Control method for image acquisition in imaging system and wafer defect detection equipment

Abstract

The present invention relates to a control method for image acquisition in an imaging system and a wafer defect detection device. The control method for image acquisition in the imaging system comprises: calibrating the position deviation of a motion stage during motion using a standard test silicon wafer, wherein the standard test silicon wafer includes a plurality of symmetrically distributed marks, one of which is located at the center of the standard test silicon wafer; obtaining a nominal position signal of the motion stage using a grating ruler; calculating the actual position of the motion stage based on the nominal position signal and the position deviation; generating a trigger signal based on the actual position to trigger a TDI camera for image acquisition; and solving the problem of low synchronization accuracy between the speed of the motion stage and the line frequency of the TDI camera.

Description

Technical Field

[0001] The present invention relates to the field of control, and in particular to a control method for image acquisition in an imaging system, a wafer defect detection device and a camera triggering method thereof. Background Art

[0002] The chip manufacturing process involves hundreds of process steps such as oxidation, photolithography, etching, ion implantation, thin film deposition and polishing. Each process step may introduce deviations relative to the chip design layout. These deviations will cause defects in the IC chip through transmission and accumulation during the chip manufacturing process, such as protruding defects (the extreme case is bridging defects), recessed defects (the extreme case is broken wire defects) and isolated particle defects.

[0003] Patterned wafer defect inspection equipment is used to detect various defects in the manufacturing process of IC chips, such as Figure 1 The figure shows a schematic diagram of the structure of a prior art patterned wafer defect detection device. The TDI (Time Delay Integration) sensor is a novel photoelectric sensor that enables rapid imaging of high-speed moving patterned wafers and is a key component in image acquisition for patterned wafer defect detection equipment. The TDI sensor exposes the same target multiple times and utilizes delayed integration technology to significantly enhance the collection of reflected light, resulting in advantages such as high responsiveness and a wide dynamic range.

[0004] Combine Figure 1 Existing technical solutions generally use the grating scale encoder signal as an external trigger source, directly connecting it to the TDI camera. Photoelectric sensors are installed at the starting and ending points of the scan. Image acquisition begins after receiving the switching signal from the starting photoelectric sensor and ends after receiving the switching signal from the ending photoelectric sensor. During the scanning process, the TDI camera's line scan rate, or line frequency, must be strictly synchronized with the target's motion rate. Otherwise, the image will be blurred and the target's image information cannot be accurately extracted. Wafer defect inspection equipment uses a moving stage to move the wafer. Due to the random fluctuations in the moving stage's scanning speed, the TDI camera's line frequency and the wafer's motion rate do not match, affecting image quality and reducing defect detection accuracy. Moving stage scanning speed = object-side pixel size * TDI line frequency, where object-side pixel size = TDI camera pixel size / optical magnification. Due to the random fluctuations in the moving stage's scanning speed during the scanning process, the TDI line frequency must be adjusted accordingly in real time to conform to the above formula. Otherwise, the image will be blurred. Summary of the Invention

[0005] In view of the technical problems existing in the prior art, the present invention provides a synchronous control card, a wafer defect detection device and a TDI camera triggering method thereof, which solve the problem of low synchronization accuracy between the speed of the motion stage and the line frequency of the TDI camera.

[0006] According to a first aspect of the present invention, a method for controlling image acquisition in an imaging system is provided, comprising: calibrating a position deviation of a motion stage during motion using a standard test silicon wafer, wherein the standard test silicon wafer includes a plurality of symmetrically distributed marks, one of which is located at the center of the standard test silicon wafer;

[0007] Obtaining a nominal position signal of the motion stage through a grating ruler;

[0008] calculating the actual position of the motion stage based on the nominal position signal and the position deviation;

[0009] Based on the actual position, a trigger signal is generated to trigger the TDI camera to perform image acquisition.

[0010] On the basis of the above technical solution, the present invention can also make the following improvements.

[0011] Optionally, calibrating the position deviation of the motion stage during the motion process by using a standard test silicon wafer includes:

[0012] Loading the standard test silicon wafer, acquiring an image of each mark at the center of the TDI camera's field of view, and recording the corresponding position signal value of the motion stage;

[0013] Using the image of the mark located at the center of the standard test silicon wafer as a template, obtaining the position offset between each mark and the center of the field of view of the TDI camera based on an image template matching algorithm;

[0014] Obtaining a rotation residual of the standard test silicon wafer relative to the motion stage;

[0015] Calculating a first deviation of an actual position of any marking point relative to a theoretical position based on the position offset and the rotation residual;

[0016] Calculate the second deviation at any position between each two adjacent marking points by linear interpolation;

[0017] Based on the first deviation and the second deviation, position deviations of the motion platform at different positions during the motion process are obtained.

[0018] Optionally, a first deviation of the actual position of the arbitrary marking point relative to the theoretical position satisfies the following relationship:

[0019] ΔXsij=(Xsij-Xs00+ΔXij)+(d*i*cosRz+d*j*sinRz),

[0020] ΔYsij=(Ysij-Ys00+ΔYij)+(d*j*cosRz-d*i*sinRz),

[0021] The marking points are arranged at intervals of d along the X and Y directions in a plane rectangular coordinate system with the center of the standard test silicon wafer as the origin. i and j are the numbers of the marking points along the X and Y directions, respectively. The marking point at the center of the standard test silicon wafer is numbered (0,0), the first marking point to the right of the marking point (0,0) is numbered (1,0), the first marking point above the marking point (0,0) is numbered (0,1), and so on.

[0022] Rz is the rotation residual of the standard test silicon wafer relative to the motion stage;

[0023] Xs00 and Ys00 are the positions (Xs00, Ys00) of the motion stage when moving the marker point (0, 0) to the center of the field of view of the TDI camera;

[0024] Xsij, Ysij are the positions (Xsij, Ysij) of the motion stage when it moves to the theoretical position of the marker point (i, j), and ΔXij, ΔYij are the deviations between the marker point (i, j) and the center of the field of view of the TDI camera at this time.

[0025] Optionally, the motion platform performs reciprocating motion multiple times along a preset path, and corresponding starting and ending positions are set for each motion stroke along the same direction.

[0026] Optionally, generating a trigger signal based on the actual position to trigger the TDI camera to capture an image includes:

[0027] Calculating an average movement speed of the motion stage within a corresponding time interval based on the actual position of the motion stage and the running time of the motion stage;

[0028] The trigger signal matching the average motion speed of the motion stage and the optical magnification of the imaging system is generated to trigger the TDI camera to acquire images.

[0029] Optionally, generating a trigger signal based on the actual position to trigger the TDI camera to capture an image includes:

[0030] Based on the pixel size of the TDI camera, a number of trigger positions are set, and the distance between each two adjacent trigger positions = the pixel size of the TDI camera / the optical magnification of the imaging system;

[0031] When the actual position of the motion stage is at the trigger position, the trigger signal is generated to trigger the TDI camera to capture images.

[0032] Optionally, the average speed of the motion stage and the line frequency of the TDI camera capturing images satisfy the following relationship: average moving speed of the motion stage = (TDI camera pixel size / optical magnification)*TDI camera capturing image line frequency.

[0033] According to a second aspect of the present invention, a wafer defect detection device is provided, the device including an imaging system and a control module, the imaging system including a motion stage and a TDI camera, the control module using a control method for image acquisition in an imaging system provided in an embodiment of the present invention to control the imaging system to acquire images of the wafer, and perform defect analysis based on the acquired images.

[0034] Optionally, the wafer defect detection equipment further includes: a host computer;

[0035] After the motion platform completes the motion distance of any row, the number of the trigger signals sent is reported to the host computer.

[0036] Optionally, the actual position of the moving stage corresponding to the trigger start moment is sent to the host computer, and the host computer calculates the position of the defect on the wafer based on the actual position of the moving stage corresponding to the trigger start moment.

[0037] The present invention provides a control method for image acquisition in an imaging system and a wafer defect detection device. The method calibrates the scanning direction position error caused by the flatness and straightness of the moving axis and the surface shape of the grating scale mounting surface through a preset position deviation. The preset position deviation is obtained through experiments and has high accuracy. The present invention does not use a switch signal as a trigger acquisition signal. The sampling frequency of the switch signal is generally around 1kHz. Under the condition of a conventional scanning speed of 300mm / s for the moving stage, the maximum starting point error of the defect position calculation is 300μm. However, such equipment usually requires the reported defect position accuracy to be 3μm. Therefore, collecting the switch signal as a trigger acquisition signal cannot achieve the required accuracy. The number of trigger signals issued can be obtained and compared with the actual number of trigger rows of the camera to facilitate analysis of whether there is signal loss and to determine whether a row is lost. The photoelectric switch position in the prior art is fixed, and there is a serious waste of work time when used in circular wafer scanning scenarios. The present invention can independently set the starting point, end point and scanning direction of each row during multi-row scanning, which can meet the most efficient serpentine scanning path requirements. The independent setting of each row scan can reduce invalid tracks and improve equipment yield. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1A schematic diagram of the structure of a patterned wafer defect detection device in the prior art;

[0039] Figure 2 A schematic structural diagram of a standard test silicon wafer with multiple marking points provided by an embodiment of the present invention;

[0040] Figure 3 A schematic diagram of an embodiment of wafer scanning provided by the present invention;

[0041] Figure 4 A schematic structural diagram of an embodiment of a wafer defect detection device provided by an embodiment of the present invention;

[0042] Figure 5 A schematic diagram of the working principle of an embodiment of a synchronous control card in a wafer defect detection device provided by an embodiment of the present invention;

[0043] 1. TDI camera, 2. Imaging system, 3. Marble frame, 4. Wafer stage, 5. Start and end point sensors, 6. X-axis, 7. Y-axis, 8. Grating scale system, 9. Synchronous control card. DETAILED DESCRIPTION

[0044] The principles and features of the present invention are described below with reference to the accompanying drawings. The examples given are only used to explain the present invention and are not used to limit the scope of the present invention.

[0045] Example 1

[0046] Embodiment 1 provided by the present invention is an embodiment of a control method for image acquisition in an imaging system provided by the present invention. The embodiment of the control method for image acquisition in an imaging system includes:

[0047] The position deviation of the motion stage during the motion process is calibrated by a standard test silicon wafer, wherein the standard test silicon wafer includes a plurality of symmetrically distributed marks, and one of the marks is located at the center of the standard test silicon wafer.

[0048] The nominal position signal of the motion stage is obtained through the grating ruler.

[0049] Based on the nominal position signal and the position deviation, the actual position of the motion stage is calculated.

[0050] Based on the actual position, a trigger signal is generated to trigger the TDI camera to acquire images.

[0051] In practice, this position deviation is obtained through calibration using a standard test silicon wafer. The synchronous control card uses a pre-calibrated error table to correct the acquired encoder position to the actual position. This position deviation is caused by variations in the flatness and straightness of the moving axis, as well as the surface shape of the scale mounting surface. Within a small range, it can usually be approximated as a linear error. Calibration is performed using alignment marks spaced 1-5 mm apart on the standard test silicon wafer, with linear interpolation used to compensate between calibration points.

[0052] Specifically, in a possible embodiment, the process of calibrating the position deviation of the motion stage during motion using a standard test silicon wafer includes:

[0053] Load the standard test silicon wafer, acquire an image of each mark at the center of the TDI camera's field of view, and record the corresponding position signal value of the motion stage.

[0054] Using the image of the mark located at the center of the standard test silicon wafer as a template, the position offset between each mark and the center of the TDI camera's field of view is obtained based on the image template matching algorithm.

[0055] Obtain the rotation residual of the standard test silicon wafer relative to the motion stage.

[0056] Based on the position offset and the rotation residual, the first deviation of the actual position of any marker point relative to the theoretical position is calculated.

[0057] The second deviation at any position between each two adjacent marking points is calculated by linear interpolation.

[0058] Based on the first deviation and the second deviation, position deviations of the motion platform at different positions during the motion process are obtained.

[0059] Specifically, the theoretical position of the marking point is the position design value of each marking point in the standard test silicon wafer. In a possible embodiment, the first deviation of the actual position of any marking point relative to the theoretical position satisfies the following relationship:

[0060] ΔXsij=(Xsij-Xs00+ΔXij)+(d*i*cosRz+d*j*sinRz),

[0061] ΔYsij=(Ysij-Ys00+ΔYij)+(d*j*cosRz-d*i*sinRz),

[0062] The marking points are arranged at intervals of d along the X and Y directions in a plane rectangular coordinate system with the center of the standard test silicon wafer as the origin. i and j are the numbers of the marking points along the X and Y directions, respectively. The marking point at the center of the standard test silicon wafer is numbered (0,0), the first marking point to the right of the marking point (0,0) is numbered (1,0), the first marking point above the marking point (0,0) is numbered (0,1), and so on.

[0063] Rz is the rotation residual of the standard test silicon wafer relative to the motion stage.

[0064] Xs00 and Ys00 are the positions of the motion stage (Xs00, Ys00) when the moving marker point (0,0) is moved to the center of the TDI camera's field of view.

[0065] Xsij and Ysij are the positions (Xsij, Ysij) of the motion stage when it moves to the theoretical position of the marker point (i, j), and ΔXij and ΔYij are the deviations between the marker point (i, j) and the center of the TDI camera field of view at this time.

[0066] like Figure 2 The figure shows a schematic diagram of the structure of a standard test silicon wafer including multiple marking points provided by an embodiment of the present invention, combined with Figure 2 It can be seen that the marking points are densely spaced with equal spacing along the X and Y directions, with the center of the silicon wafer as the origin. Specifically, the spacing can be 2 mm.

[0067] In a specific implementation, the method for calculating the preset position deviation may be:

[0068] Step 1: Initialize the motion stage, turn on the autofocus system, and adjust the imaging system to the maximum magnification. The corresponding object-space pixel size should be less than 200nm, and the alignment algorithm accuracy should be 0.1 pixel.

[0069] Step 2: Load a standard test silicon wafer containing multiple markers and align it. The absolute value of the rotational residual Rz (clockwise is positive) of the silicon wafer relative to the motion stage must be less than 10urad.

[0070] Step 3: Move the mark point at the center of the standard test silicon wafer to the center of the camera field of view, take a picture as a template, and record the position of the motion stage at this time (Xs00, Ys00) (both in um).

[0071] Step 4: traverse all the marking points on the standard test silicon wafer, record the motion stage position (Xsij, Ysij) corresponding to the marking point ij (both in um), and calculate the deviation (ΔXij, ΔYij) (both in um) between the marking point ij and the center of the camera field of view based on the template matching algorithm.

[0072] Step 5: Calculate and record the first deviation of the actual position of any marking point ij relative to the theoretical position.

[0073] In this specific embodiment, the interval d between the marking points arranged in the standard test silicon wafer is 2000 μm. In this case, the calculation formula of the first deviation is:

[0074] ΔXsij=(Xsij-Xs00+ΔXij)+(2000*i*cosRz+2000*j*sinRz)

[0075] ΔYsij=(Ysij-Ys00+ΔYij)+(2000*j*cosRz-2000*i*sinRz)

[0076] Step 6: Calculate the second deviation at any position between each two adjacent marking points by linear interpolation.

[0077] like Figure 3 A schematic diagram of an embodiment of wafer scanning is shown, Figure 3 It can be seen that in a possible embodiment, the motion platform performs reciprocating motion multiple times along a preset path, and each motion stroke along the same direction is set with a corresponding starting point and end point.

[0078] In practice, the motion stage can perform multi-line or single-line motion. When performing multi-line motion scanning, the start, end, and scanning direction of each line can be independently set, meeting the requirements of the most efficient serpentine scanning path. Independent settings for each scanning line can reduce invalid trajectories and improve equipment productivity.

[0079] In one embodiment provided by the present invention, the line frequency of the TDI camera is adjusted in real time based on the actual position of the motion stage so that the product of the object-side pixel size and the line frequency of the TDI camera is consistent with the moving speed of the motion stage, thereby obtaining a clear dynamic target image, that is, satisfying the following relationship: moving speed of the motion stage = object-side pixel size * TDI line frequency, wherein the object-side pixel size = TDI camera pixel size / optical magnification. Based on the above relationship, the trigger frequency of the TDI camera imaging is obtained in real time, and the preset rules for sending the trigger signal can be speed synchronization mode and position trigger mode. In speed synchronization mode, the current speed of the motion stage is calculated and a trigger signal with a matching frequency is generated to the camera. In position trigger mode, the synchronization control card automatically generates a trigger position sequence according to the set object-side pixel size, and sends a trigger signal to the camera whenever the motion stage reaches a position in the sequence.

[0080] In specific implementation, Figure 5 As shown, the grating scale encoder includes: an X-axis encoder and a Y-axis encoder, which respectively obtain the position signals of the X-axis and the Y-axis.

[0081] The type and frequency of the grating scale encoder differ between speed synchronization mode and position trigger mode. Specifically, in speed synchronization mode, the encoder can acquire position signals at a frequency of 4kHz. The grating scale communicates with the synchronous control card via the BISS-C protocol at a communication frequency of 4kHz. In position trigger mode, the encoder can acquire position signals at a frequency of 10MHz. The motion stage grating scale directly transmits voltage analog signals to the synchronous control card at a communication frequency of 10MHz.

[0082] Specifically, in a possible embodiment, in the speed synchronization mode, the process of generating a trigger signal based on the actual position to trigger the TDI camera to perform image acquisition includes:

[0083] The average movement speed of the motion platform within a corresponding time interval is calculated based on the actual position of the motion platform and the running time of the motion platform.

[0084] A trigger signal matching the average motion speed of the motion stage and the optical magnification of the imaging system is generated to trigger the TDI camera for image acquisition.

[0085] In a specific implementation, the control process of the speed synchronization mode can be:

[0086] Before starting the scan, set the initial scanning direction, external trigger frequency, object space pixel size, and the start and end coordinates of each line.

[0087] During scanning detection, the moving stage first accelerates to the set speed along the initial scanning direction and maintains uniform motion, receiving the position signal of the grating encoder at a fixed frequency (for example, 4kHz). When the received position signal is between the starting point and the end point, the average speed of the moving stage every 50 to 200 signals is calculated, and an external trigger pulse with a frequency matching this speed is generated.

[0088] At the same time, the pre-calibrated position deviation is used to send the compensated motion stage starting position coordinates to the host computer to calculate the position of the defect on the wafer.

[0089] In another possible embodiment, in the position trigger mode, the process of generating a trigger signal based on the actual position to trigger the TDI camera to perform image acquisition includes:

[0090] Based on the pixel size of the TDI camera, set several trigger positions. The distance between each two adjacent trigger positions = the pixel size of the TDI camera / the optical magnification of the imaging system;

[0091] When the actual position of the motion stage is at the trigger position, a trigger signal is generated to trigger the TDI camera to acquire images.

[0092] In a specific implementation, the control process of the position trigger mode can be:

[0093] Before scanning begins, set the initial scanning direction, external trigger frequency, object-space pixel size, and the start and end coordinates of each line. Calculate the coordinates of each pulse trigger position (intervals equal to the object-space pixel size) based on the pre-calibrated position deviations.

[0094] During scanning detection, the motion stage first accelerates to the set speed along the initial scanning direction and maintains uniform motion, receives the encoder position signal at a fixed frequency (for example, 10MHz), and generates an external trigger pulse every time it passes a trigger position.

[0095] At the same time, the pre-calibrated position deviation is used to send the compensated motion stage starting position coordinates to calculate the position of the defect on the wafer.

[0096] Example 2

[0097] Example 2 provided by the present invention is an embodiment of a wafer defect detection device provided by the present invention. The embodiment of the wafer defect detection device includes: an imaging system and a control module. The imaging system includes a motion stage and a TDI camera. The control module adopts a control method for image acquisition in an imaging system provided by an embodiment of the present invention to control the imaging system to acquire images of the wafer, and perform defect analysis based on the acquired images.

[0098] It can be understood that the control method for image acquisition in an imaging system of a wafer defect detection device provided by the present invention corresponds to the control method for image acquisition in an imaging system provided by the aforementioned embodiments. The relevant technical features of a wafer defect detection device can refer to the relevant technical features of the control method for image acquisition in an imaging system, which will not be repeated here.

[0099] In a possible embodiment, the control module includes a host computer. After the motion platform completes a movement distance of any row, the number of trigger signals sent is reported to the host computer.

[0100] Figure 4 A schematic structural diagram of an embodiment of a wafer defect detection device provided by an embodiment of the present invention is provided. Figure 5 A schematic diagram of the working principle of an embodiment of a synchronous control card in a wafer defect detection device provided by an embodiment of the present invention, combined with Figure 4 and Figure 5 It can be seen that in an embodiment of a wafer defect detection device provided by the present invention, the hardware of the control module can be a host computer and a synchronous control card. Figure 5In the system, the X-axis and Y-axis drivers control the X-axis and Y-axis motors by reading the X-axis and Y-axis encoders to obtain rotor speed, rotor position, and mechanical position, respectively. The synchronous control card's scale encoder obtains position signals for the X-axis and Y-axis respectively by reading encoder signals from the X-axis and Y-axis encoders. The host computer communicates with the synchronous control card to calculate the actual position of the motion stage based on its nominal position signal and position deviation. This calculation generates trigger pulses to control the TDI camera for image acquisition.

[0101] Specific, combined Figure 2 - Figure 5 It can be seen that, in a possible embodiment, the process of the host computer controlling the synchronous control card to perform defect calculation can be:

[0102] After the motion platform completes the motion distance of any row, the synchronous control card 9 reports the number of trigger signals sent to the host computer.

[0103] After each line scan is completed, the synchronization control card 9 can report the total number of triggers that should be triggered and the total number of actual triggers to the host computer, so that the host computer can compare the number of lines actually triggered with the TDI camera to analyze whether there is signal loss.

[0104] At the same time, the pre-calibrated position deviation is used to send the compensated motion stage starting position coordinates to the host computer so that the host computer can calculate the position of the defect on the wafer.

[0105] The synchronous control card 9 sends the actual position of the starting point of the moving stage to the host computer based on the preset position deviation, and the host computer calculates the position of the defect on the wafer based on the actual position of the starting point of the moving stage.

[0106] An embodiment of the present invention provides a control method for image acquisition in an imaging system and a wafer defect detection device. The method calibrates the error between the actual position of the grating scale affected by the surface shape of the installation surface and the preset position deviation. The preset position deviation is obtained through experiments and has high accuracy. The present invention does not need to use a switch signal as a trigger acquisition signal. The sampling frequency of the switch signal is generally around 1kHz. When the motion stage scans at a speed of 100mm / s, the maximum starting point error of the defect position calculation is 0.1mm, and the defect position accuracy is 3μm. Therefore, there is no need to collect the switch signal as a trigger acquisition signal, which can further improve the synchronization accuracy. The number of trigger signals issued can be obtained and compared with the actual number of trigger rows of the camera to facilitate analysis of whether there is signal loss and to determine whether a row is lost. The photoelectric switch position in the prior art is fixed, and there is a serious waste of work time when used in a circular wafer scanning scenario. The present invention can independently set the starting point, end point and scanning direction of each row during multi-row scanning, which can meet the most efficient serpentine scanning path requirements. The independent setting of each row scan can reduce invalid trajectories and improve equipment yield.

[0107] It should be noted that, in the above embodiments, the description of each embodiment has its own focus. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant description of other embodiments.

[0108] It will be understood by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Thus, the present invention may take the form of an entirely hardware embodiment, an entirely software embodiment, or an embodiment combining software and hardware. Furthermore, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to magnetic disk storage, CD-ROM, optical storage, etc.) containing computer-usable program code.

[0109] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowcharts and / or block diagrams, as well as combinations of processes and / or blocks in the flowcharts and / or block diagrams, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded computer, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowcharts and / or block diagrams. Figure 1 a process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0110] These computer program instructions may also be stored in a computer readable memory that can direct a computer or other programmable data processing device to work in a specific manner, so that the instructions stored in the computer readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 a process or multiple processes and / or boxes Figure 1 The function specified in one or more boxes.

[0111] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operational steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing the instructions executed on the computer or other programmable device for implementing the process. Figure 1 a process or multiple processes and / or boxes Figure 1 The steps for the function specified in one or more boxes.

[0112] Although the preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0113] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A control method for image acquisition in an imaging system, wherein the imaging system comprises a motion stage and a TDI camera, characterized in that: include: Calibrate the position deviation of the motion stage at different positions during the motion process using a standard test silicon wafer, wherein the standard test silicon wafer includes a plurality of symmetrically distributed marks and one of the marks is located at the center of the standard test silicon wafer; Obtaining a nominal position signal of the motion stage through a grating ruler; calculating the actual position of the motion stage based on the nominal position signal and the position deviation; Based on the actual position, generating a trigger signal to trigger the TDI camera to perform image acquisition; The step of generating a trigger signal based on the actual position to trigger the TDI camera to perform image acquisition includes: Calculating an average movement speed of the motion stage within a corresponding time interval based on the actual position of the motion stage and the running time of the motion stage; generating the trigger signal that matches the average motion speed of the motion stage and the optical magnification of the imaging system to trigger the TDI camera to acquire images; or, Based on the pixel size of the TDI camera, several trigger positions are set, and the distance between each two adjacent trigger positions = the pixel size of the TDI camera / the optical magnification of the imaging system; when the actual position of the motion stage is at the trigger position, the trigger signal is generated to trigger the TDI camera to capture the image.

2. The control method according to claim 1, characterized in that: The method of calibrating the position deviation of the motion stage during the motion process by using a standard test silicon wafer includes: Loading the standard test silicon wafer, acquiring an image of each mark at the center of the TDI camera's field of view, and recording the corresponding position signal value of the motion stage; Using the image of the mark located at the center of the standard test silicon wafer as a template, obtaining the position offset between each mark and the center of the field of view of the TDI camera based on an image template matching algorithm; Obtaining a rotation residual of the standard test silicon wafer relative to the motion stage; Calculating a first deviation of an actual position of any marking point relative to a theoretical position based on the position offset and the rotation residual; Calculate the second deviation at any position between each two adjacent marking points by linear interpolation; Based on the first deviation and the second deviation, position deviations of the motion platform at different positions during the motion process are obtained.

3. The control method according to claim 2, characterized in that: The first deviation of the actual position of the arbitrary marking point relative to the theoretical position satisfies the following relationship: ΔXsij= (Xsij-Xs00+ΔXij)+(d*i*cosRz+d*j*sinRz), ΔYsij= (Ysij-Ys00+ΔYij)+(d*j*cosRz-d*i*sinRz), The marking points are arranged at intervals of d along the X and Y directions in a plane rectangular coordinate system with the center of the standard test silicon wafer as the origin, i and j are the numbers of the marking points along the X and Y directions, respectively. The marking point at the center of the standard test silicon wafer is numbered (0, 0), the first marking point to the right of the marking point (0, 0) is numbered (1, 0), the first marking point above the marking point (0, 0) is numbered (0, 1), and so on. Rz is the rotation residual of the standard test silicon wafer relative to the motion stage; Xs00 and Ys00 are the positions of the motion stage (Xs00, Ys00) when moving the marker point (0, 0) to the center of the field of view of the TDI camera; Xsij, Ysij are the positions (Xsij, Ysij) of the motion stage when it moves to the theoretical position of the marker point (i, j), and ΔXij, ΔYij are the deviations between the marker point (i, j) and the center of the field of view of the TDI camera at this time.

4. The control method according to claim 1, wherein: The motion platform performs reciprocating motion multiple times along a preset path, and each motion stroke along the same direction is provided with a corresponding starting point and an end point.

5. The control method according to claim 1, characterized in that: The average speed of the motion stage and the line frequency of the TDI camera collecting images satisfy the following relationship: average moving speed of the motion stage = (TDI camera pixel size / optical magnification)*TDI camera collecting image line frequency.

6. A wafer defect detection device, comprising an imaging system and a control module, wherein the imaging system comprises a motion stage and a TDI camera, characterized in that: The control module uses the control method for image acquisition in an imaging system according to any one of claims 1 to 5 to control the imaging system to acquire images of the wafer, and performs defect analysis based on the acquired images.

7. The wafer defect detection equipment according to claim 6, characterized in that: The control module includes: a host computer; After the motion platform completes the motion distance of any row, the number of the trigger signals sent is reported to the host computer.

8. The wafer defect detection equipment according to claim 7, characterized in that: The actual position of the motion stage corresponding to the trigger start time is sent to the host computer, and the host computer calculates the position of the defect on the wafer based on the actual position of the motion stage corresponding to the trigger start time.

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