A kind of adhesive film and its preparation method and application

Abstract

The application discloses a glue film and a preparation method and application thereof, and relates to the technical field of semiconductors. The glue film provided by the application comprises a first glue film layer and a second glue film layer which are alternately arranged in multiple layers. The soft and hard alternating bonding structure can simultaneously realize the equal elastic modulus of the glue film and the surface compressive stress of the silicon carbide wafer during polishing of the silicon carbide wafer, realizes the excellent effect of small subsurface crack depth and zero surface crack, greatly improves the structural reliability and integrity of the temporary bonding of the silicon carbide wafer, and solves the technical defects of excessive stress and easy crack in the traditional bonding scheme. In addition, the multiple layers of the glue film significantly reduce the equivalent elastic modulus of the glue film, effectively alleviate the stress concentration problem in the bonding process, and significantly improve the yield and polishing efficiency of the polished silicon carbide wafer.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to an adhesive film, its preparation method, and its application. Background Technology

[0002] With the continuous evolution of semiconductor manufacturing processes, wafer-level packaging and advanced processes place increasingly stringent demands on the mechanical stability and surface integrity of wafers in back-end processes. Temporary bonding technology, as a key supporting process for wafer thinning, back-side processing, and 3D integration, directly impacts the yield and reliability of the final product due to the performance of its core material, the temporary bonding film. In practical applications, the film must maintain stable wafer fixation under multiple harsh conditions, including high temperatures (>150℃), high shear forces (such as the positive pressure and relative sliding applied by the polishing head during CMP), and highly corrosive slurries (containing SiO2 or CeO2 abrasive particles and oxidants / complexing agents with extreme pH values).

[0003] Current mainstream temporary bonding film systems mainly include thermoplastic polymer systems (such as acrylates and styrene-isoprene copolymers), thermosetting epoxy modified systems, and UV-curable acrylate systems. These systems achieve bonding and debonding functions at different stages through glass transition, cross-linking curing, and photochemical reactions, respectively. However, when facing the processing requirements of next-generation semiconductor materials, the inherent characteristics of these material systems are increasingly at odds with the process requirements. During CMP (Continuous Metal Processing), creep or localized peeling is prone to occur, causing wafer edge warping or central region floating. This leads to uneven polishing removal rates, with both over-polishing at the edges and under-polishing at the center. Ultimately, the surface smoothness of the polished wafer fails to meet the control requirements of advanced packaging for warpage and surface roughness. Furthermore, existing film systems often rely on thermal release or laser ablation mechanisms during the debonding stage. Their interface separation behavior is often accompanied by sudden stress release, which may also induce secondary microcracks.

[0004] Therefore, how to fix silicon carbide wafers while suppressing the generation of microcracks on the wafer surface and controlling the smooth morphology of the adhesive film after polishing has become one of the key bottlenecks that urgently need to be solved in the current wafer-level temporary bonding technology.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The purpose of this invention is to provide an adhesive film, its preparation method, and its application, so as to solve or improve the above-mentioned technical problems.

[0007] This invention is implemented as follows: In a first aspect, the present invention provides an adhesive film, the adhesive film comprising multiple alternating layers of first adhesive film and second adhesive film; Let the number of layers of the adhesive film be N, where N = 8 - 16 and is an even number; The thickness of each adhesive film layer is 0.03mm-0.15mm.

[0008] In an optional embodiment, the first adhesive layer is a thermal adhesive layer that contacts the second adhesive layer or the wafer during bonding; the second adhesive layer is a photoresist layer that contacts the first adhesive layer or the carrier during bonding.

[0009] In an optional embodiment, the raw material for preparing the hot adhesive film layer is selected from at least one of polyimide, polyolefin and copolyamide; Among them, the polyolefins are selected from ethylene-propylene copolymers, and the polyolefins are selected from at least one of ethylene-propylene copolymers, polypropylene, polyethylene, poly-1-butene, polyisobutylene and ethylene-butene copolymers; And / or, the raw materials for preparing the photoresist film include a film-forming resin, a photoactive compound / photoinitiator, and a solvent in a mass ratio of (20-30):(3-5):(77-65); The film-forming resin is selected from at least one of phenolic resin, poly(p-hydroxystyrene) and its derivatives, polymethyl methacrylate and polymethyl methacrylate copolymer; The photoactive compound / photoinitiator is selected from at least one of the following: diazonaphthoquinone sulfonate, triphenylsulfonium salt, diphenyliodonium salt, oxime ester photoacids, triazine photoacids, and naphthalimide photoacids; The solvent is selected from at least one of propylene glycol methyl ether acetate, ethyl lactate, cyclohexanone, propylene glycol monomethyl ether, and butyl acetate.

[0010] In an optional embodiment, the equivalent elastic modulus of the obtained adhesive film is 8MPa-15MPa when the temperature is 40℃-50℃.

[0011] Secondly, the present invention provides a method for preparing an adhesive film as described in any of the foregoing embodiments, comprising the following steps: Photoresist film layer and thermal adhesive film layer are sequentially prepared on the surface of the carrier until the total number of film layers is N and ends with the thermal adhesive film layer, thus obtaining the adhesive film.

[0012] In an optional embodiment, the preparation of the photoresist film layer includes: mixing the raw materials of the photoresist film layer evenly according to a certain ratio, and then preparing the photoresist film layer by spin coating, wherein the rotation speed is 1000rpm-2000rpm. The prepared photoresist film layer is dried at a temperature of 90℃-100℃ for 30s-60s. And / or, the hot adhesive film layer is obtained by vacuum pressing, with a vacuum degree of 700Pa-1000Pa and a pressure of 0.2MPa-0.4MPa.

[0013] Thirdly, the present invention provides the application of the adhesive film as described in any of the foregoing embodiments in the polishing of silicon carbide wafers.

[0014] In an optional implementation, polishing the silicon carbide wafer includes the following steps: The silicon carbide wafer to be polished is fixed to a carrier with a film. After chemical mechanical polishing, thermal peeling and ultraviolet peeling are performed sequentially to remove one first adhesive film layer and one second adhesive film layer, thus obtaining a silicon carbide wafer and a carrier with N-2 adhesive film layers. N / 2 silicon carbide wafers were prepared by repeated fixation, chemical mechanical polishing, thermal exfoliation, and ultraviolet exfoliation.

[0015] In an optional embodiment, the temperature of thermal stripping is 10°C-20°C higher than the glass transition temperature of the raw material, and the time is 4-6 minutes. And / or, the wavelength of ultraviolet ablation is 365nm-385nm, and the intensity is 15mW / cm. 2 -50mW / cm 2 ; And / or, chemical mechanical polishing treatment includes: polishing pressure of 200 g / cm 2 -500g / cm 2 The polishing time is 0.5h-2h, the polishing solution includes a potassium permanganate solution with a mass concentration of 5%-10% and an alumina solution with a mass concentration of 2%-5%, the rotation speed is 20rpm-100rpm, and the temperature is 20℃-50℃.

[0016] In an optional embodiment, the subsurface crack depth of the obtained silicon carbide wafer is <1μm, and the yield of crack-free silicon carbide wafers is ≥99%.

[0017] The present invention has the following beneficial effects: In summary, the adhesive film of this invention features an alternating soft and hard bonding structure of a first adhesive film layer and a second adhesive film layer. During the polishing process of silicon carbide wafers, it can simultaneously achieve equal elastic modulus of the adhesive film and surface compressive stress of the silicon carbide wafer, resulting in excellent effects of minimal subsurface crack depth and zero surface cracks. This significantly improves the structural reliability and integrity of the temporary bonding of silicon carbide wafers and solves the technical defects of traditional bonding schemes, such as excessive stress and easy cracking. Furthermore, the multi-layered arrangement of the adhesive film significantly reduces the equivalent elastic modulus of the adhesive film, effectively alleviating the stress concentration problem during the bonding process and significantly improving the yield and polishing efficiency of the silicon carbide wafers obtained from polishing. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a photograph of the film adhered to the wafer in Example 1; Figure 2 A photograph of the finished chip in Comparative Example 1; Figure 3 This is a photograph of the finished chip in Comparative Example 2; Figure 4 This is a photograph of the finished wafer from Example 1. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0021] In a first aspect, the present invention provides an adhesive film, the adhesive film comprising multiple alternating layers of first adhesive film and second adhesive film; Let the number of layers of the adhesive film be N, where N = 8 - 16 and is an even number; The thickness of each adhesive film layer is 0.03mm-0.15mm.

[0022] It should be noted that the first adhesive layer is a thermoplastic adhesive layer, while the second adhesive layer is a photoresist layer with high rigidity. The composite adhesive film, formed by the alternating bonding of these two layers and the soft / hard spacer combination, softens the thermoplastic adhesive layer to form a buffer layer during silicon carbide wafer polishing, while the photoresist layer maintains the rigidity of the microstructure. This synergistic effect suppresses the generation of microcracks on the SiC surface, which is beneficial for controlling the morphological smoothness of the silicon carbide wafer after polishing. The multi-layered adhesive film configuration improves efficiency when polishing batches of wafers.

[0023] If the adhesive film is a single first adhesive film layer (thermal adhesive film layer) or a single second adhesive film layer (photoresist film layer), its equivalent elastic modulus is relatively high; the maximum compressive stress on the surface of the silicon carbide wafer is high. Specifically, when only a photoresist film layer with hard adhesive is pasted, its maximum compressive stress on the surface is 850 MPa, and when only a thermal adhesive film layer with soft adhesive is pasted, its maximum compressive stress on the surface is 210 MPa, which is much higher than the maximum compressive stress of 180 MPa of the present invention.

[0024] In an optional embodiment, the first adhesive layer is a thermal adhesive layer, which contacts the second adhesive layer or the wafer during bonding; the second adhesive layer is a photoresist layer, which contacts the first adhesive layer or the carrier during bonding. The thermal adhesive layer experiences a sharp decrease in adhesion upon heating, enabling the separation of the silicon carbide wafer from the photoresist; the photoresist layer loses its adhesion under ultraviolet light irradiation, achieving separation from the thermal adhesive layer.

[0025] In the chemical mechanical polishing process, multiple films work together. The thermal adhesive film softens to form a flexible buffer layer, while the photoresist maintains the rigid structure, achieving "local flexible buffering + overall rigid support".

[0026] The photoresist film acts as a "rigid skeleton" within the photoresist film. Specifically, the photoresist film (such as SU-8, modulus ≈ 4 GPa) maintains rigidity at polishing temperatures, preventing overall bending deformation of the wafer. If only a thermoplastic hot-resist film is used, it is a soft adhesive, and at polishing temperatures, the wafer will experience macroscopic deflection under pressure (deflection > 50 μm), which can trigger tensile stress and lead to cracking. The alternation of soft and hard layers achieves the optimal solution of "local flexible buffering + overall rigid support".

[0027] It should be noted that the multilayer soft-hard alternating bonding structure of the present invention can simultaneously achieve excellent effects such as low elastic modulus, low surface compressive stress, minimal subsurface crack depth and zero surface cracks, which greatly improves the structural reliability and wafer integrity of temporary bonding of SiC wafers and solves the technical defects of excessive stress and easy cracking of traditional bonding schemes.

[0028] For example, when the number of layers N of the adhesive film is 8, a photoresist film layer is first prepared on the surface of the carrier, followed by a thermal adhesive film layer, a photoresist film layer, a thermal adhesive film layer, a photoresist film layer, a thermal adhesive film layer, a photoresist film layer, and a thermal adhesive film layer in sequence, and finally ends with a thermal adhesive film layer. A silicon carbide wafer is fixedly attached to the other side of the thermal adhesive film layer for chemical mechanical polishing.

[0029] In an optional embodiment, the raw material for preparing the hot adhesive film layer is selected from at least one of polyimide, polyolefin and copolyamide; Among them, the polyolefins are selected from ethylene-propylene copolymers, and the polyolefins are selected from at least one of ethylene-propylene copolymers, polypropylene, polyethylene, poly-1-butene, polyisobutylene and ethylene-butene copolymers.

[0030] It should be noted that when the glass transition temperature (Tg) of the hot-melt adhesive film material is too high, its modulus at room temperature is too large. This causes the silicon carbide wafer to bear significant residual stress during thermal cycling due to the mismatch of the coefficient of thermal expansion (CTE), which can easily induce microcracks on the wafer surface, especially in ultra-thin wafers (<100μm) or highly brittle materials (such as SiC and GaN). When the Tg of the adhesive film is too low, it is prone to creep or local peeling during CMP, causing edge warping or central region floating of the wafer. This leads to uneven polishing removal rate, with over-polishing at the edges and under-polishing at the center. Ultimately, the surface smoothness of the polished wafer is difficult to meet the advanced packaging requirements for warpage ≤5μm and surface roughness Ra≤0.5nm.

[0031] And / or, the raw materials for preparing the photoresist film include a film-forming resin, a photoactive compound / photoinitiator, and a solvent in a mass ratio of (20-30):(3-5):(77-65); The film-forming resin is selected from at least one of phenolic resin, poly(p-hydroxystyrene) and its derivatives, polymethyl methacrylate and polymethyl methacrylate copolymer; The photoactive compound / photoinitiator is selected from at least one of the following: diazonaphthoquinone sulfonate, triphenylsulfonium salt, diphenyliodonium salt, oxime ester photoacids, triazine photoacids, and naphthalimide photoacids; The solvent is selected from at least one of propylene glycol methyl ether acetate, ethyl lactate, cyclohexanone, propylene glycol monomethyl ether, and butyl acetate. The solvent dissolves other substances in the photoresist and also adjusts the viscosity.

[0032] In optional embodiments, the raw materials for preparing the photoresist film layer also include additives, such as crosslinking agents and surfactants, which are selected reasonably according to actual needs.

[0033] In an optional embodiment, the equivalent elastic modulus of the obtained adhesive film is 8MPa-15MPa when the temperature is 40℃-50℃.

[0034] Secondly, the present invention provides a method for preparing an adhesive film as described in any of the foregoing embodiments, comprising the following steps: Photoresist film layer and thermal adhesive film layer are sequentially prepared on the surface of the carrier until the total number of film layers is N and ends with the thermal adhesive film layer, thus obtaining the adhesive film.

[0035] The preparation of the adhesive film must be carried out in a clean environment. In an optional embodiment, the preparation of the photoresist film layer includes: mixing the raw materials of the photoresist film layer evenly according to a certain ratio, and then preparing the photoresist film layer by spin coating, wherein the rotation speed is 1000rpm-2000rpm. The prepared photoresist film layer is dried at a temperature of 90℃-100℃ for 30s-60s.

[0036] It should be noted that after the raw materials for the photoresist film are mixed evenly, they still need to be filtered. The pore size of the filter membrane is 0.1μm-1μm. There are no particular restrictions on the equipment and form of drying; either hot plate drying or oven drying can be selected according to actual needs.

[0037] Furthermore, the raw material components of the photoresist layer are mixed uniformly under light-protected conditions according to precise proportions. Then, to ensure purity, the resist solution undergoes multi-stage precision filtration, first through a plate-and-frame filter, and then finally filtered through a 0.2μm filter membrane in an ultra-clean room (e.g., Class 100) to remove submicron particles. It should be noted that for high-end photoresists, special methods are required to control the metal impurity content to extremely low levels (e.g., below 10 ppb).

[0038] In this embodiment of the invention, the complete film preparation process typically includes three key stages: substrate pretreatment, spin coating, and pre-baking (also called soft baking). A detailed analysis follows: The substrate pretreatment includes cleaning the surface of the silicon carbide wafer, ensuring it is free of contaminants and water stains. If water molecules are adsorbed or organic contaminants are present on the surface of the silicon carbide wafer, a hydrophilic surface will be formed, resulting in poor wettability and insufficient adhesion of the photoresist.

[0039] Spin coating is a core step determining film thickness and uniformity. Its principle is to use centrifugal force to diffuse the photoresist into a uniform thin film. In this embodiment of the invention, the key parameters affecting film thickness include: photoresist viscosity, spin coating speed (1000 rpm-2000 rpm), and spin coating time (2 s-5 s). Among these, the spin speed and film thickness are inversely proportional; the higher the speed and the longer the time, the thinner the film. However, excessively high speeds will accelerate solvent evaporation, which in turn affects film stability. Therefore, the spin coating speed and time need to be adjusted appropriately according to actual needs.

[0040] Pre-baking process: A vacuum hot plate system is used, with the temperature set at 90℃-100℃ and the time at 30s-60s. The hot plate has fast heat conduction and good temperature uniformity, which can significantly reduce the differences in solvent residue caused by uneven temperature field. After baking, a cooling plate step is added to ensure that the silicon carbide substrate cools to room temperature before entering the exposure process. For thicker films, a waiting time is added before exposure to allow for re-absorption of water, ensuring development speed and contrast.

[0041] In an optional implementation, if it is required that the photoresist film be made into a specific shape, such as a circle, rectangle, triangle, etc., a template of the corresponding shape needs to be placed on the upper surface of the photoresist, and then ultraviolet light is applied to the template. The part that is irradiated with ultraviolet light is called the exposed area, and the part that is not irradiated with ultraviolet light is called the unexposed area. Based on this characteristic, photoresist layers of various shapes can be made.

[0042] Since the developer can only react with unexposed areas, it can be used to remove the film from unexposed areas.

[0043] And / or, the hot adhesive film layer is obtained by vacuum pressing, with a vacuum degree of 700Pa-1000Pa and a pressure of 0.2MPa-0.4MPa.

[0044] The adhesive film ends with a hot adhesive film layer, on which the silicon carbide wafer to be polished is adhered and fixed, wherein the surface of the silicon carbide wafer to be processed is away from the hot adhesive film layer.

[0045] Thirdly, the present invention provides the application of the adhesive film as described in any of the foregoing embodiments in the polishing of silicon carbide wafers.

[0046] In an optional implementation, polishing the silicon carbide wafer includes the following steps: The silicon carbide wafer to be polished is fixed to a carrier with a film. After chemical mechanical polishing, thermal peeling and ultraviolet peeling are performed sequentially to remove one first adhesive film layer and one second adhesive film layer, thus obtaining a silicon carbide wafer and a carrier with N-2 adhesive film layers. N / 2 silicon carbide wafers were prepared by repeated fixation, chemical mechanical polishing, thermal exfoliation, and ultraviolet exfoliation.

[0047] For example, the silicon carbide wafer polishing process is described with an 8-layer adhesive film, and it specifically includes the following steps: The first silicon carbide wafer to be polished is fixed to a carrier with eight layers of adhesive film. After chemical mechanical polishing, it is then subjected to thermal and ultraviolet peeling to remove one layer of the first adhesive film and one layer of the second adhesive film, resulting in a first silicon carbide wafer and a carrier with six layers of adhesive film. The second silicon carbide wafer to be polished is fixed to a carrier with six layers of adhesive film. After chemical mechanical polishing, it is then subjected to thermal and ultraviolet peeling to remove one layer of the first adhesive film and one layer of the second adhesive film, resulting in a second silicon carbide wafer and a carrier with four layers of adhesive film. The third silicon carbide wafer to be polished... The wafer is fixed to a carrier with four layers of adhesive film. After chemical mechanical polishing, it is then subjected to thermal and ultraviolet peeling to remove one layer of the first adhesive film and one layer of the second adhesive film, resulting in a third silicon carbide wafer and a carrier with two layers of adhesive film. The fourth silicon carbide wafer to be polished is fixed to a carrier with two layers of adhesive film. After chemical mechanical polishing, it is then subjected to thermal and ultraviolet peeling to remove one layer of the first adhesive film and one layer of the second adhesive film, resulting in a fourth silicon carbide wafer and a carrier. At this point, the adhesive film on the surface of the carrier is completely peeled off, resulting in a total of four silicon carbide wafers.

[0048] It should be noted that during the polishing process, the hot adhesive film in the composite film undergoes a softening transformation, forming a continuous low-modulus buffer layer. The overall equivalent elastic modulus is significantly lower than that of SiC (≈450GPa) and traditional hard adhesive (≈3GPa). The elastic modulus drops sharply from hundreds of MPa at room temperature to 10MPa, close to that of soft rubber, which causes a significant decrease in the local peak stress of the wafer, below the crack initiation threshold of SiC of 60MPa-100MPa.

[0049] During chemical mechanical polishing (CMP), the applied polishing pressure passes through multiple soft / hard interfaces, causing each hot-melt adhesive film layer to undergo viscoelastic deformation, converting mechanical energy into heat energy, resulting in hysteresis loss and delamination energy absorption. Assuming the adhesive film has four hot-melt adhesive film layers, each absorbing 20% ​​of the impact energy, the total absorption rate is >60%, and the effective energy transferred to the SiC surface is reduced to less than 1 / 3 of that of a traditional single-layer hard adhesive.

[0050] During chemical mechanical polishing (CMP), interfacial slippage between the first and second adhesive layers is permissible. The interfacial shear strength between the first and second adhesive layers is 0.2 MPa-0.5 MPa. This setting can release the transverse shear stress accumulated during polishing and prevent stress from being transmitted to the interior of the wafer, which could lead to the formation of microcracks in the wafer.

[0051] In an optional implementation, the thermal stripping temperature is 10°C-20°C higher than the glass transition temperature of the raw material, and the time is 4-6 minutes. After chemical mechanical polishing, the multilayer adhesive film, along with the polished wafer, is removed from the equipment and placed on a heating stage. A suitable stripping temperature is set, and after heating for a certain period of time, the adhesiveness of the thermal adhesive film layer decreases sharply, achieving the separation of the silicon carbide wafer and the photoresist. After thermal stripping, the top layer of the adhesive film is the photoresist layer, which needs to be de-adhesiveted by ultraviolet irradiation to be peeled off.

[0052] And / or, the wavelength of ultraviolet ablation is 365nm-385nm, and the intensity is 15mW / cm. 2 -50mW / cm 2 After the UV stripping is completed, the top layer of the adhesive film is a hot adhesive film layer, which is directly used to bond the next silicon carbide wafer to be polished.

[0053] And / or, the chemical mechanical polishing treatment includes: a polishing pressure of 200 g / cm. 2 -500g / cm 2 The polishing time is 0.5h-2h, the polishing solution includes a potassium permanganate solution with a mass concentration of 5%-10% and an alumina solution with a mass concentration of 2%-5%, the rotation speed is 20rpm-100rpm, and the temperature is 20℃-50℃.

[0054] Furthermore, the chemical mechanical polishing treatment includes: a polishing pressure of 200 g / cm. 2 -500g / cm 2 Polishing time is 1-2 hours, rotation speed is 40-60 rpm, and temperature is 30℃-50℃.

[0055] In an optional embodiment, the subsurface crack depth of the obtained silicon carbide wafer is <1μm, and the yield of crack-free silicon carbide wafers is ≥99%.

[0056] Using the adhesive film provided in the embodiments of the present invention for polishing silicon carbide wafers is beneficial to completely eliminate surface crack defects of silicon carbide wafers. Moreover, the multi-layer setting of the adhesive film significantly reduces the equivalent elastic modulus of the adhesive film, effectively alleviates the stress concentration problem in the bonding process, and significantly improves the yield and polishing efficiency of the silicon carbide wafers obtained by polishing.

[0057] In summary, the polishing of silicon carbide wafers includes the following steps: (1) Preparation of adhesive film Photoresist film layer and thermal adhesive film layer are sequentially prepared on the surface of the carrier until the total number of film layers is N and ends with the thermal adhesive film layer, thus obtaining the adhesive film.

[0058] The number of layers of the adhesive film is N, where N = 8-16 and is an even number; the thickness of each adhesive film layer is 0.03mm-0.15mm.

[0059] The preparation of the photoresist film includes: After the raw materials for the photoresist film are mixed evenly according to the ratio, the photoresist film is prepared by spin coating, wherein the rotation speed is 1000rpm-2000rpm. The prepared photoresist film layer is dried at a temperature of 90℃-100℃ for 30s-60s. The hot adhesive film layer is obtained by vacuum pressing, with a vacuum degree of 700Pa-1000Pa and a pressure of 0.2MPa-0.4MPa.

[0060] The film-forming resin is selected from at least one of phenolic resin, poly(p-hydroxystyrene) and its derivatives, polymethyl methacrylate and polymethyl methacrylate copolymer; the photoactive compound / photoinitiator is selected from at least one of diazonaphthoquinone sulfonate, triphenylsulfonium salt, diphenyliodonium salt, oxime ester photoacids, triazine photoacids and naphthalenedicarboximide photoacids; the solvent is selected from at least one of propylene glycol methyl ether acetate, ethyl lactate, cyclohexanone, propylene glycol monomethyl ether and butyl acetate.

[0061] (2) Fixation The silicon carbide wafer to be polished is fixed to the adhesive film obtained in step (1). The surface of the silicon carbide wafer to be processed is located away from the adhesive film layer. A schematic diagram of the structure after bonding is shown below. Figure 1 .

[0062] (3) Chemical mechanical polishing treatment Chemical mechanical polishing: polishing pressure 200 g / cm 2 -500g / cm 2 The polishing time is 0.5h-2h, the polishing solution includes a potassium permanganate solution with a mass concentration of 5%-10% and an alumina solution with a mass concentration of 2%-5%, the rotation speed is 20rpm-100rpm, and the temperature is 20℃-50℃.

[0063] (4) Peeling treatment The multilayer film after chemical mechanical polishing in step (3), along with the polished wafer, is removed from the equipment for thermal and ultraviolet peeling.

[0064] The thermal stripping temperature is 10℃-20℃ higher than the glass transition temperature of the raw material, and the time is 4-6 minutes. After thermal stripping, the silicon carbide wafer and photoresist are separated, and the remaining film is subjected to ultraviolet stripping.

[0065] The ultraviolet ablation wavelength is 365nm-385nm, and the intensity is 15mW / cm. 2 -50mW / cm 2After UV stripping, the top layer of the adhesive film is a hot adhesive film layer, which is directly used to bond the next silicon carbide wafer to be polished.

[0066] Repeat steps (2) to (4) to obtain N / 2 silicon carbide wafers.

[0067] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0068] Example 1 This embodiment provides a method for polishing silicon carbide wafers, including the following steps: (1) Preparation of adhesive film Photoresist film layer and thermal adhesive film layer are sequentially prepared on the surface of the carrier until the total number of film layers is N and ends with the thermal adhesive film layer, thus obtaining the adhesive film.

[0069] The number of film layers is 10, which is an even number; the thickness of each film layer is 0.08 mm.

[0070] The process involves first preparing a photoresist film layer on the carrier surface, followed by a thermal adhesive film layer, a photoresist film layer, a thermal adhesive film layer, a photoresist film layer, a thermal adhesive film layer, a photoresist film layer, a thermal adhesive film layer, a photoresist film layer, and a thermal adhesive film layer, for a total of 10 adhesive films. The process ends with a thermal adhesive film layer, on which a silicon carbide wafer is fixedly attached for chemical mechanical polishing.

[0071] The preparation of the photoresist film includes: After the raw materials for the photoresist film are mixed evenly according to the ratio, the photoresist film is prepared by spin coating. The spin coating speed is 1500 rpm and the spin coating time is 4 s. The prepared photoresist film layer was dried at a temperature of 95°C for 50 seconds. The hot adhesive film layer is obtained by vacuum pressing, with a vacuum degree of 850 Pa and a pressure of 0.3 MPa.

[0072] The film-forming resin is a phenolic resin, the photoactive compound / photoinitiator is diazonaphthoquinone sulfonate, and the solvent is propylene glycol methyl ether acetate.

[0073] (2) Fixation The silicon carbide wafer to be polished is fixed to the adhesive film obtained in step (1). The surface of the silicon carbide wafer to be processed is located away from the adhesive film layer. A schematic diagram of the structure after bonding is shown below. Figure 1 .

[0074] (3) Chemical mechanical polishing treatment Chemical mechanical polishing: polishing pressure 350 g / cm 2The polishing time was 1.5 hours. The polishing solution consisted of a 7% potassium permanganate solution and a 3.5% alumina solution. The rotation speed was 55 rpm and the temperature was 35°C.

[0075] (4) Peeling treatment The multilayer film after chemical mechanical polishing in step (3), along with the polished wafer, is removed from the equipment for thermal and ultraviolet peeling.

[0076] The thermal stripping temperature is 18°C ​​higher than the glass transition temperature of the raw material, and the time is 5 minutes. After thermal stripping, the silicon carbide wafer and photoresist are separated, and the remaining film is then subjected to ultraviolet stripping.

[0077] The ultraviolet ablation wavelength was 365 nm, and the intensity was 30 mW / cm. 2 After UV stripping, the top layer of the adhesive film is a hot adhesive film layer, which is directly used to bond the next silicon carbide wafer to be polished.

[0078] Repeat steps (2) to (4) to obtain N / 2 silicon carbide wafers.

[0079] Experimental Example 1 This experiment was used to investigate the effect of the number of adhesive film layers on the preparation of silicon carbide wafers. The preparation process was the same as in Example 1, except that the total number of adhesive film layers was different in step (1) of preparing the adhesive film. The equivalent elastic modulus of the adhesive film, the subsurface crack depth of the silicon carbide wafer, and the number of cracks were summarized at 40°C. The relevant results are shown in Table 1.

[0080] Among them, the equivalent elastic modulus of the adhesive film was tested using an electronic universal testing machine to perform uniaxial tension on a standard dumbbell-shaped specimen. The computer collected the data and plotted the stress-strain curve. The elastic modulus was obtained by calculating the slope of the elastic deformation section of the curve (usually the strain range of 0.05%-0.25%). The subsurface crack depth was tested using a microscope to determine the crack layer depth. The number of cracks was tested by counting them with a high-intensity lamp.

[0081] Table 1. Effect of film layer number on silicon carbide wafer fabrication

[0082] As can be seen from the data in Table 1, the more layers of adhesive film there are, the smaller the equivalent elastic modulus of the adhesive film, and the less likely it is to crack.

[0083] Experimental Example 2 This experiment was used to investigate the effect of film thickness on the preparation of silicon carbide wafers. The preparation process was the same as in Example 1, except that the total number of film layers was different in step (1) of preparing the adhesive film. The equivalent elastic modulus of the adhesive film, the subsurface crack depth of the silicon carbide wafer, and the number of cracks were summarized at 40°C. The relevant results are shown in Table 2.

[0084] Table 2. Effect of film thickness on the fabrication of silicon carbide wafers (N=10)

[0085] As can be seen from the data in Table 2, the thicker the adhesive film, the smaller the equivalent elastic modulus of the adhesive film, and thus the smaller the subsurface crack depth and the number of cracks.

[0086] Comparative Example 1 This comparative example provides a silicon carbide wafer polishing method, including the following steps: The preparation process is the same as in Example 1, except that: in step (1), only one photoresist film layer with a thickness of 0.1 mm is prepared on the carrier surface. The finished wafer after polishing is shown in the image. Figure 2 .

[0087] Comparative Example 2 This comparative example provides a silicon carbide wafer polishing method, including the following steps: The preparation process is the same as in Example 1, except that: in step (1), only one hot adhesive film layer with a thickness of 0.1 mm is prepared on the carrier surface. The finished wafer after polishing is shown in the image below. Figure 3 .

[0088] For ease of comparison, the equivalent elastic modulus of the adhesive film, the subsurface crack depth of the silicon carbide wafer, and the number of cracks in Example 1 and Comparative Examples 1-2 during the preparation of silicon carbide wafers are summarized, and the relevant results are shown in Table 3.

[0089] Table 3. Effect of the adhesive film on the preparation of silicon carbide wafers

[0090] As can be seen from the data in Table 3, the film state of Example 1 (see Table 3) is as follows: Figure 4 The film state is better than that of Comparative Example 1 and Comparative Example 2 (wherein) Figure 4 No cracks Figure 2 There is only one crack, but it is long. Figure 3 (There is only one crack, and the crack is short). The subsurface crack depth and number of cracks in Example 1 are better than those in Comparative Example 1 and Example 2.

[0091] In summary, the adhesive film of this invention features an alternating soft and hard bonding structure of a first adhesive film layer and a second adhesive film layer. During the polishing process of silicon carbide wafers, it can simultaneously achieve equal elastic modulus of the adhesive film and surface compressive stress of the silicon carbide wafer, resulting in excellent effects of minimal subsurface crack depth and zero surface cracks. This significantly improves the structural reliability and integrity of the temporary bonding of silicon carbide wafers and solves the technical defects of traditional bonding schemes, such as excessive stress and easy cracking. Furthermore, the multi-layered arrangement of the adhesive film significantly reduces the equivalent elastic modulus of the adhesive film, effectively alleviating the stress concentration problem during the bonding process and significantly improving the yield and polishing efficiency of the silicon carbide wafers obtained from polishing.

[0092] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A film, characterized in that, The adhesive film comprises multiple alternating layers of first and second adhesive film; Let the number of layers of the adhesive film be N, where N = 8-16 and is an even number; The thickness of each adhesive film layer is 0.03mm-0.15mm.

2. The adhesive film according to claim 1, characterized in that, The first adhesive layer is a thermal adhesive layer, which contacts the second adhesive layer or the wafer during bonding; the second adhesive layer is a photoresist layer, which contacts the first adhesive layer or the carrier during bonding.

3. The adhesive film according to claim 1, characterized in that, The raw materials for preparing the hot adhesive film layer are selected from at least one of polyimide, polyolefin and copolyamide; Among them, the polyolefins are selected from ethylene-propylene copolymers, and the polyolefins are selected from at least one of ethylene-propylene copolymers, polypropylene, polyethylene, poly-1-butene, polyisobutylene and ethylene-butene copolymers; And / or, the raw materials for preparing the photoresist film layer include a film-forming resin, a photoactive compound / photoinitiator and a solvent in a mass ratio of (20-30):(3-5):(77-65); The film-forming resin is selected from at least one of phenolic resin, poly(p-hydroxystyrene) and its derivatives, polymethyl methacrylate and polymethyl methacrylate copolymer; The photoactive compound / photoinitiator is selected from at least one of diazonaphthoquinone sulfonate, triphenylsulfonium salt, diphenyliodonium salt, oxime ester photoacids, triazine photoacids, and naphthalimide photoacids; The solvent is selected from at least one of propylene glycol methyl ether acetate, ethyl lactate, cyclohexanone, propylene glycol monomethyl ether, and butyl acetate.

4. The adhesive film according to claim 1, characterized in that, At a temperature of 40℃-50℃, the equivalent elastic modulus of the tested adhesive film is 8MPa-15MPa.

5. A method for preparing an adhesive film as described in any one of claims 1-4, characterized in that, Includes the following steps: Photoresist film layer and thermal adhesive film layer are sequentially prepared on the surface of the carrier until the total number of film layers is N and ends with the thermal adhesive film layer, thus obtaining the adhesive film.

6. The preparation method according to claim 5, characterized in that, The preparation of the photoresist film includes: After the raw materials for the photoresist film are mixed evenly according to the ratio, the photoresist film is prepared by spin coating, wherein the rotation speed is 1000rpm-2000rpm. The prepared photoresist film layer is dried at a temperature of 90℃-100℃ for 30s-60s. And / or, the hot adhesive film layer is obtained by vacuum pressing, with a vacuum degree of 700Pa-1000Pa and a pressure of 0.2MPa-0.4MPa.

7. The application of the adhesive film as described in any one of claims 1-4 in the polishing of silicon carbide wafers.

8. The application according to claim 7, characterized in that, Polishing silicon carbide wafers includes the following steps: The silicon carbide wafer to be polished is fixed to a carrier with a film. After chemical mechanical polishing, thermal peeling and ultraviolet peeling are performed sequentially to remove one first adhesive film layer and one second adhesive film layer, thus obtaining a silicon carbide wafer and a carrier with N-2 adhesive film layers. The fixation process, the chemical mechanical polishing process, the thermal stripping process, and the ultraviolet stripping process are repeated to obtain N / 2 silicon carbide wafers.

9. The application according to claim 8, characterized in that, The temperature of the thermal stripping is 10°C-20°C higher than the glass transition temperature of the raw material, and the time is 4-6 minutes. And / or, the wavelength of the ultraviolet ablation is 365nm-385nm, and the intensity is 15mW / cm. 2 -50mW / cm 2 ; And / or, the chemical mechanical polishing treatment includes: a polishing pressure of 200 g / cm. 2 -500g / cm 2 The polishing time is 0.5h-2h, the polishing solution includes a potassium permanganate solution with a mass concentration of 5%-10% and an alumina solution with a mass concentration of 2%-5%, the rotation speed is 20rpm-100rpm, and the temperature is 20℃-50℃.

10. The application according to claim 8, characterized in that, The subsurface crack depth of the prepared silicon carbide wafer is <1μm, and the yield of crack-free silicon carbide wafers is ≥99%.

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