Method for preparing 3D nano structure on curved surface substrate and curved surface substrate

Abstract

The invention discloses a method for preparing a 3D nano structure on a curved-surface substrate and the curved-surface substrate, and belongs to the technical field of micro-nano manufacturing. According to the method, sequentially stacked photoresist films are obtained on the surface of the curved-surface substrate through the steps of substrate preparation, gluing, transfer printing, overlapping and repeated gluing and transfer printing, then the curved-surface substrate with a 3D nanostructure is obtained through exposure and development, so that the photoresist which is incompatible in solvent and different in sensitivity can realize multi-layer cross stacking on the curved-surface substrate, and therefore, the yield of the curved-surface substrate is improved. The 3D nano-structure with the complex shape is processed on the curved surface substrate through the one-time exposure and development technology, so that the precision error and the size error of the engraving and sleeving position in the traditional engraving and sleeving technology are avoided, and the high-precision manufacturing of the 3D nano-structure with the complex shape is realized; a new solution is provided for manufacturing of a 3D nano structure with a complex shape in the fields of micro-nano manufacturing, optics, biology, surface science and bionics.

Description

Technical Field

[0001] This invention relates to the field of micro-nano manufacturing technology, and in particular to a method for preparing 3D nanostructures on a curved substrate and the curved substrate itself. Background Technology

[0002] Microlithography is a core enabling technology in modern science and technology, with wide applications in aerospace, integrated circuits, life sciences, the Internet of Things, augmented reality, and quantum technology. Microlithography has reached the pinnacle in the fabrication of planar two-dimensional structures, with a processing precision exceeding 10 nm. However, the fabrication of 3D nanostructures on curved substrates, especially complex-shaped 3D nanostructures, still faces bottlenecks. Traditional lithography techniques typically employ multi-layer overlay to fabricate 3D nanostructures; however, overlay errors exist during the process, and multiple lithography steps significantly increase manufacturing costs. Furthermore, uniform photoresist coating on curved substrates is also a challenge. These challenges limit the reliable fabrication of complex 3D nanostructures and their application in micro / nano optoelectronic devices. Summary of the Invention

[0003] The main objective of this invention is to provide a method for fabricating 3D nanostructures on curved substrates and a curved substrate, thereby solving the technical problem of the difficulty in fabricating 3D nanostructures on curved substrates.

[0004] To achieve the above objectives, the present invention provides a method for fabricating 3D nanostructures on a curved substrate, comprising the following steps: Substrate preparation: providing curved substrates and thermally release stamps; Coating: Spin-coating photoresist onto the surface of the heat-release stamp; Transfer: The side of the thermally release stamp containing the photoresist is attached to the surface of the curved substrate. After the thermally release stamp and the curved substrate make conformal contact, the photoresist is transferred to the surface of the curved substrate to obtain a photoresist film. The thermally release stamp is then peeled off. Stacking: Repeat the coating step and the transfer step to transfer the photoresist spin-coated onto the surface of the thermally release stamp to the surface of the photoresist film obtained in the previous transfer, and peel off the thermally release stamp to achieve the sequential stacking of multiple photoresist films on the surface of the curved substrate to obtain a photoresist layer. Exposure and development: The photoresist layer is patterned and developed to obtain a curved substrate with a 3D nanostructure.

[0005] In some embodiments of the present invention, the Gaussian curvature of the curved substrate is 0; And / or, the curved substrate includes at least one of silicon oxide, metal, and glass; And / or, the thickness of a single photoresist film ranges from 50 nm to 200 nm.

[0006] In some embodiments of the present invention, the heat-release stamp comprises polydimethylsiloxane.

[0007] In some embodiments of the present invention, the heat release stamp is polydimethylsiloxane, and the preparation method of the heat release stamp includes: mixing a silicon polymer with a crosslinking agent, removing air bubbles and heating to cure to obtain the heat release stamp.

[0008] In some embodiments of the present invention, the photoresist includes at least one of PMMA, HSQ, AR-N 7520, and SU-8.

[0009] In some embodiments of the present invention, the photoresist layer comprises a first photoresist film and a second photoresist film stacked sequentially, wherein: The first photoresist film is PMMA, and the second photoresist film is HSQ, or; The first photoresist film is PMMA, and the second photoresist film is AR-N 7520, or; The first photoresist film is PMMA, and the second photoresist film is SU-8, or; The first photoresist film is HSQ, and the second photoresist film is AR-N 7520, or; The first photoresist film is HSQ, and the second photoresist film is SU-8, or; The first photoresist film is AR-N 7520, and the second photoresist film is SU-8.

[0010] In some embodiments of the present invention, the transfer method includes a heat release method.

[0011] In some embodiments of the present invention, the heat release temperature of the heat release method is 60°C to 200°C, and the heat release time is 3 min to 8 min.

[0012] In some embodiments of the present invention, the number of times the superimposed steps are performed is 1 to 10.

[0013] The present invention also provides a curved substrate, which is prepared by the method described above for preparing 3D nanostructures on a curved substrate, wherein the surface of the curved substrate has 3D nanostructures.

[0014] The beneficial effects that this invention can achieve are: This invention enables the repeated spin-coating of photoresist directly onto a thermal release stamp, allowing for the multi-layer cross-stacking of different types of photoresists with incompatible solvents and varying sensitivities on a curved substrate. Furthermore, it enables the fabrication of complex-shaped 3D nanostructures on curved substrates using a single exposure and development process. This avoids the positional and dimensional errors inherent in traditional engraving techniques, achieving high-precision manufacturing of complex-shaped 3D nanostructures. This provides a new solution for the fabrication of complex-shaped 3D nanostructures in micro / nano manufacturing, optics, biology, surface science, and bionics. Attached Figure Description

[0015] 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 are 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 the structures shown in these drawings without creative effort.

[0016] Figure 1 This is a schematic diagram of the process for fabricating 3D nanostructures on a curved substrate according to an embodiment of the present invention; Figure 2 This is a SEM image of a 3D nanostructure on a curved substrate according to an embodiment of the present invention.

[0017] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0018] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0019] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0020] In this invention, descriptions involving "first," "second," etc., are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination should be considered non-existent and not within the scope of protection claimed by this invention.

[0021] This invention provides a method for fabricating 3D nanostructures on a curved substrate, comprising the following steps: Substrate preparation: providing curved substrates and thermally release stamps; Coating: Spin-coating photoresist onto the surface of the heat-release stamp; Transfer printing: The side of the thermally release stamp containing photoresist is attached to the surface of the curved substrate. Once the thermally release stamp and the curved substrate make conformal contact, the photoresist is transferred to the surface of the curved substrate to obtain a photoresist film. Then, the thermally release stamp is peeled off. Stacking: Repeat the coating and transfer steps to transfer the photoresist spin-coated onto the surface of the thermally release stamp to the surface of the photoresist film obtained in the previous transfer, and peel off the thermally release stamp to achieve the sequential stacking of multiple photoresist films on the surface of the curved substrate to obtain a photoresist layer. Exposure and development: Pattern exposure and development of the photoresist layer to obtain a curved substrate with a 3D nanostructure.

[0022] This invention enables the repeated spin-coating of photoresist directly onto a thermal release stamp, allowing for the multi-layer cross-stacking of different types of photoresists with incompatible solvents and varying sensitivities on a curved substrate. Furthermore, it enables the fabrication of complex-shaped 3D nanostructures on curved substrates using a single exposure and development process. This avoids the positional and dimensional errors inherent in traditional engraving techniques, achieving high-precision manufacturing of complex-shaped 3D nanostructures. This provides a new solution for the fabrication of complex-shaped 3D nanostructures in micro / nano manufacturing, optics, biology, surface science, and bionics.

[0023] In the substrate preparation step, the curved substrate can be cleaned by: ultrasonically cleaning the curved substrate in acetone solution for 1 minute, followed by ultrasonic cleaning in isoacetone solution for 1 minute, and then drying it with nitrogen gas.

[0024] In some embodiments, oxygen plasma treatment of the curved substrate and the thermally release stamp can introduce polar groups such as hydrophilic hydroxyl groups, enabling low-stress, bubble-free conformal contact between the thermally release stamp and the curved substrate. This also enhances the wettability and adhesion between the photoresist, the thermally release stamp, and the curved substrate, preventing slippage, wrinkles, or delamination during subsequent transfer. This ensures the positional accuracy and quality of the multilayer photoresist film on the curved substrate, laying the foundation for fabricating complex 3D nanostructures on the surface of the curved substrate through a single exposure and development process.

[0025] In some embodiments, the oxygen plasma treatment time for the curved substrate is 5 minutes, and the oxygen plasma treatment time for the heat-release stamp is 1 minute.

[0026] In some embodiments, the Gaussian curvature of the curved substrate is 0. Choosing a curved substrate with 0 Gaussian curvature ensures that the thermally release stamp and the curved substrate can conformally bond without wrinkles, while also resulting in a more uniform thickness and more concentrated stress in the photoresist layer attached to the curved substrate. This leads to uniform thickness and clear interfaces in each photoresist film layer, ultimately achieving a high-fidelity, distortion-free 3D nanostructure in a single exposure and development cycle.

[0027] In some embodiments, the curved substrate includes at least one of silicon oxide, metal, and glass.

[0028] In some embodiments, the heat release stamp comprises polydimethylsiloxane (PDMS).

[0029] In some embodiments, the thermal release stamp is PDMS, and the preparation method of the thermal release stamp includes: mixing a silicon polymer with a crosslinking agent, removing air bubbles and heating to cure to obtain the thermal release stamp. The step of removing air bubbles can avoid the formation of pinholes on the stamp surface after curing, thereby improving the quality of photoresist transfer.

[0030] In some embodiments, the silicon polymer includes a polydimethylsiloxane prepolymer, and the crosslinking agent includes a hydrogen-containing silicone oil.

[0031] In some embodiments, the mass ratio of silicon polymer to crosslinking agent is (9~11):(0.5~1.5), which can be 10:1.

[0032] In some embodiments, after the silicon polymer and the crosslinking agent are mixed, they are stirred with a glass rod to promote the mixing of the silicon polymer and the crosslinking agent. The stirring time is determined according to the need to ensure that the silicon polymer and the crosslinking agent are completely mixed, and may be 10 minutes.

[0033] The temperature and time for heat curing can be determined according to the material of the heat release stamp. In some embodiments, the temperature for heat curing can be 80°C and the time for heat curing can be 3 hours.

[0034] In some embodiments, air bubbles can be removed by vacuuming. For example, the mixed silicon polymer and crosslinking agent are placed in a vacuum vessel and vacuumed for 30 minutes to remove air bubbles.

[0035] In some embodiments, the photoresist includes at least one of PMMA, HSQ, AR-N 7520, and SU-8. By repeatedly spin-coating the photoresist directly onto a thermal release stamp, the present invention enables the multilayer cross-stacking of different types of photoresists with incompatible solvents and different sensitivities on a curved substrate, forming a photoresist layer composed of different types of photoresist films, thus expanding the application range.

[0036] The mass concentration of the photoresist can be determined according to the actual situation. In some embodiments, the mass concentration of the photoresist can be 3% to 10%.

[0037] After the photoresist is spin-coated onto the surface of the substrate, the spin-coating parameters can be set according to the required thickness. In some embodiments, the spin-coating parameters are low speed 500r / 5s and high speed 4000r / 60s, which can obtain a photoresist film with a uniform and appropriate thickness on the surface of the substrate.

[0038] In this invention, the photoresist layer comprises at least two or more stacked photoresist films, which can be any combination of negative electron beam photoresists with different sensitivities.

[0039] In some embodiments, the photoresist layer includes a first photoresist film and a second photoresist film stacked sequentially, wherein: The first photoresist film is PMMA, and the second photoresist film is HSQ, or; The first photoresist film is PMMA, and the second photoresist film is AR-N 7520, or; The first photoresist film is PMMA, and the second photoresist film is SU-8, or; The first photoresist film is HSQ, and the second photoresist film is AR-N 7520, or; The first photoresist film is HSQ, and the second photoresist film is SU-8, or; The first photoresist film is AR-N 7520, and the second photoresist film is SU-8.

[0040] In some embodiments, the thickness of a photoresist film ranges from 50nm to 200nm, and can be 50nm, 80nm, 100nm, 120nm, 150nm, 180nm, 200nm, etc.

[0041] In some embodiments, the transfer method includes heat release.

[0042] The temperature and time of the thermal release method can be determined according to the type of photoresist, so that the photoresist can be completely transferred to the surface of the curved substrate or the surface of the photoresist film obtained in the previous transfer.

[0043] In some embodiments, the heat release temperature of the heat release method is 60°C to 200°C, and the heat release time is 3 min to 8 min.

[0044] In some embodiments, the photoresist is HSQ, the thermal release temperature is 80°C, and the thermal release time is 5 minutes. In other embodiments, the thermal release temperature may be 85°C, and the thermal release time may be 1 minute. In some embodiments, the photoresist is PMMA, the heat release temperature is 120°C, and the heat release time is 1 min. In other embodiments, the heat release temperature can be 80°C, and the baking time can be 5 min.

[0045] In some embodiments, the photoresist is AR-N 7520, the thermal release temperature is 85°C, and the thermal release time is 1 min.

[0046] In some embodiments, the photoresist is SU-8, the heat release temperature is 90°C, and the heat release time is 2 min.

[0047] In some embodiments, the stacking steps are performed 1 to 10 times, meaning the photoresist film in the photoresist layer can be 2, 3, 4, 5, 6, 7, 8, 9, 10, or 11 layers. The method of the present invention allows for the stacking of 2 to 11 different photoresist films before a single exposure, enabling the construction of complex 3D structures by adjusting the number of layers.

[0048] In some embodiments, an electron beam exposure device, Raith 150 two, is used for exposure at a voltage of 30 kV and an aperture of 30 μm to perform point exposure on the photoresist layer.

[0049] The exposed sample is immersed in a developing solution for development. The developing solution includes at least one of NaOH solution, salt developing solution, propylene glycol methyl ether acetate (PGMEA), and AR 300-46. The NaOH solution has a mass concentration of 1%, and the salt developing solution comprises a mixture of a 1% NaOH solution and a 4% NaCl solution.

[0050] The present invention also provides a curved substrate, which is prepared by the method described above for preparing 3D nanostructures on the curved substrate. The surface of the curved substrate has 3D nanostructures and is suitable for micro-nano manufacturing, optics, biology, surface science and bionics.

[0051] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0052] Example 1 refer to Figure 1 , Figure 1 This is a schematic diagram of the process for fabricating 3D nanostructures on a curved substrate in this embodiment. The fabrication steps are as follows: Substrate preparation: Select a clean silicon oxide substrate, ultrasonically clean it in acetone solution for 1 min, ultrasonically clean it in isopropanol solution for 1 min, and then dry it with nitrogen gas.

[0053] Preparation of heat-release stamps: Weigh 30g of silicon polymer and 3g of crosslinking agent into a glass beaker, stir with a glass rod for 10 min to mix them completely, and place in a vacuum vessel for 30 min to completely remove air bubbles. Then pour into the corresponding mold and bake in an oven at 80℃ for 3 h to cure and obtain PDMS heat-release stamps.

[0054] Coating: Spin-coat the surface of the PDMS thermally release stamp with 6% HSQ photoresist by low speed 500r / 5s and high speed 4000r / 60s.

[0055] Transfer: The side of the PDMS thermally release stamp with HSQ photoresist is attached to the surface of the curved substrate. After conformal contact is achieved, it is baked on a hot plate at 80°C for 5 minutes to transfer the HSQ photoresist to the surface of the curved substrate to obtain an HSQ photoresist film. The PDMS thermally release stamp is then peeled off.

[0056] Stacking: A 3% PMMA photoresist was spin-coated onto the surface of a PDMS thermally release stamp. The spin-coating parameters were 500r / 5s at low speed and 4000r / 60s at high speed. The side of the PDMS thermally release stamp with PMMA photoresist was attached to the surface of the HSQ photoresist film on the curved substrate. After achieving common contact, the film was baked on a hot plate at 120°C for 1 min to transfer the PMMA photoresist to the surface of the HSQ photoresist film, thus obtaining the PMMA photoresist film. The PDMS thermally release stamp was then peeled off, achieving the stacking of the HSQ / PMMA photoresist films. Next, a 7% (w / w) concentration of AR-N 7520 photoresist was spin-coated onto the surface of the peeled PDMS thermally release stamp. The spin-coating parameters were 500 rpm for 5 seconds at low speed and 4000 rpm for 60 seconds at high speed. The side of the PDMS thermally release stamp with AR-N 7520 photoresist was attached to the surface of the curved PMMA photoresist film. After achieving common contact, it was baked on an 85°C hot plate for 1 minute to transfer the AR-N 7520 photoresist to the surface of the PMMA photoresist film, thus obtaining the AR-N 7520 photoresist film. The PDMS thermally release stamp was then peeled off, achieving the stacking of the HSQ / PMMA / AR-N 7520 photoresist films. Exposure and development: Using an electron beam exposure device Raith 150 two, the three-layer photoresist film was exposed at a high voltage of 30KV and a 30 μm aperture. The exposed films were then immersed in a mixed solution of AR 300-46, methyl isobutyl ketone (MIBK):isopropanol (IPA) = 3:1 (v / v), and 1% NaOH solution for 1 min each. Finally, the films were dried with nitrogen to obtain a curved substrate with a complex 3D nanostructure.

[0057] The 3D nanostructures on the curved substrate of Example 1 were observed using a scanning electron microscope. Figure 2 The image shows a SEM image of a 3D nanostructure, revealing a complex 3D nanostructure formed on the surface of a curved substrate.

[0058] Example 2 Substrate preparation: Select a clean silicon oxide substrate, ultrasonically clean it in acetone solution for 1 min, ultrasonically clean it in isopropanol solution for 1 min, and then dry it with nitrogen gas.

[0059] Preparation of heat-release stamps: Weigh 30g of silicon polymer and 3g of crosslinking agent into a glass beaker, stir with a glass rod for 10 min to mix them completely, and place in a vacuum vessel for 30 min to completely remove air bubbles. Then pour into the corresponding mold and bake in an oven at 80℃ for 3 h to cure and obtain PDMS heat-release stamps.

[0060] Coating: Spin-coat 3% PMMA photoresist onto the PDMS thermally release stamp. Spin-coating parameters are 500r / 5s at low speed and 4000r / 60s at high speed.

[0061] Transfer: The side of the PDMS thermally release stamp with PMMA photoresist is attached to the surface of the curved substrate. After conformal contact is achieved, it is baked on a hot plate at 80°C for 5 minutes to transfer the PMMA photoresist to the surface of the curved substrate, forming a PMMA photoresist film. The PDMS thermally release stamp is then peeled off. Stacking: 3% SU-8 photoresist was spin-coated onto the surface of a PDMS thermally release stamp. The spin-coating parameters were 500r / 5s at low speed and 4000r / 60s at high speed. The side of the PDMS thermally release stamp with SU-8 photoresist was attached to the surface of the PMMA photoresist film on the curved substrate. After achieving common contact, the film was baked on a hot plate at 90°C for 2 minutes to transfer the SU-8 photoresist to the surface of the PMMA photoresist film. The PDMS thermally release stamp was then peeled off to achieve the stacking of the PMMA / SU-8 photoresist films. Next, a 6% HSQ photoresist was spin-coated onto the surface of the peeled PDMS thermally release stamp. The spin-coating parameters were 500 rpm for 5 seconds at low speed and 4000 rpm for 60 seconds at high speed. The side of the PDMS thermally release stamp with HSQ photoresist was attached to the surface of the curved SU-8 photoresist film. After achieving common contact, it was baked on an 85°C hot plate for 1 minute to transfer the HSQ photoresist to the surface of the SU-8 photoresist film, thus obtaining the HSQ photoresist film. The PDMS thermally release stamp was then peeled off, achieving the stacking of PMMA / SU-8 / HSQ photoresist films. Exposure and development: Using an electron beam exposure device Raith 150 two, the three layers of adhesive were exposed at a high voltage of 30KV and a 30 μm aperture. The exposed films were then immersed in a mixed solution of MIBK:IPA=3:1, a PGMEA solution, and a 1% NaOH solution for 1 min each, and finally dried with nitrogen to obtain a curved substrate with a complex 3D nanostructure.

[0062] The above are merely preferred embodiments of the present invention and do not limit the scope of the patent. Any equivalent structural or procedural transformations made based on the description and drawings of the present invention, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of the present invention.

Claims

1. A method for fabricating 3D nanostructures on a curved substrate, characterized in that, Includes the following steps: Substrate preparation: providing curved substrates and thermally release stamps; Coating: Spin-coating photoresist onto the surface of the heat-release stamp; Transfer: The side of the thermally release stamp containing the photoresist is attached to the surface of the curved substrate. After the thermally release stamp and the curved substrate make conformal contact, the photoresist is transferred to the surface of the curved substrate to obtain a photoresist film. The thermally release stamp is then peeled off. Stacking: Repeat the coating step and the transfer step to transfer the photoresist spin-coated onto the surface of the thermally release stamp to the surface of the photoresist film obtained in the previous transfer, and peel off the thermally release stamp to achieve the sequential stacking of multiple photoresist films on the surface of the curved substrate to obtain a photoresist layer. Exposure and development: The photoresist layer is patterned and developed to obtain a curved substrate with a 3D nanostructure.

2. The method for fabricating 3D nanostructures on a curved substrate according to claim 1, characterized in that, The Gaussian curvature of the curved substrate is 0; And / or, the curved substrate includes at least one of silicon oxide, metal, and glass; And / or, the thickness of a single photoresist film ranges from 50 nm to 200 nm.

3. The method for fabricating 3D nanostructures on a curved substrate according to claim 1, characterized in that, The heat-release stamp comprises polydimethylsiloxane.

4. The method for fabricating 3D nanostructures on a curved substrate according to claim 3, characterized in that, The heat-release stamp is polydimethylsiloxane, and the preparation method of the heat-release stamp includes: mixing a silicon polymer with a crosslinking agent, removing air bubbles and heating to cure to obtain the heat-release stamp.

5. The method for fabricating 3D nanostructures on a curved substrate according to claim 1, characterized in that, The photoresist includes at least one of PMMA, HSQ, AR-N 7520, and SU-8.

6. The method for fabricating 3D nanostructures on a curved substrate according to claim 5, characterized in that, The photoresist layer comprises a first photoresist film and a second photoresist film stacked sequentially, wherein: The first photoresist film is PMMA, and the second photoresist film is HSQ, or; The first photoresist film is PMMA, and the second photoresist film is AR-N 7520, or; The first photoresist film is PMMA, and the second photoresist film is SU-8, or; The first photoresist film is HSQ, and the second photoresist film is AR-N 7520, or; The first photoresist film is HSQ, and the second photoresist film is SU-8, or; The first photoresist film is AR-N 7520, and the second photoresist film is SU-8.

7. The method for fabricating 3D nanostructures on a curved substrate according to claim 1, characterized in that, The transfer method includes the heat release method.

8. The method for fabricating 3D nanostructures on a curved substrate according to claim 7, characterized in that, The heat release temperature of the heat release method is 60℃~200℃, and the heat release time is 3min~8min.

9. The method for fabricating 3D nanostructures on a curved substrate according to any one of claims 1 to 8, characterized in that, The number of times the superposition step is performed is 1 to 10.

10. A curved substrate, characterized in that, The curved substrate is prepared by the method for preparing 3D nanostructures on a curved substrate as described in any one of claims 1 to 9, wherein the surface of the curved substrate has 3D nanostructures.

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