Scanning electron beam imaging apparatus, method

Abstract

The application relates to a scanning electron beam imaging device and method. The device comprises: an electron optical column for emitting an electron beam to a sample surface; a deflector for applying an electric field and / or a magnetic field to the electron beam to deflect the electron beam; a detector module for collecting signal electrons emitted by the sample under bombardment of the electron beam and converting the signal electrons into an image signal; an imaging module connected to the detector module for generating an image of the sample surface according to the image signal; a scanning imaging control module for providing a scanning signal to the deflector to deflect and scan the electron beam, wherein the scanning signal comprises a scanning signal for imaging and scanning the sample surface and a scanning signal for regulating a charge accumulation level of the sample surface; and the scanning imaging control module sends a sampling trigger signal to the detector module to obtain the image signal while providing the imaging scanning signal to the deflector.

Description

Technical Field

[0001] This application relates to the field of scanning imaging technology, and in particular to a scanning electron beam imaging device and method. Background Technology

[0002] Scanning electron beam imaging devices are widely used in scientific research for the microscopic imaging and analysis of the surface structures of various solid materials. With the development of modern microfabrication and semiconductor integrated circuit industries, scanning electron beam imaging devices are also increasingly used in online measurement and defect detection on production lines. This requires not only high imaging quality, but also that the detection process be non-destructive to the sample and have high measurement accuracy and detection sensitivity.

[0003] Traditionally, a scanning electron beam imaging device, such as Figure 1 As shown. The device includes:

[0004] Sample 30;

[0005] The electron optics tube 10 is mainly used to emit a primary electron beam and focus it on the sample surface to excite secondary electrons and / or backscattered electrons, which are collectively referred to as signal electrons below.

[0006] The deflector 20 is a multi-pole field device composed of multiple axially symmetrical electrodes or magnetic poles, which is set in the coaxial optical path with the electron optical lens barrel to realize the deflection scanning of the electron beam in two mutually perpendicular directions.

[0007] Detector module 40 is used to collect signal electrons and convert them into electrical signals;

[0008] The scanning signal generator 501 outputs a scanning signal waveform to drive the deflector and achieve the scanning required for imaging.

[0009] The imaging module 601 reconstructs, displays, and stores image signals;

[0010] There are two types of deflectors: electric deflectors and magnetic deflectors. Therefore, there are also two types of drive signals: voltage signals and current signals. The following description uses electric deflectors as an example, but the basic principle also applies to magnetic deflectors.

[0011] Scan signal generator 501 generates Figure 2 The two scanning signals V shown in (a) and (b) have different frequencies. L and V F and the dual signal (i.e., the signal with opposite polarity -V) L and -V F (No illustration shown); To achieve imaging scanning at an arbitrary angle θ with respect to the deflector electrode orientation, the scanning signal generator will also process signal V. L and V FVector decomposition based on the electrode azimuth angle θ, i.e. ±V LX =V L *cosθ, ±V LY =V L *Sinθ, ±V FX =V F *cos(θ+90) and ±V FY =V F *Sin(θ+90) yields the component signals on each electrode. The signal components on the same electrode are superimposed and output to two sets of mutually perpendicular electrodes of the deflector, called the X deflection electrode set and the Y deflection electrode set. The deflector generates a transverse electric field and / or magnetic field in a plane perpendicular to the optical axis, exerting an electromagnetic force on the passing electron beam. Under the influence of the electromagnetic force, the electron beam will generate on the sample surface... Figure 2 (c) The scan trajectory, which resembles a grating, is also known as grating scanning; the scan signal contains a high-frequency signal, such as V in Figure 2(a). L This will produce a scan along the L direction as shown in Figure 2(c), where segment 3010 is the forward scan, during which the signal obtained by the detector module is used for imaging; segment 3011 is the retrace scan, during which the signal does not participate in imaging. Figure 2 (c) is represented by a dashed line; the scan signal has a lower frequency signal, such as V in Figure 2(b). F This will produce a line-by-line offset in the F direction as shown in Figure 2(c), where segment 4010 is the forward scan, covering the period of N line scans; segment 4011 is the frame back scan. Figure 2 (c) is represented by a dashed line; the forward scan is also called the line or frame scan period, and the scan signal waveform must meet the linearity requirement; the retrace scan is also called the line or frame scan preparation period; it does not participate in imaging during this period, so there is no linearity requirement for the waveform.

[0012] During scanning electron beam imaging, the interaction between the electron beam and the sample leads to an imbalance in surface charge neutrality. Generally, a single electron beam scan of the sample surface excites secondary electrons and backscattered electrons, collectively referred to as signal electrons. The charge accumulation on the sample surface is determined by the total number of signal electrons excited and escaping; the total number of signal electrons excited by a unit primary electron is defined as the electron yield η; if η > 1, it means that positive charge will accumulate on the surface; if η < 1, it means that negative charge will accumulate on the surface.

[0013] For non-conductive or poorly grounded samples, charge accumulation does not dissipate quickly and requires other methods. In traditional scanning methods, repetitive raster scanning causes surface charge to accumulate in a single direction until equilibrium is reached. Excessive surface charge accumulation leads to defocusing and distortion, severely impacting image quality. One approach to overcome this problem is to deposit a metal film on the sample surface or ground it. However, this method conflicts with the product's manufacturing process requirements and fails to meet the basic requirements of non-destructive testing.

[0014] To avoid damaging the sample, another approach is to perform one or more repeated pre-scans on the area to be tested using a scanning waveform different from that used for imaging. After the surface charge reaches a certain equilibrium, a final scan is performed, simultaneously acquiring the final image. This method has three main drawbacks: first, the deflection waveform generator can only produce one set of raster (line and frame) scanning waveforms, requiring frequent system switching between pre-scan and imaging scans; second, even without considering the time loss due to frequent switching, the pre-scan method can only condition the surface charge accumulation at frame intervals or frequencies, limiting the scenarios it can address. In practice, in some applications, the charge on the sample surface accumulates to a level affecting image quality within the imaging time of one frame, requiring higher-frequency adjustments to the surface charge accumulation. Therefore, traditional pre-scan methods cannot meet the application requirements of special scenarios, especially the online measurement and defect detection needs of patterned wafers in integrated circuit manufacturing. The device or method proposed in this invention aims to solve this problem.

[0015] The aforementioned signal electron yield η is related not only to the surface characteristics of the sample but also to various parameters of the primary electron beam, including characteristic parameters such as energy, beam current, and spot size, and scanning parameters such as scanning time and scanning range. Therefore, changing the scanning waveform parameters and characteristic parameters of the electron beam can alter the signal electron yield η, thereby adjusting the direction and level of charge accumulation. These two aspects of conditioning the charge accumulation on the sample surface constitute the basis of this invention. Summary of the Invention

[0016] Based on this, a scanning electron imaging device and method can be developed that can more flexibly and at a higher frequency adjust the charge accumulation on the sample surface during the scanning electron beam imaging process, thereby meeting the requirements for high-quality imaging.

[0017] A scanning electron beam imaging apparatus, the apparatus comprising:

[0018] Sample stage, used for clamping and positioning samples;

[0019] An electron optics tube for emitting an electron beam toward the sample, the electron beam being focused on the sample surface;

[0020] Deflector, used to apply an electric field and / or magnetic field to the electron beam to deflect the electron beam;

[0021] The detector module is used to collect the signal electrons emitted by the sample when it is bombarded by the electron beam, and to convert the signal electrons into image signals;

[0022] An imaging module, connected to the detector module, is used to generate an image of the sample surface based on the image signal;

[0023] A scanning imaging control module, connected to the deflector and the detector module, is used to provide scanning signals to the deflector to generate the electric field and / or magnetic field, wherein the scanning signals include scanning signals for imaging scanning of the sample surface and scanning signals for conditioning the charge accumulation level of the sample surface.

[0024] The scanning imaging control module, while providing the imaging scanning signal to the deflector, also sends a sampling trigger signal to the detector module to acquire the image signal.

[0025] In one embodiment, the scanning signal includes a line scanning signal and a frame scanning signal, wherein one cycle of the line scanning signal includes a line imaging scanning period and a line conditioning scanning period, and one cycle of the frame scanning signal includes a frame imaging scanning period. The duration of the frame imaging scanning period is greater than or equal to the duration of at least one of the line scanning signals. The line imaging scanning period and the frame imaging scanning period are used to perform imaging scanning of the sample surface. The line conditioning scanning period is used to adjust the charge accumulation on the sample surface. During the line conditioning scanning period, the scanning imaging control module provides a conditioning signal to the deflector. The waveform parameters of the conditioning scanning signal are related to the charge accumulation on the sample surface, and the waveform parameters include the amplitude, slope, and duration of the scanning signal.

[0026] In one embodiment, the scanning imaging control module can also control the electron optical tube parameters to change the parameters of the electron beam emitted by the electron optical tube during the conditioning scanning period, so as to adjust the accumulated charge level on the sample surface. The electron beam parameters include at least one of the electron beam spot size, the electron beam current, and the electron beam energy.

[0027] In one embodiment, the line scanning signal further includes: a line imaging scan preparation period, located before the line imaging scan period, for adjusting the initial amplitude of the line imaging signal generated during the line imaging scan period; and a line conditioning scan preparation period, located before the line conditioning scan period, for adjusting the initial amplitude of the conditioning signal generated during the line conditioning scan period.

[0028] In one embodiment, the row scan signal includes a row imaging scan signal and a row conditioning scan signal; the row imaging scan signal and the row conditioning scan signal are sequentially connected, wherein the row conditioning scan signal is connected before and / or after the row imaging scan signal; wherein the row imaging scan signal is output during the row imaging scan period, and the row conditioning scan signal is output during the row conditioning scan period;

[0029] The frame scan signal includes a frame imaging scan signal and a frame conditioning scan signal; the frame imaging scan signal and the frame conditioning scan signal are connected sequentially, wherein the frame conditioning scan signal is connected before and / or after the frame imaging scan signal; wherein the frame imaging scan signal is output during the frame imaging scan period.

[0030] In one embodiment, the frame scanning signal further includes: a frame imaging scan preparation period, located before the frame imaging scan period, for adjusting the initial amplitude of the frame imaging signal generated during the frame imaging scan period; and a frame conditioning scan preparation period, located before the frame conditioning scan period, for adjusting the initial amplitude of the conditioning signal generated during the frame conditioning scan period.

[0031] In one embodiment, when the frame scan signal includes a frame conditioning scan signal, the line scan signal is externally attached to an external line scan signal corresponding to the frame conditioning scan signal, and the duration of the frame conditioning scan signal is greater than or equal to the duration of at least one of the external line scan signals.

[0032] In one embodiment, the scanning imaging control module is used to perform multiple repeated imaging scans on the same location on the sample surface to acquire multiple initial image signals, and to take the average value of the multiple initial image signals as the image signal; it is also used to perform multiple repeated conditioning scans on the sample surface to enhance or accelerate the charge adjustment of the sample surface.

[0033] In one embodiment, the scanning imaging control module is configured to adjust the waveform parameters of the conditioning scanning signal until the accumulated charge on the sample surface meets the imaging conditions when the accumulated charge on the sample surface does not meet the imaging conditions. The waveform parameters of the conditioning scanning signal include at least one of the duration of the conditioning scanning signal, the amplitude of the conditioning scanning signal, and the rate of change of the conditioning scanning signal.

[0034] In one embodiment, the scanning imaging control module is further configured to adjust the parameters of the conditioning control signal when the accumulated charge on the sample surface does not meet the imaging conditions, and apply it to the corresponding component of the electron optical tube to change the parameters of the electron beam until the accumulated charge on the sample surface meets the imaging conditions. The electron beam characteristic parameters that the conditioning control signal can control include electron beam energy, current, and beam spot size.

[0035] A scanning electron beam imaging method, the method being applied to a scanning electron beam imaging device, the method comprising:

[0036] An electron beam is emitted toward the sample surface and focused on the sample surface;

[0037] A line scan signal and a frame scan signal are applied to the deflector to deflect the electron beam, wherein the scan signal includes a conditioning scan signal for adjusting the accumulated charge on the sample surface and an imaging scan signal for imaging the sample surface.

[0038] During the line imaging scanning period, the signal electrons excited when the sample surface receives the electron beam are acquired to obtain the image signal;

[0039] An image of the sample surface is generated based on the image signal.

[0040] In one embodiment, one cycle of the line scan signal includes a line imaging scan period and a conditioning scan period, and the frame scan signal includes a frame imaging scan period, wherein the conditioning scan period is used to balance the accumulated charge on the sample surface, the line imaging scan period and the frame imaging scan period are used for scanning imaging, and the duration of the frame imaging scan period is greater than or equal to the duration of at least one of the line scan signals.

[0041] The method further includes: adjusting the signal parameters of the conditioning scan signal so that the accumulated charge on the sample surface meets the imaging conditions.

[0042] In one embodiment, a period of the frame scanning signal includes a frame imaging scanning period and a frame conditioning scanning period. When the frame scanning signal includes the frame conditioning scanning period, the line scanning signal is externally equipped with an external line scanning period corresponding to the frame conditioning scanning period. The duration of the frame conditioning scanning period is greater than or equal to the duration of at least one of the external line scanning periods.

[0043] The method further includes: adjusting the signal parameters of the conditioning scan signal during the frame conditioning scan period so that the accumulated charge on the sample surface meets the imaging conditions.

[0044] In one embodiment, the method further includes: adjusting the parameters of the electron beam to make the accumulated charge on the sample surface meet the imaging conditions, wherein the parameters of the electron beam include at least one of the electron beam spot size, the electron beam current, and the electron beam energy.

[0045] In one embodiment, the method further includes:

[0046] Determine the image quality of the sample;

[0047] If the quality of the sample image meets the standard, then the sample image quality is deemed acceptable.

[0048] If the quality of the sample image is substandard, then the number of image optimization iterations is obtained;

[0049] If the number of image optimization iterations exceeds the maximum allowed number, the sample image quality is deemed unqualified.

[0050] If the number of image optimization iterations does not exceed the maximum allowed number, change the waveform parameters of the row conditioning scan signal and the frame conditioning scan signal driving the deflector to adjust the charge accumulated on the sample surface;

[0051] The parameters of the electron beam are adjusted to adjust the surface charge accumulation.

[0052] The steps of adjusting the waveform parameters of the line scan signal and frame scan signal to adjust the charge accumulated on the sample surface, and adjusting the parameters of the electron beam to adjust the charge accumulated on the surface, are repeated until the sample image quality is qualified, or the number of times the above steps are repeated exceeds the maximum allowable number of times. The number of image optimization iterations is the number of times the above steps are repeated.

[0053] The aforementioned scanning electron imaging apparatus and method, by setting up an electron optical tube, can emit and focus an electron beam onto the sample surface. By outputting row and frame scanning signals to a deflector, the electron beam is controlled to perform raster scanning on the sample surface. By configuring the waveform parameters of the imaging and conditioning scanning periods of the row and frame scanning signals, and the corresponding electron beam parameters, the electron beam can perform imaging and conditioning scanning of the sample surface. Image signals are simultaneously acquired during the imaging scanning period for imaging. During the conditioning scanning period, no image signals are sampled; the signal is only used to measure the level of charge accumulation on the sample surface, ensuring high-quality electron beam imaging. By setting up a sampling module, the excited electron beam emitted by the sample surface after receiving the electron beam can be acquired. The sampling module only samples during the row imaging scanning period, ensuring that the sampled excited electron beams are all obtained based on the imaging signal. By setting up an imaging module, an image can be generated based on the excited electron beam, thus completing the entire imaging process. Through the scheme of this application, by introducing conditioning scanning signals into the row and frame scanning periods of the scanning signal, the surface charge state of the sample surface at different frequencies can be conditioned. By incorporating the conditioning scan signal into the frame scan signal—that is, switching between imaging and conditioning scans at the highest frequency based on the frame scan duration—the charge state of the sample surface is conditioned. This method is faster and more effective than traditional pre-scanning. Similarly, by incorporating the conditioning scan signal into the line scan signal—switching between imaging and conditioning scans at the highest frequency based on the line scan duration—it is possible to switch between imaging and conditioning scans more frequently, line by line, during the imaging process of a single frame. This allows for more timely adjustment of the sample surface charge level to the desired state, ensuring that the sample surface remains in the same state during each line of imaging scans within a frame, thus guaranteeing image signal stability. The line conditioning scan, frame conditioning scan, line imaging scan, and imaging scan introduced in this scheme can also be independently repeated multiple times to form a complete scan signal, satisfying the requirements for repeated conditioning and imaging scans at the line and frame levels. The final image from repeated imaging scans can be the average of the image signals at corresponding positions to further improve the image signal-to-noise ratio. Attached Figure Description

[0054] To more clearly illustrate the technical solutions in the embodiments of this application or the conventional technology, the drawings used in the description of the embodiments or the conventional technology will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0055] Figure 1 This is a schematic diagram of the scanning imaging principle of a conventional scanning electron beam imaging device in one embodiment;

[0056] Figure 2This is a schematic diagram illustrating the implementation of a conventional scanning signal waveform, i.e., raster scanning, in one embodiment.

[0057] Figure 3 This is a diagram of a scanning electron beam imaging apparatus including front and rear conditioning scans in one embodiment;

[0058] Figure 4 A diagram of a scanning electron beam imaging apparatus including frame-conditioning scanning in another embodiment;

[0059] Figure 5 This is a schematic diagram of the output signal of the scan control module in one embodiment;

[0060] Figure 6 This is a diagram illustrating several combinations and variations of imaging scan and conditioning scan signal waveforms in one embodiment;

[0061] Figure 7 This is an example diagram illustrating several combinations and variations of the imaging scan and conditioning scan signal waveforms in another embodiment;

[0062] Figure 8 This is an example diagram of the output signal of the scan control module in one embodiment;

[0063] Figure 9 This is a block diagram of the output signal of the scan control module in one embodiment;

[0064] Figure 10 This is a single-line scan signal waveform diagram for implementing repeated line conditioning scan and repeated line imaging scan in one embodiment;

[0065] Figure 11 This is a single-frame scan signal waveform diagram for implementing repeated frame conditioning scan and repeated frame imaging scan in one embodiment;

[0066] Figure 12 This is a single-line scan signal waveform diagram for implementing repeated frame conditioning scan and repeated frame imaging scan in one embodiment;

[0067] Figure 13 The image shows the waveforms of the line scan and frame scan signals for implementing repeated frame image scanning in one embodiment.

[0068] Figure 14 This is a signal waveform diagram of the basic unit of the scanning signal in one embodiment;

[0069] Figure 15 This is a flowchart of a scanning electron beam imaging method in one embodiment.

[0070] Explanation of key markings in the attached diagram:

[0071] 10-Electron optics tube, 20-Deflector, 21-First electrode plate, 22-Second electrode plate, 23-Third electrode plate, 24-Fourth electrode plate, 30-Sample, 34-Raster scanning range, 40-Detector module, 50-Scanning imaging control module, 60-Imaging module, 101-Main electron beam, 102-Signal electrons, 300-Line scan signal, 301-Line imaging scan, 302, 303-Line conditioning scan, 304, 305-Frame conditioning line scan, 30x0 line scan period, 30x1 line scan preparation period; 400-Frame scan signal, 402, 403-Frame conditioning scan, 40x0-Frame scan period, 40x0-Frame scan preparation period, 70-Processor. Detailed Implementation

[0072] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings, which illustrate embodiments of the present application. However, the present application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of this application will be thorough and complete.

[0073] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0074] It should be noted that when one element is considered to be "connected" to another element, it can be directly connected to the other element or connected to the other element through an intermediary element. Furthermore, in the following embodiments, "connection" should be understood as "electrical connection," "communication connection," etc., if there is transmission of electrical signals or data between the connected objects.

[0075] When used herein, the singular forms of “a,” “an,” and “the” may also include the plural forms unless the context clearly indicates otherwise. It should also be understood that the terms “comprising,” “including,” or “having,” etc., specify the presence of the stated feature, whole, step, operation, component, part, or combination thereof, but do not preclude the possibility of the presence or addition of one or more other features, wholes, steps, operations, components, parts, or combinations thereof.

[0076] In one embodiment, such as Figure 3 As shown, a scanning electron beam imaging device is provided, which includes: an electron optical lens tube 10, a deflector 20, a sample 30, a detector module 40, a scanning imaging control module 50, and a sampling imaging module 60.

[0077] in:

[0078] Electron optics tube 10 is used to emit a primary electron beam 101 onto the sample 30 and focus it on the sample surface. The optical axis of the electron optics tube is defined as the Z-axis of the spatial coordinate system. Deflector 20 is coaxial with the optical axis and located on the path of the primary electron beam 101. The scanning imaging control module outputs a scanning signal to drive the deflector, causing the deflector to generate a spatial electric field and / or magnetic field in the paraxial region. The electric field and / or magnetic field deflect the primary electron beam 101, generating a magnetic field on the sample surface. Figure 3 The grating scanning trajectory shown in Figure 34 (description of the scanning trajectory follows) is as follows: The interaction between the primary electron beam 101 and the sample surface excites secondary electrons and other electrons (hereinafter collectively referred to as signal electrons 102), the strength of which reflects the microscopic morphology or physical characteristics. The signal electrons are captured by the detector module 40 and converted into electrical signals. The signal electrons excited on the scanning grating trajectory are collected point by point, and finally the image synthesis module 70 constructs an image.

[0079] For example, the electron optical tube 10 is a scanning electron microscope (SEM), which is an observation method between transmission electron microscopy and optical microscopy. It uses a narrow, focused high-energy electron beam to scan the sample, and through the interaction between the beam and the material, it excites various physical information, collects, amplifies, and re-images this information to achieve the purpose of characterizing the microscopic morphology of the material.

[0080] Specifically, the line scan signal includes a line imaging scan period for generating the line imaging signal and a line conditioning scan period for generating the conditioning signal, and the frame scan signal includes a frame imaging scan period for generating the frame imaging signal. The duration of the frame imaging scan period is greater than or equal to the duration of at least one line scan signal, wherein the conditioning signal is used to control the electron beam deflection to balance the accumulated charge on the sample surface.

[0081] Deflector 20 is typically an axisymmetric dipolar field device. A dipolar field device refers to an electric field with positive and negative polarities or a magnetic field with north and south poles generated in space by applying appropriate voltage or current excitation to multiple electrodes or coils. The former is called an electric deflector, and the latter is called a magnetic deflector. The following description uses an electric deflector as an example, but its basic principle also applies to the case of magnetic deflection, and will not be repeated.

[0082] In one embodiment, such as Figure 3As shown, deflector 2020 is an electric deflector 20 consisting of four electrodes (21, 22, 23, 24). The electrode structure and number of the deflector 20 are typically divided into two groups, each containing at least two symmetrical electrodes. The two groups have identical structures and are spatially separated by a 90° angle. For ease of description, one group is defined as the X deflection electrodes (electrodes 23 and 24), and the other as the Y deflection electrodes (21 and 22). Positive and negative polarity excitations (called dual excitations) need to be applied to each pair of opposing electrodes to generate a bipolar electric field in space. The direction of the electric field is determined by the intensity and polarity distribution of the excitation signals on the X and Y deflection electrodes. Since the deflection drive is based on dual excitations, for simplicity, the polarity characteristics of the deflection signals discussed later will not be described.

[0083] Specifically, the deflector 20 generates an alternating electric field, causing the electron beam to be deflected by the electric force within the electric field. This causes the electron beam to reciprocate along both the X-axis and Y-axis. Within one cycle of movement along the Y-axis, the electron beam reciprocates multiple cycles along the X-axis, thus forming multiple scans. Within one cycle along the Y-axis, one frame of scanning is completed. Therefore, each frame of the image includes multiple scans, thus completing a full scan of the sample surface.

[0084] If the signal applied to deflector 20 is an alternating signal, the resulting deflection behavior is a line scan. If two sets of alternating signals VL and VF exist simultaneously and are applied to the X and Y deflection electrode groups of deflector 2020 respectively, then... Figure 3The grating scanning is shown in Figure 34. The higher-frequency signal (denoted by VL) performs scanning in the direction parallel to the grating (or the row direction L), and is defined as the row scanning signal. The other set of lower-frequency signals (denoted by VF) performs scanning in the direction perpendicular to the grating (or the frame direction F), and is defined as the frame scanning signal. If the purpose of the scanning is to image the sample and is accompanied by signal sampling, the scanning is also called imaging scanning, or specifically row imaging scanning or frame imaging scanning. If the purpose of the scanning is to condition the sample surface, the scanning is also called conditioning scanning. The scanning direction (L, F) can be the same as or different from the orientation direction (X, Y) of the deflection electrode. To achieve grating scanning with the scanning direction (L, F) at an arbitrary angle θ to the deflection electrode group direction (X, Y), the VL and VF signals need to be vector-decomposed according to the electrode azimuth angle θ to obtain the signal components that should be present on each electrode: VLX = VL*cos(θ), VLY = VL*Sin(θ), VFX = VF*cos(θ+90), and VFY = VF*Sin(θ+90). The signal components on the same electrode are superimposed as VX = VLX + VFX and VY = VLY + VFY, which dual-drives each electrode of the deflector 20. The various structures and compositions of the deflector 20, the basic forms of the deflection signals, and the synthesis and excitation methods are basic practices in the relevant fields of this invention and will not be elaborated here.

[0085] During scanning electron beam imaging, the interaction between the electron beam and the sample leads to an imbalance in surface charge neutrality. Generally, a single electron beam scan of the sample surface excites secondary electrons and backscattered electrons, collectively referred to as signal electrons. If the total number of signal electrons excited by a single primary electron is defined as the electron yield η, then if η > 1, it means that positive charge accumulates on the surface; if η < 1, it means that negative charge accumulates on the surface. The signal electrons excited at the point of excitation by the preceding electron beam imaging will alter the charge accumulation on the sample surface, thus affecting subsequent electron beam scanning and imaging.

[0086] The yield η of signal electrons is related not only to the sample's material, morphology, and conductivity, but also to various parameters of the scanning electron beam, including scanning parameters such as scanning time and scanning range, and characteristic parameters such as energy, beam current, and spot size. Therefore, changing the scanning waveform parameters and characteristic parameters of the electron beam can alter the yield η of signal electrons, thereby adjusting the direction and level of charge accumulation. This conditioning effect on charge accumulation on the sample surface is crucial. The control of these two parameters can be integrated into the system's scanning waveform generation and sampling timing control, forming the basis of the so-called conditioning scan of this invention.

[0087] In one embodiment of this invention, the output of the scanning imaging control module is as follows: Figure 5 The scan signal and drive control signal are shown.

[0088] The scan signal comprises two paths: a line scan signal period signal 300 and a frame scan signal period signal 400 (one frame). One period of the frame scan signal 400 covers at least one period 300 of the line scan signal. One line scan signal period 300 comprises at least one segment of line imaging scan signal 301 and at least one segment of line conditioning scan signal (302 or / and 303). The line imaging scan signal 301 consists of two parts: a line imaging scan period 3010 (typically linear) and a line imaging scan preparation period 3011. Similarly, the line conditioning scan signal 302 (or / and 303) consists of two parts: a line conditioning scan period 3020 (or / and 3030) (typically linear) and a line conditioning scan preparation period 3021 (or / and 3022).

[0089] based on Figure 5 The scanning waveform, Figure 3 The grating area shown in Figure 34 is covered by multiple line scans. Each frame begins at a starting point (top left corner in the figure), and each line scan consists of two time periods: a conditioning scan corresponding to 3020 (and / or 3030) and an imaging scan corresponding to 3010. The transition between these time periods is completed by corresponding scan preparation time periods 3011, 3021, and 3031, which set the scan signal to the starting point of the next time period, indicated by dashed lines in the figure. The frame scan signal 4010 advances at a fixed slope, causing the starting point of each line scan time period to advance a specific distance in the F direction. If the advancing distance is much smaller than the beam spot diameter, the conditioning scans 3020 and / or 3030 before and after the line sampling scan 3010 can be approximated as line conditioning scans covering the same line. This process repeats for each line scan until the end point of the frame is reached (bottom right corner in the figure), completing one frame scan. The frame scan signal 4011 returns the frame scan signal from the end point to the starting point, preparing for the next frame scan.

[0090] In another embodiment, the scanning imaging control module 50 not only outputs imaging scanning signals and conditioning scanning signals, but can also simultaneously output other control signals to adjust or change the characteristic parameters of the electron beam emitted by the electron optical tube, such as energy, current, and beam spot, to adjust the charge accumulation on the sample surface. During conditioning scanning, appropriate control of these characteristic parameter changes can effectively adjust the direction and speed of charge accumulation on the sample surface; these are hereinafter collectively referred to as conditioning control signals.

[0091] For example, after the electron beam falls on the sample surface, it can excite signal electrons related to the morphology and material of the sample surface. The detector module is an electron detector that can collect and amplify the excited electron beam, converting it into an imaging electron signal. Furthermore, the excited electron beam is only collected during the imaging scan period, ensuring that the sampled electrons correspond to the imaging signal. Signal electrons corresponding to the conditioning signal period are not collected, thus preventing imaging interference. The electrons excited during the conditioning scan period only condition the surface charge state and are not used for imaging.

[0092] Conditioning control signals and scanning signals, such as Figure 5 As shown in section 600: When the horizontal scanning signal 300 enters the horizontal conditioning scanning stage 3020 (and / or 3030), the conditioning control signal 600 undergoes a level step. The scanning imaging control module generates a conditioning control signal according to this mode, and its output is connected to the control module of the corresponding electron optical tube, triggering changes in the characteristic parameters of the corresponding electron beam, such as energy, current, and beam spot, which remain unchanged during the subsequent horizontal conditioning scanning period until the conditioning scanning 3020 (and / or 3030) ends. At this point, the conditioning control signal 600 returns to its original level step, and the characteristic parameters of the electron beam are also reset to their original state, ready for imaging. When entering the horizontal imaging scanning stage 3010, the sampling signal 500 is simultaneously triggered and output, and the connected sampling imaging module starts simultaneously to sample the signal electrons at each point during the imaging scanning process, completing the imaging of the raster scanning imaging area.

[0093] In all embodiments of the present invention, the scanning imaging control module differs from the traditional scanning waveform generator in that: 1. In addition to generating the imaging scanning signal, it also generates a conditioning scanning signal, which is then combined into a unified line scanning signal and / or frame scanning signal. 2. While outputting the conditioning scanning signal, it also outputs a conditioning control signal, which acts on the corresponding components of the electron optical lens barrel.

[0094] In one embodiment of the present invention, such as Figure 3The scanning imaging control module 50 provides the deflector 20 with signals for imaging scanning and conditioning scanning. The conditioning scanning period is embedded in the line scanning signal of the imaging scan. That is, one cycle of the line scanning signal includes the line imaging scanning period and the line conditioning scanning period. The line conditioning scanning period is located before and / or after the line imaging scanning period. The corresponding frame scanning signal covers at least one line scanning signal cycle. The line conditioning scan is for the purpose of electron beam scanning imaging, and its waveform parameters are determined by image parameters, such as the number of image pixels, pixel size, or imaging magnification. The conditioning scan signal is for the purpose of adjusting the charge accumulation on the sample surface, and its waveform parameters, such as amplitude, slope, and duration, are determined according to the conditioning effect of the charge status on the sample surface. The signal waveforms of the line conditioning scan and the line imaging scan can be the same or different. During the line imaging scan, the scanning imaging control module also sends a sampling trigger signal to the detector module to acquire image information.

[0095] In one embodiment, a conditioning scan signal appears within a line scan signal. One cycle of the line scan signal comprises a line imaging scan period and a line conditioning scan period. The line conditioning scan period is located before and / or after the line imaging scan period. A corresponding frame scan signal covers at least one cycle of the line scan signal.

[0096] In one embodiment, the line scan signal further includes a line imaging scan preparation period, which is connected before the line imaging scan period. If a conditioning scan period exists before the line imaging scan period, the line imaging scan preparation period is connected between the line imaging scan period and the conditioning scan period, and is used to adjust the starting amplitude of the line imaging scan signal in the line imaging scan period.

[0097] In one embodiment, the line scan signal further includes a conditioning scan preparation period, which is connected before the conditioning scan period. If there is a line imaging scan period before the conditioning scan period, the conditioning scan preparation period is connected between the line imaging scan period and the conditioning scan period, and is used to adjust the starting amplitude of the conditioning scan signal in the conditioning scan period.

[0098] In another embodiment, the conditioning scan signal may also appear in the frame scan signal. One period of the frame scan signal includes a frame imaging scan period and a frame conditioning scan period. The frame imaging scan period covers at least one line scan signal period. The line scan signal period may or may not include a line conditioning scan. During the frame conditioning scan period, a corresponding frame conditioning line scan signal is required, placed outside the line scan signal, and the duration of the frame conditioning scan signal at least covers the duration of one frame conditioning line scan signal to constitute a complete frame scan.

[0099] In one embodiment, the frame imaging scan period and the frame conditioning scan period are sequentially connected, wherein the frame conditioning scan period is located before and / or after the frame imaging scan period.

[0100] In one embodiment, the frame scanning signal further includes a frame imaging scan preparation period, which is located before the frame imaging scan period. If a frame conditioning scan period exists before the frame imaging scan period, the frame imaging scan preparation period is connected between the frame imaging scan period and the frame conditioning scan period, and is used to adjust the signal of the frame imaging scan period to reach its initial amplitude.

[0101] In one embodiment, the frame scan signal further includes a frame conditioning scan preparation period, which is located before the frame conditioning scan period. If there is a frame imaging scan period before the frame conditioning scan period, the frame conditioning scan preparation period is connected between the frame imaging scan period and the frame conditioning scan period, and is used to adjust the signal of the frame conditioning scan period to reach its initial amplitude.

[0102] In all embodiments, the amplitude of the signal changes monotonically and linearly with time during each scanning period.

[0103] In all embodiments, the amplitude of the signal in each scanning period undergoes at least one periodic linear change over time.

[0104] Figure 5 In the illustrated embodiment, the waveforms of the scanning signal at different time periods can also have various combinations of variations:

[0105] Line conditioning scans can occur before (302), after (303), or both before and after imaging scan 301. Specifically, such as Figure 6 In the embodiments shown in (a) and (c), the line conditioning scan 302 occurs before the line imaging scan 301. Figure 6 In the embodiments shown in (b) and (d), the line conditioning scan period 303 occurs after the line imaging scan period 301. Figure 5 In the illustrated embodiment, there are line conditioning scans 302 and 303 before and after line imaging scan 301.

[0106] Specifically, if the row conditioning scan (e.g., 302) is performed before the row imaging scan 301, the position of the row corresponding to the upper surface of the sample will be pre-scanned by the electron beam with the row conditioning scan signal 302 before being scanned by the electron beam with the row imaging scan signal 301. The charge level of the row to be imaged on the surface of the sample 30 will be "pre-charged" into a certain equilibrium state, which can improve the signal-to-noise ratio of subsequent imaging scans. If the row conditioning scan (e.g., 303) occurs after the row imaging scan 301, the corresponding row will be covered by the electron beam according to the row conditioning scan settings, and the charge changes left after the 301 scan will be "post-erased" to prevent the charge on the sample surface from accumulating continuously and affecting the imaging quality of subsequent adjacent rows. Figure 5 The line scan signal shown has conditioning scans 302 and 303 before and after the line imaging scan 301, which is suitable for the imaging needs of some specific samples. The imaging scan requires both "pre-charging" and "post-erasing" to maintain stable imaging quality.

[0107] In one embodiment, such as Figure 5 The horizontal scanning signal 300 includes a horizontal imaging scanning signal 301 and horizontal conditioning scanning signals 302 and 303, and its waveform can be a sawtooth wave or a triangular wave. 3010, 3020, and 3030 represent the scanning stages of 301, 302, and 303, respectively. 3011, 3021, and 3031 represent the preparation stages for scanning 301, 302, and 303, respectively. For example, 3011 is the horizontal imaging scanning preparation period, during which the horizontal scanning signal amplitude transitions from the end amplitude of the horizontal conditioning scanning signal to the beginning amplitude of the horizontal imaging scanning signal. 3021 and 3031 are the horizontal conditioning scanning preparation periods, during which the horizontal scanning signal amplitude transitions from the end amplitude of the horizontal imaging scanning signal to the beginning amplitude of the conditioning scanning signal.

[0108] The waveform trends in each scanning period can be different; they can be monotonically rising or falling (upper triangular wave or lower triangular wave), and they can be independent of each other. In one embodiment, such as... Figure 6 (c) During the line conditioning scan period, signal 3020 decreases linearly, while during the line sampling period, signal 3010 increases. In another embodiment, such as Figure 6 (d) During the horizontal imaging scan period, signal 3010 decreases linearly, while signal 3030 increases during the horizontal conditioning scan period. The amplitude of the signal can also be different for each scan period. The same principle applies to frame scan signals, such as... Figure 7 This is one implementation. The rising or falling waveform of the scanning waveform, in the direction of raster scanning, represents a reversal of the scanning direction. Aside from a change in the timing of the image signal, it has no other impact. The effect on the timing of the image signal can be easily converted from spatial geometric relationships, and this patent will not elaborate further.

[0109] When only one scan period exists, the signal during that scan period will repeat, and there will be transitional phases at the beginning and end of the signal; this phase is usually called the retrace phase. Figure 2 In the traditional scan shown in (a), the line scan only includes the line imaging scan. There is a time transition between the end amplitude of each line imaging scan and the start amplitude of the next line imaging scan; this is called line retrace. In... Figure 7 (e) In one embodiment of the present invention, the frame scanning signal 400 only includes the frame imaging scanning period 4010. The frame imaging scanning signal 4010 will occur repeatedly. There will be an amplitude transition 4011 from the end of one frame imaging scanning signal to the start of the next frame imaging scanning, which is called frame retrace.

[0110] The frame scan waveform, besides changing continuously in the form of a triangular wave or a sawtooth wave, can also change in a stepped manner. In one embodiment, such as... Figure 7 (f) During the frame imaging scanning period, signal 401 remains constant within one cycle of the line scan. After each line is completed, the signal amplitude increases or decreases by one unit. The overall waveform amplitude changes in one scanning period according to an upward or downward trend.

[0111] In such Figure 5 In the illustrated embodiment, the scanning imaging control module 50 also outputs other control signals, including two types: a sampling trigger signal 500 and a conditioning control signal 600.

[0112] The sampling trigger signal 500 occurs only during the imaging scan phase. It is primarily associated with the horizontal imaging scan period 301. The sampling trigger signal 500 will generate a step before or after the horizontal scan signal 300 enters the imaging scan period 301; it can be either an increase or a decrease, triggering the external circuitry to continuously sample the image signal from the detector module until around the end of the imaging scan period, at which point a reverse step is generated, triggering the sampling to stop. The sampling trigger signal 500 can also emit pulse signals (as shown by the vertical lines in 500) before or after the horizontal imaging scan signal enters the imaging scan period, with the number of pulses equal to the number of points sampled in the horizontal scan. The entire time span of both sampling signals can be longer than the duration of the imaging scan, but the effective sampling duration (i.e., sampling occurring during the linear scan period) is no longer than the duration of the imaging scan period.

[0113] The conditioning control signal 600 primarily occurs during the conditioning scan phase. It is mainly associated with signals 302 or 303 during the horizontal conditioning scan period. The conditioning control signal 600 steps when the horizontal scan signal 300 enters the preparation phase of the horizontal conditioning scan; this step can be either an increase or a decrease. This triggers the external circuitry to drive and adjust the relevant modules of the electron optics tube, thereby changing the characteristic parameters of the electron beam. The controlled modules may include, but are not limited to, the driving circuit of the electron source, the driving circuit of the lens, the voltage bias circuit of the sample, the beam gate driving circuit, etc. Changes in these driving parameters will alter the energy, current, and spot size of the electron beam, affecting the yield of secondary electrons excited after the electron beam lands on the sample, thus changing the level of surface charge accumulation.

[0114] Specifically, if the line conditioning scan period precedes the line imaging scan period, the charge balance of the sample surface can be adjusted before the line imaging scan signal is sent, thereby ensuring the imaging quality of the subsequent line imaging scan signal. This is suitable for situations where the sample surface has not received an electron beam scan before and needs to be charged and balanced before imaging. If the line conditioning scan period follows the line imaging scan period, the charge on the sample surface is restored to a preset state after the line imaging scan signal is sent, thus facilitating the next electron beam imaging.

[0115] Specifically, when the frame scan signal includes a frame conditioning scan period, the line scan signal has an external scan period corresponding to the frame conditioning scan period, which is used to keep the line scan signal synchronized with the frame scan signal.

[0116] Specifically, a frame conditioning scan period is also set in the frame scan signal, and external scan periods are set before and after the line scan signal. By setting external scan periods in the line scan signal, the line scan signal can be aligned with the frame scan signal in time and space. That is, when a frame conditioning scan period is also set in the frame scan signal, the frame imaging scan period of the frame scan signal is still aligned with the line scan signal, thereby ensuring normal imaging.

[0117] Specifically, setting a line conditioning scan period in the line scan signal allows for frequent sending of conditioning signals at line imaging scan intervals during the formation of one image frame. The scanning electron beam then adjusts the accumulated charge level on the sample surface, enabling more timely adjustments and multiple adjustments within a short period. This is suitable for situations where the sample surface charge changes rapidly. Conversely, setting a frame conditioning scan period in the frame scan signal is suitable for situations where the sample surface charge changes slowly. During the scanning of one image frame, the sample surface charge does not change significantly, so a conditioning scan period only needs to be set before or after scanning one image frame to adjust the surface charge level.

[0118] Specifically, by setting a line imaging scan preparation period before the line imaging scan period, the starting amplitude of the line imaging scan period can be set to a preset value, thereby enabling the setting of the starting amplitude of the line imaging scan period according to the actual imaging requirements, which facilitates imaging.

[0119] Specifically, by setting a conditioning scan preparation period before the conditioning scan period, the starting amplitude of the conditioning scan period can be set to a preset value, thereby setting the starting amplitude of the conditioning scan period. This allows for setting according to the actual charge balancing requirements, facilitating better balancing of the charge on the sample surface.

[0120] Specifically, the waveform parameters of the conditioning scan signal can be set according to the actual accumulated charge on the sample surface and the actual needs. The signal parameters can be adjusted according to the imaging quality of the final image until the imaging quality of the image meets the requirements. At this point, the conditioning scan signal can meet the expected surface charge level of the sample.

[0121] In another embodiment of this invention, the scanning imaging control module outputs as follows: Figure 8 The scan signal shown is a typical example. This example's scan signal has the following characteristics:

[0122] In addition to frame imaging scan 401, frame conditioning scan 402 and / or 403 are included in frame scanning signal 400. Frame imaging scan 401 is matched with line scanning signal 300. One period of frame imaging scan 401 covers at least one period of line scanning signal 300. Frame conditioning scan 402 occurs before frame imaging scan 401. Frame conditioning scan 402 is equipped with a separate line scanning signal 304. One period of frame conditioning scan 402 covers at least one period of frame conditioning line scanning signal 304. Frame conditioning scan 403 occurs after frame imaging scan 401. Frame conditioning scan 403 is equipped with a separate line scanning signal 305. One period of frame conditioning scan 403 covers at least one period of frame conditioning line scanning signal 305.

[0123] Specifically, if the frame conditioning scan (e.g., 402) is performed before the frame imaging scan 401, the frame can be scanned by the electron beam before entering the imaging scan 401, and the charge level of the sample 30 surface to be scanned will be "pre-charged," which can improve the signal-to-noise ratio of subsequent imaging scans. If the frame conditioning scan (e.g., 403) occurs after the frame imaging scan 401, the charge left on the imaging sample surface can be "post-erased" after the frame imaging scan is completed, so as to prevent the charge level on the sample surface from being too high and affecting the imaging quality of subsequent adjacent frames. Figure 8In the frame scan signal shown, there are conditioning scans 402 and 403 before and after frame imaging scan 401. This is suitable for specific samples that require "pre-charging" before imaging scan and "post-erasing" after scan in order to maintain stable imaging quality.

[0124] In one embodiment, the waveforms of frame imaging scan 401 and frame conditioning scans 402 and 303 can be sawtooth or triangular wave shapes. 4010, 4020, and 4030 represent the scanning periods of frame scans 401, 402, and 403, respectively. 4011, 4021, and 4031 represent the preparation periods for frame scans 401, 402, and 403, respectively. For example, 4011 is the preparation period for frame imaging scan, during which the frame scan signal amplitude transitions from the end amplitude of the frame conditioning scan signal to the beginning amplitude of the frame imaging scan signal. 4021 and 4031 are the preparation periods for line conditioning scan, during which the frame scan signal amplitude transitions from the end amplitude of frame imaging scan signal 401 to the beginning amplitude of frame conditioning scan signals 402 and 403. The trends of the waveforms in each scanning period can be different; they can be monotonically rising or falling, and they can be independent of each other, which will not be elaborated further here.

[0125] The scanning signals in this embodiment include frame imaging scanning signal 401, frame conditioning scanning signals 402 and 403, and frame conditioning line scanning signals 304 and 305. The waveform trends of each of these signals during their respective scanning periods can be different; they can be monotonically rising or falling (upper triangular wave or lower triangular wave), and they can be independent of each other. The rise or fall of the waveform reflects the scanning direction, which is due to the reversal of the electron beam scanning direction, and the timing of the image signal also changes accordingly. By transforming the image signal according to the spatiotemporal relationship, the final image can be obtained. This patent will not elaborate further.

[0126] In this embodiment, the frame scanning waveform, in addition to changing continuously in the form of a triangular wave or a sawtooth wave, can also change incrementally or incrementally in a stepwise manner. That is, it remains constant within one line of time, and in a complete frame scanning period, its amplitude starts from the initial value and monotonically increases or decreases by one step after each line of scanning, until it reaches the final value of the amplitude.

[0127] Similarly, in one embodiment of this invention patent, such as Figure 8 The scanning imaging control module also outputs control signals, including two types: a sampling trigger signal 500 and a conditioning control signal 600.

[0128] The sampling trigger signal 500 occurs only during the imaging scan phase. It is primarily associated with the horizontal imaging scan period 301. The sampling trigger signal 500 will generate a step before or after the horizontal scan signal 300 enters the imaging scan period 301; it can be either an increase or a decrease, triggering the external circuitry to continuously sample the image signal from the detector module until around the end of the imaging scan period, at which point a reverse step is generated, triggering the sampling to stop. The sampling trigger signal 500 can also emit pulse signals (as shown by the vertical lines in 500) before or after the horizontal imaging scan signal enters the imaging scan period, with the number of pulses equal to the number of points sampled in the horizontal scan. The entire time span of both sampling signals can be longer than the duration of the imaging scan, but the effective sampling duration (i.e., sampling occurring during the linear scan period) is no longer than the duration of the imaging scan period.

[0129] The conditioning control signal 600 primarily occurs during the line and frame conditioning scan phases. Specifically, it is associated with line conditioning scan periods 302 and / or 303, and with frame conditioning scan periods 402 and 403. The conditioning control signal 600 experiences a step change (either an increase or a decrease) when the line conditioning scan signals 302 and 303, and the frame conditioning scan signals 402 and 403, enter the preparation phase of the conditioning scan. This triggers the external circuitry to drive and adjust the relevant modules of the electron optics tube, thereby altering the characteristic parameters of the electron beam. The controlled modules may include, but are not limited to, the driving circuitry of the electron source, the driving circuitry of the lens, the voltage bias circuitry of the sample, the driving circuitry of the beam gate, etc. Changes in these driving parameters alter the energy, current, and spot size of the electron beam, affecting the yield of secondary electrons excited after the electron beam lands on the sample, thus changing the level of surface charge accumulation.

[0130] In the foregoing embodiments, the scanning and other control signal waveforms generated by the scanning imaging control module can also be... Figure 9 The block diagram shown illustrates this. In the block diagram, frame scan signal 400 includes frame imaging scan signal 401 and frame conditioning scan signals 402 and / or 403. Frame imaging scan signal 401 consists of two parts: an imaging scan period 4010 and a preparation phase 4011. Frame conditioning scan signals 402 and / or 403 consist of two parts: a conditioning scan period 4020 (and / or 4030) and a conditioning scan preparation period 4021 (and / or 4031). Frame conditioning scan signals 402 and 403 can exist individually, simultaneously, or not at all. In the block diagram, the line scan signal within one frame scan cycle is labeled 3000, and its duration includes the external line conditioning scan signal 304 for line L4, the built-in line scan signal 300 for line L, and the external line conditioning scan 305 for line L5. Or, more generally, it can be described as follows:

[0131] 3000 = 304 * L4 + 300 * L + 305 * L5.

[0132] Mapped to the corresponding frame scan signal 400:

[0133] 401=300*L. 402=304*L4. 403=305*L.

[0134] One cycle of frame conditioning scan signal 402 covers L4 cycles of external line conditioning scan signals 304. One cycle of frame imaging scan signal 401 covers L cycles of line scan signals 300. One cycle of frame conditioning scan signal 403 covers L5 cycles of external line conditioning scan signals 305. L, L4, and L5 are positive integers. If L, L4, or L5 is zero, it means that the corresponding frame conditioning scan 402, 403, or frame imaging scan 401 does not exist. If frame conditioning scan 402, 403, or frame imaging scan 401 exists, then the corresponding L4 or L5 or L should be an integer not less than 1.

[0135] In another embodiment of this invention, the built-in line scanning signal unit 300 may also have, for example, Figure 10 The repetition pattern shown is as follows: the included line conditioning scan signal 302 can be repeated L2 times, the line imaging scan signal 301 can be repeated L1 times, and the line conditioning scan signal 303 can be repeated L3 times. The built-in line scan signal 300 can be represented as...

[0136] 300 = 301*L1 + 302*L2 + 303*L3;

[0137] L1, L2, and L3 are integers. If L1, L2, and L3 are zero, it means that the corresponding line conditioning scan signal 302, 303 or line imaging scan signal 301 does not exist. Mapped to the corresponding frame imaging scan signal 401, there are...

[0138] 401=300*L=(301*L1+302*L2+303*L3)*L

[0139] If line conditioning scan 302 or 303 or line imaging scan 301 exists, then the corresponding L2 or L3 or L1 should be an integer not less than 1. This is because during the line scan signal, the corresponding frame scan signal remains unchanged, such as... Figure 7 As shown in (f), or a slow linear change, such as Figure 7(e) The scan will remain almost in one line. During the line imaging scan signal 301, the sampling trigger signal 500 triggers the image sampling module to repeatedly sample the image signal on one line L1 times. Therefore, the signal can be averaged L1 times to obtain the average signal of one line. The frame scan signal 401 covers the line scan signals 300 of L lines, thus obtaining a frame image of L lines, each line averaged L1 times. This is the so-called scanning signal mode with multiple lines of repeated conditioning scans and multiple lines of repeated imaging scans, where the average of multiple lines of imaging signals in the same position constitutes the final image.

[0140] In another embodiment of this invention, the frame scanning signal unit 400 may further have, as shown in the following example: Figure 11 The repetition pattern shown is as follows: the frame imaging scan signal 401 can be repeated M1 times, the frame conditioning scan signal 402 can be repeated M2 times, and the frame conditioning scan signal 403 can be repeated M3 times. The frame scan signal 400 can be represented as 400 = 402*M2 + 401*M1 + 403*M3; where M1, M2, and M3 are integers. Mapped to the corresponding line scan signals are...

[0141] 300=304*L4*M2+300*L*M1+305*L5*M3

[0142] =304*L4*M2+(301*L1+302*L2+303*L3)*L*M1+305*L5*M3

[0143] If M1, M2, and M3 are zero, it means that the corresponding frame conditioning scan signal 402, 403 or frame imaging scan signal 401 does not exist. If frame conditioning scan 402 or 403 or frame imaging scan 401 exists, then the corresponding M2 or M3 or M1 should be an integer not less than 1. Because during the frame scanning signal period, during the corresponding sampling trigger signal 500, the image sampling module repeatedly samples the image signal at a position of one frame M1 times, so the signal can be averaged M1 times to obtain the image signal after M1 frame average. This is the so-called scanning signal mode that combines multiple repeated frame conditioning scans and has multiple repeated imaging scans, and the average of multiple frames constitutes the final image.

[0144] In another embodiment of this invention, Figure 10 and Figure 11 The corresponding signals can be combined, at this time Figure 10 The signal can be Figure 12 express,

[0145] In another embodiment of this invention, the frame scan signal unit 400 can also be simply repeated M times, such as... Figure 13As shown. If the position of sample 30 does not change during this period, the corresponding sampling signal 500 is repeated M times, thus obtaining the average signal of M frames of an image. This is also a scan signal that includes line conditioning and / or frame conditioning scanning, satisfying the averaging of multiple frame image signals.

[0146] exist Figure 9 Figure 13 In the illustrated embodiment, the conditioning control signal 500 occurs synchronously with the conditioning scan signals 402 / 403 and 302 / 303 / 304 / 305. Figures 10-13 (Not specified in the text) is used to trigger the electron optics barrel control module to adjust the electron beam characteristic parameters. The sampling control signal 600 is synchronized with the line imaging scan signal 301. Figures 10-13 (Not shown in the figure) is used to trigger the image sampling module to sample image signals. The external circuit module can respond to signals 500 and / or 600 with either a rising edge trigger or a falling edge trigger. For the sampling trigger signal 500, it can also be output in the form of clock pulses, sampling the image signal of the pixel unit corresponding to each clock cycle. During different line or frame conditioning scans, separate conditioning control signals can also be output, as shown in Figures 502-504, which can be used to control the same or different components of the electron optical tube to adjust different electron beam characteristic parameters. The conditioning control signal 500, or the independent time-segment conditioning control parameters 502-504, do not overlap with the sampling trigger signal 600 in time.

[0147] exist Figures 9-13 In the illustrated embodiments, the basic unit of the scanning signal can be represented by y0x: y=3 represents line scanning, y=4 represents frame scanning, x=1 represents imaging scanning, and x>1 represents conditioning scanning. The basic signal unit comprises two segments: a scanning time period y0x0 and a scanning preparation time period y0x1, such as... Figure 14 The scanning period y0x0 is the linear segment of the scanning signal y0x, where the amplitude changes monotonically and linearly with time, either increasing or decreasing monotonically to achieve linear scanning. The scanning preparation period y0x1 is the non-linear segment of the scanning signal y0x, used to adjust the amplitude of the scanning signal y0x from the final value of the previous scanning period y0x1 to the starting value of the next scanning period y0x1, preparing it for linear scanning. For example, for the line imaging scanning signal 301, 3010 is the line imaging scanning period, and 3011 is the line imaging scanning preparation period. For the frame conditioning scanning signal 403, 4030 is the frame conditioning scanning period, and 4031 is the frame conditioning scanning preparation period. During the scanning preparation period y0x1, the waveform change is not required to be linear; only a fast and smooth transition of the signal is needed.

[0148] exist Figures 9-13In the illustrated embodiment, the block diagrams of each unit scan signal are represented by different heights or widths, meaning that the amplitude and duration of each scan signal can be the same or different. The repetition periods (number of times) L2, L4, L5, M, M1, and M2 of the unit scan signal waveforms associated with each conditioning scan can be the same or different, or they can be zero, meaning that frame conditioning scans and line conditioning scans can exist simultaneously, separately, or not at all. The repetition periods L1, L, and M of the imaging scan signal units are not less than 1. L is the number of rows that make up a frame image. L1 indicates that a row contains L1 repeated scans, which can be processed by the image processing unit into an image with a row average. M indicates that a frame image is scanned M times, which can be processed by the image processing unit into an image with a frame average.

[0149] In one embodiment, such as Figure 4 As shown, the device also includes: a processor 70, which is connected to the scanning imaging control module 50, the electron optical lens barrel 10, and the imaging module 60, respectively. Its function is:

[0150] Connected to the scanning imaging control module 50, it sends waveform parameters for each time period of the control scanning signal to generate the required signal waveforms that include imaging scanning and conditioning scanning. The imaging scanning signal must meet the requirements of the image parameters, and the conditioning scanning signal must meet the intensity and frequency requirements of the electron beam irradiation on the sample surface. Before or after the imaging scanning, the level of charge accumulation on the sample surface is conditioned to meet the imaging quality requirements. The signal parameters of the conditioning scanning signal include at least one of the following: the duration of the conditioning scanning signal, the amplitude of the conditioning scanning signal, and the rate of change of the conditioning scanning signal.

[0151] Connected to the electron optics tube 10, its purpose is to control the electron source, lenses, beam gate, etc. of the electron optics tube to change the characteristic parameters of the electron beam, given the limited adjustment of charge accumulation on the sample surface by a single conditioning scan, thereby achieving more effective conditioning of the charge accumulation level on the sample surface and meeting imaging quality requirements. The characteristic parameters of the electron beam include, but are not limited to, the energy, current, and beam spot size of the electron beam.

[0152] Together with the imaging module 60, it acquires images, processes images, determines image quality and the effectiveness of conditioning scanning and conditioning control, and drives related components to perform further optimization control.

[0153] Specifically, the processor 70 is capable of transmitting waveform parameter scanning imaging control module 50, causing it to generate and output corresponding line scanning signal 300 and frame scanning signal 400, and adjusting the timing phase of line scanning signal 300 and frame scanning signal 400.

[0154] In this embodiment, the processor 70 can also acquire images from the imaging sampling module and adjust the signal parameters of the conditioning scanning signal according to the final image quality to drive the electron optical tube, thereby changing the conditioning effect of charge accumulation on the sample surface in order to improve the imaging quality.

[0155] In one embodiment, such as Figure 15 As shown, a scanning electron beam imaging method is provided, the method comprising:

[0156] In step S1300, the scanning imaging control module (host computer) issues the initial operating mode and parameters of the electron optical tube scanning imaging control module, and initializes the system.

[0157] In step S1302, the electron optical tube generates a focused electron beam that is emitted toward the sample surface.

[0158] In step S1304, the scanning imaging control module generates the waveform of the imaging scanning signal (which may not include conditioning scanning) and samples the timing of the trigger signal.

[0159] Step S1306: The scanning imaging control module (host computer) performs scanning and acquires images simultaneously, and the image quality is judged automatically or manually.

[0160] Step S1308: Determine the image quality. If the image meets the requirements, proceed to step S1318. If the image does not meet the requirements, proceed to step S1310 to perform image optimization iterations.

[0161] Step S1310: Determine the number of image optimization iterations. If the number exceeds the maximum allowed number, proceed to step S1320. If the number does not exceed the maximum allowed number, proceed to step S1312.

[0162] Step S1312: Introduce conditioning scan or adjust conditioning scan parameters, change the coverage and time of conditioning scan, etc., to adjust the yield of secondary electrons or other electrons generated by primary electrons and adjust the balance level of surface accumulated charge.

[0163] Step S1314 (optional) synchronously introduces conditioning control or adjusts conditioning parameters to change the characteristic parameters of the electron beam emitted by the electron optics tube, including but not limited to energy, beam current, and spot size. This is also used to adjust the yield of secondary electrons or other electrons excited by primary electrons, and to adjust the balance level of surface accumulated charge.

[0164] Steps S1306 to S1314 are repeated cyclically until the image quality meets the requirements, at which point the process terminates normally in step 1318. Alternatively, if the number of iterations exceeds the limit, the process terminates abnormally in step 1320.

[0165] In the aforementioned imaging method examples, the conditioning scan period can be added to the line scan signal, and can occur before or after the line sampling scan. The frame scan signal must cover at least one complete cycle of the line scan signal. Since frame conditioning scanning requires corresponding line scans to form a complete raster scan, frame conditioning scanning has corresponding line scans, i.e., frame conditioning line scan signals, or external line scan signals, appended before or after the aforementioned line scan signals. The frame conditioning scan signal must cover at least one complete cycle of the frame conditioning line scan signal.

[0166] In this embodiment of the method, an electron beam for imaging is emitted onto the sample surface. Then, a line scan signal and a scan signal along the F direction are applied to the X and Y electrode groups of the deflector, causing the electron beam to scan along the L direction. The frame scan signals VL and VF, (L, F) and (X, Y) can be at any angle θ.

[0167] The line scan signal VL may include a line conditioning scan signal. The frame scan signal VF may also include a frame conditioning scan signal. During all conditioning scans, the excited signal electrons are not used for imaging; instead, the direction and rate of charge accumulation on the sample surface are changed by adjusting the yield of signal electrons, so that the charge on the sample surface reaches the expected balance and meets the imaging quality requirements.

[0168] If the conditioning scan is embedded in the line scan signal, and each frame of imaging scan includes multiple line scan signals, that is, a frame of image includes multiple line scan signals, and each line scan signal contains a line conditioning scan period, the setting of the line conditioning scan parameters can be different from the frame imaging scan parameters. In addition, the electron beam characteristic parameters can be adjusted at the same time to most effectively adjust the charge status of the sample surface. Thus, during the imaging process of a frame of image, the charge status of the sample surface can be frequently adjusted so that the charge accumulation on the sample surface is maintained within a specific range, thereby obtaining good and stable image quality for each imaging scan.

[0169] If conditioning scanning is embedded in the frame scanning signal, that is, at least one conditioning scanning process is added during the imaging scanning process of each frame. This allows a frame conditioning scan to be added before or after the imaging scanning of each frame image is completed, and before moving the sample to the next position. The setting of its scanning parameters can be different from the frame imaging scanning signal. In addition, the electron beam characteristic parameters can be adjusted at the same time to most effectively adjust the charge status of the sample surface, so that the charge accumulation on the sample surface is maintained within a specific range. This allows the charge accumulation between frames to be controlled, ensuring that the imaging scan obtains good and stable image quality.

[0170] Those skilled in the art will understand that all or part of the processes in the methods of the above embodiments can be implemented by a computer program instructing related hardware. The computer program can be stored in a non-volatile computer-readable storage medium. When executed, the computer program can include the processes of the embodiments of the above methods. Any references to memory, storage, databases, or other media used in the embodiments provided in this application can include at least one of non-volatile and volatile memory. Non-volatile memory can include read-only memory (ROM), magnetic tape, floppy disk, flash memory, or optical storage, etc. Volatile memory can include random access memory (RAM) or external cache memory. By way of illustration and not limitation, RAM can be in various forms, such as static random access memory (SRAM) or dynamic random access memory (DRAM), etc.

[0171] In the description of this specification, references to terms such as "some embodiments," "other embodiments," and "ideal embodiments" indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative descriptions of the above terms do not necessarily refer to the same embodiments or examples.

[0172] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0173] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims.

Claims

1. A scanning electron beam imaging device, characterized in that, The device includes: Sample stage, used for clamping and positioning samples; An electron optics tube for emitting an electron beam toward the sample, the electron beam being focused on the sample surface; Deflector, used to apply an electric field and / or magnetic field to the electron beam to deflect the electron beam; The detector module is used to collect the signal electrons emitted by the sample when it is bombarded by the electron beam, and to convert the signal electrons into image signals; An imaging module, connected to the detector module, is used to generate an image of the sample surface based on the image signal; A scanning imaging control module, connected to the deflector and the detector module, is used to provide scanning signals to the deflector to generate the electric field and / or magnetic field. The scanning signals include scanning signals for imaging the sample surface and conditioning scanning signals for conditioning the charge accumulation level of the sample surface. The scanning signals include row scanning signals and frame scanning signals. One cycle of the row scanning signal includes a row imaging scanning period and a row conditioning scanning period. One cycle of the frame scanning signal includes a frame imaging scanning period. The duration of the frame imaging scanning period is greater than or equal to the duration of at least one row scanning signal. The row imaging scanning period and the frame imaging scanning period are used to achieve imaging scanning of the sample surface. The row conditioning scanning period is used to adjust the charge accumulation on the sample surface. The imaging control module provides a conditioning signal to the deflector. The waveform parameters of the conditioning scan signal are related to the charge accumulation on the sample surface. The waveform parameters include the amplitude, slope, and duration of the scan signal. The line scan signal includes a line imaging scan signal and a line conditioning scan signal. The line imaging scan signal and the line conditioning scan signal are sequentially connected, wherein the line conditioning scan signal is connected before and / or after the line imaging scan signal. The line imaging scan signal is output during the line imaging scan period, and the line conditioning scan signal is output during the line conditioning scan period. The frame scan signal includes a frame imaging scan signal and a frame conditioning scan signal. The frame imaging scan signal and the frame conditioning scan signal are sequentially connected, wherein the frame conditioning scan signal is connected before and / or after the frame imaging scan signal. The frame imaging scan signal is output during the frame imaging scan period. The scanning imaging control module, while providing the imaging scanning signal to the deflector, also sends a sampling trigger signal to the detector module to acquire the image signal.

2. The apparatus according to claim 1, characterized in that, The scanning imaging control module controls the electron optical tube parameters to change the parameters of the electron beam emitted by the electron optical tube during the conditioning scanning period, so as to adjust the accumulated charge level on the sample surface. The electron beam parameters include at least one of the electron beam spot size, the electron beam current, and the electron beam energy.

3. The apparatus according to claim 1, characterized in that, The line scan signal also includes: The line imaging scan preparation period, located before the line imaging scan period, is used to adjust the initial amplitude of the line imaging signal generated during the line imaging scan period; The line conditioning scan preparation period, located before the line conditioning scan period, is used to adjust the initial amplitude of the conditioning signal generated during the line conditioning scan period.

4. The apparatus according to claim 1, characterized in that, The frame scan signal also includes: The frame imaging scan preparation period, which is located before the frame imaging scan period, is used to adjust the initial amplitude of the frame imaging signal generated during the frame imaging scan period. The frame conditioning scan preparation period, which is located before the frame conditioning scan period, is used to adjust the initial amplitude of the conditioning signal generated during the frame conditioning scan period.

5. The apparatus according to claim 1, characterized in that, When the frame scan signal includes a frame conditioning scan signal, the line scan signal is externally equipped with an external line scan signal corresponding to the frame conditioning scan signal, and the duration of the frame conditioning scan signal is greater than or equal to the duration of at least one of the external line scan signals.

6. The apparatus according to claim 1, characterized in that, The scanning imaging control module is used to perform multiple repeated imaging scans on the same location on the sample surface to acquire multiple initial image signals, and to take the average value of the multiple initial image signals as the image signal; it is also used to perform multiple repeated conditioning scans on the sample surface to enhance or accelerate the charge adjustment of the sample surface.

7. The apparatus according to claim 1, characterized in that, The scanning imaging control module is used to adjust the waveform parameters of the conditioning scanning signal until the accumulated charge on the sample surface meets the imaging conditions when the accumulated charge on the sample surface does not meet the imaging conditions. The waveform parameters of the conditioning scanning signal include at least one of the duration of the conditioning scanning signal, the amplitude of the conditioning scanning signal, and the rate of change of the conditioning scanning signal.

8. The apparatus according to claim 1, characterized in that, The scanning imaging control module is also used to adjust the parameters of the conditioning control signal when the accumulated charge on the sample surface does not meet the imaging conditions, and apply it to the corresponding component of the electron optical tube to change the parameters of the electron beam until the accumulated charge on the sample surface meets the imaging conditions. The electron beam characteristic parameters that the conditioning control signal can control include electron beam energy, current, and beam spot size.

9. A scanning electron beam imaging method, characterized in that, The method is applied to the apparatus as described in any one of claims 1-8, the method comprising: An electron beam is emitted toward the sample surface and focused on the sample surface; A line scan signal and a frame scan signal are applied to the deflector to deflect the electron beam, wherein the scan signal includes a conditioning scan signal for adjusting the accumulated charge on the sample surface and an imaging scan signal for imaging the sample surface. During the line imaging scanning period, the signal electrons excited when the sample surface receives the electron beam are acquired to obtain the image signal; An image of the sample surface is generated based on the image signal.

10. The method according to claim 9, characterized in that, The row scan signal includes a row imaging scan period and a conditioning scan period in one cycle, and the frame scan signal includes a frame imaging scan period. The conditioning scan period is used to balance the accumulated charge on the sample surface. The row imaging scan period and the frame imaging scan period are used for scanning and imaging. The duration of the frame imaging scan period is greater than or equal to the duration of at least one row scan signal. The method further includes: adjusting the signal parameters of the conditioning scan signal so that the accumulated charge on the sample surface meets the imaging conditions.

11. The method according to claim 10, characterized in that, One period of the frame scanning signal includes a frame imaging scanning period and a frame conditioning scanning period. When the frame scanning signal includes the frame conditioning scanning period, the line scanning signal is externally equipped with an external line scanning period corresponding to the frame conditioning scanning period. The duration of the frame conditioning scanning period is greater than or equal to the duration of at least one of the external line scanning periods. The method further includes: adjusting the signal parameters of the conditioning scan signal during the frame conditioning scan period so that the accumulated charge on the sample surface meets the imaging conditions.

12. The method according to any one of claims 9-11, characterized in that, The method further includes: adjusting the parameters of the electron beam so that the accumulated charge on the sample surface meets the imaging conditions, wherein the parameters of the electron beam include at least one of the electron beam spot size, the electron beam current, and the electron beam energy.

13. The method according to claim 12, characterized in that, The method further includes: Determine the image quality of the sample; If the quality of the sample image meets the standard, then the sample image quality is deemed acceptable. If the quality of the sample image is substandard, then the number of image optimization iterations is obtained; If the number of image optimization iterations exceeds the maximum allowed number, the sample image quality is deemed unqualified. If the number of image optimization iterations does not exceed the maximum allowed number, change the waveform parameters of the row conditioning scan signal and the frame conditioning scan signal driving the deflector to adjust the charge accumulated on the sample surface; The parameters of the electron beam are adjusted to adjust the surface charge accumulation. The steps of adjusting the waveform parameters of the line scan signal and frame scan signal to adjust the charge accumulated on the sample surface, and adjusting the parameters of the electron beam to adjust the charge accumulated on the surface, are repeated until the sample image quality is qualified, or the number of times the above steps are repeated exceeds the maximum allowable number of times. The number of image optimization iterations is the number of times the above steps are repeated.

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