Apparatus using multiple charged particle beams

Abstract

The present disclosure proposes an anti-rotation lens and uses it as an anti-rotation condenser lens in a multi-beam apparatus with a pre-sub-beam forming mechanism. The anti-rotation condenser lens keeps the rotation angle of the sub-beams unchanged when changing its current, thereby enabling the pre-sub-beam forming mechanism to block as many unused electrons as possible. In this way, the multi-beam apparatus can observe a sample with high resolution and high throughput, and can be used as a yield management tool to check and / or review defects on wafers / masks in the semiconductor manufacturing industry.

Description

[0001] This application is a divisional application of the invention patent application with the international filing date of December 22, 2017, which entered the Chinese national phase on June 27, 2019, with Chinese national application number 201780081259.5 and the invention title "Device using multiple charged particle beams".

[0002] Cross-references to related applications

[0003] This application claims priority to U.S. Application 62 / 440,493, filed December 30, 2016, the entire contents of which are incorporated herein by reference. Technical Field

[0004] The embodiments provided herein disclose charged particle devices having multiple charged particle beams, and more specifically disclose an apparatus for observing or examining samples using multiple charged particle beams. Background Technology

[0005] When manufacturing semiconductor IC chips, pattern defects and / or unwanted particles (residues) inevitably occur on the wafer and / or mask during the manufacturing process, significantly reducing yield. For example, unwanted particles are particularly problematic for patterns with small critical feature dimensions, which have been adopted to meet increasingly sophisticated IC chip performance requirements. Therefore, traditional yield management tools with optical beams are becoming increasingly ineffective due to diffraction effects, and yield management tools with electron beams are being used more frequently as electron beams (when compared to photon beams) have shorter wavelengths, thus providing superior spatial resolution.

[0006] Currently, production management tools with electron beams operate on the principle of scanning electron microscopy (SEM) with a single electron beam, thus offering higher resolution but not the throughput required for large-scale production. While higher current single electron beams can be used to increase throughput, the Coulomb effect fundamentally reduces the excellent spatial resolution as the beam current increases.

[0007] To overcome throughput limitations, instead of using a single electron beam with a large current, one solution is to use multiple electron beams, each with a small current. These multiple electron beams form multiple probe points on the surface of the sample being observed or examined. These multiple probe points can simultaneously scan multiple small scan areas within a large observation area on the sample surface. Electrons at each probe point generate secondary electrons from the sample surface where they land, and these secondary electrons form a secondary electron beam.

[0008] Secondary electrons include slow secondary electrons (energy ≤ 50 eV) and backscattered electrons (energy close to the electron's landing energy). Secondary electron beams from multiple small scan regions can be collected simultaneously by multiple electron detectors. As a result, images of large observation areas, including all small scan regions, can be obtained much faster than using a single beam scan.

[0009] Multiple electron beams can be obtained from multiple electron sources or from a single electron source. In the former case, the multiple electron beams are typically focused onto multiple small scanning regions within multiple columns and scan these regions, with secondary electrons from each scanning region detected by an electron detector within the corresponding column. Therefore, this device is often referred to as a multi-column device. On the sample surface, the beam spacing or pitch is approximately on the order of a few millimeters to tens of millimeters.

[0010] In the latter case, the source conversion unit actually forms multiple sub-sources from a single electron source. The source conversion unit includes a beamlet confinement (or sub-beamforming) mechanism with multiple beam-confinement openings and an image forming mechanism with multiple electro-optical elements. The primary electron beam generated by the single electron source is divided into multiple secondary beams or sub-beams by the multiple beam-confinement openings, and the multiple electro-optical elements influence the multiple sub-beams to form multiple parallel (virtual or real) images of the single electron source. Each image can serve as a sub-source emitting a corresponding sub-beam. To make more sub-beams available for higher throughput, the sub-beam spacing in the source conversion unit is configured to be as small as possible, typically on the micrometer scale.

[0011] Within a single column, a primary projection imaging system can be used to project multiple parallel images onto a sample surface, forming multiple detector points thereon. Multiple sub-beams can be deflected using a common deflection scanning unit to scan multiple detector points across multiple small scanning regions, where each detector point formed by a sub-beam is scanned within its corresponding small scanning region. Secondary electron beams generated from the multiple small scanning regions are guided by a beam splitter into a secondary projection imaging system, and then focused by the secondary projection imaging system for detection by multiple detection elements of an electron detection device, where each secondary electron beam generated from a small scanning region is detected by one detection element of the electron detection device. These multiple detection elements can be multiple electron detectors placed side-by-side or multiple pixels of a single electron detector. Therefore, this device is often referred to as a multi-beam device.

[0012] Sub-beam confinement mechanisms are typically conductive plates with multiple through-holes, which together form multiple beam-confinement openings. For the image-forming mechanism, each electro-optical element can be an electrostatic microlens that focuses a sub-beam to form one of a plurality of parallel real images; or an electrostatic micro-deflector that deflects a sub-beam to form one of a plurality of parallel virtual images. Because the current density associated with the real image is higher, the Coulomb effect is weaker in a virtual image than in a real image.

[0013] To reduce the Coulomb effect in the space above the source conversion unit, a pre-beamforming mechanism with multiple sub-beamforming apertures can be placed close to the single electron source to pre-trimme the primary electron beam as early as possible. Most electrons in the primary electron beam that are not used to form multiple detector points cannot pass through the multiple sub-beamforming apertures. The current at multiple detector points can be altered by adjusting the focusing capability of the condenser lens between the single electron source and the source conversion unit. Typically, the condenser lens is a magnetic lens, and the multiple sub-beams rotate around the optical axis of the condenser lens. The rotation angle varies with the focusing capability. Variations in the rotation angle can introduce mismatches between the multiple sub-beams between the pre-beamforming mechanism and the sub-beam confinement mechanism, thereby increasing the differences in current between the multiple detector points. These current differences degrade the throughput for observing or inspecting samples. Summary of the Invention

[0014] Embodiments of this disclosure provide a multi-beam apparatus with high resolution and high throughput for observing or inspecting samples under varying imaging conditions, such as current at the probe points and landing energy of the sub-beams. The embodiments utilize a pre-sub-beamforming mechanism and an anti-rotation condenser lens or a movable anti-rotation condenser lens to reduce the Coulomb effect, thereby improving the spatial resolution of the sample image. The condenser lens can maintain current uniformity across multiple probe points as its current changes. As a result, the multi-beam apparatus facilitates the use of yield management tools to inspect and / or view defects on wafers / masks in the semiconductor manufacturing industry.

[0015] In some embodiments, an anti-rotation lens is provided, having focusing capability for focusing a charged particle beam. The anti-rotation lens includes a first magnetic lens configured to generate a first magnetic field and aligned with the optical axis of the anti-rotation lens. The anti-rotation lens also includes a second magnetic lens configured to generate a second magnetic field and aligned with the optical axis. The focusing capability of the anti-rotation lens can be adjusted by changing the first magnetic field and the second magnetic field, and the first magnetic field and the second magnetic field have opposite directions on the optical axis.

[0016] In some embodiments, an anti-rotation lens is provided, having focusing capability for focusing a charged particle beam. The anti-rotation lens includes a magnetic lens configured to generate a magnetic field and aligned with the optical axis of the anti-rotation lens. The anti-rotation lens also includes an electrostatic lens configured to generate an electrostatic field and aligned with the optical axis. The magnetic field and the electrostatic field at least partially overlap, and the focusing capability of the anti-rotation lens can be adjusted by changing the magnetic field and / or the electrostatic field.

[0017] In some embodiments, a movable anti-rotation lens is provided, having focusing capability for focusing a charged particle beam. The movable anti-rotation lens includes a first magnetic lens configured to generate a first magnetic field and aligned with the optical axis of the movable anti-rotation lens. The movable anti-rotation lens also includes a second magnetic lens configured to generate a second magnetic field and aligned with the optical axis. The movable anti-rotation lens further includes a third magnetic lens configured to generate a third magnetic field and aligned with the optical axis. The focusing capability and principal plane of the movable anti-rotation lens can be adjusted by changing the first magnetic field, the second magnetic field, and / or the third magnetic field, and two of the first, second, and third magnetic fields have opposite directions on the optical axis.

[0018] In some embodiments, a movable anti-rotation lens with focusing capability for focusing a charged particle beam is disclosed. The movable anti-rotation lens includes an anti-rotation lens configured to be aligned with the optical axis of the movable anti-rotation lens. The movable anti-rotation lens also includes a lens configured to be aligned with the optical axis. The focusing capability and principal plane of the movable anti-rotation lens can be adjusted by changing the focusing capability of the anti-rotation lens and / or the focusing capability of the lens, and wherein the principal plane can be adjusted relative to the source generating the charged particle beam.

[0019] In some embodiments, a movable anti-rotation lens with focusing capability for focusing a charged particle beam is disclosed. The movable anti-rotation lens includes a first anti-rotation lens configured to be aligned with the optical axis of the movable anti-rotation lens. The movable anti-rotation lens also includes a second anti-rotation lens configured to be aligned with the optical axis. The focusing capability and principal plane of the movable anti-rotation lens can be adjusted by changing the focusing capability of the first anti-rotation lens and / or the focusing capability of the second anti-rotation lens.

[0020] In some embodiments, a multi-beam device for observing a sample is disclosed. The multi-beam device includes: an electron source configured to generate a primary electron beam; and a condenser lens configured to focus the primary electron beam, and is one of an anti-rotation lens or a movable anti-rotation lens. The multi-beam device further includes: a source conversion unit configured to form multiple images of the electron source through multiple sub-beams of the primary electron beam; an objective lens configured to focus the multiple sub-beams onto a surface and form multiple detection points thereon; and an electron detection device having multiple detection elements configured to detect multiple secondary beams generated from the multiple detection points of the sample. The multi-beam device may further include a pre-sub-beamforming mechanism located between the electron source and the condenser lens, and including multiple sub-beamforming apertures. The condenser lens is used to maintain the rotation angle of the multiple sub-beams unchanged or substantially unchanged when the detection current of the multiple detection points is changed.

[0021] In some embodiments, a method is provided for configuring an anti-rotation lens for focusing a charged particle beam. The method includes generating a first magnetic field through a first magnetic lens aligned with the optical axis of the anti-rotation lens. The method further includes generating a second magnetic field through a second magnetic lens aligned with the optical axis. The method also includes generating a focusing capability of the anti-rotation lens using the first and second magnetic fields. The first and second magnetic fields have opposite directions along the optical axis.

[0022] In some embodiments, a method is provided for configuring an anti-rotation lens for focusing a charged particle beam. The method includes generating a magnetic field via a magnetic lens and generating an electrostatic field via an electrostatic lens. The method further includes generating the focusing capability of the anti-rotation lens via the magnetic field and / or the electrostatic field, wherein the magnetic field and the electrostatic field at least partially overlap.

[0023] In some embodiments, a method is provided for configuring a movable anti-rotation lens for focusing a charged particle beam. The method includes generating a first magnetic field through a first magnetic lens aligned with the optical axis of the movable anti-rotation lens, generating a second magnetic field through a second magnetic lens aligned with the optical axis, and generating a third magnetic field through a third magnetic lens aligned with the optical axis. The method further includes generating a focusing capability of the movable anti-rotation lens through the first magnetic field, the second magnetic field, and / or the third magnetic field, wherein two of the first magnetic field, the second magnetic field, and the third magnetic field have opposite directions along the optical axis.

[0024] In some embodiments, a method is provided for configuring a multi-beam apparatus for observing a sample. The method includes trimming a primary electron beam from an electron source into a plurality of sub-beams by a pre-sub-beamforming mechanism located between an electron source and a condenser lens, and using the plurality of sub-beams by a source conversion unit to form a plurality of images of the electron source. The method further includes forming a plurality of detection points on the sample by projecting the plurality of images onto the sample, and adjusting the condenser lens to maintain a constant or substantially constant rotation angle of the plurality of sub-beams when the detection current of the plurality of detection points is changed, wherein the condenser lens is one of an anti-rotation lens or a movable anti-rotation lens.

[0025] In some embodiments, a non-transitory computer-readable medium is provided. The non-transitory computer-readable medium stores a set of instructions executable by one or more processors of a multi-beam device to cause the multi-beam device to perform a method for configuring an anti-rotation lens for focusing a charged particle beam. The method includes: instructing a first magnetic lens to generate a first magnetic field, wherein the first magnetic lens is aligned with the optical axis of the anti-rotation lens; and instructing a second magnetic lens to generate a second magnetic field, wherein the second magnetic lens is aligned with the optical axis. The first magnetic field and the second magnetic field generate the focusing capability of the anti-rotation lens and have opposite directions on the optical axis.

[0026] In some embodiments, a non-transitory computer-readable medium is provided. The non-transitory computer-readable medium stores a set of instructions executable by one or more processors of a multi-beam device to cause the multi-beam device to perform a method for configuring an anti-rotation lens for focusing a charged particle beam. The method includes: instructing a magnetic lens to generate a magnetic field, and instructing an electrostatic lens to generate an electrostatic field. The magnetic field and / or the electrostatic field generate the focusing capability of the anti-rotation lens. Moreover, the magnetic field and the electrostatic field at least partially overlap.

[0027] In some embodiments, a non-transitory computer-readable medium is provided. The non-transitory computer-readable medium stores a set of instructions executable by one or more processors of a multi-beam device to cause the multi-beam device to perform a method for configuring a movable anti-rotation lens for focusing a charged particle beam. The method includes: instructing a first magnetic lens to generate a first magnetic field, wherein the first magnetic lens is aligned with the optical axis of the movable anti-rotation lens; instructing a second magnetic lens to generate a second magnetic field, wherein the second magnetic lens is aligned with the optical axis; and instructing a third magnetic lens to generate a third magnetic field, wherein the third magnetic lens is aligned with the optical axis. The first magnetic field, the second magnetic field, and / or the third magnetic field generate the focusing capability of the movable anti-rotation lens. Furthermore, two of the first magnetic field, the second magnetic field, and the third magnetic field have opposite directions on the optical axis.

[0028] Other advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings, in which certain embodiments of the invention are illustrated by way of illustration and example. Attached Figure Description

[0029] Figure 1A and Figure 1B Each of these is a schematic diagram illustrating an exemplary configuration of a multi-beam device.

[0030] Figure 2A yes Figure 1A and Figure 1B A cross-sectional view of the pre-sub-beamforming mechanism in the XY plane, illustrating exemplary points of the primary electron beam and three sub-beams.

[0031] Figure 2B , Figure 2C , Figure 2D and Figure 2E yes Figure 1A and Figure 1B The cross-sectional view of the sub-beam limiting mechanism in the XY plane shows exemplary points of the three sub-beams and the three beam limiting openings.

[0032] Figure 3A and Figure 3B Each figure is a schematic diagram illustrating an exemplary configuration of an anti-rotation lens according to an embodiment of the present disclosure.

[0033] Figure 3C and Figure 3D Each figure illustrates an embodiment according to the present disclosure. Figure 3A A schematic diagram of an exemplary magnetic field distribution.

[0034] Figure 4A , Figure 4B and Figure 4CEach figure is a schematic diagram illustrating an exemplary configuration of an anti-rotation lens according to an embodiment of the present disclosure.

[0035] Figure 5A This is a schematic diagram illustrating an exemplary configuration of a movable anti-rotation lens according to an embodiment of the present disclosure.

[0036] Figure 5B , Figure 5C and Figure 5D Each figure illustrates an embodiment according to the present disclosure. Figure 5A A schematic diagram of an exemplary magnetic field distribution.

[0037] Figure 6A and Figure 6B Each figure illustrates a schematic diagram of an exemplary configuration of a movable anti-rotation lens according to an embodiment of the present disclosure.

[0038] Figure 7A and Figure 7B Each figure illustrates a schematic diagram of an exemplary configuration of a movable anti-rotation lens according to an embodiment of the present disclosure.

[0039] Figure 8A This is a schematic diagram illustrating an exemplary configuration of a multi-beam device according to an embodiment of the present disclosure.

[0040] Figure 8B and Figure 8C Each figure illustrates an embodiment according to the present disclosure. Figure 8A An exemplary configuration of the pre-beamforming mechanism.

[0041] Figure 9A and Figure 9C The figure illustrates a schematic diagram of an exemplary configuration of a multi-beam device and beam path according to embodiments of the present disclosure.

[0042] Figure 9B The figure illustrates an embodiment according to the present disclosure. Figure 9A and Figure 9C A schematic diagram of an exemplary configuration of a pre-beamforming mechanism.

[0043] Figure 10 This is a schematic diagram illustrating an exemplary configuration of a multi-beam device according to an embodiment of the present disclosure.

[0044] Figure 11A and Figure 11C This is a schematic diagram illustrating an exemplary configuration of a multi-beam device and beam path according to embodiments of the present disclosure.

[0045] Figure 11B The figure illustrates an embodiment according to the present disclosure. Figure 11A and Figure 11C A schematic diagram of an exemplary configuration of a pre-beamforming mechanism.

[0046] Figure 12A and Figure 12B Each figure is a schematic diagram illustrating an exemplary configuration of a pre-beamforming mechanism according to an embodiment of the present disclosure.

[0047] Figure 13 The figure illustrates a configuration according to an embodiment of the present disclosure. Figure 12A A schematic diagram of an exemplary configuration of a multi-beam device for a pre-beam forming mechanism.

[0048] Figure 14 The figure illustrates a configuration according to an embodiment of the present disclosure. Figure 12A A schematic diagram of an exemplary configuration of a multi-beam device for a pre-beam forming mechanism.

[0049] Figure 15A This is a schematic diagram illustrating an exemplary configuration of a multi-beam device according to an embodiment of the present disclosure.

[0050] Figure 15B The figure illustrates an embodiment according to the present disclosure. Figure 15A A schematic diagram of the scanning path of the sub-beam on the sample surface.

[0051] Figure 15C The figure illustrates an embodiment according to the present disclosure. Figure 15A A schematic diagram of the scanning path of the secondary beam on the detection element of an electronic testing device. Detailed Implementation

[0052] 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, wherein, unless otherwise stated, the same numbers in different drawings represent the same or similar elements. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations consistent with the present invention. Rather, they are merely examples of apparatuses and methods consistent with the aspects of the invention as described in the appended claims.

[0053] For clarity, the relative dimensions of the components in the accompanying drawings may be exaggerated. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and only the differences with respect to the various embodiments are described.

[0054] Without limiting the scope of protection, all descriptions and drawings of the embodiments will be referred to as electron beams by way of example. However, the embodiments are not intended to limit the disclosed embodiments to specific charged particles.

[0055] Embodiments of this application relate to charged particle devices or multi-beam devices having multiple charged particle beams. More specifically, they relate to an apparatus that simultaneously acquires images of multiple scanned areas of an observation region on a sample surface using multiple charged particle beams. This apparatus can be used in the semiconductor manufacturing industry to inspect and / or view defects on wafers / masks at high resolution and high throughput.

[0056] Furthermore, embodiments of this application relate to a pre-sub-beamforming mechanism and an anti-rotation condenser lens or a movable anti-rotation condenser lens to reduce the Coulomb effect in a multi-beam device and thus improve the spatial resolution of images of multiple small scan areas of a sample under observation or inspection. In a multi-beam device, a pre-sub-beamforming mechanism having multiple sub-beamforming apertures trims a primary electron beam from a single electron source into multiple sub-beams. An anti-rotation condenser lens or a movable anti-rotation condenser lens focuses the multiple sub-beams to be incident on a source conversion unit, and the source conversion unit forms multiple parallel images of the single electron source through the multiple sub-beams. The parallel images are projected onto the sample surface (via an objective lens) and multiple detector points are formed thereon. The multiple sub-beams can be deflected to scan the multiple detector points in the small scan area by at least one of the deflection scanning unit and the source conversion unit. The current at the detector points can be limited by the source conversion unit and can be changed by adjusting the anti-rotation condenser lens, or it can be limited by the pre-sub-beamforming mechanism and can be changed by changing the size of the sub-beamforming aperture. The source conversion unit can reduce the size of the probe point and the size difference between probe points by compensating for its off-axis aberrations.

[0057] Furthermore, the disclosed embodiments provide configurations of a pre-sub-beamforming mechanism, an anti-rotation condenser lens, a movable anti-rotation condenser lens, and a corresponding multi-beam device. For illustrative purposes, three sub-beams are shown in most embodiments, but the actual number of sub-beams can be arbitrary. Deflection scanning units, beam splitters, secondary projection imaging systems, electronic detection devices, and any combinations thereof can be incorporated into the multi-beam device and are not shown or occasionally mentioned in the description of the embodiments.

[0058] According to embodiments of this disclosure, the X, Y, and Z axes are Cartesian coordinates. The main optical axis of the multi-beam device is located on the Z-axis, and the primary electron beam from a single electron source travels along the Z-axis.

[0059] When the electron beam passes through a magnetic lens with the optical axis on the Z-axis, the focusing power 1 / f of the magnetic lens and the rotation angle θ of the electron beam around the optical axis are determined by its magnetic field and can be calculated by equations (1) and (2).

[0060] (1)

[0061] (2)

[0062] Here, the variables e, m, and V are the electron's charge, mass, and energy; B(z) is the magnetic field along the Z-axis; and z1 and z2 are the starting and ending positions of the electron beam along the Z-axis. Therefore, the rotation angle θ essentially varies with the focusing power 1 / f of the magnetic lens. According to equations (1) and (2), the rotation angle θ is related to the polarity of the magnetic field B(z) along the axis, but not to the focusing power 1 / f. Therefore, if the polarity along the Z-axis is different, the focusing power 1 / f can be changed without affecting the rotation angle, and the corresponding lens is an anti-rotation lens (ARL).

[0063] Now for reference Figure 1AThis is a schematic diagram illustrating an exemplary configuration of a conventional multi-beam device 100A. The multi-beam device 100A includes an electron source 101, a pre-sub-beamforming mechanism 172, a condenser lens 110, a source conversion unit 120, and an objective lens 131. The sub-beamforming apertures 172_1, 172_2, and 172_3 of the pre-sub-beamforming mechanism 172 trim the primary electron beam 102 generated by the electron source 101 into three sub-beams 102_1, 102_2, and 102_3 located close to the electron source 101 and far from the source conversion unit 120 (where 102_2 and 102_3 are off-axis sub-beams not on the main optical axis 100_1 of the device 100A). The condenser lens 110 focuses the three sub-beams 102_1 to 102_3 onto the source conversion unit 120. The source conversion unit 120 includes: a pre-sub-beam bending mechanism 123 with three pre-bending micro-deflectors 123_1, 123_2, and 123_3; a sub-beam limiting mechanism 121 with three beam limiting openings 121_1 to 121_3; and an image forming mechanism 122 with three image forming micro-deflectors 122-1_1, 122-1_2, and 122-1_3. The three pre-bending micro-deflectors 123_1 to 123_3 deflect the three sub-beams 102_1 to 102_3 that are perpendicularly incident on the three beam limiting openings 121_1 to 121_3. The beam limiting openings 121_1, 121_2, and 121_3 cut off the residual peripheral electrons of the three sub-beams 102_1 to 102_3, and thus limit their current. The three images are formed by micro-deflectors 122-1_1 to 122-1_3, which deflect the three sub-beams 102_1 to 102_3 toward the principal optical axis 100_1 and form three virtual images of the electron source 101. Objective lens 131 focuses the three deflected sub-beams 102_1 to 102_3 onto surface 7 of sample 8, that is, projects the three virtual images onto surface 7. The three images formed by the three sub-beams 102_1 to 102_3 on surface 7 form three detection points 102_1S, 102_2S, and 102_3S on it. The deflection angles of the sub-beams 102_1 to 102_3 caused by the image forming micro-deflectors 122-1_1 to 122-1_3 are adjusted to reduce the off-axis aberrations of the three detection points 102_1S to 102_3S caused by the objective lens 131, and the three deflected sub-beams thus pass through or approach the front focal point of the objective lens 131.

[0064] The current can be changed by adjusting the focusing capability of the condenser lens 110. However, when the current changes, the positions of the sub-beams 102_1~102_3 change relative to the beam-limiting openings 121_1~121_3. Therefore, a mismatch may occur between a sub-beam originating from the sub-beam forming aperture and its corresponding beam-limiting opening. The condenser lens 110 can be configured as an electrostatic, magnetic, or electromagnetic composite lens. Compared to an electrostatic lens, a magnetic condenser lens has smaller aberrations. For an electrostatic condenser lens, the mismatch is only along the radial direction, which is perpendicular to the principal optical axis 100_1, such as... Figure 2C As shown in the diagram. For magnetic or electromagnetic compounds, due to the change in the rotation angle of the sub-beams 102_1~102_3, the mismatch occurs both radially and in the rotational direction, as shown in the diagram. Figure 2E As shown in the image.

[0065] In some embodiments, the condenser lens 110 is configured to be magnetic, which can cause the off-axis sub-beams 102_2 and 102_3 passing through the pre-sub-beamforming mechanism 172 to land on the sub-beam confinement mechanism 121 with a rotational angle. The rotational angle varies with the focusing capability of the condenser lens 110. Complete filling of the sub-beams 102_2 and 102_3 in the beam confinement openings 121_2 and 121_3 can be achieved by enlarging the size of the sub-beamforming apertures 172_2 and 172_3. Enlarging the size of the sub-beamforming apertures can introduce more unused electrons and thus increase the Coulomb effect in the space between the pre-sub-beamforming mechanism 172 and the source conversion unit 120. The spatial resolution of the image in small scan areas deteriorates. Complete filling of the sub-beams 102_2 and 102_3 in the beam confinement openings 121_2 and 121_3 can also be achieved by keeping the rotational angle constant or substantially constant when the focusing capability of the condenser lens 110 changes. This solution uses an anti-rotation lens as the condenser lens 110.

[0066] Now for reference Figure 1B , Figure 1BThis is a schematic diagram illustrating another exemplary configuration of the multi-beam device 200A. The multi-beam device 200A includes an electron source 101, a pre-sub-beamforming mechanism 172, a movable condenser lens 210, a source conversion unit 220, and an objective lens 131. The primary electron beam 102 generated by the electron source 101 is trimmed into three sub-beams 102_1, 102_2, and 102_3 by the three sub-beam forming apertures 172_1, 172_2, and 172_3 of the pre-sub-beamforming mechanism 172. The movable condenser lens 210 focuses the three sub-beams 102_1 to 102_3 so that they are incident perpendicularly onto the source conversion unit 220. The source conversion unit 220 includes a sub-beam confinement mechanism 121 with three beam confinement openings 121_1 to 121_3 and an image forming mechanism 122-1 with three image forming micro-deflectors 122-1_1, 122-1_2, and 122-1_3. The beam confinement openings 121_1, 121_2, and 121_3 block residual peripheral electrons from the three sub-beams 102_1 to 102_3, thus limiting their current. The three image forming micro-deflectors 122-1_1 to 122-1_3 deflect the three sub-beams 102_1 to 102_3 toward the main optical axis 200_1 and form three virtual images of the electron source 101. The objective lens 131 focuses the three deflected sub-beams 102_1 to 102_3 onto the surface 7 of the sample 8, that is, projects the three virtual images onto the surface 7. The three images formed by the three sub-beams 102_1 to 102_3 on surface 7 form three detection points 102_1S, 102_2S, and 102_3S. The deflection angles of the sub-beams 102_1 to 102_3 caused by the image forming micro-deflectors 122-1_1 to 122-1_3 are adjusted to reduce the off-axis aberrations of the three detection points 102_1S to 102_3S caused by the objective lens 131, and the three deflector beams thus pass through or approach the front focal point of the objective lens 131.

[0067] The movable condenser lens 210 is configured such that the position of its first principal plane 210_2 is movable. By adjusting the position and focusing capability of the first principal plane 210_2 of the movable condenser lens 210, the current of the sub-beams 102_1 to 102_3 can be changed while maintaining that the sub-beams 102_1 to 102_3 are incident perpendicularly onto the source conversion unit 120. However, when the current changes, the position of the sub-beams 102_1 to 102_3 changes relative to the beam limiting openings 121_1 to 121_3. A mismatch may occur between one sub-beam and its corresponding beam limiting opening due to the sub-beam forming aperture. The movable condenser lens 210 can be configured as an electrostatic, magnetic, or electromagnetic composite lens. As mentioned above, the mismatch occurs only along the radial direction of the electrostatic condenser lens (perpendicular to the principal optical axis 200_1), or along both the radial and rotational directions of the magnetic or electromagnetic composite condenser lens.

[0068] In some embodiments, the movable condenser lens 210 is configured to be magnetic, which can cause the off-axis sub-beams 102_2 and 102_3 to pass through the pre-beamforming mechanism 172 and land on the sub-beam confinement mechanism 121 with a rotational angle. The rotational angle varies with the position of the first principal plane of the movable condenser lens 210 and its focusing capability. Complete filling of the sub-beams 102_2 and 102_3 in the beam confinement openings 121_2 and 121_3 can be achieved by enlarging the size of the sub-beamforming apertures 172_2 and 172_3. Enlarging the size of the sub-beamforming apertures can introduce more unused electrons and thus increase the Coulomb effect in the space between the pre-beamforming mechanism 172 and the source conversion unit 120. Consequently, the spatial resolution of the image in small scan areas deteriorates. When the position and focusing capability of the first principal plane of the movable condenser lens 210 change, complete filling of the sub-beams 102_2 and 102_3 in the beam limiting openings 121_2 and 121_3 can be achieved by keeping the rotation angle constant. This solution uses an anti-rotation lens with a movable first principal plane, namely, a movable anti-rotation lens (MARL), as the movable condenser lens 210.

[0069] Now for reference Figures 2A to 2E . Figure 2A yes Figure 1A and Figure 1B A cross-sectional view of the pre-sub-beamforming mechanism 172 in the XY plane, illustrating exemplary points of the primary electron beam and three sub-beams. Figures 2B to 2E They are Figure 1A and Figure 1B A cross-sectional view of the sub-beam limiting mechanism 121 in the XY plane, illustrating exemplary points of the three sub-beams and the three beam limiting openings.

[0070] exist Figure 2A In the process, the primary electron beam 102 irradiates the pre-sub-beam forming mechanism 172, wherein sub-beam forming apertures 172_1 to 172_3 are arranged along the X-axis. If Figure 1A Condensing lens 110 or Figure 1B The movable focusing lens 210 is electrostatic, which allows the sub-beams 102_1~102_3 to be incident on the sub-beam limiting mechanism 121 along the X-axis, such as... Figure 2B and Figure 2C As shown in the diagram. The three sub-beams 102_1~102_3 are in... Figure 2C China and Belgium Figure 2B The focus is more intense in the middle. Therefore, Figure 2C The current ratio of the three sub-beams 102_1~102_3 in the middle Figure 2B The larger of them. If Figure 1A Condensing lens 110 or Figure 1B If the movable condenser lens 210 is a magnetic or electromagnetic compound, then the sub-beams 102_1~102_3 are incident on the sub-beam limiting mechanism 121 by a rotation angle around the optical axis of the corresponding condenser lens, such as... Figure 2D and Figure 2E As shown in the diagram. Sub-beams 102_1~102_3 are in Figure 2E China and Belgium in Figure 2D The sub-beams are more strongly focused. Therefore, sub-beams 102_1~102_3 are... Figure 2E China and Belgium in Figure 2D The beam is incident on the sub-beam confinement mechanism 121 with a larger current and a larger rotation angle. Figure 2E In this configuration, the two edge sub-beams 102_2 and 102_3 rotate partially away from the beam limiting openings 121_2 and 121_3, and if the beam limiting openings 121_1 to 121_3 have the same radial dimension, the current they carry after passing through the beam limiting openings 121_2 and 121_3 can be different from the current of the central sub-beam 102_1.

[0071] Anti-rotation lenses have the ability to vary the focusing angle without affecting the rotation angle of the passing electron beam. If Figure 1A The condenser lens 110 in the middle is an anti-rotation lens, which can eliminate... Figure 2E The mismatch in the lens. The anti-rotation lens can be formed by two magnetic lenses, or by one magnetic lens and one electrostatic lens. For an electron beam, its focusing capability can be changed without affecting the rotation angle of the electron beam by appropriately adjusting the excitation of the lenses inside the anti-rotation lens.

[0072] Now for reference Figure 3A and Figure 3B , Figure 3A and Figure 3B Each figure illustrates a schematic diagram of an exemplary configuration of an anti-rotation lens including two magnetic lenses according to an embodiment of the present disclosure. Meanwhile, refer to... Figure 3C and Figure 3D , Figure 3C and Figure 3D The figures also illustrate embodiments according to this disclosure. Figure 3A and Figure 3B A schematic diagram of an exemplary magnetic field distribution.

[0073] exist Figure 3A In this configuration, the two single magnetic lenses, ARL-1-1 and ARL-1-2, of the anti-rotation lens ARL-1 are aligned with its optical axis ARL-1_1 (on the Z-axis). The magnetic lenses ARL-1-1 and ARL-1-2 are excited to generate a magnetic field, the distribution of which on the optical axis ARL-1_1 is B. ARL-1-1 (z) and B ARL-1-2(z) has the opposite polarity, such as Figure 3C or Figure 3D As shown in the diagram, the on-axis magnetic field B can be adjusted based on an appropriate ratio. ARL-1-1 (z) and B ARL-1-2 (z). Therefore, its focusing capability can be adjusted without affecting the total rotation angle of the electron beam passing through the anti-rotation lens ARL-1.

[0074] It should be understood that in some embodiments, two single magnetic lenses can be connected to partially share a common magnetic circuit. For example, as... Figure 3B As shown, the two magnetic lenses ARL-2-1 and ARL-2-2 of the anti-rotation lens ARL-2 are configured to partially share a common magnetic circuit between them.

[0075] Figure 3A The diagram also illustrates what would happen if, in situations such as... Figure 1A How does the anti-rotation lens ARL-1 function when used as a condenser lens in a multi-beam device such as the condenser lens 110 shown? For example, when the magnetic field B... ARL-1-1 (z) and B ARL-1-2 (z) is set to have the same distribution but opposite polarity, such as Figure 3C As shown, the primary electron beam 102 is focused as Figure 3A The solid line in the diagram. If a single electron source 101 is not immersed in the total on-axis magnetic field B(z), the total on-axis magnetic field B(z) is magnetic field B. ARL-1-1 (z) and B ARL-1-2 The sum of (z) indicates that the total rotation angle of the primary electron beam 102 is zero after leaving the anti-rotation lens ARL-1. When B ARL-1-1 (z) and B ARL-1-2 (z) When increasing by the same amount, such as Figure 3D As shown, the focusing capability of the primary electron beam 102 is increased (e.g., as...). Figure 3A (As shown by the dashed line in the diagram), and after leaving the anti-rotation lens ARL-1, the rotation angle of the primary electron beam 102 remains zero. If a single electron source 101 is immersed in the total on-axis magnetic field B(z), then relative to... Figure 3C The rotation angle is not zero. B ARL-1-1 (z) and B ARL-1-2 (z) can be increased at an appropriate rate to keep the rotation angle constant while increasing the focusing ability.

[0076] Now for reference Figure 4A , Figure 4B and Figure 4C Each of these is a schematic diagram illustrating an exemplary configuration of an anti-rotation lens, including an electrostatic lens and a magnetic lens, according to embodiments of the present disclosure. Figure 4AIn this design, the anti-rotation lens ARL-3 comprises an electrostatic lens ARL-3-1 formed by three electrodes ARL-3-1_e1, ARL-3-1_e2, and ARL-3-1_e3, and a magnetic lens ARL-3-2. The electrostatic field of the electrostatic lens ARL-3-1 and the magnetic field of the magnetic lens ARL-3-2 are configured to partially overlap each other. Therefore, the energy of the electron beam passing through the magnetic field varies with the electrostatic field, and its rotation angle depends on both the magnetic and electrostatic fields. Thus, by changing the magnetic and electrostatic fields in appropriate ratios, the focusing capability of the anti-rotation lens ARL-3 can be altered without affecting the rotation angle of the electron beam after it leaves the anti-rotation lens ARL-3.

[0077] exist Figure 4B In this design, the anti-rotation lens ARL-4 comprises an electrostatic lens ARL-4-1 formed by three electrodes ARL-4-1_e1, ARL-4-1_e2, and ARL-4-1_e3, and a magnetic lens ARL-4-2. The electrostatic field of the electrostatic lens ARL-4-1 and the magnetic field of the magnetic lens ARL-4-2 completely overlap; therefore, maintaining a constant rotation angle can be achieved more effectively.

[0078] exist Figure 4C In this design, the anti-rotation lens ARL-5 comprises an electrostatic lens ARL-5-1 and a magnetic lens ARL-5-2. The electrostatic lens ARL-5-1 is formed by two end electrodes ARL-5-1_e1 and ARL-5-1_e3, and a center electrode ARL-5-1_e2 located between them. The two end electrodes ARL-5-1_e1 and ARL-5-1_e3 are also the two pole pieces of the magnetic lens ARL-5-2. Therefore, the configuration is more compact and simpler.

[0079] The movable anti-rotation lens has a movable first principal plane. For an electron beam, the focusing capability of the movable anti-rotation lens and the position of the first principal plane can be changed without affecting the rotation angle of the electron beam. If Figure 1B The movable focusing lens 210 is a movable anti-rotation lens, which can eliminate... Figure 2E The mismatch is shown in the diagram. The movable anti-rotation lens can be formed by three magnetic lenses, one anti-rotation lens and one conventional lens (electrostatic or magnetic), or two anti-rotation lenses. For an electron beam, by appropriately adjusting the excitation of the lenses within the movable anti-rotation lens, its first principal plane and focusing capability can be changed simultaneously without affecting the rotation angle of the electron beam.

[0080] Now to Figure 5A For reference, Figure 5A This is a schematic diagram illustrating an exemplary configuration of a movable anti-rotation lens including three magnetic lenses according to an embodiment of the present disclosure. Also, [the following is also mentioned...] Figure 5B , Figure 5C and Figure 5D For reference, Figure 5B , Figure 5C and Figure 5D The figures respectively illustrate embodiments according to this disclosure. Figure 5A A schematic diagram of an exemplary magnetic field distribution. Figure 5A In the movable anti-rotation lens MARL-1, the three single magnetic lenses MARL-1-1, MARL-1-2, and MARL-1-3 are aligned with their optical axis MARL-1_1 (on the Z-axis). Two or all of the single magnetic lenses MARL-1-1 to MARL-1-3 can be configured to be partially connected and share a common magnetic circuit. The magnetic lenses MARL-1-1 to MARL-1-3 are excited to generate a magnetic field, the axial distribution of which (the field on the optical axis MARL-1_1) is B. MARL-1-1 (z), B MARL-1-2 (z) and B MARL-1-3 (z). On-axis magnetic field B MARL-1-1 (z), B MARL-1-2 (z) and B MARL-1-3 The two magnetic fields in (z) have opposite polarities, such as Figure 5B ~ Figure 5D As shown in the diagram, the excitation of the magnetic lenses MARL-1-1 to MARL-1-3 is configured to change the distribution of the total on-axis magnetic field, which is the on-axis magnetic field B. MARL-1-1 (z), B MARL-1-2 (z) and B MARL-1-3 The sum of (z) is used to move the first primary position and adjust the focusing capability of the movable anti-rotation lens MARL-1. Within the distribution of the total on-axis magnetic field, its polarity alternates between the direction along the Z-axis and the direction opposite to the Z-axis to keep the total rotation angle constant.

[0081] Figure 5A The diagram also illustrates what happens if, as... Figure 1B How does the movable anti-rotation lens function when used as a movable condenser lens in a multi-beam device with a movable condenser lens 210? For example, when the on-axis magnetic lenses MARL-1-1 to MARL-1-3 are excited to make the magnetic field B... MARL-1-1 (z) and B MARL-1-2 When the distribution of (z) is the same but the polarity is opposite and the magnetic field BMARL-1-3(z) is equal to zero, such as Figure 5B As shown, the first principal plane is located Figure 5AAt plane P1-3, which is close to the single electron source 101, the primary electron beam 102 from the single electron source 101 is collimated at plane P1-3 and has a beam width 102W_P1-3 after exiting the movable condenser lens MARL-1. If the single electron source 101 is not immersed in the total on-axis magnetic field, the rotation angle of the primary electron beam 102 after exiting the movable condenser lens MARL-1 is zero. The on-axis magnetic field B is adjusted by changing the excitation of the magnetic lens. MARL-1-1 (z), B MARL-1-2 (z) and B MARL-1-3 (z), such as Figure 5C As shown, the first principal plane is moved away from the single electron source 101 to plane P1-1, as... Figure 5A As shown in the diagram, the primary electron beam 102 is collimated at plane P1-1, and has an increased beam width 102W_P1-1 at the same rotation angle when the beam width is 102W_P1-3. The on-axis magnetic field B is tuned by further changing the excitation of the magnetic lens. MARL-1-1 (z), B MARL-1-2 (z) and B MARL-1-3 (z), such as Figure 5D As shown, the first principal plane is further moved from the single electron source 101 to plane P1-2, as... Figure 5A As shown in the diagram, the primary electron beam 102 is collimated at plane P1-2, and has a further increased beam width 102W_P1-2 with the same rotation angle when the beam width is 102W_P1-3 or 102W_P1-1. The first principal plane can be configured to move between planes P1-3 and P1-2, so that the primary electron beam 102 can be collimated and exit with a changed beam width and an unchanged rotation angle.

[0082] Now to Figure 6A For reference, Figure 6A This diagram illustrates an exemplary configuration of a movable anti-rotation lens according to an embodiment of the present disclosure, comprising an anti-rotation lens and a conventional electrostatic lens. The anti-rotation lens MARL-2-1 and the electrostatic lens MARL-2-2 of the movable anti-rotation lens MARL-2 are aligned with its optical axis MARL-2_1. The anti-rotation lens MARL-2-1 includes two magnetic lenses MARL-2-1-1 and MARL-2-1-2, similar to... Figure 3AThe anti-rotation lens ARL-1 is included. The electrostatic lens MARL-2-2 includes three electrodes MARL-2-2_e1, MARL-2-2_e2, and MARL-2-2_e3. The first main plane of the movable anti-rotation lens MARL-2 can be configured to be positioned at plane P2-3 between the two monomagnetic lenses MARL-2-1-1 and MARL-2-1-2 in response to the electrostatic lens MARL-2-2 being closed (OFF) and the anti-rotation lens MARL-2-1 being open (ON). The first main plane can also be configured to be positioned closer to the center electrode MARL-2-2_e2 and at plane P2-2 between the two end electrodes MARL-2-2_e3 and MARL-2-2_e1 in response to the anti-rotation lens MARL-2-1 being closed (OFF) and the electrostatic lens MARL-2-2 being open (ON). By adjusting the focusing power ratio of the anti-rotation lens MARL-2-1 and the electrostatic lens MARL-2-2, the first principal plane can be configured to move between planes P2-3 and P2-2. The anti-rotation lens MARL-2-1 maintains a constant rotation angle equal to a specific value during the movement of the first principal plane. The electrostatic lens MARL-2-2 does not have a rotation function. Therefore, if the specific value is not zero, the electrostatic lens MARL-2-2 must work in conjunction with the anti-rotation lens MARL-2-1. As a result, the range of movement of the first principal plane is reduced.

[0083] Now to Figure 6B For reference, Figure 6B This diagram illustrates an exemplary configuration of a movable anti-rotation lens according to an embodiment of the present disclosure, comprising an anti-rotation lens and a conventional magnetic lens. The anti-rotation lens MARL-3-1 and the magnetic lens MARL-3-2 of the movable anti-rotation lens MARL-3 are aligned with its optical axis MARL-3_1. The anti-rotation lens MARL-3-1 includes an electrostatic lens MARL-3-1-1 and a magnetic lens MARL-3-1-2, similar to... Figure 4C The anti-rotation lens ARL-5 is used in this system.

[0084] The first principal plane of the movable anti-rotation lens MARL-3 can be configured to be positioned at plane P3-3, intersecting with the electrode MARL-3-1_e2 of the anti-rotation lens MARL-3-1, in response to the magnetic lens MARL-3-2 being closed (OFF) and the anti-rotation lens MARL-3-1 being open (ON). The first principal plane can also be configured to be located at plane P3-2 between the two pole pieces of the magnetic lens MARL-3-2, in response to the anti-rotation lens MARL-3-1 being closed (OFF) and the magnetic lens MARL-3-2 being open (ON). By adjusting the focusing power ratio of the anti-rotation lens MARL-3-1 and the magnetic lens MARL-3-2, the first principal plane can be configured to move between planes P3-3 and P3-2. During the movement of the first principal plane, the rotation angle caused by the anti-rotation lens MARL-3-1 can be adjusted relative to the rotation angle caused by the magnetic lens MARL-3-2, so as to keep the total rotation angle caused by the movable anti-rotation lens MARL-3 constant.

[0085] Now to Figure 7A and Figure 7B For reference, Figure 7A and Figure 7B Each figure illustrates a schematic diagram of an exemplary configuration of a movable anti-rotation lens having two anti-rotation lenses according to an embodiment of the present disclosure. Figure 7A In the movable anti-rotation lens MARL-4, two anti-rotation lenses, MARL-4-1 and MARL-4-2, are aligned with its optical axis, MARL-4_1. Anti-rotation lens MARL-4-1 includes magnetic lenses MARL-4-1-1 and MARL-4-1-2. Anti-rotation lens MARL-4-2 includes magnetic lenses MARL-4-2-1 and MARL-4-2-2. Both anti-rotation lenses MARL-4-1 and MARL-4-2 are similar to... Figure 3AThe anti-rotation lens ARL-1 is used. The first principal plane of the movable anti-rotation lens MARL-4 can be configured to be positioned at plane P4-3 between magnetic lenses MARL-4-1-1 and MARL-4-1-2 in response to anti-rotation lens MARL-4-1 being open (ON) and anti-rotation lens MARL-4-2 being closed (OFF). The first principal plane can also be configured to be positioned at plane P4-2 between magnetic lenses MARL-4-2-1 and MARL-4-2-2 in response to anti-rotation lens MARL-4-1 being closed (OFF) and anti-rotation lens MARL-4-2 being open (ON). By adjusting the focusing power ratio of anti-rotation lenses MARL-4-1 and MARL-4-2, the first principal plane can be configured to move between planes P4-3 and P4-2. When the first principal plane moves, the rotation angle caused by each anti-rotation lens MARL-4-1 and MARL-4-2 can be adjusted to zero to eliminate the total rotation angle, or set to keep the total rotation angle constant.

[0086] exist Figure 7B In the movable anti-rotation lens MARL-5, the anti-rotation lenses MARL-5-1 and MARL-5-2 are aligned with its optical axis MARL-5_1. The anti-rotation lens MARL-5-1 includes magnetic lenses MARL5-1-1 and MARL-5-1-2, similar to... Figure 3A The anti-rotation lens ARL-1 is included. The anti-rotation lens MARL-5-2 includes the electrostatic lens MARL-5-2-1 and the magnetic lens MARL-5-2-2, similar to... Figure 4CThe anti-rotation lens ARL-5 is used. In response to anti-rotation lens MARL-5-1 being on (ON) and anti-rotation lens MARL-5-2 being off (OFF), the first principal plane of the movable anti-rotation lens MARL-5 can be positioned at plane P5-3 within anti-rotation lens MARL-5-1. In response to anti-rotation lens MARL-5-1 being off (OFF) and anti-rotation lens MARL-5-2 being on (ON), the first principal plane can also be located at plane P5-2, intersecting with the electrode MARL-5-2-1_e2 of anti-rotation lens MARL-5-2. By adjusting the focusing capability ratio of anti-rotation lenses MARL-5-1 and MARL-5-2, the first principal plane can be configured to move between planes P5-3 and P5-2. The rotation angle caused by anti-rotation lens MARL-5-2 is generally not zero (it is zero only when magnetic lens MARL-5-2-2 is off (OFF)). When the first principal plane moves, the rotation angle caused by the anti-rotation lens MARL-5-1 can be adjusted accordingly in response to the anti-rotation lens MARL-5-2 to keep the total rotation angle constant. In other words, when the anti-rotation lens MARL-5-2 is closed (OFF), the rotation angle caused by the anti-rotation lens MARL-5-1 cannot be zero, and when the anti-rotation lens MARL-5-2 is open (ON), it can be zero. Therefore, plane P5-3 is close to one of the magnetic lenses MARL-5-1-1 and MARL-5-1-2. Placing plane P5-3 close to the magnetic lens MARL-5-1-1 is preferred because this placement expands the usable range between planes P5-3 and P5-2.

[0087] In multi-beam devices that use focusing lenses to change the current of multiple sub-beams and employ pre-sub-beamforming mechanisms to reduce the Coulomb effect, such as Figure 1A If the condenser lens is constructed from the aforementioned anti-rotation lens to become an anti-rotation condenser lens, the Coulomb effect can be further reduced. When its current is changed, the anti-rotation condenser lens can maintain the rotation angle of the multiple sub-beams unchanged or substantially unchanged, thus eliminating the mismatch between the multiple sub-beams and their corresponding beam-limiting openings. Therefore, it is not necessary to enlarge the size of the sub-beamforming aperture in the pre-sub-beamforming mechanism to cover the mismatch, and thus more unused electrons can be blocked.

[0088] Now to Figure 8A For reference, Figure 8AThis is a schematic diagram illustrating an exemplary configuration of a multi-beam device 300A according to an embodiment of the present disclosure. A primary electron beam 102 generated by an electron source 101 is trimmed into three sub-beams 102_1, 102_2, and 102_3 by three sub-beam forming apertures 172_1, 172_2, and 172_3 of a pre-sub-beam forming mechanism 172. An anti-rotation focusing lens 110AR focuses the sub-beams 102_1 to 102_3 onto the source conversion unit 320.

[0089] The source conversion unit 320 includes a pre-sub-beam bending mechanism 123 with three pre-bending micro-deflectors 123_1, 123_2 and 123_3, a sub-beam limiting mechanism 121 with three beam limiting openings 121_1 to 121_3, a sub-beam compensation mechanism 322-2 with three micro-compensators 322-2_1, 322-2_2 and 322-2_3, and an image forming mechanism 322-1 with three image forming micro-deflectors 322-1_1, 322-1_2 and 322-1_3.

[0090] Three pre-bent micro-deflectors 123_1~123_3 deflect three sub-beams 102_1~102_3 to be incident perpendicularly onto three beam-limiting openings 121_1~121_3. The beam-limiting openings 121_1~121_3 block residual peripheral electrons from the three sub-beams 102_1~102_3, thereby limiting their current. The three sub-beams 102_1~102_3 are then incident along their optical axes onto three micro-compensators 322-2_1~322-2_3. Finally, the three sub-beams 102_1~102_3 enter the three image-forming micro-deflectors 322-1_1~322-1_3 along their optical axes. The image forming micro-deflectors 322-1_1~322-1_3 deflect the sub-beams 102_1~102_3 toward the main optical axis 300_1 of the device 300A, and form three virtual images of the electron source 101.

[0091] Objective lens 131 can focus three deflected sub-beams 102_1 to 102_3 onto the surface 7 of the sample 8 under observation or inspection, that is, project three virtual images onto the surface 7. The three images formed by the sub-beams 102_1 to 102_3 on the surface 7 are formed at three detection points 102_1S, 102_2S, and 102_3S on the surface 7. The deflection angle of the deflected sub-beams 102_1 to 102_3 is adjusted to reduce the off-axis aberrations of the three detection points 102_1S to 102_3S caused by objective lens 131, and the three deflected sub-beams thus pass through or approach the front focal point of objective lens 131. Micro-compensators 322-2_1 to 322-2_3 are adjusted to compensate for the residual field curvature and astigmatic aberration of the detection points 102_1S to 102_3S. The image forming mechanism 322-1 may also include an auxiliary micro-compensator for aberration compensation, which works together with the sub-beam compensation mechanism 322-2.

[0092] Now to Figure 8B and Figure 8C For reference, Figure 8B and Figure 8C According to embodiments of this disclosure Figure 8A A cross-sectional view of the pre-beam forming mechanism 172 in the XY plane. By adjusting the focusing capability of the anti-rotation condenser lens 110AR, the detection current of the detection points 102_1S~102_3S can be changed. Figure 8B The dimensions and positions of the three sub-beams 102_1 to 102_3 are shown for two different focusing configurations. The focusing capability is stronger in the second configuration than in the first configuration. In the first configuration, only electrons within the small circle markers 102_1 to 102_3 can pass through the three beam-limiting openings 121_1 to 121_3. In the second configuration, only electrons within the large circle markers 102_1 to 102_3 can pass through the three beam-limiting openings 121_1 to 121_3. Therefore, the detection current at the three detection points 102_1S to 102_3S is greater in the second configuration than in the first configuration. Because the anti-rotation condenser lens 110AR maintains a constant rotation angle for the sub-beams 102_1 to 102_3 relative to both configurations, the circle markers of the sub-beams 102_1 to 102_3 move only in the radial direction.

[0093] The shape and size of the sub-beam forming apertures 172_1 to 172_3 are configured to cover the area marked by the circles covering the sub-beams 102_1 to 102_3 when the focusing capability is adjusted within two settings (maximum focusing capability, minimum focusing capability). The shape of each sub-beam forming aperture can be configured to make its size as small as possible, thereby correspondingly reducing the Coulomb effect. Figure 8BIn this design, the sub-beam forming apertures 172_1 to 172_3 are circular, and the central sub-beam forming aperture 172_1 is smaller than the edge sub-beam forming apertures 172_2 and 172_3. The shapes of the sub-beam forming apertures can be different, such as... Figure 8C relative to Figure 8B The same settings for focusing capability are shown in [the image / image / etc.]. Figure 8C In the embodiment, the central sub-beamforming aperture 172_1 is circular, the left-edge sub-beamforming aperture 172_2 is polygonal, and the right-edge sub-beamforming aperture 172_3 is elliptical. Based on the same principle, the size and shape of the sub-beamforming apertures can be arbitrary. The sizes and shapes of the sub-beamforming apertures disclosed in this embodiment are for illustrative purposes only and are not limiting.

[0094] Now to Figure 9A For reference, Figure 9A This is a schematic diagram illustrating an exemplary configuration of a multi-beam device 400A according to an embodiment of the present disclosure. In this embodiment, the sub-beam forming apertures 472_1, 472_2, and 472_3 of the pre-sub-beam forming mechanism 472 divide the primary electron beam 102 into three sub-beams 102_1 to 102_3, and simultaneously serve as beam limiting apertures to limit the current of the sub-beams. Therefore, with Figure 8A In comparison, all unused electrons are blocked earlier, thus reducing the Coulomb effect to a greater extent. Electrons from sub-beams 102_1~102_3 striking the edges of sub-beam forming apertures 472_1~472_3 can generate scattered electrons. These scattered electrons deviate from the normal path of sub-beams 102_1~102_3 and become background noise in the image generated by sub-beams 102_1~102_3. In the source conversion unit 420, the beam-limiting openings 421_1, 421_2, and 421_3 of the sub-beam limiting mechanism 421 serve as contrast apertures to block scattered electrons. The sub-beam limiting mechanism 421 can also be located between the sub-beam compensation mechanism 322-2 and the image forming mechanism 322-1.

[0095] The detection currents at the three detection points 102_1S to 102_3S can be changed by altering the dimensions of the sub-beamforming apertures 472_1 to 472_3. To change the dimensions, the movable pre-beamforming mechanism 472 can be configured to be movable and have two or more aperture groups. The dimensions of the apertures in one group can differ from those in another group. The pre-beamforming mechanism 472 can be moved to set an aperture in one aperture group to be used as a sub-beamforming aperture.

[0096] Now to Figure 9B For reference, Figure 9B The figure illustrates an embodiment according to the present disclosure. Figure 9AA schematic diagram of an exemplary configuration of the movable pre-beamforming mechanism 472. Figure 9B In this design, the movable pre-beamforming mechanism 472 has two aperture groups. The dimensions and spacing of apertures 472_1-1, 472_2-1, and 472_3-1 in group 472-1 are configured to be smaller than the dimensions and spacing of apertures 472_1-2, 472_2-2, and 472_3-2 in group 472-2. Therefore, the detection current provided by group 472-1 is less than that of group 472-2.

[0097] When group 472-1 is selected, the pre-sub-beam forming mechanism 472 is moved so that apertures 472_1-1 to 472_3-1 can divide the primary electron beam 102 into sub-beams 102_1 to 102_3. The corresponding paths of sub-beams 102_1 to 102_3 are as follows: Figure 9A As shown in the diagram. When group 472-2 is selected, the pre-sub-beam forming mechanism 472 is moved such that apertures 472_1-2 to 472_3-2 can divide the primary electron beam 102 into sub-beams 102_1 to 102_3. The corresponding paths of sub-beams 102_1 to 102_3 are as follows. Figure 9C As shown in the image.

[0098] Sub-beams 102_1~102_3 in Figure 9C China and Belgium in Figure 9A The beam is more strongly focused so that it enters the pre-bending micro-deflectors 123_1~123_3 of the pre-beam bending mechanism 123. When using different aperture sets, the anti-rotation condenser lens 110AR keeps the rotation angle of the sub-beams 102_1~102_3 constant. Therefore, the aperture sets can be placed in parallel, and the pre-beam forming mechanism 472 does not need to rotate when the aperture sets are changed. This non-rotation simplifies the structure of the pre-beam forming mechanism 472.

[0099] In multi-beam devices that use movable focusing lenses to change the current of multiple sub-beams and employ pre-sub-beamforming mechanisms to reduce the Coulomb effect, such as Figure 1B If the movable condenser lens is constructed from the aforementioned movable anti-rotation lens to become a movable anti-rotation condenser lens, the Coulomb effect can be further reduced. When its current is changed, the movable anti-rotation condenser lens can maintain the rotation angles of the multiple sub-beams unchanged or substantially unchanged, thus eliminating the mismatch between the multiple sub-beams and their corresponding beam-limiting openings. If the change is no greater than 6°, the rotation angles of the multiple sub-beams can be considered substantially unchanged. Therefore, it is not necessary to increase the size of the sub-beam forming aperture in the pre-sub-beam forming mechanism to cover the mismatch, and thus more unused electrons can be blocked.

[0100] Now to Figure 10 For reference, Figure 10This is a schematic diagram illustrating an exemplary configuration of a multi-beam device 500A according to an embodiment of the present disclosure. In these embodiments, a primary electron beam 102 generated by an electron source 101 is trimmed into three sub-beams 102_1, 102_2, and 102_3 by three sub-beam forming apertures 172_1, 172_2, and 172_3 of a pre-sub-beam forming mechanism 172. A movable anti-rotation condenser lens 210AR focuses the sub-beams 102_1 to 102_3 so that they are vertically incident on the source conversion unit 520.

[0101] The source conversion unit 520 includes a sub-beam limiting mechanism 121 with three beam limiting openings 121_1 to 121_3, a sub-beam compensation mechanism 322-2 with three micro-compensators 322-2_1, 322-2_2, and 322-2_3, and an image forming mechanism 322-1 with three image forming micro-deflectors 322-1_1, 322-1_2, and 322-1_3. The beam limiting openings 121_1 to 121_3 block residual peripheral electrons from the three sub-beams 102_1 to 102_3, thereby limiting their current. The three sub-beams 102_1 to 102_3 are incident on the three micro-compensators 322-2_1 to 322-2_3 along their respective optical axes. Then, the three sub-beams 102_1~102_3 enter the three image-forming micro-deflectors 322-1_1~322-1_3 along their respective optical axes. The image-forming micro-deflectors 322-1_1~322-1_3 deflect the sub-beams 102_1~102_3 toward the main optical axis 500_1 of the device 500, and form three virtual images of the electron source 101.

[0102] Objective lens 131 focuses three deflected sub-beams 102_1 to 102_3 onto surface 7 of the sample 8 under observation, that is, projects three virtual images onto surface 7. The images formed by the sub-beams 102_1 to 102_3 on surface 7 generate three detection points 102_1S, 102_2S, and 102_3S on surface 7.

[0103] The deflection angles of the deflected sub-beams 102_1 to 102_3 are adjusted to reduce the off-axis aberrations of the three detection points 102_1s to 102_3s caused by the objective lens 131, and the three deflected sub-beams thus pass through or approach the front focal point of the objective lens. Micro-compensators 322-2_1 to 322-2_3 are adjusted to compensate for the residual field curvature and astigmatic aberration of the detection points 102_1s to 102_3s. The image forming mechanism 322-1 may also include auxiliary micro-compensators for aberration compensation, which work together with the sub-beam compensation mechanism 322-2.

[0104] By adjusting the focusing capability of the movable anti-rotation condenser lens 210AR and correspondingly moving the position of its first principal plane 210AR_2, the detection current of the detection points 102_1S~102_3S can be changed, while maintaining the sub-beams 102_1~102_3 perpendicularly incident on the source conversion unit 520 and having an unchanged or substantially unchanged rotation angle. Figure 8B This can also be used to illustrate two example configurations relative to the focusing capability and the first principal plane 210AR_2, as well as the size and position of the three sub-beams 102_1 to 102_3 on the pre-sub-beamforming mechanism 172. The focusing capability in the second configuration is stronger than that in the first configuration, and the position of the first principal plane in the second configuration is closer to the electron source 101 than that in the first configuration. For the first configuration, only electrons within the small circle markers 102_1 to 102_3 can pass through the three beam-limiting openings 121_1 to 121_3. For the second configuration, only electrons within the large circle markers 102_1 to 102_3 can pass through the three beam-limiting openings 121_1 to 121_3. Therefore, the detection current at the three detection points 102_1S to 102_3S is greater in the second configuration than in the first configuration. Since the anti-rotation condenser lens 210AR can keep the rotation angle of the sub-beams 102_1 to 102_3 constant relative to both settings, the circle markings of the sub-beams 102_1 to 102_3 only move in the radial direction.

[0105] The shape and size of the sub-beam forming apertures 172_1 to 172_3 are configured to cover the area covered by the circular markings of the sub-beams 102_1 to 102_3 when the movable anti-rotation condenser lens 210AR is adjusted within two settings. The shape of each sub-beam forming aperture can be configured to reduce its size, thereby correspondingly reducing the Coulomb effect. It should be understood that the size of each sub-beam forming aperture can be reduced as much as possible to correspondingly reduce the Coulomb effect as much as possible. Therefore, the shapes of the sub-beam forming apertures can be identical (e.g., as shown in the image). Figure 8B (as shown) or different from each other (e.g., as shown) Figure 8C (As shown in the diagram). The sub-beam forming apertures 172_1 to 172_3 can be configured as circular, elliptical, polygonal, or any other arbitrary shape.

[0106] Now to Figure 11A Referring to the figure below is a schematic diagram of an exemplary configuration of a multi-beam device 600A according to an embodiment of the present disclosure. In this embodiment, the sub-beam forming apertures 672_1, 672_2, and 672_3 of the pre-sub-beam forming mechanism 672 can divide the primary electron beam 102 into three sub-beams 102_1 to 102_3, and simultaneously serve as beam limiting apertures to limit the current of the sub-beams. Therefore, with Figure 10In comparison, all unused electrons are blocked earlier, thus reducing the Coulomb effect to a greater extent. Electrons from sub-beams 102_1 to 102_3 can generate scattered electrons by striking the edges of sub-beam forming apertures 672_1 to 672_3. These scattered electrons deviate from the normal path of sub-beams 102_1 to 102_3 and become background noise in the image generated by sub-beams 102_1 to 102_3. In the source conversion unit 620, the beam-limiting openings 621_1, 621_2, and 621_3 of the sub-beam limiting mechanism 621 serve as contrast apertures to block scattered electrons. The sub-beam limiting mechanism 621 can also be located between the sub-beam compensation mechanism 322-2 and the image forming mechanism 322-1.

[0107] The detection current of the three detection points 102_1S~102_3S can be changed by altering the dimensions of the three sub-beamforming apertures 672_1~672_3. To change the dimensions, the pre-sub-beamforming mechanism 672 can be configured to be movable and have two or more aperture groups. The aperture dimensions in one group differ from those in another group. The pre-sub-beamforming mechanism 672 can be moved to set an aperture in one aperture group to be used as a sub-beamforming aperture.

[0108] Now to Figure 11B For reference, Figure 11B The figure illustrates an embodiment according to the present disclosure. Figure 11A A schematic diagram of an exemplary configuration of the movable pre-beamforming mechanism 672. Figure 11B In this design, the movable pre-sub-beamforming mechanism 672 has two aperture groups. The size and spacing of apertures 672_1-1, 672_2-1, and 672_3-1 in group 672-1 are configured to be smaller than the size and spacing of apertures 672_1-2, 672_2-2, and 672_3-2 in group 672-2. The probe current provided by group 672-1 is smaller than that of group 672-2. When group 672-1 is selected, the pre-sub-beamforming mechanism 672 is moved such that apertures 672_1-1 to 672_3-1 can divide the primary electron beam 102 into sub-beams 102_1 to 102_3. The corresponding paths of sub-beams 102_1 to 102_3 are as follows: Figure 11A As shown in the diagram. When group 672-2 is selected, the pre-sub-beam forming mechanism 672 is moved such that apertures 672_1-2 to 672-3-2 can divide the primary electron beam 102 into sub-beams 102_1 to 102_3. The corresponding paths of sub-beams 102_1 to 102_3 are as follows. Figure 11C As shown in the image.

[0109] Sub-beams 102_1~102_3 in Figure 11C China and Belgium in Figure 11AThe beam is focused more strongly and earlier. When using different aperture groups, the movable anti-rotation lens 210AR maintains a constant rotation angle. Therefore, the aperture groups can be placed in parallel, and the pre-beam forming mechanism 672 does not need to rotate when the aperture groups are changed. This non-rotation simplifies the structure of the pre-beam forming mechanism 672.

[0110] For multi-beam devices, more sub-beams are needed to achieve higher throughput. To make more sub-beams available, the sub-beam spacing in the source conversion unit is configured to be as small as possible. For multi-beam devices, a larger range of probe point current variations is required to enable the observation or examination of a wider variety of samples. Therefore, for devices such as... Figure 8A Example 300A and Figure 10 In multi-beam devices such as the 500A, the detector current varies within a specific range. If the sub-beam spacing is small enough, some sub-beamforming apertures of the pre-sub-beamforming mechanism 172 may partially overlap, such as... Figures 12A-12B As shown, partially overlapping sub-beamforming apertures can be configured as a combined sub-beamforming aperture. Sub-beams passing through two adjacent beam-limiting openings in the source conversion unit can pass together through this combined sub-beamforming aperture.

[0111] Now to Figure 12A and Figure 12B For reference, Figure 12A and Figure 12B The figure illustrates a pre-beamforming mechanism (e.g., according to an embodiment of the present disclosure) Figure 8A A cross-sectional view of the XY plane of the pre-beam forming mechanism 172. Figure 12A An example with five sub-beams 102_1, 102_2, 102_3, 102_4, and 102_5 is shown. The small circles marking sub-beams 102_1 to 102_5 correspond to those with small probe currents, and the large circles marking sub-beams 102_1 to 102_5 correspond to those with large probe currents. Sub-beams 102_2 and 102_4 pass through the combined sub-beam forming aperture 172_2+4, and sub-beams 102_3 and 102_5 pass through the combined sub-beam forming aperture 172_3+5. Similarly, the combined sub-beam forming aperture can be configured with different shapes and sizes to block as many unused electrons as possible. For example, the combined sub-beam forming aperture 172_2+4 is elliptical, and the combined sub-beam forming aperture 172_3+5 is polygonal. Figure 12B An example with twenty-five sub-beams is shown. The pre-sub-beamforming mechanism 172 has four combined sub-beamforming apertures and seventeen individual sub-beamforming apertures.

[0112] Now to Figures 13 to 14 For reference, Figure 13 and Figure 14 Each figure illustrates an embodiment of the present disclosure having Figure 12A A schematic diagram of an exemplary configuration of a multi-beam device for a pre-beam forming mechanism. Figure 13 The configuration of the multi-beam device 310A in the middle is similar to Figure 8A The configuration of the multi-beam device 300A. Figure 13 In the multi-beam device 310A, there are five sub-beams 102_1, 102_2, 102_3, 102_4, and 102_5. The pre-sub-beam forming mechanism 172 has three sub-beam forming apertures 172_1, 172_2+4, and 172_3+5, and the sub-beam forming apertures 172_2+4 and 172_3+5 are combined sub-beam forming apertures. The central sub-beam 102_1 passes through the central sub-beam forming aperture 172_1, the two left sub-beams 102_2 and 102_4 pass through the left sub-beam forming aperture 172_2+4, and the two right sub-beams 102_3 and 102_5 pass through the right sub-beam forming aperture 172_3+5.

[0113] Figure 14 The configuration of the multi-beam device 510A in the middle is similar to Figure 10 The configuration of the 500A multi-beam device. Figure 14 In the configuration of the multi-beam device 510A, there are five sub-beams 102_1, 102_2, 102_3, 102_4, and 102_5. The pre-sub-beam forming mechanism 172 has three sub-beam forming apertures 172_1, 172_2+4, and 172_3+5, and the sub-beam forming apertures 172_2+4 and 172_3+5 are combined sub-beam forming apertures. The central sub-beam 102_1 passes through the central sub-beam forming aperture 172_1, the two left sub-beams 102_2 and 102_4 pass through the left sub-beam forming aperture 172_2+4, and the two right sub-beams 102_3 and 102_5 pass through the right sub-beam forming aperture 172_3+5.

[0114] Return to reference Figure 1AIn a conventional apparatus, multiple detector points 102_1S~102_3S are deflected by a common deflection scanning unit to scan multiple small scanning regions. Therefore, the scanning characteristics (such as scanning direction, scanning range, and scanning speed) of all sub-beams are identical. However, for some samples under observation or examination, the pattern characteristics in different small scanning regions may be very different. To obtain better image contrast from images generated by multiple detector points, the scanning characteristics of some or all sub-beams need to be different and better configured individually according to the pattern characteristics in each small scanning region. Each image-forming micro-deflector in the aforementioned source conversion unit can perform an individual deflection scan.

[0115] Now to Figures 15A to 15C For reference, Figures 15A to 15C This is a schematic diagram illustrating an exemplary configuration of a multi-beam device 700A with individual deflection scanning according to an embodiment of the present disclosure. Although Figure 15A The configuration of the multi-beam device 700A in the middle and Figure 1A The configuration of the multi-beam device 100A is somewhat similar to that of the multi-beam device 700A, but the multi-beam device 700A also includes an image forming mechanism 722 of the source conversion unit 720. Figure 15A In the image forming mechanism 722, each image forming micro-deflector 722_1, 722_2 and 722_3 can deflect one of the sub-beams 102_1, 102_2 and 102_3 to form a virtual image of the electron source 101, and additionally deflect another sub-beam dynamically to scan the corresponding detection point on the small scanning area. Figure 15B The figure illustrates an exemplary scanning path for probe points 102_1S, 102_2S, and 102_3S. Probe point 102_1S scans region A1 in the dashed outline along the direction between the X-axis and Y-axis, probe point 102_2S scans region A2 in the dashed outline along the X-axis, and probe point 102_3S scans region A3 in the dashed outline along the Y-axis.

[0116] exist Figure 15A In this process, auxiliary beams or signal beams 102_1se, 102_2se, and 102_3se are generated from scanning areas A1, A2, and A3 by probe spots 102_1S~102_3S. Beam splitter 160 deflects the secondary beams 102_1se~102_3se to enter the secondary projection imaging system 150. The secondary projection imaging system 150 focuses the secondary beams 102_1se~102_3se for detection by detection elements 140_1, 140_2, and 140_3 of the electronic detection device 140M. Figure 15CThe figure illustrates exemplary scanning paths of the secondary beams 102_1se~102_3se on detection elements 140_1, 140_2, and 140_3. If the scanning path of each secondary beam exceeds the corresponding detection element, an anti-scan deflection unit (ASD) is placed in front of the electronic detection device 140M. Figure 15A (Not shown in the image) can be used to at least partially counteract the motion of the secondary beam on the detection elements 140_1 to 140_3.

[0117] The embodiments may be further described using the following terms:

[0118] 1. A rotation-resistant lens having focusing capability for focusing a charged particle beam, comprising:

[0119] A first magnetic lens, configured to generate a first magnetic field and aligned with the optical axis of the anti-rotation lens; and

[0120] A second magnetic lens is configured to generate a second magnetic field and align it with the optical axis, wherein the focusing capability of the anti-rotation lens is adjustable by changing the first magnetic field and the second magnetic field, and the first magnetic field and the second magnetic field have opposite directions on the optical axis.

[0121] 2. The anti-rotation lens according to Clause 1, wherein the focusing capability is adjustable while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0122] 3. The anti-rotation lens according to Clause 2, wherein the rotation angle is zero.

[0123] 4. A rotation-resistant lens having focusing capability for focusing a charged particle beam, comprising:

[0124] A magnetic lens, configured to generate a magnetic field and aligned with the optical axis of the anti-rotation lens; and

[0125] An electrostatic lens is configured to generate an electrostatic field and align it with the optical axis, wherein the magnetic field and the electrostatic field at least partially overlap, and the focusing capability of the anti-rotation lens is adjustable by changing the magnetic field and / or the electrostatic field.

[0126] 5. The anti-rotation lens according to Clause 4, wherein the focusing capability is adjustable while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0127] 6. The anti-rotation lens according to Clause 4, wherein the rotation angle is zero.

[0128] 7. A movable anti-rotation lens having focusing capability for focusing a charged particle beam, comprising:

[0129] A first magnetic lens, configured to generate a first magnetic field and aligned with the optical axis of the movable anti-rotation lens;

[0130] A second magnetic lens, configured to generate a second magnetic field and aligned with the optical axis; and

[0131] A third magnetic lens is configured to generate a third magnetic field and align it with the optical axis, wherein the principal plane of the movable anti-rotation lens and the focusing capability are adjustable by changing the first magnetic field, the second magnetic field and / or the third magnetic field, and two of the first magnetic field, the second magnetic field and the third magnetic field have opposite directions on the optical axis.

[0132] 8. The movable anti-rotation lens according to Clause 7, wherein the focusing capability and the principal plane are adjustable while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0133] 9. The movable anti-rotation lens according to Clause 8, wherein the rotation angle is zero.

[0134] 10. A movable anti-rotation lens having focusing capability for focusing a charged particle beam, comprising:

[0135] Anti-rotation lens, the anti-rotation lens being configured to align with the optical axis of the movable anti-rotation lens; and

[0136] A lens configured to be aligned with the optical axis, wherein the focusing capability and principal plane of the movable anti-rotation lens are adjustable by changing the focusing capability of the anti-rotation lens and / or the focusing capability of the lens, and wherein the principal plane is adjustable relative to the source generating the charged particle beam.

[0137] 11. The movable anti-rotation lens according to Clause 10, wherein the focusing capability and the principal plane are adjustable while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0138] 12. The movable anti-rotation lens according to Clause 11, wherein the rotation angle is zero.

[0139] 13. The movable anti-rotation lens according to Clause 10, wherein the lens is an electrostatic lens.

[0140] 14. The movable anti-rotation lens according to Clause 10, wherein the lens is a magnetic lens.

[0141] 15. A movable anti-rotation lens having focusing capability for focusing a charged particle beam, comprising:

[0142] A first anti-rotation lens, configured to be aligned with the optical axis of the movable anti-rotation lens; and

[0143] A second anti-rotation lens is configured to be aligned with the optical axis, wherein the focusing capability and principal plane of the movable anti-rotation lens are adjustable by changing the focusing capability of the first anti-rotation lens and / or the second anti-rotation lens.

[0144] 16. The movable anti-rotation lens according to Clause 15, wherein the focusing capability and the principal plane of the movable anti-rotation lens are adjustable while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0145] 17. The movable anti-rotation lens according to Clause 16, wherein the rotation angle is zero.

[0146] 18. A multi-beam device for observing samples, comprising:

[0147] An electron source, configured to generate a primary electron beam;

[0148] A condenser lens, configured to focus the primary electron beam, and is one of an anti-rotation lens or a movable anti-rotation lens;

[0149] A source conversion unit configured to form multiple images of the electron source through multiple sub-beams of the primary electron beam;

[0150] Objective lens, configured to focus the plurality of sub-beams onto a surface and form a plurality of detection points on the surface; and

[0151] An electronic detection device having multiple detection elements configured to detect multiple secondary beams generated by multiple detection points from a sample.

[0152] 19. The multi-beam device according to Clause 18 further includes a pre-beamforming mechanism located between the electron source and the focusing lens, and including a plurality of sub-beamforming apertures.

[0153] 20. The multi-beam apparatus according to Clause 19, wherein the plurality of sub-beam forming apertures are configured to trim the primary electron beam into a plurality of sub-beams.

[0154] 21. The multi-beam device according to Clause 20, wherein the condenser lens is configured to focus multiple sub-beams at multiple rotation angles to be incident on the source conversion unit.

[0155] 22. The multi-beam device according to Clause 21, wherein the plurality of rotation angles remain unchanged or substantially unchanged when the detection current of the plurality of detection points changes.

[0156] 23. The multi-beam apparatus according to any one of clauses 20 to 22, wherein the plurality of sub-beams constitute the plurality of sub-beams.

[0157] 24. The multi-beam apparatus according to any one of clauses 19 to 23, wherein the probe current is changeable by altering the size of the apertures of the plurality of sub-beams.

[0158] 25. The multi-beam apparatus according to any one of clauses 20, 23 and 24, wherein the source conversion unit includes a plurality of beam limiting openings configured to shape the plurality of sub-beams into the plurality of sub-beams.

[0159] 26. The multi-beam device according to any one of clauses 18 to 25, wherein the detection current can be changed by adjusting the focusing capability of the condenser lens.

[0160] 27. The multi-beam apparatus according to any one of clauses 19 to 26, wherein the plurality of sub-beam forming apertures are configured to block electrons not present at the plurality of detection points.

[0161] 28. The multi-beam apparatus according to any one of clauses 18 to 27, wherein the source conversion unit includes an image forming mechanism configured to deflect the plurality of sub-beams to form the plurality of images.

[0162] 29. The multi-beam apparatus according to Clause 28, wherein the image forming mechanism includes a plurality of electro-optical elements configured to deflect the plurality of sub-beams to form the plurality of images.

[0163] 30. The multi-beam apparatus according to any one of clauses 28 and 29, wherein the deflection angles of the plurality of sub-beams are individually set to reduce aberrations at the plurality of detection points.

[0164] 31. The multi-beam apparatus according to Clause 29, wherein the plurality of electro-optical elements are configured to compensate for off-axis aberrations of the plurality of detection points.

[0165] 32. The multi-beam apparatus according to any one of clauses 18 to 31, wherein the source conversion unit includes a sub-beam compensation mechanism configured to compensate for off-axis aberrations of the plurality of detector points.

[0166] 33. The multi-beam apparatus according to Clause 32, wherein the plurality of electro-optical elements and the sub-beam compensation mechanism together compensate for aberrations at the plurality of detection points.

[0167] 34. The multi-beam device according to Clause 29 further includes a deflection scanning unit positioned below the source conversion unit.

[0168] 35. The multi-beam apparatus according to Clause 34, wherein the deflection scanning unit is configured to deflect the plurality of sub-beams to scan the plurality of detection points.

[0169] 36. The multi-beam apparatus according to any one of clauses 34 and 35, wherein the plurality of electro-optical elements are configured to deflect the plurality of sub-beams to scan the plurality of detection points.

[0170] 37. The multi-beam apparatus according to any one of clauses 34 and 35, wherein the deflection scanning unit and the plurality of electro-optical elements are configured to deflect the plurality of sub-beams together to scan the plurality of detection points.

[0171] 38. The multi-beam device according to Clause 29, wherein the plurality of electro-optical elements are configured to deflect the plurality of sub-beams to scan the plurality of detection points.

[0172] 39. The multi-beam apparatus according to any one of clauses 36 to 38, wherein one or more of the plurality of detection points may be different in one or more scanning features.

[0173] 40. The multi-beam device according to clause 39, wherein one of the scanning features includes a scanning direction.

[0174] 41. The multi-beam device according to Clause 39, wherein one of the scanning features includes a scan size.

[0175] 42. The multi-beam apparatus according to clause 39, wherein one of the scanning features includes scanning speed.

[0176] 43. The multi-beam device according to any one of clauses 36 to 39 further includes an anti-scanning deflection unit, the anti-scanning deflection unit being placed in front of the electronic detection device and configured to deflect the plurality of secondary beams to the plurality of detection elements.

[0177] 44. A method for configuring an anti-rotation lens for focusing a charged particle beam, the method comprising:

[0178] A first magnetic field is generated by a first magnetic lens aligned with the optical axis of the anti-rotation lens;

[0179] A second magnetic field is generated by a second magnetic lens aligned with the optical axis; and

[0180] The focusing capability of the anti-rotation lens is generated by the first magnetic field and the second magnetic field, wherein the first magnetic field and the second magnetic field have opposite directions on the optical axis.

[0181] 45. The method according to Clause 44 further comprises: altering the focusing capability by adjusting the first magnetic field and the second magnetic field while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0182] 46. ​​A method for configuring an anti-rotation lens for focusing a charged particle beam, the method comprising:

[0183] A magnetic field is generated by a magnetic lens;

[0184] An electrostatic field is generated by an electrostatic lens; and

[0185] The focusing capability of the anti-rotation lens is generated by the magnetic field and / or the electrostatic field, wherein the magnetic field and the electrostatic field at least partially overlap.

[0186] 47. The method according to Clause 46 further includes altering the focusing capability by adjusting the magnetic field and / or the electrostatic field while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0187] 48. A method for configuring a movable anti-rotation lens for focusing a charged particle beam, the method comprising:

[0188] A first magnetic field is generated by a first magnetic lens aligned with the optical axis of the movable anti-rotation lens;

[0189] A second magnetic field is generated by a second magnetic lens aligned with the optical axis;

[0190] A third magnetic field is generated by a third magnetic lens aligned with the optical axis; and

[0191] The focusing capability of the movable anti-rotation lens is generated by the first magnetic field, the second magnetic field, and / or the third magnetic field, wherein two of the first magnetic field, the second magnetic field, and the third magnetic field have opposite directions on the optical axis.

[0192] 49. The method according to Clause 48 further comprises: altering the focusing capability and moving the principal plane of the movable anti-rotation lens by adjusting the first magnetic field, the second magnetic field and / or the third magnetic field while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0193] 50. A method for configuring a multi-beam device for observing a sample, the method comprising:

[0194] The primary electron beam from the electron source is trimmed into multiple sub-beams by a pre-sub-beamforming mechanism positioned between the electron source and the condenser lens.

[0195] Multiple images of the electron source are formed using the multiple sub-beams through the source conversion unit;

[0196] Multiple detection points are formed on the sample by projecting the multiple images onto the sample; and

[0197] The condenser lens is adjusted so that when the detection current of the plurality of detection points is changed, the rotation angle of the plurality of sub-beams remains unchanged or substantially unchanged, wherein the condenser lens is one of an anti-rotation lens or a movable anti-rotation lens.

[0198] 51. The method according to Clause 50 further comprises: adjusting the source conversion unit to scan the plurality of probe points on the sample.

[0199] 52. A non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a multi-beam device to cause the multi-beam device to perform a method for configuring an anti-rotation lens for focusing a charged particle beam, the method comprising:

[0200] Instructing a first magnetic lens to generate a first magnetic field, wherein the first magnetic lens is aligned with the optical axis of the anti-rotation lens; and

[0201] The second magnetic lens is instructed to generate a second magnetic field, wherein the second magnetic lens is aligned with the optical axis, wherein:

[0202] The first magnetic field and the second magnetic field generate the focusing capability of the anti-rotation lens, and

[0203] The first magnetic field and the second magnetic field have opposite directions on the optical axis.

[0204] 53. The non-transitory computer-readable medium according to clause 52, wherein the instruction set is executable by the one or more processors of the multi-beam device to cause the multi-beam device to perform further actions:

[0205] The first magnetic field and the second magnetic field are adjusted to adjust the focusing capability while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0206] 54. A non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a multi-beam device to cause the multi-beam device to perform a method for configuring an anti-rotation lens for focusing a charged particle beam, the method comprising:

[0207] Indicates that the magnetic lens generates a magnetic field; and

[0208] The electrostatic lens indicates that an electrostatic field is generated, wherein:

[0209] The magnetic field and / or the electrostatic field generate the focusing ability of the anti-rotation lens, and

[0210] The magnetic field and the electrostatic field at least partially overlap.

[0211] 55. The non-transitory computer-readable medium according to Clause 54, wherein the instruction set is executable by the one or more processors of the multi-beam device to cause the multi-beam device to perform further actions:

[0212] Adjust the magnetic field and / or the electrostatic field to change the focusing capability while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0213] 56. A non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a multi-beam device to cause the multi-beam device to perform a method for configuring an anti-rotation lens for focusing a charged particle beam, the method comprising:

[0214] The first magnetic lens is instructed to generate a first magnetic field, wherein the first magnetic lens is aligned with the optical axis of the movable anti-rotation lens;

[0215] Instructing the second magnetic lens to generate a second magnetic field, wherein the second magnetic lens is aligned with the optical axis; and

[0216] The third magnetic lens is instructed to generate a third magnetic field, wherein the third magnetic lens is aligned with the optical axis; wherein

[0217] The first magnetic field, the second magnetic field, and / or the third magnetic field generate the focusing capability of the movable anti-rotation lens, and

[0218] Two of the first magnetic field, the second magnetic field, and the third magnetic field have opposite directions on the optical axis.

[0219] 57. The non-transitory computer-readable medium according to Clause 56, wherein the instruction set is executable by the one or more processors of the multi-beam device to cause the multi-beam device to further perform:

[0220] Adjust the first magnetic field, the second magnetic field, and / or the third magnetic field to change the focusing capability and move the main plane of the movable anti-rotation lens while keeping the rotation angle of the charged particle beam constant or substantially constant.

[0221] It should be understood that the controller of a multi-beam device can use software to control the aforementioned functionality. For example, the controller can send instructions to the lenses to generate appropriate fields (e.g., magnetic or electrostatic fields). This software can be stored on a non-transitory computer-readable medium. Conventional forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid-state drives, magnetic tape or any other magnetic data storage media, CD-ROMs, any other optical data storage media, any physical media with a perforated pattern, RAM, PROMs and EPROMs, FLASH-EPROMs or any other flash memory, NVRAM, caches, registers, any other memory chips or cassette tapes, and their network versions.

[0222] Although the invention has been explained in conjunction with preferred embodiments thereof, it should be understood that other modifications and variations may be made without departing from the spirit and scope of the invention as claimed below.

Claims

1. A movable anti-rotation lens having focusing capability for focusing a charged particle beam, comprising: An anti-rotation lens, wherein the anti-rotation lens is configured to be aligned with the optical axis of the movable anti-rotation lens; and A lens configured to be aligned with the optical axis, wherein the focusing capability and principal plane of the movable anti-rotation lens are adjustable up and down along the optical axis by changing the focusing capability of the anti-rotation lens and / or the focusing capability of the lens, and wherein the principal plane is adjustable relative to the source generating the charged particle beam.

2. The movable anti-rotation lens of claim 1, wherein, While keeping the rotation angle of the charged particle beam constant, the focusing capability and the main plane are adjustable.

3. The movable anti-rotation lens of claim 2, wherein, The rotation angle is zero.

4. The movable anti-rotation lens of claim 1, wherein, The lens is an electrostatic lens.

5. The movable anti-rotation lens according to claim 1, wherein, The lens is a magnetic lens.

6. A movable anti-rotation lens having focusing capability for focusing a charged particle beam, comprising: A first anti-rotation lens, configured to be aligned with the optical axis of the movable anti-rotation lens; and A second anti-rotation lens is configured to be aligned with the optical axis, wherein the focusing capability and principal plane of the movable anti-rotation lens are adjustable up and down along the optical axis by changing the focusing capability of the first anti-rotation lens and / or the second anti-rotation lens.

7. The movable anti-rotation lens according to claim 6, wherein, While keeping the rotation angle of the charged particle beam constant, the focusing capability and the main plane of the movable anti-rotation lens are adjustable.

8. The movable anti-rotation lens according to claim 7, wherein, The rotation angle is zero.

9. A multi-beam device for observing samples, comprising: An electron source, configured to generate a primary electron beam; A condenser lens is configured to focus the primary electron beam and is one of an anti-rotation lens or a movable anti-rotation lens, wherein the focusing capability and principal plane of the condenser lens are adjustable up and down along the optical axis of the condenser lens by changing the focusing capability of the condenser lens, and wherein the principal plane is adjustable relative to the electron source. A source conversion unit configured to form multiple images of the electron source through a plurality of first sub-beams of the primary electron beam; Objective lens, configured to focus the plurality of first sub-beams onto a surface and form a plurality of detection points on the surface; and An electronic detection device having multiple detection elements configured to detect multiple secondary beams generated by multiple detection points from a sample.

10. The multi-beam device according to claim 9 further includes a pre-sub-beam forming mechanism located between the electron source and the focusing lens, and including a plurality of sub-beam forming apertures.

11. The multi-beam device according to claim 10, wherein, The plurality of sub-beam forming apertures are configured to trim the primary electron beam into a plurality of second sub-beams.

12. The multi-beam device according to claim 11, wherein, The condenser lens is configured to focus the plurality of second sub-beams at multiple rotation angles so that they are incident on the source conversion unit.

13. The multi-beam device according to claim 12, wherein, When the detection current at the plurality of detection points changes, the plurality of rotation angles remain unchanged.

14. The multi-beam device according to any one of claims 11 to 13, wherein, The plurality of second sub-beams constitute the plurality of first sub-beams.

15. The multi-beam device according to claim 13, wherein, The detection current can be changed by altering the size of the apertures formed by the multiple sub-beams.

16. The multi-beam device according to claim 11, wherein, The source conversion unit includes a plurality of beam limiting openings configured to shape the plurality of second sub-beams into the plurality of first sub-beams.

17. The multi-beam device according to claim 13, wherein, The detection current can be changed by adjusting the focusing capability of the condenser lens.

18. The multi-beam device according to any one of claims 10 to 13, wherein, The plurality of sub-beam forming apertures are configured to block electrons that are not in the plurality of detection points.

19. The multi-beam device according to any one of claims 9 to 13, wherein, The source conversion unit includes an image forming mechanism configured to deflect the plurality of first sub-beams to form the plurality of images.

20. The multi-beam device according to claim 19, wherein, The image forming mechanism includes a plurality of electro-optical elements configured to deflect the plurality of first sub-beams to form the plurality of images.

21. The multi-beam device according to claim 19, wherein, The deflection angles of the plurality of first sub-beams are individually set to reduce aberrations at the plurality of detection points.

22. The multi-beam device according to claim 20, wherein, The plurality of electro-optical elements are configured to compensate for off-axis aberrations at the plurality of detection points.

23. The multi-beam device according to claim 20, wherein, The source conversion unit includes a sub-beam compensation mechanism configured to compensate for off-axis aberrations of the plurality of detector points.

24. The multi-beam device according to claim 23, wherein, The plurality of electro-optical elements and the sub-beam compensation mechanism together compensate for the aberrations of the plurality of detection points.

25. The multi-beam device of claim 20, further comprising a deflection scanning unit positioned below the source conversion unit.

26. The multi-beam device according to claim 25, wherein, The deflection scanning unit is configured to deflect the plurality of first sub-beams to scan the plurality of detection points.

27. The multi-beam device according to claim 25, wherein, The plurality of electro-optical elements are configured to deflect the plurality of first sub-beams to scan the plurality of detection points.

28. The multi-beam device according to claim 25, wherein, The deflection scanning unit and the plurality of electro-optical elements are configured to deflect the plurality of first sub-beams together to scan the plurality of detection points.

29. The multi-beam device according to claim 20, wherein, The plurality of electro-optical elements are configured to deflect the plurality of first sub-beams to scan the plurality of detection points.

30. The multi-beam device according to claim 27, wherein, One or more of the plurality of detection points can be different in one or more scanning features.

31. The multi-beam device according to claim 30, wherein, One of the scanning features is the scanning direction.

32. The multi-beam device according to claim 30, wherein, One of the scanning features is the scan size.

33. The multi-beam device according to claim 30, wherein, One of the scanning features is scanning speed.

34. The multi-beam device of claim 27 further includes an anti-scanning deflection unit, the anti-scanning deflection unit being placed in front of the electronic detection device and configured to deflect the plurality of secondary beams to the plurality of detection elements.

35. A method for configuring a multi-beam device for observing a sample, the method comprising: The primary electron beam from the electron source is trimmed into multiple sub-beams by a pre-sub-beamforming mechanism positioned between the electron source and the condenser lens. Multiple images of the electron source are formed using the multiple sub-beams through the source conversion unit; Multiple detection points are formed on the sample by projecting the multiple images onto the sample; as well as The condenser lens is adjusted to maintain the rotation angle of the multiple sub-beams unchanged when the detection current of the multiple detection points is changed. The condenser lens is either an anti-rotation lens or a movable anti-rotation lens. The focusing capability of the condenser lens and its principal plane are adjustable up and down along the optical axis of the condenser lens by changing the focusing capability of the condenser lens. The principal plane is adjustable relative to the electron source.

36. The method of claim 35, further comprising: Adjust the source conversion unit to scan the plurality of probe points on the sample.

37. A non-transitory computer-readable medium storing a set of instructions executable by one or more processors of a multi-beam device to cause the multi-beam device to perform a method for configuring an anti-rotation lens for focusing a charged particle beam, the method comprising: The magnetic lens indicates the magnetic field it generates. as well as The electrostatic lens indicates that an electrostatic field is generated, wherein: The magnetic field and / or the electrostatic field generate the focusing ability of the anti-rotation lens, and The magnetic field and the electrostatic field at least partially overlap. The anti-rotation lens mentioned therein is a movable anti-rotation lens according to any one of claims 1-8.

38. The non-transitory computer-readable medium according to claim 37, wherein, The instruction set can be executed by one or more processors of the multi-beam device to enable the multi-beam device to perform further operations: Adjust the magnetic field and / or the electrostatic field to change the focusing capability while keeping the rotation angle of the charged particle beam constant.

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