Degradable temporary bonding adhesive, silicon carbide wafer bonding method, and silicon carbide wafer sheet

Abstract

The application discloses a degradable temporary bonding glue, a silicon carbide wafer bonding method and a silicon carbide wafer sheet, and relates to the technical field of semiconductors.The degradable temporary bonding glue provided by the application is targeted at the characteristics of high frequency and high power of a silicon carbide device, and the doped light-heat conversion filler has the characteristics of high thermal conductivity and insulation, thereby solving the problems of poor thermal conductivity of a traditional polymer glue layer and heat accumulation during wafer processing.The degradable temporary bonding glue has not only thermal degradation performance but also solvent degradation performance, can maintain stability during processing, and can rapidly disintegrate through specific trigger conditions during debonding, so that the degradation products after debonding are dissolved in specific solvents or undergo gasification, and mechanical external force is not needed to be applied for peeling, thereby fundamentally solving the risk of fragmentation of the sheet caused by pulling and tearing during the separation process.The silicon carbide wafer bonding has the characteristics of high safety, high cleanliness and high production efficiency, and in addition, the silicon carbide wafer is also unlocked to perform high-temperature and high-quality back processing in an ultrathin state.

Description

Technical Field

[0001] This invention relates to the field of semiconductor technology, and more specifically, to biodegradable temporary bonding adhesive, silicon carbide wafer bonding method, and silicon carbide wafer thin film. Background Technology

[0002] Silicon carbide (SiC) power devices are widely used in power electronics due to their excellent high-voltage, high-temperature, and high-frequency characteristics. To reduce the on-resistance of these devices, the SiC substrate typically needs to be thinned to 100 micrometers or even less than 50 micrometers. This ultra-thin wafer presents numerous challenges in subsequent processing: due to the significant reduction in mechanical strength, conventional wafer processing methods such as back-side metallization, ion implantation, alignment, and vacuum adsorption are prone to warping, cracking, or microcrack propagation; simultaneously, the temporary bonding methods employed suffer from colloidal decomposition at high temperatures, contaminating the device surface; difficulty in completely removing residual organic matter; residual stress after cooling leading to wafer deformation; and chemical corrosion damage to the SiC material surface.

[0003] Ensuring a strong bond between the SiC wafer and the carrier wafer during the back-side bonding process, and then completely separating the processed SiC wafer from the carrier wafer through a debonding process after completion, is one of the technical bottlenecks that existing temporary bonding technologies urgently need to address in practical applications.

[0004] In view of this, the present invention is proposed. Summary of the Invention

[0005] The purpose of this invention is to provide a biodegradable temporary bonding adhesive, a silicon carbide wafer bonding method, and silicon carbide wafer sheets to solve or improve the above-mentioned technical problems.

[0006] This invention is implemented as follows: In a first aspect, the present invention provides a biodegradable temporary bonding adhesive, comprising the following components by weight percentage: The main chain polymer is 50wt%-60wt%, photothermal conversion filler is 4wt%-8wt%, acid-induced degradation agent is 3wt%-7wt%, toughening modifier is 2wt%-5wt%, solvent is 25wt%-30wt%, and coupling agent is 0.5wt%-2wt%.

[0007] In an optional embodiment, the main chain polymer is a thermally degradable compound, including at least one of azo bonds and acetal structures; wherein the thermally degradable compound with azo bonds is selected from at least one of polyimide and polydiethylamine; and the thermally degradable compound with an acetal structure is selected from at least one of polyoxymethylene and methyl acetal. And / or, the photothermal conversion filler is selected from at least one of nanographene and carbon nanotubes.

[0008] In an optional embodiment, the acid-degrading agent is a photoacid-generating agent selected from at least one of diaryliodonium hexafluorophosphate and triphenylsulfonium hexafluoroantimonate; And / or, the toughening modifier is selected from at least one of butadiene-acrylonitrile copolymer and polyetheramine.

[0009] In an optional embodiment, the solvent is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide; And / or, the coupling agent is at least one of a silane coupling agent and an aluminate coupling agent.

[0010] In a second aspect, the present invention provides a silicon carbide wafer bonding method, wherein a biodegradable temporary bonding adhesive as described in any of the foregoing embodiments is used for silicon carbide wafer bonding; Silicon carbide wafer bonding includes the following steps: After mixing the components of the biodegradable temporary bonding adhesive in a certain proportion, the mixture is coated onto the surface of a substrate and dried to form a solid adhesive film. The front side of the silicon carbide wafer with the completed device fabrication is aligned with the solid adhesive film, and then heated and pressurized under vacuum conditions to obtain a composite silicon carbide wafer. Silicon carbide wafers are prepared by thinning, back-side metallization, debonding, and post-processing of composite silicon carbide wafers.

[0011] In an optional embodiment, the carrier is selected from borosilicate glass or molybdenum sheet; And / or, the drying temperature is 110℃-125℃; And / or, when preparing composite silicon carbide wafers, the heating temperature is 200℃-250℃, the pressure is 28MPa-32MPa, and the processing time is 28min-35min; And / or, the bonding strength of the composite silicon carbide wafer is 20MPa-22MPa, and the heat resistance temperature is 340℃-380℃.

[0012] In an optional embodiment, the thinning process is selected from at least one of grinding, rough polishing, and fine polishing; after the thinning process, the thickness of the silicon carbide wafer sheet is 70μm-80μm; And / or, the metal electrode deposited on the back side is selected from at least one of Ti, Ni and Ag.

[0013] In an optional implementation, the debonding process includes the following steps: The composite silicon carbide wafer is immersed in a solvent and subjected to UV irradiation for 1-3 minutes to debond. The solvent consists of N-methylpyrrolidone and p-toluenesulfonic acid, with the p-toluenesulfonic acid having a volume fraction of 0.3%-0.8%. The UV light wavelength is 280nm-315nm, and the intensity is 20mW / cm². 2 -50mW / cm 2 .

[0014] In an optional embodiment, the post-treatment includes a cleaning process and a drying process; wherein the cleaning agent is selected from at least one of acetone, an alcohol solution, and water; The drying temperature is 55℃-65℃.

[0015] Thirdly, the present invention provides a silicon carbide wafer thin film, which is prepared by the silicon carbide wafer bonding method as described in any of the foregoing embodiments.

[0016] The present invention has the following beneficial effects: The biodegradable temporary bonding adhesive provided in this invention is designed for the high-frequency, high-power characteristics of silicon carbide devices. The doped photothermal conversion filler exhibits high thermal conductivity and insulation, solving the problems of poor thermal conductivity and heat accumulation during wafer processing associated with traditional polymer adhesives. This biodegradable temporary bonding adhesive not only possesses thermal degradation properties but also solvent degradation properties, maintaining stability during processing. Furthermore, it rapidly disintegrates under specific triggering conditions during debonding. The degradation products after debonding dissolve in specific solvents or vaporize, eliminating the need for mechanical peeling and fundamentally solving the risk of breakage caused by tearing during wafer separation. Silicon carbide wafer bonding offers high safety, high cleanliness, and high production efficiency. Moreover, it unlocks high-temperature, high-quality back-side processing of ultra-thin silicon carbide wafers. Attached Figure Description

[0017] 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.

[0018] Figure 1 This is a surface morphology image of the silicon carbide wafer thin film obtained after debonding in Example 1; Figure 2 The image shows the surface morphology of the silicon carbide wafer obtained after debonding in Comparative Example 1. Figure 3 The image shows the surface morphology of the silicon carbide wafer obtained after debonding in Comparative Example 2. Figure 4The image shows the surface morphology of the silicon carbide wafer thin film obtained after debonding in Comparative Example 3. Figure 5 This is a schematic diagram of the bonded composite silicon carbide wafer structure.

[0019] Explanation of key component symbols: 1-Silicon carbide wafer; 101-Silicon surface; 102-Carbon surface; 2-Adhesive layer; 3-Carrier wafer; 4-Composite silicon carbide wafer. 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 a biodegradable temporary bonding adhesive, comprising the following components by weight percentage: The main chain polymer is 50wt%-60wt%, photothermal conversion filler is 4wt%-8wt%, acid-induced degradation agent is 3wt%-7wt%, toughening modifier is 2wt%-5wt%, solvent is 25wt%-30wt%, and coupling agent is 0.5wt%-2wt%.

[0022] The characteristics of each component are analyzed as follows: The main-chain polymer, as the backbone component of the biodegradable temporary bonding adhesive, possesses high-temperature stability and a biodegradable mechanism, withstanding temperatures above 350°C. It can undergo chain-breaking degradation upon exposure to specific wavelengths of light or high temperatures, eliminating the need for mechanical peeling. The appropriate use of the main-chain polymer achieves a balance between adhesion, temperature resistance, and biodegradability between the silicon carbide wafer 1 and the carrier 3, resulting in optimal performance. Insufficient dosage leads to low adhesive strength, making it suitable for thin-film processing where adhesive strength requirements are not high; otherwise, edge delamination is likely during thinning. Excessive dosage makes debonding difficult and requires high laser energy, potentially damaging the silicon carbide wafer 1.

[0023] Photothermal conversion filler can absorb the energy of a specific laser and convert it into heat energy, triggering internal degradation; at the same time, it improves the thermal conductivity of adhesive layer 2. When used properly, photothermal conversion filler exhibits sensitive photothermal response and short debonding time; however, insufficient filler has the following drawbacks: no photothermal response and difficult debonding; poor adhesion between silicon carbide wafer 1 and carrier 3, insufficient light absorption, requiring additional high laser power; excessive filler will increase the brittleness of adhesive layer 2.

[0024] The acid-induced degradation agent is a photoacid-generating agent, and its debonding speed is determined by its compatibility with the light source. Under UV irradiation, it decomposes to produce acid, which is beneficial for catalyzing the degradation of acetals or polyester structures. Proper use of the acid-induced degradation agent can balance storage stability and debonding efficiency, leaving no residue after debonding and being non-corrosive to silicon carbide wafers, meeting the needs of high-speed production lines. The acid-induced degradation agent is prone to decomposition and inactivation at high temperatures and requires refrigerated storage at 0-8°C. Insufficient dosage makes effective degradation triggering difficult, suitable for scenarios where debonding speed is not critical; excessive dosage results in a narrow storage window, making mass production uncontrollable and posing certain risks.

[0025] Toughening modifiers determine the processing yield of ultrathin wafers, primarily affecting warpage and stress control. Adding toughening modifiers reduces the brittleness of the adhesive layer 2, absorbs stress during processing, and prevents wafer warpage. Toughening modifiers can withstand temperatures above 350℃. Appropriate dosage achieves optimal stress buffering and performance balance, with minimal, negligible, residue after debonding. Insufficient dosage results in poor stress buffering; excessive dosage, while suitable for processing ultrathin wafers (thickness ≤ 50μm), significantly reduces temperature resistance to 330℃, increasing the risk of high-temperature operations.

[0026] The solvent is used to adjust the viscosity of the biodegradable temporary bonding adhesive, so that the biodegradable temporary bonding adhesive can be successfully formed on the carrier 3.

[0027] Coupling agents can enhance the adhesion between the adhesive film and the SiC wafer and substrate 3, and improve the bonding strength.

[0028] In an optional embodiment, the main chain polymer is a thermally degradable compound, including at least one of an azo bond and an acetal structure; wherein the thermally degradable compound with an azo bond is selected from at least one of polyimide and polydiethylamine; and the thermally degradable compound with an acetal structure is selected from at least one of polyoxymethylene and methyl acetal.

[0029] For example, the amount of main chain polymer used, by weight percentage, can be selected from any one of 50wt%, 52wt%, 55wt%, 56wt%, 58wt%, and 60wt%, or other values ​​in the range of 50wt%-60wt%.

[0030] It should be noted that if the thermal degradation compound of the azo bond is a polyimide, the molecular weight of the polyimide is selected from 400 g / mol to 500 g / mol.

[0031] And / or, the photothermal conversion filler is selected from at least one of nano-graphene and carbon nanotubes; wherein, the nano-graphene absorbs specific laser energy and converts it into heat energy, triggering internal degradation; and simultaneously improves the thermal conductivity of the adhesive layer 2. Exemplarily, the amount of photothermal conversion filler, by mass percentage, can be selected from any one of 4wt%, 5wt%, 5.5wt%, 6wt%, 7wt%, and 8wt%, or other values ​​within the range of 4wt%-8wt%.

[0032] In an optional embodiment, the acid-degrading agent is a photoacid-generating agent selected from at least one of diaryliodonium hexafluorophosphate and triphenylsulfonium hexafluoroantimonate; exemplaryly, the amount of acid-degrading agent used, by mass percentage, can be selected from any one of 3wt%, 3.5wt%, 4wt%, 5wt%, 6wt%, and 7wt%, or other values ​​in the range of 3wt%-7wt%.

[0033] And / or, the toughening modifier is selected from at least one of butadiene-acrylonitrile copolymer and polyetheramine. For example, the amount of toughening modifier used, by weight percentage, may be selected from any one of 2wt%, 2.5wt%, 3wt%, 3.5wt%, 4wt%, and 5wt%, or other values ​​in the range of 2wt% to 5wt%.

[0034] In an optional embodiment, the solvent is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide, and N,N-dimethylformamide; exemplaryly, the amount of solvent used, by weight percentage, may be selected from any one of 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, and 30wt%, or other values ​​in the range of 25wt%-30wt%.

[0035] And / or, the coupling agent is at least one of a silane coupling agent and an aluminate coupling agent. For example, the amount of silane coupling agent used, by weight percentage, may be selected from any one of 0.5wt%, 1wt%, 1.5wt%, 1.8wt%, and 2wt%, or other values ​​in the range of 0.5wt% to 2wt%.

[0036] Among them, silane coupling agents are selected as needed, such as KH-560, KH-570, etc.; aluminate coupling agents are selected as needed, such as ACA-K30, AL-820, etc.

[0037] In a second aspect, the present invention provides a method for bonding silicon carbide wafer 1, wherein the silicon carbide wafer 1 is bonded using a biodegradable temporary bonding adhesive as described in any of the foregoing embodiments. Silicon carbide wafer bonding includes the following steps: After mixing the components of the biodegradable temporary bonding adhesive in proportion, the mixture is coated onto the surface of the carrier 3 and dried to form a solid adhesive film. The front side of the silicon carbide wafer 1, after the device fabrication is completed, is aligned with the solid adhesive film. After heating and pressurizing under vacuum conditions, a composite silicon carbide wafer 4 is obtained. After thinning, back-side metallization, debonding and post-processing, composite silicon carbide wafer 4 is used to prepare silicon carbide wafer 1 thin film.

[0038] In an optional embodiment, the carrier 3 is selected from borosilicate glass or molybdenum sheet; the thermal expansion coefficient of the carrier 3 is close to that of silicon carbide, ensuring the uniformity and integrity of the bonding interface and preventing the silicon carbide wafer 1 from cracking and warping during high-temperature cooling.

[0039] The present invention does not impose any particular limitation on the coating method of the biodegradable temporary bonding adhesive on the carrier 3. The coating method can be selected as either blade coating or spin coating as needed. In the specific embodiment of the present invention, spin coating is used.

[0040] And / or, the drying temperature is 110°C-125°C; drying at this temperature helps remove most of the solvent in the biodegradable temporary bonding adhesive, forming a solid adhesive film on the surface of the carrier 3. Exemplarily, the drying temperature is selected from any one of 110°C, 115°C, 120°C, and 125°C, or other values ​​within the range of 110°C-125°C.

[0041] When preparing the composite silicon carbide wafer 4, the front side (i.e., carbon surface 102) of the silicon carbide wafer 1 with the device fabrication completed is facing down and aligned with the solid adhesive film on the carrier 3; it is placed in a special bonding cavity, vacuumed, heated and pressurized, and after cooling, the bonded silicon carbide wafer 1 is taken out, thus obtaining the composite silicon carbide wafer 4.

[0042] And / or, when preparing composite silicon carbide wafer 4, the heating temperature is 200℃-250℃, the pressure is 28MPa-32MPa, and the processing time is 28min-35min.

[0043] When the solid adhesive film formed by the biodegradable temporary bonding adhesive is heated and pressurized under vacuum conditions, it softens and flows, filling the uneven structure on the surface of the silicon carbide wafer 1, and then undergoes chemical cross-linking to form a strong but reversible bond between the silicon carbide wafer 1 and the carrier 3.

[0044] And / or, the bonding strength of the composite silicon carbide wafer 4 is 20MPa-22MPa, and the heat resistance temperature is 340℃-380℃.

[0045] In an optional embodiment, the thinning process is selected from at least one of grinding, rough polishing, and fine polishing; after the thinning process, the thickness of the silicon carbide wafer 1 is 70μm-80μm; specifically, the bonded composite silicon carbide wafer 4 is subjected to back-side grinding and CMP polishing until the target thickness is achieved. A schematic diagram of the structure of the composite silicon carbide wafer 4 is shown below. Figure 5 It includes a carrier 3, an adhesive layer 2 (i.e., a biodegradable temporary bonding adhesive), and SiC.

[0046] And / or, the metal electrode deposited on the back side is selected from at least one of Ti, Ni and Ag.

[0047] Backside metallization deposition specifically involves depositing metal electrodes (such as Ti / Ni / Ag) on ​​the thinned SiC backside (i.e., silicon surface 101).

[0048] In an optional implementation, the debonding process includes the following steps: The composite silicon carbide wafer 4 is immersed in a solvent and subjected to UV irradiation for 1-3 minutes to debond. The solvent includes N-methylpyrrolidone and p-toluenesulfonic acid, with the volume fraction of p-toluenesulfonic acid being 0.3%-0.8%. The UV light activates the photoacid-generating agent in the adhesive layer 2, producing acidic substances. These acidic substances catalyze the hydrolysis of the acetal structure in the pre-designed acid-induced degradation agent in the degradable temporary adhesive layer 2, thereby dissolving the adhesive layer 2. The SiC wafer then floats on the liquid surface, and the silicon carbide wafer is retrieved.

[0049] Ultraviolet light has a wavelength of 280nm-315nm and an intensity of 20mW / cm². 2 -50mW / cm 2 .

[0050] Ultraviolet light of suitable wavelength and intensity results in rapid debonding. PAG has a high absorption peak in this band, improving acid production efficiency. With appropriate thermal effects, the debonding time is 1-3 minutes, balancing efficiency and safety. Long-wavelength, high-energy ultraviolet light has low photon energy and will not damage SiC or device structures. However, the debonding speed is slow, and PAG absorption efficiency is generally low. It needs to be degraded in conjunction with the heat generated by photothermal fillers, with a time of 5-10 minutes. Short-wavelength, low-energy ultraviolet light may damage the passivation layer or metal electrodes on the SiC surface with high-energy photons, causing photo-induced damage. Surface debonding is rapid and will directly break the chemical bonds on the polymer surface. However, the penetration depth is shallow, and thick adhesive layers need to be degraded in conjunction with thermal degradation.

[0051] In an optional embodiment, the post-treatment includes cleaning and drying; wherein the cleaning agent is selected from at least one of acetone, alcohol solution, and water; the alcohol solution can be selected from methanol solution, ethanol solution, and isopropanol solution, etc., depending on actual needs. The type of water can be selected from purified water, deionized water, and ultrapure water, etc., as needed.

[0052] For example, in a specific embodiment of the present invention, the cleaning process is as follows: first, rinse with acetone spray to remove the dissolved residual adhesive layer 2; then rinse the surface of the silicon carbide wafer 1 with anhydrous ethanol and pure water in sequence to obtain a clean silicon carbide wafer 1.

[0053] The drying temperature is 55℃-65℃. The drying method is not particularly limited; the silicon carbide wafer can be placed on a hot plate platform for drying, or it can be dried with nitrogen gas.

[0054] In summary, the silicon carbide wafer 1 provided in this embodiment of the invention is prepared using the following steps: Step 1: Preparation and Coating of Carrier 3 Selection of carrier 3: Select borosilicate glass or molybdenum sheet with a thermal expansion coefficient close to that of SiC as carrier 3.

[0055] Coating process: The biodegradable temporary bonding adhesive prepared in proportion is uniformly coated onto the carrier 3 by spin coating.

[0056] Drying process: Heating at 110℃-125℃ removes most of the solvent and forms a solid film.

[0057] Step 2: Temporary bonding (wafer face down) Alignment process: Align the SiC wafer (front side) with the adhesive film on the carrier 3 after the device fabrication is completed.

[0058] Vacuum heating and pressurization: Place it in a special bonding cavity, evacuate, heat to 200℃-250℃, and apply pressure of 28MPa-32MPa for 28min-35min; after cooling, take out the bonded silicon carbide wafer 1 to obtain the composite silicon carbide wafer 4.

[0059] Step 3: Thinning process and back-side metallization Thinning process: The composite silicon carbide wafer 4 obtained in step 2 is sent for back-side grinding and CMP polishing until the target thickness of 70μm-80μm is achieved.

[0060] Backside metallization: Deposit a metal electrode (at least one of Ti, Ni and Ag) on ​​the backside of a thinned SiC.

[0061] Step 4: Debonding The composite silicon carbide wafer 4, after the backside metallization treatment in step 3, is immersed in a mixed solvent of N-methylpyrrolidone (NMP) and p-toluenesulfonic acid (p-toluenesulfonic acid volume fraction is 0.3%-0.8%), while being irradiated with UV light with a wavelength of 280nm-315nm and an intensity of 20mW / cm². 2 -50mW / cm 2 The adhesive layer 2 dissolves, and the SiC wafer floats on the liquid surface. The silicon carbide wafer 1 is then retrieved.

[0062] Step 5: Post-processing Under normal temperature conditions, the dissolved residual adhesive layer 2 is removed by rinsing with acetone spray. Then, the surface of the silicon carbide wafer 1 is rinsed with anhydrous ethanol and pure water, and finally dried on a hot plate at 60°C or under nitrogen to obtain a clean silicon carbide wafer 1.

[0063] Thirdly, the present invention provides a silicon carbide wafer 1 thin film, which is prepared by the silicon carbide wafer 1 bonding method as described in any of the foregoing embodiments.

[0064] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0065] Example 1 This embodiment provides a silicon carbide wafer 1, and the preparation method includes the following steps: Step 1: Preparation and Coating of Carrier 3 Selection of carrier 3: Borosilicate glass with a thermal expansion coefficient close to that of SiC is selected as carrier 3.

[0066] Coating process: The biodegradable temporary bonding adhesive prepared in proportion is uniformly coated onto the carrier 3 by spin coating.

[0067] The components of the biodegradable temporary bonded adhesive, by weight percentage, include: 55 wt% main chain polymer (thermally degradable polyimide containing azo bonds), 5 wt% photothermal conversion filler (nanographene), 5 wt% acid-induced degradation agent (diaryliodonium hexafluorophosphate), 3 wt% toughening modifier (butadiene-acrylonitrile copolymer), 28 wt% solvent, and 1.5 wt% coupling agent (silane coupling agent KH-560).

[0068] Drying process: Heating at 120°C removes most of the solvent, forming a solid film.

[0069] Step 2: Temporary bonding (wafer face down) Alignment process: Align the SiC wafer (front side) with the adhesive film on the carrier 3 after the device fabrication is completed.

[0070] Vacuum heating and pressurization: Place it in a special bonding cavity, evacuate, heat to 220°C, and apply a pressure of 30MPa for 30 minutes; after cooling, take out the bonded silicon carbide wafer 1 to obtain the composite silicon carbide wafer 4.

[0071] Step 3: Thinning process and back-side metallization Thinning process: The composite silicon carbide wafer 4 obtained in step 2 is sent for back-side grinding and CMP polishing until the target thickness of 80μm is achieved.

[0072] Backside metallization: Deposit a metal electrode (Ti) on the back side of a thinned SiC.

[0073] Step 4: Debonding The composite silicon carbide wafer 4, after the backside metallization treatment in step 3, is immersed in a mixed solvent of N-methylpyrrolidone (NMP) and p-toluenesulfonic acid (0.5% by volume) while being irradiated with UV light at a wavelength of 308 nm and an intensity of 50 mW / cm². 2 The adhesive layer 2 dissolves, and the SiC wafer floats on the liquid surface. The silicon carbide wafer 1 is then retrieved.

[0074] Step 5: Post-processing Under normal temperature conditions, the dissolved residual adhesive layer 2 is removed by rinsing with acetone spray. Then, the surface of the silicon carbide wafer 1 is rinsed with anhydrous ethanol and pure water, and finally dried on a hot plate at 60°C or under nitrogen to obtain a clean silicon carbide wafer 1.

[0075] Experimental Example 1 This experimental example is used to investigate the effect of photothermal conversion filler (nanographene) on the performance of composite silicon carbide wafer 4. The only difference between this example and Example 1 is the amount of photothermal conversion filler used. The relevant results are summarized in Table 1.

[0076] Table 1. Effect of photothermal conversion filler on the performance of composite silicon carbide wafers.

[0077] Experimental Example 2 This experimental example is used to investigate the effect of the main chain polymer (polyimide) on the performance of the composite silicon carbide wafer 4. The only difference between this example and Example 1 is the amount of main chain polymer used. The relevant results are summarized in Table 2.

[0078] Table 2. Effect of main-chain polymers on the performance of composite silicon carbide wafers.

[0079] Experimental Example 3 This experiment was used to investigate the effect of photo-induced acid-generating agent (diaryliodonium hexafluorophosphate) on the performance of composite silicon carbide wafer 4. The only difference between this experiment and Example 1 is the amount of diaryliodonium hexafluorophosphate used. The relevant results are summarized in Table 3.

[0080] Table 3. Effects of photoacid-generating agents on the performance of composite silicon carbide wafers.

[0081] Test Example 4 This experimental example was used to investigate the effect of toughening modifier (butadiene-acrylonitrile copolymer) on the performance of composite silicon carbide wafer 4. The only difference between this example and Example 1 is the amount of butadiene-acrylonitrile copolymer used. The relevant results are summarized in Table 4.

[0082] Table 4. Effect of toughening modifiers on the properties of composite silicon carbide wafers.

[0083] Experimental Example 5 This experimental example is used to investigate the effect of ultraviolet light on the performance of composite silicon carbide wafer 4 during debonding treatment. The only difference between this example and Example 1 is the wavelength and intensity of the ultraviolet light. The relevant results are summarized in Table 5.

[0084] Table 5. Effects of UV light on the performance of composite silicon carbide wafers.

[0085] Comparative Example 1 This comparative example provides a silicon carbide wafer 1, the preparation method of which includes the following steps: The bonding step includes: Step 1: Heat the carrier 3 and apply wax. Place the carrier 3 on a hot plate and heat it to the melting point of the wax. Use a spin coater to evenly coat the wax onto the surface of the carrier 3. Keep the hot plate temperature at 120°C and the wax coating thickness at 15 µm. The wax liquid should form a uniform "liquid pool" on the hot plate.

[0086] Step 2: Alignment and bonding. Align the device wafer with the wax-coated carrier 3 and place it into the bonding machine. Heat and pressurize to make the wax layer evenly distributed. The bonding pressure is 0.34 bar and the bonding temperature is 120℃. The final temperature is gradually reduced to 65℃. This process must be carried out in a vacuum environment (<24 mbar) to eliminate air bubbles.

[0087] Step 3: Cooling and curing. The wax layer is cured by slowly cooling down under a certain pressure. The cooling method is natural cooling. If the cooling rate is too fast, it will cause excessive thermal stress, which may cause wafer warping or cracking.

[0088] The debonding step employs the hot-slip method, including: Step 1: Reheat the bonded pair to above the softening temperature of the wax. The heating temperature is 120℃ (the viscosity will decrease significantly when it melts). The temperature is higher than the temperature during the processing. If it is lower than the critical value for thermal decomposition of the material, the entire bonding system needs to be heated simultaneously.

[0089] Step 2: The wax layer softens significantly, and shear or pushing forces are applied to separate the wafer. Typical debonding temperature: 200°C. Low-stress separation can be achieved with minimal mechanical force.

[0090] Step 3: Clean the wafer to remove residual wax layer using NMP cleaning.

[0091] Comparative Example 2 This comparative example provides a silicon carbide wafer 1, the preparation method of which includes the following steps: The bonding step includes: Step 1: Prepare for film application. Select the appropriate size of heat release tape and peel off the protective layer. Tape thickness: generally 100 µm. Operate in a clean environment.

[0092] Step 2: Wafer attachment. Smoothly attach the tape to the carrier 3. The attachment temperature is room temperature. Use rollers or a laminator to apply pressure and remove air.

[0093] Step 3: Pressing the carrier 3 together. The carrier 3 is pressed together with the device wafer with the attached adhesive tape. The pressing pressure is 0.35 MPa and the pressing temperature is 100℃, which makes it easy to control the generation of bubbles.

[0094] Step 4: Curing / stabilization. Allow the tape to cool naturally to room temperature. Once fully cured, the tape provides stable adhesion. After bonding, the tape offers high shear strength. All subsequent process temperatures must be below the debonding temperature; otherwise, premature failure may occur.

[0095] The debonding steps include: Step 1: Heat activation. Heat the bonded pair to the debonding temperature of the heat release tape, which is 190°C. The equipment used is a typical ESR pyrolysis bonder.

[0096] Step 2: Maintain the temperature for 2.5 minutes and wait for the foamed microspheres to expand and rupture.

[0097] Step 3: The microspheres of the separated wafer break down, the adhesive force disappears, and the wafer automatically slides off the tape. It can be gently picked up with a vacuum chuck, leaving almost no adhesive residue and requiring no subsequent cleaning.

[0098] Step 4: After removing the adhesive tape, the carrier 3 can be reused by using a hot air gun or solvent to remove any residual adhesive. The carrier 3 can be recycled and reused.

[0099] Comparative Example 3 This comparative example provides a silicon carbide wafer 1, the preparation method of which includes the following steps: The bonding step includes: Step 1: Spin-coat or spray-coat a laser-responsive temporary bonding material (containing UV absorber) onto glass slide 3 with a thickness of 200 nm and a spin-coating speed of 800 rpm for the TBA layer; Step 2: Soft bake to remove solvent and perform preliminary curing. The soft bake temperature is 180℃ and the time is 4 min.

[0100] Step 3: Press and bond the carrier 3 to the device wafer in a vacuum environment. The bonding pressure is 0.4 MPa, the bonding temperature is 200℃, and the vacuum degree is <10 mbar to ensure no air bubbles.

[0101] Step 4: Ultraviolet (UV) light is irradiated through slide 3 to cure the temporary bonding adhesive. The UV wavelength is 365 nm (matching the transmittance of slide 3), and the exposure energy is 1500 mJ / cm². 2 The material of slide 3 needs to be transparent to UV wavelengths.

[0102] Step 5: Use ultrasonic scanning (CSAM) or a film thickness gauge to check the bonding quality, voids, and thickness uniformity.

[0103] The debonding steps include: Step 1: Place the bonded pair in the laser debonding device with the back side facing up (glass slide 3 facing up). The debonding process is carried out at room temperature to avoid thermal expansion stress causing fragmentation.

[0104] Step 2: Laser scanning, irradiating the photothermal conversion layer or bonding interface through the transparent substrate 3, with a laser wavelength of 308 nm and an energy density of 130 mJ / cm². 2 .

[0105] Step 3: Instantaneous photothermal conversion or photochemical reaction of LTHC layer, interface decomposition to generate air gap, irradiation time of 1 minute per sheet, wire bundle shaping energy non-uniformity <10%.

[0106] Step 4: The interface no longer has effective adhesion. The wafer and carrier 3 separate naturally or are gently picked up without additional external force, resulting in almost zero stress debonding.

[0107] Step 5: Clean and remove residual bonding adhesive using NMP as the cleaning solution.

[0108] Example 1 and Comparative Examples 1-3 were compared, and the results are summarized in Table 6.

[0109] Table 6 Comparison results of Example 1 and Comparative Examples 1-3

[0110] Test Example 1 This test example performs surface analysis on silicon carbide wafers 1 prepared in Example 1 and Comparative Examples 1-3, respectively. Related images can be found in [link to relevant images]. Figures 1-4 ,in, Figure 1 This is a surface analysis image of the silicon carbide wafer 1 obtained after debonding in Example 1; Figure 2 The surface analysis diagram of the silicon carbide wafer 1 obtained after debonding in Comparative Example 1 is shown. Figure 3 The surface analysis diagram of the silicon carbide wafer 1 obtained after debonding in Comparative Example 2 is shown. Figure 4 This is a surface analysis diagram of the silicon carbide wafer 1 obtained after debonding in Comparative Example 3.

[0111] Combination Figures 1-4 It can be seen that, Figure 1 The surface of the silicon carbide wafer 1 is clean, with no residual adhesive or ablation. Figure 2 Silicon carbide wafers experience high thermal stress at high temperatures, which can cause damage. Figure 3 There are residues on the edge of the silicon carbide wafer 1, indicating edge chipping. Figure 4 Edge ablation was observed on a silicon carbide wafer.

[0112] In summary, this invention combines material innovation (biodegradable temporary bonding adhesive) with process innovation (dual-response triggering) to address the processing needs of hard, brittle, high-temperature, and high-value thin wafers like SiC. It not only eliminates the dangerous mechanical peeling and cumbersome wax cleaning process, providing higher safety and cleanliness for SiC wafer operations, but also unlocks the possibility of performing high-temperature, high-quality back-side processes in an ultra-thin state.

[0113] 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 biodegradable temporary bonding adhesive, characterized in that, By mass percentage, it includes the following components: The main chain polymer is 50wt%-60wt%, photothermal conversion filler is 4wt%-8wt%, acid-induced degradation agent is 3wt%-7wt%, toughening modifier is 2wt%-5wt%, solvent is 25wt%-30wt%, and coupling agent is 0.5wt%-2wt%.

2. The biodegradable temporary bonding adhesive according to claim 1, characterized in that, The main chain polymer is a thermally degradable compound, including at least one of azo bonds and acetal structures; wherein, the thermally degradable compound with azo bonds is selected from at least one of polyimide and polydiethylamine; and the thermally degradable compound with an acetal structure is selected from at least one of polyoxymethylene and methyl acetal. And / or, the photothermal conversion filler is selected from at least one of nanographene and carbon nanotubes.

3. The biodegradable temporary bonding adhesive according to claim 1, characterized in that, The acid-induced degradation agent is a photo-induced acid-producing agent, selected from at least one of diaryliodonium hexafluorophosphate and triphenylsulfonium hexafluoroantimonate; And / or, the toughening modifier is selected from at least one of butadiene-acrylonitrile copolymer and polyetheramine.

4. The biodegradable temporary bonding adhesive according to claim 1, characterized in that, The solvent is selected from at least one of N-methylpyrrolidone, dimethyl sulfoxide and N,N-dimethylformamide; And / or, the coupling agent is at least one of a silane coupling agent and an aluminate coupling agent.

5. A silicon carbide wafer bonding method, characterized in that, Silicon carbide wafer bonding is performed using the biodegradable temporary bonding adhesive as described in any one of claims 1-4; Silicon carbide wafer bonding includes the following steps: After mixing the components of the biodegradable temporary bonding adhesive in a certain proportion, the mixture is coated onto the surface of a substrate and dried to form a solid adhesive film. The front side of the silicon carbide wafer with the completed device fabrication is aligned with the solid adhesive film, and after heating and pressurizing under vacuum conditions, a composite silicon carbide wafer is obtained. The composite silicon carbide wafer is subjected to thinning, back-side metallization, debonding, and post-processing to obtain silicon carbide wafer sheets.

6. The silicon carbide wafer bonding method according to claim 5, characterized in that, The carrier is selected from borosilicate glass or molybdenum sheet; And / or, the drying temperature is 110℃-125℃; And / or, when preparing composite silicon carbide wafers, the heating temperature is 200℃-250℃, the pressure is 28MPa-32MPa, and the processing time is 28min-35min; And / or, the bonding strength of the composite silicon carbide wafer is 20MPa-22MPa, and the heat resistance temperature is 340℃-380℃.

7. The silicon carbide wafer bonding method according to claim 5, characterized in that, The thinning process is selected from at least one of grinding, rough polishing and fine polishing; after the thinning process, the thickness of the silicon carbide wafer is 70μm-80μm; And / or, the metal electrode deposited on the back side is selected from at least one of Ti, Ni and Ag.

8. The silicon carbide wafer bonding method according to claim 5, characterized in that, The debonding process includes the following steps: The composite silicon carbide wafer is immersed in a solvent and subjected to UV irradiation for 1-3 minutes to debond. The solvent is N-methylpyrrolidone, and the solute is p-toluenesulfonic acid with a volume fraction of 0.3%-0.8%. Ultraviolet light has a wavelength of 280nm-315nm and an intensity of 20mW / cm². 2 -50mW / cm 2 .

9. The silicon carbide wafer bonding method according to claim 5, characterized in that, The post-processing includes a cleaning process and a drying process; wherein the cleaning agent is selected from at least one of acetone, alcohol solution and water; The drying process is carried out at a temperature of 55℃-65℃.

10. A silicon carbide wafer thin film, characterized in that, It is prepared by the silicon carbide wafer bonding method as described in any one of claims 5-9.

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