An imaging system

Abstract

The present invention discloses an imaging system. The imaging system includes: an imaging device, a host computer, and an external device; the imaging device includes a camera, an image acquisition card, and a battery, the camera is connected to the image acquisition card, and the battery is connected to the camera and the image acquisition card respectively; the image acquisition card includes an image processing unit, a wireless communication unit, and a synchronization unit, the wireless communication unit is connected to the image processing unit and the synchronization unit respectively, and the wireless communication unit is used to receive a synchronization instruction issued by the host computer and output it; the image processing unit is used to send the synchronization instruction to the camera; the synchronization unit is used to trigger the external device according to the synchronization instruction, so that the external device and the camera run synchronously. In the present invention, the cables in the imaging device will not be deformed during movement, avoiding the situation that the cable deformation disturbance interferes with imaging components such as the camera; the host computer transmits the synchronization instruction through the wireless communication unit, so that the external device and the camera run synchronously, which can improve the focus tracking speed and accuracy. Thereby improving the imaging accuracy.

Description

Technical Field

[0001] The present invention relates to the technical field of optical imaging, and in particular to an imaging system. Background Art

[0002] In the advanced integrated circuit chip manufacturing process, the optical overlay alignment of the critical layer directly affects the performance, yield and reliability of the device. Therefore, the overlay error (OL) is one of the most important indicators in the manufacturing process.

[0003] The image-based overlay (IBO) measurement device is the most commonly used overlay measurement system at present. The IBO device usually includes an optical imaging system, a precision stage, a material transfer system, etc. Among them, there are many cables in the optical imaging system. The cables will bend during actual use, and the bending will cause the cable disturbance to be transmitted to the imaging component, bringing interference to the imaging component and affecting the imaging accuracy. Summary of the Invention

[0004] The present invention provides an imaging system to improve the imaging accuracy.

[0005] The present invention provides an imaging system, including: an imaging device, a host computer and an external device;

[0006] The imaging device includes a camera, an image acquisition card and a battery. The camera is connected to the image acquisition card, and the battery is respectively connected to the camera and the image acquisition card;

[0007] The image acquisition card includes an image processing unit, a wireless communication unit and a synchronization unit. The wireless communication unit is respectively connected to the image processing unit and the synchronization unit, and the wireless communication unit is used to receive the synchronization instruction sent by the host computer and output it;

[0008] The image processing unit is used to send the synchronization instruction to the camera;

[0009] The synchronization unit is used to trigger the external device according to the synchronization instruction, so that the external device and the camera run synchronously.

[0010] In the present invention, the imaging device includes a battery, a camera, and an image acquisition card, which move as an integral structure. During the movement, the cables inside the imaging device will not deform, and there is no situation where the cables return to their original state after being bent. Therefore, there is no interaction between the cable ends and the connection components, avoiding the situation where cable deformation disturbances interfere with imaging components such as cameras. The image acquisition card of the imaging device includes a wireless communication unit and a synchronization unit. The wireless communication unit transmits synchronization instructions to the image processing unit and the synchronization unit to enable the external device and the camera to operate synchronously, which can improve the focus tracking speed and accuracy. Thus, the imaging accuracy is improved.

[0011] It should be understood that the content described in this part is not intended to identify the key or important features of the embodiments of the present invention, nor is it used to limit the scope of the present invention. Other features of the present invention will become easily understood through the following description. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following will briefly introduce the drawings required for the description of the embodiments. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0013] Figure 1 is a schematic diagram of an imaging system provided by an embodiment of the present invention;

[0014] Figure 2 is a schematic diagram of another imaging system provided by an embodiment of the present invention;

[0015] Figure 3 is a schematic diagram of yet another imaging system provided by an embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0016] In order to enable those skilled in the art to better understand the solution of the present invention, the following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0017] It should be noted that the terms "first", "second", etc. in the description, claims and above-mentioned drawings of the present invention are used to distinguish similar objects, and do not necessarily have to be used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged under appropriate circumstances, so that the embodiments of the present invention described here can be implemented in an order other than those illustrated or described here. In addition, the terms "comprising" and "having" and any variations thereof are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device comprising a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0018] Figure 1 is a schematic diagram of an imaging system provided by an embodiment of the present invention. As Figure 1 shown, the imaging system includes: an imaging device 10, a host computer 11 and an external device 12; the imaging device 10 includes a battery 13, a camera 14 and an image acquisition card 15, the camera 14 is connected to the image acquisition card 15, and the battery 13 is respectively connected to the camera 14 and the image acquisition card 15; the image acquisition card 15 includes an image processing unit 16, a wireless communication unit 17 and a synchronization unit 18, the wireless communication unit 17 is respectively connected to the image processing unit 16 and the synchronization unit 18, and the wireless communication unit 17 is used to receive a synchronization instruction sent by the host computer 11 and output it; the image processing unit 16 is used to send the synchronization instruction to the camera 14; the synchronization unit 18 is used to trigger the external device 12 according to the synchronization instruction, so that the external device 12 and the camera 14 run synchronously.

[0019] In this embodiment, the imaging system includes an imaging device 10, and the imaging device 10 can collect images and generate corresponding image signals. The imaging system includes a host computer 11, and the host computer 11 can be a device such as a computer or an industrial control computer capable of performing image data processing. The imaging system includes an external device 12, and the external device 12 can be a moving stage, and a sample to be measured is carried on the moving stage, and the imaging device 10 collects an image of the sample to be measured on the moving stage. Based on this, in the imaging system, the imaging device 10 is located above the external device 12, and the host computer 11 communicates with the imaging device 10.

[0020] The imaging device 10 is an integral structure enclosed by a housing. The imaging device 10 at least includes a battery 13, a camera 14, and an image acquisition card 15. The battery 13, the camera 14, and the image acquisition card 15 are housed in the inner cavity formed by the housing. At least one cable is also housed in the inner cavity of the housing of the imaging device 10, and the cable is used to connect at least two components in the imaging device 10. Since the imaging device 10 is an integral structure, when the imaging device 10 moves, the cables in its inner cavity will not deform, and there will be no situation where the cables are bent and then restored to their original state. Therefore, there will be no interaction between the cable ends and the connecting components, and thus no situation where the deformation disturbance of the cables interferes with the connecting components. In this embodiment, the imaging device 10 has integration and intelligence, with a simple structure and easy to implement. Optionally, in the imaging device 10, the camera 14 and the image acquisition card 15 are fixed on the same base plate; in other embodiments, it is also optional that both the camera and the image acquisition card are fixed on the inner wall of the housing of the imaging device.

[0021] The camera 14 is connected to the image acquisition card 15. Optionally, the camera 14 is connected to the image acquisition card 15 through a specific camera line, a camera link cable. Specifically, camera link interfaces are provided on both the camera 14 and the image acquisition card 15. The camera link interface of the camera 14 is connected to the camera link interface of the image acquisition card 15 through a cable, and this cable, the specific camera line, is a camera link cable that follows the camera link protocol. However, it is not limited to this. In other embodiments, it is also optional that the camera is connected to the image acquisition card through an Ethernet cable. Correspondingly, Ethernet interfaces are provided on both the camera and the image acquisition card, and the Ethernet interface of the camera is connected to the Ethernet interface of the image acquisition card through a cable. This embodiment is described by taking the camera 14 being connected to the image acquisition card 15 through a camera link cable as an example; those skilled in the art can understand that the connecting cables between the camera and the image acquisition card in other embodiments can be replaced with other types.

[0022] The camera 14 captures an image of the sample to be measured with the assistance of a light source, converts the optical signal into an electrical signal, converts the electrical signal into an image signal, and then transmits it to the image acquisition card 15 through a Camera link cable. The image acquisition card 15 stores the image signal and transmits it to the host computer 11. In other embodiments, it is also optional that the image acquisition card converts the electrical signal provided by the camera into an image signal. Specifically, the camera converts the optical signal into an electrical signal and then transmits the electrical signal to the image acquisition card through a Camera link cable. The image acquisition card converts the electrical signal into an image signal, stores it, and transmits it to the host computer. The image acquisition card 15 also receives the control signal or instruction from the host computer 11 and transmits it to the camera 14 through the Camera link cable. When the imaging device 10 moves, the Camera link cable connecting the camera 14 and the image acquisition card 15 does not deform. Therefore, the Camera link cable does not interfere with the camera 14 and the image acquisition card 15, improving the imaging accuracy. The camera 14 can be an industrial camera, but is not limited to this type. The image acquisition card 15 includes an FPGA chip. Integrating the image acquisition card 15 and the camera 14 can greatly improve the compatibility of the FPGA in the image acquisition card 15, and thus can handle industrial cameras with multiple current protocols, not limited to the Camera link protocol.

[0023] The battery 13 is respectively connected to the camera 14 and the image acquisition card 15. The battery 13 serves as a power supply and supplies power to the camera 14 and the image acquisition card 15 respectively to facilitate the normal operation of the imaging device 10. Optionally, a power supply line is connected between the battery 13 and the camera 14, and the battery 13 provides the corresponding electrical signal to the camera 14 through this power supply line; another power supply line is connected between the battery 13 and the image acquisition card 15, and the battery 13 provides the corresponding electrical signal to the image acquisition card 15 through this power supply line. In other embodiments, it is also optional that the battery supplies power to the camera and the image acquisition card respectively through the connection cable between the camera and the image acquisition card. The battery is connected to the Camera link cable, and the battery provides the corresponding electrical signal to the camera through the Camera link cable. At the same time, the battery also provides the corresponding electrical signal to the image acquisition card through the Camera link cable. The battery 13 can be a lithium battery, but is not limited to this type; the battery 13 can also include other functions and components, such as low-voltage monitoring, regular charging and maintenance, etc. In this embodiment, the battery 13 can be fixed on the camera 14.

[0024] The image acquisition card 15 includes an image processing unit 16, a wireless communication unit 17, and a synchronization unit 18. The wireless communication unit 17 is respectively connected to the image processing unit 16 and the synchronization unit 18. The image processing unit 16 includes an FPGA chip. Optionally, the wireless communication unit 17 includes a 5G communication chip; correspondingly, the host computer 11 includes a supporting 5G communication chip. The host computer 11 and the image acquisition card 15 communicate through two 5G communication chips. The communication bandwidth of the 5G communication chip is 10 Gbps, and the bandwidth of Camera link Base is 2 Gbps, which can significantly improve the bandwidth. In other embodiments, it is also optional that the wireless communication unit and the host computer respectively include other types of wireless communication units, such as ZigBee communication units, but not limited thereto. As Figure 1 shown, the dotted line between the imaging device 10 and the host computer 11 indicates that the two use wireless communication. Optionally, the dotted line between the imaging device 10 and the external device 12 indicates that the two can use wireless transmission.

[0025] Optionally, the image processing unit 16 is connected to the camera 14, and is used to send the image signal collected by the camera 14 to the host computer 11 through the wireless communication unit 17. Optionally, the image processing unit 16 is connected to the camera 14 through a specific camera line, camera link. The image processing unit 16 is used to send a synchronization instruction to the camera 14 through the specific camera line, camera link. Specifically, in the image acquisition card 15, the image processing unit 16 is connected to the camera 14 through a camera link cable. The wireless communication unit 17 communicates with the host computer 11 wirelessly. The synchronization unit 18 communicates with the external device 12 wirelessly. The wireless communication unit 17 is respectively connected to the image processing unit 16 and the synchronization unit 18. The image processing unit 16 obtains the image signal of the camera 14 through the camera link cable, and then transmits the image signal to the host computer 11 through the wireless communication unit 17. The host computer 11 analyzes and processes the image signal of the camera 14. The control signal of the host computer 11 is transmitted to the image processing unit 16 through the wireless communication unit 17. The image processing unit 16 transmits the control signal to the camera 14 through the camera link cable to drive the camera 14 to work. If synchronous control is required, the synchronization instruction of the host computer 11 is transmitted to the wireless communication unit 17; sequentially, after the wireless communication unit 17 analyzes the synchronization instruction, it transmits the analyzed synchronization instruction to the image processing unit 16 and the synchronization unit 18 respectively; sequentially, the image processing unit 16 sends the synchronization instruction to the camera 14 through the camera link cable, and the synchronization unit 18 triggers the external device 12 according to the synchronization instruction. Thus, under the control of the synchronization instruction, the external device 12 and the camera 14 can run synchronously, so that the operations of the camera 14 and the external device 12 can be synchronized.

[0026] If the signals between the host computer and the camera are wirelessly transmitted, and the signals between the host computer and the external device are wiredly transmitted, there may be a delay in the signal transmission between the host computer and the external device compared to the signal transmission between the host computer and the camera. This can cause the camera and the external device to operate out of sync, resulting in imaging failure of the imaging device. In this embodiment, the signals between the host computer 11 and the camera 14 are wirelessly transmitted, and the signals between the host computer 11 and the external device 12 are wirelessly transmitted. Then, there is no delay in the signal transmission between the host computer 11 and the external device 12 compared to the signal transmission between the host computer 11 and the camera 14. Thus, the camera 14 and the external device 12 can operate synchronously, thereby improving the imaging efficiency and accuracy of the imaging device.

[0027] As described above, the imaging system has an imaging function. The image signal and the control signal are transmitted between the imaging device 10 and the host computer 11 through the wireless communication unit 17, which can meet the current optical imaging application scenarios. In addition, the external device 12 can be a moving stage. Then, the imaging system has a focus tracking function. The host computer 11 transmits a synchronization instruction to the synchronization unit 18 and the image processing unit 16 through the wireless communication unit 17 to drive the external device 12 and the camera 14 to operate synchronously, which can meet the current focus tracking application scenarios. Among them, the wireless communication unit 17 analyzes the synchronization instruction and then transmits the analyzed synchronization instruction to the synchronization unit 18 and the image processing unit 16 respectively, so that there is no time delay between the external device 12 and the camera 14.

[0028] The optional imaging system includes a synchronization trigger mode and an image transmission mode; in the synchronization trigger mode, the host computer 11 and the wireless communication unit 17 perform unidirectional transmission; in the image transmission mode, the host computer 11 and the wireless communication unit 17 perform bidirectional transmission. Specifically, when the host computer 11 issues a synchronization instruction, the imaging system switches to the synchronization trigger mode. At this time, the wireless communication unit 17 can only receive the synchronization instruction from the host computer 11 and unidirectionally send it to the image processing unit 16 and the synchronization unit 18. The wireless communication unit 17 does not report signals to the host computer 11, realizing the unidirectional communication from the host computer 11 to the wireless communication unit 17. This synchronization hard trigger can ensure that the reliability of the trigger synchronization instruction is not interfered by other signals, guaranteeing the focus tracking speed and accuracy. When the imaging system switches to the image transmission mode, the wireless communication unit 17 can receive the control signal from the host computer 11 and send it to the image processing unit 16, and can also receive the image signal from the image processing unit 16 and send it to the host computer 11, realizing the bidirectional communication between the host computer 11 and the wireless communication unit 17.

[0029] In the present invention, the imaging device includes a battery, a camera, and an image acquisition card, and moves as an integrated structure. During the movement, the cables inside the imaging device will not deform, and there will be no situation where the cables are bent and then restored to the original state. Therefore, there will be no interaction between the cable ends and the connecting components, avoiding the situation where cable deformation disturbs imaging components such as the camera. The image acquisition card of the imaging device includes a wireless communication unit and a synchronization unit. The wireless communication unit transmits synchronization instructions to the image processing unit and the synchronization unit, so that the external device and the camera can operate synchronously, which can improve the focus tracking speed and accuracy. Thus, the imaging accuracy of the imaging system is improved.

[0030] Optionally, the synchronization unit includes a transmitting part, and the external device includes a receiving part; the transmitting part is used to transmit a first signal under the trigger of the synchronization instruction, and the receiving part is used to receive the first signal.

[0031] Figure 2 It is a schematic diagram of another imaging system provided by an embodiment of the present invention. As Figure 2 shown, in the imaging device 10, the synchronization unit 18 includes a transmitting part 19, and the external device 12 includes a receiving part 20. One synchronization unit 18 is correspondingly arranged with one external device 12.

[0032] After the wireless communication unit 17 receives the synchronization instruction sent by the host computer 11, the wireless communication unit 17 parses the synchronization instruction, and then sends the parsed synchronization instruction to the image processing unit 16 and the synchronization unit 18 respectively. Optionally, during this period, the wireless communication unit 17 can only receive the synchronization instruction from the host computer 11, ensuring that the synchronization instruction transmission process is not interfered by other signals and improving the synchronization precision control. It should be noted that the wireless communication unit 17 can send the synchronization instruction to the image processing unit 16 and the synchronization unit 18 simultaneously to ensure the synchronous operation of the camera 14 and the external device 12; or, the synchronization instruction carries clock information, and the wireless communication unit 17 can send the synchronization instruction to the image processing unit 16 and the synchronization unit 18 respectively, and the camera 14 and the external device 12 achieve synchronous operation according to the clock information.

[0033] The image processing unit 16 sends the received synchronization instruction to the camera 14 to drive the camera 14 to work.

[0034] After the synchronization unit 18 receives the synchronization instruction, it triggers the transmitting part 19 to transmit a first signal. It can be understood that if the synchronization unit 18 does not receive the synchronization instruction, the signal transmitted by the transmitting part 19 is different from the first signal, or the transmitting part 19 does not transmit any signal. The first signal can be a signal with a certain specific parameter, such as a specific waveform, specific light, specific frequency, specific voltage, or specific current, etc.

[0035] After the receiving unit 20 of the external device 12 receives the first signal, it can trigger the external device 12 to work. Here, the first signal is the trigger control signal of the external device 12. It can be understood that if the signal received by the receiving unit 20 is different from the first signal, or the receiving unit 20 does not receive any signal, the external device 12 will not be triggered to work.

[0036] Optionally, the transmitting unit 19 includes a light-emitting device that emits a first optical signal under the trigger of a synchronization instruction; the receiving unit 20 includes a photosensitive device that is used to detect whether there is an optical signal and convert the received first optical signal into an electrical signal. Optionally, the light-emitting device is a light-emitting diode; the photosensitive device is a photoelectric sensor.

[0037] In this embodiment, since the transmitting unit 19 includes a light-emitting device, the optical signal emitted by the light-emitting device is the first optical signal, and the first optical signal is the first signal. If the light-emitting device is a light-emitting diode, after the synchronization unit 18 receives the synchronization instruction, the synchronization instruction can control the light-emitting diode to conduct, and the conducting light-emitting diode emits light, and this optical signal is the first optical signal.

[0038] Since the receiving unit 20 includes a photosensitive device, the photosensitive device can receive the optical signal. When the photosensitive device detects that the received optical signal is the first optical signal, the photosensitive device can convert the received first optical signal into an electrical signal, and this electrical signal can trigger the external device 12 to work as a trigger control signal. Optionally, the photosensitive device is a photosensitive sensor. The transmitting unit 19 emits the first optical signal, and the receiving unit 20 receives the first optical signal, which can realize the wireless transmission between the synchronization unit 18 and the external device 12.

[0039] Optionally, the imaging system includes n external devices, where n is greater than 1; the image acquisition card in the imaging device includes n synchronization units, and one synchronization unit is correspondingly arranged with one external device. The synchronization unit is used to trigger the corresponding external device to operate according to the synchronization instruction, so that at least one external device and the camera operate synchronously. Optionally, the n external devices at least include a shutter and a moving stage.

[0040] Figure 3 is a schematic diagram of another imaging system provided by an embodiment of the present invention. As Figure 3As shown, the imaging system includes n external devices, respectively labeled as external device B1, external device B2, …, external device Bn. Correspondingly, the image acquisition card in the imaging device 10 includes n synchronization units, respectively labeled as synchronization unit A1, synchronization unit A2, …, synchronization unit An. One synchronization unit is correspondingly set with one external device, so synchronization unit A1 corresponds to external device B1, synchronization unit A2 corresponds to external device B2, …, synchronization unit An corresponds to external device Bn. It can be understood that the first signal sent by synchronization unit A1 can only be used to trigger the operation of external device B1, the first signal sent by synchronization unit A2 can only be used to trigger the operation of external device B2, and so on. The first signal sent by synchronization unit An can only be used to trigger the operation of external device Bn. Then, the host computer 11 can control the camera 14 and at least one external device to work synchronously according to the requirements of the scenario. Optionally, external device B1 is a moving stage, external device B2 is a shutter, but not limited thereto. The imaging system may also include other external devices. Then, those skilled in the art can reasonably design the synchronization unit and external devices according to the requirements of the product, without specific limitations. Thus, the synchronization of components such as the camera, the moving stage, and possibly the extended shutter is achieved.

[0041] Specifically, the host computer 11 performs wireless communication with the wireless communication unit 17 in the imaging device 10. The wireless communication unit 17 is connected to the camera 14 through the image processing unit 16, and the wireless communication unit 17 is also respectively connected to n synchronization units. It should be noted that the wireless communication unit 17 may include at least one synchronization interface. Then, the wireless communication unit 17 can output synchronization instructions to the image processing unit 16 and multiple synchronization units simultaneously through one synchronization interface, or the wireless communication unit 17 can output synchronization instructions to one component through one synchronization interface. Without specific limitations, those skilled in the art can reasonably design the number and connection method of the synchronization interfaces of the wireless communication unit according to the requirements of the product.

[0042] The imaging system provided by the embodiments of the present invention can be applied to various optical imaging scenarios, and is particularly suitable for the Image based Overlay (IBO) scenario. In the advanced integrated circuit chip manufacturing process, the optical overlay alignment of the critical layer directly affects the performance, yield, and reliability of the device. Therefore, the overlay (OL) is one of the most important indicators in the manufacturing process. This imaging system can be used as an IBO device and applied to the overlay measurement process. Most of the imaging devices in the imaging system are optical imaging devices, and the external devices are precision motion stages or material transfer systems, etc. The imaging system also includes a light source and a lighting module, as well as a focus tracking module (piezoelectric, objective lens, etc.). The light source and the lighting module provide the required light for the overlay error detection, and the focus tracking module mainly drives the objective lens assembly to move by the piezoelectric ceramic PZT (Piezoelectric Transducer) to find the best focal plane. The light source and the lighting module are fixed on the base, and the focus tracking module and the imaging device are hung on the moving Z-axis. The Z-axis drives these components to move up and down to adjust the focal length with the external device.

[0043] In this embodiment, the imaging device moves as a whole on the Z-axis, and the cables will not deform. Therefore, the internal cables of the imaging device will not interfere with the camera. In particular, the influence of the Cameralink cable between the camera and the image acquisition card on imaging is avoided, improving the imaging effect, and thus the overlay measurement accuracy can be improved. As a whole, the imaging device has a simple structure and no camera wiring requirements, which can reduce or eliminate the interference of internal cable disturbances on imaging.

[0044] The imaging system provided by the present invention can be used for overlay measurement, and the process is as follows:

[0045] 1) In the focal plane calibration scenario, to perform focal plane calibration, control the Coarse Z-axis for coarse scanning, close the shutter, and use the CMOS camera to take pictures. The industrial computer analyzes the image sharpness to obtain a better focal plane; then control the PZT-Z for fine scanning, synchronously trigger the camera to take pictures, and the image acquisition card sends the pictures to the 5G module of the industrial computer through the 5G antenna, and then the CPU transmitted through the PCIE bus analyzes the image sharpness to obtain the best focal plane, and calibrate this position as the best focal plane position of this batch of silicon wafers; then open the shutter, control the PZT-Z to perform fine scanning near the scanned focal plane and synchronously collect the PD signal, analyze the best position of the interference signal, and obtain the deviation between this position and the best focal plane as the System Focus Offset (SFO) of the system;

[0046] 2) Preparation stage: The silicon wafer is located at the calibrated focal plane position, the light intensity is set, and at this time, coarse focusing is performed. The measurement plane in the scene is within the range of coarse focusing. The shutter is opened, PZT-Z performs a coarse scan, synchronously collects the PD signal, feeds back the position of the measurement plane by analyzing the interference signal, and performs SFO compensation to obtain the focal plane position, and controls the movement of PZT-Z to the analyzed focal plane position to achieve coarse focusing;

[0047] 3) Mark acquisition: In the scene, the shutter needs to be closed, the silicon wafer carrier stage is controlled to perform XY-direction scanning, the CMOS camera is triggered synchronously to take pictures, the detection mark is moved to the set position at the center of the field of view, and then the carrier stage is controlled to rotate around Rz to straighten the mark to achieve mark acquisition;

[0048] 4) Fine focusing: In the scene, the mark is located at the center of the field of view. The shutter is opened. According to the result of coarse focusing, PZT-Z performs a fine scan, synchronously collects the PD signal, feeds back the position of the measurement plane by analyzing the interference signal, and performs SFO compensation to obtain the focal plane position, and controls the movement of PZT-Z to the analyzed optimal focal plane position to achieve fine focusing;

[0049] 5) Detection and photographing: In the scene, the shutter is closed. After the measurement plane is finely focused, the imaging system can achieve 100-fold microscopic imaging of the overlay image, providing images with high image quality and high signal-to-noise ratio for overlay error analysis. Among them, the illumination band is adjustable, the brightness is adjustable, and the NA is adjustable.

[0050] In the imaging process provided by the embodiment of the present invention, the camera is not affected by line disturbances, and the camera and the moving stage can move synchronously, which can improve the detection accuracy.

[0051] It should be understood that various forms of the processes shown above can be used, steps can be reordered, added or deleted. For example, the steps described in the present invention can be executed in parallel, sequentially, or in a different order, as long as the desired results of the technical solution of the present invention can be achieved. There is no limitation herein.

[0052] The above specific embodiments do not constitute a limitation to the protection scope of the present invention. Those skilled in the art should understand that various modifications, combinations, sub-combinations and substitutions can be made according to design requirements and other factors. Any modifications, equivalent substitutions and improvements made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. An imaging system, characterized in that, it includes: an imaging device, a host computer, and an external device; the imaging device includes a camera, an image acquisition card, and a battery, the camera is connected to the image acquisition card, and the battery is respectively connected to the camera and the image acquisition card; the image acquisition card includes an image processing unit, a wireless communication unit, and a synchronization unit, the wireless communication unit is respectively connected to the image processing unit and the synchronization unit, and the wireless communication unit is used to receive the synchronization instruction sent by the host computer, and after parsing the synchronization instruction, transmit the parsed synchronization instruction to the image processing unit and the synchronization unit respectively; the image processing unit is used to send the synchronization instruction to the camera; the synchronization unit is used to trigger the external device according to the synchronization instruction, so that the external device and the camera run synchronously, wherein the synchronization instruction carries clock information, and the camera and the external device realize synchronous operation according to the clock information in the synchronization instruction; the imaging device is an integral structure wrapped by a housing, and the imaging device moves as an integral structure, wherein the wireless communication unit communicates with the host computer wirelessly, and the synchronization unit communicates with the external device wirelessly; the external device includes a moving stage for carrying a sample to be measured; in the imaging system, the imaging device is located above the external device, and the imaging device is used to collect an image of the sample to be measured on the moving stage; the synchronization unit includes a transmitting part, and the external device includes a receiving part; the transmitting part is used to transmit a first signal under the trigger of the synchronization instruction, and the receiving part is used to receive the first signal; the transmitting part includes a light-emitting device, and the light-emitting device emits a first optical signal under the trigger of the synchronization instruction; the receiving part includes a photosensitive device, and the photosensitive device is used to detect whether there is an optical signal and convert the received first optical signal into an electrical signal.

2. The imaging system according to claim 1, characterized in that, the image processing unit is connected to the camera and is used to send the image signal collected by the camera to the host computer through the wireless communication unit.

3. The imaging system according to claim 1, characterized in that, the image processing unit is connected to the camera through a specific camera line camera link, and the image processing unit is used to send the synchronization instruction to the camera through the specific camera line.

4. The imaging system according to claim 1, characterized in that, the light-emitting device is a light-emitting diode; the photosensitive device is a photoelectric sensor.

5. The imaging system according to claim 1, characterized in that, the wireless communication unit includes a 5G communication chip.

6. The imaging system according to claim 1, characterized in that, the imaging system includes n external devices, where n is greater than 1; The image acquisition card in the imaging device includes n synchronization units. One synchronization unit is correspondingly set with one external device. The synchronization unit is used to trigger the corresponding external device to operate according to the synchronization instruction, so that at least one external device and the camera operate synchronously.

7. The imaging system according to claim 6, wherein, the n external devices at least include a shutter and a motion stage.

8. The imaging system according to claim 1, wherein, the imaging system includes a synchronous trigger mode and an image transmission mode; in the synchronous trigger mode, the host computer and the wireless communication unit perform unidirectional transmission; in the image transmission mode, the host computer and the wireless communication unit perform bidirectional transmission.

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