A method for transferring epitaxial thin films and its application

Abstract

This invention provides a method for transferring epitaxial thin films and its application. The transfer method includes sequentially performing a first temporary bonding, a second temporary bonding, a first temporary debonding, bonding to a target substrate, a second temporary debonding, and removal of the silicon substrate, thereby achieving the transfer of the epitaxial thin film. In this invention, the transfer method can effectively avoid damage to the epitaxial thin film caused by laser and stress during the transfer process, improving device performance and lifespan, and is applicable to epitaxial thin films of different sizes and materials.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device transfer technology, specifically relating to a method for transferring epitaxial thin films and its application. Background Technology

[0002] With the rapid development of microelectronics and optoelectronics technologies, the demand for high-performance semiconductor materials is increasing. Gallium nitride (GaN), as a wide-bandgap semiconductor material, has shown great application potential in high-power, high-frequency, and high-temperature electronic devices and optoelectronic devices due to its excellent electronic properties and physical stability. However, the fabrication and application of GaN face some challenges, especially in substrate selection and device integration.

[0003] Traditional GaN epitaxy typically uses sapphire (Al₂O₃) and silicon carbide (SiC) as substrate materials. Sapphire is widely used in LEDs due to its excellent optical properties, while silicon carbide is the preferred substrate for electronic devices due to its similar lattice constant and thermal conductivity to GaN. However, these materials also have some limitations: 1. Cost: The cost of sapphire and SiC substrates is relatively high, which limits the widespread application and cost-effectiveness of GaN-based devices. 2. Wafer size limitations: Compared with silicon substrates, sapphire and SiC substrates have smaller wafer sizes, which affects production efficiency and large-scale production. 3. Processing difficulty: Sapphire has high hardness, making it difficult to process, while SiC also has relatively high processing costs.

[0004] To address these challenges, researchers have begun exploring methods for epitaxially transferring GaN onto silicon (Si) substrates. Silicon substrates offer several advantages: 1. Cost-effectiveness: Lower production costs help reduce overall manufacturing costs. 2. Wafer size: Silicon substrates allow for larger wafer sizes, improving production efficiency. 3. Thermal conductivity: Silicon's thermal conductivity is superior to sapphire and close to that of SiC, contributing to improved device heat dissipation. 4. Processing compatibility: Mature processing technologies for silicon substrates facilitate subsequent device fabrication and integration. 5. Environmental friendliness: The recycling and reuse of silicon materials are more mature, reducing environmental impact.

[0005] However, in traditional epitaxial layer transfer processes, the use of high-power lasers can lead to localized overheating of the material, resulting in thermal damage. Furthermore, defect states generated by the interaction between the laser and the material can also affect device performance. Additionally, due to lattice mismatch and limitations in growth conditions, the epitaxial layer is prone to stress during transfer, which can lead to material fracture or degraded device performance.

[0006] Therefore, developing a transfer method that can effectively reduce laser damage and stress damage during the transfer of epitaxial thin films is an urgent problem to be solved in this field. Summary of the Invention

[0007] To address the shortcomings of existing technologies, the present invention aims to provide a method for transferring epitaxial thin films and its applications. This transfer method effectively avoids laser damage to the epitaxial thin film during the transfer process and overcomes limitations imposed by lattice mismatch and growth conditions, preventing stress damage to the epitaxial thin film. This facilitates the fabrication of high-performance, low-cost, and environmentally friendly semiconductor devices.

[0008] To achieve this objective, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a method for transferring an epitaxial thin film, the method comprising:

[0010] (1) A first temporary bonding layer is disposed on the surface of a first substrate, and an epitaxial layer film is disposed on the surface of a silicon substrate. The first substrate and the silicon substrate are bonded together using the first temporary bonding layer and the epitaxial layer film as bonding surfaces to obtain a first substrate.

[0011] (2) A second temporary bonding layer is formed on the surface of the second substrate. The side of the silicon substrate away from the first temporary bonding layer and the second temporary bonding layer are used as bonding surfaces. The first substrate obtained in step (1) is bonded to the second substrate to obtain the second substrate.

[0012] (3) Debond the second substrate obtained in step (2), remove the first temporary bonding layer and the first substrate, and obtain the third substrate;

[0013] (4) A glue layer is provided on the surface of the target substrate, and the epitaxial layer film and the glue layer are used as bonding surfaces to bond the third substrate obtained in step (3) to the target substrate to obtain the fourth substrate.

[0014] (5) Debond the fourth substrate obtained in step (4), remove the second temporary bonding layer and the second substrate, and obtain the fifth substrate;

[0015] (6) Remove the silicon substrate from the fifth substrate obtained in step (5) to achieve the transfer of the epitaxial thin film.

[0016] In this invention, the transfer method achieves effective control of the stress on the epitaxial thin film by sequentially bonding a first temporary bonding layer and a second temporary bonding layer to both sides of a silicon substrate on which an epitaxial thin film is formed, reducing the risk of stress-induced damage during the transfer process. Furthermore, it avoids damage caused by lasers, significantly improving device performance and reliability, and extending device lifespan. Moreover, the transfer method is applicable to epitaxial thin films of different sizes and materials, exhibiting good scalability and wide application, which helps to promote further miniaturization and integration of semiconductor devices, meeting the growing market demand.

[0017] Preferably, in step (1), the first substrate comprises a silicon wafer.

[0018] In this invention, the silicon wafer includes, but is not limited to, 4-inch silicon wafers, 6-inch silicon wafers, 8-inch silicon wafers, and 12-inch silicon wafers.

[0019] Preferably, the thickness of the first temporary bonding layer is 2 to 80 μm, for example, it can be 2 μm, 5 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 14 μm, 16 μm, 20 μm, 25 μm, 30 μm, 35 μm, 40 μm, 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 75 μm, 80 μm, etc.

[0020] Preferably, the thickness uniformity of the first temporary bonding layer is ≤5%, for example, it can be 0%, 1%, 2%, 3%, 4%, 5%, etc.

[0021] Preferably, the material of the first temporary bonding layer includes temporary bonding adhesive and / or temporary bonding wax.

[0022] In this invention, the material of the first temporary bonding layer is preferably a thermally slip-debonding temporary bonding material. Using a thermally slip-debonding temporary bonding material can avoid damage to the epitaxial thin film by the laser. The material of the first temporary bonding layer is preferably a material with a similar elastic modulus, coefficient of thermal expansion, and Poisson's ratio to the silicon substrate on which the epitaxial thin film is disposed. Exemplary examples include, but are not limited to, hot slip adhesives from Shenzhen Huaxun Semiconductor Materials Co., Ltd.: WLP TB1120, WLPTB130, WLP TB140, etc.; and hot slip waxes: WLP TB1300, WLP TB1310, etc.

[0023] Preferably, the method of step (1) of forming a first temporary bonding layer on the surface of a first substrate includes: coating the surface of the first substrate with a material of the first temporary bonding layer, curing or leveling it to obtain the first temporary bonding layer.

[0024] In this invention, when the material is a bonding adhesive, it is a curing step; when the material is a bonding wax, it is a leveling step.

[0025] Preferably, the curing or leveling temperature is 80–160°C, for example, 80°C, 85°C, 90°C, 95°C, 100°C, 105°C, 110°C, 115°C, 120°C, 130°C, 140°C, 150°C, 160°C, etc.; the time is 1–30 min, for example, 1 min, 2 min, 4 min, 6 min, 8 min, 10 min, 12 min, 14 min, 16 min, 18 min, 20 min, 22 min, 24 min, 26 min, 28 min, 30 min, etc.

[0026] In this invention, the first temporary bonding layer can provide sufficient mechanical support for the silicon-based epitaxial film and can also release stress in advance to facilitate subsequent processes such as thinning, polishing, high-temperature and high-pressure bonding, debonding, and cleaning, thereby avoiding stress damage to the epitaxial film caused by the aforementioned processes and improving the processing safety of the device.

[0027] Preferably, the bonding temperature in step (1) is 100-150℃, for example, it can be 100℃, 102℃, 104℃, 106℃, 108℃, 110℃, 112℃, 114℃, 116℃, 118℃, 120℃, 122℃, 124℃, 126℃, 128℃, 130℃, 132℃, 134℃, 136℃, 138℃, 140℃, 142℃, 144℃, 146℃, 148℃, 150℃, etc.

[0028] Preferably, the bonding pressure in step (1) is 0–2000 Pa, for example, it can be 0 Pa, 50 Pa, 80 Pa, 100 Pa, 120 Pa, 150 Pa, 180 Pa, 200 Pa, 250 Pa, 300 Pa, 350 Pa, 400 Pa, 450 Pa, 500 Pa, 550 Pa, 600 Pa, 650 Pa, 700 Pa, 750 Pa, 800 Pa, 850 Pa, 900 Pa, or 950 Pa. The values ​​are 1000 Pa, 1050 Pa, 1100 Pa, 1150 Pa, 1200 Pa, 1250 Pa, 1300 Pa, 1350 Pa, 1400 Pa, 1450 Pa, 1500 Pa, 1550 Pa, 1600 Pa, 1650 Pa, 1700 Pa, 1750 Pa, 1800 Pa, 1850 Pa, 1900 Pa, 1950 Pa, 2000 Pa, etc., more preferably 500-1300 Pa. Preferably, the bonding time in step (1) is 1-10 min, for example, it can be 1 min, 2 min, 3 min, 4 min, 5 min, 6 min, 7 min, 8 min, 9 min, 10 min, etc.

[0029] Preferably, the vacuum degree of bonding in step (1) is <10 Pa, for example, it can be 1 Pa, 2 Pa, 3 Pa, 4 Pa, 5 Pa, 6 Pa, 7 Pa, 8 Pa, 9 Pa, etc.

[0030] In this invention, the bonding in step (1) is carried out using a specific process, which can achieve low-stress bonding of epitaxial thin film bonding pairs, reduce wafer warpage, and reduce stress damage to epitaxial thin films.

[0031] Preferably, after bonding in step (1), the process further includes cleaning, thinning and / or polishing the silicon substrate.

[0032] In this invention, the cleaning includes cleaning using a plasma device.

[0033] Preferably, the thickness of the thinning to the silicon substrate is 50-100 μm, for example, it can be 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, etc.

[0034] Preferably, in step (2), the second substrate comprises at least one of silicon carbide, sapphire, and glass.

[0035] Preferably, the second temporary bonding layer includes a laser emission layer and a second adhesive layer disposed sequentially, wherein the laser emission layer is stacked with the second substrate; and the second adhesive layer is bonded to the side of the silicon substrate away from the first temporary bonding layer.

[0036] Preferably, the thickness of the laser emission layer is 200nm to 5μm, for example, it can be 200nm, 250nm, 300nm, 350nm, 400nm, 450nm, 500nm, 550nm, 600nm, 650nm, 700nm, 800nm, 900nm, 1μm, 2μm, 3μm, 4μm, 5μm, etc.

[0037] Preferably, the thickness uniformity of the laser release layer is ≤20%, for example, it can be 0%, 2%, 4%, 6%, 8%, 10%, 12%, 14%, 16%, 18%, 20%, etc.

[0038] In this invention, the material of the laser release layer is preferably a material with a similar elastic modulus, coefficient of thermal expansion and Poisson's ratio to the silicon substrate on which the epitaxial thin film is disposed. Exemplary examples include, but are not limited to, WLP LB210, WLP RL420, WLP LB230 and WLP LB260 from Shenzhen Huaxun Semiconductor Materials Co., Ltd.

[0039] Preferably, the thickness of the second adhesive layer is 2 to 80 μm, for example, it can be 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, 12 μm, 14 μm, 16 μm, 18 μm, 20 μm, 22 μm, 24 μm, 26 μm, 28 μm, 30 μm, 32 μm, 34 μm, 36 μm, 38 μm, 40 μm, 42 μm, 44 μm, 46 μm, 48 μm, 50 μm, 52 μm, 55 μm, 58 μm, 60 μm, 62 μm, 65 μm, 68 μm, 70 μm, 72 μm, 75 μm, 78 μm, 80 μm, etc.

[0040] Preferably, the thickness uniformity of the second adhesive layer is ≤10%, for example, it can be 0%, 2%, 4%, 6%, 8%, 10%, etc.

[0041] Preferably, the warpage after bonding in step (1) or step (2) is <50μm, and the total thickness deviation of the bond pair is <10μm.

[0042] In this invention, the material of the second adhesive layer includes temporary bonding materials; exemplary, including but not limited to WLP TB4130, WLP TB4170, WLP TB4171, WLP TB4172, WLPTB4180, etc. from Shenzhen Huaxun Semiconductor Materials Co., Ltd.

[0043] Preferably, step (2) of forming a second temporary bonding layer on the surface of the second substrate includes: coating a laser release layer material on the surface of the second substrate, performing a first curing to obtain a laser release layer; coating a second adhesive layer material on the surface of the laser release layer, performing a second curing to obtain the second temporary bonding layer.

[0044] In this invention, the second temporary bonding layer can serve as a stress buffer layer, which can reduce stress damage to the epitaxial film during the transfer process.

[0045] Preferably, the first curing includes curing through a first heat preservation, a heating, a second heat preservation, and a cooling process.

[0046] Preferably, the temperature of the first heat preservation is 70 to 150°C, for example, it can be 70°C, 75°C, 80°C, 85°C, 90°C, 95°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.; the time is 1 to 10 minutes, for example, it can be 1 minute, 2 minutes, 3 minutes, 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, etc.

[0047] Preferably, the heating rate is 3 to 40°C / min, for example, it can be 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min, 8°C / min, 9°C / min, 10°C / min, 15°C / min, 20°C / min, 25°C / min, 30°C / min, 35°C / min, 40°C / min, etc.

[0048] Preferably, the temperature of the second heat preservation is 200-400℃, for example, 200℃, 210℃, 220℃, 230℃, 240℃, 260℃, 280℃, 300℃, 320℃, 340℃, 360℃, 380℃, 400℃, etc.; the time is 10-80min, for example, 10min, 20min, 30min, 40min, 50min, 60min, 70min, 80min, etc.

[0049] Preferably, the temperature drop is below 150°C, for example, it can be 20°C, 40°C, 60°C, 80°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.; the cooling rate is 5 to 20°C / min, for example, it can be 5°C / min, 6°C / min, 8°C / min, 10°C / min, 12°C / min, 14°C / min, 16°C / min, 18°C / min, 20°C / min, etc.

[0050] Preferably, the second curing includes multi-temperature gradient curing, and more preferably, it includes at least a first gradient and a second gradient.

[0051] Preferably, the heat preservation temperature of the first gradient is 70-150℃, for example, it can be 70℃, 75℃, 80℃, 85℃, 90℃, 95℃, 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, etc.; the time is 1-10min, for example, it can be 1min, 2min, 3min, 4min, 5min, 6min, 7min, 8min, 9min, 10min, etc.

[0052] Preferably, the heating rate from the first gradient to the second gradient is 3 to 40 °C / min, for example, it can be 3 °C / min, 4 °C / min, 5 °C / min, 6 °C / min, 7 °C / min, 8 °C / min, 9 °C / min, 10 °C / min, 15 °C / min, 20 °C / min, 25 °C / min, 30 °C / min, 35 °C / min, 40 °C / min, etc.

[0053] Preferably, the heat preservation temperature of the second gradient is 180-250℃, for example, it can be 180℃, 190℃, 200℃, 210℃, 220℃, 230℃, 240℃, 250℃, etc.; the time is 3-20min, for example, it can be 3min, 5min, 8min, 10min, 12min, 15min, 18min, 20min, etc.

[0054] Preferably, the temperature drops below 150°C after the second gradient, for example, it can be 20°C, 40°C, 60°C, 80°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, etc.; the cooling rate is 5 to 20°C / min, for example, it can be 5°C / min, 6°C / min, 8°C / min, 10°C / min, 12°C / min, 14°C / min, 16°C / min, 18°C / min, 20°C / min, etc.

[0055] In this invention, the methods for obtaining the first temporary bonding layer and the coating in the second temporary bonding layer are each independent, including but not limited to spin coating; the curing conditions can be selected according to the temporary bonding material, and curing is complete; after curing, the material is cooled to room temperature for later use.

[0056] Preferably, the bonding temperature in step (2) is 180 to 250°C, for example, it can be 180°C, 182°C, 185°C, 188°C, 190°C, 192°C, 195°C, 198°C, 200°C, 202°C, 204°C, 206°C, 208°C, 210°C, 212°C, 214°C, 216°C, 218°C, 220°C, 224°C, 226°C, 228°C, 230°C, 232°C, 234°C, 236°C, 238°C, 240°C, 242°C, 244°C, 246°C, 248°C, 250°C, etc.

[0057] Preferably, the bonding pressure in step (2) is 15,000 to 300,000 Pa, for example, it can be 15,000 Pa, 20,000 Pa, 30,000 Pa, 40,000 Pa, 50,000 Pa, 60,000 Pa, 70,000 Pa, 80,000 Pa, 90,000 Pa, 100,000 Pa, 120,000 Pa, 140,000 Pa, 160,000 Pa, 180,000 Pa, 200,000 Pa, 220,000 Pa, 240,000 Pa, 260,000 Pa, 280,000 Pa, 300,000 Pa, etc., and more preferably 50,000 to 150,000 Pa.

[0058] Preferably, the bonding time in step (2) is 5 to 20 minutes, for example, it can be 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, etc.

[0059] Preferably, the vacuum degree of bonding in step (2) is <10 Pa, for example, it can be 1 Pa, 2 Pa, 3 Pa, 4 Pa, 5 Pa, 6 Pa, 7 Pa, 8 Pa, 9 Pa, etc.

[0060] Preferably, the debonding method in step (3) includes thermal slip debonding.

[0061] Preferably, the debonding temperature in step (3) is 100 to 200°C, for example, 100°C, 120°C, 140°C, 160°C, 180°C, 200°C, etc.

[0062] Preferably, the debonding slip velocity in step (3) is <2 mm / s, for example, it can be 0.2 mm / s, 0.4 mm / s, 0.6 mm / s, 0.8 mm / s, 1 mm / s, 1.2 mm / s, 1.4 mm / s, 1.6 mm / s, 1.8 mm / s, etc.

[0063] Preferably, step (3) further includes a cleaning step after debonding.

[0064] In this invention, the cleaning includes spin-coating cleaning or immersion cleaning to remove residual material from the first temporary bonding layer. A suitable cleaning agent can be used, followed by rinsing and drying. Preferably, the debonding method in step (5) includes laser debonding.

[0065] Preferably, the laser energy for debonding in step (5) is ≥120 mJ / cm². 2 For example, it can be 120mj / cm 2 140mj / cm 2 160mj / cm 2 180mj / cm 2 200mj / cm 2 240mj / cm 2 260mj / cm 2 280mj / cm 2 300mj / cm 2 350mj / cm 2 400mj / cm 2 450mj / cm 2 500mj / cm 2 550mj / cm 2 600mj / cm 2 650mj / cm 2 700mj / cm 2 750mj / cm 2 800mj / cm 2 850mj / cm 2 900mj / cm 2 950mj / cm 2 1000mj / cm 2 The preferred values ​​are 120–800 mJ / cm³. 2 .

[0066] Preferably, the laser used for debonding in step (5) includes visible light and / or ultraviolet light.

[0067] In this invention, the laser debonding mode includes a pulse mode and / or a flat-top mode; the pulse width is less than 1 mm.

[0068] In this invention, the second temporary bonding layer is debonded by laser, and the laser debonding is controlled by a specific process, which can efficiently separate the epitaxial thin film and reduce stress damage and laser damage to the epitaxial thin film. If the laser energy is too high, it will damage the silicon substrate or the epitaxial thin film. Using infrared light for the laser will also damage the silicon substrate or the epitaxial thin film.

[0069] Preferably, step (5) further includes a cleaning step after debonding.

[0070] In this invention, in step (5), the cleaning includes spin-coating cleaning or immersion cleaning to remove the residual materials of the second adhesive layer and laser release layer. The corresponding cleaning agent can be used for cleaning, followed by water washing and drying.

[0071] In this invention, the cleaning agents include, but are not limited to, TBR2 and Remover3 from Shenzhen Huaxun Semiconductor Materials Co., Ltd.

[0072] Preferably, the method for removing the silicon substrate in step (6) includes plasma etching and / or chemical etching.

[0073] Preferably, the gas used in the plasma etching method includes gas A and gas B; gas A includes at least one of carbon tetrafluoride, sulfur hexafluoride, or octafluorocyclobutane; and gas B includes oxygen or a mixture of oxygen and at least one of argon or helium.

[0074] In this invention, the volume ratio of gas A to gas B is (3-5):1, for example, it can be 3:1, 3.5:1, 4:1, 4.5:1, 5:1, etc.

[0075] In this invention, plasma etching and chemical etching are preferred methods; plasma etching is used to expose the edge of the epitaxial thin film, and then chemical etching is used.

[0076] Preferably, the reagents for the chemical etching method include at least one of hydrofluoric acid, nitric acid, or water, preferably a mixture of hydrofluoric acid, nitric acid, and water, wherein the volume ratio of hydrofluoric acid, nitric acid, and water is (0.5-1.5):1, and the specific values ​​of (0.5-1.5) can be, for example, 0.5, 0.6, 0.8, 1, 1.2, 1.4, 1.5, etc.

[0077] Preferably, the corrosion rate of the chemical etching method is 0.2 to 2.2 μm / min, for example, it can be 0.2 μm / min, 0.4 μm / min, 0.6 μm / min, 0.8 μm / min, 1 μm / min, 1.2 μm / min, 1.4 μm / min, 1.6 μm / min, 1.8 μm / min, 2 μm / min, 2.2 μm / min, etc.

[0078] Preferably, the epitaxial thin film includes at least one of gallium nitride thin film, silicon dioxide thin film, silicon nitride thin film, and metal thin film.

[0079] As a preferred technical solution of the present invention, the transfer method includes:

[0080] (1) A first temporary bonding layer with a thickness of 2 to 80 μm and a thickness uniformity of ≤5% is coated on the surface of the first substrate and cured at 80 to 160°C for 1 to 30 min to obtain the first temporary bonding layer; an epitaxial layer film is formed on the surface of the silicon substrate, and the first substrate and the silicon substrate are bonded together at a temperature of 100 to 150°C, a pressure of 0 to 2000 Pa, and a vacuum degree of <10 Pa for 1 to 10 min, the silicon substrate is cleaned and thinned to 50 to 100 μm to obtain the first substrate;

[0081] (2) A laser emission layer material with a thickness of 200 nm to 5 μm and a thickness uniformity of ≤20% is coated on the surface of the second substrate. The substrate is kept at 70 to 150 °C for 1 to 10 min. Then, the temperature is increased to 200 to 400 °C at a rate of 3 to 40 °C / min and kept at 10 to 80 min. The temperature is then reduced to below 150 °C at a rate of 5 to 20 °C / min and cooled to obtain the laser emission layer. A second adhesive layer material with a thickness of 2 to 80 μm and a thickness uniformity of ≤10% is coated on the surface of the laser emission layer. The material is then cured in a multi-temperature gradient to obtain the second temporary bonding layer. The multi-temperature gradient curing includes at least the following steps: holding at 70-150°C for 1-10 min, raising the temperature to 180-250°C at a rate of 3-40°C / min, holding at 180-250°C for 3-20 min, and then lowering the temperature to below 150°C at a rate of 5-20°C / min; using the side of the silicon substrate away from the first temporary bonding layer and the second adhesive layer as the bonding surface, bonding the first substrate obtained in step (1) to the second substrate at a temperature of 180-250°C, a pressure of 15000-300000Pa, and a vacuum degree of <10Pa for 5-20 min to obtain the second substrate;

[0082] (3) Perform thermal sliding debonding on the second substrate obtained in step (2), clean it, remove the first temporary bonding layer and the first substrate, and obtain the third substrate;

[0083] (4) A glue layer is provided on the surface of the target substrate, and the epitaxial layer film and the glue layer are used as bonding surfaces to bond the third substrate obtained in step (3) to the target substrate to obtain the fourth substrate.

[0084] (5) The fourth substrate obtained in step (4) is subjected to a laser energy ≥120mJ / cm 2 Laser debonding is performed under the following conditions: the laser used for debonding includes visible light and / or ultraviolet light; cleaning is performed to remove the second temporary bonding layer and the second substrate, resulting in the fifth substrate.

[0085] (6) The silicon substrate obtained in step (5) is removed by plasma etching and / or chemical etching to achieve the transfer of the epitaxial thin film.

[0086] In this invention, the silicon-based epitaxial thin film can be obtained commercially or prepared using conventional methods.

[0087] In this invention, in step (4), the material and thickness of the adhesive layer can be selected according to the actual situation. This invention does not limit them. As long as the permanent bonding between the epitaxial thin film and the target substrate can be achieved, the curing conditions of the adhesive layer depend on the material. As long as the curing is complete, the material of the target substrate includes, but is not limited to, glass. The bonding process parameters depend on the selected adhesive layer material. It can be high-temperature curing, high-temperature and high-pressure curing, etc.

[0088] In this invention, depending on actual needs or for ease of transfer of subsequent processes, different processes can be performed on the side of the target substrate away from the adhesive layer in the fourth substrate, such as adhesive coating and curing, photolithography and development, electroplating, physical and chemical deposition, metal etching, organic etching, high-pressure permanent bonding, etc.; for example, the side of the target substrate away from the adhesive layer can be surface treated using a plasma surface treatment device, and then a copper block can be embedded to align it; then pre-bonding can be performed under vacuum, room temperature, and pressure of 1 to 25 kN, followed by high-temperature annealing at 220°C to 350°C for 3 to 5 minutes.

[0089] In a second aspect, the present invention provides an application of the transfer method according to the first aspect in the fabrication of a semiconductor device.

[0090] The numerical range described in this invention includes not only the point values ​​listed above, but also any point values ​​within the numerical ranges not listed above. Due to space limitations and for the sake of brevity, this invention will not exhaustively list all the specific point values ​​included in the range.

[0091] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0092] The epitaxial thin film transfer method provided by this invention achieves effective control of the stress of the epitaxial thin film by sequentially bonding a first temporary bonding layer and a second temporary bonding layer to both sides of a silicon substrate on which the epitaxial thin film is disposed, reducing the risk of stress-induced damage during the transfer process; it can also avoid damage caused by laser, significantly improving the performance and reliability of the device and extending its service life; and the transfer method is applicable to epitaxial thin films of different sizes and materials, with good scalability and wide application, which helps to promote the further miniaturization and integration of semiconductor devices and meet the growing market demand. Attached Figure Description

[0093] Figure 1 This is a schematic diagram of the structure of a silicon substrate with an epitaxial thin film on its surface in Embodiment 1 of the present invention;

[0094] Wherein, 1-silicon substrate; 2-GaN epitaxial thin film;

[0095] Figure 2 This is a schematic diagram of the structure of the first substrate in Embodiment 1 of the present invention;

[0096] Wherein, 1-silicon substrate; 2-GaN epitaxial thin film; 3-first temporary bonding layer; 4-first substrate;

[0097] Figure 3 This is a schematic diagram of the structure of the second substrate in Embodiment 1 of the present invention;

[0098] Wherein, 1-silicon substrate; 2-GaN epitaxial thin film; 3-first temporary bonding layer; 4-first substrate; 5-second temporary bonding layer; 6-second substrate. Detailed Implementation

[0099] The technical solution of the present invention will be further illustrated below through specific embodiments. Those skilled in the art should understand that the embodiments described are merely illustrative of the present invention and should not be construed as limiting the invention in any way.

[0100] All materials used in this invention are commercially available or prepared using conventional methods. Unless otherwise specified, the materials used in this invention are as follows:

[0101] First temporary bonding layer material: WLP TB1120 from Shenzhen Huaxun Semiconductor Materials Co., Ltd.;

[0102] Laser emission material: WLP LB210 from Shenzhen Huaxun Semiconductor Materials Co., Ltd.;

[0103] Second adhesive layer material: WLP TB4130 from Shenzhen Huaxun Semiconductor Materials Co., Ltd.;

[0104] A silicon substrate with an epitaxial thin film on its surface: its structural schematic diagram is shown below. Figure 1 As shown, it includes a silicon substrate 1 and a GaN epitaxial layer thin film 2; the silicon substrate is an 8-inch silicon wafer, and the thickness of the GaN epitaxial layer thin film is 10 μm.

[0105] In this invention, thickness uniformity can be obtained by comparing the maximum and minimum thickness of the coating layer; thickness uniformity = (maximum thickness - minimum thickness) / maximum thickness × 100%.

[0106] Example 1

[0107] This embodiment provides a method for transferring GaN epitaxial thin films, specifically including the following steps:

[0108] (1) A 10 μm thick WLP TB1120 with a thickness uniformity of 3% was spin-coated onto the surface of an 8-inch silicon wafer and cured at 110°C for 10 min to obtain a first substrate with a first temporary bonding layer on its surface; the first temporary bonding layer and the epitaxial layer film were used as bonding surfaces, and the silicon substrate with the epitaxial layer film on its surface was bonded to the first substrate at 120°C, a pressure of 955 Pa, and a vacuum of 5 Pa for 5 min. The silicon substrate was cleaned using a plasma device and thinned to 70 μm to obtain the first substrate.

[0109] (2) A 500 nm thick WLP LB210 with a thickness uniformity of 10% was coated on the surface of a silicon carbide substrate. The substrate was held at 115 °C for 5 min, then heated to 350 °C at a rate of 5 °C / min and held for 30 min. The substrate was then cooled to 120 °C at a rate of 10 °C / min and cooled to room temperature to obtain a laser emission layer. A 16 μm thick WLP with a thickness uniformity of 5% was then coated on the surface of the laser emission layer. TB4130 is heated at 115°C for 5 minutes, then heated to 200°C at a rate of 5°C / min, held for 10 minutes, and then cooled to 120°C at a rate of 10°C / min to room temperature to obtain the second adhesive layer, which is the second substrate with the second temporary bonding layer on its surface; the side of the silicon substrate away from the first temporary bonding layer and the second adhesive layer are used as the bonding surface, and the first substrate obtained in step (1) and the second substrate are bonded at 215°C, with a pressure of 95541 Pa and a vacuum of 6 Pa for 10 minutes to obtain the second substrate;

[0110] (3) The second substrate obtained in step (2) is debonded using a hot sliding debonding device. The temperature of the hot sliding debonding device is 150°C for the upper heating plate and 150°C for the lower heating plate, and the sliding speed is 1 mm / s. Then, the substrate is soaked and cleaned with a cleaning agent (acetone) until there is no residue of the first temporary bonding layer on the surface. It is then washed with deionized water and dried to remove the first temporary bonding layer and the first substrate, thus obtaining the third substrate.

[0111] (4) An adhesive layer (material is WLPTB5160 from Shenzhen Huaxun Semiconductor Materials Co., Ltd., with a thickness of 30μm) is set on the surface of the target substrate. The epitaxial layer film and the adhesive layer are used as bonding surfaces. The third substrate obtained in step (3) is bonded to the target substrate at 220°C, pressure of 31847Pa, and vacuum of 6Pa for 10 minutes to obtain the fourth substrate.

[0112] (5) The fourth substrate obtained in step (4) is debonded using ultraviolet laser (wavelength 355nm), wherein the laser energy is 400mJ / cm. 2 The laser mode is pulsed mode with a pulse width of less than 1 mm. After debonding, the substrate is immersed and cleaned with a cleaning agent (TBR2) until there is no second temporary bonding layer residue on the surface. Then, it is washed with deionized water and dried to remove the second temporary bonding layer and silicon carbide substrate, thus obtaining the fifth substrate.

[0113] (6) The fifth substrate obtained in step (5) is first subjected to plasma etching until the edge of the GaN epitaxial layer is exposed, and then the silicon substrate is removed by chemical etching to realize the transfer of the epitaxial layer; wherein, the plasma etching method uses carbon tetrafluoride and oxygen in a volume ratio of 4:1; the chemical etching method uses hydrofluoric acid, nitric acid and water in a volume ratio of 1:1:1, and the etching rate is 1 μm / min.

[0114] In this invention, the structural schematic diagram of the first substrate is as follows: Figure 2 As shown, the substrate includes a silicon substrate 1, a GaN epitaxial thin film 2, a first temporary bonding layer 3, and a first substrate 4; a schematic diagram of the structure of the second substrate is shown below. Figure 3 As shown, it includes a silicon substrate 1, a GaN epitaxial thin film 2, a first temporary bonding layer 3, a first substrate 4, a second temporary bonding layer 5, and a second substrate 6.

[0115] Example 2

[0116] This embodiment provides a method for transferring GaN epitaxial thin films, specifically including the following steps:

[0117] (1) A 15 μm thick WLP TB1120 with a thickness uniformity of 1% was spin-coated onto the surface of an 8-inch silicon wafer and cured at 120°C for 5 min to obtain a first substrate with a first temporary bonding layer on its surface; the first temporary bonding layer and the epitaxial layer film were used as bonding surfaces, and the silicon substrate with the epitaxial layer film on its surface was bonded to the first substrate at 135°C, a pressure of 1115 Pa, and a vacuum of 8 Pa for 3 min. The silicon substrate was cleaned using a plasma device and thinned to 50 μm to obtain the first substrate.

[0118] (2) A WLP LB210 with a thickness of 600 nm and a thickness uniformity of 8% was coated on the surface of a silicon carbide substrate. The substrate was held at 125 °C for 3 min, then heated to 390 °C at a rate of 8 °C / min and held for 20 min. The substrate was then cooled to 130 °C at a rate of 15 °C / min and cooled to room temperature to obtain a laser emission layer. A WLP with a thickness of 20 μm and a thickness uniformity of 2% was coated on the surface of the laser emission layer. TB4130 is heated at 125°C for 3 minutes, then heated to 180°C at a rate of 8°C / min, held for 20 minutes, and then cooled to 130°C at a rate of 15°C / min to room temperature to obtain the second bonding layer, which is a silicon carbide substrate with the second temporary bonding layer on its surface; the side of the silicon substrate away from the first temporary bonding layer and the second bonding layer are used as the bonding surface, and the first substrate obtained in step (1) is bonded to the silicon carbide substrate at 225°C, a pressure of 63694Pa, ​​and a vacuum of 5Pa for 15 minutes to obtain the second substrate;

[0119] (3) The second substrate obtained in step (2) is debonded using a hot sliding debonding device. The temperature of the hot sliding debonding device is 140°C for the upper heating plate and 160°C for the lower heating plate. The sliding speed is 0.5 mm / s. Then, the substrate is soaked and cleaned with a cleaning agent (acetone) until there is no residue of the first temporary bonding layer on the surface. It is then washed with deionized water and dried to remove the first temporary bonding layer and the first substrate, thus obtaining the third substrate.

[0120] (4) A glue layer is provided on the surface of the target substrate, and the epitaxial layer film and the glue layer are used as bonding surfaces to bond the third substrate obtained in step (3) to the target substrate to obtain the fourth substrate.

[0121] (5) The fourth substrate obtained in step (4) is debonded using ultraviolet laser (wavelength 355nm), wherein the laser energy is 300mJ / cm. 2 The laser mode is pulsed mode with a pulse width of less than 1 mm. After debonding, the surface is immersed and cleaned with a cleaning agent (TBR2) until there is no second temporary bonding layer residue. Then, it is washed with deionized water and dried to remove the second temporary bonding layer and silicon carbide substrate, thus obtaining the fifth substrate.

[0122] (6) The fifth substrate obtained in step (5) is first subjected to plasma etching until the edge of the GaN epitaxial layer is exposed, and then the silicon substrate is removed by chemical etching to realize the transfer of the epitaxial layer; wherein, the plasma etching method uses carbon tetrafluoride and oxygen in a volume ratio of 4:1; the chemical etching method uses hydrofluoric acid, nitric acid and water in a volume ratio of 1:1:1, and the etching rate is 1 μm / min.

[0123] Example 3

[0124] This embodiment provides a method for transferring GaN epitaxial thin films. The only difference between this method and Embodiment 1 is that, in step (1), a silicon substrate with an epitaxial thin film on its surface is bonded to a first substrate at 105°C, a pressure of 796 Pa, and a vacuum of 5 Pa for 8 minutes; in step (2), the first substrate obtained in step (1) is bonded to a silicon carbide substrate at 205°C, a pressure of 127388 Pa, and a vacuum of 5 Pa for 6 minutes; and in step (5), the laser energy is 200 mJ / cm². 2 Other steps and process parameters are the same as in Example 1.

[0125] Example 4

[0126] This embodiment provides a method for transferring GaN epitaxial thin film. The only difference between this method and Embodiment 1 is that in step (1), the silicon substrate with the epitaxial thin film on its surface is bonded to the first substrate at 95°C, 1433 Pa, and a vacuum of 5 Pa for 15 min. The other steps and process parameters are the same as in Embodiment 1.

[0127] Example 5

[0128] This embodiment provides a method for transferring GaN epitaxial thin film. The only difference between this method and Embodiment 1 is that in step (1), the silicon substrate with the epitaxial thin film on its surface is bonded to the first substrate at 160°C, a pressure of 478 Pa, and a vacuum of 5 Pa for 0.5 min. The other steps and process parameters are the same as in Embodiment 1.

[0129] Example 6

[0130] This embodiment provides a method for transferring GaN epitaxial thin films. The only difference between this method and Embodiment 1 is that in step (2), the first substrate obtained in step (1) is bonded to the silicon carbide substrate at 190°C, a pressure of 191083 Pa, and a vacuum of 5 Pa for 25 min. All other steps and process parameters are the same as in Embodiment 1.

[0131] Example 7

[0132] This embodiment provides a method for transferring GaN epitaxial thin films. The only difference between this method and Embodiment 1 is that in step (2), the first substrate obtained in step (1) is bonded to the silicon carbide substrate at 270°C, a pressure of 15924 Pa, and a vacuum of 5 Pa for 4 minutes. The other steps and process parameters are the same as in Embodiment 1.

[0133] Example 8

[0134] This embodiment provides a method for transferring GaN epitaxial thin films. The only difference between this method and Embodiment 1 is that, in step (5), the laser energy is 1400 mJ / cm².2 Other steps and process parameters are the same as in Example 1.

[0135] Comparative Example 1

[0136] This comparative example provides a method for transferring GaN epitaxial thin films. The only difference between this method and Example 1 is that steps (2) and (5) are omitted, and the order of steps (3), (4), and (6) is reversed. That is, the transfer method includes the sequential steps (1) bonding, (6) etching away the silicon substrate, (4) transferring to the target substrate, and (3) thermally sliding and debonding to remove the first temporary bonding layer and the first substrate, thereby realizing the transfer of GaN epitaxial thin films. Other steps and process parameters are the same as in Example 1.

[0137] Performance testing

[0138] The bonding and transfer effects of the transfer methods provided in Examples 1-8 and Comparative Example 1 were observed by visual inspection. Among them, the absence of bubbles on the bonding surface and reasonable warpage (<50μm) indicate a good bonding effect. The film after transfer is intact and free of cracks, indicating a good transfer effect. The degree of bonding warpage was tested using a thin film stress meter.

[0139] The specific test results are shown in Table 1:

[0140] Table 1

[0141] Bonding effect Transfer effect Example 1 No air bubbles, reasonable warpage The film is intact and crack-free. Example 2 No air bubbles, reasonable warpage The film is intact and crack-free. Example 3 No air bubbles, reasonable warpage The film is intact and crack-free. Example 4 Bubbles are present Film breakage Example 5 Bubbles are present Film breakage Example 6 Bubbles are present Film breakage Example 7 Excessive warping Film breakage Example 8 No air bubbles, reasonable warpage Film breakage Comparative Example 1 No air bubbles, reasonable warpage Film breakage

[0142] As shown in Table 1, the epitaxial thin film transfer method provided by the present invention, by sequentially bonding a first temporary bonding layer and a second temporary bonding layer to both sides of a silicon substrate on which the epitaxial thin film is disposed, can effectively avoid or reduce damage to the epitaxial thin film caused by laser and stress during the transfer process, and complete the transfer of the epitaxial thin film efficiently and without damage, which is beneficial to improving device performance and extending device lifespan; moreover, the transfer method has good universality and can be applied to epitaxial thin films of different sizes and materials, which helps to promote the further miniaturization and integration of semiconductor devices and meet the growing market demand.

[0143] The applicant declares that the above description is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention fall within the protection and disclosure scope of the present invention.

Claims

1. A method for transferring an epitaxial thin film, characterized in that, The transfer method includes: (1) A first temporary bonding layer with a thickness of 2~80 μm and a thickness uniformity of ≤5% is coated on the surface of the first substrate and cured at 80~160℃ for 1~30 min to obtain the first temporary bonding layer; an epitaxial layer film is formed on the surface of the silicon substrate, and the first temporary bonding layer and the epitaxial layer film are used as bonding surfaces. The first substrate and the silicon substrate are bonded at a temperature of 100~150℃, a pressure of 0~2000 Pa, and a vacuum degree of <10 Pa for 1~10 min. The silicon substrate is cleaned and thinned to 50~100 μm to obtain the first substrate. (2) A laser-emitting layer material with a thickness of 200 nm to 5 μm and a thickness uniformity of ≤20% is coated on the surface of the second substrate. The substrate is then heated at 70 to 150 °C for 1 to 10 min, then heated to 200 to 400 °C at a rate of 3 to 40 °C / min, held for 10 to 80 min, and then cooled to below 150 °C at a rate of 5 to 20 °C / min to obtain the laser-emitting layer. A second adhesive layer material with a thickness of 2 to 80 μm and a thickness uniformity of ≤10% is coated on the surface of the laser-emitting layer. The material is then subjected to multi-temperature gradient curing to obtain the second temporary bonding layer. The multi-temperature gradient curing includes at least heating at 70 to 150 °C for 1 to 10 min, heating to 180 to 250 °C at a rate of 3 to 40 °C / min, and holding for 3 to 20 min. After min, the temperature is reduced to below 150℃ at a rate of 5~20℃ / min; the side of the silicon substrate away from the first temporary bonding layer and the second adhesive layer are used as the bonding surface, and the first substrate obtained in step (1) and the second substrate are bonded for 5~20 min under the conditions of temperature of 180~250℃, pressure of 15000~300000 Pa and vacuum degree <10 Pa to obtain the second substrate; (3) Perform thermal sliding debonding on the second substrate obtained in step (2), clean it, remove the first temporary bonding layer and the first substrate, and obtain the third substrate; (4) An adhesive layer is formed on the surface of the target substrate, and the third substrate obtained in step (3) is bonded to the target substrate with the epitaxial layer film and the adhesive layer as the bonding surface to obtain the fourth substrate; (5) The fourth substrate obtained in step (4) is subjected to a laser energy ≥120 mJ / cm 2 Laser debonding is performed under the following conditions: the laser used for debonding includes visible light and / or ultraviolet light; cleaning is performed to remove the second temporary bonding layer and the second substrate, resulting in the fifth substrate. (6) The fifth substrate obtained in step (5) is subjected to plasma etching and / or chemical etching to remove the silicon substrate, thereby realizing the transfer of the epitaxial thin film.

2. The transfer method according to claim 1, characterized in that, Step (1) The first substrate comprises a silicon wafer.

3. The transfer method according to claim 1, characterized in that, The material of the first temporary bonding layer includes temporary bonding adhesive and / or temporary bonding wax.

4. The transfer method according to claim 1, characterized in that, After bonding in step (1), the process also includes polishing the silicon substrate.

5. The transfer method according to claim 1, characterized in that, Step (2) The second substrate includes at least one of silicon carbide, sapphire, and glass.

6. The transfer method according to claim 1, characterized in that, The warpage after bonding in step (1) or step (2) is <50 μm, and the total thickness deviation of the bond pair is <10 μm.

7. The transfer method according to claim 1, characterized in that, The bonding pressure in step (2) is 50,000~150,000 Pa.

8. The transfer method according to claim 1, characterized in that, The debonding temperature in step (3) is 100~200℃.

9. The transfer method according to claim 1, characterized in that, The debonding slip velocity in step (3) is <2 mm / s.

10. The transfer method according to claim 1, characterized in that, The plasma etching method uses gases A and B; gas A includes at least one of carbon tetrafluoride, sulfur hexafluoride, or octafluorocyclobutane; gas B includes oxygen or a mixture of oxygen and at least one of argon or helium.

11. The transfer method according to claim 1, characterized in that, The reagents used in the chemical etching method include hydrofluoric acid, nitric acid, and water.

12. The transfer method according to claim 1, characterized in that, The corrosion rate of the chemical etching method is 0.2~2.2 μm / min.

13. The transfer method according to claim 1, characterized in that, The epitaxial thin film includes at least one of gallium nitride thin film, silicon dioxide thin film, and silicon nitride thin film.

14. The application of the transfer method according to any one of claims 1 to 13 in the fabrication of a semiconductor device.

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