Apparatus and method for detecting time-dependent defects in fast charging devices

Abstract

Disclosed is an improved charged particle beam inspection apparatus, and more particularly, a particle beam apparatus for inspecting a wafer, including an improved scanning mechanism for detecting fast charge defects. An improved charged particle beam inspection apparatus may include a charged particle beam source that transports charged particles toward and scans a region of a wafer. The improved charged particle beam apparatus may also include a controller including circuitry to generate a plurality of images of the region within a time series, the images being compared to detect fast charge defects.

Description

[0001] Description of the case

[0002] This application is a divisional application of the Chinese national phase patent application of the PCT application with international application number PCT / EP2019 / 074585, Chinese national application number 201980061018.3, and invention name "Apparatus and method for detecting time-related defects in fast charging equipment". Technical Field

[0003] The embodiments provided herein disclose a particle beam inspection apparatus, and more particularly disclose a particle beam inspection apparatus including an improved scanning mechanism. Background Art

[0004] When manufacturing semiconductor integrated circuit (IC) chips, pattern defects or uninvited particles (residues) inevitably appear on the wafer or mask during the manufacturing process, thereby reducing the yield. For example, uninvited particles can be troublesome for patterns with smaller critical feature sizes that have been adopted to meet the increasingly advanced performance requirements of IC chips.

[0005] Pattern inspection tools with charged particle beams have been used to detect defects or uninvited particles. These tools typically use a scanning electron microscope (SEM). In an SEM, a primary electron beam with relatively high energy is decelerated so as to land on a sample with a relatively low landing energy, and is focused to form a detection spot thereon. Due to this primary electron focused detection spot, secondary electrons will be generated from the surface. Secondary electrons may include backscattered electrons, secondary electrons, or Auger electrons generated due to the interaction of primary electrons with the wafer. By scanning the detection spot over the sample surface and collecting secondary electrons, the pattern inspection tool can acquire an image of the sample surface. Summary of the invention

[0006] Embodiments provided herein disclose a charged particle beam system for inspecting a wafer, and more particularly, disclose a charged particle beam system for inspecting a wafer including an improved scanning mechanism.

[0007] In some embodiments, a charged particle beam system for inspecting a wafer includes a charged particle beam source and a controller. The charged particle beam source includes a circuit to transmit charged particles to the surface of the wafer in a time sequence. The circuit in the charged particle beam source also scans an area of ​​the wafer, wherein the area includes multiple rows of pixels. The controller includes a circuit to generate a set of N images of the area in a time sequence. N can be an integer. The controller includes a circuit to compare the set of N images to detect defects that produce high resistance structures in the area of ​​the wafer.

[0008] In some embodiments, a method for inspecting a wafer is provided. The method uses a charged particle beam system having a charged particle beam source to deliver charged particles to a surface of the wafer in a time series. The method includes scanning an area of ​​the wafer, wherein the area includes a plurality of rows of pixels. The method also includes generating a set of N images of the area in a time series, wherein N is an integer. The method also includes comparing the set of N images to detect defects that create a high resistance structure in the area of ​​the wafer.

[0009] In some embodiments, a non-transitory computer readable medium is provided, which stores an instruction set that can be executed by a processor of a charged particle beam system. The instruction causes the charged particle beam system to perform a method, wherein a charged particle beam source of the charged particle beam system transmits charged particles to a surface of a wafer in a time sequence. The method includes scanning an area of ​​the wafer, wherein the area includes multiple rows of pixels. The method also includes generating a set of N images of the area in a time sequence, wherein N is an integer. The method also includes comparing the set of N images to detect defects that produce high resistance structures in the area of ​​the wafer.

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

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

[0012] Figure 1 is a schematic diagram illustrating an exemplary charged particle beam inspection system according to an embodiment of the present disclosure.

[0013] Figure 2 is a schematic diagram illustrating an exemplary electron beam tool according to an embodiment of the present disclosure.

[0014] Figure 3 is an exemplary graph showing the yield of secondary electrons relative to the landing energy of primary electrons.

[0015] Figure 4 is a schematic diagram showing the voltage contrast response of a wafer.

[0016] Figure 5A and 5B is a schematic diagram of an exemplary voltage contrast image within a time series according to an embodiment of the present disclosure.

[0017] Fig. 6A , 6B 6C are schematic diagrams of exemplary voltage contrast images related to surface potential changes within a time series according to an embodiment of the present disclosure.

[0018] Figure 7 is a schematic diagram of a conventional scanning sequence.

[0019] Fig. 8A and 8B is a schematic diagram of an exemplary scanning sequence according to an embodiment of the present disclosure.

[0020] Fig.9A , 9B , 9C and 9D are schematic diagrams of exemplary scanning sequences according to an embodiment of the present disclosure.

[0021] Fig. 10A and 10B is a schematic diagram of an exemplary scanning sequence according to an embodiment of the present disclosure.

[0022] Fig.11 is a flow chart illustrating an exemplary method for detecting time-dependent defects according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0023] Reference will now be made in detail to the exemplary embodiments, examples of which are shown in the accompanying drawings. The following description refers to the accompanying drawings, and 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 consistent with the present invention. Instead, they are merely examples of devices and methods consistent with various aspects of the present invention described in the appended claims.

[0024] The enhanced computing power of electronic devices can be achieved by significantly increasing the packaging density of circuit components such as transistors, capacitors, diodes, etc. on IC chips while reducing the physical size of the devices. For example, the IC chip of a smart phone (i.e., the size of a thumb) can include more than 2 billion transistors, each of which is less than 1 / 1000 the size of a human hair. Therefore, it is not surprising that semiconductor IC manufacturing is a complex and time-consuming process with hundreds of individual steps. Even if one step goes wrong, it is likely to greatly affect the functionality of the final product. Even a "fatal defect" can cause the device to fail. The goal of the manufacturing process is to increase the overall yield of the process. For example, to achieve a 75% yield for a 50-step process, the yield of each individual step must be greater than 99.4%, and if the yield of the individual step is 95%, the yield of the entire process will drop to 7%.

[0025] While high process yields are desired in IC chip manufacturing equipment, it is also essential to maintain high wafer throughput (defined as the number of wafers processed per hour). High process yields and high wafer throughput can be affected by the presence of defects, especially when operator intervention is required to detect the defects. Therefore, high-throughput inspection and micro- and nano-scale defect identification by inspection tools (such as SEM) are critical to maintaining high yields and low costs.

[0026] The SEM scans the surface of the wafer with a focused electron beam. The electrons interact with the wafer and generate secondary electrons. By scanning the wafer with the electron beam and capturing the secondary electrons with a detector, the SEM generates an image of the wafer that shows the internal device structure beneath the inspected wafer area. Conventional SEM inspection tools acquire a single image of a wafer area and compare the acquired image with a reference image representing the corresponding device structure without any defects. Differences detected from the image comparison can indicate defects in the wafer.

[0027] However, such conventional inspection techniques (e.g., capturing only a single image at any point in time) may not be useful for identifying defects in thin device structures because the electrical properties of defective thin structures may change over time. For example, even if a defect does exist in the wafer under inspection, due to this time-dependent behavior of the thin structure, a single acquired image may sometimes be captured at the right moment and show a difference from the reference image, but other times, the acquired image may not show any difference at all. Therefore, conventional SEM inspection tools cannot reliably identify defects in thin device structures.

[0028] Some newer SEMs acquire multiple images from the same area of ​​the wafer. By comparing multiple images of the same location (the images were sampled at different times), these newer SEMs can detect changes in electrical properties caused by thin device defects within an area of ​​the wafer.

[0029] However, even these newer SEMs may not be able to capture the ultrafast time-dependent defects that are often present in high-resistance device structures. A significant problem that these newer SEMs may even face is that the conventional electronic scanning mechanisms used in these SEMs are not fast enough to acquire multiple images at the high rates required to identify ultrafast time-dependent defects.

[0030] One aspect of the present disclosure includes an improved scanning mechanism that can generate multiple images in succession at very high speeds, so that the SEM can reliably detect ultrafast time-dependent defects. For example, the improved scanning mechanism uses line-by-line or pixel-by-pixel scanning, thereby greatly improving the image sampling speed in some embodiments.

[0031] For clarity, the relative sizes of components in the accompanying drawings may be exaggerated. In the following description of the drawings, the same or similar reference numerals refer to the same or similar components or entities, and only the differences with respect to the various embodiments are described. As used herein, unless otherwise expressly stated, the term "or" covers all possible combinations unless not feasible. For example, if it is stated that the database may include A or B, then unless otherwise expressly stated or not feasible, the database may include A or B or A and B. As a second example, if it is stated that the database may include A, B, or C, then unless otherwise stated or not feasible, the database may include A or B or C or A and B or A and C or B and C or A and B and C.

[0032] Reference now Figure 1 , Figure 1 is a schematic diagram illustrating an exemplary charged particle beam inspection system 100 according to an embodiment of the present disclosure. Figure 1 As shown, the charged particle beam inspection system 100 includes a main chamber 10, a load lock chamber 20, an electron beam tool 40, and an equipment front end module (EFEM) 30. The electron beam tool 40 is located in the main chamber 10. Although the description and drawings refer to electron beams, it should be understood that the embodiments are not intended to limit the present disclosure to specific charged particles.

[0033] The EFEM 30 includes a first load port 30a and a second load port 30b. The EFEM 30 may include other load ports. The first load port 30a and the second load port 30b may, for example, accommodate a wafer front opening unified pod (FOUP) containing wafers (e.g., semiconductor wafers or wafers made of other materials) or samples (wafers and samples are collectively referred to as "wafers" hereinafter) to be inspected. One or more robot arms (not shown) in the EFEM 30 transport the wafers to the load lock chamber 20.

[0034] The load lock chamber 20 may be connected to a load lock vacuum pump system (not shown) that removes gas molecules in the load lock chamber 20 to reach a first pressure below atmospheric pressure. After reaching the first pressure, one or more robot arms (not shown) transport the wafer from the load lock chamber 20 to the main chamber 10. The main chamber 10 is connected to a main chamber vacuum pump system (not shown) that removes gas molecules in the main chamber 10 to reach a second pressure below the first pressure. After reaching the second pressure, the wafer is inspected by an electron beam tool 40. In some embodiments, the electron beam tool 40 may include a single beam electron inspection tool. In other embodiments, the electron beam tool 40 may include a multi-beam electron inspection tool.

[0035] The controller 50 is electrically connected to the electron beam tool 40. The controller 50 may be a computer configured to perform various controls of the charged particle beam inspection system 100. Figure 1 30, but it should be understood that the controller 50 can be part of the structure. Although the present disclosure provides an example of a main chamber 10 that houses an electron beam inspection tool, it should be noted that the various aspects of the present disclosure in its broadest sense are not limited to chambers that house electron beam inspection tools. Rather, it should be understood that the aforementioned principles can also be applied to other tools that operate at a second pressure.

[0036] Reference now Figure 2 , Figure 2 is a schematic diagram illustrating an exemplary imaging system 200 including an electron beam tool 40 and an image processing system 250 according to an embodiment of the present disclosure.

[0037] like Figure 2 As shown, the electron beam tool 40 may include a motorized stage 201 and a wafer holder 202, the wafer holder 202 being supported by the motorized stage 201 to hold a wafer 203 to be inspected. The electron beam tool 40 may also include a composite objective 204, an electron detector 206 (which includes an electron sensor surface), an objective aperture 208, a condenser lens 210, a beam limiting aperture 212, a gun aperture 214, an anode 216, and a cathode 218, one or more of which may be aligned with an optical axis 217 of the electron beam tool 40. In some embodiments, the detector 206 may be arranged offset from the axis 217.

[0038] In some embodiments, the composite objective 204 may include a modified swing objective delayed immersion lens (SORIL), which may include a pole piece 204a, a control electrode 204b, a deflector or a set of deflectors 204c, and an excitation coil 204d. The electron beam tool 40 may additionally include an energy dispersive X-ray spectrometer (EDS) detector (not shown) to characterize the materials on the wafer.

[0039] A primary electron beam 220 may be emitted from the cathode 218 by applying a voltage between the anode 216 and the cathode 218. The primary electron beam 220 may pass through the gun aperture 214 and the beam limiting aperture 212, both of which may determine the current of the electron beam entering the condenser lens 210, which is located below the beam limiting aperture 212. The condenser lens 210 may focus the primary electron beam 220 before the beam enters the objective lens aperture 208 to set the current of the electron beam before the electron beam enters the compound objective lens 204.

[0040] The composite objective lens 204 can focus the primary electron beam 220 onto the wafer 203 for inspection, and can form a detection spot 222 on the surface of the wafer 203. The deflector 204c can deflect the primary electron beam 220 to scan the detection spot 222 above the wafer 203. For example, during the scanning process, the deflector 204c can be controlled to deflect the primary electron beam 220 to different positions on the top surface of the wafer 203 at different time points in sequence to provide data for image reconstruction for different parts of the wafer 203. In addition, in some embodiments, the deflector 204c can also be controlled to deflect the primary electron beam 220 to specific locations on different sides of the wafer 203 at different time points to provide data for stereoscopic image reconstruction of the wafer structure at the position. In addition, in some embodiments, the anode 216 and the cathode 218 can be configured to generate multiple primary electron beams 220, and the electron beam tool 40 can include multiple deflectors 204c to project multiple primary electron beams 220 to different parts / sides of the wafer 203 at the same time.

[0041] When current is applied to the excitation coil 204d, an axially symmetric (i.e., symmetrical about the optical axis 217) magnetic field can be generated in the wafer surface region. A portion of the wafer 203 scanned by the primary electron beam 220 can be immersed in the magnetic field. In some embodiments, different voltages can be applied to the wafer 203, the pole piece 204a, and the control electrode 204b to generate an axially symmetric delayed electric field near the wafer surface. The electric field can reduce the energy of the incident primary electron beam 220 near the wafer surface before the electrons of the beam hit the wafer 203. The control electrode 204b, which is electrically isolated from the pole piece 204a, can control the axially symmetric electric field on the wafer to prevent micro-arcing of the wafer and ensure that the appropriate beam is focused at the wafer surface together with the axially symmetric magnetic field.

[0042] Upon receiving the primary electron beam 220, a secondary electron beam 230 is emitted from a portion of the wafer 203. The secondary electron beam 230 may include backscattered electrons, secondary electrons, or Auger electrons generated due to the interaction of the primary electrons with the wafer 203. The secondary electron beam 230 may be received by a sensor surface of the electron detector 206. In some embodiments, the electron detector 206 may generate a signal (e.g., voltage, current, etc.) representing the intensity of the secondary electron beam 230, and the signal may be provided to an image processing system 250 in communication with the electron detector 206. The intensity of the secondary electron beam 230 may vary depending on the external or internal structure of the wafer 203, and thus may indicate whether the wafer 203 includes a defect. Moreover, as described above, the primary electron beam 220 may be projected onto different locations on the top surface of the wafer 203, or onto specific locations on different sides of the wafer 203, to generate secondary electron beams 230 of different intensities. Therefore, by mapping the intensity of the secondary electron beam 230 to the region of the wafer 203, the image processing system 250 may reconstruct an image reflecting the characteristics of the internal or external structure of the wafer 203.

[0043] In some embodiments, the imaging system 200 may further include an image processing system 250, which includes an image acquisition device 260, a storage device 270, and a controller 50. The image acquisition device 260 may include one or more processors. For example, the image acquisition device 260 may include a computer, a server, a mainframe, a terminal, a personal computer, any kind of mobile computing device, etc., or a combination thereof. The image acquisition device 260 may be communicatively coupled to the detector 206 of the electron beam tool 40 through a medium such as an electrical conductor, a fiber optic cable, a portable storage medium, IR, Bluetooth, the Internet, a wireless network, a wireless broadcast, or a combination thereof. In some embodiments, the image acquisition device 260 may receive a signal from the detector 206 and may construct an image. The image acquisition device 260 may thus acquire an image of the wafer 203. The image acquisition device 260 may also perform various post-processing functions, such as generating a contour, superimposing an indicator on the acquired image, and the like. The image acquisition device 260 may be configured to perform adjustments to the brightness and contrast of the acquired image, and the like. In some embodiments, the storage device 270 may be a storage medium such as a hard disk, a flash drive, a cloud storage, a random access memory (RAM), other types of computer readable memory, etc. The storage device 270 may be coupled to the image acquirer 260 and may be used to save the scanned raw image data as a raw image and save a post-processed image. The image acquirer 260 and the storage device 270 may be connected to the controller 50. In some embodiments, the image acquirer 260, the storage device 270, and the controller 50 may be integrated into a control unit.

[0044] In some embodiments, the image acquirer 260 may acquire one or more images of the sample based on the imaging signal received from the detector 206. The imaging signal may correspond to a scanning operation for performing charged particle imaging. The acquired image may be a single image including multiple imaging regions. The single image may be stored in the storage device 270. The single image may be an original image that may be divided into multiple regions. Each region may include an imaging region containing features of the wafer 203. The acquired image may include multiple images of a single imaging region of the wafer 203 sampled multiple times within a time series. The multiple images may be stored in the storage device 270. In some embodiments, the image processing system 250 may be configured to perform image processing steps on multiple images of the same position of the wafer 203.

[0045] In some embodiments, the image processing system 250 may include a measurement circuit (e.g., an analog-to-digital converter) to obtain the distribution of the detected secondary electrons. The electron distribution data collected during the detection time window is combined with the corresponding scan path data of the primary electron beam 220 incident on the wafer surface, and 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 wafer 203, and thus can be used to reveal any defects that may exist in the wafer.

[0046] In addition, despite Figure 2 The electron beam tool 40 is shown using a single primary electron beam, but it should be understood that the electron beam tool 40 can also be a multi-beam inspection tool using multiple primary electron beams. The present disclosure does not limit the number of primary electron beams used in the electron beam tool 40.

[0047] Reference now Figure 3 , Figure 3 is an exemplary graph showing the yield of secondary electrons relative to the landing energy of the primary electrons. Figure 2 The landing energy of the primary electron beam 220) is different from that of the secondary electron beam (such as Figure 2 The yield is a relationship between the yield of the secondary electron beam 230 of the primary electron beam 230. The yield indicates how many secondary electrons are generated in response to the collision of the primary electrons. For example, a yield above 1.0 indicates that the amount of secondary electrons generated is greater than the amount of primary electrons that have landed on the wafer. Similarly, a yield below 1.0 indicates that a smaller amount of secondary electrons can be generated in response to the impact of the primary electrons.

[0048] like Figure 3As shown in the graph of , when the landing energy of the primary electrons is in the range of E1 to E2, more electrons may leave the wafer surface than have landed on the surface, thus generating a positive potential on the wafer surface. In some embodiments, defect inspection may be performed within the aforementioned range of landing energy, which is referred to as a "positive mode". Figure 4 As described in more detail, a device structure with a higher positive surface potential can produce a darker voltage contrast image because the detector (such as Figure 2 The detector 206) can receive a smaller amount of secondary electrons.

[0049] When the landing energy is lower than E1 or higher than E2, a smaller number of electrons can leave the surface, thereby generating a negative potential at the surface. In some embodiments, defect inspection can be performed within this range of landing energies, which is referred to as a "negative mode." Device structures with higher negative surface potentials can produce brighter voltage contrast images of the wafer.

[0050] In some embodiments, the landing energy of the primary electron beam can be controlled by the total bias voltage between the electron gun and the wafer.

[0051] Reference now Figure 4 , Figure 4 is a schematic diagram showing the voltage contrast response of a device structure of a wafer. In some embodiments, a voltage contrast method of a charged particle inspection system can be used to detect physical and electrical defects in a wafer. In order to detect defects using voltage contrast images, a process known as pre-charging is typically employed, in which charged particles are applied to the area to be inspected prior to inspection.

[0052] In some embodiments, an electron beam tool can be used to inspect a wafer (such as a wafer having a voltage contrast response) based on the wafer's voltage contrast response to a single electron beam exposure. Figure 2 In some embodiments, the wafer may include a test device 420 developed on top of a substrate 410. In some embodiments, the test device 420 may include a plurality of device structures 430 and 440 separated by an insulating material 450. For example, the device structure 430 is connected to the structure 410. In contrast, the device structure 440 is separated by the insulating material 450, which creates a thin insulator structure 470 between the device structure 440 and the substrate 410 (e.g., a thin oxide).

[0053] When electron beam tools such as Figure 2 The electron beam tool 40) uses primary electrons (such as Figure 2 When the primary electron beam 220 of the test device 420 is scanned, the secondary electrons (such as Figure 2 A secondary electron beam 230) can be generated from the surface. Figure 2 As described, when the landing energy of the primary electrons is in the range of E1 to E2 (so that the yield is above 1.0), more electrons leave the wafer surface than land on the surface, thereby generating a positive potential at the wafer surface.

[0054] Figure 4 4 shows how positive potential is accumulated at the wafer surface. For example, after the electron beam scans the test device 420 (e.g., in the pre-charge phase), the device structure 440 can retain more positive charge, thereby generating a positive potential at the surface of the device structure 440, because the device structure 440 is not connected to the electrical ground in the substrate. In contrast, although primary electrons with the same landing energy (thus resulting in the same yield) have been applied, the device structure 430 can retain less positive charge because the accumulated positive charge can be neutralized by additional electrons provided through the connection to the substrate 410.

[0055] Image processing systems (such as Figure 2 The image processing system 250 of the device structure 430 can generate voltage contrast images 435 and 445 for the corresponding device structures 430 and 440, respectively. For example, the device structure 430 is shorted to ground and may not retain accumulated positive charge. In this way, when the primary electron beam lands on the wafer surface during the inspection phase, the device structure 430 can repel more secondary electrons, thereby producing brighter areas on the voltage contrast image. In contrast, the device structure 440 has no connection to the substrate or any other ground, and therefore can retain accumulated positive charge, which may cause the device structure 440 to repel fewer secondary electrons during the inspection phase, thereby producing darker areas on the voltage contrast image.

[0056] Conventional defect inspection tools use electrons to accumulate an electrical potential on the wafer surface during a precharge phase. After precharge, the inspection tool acquires images of multiple dies within the wafer. Because all dies may contain the same device structure, defects can be detected by comparing the voltage contrast differences of these images from multiple dies. For example, if the voltage contrast level of one of the images is lower or higher than another image, it can be determined that the corresponding die has a defect where a mismatch exists. Conventional inspection techniques assume that the surface potential accumulated during the precharge phase will remain constant throughout the inspection phase and remain above the detection threshold of the electron beam tool.

[0057] However, as semiconductor process technology nodes shrink (e.g., 10nm, 7nm and lower), the accumulated surface potential level may change during the inspection phase due to the effects of electrical breakdown or tunneling, resulting in the inability to detect thin device defects. When a sufficiently high voltage is applied to a high resistance thin device structure such as insulator structure 470 (e.g., a thin oxide), leakage current may flow through the high resistance structure, thereby preventing the structure from acting as an ideal insulator. This may affect circuit function and cause failures. Similar leakage current effects may also occur through structures having an improperly formed material or high resistance metal layer (e.g., a cobalt silicide (e.g., CoSi, CoSi2, Co2Si, Co3Si, etc.) layer) between a tungsten (W) plug and a source or drain region of a field effect transistor (FET).

[0058] exist Figure 4 Insulator structure 470 may represent a thin defect that is susceptible to such a breakdown effect. For example, due to manufacturing errors, insulator structure 470 may have been defectively created in device structure 440 even though both device structures 430 and 440 are designed to be in contact with substrate 410 and have the same function. A defective etching process may leave behind a thin oxide, resulting in an undesirable resistive plug (e.g., an open circuit) between two structures that are believed to be electrically connected (e.g., device structure 440 and substrate 410).

[0059] In this case, if the insulator structure 470 is thick enough (e.g., greater than 10 nm), the positive charge accumulated in the device structure 440 will not leak through the insulator structure 470, and therefore, a conventional defect inspection tool can detect the defect by acquiring a sample image during the inspection phase and comparing the image with the reference image. As a result, a voltage contrast difference between 435 and 445 can be detected, indicating a defect in the device structure 440 (e.g., the insulator structure 470).

[0060] However, as insulator structure 470 becomes thinner (e.g., less than 10 nm), there is a higher probability that the level of positive surface potential accumulated in device structure 440 will decrease over time due to the leakage current described above. As device structure 440 loses positive charge, the voltage contrast level may also change over time from darker (e.g., image 445) to lighter (e.g., image 446), and eventually the inspection tool may not detect anything because the voltage contrast level is below the threshold of the detector (e.g., image 447). As a result, by the time the inspection phase begins and the inspection tool begins sampling voltage contrast images, the positive potential accumulated in device structure 440 may all disappear due to the leakage current through the thin insulator structure 470, so that there is no difference in surface potential between device structures 430 and 440. In this case, if the inspection tool samples the image after all the positive charge disappears, then conventional defect inspection tools may not be able to reliably detect thin device defects. For example, the inspection tool may not be able to detect any difference between voltage contrast image 435 (from device structure 430) and voltage contrast image 447 (from device structure 440).

[0061] Therefore, in order to detect thin device defects that are susceptible to the above-mentioned time-dependent changes in the accumulated surface potential, the inspection tool can sample multiple images of the wafer in one or more time sequences while gradually increasing the surface potential so that the time-dependent changes can be captured through the sequence of multiple images. In addition, in some embodiments, the inspection tool can use low-energy primary electrons to gradually charge the wafer without causing such breakdown effects during the pre-charge stage. In other embodiments, the inspection tool can sample and form a voltage contrast image while performing the pre-charge, so that transient voltage contrast changes can be captured even during the pre-charge stage.

[0062] The foregoing description has described the presence of a short circuit condition causing the corresponding feature to appear bright, and the presence of an open circuit condition causing the corresponding feature to appear dark. However, those skilled in the art will appreciate that the appearance of bright and dark may vary and even be reversed depending on the actual processing of the test structure or the setup of the electron beam tool.

[0063] Reference now Figure 5A , Figure 5A is a schematic diagram of an exemplary voltage contrast image in a time series according to an embodiment of the present disclosure. In some embodiments, the defect inspection process may include a pre-charge phase 501 and an inspection phase 503. In the pre-charge phase 501, an imaging system (such as Figure 2The imaging system 200 in FIG. 5 uses electrons to build up a potential on the wafer surface. As described above, to detect thin device defects, the imaging system can use low energy electrons to gradually build up the surface potential without causing breakdown or tunneling while performing pre-charging. In the inspection phase 503, in some embodiments, the imaging system can sample the wafer (such as Figure 2 By comparing multiple voltage contrast images of the same location but from different times, the system can detect changes in surface potential over time, which indicates device breakdown or tunneling effects due to thin device defects.

[0064] For example, Figure 5A As shown, at the beginning of the pre-charge phase 501, the surface potential may not be sufficient to show any detectable voltage contrast regions, as shown in voltage contrast images 510 and 512. At the end of the pre-charge phase, dark voltage contrast (DVC) regions 560a, 562a, and 564a may begin to appear (e.g., at time Tpre3).

[0065] In some embodiments, during the pre-charge phase 501, an electron beam tool (such as Figure 2 The electron beam tool 40 in FIG. 4A can use primary electrons with lower energy than conventional systems to avoid device breakdown during the pre-charge phase (eg, before sampling of the voltage contrast image begins), as described above.

[0066] In other embodiments, the electron beam tool may skip the pre-charge phase 501 and begin the inspection process to detect thin device structure defects with the inspection phase 503. In such embodiments, the electron beam tool may begin sampling images once the inspection process begins. Because there is no pre-charge of potential at the surface of the wafer, the main beam scan for image generation may be used to gradually accumulate charge at the surface of the wafer while continuously sampling images.

[0067] After the precharge is completed, the electron beam tool may begin sampling images from an area of ​​the wafer multiple times in a time sequence. Figure 5A As shown, a plurality of images 530, 532, 534, 536, and 538 are sampled at times T1, T2, T3, T4, and T5, respectively, during the inspection phase.

[0068] At time T1, image 530 shows that there are three DVC regions 560a, 562a, and 564a. DVC regions 560b, 562b, and 564b may represent three device structures (such as Figure 4At times T2 and T3, images 532 and 534 show that DVC regions 560b, 562b, and 564b are detected again, which may indicate that the accumulated positive charge is retained in the device structure and remains unchanged from time T1.

[0069] At time T4, image 536 shows that DVC region 562b disappears while DVC regions 560b and 564b still exist. This may indicate that the corresponding device structure for DVC region 562b may lose the accumulated positive charge due to leakage current, causing the surface potential to drop to an undetectable level (e.g., breakdown effect). When a high voltage is applied to a thin structure (e.g., Figure 4 When the device structure is thinner than the insulator structure 470, the leakage current may flow through the thin structure even if the structure is made of an insulating material. When the device structure is thinner, the leakage current rate is higher. For example, if the thickness of the device structure is less than 10nm, for example, the device breakdown may occur more frequently. Therefore, due to the device breakdown caused by the thin device structure defect, the positive charge accumulated at the corresponding device structure of the DVC region 562b may have been neutralized.

[0070] In some embodiments, thin device structure defects can be identified by detecting this transient effect on the surface potential. For example, the electron beam tool can compare multiple images of the same location, such as images 530, 532, 534, 536, and 538, and detect changes in the DVC area over a time series to identify thin device structure defects. In some embodiments, by comparing multiple voltage contrast images of the same location but from different times, the system can detect changes in the surface potential over time, which indicates device breakdown due to a thin device defect. For example, as Figure 5B As shown, voltage contrast images 534 (sampled at time T3) and 536 (sampled at time T4) show that DVC region 562b has disappeared between times T3 and T4, and thus may indicate that the corresponding device structure may include a thin device structure defect.

[0071] although Figure 5A An example with five images is shown, but it should be understood that two or more images may be used to detect thin device structure defects. Figure 5A and 5B The images shown in show a detection mechanism using dark voltage contrast, but it will be appreciated that bright voltage contrast may also be used when the e-beam tool is operated in negative mode.

[0072] In some embodiments, a positive surface potential can accumulate because the electron beam tool operates in a positive mode (e.g., E1 < landing energy < E2). In other embodiments, a negative potential can accumulate because the electron beam tool operates in a negative mode (e.g., landing energy < E1 or landing energy > E2).

[0073] Now refer to Fig. 6A 、 6B and 6C, Fig. 6A 、 6B and 6C are schematic diagrams of exemplary voltage contrast images related to changes in surface potential within a time series according to embodiments of the present disclosure.

[0074] Fig. 6A illustrates the time characteristics of defects in a slow charging device structure. During an inspection period, an electron beam tool (such as Figure 2 electron beam tool 40) can continuously scan the wafer with an electron beam. This continuous scanning can cause positive charges to accumulate in the device structure (such as Figure 4 device structure 440). For a slow charging device structure, this charge accumulation occurs slowly, and thus as Fig. 6A shown, the surface potential slowly increases over a long period of time. For example, in Fig. 6A , the surface potential gradually increases from time zero to time T4, and the first breakdown does not occur until time Tbreak1. Because the surface potential levels at times T1, T2, T3, and T4 are higher than the threshold voltage 615 of a detector (such as Figure 2 electron detector 206), three DVC regions 640, 642, and 644 may appear on the voltage contrast images 630, 632, 634, and 636 (sampled at times T1, T2, T3, and T4 respectively). However, after the breakdown at time Tbreak1, the surface potential drops to approximately zero at time T5 (and thus below the threshold voltage 615), resulting in the disappearance of the DVC region 642 from the voltage contrast image 638 (sampled at time T5). As a result, the electron beam tool can identify the defect by comparing image 638 with images 630, 632, 634, and 636.

[0075] Figure 6B illustrates the time characteristics of another slow charging device structure. Figure 6B The surface potential in Fig. 6AIncreases faster, therefore, breakdown occurs faster. However, because the time between consecutive breakdowns (e.g., from Tbreak1 to Tbreak2) is longer than the sampling period (e.g., from T1 to T2), defects can still be reliably detected when multiple images are compared. For example, when the surface potential level is above threshold 615, images 650, 654, and 658 show three DVC regions 660, 662, and 664 because these images are sampled at T1, T3, and T5. When the surface potential drops below threshold 615 after Tbreak1 and Tbreak2 breakdowns, images 652 and 656 do not show DVC region 662 because images 652 and 656 are sampled at T2 and T4. Therefore, the electron beam tool is able to identify defects by comparing images 652 and 656 with images 650, 654, and 658.

[0076] on the contrary, Figure 6C The temporal behavior of defects in a very fast-charging device structure is shown. Figure 6C As shown in the graph of , surface charge can accumulate very quickly in this device structure, and therefore breakdown can occur more frequently. The period between successive breakdowns (e.g., from Tbreak1 to Tbreak2) is shorter than the sampling period (e.g., from T1 to T2). This fast breakdown behavior prevents electron beam tools from reliably detecting defects in fast charging device structures. For example, in Figure 6C In FIG. 6 , all five images 670, 672, 674, 676, and 678 are sampled immediately after breakdown when the surface potential level is below the detector threshold 615. Therefore, only two DVC regions 680 and 684 may appear in these five images. Therefore, the electron beam tool may not be able to identify defects in the fast charging device structure.

[0077] One approach to improving the reliability of defect detection in fast-charge device structures is to increase the image sampling rate (e.g., shorten the sampling period between images). Figure 7

[0043] As shown in the mechanism of a conventional scan sequence, conventional electron beam tools are often limited by increasing sampling rates.

[0078] Reference now Figure 7 , Figure 7 Schematic diagram of a conventional scanning sequence. Conventional electron beam tools typically generate images by raster scanning the electron beam across a wafer sample. Figure 7An exemplary raster scan sequence for generating an image of 5×5 pixels is shown. In a raster scan, the electron beam moves horizontally from left to right (e.g., from pixel 711 to pixel 715) at a steady rate to scan a row of pixels (e.g., pixels 711, 712, 713, 714, and 715) (or a line of pixels) across the wafer. Once the electron beam reaches the last pixel in a row being scanned (e.g., pixel 715), the electron beam quickly moves back to the first pixel in the next row (e.g., 721), where scanning of the next row can begin. These steps can be repeated until the last row (e.g., a row with pixels 751, 752, 753, 754, and 755) is scanned. At this point, the electron beam can move back to the first pixel in the first row (e.g., pixel 711) to begin scanning the area again to generate another image. Alternatively, the electron beam can be repositioned to a different location where scanning of a different area of ​​the wafer can begin.

[0079] The step of moving the electron beam quickly from one position to another without actually scanning is called retrace. Figure 7 Retrace 771, 772, 773, 774, and 775 are shown. Moving the electron beam from the last pixel in one row to the first pixel in the next row (e.g., retrace 771, 772, 773, or 774) is called horizontal retrace. Moving the electron beam from the last row to the first row (e.g., retrace 775) is called vertical retrace. The extra time required for retrace is called line overhead.

[0080] In raster scanning, images are generated sequentially (i.e., the second image scan may not begin until the first image scan is complete). Therefore, the speed of sampling multiple images back-to-back can be determined by the time required to scan the entire area. For example, scanning Figure 7 The shortest time required to scan the entire area (5×5 pixel area) can be expressed as 25tp+4thr+tvr, because all 25 pixels should be scanned, where tp represents the time required to scan one pixel; thr represents the additional line burden of each horizontal retrace; tvr represents the additional line burden of each vertical retrace.

[0081] Therefore, an electron beam tool using conventional raster scanning is limited to generating an image every 25tp+4thr+tvr at best. For example, after scanning pixel 711, the electron beam may not return to pixel 711 again until all the remaining 24 pixels have been scanned, which is 25tp+4thr+tvr later. This means that the time difference between scanning two consecutive images for the same pixel is 25tp+4thr+tvr. Figure 6CAs explained in , conventional e-beam tools may not be able to reliably detect defects in fast charge structures if breakdown in the fast charge device structure occurs more frequently than 25tp+4thr+tvr.

[0082] Reference now Fig. 8A and 8B , Fig. 8A and 8B is a schematic diagram of an exemplary scanning sequence according to an embodiment of the present disclosure. In some embodiments, if an electron beam tool (such as Figure 2 If an electron beam tool 40) can scan each row multiple times before moving to the next row, images can be generated more frequently. Fig. 8A As shown, the electron beam may scan a first row (eg, a row having pixels 811, 812, 813, 814, and 815) three times (eg, scanning 861, 871, and 881) and then move to pixel 821 to scan the next row.

[0083] After all five lines have been scanned (three times each), an image processing system (such as Figure 2 The image processing system 250 can reconstruct three images by reassembling the scan data generated during each scan, such as Figure 8B As shown. For example, image 860 may include scan data from each of the first scans (861, 862, 863, 864, and 865) of the row. Image 870 may include scan data from each of the second scans (871, 872, 873, 874, and 875) of the row. Image 880 may include scan data from each of the third scans (881, 882, 883, 884, and 885) of the row.

[0084] Since scanning is performed on a per-row basis, in such an embodiment the electron beam can be Figure 7 The conventional raster scan shown returns to the same pixel faster. For example, after scanning pixel 811 via scan 861, the electron beam can return to pixel 811 just 5tp+thr ​​later and generate image data again via scan 871. Therefore, the time gap between the same pixel in consecutive images (such as the first pixel in image 860 and the first pixel in image 870) can be 5tp+thr, which is faster than Figure 7 The 25tp+4thr+tvr in the conventional raster scan shown is much shorter, assuming that tp and thr remain the same as in the conventional raster scan in such an embodiment. As a result, an e-beam tool using such an embodiment is better able to detect time-dependent defects in fast charging device structures.

[0085] Reference now Fig.9A , 9B, 9C and 9D, Fig.9A , 9B , 9C and 9D are schematic diagrams of exemplary scanning sequences according to embodiments of the present disclosure. In some embodiments, the electron beam tool can perform bidirectional scanning. For example, Fig.9A As shown, the electron beam can scan the first row (e.g., the row with pixels 911, 912, 913, 914, and 915) four times in alternating directions (e.g., changing the scanning direction each time). In such an embodiment, the horizontal retrace step (and the corresponding time thr) between each scan can be eliminated, thereby improving the overall throughput of the inspection system.

[0086] Additionally, in some embodiments, bidirectional scanning can improve the balance between pixels in which positive charge is accumulated by a single scan of the electron beam. Imbalance between pixels occurs because the electron beam typically affects the pixel currently being scanned as well as the next pixel in the scan direction. Thus, unidirectional scanning can produce unbalanced charge in the scan direction. In some embodiments, bidirectional scanning can improve the overall balance between pixels in each row.

[0087] Can be used with the above Figure 8B After completing the scan of all five rows, in some embodiments, the image processing system (such as Figure 2 The image processing system 250 of FIG. 2 can reconstruct four images (each image corresponding to one of the four scans) by reassembling the scan data generated during the scan of each row, as shown in FIG. Fig. 9B shown.

[0088] Fig. 9C Another embodiment of a bidirectional scanning sequence is shown. In some embodiments, the electron beam can scan the first row three times in alternating directions. When the scan of the first row is completed at pixel 915, instead of horizontally retrace back to pixel 921 (the first pixel of the second row), the first scan of the second row can be performed in the other direction from pixel 925 to pixel 921.

[0089] Image reconstruction can be performed similarly. After completing the scan of all five rows, in some embodiments, the image processing system can reconstruct three images, such as Fig.9D shown.

[0090] Reference now Fig. 10A and 10B , Fig. 10A and 10Bis a schematic diagram of an exemplary scanning sequence according to an embodiment of the present disclosure. In some embodiments, if scanning is performed on a per-pixel basis, the sampling speed of the electron beam tool can also be increased (i.e., the electron beam can scan each pixel multiple times before moving to the next pixel). For example, Fig.9A As shown, the electron beam can scan the first pixel (e.g., pixel 1011) three times before moving to the next pixel (e.g., pixel 1012). After completing the scanning of all pixels in the first row (e.g., pixels 1011, 1012, 1013, 1014, and 1015), the electron beam can horizontally retrace to the next row.

[0091] Can be used with the above Figure 8B Image reconstruction is performed in a similar manner as described in . In some embodiments, after completing the scanning of all pixels involving each pixel in five rows (each pixel is scanned three times), in some embodiments, the image processing system (such as Figure 2 The image processing system 250 can reconstruct the three images by reassembling the scan data generated during the scanning of each pixel, such as Fig. 10B For example, image 1060 may include scan data from each of the first scans of pixels. Image 1070 may include scan data from each of the second scans of pixels. Image 1080 may include scan data from each of the third scans of pixels.

[0092] In such an embodiment, the electron beam can be Figure 7 The conventional raster scan shown returns to the same pixel faster. For example, since the same pixel is scanned multiple times before the next pixel is scanned, after scanning pixel 1011, the electron beam can return to pixel 1011 just after tp and generate image data again. Therefore, the time gap between the same pixel in consecutive images (such as the first pixel in image 1060 and the first pixel in image 1070) can be tp, which is less than tp. Figure 7 The 25tp+4thr+tvr in the conventional raster scan shown is much shorter, assuming that tp remains the same as in the conventional raster scan in such an embodiment. As a result, an e-beam tool using such an embodiment is capable of detecting time-dependent defects in very fast charging device structures.

[0093] Reference now Fig.11 , Fig.11 is a flow chart illustrating an exemplary method for detecting time-dependent defects according to an embodiment of the present disclosure. The method may be performed by an electron beam tool such as Figure 2 Electron beam tools 40) and image processing systems (such as Figure 2 The image processing system 250 is executed.

[0094] In step 1110, an electron beam tool delivers an electron beam (such as Figure 2 When the electron beam tool scans the surface of the wafer with primary electrons, secondary electrons (such as Figure 2 A secondary electron beam 230) can be generated from the surface. During inspection, the electron beam tool can continuously scan the wafer with the electron beam. This continuous scanning can cause positive charges to be deposited on device structures such as Figure 4 For a slow charging device structure, the surface potential can increase slowly over a long period of time and can be measured by sampling and comparing multiple images (such as Fig. 6A However, for fast-charge device structures, the surface potential can change more rapidly, causing breakdown to occur more frequently. Even if multiple images can be acquired, the surface potential level can be below the detector threshold (such as Figure 6C 615) when sampling these multiple images (such as Figure 6C 670, 672, 674, 676, and 678 in FIG. 4 ). Therefore, electron beam tools may not be able to identify defects in fast charging device structures.

[0095] One approach to improving the reliability of defect detection in fast charge device structures is to increase the image sampling rate (i.e., reduce the sampling period). However, conventional electron beam tools are limited in sampling rate increases due to the sequential nature of conventional raster scan sequences (i.e., the second image scan cannot begin until the first image scan is complete).

[0096] In some embodiments, images can be generated more frequently if the e-beam tool scans each row multiple times before horizontally retracement to the next row.

[0097] In step 1120, the electron beam tool scans the first row N times before moving to the next row. In some embodiments, the tool may be as follows: Fig. 8A , 9A In some embodiments, the tool may scan the next pixel in the row N times, as shown in FIG. Fig. 10A The pixel is scanned repeatedly N times as shown.

[0098] In step 1130, after scanning the first row is complete, the electron beam tool moves the electron beam to the next row and scans the second row N times. Steps 1120 and 1130 are repeated until all rows have been scanned. In some embodiments, horizontal retrace may be required to reposition the electron beam at the first pixel of the next row, such as Fig. 8A In other embodiments, horizontal retrace can be omitted by utilizing bidirectional scanning, such as Fig.9Aand 9C shown.

[0099] In step 1140, after all rows have been scanned, the image processing system (such as Figure 2 An image processing system 250) processes the data collected while scanning the wafer and reassembles the corresponding data to reconstruct a set of N images, where N is any integer.

[0100] For example, Figure 8B As shown, after completing the scan of all five rows (three times each), the image processing system uses the data collected during the scan to reconstruct three images. For example, Figure 8B Image 860 includes scan data from each of the first scans (861, 862, 863, 864, and 865) of each row. Figure 8B Image 870 of FIG. 8 includes scan data from each of the second scans (871, 872, 873, 874, and 875) of each row. Image 880 of FIG. 880 includes scan data from each of the third scans (881, 882, 883, 884, and 885) of each row.

[0101] Use the above reference Fig. 8A and 8B With the method described, an electron beam tool can generate multiple images with shorter time gaps between the same pixels in these images. For example, after scanning pixel 811 via scan 861, the electron beam can return to pixel 811 after just 5tp+thr ​​and generate image data again via scan 871, where tp represents the time required to scan one pixel; thr represents the line overhead for each horizontal retrace; and tvr represents the line overhead for the vertical retrace. Therefore, the time gap between the same pixel in consecutive images (such as the first pixel in image 860 and the first pixel in image 870) can be 5tp+thr, which is much shorter than the 25tp+4thr+tvr required by conventional electron beam tools, assuming that in such an embodiment tp and thr remain the same as in conventional electron beam tools.

[0102] The embodiments may be further described using the following terms:

[0103] 1. A charged particle beam system for inspecting a wafer, comprising:

[0104] A charged particle beam source comprising circuitry to:

[0105] delivering charged particles to a surface of the wafer in a time series; and

[0106] scanning an area of ​​the wafer, wherein the area includes a plurality of rows of pixels; and

[0107] A controller comprising circuitry to:

[0108] generating a set of N images of the region in the time series, where N is an integer; and

[0109] The set of N images are compared to detect defects that create high resistance structures in the region of the wafer.

[0110] 2. The system of clause 1, wherein the charged particle beam source comprises circuitry to:

[0111] scanning the first row of the plurality of rows N times, and

[0112] After scanning the first row is completed, scanning a second row of the plurality of rows N times; and

[0113] wherein the controller comprises circuitry to:

[0114] generating a first set of N data based on scanning the first row,

[0115] generating a second set of N data based on scanning the second row, and

[0116] The set of N images is generated based on corresponding data in the first set of N data and the second set of N data.

[0117] 3. The system of clause 2, wherein the charged particle beam source comprises circuitry to:

[0118] Scanning the first row N times in alternating directions each time, and

[0119] The second row is scanned N times each time in alternating directions.

[0120] 4. The system of clause 1, wherein the charged particle beam source comprises circuitry to:

[0121] scanning a first pixel in a first row of the plurality of rows N times, and

[0122] After scanning of the first pixel in the first row is completed, scanning the second pixel in the first row of the plurality of rows N times; and

[0123] wherein the controller comprises circuitry to:

[0124] generating a first set of N data based on scanning the first pixel,

[0125] generating a second set of N data based on scanning the second pixel, and

[0126] The set of N images is generated based on corresponding data in the first set of N data and the second set of N data.

[0127] 5. A system according to any one of clauses 2 to 4, wherein the controller comprises circuitry to:

[0128] storing the first group of N data and the second group of N data, and

[0129] The corresponding data in the first set of N data and the second set of N data are retrieved to generate the set of N images.

[0130] 6. A system according to any one of clauses 2 to 5, wherein the controller also includes a circuit to generate the set of N images by combining the first data in the first set of N data and the first data in the second set of N data, and combining the second data in the first set of N data and the second data in the second set of N data.

[0131] 7. A system according to any of clauses 1 to 6, wherein the set of N images comprises information indicative of a voltage contrast level.

[0132] 8. The system of clause 7, wherein the controller includes circuitry to detect differences between the voltage contrast levels of the set of N images to identify the defect.

[0133] 9. The system of any of clauses 1 to 8, wherein the defect comprises an electrical defect associated with electrical leakage in the high resistance structure in the region of the wafer.

[0134] 10. The system of clause 9, wherein the high resistance structure enables formation of a fast charging device.

[0135] 11. The system of any of clauses 1 to 10, wherein the defect creating the high resistance structure is caused by improper formation of a material.

[0136] 12. The system of any of clauses 1 to 10, wherein the defects that create the high resistance structure are caused by thin device structures.

[0137] 13. The system of any of clauses 1 to 12, wherein the thin device structure comprises a thin oxide remaining after an etching process.

[0138] 14. A method of inspecting a wafer using a charged particle beam system having a charged particle beam source that delivers charged particles to a surface of the wafer in a time sequence, the method comprising:

[0139] scanning an area of ​​the wafer, wherein the area includes a plurality of rows of pixels;

[0140] generating a set of N images of the region in the time series, where N is an integer; and

[0141] The set of N images are compared to detect defects that create high resistance structures in the region of the wafer.

[0142] 15. The method according to clause 14, further comprising:

[0143] Scanning a first row of the plurality of rows N times;

[0144] After scanning the first row is completed, scanning a second row of the plurality of rows N times;

[0145] generating a first set of N data based on scanning the first row;

[0146] generating a second set of N data based on scanning the second row; and

[0147] The set of N images is generated based on corresponding data in the first set of N data and the second set of N data.

[0148] 16. A method according to clause 15, wherein:

[0149] Scanning the first row N times includes scanning the first row N times in alternating directions each time, and

[0150] Scanning the second row N times includes scanning the second row N times each time in alternating directions.

[0151] 17. The method according to clause 14, further comprising:

[0152] Scanning a first pixel in a first row of the plurality of rows N times;

[0153] After scanning the first pixel in the first row is completed, scanning the second pixel in the first row of the plurality of rows N times;

[0154] generating a first set of N data based on scanning the first pixel;

[0155] generating a second set of N data based on scanning the second pixel; and

[0156] The set of N images is generated based on corresponding data in the first set of N data and the second set of N data.

[0157] 18. The method according to any one of clauses 15 to 17, further comprising:

[0158] storing the first group of N data and the second group of N data; and

[0159] The corresponding data in the first set of N data and the second set of N data are retrieved to generate the set of N images.

[0160] 19. The method according to any one of clauses 15 to 18 further includes generating the set of N images by combining the first data in the first set of N data and the first data in the second set of N data, and combining the second data in the first set of N data and the second data in the second set of N data.

[0161] 20. A method according to any of clauses 14 to 19, wherein the set of N images comprises information indicative of a voltage contrast level.

[0162] 21. The method according to clause 20, further comprising:

[0163] Differences between the voltage contrast levels of the set of N images are detected to identify the defect.

[0164] 22. A non-transitory computer readable medium storing a set of instructions executable by a processor of a charged particle beam system to cause the charged particle beam system to perform a method, wherein a charged particle beam source of the charged particle beam system delivers charged particles to a surface of a wafer in a time sequence, the method comprising:

[0165] scanning an area of ​​the wafer, wherein the area includes a plurality of rows of pixels;

[0166] generating a set of N images of the region in the time series, where N is an integer; and

[0167] The set of N images are compared to detect defects that create high resistance structures in the region of the wafer.

[0168] 23. The computer-readable medium of clause 22, wherein the set of instructions is executable by the processor of the charged particle beam system to cause the charged particle beam system to further perform:

[0169] Scanning a first row of the plurality of rows N times;

[0170] After scanning the first row is completed, scanning a second row of the plurality of rows N times;

[0171] generating a first set of N data based on scanning the first row;

[0172] generating a second set of N data based on scanning the second row; and

[0173] The set of N images is generated based on corresponding data in the first set of N data and the second set of N data.

[0174] 24. The computer-readable medium of clause 23, wherein the set of instructions is executable by the processor of the charged particle beam system to cause the charged particle beam system to further perform:

[0175] Scanning the first row N times each time in alternating directions; and

[0176] The second row is scanned N times each time in alternating directions.

[0177] 25. The computer-readable medium of clause 22, wherein the set of instructions is executable by the processor of the charged particle beam system to cause the charged particle beam system to further perform:

[0178] Scanning a first pixel in a first row of the plurality of rows N times;

[0179] After scanning the first pixel in the first row is completed, scanning the second pixel in the first row of the plurality of rows N times;

[0180] generating a first set of N data based on scanning the first pixel;

[0181] generating a second set of N data based on scanning the second pixel; and

[0182] The set of N images is generated based on corresponding data in the first set of N data and the second set of N data.

[0183] 26. The computer readable medium of any one of clauses 23 to 25, wherein the set of instructions is executable by the processor of the charged particle beam system to cause the charged particle beam system to further perform:

[0184] storing the first group of N data and the second group of N data; and

[0185] The corresponding data in the first set of N data and the second set of N data are retrieved to generate the set of N images.

[0186] 27. A computer-readable medium according to any one of clauses 23 to 26, wherein the instruction set is capable of being executed by the processor of the charged particle beam system to cause the charged particle beam system to further generate the set of N images by combining the first data in the first set of N data and the first data in the second set of N data, and combining the second data in the first set of N data and the second data in the second set of N data.

[0187] 28. A computer readable medium according to any one of clauses 22 to 27, wherein the set of instructions is executable by the processor of the charged particle beam system to cause the charged particle beam system, wherein the set of N images includes information indicative of a voltage contrast level.

[0188] 29. The computer-readable medium of clause 28, wherein the set of instructions is executable by the processor of the charged particle beam system to cause the charged particle beam system to further perform:

[0189] Differences between the voltage contrast levels of the set of N images are detected to identify the defect.

[0190] It should be understood that the image processing system can use software to control the above functions. For example, an electron beam tool can control the movement of the electron beam for scanning a wafer or a stage to the wafer. The image processing system can reconstruct the image of the wafer according to the data collected when scanning the wafer. In addition, the image processing system can perform an image processing algorithm to adjust the brightness or contrast of the reconstructed image. The software can be stored on a non-transient computer readable medium. Common forms of non-transient media include, for example, floppy disks, flexible disks, hard disks, solid-state drives, tapes or any other magnetic data storage media, CD-ROMs, any other optical data storage media, any physical media with hole patterns, RAM, PROM and EPROM, cloud storage, FLASH-EPROM or any other flash memory, NVRAM, caches, registers, any other memory chips or cassettes, and network versions of the above.

[0191] Although the disclosed embodiments have been described with respect to the preferred embodiments thereof, it should be understood that other modifications and variations may be made without departing from the spirit and scope of the subject matter as hereinafter claimed.

Claims

1. A non-transitory computer readable medium storing a set of instructions executable by a controller of a charged particle beam system to cause the charged particle beam system to perform a method comprising the following operations when a charged particle beam source delivers charged particles to a wafer surface in a time sequence: scanning an area of ​​the wafer; generating a set of images of the region in the time series; and The resulting set of images are compared to detect defects.

2. The non-transitory computer readable medium of claim 1 , wherein the region comprises a plurality of rows of pixels, and the set of instructions is executable by the controller of the charged particle beam system to cause the charged particle beam system to further perform: Scanning a first row of the plurality of rows N times, where N is an integer; After completing the scanning of the first row, scanning a second row of the plurality of rows N times; generating a first set of N data based on scanning the first row; generating a second set of N data based on scanning the second row; as well as The set of images is generated based on corresponding data in the first set of N data and the second set of N data.

3. The non-transitory computer readable medium of claim 2, wherein the set of instructions is executable by the controller of the charged particle beam system to cause the charged particle beam system to further perform: Scanning the first row N times each time in alternating directions; and The second row is scanned N times each time in alternating directions.

4. The non-transitory computer readable medium of claim 2, wherein the set of instructions is executable by the controller of the charged particle beam system to cause the charged particle beam system to further perform: Scanning a first pixel in a first row of the plurality of rows N times; After completing scanning of the first pixel in the first row, scanning the second pixel in the first row of the plurality of rows N times; generating a first set of N data based on scanning the first pixel; generating a second set of N data based on scanning the second pixel; as well as The set of images is generated based on corresponding data in the first set of N data and the second set of N data.

5. The non-transitory computer readable medium of claim 2, wherein the set of instructions is executable by the controller of the charged particle beam system to cause the charged particle beam system to further perform: storing the first group of N data and the second group of N data, and The corresponding data in the first set of N data and the second set of N data are retrieved to generate the set of images.

6. The non-transitory computer readable medium of claim 2, wherein the set of instructions is executable by the controller of the charged particle beam system to cause the charged particle beam system to further perform: The set of images is generated by combining first data in the first set of N data with first data in the second set of N data, and combining second data in the first set of N data with second data in the second set of N data. 7 . The non-transitory computer readable medium of claim 1 , wherein the set of images includes information indicative of voltage contrast.

8. The non-transitory computer readable medium of claim 7, wherein the set of instructions is executable by the controller of the charged particle beam system to cause the charged particle beam system to further perform: Differences between the voltage contrasts of the set of images are detected to identify the defect.

9. The non-transitory computer readable medium of any one of claims 1 to 6, wherein the defect comprises an electrical defect associated with electrical leakage in a high resistance structure in the region of the wafer.

10. The non-transitory computer readable medium of claim 9, wherein the high resistance structure enables formation of a fast charging device.

Images