System and method for aligning an electron beam in a multibeam inspection device

Abstract

Disclosed is an improved charged particle beam inspection apparatus, and more particularly, a particle beam inspection apparatus including an improved alignment mechanism. An improved charged particle beam inspection apparatus may include a second electron detection device to generate one or more images of one or more beam spots in a plurality of secondary electron beams during the alignment mode. The beam speckle image may be used to determine an alignment characteristic of one or more of the plurality of secondary electron beams and adjust a configuration of the secondary electron projection system.

Description

[0001] This application is a divisional application filed on September 20, 2019, the international application date, entered the Chinese national phase on April 16, 2021, with application number 201980068721.7, and the invention name is “System and method for aligning electron beams in a multi-beam inspection device”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Application No. 62 / 748,251 filed on October 19, 2018, and the above application is incorporated herein by reference in its entirety. Technical Field

[0004] Embodiments provided herein disclose a particle beam inspection apparatus, and more particularly, provide a particle beam inspection apparatus including an improved alignment mechanism. Background Art

[0005] When manufacturing semiconductor integrated circuit (IC) chips, pattern defects or uninvited particles (residues) inevitably appear on the wafer or mask during the manufacturing process, thereby reducing the yield. For example, for patterns with smaller critical feature sizes that have been adopted to meet the increasingly advanced performance requirements of IC chips, uninvited particles may become a problem.

[0006] Pattern inspection tools with charged particle beams have been used to detect defects or uninvited particles. These tools typically use a scanning electron microscope (SEM). In an SEM, a beam of relatively high energy primary electrons is decelerated and lands on a sample with a relatively low landing energy, and is focused to form a detection spot thereon. Due to the focused detection spot of the primary electrons, secondary electrons will be generated from the surface. The secondary electrons may include backscattered electrons, secondary electrons, or Auger electrons generated due to the interaction of the primary electrons with the sample. By scanning the detection spot on the sample surface and collecting the secondary electrons, the pattern inspection tool can obtain an image of the sample surface. Summary of the invention

[0007] Embodiments provided herein disclose a particle beam inspection apparatus, and more particularly, provide a particle beam inspection apparatus including an improved alignment mechanism.

[0008] In some embodiments, a charged particle beam apparatus for inspecting a wafer may include a first electron detection device and a second electron detection device. The first electron detection device may detect a plurality of secondary electron beams used for inspection of the wafer. The second electron detection device may generate one or more images of one or more beam spots of the plurality of secondary electron beams and may be configured to determine an alignment characteristic associated with the first electron detection device.

[0009] In some embodiments, a method for inspecting a wafer using a charged particle beam system is provided. The charged particle beam system may include a secondary projection system for projecting a plurality of secondary electron beams onto a detection surface of a first electron detection device. The method may include generating one or more images of one or more beam spots of the plurality of secondary electron beams using a second electron detection device. The method may also include determining an alignment characteristic associated with the first electron detection device based on the one or more images of the one or more beam spots of the plurality of secondary electron beams.

[0010] Other advantages of the invention will become apparent from the following description taken in conjunction with the accompanying drawings which show by way of illustration and example certain embodiments of the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The above and other aspects of the present disclosure will become more apparent from the following description of exemplary embodiments with reference to the attached drawings.

[0012] Figure 1A is a schematic diagram illustrating an exemplary charged particle beam inspection system in accordance with an embodiment of the present disclosure.

[0013] Figure 1B is a schematic diagram illustrating an exemplary particle beam tool according to an embodiment of the present disclosure.

[0014] Figure 2 is a schematic diagram illustrating an exemplary electronic imaging device using an electron-to-light converter according to an embodiment of the present disclosure.

[0015] Figure 3A , Figure 3B , Figure 3C and Figure 3D is a schematic diagram illustrating an exemplary multi-beam electron beam tool in accordance with an embodiment of the present disclosure.

[0016] Figure 4A , Figure 4B , Figure 4C and Figure 4D is a schematic diagram illustrating an exemplary multi-beam electron beam tool in accordance with an embodiment of the present disclosure.

[0017] Figure 5A , Figure 5B , Figure 5C and Figure 5D is a schematic diagram illustrating an exemplary multi-beam electron beam tool in accordance with an embodiment of the present disclosure.

[0018] Fig. 6A , Figure 6B and Figure 6C is a schematic diagram illustrating an exemplary multi-beam electron beam tool in accordance with an embodiment of the present disclosure.

[0019] Figure 7 is a flow chart illustrating steps of an exemplary alignment operation using an embodiment of the multi-beam electron beam tool in accordance with an embodiment of the present disclosure. DETAILED DESCRIPTION

[0020] Reference will now be made in detail to exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following description refers to the accompanying drawings, wherein, unless otherwise indicated, the same numbers in different figures represent the same or similar elements. The embodiments given in the following description of the exemplary embodiments do not represent all embodiments according to the present invention. Instead, they are merely examples of devices and methods according to the relevant aspects of the present invention as described in the attached claims.

[0021] Improved computing power of electronic devices can be achieved by significantly increasing the packing density of circuit components such as transistors, capacitors, diodes, etc. on IC chips, while reducing the physical size of the device. For example, the IC chip of a thumbnail-sized smartphone can include more than 2 billion transistors, each of which is less than 1 / 1000 the size of a human hair. It is therefore not surprising that semiconductor IC manufacturing is a complex and time-consuming process with hundreds of individual steps. Even an error in one step has the potential to seriously affect the functionality of the final product. Even a "fatal defect" can cause device failure. The goal of the manufacturing process is to increase the overall yield of the process. For example, for a 50-step process to achieve a 75% yield, each individual step must have a yield greater than 99.4%, and if the yield of the individual step is 95%, the yield of the entire process drops to 7%.

[0022] While high process yield is desirable in IC chip fabrication facilities, it is also necessary to maintain high wafer throughput, which is defined as the number of wafers processed per hour. High process yield and high wafer throughput can be affected by the presence of defects, especially when operator intervention is required to review the defects. Therefore, high throughput detection and identification of micron and nanometer-sized defects by inspection tools (such as SEM) is necessary to maintain high yield and low cost.

[0023] SEM scanning uses a focused electron beam to scan the surface of a wafer. The electrons interact with the wafer and generate secondary electrons. By scanning the wafer with the electron beam and capturing the secondary electrons with a detector, the SEM creates an image of the wafer that shows the internal device structure in the area of ​​the wafer being inspected.

[0024] For high throughput inspection, some newer inspection systems use multiple electron beams. Since multiple electron beams can scan different parts of the wafer at the same time, a multi-beam electron inspection system can inspect the wafer at a significantly higher speed than a single-beam system. However, conventional multi-beam inspection systems may suffer from low inspection accuracy due to crosstalk between adjacent electron beams. One of the main sources of crosstalk is the misalignment between different parts of the inspection system with respect to the path of the electron beam travel. For example, a detector that captures a secondary electron beam should be properly aligned with a lens that controls the alignment characteristics (such as focus and position) of the secondary electron beam associated with the detector; otherwise, the secondary electron beam will interfere with the detection of an adjacent secondary electron beam.

[0025] One aspect of the present disclosure includes an electron beam image viewer that can generate images of multiple secondary electron beams. These images can be used to determine how well the electron optical elements (such as lenses, beam splitters, and electron detectors) in the inspection system are aligned, and to determine whether any adjustments need to be made to one or more of the electron optical elements. The image can be further used to determine the focus quality of the secondary electron beam, such as whether the secondary electron beam will form a spot of the desired size, shape, position, etc. on the detector, and to determine whether any adjustments are needed. These determinations or adjustments can be made by a computer within the multi-beam inspection system, or can be made by an operator who visually inspects the images of the secondary electron beams.

[0026] The relative sizes of the parts in the accompanying drawings may be enlarged for clarity. In the following description of the accompanying drawings, the same or similar reference numerals refer to the same or similar components or entities, and only describe the differences about individual embodiments. As used herein, unless otherwise specifically noted, the term "or" includes all possible combinations, except for infeasible situations. For example, if it is pointed out that a database can include A or B, then unless otherwise specifically noted or infeasible, the database may include A, or B, or A and B. As a second example, if it is pointed out that a database can include A, B, or C, then unless otherwise specifically noted or infeasible, the database may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0027] Reference now Figure 1A , which is a schematic diagram illustrating an exemplary charged particle beam inspection system 100 according to an embodiment of the present disclosure. Figure 1A As shown in FIG, a charged particle beam inspection system 100 includes a main chamber 10, a load lock chamber 20, an electron beam tool 40, and an equipment front end module (EFEM) 30. The electron beam tool 40 is located in the main chamber 10. Although the description and drawings are directed to electron beams, it is to be appreciated that the embodiments are not intended to limit the present disclosure to specific charged particles.

[0028] The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include additional (multiple) loading ports. The first loading port 30a and the second loading port 30b may, for example, receive a front opening unified pod (FOUP) of a wafer, which contains wafers (e.g., semiconductor wafers or wafers made of other (multiple) materials) or samples (wafers and samples are collectively referred to as "wafers" hereinafter) to be inspected. One or more robotic arms (not shown) in the EFEM 30 transport the wafers to the loading lock chamber 20.

[0029] The load lock chamber 20 can be connected to a load lock vacuum pump system (not shown) that removes gas molecules in the load lock chamber 20 to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robotic arms (not shown) transport the wafer from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown) that removes gas molecules in the main chamber 10 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is inspected by the 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.

[0030] The controller 50 is electrically 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 circuits configured to perform various signal and image processing functions. Figure 1A 30, but it will be appreciated that the controller 50 may be part of the structure. Although the present disclosure provides an example of a main chamber 10 housing an electron beam inspection tool, it should be noted that aspects of the present disclosure in its broadest sense are not limited to chambers housing electron beam inspection tools. Rather, it will be appreciated that the above principles may also be applied to other tools operating at a second pressure.

[0031] Reference now Figure 1B, which is a schematic diagram illustrating an exemplary particle beam tool 40 according to an embodiment of the present disclosure, the particle beam tool 40 includes a Figure 1A A multi-beam electron inspection tool that is part of an exemplary charged particle beam inspection system 100. The multi-beam electron beam tool 40 (also referred to herein as the device 40) includes an electron source 101, a gun hole plate 171, a bunching lens 110, a source conversion unit 120, a primary projection optical system 130, a sample 108, a secondary projection system 150, a first electron detection device 140 and a second electron detection device 190. The primary projection optical system 130 may include an objective lens 131. The electron detection device 140 may include a plurality of detection elements 141, 142 and 143. The beam splitter 133 and the deflection scanning unit 132 may be positioned inside the primary projection optical system 130.

[0032] The electron source 101, the aperture plate 171, the condenser lens 110, the source conversion unit 120, the beam splitter 133, the deflection scanning unit 132 and the primary projection optical system 130 can be aligned with the main optical axis 104 of the device 40. The secondary projection system 150 and the electron detection device 140 can be aligned with the secondary optical axis 151 of the device 40.

[0033] The electron source 101 may include a cathode (not shown) and an extractor or anode (not shown), wherein during operation, the electron source 101 is configured to emit primary electrons from the cathode, and the primary electrons are extracted or accelerated by the extractor and / or anode to form a primary electron beam 102, which forms a primary beam cross (virtual or real) 103. The primary electron beam 102 can be visualized as being emitted from the primary beam cross 103.

[0034] The source conversion unit 120 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 111, 112, 113 of the primary electron beam 102 and form a plurality of parallel images (virtual or real) of the primary beam intersection 103, wherein each of the primary beamlets 111, 112, and 113 has an image. The field curvature compensator array may include a plurality of micro lenses to compensate for the field curvature distortion of the primary beamlets 111, 112, and 113. The astigmatism compensator array may include a plurality of micro stigmators to compensate for the astigmatism distortion of the primary beamlets 111, 112, and 113. The beam limiting aperture array may be configured to limit the diameters of the individual primary beamlets 111, 112, and 113. Figure 1B Three primary sub-beams 111, 112 and 113 are shown as examples, and it will be appreciated that the source conversion unit 120 may be configured to form any number of primary sub-beams. The controller 50 may be connected to Figure 1A The controller 50 may be used to control various parts of the charged particle beam inspection system 100, such as the first electron detection device 140, the secondary electron detection device 190, or the secondary projection system 150. In some embodiments, as explained in further detail below, the controller 50 may perform various image and signal processing functions. The controller 50 may also generate various control signals to manage the operation of the charged particle beam inspection system 100.

[0035] The condenser lens 110 is configured to focus the primary electron beam 102. The condenser lens 110 can be further configured to adjust the current of the primary sub-beams 111, 112 and 113 downstream of the source conversion unit 120 by changing the focusing ability of the condenser lens 110. Alternatively, the current can be changed by changing the radial size of the beam-limiting holes corresponding to the individual primary sub-beams within the beam-limiting hole array. The current can be changed by changing both the radial size of the beam-limiting holes and the focusing ability of the condenser lens 110. The condenser lens 110 can be a movable condenser lens, which can be configured so that the position of its first principal plane is movable. The movable condenser lens can be configured to be magnetic, which can cause the off-axis sub-beams 112 and 113 to land on the beamlet limiting mechanism at a rotation angle. The rotation angle varies with the focusing ability of the movable condenser lens and the position of its first principal plane. In some embodiments, the movable condenser lens may be a movable anti-rotation condenser lens, which involves an anti-rotation lens having a movable first principal plane.

[0036] The objective lens 131 can be configured to focus the sub-beams 111, 112 and 113 onto the sample 108 for inspection, and in the current embodiment, three detection spots 121, 122 and 123 can be formed on the surface of the sample 108. The aperture plate 171 is configured to block peripheral electrons of the primary electron beam 102 in operation to reduce the Coulomb effect. The Coulomb effect will amplify the size of each of the detection spots 121, 122 and 123 of the primary sub-beams 111, 112 and 113, and thus degrade the inspection scheme.

[0037] For example, the beam splitter 133 may be a Wien filter including an electrostatic deflector ( Figure 1B 1 ). In operation, the beam splitter 133 can be configured to exert an electrostatic force on individual electrons of the primary sub-beams 111, 112, and 113 through an electrostatic dipole field. The electrostatic force is equal in magnitude but opposite in direction to the magnetic force exerted on the individual electrons by the magnetic dipole field of the beam splitter 133. Therefore, the primary sub-beams 111, 112, and 113 can pass through the beam splitter 133 at least substantially straight with a deflection angle that is at least substantially zero.

[0038] The deflection scanning unit 132 is configured in operation to deflect the primary beamlets 111, 112, and 113 so that the detection spots 121, 122, and 123 are scanned across individual scanning areas in a section of the surface of the sample 108. In response to the primary beamlets 111, 112, and 113 being incident on the detection spots 121, 122, and 123, electrons are shaken off the sample 108 and three secondary electron beams 161, 162, and 163 are generated. Each of the secondary electron beams 161, 162, and 163 typically includes electrons with different energies, including secondary electrons (having an electron energy of ≤50 eV) and backscattered electrons (having an electron energy between 50 eV and the landing energy of the primary beamlets 111, 112, and 113). The beam splitter 133 is configured to deflect the secondary electron beams 161, 162, and 163 toward the secondary projection system 150. The secondary projection system 150 then focuses the secondary electron beams 161, 162 and 163 onto the detection elements 141, 142 and 143 of the electron detection device 140. The detection elements 141, 142 and 143 are arranged to detect the corresponding secondary electron beams 161, 162 and 163 and generate corresponding signals, which are sent to a signal processing system (not shown) to, for example, construct an image of the corresponding scanned area of ​​the sample 108.

[0039] In some embodiments, the detection elements 141, 142, and 143 detect the corresponding secondary electron beams 161, 162, and 163, respectively, and generate corresponding intensity signal outputs (not shown) to the image processing system (e.g., the controller 50). In some embodiments, the detection elements 141, 142, and 143 may include one or more pixels. The intensity signal output of the detection element may be the sum of the signals generated by all pixels within the detection element.

[0040] For a multi-beam system, crosstalk in the output signals from adjacent beams can be caused by distortions in the secondary projection system 150 or the deflection accuracy of the secondary electron beams in the beam splitter 133. A variety of factors may cause distortion or dispersion. For example, the beam splitter 133, which changes the direction of the secondary electron beams toward the detector, may deflect the secondary electron beams 161, 162, and 163 at an inaccurate angle. Moreover, the electron detection device 140 or the secondary projection system 150 may not be properly aligned with the secondary optical axis 151. When these misalignments exist, the secondary electron beams 161, 162, and 163 may be affected by undesirable distortions, magnification errors, or rotation angle errors, resulting in distorted shapes, positions, or excessive expansion of beam spots, which in turn may cause overlap or crosstalk between adjacent beams. Therefore, in situations such as Figure 1BIn a multi-beam wafer inspection system of a multi-beam electron beam tool 40 shown in FIG. 4 , reducing these misalignments is important to obtaining accurate image reconstruction of a sample (eg, wafer) for inspection.

[0041] In some embodiments, an electronic image viewer such as the second electron detection device 190 can be used to verify the shape and position of the secondary electron beam spot and determine the alignment characteristics of the secondary electron beam, such as determining whether there is any misalignment in the secondary electron projection path (including the beam splitter 133 and the secondary projection system 150), and whether or to what extent the secondary electron beam is sufficiently focused to form a desired beam spot size, shape, position, etc.

[0042] In some embodiments, the multi-beam electron beam tool 40 can implement two different operating modes, such as an inspection mode and an alignment mode. During the inspection mode, the secondary electron beams 161, 162, and 163 can be directed toward the first electron detection device 140, which then generates an image signal based on the received secondary electron beams. And then, the controller 50 can generate an image of the sample 108 based on the image signal from the first electron detection device 140.

[0043] During the alignment mode, the secondary electron beams 161, 162 and 163 may be directed toward the second electron detection device 190. The second electron detection device 190 may generate images of one or more beam spots of the secondary electron beams on the surface of the detection device. The images of these beam spots may then be used to determine alignment characteristics of the secondary electron beams associated with the first electron detection device 140, which may be affected by the alignment of the secondary projection system 150 itself or the alignment of the secondary electron beams with respect to the secondary projection system 150.

[0044] In some embodiments, the controller 50 may include signal processing circuitry to perform beam boundary determination and beam intensity determination in real time based on the beam spot image generated by the second electron detection device 190 during the alignment mode. A high-speed real-time processor may provide information about how the secondary projection system 150 and beam splitter 133 perform in real time so that any performance deviations (e.g., the shape and position of each beam, the geometry of the electron beam grid, unexpected movement of part or all of the beam due to imperfections in component manufacturing and assembly, drift during long-term operation) may be detected and addressed. In some embodiments, the controller 50 may automatically adjust the configuration of the secondary projection system 150 to calibrate the images of the secondary electron beams 161, 162, and 163.

[0045] In some embodiments, the controller 50 may include an image processing system, which includes an image acquisition device (not shown), a memory (not shown). The image acquisition device may include one or more processors. For example, the image acquisition device may include a computer, a server, a mainframe, a terminal, a personal computer, and various mobile computing devices, etc., or a combination thereof. The image acquisition device may be coupled to the electronic detection device 140 of the device 40 through a medium communication, in particular, the above-mentioned medium is such as an electrical conductor, an optical fiber cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, radio, or a combination thereof. In some embodiments, the image acquisition device may receive a signal from the electronic detection device 140 and may construct an image. The image acquisition device may thus acquire an image of the sample 108. The image acquisition device may also perform various post-processing functions, such as generating a contour, superimposing an indicator on the acquired image, and the like. The image acquisition device may be configured to perform adjustments to the brightness and contrast of the acquired image, etc. In some embodiments, the memory may be a storage medium, such as a hard disk, a flash drive, a cloud storage, a random access memory (RAM), other types of computer-readable memory, and the like. The memory may be coupled to the image acquirer and may be used to store scanned raw image data as an initial image as well as post-processed images.

[0046] In some embodiments, the image acquirer may acquire one or more images of the sample based on the imaging signal received from the electronic detection device 140. The imaging signal may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image including multiple imaging areas. The single image may be stored in the memory. The single image may be an initial image, which may be divided into multiple partitions. Each partition may include an image area containing features of the sample 108. The acquired image may include multiple images of a single imaging area of ​​the sample 108 sampled multiple times within a time series. The multiple images may be stored in the memory. In some embodiments, the controller 50 may be configured to perform an image processing step using multiple images of the same position of the sample 108.

[0047] In some embodiments, the controller 50 may include a measurement circuit (e.g., an analog-to-digital converter) to obtain the distribution of the detected secondary electrons. The electron distribution data collected during the detection time window can be used to reconstruct an image of the inspected wafer structure in combination with the corresponding scan path data of the primary electron beam 102 incident on the wafer surface. The reconstructed image can be used to reveal various features of the internal or external structure of the sample 108, and thus can be used to reveal any defects that may be present in the wafer.

[0048] Although Figure 1BThe apparatus 40 is shown using three primary electron beams, but it will be appreciated that any number of primary electron beams may be used with the apparatus 40. The present disclosure is not limited to the number of primary electron beams used in the apparatus 40.

[0049] Reference now Figure 2 , which is a schematic diagram illustrating an exemplary electronic imaging device 200 having an electron-to-light converter according to an embodiment of the present disclosure. The electronic imaging device 200 may include, in particular, an electron-to-light converter 210 and an optical imaging device such as an optical camera 220. The electron-to-light converter 210 may convert incoming electron beams 241, 242, and 243 into light beams 251, 252, and 253. In some embodiments, the electron-to-light converter 210 may include a scintillator, or any other device or material suitable for converting electrons into photons. When struck by the incoming electron beams 241, 242, and 243, the electron-to-light converter 210 absorbs the energy of the electron beams and re-emits the absorbed energy in the form of photons (e.g., light beams 251, 252, and 253).

[0050] The optical camera 220 may include an optical lens 221 and an image sensor 222. The optical lens 221 may focus the light beams 251, 252, and 253 onto the surface of the image sensor 222. When it receives the focused light beams 251, 252, and 253, the image sensor 222 may generate corresponding electrical signals. In some embodiments, an image processing system (such as Figure 1B A controller 50) can generate an image of the electron beams 241, 242, and 243 based on the electrical signal generated by the image sensor 222. In some embodiments, the image sensor 222 may include a charge coupled device (CCD) sensor, a complementary metal oxide semiconductor (CMOS) sensor, or any other device suitable for generating an electrical signal in response to incoming light.

[0051] In some embodiments, electronic imaging device 220 may be used as an electronic image viewer for alignment, such as Figure 1B The second electronic detection device 190 in.

[0052] Reference now Figure 3A , 3B , 3C and 3D, which are schematic diagrams illustrating exemplary multi-beam electron beam tools according to embodiments of the present disclosure. In some embodiments, a multi-beam electron beam tool (such as Figure 1B The electron beam tool 40 in FIG. 4 may include a secondary projection system 150 (similar to Figure 1B The secondary projection system 150 in FIG. 1 ), the first electronic detection device 140 (similar to Figure 1B The first electronic detection device 140 in FIG. 1 ), and the movable second electronic detection device 301 (similar to Figure 1B In some embodiments, the movable second electronic detection device 301 can be configured to move relative to the first electronic detection device 140 in a direction that, in some embodiments, can be substantially perpendicular to the secondary optical axis 151. In some embodiments, the detection surface of the first electronic detection device 140 and the detection surface of the movable second electronic detection device 301 can be parallel.

[0053] Figure 3A 1 shows a multi-beam electron beam tool during inspection mode. When the tool is in inspection mode, the movable second electron detection device 301 can be moved out of the path of the secondary electron beams 161i, 162i and 163i (eg, Figure 3C and Figure 3D , which are focused onto a detection surface 144 of the first electron detection device 140 ), and thus allow the first electron detection device 140 to receive the secondary electron beams 161i , 162i and 163i for inspection.

[0054] Figure 3B 1 shows a multi-beam electron beam tool during alignment mode. When the tool is in alignment mode, the movable second electron detection device 301 can be moved between the secondary projection system 150 and the first electron detection device 140 and positioned between them, and thus intercept the secondary electron beams 161, 162 and 163 (such as Figure 3C and Figure 3D , which is focused onto the detection surface 311 of the movable second electron detection device 301 ). In some embodiments, the movable second electron detection device 301 can convert the intercepted secondary electron beam into light beams 361 , 362 and 363 .

[0055] In some embodiments, the movable second electronic detection device 301 may include an electronic imaging device using an electron-to-light converter (such as Figure 2 The electronic imaging device 200 shown in FIG. Figure 3C 3 shows an internal schematic diagram of an exemplary movable second electron detection device 301. In such an embodiment, the movable second electron detection device 301 may include a movable conversion guide device 302 and an optical camera 320. The movable conversion guide device 302 may include an electron-light converter 310 and a reflector 330. The electron-light converter 310 may convert the incoming secondary electron beams 161, 162, and 163 into light beams 361, 362, and 363. As described above with respect to Figure 2 As explained, in some embodiments, the electron-to-light converter 310 may include a scintillator, or any other device or material suitable for converting electrons into photons.

[0056] In such an embodiment, the movable conversion guide device 302 can be configured to move relative to the first electron detection device 140 in a direction that, in some embodiments, can be substantially perpendicular to the secondary optical axis 151. In such an embodiment, during the inspection mode, the movable conversion guide device 302 can be moved out of the path of the secondary electron beams 161, 162, and 163, and thus allow the first electron detection device 140 to receive the secondary electron beams 161i, 162i, and 163i for inspection. During the alignment mode, the movable conversion guide device 302 can be moved into the secondary projection system ( Figure 3C 361, 362 and 363, and then directs those beams toward the optical camera 320 using the reflector 330.

[0057] In some embodiments, only the movable transition guide 302 may be configured to move. In other embodiments, the movable second electron detection device 301 including the transition guide may be configured to move relative to the first electron detection device 140 .

[0058] In some embodiments, the optical camera 320 may include an optical lens 321 and an image sensor 322. The optical lens 321 may focus the directed light beams 361, 362, and 363 onto the surface of the image sensor 322. Upon receiving the focused light beams 361, 362, and 363, the image sensor 322 may generate corresponding electrical signals. In some embodiments, an image processing system (such as Figure 1B A controller 50) can process the electrical signals and generate an image of the electron beams 161, 162, and 163 based on the electrical signals from the image sensor 322. In some embodiments, the image sensor 322 may include a charge coupled device (CCD) sensor, a complementary metal oxide semiconductor (CMOS) sensor, or any other device suitable for generating electrical signals in response to incoming light.

[0059] In some embodiments, the movable second electron detection device 301 may not include the reflector 330. Instead, the optical camera 320 may be configured to detect the electron-to-light converter 310 (e.g., Figure 2 However, as shown in FIG. Figure 3CAs shown in , the use of the reflector 330 can allow the electron-to-light converter 310 to be placed closer to the first electron detection device 140 during the alignment mode, so that the image of the secondary electron beam captured during the alignment mode can closely represent the alignment characteristics of the secondary electron beams 161, 162 and 163 associated with the first electron detection device 140.

[0060] In some embodiments, Figure 3D As shown in , the movable second electronic detection device 301 may include a direct detection device (DDD) 340. During the alignment mode, the direct detection device 340 can directly detect the secondary electron beams 161, 162 and 163, and thus the electron-light conversion step can be omitted. During the inspection mode, the direct detection device 340 can be moved out of the path of the secondary electron beams 161, 162 and 163, and thus allow the first electronic detection device 140 to receive the secondary electron beams 161i, 162i and 163i for inspection. In some embodiments, the direct detection device 340 may include one or more CMOS sensors configured to directly detect the secondary electron beams and generate corresponding electrical signals.

[0061] Reference now Figure 4A , 4B 4C and 4D, which are schematic diagrams illustrating exemplary multi-beam electron beam tools according to embodiments of the present disclosure. In some embodiments, a multi-beam electron beam tool (such as Figure 1B The electron beam tool 40 in FIG. 4 may include a secondary projection system 150 (similar to Figure 1B The secondary projection system 150 in FIG. 1 ), the movable first electronic detection device 140 (similar to Figure 1B The first electronic detection device 140 in the embodiment and the second electronic detection device 401 (similar to Figure 1B In such an embodiment, the movable first electronic detection device 140 may be configured to move relative to the second electronic detection device 401 in a direction that, in some embodiments, may be substantially perpendicular to the secondary optical axis 151. In some embodiments, the detection surface of the movable first electronic detection device 140 and the detection surface of the second electronic detection device 401 may be parallel.

[0062] Figure 4A 1 shows a multi-beam electron beam tool during alignment mode. When the tool is in alignment mode, the movable first electron detection device 140 can be moved out of the path of the secondary electron beams 161, 162 and 163, and thus allow the second electron detection device 401 to receive the secondary electron beams 161a, 162a and 163a (such as Figure 4C and Figure 4D, which is focused onto the detection surface 411 of the second electron detection device 301) for alignment.

[0063] Figure 4B 1 shows a multi-beam electron beam tool during inspection mode. When the tool is in inspection mode, the movable first electron detection device 140 can be moved between the secondary projection system 150 and the second electron detection device 401 and positioned between them, and thus the movable first electron detection device 140 receives the secondary electron beams 161, 162 and 163 (such as Figure 4C and Figure 4D , which is focused onto the detection surface 144 of the movable first electronic detection device 140) for inspection.

[0064] Figure 4C A second electron detection device 401 is shown, which includes an imaging device based on an electron-to-light converter (such as Figure 2 In some embodiments, the second electron detection device 401 may include an electron-light converter 410 and an optical camera 420. The electron-light converter 410 may convert the incoming secondary electron beams 161, 162, and 163 into light beams 461, 462, and 463. The optical camera 420 may include an optical lens 421 and an image sensor 422. The image sensor 422 may detect the light beams 461, 462, and 463. Figure 3C As described, the second electron detection device 401 can detect the incoming secondary electron beams 161, 162, and 163, and generate electrical signals to produce one or more images of beam spots of the incoming secondary electron beams 161, 162, and 163. Figure 4C The second electron detection device 401 is shown without a reflector, but a second electron detection device with a reflector (such as Figure 3C A movable second electronic detection device 301 in the embodiment of the present invention.

[0065] Figure 4D A second electron detection device 401 is shown that includes a direct detection device (DDD) 440. The direct detection device 440 can directly detect the secondary electron beams 161, 162, and 163, and thus the electron-light conversion step can be omitted. In some embodiments, the direct detection device 440 can include one or more CMOS sensors that are configured to directly detect the secondary electron beams and generate corresponding electrical signals.

[0066] Reference now Figure 5A and 5B, which are schematic diagrams illustrating exemplary multi-beam electron beam tools according to embodiments of the present disclosure. In some embodiments, the multi-beam electron beam tool may include a movable first electron detection device 140 and a movable second electron detection device 501 positioned side by side. In such embodiments, the first electron detection device 140 and the second electron detection device 501 may be configured to move together in a direction, which in some embodiments may be substantially perpendicular to the secondary optical axis 151. In such embodiments, during the inspection mode (e.g. Figure 5A ), both electronic detection devices can be moved in a first direction (e.g., toward Figure 5A ), so that the first electron detection device 140 can be positioned to receive the secondary electron beams 161, 162 and 163. During this alignment mode (such as Figure 5B ), both electronic detection devices can be moved in a second direction (e.g., toward Figure 5B 1 and 163. In some embodiments, the detection surface of the first electron detection device 140 and the detection surface of the second electron detection device 501 may be parallel.

[0067] As explained above with respect to previous embodiments, in some embodiments, the second electron detection device 501 may include an imaging device based on an electron-to-light converter (such as Figure 3C The second electronic detection device 301 or Figure 4C In some embodiments, the second electronic detection device 501 may include a direct detection device (such as Figure 3D The second electronic detection device 301 or Figure 4D The second electronic detection device 401 in the embodiment of the present invention.

[0068] Reference now Figure 5C and 5D , which are schematic diagrams illustrating exemplary multi-beam electron beam tools according to embodiments of the present disclosure. In some embodiments, the multi-beam electron beam tool may include a rotatable first electron detection device 140 and a rotatable second electron detection device 501 positioned side by side. In such an embodiment, the first electron detection device 140 and the second electron detection device 501 may be configured to rotate together around a rotation axis 550 clockwise or counterclockwise to align the rotatable first electron detection device 140 or the rotatable second electron detection device 501 to detect the secondary electron flow during an inspection mode or an alignment mode, respectively. In such an embodiment, during the inspection mode (such as Figure 5C), both electron detection devices can be rotated so that the first electron detection device 140 is positioned to receive the secondary electron beams 161, 162 and 163 for inspection. During this alignment mode (as shown in FIG. Figure 5D ), both electron detection devices can be rotated 180 degrees from the position in the inspection mode so that the second electron detection device 501 receives the secondary electron beams 161, 162, and 163. In some embodiments, the detection surface of the first electron detection device 140 and the detection surface of the second electron detection device 501 can be parallel.

[0069] As explained above with respect to previous embodiments, in some embodiments, the second electron detection device 501 may include an imaging device based on an electron-to-light converter (such as Figure 3C The movable second electronic detection device 301 or Figure 4C In some embodiments, the second electronic detection device 501 may include a direct detection device (such as Figure 3D The movable second electronic detection device 301 or Figure 4D The second electronic detection device 401 in the embodiment of the present invention.

[0070] Reference now Fig. 6A , 6B 6C, which are schematic diagrams illustrating exemplary multi-beam electron beam tools according to embodiments of the present disclosure. Fig. 6A As shown in , the multi-beam electron beam tool can include a first electron detection device 140 and a second electron detection device 601 positioned side by side. In such an embodiment, a deflector 691 can be used to direct the secondary electron beams 161, 162, and 163 to the second electron detection device 601 during the alignment mode as secondary electron beams 161a, 162a, and 163a as shown. On the other hand, during the inspection mode, the deflector 691 can be disabled so that the secondary electron beams 161, 162, and 163 can travel straight to the first electron detection device 140 as secondary electron beams 161i, 162i, and 163i as shown for inspection. In some embodiments, the detection surface of the first electron detection device 140 and the detection surface of the second electron detection device 601 can be parallel.

[0071] In some embodiments, more than one deflector may be used to change the direction of the secondary electron beam during the alignment mode. Figure 6B and Figure 6CAs shown in , the multi-beam electron beam tool may include a first deflector (deflector 691) and a second deflector (deflector 692). During the alignment mode, the first deflector 691 may be enabled to direct the secondary electron beams 161, 162, and 163 toward the second electron detection device 601, as shown as secondary electron beams 161a, 162a, and 163a, and the second deflector 692 may also be enabled to compensate for the deflection distortion caused by the first deflector 691, so that the second electron detection device 601 can detect the secondary electron beams 161a, 162a, and 163a with low distortion. In some embodiments, the detection surface of the first electron detection device 140 and the detection surface of the second electron detection device 601 may be parallel.

[0072] The location of the second deflector 692 may be flexible. In some embodiments, the first electron detection device 140 and the second electron detection device 601 may be positioned close to each other, which provides a higher similarity between the images captured during the inspection mode and the images captured during the alignment mode. In such a case, the second electron beam paths during the inspection mode and the alignment mode may be substantially close to each other. As a result, there may be no space between the two sets of paths to place the second deflector 692. In such a case, as shown in FIG. Figure 6C As shown in , the second deflector 692 can be positioned further away to enclose both sets of beam paths, so that the first electron detection device 140 and the second electron detection device 601 can be positioned substantially close to each other.

[0073] As explained above with respect to previous embodiments, in some embodiments, the second electron detection device 601 may include an imaging device based on an electron-to-light converter (such as Figure 3C The movable second electronic detection device 301 or Figure 4C In some embodiments, the second electronic detection device 601 may include a direct detection device (such as Figure 3D The movable second electronic detection device 301 or Figure 4D The second electronic detection device 401 in the embodiment of the present invention.

[0074] Reference now Figure 7 , which is a flow chart illustrating steps of an exemplary alignment operation using an embodiment of the multi-beam electron beam tool according to an embodiment of the present disclosure. The method can be performed by a multi-beam electron beam tool (such as Figure 1B The electron beam tool 40 is used to perform the operation.

[0075] At step 710, the multi-beam electron beam tool determines whether alignment mode is enabled. In some embodiments, the multi-beam electron beam tool can implement two different operating modes, such as an inspection mode and an alignment mode. During the inspection mode, a first electronic inspection device (such as Figure 3A and 3B The electronic inspection device 140 can receive the secondary electron beam (such as Figure 3A and 3B During this alignment mode, a second electronic inspection device (such as Figure 3A and 3B The movable second electronic inspection device 301 of the embodiment of the present invention can receive the secondary electron beam. The second electronic inspection device can be used to check the shape and position of the secondary electron beam spot and determine the alignment characteristics of the secondary electron beam, such as determining whether there is a misalignment in the secondary electron projection path and the degree of misalignment. This misalignment, which may cause degradation in the quality of the generated sample image, may be caused by a variety of reasons. For example, a beam splitter (such as a Figure 1B The beam splitter 133 in the secondary projection system may cause the secondary electron beam to be deflected at an inaccurate angle. Figure 1B , 3A and the secondary projection system 150 in 3B) may not be aligned with the secondary optical axis (such as Figure 1B , 3A 3B). In addition, the electronic inspection device may not be properly aligned with the secondary optical axis. When these misalignments exist, the secondary electron beam may be affected by undesirable distortion, magnification errors, or rotation angle errors, thereby resulting in a distorted shape, position, or excessive expansion of the beam spot, which in turn may cause overlap or crosstalk between adjacent beams.

[0076] At step 720, the multi-beam electron beam tool positions the second electron detection device according to the secondary optical axis so that the second electron detection device, but not the first electron detection device, can receive the secondary electron beam.

[0077] At step 730, the multi-beam electron beam tool detects the received secondary electron beam using the second electron beam detection device, and the second electron beam detection device generates a corresponding electrical image signal in response to the detected secondary electron beam.

[0078] At step 740, the multi-beam electron beam tool generates one or more beam spot images of the secondary electron beam based on the electrical image signal output by the second electron detection device. In some embodiments, the second electron detection device is connected to a controller (such as Figure 1BThe controller 50 in the embodiment may include an image processing system configured to generate a beam spot image of the secondary electron beam based on the image signal from the second electron detection device.

[0079] At step 750, the multi-beam electron beam tool determines an alignment characteristic of the secondary electron beam associated with the first electron detection device. In some embodiments, the determination may be performed automatically by the multi-beam electron beam tool (e.g., by the controller). In other embodiments, the determination may be performed manually by an operator of the multi-beam electron beam tool.

[0080] The embodiments may be further described using the following terms:

[0081] 1. A charged particle beam apparatus for inspecting a wafer, comprising:

[0082] a first electron detection device for detecting a plurality of secondary electron beams used for inspection of the wafer; and

[0083] A second electron detection device is used to generate one or more images of one or more beam spots of the plurality of secondary electron beams, wherein the second electron detection device is configured to determine an alignment characteristic associated with the first electron detection device.

[0084] 2. An apparatus according to claim 1, wherein the alignment characteristic associated with the first electron detection device includes the following characteristics of one or more of the multiple secondary electron beams, which are related to the alignment of one or more of the multiple secondary electron beams and the first electron detection device.

[0085] 3. The device according to any one of clauses 1 and 2, further comprising a secondary projection system for projecting the plurality of secondary electron beams onto a detection surface of the first electron detection device or a detection surface of the second electron detection device.

[0086] 4. The apparatus according to clause 3, wherein the secondary projection system is aligned with the secondary optical axis

[0087] 5. The apparatus according to clause 4, wherein the secondary projection system projects the plurality of secondary electron beams onto a detection surface of the first electron detection device in an inspection mode and onto a detection surface of the second electron detection device in an alignment mode.

[0088] 6. The apparatus according to any one of clauses 1 to 5, further comprising a controller comprising a circuit for determining an alignment characteristic associated with the first electron detection device, wherein the alignment characteristic is determined based on the one or more images of the one or more beam spots of the multiple secondary electron beams.

[0089] 7. An apparatus according to claim 6, wherein the controller includes circuitry for providing a user interface for a user to adjust the configuration of the secondary projection system based on the determined alignment characteristic to calibrate the alignment of one or more of the plurality of secondary electron beams with the first electron detection device.

[0090] 8. An apparatus according to claim 6, wherein the controller includes a circuit for automatically adjusting the configuration of the secondary projection system based on the determined alignment characteristic, wherein the automatic adjustment of the configuration of the secondary projection system is used to calibrate the alignment of one or more of the plurality of secondary electron beams with the first electron detection device.

[0091] 9. An apparatus according to any one of clauses 1 to 8, wherein the alignment characteristic comprises a focusing quality of the one or more beam spots of the plurality of secondary electron beams.

[0092] 10. The apparatus according to any one of clauses 1 to 9, wherein the second electronic detection means comprises:

[0093] an electron-light conversion unit configured to convert the plurality of secondary electron beams into a plurality of light beams, and

[0094] An optical camera is used to generate one or more images of the one or more beam spots of the plurality of secondary electron beams based on the plurality of light beams.

[0095] 11. The apparatus according to clause 10, wherein the second electronic detection device further comprises a mirror for directing the plurality of light beams toward the optical camera.

[0096] 12. The device according to any of clauses 10 and 11, wherein the electron-light conversion unit comprises a scintillator.

[0097] 13. The apparatus of any of clauses 10 to 12, wherein the optical camera comprises a charge coupled device (CCD) sensor or a complementary metal oxide semiconductor (CMOS) sensor.

[0098] 14. Apparatus according to any one of clauses 1 to 9, wherein the second electron detection device comprises a direct detection device (DDD) for generating the one or more images of the one or more beam spots of the plurality of secondary electron beams.

[0099] 15. The apparatus of clause 14, wherein the direct detection device comprises a CMOS sensor configured to detect the plurality of secondary electron beams and generate corresponding electrical signals.

[0100] 16. Apparatus according to any of clauses 1 to 15, wherein the second electronic detection means is configured to move relative to the first electronic detection means.

[0101] 17. The apparatus according to clause 16, wherein the second electronic detection device is further configured to:

[0102] In preparation for the alignment mode, moving in a first direction so that the second electron detection device receives the plurality of secondary electron beams, and

[0103] In preparation for the inspection mode, movement is made in the second direction so that the first electron detection device receives the plurality of secondary electron beams.

[0104] 18. Apparatus according to any of clauses 1 to 15, wherein the first electronic detection means is configured to move relative to the second electronic detection means.

[0105] 19. The apparatus according to clause 18, wherein the first electronic detection device is further configured to:

[0106] In preparation for the inspection mode, moving in a first direction so that the first electron detection device receives the plurality of secondary electron beams, and

[0107] In preparation for the alignment mode, movement is made along a second direction so that the second electron detection device receives the plurality of secondary electron beams.

[0108] 20. The apparatus according to any of clauses 1 to 15, wherein the first electronic detection means and the second electronic detection means are positioned side by side and are configured to move together.

[0109] 21. The apparatus according to any of clauses 1 to 15, wherein the first electronic detection means and the second electronic detection means are positioned relative to a rotation axis and are configured to rotate together about the rotation axis to switch between an inspection mode and an alignment mode.

[0110] 22. Apparatus according to any of clauses 20 and 21, wherein the first electron detection device is configured to receive the plurality of secondary electron beams in an inspection mode and the second electron detection device is configured to receive the plurality of secondary electron beams in an alignment mode.

[0111] 23. The apparatus according to any of clauses 1 to 15, further comprising a deflector to direct the plurality of secondary electron beams towards the second electron detection device in an alignment mode.

[0112] 24. The device according to any one of clauses 1 to 23, wherein the detection surface of the first electronic detection device is substantially located on a first plane, and the detection surface of the second electronic detection device is substantially located on a second plane, and the first plane and the second plane are parallel.

[0113] 25. A method for inspecting a wafer using a charged particle beam system, the charged particle beam system having a secondary projection system for projecting a plurality of secondary electron beams onto a detection surface of a first electron detection device, the method comprising:

[0114] generating one or more images of one or more beam spots of the plurality of secondary electron beams using a second electron detection device; and

[0115] An alignment characteristic associated with the first electron detection device is determined based on the one or more images of the one or more beam spots of the plurality of secondary electron beams.

[0116] 26. The method of clause 25, further comprising determining, using a controller, an alignment characteristic associated with the first electron detection device determined based on the one or more images of the one or more beam spots of the plurality of secondary electron beams.

[0117] 27. The method of clause 26, further comprising providing a user interface using the controller for a user to adjust a configuration of the secondary projection system based on the determined alignment characteristic to calibrate alignment of one or more of the plurality of secondary electron beams with the first electron detection device.

[0118] 28. The method of clause 26, further comprising using the controller to automatically adjust a configuration of the secondary projection system based on the determined alignment characteristic to calibrate alignment of one or more of the plurality of secondary electron beams with the first electron detection device.

[0119] 29. The method according to any of clauses 25 to 28, wherein the alignment characteristic comprises a focusing quality of the one or more beam spots of the plurality of secondary electron beams.

[0120] 30. The method of clause 29, wherein automatically adjusting comprises adjusting a configuration of the second projection system to calibrate a focus quality of the one or more beam spots of the plurality of secondary electron beams.

[0121] 31. The method according to any one of clauses 25 to 30 further comprises moving the second electron detection device relative to the first electron detection device so that the second electron detection device can receive the multiple secondary electron beams during the alignment mode and the first electron detection device can receive the multiple secondary electron beams during the inspection mode.

[0122] 32. The method according to any one of clauses 25 to 30 further comprises moving the first electron detection device relative to the second electron detection device so that the second electron detection device can receive the multiple secondary electron beams during the alignment mode and the first electron detection device can receive the multiple secondary electron beams during the inspection mode.

[0123] 33. The method according to any one of clauses 25 to 30 further comprises moving the first electron detection device and the second electron detection device together so that the second electron detection device can receive the multiple secondary electron beams during the alignment mode and the first electron detection device can receive the multiple secondary electron beams during the inspection mode.

[0124] 34. The method according to any one of clauses 25 to 30 further comprises rotating the first electron detection device and the second electron detection device together around a rotation axis so that the second electron detection device can receive the multiple secondary electron beams during an alignment mode and the first electron detection device can receive the multiple secondary electron beams during an inspection mode.

[0125] 35. The method according to any of clauses 25 to 30, further comprising directing the plurality of secondary electron beams towards the second electron detection device using a deflector in an alignment mode.

[0126] 36. The method according to any of clauses 25 to 35, wherein the first electron detection device is configured to receive the plurality of secondary electron beams in the inspection mode and the second electron detection device is configured to receive the plurality of secondary electron beams in the alignment mode.

[0127] 37. The method according to any one of clauses 25 to 36, wherein the detection surface of the first electronic detection device is substantially located on a first plane, and the detection surface of the second electronic detection device is substantially located on a second plane, and the first plane and the second plane are parallel.

[0128] It is to be appreciated that the multi-beam electron beam tool may use software to perform the functions described above. For example, the multi-beam electron beam tool may perform image processing to generate a beam spot pattern of the received secondary electron beam. Moreover, the multi-beam electron beam tool may also perform software functions to automatically determine the alignment characteristics of the secondary electron beam associated with the first electron detection device. In addition, the multi-beam electron beam tool may control and adjust the secondary projection system (e.g., Figure 1BThe software may be stored on a non-transitory computer readable medium. For example, common forms of non-transitory media include floppy disks, diskettes, hard disks, solid-state drives, tapes, or any other magnetic data storage medium, CD-ROMs, any other optical storage medium, physical media with hole patterns, RAM, PROMs and EPROMs, cloud storage, FLASH-EPROMs or any other flash memory, NVRAMs, caches, registers, any other memory chips or cartridges, and networked versions thereof.

[0129] Although the disclosed embodiments have been explained with respect to the preferred embodiments thereof, it is to be understood that other modifications and variations may be made without departing from the spirit and scope of the subject matter as subsequently claimed.

Claims

1. A charged particle beam apparatus for inspecting a wafer, comprising: a first electron detection device for detecting a plurality of secondary electron beams used for inspection of the wafer; and A second electron detection device for generating one or more images of one or more beam spots of the plurality of secondary electron beams, wherein the second electron detection device is configured to determine an alignment characteristic associated with the first electron detection device.

2. An apparatus according to claim 1, wherein the alignment characteristics associated with the first electron detection device include the following characteristics of one or more secondary electron beams in the plurality of secondary electron beams, and the characteristics are related to the alignment of the one or more secondary electron beams in the plurality of secondary electron beams and the first electron detection device.

3. The device according to any one of claims 1 and 2, further comprising a secondary projection system for projecting the plurality of secondary electron beams onto a detection surface of the first electron detection device or a detection surface of the second electron detection device.

4. The apparatus of claim 3, wherein the secondary projection system is aligned with a secondary optical axis.

5. The apparatus of claim 4, wherein the secondary projection system projects the plurality of secondary electron beams onto a detection surface of the first electron detection device in an inspection mode and onto a detection surface of the second electron detection device in an alignment mode.

6. The apparatus according to any one of claims 1 to 5, further comprising a controller comprising a circuit for determining an alignment characteristic associated with the first electron detection device based on the one or more images of the one or more beam spots of the plurality of secondary electron beams.

7. An apparatus according to claim 6, wherein the controller includes circuitry for providing a user interface for a user to adjust a configuration of the secondary projection system based on the determined alignment characteristic to calibrate the alignment of one or more of the plurality of secondary electron beams with the first electron detection device.

8. The apparatus of claim 6 , wherein the controller comprises circuitry for automatically adjusting a configuration of the secondary projection system based on the determined alignment characteristic, the automatic adjustment of the configuration of the secondary projection system being used to calibrate the alignment of one or more of the plurality of secondary electron beams with the first electron detection device.

9. The apparatus according to any one of claims 1 to 8, wherein the alignment characteristic comprises a focusing quality of the one or more beam spots of the plurality of secondary electron beams.

10. The device according to any one of claims 1 to 9, wherein the second electron detection device comprises: an electron-light conversion unit configured to convert the plurality of secondary electron beams into a plurality of light beams, and An optical camera is used to generate one or more images of the one or more beam spots of the plurality of secondary electron beams based on the plurality of light beams.

11. The apparatus of claim 10, wherein the second electronic detection device further comprises a mirror for directing the plurality of light beams toward the optical camera.

12. The device according to any one of claims 10 and 11, wherein the electron-light conversion unit comprises a scintillator.

13. The apparatus of any one of claims 10 to 12, wherein the optical camera comprises a charge coupled device (CCD) sensor or a complementary metal oxide semiconductor (CMOS) sensor.

14. The apparatus according to any one of claims 1 to 9, wherein the second electron detection device comprises a direct detection device (DDD) for generating the one or more images of the one or more beam spots of the plurality of secondary electron beams. 15 . The apparatus of claim 14 , wherein the direct detection device comprises a CMOS sensor configured to detect the plurality of secondary electron beams and generate corresponding electrical signals.

16. The apparatus according to any one of claims 1 to 15, wherein the second electron detection device is configured to move relative to the first electron detection device.

17. The apparatus according to claim 16, wherein the second electronic detection device is further configured to: In preparation for the alignment mode, moving in a first direction so that the second electron detection device receives the plurality of secondary electron beams, and In preparation for the inspection mode, movement is performed in a second direction so that the first electron detection device receives the plurality of secondary electron beams.

18. The apparatus according to any one of claims 1 to 15, wherein the first electron detection device is configured to move relative to the second electron detection device.

19. The apparatus of claim 18, wherein the first electron detection device is further configured to: In preparation for the inspection mode, moving in a first direction so that the first electron detection device receives the plurality of secondary electron beams, and In preparation for the alignment mode, movement is performed in a second direction so that the second electron detection device receives the plurality of secondary electron beams.

20. The apparatus according to any one of claims 1 to 15, wherein the first electron detection device and the second electron detection device are positioned side by side and are configured to move together.

21. The apparatus according to any one of claims 1 to 15, wherein the first and second electron detection devices are positioned relative to a rotation axis and are configured to rotate together about the rotation axis to switch between an inspection mode and an alignment mode.

22. The apparatus of any one of claims 20 and 21, wherein the first electron detection device is configured to receive the plurality of secondary electron beams in an inspection mode, and the second electron detection device is configured to receive the plurality of secondary electron beams in an alignment mode.

23. The apparatus according to any one of claims 1 to 15, further comprising a deflector for directing the plurality of secondary electron beams towards the second electron detection device in an alignment mode.

24. The apparatus according to any one of claims 1 to 23, wherein the detection surface of the first electron detection device is substantially located on a first plane, and the detection surface of the second electron detection device is substantially located on a second plane, and the first plane and the second plane are parallel.

25. A method for inspecting a wafer using a charged particle beam system, the charged particle beam system having a secondary projection system for projecting a plurality of secondary electron beams onto a detection surface of a first electron detection device, the method comprising: generating one or more images of one or more beam spots of the plurality of secondary electron beams using a second electron detection device; and An alignment characteristic associated with the first electron detection device is determined based on the one or more images of the one or more beam spots of the plurality of secondary electron beams.

26. The method of claim 25, further comprising determining, using a controller, an alignment characteristic associated with the first electron detection device determined based on the one or more images of the one or more beam spots of the plurality of secondary electron beams.

27. The method of claim 26, further comprising providing, using the controller, a user interface for a user to adjust a configuration of the secondary projection system based on the determined alignment characteristic to calibrate the alignment of the one or more of the plurality of secondary electron beams with the first electron detection device.

28. The method of claim 26, further comprising automatically adjusting, using the controller, a configuration of the secondary projection system based on the determined alignment characteristic to calibrate alignment of the one or more of the plurality of secondary electron beams with the first electron detection device.

29. The method of any one of claims 25 to 28, wherein the alignment characteristic comprises a focus quality of the one or more beam spots of the plurality of secondary electron beams.

30. The method of claim 29, wherein automatically adjusting comprises adjusting a configuration of the second projection system to calibrate the focus quality of the one or more beam spots of the plurality of secondary electron beams.

31. The method according to any one of claims 25 to 30 further includes moving the second electron detection device relative to the first electron detection device so that the second electron detection device can receive the multiple secondary electron beams during an alignment mode and the first electron detection device can receive the multiple secondary electron beams during an inspection mode.

32. The method according to any one of claims 25 to 30 further includes moving the first electron detection device relative to the second electron detection device so that the second electron detection device can receive the multiple secondary electron beams during an alignment mode and the first electron detection device can receive the multiple secondary electron beams during an inspection mode.

33. The method according to any one of claims 25 to 30 further includes moving the first electron detection device and the second electron detection device together so that the second electron detection device can receive the multiple secondary electron beams during an alignment mode and the first electron detection device can receive the multiple secondary electron beams during an inspection mode.

34. The method according to any one of claims 25 to 30 further includes rotating the first electron detection device and the second electron detection device together around a rotation axis so that the second electron detection device can receive the multiple secondary electron beams during an alignment mode and the first electron detection device can receive the multiple secondary electron beams during an inspection mode.

35. The method of any one of claims 25 to 30, further comprising directing the plurality of secondary electron beams towards the second electron detection device using a deflector in an alignment mode.

36. The method of any one of claims 25 to 35, wherein the first electron detection device is configured to receive the plurality of secondary electron beams in the inspection mode, and the second electron detection device is configured to receive the plurality of secondary electron beams in the alignment mode.

37. The method according to any one of claims 25 to 36, wherein the detection surface of the first electron detection device is substantially located on a first plane, and the detection surface of the second electron detection device is substantially located on a second plane, and the first plane and the second plane are parallel.

Images