Metasurface device processing method based on super-resolution interference lithography combined with secondary exposure

Abstract

The present disclosure provides a metasurface device processing method based on super-resolution interference lithography combined with secondary exposure, comprising: preparing a sequentially stacked medium layer, photoresist layer and metal layer on the surface of a substrate containing a functional layer to form a super-resolution interference lithography multilayer film structure with surface plasmon enhanced; performing super-resolution interference lithography on the super-resolution interference lithography multilayer film structure to form a super-resolution periodic basic pattern in the photoresist layer; removing the metal layer; performing secondary exposure on the photoresist layer with the super-resolution periodic basic pattern formed thereon, and then developing to form a super-resolution periodic target pattern with different characteristic sizes in different exposure areas in the photoresist layer; wherein the different exposure areas have different additional exposure doses; transferring the super-resolution periodic target pattern from the photoresist layer to the substrate containing the functional layer to obtain a metasurface device.

Description

Technical Field

[0001] This disclosure relates to the field of micro-nano lithography and metasurface manufacturing technology, specifically to a metasurface device fabrication method based on super-resolution interference lithography combined with secondary exposure. Background Technology

[0002] Metasurface devices are typically composed of subwavelength-scale micro / nano cell arrays. By adjusting the characteristic dimensions, duty cycle, aperture size, or arrangement parameters of the cells, the phase, amplitude, and polarization of light waves can be controlled. Therefore, they have significant application value in fields such as superlenses, wavefront shaping, and optical field manipulation. The fabrication of metasurfaces not only requires high resolution but also the ability to stably fabricate dimensionally controllable micro / nano structures over a large area.

[0003] Among related technologies, metasurface fabrication methods mainly include traditional projection lithography, electron beam direct writing lithography, and nanoimprint lithography. Traditional projection lithography is limited by the diffraction limit, and its resolution typically only reaches the wavelength range. While electron beam direct writing lithography offers high precision, it suffers from low processing efficiency and high cost, making it unsuitable for large-area device fabrication. Nanoimprint lithography is suitable for structure replication, but its processing results are highly dependent on the template, limiting the flexibility of structure control. All of these methods have certain limitations in achieving high resolution, large area, and low cost in metasurface fabrication. Summary of the Invention

[0004] In view of this, the present disclosure provides a metasurface device fabrication method based on super-resolution interferometric lithography combined with secondary exposure, which can at least partially solve the above-mentioned technical problems.

[0005] This disclosure provides a method for fabricating metasurface devices based on super-resolution interference lithography combined with secondary exposure, comprising: preparing a dielectric layer, a photoresist layer, and a metal layer sequentially stacked on the surface of a substrate containing a functional layer to form a surface plasmon-enhanced super-resolution interference lithography multilayer film structure; performing super-resolution interference lithography on the super-resolution interference lithography multilayer film structure to form a super-resolution periodic basic pattern in the photoresist layer; removing the metal layer; performing secondary exposure on the photoresist layer with the super-resolution periodic basic pattern formed, followed by development, to form a super-resolution periodic target pattern with different feature sizes in different exposure regions in the photoresist layer; wherein, different exposure regions have different additional exposure doses; transferring the super-resolution periodic target pattern from the photoresist layer to the substrate containing the functional layer to obtain the metasurface device.

[0006] According to embodiments of this disclosure, a dielectric layer, a photoresist layer, and a metal layer are sequentially stacked on the surface of a substrate containing a functional layer, including: preparing the metal layer using a thermal evaporation method, an electron beam evaporation method, a magnetron sputtering method, an ion beam sputtering method, a pulsed laser deposition method, or an atomic layer deposition method; preparing the photoresist layer using a spin coating method; and preparing the dielectric layer using an electron beam evaporation method, a magnetron sputtering method, or an atomic layer deposition method.

[0007] According to embodiments of this disclosure, a metal layer is prepared using a metallic or alloy material whose real dielectric constant is negative at the exposure wavelength and whose ratio of the imaginary dielectric constant to the absolute value of the real dielectric constant is not greater than 0.5; a dielectric layer is prepared using a dielectric material whose real dielectric constant is not less than 2.0 and whose imaginary dielectric constant is not greater than 0.1 at the exposure wavelength.

[0008] According to embodiments of this disclosure, a dielectric layer, a photoresist layer, and a metal layer are sequentially stacked on the surface of a substrate containing a functional layer to form a surface plasmon-enhanced super-resolution interference lithography multilayer film structure. The method further includes: characterizing the structural parameters of the prepared super-resolution interference lithography multilayer film structure to obtain parameter characterization results; adjusting the process parameters for preparing the super-resolution interference lithography multilayer film structure based on the difference between the parameter characterization results and the target design parameters of the super-resolution interference lithography multilayer film structure, until the parameter characterization results of the prepared super-resolution interference lithography multilayer film structure match the target design parameters of the super-resolution interference lithography multilayer film structure.

[0009] According to embodiments of this disclosure, super-resolution interference lithography is performed on a multilayer film structure to form a super-resolution periodic basic pattern in a photoresist layer. This includes: fixing an interference lithography mask and a substrate with the multilayer film structure formed thereon in a mask stage and a substrate stage of a super-resolution lithography apparatus, respectively; controlling the working distance between the interference lithography mask and the multilayer film structure to a target distance; and then performing super-resolution interference lithography on the multilayer film structure using a preset exposure dose to form a periodically uniform line or hole / pillar array pattern in the photoresist layer.

[0010] According to embodiments of this disclosure, a two-dimensional mask is used to form a periodically uniform array of holes / pillars in a photoresist layer through a single super-resolution interference lithography process; or, a one-dimensional mask is used to form a periodically uniform array of holes / pillars in a photoresist layer through two superimposed super-resolution interference lithography processes performed by rotating the mask by 90°.

[0011] According to embodiments of this disclosure, removing the metal layer includes: removing the metal layer above the photoresist layer using a dry process or a wet process to expose the photoresist layer.

[0012] According to embodiments of this disclosure, a secondary exposure of a photoresist layer with a super-resolution periodic basic pattern includes: fixing a substrate after removing the metal layer in a substrate stage of a super-resolution lithography apparatus; fixing a grayscale mask or grayscale filter in a mask stage of a super-resolution lithography apparatus; controlling the working distance between the mask and the photoresist layer to a target distance; and then performing a secondary exposure on the photoresist layer using a preset exposure dose.

[0013] According to embodiments of this disclosure, the method further includes controlling the development boundary position by varying the total exposure dose in different exposure areas during a secondary exposure.

[0014] According to embodiments of this disclosure, the photoresist layer is developed using a developer that matches the photoresist layer; and an etching transfer process is used to etch and transfer a super-resolution periodic target pattern from the photoresist layer to the functional layer to obtain a metasurface device.

[0015] The metasurface device fabrication method based on super-resolution interference lithography combined with secondary exposure provided in this disclosure has at least the following technical effects.

[0016] A surface plasmon-enhanced super-resolution interference lithography (SCI) film structure was fabricated on a substrate. SCI was then performed on the SCI to obtain a uniformly periodic, high-resolution, large-area basic array pattern. Based on this, a second grayscale exposure was used to control the exposure dose in different regions, achieving regional control of the feature sizes of metasurface line units and hole / pillar units. This allowed different regions within the same lattice to obtain units of different sizes, resulting in metasurface device structures with varying unit sizes.

[0017] This processing method uses different additional exposure doses for different regions and controls the development boundary position by varying the total exposure dose. This allows for the adjustment of the size of the basic units of the super-resolution periodic basic pattern while maintaining a constant center distance, thereby improving the processing resolution of the metasurface units.

[0018] This processing method uses super-resolution interference lithography to determine the period and uses multiple exposure areas with different additional exposure doses in the secondary exposure to adjust the size of the partitions. It separates the "period determination" and "size adjustment", which not only ensures the consistency of the basic pattern layout, but also improves the flexibility of subsequent structural design. It is suitable for the fabrication of metasurface devices with fixed center distance.

[0019] This processing method introduces super-resolution interference lithography into the fabrication of metasurface devices, enabling the fabrication of high-resolution, large-area periodic array structures. This makes it possible to apply metasurfaces to the ultraviolet and deep ultraviolet bands (where the required structural unit center distance and size are very small). Attached Figure Description

[0020] The above and other objects, features and advantages of this disclosure will become clearer from the following description of embodiments of this disclosure with reference to the accompanying drawings.

[0021] Figure 1 The flowchart illustrates a metasurface device fabrication method based on super-resolution interference lithography combined with secondary exposure according to an embodiment of the present disclosure.

[0022] Figure 2 The diagram schematically illustrates the device structure corresponding to each operation in the fabrication process of a metasurface device based on super-resolution interferometric lithography combined with secondary exposure according to an embodiment of the present disclosure.

[0023] Figure 3 A schematic diagram of a super-resolution interference lithography multilayer film structure according to an embodiment of the present disclosure is shown.

[0024] Figure 4 The diagram schematically illustrates the device structure corresponding to each operation in the fabrication process of a metasurface device based on deep ultraviolet super-resolution interference lithography combined with secondary exposure according to an embodiment of the present disclosure.

[0025] Figure 5 The diagram schematically illustrates the exposure dose distribution and light field distribution of a one-dimensional grating mask in the photoresist after the first super-resolution interference lithography according to an embodiment of the present disclosure.

[0026] Figure 6 A simulation diagram illustrating a wire grid metasurface with a fixed center distance according to an embodiment of the present disclosure is shown.

[0027] Figure 7 The diagram schematically illustrates the exposure dose distribution and light field distribution in the photoresist after two super-resolution interference lithography rotations and superpositions according to embodiments of the present disclosure.

[0028] Figure 8 The illustration schematically shows a simulation of a cylindrical unit metasurface with a fixed center distance according to an embodiment of the present disclosure. Detailed Implementation

[0029] The embodiments of the present disclosure will now be described with reference to the accompanying drawings. However, it should be understood that these descriptions are exemplary only and are not intended to limit the scope of the disclosure. In the following detailed description, numerous specific details are set forth to provide a thorough understanding of the embodiments of the present disclosure for ease of explanation. However, it will be apparent that one or more embodiments may be practiced without these specific details. Furthermore, descriptions of well-known structures and techniques are omitted in the following description to avoid unnecessarily obscuring the concepts of the present disclosure.

[0030] In realizing this disclosure, it was discovered that applying interference lithography to the fabrication of periodic nanostructures offers high processing efficiency and good uniformity, while also offering the advantages of large area and low cost. However, due to the fixed dose distribution formed in a single exposure, the obtained regular patterns have fixed periods and limited feature sizes.

[0031] Based on the method of interference lithography combined with grayscale pattern secondary exposure, a grayscale mask is introduced after the first interference exposure for dose superposition, thereby achieving local development boundary adjustment and obtaining continuously changing feature sizes in the same periodic structure, providing a new technical approach for the preparation of metasurface structures.

[0032] However, due to limitations in the exposure wavelength and interference conditions used, far-field interferometric exposure cannot further improve pattern resolution. It is also difficult to effectively control the precise manipulation of metasurface holes and line unit structures at smaller feature sizes. Especially for high-resolution metasurface fabrication under fixed center-to-center distance conditions, it is difficult to meet the requirements for effective control of hole and line unit structures below 100 nanometers.

[0033] In view of this, embodiments of the present disclosure provide a metasurface device fabrication method based on super-resolution interference lithography combined with secondary exposure, which further improves pattern resolution while taking into account high resolution, large area and low cost, and achieves effective control over hole and line unit structures below 100 nanometers, so as to meet the needs of high-resolution metasurface device fabrication.

[0034] The following is a detailed description with reference to the accompanying drawings and specific embodiments.

[0035] Figure 1 The flowchart illustrates a metasurface device fabrication method based on super-resolution interference lithography combined with secondary exposure according to an embodiment of the present disclosure. Figure 2 The diagram schematically illustrates the device structure corresponding to each operation in the fabrication process of a metasurface device based on super-resolution interferometric lithography combined with secondary exposure according to an embodiment of the present disclosure.

[0036] like Figure 1 and Figure 2 As shown, the metasurface device fabrication method based on super-resolution interference lithography combined with secondary exposure in this embodiment may include operations S101 to S105.

[0037] In operation S101, a dielectric layer, a photoresist layer, and a metal layer are sequentially stacked on the surface of a substrate containing a functional layer to form a surface plasmon-enhanced super-resolution interference lithography multilayer film structure.

[0038] According to embodiments of this disclosure, the functional layer can be directly formed on the substrate and can be used for interface adaptation and optical control. In the surface plasmon-enhanced super-resolution interference lithography multilayer film structure, the refractive index and thickness of the functional layer can determine the excitation conditions of surface plasmons.

[0039] In operation S102, super-resolution interference lithography is performed on the multilayer film structure to form a super-resolution periodic basic pattern in the photoresist layer.

[0040] According to embodiments of this disclosure, near-field interference of ordinary light is replaced by near-field interference of surface plasmons excited by a metal layer, forming enhanced interference fringes with a period much smaller than λ / 2 in the photoresist. After exposure and development, a super-resolution periodic basic pattern is obtained.

[0041] In operation S103, the metal layer is removed.

[0042] According to embodiments of this disclosure, the metal layer above the photoresist is removed to expose the photoresist layer, which facilitates subsequent development.

[0043] In operation S104, the photoresist layer with the super-resolution periodic basic pattern is exposed a second time and then developed to form super-resolution periodic target patterns with different feature sizes in different exposure areas of the photoresist layer.

[0044] According to embodiments of this disclosure, different exposure areas in the secondary exposure have different additional exposure doses. That is, different exposure doses are used for secondary exposure of different exposure areas to control the pattern size of different areas.

[0045] In operation S105, the super-resolution periodic target pattern is transferred from the photoresist layer to the substrate containing the functional layer to obtain the metasurface device.

[0046] According to embodiments of this disclosure, the super-resolution periodic target pattern is transferred layer by layer down to the metal layer and the dielectric layer, and finally the photoresist layer is removed, so that the super-resolution periodic target pattern structure "grows" on the substrate, thereby obtaining a metasurface device.

[0047] In some embodiments, the preparation of a dielectric layer, a photoresist layer, and a metal layer stacked sequentially on the surface of a substrate containing a functional layer may include: using a thermal evaporation method, an electron beam evaporation method, a magnetron sputtering method, an ion beam sputtering method, a pulsed laser deposition method, a chemical vapor deposition method, or an atomic layer deposition method; using a spin coating method to prepare a photoresist layer; and using an electron beam evaporation method, a magnetron sputtering method, or an atomic layer deposition method to prepare a dielectric layer.

[0048] Furthermore, a metal layer is prepared using a metal or alloy material whose real part of dielectric constant is negative and whose ratio of the absolute value of the imaginary part of dielectric constant to the real part of dielectric constant is not greater than 0.5 at the exposure wavelength; and a dielectric layer is prepared using a dielectric material whose real part of dielectric constant is not less than 2.0 and whose imaginary part of dielectric constant is not greater than 0.1 at the exposure wavelength.

[0049] An exemplary metal layer material includes aluminum, which has a dielectric constant of -2.73 in the real part and 0.5 in the imaginary part at a wavelength of 193 nm. The dielectric layer material includes silicon dioxide, which has a dielectric constant of 2.4555 at a wavelength of 193 nm.

[0050] In some embodiments, a dielectric layer, a photoresist layer, and a metal layer are sequentially stacked on the surface of a substrate containing a functional layer to form a surface plasmon-enhanced super-resolution interference lithography multilayer film structure. The method further includes: characterizing the structural parameters of the super-resolution interference lithography multilayer film structure to obtain parameter characterization results; adjusting the process parameters for preparing the super-resolution interference lithography multilayer film structure based on the difference between the parameter characterization results and the target design parameters of the super-resolution interference lithography multilayer film structure, until the parameter characterization results of the prepared super-resolution interference lithography multilayer film structure match the target design parameters of the super-resolution interference lithography multilayer film structure.

[0051] According to embodiments of this disclosure, under ultraviolet or deep ultraviolet wavelengths, metal and dielectric materials with matching dielectric constants are selected to construct a surface plasmon-enhanced super-resolution interference photolithography multilayer film structure consisting of a metal layer, a photoresist layer, and a dielectric layer on a substrate. By combining the optimization of film layer parameters, a surface plasmon super-resolution interference structure with high spatial frequency enhancement is formed, thereby forming a super-resolution periodic basic pattern in the photoresist.

[0052] According to embodiments of this disclosure, parameters such as thickness, roughness, and dielectric constant of each layer in a super-resolution interference lithography multilayer film structure can be characterized. The characterization results are compared with the designed film thickness range and roughness requirements. If they do not match, the process parameters need to be adjusted to meet the multilayer film parameter requirements. For example, the film thickness and dielectric constant are measured using an ellipsometer, and the film roughness is tested using an atomic force microscope.

[0053] In some embodiments, super-resolution interference lithography (SCI) is performed on a multilayer film structure to form a super-resolution periodic basic pattern in a photoresist layer. This includes: fixing an interference lithography mask and a substrate with the multilayer film structure formed thereon in a super-resolution lithography apparatus, respectively, on a mask stage and a substrate stage; controlling the working distance between the interference lithography mask and the multilayer film structure to a target distance; and then performing super-resolution interference lithography on the multilayer film structure using a preset exposure dose to form a periodically uniform line or hole / pillar array pattern in the photoresist layer. For example, the working distance between the mask and the multilayer film structure can be controlled by a displacement stage (e.g., a high-precision Z-axis displacement stage).

[0054] According to embodiments of this disclosure, the super-resolution periodic base pattern can be stripes or a hole / pillar array. Both the line structure and the hole / pillar array structure serve as the initial pattern for subsequent metasurface units, and the period or center distance is determined by super-resolution lithography.

[0055] Furthermore, for hole / pillar array structures, a two-dimensional mask can be used to form a periodically uniform hole / pillar array pattern in the photoresist layer through a single super-resolution interference lithography (SCI) process. Alternatively, a one-dimensional mask can be used, and a periodically uniform hole / pillar array pattern can be formed in the photoresist layer through two superimposed SCI processes performed by rotating the mask by 90°.

[0056] In some embodiments, removing the metal layer may include: using a dry process or a wet process to remove the metal layer above the photoresist layer to expose the photoresist layer.

[0057] In some embodiments, secondary exposure of a photoresist layer with a super-resolution periodic base pattern includes: fixing a substrate with the metal layer removed in a wafer stage of a super-resolution lithography apparatus; fixing a grayscale mask or grayscale filter in a mask stage of the super-resolution lithography apparatus; controlling the working distance between the mask and the photoresist layer to a target distance; and then performing secondary exposure on the photoresist layer using a preset exposure dose. For example, the working distance between the mask and the photoresist layer can be controlled by a displacement stage (e.g., a high-precision Z-axis displacement stage).

[0058] In some embodiments, the processing method may further include controlling the development boundary position by varying the total exposure dose in different exposure areas during secondary exposure.

[0059] According to embodiments of this disclosure, after forming a super-resolution periodic basic pattern based on super-resolution interference lithography, the dose of the secondary superimposed exposure is adjusted using grayscale masks, grayscale filters, etc., so that different exposure areas receive different additional exposure doses. The development boundary position is controlled by changing the total exposure dose, thereby achieving adjustment of the feature size of different regions under a fixed center distance. For line structures, the feature size manifests as a change in linewidth. For hole / pillar structures, the feature size manifests as a change in aperture. The secondary exposure does not change the period or center distance formed by the primary exposure (super-resolution interference lithography), but only adjusts the local dose distribution to obtain spatial size variation units suitable for metasurface devices.

[0060] After the second layer of exposure is completed, the super-resolution periodic target pattern in the photoresist is developed to obtain line structures or hole / pillar structures with different feature sizes in different exposure areas, forming a metasurface structure with a fixed center distance. Then, the photoresist pattern is transferred to the substrate through an etching transfer process to obtain the final metasurface device.

[0061] Furthermore, the photoresist layer can be developed using a developer compatible with the photoresist layer. An etching transfer process can then be used to etch and transfer the super-resolution periodic target pattern from the photoresist layer to the functional layer.

[0062] To make the objectives, technical solutions, and advantages of this disclosure 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 not intended to limit the scope of this disclosure. All other embodiments obtained by those skilled in the art based on the embodiments of this disclosure without inventive effort are within the scope of protection of this disclosure.

[0063] Figure 3 A schematic diagram of a super-resolution interference lithography multilayer film structure according to an embodiment of the present disclosure is shown. Figure 4 The diagram schematically illustrates the device structure corresponding to each operation in the fabrication process of a metasurface device based on deep ultraviolet super-resolution interference lithography combined with secondary exposure according to an embodiment of the present disclosure.

[0064] like Figure 3 and Figure 4 As shown, the fabrication of metasurface devices using deep ultraviolet super-resolution interference lithography combined with secondary exposure may include the following steps S1 to S6.

[0065] S1 employs a 193nm deep ultraviolet wavelength. Aluminum and silicon dioxide, with their low losses, are selected as the metal and dielectric layers, respectively, in the super-resolution interference lithography multilayer structure. The dielectric constants of these two materials at 193nm are -2.73+0.5i and 2.4555, respectively. Using these two materials, an aluminum transmission layer-photoresist layer-silicon dioxide layer was designed. Optimization was performed by considering the parameter ranges of each layer to ensure the optical transfer function in the photoresist exhibits bandpass characteristics. After optimization, the thicknesses of the aluminum transmission layer, photoresist layer, and silicon dioxide layer are 15nm, 30nm, and 90nm, respectively.

[0066] S2. A silicon dioxide layer was prepared on the substrate using electron beam evaporation, followed by spin coating of a photoresist layer, and finally thermal evaporation to prepare an aluminum transmission layer. The thicknesses of the aluminum transmission layer-photoresist layer-silicon dioxide layer were measured using an ellipsometer to be 14.83 nm, 30.26 nm, and 89.77 nm, respectively, and the dielectric constants were -2.65 +0.48i, 2.70 +0.03i, and 2.457, respectively. The average roughness of the film was measured to be 0.78 nm using an atomic force microscope.

[0067] S3. Fix a 180nm periodic line mask and a substrate with a super-resolution interference lithography multilayer film structure in the mask stage and substrate stage of the super-resolution lithography apparatus, respectively. Adjust the mask-substrate working distance and exposure dose, and then perform a super-resolution interference exposure to obtain a 90nm period and 45nm width line grid pattern. Alternatively, use a 180nm mask to perform two super-resolution interference lithography steps by rotating it 90° to obtain a cylinder with a 45nm diameter and a 90nm period.

[0068] S4. The substrate after one exposure is placed in an acidic solution of a certain concentration to allow the aluminum transmission layer to react with the acid. After the reaction is complete, the sample is removed, rinsed with deionized water, and then dried.

[0069] S5, the substrate with exposed photoresist layer is fixed in the stage of the super-resolution lithography device, and the grayscale filter is fixed in the mask stage of the super-resolution lithography device. After alignment, a dose of 400mJ is selected to perform a second superposition exposure on the grid sample to obtain a grid array with a period of 18nm to 30nm and a line width of 18nm to 30nm. A dose of 200mJ is selected to perform a second superposition exposure on the photoresist layer forming the cylindrical array to obtain a cylindrical array with a period of 25nm to 38nm and a cylinder diameter of 25nm to 38nm.

[0070] S6. The photoresist layer is developed, and the exposed pattern of the photoresist layer is etched and transferred to the substrate (silicon substrate, as a functional layer) using a dry etching process to obtain a grid or cylindrical array with different cell widths and cell diameters.

[0071] Figure 5 The diagram schematically illustrates the exposure dose distribution and light field distribution of a one-dimensional grating mask in the photoresist after the first super-resolution interference lithography according to an embodiment of the present disclosure. Figure 5 (a) is the exposure dose distribution map. Figure 5 (b) shows the light field distribution.

[0072] like Figure 5 As shown, in the designed super-resolution interference lithography multilayer film structure consisting of a metal layer, a photoresist layer, and a dielectric layer, the first exposure forms a periodically stable grid pattern within the photoresist, with its center distance determined by plasmon interference conditions. This basic pattern provides an initial template for subsequent secondary exposure control.

[0073] Figure 6 A simulation diagram illustrating a wire grating metasurface with a fixed center distance according to an embodiment of the present disclosure is shown schematically. Figure 6 (a) Figure 6 (c) shows the dose distribution after the second exposure following the grayscale filter. Figure 6 (b) Figure 6The middle (d) shows the structural pattern after photoresist development (color indicates line width).

[0074] like Figure 6 As shown, with the fringe center position remaining unchanged, different grayscale filters correspond to different additional exposure doses, leading to changes in the development threshold position and thus differences in the linewidth of the resulting line structure. In other words, the second exposure changes the feature size of the grating, rather than the period or center distance determined by the first exposure.

[0075] Furthermore, as the intensity of the secondary exposure changes, the edge position of the line structure shifts accordingly, ultimately forming a wire grid array with a fixed center distance but varying linewidths. This result demonstrates that this disclosure can achieve spatial control of linewidth under a fixed center distance, thereby obtaining metasurface devices with varying linewidths, such as one-dimensional beam-splitting metasurface devices. This embodiment verifies that combining super-resolution interference lithography with secondary exposure dose modulation can effectively achieve the fabrication of high-resolution metasurface devices.

[0076] Figure 7 The illustration schematically shows the exposure dose distribution and light field distribution in the photoresist after two super-resolution interferometric lithography rotations and superpositions according to embodiments of the present disclosure. Figure 7 (a) is the exposure dose distribution map. Figure 7 (b) shows the light field distribution.

[0077] like Figure 7 As shown, under the designed multilayer film structure consisting of a metal layer, a photoresist layer, and a dielectric layer, and under the specified exposure conditions, the first exposure forms a basic pattern of cylindrical arrays with a fixed center distance in the photoresist. The position of each cylindrical unit is determined by the distribution of the plasmon interference field. This basic pattern maintains a uniform arrangement period, providing a foundation for subsequent secondary exposures to control the size of the cylindrical units.

[0078] Figure 8 A schematic diagram illustrating a simulation of a cylindrical unit metasurface with a fixed center distance according to an embodiment of the present disclosure is provided. Figure 8 (a) Figure 8 (c) shows the dose distribution after the second exposure following the grayscale filter. Figure 8 (b) Figure 8 The image in (d) shows the structure pattern after photoresist development (color indicates aperture size).

[0079] like Figure 8As shown, different grayscale filters introduce different additional exposure doses, causing changes in the development boundary of the cylindrical structure, which in turn leads to differences in the aperture after development, while the center position of the cylindrical unit and the array center distance remain unchanged. Therefore, the second exposure is mainly used to control the size of the cylindrical unit, without altering the basic arrangement established in the first exposure.

[0080] Furthermore, this processing method enables effective control of the cylinder dimensions under a fixed center distance, thereby forming a two-dimensional metasurface structure with different cylindrical unit sizes in different regions. This embodiment demonstrates that this disclosure is not only applicable to the processing of one-dimensional wire-grid metasurfaces, but also to the processing of two-dimensional cylindrical unit metasurfaces, providing an effective technical solution for the processing of high-resolution metasurfaces.

[0081] The embodiments of this disclosure have been described above. However, these embodiments are for illustrative purposes only and are not intended to limit the scope of this disclosure. Although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination. The scope of this disclosure is defined by the appended claims and their equivalents. Various substitutions and modifications can be made by those skilled in the art without departing from the scope of this disclosure, and all such substitutions and modifications should fall within the scope of this disclosure.

Claims

1. A method for fabricating metasurface devices based on super-resolution interferometric lithography combined with secondary exposure, characterized in that, include: A dielectric layer, a photoresist layer, and a metal layer are sequentially stacked on the surface of a substrate containing a functional layer to form a surface plasmon-enhanced super-resolution interference lithography multilayer film structure. Super-resolution interference lithography is performed on the super-resolution interference lithography multilayer film structure to form a super-resolution periodic basic pattern in the photoresist layer; Remove the metal layer; The photoresist layer with the super-resolution periodic basic pattern is subjected to secondary exposure and then development to form a super-resolution periodic target pattern with different feature sizes in different exposure areas in the photoresist layer; wherein, the different exposure areas have different additional exposure doses. The super-resolution periodic target pattern is transferred from the photoresist layer to a substrate containing a functional layer to obtain a metasurface device.

2. The method for fabricating metasurface devices according to claim 1, characterized in that, The step of fabricating a dielectric layer, a photoresist layer, and a metal layer sequentially stacked on the surface of a substrate containing a functional layer includes: The metal layer is prepared by thermal evaporation, electron beam evaporation, magnetron sputtering, ion beam sputtering, pulsed laser deposition, or atomic layer deposition. The photoresist layer was prepared by spin coating. The dielectric layer is prepared by electron beam evaporation, magnetron sputtering or atomic layer deposition.

3. The method for fabricating metasurface devices according to claim 1 or 2, characterized in that, The metal layer is prepared using a metallic or alloy material whose real part of dielectric constant is negative at the exposure wavelength and whose ratio of the absolute value of the imaginary part of dielectric constant to the absolute value of the real part of dielectric constant is not greater than 0.5; The dielectric layer is prepared using a dielectric material with a real part of dielectric constant not less than 2.0 and an imaginary part of dielectric constant not greater than 0.1 at the exposure wavelength.

4. The processing method according to claim 1, characterized in that, The method of fabricating a dielectric layer, a photoresist layer, and a metal layer sequentially stacked on the surface of a substrate containing a functional layer to form a surface plasmon-enhanced super-resolution interference photolithography multilayer film structure further includes: The structural parameters of the prepared super-resolution interference lithography multilayer film structure were characterized, and the parameter characterization results were obtained. The process parameters for preparing the super-resolution interference lithography multilayer film structure are adjusted based on the difference between the parameter characterization results and the target design parameters of the super-resolution interference lithography multilayer film structure, until the parameter characterization results of the prepared super-resolution interference lithography multilayer film structure match the target design parameters of the super-resolution interference lithography multilayer film structure.

5. The method for fabricating metasurface devices according to claim 1, characterized in that, The super-resolution interference lithography process, which involves forming a super-resolution periodic basic pattern in the photoresist layer, includes: The interference lithography mask and the substrate on which the super-resolution interference lithography multilayer film structure is formed are respectively fixed in the mask stage and the substrate stage of the super-resolution lithography apparatus; After controlling the working distance between the interference lithography mask and the super-resolution interference lithography multilayer film structure to the target distance, super-resolution interference lithography is performed on the super-resolution interference lithography multilayer film structure using a preset exposure dose to form a periodically uniform line or hole / pillar array pattern in the photoresist layer.

6. The method for fabricating metasurface devices according to claim 5, characterized in that, Using a two-dimensional mask, a periodically uniform array of holes / pillars is formed in the photoresist layer through a single super-resolution interference lithography process; Alternatively, a one-dimensional mask can be used to form a periodically uniform array of holes / pillars in the photoresist layer by performing two superimposed super-resolution interference lithography steps with a 90° rotation.

7. The method for fabricating metasurface devices according to claim 1, characterized in that, The removal of the metal layer includes: The metal layer above the photoresist layer is removed using a dry or wet process to expose the photoresist layer.

8. The method for fabricating metasurface devices according to claim 1, characterized in that, The second exposure of the photoresist layer with the super-resolution periodic basic pattern includes: The substrate after removing the metal layer is fixed in the stage of the super-resolution lithography apparatus, and the grayscale mask or grayscale filter is fixed in the mask stage of the super-resolution lithography apparatus. After controlling the working distance between the mask and the photoresist layer to the target distance, the photoresist layer is subjected to secondary exposure using a preset exposure dose.

9. The method for fabricating metasurface devices according to claim 1, characterized in that, Also includes: The development boundary position is controlled by varying the total exposure dose in different exposure areas during secondary exposure.

10. The method for fabricating metasurface devices according to claim 1, characterized in that, The photoresist layer is developed using a developer that is compatible with the photoresist layer; The super-resolution periodic target pattern is etched and transferred from the photoresist layer to the functional layer using an etching transfer process to obtain the metasurface device.

Images