Preparation method of super-structure lens based on nanoimprint lithography
By fabricating metalens structures on polymethyl methacrylate and transferring them onto silicon and quartz glass substrates using nanoimprint technology, the problems of high fabrication cost and low consistency of metalenses have been solved, enabling large-scale mass production and making them suitable for optical components and integrated optics.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-01-21
- Publication Date
- 2026-04-03
AI Technical Summary
Existing meta-lenses have high manufacturing costs and low product consistency, making large-scale mass production difficult.
A metalens fabrication method based on nanoimprinting was adopted. First, a metalens structure was prepared on polymethyl methacrylate as an initial template. It was then copied onto an elastomer composite substrate using electron beam lithography and nanoimprinting technology, and then transferred to a silicon substrate and a quartz glass substrate. The structure transfer was achieved using etching technology.
It reduces manufacturing costs, improves product consistency, and enables large-scale stable mass production, making it suitable for optical components and integrated optics.
Smart Images
Figure CN121784876A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of nanofabrication technology, and more specifically to a method for preparing metalenses based on nanoimprinting. Background Technology
[0002] Metalenses, as artificial two-dimensional optical elements based on metasurfaces, achieve precise control over the amplitude, phase, and polarization state of light waves by arranging subwavelength-scale nanostructures on their substrates. Specifically, metalenses introduce an additional phase related to the azimuth angle through the spatial rotation of anisotropic nanostructures, providing phase coverage across the entire 2π range for circularly polarized light. They demonstrate enormous application potential in cutting-edge fields such as compact imaging, AR / VR displays, spectral analysis, and polarization optics.
[0003] Metalenses require fabrication processes compatible with mature CMOS technologies. Traditional methods for fabricating metalenses rely on techniques such as electron beam lithography and DUV lithography, which depend on direct writing with high-precision energy beams. These methods offer significant advantages in fabricating small batches of high-precision patterns. However, to move metalenses from laboratory prototypes to large-scale commercial applications, low-cost, high-throughput, and highly consistent micro / nano fabrication technologies are a critical hurdle that must be overcome. The aforementioned methods suffer from high equipment purchase and maintenance costs, cumbersome and time-consuming single-wafer process steps, and difficulty in scaling up to large-area mass production. The overall cost prevents them from moving from theoretical design to large-scale manufacturing and application. Summary of the Invention
[0004] In view of the technical problems existing in the background art, this application provides a method for preparing metalenses based on nanoimprinting, which aims to solve the problems of high preparation cost, low product consistency and difficulty in large-area mass production of existing metalenses.
[0005] This application provides a method for fabricating metalenses based on nanoimprinting, comprising the following steps: S1. Polymethyl methacrylate is spin-coated onto the surface of silicon substrate 1. After drying, electron beam lithography, development, and fixing are performed to obtain a polymethyl methacrylate-based template with a metalens structure. S2. A silica layer is deposited on a polymethyl methacrylate template and subjected to a low surface energy treatment to obtain a first substrate; S3. Nanoimprinting is performed on the first substrate using a polymer elastomer substrate one, so that the metalens structure on the first substrate is imprinted onto the polymer elastomer substrate one to obtain the second substrate; S4. A sacrificial layer and an imprint layer are sequentially spin-coated onto silicon substrate II to obtain a pretreated imprint substrate; S5. The pre-treated imprinted substrate is imprinted using the second substrate, so that the metastructure on the second substrate is imprinted onto the imprinted layer of the pre-treated imprinted substrate. Then, the imprinted layer and the sacrificial layer are etched until the silicon substrate is exposed to obtain the third substrate. S6. A metal layer is deposited on the surface of the third substrate, and then the sacrificial layer and the imprint layer in the third substrate are removed to obtain a fourth substrate; S7. Using the metal layer as a mask, etch the silicon substrate of the fourth substrate, then clean off the metal layer, and then perform a low surface energy treatment to obtain the fifth substrate; S8. Nanoimprinting is performed on the fifth substrate using a second polymer elastomer substrate to imprint the metalens structure on the fifth substrate onto the second polymer elastomer substrate, thereby obtaining a sixth substrate. S9. Prepare a quartz glass substrate and use nanoimprinting technology to imprint the metalens structure on the sixth substrate onto the quartz glass substrate to obtain a metalens.
[0006] In the technical solution of this application embodiment, a metalens structure is first prepared on polymethyl methacrylate (PMMA) using electron beam lithography, serving as an initial template. The metalens structure is then copied onto an elastomer composite substrate, and subsequently transferred to a silicon substrate using etching technology. Finally, nanoimprint lithography is used to transfer the metalens structure from the silicon substrate to a high-refractive-index ultraviolet nanoimprint adhesive on a quartz glass substrate, yielding the metalens. This application first photolithographically creates the metalens nanostructure on PMMA as an initial template, rather than directly etching the substrate to create the adhesive template. Template preparation is simple and reusable, and the elastomer template can be repeatedly copied using nanoimprint lithography in subsequent steps, eliminating the need to start from scratch. The nanoimprint-based metalens structure preparation method provided by this invention is simple to operate, significantly reduces costs, and can be mass-produced stably on a large scale, showing broad application prospects in optical components and integrated optics.
[0007] In some embodiments, in step S1, the spin coating rate is 3000~3500 rpm, the spin coating time is 35~40s, and the spin coating thickness is 90~120nm.
[0008] In this embodiment, by spin-coating a specific thickness of polymethyl methacrylate (PMMA) onto a silicon substrate and then performing photolithography on the PMMA as an initial template, direct etching on the silicon substrate can be avoided, improving reusability and significantly reducing costs. Furthermore, PMMA is not a photosensitive material; it does not react to ultraviolet (UV) light but is an electron beam-sensitive resist. When an electron beam irradiates PMMA, it induces polymer chain breakage, making the exposed area easier to dissolve in the developer, achieving a resolution of less than 10 nm.
[0009] In some embodiments, the preparation method of the polymer elastomer substrate in step S3 specifically includes the following steps: S31. Apply imprinting adhesive to the surface of a silicon substrate to obtain a pretreated silicon substrate; S32. Lay the polymer elastomer substrate flat on the surface of the pretreated silicon substrate to absorb the imprinting adhesive for 6~10 minutes to obtain polymer elastomer template one.
[0010] In this embodiment, a polymer elastomer substrate is prepared, and the metalens structure on the initial template is transferred to the polymer elastomer substrate to facilitate subsequent imprinting using the polymer elastomer template.
[0011] In some embodiments, in step S4, the sacrificial layer is a water-soluble polymer material or an oil-soluble polymer material with a mass concentration of 1.5%, and the spin-coating thickness of the sacrificial layer is 55~70 nm.
[0012] In this embodiment, a sacrificial layer is provided, which is readily soluble in acetone solution to facilitate the subsequent separation process.
[0013] In some embodiments, in step S4, the imprinting layer is a UV nanoimprinting adhesive with a mass concentration of 3%, and the spin-coating thickness of the imprinting layer is 55~70nm.
[0014] In this embodiment, by setting an imprint layer, the metalens structure on the initial template can be successfully transferred to the polymer elastomer template.
[0015] In some embodiments, step S5 specifically includes the following steps: The inductively coupled plasma etching method is used to sequentially etch the imprint layer and the sacrificial layer with one or more gases selected from O2 and CHF3 until the silicon substrate is exposed.
[0016] In this embodiment, the imprint layer and the sacrificial layer are etched to remove the residual layer and expose the silicon substrate, which facilitates subsequent metal deposition and separation.
[0017] In some embodiments, in step S6, the metal layer is a Cr layer; the deposition method of the metal layer is thermal evaporation coating.
[0018] In this embodiment, a metal layer is deposited, and then etched using the metal layer as a mask in subsequent processes.
[0019] In some embodiments, step S9 specifically includes the following steps: spin-coating a UV nanoimprint adhesive containing 35wt% TiO2 particles onto a quartz glass substrate at a spin-coating rate of 3000 rpm, a spin-coating time of 40 s, and a spin-coating thickness of 300 nm.
[0020] In this embodiment, a high-refractive-index nanoimprint adhesive is spin-coated onto a quartz glass substrate. Ordinary ultraviolet nanoimprint adhesives have a low refractive index, making it difficult for the imprinted metalens structure to function. The refractive index of the ultraviolet nanoimprint adhesive can be increased by doping with TiO2 particles.
[0021] In some embodiments, step S7 specifically includes the following steps: Inductively coupled plasma etching was used to etch the silicon substrate using a mixture of O2, CF4, CHF3 and SF6 gases.
[0022] In this embodiment, the gas flow rate is continuously adjusted to achieve the best etching effect.
[0023] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description
[0024] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.
[0025] Figure 1 This is a process flow diagram of the metalens prepared in Example 1.
[0026] Figure 2 This is a SEM image of the metalens prepared in Example 1.
[0027] Figure Labels 11-Polymethyl methacrylate layer; 12-Silicon substrate one; 3-Polymer elastomer substrate one; 41-Silica; 5-Second substrate; 61-Imprint layer; 62-Sacrificial layer; 7-Third substrate; 8-Fourth substrate; 81-Metal layer; 9-Polymer elastomer substrate two; 10-Sixth substrate; 11-Quartz glass substrate; 12-Meta-lens. Detailed Implementation
[0028] The embodiments of the technical solution of this application are described in detail below. The following embodiments are only used to illustrate the technical solution of this application more clearly, and are therefore only examples, and should not be used to limit the scope of protection of this application.
[0029] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.
[0030] To address the problems of high fabrication cost, low product consistency, and difficulty in large-scale mass production of existing metalenses, this application provides a method for fabricating metalenses based on nanoimprinting. This application utilizes electron beam lithography to fabricate a metalens structure on polymethyl methacrylate (PMMA) as an initial template. The metalens structure is then copied onto an elastomer composite substrate, and etched to transfer it to a silicon substrate. Finally, nanoimprinting is used to transfer the metalens structure from the silicon substrate to a high-refractive-index ultraviolet nanoimprint adhesive on a quartz glass substrate. This method provides a simple and efficient way to obtain metalenses with uniform morphology and stable mechanical properties. Electron beam lithography is time-consuming; in traditional methods, if any subsequent step fails, electron beam lithography must be repeated on the silicon substrate, which is time-consuming, labor-intensive, and costly. This application first lithographically creates the metalens nanostructure on PMMA as an initial template instead of directly lithographicating on the substrate to create a template. This template preparation is simple and reusable, and the elastomer template can be repeatedly copied using nanoimprinting in subsequent steps, eliminating the need to start from scratch. The method for fabricating metalens structures based on nanoimprinting provided by this invention is simple to operate, greatly saves costs, and can be mass-produced stably on a large scale, and has broad application prospects in the fields of optical components and integrated optics.
[0031] This application provides a method for fabricating a metalens based on nanoimprinting, comprising the following steps: S1. Polymethyl methacrylate is spin-coated onto the surface of silicon substrate 1. After drying, electron beam lithography, development, and fixing are performed to obtain a polymethyl methacrylate-based template with a metalens structure. S2. A silica layer is deposited on a polymethyl methacrylate template and subjected to a low surface energy treatment to obtain a first substrate; S3. Nanoimprinting is performed on the first substrate using a polymer elastomer substrate one, so that the metalens structure on the first substrate is imprinted onto the polymer elastomer substrate one to obtain the second substrate; S4. A sacrificial layer and an imprint layer are sequentially spin-coated onto silicon substrate II to obtain a pretreated imprint substrate; S5. The pre-treated imprinted substrate is imprinted using the second substrate, so that the metastructure on the second substrate is imprinted onto the imprinted layer of the pre-treated imprinted substrate. Then, the imprinted layer and the sacrificial layer are etched until the silicon substrate is exposed to obtain the third substrate. S6. A metal layer is deposited on the surface of the third substrate, and then the sacrificial layer and the imprint layer in the third substrate are removed to obtain a fourth substrate; S7. Using the metal layer as a mask, etch the silicon substrate of the fourth substrate, then clean off the metal layer, and then perform a low surface energy treatment to obtain the fifth substrate; S8. Nanoimprinting is performed on the fifth substrate using a second polymer elastomer substrate to imprint the metalens structure on the fifth substrate onto the second polymer elastomer substrate, thereby obtaining a sixth substrate. S9. Prepare a quartz glass substrate and use nanoimprinting technology to imprint the metalens structure on the sixth substrate onto the quartz glass substrate to obtain a metalens.
[0032] In the technical solution of this application embodiment, a metalens structure is first prepared on polymethyl methacrylate (PMMA) using electron beam lithography, serving as an initial template. The metalens structure is then copied onto an elastomer composite substrate, and subsequently transferred to a silicon substrate using etching technology. Finally, nanoimprint lithography is used to transfer the metalens structure from the silicon substrate to a high-refractive-index ultraviolet nanoimprint adhesive on a quartz glass substrate, yielding the metalens. This application first photolithographically patterns the metalens nanostructure on PMMA as an initial template, rather than directly etching on the silicon substrate to create an adhesive template. Template preparation is simple and reusable, and the elastomer template can be repeatedly copied using nanoimprint lithography in subsequent steps, eliminating the need to start from scratch. The nanoimprint-based metalens structure preparation method provided by this invention is simple to operate, significantly reduces costs, and can be mass-produced stably on a large scale, showing broad application prospects in optical components and integrated optics.
[0033] Furthermore, in some embodiments, in step S1, the spin coating rate is 3000~3500 rpm, the spin coating time is 35~40s, and the spin coating thickness is 90~120nm.
[0034] In the technical solution of this application embodiment, by spin-coating a polymethyl methacrylate (PMMA) of a specific thickness onto a silicon substrate and then performing photolithography on the PMMA as an initial template, direct photolithography on the silicon substrate can be avoided, improving reusability and significantly reducing costs. Furthermore, PMMA is not a photosensitive material; it does not react to ultraviolet (UV) light but is an electron beam-sensitive resist. When an electron beam irradiates PMMA, it induces polymer chain breakage, making the exposed area easier to dissolve in the developer, achieving a resolution of less than 10 nm.
[0035] Furthermore, in some embodiments, in step S1, the silicon substrate is a p-doped n-type single-sided polished silicon wafer with a crystal orientation of <100> The resistivity is 1~10 Ωcm -2 The thickness is 500±0.3μm.
[0036] Furthermore, in some embodiments, in step S1, the concentration of polymethyl methacrylate is 2%.
[0037] Furthermore, in some embodiments, in step S1, the drying temperature is 150~180℃ and the drying time is 2~5min.
[0038] Furthermore, in some embodiments, in step S1, the developing solution is a mixture of methyl isobutyl ketone and isopropanol in a mass ratio of 1:3; the developing time is 10-25 seconds; and the fixing solution is isopropanol, with a fixing time of 30 seconds.
[0039] Furthermore, in some embodiments, in step S2, the deposition method is plasma-enhanced chemical vapor deposition, and the deposition thickness is 10~15 nm.
[0040] In the technical solution of this application embodiment, the deposited silicon dioxide layer can enable surface energy-treated reagents to be better adsorbed on the metalens structure of polymethyl methacrylate.
[0041] Furthermore, in some embodiments, in step S2, the reagent for the low surface energy treatment is heptadecafluoropolyether silane; the temperature for the low surface energy treatment is 80~95℃; and the time for the low surface energy treatment is 5~8h.
[0042] Furthermore, in some embodiments, step S3, the method for preparing the polymer elastomer substrate, specifically includes the following steps: S31. Apply imprinting adhesive to the surface of a silicon substrate to obtain a pretreated silicon substrate; S32. Lay the polymer elastomer substrate flat on the surface of the pretreated silicon substrate to absorb the imprinting adhesive for 6~10 minutes to obtain polymer elastomer template one.
[0043] In the technical solution of this application embodiment, a polymer elastomer substrate is prepared, and the meta-lens structure on the initial template is transferred to the polymer elastomer substrate, which facilitates subsequent imprinting using the polymer elastomer template.
[0044] Furthermore, in some embodiments, step S3 specifically includes the following steps: under nitrogen atmosphere, a first substrate is covered on a polymer elastomer template, and after applying a certain pressure, it is exposed to ultraviolet light for 5-10 minutes.
[0045] Furthermore, in some embodiments, in step S4, the sacrificial layer is a water-soluble polymer material or an oil-soluble polymer material with a mass concentration of 1.5%. The water-soluble polymer material is one or a mixture of two of polyvinyl alcohol and polyvinylpyrrolidone, and the oil-soluble polymer material is polymethyl methacrylate. The spin-coating thickness of the sacrificial layer is 55~70 nm.
[0046] In the technical solution of this application embodiment, a sacrificial layer is provided, which is easily soluble in acetone solution to facilitate the subsequent separation process.
[0047] Furthermore, in some embodiments, in step S4, the imprinting layer is a 3% (w / w) UV nanoimprint adhesive, and the material of the imprint adhesive is at least one of polydimethylsiloxane, polytetrafluoroethylene, polyvinyl chloride, and acrylate; the spin-coating thickness of the imprinting layer is 55~70 nm.
[0048] In the technical solution of this application embodiment, by setting an imprint layer, the meta-lens structure on the initial template can be successfully transferred to the polymer elastomer template.
[0049] Furthermore, in some embodiments, step S5 specifically includes the following steps: The inductively coupled plasma etching method is used to sequentially etch the imprint layer and the sacrificial layer with one or more gases selected from O2 and CHF3 until the silicon substrate is exposed.
[0050] Furthermore, in some embodiments, the etching gas of the imprinted layer is a mixture of O2 and CHF3, wherein the gas flow rate of O2 is 20 sccm and the gas flow rate of CHF3 is 2 sccm; the etching gas of the sacrificial layer is O2 with a gas flow rate of 10 sccm.
[0051] In the technical solution of this application embodiment, the residual layer is removed by etching the imprint layer and the sacrificial layer to expose the silicon substrate, which facilitates subsequent metal deposition and separation.
[0052] Furthermore, in some embodiments, step S5 specifically includes the following steps: under nitrogen atmosphere, a second substrate is covered on the pretreated imprinting substrate, and after applying a certain pressure, it is exposed to ultraviolet light for 5-10 minutes.
[0053] Furthermore, in some embodiments, in step S6, the metal layer is a Cr layer; the deposition method of the metal layer is a thermal evaporation coating method.
[0054] Furthermore, in some embodiments, the thermal evaporation coating method specifically includes the following steps: under high vacuum conditions, Cr metal is heated and evaporated, causing it to vaporize and deposit into a film on the substrate surface, wherein the deposition rate is 0.1~0.7 nm / s and the deposition thickness is 30~40 nm.
[0055] In the technical solution of this application embodiment, a metal layer is deposited, and then the metal layer is used as a mask for etching in subsequent processes.
[0056] Furthermore, in some embodiments, step S6 specifically includes the following steps: ultrasonic cleaning in acetone and ethanol sequentially for 5-10 minutes.
[0057] Furthermore, in some embodiments, step S7 specifically includes the following steps: Inductively coupled plasma etching was used to etch a silicon substrate using a mixture of O2, CF4, CHF3 and SF6 gases. The flow rates of O2, CF4, CHF3 and SF6 were 5 sccm, CF4 and SF6 respectively.
[0058] In the technical solution of this application embodiment, the best etching effect is achieved by continuously adjusting the gas flow rate.
[0059] Furthermore, in some embodiments, in step S7, the cleaning reagent is a mixed solution of cerium ammonium nitrate, acetic acid, and pure water, and the mass ratio of cerium ammonium nitrate, acetic acid, and pure water is 8:22:77; the cleaning method is ultrasonic cleaning.
[0060] Furthermore, in some embodiments, in step S7, the reagent for the low surface energy treatment is heptadecafluoropolyether silane; the temperature for the low surface energy treatment is 80~95℃; and the time for the low surface energy treatment is 5~8h. Furthermore, in some embodiments, in step S8, the preparation method of the second polymer elastomer substrate is the same as that of the first polymer elastomer substrate.
[0061] Furthermore, in some embodiments, step S8 specifically includes the following steps: under nitrogen atmosphere, covering the fifth substrate with a polymer elastomer substrate II, applying a certain pressure, and then exposing to ultraviolet light for 5-10 minutes.
[0062] Furthermore, in some embodiments, step S9 specifically includes the following steps for preparing the quartz glass substrate: spin-coating an ultraviolet nanoimprint adhesive containing 35wt% TiO2 particles onto the quartz glass substrate at a spin-coating rate of 3000 rpm, a spin-coating time of 40 s, and a spin-coating thickness of 300 nm.
[0063] In the technical solution of this application embodiment, a high-refractive-index nanoimprint adhesive is spin-coated on a quartz glass substrate. Ordinary ultraviolet nanoimprint adhesives have a low refractive index, making it difficult for the imprinted metalens structure to function. The refractive index of the ultraviolet nanoimprint adhesive can be increased by doping with TiO2 particles.
[0064] Furthermore, in some embodiments, step S9 specifically includes the following steps: under nitrogen atmosphere, a sixth substrate is covered on a quartz glass substrate, and after applying a certain pressure, it is exposed to ultraviolet light for 5-10 minutes.
[0065] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.
[0066] Example 1 This embodiment provides a method for fabricating metalenses based on nanoimprinting, such as... Figure 1 As shown, the specific steps include the following: (1) In the crystal orientation <100> The resistivity is 8 Ωcm -2 On a p-doped n-type single-sided silicon substrate with a thickness of 500 μm, a 2% polymethyl methacrylate (PMMA) was spin-coated at 3000 rpm for 40 s, resulting in a PMMA thickness of 100 nm. The substrate was then heated on a hot stage at 170 °C for 7 min, followed by electron beam exposure. Subsequently, the substrate was immersed sequentially in a solution of methyl isobutyl ketone (MOH) and isopropanol in a 1:3 mass ratio, and in an isopropanol solution for 20 s and 30 s, respectively, to obtain a PMMA-based template with a metalens structure.
[0067] (2) A 10 nm silicon dioxide layer was deposited on a polymethyl methacrylate template by plasma-enhanced chemical vapor deposition. Then, the substrate was placed in a vacuum environment and treated with a heptadecanofluoropolyether silane reagent for low surface energy. The temperature during the low surface energy treatment was set to 85 °C and the holding time was 7 h to obtain the first substrate.
[0068] (3) Apply imprinting adhesive to the surface of the silicon substrate, then lay the polymer elastomer substrate flat on the surface, absorb the imprinting adhesive for 7 minutes, and obtain polymer elastomer template one; cover the obtained polymer elastomer template one with the first substrate, expose it to ultraviolet light for 10 minutes in a nitrogen atmosphere, and then demold to obtain the second substrate.
[0069] (4) A 1.5% polymethyl methacrylate layer with a mass concentration of 3000 rpm was spin-coated on silicon substrate II for 40 s and a sacrificial layer with a thickness of 65 nm was spin-coated; then a 3% polydimethylsiloxane layer with a mass concentration of 3% was spin-coated on silicon substrate II for 40 s and a thickness of 65 nm was spin-coated to obtain a pretreated imprint substrate.
[0070] (5) Under nitrogen atmosphere, a second substrate is placed on the pretreated imprinted substrate and subjected to a certain pressure. After UV exposure for 10 min, inductively coupled plasma etching is used to sequentially etch the imprinted layer and the sacrificial layer until the silicon substrate is exposed, thus obtaining the third substrate. The etching gas for the imprinted layer is a mixture of O2 and CHF3, with a gas flow rate of 20 sccm for O2 and 2 sccm for CHF3. The etching gas for the sacrificial layer is O2 with a gas flow rate of 10 sccm.
[0071] (6) A 35 nm Cr layer was deposited on the surface of the third substrate at a rate of 0.4 nm / s using thermal evaporation deposition method. Then the substrate was ultrasonically cleaned in acetone and ethanol for 10 min in sequence to obtain the fourth substrate.
[0072] (7) The silicon substrate of the fourth substrate was etched by using an inductively coupled plasma etching method with a mixture of O2, CF4, CHF3 and SF6 gas. The gas flow rate of O2 was 5 sccm, the gas flow rate of CF4 was 8 sccm, the gas flow rate of CHF3 was 44 sccm and the gas flow rate of SF6 was 5 sccm. Then, the Cr layer on the silicon template was ultrasonically cleaned with a mixed solution of cerium ammonium nitrate, acetic acid and pure water in a mass ratio of 8:22:77. The substrate was then subjected to low surface energy treatment. The temperature during the low surface energy treatment was set to 85℃ and the holding time was 7h to obtain the fifth substrate.
[0073] (8) Apply imprinting adhesive to the surface of the silicon substrate, then lay the polymer elastomer substrate flat on the surface, absorb the imprinting adhesive for 7 minutes, and obtain polymer elastomer template two; under nitrogen atmosphere, cover the polymer elastomer substrate two on the fifth substrate, apply a certain pressure, and expose to ultraviolet light for 10 minutes to obtain the sixth substrate.
[0074] (9) A UV nanoimprint adhesive containing 35 wt% TiO2 particles was spin-coated onto a quartz glass substrate at a spin-coating rate of 3000 rpm for 40 s and a spin-coating thickness of 300 nm to obtain a quartz glass substrate. Then, a sixth substrate was covered onto the quartz glass substrate under a nitrogen atmosphere and a certain pressure was applied before UV exposure for 10 min to obtain a meta-lens.
[0075] The SEM image of the metalens prepared in this embodiment is as follows: Figure 2 As shown.
[0076] Depend on Figure 2 The SEM images show that the fabricated metalens structure has no obvious defects and has high fidelity.
[0077] Comparative Example 1 Comparative Example 1 provides a method for preparing a metalens based on nanoimprinting. The difference from Example 1 is that no silicon dioxide layer is deposited in step (2). The other steps are roughly the same as in Example 1 and will not be repeated here.
[0078] In the lens fabrication process of this comparative example, obvious delamination occurred. This is because the heptadecimal polyether silane reagent requires silanol groups as adhesion sites. Polymethyl methacrylate cannot directly bind with the heptadecimal polyether silane reagent, and cannot complete the low surface energy treatment, resulting in peeling during subsequent imprinting.
[0079] In summary, this application provides a method for fabricating metalenses based on nanoimprinting. This application utilizes electron beam lithography to fabricate a metalens structure on polymethyl methacrylate (PMMA) as an initial template. The metalens structure is then replicated onto an elastomer composite substrate, and subsequently transferred to a silicon substrate using etching technology. Finally, nanoimprinting technology is used to transfer the metalens structure from the silicon substrate to a high-refractive-index ultraviolet nanoimprint adhesive on a quartz glass substrate. This method allows for a simple and efficient acquisition of metalens structures with uniform morphology and stable mechanical properties. Electron beam lithography is time-consuming; in traditional methods, if any subsequent step fails, electron beam lithography must be repeated on the silicon substrate, which is time-consuming, labor-intensive, and costly. This application first lithographically creates the metalens nanostructure on PMMA as an initial template instead of directly etching on the substrate to create the adhesive template. The template preparation is simple and reusable, and the elastomer template can be repeatedly replicated using nanoimprinting in subsequent steps, eliminating the need to start from scratch. The method for fabricating metalens structures based on nanoimprinting provided by this invention is simple to operate, greatly saves costs, and can be mass-produced stably on a large scale, and has broad application prospects in the fields of optical components and integrated optics.
[0080] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.
Claims
1. A method for fabricating metalenses based on nanoimprinting, characterized in that, Includes the following steps: S1. Polymethyl methacrylate is spin-coated onto the surface of silicon substrate 1. After drying, electron beam lithography, development, and fixing are performed to obtain a polymethyl methacrylate-based template with a metalens structure. S2. A silica layer is deposited on a polymethyl methacrylate template and subjected to a low surface energy treatment to obtain a first substrate; S3. Nanoimprinting is performed on the first substrate using a polymer elastomer substrate one, so that the metalens structure on the first substrate is imprinted onto the polymer elastomer substrate one to obtain the second substrate; S4. A sacrificial layer and an imprint layer are sequentially spin-coated onto silicon substrate II to obtain a pretreated imprint substrate; S5. The pre-treated imprinted substrate is imprinted using the second substrate, so that the metastructure on the second substrate is imprinted onto the imprinted layer of the pre-treated imprinted substrate. Then, the imprinted layer and the sacrificial layer are etched until the silicon substrate is exposed to obtain the third substrate. S6. A metal layer is deposited on the surface of the third substrate, and then the sacrificial layer and the imprint layer in the third substrate are removed to obtain a fourth substrate; S7. Etch the silicon substrate of the fourth substrate using the metal layer as a mask, then clean off the metal layer, and then perform a low surface energy treatment to obtain the fifth substrate; S8. Nanoimprinting is performed on the fifth substrate using a second polymer elastomer substrate to imprint the metalens structure on the fifth substrate onto the second polymer elastomer substrate, thus obtaining a sixth substrate. S9. Prepare a quartz glass substrate and use nanoimprinting technology to imprint the metalens structure on the sixth substrate onto the quartz glass substrate to obtain a metalens.
2. The method for fabricating a metalens based on nanoimprinting according to claim 1, characterized in that, In step S1, the spin coating rate is 3000~3500 rpm, the spin coating time is 35~40s, and the spin coating thickness is 90~120nm.
3. The method for fabricating a metalens based on nanoimprinting according to claim 1, characterized in that, In step S3, the preparation method of the polymer elastomer substrate one specifically includes the following steps: S31. Apply imprinting adhesive to the surface of a silicon substrate to obtain a pretreated silicon substrate; S32. Lay the polymer elastomer substrate flat on the surface of the pretreated silicon substrate and absorb the imprinting adhesive for 6~10 minutes to obtain polymer elastomer substrate one.
4. The method for fabricating a metalens based on nanoimprinting according to claim 1, characterized in that, In step S4, the sacrificial layer is a water-soluble or oil-soluble polymer material with a mass concentration of 1.5%, and the spin-coating thickness of the sacrificial layer is 55~70nm.
5. The method for fabricating a metalens based on nanoimprinting according to claim 1, characterized in that, In step S4, the imprinting layer is a UV nanoimprinting adhesive with a mass concentration of 3%, and the spin-coating thickness of the imprinting layer is 55~70nm.
6. The method for fabricating a metalens based on nanoimprinting according to claim 1, characterized in that, In step S5, the etching specifically includes the following steps: The inductively coupled plasma etching method is used to sequentially etch the imprint layer and the sacrificial layer with one or more gases selected from O2 and CHF3 until the silicon substrate is exposed.
7. The method for fabricating a metalens based on nanoimprinting according to claim 1, characterized in that, In step S6, the metal layer is a Cr layer; the deposition method of the metal layer is thermal evaporation coating.
8. The method for fabricating a metalens based on nanoimprinting according to claim 1, characterized in that, In step S9, the preparation of the quartz glass substrate specifically includes the following steps: spin-coating an ultraviolet nanoimprint adhesive containing 35wt% TiO2 particles onto the quartz glass substrate at a spin-coating rate of 3000 rpm for 40 s and a spin-coating thickness of 300 nm.
9. The method for fabricating a metalens based on nanoimprinting according to claim 1, characterized in that, In step S7, the etching specifically includes the following steps: Inductively coupled plasma etching was used to etch the silicon substrate using a mixture of O2, CF4, CHF3 and SF6 gases.