A grinding table and wafer thinning apparatus

Abstract

This invention discloses a grinding worktable and a wafer thinning device. The grinding worktable includes a mounting plate, a support ring, and a base stacked from top to bottom. The mounting plate is used to support a suction cup. The support ring is fixedly connected to the base. The mounting plate is connected to a drive mechanism in the base. The support ring has an air-floating structure inside to enable the mounting plate to rotate under the drive of the drive mechanism when it is suspended above the support ring. The upper surface of the support ring has three highest points with the same height, so that the mounting plate remains horizontal when it abuts against the upper surface of the support ring.

Description

Technical Field

[0001] This invention relates to the field of ultra-precision wafer grinding technology, and more particularly to a grinding table and wafer thinning equipment. Background Technology

[0002] Currently, the semiconductor industry manufactures semiconductor chips by forming electronic circuits such as ICs (Integrated Circuits) or LSIs (Large Scale Integrations) on the surface of semiconductor wafers. Before the wafer is diced into semiconductor chips, the back side of the wafer is ground using a grinding and thinning process. This back side refers to the side opposite to the device side where the electronic circuits are formed, also known as the substrate. Wafer back side thinning refers to the high-precision grinding of various materials such as silicon wafers or compound semiconductors before packaging, reducing their thickness to a suitable ultra-thin shape.

[0003] The grinding table consists of multiple layers. The surface flatness or levelness of each layer will affect the surface flatness or levelness of the top layer. In particular, due to the large diameter and long circumference of the grinding table, the actual surface accuracy may not be ideal due to limitations in precision capability or installation factors. Random installation errors may occur, resulting in unstable contact between different surfaces, which ultimately affects the consistency of ultra-precision grinding. Summary of the Invention

[0004] This invention provides a grinding table and a wafer thinning device, which aims to at least solve one of the technical problems existing in the prior art.

[0005] A first aspect of the present invention provides a grinding worktable, comprising a mounting plate, a support ring, and a base stacked sequentially from top to bottom. The mounting plate is used to support a suction cup. The support ring is fixedly connected to the base. The mounting plate is connected to a drive mechanism in the base. The support ring has an air-floating structure inside, so that the mounting plate can rotate under the drive of the drive mechanism when it is suspended above the support ring. The upper surface of the support ring has three highest points with the same height, so that the mounting plate remains horizontal when it abuts against the upper surface of the support ring.

[0006] In one embodiment, the highest point of the upper surface of the support ring is 1 to 50 μm higher than the lowest point.

[0007] In one embodiment, the three highest points are evenly distributed along the circumference of the support ring.

[0008] In one embodiment, the highest and lowest points of the upper surface of the support ring transition smoothly.

[0009] In one embodiment, the upper surface of the support ring has an undulating shape.

[0010] In one embodiment, the highest point is arranged close to the workpiece being ground.

[0011] In one embodiment, the outer wall of the support ring is provided with an air distribution connector, the support ring has an air passage inside, and the upper surface of the support ring is provided with multiple air holes. Air enters through the air distribution connector and exits through the air holes to use air pressure to lift the mounting plate and the suction cup on it together.

[0012] In one embodiment, the material hardness of the support ring is between 2.5 and 5.

[0013] In one embodiment, the mounting plate includes an upper layer and a lower layer, the upper layer including a partition plate and a waterproof cover, and the lower layer including an indexing plate.

[0014] A second aspect of the present invention provides a wafer thinning apparatus, comprising:

[0015] A suction cup is used to hold the wafer and rotate it.

[0016] The grinding table described above is used to support a preset number of the suction cups and drive all the suction cups to rotate as a whole;

[0017] Grinding workpieces, used for grinding and thinning wafers.

[0018] The beneficial effects of the embodiments of the present invention include: ensuring that the mounting plate remains absolutely horizontal or absolutely flat when it abuts against the support ring, thereby ensuring good contact stability and certainty. Attached Figure Description

[0019] The advantages of the present invention will become clearer and easier to understand through the detailed description taken in conjunction with the following accompanying drawings, but these drawings are merely illustrative and do not limit the scope of protection of the present invention, wherein:

[0020] Figure 1 This invention illustrates a wafer thinning apparatus according to an embodiment of the present invention;

[0021] Figures 2 to 4 A grinding table according to an embodiment of the present invention is shown;

[0022] Figure 5 This invention illustrates a support ring and an indexing plate according to an embodiment of the present invention;

[0023] Figure 6 The relative positions of the support ring and the grinding workpiece provided in one embodiment of the present invention are shown. Detailed Implementation

[0024] The technical solutions of the present invention will be described in detail below with reference to specific embodiments and accompanying drawings. The embodiments described herein are specific implementations of the present invention, used to illustrate the concept of the present invention; these descriptions are explanatory and exemplary, and should not be construed as limiting the implementation methods and scope of protection of the present invention. It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. In addition to the embodiments described herein, those skilled in the art can employ other obvious technical solutions based on the content disclosed in the claims and specification of this application. These technical solutions include those that make any obvious substitutions and modifications to the embodiments described herein. It should be understood that, unless specifically stated otherwise, for ease of understanding, the following description of specific embodiments of the present invention is based on the premise that the relevant equipment, devices, components, etc., are in their original static state and are not given external control signals or driving forces.

[0025] Furthermore, it should be noted that the terms used in this application to indicate orientation, such as front, back, up, down, left, right, top, bottom, front, back, horizontal, and vertical, are merely for ease of explanation and to aid in the understanding of relative position or direction, and are not intended to limit the orientation of any device or structure.

[0026] To illustrate the technical solution described in this invention, the following description will be provided with reference to the accompanying drawings and embodiments.

[0027] In this application, a wafer is also referred to as a wafer, silicon wafer, substrate, or substrate, etc., which have the same meaning and practical function.

[0028] The wafer thinning equipment provided in this embodiment is mainly used for back-side thinning of wafers. The back-side refers to the side of the wafer where no devices are laid, which is generally a substrate. The substrate material can be silicon, silicon oxide, silicon nitride, silicon carbide, sapphire, etc.

[0029] Figure 1 An embodiment of the present invention provides a wafer thinning apparatus, comprising:

[0030] Equipment front-end module 1 is used to realize the entry and exit of wafers. Equipment front-end module 1 is set at the front end of the wafer thinning equipment. Equipment front-end module 1 is a transition module that realizes the transfer of wafers from the outside to the inside of the equipment, so as to realize the "dry entry and dry exit" of wafers.

[0031] Grinding module 3 is used to grind the wafer, the grinding including rough grinding and fine grinding, and grinding module 3 is located at the end of the wafer thinning equipment;

[0032] The polishing module 2 is used to perform chemical mechanical polishing on the wafer after the grinding is completed. It also has the function of transferring the wafer between the three modules (equipment front-end module 1, grinding module 3 and polishing module 2). The polishing module 2 is located between the equipment front-end module 1 and the grinding module 3.

[0033] Understandable Figure 1 The wafer thinning device shown is only one example. In other implementations, the polishing module 2 can be omitted, leaving only the front-end module 1 and the grinding module 3. In addition, the grinding module 3 can also include multiple grinding passes, such as 3 passes, 4 passes, 5 passes, etc. Similar modified embodiments that can achieve the wafer grinding and thinning function should fall within the protection scope of this application.

[0034] Device front-end module 1:

[0035] The front-end module 1 of the equipment includes a wafer storage unit and a first transmission unit. The wafer storage unit is located on one side of the front end of the wafer thinning equipment, and the first transmission unit is located between the wafer storage unit and the polishing module 2 to realize the transmission of the wafer between the wafer storage unit and the polishing module 2.

[0036] A wafer storage unit consists of multiple front-opening unified pods (FOUPs), specifically two, three, or more.

[0037] The first transfer unit includes a wafer pick-and-place robot. The wafer pick-and-place robot can rotate, extend, or fold and retract, and can also move along a transfer track. The wafer pick-and-place robot can retrieve wafers to be processed from the wafer storage unit through the door structure of the wafer transfer box and send them to the polishing module 2, and can also receive processed wafers from the polishing module 2 and place them into the wafer transfer box.

[0038] Polishing Module 2:

[0039] The polishing module 2 includes a second transmission unit, a third transmission unit, a chemical mechanical polishing unit, and a post-processing unit. The second transmission unit, the chemical mechanical polishing unit, and the post-processing unit occupy the edges of the polishing module 2, respectively, while the third transmission unit is located in the center.

[0040] Specifically, the second transfer unit is located on one edge of the polishing module 2 and distributed along the length of the device, connecting the front-end module 1 and the grinding module 3. The chemical mechanical polishing unit is located on the other edge of the polishing module 2 and is adjacent to the grinding module 3 and the second transfer unit. The post-processing unit is located on yet another edge of the polishing module 2 and is adjacent to the front-end module 1, the second transfer unit, and the chemical mechanical polishing unit. The third transfer unit is located near the center of the polishing module 2 and is surrounded by the second transfer unit, the chemical mechanical polishing unit, and the post-processing unit, used to realize the mutual transfer of wafers between the second transfer unit, the chemical mechanical polishing unit, and the post-processing unit.

[0041] In one embodiment, the second transfer unit includes a temporary storage section and a moving buffer section for temporarily storing and transporting wafers. The temporary storage section is located near the front-end module 1 of the device and is used for temporarily storing or transferring wafers. The moving buffer section is arranged along the direction from the front-end module 1 of the device to the grinding module 3 and is bidirectionally movable.

[0042] In one embodiment, the third transfer unit includes a central robot arm for transferring the ground wafer from the moving buffer section to the chemical mechanical polishing unit, transferring the polished wafer from the chemical mechanical polishing unit to the post-processing unit, and transferring the cleaned wafer from the post-processing unit to the temporary storage section.

[0043] After the wafer is taken out from the front-end module 1 of the equipment, it is transported to the grinding module 3 via the second transmission unit for grinding. After grinding is completed in the grinding module 3, the wafer is transported to the chemical mechanical polishing unit via the second and third transmission units for polishing. After polishing and cleaning, the wafer is then transferred back to the front-end module 1 of the equipment via the third and second transmission units.

[0044] The post-processing unit is used to clean and dry the polished wafers, and may include a horizontal brushing device and a single-chamber cleaning device.

[0045] Grinding Module 3:

[0046] The grinding module 3 includes a grinding unit 31, a cleaning unit, and a fourth transmission unit.

[0047] The grinding unit 31 is used to perform wafer grinding and thickness measurement. For example... Figure 1 As shown, the grinding unit 31 includes a grinding table 40, chucks 60 mounted on the grinding table 40, and grinding workpieces 50 corresponding to the positions of the chucks 60. The chucks 60 are used to hold and rotate the wafer; specifically, porous ceramic chucks can be used to vacuum-adsorb the wafer. The grinding table 40 carries a preset number of chucks 60 and rotates all of them as a whole. The grinding workpieces 50 are used to perform grinding and thinning processes on the wafer.

[0048] The grinding table 40 is used to hold the wafer and can rotate about its vertical central axis. For example... Figure 1 As shown, in one embodiment, three suction cups 60 are provided, which can rotate between the rough grinding station, the fine grinding station, and the loading / unloading station. The workpiece 50 being ground can be a grinding wheel. Figure 1 The two grinding wheels are used for rough grinding and fine grinding, respectively. It is understandable that... Figure 1 This is just one example; the number of suction cups 60 and the number of grinding wheels can also be other values, such as 1, 2, 4, 5, 6, etc. for the number of suction cups 60, and 1, 3, 4, etc. for the number of grinding wheels.

[0049] The cleaning unit is used to perform suction cup 60 cleaning, polishing, and wafer cleaning.

[0050] The fourth transfer unit includes a grinding robot for transferring wafers. This grinding robot, used in grinding module 3, is used to transfer wafers between grinding unit 31 and the second transfer unit. Specifically, it transfers wafers between the suction cup 60 and the moving buffer unit corresponding to the loading / unloading station. The grinding robot picks up a wafer from the moving buffer unit of the second transfer unit and feeds it into grinding unit 31 for grinding. After grinding and cleaning, the grinding robot picks up the wafer from grinding unit 31 and places it in the moving buffer unit for subsequent wafer transfer. The grinding robot has internal vacuum lines to achieve vacuum wafer adsorption. Alternatively, the grinding robot can also be implemented using a mechanism with grippers.

[0051] like Figure 1 As shown, the centers of the three chucks 60 form a 120° angle with the center of the grinding table 40. The three chucks 60 rotate between three stations: a rough grinding station, a fine grinding station, and a loading / unloading station. Two stations relative to the grinding wheel are used for rough grinding and fine grinding, respectively, while the remaining station is used for wafer loading / unloading and cleaning. The rotation of the grinding table 40 drives the three chucks 60 to switch between these three stations, allowing the chucks 60 to carry the wafers in a cyclical movement following the loading / unloading station - rough grinding station - fine grinding station - loading / unloading station.

[0052] During the grinding process, the working process of the grinding table 40 includes:

[0053] 1) The grinding robot transports the wafer to the grinding table 40, fixing the wafer on the chuck 60 corresponding to the loading and unloading station;

[0054] 2) The grinding table rotates 120° clockwise, and the wafer moves to the rough grinding station for rough grinding;

[0055] 3) After rough grinding is completed, the grinding table is rotated 120° in the forward direction, and the wafer is moved to the fine grinding station for fine grinding;

[0056] 4) After the fine grinding is completed, the grinding table 40 rotates 240° in the opposite direction, and the wafer moves to the loading and unloading station;

[0057] 5) After grinding, the wafers are cleaned and dried during the loading and unloading process and then removed by the grinding robot.

[0058] In this embodiment, multiple suction cups 60 are arranged on the grinding table 40. Each suction cup 60 can rotate independently. The grinding table 40 can rotate around its vertical central axis so that the grinding table 40 drives the multiple suction cups 60 to rotate and move as a whole, thereby realizing the transfer of the suction cups 60 between different workstations. After the suction cups 60 rotate and move to the preset position, the grinding table 40 needs to be kept stationary.

[0059] To achieve the air-floating structure and surface flatness requirements of the grinding table 40, such as Figures 2 to 4 As shown, an embodiment of the present invention provides a grinding worktable 40, which includes a mounting plate 41, a support ring 42 and a base 43 stacked from top to bottom.

[0060] Mounting plate 41 is used to support suction cup 60. For example... Figure 4 As shown, in one embodiment, the mounting plate 41 includes an upper layer and a lower layer fixedly connected. The upper layer includes a partition plate 411 and a waterproof cover 412, and the lower layer includes an indexing plate 413. The partition plate 411 is used to divide the upper surface of the circular grinding table 40 into multiple uniform fan-shaped areas along the radial direction. The partition plate 411 is radially arranged and has multiple pieces. Each fan-shaped area is provided with a waterproof cover 412, which is fixedly connected to two adjacent partition plates 411. Each waterproof cover 412 has mounting holes on its surface for mounting a suction cup 60. The suction cup 60 is covered by the waterproof cover 412, which can receive waste material and waste liquid generated during grinding. The lower indexing plate 413 is generally circular and matches the size of the upper layer. The indexing plate 413 also has multiple evenly distributed mounting holes on its surface to allow the suction cup 60 to pass through. In addition, the mounting plate 41 is connected to the drive mechanism in the base 43. Specifically, the lower indexing plate 413 can be connected to the drive mechanism below. Under the drive of the drive mechanism, the indexing plate 413 drives the partition plate 411, the waterproof cover 412 and multiple suction cups 60 to rotate synchronously.

[0061] The suction cup 60 is fixed by three evenly distributed support points on the indexing plate 413. One of these three points is a fixed support, and the other two are height-adjustable supports to adjust the angle of the suction cup plane relative to the grinding wheel.

[0062] like Figure 2 and Figure 4As shown, the support ring 42 is located below the mounting plate 41. The size of the support ring 42 matches that of the mounting plate 41. Specifically, the outer diameter of the support ring is 1100-1300 mm, the ring width of the support ring is 80-120 mm, the hardness of the material of the support ring is between 2.5 and 5, the material is preferably marble, etc., and the surface roughness of the support ring is better than Ra0.8 μm.

[0063] The mounting plate 41 and the support ring 42 are not fixed together to achieve the air flotation function. When air flotation is activated, the support ring 42 supports the mounting plate 41 under the action of air buoyancy, that is, the mounting plate 41 floats relative to the support ring 42, and a gap is formed between the lower surface of the mounting plate 41 and the upper surface of the support ring 42, thereby enabling the drive mechanism to rotate the mounting plate 41. When air flotation is stopped, the mounting plate 41 falls and abuts against the support ring 42. Under the action of gravity of the mounting plate 41 and the suction cup 60, the friction between the lower surface of the mounting plate 41 and the upper surface of the support ring 42 is large enough to ensure that the mounting plate 41 remains stationary during the grinding process to provide a stable support environment. Furthermore, the mounting plate 41 can be kept stationary by vacuuming, and a negative pressure source can be connected through the air distribution connector 421 and the air hole 422 to further form an adsorption force between the mounting plate 41 and the support ring 42, which can better ensure stability.

[0064] In one embodiment, the support ring 42 is fixedly connected to the base 43. The upper surface of the base 43 has a protruding annular boss, the size of which matches the size of the support ring 42, and the bottom of the support ring 42 is fixed to the annular boss.

[0065] In one embodiment, the support ring 42 is provided with an air flotation structure to enable the mounting plate 41 to rotate under the drive of the drive mechanism when it is suspended above the support ring 42.

[0066] like Figure 5 As shown, the air flotation structure is implemented by: an air distribution connector 421 is provided on the outer wall of the support ring 42, an air passage is provided inside the support ring 42, and multiple air holes 422 are provided on the upper surface of the support ring 42. Air is introduced through the air distribution connector 421 and discharged from the air holes 422 so as to use air pressure to float the mounting plate 41 together with the suction cup 60 on it.

[0067] To ensure that the mounting plate 41 remains absolutely horizontal or absolutely flat when it abuts against the support ring 42, such as Figure 5 As shown, in one embodiment of the present invention, the upper surface of the support ring 42 has at least three highest points H with completely consistent heights, so that the mounting plate 41 remains horizontal when it abuts against the upper surface of the support ring 42.

[0068] The upper surface of the support ring 42 serves as the air-bearing surface, requiring high precision. However, due to limitations in precision capabilities or installation factors, the precision of the upper surface of the support ring 42 is not ideal, leading to random installation errors. In other words, no matter how perfectly flat the upper surface of the support ring 42 is required during processing, unevenness is highly likely to occur after installation or operation. Therefore, this embodiment of the invention specifically processes the support ring 42 to have three evenly distributed highest points H. Based on the principle of three points determining the plane, this ensures that the mounting plate 41 remains absolutely horizontal or absolutely flat when it abuts against the support ring 42, thereby guaranteeing good contact stability and certainty.

[0069] The embodiments of the present invention avoid an extreme phenomenon: if the support ring 42 undergoes an arched deformation along a certain diameter, the mounting disk 41 will be in an unstable contact state on the support ring 42. During the grinding process, under different grinding wheels, different processes, and different loads, the mounting disk 41 and the suction cup 60 on it will be in an unstable state, thereby destroying the consistency of wafer grinding.

[0070] like Figure 5 As shown, the support ring 42 is annular, and its upper surface has an undulating shape, which can be wave-like. Preferably, there are three highest points H, and these three highest points H have the same height. It is understood that there can also be 4, 5, 6, etc., highest points H with the same height, which can also achieve the three-point definition of the plane. The specific number of highest points H is not limited to the values ​​listed above, and can be designed according to actual needs in other embodiments. All technical ideas disclosed in this application and the basic principles of this application should be covered by the claims of this invention.

[0071] Specifically, the support ring 42 can be processed in the following ways: the upper surface of the support ring 42 can be directly machined into an undulating shape during manufacturing; or a special tooling can be used to grind the upper surface of the support ring 42 into this special shape; or the support ring 42 can be divided into multiple parts and assembled into a structure with multiple high points, for example, by adding several thin pads to the mounting surface to form a protrusion.

[0072] In one embodiment, the highest point H of the upper surface of the support ring 42 is 1–50 μm higher than the lowest point L, preferably 2–8 μm, to ensure effective air buoyancy. Further, as... Figure 5 As shown, air holes 422 are provided at both the highest point H and the lowest point L on the upper surface of the support ring 42, or air holes 422 can be provided only at the highest point H, thereby achieving a uniform air flotation effect.

[0073] like Figure 6As shown, the three highest points H are evenly distributed along the circumference of the support ring 42, and the lowest point L is also evenly distributed. The highest points H and the lowest points L are also evenly distributed. The lines connecting the centers of the three highest points H to the center of the support ring 42 form a 120° angle with each other. Further, as... Figure 6 As shown, the highest point H can be as close as possible to the workpiece being ground, i.e., the grinding wheel arrangement.

[0074] like Figure 5 As shown, there is a smooth transition between the highest point H and the lowest point L on the upper surface of the support ring 42.

[0075] The embodiments of the present invention can ensure an absolutely reliable and stable contact state of the grinding table 40 during the grinding process, ensuring stable and reliable support of the chuck 60, thereby improving the stability of grinding. When different chucks 60 rotate to below the workpiece 50, the support state of the chucks 60 can still remain consistent, thereby improving the stability of maintaining a uniform surface flatness during grinding of different wafers at different stations. The accompanying drawings are schematic diagrams to help illustrate the concept of the present invention, schematically showing the shape of each part and its interrelationship. It should be understood that, in order to clearly show the structure of each component of the embodiments of the present invention, the drawings are not drawn to the same scale, and the same reference numerals are used to indicate the same parts in the drawings.

[0076] In the description of this specification, the references to terms such as "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., indicate that a specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0077] Although embodiments of the invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A grinding worktable, characterized in that, The device comprises a mounting plate, a support ring, and a base stacked sequentially from top to bottom. The mounting plate supports the suction cup. The support ring is fixedly connected to the base. The mounting plate is connected to a drive mechanism in the base. The support ring has an internal air-floating structure to allow the mounting plate to rotate under the drive mechanism when suspended above the support ring. The upper surface of the support ring has three highest points of the same height, ensuring that the mounting plate remains horizontal when it abuts against the upper surface of the support ring. The highest point of the upper surface of the support ring is 1–50 μm higher than the lowest point.

2. The grinding table as described in claim 1, characterized in that, The three highest points are evenly distributed along the circumference of the support ring.

3. The grinding table as described in claim 1, characterized in that, The highest and lowest points on the upper surface of the support ring transition smoothly.

4. The grinding table as described in claim 1, characterized in that, The upper surface of the support ring has an undulating shape.

5. The grinding table as described in claim 1, characterized in that, The highest point is arranged close to the workpiece being ground.

6. The grinding table as described in claim 1, characterized in that, The outer wall of the support ring is provided with an air distribution connector, the inside of the support ring has an air passage, and the upper surface of the support ring is provided with multiple air holes. Air enters through the air distribution connector and exits through the air holes to use air pressure to lift the mounting plate and the suction cup on it together.

7. The grinding table as described in claim 1, characterized in that, The material hardness of the support ring is between 2.5 and 5.

8. The grinding table as described in claim 1, characterized in that, The mounting plate includes an upper layer and a lower layer. The upper layer includes a partition plate and a waterproof cover, and the lower layer includes an indexing plate.

9. A wafer thinning apparatus, characterized in that, include: A suction cup is used to hold the wafer and rotate it. The grinding table as described in any one of claims 1 to 8 is used to support a predetermined number of the suction cups and drive all the suction cups to rotate as a whole; Grinding workpieces, used for grinding and thinning wafers.

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