Control circuit, control system and detection system of line scanning camera

Abstract

The utility model discloses a control circuit, a control system and a detection system of a line scanning camera, which are used for solving the problem of low line scanning efficiency when a fixed frame mode is used for linearly scanning a wafer. The control circuit comprises a position encoder and an image acquisition card; one end of the position encoder is connected with the image acquisition card; the other end of the image acquisition card is connected with the industrial computer.

Description

Technical Field

[0001] The utility model relates to the field of machine vision, in particular to a control circuit, a control system and a detection system of a line scan camera. Background Art

[0002] In machine vision, line scan cameras are the best solution for inspecting continuous or rolling objects. Typically, a line scan camera captures only one line as an image and sends it to a computer. The computer then stitches all the received images together to create a complete image of the object.

[0003] Existing wafer inspection techniques in the semiconductor industry use software to set a fixed frame, thereby controlling the wafer's motion speed to match the scanning speed of the line scan camera, thereby obtaining a complete image of the wafer. However, due to the varying lengths of wafer rows, this fixed frame approach often results in excessive blank space in the scanned image, leading to low line scan efficiency. Utility Model Content

[0004] The embodiments of the present invention provide a control circuit, a control system, and a detection system for a line scan camera to solve the problem of low line scan efficiency when linear scanning of a wafer is performed using a fixed frame method.

[0005] In a first aspect, the present invention provides a control circuit for a line scan camera, the control circuit comprising a position encoder and an image acquisition card;

[0006] One end of the position encoder is connected to the image acquisition card, and the other end is connected to the motion platform;

[0007] The other end of the image acquisition card is connected to an industrial computer.

[0008] In one possible design, the position encoder includes a frame grabber card, an encoder card, and an external trigger module;

[0009] One end of the external trigger module is connected to the encoder card, and the other end is connected to the frame grabber card;

[0010] The other end of the encoder card is connected to the motion platform;

[0011] The other end of the frame grabber card is connected to the image acquisition card.

[0012] In one possible design, the external trigger module includes: a level output unit;

[0013] One end of the level output unit is connected to the encoder card, and the other end is connected to the frame grabber card.

[0014] In one possible design, the motion platform includes a motion encoder and a transmitter;

[0015] One end of the mobile encoder is connected to the position encoder, and the other end is connected to the transmitter.

[0016] In one possible design, the control circuit further includes an independent power supply;

[0017] The negative terminal of the independent power supply is short-circuited with the image acquisition card;

[0018] The positive terminal of the independent power supply is connected to the resistor;

[0019] The other end of the resistor is connected to the image acquisition card.

[0020] In one possible design, the control circuit further includes an internal power supply;

[0021] The positive terminal of the internal power supply is connected to the position encoder.

[0022] In a second aspect, a control system for a line scan camera is provided, such as the control circuit and control mechanism described above;

[0023] The control mechanism includes a signal output device;

[0024] The signal output device is used to send the starting and ending coordinates of the motion platform to the control circuit to control the motion platform in the control circuit to reach the scanning position.

[0025] In one possible design, the control mechanism further includes a matching device;

[0026] The matching device is used to control the scanning speed of the image acquisition card that matches the motion platform with the control circuit.

[0027] In one possible design, the control mechanism further includes a setting device;

[0028] The setting device is used to set the high level of the external trigger module of the control circuit to a continuous high level signal to be output to the frame grabber card of the control circuit.

[0029] In a third aspect, an image defect detection system is provided, comprising the control system, splicing module, and detection module described above;

[0030] The splicing module splices the images output by the control system in sequence to obtain a spliced ​​image; and sends the spliced ​​image to the detection module.

[0031] The control circuit, control system, and detection system of the line scan camera described above include a control circuit comprising a position encoder and an image acquisition card; one end of the position encoder is connected to the image acquisition card, and the other end is connected to a motion platform; the other end of the image acquisition card is connected to an industrial computer. Because the position encoder can accurately identify the position of the wafer on the motion platform, the control circuit transmits the wafer's position to the image acquisition card in the line scan camera, allowing the image acquisition card to capture images based on the wafer's actual position. The captured image only captures the entire wafer, eliminating the large amount of blank space in images generated by existing technologies, effectively improving line scan efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative labor.

[0033] Figure 1 This is a schematic diagram of a control system for a line scan camera in one embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of a control circuit of a line scan camera in one embodiment of the present invention;

[0035] Figure 3 This is another schematic diagram of the control circuit of the line scan camera in one embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram of a trigger pulse signal of a position encoder in one embodiment of the present utility model;

[0037] Figure 5 This is a schematic diagram of a trigger pulse signal of a position encoder in one embodiment of the present utility model;

[0038] Figure 6 This is a schematic diagram of a trigger pulse signal of a position encoder in one embodiment of the present invention. DETAILED DESCRIPTION

[0039] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] It should be understood that the present invention can be implemented in various forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art. In the drawings, the dimensions and relative dimensions of layers and regions may be exaggerated for clarity. Like reference numerals denote like elements throughout.

[0041] It should be understood that when an element or layer is referred to as being "on," "adjacent to," "connected to," or "coupled to" another element or layer, it may be directly on, adjacent to, connected to, or coupled to the other element or layer, or there may be intervening elements or layers. Conversely, when an element is referred to as being "directly on," "directly adjacent to," "directly connected to," or "directly coupled to" another element or layer, there are no intervening elements or layers. It should be understood that although the terms first, second, third, etc. may be used to describe various elements, components, regions, layers, and / or parts, these elements, components, regions, layers, and / or parts should not be limited by these terms. These terms are merely used to distinguish one element, component, region, layer, or part from another element, component, region, layer, or part. Therefore, without departing from the teachings of the present invention, the first element, component, region, layer, or part discussed below may be represented as a second element, component, region, layer, or part.

[0042] Spatially relative terms such as "under," "beneath," "below," "under," "above," "above," etc., may be used herein for convenience of description to describe the relationship of one element or feature shown in the figures to other elements or features. It should be understood that the spatially relative terms are intended to include different orientations of the device in use and operation in addition to the orientations shown in the figures. For example, if the device in the drawings is flipped, then the elements or features described as "under" or "beneath" or "beneath" the other elements will be oriented as "over" the other elements or features. Thus, the exemplary terms "under" and "under" may include both the upper and lower orientations. The device may be oriented otherwise (rotated 90 degrees or in other orientations) and the spatial descriptors used herein are interpreted accordingly.

[0043] The purpose of the terms used herein is only to describe specific embodiments and is not intended to limit the present invention. When used herein, the singular forms "a", "an" and "the" are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "comprising" and / or "including", when used in this specification, determine the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0044] In order to fully understand the present invention, the following description will provide detailed structures and steps to illustrate the technical solutions proposed by the present invention. The preferred embodiments of the present invention are described in detail below. However, in addition to these detailed descriptions, the present invention may also have other implementation methods.

[0045] Line scan cameras are high-speed, high-precision, specialized industrial inspection cameras that capture real-time images of wafers continuously within their frame. The line scan camera's frame grabber sends the captured images to an industrial computer, which processes them and identifies defects in the wafers.

[0046] In existing wafer defect detection technologies, the first approach involves using an area scan camera to scan an area, but this method is inefficient. The second approach involves using a line scan camera in fixed-frame mode to capture and stitch images. However, due to the varying sizes of each wafer, this approach results in a significant amount of white space in the generated images, making line scan cameras inefficient and wasting a significant amount of storage space.

[0047] Furthermore, existing technologies often use a 24V high-level I / O (IO) + fixed frame rate method to control the frame grabber. This results in significant command errors, which can lead to excessive white space in the final captured image. This not only reduces the efficiency of the line scan camera but also wastes storage space. Furthermore, an I / O module is required, increasing the number of parts and assembly steps, leading to higher costs.

[0048] In one embodiment, if Figure 2 As shown, a control circuit for a line scan camera is provided, which includes a position encoder and an image acquisition card; one end of the position encoder is connected to the image acquisition card, and the other end is connected to a motion platform; the other end of the image acquisition card is connected to an industrial computer.

[0049] The position encoder is a PEG position encoder, while the line scan camera's frame grabber has a line trigger function. The PEG position encoder triggers the frame grabber, while the line scan camera's line trigger synchronizes the image motion on the sensor with the sensor's integration time.

[0050] This embodiment essentially replaces the IO module with a position encoder, effectively preventing various problems caused by the IO module.

[0051] It should be noted that since the position encoder can accurately identify the position of the wafer on the motion platform, the position of the wafer will be transmitted to the image acquisition card in the line scan camera through the control circuit, so that the image acquisition card can capture the image according to the actual position of the wafer. The captured image only exists in the entire wafer, and there will not be a large amount of blank space like the image generated by the existing technology, which effectively improves the line scan efficiency.

[0052] In one embodiment, if Figure 3 As shown, the position encoder includes a frame grabber card, an encoder card and an external trigger module; one end of the external trigger module is connected to the encoder card, and the other end is connected to the frame grabber card; the other end of the encoder card is connected to the motion platform; and the other end of the frame grabber card is connected to the image acquisition card.

[0053] Among them, the external trigger module is to receive the pulse signal of the encoder card, convert the signal into a high-level or low-level signal, and then control the image acquisition card to scan or stop scanning.

[0054] For example, setting External Trigger Detection to Active High triggers the image on a continuously high-level signal and stops capturing images when the signal drops to a low level.

[0055] In this embodiment, the External Trigger Level is preferably an input voltage (including but not limited to TTL, 12V, 24V), and 24V is preferably used in this embodiment.

[0056] It should be noted that if Figure 4 As shown in the figure, a pulse signal from the encoder card is the command for the line scan camera to capture a single line of image. When the encoder card pulses, its pulse frequency replaces the line frequency of the frame grabber, resulting in image capture based on the pulse frequency. Because the pulse frequency is based on the position encoder, the resulting image is based on the position of the wafer itself, resulting in an image that matches the wafer width. This effectively prevents excess white space in the image and improves the efficiency of the line scan camera.

[0057] In one embodiment, if Figure 5As shown, the position encoder triggers a pulse signal, which in turn triggers the line scan camera to capture a line. When encoder trigger mode is enabled, the encoder output pulse frequency replaces the line scan camera's internal acquisition frequency. Clicking "Grab" for continuous acquisition causes the X-axis to continuously reciprocate. During this time, carefully observe the direction of motion and the appropriate capture positions (start and end positions) before capturing images.

[0058] In one embodiment, the position encoder responds to a hard-trigger connection. In the prior art, issuing instructions is prone to communication delays, which in turn causes deviations in the scanned wafer image and makes it impossible to stitch. However, this embodiment uses a hard-trigger connection for response. The hard-trigger connection responds very quickly with almost no delay, so the final wafer image has almost no deviation, further improving the accuracy and efficiency of the line scan camera. In particular, compared to the prior art IO module, which is prone to delays and makes the final puzzle difficult, this embodiment uses a position encoder and hard-trigger connection, so the delay is negligible and will not cause puzzle errors.

[0059] In one embodiment, the external trigger module includes: a level output unit; one end of the level output unit is connected to the encoder card, and the other end is connected to the frame grabber card.

[0060] It should be noted that the level output unit is a unit that outputs a continuous high-level signal or a low-level signal. It is worth noting that the existing IO technology often fails to produce a continuous high-level signal, which often results in delayed triggering of the scan command, causing serious puzzle errors. The level output unit can output a continuous high-level signal when scanning is required. Compared to the existing method of using IO to control line scan cameras for scanning, the encoder card used in this embodiment has a smaller delay in triggering the scan, which does not cause errors in subsequent puzzles.

[0061] In one embodiment, if Figure 3 The motion platform shown includes a mobile encoder and a transmitter; one end of the mobile encoder is connected to the position encoder, and the other end is connected to the transmitter.

[0062] Among them, such as Figure 3 As shown in the figure, when the motion platform accelerates or decelerates, the encoder starts to generate pulse signals, but the line scan camera does not start capturing images at this time. Instead, it waits until the wafer moves to the starting position and the frame trigger receives a rising edge signal, at which point the line scan camera starts scanning.

[0063] It should be noted that the pixel width of each image requires a pulse signal from the position encoder. If too few pulses are supplied, the image will be missing, while too many pulses will cause the image to be stretched and distorted. Therefore, this embodiment connects the position encoder to the motion encoder to ensure a reasonable scanning line frequency and line height, ultimately capturing the wafers on the conveyor perfectly and further improving the efficiency of the line scan camera.

[0064] In one embodiment, the pulse of the position encoder is made to conform to the pixel width of an image by the following formula:

[0065]

[0066] This formula can be calculated by an industrial computer, and the results are sent to a control unit. The control unit then transmits the signal to the control circuit. This ensures that each image pixel corresponds to a pulse signal, effectively ensuring that the final image is complete and distortion-free, further improving the efficiency of line scan cameras.

[0067] In one embodiment, a 6-inch silicon wafer is placed on the motion platform. An industrial computer then controls the application of a 6-inch negative pressure to securely hold the wafer. When the wafer on the motion platform is positioned directly below the line scan camera, the light source is turned on, the Z-axis height is adjusted, and focus is performed. The industrial computer then calculates the line frequency and line height using the following formula. Based on these values, the motion platform's rotational speed is then calculated, ensuring the motion platform accurately matches the line scan camera's scanning speed.

[0068] Where row height is the height of the image, and the formula for calculating row frequency is:

[0069]

[0070] It should be noted that this embodiment describes the important role of the industrial computer in the entire scanning process. Its calculation of line height and line frequency enables the pulses to accurately correspond to the pixels of the image, preventing the loss or deformation of image information due to too many or too few pulses, thereby effectively improving the efficiency of the line scan camera.

[0071] In one embodiment, the control circuit further includes an independent power supply; the negative terminal of the independent power supply is short-circuited with the image acquisition card; the positive terminal of the independent power supply is connected to a resistor; and the other end of the resistor is connected to the image acquisition card.

[0072] The resistor is a 2K resistor, with a V / R ratio of 1, ensuring a current of 5mA. Due to the short circuit of the independent power supply, the two lines connected to the image acquisition card are used as independent twisted pairs and shielded cables to ensure that all high-power power is intercepted to the ground grid.

[0073] It should be noted that the independent power supply here actually enables the image acquisition card to better scan according to the acquired pulse signal, further ensuring that each pulse signal can be responded to in a timely manner, thereby further improving the efficiency of the line scan camera.

[0074] In one embodiment, the control circuit further includes an internal power supply; a positive terminal of the internal power supply is connected to the position encoder.

[0075] The position encoder is powered by the positive electrode. The internal power supply is not connected to any external circuit and directly supplies power to the position encoder.

[0076] It should be noted that the reason why a separate internal power supply is required here, which is directly powered by the positive pole, can further ensure that the pulses given by the position encoder are accurate and reasonable, thereby ensuring the accurate shooting of the wafer by the line scan camera in the subsequent steps, thereby further improving the efficiency of the line scan camera.

[0077] In one embodiment, the utility model provides a control system for a line scan camera, comprising a control circuit and a control mechanism as described in the above embodiment; the control mechanism includes a signal output device; the signal output device is used to send the start and end coordinates of the motion platform to the control circuit to control the motion platform in the control circuit to reach a scanning position.

[0078] The starting and ending coordinates include the starting point coordinates and the ending point coordinates.

[0079] It should be noted that this embodiment is different from the prior art. Figure 6 As shown, X0-X1 is the interval for the line scan camera to be triggered to take pictures, and P0-P1 is the actual movement interval of the motion platform. That is, the existing technology requires real-time polling of the coordinate position of the wafer, which results in the instruction triggering the scanning position and then issuing an IO high-level instruction for picture acquisition, which will cause a delay in the IO high-level triggering, which will cause a communication delay error, and the actual scanned position will be different from the instruction issued by reading the coordinates. However, this embodiment Figure 5 What is shown is only the acquisition of the start and end coordinates, which are used to correspond to the start and completion of image acquisition, and then the image acquisition is controlled by high-level voltage and low-level voltage. The delay is small and the final image is more accurate.

[0080] In one embodiment, the motion platform moves the wafer edge below the line scan camera, allowing the camera to scan the edge. A 5mm margin is added to the coordinates of this edge to record the movement, and this point serves as the starting coordinate to trigger the image capture. The same applies to the end coordinates. This allows the line scan camera to accurately capture the starting and ending positions, ensuring that the final image is free of excessive white space and information loss, thereby improving the efficiency of the line scan camera.

[0081] In one embodiment, the control mechanism further includes a matching device; the matching device is used to control the scanning speed of the image acquisition card that matches the motion platform with the control circuit.

[0082] It should be noted that the movement speed of the wafer is controlled to match the scanning speed of the image acquisition card in order to obtain a clearer wafer image and improve the efficiency of the line scan camera.

[0083] In one embodiment, the control mechanism further includes a setting device; the setting device is used to set the high level of the external trigger module of the control circuit to a continuous high level signal to be output to the frame grabber card of the control circuit.

[0084] It should be noted that this embodiment uses the position encoder to continuously output high-level signals, ensuring that the signals received by the image acquisition card are not only accurate but also have low delay, making the final wafer image more accurate and effectively improving the efficiency of the line scan camera.

[0085] like Figure 1 As shown, the line scan camera of the present invention is suspended above the motion platform, and the control system calculates the line scan frequency according to the axis motion speed of the motion platform. Then, the motion platform is controlled to reach the preset scanning starting point, and the line scan camera is controlled to scan the wafer at the preset frequency. Next, the line scan frequency is set and the line scan light source is turned on. The movement speed of the wafer is then controlled to match the scanning speed of the line scan camera, thereby forming a complete and clear wafer image. Finally, the surface image of the wafer is collected, and the surface defects are identified, thereby completing the wafer inspection. Compared with the prior art, the triggering method between the line scan device structures of the present invention is PEG position triggering (single-ended continuous high level). This makes scanning debugging simpler, more flexible, faster, and less expensive. At the same time, it not only widens the scanning format, but also greatly improves the accuracy and efficiency of the line scan camera.

[0086] In one embodiment, a system for detecting image defects is provided, comprising a control system, a stitching module, and a detection module as described in the above embodiment; the stitching module stitches images output by the control system in sequence to obtain a stitched image; and sends the stitched image to the detection module.

[0087] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. These modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention, and should all be included in the scope of protection of the present invention.

Claims

1. A control circuit for a line scan camera, characterized in that: The control circuit includes a position encoder and an image acquisition card; One end of the position encoder is connected to the image acquisition card, and the other end is connected to the motion platform; The other end of the image acquisition card is connected to an industrial computer.

2. The control circuit according to claim 1, wherein: The position encoder includes a frame grabber card, an encoder card and an external trigger module; One end of the external trigger module is connected to the encoder card, and the other end is connected to the frame grabber card; The other end of the encoder card is connected to the motion platform; The other end of the frame grabber card is connected to the image acquisition card.

3. The control circuit according to claim 2, wherein: The external trigger module includes: a level output unit; One end of the level output unit is connected to the encoder card, and the other end is connected to the frame grabber card.

4. The control circuit according to claim 1, wherein: The motion platform includes a mobile encoder and a transmitter; One end of the mobile encoder is connected to the position encoder, and the other end is connected to the transmitter.

5. The control circuit according to claim 1, wherein: The control circuit also includes an independent power supply; The negative terminal of the independent power supply is short-circuited with the image acquisition card; The positive terminal of the independent power supply is connected to the resistor; The other end of the resistor is connected to the image acquisition card.

6. The control circuit according to claim 1, wherein: The control circuit also includes an internal power supply; The positive terminal of the internal power supply is connected to the position encoder.

7. A control system for a line scan camera, characterized in that: The control circuit and control mechanism according to claim 1; The control mechanism includes a signal output device; The signal output device is used to send the starting and ending coordinates of the motion platform to the control circuit to control the motion platform in the control circuit to reach the scanning position.

8. The control system according to claim 7, wherein: The control mechanism further includes a matching device; The matching device is used to control the scanning speed of the image acquisition card that matches the motion platform with the control circuit.

9. The control system according to claim 7, wherein: The control mechanism further includes a setting device; The setting device is used to set the high level of the external trigger module of the control circuit to a continuous high level signal to be output to the frame grabber card of the control circuit.

10. A system for detecting image defects, characterized in that: comprising the control system, splicing module and detection module as claimed in claim 7; The splicing module splices the images output by the control system in sequence to obtain a spliced ​​image; and sends the spliced ​​image to the detection module.

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