In-lens wafer pre-charge and inspection using multiple beams

Abstract

A charged particle system (400) may include a first charged particle beam source disposed on a first axis (470), and a second charged particle beam source (420) disposed on a second axis. A deflector (430) disposed on the first shaft may also be provided. The deflector may be configured to deflect the beam generated from the second charged particle beam source toward the sample (403). A method of operating a charged particle beam system includes switching between a first state of operating a deflector (430) and a second state. In the first state, a first charged particle beam generated from the first charged particle beam source may be extinguished, and a second charged particle beam generated from the second charged particle beam source may be directed toward the sample. In the second state, the second charged particle beam may be extinguished and the first charged particle beam may be directed toward the sample.

Description

[0001] This application is a divisional application filed on November 22, 2019, the international application date, entered the Chinese national phase on June 29, 2021, with application number 201980087174.7 and invention name “Charged particle beam system and operation method thereof”.

[0002] CROSS-REFERENCE TO RELATED APPLICATIONS

[0003] This application claims priority to U.S. Application No. 62 / 787,128, filed December 31, 2018, which is incorporated herein by reference in its entirety. Technical Field

[0004] Various embodiments provided herein relate to charged particle optical systems that may be applied to charged particle devices having one or more charged particle beams, such as electron microscopy devices utilizing one or more electron beams. Background Art

[0005] During the manufacturing process of integrated circuits (ICs), circuit components may be inspected to ensure that they are manufactured as designed and are free of defects. Pattern defects, uninvited particles (e.g., residues), etc. may appear on a wafer or mask during manufacturing, thereby reducing the yield. For example, uninvited particles may be troublesome for patterns with smaller critical feature sizes, which may have been adopted to meet the increasingly advanced performance requirements of IC chips.

[0006] Charged particle (e.g., electron) beam microscopes, such as scanning electron microscopes (SEM) or transmission electron microscopes (TEM), can have resolutions down to less than a nanometer, which can be used as practical tools for inspecting IC components with feature sizes down to, for example, sub-100 nanometer scale. In a SEM tool, a primary electron beam with relatively high energy can be decelerated to land on a sample with a relatively low landing energy and focused to form a probe spot thereon. Since the primary electrons are incident on the sample at the focused probe spot, secondary electrons may be generated from the surface. By scanning the probe spot over the sample surface and collecting the secondary electrons, the detection tool can obtain an image of the sample surface.

[0007] In some applications, voltage contrast methods can be used with charged particle beam inspection systems to detect physical and electrical defects on samples. However, these conventional systems are in need of improvement. Summary of the invention

[0008] Embodiments of the present disclosure may provide a charged particle optical system, which may include a first charged particle beam source disposed on a first axis and a second charged particle beam source that may be disposed on a second axis. A component disposed on the first axis may also be provided, the component being configured to deflect a beam generated from the second charged particle beam source toward a sample. The first charged particle beam source may be a primary electron beam source of a scanning electron microscope. The component may include a deflector, an electrostatic lens, a magnetic lens, a Wien filter, and the like.

[0009] A method of operating a charged particle beam system may also be provided. The method may include switching between a first state and a second state of an operating component. The component may be configured to generate a magnetic field or an electric field. In the first state, a first charged particle beam generated from a first charged particle beam source may be extinguished, and a second charged particle beam generated from a second charged particle beam source may be directed toward a sample. In the second state, the second charged particle beam may be extinguished, and the first charged particle beam may be directed toward the sample. The first state may correspond to a pre-charging operation, and the second state may correspond to an imaging operation.

[0010] According to some embodiments, switching between pre-charging and imaging can be performed faster and more efficiently. Furthermore, the flexibility of system design can be enhanced.

[0011] Additional objects and advantages of the disclosed embodiments are partially set forth in the following description, and these objects and advantages become apparent in part from the description, or may be learned through the practice of the embodiments. The objects and advantages of the disclosed embodiments may be realized and obtained through the elements and combinations set forth in the present disclosure. However, the exemplary embodiments of the present disclosure do not necessarily need to achieve such exemplary objects and advantages, and some embodiments may not achieve any of the objects and advantages.

[0012] It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosed embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The above and other aspects of the present disclosure will become more apparent through the description of exemplary embodiments in conjunction with the accompanying drawings, in which

[0014] Figure 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system according to an embodiment of the present disclosure.

[0015] Figure 2A and Figure 2B An exemplary electron beam tool according to an embodiment of the present disclosure is illustrated, which may be Figure 1 Part of an electron beam inspection system.

[0016] Figure 3 Exemplary time characteristics of charging and checking according to an embodiment of the present disclosure are illustrated.

[0017] Figure 4 An exemplary electron beam tool according to an embodiment of the present disclosure is illustrated, which may be Figure 1 Part of an electron beam inspection system. DETAILED DESCRIPTION

[0018] Reference is now made in detail to the exemplary embodiments, examples of which are illustrated in the accompanying drawings. The following descriptions all refer to the accompanying drawings, wherein the same reference numerals in different drawings represent the same or similar elements unless otherwise specified. 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 systems, devices, and methods consistent with aspects related to the present invention as set forth in the appended claims. For clarity, the relative sizes of the components in the drawings may be exaggerated.

[0019] The increased computing power of electronic devices while reducing the physical size of the devices can be achieved by significantly increasing the packaging density of circuit components (such as transistors, capacitors, diodes, etc.) on IC chips. For example, in a smartphone, an IC chip (which may be only the size of a fingernail) may contain more than 2 billion transistors, each less than 1 / 1000 the size of a human hair. Not surprisingly, semiconductor IC manufacturing is a complex process with hundreds of individual steps. Even an error in one step may significantly affect the functionality of the final product. Even one "fatal defect" may 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 obtain a 75% yield, each individual step yield must be greater than 99.4%, and if the individual step yield is 95%, the overall process yield drops to 7%.

[0020] The ability to ensure defects are detected with high accuracy and resolution while maintaining high throughput (e.g., defined as the number of wafers processed per hour) is becoming increasingly important. High process yields and high wafer throughputs can be impacted by the presence of defects, especially when operator intervention is involved. Therefore, detecting and identifying micron-sized defects and nano-sized defects by inspection tools such as SEM is very important to maintain high yields and low costs.

[0021] As stated above, in some applications, physical and electrical defects on a sample can be detected using a voltage contrast method of a charged particle beam detection system. In order to detect voltage contrast defects, a process called pre-charging is typically employed, in which charged particles are applied to the area to be inspected prior to inspection. The benefits of pre-charging can include, among other things: 1) the ability to supply enough charged particles to the wafer to generate a voltage on the features of the wafer sufficient to cause the defective features and surrounding non-defective features to appear different under inspection (e.g., voltage contrast inspection); and 2) enhancing the voltage contrast signal of the defect, so that a satisfactory signal-to-noise ratio (SNR) can be obtained, and the defect can be easily detected in a charged particle detection system.

[0022] In conventional systems, pre-charging can be accomplished by scanning the primary beam of a charged particle inspection tool over the sample surface prior to inspection using the primary beam. Alternatively, a separate charged particle source can be used to pre-charge the wafer surface and set the charging conditions. A separate charged particle source, such as a dedicated flood beam electron gun, can be used to enhance the voltage contrast defect signal, thereby improving defect detection sensitivity or throughput. During the flood process, a flood gun can be used to provide a relatively large amount of electrons to charge a predefined area. Thereafter, the primary electron source of the electron beam inspection system can be applied to scan an area within the pre-charged area to achieve imaging of the area.

[0023] However, current pre-charging techniques may face some of the following limitations. First, there may be a critical charge decay time in certain applications. For example, the charge accumulated on the sample surface may decay relatively quickly, so some applications may require a quick switch from pre-charging to inspection. This may impose constraints on the systems and methods used for inspection. Additionally, some current techniques may involve physically moving the platform supporting the sample, which is time consuming and also introduces error sources.

[0024] Second, throughput may be limited. For example, some applications (e.g., 3D NAND) may require precharging on a per-stripe basis. Frequent switching between precharging and checking scans may be required. The time and expense associated with switching events may negatively impact process throughput.

[0025] Third, when a dedicated flood gun is provided, its performance may be limited by cost constraints due to being a subcomponent of other subsystems in the charged particle detection system or due to delays caused by the sample having to be physically moved to enter the beam path of the flood gun. Further, a conventional flood gun may have more simplified control compared to, for example, the primary beam source of an SEM. Thus, the flood gun may have limited controllability and low precision. Additionally, attempts to address these limitations by modifying the dedicated flood gun to have more precise controllability may be impractical and expensive. Moreover, packaging constraints may limit the amount of modification that may be made to a dedicated flood gun that occupies space in a charged particle beam inspection system.

[0026] Fourth, when the primary beam of the inspection system is used for pre-charging, primary beam flooding may cause aperture contamination. The primary beam of the inspection system may be configured to expose the aperture to a large amount of electrons, and the aperture may be easily contaminated.

[0027] To summarize these traditional inspection tools, pre-charging of the sample can be used to deposit charge on the sample surface before imaging. In some applications, the accumulated charge on the sample may decay quickly. Therefore, it may be necessary to switch back and forth between the pre-charging process and the imaging process in order to maintain the appropriate charge level on the sample to continue imaging. However, switching between pre-charging and imaging may involve many complex issues. For example, as discussed above, switching may be too time consuming, detrimental to throughput, difficult to control, and may cause aperture contamination. Therefore, there is a need for improved systems and methods that may facilitate pre-charging and imaging.

[0028] The present disclosure particularly provides a system and method for charged particle imaging. In some embodiments, in addition to the primary charged particle beam source, a second dedicated charged particle beam source is also provided. The primary charged particle beam source and the second charged particle beam source can be configured to share a single objective lens. The second charged particle beam source can be arranged at a specific angle or angle range so that it can generate a beam whose trajectory can be adjusted by an alignment deflector (e.g., a Wein filter). Further, the alignment deflector can be configured to operate in a first operating state and a second operating state, wherein the change between the first operating state and the second operating state involves adjusting the voltage applied to the alignment deflector. Therefore, it is possible to switch between a first state of a charged particle beam system in which pre-charging can be performed and a second state in which imaging can be performed more quickly.

[0029] Without limiting the scope of the present disclosure, the description and drawings of the embodiments may illustratively refer to the use of electron beams. However, the embodiments are not intended to limit the present invention to specific charged particles. For example, systems and methods for beam forming may be applied to photons, x-rays, and ions, etc. Furthermore, the term "beam" may refer to a primary electron beam, a primary electron beamlet, a secondary electron beam, or a secondary electron beamlet, etc.

[0030] As used herein, unless specifically stated otherwise, the term "or" encompasses all possible combinations unless not feasible. For example, if it is stated that a component includes A or B, then unless otherwise specifically stated or not feasible, the component may include A, or B, or A and B. As a second example, if it is stated that a component includes A, B, or C, then unless otherwise specifically stated or not feasible, the component may include A, or B, or C, or A and B, or A and C, or B and C, or A and B and C.

[0031] Various embodiments of the present disclosure may achieve numerous other advantages, which shall be discussed below.

[0032] Now, refer to Figure 1 ,Should Figure 1 An exemplary electron beam inspection (EBI) system 10 is illustrated, which may include a detector, according to an embodiment of the present disclosure. The EBI system 10 may be used for imaging. Figure 1 As shown, the EBI system 10 includes a main chamber 11, a load / lock chamber 20, an electron beam tool 100, and an equipment front end module (EFEM) 30. The electron beam tool 100 is located in the main chamber 11. The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include one or more load ports. The first load port 30a and the second load port 30b receive a wafer front opening integration unit (FOUP) containing a wafer (e.g., a semiconductor wafer or a wafer made of other materials) or a sample to be inspected (wafers and samples may be collectively referred to as "wafers" herein).

[0033] One or more robots (not shown) in the EFEM 30 can transport the wafer to the load / lock chamber 20. The load / lock chamber 20 is connected to a load / lock vacuum pump system (not shown), which removes gas molecules in the load / lock chamber 20 to reach a first pressure lower than atmospheric pressure. After reaching the first pressure, one or more robots (not shown) can transport the wafer from the load / lock chamber 20 to the main chamber 11. The main chamber 11 is connected to a main chamber vacuum pump system (not shown), which removes gas molecules in the main chamber 11 to reach a second pressure lower than the first pressure. After reaching the second pressure, the wafer is inspected by the electron beam tool 100. The electron beam tool 100 can be a single beam system or a multi-beam system. The controller 109 is electrically connected to the electron beam tool 100, and can also be electrically connected to other components. The controller 109 can be a computer configured to perform various controls of the EBI system 10. Although the controller 109 is Figure 1 1. The controller 109 is shown as being located outside the structure including the main chamber 11, the load / lock chamber 20, and the EFEM 30, but it should be appreciated that the controller 109 may be part of the structure.

[0034] Figure 2A is a schematic diagram illustrating an exemplary electron beam tool 100A that may be used in an EBI system 10 according to the disclosed embodiments. Figure 2A As shown, the electron beam tool 100A includes a motorized stage 150 and a wafer holder 102, which is supported by the motorized stage 150 to hold a wafer to be inspected 103. The electron beam tool 100A also includes a compound objective lens 104, an electron detector 106, an objective lens aperture 108, a focusing lens 110, a beam limiting aperture 112, a gun aperture 114, an anode 116, and a cathode 118, one or more of which can be aligned with the optical axis 170 of the electron beam tool 100A.

[0035] In some embodiments, the composite objective 104 may include a modified swing objective retarding immersion lens (SORIL) including a pole piece 104a, a control electrode 104b, a deflector or a set of deflectors 104c, and an excitation coil 104d. The electron beam tool 100A may additionally include an energy dispersive X-ray spectrometer (EDS) detector (not shown) to characterize materials on the wafer.

[0036] By applying a voltage between the anode 116 and the cathode 118, a primary electron beam 120 may be emitted from the cathode 118. The primary electron beam 120 passes through the gun aperture 114 and the beam limiting aperture 112, both of which may determine the current of the electron beam entering the focusing lens 110, which is located below the beam limiting aperture 112. The focusing lens 110 may focus the primary electron beam 120 before the beam enters the objective aperture 108 to set the current of the electron beam before entering the compound objective lens 104.

[0037] The composite objective lens 104 can focus the primary electron beam 120 onto the wafer 103 for inspection, and can form a probe spot 122 on the surface of the wafer 103. The deflector 104c deflects the primary electron beam 120 to scan the probe spot 122 on the wafer 103. For example, during the scanning process, the deflector 104c can be controlled to sequentially deflect the primary electron beam 120 to different positions on the top surface of the wafer 103 at different time points to provide data for image reconstruction of different parts of the wafer 103. Moreover, the deflector 104c can also be controlled to deflect the primary electron beam 120 to different sides of the wafer 103 at specific positions and different connection points to provide data for stereoscopic image reconstruction of the wafer structure at the position. Further, in some embodiments, the anode 116 and the cathode 118 can be configured to generate multiple primary electron beams 120, and the electron beam tool 100A can include multiple deflectors 104c to simultaneously project multiple primary electron beams 120 to different parts or sides of the wafer 103.

[0038] When current is applied to the excitation coil 104d, an axisymmetric (i.e., symmetrical about the optical axis 170) magnetic field can be generated in the region of the wafer surface. A portion of the wafer 103 scanned by the primary electron beam 120 can be immersed in the magnetic field. Different voltages can be applied to the wafer 103, the pole piece 104a, and the control electrode 104b to generate an axisymmetric deceleration electric field near the wafer surface. The electric field can reduce the energy of the primary electron beam 120 striking the wafer 103 before it collides with the wafer 103. The control electrode 104b, which is electrically isolated from the pole piece 104a, can control the axisymmetric electric field on the wafer to prevent micro-arcing of the wafer, and together with the axisymmetric magnetic field, ensure proper beam focusing at the wafer surface.

[0039] Upon receiving the primary electron beam 120, the secondary electron beam 130 may be emitted from a portion of the wafer 103. The secondary electron beam 130 may be received by a sensor surface of the electron detector 106. The electron detector 106 may generate a signal (voltage, current, etc.) representing the intensity of the secondary electron beam 130, and provide the signal to a controller 109 that may communicate with the electron detector 106. The intensity of the secondary electron beam 130 may vary depending on the external structure or internal structure of the wafer 103. Moreover, as discussed above, the primary electron beam 120 may be projected onto different locations on the top surface of the wafer 103, or onto different sides of the wafer 103 at a specific location, to generate secondary electron beams 130 of different intensities. By mapping the intensity of the secondary electron beam 130 to the location of the wafer 103, the controller 109 may reconstruct an image reflecting the internal structure or external structure of the wafer 103.

[0040] Moreover, despite Figure 2A An example of an electron beam tool 100A that can use a single primary electron beam is shown, but the EBI system 10 can include an electron beam tool 100 that can also be a multi-beam inspection tool using multiple primary electron beams. The application does not limit the number of primary electron beams used in the electron beam tool 100.

[0041] For example, Figure 2B As shown, an electron beam tool 100B (also referred to herein as an apparatus 100A) may be provided, the electron beam tool 100B comprising an electron source 202, a gun aperture 204, a focusing lens 206, a primary electron beam 210 emitted from the electron source 202, a source conversion unit 212, a plurality of sub-beams 214, 216 and 218 of the primary electron beam 210, a primary projection optical system 220, a wafer stage ( Figure 2B ), a plurality of secondary electron beams 236, 238 and 240, a secondary optical system 242, and an electronic detection device 244. A controller, an image processing system, etc. may be coupled to the electronic detection device 244. The primary projection optical system 220 may include a beam splitter 222, a deflection scanning unit 226, and an objective lens 228. The electronic detection device 244 may include detection sub-areas 246, 248 and 250.

[0042] Electron source 202, gun aperture 204, focusing lens 206, source conversion unit 212, beam splitter 222, deflection scanning unit 226, and objective lens 228 may be aligned with primary optical axis 260 of apparatus 100A. Secondary optical system 242 and electron detection device 244 may be aligned with secondary optical axis 252 of apparatus 100A.

[0043] The electron source 202 may include a cathode, an extractor, or an anode, wherein primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 210 having an intersection point (virtual or real) 208. The primary electron beam 210 may be considered to be emitted from the intersection point 208. The gun aperture 204 may block peripheral electrons of the primary electron beam 210 to reduce the size of the probe spots 270, 272, and 274.

[0044] The source conversion unit 212 may include an imaging element array ( Figure 2B not shown) and the beam limiting aperture array ( Figure 2B 214 , 216 , and 218 . The imaging element array may include a micro-deflector or a micro-lens array. The imaging element array may form multiple parallel images (virtual or real) of the intersection 208 with the multiple sub-beams 214 , 216 , and 218 of the primary electron beam 210 . The beam limiting aperture array may limit the multiple sub-beams 214 , 216 , and 218 .

[0045] The converging lens 206 can focus the primary electron beam 210. The current of the sub-beams 214, 216 and 218 downstream of the source conversion unit 212 can be changed by adjusting the focusing power of the converging lens 206 or by changing the radial size of the corresponding beam limiting apertures in the beam limiting aperture array. The converging lens 206 can be a movable converging lens, which can be configured so that the position of its first principal plane is movable. The movable converging lens can be configured to be magnetic, which can cause the off-axis sub-beams 216 and 218 to land on the sub-beam limiting aperture at a rotation angle. The rotation angle changes with the focusing power and the position of the first principal plane of the movable converging lens. In some embodiments, the movable converging lens can be a movable anti-rotation converging lens, which includes an anti-rotation lens having a movable first principal plane. The movable converging lens is further described in U.S. Publication No. 2017 / 0025241, which is incorporated by reference in its entirety.

[0046] Objective lens 228 may focus beamlets 214 , 216 , and 218 onto wafer 230 for inspection and may form a plurality of probe spots 270 , 272 , and 274 on the surface of wafer 230 .

[0047] The beam splitter 222 can be a Wien filter type beam splitter that generates an electrostatic dipole field and a magnetic dipole field. In some embodiments, if the electrostatic dipole field and the magnetic dipole field are applied, the force exerted by the electrostatic dipole field on the electrons of the sub-beams 214, 216, and 218 can be equal in magnitude and opposite in direction to the force exerted by the magnetic dipole field on the electrons. Therefore, the sub-beams 214, 216, and 218 can pass straight through the beam splitter 222 at a zero deflection angle. However, the total dispersion of the sub-beams 214, 216, and 218 generated by the beam splitter 222 can also be non-zero. The beam splitter 222 can separate the secondary electron beams 236, 238, and 240 from the sub-beams 214, 216, and 218, and guide the secondary electron beams 236, 238, and 240 toward the secondary optical system 242.

[0048] The deflection scanning unit 226 can deflect the beamlets 214, 216, and 218 to scan the probe spots 270, 272, and 274 on the surface area of ​​the wafer 230. The secondary electron beams 236, 238, and 240 can include electrons with energy distributions, including secondary electrons and backscattered electrons. The secondary optical system 242 can focus the secondary electron beams 236, 238, and 240 onto the detection sub-regions 246, 248, and 250 of the electron detection device 244. The detection sub-regions 246, 248, and 250 can be configured to detect the corresponding secondary electron beams 236, 238, and 240, and generate corresponding signals, which are used to reconstruct an image of the surface area of ​​the wafer 230.

[0049] Now, refer to Figure 3 ,Should Figure 3 Exemplary time characteristics of charging and checking are illustrated. Figure 3 The horizontal axis of the graph represents time. Figure 3 The ordinate of the graph of represents the amount of charge on the wafer surface in arbitrary units. In some embodiments, for example, wafer preconditioning can be performed prior to inspection, defect review, or other types of imaging. Preconditioning can include precharging the wafer surface. Precharging can be used to enhance voltage contrast type defect signals, for example, as discussed in U.S. Patent Nos. 8,748,815 and 8,759,762, the entire contents of which are incorporated herein by reference.

[0050] like Figure 3 As shown, during the charging period 310, the wafer surface can accumulate charge. The charging period 310 can include a transition period 311 and a steady-state period 312. In the transition period 311, the charge can be built up relatively quickly; and in the steady-state period 312, the charging rate can be reduced and the charge can be close to a maximum value. The charging period 310 can be described by a time constant. The charging period 310 can correspond to applying a pre-charge beam to the wafer.

[0051] During the inspection period 320, the charge may dissipate. The inspection period 320 may correspond to a time when the pre-charge beam is no longer applied to the wafer. In some embodiments, the charge may dissipate quickly from the wafer surface, leaving little time to perform an inspection. For example, after applying the pre-charge beam to the sample, time may elapse while the equipment switches from the pre-charge beam to the inspection beam, and a time Tb may be reached at which the surface charge of the sample is reduced to zero or close to zero before the inspection may be completed, resulting in certain defects such as not being detected during the voltage contrast inspection. Therefore, it may be necessary to perform the pre-charge again.

[0052] Additionally, in some applications, detection performance may be limited by the time it takes to switch between pre-charging and imaging (also called switching time.) If the charge dissipates before the detection beam engages the sample due to the switching time, no amount of pre-charging will enable effective detection of certain defects.

[0053] Some applications may require a predetermined amount of charge to remain on the wafer before inspection. In some embodiments, charge decay may be an important parameter for imaging. In particular, some applications may use samples with very high charge decay rates, so it may be necessary to switch between pre-charge and imaging modes very quickly or very frequently.

[0054] Now, refer to Figure 4 ,Should Figure 4 An exemplary electron beam tool 400 is shown, which may also be Figure 1 The electron beam tool 400 (also referred to herein as "device 400") can be similar to the device 100A or 100B. The electron beam tool 400 includes a primary electron beam source 410 that can be used for imaging (such as defect inspection). The primary electron beam source 410 can include, among other things, a cathode, an anode, and an aperture. The primary electron beam source 410 can also include a lens. The primary electron beam source 410 can be configured to emit electrons along a primary optical axis 470 to project onto the wafer 403.

[0055] The device 400 may also be provided with a second electron beam source 420. The second electron beam source 420 may be a separate component that is separated and physically separated from the primary electron beam source 410. The second electron beam source 420 may include components similar to the primary electron beam source and may be configured to emit electrons along a second optical axis. The second optical axis may form an angle β with the main optical axis 470. The second electron beam source 420 may be installed so as to form a certain angle relative to the main column of the device 400. In some embodiments, the angle β may be less than or equal to 30 degrees. The angle β may be determined based on packaging constraints. In some embodiments, the angle β may be within 10 to 20 degrees. The second electron beam source 420 may be used for pre-conditioning, such as pre-charging of the wafer 403.

[0056] The second electron beam source 420 may include a gun aperture 421, a lens 422, and an extinguisher 423. The lens 422 may be an electrostatic lens. The lens 422 may be used to control the spot size of the electron beam generated by the second electron beam source 420. In some embodiments, the lens 422 may be a magnetic lens. The extinguisher 423 may be configured to switch the beam generated from the second electron beam source 420 from an on state to an off state.

[0057] In some embodiments, the charged particle beam system may include a first charged particle beam source configured to provide a first charged particle to image the sample at a first time. For example, the device 400 may include a primary electron beam source 410, which may be configured to provide primary electrons that can be used to image the wafer 403. The charged particle beam system may also include a component configured to provide a second charged particle to pre-condition the sample at a second time. For example, the device 400 may include a second electron beam source 420, which may be configured to provide flood electrons to the wafer 403. The charged particle beam system may also include a component configured to generate an electrostatic field or a magnetic field to affect the first charged particle to impact the sample at a first time and affect the second charged particle to impact the sample at a second time.

[0058] The device 400 may include a lower column including an alignment deflector 430, a scanning deflector 432, and an objective lens 435, all or some of which may be aligned with the main optical axis 470. The alignment deflector 430 may include a component configured to generate an electrostatic field or a magnetic field. The component may generate both an electrostatic field and a magnetic field and may be used as a velocity filter for charged particles. The alignment deflector 430 may include a magnetic lens. The alignment deflector 430 may include an electrostatic lens. In some embodiments, the alignment deflector 430 may include a Wien filter. The alignment deflector 430 may be used as a beam splitter to separate charged particles having different velocities from each other. The alignment deflector 430 may affect charged particles traveling through it. In some embodiments, the effect of the alignment deflector 430 may include enabling electrons to travel straight through the alignment deflector 430. For example, the alignment deflector 430 can be configured such that electrons traveling from the primary electron beam source 410 along the primary optical axis 470 toward the wafer 403 are allowed to travel straight through the alignment deflector 430 while secondary electrons or backscattered electrons traveling back from the wafer 403 are deflected. Figure 2B In the example of FIG. 2 , the beam splitter 222 may be configured to affect the secondary beam by shifting the secondary beam toward the electronic detection device 244 by an angle α.

[0059] return Figure 4 , the apparatus 400 may further include an objective lens 435. The second electron beam source 420 may be configured as an in-lens system. For example, only one objective lens may be provided to both the primary electron beam source 410 and the second electron beam source 420. The second electron beam source 420 may bypass the column aperture 411 that may be provided for the primary electron beam source 410. Therefore, controlling the imaging conditions of the second electron beam source 420 may be performed separately from the primary electron beam source 410. The imaging conditions for the primary electron beam source 410, which may be relatively sensitive, may remain intact, while the conditions for the second electron beam source 420 may be manipulated without affecting the primary electron beam source 410. For example, the levels of beam current and focus may be adjusted independently.

[0060] The second electron beam source 420 can be shielded from the primary electron beam source 410. For example, electromagnetic shielding can be provided around some or all of the components included in the second electron beam source 420. In some embodiments, the lens 422 of the second electron beam source 420 can be provided as an electrostatic lens. Compared to, for example, a magnetic lens, the electrostatic lens can reduce interference with the primary electron beam source 410. In some embodiments, an electromagnetic shielding tube can be provided around some or all of the components of the second electron beam source 420, or around the beam, so as to shield the beam from electromagnetic interference.

[0061] The gun aperture 421 of the second electron beam source 420 may include an adjustable aperture. The adjustable aperture may be a movable aperture including a plurality of aperture holes that may be used to select different beam currents to flood the wafer 403. The extinguisher 423 may be used to extinguish the beam of the second electron beam source 420 at certain times, for example, to divert the beam of the second electron beam source 420 away from the wafer 403 during image scanning by the primary electron beam source 410.

[0062] In operation, the device 400 can be controlled in two states, for example, as follows. The first state may include precharging, while the second state may include imaging. In the first state, the primary electron beam source 410 can be used to generate a primary electron beam along the main optical axis 470. The primary electron beam can be extinguished. For example, a deflector can be provided, which is controlled to cause the primary electron beam to be transferred from a trajectory parallel to the main optical axis 470. Therefore, the primary electron beam can be transferred away from a sample, such as a wafer 403. While the beam from the primary electron beam source 410 is extinguished, the second electron beam source 420 can generate an electron beam. The beam generated by the second electron beam source 420 can be used to precharge the wafer 403. During precharging, the alignment deflector 430 can be set to a first operating state. The alignment deflector 430 can be configured so that in the first operating state, the beam generated by the second electron beam source 420 is directed to the wafer 403. For example, the alignment deflector 430 can be set using a first predetermined setting of voltage and current.

[0063] In the second state, after pre-charging, the beam generated by the secondary electron beam source 420 can be extinguished, and the primary beam generated by the primary electron beam source 410 can begin to scan a point of interest (POI) on the surface of the wafer 403. During the second state, the alignment deflector 430 can be set to a second operating state. The alignment deflector 430 can be configured such that in the second operating state, the beam generated by the primary electron beam source 410 is directed to the wafer 403. For example, the alignment deflector 430 can be set using a second predetermined setting of voltage and current.

[0064] The arrangement of the components in the primary electron beam source 410 can be maintained in the first state and the second state. For example, the converging lens can operate in the same operating conditions in the first state and the second state. Further, other components can also maintain their arrangement. For example, the objective lens 435 can operate in the same operating conditions in the first state and the second state. The objective lens 435 can be configured to focus the beam generated from the primary electron beam source 410 to form a probe spot on the wafer 403 in the second state.

[0065] In the first state, as discussed above, the electron beam tool can be configured to operate in a charging period 310, as described below with reference to Figure 3 Meanwhile, in the second state, the electron beam tool can be configured to operate in the inspection period 320, as described above with reference to Figure 3 discussed.

[0066] In some embodiments, the components of the EBI system 10 may be configured to switch between a first state and a second state. For example, the controller 109 may be configured to switch operating states. The controller 109 may send instructions to various components of a charged particle beam system (such as a system including an electron beam tool 100A, an electron beam tool 100B, or an electron beam tool 400). A beam splitter, an alignment deflector, or a Wein filter may be configured to switch between a first operating state and a second operating state. For example, the alignment deflector 430 may be configured to change an operating voltage from a first voltage to a second voltage. The first voltage may be used for a first operating state and may be greater than a second voltage that may be used for a second operating state. The switching between the first state and the second state may be achieved by changing the operating voltage of the alignment deflector 430 and changing the state of the extinguisher of the primary electron beam source 410 and the second electron beam source 420, thereby switching which beam in the beam generated by the primary electron beam source 410 and the second electron beam source 420 is directed to the wafer 403.

[0067] The switch between the first state and the second state may include only changing the voltage of the alignment deflector 430. The current level applied to the alignment deflector 430 may remain constant between the first state and the second state. Although the alignment deflector 430 may be configured to generate both an electrostatic field and a magnetic field, the switch between the first state and the second state may only require changing the voltage applied to the alignment deflector 430, thereby only changing the electrostatic part of the field generated by the alignment deflector 430. At the same time, the magnetic field generated by the alignment deflector 430 may remain constant between the first state and the second state. In some embodiments, changing the magnetic field may involve a hysteresis effect, and a relatively long period of time may be required before the magnetic field stabilizes. However, in some embodiments of the present disclosure, the switch between the first state and the second state can be achieved by only changing the electrostatic field. The electrostatic field can be changed quickly and without hysteresis. Therefore, the additional impact on the beam passing through the alignment deflector 430 can be minimized.

[0068] For example, in some embodiments, changing the voltage applied to the alignment deflector 430 between values ​​of 200 V and 800 V may take a change time of 0.1 ms to 0.2 ms. In contrast, adjusting the magnetic field generated by the magnetic lens may take several seconds.

[0069] In some embodiments, taking into account various criteria, angle β can be set to a minimum. For example, the smaller the angle β, the smaller the voltage difference required for the switching operating state of the alignment deflector 430. The smaller voltage difference between the operating states can correspond to the lower speed required for switching. Further, higher angles may require higher voltages, which may lead to increased manufacturing constraints on the components of the charged particle beam system. For example, using components designed for higher voltages may bring about the complexity of manufacturing and design. In some embodiments, angle β can be set so that only the electrostatic components of the alignment deflector 430 need to be adjusted to transfer the beam generated from the second electron beam source 420 to reach the wafer 403.

[0070] In addition, during the first state, in the case of pre-charging being performed, signal detection cannot be ignored. The beam generated from the second electron beam source 420 can be applied to the wafer 403 for pre-charging, but during the pre-charging, it may not be necessary to measure the signal. Therefore, even if a large number of electrons can be generated based on the interaction of the beam generated from the second electron beam source 420 with the surface of the wafer 403, the collection of secondary electrons or backscattered electrons may not be a problem. Therefore, the electrons traveling from the wafer 403 can be guided toward other areas of the device 400. It is not necessary to guide the secondary electrons from the wafer 403 in the first state to the detector 444. On the contrary, since a large number of electrons may be incident on the wafer 403, it may be beneficial that the secondary electrons or backscattered electrons are diverted and prevented from reaching the detector 444 to avoid contaminating the detector 444.

[0071] When the alignment deflector 430 is configured to divert the beam generated from the second electron beam source 420 to reach the wafer 403, the electrostatic field and the magnetic field generated from the alignment deflector 430 may be unbalanced. Therefore, when passing through the alignment deflector 430 again, the electrons generated by the interaction of the primary electron beam with the surface of the wafer 403 may be caused to travel in a direction away from the detector 444. Therefore, when the alignment deflector 430 is configured to divert the electron beam generated from the second electron beam source 420 to reach the wafer 403, it can also be ensured that other electrons are blocked from reaching the detector 444.

[0072] For example, the basic setting of the alignment deflector 430 can be to balance the electrostatic and magnetic fields so that the electron beam generated from the primary electron beam source 410 is allowed to travel straight through the alignment deflector 430 without substantially changing its trajectory. Upon interacting with the surface of the wafer 403, the secondary charged particles (such as secondary electrons or backscattered electrons) can be directed back in the opposite direction toward the primary electron beam source 410. In some embodiments, the secondary charged particles can be directed toward an on-axis detector (such as detector 444), such as Figure 4In other embodiments, the secondary charged particles may be directed toward an off-axis detector, such as electron detector device 244, as shown. Figure 2B The alignment deflector may be configured such that in the second state the secondary charged particles are directed towards the detector, whereas in the first state the secondary charged particles are directed to a location other than the detector.

[0073] In some embodiments, the need for pre-charging using the primary electron beam source 410 may be avoided. Thus, contamination of the column aperture 411 may be reduced. For example, in some embodiments, when the primary electron beam source 410 is configured to generate a relatively wide beam, some portions of the beam may be incident on the top surface of the column aperture 411. The current of the primary electron beam may be high, and thus may cause high heat and high contamination on the column aperture 411, particularly when the primary electron beam is configured to flood.

[0074] Compared with the primary electron beam source 410, the second electron beam source 420 may have different design requirements. For example, because the second electron beam source 420 may be used only for pre-charging and not for detailed inspection, the design criteria of the second electron beam source 420 may only include ensuring that a predetermined number of electrons reach the sample. Parameters such as beam shape and size may not be particularly relevant. In some embodiments, a rough beam shape with a diameter of several microns may be suitable for use as a pre-charged beam. Therefore, compared with the primary electron beam source 410, the selection of components for the second electron beam source 420 may not necessarily be very strict, and the second electron beam source 420 may be provided in an inexpensive manner and with greater design flexibility. Further, in some embodiments, because a pre-charged beam may not be required to scan across the sample, a scanning deflector may be omitted from the second electron beam source 420.

[0075] In some embodiments, the time required to switch between the pre-charge mode and the imaging mode can be significantly reduced. For example, the switching time can be reduced to the order of nanoseconds. The switch between the first state and the second state can be achieved simply by adjusting the voltage applied to the alignment deflector (such as a Wein filter). The imaging duty cycle and the pre-charge time can be optimized with greater flexibility depending on the application.

[0076] The embodiments may also be described using the following terms:

[0077] 1. A charged particle beam system, comprising:

[0078] a first charged particle beam source disposed on a first axis;

[0079] a second charged particle beam source; and

[0080] A component is arranged on the first axis and is configured to deflect the beam generated from the second charged particle beam source toward the sample.

[0081] 2. A charged particle beam system according to clause 1, wherein the component is configured to generate a magnetic field or an electric field.

[0082] 3. A charged particle beam system according to clause 2, wherein the component configured to generate a magnetic field or an electric field comprises a deflector configured to generate a magnetic field and an electric field.

[0083] 4. Charged particle beam system according to any of the preceding clauses, wherein the component is arranged in the region of the objective.

[0084] 5. The charged particle beam system according to clause 4, wherein only one objective lens is arranged in the charged particle beam system.

[0085] 6. A charged particle system according to any of the preceding clauses, further comprising a driver configured to supply an adjustable voltage to the component.

[0086] 7. A charged particle beam system according to any of the preceding clauses, wherein the charged particle beam system is configured to switch between a first state and a second state, wherein in the second state, a first charged particle beam generated from a first charged particle beam source is directed toward a sample, and in the first state, a second charged particle beam generated from a second charged particle beam source is directed toward the sample.

[0087] 8. The charged particle beam system of clause 7, wherein the component is configured to switch between the first state and the second state.

[0088] 9. The charged-particle beam system of clause 8, further comprising a controller configured to switch the component between the first state and the second state.

[0089] 10. The charged particle beam system according to any of the preceding clauses, wherein an angle between a second axis on which the second charged particle beam source is arranged and the first axis is less than 30 degrees.

[0090] 11. The charged particle beam system of clause 10, wherein the angle is between 10 and 20 degrees.

[0091] 12. The charged particle beam system according to any of the preceding clauses, further comprising an electrostatic lens disposed in the second charged particle beam source, the electrostatic lens being configured to focus a beam generated therefrom.

[0092] 13. A method of operating a charged particle beam system, the method comprising:

[0093] switching between a first state and a second state of an operating component, the component being configured to generate a magnetic field and an electric field,

[0094] wherein in the first state, a first charged particle beam generated from a first charged particle beam source is extinguished, and a second charged particle beam generated from a second charged particle beam source is guided toward the sample, and

[0095] In the second state, the second charged particle beam is extinguished and the first charged particle beam is directed toward the sample.

[0096] 14. The method according to clause 13, further comprising:

[0097] supplying a first voltage to the component in the first state; and

[0098] A second voltage is supplied to the component in the second state.

[0099] 15. The method of clause 14, wherein the first voltage is less than the second voltage.

[0100] 16. A charged particle beam system comprising:

[0101] a first charged particle beam source configured to provide first charged particles to image the sample at a first time;

[0102] a second charged particle beam source configured to provide second charged particles to precondition the sample at a second time; and

[0103] A component is configured to generate an electrostatic field or a magnetic field to affect the first charged particles to impact the sample at the first time and to affect the second charged particles to impact the sample at the second time.

[0104] 17. A charged particle beam system according to clause 16, wherein the component is a magnetic lens.

[0105] 18. A charged particle beam system according to clause 16, wherein the component is a deflector.

[0106] 19. A charged particle beam system according to clause 16, wherein the component is an electrostatic lens.

[0107] 20. The charged particle beam system of clause 16, wherein the component is a Wien filter.

[0108] 21. The charged-particle beam system of clause 16, wherein the component configured to generate an electrostatic field or a magnetic field comprises a component configured to generate an electrostatic field and a magnetic field.

[0109] 22. Charged particle beam system according to any of clauses 16 to 21, wherein the component is arranged in the region of the objective.

[0110] 23. The charged particle beam system according to clause 22, wherein only one objective lens is arranged in the charged particle beam system.

[0111] 24. A charged particle beam system according to any of clauses 16 to 23, further comprising a driver configured to supply an adjustable voltage to the component.

[0112] 25. A charged particle beam system according to any one of clauses 16 to 24, wherein the charged particle beam system is configured to switch between a first state and a second state, wherein in the second state the first charged particle beam is directed toward the sample, and in the first state the second charged particle beam is directed toward the sample.

[0113] 26. The charged-particle beam system of clause 25, wherein the component is configured to switch between the first state and the second state.

[0114] 27. The charged-particle beam system of clause 26, further comprising a controller configured to switch the component between the first state and the second state.

[0115] 28. A charged particle beam system according to any of clauses 16 to 27, wherein an angle between a first axis on which the first charged particle beam source is arranged and a second axis on which the second charged particle beam source is arranged is less than 30 degrees.

[0116] 29. A charged particle beam system according to clause 28, wherein the angle is between 10 and 20 degrees.

[0117] 30. The charged particle beam system according to any of clauses 16 to 29, further comprising an electrostatic lens disposed in the second charged particle beam source, the electrostatic lens being configured to focus a beam generated therefrom.

[0118] Aspects of the present disclosure may be advantageously applied in applications such as 3D NAND and DRAM, for example, where decay time may be a critical parameter, and thus shortening the switching time between precharge and imaging may yield many benefits. Still further, aspects of the present disclosure may be particularly applicable to certain types of defect inspection, such as voltage contact defects, including, for example, shorted gates, floating gates, and open interconnects.

[0119] In some embodiments, a controller may be provided to control the charged particle beam system. For example, Figure 1A controller 109 connected to the EBI system 10 is illustrated. The controller can instruct components of the charged particle beam system to perform various functions, such as controlling a charged particle beam source to generate a charged particle beam, controlling a deflector to scan a charged particle beam across a sample, controlling switching between a first state and a second state, and controlling a driver to apply a voltage or other signal to a lens or other component, such as an alignment deflector. The controller can also perform various post-processing functions, image acquisition, image segmentation, image processing, generating contours, superimposing indicators on the acquired image, etc. The controller can include a storage device as a storage medium, such as a hard disk, a cloud storage device, a random access memory (RAM), other types of computer readable memory, etc. The storage device can be used to save the scanned raw image data as a raw image, or to save a post-processed image. The controller can communicate with cloud storage. A non-transitory computer readable medium can be provided, which stores instructions for the processor of the controller 109 to perform beamforming, lens control, or other functions and methods consistent with the present disclosure. 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, PROM and EPROM, FLASH-EPROM or any other flash memory, NVRAM, cache, registers, any other memory chip or cartridge, and networked versions of these.

[0120] Although the present invention has been explained with respect to some exemplary embodiments, it should be understood that other modifications and variations may be made without departing from the spirit and scope of the present invention as claimed below. For example, although the composite lens has been discussed with reference to application as a first zoom lens, the composite lens may be used as a second zoom lens or other lens in a particle optical system. Further, one or more lenses or other optical components may be added at various points for the particular configuration of the exemplary particle optical system discussed herein. Optical components may be provided for, for example, magnification, scaling, and image anti-rotation, etc.

Claims

1. A charged particle beam system, comprising: a first charged particle beam source; a second charged particle beam source; as well as a component configured to deflect a beam generated from said second charged particle beam source toward a sample; Wherein the charged particle beam system is configured to switch between a first state and a second state, wherein: In the second state, the first charged particle beam generated from the first charged particle beam source is directed toward the sample, In the first state, a second charged particle beam generated from the second charged particle beam source is directed toward the sample; and In both the first state and the second state, the operating conditions of the focusing lens of the first charged particle beam source and the objective lens of the charged particle beam system are maintained. 2 . The charged particle beam system of claim 1 , wherein the component is configured to generate a magnetic field or an electric field. 3 . The charged particle beam system of claim 2 , wherein the component configured to generate the magnetic field or the electric field comprises a deflector configured to generate the magnetic field and the electric field. The charged particle beam system according to claim 1 , wherein the component is arranged in the region of the objective. The charged particle beam system according to claim 4 , wherein only one objective lens is arranged in the charged particle beam system. 6 . The charged-particle beam system of claim 1 , further comprising a driver configured to supply an adjustable voltage to the component.

7. The charged-particle beam system of claim 1, wherein the component is configured to switch between the first state and the second state. 8 . The charged particle beam system of claim 7 , further comprising a controller configured to switch the component between the first state and the second state. 9 . The charged particle beam system of claim 1 , wherein an angle between a second axis and the first axis is less than 30 degrees, and the second charged particle beam source is disposed on the second axis.

10. The charged particle beam system of claim 9, wherein the angle is 10 to 20 degrees. 11 . The charged particle beam system according to claim 1 , further comprising an electrostatic lens disposed in the second charged particle beam source, the electrostatic lens being configured to focus the beam generated from the second charged particle beam source.

12. A non-transitory computer readable medium having a set of instructions stored thereon, the set of instructions being configured to cause a charged particle beam system to: switching between a first state and a second state of operating a component, the component being configured to generate a magnetic field and an electric field, wherein in the first state, a first charged particle beam generated from a first charged particle beam source is extinguished, and a second charged particle beam generated from a second charged particle beam source is guided toward the sample, and In the second state, the second charged particle beam is extinguished, and the first charged particle beam is directed toward the sample.

13. The non-transitory computer readable medium of claim 12, further comprising: supplying a first voltage to the component in the first state; as well as A second voltage is supplied to the component in the second state.

14. The non-transitory computer readable medium of claim 13, wherein the first voltage is less than the second voltage.

15. A charged particle beam system, comprising: a first charged particle beam source configured to provide first charged particles to image the sample at a first time; a second charged particle beam source configured to provide second charged particles to precondition the sample at a second time; as well as A component is configured to generate an electrostatic field or a magnetic field to affect the first charged particles to impact the sample at the first time and to affect the second charged particles to impact the sample at the second time.

16. The charged particle beam system of claim 15, wherein the component is a magnetic lens.

17. The charged particle beam system of claim 15, wherein the component is a deflector.

18. The charged particle beam system of claim 15, wherein the component is an electrostatic lens.

19. The charged particle beam system of claim 15, wherein the component is a Wien filter.

20. The charged-particle beam system of claim 15, wherein the component configured to generate the electrostatic field or the magnetic field comprises the component configured to generate the electrostatic field and the magnetic field.

21. A charged particle beam system according to any one of claims 15 to 20, wherein the component is arranged in the region of the objective.

22. The charged particle beam system of claim 21, wherein only one objective lens is provided in the charged particle beam system.

23. The charged particle beam system of any one of claims 15 to 22, further comprising a driver configured to supply an adjustable voltage to the component.

24. A charged particle beam system according to any one of claims 15 to 23, wherein the charged particle beam system is configured to switch between a first state and a second state, wherein in the second state, the first charged particles are directed toward the sample, and in the first state, the second charged particles are directed toward the sample.

25. The charged particle beam system of claim 24, wherein the component is configured to switch between the first state and the second state.

26. The charged particle beam system of claim 25, further comprising a controller configured to switch the component between the first state and the second state.

27. The charged particle beam system according to any one of claims 15 to 26, wherein an angle between a first axis on which the first charged particle beam source is disposed and a second axis on which the second charged particle beam source is disposed is less than 30 degrees.

28. The charged particle beam system of claim 27, wherein the angle is 10 to 20 degrees.

29. The charged particle beam system according to any one of claims 15 to 28, further comprising an electrostatic lens disposed in the second charged particle beam source, the electrostatic lens being configured to focus a beam generated from the second charged particle beam source.

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