System and method for defect detection by voltage contrast imaging

Abstract

Systems and methods for detecting defects in a sample using a charged particle beam device are disclosed. The apparatus may include a charged particle source configured to emit charged particles and a controller including circuitry configured to: illuminate a region of a sample including a plurality of features with a first dose of charged particles of a primary charged particle beam; examining a plurality of features using a second dose of charged particles of the primary charged particle beam, acquiring images of the examined plurality of features; and determining whether there is a defect based on a gray level value of a feature of the plurality of features, where the first dose is less than a saturation dose, and where the saturation dose includes a total number of charged particles exceeding a charge storage capacity of the feature.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to U.S. Application No. 63 / 352,924, filed on June 16, 2022, and the entire contents of which are incorporated herein by reference. Technical Field

[0003] Embodiments provided herein disclose a charged particle beam apparatus, and more particularly, disclose a system and method for improving voltage contrast defect detection capabilities in three-dimensional (3D) structures. Background Art

[0004] During the manufacturing process of integrated circuits (ICs), unfinished or finished circuit components are inspected to ensure that they are manufactured according to the design and are free of defects. Inspection systems using optical microscopes or charged particle (e.g., electron) beam microscopes such as scanning electron microscopes (SEMs) can be used. As the complexity of device architectures increases, accurately inspecting 3D structures becomes increasingly important. Although voltage contrast inspection techniques can be used to detect buried physical or electrical defects in such complex device structures, existing technologies have problems such as low inspection throughput, strict requirements for stage positioning and high movement accuracy, and limited size of the region of interest. Summary of the invention

[0005] One aspect of the present invention relates to a charged particle beam device for detecting defects in a sample. The charged particle beam device may include a charged particle source, which is configured to emit charged particles, and the emitted charged particles form a primary charged particle beam. The device may also include a controller, which includes a circuit system, which is configured to: irradiate a region of the sample including multiple features using a first dose of charged particles of the primary charged particle beam; inspect multiple features using a second dose of charged particles of the primary charged particle beam, the second dose being different from the first dose; acquire an image of the inspected multiple features; and determine whether there is a defect based on the grayscale value of a feature in the multiple features, the grayscale value being determined based on the acquired image of the multiple features, wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds the charge storage capacity of the feature.

[0006] Another aspect of the present invention relates to a charged particle beam device for detecting defects in a sample. The charged particle beam device may include a charged particle source configured to emit charged particles, and the emitted charged particles form a primary charged particle beam. The device may also include a controller, the controller including a circuit system, the circuit system configured to: irradiate a region of the sample including a plurality of contact pads using a first dose of charged particles of the primary charged particle beam, the plurality of contact pads being configured to form an electrical connection to a corresponding plurality of word lines of a memory device; inspect the plurality of contact pads using a second dose of charged particles of the primary charged particle beam, the second dose being different from the first dose; acquire an image of the inspected plurality of contact pads; and determine whether there is a defect based on a grayscale value of a contact pad in the plurality of contact pads, the grayscale value being determined based on the acquired image of the plurality of contact pads, wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds the charge storage capacity of a word line in the plurality of word lines.

[0007] Another aspect of the present invention relates to a method for detecting defects in a sample using a charged particle beam device. The method may include: irradiating an area including multiple features of the sample using a charged particle beam to charge each of the multiple features using a first dose of charged particles of the charged particle beam; inspecting the multiple features using a second dose of charged particles of the charged particle beam, the second dose being different from the first dose; acquiring an image of the inspected multiple features; and determining whether a defect exists based on a grayscale value of the feature, the grayscale value being determined based on the acquired image of the multiple features, wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds the charge storage capacity of the feature.

[0008] Another aspect of the present invention relates to a method for detecting defects in a sample using a charged particle beam device. The method may include: irradiating a region of the sample including a plurality of features using a charged particle beam to charge each of the plurality of features using a first dose of charged particles of the charged particle beam; inspecting the plurality of features using a second dose of charged particles of the charged particle beam, the second dose being different from the first dose; acquiring an image of the inspected plurality of features; and determining whether a defect exists based on a grayscale value of the feature, the grayscale value being determined based on the acquired image of the plurality of features, wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds the charge storage capacity of the feature.

[0009] Another aspect of the present invention relates to a method for detecting defects in a sample using a charged particle beam device. The method may include: irradiating a region of the sample including a plurality of contact pads using a charged particle beam to charge each of the plurality of contact pads using a first dose of charged particles of the charged particle beam, the plurality of contact pads being configured to form an electrical connection with a corresponding plurality of word lines of a memory device; inspecting the plurality of contact pads using a second dose of charged particles of the charged particle beam, the second dose being different from the first dose; acquiring an image of the plurality of contact pads; and determining whether a defect exists based on a grayscale value of a contact pad in the plurality of contact pads, the grayscale value being determined based on the acquired image of the plurality of contact pads, wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of a word line in the plurality of word lines.

[0010] Another aspect of the present invention relates to a non-transitory computer-readable medium storing a set of instructions that can be executed by one or more processors of a charged particle beam device to cause the charged particle beam device to perform a method for detecting defects in a sample using the charged particle beam device. The method may include: irradiating an area of ​​the sample including a plurality of features using a charged particle beam to charge each of the plurality of features using a first dose of charged particles of the charged particle beam; inspecting the plurality of features using a second dose of charged particles of the charged particle beam, the second dose being different from the first dose; acquiring an image of the inspected plurality of features; and determining whether a defect exists based on a grayscale value of the feature, the grayscale value being determined based on the acquired image of the plurality of features, wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds the charge storage capacity of the feature.

[0011] Another aspect of the present invention relates to a non-transitory computer-readable medium storing a set of instructions that can be executed by one or more processors of a charged particle beam device to cause the charged particle beam device to perform a method for detecting defects in a sample using the charged particle beam device. The method may include: irradiating an area of ​​the sample including a plurality of contact pads using a charged particle beam to charge each of the plurality of contact pads using a first dose of charged particles of the charged particle beam, the plurality of contact pads being configured to form an electrical connection with a corresponding plurality of word lines of a memory device; inspecting the plurality of contact pads using a second dose of charged particles of the charged particle beam, the second dose being different from the first dose; acquiring an image of the plurality of contact pads; and determining whether a defect exists based on a grayscale value of a contact pad in the plurality of contact pads, the grayscale value being determined based on the acquired image of the plurality of contact pads, wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of a word line in the plurality of word lines.

[0012] Other advantages of the embodiments of the present disclosure will become apparent from the following description taken in conjunction with the accompanying drawings, in which certain embodiments of the present invention are set forth by way of illustration and example. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a schematic diagram illustrating an exemplary electron beam inspection (EBI) system according to an embodiment of the present invention.

[0014] Figure 2 It is a diagram illustrating that the embodiment according to the present disclosure may be Figure 1 A schematic diagram of an exemplary electron beam tool that is a portion of an exemplary electron beam inspection system.

[0015] Figure 3 is a schematic diagram illustrating a ladder structure of an exemplary 3D NAND memory device.

[0016] Figure 4 Illustrated is a schematic representation of a grayscale value signal of a contact connected to a non-defective word line when a dose of charged particles is applied according to an embodiment of the present disclosure.

[0017] Figure 5 Illustrated is a schematic representation of a grayscale value signal in response to applying a dose of charged particles from a charged particle beam in a pre-scan mode according to an embodiment of the present disclosure.

[0018] Figure 6 A schematic diagram of word lines and corresponding contacts exposed to a pre-scan and a subsequent inspection scan performed in a region of interest (ROI) according to an embodiment of the present disclosure is illustrated.

[0019] Figure 7 A perspective view of an exemplary word line stack is illustrated in accordance with an embodiment of the present invention.

[0020] Fig. 8A A cross-sectional view of an exemplary word line stack including defects in accordance with an embodiment of the present invention is illustrated.

[0021] Figure 8B An exploded view of an exemplary word line in accordance with an embodiment of the present invention is illustrated.

[0022] Fig. 9 is a data graph of simulated capacitance values ​​of capacitors with varying thicknesses according to an embodiment of the present disclosure.

[0023] Fig.10 is a process flow chart of an exemplary method for detecting defects according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0024] Now, reference is made in detail to the exemplary embodiments, examples of which are shown in the accompanying drawings. The following description refers to the accompanying drawings, wherein, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. The implementations set forth in the following description of the exemplary embodiments do not represent all implementations. Instead, they are merely examples of devices and methods according to aspects related to the disclosed embodiments described in the appended claims. For example, although some embodiments are described in the context of utilizing electron beams, the present disclosure is not limited thereto. Other types of charged particle beams may be similarly applied. Further, other imaging systems such as optical imaging, photoelectric detection, x-ray detection, etc. may be used.

[0025] Electronic devices consist of circuits formed on a silicon wafer called a substrate. Many circuits can be formed together on the same silicon wafer and are called integrated circuits or ICs. The size of these circuits has been significantly reduced so that more of them can fit on a substrate. For example, an IC chip in a smartphone can be as small as a thumbnail and can also include more than 2 billion transistors, each of which is less than 1 / 1000 the size of a human hair.

[0026] Manufacturing these extremely small ICs is a complex, time-consuming and expensive process, typically involving hundreds of individual steps. An error in even one step can result in a defect in the finished IC, thereby rendering it useless. Therefore, one goal of the manufacturing process is to avoid such defects in order to maximize the number of functional ICs manufactured in the process, that is, to increase the overall yield of the process.

[0027] One component of improving yield is to monitor the chip manufacturing process to ensure that it produces a sufficient number of functional integrated circuits. One way to monitor the process is to inspect the chip circuit structure at various stages of its formation. Inspection can be performed using a scanning electron microscope (SEM). The SEM can be used to image these extremely small structures, in effect, taking "photos" of the structures. The image can be used to determine whether the structure was formed correctly and whether it was formed in the correct location. If the structure is defective, the process can be adjusted so that the defect is less likely to occur again.

[0028] In semiconductor devices, buried defects such as voids or particles may result in full open and leakage (short circuit), or in some cases partial open or partial leakage. Existing voltage contrast inspection techniques used to detect such defects involve flood exposure of the surface with negatively charged particles (e.g., electrons), and rely on differences in surface potential measurements of structures on the surface. The grayscale level of pixels representing surface areas with high surface potential is higher than the grayscale level of pixels representing areas with lower surface potential (appearing brighter in SEM images). The grayscale level of the structure is compared to a reference grayscale level to detect defects. Existing techniques for detecting defects using voltage contrast inspection are based on a selective pre-scanning method, in which a small portion of the feature of interest is charged using a saturation dose of charged particles. Some of the several disadvantages associated with this method include low inspection throughput, high requirements for stage positioning and movement accuracy, limitations on the scannable size of the region of interest, unstable charging control, etc.

[0029] Some embodiments of the present invention relate to an apparatus and method for detecting defects in a sample by voltage contrast inspection. The method may include a pre-scanning step and an inspection step. In the pre-scanning step, a low dose of charged particles may be used to irradiate one or more features such as contact pads connected to word lines of a 3D NAND device. The dose of charged particles used for the pre-scanning step may be lower than a threshold dose. In the inspection step, after the pre-scanning step, a second dose of charged particles may be used to inspect the features, which may generate signal charged particles, such as secondary electrons or backscattered electrons in a SEM, when interacting with the features. Defects in the features may be detected based on the grayscale value of the features in the acquired image. Non-defective features exposed to a low-dose pre-scan may appear as dark pixels or exhibit dark voltage contrast signals, while defective features associated with defects may appear as bright pixels or exhibit bright voltage contrast signals exposed to a low-dose pre-scan. Using low-dose pre-scan flooding of charged particles to detect defects in complex device architectures such as defects in 3D NAND devices can enable inspection of larger areas of interest with less stringent requirements on stage positioning and movement accuracy while maintaining high inspection throughput.

[0030] For the sake of clarity, the relative size of parts in the accompanying drawings may be enlarged. In the following description of the drawings, the same or similar reference numerals refer to the same or similar parts or entities, and only describe the difference about each embodiment. As used herein, unless otherwise specifically stated or infeasible, the term "or" encompasses all possible combinations. For example, if the description part can include A or B, then unless otherwise specifically stated or infeasible, the part can include A, or B, or A and B. As a second example, if the description part can include A, B or C, then unless otherwise specifically stated or infeasible, the part can 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] Reference now Figure 1 , Figure 1 An exemplary electron beam inspection (EBI) system 100 is illustrated in accordance with an embodiment of the present disclosure. Figure 1 As shown, the charged particle beam detection 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 within the main chamber 10. Although the description and drawings are directed to electron beams, it should be appreciated that the embodiments are not intended to limit the present disclosure to specific charged particles.

[0032] The EFEM 30 includes a first loading port 30a and a second loading port 30b. The EFEM 30 may include one or more additional loading ports. The first loading port 30a and the second loading port 30b receive a wafer front opening pod (FOUP) containing wafers (e.g., semiconductor wafers, or wafers made of one or more other materials) or samples to be inspected (wafers and samples are collectively referred to as "wafers" hereinafter). One or more robotic arms (not shown) in the EFEM 30 transfer the wafers to the load-lock chamber 20.

[0033] The load-lock chamber 20 is 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) transfer the wafer from the load-lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum 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 subjected to inspection by an electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single beam inspection tool. In other embodiments, the electron beam tool 40 may include a multi-beam inspection tool.

[0034] The controller 50 may be electrically connected to the electron beam tool 40 and may also be electrically connected to other components. The controller 50 may be a computer configured to perform various controls for the charged particle beam inspection system 100. The controller 50 may also include processing circuitry configured to perform various signal and image processing functions. Figure 1 Controller 50 is shown as being outside of the structure including main chamber 10, load-lock chamber 20, and EFEM 30, but it should be appreciated that controller 50 may be part of the structure.

[0035] Although the present disclosure provides an example of a main chamber 10 housing an electron beam inspection system, it should be noted that aspects of the present disclosure in its broadest sense are not limited to chambers housing electron beam inspection systems. Rather, it should be appreciated that the aforementioned principles may also be applied to other chambers.

[0036] Reference now Figure 2 , Figure 2 is a schematic diagram illustrating an exemplary configuration of an electron beam tool 40 according to an embodiment of the present disclosure, which may be Figure 1 The electron beam tool 40 (also referred to herein as the device 40) may include an electron emitter, which may include a cathode 203, an extractor electrode 205, a gun aperture 220, and an anode 222. The electron beam tool 40 may also include a Coulomb aperture array 224, a focusing lens 226, a beam limiting aperture array 235, an objective lens assembly 232, and an electron detector 244. The electron beam tool 40 may also include a sample holder 236 supported by a motorized stage 234 to hold a sample 250 to be inspected. It should be appreciated that other related components may be added or omitted as desired.

[0037] In some embodiments, the electron emitter may include a cathode 203, an anode 222, where primary electrons may be emitted from the cathode and extracted or accelerated to form a primary electron beam 204 that forms a primary beam cross 202. The primary electron beam 204 may be visualized as being emitted from the primary beam cross 202.

[0038] In some embodiments, the electron emitter, focusing lens 226, objective lens assembly 232, beam limiting aperture array 235, and electron detector 244 can be aligned with the primary optical axis 201 of the device 40. In some embodiments, the electron detector 244 can be positioned offset from the primary optical axis 201 along a secondary optical axis (not shown).

[0039] In some embodiments, the objective lens assembly 232 may include a modified swinging objective deceleration immersion lens (SORIL) including a pole piece 232a, a control electrode 232b, a beam manipulator assembly including deflectors 240a, 240b, 240d, and 240e, and an excitation coil 232d. In a general imaging process, a primary electron beam 204 emitted from the tip of the cathode 203 is accelerated by an accelerating voltage applied to the anode 222. Portions of the primary electron beam 204 pass through the apertures in the gun aperture 220 and the Coulomb aperture array 224, and are focused by a focusing lens 226 so as to pass through the apertures in the beam limiting aperture array 235 in whole or in part. Electrons passing through the apertures in the beam limiting aperture array 235 may be focused by the modified SORIL lens to form a detection spot on the surface of the sample 250, and the electrons are deflected by one or more deflectors of the beam manipulator assembly to scan the surface of the sample 250. Secondary electrons emitted from the sample surface may be collected by electron detector 244 to form an image of the scanned region of interest.

[0040] In the objective lens assembly 232, the excitation coil 232d and the pole piece 232a can generate a magnetic field. A portion of the sample 250 scanned by the primary electron beam 204 can be immersed in the magnetic field and can be charged, which in turn creates an electric field. The electric field can reduce the energy of the primary electron beam 204 that strikes near and on the surface of the sample 250. The control electrode 232b electrically isolated from the pole piece 232a can control, for example, the electric field above and on the sample 250 to reduce the aberration of the objective lens assembly 232, and control the focusing of the signal electron beam to obtain high detection efficiency, or avoid arc discharge to protect the sample. One or more deflectors of the beam manipulator assembly can deflect the primary electron beam 204 to facilitate beam scanning on the sample 250. For example, during the scanning process, the deflectors 240a, 240b, 240d and 240e can be controlled to deflect the primary electron beam 204 to different positions on the top surface of the sample 250 at different time points to provide data for image reconstruction of different parts of the sample 250. It should be noted that the order of 240a to 240e may be different in different embodiments.

[0041] Upon receiving the primary electron beam 204, backscattered electrons (BSE) and secondary electrons (SE) may be emitted from the portion of the sample 250. The beam splitter may direct one or more secondary electron beams or scattered electron beams including backscattered electrons and secondary electrons to the sensor surface of the electron detector 244. The detected secondary electron beam may form a corresponding beam spot on the sensor surface of the electron detector 244. The electron detector 244 may generate a signal (e.g., voltage, current) representing the intensity of the received secondary electron beam spot and provide the signal to a processing system (such as a controller 50). The intensity of the secondary electron beam or backscattered electron beam and the resulting secondary electron beam spot may vary depending on the external structure or internal structure of the sample 250. Moreover, as discussed above, the primary electron beam 204 may be deflected to different locations on the top surface of the sample 250 to generate secondary electron beams or scattered electron beams (and resulting beam spots) of different intensities. Therefore, by mapping the intensity of the secondary electron beam spot with the position of the sample 250 , the processing system can reconstruct an image of the wafer sample 250 that reflects the internal structure or external structure of the wafer sample 250 .

[0042] In some embodiments, the controller 50 may include an image processing system including an image acquisition device (not shown) and a storage device (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, any kind of mobile computing device, or a combination thereof. The image acquisition device may be communicatively coupled to the electronic detector 244 of the device 40 through a medium such as an electrical conductor, a fiber optic 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 detector 244 and may construct an image. Thus, the image acquisition device may acquire images of various regions of the sample 250. The image acquisition device may also perform various post-processing functions, such as generating contours, superimposing indicators on the acquired image, and the like. The image acquisition device may be configured to perform adjustments to brightness and contrast, etc., on the acquired image. In some embodiments, the storage device may be a storage medium such as a hard disk, a flash drive, a cloud storage device, a random access memory (RAM), other types of computer-readable memory, and the like. The storage device may be coupled to the image acquirer and may be used to save the scanned raw image data as an initial image and to save a post-processed image.

[0043] In some embodiments, the controller 50 may include a measurement circuit system (e.g., an analog-to-digital converter) to obtain the distribution of the detected secondary electrons and backscattered electrons. In combination with the corresponding scan path data of the primary beam 204 incident on the sample (e.g., wafer) surface, the electron distribution data collected during the detection time window can be used to reconstruct an image of the inspected wafer structure. The reconstructed image can be used to reveal various features of the internal or external structure of the sample 250, and thus can be used to reveal any defects that may exist in the wafer.

[0044] In some embodiments, the controller 50 can control the motorized stage 234 to move the sample 250 during inspection. In some embodiments, the controller 50 can enable the motorized stage 234 to continuously move the sample 250 in one direction at a constant speed. In other embodiments, the controller 50 can enable the motorized stage 234 to change the movement speed of the sample 250 over time depending on the steps of the scanning process.

[0045] Now, refer to Figure 3 , Figure 3 A schematic diagram of an exemplary memory device 300 having a "staircase" structure is illustrated. The device 300 may include a plurality of memory cells stacked vertically on a substrate 310. The device 300 may be fabricated, for example, by depositing a plurality of alternating dielectric material layers, such as oxide and nitride films 325. The memory device 300 may include horizontal word lines 320, which may be formed by backfilling with a conductive material, such as tungsten, after a sacrificial layer (e.g., a nitride film in the stack) has been removed. The memory cell formation in the device 300 may also include step etching of dielectric film pairs and metal filling of contact channels 330, which include contact pads 340 to enable formation of bit line bus contacts ( Figure 3(not shown in the figure). At each step, multiple word line lithography steps with repeated vertical step etching and 2D trimming can be performed to provide the "up and down" shape of the WL step for use in a 3D NAND device. This series of process steps requires precise etching step profile analysis, trimming etching uniformity, and pullback CD control of the WL contact. The length of the WL step may increase as more memory cells are stacked vertically to improve efficiency, storage density, etc. The device 300 may include a film stack with a thickness of >64 layers or >96 layers or even >124 layers in some cases. Vertical channel holes (not shown) can also be produced using high aspect ratio (HAR) etching throughout the film stack. In some cases, the HAR can be >100:1. Individual memory cells within each layer can be electrically connected by, for example, word line replacement metal fills provided by materials such as tungsten. The word line metal fill can include a gap-free fill of complex, narrow, lateral structures with minimal stress on the device stack. In practice, manufacturing 3D NAND devices is extremely challenging, and it may be necessary to detect physical or electrical defects generated during or after the manufacturing of such complex device structures.

[0046] Detecting buried defects in vertical high-density structures (such as 3D NAND flash memory device 300) can be challenging. One of several ways to detect buried electrical defects or electrical defects on surfaces in such devices is to use a voltage contrast method in a SEM. In this method, differences in electrical conductivity in a material, structure, or region of a sample result in contrast differences in its SEM image. In the context of defect detection, electrical defects beneath the surface of a sample may generate charging changes on the surface of the sample, so electrical defects can be detected by the contrast of the SEM image of the sample surface. To enhance the voltage contrast, a process known as pre-charging or flooding can be employed, in which a region of interest of the sample can be exposed to a large beam current before inspection using a small beam current but high imaging resolution. For inspection, some advantages of flooding can include reducing the charging of the wafer to minimize image distortion due to charging, and in some cases, increasing the charging of the wafer to enhance the difference between defective features and surrounding non-defective features in the image, etc. Some inspection systems (such as SEMs) equipped to detect wafer defects using a voltage contrast method can operate in multiple modes (such as a flooding mode for highlighting defects, followed by an inspection mode for detecting defects). In flood mode, it may be preferable to allow the most electrons to pass through the aperture and to maximize the beam current of the primary electron beam illuminating the sample to enhance voltage contrast. However, in inspection mode, a small probe spot with a small beam current may be ideal for high-resolution imaging.

[0047] In semiconductor devices, buried defects such as voids or particles may result in full open and leakage (short circuit), or in some cases partial open or partial leakage. Existing voltage contrast inspection techniques used to detect such defects involve flood exposure of negatively charged particles (e.g., electrons) on the surface and rely on differences in surface potential measurements of structures on the surface. Pixels representing surface areas with high surface potential have higher gray levels (appear brighter in the SEM image) than pixels representing areas of lower surface potential. The gray level of the structure is compared to a reference gray level to detect defects.

[0048] Now, refer to Figure 4 , Figure 4 It is a schematic representation of a grayscale value signal of a contact connected to a defect-free word line when a dose of charged particles is applied according to an embodiment of the present invention. In this context, a "defect-free" feature is referred to as a feature, structure or device that does not have a physical defect or an electrical defect or is not associated with the defect. In some cases, physical defects such as under-etched metal lines or over-etched dielectric films may cause electrical defects. As used herein, the grayscale value of a feature refers to the grayscale of the feature as observed in an image (e.g., a SEM image). As an example, in an 8-bit grayscale image, there may be 256 discrete grayscale levels and a grayscale value between "0" and "255" may be assigned to each pixel, where grayscale 0 indicates a dark pixel and grayscale 255 indicates a bright pixel. In the context of the present disclosure, "dose" refers to the total number of charged particles to which a feature may be exposed. In some embodiments, the charged particles may include electrons, for example, electrons in a SEM. In the case where the dose includes electrons, the dose may be expressed as the total number of electrons, or the total charge (in coulombs) carried by the total number of electrons. It will be appreciated that the charge of an electron may be 1.6×10 -19 Coulombs. A dose of charged particles may be applied, for example, by applying a voltage signal configured to supply a desired number of charges or charged particles to the contacts.

[0049] Figure 4 A curve 405 representing the relationship between the grayscale value signal and the dose for a defect-free feature is illustrated. In some embodiments, a feature may refer to a contact pad configured to form an electrical connection with a capacitor or a word line. In some embodiments, a feature may refer to a capacitor, a metal line, a word line, a bit line, a gate structure, or any component of a circuit. Figure 4 In the context of , the feature refers to the word line of a 3D NAND device. A word line (e.g., Figure 3 The word line 320) may include a capacitor having a plate structure.

[0050] like Figure 4As shown, at lower doses of charged particles, non-defective word lines may be able to store charged particles, behaving similarly to charge sinks or grounded capacitors. At such lower doses, the contact pads corresponding to non-defective word lines may appear as dark pixels in the image. This area of ​​low dose and low grayscale value is indicated as dark voltage contrast ( Figure 4 As the dose increases, the capacitor is “charged” because it can no longer dissipate the injected charge. The dose corresponding to the start of capacitor charging (denoted as D T ) is called the threshold dose. Region 410 may be called the transition region, where the capacitor continues to be charged. In this region, the injected charge is stored in the capacitor and the surface potential of the capacitor increases significantly. The rise in surface potential appears as a sharp rise in the grayscale value signal. The capacitor is at dose D S (saturation dose). This area of ​​high dose and high grayscale value signal is indicated as bright voltage contrast ( Figure 4 BVC area) area. At saturation dose D S Under and over saturation dose D S When the input charge is reflected back due to the high surface potential of the capacitor, the corresponding pixel appears bright. It should be appreciated that for illustrative purposes, curve 405 is a schematic representation of the relationship between the grayscale value signal and the charge dose applied to the non-defective word line, rather than an actual data graph. Curve 405 is not drawn to scale.

[0051] In some embodiments, the threshold dose D T A range of dose values ​​may be included. For example, a threshold dose range may be T Within 5% of D T Within 10% of D T In some embodiments, the transition region 410 may include a threshold dose D T and saturation dose D S In some embodiments, the saturation dose D S A range of dose values ​​may be included. For example, a saturation dose range may be S % or within D S Within 10% of D S It should be appreciated that the threshold dose, transition region, or saturation dose of a feature may be based on several factors including, but not limited to, manufacturing materials, presence of defects, dimensions of the feature, etc.

[0052] In some existing voltage contrast-based techniques for inspecting 3D NAND device structures, a flood mode of operation or a pre-scan mode of operation may include selectively "charging" or exposing a portion of a region of interest (ROI) of a sample using a large number of charged particles. As an example, a selected word line contact or a few selected word line contacts may be charged by an overdose pre-scan using a charged particle beam (such as a primary electron beam in a SEM). In this context, an overdose pre-scan refers to using a dose equal to or greater than the saturation dose D S beam exposure features. The pre-scan may be followed by a detection scan that includes inspecting adjacent word line contacts in the presence of a charged particle beam with a small beam current. If there is an electrical connection (e.g., leakage) between the pre-scanned word line contact and the adjacent word line contact, the charge injected into the pre-scanned word line contact may travel to the adjacent word line contact, causing the adjacent word line contact to be "charged" and appear as a bright pixel in the image. If there is no electrical connection between the two word line contacts, essentially no charge flows to the adjacent word line contacts, causing the adjacent word line contacts to appear as dark pixels (low grayscale value signals). Although the selective pre-scan method appears to be effective, there are several associated challenges, some of which include: low inspection throughput, high stage accuracy requirements, limited scanned area of ​​interest, or unstable charging control. Therefore, it may be necessary to detect defects in 3D NAND structures while overcoming one or more challenges of existing voltage contrast inspection techniques.

[0053] Now, refer to Figure 5 , Figure 5 A schematic representation of a grayscale value signal in response to applying a dose of charged particles from a charged particle beam in a pre-scan mode according to an embodiment of the present disclosure is illustrated. Curve 510 represents a grayscale value signal of a word line contact connected to a non-defective word line in response to applying a dose of charged particles from a charged particle beam. Curve 520 represents a grayscale value signal of a word line contact connected to a defective word line in response to applying a dose of charged particles from a charged particle beam. Defects may include, but are not limited to, word line-to-word line leakage or a word line-to-word line electrical short between two word lines.

[0054] In the context of the present disclosure, the dose of charged particles from the charged particle beam applied is referred to as the reference saturation dose D SThe total number of charges (e.g., electrons in an electron beam) applied. In some embodiments, if the ratio between the applied dose of charged particles and the saturation dose of the charged particles is less than 1, the applied dose may be an underdose of charged particles. In some embodiments, the underdose of applied charges may refer to a ratio of the applied dose to the saturation dose between 0.4 and 0.8, or between 0.45 and 0.75, or between 0.5 and 0.70, or between 0.55 and 0.65, or between 0.55 and 0.6. In some embodiments, the ratio of the total number of applied charges to the saturation dose may be 0.55. In some embodiments, if the ratio between the applied dose of charged particles and the saturation dose is 1 or higher, the applied dose may be an overdose of charged particles.

[0055] In the existing selective pre-scanning technology, an overdose or saturation dose can be applied to a few selected contacts. Under the saturation dose, the contacts connected to the defective word line and the non-defective word line can appear as bright pixels with a high word line signal, such as Figure 5 , as represented by curve 510. Grayscale value signal comparison cannot provide contrast differences of corresponding pixels. However, because only a few selected contacts are configured to receive a certain dose of charge, defects can be detected based on the grayscale value signals of contacts adjacent to the contacts to which the signal is applied. In other words, although all contacts to which an overdose pre-scan signal is applied may appear bright, the grayscale value signals of contacts to which no signal is applied can be checked to determine defects. As discussed above, the selective pre-scan method has several disadvantages, including low throughput, small ROI, strict requirements on stage accuracy, or unstable charging control, which makes the inspection technology less than perfect.

[0056] like Figure 5 As shown, the grayscale value signal of the contact connected to the defective word line may be saturated at a much lower dose value compared to the non-defective word line. At a dose value corresponding to the maximum grayscale value signal of curve 520, the grayscale value signal of the contact connected to the non-defective word line shown by curve 510 is low, indicating a dark pixel. However, at the same dose value, the grayscale value signal of the contact connected to the defective word line shown by curve 520 is the maximum, indicating a bright pixel. In some embodiments, at a dose value less than the saturation dose, the contrast of the grayscale values ​​of the contacts connected to the defective word line and the non-defective word line can be used to identify defects in a pre-scan mode or a flood mode.

[0057] Now, refer to Figure 6 , Figure 6A schematic diagram of word lines and corresponding contacts exposed to pre-scan and detection scans performed in a region of interest (ROI) 600, according to an embodiment of the present disclosure, is illustrated. Although the ROI 600 is shown as including only five word lines 620 and word line contacts 630, it should be appreciated that the ROI may include more or fewer word lines and corresponding word line contacts. Figure 6 Illustrated is a side elevation view of a portion of a stair structure, such as a stair structure in a 3D NAND device.

[0058] ROI 600 may include word lines 620 and high aspect ratio contacts 630 corresponding to the word lines. In some embodiments, a pre-scan signal 605 including an underdose of charged particles (e.g., electrons) may be applied to each word line contact 630. As an example, if the saturation dose of the word line contacts is 5000 electrons (or approximately 8×10 -16 C), the underdose signal can be 2750 electrons (or about 4×10 -16 C). In some embodiments, the ratio between the signal corresponding to the underdose and the signal corresponding to the saturation dose can be less than 0.8, or less than 0.75, or less than 0.7, or less than 0.6, or less than 0.5. In some embodiments, the ratio can be 0.55. The pre-scan mode or flood mode in the voltage contrast technique can inject charge into the features of interest in the ROI. In some embodiments, the charged particles that flood the ROI can include, but are not limited to, electrons.

[0059] In some embodiments, a detection or inspection signal 610 may be applied after the pre-scan signal. In some embodiments, the detection signal 610 may be applied to each word line contact 630. The detection signal may be applied using a charged particle beam with a small beam current to form a small detection spot. The small detection spot may allow high resolution imaging, etc. Because the detection signal includes a small beam current signal, it does not affect the charge state of the word line or the response signal of the word line contact exposed to the pre-scan signal. In some embodiments, a multi-beam device may be used to perform a voltage contrast inspection of a defect. In such cases, multiple charged particle beams with small beam currents may be used to apply the detection signal.

[0060] like Figure 6As illustrated, pixel 660 represents an image of a contact connected to a non-defective word line 620, and pixel 670 represents an image of a contact connected to word lines 640 and 644 associated with defect 650. In some embodiments, defect 650 may include a charge leakage path formed by a conductive material, such as between word line 640 and word line 644. Defect 650 may cause word line 640 and word line 644 to be electrically connected to each other, thereby forming a word line-word line leakage defect. In some embodiments, pixels 660 and 670 may represent SEM images acquired based on (but not limited to) secondary electrons or backscattered electrons. As previously referenced Figure 5 As discussed, underdose prescanning can enable defects to be indicated based on voltage contrast between pixels representing non-defective wordline contacts and defective contacts or between pixels representing defective contact pairs. Underdose prescanning of a sample's ROI has many advantages over existing voltage contrast inspection techniques that use a saturation dose to flood the sample in a prescan mode. The underdose prescan method can have some or all of the advantages discussed herein.

[0061] i. High inspection throughput - Low doses of charged particles during flood mode may result in significant increases in throughput, at least because a larger field of view (FOV) and lower average voltage signal can be applied during pre-scan. Additionally, primary beam flood (PBF) and high voltage (HV) flood are applicable, which may charge the WL more efficiently than conventional inspection techniques.

[0062] ii. Larger ROI - The region of interest can be expanded to pre-scan a larger area, such as the entire stepped structure of a 3D NAND device.

[0063] iii. Requirements for stage accuracy flexible Because the ROI can be expanded to cover larger areas and more features with a large field of view (FOV), the accuracy requirements for positioning the stage may be less stringent.

[0064] iv. Compatibility and scalability The proposed underdose pre-scan is compatible with both single charged particle beam devices as well as multi-beam devices. The method can be widely used across a variety of inspection tools without the need for additional hardware, design modifications or controller modifications.

[0065] Figure 7A perspective view of an exemplary stack 700 of word lines according to some embodiments of the present invention is illustrated. Although only four word lines or word line plates (WP) are shown, it should be appreciated that any number of word lines may be present in the word line stack of a 3D NAND device, as appropriate. In some embodiments, the word lines may include capacitors or parallel plate capacitors. As an example, the word line 740 may be a rectangular three-dimensional plate having a length, width, and thickness along the x-axis, y-axis, and z-axis, respectively. For purposes of illustration, Figure 7 , the orientation of the axis is represented in . In some embodiments, the aspect ratio of the word line can be 4000:60:1. It should be appreciated that the aspect ratio may also be higher or lower. As used herein, the aspect ratio of a word line refers to the ratio between the length, width and thickness of the word line. In some embodiments, word line 720 may have a length of several millimeters (mm), a width of several microns (μm), and a thickness of several nanometers (nm). For example, word line 720 may be 2mm long, 10μm wide, and 100nm thick. Defect 750 may electrically connect WL 740 and 744 so that the word line pair appears as a defective word line. Defect 750 may provide a charge leakage path between word line 740 and word line 744, thereby forming a word line-word line leakage defect.

[0066] Now, refer to Fig. 8A , Fig. 8A A cross-sectional view 800 of an exemplary word line stack including defects according to an embodiment of the present invention is illustrated. The word line stack 800 may be Figure 7 The word line stack 700 is similar. A word line, such as word line 820, may include multiple surfaces including a top surface 802, a bottom surface 804, a front surface 806, a rear surface 808, and side surfaces 812 and 814, such as Figure 8B As shown in the figure, Figure 8B is an exploded view of a word line. In some embodiments, WL 820 may provide multiple surfaces for charge accumulation. However, the charge distribution across different surfaces may be based on the dimensions of the surfaces. Most of the charge may be distributed on the top and bottom surfaces (e.g., Figure 8B The capacitance of word line 820 may be primarily dependent on the area of ​​top surface 802 and bottom surface 804, and weakly dependent on the remaining front, rear, and side surfaces 806, 808, 812, and 814, respectively.

[0067] Return to Fig. 8A, word lines 820 and 860 represent non-defective word lines, and word lines 840 and 844 represent defective word lines electrically connected to each other through a defect 850. In some embodiments, applying a voltage signal to non-defective word line 820 may cause most of the charge 815 to accumulate on the top surface and the bottom surface, which are separated by a distance equal to the thickness of word line 820. In the presence of a defect 850 that forms a word line-word line leakage path, word lines 840 and 844 may act as a single capacitor 870. In this case, the bottom surface of word line 840 and the top surface of word line 844 that are electrically connected to each other through defect 850 may not store any charge. The thickness of the single capacitor 870 may be twice that of a non-defective word line (e.g., word line 820), but the area of ​​the top surface and the bottom surface is substantially similar, so that the total capacitance is slightly increased. In other words, if the word line pair is electrically shorted to form a single capacitor (such as capacitor 870), the total capacitance of the defective word line pair may increase by a small amount, but it may receive charge from two separate contacts corresponding to word lines 840 and 844, causing single capacitor 870 to charge faster than the non-defective word lines and reach saturation earlier, as shown in FIG. Figure 5 This effect allows a lower dose (e.g., 0.55 times the saturation dose) to be applied to each contact or contact pad and saturates the defective word line while the non-defective word line remains unsaturated. For example, the difference in grayscale value signals at 0.55 times the saturation dose can be used to determine if there is a defect causing leakage between two word lines.

[0068] In some embodiments, for example, a Monte Carlo simulation model based on a random walk boundary method can be used to simulate the total capacitance of a single capacitor 870. It should be appreciated that other simulation models and methods can be used to simulate the capacitance values ​​of capacitors with known dimensions. The model can also approximate the dimensions to numerically and theoretically predict the capacitance of the capacitor. Fig. 9 A data graph illustrating simulated capacitance values ​​over a range of capacitor thicknesses according to some embodiments of the present disclosure is illustrated.

[0069] like Fig. 9 As illustrated and as previously discussed, increasing the thickness of the capacitor increases the capacitance by a smaller amount than increasing the capacitance by increasing the area of ​​the top and bottom surfaces. Fig. 9 The data graphs shown represent simulated or predicted capacitance values ​​(in units of 4πε*10 -5Farads). The slope of the line connecting the data points for capacitance values ​​of different thicknesses of the capacitor indicates the dependency. In some cases, increasing the thickness by a factor of 2 may increase the capacitance by 15% or less, 12% or less, 10% or less, 8% or less, 6% or less, or 5% or less.

[0070] Now, refer to Fig.10 , Fig.10 1 is a process flow diagram showing an exemplary method 1000 for detecting defects using a charged particle beam apparatus according to an embodiment of the present disclosure. Figure 2 As shown, one or more steps of method 1000 may be performed by controller 50 of EBI system 100. For example, controller 50 may instruct a module of a charged particle beam device to activate a charged particle source to generate a primary charged particle beam (e.g., an electron beam) to apply a signal to a sample (e.g., Figure 2 Charging multiple features in a region of interest of a sample 250) and performing other functions.

[0071] In step 1010, a charged particle source is activated to emit charged particles. The charged particles may form a charged particle beam (e.g., Figure 2 The electron source may be controlled by a controller (e.g., Figure 2 For example, the electron source may be controlled to emit primary electrons along the primary optical axis (e.g., Figure 2 The electron source may be remotely activated, for example, by using software, an application, or a set of instructions for a processor of a controller to power the electron source through a control circuit system. The primary electron beam may pass through a Coulomb aperture array (e.g., Figure 2 Coulomb aperture array 224) and beam-limiting aperture array (e.g., Figure 3 The beam limiting aperture array 305 is used to adjust the beam size or beam current of the primary electron beam and form a beam incident on the sample (for example, Figure 2 of the sample 250).

[0072] In step 1020, a region of interest (ROI) of the sample is irradiated with a first dose of charged particles from a primary charged particle beam. The ROI may include multiple features, such as a plurality of word lines (e.g., Figure 3 The word line 320 or Figure 7 A contact or contact pad (eg, Figure 3Step 1020 may include a pre-scan mode or a flood mode of the voltage contrast inspection technique, wherein each feature of interest in the region of interest is flooded with a first dose of charged particles (such as, for example, electrons from a primary electron beam in a SEM tool). The first dose of charged particles may be less than a saturation dose (e.g., Figure 4 Saturation dose D S ). Illuminating a feature of interest can enable identification of defects based on the stored charge, which forms a grayscale value contrast signal of the feature in an acquired image (such as a SEM image).

[0073] In step 1030, a second dose of charged particles of the primary charged particle beam may be used to inspect the step structure in the region of interest (eg, Figure 3 The second dose of charged particles can be substantially less than the first dose, such that the second dose has a negligible effect on the charge state of the feature of interest caused by exposure to the first dose of charged particles.

[0074] In some embodiments, a charged particle detector can be used to detect signal charged particles generated from a region of interest of a sample upon interaction with charged particles of a primary charged particle beam. An image can be formed based on the detected signal charged particles. The formed image can include a SEM image or other suitable grayscale image.

[0075] In step 1040, defects may be detected based on grayscale values ​​of features in the acquired image. Features (e.g., Figure 3 The contact pad 340 of the corresponding word line can form a pixel with a grayscale value based on the presence of a defect in the corresponding word line. For example, if the word line pair is connected by a defect (e.g., Figure 6 Defects of 650 or Figure 7 If the word lines are electrically connected to each other (defective word lines 750), the corresponding contact pads may appear as bright pixels with high grayscale value signals in the acquired image. For non-defective word lines, the corresponding contact pads may appear as darker pixels with low grayscale value signals, thereby enabling detection of defects based on the grayscale value signals of the pixels representing the contact pads connected to the corresponding word lines.

[0076] Some of the advantages of the underdose pre-scan method include improved inspection throughput, larger region of interest, less stringent requirements on stage accuracy, compatibility with single-beam inspection devices and multi-beam inspection devices, stability of charge control, etc.

[0077] A non-transitory computer-readable medium may be provided that stores a controller (eg, Figure 1 Instructions for a processor of a controller 50) for performing the following operations: image inspection, image acquisition, activating a charged particle source, irradiating an area of ​​a sample with a first dose of charged particles, inspecting an area of ​​the sample with a second dose of charged particles different from the first dose, determining whether a defect exists based on grayscale values ​​of features of an image of the area of ​​the sample acquired, etc. Common forms of non-transitory media include, for example, floppy disks, flexible disks, hard disks, solid-state drives, magnetic tapes or any other magnetic data storage media, compact disk read-only memories (CD-ROMs), any other optical data storage media, any physical media with a pattern of holes, random access memories (RAMs), programmable read-only memories (PROMs) and erasable programmable read-only memories (EPROMs), FLASH-EPROMs or any other flash memory, non-volatile random access memories (NVRAMs), caches, registers, any other memory chips or boxes, and networked versions thereof.

[0078] Embodiments of the present disclosure may also be described using the following terms.

[0079] 1. A charged particle beam device, comprising:

[0080] a charged particle source configured to emit charged particles, wherein the emitted charged particles form a primary charged particle beam;

[0081] A controller comprising a circuit system configured to:

[0082] irradiating a region of the sample including a plurality of features with a first dose of charged particles of the primary charged particle beam;

[0083] inspecting the plurality of features using a second dose of the charged particles of the primary charged particle beam, the second dose being different from the first dose;

[0084] acquiring an image of the plurality of features inspected; and

[0085] determining whether there is a defect based on a grayscale value of a feature among the plurality of features, the grayscale value being determined according to the acquired image of the plurality of features,

[0086] Wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of the characteristic.

[0087] 2. The apparatus according to clause 1 further comprises a charged particle detector configured to detect a plurality of signal charged particles generated when the charged particles interact with the plurality of features on the sample.

[0088] 3. The apparatus of clause 2, wherein the controller has circuitry further configured to form the image based on the detected plurality of signal charged particles.

[0089] 4. The apparatus of any of clauses 1 to 3, wherein the feature comprises a contact pad configured to form an electrical connection to a capacitor.

[0090] 5. The apparatus of clause 4, wherein the capacitor comprises a word line of a memory device.

[0091] 6. The device of clause 5, wherein the defect comprises an electrical short or a current leakage path between at least two word lines.

[0092] 7. An apparatus according to any one of clauses 1 to 6, wherein the controller having circuitry is further configured to: identify at least one feature associated with the defect based on the gray level of the at least one feature.

[0093] 8. An apparatus according to any one of clauses 1 to 7, wherein grayscale values ​​of defective features irradiated using the first dose of charged particles are higher than grayscale values ​​of non-defective features irradiated using the first dose of charged particles.

[0094] 9. Apparatus according to any one of clauses 1 to 8, wherein the second dose of charged particles is less than the first dose.

[0095] 10. Apparatus according to any of clauses 1 to 9, wherein the second dose of charged particles is less than the saturation dose.

[0096] 11. A device according to any of clauses 1 to 10, wherein the first dose is less than a threshold dose comprising a total number of charged particles substantially similar to the charge storage capacity of the feature.

[0097] 12. The apparatus of clause 11, wherein the threshold dose is less than the saturation dose.

[0098] 13. The device according to any of clauses 1 to 12, wherein a ratio of the first dose of charged particles to the saturation dose is between 0.4 and 0.8.

[0099] 14. The device according to clause 13, wherein the ratio is between 0.5 and 0.7.

[0100] 15. The device of clause 13, wherein the ratio is between 0.55 and 0.65.

[0101] 16. The apparatus of clause 13, wherein the ratio is 0.55.

[0102] 17. A charged particle beam device comprising:

[0103] The method comprises a charged particle source configured to emit charged particles, wherein the emitted charged particles form a primary charged particle beam;

[0104] A controller comprising a circuit system configured to:

[0105] irradiating a region of the sample including a plurality of contact pads with a first dose of charged particles of the primary charged particle beam, the plurality of contact pads being configured to form electrical connections to a corresponding plurality of word lines of a memory device;

[0106] inspecting the plurality of contact pads using a second dose of charged particles of the primary charged particle beam, the second dose being different from the first dose;

[0107] acquiring an image of the inspected plurality of contact pads; and

[0108] determining whether there is a defect based on a grayscale value of a contact pad among the plurality of contact pads, the grayscale value being determined according to the acquired image of the plurality of contact pads,

[0109] Wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of a word line in the plurality of word lines.

[0110] 18. The apparatus of clause 17, further comprising a charged particle detector configured to detect a plurality of signal charged particles generated when the charged particles interact with the plurality of contact pads on the sample.

[0111] 19. The apparatus of clause 18, wherein the controller has circuitry further configured to form the image based on the detected plurality of signal charged particles.

[0112] 20. The device of any of clauses 17 to 19, wherein the plurality of word lines comprises a plurality of capacitors.

[0113] 21. The device of any of clauses 17 to 20, wherein the defect comprises an electrical short or a current leakage path between at least two word lines of the plurality of word lines.

[0114] 22. The apparatus of any of clauses 17 to 21, wherein the controller having circuitry is further configured to: identify at least one contact pad associated with the defect based on a gray level of the at least one contact pad.

[0115] 23. A device according to any one of clauses 17 to 22, wherein the grayscale value of the contact pad corresponding to the defective word line irradiated using the first dose of charged particles is higher than the grayscale value of the contact pad corresponding to the non-defective contact pad irradiated using the first dose of charged particles.

[0116] 24. Apparatus according to any of clauses 17 to 23, wherein the second dose of charged particles is less than the first dose.

[0117] 25. Apparatus according to any of clauses 17 to 24, wherein the second dose of charged particles is less than the saturation dose.

[0118] 26. The device of any of clauses 17 to 25, wherein the first dose is less than a threshold dose comprising a total number of charged particles substantially similar to the charge storage capacity of a word line in the plurality of word lines.

[0119] 27. The device of clause 26, wherein the threshold dose is less than the saturation dose.

[0120] 28. Apparatus according to any of clauses 17 to 27, wherein a ratio of the first dose of charged particles to the saturation dose is between 0.4 and 0.8.

[0121] 29. The device according to clause 28, wherein the ratio is between 0.5 and 0.7.

[0122] 30. The device of clause 28, wherein the ratio is between 0.55 and 0.65.

[0123] 31. The apparatus of clause 28, wherein the ratio is 0.55.

[0124] 32. A method for detecting defects using a charged particle beam apparatus, the method comprising:

[0125] irradiating a region of a sample including a plurality of features with a charged particle beam to charge each of the plurality of features with a first dose of charged particles of the charged particle beam;

[0126] inspecting the plurality of features using a second dose of charged particles of the charged particle beam, the second dose being different from the first dose;

[0127] acquiring an image of the plurality of features inspected; and

[0128] determining whether there is a defect based on a grayscale value of a feature, the grayscale value being determined based on the acquired image of the plurality of features,

[0129] Wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of the characteristic.

[0130] 33. The method according to clause 32 further includes: using a charged particle detector to detect a plurality of signal charged particles generated when the charged particles interact with the plurality of features on the sample.

[0131] 34. The method of clause 33, further comprising: forming the image based on the detected plurality of signal charged particles.

[0132] 35. A method as recited in any of clauses 32 to 34, wherein the feature comprises a contact pad configured to form an electrical connection to a capacitor.

[0133] 36. The method of clause 35, wherein the capacitor comprises a word line of a memory device.

[0134] 37. The method of clause 36, wherein the defect comprises an electrical short or a current leakage path between at least two word lines.

[0135] 38. The method of any of clauses 32 to 37, further comprising identifying at least one feature associated with the defect based on the gray level of the at least one feature.

[0136] 39. A method according to any of clauses 32 to 38, wherein the grayscale values ​​of defective features irradiated using the first dose of charged particles are higher than the grayscale values ​​of non-defective features irradiated using the first dose of charged particles.

[0137] 40. The method of any of clauses 32 to 39, wherein the second dose of charged particles is less than the first dose.

[0138] 41. The method of any of clauses 32 to 40, wherein the second dose of charged particles is less than the saturation dose.

[0139] 42. A method according to any of clauses 32 to 41, wherein the first dose is less than a threshold dose comprising a total number of charged particles substantially similar to the charge storage capacity of the feature.

[0140] 43. The method of clause 42, wherein the threshold dose is less than the saturation dose.

[0141] 44. A method according to any of clauses 32 to 43, wherein a ratio of the first dose of charged particles to the saturation dose is between 0.4 and 0.8.

[0142] 45. A method according to clause 44, wherein the ratio is between 0.5 and 0.7.

[0143] 46. ​​A method according to clause 44, wherein the ratio is between 0.55 and 0.65.

[0144] 47. A method according to clause 44, wherein the ratio is 0.55.

[0145] 48. A method for detecting defects using a charged particle beam apparatus, the method comprising:

[0146] irradiating a region of the sample including a plurality of contact pads with a charged particle beam to charge each of the plurality of contact pads with a first dose of charged particles of the charged particle beam, the plurality of contact pads being configured to form an electrical connection with a corresponding plurality of word lines of a memory device;

[0147] inspecting the plurality of contact pads using a second dose of charged particles of the charged particle beam, the second dose being different than the first dose;

[0148] acquiring an image of the plurality of contact pads; and

[0149] determining whether there is a defect based on a grayscale value of a contact pad among the plurality of contact pads, the grayscale value being determined according to the acquired image of the plurality of contact pads,

[0150] Wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of a word line in the plurality of word lines.

[0151] 49. The method of clause 48, further comprising: detecting, using a charged particle detector, a plurality of signal charged particles generated when the charged particles interact with the plurality of contact pads on the sample.

[0152] 50. The method of clause 49, further comprising forming the image based on the detected plurality of signal charged particles.

[0153] 51. The method of any of clauses 48 to 50, wherein the plurality of word lines comprises a plurality of capacitors.

[0154] 52. The method of any of clauses 48 to 51, wherein the defect comprises an electrical short or a current leakage path between at least two word lines of the plurality of word lines.

[0155] 53. The method of any of clauses 48 to 52, further comprising identifying at least one contact pad associated with the defect based on the gray level of the at least one contact pad.

[0156] 54. A method according to any one of clauses 48 to 53, wherein the grayscale value of the contact pad corresponding to the defective word line irradiated using the first dose of charged particles is higher than the grayscale value of the contact pad corresponding to the non-defective contact pad irradiated using the first dose of charged particles.

[0157] 55. A method according to any of clauses 48 to 54, wherein the second dose of charged particles is less than the first dose.

[0158] 56. A method according to any of clauses 48 to 55, wherein the second dose of charged particles is less than the saturation dose.

[0159] 57. The method of any of clauses 48 to 56, wherein the first dose is less than a threshold dose comprising a total number of charged particles substantially similar to the charge storage capacity of a word line in the plurality of word lines.

[0160] 58. The method of clause 57, wherein the threshold dose is less than the saturation dose.

[0161] 59. A method according to any of clauses 48 to 58, wherein a ratio of the first dose of charged particles to the saturation dose is between 0.4 and 0.8.

[0162] 60. The method of clause 59, wherein the ratio is between 0.5 and 0.7.

[0163] 61. A method according to clause 59, wherein the ratio is between 0.55 and 0.65.

[0164] 62. A method according to clause 59, wherein the ratio is 0.55.

[0165] 63. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a charged particle beam apparatus to cause the charged particle beam apparatus to perform a method for detecting defects, the method comprising:

[0166] activating a charged particle source, the charged particle source being configured to emit charged particles, the emitted charged particles forming a primary charged particle beam;

[0167] irradiating a region of a sample including a plurality of features using the charged particle beam to charge each of the plurality of features using a first dose of charged particles of the charged particle beam;

[0168] inspecting the plurality of features using a second dose of charged particles of the charged particle beam, the second dose being different from the first dose;

[0169] acquiring an image of the plurality of features inspected; and

[0170] determining whether there is a defect based on a grayscale value of a feature, the grayscale value being determined based on the acquired image of the plurality of features,

[0171] Wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of the characteristic.

[0172] 64. A non-transitory computer readable medium storing a set of instructions executable by one or more processors of a charged particle beam apparatus to cause the charged particle beam apparatus to perform a method for detecting defects, the method comprising:

[0173] activating a charged particle source, the charged particle source being configured to emit charged particles, the emitted charged particles forming a primary charged particle beam;

[0174] irradiating a region of a sample including a plurality of contact pads using the charged particle beam to charge each of the plurality of contact pads using a first dose of charged particles of the charged particle beam, the plurality of contact pads being configured to form an electrical connection with a corresponding plurality of word lines of a memory device;

[0175] inspecting the plurality of contact pads using a second dose of charged particles of the charged particle beam, the second dose being different than the first dose;

[0176] acquiring an image of the plurality of contact pads; and

[0177] determining whether there is a defect based on a grayscale value of a contact pad among the plurality of contact pads, the grayscale value being determined according to the acquired image of the plurality of contact pads,

[0178] Wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of a word line in the plurality of word lines.

[0179] It should be appreciated that the embodiments of the present invention are not limited to the exact configurations described above and illustrated in the accompanying drawings, and that various modifications and changes may be made without departing from the scope of the present invention. The present disclosure has been described in conjunction with various embodiments, and other embodiments of the present invention will be apparent to those skilled in the art, given the specification and practice of the invention disclosed herein. The specification and embodiments are to be considered exemplary only, with the true scope and spirit of the present invention being indicated by the appended claims.

[0180] The above description is intended to be illustrative rather than limiting. Therefore, it will be apparent to those skilled in the art that modifications may be made from the description without departing from the scope of the claims set forth below.

Claims

1. A charged particle beam device, comprising: a charged particle source configured to emit charged particles, wherein the emitted charged particles form a primary charged particle beam; A controller comprising a circuit system configured to: irradiating a region of the sample including a plurality of features with a first dose of charged particles of the primary charged particle beam; inspecting the plurality of features using a second dose of the charged particles of the primary charged particle beam, the second dose being different from the first dose; acquiring an image of the plurality of features inspected; as well as determining whether there is a defect based on a grayscale value of a feature among the plurality of features, the grayscale value being determined according to the acquired image of the plurality of features, Wherein the first dose is less than a saturation dose, and wherein the saturation dose includes a total number of charged particles that exceeds a charge storage capacity of the characteristic.

2. The apparatus according to claim 1 further comprises a charged particle detector configured to detect a plurality of signal charged particles generated when the charged particles interact with the plurality of features on the sample. 3 . The apparatus of claim 2 , wherein the controller has circuitry further configured to form the image based on the detected plurality of signal charged particles. 4 . The apparatus of claim 1 , wherein the feature comprises a contact pad configured to form an electrical connection to a capacitor.

5. The apparatus of claim 4, wherein the capacitor comprises a word line of a memory device. 6 . The device of claim 5 , wherein the defect comprises an electrical short or a current leakage path between at least two word lines.

7. The apparatus of claim 1, wherein the controller having circuitry is further configured to identify at least one feature associated with the defect based on the grayscale level of the at least one feature. 8 . The apparatus of claim 1 , wherein a grayscale value of a defective feature irradiated with the first dose of charged particles is higher than a grayscale value of a non-defective feature irradiated with the first dose of charged particles.

9. The apparatus of claim 1, wherein the second dose of charged particles is less than the first dose.

10. The apparatus of claim 1, wherein the second dose of charged particles is less than the saturation dose.

11. The apparatus of claim 1, wherein the first dose is less than a threshold dose comprising a population of charged particles substantially similar to the charge storage capacity of the feature. The device according to claim 11 , wherein the threshold dose is less than the saturation dose.

13. The apparatus of claim 1, wherein a ratio of the first dose of charged particles to the saturation dose is between 0.4 and 0.

8.

14. The device of claim 13, wherein the ratio is between 0.5 and 0.

7.

15. The device of claim 13, wherein the ratio is between 0.55 and 0.65.

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