Method for manufacturing a master for nanoimprint fabrication of a titania superlens, master and method for fabricating a titania superlens

Abstract

The application provides a manufacturing method of a master plate for nanoimprint preparation of a titanium dioxide superlens, the master plate and a method for preparing the titanium dioxide superlens, and belongs to the technical field of micro-nano optical manufacturing. A titanium dioxide layer is prepared on the surface of a superlens substrate, then an adhesion-increasing layer is prepared on the surface of the titanium dioxide layer, and then N periodic marks for defining the positions of N periodic units are etched; a heat nanoimprint method is adopted to obtain an IPS working mold according to the master plate for nanoimprint preparation of the titanium dioxide superlens, an anti-adhesion layer is prepared on the surface of the IPS working mold, and then a chromium layer is prepared on the anti-adhesion layer; the N periodic marks of the processed IPS working mold are aligned with the N periodic marks on the processed superlens substrate, and then ultraviolet nanoimprint is performed to obtain the titanium dioxide superlens. The application mainly relies on the nanoimprint technology with relatively low cost, and significantly reduces the equipment investment and processing cost.

Description

Technical Field

[0001] This invention relates to the field of micro-nano optical manufacturing technology, specifically to a method for manufacturing a master plate for nanoimprinting titanium dioxide superlenses, the master plate, and a method for preparing titanium dioxide superlenses. Background Technology

[0002] Superlenses, a type of planar optical device based on subwavelength nanostructure arrays, rely on precise control of the geometric parameters (such as shape and size) and spatial arrangement of the nanostructures to flexibly manipulate the phase, amplitude, and polarization state of incident light waves, thereby achieving focusing and imaging functions similar to traditional curved optical elements. Compared to traditional optical elements, superlenses possess disruptive characteristics such as lightweight and thinness, flat structure, and ease of integration with other devices, demonstrating strong application potential in fields such as smartphone camera modules, high-resolution microscopic imaging systems, and automotive LiDAR.

[0003] In the selection of materials for superlenses, titanium dioxide (TiO2) stands out due to its excellent optical properties in the visible light band—a refractive index of over 2.4 and an extinction coefficient close to 0, which effectively reduces light energy loss, making it the preferred material for fabricating high-performance superlenses. However, the mainstream technologies in the current field of superlens fabrication still have significant limitations: although electron beam lithography can achieve subwavelength-level processing accuracy, its processing efficiency is extremely low (typically only at the millimeter level per hour), equipment and operating costs are high, and it is difficult to overcome the bottleneck in the fabrication of large-size devices, thus failing to meet the needs of industrial mass production. Summary of the Invention

[0004] The purpose of this invention is to address the shortcomings of existing technologies by providing a method for manufacturing a master plate for nanoimprinting titanium dioxide superlenses, comprising:

[0005] Step 1: Divide the superlens micro / nano structure into N periodic units, and use N periodic markers to define the positions of the N periodic units;

[0006] Step 2: Using photolithography, a periodic unit and corresponding periodic marker are etched onto the first substrate to obtain a substrate containing... The first mold of the superlens micro / nano structure is used to etch N periodic marks on the second substrate using photolithography, resulting in the second substrate with etched periodic marks.

[0007] Step 3, with... The first mold of the superlens micro / nano structure serves as the master substrate for the first transfer. Periodic markings are used as alignment marks, an IPS transfer mold is used as the transfer medium, and a thermal nanoimprinting method is employed for transfer. Two adjacent microlenses are then transferred onto the second substrate with the etched periodic markings. Micro-nano structures of superlenses were obtained, containing A second mold for a superlens micro / nano structure;

[0008] Step 4, with... The second mold for the superlens micro / nano structure serves as the master plate for the second transfer. Periodic markings are used as alignment marks, an IPS transfer mold is used as the transfer medium, and a nanoimprinting method is employed for the transfer, transferring the second transfer master plate... The micro / nanostructure of the superlens is transferred back to the master substrate for a second transfer at adjacent positions, resulting in a micro / nanostructure containing... The second mold containing the micro-nano structure of the superlens is used as the master mold for the next transfer. The transfer is repeated using periodic marks as alignment marks, an IPS transfer mold as the transfer medium, and a thermal nanoimprinting method. The number of micro-nano structures of the superlens on the second mold is increased sequentially until a second mold containing the complete micro-nano structure of the superlens is obtained, which serves as the master mold for nanoimprinting to prepare titanium dioxide superlenses.

[0009] Furthermore, the first substrate is made of silicon or quartz, and the second substrate is made of quartz.

[0010] Furthermore, the photolithography process is ultraviolet lithography or electron beam lithography.

[0011] Furthermore, the specific details of the transfer process, which uses periodic marks as alignment marks, an IPS transfer mold as the transfer medium, and a thermal nanoimprint method, are as follows:

[0012] The current master plate to be transferred is then subjected to a thermal nanoimprinting method to obtain a material with the same properties as the current master plate. An IPS transfer mold with a complementary structure of superlens micro / nano structures and periodic markings. The number of periodic primitives, based on those currently being transferred to the master plate. An IPS transfer mold with a complementary structure of superlens micro / nano structures and periodic markings is used to transfer the current transfer master onto the master substrate using a thermal nanoimprinting method. The micro-nano structure of the superlens and the periodic markings are transferred onto the target mold.

[0013] A master plate prepared by the above-described method for fabricating a master plate for nanoimprinting titanium dioxide superlenses.

[0014] A method for fabricating a titanium dioxide superlens using the aforementioned master plate for nanoimprint fabrication of titanium dioxide superlenses includes:

[0015] Step 1: A titanium dioxide layer is prepared on the surface of the superlens substrate, and then an adhesive layer is prepared on the surface of the titanium dioxide layer. N periodic marks for specifying the positions of N periodic primitives are etched on the superlens substrate with the titanium dioxide layer and adhesive layer on the surface by photolithography to obtain the processed superlens substrate.

[0016] Step 2: Using the thermal nanoimprinting method, an IPS working mold is obtained based on the mother plate used for nanoimprinting to prepare titanium dioxide superlenses. The IPS working mold has a structure that is complementary to the micro-nano structure and periodic markings of the superlenses on the mother plate used for nanoimprinting to prepare titanium dioxide superlenses. An anti-adhesion layer is prepared on the surface of the IPS working mold, and then a chromium layer is prepared on the anti-adhesion layer to obtain the processed IPS working mold.

[0017] Step 3: Align the N periodic marks of the processed IPS working mold with the N periodic marks on the processed superlens substrate and perform ultraviolet nanoimprinting to obtain a titanium dioxide superlens.

[0018] Furthermore, the specific method for preparing a titanium dioxide layer on the surface of the superlens substrate is as follows: a titanium dioxide layer is prepared on the surface of the superlens substrate using a magnetron sputtering process.

[0019] Furthermore, the specific method for preparing the tackifying layer on the surface of the titanium dioxide layer is as follows: N-[3-(trimethoxysilyl)propyl]ethylenediamine solution is deposited on the surface of the titanium dioxide layer by spin coating, and the tackifying layer is obtained after heat treatment.

[0020] Furthermore, the specific method for preparing an anti-adhesion layer on the surface of the IPS working mold is as follows: the IPS working mold and perfluorooctyltrichlorosilane are placed together in a vacuum drying oven for vacuum baking.

[0021] Furthermore, the specific method for preparing the chromium layer on the anti-adhesion layer is as follows: a chromium layer is prepared on the surface of the anti-adhesion layer using a magnetron sputtering process.

[0022] The beneficial effects of this invention are as follows:

[0023] 1. This invention does not directly manufacture a complete large-size mold. Instead, it first divides the superlens micro / nano structure into N periodic primitives. A small first mold containing a single primitive is first fabricated. Then, using IPS material as the transfer medium, the number of structural components is sequentially multiplied through multiple thermal nanoimprinting processes. This method transforms the time-consuming and lengthy high-precision direct-write processing into a highly efficient pattern replication and splicing process, greatly improving manufacturing efficiency.

[0024] 2. To achieve high-quality stitching, this invention uses photolithography to create precise periodic marks on the first mold and the second substrate in the initial stage. These marks are used for high-precision visual alignment during each transfer. This step-by-step, small-scale precise alignment ensures that the final stitching seam is extremely small, without affecting the imaging quality of the superlens.

[0025] 3. This invention does not involve doping titanium dioxide nanoparticles into the imprinting adhesive. Instead, a uniform and dense pure titanium dioxide layer is first prepared on the superlens substrate by magnetron sputtering. Subsequently, an IPS working mold replicated from the master substrate is used for ultraviolet nanoimprinting to directly etch the structure into the titanium dioxide layer. This method ensures that the final nanostructure possesses the high refractive index (≥2.4) and low optical loss of pure titanium dioxide, thereby guaranteeing the excellent optical performance of the superlens.

[0026] 4. To ensure adhesion and release between the material layers, this invention spin-coates an adhesion-enhancing layer on top of the titanium dioxide layer. This enhances the adhesion between the UV imprinting adhesive and the titanium dioxide surface, effectively preventing delamination defects during pattern transfer. An anti-adhesion layer and a chromium layer are sequentially prepared on the surface of the IPS working mold. The anti-adhesion layer ensures smooth demolding after imprinting and protects the mold structure; the chromium layer acts as a hard mask, protecting the IPS mold during titanium dioxide etching and extending its lifespan. These measures collectively guarantee high yield and process stability in mass production.

[0027] 5. This invention only requires the initial fabrication of a small unit mold using high-precision photolithography equipment. Subsequent scaling and replication processes primarily rely on relatively low-cost nanoimprint lithography. This reduces the long-term occupancy of extremely expensive direct-write equipment, significantly lowering equipment investment and processing costs. Multiple IPS working molds can be rapidly replicated from a single motherboard for parallel production, greatly improving production efficiency and making it highly suitable for large-scale, industrialized manufacturing. Attached Figure Description

[0028] Figure 1 This is a flowchart illustrating the large-scale fabrication process of the superlens of the present invention.

[0029] Figure 2 This is a schematic diagram of the planar structure of the first mold of the present invention.

[0030] Figure 3 This is a schematic diagram of the vertical structure of the first mold of the present invention.

[0031] Figure 4 This is a schematic diagram of the planar structure of the second base of the second mold of the present invention.

[0032] Figure 5 This is a schematic diagram of the first stage of the preparation process in the preparation of the second mold of the present invention.

[0033] Figure 6 This is a schematic diagram of the second stage of the preparation process in the second mold of the present invention.

[0034] Figure 7 This is a schematic diagram of the structure of the working mold plane of the IPS of the present invention.

[0035] Figure 8 This is a schematic diagram of the vertical structure of the IPS working mold of the present invention.

[0036] Figure 9 This is a schematic diagram of the structure of the superlens substrate and its surface coating of the present invention.

[0037] Figure 10 This is a schematic diagram of the planar structure of the superlens substrate of the present invention.

[0038] Figure 11 This is a schematic diagram of the structure of the superlens of the present invention.

[0039] Figure 12 This is a schematic diagram of the superlens micro / nano structure of the present invention.

[0040] Figure reference numerals: 1-Superlens substrate; 2-Periodic element; 3-First substrate; 4-Second substrate; 5-Periodic marker; 6-Titanium dioxide layer; 7-Adhesion layer; 8-Anti-adhesion layer; 9-Chromium layer; 10-IPS substrate; 11-Complementary structure of the superlens micro / nano structure; 12-Superlens micro / nano structure. Detailed Implementation

[0041] To make the technical problems, technical solutions, and beneficial effects to be solved by this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and are not intended to limit the scope of this application.

[0042] Definitions:

[0043] Thermal nanoimprinting is a patterning process based on thermoplastic polymer materials. The process involves softening the imprinting adhesive through heating, then applying mechanical pressure to press nanostructures from a mold into the adhesive layer. After cooling and solidification, the material is demolded, ultimately forming a micro / nano pattern on the substrate surface that complements the mold. This method focuses on addressing the insufficient precision caused by the optical diffraction limit in traditional photolithography, and is particularly suitable for the mass production of high aspect ratio, subwavelength-scale structures.

[0044] UV nanoimprinting: a highly efficient micro-nano pattern replication technology. Its core principle is to transfer the nanostructure pattern on the mold to a substrate coated with liquid UV imprinting adhesive by using UV light curing instead of heating and pressurization.

[0045] IPS (Insulated Stone Styrene): Impact-resistant polystyrene, a high-performance thermoplastic polymer, is specifically used as a working mold material in nanoimprinting processes. High-cost quartz or silicon master molds serve as the original, and multiple IPS working molds are rapidly replicated through thermal nanoimprinting. During this process, the structure of the IPS mold complements the master mold, with convex shapes becoming concave shapes, laying the foundation for subsequent pattern transfer to the product. In this invention, both the IPS working mold and the IPS transfer mold refer to molds made from IPS material. The IPS working mold is the mold ultimately used to produce titanium dioxide superlenses, while the IPS transfer mold is the mold used for transfer during the fabrication of the master plate for nanoimprinting the preparation of titanium dioxide superlenses.

[0046] Example 1

[0047] Nanoimprinting is an advanced micro / nano fabrication technology. Its core principle is to mechanically imprint nanoscale patterns onto a resist material coated on a substrate, which is then cured to form a pattern, thus enabling the mass production of nanoscale patterns. Although nanoimprinting has high throughput potential, there are two major problems when applied directly to titanium dioxide (TiO2) substrates: (1) the etching selectivity ratio between titanium dioxide and imprinting adhesive is low, resulting in poor pattern transfer fidelity; (2) the refractive index of imprinting adhesive doped with titanium dioxide nanoparticles is much lower than that of pure titanium dioxide, which seriously impairs optical performance. In addition, the size of a single nanoimprinting mold is limited, making it difficult to directly imprint large-area superlenses. Based on the above problems, there is an urgent need to develop a new technology for the large-scale fabrication of titanium dioxide superlenses that balances processing accuracy, efficiency, and cost.

[0048] The proposed fabrication involves a circular superlens with a diameter of 60 mm, whose basic structural unit is as follows: Figure 11 As shown. The superlens substrate 1 is a double-sided polished fused silica sheet, which contains a titanium dioxide micro / nano structure array, namely the superlens micro / nano structure 12. The basic structural unit of the superlens micro / nano structure 12 is shown in the figure. Figure 12 As shown, the superlens micro / nanostructure 12 consists of titanium dioxide nanopillars of the same height but different diameters. By changing the duty cycle of the nanopillars, the equivalent refractive index is adjusted, thereby modulating the phase of the incident light wave. The phase modulation amount of the micro / nanostructure units at different positions is shown. ,in This is the distance between the focusing axis and the plane of the superlens. The incident light wavelength, For the focusing axis at Projected coordinates on the axis. In this embodiment, , , .

[0049] Figure 12This is a schematic diagram of a superlens unit structure. When circularly polarized light is incident, while ensuring high reflection efficiency, the difference in phase modulation exceeds [a certain value] when the diameter of the titanium dioxide circular nanopillar changes. To optimize the objective, the preferred size parameters of the obtained micro / nano structure units are: unit structure period. Height of titanium dioxide nanopillars diameter of titanium dioxide nanopillars exist to between.

[0050] In this embodiment, the overall length and width of the superlens are on the millimeter scale, while the required processing precision is 40 nm. Traditional processing techniques, such as photolithography and laser direct writing, are difficult to meet the fabrication requirements of such large-format, high-precision micro / nano structures, resulting in problems such as low processing precision, long cycle time, high cost, and large seams. Therefore, this invention provides a method for manufacturing a mother plate for nanoimprint fabrication of titanium dioxide superlenses, used for batch processing of superlenses, specifically including the following steps:

[0051] Step 1: Divide the superlens micro / nano structure 12 into N periodic units 2, and use N periodic markers 5 to specify the positions of the N periodic units 2;

[0052] Step 2: A periodic unit 2 and a corresponding periodic mark 5 are etched on the first substrate 3 using photolithography to obtain a substrate containing... The first mold of the superlens micro / nano structure 12 is used to etch N periodic marks 5 on the second substrate 4 through photolithography, thus obtaining the second substrate 4 with etched periodic marks 5.

[0053] Step 3, with... The first mold of the superlens micro / nano structure 12 serves as the master plate for the first transfer. The transfer is performed using a thermal nanoimprinting method, with an IPS transfer mold as the transfer medium and periodic marks 5 as alignment marks. Two adjacent microlenses are transferred onto the second substrate 4, on which the periodic marks 5 have been etched. 12 micro / nano structures of superlenses were obtained, containing The second mold of the superlens micro / nano structure 12;

[0054] Step 4, with... The second mold of the superlens micro / nano structure 12 serves as the master plate for the second transfer. Using periodic marks 5 as alignment marks, an IPS transfer mold as the transfer medium, and a nanoimprinting method, the transfer is performed, transferring the master plate for the second transfer. The superlens micro / nano structure 12 is transferred back to the master substrate for a second transfer at adjacent positions, resulting in a micro / nano structure containing... The second mold containing the superlens micro / nano structure 12 is used as the master mold for the next transfer. The thermal nanoimprinting method is repeated, using the IPS transfer mold as the transfer medium and the periodic mark 5 as the alignment mark for transfer. The number of superlens micro / nano structures 12 on the second mold is increased sequentially until a second mold containing the complete superlens micro / nano structure 12 is obtained, which serves as the master mold for nanoimprinting to prepare titanium dioxide superlenses.

[0055] Manufacturing the master mold initially requires methods such as electron beam lithography or high-end ultraviolet lithography. Electron beam lithography, in particular, while offering extremely high precision, is very slow. Ensuring the uniformity of lithography and etching processes on a large substrate is extremely difficult; even minute process fluctuations can lead to performance differences in different areas of the superlens, affecting optical performance. This invention avoids the efficiency bottleneck of traditional single-stage lithography through step-by-step transfer. Utilizing periodic markers as alignment marks ensures positional accuracy during the transfer process, reducing splicing errors and thus guaranteeing the optical performance of the superlens. This is because each transfer occurs within a small area, using a high-precision vision alignment system to align the marks on the IPS transfer mold with the marks on the target substrate. Since the splicing area is relatively small each time, cumulative errors can be controlled to an extremely low level. The use of thermal nanoimprinting and the IPS transfer medium allows for repeated transfer processes, improving process reliability and consistency. The thermoplasticity of the IPS material allows for multiple uses, reducing mold wear.

[0056] In a preferred embodiment, the first substrate 3 is made of silicon or quartz, and the second substrate 4 is made of quartz. Silicon is less expensive and easier to process, while quartz has high optical transparency and stability, ensuring the durability and optical performance of the substrate during the nanoimprinting process.

[0057] As a preferred embodiment, the photolithography process is ultraviolet lithography or electron beam lithography. These two etching methods are direct-write processes, where the designed pattern is directly drawn on a substrate coated with photoresist using photons or electron beams. After development and etching steps, the pattern is permanently etched onto the substrate. Their task is to create the initial, high-precision master template or reference marks. The unique periodic primitive on the first substrate 3, and the crucial set of periodic alignment marks on the second substrate 4, are the original patterns that need to be defined precisely for the first time. Nanoimprinting is a pattern replication technology. It does not inherently possess the ability to create new patterns; instead, it requires an existing master template with the target structure, and the pattern is copied onto the transfer adhesive or final material through mechanical imprinting.

[0058] As a preferred embodiment, the transfer process using thermal nanoimprinting, with an IPS transfer mold as the transfer medium and periodic markers 5 as alignment marks, is specifically as follows: The current transfer motherboard is subjected to thermal nanoimprinting to obtain a material with the same alignment as the current transfer motherboard. An IPS transfer mold with a complementary structure of 12 micro / nano-structured superlenses and 5 periodic markers. The number of periodic primitives 2 is determined by their relationship to the currently transferred master plate. An IPS transfer mold with a complementary structure of 12 micro / nano-structured superlenses and 5 periodic markers was created using a thermal nanoimprinting method, transferring the current transfer master onto the master substrate. A micro / nano structure 12 of a superlens and periodic markings 5 ​​were transferred onto a target mold. Complementary structure conversion improved the fidelity of the pattern transfer and reduced distortion. Parameter control of thermal nanoimprinting ensured complete replication of the structure, thereby enhancing the phase modulation accuracy of the superlens.

[0059] The following example further illustrates the manufacturing method of the master plate used for nanoimprinting of titanium dioxide superlenses.

[0060] Based on the periodicity of the superlens micro / nano structure 12, periodic primitive 2, equivalent to 1 / 16 of the superlens micro / nano structure 12, is extracted from the superlens micro / nano structure 12. (Refer to...) Figure 2 A photoresist or electron beam resist is spin-coated onto the surface of the first substrate 3. After ultraviolet lithography or electron beam exposure, development, etching, and removal of residual resist, a first mold with periodic motifs 2 and periodic marks 5 is fabricated on the surface of the first substrate 3. The first substrate 3 uses a 4-inch silicon wafer as the initial mold substrate, with an outer radius of 50 mm, a sector angle of 22.5°, and a height difference of H between the periodic motifs 2 and the first substrate 3. Figure 3 As shown.

[0061] A double-sided polished fused silica sheet was used as the second substrate 4. Sixteen cross-shaped periodic marks 5 were prepared on the second substrate 4 using ultraviolet lithography, and numbers and letters were assigned to correspond to the imprinting sequence. The periodic marks 5 were evenly distributed around the center of the double-sided polished fused silica sheet. A layer of ultraviolet imprinting adhesive was then spin-coated onto the imprinted area, and the area was baked on a hot plate. Figure 4 As shown.

[0062] A first IPS transfer mold was prepared based on a first mold using a thermal nanoimprinting method.

[0063] On the second substrate 4, a visual alignment system of a nanoimprint device, such as Figure 5 As shown, the first IPS transfer mold is aligned with the periodic marks 5A1 and A2 on the second substrate 4 (alignment accuracy ≤ 10 nm), and a 50 N / cm² pressure is applied. 2The pressure is applied and the material is kept at 150℃ for 10 minutes to cure, followed by demolding.

[0064] The first IPS transfer mold was cleaned to remove any residual film.

[0065] The first IPS transfer mold is rotated to the next adjacent imprinting area, aligned with the periodic marks 5A3 and A4, and imprinted again. Thus, a 1 / 8 superlens micro / nano structure 12 is obtained on the second substrate 4.

[0066] A second IPS transfer mold was fabricated using a thermal nanoimprinting method based on a second substrate 4 having a 1 / 8 superlens micro / nanostructure 12. The same method was then used to obtain the second substrate 4 having a 1 / 4 superlens micro / nanostructure 12. The above method was repeated as follows... Figure 6 As shown, a second substrate 4 with a complete superlens micro / nano structure 12 is finally obtained, which is the mother plate used for nanoimprint fabrication of titanium dioxide superlenses.

[0067] Example 2

[0068] The method for fabricating titanium dioxide superlenses using the master plate for nanoimprint fabrication of titanium dioxide superlenses in Example 1 is as follows: Figure 1 As shown, it includes:

[0069] Step 1: A titanium dioxide layer 6 is prepared on the surface of the superlens substrate 1, and an adhesive layer 7 is prepared on the surface of the titanium dioxide layer 6. The superlens substrate 1 with the titanium dioxide layer 6 and the adhesive layer 7 is etched with N periodic marks 5 to specify the positions of N periodic units 2 by photolithography to obtain the processed superlens substrate 1.

[0070] Step 2: Using the thermal nanoimprinting method, an IPS working mold is obtained based on the mother plate used for nanoimprinting to prepare titanium dioxide superlenses. The IPS working mold has a structure that is complementary to the superlens micro / nano structure 12 and periodic marking 5 on the mother plate used for nanoimprinting to prepare titanium dioxide superlenses. An anti-adhesion layer 8 is prepared on the surface of the IPS working mold, and then a chromium layer 9 is prepared on the anti-adhesion layer 8 to obtain the processed IPS working mold.

[0071] Step 3: Align the N periodic marks 5 on the processed IPS working mold with the N periodic marks 5 on the processed superlens substrate 1, and perform ultraviolet nanoimprinting to obtain a titanium dioxide superlens.

[0072] Titanium dioxide layer 6 is the functional core of the superlens, and this layer will eventually form the superlens micro / nano structure 12 through etching. Ultraviolet nanoimprinting (coating with imprinting adhesive) is required on top of titanium dioxide layer 6. However, the adhesion between the surface of titanium dioxide layer 6 and the organic imprinting adhesive may be insufficient, easily leading to delamination and pattern defects during imprinting or subsequent processes. The tackifying layer 7 (N-[3-(trimethoxysilyl)propyl]ethylenediamine) enhances adhesion. One end of its molecule (silyl group) reacts chemically with the titanium dioxide surface to form a strong bond, while the other end (amine group) bonds well with the subsequent imprinting adhesive. The spin-coating followed by heat treatment is precisely to facilitate this chemical bonding.

[0073] The core function of the IPS working mold is to transfer the pattern from the master substrate used for nanoimprint fabrication of titanium dioxide superlenses onto the superlens substrate 1. After nanoimprinting, the mold must be able to separate smoothly from the cured imprinting adhesive without damaging the pattern. The anti-stick layer 8 (perfluorooctyltrichlorosilane) greatly reduces the force required for demolding by forming a low surface energy monolayer, preventing mold sticking. The main function of the chromium layer 9 is not anti-sticking, but rather as a durable hard mask in subsequent etching processes. When the imprinting adhesive pattern is transferred to the titanium dioxide layer 6, reactive ion etching is required. The chromium layer 9 has an extremely high etching selectivity, protecting the underlying IPS working mold and the anti-stick layer 8 from damage during the etching process, significantly extending the service life of the IPS working mold.

[0074] In a preferred embodiment, the specific method for preparing the titanium dioxide layer 6 on the surface of the superlens substrate 1 is as follows: the titanium dioxide layer 6 is prepared on the surface of the superlens substrate 1 using a magnetron sputtering process. The sputtering process can achieve a uniform and dense coating, improving the optical performance and durability of the superlens.

[0075] In a preferred embodiment, the specific method for preparing the adhesion-enhancing layer 7 on the surface of the titanium dioxide layer 6 is as follows: N-[3-(trimethoxysilyl)propyl]ethylenediamine solution is deposited on the surface of the titanium dioxide layer 6 using a spin-coating method, followed by heat treatment to obtain the adhesion-enhancing layer 7. This enhances the adhesion between the titanium dioxide layer and the imprinting adhesive, reduces the risk of interface failure, and thus improves the manufacturing yield.

[0076] As a preferred embodiment, the specific method for preparing the anti-stick layer 8 on the surface of the IPS working mold is as follows: the IPS working mold and perfluorooctyltrichlorosilane are placed together in a vacuum drying oven for vacuum baking. This forms a low surface energy layer, which facilitates demolding and extends the service life of the IPS mold.

[0077] In a preferred embodiment, the specific method for preparing the chromium layer 9 on the anti-adhesion layer 8 is as follows: the chromium layer 9 is prepared on the surface of the anti-adhesion layer 8 using a magnetron sputtering process. The chromium layer 9 acts as a hard mask, protecting the structure during etching and improving the accuracy of pattern transfer.

[0078] The following example further illustrates the method of preparing titanium dioxide superlenses using a master plate for nanoimprinting.

[0079] Using a thermal nanoimprinting method, an IPS working mold was obtained from the second substrate 4 with the complete superlens micro / nano structure 12 described in Example 1, as shown below. Figure 7 As shown, the IPS working mold includes an IPS substrate 10, a complementary structure 11 of a superlens micro / nano structure, and periodic markers 5;

[0080] like Figure 8 As shown, the IPS working mold was cleaned with oxygen plasma for 2 minutes, and then placed in a vacuum drying oven with perfluorooctyltrichlorosilane and vacuum baked at 80°C for 30 minutes to form a low surface energy anti-stick layer 8 on the surface of the IPS working mold.

[0081] The IPS working mold was coated using magnetron sputtering to deposit a 30-nanometer chromium layer on its surface.

[0082] like Figure 9 , 10 As shown, the superlens substrate 1 is coated with a double-sided polished fused silica sheet as the superlens substrate 1. The superlens substrate 1 is immersed in a piranha solution prepared by 98% concentrated sulfuric acid and hydrogen peroxide in a ratio of 7:3 for 20 minutes. Then, an 800nm ​​thick titanium dioxide layer 6 is prepared on the superlens substrate 1 by magnetron sputtering with an argon gas pressure of 0.1Pa and a power of 100W.

[0083] Superlens substrate adhesion enhancement: To improve the adhesion between the superlens substrate 1 and the IPS substrate 10, an adhesion enhancer (such as N-[3-(trimethoxysilyl)propyl]ethylenediamine solution) is deposited on the surface of the titanium dioxide layer 6 by spin coating, followed by heat treatment on a hot plate at 150°C for 1 minute. This process ultimately forms an adhesion enhancement layer 7 with a thickness of less than 10 nanometers.

[0084] Sixteen cross-shaped periodic marks 5 were prepared on a superlens substrate 1 with a titanium dioxide layer 6 and an adhesive layer 7 using ultraviolet lithography and marked with numbers and letters corresponding to the imprinting sequence. The alignment marks were evenly distributed around the center. The imprinting area was then spin-coated with a layer of ultraviolet imprinting adhesive and baked on a hot plate.

[0085] Alignment is achieved by periodic marks 5, C1-C16 and B1-B16 on the superlens substrate 1 and the IPS working mold. The two are brought into contact and a certain pressure is applied by a nanoimprinting device. The mixture is cured at 150°C for 10 minutes and then demolded.

[0086] Using imprinting adhesive as a mask, reactive ion etching was employed to etch the superlens micro / nano structure 12 onto the superlens substrate 1. The imprinting adhesive was then removed using oxygen plasma to fabricate the structure. Figure 11 The titanium dioxide superlens shown;

[0087] This invention enables the large-scale fabrication of 60mm diameter superlenses, which can be expanded to 120mm diameter through splicing, with splicing seams ≤100nm, without affecting imaging quality. It meets the needs of biological microscopes for large-area superlenses to improve the field of view, the need for thinner and lighter mobile phone lens modules, and the need for 50-80mm diameter titanium dioxide superlenses for automotive lidar. It is applicable to lidar, microscopic imaging, and smartphone fields.

[0088] Compared with existing metasurface fabrication technologies, the cross-stepping imprinting technology of this invention achieves breakthroughs in fabrication efficiency, cost control, and large-area processing capabilities through innovative process design. Traditional technologies have significant limitations: although electron beam lithography can achieve subwavelength precision (~10nm), the processing speed is extremely slow (on the order of millimeters / hour) and the cost per unit is high (on the order of tens of thousands of yuan), making it only suitable for laboratory prototype development; although laser direct writing significantly improves speed, it is limited by the optical diffraction limit, making it difficult to achieve stable processing of periodic structures below 160nm; although ultraviolet lithography is suitable for mass production, it requires customized high-precision masks (especially for large-format designs at the centimeter level), and the minimum linewidth is limited by the wavelength of the light source (usually >100nm), making it difficult to meet the phase modulation requirements of the subwavelength structures in this solution.

[0089] The core breakthrough of this invention lies in the spin embossing + nano-transfer embossing splicing process. By extracting periodic units to prepare a millimeter-level master mold, the first embossing forms a surrounding pattern area, and the second embossing precisely fills the area. The splicing accuracy is controlled to 40nm by periodic marking 5. Moreover, it eliminates the need for a large-size master mold to replicate adjacent micro-nano structure patterns through spin embossing to create a complete superlens master mold. Compared to electron beam exposure for directly processing the entire lens (which takes several days), the efficiency of subsequent mold embossing replication is improved by more than 100 times. Traditional embossing is limited by the size of the mold, and large-format processing requires physical splicing, resulting in interface misalignment. This solution uses nano-embossing to replicate adjacent micro-nano structure patterns to create a complete master mold. The first embossing forms a surrounding pattern area, and the second embossing precisely fills the adjacent area, achieving a splicing accuracy of 40nm.

[0090] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit its scope of protection. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that after reading the present invention, they can still make various changes, modifications or equivalent substitutions to the specific implementation of the invention, but these changes, modifications or equivalent substitutions are all within the scope of protection of the pending claims of the invention.

Claims

1. A method for manufacturing a master plate for nanoimprint fabrication of titanium dioxide superlenses, characterized in that, include: Step 1: Divide the superlens micro / nano structure (12) into N periodic units (2) and use N periodic markers (5) to specify the positions of the N periodic units (2); Step 2: A periodic unit (2) and a corresponding periodic mark (5) are etched on the first substrate (3) using photolithography to obtain a sample containing... The first mold of the super lens micro-nano structure (12) is used to etch N periodic marks (5) on the second substrate (4) by photolithography to obtain the second substrate (4) with etched periodic marks (5). Step 3, with... The first mold of the superlens micro / nano structure (12) is the master plate for the first transfer. The transfer is carried out by using the thermal nanoimprinting method, with the IPS transfer mold as the transfer medium and the periodic mark (5) as the alignment mark. Two adjacent ones are transferred on the second substrate (4) after the periodic mark (5) has been etched. A superlens micro / nano structure (12) was obtained, containing The second mold of the superlens micro / nano structure (12); Step 4, with... The second mold of the superlens micro / nano structure (12) serves as the master plate for the second transfer. Periodic marks (5) are used as alignment marks, an IPS transfer mold is used as the transfer medium, and a nanoimprinting method is employed for transfer. The master plate for the second transfer is then... The superlens micro / nano structure (12) is transferred back to the master plate for the second transfer at adjacent positions to obtain a micro / nano structure containing a superlens micro / nano structure. The second mold containing the superlens micro / nano structure (12) is used as the master mold for the next transfer. The thermal nanoimprinting method is repeated, using the IPS transfer mold as the transfer medium and the periodic mark (5) as the alignment mark for transfer. The number of superlens micro / nano structures (12) on the second mold is increased sequentially until a second mold containing the complete superlens micro / nano structure (12) is obtained, which serves as the master mold for nanoimprinting to prepare titanium dioxide superlenses.

2. The method for manufacturing a master plate for nanoimprinting titanium dioxide superlenses according to claim 1, characterized in that: The first substrate (3) is made of silicon or quartz, and the second substrate (4) is made of quartz.

3. The method for manufacturing a master plate for nanoimprinting titanium dioxide superlenses according to claim 1, characterized in that: The photolithography process is ultraviolet lithography or electron beam lithography.

4. The method for manufacturing a master plate for nanoimprinting titanium dioxide superlenses according to claim 1, characterized in that, The specific details of the transfer process using the thermal nanoimprinting method, with an IPS transfer mold as the transfer medium and periodic marks (5) as alignment marks, are as follows: The current master plate to be transferred is then subjected to a thermal nanoimprinting method to obtain a material with the same properties as the current master plate. An IPS transfer mold with a complementary structure of superlens micro / nano structure (12) and periodic markings (5), The number of periodic primitives (2) is determined by the number of primitives currently being transferred to the master plate. The IPS transfer mold with complementary structures of superlens micro / nano structures (12) and periodic markings (5) is applied using a thermal nanoimprinting method to transfer the current transfer master plate. The superlens micro / nano structure (12) and periodic markings (5) are transferred onto the target mold.

5. A master plate prepared by the method for preparing a master plate for nanoimprinting of titanium dioxide superlenses according to any one of claims 1 to 4.

6. A method for preparing a titanium dioxide superlens using the master plate for nanoimprinting of titanium dioxide superlenses as described in claim 5, characterized in that, include: Step 1: A titanium dioxide layer (6) is prepared on the surface of the superlens substrate (1), and an adhesive layer (7) is prepared on the surface of the titanium dioxide layer (6). The superlens substrate (1) with the titanium dioxide layer (6) and the adhesive layer (7) is etched with N periodic marks (5) to specify the positions of N periodic units (2) by photolithography, and the processed superlens substrate (1) is obtained. Step 2: Using the thermal nanoimprinting method, an IPS working mold is obtained based on the mother plate used for nanoimprinting to prepare titanium dioxide superlenses. The IPS working mold has a structure that is complementary to the superlens micro / nano structure (12) and periodic marking (5) on the mother plate used for nanoimprinting to prepare titanium dioxide superlenses. An anti-adhesion layer (8) is prepared on the surface of the IPS working mold, and then a chromium layer (9) is prepared on the anti-adhesion layer (8) to obtain the processed IPS working mold. Step 3: Align the N periodic marks (5) on the processed IPS working mold with the N periodic marks (5) on the processed superlens substrate (1) and perform ultraviolet nanoimprinting to obtain a titanium dioxide superlens.

7. The method for preparing a titanium dioxide superlens from a mother plate according to claim 6, characterized in that, The specific method for preparing a titanium dioxide layer (6) on the surface of the superlens substrate (1) is as follows: A titanium dioxide layer (6) was prepared on the surface of a superlens substrate (1) using a magnetron sputtering process.

8. The method for preparing a titanium dioxide superlens from a mother plate according to claim 6, characterized in that, The specific method for preparing the adhesion-enhancing layer (7) on the surface of the titanium dioxide layer (6) is as follows: N-[3-(trimethoxysilyl)propyl]ethylenediamine solution was deposited on the surface of titanium dioxide layer (6) by spin coating, and then heat-treated to obtain tackifying layer (7).

9. The method for preparing a titanium dioxide superlens from a mother plate according to claim 6, characterized in that, The specific method for preparing the anti-adhesion layer (8) on the surface of the IPS working mold is as follows: The IPS working mold and perfluorooctyltrichlorosilane were placed together in a vacuum drying oven for vacuum baking.

10. The method for preparing a titanium dioxide superlens from a mother plate according to claim 6, characterized in that, The specific method for preparing the chromium layer (9) in the anti-adhesion layer (8) is as follows: A chromium layer (9) was prepared on the surface of the anti-adhesion layer (8) by magnetron sputtering.

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