Composite peeling structure, peeling method, wafer-level flexible device and preparation method thereof

Abstract

This invention discloses a composite exfoliation structure, an exfoliation method, a wafer-level flexible device, and a method for fabricating the same. The composite exfoliation structure includes a stress-regulating layer and a separation layer stacked together. The stress-regulating layer is formed of an elastic or tough material, and the separation layer is formed of a material with weak interlayer bonding. Under the same stress induction, the stress-regulating layer and the separation layer exhibit different deformation amounts and / or deformation modes. The interfacial stress induced by stress in the stress-regulating layer and the separation layer is greater than the interlayer bonding force of the separation layer. Furthermore, the stress-regulating layer, which generates structural deformation, can also induce and regulate the magnitude, direction, and distribution of stress within the separation layer, thereby inducing shear stress and normal stress in the separation layer. These shear stress and normal stress can drive the separation of the layers. This invention avoids the risk of physical damage, improves the uniformity and reliability of exfoliation, and is more suitable for the large-scale fabrication of large-area flexible devices.

Description

Technical Field

[0001] This invention specifically relates to a composite peeling structure, peeling method, wafer-level flexible device and its fabrication method, belonging to the field of flexible device technology. Background Technology

[0002] With the rapid development of wearable devices, flexible displays, and other fields, flexible electronic devices have gradually become a research hotspot. Flexible electronic devices can operate under bending, twisting, and even stretching conditions, providing more application scenarios for portable and wearable devices. Flexible devices can be applied in various fields, such as flexible displays, wearable ultraviolet photodetectors, flexible radio frequency and power devices, etc. These devices not only meet the needs of portable devices but also achieve more efficient and stable performance. For example, flexible nitride ultraviolet photodetectors can be applied in environmental monitoring and biological detection, while flexible nitride power devices can function in flexible high-frequency circuits. Although nitride materials have significant performance advantages, their rigidity and brittleness pose challenges to the direct growth of high-quality gallium nitride thin films on flexible substrates. Therefore, how to transfer devices from traditional rigid substrates (such as sapphire and silicon) to flexible substrates (such as polyimide and metal foil) has become a problem that needs to be solved.

[0003] To achieve flexible structure formation, researchers have proposed various exfoliation techniques, such as using two-dimensional materials (e.g., h-BN, graphene) as sacrificial or release layers to detach prefabricated devices from rigid substrates. However, existing exfoliation methods mainly rely on mechanical exfoliation or wet etching processes, which are not only complex to operate but may also cause potential damage to the devices, affecting the performance and yield of flexible devices. Two-dimensional materials, due to their layered structure and low interlayer binding energy, have been widely studied as release layer materials. By appropriately controlling their interfaces, the interlayer properties of two-dimensional materials can be used to peel the upper semiconductor material from the rigid substrate, achieving flexible device transfer. However, relying solely on the layered properties of two-dimensional materials for mechanical exfoliation may face many problems. For example, mechanical exfoliation may introduce additional stress, damaging the device structure and affecting its electrical performance; in addition, mechanical exfoliation leads to uncontrollable interface states, affecting the flexibility and durability of the device; the mechanical exfoliation process may cause uneven separation of the interface, reducing the device yield.

[0004] Currently, the fabrication schemes for flexible devices are as follows: (1) Direct Epitaxial Growth of Flexible Substrates: Flexible thin films are obtained by direct epitaxial growth on flexible substrates, followed by photolithography and other processes to fabricate flexible devices. This method has the following disadvantages: (a) Thermal Stability Limitations: Flexible substrates have poor thermal stability, making high-temperature epitaxial growth techniques such as MOCVD unusable. Low-temperature growth techniques or improved substrate materials are needed to address this challenge. (b) Epitaxial Quality Control: The surface smoothness and mechanical strength of flexible substrates are not as good as those of rigid substrates, making them prone to introducing defects that affect the crystal quality of the thin film and the performance of electronic devices. (c) Interface Adhesion: The interface adhesion between the flexible substrate and the thin film is weak, which may lead to peeling or cracking of the film under stress, requiring improved interface treatment techniques. (d) Chemical and Physical Stability: Flexible substrates may be less stable than traditional substrates under certain chemical environments, which can affect the durability of materials and the lifespan of devices. In addition, the physical properties of the flexible substrate may change during epitaxial growth, affecting the stress and structural integrity of the epitaxial layer.

[0005] (2) Rigid Substrate Epitaxial Thin Film Removal and Substrate Transfer to Flexible Substrate via Wet Etching: High-quality thin films are epitaxially grown on a rigid substrate and devices are fabricated. A suitable chemical etchant is then used to remove the rigid substrate, and the device is transferred to a flexible substrate. This method has the following disadvantages: (a) Effects of Chemical Solutions on the Thin Film: The chemical solutions used during rigid substrate removal may corrode or chemically react with the film surface, affecting the electrical and optical properties of the film. Solution residues may also contaminate the film, leading to increased surface roughness and deterioration of electronic performance, affecting the performance and stability of the device. (b) Process Complexity and Repeatability: Chemical solution removal technology requires precise control of the type, concentration, temperature, and processing time of the chemical solution to avoid excessive damage to the film. This high-precision process control increases the complexity of the production process and may affect the repeatability and productivity of the process, especially in large-scale manufacturing. (c) Environmental and Safety Issues: Using chemical solutions to remove the substrate may generate harmful waste liquids and byproducts. Disposing of these chemical wastes requires additional safety and environmental protection measures. This not only increases costs but also necessitates strict adherence to environmental regulations to prevent potential harm to the environment and human health.

[0006] (3) Rigid substrate epitaxial film removal and substrate transfer to flexible substrate via dry etching: High-quality thin films are epitaxially grown on a rigid substrate and devices are fabricated. Appropriate gas type, gas flow rate, etching power, and etching time are selected to remove the rigid substrate, and the device is then transferred to a flexible substrate. This method has the following drawbacks: (a) Stress and damage during etching: Dry etching processes (such as plasma etching) may introduce mechanical stress and defects into the thin film, especially when the etching depth is uneven or the etching rate is unstable. The presence of stress and defects affects the structural integrity and electrical properties of the thin film, increases the surface roughness, and may lead to crack formation. (b) Etching selectivity and uniformity: Achieving high selective etching of the thin film during dry etching is a challenge, especially in micro- and nano-scale fabrication. If the etching selectivity is low, areas that do not need to be processed may be etched inadvertently, causing a deterioration in device characteristics. Furthermore, etching uniformity is also crucial for large-area thin films; uneven etching can lead to variations in film thickness, thus affecting electrical and optical properties. (c) Environmental and safety issues: Dry etching typically involves toxic or corrosive gases, such as chlorine or fluorine, which require specialized handling and emission systems to ensure safe operation. Handling these gases increases reliance on environmental control systems and raises environmental safety risks and costs during the manufacturing process.

[0007] (4) Epitaxial film with sacrificial layer on rigid substrate and transfer to flexible substrate via tape: The sacrificial layer and sample film are epitaxially grown on a rigid substrate and the device is fabricated. The film is then peeled off with tape and transferred to a flexible substrate. This method has the following disadvantages: (a) Mechanical damage to the film: During the transfer process, peeling with tape may cause mechanical damage, cracks, warping, or increased surface roughness of the film. These damages not only reduce the quality of the film but may also affect its electrical and optical properties. (b) Difficulty in scaling up: Although the tape transfer process is simple, achieving high repeatability and large-scale production is challenging. Due to limitations in manual operation or equipment, the performance of each batch of film may be inconsistent, thus affecting the overall reliability and performance of the device. (c) Impact of tape residue: Residue may be left after the tape adhesion process. This residue may contaminate the film surface, affecting its surface quality and interfacial electrical properties.

[0008] (5) Epitaxial film with sacrificial layer on rigid substrate and transfer to flexible substrate via chemical solution peeling: A sacrificial layer and sample film are epitaxially grown on a rigid substrate, and the device is fabricated. The film is then peeled off using chemical solution peeling technology and transferred to a flexible substrate. This method has the following disadvantages: (a) Difficulty in large-scale production: While chemical solution peeling technology performs well at laboratory scale, it may face challenges in uniformity control during large-scale production. Maintaining the consistency and uniformity of large-area films requires strict process control; otherwise, problems such as uneven peeling and edge effects may occur, affecting the performance of the final device. (b) Environmental and safety issues: Chemical solutions are often corrosive and potentially harmful to the environment. Proper handling of waste liquids and solution gases is necessary to ensure the safety of the laboratory and production environments. These additional processing steps increase the complexity and cost of the manufacturing process. Summary of the Invention

[0009] The main objective of this invention is to provide a composite peeling structure, peeling method, wafer-level flexible device and its fabrication method, which achieves stable peeling of flexible semiconductor devices by precisely controlling stress distribution, thereby overcoming the shortcomings of the prior art.

[0010] To achieve the aforementioned objectives, the technical solution adopted by this invention includes: A first aspect of the present invention provides a composite peeling structure comprising: a stress-regulating layer and a separation layer stacked together, wherein the stress-regulating layer is formed of a material having elasticity or toughness, and the separation layer is formed of a material having weak interlayer bonding force; the stress-regulating layer and the separation layer produce structural deformations of different magnitudes and / or deformation modes under the same stress induction; the interfacial stress generated by stress induction in the stress-regulating layer and the separation layer is greater than the interlayer bonding force of the separation layer; and the stress-regulating layer that generates structural deformation can also induce and regulate the magnitude, direction, and stress distribution of stress within the separation layer, thereby inducing shear stress and normal stress in the separation layer, wherein the shear stress and the normal stress can drive the separation of the layers.

[0011] A second aspect of the present invention provides a peeling method for the composite peeling structure, comprising: Stress induction is applied to the composite peeling structure to cause structural deformation of the stress-adjusting layer, and the interfacial stress generated by the stress induction between the stress-adjusting layer and the separation layer is greater than the interlayer bonding force of the separation layer. The magnitude, direction, and stress distribution of the stress in the separation layer are induced and controlled by the stress-adjusting layer that causes structural deformation. Shear stress and normal stress are induced in the separation layer, and the shear stress and normal stress drive the separation of the layers.

[0012] A third aspect of this invention provides a method for fabricating a wafer-level flexible device, comprising: The composite release structure is formed on a rigid substrate, and a device structure layer is fabricated on the composite release structure to form a first intermediate structure, wherein the stress adjustment layer is disposed on the rigid substrate, and the device structure layer is disposed on the release layer; The temporary support carrier is combined with the device structure layer of the first intermediate structure to form the second intermediate structure; The peeling method using the composite peeling structure causes interlayer separation of the separation layers of the composite peeling structure, including a portion of the device structure layer as a third intermediate structure. The separation layer of the third intermediate structure is combined with the flexible substrate, and then the temporary support carrier is removed to obtain a wafer-level flexible device.

[0013] A fourth aspect of the present invention provides a highly sensitive flexible electronic device, which is prepared by the method for preparing the wafer-level flexible device.

[0014] Compared with the prior art, the advantages of the present invention include: This invention provides a composite peeling structure in which the separation layer and stress-adjusting layer work together to protect the structural integrity and electrical performance of flexible devices, making it particularly suitable for use in highly sensitive flexible electronic devices.

[0015] The stress-induced peeling provided by this invention controls the induction of external stress, such as temperature, air pressure, humidity, and mechanical stress, to induce shear stress and normal stress within the separation layer in the stress-adjusting layer. This disrupts the weak bonds between the separation layers, achieving interlayer separation and thus enabling a controllable peeling process. Compared to traditional mechanical peeling methods, this invention avoids the risk of physical damage and improves the uniformity and reliability of peeling. Especially in wafer-level manufacturing, the peeling process is more stable and efficient by adjusting stress distribution parameters, making it suitable for the large-scale fabrication of large-area flexible devices. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of a composite peeling structure provided in a typical embodiment of the present invention; Figure 2 This is a schematic diagram of the fabrication process of a wafer-level flexible semiconductor device based on a composite peeling structure and wafer-level bonding technology, provided in a typical embodiment of the present invention. Detailed Implementation

[0017] In view of the shortcomings of the prior art, the inventors of this invention, through long-term research and extensive practice, have proposed the technical solution of this invention. The following will further explain and illustrate this technical solution, its implementation process, and its principles.

[0018] This invention achieves peeling by controlling stress distribution, thus solving the problems of easy damage and difficulty in large-area flexible transfer during the peeling process of existing technologies. By designing a composite peeling structure and combining wafer-level bonding process and stress control induction technology, wafer-level non-destructive peeling and efficient transfer of devices are achieved, meeting the needs of large-scale production of flexible devices.

[0019] A first aspect of the present invention provides a composite peeling structure comprising a stress-regulating layer and a separation layer stacked together. The stress-regulating layer is formed of a material with elasticity or toughness, and the separation layer is formed of a material with weak interlayer bonding. The stress-regulating layer and the separation layer produce structural deformations and / or deformation modes different under the same stress induction. The interfacial stress generated by stress induction in the stress-regulating layer and the separation layer is greater than the interlayer bonding force of the separation layer. Furthermore, the stress-regulating layer that generates structural deformation can also induce and regulate the magnitude, direction, and stress distribution of stress within the separation layer, thereby inducing shear stress and normal stress in the separation layer. The shear stress and the normal stress can drive the separation of the layers.

[0020] Furthermore, the main function of the stress-regulating layer is to uniformly regulate and control the stress during the peeling process. If the selected material does not have sufficient stress-regulating capacity, stress concentration may occur during peeling, leading to localized damage or uneven peeling. Therefore, the stress-regulating layer must have good elasticity or toughness. Secondly, compatibility with the separation layer in terms of physical and chemical properties also needs to be considered. The elastic modulus of the stress-regulating layer is 1 GPa to 200 GPa, which allows for the gradual release of stress during peeling while preventing excessive material deformation that could lead to unstable peeling.

[0021] Furthermore, the stress-regulating layer is made of a metallic material with an elastic modulus of 10 GPa to 150 GPa, a polymer material with a molecular weight greater than 100,000, or a composite material with a reinforcing phase volume fraction of 5% to 40% and an elastic modulus of 50 GPa to 200 GPa.

[0022] Furthermore, the metallic material includes at least one of copper, aluminum, and titanium, but is not limited thereto.

[0023] Furthermore, the polymer material includes at least one of PMMA, PI, and PEEK, but is not limited thereto.

[0024] Furthermore, the composite material includes aluminum-based composite materials, such as graphite fiber / aluminum-based composite material (C / Al), silicon carbide fiber / aluminum-based composite material (SiC / Al), aluminum silicate fiber / aluminum-based composite material (Al2SiO5 / Al), etc., but is not limited to these.

[0025] Furthermore, the thickness of the stress-adjusting layer is 50nm~100nm.

[0026] Furthermore, the interlayer bonding force of the separation layer is 10 mJ / m² ~ 50 mJ / m².

[0027] Furthermore, the material of the separation layer includes, but is not limited to, h-BN, graphene, or molybdenum disulfide.

[0028] Furthermore, the thickness of the separation layer is 5nm~30nm.

[0029] In a more specific implementation, the difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion is: This is to ensure that the interfacial stress between the stress-adjusting layer and the separation layer caused by temperature changes is greater than the interlayer bonding force of the separation layer.

[0030] A second aspect of the present invention provides a peeling method for the composite peeling structure, comprising: Stress induction is applied to the composite peeling structure to cause structural deformation of the stress-adjusting layer, and the interfacial stress generated by the stress induction between the stress-adjusting layer and the separation layer is greater than the interlayer bonding force of the separation layer. The magnitude, direction, and stress distribution of the stress in the separation layer are induced and controlled by the stress-adjusting layer that causes structural deformation. Shear stress and normal stress are induced in the separation layer, and the shear stress and normal stress drive the separation of the layers.

[0031] In a more specific implementation, the difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion is: The peeling method includes: first, heating the composite peeling structure to a first temperature; then cooling the composite peeling structure to a second temperature, wherein the thermal shrinkage amplitude of the stress-adjusting layer is greater than that of the separation layer.

[0032] It should be noted that when using temperature changes to induce stress in the composite debonding structure, the heating and cooling temperatures are determined in situ during the bonding process in the bonding equipment. The temperature setting must comprehensively consider the following factors: the difference in the thermal expansion coefficients of the materials, as this difference determines the magnitude of the thermal stress; the thermal stability of the materials, ensuring that the temperature range does not lead to material degradation or interface damage; and the determination of stress, firstly through theoretical prediction. The stress σ is determined using the following formula: σ = E·ΔT·(α1-α2), where E is the elastic modulus of the stress-adjusting layer, α1 is the thermal expansion coefficient of the stress-adjusting layer and α2 is the separation layer, and ΔT is the temperature difference. By calculating the stress value and comparing it with the interface bonding strength (force), it is predicted whether the stress is sufficient for separation. Secondly, the stress profilometer included in the bonding equipment uses a laser spot to scan the surface, records changes in surface morphology through interference or displacement sensors, and then calculates the film stress by measuring the curvature change of the sample. For example, for h-BN, the separation conditions typically used are 0.05-0.5 MPa, therefore the curvature change corresponding to the stress profilometer is 0.0005~0.005 mm. -1 .

[0033] Furthermore, the temperature difference between the first temperature and the second temperature is 75℃~400℃.

[0034] Furthermore, the first temperature is 150℃~400℃, and the second temperature is 25℃~75℃.

[0035] Furthermore, during the cooling process, the cooling rate of the composite exfoliation structure is 40℃ / min to 60℃ / min. It should be noted that during the cooling process, the cooling rate directly affects the generation and distribution of stress, as well as the integrity of the material and interface. If the cooling rate is too high, it will lead to stress concentration and uneven separation, while if the cooling rate is too low, it will lead to insufficient stress.

[0036] A third aspect of this invention provides a method for fabricating a wafer-level flexible device, comprising:

[0037] The composite release structure is formed on a rigid substrate, and a device structure layer is fabricated on the composite release structure to form a first intermediate structure, wherein the stress adjustment layer is disposed on the rigid substrate, and the device structure layer is disposed on the release layer; The temporary support carrier is combined with the device structure layer of the first intermediate structure to form the second intermediate structure; The peeling method using the composite peeling structure causes interlayer separation of the separation layers of the composite peeling structure, including a portion of the device structure layer as a third intermediate structure. The separation layer of the third intermediate structure is combined with the flexible substrate, and then the temporary support carrier is removed to obtain a wafer-level flexible device.

[0038] In a more specific implementation, the method for fabricating the wafer-level flexible device specifically includes: The temporary support carrier plate is bonded to the device structure layer of the first intermediate structure to form a second intermediate structure; This causes interlayer separation in the separation layer of the composite peeling structure; The separation layer of the third intermediate structure is bonded to the flexible substrate, and the temporary support carrier is debonded to the device structure layer to remove the temporary support carrier.

[0039] A fourth aspect of the present invention provides a highly sensitive flexible electronic device, which is prepared by the method for preparing the wafer-level flexible device.

[0040] The following will further explain the technical solution, its implementation process and principle in conjunction with the accompanying drawings and specific implementation examples. Unless otherwise specified, the epitaxial growth equipment, epitaxial growth process, semiconductor device structure fabrication process, bonding equipment and other technologies used in this invention are known to those skilled in the art and are not specifically limited here.

[0041] For a more specific implementation plan, please refer to Figure 1 and Figure 2 A method for fabricating a wafer-level flexible semiconductor device based on a composite peeling structure and wafer-level bonding technology, comprising the following steps: 1) Fabrication of semiconductor devices with composite lift-off structures: 1.1) Provide a rigid substrate and perform organic cleaning on the rigid substrate.

[0042] Rigid substrates can be selected from c-plane or beveled sapphire substrates with off-axis angles, etc. Rigid substrates can be selected from the 2 / 4 / 6 / 8-inch wafer-level or small-size rigid substrates obtained by dicing currently available on the market; 1.2) A stress-regulating layer with a thickness of 50 nm to 100 nm is formed on a rigid substrate using commercially mature deposition processes such as electron beam evaporation, sputtering, CVD, spin coating, atomic layer deposition, and solution deposition. The elastic modulus of the stress-regulating layer is 1 GPa to 200 GPa. Specifically, the material of the stress-regulating layer can be a metal material with an elastic modulus of 10 GPa to 150 GPa, a polymer material with a molecular weight greater than 100,000, or a composite material with a reinforcing phase volume fraction of 5% to 40% and an elastic modulus of 50 GPa to 200 GPa, etc., which have good elasticity or toughness. The stress-regulating layer can gradually release stress during the peeling process to prevent sudden stress concentration from damaging the device.

[0043] It should be noted that the main function of the stress-regulating layer in this invention is to uniformly regulate and control the stress during the peeling process. If the selected material does not have sufficient stress-regulating capacity, stress concentration may occur during peeling, leading to localized damage or uneven peeling. Therefore, the stress-regulating layer must have good elasticity or toughness. Secondly, compatibility with the separation layer in terms of physical and chemical properties also needs to be considered. The elastic modulus of the stress-regulating layer is 1 GPa to 200 GPa, which allows for the gradual release of stress during peeling while preventing excessive material deformation that could lead to unstable peeling.

[0044] 1.3) Commercially mature growth methods such as MOCVD, MBE, ALD, HVPE, and PECVD are used to form a separation layer with a thickness of 5nm to 30nm on the stress-adjusting layer, forming a composite exfoliation structure. The material of the separation layer can be a material with weak interlayer bonding, such as h-BN, graphene, or molybdenum disulfide. The selection of a material with weak interlayer bonding facilitates controllable interlayer separation after stress-induced conditions are applied. During the interlayer separation process, the composite exfoliation structure buffers and releases stress through the stress response characteristics of the stress-adjusting layer and the separation layer.

[0045] It should be noted that when the separation layer and stress-regulating layer are subjected to stress induction (conditions including temperature, air pressure, humidity, mechanical stress, etc.), both the stress-regulating layer and the separation layer undergo stress changes—corresponding to structural deformation—under the same stress induction. However, the deformation amounts and / or deformation modes of the two layers differ. Furthermore, the stress-regulating layer, which induces structural deformation, can also induce and regulate the magnitude, direction, and distribution of stress within the separation layer, thereby inducing shear stress and normal stress in the separation layer. At this point, the interfacial stress between the stress-regulating layer and the separation layer is greater than the interlayer bonding force of the separation layer. The shear stress and the normal stress drive the separation layer to undergo interlayer separation. Specifically, the stress-regulating layer (such as certain elastic or tough materials) plays a role in gradually releasing stress and uniformly controlling stress distribution during the separation process of the composite exfoliation structure. This innovative structural design not only optimizes the exfoliation process but also ensures the protection of the device layers during exfoliation, avoiding the device damage problems common in traditional methods.

[0046] 1.4) The sample with the completed composite lift-off structure is placed in an epitaxial device such as MOCVD, and a device layer of a semiconductor device is obtained by epitaxial growth on the lift-off layer. The device layer of the semiconductor device can be a device structure layer of an electrical or optical device. For example, the device layer of the semiconductor device can be an epitaxial layer of a GaN HEMT device.

[0047] 2) Wafer-level bonding technology and stress-induced peeling transfer: 2.1) Provide a temporary support substrate and use a spin coater to form a bonding adhesive on the surface of the temporary support substrate. The bonding adhesive can be a commercially available epoxy resin, polyimide adhesive, acrylic adhesive, etc., depending on the conditions. The parameters of the spin-coating bonding adhesive can be selected according to the type of bonding adhesive and the sample size. For example, the temporary support substrate can be a glass substrate, etc., and the spin coater speed can be 2000 r / 30s.

[0048] 2.2) Place the temporary support substrate that has been homogenized and the sample with the device layer of the semiconductor device into the bonding machine for bonding operation to bond the temporary support substrate and the device layer of the semiconductor device.

[0049] It should be noted that the pressure applied during bonding should be within the controllable range of the equipment and the tolerance of the device. The bonding pressure and temperature need to be adjusted according to specific experimental requirements, bonding adhesive characteristics, and material properties. For example, the bonding pressure can be 5N to 20N, and the temperature can be 150℃ to 400℃ (depending on the bonding adhesive, but not exceeding the debonding temperature of the bonding adhesive). It is important to note that the bonding pressure should be sufficient to ensure uniform distribution and complete contact of the bonding adhesive at the bonding interface, while avoiding excessive pressure that could lead to material deformation. Furthermore, during the bonding process, an in-situ monitoring system can be used to monitor changes in the sample's temperature, pressure, and stress to ensure that the composite debonded structures can separate under suitable conditions, avoiding damage. For example, a stress profilometer can be used to monitor changes in sample curvature to determine stress distribution.

[0050] 2.3) Monitor the temperature, pressure, stress distribution, etc. of the sample after the temporary support carrier and the semiconductor device are bonded by the in-situ monitoring system, change at least one of the temperature, air pressure, and humidity of the environment in which the composite release structure is located, and / or apply mechanical stress to the composite release structure to cause interlayer separation of the separation layer.

[0051] For example, the sample temperature is restored to a specific temperature, which refers to the temperature at which sufficient stress is generated to induce separation of the separation layer. This temperature varies depending on the material of the separation layer. This process involves cooling after bonding to achieve stress induction. Considering the difference in thermal expansion coefficients between the stress-regulating layer and the separation layer, the temperature is lowered at a relatively high rate to generate stress, causing interlayer separation. The specific temperature of the sample is also determined based on the curvature change determined by a stress profilometer. For most separation layer materials, stress-induced separation can be achieved within the range of 25℃ to 75℃.

[0052] 2.4) The separation layer of the sample containing the semiconductor device layer is bonded to the flexible substrate using the self-alignment and pressure of the bonding machine. The pressure, temperature, and other conditions applied during bonding should ensure a stable bond between the separation layer and the flexible substrate. The flexible substrate can be made of commercially available and mature materials such as polydimethylsiloxane, metal foil, other organic materials, and composite materials.

[0053] 2.5) Place the bonded sample into a debonding machine to release the bond between the temporary support substrate and the device layer of the semiconductor device, thereby removing the temporary support substrate and obtaining a wafer-level flexible semiconductor device.

[0054] The debonding conditions can be determined based on the debonding temperature of the bonding adhesive, which is generally 200℃~350℃.

[0055] The following specific implementation case will further explain the technical solution, its implementation process and principles.

[0056] Example 1 The fabrication method of a 4-inch flexible GaN HEMT device includes the following steps: 1) After organic cleaning of the sapphire substrate, a Cu metal layer with a thickness of 50 nm was deposited on the sapphire substrate by electron beam evaporation. Then, an h-BN layer with a thickness of 5 nm was epitaxially grown on the Cu metal layer by MOCVD.

[0057] 2) Place the sample obtained in step 1) into an MOCVD device, epitaxially obtain a 4-inch AlGaN / GaN epitaxial wafer on the h-BN layer and pattern it to fabricate a GaN HEMT device.

[0058] 3) Spin-coat bonding adhesive onto a 4-inch glass substrate at 2000 rpm for 30 seconds; 4) Place the 4-inch glass substrate and the 4-inch GaN HEMT device sample that have been homogenized into the bonding machine, heat it to 120°C, apply 8N pressure, and the equipment will perform bonding operation by self-alignment. During the bonding process, the changes in sample temperature, pressure, stress and other conditions are monitored by the in-situ monitoring system (stress profiler). 5) The bonded sample from step 4) is heated. Due to the significant difference in the coefficients of thermal expansion between Cu and h-BN, transverse stress is generated between the two at the interface during the heating process. When the temperature reaches 200℃ and sufficient stress is generated, the bonding pressure is removed, and the temperature is gradually reduced to 75℃ at a rate of 60℃ / min. This causes thermal shrinkage stress to be generated at the interface between the Cu metal layer and the h-BN layer. Since the shrinkage of the Cu metal layer is large, the interface will bear stress in the opposite direction to that during heating, and the h-BN layers will separate.

[0059] 6) Place the sample with GaN HEMT device and the flexible PET substrate into a bonding machine. At 100°C, apply a pressure of 5N using the bonding machine to bond the h-BN layer of the sample with GaN HEMT device to the flexible PET substrate.

[0060] 7) After ensuring that the bonding is completed, place the bonded sample into the debonding machine and heat it to 260°C to reach the dissociation temperature of the selected polyimide bonding adhesive, so as to separate the glass substrate from the sample on the flexible PET substrate, thereby completing the fabrication of the 4-inch flexible GaN HEMT device.

[0061] Example 2 The fabrication method of a 4-inch flexible GaN HEMT device includes the following steps: 1) After organic cleaning of the sapphire substrate, a Cu metal layer with a thickness of 80 nm is deposited on the sapphire substrate by electron beam evaporation. Then, an h-BN layer with a thickness of 10 nm is epitaxially grown on the Cu metal layer by MOCVD.

[0062] 2) Place the sample obtained in step 1) into an MOCVD device, epitaxially obtain a 4-inch AlGaN / GaN epitaxial wafer on the h-BN layer and pattern it to fabricate a GaN HEMT device.

[0063] 3) Spin-coat bonding adhesive onto a 4-inch glass substrate at 2000 rpm for 30 seconds; 4) Place the 4-inch glass substrate and the 4-inch GaN HEMT device sample that have been homogenized into the bonding machine, heat it to 120°C, apply 8N pressure, and the equipment will perform bonding operation by self-alignment. During the bonding process, the changes in sample temperature, pressure, stress and other conditions are monitored by the in-situ monitoring system (stress profiler). 5) The bonded sample from step 4) is heated. Due to the significant difference in the coefficients of thermal expansion between Cu and h-BN, transverse stress is generated between the two at the interface during the heating process. When the temperature reaches 200℃ and sufficient stress is generated, the bonding pressure is removed, and the temperature is gradually reduced to 75℃ at a rate of 60℃ / min. This causes thermal shrinkage stress to be generated at the interface between the Cu metal layer and the h-BN layer. Since the shrinkage of the Cu metal layer is large, the interface will bear stress in the opposite direction to that during heating, and the h-BN layers will separate.

[0064] 6) Place the sample with GaN HEMT device and the flexible PET substrate into a bonding machine. At 100°C, apply a pressure of 5N using the bonding machine to bond the h-BN layer of the sample with GaN HEMT device to the flexible PET substrate.

[0065] 7) After ensuring that the bonding is completed, place the bonded sample into the debonding machine and heat it to 260°C to reach the dissociation temperature of the selected polyimide bonding adhesive, so as to separate the glass substrate from the sample on the flexible PET substrate, thereby completing the fabrication of the 4-inch flexible GaN HEMT device.

[0066] Example 3 The fabrication method of a 4-inch flexible GaN HEMT device includes the following steps: 1) After organic cleaning of the sapphire substrate, a Cu metal layer with a thickness of 100 nm is deposited on the sapphire substrate by electron beam evaporation. Then, an h-BN layer with a thickness of 30 nm is epitaxially grown on the Cu metal layer by MOCVD.

[0067] 2) Place the sample obtained in step 1) into an MOCVD device, epitaxially obtain a 4-inch AlGaN / GaN epitaxial wafer on the h-BN layer and pattern it to fabricate a GaN HEMT device.

[0068] 3) Spin-coat bonding adhesive onto a 4-inch glass substrate at 2000 rpm for 30 seconds; 4) Place the 4-inch glass substrate and the 4-inch GaN HEMT device sample that have been homogenized into the bonding machine, heat it to 120°C, apply 8N pressure, and the equipment will perform bonding operation by self-alignment. During the bonding process, the changes in sample temperature, pressure, stress and other conditions are monitored by the in-situ monitoring system (stress profiler). 5) The bonded sample from step 4) is heated. Due to the significant difference in the coefficients of thermal expansion between Cu and h-BN, transverse stress is generated between the two at the interface during the heating process. When the temperature reaches 200℃ and sufficient stress is generated, the bonding pressure is removed, and the temperature is gradually reduced to 75℃ at a rate of 60℃ / min. This causes thermal shrinkage stress to be generated at the interface between the Cu metal layer and the h-BN layer. Since the shrinkage of the Cu metal layer is large, the interface will bear stress in the opposite direction to that during heating, and the h-BN layers will separate.

[0069] 6) Place the sample with GaN HEMT device and the flexible PET substrate into a bonding machine. At 100°C, apply a pressure of 5N using the bonding machine to bond the h-BN layer of the sample with GaN HEMT device to the flexible PET substrate.

[0070] 7) After ensuring that the bonding is completed, place the bonded sample into the debonding machine and heat it to 260°C to reach the dissociation temperature of the selected polyimide bonding adhesive, so as to separate the glass substrate from the sample on the flexible PET substrate, thereby completing the fabrication of the 4-inch flexible GaN HEMT device.

[0071] Example 4 1) After organic cleaning of the sapphire substrate, an Al metal layer with a thickness of 50 nm was deposited on the sapphire substrate by electron beam evaporation. Then, an h-BN layer with a thickness of 5 nm was epitaxially grown on the Al metal layer by MOCVD.

[0072] 2) Place the sample obtained in step 1) into an MOCVD device, epitaxially obtain a 4-inch AlGaN / GaN epitaxial wafer on the h-BN layer and pattern it to fabricate a GaN HEMT device.

[0073] 3) Spin-coat bonding adhesive onto a 4-inch glass substrate at 2000 rpm for 30 seconds; 4) Place the 4-inch glass substrate and the 4-inch GaN HEMT device sample that have been homogenized into the bonding machine, heat it to 120°C, apply 8N pressure, and the equipment will perform bonding operation by self-alignment. During the bonding process, the changes in sample temperature, pressure, stress and other conditions are monitored by the in-situ monitoring system (stress profiler). 5) The bonded sample from step 4) is heated. Due to the significant difference in the coefficients of thermal expansion between Al and h-BN, transverse stress is generated between the two interfaces during the heating process. When the temperature reaches 200℃ and sufficient stress is generated, the bonding pressure is removed, and the temperature is gradually reduced to 75℃ at a rate of 30℃ / min. This causes thermal shrinkage stress to be generated at the interface between the Al metal layer and the h-BN layer. Since the shrinkage of the Al metal layer is large, the interface will bear stress in the opposite direction to that during heating, and the h-BN layers will separate.

[0074] 6) Place the sample with GaN HEMT device and the flexible PET substrate into a bonding machine. At 100°C, apply a pressure of 5N using the bonding machine to bond the h-BN layer of the sample with GaN HEMT device to the flexible PET substrate.

[0075] 7) After ensuring that the bonding is completed, place the bonded sample into the debonding machine and heat it to 260°C to reach the dissociation temperature of the selected polyimide bonding adhesive, so as to separate the glass substrate from the sample on the flexible PET substrate, thereby completing the fabrication of the 4-inch flexible GaN HEMT device.

[0076] Example 5 The fabrication method of a 4-inch flexible GaN HEMT device includes the following steps: 1) After organic cleaning of the sapphire substrate, a Cu metal layer with a thickness of 50 nm is deposited on the sapphire substrate by electron beam evaporation. Then, a graphene layer with a thickness of 5 nm is epitaxially grown on the Cu metal layer by MOCVD.

[0077] 2) Place the sample obtained in step 1) into an MOCVD device, epitaxially obtain a 4-inch AlGaN / GaN epitaxial wafer on the graphene layer and pattern it to fabricate a GaN HEMT device.

[0078] 3) Spin-coat bonding adhesive onto a 4-inch glass substrate at 2000 rpm for 30 seconds; 4) Place the 4-inch glass substrate and the 4-inch GaN HEMT device sample that have been homogenized into the bonding machine, heat it to 120°C, apply 8N pressure, and the equipment will perform bonding operation by self-alignment. During the bonding process, the changes in sample temperature, pressure, stress and other conditions are monitored by the in-situ monitoring system (stress profiler). 5) The bonded sample from step 4) is heated. Due to the significant difference in the coefficients of thermal expansion between Cu and graphene, transverse stress is generated at the interface between the two during the heating process. When the temperature reaches 150°C and sufficient stress is generated, the bonding pressure is removed, and the temperature is gradually reduced to 25°C at a rate of 30°C / min. This causes thermal shrinkage stress to be generated at the interface between the Cu metal layer and the graphene layer. Since the shrinkage of the Cu metal layer is large, the interface will bear stress in the opposite direction to that during heating, and the graphene layers will separate.

[0079] 6) Place the sample with GaN HEMT device and the flexible PET substrate into a bonding machine. At 100°C, apply a pressure of 5N using the bonding machine to bond the graphene layer of the sample with GaN HEMT device to the flexible PET substrate.

[0080] 7) After ensuring that the bonding is completed, place the bonded sample into the debonding machine and heat it to 260°C to reach the dissociation temperature of the selected polyimide bonding adhesive, so as to separate the glass substrate from the sample on the flexible PET substrate, thereby completing the fabrication of the 4-inch flexible GaN HEMT device.

[0081] Example 6 The fabrication method of a 4-inch flexible GaN HEMT device includes the following steps: 1) After organic cleaning of the sapphire substrate, a PMMA metal layer with a thickness of 50nm is deposited on the sapphire substrate by electron beam evaporation. Then, an h-BN layer with a thickness of 5nm is epitaxially grown on the PMMA metal layer by MOCVD.

[0082] 2) Place the sample obtained in step 1) into an MOCVD device, epitaxially obtain a 4-inch AlGaN / GaN epitaxial wafer on the h-BN layer and pattern it to fabricate a GaN HEMT device.

[0083] 3) Spin-coat bonding adhesive onto a 4-inch glass substrate at 2000 rpm for 30 seconds; 4) Place the 4-inch glass substrate and the 4-inch GaN HEMT device sample that have been homogenized into the bonding machine, heat it to 120°C, apply 8N pressure, and the equipment will perform bonding operation by self-alignment. During the bonding process, the changes in sample temperature, pressure, stress and other conditions are monitored by the in-situ monitoring system (stress profiler). 5) The bonded sample from step 4) is heated. Due to the significant difference in the coefficients of thermal expansion between PMMA and h-BN, transverse stress is generated at the interface between the two during the heating process. When the temperature reaches 210℃ and sufficient stress is generated, the bonding pressure is removed, and the temperature is gradually reduced to 45℃ at a rate of 40℃ / min. This causes thermal shrinkage stress to be generated at the interface between the PMMA metal layer and the h-BN layer. Since the shrinkage of the PMMA metal layer is large, the interface will bear stress in the opposite direction to that during heating, and the h-BN layers will separate.

[0084] 6) Place the sample with GaN HEMT device and the flexible PET substrate into a bonding machine. At 100°C, apply a pressure of 5N using the bonding machine to bond the h-BN layer of the sample with GaN HEMT device to the flexible PET substrate.

[0085] 7) After ensuring that the bonding is completed, place the bonded sample into the debonding machine and heat it to 260°C to reach the dissociation temperature of the selected polyimide bonding adhesive, so as to separate the glass substrate from the sample on the flexible PET substrate, thereby completing the fabrication of the 4-inch flexible GaN HEMT device.

[0086] It should be noted that, as given above, an example of applying stress-induced stress to the composite peeling structure by changing the temperature to achieve interlayer separation is provided. The present invention also obtained a series of embodiments by adjusting the air pressure and / or humidity of the environment in which the composite peeling structure is located, and / or by applying mechanical stress to the composite peeling structure, etc., and the results are basically the same as those of embodiments 1-6.

[0087] The stress-regulating layer of the composite peeling structure used in this invention is designed in conjunction with wafer-level bonding process for peeling. The stress-regulating layer is made of elastic or tough materials that can gradually release stress during the peeling process. Compared with traditional technology, this method of precisely controlling stress release through the stress-regulating layer can significantly improve the accuracy and stability of the peeling process.

[0088] The composite peeling structure provided by this invention adopts a multi-layer composite structure, including an easily peelable separation layer and a stress-regulating layer with stress-regulating characteristics, so that the stress during the peeling process can be evenly distributed, reducing sudden interface damage, thereby avoiding device damage and ensuring the integrity and non-destructive nature of the peeling.

[0089] The stress-controlled induced material peeling method of this invention transfers the device from a rigid substrate to a flexible substrate. By adjusting the induction method, a controllable stress distribution is achieved inside the composite peeling structure, thereby achieving the peeling effect. This stress-induced peeling method avoids the physical damage to the material structure in traditional methods and is especially suitable for thin films and flexible electronic devices.

[0090] This invention employs a wafer-level bonding process between the device and the flexible substrate, providing a large-area, uniform, and robust bond. Wafer-level bonding not only simplifies the process flow but also provides stable support for subsequent peeling processes, thereby enabling the large-scale fabrication of flexible devices.

[0091] It should be understood that the above embodiments are merely illustrative of the technical concept and features of the present invention, and are intended to enable those skilled in the art to understand the content of the present invention and implement it accordingly. They should not be construed as limiting the scope of protection of the present invention. All equivalent changes or modifications made in accordance with the spirit and essence of the present invention should be covered within the scope of protection of the present invention.

Claims

1. A composite peeling structure, characterized in that, include: The stress-regulating layer and the separation layer are stacked together. The stress-regulating layer is formed of an elastic or tough material, and the separation layer is formed of a material with weak interlayer bonding. The stress-regulating layer and the separation layer produce different deformation amounts and / or deformation modes under the same stress induction. The interfacial stress generated by the stress induction in the stress-regulating layer and the separation layer is greater than the interlayer bonding force of the separation layer. Furthermore, the stress-regulating layer that generates structural deformation can also induce and regulate the magnitude, direction, and stress distribution of stress within the separation layer, thereby inducing shear stress and normal stress in the separation layer. The shear stress and the normal stress can drive the separation of the layers.

2. The composite peeling structure according to claim 1, characterized in that: The elastic modulus of the stress-adjusting layer is 1 GPa to 200 GPa; Preferably, the stress-adjusting layer is made of a metallic material with an elastic modulus of 10 GPa to 150 GPa, a polymer material with a molecular weight greater than 100,000, or a composite material with a reinforcing phase volume fraction of 5% to 40% and an elastic modulus of 50 GPa to 200 GPa. Preferably, the metallic material includes at least one of copper, aluminum, and titanium; Preferably, the polymer material includes at least one of PMMA, PI, and PEEK; Preferably, the composite material includes an aluminum-based composite material; Preferably, the thickness of the stress-adjusting layer is 50nm~100nm.

3. The composite peeling structure according to claim 1, characterized in that: The interlayer bonding force of the separation layer is 10 mJ / m² ~ 50 mJ / m²; Preferably, the material of the separation layer includes h-BN, graphene, or molybdenum disulfide; Preferably, the thickness of the separation layer is 5nm to 30nm.

4. The composite peeling structure according to claim 1, 2, or 3, characterized in that: The stress-adjusting layer has a first coefficient of thermal expansion, and the separation layer has a second coefficient of thermal expansion. The difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion is [value missing]. The interfacial stress caused by temperature changes in the composite peeling structure is greater than the interlayer bonding strength of the separation layer.

5. The peeling method for the composite peeling structure as described in any one of claims 1-4, characterized in that, include: Stress induction is applied to the composite peeling structure to cause structural deformation of the stress-adjusting layer, and the interfacial stress generated by the stress induction between the stress-adjusting layer and the separation layer is greater than the interlayer bonding force of the separation layer. The magnitude, direction, and stress distribution of the stress in the separation layer are induced and controlled by the stress-adjusting layer that causes structural deformation. Shear stress and normal stress are induced in the separation layer, and the shear stress and normal stress drive the separation of the layers.

6. The peeling method according to claim 5, characterized in that: The stress-adjusting layer has a first coefficient of thermal expansion, and the separation layer has a second coefficient of thermal expansion. The difference between the first coefficient of thermal expansion and the second coefficient of thermal expansion is [value missing]. Furthermore, the stripping method includes: First, the composite peeling structure is heated to a first temperature; then, the composite peeling structure is cooled to a second temperature, wherein the thermal shrinkage of the stress-adjusting layer is greater than that of the separation layer. Preferably, the temperature difference between the first temperature and the second temperature is 75℃~400℃; Preferably, the first temperature is 150℃~400℃, and the second temperature is 25℃~75℃; Preferably, during the cooling process, the cooling rate of the composite exfoliation structure is 40℃ / min to 60℃ / min.

7. The peeling method according to claim 5, characterized in that, The method of applying stress-induced stress to the composite peeling structure includes: adjusting the air pressure and / or humidity of the environment in which the composite peeling structure is located, and / or applying mechanical stress to the composite peeling structure.

8. A method for fabricating a wafer-level flexible device, characterized in that, include: A composite release structure as described in any one of claims 1-4 is formed on a rigid substrate, a device structure layer is fabricated on the composite release structure, and a first intermediate structure is formed, wherein the stress adjustment layer is disposed on the rigid substrate, and the device structure layer is disposed on the release layer; The temporary support carrier is combined with the device structure layer of the first intermediate structure to form the second intermediate structure; The peeling method of the composite peeling structure according to any one of claims 5-7 is used to cause interlayer separation of the separation layer of the composite peeling structure, wherein a portion of the device structure layer is used as a third intermediate structure. The separation layer of the third intermediate structure is combined with the flexible substrate, and then the temporary support carrier is removed to obtain a wafer-level flexible device.

9. The method for fabricating a wafer-level flexible device according to claim 8, characterized in that, Specifically, it includes: The temporary support carrier plate is bonded to the device structure layer of the first intermediate structure to form a second intermediate structure; This causes interlayer separation in the separation layer of the composite peeling structure; The separation layer of the third intermediate structure is bonded to the flexible substrate, and the temporary support carrier is debonded to the device structure layer to remove the temporary support carrier.

10. A highly sensitive flexible electronic device, characterized in that: The highly sensitive flexible electronic device is prepared by the wafer-level flexible device preparation method described in claim 8 or 9.

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