Adhesive layer of grinding wheel for wafer thinning, preparation method and grinding wheel for wafer thinning

Abstract

The invention provides an adhesive layer of a grinding wheel for wafer thinning, a preparation method and the grinding wheel for wafer thinning. The adhesive layer is provided with two or more small layers from bottom to top, the thermal expansion coefficients of the small layers are monotonically decreased, the longitudinal thermal conductivity of the small layers is monotonically increased, the surface energy of ceramic filler in raw material composition is monotonically decreased, and the rigidity of the ceramic filler is monotonically decreased; each small layer is subjected to induced orientation treatment by using a magnetic field perpendicular to the direction of the plane where the small layer is located before curing; according to the adhesive layer, gradient CTE composite modifier integrated design is matched with vertical heat conduction filler gradient and orientation design, gradual transition of the thermal expansion coefficient and vertical heat conduction from the grinding wheel base body side to the grinding material layer side is achieved, and a penetrating vertical heat conduction chain in the top-bottom direction is formed to open up a direct path for longitudinal efficient heat dissipation.

Description

[0001] This application is a divisional application of the invention patent application filed on October 28, 2025, with application number 2025115509830. Technical Field

[0002] This application belongs to the field of wafer grinding technology, specifically relating to an adhesive layer for a wafer thinning grinding wheel, its preparation method, and the grinding wheel itself. Background Technology

[0003] 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.

[0004] 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 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.

[0005] 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 ≤10μm, TTV ≤1.5μm, and Ra ≤5nm) while also considering manufacturing costs and production efficiency.

[0006] In wafer grinding systems, the difference in coefficients of thermal expansion (CTE) among the grinding wheel substrate, abrasive layer, and adhesive layer affects each other through stress transmission. In current mainstream wafer grinding systems, the adhesive layer typically uses traditional epoxy resin adhesive, and the grinding wheel substrate usually uses a metal / ceramic substrate. There is a significant difference in CTE between traditional epoxy resin adhesive (CTE of 60-80 ppm / ℃), the metal / ceramic substrate (e.g., aluminum alloy with a CTE of approximately 23 ppm / ℃), and the abrasive layer. Temperature changes can induce interfacial shear stress, leading to encapsulation delamination, microcracks, or decreased precision. Even with the adhesive layer as a buffer, the difference in CTE between the grinding wheel substrate and the abrasive layer can still cause the abrasive layer to detach and the substrate to deform. This deformation is then transmitted through the abrasive layer to the grinding interface, affecting cutting stability and causing damage to the wafer surface.

[0007] In semiconductor wafer thinning processes, balancing grinding efficiency and processing quality has always been a pain point in the industry. When traditional grinding wheels increase feed rate to improve up to 1000 kilohertz (UPH), the mismatch in the coefficients of thermal expansion (CTE) of the wheel substrate, abrasive layer, and adhesive layer often exacerbates interface deformation and grinding vibration, leading to an increase in wafer surface roughness Ra. This contradiction is particularly pronounced in the Z2 finishing stage, where blindly increasing the feed rate (i.e., accelerating the feed speed) affects wafer surface integrity, while conservative feed rate parameters limit capacity expansion. Therefore, it is necessary to achieve an increase in up to 1000 kilohertz while maintaining stable surface roughness, thus balancing high efficiency and precision machining.

[0008] Currently, some new technologies have emerged in the industry in an attempt to increase the processing capacity per hour while maintaining stable surface roughness. However, these new technologies have many problems and cannot effectively solve the problem of mismatch between the thermal expansion coefficients of the abrasive layer and the substrate during wafer thinning.

[0009] For example, CN117245570A discloses a wafer thinning grinding wheel, which is composed of a substrate, a first adhesive layer, an epoxy resin buffer layer (thickness 20-50μm), a second adhesive layer and a grinding layer. The epoxy resin buffer layer is sandwiched between the first adhesive layer and the second adhesive layer, which prevents wafer microcracks by relieving impact and maintaining rigidity. However, it has many defects in solving the problem of mismatch between the thermal expansion coefficients of the abrasive layer and the substrate, including: (1) The thickness of the buffer layer restricts the processing accuracy and thinning limit: the elastic deformation, dynamic vibration and thermal expansion of the epoxy resin buffer layer with a thickness of 20-50μm compress the effective controllable removal amount, making it difficult to achieve stable thinning of ultra-thin wafers with a thickness of <50μm; (2) Elastic deformation exacerbates the instability of ultra-thin processing: the elastic deformation of the buffer layer may cause uneven local contact between the grinding layer and the wafer, affecting the surface accuracy (such as total thickness change TTV, Warp); the epoxy resin buffer layer fluctuates in elastic modulus at high temperature, which can easily cause thermal stress microcracks; (3) Insufficient dynamic rigidity: the epoxy resin buffer layer reduces the rigidity of the system, and vibration is easily generated in ultra-precision grinding, which leads to the deterioration of the wafer surface roughness (Ra).

[0010] For example, CN118931445A discloses an epoxy resin adhesive with an ultra-low coefficient of thermal expansion. This epoxy resin adhesive has high strength and heat resistance, and solves the problems of temperature sensitivity and internal stress of traditional epoxy resin adhesives in extreme environments. When used on a grinding wheel, it can reduce the risk of chipping edges during wafer thinning in three-dimensional integrated circuit packaging (i.e., 3D IC packaging). However, it has many shortcomings in solving the problem of mismatch between the thermal expansion coefficients of the abrasive layer and the substrate, including: (1) Unknown thermal expansion coefficient: It focuses on the formulation and preparation method of epoxy resin adhesive with ultra-low expansion coefficient, and emphasizes the combination of low expansion ceramic filler modified by silane coupling agent and epoxy resin to reduce the thermal expansion coefficient, without specifying the thermal expansion coefficient data; (2) Unknown thermal conductivity: Although the ceramic filler used may have a certain thermal conductivity, the thermal conductivity value is not mentioned, making it difficult to determine whether it meets the heat dissipation requirements of three-dimensional stacked chips; (3) Filler dispersion and toughness defects: High filler content of ceramic filler is prone to agglomeration, resulting in uneven local thermal expansion coefficient, microcracks under extreme thermal cycling, and high filler content reduces the toughness and impact resistance of the adhesive layer, which can easily cause the edge of ultra-thin wafers with a thickness of <50μm to break brittlely during grinding vibration, thus offsetting the benefits of matching thermal expansion coefficient.

[0011] In summary, new technological solutions are still needed to address the challenges of balancing grinding efficiency and processing quality during wafer thinning due to the mismatch in thermal expansion coefficients between the abrasive layer of the grinding wheel and the substrate, as well as the issue of brittle fracture at the edges of ultrathin wafers caused by the mismatch in thermal expansion coefficients between the abrasive layer of the grinding wheel and the substrate during ultrathin wafer stacking (ultrathin wafers refer to reducing the thickness of wafers to no more than 50 μm). Summary of the Invention

[0012] The purpose of this application is to provide a technical solution that can solve the problem of grinding efficiency and processing quality being unable to be balanced due to the mismatch between the thermal expansion coefficients of the abrasive layer of the grinding wheel and the substrate during wafer thinning, as well as the problem of brittle fracture at the edge of ultra-thin wafers caused by the mismatch between the thermal expansion coefficients of the abrasive layer of the grinding wheel and the substrate during ultra-thinning of stacked wafers (ultra-thinning refers to reducing the thickness of the wafer to no more than 50 μm).

[0013] To achieve the above objectives, the present application provides an adhesive layer for a wafer thinning grinding wheel, a preparation method thereof, and a wafer thinning grinding wheel.

[0014] In the technical solution provided in this application, the wafer thinning equipment includes a wafer thinning grinding wheel, which is mounted on the grinding shaft of the wafer thinning equipment. The wafer thinning grinding wheel includes a grinding wheel base, an adhesive layer and an abrasive layer, and the abrasive layer is fixed to the grinding wheel base by the adhesive layer. The adhesive layer consists of two or more sub-layers from bottom to top; each sub-layer independently comprises a resin system, ceramic filler, and vertically thermally conductive filler. The coefficient of thermal expansion of each small layer from bottom to top decreases monotonically, the longitudinal thermal conductivity increases monotonically, and the surface energy and rigidity of the ceramic filler in the raw material composition decrease monotonically. The bottom layer is used to contact the grinding wheel substrate, and the top layer is used to contact the abrasive layer; Each sublayer is induced to orient itself using a magnetic field perpendicular to the plane of the sublayer before curing. This induced orientation treatment of each sublayer before curing effectively achieves the orientation of the vertical thermally conductive filler, causing the adhesive layer to form a vertical thermally conductive chain along the top and bottom direction, thereby maximizing the thermal conductivity in the vertical direction.

[0015] The thinning equipment provided in this application uses a wafer thinning grinding wheel with a special structure. This special structured grinding wheel employs a bonding layer with a special structure. By utilizing the thinning grinding wheel with the special structured bonding layer, the thinning equipment can effectively avoid the problem of grinding efficiency and processing quality being compromised due to the mismatch between the thermal expansion coefficients of the abrasive layer and the substrate during wafer thinning, as well as the problem of brittle fracture at the edge of ultra-thin wafers caused by the mismatch between the thermal expansion coefficients of the abrasive layer and the substrate during ultra-thinning of stacked wafers (ultra-thinning refers to thinning the wafer to a thickness of no more than 50μm).

[0016] Specifically, the adhesive layer with a special structure adopts an integrated design of gradient CTE composite modifier and vertical thermal conductive filler gradient and orientation design to achieve a gradual transition of thermal expansion coefficient and vertical thermal conductivity from the grinding wheel substrate side to the abrasive layer side, and forms a through vertical thermal conductive chain along the top and bottom direction to open a direct path for efficient longitudinal heat dissipation; thereby assisting the thinning equipment to effectively avoid the problem of grinding efficiency and processing quality not being able to be balanced due to the mismatch of thermal expansion coefficients between the abrasive layer and the substrate of the grinding wheel used for wafer thinning, as well as the problem of brittle fracture of the edge of the ultrathin wafer caused by the mismatch of thermal expansion coefficients between the abrasive layer and the substrate of the grinding wheel during the ultrathin thinning of stacked wafers (ultrathin thinning refers to thinning the wafer to a thickness of no more than 50μm).

[0017] In some preferred technical solutions, the structure of the wafer thinning equipment may be, but is not limited to, the structure of an existing wafer thinning equipment equipped with a grinding wheel.

[0018] In some preferred technical solutions, the grinding wheel matrix is ​​made of a metal matrix composite material, such as one or more combinations of aluminum alloy and copper alloy.

[0019] In some preferred technical solutions, the abrasive layer uses diamond abrasive grains.

[0020] In some preferred embodiments, the resin system includes epoxy resin and reactive diluent.

[0021] In some preferred technical solutions, the epoxy resin in the resin system is selected from one or more of epoxy resin E51, epoxy resin E44 and bio-based epoxy resin.

[0022] In some preferred technical solutions, the active diluent in the resin system is selected from one or more combinations of butyl glycidyl ether, C12-C14 alkyl glycidyl ether and neodecanoic acid glycidyl ether (CAS: 26761-45-5).

[0023] In some preferred technical solutions, the mass ratio of epoxy resin to reactive diluent in the resin system is 3-5:1 (e.g., 4:1).

[0024] In some preferred technical solutions, the adhesive layer consists of three or more sub-layers from bottom to top; In a more preferred embodiment, the adhesive layer consists of three smaller layers with a monotonically decreasing coefficient of thermal expansion from bottom to top.

[0025] In some preferred technical solutions, the coefficient of thermal expansion of the bottom layer is 12-20 ppm / ℃ (the coefficient of thermal expansion is measured under normal pressure conditions in the range of 20 to 200℃), the coefficient of thermal expansion of the top layer is 5-10 ppm / ℃ (the coefficient of thermal expansion is measured under normal pressure conditions in the range of 20 to 200℃), and the difference in the coefficient of thermal expansion between adjacent layers does not exceed (i.e., is less than or equal to) 10 ppm / ℃.

[0026] In some preferred technical solutions, the adhesive layer consists of three or more sub-layers from bottom to top, with an intermediate sub-layer M located between the bottom and top sub-layers having a thermal expansion coefficient of 10-15 ppm / ℃ (the thermal expansion coefficient is measured under normal pressure conditions within the range of 20 to 200℃). In a more preferred technical solution, the ceramic filler in the raw material composition of the intermediate layer M uses a ceramic material with a negative coefficient of thermal expansion. In a more preferred technical solution, the surface energy of the ceramic filler in the raw material composition of the intermediate layer M is 42-46 mN / m; In a more preferred technical solution, the longitudinal thermal conductivity of the intermediate layer M is 2.0-2.4 W / m·K; In a more preferred technical solution, the elastic modulus of the ceramic filler in the raw material composition of the intermediate layer M is 4-8 GPa.

[0027] In some preferred technical solutions, the coefficient of thermal expansion of the bottom layer is 15-20 ppm / ℃ (the coefficient of thermal expansion is measured under normal pressure conditions in the range of 20 to 200℃).

[0028] In some preferred technical solutions, the coefficient of thermal expansion of the top layer is 5-8 ppm / ℃ (the coefficient of thermal expansion is measured under normal pressure conditions in the range of 20 to 200℃).

[0029] In some preferred technical solutions, the ceramic filler in the raw material composition of the bottom layer uses ceramic materials with a positive coefficient of thermal expansion.

[0030] In some preferred technical solutions, the ceramic filler in the raw material composition of the top layer uses ceramic materials with a negative coefficient of thermal expansion.

[0031] In some preferred technical solutions, the surface energy of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 46 mN / m; In a more preferred technical solution, the surface energy of the ceramic filler in the raw material composition of the bottom layer is 46-50 mN / m.

[0032] In some preferred technical solutions, the surface energy of the ceramic filler in the raw material composition of the top layer is less than or equal to 42 mN / m; In a more preferred technical solution, the surface energy of the ceramic filler in the raw material composition of the top layer is 38-42 mN / m.

[0033] In some preferred technical solutions, the elastic modulus of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 8 GPa; In a more preferred technical solution, the elastic modulus of the ceramic filler in the raw material composition of the bottom layer is 8-12 GPa.

[0034] In some preferred technical solutions, the elastic modulus of the ceramic filler in the raw material composition of the top layer is less than or equal to 4 GPa; In a more preferred technical solution, the elastic modulus of the ceramic filler in the raw material composition of the top layer is 2-4 GPa.

[0035] In some preferred technical solutions, the concentration of ceramic filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer as 100%) increases monotonically.

[0036] In some preferred technical solutions, the ceramic filler in the raw material composition of each sublayer is a ceramic material that has undergone surface modification treatment; In a more preferred technical solution, the degree of organic matter of the modifier used for surface modification treatment of ceramic fillers in each small layer of raw materials from bottom to top increases monotonically. In a more preferred embodiment, the ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material.

[0037] In a more preferred technical solution, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a ceramic material modified with KH560.

[0038] In a further preferred technical solution, the ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material with a positive coefficient of thermal expansion, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material with a negative coefficient of thermal expansion. In a further preferred technical solution, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a ceramic material with a negative thermal expansion coefficient modified by KH560.

[0039] In some preferred technical solutions, the ceramic filler in the bottom sublayer raw material composition includes KH550 modified cordierite and / or KH550 modified spodumene; the ceramic filler in the top sublayer raw material composition includes KH570 modified sodium zirconium phosphate (NaZr2(PO4)3) and / or KH570 modified aluminum titanate. In a more preferred embodiment, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M includes KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate.

[0040] In some preferred technical solutions, based on the mass of the resin system in the bottom sublayer raw material composition being 100%, the mass content of the ceramic filler in the bottom sublayer raw material composition is 35-45% (e.g., 40%); based on the mass of the resin system in the top sublayer raw material composition being 100%, the mass content of the ceramic filler in the top sublayer raw material composition is 55-65% (e.g., 60%); in a further preferred technical solution, when an intermediate sublayer M is present, the ceramic filler in the intermediate sublayer M raw material composition includes KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate, and based on the mass of the resin system in the intermediate sublayer M raw material composition being 100%, the mass content of the ceramic filler in the intermediate sublayer M raw material composition is 45-55% (e.g., 50%).

[0041] In some preferred technical solutions, the longitudinal thermal conductivity of the bottom layer is less than or equal to 1.8 W / m·K; In a more preferred technical solution, the longitudinal thermal conductivity of the bottom layer is 1.4-1.8 W / m·K.

[0042] In some preferred technical solutions, the longitudinal thermal conductivity of the top layer is greater than or equal to 3.2 W / m·K; In a more preferred technical solution, the longitudinal thermal conductivity of the top layer is 3.2-3.8 W / m·K.

[0043] In some preferred technical solutions, the vertical thermally conductive filler includes a first vertical thermally conductive filler and a second vertical thermally conductive filler. The first vertical thermally conductive filler is made of a first thermally conductive material that can provide a thermally conductive skeleton, and the second thermally conductive filler is made of a second thermally conductive material that can fill the gaps in the first thermally conductive filler.

[0044] In some preferred technical solutions, the vertical thermally conductive filler in the raw material composition of each of the sub-layers is the same; by using the same vertical thermally conductive filler, on the one hand, it can better ensure that the thermal conductivity is gradually changing rather than abruptly changing, and on the other hand, it can better ensure that the orientation behavior of each layer of vertical thermally conductive filler is consistent under a magnetic field, thereby better guaranteeing the construction effect of the "thermal conductive chain".

[0045] In some preferred technical solutions, the vertical thermally conductive filler in the raw material composition of each of the sub-layers is a thermally conductive material that has been surface-modified using KH560.

[0046] In some preferred technical solutions, the first thermally conductive material includes one or more of diamond thermally conductive materials and cubic boron nitride (cBN) thermally conductive materials; In a more preferred technical solution, the first thermally conductive material is diamond thermally conductive material.

[0047] In some preferred technical solutions, the second thermally conductive material includes one or more of aluminum nitride (AlN) thermally conductive material, silicon nitride (Si3N4) thermally conductive material, and beryllium oxide (BeO) thermally conductive material; In a more preferred technical solution, the second thermally conductive material is aluminum nitride thermally conductive material.

[0048] In some preferred technical solutions, the mass ratio of the first thermally conductive material to the second thermally conductive material in the vertical thermally conductive filler is 4-2:1 (e.g., 3:1).

[0049] In some preferred technical solutions, the concentration of vertical thermally conductive filler in the raw material composition of each small layer from bottom to top (based on the mass of the resin system of the corresponding small layer as 100%) increases monotonically. In a more preferred embodiment, based on the mass of the resin system in the bottom layer raw material composition being 100%, the mass content of the vertical thermally conductive filler in the bottom layer raw material composition is 5-9% (e.g., 8%); based on the mass of the resin system in the top layer raw material composition being 100%, the mass content of the vertical thermally conductive filler in the top layer raw material composition is 11-20% (e.g., 15%). In a more preferred embodiment, when an intermediate layer M is present, the mass content of the vertical thermally conductive filler in the raw material composition of the intermediate layer M is 9-11% (e.g., 10%), taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%.

[0050] In some preferred technical solutions, the raw material composition of each sublayer independently includes a transverse thermally conductive filler, which includes one or more of graphene nanosheets (GNP), plasma-treated alumina nanosheets, and plasma-treated boron nitride nanosheets (p-BNNS). Adding transverse thermally conductive filler can assist in the diffusion of heat in the planar direction, allowing heat to be transferred more evenly to the vertical thermal conductive chain and avoiding local hot spots; In a more preferred embodiment, the transverse thermally conductive filler in the raw material composition of each of the sub-layers is the same; In a more preferred technical solution, the transverse thermally conductive filler in the raw material composition of each small layer is plasma-treated boron nitride nanosheets (p-BNNS); plasma-treated boron nitride nanosheets (p-BNNS) are also excellent insulators, and there is no need to pay attention to conductivity when adding them to avoid insulation failure, and they show excellent effects after addition. In a more preferred technical solution, the concentration of the transverse thermally conductive filler in the raw material composition of each small layer from bottom to top (based on the mass of the resin system of the corresponding small layer being 100%) increases monotonically. In a further preferred embodiment, taking the mass of the resin system in the bottom sublayer as 100%, the mass content of the transverse thermally conductive filler in the bottom sublayer is 5-6% (e.g., 5%); taking the mass of the resin system in the top sublayer as 100%, the mass content of the transverse thermally conductive filler in the top sublayer is 6-8% (e.g., 7%). In a further preferred embodiment, when an intermediate sublayer M is present, the mass content of the transverse thermally conductive filler in the raw material composition of the intermediate sublayer M is 8-10% (e.g., 10%), taking the mass of the resin system in the raw material composition of the intermediate sublayer M as 100%.

[0051] In some preferred technical solutions, the raw material composition of each sublayer independently includes conductive reinforcing filler, which includes one or more of carboxylated carbon nanotubes, silver-plated nanoparticles, graphene, etc. When the back side of the wafer needs to be electrically grounded or to discharge static electricity (ESD) through the adhesive layer, conductive reinforcement filler needs to be added to the material composition of each sublayer; when there is no need for conductivity, conductive reinforcement filler should not be added. In a more preferred embodiment, the conductive reinforcing filler in the raw material composition of each of the sub-layers is the same; In a more preferred technical solution, the concentration of conductive reinforcing filler in the raw material composition of each small layer from bottom to top (based on the mass of the resin system of the corresponding small layer being 100%) increases monotonically. In a further preferred embodiment, taking the mass of the resin system in the bottom sublayer as 100%, the mass content of the conductive reinforcing filler in the bottom sublayer is 1-1.5% (e.g., 1%); taking the mass of the resin system in the top sublayer as 100%, the mass content of the conductive reinforcing filler in the top sublayer is 1.5-3% (e.g., 2%). In a further preferred embodiment, when an intermediate sublayer M is present, the mass content of the conductive reinforcing filler in the raw material composition of the intermediate sublayer M is 1-1.5% (e.g., 1%), taking the mass of the resin system in the raw material composition of the intermediate sublayer M as 100%.

[0052] In some preferred technical solutions, the thickness of each sublayer in the adhesive layer is independently set to 8-23 μm; In a more preferred technical solution, the thickness of each layer decreases monotonically from bottom to top; In a further preferred embodiment, the thickness of the bottom layer is 18-23 μm (e.g., 20 μm), and the thickness of the top layer is 8-12 μm (e.g., 10 μm). In a further preferred embodiment, when an intermediate sublayer M is present, the thickness of the intermediate sublayer M is 12-18 μm (e.g., 15 μm).

[0053] In some preferred embodiments, the adhesive layer is prepared by a method comprising the following steps: 1) Apply each small layer of coating to the grinding wheel substrate in the order from the bottom layer to the top layer; The coating process for each sublayer, except for the top sublayer, independently includes: preparing a raw material mixture according to the composition of the sublayer raw material and coating the raw material mixture into a layer, then applying a magnetic field perpendicular to the plane of the sublayer for orientation induction treatment, and then pre-curing to a gel state; the coating process for the top sublayer includes: preparing a raw material mixture according to the composition of the sublayer raw material and coating the raw material mixture into a layer, then applying a magnetic field perpendicular to the plane of the sublayer for orientation induction treatment; 2) After completing the coating process of each small layer, the adhesive layer is prepared by gradient heating and curing.

[0054] In some preferred technical solutions, the pre-curing temperature of each of the sub-layers, except for the bottom and top sub-layers, is higher than the curing temperature of the adjacent bottom layer during the pre-curing process; this helps to strengthen the chemical bond between them and the adjacent bottom layer.

[0055] In some preferred technical solutions, the gradient temperature curing includes: first heating to 50-70℃ (e.g., 60℃) and holding for 0.8-1.2h (e.g., 1h), then heating to 80-120℃ (e.g., 100℃) and holding for 1.5-2.5h (e.g., 2h), and then heating to 130-170℃ (e.g., 150℃) and holding for 2-4h (e.g., 3h).

[0056] In some preferred technical solutions, during the gradient heating and curing process, the heating rate is 1-3℃ / min (e.g., 2℃ / min); a suitable heating rate can better avoid stress concentration.

[0057] In the technical solution provided in this application, the wafer thinning method includes wafer thinning using the wafer thinning equipment provided in this application.

[0058] In some preferred technical solutions, wafer thinning refers to ultra-thinning of 3D IC wafers (ultra-thinning refers to thinning the wafer to a thickness of no more than 50μm). In a more preferred technical solution, the 3D IC wafer is thinned to a thickness of no more than 10μm; In a more preferred technical solution, during the ultra-thinning process of 3D IC wafers, the feed rate is 0.5-0.8μm / s, and the processing accuracy meets the requirement of a surface roughness of 10-20nm.

[0059] The technical solution provided in this application can effectively solve the problem of not being able to simultaneously achieve grinding efficiency and processing quality due to the mismatch between the thermal expansion coefficients of the abrasive layer of the grinding wheel and the substrate during wafer thinning, and the problem of brittle fracture at the edge of ultra-thin wafers caused by the mismatch between the thermal expansion coefficients of the abrasive layer of the grinding wheel and the substrate during ultra-thin wafer thinning (ultra-thin wafer thinning refers to reducing the thickness of the wafer to no more than 50μm). Compared with the prior art, it reduces interface stress and thermal deformation differences, and can increase the feed rate and improve processing efficiency under the same grinding accuracy requirements, while maintaining the same surface roughness, as detailed below: (1) Feed rate: The feed rate of the technical solution provided in this application can be increased by at least 30% compared with the current mainstream technical solution. When using the current mainstream technical solution for wafer thinning, the feed rate can usually only reach 0.3-0.6μm / s in order to achieve the processing quality standard (surface roughness of 10-20nm). When using the technical solution provided in this application for wafer thinning, the feed rate can reach 0.5-0.8μm / s in order to achieve the processing quality standard (surface roughness of 10-20nm).

[0060] (2) Grinding UPH: Due to the 30% increase in feed rate, under the same machining accuracy requirements, the UPH of the grinding unit in the Z2 stage (Z2 removes 40um) increases by 30% simultaneously. Attached Figure Description

[0061] Figure 1 This is a three-dimensional structural diagram of a wafer thinning device.

[0062] Figure 2 This is a side view schematic diagram of the structure of a wafer thinning equipment.

[0063] Figure 3 This is a side view schematic diagram of the structure of a grinding wheel used for wafer thinning.

[0064] Figure 4 A bottom view of the structure of a grinding wheel used for wafer thinning.

[0065] Figure 5 A three-dimensional structural diagram of a grinding wheel used for wafer thinning.

[0066] Figure 6 This is a schematic diagram of the raw material composition of the adhesive layer.

[0067] Figure 7 This is a flowchart of the wafer thinning operation. Detailed Implementation

[0068] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some, not all, of the embodiments of this application. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this application.

[0069] A specific embodiment of the first aspect of this application provides an adhesive layer for a wafer thinning grinding wheel, wherein the adhesive layer for the wafer thinning grinding wheel has two or more sub-layers arranged from bottom to top; the raw material composition of each sub-layer independently includes a resin system, ceramic filler and vertical thermally conductive filler; The coefficient of thermal expansion of each small layer from bottom to top decreases monotonically, the longitudinal thermal conductivity increases monotonically, and the surface energy and rigidity of the ceramic filler in the raw material composition decrease monotonically. The bottom layer is used to contact the grinding wheel substrate, and the top layer is used to contact the abrasive layer; Each sublayer is subjected to orientation-inducing treatment using a magnetic field perpendicular to the plane of the sublayer before curing.

[0070] This adhesive layer employs an integrated design of gradient CTE composite modifier, combined with a gradient and orientation design of vertical thermally conductive filler. This achieves a gradual transition in thermal expansion coefficient and vertical thermal conductivity from the grinding wheel substrate side to the abrasive layer side, forming a through-type vertical thermal conductive chain along the top and bottom directions. This provides a direct path for efficient longitudinal heat dissipation. Consequently, it assists grinding wheels used for wafer thinning in effectively avoiding the inability to balance grinding efficiency and processing quality due to the mismatch between the thermal expansion coefficients of the abrasive layer and the substrate during wafer thinning. It also addresses the issue of brittle fracture at the edges of ultra-thin wafers caused by the mismatch between the thermal expansion coefficients of the abrasive layer and the substrate during ultra-thinning of stacked wafers (ultra-thinning refers to reducing the thickness of a wafer to no more than 50 μm).

[0071] Furthermore, the resin system includes epoxy resin and reactive diluent.

[0072] Furthermore, in the resin system, the epoxy resin is selected from one or more combinations of epoxy resin E51, epoxy resin E44, and bio-based epoxy resin.

[0073] Furthermore, in the resin system, the reactive diluent is selected from one or more of butyl glycidyl ether, C12-C14 alkyl glycidyl ether and neodecanoic acid glycidyl ether (CAS: 26761-45-5).

[0074] Furthermore, in the resin system, the mass ratio of epoxy resin to reactive diluent is 3-5:1 (e.g., 4:1).

[0075] Furthermore, the adhesive layer of the wafer thinning grinding wheel has three or more small layers from bottom to top; Furthermore, the adhesive layer of the wafer thinning grinding wheel is provided with three small layers with a monotonically decreasing coefficient of thermal expansion from bottom to top.

[0076] Furthermore, the coefficient of thermal expansion of the bottom layer is 12-20 ppm / ℃, the coefficient of thermal expansion of the top layer is 5-10 ppm / ℃, and the difference in the coefficient of thermal expansion between adjacent layers is less than or equal to 10 ppm / ℃.

[0077] Furthermore, the adhesive layer of the wafer thinning grinding wheel has three or more sub-layers from bottom to top, and there is an intermediate sub-layer M between the bottom sub-layer and the top sub-layer with a thermal expansion coefficient of 10-15ppm / ℃ (the thermal expansion coefficient is measured under normal pressure in the range of 20 to 200℃).

[0078] Furthermore, the coefficient of thermal expansion of the bottom layer is 15-20 ppm / ℃ (the coefficient of thermal expansion was measured under normal pressure conditions in the range of 20 to 200℃).

[0079] Furthermore, the coefficient of thermal expansion of the top layer is 5-8 ppm / ℃ (the coefficient of thermal expansion was measured under normal pressure conditions in the range of 20 to 200℃).

[0080] Furthermore, the adhesive layer of the wafer thinning grinding wheel is composed of three small layers with a monotonically decreasing coefficient of thermal expansion from bottom to top, namely the bottom small layer, the middle small layer M, and the top small layer; Furthermore, the coefficient of thermal expansion of the bottom layer is 15-20 ppm / ℃, the coefficient of thermal expansion of the top layer is 5-8 ppm / ℃, and the coefficient of thermal expansion of the middle layer M is 10-15 ppm / ℃.

[0081] By making the coefficient of thermal expansion of the bottom layer close to that of the silicon wafer, thermal stress can be minimized, thereby better reducing the microcrack rate at the wafer edge.

[0082] Furthermore, the ceramic filler in the raw material composition of the bottom layer uses ceramic materials with a positive coefficient of thermal expansion.

[0083] Furthermore, the ceramic filler in the top layer of raw materials uses ceramic materials with a negative coefficient of thermal expansion.

[0084] Furthermore, the ceramic filler in the raw material composition of the intermediate layer M uses ceramic materials with a negative coefficient of thermal expansion.

[0085] Furthermore, the surface energy of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 46 mN / m; even further, the surface energy of the ceramic filler in the raw material composition of the bottom layer is 46-50 mN / m.

[0086] Furthermore, the surface energy of the ceramic filler in the raw material composition of the top layer is less than or equal to 42 mN / m; even further, the surface energy of the ceramic filler in the raw material composition of the top layer is 38-42 mN / m.

[0087] Furthermore, the surface energy of the ceramic filler in the raw material composition of the intermediate layer M is 42-46 mN / m.

[0088] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 8 GPa; even further, the elastic modulus of the ceramic filler in the raw material composition of the bottom layer is 8-12 GPa.

[0089] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the top layer is less than or equal to 4 GPa; even further, the elastic modulus of the ceramic filler in the raw material composition of the top layer is 2-4 GPa.

[0090] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the intermediate layer M is 4-8 GPa.

[0091] Furthermore, the longitudinal thermal conductivity of the bottom layer is less than or equal to 1.8 W / m·K; even further, the longitudinal thermal conductivity of the bottom layer is 1.4-1.8 W / m·K.

[0092] Furthermore, the longitudinal thermal conductivity of the top layer is greater than or equal to 3.2 W / m·K; even further, the longitudinal thermal conductivity of the top layer is 3.2-3.8 W / m·K.

[0093] Furthermore, the longitudinal thermal conductivity of the intermediate layer M is 2.0-2.4 W / m·K; Furthermore, the concentration of ceramic filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically.

[0094] Furthermore, the ceramic filler in the raw material composition of each sublayer is a ceramic material that has undergone surface modification treatment.

[0095] Furthermore, the degree of organic matter in the modifiers used for surface modification treatment of ceramic fillers in each small layer of raw material from bottom to top increases monotonically.

[0096] Furthermore, the ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a ceramic material modified with KH560.

[0097] Furthermore, the ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material with a positive coefficient of thermal expansion, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material with a negative coefficient of thermal expansion. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a ceramic material with a negative thermal expansion coefficient modified by KH560.

[0098] Furthermore, the ceramic filler in the bottom layer raw material composition includes KH550 modified cordierite and / or KH550 modified spodumene; the ceramic filler in the top layer raw material composition includes KH570 modified sodium zirconium phosphate (NaZr2(PO4)3) and / or KH570 modified aluminum titanate. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M includes KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate; Furthermore, cordierite and / or spodumene are ultrasonically treated in a mixture of KH550 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the bottom layer raw material composition. Furthermore, sodium zirconium phosphate and / or aluminum titanate are ultrasonically treated in a mixture of KH570 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the top layer raw material composition. Furthermore, zirconium tungstate and / or zirconium phosphate are ultrasonically treated in a mixture of KH560 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the intermediate small layer M raw material composition. Furthermore, in the bottom layer of raw material composition, the mass ratio of KH550 modified cordierite to KH550 modified spodumene in the surface-modified ceramic filler is 0.5-2:1; Furthermore, in the top layer of raw material composition, the mass ratio of KH570 modified sodium zirconium phosphate and / or KH570 modified aluminum titanate in the surface-modified ceramic filler is 0.5-2:1; Furthermore, in the intermediate small layer M raw material composition, the mass ratio of KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate in the surface-modified ceramic filler is 0.5-2:1.

[0099] Further, taking the mass of the resin system in the bottom sublayer raw material composition as 100%, the mass content of the ceramic filler in the bottom sublayer raw material composition is 35-45% (e.g., 40%); taking the mass of the resin system in the top sublayer raw material composition as 100%, the mass content of the ceramic filler in the top sublayer raw material composition is 55-65% (e.g., 60%); in a further preferred embodiment, when an intermediate sublayer M is present, the ceramic filler in the intermediate sublayer M raw material composition includes KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate, and taking the mass of the resin system in the intermediate sublayer M raw material composition as 100%, the mass content of the ceramic filler in the intermediate sublayer M raw material composition is 45-55% (e.g., 50%).

[0100] Furthermore, the vertical thermally conductive filler includes a first vertical thermally conductive filler and a second vertical thermally conductive filler. The first vertical thermally conductive filler is made of a first thermally conductive material that can provide a thermally conductive framework, and the second thermally conductive filler is made of a second thermally conductive material that can fill the gaps in the first thermally conductive filler.

[0101] Furthermore, the vertically thermally conductive filler in the raw material composition of each of the sub-layers is the same.

[0102] Furthermore, the vertical thermally conductive filler in the raw material composition of each of the sub-layers is a thermally conductive material that has been surface-modified using KH560; Furthermore, a surface-modified thermally conductive material using KH560 was prepared using the following method: The thermally conductive material is placed in a mixture of KH560 and an organic solvent (e.g., ethanol and / or isopropanol) and ultrasonically treated for 0.5-3 hours (e.g., 1 hour). The ultrasonically treated solid product is then dried at 50-70°C (e.g., 60°C) to complete the surface modification of the vertical thermally conductive filler using KH560.

[0103] Furthermore, the first thermally conductive material includes one or more combinations of diamond thermally conductive material and cubic boron nitride (cBN) thermally conductive material; even further, the first thermally conductive material is diamond thermally conductive material.

[0104] Furthermore, the second thermal conductive material includes one or more of aluminum nitride (AlN) thermal conductive material, silicon nitride (Si3N4) thermal conductive material, and beryllium oxide (BeO) thermal conductive material; even further, the second thermal conductive material is aluminum nitride thermal conductive material.

[0105] Furthermore, the particle size of the first thermally conductive material in the vertical thermally conductive filler is 8-12 μm (e.g., 10 μm).

[0106] Furthermore, the particle size of the second thermally conductive material in the vertical thermally conductive filler is 1-3 μm (e.g., 2 μm).

[0107] Furthermore, in the vertical thermally conductive filler, the mass ratio of the first thermally conductive material to the second thermally conductive material is 4-2:1 (e.g., 3:1).

[0108] Furthermore, the concentration of vertically thermally conductive filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically.

[0109] Furthermore, taking the mass of the resin system in the bottom sublayer as 100%, the mass content of the vertical thermally conductive filler in the bottom sublayer is 5-9% (e.g., 8%); taking the mass of the resin system in the top sublayer as 100%, the mass content of the vertical thermally conductive filler in the top sublayer is 11-20% (e.g., 15%). Furthermore, when an intermediate layer M is present, taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%, the mass content of the vertical thermally conductive filler in the raw material composition of the intermediate layer M is 9-11% (e.g., 10%).

[0110] Furthermore, the raw material composition of each sublayer independently includes a transverse thermally conductive filler, which includes one or more of graphene nanosheets, plasma-treated alumina nanosheets, and plasma-treated boron nitride nanosheets; even further, the transverse thermally conductive filler in the raw material composition of each sublayer is plasma-treated boron nitride nanosheets (p-BNNS).

[0111] Furthermore, the transverse thermally conductive filler in the raw material composition of each of the sub-layers is the same.

[0112] Furthermore, the concentration of transverse thermally conductive filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically. Furthermore, taking the mass of the resin system in the bottom sublayer as 100%, the mass content of the transverse thermally conductive filler in the bottom sublayer is 5-6% (e.g., 5%); taking the mass of the resin system in the top sublayer as 100%, the mass content of the transverse thermally conductive filler in the top sublayer is 6-8% (e.g., 7%). Furthermore, when an intermediate layer M is present, taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%, the mass content of the transverse thermally conductive filler in the raw material composition of the intermediate layer M is 8-10% (e.g., 10%).

[0113] Furthermore, the raw material composition of each sublayer independently includes conductive reinforcing filler, which includes one or more of carboxylated carbon nanotubes, silver-plated nanoparticles, graphene, etc.

[0114] Furthermore, the conductive reinforcing filler in the raw material composition of each of the aforementioned sublayers is the same; Furthermore, the concentration of conductive reinforcing filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically. Furthermore, based on the mass of the resin system in the bottom sublayer raw material composition being 100%, the mass content of the conductive reinforcing filler in the bottom sublayer raw material composition is 1-1.5% (e.g., 1%); based on the mass of the resin system in the top sublayer raw material composition being 100%, the mass content of the conductive reinforcing filler in the top sublayer raw material composition is 1.5-3% (e.g., 2%). Furthermore, when an intermediate sublayer M is present, taking the mass of the resin system in the raw material composition of the intermediate sublayer M as 100%, the mass content of the conductive reinforcing filler in the raw material composition of the intermediate sublayer M is 1-1.5% (e.g., 1%).

[0115] Furthermore, the thickness of each sublayer in the adhesive layer of the wafer thinning grinding wheel is independently set to 8-23 μm.

[0116] Furthermore, the thickness of each sub-layer decreases monotonically from bottom to top; Furthermore, the thickness of the bottom sublayer is 18-23 μm (e.g., 20 μm), and the thickness of the top sublayer is 8-12 μm (e.g., 10 μm). Furthermore, when an intermediate sublayer M is present, the thickness of the intermediate sublayer M is 12-18 μm (e.g., 15 μm).

[0117] A specific embodiment of the second aspect of this application provides a method for preparing an adhesive layer for a wafer thinning grinding wheel, used to prepare the adhesive layer for the wafer thinning grinding wheel provided in the specific embodiment of the first aspect of this application, wherein the preparation method includes: 1) Apply each small layer of coating to the grinding wheel substrate in the order from the bottom layer to the top layer; The coating process for each sublayer, except for the top sublayer, independently includes: preparing a raw material mixture according to the composition of the sublayer raw material and coating the raw material mixture into a layer, then applying a magnetic field perpendicular to the plane of the sublayer for orientation induction treatment, and then pre-curing to a gel state; the coating process for the top sublayer includes: preparing a raw material mixture according to the composition of the sublayer raw material and coating the raw material mixture into a layer, then applying a magnetic field perpendicular to the plane of the sublayer for orientation induction treatment; Before pre-curing after coating, the raw material mixture is subjected to a magnetic field to induce orientation. The raw material mixture is in a liquid or semi-fluid state, and the filler in the raw material mixture can rotate freely in the liquid. When a magnetic field is applied at this time, the filler can easily adjust its direction according to its magnetic susceptibility to achieve directional arrangement. The vertical magnetic field will induce the vertical thermally conductive filler to align its easily magnetized axis (usually the long axis) along the direction of the magnetic field line, thereby forming a vertical thermally conductive chain from bottom to top, maximizing the thermal conductivity in the vertical direction. 2) After completing the coating process of each small layer, the wafer is cured by gradient heating to prepare the adhesive layer of the wafer thinning grinding wheel.

[0118] Furthermore, during the pre-curing process, the pre-curing temperature of all the sub-layers except the bottom and top sub-layers is higher than the curing temperature of the adjacent bottom layer.

[0119] Furthermore, the gradient temperature curing includes: first heating to 50-70℃ and holding for 0.8-1.2h, then heating to 80-120℃ and holding for 1.5-2.5h, and then heating to 130-170℃ and holding for 2-4h.

[0120] Furthermore, during the gradient heating and curing process, the heating rate is 1-3°C / minute (e.g., 2°C / minute).

[0121] Furthermore, during the coating process of each sublayer, when a magnetic field perpendicular to the plane of the sublayer is applied, the intensity of the applied magnetic field is 0.3-0.7T (e.g., 0.5T), and the duration of the magnetic field is 20-40s (e.g., 30s).

[0122] Furthermore, when performing the bottom layer coating treatment, the grinding wheel substrate is preheated to 45-55°C (e.g., 50°C) before coating the raw material mixture into layers, which reduces the viscosity of the raw material mixture and facilitates uniform coating.

[0123] Furthermore, during the coating process of each small layer, when coating the raw material mixture into layers, a spin coating method is used, and the rotation speed during the spin coating process is 800-1800 rpm; Furthermore, during the coating process, the rotation speed of each small layer increases monotonically from bottom to top during spin coating. More preferably, during the coating process, the bottom layer rotates at a speed of 800-1100 rpm (e.g., 1000 μm) during spin coating, and the top layer rotates at a speed of 1300-1800 rpm (e.g., 1500 μm) during spin coating; when an intermediate layer M is present, the intermediate layer M rotates at a speed of 1100-1300 rpm (e.g., 1200 μm) during spin coating.

[0124] A specific embodiment of the third aspect of this application provides a wafer thinning grinding wheel. This wafer thinning grinding wheel has an adhesive layer with a special structure, as provided in the specific embodiment of the first aspect of this application, disposed between the grinding wheel substrate and the abrasive layer. Specifically, the wafer thinning grinding wheel includes a grinding wheel substrate, an adhesive layer, and an abrasive layer. The abrasive layer is fixed to the grinding wheel substrate by the adhesive layer. The adhesive layer has two or more sub-layers arranged from bottom to top. The raw material composition of each sub-layer independently includes a resin system, ceramic filler, and vertically thermally conductive filler. The coefficient of thermal expansion of each small layer from bottom to top decreases monotonically, the longitudinal thermal conductivity increases monotonically, and the surface energy and rigidity of the ceramic filler in the raw material composition decrease monotonically. The bottom layer is used to contact the grinding wheel substrate, and the top layer is used to contact the abrasive layer; Each sublayer is induced to orient itself using a magnetic field perpendicular to the plane in which the sublayer is located before curing.

[0125] This wafer thinning grinding wheel effectively avoids the problem of grinding efficiency and processing quality being compromised due to the mismatch between the thermal expansion coefficients of the abrasive layer and the substrate during the wafer thinning process, as well as the problem of brittle fracture at the edge of the ultrathin wafer caused by the mismatch between the thermal expansion coefficients of the abrasive layer and the substrate during the ultrathinning process of stacked wafers (ultrathinning refers to reducing the thickness of the wafer to no more than 50μm).

[0126] Specifically, the adhesive layer with a special structure adopts an integrated design of gradient CTE composite modifier and a gradient and orientation design of vertical thermally conductive filler to achieve a gradual transition of thermal expansion coefficient and vertical thermal conductivity from the grinding wheel substrate side to the abrasive layer side, and forms a through vertical thermal conductive chain along the top and bottom direction to open a direct path for efficient longitudinal heat dissipation; thereby assisting the grinding wheel for wafer thinning to effectively avoid the problem of grinding efficiency and processing quality not being able to be balanced due to the mismatch of thermal expansion coefficients between the abrasive layer and the substrate during the wafer thinning process, as well as the problem of brittle fracture of the edge of the ultrathin wafer caused by the mismatch of thermal expansion coefficients between the abrasive layer and the substrate during the ultrathinning of stacked wafers (ultrathinning refers to thinning the wafer to a thickness of no more than 50μm).

[0127] Furthermore, the resin system includes epoxy resin and reactive diluent.

[0128] Furthermore, in the resin system, the epoxy resin is selected from one or more combinations of epoxy resin E51, epoxy resin E44, and bio-based epoxy resin.

[0129] Furthermore, in the resin system, the reactive diluent is selected from one or more of butyl glycidyl ether, C12-C14 alkyl glycidyl ether and neodecanoic acid glycidyl ether (CAS: 26761-45-5).

[0130] Furthermore, in the resin system, the mass ratio of epoxy resin to reactive diluent is 3-5:1 (e.g., 4:1).

[0131] Furthermore, the adhesive layer consists of three or more sub-layers from bottom to top; Furthermore, the adhesive layer comprises three sub-layers with a monotonically decreasing coefficient of thermal expansion from bottom to top. Specifically, the bottom sub-layer has a coefficient of thermal expansion of 12-20 ppm / ℃, the top sub-layer has a coefficient of thermal expansion of 5-10 ppm / ℃, and the difference in coefficient of thermal expansion between adjacent sub-layers is less than or equal to 10 ppm / ℃.

[0132] Furthermore, the adhesive layer consists of three or more sub-layers from bottom to top, with an intermediate sub-layer M located between the bottom and top sub-layers having a thermal expansion coefficient of 10-15 ppm / ℃ (the thermal expansion coefficient is measured under normal pressure conditions within the range of 20 to 200℃).

[0133] Furthermore, the coefficient of thermal expansion of the bottom layer is 15-20 ppm / ℃ (the coefficient of thermal expansion was measured under normal pressure conditions in the range of 20 to 200℃).

[0134] Furthermore, the coefficient of thermal expansion of the top layer is 5-8 ppm / ℃ (the coefficient of thermal expansion was measured under normal pressure conditions in the range of 20 to 200℃).

[0135] Furthermore, the adhesive layer consists of three smaller layers with a monotonically decreasing coefficient of thermal expansion from bottom to top: a bottom layer, a middle layer M, and a top layer. Furthermore, the coefficient of thermal expansion of the bottom layer is 15-20 ppm / ℃, the coefficient of thermal expansion of the top layer is 5-8 ppm / ℃, and the coefficient of thermal expansion of the middle layer M is 10-15 ppm / ℃.

[0136] Furthermore, the ceramic filler in the raw material composition of the bottom layer uses ceramic materials with a positive coefficient of thermal expansion.

[0137] Furthermore, the ceramic filler in the top layer of raw materials uses ceramic materials with a negative coefficient of thermal expansion.

[0138] Furthermore, the ceramic filler in the raw material composition of the intermediate layer M uses ceramic materials with a negative coefficient of thermal expansion.

[0139] Furthermore, the surface energy of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 46 mN / m; even further, the surface energy of the ceramic filler in the raw material composition of the bottom layer is 46-50 mN / m.

[0140] Furthermore, the surface energy of the ceramic filler in the raw material composition of the top layer is less than or equal to 42 mN / m; even further, the surface energy of the ceramic filler in the raw material composition of the top layer is 38-42 mN / m.

[0141] Furthermore, the surface energy of the ceramic filler in the raw material composition of the intermediate layer M is 42-46 mN / m.

[0142] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 8 GPa; even further, the elastic modulus of the ceramic filler in the raw material composition of the bottom layer is 8-12 GPa.

[0143] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the top layer is less than or equal to 4 GPa; even further, the elastic modulus of the ceramic filler in the raw material composition of the top layer is 2-4 GPa.

[0144] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the intermediate layer M is 4-8 GPa.

[0145] Furthermore, the longitudinal thermal conductivity of the bottom layer is less than or equal to 1.8 W / m·K; even further, the longitudinal thermal conductivity of the bottom layer is 1.4-1.8 W / m·K.

[0146] Furthermore, the longitudinal thermal conductivity of the top layer is greater than or equal to 3.2 W / m·K; even further, the longitudinal thermal conductivity of the top layer is 3.2-3.8 W / m·K.

[0147] Furthermore, the longitudinal thermal conductivity of the intermediate layer M is 2.0-2.4 W / m·K; Furthermore, the concentration of ceramic filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically.

[0148] Furthermore, the ceramic filler in the raw material composition of each sublayer is a ceramic material that has undergone surface modification treatment.

[0149] Furthermore, the degree of organic matter in the modifiers used for surface modification treatment of ceramic fillers in each small layer of raw material from bottom to top increases monotonically.

[0150] Furthermore, the ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a ceramic material modified with KH560.

[0151] Furthermore, the ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material with a positive coefficient of thermal expansion, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material with a negative coefficient of thermal expansion. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a ceramic material with a negative thermal expansion coefficient modified by KH560.

[0152] Furthermore, the ceramic filler in the bottom layer raw material composition includes KH550 modified cordierite and / or KH550 modified spodumene; the ceramic filler in the top layer raw material composition includes KH570 modified sodium zirconium phosphate (NaZr2(PO4)3) and / or KH570 modified aluminum titanate. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M includes KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate; Furthermore, cordierite and / or spodumene are ultrasonically treated in a mixture of KH550 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the bottom layer raw material composition. Furthermore, sodium zirconium phosphate and / or aluminum titanate are ultrasonically treated in a mixture of KH570 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the top layer raw material composition. Furthermore, zirconium tungstate and / or zirconium phosphate are ultrasonically treated in a mixture of KH560 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the intermediate small layer M raw material composition. Furthermore, in the bottom layer of raw material composition, the mass ratio of KH550 modified cordierite to KH550 modified spodumene in the surface-modified ceramic filler is 0.5-2:1; Furthermore, in the top layer of raw material composition, the mass ratio of KH570 modified sodium zirconium phosphate and / or KH570 modified aluminum titanate in the surface-modified ceramic filler is 0.5-2:1; Furthermore, in the intermediate small layer M raw material composition, the mass ratio of KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate in the surface-modified ceramic filler is 0.5-2:1.

[0153] Further, taking the mass of the resin system in the bottom sublayer raw material composition as 100%, the mass content of the ceramic filler in the bottom sublayer raw material composition is 35-45% (e.g., 40%); taking the mass of the resin system in the top sublayer raw material composition as 100%, the mass content of the ceramic filler in the top sublayer raw material composition is 55-65% (e.g., 60%); in a further preferred embodiment, when an intermediate sublayer M is present, the ceramic filler in the intermediate sublayer M raw material composition includes KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate, and taking the mass of the resin system in the intermediate sublayer M raw material composition as 100%, the mass content of the ceramic filler in the intermediate sublayer M raw material composition is 45-55% (e.g., 50%).

[0154] Furthermore, the vertical thermally conductive filler includes a first vertical thermally conductive filler and a second vertical thermally conductive filler. The first vertical thermally conductive filler is made of a first thermally conductive material that can provide a thermally conductive framework, and the second thermally conductive filler is made of a second thermally conductive material that can fill the gaps in the first thermally conductive filler.

[0155] Furthermore, the vertically thermally conductive filler in the raw material composition of each of the sub-layers is the same.

[0156] Furthermore, the vertical thermally conductive filler in the raw material composition of each of the sub-layers is a thermally conductive material that has been surface-modified using KH560; Furthermore, a surface-modified thermally conductive material using KH560 was prepared using the following method: The thermally conductive material is placed in a mixture of KH560 and an organic solvent (e.g., ethanol and / or isopropanol) and ultrasonically treated for 0.5-3 hours (e.g., 1 hour). The ultrasonically treated solid product is then dried at 50-70°C (e.g., 60°C) to complete the surface modification of the vertical thermally conductive filler using KH560.

[0157] Furthermore, the first thermally conductive material includes one or more combinations of diamond thermally conductive material and cubic boron nitride (cBN) thermally conductive material; even further, the first thermally conductive material is diamond thermally conductive material.

[0158] Furthermore, the second thermal conductive material includes one or more of aluminum nitride (AlN) thermal conductive material, silicon nitride (Si3N4) thermal conductive material, and beryllium oxide (BeO) thermal conductive material; even further, the second thermal conductive material is aluminum nitride thermal conductive material.

[0159] Furthermore, the particle size of the first thermally conductive material in the vertical thermally conductive filler is 8-12 μm (e.g., 10 μm).

[0160] Furthermore, the particle size of the second thermally conductive material in the vertical thermally conductive filler is 1-3 μm (e.g., 2 μm).

[0161] Furthermore, in the vertical thermally conductive filler, the mass ratio of the first thermally conductive material to the second thermally conductive material is 4-2:1 (e.g., 3:1).

[0162] Furthermore, the concentration of vertically thermally conductive filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically.

[0163] Furthermore, taking the mass of the resin system in the bottom sublayer as 100%, the mass content of the vertical thermally conductive filler in the bottom sublayer is 5-9% (e.g., 8%); taking the mass of the resin system in the top sublayer as 100%, the mass content of the vertical thermally conductive filler in the top sublayer is 11-20% (e.g., 15%). Furthermore, when an intermediate layer M is present, taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%, the mass content of the vertical thermally conductive filler in the raw material composition of the intermediate layer M is 9-11% (e.g., 10%).

[0164] Furthermore, the raw material composition of each sublayer independently includes a transverse thermally conductive filler, which includes one or more of graphene nanosheets, plasma-treated alumina nanosheets, and plasma-treated boron nitride nanosheets; even further, the transverse thermally conductive filler in the raw material composition of each sublayer is plasma-treated boron nitride nanosheets (p-BNNS).

[0165] Furthermore, the transverse thermally conductive filler in the raw material composition of each of the sub-layers is the same.

[0166] Furthermore, the concentration of transverse thermally conductive filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically. Furthermore, taking the mass of the resin system in the bottom sublayer as 100%, the mass content of the transverse thermally conductive filler in the bottom sublayer is 5-6% (e.g., 5%); taking the mass of the resin system in the top sublayer as 100%, the mass content of the transverse thermally conductive filler in the top sublayer is 6-8% (e.g., 7%). Furthermore, when an intermediate layer M is present, taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%, the mass content of the transverse thermally conductive filler in the raw material composition of the intermediate layer M is 8-10% (e.g., 10%).

[0167] Furthermore, the raw material composition of each sublayer independently includes conductive reinforcing filler, which includes one or more of carboxylated carbon nanotubes, silver-plated nanoparticles, graphene, etc.

[0168] Furthermore, the conductive reinforcing filler in the raw material composition of each of the aforementioned sublayers is the same; Furthermore, the concentration of conductive reinforcing filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically. Furthermore, based on the mass of the resin system in the bottom sublayer raw material composition being 100%, the mass content of the conductive reinforcing filler in the bottom sublayer raw material composition is 1-1.5% (e.g., 1%); based on the mass of the resin system in the top sublayer raw material composition being 100%, the mass content of the conductive reinforcing filler in the top sublayer raw material composition is 1.5-3% (e.g., 2%). Furthermore, when an intermediate sublayer M is present, taking the mass of the resin system in the raw material composition of the intermediate sublayer M as 100%, the mass content of the conductive reinforcing filler in the raw material composition of the intermediate sublayer M is 1-1.5% (e.g., 1%).

[0169] Furthermore, the thickness of each sublayer in the adhesive layer is independently set to 8-23 μm.

[0170] Furthermore, the thickness of each sub-layer decreases monotonically from bottom to top; Furthermore, the thickness of the bottom sublayer is 18-23 μm (e.g., 20 μm), and the thickness of the top sublayer is 8-12 μm (e.g., 10 μm). Furthermore, when an intermediate sublayer M is present, the thickness of the intermediate sublayer M is 12-18 μm (e.g., 15 μm).

[0171] Furthermore, the grinding wheel matrix is ​​made of a metal matrix composite material, such as one or more combinations of aluminum alloys and copper alloys. The grinding wheel matrix may be, but is not limited to, the grinding wheel matrix used in existing grinding wheels.

[0172] Furthermore, the abrasive layer uses diamond abrasive grains. The grinding wheel matrix may, but is not limited to, using the abrasive layer found in existing grinding wheels.

[0173] A specific embodiment of the fourth aspect of this application provides a method for preparing a wafer thinning grinding wheel to prepare the wafer thinning grinding wheel provided in the third aspect embodiment of this application, comprising: preparing an adhesive layer for the wafer thinning grinding wheel between the grinding wheel substrate and the abrasive layer according to the method for preparing an adhesive layer for the wafer thinning grinding wheel provided in the specific embodiment of the second aspect of this application as described below, and using the adhesive layer to bond the grinding wheel substrate and the abrasive layer together, thereby preparing the wafer thinning grinding wheel; specifically, the method for preparing the wafer thinning grinding wheel includes: 1) Apply each small layer of coating to the grinding wheel substrate in the order from the bottom layer to the top layer; The coating process for each sublayer, except for the top sublayer, independently includes: preparing a raw material mixture according to the composition of the sublayer raw material and coating the raw material mixture into a layer, then applying a magnetic field perpendicular to the plane of the sublayer for orientation induction treatment, and then pre-curing to a gel state; the coating process for the top sublayer includes: preparing a raw material mixture according to the composition of the sublayer raw material and coating the raw material mixture into a layer, then applying a magnetic field perpendicular to the plane of the sublayer for orientation induction treatment; Before pre-curing after coating, the raw material mixture is subjected to a magnetic field to induce orientation. The raw material mixture is in a liquid or semi-fluid state, and the filler in the raw material mixture can rotate freely in the liquid. When a magnetic field is applied at this time, the filler can easily adjust its direction according to its magnetic susceptibility to achieve directional arrangement. The vertical magnetic field will induce the vertical thermally conductive filler to align its easily magnetized axis (usually the long axis) along the direction of the magnetic field line, thereby forming a vertical thermally conductive chain from bottom to top, maximizing the thermal conductivity in the vertical direction. 2) After completing the coating process of each small layer, gradient temperature rise curing is performed to obtain the adhesive layer of the wafer thinning grinding wheel connected to the grinding wheel substrate; 3) Press and bond the top surface of the adhesive layer of the wafer thinning grinding wheel connected to the grinding wheel substrate to the abrasive layer, and then perform overall curing, thereby realizing the bonding of the grinding wheel substrate and the abrasive layer into one piece by using the adhesive layer to prepare the wafer thinning grinding wheel.

[0174] Furthermore, during the pre-curing process, the pre-curing temperature of all the sub-layers except the bottom and top sub-layers is higher than the curing temperature of the adjacent bottom layer.

[0175] Furthermore, the gradient temperature curing includes: first heating to 50-70℃ and holding for 0.8-1.2h, then heating to 80-120℃ and holding for 1.5-2.5h, and then heating to 130-170℃ and holding for 2-4h.

[0176] Furthermore, during the gradient heating and curing process, the heating rate is 1-3°C / minute (e.g., 2°C / minute).

[0177] Furthermore, during the coating process of each sublayer, when a magnetic field perpendicular to the plane of the sublayer is applied, the intensity of the applied magnetic field is 0.3-0.7T (e.g., 0.5T), and the duration of the magnetic field is 20-40s (e.g., 30s).

[0178] Furthermore, when performing the bottom layer coating treatment, the grinding wheel substrate is preheated to 45-55°C (e.g., 50°C) before coating the raw material mixture into layers, which reduces the viscosity of the raw material mixture and facilitates uniform coating.

[0179] Furthermore, during the coating process of each small layer, when coating the raw material mixture into layers, a spin coating method is used, and the rotation speed during the spin coating process is 800-1800 rpm; Furthermore, during the coating process, the rotation speed of each small layer increases monotonically from bottom to top during spin coating. More preferably, during the coating process, the bottom layer rotates at a speed of 800-1100 rpm (e.g., 1000 μm) during spin coating, and the top layer rotates at a speed of 1300-1800 rpm (e.g., 1500 μm) during spin coating; when an intermediate layer M is present, the intermediate layer M rotates at a speed of 1100-1300 rpm (e.g., 1200 μm) during spin coating.

[0180] A specific embodiment of the fifth aspect of this application provides a wafer thinning apparatus, which is equipped with a wafer thinning grinding wheel provided in the specific embodiment of the third aspect of this application; specifically, the wafer thinning apparatus is equipped with a wafer thinning grinding wheel, which has an adhesive layer with a special structure provided in the specific embodiment of the first aspect of this application between the grinding wheel substrate and the abrasive layer; specifically: the wafer thinning apparatus includes a wafer thinning grinding wheel, which is mounted on the grinding shaft of the wafer thinning apparatus; the wafer thinning grinding wheel includes a grinding wheel substrate, an adhesive layer and an abrasive layer; the abrasive layer is fixed to the grinding wheel substrate by the adhesive layer; the adhesive layer has two or more sub-layers from bottom to top; the raw material composition of each sub-layer independently includes a resin system, ceramic filler and vertical thermally conductive filler; The coefficient of thermal expansion of each small layer from bottom to top decreases monotonically, the longitudinal thermal conductivity increases monotonically, and the surface energy and rigidity of the ceramic filler in the raw material composition decrease monotonically. The bottom layer is used to contact the grinding wheel substrate, and the top layer is used to contact the abrasive layer; Each sublayer is induced to orient itself using a magnetic field perpendicular to the plane in which the sublayer is located before curing.

[0181] This wafer thinning equipment uses a wafer thinning grinding wheel with a special structure and a bonding layer with a special structure. By using a thinning grinding wheel with a special bonding layer, this equipment can effectively avoid the problem of grinding efficiency and processing quality being compromised due to the mismatch between the thermal expansion coefficients of the abrasive layer of the grinding wheel and the substrate during wafer thinning, as well as the problem of brittle fracture at the edge of ultra-thin wafers caused by the mismatch between the thermal expansion coefficients of the abrasive layer of the grinding wheel and the substrate during ultra-thinning of stacked wafers (ultra-thinning refers to thinning the wafer to a thickness of no more than 50μm).

[0182] Specifically, the adhesive layer with a special structure adopts an integrated design of gradient CTE composite modifier and vertical thermal conductive filler gradient and orientation design to achieve a gradual transition of thermal expansion coefficient and vertical thermal conductivity from the grinding wheel substrate side to the abrasive layer side, and forms a through vertical thermal conductive chain along the top and bottom direction to open a direct path for efficient longitudinal heat dissipation; thereby assisting the thinning equipment to effectively avoid the problem of grinding efficiency and processing quality not being able to be balanced due to the mismatch of thermal expansion coefficients between the abrasive layer and the substrate of the grinding wheel used for wafer thinning, as well as the problem of brittle fracture of the edge of the ultrathin wafer caused by the mismatch of thermal expansion coefficients between the abrasive layer and the substrate of the grinding wheel during the ultrathin thinning of stacked wafers (ultrathin thinning refers to thinning the wafer to a thickness of no more than 50μm).

[0183] Furthermore, the resin system includes epoxy resin and reactive diluent.

[0184] Furthermore, in the resin system, the epoxy resin is selected from one or more combinations of epoxy resin E51, epoxy resin E44, and bio-based epoxy resin.

[0185] Furthermore, in the resin system, the reactive diluent is selected from one or more of butyl glycidyl ether, C12-C14 alkyl glycidyl ether and neodecanoic acid glycidyl ether (CAS: 26761-45-5).

[0186] Furthermore, in the resin system, the mass ratio of epoxy resin to reactive diluent is 3-5:1 (e.g., 4:1).

[0187] Furthermore, the adhesive layer consists of three or more sub-layers from bottom to top; Furthermore, the adhesive layer consists of three smaller layers with a monotonically decreasing coefficient of thermal expansion from bottom to top.

[0188] Furthermore, the coefficient of thermal expansion of the bottom layer is 12-20 ppm / ℃, the coefficient of thermal expansion of the top layer is 5-10 ppm / ℃, and the difference in the coefficient of thermal expansion between adjacent layers is less than or equal to 10 ppm / ℃.

[0189] Furthermore, the adhesive layer consists of three or more sub-layers from bottom to top, with an intermediate sub-layer M located between the bottom and top sub-layers having a thermal expansion coefficient of 10-15 ppm / ℃ (the thermal expansion coefficient is measured under normal pressure conditions within the range of 20 to 200℃).

[0190] Furthermore, the coefficient of thermal expansion of the bottom layer is 15-20 ppm / ℃ (the coefficient of thermal expansion was measured under normal pressure conditions in the range of 20 to 200℃).

[0191] Furthermore, the coefficient of thermal expansion of the top layer is 5-8 ppm / ℃ (the coefficient of thermal expansion was measured under normal pressure conditions in the range of 20 to 200℃).

[0192] Furthermore, the adhesive layer consists of three smaller layers with a monotonically decreasing coefficient of thermal expansion from bottom to top: a bottom layer, a middle layer M, and a top layer. Furthermore, the coefficient of thermal expansion of the bottom layer is 15-20 ppm / ℃, the coefficient of thermal expansion of the top layer is 5-8 ppm / ℃, and the coefficient of thermal expansion of the middle layer M is 10-15 ppm / ℃.

[0193] Furthermore, the ceramic filler in the raw material composition of the bottom layer uses ceramic materials with a positive coefficient of thermal expansion.

[0194] Furthermore, the ceramic filler in the top layer of raw materials uses ceramic materials with a negative coefficient of thermal expansion.

[0195] Furthermore, the ceramic filler in the raw material composition of the intermediate layer M uses ceramic materials with a negative coefficient of thermal expansion.

[0196] Furthermore, the surface energy of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 46 mN / m; even further, the surface energy of the ceramic filler in the raw material composition of the bottom layer is 46-50 mN / m.

[0197] Furthermore, the surface energy of the ceramic filler in the raw material composition of the top layer is less than or equal to 42 mN / m; even further, the surface energy of the ceramic filler in the raw material composition of the top layer is 38-42 mN / m.

[0198] Furthermore, the surface energy of the ceramic filler in the raw material composition of the intermediate layer M is 42-46 mN / m.

[0199] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 8 GPa; even further, the elastic modulus of the ceramic filler in the raw material composition of the bottom layer is 8-12 GPa.

[0200] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the top layer is less than or equal to 4 GPa; even further, the elastic modulus of the ceramic filler in the raw material composition of the top layer is 2-4 GPa.

[0201] Furthermore, the elastic modulus of the ceramic filler in the raw material composition of the intermediate layer M is 4-8 GPa.

[0202] Furthermore, the longitudinal thermal conductivity of the bottom layer is less than or equal to 1.8 W / m·K; even further, the longitudinal thermal conductivity of the bottom layer is 1.4-1.8 W / m·K.

[0203] Furthermore, the longitudinal thermal conductivity of the top layer is greater than or equal to 3.2 W / m·K; even further, the longitudinal thermal conductivity of the top layer is 3.2-3.8 W / m·K.

[0204] Furthermore, the longitudinal thermal conductivity of the intermediate layer M is 2.0-2.4 W / m·K; Furthermore, the concentration of ceramic filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically.

[0205] Furthermore, the ceramic filler in the raw material composition of each sublayer is a ceramic material that has undergone surface modification treatment.

[0206] Furthermore, the degree of organic matter in the modifiers used for surface modification treatment of ceramic fillers in each small layer of raw material from bottom to top increases monotonically.

[0207] Furthermore, the ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a ceramic material modified with KH560.

[0208] Furthermore, the ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material with a positive coefficient of thermal expansion, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material with a negative coefficient of thermal expansion. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a ceramic material with a negative thermal expansion coefficient modified by KH560.

[0209] Furthermore, the ceramic filler in the bottom layer raw material composition includes KH550 modified cordierite and / or KH550 modified spodumene; the ceramic filler in the top layer raw material composition includes KH570 modified sodium zirconium phosphate (NaZr2(PO4)3) and / or KH570 modified aluminum titanate. Furthermore, when an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M includes KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate; Furthermore, cordierite and / or spodumene are ultrasonically treated in a mixture of KH550 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the bottom layer raw material composition. Furthermore, sodium zirconium phosphate and / or aluminum titanate are ultrasonically treated in a mixture of KH570 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the top layer raw material composition. Furthermore, zirconium tungstate and / or zirconium phosphate are ultrasonically treated in a mixture of KH560 and an organic solvent (e.g., ethanol and / or isopropanol) for 1-3 hours (e.g., 2 hours), and then the ultrasonically treated solid product is dried and ground to a particle size of no more than 5 μm, thereby obtaining the ceramic filler in the intermediate small layer M raw material composition. Furthermore, in the bottom layer of raw material composition, the mass ratio of KH550 modified cordierite to KH550 modified spodumene in the surface-modified ceramic filler is 0.5-2:1; Furthermore, in the top layer of raw material composition, the mass ratio of KH570 modified sodium zirconium phosphate and / or KH570 modified aluminum titanate in the surface-modified ceramic filler is 0.5-2:1; Furthermore, in the intermediate small layer M raw material composition, the mass ratio of KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate in the surface-modified ceramic filler is 0.5-2:1.

[0210] Further, taking the mass of the resin system in the bottom sublayer raw material composition as 100%, the mass content of the ceramic filler in the bottom sublayer raw material composition is 35-45% (e.g., 40%); taking the mass of the resin system in the top sublayer raw material composition as 100%, the mass content of the ceramic filler in the top sublayer raw material composition is 55-65% (e.g., 60%); in a further preferred embodiment, when an intermediate sublayer M is present, the ceramic filler in the intermediate sublayer M raw material composition includes KH560 modified zirconium tungstate and / or KH560 modified zirconium phosphate, and taking the mass of the resin system in the intermediate sublayer M raw material composition as 100%, the mass content of the ceramic filler in the intermediate sublayer M raw material composition is 45-55% (e.g., 50%).

[0211] Furthermore, the vertical thermally conductive filler includes a first vertical thermally conductive filler and a second vertical thermally conductive filler. The first vertical thermally conductive filler is made of a first thermally conductive material that can provide a thermally conductive framework, and the second thermally conductive filler is made of a second thermally conductive material that can fill the gaps in the first thermally conductive filler.

[0212] Furthermore, the vertically thermally conductive filler in the raw material composition of each of the sub-layers is the same.

[0213] Furthermore, the vertical thermally conductive filler in the raw material composition of each of the sub-layers is a thermally conductive material that has been surface-modified using KH560; Furthermore, a surface-modified thermally conductive material using KH560 was prepared using the following method: The thermally conductive material is placed in a mixture of KH560 and an organic solvent (e.g., ethanol and / or isopropanol) and ultrasonically treated for 0.5-3 hours (e.g., 1 hour). The ultrasonically treated solid product is then dried at 50-70°C (e.g., 60°C) to complete the surface modification of the vertical thermally conductive filler using KH560.

[0214] Furthermore, the first thermally conductive material includes one or more combinations of diamond thermally conductive material and cubic boron nitride (cBN) thermally conductive material; even further, the first thermally conductive material is diamond thermally conductive material.

[0215] Furthermore, the second thermal conductive material includes one or more of aluminum nitride (AlN) thermal conductive material, silicon nitride (Si3N4) thermal conductive material, and beryllium oxide (BeO) thermal conductive material; even further, the second thermal conductive material is aluminum nitride thermal conductive material.

[0216] Furthermore, the particle size of the first thermally conductive material in the vertical thermally conductive filler is 8-12 μm (e.g., 10 μm).

[0217] Furthermore, the particle size of the second thermally conductive material in the vertical thermally conductive filler is 1-3 μm (e.g., 2 μm).

[0218] Furthermore, in the vertical thermally conductive filler, the mass ratio of the first thermally conductive material to the second thermally conductive material is 4-2:1 (e.g., 3:1).

[0219] Furthermore, the concentration of vertically thermally conductive filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically.

[0220] Furthermore, taking the mass of the resin system in the bottom sublayer as 100%, the mass content of the vertical thermally conductive filler in the bottom sublayer is 5-9% (e.g., 8%); taking the mass of the resin system in the top sublayer as 100%, the mass content of the vertical thermally conductive filler in the top sublayer is 11-20% (e.g., 15%). Furthermore, when an intermediate layer M is present, taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%, the mass content of the vertical thermally conductive filler in the raw material composition of the intermediate layer M is 9-11% (e.g., 10%).

[0221] Furthermore, the raw material composition of each sublayer independently includes a transverse thermally conductive filler, which includes one or more of graphene nanosheets, plasma-treated alumina nanosheets, and plasma-treated boron nitride nanosheets; even further, the transverse thermally conductive filler in the raw material composition of each sublayer is plasma-treated boron nitride nanosheets (p-BNNS).

[0222] Furthermore, the transverse thermally conductive filler in the raw material composition of each of the sub-layers is the same.

[0223] Furthermore, the concentration of transverse thermally conductive filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically. Furthermore, taking the mass of the resin system in the bottom sublayer as 100%, the mass content of the transverse thermally conductive filler in the bottom sublayer is 5-6% (e.g., 5%); taking the mass of the resin system in the top sublayer as 100%, the mass content of the transverse thermally conductive filler in the top sublayer is 6-8% (e.g., 7%). Furthermore, when an intermediate layer M is present, taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%, the mass content of the transverse thermally conductive filler in the raw material composition of the intermediate layer M is 8-10% (e.g., 10%).

[0224] Furthermore, the raw material composition of each sublayer independently includes conductive reinforcing filler, which includes one or more of carboxylated carbon nanotubes, silver-plated nanoparticles, graphene, etc.

[0225] Furthermore, the conductive reinforcing filler in the raw material composition of each of the aforementioned sublayers is the same; Furthermore, the concentration of conductive reinforcing filler in the raw material composition of each sub-layer from bottom to top (based on the mass of the resin system of the corresponding sub-layer being 100%) increases monotonically. Furthermore, based on the mass of the resin system in the bottom sublayer raw material composition being 100%, the mass content of the conductive reinforcing filler in the bottom sublayer raw material composition is 1-1.5% (e.g., 1%); based on the mass of the resin system in the top sublayer raw material composition being 100%, the mass content of the conductive reinforcing filler in the top sublayer raw material composition is 1.5-3% (e.g., 2%). Furthermore, when an intermediate sublayer M is present, taking the mass of the resin system in the raw material composition of the intermediate sublayer M as 100%, the mass content of the conductive reinforcing filler in the raw material composition of the intermediate sublayer M is 1-1.5% (e.g., 1%).

[0226] Furthermore, the thickness of each sublayer in the adhesive layer is independently set to 8-23 μm.

[0227] Furthermore, the thickness of each sub-layer decreases monotonically from bottom to top; Furthermore, the thickness of the bottom sublayer is 18-23 μm (e.g., 20 μm), and the thickness of the top sublayer is 8-12 μm (e.g., 10 μm). Furthermore, when an intermediate sublayer M is present, the thickness of the intermediate sublayer M is 12-18 μm (e.g., 15 μm).

[0228] Furthermore, the grinding wheel matrix is ​​made of a metal matrix composite material, such as one or more combinations of aluminum alloys and copper alloys. The grinding wheel matrix may be, but is not limited to, the grinding wheel matrix used in existing grinding wheels.

[0229] Furthermore, the abrasive layer uses diamond abrasive grains. The grinding wheel matrix may, but is not limited to, using the abrasive layer found in existing grinding wheels.

[0230] Furthermore, the structure of the wafer thinning equipment can be, but is not limited to, the structure of existing wafer thinning equipment equipped with grinding wheels.

[0231] A specific embodiment of the sixth aspect of this application provides a wafer thinning method, which uses the wafer thinning equipment provided by the technical solution of the fourth aspect of this application to perform wafer thinning.

[0232] Furthermore, wafer thinning refers to the ultra-thinning of 3D IC wafers (ultra-thinning refers to reducing the thickness of the wafer to no more than 50μm). Furthermore, the thickness of 3D IC wafers is reduced to no more than 10μm; Furthermore, during the ultra-thinning process of 3D IC wafers, the feed rate is 0.5-0.8um / s, and the surface roughness of the resulting wafer product is 10-20nm.

[0233] Example 1 This embodiment provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, and an adhesive layer for the wafer thinning grinding wheel.

[0234] The adhesive layer of the wafer thinning grinding wheel provided in this embodiment is prepared by the following method: (1) Mix the raw materials according to the composition of the bottom layer and then ultrasonically disperse them for 30 minutes and mechanically stir them for 2 hours to obtain the raw material mixture. Spin coat the raw material mixture into a layer on a grinding wheel substrate preheated to 50°C (rotate at 1000 rpm for 30 seconds). Then apply a magnetic field perpendicular to the plane of the layer (the magnetic field strength is 0.5T and the time is 30 seconds) to induce orientation treatment. Then pre-cur it at 60°C for 30 minutes until the bottom layer is in a gel state. The composition of the bottom layer raw materials is as follows: Figure 6 As shown, the material consists of a resin system, ceramic filler accounting for 40% of the total mass of the resin system, vertical thermally conductive filler accounting for 8% of the total mass of the resin system, transverse thermally conductive filler accounting for 5% of the total mass of the resin system, and conductive reinforcing filler accounting for 1% of the total mass of the resin system. The resin system is composed of epoxy resin E51 and butyl glycidyl ether in a mass ratio of 8:2. The ceramic filler is cordierite and spodumene with KH550 surface modification treatment. The vertical thermally conductive filler is diamond and aluminum nitride with KH560 surface modification treatment. The transverse thermally conductive filler is boron nitride nanosheets with plasma treatment. The conductive reinforcing filler is carboxylated carbon nanotubes. The plasma-treated boron nitride nanosheets (p-BNNS) used in this embodiment were prepared by the following method: hexagonal boron nitride powder was placed in a plasma treatment device and subjected to plasma bombardment in an oxygen-containing atmosphere, thereby simultaneously achieving the exfoliation and surface functionalization of boron nitride. After dispersion, centrifugation, and drying, the product was obtained. The carboxylated carbon nanotubes (f-CNTs) used in this embodiment were prepared by the following method: carbon nanotubes were placed in a mixture of concentrated sulfuric acid and concentrated nitric acid, refluxed at 60-120°C for 2-8 hours, cooled, filtered, washed with water until neutral, and dried to obtain the final product. Cordierite and spodumene with KH550 surface modification were prepared by the following method: Cordierite and spodumene in a mass ratio of 1:1 were placed in a mixture of KH550 and organic solvent ethanol and ultrasonically treated for 2 hours. The ultrasonically treated solid product was then dried and ground to a particle size of no more than 5 μm, thus obtaining cordierite and spodumene with KH550 surface modification. The mass ratio of cordierite and spodumene, KH550 and ethanol was 1:0.015:10. Cordierite and spodumene are ceramic materials with a positive coefficient of thermal expansion. The surface energy of cordierite and spodumene after KH550 surface modification treatment is 48 mN / m and the elastic modulus is 10 GPa. The KH560 surface-modified diamond and aluminum nitride were prepared by the following method: diamond (particle size of 10 μm) and aluminum nitride (particle size of 2 μm) in a mass ratio of 3:1 were placed in a mixture of KH560 and organic solvent ethanol and ultrasonically treated for 1 h. The solid product after ultrasonic treatment was then dried at 60 °C to obtain KH560 surface-modified diamond and aluminum nitride. The mass ratio of diamond and aluminum nitride, KH560 and ethanol was 1:0.1:10.

[0235] (2) Mix the raw materials according to the composition of the intermediate layer M and then perform ultrasonic dispersion for 30 minutes and mechanical stirring for 2 hours to obtain the raw material mixture. Spin coat the raw material mixture onto the bottom layer in a layered form (rotate at 1200 rpm for 30s). Then apply a magnetic field perpendicular to the plane of the layer (magnetic field strength of 0.5T for 30s) to induce orientation treatment. Then pre-cur it at 80℃ for 30 minutes until the intermediate layer M is in a gel state. Using a curing temperature 80℃ higher than that of the bottom layer for pre-curing the intermediate layer M can accelerate the gelation of the intermediate layer and strengthen the chemical bond between the intermediate layer M and the bottom layer. The intermediate layer M material consists of a resin system, ceramic filler accounting for 50% of the total mass of the resin system, vertical thermally conductive filler accounting for 10% of the total mass of the resin system, transverse thermally conductive filler accounting for 7% of the total mass of the resin system, and conductive reinforcing filler accounting for 1% of the total mass of the resin system. The resin system consists of epoxy resin E51 and butyl glycidyl ether in a mass ratio of 8:2. The ceramic filler is zirconium tungstate and zirconium phosphate with KH560 surface modification treatment. The vertical thermally conductive filler is diamond and aluminum nitride with KH560 surface modification treatment. The transverse thermally conductive filler is boron nitride nanosheets with plasma treatment. The conductive reinforcing filler is carboxylated carbon nanotubes. Zirconium tungstate and zirconium phosphate with KH560 surface modification were prepared by the following method: Zirconium tungstate and zirconium phosphate with a mass ratio of 1:1 were placed in a mixture of KH560 and organic solvent ethanol and ultrasonically treated for 2 hours. The solid product after ultrasonic treatment was then dried to obtain Zirconium tungstate and zirconium phosphate with KH560 surface modification. The mass ratio of Zirconium tungstate and zirconium phosphate, KH560 and ethanol was 1:0.02:12. Zirconium tungstate and zirconium phosphate are ceramic materials with negative thermal expansion coefficient. The surface energy of zirconium tungstate and zirconium phosphate after KH560 surface modification treatment is 44 mN / m and the elastic modulus is 6 GPa. The KH560 surface-modified diamond and aluminum nitride were prepared using the same preparation method as the KH560 surface-modified diamond and aluminum nitride used in the raw material composition of the bottom layer.

[0236] (3) Mix the raw materials according to the composition of the top layer and then perform ultrasonic dispersion for 30 minutes and mechanical stirring for 2 hours to obtain the raw material mixture. Spin coat the raw material mixture on the middle layer M into a layer (rotate at a speed of 1500 rpm for 30s), and then apply a magnetic field perpendicular to the plane of the layer (the magnetic field strength is 0.5T and the time is 30s) to induce orientation. The top layer consists of a resin system, ceramic fillers accounting for 60% of the total mass of the resin system, vertical thermally conductive fillers accounting for 15% of the total mass of the resin system, horizontal thermally conductive fillers accounting for 10% of the total mass of the resin system, and conductive reinforcing fillers accounting for 2% of the total mass of the resin system. The resin system consists of epoxy resin E51 and butyl glycidyl ether in a mass ratio of 8:2. The ceramic fillers are KH570 modified sodium zirconium phosphate and aluminum titanate. The vertical thermally conductive fillers are KH560 surface-modified diamond and aluminum nitride. The horizontal thermally conductive fillers are plasma-treated boron nitride nanosheets. The conductive reinforcing fillers are carboxylated carbon nanotubes. KH570-modified sodium zirconium phosphate and aluminum titanate were prepared by the following method: sodium zirconium phosphate and aluminum titanate in a mass ratio of 1:1 were placed in a mixture of KH570 and organic solvent ethanol and ultrasonically treated for 2 hours. The solid product after ultrasonic treatment was then dried to obtain KH570-modified sodium zirconium phosphate and aluminum titanate. The mass ratio of sodium zirconium phosphate and aluminum titanate, KH570 and ethanol was 1:0.02:12. Sodium zirconium phosphate and aluminum titanate are ceramic materials with extremely low negative coefficients of thermal expansion. KH570 modified sodium zirconium phosphate and aluminum titanate have a surface energy of 40 mN / m and an elastic modulus of 3 GPa. The KH560 surface-modified diamond and aluminum nitride were prepared using the same preparation method as the KH560 surface-modified diamond and aluminum nitride used in the raw material composition of the bottom layer.

[0237] (4) Gradient temperature curing is performed to prepare the adhesive layer of the wafer thinning grinding wheel; wherein, the gradient temperature curing includes: heating at a rate of 2℃ / min, first heating to 60℃ and holding for 1h, then heating to 100℃ and holding for 2h, and then heating to 150℃ and holding for 3h.

[0238] The adhesive layer of the wafer thinning grinding wheel provided in this embodiment consists of a bottom layer with a thickness of 20 μm, a middle layer M with a thickness of 15 μm, and a top layer with a thickness of 10 μm from bottom to top. The coefficient of thermal expansion of the bottom layer is 18 ppm / ℃ and is used to contact the grinding wheel substrate. The coefficient of thermal expansion of the middle layer M is 12 ppm / ℃, and the coefficient of thermal expansion of the top layer is 6.5 ppm / ℃ and is used to contact the abrasive layer.

[0239] The wafer thinning grinding wheel provided in this embodiment, such as Figure 3 , Figure 4 , Figure 5 As shown, an adhesive layer 200 is provided between the grinding wheel substrate 100 and the abrasive layer 300, wherein the adhesive layer 200 adopts the adhesive layer of the wafer thinning grinding wheel provided in this embodiment. The wafer thinning grinding wheel adopts a cup-shaped grinding wheel structure.

[0240] The grinding wheel substrate 100 is made of aluminum alloy. The abrasive layer 300 includes multiple grinding blocks 3001, each with rounded corners. Each grinding block 3001 is composed of diamond abrasive grains and a porous ceramic binder. The diamond abrasive grains are the cutting body and perform the grinding action, while the porous ceramic binder acts as a skeleton to fix the diamond abrasive grains. An annular groove is formed in the middle of the annular bottom surface of the grinding wheel substrate 100 along the circumference of the grinding wheel. The grinding blocks 3001 are inserted into the groove of the grinding wheel substrate 100 and arranged at intervals along the circumference of the grinding wheel. An adhesive layer 200 is disposed between the bottom of the annular groove and the grinding blocks 3001 to connect the grinding blocks 3001 to the grinding wheel substrate 100. This wafer thinning grinding wheel is prepared by the following method: 1) The adhesive layer of the wafer thinning grinding wheel is prepared according to the preparation method of the adhesive layer of the wafer thinning grinding wheel in this embodiment; the prepared adhesive layer is connected to the grinding wheel substrate; 2) The top surface of the adhesive layer prepared in step 1) is brought into contact with the abrasive layer and pressed and bonded at 70°C and 2MPa for 60 minutes, so that the top surface of the adhesive layer and the abrasive layer form a tight physical entanglement and a preliminary chemical bond. 3) Then, the product obtained in step 2) is subjected to step-by-step thermal curing, specifically by holding it at 80°C for 2 hours and at 120°C for 4 hours in sequence, so that the interface between the adhesive layer and the abrasive layer undergoes a full cross-linking reaction and achieves chemical bonding at the interface. 4) Allow the product from step 3) to cool naturally to room temperature, thereby bonding the grinding wheel substrate and the abrasive layer together using the adhesive layer to obtain the finished grinding wheel; perform visual inspection and non-destructive testing (by ultrasonic scanning) on ​​the finished grinding wheel to ensure that there is no delamination or bubbles, and finally obtain the grinding wheel for wafer thinning.

[0241] The structure of the wafer thinning equipment provided in this embodiment is as follows: Figure 1 , Figure 2 As shown, it includes a grinding device 2 and an adsorption platform 3. 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 is mounted on the grinding shaft of the wafer thinning equipment and can rotate circumferentially to grind the back of the wafer.

[0242] The grinding wheel 23 is the wafer thinning grinding wheel provided in this embodiment.

[0243] The grinding device 2 includes a feed assembly 21, a rotating 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 is mounted at the lower end of the rotating shaft 22. The rotating shaft 22 is used to rotate the grinding wheel 23 around its axis of rotation. The feed assembly 21 can drive the rotating 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 back side of the wafer under the drive of the feed assembly 21. At this time, both the grinding wheel 23 and the wafer are rotating in the same direction but at different speeds. The grinding wheel 23 is used to grind the back side of the wafer. The feed assembly 21 includes a linear guide that guides the movement direction of the rotating shaft 22 and a ball screw-slider mechanism that moves the rotating shaft 22 up and down.

[0244] 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 porous alumina material, 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. 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 is provided with a tilting device that tilts relative to the grinding wheel 23, and the grinding device 2 is provided with a tilting structure that tilts the rotation axis 22. Thus, the contact between the grinding wheel 23 and the wafer can be adjusted to grind the wafer into the desired shape.

[0245] 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 a CPU, memory, etc. The functions of the control device can be implemented through software control or hardware operation. The control device can control the movement of the feed assembly 21, 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. When abnormalities occur, it promptly issues alarms and takes corresponding protective measures to ensure the safety of the equipment and operators. In this embodiment, the control device used in existing wafer thinning equipment for controlling the operation of the grinding device can be employed.

[0246] This embodiment provides a first wafer thinning method. It involves thinning a stacked wafer composed of two 775μm wafers bonded together, aiming to reduce the upper (to be thinned) wafer to 10μm. While keeping the bottom wafer thickness constant at 775μm, the total thickness of the stacked wafers will decrease from the initial 1550μm to 785μm. The grinding accuracy meets a surface roughness of 10-20nm. Specifically, it includes: First, a coarse grinding wafer thinning device (the only difference from the wafer thinning device provided in this embodiment of the application is that the grinding wheel is a coarse grinding wheel) is used to coarsely grind and thin the stacked wafers; wherein, the coarse grinding wheel and the adsorption platform (i.e., the platform used to adsorb and fix the wafer to be processed) rotate in the same direction, the rotation speed of the coarse grinding wheel is 4800 rpm, and the rotation speed of the adsorption platform is 300 rpm; while the coarse grinding wheel is rotating, it is fed downwards at feed speeds of 5μm / s, 4μm / s, and 3μm / s in sequence, and the flow rate of cooling water during the grinding process is 4L / min; After rough grinding to a total thickness of 825 μm for the stacked wafers, the wafer thinning equipment provided in this embodiment is used for fine grinding to a total thickness of 785 μm for the stacked wafers. The grinding wheel and the adsorption platform (i.e., the platform used to adsorb and fix the wafers to be processed) rotate in the same direction. The rotation speed of the grinding wheel is 4800 rpm and the rotation speed of the adsorption platform is 300 rpm. The cooling water flow rate during grinding is 4 L / min. The feed speed of the grinding wheel is the maximum feed speed under the condition that the grinding accuracy meets the surface roughness of 10-20 nm.

[0247] The specific operation process for wafer thinning is as follows: Figure 7 As shown, it includes: A100. Vacuum adsorption fixes the wafer onto the adsorption platform.

[0248] In this embodiment, before performing the wafer thinning operation, the surface of the adsorption platform 3 is wiped clean with a lint-free cloth dampened with an appropriate amount of alcohol to ensure that the surface of the adsorption platform 3 is clean and free of impurities, so as to avoid impurities affecting the adsorption effect and grinding quality of the wafer. The wafer to be thinned is placed on the adsorption platform 3 using a vacuum suction pen, ensuring that the center of the wafer is aligned with the center of the adsorption platform 3. The vacuum source connected to the adsorption platform 3 is activated by the control device. The porous structure inside the adsorption platform 3 forms a negative pressure under the action of vacuum, adsorbing the wafer onto its surface. To ensure a firm adsorption, the vacuum degree of the adsorption platform 3 is monitored in real time by the control device. When the vacuum degree reaches a preset value, it indicates that the wafer has been stably adsorbed and the next operation can be carried out.

[0249] A200, the grinding wheel moves down to contact the back side of the wafer under the drive of the feed assembly.

[0250] In this embodiment, the control feed assembly 21 drives the rotating shaft 22 and the grinding wheel 23 to move vertically downwards until the grinding surface of the grinding wheel contacts the back side of the wafer. Specifically, the target position parameter of the grinding wheel 23 is input into the control device. This parameter is determined based on factors such as the wafer thickness, grinding allowance, and the initial position of the grinding wheel 23. The control device sends a command to the feed assembly 21 to precisely control the movement direction of the feed assembly 21, ensuring that it moves vertically downwards. The feed assembly 21 drives the grinding wheel 23 to move downwards smoothly at a set speed. During the movement, the control device monitors the position information of the feed assembly 21 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.

[0251] The A300, grinding wheel, and adsorption platform rotate in the same direction, while the grinding wheel feeds downwards to grind the back side of the wafer as it rotates.

[0252] In this embodiment, the grinding wheel 23 and the adsorption platform 3 rotate in the same direction, while the grinding wheel 23 is fed downwards. The rotational speed of the grinding wheel 23 is greater than that of the adsorption platform 3 to grind the back side of the wafer. Specifically, the control device starts the grinding wheel 23 and the adsorption platform 3 at the same time. The grinding wheel 23 rotates at a set speed, while the adsorption platform 3 and the wafer adsorbed on it rotate in the same direction at a relatively low speed. After the grinding wheel 23 and the adsorption platform 3 reach a stable rotational state, the control device continues to control the feed assembly 21 to feed the grinding wheel 23 to the back side of the wafer to grind the wafer surface.

[0253] A400: Once the wafer has been ground to the target thickness, stop the rotation and feed of the grinding wheel and the adsorption platform, and move the grinding wheel upwards to reset and detach it from the wafer surface.

[0254] In this embodiment, a non-contact thickness sensor installed near the grinding wheel 23 is used to continuously monitor the thickness change of the wafer. When the thickness data received by the control device shows that the wafer has been ground to the target thickness, the grinding is determined to be complete. After the wafer is ground to the target thickness, the grinding wheel 23 and the adsorption platform 3 stop rotating. Subsequently, the control device starts the feed assembly 21 to drive the grinding wheel 23 to move 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 the grinding wheel stops rotating.

[0255] A500 releases the vacuum adsorption of the wafer by the adsorption platform and transfers the wafer.

[0256] In this embodiment, the control device shuts off the vacuum source and switches to a compressed air source or a water source; compressed air or water flows into the adsorption platform 3, disrupting the negative pressure state between the adsorption platform 3 and the wafer, thereby releasing the adsorption force; using a vacuum pen or other precision gripping tool, the thinned wafer is removed from the adsorption platform 3, completing the entire wafer thinning process.

[0257] Table 1 shows the maximum feed rate during each stage of wafer thinning, provided that the grinding accuracy meets the surface roughness requirement of 10-20 nm.

[0258] The results are shown in Table 2.

[0259] Comparative Example 1 This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, and an adhesive layer for the wafer thinning grinding wheel.

[0260] The adhesive layer of the wafer thinning grinding wheel provided in this comparative example is an epoxy resin layer.

[0261] The only difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the adhesive layer of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0262] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0263] The wafer thinning method provided in this embodiment differs from the first wafer thinning method provided in Embodiment 1 only in that it uses the wafer thinning equipment provided in this comparative example. The results are shown in Table 1.

[0264] Table 1

[0265] Comparative Example 2 This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, and an adhesive layer for the wafer thinning grinding wheel.

[0266] The adhesive layer of the wafer thinning grinding wheel provided in this comparative example differs from that of the wafer thinning grinding wheel provided in Example 1 only in that: the surface-modified ceramic filler in the middle layer M of the adhesive layer of the wafer thinning grinding wheel uses cordierite and spodumene surface-modified with KH560 (the difference from the surface-modified ceramic filler in the bottom layer is that KH560 is used instead of KH550 for surface modification), and the addition concentration of the surface-modified ceramic filler in the middle layer M is 40% instead of 50%; the surface-modified ceramic filler in the top layer of the adhesive layer of the wafer thinning grinding wheel uses cordierite and spodumene surface-modified with KH570 (the difference from the surface-modified ceramic filler in the bottom layer is that KH570 is used instead of KH550 for surface modification), and the addition concentration of the surface-modified ceramic filler in the top layer is 40% instead of 60%.

[0267] The only difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the adhesive layer of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0268] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0269] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 is only that: the wafer thinning equipment provided in this comparative example is used; and the feed rate used in each stage of wafer thinning in this comparative example is lower than the feed rate used in each stage of wafer thinning in Example 1. The results are shown in Table 2.

[0270] Comparative Example 3 This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, and an adhesive layer for the wafer thinning grinding wheel.

[0271] The difference between the adhesive layer of the wafer thinning grinding wheel provided in this comparative example and the adhesive layer of the wafer thinning grinding wheel provided in Example 1 is only that: (1) no vertical thermally conductive filler is added to the raw material composition of the bottom layer, the middle layer M and the top layer of the adhesive layer of the wafer thinning grinding wheel; and (2) no magnetic field is applied.

[0272] The only difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the adhesive layer of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0273] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0274] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 lies only in the use of the wafer thinning equipment provided in this comparative example; the feed rate used in each stage of wafer thinning in this comparative example is lower than the feed rate used in each stage of wafer thinning in Example 1. The results are shown in Table 2.

[0275] Comparative Example 4 This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, and an adhesive layer for the wafer thinning grinding wheel.

[0276] The only difference between the adhesive layer of the wafer thinning grinding wheel provided in this comparative example and the adhesive layer of the wafer thinning grinding wheel provided in Example 1 is that no magnetic field is applied.

[0277] The only difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the adhesive layer of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0278] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0279] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 lies only in the use of the wafer thinning equipment provided in this comparative example; the feed rate used in each stage of wafer thinning in this comparative example is lower than the feed rate used in each stage of wafer thinning in Example 1. The results are shown in Table 2.

[0280] Comparative Example 5 This comparative example provides a wafer thinning device, a wafer thinning method, a wafer thinning grinding wheel, and an adhesive layer for the wafer thinning grinding wheel.

[0281] The adhesive layer of the wafer thinning grinding wheel provided in this comparative example differs from that of the wafer thinning grinding wheel provided in Example 1 only in that: the surface-modified ceramic filler in the middle sub-layer M of the adhesive layer of the wafer thinning grinding wheel uses zirconium tungstate and zirconium phosphate surface-modified with KH550 (the difference from the surface-modified ceramic filler in the middle sub-layer M of the adhesive layer of the wafer thinning grinding wheel in Example 1 is that KH550 is used instead of KH560 for surface modification); the surface-modified ceramic filler in the top sub-layer of the adhesive layer of the wafer thinning grinding wheel uses sodium zirconium phosphate and aluminum titanate surface-modified with KH550 (the difference from the surface-modified ceramic filler in the top sub-layer of the adhesive layer of the wafer thinning grinding wheel in Example 1 is that KH550 is used instead of KH570 for surface modification).

[0282] The only difference between the wafer thinning grinding wheel provided in this comparative example and the wafer thinning grinding wheel provided in Example 1 is that the adhesive layer of the wafer thinning grinding wheel is the same as that of the wafer thinning grinding wheel provided in this comparative example.

[0283] The only difference between the wafer thinning equipment provided in this comparative example and the wafer thinning equipment provided in Example 1 is that the wafer thinning grinding wheel used is the wafer thinning grinding wheel provided in this comparative example.

[0284] The difference between the wafer thinning method provided in this comparative example and the wafer thinning method provided in Example 1 lies only in the use of the wafer thinning equipment provided in this comparative example; the feed rate used in each stage of wafer thinning in this comparative example is lower than the feed rate used in each stage of wafer thinning in Example 1. The results are shown in Table 2.

[0285] Table 2

[0286] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An adhesive layer for a wafer thinning grinding wheel, characterized in that, The adhesive layer consists of two or more sub-layers from bottom to top; each sub-layer independently comprises ceramic filler and vertical thermally conductive filler. The coefficient of thermal expansion of each small layer from bottom to top decreases monotonically, the longitudinal thermal conductivity increases monotonically, the surface energy of the ceramic filler in the raw material composition decreases monotonically, and the rigidity decreases monotonically; the bottom small layer is used to contact the grinding wheel matrix, and the top small layer is used to contact the abrasive layer; Each sublayer is induced to orient itself using a magnetic field perpendicular to the plane in which the sublayer is located before curing.

2. The adhesive layer of the wafer thinning grinding wheel according to claim 1, characterized in that, The coefficient of thermal expansion of the bottom layer is 12-20 ppm / ℃, the coefficient of thermal expansion of the top layer is 5-10 ppm / ℃, and the difference in the coefficient of thermal expansion between adjacent layers is less than or equal to 10 ppm / ℃.

3. The adhesive layer of the wafer thinning grinding wheel according to claim 2, characterized in that, The adhesive layer consists of three or more sub-layers with a monotonically decreasing coefficient of thermal expansion from bottom to top; there is an intermediate sub-layer M between the bottom sub-layer and the top sub-layer with a coefficient of thermal expansion of 10-15 ppm / ℃.

4. The adhesive layer of the wafer thinning grinding wheel according to claim 1 or 3, characterized in that, Includes at least one of the following features 1)-3): 1) The surface energy of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 46 mN / m, and the surface energy of the ceramic filler in the raw material composition of the top layer is less than or equal to 42 mN / m; When an intermediate sublayer M is present, the surface energy of the ceramic filler in the raw material composition of the intermediate sublayer M is 42-46 mN / m; 2) The elastic modulus of the ceramic filler in the raw material composition of the bottom layer is greater than or equal to 8 GPa, and the elastic modulus of the ceramic filler in the raw material composition of the top layer is less than or equal to 4 GPa. When an intermediate sublayer M is present, the elastic modulus of the ceramic filler in the raw material composition of the intermediate sublayer M is 4-8 GPa. 3) The longitudinal thermal conductivity of the bottom layer is less than or equal to 1.8 W / m·K, and the longitudinal thermal conductivity of the top layer is greater than or equal to 3.2 W / m·K; When an intermediate layer M is present, the longitudinal thermal conductivity of the intermediate layer M is 2.0-2.4 W / m·K.

5. The adhesive layer of the wafer thinning grinding wheel according to claim 1 or 3, characterized in that, Includes at least one of the following features 1)-2): 1) The ceramic filler in the bottom layer uses ceramic materials with a positive coefficient of thermal expansion, while the ceramic filler in the top layer uses ceramic materials with a negative coefficient of thermal expansion. When an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M uses ceramic materials with a negative coefficient of thermal expansion. 2) The ceramic filler in the bottom layer of raw materials is a KH550 modified ceramic material, and the ceramic filler in the top layer of raw materials is a KH570 modified ceramic material; When an intermediate sublayer M is present, the ceramic filler in the raw material composition of the intermediate sublayer M is a KH560 modified ceramic material.

6. The adhesive layer of the wafer thinning grinding wheel according to claim 1 or 3, characterized in that, Includes at least one of the following features 1)-2): 1) The concentration of ceramic filler in the raw material composition of each small layer from bottom to top increases monotonically; Based on the resin system's mass being 100% in the bottom layer raw material composition, the ceramic filler content in the bottom layer raw material composition is 35-45% by mass; based on the resin system's mass being 100% in the top layer raw material composition, the ceramic filler content in the top layer raw material composition is 55-65% by mass. When an intermediate sublayer M is present, taking the mass of the resin system in the raw material composition of the intermediate sublayer M as 100%, the mass content of ceramic filler in the raw material composition of the intermediate sublayer M is 45-55%. 2) The concentration of vertically thermally conductive filler in the raw material composition of each small layer from bottom to top increases monotonically; Based on the resin system in the bottom layer raw material composition being 100% by mass, the mass content of the vertical thermally conductive filler in the bottom layer raw material composition is 5-9% by mass; Taking the resin system in the top layer raw material composition as 100% by mass, the mass content of the vertical thermally conductive filler in the top layer raw material composition is 11-20% by mass; When an intermediate layer M is present, taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%, the mass content of the vertical thermally conductive filler in the raw material composition of the intermediate layer M is 9-11%.

7. The adhesive layer of the wafer thinning grinding wheel according to claim 1, characterized in that, The vertical thermally conductive filler includes a first vertical thermally conductive filler and a second vertical thermally conductive filler. The first vertical thermally conductive filler is made of a first thermally conductive material that can provide a thermally conductive skeleton, and the second thermally conductive filler is made of a second thermally conductive material that can fill the gaps in the first thermally conductive filler. The first thermal conductive material includes one or more of diamond thermal conductive materials and cubic boron nitride thermal conductive materials; The second thermally conductive material includes one or a combination of two or more of aluminum nitride thermally conductive materials, silicon nitride thermally conductive materials, and beryllium oxide thermally conductive materials.

8. The adhesive layer of the wafer thinning grinding wheel according to claim 1 or 3, characterized in that, Includes at least one of the following features 1)-2): 1) The raw material composition of each sublayer independently includes a transverse thermally conductive filler, which includes one or more of the following: graphene nanosheets, plasma-treated alumina nanosheets, and plasma-treated boron nitride nanosheets. 2) The raw material composition of each sublayer independently includes conductive reinforcing filler, which includes one or more of carboxylated carbon nanotubes, silver-plated nanoparticles, and graphene.

9. The adhesive layer of the wafer thinning grinding wheel according to claim 8, characterized in that, When there is transverse thermally conductive filler, the transverse thermally conductive filler in the raw material composition of each of the sub-layers is the same; When conductive reinforcing fillers are present, the conductive reinforcing fillers in the raw material composition of each of the sublayers are the same.

10. The adhesive layer of the wafer thinning grinding wheel according to claim 8, characterized in that, When transverse thermally conductive filler is present, the concentration of transverse thermally conductive filler in the raw material composition of each small layer from bottom to top increases monotonically. Based on the resin system in the bottom layer raw material composition being 100% by mass, the mass content of the transverse thermally conductive filler in the bottom layer raw material composition is 5-6% by mass; Based on the resin system in the top layer raw material composition being 100% by mass, the mass content of the transverse thermally conductive filler in the top layer raw material composition is 6-8% by mass; When an intermediate layer M is present, taking the mass of the resin system in the raw material composition of the intermediate layer M as 100%, the mass content of the transverse thermally conductive filler in the raw material composition of the intermediate layer M is 8-10%. When conductive reinforcing fillers are present, the concentration of conductive reinforcing fillers in the raw material composition of each small layer from bottom to top increases monotonically. Based on the resin system in the bottom layer raw material composition being 100% by mass, the mass content of conductive reinforcing filler in the bottom layer raw material composition is 1-1.5% by mass. Based on the resin system comprising 100% of the top layer raw material composition, the mass content of the conductive reinforcing filler in the top layer raw material composition is 1.5-3%; When an intermediate sublayer M is present, the mass content of the conductive reinforcing filler in the intermediate sublayer M raw material composition is 1-1.5%, taking the mass of the resin system in the intermediate sublayer M raw material composition as 100%.

11. The adhesive layer of the wafer thinning grinding wheel according to claim 1 or 3, characterized in that, The thickness of each sublayer decreases monotonically from bottom to top; the thickness of the bottom sublayer is 18-23 μm, and the thickness of the top sublayer is 8-12 μm. When an intermediate sublayer M is present, the thickness of the intermediate sublayer M is 12-18 μm.

12. The method for preparing the adhesive layer of the wafer thinning grinding wheel according to any one of claims 1-11, characterized in that, Includes the following steps: 1) Apply each small layer of coating to the grinding wheel substrate in the order from the bottom layer to the top layer; 2) After completing the coating process of each small layer, the adhesive layer is prepared by gradient temperature curing.

13. The method for preparing the adhesive layer of the wafer thinning grinding wheel according to claim 12, characterized in that, The coating process for each sublayer, except for the top sublayer, independently includes: preparing a raw material mixture according to the composition of the sublayer raw material and coating the raw material mixture into a layer, then applying a magnetic field perpendicular to the plane of the sublayer for orientation induction treatment, and then pre-curing to a gel state; the coating process for the top sublayer includes: preparing a raw material mixture according to the composition of the sublayer raw material and coating the raw material mixture into a layer, then applying a magnetic field perpendicular to the plane of the sublayer for orientation induction treatment; The gradient temperature curing process includes: first heating to 50-70℃ and holding for 0.8-1.2h, then heating to 80-120℃ and holding for 1.5-2.5h, and then heating to 130-170℃ and holding for 2-4h.

14. A grinding wheel for wafer thinning, characterized in that, The assembly includes an adhesive layer for a wafer thinning grinding wheel as described in any one of claims 1-11 or an adhesive layer prepared by the preparation method described in any one of claims 12-13, and further includes a grinding wheel substrate and an abrasive layer, wherein the abrasive layer is fixed to the grinding wheel substrate by the adhesive layer. The abrasive layer includes multiple abrasive blocks. An annular groove is formed in the middle of the annular bottom surface of the grinding wheel base along the circumference of the grinding wheel. The abrasive blocks are inserted into the groove of the grinding wheel base and arranged at intervals along the circumference of the grinding wheel. The adhesive layer is disposed between the bottom of the annular groove and the abrasive blocks.

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