A water / weak acid soluble multinary oxide sacrificial layer electrode transfer method

Abstract

The present application relates to the technical field of microelectronic device manufacturing, and particularly relates to a cleaning electrode transfer method of water / weak acid soluble multi-component oxide sacrificial layer. The method comprises the following steps: preparing a multi-component oxide film as a sacrificial layer on a single crystal substrate; making a patterned electrode and covering a thermal release support layer thereon; selectively dissolving the sacrificial layer by immersing in deionized water or weak acid aqueous solution, so that the electrode / support layer stack is separated from the substrate; and then transferring the stack to a target substrate, heating to make the support layer desorb, and completing the electrode transfer. The present application uses water or weak acid etching, avoids highly toxic reagents such as hydrofluoric acid, is green and safe, the transfer process is mild, the electrode pattern is complete and the interface is clean, and particularly, for Ti / Cr adhesion layer electrodes, a nanoscale oxide residual layer can be naturally reserved as a controllable oxygen ion source of oxygen vacancy memristor, which significantly improves the device performance.

Description

Technical Field

[0001] This invention relates to the field of microelectronic device manufacturing technology, and specifically to a method for cleaning electrode transfer of a water / weak acid soluble multi-component oxide sacrificial layer. Background Technology

[0002] In the field of microelectronic device manufacturing, electrode transfer technology has become a key alternative process to avoid physical or chemical damage that may be caused by directly depositing metal electrodes on the surface of sensitive functional layers. Currently, commonly used temporary substrates or transfer media mainly include polymers such as single-crystal silicon, graphene, and polydimethylsiloxane (PDMS).

[0003] When using single-crystal silicon as the substrate, the dangling bonds on its surface make electrode-substrate separation exceptionally difficult. This often necessitates surface treatment with toxic reagents such as hexamethyldisilazane (HMDS) vapor to reduce adhesion, or etching separation using highly corrosive and toxic solutions like hydrofluoric acid. These processes not only pose environmental and safety risks but also make it difficult to retain the intended functional nano-oxide interface layer between the electrode and the target substrate. Graphene, with its smooth van der Waals surface, provides lower adhesion for electrode separation, alleviating the separation problem to some extent. However, it is prone to cracking and debris residue during transfer, potentially contaminating the electrode interface and affecting device performance. Other polymer transfer media, such as PDMS, while lower in cost and possessing some flexibility, may leave organic impurities or introduce internal stress during use, thereby compromising the integrity of the electrode structure and the cleanliness of the interface.

[0004] In recent years, water-soluble oxide materials (such as Sr4Al2O7) have made significant progress as sacrificial layers in the fabrication of self-supporting oxide single-crystal thin films. However, this technology is primarily geared towards the stripping and transfer of functional oxide thin films. When attempting to apply this approach to the clean and non-destructive transfer of interface-sensitive patterned metal electrodes, a series of new and unresolved technical challenges arise: such as maintaining the integrity of the pattern, the lack of precise control over interface properties, and process adaptability issues. For next-generation memristors and other devices that rely on interfacial ion migration, such as oxygen vacancy migration, the chemical state and physical structure of the interface are crucial.

[0005] Therefore, how to combine the environmental advantages of water-soluble / weakly acid-soluble oxide sacrificial layers with the clean, non-destructive, and interface-controllable transfer of patterned metal electrodes to develop an environmentally friendly, cost-controllable electrode transfer alternative that can achieve a high-quality clean interface has become a technical challenge that urgently needs to be overcome. Summary of the Invention

[0006] The purpose of this invention is to overcome the defects of existing electrode transfer technologies, such as interface contamination, use of toxic reagents, and inability to precisely control interface characteristics; and to address the problems of poor electrode pattern integrity, uncontrollable interface characteristics, and insufficient process compatibility when applying water-soluble / weak acid-soluble oxide sacrificial layer technology to the clean transfer of patterned metal electrodes, and to provide a clean electrode transfer method using water / weak acid-soluble multi-component oxide sacrificial layers.

[0007] The technical solution of this invention is implemented as follows: In a first aspect, the present invention proposes a method for cleaning electrode transfer of a water / weakly acid-soluble multi-component oxide sacrificial layer, comprising the following steps: S1. Provide a single crystal substrate and prepare a multi-element oxide thin film as a sacrificial layer on it; S2. Fabricate the electrode to be transferred on the multi-element oxide film; S3. Cover the surface of the electrode to be transferred and the multi-electrode oxide film with a heat release support layer to form a stacked structure; S4. Immerse the stacked structure in a selective etching solution corresponding to the multi-component oxide film to dissolve the multi-component oxide film and separate the stacked structure of the electrode to be transferred and the heat release support layer from the single crystal substrate. The selective etching solution includes deionized water or a weak acid aqueous solution; S5. Transfer the stacked structure of the separated electrode to be transferred and the heat release support layer to the target substrate, and make the electrode to be transferred into contact with the target substrate; S6. The heat release support layer is separated from the electrode to be transferred by heating.

[0008] Preferably, the multi-element oxide film includes Sr3Al2O6 film, Sr4Al2O7 film, and SrCoO film. 2.5 Thin film or SrFeO 2.5 film.

[0009] Preferably, in the selective etching solution, SrCoO 2.5 Thin film or SrFeO 2.5 The thin films include aqueous solutions of acetic acid or citric acid; for Sr3Al2O6 or Sr4Al2O7 thin films, deionized water with a resistivity greater than 18.2 MΩ·cm is used.

[0010] Specifically, choose a weak acid with a pH value between 2.5 and 3.5, preferably an acetic acid solution with a volume concentration of 5% to 40%, or a citric acid solution with a mass concentration of 0.25% to 1%, as well as vinegar, Sprite, etc.; when the pH value is less than 2.5, the heat-sensitive adhesive coated on the heat-release film will fail; if the pH value is greater than 3.5, SrCoO 2.5The dissolution rate will decrease significantly if the pH value is close to 7 or higher; SrCoO 2.5 Dissolution will stop; the theoretical maximum resistivity of ultrapure water at 25°C is 18.2 MΩ·cm, which is close to complete deionization; in etching, if ordinary water is used, residual ions and impurities may participate in chemical reactions, leading to unstable etching rates and film surface contamination. Therefore, ultrapure water is required to maintain process controllability and repeatability.

[0011] Preferably, the thickness of the multi-element oxide film is 10 nm to 200 nm.

[0012] Specifically, when the film thickness is too thin, the film may be discontinuous or have poor coverage, making it prone to breakage during subsequent patterning electrode processes and transfer, leading to sacrificial layer failure and electrode pattern damage. When the film thickness is too thick, although mechanical support is enhanced, the film growth time will be significantly prolonged, not only reducing process efficiency but also worsening the surface flatness of the film, resulting in an uneven lower surface of the electrode. In addition, an excessively thick film may lead to uneven etching, especially below the edge of the pattern, where incompletely dissolved sacrificial layer residues may remain due to poor diffusion. A thickness in the range of 10~200 nm can ensure both the continuity of the film and sufficient mechanical strength to support the patterned electrode, while also ensuring the flatness of the lower surface of the electrode after etching, thus ensuring the efficiency and success rate of the transfer process.

[0013] Preferably, the single-crystal substrate comprises SrTiO3, LaAlO3, or (LaAlO3). 0.3 (SrAl 0.5 Ta 0.5 O3) 0.7 DyScO3 or K2Ti8O 17 Substrate.

[0014] More preferably, the method for fabricating the electrode to be transferred in step S2 includes: using a conventional photolithography process or a hard mask for masking, and then depositing electrode metal by electron beam evaporation or magnetron sputtering.

[0015] Preferably, the heat-release support layer comprises a heat-release PET film.

[0016] More preferably, the heat release support layer is a polymer film with heat-release properties; it is covered on the surface of the electrode and the multi-element oxide film, and the initial bonding is usually achieved by applying a slight pressure (0.1~0.5 MPa) at room temperature (25~35℃).

[0017] More preferably, after the separation in step S4 is completed, the separated electrode / support layer stack structure is rinsed with deionized water to remove residual etching solution and reaction products on its surface.

[0018] More preferably, step S5 specifically includes: accurately aligning and placing the cleaned electrode / heat release support layer stacked structure onto the target substrate using a precision transfer tool (micro-manipulation probe stage); and applying slight pressure (0.05~0.2MPa) to ensure initial contact.

[0019] More preferably, the target substrate comprises a silicon wafer or a flexible polymer substrate with an oxide semiconductor functional layer deposited thereon.

[0020] Preferably, the heating in step S6 is a two-stage heating: first heating to 50 ℃±2 ℃ and holding for 10 min, then heating to 80~150 ℃ and holding for more than 10 min; this can ensure that the heat release film completely loses its stickiness.

[0021] Specifically, controlling the temperature in the second stage between 80℃ and 150℃ is a comprehensive consideration of the performance of the heat-release support layer and the safety of the device. This temperature range is crucial for achieving complete and controllable failure of the heat-release support layer's adhesion. If the heating temperature is too low, the support layer will not reach its critical temperature for complete heat release, and its adhesion will not decrease sufficiently. This will result in the adhesion still being sufficient to "grip" the electrode during peeling, potentially causing the electrode to fail to detach completely from the support layer or to break during peeling, leading to transfer failure. If the heating temperature is too high, the polymer substrate or adhesive of the support layer may become excessively softened, thermally decomposed, or even carbonized, producing difficult-to-remove organic residues that contaminate the electrode-substrate interface. At the same time, excessively high temperatures may cause thermal damage to the heat-sensitive target substrate or functional layer, and lead to electrode pattern deformation due to increased thermal stress. A more preferable temperature is 100~120℃, which ensures complete and controllable failure of the support layer's adhesion, thereby achieving clean and complete electrode peeling, while minimizing the aforementioned high-temperature risks and ensuring the reliability and repeatability of the process.

[0022] More preferably, the heating process can be carried out on an atmospheric pressure heating stage or a vacuum heating chamber to completely de-adhere the heat release support layer, thereby achieving its clean and complete separation from the electrode; after the sample cools to room temperature or a temperature that can be directly operated with tools, the de-adhesive heat release support layer is gently peeled off or detached with tweezers or other tools, and finally the desired electrode structure is obtained on the target substrate.

[0023] Preferably, the electrode to be transferred comprises a single-layer metal electrode of gold, silver, platinum, or palladium, or a double-layer electrode of titanium / gold or chromium / gold.

[0024] In a second aspect, the present invention provides a memristor device, the electrodes of which are fabricated by transfer using the method described in the first aspect.

[0025] Preferably, when the electrode to be transferred is a titanium / gold or chromium / gold bilayer structure, a nanoscale oxide residue layer formed by the natural oxidation of the titanium or chromium adhesion layer in the electrode to be transferred is retained between the electrode to be transferred and the target substrate. The chemical composition of the oxide residue layer includes TiO2 or Cr2O3.

[0026] Compared with the prior art, the advantages of the present invention are as follows: (1) The present invention uses water or weak acid (such as acetic acid or citric acid) as etching solution, which completely avoids highly toxic and corrosive reagents such as HF, and the process is green and safe.

[0027] (2) The present invention achieves complete, low-stress peeling and transfer of electrodes by combining gentle wet etching with a heat release support layer, resulting in a clean interface and no organic or debris contamination.

[0028] (3) This invention uniquely utilizes the transfer process itself to naturally form and retain a nanoscale functional oxide residue layer (TiO2) between the electrode (especially the Ti or Cr-containing adhesion layer) and the target substrate. x or CrO x This layer can serve as a controllable oxygen ion source for oxygen vacancy memristors, significantly improving the resistance switching uniformity and cycle durability of the device.

[0029] (4) The present invention can transfer fine and complex graphics such as stripes with a line width of 50μm, with complete graphics and clear edges.

[0030] (5) This invention does not require complex equipment, is safe and easy to operate, and is particularly suitable for the fabrication of advanced electronic devices such as oxygen vacancy memristors that require a controllable oxide residual layer to be retained at the electrode-functional layer interface. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 A schematic flowchart of the electrode transfer method provided by the present invention; Figure 2 This is a schematic diagram of the structure of the present invention after depositing a multi-element oxide thin film on a single crystal substrate; Figure 3 This is a schematic diagram of the structure of the present invention after patterned electrodes are fabricated on a multi-component oxide thin film; Figure 4 This is a schematic diagram of the stacked structure of the present invention after the heat release support layer is covered; Figure 5 This is a schematic diagram of the electrode / support layer stack structure selectively etched away according to the present invention; Figure 6 This is a schematic diagram of the structure after the electrode is transferred to the target substrate according to the present invention; Figure 7 This is a schematic diagram of the final structure after the heat release support layer is removed by heating and the electrode transfer is completed according to the present invention. Figure 8 Schematic diagrams of single-layer and double-layer electrodes, and their nanoscale oxide residue layers; Figure 9 This is a schematic diagram of the electrode after transfer in Embodiment 1 of the present invention; Figure 10 This is a schematic diagram of the electrode after transfer in Embodiment 2 of the present invention; Figure 11 This is a schematic diagram of the electrode after transfer in Embodiment 3 of the present invention; Figure 12 This is a schematic diagram of the electrode after transfer in Comparative Example 1 of the present invention.

[0033] Among them, 1-single crystal substrate, 2-multi-element oxide thin film, 3-electrode to be transferred, 4-heat release support layer, 5-target substrate, 6-metal conductive layer, 7-adhesion layer. Detailed Implementation

[0034] The embodiments of the present invention are described in detail below. These embodiments are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention.

[0035] The electrode transfer method provided by this invention utilizes a type of multi-element oxide film soluble in water or weak acid as a sacrificial layer, combined with a heat release support layer, to achieve an environmentally friendly, simple, and precisely controllable metal electrode transfer technology.

[0036] The core of this method lies in achieving complete and low-damage electrode stripping through selective chemical etching and reliable bonding of the electrode to the target substrate through a programmed thermal release process. Specifically, a flat multi-element oxide sacrificial layer is first prepared on a single-crystal substrate, followed by the fabrication of a patterned metal electrode and the covering of a thermal release support layer. The sacrificial layer is dissolved by immersing the stacked structure in a corresponding selective etching solution (such as a weak acid solution or high-purity deionized water), achieving clean separation of the electrode from the substrate. After rinsing, the separated electrode structure is transferred to the target substrate, and the thermal release support layer is desorbed through a two-stage heating process (e.g., first holding at 50°C for 10 min, then raising the temperature to 80-150°C and holding for 15 min), ultimately obtaining a high-quality electrode structure with a clean interface.

[0037] Furthermore, a significant feature and innovation of the method described in this invention lies in its ability to naturally form and retain a nanoscale functional interface layer between the electrode and the target substrate using the transfer process itself. Specifically, when using reactive metals such as titanium (Ti) and chromium (Cr) as the adhesion layer for the electrode, they will naturally oxidize during the process, forming an extremely thin residual layer of oxides such as TiO2 or Cr2O3 at the bottom of the electrode. This residual layer is not a process defect, but a functional layer that is intentionally utilized. In devices such as oxygen-vacancy memristors, this oxide layer can serve as a controllable oxygen ion source, providing the necessary oxygen ions for the formation and stabilization of conductive filaments, thereby significantly improving the resistive switching uniformity and cycle durability of the device. This is something that traditional transfer methods using highly corrosive etching solutions such as HF (which completely destroy or remove such interface layers) cannot achieve, thus realizing an organic combination of environmentally friendly processes and high-performance interface control.

[0038] It is important to note that the method of this invention not only achieves the clean transfer of patterned metal electrodes, but its process characteristics also allow for beneficial and constructive control of the electrode-target substrate interface. Existing techniques, such as HF etching, while pursuing clean stripping, often completely destroy the natural oxide layer or predetermined interface at the bottom of the electrode. In contrast, the water or weak acid etching solution used in this invention is relatively gentle on the oxide layers of metals such as Ti and Cr, allowing the thin oxide layer naturally formed during electrode fabrication to be retained after transfer. This retained nanoscale oxide residue layer plays a crucial role in constructing high-performance electronic devices.

[0039] It should be noted that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. Furthermore, in the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0040] In this document, the terms “containing,” “comprising,” or “including” are open-ended expressions, meaning they include the contents specified in this invention but do not exclude other aspects.

[0041] In this document, the terms “optional,” “optionally,” or “optional” generally refer to an event or condition that may, but may not, occur, and the description includes both cases in which the event or condition occurs and cases in which the event or condition does not occur.

[0042] The technical solutions in the embodiments of the present invention will be clearly and completely described below. 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 protection scope of the present invention.

[0043] Unless otherwise specified, all reagents used in this invention can be purchased from the market.

[0044] The SrTiO3 single crystal substrate, LaAlO3 single crystal substrate, and 0.7 wt% Nb:SrTiO3 target substrate were all purchased from Hefei Kejing Technology Co., Ltd.; the 25% acetic acid aqueous solution was prepared using AR-grade 99.5% glacial acetic acid and deionized water purchased from Beijing Inokai Technology Co., Ltd.; and the high-purity deionized water with a resistivity of 18.2 MΩ·cm was produced by UPT-I-10T ultrapure water system.

[0045] Example 1 This embodiment provides a SrCoO 2.5 The transfer method for transferring a 50 nm thick square gold electrode as a sacrificial layer includes the following steps: (1) Provide a SrTiO3 (STO) single crystal substrate 1, and use PLD to prepare SrCoO on it. 2.5 Thin film 2 serves as the sacrificial layer; the specific PLD process parameters are: substrate temperature 750 ℃, oxygen partial pressure 13 Pa, and laser energy density 1.5 J / cm². 2 The laser pulse frequency was 5 Hz; the deposition lasted for 20 min, resulting in a smooth SrCoO layer with a thickness of 30 nm. 2.5 film; (2) In the SrCoO 2.5 Patterned gold electrodes 3 are fabricated on thin film 2; the specific process is as follows: first, on SrCoO... 2.5 A layer of photoresist was spin-coated onto the surface of film 2, followed by UV exposure through a photomask. After development, a square electrode pattern was formed. The sample was then placed in an electron beam evaporation deposition machine to deposit a 50 nm thick gold electrode 3 at a deposition rate controlled at 0.5 Å / s. Finally, excess photoresist and metal were removed in acetone to obtain a clean square gold electrode 3 pattern with electrode dimensions of 50 μm × 50 μm. Figure 3 and Figure 9 The structure shown; (3) In the gold electrode 3 and the exposed SrCoO 2.5 A heat-release PET film is coated on the surface of film 2 as a heat-release support layer 4, corresponding to Figure 4The structure shown; a pressure of 0.2 MPa is applied at room temperature (25 °C) to allow the heat release support layer 4 to bond with the gold electrode 3 and SrCoO. 2.5 Thin film 2 adheres tightly to the surface to form SrCoO 2.5 A stacked structure of thin film 2 / gold electrode 3 / heat release support layer 4; (4) Immerse the above-mentioned stacked structure in a 25% volume concentration aqueous solution of acetic acid (selective etching solution); sacrificial layer SrCoO 2.5 Thin film 2 reacts chemically with a weak acid and dissolves; the entire process lasts for 10 hours at room temperature (25 °C). After etching, the gold electrode 3 / heat release support layer 4 stacked structure automatically separates from the STO single crystal substrate 1. Figure 5 The structure shown is rinsed three times with high-purity deionized water with a resistivity greater than 18.2 MΩ·cm to remove residual acetic acid and reaction products from the surface. (5) Take out the cleaned gold electrode 3 / thermal release support layer 4 stacked structure and place it in Hf after coating with deionized water. 0.5 Zr 0.5 On the O2 target substrate 5; a micro-manipulation probe stage is used for precise alignment, aligning the gold electrode 3 with the predetermined position on the target substrate 5; a slight pressure of 0.1 MPa is applied and held for 30 s to ensure initial contact between the gold electrode 3 and the surface of the target substrate 5, corresponding to... Figure 6 The structure shown; (6) Place the target substrate 5 with electrode 3 and heat release support layer 4 on a normal pressure heating stage; use a two-stage heating method for heating: the first stage heats to 50 ℃ and holds for 10 min; the second stage heats to 110 ℃ and holds for 15 min; after heating, gently peel off the heat release PET film 4, which has lost its adhesiveness, with tweezers, thus obtaining a complete square gold electrode 3 on the target substrate 5, corresponding to Figure 7 and Figure 9 The structure shown.

[0046] Using the above process, a 50 μm × 50 μm square gold electrode 3 was successfully and cleanly transferred from a temporary SrTiO3 single crystal substrate 1 to an Hf substrate. 0.5 Zr 0.5 The gold electrode 3 was deposited on the O2 target substrate 5. Microscopic observation showed that the transferred gold electrode 3 had a complete pattern, clear edges, and no visible wrinkles, breaks, or contamination. This example demonstrates the effectiveness of using weakly acid-soluble SrCoO2. 2.5 Thin film 2 serves as a sacrificial layer, demonstrating the feasibility of combining the heat-release support layer 4 with a selective wet etching transfer path. The entire process avoids the use of toxic etching agents such as hydrofluoric acid, showcasing the environmental friendliness and safety of the process. Furthermore, a clean interface is formed between the gold electrode 3 and the target substrate 5, laying the foundation for the subsequent fabrication of functional devices.

[0047] Example 2 This embodiment provides a method for transferring a circular electrode of 20 nm Ti / 50 nm Pt using Sr3Al2O6 as a sacrificial layer, including the following steps: (1) A LaAlO3 single crystal substrate 1 is provided, and a Sr3Al2O6 thin film 2 is prepared on it using PLD as a sacrificial layer; the specific PLD process parameters are: substrate temperature 800 ℃, oxygen partial pressure 1 Pa, laser energy density 1.8 J / cm 2 The laser pulse frequency was 3 Hz; the deposition lasted for 16 min, and a smooth Sr3Al2O6 film with a thickness of 10 nm was obtained. (2) A patterned titanium / platinum electrode 3 was fabricated on the Sr3Al2O6 thin film 2. The specific process is as follows: A tungsten alloy hard mask with an electrode pattern was used as a barrier layer, and the sample was placed in an electron beam evaporation coating machine. A 10 nm thick titanium adhesion layer 7 and a 50 nm thick platinum conductive layer 6 were deposited sequentially, with deposition rates controlled at 0.5 Å / s and 1.0 Å / s, respectively. Finally, the hard mask was removed to obtain a circular titanium / platinum electrode pattern 3 with an electrode size of 50 μm in diameter. Figure 3 and Figure 10 The structure shown; (3) The method of covering the heat release support layer 4 is the same as in Example 1; (4) The above-mentioned stacked structure was immersed in high-purity deionized water with a resistivity of 18.2 MΩ·cm; the sacrificial layer Sr3Al2O6 film 2 dissolved in water, and the whole process lasted for 10 min at room temperature (25 ℃); after etching, the titanium / platinum electrode 3 / heat release support layer 4 stacked structure automatically separated from the LaAlO3 single crystal substrate 1, corresponding to Figure 5 The structure shown is washed three times with high-purity deionized water with a resistivity greater than 18.2 MΩ·cm to remove residual reaction products on the surface. (5) The cleaned titanium / platinum electrode 3 / heat release support layer 4 stacked structure is retrieved and placed on the 0.7 wt% Nb:SrTiO3 target substrate 5 coated with deionized water; precise alignment is performed using a micro-manipulation probe stage to align the titanium / platinum electrode 3 with the predetermined position on the target substrate 5; a pressure of 0.1 MPa is applied slightly and held for 30 s to ensure initial contact between the titanium / platinum electrode 3 and the surface of the target substrate 5, corresponding to... Figure 6 The structure shown; (6) Place the target substrate 5 with electrode 3 and heat release support layer 4 on a normal pressure heating stage; use a two-stage heating method for heating: the first stage heats to 48 ℃ and holds for 10 min; the second stage heats to 80 ℃ and holds for 15 min; after heating, gently peel off the heat release PET film 4, which has lost its adhesiveness, with tweezers, thus obtaining a complete circular titanium / platinum electrode 3 on the target substrate 5, corresponding to Figure 7 and Figure 10 The structure shown; and a titanium oxide residual layer 7, such as TiO2, is retained between the titanium / platinum electrode 3 and the target substrate 5, with a cross-section as shown. Figure 8 As shown in (b) of the diagram.

[0048] This embodiment utilizes a gentle process of dissolving the Sr3Al2O6 sacrificial layer with deionized water, completely preserving the nanoscale TiO2 oxide residue layer naturally formed at the bottom of the Ti adhesion layer during electrode deposition. This interface structure contrasts sharply with Comparative Example 1. This preserved oxide interface layer provides a controllable oxygen ion source for the fabrication of oxygen-vacancy memristors, helping to stabilize the formation and breakage of conductive filaments, thereby potentially enabling the device to exhibit superior resistive switching uniformity and cycle durability. This embodiment not only verifies the feasibility of the water-soluble sacrificial layer route but also demonstrates the unique ability of the method of this invention to precisely construct and preserve functional interfaces while achieving clean electrode transfer.

[0049] Example 3 This embodiment provides a SrFeO 2.5 The transfer method for transferring a 50 nm thick strip gold electrode as a sacrificial layer includes the following steps: (1) Provide a SrTiO3 single crystal substrate 1, and use PLD to prepare SrFeO on it. 2.5 Thin film 2 serves as the sacrificial layer; the specific PLD process parameters are: substrate temperature 750 ℃, oxygen partial pressure 1 Pa, and laser energy density 1.5 J / cm². 2 The laser pulse frequency was 5 Hz; the deposition lasted for 120 min, resulting in a smooth SrFeO layer with a thickness of 200 nm. 2.5 film; (2) In the SrFeO 2.5 Patterned gold electrodes 3 were fabricated on thin film 2. The specific process is as follows: using a tungsten alloy hard mask with a striped electrode pattern as a barrier layer, the sample was placed in an electron beam evaporation coating machine; a 50 nm thick gold (Au) conductive layer 6 was deposited at a deposition rate of 0.5 Å / s; finally, the hard mask was removed to obtain the striped Au electrode pattern with a linewidth of 50 μm. Figure 3 and Figure 11 The structure shown; (3) The method of covering the heat release support layer 4 is the same as in Example 1; (4) Immerse the above-mentioned laminated structure in an aqueous solution of acetic acid with a volume concentration of 25%; sacrificial layer SrFeO 2.5 Thin film 2 reacts chemically with a weak acid and dissolves; the entire process lasts for 20 h at room temperature (25 °C). After etching, the gold electrode 3 / heat release support layer 4 stacked structure automatically separates from the STO single crystal substrate 1. Figure 5 The structure shown is rinsed three times with high-purity deionized water with a resistivity greater than 18.2 MΩ·cm to remove residual acetic acid and reaction products from the surface. (5) Take out the cleaned gold electrode 3 / thermal release support layer 4 stacked structure and place it in a SrFeO layer coated with deionized water. 2.5 On the target substrate 5; a micro-manipulation probe stage is used for precise alignment to ensure that the gold electrode 3 is aligned with the predetermined position on the target substrate 5; a slight pressure of 0.1 MPa is applied and held for 30 s to ensure initial contact between the gold electrode 3 and the surface of the target substrate 5. Figure 6 The structure shown; (6) Place the target substrate 5 with electrode 3 and heat release support layer 4 on a normal pressure heating stage; use a two-stage heating method for heating: the first stage heats to 52 ℃ and holds for 10 min; the second stage heats to 150 ℃ and holds for 15 min; after heating, gently peel off the heat release PET film 4, which has lost its adhesiveness, with tweezers, thus obtaining a complete strip gold electrode 3 on the target substrate 5, corresponding to Figure 7 and Figure 11 The structure shown.

[0050] This embodiment successfully transferred a 50 μm linewidth strip gold electrode from a SrTiO3 temporary substrate to a SrFeO substrate. 2.5 Target substrate. Microscopic characterization showed that the transferred strip electrode pattern was continuous and complete, with clear edges, and no breaks, wrinkles, or obvious deformation. This strip electrode structure, as a typical complex pattern with a high aspect ratio, demonstrates the high-fidelity transfer capability of the method of this invention for fine and complex patterned electrodes, providing a reliable technical solution for integrating high-precision patterned metal electrodes in advanced oxide electronic devices.

[0051] Comparative Example 1 This comparative example provides a traditional electrode transfer method based on a silicon wafer / PMMA / hydrofluoric acid system, including the following steps: (1) A single-crystal silicon wafer with a silicon dioxide layer formed by surface thermal oxidation is provided as a substrate. A tungsten alloy hard mask with an electrode pattern is used as a barrier layer. A 10 nm thick titanium adhesion layer and a 50 nm thick gold conductive layer are deposited sequentially by electron beam evaporation. The deposition rates are controlled at 0.5 Å / s and 1.0 Å / s, respectively. Finally, the hard mask is removed to obtain a circular titanium / gold electrode pattern with a diameter of 50 μm. Figure 12 The structure shown; (2) Spin-coating polymethyl methacrylate (PMMA) solution onto the patterned electrode and silicon wafer surface, and curing it at 150 °C for 10 min to form a support layer; (3) After mixing 40% hydrofluoric acid (HF) aqueous solution with deionized water at a volume ratio of 1:1, a hydrofluoric acid aqueous solution with a mass concentration of about 21% is obtained. The PMMA / electrode / SiO2 / Si composite structure is immersed in the above HF aqueous solution, and the SiO2 layer is etched away to separate the PMMA / electrode stack from the silicon substrate. (4) The separated PMMA / electrode stack was transferred to a 0.7% doped Nb:SrTiO3 target substrate, aligned and bonded, and then immersed in acetone solution to dissolve the PMMA support layer, ultimately leaving a titanium electrode on the target substrate. Figure 12 The structure shown.

[0052] The results show that this method cannot form or retain a nanoscale TiO2 layer at the bottom of the electrode, and the electrode cross-section is as follows: Figure 8 As shown in (a) above. Because the HF etching solution reacts violently with the Ti layer while dissolving the SiO2 sacrificial layer, it completely removes the extremely thin TiO2 interface layer naturally formed during electrode deposition. Simultaneously, the lack of controllable oxidation conditions—the acetone dissolution of PMMA is a room-temperature liquid-phase reaction—makes it impossible to provide a high-temperature or oxidizing atmosphere, thus hindering the re-oxidation of the Ti layer to form structurally stable TiO2. This comparative example reveals the inherent defects of the traditional method, which contrasts sharply with the present invention: in terms of environmental and safety risks, HF is a highly toxic and corrosive reagent, posing a significant threat to operational safety and environmental protection; in terms of interface function loss, the electrode-substrate interface is only a physical contact and cannot retain a functional oxide layer.

[0053] Comparative Example 2 The difference between this comparative example and the embodiment is that the SrCoO prepared in step (1) 2.5 The film thickness was controlled at 3 nm. The specific PLD process parameters were: substrate temperature 750 ℃, oxygen partial pressure 13 Pa, and laser energy density 1.5 J / cm². 2 The laser pulse frequency was 2 Hz; the deposition lasted for 5 min, resulting in a smooth SrCoO layer with a thickness of 3 nm. 2.5 Thin film; otherwise consistent with Example 1.

[0054] The results showed that the ultrathin sacrificial layer exhibited a discontinuous island-like structure immediately after deposition. During subsequent electron beam evaporation deposition of the gold electrode and the covering heat-releasing support layer, localized cracking occurred due to insufficient mechanical strength. During selective etching, the cracks directly exposed the underlying SrTiO3 substrate, exposing it to the acetic acid solution. Simultaneously, the gold electrode pattern above suffered severe wrinkling and fracture due to localized loss of support, resulting in complete transfer failure. This indicates that a sacrificial layer thickness of less than 10 nm cannot provide effective mechanical support.

[0055] Comparative Example 3 The difference between this comparative example and the embodiment is that the SrCoO prepared in step (1) 2.5 The film thickness was controlled at 300 nm. The specific PLD process parameters were: substrate temperature 750 ℃, oxygen partial pressure 13 Pa, and laser energy density 1.5 J / cm². 2 The laser pulse frequency was 10 Hz; the deposition duration was 100 min, resulting in a smooth SrCoO layer with a thickness of 300 nm. 2.5 Thin film; otherwise consistent with Example 1.

[0056] The results show that this thickness significantly increases the pulsed laser deposition time, and atomic force microscopy (AFM) characterization reveals increased surface roughness and decreased flatness. The underlying surface morphology of the gold electrode deposited on this rough surface deteriorates accordingly, leading to uneven electrode-substrate interface contact. During selective etching, the etchant diffusion path within the thickened sacrificial layer is prolonged, resulting in insufficient local exchange, particularly below the pattern edges, where sacrificial layer residue is prone to occur. Ultimately, the interface quality of the transferred electrode decreases, and process reliability is reduced. This comparative example demonstrates that an excessively thick sacrificial layer impairs deposition efficiency, degrades interface morphology, and introduces the risk of etching residue, thus highlighting the importance of controlling the thickness within an appropriate range.

[0057] Comparative Example 4 The difference between this comparative example and the embodiment is that the heating temperature in the second stage of step (6) is adjusted to 70 °C and maintained for 15 min, while the rest is the same as in embodiment 1.

[0058] The results showed that the adhesiveness of the heat-release PET support layer did not completely disappear after treatment at this temperature. Significant adhesion was felt when attempting to peel the support layer with tweezers. During the peeling process, the gold electrodes failed to detach completely from the support layer; most of the electrode area remained firmly on the support layer, while some areas in contact with the target substrate were torn apart, resulting in electrode pattern damage and leaving only incomplete electrode fragments on the target substrate. This indicates that insufficient heating temperature prevented the heat-release support layer from reaching an effective release state, causing the electrodes to fail to transfer successfully from the support layer to the target substrate, resulting in complete process failure.

[0059] Comparative Example 5 The difference between this comparative example and the embodiment is that the heating temperature in the second stage of step (6) is adjusted to 160°C and maintained for 15 min, while the rest is the same as in embodiment 1.

[0060] The results showed that at this high temperature, the heat-released PET support layer underwent significant shrinkage and deformation, accompanied by color deepening, indicating partial carbonization. After peeling, brown organic residues were observed on the target substrate and the gold electrode surface. Furthermore, due to increased thermal stress at high temperatures, slight warping occurred at some gold electrode edges. This indicates that excessively high heating temperatures can cause thermal degradation of the support layer, generating contaminants that are difficult to remove, and affecting the morphology and interface quality of the electrodes due to thermal stress.

[0061] The embodiments described above are some, but not all, of the embodiments of the present invention; the detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention; all other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for transferring a clean electrode with a water / weak acid-soluble multi-component oxide sacrificial layer, characterized in that, Includes the following steps: S1. Provide a single crystal substrate (1) and prepare a multi-element oxide thin film (2) on it as a sacrificial layer; S2. Fabricate the electrode to be transferred (3) on the multi-element oxide film (2); S3. A heat release support layer (4) is covered on the surface of the electrode to be transferred (3) and the multi-element oxide film (2) to form a stacked structure; S4. Immerse the stacked structure in a selective etching solution corresponding to the multi-element oxide film (2) to dissolve the multi-element oxide film (2) and separate the stacked structure of the electrode to be transferred (3) and the heat release support layer (4) from the single crystal substrate (1). The selective etching solution includes deionized water or a weak acid aqueous solution; S5. Transfer the stacked structure of the separated electrode to be transferred (3) and the heat release support layer (4) to the target substrate (5) and make the electrode to be transferred (3) contact the target substrate (5); S6. The heat release support layer (4) is separated from the electrode to be transferred (3) by heating.

2. The method according to claim 1, characterized in that, The multi-element oxide thin film (2) includes Sr3Al2O6 thin film, Sr4Al2O7 thin film, and SrCoO. 2.5 Thin film or SrFeO 2.5 film.

3. The method according to claim 2, characterized in that, The selective etching solution includes an aqueous solution of acetic acid or an aqueous solution of citric acid, used for SrCoO 2.5 Thin film or SrFeO 2.5 For thin films; or, the selective etching solution is deionized water with a resistivity greater than 18.2 MΩ·cm, used for Sr3Al2O6 thin films or Sr4Al2O7 thin films.

4. The method according to claim 1, characterized in that, The thickness of the multi-element oxide film (2) is 10 nm to 200 nm.

5. The method according to claim 1, characterized in that, The single-crystal substrate (1) includes SrTiO3, LaAlO3, and (LaAlO3). 0.3 (SrAl 0.5 Ta 0.5 O3) 0.7 DyScO3 or K2Ti8O 17 Substrate.

6. The method according to claim 1, characterized in that, The heat-release support layer (4) includes a heat-release PET film.

7. The method according to claim 1, characterized in that, The heating in step S6 is a two-stage temperature increase: first, heat to 50 ℃±2 ℃ and hold for 10 min, then heat to 80~150 ℃ and hold for more than 10 min.

8. The method according to claim 1, characterized in that, The electrode to be transferred (3) includes a single-layer metal electrode of gold, silver, platinum, or palladium, or a double-layer structure electrode of titanium / gold or chromium / gold.

9. A memristor device, characterized in that, The electrode is prepared by transfer using the method described in any one of claims 1 to 8.

10. The memristor device according to claim 9, characterized in that, When the electrode to be transferred (3) is a titanium / gold or chromium / gold bilayer structure, a nanoscale oxide residue layer formed by the natural oxidation of the titanium or chromium adhesion layer (7) in the electrode to be transferred (3) is retained between the electrode to be transferred (3) and the target substrate (5). The chemical composition of the oxide residue layer includes TiO2 or Cr2O3.

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