A dual-station pre-alignment system for edge-cut wafers

Abstract

This invention discloses a dual-station pre-alignment system suitable for edge-cutting wafers, relating to the field of semiconductor manufacturing technology. It includes a pre-alignment base plate and two structurally symmetrical and completely independent pre-alignment stations arranged side-by-side on the base plate. Each pre-alignment station integrates a wafer handling robot, a load-bearing rotation unit, dual vision sensing units, an active lifting mechanism, and a distributed control module. This invention revolutionizes the traditional "serial pipeline" into a "parallel pipeline," allowing the most time-consuming vision-based precision alignment process to completely overlap with the robot's loading and unloading process on the time axis. This significantly reduces the average processing time of a single wafer, making the overall cycle time of the pre-alignment stage depend only on the processing speed of the slower of the two parallel stations, thereby achieving an almost linear increase in production capacity. This eliminates the pre-alignment stage from being a bottleneck in overall system capacity, enabling it to match or even exceed the pace of high-speed exposure light sources, maximizing equipment utilization.

Description

Technical Field

[0001] This invention relates to the field of semiconductor manufacturing technology, and more specifically to a dual-station pre-alignment system suitable for edge-cut wafers. Background Technology

[0002] In semiconductor lithography equipment, the production efficiency of the pre-alignment process is one of the key factors determining the overall machine capacity. Currently, the widely used single-station pre-alignment system suffers from fundamental and insurmountable shortcomings in production efficiency, becoming a bottleneck restricting the overall performance improvement of the exposure machine. Its specific drawbacks are as follows:

[0003] Existing single-station pre-alignment systems consist of only one processing station and one set of actuators. A series of operations, including wafer loading, positioning, alignment, and unloading, must be performed sequentially and strictly in this single station. This means that during the entire pre-alignment cycle, the system can only perform one operation at any given time: when the robot is loading or unloading, the alignment sensor and rotating mechanism are idle; and when the vision system is performing fine alignment, the robot must wait for it to complete before performing the next pick-and-place operation.

[0004] This "load-align-unload" single-station system results in a significant amount of unproductive idle time being embedded in the processing cycle of each wafer, thus limiting the theoretical processing capacity of the single-station system. As the speed of the exposure light source in lithography machines continues to increase, this low-speed serial pre-alignment mode can no longer keep up. Ultimately, this forces core components for high-speed exposure to frequently wait for wafers, leading to decreased equipment utilization and overall capacity loss. Therefore, developing a novel pre-alignment structure that can overcome the bottleneck of serial processing and achieve parallel operation is crucial for unlocking the full capacity potential of exposure equipment.

[0005] In response, this application proposes a dual-station pre-alignment system suitable for edge-trimmed wafers to solve the above-mentioned problems. Summary of the Invention

[0006] The purpose of this invention is to provide a dual-station pre-alignment system suitable for edge-trimmed wafers, so as to solve the inherent defects in production efficiency of the existing single-station pre-alignment system.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] A dual-station pre-alignment system for edge-cutting wafers, comprising:

[0009] A pre-alignment base plate, and two structurally symmetrical and completely independent pre-alignment stations arranged side by side on the pre-alignment base plate. Each pre-alignment station integrates a wafer handling robot, a load-bearing rotation unit, a dual vision sensing unit, and an active lifting mechanism.

[0010] The distributed control module includes a central scheduling layer and two station control layers corresponding to the pre-alignment stations. The station control layers are electrically connected to the functional units of the corresponding stations. The central scheduling layer is used to coordinate the two pre-alignment stations to synchronously execute the wafer processing flow and schedule the exposure light source unit. It is used to complete the wafer pose detection and alignment operations in parallel through the two pre-alignment stations, and cooperate with the central scheduling layer to realize parallel alignment-alternating exposure to eliminate process waiting time.

[0011] Furthermore, a vertical wall and two lower pads are fixedly installed on the top of the pre-aligned base plate;

[0012] The bottom plate is vertically fixedly mounted with a guide rail base plate and multiple upright plates. The top of the multiple upright plates is jointly mounted with an upper cover plate II. The top of the upper cover plate II has a through hole, and a funnel is fixedly mounted on the inner wall of the through hole.

[0013] A support plate is fixedly installed on the top of the wall.

[0014] Furthermore, the dual-vision sensing unit includes an edge camera, a center camera, a camera connection plate, a coordinate measuring machine, and an upper cover plate.

[0015] The coordinate measuring machine is fixed to the top of the support plate, and the edge camera and the center camera are mounted on the coordinate measuring machine through the camera connecting plate, with the edge camera located outside the center camera;

[0016] The central camera is set vertically downwards and is used to photograph the stationary wafer to determine the coordinates of the center.

[0017] The edge camera is used to continuously capture edge images during wafer rotation and identify the cutting edge orientation.

[0018] The top cover is secured to the edge of the support plate with a snap fastener.

[0019] Furthermore, the active lifting mechanism includes a stepper motor, a guide rail base plate, a drive pulley, a synchronous belt, a ball screw, a driven pulley, a guide rail mounting plate, and a guide rail slider pair;

[0020] The stepper motor is fixedly installed on the top of the lower pad, and the output shaft of the stepper motor passes through the inner wall of the lower pad and the pre-aligned base plate and is fixedly installed with a drive pulley.

[0021] The guide rail mounting plate is fixedly installed on the top of the lower pad, and a guide rail base plate is fixedly installed on the guide rail mounting plate. The guide rail slider pair is slidably connected to the guide rail base plate.

[0022] The bottom end of the ball screw passes through the lower pad and extends to the bottom of the lower pad. The ball screw is rotatably sleeved with the lower pad. The nut of the ball screw is fixedly connected to the guide rail slider pair. The driven pulley is fixedly connected to the bottom end of the ball screw. The synchronous belt is sleeved between the driven pulley and the driving pulley. The stepper motor drives the ball screw to move linearly, which is used to drive the chuck to perform high-precision rotational scanning to complete the wafer coarse alignment.

[0023] Furthermore, a sensor is fixedly installed on the guide rail base plate, and a sensor baffle is fixedly installed on the guide rail slider pair. The sensor cooperates with the sensor baffle to detect the lifting position of the suction cup. A switch base is installed on the top of the lower pad plate to control the power supply of the sensor.

[0024] Furthermore, the bearing rotation unit includes a suction cup, a stepper motor, and a motor bracket;

[0025] The motor bracket is fixed to one end of the guide rail slider pair, the second stepper motor is fixedly mounted on the motor bracket, and a suction cup is fixedly mounted on the output shaft of the second stepper motor, with a wafer adsorbed on the top of the suction cup.

[0026] Furthermore, the workstation control layer includes a programmable logic controller (PLC) and an independent vision processing computer; the vision processing computer is electrically connected to the edge camera and the center camera, and is used to run vision processing algorithms, perform circle center positioning calculations and edge recognition operations, and output pose compensation data;

[0027] The PLC is connected to the vision processing computer, stepper motor one, stepper motor two, suction cup, and wafer handling robot arm, and is used to receive pose compensation data and control the timing of the actions of each actuator.

[0028] Compared with existing technologies, this invention provides a dual-station pre-alignment system suitable for edge-cutting wafers. This system innovates the traditional "serial pipeline" into a "parallel pipeline," allowing the most time-consuming visual precision alignment process and the robotic loading / unloading process to completely overlap on the time axis. This significantly reduces the average processing time of a single wafer, making the overall cycle time of the pre-alignment stage depend only on the processing speed of the slower of the two parallel stations, rather than the sum of the two, thus achieving a near-linear increase in production capacity. This eliminates the pre-alignment stage from being a bottleneck in overall machine capacity, enabling it to match or even exceed the pace of high-speed exposure light sources, maximizing equipment utilization, and providing key technological support for a leap in the production capacity of high-end lithography machines. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0030] Figure 1 This is a perspective view of the present invention;

[0031] Figure 2 This is the left side view of the present invention;

[0032] Figure 3 This is the front view of the present invention;

[0033] Figure 4 This is the pre-aligned left view of the present invention;

[0034] Figure 5 This is a pre-aligned rear view of the present invention.

[0035] Explanation of reference numerals in the attached figures:

[0036] 1. Edge camera; 2. Center camera; 3. Camera connection plate; 4. Coordinate measuring machine; 5. Support plate; 6. Top cover plate one; 7. Wafer; 8. Funnel; 9. Top cover plate two; 10. Vertical plate; 11. Pre-alignment base plate; 12. Stepper motor one; 13. Lower pad plate; 14. Switch base; 15. Guide rail base plate; 16. Suction cup; 17. Drive pulley; 18. Synchronous belt; 19. Ball screw; 20. Sensor; 21. Driven pulley; 22. Guide rail mounting plate; 23. Sensor baffle; 24. Stepper motor two; 25. Motor bracket; 26. Vertical wall; 27. Guide rail slider pair. Detailed Implementation

[0037] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0038] As attached Figure 1 To be continued Figure 5 As shown:

[0039] Example 1:

[0040] A dual-station pre-alignment system for edge-cutting wafers, comprising:

[0041] The pre-alignment base plate 11 and two structurally symmetrical and completely independent pre-alignment stations arranged side by side on the pre-alignment base plate 11, each of the pre-alignment stations integrating a wafer handling robot, a load-bearing rotation unit, a dual vision sensing unit, and an active lifting mechanism;

[0042] The distributed control module includes a central scheduling layer and two station control layers corresponding to the pre-alignment stations. The station control layers are electrically connected to the functional units of the corresponding stations. The central scheduling layer is used to coordinate the two pre-alignment stations to synchronously execute the wafer processing flow and schedule the exposure light source unit. It is used to complete the wafer pose detection and alignment operations in parallel through the two pre-alignment stations, and cooperate with the central scheduling layer to realize parallel alignment-alternating exposure to eliminate process waiting time.

[0043] Specifically, the top of the pre-aligned base plate 11 is fixedly installed with a vertical wall 26 and two lower pads 13;

[0044] The bottom plate 13 is vertically fixedly mounted with a guide rail base plate 15 and multiple upright plates 10. The top of the multiple upright plates 10 is jointly mounted with an upper cover plate 2 9. The top of the upper cover plate 2 9 is provided with a through hole, and a funnel 8 is fixedly mounted on the inner wall of the through hole.

[0045] A support plate 5 is fixedly installed on the top of the vertical wall 26.

[0046] Specifically, the dual vision sensing unit includes an edge camera 1, a center camera 2, a camera connection plate 3, a coordinate measuring machine 4, and an upper cover plate 6;

[0047] The coordinate measuring machine 4 is fixed to the top of the support plate 5. The edge camera 1 and the center camera 2 are mounted on the coordinate measuring machine 4 through the camera connecting plate 3. The edge camera 1 is located outside the center camera 2.

[0048] The central camera 2 is set vertically downwards and is used to photograph the stationary wafer 7 to determine the center coordinates.

[0049] The edge camera 1 is used to continuously capture edge images during the rotation of the wafer 7 and identify the cutting edge orientation;

[0050] The top cover plate is secured to the edge of the support plate 5 with a snap fastener 6.

[0051] Specifically, the active lifting mechanism includes a stepper motor 12, a guide rail base plate 15, an active pulley 17, a synchronous belt 18, a ball screw 19, a driven pulley 21, a guide rail mounting plate 22, and a guide rail slider pair 27.

[0052] The stepper motor 12 is fixedly installed on the top of the lower pad 13, and the output shaft of the stepper motor 12 passes through the inner wall of the lower pad 13 and the pre-aligned base plate 11 and is fixedly installed with a drive pulley 17.

[0053] The guide rail mounting plate 22 is fixedly installed on the top of the lower pad plate 13. The guide rail base plate 15 is fixedly installed on the guide rail mounting plate 22. The guide rail slider pair 27 is slidably connected to the guide rail base plate 15.

[0054] The bottom end of the ball screw 19 passes through the lower pad 13 and extends to the bottom of the lower pad 13. The ball screw 19 is rotatably sleeved with the lower pad 13. The nut of the ball screw 19 is fixedly connected to the guide rail slider pair 27. The driven pulley 21 is fixedly connected to the bottom end of the ball screw 19. The synchronous belt 18 is sleeved between the driven pulley 21 and the driving pulley 17.

[0055] Specifically, a sensor 20 is fixedly installed on the guide rail base plate 15, and a sensor baffle 23 is fixedly installed on the guide rail slider pair 27. The sensor 20 and the sensor baffle 23 cooperate to detect the lifting position of the suction cup 16. A switch base 14 is installed on the top of the lower pad plate 13 to control the power supply of the sensor 20.

[0056] Specifically, the bearing rotation unit includes a suction cup 16, a stepper motor 24, and a motor bracket 25;

[0057] The motor bracket 25 is fixed to one end of the guide rail slider pair 27, the second stepper motor 24 is fixedly installed on the motor bracket 25, and the output shaft of the second stepper motor 24 is fixedly installed with a suction cup 16, and the top of the suction cup 16 is adsorbed with a wafer 7.

[0058] Specifically, the workstation control layer includes a programmable logic controller (PLC) and a separate vision processing computer;

[0059] The vision processing computer is electrically connected to the edge camera 1 and the center camera 2, and is used to run vision processing algorithms, perform circle center positioning calculation, edge recognition calculation, and output pose compensation data.

[0060] The PLC is connected to the vision processing computer, stepper motor 12, stepper motor 24, suction cup 16, and wafer handling robot, and is used to receive pose compensation data and control the timing of the actions of each actuator.

[0061] As can be seen from the above, after the main control system issues the command, the wafer handling robot at the first station and the wafer handling robot at the second station move synchronously, picking up wafers from their respective feed ports and placing them onto the vacuum chuck 16 at their respective stations almost simultaneously. This process is completely overlapping in time. The PLC directly drives the corresponding stepper motor 12 to rotate through the IO module or pulse command, which in turn drives the drive pulley 17 to rotate, thereby driving the driven pulley 21 to rotate through the synchronous belt 18, which in turn drives the ball screw 19 to rotate. The nut on the ball screw 19 drives the guide rail slider pair 27 to move vertically along the guide rail base plate 15. The forward and reverse rotation of the stepper motor 12 further drives the guide rail slider pair 27 to move up and down vertically, thereby adjusting the height of the guide rail slider pair 27.

[0062] The guide rail slider 27 moves the motor bracket 25 and sensor baffle 23 together. Through the sensor baffle 23 and sensor 20, the height of the guide rail slider 27 and motor bracket 25 is determined. The heights of the motor bracket 25, stepper motor 24, and suction cup 16 are then determined, facilitating adjustment of the suction cup 16's height. This allows for active lifting and lowering of the suction cup 16. Combined with visual feedback, this enables rapid and gentle wafer center pre-alignment, reducing mechanical contact and potential damage to the wafer edges.

[0063] In addition, the PLC drives the stepper motor 24 to rotate, which in turn drives the suction cup 16 to rotate with high precision, making it easy to scan through the central camera to calculate the current center position deviation.

[0064] Example 2:

[0065] Based on the above system, the working method for achieving efficient parallel pre-alignment includes the following steps:

[0066] Step 1: Synchronous loading: After the main control system issues the instruction, the wafer handling robot at the first station and the wafer handling robot at the second station move synchronously, respectively picking up wafer 7 from their respective feeding ports and placing wafer 7 onto the vacuum chuck at their respective stations almost simultaneously. This process is completely overlapping in time.

[0067] Step Two: Parallel Processing and Measurement: After the two wafers are loaded, the two workstations enter a completely independent and parallel execution process:

[0068] Active coarse alignment and center measurement: The lifting mechanism of each station performs a slight descent-ascent action according to the preset trajectory, and the guide mechanism completes the initial centering. Then, the central camera 2 takes a picture and accurately calculates the current center position deviation.

[0069] Rotational scanning and edge detection: The suction cup 16 rotates at least 360°, the edge camera 1 continuously captures images for edge detection, and the image processing unit analyzes the images in real time to accurately identify the corner coordinates of the edge.

[0070] Data reporting: Each workstation controller uploads the calculated final pose compensation parameters to the main control system. At this point, the pre-alignment processes for the two wafers 7 are completed in parallel without interference.

[0071] Step 3: Alternating Exposure and Unloading: After receiving data from both workstations, the main control system immediately schedules the exposure light source unit. The light source first exposes the aligned wafer 7 at the first workstation. After exposure, the wafer handling robot at the first workstation immediately removes it and places it in the downstream port. Simultaneously, while the first wafer 7 is being exposed, the second workstation completes the pre-alignment of the next wafer 7 and enters the ready state. The light source then switches to the second workstation for exposure, thus forming a continuous dual-workstation high-efficiency production cycle.

[0072] As can be seen from the above, this invention employs two physically symmetrical and independent pre-alignment units (left and right workstations), each containing a dedicated robotic arm, support mechanism, vision sensor, and drive system. This design creates a parallel hardware foundation in space, achieving complete decoupling of the two workstations in terms of processing flow through hardware resource configuration. The left and right workstations do not need to wait for each other or share resources, thus eliminating idle time caused by resource contention in traditional single-workstation systems.

[0073] This invention achieves overlapping operations on the processing timeline through precise task scheduling. While one workstation (e.g., the left workstation) is performing the time-consuming step of visual alignment, another workstation (the right workstation) can simultaneously perform operations such as wafer pre-alignment. This design, which parallelizes non-productive and productive operations in time, means that the overall throughput of the system is no longer limited by the complete processing cycle of a single wafer, but is determined by the most time-consuming single step, thereby greatly improving production efficiency.

[0074] To ensure process quality during parallel operation at two workstations, this invention employs a high-precision independent closed-loop control system. Each workstation constitutes an independent control loop, with its vision sensor, rotary motor, and lifting mechanism all undergoing closed-loop adjustment based on real-time data from the wafer at that workstation. This design ensures that the alignment accuracy of the two workstations does not affect each other, achieving the same or even better positioning accuracy as a single-workstation system, while avoiding potential mechanical vibrations or control interference between the two workstations, thus achieving a balance between efficiency and precision.

[0075] As shown above, this system innovates the traditional "serial pipeline" into a "parallel pipeline," allowing the most time-consuming visual alignment process and the robotic loading / unloading process to completely overlap on the time axis. This significantly reduces the average processing time of a single wafer, ensuring that the overall cycle time of the pre-alignment stage depends only on the processing speed of the slower of the two parallel stations, rather than the sum of the two, thus achieving an almost linear increase in production capacity.

[0076] This ensures that the pre-alignment process is no longer a bottleneck for overall machine production capacity, and can match or even exceed the pace of high-speed exposure light sources, maximizing equipment utilization and providing key technical support for the leap in production capacity of high-end lithography machines.

[0077] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A dual station pre-alignment system suitable for edge trimming wafers, characterized by, The application relates to a double-prealignment station for wafer alignment and exposure, which comprises a prealignment base plate (11) and two structure-symmetrical and completely independent prealignment stations arranged on the prealignment base plate (11), each of the prealignment stations is integrated with a wafer carrying manipulator, a bearing rotating unit, a double-vision sensing unit and a positive lifting mechanism. A distributed control module comprises a central scheduling layer and two station control layers corresponding to the prealignment stations respectively, the station control layer is electrically connected with each functional unit of the corresponding station, and the central scheduling layer is used for coordinating the two prealignment stations to synchronously execute a wafer processing flow and scheduling an exposure light source unit, is used for completing the position detection and alignment operation of the wafer through the two prealignment stations in parallel, and realizes parallel alignment-alternative exposure in cooperation with the central scheduling layer, so that the process waiting time is eliminated. A vertical wall (26) and two lower backing plates (13) are fixedly installed on the top of the prealignment base plate (11).

2. A dual station pre-alignment system for edge trimmed wafers as defined in claim 1, wherein, A guide rail base plate (15) and a plurality of vertical plates (10) are vertically fixedly installed on the top of the lower backing plate (13), a top cover plate II (9) is jointly installed on the top of the plurality of vertical plates (10), a through hole is formed in the top of the top cover plate II (9), and a funnel (8) is fixedly installed on the inner wall of the through hole. A supporting plate (5) is fixedly installed on the top of the vertical wall (26). The double-vision sensing unit comprises an edge camera (1), a center camera (2), a camera connecting plate (3), a three-coordinate instrument (4) and a top cover plate I (6).

3. A dual station pre-alignment system for edge trimmed wafers as defined in claim 2, wherein, The three-coordinate instrument (4) is fixed on the top of the supporting plate (5), the edge camera (1) and the center camera (2) are installed on the three-coordinate instrument (4) through the camera connecting plate (3), and the edge camera (1) is located outside the center camera (2). The center camera (2) is vertically downward arranged and used for shooting a wafer (7) in a static state to determine the center coordinate. The edge camera (1) is used for continuously capturing edge images in the rotating process of the wafer (7) and identifying the cutting edge direction. The top cover plate I (6) is buckled and fixed on the edge of the supporting plate (5). The positive lifting mechanism comprises a step motor I (12), a guide rail base plate (15), a driving belt pulley (17), a synchronous belt (18), a ball screw (19), a driven belt pulley (21), a guide rail mounting plate (22) and a guide rail slider pair (27).

4. A dual station pre-alignment system for edge trimmed wafers as defined in claim 2, wherein, The step motor I (12) is fixedly installed on the top of the lower backing plate (13), and the output shaft of the step motor I (12) penetrates the inner walls of the lower backing plate (13) and the prealignment base plate (11) and is fixedly installed with the driving belt pulley (17). The guide rail mounting plate (22) is fixedly installed on the top of the lower backing plate (13), the guide rail mounting plate (22) is fixedly installed with the guide rail base plate (15), and the guide rail base plate (15) is slidably connected with the guide rail slider pair (27). ​ The bottom end of the ball screw (19) passes through the lower pad (13) and extends to the bottom of the lower pad (13). The ball screw (19) is rotatably sleeved with the lower pad (13). The nut of the ball screw (19) is fixedly connected to the guide rail slider pair (27). The driven pulley (21) is fixedly connected to the bottom end of the ball screw (19). The synchronous belt (18) is sleeved between the driven pulley (21) and the driving pulley (17).

5. A dual station pre-alignment system for edge trimmed wafers as defined in claim 4 wherein, A sensor (20) is fixedly installed on the guide rail base plate (15), and a sensor baffle (23) is fixedly installed on the guide rail slider pair (27). The sensor (20) cooperates with the sensor baffle (23). A switch seat (14) is installed on the top of the lower pad plate (13) to control the power supply of the sensor (20).

6. A dual station pre-alignment system for edge trimmed wafers as defined in claim 4 wherein, The bearing rotation unit includes a suction cup (16), a stepper motor (24), and a motor bracket (25). The motor bracket (25) is fixed to one end of the guide rail slider pair (27), the second stepper motor (24) is fixedly installed on the motor bracket (25), and the output shaft of the second stepper motor (24) is fixedly installed with a suction cup (16), and the top of the suction cup (16) is adsorbed with a wafer (7).

7. A dual station pre-alignment system for edge trimmed wafers as defined in claim 3 wherein, The workstation control layer includes a programmable logic controller (PLC) and an independent vision processing computer; the vision processing computer is electrically connected to the edge camera (1) and the center camera (2) and is used to run vision processing algorithms, perform center positioning calculations, edge recognition operations, and output pose compensation data. The PLC is connected to the vision processing computer, stepper motor 1 (12), stepper motor 2 (24), suction cup (16) and wafer handling robot, and is used to receive pose compensation data and control the action sequence of each actuator.

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