Wafer thinning apparatus and thinning method

Abstract

The application relates to the technical field of integrated circuit manufacturing, and discloses wafer thinning equipment and a thinning method. The wafer thinning equipment comprises a grinding device and an adsorption platform. The adsorption platform is used for supporting a wafer and rotating the wafer. The grinding device is arranged above the adsorption platform in a lifting mode. The lower part of the grinding device is provided with a grinding wheel used for grinding the wafer. The grinding wheel comprises a base material and a plurality of grinding blocks. The grinding blocks are fixed to the base material through an adhesive layer. The grinding block comprises a ceramic base, grinding particles distributed in the ceramic base, and a composite nano coating coated on the surface of the grinding particles and used for enhancing the interface bonding strength of the grinding particles and the ceramic base. The composition of the composite nano coating comprises cerium oxide and zirconium oxide. Through the technical scheme, the problems of short service life of the grinding wheel and poor surface quality of the thinned wafer in the related art are solved.

Description

Technical Field

[0001] This application relates to the field of integrated circuit manufacturing technology, and more specifically, to a wafer thinning apparatus and thinning method. Background Technology

[0002] Three-dimensional integrated circuits (3D ICs) are an important technological path for the semiconductor industry to continue Moore's Law and improve chip performance and integration. The core idea is to stack multiple chips or functional layers vertically and achieve interlayer electrical connections through interconnection technologies such as through-silicon vias (TSVs), thereby achieving higher functional density within a limited space.

[0003] Wafer thinning is a key supporting process in 3D IC manufacturing, its main purpose being to reduce the wafer's thickness from its original level to an ultra-thin state suitable for vertical integration. Ultra-thin wafers are the physical basis for achieving 3D stacking and are crucial for optimizing electrical performance and thermal management. As the number of 3D IC stacking layers increases, the requirements for the thinning thickness of individual wafers become increasingly stringent. Simultaneously, 3D IC technology places extremely high demands on the surface quality of the thinned wafer, including excellent Total Thickness Variation (TTV) and extremely low Roughness Average (Ra), to ensure the accuracy, consistency, and stability of subsequent bonding processes.

[0004] To achieve the aforementioned thinning targets, wafer thinning equipment typically utilizes the physical grinding action of grinding wheels to process ultra-thin wafers. Such equipment must have its grinding structure and grinding process precisely designed and controlled to meet the requirements for ultra-thin wafer processing (such as thickness ≤10 μm, TTV ≤1.5 μm, and Ra ≤5 nm) while also considering manufacturing costs and production efficiency.

[0005] As a crucial component in wafer thinning equipment, the performance of the wafer thinning wheel directly determines the surface quality of the thinned wafer. Ideally, the wheel needs to meet three requirements simultaneously: (1) it needs appropriate elasticity to buffer grinding stress; (2) it must have sufficient rigidity to ensure the surface quality of the shape; and (3) it must maintain excellent self-sharpening properties to achieve stable grinding. However, currently, the mechanical properties of grinding wheels are poor, and their fracture toughness is low, making them unable to withstand the stress under high-speed grinding, resulting in poor surface quality of the thinned wafer. Summary of the Invention

[0006] This application proposes wafer thinning equipment and thinning method, thereby solving or at least alleviating one or more of the above-mentioned problems and other problems existing in the prior art.

[0007] The technical solution of this application is as follows:

[0008] This application proposes a wafer thinning device, including a grinding device and an adsorption platform, wherein the adsorption platform is used to support the wafer and drive the wafer to rotate.

[0009] The grinding device is raised and lowered above the adsorption platform, and the lower part of the grinding device has a grinding wheel for grinding wafers; the grinding wheel is driven by the grinding device and performs grinding through axial feed;

[0010] The grinding wheel includes a base material and a plurality of grinding blocks, the grinding blocks being fixed to the base material by an adhesive layer;

[0011] The grinding block includes:

[0012] Ceramic matrix;

[0013] Abrasive particles are distributed within the ceramic matrix;

[0014] A composite nano-coating is applied to the surface of the abrasive grains to enhance the interfacial bonding strength between the abrasive grains and the ceramic matrix.

[0015] The composite nanocoating consists of cerium oxide and zirconium oxide.

[0016] As a further technical solution, the raw material of the composite nano-coating includes zirconium / cerium composite nano-sol, which comprises the following components by weight: 1-1.5 parts of oxygen-containing zirconium source, 1.8-2.5 parts of oxygen-containing cerium source, and 2-3.5 parts of complex acid.

[0017] As a further technical solution, the oxygen-containing zirconium source is zirconium nitrate; the oxygen-containing cerium source is cerium nitrate, and the cerium nitrate is cerium nitrate recovered from cerium-containing grinding waste liquid using ammonium nitrate as a recovery agent.

[0018] As a further technical solution, the grinding wheel also includes pores distributed in a multi-level stacked pattern.

[0019] As a further technical solution, the raw materials of the grinding block include: abrasive grains, polymer microspheres, ceramic binder sol, and zirconium / cerium composite nano-sol for coating the abrasive grains.

[0020] As a further technical solution, the polymer microspheres are polymer microspheres modified with a silane coupling agent.

[0021] As a further technical solution, the polymer microspheres include a first polymer microsphere with an average particle size of 100~110 μm, a second polymer microsphere with an average particle size of 15~25 μm, and a third polymer microsphere with an average particle size of 3~5 μm.

[0022] As a further technical solution, the weight ratio of the first polymer microsphere to the second polymer microsphere and the third polymer microsphere is 3~4:2.5~3.5:2~3.

[0023] As a further technical solution, the ceramic matrix comprises silicon oxide, aluminum oxide, and boron oxide.

[0024] As a further technical solution, the ceramic binder sol comprises the following components by weight: 28-32 parts of oxygen-containing silicon source, 5-6.5 parts of oxygen-containing aluminum source, 1.5-2 parts of oxygen-containing boron source, and 4-6 parts of complexing acid.

[0025] As a further technical solution, the grinding apparatus includes:

[0026] The feeding assembly is vertically connected above the adsorption platform;

[0027] A rotating shaft is driven by the feed assembly to move up and down, and the grinding wheel is coaxially connected to the bottom end of the rotating shaft.

[0028] As a further technical solution, the adsorption platform includes:

[0029] The worktable has a chuck spindle at the bottom, which drives the worktable to rotate.

[0030] An adsorption disk, disposed on the worktable, is used to adsorb wafers. The adsorption disk can drive the wafers to rotate synchronously under the action of the worktable.

[0031] The present invention also proposes a thinning method, which uses the aforementioned wafer thinning equipment to perform a wafer thinning process.

[0032] As a further technical solution, the following steps are included:

[0033] A100. Vacuum adsorption fixes the wafer onto the adsorption platform;

[0034] A200, the control feed assembly drives the rotating shaft and grinding wheel to move downward in the vertical direction until the grinding surface of the grinding wheel contacts the wafer;

[0035] A300: The grinding wheel and the adsorption platform rotate in the same direction, while the grinding wheel is fed downwards. The rotational speed of the grinding wheel is greater than that of the adsorption platform to grind the wafer.

[0036] A400: When the wafer is ground to the target thickness, stop the rotation and feed of the rotating shaft and the adsorption platform, and control the feed assembly to drive the grinding wheel to move upward and reset, so that the grinding surface of the grinding wheel is separated from the wafer surface;

[0037] A500, release the vacuum adsorption of the adsorption platform and transfer the wafer.

[0038] The beneficial effects of this application are as follows:

[0039] The wafer thinning equipment provided in this application improves the grinding wheel by coating the abrasive grain surface with a composite nano-coating of cerium oxide (CeO2) and zirconium oxide (ZrO2), which improves bending strength and extends the service life of the grinding wheel, thereby ensuring the surface quality of the thinned wafer. Specifically, the above effects are achieved through the following three aspects:

[0040] (1) In this application, the grinding wheel uses a ceramic matrix. If the ceramic matrix is ​​directly combined with the abrasive grains, the bending strength will be low due to the interfacial bonding strength between the abrasive grains and the ceramic matrix. Moreover, the interfacial bonding strength problem will also cause the abrasive grains to fall off easily during the wafer thinning process, resulting in poor surface quality of the thinned wafer. In the composite nano-coating of this application, cerium oxide itself is a dispersed phase, which can be combined with zirconium oxide to give full play to the dispersion toughening effect, increase the interfacial bonding strength between the ceramic matrix and the abrasive grains, and also increase the holding force of the composite nano-coating on the abrasive grains, thereby preventing the abrasive grains from falling off during the thinning grinding process, extending the service life of the grinding wheel, and avoiding wafer scratches caused by abrasive grain falling off, thus ensuring the surface quality of the thinned wafer.

[0041] (2) In the composite nano-coating of this application, cerium oxide stabilizes the tetragonal phase of zirconium oxide through ion doping and inhibits its room temperature phase transformation; under the action of grinding stress, zirconium oxide undergoes a controllable transformation from tetragonal phase to monoclinic phase, thereby releasing stress, inhibiting cracks, strengthening phase transformation toughening, improving the mechanical properties of the grinding wheel, and ensuring the surface quality of the wafer after thinning.

[0042] (3) The composite nano-coating of this application is free of alkali metal ions and carbon and nitrogen impurities, and will not form a loose glass phase structure. This is beneficial to improving the mechanical properties of the grinding wheel and reducing wafer scratches and metal ion contamination caused by abrasive grain shedding during grinding. It not only ensures the surface quality of the wafer after thinning, but also achieves effective control of ion contamination during the thinning process, so that the thinning process of advanced chips such as three-dimensional integrated circuit chips and high bandwidth memory chips has high yield and high consistency. Attached Figure Description

[0043] The present application will now be described in further detail with reference to the accompanying drawings and specific embodiments.

[0044] Figure 1 This is a schematic diagram of the structure of a wafer thinning apparatus according to one embodiment of this application;

[0045] Figure 2 for Figure 1 Side view of the grinding device and adsorption platform of the wafer thinning equipment;

[0046] Figure 3 A flowchart illustrating the specific steps of the wafer thinning method provided in this application;

[0047] Figure 4 for Figure 2 A schematic diagram of the structure of the grinding wheel in the diagram;

[0048] Figure 5 for Figure 4 A schematic diagram of the grinding block of a medium-sized grinding wheel;

[0049] Figure 6 The image shows a SEM image of the grinding block prepared in Example 8.

[0050] Figure 7 This is a partial enlarged SEM image of the grinding block prepared in Example 8;

[0051] Figure 8 To and Figure 7 The corresponding EDS layered diagram of zirconium;

[0052] Figure 9 To and Figure 7 The corresponding EDS layered diagram of cerium;

[0053] Figure 10 The image shows the XRD pattern of the grinding block prepared in Example 8.

[0054] Figure 11 This is a TEM image of the cerium-containing grinding waste liquid in Example 8.

[0055] Reference numerals: 1. Equipment base; 2. Grinding device; 22. Rotary shaft; 23. Grinding wheel; 231. Substrate; 232. Grinding block; 2321. Abrasive grain; 2322. Composite nano-coating; 2323. Pores; 2324. Ceramic substrate; 23231. Large pores; 23232. Medium pores; 23233. Small pores; 3. Adsorption platform; 31. Chuck spindle; 32. Worktable; 33. Adsorption disk; 4. Rotary disk. Detailed Implementation

[0056] The technical solutions in the embodiments of this application will be clearly and completely described below with reference to the embodiments of this application. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0057] To keep the drawings concise, each drawing only schematically shows the parts relevant to the disclosure; these do not represent the actual structure of the product. Furthermore, for ease of understanding, in some drawings, only one of components with the same structure or function is schematically shown, or only one is labeled. In this document, "one" not only means "only one," but can also mean "more than one," and "several" includes "two" and "more than two."

[0058] In this document, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to fixed connections, detachable connections, or integral connections; they can refer to mechanical connections or electrical connections; they can refer to direct connections or indirect connections through an intermediate medium; and they can refer to the internal communication between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0059] In this application, unless otherwise expressly specified and limited, "above" or "below" the second feature can include direct contact between the first and second features, or contact between the first and second features through another feature between them. Furthermore, "above," "over," and "on top" of the second feature includes the first feature directly above or diagonally above the second feature, or simply indicates that the first feature is at a higher horizontal level than the second feature. "Below," "below," and "under" the second feature includes the first feature directly below or diagonally below the second feature, or simply indicates that the first feature is at a lower horizontal level than the second feature.

[0060] In the description of this embodiment, terms such as "upper," "lower," "left," and "right" are based on the orientation or positional relationship shown in the accompanying drawings. They are used only for the convenience of description and simplification of operation, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this application.

[0061] Furthermore, in the description of this application, the terms "first," "second," etc., are used only to distinguish descriptions and should not be construed as indicating or implying relative importance.

[0062] It should be understood that, unless the context clearly indicates otherwise, the terms “comprising,” “including,” or “having” as used herein refer to the presence of an element, but do not exclude the presence or addition of one or more other elements. Furthermore, as used herein, “comprising” and / or “including” indicate the presence of shapes, numbers, steps, operations, members, elements, and / or combinations thereof, and do not exclude the presence or addition of one or more other shapes, numbers, operations, elements, and / or combinations thereof.

[0063] In this application, the numerical range indicated by "~" refers to the range of values ​​specified as the lower and upper limits, respectively, before or after the term. When multiple values ​​for the upper or lower limit of any numerical range are mentioned, the range disclosed herein can be understood as a range with any one of the mentioned upper limits as its upper limit and any one of the mentioned lower limits as its lower limit.

[0064] In the following text, the average particle size can be measured using a commercially available laser particle size analyzer.

[0065] Reference Figure 1 and Figure 2 , Figure 1 The image shows a wafer thinning device. Figure 2 for Figure 1 The side view of the grinding device 2 and the adsorption platform 3 of the wafer thinning equipment. The wafer thinning equipment includes a device base 1, on which a rotating disk 4 is provided. Above the rotating disk 4, multiple adsorption platforms 3 are arranged at intervals along the circumference. The rotating disk 4 can rotate around its own central axis to change the position of the adsorption platform 3, so that the wafer supported by the adsorption platform 3 can switch between the rough grinding station, the fine grinding station and the loading and unloading station.

[0066] Furthermore, an upright support is provided at the end of the equipment base 1, and a grinding device 2 is provided on the side of the support. There are two grinding devices 2, corresponding to a rough grinding section and a fine grinding section. The two have similar structures and are equipped with a feed assembly (not shown) that drives the grinding wheel 23 to move up and down and a mechanism that drives the grinding wheel to rotate along the rotating shaft 22. The feed assembly includes a lifting motor (not shown), which is slidably connected to the housing of the rotating shaft through a lead screw. The housing is slidably connected to the side of the column so that the vertical movement of the rotating shaft 22 is realized by the rotation of the lifting motor, thereby changing the position of the grinding wheel 23 relative to the adsorption platform 3.

[0067] The adsorption platform 3 is used to support the wafer and drive the wafer to rotate. The grinding device 2 is raised and lowered above the adsorption platform 3. The lower part of the grinding device 2 has a grinding wheel 23 that can rotate circumferentially to grind the wafer.

[0068] Grinding device 2 includes a feed assembly, a rotary shaft 22, and a grinding wheel 23. The grinding block 232 within the grinding wheel 23 ( Figure 4(Shown) This is used for grinding wafers. The grinding wheel 23 can be a cup-shaped grinding wheel, mounted at the lower end of the rotating shaft 22. The rotating shaft 22 is used to rotate the grinding wheel 23 about its axis of rotation. The feed assembly can drive the rotating shaft 22 and the grinding wheel 23 to move up and down synchronously. When the wafer needs to be ground, the grinding wheel 23 moves under the drive of the feed assembly until its bottom surface contacts the surface of the wafer. At this time, both the grinding wheel 23 and the wafer are rotating in the same direction but at different speeds, and the surface of the wafer is ground using the grinding wheel 23. The feed assembly has a known construction and includes, for example, multiple linear guides that guide the movement direction of the rotating shaft 22 and a ball screw-slider mechanism that moves the rotating shaft 22 up and down.

[0069] Figure 4 The diagram shows the structure of the grinding wheel 23. Figure 5 A schematic diagram of the structure of the grinding block 232 is shown. The grinding wheel 23 includes a base material 231 and a plurality of grinding blocks 232. The grinding blocks 232 are fixed to the base material 231 by an adhesive layer.

[0070] Grinding block 232 includes:

[0071] Ceramic matrix 2324;

[0072] Abrasive particles 2321 are distributed in the ceramic matrix 2324;

[0073] A composite nano-coating 2322 is applied to the surface of the abrasive grains 2321 to enhance the interfacial bonding strength between the abrasive grains and the ceramic matrix.

[0074] The composite nanocoating 2322 consists of cerium oxide and zirconium oxide.

[0075] In this application, the substrate 231 provides a good supporting foundation for the grinding block 232, capable of withstanding the grinding force generated by the grinding block 232 during grinding, ensuring the stability of the grinding block 232 during high-speed rotation, and ensuring that the grinding block 232 will not deform due to force, enabling the grinding wheel 23 to continuously and stably perform wafer grinding. In the grinding block 232, the abrasive grains 2321, with their extremely high hardness, can grind rapidly and continuously, achieving wafer thinning while improving grinding efficiency. Coating the surface of the abrasive grains 2321 with a composite nano-coating 2322 can significantly improve the interfacial bonding strength between the abrasive grains 2321 and the ceramic substrate 2324. The composite nano-coating 2322 stabilizes the tetragonal phase of zirconium oxide through cerium oxide solid solution, utilizing its phase transformation toughening effect to enhance the holding force on the abrasive grains 2321, effectively reducing abnormal particle shedding during grinding, lowering the wafer chipping rate, extending the service life of the grinding wheel 23, and improving the wafer grinding quality.

[0076] In one embodiment of this application, the grinding block 232 further includes pores 2323, which are distributed throughout the interior of the grinding block 232. (See also...) Figure 5In this application, the pores 2323 are distributed in a multi-level stack inside the grinding block 232. That is, the pores 2323 are composed of large pores 23231, medium pores 23232 and small pores 23233 with different particle sizes. The medium pores 23232 fill the gaps between the large pores 23231, and the small pores 23233 fill the remaining gaps, so as to form a multi-level pore system dominated by large pores 23231.

[0077] Specifically, the large atmospheric pores (23231) can quickly remove chips and dissipate heat, preventing grinding efficiency and quality from being reduced due to chip clogging. They can significantly improve the overall chip removal and heat dissipation capabilities of the grinding block. However, the large atmospheric pores are relatively scattered and it is difficult to form a connected chip removal channel. By filling the gaps between the large atmospheric pores with medium and small pores, although their chip removal and heat dissipation capabilities are not as good as those of the large atmospheric pores, they are conducive to forming a connected chip removal channel together with the large atmospheric pores, accelerating heat dissipation and chip removal. This significantly improves the surface quality of the grinding wheel, not only improving the surface roughness of the wafer, but also reducing the number of times the grinding wheel needs to be dressed due to chip clogging, increasing the number of wafers processed per hour, and extending the service life of the grinding wheel. Furthermore, the medium-sized pores 23232 filling the gaps between the large pores alter the original transmission direction of grinding stress, slowing down the transmission speed and achieving the effect of dispersing grinding stress. Meanwhile, the small pores 23233 mitigate the weakening of interfacial bonding strength caused by large pores, making the distribution of the ceramic matrix 2324 around the abrasive grains 2321 more compact and uniform, increasing the holding force on the abrasive grains 2321, and preventing the abrasive grains 2321 from detaching and chipping during wafer grinding, thus affecting the wafer grinding quality. Therefore, medium and small pores are beneficial to improving wafer surface roughness in different dimensions. Thus, through multi-level stacked pores, the chip removal, heat dissipation, buffering capacity, and abrasive grain stability of the grinding block are significantly improved. While meeting the bending strength requirements, the grinding wheel life is significantly increased, greatly improving the wafer surface grinding quality.

[0078] In one embodiment of this application, the abrasive grain 2321 can be one of diamond abrasive, corundum abrasive, silicon carbide abrasive, or cubic boron nitride abrasive. Diamond is a commonly used abrasive in wafer grinding; however, diamond is prone to graphitization during high-temperature sintering, while silicon carbide abrasives are easily oxidized at high temperatures to form a SiO2 film, resulting in poor mechanical properties of the grinding wheel. In this application, because a composite nano-coating is applied to the surface of the abrasive grain, sintering can be achieved at a lower temperature (below 600°C), fundamentally avoiding oxidation or graphitization of the abrasive under high-temperature conditions, improving the mechanical properties of the grinding wheel, and ensuring the surface quality of the thinned wafer.

[0079] In one embodiment of this application, the average particle size of both zirconium oxide and cerium oxide is in the nanometer range. In the composite nanocoating 2322, the nano-sized zirconium oxide / cerium oxide composite phase can fully exert its toughening effect, further suppress crack propagation, and ensure the stability of the grinding wheel 23 during grinding.

[0080] In one embodiment of this application, the ceramic substrate 2324 is composed of silicon oxide, aluminum oxide, and boron oxide, and has high mechanical strength and hardness. During the wafer thinning process, it is used to withstand centrifugal force and grinding force, prevent the grinding block 232 from deforming or breaking due to force, and ensure the stability of the grinding process.

[0081] In one embodiment of this application, the grinding apparatus 2 includes:

[0082] The feeding assembly is lifted and connected above the adsorption platform 3;

[0083] The rotating shaft 22 is driven by the feed assembly to move up and down, and the grinding wheel 23 is coaxially connected to the lower end of the rotating shaft 22.

[0084] In this application, the feed assembly and the rotary axis 22 work together to ensure the flatness of the wafer surface during grinding. The feed assembly provides a stable vertical feed path for the rotary axis 22 to drive the grinding wheel 23; the rotary axis 22 can control the radial runout to a very small range, ensuring that the grinding wheel 23 maintains uniform contact with the wafer surface throughout the rotation process. The coordinated operation of the feed assembly and the rotary axis 22 results in a thinned wafer with good flatness.

[0085] In one embodiment of this application, the adsorption platform 3 includes:

[0086] The worktable 32 has a chuck spindle 31 at the bottom, which drives the worktable 32 to rotate.

[0087] The adsorption disk 33 is set on the worktable disk 32 and is used to adsorb the wafer. The adsorption disk 33 can drive the wafer to rotate synchronously under the action of the worktable disk 32.

[0088] In this application, during the actual operation of the wafer thinning equipment, the chuck spindle 31, the worktable 32, and the adsorption disk 33 work together to provide stable adsorption for the grinding wheel 23 to grind the wafer. The chuck spindle 31 controls the rotation speed and direction of the worktable 32, which in turn stably drives the adsorption disk 33 and the wafer to rotate synchronously. The adsorption disk 33 always firmly adsorbs the wafer, ensuring that the wafer maintains a stable position even under high-speed rotation. This synergistic effect prevents poor wafer surface flatness caused by wafer displacement during grinding.

[0089] In another embodiment of this application, the wafer thinning equipment may include multiple adsorption platforms 3, which are used to adsorb different wafers. The multiple adsorption platforms 3 are installed on the same rotating disk 4 and are spaced apart in the circumferential direction of the rotating disk 4. The rotating disk 4 can drive the different adsorption platforms 3 to rotate below the grinding device 2, thereby grinding the corresponding wafers.

[0090] like Figure 1 The wafer thinning equipment shown includes three adsorption platforms 3, which are circumferentially spaced on a rotating disk 4. Simultaneously, two grinding devices 2 are provided: one for rough grinding of the wafer and the other for fine grinding. The rotating disk 4 can drive the adsorption platforms 3 to rotate, allowing for sequential rough and fine grinding of the wafers on the same adsorption platform 3, thus improving the wafer grinding efficiency.

[0091] According to another aspect of this application, this application also proposes a wafer thinning method, which uses the above-mentioned wafer thinning equipment to perform wafer thinning processing.

[0092] In one embodiment of this application, such as Figure 3 As shown, the wafer thinning method may include the following steps:

[0093] A100. Vacuum adsorption fixes the wafer onto the adsorption platform 3;

[0094] A200, the control feed assembly drives the rotary shaft 22 and the grinding wheel 23 to move downward in the vertical direction until the grinding surface of the grinding wheel 23 contacts the wafer;

[0095] A300, the grinding wheel 23 and the adsorption platform 3 rotate in the same direction, while the grinding wheel 23 is fed downward. The rotation speed of the grinding wheel 23 is greater than the rotation speed of the adsorption platform 3, so as to grind the wafer.

[0096] A400. When the wafer is ground to the target thickness, stop the rotation and feed of the rotating shaft 22 and the adsorption platform 3, and control the feed assembly to drive the grinding wheel 23 to move upward and reset, so that the grinding surface of the grinding wheel 23 is separated from the wafer surface.

[0097] A500, release the vacuum adsorption of the adsorption platform, and transfer the wafer.

[0098] In this application, the thinning method enables precise wafer thinning. First, the wafer is adsorbed onto the adsorption platform 3 to ensure stable positioning during processing, providing a stable foundation for subsequent processes. Then, the feed assembly drives the grinding wheel 23 downward until it contacts the wafer, achieving precise initiation of the grinding operation. During the grinding stage, the grinding wheel 23 and the adsorption platform 3 rotate in the same direction, with the grinding wheel 23 rotating at a higher speed than the adsorption platform 3. Simultaneously, the grinding wheel 23 continues to feed downward. Through the coordinated control of the speed difference and feed amount, the wafer is ground. When the wafer thickness reaches the target value, the rotation of the grinding wheel 23 and the adsorption platform 3 is immediately stopped, and the feed assembly drives the grinding wheel 23 upward to detach from the wafer, avoiding over-processing. Finally, the adsorption force of the adsorption platform 3 on the wafer is released, and the wafer transfer is completed, forming a closed loop in the entire process.

[0099] The key to the entire process is: First, by positioning the adsorption platform 3 and controlling the feed of the grinding wheel 23, the wafer is ensured to be subjected to uniform force during the thinning process, which effectively improves the flatness and processing accuracy of the wafer; Second, the design of rotation in the same direction and speed difference reduces stress concentration during the grinding process, reduces the risk of wafer damage, and improves product yield; Third, the fully automated operation improves processing efficiency and stability, making it suitable for large-scale production scenarios.

[0100] In one embodiment of this application, in step A300, the rotational speed of the grinding wheel 23 is 3000~5000 rpm, and the rotational speed of the adsorption platform 3 is 200~400 rpm. The rotational speed of the grinding wheel 23 can be, for example, 3000 rpm, 4000 rpm, or 5000 rpm; the rotational speed of the adsorption platform 3 can be, for example, 200 rpm, 300 rpm, or 400 rpm, but is not limited to the listed values. Other unlisted values ​​within the range are also applicable.

[0101] In this application, the high-speed differential rotation of the grinding wheel 23 and the adsorption platform 3, in conjunction with their co-rotation, ensures that the contact trajectory between the grinding wheel 23 and the wafer surface is continuously spirally distributed, avoiding thickness deviations caused by localized repeated grinding and helping to keep the total thickness deviation of the wafer after thinning stable at a low level. On the other hand, it reduces the reverse impact of the grinding wheel 23 on the wafer surface. Combined with the continuous grinding characteristics of high speed, it can reduce the instantaneous grinding force, reduce lattice distortion and microcrack generation, and help to keep the subsurface damage of the wafer after thinning stable at a low level.

[0102] In one embodiment of this application, in step A300, the downward feed rate is 2~6 μm / s, for example, it can be 2 μm / s, 4 μm / s, or 6 μm / s, but it is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0103] In this application, the grinding wheel 23 is controlled to feed downward at a speed of 2~6 μm / s while rotating, which can achieve uniform grinding layer by layer, effectively control the total thickness deviation of the wafer after thinning, and avoid local over-grinding or thickness fluctuation caused by excessive feed.

[0104] According to another aspect of this application, this application also proposes a grinding wheel, including a substrate 231 and a plurality of grinding blocks 232 disposed on the surface of the substrate 231 for grinding wafers. The raw materials of the grinding blocks 232 include the following components: abrasive grains, polymer microspheres, ceramic binder sol, and zirconium / cerium composite nano-sol for coating the abrasive grains. The zirconium / cerium composite nano-sol is calcined and then coated on the surface of the abrasive grains to form a composite nano-coating. The composite nano-coating consists of cerium oxide and zirconium oxide.

[0105] In terms of composition, polymer microspheres, as pore-forming agents, can effectively regulate the pore structure inside the grinding block 232, achieving the functions of chip removal, heat dissipation, and dispersion of grinding stress. The polymer microspheres can be polystyrene microspheres or polymethyl methacrylate microspheres, with polymethyl methacrylate microspheres being preferred. The zirconium / cerium composite nanosol can be sintered at a low temperature below 600°C to form a composite toughened structure with zirconium oxide / cerium oxide, which can inhibit crack propagation, improve the service life of the grinding wheel 23, and ensure the grinding quality of the wafer.

[0106] In one embodiment of this application, the zirconium / cerium composite nanosol comprises the following components by weight: 1-1.5 parts of oxygen-containing zirconium source, 1.8-2.5 parts of oxygen-containing cerium source, and 2-3.5 parts of complexing acid.

[0107] In one embodiment of this application, the ceramic binder sol comprises the following components in parts by weight: 28-32 parts of oxygen-containing silicon source, 5-6.5 parts of oxygen-containing aluminum source, 1.5-2 parts of oxygen-containing boron source, and 4-6 parts of complexing acid.

[0108] In one embodiment of this application, the complexing acid is one or more of citric acid, acetic acid, and oxalic acid, preferably citric acid.

[0109] In one embodiment of this application, the oxygen-containing zirconium source is zirconium nitrate; the oxygen-containing cerium source is cerium nitrate, which is recovered from cerium-containing grinding waste liquid by using ammonium nitrate as a recovery agent. This application recycles resources from cerium-containing grinding waste liquid by using ammonium nitrate as a recovery agent, replacing the strong acid dissolution in the prior art, reducing energy consumption and production costs, and is suitable for scenarios with strict environmental protection requirements and the pursuit of high-purity products in wafer thinning.

[0110] In one embodiment of this application, the polymer microspheres include a first polymer microsphere with an average particle size of 100-110 μm, a second polymer microsphere with an average particle size of 15-25 μm, and a third polymer microsphere with an average particle size of 3-5 μm.

[0111] In one embodiment of this application, the weight ratio of the first polymer microsphere to the second and third polymer microspheres is 3~4:2.5~3.5:2~3, for example, it can be 3:2.5:2, 3.5:3:2.5, or 4:3.5:3, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0112] In this application, when the weight ratio of the first polymer microsphere to the second and third polymer microspheres is 3~4:2.5~3.5:2~3, the multi-pore structure reaches its optimal state, and the pore structure has the best effect on improving the overall performance of the grinding block 232, which can further improve the grinding quality of the wafer.

[0113] In one embodiment of this application, the abrasive grain 2321 is preferably diamond modified with a silane coupling agent; the polymer microspheres are polymer microspheres modified with a silane coupling agent.

[0114] In this application, the silane coupling agent can bond with the hydroxyl groups on the diamond surface through hydrolysis. After modification with the silane coupling agent, the final nanocomposite coating 2322 can chemically bond with the diamond, improving the interfacial bonding strength between the composite nanocoating 2322 and the diamond. Modification with the silane coupling agent can reduce the hydrophilicity of the polymer microspheres, preventing their aggregation in the gel system due to hydrophilic groups on their surface, and improving their dispersion ability in the gel system.

[0115] In one embodiment of this application, the raw material of grinding block 232 also includes 3 to 5 parts by weight of dispersant, for example, 3, 4 or 5 parts, but not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0116] In this application, the dispersant can be a silane coupling agent. By adding the dispersant, the hydrophilicity of diamond and polymer microspheres can be reduced, making them easier to disperse in the gel system, thereby ensuring the uniformity of the internal composition of the grinding block 232 and improving the grinding quality of the wafer.

[0117] According to another aspect of this application, a method for preparing the aforementioned grinding wheel is also provided, comprising the following steps:

[0118] B100. The abrasive grains are immersed in zirconium / cerium composite nanosol and dried to obtain sol-coated abrasive grains.

[0119] B200, calcine the sol-coated abrasive particles at 450~550℃ for 2~4 h to obtain zirconium / cerium composite nano-coated abrasive particles;

[0120] B300: Add polymer microspheres, dispersant and zirconium / cerium composite nano-coated abrasive particles to ceramic binder sol, mix evenly to obtain slurry;

[0121] B400. The slurry is injected into the mold, cold-pressed, and sintered to obtain grinding block 232.

[0122] B500. The grinding block 232 is placed on the surface of the substrate 231 to obtain the grinding wheel 23.

[0123] In this application, abrasive grains are thoroughly wetted with a zirconium / cerium composite nanosol, and then sintered at a temperature below 600°C. A composite nano-coating 2322 is then coated onto the surface of the abrasive grains 2321 using a sol-gel method, which significantly improves the interfacial bonding strength between the composite nano-coating 2322, the abrasive grains 2321, and the ceramic substrate 2324. The composite nano-coating 2322 stabilizes the tetragonal phase of zirconium oxide through cerium oxide solid solution, and its phase transformation toughening effect enhances the holding force on the abrasive grains 2321, effectively reducing abnormal particle shedding during grinding, lowering the wafer edge chipping rate, extending the service life of the grinding wheel 23, and improving the grinding quality of the wafer. In step B200, by setting the temperature and holding time, synchronous crystallization of zirconium oxide and cerium oxide can be ensured, avoiding phase separation or uneven size.

[0124] In one embodiment of this application, in step B200, the heating rate is 4~6℃ / min. For example, the heating rate can be 4℃ / min, 5℃ / min, or 6℃ / min, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable. By setting a slower heating rate, structural damage or component segregation due to excessive gas escape can be avoided.

[0125] In one embodiment of this application, step B100 includes the following steps:

[0126] B110. Dissolve 1-1.5 parts zirconium nitrate and 1.8-2.5 parts cerium nitrate in water, adjust the pH to 2-3, add 2-3.5 parts complexing acid to complex, adjust the pH to 6-7, stir in a water bath at 65-75℃ for 5-7 h to obtain zirconium / cerium composite nanosol.

[0127] B120. 15-18 parts of abrasive particles and 0.3-0.5 parts of silane coupling agent are ultrasonically treated with anhydrous ethanol for 15-20 min, and then dried to obtain modified abrasive particles.

[0128] B130. The modified abrasive grains are immersed in zirconium / cerium composite nanosol and dried to obtain sol-coated abrasive grains.

[0129] The complexing acid is one or more of citric acid, acetic acid, and oxalic acid, with citric acid being preferred. The acid complexation process can regulate the reactivity of metal ions in the raw materials. Through the action of acid, metal ions form complexes with acid radicals, changing the state of the metal ions and making them more responsive to other components. This is beneficial for the composite binder to form a denser and more stable structure during sintering.

[0130] In this application, by modifying the abrasive grains with silane, the final composite nano-coating 2322 can form a chemical bond coating on the surface of the abrasive grains 2321, thereby improving the interfacial bonding strength between the composite nano-coating 2322 and the abrasive grains 2321.

[0131] In this application, adjusting the pH to acidic before complexation with complexing acids can prevent the precipitation of zirconium and cerium ions, thus avoiding affecting the uniformity of the sol. When the pH is 2-3, it can prevent the hydrolysis of metal ions from being inhibited due to excessively low pH, which would prevent the formation of enough precursors to construct the gel network structure. On the other hand, it can prevent the hydrolysis of metal ions from being too rapid due to excessively high pH, ​​which would lead to the formation of large-particle precipitates in local areas and affect the uniformity of the sol.

[0132] In this application, when the water bath stirring temperature is 65~75℃ and the time is 5~7 h, on the one hand, the hydrolysis reaction and the polycondensation reaction can proceed at an appropriate rate, so that the formation of uneven gel is not caused by the reaction rate being too fast, and the preparation cycle is not prolonged due to the reaction rate being too slow; on the other hand, it helps the zirconium ions and cerium ions to be better dispersed in the system.

[0133] In one embodiment of this application, cerium nitrate is recovered from cerium-containing grinding waste liquid by using ammonium nitrate as a recovery agent, preferably from the grinding liquid of chemical mechanical polishing, thereby helping to alleviate the scarcity of cerium resources.

[0134] The treatment of chemical mechanical polishing (CMP) waste fluid has always been a complex and costly process. Existing processes require the use of strong acids to dissolve impurities in the cerium-containing polishing fluid, followed by a precipitation-calcination process to recover cerium oxide, which can then be reused as an abrasive in new polishing fluids. This process not only involves high corrosion and wear on equipment due to the strong acid but also releases toxic gases such as chlorine and sulfur dioxide, and is prone to side reactions that reduce cerium recovery rates.

[0135] In one embodiment of this application, cerium nitrate is obtained by the following steps: after crushing, enriching and centrifuging cerium-containing grinding waste liquid, a chelating agent and ammonium nitrate are added, followed by ball milling, separation, concentration and drying to obtain cerium nitrate.

[0136] The cerium nitrate in this application is derived from cerium-containing grinding waste liquid, which helps reduce costs and increase production capacity. On the other hand, this application uses the NH4NO3 recovery method, which solves the problem that existing physical separation technologies can only remove coarse particulate impurities with an average particle size greater than 10 μm, and have insufficient removal rates for alumina nanoparticles and silica nanoparticles with an average particle size less than 100 nm, through a synergistic mechanism of physical and chemical methods. By replacing traditional strong acids with NH4NO3, strong acid-free dissolution is achieved, which has advantages such as strong environmental friendliness, high impurity removal rate, high product purity, low reagent cost, high recovery rate, and low wastewater treatment cost.

[0137] In one embodiment of this application, ultrasonic treatment is used during crushing. The frequency of ultrasonic treatment is 20-60 kHz, and the power is 200-500 W. On the one hand, ultrasound generates a strong cavitation effect in cerium-containing grinding waste liquid, which assists in the crushing and refining of particles; on the other hand, it can also make the components in the whole system more uniformly distributed, avoiding local concentrations that are too high or too low, and providing a more uniform environment for subsequent enrichment. The frequency of ultrasonic treatment can be 20 kHz, 40 kHz, or 60 kHz; the power can be 200 W, 300 W, 400 W, or 500 W, but is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0138] In one embodiment of this application, enrichment is achieved using magnetic adsorption. The magnetic field strength for magnetic adsorption is 3-8 T, for example, 3 T, 4 T, 5 T, 6 T, 7 T, or 8 T, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable. Since cerium oxide can interact with the magnetic field, it can be effectively adsorbed and separated. Therefore, in this application, magnetic adsorption is used for enrichment. When the magnetic field strength for magnetic adsorption is 3-8 T, magnetic adsorption exhibits high selectivity for cerium enrichment and poor adsorption of other impurities, effectively separating cerium oxide from impurities, thereby improving the purity of the subsequently recovered cerium nitrate.

[0139] In one embodiment of this application, the centrifugation speed is 8000~10000 rpm, for example, 8000 rpm, 9000 rpm, or 10000 rpm, but not limited to the listed values; other unlisted values ​​within the above range are also applicable. In this application, when the centrifugation speed is 8000~10000 rpm, nano-sized cerium oxide particles can achieve efficient sedimentation, thereby separating them from the waste liquid and providing pure raw materials for subsequent steps.

[0140] In one embodiment of this application, the ball mill rotates at a speed of 600 to 1000 rpm for 1 to 4 hours. For example, the rotation speed can be 600 rpm, 800 rpm, or 1000 rpm, but it is not limited to the listed values. Other unlisted values ​​within the above range are also applicable.

[0141] In this application, zirconia balls are used as the milling medium during ball milling to mechanically disrupt the crystal structure of cerium oxide. When the ball milling speed is 600~1000 rpm and the time is 1~4 h, the collision frequency and force between the milling medium and the cerium oxide particles are moderate, which can break larger particles into smaller particles, increase the specific surface area of ​​the cerium oxide particles, and facilitate subsequent reactions with nitrate ions.

[0142] In one embodiment of this application, after adding the chelating agent and ammonium nitrate, the concentration of the chelating agent is 0.5~1.5 mol / L, and the concentration of ammonium nitrate is 2~4 mol / L. For example, the concentration of the chelating agent can be 0.5 mol / L, 1 mol / L, or 1.5 mol / L; the concentration of ammonium nitrate can be 2 mol / L, 3 mol / L, or 4 mol / L, but is not limited to the listed values; other unlisted values ​​within the above range are also applicable. The chelating agent can be ethylenediaminetetraacetic acid, sodium tripolyphosphate, or ethylenediaminetetramethylenephosphonic acid, preferably ethylenediaminetetraacetic acid.

[0143] In this application, the chelating agent can form stable complexes with impurity ions such as aluminum and silicon, while cerium oxide does not participate in the reaction due to its high chemical stability. When the concentration of the chelating agent is 0.5~1.5 mol / L, the interference of impurity ions can be minimized. Ammonium nitrate provides nitrate ions for the formation of cerium nitrate. When the concentration of ammonium nitrate is 2~4 mol / L, sufficient nitrate ions and cerium ions can be combined to promote the formation of cerium nitrate.

[0144] In one embodiment of this application, in step B300, the ceramic binder sol is obtained through the following steps: 28-32 parts of an oxygen-containing silicon source, 5-6.5 parts of an oxygen-containing aluminum source, and 1.5-2 parts of an oxygen-containing boron source are dissolved in a solvent; 4-6 parts of a complexing acid are added; the pH is adjusted to 4-5; the mixture is stirred in a water bath at 60-80°C for 5-7 hours; and then aged for 36-60 hours to obtain the ceramic binder sol. The solvent is a mixture of ethanol and water, with a volume ratio of ethanol to water of 1:1-2, for example, 1:1, 1:1.5, or 1:2, but not limited to the listed values; other unlisted values ​​within the above range are also applicable.

[0145] In this application, when the aging time is 36 to 60 hours, on the one hand, the gel network structure can be made more compact, and on the other hand, impurities in the system have enough time to accumulate and precipitate, thereby improving the purity of the composite binder.

[0146] In one embodiment of this application, in step B300, the polymer microspheres include a first polymer microsphere with an average particle size of 100-110 μm, a second polymer microsphere with an average particle size of 15-25 μm, and a third polymer microsphere with an average particle size of 3-5 μm.

[0147] In one embodiment of this application, the weight ratio of the first polymer microsphere to the second and third polymer microspheres is 3~4:2.5~3.5:2~3.

[0148] In one embodiment of this application, the polymer microspheres are polymer microspheres modified with a silane coupling agent.

[0149] In one embodiment of this application, step B300 includes the following steps: adding 7-10 parts of polymer microspheres, 3-5 parts of dispersant, and zirconium / cerium composite nano-coating abrasive particles obtained in step B200 to a ceramic binder sol, mixing them evenly to obtain a slurry.

[0150] In one embodiment of this application, step B300, cold pressing is performed in three stages:

[0151] In the first stage, the pressure is increased to 8-12 MPa at a rate of 5-10 MPa / s and held for 1-2 minutes.

[0152] In the second stage, the pressure is increased to 40-55 MPa at a rate of 5-10 MPa / s and held for 2-4 minutes.

[0153] In the third stage, the pressure is increased to 80-90 MPa at a rate of 5-10 MPa / s, held for 4-6 minutes, and then depressurized to 0 MPa at a rate of 5-8 MPa / s.

[0154] In this application, cold pressing is carried out in three stages to ensure uniform density of the blank. In the first stage, the slurry is initially compacted to remove surface air. In the second stage, the blank gradually densifies under medium pressure, and the internal pores gradually decrease. In the third stage, high pressure promotes densification of the blank, ensuring uniform density, and then the blank is smoothly pushed out of the mold to avoid cracking caused by mechanical impact.

[0155] In one embodiment of this application, in step B300, sintering is carried out in four stages under inert gas protection:

[0156] In the first stage, the temperature is increased to 200-210℃ at a heating rate of 4.5-5℃ / min, and held for 1-1.5 hours.

[0157] In the second stage, the temperature is increased to 230-240℃ at a heating rate of 1.5-2℃ / min, and held for 0.5-1 h.

[0158] In the third stage, the temperature is increased to 390-400℃ at a heating rate of 0.5-1℃ / min, and held for 2-2.5 hours.

[0159] In the fourth stage, the temperature is further increased to 570-580℃ at a heating rate of 2.5-3℃ / min, held for 3-3.5 h, and then cooled to room temperature with the furnace.

[0160] In this application, sintering is carried out under inert gas protection, such as nitrogen protection, to prevent abrasive grain oxidation. In the first stage of sintering, residual solvent is removed to prevent internal cracking of the abrasive block 232. In the second stage, the polymer microspheres begin to soften. In the third stage, the polymer microspheres begin to slowly decompose, forming pores. The gases produced during decomposition are promptly removed with the inert gas to prevent internal pressure damage to the blank. In the fourth stage, the in-situ generation of boron oxide liquid phase from an oxygen-containing boron source, such as boric acid, also avoids high-temperature graphitization when diamond is used as an abrasive grain.

[0161] The present application will be described in detail below with reference to examples. The embodiments described below according to the present application can be modified in various forms, therefore the scope of the present application should not be construed as limited to the embodiments described in detail below. Examples are provided to help those skilled in the art to more easily understand the present application.

[0162] Unless otherwise specified, all parts in the following examples and comparative examples are by weight. The average particle size of the diamond is 2.5 μm. The cerium-containing grinding waste liquid is composed of the following components by weight percentage: cerium oxide 14.26%, silicon dioxide 3.21%, potassium persulfate 0.51%, citric acid 0.23%, 1,2,4-triazole 0.08%, nonylphenol polyoxyethylene ether 0.17%, and the balance is water. The dispersant is silane coupling agent KH570.

[0163] Example 1

[0164] like Figure 1 and Figure 2 The wafer thinning equipment shown includes a substrate 1, on which a rotating disk 4 is mounted. Above the rotating disk 4 are multiple adsorption platforms 3 spaced apart along the circumference. The rotating disk 4 can rotate around its central axis to change the position of the adsorption platforms 3, so that the wafers supported by the adsorption platforms 3 can switch between rough grinding station, fine grinding station and loading / unloading station.

[0165] The end of the equipment base 1 is equipped with an upright support, and two grinding devices 2 are arranged on the side of the support. One is a rough grinding part and the other is a fine grinding part. The two have similar structures and are equipped with a feed assembly (not shown) that drives the grinding wheel 23 to move up and down and a mechanism that drives the grinding wheel to rotate along the rotating shaft 22. The feed assembly includes a lifting motor (not shown), which is slidably connected to the housing of the rotating shaft through a lead screw. The housing is slidably connected to the side of the column so that the rotation of the lifting motor realizes the vertical movement of the rotating shaft 22, thereby changing the position of the grinding wheel 23 relative to the adsorption platform 3.

[0166] The adsorption platform 3 is used to support the wafer and drive the wafer to rotate. The grinding device 2 is raised and lowered above the adsorption platform 3. The lower part of the grinding device 2 has a grinding wheel 23 that can rotate circumferentially to grind the wafer.

[0167] The grinding apparatus 2 includes a feed assembly, a rotary shaft 22, and a grinding wheel 23. The grinding block 232 in the grinding wheel 23 is used to grind the wafer. The grinding wheel 23 may be a cup-shaped grinding wheel, mounted at the lower end of the rotary shaft 22. The rotary shaft 22 is used to rotate the grinding wheel 23 about its axis of rotation. The feed assembly can drive the rotary shaft 22 and the grinding wheel 23 to move up and down synchronously. When the wafer needs grinding, the grinding wheel 23 moves down to its bottom surface and contacts the wafer under the drive of the feed assembly. At this time, both the grinding wheel 23 and the wafer are rotating in the same direction but at different speeds, and the grinding wheel 23 is used to grind the wafer. The feed assembly has a known structure and includes, for example, multiple linear guides that guide the movement direction of the rotary shaft 22 and a ball screw-slider mechanism that moves the rotary shaft 22 up and down.

[0168] The grinding wheel 23 includes a plurality of grinding blocks 232, which may be rounded rectangles or fan-shaped, and at least a portion of these grinding blocks 232 are embedded in an annular groove and spaced apart from each other on the substrate 231. The substrate 231 can be fastened to the lower end of the rotating shaft 22 by bolts.

[0169] The adsorption platform 3 has a chuck spindle 31, a worktable 32, and an adsorption disk 33. The chuck spindle 31 moves along the axis of rotation. The adsorption disk 33, made of a porous material such as alumina, is embedded in the upper surface of the worktable 32. The adsorption platform 3 has a conduit that penetrates its interior and extends to its surface. The conduit is connected to a vacuum source, a compressed air source, or a water supply source via a rotary joint. When the vacuum source is activated, the wafer placed on the adsorption platform 3 is adsorbed by the adsorption disk 33. Conversely, when the compressed air source or water supply source is activated, the adsorption between the wafer and the adsorption disk 33 is released. The adsorption platform 3 may be equipped with a tilting device that tilts relative to the grinding wheel 23, or the grinding device 2 may be equipped with a tilting structure that tilts the rotation axis 22. This allows adjustment of the contact between the grinding block 232 and the wafer to grind the wafer into the desired shape.

[0170] The operation of the grinding device 2 is controlled by a control device. The control device controls each component of the grinding device 2. The control device includes, for example, a CPU and a memory. Furthermore, the function of the control device can be implemented through software control or through hardware operation. For example, the control device can control the movement of the feed assembly, the rotary axis 22, and the chuck spindle 31 according to preset grinding process parameters, such as feed rate and rotational speed, to achieve an automated grinding process. Simultaneously, the control device also has fault diagnosis and alarm functions, capable of monitoring the operating status of each part of the equipment in real time, issuing alarms promptly and taking corresponding protective measures when abnormalities occur, ensuring the safety of the equipment and operators.

[0171] Example 2

[0172] The wafer thinning method, using the wafer thinning equipment of Example 1, includes the following steps:

[0173] A100. Vacuum adsorption fixes the wafer onto adsorption platform 3:

[0174] A110. Preparation: Before performing wafer thinning operation, ensure that the surface of the adsorption platform 3 is clean and free of impurities to avoid impurities affecting the adsorption effect and grinding quality of the wafer. You can use a lint-free cloth dipped in an appropriate amount of alcohol to wipe and clean the surface of the adsorption platform 3.

[0175] A120. Place the wafer: Use a vacuum pen or other precision gripping tool to place the wafer to be thinned on the adsorption platform 3, ensuring that the center of the wafer is aligned with the center of the adsorption platform 3.

[0176] A130. Initiating Vacuum Adsorption: The vacuum source connected to the adsorption platform 3 is activated via the control device. The porous structure inside the adsorption platform 3 creates a negative pressure under vacuum, adsorbing the wafer onto its surface. To ensure strong adsorption, the vacuum level of the adsorption platform 3 can be monitored in real time via the control device. When the vacuum level reaches the preset value, it indicates that the wafer has been stably adsorbed and the next step can be performed.

[0177] A200, the control feed assembly drives the rotary axis and grinding wheel to move vertically downwards until the grinding surface of the grinding wheel contacts the wafer:

[0178] A210. Parameter setting: Input the target position parameter for the movement of the grinding wheel 23 into the control device. This parameter is determined based on factors such as the thickness of the wafer, the grinding allowance, and the initial position of the grinding wheel 23.

[0179] A220. Start the feed assembly: The control device sends a command to the feed assembly to precisely determine its direction of movement, ensuring it moves vertically downwards. The feed assembly drives the grinding wheel 23 to move smoothly downwards at a set speed. During the movement, the control device monitors the position information of the feed assembly in real time and compares it with the preset target position. When it approaches the target position, the feed speed is reduced to achieve precise alignment.

[0180] A300: The grinding wheel 23 and the adsorption platform 3 rotate in the same direction, simultaneously driving the grinding wheel 23 downward. The rotational speed of the grinding wheel 23 is greater than that of the adsorption platform 3, in order to grind the wafer.

[0181] A310, Rotary Start: The control device simultaneously starts the grinding wheel 23 and the adsorption platform 3. The grinding wheel 23 rotates at a high speed at a set speed, while the adsorption platform 3 and the wafers adsorbed on it rotate in the same direction at a relatively low speed.

[0182] A320. Grinding: After the grinding wheel 23 and the adsorption platform 3 reach a stable rotation state, the control device continues to control the feed assembly, causing the grinding wheel 23 to feed onto the wafer. During the feeding process, a pressure sensor mounted on the grinding wheel 23 monitors the contact pressure between the grinding wheel 23 and the wafer in real time and feeds it back to the control device. When the pressure reaches a preset value, such as 5 N, the control device stops the feeding action of the feed assembly to ensure that the grinding wheel 23 and the wafer maintain a suitable grinding pressure, which ensures the grinding effect while avoiding excessive pressure that could damage the wafer. After the grinding wheel 23 and the wafer are adjusted to a suitable grinding pressure, the grinding wheel 23 and the adsorption platform 3 continue to rotate, and the grinding block 232 of the grinding wheel 23 grinds the surface of the wafer.

[0183] Grinding Parameter Monitoring and Adjustment: During the grinding process, the control device monitors several key parameters in real time, such as the rotational speed of the grinding wheel 23, the rotational speed of the adsorption platform 3, the grinding pressure, and the grinding time. These parameter information is collected in real time by sensors installed in key parts of the wafer thinning equipment, such as speed sensors, pressure sensors, and thickness sensors, and fed back to the control device. The control device dynamically adjusts the grinding process based on the preset grinding process model and the actual collected parameter data.

[0184] A400: When the wafer is ground to the target thickness, stop the rotation of the rotary axis and the adsorption platform, and stop the feed. Control the feed assembly to drive the grinding wheel to move upward and reset, so that the grinding surface of the grinding wheel is separated from the wafer surface.

[0185] A410. Thickness Detection and Judgment: A non-contact thickness sensor installed near the grinding wheel 23 continuously monitors the thickness change of the wafer and feeds back the real-time thickness data to the control device. When the control device receives thickness data showing that the wafer has been ground to the target thickness, it determines that the grinding is complete.

[0186] A420. Stopping Rotation and Separating the Grinding Wheel: The control device immediately issues a command to stop the rotation of the grinding wheel 23 and the adsorption platform 3. Subsequently, the control device activates the feed assembly to move the grinding wheel 23 upward at a set speed, so that the grinding wheel 23 is quickly separated from the wafer, avoiding unnecessary damage caused by prolonged contact between the grinding wheel 23 and the wafer surface after it stops rotating.

[0187] A500: De-attach to the wafer and transfer the wafer.

[0188] A510. Gas Source Switching: The control device shuts off the vacuum source and switches to either compressed air or water supply, depending on the actual process. Compressed air or water enters the adsorption platform 3, disrupting the negative pressure between the adsorption platform 3 and the wafer, thereby releasing the adsorption force.

[0189] A520. Wafer Removal: Using a vacuum pen or other precision gripping tools, the thinned wafer is removed from the adsorption platform 3, completing the entire wafer thinning process.

[0190] Example 3

[0191] The method for preparing a grinding wheel includes the following steps:

[0192] B110. Dissolve 1.3 parts of zirconium nitrate and 2.2 parts of cerium nitrate (commercially available nano-grade) in 60 parts of water, add hydrochloric acid to adjust the pH to 2.5, add 3 parts of citric acid to complex, stir evenly, adjust the pH to 6.5 with ammonia, and treat with water bath stirring at 70℃ for 6 h to obtain zirconium / cerium composite nano sol.

[0193] B120. 16.5 parts of diamond and 0.4 parts of silane coupling agent KH570 were ultrasonically cleaned with anhydrous ethanol for 15 min, dried at 80℃ and then sieved to obtain modified diamond.

[0194] B130. The modified diamond is immersed in the above zirconium / cerium composite nanosol and dried to obtain sol-coated diamond.

[0195] B200. The above-mentioned sol-coated diamond was heated to 500℃ at 5℃ / min and calcined for 3 h to obtain zirconium / cerium composite nano-coated diamond.

[0196] B210. Dissolve 30 parts of tetraethyl orthosilicate, 5.8 parts of aluminum nitrate, and 1.8 parts of boric acid in 450 parts of mixed solvent (the mixed solvent is a solvent with a volume ratio of ethanol and water of 1:1), add 5 parts of citric acid to complex, adjust the pH value to 4.5 with hydrochloric acid, stir in a water bath at 70°C for 6 h, and age for 48 h to obtain ceramic binder sol.

[0197] B300, 8.5 parts of polymethyl methacrylate microspheres (average particle size of 100 μm), 4 parts of dispersant, and the above-mentioned zirconium / cerium composite nano-coated diamond were added to the above-mentioned ceramic binder sol. The mixture was ultrasonically treated in an ice-water bath at 300 W for 40 min to prevent gelation, and then magnetically stirred at 1000 rpm for 3 h until homogeneous to obtain a slurry.

[0198] B400. The slurry is injected into the mold, cold-pressed, and sintered to obtain the grinding block;

[0199] Cold pressing is carried out in three stages:

[0200] In the first stage, the pressure is increased to 10 MPa at a rate of 5 MPa / s and held for 1 min.

[0201] In the second stage, the pressure is increased to 50 MPa at a rate of 5 MPa / s and held for 2 minutes.

[0202] In the third stage, the pressure is increased to 80 MPa at a rate of 5 MPa / s, held for 5 minutes, and then depressurized to 0 MPa at a rate of 5 MPa / s.

[0203] Sintering was carried out in four stages under nitrogen protection (nitrogen flow rate of 1.5 L / min):

[0204] In the first stage, the temperature is increased to 200℃ at a heating rate of 5℃ / min and held for 1 hour.

[0205] In the second stage, the temperature was increased to 240℃ at a rate of 2℃ / min and held for 0.5 h.

[0206] In the third stage, the temperature was increased to 400℃ at a rate of 1℃ / min and held for 2 hours.

[0207] In the fourth stage, the temperature was increased to 580℃ at a rate of 3℃ / min, held for 3 hours, and then cooled to room temperature in the furnace.

[0208] B500: The grinding block is bonded to the surface of the aluminum substrate to obtain the grinding wheel.

[0209] Example 4

[0210] The difference between this embodiment and embodiment 3 is as follows:

[0211] The polymethyl methacrylate microspheres are modified polymethyl methacrylate microspheres. The specific modification method is as follows: 8.5 parts of polymethyl methacrylate microspheres and 0.8 parts of silane coupling agent KH570 are added to anhydrous ethanol, ultrasonically cleaned at 300 W for 20 min, and then dried at 80℃ for 2 h to obtain the product.

[0212] Everything else is the same as in Example 3.

[0213] Example 5

[0214] The only difference between this embodiment and Embodiment 4 is that in this embodiment, cerium nitrate is prepared from cerium-containing grinding waste liquid. The specific preparation method is as follows: the cerium-containing grinding waste liquid is ultrasonically crushed (ultrasonic frequency 40 kHz, power 300 W), and then directionally adsorbed and enriched using a superconducting magnet (magnetic field strength 5 T). After high-speed centrifugation at 10000 rpm, impurities are removed to obtain a mixed liquid. The mixed liquid is loaded into a planetary ball mill, and ethylenediaminetetraacetic acid is added to a concentration of 1 mol / L and ammonium nitrate is added to a concentration of 3 mol / L. Zirconia balls are used as the ball milling medium, and the mixture is ball-milled at 800 rpm for 2.5 h. After filtration, the filtrate is evaporated and concentrated at 80℃, cooled to 8℃ for crystallization for 12 h, and then vacuum dried at 60℃ for 4 h to obtain anhydrous cerium nitrate.

[0215] Example 6

[0216] The only difference between this embodiment and Embodiment 5 is that, in this embodiment, the average particle size of the modified polymethyl methacrylate microspheres is 20 μm.

[0217] Example 7

[0218] The only difference between this embodiment and Embodiment 5 is that, in this embodiment, the average particle size of the modified polymethyl methacrylate microspheres is 4 μm.

[0219] Example 8

[0220] The only difference between this embodiment and Example 5 is that, in this embodiment, the modified polymethyl methacrylate microspheres include 3.5 parts of the first modified polymethyl methacrylate microspheres (average particle size of 100 μm), 2.5 parts of the second modified polymethyl methacrylate microspheres (average particle size of 20 μm), and 2.5 parts of the third modified polymethyl methacrylate microspheres (average particle size of 4 μm).

[0221] A schematic diagram of the structure of the grinding block in the grinding wheel prepared in this embodiment is shown below. Figure 5 As shown, the SEM image of the grinding block in the grinding wheel is as follows. Figure 6 As shown in the figure, the porous structure is distributed in a multi-level packing pattern with different particle sizes. Pore 2323 is composed of large pores 23231, medium pores 23232, and small pores 23233 with different particle sizes. A magnified view of a part of the grinding block is shown below. Figure 7 As shown, and Figure 7 The corresponding EDS layered diagram of zirconium is as follows: Figure 8 As shown, and Figure 7 The corresponding EDS layered diagram of cerium is as follows: Figure 9 As shown, from Figures 7-9 As can be seen, the composite nano-coating completely covers the diamond surface, confirming that the composite nano-coating prepared by the gel-sol method has excellent coating properties with diamond. Figure 10 The image shows the XRD pattern of the grinding block. There are diffuse peaks between 20° and 40°, corresponding to the amorphous glass phase structure in the ceramic matrix. There are diffraction peaks around 43° and 76°, corresponding to diamond. No diffraction peaks of graphite were found in the XRD pattern, indicating that this application can avoid the high-temperature graphitization of diamond. Figure 11 The image shows a TEM image of cerium-containing grinding waste liquid. It can be seen from the image that the cerium oxide is nanoscale. The cerium oxide nanoparticles have good dispersibility and uniform particle size, and can be recycled and reused.

[0222] Example 9

[0223] The method for preparing a grinding wheel includes the following steps:

[0224] B100. Dissolve 1 part zirconium nitrate and 1.8 parts cerium nitrate in 60 parts water, add hydrochloric acid to adjust the pH to 2, add 2 parts citric acid to complex, stir evenly, adjust the pH to 6 with ammonia, and treat with water bath stirring at 65℃ for 5 h to obtain zirconium / cerium composite nanosol.

[0225] Cerium nitrate was prepared from cerium-containing grinding waste liquid. The specific preparation method was as follows: the cerium-containing grinding waste liquid was ultrasonically crushed (ultrasonic frequency 20 kHz, power 200 W), and then directionally adsorbed and enriched using a superconducting magnet (magnetic field strength 3 T). After high-speed centrifugation at 8000 rpm, impurities were removed to obtain a mixed liquid. The mixed liquid was loaded into a planetary ball mill, and ethylenediaminetetraacetic acid was added to a concentration of 0.5 mol / L and ammonium nitrate was added to a concentration of 2 mol / L. Zirconia balls were used as the ball milling medium, and the mixture was ball milled at 600 rpm for 4 h. After filtration, the filtrate was evaporated and concentrated at 70℃, cooled to 8℃ for crystallization for 12 h, and then vacuum dried at 60℃ for 4 h to obtain anhydrous cerium nitrate.

[0226] B120. 15 parts of diamond and 0.3 parts of silane coupling agent KH570 were ultrasonically cleaned with anhydrous ethanol for 15 min, dried at 80℃ and then sieved to obtain modified diamond.

[0227] B130. The modified diamond is immersed in the above zirconium / cerium composite nanosol and dried to obtain sol-coated diamond.

[0228] B200. The above-mentioned sol-coated diamond was heated to 450℃ at 4℃ / min and calcined for 2 h to obtain zirconium / cerium composite nano-coated diamond.

[0229] B210. Dissolve 28 parts of tetraethyl orthosilicate, 5 parts of aluminum nitrate, and 1.5 parts of boric acid in 430 parts of mixed solvent (the mixed solvent is a solvent with a volume ratio of ethanol and water of 1:1.5), add 4 parts of citric acid to complex, adjust the pH value to 4 with hydrochloric acid, stir in a water bath at 65°C for 5 h, and age for 36 h to obtain ceramic binder sol.

[0230] B220: 3.5 parts of polymethyl methacrylate microspheres with an average particle size of 100 μm, 2.5 parts of polymethyl methacrylate microspheres with an average particle size of 15 μm, 2 parts of polymethyl methacrylate microspheres with an average particle size of 3 μm, and 0.5 parts of silane coupling agent KH570 were added to anhydrous ethanol, ultrasonically cleaned at 300 W for 20 min, and then dried at 80 °C for 2 h to obtain modified polymethyl methacrylate microspheres.

[0231] B300, the above modified polymethyl methacrylate microspheres, 3 parts of dispersant and the above zirconium / cerium composite nano-coated diamond were added to the above ceramic binder sol, ultrasonically treated in an ice water bath at 300 W for 40 min to prevent gelation, and then magnetically stirred at 1000 rpm for 3 h until uniform to obtain slurry.

[0232] B400. The slurry is injected into the mold, cold-pressed, and sintered to obtain the grinding block;

[0233] Cold pressing is carried out in three stages:

[0234] In the first stage, the pressure is increased to 8 MPa at a rate of 5 MPa / s and held for 2 minutes.

[0235] In the second stage, the pressure is increased to 40 MPa at a rate of 5 MPa / s and held for 4 minutes.

[0236] In the third stage, the pressure is increased to 80 MPa at a rate of 5 MPa / s, held for 6 minutes, and then depressurized to 0 MPa at a rate of 5 MPa / s.

[0237] Sintering was carried out in four stages under nitrogen protection (nitrogen flow rate of 1.5 L / min):

[0238] In the first stage, the temperature was increased to 200℃ at a heating rate of 4.5℃ / min and held for 1.5 h.

[0239] In the second stage, the temperature was increased to 230℃ at a rate of 1.5℃ / min and held for 1 hour.

[0240] In the third stage, the temperature was increased to 390℃ at a rate of 0.5℃ / min and held for 2.5 h.

[0241] In the fourth stage, the temperature was increased to 570℃ at a heating rate of 2.5℃ / min, held at that temperature for 3.5 h, and then cooled to room temperature with the furnace.

[0242] B500: The grinding block is bonded to the surface of the aluminum substrate to obtain the grinding wheel.

[0243] Example 10

[0244] The method for preparing a grinding wheel includes the following steps:

[0245] B110. Dissolve 1.5 parts zirconium nitrate and 2.5 parts cerium nitrate in 70 parts water, add hydrochloric acid to adjust the pH to 4, add 3.5 parts citric acid to complex, stir evenly, adjust the pH to 7 with ammonia, and treat in a water bath at 75℃ for 5 h to obtain zirconium / cerium composite nanosol; wherein, cerium nitrate is prepared from cerium-containing grinding waste liquid. The specific preparation method is as follows: the cerium-containing grinding waste liquid is ultrasonically crushed (ultrasonic frequency 60 kHz, power 500 W), and then directionally adsorbed and enriched with a superconducting magnet (magnetic field strength 8 T). After high-speed centrifugation at 8000 rpm, impurities are removed to obtain a mixture. The mixture is loaded into a planetary ball mill, ethylenediaminetetraacetic acid is added to a concentration of 1.5 mol / L, ammonium nitrate is added to a concentration of 4 mol / L, and zirconium oxide balls are used as the ball milling medium. The mixture is ball milled at 1000 rpm for 1 h, filtered, and the filtrate is evaporated and concentrated at 90℃, then cooled to 8℃ for crystallization. h, then vacuum dried at 60℃ for 4 h to obtain anhydrous cerium nitrate;

[0246] B120. 18 parts of diamond and 0.5 parts of silane coupling agent KH570 were ultrasonically cleaned with anhydrous ethanol for 15 min, dried at 80℃ and then sieved to obtain modified diamond.

[0247] B130. The modified diamond is immersed in the above zirconium / cerium composite nanosol and dried to obtain sol-coated diamond.

[0248] B200. The above-mentioned sol-coated diamond was heated to 550℃ at 6℃ / min and calcined for 4 h to obtain zirconium / cerium composite nano-coated diamond.

[0249] B210. Dissolve 32 parts of tetraethyl orthosilicate, 6.5 parts of aluminum nitrate, and 2 parts of boric acid in 480 parts of a mixed solvent (the mixed solvent is a solvent with a volume ratio of ethanol and water of 1:2). Add 6 parts of citric acid to complex the mixture. Adjust the pH value to 5 with hydrochloric acid. Stir the mixture in a water bath at 75°C for 7 hours and then age it for 60 hours to obtain a ceramic binder sol.

[0250] B220. Four parts of polymethyl methacrylate microspheres with an average particle size of 110 μm, three parts of polymethyl methacrylate microspheres with an average particle size of 25 μm, three parts of polymethyl methacrylate microspheres with an average particle size of 5 μm, and one part of silane coupling agent KH570 were added to anhydrous ethanol. After ultrasonic cleaning at 300 W for 20 min, the microspheres were dried at 80 °C for 2 h to obtain modified polymethyl methacrylate microspheres.

[0251] B300, the above modified polymethyl methacrylate microspheres, 5 parts of dispersant and the above zirconium / cerium composite nano-coated diamond were added to the above ceramic binder sol, ultrasonically treated in an ice water bath at 300 W for 40 min to prevent gelation, and then magnetically stirred at 1000 rpm for 3 h until uniform to obtain slurry.

[0252] B400. The slurry is injected into the mold, cold-pressed, and sintered to obtain the grinding block;

[0253] Cold pressing is carried out in three stages:

[0254] In the first stage, the pressure is increased to 12 MPa at a rate of 10 MPa / s and held for 1 min.

[0255] In the second stage, the pressure is increased to 55 MPa at a rate of 10 MPa / s and held for 2 minutes.

[0256] In the third stage, the pressure is increased to 90 MPa at a rate of 10 MPa / s, held for 4 minutes, and then depressurized to 0 MPa at a rate of 10 MPa / s.

[0257] Sintering was carried out in four stages under nitrogen protection (nitrogen flow rate of 1.5 L / min):

[0258] In the first stage, the temperature was increased to 200℃ at a heating rate of 4.5℃ / min and held for 1.5 h.

[0259] In the second stage, the temperature was increased to 230℃ at a rate of 1.5℃ / min and held for 1 hour.

[0260] In the third stage, the temperature was increased to 390℃ at a rate of 0.5℃ / min and held for 2.5 h.

[0261] In the fourth stage, the temperature was increased to 570℃ at a heating rate of 2.5℃ / min, held at that temperature for 3.5 h, and then cooled to room temperature with the furnace.

[0262] B500: The grinding block is bonded to the surface of the aluminum substrate to obtain the grinding wheel.

[0263] Example 11

[0264] The only difference between this embodiment and embodiment 8 is that in step B110 of this embodiment, the amount of zirconium nitrate added is 0.65 parts and the amount of cerium nitrate added is 1.1 parts.

[0265] Example 12

[0266] The only difference between this embodiment and embodiment 8 is that in step B110 of this embodiment, the amount of zirconium nitrate added is 2.6 parts and the amount of cerium nitrate added is 4.4 parts.

[0267] Comparative Example 1

[0268] The only difference between this comparative example and Example 8 is that zirconium nitrate was not added in step B110 of this example.

[0269] Comparative Example 2

[0270] The only difference between this comparative example and Example 8 is that cerium nitrate was not added in step B110 of this example.

[0271] Experimental Example 1: Mechanical Property Testing

[0272] The bending performance of the grinding blocks in Examples 3-12 and Comparative Examples 1-2 was tested. The specific test method was as follows: the grinding block sample was cut into rectangular strips of 3mm×4mm×45-50mm, the surface was ground to roughness Ra≤5nm, and the two end faces were perpendicular to the long axis with flatness deviation≤0.02mm.

[0273] The electronic universal testing machine conforming to ASTM E4 standard is equipped with a semi-hinged three-point bending fixture, with a lower support roller diameter of 3mm and a span of 30mm. The upper pressure head has a diameter of 3mm and is located at the midpoint of the span. The hardness of the fixture bearing cylinder is ≥HRC40.

[0274] The sample is placed horizontally on the support roller with its long axis perpendicular to the support roller. The midpoint of the span is aligned with the upper pressure head. A preload of 5-10N is applied to eliminate the gap. After confirming uniform contact, the sample is continuously loaded until it breaks. The load-displacement curve is recorded with a fracture load accuracy of ±0.5%.

[0275] Experiment Example 2 Grinding Performance Test

[0276] The grinding wheels prepared in Examples 3-12 and Comparative Examples 1-2 were used to grind 12-inch wafers. The surface roughness Ra of the thinned wafers and the service life of the grinding wheels were measured. The specific test method was as follows: The wafer was adsorbed onto the adsorption platform; the grinding wheel with an outer diameter of 300 mm × inner diameter of 237 mm × height of 32 mm was moved down to contact the wafer under the drive of the feed assembly; the grinding wheel and the adsorption platform rotated in the same direction, with the grinding wheel rotating at 4800 rpm and the adsorption platform rotating at 300 rpm; during rough grinding, the grinding wheel was fed downwards at a feed rate of 5 / 4 / 3 μm / s while rotating, and the cooling water flow rate was 4 L / min during the grinding process; after rough grinding, the grinding wheel prepared in this grinding block was used for fine grinding, with the grinding wheel being fed downwards at a feed rate of 0.3 / 0.2 / 0.1 μm / s while rotating, and the cooling water flow rate was 4 L / min during the grinding process, until the wafer grinding removal amount was 765. μm, the grinding wheel and adsorption platform stop rotating, the feed assembly drives the grinding wheel to move upward until it separates from the wafer; the adsorption platform releases the wafer from the wafer, and the wafer is transferred for testing.

[0277] The test results of the mechanical properties of the grinding block and the grinding performance of the grinding wheel are shown in Table 1 below.

[0278] Table 1. Test results of mechanical properties of grinding blocks and grinding performance of grinding wheels.

[0279]

[0280] As shown in Table 1, the bending strength, grinding wheel life, and surface roughness Ra of the thinned wafer obtained in Example 8 are significantly better than those in Comparative Examples 1 and 2. This indicates that compared with cerium oxide coating or zirconium oxide coating, the composite nano-coating of this application can significantly improve the mechanical properties of the grinding block and the grinding performance of the grinding wheel. This is because the zirconium oxide / cerium oxide composite phase obtained after sintering can improve the mechanical properties of the grinding block and the grinding performance of the grinding wheel through the synergistic effect of dispersion toughening and phase transformation toughening.

[0281] In Example 8, both the grinding wheel life and the surface roughness Ra of the thinned wafer were superior to those in Examples 5-7. This indicates that the multi-level stacked pores are beneficial for improving grinding wheel life and wafer surface grinding quality. This is because medium and small pores, together with large pores, form interconnected chip removal channels, accelerating heat dissipation and chip removal, thereby improving the grinding surface quality, wafer surface roughness, reducing the number of grinding wheel dressings due to chip clogging, increasing the number of wafers processed per hour, and extending grinding wheel life. Furthermore, the medium pores filling the gaps between large pores alter the original transmission direction of grinding stress, slowing down the transmission speed and achieving the effect of dispersing grinding stress. Small pores also mitigate the weakening of interfacial bonding strength caused by large pores, preventing abrasive grain shedding and edge chipping during wafer grinding, which affects the wafer grinding quality. Therefore, through multi-level stacked pores, the chip removal, heat dissipation, buffering capacity, and abrasive grain stability of the grinding block can be improved. While meeting the bending strength requirements, this also helps to increase grinding wheel life and improve wafer surface grinding quality.

[0282] The bending strength, grinding wheel life, and surface roughness Ra of the thinned wafer obtained in Example 5 are comparable to those in Example 4, indicating that the cerium nitrate prepared from cerium-containing grinding waste liquid in this application can be used to prepare composite binders with effects comparable to commercially available nano-sized cerium nitrate. This can reduce costs while ensuring the mechanical properties of the grinding block and the grinding performance of the grinding wheel.

[0283] The bending strength, grinding wheel life, and surface roughness Ra of the thinned wafer obtained in Example 4 are all better than those in Example 3. This indicates that when the abrasive grains and polymer microspheres are modified with silane coupling agents, the mechanical properties of the abrasive block and the grinding performance of the grinding wheel can be further improved. This is because silane coupling agents can reduce the hydrophilicity of diamond and polymer microspheres, improve their dispersion ability in the gel system, and ensure the uniformity of the internal components of the abrasive block.

[0284] The above are merely specific embodiments of this application, but the scope of protection of this application is not limited thereto. Any person skilled in the art can easily conceive of various equivalent modifications or substitutions within the technical scope disclosed in this application, and these modifications or substitutions should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A wafer thinning equipment, characterized in that, It includes a grinding device and an adsorption platform, wherein the adsorption platform is used to support the wafer and drive the wafer to rotate; The grinding device is raised and lowered above the adsorption platform, and the lower part of the grinding device has a grinding wheel for grinding wafers; the grinding wheel is driven by the grinding device and performs grinding through axial feed; The grinding wheel includes a base material and a plurality of grinding blocks, the grinding blocks being fixed to the base material by an adhesive layer; The grinding block includes: Ceramic matrix; Abrasive particles are distributed within the ceramic matrix; A composite nano-coating is applied to the surface of the abrasive grains to enhance the interfacial bonding strength between the abrasive grains and the ceramic matrix. The preparation method of the composite nano-coating includes the following steps: immersing the abrasive grains in zirconium / cerium composite nano-sol and drying them to obtain sol-coated abrasive grains; heating the sol-coated abrasive grains to 450~550℃ and calcining them for 2~4 hours to obtain the composite nano-coating applied to the surface of the abrasive grains. The composite nanocoating comprises cerium oxide and zirconium oxide; The raw material for the composite nano-coating includes zirconium / cerium composite nano-sol, which comprises the following components by weight: 1-1.5 parts of oxygen-containing zirconium source, 1.8-2.5 parts of oxygen-containing cerium source, and 2-3.5 parts of complex acid; The ceramic matrix comprises silicon oxide, aluminum oxide, and boron oxide.

2. The wafer thinning equipment according to claim 1, characterized in that, The oxygen-containing zirconium source is zirconium nitrate; the oxygen-containing cerium source is cerium nitrate, and the cerium nitrate is cerium nitrate recovered from cerium-containing grinding waste liquid using ammonium nitrate as a recovery agent.

3. The wafer thinning equipment according to claim 1, characterized in that, The grinding wheel also includes pores distributed in a multi-level stacked pattern.

4. The wafer thinning equipment according to claim 3, characterized in that, The raw materials of the grinding wheel include: abrasive grains, polymer microspheres, ceramic binder sol, and zirconium / cerium composite nano-sol for coating the abrasive grains.

5. The wafer thinning equipment according to claim 4, characterized in that, The polymer microspheres are polymer microspheres modified with silane coupling agents.

6. The wafer thinning apparatus according to claim 4, characterized in that, The polymer microspheres include a first polymer microsphere with an average particle size of 100-110 μm, a second polymer microsphere with an average particle size of 15-25 μm, and a third polymer microsphere with an average particle size of 3-5 μm.

7. The wafer thinning equipment according to claim 6, characterized in that, The weight ratio of the first polymer microsphere to the second polymer microsphere and the third polymer microsphere is 3~4:2.5~3.5:2~3.

8. The wafer thinning equipment according to claim 4, characterized in that, The ceramic binder sol comprises the following components by weight: 28-32 parts of oxygen-containing silicon source, 5-6.5 parts of oxygen-containing aluminum source, 1.5-2 parts of oxygen-containing boron source, and 4-6 parts of complexing acid.

9. The wafer thinning apparatus according to any one of claims 1 to 8, characterized in that, The grinding apparatus includes: The feeding assembly is vertically connected above the adsorption platform; A rotating shaft is driven by the feed assembly to move up and down, and the grinding wheel is coaxially connected to the bottom end of the rotating shaft.

10. The wafer thinning apparatus according to any one of claims 1 to 8, characterized in that, The adsorption platform includes: The worktable has a chuck spindle at the bottom, which drives the worktable to rotate. An adsorption disk, disposed on the worktable, is used to adsorb wafers. The adsorption disk can drive the wafers to rotate synchronously under the action of the worktable.

11. A thinning method, characterized in that, The wafer is thinned using the wafer thinning apparatus according to any one of claims 1 to 10.

12. The thinning method according to claim 11, characterized in that, Includes the following steps: A100. Vacuum adsorption fixes the wafer onto the adsorption platform; A200, the control feed assembly drives the rotating shaft and grinding wheel to move downward in the vertical direction until the grinding surface of the grinding wheel contacts the wafer; A300: The grinding wheel and the adsorption platform rotate in the same direction, while the grinding wheel is fed downwards. The rotational speed of the grinding wheel is greater than that of the adsorption platform to grind the wafer. A400: When the wafer is ground to the target thickness, stop the rotation and feed of the rotating shaft and the adsorption platform, and control the feed assembly to drive the grinding wheel to move upward and reset, so that the grinding surface of the grinding wheel is separated from the wafer surface; A500, release the vacuum adsorption of the adsorption platform and transfer the wafer.

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