Wafer thinning equipment and thinning methods

Abstract

This invention discloses a wafer thinning apparatus and a thinning method. The grinding structure of the grinding wheel in the wafer thinning apparatus includes a flexible assembly and multiple first rigid microstructures. The multiple first rigid microstructures are arranged three-dimensionally at intervals within the flexible assembly and stacked in the feed direction of the grinding structure. The spaces between the multiple first rigid microstructures are filled by the flexible assembly. The thinning method uses the wafer thinning apparatus and includes simultaneously increasing the feed speed and rotational speed of the grinding wheel. This invention improves grinding efficiency, reduces surface damage to the wafer, lowers the surface roughness of the wafer, and makes the wafer surface smoother, thus facilitating the high-precision integration requirements of the wafer chip.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of semiconductor grinding processing, in particular to a wafer thinning device and a thinning method. BACKGROUND

[0002] With the rapid development of the semiconductor industry towards high-density integration and high-performance packaging, Chiplet integration technology has become one of the core paths to break through the bottleneck of Moore's Law due to its advantages of flexible combination, cost optimization and performance improvement. Under this technical framework, wafer thinning as a key process directly affects the heat dissipation performance, packaging thickness and bonding reliability of the chip. By precisely removing the excess material on the back of the wafer, this wafer thinning process can significantly reduce signal transmission delay, reduce packaging volume, and provide a foundation for multi-chip stacking. Therefore, it puts forward strict requirements on the processing precision, surface quality and processing efficiency of wafer thinning, including the requirement of thickness uniformity, i.e. the total thickness variation (TTV) needs to be controlled at the micron level or even nanometer level, and the surface needs to be scratch-free and free of subsurface damage.

[0003] Currently, grinding wheel grinding has become one of the mainstream processes for wafer thinning due to its high efficiency. Material removal is achieved through high-speed rotating grinding wheels. However, the core challenge of this process is the stress concentration phenomenon during the operation of the grinding wheel, which is particularly pronounced under high-speed rotation and heavy load processing conditions. Stress concentration not only causes the initiation and propagation of microcracks in the grinding wheel, increasing the risk of sudden fracture, but also affects the processing quality of the wafer, fundamentally restricting the working stability of the grinding wheel and the processing precision of the wafer thinning, and becoming a major bottleneck for improving the reliability of Chiplet integration technology.

[0004] In the prior art, although reducing the grinding depth and increasing the grinding wheel speed can reduce stress concentration, it also causes problems such as a decrease in material removal rate (MRR) and a shortening of the grinding wheel life. Therefore, it is necessary to consider the grinding wheel life and processing efficiency while ensuring the processing quality. SUMMARY

[0005] The purpose of the present application is to provide a wafer thinning device and a thinning method to solve the technical problem that the grinding wheel is prone to stress concentration during wafer thinning, causing unstable operation of the grinding wheel and limiting the processing precision of wafer thinning.

[0006] The above-mentioned purpose of the present application can be realized by using the following technical solutions:

[0007] The application provides a wafer thinning device, comprising a grinding wheel, which is installed on a grinding shaft of the wafer thinning device; the grinding wheel comprises a grinding wheel base and a plurality of grinding structures, and the plurality of grinding structures are fixed to the grinding wheel base through an adhesive layer; wherein the grinding structure comprises a flexible combination body and a plurality of first rigid microstructures, the plurality of first rigid microstructures are arranged in the flexible combination body in a three-dimensional manner and are stacked in a feeding direction of the grinding structure, and the space between the plurality of first rigid microstructures is filled with the flexible combination body.

[0008] In an embodiment of the application, the grinding structure comprises a plurality of composite grinding layers stacked in the feeding direction, each of the composite grinding layers comprises a flexible combination layer and a plurality of first rigid microstructures distributed in the flexible combination layer in a spaced manner, and the flexible combination layers of the composite grinding layers are combined to form the flexible combination body.

[0009] In an embodiment of the application, two adjacent first rigid microstructures in the feeding direction are stacked in a staggered manner.

[0010] In an embodiment of the application, the width of the first rigid microstructure in the vertical direction of the feeding direction is 20-30 μm.

[0011] In an embodiment of the application, the interval width between two adjacent first rigid microstructures in the feeding direction is 10-20 μm, and the interval width between two adjacent first rigid microstructures in the vertical direction of the feeding direction is 5-10 μm.

[0012] In an embodiment of the application, the first rigid microstructure is in the form of a sheet.

[0013] In an embodiment of the application, the first rigid microstructure has a face portion and an edge portion, and the charge of the face portion is opposite to at least part of the charge of the edge portion.

[0014] In an embodiment of the application, the first rigid microstructure comprises a rigid sheet body made of a rigid material.

[0015] In an embodiment of the application, the rigid sheet body is a layered mineral sheet, a graphene oxide sheet, a hexagonal boron nitride sheet and / or a molybdenum disulfide sheet.

[0016] In an embodiment of the application, the layered mineral sheet is a mica sheet and / or a vermiculite sheet.

[0017] In an embodiment of the application, the first rigid microstructure further comprises a molecular interface modification layer formed by an anionic polymer, and the molecular interface modification layer is located on the surface of the rigid sheet body.

[0018] In an embodiment of the present application, the anionic polymer is polyaspartic acid, polyglutamic acid, polyacrylic acid sodium, polystyrene sulfonic acid sodium, sodium carboxymethyl cellulose or sodium alginate.

[0019] In an embodiment of the present application, the first rigid microstructure further comprises a nano-reinforced layer formed by nanoparticles, the nano-reinforced layer being located on the surface of the molecular interface modification layer and / or the surface of the rigid sheet.

[0020] In an embodiment of the present application, the material of the nanoparticles is silicon dioxide, aluminum oxide, zirconium oxide, titanium carbide, amorphous calcium carbonate or hydroxyapatite.

[0021] In an embodiment of the present application, the particle size of the nanoparticles is 100 nm-200 nm.

[0022] In an embodiment of the present application, the grinding structure further comprises a plurality of second rigid microstructures, the plurality of second rigid microstructures being dispersed in the flexible binder.

[0023] In an embodiment of the present application, the second rigid microstructure comprises abrasive particles.

[0024] In an embodiment of the present application, the material of the abrasive particles is diamond, cubic boron nitride, silicon carbide or plated abrasive.

[0025] In an embodiment of the present application, the particle size of the abrasive particles is 0.8 μm±0.2 μm.

[0026] In an embodiment of the present application, the material of the flexible binder is polyimide resin, polyurethane, polyimide resin, epoxy resin or silicone rubber.

[0027] In an embodiment of the present application, the grinding structure further comprises a plurality of micro-porous structures, the plurality of micro-porous structures being dispersed in the flexible binder.

[0028] In an embodiment of the present application, the pore size of the micro-porous structure is 1 μm-5 μm.

[0029] The present application also provides a thinning method, which uses the wafer thinning device to thin a wafer, and the thinning method comprises simultaneously increasing the feed rate and the rotation speed of the grinding wheel.

[0030] In an embodiment of the present application, the feed rate of the grinding wheel is greater than 3 μm / s; and the rotation speed of the grinding wheel is greater than 4000 rpm / min.

[0031] The present application has the following characteristics and advantages:

[0032] The grinding structure in the application, a plurality of first rigid microstructures are arranged three-dimensionally and stacked in the feeding direction, and the interval spaces between the plurality of first rigid microstructures are filled with the flexible combination body, so that the flexible combination layer is used for buffering, the grinding stress can be effectively dispersed, the problem of stress concentration is avoided, and on the one hand, the simultaneous improvement of the feeding speed and the rotating speed is facilitated, so that the grinding efficiency, that is, the material removal rate, can be effectively improved, and on the other hand, due to the uniformization of the stress, the surface damage of the machined surface of the workpiece is reduced, the machined surface is smoother, and the machining precision is improved; and the flexible combination body can also reduce the vibration and thermal influence in the grinding process, reduce the fluctuation of the grinding force, and improve the stability of the machining; in addition, the high wear resistance of the first rigid microstructure and the toughness of the flexible combination body are used in cooperation, so that the grinding structure has a longer service life.

[0033] The grinding structure in the application, by stacking the adjacent two first rigid microstructures in the feeding direction, the adjacent two first rigid microstructures are stacked in the feeding direction, and the flexible combination layer between the two first rigid microstructures and the interval spaces can better cooperate, so that the stability of the grinding structure is further improved.

[0034] The grinding structure in the application, the first rigid microstructure is a two-dimensional sheet structure, the plurality of first rigid microstructures and the flexible combination body cooperate to form a “brick-mud” structure, the plurality of first rigid microstructures can be stacked in the feeding direction more stably, so that the bearing capacity in the feeding direction is better, and the contact area of the flexible combination body and each first rigid microstructure is increased, which is not only beneficial to improve the combination stability of the flexible combination body and each first rigid microstructure, but also beneficial to the flexible combination body to better disperse the grinding stress.

[0035] The grinding structure in the application, the anionic high molecular polymer is used to form a molecular interface modification layer on the surface of the rigid sheet body, so that the interface bonding force between the first rigid microstructure and the flexible combination body can be enhanced, and the stability of the grinding structure is further improved.

[0036] The grinding structure in the application, the nano particles are used to form a nano enhancement layer by being combined on the surface of the rigid sheet body and / or the surface of the molecular interface modification layer, so that the nano particles can be pinned on the surface of the rigid sheet body, the nano particles can hinder crack propagation by deformation or phase change, the stability of the grinding structure is further improved, and / or the flexible molecular chain bridge is formed between the nano particles and the molecular interface modification layer, so that the dynamic bonding absorption capacity is improved.

[0037] The wafer thinning device and the thinning method can improve the grinding efficiency, reduce the surface damage of the wafer, reduce the surface roughness of the wafer, and make the surface of the wafer more flat, thereby meeting the high-precision integration requirement of the chiplet. BRIEF DESCRIPTION OF DRAWINGS

[0038] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor.

[0039] Figure 1 It is a microstructure diagram of the grinding structure in the present application.

[0040] Figure 2 It is Figure 1 It is an enlarged view of A in the present application.

[0041] Figure 3 It is a structure diagram of the grinding structure applied to the grinding wheel in the present application.

[0042] Figure 4 It is a stress distribution nephogram of the grinding structure in the present application in the feeding direction.

[0043] Figure 5 It is a stress distribution nephogram of the grinding structure in the prior art in the feeding direction.

[0044] Figure 6 It is a microstructure diagram of the first rigid microstructure in the present application.

[0045] Figure 7 It is a principle diagram of the first rigid microstructure in the present application.

[0046] Figure 8 It is a three-dimensional structure diagram of the wafer grinding device in the present application.

[0047] In the figure:

[0048] 100, grinding structure; 1, flexible combination; 11, flexible combination layer; 2, first rigid microstructure; 21, rigid sheet body; 22, molecular interface modification layer; 221, anionic polymer; 23, nano-enhanced layer; 231, nanoparticles; 3, composite grinding layer; 4, second rigid microstructure; 41, abrasive particles; 5, microporous structure;

[0049] 200, grinding wheel; 201, grinding wheel base;

[0050] 300 wafer thinning apparatus; 301 grinding shaft. DETAILED DESCRIPTION

[0051] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0052] Embodiment one

[0053] As shown in Figure 1 and Figure 2 The present application provides a grinding structure 100, which comprises a flexible combination body 1 and a plurality of first rigid microstructures 2, the plurality of first rigid microstructures 2 are arranged in the flexible combination body 1 in a three-dimensional manner and are stacked in the feeding direction Y of the grinding structure 100, and the space between the plurality of first rigid microstructures 2 is filled with the flexible combination body 1.

[0054] The plurality of first rigid microstructures 2 are arranged in the flexible combination body 1 in a three-dimensional manner and are stacked in the feeding direction Y of the grinding structure 100, which means that the plurality of first rigid microstructures 2 are arranged in a spaced manner in the feeding direction Y of the grinding structure 100 and in two plane directions X (such as transverse and longitudinal directions; or circumferential and radial directions) perpendicular to the feeding direction Y, and the two first rigid microstructures 2 adjacent in the feeding direction Y at least partially correspond to each other.

[0055] It should be emphasized that the present application defines the first rigid microstructure 2 in order to highlight that the present application is an optimization of the microstructure of the grinding structure 100. In the embodiments of the present application, the width W of the first rigid microstructure 2 in the direction perpendicular to the feeding direction Y (i.e. the plane direction X) is 20 μm to 30 μm.

[0056] The grinding structure 100 of the present application, the plurality of first rigid microstructures 2 are arranged three-dimensionally and stacked in the feeding direction Y, and the interval spaces between the plurality of first rigid microstructures 2 are all filled with the flexible bonding layer 11, so that the grinding stress can be effectively dispersed by the buffering of the flexible bonding layer 11, thereby avoiding the problem of stress concentration, and on the one hand, it is beneficial to realize the simultaneous improvement of the feeding speed and the rotating speed, thereby effectively improving the grinding efficiency, that is, the material removal rate, and on the other hand, due to the uniformization of the stress, it is beneficial to reduce the surface damage of the machined surface of the workpiece, so that the machined surface is smoother, thereby improving the machining precision; and the flexible bonding layer 11 can also reduce vibration and thermal influence, reduce the fluctuation of grinding force, thereby improving the stability of machining; in addition, the synergistic effect of the high wear resistance of the first rigid microstructure 2 and the toughness of the flexible bonding layer 11 makes the grinding structure 100 have a longer service life.

[0057] As shown in Figure 3 The grinding structure 100 of the present application is particularly suitable for application to the grinding wheel 200, and a plurality of grinding structures 100 are arranged at intervals along the circumference of the grinding wheel 200. Of course, the grinding structure 100 of the present application can also produce the above beneficial effects when applied to other grinding tools.

[0058] In order to better understand and illustrate the above beneficial effects of the present application, in combination with Figure 4 The grinding structure 100 of the present application, the stress starts from the central high-value area (i.e. the area showing red to yellow), and by the buffering effect of the flexible bonding body 1, it can smoothly transition to the peripheral large-area low-stress area (i.e. the area showing blue-green to blue), so that in such an orderly stress transmission mode, the stress can be dispersed to a wider area through the layered stacking structure, thereby effectively avoiding the stress concentration phenomenon; moreover, the layered stacking structure transmits the concentrated stress in the form of force flow diffusion to multiple directions and wide areas through the multi-phase interface mechanics conduction mechanism, and by increasing the stress transmission path, the stress can be more reasonably dispersed, further preventing the grinding structure 100 from producing cracks due to excessive stress concentration, and optimizing the regulation efficiency of the structure to high stress. In contrast Figure 5 As shown in

[0059] Specifically, as shown in Figure 1As shown, the flexible composite 1 is cured and molded using a binder; wherein the binder is polyimide resin, polyurethane, epoxy resin, or silicone rubber. The dynamic viscosity η of the binder is preferably 0.15 Pa·s. The grinding structure 100 includes multiple composite grinding layers 3 stacked along the feed direction Y. Each composite grinding layer 3 includes a flexible bonding layer 11 and multiple first rigid microstructures 2 distributed at intervals in the flexible bonding layer 11. The flexible bonding layers 11 of each composite grinding layer 3 are combined to form the flexible composite 1. By layering the grinding structure 100 into multiple composite grinding layers 3 along the feed direction Y, it is convenient to prepare multiple composite grinding layers 3 layer by layer by mixing multiple first rigid microstructures 2 with the binder to form a coating liquid, and then preparing multiple composite grinding layers 3 by slit coating, thereby obtaining the grinding structure 100. It also facilitates the control of the arrangement of multiple first rigid microstructures 2. Preferably, only one layer of the first rigid microstructure 2 is laid flat in each flexible bonding layer 11, thereby facilitating control over the arrangement of the first rigid microstructure 2 in each layer. The preparation method of the grinding structure 100 of the present invention is described in Embodiment Two, and will not be detailed here.

[0060] like Figure 1 As shown, in the embodiment of the present invention, two adjacent first rigid microstructures 2 are stacked in a staggered manner in the feed direction Y. That is, only a portion of the two adjacent first rigid microstructures 2 overlaps in the feed direction Y, while the other portion is staggered. This ensures that the space between the multiple first rigid microstructures 2 arranged in the same layer is at least partially covered by the multiple first rigid microstructures 2 in the adjacent layer, allowing the multiple first rigid microstructures 2 to cooperate in bearing the load in the feed direction Y. Therefore, the grinding structure 100 of the present invention, by staggering the stacking of two adjacent first rigid microstructures 2 in the feed direction Y, enables the two adjacent first rigid microstructures 2 to have a higher load-bearing capacity in the feed direction Y, and allows the two adjacent first rigid microstructures 2 and the flexible bonding layer 11 in the space between them to work together better, thereby further improving the stability of the grinding structure 100.

[0061] Specifically, the first rigid microstructure 2 has a face and an edge, and the charge on the face is opposite to at least part of the charge on the edge. Thus, when multiple composite grinding layers 3 are prepared layer by layer by slit coating, the first rigid microstructure 2 in two adjacent composite grinding layers 3 can automatically achieve misaligned stacking under the action of electrostatic attraction.

[0062] In addition, combined Figure 1 and Figure 2As shown, in order to improve the rigid bearing capacity of the grinding structure 100, the present application optimizes the interval width between the plurality of first rigid microstructures 2, that is, the arrangement density of the plurality of first rigid microstructures 2 in the flexible combination body 1. The interval width J1 between the first rigid microstructures 2 of the adjacent two composite grinding layers 3 is 10-20 μm, that is, the interval width between the adjacent two first rigid microstructures 2 in the feeding direction Y is 10-20 μm. The interval width J2 between the plurality of first rigid microstructures 2 of the same composite grinding layer 3 is 5-10 μm, that is, the interval width between the adjacent two first rigid microstructures 2 in the plane direction X is 5-10 μm.

[0063] As shown, in the embodiment of the present application, the first rigid microstructure 2 is generally in the form of a sheet, and since it is a microstructure, it is equivalent to a two-dimensional sheet structure with negligible thickness, so that the plurality of first rigid microstructures 2 and the flexible combination body 1 form a "brick-mud" structure, the plurality of first rigid microstructures 2 can be more stably stacked in the feeding direction Y, thereby having better bearing capacity in the feeding direction Y, and the contact area between the flexible combination body 1 and each first rigid microstructure 2 is increased, which is not only beneficial to improve the combination stability of the flexible combination body 1 and each first rigid microstructure 2, but also beneficial to the flexible combination body 1 to better disperse the grinding stress. Figure 1 Specifically, as shown in

[0064] and Figure 6 and Figure 7 As shown, the first rigid microstructure 2 comprises a rigid sheet 21 made of a rigid material. The size and shape of each rigid sheet 21 can be the same or different. The material of each rigid sheet 21 can be the same or different. The rigid sheet 21 can be, but is not limited to, a layered mineral sheet, a graphene oxide flake, a hexagonal boron nitride flake, and / or a molybdenum disulfide flake; wherein the layered mineral sheet can be, but is not limited to, a mica sheet and / or a vermiculite sheet.

[0065] As shown in Figure 6 and Figure 7 As shown in the embodiment of the present application, the first rigid microstructure 2 further comprises a molecular interface modification layer 22 formed by an anionic polymer 221, and the molecular interface modification layer 22 is located on the surface of the rigid sheet 21. The grinding structure 100 of the present application forms the molecular interface modification layer 22 on the surface of the rigid sheet 21 by using the anionic polymer 221, so as to enhance the interface bonding force between the first rigid microstructure 2 and the flexible combination body 1, and further improve the stability of the grinding structure 100.

[0066] Specifically, the anionic polymer 221 can be, but is not limited to, polyaspartic acid (PAsp), polyglutamic acid (PGA), sodium polyacrylate (PAAS), sodium polystyrene sulfonate (PSS), sodium carboxymethyl cellulose (CMC), or sodium alginate (ALG). Furthermore, in embodiments of the present invention, the first rigid microstructure 2 forms a negatively charged face and locally positively charged edges by providing a molecular interface modification layer 22.

[0067] In one specific embodiment of the present invention, the rigid sheet 21 is a mica sheet, and the anionic polymer 221 is polyaspartic acid. The carboxylic acid groups of polyaspartic acid ( The first rigid microstructure 2 forms a hydrogen bond network with the hydroxyl groups (-OH) on the surface of the mica sheet, which is a dynamic reversible bond, thereby giving it the ability to dissipate interfacial energy, that is, to buffer stress through bond breaking and recombination when under load.

[0068] Combination Figure 6 and Figure 7 As shown, in an embodiment of the present invention, the first rigid microstructure 2 further includes a nano-reinforcing layer 23 formed by nanoparticles 231. The nano-reinforcing layer 23 may be located on the surface of the molecular interface modification layer 22, and a flexible molecular chain bridge is formed between the nanoparticles 231 and the molecular interface modification layer 22, thereby absorbing capacity through dynamic bonding; and / or the nano-reinforcing layer 23 may also be located on the surface of the rigid sheet 21, and the nanoparticles 231 are pinned on the surface of the rigid sheet 21, so that the nanoparticles 231 can hinder crack propagation through their own deformation or phase transformation.

[0069] In one specific embodiment of the present invention, the rigid sheet 21 is a mica sheet, the anionic polymer 221 is polyaspartic acid, and the nanoparticles 231 are amorphous calcium carbonate (ACC). On the one hand, the carboxylic acid groups of the polyaspartic acid (… ) and amorphous calcium carbonate Chelation forms flexible molecular chain bridges that can dynamically bond and absorb energy; on the other hand, the nanoparticles 231 are pinned to the surface of the mica sheet, so that crack propagation must bypass the nanoparticles 231 and consume additional energy. Therefore, the nanoparticles 231 can hinder crack propagation through their own deformation or phase transformation, thereby enhancing toughness.

[0070] Specifically, the material of nanoparticles 231 can be, but is not limited to, silicon dioxide, alumina, nano-zirconium oxide, titanium carbide, amorphous calcium carbonate, or hydroxyapatite. The particle size of nanoparticles 231 is preferably 100 nm to 200 nm.

[0071] In addition, such as Figure 7As shown, in order to further improve the wear resistance of the grinding structure 100, in the embodiment of the present application, the grinding structure 100 further comprises a plurality of second rigid microstructures 4, which are dispersed in the flexible binder 1. Specifically, the second rigid microstructure 4 is in the form of a particle, including but not limited to abrasive particles 41. The particle size of the abrasive particles 41 is 0.8pm±0.2pm. Among them, the material of the abrasive particles 41 is diamond, cubic boron nitride, silicon carbide or plated abrasive.

[0072] As shown in the embodiment of the present application, the grinding structure 100 further comprises a plurality of second rigid microstructures 4, which are dispersed in the flexible binder 1. Specifically, the second rigid microstructure 4 is in the form of a particle, including but not limited to abrasive particles 41. The particle size of the abrasive particles 41 is 0.8pm±0.2pm. Among them, the material of the abrasive particles 41 is diamond, cubic boron nitride, silicon carbide or plated abrasive. Figure 7 As shown, in order to further improve the wear resistance of the grinding structure 100, in the embodiment of the present application, the grinding structure 100 further comprises a plurality of second rigid microstructures 4, which are dispersed in the flexible binder 1. Specifically, the second rigid microstructure 4 is in the form of a particle, including but not limited to abrasive particles 41. The particle size of the abrasive particles 41 is 0.8pm±0.2pm. Among them, the material of the abrasive particles 41 is diamond, cubic boron nitride, silicon carbide or plated abrasive.

[0073] As shown, in order to further improve the wear resistance of the grinding structure 100, in the embodiment of the present application, the grinding structure 100 further comprises a plurality of second rigid microstructures 4, which are dispersed in the flexible binder 1. Specifically, the second rigid microstructure 4 is in the form of a particle, including but not limited to abrasive particles 41. The particle size of the abrasive particles 41 is 0.8pm±0.2pm. Among them, the material of the abrasive particles 41 is diamond, cubic boron nitride, silicon carbide or plated abrasive.

[0074] Figure 1 As shown, in order to further improve the wear resistance of the grinding structure 100, in the embodiment of the present application, the grinding structure 100 further comprises a plurality of second rigid microstructures 4, which are dispersed in the flexible binder 1. Specifically, the second rigid microstructure 4 is in the form of a particle, including but not limited to abrasive particles 41. The particle size of the abrasive particles 41 is 0.8pm±0.2pm. Among them, the material of the abrasive particles 41 is diamond, cubic boron nitride, silicon carbide or plated abrasive.

[0075] The grinding structure 100 in the embodiment has the same specific structure, working principle and beneficial effects as the grinding structure 100 in the first embodiment, and will not be described here.

[0076] The preparation method of the grinding structure 100 of the present application uses the method of slot coating to form the plurality of composite grinding layers 3 one by one, so as to form the grinding structure 100 by stacking, so that the plurality of first rigid microstructures 2 are arranged in three dimensions in the flexible binder 1, and the operation is simple and easy to prepare.

[0077] In the step of preparing the coating liquid, the weight ratio of the plurality of first rigid microstructures 2 in the coating liquid is 40% to 60%, that is, the weight of all the first rigid microstructures 2 accounts for 40% to 60% of the weight of the coating liquid.

[0078] ​In the coating and curing forming step, the plurality of first rigid microstructures 2 in the coating solution are oriented and arranged in a layer parallel to the substrate under the shearing force of the slot coating. The gap of the doctor blade of the slot coating can be adjusted according to requirements. In an embodiment of the present application, the gap of the doctor blade of the slot coating is 40 pm ± 5 pm.

[0079] In the coating and curing forming step, the binder of each composite grinding layer 3 is pre-cured at a first preset temperature, then hot-pressed at a preset pressure, and finally cross-linked at a second preset temperature. By curing the binder of each layer in stages to form a flexible bonding layer 11, the flexible bonding layer 11 is prevented from shrinking too quickly and cracking. In a specific embodiment of the present application, the first preset temperature is 200°C. The preset pressure is 10 MPa. The second preset temperature is 175°C.

[0080] In addition, the preparation method of the present application can further include cutting the formed grinding structure 100 into a desired shape, such as Figure 3 As shown in the figure, in this embodiment, the grinding structure 100 is a fan-shaped block structure.

[0081] In combination with Figure 6 and Figure 7 As shown in the figure, in an embodiment of the present application, the preparation method further includes preparing a plurality of first rigid microstructures 2, specifically including the following steps: preparing a plurality of rigid pieces 21; preparing a saturated aqueous solution of anionic high molecular polymer 221; placing each rigid piece 21 in the saturated aqueous solution for molecular interface modification, so that the anionic high molecular polymer 221 forms a molecular interface modification layer 22 on the surface of each rigid piece 21, and the charge of the face of the first rigid microstructure 2 and the local charge of the edge portion are opposite. Further, in the coating and curing forming step, the first rigid microstructures 2 of two adjacent composite grinding layers 3 can be stacked by electrostatic attraction.

[0082] In some embodiments of the present application, the molecular interface modification treatment of placing each rigid piece 21 in the saturated aqueous solution includes the following steps: high-speed homogenization treatment and ultrasonic dispersion treatment of each rigid piece 21 in the saturated aqueous solution. Specifically, the rotation speed of the high-speed homogenization treatment is 12000 rpm, and the time is 2 hours. The temperature of the ultrasonic dispersion treatment is 50°C, and the time is 1 hour.

[0083] In other embodiments of the present application, the molecular interface modification treatment of placing each rigid piece 21 in the saturated aqueous solution includes the following steps: freeze-drying treatment and spray-drying treatment of each rigid piece 21 in the saturated aqueous solution.

[0084] In combination with Figure 6 and Figure 7As shown, in the embodiment of the present application, the preparation of the plurality of first rigid microstructures 2 further comprises: mixing the rigid sheet body 21 with the molecular interface modification layer 22 with the nanoparticles 231, so that the nanoparticles 231 form a nano-enhanced layer 23 on the surface of the rigid sheet body 21 and the surface of the molecular interface modification layer 22. In addition, after the nano-enhanced layer 23 is formed, the plurality of first rigid microstructures 2 are subjected to vacuum filtration-ethanol washing treatment to clean the residual reaction solution on the surface of the first rigid microstructure 2 and quickly filter out the liquid.

[0085] In the embodiment of the present application, the mixing ratio of the rigid sheet body 21 to the nanoparticles 231 is 4:1 to 9:1. In a specific embodiment of the present application, the rigid sheet body 21 is a mica sheet, the nanoparticles 231 are amorphous calcium carbonate, and the mixing ratio of the rigid sheet body 21 to the nanoparticles 231 is 4:1.

[0086] In the embodiment of the present application, the preparation of the coating liquid further comprises: dispersing the abrasive particles 41 in the binder.

[0087] In the embodiment of the present application, the preparation of the coating liquid further comprises: dispersing the pore-forming agent in the binder so that the pore-forming agent decomposes to form the microporous structure 5 in the binder.

[0088] In the embodiment of the present application, in the coating liquid, the weight ratio of the plurality of first rigid microstructures 2 is 20% to 60%, the weight ratio of the abrasive particles 41 is 20% to 70%, and the weight ratio of the pore-forming agent is 5% to 15%. In a specific embodiment of the present application, the material of the abrasive particles 41 is diamond, the pore-forming agent is ammonium bicarbonate (NH4HCO3), and the weight ratio of the plurality of first rigid microstructures 2, the abrasive particles 41, and the pore-forming agent is 4:5:1.

[0089] Embodiment three

[0090] In combination Figure 1 And Figure 3 As shown, the present application also provides a grinding wheel 200 comprising a plurality of grinding structures 100. The grinding wheel 200 further comprises a grinding wheel base 201, and the plurality of grinding structures 100 are fixed to the grinding wheel base 201 through an adhesive layer. The grinding structure 100 in this embodiment has the same specific structure, working principle and beneficial effects as the grinding structure 100 in Embodiment One, and will not be described here.

[0091] The grinding wheel 200 of the present application is advantageous in improving the machining precision, machining stability, machining efficiency and service life of the grinding wheel 200 by bonding and fixing a plurality of grinding structures 100 of the present application to the grinding wheel base 201.

[0092] Specifically, one end of the grinding wheel base 201 is bonded and fixed with a plurality of grinding structures 100, and the plurality of grinding structures 100 are arranged and disposed along the circumference of the grinding wheel base 201. The other end of the grinding wheel base 201 is a mounting end for mounting on the grinding shaft 301, so as to drive the grinding wheel 200 to rotate and move along the feeding direction Y through the grinding shaft 301.

[0093] Embodiment four

[0094] In combination Figure 3 As shown, the present application also provides a preparation method of the grinding wheel 200, for preparing the grinding wheel 200, the preparation method comprises the following steps: preparing the grinding wheel base 201; and bonding and fixing the plurality of grinding structures 100 on the grinding wheel base 201. The grinding wheel 200 in this embodiment has the same specific structure, working principle and beneficial effects as the grinding wheel 200 in the third embodiment, and will not be repeated here.

[0095] In some embodiments of the present application, the grinding wheel base 201 is made of 6061-T6 / T651 aluminum alloy; the plurality of grinding structures 100 are bonded on the grinding wheel base 201 along the circumference of the grinding wheel base 201 through epoxy glue, thereby obtaining the grinding wheel 200; and then, the grinding wheel 200 is ground and opened on a surface grinding machine with a metal bond diamond dresser, and the parallelism of the grinding surface of each grinding structure 100 after correction is 0.005mm.

[0096] Embodiment five

[0097] As Figure 8 shown, the present application also provides a wafer thinning equipment 300, comprising the grinding wheel 200, and the grinding wheel 200 is mounted on the grinding shaft 301 of the wafer thinning equipment 300. The grinding wheel 200 is driven to rotate and move along the feeding direction Y through the grinding shaft 301. The grinding wheel 200 in this embodiment has the same specific structure, working principle and beneficial effects as the grinding wheel 200 in the third embodiment, and will not be repeated here. The other structures of the wafer thinning equipment 300 can be the same as the prior art, and will not be repeated here.

[0098] Embodiment six

[0099] In combination Figure 8 shown, the present application also provides a thinning method, which uses the wafer thinning equipment 300 to thin the wafer. The wafer thinning equipment 300 in this embodiment has the same specific structure, working principle and beneficial effects as the wafer thinning equipment 300 in the third embodiment, and will not be repeated here.

[0100] The thinning method of the present application comprises simultaneously increasing the feed speed and the rotation speed of the grinding wheel 200. The present application can improve the grinding efficiency, reduce the surface damage of the wafer, reduce the surface roughness of the wafer, and make the surface of the wafer more flat, thereby facilitating to meet the high-precision integration requirement of Chiplet.

[0101] In the embodiments of the present application, the feed speed of the grinding wheel 200 is greater than 3 μm / s, and the rotation speed of the grinding wheel 200 is greater than 4000 rpm / min.

[0102] In a specific embodiment of the present application, the feed speed of the grinding wheel 200 is 5 μm / s, and the rotation speed of the grinding wheel 200 is greater than 5000 rpm / min. In another comparative example, the wafer is ground and thinned by using the grinding wheel 200 of the prior art, the feed speed of the grinding wheel 200 is 3 μm / s, and the rotation speed of the grinding wheel 200 is 4000 rpm / min.

[0103] In the case of the same grinding and thinning amount, in the specific embodiment of the present application, the surface roughness of the wafer after processing is Ra 12 nm, and the material removal rate is 248 μm 3 / min; and in the comparative example, the surface roughness of the wafer after processing is Ra 15 nm, and the material removal rate is 156 μm 3 / min.

[0104] In order to better understand and implement the present application, the grinding wheels of some embodiments of the present application and the grinding wheels of the comparative examples are provided, and the grinding performance of the grinding wheels for wafer thinning processing is tested:

[0105] The weight ratio of each component of the grinding structure of the grinding wheel of each embodiment and the comparative example one is as follows:

[0106]

[0107] In addition, there is another comparative example two, which is a grinding wheel of the prior art purchased from outside.

[0108] The performance of each embodiment and the comparative example is as follows:

[0109]

[0110] The end-of-life standard of the grinding wheel is that the height of the grinding structure 100 is less than 1 mm, and the service life refers to the number of wafers processed by the grinding wheel 200 before the end of its service life under the condition of the same grinding and thinning amount. For example, the grinding wheel of the embodiment one can process 632 wafers, and the grinding wheel of the comparative example one can only process 412 wafers.

[0111] In addition, the surface roughness Ra of the thinned wafer and the service life of the grinding wheel 200 are measured, and the specific test method is as follows: first, the coarse grinding wheel and the adsorption platform (i.e., the platform used to adsorb and fix the wafer to be processed) are rotated 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; during coarse thinning, the coarse grinding wheel is fed downward at a feeding speed of 5 μm / s, 4 μm / s or 3 μm / s in turn while rotating, and the flow rate of the cooling water during the grinding process is L / min; after coarse thinning, fine grinding thinning is performed using the grinding wheel 200 in the application, the grinding wheel 200 is fed downward at a feeding speed of 0.3 μm / s, 0.2 μm / s or 0.1 μm / s in turn while rotating, the flow rate of the cooling water during the grinding process is 4 L / min, and the grinding process is continued until the removal amount of the wafer is 765 μm; the grinding wheel 200 and the adsorption platform stop rotating, the feeding assembly drives the grinding wheel 200 to move upward until the grinding wheel 200 is separated from the wafer; the adsorption of the wafer by the adsorption platform is released, and the thinned wafer is transferred for detection.

[0112] In summary, the grinding structure 100 of the application has better grinding performance than the comparative examples and the prior art.

[0113] The above only describes several embodiments of the application, and those skilled in the art can make various modifications or changes to the embodiments of the application according to the disclosed content of the application without departing from the spirit and scope of the application.

Claims

1. A wafer thinning device, characterized in that, The grinding wheel is mounted on a grinding shaft of the wafer thinning device, and comprises a grinding wheel base and a plurality of grinding structures fixed to the grinding wheel base by an adhesive layer. The grinding structure comprises a flexible combination body and a plurality of first rigid microstructures, which are arranged in the flexible combination body in a three-dimensional manner and are stacked in a feeding direction of the grinding structure, and the space between the first rigid microstructures is filled with the flexible combination body. The grinding structure comprises a plurality of composite grinding layers stacked in the feeding direction, each of the composite grinding layers comprises a flexible combination layer and a plurality of first rigid microstructures arranged in the flexible combination layer in a spaced manner, and the flexible combination layers of the composite grinding layers are combined to form the flexible combination body. The first rigid microstructure comprises a rigid sheet body made of a rigid material.

2. The wafer thinning device of claim 1, wherein The two first rigid microstructures adjacent in the feeding direction are stacked in a staggered manner.

3. The wafer thinning device of claim 1, wherein The width of the first rigid microstructure in the direction perpendicular to the feeding direction is 20-30 μm.

4. The wafer thinning device of claim 1, wherein The interval width between the two first rigid microstructures adjacent in the feeding direction is 10-20 μm, and the interval width between the two first rigid microstructures adjacent in the direction perpendicular to the feeding direction is 5-10 μm.

5. The wafer thinning device of claim 1, wherein The first rigid microstructure is in the form of a sheet.

6. The wafer thinning device of claim 1, wherein The first rigid microstructure has a face portion and an edge portion, and the charge of the face portion is opposite to at least part of the charge of the edge portion.

7. The wafer thinning device of claim 1, wherein The rigid sheet body is a layered mineral sheet, a graphene oxide sheet, a hexagonal boron nitride sheet, and / or a molybdenum disulfide sheet.

8. The wafer thinning device of claim 7, wherein The layered mineral sheet is a mica sheet and / or a vermiculite sheet.

9. The wafer thinning device of claim 1, wherein The first rigid microstructure further comprises a molecular interface modification layer formed by an anionic polymer, which is located on the surface of the rigid sheet body.

10. The wafer thinning device of claim 9, wherein The anionic polymer is polyaspartic acid, polyglutamic acid, polyacrylic acid sodium, polystyrene sulfonic acid sodium, carboxymethyl cellulose sodium, or sodium alginate.

11. The wafer thinning device of claim 9, wherein The first rigid microstructure further comprises a nano-enhanced layer formed by nanoparticles, which is located on the surface of the molecular interface modification layer and / or the surface of the rigid sheet body.

12. The wafer thinning device of claim 11, wherein The material of the nanoparticles is silicon dioxide, aluminum oxide, zirconium oxide, titanium carbide, amorphous calcium carbonate or hydroxyapatite.

13. The wafer thinning apparatus of claim 11, wherein, The particle size of the nanoparticles is 100-200 nm.

14. The wafer thinning apparatus of any one of claims 1-6, wherein, The grinding structure further comprises a plurality of second rigid microstructures dispersed in the flexible binder.

15. The wafer thinning apparatus of claim 14, wherein, The second rigid microstructures comprise abrasive particles.

16. The wafer thinning apparatus of claim 15, wherein, The material of the abrasive particles is diamond, cubic boron nitride, silicon carbide or coated abrasive.

17. The wafer thinning apparatus of claim 15, wherein, The particle size of the abrasive particles is 0.8 ± 0.2 μm.

18. The wafer thinning apparatus of any one of claims 1-6, wherein, The material of the flexible binder is polyimide resin, polyurethane, polyimide resin, epoxy resin or silicone rubber.

19. The wafer thinning apparatus of any one of claims 1-6, wherein, The grinding structure further comprises a plurality of micro-porous structures dispersed in the flexible binder.

20. The wafer thinning apparatus of claim 19, wherein, The pore size of the micro-porous structures is 1-5 μm.

21. A thinning method characterized by, The wafer thinning apparatus of any one of claims 1-20 is used to thin a wafer, and the thinning method comprises simultaneously increasing the feed rate and the rotational speed of the grinding wheel.

22. The thinning method of claim 21, wherein, The feed rate of the grinding wheel is greater than 3 μm / s; and the rotational speed of the grinding wheel is greater than 4000 rpm / min.

Images