Systems and methods for scanning sample using multi-beam inspection apparatus

Abstract

To provide improved systems and methods for inspection of a sample using a particle beam inspection apparatus, and more specifically, systems and methods for scanning a sample with a plurality of charged particle beams.SOLUTION: A multi-beam tool is provided comprising a beam configuration system including: a charged-particle source for generating a primary beam of charged particles; a stage configured to hold a sample; and a deflector system between the charged-particle source and the stage configured to split the primary beam into an array of beams. The beam configuration system is configured to provide a rotated beam configuration with a rotation angle determined based on the number of beams in a row of the array of beams.SELECTED DRAWING: Figure 19

Description

[Technical field]

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims priority to U.S. patent application Ser. No. 62 / 684,138, filed June 12, 2018, U.S. patent application Ser. No. 62 / 787,227, filed December 31, 2018, and U.S. patent application Ser. No. 62 / 850,461, filed May 20, 2019, which are incorporated by reference in their entireties herein.

[0002] TECHNICAL FIELD

[0002] Embodiments provided herein relate generally to inspection of a sample using a particle beam inspection device, and more specifically to a system and method for scanning a sample with multiple charged particle beams. [Background technology]

[0003]

[0003] When manufacturing semiconductor integrated circuit (IC) chips, pattern defects or unwanted particles (residues) inevitably occur on the wafer or mask during the manufacturing process, thereby reducing yield. For example, unwanted particles can be problematic for patterns with smaller critical feature dimensions that have been adopted to meet the increasingly higher performance requirements of IC chips.

[0004]

[0004] Pattern inspection tools using charged particle beams have been used to detect defects or unwanted particles. These tools typically employ scanning electron microscopes (SEMs). In an SEM, a beam of relatively high energy primary electrons is decelerated to impinge on a sample with a relatively low landing energy and focused to form a probe spot on the sample. This focused probe spot of primary electrons generates secondary electrons from the surface. The secondary electrons may include backscattered, secondary, or Auger electrons resulting from the interaction of the primary electrons with the sample. By scanning the probe spot across the sample surface and collecting the secondary electrons, the pattern inspection tool can obtain an image of the sample surface. Summary of the Invention

[0005]

[0005] Embodiments provided herein disclose a particle beam inspection system, and more specifically, an inspection system using multiple charged particle beams.

[0006]

[0006] In some embodiments, a multi-beam tool is provided. The multi-beam tool includes a beam configuration system including a charged particle source for generating a primary beam of charged particles, a stage for holding a sample, and a deflector system between the source and the stage configured to split the primary beam into an array of beams. The beam configuration system is configured to provide a rotating beam configuration with a rotation angle determined based on a number of beams in a row of the array of beams.

[0007]

[0007] In some embodiments, a multi-beam tool is provided, the multi-beam tool including a charged particle source for generating a primary beam of charged particles, a stage configured to hold a sample and configured to move in a first direction, and a deflector system between the charged particle source and the stage, the deflector system configured to split the primary beam into n beams, where n is an integer and n>2, rotate the n beams relative to the first direction such that the n beams are spaced apart along the first direction, and deflect the n beams to simultaneously i) follow the movement of the stage, and ii) scan one or more sets of n scan lines across a surface of the sample.

[0008] In some embodiments, a multi-beam tool is provided that includes a beam configuration system including a charged particle source configured to generate a primary beam of charged particles, a stage configured to hold a sample and configured to move in a first direction, and a deflector system between the charged particle source and the stage. The deflector system is configured to split the primary beam into an array of beams. The beam construction system is configured to: deflect the array of beams via the deflector system to i) scan a first set of scan lines within a field of view of the beam construction system, and ii) follow the movement of the stage during the scanning of the first set of scan lines, where the first set of scan lines span a first distance along a first direction; move the stage the first distance in the first direction after the first set of scan lines are scanned; deflect the array of beams via the deflector system to i) scan a second set of scan lines within a field of view of the beam construction system, and ii) follow the movement of the stage during the scanning of the second set of scan lines; move the stage in the first direction as the first and second sets of scan lines are scanned.

[0009]

[0009] In some embodiments, a method of controlling multiple charged particle beams to scan a sample is provided, the method including: generating, by a multi-beam tool, a primary beam of charged particles; splitting, by the multi-beam tool, the primary beam into an array of beams; and rotating, by the multi-beam tool, the array of beams relative to the sample to be scanned by a rotation angle determined based on a number of beams in a row of beams of the array.

[0010]

[0010] In some embodiments, a method of controlling multiple charged particle beams to scan a sample is provided, the method including: moving the sample in a first direction by a multi-beam tool; generating a primary beam of charged particles by the multi-beam tool; splitting the primary beam into n beams by the multi-beam tool, where n is an integer and n>2; rotating the n beams relative to the first direction such that the n beams are spaced apart along the first direction; and deflecting the n beams by the multi-beam tool to simultaneously i) follow the movement of the sample and ii) scan one or more sets of n scan lines across a surface of the sample.

[0011] In some embodiments, a method for controlling multiple charged particle beams to scan a sample is provided. The method includes moving the sample in a first direction; generating a primary beam of charged particles with the multibeam tool; splitting the primary beam into an array of beams with the multibeam tool; deflecting the array of beams with the multibeam tool to i) scan a first set of scan lines within a field of view of the multibeam tool and ii) follow the movement of the sample during the scanning of the first set of scan lines, where the first set of scan lines span a first distance along the first direction; after the first set of scan lines are scanned, moving the sample a first distance in the first direction with the multibeam tool; deflecting the array of beams with the multibeam tool to i) scan a second set of scan lines within a field of view of the multibeam tool and ii) follow the movement of the sample during the scanning of the second set of scan lines; moving the sample in the first direction with the multibeam tool as the first and second sets of scan lines are scanned.

[0012]

[0012] In some embodiments, a non-transitory computer readable medium is provided having stored thereon a set of instructions executable by a controller coupled to a multi-beam tool to cause the controller to perform a method including instructing a beam configuration system of the multi-beam tool to rotate an array of charged particle beams relative to a sample to be scanned by the multi-beam tool by a rotation angle determined based on a number of beams in a row of the array of beams: The multi-beam tool generates a primary beam of charged particles and splits the primary beam into an array of charged particle beams.

[0013]

[0013] In some embodiments, a non-transitory computer readable medium is provided having a set of instructions stored thereon, the set of instructions being executable by a controller coupled to a multi-beam tool to cause the controller to perform a method including: directing a sample stage of the multi-beam tool to move a sample in a first direction, the multi-beam tool generating a primary beam of charged particles and splitting the primary beam into n beams, where n is an integer and n>2; directing a beam construction system of the multi-beam tool to rotate the n beams relative to the first direction such that the n beams are spaced apart along the first direction; and directing the beam construction system to deflect the n beams to simultaneously i) follow the movement of the sample and ii) scan one or more sets of n scan lines across a surface of the sample.

[0014] In some embodiments, a non-transitory computer readable medium having stored thereon a set of instructions executable by a controller coupled to a multi-beam tool to cause the controller to perform a method that includes: The method includes: directing a sample stage of a multi-beam tool to move a sample in a first direction, the multi-beam tool generating a primary beam of charged particles and splitting the primary beam into an array of beams; deflecting the array of beams to i) scan a first set of scan lines within a field of view of the multi-beam tool and ii) instructing a beam construction system of the multi-beam tool to follow the movement of the sample during the scanning of the first set of scan lines, where the first set of scan lines span a first distance along a first direction; after the first set of scan lines are scanned, directing a sample holder to move the sample a first distance in the first direction; deflecting the array of beams to i) scan a second set of scan lines within a field of view of the multi-beam tool and ii) instructing the beam construction system to follow the movement of the sample during the scanning of the second set of scan lines; moving the sample in the first direction as the first and second sets of scan lines are scanned.

[0015]

[0015] Disclosed embodiments provide a method for scanning an area of ​​a sample using N charged particle beams, where N is an integer equal to or greater than 2, and the area of ​​the sample includes a plurality of scan sections of N consecutive scan lines. The method includes: moving a position of the sample in a first direction; scanning a first scan line of at least some of the plurality of scan sections with a first charged particle beam of the N charged particle beams moving toward a probe spot of the first charged particle beam; scanning a second scan line of at least some of the plurality of scan sections with a second charged particle beam of the N charged particle beams moving toward a probe spot of the second charged particle beam.

[0016]

[0016] The disclosed embodiments provide a non-transitory computer-readable medium storing a set of instructions, which are executable by one or more processors of a charged particle beam system to cause the charged particle beam system to perform a method using a charged particle beam source for delivering N charged particle beams to a surface of a sample in a time sequence, the method including: moving a position of the sample in a first direction; scanning a first scan line of at least some of the multiple scan sections moving toward a probe spot of the first charged particle beam with a first charged particle beam of the N charged particle beams; scanning a second scan line of at least some of the multiple scan sections moving toward a probe spot of the second charged particle beam with a second charged particle beam of the N charged particle beams.

[0017]

[0017] The disclosed embodiments also provide a method of scanning a sample with a multi-beam inspection system utilizing N×M charged particle beams, where N is an integer equal to or greater than 2. The method includes: positioning the N charged particle beams such that each of the N charged particle beams scans a different scan line of a first set of N adjacent scan lines; scanning the first set of N adjacent scan lines of the sample while the sample is moving in a first direction at a first velocity by using the N charged particle beams; repositioning the N charged particle beams such that each of the N charged particle beams scans a different scan line of a second set of adjacent scan lines relative to a start of scanning the first set of N adjacent scan lines; scanning the second set of N adjacent scan lines of the sample while the sample is moving in a first direction at a first velocity by using the N charged particle beams.

[0018]

[0018] The disclosed embodiments also provide a method of scanning a sample disposed on a stage by a multi-beam inspection system utilizing an N x M array of charged particle beams, where N and M are each an integer equal to or greater than 2. The method includes positioning the N x M array of charged particle beams such that each beam of the N x M array of charged particle beams at a first set of positions can scan a different scan section of the first set of N by M scan sections of the sample. The method also includes scanning scan lines of at least some of the scan sections of the first set of N by M scan sections of the sample while the stage is moving at a first velocity in a first direction by using the N x M array of charged particle beams. The method also includes repositioning the N x M array of charged particle beams such that each beam of the N x M array of charged particle beams at a second set of positions can scan a different scan section of the second set of N by M scan sections of the sample relative to a start of scanning the first set of N by M scan sections. The method also includes scanning scan lines of at least some of the N by M scan sections of a second set of the sample while the stage is moving in a first direction at a first velocity using an N by M array of charged particle beams.

[0019]

[0019] Other advantages of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, in which there are shown, by way of illustration and example, certain embodiments of the invention.

[0020]

[0020] The above and other aspects of the present disclosure will become more apparent from the following description of exemplary embodiments taken in conjunction with the accompanying drawings. [Brief description of the drawings]

[0021] [Figure 1] 1 is a schematic diagram illustrating an exemplary charged particle beam inspection system consistent with an embodiment of the present disclosure. [Diagram 2]

[0022] FIG. 1 is a schematic diagram illustrating an exemplary electron beam tool consistent with an embodiment of the present disclosure. [Figure 3A]

[0023] 1 illustrates a schematic diagram of the use of multiple beams of charged particles to inspect a sample; [Figure 3B] 1 illustrates a schematic diagram of inspecting a sample using multiple beams of charged particles; [Figure 3C]

[0024] 3B illustrates a schematic representation of the movement of one of the probe spots of FIG. 3A relative to the sample during one of the periods T1, T2, and T3. [Figure 3D]

[0024] Figure 3B shows a schematic representation of the movement of one of the probe spots of Figure 3B relative to the sample during one of the periods T1, T2, and T3. [Figure 4A]

[0025] 1A-1C are schematic diagrams illustrating the use of multiple beams of charged particles to inspect a sample, consistent with embodiments of the present disclosure; [Figure 4B] 1 illustrates a schematic diagram of inspecting a sample using multiple beams of charged particles consistent with an embodiment of the present disclosure. [Figure 5A]

[0026] 1A-1C are schematic diagrams illustrating the use of multiple beams of charged particles to inspect a sample, consistent with embodiments of the present disclosure; [Figure 5B] 1 illustrates a schematic diagram of inspecting a sample using multiple beams of charged particles consistent with an embodiment of the present disclosure. [Figure 6]

[0027] 1A-1C are schematic diagrams illustrating the use of multiple beams of charged particles to inspect a sample, consistent with embodiments of the present disclosure; [Figure 7]

[0028] 1 is a flow chart illustrating steps of an exemplary multi-beam scanning method consistent with embodiments of the present disclosure. [Figure 8A]

[0029] A schematic diagram showing the distribution of multiple primary beamlets on the surface of a sample before and after rotating the primary beamlets around the optical axis of the electron beam inspection system shown in Figure 1, consistent with an embodiment of the present disclosure. [Figure 8B]

[0030] A schematic diagram showing the scan pattern of multiple primary beamlets on the surface of a sample before and after rotating the primary beamlets about the optical axis of the electron beam inspection system shown in FIG. 1, consistent with an embodiment of the present disclosure. [Figure 9]

[0031] FIG. 8C is a schematic diagram illustrating a process for selecting the rotation angles of the primary beamlets shown in FIGS. 8A and 8B, consistent with an embodiment of the present disclosure. [Figure 10]

[0032] 1 is a flow diagram of a multi-beam scanning method consistent with an embodiment of the present disclosure. [Figure 11]

[0033] FIG. 1 is a schematic diagram illustrating a multi-beam interlaced scan pattern consistent with an embodiment of the present disclosure. [Figure 12]

[0034] FIG. 1 is a schematic diagram showing the movement trajectories of multiple probe spots relative to a sample during an interlaced scan, consistent with an embodiment of the present disclosure. [Figure 13]

[0035] FIG. 1 is a schematic diagram illustrating a multi-beam interlaced scan pattern consistent with an embodiment of the present disclosure. [Figure 14]

[0036] 1 is a flow diagram of a multi-beam interlaced scanning method consistent with an embodiment of the present disclosure. [Figure 15]

[0037] FIG. 1 is a schematic diagram illustrating a multi-beam semi-interlaced scan pattern consistent with an embodiment of the present disclosure. [Figure 16]

[0038] 4 is a flow diagram of a multi-beam semi-interlaced scanning method consistent with an embodiment of the present disclosure. [Figure 17]

[0039] 1A-1C are schematic diagrams illustrating the distribution of multiple primary beamlets on a surface of a sample before and after beam repositioning, consistent with embodiments of the present disclosure. [Figure 18]

[0040] FIG. 1 is a schematic diagram illustrating a multi-beam scan pattern in “continuous scan” mode, consistent with an embodiment of the present disclosure. [Figure 19]

[0041] 1 is a schematic diagram illustrating an example scan pattern using a rotated set of primary beamlets consistent with embodiments of the present disclosure. FIG. [Figure 20A]

[0042] FIG. 20 is a schematic diagram illustrating an example multi-beam scan pattern using the rotated primary beamlets shown in FIG. 19, consistent with an embodiment of the present disclosure. [Figure 20B] FIG. 20 is a schematic diagram illustrating an exemplary multi-beam scan pattern using the rotated primary beamlets shown in FIG. 19, consistent with an embodiment of the present disclosure. [Figure 20C] FIG. 20 is a schematic diagram illustrating an exemplary multi-beam scan pattern using the rotated primary beamlets shown in FIG. 19, consistent with an embodiment of the present disclosure. [Figure 20D] FIG. 20 is a schematic diagram illustrating an exemplary multi-beam scan pattern using the rotated primary beamlets shown in FIG. 19, consistent with an embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022]

[0043] Reference will now be made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, in which like numbers in different drawings represent the same or similar elements unless otherwise noted. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations consistent with the present invention. Instead, they are merely examples of apparatus and methods consistent with aspects related to the present invention as recited in the appended claims.

[0023]

[0044] Electronic devices consist of circuits formed on a piece of silicon called a substrate. Many circuits may be formed together on the same piece of silicon and are called an integrated circuit, or IC. The dimensions of these circuits have been dramatically reduced so that many more circuits can fit on a substrate. For example, an IC chip in a smartphone can be as small as a thumbnail yet contain over 2 billion transistors, with each transistor measuring less than 1 / 1000th the size of a human hair.

[0024]

[0045] Manufacturing these extremely small ICs is a complex, time-consuming, and expensive process that often involves hundreds of individual steps. An error in just one step can result in a defect in the finished IC, rendering it useless. Thus, one goal of the manufacturing process is to avoid such defects and maximize the number of functional ICs produced in the process, i.e., to increase the overall yield of the process.

[0025]

[0046] One component of improving yield is monitoring the chip fabrication process to ensure that a sufficient number of functional integrated circuits are being produced. One way to monitor the process is to inspect the chip circuit structures at various stages in their formation. Inspection can be performed using a scanning electron microscope (SEM). An SEM allows one to image these very small structures, essentially taking a "picture" of them. This image can be used to determine if the structures were formed properly, and if they were formed in the proper location. If the structures are defective, the process can be adjusted to make it less likely that the defects will occur again.

[0026]

[0047] An SEM scans the surface of a sample with a focused beam of primary electrons that interact with the sample and generate secondary electrons. By scanning the sample with the focused beam and capturing the secondary electrons with a detector, an SEM generates an image of the scanned area of ​​the sample.

[0027]

[0048] A conventional SEM generates an image by raster scanning an electron beam across a sample held on a stage. Raster scanning is performed by moving the primary beam to scan a line of pixels across the sample, and after reaching the last pixel of the scan line, moving the primary beam back to scan the first pixel of the next line, and repeating the process. The extra time required / expended to move the beam from the last pixel of one line to the first pixel of the next line is called line overhead. Typically, in a conventional SEM system, the stage is kept stationary while the primary electron beam raster scans the sample area (e.g., a set of one or more scan lines) within its field of view. After an area is completely scanned, the stage jumps to move an unscanned sample area into the field of view so that the primary beam can begin scanning the new area. For high throughput inspection, some of the newer inspection systems use multiple electron beams. Because multiple electron beams can scan different parts of the wafer simultaneously, multi-beam electron inspection systems can inspect wafers much faster than single-beam systems.

[0028]

[0049] However, even these newer systems, which typically use multiple electron beams, still employ the same raster scanning technique while keeping the sample stage stationary. After the multiple beams finish scanning the current sample area in their respective fields of view, the sample stage or beam may need to make a large "jump" to a sample area that has not yet been scanned. Furthermore, scanning may need to be stopped every time the sample stage moves, and can only be resumed after the stage has fully settled, which ultimately results in a significant amount of unproductive time.

[0029]

[0050] One aspect of the present disclosure relates to systems and methods for arranging, configuring, or controlling multiple electron beams to simultaneously and sequentially scan a sample. As described in detail below, the disclosed systems and methods can reduce or minimize line overhead associated with raster scanning or stage movement latency. Additionally, the disclosed systems and methods can optimize the movement of multiple electron beams into simple repetitive up and down movements without requiring large "jump" movements to areas not yet scanned, thereby increasing overall inspection throughput and reducing the complexity of the control mechanism of the multi-beam tool.

[0030]

[0051] The relative dimensions of components in the drawings may be exaggerated for clarity. In the following description of the drawings, the same or similar reference numbers refer to the same or similar components or entities, and only the differences with respect to the individual embodiments are described. As used herein, unless otherwise stated, the term "or" includes all possible combinations unless impracticable. For example, if a component is described as including A or B, the component may include A, or B, or A and B, unless otherwise stated or impracticable. As a second example, if a component is described as including A, B, or C, the component may include A, or B, or C, or A and B, or C, or A and B, and C, unless otherwise stated or impracticable.

[0031]

[0052] Reference is now made to Figure 1, which is a schematic diagram illustrating an exemplary charged particle beam inspection system 100 consistent with embodiments of the present disclosure. As shown in Figure 1, the charged particle beam inspection system 100 includes a main chamber 10, a load lock chamber 20, an electron beam tool 40, and a front end of equipment module (EFEM) 30. The electron beam tool 40 is disposed within the main chamber 10. Although the description and drawings relate to an electron beam, it will be understood that the embodiments are not used to limit the present disclosure to any particular charged particle.

[0032]

[0053] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include additional load ports. The first load port 30a and the second load port 30b may receive, for example, a wafer FOUP (front opening unified pod) that contains wafers (e.g., semiconductor wafers, or wafers made of other materials) or samples (wafers and samples are hereinafter collectively referred to as "wafers") to be inspected. One or more robotic arms (not shown) in the EFEM 30 transport the wafers to the load lock chamber 20.

[0033]

[0054] The load lock chamber 20 may be connected to a load lock vacuum pumping system (not shown) that removes gas molecules within the load lock chamber 20 to reach a first pressure that is lower than atmospheric pressure. After the first pressure is reached, one or more robotic arms (not shown) transport the wafer from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pumping system (not shown) that removes gas molecules within the main chamber 10 to reach a second pressure that is lower than the first pressure. After the second pressure is reached, the wafer is subjected to inspection by an electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single beam electron inspection tool. In other embodiments, the electron beam tool 40 may include a multi-beam electron inspection tool.

[0034]

[0055] The controller 50 is electronically connected to the electron beam tool 40. The controller 50 may be a computer configured to perform various controls of the charged particle beam inspection system 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. Although the controller 50 is shown in FIG. 1 as being external to the structure including the main chamber 10, the load lock chamber 20, and the EFEM 30, it will be understood that the controller 50 may also be part of this structure. It should be noted that while the present disclosure provides an example of a main chamber 10 housing an electron beam inspection tool, aspects of the present disclosure in its broadest sense are not limited to chambers housing an electron beam inspection tool. Rather, it will be understood that the principles described above may also be applied to other tools operating under a second pressure.

[0035]

[0056] Referring now to FIG. 2, FIG. 2 is a schematic diagram illustrating an exemplary electron beam tool 40 including a multi-beam electron inspection tool that is part of the exemplary charged particle beam inspection system 100 of FIG. 1 consistent with an embodiment of the present disclosure. The multi-beam electron beam tool 40 (also referred to herein as apparatus 40) includes an electron source 201, a gun aperture plate 271, a condenser lens 210, a source conversion unit 220, a primary projection optics 230, a motorized stage 209, and a sample holder 207 supported by the motorized stage 209 for holding a sample 208 (e.g., a wafer or a photomask) to be inspected. The multi-beam electron beam tool 40 may further include a secondary projection system 250 and an electron detection device 240. The primary projection optics 230 may include an objective lens 231. The electron detection device 240 may include a plurality of detection elements 241, 242, and 243. A beam separator 233 and a deflection scanning unit 232 may be disposed inside the primary projection optics 230.

[0036]

[0057] The electron source 201, the gun aperture plate 271, the collector lens 210, the source conversion unit 220, the beam separator 233, the deflection scanning unit 232, and the primary projection optics 230 may be aligned with a primary optical axis 204 of the apparatus 40. The secondary projection system 250 and the electron detection device 240 may be aligned with a secondary optical axis 251 of the apparatus 40.

[0037]

[0058] The electron source 201 may include a cathode (not shown) and an extractor or anode (not shown), and in operation the electron source 201 is configured to emit primary electrons from the cathode, which are extracted or accelerated by the extractor and / or anode to form a primary electron beam 202, which forms a (virtual or real) primary beam crossover 203. The primary electron beam 202 may be visualized as emitting from the primary beam crossover 203.

[0038]

[0059] The source conversion unit 220 may include an image forming element array (not shown), a field curvature compensator array (not shown), an astigmatism compensator array (not shown), and a beam limiting aperture array (not shown). The image forming element array may include a plurality of micro deflectors or micro lenses to affect a plurality of primary beamlets 211, 212, 213 of the primary electron beam 202 and form a plurality of (virtual or real) parallel images of the primary beam crossover 203, one for each of the primary beamlets 211, 212, and 213. The field curvature compensator array may include a plurality of micro lenses to compensate for the field curvature aberration of the primary beamlets 211, 212, and 213. The astigmatism compensator array may include a plurality of micro astigmatism correctors to compensate for the astigmatism of the primary beamlets 211, 212, and 213. The beam-limiting aperture array may be configured to limit the diameter of the individual primary beamlets 211, 212, and 213. FIG. 2 shows three primary beamlets 211, 212, and 213 by way of example, it being understood that the source conversion unit 120 may be configured to form any number of primary beamlets. The controller 50 may be connected to various parts of the charged particle beam inspection system 100 of FIG. 1, such as the electronic detection device 240, the primary projection optics 230, or the motorized stage 209. In some embodiments, the controller 50 may perform various image and signal processing functions, as described in more detail below. The controller 50 may also generate various control signals to control the operation of the charged particle beam inspection system 100.

[0039]

[0060] The collector lens 210 is configured to focus the primary electron beam 202. The collector lens 210 may further be configured to adjust the current of the primary beamlets 211, 212, and 213 downstream of the source conversion unit 220 by varying the focusing power of the collector lens 210. Alternatively, the current may be varied by changing the radial size of the beam-limiting apertures within the beam-limiting aperture array corresponding to the individual primary beamlets. The current may be varied by changing both the radial size of the beam-limiting apertures and the focusing power of the collector lens 210. The collector lens 210 may be a movable collector lens that may be configured such that the position of a first principal plane is movable. The movable collector lens may be configured to be magnetic, which may result in the off-axis beamlets 212 and 213 entering the beamlet limiting mechanism with a rotation angle. The rotation angle varies with the focusing power and the position of the first principal plane of the movable collector lens. In some embodiments, the movable focusing lens may be a movable anti-rotation focusing lens, which includes an anti-rotation lens having a movable first principal plane.

[0040]

[0061] The objective lens 231 may be configured to focus the beamlets 211, 212, and 213 onto the sample 208 for inspection, and in the current embodiment, may form three probe spots 221, 222, and 223 on the surface of the sample 208. The gun aperture plate 271 is configured, in operation, to block ambient electrons of the primary electron beam 202 to reduce the Coulomb effect, which may increase the size of each of the probe spots 221, 222, and 223 of the primary beamlets 211, 212, 213, and thus reduce the inspection resolution.

[0041]

[0062] The beam separator 233 may be, for example, a Wien filter including electrostatic deflectors generating electrostatic and magnetic dipole fields (not shown in FIG. 2). In operation, the beam separator 233 may be configured to exert an electrostatic force by the electrostatic dipole field on individual electrons of the primary beamlets 211, 212, and 213. The electrostatic force is equal in magnitude but opposite in direction to the magnetic force exerted by the magnetic dipole field of the beam separator 233 on the individual electrons. Thus, the primary beamlets 211, 212, and 213 may pass at least substantially straight through the beam separator 233 with at least substantially zero deflection angle.

[0042]

[0063] In operation, the deflection scanning unit 232 is configured to deflect the primary beamlets 211, 212, and 213 to scan the probe spots 221, 222, and 223 across respective scan areas within a section of the surface of the sample 208. In response to the incidence of the primary beamlets 211, 212, and 213 at the probe spots 221, 222, and 223, electrons emerge from the sample 208 and three secondary electron beams 261, 262, and 263 are generated. Each of the secondary electron beams 261, 262, and 263 typically includes electrons having different energies including secondary electrons (having an electron energy of 50 eV or less) and backscattered electrons (having an electron energy between 50 eV and the landing energy of the primary beamlets 211, 212, and 213). The beam separator 233 is configured to deflect the secondary electron beams 261, 262, and 263 towards the secondary projection system 250. The secondary projection system 250 then focuses the secondary electron beams 261, 262, and 263 onto the detector elements 241, 242, and 243 of the electron detection device 240. The detector elements 241, 242, and 243 are configured to detect corresponding secondary electron beams 261, 262, and 263 and generate corresponding signals that are sent to the controller 50 or a signal processing system (not shown), for example to construct an image of a corresponding scan area of ​​the sample 208.

[0043]

[0064] In some embodiments, detector elements 241, 242, and 243 detect corresponding secondary electron beams 261, 262, and 263, respectively, and generate corresponding intensity signal outputs (not shown) to an image processing system (e.g., controller 50). In some embodiments, each detector element 241, 242, and 243 may include one or more pixels. The intensity signal output of a detector element may be the sum of signals generated by all the pixels in the detector element.

[0044]

[0065] In some embodiments, the controller 50 may include an image processing system including an image acquirer (not shown), storage (not shown). The image acquirer may include one or more processors. For example, the image acquirer may include a computer, a server, a mainframe host, a terminal, a personal computer, any type of portable computing device, or the like, or a combination thereof. The image acquirer may be communicatively coupled to the electronic detection device 240 of the apparatus 40 via a medium, such as electrical conductors, fiber optic cables, portable storage media, IR, Bluetooth, Internet, wireless network, wireless communication, or a combination thereof, among others. In some embodiments, the image acquirer may receive signals from the electronic detection device 240 and construct an image. The image acquirer may thus acquire an image of the sample 208. The image acquirer may also perform various post-processing functions, such as generating contour lines, overlaying indicators on the acquired image, etc. The image acquirer may be configured to perform adjustments, such as brightness and contrast, of the acquired image. In some embodiments, the storage may be a storage medium such as a hard disk, a flash drive, cloud storage, random access memory (RAM), other types of computer readable memory, etc. The storage may be coupled to the image acquirer and may be used to store raw scanned image data as original images and to store processed images.

[0045]

[0066] In some embodiments, the image acquirer may acquire one or more images of the sample based on an imaging signal received from the electronic detection device 240. The imaging signal may correspond to a scanning operation to perform charged particle imaging. The acquired image may be a single image including multiple imaging areas. The single image may be stored in storage. The single image may be an original image that may be divided into multiple regions. Each of the regions may include an imaging area that encompasses a feature of the sample 208. The acquired image may include multiple images of a single imaging area of ​​the sample 208 sampled multiple times in a time sequence. The multiple images may be stored in storage. In some embodiments, the controller 50 may be configured to perform an image processing step using multiple images of the same location of the sample 208.

[0046]

[0067] In some embodiments, the controller 50 may include measurement circuitry (e.g., an analog-to-digital converter) to obtain a distribution of the detected secondary electrons. The electron distribution data collected during the detection time window may be used in combination with corresponding scan path data of the primary electron beam 202 incident on the wafer surface to reconstruct an image of the wafer structure under inspection. The reconstructed image may be used to reveal various features of the internal or external structure of the sample 208, thereby revealing defects that may be present in the wafer.

[0047]

[0068] In some embodiments, the controller 50 may control the motorized stage 209 to move the sample 208 during inspection of the sample 208. In some embodiments, the controller 50 may enable the motorized stage 209 to move the sample 208 continuously in one direction at a constant speed. In other embodiments, the controller 50 may enable the motorized stage 209 to vary the speed at which the sample 208 moves over time depending on the step of the scanning process.

[0048]

[0069] 2 shows apparatus 40 using three primary electron beamlets, it will be understood that apparatus 40 may generate or use two or more primary electron beamlets, and this disclosure does not limit the number of primary electron beamlets used in apparatus 40.

[0049]

[0070] Reference is now made to Figures 3A and 3B, which diagrammatically illustrate the use of multiple beams of charged particles to inspect a sample. In the embodiment illustrated by Figures 3A and 3B, four primary beamlets generate four probe spots 310A-310D on a sample (such as sample 208 in Figure 2). Figure 3A illustrates the movement of the four probe spots 310A-310D relative to the sample. Figure 3B illustrates the movement of the four probe spots 310A-310D and the sample relative to an absolute reference coordinate system. The four probe spots 310A-310D may be arranged in a line, although this is not necessarily the case. In the illustrated embodiment, the diameter of the four probe spots is W. However, in the disclosed embodiment, the diameters of the probe spots are not necessarily the same. The area 300 to be inspected is rectangular in shape, although this is not necessarily the case. For ease of explanation, two directions x and y are defined in the absolute reference coordinate system. The x and y directions are perpendicular to each other.

[0050]

[0071] In some embodiments, the motion of the probe spots may be coordinated with the motion of the sample. For example, as shown in FIG. 3A, the four probe spots 310A-310D move in the x direction by a length L relative to the sample during a period T1, but do not move in the y direction. Correspondingly, as shown in FIG. 3B, during the same period T1, the sample moves in the y direction by a length K relative to the absolute reference coordinate system, but does not move in the x direction relative to the absolute reference coordinate system, and the four probe spots 310A-310D move in the y direction by a length K relative to the absolute reference coordinate system, but move in the x direction by a length L relative to the absolute reference coordinate system. Thus, during the period T1, the four probe spots 310A-310D move in the y direction at the same speed as the sample.

[0051]

[0072] The directions of movement of the probe spots 310A-310D during time period T1 do not have to be the same. The lengths by which the probe spots 310A-310D move during time period T1 do not have to be the same. The probe spots 310A-310D may or may not move relative to each other.

[0052]

[0073] In the embodiment shown by Figures 3A and 3B, during a period T1, four sub-regions 301A, 302A, 303A, and 304A are inspected by four probe spots 310A, 310B, 310C, and 310D, respectively. At the end of the period T1, the four probe spots 310A-310D move by a length L in the -x direction relative to the absolute reference coordinate system and move by a width W (i.e., the width of one of the four probe spots 310A-310D) in the -y direction relative to the absolute reference coordinate system. Thus, relative to the sample, the four probe spots 310A-310D move to the -x ends of the sub-regions 301B, 302B, 303B, and 304B, respectively, which may be adjacent to the sub-regions 301A, 302A, 303A, and 304A, respectively. In this way, after reaching the last pixel of a scan line, each probe spot traverses back to the beginning of the next scan line. Adjacent scan lines may be separated by a distance corresponding to the pixel size of the image produced by the electron beam tool. The extra time required for the flyback is called the line overhead. In some cases, this flyback may be fast enough that the line overhead is negligible. Furthermore, the line overhead may be included in the period T1.

[0053]

[0074] During periods T2 and T3, the four probe spots 310A-310D and the sample move in the same manner as during period T1. In this way, the four sub-regions 301B, 302B, 303B, and 304B are inspected during T2, and the four sub-regions 301C, 302C, 303C, and 304C are inspected by the four probe spots 310A-310D during T3.

[0054]

[0075] At the end of period T2, the four probe spots 310A-310D move to the -x ends of subregions 301C, 302C, 303C, and 304C, respectively, in the same manner as at the end of period T1. Subregions 301C, 302C, 303C, and 304C may be adjacent to subregions 301B, 302B, 303B, and 304B, respectively.

[0055]

[0076] In the embodiment shown by Figures 3A and 3B, the pitch S of the four probe spots 310A-310D in the y direction is equal to 3W. Thus, at the end of the period T3, the combination of inspected sub-areas 301C, 301B, 301A, 302C, 302B, 302A, ... 304A has no gaps in the y direction. At the end of the period T3, the four probe spots 310A-310D may move by a length L in the -x direction relative to the absolute reference coordinate system and by 10W in the -y direction relative to the absolute reference coordinate system. For example, at the end of the period T3, the probe spot 310D needs to move from the +x end of the sub-area 304C to the -x end of the sub-area 304D. In essence, the probe spot 310D moves by a length L in the -x direction and by 10W in the -y direction relative to the absolute reference coordinate system. The 10W movement in the -y direction can be realized by deflecting the four primary beamlets in the -y direction. Alternatively or additionally, such a movement can be realized by moving the sample in the y direction. Thus, relative to the sample, the four probe spots 310A-310D move to the -x ends of the sub-regions 301D, 302D, 303D, and 304D, respectively, among which the sub-region 304D may be adjacent to the sub-region 301C. After this movement, the four probe spots 310A-310D are in the same position relative to the absolute reference coordinate system as at the beginning of the period T1. Additional sub-regions (e.g., 301D, 302D, 303D, 304D, etc.) may be inspected by the four probe spots 310A-310D during additional periods (e.g., period T4).

[0056]

[0077] During periods T1-T3, the sample moves by 3K (see FIG. 3B) in the y direction relative to the absolute reference coordinate system, the four probe spots 310A-310D move by zero in the y direction relative to the absolute reference coordinate system, and the four probe spots 310A-310D move by 12W in the -y direction relative to the sample. Thus, 3K is equal to 12W, i.e., K is equal to 4W. The velocity of the sample during periods T1-T3 may remain constant.

[0057]

[0078] Generalizing, if the number of probe spots is M and the pitch of the probe spots in the x-direction is S=NW, where N is an integer greater than or equal to 1, then the number of periods required for a combination of the test sub-areas to produce no gaps in the x-direction is N, and the distance K traveled by the sample during each period is equal to MW. In the example of Figures 3A and 3B, N=3, M=4, and K=4W.

[0058]

[0079] FIG. 3C shows a schematic representation of the movement of one of the probe spots 310A-310D relative to the sample during one of the periods T1, T2, and T3. Relative to the sample, the probe spot moves only in the x direction during this period by a distance L, but not in the y direction. FIG. 3D shows a schematic representation of the movement of that probe spot relative to an absolute reference frame during this period. Relative to the absolute reference frame, the probe spot moves in the x direction by a distance L and in the y direction by a distance K during this period. Relative to the absolute reference frame, the direction of movement of the probe spot and the direction of movement of the sample have an angle θ=arctan(L / K).

[0059]

[0080] In the embodiment described above, it is necessary for the probe spots 310A-310D to make a "jump" of 10W in the -y direction relative to the absolute reference coordinate system at the end of the period T3. However, in some embodiments, no such jump is made at the end of the period T3. Instead, the four probe spots 310A-310D move continuously to the ends of the next adjacent sub-regions in the same manner as at the end of the periods T1 and T2. Specifically, referring to FIG. 3A, at the end of the period T3, the probe spot 310D moves to the -x end of the sub-region 303A previously scanned by the probe spot 310C, the probe spot 310C moves to the -x end of the sub-region 302A previously scanned by the probe spot 310B, the probe spot 310B moves to the -x end of the sub-region 301A previously scanned by the probe spot 310A, and the probe spot 310A moves to the -x end of the sub-region 304D adjacent to the sub-region 301C. In this way, each of the four probe spots 310A-310D examines the same sub-region separately, i.e. some sub-regions may be scanned four times by the primary beamlets, and frame averaging can therefore be performed to improve the signal-to-noise ratio of the sample image constructed using the multiple signals generated.

[0060]

[0081] Reference is now made to Figures 4A and 4B, which diagrammatically illustrate the use of multiple beams of charged particles to inspect a sample, according to an exemplary embodiment of the present disclosure. In the embodiment illustrated by Figures 4A and 4B, three primary beamlets may generate three probe spots 451, 452, and 453 on a sample (such as sample 208 in Figure 2). Figure 4A illustrates the movement of the three probe spots 451, 452, 453 relative to the sample. Figure 4B illustrates the movement of the three probe spots 451, 452, 453 and the sample relative to an absolute reference coordinate system. The three probe spots 451, 452, 453 may, but need not, be arranged in a line. For ease of explanation, two directions x and y are defined in the absolute reference coordinate system. The x and y directions are perpendicular to each other.

[0061]

[0082] In some embodiments, the scan area 460 of the sample to be inspected is rectangular in shape, but this is not necessarily the case. The scan area 460 of the sample may be divided into a number of scan lines 400, 401, 402, ..., 434, and 435. The width of the scan lines may match or be substantially similar to the width of the probe spots. In such embodiments, a scan line may be scanned and inspected by a probe spot. Although FIG. 4A shows 36 scan lines (scan lines 400-435), it will be understood that the scan area 460 may include any number of scan lines depending on the size of the scan area 460 and the width of the probe spots.

[0062]

[0083] In some embodiments, every three consecutive scan lines may be grouped together to form a scan section. For example, the first three scan lines 400, 401, 402 may form a scan section 471, the next three scan lines 403, 404, 405 may form a scan section 472, the next three scan lines 406, 407, 408 may form a scan section 473, and so on. In some embodiments, the three probe spots 451, 452, 453 may be positioned such that each probe spot scans only the corresponding scan line of the scan section. For example, as shown in FIG. 4A, probe spot 451 may be configured to scan the first scan line (far right) in the scan section, probe spot 452 may be configured to scan the second scan line (middle) in the scan section, and probe spot 453 may be configured to scan the third scan line (far left) in the scan section. Thus, in such an embodiment, probe spot 451 may scan 400, 403, 406, ..., 415 during periods T1, T2, T3, ..., T6, respectively, and so on, probe spot 452 may scan 404, 407, 410, ..., 423 during periods T1, T2, T3, ..., T6, respectively, and so on, and probe spot 453 may scan 408, 411, 414, ..., 423 during periods T1, T2, T3, ..., T6, respectively, and so on. While Figures 4A and 4B show the movement of the probe spots and sample during the first six periods (T1-T6), it will be understood that the sequence may continue until the sample has been completely scanned and inspected.

[0063]

[0084] In some embodiments, during each period, the sample may move in the y direction by a length K relative to the absolute reference coordinate system while the probe spots 451, 452, and 453 scan the scan lines. In such embodiments, the sample may not move in the x direction relative to the absolute reference coordinate system. Accordingly, during each period, the probe spots 451, 452, and 453, while moving in the x direction to scan the scan lines, may also move in the y direction at the same speed (e.g., speed K) as the sample, thereby following the movement of the sample as it scans the scan lines. After the scan is completed, the probe spots 451, 452, and 453 may move back in the -x and -y directions to the start of the next set of scan lines. In other embodiments, during each period, the probe spots 451, 452, and 453 may move only in the x direction, but not in the y direction, relative to the absolute reference coordinate system. Thus, in such embodiments, the scan lines may be angled relative to the sample away from the direction of sample movement (ie, not perpendicular to the y direction) to accommodate sample movement.

[0064]

[0085] For example, as shown in FIG. 4B, the sample may move 3W (i.e., the width of a scan section) per period (i.e., K=3W per period), thereby providing a new scan section for the probe spots in each period. In such an embodiment, during the first half of period T1, the probe spots 451, 452, 453 may also move 1.5W in the y direction while moving in the x direction to scan scan lines 400, 404, 408, respectively. After the scan is completed, during the second half of period T1, the probe spots 451, 452, and 453 may also move 1.5W in the -y direction to the start of the next set of scan lines (e.g., 403, 407, and 411) while moving back in the -x direction. In this way, after reaching the last pixel of a scan line, each probe spot crosses back to the start of the next scan line. During subsequent periods (e.g., T2, T3, ...), the probe spots 451, 452, 453 and the sample may repeatedly move in the same manner as during period T1. Thus, scan lines 403, 407, and 411 may be scanned during period T2, scan lines 406, 410, 414 may be scanned during period T3, and so on.

[0065]

[0086] In contrast to the embodiment described with respect to Figures 3A and 3B, in which the probe spots need to make a "jump" in the -y direction at the end of period T3, in the embodiment shown in Figures 4A and 4B, no such "jump" is required because each probe spot only scans its corresponding set of scan lines of the scan section. Instead of making a "jump", the probe spots 451, 452, and 453 may continuously repeat the motion described above to scan the scan lines while the sample is moving.

[0066]

[0087] In general, the sample migration speed K may be determined as follows: K=MW / period Equation (1) where M is the number of probe spots and W is the width of the probe spots. Furthermore, the pitch S of the probe spots may be determined as follows: S=(nM+1)×W Formula (2) where n is an integer equal to or greater than 2. In the example of Figures 4A and 4B, the number of probe spots is 3 (i.e., M=3) and n=1, so K=3W and S=4W per period. Although Figures 4A and 4B show an exemplary embodiment using three probe spots (i.e., M=3), it will be understood that any number of probe spots may be used to scan a sample.

[0067]

[0088] In some embodiments, some scan lines in the first two scan sections (e.g., scan sections 471 and 472) may not be scanned by the scan sequence described above. Thus, in some embodiments, scan area 460 may need to include buffer area 490 that does not need to be examined. In such embodiments, all scan lines (e.g., scan lines 406, 407, 408, 409, ..., etc.) except for the scan lines in buffer area 490 may be scanned continuously without gaps. Although only one buffer area (e.g., buffer area 490) is shown in Figures 4A and 4B, it will be understood that scan area 460 may include more than one buffer area. For example, another buffer area (not shown) may be included at the end of scan area 460 (e.g., the leftmost scan section).

[0068]

[0089] Reference is now made to Figures 5A and 5B, which diagrammatically illustrate the use of multiple beams of charged particles to inspect a sample, according to an exemplary embodiment of the present disclosure, which show an embodiment having the same scanning configuration as Figures 4A and 4B, except that the pitch S of the probe spots (e.g., the distance between probe spots 551 and 552 in Figure 5A) is larger in the embodiment shown in Figures 5A and 5B.

[0069]

[0090] Similar to FIG. 4A, the scan area 560 of the sample may be divided into multiple scan lines 500, 501, 502, ..., 534, and 535. The width of the scan lines may match or be substantially similar to the width of the probe spots. In such an embodiment, a scan line may be scanned and inspected by a probe spot. Although FIG. 5A shows 36 scan lines (scan lines 500-535), it will be understood that the scan area 560 may include any number of scan lines depending on the size of the scan area 560 and the width of the probe spots.

[0070]

[0091] In some embodiments, every three consecutive scan lines may be grouped together to form a scan section. For example, the first three scan lines 500, 501, 502 may form a scan section 571, the next three scan lines 503, 504, 505 may form a scan section 572, and so on. In some embodiments, the three probe spots 551, 552, 553 may be positioned such that each probe spot scans only the corresponding scan line of the scan section. For example, as shown in FIG. 5A, probe spot 551 may be configured to scan the first scan line (far right) in the scan section, probe spot 552 may be configured to scan the second scan line (middle) in the scan section, and probe spot 553 may be configured to scan the third scan line (far left) in the scan section. Thus, in such an embodiment, probe spot 551 may scan 500, 503, 506, ..., 521 during periods T1, T2, T3, ..., T8, respectively, and so on, probe spot 552 may scan 507, 510, 513, ..., 528 during periods T1, T2, T3, ..., T8, respectively, and so on, and probe spot 553 may scan 514, 517, 520, ..., 535 during periods T1, T2, T3, ..., T8, respectively, and so on. While Figures 5A and 5B show the movement of the probe spots and sample during the first eight periods (T1-T8), it will be understood that the sequence may continue until the sample has been completely scanned and inspected.

[0071]

[0092] Similar to the embodiment shown in Figures 4A and 4B, during each period, the sample may move in the y direction by a length K relative to an absolute reference coordinate system while the probe spots 551, 552, and 553 scan the scan lines. In such an embodiment, the sample may not move in the x direction relative to the absolute reference coordinate system. Accordingly, during each period, the probe spots 551, 552, and 553, while moving in the x direction to scan the scan lines, may also move in the y direction at the same speed (e.g., speed K) as the sample, thereby following the movement of the sample as it scans the scan lines. After the scan is completed, the probe spots 551, 552, and 553 may move back in the -x and -y directions to the start of the next set of scan lines.

[0072]

[0093] For example, as shown in FIG. 5B, the sample may move 3W (i.e., the width of a scan section) per period (i.e., K=3W per period), thereby providing a new scan section to the probe spots in each period. In such an embodiment, during the first half of period T1, the three probe spots 551, 552, 553 may also move 1.5W in the y direction while moving in the x direction to scan scan lines 500, 507, 514, respectively. After the scan is completed, during the second half of period T1, the probe spots 551, 552, and 553 may also move 1.5W in the -y direction to the start of the next set of scan lines (e.g., 503, 510, and 517) while moving back in the -x direction. In this way, after reaching the last pixel of a scan line, each probe spot crosses back to the start of the next scan line. During subsequent periods (e.g., T2, T3, ...), the probe spots 551, 552, 553 and the sample may repeatedly move in the same manner as during period T1. Thus, scan lines 503, 510, and 517 may be scanned during period T2, scan lines 506, 513, 520 may be scanned during period T3, and so on.

[0073]

[0094] 4A and 4B, in the embodiment shown in Figures 5A and 5B, there is no need to perform a "jump" because each probe spot only scans a corresponding set of scan lines of the scan section. Instead of performing a "jump," probe spots 551, 552, and 553 may continuously repeat the motion described above to scan the scan lines while the sample is moving.

[0074]

[0095] As described with respect to FIGS. 4A and 4B, the sample movement speed K may be determined as follows: K=MW / period Equation (3) where M is the number of probe spots and W is the width of the probe spots. Furthermore, the pitch S of the probe spots may be determined as follows: S=(nM+1)×W Equation (4) Here, n is an integer of 2 or more.

[0075]

[0096] 5A and 5B show an embodiment where the number of probe spots is 3 (i.e., M=3) and n=2. Thus, the speed K is equal to 3W per period and the pitch S is equal to 7W.

[0076]

[0097] In some embodiments, some scan lines in the first four scan sections (e.g., scan sections 571, 572, 573, and 574) may not be scanned by the scan sequence described above. Thus, in some embodiments, scan area 560 may need to include buffer area 590 that does not need to be examined. In such embodiments, apart from the scan lines in buffer area 590, all scan lines (e.g., scan lines 512, 513, 514, 515, ..., etc.) may be scanned continuously without gaps. Although only one buffer area (e.g., buffer area 590) is shown in Figures 5A and 5B, it will be understood that scan area 560 may include more than one buffer area. For example, another buffer area (not shown) may be included at the end of scan area 560 (e.g., the leftmost scan section).

[0077]

[0098] Reference is now made to FIG. 6, which illustrates a schematic diagram of inspecting a sample using multiple beams of charged particles, according to an exemplary embodiment of the present disclosure. Although FIGS. 4A, 4B, 5A, and 5B illustrate three probe spots (e.g., probe spots 451, 452, 453 in FIGS. 4A and 4B and probe spots 551, 552, 553 in FIGS. 5A and 5B) aligned in a row along the direction of movement of the sample (such as sample 208 in FIG. 2), the probe spots, and thus the primary beamlets, may have other spatial arrangements. In some embodiments, the multiple primary beamlets may be arranged in a matrix. For example, as shown in FIG. 6, nine probe spots 601, 602, ..., 609 may be arranged in a 3x3 matrix configuration. In such an embodiment, a first row of probe spots (601, 602, 603) may scan a first scan area 660A. Similarly, the second row (604, 605, 606) and the third row (607, 608, 609) may scan the second scan area 660B and the third scan area 660C, respectively. Although FIG. 6 shows that the probe spots of adjacent rows scan adjacent scan areas, it will be understood that the probe spots of adjacent rows may also scan non-adjacent scan areas. For example, the probe spots of the first row (601, 602, 603) may scan the first scan area 660A, while the probe spots of the second row (604, 605, 606) may scan the third scan area 660C.

[0078]

[0099] Similar to the embodiments shown above, a sample including scan areas 660A, 660B, and 660C may be constantly moved in the y direction with a velocity K relative to an absolute reference frame while scan lines within scan areas 660A, 660B, and 660C are simultaneously scanned by three rows of probe spots. In such an embodiment, each scan area (e.g., 660A, 660B, or 660C) may be scanned in the same manner as described with respect to Figures 4A and 4B.

[0079]

[0100] As described with respect to FIG. 4A and FIG. 4B, some scan lines in the first two scan sections (e.g., scan sections 671 and 672) may not be scanned by the scan sequence described above. Thus, in some embodiments, scan areas 660A, 660B, and 660C may need to include a buffer area 690 that does not need to be examined. In such embodiments, apart from the scan lines in buffer area 690, all scan lines (e.g., scan lines in scan sections 673, 674, 675, ..., etc.) may be scanned continuously without gaps. Although only one buffer area (e.g., buffer area 690) is shown in FIG. 6, it will be understood that scan areas 660A, 660B, and 660C may include two or more buffer areas. For example, another buffer area (not shown) may be included at the end of scan areas 660A, 660B, and 660C (e.g., the leftmost scan section).

[0080]

[0101] Although FIG. 6 shows a primary beamlet configuration with nine probe spots 601-609 arranged in a 3×3 matrix, it will be understood that the principles disclosed herein may be applied to any number and configuration of primary beamlets, such as primary beamlets arranged in a 3×2, 4×4, 5×5, 3×5, 8×5, 20×20, or any size matrix configuration.

[0081]

[0102] Reference is now made to Figure 7, which is a flow diagram illustrating steps of an exemplary multi-beam scanning method consistent with embodiments of the present disclosure, which may be performed by a multi-beam electron beam tool (such as electron beam tool 40 of Figure 1).

[0082]

[0103] In step 710, the multi-beam electron beam tool delivers N charged particle beamlets to a surface of an area of ​​a sample under inspection (such as sample 208 in FIG. 2), which generate N probe spots on the sample (such as probe spots 451, 452, and 453 in FIG. 4A). In some embodiments, the scan area of ​​the sample may be divided into multiple scan lines (such as scan lines 400, 401, 402, ..., 435 in FIG. 4A), and every N consecutive scan lines may be grouped to form a scan section. For example, as shown in FIG. 4A where three probe spots are used, the first three scan lines 400, 401, 402 may form scan section 471, the next three scan lines 403, 404, 405 may form scan section 472, and so on.

[0083]

[0104] In step 720, the multi-beam electron beam tool controls a motorized sample stage (such as motorized stage 209 of FIG. 2) to move the sample in a first direction while the sample is scanned and inspected. In some embodiments, the sample may move continuously at a constant speed. In other embodiments, the speed of sample movement may vary over time depending on the step of the scanning process. It will be appreciated that step 720 may occur before step 710, or the operations of steps 710 and 720 may be initiated simultaneously.

[0084]

[0105] In steps 730 and 740, the multi-beam electron beam tool deflects the N charged particle beamlets to move the N probe spots over the surface of the sample to scan the scan line. For example, during each period, the multi-beam electron beam tool moves the N probe spots in a second direction (such as the x direction in FIGS. 4A and 4B) to scan the scan line while also moving them in a first direction (i.e., the direction of sample movement, such as the y direction in FIGS. 4A and 4B) at the same speed as the sample (e.g., speed K) to thereby follow the movement of the sample while scanning the scan line. After the scan is completed, the N probe spots may move back to the start of the next set of scan lines.

[0085]

[0106] In some embodiments, the N probe spots are positioned such that each probe spot scans a corresponding scan line of the scan section. For example, a first probe spot (such as probe spot 451 in FIG. 4A) may be configured to scan only the first scan line of the scan section, a second probe spot (such as probe spot 452 in FIG. 4A) may be configured to scan only the second scan line of the scan section, and similarly, an Nth probe spot may be configured to scan only the Nth scan line of the scan section. In this way, the multi-beam electron beam tool does not need to make large "jump" movements because each probe spot scans only a corresponding set of scan lines with little, if any, overlap. Instead of making "jumps," the N probe spots may continuously repeat the above-mentioned movements along the scan lines of the sample while the sample is moving in the first direction.

[0086]

[0107] Although Figures 3A and 3B show four probe spots 310A-310D aligned in a row along the direction of sample movement, the probe spots, and therefore the primary beamlets, may have other spatial arrangements. For example, multiple primary beamlets may be arranged in a matrix, as shown in Figures 8A and 8B. Figure 8A is a schematic diagram illustrating the distribution of multiple primary beamlets (e.g., primary beamlets 211, 212, and 213 in Figure 2) on the surface of the sample before and after rotating the primary beamlets about an optical axis (e.g., primary optical axis 204 in Figure 2) consistent with embodiments of the present disclosure. Figure 8B is a schematic diagram illustrating the scan pattern of multiple primary beamlets on the surface of the sample before and after rotation consistent with embodiments of the present disclosure. Although Figures 8A and 8B show four probe spots (or primary beamlets) arranged in a 2 x 2 matrix, it is contemplated that the principles disclosed herein may be applied to any number of primary beamlets, such as primary beamlets arranged in a 3 x 3, 4 x 5, 5 x 5, or 20 x 20 matrix.

[0087]

[0108] 8A and 8B, four probe spots 810A-810D may be initially arranged in a 2x2 matrix, with each column of the matrix aligned with the direction of sample movement (see left side of Figs. 8A and 8B). Each of the probe spots 810A-810D may perform an xy scan of a portion of an area 800 on the sample in a manner similar to that shown in Figs. 3A-3D. Consistent with disclosed embodiments, the four probe spots 810A-810D may be rotated relative to the sample such that each of the four probe spots 810A-810D may move on non-overlapping scan lines (see right side of Figs. 8A and 8B). Adjacent scan lines may be separated by a distance corresponding to the pixel size of an image generated by the electron beam tool. This rotation may be achieved by, but is not limited to, controlling the deflection scanning unit 232 of FIG. 2 to rotate the primary beamlets, or by repositioning the array of imaging elements in the electron beam tool 40, or by rotating the sample. After the rotation, each of the probe spots 810A-810D may move on a longer scan line without overlapping. Since the time for the probe spots to switch scan lines is fixed, the time overhead associated with each scan line may be reduced and the overall throughput of the electron beam tool 40 may be improved.

[0088]

[0109] As shown by the right side of FIG. 8B, after the beam rotation, the four probe spots 810A-810D are no longer aligned along the sample movement direction. Therefore, the actual area scanned by the four probe spots 810A-810D (area covered by the scan lines) is larger than the field of view of the electron beam tool. Specifically, in FIG. 8B, area 800 is the area imaged by the electron beam tool. Each of scan lines 1, 2, 3, 4, ..., is longer than the width of area 800, so that all scan lines can collectively cover area 800.

[0089]

[0110] 9 is a schematic diagram showing a method for selecting a rotation angle for the rotation process shown in FIGs. 8A and 8B, consistent with an embodiment of the present disclosure. For illustrative purposes only, FIG. 9 shows nine probe spots 1, 2, 3, 4, ..., 9 arranged in a matrix. Before rotation occurs, the probe spots have a pitch size S along the direction of sample movement. After the pattern of probe spots is rotated by an angle, the beam distance D along the direction of movement has the following relationship: D 12 =D 23 =D 45 =D 56 =D 78 =D 89 =Ssinφ Equation (5) D 34 =D 67 =Scosφ-2Ssinφ Formula (6)

[0090]

[0111] Consistent with the disclosed embodiments, one rotation angle φ can cause the probe spots to have the same beam distance D along the translation direction, i.e. D 12 =D 34 Formula (7) The above equations (5) to (7) yield: Scosφ-2Ssinφ=Ssinφ Formula (8) Therefore,

number

[0091]

[0112] To generalize the above calculation to probe spots (i.e., primary beamlets) arranged in an M × N matrix (i.e., a matrix with M rows and N columns, where the columns of the matrix are initially aligned with the sample motion direction), the beam distance D along the motion direction needs to satisfy: D 1、2 =D N、N+1 Formula (10) In addition, the rotation angle must satisfy the following: Scosφ-(N-1)Ssinφ=Ssinφ Formula (11) Therefore, the appropriate rotation angle φ is:

number

[0092]

[0113] In some embodiments, it may be preferred that the probe spots are arranged in an N×N matrix or in a hexagonal shape to achieve a better fill factor for the round, optically aberration-free zone of each probe spot. Nevertheless, the rotation angle is

number

[0093]

[0114] Figure 10 is a flow diagram of a multi-beam scanning method 1000 consistent with the embodiments shown in Figures 8A, 8B, and 9. For example, method 1000 may be used in electron beam tool 40 to improve system throughput. With reference to Figure 10, method 1000 includes the following steps.

[0094]

[0115] In step 1010, an electron beam tool (e.g., electron beam tool 40 of FIGS. 1 and 2) generates an array of primary beamlets and projects them onto the surface of a sample (e.g., sample 208 of FIG. 2). The primary beamlets form an array of probe spots within the area to be inspected. The array of probe spots forms a predetermined pattern, such as an N×N matrix. In some embodiments, each column of the N×N matrix may be aligned with the direction of movement of the sample.

[0095]

[0116] In step 1020, the electron beam tool rotates the array of primary beamlets around the primary optical axis of the electron beam tool (e.g., primary optical axis 204 in FIG. 2). This rotation may be performed in a manner similar to that described in FIG. 9. The rotation is performed relative to the sample. In various embodiments, the electron beam tool may perform the rotation by controlling the deflection scanning unit 232 to rotate the primary beamlets, or by repositioning an array of imaging elements in the electron beam tool 40, or by rotating the sample. The rotation angle may be determined, among other things, by:

number

[0096]

[0117] In step 1030, the electron beam tool deflects the array of primary beamlets to scan across the field of view of the tool. As the beam is rotated, the array of primary beamlets may be able to scan along longer scan lines with no overlap, as shown in Figure 8B and on the right side of Figure 11. Adjacent scan lines may be separated by a distance corresponding to the pixel size of the image produced by the electron beam tool.

[0097]

[0118] In step 1040, after the area of ​​the sample under the field of view has been scanned, the e-beam tool moves an unscanned area of ​​the sample into the field of view. For example, as shown in FIG. 3A, at the end of T3, the probe spots 310A-310D may move to the next unscanned area, including sub-regions 301D, 302D, 303D, 304D, etc. Thus, step 1030 may be repeated to continue scanning the unscanned areas.

[0098]

[0119] In the disclosed embodiment, steps 1030 and 1040 may be repeated until the entire sample is inspected. Thus, the electron beam tool may need to operate in a "step-and-scan" mode, in which the sample stage (e.g., motorized stage 209) remains in one position while deflecting the array of primary beamlets to scan areas that are within the field of view (step 1030), and then moves (or "steps") to the next position such that areas not yet scanned "jump" (step 1030) into the field of view of the electron beam tool. For example, a 10W movement in the -y direction may be achieved by moving the sample in the y direction at the end of period T3, as described in connection with Figures 3A and 3B. However, in the "step-and-scan" mode, the scan involves repeatedly waiting for the sample stage to step and settle, so that the "step-and-scan" mode is typically slower than the "continuous scan" mode, in which the sample stage moves continuously at a slower speed while deflecting the primary beamlets to scan the sample.

[0099]

[0120] To enable the beam rotation methods described above to be used in a faster "continuous scan" mode, the rotated primary beamlets may be configured to scan the sample using an interlaced scan pattern as described in Figure 11, which shows an exemplary multi-beam interlaced scan pattern consistent with embodiments of the present disclosure. As shown in Figure 11, after the probe spots 810A-810D in Figures 8A and 8B are rotated, the e-beam tool may control the primary beamlets as follows: probe spot 810A moves along scan lines 1, 5, 9, 13, 17, etc.; probe spot 810B moves along scan lines 2, 6, 10, 14, 18, etc.; probe spot 810C moves along scan lines 3, 7, 11, 15, 19, etc.; and probe spot 810D moves along scan lines 4, 8, 12, 16, 20, etc. These scan lines are substantially parallel to each other. In this way, the probe spots 810A-810D can be moved between different scan lines while the sample stage is moving continuously. By using such a technique, large "jumps" in the sample stage can be avoided.

[0100]

[0121] The right side of FIG. 11 shows an exemplary movement trajectory of the probe spot relative to the absolute reference coordinate system. This trajectory can be divided into four phases. In phase 1, the probe spot follows the movement of the sample and scans along a first direction. In phase 2, the probe spot moves in the opposite direction to the movement of the sample to reach the start of the second scan line. In phase 3, the probe spot follows the movement of the sample and scans along a second direction. In phase 4, the probe spot moves in the opposite direction to the movement of the sample to reach the start of the third scan line. These four phases are repeated during interlaced scanning.

[0101]

[0122] Figure 12 illustrates exemplary motion trajectories of probe spots 810A-810D relative to a sample during an interlaced scan consistent with the embodiment illustrated in Figure 11. Referring to Figure 12, motion trajectories 81, 82, 83, and 84 correspond to probe spots 810A-810D, respectively. Each of motion trajectories 81, 82, 83, and 84 has a continuous pattern formed during successive motions of the sample.

[0102]

[0123] Although in the above-described embodiments, interlaced scanning is used in conjunction with beam rotation, it is contemplated that interlaced scanning may also be applied to multi-beam scanning without beam rotation. FIG. 13 is a schematic diagram illustrating a multi-beam interlaced scan pattern without beam rotation consistent with an embodiment of the present disclosure. Referring to FIG. 13, the probe spots 810A-810D are arranged in a 2×2 matrix, and each column of the matrix is ​​aligned with the direction of movement of the sample. That is, the pattern of the probe spots 810A-810D is not rotated with respect to the sample. As the sample moves continuously along a particular direction (e.g., the downstream direction as shown in FIG. 13), the area in the region 800 that has not yet been scanned first enters the field of view of the probe spots 810A and 810B, and then enters the field of view of the probe spots 810C and 810D. Each of the probe spots 810A-810D may form a scan line on the region 800. By appropriately controlling the beam distance between the probe spots 810A and 810C along the sample moving direction, i.e., the beam pitch, the scan line formed by the probe spots 810A and 810C can have an interlaced pattern. Similarly, by appropriately controlling the beam distance between the probe spots 810B and 810D along the sample moving direction, i.e., the beam pitch, the scan line formed by the probe spots 810B and 810D can have an interlaced pattern. With interlaced scanning, multi-beam scanning can be combined with a high-speed "continuous scan mode" with or without beam rotation. Thus, the throughput of the system is improved. Furthermore, since beam rotation is not required, the complexity of the detector (e.g., the electronic detector 240 in FIG. 2) associated with beam rotation can be avoided.

[0103]

[0124] Figure 14 is a flow diagram of a multi-beam interlaced scanning method 1400 consistent with the embodiments shown in Figures 11-13. For example, the method 1400 may be used in an electron beam tool 40 to improve system throughput. With reference to Figure 14, the method 1400 includes the following steps:

[0104]

[0125] In step 1410, an electron beam tool (e.g., electron beam tool 40 of FIGS. 1 and 2) generates and projects an array of N primary beamlets onto a surface of a sample (e.g., sample 208 of FIG. 2), where N is an integer greater than or equal to 2. The primary beamlets form an array of N probe spots within the area to be inspected.

[0105]

[0126] In step 1420, the electron beam tool controls the sample to move continuously. For example, the electron beam tool may control a stage (e.g., motorized stage 209 of FIG. 2) to move the sample continuously.

[0106]

[0127] In step 1430, as shown in FIGS. 11-13, the electron beam tool deflects the N primary beamlets to simultaneously i) follow the movement of the sample and ii) scan N scan lines across the surface of the sample, respectively.

[0107]

[0128] In step 1440, after the N scan lines have been scanned, the electron beam tool deflects the N primary beamlets relative to the sample by N scan lines in a direction opposite to the direction of sample movement, such that the probe spots formed by the primary beamlets reach the beginning of a new group of scan lines. Consistent with disclosed embodiments, steps 1430 and 1440 are repeatedly performed to form an interlaced scan pattern, such as the interlaced scan patterns shown in Figures 11-13.

[0108]

[0129] As mentioned above, to form an interlaced scan pattern, it may be necessary to carefully space the primary beamlets or corresponding probe spots. For example, with a beam pitch of 10 μm, it may be necessary to limit the beam alignment error to within 1 nm to avoid undesirable gaps between adjacent probe spots that would leave parts of the sample unscanned. To relax the requirements on beam alignment, in some embodiments, a semi-interface scan may be used.

[0109]

[0130] FIG. 15 is a schematic diagram illustrating a multi-beam semi-interlaced scan pattern consistent with an embodiment of the present disclosure. As shown in FIG. 15, each of the probe spots 810A-810D may first perform a continuous xy scan (e.g., scan multiple scan lines) within a small area while the sample stage moves continuously. After the xy scan is completed, the sample makes a small "jump" to move to the next unscanned area within the field of view of the probe spots 810A-810D. Thus, the area scanned by the probe spots 810A and 810C may form an interlaced pattern, and the area scanned by the probe spots 810B and 810D may form an interlaced pattern.

[0110]

[0131] Semi-interfaced scanning uses appropriate spacing between probe spots 810A and 810C, and between probe spots 810B and 810D. However, compared to interlaced scanning, beam alignment is less important in semi-interfaced scanning because the interlaced areas can overlap somewhat. Furthermore, compared to the typical "step-and-scan" mode, in semi-interfaced scanning, the sample stage makes relatively small "jumps" and therefore takes less time to jump and settle. Thus, semi-interfaced scanning may improve the throughput of the system.

[0111]

[0132] 16 is a flow diagram of a multi-beam semi-interlaced scanning method consistent with an embodiment of the present disclosure. For example, the method 1600 may be used in an e-beam tool (e.g., e-beam tool 40 of FIGS. 1 and 2) to improve system throughput. With reference to FIG. 16, the method 1600 includes the following steps:

[0112]

[0133] In step 1610, the electron beam tool generates and projects an array of N primary beamlets onto a surface of a sample (e.g., sample 208 in FIG. 2), where N is an integer greater than or equal to 2. The primary beamlets form an array of N probe spots within the area to be inspected.

[0113]

[0134] In step 1620, the electron beam tool controls the sample to move continuously. For example, the electron beam tool may control a stage (e.g., motorized stage 209 of FIG. 2) to move the sample continuously.

[0114]

[0135] In step 1630, as shown in Figure 15, the electron beam tool deflects the N primary beamlets to simultaneously i) follow the movement of the sample and ii) scan a set of M scan lines within the field of view of each beamlet across the surface of the sample, respectively, where M is an integer greater than or equal to 2.

[0115]

[0136] In step 1640, after the N primary beamlets have scanned a set of M scan lines within their respective fields of view, the e-beam tool moves the sample to expose areas not yet scanned to the fields of view of the N primary beamlets, as shown in Figure 15. In some embodiments, the e-beam tool moves the sample by M scan lines. In this manner, the areas scanned by the primary beamlets can form an interlaced pattern.

[0116]

[0137] Consistent with disclosed embodiments, steps 1630 and 1640 are performed repeatedly to produce an interlaced scan pattern similar to that shown in Figure 15. Additionally, the semi-interlaced scanning process illustrated by Figures 15 and 16 may be used with or without beam rotation.

[0117]

[0138] As mentioned above, the continuous scan mode can usually achieve a faster speed and therefore a higher throughput than the step-and-scan mode. FIG. 17 is a schematic diagram showing the distribution of multiple primary beamlets in the continuous scan mode, consistent with an embodiment of the present disclosure. Referring to FIG. 17, an e-beam tool (e.g., e-beam tool 40 of FIGS. 1 and 2) may have nine primary beamlets 171, 172, 173, ..., and 179. In some embodiments, the nine primary beamlets may be aligned in a straight line perpendicular to the sample movement direction and separated by equal intervals (see the left side of FIG. 17) to enable the e-beam tool to be applied in the continuous scan mode. In this way, each primary beamlet can scan the sample continuously without jumping. However, as described above in connection with FIGS. 8A and 8B, under this arrangement, the fields of view of the probe spots overlap, and therefore the throughput of the system is not maximized. To improve the throughput of the system, some or all of the primary beamlets may be repositioned relative to other primary beamlets along the direction of sample movement (see the right side of FIG. 17) so that the beam distance along the direction perpendicular to the sample is effectively increased. In this way, each primary beamlet can scan a longer scan line, similar to the beam rotation shown in FIGS. 8A and 8B. Furthermore, the electron beam tool may control the repositioned primary beamlets to perform an interlaced scan in a manner similar to that shown in FIGS. 7 and 8 so that the electron beam tool continues to operate in a continuous scan mode.

[0118]

[0139] The embodiment of Fig. 17 may also be adapted to include multiple primary beamlets aligned along the sample movement direction. For example, referring to Fig. 18, the electron beam tool may further include primary beamlets 181-189 aligned along the sample movement direction with the primary beamlets 171-179, respectively, and separated from the primary beamlets 171-179 by an equal distance along the sample movement direction. Each pair of primary beamlets aligned along the sample movement direction may be controlled to perform semi-interlaced scanning in a manner similar to that shown in Fig. 15 to reduce or avoid large jumps. Alternatively, the group of primary beamlets 171-179 and the group of primary beamlets 181-189 may perform interlaced scanning separately (not shown in Fig. 18), in which case each pair of primary beamlets aligned along the sample movement direction may successively scan the same area, and thus frame averaging may be performed.

[0119]

[0140] Reference is now made to Figure 19, which is a schematic diagram illustrating an example scan pattern using a set of rotated primary beamlets consistent with embodiments of the present disclosure. As previously mentioned, to achieve higher system throughput, it is desirable for each primary beamlet to scan a longer scan line. The throughput of the inspection system can also be increased by maintaining a continuous, constant motion of the sample during inspection (e.g., the continuous scan mode described in the previous section).

[0120]

[0141] FIG. 19 illustrates a multi-beam inspection system having a 3×3 array of primary beamlets generating nine probe spots 1901, 1902, ..., 1909 arranged in a 3×3 matrix configuration. As in the previous embodiment, a sample (e.g., sample 208 in FIG. 2) may be moved in the y-direction at a constant velocity K while the sample is scanned by the 3×3 array of probe spots 1901-1909. In some embodiments, the 3×3 array of primary beamlets may be rotated by an angle relative to the sample movement direction. The rotation angle may be determined by the number of primary beamlets in a row (e.g., 3 for a 3×3 array configuration), as described in equation (12) with respect to FIG. 9. In some embodiments, the sample may be rotated by the rotation angle, such that the probe spots are effectively rotated relative to the sample movement direction. In some embodiments, the beamlets and sample may be rotated simultaneously, such that the beamlets are rotated by the rotation angle relative to the sample movement direction.

[0121]

[0142] In some embodiments, the probe spots 1901-1909 may scan the sample in a direction perpendicular to the direction of sample movement. For example, the probe spots 1901-1909 may scan in the x-direction as indicated by arrows 1921-1929 while the sample moves in the y-direction. In such embodiments, the scan width of the primary beamlets may be determined by how widely each primary beamlet can scan the sample without causing too much overlap between the areas scanned by adjacent primary beamlets (e.g., the range of movement of the probe spot 1901 as indicated by the length of arrow 1921). Although this rotated beamlet configuration can support a continuous scan mode, this relatively short x-direction scan width may limit the improvement of the system throughput because the overhead of the scan pattern (e.g., the relative proportion of non-scanning beam movement to scanning beam movement) may be significantly high.

[0122]

[0143] In some embodiments, the probe spots 1901-1909 may scan the sample in a direction parallel to the direction of sample movement. For example, the probe spots 1901-1909 may move in the y-direction as shown by arrows 1931-1939 while the sample also moves in the y-direction. In such embodiments, the scan width of the primary beamlets is not limited by the configuration (e.g., pitch or rotation angle) of the primary beamlets because increasing the scan width does not result in overlap between areas scanned by adjacent beamlets. Increasing the scan width may also improve the throughput of the system because the overhead of the scan pattern may be significantly reduced.

[0123]

[0144] Although FIG. 19 shows a primary beamlet configuration with nine probe spots 1901-1909 arranged in a 3×3 matrix, it will be understood that the principles disclosed herein may be applied to any number and configuration of primary beamlets, such as primary beamlets arranged in a 3×2, 4×4, 5×5, 3×5, 8×5, 20×20, or any size matrix configuration.

[0124]

[0145] 20A, 20B, 20C, and 20D, which are schematic diagrams illustrating an exemplary multi-beam scan pattern using rotated primary beamlets as shown in FIG. 19, consistent with embodiments of the present disclosure. In some embodiments, the scan direction of probe spots 1901-1909 is parallel to the sample movement direction. In such embodiments, each probe spot scans multiple scan sections disposed along the sample movement direction. For example, as shown in FIG. 20A, a first row of scan sections (e.g., scan sections 2011, 2021, etc.) may be scanned by a primary beamlet corresponding to probe spot 1901. Similarly, a second row of scan sections (e.g., scan sections 2012, 2022, etc.) may be scanned by a primary beamlet corresponding to probe spot 1902. Similarly, the scan sections of the third, fourth, fifth, sixth, seventh, eighth, and ninth rows may be scanned by probe spots 1903, 1904, 1905, 1906, 1907, 1908, and 1909, respectively.

[0125]

[0146] In some embodiments, each scan section is scanned using a raster scan pattern. For example, within section 2011, the probe spot 1901 scans a scan line through a scan route 2071, and then follows a return route 2072 back to the other side to start scanning the next scan line. These steps may be performed repeatedly until all scan lines of the scan section have been scanned. Although FIG. 20A shows a raster scan pattern within each scan section, it will be understood that any other scanning method may be used to scan each scan section. For example, in some embodiments, the probe spot 1901 may scan back in the opposite direction, e.g., from right to left and back to left to right.

[0126]

[0147] In some embodiments, the probe spots 1901-1909 may first scan a first set of scan sections (e.g., scan sections 2011, 2012, 2013, ..., 2019). After completing the scan of the first set of scan sections, the probe spots 1901-1909 may be repositioned to prepare to scan a second set of scan sections (e.g., scan sections 2021, 2022, 2023, ..., 2029). As shown in FIG. 20B, repositioning the primary beamlets may include moving each probe spot from where the first set of scans ended to where the second set of scans begins, as indicated by arrows 2081, 2082, 2083, ..., 2089. After repositioning, the probe spots 1901-1909 may begin scanning the second set of scan sections. In some embodiments, the steps of scanning and repositioning may be repeated until the entire sample area of ​​interest has been scanned and inspected. Although FIG. 20B shows the first set of scans ending at the right-most corner, it will be appreciated that the end point of the scans may vary depending on the various scan patterns used. For example, as described in the previous section, if the opposite direction is used for scanning and backtracking (e.g., scanning from right to left and backtracking from left to right), the first set of scans may end at the left-most corner. In such cases, the relocation distance may be shorter.

[0127]

[0148] To avoid gaps in scanned data between adjacent scan sections (e.g., between scan sections 2011 and 2021) that may be introduced during repositioning of the primary beamlets, adjacent scan sections may partially overlap. For example, as shown in FIG. 20C, scan sections 2011 and 2021 may partially overlap, thereby generating overlap region 2091. Similarly, scan sections 2012 and 2022 may generate overlap region 2092. These overlap regions may be scanned more than once. For example, overlap region 2091 may be scanned first during a scan of scan section 2011 and then a second time during a scan of scan section 2021. A controller (e.g., controller 50 of FIG. 2) may collect scan data including multiple scan data from each overlap region and process the scan data to generate successive images of the sample for inspection.

[0128]

[0149] In some embodiments, the scanning and repositioning steps may be performed while a stage holding the sample is moving continuously at a constant speed. In such embodiments, the movement of the probe spot may be adjusted to accommodate the continuous movement of the stage. For example, FIG. 20D shows the movement of the probe spot 1901 over time relative to a fixed position of a multi-beam inspection tool when scanning is performed while the sample is moving continuously in the y direction. In such a situation, the routes of the beamlets for the scanning (e.g., scan route 2071) and backtracking (e.g., backtracking route 2072) steps may be adjusted to accommodate the movement of the stage. For example, the scan route 2071 may be lengthened because the sample is also moving in the same direction. The backtracking route 2072 may be shortened because the sample is moving in the opposite direction to the backtracking direction, e.g., the sample may have moved further to the right by the time the probe spot 1901 returns to the left side.

[0129]

[0150] As described with respect to previous embodiments, in some embodiments the controller controls the movement of the primary beamlets and stage such that the primary beamlets simply repeat a certain movement pattern. By controlling the speed of scanning, backtracking, repositioning, and stage movement, the controller can cause the probe spot 1901 to continuously repeat a movement pattern such as that shown in FIG. 20B.

[0130]

[0151] For example, with respect to FIG. 20D, at T1, the probe spot 1901 is positioned at position A to start scanning the scan section 2011. During the period from T1 to T2, the probe spot 1901 scans and moves back and forth while the sample moves continuously in the y direction until the probe spot 1901 completes scanning the last scan line of the section. At T2, the probe spot 1901 reaches position B at the completion of scanning the scan section 2011. During the period from T2 to T3, the probe spot 1901 is repositioned back to position A while the sample moves continuously in the y direction. At T3, the probe spot 1901 is repositioned back to position A. At the same time, at T3, the next scan section (e.g., scan section 2021) may be approaching and the top left corner of the scan section 2021 (where scanning within the section begins) may be aligned with position A. Thus, in such a scenario, the probe spot 1901 may simply continuously repeat this movement pattern between position A and position B, as shown in Figure 20D. This repeated movement of the probe spot 1901 may cause the scan sections of the corresponding row (e.g., scan sections 2011, 2021, 2031, etc.) to be successively scanned by the probe spot 1901.

[0131]

[0152] Although Figures 20A, 20B, and 20C show a primary beamlet configuration with nine probe spots 1901-1909 arranged in a 3 x 3 matrix, it will be understood that the principles disclosed herein may apply to any number and configuration of primary beamlets, such as primary beamlets arranged in a 3 x 2, 4 x 4, 5 x 5, 3 x 5, 8 x 5, 20 x 20, or any size matrix configuration.

[0132]

[0153] The embodiments may be further described using the following clauses. Clause 1. A multi-beam tool comprising: a beam configuration system including a charged particle source for generating a primary beam of charged particles, a stage for holding the sample, and a deflector system between the charged particle source and the stage configured to split the primary beam into an array of beams; A multi-beam tool, wherein the beam configuration system is configured to provide a rotated beam configuration with a rotation angle determined based on the number of beams in a row of the array of beams. Clause 2. The array of beams is arranged about an optical axis of the multi-beam tool; 2. The multi-beam tool of claim 1, wherein the rotating beam configuration includes a stage configured to rotate about an optical axis. Clause 3. The array of beams is arranged about an optical axis of the multi-beam tool; 2. The multi-beam tool of claim 1, wherein the rotating beam configuration includes a deflector system configured to rotate the array of beams about an optical axis. Clause 4. The multi-beam tool is configured to generate an image of a surface area of ​​the sample; 4. A multi-beam tool as described in any one of clauses 1 to 3, wherein the rotating beam configuration enables the array of beams to scan an area larger than the surface area to be imaged. Clause 5. The stage is configured to move along a first direction; A multi-beam tool as described in any one of clauses 1 to 4, wherein scanning the array of beams across the field of view includes scanning the array of beams along a second direction through a set of scan lines that cover the field of view. Clause 6. The multi-beam tool of clause 5, wherein the second direction is substantially perpendicular to the first direction relative to the sample. Clause 7. The multi-beam tool of clause 5, wherein the second direction is substantially parallel to the first direction relative to the sample. Clause 8. A multi-beam tool as described in any one of clauses 5 to 7, wherein the set of scan lines are spaced apart a distance corresponding to the pixel size of an image produced by the multi-beam tool. Clause 9. A multi-beam tool as described in any one of clauses 1 to 8, wherein the beam configuration system further includes a controller coupled to the stage, the controller configured to control movement of the stage. Clause 10. A multi-beam tool as described in any one of clauses 1 to 9, wherein the beam configuration system further includes a controller coupled to the deflector system, the controller configured to control the deflector system to deflect the array of beams. Clause 11. A multi-beam tool comprising: a beam configuration system including a charged particle source for generating a primary beam of charged particles, a stage configured to hold the sample and configured to move in a first direction, and a deflector system between the charged particle source and the stage, the beam configuration system comprising: splitting the primary beam into n beams, where n is an integer and n>=2; rotating the n beams relative to a first direction such that the n beams are spaced apart along the first direction; A multi-beam tool configured to deflect n beams to simultaneously i) follow the movement of a stage and ii) scan one or more sets of n scan lines across a surface of the sample. Clause 12. The one or more sets of n scan lines include a first set of n scan lines extending over a first distance along a first direction; The beam construction system further comprises: offsetting the n beams a first distance along a direction opposite to the first direction after the first set of n scan lines have been scanned; 12. The multi-beam tool of claim 11, configured to deflect the n beams to simultaneously i) follow the movement of the stage and ii) scan a second set of n scan lines across the surface of the sample. Clause 13. A multi-beam tool as described in clause 12, wherein the first and second sets of n scan lines are substantially parallel lines. Clause 14. A multi-beam tool as described in any one of clauses 12 and 13, wherein each of the first and second sets of n scan lines are spaced apart a distance corresponding to the pixel size of the image generated by the multi-beam tool. Clause 15. A multi-beam tool described in any one of clauses 11 to 14, wherein one or more sets of n scan lines are aligned along a second direction substantially perpendicular to the first direction relative to the sample. Clause 16. A multi-beam tool described in any one of clauses 11 to 14, wherein one or more sets of n scan lines are aligned along a second direction substantially parallel to the first direction relative to the sample. Clause 17. n beams are projected onto a surface of a sample to form n probe spots on the surface; 17. The multi-beam tool of any one of clauses 11 to 16, wherein the n beams following the movement of the stage includes the n probe spots moving in the first direction at the same speed as the stage. Clause 18. A multi-beam tool according to any one of clauses 11 to 17, wherein the stage moves at a constant speed. Article 19. The beam construction system is 19. A multi-beam tool as described in any one of clauses 11 to 18, configured to rotate the n beams by a rotation angle determined based on the number of beams in the row of n beams. Clause 20. n beams are arranged around an optical axis of a multi-beam tool, 20. The multi-beam tool of claim 19, wherein the beam configuration system is configured to rotate the n beams includes the beam configuration system being configured to rotate a stage about an optical axis. Clause 21. n beams are arranged around an optical axis of the multi-beam tool, 20. The multi-beam tool of claim 19, wherein the beam configuration system configured to rotate the n beams includes a deflector system configured to rotate the n beams about an optical axis. Clause 22. A multi-beam tool as described in any one of clauses 11 to 21, wherein the beam configuration system further includes a controller coupled to the stage, the controller configured to control movement of the stage. Clause 23. A multi-beam tool described in any one of clauses 11 to 22, wherein the beam configuration system further includes a controller coupled to the deflector system, the controller configured to control the deflection of the n beams. Clause 24. A multi-beam tool comprising: a beam configuration system including a charged particle source configured to generate a primary beam of charged particles, a stage configured to hold the sample and configured to move in a first direction, and a deflector system between the charged particle source and the stage configured to split the primary beam into an array of beams; The beam construction system is deflecting the array of beams via a deflector system to i) scan a first set of scan lines within a field of view of the beam configuration system; and ii) following the movement of the stage during the scanning of the first set of scan lines, where the first set of scan lines span a first distance along a first direction; moving the stage a first distance in a first direction after the first set of scan lines has been scanned; Deflecting the array of beams via a deflector system to i) scan a second set of scan lines within a field of view of the beam configuration system, and ii) follow the movement of the stage during the scanning of the second set of scan lines; The multi-beam tool is configured to move the stage in a first direction as the first and second sets of scan lines are scanned. Clause 25. The array of beams includes a first beam, a beam configuration system configured to deflect an array of beams via a deflector system to i) scan a first set of scan lines within a field of view of the beam configuration system, and ii) follow the movement of the stage during the scanning of the first set of scan lines; deflecting the first beam to simultaneously i) follow the movement of the stage and ii) scan the first scan line; deflecting the first beam a predetermined distance along a direction opposite to the first direction after the first scan line has been scanned; 25. A multi-beam tool as described in clause 24, comprising a beam configuration system configured to deflect the first beam to simultaneously i) follow the movement of the stage and ii) scan the second scan line. Clause 26. The beam forming system further comprises: configured to project the array of beams onto a surface of the sample to form an array of probe spots on the surface; 26. A multi-beam tool as claimed in any one of clauses 24 and 25, wherein the array of beams following the movement of the stage comprises the array of probe spots moving in the first direction at the same speed as the stage. Clause 27. A multi-beam tool described in any one of clauses 24 to 26, wherein during scanning of the first and second sets of scan lines, the beam configuration system is further configured to move the stage in the first direction at a constant velocity. Clause 28. A multi-beam tool as described in any one of clauses 24 to 27, wherein each of the first and second sets of scan lines are spaced apart a distance corresponding to the pixel size of an image generated by the multi-beam tool. Clause 29. A multi-beam tool according to any one of clauses 24 to 28, wherein the first and second sets of scan lines are substantially perpendicular to the first direction relative to the sample. Clause 30. A multi-beam tool according to any one of clauses 24 to 29, wherein the first and second sets of scan lines are substantially parallel lines. Clause 31. A multi-beam tool according to any one of clauses 24 to 30, wherein the beam configuration system further comprises a controller coupled to the stage, the controller configured to control movement of the stage. Clause 32. A multi-beam tool as described in any one of clauses 24 to 31, wherein the beam configuration system further includes a controller coupled to the deflector system, the controller configured to control deflection of the array of beams. Clause 33. A method comprising: generating a primary beam of charged particles by a multi-beam tool; splitting the primary beam into an array of beams by a multi-beam tool; and rotating the array of beams by a rotation angle determined based on the number of beams in a row of the array of beams relative to a sample to be scanned by the multi-beam tool. Clause 34. The method of clause 33, wherein rotating the array of beams relative to the sample includes rotating the sample about an optical axis of the multi-beam tool. Clause 35. The method of clause 33, wherein rotating the array of beams relative to the sample includes rotating the array of beams about an optical axis of the multi-beam tool. Clause 36. A method according to any one of clauses 33 to 35, wherein rotating the array of beams relative to the sample enables the array of beams to scan an area larger than the surface area of ​​the sample imaged by the multi-beam tool. Clause 37. The method further comprising: moving the sample along a first direction through the multi-beam tool; 37. The method of any one of clauses 33 to 36, wherein the array of beams scans a set of scan lines along a second direction covering the surface area to be imaged. Clause 38. The method of clause 37, wherein the second direction is substantially perpendicular to the first direction relative to the sample. Clause 39. The method of clause 37, wherein the second direction is substantially parallel to the first direction relative to the sample. Clause 40. A method according to any one of clauses 37 to 39, wherein the set of scan lines are spaced apart by a distance corresponding to a pixel size of an image produced by the multi-beam tool. Clause 41. A method comprising: Moving the sample in a first direction with a multi-beam tool; generating a primary beam of charged particles by a multi-beam tool; splitting the primary beam into n beams by a multi-beam tool, where n is an integer and n>=2; rotating the n beams with the multi-beam tool relative to a first direction such that the n beams are spaced along the first direction; 13. A method comprising: deflecting n beams with a multi-beam tool to simultaneously i) follow the movement of the sample and ii) scan one or more sets of n scan lines across a surface of the sample. Clause 42. The one or more sets of n scan lines include a first set of n scan lines extending over a first distance along a first direction, the method further comprising: offsetting the n beams by the distance along a direction opposite the first direction by the multi-beam tool after the first set of n scan lines have been scanned; 42. The method of claim 41, comprising deflecting the n beams by the multi-beam tool to simultaneously i) follow the movement of the sample and ii) scan a second set of n scan lines across a surface of the sample. Clause 43. The method of clause 42, wherein the first and second sets of n scan lines are substantially parallel lines. Clause 44. A method according to any one of clauses 42 and 43, wherein each of the n scan lines of the first and second sets are spaced apart by a distance corresponding to the pixel size of the image produced by the multi-beam tool. Clause 45. A method according to any one of clauses 42 to 44, wherein one or more sets of n scan lines are aligned along a second direction substantially perpendicular to the first direction relative to the sample. Clause 46. A method according to any one of clauses 42 to 44, wherein one or more sets of n scan lines are aligned along a second direction substantially parallel to the first direction relative to the sample. Clause 47. A method according to any one of clauses 45 to 46, wherein the first set of n scan lines covers a field of view of the multi-beam tool along the second direction. Clause 48. The n beams are projected onto a surface of the sample to form n probe spots on the surface, the method further comprising: 48. The method of any one of clauses 42-47, comprising deflecting the n beams so that the n probe spots move in a first direction at the same speed as the sample. Clause 49. The method of any one of clauses 42 to 48, wherein moving the sample in a first direction comprises moving the sample in the first direction at a constant velocity. Clause 50. A method comprising: Moving the sample in a first direction; generating a primary beam of charged particles by a multi-beam tool; splitting the primary beam into an array of beams by a multi-beam tool; deflecting an array of beams with a multi-beam tool to i) scan a first set of scan lines within a field of view of the multi-beam tool, and ii) follow movement of the sample during scanning of the first set of scan lines, wherein the first set of scan lines extend over a first distance along a first direction; moving the sample by the multi-beam tool a first distance in a first direction after the first set of scan lines have been scanned; deflecting, by the multi-beam tool, the array of beams to i) scan a second set of scan lines within a field of view of the multi-beam tool, and ii) follow the movement of the sample while scanning the second set of scan lines; and moving the sample in a first direction with the multi-beam tool as the first and second sets of scan lines are scanned. Clause 51. Deflecting the array of beams to i) scan a first set of scan lines within a field of view of the multi-beam tool, and ii) follow the movement of the sample during the scanning of the first set of scan lines, deflecting a first beam in the array of beams to simultaneously i) follow the movement of the sample and ii) scan a first scan line; deflecting the first beam a predetermined distance along a direction opposite the first direction after the first scan line has been scanned; 51. The method of claim 50, comprising deflecting the first beam to simultaneously i) follow the movement of the sample and ii) scan the second scan line. Clause 52. A method according to any one of clauses 50 and 51, wherein deflecting the array of beams to follow the movement of the sample comprises deflecting the array of beams so that an array of probe spots formed by the array of beams on the sample moves in a first direction at the same speed as the sample. Clause 53. The method of any one of clauses 50-52, further comprising moving the sample in the first direction at a constant velocity during scanning of the first and second sets of scan lines. Clause 54. A method according to any one of clauses 50 to 53, wherein each of the first and second sets of scan lines are spaced apart by a distance corresponding to the pixel size of an image produced by the multi-beam tool. Clause 55. A method according to any one of clauses 50 to 54, wherein the first and second sets of scan lines are substantially perpendicular to the first direction relative to the sample. Clause 56. A method according to any one of clauses 50 to 55, wherein the first and second sets of scan lines are substantially parallel lines. Clause 57. A non-transitory computer readable medium storing a set of instructions executable by a controller coupled to a multi-beam tool and causing the controller to perform a method comprising: instructing a beam configuration system of the multi-beam tool to rotate the array of charged particle beams relative to a sample to be scanned by the multi-beam tool by a rotation angle determined based on a number of beams in a row of the array of beams; A multi-beam tool is a method for generating a primary beam of charged particles and splitting the primary beam into an array of charged particle beams. Clause 58. The array of charged particle beams is arranged around an optical axis of the multi-beam tool, and the set of instructions further comprises a controller: 58. The medium of claim 57, adapted to direct a sample stage of a multi-beam system to rotate the sample about an optical axis. Clause 59. The array of beams is arranged around an optical axis of the multi-beam tool, and the set of instructions further comprises a controller: 58. The medium of claim 57, adapted to instruct a beam configuration system to rotate the array of charged particle beams about an optical axis. Clause 60. The set of instructions further provides that the controller: Controlling the multibeam tool to generate an image of a surface area of ​​the sample; 60. The medium of any one of clauses 57 to 59, further comprising instructing a beam configuration system to move the array of charged particle beams over an area larger than the surface area to be imaged. Clause 61. The set of instructions further provides that the controller: Directing a sample stage of the multibeam tool to move the sample along a first direction; The medium of clause 60, further comprising instructing the beam configuration system to move the array of charged particle beams along a second direction to scan a set of scan lines covering a field of view. Clause 62. The medium of clause 61, wherein the second direction is substantially perpendicular to the first direction relative to the sample. Clause 63. The medium of clause 61, wherein the second direction is substantially parallel to the first direction relative to the sample. Clause 64. A medium described in any one of clauses 61 to 63, wherein the set of scan lines are spaced apart a distance corresponding to the pixel size of the image produced by the multi-beam tool. Clause 65. A non-transitory computer readable medium storing a set of instructions executable by a controller coupled to a multi-beam tool and causing the controller to perform a method comprising: directing a sample stage of a multi-beam tool to move a sample in a first direction, the multi-beam tool generating a primary beam of charged particles and splitting the primary beam into n beams, where n is an integer and n>2; instructing a beam configuration system of the multi-beam tool to rotate the n beams relative to a first direction such that the n beams are spaced along the first direction; and instructing a beam configuration system to deflect n beams to simultaneously i) follow the movement of the sample and ii) scan one or more sets of n scan lines across a surface of the sample. Clause 66. The one or more sets of n scan lines include a first set of n scan lines extending over a first distance along a first direction, and the set of instructions further includes the controller: directing the beam construction system to offset the n beams by the distance along a direction opposite the first direction after the first set of n scan lines have been scanned; and instructing the beam configuration system to deflect the n beams to simultaneously i) follow the movement of the sample and ii) scan a second set of n scan lines across a surface of the sample. Clause 67. The medium of clause 66, wherein the first and second sets of n scan lines are substantially parallel lines. Clause 68. A medium described in any one of clauses 66 and 67, wherein each of the n scan lines of the first and second sets are spaced apart by a distance corresponding to the pixel size of the image generated by the multi-beam tool. Clause 69. The set of instructions further provides that the controller: The medium of any one of clauses 65 to 68, further comprising instructing the beam configuration system to move one or more sets of n scan lines relative to the sample along a second direction substantially perpendicular to the first direction. Clause 70. The set of instructions further provides that the controller: The medium of any one of clauses 65 to 68, further comprising instructing the beam configuration system to move one or more sets of n scan lines relative to the sample along a second direction substantially parallel to the first direction. Clause 71. A medium described in any one of clauses 69 and 70, wherein the first set of n scan lines covers a field of view of the multi-beam tool along the second direction. Clause 72. The n beams are projected onto a surface of the sample to form n probe spots on the surface, and the set of instructions further comprises: a controller: The medium of any one of clauses 65 to 71, further comprising instructing the beam configuration system to deflect the n beams so that the n probe spots move in a first direction at the same speed as the sample. Clause 73. The set of instructions further provides that the controller: 73. The medium of any one of clauses 65 to 72, wherein the sample stage is instructed to move the sample in a first direction at a constant velocity. Clause 74. A non-transitory computer readable medium storing a set of instructions executable by a controller coupled to a multi-beam tool and causing the controller to perform a method comprising: directing a sample stage of a multi-beam tool to move a sample in a first direction, the multi-beam tool generating a primary beam of charged particles and splitting the primary beam into an array of beams; directing a beam configuration system of the multi-beam tool to deflect an array of beams to i) scan a first set of scan lines within a field of view of the multi-beam tool, and ii) follow movement of the sample during scanning of the first set of scan lines, where the first set of scan lines extend over a first distance along a first direction; directing the sample holder to move the sample a first distance in a first direction after the first set of scan lines have been scanned; directing the beam configuration system to deflect the array of beams to i) scan a second set of scan lines within a field of view of the multi-beam tool, and ii) follow the movement of the sample while scanning the second set of scan lines; and directing the sample holder to move the sample in a first direction as the first and second sets of scan lines are scanned. Clause 75. The array of beams includes a first beam, and the set of instructions further comprises a controller controlling the beam configuration system to: deflecting the first beam to simultaneously i) follow the movement of the sample and ii) scan a first scan line; deflecting the first beam a predetermined distance along a direction opposite to the first direction after the first scan line has been scanned; 75. The medium of claim 74, wherein the first beam is deflected to simultaneously i) follow the movement of the sample and ii) direct the second scan line to be scanned. Clause 76. The array of beams is projected onto a surface of the sample to form an array of probe spots on the surface, the set of instructions further comprising a controller configured to: The medium of any one of clauses 74 and 75, further comprising instructing the beam configuration system to deflect the array of beams so that the array of probe spots moves in a first direction at the same speed as the sample. Clause 77. The set of instructions further provides that the controller: The medium of any one of clauses 74 to 76, wherein the sample stage is instructed to move the sample in a first direction at a constant velocity during scanning of the first and second sets of scan lines. Clause 78. A medium described in any one of clauses 74 to 77, wherein each of the first and second sets of scan lines are spaced apart a distance corresponding to the pixel size of the image produced by the multi-beam tool. Clause 79. The medium of any one of clauses 74 to 78, wherein the first and second sets of scan lines are substantially perpendicular to the first direction relative to the sample. Clause 80. The medium of any one of clauses 74-79, wherein the first and second sets of scan lines are substantially parallel lines. Clause 81. A method of scanning an area of ​​a sample using N charged particle beams, N being an integer equal to or greater than 2, the area of ​​the sample including a plurality of scan sections of N consecutive scan lines, the method comprising: Moving a position of the sample in a first direction; scanning a first scan line of at least some of the scan sections of the plurality of scan sections with a first charged particle beam of the N charged particle beams moving toward a probe spot of the first charged particle beam; and scanning a second scan line of at least some of the scan sections of the plurality of scan sections with a second charged particle beam of the N charged particle beams moving toward a probe spot of the second charged particle beam. Clause 82. The method of clause 81, wherein moving the position of the sample in a first direction includes constantly moving the position of the sample at a first velocity. Clause 83. A method according to any one of clauses 81 and 82, wherein the scan lines are arranged perpendicular to the first direction. Clause 84. A method according to any one of clauses 81 and 82, wherein the scan lines are inclined away from the first direction to accommodate movement of the position of the sample in the first direction. Clause 85. The method of any one of clauses 81-84, wherein a first scan line of the plurality of scan sections is arranged parallel to a second scan line of the plurality of scan sections. Clause 86. A method according to any one of clauses 81 to 85, further comprising deflecting the N charged particle beams and moving probe spots of the N charged particle beams in a second direction from their respective start positions to their respective end positions to follow the movement of the sample while scanning a set of scan lines. Clause 87. The method of clause 86, further comprising deflecting the N charged particle beams to move the probe spots of the N charged particle beams in a third direction from their respective end positions to their respective start positions, and repositioning the probe spots back to their respective start positions in preparation for scanning a next set of scan lines. Clause 88. The method of any one of clauses 81 to 87, wherein the second direction is substantially opposite to the third direction. Clause 89. Deflecting the N charged particle beams to move a probe spot of the N charged particle beams in a second direction includes deflecting the N charged particle beams to move a probe spot of the N charged particle beams in a second direction at a second velocity; 89. The method of any one of clauses 86 to 88, wherein deflecting the N charged particle beams to move a probe spot of the N charged particle beams in a third direction comprises deflecting the N charged particle beams to move a probe spot of the N charged particle beams in the third direction at a third velocity. Clause 90. The method of clause 89, wherein the second speed and the third speed are the same. Clause 91. The method of any one of clauses 82 to 90, wherein the first speed is related to the size of the scan section. Clause 92. The method of any one of clauses 82-90, wherein the first speed is determined based on the length of the scan line, the second speed, and the third speed. Clause 93. The method of any one of clauses 81 to 92, wherein the sample comprises a wafer or a photomask. Clause 94. A non-transitory computer readable medium storing a set of instructions, the set of instructions being executable by one or more processors of a charged particle beam system, comprising: a charged particle beam source for delivering N charged particle beams to a surface of a sample in a time sequence; a method for providing a charged particle beam system to the charged particle beam system, the method comprising: Moving a position of the sample in a first direction; scanning a first scan line of at least some of the scan sections of the plurality of scan sections with a first charged particle beam of the N charged particle beams moving toward a probe spot of the first charged particle beam; and scanning a second scan line of at least some of the scan sections of the plurality of scan sections with a second charged particle beam of the N charged particle beams moving toward a probe spot of the second charged particle beam. Clause 95. The computer-readable medium of clause 94, wherein moving the position of the sample in a first direction includes constantly moving the position of the sample at a first velocity. Clause 96. The computer-readable medium of any one of clauses 94 and 95, wherein the scan lines are arranged substantially perpendicular to the first direction. Clause 97. The computer-readable medium of any one of clauses 94-96, wherein a first scan line of the plurality of scan sections is positioned substantially parallel to a second scan line of the plurality of scan sections. Clause 98. The method may be executed by one or more processors, and the controller may further: The computer readable medium of any one of clauses 94 to 97, wherein the set of instructions is to deflect the N charged particle beams and move probe spots of the N charged particle beams in a second direction from their respective starting positions to their respective end positions to follow the movement of the sample while scanning a set of scan lines. Clause 99. The method may be executed by one or more processors, and the controller may further: The computer readable medium of clause 98, a set of instructions to deflect the N charged particle beams to move probe spots of the N charged particle beams in a third direction from their respective end positions to their respective start positions, and then reposition the probe spots back to their respective start positions in preparation for scanning a next set of scan lines. Clause 100. The computer-readable medium of any one of clauses 94-99, wherein the second direction is substantially opposite to the third direction. Clause 101. Deflecting the N charged particle beams to move a probe spot of the N charged particle beams in a second direction includes deflecting the N charged particle beams to move a probe spot of the N charged particle beams in a second direction at a second velocity; The computer-readable medium of any one of clauses 98 to 100, wherein deflecting the N charged particle beams to move a probe spot of the N charged particle beams in a third direction includes deflecting the N charged particle beams to move a probe spot of the N charged particle beams in the third direction at a third velocity. Clause 102. The computer-readable medium of clause 101, wherein the second rate and the third rate are substantially the same. Clause 103. The computer-readable medium of any one of clauses 95-102, wherein the first speed is related to the size of the scan section. Clause 104. The computer-readable medium of any one of clauses 95-102, wherein the first velocity is determined based on the length of the scan line, the second velocity, and the third velocity. Clause 105. A method of scanning a sample with a multi-beam inspection system utilizing at least N charged particle beams, where N is an integer equal to or greater than 2, comprising: Arranging the N charged particle beams such that each of the N charged particle beams scans a different scan line of the first set of N adjacent scan lines; scanning a first set of N adjacent scan lines of the sample while the sample is moving in a first direction at a first velocity using the N charged particle beams; repositioning the N charged particle beams relative to a start of scanning the first set of N adjacent scan lines such that each beam of the N charged particle beams scans a different scan line of the second set of adjacent scan lines; and scanning a second set of N adjacent scan lines of the sample while the sample is moving in a first direction at a first velocity using the N charged particle beams. Clause 106. The method of clause 105, wherein the multi-beam inspection system utilizes N×M charged particle beams, where M is an integer greater than or equal to 1. Clause 107. The method of clause 106, wherein the N×M charged particle beam forms an N×M array of charged particle beams, M being an integer greater than or equal to 2, and the N charged particle beams being a first linear arrangement of the N charged particle beams of the N×M array of charged particle beams. Clause 108. The method of clause 107, wherein M is equal to N. Clause 109. The second set of N charged particle beams is a second linear arrangement of N charged particle beams of the N×M array of charged particle beams, the method further comprising: Arranging the second linear arrangement of the N charged particle beams such that each beam of the second linear arrangement of the N charged particle beams scans a different scan line of the third set of N adjacent scan lines; scanning a third set of N adjacent scan lines of the sample while the sample is moving in a first direction at a first velocity using a second set of N charged particle beams; repositioning the second linear arrangement of the N charged particle beams relative to a start of scanning the third set of N adjacent scan lines such that each beam of the second linear arrangement of the N charged particle beams scans a different scan line of the fourth set of adjacent scan lines; The method of claim 107, comprising: scanning a fourth set of N adjacent scan lines of the sample while the sample is moving in a first direction at a first velocity by using a second set of N charged particle beams. Clause 110. The method of clause 109, wherein the first set of scans is matched to the third set of scans and the second set of scans is matched to the fourth set of scans. Clause 111. The method of clause 110, wherein the first set of scans is performed substantially simultaneously with the third set of scans and the second set of scans is performed substantially simultaneously with the fourth set of scans. Clause 112. The method of clause 105, wherein positioning of the N charged particle beams occurs prior to a first set of scans, the first set of scans occurs prior to repositioning, and the repositioning occurs prior to a second set of scans, and the sample moves continuously at substantially a first velocity from a time when the first set of scans begins to a time when the second set of scans ends. Clause 113. Repositioning the N charged particle beams relative to a start of scanning the N adjacent scan lines of the second set such that each beam of the N charged particle beams scans a different scan line of the third set of adjacent scan lines; scanning a third set of N adjacent scan lines of the sample while the sample is moving in the first direction at the first velocity using the N charged particle beams; the sample is moved continuously at substantially the first speed from a time when the first set of scans begins to a time when the third set of scans begins; the first direction is substantially parallel to a y-axis of the sample, and movement relative to the sample in the first direction is along the y-axis with increasing y-coordinate values; the scan line at the beginning end of the first set is located at a y coordinate of samples that is greater than the y coordinates of all other scan lines in the first set and the scan lines in the second and third sets; a scan line at the beginning of the third set is located at a y coordinate of a sample that is less than the y coordinate of all scan lines in the first set and the second set and greater than the y coordinate of all other scan lines in the third set; The method of claim 105, wherein the distance traveled by the sample relative to a fixed point of the multi-beam inspection system from the time the first set of scans begins to the time the third set of scans begins is substantially equal to the distance along the y-axis from the scan line at the beginning end of the first set to the scan line at the beginning of the third set. Clause 114. The method of clause 113, wherein positioning of the N charged particle beams is performed prior to a first set of scans, the first set of scans is performed prior to repositioning to enable a second set of scans, the second set of scans is performed prior to repositioning to enable a third set of scans, and the second set of scans is performed prior to repositioning to enable a third set of scans. Clause 115. A method for scanning a sample disposed on a stage by a multi-beam inspection system utilizing an N×M array of charged particle beams, where N and M are each an integer greater than or equal to 2, the method comprising: positioning an N by M array of charged particle beams such that each beam of the N by M array of charged particle beams at a first set of positions scans a different one of the N by M scan sections of the first set of samples; scanning scan lines of at least some of the N by M scan sections of a first set of the sample while the stage is moving in a first direction at a first velocity using an N by M array of charged particle beams; repositioning the N by M array of charged particle beams relative to a start of scanning the first set of N by M scan sections such that each beam of the N by M array of charged particle beams at the second set of positions scans a different one of the second set of N by M scan sections of the sample; and scanning scan lines of at least some of the N by M scan sections of a second set of the sample while the stage is moving in a first direction at a first velocity using an N by M array of charged particle beams. Clause 116. The method of clause 115, wherein the scan lines are arranged substantially parallel to the first direction. Clause 117. The method of any one of clauses 115 and 116, further comprising deflecting the N x M array of charged particle beams to accommodate movement of the stage while scanning the scan line. Clause 118. The method of any one of clauses 115 to 117, wherein repositioning the N×M array of charged particle beams is performed while the stage is moving in a first direction at a first velocity. Clause 119. The method of clause 118, further comprising deflecting the N x M array of charged particle beams to accommodate movement of the stage while repositioning the N x M array of charged particle beams. Clause 120. A method according to any one of clauses 115 to 119, wherein corresponding positions of the first set of positions and the second set of positions of the N×M array of charged particle beams relative to a fixed point of the multi-beam inspection system are substantially the same. Clause 121. The method of any one of clauses 115 to 120, further comprising rotating the N×M array of charged particle beams about an optical axis of the multi-beam inspection system. Clause 122. The method of any one of clauses 115 to 120, further comprising rotating the stage about an optical axis of the multi-beam inspection system. Clause 123. The method of any one of clauses 115 to 122, wherein a scan section of the N by M scan sections of a first set of samples partially overlaps a scan section of the N by M scan sections of a second set of samples to generate an overlap region. Clause 124. The method of clause 123, wherein the overlap region is scanned multiple times. Clause 125. The method of clause 124, wherein the overlap region is scanned a first time when N by M scan sections of a first set of samples are scanned, and the overlap region is scanned a second time when N by M scan sections of a second set of samples are scanned. Clause 126. While scanning the first set of N by M scan sections of the sample, acquiring first scan data of an overlap region; acquiring second scan data of the overlap region while scanning a second set of N by M scan sections of the sample; 126. The method of claim 125, further comprising processing the first and second scan data of the overlap region to generate a continuous image of the sample. Clause 127. The method of any one of clauses 115-126, further comprising controlling movement of the stage by a controller coupled to the stage. Clause 128. The method of any one of clauses 115 to 127, wherein M is equal to N.

[0133]

[0154] It will be appreciated that the multi-beam e-beam tool may use software to perform the functions described above. For example, the multi-beam e-beam tool may control a motorized sample stage to move the sample while the scan is in progress. The multi-beam e-beam tool may also control and deflect the primary beamlets to move the probe spot along the scan line while the sample is constantly moving. Additionally, the multi-beam e-beam tool may perform image processing to generate beam spot images of the received secondary electron beams. The software may be stored on a non-transitory computer readable medium. Common forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid state drives, magnetic tape or any other magnetic data storage medium, CD-ROMs, any other optical data storage medium, any physical medium with a pattern of holes, RAM, PROMs, and EPROMs, cloud storage, FLASH-EPROM or any other flash memory, NVRAM, caches, registers, any other memory chips or cartridges, and networked versions of the above.

[0134]

[0155] Although the disclosed embodiments have been described in connection with preferred embodiments, it should be understood that other modifications and variations can be made without departing from the spirit and scope of the subject matter hereinafter claimed.

Claims

1. 1. A multi-beam tool, comprising: a beam configuration system including a charged particle source for generating a primary beam of charged particles, a stage configured to hold a sample, and a deflector system between the charged particle source and the stage configured to split the primary beam into an array of beams; A multi-beam tool, wherein the beam configuration system is configured to provide a rotated beam configuration with a rotation angle determined based on a number of beams in a row of the array of beams.

2. the array of beams is arranged about an optical axis of the multi-beam tool; The multi-beam tool of claim 1 , wherein the rotating beam arrangement includes the stage configured to rotate about the optical axis.

3. the array of beams is arranged about an optical axis of the multi-beam tool; The multi-beam tool of claim 1 , wherein the rotating beam arrangement includes the deflector system configured to rotate the array of beams about the optical axis.

4. the multi-beam tool is configured to generate an image of a surface area of ​​the sample; The multi-beam tool of claim 1 , wherein the rotating beam configuration enables the array of beams to scan an area larger than the surface area to be imaged.

5. the stage is configured to move along a first direction; The multi-beam tool of claim 1 , wherein scanning the array of beams across the field of view comprises scanning the array of beams along a second direction through a set of scan lines covering the field of view.

6. The multi-beam tool of claim 5 , wherein the second direction is substantially perpendicular to the first direction relative to the sample.

7. The multi-beam tool of claim 5 , wherein the second direction is substantially parallel to the first direction relative to the sample.

8. The multi-beam tool of claim 5 , wherein the set of scan lines are spaced apart a distance corresponding to a pixel size of an image produced by the multi-beam tool.

9. The multi-beam tool of claim 1 , wherein the beam configuration system further comprises a controller coupled to the stage, the controller configured to control movement of the stage.

10. The multi-beam tool of claim 1 , wherein the beam configuration system further comprises a controller coupled to the deflector system, the controller configured to control the deflector system to deflect the array of beams.

11. 1. A method comprising: generating a primary beam of charged particles by a multi-beam tool; splitting the primary beam into an array of beams by the multi-beam tool; causing the multi-beam tool to rotate the array of beams relative to the sample to be scanned by a rotation angle determined based on the number of beams in a row of the array of beams.

12. The method of claim 11 , wherein causing the array of beams to have a rotated orientation relative to the sample comprises rotating the sample about an optical axis of the multi-beam tool.

13. The method of claim 11 , wherein causing the array of beams to have a rotated orientation relative to the sample comprises rotating the array of beams about an optical axis of the multi-beam tool.

14. 12. The method of claim 11, wherein having the array of beams have a rotated orientation relative to the sample enables the array of beams to scan an area larger than a sample surface area imaged by the multi-beam tool.

15. and further comprising: moving the sample along a first direction with the multi-beam tool; The method of claim 11 , wherein the array of beams scans a set of scan lines along a second direction covering the imaged surface area.

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