A thin film cantilever and a method of manufacturing the same

Abstract

The application discloses a thin film cantilever beam and a preparation method thereof, and relates to the technical field of two-dimensional material device construction and micro-nano processing technology. The core processes of designing a symmetrical mask plate, uniform coating, UV exposure, development, fixing, inductively coupled plasma etching, uniform coating, UV exposure, development, fixing, inductively coupled plasma etching, cleaning, solution soaking and metal layer plating are used to prepare a thin film cantilever beam which can be repeatedly prepared and used to transfer two-dimensional materials, so that the transfer cost of the two-dimensional materials is reduced, the transfer efficiency of the two-dimensional materials is improved, the pollution of the two-dimensional materials by organic matters is reduced, and the quality of the two-dimensional materials is improved. The laminated two-dimensional materials are repeatedly transferred by using the finally prepared thin film cantilever beam, and the transfer time of the two-dimensional materials is significantly reduced.

Description

Technical Field

[0001] This invention relates to the field of two-dimensional material device fabrication and micro / nano fabrication technology, and in particular to a thin-film cantilever beam and its preparation method. Background Technology

[0002] The existing technology for dry transfer of two-dimensional materials using the PDMS stamping method involves: rapidly pressing a glass slide containing the two-dimensional material onto a substrate to ensure close adhesion between the PDMS film and the substrate; after the two-dimensional material has adhered to the substrate, slowly lifting the glass slide to separate the PDMS film from the substrate, thus transferring the two-dimensional material onto the substrate. When transferring large quantities of two-dimensional material, a three-dimensional robotic arm is required for observation under a high-powered microscope.

[0003] The steps for wet transfer of two-dimensional materials using PC film assistance are as follows: methyl methacrylate is coated onto a metal substrate on which a monolayer of two-dimensional material has been grown; the two-dimensional material is transferred to the target location by etching away the metal with hydrochloric acid; and then the methyl methacrylate on the surface of the two-dimensional material is removed with acetone.

[0004] The steps for dry transfer of two-dimensional materials using PPC thermal release adhesive are as follows: attach a PPC film to the surface of the two-dimensional material or coat the material with PPC; mechanically peel the PPC and the two-dimensional material from the growth substrate using thermal release adhesive tape; after aligning with the target substrate, heat to the release temperature of PPC; the adhesion of PPC decreases sharply and partially decomposes after being heated, allowing the two-dimensional material to be released onto the target substrate.

[0005] The shortcomings of existing technologies are: the transfer media are all disposable polymers with poor reusability, resulting in high transfer costs and low efficiency of two-dimensional materials; when using dry and wet methods to transfer two-dimensional materials, the organic matter, polymer decomposition products and corrosion liquids introduced by the polymer transfer media directly contact the surface of the two-dimensional material remain on the surface of the two-dimensional material, resulting in poor quality of the two-dimensional material and long transfer time. Summary of the Invention

[0006] In view of this, embodiments of the present invention provide a thin-film cantilever beam and its preparation method to solve the technical problems of high transfer cost, low efficiency, poor quality and long time of two-dimensional materials.

[0007] In a first aspect, a method for preparing a thin-film cantilever beam is provided, the method comprising:

[0008] Step 100: The wafer with thin film on both sides is sliced, cleaned for the first time, and baked to obtain the dried wafer with thin film on both sides.

[0009] Step 200: Spin-coat photoresist onto the first surface of the wafer and perform post-baking treatment to obtain the wafer with thin films on both sides and photoresist on the first surface after post-baking.

[0010] Step 300: Using a mask, the wafer is subjected to a first exposure process, a first development process, a first fixing process, a first etching process, and a second cleaning process in sequence to obtain the wafer with the first surface etched.

[0011] Step 400: Spin-coat the photoresist onto the second surface of the wafer and perform a post-baking process to obtain the wafer with thin films on both sides and the photoresist on the second surface after post-baking;

[0012] Step 500: Using the mask, the wafer is subjected to a second exposure process, a second development process, a second fixing process, a second etching process, and a third cleaning process in sequence to obtain the wafer with the second surface etched.

[0013] Step 600: The wafer is placed in a pre-prepared solution for immersion treatment, a fourth cleaning treatment, and metal coating treatment on the first surface to obtain the thin film cantilever beam.

[0014] In a second aspect, a thin-film cantilever beam is provided, which is prepared using the thin-film cantilever beam preparation method described in the first aspect.

[0015] The advantages of this invention compared to the prior art are:

[0016] By preparing a reusable thin-film cantilever beam for the transfer of two-dimensional materials, the transfer cost of two-dimensional materials is reduced, the transfer efficiency of two-dimensional materials is improved, the contamination of two-dimensional materials by organic matter is reduced, and the quality of two-dimensional materials is improved. The repeated transfer of two-dimensional materials by the finally prepared thin-film cantilever beam significantly reduces the transfer time of two-dimensional materials. Attached Figure Description

[0017] To more clearly illustrate the technical solutions in the embodiments of the present invention, 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.

[0018] Figure 1 This is a schematic flowchart of a method for preparing a thin-film cantilever beam according to Embodiment 1 of the present invention;

[0019] Figure 2aThis is an optical microscope photograph of a square wafer obtained after the first exposure and first development processes, as provided in Embodiment 1 of the present invention. Figure 2b This is an optical microscope image of a square wafer obtained after the first etching process, as provided in Embodiment 1 of the present invention.

[0020] Figure 3a This is an optical microscope image of the square wafer obtained after the second etching process, as provided in Embodiment 1 of the present invention. Figure 3b An optical microscope image of a square wafer obtained after immersion treatment, provided in Embodiment 1 of the present invention;

[0021] Figure 4a These are optical microscope images of the thin-film cantilever beam and hBN two-dimensional material provided in Embodiment 10 of the present invention. Figure 4b These are optical microscope images of the hBN two-dimensional material lifted by a thin-film cantilever beam according to Embodiment 10 of the present invention. Figure 4c This is an optical microscope image of the thin-film cantilever beam with hBN two-dimensional material provided in Embodiment 10 of the present invention.

[0022] Figure 5a These are atomic force microscope images of hBN two-dimensional material placed under a thin-film cantilever beam, as provided in Embodiment 10 of this invention. Figure 5b These are atomic force microscope images of the PC film and hBN two-dimensional material provided in Embodiment 10 of the present invention.

[0023] Figure 6-1 This is a photograph of a wafer with thin films on both sides and photoresist on the first surface after post-baking, provided in Embodiment 10 of the present invention, after the first surface is aligned with the mask. Figure 6-2 This is a photograph of a wafer with thin films on both sides and photoresist on the first surface after the first exposure, as provided in Embodiment 10 of the present invention. Figure 6-3 This is a photograph of the wafer with the first surface etched, provided in Embodiment 10 of the present invention. Figure 6-4 This is a photograph of a wafer with thin films on both sides and photoresist on the second surface after post-baking, provided in Embodiment 10 of the present invention, after the second surface is aligned with the mask. Figure 6-5 This is a photograph of a wafer with thin films on both sides and photoresist on the second surface after the second exposure, as provided in Embodiment 10 of the present invention. Figure 6-6 This is a photograph of the wafer with the second surface etched, as provided in Embodiment 10 of the present invention. Figure 6-7 This is a photograph of the wafer after immersion treatment provided in Embodiment 10 of the present invention. Figure 6-8 This is a photograph of the thin-film cantilever beam provided in Embodiment 10 of the present invention. Figure 6-9 This is a photograph of a thin-film cantilever beam with hBN two-dimensional material adhered to it, provided in Embodiment 10 of the present invention. Detailed Implementation

[0024] To make the technical problems, technical solutions, and beneficial effects solved by this application clearer, the following detailed description is provided in conjunction with embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0025] like Figure 1 The diagram shown is a flowchart illustrating a method for preparing a thin-film cantilever beam according to Embodiment 1 of the present invention. This method may include the following steps:

[0026] Step 100: The wafer with thin film on both sides is sliced, cleaned for the first time, and baked to obtain the dried wafer with thin film on both sides.

[0027] Double-sided wafers with thin films refer to circular single-crystal silicon wafers with flexible thin films on both sides (circular wafers made from high-purity single-crystal silicon after cutting and polishing), which are the core substrate for fabricating thin-film cantilever beams. Slicing refers to the process of dividing large double-sided wafers with thin films into smaller square wafers using dicing or cutting processes. The first cleaning process involves using standard semiconductor cleaning procedures (such as ultrasonic cleaning or rinsing with deionized water, acetone, or isopropanol) to remove silicon chips, dust, surface-adhered particles, and contaminants such as oil and organic matter that may have been picked up during the slicing process. The baking process involves placing the cleaned square wafers with thin films on a constant-temperature hot plate for baking. The purpose is to remove moisture or residual solvents (such as acetone or isopropanol) adsorbed on the silicon nitride film and enhance the adhesion between the film and the photoresist.

[0028] In this embodiment, preferably, the flexible thin film on both sides of the wafer is a silicon nitride (Si3N4) film with a thickness of 500nm-1000nm. Preferably, the solvent for the first cleaning treatment is deionized water. The baking treatment refers to dehydration baking, preferably, the dehydration baking temperature is 100℃-140℃, and the dehydration baking time is 5min.

[0029] Step 200: Spin-coat photoresist onto the first surface of the wafer and perform post-baking treatment to obtain the wafer with thin films on both sides and photoresist on the first surface after post-baking.

[0030] In this context, photoresist refers to ultraviolet photoresists such as AZ1500 and SU8. The first surface refers to either the front or back surface of the wafer. Spin-coating photoresist involves dropping liquid photoresist onto the wafer surface and using high-speed centrifugal force (spin coating) to evenly spread the photoresist onto the silicon nitride film on the first surface of the wafer, forming a uniform and smooth photoresist film. Post-baking refers to the process of heating the wafer, which has film on both sides and photoresist on the first surface after spin-coating, on a constant-temperature hot plate. The purpose is to remove residual solvent from the photoresist and enhance the adhesion between the photoresist film and the silicon nitride film.

[0031] In this embodiment, preferably, the photoresist is AZ1500 ultraviolet photoresist. The post-baking temperature is 80℃-90℃, and the post-baking time is 30 minutes; preferably, the post-baking temperature is 90℃.

[0032] Step 300: Using a mask, the wafer is subjected to a first exposure process, a first development process, a first fixing process, a first etching process, and a second cleaning process in sequence to obtain the wafer with the first surface etched.

[0033] In photolithography, a photomask is a photolithographic material with a specific perforated pattern, serving as the core template for transferring patterns. The first exposure process involves aligning the photoresist-coated first surface of the wafer with the photomask and irradiating it under ultraviolet (UV) light. The UV light penetrates the light-transmitting areas of the photomask, causing a photochemical reaction in the corresponding photoresist areas, forming a pattern (cantilever beam pattern) on the first surface of the wafer that matches the photomask. The first development process involves immersing the wafer, after the first exposure, into a developing solution. Utilizing the difference in solubility between exposed and unexposed areas in the developing solution, the photoresist in the photosensitive areas of the first surface of the wafer is selectively dissolved, exposing the underlying silicon nitride film, thus creating the desired cantilever beam pattern on the photoresist layer of the first surface of the wafer. The first fixing process involves rinsing and fixing the wafer with deionized water after the first development process. This removes residual developing solution and dissolved substances, fixing the photoresist pattern (cantilever beam pattern) onto the first surface of the wafer and preventing further development reactions, thus avoiding pattern distortion due to over-development. The first etching process involves using photoresist as a hard mask to selectively remove the thin film (silicon nitride film not covered by photoresist) exposed to air on the first surface of the wafer, transferring the pattern (cantilever beam pattern) from the photoresist onto the silicon nitride film on the first surface of the wafer. The second cleaning process involves rinsing the wafer after the first etching with deionized water or organic solvents (such as acetone or isopropanol) to remove polymer byproducts, residual photoresist, and particulate matter generated during the etching process.

[0034] In this embodiment, the photomask refers to a specially made symmetrical photomask with a cantilever beam pattern. By aligning the lower left corner of the first surface of the wafer containing photoresist with the photomask, the cantilever beam pattern is precisely transferred onto the photoresist on the first surface of the wafer during the first exposure. Preferably, the first exposure is ultraviolet (UV) exposure. The first etching is inductively coupled plasma (ICP) etching, and the first etching time is 40s-60s, preferably 60s.

[0035] In this embodiment, as Figure 2a The image shown is a microscope photograph of the square wafer obtained after the first exposure and first development processes. Figure 2b The image shown is a photograph of the square wafer obtained after the first etching process under an optical microscope.

[0036] Step 400: Spin-coat the photoresist onto the second surface of the wafer and perform a post-baking process to obtain the wafer with thin films on both sides and the photoresist on the second surface after post-baking;

[0037] The second surface refers to the other surface of the wafer besides the first surface. Spin-coating photoresist involves dropping liquid photoresist onto the surface of the wafer and using centrifugal force during high-speed rotation (spin coating method) to evenly spread the photoresist onto the silicon nitride film on the second surface of the wafer, forming a uniform and smooth photoresist film. Post-baking involves placing the wafer, which has film on both sides and photoresist on the second surface after spin-coating, on a constant-temperature hot plate for heating. The purpose is to remove residual solvent from the photoresist and enhance the adhesion between the photoresist film and the silicon nitride film.

[0038] In this embodiment, the temperature of the post-drying treatment is 80℃-90℃, and the time of the post-drying treatment is 30 minutes. Preferably, the temperature of the post-drying treatment is 90℃.

[0039] Step 500: Using the mask, the wafer is subjected to a second exposure process, a second development process, a second fixing process, a second etching process, and a third cleaning process in sequence to obtain the wafer with the second surface etched.

[0040] The second exposure process involves aligning the spin-coated photoresist-coated second surface of the wafer with a photomask and then irradiating it with ultraviolet (UV) light. The UV light penetrates the light-transmitting areas of the photomask, causing a photochemical reaction in the corresponding photoresist areas, forming a pattern (cantilever beam pattern) on the second surface of the wafer that matches the photomask. The second development process involves immersing the wafer, after the second exposure, into a developing solution. Utilizing the difference in solubility between the exposed and unexposed areas in the developing solution, the photoresist in the photosensitive areas of the second surface of the wafer is selectively dissolved, exposing the underlying silicon nitride film, thus creating the desired cantilever beam pattern on the photoresist layer of the second surface. The second fixing process involves rinsing and fixing the wafer with deionized water after the second development process. This removes residual developing solution and dissolved substances, fixing the photoresist pattern (cantilever beam pattern) to the second surface of the wafer and preventing further development, thus avoiding pattern distortion due to over-development. The second etching process involves using photoresist as a hard mask to selectively remove the thin film (silicon nitride film not covered by photoresist) exposed to air on the second surface of the wafer, transferring the pattern (cantilever beam pattern) from the photoresist onto the silicon nitride film on the second surface of the wafer. The third cleaning process involves rinsing the wafer after the second etching with deionized water or organic solvents (such as acetone or isopropanol) to remove polymer byproducts, residual photoresist, and particulate matter generated during the etching process.

[0041] In this embodiment, the photomask refers to a specially designed symmetrical photomask with a cantilever beam pattern. By aligning the lower right corner of the second surface of the wafer containing photoresist with the photomask, the cantilever beam pattern is precisely transferred onto the photoresist on the second surface of the wafer during the second exposure. Preferably, the second exposure process is ultraviolet (UV) exposure. The second etching process is inductively coupled plasma (ICP) etching, and the second etching process takes 40-60 seconds, preferably 60 seconds.

[0042] In this embodiment, as Figure 3a The image shown is an optical microscope photograph of the square wafer obtained after the second etching process.

[0043] Step 600: The wafer is placed in a pre-prepared solution for immersion treatment, a fourth cleaning treatment, and metal coating treatment on the first surface to obtain the thin film cantilever beam.

[0044] The pre-prepared solution refers to a pre-mixed potassium hydroxide (KOH) solution of a specific mass concentration. Immersion treatment involves completely immersing the double-sided etched wafer in the potassium hydroxide solution. This utilizes the high corrosiveness of potassium hydroxide to silicon and its near-non-corrosiveness to silicon nitride, allowing the solution to penetrate the silicon substrate from the wafer edge, gradually removing the silicon wafer in direct contact with the solution. This results in multiple silicon nitride thin film cantilever beams with cantilever beam patterns etched on both the first and second surfaces. The fourth cleaning process involves rinsing the wafer after immersion treatment with deionized water and organic solvents (such as acetone and isopropanol) to remove residual KOH solution, silicon corrosion products, and attached particles. Metal coating treatment involves depositing a metal layer using electron beam evaporation. A layer of chromium (Cr) or titanium (Ti) is deposited on the first surface of the thin film cantilever beam as an adhesion layer, followed by a layer of gold (Au) as a functional layer. This is to precisely control the surface adhesion force at the tip of the thin film cantilever beam, enabling the pickup and release of two-dimensional materials. A thin-film cantilever beam is a beam-shaped two-dimensional heterogeneous micro / nano device with a silicon nitride thin film as the main body, a metal layer deposited on the first surface, which can be repeatedly fabricated and used, and allows for the rapid transfer of two-dimensional materials. Placing the thin-film cantilever beam on a support of a two-dimensional material transfer platform enables the repeated transfer of stacked two-dimensional materials.

[0045] In this embodiment, preferably, the pre-prepared solution is a 30% (w / w) potassium hydroxide (KOH) solution. Preferably, the immersion temperature is 80°C, and the immersion time is 7 hours. Preferably, the solvent for the fourth cleaning treatment is water, acetone, and isopropanol. The metal coating treatment is performed by depositing a metal layer using electron beam evaporation on the first surface of the wafer. Preferably, the metal layer in the electron beam evaporation metal coating treatment is a layer of chromium (Cr) with a thickness of 0.5 nm-2 nm or titanium (Ti) with a thickness of 0.5 nm-2 nm, and a layer of gold (Au) with a thickness of 0.1 nm-1 nm.

[0046] In this embodiment, as Figure 3b The image shown is a photograph of the square wafer obtained after the immersion treatment under an optical microscope.

[0047] In Embodiment 1 of this invention, a reusable thin-film cantilever beam is used to transfer two-dimensional materials, which reduces the transfer cost, improves the transfer efficiency, reduces organic pollution, and improves the quality of two-dimensional materials. By using the prepared thin-film cantilever beam to repeatedly transfer stacked two-dimensional materials, the transfer time of two-dimensional materials is significantly reduced.

[0048] In Example 2, in step 100, the thin film includes a silicon nitride thin film with a thickness of 500nm-1000nm, the solvent for the first cleaning treatment includes deionized water, the baking treatment temperature is 100℃-140℃, and the baking treatment time is 5min.

[0049] In this embodiment, preferably, both sides of the wafer are silicon nitride (Si3N4) films with a thickness of 500nm-1000nm. The solvent for the first cleaning treatment is deionized water, the baking treatment is dehydration baking, the baking temperature is 100℃-140℃, and the baking time is 5min.

[0050] In Embodiment 2 of this invention, a single-crystal silicon wafer with silicon nitride thin films on both sides is selected as the main material of the thin-film cantilever beam. The specific thickness range of the silicon nitride thin film is limited, and specific baking parameters are used. This ensures the bonding stability between the silicon nitride thin film and the single-crystal silicon wafer substrate, and effectively removes the solvent and residual moisture adsorbed on the film surface. This provides a clean and dry substrate surface for subsequent spin-coating of photoresist, laying the foundation for the final preparation of a thin-film cantilever beam that can rapidly transfer two-dimensional materials. This reduces the contamination of two-dimensional materials by organic matter from the source and improves the quality of two-dimensional materials.

[0051] In Example 3, in steps 200 and 400, the photoresist includes ultraviolet photoresist, the temperature of the post-baking process is 80℃-90℃, and the time of the post-baking process is 30 minutes.

[0052] Among them, photoresist refers to ultraviolet photoresist such as AZ1500 and SU8. Ultraviolet photoresist is a type of photosensitive material that is sensitive to ultraviolet light (UV) and is used in micro-nano lithography processes. Because it has ultraviolet photosensitive imaging characteristics, it can undergo photochemical reactions under ultraviolet light irradiation. Therefore, it is often used as a hard mask in the etching process to achieve precise transfer of specific cutout patterns.

[0053] In this embodiment, preferably, the photoresist is AZ1500 ultraviolet photoresist, the post-baking temperature is 90°C, and the post-baking time is 30 minutes.

[0054] In Embodiment 3 of this invention, by limiting the type of photoresist to ultraviolet photoresist and using specific post-baking parameters, the photoresist's photosensitivity and film quality are ensured, while residual solvents in the photoresist are effectively removed. This enhances the adhesion between the photoresist film and the silicon nitride film, avoiding problems such as film detachment and pattern distortion during subsequent exposure and etching processes. It improves the accuracy and process stability of the photolithography pattern, ensuring the forming quality of the final thin-film cantilever beam and improving the reliability and efficiency of two-dimensional material transfer.

[0055] In Embodiment 4, in steps 300 and 500, both the first exposure process and the second exposure process include exposure processing using ultraviolet light.

[0056] The exposure process using ultraviolet light refers to aligning the first and second surfaces of a wafer coated with ultraviolet photoresist with a specially made symmetrical photomask with a cantilever beam pattern, and then irradiating it under ultraviolet (UV) light. The ultraviolet light passes through the light-transmitting area of ​​the photomask, causing a photochemical reaction in the corresponding ultraviolet photoresist, thereby imprinting the cantilever beam pattern on the photomask onto the ultraviolet photoresist.

[0057] In this embodiment, during the first exposure, the lower left corner of the first surface of the wafer is aligned with the mask, and during the second exposure, the lower right corner of the second surface of the wafer is aligned with the mask.

[0058] In Embodiment 4 of this invention, by limiting both exposure processes to ultraviolet irradiation and using the same symmetrical mask for double-sided photolithography on a square wafer, the precise alignment and consistent forming of the cantilever beam patterns on the first and second surfaces of the wafer are ensured. This avoids deviations in the cantilever beam patterns caused by differences in exposure type or alignment method, thus guaranteeing the structural integrity and performance stability of the final thin-film cantilever beam. It also avoids asymmetry or damage to the thin-film cantilever beam caused by misalignment of the double-sided cantilever beam patterns, improving the yield of the final thin-film cantilever beam and the reliability of two-dimensional material transfer, and increasing the efficiency of two-dimensional material transfer.

[0059] In Example 5, in steps 300 and 500, both the first etching process and the second etching process include inductively coupled plasma etching, and the inductively coupled plasma etching time is 40s-60s.

[0060] Inductively coupled plasma (ICP) etching is a dry etching process that uses inductive coupling to generate high-density plasma, which is then accelerated by an electric field to physically bombard and chemically react on the surface of a material.

[0061] In this embodiment, an inductively coupled plasma (ICP) etching process is used, with photoresist as a hard mask. The high-energy characteristics of plasma are utilized to selectively etch the silicon nitride thin films exposed to air (not covered by photoresist) on the first and second surfaces of the wafer, thereby accurately transferring the cantilever beam pattern on the photoresist to the silicon nitride thin films on the first and second surfaces of the wafer.

[0062] In Embodiment 5 of this invention, by limiting both etching processes to inductively coupled plasma etching and specifying the etching time, the consistency of the etching rate and etching depth of the silicon nitride thin film on the first and second surfaces of the wafer is ensured. Precise time control ensures that the silicon nitride thin film is fully etched to form a complete cantilever beam pattern, while preventing excessive etching from damaging the silicon substrate or photoresist hard mask. Utilizing the advantages of strong anisotropy and high etching precision of inductively coupled plasma etching, the problem of rough pattern edges is avoided. This provides process assurance for the dimensional accuracy and edge sharpness of the cantilever beam pattern on the first and second surfaces, improves the mechanical integrity and yield of the finally prepared thin film cantilever beam, and effectively enhances the reliability and accuracy of the two-dimensional material transfer process.

[0063] In Example 6, in step 600, the pre-prepared solution includes a first mass fraction of potassium hydroxide solution, the soaking temperature is 60℃-90℃, and the soaking time is 1 hour-10 hours.

[0064] In this embodiment, preferably, the pre-prepared solution is a 30% (w / w) potassium hydroxide (KOH) solution. Preferably, the soaking temperature is 80°C and the soaking time is 7 hours.

[0065] In Embodiment Six of this invention, a 30% potassium hydroxide (KOH) solution was used as the selective etching solution for the silicon substrate, and the parameters of the immersion treatment were clearly defined. Utilizing the strong corrosiveness of potassium hydroxide solution to single-crystal silicon and its excellent selectivity towards silicon nitride films with almost no corrosion, the silicon substrate was efficiently and completely removed while the silicon nitride film cantilever beam remained undamaged. Precise temperature and time control ensured both sufficient etching removal of the silicon substrate and prevented damage to the silicon nitride film due to excessive immersion time or temperature. This guaranteed the structural integrity of the final thin-film cantilever beam, improved the consistency and yield of the thin-film cantilever beam fabrication, and provided a reliable device foundation for the reproducible, clean transfer of two-dimensional materials without interlayer contamination.

[0066] In Example 7, in step 600, the solvent for the fourth cleaning process includes water, acetone, and isopropanol.

[0067] In this embodiment, the preferred solvents for the fourth cleaning process are water, acetone, and isopropanol.

[0068] In Embodiment Seven of this invention, by limiting the solvent composition of the fourth cleaning process, the strong solubility of water is used to remove residual potassium hydroxide solution and water-soluble impurities. Acetone is used to remove organic contaminants and silicon corrosion byproducts. Isopropanol is then used for displacement cleaning to achieve rapid drying of the first and second surfaces of the wafer. This ensures that the wafer surface is clean and free of impurities after cleaning, avoiding the impact of contaminant residue on subsequent metal coating processes and the performance of the final thin-film cantilever beam. It also achieves precise control of the adhesion force at the tip of the thin-film cantilever beam, further improving the preparation quality and performance of the thin-film cantilever beam, and ensuring the stability and reliability of the process for the two-dimensional material to be free of interlayer contamination and capable of repeated clean transfer.

[0069] In Example 8, in step 600, the metal coating process includes a metal layer deposition process using electron beam evaporation. The metal layer in the metal layer deposition process using electron beam evaporation is a layer of chromium with a thickness of 0.5nm-2nm or a layer of titanium with a thickness of 0.5nm-2nm, and a layer of gold with a thickness of 0.1nm-1nm.

[0070] In this embodiment, the metal coating process is performed by electron beam evaporation to deposit a metal layer on the first surface of the wafer. Preferably, the metal layer in the electron beam evaporation process is a layer of chromium (Cr) with a thickness of 0.5 nm-2 nm or titanium (Ti) with a thickness of 0.5 nm-2 nm, or a layer of gold (Au) with a thickness of 0.1 nm-1 nm.

[0071] Embodiment 8 of this invention defines the specific method of metal coating treatment and clarifies the composition and thickness range of the metal layer. The electron beam evaporation process for metal coating precisely controls the thickness and uniformity of the metal layer. Using a chromium (Cr) or titanium (Ti) layer as an adhesion layer enhances the bonding force between the gold (Au) layer and the surface of the silicon nitride thin film cantilever beam, preventing metal layer detachment during the transfer of two-dimensional materials. The gold (Au) layer, as a functional layer, precisely controls the surface adhesion force at the tip of the thin film cantilever beam, enabling it to both pick up two-dimensional materials and release them onto the target substrate. By limiting the specific thickness range of each metal layer, the adhesion effect of the adhesion layer and the performance of the functional layer are ensured, while avoiding excessively high or low thicknesses that could affect the mechanical properties of the thin film cantilever beam and the transfer effect of the two-dimensional material. This further improves the structural stability and reliability of the thin film cantilever beam, ensuring that two-dimensional materials can be transferred cleanly, without damage or interlayer contamination, and with repeatability.

[0072] Embodiment 9 of this application also provides a thin-film cantilever beam, which is prepared using the thin-film cantilever beam preparation method described in Embodiments 1 to 8 of this application.

[0073] In Embodiment 10, the thin-film cantilever beam includes an intermediate silicon layer, a first surface of the intermediate silicon layer disposed below a first region of the first surface of the first silicon nitride layer, a second surface of the intermediate silicon layer disposed above the first surface of the second silicon nitride layer, a second surface of the first silicon nitride layer disposed below the first surface of the metal layer, and a second region of the first surface of the first silicon nitride layer exposed to air.

[0074] In this embodiment, the structure of the thin-film cantilever beam is as follows: Figure 6-8 As shown in Figure 4, Figure 4a These are optical microscope images of a thin-film cantilever beam and hBN two-dimensional material. Figure 4b An optical microscope image of hBN two-dimensional material lifted by a thin-film cantilever beam. Figure 4c An optical microscope image of hBN two-dimensional material used to support a thin-film cantilever beam. (Figure 5) Figure 5a An atomic force microscope image of hBN two-dimensional material used to support a thin-film cantilever beam. Figure 5b An atomic force microscope image of hBN two-dimensional material transferred using a PC film: The roughness (Ra) of the hBN two-dimensional material transferred using a film cantilever beam is only 143.5 pm, which is much smaller than the roughness (Ra) of 599.6 pm of the hBN two-dimensional material transferred using a traditional PC film.

[0075] In Embodiment 10 of the present invention, the roughness of hBN two-dimensional material transferred using a thin-film cantilever beam is compared with that of hBN two-dimensional material transferred using a conventional PC thin film. This verifies that the thin-film cantilever beam prepared by the present invention has superior performance, reduces the roughness of the transferred two-dimensional material, and improves the quality of the transferred two-dimensional material.

[0076] In this application, "multiple" refers to two or more.

[0077] In this application, unless otherwise expressly defined, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0078] The terms “first,” “second,” “third,” “fourth,” etc., in this application (if present) are used to distinguish similar objects and are not necessarily used to describe a specific order or sequence.

[0079] In this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. Additionally, in this application, the character " / " generally indicates that the preceding and following related objects have an "or" relationship.

[0080] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, if the method includes steps A and B, it means that the method may include steps A and B performed sequentially, or it may include steps B and A performed sequentially. For example, if the method may also include step C, it means that step C may be added to the method in any order. For example, the method may include steps A, B, and C, or it may include steps A, C, and B, or it may include steps C, A, and B, etc.

[0081] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.

Claims

1. A method for preparing a thin-film cantilever beam, characterized in that, The method for preparing the thin-film cantilever beam includes: Step 100: The wafer with thin film on both sides is sliced, cleaned for the first time, and baked to obtain the dried wafer with thin film on both sides. Step 200: Spin-coat photoresist onto the first surface of the wafer and perform post-baking treatment to obtain the wafer with thin films on both sides and photoresist on the first surface after post-baking. Step 300: Using a mask, the wafer is subjected to a first exposure process, a first development process, a first fixing process, a first etching process, and a second cleaning process in sequence to obtain the wafer with the first surface etched. Step 400: Spin-coat the photoresist onto the second surface of the wafer and perform a post-baking process to obtain the wafer with thin films on both sides and the photoresist on the second surface after post-baking; Step 500: Using the mask, the wafer is subjected to a second exposure process, a second development process, a second fixing process, a second etching process, and a third cleaning process in sequence to obtain the wafer with the second surface etched. Step 600: The wafer is placed in a pre-prepared solution for immersion treatment, a fourth cleaning treatment, and metal coating treatment on the first surface to obtain the thin film cantilever beam.

2. The method for preparing a thin-film cantilever beam according to claim 1, characterized in that, In step 100, the thin film includes a silicon nitride thin film with a thickness of 500nm-1000nm, the solvent for the first cleaning treatment includes deionized water, the baking treatment temperature is 100℃-140℃, and the baking treatment time is 5min.

3. The method for preparing a thin-film cantilever beam according to claim 1, characterized in that, In steps 200 and 400, the photoresist includes ultraviolet photoresist, the post-baking temperature is 80℃-90℃, and the post-baking time is 30 minutes.

4. The method for preparing a thin-film cantilever beam according to claim 1, characterized in that, In steps 300 and 500, both the first exposure process and the second exposure process include exposure processing using ultraviolet light.

5. The method for preparing a thin-film cantilever beam according to claim 1, characterized in that, In steps 300 and 500, both the first etching process and the second etching process include inductively coupled plasma etching, and the inductively coupled plasma etching time is 40s-60s.

6. The method for preparing a thin-film cantilever beam according to claim 1, characterized in that, In step 600, the pre-prepared solution includes a potassium hydroxide solution with a first mass fraction, the soaking temperature is 60℃-90℃, and the soaking time is 1 hour-10 hours.

7. The method for preparing a thin-film cantilever beam according to claim 1, characterized in that, In step 600, the solvent for the fourth cleaning process includes water, acetone, and isopropanol.

8. The method for preparing a thin-film cantilever beam according to claim 1, characterized in that, In step 600, the metal coating process includes a metal layer deposition process using electron beam evaporation. The metal layer in the metal layer deposition process using electron beam evaporation is a layer of chromium with a thickness of 0.5nm-2nm or a layer of titanium with a thickness of 0.5nm-2nm, and a layer of gold with a thickness of 0.1nm-1nm.

9. A membrane cantilever beam, characterized in that, The thin-film cantilever beam is prepared using the method for preparing a thin-film cantilever beam as described in any one of claims 1-8.

10. The membrane cantilever beam according to claim 9, characterized in that, The thin-film cantilever beam includes an intermediate silicon layer, a first surface of the intermediate silicon layer disposed below a first region of the first surface of the first silicon nitride layer, a second surface of the intermediate silicon layer disposed above the first surface of the second silicon nitride layer, a second surface of the first silicon nitride layer disposed below the first surface of the metal layer, and a second region of the first surface of the first silicon nitride layer exposed to air.

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