1, 121_2, 121_3. Although FIG. 3 shows only three apertures, it is understood that any number of apertures can be used as needed and appropriate. The beam-limiting apertures 121_1, 121_2, 121_3 can limit the size of the beamlets 102_1, 102_2, 102_3 of the primary electron beam 102. The image forming element array 122 can include image forming deflectors 122_1, 122_2, 122_3. The deflectors 122_1, 122_2, 122_3 can be configured to deflect the beamlets 102_1, 102_2, 102_3 by changing the angle towards the main optical axis 100_1. In some embodiments, the deflectors deflect the beamlets more the further away from the main optical axis 100_1. Moreover, the image forming element array 122 can include multiple layers (not shown), and the deflectors 122_1, 122_2, 122_3 can be provided in separate layers. The deflectors 122_1, 122_2, 122_3 can be individually controlled independent of each other. In some embodiments, the deflectors can be controlled to adjust the pitch of the probe spots (e.g., 102_1S, 102_2S, 102_3S) formed on the surface of the sample 190. As referred to herein, the pitch of the probe spots may be defined as the distance between two immediately adjacent probe spots on the surface of the sample 190.

[0068]

[0086] The deflector located at the center of the image forming element array 122 may be aligned with the main optical axis 100_1 of the multi-beam device 300. Thus, in some embodiments, the central deflector may be configured to keep the trajectory of the beamlet 102_1 straight. In some embodiments, the central deflector may be omitted. However, in some embodiments, the primary electron source 101 is not necessarily aligned with the center of the source conversion unit 120. Moreover, although FIG. 3 shows a side view of the device 300 with the beamlet 102_1 located on the main optical axis 100_1, it is understood that the beamlet 102_1 may be located outside the main optical axis 100_1 when viewed from a different side. That is, in some embodiments, the beamlets 102_1, 102_2, 102_3 may all be off-axis. The off-axis components may be offset with respect to the main optical axis 100_1.

[0069]

[0087] The deflection angles of the deflected beamlets can be set based on one or more criteria. As shown in FIG. 3, the deflectors 122_2 and 122_3 can deflect the off-axis beamlets radially outward or away from the main optical axis 100_1 (not shown). In some embodiments, the deflectors 122_2 and 122_3 can deflect the off-axis beamlets radially inward or towards the main optical axis 100_1. The deflection angles of the beamlets can be set so that the beamlets 102_1, 102_2, 102_3 land perpendicularly on the sample 190. Off-axis aberrations of the image caused by lenses (such as the objective lens 131) can be reduced by adjusting the paths of the beamlets through the lenses. Thus, the deflection angles of the off-axis beamlets 102_2 and 102_3 generated by the deflectors 122_2 and 122_3 can be set such that the probe spots 102_2S and 102_3S have small aberrations. The beamlets can be deflected to pass through or near the front focus of the objective lens 131 to reduce the aberrations of the off-axis probe spots 102_2S and 102_3S. In some embodiments, the deflectors can be set such that the beamlets 102_1, 102_2, 102_3 land perpendicularly on the sample 1 while the probe spots 102_1S, 102_2S, 102_3S have small aberrations.

[0070]

[0088] The pre-beamlet forming aperture mechanism 172 may include a Coulomb aperture array. A central aperture (also referred to herein as an on-axis aperture) of the pre-beamlet forming mechanism 172 and a central deflector of the source conversion unit 120 may be aligned with the main optical axis 100_1 of the multi-beam device 300. The pre-beamlet forming mechanism 172 may be provided with a number of pre-reduction apertures (e.g., Coulomb aperture arrays) 172_1, 172_2, 172_3. The central aperture 172_1 of the pre-beamlet forming mechanism 172 may be aligned with the main optical axis 100_1 and may be provided above the collecting lens 110 and near the electron source 101. In FIG. 3, when the primary electron beam 102 passes through the three pre-reduction apertures, three beamlets 102_1, 102_2, 102_3 are generated, and most of the remaining part of the primary electron beam 102 is deleted. That is, the pre-beamlet forming mechanism 172 can prune most or most of the electrons from the primary electron beam 102 that do not form the three beamlets 102_1, 102_2, 102_3. The pre-beamlet forming mechanism 172 can prune the electrons that are not ultimately used to form the probe spots 102_1S, 102_2S, 102_3S before the primary electron beam 102 enters the source conversion unit 120. In this manner, the Coulomb effect can be significantly reduced above the beam-limiting aperture array 121. As used in this disclosure, "pre-beamlet" refers to a primary beamlet that has an intermediate beam current value before entering the beam-limiting aperture. In some embodiments, a gun aperture plate (not shown) may be provided near the electron source 101 to filter out electrons at an early stage, while a pre-beamlet forming mechanism 172 may also be provided to further filter out electrons around a number of beamlets. While Figure 3 shows three apertures in the pre-beamlet forming mechanism 172, it is understood that there may be any number of apertures as needed and appropriate.

[0071]

[0089] In some embodiments, the pre-beamlet forming mechanism 172 may be located below the condenser lens 110. The closer the pre-beamlet forming mechanism 172 is located to the electron source 101, the more effectively the Coulomb effect can be reduced. In some embodiments, the gun aperture plate may be omitted when the pre-beamlet forming mechanism 172 can be positioned close enough to the electron source 101 while still being manufacturable. In some embodiments, the pre-beamlet forming mechanism 172 may be located along a plane 172P perpendicular to the primary optical axis 100_1.

[0072]

[0090] The focusing lens 110 can be configured to be adjustable to adjust the current of the beamlets 102_1, 102_2, 102_3. The adjustable focusing lens 110 can have a principal plane 110_2 perpendicular to the principal optical axis 100_1 as shown in FIG. 3. The principal plane 110_2 can be moved along the principal optical axis 100_1 of the multi-beam device 300. For example, the principal plane 110_2 can be moved further away from the electron source 101 to reduce the current of the beamlets 102_1, 102_2, 102_3, and the principal plane 110_2 can be moved closer to the electron source 101 to increase the current of the beamlets 102_1, 102_2, 102_3. In addition, the current of the beamlets 102_1, 102_2, 102_3 can be changed by changing the size of the beam-limiting apertures 121_1, 121_2, 121_3 of the beam-limiting aperture array 121.

[0073]

[0091] 4A-4C, which show schematic diagrams of exemplary charged particle beam profiles (e.g., electron beam profiles) with varying probe current projected onto plane 172P consistent with embodiments of the present disclosure. The beam profiles (e.g., PC1, PC2, PC3) represent virtual projections onto plane 172P of beamlets exiting beam-limiting aperture array 121. The circles representing the beam profiles shall be considered as visual aids for the size of the probing beamlets exiting beam-limiting aperture array and the size of the portion of the beamlets from which the corresponding probing beamlets are generated. FIGS. 4A-4C show the beam profiles of beamlets 102_1, 102_2, 102_3 downstream of beam-limiting aperture array 121 in a configuration including an adjustable anti-rotation electrostatic focusing lens, where the rotation angle is not altered when the focusing power of focusing lens 110 and the position of principal plane 110_2 are changed. It is understood that the beam profile on the plane 172P of the pre-beamlet forming mechanism 172 is a virtual projection shown for illustrative purposes only.

[0074]

[0092] 4A shows the beam profile of beamlets 102_1, 102_2, 102_3 with high beam current (represented as probe current 3 (PC3)) projected onto plane 172P. The electrons constituting beam profile PC3 may identify a portion of the electrons of each of beamlets 102_1, 102_2, 102_3 passing through a corresponding aperture of beam-limiting aperture array 121, and the remaining electrons of beamlets 102_1, 102_2, 102_3 may be blocked by beam-limiting aperture array 121. The current of the beamlets passing through the apertures of pre-beamlet forming mechanism 172 may be based on, for example, the position of the principal plane 110_2 of focusing lens 110 along the principal optical axis 100_1 and the size of the corresponding aperture of beam-limiting aperture array 121. 4A, the principal plane 110_2 of the focusing lens 110 is closer to the electron source 101 and located below the pre-beamlet forming mechanism 172, which may result in higher beam currents for the on-axis beamlet 102_1 and the off-axis beamlets 102_2 and 102_3 downstream of the beam-limiting aperture array 121. The dashed circles representing PC1 and PC2 are merely for illustrative purposes.

[0075]

[0093] 4B shows the beam profiles of the beamlets 102_1, 102_2, 102_3 with a medium beam current (represented as probe current 2 (PC2)) projected onto the plane 172P. The electrons constituting the beam profile PC2 may identify a portion of the electrons of each of the beamlets 102_1, 102_2, 102_3 that pass through a corresponding aperture of the beam-limiting aperture array 121, and the remaining electrons of the beamlets 102_1, 102_2, 102_3 may be blocked by the beam-limiting aperture array 121. The current of the beamlets passing through the apertures of the pre-beamlet forming mechanism 172 may be based on, for example, the position of the principal plane 110_2 of the focusing lens 110 along the principal optical axis 100_1 and the size of the corresponding aperture of the beam-limiting aperture array 121. For example, for the beamlet profile shown in FIG. 4B, the principal plane 110_2 of the focusing lens 110 is located closer to the center of the distance between the pre-beamlet forming mechanism 172 and the beam-limiting aperture array 121, resulting in a medium beam current of on-axis beamlet 102_1 and off-axis beamlets 102_2 and 102_3 exiting the beam-limiting aperture array 121. In some embodiments, the position of the beamlet profile PC2 may shift along an axis (e.g., the x-axis) with a change in beam current resulting from a change in the focusing power of the focusing lens 110. In some embodiments, the position of the beamlet profile PC2 may change in multiple axes (e.g., the x-axis and the y-axis).

[0076]

[0094] 4C shows the beam profiles of the beamlets 102_1, 102_2, 102_3 with low beam current (represented as probe current 1 (PC1)) projected onto the plane 172P. The electrons constituting the beam profile PC1 may identify a portion of the electrons of each of the beamlets 102_1, 102_2, 102_3 that pass through a corresponding aperture of the beam-limiting aperture array 121, and the remaining electrons of the beamlets 102_1, 102_2, 102_3 may be blocked by the beam-limiting aperture array 121. The current of the beamlets passing through the apertures of the pre-beamlet forming mechanism 172 may be based on, for example, the position of the principal plane 110_2 of the focusing lens 110 along the principal optical axis 100_1 and the size of the corresponding aperture of the beam-limiting aperture array 121. For example, for the beamlet profile shown in Figure 4C, the principal plane 110_2 of the focusing lens 110 is located between the pre-beamlet forming mechanism 172 and the beam-limiting aperture array 121, but closer to the beam-limiting aperture array 121, resulting in low beam currents of the on-axis beamlet 102_1 and the off-axis beamlets 102_2 and 102_3 exiting the beam-limiting aperture array 121. It is understood that the position of the beamlet profile PC1 may shift along an axis (e.g., the x-axis) with changing beam currents. In some embodiments, the position of the beamlet profile PC1 may change in multiple axes (e.g., the x-axis and the y-axis).

[0077]

[0095] 5A-5C, which show schematic diagrams of exemplary charged particle beam profiles (e.g., electron beam profiles) with varying probe current projected onto a plane 172P consistent with embodiments of the present disclosure. FIGS. 5A-5C show projected beam profiles of beamlets 102_1, 102_2, 102_3 exiting a beam-limiting aperture array 121 in a configuration including an adjustable electromagnetic focusing lens, which causes off-axis beamlets 102_2 and 102_3 to be irradiated onto the beam-limiting aperture array 121 at a rotation angle. The rotation angle can be changed along with the focusing power of the adjustable focusing lens 110 or the position of the principal plane 110_2 of the adjustable focusing lens 110 along the principal optical axis 100_1. The projected beam profile on the plane 172P of the pre-beamlet forming mechanism 172 is a virtual projection shown for illustrative purposes only.

[0078]

[0096] 5A-5C show profiles of beamlets 102_1, 102_2, 102_3 (denoted as PC1, PC2, and PC3) with varying beam current. The current of the beamlets passing through the apertures of the pre-beamlet forming mechanism 172 may be based on, for example, the position of the principal plane 110_2 of the focusing lens 110 along the principal optical axis 100_1 and the size of the corresponding apertures of the beam-limiting aperture array 121.

[0079]

[0097] 5B and 5C, respectively, beamlet profile PC3 appears larger based on the relative positioning of the collector lens 110, the electron source 101, and the pre-beamlet forming mechanism 172. For example, when the principal plane 110_2 of the collector lens 110 is closer to the electron source 101 and located below the pre-beamlet forming mechanism 172, beamlet profile PC3 appears larger than when the principal plane 110_2 of the collector lens 110 is located further away from the electron source 101 and closer to the beam-limiting aperture array 121.

[0080]

[0098] 5B, the principal plane 110_2 of the focusing lens 110 is located closer towards the center of the distance between the pre-beamlet forming mechanism 172 and the beam-limiting aperture array 121, resulting in on-axis beamlet 102_1 and off-axis beamlets 102_2 and 102_3 having a medium beam current exiting the beam-limiting aperture array 121. The profile of the beam with a medium beam current is represented by PC2.

[0081]

[0099] 5C, the principal plane 110_2 of the focusing lens 110 is located closer to the beam-limiting aperture array 121, resulting in smaller beam currents of the on-axis beamlet 102_1 and the off-axis beamlets 102_2 and 102_3 exiting the beam-limiting aperture array 121. The projection of the beam with the small beam current is represented by PC1.

[0082]

[0100] In some embodiments, in a multi-beam device 300 including an adjustable electromagnetic compound focusing lens, the position of the beamlet profile PC1, PC2, or PC3 may vary along both axes (e.g., x-axis and y-axis) such that the position may be traced along a curved path as shown in Figures 5A-5C. As used herein, the position of the beamlet may refer to the position of the central axis of the beamlet.

[0083]

[0101] 6A and 6B, which show schematic diagrams of an exemplary arrangement of apertures of a pre-beamlet forming mechanism 172 consistent with embodiments of the present disclosure. In some embodiments, as shown in FIG. 6A, the pre-beamlet forming mechanism 172 may include an on-axis aperture 172_1 and off-axis apertures 172_2 and 172_3. The on-axis aperture 172_1 may be configured to generate an on-axis beamlet 102_1 from the primary charged particle beam 102. In some embodiments, the on-axis aperture 172_1 may be large enough to allow beamlets of various sizes, such as PC1, PC2, or PC3, to pass through. In some embodiments, the geometric center of the on-axis aperture 172_1 may be aligned with the primary optical axis 100_1. The on-axis aperture 172_1 may have a circular, elliptical, substantially circular cross-section, or other suitable cross-section.

[0084]

[0102] Off-axis apertures 172_2 and 172_3 can be configured to generate off-axis beamlets 102_2 and 102_3, respectively. As shown in FIG. 6A, off-axis apertures 172_2 and 172_3 can be configured to allow the passage of beamlets with high probe currents while keeping the total aperture size small to minimize Coulomb effects. For example, one or more of the off-axis apertures (e.g., apertures 172_2 and 172_3) can be elliptical with a tapered shape along the major axis, a truncated cone with rounded ends, or other suitable shapes. In some embodiments, the off-axis apertures can be symmetric or asymmetric along the axis.

[0085]

[0103] In some embodiments, the off-axis beamlet 102_2 exiting the pre-beamlet forming mechanism 172 may have a shape substantially similar to the shape of the off-axis aperture 172_2. The profile of the beamlet exiting the aperture of the beam-limiting aperture array 121 may be represented as PC1, PC2, or PC3 based on the position of the focusing lens 110 and the size of the aperture of the beam-limiting aperture array 121. The cross-section of the off-axis beamlets exiting the beam-limiting aperture array 121, such as the off-axis beamlets 102_2 and 102_3, may be circular or substantially circular.

[0086]

[0104] In some embodiments, as shown in FIG. 6B, the pre-beamlet forming mechanism 172 may include one on-axis aperture 172_1 and eight off-axis apertures, such as apertures 172_2, 172_3, 172_4, 172_5, 172_6, 172_7, 172_8, 172_9, configured to generate nine beamlets from the primary electron beam 102. The off-axis apertures may be arranged symmetrically or asymmetrically around the on-axis aperture 172_1. Each off-axis aperture may be uniform in shape, size, or cross-section. In some embodiments, the off-axis apertures may be non-uniform in shape, size, or cross-section. Although FIG. 6B shows nine apertures, it is understood that there may be any number of apertures and corresponding beamlets, as desired.

[0087]

[0105] 7A and 7B, which show schematic diagrams of an exemplary arrangement of apertures of the pre-beamlet forming mechanism 172, consistent with embodiments of the present disclosure. In some embodiments, as shown in FIG. 7A, the pre-beamlet forming mechanism 172 may include an on-axis aperture 172_1 and off-axis apertures 172_2C and 172_3C. The off-axis apertures (e.g., 172_2C and 172_3C) may be curved ellipses that narrow as the apertures approach the origin of the xy coordinates, and the primary optical axis 100_1 passes substantially through the origin of the xy plane. In some embodiments, the orientation of the off-axis apertures 172_2C and 172_3C may be based on the rotation angle of the beamlet as it passes through the electromagnetic focusing lens and the position of the apertures of the beam-limiting aperture array 121. In some embodiments, the rotation of the beamlet may vary based on electrical excitation of the focusing lens.

[0088]

[0106] In some embodiments, as shown in FIG. 7B, the pre-beamlet forming mechanism 172 may include one on-axis aperture 172_1 and eight off-axis apertures, such as apertures 172_2C, 172_3C, 172_4C, 172_5C, 172_6C, 172_7C, 172_8C, 172_9C, configured to generate nine beamlets from the primary electron beam 102. The off-axis apertures may be arranged such that there is no overlap between adjacent apertures. In some embodiments, the off-axis apertures may be uniform in shape, size, orientation, or cross-section. In some embodiments, the apertures may be non-uniform in shape, size, orientation, or cross-section.

[0089]

[0107] In some embodiments, the Coulomb effect of the region between the pre-beamlet forming mechanism 172 and the beam-limiting aperture array 121 may depend on the size of the beamlets generated by the apertures of the pre-beamlet forming mechanism 172. For example, the off-axis beamlets (e.g., 102_2 and 102_3 in FIG. 6A) may have a larger Coulomb effect compared to the on-axis beamlets (e.g., 102_1 in FIG. 6A) because the total area of ​​the non-circular off-axis aperture (e.g., 172_2 or 172_3 in FIG. 6A) is larger than the total area of ​​the circular on-axis aperture 172_1. The difference in the Coulomb effect between the on-axis and off-axis beamlets may result in a difference in resolution in the image. For example, the region of the image corresponding to the probe spot formed by the off-axis beamlets 102_2 and 102_3 may have a lower resolution than the region of the image corresponding to the probe spot formed by the on-axis beamlet 102_1. Differences in resolution within the images are undesirable as they can affect a user's ability to reliably analyze and detect defects.

[0090]

[0108] 8A and 8B, which show schematic diagrams of example arrangements of apertures of the pre-beamlet forming mechanism 172 of the multi-beam device 300, consistent with embodiments of the present disclosure. FIG. 8A shows an arrangement of three apertures of the multi-beam device 300 including an adjustable anti-rotation electrostatic focusing lens (e.g., focusing lens 110 of FIG. 3), where the rotation angle does not change with the change in focusing power and the position of the principal plane 110_2 of the focusing lens 110. FIG. 8B shows an arrangement of three apertures of the multi-beam device 300 including an adjustable electromagnetic focusing lens, where the off-axis beamlets 102_2 and 102_3 can be incident on the beam-limiting aperture array 121 at a rotation angle. The rotation angle can be changed along with the focusing power of the adjustable focusing lens 110 or the position of the principal plane of the adjustable focusing lens 110 (eg, the principal plane 110_2 in FIG. 3) along the principal optical axis 100_1.

[0091]

[0109] As shown in Figures 8A and 8B, the size of the on-axis aperture 172_1 can be enlarged, so that the difference between the total area of ​​the on-axis aperture 172_1 and the total area of ​​the off-axis apertures (e.g., 172_2 and 172_3) is reduced, and thus the difference in resolution in the image generated by the probe spots (e.g., probe spots 102_1S, 102_2S, 102_3S in Figure 3) is minimized. Although Figures 8A and 8B show a circular on-axis aperture 172_1, other cross-sections can be used, including but not limited to elliptical, polygonal, triangular, or any non-circular cross-section. In some embodiments, the shape and size of the on-axis aperture 172_1 can be similar to the off-axis aperture (e.g., off-axis aperture 172_2 in Figure 8A or off-axis aperture 172_2C in Figure 8B).

[0092]

[0110] Referring now to FIG. 9, FIG. 9 illustrates an exemplary arrangement of apertures in the beam-limiting aperture array 121 consistent with embodiments of the present disclosure. Although FIG. 9 illustrates nine apertures, the beam-limiting aperture array 121 may include any number of apertures. In some embodiments, the beam-limiting aperture array 121 may include apertures arranged in a regular pattern, such as a pattern having a rectangular, circular, spiral, polygonal, or similar shape. In some embodiments, the apertures in the beam-limiting aperture array 121 may be uniform in shape, size, cross-section, pitch, or any combination thereof. As used herein, the pitch of an array having circular apertures may refer to the distance between the centers of two immediately adjacent apertures. In some embodiments, the apertures in the beam-limiting aperture array 121 may be randomly arranged and may be non-uniform in shape, size, cross-section, pitch, or any combination thereof.

[0093]

[0111] In some embodiments, the number of apertures in the beam-limiting aperture array 121 can determine the number of beamlets that are incident on the sample surface and generate probe spots. In some embodiments, the number of apertures in the beam-limiting aperture array 121 can be equal to, less than, or greater than the number of apertures in the pre-beamlet forming mechanism 172.

[0094]

[0112] In some embodiments, the beam-limiting aperture array 121 may be located below the condenser lens 110, as shown in FIG. 3. The condenser lens 110 may be configured to collimate the beamlets 102_1, 102_2, 102_3, such that the beamlets 102_1, 102_2, 102_3 are substantially parallel to the primary optical axis 100_1 and perpendicularly incident on the beam-limiting aperture array 121. In some embodiments, the condenser lens 110 may collimate the beamlets generated by the apertures 172_1-172_9 of the pre-beamlet forming mechanism 172 of FIG. 7B, such that the beamlets are substantially parallel to the primary optical axis 100_1 and perpendicularly incident on the beam-limiting aperture array 121 of FIG. The size of the apertures in the beam-limiting aperture array 121 can determine the size of the beamlets exiting the source conversion unit 120, and ultimately the size of the probe spots generated on the surface of the sample 190.

[0095]

[0113] 10, which illustrates an example contour of an aperture of a pre-beamlet forming mechanism 172 of a multi-beam device 300 including an electromagnetic compound focusing lens and beam-limiting aperture array 121, consistent with an embodiment of the present disclosure. In some embodiments, the pitch of the apertures of the beam-limiting aperture array 121 may be so small that the corresponding off-axis apertures of the pre-beamlet forming mechanism 172 include overlapping regions 1010_1, 1010_2, 1010_3, 1010_4, as shown in FIG. For example, off-axis apertures 1072_3 and 1072_9 may include overlap region 1010_1, off-axis apertures 1072_5 and 1072_8 may include overlap region 1010_2, off-axis apertures 1072_2 and 1072_7 may include overlap region 1010_3, and off-axis apertures 1072_4 and 1072_6 may include overlap region 1010_4. In some embodiments, the overlap regions may be uniform in shape and size or non-uniform in shape and size.

[0096]

[0114] In some embodiments, overlap of aperture profiles of the pre-beamlet forming mechanism 172 may occur due to large variations in probe current based on a combination of the position of the focusing lens 110 and the aperture size of the beam-limiting aperture array 121. For example, if the focusing lens is positioned closer to a beam-limiting aperture array 121 that includes apertures with a small pitch, the corresponding apertures of the pre-beamlet forming mechanism 172 may partially overlap (e.g., overlap region 1010_1).

[0097]

[0115] 11A, which illustrates an example arrangement of partial overlap apertures of a pre-beamlet forming mechanism 172 consistent with embodiments of the present disclosure. The pre-beamlet forming mechanism 172 of FIG. 11A may include one on-axis aperture 1172_1 and four off-axis merge apertures 1101C, 1102C, 1103C, 1104C. In some embodiments, the apertures of the pre-beamlet forming mechanism 172 including the overlap region 1010 of FIG. 10 may merge to form the off-axis merge apertures 1101C, 1102C, 1103C, 1104C. For example, off-axis apertures 1172_3 and 1172_9 can be merged to form off-axis merge aperture 1101C, off-axis apertures 1172_5 and 1172_8 can be merged to form off-axis merge aperture 1102C, off-axis apertures 1172_2 and 1172_7 can be merged to form off-axis merge aperture 1103C, and off-axis apertures 1172_4 and 1172_6 can be merged to form off-axis merge aperture 1104C.

[0098]

[0116] In some embodiments, the size of the on-axis aperture 1172_1 in FIG. 11A can be adjusted accordingly to reduce the difference in the total area of ​​the off-axis merge aperture, such as 1101C, and the on-axis aperture 1172_1, thus minimizing the difference in resolution in the image due to changes in the Coulomb effect, as discussed with respect to FIGS. 8A and 8B.

[0099]

[0117] 11B, which illustrates an example arrangement of apertures of a pre-beamlet forming mechanism 172B consistent with embodiments of the present disclosure. The pre-beamlet forming mechanism 172B of FIG. 11B may include one on-axis aperture 1172_1 and at least one off-axis aperture set 1105C. As shown in FIG. 11B, in some embodiments, the pre-beamlet forming mechanism 172B may include multiple off-axis aperture sets 1105C.

[0100]

[0118] In some embodiments, the pre-beamlet forming mechanism 172B may include a planar structure having multiple apertures. The planar structure may be made of materials including metals, alloys, composites, semiconductors, or the like. In some embodiments, the materials may be conductive or may be coated with a conductive material. The apertures of the pre-beamlet forming mechanism 172B may be formed using techniques including, but not limited to, machining, microelectromechanical system (MEMS) fabrication techniques, chemical etching, laser cutting, and the like.

[0101]

[0119] In some embodiments, the pre-beamlet forming mechanism 172B can be aligned such that the geometric center of the on-axis aperture 1172_1 coincides with the primary optical axis 100_1. The cross section of the on-axis aperture 1172_1 can be circular or substantially circular. In some embodiments, at least a portion of the on-axis primary beamlet formed by the on-axis aperture 1172_1 can be incident on an on-axis aperture of the beam-limiting aperture array 121. In some embodiments, the size of the on-axis aperture 1172_1 can be configured to be larger than or substantially similar to the size of the corresponding on-axis aperture of the beam-limiting aperture array 121. In some embodiments, the size of the on-axis aperture of the beam-limiting aperture array 121 can determine the size of the probing beamlet exiting the beam-limiting aperture array 121.

[0102]

[0120] In a multi-beam SEM, it may be desirable to generate multiple beams with a large current range to enable the tool to be used for low and high resolution imaging. Although a large and continuous current range can be achieved by increasing the size of the aperture, a large aperture can negatively impact the mechanical and structural integrity of the structure (e.g., the aperture array) and increase Coulomb interaction effects, among other issues. It may be desirable to fabricate an aperture array that allows the generation of multiple beams and large current ranges while maintaining mechanical and structural integrity.

[0103]

[0121] In some embodiments, the pre-beamlet forming mechanism 172B may include an off-axis aperture set 1105C including exemplary off-axis apertures 1105C_1, 1105C_2, 1105C_3, 1105C_4, 1105C_5, 1105C_6. The apertures in the off-axis aperture set 1105C may enable the generation of beamlets with a discrete current range, as opposed to the continuous current range provided by a larger aperture of comparable size. Although the off-axis aperture set 1105C is shown to include six off-axis apertures, it is understood that there may be any number of off-axis apertures as needed and appropriate.

[0104]

[0122] The pre-beamlet forming mechanism 172B as shown in FIG. 11B can be used in an apparatus configured to generate a 5×5 array of probing beamlets. In some embodiments, each off-axis aperture set 1105C and on-axis aperture 1172_1 can be associated with a corresponding aperture of the beam-limiting aperture array 121 of FIG. 3. For example, based on the association, the number of off-axis aperture sets of the pre-beamlet forming mechanism 172B can be equal to the number of off-axis apertures of the beam-limiting aperture array 121. The number of probing beamlets to be generated, and therefore the number of apertures including the off-axis aperture set 1105C and on-axis apertures of the pre-beamlet forming mechanism 172B, can be determined based on the application and the number of discrete current settings desired. For example, a 7×7 array of apertures can be used in applications where a larger current range of probing beamlets is desired, and a 3×3 array of apertures can be used in applications or tools with space limitations.

[0105]

[0123] The pre-beamlet formation mechanism 172B of a multi-beam device (eg, EBI system 100 of FIG. 1) may have some or all of the advantages discussed herein, among others. i. Large beam current range - To perform multiple operations or functions with a multi-beam SEM, a large range of beam currents may be desirable. The range of beam currents can be increased by providing apertures of various sizes in the off-axis aperture set, as shown in FIG. 11B, while reducing Coulomb interaction effects. ii. Enhanced structural integrity - the apertures in an off-axis aperture set can be separated by the material of the pre-beamlet forming mechanism 172B, thus maintaining the mechanical rigidity of the structure while increasing the range of beam currents for inspecting samples. iii. Reduced Coulomb interaction effects - Coulomb interaction is a function of the transmission area of ​​the aperture array and therefore increases with the size of the aperture for the system. The apertures of the off-axis aperture set allow for the production of a large range of beam currents while reducing the transmission area of ​​electrons, thereby reducing Coulomb interaction effects and thus improving imaging resolution. iv. Manufacturability - Fabricating the apertures of an aperture array such as the pre-beamlet forming mechanism 172 may involve removing material to form paths for passing electrons. While larger apertures increase the continuous current range, they may negatively impact the manufacturability of the array due to insufficient supporting material remaining after the formation of the apertures. The pre-beamlet forming mechanism 172B may be simply and reliably manufacturable because the apertures in the off-axis aperture set are separated by the material from which the pre-beamlet forming mechanism 172B is made.

[0106]

[0124] In some embodiments, the sizes of the off-axis apertures (e.g., 1105C_1, 1105C_2, 1105C_3, 1105C_4, 1105C_5, 1105C_6) of the off-axis aperture set 1105C may vary. As shown in FIG. 11B, the radii of the circular off-axis apertures may vary. For example, the radius of aperture 1105C_1 may be smaller than the radius of aperture 1105C_2, which may be smaller than the radius of aperture 1105C_3, which may be smaller than the radius of aperture 1105C_4, which may be smaller than the radius of aperture 1105C_5, which may be smaller than the radius of aperture 1105C_6. In some embodiments, the size of at least two off-axis apertures of the off-axis aperture set may be different. The size of the off-axis aperture may determine the current of the primary beamlet generated from the off-axis aperture, and apertures of different sizes may enable the generation of beamlets with a larger current range. In some embodiments, the off-axis apertures of the off-axis aperture set 1105C can be smaller than, equal to, or larger than the corresponding off-axis apertures of the beam-limiting aperture array 121.

[0107]

[0125] In some embodiments, the cross-section of the apertures of the off-axis aperture set 1105C may be circular, rectangular, substantially circular, elliptical, or polygonal or the like. The cross-section of the aperture may determine the cross-section and shape of the primary beamlet generated thereby. In some embodiments, the off-axis aperture set 1105C may include apertures with different cross-sections. For example, apertures 1105C_1 and 1105C_3 may be circular, and apertures 1105C_2 and 1105C_4 may be elliptical.

[0108]

[0126] In some embodiments, the pitch of the apertures in the off-axis aperture set 1105C may be uniform. In the context of this disclosure, in the case of circular apertures, the pitch may be defined as the shortest distance between the geometric centers of directly adjacent apertures, as shown in FIG. 11B. In some embodiments, the pitch of the apertures in the off-axis aperture set 1105C may be non-uniform.

[0109]

[0127] In some embodiments, the apertures of the off-axis aperture set 1105C may be arranged along a curved path, as shown by the imaginary path (e.g., paths 1172_P1 and 1172_P2 in FIG. 11B). The dashed lines showing the imaginary paths 1172_P1 and 1172_P2 are for illustrative purposes only. It is understood that the radius of the curved line of the path along which the apertures of the off-axis aperture set are arranged may vary between the off-axis aperture sets. It is also understood that the apertures of the off-axis aperture set (e.g., 1105C in FIG. 11B) may be arranged along multiple paths having different radii of the curved line. In some embodiments, the apertures of the off-axis aperture set 1105C may be arranged along a straight path. In some embodiments, the path along which the apertures of the off-axis aperture set 1105C are arranged may be based on the characteristics of the collection lens 110.

[0110]

[0128] In some embodiments, an off-axis aperture set may intersect with an adjacent off-axis aperture set, such that an aperture may correspond to multiple off-axis aperture sets. For example, aperture 1105C_8 may correspond to an off-axis aperture set along path 1172_P1 and an off-axis aperture set along path 1172_P2. In some embodiments, an off-axis aperture set may intersect with one or more off-axis aperture sets. In some embodiments, an aperture of an off-axis aperture set may be positioned directly adjacent to an aperture of the intersecting off-axis aperture set such that at least a portion of the apertures overlap one another.

[0111]

[0129] It should be noted that the curved tapered ellipse 1172_V, indicating the boundary within which the apertures of the off-axis aperture set 1105C may be placed, is merely a visual aid for illustrative purposes.

[0112]

[0130] In some embodiments, each aperture of the off-axis aperture set 1105C can generate a primary beamlet that is incident on the collector lens 110 disposed downstream of the pre-beamlet forming mechanism 172B. In some embodiments, the collector lens 110 can include an adjustable electromagnetic lens configured to form a primary beamlet into a corresponding probing beamlet of the multiple probing beamlets exiting the beam-limiting aperture array 121. Based on the setting of the collector lens 110, the primary beamlet formed by the aperture of the off-axis aperture set 1105C can be incident on a corresponding aperture of the beam-limiting aperture array 121 at a rotation angle. The rotation angle can be changed together with the focusing power of the adjustable collector lens 110 or the position of the principal plane 110_2 of the adjustable collector lens 110 along the principal optical axis 100_1. For example, if the focusing lens 110 is positioned closer to the electron source 101, the probing beamlet generated from the aperture 1105C_6 may be incident on the corresponding off-axis aperture of the beam-limiting aperture array 121. If the size of the corresponding off-axis aperture of the beam-limiting aperture array 121 is larger than the size of the aperture 1105C_6, the probe current of the probing beamlet exiting the corresponding aperture of the beam-limiting aperture array 121 may be determined based on the size of the aperture 1105C_6 of the pre-beamlet forming mechanism 172B. Alternatively, if the size of the corresponding off-axis aperture of the beam-limiting aperture array 121 is smaller than the size of the aperture 1105C_6, the probe current of the probing beamlet exiting the corresponding aperture of the beam-limiting aperture array 121 may be determined based on the size of the aperture of the beam-limiting aperture array 121.

[0113]

[0131] In some embodiments, the off-axis aperture set 1105C may also be referred to as a pre-beamlet forming aperture set 1105C. The probe current of the corresponding probing beamlet may be determined based on the characteristics of the apertures of the pre-beamlet forming aperture set 1105C. Each aperture of the pre-beamlet forming aperture set 1105C (e.g., apertures 1105C_1-1105_C6) may be configured to affect the probe current of the probing beamlet. The characteristics of the apertures of the pre-beamlet forming aperture set 1105C may include, but are not limited to, size, shape, or location, among other array characteristics. The probe current of the probing beamlet may be discretely adjustable, for example, based on the size of the apertures of the pre-beamlet forming aperture set 1105C forming the primary beamlet.

[0114]

[0132] In some embodiments, adjusting the position of the condenser lens 110 along the main optical axis 100_1 may affect or influence the probe current of the probing beamlet formed by the corresponding primary beamlet. As an example, the condenser lens 110 placed at a first position may cause a first portion of the primary electron beam 102 to pass through an aperture of the pre-beamlet forming aperture set 1105C to form a primary beamlet having a certain beam current value. The condenser lens 110 placed at a second location different from the first location may cause a second portion of the primary electron beam to pass through a different aperture of the pre-beamlet forming aperture set 1105C to form a different primary beamlet having a different beam current value, thus affecting the probe current of the probing beamlet formed from the corresponding primary beamlet.

[0115]

[0133] 11C, which illustrates the relationship between probe spot size and beam current of beamlets formed by the apertures of the off-axis aperture set 1105C. As shown, a larger aperture (e.g., aperture 1105C_6) allows more electrons to pass, and thus the beamlets formed may have a larger current value and a larger spot size. A smaller aperture (e.g., aperture 1105C_1 in FIG. 11B) allows fewer electrons to pass, and thus the beamlets formed by aperture 1105C_1 may have a smaller current value and a smaller spot size. The smaller beamlets may reduce Coulomb interaction effects and, as a result, improve imaging resolution. In some embodiments where apertures 1105C_1-1105C_6 have the same size, the beamlets formed by the apertures may have different current values ​​for each of the apertures. Furthermore, the current value of a beamlet formed by one aperture may be greater or less than the current value of a beamlet formed by an adjacent aperture along the virtual path.

[0116]

[0134] 11D, which illustrates an exemplary arrangement of apertures of a pre-beamlet forming mechanism 172D consistent with an embodiment of the present disclosure. Compared to the pre-beamlet forming mechanism 172B of FIG. 11B, the off-axis aperture set 1105C may include at least one non-circular aperture 1105C_7. As shown in FIG. 11D, the cross section of the aperture 1105C_7 may be elliptical. Apertures with other cross sections may also be employed, including, but not limited to, tapered elliptical, curved elliptical, polygonal, and the like.

[0117]

[0135] In some embodiments, the aperture 1105C_7 of the pre-beamlet forming mechanism 172D can be positioned closer to the primary optical axis 100_1 or the on-axis aperture 1172_1 so that the beamlet generated from the aperture 1105C_7 has a lower beam current. A larger aperture 1105C_7 can be useful in providing a continuous current range while maintaining low Coulomb interaction effects due to low beam current. In some embodiments, one or more off-axis aperture sets 1105C can include the aperture 1105C_7.

[0118]

[0136] In a multi-beam SEM, it may be desirable to generate multiple beams with a large current range to enable the tool to be used for low-resolution and high-resolution imaging. Although a large and continuous current range can be achieved by increasing the size of the aperture, a large aperture can increase Coulomb interaction effects, among other problems. For high-resolution applications, Coulomb interaction effects can limit the resolution of the resulting image (although a smaller aperture produces a smaller probe spot). Therefore, it may be desirable to fabricate an aperture array that allows the generation of multiple beams with a wide current range while reducing Coulomb interaction effects and improving image resolution.

[0119]

[0137] One of several ways to mitigate Coulomb interaction effects may include using a pre-beamlet formation mechanism 172B that includes an active aperture array. In the context of this disclosure, "active aperture" refers to an aperture or aperture assembly that can be configured to be electrically activated such that an electric field is created within the aperture or aperture assembly.

[0120]

[0138] 11E, which shows an expanded view of an exemplary active aperture 1105_C6A including an upper aperture plate 1120, an active deflector 1130, and a lower aperture plate 1140. While the active aperture 1105_C6A is shown to include three elements, it is understood that there may be more elements, such as spacer layers, microlenses, etc., as appropriate, as needed. In some embodiments, the upper aperture plate 1120, the active deflector 1130, and the lower aperture plate 1140 may be stacked without any spacer layer disposed between them. In some embodiments, the active aperture 1105_C6A may also be referred to as an active aperture assembly or active aperture stack. In some embodiments, the active aperture 1105_C6A may not include the upper aperture plate 1120, and in other embodiments, the active aperture 1105_C6A may not include the lower aperture plate 1142.

[0121]

[0139] In some embodiments, for example, aperture 1105C_6 of pre-beamlet forming mechanism 172B of FIG. 11B may include an active aperture. In some embodiments, one or more off-axis apertures of pre-beamlet forming mechanism 172B may include an active aperture, one or more off-axis aperture sets (e.g., 1105C, etc.) may include an active aperture, or pre-beamlet forming mechanism 172B may include an active aperture array. As used herein, "active aperture array" refers to an array of active apertures, such as 1105_C6A. It is understood that an active aperture array may include active apertures of different sizes, cross-sections, shapes, configurations, or materials.

[0122]

[0140] In some embodiments, the active aperture 1105_C6A may include an active aperture assembly fabricated using techniques including, but not limited to, machining, MEMS fabrication techniques, chemical etching, laser cutting, micromachining, or the like. The pre-beamlet forming mechanism 172B including the active aperture array may be fabricated from conductive, semiconductive, or insulating materials based on the application. For example, in some embodiments, the upper aperture plate 1120, the active deflector 1130, and the lower aperture plate 1140 of the active aperture 1105_C6A may be fabricated using semiconductive materials, and the spacer layer (not shown in FIG. 11E) may be fabricated using electrically insulating materials.

[0123]

[0141] In some embodiments, the top aperture plate 1120 can be configured to allow a portion of the electrons of the primary electron beam 102 to pass based on a desired current setting. The top aperture plate 1120 can include multiple off-axis apertures 1122 separated by the material from which the top aperture plate 1120 is fabricated. The off-axis apertures 1122 can include apertures having cross-sections that are circular, elliptical, rectangular, elongated, non-circular, polygonal, etc. The off-axis apertures 1122 of the active aperture array of the pre-beamlet forming mechanism 172B can be non-uniform in size, pitch, cross-section, or the like.

[0124]

[0142] In some embodiments, the lower aperture plate 1140 may include multiple off-axis apertures 1142 separated by the material from which the lower aperture plate 1140 is fabricated. The off-axis apertures 1142 may include, but are not limited to, apertures having a circular, elliptical, rectangular, elongated, non-circular, polygonal cross-section. The off-axis apertures 1142 of the active aperture array of the pre-beamlet forming mechanism 172B may be non-uniform in size, pitch, cross-section, or the like. In some embodiments, the geometric center of the off-axis aperture 1122 may be aligned with the geometric center of the corresponding off-axis aperture 1142. In some embodiments, the size of the off-axis aperture 1122 and the corresponding off-axis aperture 1142 may be substantially similar.

[0125]

[0143] In some embodiments, the upper aperture plate 1120 or the lower aperture plate 1140 can be electrically grounded. In the context of this disclosure, electrical ground refers to the reference point of the active aperture 1105_C6A from which the applied voltage is measured. For example, if the upper aperture plate 1120 or the lower aperture plate 1140 is electrically grounded and a voltage signal of +100V is applied to the active deflector 1130, the effective voltage applied to the active deflector 1130 is +100V.

[0126]

[0144] In some embodiments, the active deflector 1130 may include a monopole or multipole deflector configured to be electrically activated to affect the path of a portion of the electrons of the primary electron beam 102. Although FIG. 11E shows a two-pole deflector, the active deflector 1130 may include any number of poles as appropriate. The poles of the active deflector 1130 may be radially arranged along a plane substantially perpendicular to the main optical axis 100_1 and substantially parallel to the upper aperture 1120 or the lower aperture plate 1140. In some embodiments, the size of the aperture 1132 formed in the active deflector plate 1130 may be equal to or larger than the size of the off-axis aperture 1122 or 1142.

[0127]

[0145] Although the apertures in the off-axis aperture set allow for the generation of a large range of beam currents while reducing Coulomb interaction effects by reducing the electron transmission area, for high resolution applications further reduction of Coulomb interaction effects may be desirable. In some embodiments, the active aperture array may be configured to generate multiple off-axis beamlets from the primary electron beam 102 while further reducing Coulomb interaction effects.

[0128]

[0146] In some embodiments, the active deflector 1130 can be electrically activated by applying an electrical signal to one or more poles based on factors including the desired current setting, image resolution, or electron deflection or beamlet size, among others. In some embodiments, the electrical signal can include a voltage signal suitable for deflecting a portion of the electrons of the primary electron beam 102 that exit the off-axis aperture 1122. In some embodiments, one or more poles of the active deflector 1130 can be electrically grounded, one or more poles of the active deflector 1130 can be electrically activated, or a combination thereof, based on the desired beamlet characteristics.

[0129]

[0147] In some embodiments, the lower aperture plate 1140 may include an aperture 1142 aligned with the corresponding off-axis aperture 1132 or the corresponding off-axis aperture 1122. The size of the aperture 1142 may be smaller than the aperture 1132 of the active deflector plate 1130. In some embodiments, the aperture 1142 may be configured to block deflected electrons that exit the aperture 1132, thereby generating beamlets that contain fewer electrons, resulting in reduced Coulomb interaction effects in the generated beamlets.

[0130]

[0148] In some embodiments, the apparatus 300 may include a pre-beamlet forming mechanism 172B of FIG. 11B including one or more off-axis active aperture sets such as 1105C, and may also include a beam-limiting aperture array 121 of FIG. 3. The active aperture 1105_C6A may be configured to generate an off-axis primary beamlet (e.g., beamlet 102_2 of FIG. 2) from the primary electron beam 102. In some embodiments, for example, the beam-limiting aperture 121_2 may be configured to receive beamlet 102_2 from the corresponding primary beamlet and generate a probing beamlet having an associated beam current. The associated beam current of the probing beamlet may be adjustable based at least on the size of the off-axis aperture 1122, the electric field between the top aperture plate 1120 and the active deflector 1130, or both.

[0131]

[0149] In some embodiments, the associated beam current of the probing beamlet may be adjustable in a discrete range. For example, an off-axis active aperture set 1105_CA (not shown, but similar to 1105C in FIG. 11B in some embodiments) may include multiple off-axis active apertures (1105_C1A, 1105_C2A, 1105_C3A, 1105_C4A, 1105_C5A, 1105_C6A, not shown, but similar to 1105C_1-1105C_6 in some embodiments). One or more off-axis active apertures may differ in size, shape, or cross-section. The size of the off-axis aperture may determine the size of the beam or the number of electrons passing through, which allows for adjustment of the beam current based on the size of the off-axis active aperture through which the beam is directed. It is understood that the off-axis active aperture set 1105_CA may include fewer or more active apertures, as desired.

[0132]

[0150] In some embodiments, the voltage signal applied to the active deflector 1130 can be fixed or substantially fixed. The electric field formed as a result of the fixed voltage signal applied to the top aperture plate 1120 and the active deflector 1130 can be fixed or substantially fixed. In such cases, the beam current of the probing beamlet can be adjusted based at least on the selected aperture size of the off-axis aperture 1122. In some embodiments, the selected off-axis aperture 1122 can be predetermined or dynamically determined based on factors including, but not limited to, material, desired analysis, and resolution feedback, among others.

[0133]

[0151] In some embodiments, the voltage signal applied to the active deflector 1130 may be adjustable. The electric field formed as a result of the application of the adjustable voltage signal to the active deflector 1130 may be adjustable. In such a case, the beam current of the probing beamlet may be determined based on the electric field between the upper aperture plate 1120 and the active deflector 1130. The electric field formed by the difference in the applied voltage signal between the upper aperture plate 1120 and the active deflector 1130 may deflect the path of a portion of the charged particles (e.g., electrons) passing through the active aperture 1105_C6A, so that some of the peripheral electrons may be blocked by the lower aperture plate 1140. The primary beamlet formed may contain fewer electrons as a result of the deflection by the electric field and the blocking of the peripheral electrons, and therefore the beam current of the corresponding probing beamlet formed may be reduced.

[0134]

[0152] In some embodiments, the beam current of the probing beamlet can be adjusted by selecting the size of the aperture 1122 of the active aperture 1105_C6A, or by adjusting the electric field of the active aperture 1105_C6A by adjusting the difference between the voltage signal applied to the upper aperture plate 1120 and the voltage signal applied to the active deflector 1130, or by selecting an aperture of the beam-limiting aperture array 121 configured to generate the probing beamlet based on the size of the beamlet that is allowed to pass, or by a combination thereof.

[0135]

[0153] 11F, which illustrates a cross-sectional view of the active aperture 1105_C6A, consistent with an embodiment of the present disclosure. As shown in FIG. 11F, a portion of the primary electron beam 102 can enter the active aperture 1105_C6A through an aperture 1122 in the upper aperture plate 1120, and the beamlet 102_AA can exit the active aperture 1105_C6A through an aperture 1142 in the lower aperture plate 1140. In some embodiments, the active deflector 1130 can be electrically activated to deflect peripheral electrons of the primary electron beam 102 so that they can be blocked by the lower aperture plate 1140. The deflection of the peripheral electrons can be determined based on characteristics of an electrical signal applied to the active deflector 1130. The electrical signal can include a voltage signal, and the characteristics of the voltage signal can include polarity or amplitude, among other things.

[0136]

[0154] In some embodiments, the electrical activation of the active deflector 1130 can be dynamically adjusted based on the application, desired analysis, or system performance, among others. For example, imaging resolution can be adjusted by adjusting the electrical activation of the active deflector 1130 based on scanning resolution information obtained using a feedback mechanism. In some embodiments, the active aperture 1105_C6A can be configured to be controlled using circuitry (not shown in FIGS. 11E and 11F). The circuitry can include a microprocessor, sensing circuitry, on-off drive circuitry, voltage regulation circuitry, memory, timing circuitry, among others. It is understood that the circuitry can include other associated components as needed and appropriate.

[0137]

[0155] In some embodiments, deflector poles of active apertures of an active aperture array having substantially similar aperture sizes corresponding to current settings can be electrically grouped. Electrical grouping of deflector poles of active apertures having substantially similar sizes may be desirable because it can limit the number of electrical connections, thus improving system integration, operation and control.

[0138]

[0156] 12, which illustrates a process flow diagram depicting an exemplary method 1200 of observing a sample using a multi-beam inspection tool consistent with an embodiment of the present disclosure. Method 1200 may be performed, for example, by a controller 50 of an EBI system 100 as shown in FIG. The controller 50 may be programmed to implement one or more steps of method 1200. For example, the controller 50 may instruct modules of a charged particle beam device to activate a charged particle source to generate a charged particle beam and to perform other functions.

[0139]

[0157] In step 1210, a charged particle beam (e.g., primary electron beam 102 in FIG. 2) can be generated by activating a charged particle source (e.g., electron source 101 in FIG. 2). For example, the electron source 101 can be powered on to emit a primary electron beam formed along a main optical axis. The electron source can be activated remotely, for example, by using software, an application, or an instruction set for a processor of a controller to power the electron source through a control circuit. The primary electron beam can be reduced by a gun aperture plate (e.g., gun aperture plate 171 in FIG. 2), an aperture array (e.g., pre-beamlet forming mechanism 172 in FIG. 2), or both.

[0140]

[0158] In step 1220, after passing through a pre-beamlet forming mechanism (e.g., pre-beamlet forming mechanism 172 in FIG. 3), multiple beamlets (e.g., beamlets 102_1, 102_2, 102_3 in FIG. 3) can be generated. The number of beamlets generated can be based on the number of pre-reduction apertures of the pre-beamlet forming mechanism. For illustrative purposes, for example, three beamlets and three pre-reduction apertures are shown in FIG. 3. The beamlets generated after the primary electron beam passes through the pre-beamlet forming mechanism can include one on-axis beamlet and at least one off-axis beamlet. In some embodiments, multiple off-axis beamlets can be generated. The pre-beamlet forming mechanism can include one on-axis aperture and at least one off-axis aperture. The shape or cross section of the on-axis aperture can be circular or substantially circular. The off-axis aperture can be an elongated aperture with rounded ends and a tapered width. In some embodiments, the off-axis apertures may be elongated and curved (e.g., off-axis apertures 172_2C-172_9C of FIG. 7B, etc.). In some embodiments, one or more of the off-axis apertures may involve a first aperture that overlaps with a second aperture (e.g., merge apertures 1101C-1104C of FIG. 11A). In some embodiments, the shape of the off-axis aperture may be based on the path of the corresponding beamlet associated with the adjustable probe current of the probing beamlet, the adjustability of the plane of the focusing lens, and the properties of the second aperture array.

[0141]

[0159] In step 1230, a position of a plane (e.g., principal plane 110_2 in FIG. 3) of a collector lens (e.g., collector lens 110 in FIG. 2) can be adjusted along the principal optical axis. In some embodiments, the adjustable plane can be the principal plane of the collector lens. The position of the principal plane of the collector lens can be adjusted in relation to the position of the pre-beamlet forming mechanism and the beam-limiting aperture array (e.g., beam-limiting aperture array 121 in FIG. 3) to adjust the probe current of the probing beamlet generated by the beam-limiting aperture array. For example, when the principal plane of the collector lens is closer to the beam-limiting aperture array than the pre-beamlet forming mechanism, the beam current of the on-axis beamlets and the off-axis beamlets exiting the beam-limiting aperture array can be lower than when the principal plane is closer to the pre-beamlet forming mechanism.

[0142]

[0160] In some embodiments, in a multi-beam device including an adjustable electromagnetic focusing lens, the off-axis beamlets can be illuminated at a rotation angle to the beam-limiting aperture array. The rotation angle can be changed with the focusing power of the adjustable focusing lens or the position of the principal plane of the adjustable focusing lens along the principal optical axis. The off-axis beamlets can be rotated at an angle at which they pass through the corresponding off-axis aperture of the beam-limiting aperture array.

[0143]

[0161] In some embodiments, adjusting the position of the principal plane of the focusing lens can modify the properties of the probing beamlet exiting the beam-limiting aperture array, which may include, but are not limited to, the probe current of the probing beamlet, the fraction of the beamlet that can generate the probing beamlet, etc.

[0144]

[0162] In step 1240, a probing beamlet may be generated from the multiple beamlets by a beam-limiting aperture array (e.g., beam-limiting aperture array 121 in FIGS. 3 and 9). The characteristics of the probing beamlet may be determined based on the characteristics of the beam-limiting aperture array. The characteristics of the beam-limiting aperture array may include, but are not limited to, aperture size, cross-section, shape, pitch, and positioning. The characteristics of the probing beamlet may be determined by one or more characteristics of the beam-limiting aperture array.

[0145]

[0163] In some embodiments, the position of the beam-limiting aperture array can be fixed. For example, the beam-limiting aperture array can be located in a plane perpendicular to the main optical axis at a predefined distance from the focusing lens or pre-beamlet forming mechanism. In some embodiments, the beam-limiting aperture array can include apertures having a uniform shape, size, cross-section and pitch. In some embodiments, the apertures can also be non-uniform.

[0146]

[0164] In step 1250, the probing beamlets generated by the beam limiting aperture array can be focused and directed towards a sample (e.g., sample 190 in FIG. 2) to form probe spots (e.g., probe spots 102_1S, 102_2S, 102_3S in FIG. 2). In some embodiments, each of the multiple probing beamlets can form a probe spot on the sample. The probing beamlets can be focused using an objective lens (e.g., objective lens 131 in FIG. 3). The probing beamlets can be incident perpendicularly on the sample surface. Primary electrons of the probing beamlets incident on the sample can generate secondary electrons. The secondary electrons can be detected using a secondary electron detector or a backscattered electron detector, thus revealing information about the sample being probed.

[0147]

[0165] 13, which illustrates a process flow diagram depicting an exemplary method 1300 of observing a sample using a multi-beam inspection tool consistent with an embodiment of the present disclosure. Method 1300 may be performed, for example, by a controller 50 of an EBI system 100 as shown in FIG. The controller 50 may be programmed to implement one or more steps of method 1300. For example, the controller 50 may instruct modules of a charged particle beam device to activate a charged particle source to generate a charged particle beam and to perform other functions.

[0148]

[0166] In step 1310, a charged particle beam (e.g., primary electron beam 102 in FIG. 2) can be generated by activating a charged particle source (e.g., electron source 101 in FIG. 2). For example, the electron source 101 can be powered on to emit a primary electron beam formed along a primary optical axis (e.g., primary optical axis 100_1 in FIG. 2). The electron source can be activated remotely, for example, by using software, an application, or an instruction set for a processor of a controller to power the electron source through a control circuit. The primary electron beam can be reduced by a gun aperture plate (e.g., gun aperture plate 171 in FIG. 2), an aperture array (e.g., pre-beamlet forming mechanism 172 in FIG. 2), or both.

[0149]

[0167] In step 1320, after passing through a pre-beamlet forming mechanism (e.g., pre-beamlet forming mechanism 172B in FIG. 11B), multiple beamlets (e.g., beamlets 102_1, 102_2, 102_3 in FIG. 3) can be generated. The number of primary beamlets generated can be based on the number of apertures of the pre-beamlet forming mechanism. For illustrative purposes, for example, three beamlets and three apertures are shown in FIG. 3. The beamlets generated after the primary electron beam passes through the pre-beamlet forming mechanism can include one on-axis primary beamlet and at least one off-axis primary beamlet. In some embodiments, multiple off-axis beamlets can be generated. The pre-beamlet forming mechanism can include one on-axis aperture and at least one off-axis aperture set (e.g., off-axis aperture set 1105C in FIG. 11B). The shape or cross-section of the on-axis aperture can be circular or substantially circular. The cross-section of the apertures of the off-axis aperture set may be circular, rectangular, substantially circular, elliptical, polygonal, or the like. The cross-section of the aperture may determine the cross-section and shape of the primary beamlets generated thereby. The primary beamlets generated by the apertures of the pre-beamlet forming mechanism 172B may be incident on a collector lens (e.g., collector lens 110 in FIG. 2).

[0150]

[0168] In step 1330, the position of the plane of the collector lens (e.g., the principal plane 110_2 in FIG. 3) along the principal optical axis can be adjusted. In some embodiments, the collector lens 110 can include an adjustable electromagnetic lens configured to form a corresponding probing beamlet that exits the beam-limiting aperture array (e.g., the beam-limiting aperture array 121 in FIGS. 3 and 9). Based on the setting of the collector lens 110, the primary beamlet formed by the aperture of the off-axis aperture set can be incident on the corresponding aperture of the beam-limiting aperture array at a rotation angle. The rotation angle can be changed together with the focusing power of the adjustable collector lens or the position of the principal plane of the adjustable collector lens along the principal optical axis. For example, if the collector lens is positioned closer to the electron source, the probing beamlet generated from the aperture (e.g., 1105C_6 in FIG. 11B) can be incident on the corresponding off-axis aperture of the beam-limiting aperture array.

[0151]

[0169] In step 1340, a number of probing beamlets can be generated from a number of primary beamlets by the beam-limiting aperture array. The on-axis probing beamlets can be associated with corresponding on-axis primary beamlets, and the off-axis probing beamlets can be associated with corresponding off-axis aperture sets of the pre-beamlet forming mechanism 172B. The characteristics of the formed probing beamlets can be determined based on the characteristics of the beam-limiting aperture array. The characteristics of the beam-limiting aperture array can include, but are not limited to, the size, cross-section, shape, pitch, and positioning of the apertures. The characteristics of the probing beamlets can be determined by one or more characteristics of the beam-limiting aperture array.

[0152]

[0170] In step 1350, the probing beamlets generated by the beam limiting aperture array can be focused and directed towards a sample (e.g., sample 190 in FIG. 2) to form probe spots (e.g., probe spots 102_1S, 102_2S, 102_3S in FIG. 2). In some embodiments, each of the multiple probing beamlets can form a probe spot on the sample one by one. The probing beamlets can be focused using an objective lens (e.g., objective lens 131 in FIG. 3). The probing beamlets can be incident perpendicularly on the sample surface. Primary electrons of the probing beamlets incident on the sample can generate secondary electrons. The secondary electrons can be detected using a secondary electron detector or a backscattered electron detector, thus revealing information about the sample being probed.

[0153]

[0171] 14, which illustrates a process flow diagram depicting an exemplary method 1400 of observing a sample using a multi-beam inspection tool consistent with an embodiment of the present disclosure. Method 1400 may be performed, for example, by a controller 50 of an EBI system 100 as shown in FIG. The controller 50 may be programmed to perform one or more steps of method 1400. For example, the controller 50 may instruct modules of a charged particle beam device to activate a charged particle source to generate a charged particle beam and to perform other functions as well.

[0154]

[0172] In step 1410, a charged particle beam (e.g., primary electron beam 102 in FIG. 2) can be generated by activating a charged particle source (e.g., electron source 101 in FIG. 2). For example, the electron source 101 can be powered on to emit a primary electron beam formed along a primary optical axis (e.g., primary optical axis 100_1 in FIG. 2). The electron source can be activated remotely, for example, by using software, an application, or an instruction set for a processor of a controller to power the electron source through a control circuit. The primary electron beam can be reduced by a gun aperture plate (e.g., gun aperture plate 171 in FIG. 2), an aperture array (e.g., pre-beamlet forming mechanism 172 in FIG. 2), or both.

[0155]

[0173] In step 1420, after passing through a pre-beamlet forming mechanism (e.g., pre-beamlet forming mechanism 172B in FIG. 11B), multiple beamlets (e.g., beamlets 102_1, 102_2, 102_3 in FIG. 3) can be generated. The number of primary beamlets generated can be based on the number of apertures of the pre-beamlet forming mechanism. For illustrative purposes, for example, three beamlets and three apertures are shown in FIG. 3. The beamlets generated after the primary electron beam passes through the pre-beamlet forming mechanism can include one on-axis primary beamlet and at least one off-axis primary beamlet. In some embodiments, multiple off-axis beamlets can be generated. The pre-beamlet forming mechanism can include one on-axis aperture and at least one off-axis aperture set (e.g., off-axis aperture set 1105C in FIG. 11B).

[0156]

[0174] In some embodiments, the off-axis aperture set 1105C may include an active aperture (e.g., active aperture 1105_C6A in FIG. 11E). The exemplary active aperture 1105_C6A may include an upper aperture plate (e.g., upper aperture plate 1120 in FIG. 11E), an active deflector (e.g., active deflector 1130 in FIG. 11E), and a lower aperture plate (e.g., lower aperture plate 1140 in FIG. 11E). Although the active aperture 1105_C6A is shown to include three elements, it is understood that there may be more elements, such as spacer layers, microlenses, etc., as appropriate, as needed. In some embodiments, the active aperture 1105_C6A may include an active aperture assembly fabricated using techniques including, but not limited to, machining, MEMS fabrication techniques, chemical etching, laser cutting, micromachining, or the like. The pre-beamlet forming mechanism 172B, including the active aperture array, can be fabricated from conductive, semi-conductive or insulating materials, depending on the application.

[0157]

[0175] The upper aperture plate can be configured to allow passage of a portion of the electrons of the primary electron beam based on a desired current setting. The lower aperture plate can include multiple off-axis apertures (e.g., aperture 1142 in FIG. 11E) separated by the material from which the upper aperture plate is fabricated. The upper and lower aperture plates can be electrically grounded or maintained at a reference voltage. The active deflector can include a monopole or multipole deflector configured to be electrically activated to affect the path of a portion of the electrons of the primary electron beam.

[0158]

[0176] The active deflector can be electrically activated by applying an electrical signal to one or more poles. In some embodiments, the electrical signal can include a voltage signal suitable for deflecting a portion of the electrons of the primary electron beam that exit the off-axis aperture 1122. In some embodiments, the active deflector can be electrically activated to deflect peripheral electrons of the primary electron beam so that they can be blocked by the lower aperture plate. The deflection of the peripheral electrons can be determined based on characteristics of the electrical signal applied to the active deflector. The electrical signal can include a voltage signal, and the characteristics of the voltage signal can include polarity, amplitude, among others.

[0159]

[0177] The shape or cross-section of the on-axis apertures may be circular or substantially circular. The cross-section of the apertures of the off-axis aperture set may be circular, rectangular, substantially circular, elliptical, polygonal, or the like. The cross-section of the apertures may determine the cross-section and shape of the primary beamlets generated thereby. The primary beamlets generated by the apertures of the pre-beamlet forming mechanism 172B may be incident on a collector lens (e.g., collector lens 110 of FIG. 2).

[0160]

[0178] In step 1430, a number of probing beamlets can be generated from a number of primary beamlets by the beam-limiting aperture array. The on-axis probing beamlets can be associated with corresponding on-axis primary beamlets, and the off-axis probing beamlets can be associated with corresponding off-axis aperture sets of the pre-beamlet forming mechanism 172B. The characteristics of the formed probing beamlets can be determined based on the characteristics of the beam-limiting aperture array. The characteristics of the beam-limiting aperture array can include, but are not limited to, the size, cross-section, shape, pitch, and positioning of the apertures. The characteristics of the probing beamlets can be determined by one or more characteristics of the beam-limiting aperture array.

[0161]

[0179] In step 1440, the probing beamlets generated by the beam limiting aperture array can be focused and directed towards a sample (e.g., sample 190 in FIG. 2) to form probe spots (e.g., probe spots 102_1S, 102_2S, 102_3S in FIG. 2). In some embodiments, each of the multiple probing beamlets can form a probe spot on the sample. The probing beamlets can be focused using an objective lens (e.g., objective lens 131 in FIG. 3). The probing beamlets can be incident perpendicularly on the sample surface. Primary electrons of the probing beamlets incident on the sample can generate secondary electrons. The secondary electrons can be detected using a secondary electron detector or a backscattered electron detector, thus revealing information about the sample being probed.

[0162]

[0180] The embodiments are further described using the following clauses. 1. A charged particle source configured to generate a primary charged particle beam along a primary optical axis; a first aperture array including a first number of apertures configured to generate a number of primary beamlets from the primary charged particle beam; a focusing lens including a flat surface that is adjustable along a primary optical axis; a second aperture array including a second multiple apertures configured to generate a multiple number of probing beamlets; A charged particle beam device comprising: each of the multiple probing beamlets includes a portion of the charged particles of a corresponding primary beamlet; 13. A charged particle beam device, wherein the portion of the charged particles is determined based at least on a position of a plane of a collector lens and a characteristic of a second aperture array. 2. The apparatus of claim 1, wherein the first aperture array includes a pre-beamlet forming aperture array disposed between the charged particle source and the focusing lens. 3. An apparatus as described in clause 1 or 2, wherein the first aperture array includes an on-axis aperture configured to generate an on-axis beamlet, the on-axis beamlet being incident on an on-axis aperture of the second aperture array. 4. An apparatus described in any one of clauses 1 to 3, wherein the first aperture array includes an off-axis aperture configured to generate an off-axis beamlet, the off-axis beamlet being incident on a corresponding off-axis aperture of the second aperture array. 5. The apparatus of clause 4, wherein the off-axis apertures of the first aperture array include elongated apertures having rounded ends and tapered widths. 6. The apparatus of claim 5, wherein the off-axis apertures of the first aperture array have a curved shape. 7. An apparatus as described in any one of clauses 4 to 6, wherein the off-axis aperture is oriented to taper in width towards the main optical axis. 8. An apparatus according to any one of clauses 4 to 7, wherein the focusing lens is configured such that a portion of the off-axis beamlet forms a corresponding probing beamlet of the multiple probing beamlets. 9. An apparatus described in any one of clauses 1 to 8, wherein the second aperture array includes a beam-limiting aperture array disposed between the focusing lens and the objective lens. 10. An apparatus described in any one of clauses 1 to 9, wherein a second multiple aperture is configured to determine the size and shape of the multiple probing beamlets. 11. The apparatus of any one of clauses 1-10, wherein the characteristics of the second aperture array include at least one of a size, a shape, and an arrangement of the second plurality of apertures. 12. The apparatus of any one of clauses 1-11, wherein the focusing lens comprises an electrostatic, electromagnetic or electromagnetic hybrid lens. 13. The apparatus of any one of clauses 1-12, wherein the first multiple apertures include multiple off-axis apertures. 14. The apparatus of clause 13, wherein the multiple off-axis apertures include an aperture having a first off-axis aperture overlapping a second off-axis aperture, the first off-axis aperture enabling the second aperture array to generate a first off-axis probing beamlet, and the second off-axis aperture enabling the second aperture array to generate a second off-axis probing beamlet. 15. The apparatus of claim 13, wherein each of the multiple off-axis apertures of the first aperture array are separated by a substrate material of the first aperture array. 16. An apparatus described in any one of clauses 3 to 15, wherein the on-axis apertures of the first aperture array are substantially circular. 17. An apparatus according to any one of clauses 4 to 16, wherein an area of ​​the on-axis apertures of the first aperture array is substantially similar to an area of ​​the off-axis apertures. 18. A first multiple aperture configured to generate multiple primary beamlets from the primary charged particle beam. a first aperture array comprising: a portion of the charged particles of each primary beamlet of the multiple primary beamlets forms a corresponding probing beamlet of the multiple probing beamlets; A first aperture array, where a portion of the charged particles is determined based at least on a position of the plane of the focusing lens and a characteristic of the second aperture array, the second aperture array configured to generate a number of probing beamlets. 19. The first aperture array of clause 18, further comprising a pre-beamlet forming aperture array disposed between the charged particle source and the collector lens. 20. A first aperture array as described in clause 18 or 19, further comprising an on-axis aperture configured to generate an on-axis beamlet, wherein the on-axis beamlet is incident on an on-axis aperture of the second aperture array. 21. A first aperture array as described in any one of clauses 18 to 20, further comprising an off-axis aperture configured to generate an off-axis beamlet, the off-axis beamlet being incident on a corresponding off-axis aperture of the second aperture array. 22. The first aperture array of clause 21, wherein the off-axis apertures include elongated apertures having rounded ends and tapered widths. 23. The first aperture array of claim 22, wherein the off-axis apertures have a curved shape. 24. A first aperture array according to any one of clauses 21 to 23, wherein the off-axis apertures are oriented to narrow towards the main optical axis. 25. The first aperture array of any one of clauses 18 to 24, wherein the first multiple apertures include multiple off-axis apertures. 26. A first aperture array as described in clause 25, wherein the multiple off-axis apertures include an aperture having a first off-axis aperture overlapping a second off-axis aperture, the first off-axis aperture enabling the second aperture array to generate a first off-axis probing beamlet, and the second off-axis aperture enabling the second aperture array to generate a second off-axis probing beamlet. 27. A first aperture array as described in clause 25 or 26, wherein each of the multiple off-axis apertures is separated by a substrate material of the first aperture array. 28. The first aperture array of any one of clauses 20 to 27, wherein the on-axis apertures are substantially circular. 29. A first aperture array according to any one of clauses 21 to 28, wherein an area of ​​the on-axis apertures of the first aperture array is substantially similar to an area of ​​the off-axis apertures. 30. A method of observing a sample using a multi-beam device, comprising: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from a primary charged particle beam using a first aperture array; generating a number of probing beamlets corresponding to the number of primary beamlets using a second aperture array; adjusting a position of a plane of the collection lens along a primary optical axis relative to the first and second aperture arrays; generating a number of probe spots incident on a surface of the sample from the number of probing beamlets; A method comprising: each of the multiple probing beamlets includes a portion of the charged particles of a corresponding primary beamlet of the multiple primary beamlets; The method, wherein the portion of the charged particles is determined based at least on a position of the plane of the collection lens and a characteristic of the second aperture array. 31. The method of claim 30, wherein the characteristics of the probing beamlet are modified by adjusting the position of the plane of the focusing lens. 32. The method according to clause 30 or 31, wherein the current of the probing beamlet is modified by adjusting the position of the plane of the focusing lens. 33. The method of any one of clauses 30-32, wherein generating a number of primary beamlets includes generating on-axis beamlets and off-axis beamlets. 34. The method of claim 33, further comprising using a focusing lens to cause a portion of the off-axis beamlet to form a corresponding probing beamlet of the multiple probing beamlets. 35. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a multi-beam apparatus having first and second aperture arrays, the set of instructions comprising: activating a charged particle source to generate a primary charged particle beam; adjusting a position of a plane of the focusing lens along the primary optical axis relative to the first aperture array and the second aperture array; a multi-beam device performing a method including a first aperture array configured to generate a number of primary beamlets from the primary charged particle beam using a first number of apertures; a portion of the charged particles of each primary beamlet of the multiple primary beamlets forms a corresponding probing beamlet; A non-transitory computer readable medium, wherein the portion of the charged particles is determined based at least on a position of the plane of the focusing lens and a characteristic of the second aperture array. 36. A charged particle source configured to generate a primary charged particle beam along a primary optical axis; a first aperture array including a plurality of aperture sets configured to form a number of primary beamlets from the primary charged particle beam; A condenser lens disposed on a plane perpendicular to the main optical axis; a second aperture array including a number of apertures configured to generate a number of probing beamlets; A charged particle beam device comprising: each probing beamlet of the number of probing beamlets is associated with an aperture set of the first aperture array; A charged particle beam device, wherein an aperture of an aperture set forming a probing beamlet is determined based at least on a characteristic of a collection lens. 37. The apparatus of clause 36, wherein the first aperture array comprises a pre-beamlet forming aperture array disposed between the charged particle source and the collector lens. 38. The apparatus of clause 36 or 37, wherein the first aperture array includes an on-axis aperture configured to generate an on-axis primary beamlet, the on-axis primary beamlet being incident on an on-axis aperture of the second aperture array. 39. An apparatus described in any one of clauses 36 to 38, wherein the first aperture array includes a plurality of off-axis aperture sets configured to generate a number of off-axis primary beamlets, the off-axis primary beamlets being incident on corresponding off-axis apertures of the second aperture array. 40. The apparatus of any one of clauses 36-39, wherein each set of the plurality of off-axis aperture sets includes apertures arranged along a curved path. 41. An apparatus as described in any one of clauses 36-40, wherein each set of the plurality of off-axis aperture sets includes at least two apertures having different sizes. 42. An apparatus as described in any one of clauses 36-41, wherein each set of the plurality of off-axis aperture sets includes an aperture sized to determine the current of a corresponding primary beamlet. 43. An apparatus as described in any one of clauses 36-42, wherein each set of the plurality of off-axis aperture sets includes apertures having a uniform pitch. 44. An apparatus as described in any one of clauses 36-42, wherein each set of the plurality of off-axis aperture sets includes apertures having a non-uniform pitch. 45. An apparatus as described in any one of clauses 36 to 44, wherein the set of off-axis apertures includes apertures having a circular, rectangular, elliptical or polygonal cross-section. 46. ​​An apparatus according to any one of clauses 36 to 45, wherein the focusing lens is configured such that each primary beamlet of the multiple primary beamlets forms a corresponding probing beamlet of the multiple probing beamlets. 47. An apparatus according to any one of clauses 36 to 46, wherein the second aperture array comprises a beam-limiting aperture array disposed between the focusing lens and the objective lens. 48. An apparatus according to any one of clauses 36 to 47, wherein a second multiple aperture is configured to determine the size and shape of the multiple probing beamlets. 49. The apparatus of any one of clauses 36-48, wherein the focusing lens comprises an electrostatic, electromagnetic, or electromagnetic hybrid lens. 50. An apparatus as described in any one of clauses 38 to 49, wherein the on-axis apertures of the first aperture array are substantially circular. 51. A plurality of aperture sets configured to form a number of primary beamlets from a primary charged particle beam. a first aperture array comprising: each probing beamlet of the number of probing beamlets is associated with a respective set of the plurality of aperture sets of the first aperture array; A first aperture array, in which the apertures of the aperture set forming the probing beamlet are determined based at least on a characteristic of the focusing lens. 52. The first aperture array of clause 51, further comprising a pre-beamlet forming aperture array disposed between the charged particle source and the collector lens. 53. A first aperture array as described in clause 51 or 52, further comprising an on-axis aperture configured to generate an on-axis primary beamlet, wherein the on-axis primary beamlet is incident on an on-axis aperture of the second aperture array. 54. The first aperture array of clause 53, wherein the on-axis apertures are substantially circular. 55. A first aperture array as described in any one of clauses 51 to 54, wherein a plurality of off-axis aperture sets are configured to generate a number of off-axis beamlets, the off-axis beamlets being incident on corresponding off-axis apertures of the second aperture array. 56. The first aperture array of any one of clauses 51-55, wherein each set of the plurality of off-axis aperture sets includes apertures arranged along a curved path. 57. The first aperture array of any one of clauses 51 to 56, wherein each set of the plurality of off-axis aperture sets includes at least two apertures having different sizes. 58. A first aperture array as described in any one of clauses 51 to 57, wherein each set of the plurality of off-axis aperture sets includes an aperture sized to determine the current of a corresponding primary beamlet. 59. The first aperture array of any one of clauses 51-58, wherein each set of the plurality of off-axis aperture sets includes apertures having a uniform pitch. 60. The first aperture array of any one of clauses 51-58, wherein each set of the plurality of off-axis aperture sets includes apertures having a non-uniform pitch. 61. A first aperture array according to any one of clauses 51 to 60, wherein the plurality of off-axis aperture sets includes apertures having a circular, rectangular, elliptical or polygonal cross-section. 62. A method of observing a sample using a multi-beam device, comprising: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from a primary charged particle beam using a first aperture array; generating a number of probing beamlets corresponding to the number of primary beamlets using a second aperture array; adjusting a position of a plane of the collection lens along a primary optical axis relative to the first and second aperture arrays; generating a number of probe spots incident on a surface of the sample from the number of probing beamlets; A method comprising: each probing beamlet of the number of probing beamlets is associated with an aperture set of the first aperture array; A method, wherein apertures of an aperture set forming the probing beamlet are determined based at least on characteristics of a collection lens. 63. The method of claim 62, wherein the characteristics of the probing beamlet are modified by adjusting the position of the plane of the focusing lens. 64. The method according to clause 62 or 63, wherein the current of the probing beamlet is modified by adjusting the position of the plane of the focusing lens. 65. The method of any one of clauses 62-64, wherein generating a number of primary beamlets includes generating on-axis primary beamlets and off-axis primary beamlets. 66. The method of clause 65, further comprising using a focusing lens to cause the off-axis primary beamlet to form a corresponding probing beamlet of the multiple probing beamlets. 67. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a multi-beam device having first and second aperture arrays, the set of instructions comprising: activating a charged particle source to generate a primary charged particle beam; adjusting a position of a plane of the focusing lens along the primary optical axis relative to the first aperture array and the second aperture array; a multi-beam device performing a method including a first aperture array configured to generate a number of primary beamlets from the primary charged particle beam using a number of aperture sets; each primary beamlet of the multiple primary beamlets forms a corresponding probing beamlet; A non-transitory computer readable medium, wherein apertures of an aperture set forming a probing beamlet are determined based at least on a characteristic of a focusing lens. 68. A first aperture array including a first number of apertures configured to form a number of primary beamlets from a primary charged particle beam. 1. A charged particle beam device comprising: a first aperture plate configured to be at a first voltage; a second aperture plate configured to be at a second voltage different from the first voltage to generate an electric field that enables adjustment of a path of the charged particles of the primary charged particle beam; 13. A charged particle beam device comprising: 69. The apparatus of clause 68, further comprising a third aperture plate configured to be at a third voltage substantially similar to the first voltage. 70. A focusing lens including a flat surface that is adjustable along a primary optical axis; a second aperture array including a second multiple apertures configured to generate a multiple number of probing beamlets; 70. The apparatus of claim 68 or 69, further comprising: An apparatus, wherein each of a number of probing beamlets comprises a portion of the charged particles of a corresponding primary beamlet, the portion of the charged particles being based at least on a position of a plane of a focusing lens and a characteristic of a second aperture array. 71. The apparatus of clause 69 or 70, wherein the first and third voltages comprise a reference voltage. 72. The apparatus of any one of clauses 68-71, wherein the second aperture plate includes a charged particle beam deflector configured to adjust a path of the charged particles in response to electrical activation. 73. The apparatus of claim 72, wherein the charged particle beam deflector comprises a monopole deflector or a multipole deflector. 74. The apparatus of clause 72 or 73, wherein electrically activating the second aperture plate comprises applying a voltage signal to generate an electric field. 75. The apparatus of claim 74, wherein the path of the charged particle is adjusted based on a characteristic of a voltage signal applied to the second aperture plate. 76. The apparatus of clause 75, wherein the characteristics of the voltage signal include polarity or amplitude. 77. Each aperture of the first plurality of apertures comprises: a first aperture in a first aperture plate; a second aperture in the second aperture plate; and a third aperture of the third aperture plate; Including, a second aperture plate disposed between the first aperture plate and the third aperture plate; 77. An apparatus as described in any one of clauses 69 to 76, wherein the geometric centres of the first, second and third apertures are aligned. 78. The apparatus of clause 77, wherein the first and second apertures are different in size and the first and third apertures are substantially similar in size. 79. The apparatus of clause 77 or 78, wherein the third aperture plate is configured to block a portion of the charged particles that exit the second aperture. 80. An apparatus according to any one of clauses 70-79, wherein the first aperture array comprises a pre-beamlet forming aperture array disposed between the charged particle source and the collector lens. 81. An apparatus as described in any one of clauses 70 to 80, wherein the first aperture array includes an on-axis aperture configured to generate an on-axis beamlet, the on-axis beamlet being incident on an on-axis aperture of the second aperture array. 82. An apparatus as described in any one of clauses 70 to 81, wherein the first aperture array includes an off-axis aperture configured to generate an off-axis beamlet, the off-axis beamlet being incident on a corresponding off-axis aperture of the second aperture array. 83. The apparatus of clause 82, wherein the off-axis apertures of the first aperture array include elongated apertures having rounded ends and tapered widths. 84. The apparatus of claim 83, wherein the off-axis apertures of the first aperture array have a curved shape. 85. An apparatus as described in any one of clauses 82-84, wherein the off-axis aperture is oriented to taper in width towards the main optical axis. 86. An apparatus according to any one of clauses 82-85, wherein the focusing lens is configured such that a portion of the off-axis beamlet forms a corresponding probing beamlet of the multiple probing beamlets. 87. An apparatus as described in any one of clauses 70-86, wherein the second aperture array includes a beam-limiting aperture array disposed between the focusing lens and the objective lens. 88. The apparatus of any one of clauses 70-87, wherein a second multiple aperture is configured to determine the size and shape of the multiple probing beamlets. 89. The apparatus of any one of clauses 70-88, wherein the characteristics of the second aperture array include at least one of a size, a shape, and an arrangement of the second plurality of apertures. 90. An apparatus according to any one of clauses 70 to 89, wherein the focusing lens comprises an electrostatic, electromagnetic or electromagnetic hybrid lens. 91. The apparatus of any one of clauses 68-90, wherein the first multiple apertures include multiple off-axis apertures. 92. The apparatus of clause 91, wherein the multiple off-axis apertures include an aperture having a first off-axis aperture overlapping a second off-axis aperture, the first off-axis aperture enabling the second aperture array to generate a first off-axis probing beamlet, and the second off-axis aperture enabling the second aperture array to generate a second off-axis probing beamlet. 93. The apparatus of clause 91 or 92, wherein each of the multiple off-axis apertures of the first aperture array are separated by a substrate material of the first aperture array. 94. An apparatus as described in any one of clauses 81-93, wherein the on-axis apertures of the first aperture array are substantially circular. 95. An apparatus as described in any one of clauses 82-94, wherein an area of ​​the on-axis apertures of the first aperture array is substantially similar to an area of ​​the off-axis apertures. 96. A method of observing a sample using a charged particle beam device, comprising: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from a primary charged particle beam using a first aperture plate and a second aperture plate of a first aperture array, the first aperture plate operating at a first voltage and the second aperture plate operating at a second voltage different from the first voltage to adjust a path of the charged particles exiting the first aperture plate; generating a number of probing beamlets corresponding to the number of primary beamlets using a second aperture array; generating a number of probe spots incident on a surface of the sample from the number of probing beamlets; A method comprising: 97. The method of claim 96, further comprising operating the third aperture plate with a third voltage substantially similar to the first voltage, wherein the first and third voltages comprise reference voltages. 98. The method of clause 96 or 97, further comprising adjusting the path of the charged particles by electrically activating the second aperture plate. 99. The method of clause 98, wherein electrically activating the second aperture plate includes applying a voltage signal to generate an electric field. 100. The method of any one of clauses 96-99, further comprising adjusting a position of a plane of the focusing lens along the primary optical axis relative to the first and second aperture arrays. 101. The method of claim 100, wherein the characteristics of a number of probing beamlets are modified by adjusting the position of a plane of a focusing lens. 102. The method of clause 100 or 101, wherein the current of a number of probing beamlets is modified by adjusting the position of the plane of the focusing lens. 103. The method of any one of clauses 96-102, wherein generating a number of primary beamlets includes generating on-axis beamlets and off-axis beamlets. 104. The method of any one of clauses 100-103, further comprising using a focusing lens to cause a portion of the off-axis beamlet to form a corresponding probing beamlet of the multiple probing beamlets. 105. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a multi-beam apparatus having first and second aperture arrays, the set of instructions comprising: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from a primary charged particle beam using a first aperture plate and a second aperture plate of a first aperture array, the first and third aperture plates operating substantially at a first voltage and the second aperture plate operating at a second voltage different from the first voltage to adjust a path of the charged particles exiting the first aperture plate; generating a number of probing beamlets corresponding to the number of primary beamlets using a second aperture array; generating a number of probe spots incident on a surface of the sample from the number of probing beamlets; A non-transitory computer readable medium for causing a multi-beam device to perform a method including: 106. A first aperture array including a first number of apertures configured to form a number of primary beamlets from a primary charged particle beam, each aperture of the first number of apertures having: a first aperture plate configured to be at a first voltage; a second aperture plate configured to be at a second voltage different from the first voltage to generate an electric field between the first aperture plate and the second aperture plate; a first aperture array including: a second aperture array configured to generate probing beamlets from corresponding primary beamlets, the beam current of the probing beamlets being adjustable; 13. A charged particle beam device comprising: 107. The apparatus of clause 106, wherein the electric field between the first aperture plate and the second aperture plate is substantially fixed. 108. The apparatus of clause 106 or 107, wherein the beam current is discretely adjusted based on a size of each aperture of the first plurality of apertures of the first aperture array. 109. The apparatus of claim 106, wherein the electric field between the first aperture plate and the second aperture plate is adjustable. 110. The apparatus of clause 106 or 109, wherein the beam current is adjusted based on an electric field between the first aperture plate and the second aperture plate. 111. An apparatus according to any one of clauses 106 to 110, wherein the electric field is configured to enable adjustment of a path of the charged particles of the primary charged particle beam. 112. The apparatus of any one of clauses 106-111, further comprising a third aperture plate configured to be at a third voltage substantially similar to the first voltage. 113. The apparatus of claim 112, wherein the first and third voltages comprise a reference voltage. 114. An apparatus as described in any one of clauses 111-113, wherein the second aperture plate includes a charged particle beam deflector configured to adjust a path of the charged particles in response to electrical activation. 115. The apparatus of claim 114, wherein the charged particle beam deflector comprises a monopole deflector or a multipole deflector. 116. The apparatus of clause 114 or 115, wherein electrically activating the second aperture plate comprises applying a voltage signal to generate an electric field. 117. The apparatus of clause 116, wherein the path of the charged particle is adjusted based on a characteristic of a voltage signal applied to the second aperture plate. 118. Each aperture of the first plurality of apertures comprises: a first aperture in a first aperture plate; a second aperture in the second aperture plate; and a third aperture of the third aperture plate; Including, a second aperture plate disposed between the first aperture plate and the third aperture plate; 118. An apparatus as described in any one of clauses 106 to 117, wherein the geometric centers of the first, second and third apertures are aligned. 119. The apparatus of clause 118, wherein the first and second apertures are different in size and the first and third apertures are substantially similar in size. 120. The apparatus of clause 118 or 119, wherein the third aperture plate is configured to block a portion of the charged particles that exit the second aperture. 121. An apparatus described in any one of clauses 106 to 120, wherein the first aperture array includes an on-axis aperture configured to generate an on-axis beamlet, the on-axis beamlet being incident on an on-axis aperture of the second aperture array. 122. An apparatus described in any one of clauses 106 to 121, wherein the first aperture array includes an off-axis aperture configured to generate an off-axis beamlet, the off-axis beamlet being incident on a corresponding off-axis aperture of the second aperture array. 123. The apparatus of clause 122, wherein the off-axis apertures of the first aperture array include elongated apertures having rounded ends and tapered widths. 124. The apparatus of claim 123, wherein the off-axis apertures of the first aperture array have a curved shape. 125. An apparatus as described in any one of clauses 122-124, wherein the off-axis aperture is oriented to taper in width toward the main optical axis. 126. The apparatus of any one of clauses 122-125, further comprising a focusing lens configured to cause a portion of the off-axis beamlet to form a corresponding probing beamlet. 127. The apparatus of clause 126, wherein the second aperture array includes a beam-limiting aperture array disposed between the collecting lens and the objective lens. 128. An apparatus according to any one of clauses 106 to 127, wherein the second aperture array includes a second multiple apertures configured to generate multiple probing beamlets. 129. The apparatus of claim 128, wherein a second multiple aperture is configured to determine the size and shape of the multiple probing beamlets. 130. An apparatus according to any one of clauses 126-129, wherein the probing beamlet comprises a portion of the charged particles of the corresponding primary beamlet based at least on a position in the plane of the focusing lens and a characteristic of the second aperture array. 131. The apparatus of claim 130, wherein the characteristics of the second aperture array include at least one of a size, a shape, and an arrangement of the second plurality of apertures. 132. An apparatus according to any one of clauses 126 to 131, wherein the focusing lens comprises an electrostatic, electromagnetic or electromagnetic composite lens. 133. The apparatus of any one of clauses 106-132, wherein the first multiple apertures include multiple off-axis apertures. 134. The apparatus of clause 133, wherein the multiple off-axis apertures include an aperture having a first off-axis aperture overlapping a second off-axis aperture, the first off-axis aperture enabling the second aperture array to generate a first off-axis probing beamlet, and the second off-axis aperture enabling the second aperture array to generate a second off-axis probing beamlet. 135. The apparatus of clause 133 or 134, wherein each of the multiple off-axis apertures of the first aperture array are separated by a substrate material of the first aperture array. 136. An apparatus as described in any one of clauses 121 to 135, wherein the on-axis apertures of the first aperture array are substantially circular. 137. An apparatus according to any one of clauses 121 to 136, wherein an area of ​​the on-axis apertures of the first aperture array is substantially similar to an area of ​​the off-axis apertures. 138. A method of observing a sample using a charged particle beam device, comprising: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from a primary charged particle beam using a first aperture plate and a second aperture plate of a first aperture array, the first aperture plate operating at a first voltage and the second aperture plate operating at a second voltage different from the first voltage to adjust a path of the charged particles exiting the first aperture plate; generating probing beamlets from corresponding primary beamlets using a second aperture array, where a beam current of the probing beamlets is adjustable; generating a probe spot incident on a surface of the sample from the probing beamlet; A method comprising: 139. The method of claim 138, wherein adjusting a path of the charged particles includes deflecting the charged particles based on an electric field formed between the first aperture plate and the second aperture plate. 140. The method of clause 138 or 139, wherein the electric field between the first aperture plate and the second aperture plate is substantially fixed, and adjusting the beam current of the probing beamlet is based on a size of an aperture of the first aperture array. 141. The method of clause 138 or 139, wherein the electric field between the first aperture plate and the second aperture plate is adjustable, and adjusting the beam current of the probing beamlet comprises adjusting the electric field between the first aperture plate and the second aperture plate. 142. The method of any one of clauses 139-141, wherein deflecting the charged particles is caused by electrically activating the second aperture plate by applying a voltage signal to generate an electric field. 143. The method of any one of clauses 138-142, further comprising operating the third aperture plate with a third voltage substantially similar to the first voltage, wherein the first and third voltages comprise reference voltages. 144. The method of any one of clauses 138-143, further comprising adjusting the position of a plane of the focusing lens along the primary optical axis relative to the first and second aperture arrays. 145. The method of claim 144, wherein the characteristics of the probing beamlet are modified by adjusting the position of the plane of the focusing lens. 146. The method of clause 144 or 145, wherein the beam current of the probing beamlet is modified by adjusting the position of the plane of the focusing lens. 147. The method of any one of clauses 144-146, further comprising using a focusing lens to cause a portion of an off-axis primary beamlet to form a corresponding probing beamlet. 148. The method of any one of clauses 138-147, wherein generating a number of primary beamlets includes generating on-axis primary beamlets and off-axis primary beamlets. 149. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a multi-beam device having first and second aperture arrays, the set of instructions comprising: activating a charged particle source to generate a primary charged particle beam; generating a number of primary beamlets from a primary charged particle beam using a first aperture plate and a second aperture plate of a first aperture array, the first aperture plate operating at a first voltage and the second aperture plate operating at a second voltage different from the first voltage to adjust a path of the charged particles exiting the first aperture plate; generating probing beamlets from corresponding primary beamlets using a second aperture array, where a beam current of the probing beamlets is adjustable; generating a probe spot incident on a surface of the sample from the probing beamlet; A non-transitory computer readable medium for causing a multi-beam device to perform a method including: 150. A pre-beamlet forming aperture set configured to form a number of primary beamlets from a primary charged particle beam; a beam-limiting aperture configured to form a probing beamlet from a corresponding primary beamlet, the beam current of the probing beamlet being determined based on a characteristic of an aperture of a pre-beamlet forming aperture set that forms the primary beamlet; A charged particle beam device comprising: A charged particle beam device, wherein each aperture of the pre-beamlet forming aperture set is configured to affect the beam current of a probing beamlet to be formed. 151. The apparatus of clause 150, wherein the characteristics of the apertures of the pre-beamlet forming aperture set include the size, shape or location of the apertures. 152. The apparatus of clause 150 or 151, wherein the beam current of the probing beamlet is discretely adjusted based on the size of an aperture of the pre-beamlet forming aperture set. 153. A first array of multiple pre-beamlet forming aperture sets; a second array of multiple beam-limiting apertures disposed downstream of the first array along a major optical axis of the primary charged particle beam; 153. The apparatus of any one of clauses 150 to 152, comprising: 154. An apparatus according to any one of clauses 150 to 153, wherein an aperture of the pre-beamlet forming aperture set that forms the probing beamlet is determined based on characteristics of the focusing lens. 155. The apparatus of clause 154, wherein the characteristics of the focusing lens include a position of a plane of the focusing lens along the principal optical axis. 156. An apparatus as described in clause 154 or 155, configured such that changing the position of the plane of the focusing lens affects the beam current of the probing beamlet. 157. An apparatus as described in any one of clauses 154 to 156, wherein the focusing lens is configured to affect the beam current of the probing beamlet by directing a portion of the primary charged particle beam to pass through a different aperture of the pre-beamlet forming aperture set. 158. A focusing lens disposed at a first position in the plane is configured to pass a first portion of the primary charged particle beam through a first aperture of the pre-beamlet forming aperture set to form a first primary beamlet; An apparatus described in any one of clauses 155 to 157, wherein a focusing lens arranged at a second position in the plane is configured to cause a second portion of the primary charged particle beam to pass through a second aperture of the pre-beamlet forming aperture set to form a second primary beamlet. 159. An apparatus as described in any one of clauses 153 to 158, wherein the first array includes an on-axis aperture configured to generate on-axis primary beamlets, the on-axis primary beamlets being incident on an on-axis aperture of the second array. 160. An apparatus as described in any one of clauses 153 to 159, wherein the pre-beamlet forming aperture set includes a number of off-axis pre-beamlet forming apertures configured to generate off-axis primary beamlets, the off-axis primary beamlets being incident on corresponding off-axis beam limiting apertures of the second array. 161. The apparatus of claim 160, wherein each of the off-axis pre-beamlet forming apertures is separated by substrate material of the first array. 162. The apparatus of clause 160 or 161, wherein multiple off-axis pre-beamlet forming apertures are arranged along a curved path. 163. An apparatus as described in any one of clauses 160-162, wherein the multiple off-axis pre-beamlet forming apertures include at least two apertures having different sizes. 164. An apparatus as described in any one of clauses 160 to 163, wherein the multiple off-axis pre-beamlet forming apertures are sized to affect the beam current of a primary beamlet generated upon passing through each aperture of the multiple off-axis pre-beamlet forming apertures. 165. An apparatus as described in any one of clauses 160 to 164, wherein each aperture of the multiple off-axis pre-beamlet forming apertures has a uniform pitch. 166. The first aperture array of any one of clauses 160 to 164, wherein each aperture of the multiple off-axis pre-beamlet forming apertures has a non-uniform pitch.

[0163]

[0181] A non-transitory computer readable medium can be provided that stores instructions for a processor of a controller (e.g., controller 40 of FIG. 1) to perform image inspection, image acquisition, stage positioning, beam focusing, field adjustment, beam bending, focusing lens adjustment, activation of a charged particle source, beam deflection, electrical activation of an active aperture, etc. Common forms of non-transitory media include, for example, a floppy disk, a flexible disk, a hard disk, a solid state drive, a magnetic tape or any other magnetic data storage medium, a compact disk read only memory (CD-ROM), any other optical data storage medium, any physical medium having a pattern of holes, a random access memory (RAM), a programmable read only memory (PROM), an erasable programmable read only memory (EPROM), a flash EPROM or any other flash memory, a non-volatile random access memory (NVRAM), a cache, a register, any other memory chip or cartridge, and networked versions thereof.

[0164]

[0182] It will be understood that the embodiments of the present disclosure are not limited to the exact construction as described above and shown in the accompanying drawings, and that various modifications and changes can 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 from consideration of the specification and practice of the invention disclosed herein. It is intended that the specification and examples be considered as merely exemplary, with a true scope and spirit of the invention being indicated by the following claims.

[0165]

[0183] The above description is intended to be illustrative rather than limiting. Thus, it will be apparent to one skilled in the art that modifications can be made as described without departing from the scope of the claims set out below.

Claims

1. a first aperture array including a first number of apertures configured to generate a number of primary beamlets from the primary charged particle beam; a second aperture array including a second multiple apertures configured to generate a multiple number of probing beamlets; Including, the first multiple apertures include multiple off-axis apertures configured to generate multiple off-axis beamlets, the multiple off-axis apertures having apertures arranged along a curved path, the multiple off-axis apertures having a curved shape; Aperture array set.

2. The aperture array set of claim 1 , wherein the second multiple apertures are configured to determine a size and shape of multiple probing beamlets.

3. 3. The aperture array set of claim 1, wherein the first aperture array comprises a pre-beamlet forming aperture array disposed between a charged particle source and a collector lens.

4. The aperture array of any one of claims 1 to 3, wherein the first aperture array further comprises an on-axis aperture configured to generate on-axis beamlets.

5. The aperture array of claim 4 , wherein the on-axis beamlets are incident on on-axis apertures of the second aperture array.

6. The aperture array of any one of claims 1 to 5, wherein the multiple off-axis beamlets are incident on corresponding off-axis apertures of the second aperture array.

7. 7. An aperture array according to claim 1, wherein the multiple off-axis apertures comprise elongated apertures having rounded ends and tapered widths.

8. 8. An aperture array according to claim 1, wherein the multiple off-axis apertures are oriented to taper in width towards a main optical axis.

9. 9. An aperture array according to any preceding claim, wherein the multiple off-axis apertures include an aperture having a first off-axis aperture overlapping a second off-axis aperture.

10. 10. The aperture array of claim 9, wherein the first off-axis aperture enables the second aperture array to generate a first off-axis probing beamlet, and the second off-axis aperture enables the second aperture array to generate a second off-axis probing beamlet.

11. An aperture array according to any preceding claim, wherein each of the multiple off-axis apertures is separated by a substrate material of the first aperture array.

12. The first aperture array of claim 4 , wherein the on-axis apertures are substantially circular.

13. 5. The first aperture array of claim 4, wherein an area of ​​the on-axis aperture is substantially similar to an area of ​​the multiple off-axis apertures.

14. 1. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a multi-beam device having first and second aperture arrays, the set of instructions comprising: activating a charged particle source to generate a primary charged particle beam; adjusting a position of a plane of the focusing lens along the primary optical axis relative to the first aperture array and the second aperture array; a multi-beam device performing a method including a first aperture array configured to generate a number of primary beamlets from the primary charged particle beam using a first number of apertures; a portion of the charged particles of each primary beamlet of the multiple primary beamlets forms a corresponding probing beamlet; the first aperture array includes an off-axis aperture configured to generate an off-axis beamlet; the off-axis aperture has a curved shape; Non-transitory computer-readable medium.

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