Polymer-based dry electrode transfer method

Abstract

The invention discloses a dry-method electrode transfer method based on a polymer, and aims to solve the problems of interface pollution, solvent residue, material damage and the like when a metal electrode or a functional layer is transferred to a target substrate inevitably due to the fact that a traditional wet-method electrode transfer technology depends on solvent treatment in the field of preparation of two-dimensional material electronic devices. Specifically, residues can be introduced into an electrode / semiconductor interface by an organic solvent or a degumming agent, material oxidation or chemical reaction can be induced by a liquid-phase environment, and part of functional electrode materials are corroded or changed in components in a solution environment, so that the electrode performance is seriously influenced. The invention aims to provide a dry transfer method without using any solvent, the accurate transfer of the metal electrode or the functional layer to the target substrate or the material surface is realized by optimizing the process, and the problems of pollution, defects and material compatibility caused by wet transfer are fundamentally avoided; and the requirements of a high-performance two-dimensional device on a clean interface and stable electrode performance are met.

Description

Technical Field

[0001] This invention relates to the field of semiconductor device technology, specifically to a polymer-based dry electrode transfer method. Background Technology

[0002] In the field of two-dimensional semiconductor device fabrication, high-quality interfacial contact between electrodes and two-dimensional materials is a core factor determining device performance. Traditional vapor deposition processes involve high-temperature atomic bombardment, which can damage the atomically flat surface of two-dimensional materials. Furthermore, organic photoresists used in photolithography processes are prone to surface contamination and lattice disorder during high-temperature curing. To address these issues, electrode transfer technology has emerged: by pre-fabricating metal electrodes on an auxiliary substrate and then transferring them completely to the surface of a two-dimensional semiconductor, damage to the material from high-temperature processes can be avoided, and precise control of the interface structure can be achieved. However, traditional wet transfer technology, relying on solution processing, has three inherent drawbacks: first, residual organic solvents or resist removers can form insulating carbon-based impurities (such as amorphous carbon and polymer degradation products) at the electrode / semiconductor interface; second, the liquid environment can easily induce oxidation of two-dimensional materials (such as transition metal sulfides) or degradation of water-sensitive materials (such as black phosphorus interlayer expansion); and third, magnetic metal electrodes (such as Fe and Co) are prone to corrosion or compositional changes in solution, leading to increased contact resistance. These problems have made wet transfer electrodes unable to meet the requirements of quantum devices, high-frequency electronic devices, and other applications for atomically clean interfaces, thus driving the development of dry transfer technology.

[0003] To address the challenges of wet transfer electrodes, such as difficulty in removing polymer residues and limitations in application to water- or organic solvent-sensitive materials, dry transfer technology has been developed as a means of device fabrication. However, current dry transfer technology also faces challenges. Elastomer stamp transfer suffers from uneven mechanical stress leading to electrode deformation; van der Waals peeling relies on high-cost substrates and has low peeling efficiency; and existing dry processes struggle to operate precisely on three-dimensional structural surfaces, resulting in low efficiency in multi-electrode integration and failing to meet the demands of large-scale production. Therefore, a technological breakthrough is urgently needed.

[0004] To address the aforementioned technical shortcomings, a solution is proposed. Summary of the Invention

[0005] The purpose of this invention is to solve the problems mentioned above by proposing a polymer-based dry electrode transfer method.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] A polymer-based dry electrode transfer method includes the following steps:

[0008] S1: Provides a highly flat substrate for cleavage;

[0009] S2: Fabricate the electrode to be transferred on the surface of the substrate;

[0010] S3: A support layer is provided on the surface of the electrode;

[0011] S4: Mechanically peel the stacked structure consisting of the electrode / support layer from the surface of the substrate;

[0012] S5: Transfer the stacked structure onto the target substrate and adhere it firmly to the target substrate;

[0013] S6: Sequentially remove the support layer from the target substrate, leaving the electrodes intact.

[0014] In a preferred embodiment of the present invention, a layered material with excellent single crystal properties is selected as the substrate, and the substrate is mechanically cleaved to obtain a surface with atomic-level flatness, which serves as a carrier for subsequent electrode patterning. This type of substrate has good mechanical strength and thermal stability, can be reused, and significantly reduces transfer costs.

[0015] In a preferred embodiment of the present invention, photoresist is spin-coated onto the surface of a cleaved substrate and dried to form a photoresist layer. A patterned opening region is then formed by ultraviolet exposure and development. Subsequently, a metal material is deposited on the photoresist surface using electron beam evaporation technology to form a metal film. Finally, the photoresist is removed by a lift-off process, leaving the patterned metal layer to form the electrode to be transferred.

[0016] In a preferred embodiment of the present invention, a 100 μm thick PDMS film is laminated with a 200 μm thick PVC sheet to form a flexible support layer; the PDMS side of the support layer is gently placed on the surface of the electrode layer to achieve adhesion; due to the good self-adhesion of PDMS to an atomically flat surface, excessive pressure is not required during lamination to prevent electrode tearing due to stress release during the subsequent peeling process (step S4); after lamination, the sample can be heated to 50°C and held for 10 minutes, and then naturally cooled to room temperature, thereby enhancing the interfacial adhesion stability between PDMS and the electrode layer.

[0017] In a preferred embodiment of the present invention, the laminated structure consisting of a substrate / electrode layer / support layer is immersed in deionized water and left to stand for 12 hours, allowing water to penetrate into the interface between the substrate layers. This process can effectively alleviate the interfacial adsorption force, thereby reducing the stress required for mechanical peeling and improving the peeling integrity. Subsequently, the structure is removed and the residual moisture on the surface is blown dry to keep the surface dry. Afterward, the electrode layer / support layer is manually peeled off from the substrate as a whole. Experiments have shown that 12 hours is a suitable immersion time, which can significantly reduce the peeling difficulty and avoid electrode structure tearing or substrate fragment residue. If the immersion time exceeds 72 hours, the electrode may detach on its own in the water. If the immersion time is less than 6 hours, the peeling force increases, and there is a risk of structural damage.

[0018] In a preferred embodiment of the present invention, the PVC side of the electrode layer / support layer stack is attached to a glass plate with the PVC side facing outward to assist in the operation; the target substrate is precisely aligned using a transfer platform, and the electrode layer is attached to the surface of the target substrate with the electrode layer facing down; after alignment, a certain pressure is applied in the attached state, and the temperature is heated to 150°C and held for 5 minutes to enhance the contact strength and adhesion between the metal electrode and the target substrate; the target substrate can be a silicon oxide / single crystal silicon substrate, and the surface can be pre-transferred with two-dimensional semiconductor materials (such as MoS2, WSe2, etc.), which is suitable for constructing high-performance heterojunction devices.

[0019] In a preferred embodiment of the present invention, the support layer is first slowly peeled off from the target substrate to avoid stretching or curling of the electrode layer; after peeling, the metal electrode is firmly retained on the surface of the target substrate. No chemical solvents are used in the entire transfer process, thus avoiding interface contamination, material corrosion or other wet-process related problems.

[0020] Compared with the prior art, the beneficial effects of the present invention are:

[0021] 1. This invention employs a dry electrode transfer strategy using a cleaved substrate 1 as the starting platform. This effectively avoids the dependence on high-cost single-crystal graphene and other special substrates 1 required by traditional methods. Furthermore, it eliminates the need for chemical modifiers such as HMDS, making it more environmentally friendly and demonstrating superior transfer success rate. This method exhibits significant advantages in material cost, fabrication safety, and peeling effect. In addition, utilizing the hydrophilicity of a portion of the substrate 1, moderate water immersion before transfer reduces interfacial adsorption strength, lowers the stress required for peeling, avoids mechanical damage, and keeps the electrode interface dry, ensuring the stability of subsequent bonding and device performance. Compared to the potential problems of uneven stress, electrode deformation, or insufficient transfer accuracy in traditional dry methods, this invention provides superior structural stability and operational controllability.

[0022] Meanwhile, the present invention allows for multiple transfer operations on the same target substrate 5, or for the centralized transfer of multiple electrode structures fabricated in parallel on different substrates 1, effectively breaking the bottleneck caused by traditional serial processes, improving integration efficiency and yield, and is particularly suitable for mass production and the construction of complex device architectures.

[0023] 2. This invention provides a pure dry electrode transfer process that does not rely on any liquid treatment, significantly improving transfer efficiency and yield, reducing overall fabrication costs, and avoiding the use of toxic chemical reagents in traditional wet processes, making the process greener and safer. The technical solution of this invention has excellent substrate compatibility, enabling free transfer of electrodes from different types of substrates to any target substrate 5 without requiring special pretreatment of the substrate 1. It is applicable to various material systems such as silicon, oxides, glass, polymers, and metals. This invention completely avoids any liquid phase treatment steps during the entire electrode transfer process, eliminating solvent residue, interface contamination, and material corrosion from the source, ensuring the high cleanliness and stability required for two-dimensional devices. The transfer process of this invention can be carried out at room temperature, without relying on high-temperature heat treatment, which helps protect heat-sensitive materials, simplifies equipment configuration, and improves the versatility and flexible manufacturing capabilities of the fabrication process. The method proposed in this invention supports multiple repeated electrode transfers on the same target substrate 5, and also supports the parallel fabrication and centralized transfer of multiple electrode modules on different substrates 1, significantly improving integration efficiency and large-scale fabrication capabilities, and is suitable for the manufacturing needs of multilayer structures, heterogeneous interface construction, and large-area devices. Attached Figure Description

[0024] To facilitate understanding by those skilled in the art, the present invention will be further described below with reference to the accompanying drawings.

[0025] Figure 1 : Flowchart of the transfer electrode of the present invention.

[0026] Figure 2 Schematic diagram of a cleaved substrate.

[0027] Figure 3 : A schematic diagram of the electrode to be transferred being fabricated on the surface of the substrate.

[0028] Figure 4 A schematic diagram showing the support layer disposed on the substrate and the electrode surface.

[0029] Figure 5 : A schematic diagram of peeling the stacked structure consisting of the electrode / support layer from the surface of the substrate.

[0030] Figure 6 : A schematic diagram of attaching the stacked structure consisting of the electrode / support layer to the target substrate.

[0031] Figure 7 : A schematic diagram of removing the support layer from the stacked structure consisting of the target substrate / electrode.

[0032] 1. Substrate; 2. Metal layer; 3. Photoresist layer; 4. Support layer; 5. Target substrate. Detailed Implementation

[0033] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0034] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of the invention. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0035] Please see Figure 1 - Figure 7 A polymer-based dry electrode transfer method includes the following steps:

[0036] S1: Provides a high-flatness substrate 1 for cleaving; a layered material with excellent single crystal properties (such as natural mica) is selected as the substrate 1, and cleaving is performed mechanically to obtain a surface with atomic-level flatness, which serves as a carrier for subsequent electrode patterning; this type of substrate 1 has good mechanical strength and thermal stability, can be reused, and significantly reduces transfer costs;

[0037] S2: An electrode to be transferred is fabricated on the surface of the substrate 1; a photoresist layer 3 is formed by spin-coating and drying on the cleaved substrate 1 surface, and a patterned opening area is formed by ultraviolet exposure and development process; subsequently, a metal material is deposited on the photoresist surface using electron beam evaporation technology to form a metal film; finally, the photoresist is removed by the lift-off process, leaving the patterned metal layer 2, which constitutes the electrode to be transferred.

[0038] S3: A support layer 4 is provided on the electrode surface; a 100μm thick PDMS film is bonded to a 200μm thick PVC sheet to form a flexible support layer 4; the PDMS side of the support layer 4 is gently placed on the electrode surface to bond it; due to the good self-adhesion of PDMS to an atomically flat surface, no excessive pressure is required during bonding to prevent the electrode from tearing due to stress release during the subsequent peeling process (step S4); after bonding, the sample can be heated to 50°C and held for 10 minutes, and then naturally cooled to room temperature to enhance the interfacial adhesion stability between PDMS and the electrode layer;

[0039] S4: Mechanically peel the stacked structure composed of the electrode / support layer 4 from the surface of the substrate 1; immerse the stacked structure composed of substrate 1 / electrode layer / support layer 4 in deionized water and let it stand for 12 hours to allow water to penetrate into the interlayer interface of substrate 1; this process can effectively alleviate the interfacial adsorption force, thereby reducing the stress required for mechanical peeling and improving the peeling integrity; then remove and blow dry the residual moisture on the surface to keep the surface dry; after that, manually peel the electrode layer / support layer 4 from the substrate 1 as a whole; experiments have shown that 12 hours is a suitable soaking time, which can significantly reduce the peeling difficulty and avoid electrode structure tearing or substrate 1 fragments remaining; if the soaking time exceeds 72 hours, the electrode may fall off in the water on its own; if it is less than 6 hours, the peeling force increases, and there is a risk of structural damage.

[0040] S5: Transfer the stacked structure to the target substrate 5 and firmly attach it to the target substrate 5; attach the PVC side of the electrode layer / support layer 4 stacked structure to a glass plate with the PVC side facing outwards to assist the operation; use the transfer platform to accurately align the target substrate 5 and attach the electrode layer downwards to the surface of the target substrate 5; after alignment, apply a certain pressure in the attached state and heat to 150°C for 5 minutes to enhance the contact strength and adhesion between the metal electrode and the target substrate 5; the target substrate 5 can be a silicon oxide / single crystal silicon substrate, and the surface can be pre-transferred with two-dimensional semiconductor materials (such as MoS2, WSe2, etc.), which is suitable for constructing high-performance heterojunction devices;

[0041] S6: Sequentially remove the support layer 4 from the target substrate 5, retaining the electrode; firstly, slowly peel the support layer 4 from the target substrate 5 to avoid stretching or curling the electrode layer; after peeling, the metal electrode is firmly retained on the surface of the target substrate 5. No chemical solvents are used in the entire transfer process, avoiding interface contamination, material corrosion or other wet process-related problems.

[0042] In a preferred embodiment of the present invention, the substrate 1 material is replaced as follows: In addition to the cleaved substrate 1 (such as natural mica), other materials with high surface flatness, low cost and no surface dangling bonds (such as certain oxide single crystals, metal oxide layers, etc.) can be used as electrodes to prepare substrate 1, provided that they can maintain structural integrity and electrode interface quality during the transfer process.

[0043] In a preferred embodiment of the present invention, surface modification technology is used as an alternative: For common low-cost substrate 1 materials such as single-crystal silicon and silicon oxide, but which have surface dangling bonds or large roughness, low-cost, non-polluting surface treatment methods (such as plasma treatment, self-assembled monolayer modification, etc.) can be used to passivate and flatten their surface structure, thereby serving as a preparation platform for electrode patterning and replacing the cleaved substrate 1 in the overall process flow of the present invention.

[0044] In a preferred embodiment of the present invention, the support layer 4 system is replaced as follows: The PDMS / PVC support structure used in the present invention can be replaced with other multilayer material structures with good mechanical support and self-peeling properties, such as a transparent polyester / elastomer composite film system, to meet the requirements of different transfer strength or controllability.

[0045] In a preferred embodiment of the present invention, the heating method is replaced: the heat treatment applied during the bonding process (such as 150°C) can be replaced by light heating, far-infrared heating or micro-hot plate heating, etc. The specific method can be selected according to the thermal sensitivity characteristics of the target substrate 5, thereby achieving more flexible equipment adaptation.

[0046] In use, this invention provides a cleaved, highly flat substrate; an electrode to be transferred is fabricated on the surface of the substrate; a support layer is disposed on the surface of the electrode; the stacked structure consisting of the electrode and support layer is mechanically peeled off from the surface of the substrate; the stacked structure is transferred to a target substrate and firmly bonded to the target substrate; the support layer is then removed from the target substrate, leaving the electrode intact.

[0047] Thresholds, preset values, preset ranges, etc. are set for result comparison and analysis to determine whether they are good or bad. The value of these thresholds is determined by a combination of large-scale model analysis of sample data and human experience. They can also be adjusted appropriately based on seasonal or common-sense influences.

[0048] Furthermore, the settings for weighting ratios, influence factors, etc., are based on the magnitude of each parameter's influence on the results. The specific values ​​are allocated to ultimately reflect the impact on the results. The settings for input and storage are also determined by a combination of large-scale model analysis of sample data and human experience. Appropriate adjustments can also be made based on seasonal or rational influence conditions.

[0049] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to any specific implementation. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.

Claims

1. A polymer-based dry electrode transfer method, characterized in that, Includes the following steps: S1: Provides a highly flat substrate for cleavage (1); S2: Fabricate the electrode to be transferred on the surface of the substrate (1); S3: A support layer (4) is provided on the surface of the electrode; S4: Mechanically peel the stacked structure composed of the electrode / support layer (4) from the surface of the substrate (1); S5: Transfer the stacked structure to the target substrate (5) and adhere it firmly to the target substrate (5); S6: Sequentially remove the support layer (4) from the target substrate (5), leaving the electrode intact.

2. The polymer-based dry electrode transfer method according to claim 1, characterized in that, A layered material with excellent single crystal properties is selected as the substrate (1), and a surface with atomic-level flatness is obtained by mechanical cleaving, which serves as the carrier for subsequent electrode patterning.

3. The polymer-based dry electrode transfer method according to claim 2, characterized in that, Photoresist is spin-coated onto the surface of the cleaved substrate (1) and dried to form a photoresist layer (3), which is then exposed to ultraviolet light and developed to form a patterned opening area. Subsequently, metal material is deposited on the photoresist surface using electron beam evaporation technology to form a metal film; finally, the photoresist is removed by lift-off process, leaving the patterned metal layer (2) to form the electrode to be transferred.

4. The polymer-based dry electrode transfer method according to claim 3, characterized in that, A 100μm thick PDMS film is bonded to a 200μm thick PVC sheet to form a flexible support layer (4); the PDMS side of the support layer (4) is gently placed on the surface of the electrode layer to bond it; due to the good self-adhesion of PDMS to an atomically flat surface, no excessive pressure is required during bonding to prevent the electrode from tearing due to stress release during the S4 peeling process; after bonding, the sample can be heated to 50°C and held for 10 minutes, and then naturally cooled to room temperature to enhance the interfacial adhesion stability between PDMS and the electrode layer.

5. The polymer-based dry electrode transfer method according to claim 4, characterized in that, The stacked structure consisting of substrate (1), electrode layer, and support layer (4) was immersed in deionized water and left to stand for 12 hours to allow water to penetrate into the interlayer interface of substrate (1). Then it was removed and the residual moisture on the surface was blown off to keep the surface dry. After that, the electrode layer / support layer (4) was manually peeled off from the substrate (1) as a whole.

6. The polymer-based dry electrode transfer method according to claim 5, characterized in that, The PVC side of the electrode layer / support layer (4) stack is attached to a glass plate with the electrode layer / support layer (4) stack facing out to assist the operation. The target substrate (5) is precisely aligned using a transfer platform, and the electrode layer is attached to the surface of the target substrate (5) with the electrode layer facing down. After alignment, a certain pressure is applied in the attached state, and the temperature is heated to 150°C and held for 5 minutes to enhance the contact strength and adhesion between the metal electrode and the target substrate (5). The target substrate (5) can be a silicon oxide / single crystal silicon substrate, and two-dimensional semiconductor materials can be pre-transferred on the surface, which is suitable for building high-performance heterojunction devices.

7. The polymer-based dry electrode transfer method according to claim 6, characterized in that, First, the support layer (4) is slowly peeled off from the target substrate (5) to avoid stretching or curling the electrode layer; after peeling, the metal electrode is firmly retained on the surface of the target substrate (5), and no chemical solvents are used in the entire transfer process.

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