Wafer pre-alignment apparatus and method

Abstract

The application discloses a wafer pre-alignment device, which comprises a bottom plate, a bearing plate arranged above the bottom plate and parallel to the bottom plate, a rotating base arranged on the bearing plate, a vacuum adsorption platform arranged on the rotating base and rotating synchronously with the rotating base, and a visual detection unit arranged on one side of the rotating base and used for precise alignment of the wafer. The device further comprises a jacking centering mechanism arranged on the bottom plate, which can lift or lower the wafer on the vacuum adsorption platform and can push the wafer to move horizontally relative to the vacuum adsorption platform until the center of the wafer coincides with the center line of the vacuum adsorption platform. The application also discloses an alignment method based on the device, wherein the jacking centering mechanism is additionally arranged, the problem that the original visual detection unit cannot detect the abnormality caused by excessive wafer deviation is solved, the downtime is shortened, the overall stability of the equipment is improved, the risk of excessive wafer deviation and identification failure is reduced, and the compensation range of the pre-alignment device is improved to a certain extent.

Description

Technical Field

[0001] This invention relates to the field of wafer processing equipment technology, and in particular to a wafer pre-alignment device and pre-alignment method. Background Technology

[0002] Wafer positioning and identification are crucial steps in wafer handling and the entire IC manufacturing process. Both require a pre-aligner for reference. The purpose of wafer pre-alignment is to calculate the wafer's eccentricity and locate its notches, then compensate for the eccentricity and orient the notches accordingly, preparing for the next step of wafer identification and processing. Existing wafer pre-alignment devices are shown in the attached figure. Figure 7-8 As shown, the system includes a rotating base 4' fixed on a support plate 5', a vacuum adsorption platform 3' fixed on the rotating base 4', and a CCD vision sensor 1' mounted on one side of the rotating base 4' via a stand. The wafer 6' is placed on the vacuum adsorption platform 3' by a mechanical gripper. When the system is started, the vacuum is turned on, adsorbing and fixing the wafer. After the vacuum value reaches the set value, the rotating base 4' drives the wafer 6' on the vacuum adsorption platform 3' to rotate together. The backlight 2' on the stand is turned on, and the CCD vision sensor 1' identifies and processes the data. The system calculates the wafer's center position and the wafer's notch or flat opening position, and adjusts the notch or flat opening position to the required angle to achieve wafer pre-alignment.

[0003] However, existing pre-alignment systems that rely solely on CCD vision sensors typically have a recognition range of 304mm for 12-inch wafers, only addressing wafer offsets within ±2mm. In reality, deviations exceeding 5mm can occur unexpectedly, such as when a mechanical gripper places a wafer on a vacuum adsorption platform. When the deviation is too large, exceeding the recognition range, the pre-alignment device issues an alarm, and the machine stops. In such cases, troubleshooting is time-consuming and costly, and there's no way to fundamentally eliminate the problem. Since the equipment is highly automated, delayed or prolonged downtime will impact the equipment's effective operating time. Summary of the Invention

[0004] To overcome the above-mentioned shortcomings, the present invention aims to provide a wafer pre-alignment device that reduces the problem of abnormalities that cannot be detected by the original vision inspection unit due to excessive wafer misalignment, shortens downtime, improves the overall stability of the equipment, reduces the risk of excessive wafer misalignment and inability to identify the wafer, and can improve the compensation range of the pre-alignment device to a certain extent.

[0005] To achieve the above objectives, the technical solution adopted by the present invention is as follows: a wafer pre-alignment device, comprising a base plate, a support plate parallel to the base plate, a rotating base on the support plate, a vacuum adsorption platform rotating synchronously on the rotating base, a visual inspection unit for precise wafer alignment on one side of the rotating base, and a lifting and centering mechanism disposed on the base plate, the lifting and centering mechanism being able to lift or lower the wafer on the vacuum adsorption platform and push the wafer horizontally relative to the vacuum adsorption platform until the center of the wafer coincides with the centerline of the vacuum adsorption platform.

[0006] The beneficial effects of this invention are as follows: A lifting and centering mechanism is added, which lifts the wafer from the vacuum adsorption platform and then moves it horizontally for complete preliminary centering. This ensures that when the lifting and centering mechanism lowers the wafer onto the vacuum adsorption platform, the centerline of the wafer coincides with the platform's centerline. The wafer is then fixed in place by the vacuum adsorption platform, and a rotating base causes the wafer on the platform to rotate together. The vision inspection unit processes and calculates the wafer's center position and the position of the wafer's notch or flat end, adjusting the notch or flat end position to the required angle to achieve wafer pre-alignment. This reduces the problem of abnormalities that the original vision inspection unit could not detect due to excessive wafer misalignment, shortens downtime, improves overall equipment stability, reduces the risk of undetectable wafer misalignment, and to some extent improves the compensation range of the pre-alignment device.

[0007] Furthermore, the lifting and centering mechanism includes a lifting device and a centering device. The centering device includes a left centering baffle and a right centering baffle symmetrically arranged on both sides of the vacuum adsorption platform. Under the action of the centering drive, the left and right centering baffles move relative to or towards each other. When the left and right centering baffles move closer to each other, they push the wafer to center relative to the centerline of the vacuum adsorption platform. The centering drive can be a parallel gripper cylinder, with the left and right centering baffles respectively fixed on two pneumatic grippers of the parallel gripper cylinder. When the parallel gripper cylinder actuates, pushing the left and right centering baffles closer to each other, it pushes the wafer to move horizontally relative to the vacuum adsorption platform, achieving wafer centering and alignment; when pushing the left and right centering baffles away from each other, it releases the wafer.

[0008] Furthermore, the left centering baffle has a circular arc groove extending downwards from its upper end. The curvature of the groove matches that of the wafer. The sidewall of the wafer abuts against the sidewall of the groove, and the lower end face of the wafer abuts against the bottom of the groove. When the left and right centering baffles approach each other, the wafer is centered relative to the centerline of the vacuum adsorption platform by the push of the two grooves. The wafer is aligned and guided by the sidewall of the circular arc groove.

[0009] Furthermore, the lifting device includes a lifting drive component and a left lifting frame and a right lifting frame that move synchronously under the action of the lifting drive component. The lifting drive component is fixed to the base plate. The left and right lifting frames are symmetrically arranged relative to the vacuum adsorption platform and are fixedly connected to each other by a lifting plate. The lifting plate is connected to the output shaft of the lifting drive component. The lifting drive component is a sliding cylinder. The lifting drive component extends and retracts under the control of a solenoid valve, driving the lifting plate connected to its output shaft to rise and fall, thereby driving the left and right lifting frames to rise and fall, completing the lifting and return of the wafer.

[0010] Furthermore, the upper surfaces of the left and right lifting frames are provided with multiple contact bumps that abut against the lower surface of the wafer. These contact bumps are made of PEEK material. When the lifting device lifts the wafer, only the contact bumps abut against the lower surface of the wafer. This avoids the large contact area with the left and right lifting frames during the alignment process, which would cause high friction, generate particles, and damage the wafer.

[0011] Furthermore, the lifting device includes a lifting drive and a mounting base. The mounting base is fixed to the base plate. The output shaft of the lifting drive is fixedly connected to the centering drive. The lifting drive drives the centering device to rise and fall. The lifting drive directly drives the centering device to rise and fall, and the wafer is lifted by the bottom of the slots of the left and right centering baffles of the centering device for centering.

[0012] Furthermore, both the centering drive and the lifting drive are located between the support plate and the base plate, saving space.

[0013] The invention also provides a wafer pre-alignment method that performs two alignments to reduce the risk of excessive wafer misalignment that cannot be identified, and can improve the compensation range of the pre-alignment device to a certain extent.

[0014] To achieve the above objectives, the technical solution adopted in this invention is as follows: a wafer pre-alignment method, which firstly transfers the wafer to a vacuum adsorption platform using a robotic arm; then, a lifting and centering mechanism is activated, lifting the wafer from the vacuum adsorption platform using a lifting device, and using the groove of the centering device to perform initial coarse alignment of the wafer relative to the centerline of the vacuum adsorption platform; next, the lifting device descends, placing the wafer back onto the adsorption platform; finally, the vacuum adsorption platform adsorbs the wafer, and a rotating base drives the wafer to rotate. The position of the wafer's center and the wafer's notch or flat edge are calculated by a vision detection unit, and the notch or flat edge position is adjusted to the required angle to complete a secondary fine pre-alignment.

[0015] First, the wafer is coarsely aligned using a lifting and centering mechanism to ensure that the center of the wafer coincides with the centerline of the vacuum adsorption platform. Then, the wafer is adsorbed by the vacuum adsorption platform, and the rotating base drives the wafer to rotate. The visual inspection unit calculates the position of the wafer center and the wafer notch or flat edge position, and adjusts the notch or flat edge position to the required angle to complete the second fine pre-alignment.

[0016] Furthermore, before the initial coarse alignment, a fine pre-alignment can be performed on the wafer. This fine pre-alignment is similar to the secondary fine pre-alignment method. If the alignment accuracy of the fine pre-alignment meets the threshold requirement, the process ends; otherwise, the initial coarse alignment is performed. This reduces the problem of abnormalities that the original visual inspection unit cannot detect due to excessive wafer misalignment, shortens downtime, improves the overall stability of the equipment, reduces the risk of excessive wafer misalignment leading to unrecognizable defects, and to some extent, improves the compensation range of the pre-alignment device. Attached Figure Description

[0017] Figure 1 This is a three-dimensional structural diagram of Embodiment 1 of the present invention;

[0018] Figure 2 This is a three-dimensional structural diagram of the lifting and centering mechanism in Embodiment 1 of the present invention;

[0019] Figure 3 This is a schematic diagram of the lifting device in Embodiment 1 of the present invention;

[0020] Figure 4 This is a cross-sectional view of the left lifting frame in Embodiment 1 of the present invention.

[0021] Figure 5 This is a three-dimensional structural schematic diagram of Embodiment 2 of the present invention;

[0022] Figure 6 This is a three-dimensional structural diagram of the lifting and centering mechanism in Embodiment 2 of the present invention;

[0023] Figure 7 This is a three-dimensional structural diagram of a wafer pre-alignment device in the prior art;

[0024] Figure 8 This is a three-dimensional structural diagram of the detection status of a wafer pre-alignment device in the prior art.

[0025] In the picture:

[0026] 1' CCD vision sensor; 2' Backlight; 3 / 3' Vacuum adsorption platform; 4 / 4' Rotating base; 5 / 5' Carrier plate; 6 / 6' Wafer; 7 Left lifting frame; 8. Left centering baffle; 9. Left connecting seat; 10. Lifting plate; 11. Lifting drive component; 12. Mounting plate; 13. Parallel gripper cylinder; 14. Base plate; 15. Right connecting seat; 16. Right centering baffle; 17. Right lifting frame; 18. Vision inspection unit; 19. Contact protrusion; 20. Mounting seat. Detailed Implementation

[0027] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0028] Example 1

[0029] See appendix Figure 1-2 As shown, a wafer 6 pre-alignment device of the present invention includes a base plate 14, a support plate 5 parallel to the base plate 14, and the support plate 5 is fixed to the base plate 14 by a fixing frame. A rotating base 4 is provided on the support plate 5, and a vacuum adsorption platform 3 that rotates synchronously with the rotating base 4 is provided on the rotating base 4. The vacuum adsorption platform 3 can adsorb the wafer 6, and the rotating base 4 drives the vacuum adsorption platform 3 and the wafer 6 to rotate synchronously. A vision detection unit 18 for precise alignment of the wafer 6 is provided on one side of the rotating base 4. The vision detection unit 18 includes a stand fixed to one side of the rotating base 4, and a CCD vision sensor and a backlight are provided on the stand. The vacuum adsorption platform 3 adsorbs and fixes the wafer 6, and the rotating base 4 drives the wafer 6 on the vacuum adsorption platform 3 to rotate together. The backlight on the stand is turned on, and the CCD vision sensor identifies and processes the data. The system calculates the center position of the wafer 6 and the notch or flat opening position of the wafer 6, and adjusts the notch or flat opening position to the required angle to achieve the alignment of the wafer 6. The rotating base 4, the vacuum adsorption platform 3, and the visual inspection unit 18 are all existing technologies. The centering method and structure have been disclosed in Chinese patent application number CN201510203515.6, and will not be repeated here.

[0030] It also includes a lifting and centering mechanism set on the base plate 14. The lifting and centering mechanism includes a lifting device and a centering device. The lifting and centering mechanism can lift or lower the wafer 6 on the vacuum adsorption platform 3 and can push the wafer 6 to move horizontally relative to the vacuum adsorption platform 3 so as to push the wafer 6 to a position where the center of the wafer coincides with the center line of the vacuum adsorption platform 3.

[0031] The alignment device includes a left alignment baffle 8 and a right alignment baffle 16 symmetrically arranged on both sides of the vacuum adsorption platform 3. The left alignment baffle 8 and the right alignment baffle 16 move relative to each other or towards each other under the action of the alignment drive. The alignment drive can be a parallel gripper cylinder 13, which is fixed to the base plate 14 by a mounting plate 12. The left alignment baffle 8 and the right alignment baffle 16 are fixed to the two pneumatic grippers of the parallel gripper cylinder 13 by a left connecting seat 9 and a right connecting seat 15, respectively. The parallel gripper cylinder 13 can also be a modified parallel gripper electric cylinder, which can drive the left alignment baffle 8 and the right alignment baffle 16 to move. When the parallel gripper cylinder 13 is activated, it pushes the left alignment baffle 8 and the right alignment baffle 16 closer to each other, thus pushing the wafer 6 to move horizontally relative to the vacuum adsorption platform 3, thereby achieving the alignment and guidance of the wafer 6; when it pushes the left alignment baffle 8 and the right alignment baffle 16 away from each other, it can release the wafer 6.

[0032] The left centering baffle 8 has a circular arc groove extending downwards from its upper end. The curvature of the groove matches that of the wafer 6. The sidewall of the wafer 6 abuts against the sidewall of the groove, and the lower end face of the wafer 6 abuts against the bottom of the groove. When the left centering baffle 8 and the right centering baffle 16 approach each other, the wafer 6 is centered relative to the centerline of the vacuum adsorption platform 3 by being pushed by the two grooves. The centering and alignment of the wafer 6 is achieved by pushing the wafer 6 through the sidewall of the circular arc groove.

[0033] The lifting device includes a lifting drive 11 and a left lifting frame 7 and a right lifting frame 17 that move synchronously under the action of the lifting drive 11. The lifting drive 11 is a guide rail slide cylinder fixed on the base plate 14. The left lifting frame 7 and the right lifting frame 17 are symmetrically arranged relative to the vacuum adsorption platform 3, and a lifting plate 10 is fixedly connected between them. The lifting plate 10 is connected to the output shaft of the lifting drive 11. The lifting drive 11 extends and retracts under the control of a solenoid valve, driving the lifting plate 10 connected to its output shaft to rise and fall, thereby driving the left lifting frame 7 and the right lifting frame 17 to rise and fall, completing the lifting and return of the wafer 6. The left lifting frame 7 and the right lifting frame 17 are located between the left centering baffle 8 and the right centering baffle 16.

[0034] See attached document Figure 3-4 As shown, the upper surfaces of the left lifting frame 7 and the right lifting frame 17 are provided with multiple contact bumps 19 that can abut against the lower surface of the wafer 6. The contact bumps 19 are made of PEEK material. When the lifting device lifts the wafer 6, only the contact bumps 19 abut against the lower surface of the wafer 6, avoiding the large contact area with the left and right lifting frames 7 and 17 during the alignment process of the alignment device, which would cause high friction, generate particles, and damage the wafer 6. The lifting drive component 11 adopts a clean-type guide rail slide cylinder with a suction port to discharge generated particles, improving operational reliability.

[0035] A lifting and centering mechanism has been added. This mechanism lifts the wafer 6 from the vacuum adsorption platform 3 and then moves it horizontally for preliminary alignment. This ensures that when the lifting and centering mechanism lowers the wafer 6 onto the vacuum adsorption platform 3, its center coincides with the centerline of the platform. The vacuum adsorption platform 3 then holds the wafer 6 in place. The rotating base 4 rotates the wafer 6 on the platform, and the vision inspection unit 18 calculates the center position and the notch or flat opening position of the wafer 6. The notch or flat opening position is then adjusted to the required angle, achieving pre-alignment of the wafer 6. This reduces the problem of the vision inspection unit 18 being unable to detect abnormalities due to excessive wafer 6 offset, shortens downtime, improves overall equipment stability, reduces the risk of undetectable wafer 6 offset, and to some extent improves the compensation range of the pre-alignment device.

[0036] Both the centering drive component and the lifting drive component 11 are located between the bearing plate 5 and the base plate 14, which greatly saves space.

[0037] When pre-aligning wafer 6 based on this pre-alignment device, the alignment method includes the following steps:

[0038] A robotic arm transfers wafer 6 to the vacuum adsorption platform 3. Then, a lifting and centering mechanism is activated, lifting wafer 6 from the platform and using the groove of the centering device to perform initial coarse centering of wafer 6 relative to the centerline of the platform. Next, the lifting device descends, placing wafer 6 back onto the platform. Finally, the vacuum adsorption platform 3 adsorbs wafer 6, and the rotating base 4 rotates wafer 6. The vision detection unit 18 calculates the center position and notch / facet position of wafer 6, adjusting the notch / facet position to the required angle to complete a secondary fine pre-alignment.

[0039] First, the wafer 6 is initially coarsely aligned using a lifting and alignment mechanism to ensure that the center of wafer 6 coincides with the centerline of the vacuum adsorption platform 3. Then, wafer 6 is adsorbed by the vacuum adsorption platform 3, and the rotating base 4 rotates wafer 6. The vision detection unit 18 calculates the position of the center of wafer 6 and the position of its notch or flat edge, and adjusts the notch or flat edge to the required angle, completing the second fine pre-alignment. This avoids the need for an emergency restart of the initial coarse alignment operation if a downtime occurs during the second fine pre-alignment.

[0040] However, before the initial coarse alignment, a fine pre-alignment can be performed on wafer 6. The method for the first fine pre-alignment is the same as that for the second fine pre-alignment. If the alignment accuracy of the first fine pre-alignment meets the threshold requirement, the process ends. If the threshold requirement is not met, the vision inspection unit 18 stops abnormally, and the initial coarse alignment is performed. This reduces the problem of abnormalities that the original vision inspection unit 18 cannot detect due to excessive wafer 6 offset, shortens downtime, improves the overall stability of the equipment, reduces the risk of excessive wafer 6 offset leading to unrecognizable defects, and to some extent improves the compensation range of the pre-alignment device.

[0041] Example 2

[0042] See attached document Figure 5-6 As shown, the only difference between this embodiment and Embodiment 1 is the lifting device. In this embodiment, the lifting device includes a lifting drive 11 and a mounting base 20. The mounting base 20 is fixed on the base plate 14. The output shaft of the lifting drive 11 is fixedly connected to the centering drive. The lifting drive 11 drives the centering device to rise and fall. The lifting drive 11 directly drives the centering device to rise and fall. The wafer 6 is lifted by the bottom of the grooves of the left centering baffle 8 and the right centering baffle 16 of the centering device, and then centering is performed. Other structures are the same as in Embodiment 1.

[0043] In this embodiment, the lifting device directly lifts the centering device, enabling the left centering baffle 8 and right centering baffle 16 of the centering device to both lift the wafer 6 on the vacuum adsorption platform 3 through the bottom of the groove and to perform centering of the wafer 6. This eliminates the need for the left lifting frame 7 and right lifting frame 17, saving costs.

[0044] The above embodiments are only for illustrating the technical concept and features of the present invention. Their purpose is to enable those skilled in the art to understand the content of the present invention and implement it. They should not be used to limit the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A wafer pre-alignment method based on a wafer pre-alignment device, the wafer pre-alignment device comprising a base plate, a bearing plate parallel to the base plate arranged above the base plate, a rotating base arranged on the bearing plate, a vacuum adsorption platform arranged on the rotating base and rotating synchronously with the rotating base, and a visual detection unit arranged on one side of the rotating base for precise alignment of the wafer, characterized in that: The wafer pre-alignment device further comprises a lifting and centering mechanism arranged on the base plate, which can lift or lower the wafer on the vacuum adsorption platform and push the wafer to move horizontally relative to the vacuum adsorption platform until the center of the wafer coincides with the center line of the vacuum adsorption platform, and the lifting and centering mechanism comprises a lifting device and a centering device; the centering device comprises left and right centering baffles symmetrically arranged on both sides of the vacuum adsorption platform, which move away from or towards each other under the action of a centering driving element, and when the left and right centering baffles move towards each other, the wafer is centered relative to the center line of the vacuum adsorption platform; the left centering baffle is provided with a groove with a circular arc structure downward from its upper end face, the radius of the groove is consistent with that of the wafer, the side wall of the wafer can abut against the side wall of the groove, and the lower end face of the wafer can abut against the groove bottom, and when the left and right centering baffles move towards each other, the wafer is centered relative to the center line of the vacuum adsorption platform under the pushing of the two grooves; ​ The wafer pre-alignment method comprises the following steps: transferring the wafer to the vacuum adsorption platform by the mechanical arm; performing a fine pre-centering on the wafer, rotating the base to drive the wafer to rotate, and calculating the wafer center position and wafer gap or flat mouth position by the visual detection unit; if the centering accuracy of the fine pre-centering meets the threshold requirement, the process is ended, otherwise, the lifting and centering mechanism is started, the wafer on the vacuum adsorption platform is lifted by the lifting device, and the wafer is initially roughly centered relative to the center line of the vacuum adsorption platform by the groove of the centering device; then the lifting device is lowered, and the wafer is placed on the adsorption platform again; finally, the wafer is adsorbed by the vacuum adsorption platform, the base is rotated to drive the wafer to rotate, the wafer center position and wafer gap or flat mouth position are calculated by the visual detection unit, and the gap or flat mouth position is adjusted to the required angle, and the fine pre-centering is completed.

2. The wafer pre-alignment method of claim 1, wherein: The lifting device comprises a lifting driving element and left and right lifting frames which synchronously rise and fall under the action of the lifting driving element, the lifting driving element is fixed on the base plate, the left and right lifting frames are symmetrically arranged relative to the vacuum adsorption platform and are fixedly connected with a lifting plate therebetween, and the lifting plate is connected with the output shaft of the lifting driving element.

3. The wafer pre-alignment method of claim 2, wherein: The upper end faces of the left and right lifting frames are provided with a plurality of contact protrusions which can abut against the lower end face of the wafer, and the contact protrusions are made of peek material.

4. The wafer pre-alignment method of claim 1, wherein: The lifting device comprises a lifting driving element and a mounting seat, the mounting seat is fixed on the base plate, the output shaft of the lifting driving element is fixedly connected with the centering driving element, and the lifting driving element drives the centering device to rise and fall.

5. The wafer pre-alignment method of claim 2 or 4, wherein: The centering driving element and the lifting driving element are both located between the bearing plate and the base plate.

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