Method for exfoliating silicon carbide single crystal thin film, silicon carbide epitaxial substrate, and semiconductor device

Abstract

The present application relates to the technical field of semiconductor materials, in particular to a method for peeling off a silicon carbide single crystal film, a silicon carbide epitaxial substrate and a semiconductor device. The method comprises the following steps: bonding a temporary carrier substrate with a controllable dissociation layer on the surface to a donor substrate; then peeling off; and then bonding and peeling off the composite structure formed by peeling off to a target receptor substrate, wherein the crystal form of the temporary carrier substrate and the donor substrate is the same or compatible. The method does not directly transfer the SiC film from the donor carrier to the receptor substrate at one time, but creatively introduces a "homogeneous temporary carrier substrate" as a buffer and transfer platform, and designs a "controllable dissociation layer" to realize accurate secondary separation. Through the "two-step transfer method", the three problems of thermal mismatch, high-temperature damage and recovery loss are decoupled, which has originality and systematic advantages in the process path, and provides a new route for the manufacture of ultra-low-cost and large-size SiC substrates.

Description

Technical Field

[0001] This invention relates to the field of semiconductor materials technology, and more specifically, to a method for peeling off silicon carbide single crystal thin films, silicon carbide epitaxial substrates, and semiconductor devices. Background Technology

[0002] Silicon carbide (SiC), as the core of third-generation wide-bandgap semiconductor materials, has irreplaceable advantages in high-temperature, high-frequency, and high-power devices. However, the high cost of high-quality single-crystal SiC substrates (accounting for approximately 50% of device costs) is a major bottleneck for its industrialization. Traditional "smart lift-off" technology offers a solution to reduce substrate costs. Its typical steps include: hydrogen ion implantation into the donor SiC substrate to form a lift-off layer; bonding it to a low-cost acceptor substrate (such as polycrystalline SiC or high-resistivity silicon); and heat treatment to cause the donor substrate to split along the lift-off layer, thereby transferring the SiC thin film.

[0003] However, directly applying mature SOI smart stripping technology to SiC faces significant challenges: Thermal expansion coefficient mismatch: The thermal expansion coefficients of SiC and inexpensive acceptor substrates (such as silicon) differ greatly. In subsequent high-temperature epitaxial or annealing processes at temperatures above 1500°C, the resulting thermal stress can cause the composite substrate to bend or crack, or the SiC film to develop high-density dislocations, severely affecting device performance and yield.

[0004] High-temperature bonding requirements and damage: To obtain sufficient bond strength to withstand peel stress, high-temperature bonding (>1000°C) is usually required for SiC-SiC or SiC-other materials. This high-temperature process can exacerbate hydrogen bubble diffusion in the implantation region, destabilize the peel layer, and potentially introduce thermal stress defects.

[0005] Donor substrate recovery surface damage: After stripping, the donor substrate surface is rough and has a crystalline damage layer. Traditional polishing removes a large amount of material (several micrometers), resulting in high material loss per cycle, limited substrate reusability, and suboptimal economic efficiency.

[0006] Therefore, there is an urgent need for a new technology that is compatible with high-temperature processes, improves donor substrate recovery, and is suitable for large-size SiC thin film transfer. In view of this, the present invention is proposed. Summary of the Invention

[0007] The purpose of this invention is to provide a method for peeling off silicon carbide single-crystal thin films, silicon carbide epitaxial substrates, and semiconductor devices. The peeling method provided in this invention avoids stress caused by differences in thermal expansion coefficients, and simultaneously avoids damage to the implanted layer and materials caused by high-temperature bonding, thereby improving the crystal quality and uniformity of the peeled surface.

[0008] This invention is implemented as follows: In a first aspect, the present invention provides a method for peeling off a silicon carbide single-crystal thin film, comprising: forming a controllable dissociation layer on the surface of a single-crystal silicon carbide temporary support substrate, wherein the crystal form of the single-crystal silicon carbide temporary support substrate is the same as or compatible with the crystal form of the single-crystal silicon carbide donor substrate; Next, a single-crystal silicon carbide donor substrate with a first release layer on its surface is bonded to the single-crystal silicon carbide temporary carrier substrate to form a first composite structure, wherein the structure of the first composite structure is: single-crystal silicon carbide donor substrate - first release layer - controllable dissociation layer - single-crystal silicon carbide temporary carrier substrate; the dissociation energy of the controllable dissociation layer is lower than the release energy of the first release layer. Then, the first composite structure is peeled off for the first time, so that the first peeling layer is peeled off to form the second composite structure. The structure of the second composite structure is: silicon carbide single crystal thin film - controllable dissociation layer - single crystal silicon carbide temporary carrier substrate. Then, the second composite structure is bonded to the target acceptor substrate to form a third composite structure; the structure of the third composite structure is target acceptor substrate-silicon carbide single crystal thin film-controllable dissociation layer-single crystal silicon carbide temporary carrier substrate; Next, the third composite structure is peeled off a second time, so that the silicon carbide single crystal film is transferred to the target acceptor substrate.

[0009] In an optional implementation, the controllable dissociation layer satisfies at least one of the following requirements: (1) The thickness of the controllable dissociation layer is 50 nm-2 μm; (2) The controllable dissociation layer is any one of an amorphous silicon carbide layer, a porous silicon carbide layer, and a silicon carbide-carbon nanolayer; (3) The methods for forming the controllable dissociation layer include physical vapor deposition or chemical vapor deposition.

[0010] In an optional implementation, the conditions for forming the first composite structure satisfy at least one of the following requirements: (1) The bonding temperature is below 400℃, preferably room temperature - 300℃; (2) The bonding method is direct bonding or adhesive bonding.

[0011] In an optional implementation, the first peeling is performed by heat treatment; Preferably, the temperature of the first peeling is 400-600℃.

[0012] In an optional embodiment, the target acceptor substrate comprises any one of polycrystalline silicon carbide, high thermal conductivity silicon, and a metal with a dielectric layer on its surface.

[0013] In an optional implementation, the conditions for forming the third composite structure satisfy at least one of the following requirements: (1) The bonding temperature is below 400℃, preferably room temperature - 300℃; (2) The bonding method is any one of direct bonding, plasma-activated bonding and adhesive bonding.

[0014] In an optional implementation, the second peeling is performed by heat treatment or by applying mechanical stress; Preferably, the heat treatment temperature is 300-500℃; The applied mechanical stress is a tensile stress or shear force of 0.1-10 MPa.

[0015] In an optional implementation, the stripping method further includes at least one of the following steps: (1) It also includes: recycling the secondary single-crystal silicon carbide donor substrate formed by the first stripping to form a recycled single-crystal silicon carbide donor substrate, wherein the recycled single-crystal silicon carbide donor substrate can be recycled as a single-crystal silicon carbide donor substrate. (2) It also includes: recycling the secondary single-crystal silicon carbide temporary support substrate formed by the second stripping to form a recycled single-crystal silicon carbide temporary support substrate, wherein the recycled single-crystal silicon carbide temporary support substrate is recycled as a single-crystal silicon carbide temporary support substrate. It also includes: performing ion implantation on the surface of the single-crystal silicon carbide donor substrate to form a first release layer at a predetermined depth below the surface of the single-crystal silicon carbide donor substrate; the predetermined depth determines the thickness of the single-crystal silicon carbide film formed by the transfer of the first release layer.

[0016] Secondly, the present invention provides a silicon carbide epitaxial substrate, which is prepared by the silicon carbide single crystal thin film peeling method described in any of the foregoing embodiments.

[0017] Thirdly, the present invention provides a semiconductor device comprising the silicon carbide epitaxial substrate described in the foregoing embodiments.

[0018] The present invention has the following beneficial effects: (1) The embodiments of the present invention avoid stress caused by different coefficients of thermal expansion by transferring silicon carbide single crystal thin films to homogeneous single crystal silicon carbide temporary carrier substrates. After the silicon carbide single crystal thin films are stabilized, the silicon carbide single crystal thin films are transferred to the target acceptor substrate by bonding and secondary peeling. At this time, the influence of thermal stress has been minimized.

[0019] (2) The single-crystal silicon carbide temporary carrier substrate and the single-crystal silicon carbide donor substrate used in the embodiments of the present invention are both silicon carbide, which can obtain sufficient bonding strength at low temperature for peeling, avoiding damage to the implanted layer and material by high-temperature bonding, and improving the crystal quality and uniformity of the peeling surface.

[0020] (3) The key to the realization of “secondary transfer” in this invention is the setting of a controllable dissociation layer. In this invention, the controllable dissociation layer is preset as a “weak link”, and its dissociation energy is lower than the peeling energy of the first peeling layer that forms the silicon carbide single crystal film. This ensures that the silicon carbide single crystal film is accurately peeled to the target acceptor substrate during the second peeling, thereby perfectly releasing the single crystal silicon carbide temporary carrier substrate and protecting the integrity of the transferred silicon carbide single crystal film.

[0021] (4) The stripping method of the present invention can reduce surface damage to the single-crystal silicon carbide donor substrate, thereby enabling the amount of single-crystal silicon carbide donor substrate removed by single recycling polishing to be controlled within 1 micrometer, which greatly increases the number of times a single single-crystal silicon carbide donor substrate can be recycled (up to 15 times or more).

[0022] (5) The single-crystal silicon carbide temporary carrier substrate used in the embodiments of the present invention is a reusable "tool substrate", and the cost can be spread over countless production cycles. Its material requirements (such as resistivity and dislocation density) can be lower than those of the single-crystal silicon carbide donor substrate, further reducing the cost.

[0023] (6) The embodiments of the present invention separate the two processes of "silicon carbide single crystal thin film" and "substrate integration", which provides flexibility for heterogeneous integration. For example, the silicon carbide single crystal thin film can be finally transferred onto silicon, glass or flexible substrates for the fabrication of novel semiconductor devices. Detailed Implementation

[0024] 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.

[0025] In a first aspect, embodiments of the present invention provide a method for peeling off a silicon carbide single-crystal thin film, comprising: S1, ion implantation; Ion implantation is performed on the surface of the single-crystal silicon carbide donor substrate to form a first release layer at a predetermined depth below the surface of the single-crystal silicon carbide donor substrate; the predetermined depth determines the thickness of the single-crystal silicon carbide film to be transferred.

[0026] The ion implantation can be either hydrogen ion implantation or hydrogen-helium mixed ion implantation. The methods and conditions for ion implantation are based on existing techniques and conditions, and therefore will not be described in detail in this embodiment. The first stripping layer, after stripping and transfer, becomes a silicon carbide single-crystal thin film.

[0027] S2, forming a controllable dissociation layer; A single-crystal silicon carbide with the same or compatible crystal form as the single-crystal silicon carbide donor substrate is selected as the temporary support substrate. This embodiment of the invention uses a homogeneous single-crystal silicon carbide temporary support substrate, avoiding stress caused by differences in thermal expansion coefficients. Furthermore, this single-crystal silicon carbide temporary support substrate serves as a reusable "tool substrate," allowing costs to be spread over numerous production cycles. Its material requirements (such as resistivity and dislocation density) can be lower than those of the donor substrate, further reducing costs.

[0028] A controllable dissociation layer is formed by depositing a layer on the surface of a single-crystal silicon carbide temporary support substrate using physical vapor deposition or chemical vapor deposition. The structure of the controllable dissociation layer can be any one of an amorphous silicon carbide layer, a porous silicon carbide layer, or a silicon carbide-carbon nanolayer. The thickness of the controllable dissociation layer is 50 nm to 2 μm.

[0029] Simultaneously, the process is optimized to ensure that the dissociation energy of the controllable dissociation layer is lower than that of the first release layer. This embodiment of the invention provides a controllable dissociation layer with a dissociation energy lower than that of the first release layer; that is, the invention pre-defines a "weak point," thereby ensuring that during the second separation, the silicon carbide single-crystal film is precisely released to the target acceptor substrate, thus perfectly releasing the single-crystal silicon carbide temporary carrier substrate and protecting the integrity of the transferred silicon carbide single-crystal film.

[0030] Specifically, the process can adjust deposition parameters, such as temperature (e.g., 200-600°C), pressure (0.1-10 Torr), gas flow rate, or silicon-to-carbon ratio (e.g., the ratio of SiH4 to carbon source gas), or perform post-annealing (e.g., 500-800°C, inert atmosphere), to control the density, cohesive strength, or bonding strength of the controllable dissociation layer, so that its dissociation energy is lower than the peeling energy of the first exfoliation layer.

[0031] S3, forming the first composite structure; A first composite structure is formed by bonding a single-crystal silicon carbide donor substrate with a first release layer on its surface to a single-crystal silicon carbide temporary carrier substrate. Specifically, the implantation surface of the single-crystal silicon carbide donor substrate, i.e., the side with the first release layer, is bonded to the controllable dissociation layer of the single-crystal silicon carbide temporary carrier substrate to form the first composite structure. Thus, the structure of the first composite structure is: single-crystal silicon carbide donor substrate - first release layer - controllable dissociation layer - single-crystal silicon carbide temporary carrier substrate.

[0032] The bonding is a low-temperature bonding, specifically, direct bonding or bonding using a low-temperature adhesive is performed at a temperature below 400°C. The preferred bonding temperature is room temperature - 300°C.

[0033] The embodiments of the present invention use a homogeneous single-crystal silicon carbide temporary carrier substrate, thereby obtaining sufficient bonding strength for peeling even at low temperatures, avoiding damage to the implanted layer and materials caused by high-temperature bonding, and improving the crystal quality and uniformity of the peeling surface.

[0034] It should be noted that the room temperature is 20-40℃.

[0035] S4, First stripping; The first peeling of the first composite structure, also known as homogeneous peeling, causes the first peeling layer to peel off, forming a silicon carbide single-crystal thin film, which remains bonded to the controllable dissociation layer. In other words, after the first peeling, a secondary single-crystal silicon carbide donor substrate and a second composite structure are formed. The structure of the second composite structure is: silicon carbide single-crystal thin film - controllable dissociation layer - single-crystal silicon carbide temporary support substrate.

[0036] Specifically, the first peeling is performed by heat treatment at a temperature of 400-600℃. This embodiment of the invention employs low-temperature, low-stress peeling, resulting in extremely shallow surface damage to the single-crystal silicon carbide donor substrate. The amount removed during a single recycling polishing process can be controlled to within 1 micrometer, significantly increasing the number of times a single substrate can be recycled (up to 15 times or more).

[0037] Furthermore, embodiments of the present invention also provide a recycling process for secondary single-crystal silicon carbide donor substrates, removing the residual damaged layer (removal thickness <1μm) of the secondary single-crystal silicon carbide donor substrates, restoring their surface to device-level quality, and making them reusable as single-crystal silicon carbide donor substrates. Specifically, they are reused in steps S1-S4.

[0038] The recycling process can be carried out using conventional methods, such as, but not limited to, light polishing and cleaning.

[0039] S5, forming a third composite structure; The second composite structure is bonded to the target acceptor substrate to form the third composite structure; specifically, one side of the silicon carbide single-crystal thin film in the second composite structure is bonded to the target acceptor substrate. The target acceptor substrate is made of polycrystalline silicon carbide, high thermal conductivity silicon, or a metal with a dielectric layer on its surface. The structure of the third composite structure is: target acceptor substrate - silicon carbide single-crystal thin film - controllable dissociation layer - single-crystal silicon carbide temporary support substrate; Furthermore, the bonding method in this step can be any one of direct bonding, plasma-activated bonding, and adhesive bonding, with specific conditions including a temperature below 400°C, preferably room temperature to 300°C; a pressure of 0.1-10 kN; and a vacuum or inert gas atmosphere.

[0040] S6, Second stripping; The third composite structure is peeled off a second time, so that the silicon carbide single crystal film is transferred to the target acceptor substrate; at this time, the second peeling forms a silicon carbide single crystal film-target acceptor substrate and a secondary single crystal silicon carbide temporary carrier substrate.

[0041] Furthermore, the second peeling is performed by heat treatment or applying mechanical stress. During the second peeling, the characteristic that the controlled dissociation layer is weaker than the bonding strength of the silicon carbide single-crystal film itself can be utilized to cause selective cleavage at the bonding interface at the controlled dissociation layer, thereby achieving the final transfer of the silicon carbide film from the single-crystal silicon carbide temporary support substrate to the target acceptor substrate. In this embodiment of the invention, after the silicon carbide single-crystal film is stabilized, it is transferred to the target acceptor substrate by low-temperature bonding and mechanical means, at which point the influence of thermal stress is minimized.

[0042] Furthermore, the heat treatment temperature is 300-500℃, for example, any value between 300℃, 400℃, 500℃, etc.; the applied mechanical stress is tensile stress or shear force of 0.1-10 MPa, applied by wedging, air pressure or ultrasound.

[0043] Furthermore, the secondary single-crystal silicon carbide temporary support substrate is recycled to form a recycled single-crystal silicon carbide temporary support substrate, which is then recycled back to step S2 as a single-crystal silicon carbide temporary support substrate.

[0044] The recycling process includes surface treatment and cleaning to remove residual controllable dissociation layer material.

[0045] Secondly, the present invention provides a silicon carbide epitaxial substrate, which is prepared by the silicon carbide single crystal thin film peeling method described in any of the foregoing embodiments.

[0046] Thirdly, the present invention provides a semiconductor device comprising the silicon carbide epitaxial substrate described in the foregoing embodiments. This semiconductor device includes, but is not limited to, power devices or radio frequency devices such as Schottky diodes, MOSFETs, HEMTs, and IGBTs.

[0047] The features and performance of the present invention will be further described in detail below with reference to embodiments.

[0048] Example 1 This invention provides a method for peeling off silicon carbide single crystal thin films, comprising: S1, ion implantation; An N-type 4H-SiC substrate was selected as the single-crystal silicon carbide donor substrate, and hydrogen ions were implanted (energy ~100 keV, dose ~5E16 cm²) to form a first release layer with a depth of about 800 nm.

[0049] S2, forming a controllable dissociation layer; A low-cost 4H-SiC substrate was selected as the temporary support substrate for single-crystal silicon carbide. A 500 nm thick silicon-rich amorphous silicon carbide layer was deposited on its surface via PECVD as a controllable dissociation layer, and its cohesive strength was controlled by adjusting the silicon-to-carbon ratio. The PECVD deposition process included using SiH4 and CH4 as gas sources, a deposition temperature of 350 °C, a pressure of 1 Torr, an RF power of 200 W, a SiH4 / CH4 flow ratio of 1:2, and a deposition time of 30 minutes. After deposition, the film was annealed at 400 °C in an N2 atmosphere for 1 hour to stabilize the film.

[0050] S3, forming the first composite structure; The first release layer of the single-crystal silicon carbide donor substrate and the controllable dissociation layer of the single-crystal silicon carbide temporary carrier substrate are directly bonded at 300°C in a vacuum environment to form a first composite structure. The structure of the first composite structure is: single-crystal silicon carbide donor substrate - first release layer - controllable dissociation layer - single-crystal silicon carbide temporary carrier substrate.

[0051] S4, First stripping; The first composite structure was heat-treated at 500°C for 2 hours to achieve the first exfoliation, resulting in the second composite structure and a secondary single-crystal silicon carbide donor substrate. The second composite structure is a ~800nm ​​single-crystal 4H-SiC thin film-controllable dissociation layer-single-crystal silicon carbide temporary support substrate.

[0052] The secondary single-crystal silicon carbide donor substrate was recovered after being polished to 0.5 μm.

[0053] S5, forming a third composite structure; The SiC thin film of the second composite structure is bonded to a 6-inch polycrystalline SiC target substrate by silicon dioxide fusion bonding (approximately 800°C) to form a third composite structure. The structure of the third composite structure is polycrystalline SiC target substrate - 800nm ​​single crystal 4H-SiC thin film - controllable dissociation layer - single crystal silicon carbide temporary support substrate.

[0054] S6, Second stripping; The third composite structure was rapidly thermally annealed at 450°C, supplemented with wedge-shaped blade wedging stress, to transfer the silicon carbide single-crystal thin film to the target acceptor substrate, resulting in ~800nm ​​single-crystal 4H-SiC / SiO2 / polycrystalline SiC and a secondary single-crystal silicon carbide temporary support substrate. After cleaning, the secondary single-crystal silicon carbide temporary support substrate can be redeposited with a controllable dissociation layer and put into use.

[0055] Phenomena: The transferred film surface is smooth and crack-free. X-ray diffraction confirmed that the film is a single-crystal 4H-SiC. Raman spectroscopy showed that the film stress was low. The surface roughness of the donor substrate after recovery was <0.5nm, and it can be reused for implantation and bonding.

[0056] Example 2 This invention provides a method for peeling off silicon carbide single crystal thin films, comprising: S1, ion implantation; An N-type 6H-SiC substrate was selected as the single-crystal silicon carbide donor substrate, and hydrogen ion implantation was performed (energy ~150 keV, dose ~1E17 cm⁻¹). -2 S1) Forming a first release layer with a depth of approximately 1200 nm. S2) Forming a controllable dissociation layer; A 6H-SiC substrate was selected as a temporary support substrate for single-crystal silicon carbide. A 200 nm thick porous silicon carbide layer was deposited on its surface by LPCVD as a controllable dissociation layer, and the porosity was controlled by adjusting the etching conditions. The LPCVD deposition process included: using SiH2Cl2 and C2H2 as gas sources, a deposition temperature of 900 °C, and a pressure of 0.5 Torr, followed by electrochemical etching in HF:HNO3 solution to form a porous structure.

[0057] S3, forming the first composite structure; The first release layer of the single-crystal silicon carbide donor substrate and the controllable dissociation layer of the single-crystal silicon carbide temporary carrier substrate are bonded together with epoxy resin at room temperature to form a first composite structure.

[0058] S4, First stripping; The first composite structure was heat-treated at 400°C for 2.5 hours to achieve the first exfoliation, resulting in the second composite structure and a secondary single-crystal silicon carbide donor substrate. The second composite structure is a ~1200nm single-crystal 6H-SiC thin film-controllable dissociation layer-single-crystal silicon carbide temporary support substrate.

[0059] The secondary single-crystal silicon carbide donor substrate was recovered after polishing with 0.8μm abrasive.

[0060] S5, forming a third composite structure; The SiC thin film surface of the second composite structure is bonded to a high thermal conductivity silicon target substrate through plasma activation bonding (room temperature, N2 atmosphere) to form a third composite structure.

[0061] S6, Second stripping; The third composite structure was rapidly thermally annealed at 500°C, supplemented with wedge-shaped blade wedging stress, to obtain a ~1200nm single-crystal 6H-SiC / high thermal conductivity silicon composite structure and a secondary single-crystal silicon carbide temporary support substrate. After cleaning, the secondary single-crystal silicon carbide temporary support substrate can be redeposited with a controllable dissociation layer and put into use.

[0062] Phenomenon: The transferred film bonded well with the silicon substrate without warping; X-ray diffraction confirmed that the film was a 6H-SiC single crystal; electrical tests showed that the film resistivity met the requirements.

[0063] Example 3 This invention provides a method for peeling off silicon carbide single crystal thin films, comprising: S1, ion implantation; A 3C-SiC substrate was selected as the single-crystal silicon carbide donor substrate, and hydrogen ion implantation was performed (energy ~80 keV, dose ~8E16cm). - S2, forming a first exfoliation layer with a depth of approximately 500 nm. A 4H-SiC substrate was selected as a temporary support substrate for single-crystal silicon carbide (crystal compatibility). A 50 nm thick silicon carbide-carbon nanocomposite layer was deposited on its surface by magnetron sputtering as a controllable dissociation layer. The carbon content was controlled by adjusting the sputtering power and carbon target current. The sputtering deposition process included: co-sputtering of SiC and C targets, Ar gas pressure of 0.5 Pa, power of 200 W for SiC target and 50 W for C target, deposition time of 10 minutes, followed by vacuum annealing at 600℃ for 30 minutes.

[0064] S3, forming the first composite structure; The first release layer of the single-crystal silicon carbide donor substrate and the controllable dissociation layer of the single-crystal silicon carbide temporary carrier substrate are directly bonded at 200°C in a vacuum environment to form a first composite structure.

[0065] S4, First stripping; The first composite structure was heat-treated at 600°C for 1.5 hours to achieve the first exfoliation, resulting in the second composite structure and a secondary single-crystal silicon carbide donor substrate. The second composite structure is a ~500nm single-crystal 3C-SiC thin film-controllable dissociation layer-single-crystal silicon carbide temporary support substrate.

[0066] The secondary single-crystal silicon carbide donor substrate was recovered after being polished to 0.3 μm.

[0067] S5, forming a third composite structure; The third composite structure is formed by plasma-activated bonding (200°C, N2 atmosphere) between the SiC thin film surface of the second composite structure and a metal (AlN / Si) target substrate with a dielectric layer on its surface.

[0068] S6, Second stripping; The third composite structure was rapidly thermally annealed at 400°C, supplemented with wedge-shaped blade wedging stress, to obtain a ~500nm single-crystal 3C-SiC / AlN / Si composite structure and a secondary single-crystal silicon carbide temporary support substrate. After cleaning, the secondary single-crystal silicon carbide temporary support substrate can be redeposited with a controllable dissociation layer and put into use.

[0069] Phenomenon: The transferred film is uniform and continuous, without cracks; XRD confirms that the film is a 3C-SiC single crystal; the interfacial bonding strength meets the requirements of subsequent processes.

[0070] Comparative Example 1 This comparative example provides a method for peeling off a silicon carbide single crystal thin film. This peeling method is the same as the method for peeling off a silicon carbide single crystal thin film provided in Example 1, except that the 4H-SiC substrate is changed to a polycrystalline SiC substrate, that is, a substrate of different quality is used as a temporary carrier substrate.

[0071] Phenomena: After the first peeling, the composite substrate showed obvious warping, and some samples cracked; after being transferred to the polycrystalline SiC target substrate, cracks and dislocation pits were observed on the film surface, indicating poor crystal quality. Comparing the results of Comparative Example 1 and Example 1, it can be seen that using a homogeneous temporary support substrate avoids thermal stress, resulting in intact films and high crystal quality; while heterogeneous temporary supports lead to severe thermal mismatch, causing the substrate to bend or even crack.

[0072] Comparative Example 2 This comparative example provides a method for peeling off a silicon carbide single crystal thin film. This peeling method is the same as the method for peeling off a silicon carbide single crystal thin film provided in Example 1. The only difference is that the process of the controllable dissociation layer is not optimized, that is, the dissociation energy of the controllable dissociation layer is higher than the peeling energy of the first peeling layer (by adjusting the deposition parameters to make the bonding strength of the SiC film higher than that of the implanted layer).

[0073] Phenomenon: During the second peeling, the peeling interface did not occur in the controllable dissociation layer, but rather broke inside the silicon carbide film or at the interface with the target substrate, resulting in film damage or transfer failure.

[0074] Comparing the results of Comparative Example 2 and Example 1, it can be seen that the dissociation energy of the controllable dissociation layer being lower than that of the first peeling layer is the key to ensuring that the secondary peeling occurs accurately; without optimization, the peeling is uncontrollable and the yield is low.

[0075] Comparative Example 3 This comparative example provides a method for peeling off a silicon carbide single-crystal thin film. This method is similar to the method provided in Example 1, except that steps S2-S4 are omitted, and only steps S1, S5, and S6 are performed. Specifically, the implantation surface of the single-crystal silicon carbide donor substrate containing the first peeling layer is bonded to a 6-inch polycrystalline SiC target substrate using silicon dioxide fusion bonding (approximately 800°C). Then, rapid thermal annealing is performed at 450°C, supplemented by wedge-shaped blade wedging stress, thereby transferring the silicon carbide single-crystal thin film onto the 6-inch polycrystalline SiC target substrate.

[0076] Phenomena: The transferred film has a large number of microcracks and dislocations, and the substrate edge is severely warped; the surface of the donor substrate is rough after peeling, and the amount removed by recycling and polishing is more than 3μm.

[0077] Comparing the results of Comparative Example 3 and Example 1, it can be seen that the two-step method without introducing a temporary support substrate does not decouple the thermal stress problem, and both the film quality and substrate recovery rate are significantly reduced.

[0078] Comparative Example 4 This comparative example provides a method for peeling off a silicon carbide single crystal thin film, which is the same as the method for peeling off a silicon carbide single crystal thin film provided in Example 1, except that the first peeling temperature is increased to 800°C.

[0079] Phenomenon: After the first peeling, the damaged layer on the donor substrate surface deepens, and the coarsening of bubbles leads to uneven peeling surface and increased film surface roughness; the amount of material removed by recycling and polishing needs to be increased to more than 2μm.

[0080] Comparing Example 1 and Comparative Example 4, it can be seen that low-temperature peeling (400-600℃) is beneficial to maintaining the flatness of the peeling surface, reducing damage to the donor substrate, and improving the recycling efficiency.

[0081] Comparative Example 5 This comparative example provides a method for peeling off silicon carbide single crystal thin films, which is the same as the method for peeling off silicon carbide single crystal thin films provided in Example 1, except that the second peeling is performed using pure mechanical stress without heat treatment.

[0082] Phenomenon: During the peeling process, the film edges cracked, some areas were not completely peeled, and controllable release layer material remained at the interface.

[0083] Comparing Example 1 and Comparative Example 5, it can be seen that auxiliary heat treatment helps to reduce interfacial stress, promote uniform cleavage, and improve transfer yield.

[0084] In summary, the stripping method provided in this invention does not directly transfer the silicon carbide film from the donor carrier to the acceptor substrate in one step. Instead, it creatively introduces a "homogeneous temporary carrier substrate" as a buffer and transfer platform, and designs a "controllable dissociation layer" to achieve precise secondary separation. This "two-step transfer method" cleverly decouples the three major problems of thermal mismatch, high-temperature damage, and recycling loss, optimizing and solving them in different steps. It possesses significant originality and systematic advantages in its process path, providing a novel and highly promising technical route for the fabrication of ultra-low-cost, large-size SiC substrates.

[0085] 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 method for peeling off a silicon carbide single crystal thin film, characterized in that, include: A controllable dissociation layer is formed on the surface of a single-crystal silicon carbide temporary support substrate, wherein the crystal form of the single-crystal silicon carbide temporary support substrate is the same as or compatible with the crystal form of the single-crystal silicon carbide donor substrate. Next, a single-crystal silicon carbide donor substrate with a first release layer on its surface is bonded to the single-crystal silicon carbide temporary carrier substrate to form a first composite structure, wherein the structure of the first composite structure is: single-crystal silicon carbide donor substrate - first release layer - controllable dissociation layer - single-crystal silicon carbide temporary carrier substrate; the dissociation energy of the controllable dissociation layer is lower than the release energy of the first release layer. Then, the first composite structure is peeled off for the first time, so that the first peeling layer is peeled off to form the second composite structure. The structure of the second composite structure is: silicon carbide single crystal thin film - controllable dissociation layer - single crystal silicon carbide temporary carrier substrate. Then, the second composite structure is bonded to the target acceptor substrate to form a third composite structure; the structure of the third composite structure is target acceptor substrate-silicon carbide single crystal thin film-controllable dissociation layer-single crystal silicon carbide temporary carrier substrate; Next, the third composite structure is peeled off a second time, so that the silicon carbide single crystal film is transferred to the target acceptor substrate.

2. The method for peeling off silicon carbide single crystal thin films according to claim 1, characterized in that, The controllable dissociation layer satisfies at least one of the following requirements: (1) The thickness of the controllable dissociation layer is 50 nm-2 μm; (2) The controllable dissociation layer is any one of an amorphous silicon carbide layer, a porous silicon carbide layer, and a silicon carbide-carbon nanolayer; (3) The methods for forming the controllable dissociation layer include physical vapor deposition or chemical vapor deposition.

3. The method for peeling off silicon carbide single crystal thin films according to claim 1, characterized in that, The conditions for forming the first composite structure satisfy at least one of the following requirements: (1) The bonding temperature is below 400℃, preferably room temperature - 300℃; (2) The bonding method is direct bonding or adhesive bonding.

4. The method for peeling off silicon carbide single crystal thin films according to claim 1, characterized in that, The first peeling method is heat treatment; Preferably, the temperature of the first peeling is 400-600℃.

5. The method for peeling off silicon carbide single crystal thin films according to claim 1, characterized in that, The target acceptor substrate includes any one of polycrystalline silicon carbide, high thermal conductivity silicon, and a metal with a dielectric layer on its surface.

6. The method for peeling off silicon carbide single crystal thin films according to claim 1, characterized in that, The conditions for forming the third composite structure satisfy at least one of the following requirements: (1) The bonding temperature is below 400℃, preferably room temperature - 300℃; (2) The bonding method is any one of direct bonding, plasma-activated bonding and adhesive bonding.

7. The method for peeling off silicon carbide single crystal thin films according to claim 1, characterized in that, The second peeling is performed by heat treatment or by applying mechanical stress; Preferably, the heat treatment temperature is 300-500℃; The applied mechanical stress is a tensile stress or shear force of 0.1-10 MPa.

8. The method for peeling off silicon carbide single crystal thin films according to any one of claims 1-7, characterized in that, The stripping method further includes at least one of the following steps: (1) It also includes: recycling the secondary single-crystal silicon carbide donor substrate formed by the first stripping to form a recycled single-crystal silicon carbide donor substrate, wherein the recycled single-crystal silicon carbide donor substrate can be recycled as a single-crystal silicon carbide donor substrate. (2) It also includes: recycling the secondary single-crystal silicon carbide temporary support substrate formed by the second stripping to form a recycled single-crystal silicon carbide temporary support substrate, wherein the recycled single-crystal silicon carbide temporary support substrate is recycled as a single-crystal silicon carbide temporary support substrate. It also includes: performing ion implantation on the surface of the single-crystal silicon carbide donor substrate to form a first release layer at a predetermined depth below the surface of the single-crystal silicon carbide donor substrate; the predetermined depth determines the thickness of the single-crystal silicon carbide film formed by the transfer of the first release layer.

9. A silicon carbide epitaxial substrate, characterized in that, It is prepared by the peeling method of silicon carbide single crystal thin film as described in any one of claims 1-8.

10. A semiconductor device, characterized in that, It includes the silicon carbide epitaxial substrate as described in claim 9.