High Flow Vacuum Chuck

Abstract

The vacuum chuck of the present invention includes a vacuum buffer in fluid communication with a vacuum source, the vacuum buffer being an enclosed space within the vacuum chuck, a top plate defining surface features on a first side thereof, an internal network of distribution channels opening to the first side through through-holes, and a flow valve configured to control fluid communication between the network of distribution channels and the vacuum buffer, such that opening the flow valve applies a negative pressure between a substrate disposed on the first side of the top plate through the through-holes in the vacuum buffer and the substrate, thereby planarizing the substrate against at least a portion of the first side of the top plate.

Description

[Technical field]

[0001] The present disclosure relates to methods of planarizing a substrate, and more particularly, to using a vacuum chuck to planarize a substrate. [Background technology]

[0002] REFERENCE TO RELATED APPLICATIONS This application claims priority to U.S. Provisional Patent Application No. 63 / 104527, filed and assigned on September 23, 2020, the disclosure of which is incorporated herein by reference.

[0003] The evolution of the semiconductor manufacturing industry is placing greater demands on yield management, especially on metrology and inspection systems. Critical dimensions continue to shrink, but the industry must reduce the time to achieve high yield, high value production. Minimizing the total time from detecting a yield problem to fixing it determines the investment for semiconductor manufacturers.

[0004] Fabricating semiconductor devices, such as logic and memory devices, typically involves processing semiconductor wafers using a number of manufacturing processes to form the various features and levels of the semiconductor devices. For example, lithography is a semiconductor manufacturing process that involves transferring a pattern from a reticle to a photoresist disposed on a semiconductor wafer. Further examples of semiconductor manufacturing processes include, but are not limited to, chemical mechanical polishing (CMP), etching, deposition, and ion implantation. An array of multiple semiconductor devices fabricated on a single semiconductor wafer may be separated into individual semiconductor devices.

[0005] During the manufacturing process, planarization may be required before further processes can be performed on the substrate. The focus needs to be constantly adjusted over a wide range of values ​​if the substrate is warped, which may prevent or even impede effective inspection or metrology of the substrate. There are various methods typically used to flatten a substrate held on a chuck. First, a high vacuum flow can be applied to the substrate to flatten it against the chuck. However, this requires large vacuum lines and powerful vacuum pumps, which are difficult to integrate due to space constraints and transmit vibrations that adversely affect the manufacturing process. Second, a suction cup can be applied to the substrate to conform the shape of the warped substrate. However, the downward force applied by the suction cup is limited to the surface of the suction cup, which may cause uneven weight distribution at the beginning of the planarization cycle and may not completely flatten a highly warped substrate. Third, a clamping device can press down on the substrate. However, this carries the risk of damaging the active area of ​​the substrate, is not well adapted to various substrate thicknesses, and may not completely flatten the substrate due to uneven force distribution. Each of these methods increases the complexity of the chuck and the maintenance requirements of the manufacturing process. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] U.S. Patent No. 10,754,262 [Patent Document 2] U.S. Patent No. 6,597,432 [Patent Document 3] US Patent Application Publication No. 2017 / 0011951 [Patent Document 4] U.S. Patent No. 10,663,434 Summary of the Invention [Problem to be solved by the invention]

[0007] Therefore, there is a need for a chuck that is capable of planarizing a highly warped substrate and that is easy to manufacture. [Means for solving the problem]

[0008] An embodiment of the present disclosure may provide a vacuum chuck, comprising: a vacuum buffer in fluid communication with a vacuum source, the vacuum buffer being an enclosed space within the vacuum chuck, a top plate defining surface features on a first side, an internal network of distribution channels opening to the first side through through holes, and a flow valve configured to control fluid communication between the network of distribution channels and the vacuum buffer.

[0009] The vacuum buffer may be integral with the second side of the top plate. The vacuum buffer may be integral with a base member disposed on the second side of the top plate. The base member may be sealed to the second side of the top plate by a radially compressed sealing member.

[0010] The vacuum chuck may further include lift pins attached to the base member, the lift pins protruding through a first side of the top plate.

[0011] The vacuum chuck may further include a leveling device attached to the base member positioned against the second side of the top plate.

[0012] The vacuum chuck may further comprise a number of clamps disposed about a periphery of the top plate configured to hold an edge of a substrate disposed on a first side of the top plate.

[0013] The vacuum chuck may further comprise a plurality of suction cups disposed in the ports on the first side of the top plate and in fluid communication with a secondary vacuum source.

[0014] The surface features may have a circular pattern, a rectangular pattern, or a central across pattern. The surface features may comprise a first zone and a second zone located radially outward from the first zone. The first zone and the second zone may be independent of each other. The internal network of distribution channels may comprise a first distribution channel opening to a first side of the top plate through a through hole located in the first zone, and a second distribution channel opening to the first side of the top plate through a through hole located in the second zone. The flow valve may comprise a first valve controlling fluid communication between the first distribution channel and the vacuum buffer, and a second valve controlling fluid communication between the second distribution channel and the vacuum buffer.

[0015] The vacuum chuck may further include a vacuum regulator located between the vacuum buffer and the vacuum source to adjust the pressure in the vacuum buffer. The vacuum buffer may be at a pressure of -0.05 bar to -1 bar. The vacuum buffer may have a volume of 1 L to 10 L.

[0016] The vacuum chuck may further comprise a vacuum tube connecting the vacuum buffer to a vacuum source.

[0017] An embodiment of the present disclosure may provide a method of planarizing a substrate, comprising: providing a vacuum chuck, the vacuum chuck comprising a vacuum buffer in fluid communication with a vacuum source, the vacuum buffer being an enclosed space within the vacuum chuck; a top plate defining surface features on a first side; an internal network of distribution channels opening to the first side through through holes; and a flow valve configured to control fluid communication between the network of distribution channels and the vacuum buffer; disposing a substrate on the first side of the top plate; and opening the flow valve to apply negative pressure in the vacuum buffer from between the substrate and the first top plate side through the surface features, thereby planarizing the substrate against at least a portion of the first side of the top plate. The substrate disposed on the first side of the top plate may warp such that there is a deflection of up to 5 mm, and by planarizing the substrate against at least a portion of the first side of the top plate, the deflection may be reduced to substantially 0 mm. [Brief description of the drawings]

[0018] For a fuller understanding of the nature and objects of the present disclosure, reference should be had to the following detailed description taken in conjunction with the accompanying drawings, in which: [Figure 1] FIG. 1 illustrates a cross-sectional side view of a vacuum chuck according to one embodiment of the present disclosure. [Figure 2A] FIG. 2 illustrates a top view of a vacuum chuck according to an embodiment of the present disclosure. [Figure 2B] FIG. 13 is a top view of a vacuum chuck according to another embodiment of the present disclosure. [Figure 2C] FIG. 13 is a top view of a vacuum chuck according to another embodiment of the present disclosure. [Diagram 3] FIG. 13 is a cross-sectional side view of a vacuum chuck according to another embodiment of the present disclosure. [Figure 4] FIG. 13 is a cross-sectional side view of a vacuum chuck according to another embodiment of the present disclosure. [Diagram 5] FIG. 13 is a cross-sectional side view of a vacuum chuck according to another embodiment of the present disclosure. [Figure 6] FIG. 13 is a cross-sectional side view of a vacuum chuck according to another embodiment of the present disclosure. [Figure 7] 1 is a flow chart of a method for planarizing a substrate according to one embodiment of the present disclosure. [Figure 8] 4 is a flow chart of a method for planarizing a substrate according to another embodiment of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] Although the claimed subject matter is described with respect to certain embodiments, other embodiments, including embodiments that do not provide all of the benefits and features described herein, are also within the scope of this disclosure. Various structural, logical, process step, and electronic changes may be made without departing from the scope of the disclosure. Accordingly, the scope of the disclosure is defined solely by reference to the appended claims.

[0020] As shown in FIG. 1, an embodiment of the present disclosure can provide a vacuum chuck 100. The vacuum chuck can include a vacuum buffer 10. The vacuum buffer 10 can be in fluid communication with a vacuum source 12. The vacuum source 12 can be a vacuum pump having a power of 60 L / min to 120 L / min. For example, to planarize a thin wafer, the vacuum pump output can be 60 L / min to 90 L / min, and to planarize a thicker panel, the vacuum pump output can be 90 L / min to 120 L / min. Of course, a conventional vacuum chuck may require a much larger vacuum pump output, for example, 1500 L / min to 3000 L / min.

[0021] The vacuum buffer 10 may be connected to a vacuum source 12 via a vacuum tube 14. The vacuum tube 14 may have an inner diameter of 4 mm to 8 mm. For example, a vacuum tube 14 with an inner diameter of 5 mm may be used to flatten a 510 mm x 515 mm insulating glass panel having a thickness of 3.1 mm and a warp of 4 to 5 mm. It can be appreciated that a conventional vacuum chuck may require a vacuum tube with a much larger inner diameter, for example, an inner diameter of 38 mm to 50 mm.

[0022] The vacuum buffer 10 may be an enclosed space within the vacuum chuck 100. For example, the vacuum buffer 10 may be completely enclosed within the vacuum chuck 100 except for the input from the vacuum tube 14 and the output to the dispense point of the vacuum chuck 100. The volume of the vacuum buffer 10 may be larger than the volume of the vacuum tube 14. For example, the vacuum buffer 10 may have a volume between 1 L and 10 L. In one embodiment, the vacuum buffer 10 may have a volume of 9.5 L. The enclosed volume of the vacuum buffer 10 may be of different shapes. For example, the enclosed volume may be a single substantially rectangular prism. Alternatively, the enclosed volume may be a plurality of interconnected cells, each of which is a substantially rectangular prism.

[0023] The vacuum chuck 100 may further include a vacuum regulating valve 16. The vacuum regulating valve 16 may be disposed between the vacuum buffer 10 and the vacuum source 12. For example, the vacuum regulating valve 16 may be connected in series with the vacuum tube 14 that connects the vacuum buffer 10 to the vacuum source 12. The vacuum regulating valve 16 adjusts the pressure in the vacuum buffer 10. For example, the pressure in the vacuum buffer 10 may be -0.05 bar to -1 bar.

[0024] The vacuum chuck 100 may further include a top plate 20. The shape of the top plate 20 may vary. For example, the top plate 20 may be circular, rectangular, or any other polygonal shape. In general, the rigidity of the vacuum chuck 100 depends on the thickness of the top plate 20. For example, the top plate 20 may have a rigidity suitable for most semiconductor applications with a thickness between 15 mm and 35 mm. The length and width of the top plate 20 may vary depending on the size of the substrate to be planarized. For example, to planarize a 510 mm x 515 mm panel, the length and width of the top plate 20 may also be 510 mm x 515 mm. To planarize a smaller wafer, a smaller top plate 20 may be used. For ease of construction, the length and width of the vacuum buffer 10 may be equal to or less than the length and width of the top plate 20, and the vacuum buffer 10 may have a thickness extending in the z-direction to create a volume within the vacuum buffer 10. For example, the length and width of the vacuum buffer 10 may be equal to or less than the length and width of the planarized panel or wafer. If space constraints limit the thickness of the vacuum buffer 10 , the length and width of the vacuum buffer 10 may be greater than the length and width of the top plate 20 to create a volume within the vacuum buffer 10 .

[0025] The top plate 20 can have a first side 20a and a second side 20b opposite the first side 20a. A substrate 21 to be flattened is disposed on the first side 20a of the top plate 20. The substrate 21 can be warped into a convex, concave, or other complex shape such as a saddle or potato chip, an example of which is shown in FIG.

[0026] Surface features 22 may be defined on the first side 20a of the top plate 20. Surface features 22 may be indentations on the first side 20a of the top plate 20 or may be protrusions on the finest side 20a of the top plate. For example, surface features 22 may be a network of grooves defined on the first side 20a of the top plate 20, a porous structure defined on the first side 20a of the top plate 20, or a pin structure defined on the first side 20a of the top plate 20.

[0027] In the embodiment shown in Figures 1-6, the surface features 22 are defined as a network of grooves. The size and shape of the network of grooves 22 may correspond to the size and shape of the substrate disposed on the top plate. For example, each groove 22 may have a width and depth of 0.5 mm to 5 mm. A groove 22 having a width of 2 mm and a depth of 1.5 mm is suitable for planarizing a small wafer, while a groove 22 having a width of 4.5 mm and a depth of 2 mm is suitable for planarizing a large panel. The pattern of the surface features 22 may correspond to the size of the substrate 21 disposed on the top plate. For example, the surface features 22 may have a circular pattern (shown in Figure 2A), a rectangular pattern (shown in Figure 2B), a center-across pattern (shown in Figure 2C), any combination thereof, or other designs.

[0028] The top plate 20 may have an internal network of distribution channels 24. The internal network of distribution channels 24 may open to the first side 20a of the top plate 20 via through holes 23. For example, if the surface features 22 are a network of grooves, the network of grooves 22 may be connected to the internal network of distribution channels 24 via through holes 23. The internal network of distribution channels 24 may extend radially outward from a central distribution hub 25. The central distribution hub 25 may be located in the center of the top plate 20. Alternatively, the central distribution hub 25 may be offset from the center of the top plate 20.

[0029] The vacuum chuck 100 may further include a number of locating pins 28. The number of locating pins 28 may be attached to and protrude from the first side 20a of the top plate 20. When the substrate 21 is manually loaded into the vacuum chuck 100, the number of locating pins 28 may abut an edge of the substrate 21 to ensure proper positioning of the substrate 21 on the first side 20a of the top plate 20.

[0030] The vacuum chuck 100 may further include a flow valve 30. The flow valve 30 may be configured to control the fluid communication between the network of distribution channels 24 and the vacuum buffer 10 by a movable plug. For example, the foot flow valve 30 may be disposed adjacent to the central distribution hub 25 such that the movable plug is selectively pressed against a seat on the bottom surface of the central distribution hub 25. When the flow valve 30 is in an open position, the fluid communication between the network of distribution channels 24 and the vacuum buffer 10 may be established through the central distribution hub 25. When the flow valve 30 is in a closed position, the fluid communication between the network of distribution channels 24 and the vacuum buffer 10 may be interrupted at the central distribution hub 25. The flow valve 30 may include an O-ring disposed in a joint groove on the top of the movable plug. The O-ring may seal the vacuum buffer 10 from the central distribution hub 25 by pressing against a seat on the central distribution hub 25 when the flow valve 30 is in a closed position.

[0031] The flow valve 30 may be moved between an open position and a closed position by an actuator 32. The actuator 32 may be a pneumatic cylinder. The actuator 32 may be controlled by a controller 34. The actuator 32 may be connected to the controller 34 by wires 36. Alternatively, the actuator 32 may be wirelessly connected to the controller 34 via Bluetooth, Wi-Fi, or any other wireless communication protocol.

[0032] Various parameters may affect the size of the vacuum buffer 10 and the planarization capability of the vacuum chuck 100. One or more of the following parameters or additional parameters may be used to determine the volume of the vacuum buffer 10 required to planarize a particular substrate 21. First, the air volume under the warped substrate 21 is defined by the shape and extent of the warp. Second, the air volume between the surface features 22 on the first side 20a of the top plate 20 is defined by the depth and width of the surface features 22. Third, the air volume inside the internal network of distribution channels 24 and the central distribution hub 25. Fourth, the amount of air that leaks through the sides of the substrate 21 and through holes in the top plate 20 during the planarization process is determined by the warp, stiffness, and mass of the substrate 21. Fifth, the minimum pressure required to keep the substrate 21 fixed on the top plate 20 after planarization is defined by the stiffness of the substrate 21 and the area of ​​the bottom of the substrate 21 exposed to the vacuum by the surface features.

[0033] In an embodiment, a prototype of the vacuum chuck 100 was tested to flatten a 510 mm x 515 mm double-glazed panel with a thickness of 3.1 mm and a warp of up to 4 mm. In the test setup, the volume of the vacuum buffer was 9.5 L, the total evacuated air volume (volume under the substrate + volume between the surface features + volume in the internal network of distribution channels and the central distribution hub) was 1 L, 45% of the substrate area was in contact with the first side of the top plate, the vacuum source had a capacity of 120 L / min and was connected to the vacuum chuck by a vacuum tube with an inner diameter of 5 mm. The starting pressure in the vacuum buffer was -0.7 bar, and the ending pressure in the vacuum buffer after flattening was -0.6 bar. The duration of the flattening process was 0.1 seconds. By maintaining the vacuum pressure at -0.6 bar, the panel remained flat against the first side of the top plate. The vacuum pressure used to modify the surface features and planarize the substrate so that 95% of the bottom area of ​​the substrate is exposed to vacuum may be reduced to -0.24 bar and the volume of the vacuum buffer may be reduced to 3 L for the large panels tested. For smaller wafers, the volume of the vacuum buffer could be further reduced to 1.2 L.

[0034] According to an embodiment of the present disclosure, the surface feature 22 may include a first zone 22a and a second zone 22b located radially outward from the first zone 22a, as shown in Figure 3. For example, if the surface feature 22 has a circular pattern, the first zone 22a may be a circular region and the second zone 22b may be an annular region surrounding the first zone 22a. The first zone 22a and the second zone 22b may be independent of each other.

[0035] The internal network of distribution channels 24 may comprise first channels 24a opening into the first side 20a through through holes 23a located in the first zone 22a and second channels 24b opening into the first side 20a through through holes 23b located in the second zone 22b. The central distribution hub 25 may comprise a first hub 25a from which the first channels 24a extend radially outwardly and a second hub 25b from which the second channels 24b extend radially outwardly.

[0036] The flow valve 30 may include a first valve 30a that may control fluid communication between the first channel 24a and the vacuum buffer 10, and a second valve 30b that may control fluid communication between the second channel 24b and the vacuum buffer 10. For example, the first valve 30a may be disposed adjacent to the first hub 25a, and the second valve 30b may be disposed adjacent to the second hub 25b. A pair of actuators 32a-b may be used to control the first and second valves 30a-b, respectively. Alternatively, a single dual-action actuator may be used to control the first and second valves 30a-b. For example, the first and second valves 30a-b may be concentric and controlled by a single concentric actuator. In this manner, the vacuum chuck 100 may be operated using the first zone 22a and / or the second zone 22b of the surface feature 22 to match the size of the substrate 21 to be planarized. For example, the first zone 22a may be suitable for substrates 21 up to 200 mm in diameter, and the second zone 22b may be suitable for substrates 21 up to 300 mm in diameter.

[0037] The surface features 22 may comprise additional zones located on different portions of the first side 20a of the top plate 20. For example, the zones may correspond to different halves, third halves, or quadrants of the top plate 20, and / or the additional zones may each be disposed radially outward from one another. In each configuration, each zone is independent of the other, and corresponding distribution channels and valves are used to control fluid communication between each zone and the vacuum buffer. The zones may be selectively activated based on the size and shape of the substrate 21 to be planarized.

[0038] According to an embodiment of the present disclosure, as shown in FIG. 1, the vacuum buffer 10 may be integrated with the second side 20b of the top plate 20. For example, the vacuum buffer 10 may be an enclosed space within the top plate 20. In this manner, the vacuum chuck 100 may have a compact size to meet the size constraints of the manufacturing process. In this configuration, the actuator 32 may be located outside the vacuum buffer 10. For example, the actuator 32 may be disposed on the second side 20b of the top plate 20.

[0039] According to an embodiment of the present disclosure, as shown in FIG. 4, the vacuum buffer 10 may be integrated with a base member 40 disposed on the second side 20b of the top plate 20. The base member 40 may be a universal component of the vacuum chuck that fits top plates 20 having various sizes and geometric shapes. In this configuration, the actuator 32 may be located inside the vacuum buffer 10. For example, the vacuum buffer 10 may surround the actuator 32 inside the base member 40.

[0040] The base member 40 may include an annular protrusion 42 adjacent the flow valve 30. The annular protrusion 42 may be received by a corresponding cavity in the top plate 20. For example, the annular protrusion 42 may be received by the central distribution hub 25 of the top plate 20. In this manner, when the base member 40 is positioned on the second side 20b of the top plate 20, fluid communication between the vacuum buffer 10 and the central distribution hub 25 is established and controlled by the flow valve 30.

[0041] The base member 40 may further include a sealing member 44. The sealing member 44 may be an o-ring, a quad ring, or any suitable gasket. The sealing member 44 may be radially compressed when the annular projection 42 is received by the central distribution hub 25. In this manner, the base member 40 may be sealed to the second side 20b of the top plate 20 by the sealing member 44.

[0042] The vacuum chuck 100 may further comprise lift pins 50. The lift pins 50 may be attached to the base member 40. For example, the lift pins may be attached to the inside or outside of the base member depending on the size of the substrate. In the embodiment shown in FIG. 5, the lift pins 50 are attached to the inside of the base member 40. For example, the lift pins 50 may be attached to a notch in the top surface of the base member 40 and separated from the vacuum buffer 10. In this manner, the lift pins 50 may be accessible on the top side of the base member 40 for maintenance when the top plate 20 is removed. The lift pins 50 protrude from the first side 20a of the top plate 20. Thus, the lift pins 50 may be configured to lift the substrate 21 from the first side 20a of the top plate 20. The lift pins 50 may be controlled by the controller 34. The lift pins 50 may be connected to the controller 34 by wires 52. Alternatively, the lift pins 50 may be connected to the controller 34 wirelessly via Bluetooth, Wi-Fi, or any other wireless communication protocol. An actuator (not shown) can be used to move the lift pins 50 in and out of the top plate 20. For example, the actuator can use a combination of springs and suction, or can use other techniques to move the lift pins 50.

[0043] The vacuum chuck 100 may further include a leveling device 60. The leveling device 60 may be attached to the base member 40. In the embodiment shown in FIG. 5, the leveling device 60 is attached to the outside of the base member 40. The leveling device 60 may be disposed against the second side 20b of the top plate 20. Thus, the leveling device 60 may be configured to adjust the height of the top plate 20 relative to the base member 40. The leveling device 60 may be a passive mechanical device or an actively controlled device. For example, the leveling device 60 may be controlled by the controller 34 to keep the top plate 20 horizontal or to apply a tilt to the top plate 20. It should be understood that some optical inspection processes for the top plate 20 may be desirable to be horizontal or have a small tilt to enhance some inspection features. The leveling device 60 may be connected to the controller 34 by wires 62. Alternatively, the leveling device 60 may be wirelessly connected to the controller 34 via Bluetooth, Wi-Fi, or any other wireless communication protocol.

[0044] As shown in FIG. 6, the vacuum chuck 100 may further include a plurality of clamps 70. The plurality of clamps 70 may be disposed around the upper plate 20. The plurality of clamps 70 may be configured to hold an edge of the substrate 21 disposed on the first side 20a of the upper plate 20. The plurality of clamps 70 may be attached to the upper plate 20. Alternatively, the plurality of clamps 70 may be attached to the base member 40. The plurality of clamps 70 may not be used to actively planarize the substrate 21. Instead, the plurality of clamps 70 may be used to hold the substrate 21 to the vacuum chuck 100 before and during planarization, which is mostly performed by suction from the through holes 23 in the first side 20a of the upper plate 20. The plurality of clamps 70 may include any number of clamps based on the size and geometry of the upper plate 20 and the substrate 21. For example, if the upper plate 20 is rectangular, there may be four clamps, one disposed on each of the four edges of the upper plate 20. The plurality of clamps 70 may be controlled by the controller 34. The plurality of clamps 70 may be connected to the controller 34 by wires 72. Alternatively, the plurality of clamps 70 may be connected to the controller 34 wirelessly via Bluetooth, Wi-Fi, or any other wireless communication protocol.

[0045] The vacuum chuck may further comprise a plurality of suction cups 80. On the first side 20a of the port 82 where the plurality of suction cups 80 are located, another vacuum circuit, such as a secondary vacuum source 84, connected to the top plate 20 by a secondary vacuum tube 86 connected to the port 82. A secondary vacuum regulation valve 88 may be provided, which is disposed between the port 82 and the secondary vacuum source 84. For example, the secondary vacuum regulation valve 88 may be connected in series with the secondary vacuum tube 86 connecting the port 82 to the secondary vacuum source 84. The secondary vacuum regulation valve 88 may regulate the pressure of the plurality of suction cups 80. The plurality of suction cups 80 may not be used to actively planarize the substrate 21. Instead, the plurality of suction cups 80 may be used to hold the substrate 21 to the vacuum chuck 100 before and during planarization, which is mostly performed by suction from the through holes 23 in the first side 20a of the top plate 20. The suction cups 80 may bring the substrate 21 close to the vacuum chuck 100. This allows the vacuum chuck 100 to better grip or flatten the substrate 21. For example, the substrate 21 may be significantly warped in one spot. This warping may cause the substrate 21 to be too far away from the surface of the vacuum chuck 100 to be effectively flattened. The suction cup 80 can compensate for this distance by pulling the substrate 21 close enough to the vacuum chuck 100 that the vacuum chuck 100 can flatten the substrate 21.

[0046] The vacuum chuck 100 of the present application can flatten highly warped substrates and is simple to manufacture, which provides the following advantages over conventional methods. First, the vacuum chuck 100 can use small vacuum lines and low power vacuum sources, which may be easier to integrate in the space constraints of a manufacturing process and transmit limited vibrations. Second, the vacuum chuck 100 can provide uniform weight distribution throughout the flattening cycle, which can completely flatten highly warped substrates. Third, since no mechanical clamps are required to hold down the substrate, there may be less risk of damaging the active area of ​​the substrate, and thus it is well suited to varying substrate thicknesses. Performing image processing on a substrate flattened using the vacuum chuck 100 of the present disclosure may be less challenging, for example, because the flattened substrate is easier to focus compared to a warped substrate, and the vacuum chuck 100 transmits less vibrations.

[0047] 7, an embodiment of the present disclosure may provide a method 200 for planarizing a substrate. The method 200 may include the following steps.

[0048] At step 210, a vacuum chuck may be provided. The vacuum chuck may include a vacuum buffer in fluid communication with a vacuum source. The vacuum chuck may further include a top plate defining surface features on a first side. The internal network of distribution channels may open to the first side via through holes. The vacuum chuck may further include a flow valve configured to control fluid communication between the network of distribution channels and the vacuum buffer.

[0049] In step 220, the substrate may be placed on the first side of the top plate. The substrate may be placed on the first side of the top plate manually or using a suitable automated loading device. The vacuum chuck may include a number of locating pins attached to and protruding from the first side of the top plate. The number of locating pins may aid in placing the substrate on the first side of the top plate by ensuring proper positioning of the substrate.

[0050] The vacuum chuck may further comprise a plurality of clamps. The plurality of clamps may be disposed around the periphery of the top plate. The plurality of clamps may be configured to hold an edge of a substrate disposed on the first side of the top plate. The plurality of clamps may be attached to the top plate. Alternatively, the plurality of clamps may be attached to the base member. The plurality of clamps may not be used to actively planarize the substrate. Instead, the plurality of clamps may be used to hold the substrate to the vacuum chuck before and during planarization, which is mostly performed by suction from through-holes in the first side of the top plate. Thus, step 220 may include engaging the plurality of clamps to the edge of the substrate after the substrate is disposed on the first side of the top plate.

[0051] The vacuum chuck may further comprise a plurality of suction cups. The plurality of suction cups may be disposed at ports on the first side of the top plate and connected to a separate vacuum circuit. Alternatively, the plurality of suction cups may be used to hold the substrate to the vacuum chuck before and during planarization, most of which is performed by suction from through-holes on the first side of the top plate. Thus, step 220 may include applying the plurality of suction cups to the substrate after the substrate is disposed on the first side of the top plate.

[0052] In step 230, a flow valve may be opened to apply negative pressure between the substrate and the first top plate side through the surface features into the vacuum buffer. The flow valve may be opened by an actuator, which may flatten the substrate against at least a portion of the first top plate side.

[0053] The surface features include a first zone and a second zone located radially outward from the first zone. For example, if the surface features have a circular pattern, the first zone may be a circular region and the second zone may be an annular region surrounding the first zone. The first zone and the second zone may be independent of each other. The internal network of distribution channels may include a first channel opening to the first side through a through hole located in the first zone and a second channel opening to the first side through a through hole located in the second zone. The flow valves may include a first valve that may control fluid communication between the first distribution channel and the vacuum buffer and a second valve that may control fluid communication between the second distribution channel and the vacuum buffer. Thus, step 230 may include opening the first flow valve and / or the second flow valve to apply negative pressure from between the substrate and the first side of the top plate through the first zone and / or the second zone into the vacuum buffer.

[0054] A substrate disposed on the first side of the top plate can warp with a deflection of up to 5 mm, and by flattening the substrate against at least a portion of the first side of the top plate, the deflection can be reduced to substantially 0 mm.

[0055] According to an embodiment of the present disclosure, the method 200 may further include steps as shown in FIG.

[0056] In step 240, the flow valve can be closed to stop fluid communication between the surface features and the vacuum buffer. The flow valve may be closed by an actuator. The flow valve may be closed after the substrate is sufficiently planarized. For example, the substrate may be sufficiently planarized in 0.1 seconds or less, and then the flow valve may be closed at an appropriate time before removing the substrate from the top plate.

[0057] In step 250, the substrate may be removed from the first side of the top plate. The substrate may be removed manually from the first side of the top plate or may be removed using a suitable automated removal device, such as lift pins.

[0058] Although the present disclosure has been described with respect to one or more particular embodiments, it will be understood that other embodiments of the present disclosure may be made without departing from the scope of the present disclosure, and therefore the present disclosure is limited only by the appended claims and their reasonable interpretation.

Claims

1. A vacuum chuck comprising: a vacuum buffer in fluid communication with the vacuum source, the vacuum buffer being an enclosed space within the vacuum chuck; a top plate defining surface features on a first side; an internal network of distribution channels opening onto the first side via through holes; a flow valve disposed between the internal network of distribution channels and the vacuum buffer and configured to control fluid communication between the internal network of distribution channels and the vacuum buffer; Equipped with a vacuum chuck.

2. 2. The vacuum chuck of claim 1, wherein the vacuum buffer is integral with a second side of the top plate.

3. The vacuum chuck of claim 1 , wherein the surface features have a circular or rectangular pattern.

4. The vacuum chuck of claim 1 , wherein the surface features include a central cross pattern.

5. 2. The vacuum chuck of claim 1, wherein the vacuum buffer is integral with a base member disposed on a second side of the top plate.

6. 6. The vacuum chuck of claim 5, further comprising a lift pin attached to said base member and protruding through a first side of said top plate.

7. The vacuum chuck of claim 5 , further comprising a leveling device attached to the base member and positioned against a second side of the top plate.

8. 6. The vacuum chuck of claim 5, wherein said base member is sealed to said second side of said top plate by a radially compressed seal member.

9. 10. The vacuum chuck of claim 1, further comprising a plurality of clamps disposed about a periphery of the top plate and configured to hold an edge of a substrate disposed on a first side of the top plate.

10. The vacuum chuck of claim 1 , further comprising a plurality of suction cups disposed within ports in a first side of the top plate and in fluid communication with a secondary vacuum source.

11. the surface feature includes a first zone and a second zone located radially outward from the first zone; The vacuum chuck of claim 1 , wherein the first zone and the second zone are independent of each other.

12. 12. The vacuum chuck of claim 11, wherein the internal network of distribution channels comprises a first distribution channel opening to a first side of the top plate through a through hole located in the first zone, and a second distribution channel opening to the first side of the top plate through a through hole located in the second zone.

13. The flow valve is a first valve controlling fluid communication between the first distribution channel and the vacuum buffer; a second valve controlling fluid communication between the second distribution channel and the vacuum buffer; 13. The vacuum chuck of claim 12, comprising:

14. 2. The vacuum chuck of claim 1, further comprising a vacuum regulator disposed between said vacuum buffer and said vacuum source for regulating air pressure within said vacuum buffer.

15. 2. The vacuum chuck of claim 1, wherein the vacuum buffer has a pressure of -0.05 bar to -1 bar.

16. 2. The vacuum chuck according to claim 1, wherein the volume of the vacuum buffer is 1 L to 10 L.

17. The vacuum chuck of claim 1 , further comprising a vacuum tube connecting said vacuum buffer to said vacuum source.

18. The vacuum chuck of claim 1, wherein the internal network of distribution channels is connected to a central distribution hub and the flow valves are positioned adjacent to the central distribution hub.

19. 1. A method of planarizing a substrate, comprising: Providing a vacuum chuck, the vacuum chuck comprising: a vacuum buffer in fluid communication with the vacuum source, the vacuum buffer being an enclosed space within the vacuum chuck; a top plate defining surface features on a first side; and an internal network of distribution channels opening onto the first side via through holes; a flow valve disposed between the internal network of distribution channels and the vacuum buffer and configured to control fluid communication between the internal network of distribution channels and the vacuum buffer. placing the substrate on a first side of the top plate; opening the flow valve to apply a negative pressure between the substrate and the first side of the upper plate through the through hole into the vacuum buffer to flatten the substrate against at least a portion of the first side of the upper plate; A method for providing the above.

20. 20. The method of claim 19, wherein the substrate disposed on a first side of the top plate is warped with a bow of up to 5 mm, and the bow is reduced to substantially 0 mm by flattening the substrate against at least a portion of the first side of the top plate.

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