Meta-optical elements on curved surfaces

Abstract

The method includes the steps of: preparing a substrate having a curved surface; forming a resist layer on the curved surface; forming a patterned resist layer by patterning the resist layer on the curved surface using imprint lithography; removing residual resist material from the patterned resist layer; forming a first layer on the patterned resist layer using atomic layer deposition; and forming a first patterned layer on the curved surface by removing the patterned resist layer.

Description

Technical Field

[0001] Technical Field The present disclosure relates to an optical device including one or more meta-structures.

Background Art

[0002] Background A metasurface refers to a surface having microstructures (e.g., meta-atoms) arranged and dispersed so as to interact with light in a specific manner. For example, a metasurface may be a surface having a dispersed arrangement of nanostructures. The nanostructures can interact with light waves individually or collectively. For example, the nanostructures or other meta-atoms can change the local amplitude, local phase, or both of the incident light wave.

Summary of the Invention

Means for Solving the Problems

[0003] Summary In one aspect, the present disclosure discloses a method. The method includes the steps of preparing a substrate having a curved surface, forming a resist layer on the curved surface, forming a patterned resist layer by patterning the resist layer on the curved surface using imprint lithography, removing residual resist material from the patterned resist layer, forming a first layer on the patterned resist layer using atomic layer deposition, and forming a first patterned layer on the curved surface by removing the patterned resist layer.

[0004] Embodiments of this method can include one or more of the following. The first patterned layer on the curved surface includes a meta-structure. The meta-structure includes one or more structures formed perpendicular to the curved surface, and the height of each of the one or more meta-structures is perpendicular to the curved surface. Each of the one or more structures formed perpendicular to the curved surface has a diameter of 30 to 500 nanometers. The method includes the step of sealing the first patterned layer using a sealing material.

[0005] Embodiments of this method may include one or more of the following: The encapsulating material includes spin-on glass or a polymer. The method includes the step of exposing at least a portion of a patterned resist layer by removing a portion of a first layer. The step of exposing at least a portion of a patterned resist layer by removing a portion of a first layer includes etching the first layer. The substrate is a substrate transparent to visible light, infrared light, near-infrared light, or short-wavelength infrared light. The step of patterning the resist layer includes forming a patterned resist layer by physically contacting a mold having a pattern with the resist layer, pressing the mold and the substrate together, curing the resist, and separating the mold from the resist layer.

[0006] Embodiments of this method may include one or more of the following: The mold comprises a flexible material. The curved surface comprises a surface that is convex with respect to the substrate. The curved surface comprises a surface that is concave with respect to the substrate. The curved surface comprises a combination of multiple surfaces that are convex with respect to the substrate. The curved surface comprises a surface that is concave with respect to the substrate and a surface that is convex with respect to the substrate. The resist is a thermosetting resist or a UV-curable resist. The step of removing residual resist material comprises using a dry etching technique. The first layer comprises amorphous silicon, niobium oxide, titanium oxide, aluminum oxide, hafnium oxide, silicon oxide, titanium strontium oxide, tantalum oxide, gadolinium oxide, zirconium oxide, gallium oxide, or vanadium oxide.

[0007] In one embodiment, the present disclosure describes an apparatus comprising a substrate having a curved surface and one or more metastructures on the curved surface. The apparatus comprises one or more metastructures on the curved surface, each metastructure having a diameter up to 1000 nanometers. Details of one or more embodiments of the present invention are described in the accompanying drawings and the following description. Other features, purposes, and advantages of the present invention will become apparent from the description and drawings, as well as from the claims. [Brief explanation of the drawing]

[0008] [Figure 1] This figure shows an example of a resist patterned on a curved surface using lithography. [Figure 2A] This is a diagram showing a method for manufacturing the device. [Figure 2B] This is a diagram showing a method for manufacturing the device. [Figure 2C] This is a diagram showing a method for manufacturing the device. [Figure 2D] This is a diagram showing a method for manufacturing the device. [Figure 2E] This is a diagram showing a method for manufacturing the device. [Figure 2F] This is a diagram showing a method for manufacturing the device. [Figure 2G] This is a diagram showing a method for manufacturing the device. [Figure 2H] This is a diagram showing a method for manufacturing the device. [Figure 2I] This is a diagram showing a method for manufacturing the device. [Figure 3A] This figure shows an example of a substrate with a curved surface. [Figure 3B] This figure shows an example of a substrate with a curved surface. [Figure 3C] This figure shows an example of a substrate with a curved surface. [Figure 4A] This is a diagram showing a method for manufacturing the device. [Figure 4B] This is a diagram showing a method for manufacturing the device. [Figure 4C] This is a diagram showing a method for manufacturing the device. [Figure 4D]A diagram showing a method of manufacturing a device. [Figure 4E] A diagram showing a method of manufacturing a device. [Figure 4F] A diagram showing a method of manufacturing a device. [Figure 4G] A diagram showing a method of manufacturing a device. [Figure 4H] A diagram showing a method of manufacturing a device. [Figure 4I] A diagram showing a method of manufacturing a device. [[ID=十七]] [Figure 4J] A diagram showing a method of manufacturing a device. [Figure 4K] A diagram showing a method of manufacturing a device.

Embodiments for Carrying Out the Invention

[0009] Detailed Description In various drawings, like reference numerals indicate like elements.

[0010] A metasurface includes a surface having meta-atoms (which may sometimes also be referred to as nanostructures) arranged to interact with light in a specific way. For example, a metasurface that may be referred to as a meta-structure may be a surface having a dispersed arrangement of nanostructures. The nanostructures can interact with light waves individually or collectively. For example, the nanostructures or other meta-atoms can modify the local amplitude, local phase, or both of the incident light wave. In some cases, the metasurface can perform optical functions that were conventionally performed by refractive and / or diffractive optical elements. In some cases, the meta-atoms may be arranged in a pattern such that the metasurface functions as an optical element such as, for example, a lens, a lens array, a beam splitter, a grating, a grating coupler, a fan-out grating, a diffuser plate, or other optical elements. Also, the meta-atoms need not be arranged in a pattern. In some embodiments, the metasurface can perform other functions including polarization control, negative refractive index transmission, beam deflection, vortex generation, polarization conversion, optical filtering, and plasmonic optical functions.

[0011] The meta-atoms may be sub-wavelength nanostructures. This means that the lateral dimension of the structure parallel to the surface of the substrate is shorter than the wavelength of the light incident on the structure. For example, in some cases, the nanostructure may be a nanoscale feature having a dimension of less than 1 micron. By adjusting the geometry of the meta-atom / unit cell elements formed on the meta-structure, optical devices having different characteristics can be formed.

[0012] This disclosure describes techniques for facilitating the formation of meta-structures on curved surfaces. Lithography techniques such as maskless lithography, ultraviolet lithography, deep ultraviolet lithography, and electron beam lithography may have one or more drawbacks when forming structures on curved surfaces. For example, the structures formed by these techniques may have poor contact between the hard lithography mask or reticle and the curved surface of the substrate, or in some cases, the curved surface may disrupt the focus. In some cases, the resolution achievable with these techniques is limited and / or the structures generated may not be aligned perpendicular to the substrate surface. These drawbacks and / or other drawbacks may reduce the performance of the devices formed using these lithography processes. The techniques described herein include a process for forming a meta-structure on a curved surface and may provide a meta-structure having other potential advantages such as improved contact, surface conformity, resolution, and / or focus. As described in more detail below, the meta-structure may be formed perpendicular to the curved surface. That is, the height of each structure extends in a direction parallel to the normal of the curved surface. In some cases, the meta-structure may be formed to have a diameter of 30 to 500 nanometers. In other cases, the meta-structure may be formed to have a diameter of up to 1000 nanometers.

[0013] Figure 1 shows an example of a resist patterned on a curved surface using lithography. As shown in Figure 1, the substrate 102 includes a curved surface 106. The substrate 102 may also include a support substrate 104 on which the curved surface 106 is formed. The curved surface 106 may be a lens, such as a microlens. The microlens may be part of a microlens array. In some embodiments, the curved surface 106 may be a collimator lens, an imaging lens, a focusing lens, or a beam shaper. In other embodiments, the curved surface 106 may be an aspherical lens or an asymmetric lens, such as a lenticular lens. A resist layer 108 with the structure 110 patterned on it is formed on the curved surface 106. Although the curved surface 106 is shown as convex with respect to the substrate 102, the curved surface may be concave with respect to the substrate 102, or may have both convex and concave features. As described above, lithography techniques such as maskless lithography, ultraviolet lithography, deep ultraviolet lithography, and electron beam lithography may exhibit limitations when patterning microstructures on curved surfaces. For example, as shown in Figure 1, each of the one or more structures 110 formed on the patterned resist 108 is not aligned perpendicular to the curved surface 106. More specifically, as shown in Figure 1, structure 110A is formed in the shape of a rectangular prism, and the height of the rectangular prism extends along a direction perpendicular to the curved surface 106. On the other hand, the heights of structures 110B and 110C do not coincide with a direction perpendicular to the curved surface 106. When the resist 108 is used as a mask for subsequent etching or deposition processes, the desired pattern may not be faithfully transferred to the underlying substrate. In the case of optical elements, this limitation may result in devices exhibiting undesirable characteristics such as reduced resolution, out-of-focus areas, reduced efficiency, and excessive stray light.

[0014] Figures 2A to 2I illustrate the manufacturing process for forming a device including one or more metastructures formed on a curved surface. As shown in Figure 2A, a substrate 202 having a curved surface 206 is prepared. In some embodiments, the curved surface 206 is formed on the substrate 202. In these embodiments, the curved surface 206 and the substrate are formed from the same material. Alternatively, the substrate 202 may include a support substrate 204 on which the curved surface 206 is formed. In these embodiments, the support substrate 204 and the curved surface 206 may be formed from different materials. For example, the support substrate 204 may be formed from silicon, germanium, gallium arsenide, boroflote glass, fused silica, borosilicate glass, or any other suitable material. The curved surface 206 may be formed from a UV-curable polymer or thermoplastic. As described herein, the curved surface 206 may include a convex surface, a concave surface, or a combination of convex and concave surfaces. The curved surface 206 may be formed, for example, by nanoimprint lithography (NIL) using a mold. The substrates 202 / 204 may be selected to be optically transparent to radiation of a specific wavelength or wavelength range (e.g., infrared (IR), near-infrared (NIR), short-wave infrared (SWIR), or visible light) depending on the application in which the meta-optical structure formed on its surface is used. For example, the substrate 202 and / or the support substrate 204 may be formed from borosilicate glass or fused silica, but other materials may also be used. In some cases, the substrate 202 may include a material that reflects incident light, such as a metal or other mirrored surface.

[0015] Next, as shown in Figure 2B, at least one resist layer 208 is formed on the curved surface 206 of the substrate 202. In some embodiments, one or more resist layers may be formed on the curved surface 206. In some cases, at least one resist layer 208 includes a nanoimprint resist, which is a UV-curable resist. In other examples, at least one resist layer 208 includes a thermosetting resist. In some packaging configurations, the resist layer 208 is a high refractive index resist, including but not limited to polymethacrylate, polyurethane, or polycarbonate. The resist layer 208 may be applied by various deposition techniques. For example, in some cases, the resist layer 208 is applied by a spin-on process, a spray coating process, or an injection dispensing process.

[0016] As shown in Figure 2C, the resist layer 208 on the curved surface 206 is patterned using imprint lithography. In some cases, nanoimprint lithography is used to pattern the resist layer 208. For example, in some embodiments, a mold having the desired pattern is brought into physical contact with the resist layer 208 on the curved surface 206 of the substrate 202. The mold may be formed from a flexible material such as a UV-curable polymer or thermoplastic, and may have elasticity, deformability, and the ability to return to its original shape after deformation. For example, the mold may be formed from silicone rubber, polyurethane elastomer, natural rubber, or any other suitable elastomer material. By applying pressure to the mold and the resist layer 208, the pattern of the mold can be transferred to the resist layer 208. Because the flexible mold deforms under pressure, it can follow the shape of the curved surface 206, ensuring good contact between the mold and the curved surface 206, and allowing the desired pattern to be accurately replicated. By applying the mold to the resist layer 208, regions where the resist layer 208 is thin and other regions where the resist layer 208 is thick can be formed. The mold may include patterns complementary to the pattern of the metastructure to be formed on the curved surface 206. For example, the mold pattern may include repeating structures such as a one-dimensional linear grid or a two-dimensional linear grid. The mold pattern may include patterns such as squares, rectangles, trapezoids, rhombuses, stars, diamonds, arrowheads, or horseshoes.

[0017] Next, the resist layer 208 is cured. If the resist layer 208 is formed of a UV-curable resist, the mold and substrate 202 are exposed to ultraviolet light for a sufficient time to cure the resist. If the resist layer 208 is formed of a thermosetting resist, the mold and substrate 202 are exposed to heat to cure the resist. After the resist has been cured, the patterned resist layer 210 on the substrate 202 is exposed by separating the mold from the substrate 202. In some embodiments, when using a high refractive index nanoimprint resist with a refractive index of 1.6 to 2.0, the patterned resist 210 on the curved surface 206 may be the final apparatus or may be further processed. For example, the patterned resist 210 may include a dispersed array of metaatoms forming a one-dimensional or two-dimensional lattice on the curved surface 206. Alternatively or additionally, the patterned resist 210 may include one or more lens elements.

[0018] In contrast to UV lithography or other pattern transfer techniques, the advantage of using imprint lithography on a curved surface with a flexible mold is that the flexible mold can conform to the curved surface 206, allowing for accurate reproduction of the pattern on the curved surface 206. In contrast, when using other lithography techniques, such as UV exposure of resist via a mask, the pattern transferred to the resist may be distorted, misaligned, or not conform to the substrate surface, potentially negatively impacting the shape and performance of the manufactured device.

[0019] Next, residual resist is removed, as shown in Figure 2D. Residual resist may include, for example, resist located between structures imprinted on the resist. For example, in Figure 2D, the regions between the protrusions 211 formed by the imprint may contain residual resist that needs to be removed to expose the substrate before proceeding to the next step in manufacturing. Alternatively or additionally, residual resist may include a thin resist layer that incorporates the patterned regions. Residual resist can be removed using omnidirectional or isotropic etching techniques, such as dry etching techniques including plasma etching. In some embodiments, other suitable omnidirectional etching techniques may also be used. In some embodiments, when using high refractive index nanoimprint resists with a refractive index of 1.6 to 2.0, after removing residual resist from the patterned resist 210 on the curved surface 206, as shown in Figure 2D, the resulting structure may be the final apparatus or may be further processed.

[0020] As shown in Figure 2E, a first layer 212 is deposited on the patterned resist layer 210. In some cases, the first layer 212 may be deposited by atomic layer deposition (ALD). For example, in some cases, the first layer 212 may contain a high refractive index oxide material. In some cases, the first layer 212 may contain titanium dioxide, amorphous silicon, niobium oxide (niobium pentoxide), aluminum oxide, hafnium oxide, silicon oxide, titanium strontium oxide, tantalum oxide, gadolinium oxide, zirconium oxide, gallium oxide, or vanadium oxide. In some embodiments, the first layer 212 may contain a metal. Advantages of depositing the first layer 212 using ALD may include, for example, applying a shape-adaptive coating to the three-dimensional structure of the patterned resist layer 210, including high aspect ratio geometry, geometry with sharp edges, precise film thickness control, and a high-quality film. In particular, in some embodiments, by using imprint lithography with ALD, relatively complex geometric shapes can be formed, including but not limited to geometric shapes having cross-sections such as square, rectangular, trapezoidal, rhombus, star, diamond, arrowhead, and horseshoe shapes, and geometric shapes used in polarization-dependent devices. In some embodiments, the thickness of the deposited material fills the areas between the protrusions of the patterned resist layer 210. Thus, the thickness of the material deposited in these areas is greater than the thickness of the adjacent protrusions of the patterned resist layer 210. Figure 2E shows a single material layer 212 formed on the patterned resist layer 210, but multiple material layers may be formed on the patterned resist layer 210. The multiple layers may contain the same material or a combination of different materials. For example, in some embodiments, the multiple layers may include a structure in which a first material and a second material are alternately stacked. The first and second materials may have different refractive indices, for example, materials with high refractive indices and low refractive indices may be alternately stacked.

[0021] Next, as shown in Figure 2F, an arbitrary etch-back is performed on the first layer 212. In some cases, a portion of the first layer 212 can be etched back using wet etching or dry etching techniques. By etching back the first layer 212, the material deposited on the surface of the protrusions of the patterned resist layer 210 is removed, and a portion of the underlying patterned resist layer 210 can be exposed.

[0022] As shown in Figure 2G, after any etch-back, the patterned resist layer 210 is removed, leaving the first patterned layer 214 on the curved surface. The patterned resist layer 210 may be removed using wet etching techniques with solvents and / or oxidizing chemicals, or dry etching techniques such as plasma techniques or reactive ion etching. The patterned layer 214 formed on the curved surface 206 may include one or more metastructures as described herein. For example, the metastructures may include columnar, pillar, linear, or other shaped nanostructures. Depending on the adaptability of the imprint lithography and ALD processes in forming the metastructures, each metastructure can be formed such that the height of each metastructure extends perpendicularly to the surface of the curved substrate on which each metastructure is located. In some embodiments, after the patterned resist layer 210 is removed, as shown in Figure 2G, the resulting structure may be the final apparatus or may be further processed.

[0023] Next, as shown in Figure 2H, one or more metastructures formed on the curved surface 206 are sealed by forming an arbitrary sealing material 216 on the pattern layer 214. In some cases, the sealing material 216 is a spin-on glass material or a polymer. In some cases, the polymer includes a photoresist material that is spin-on coated and then cured, and can function as a sealing material. The sealing material 216 can function as a protective layer that helps protect the metastructure from physical, chemical, and / or environmental degradation. In some cases, the thickness of the sealing material 216 is the same as or greater than the thickness of the structure formed on the pattern layer 214. In some cases, the thickness of the sealing material 216 is at least twice the wavelength of light in the application in which the metastructure is used. In some cases, the sealing material 216 may be a material having a refractive index of 1.2 to 2.1. In some embodiments, as shown in Figure 2H, after the sealing material 216 is formed on the pattern layer 214, the resulting structure may be a final apparatus or may be further processed.

[0024] In some embodiments, an arbitrary reflective or anti-reflective coating 218 is formed, as shown in Figure 2I. The reflective or anti-reflective coating 218 may be formed on the surface of the sealing material 216, or on the surface of one or more metastructures of the pattern layer 214 when no sealing material is present. The coating 218 may be formed using physical deposition techniques such as thermal deposition, electron beam deposition, or sputtering. In some embodiments, the coating 218 may be formed using ALD. In some embodiments, the coating 218 may be formed on the back surface of the substrate 202.

[0025] As described herein, the curved surface 206 is not limited to a surface that is convex with respect to the substrate 204. Figures 3A to 3C show examples of various types of substrates having curved surfaces. Figure 3A shows a substrate 302A having both a convex surface and a concave surface with respect to the substrate 304A. Figure 3B shows a substrate 302B having a concave surface 306B with respect to the substrate 304B. Figure 3C shows a substrate 304C including a plurality of lenses arranged in an array. As described herein, a substrate can be understood as including a support layer on which the curved surface is formed.

[0026] Figures 4A to 4K illustrate a manufacturing process for forming a device containing one or more metastructures on a curved surface containing a high refractive index medium layer. The use of a high refractive index medium layer allows for the creation of metastructures with high transmittance, offering the advantage of bending light over a wider angular range. Using a high refractive index medium layer in the manufacture of optical devices enhances optical efficiency and improves the performance of the optical devices. The manufacturing process described in Figures 4A to 4K uses a subtractive process to form patterns on the curved surface. This subtractive process allows for the formation of precisely formed, clearly defined, and high-resolution metastructures.

[0027] As shown in Figure 4A, a substrate 402 is prepared. The substrate 402 may include a curved surface 406. Although shown as a convex surface relative to the substrate 402, the curved surface 406 may alternatively be concave, or may include a combination of convex and concave surfaces. The substrate 402 may include a support layer 404 on which the curved surface 406 is formed. The material of the substrate 402 and / or the support layer 404 may be selected to have optical transparency to radiation of a specific wavelength or wavelength range (e.g., infrared (IR), near-infrared (NIR), short-wave infrared (SWIR), or visible light) depending on the application in which the device will be used.

[0028] As shown in Figure 4A, a high refractive index material layer 408 can be formed on the substrate 402, for example, on a curved surface 406. In some embodiments, the high refractive index layer 408 is formed directly on the surface of the substrate, for example, on a support layer 404. The high refractive index layer 408 can include materials such as amorphous silicon, titanium dioxide, tantalum pentoxide, niobium oxide, aluminum oxide, hafnium oxide, silicon oxide, titanium strontium oxide, tantalum oxide, gadolinium oxide, zirconium oxide, gallium oxide, vanadium oxide, or silicon nitride. The high refractive index material layer 408 may be formed using various deposition techniques such as physical vapor deposition (e.g., thermal vapor deposition or sputtering) or electron beam vapor deposition.

[0029] In some embodiments, a hard mask layer 410 is formed on a high refractive index layer 408. The hard mask layer 410 may be used in a later process to transfer a pattern to the underlying high refractive index layer 408. The hard mask layer 410 may include, but is not limited to, metals such as chromium, aluminum, or titanium. In some embodiments, the hard mask layer 410 may include tungsten, titanium nitride, silicon nitride, or silicon dioxide. In some embodiments, the hard mask layer 410 may be a composite hard mask consisting of multiple layers of different materials. The hard mask layer 410 may be formed using various deposition techniques such as chemical vapor deposition, atomic layer deposition, physical vapor deposition (e.g., thermal deposition or sputtering), or electron beam deposition.

[0030] Next, as shown in Figure 4B, at least one resist layer 412 is formed on the hard mask 410. In some cases, at least one resist layer 412 includes a nanoimprint resist, which is a UV-curable resist. In other examples, at least one resist layer 412 includes a thermosetting resist. The resist layer 412 may be applied by various deposition techniques. For example, in some cases, the resist layer 412 is applied by a spin-on process, a spray coating process, or an injection distribution process.

[0031] As shown in Figure 4C, the resist layer 412 on the curved surface 406 is patterned using imprint lithography. For example, as described above with reference to Figure 2, a mold having the desired pattern is brought into physical contact with the resist layer 412. The mold may be formed from a flexible material such as a UV-curable polymer or thermoplastic, and may have elasticity, deformability, and the ability to return to its original shape after deformation. For example, the mold may be formed from silicone rubber, polyurethane elastomer, natural rubber, or any other suitable elastomer material. By applying pressure to the mold and the resist layer 412, the pattern of the mold can be transferred to the resist layer 412. Because the flexible mold deforms under pressure, it can follow the shape of the curved surface 406, ensuring good contact between the mold and the surface 406 substrate, and accurately replicating the desired pattern. By applying the mold to the resist layer 412, regions where the resist layer 412 is thin and other regions where the resist layer 412 is thick can be formed. The mold may include patterns complementary to the metastructure pattern to be formed on the curved surface 406. For example, the mold pattern may include repeating structural patterns such as a one-dimensional linear grid or a two-dimensional linear grid. The mold pattern may include patterns such as squares, rectangles, trapezoids, rhombuses, stars, diamond shapes, arrowheads, or horseshoes.

[0032] Next, the resist layer 412 is cured. If the resist layer 412 is formed of a UV-curable resist, the mold and substrate 402 are exposed to ultraviolet light for a sufficient amount of time to cure the resist. If the resist layer 412 is formed of a thermosetting resist, the mold and substrate 402 are exposed to heat to cure the resist. After the resist has been cured, the mold is separated from the substrate 402, thereby exposing the patterned resist layer 414 on the substrate 402.

[0033] Next, residual resist is removed, as shown in Figure 4D. Residual resist may include, for example, resist located between structures imprinted on the resist. Residual resist can be removed using omnidirectional or isotropic etching techniques, such as dry etching techniques including plasma etching. In some embodiments, other suitable omnidirectional etching techniques may also be used.

[0034] By removing residual resist, a portion 415 of the hard mask 410 can be exposed. As shown in Figure 4E, the exposed portion of the hard mask 410 is removed. By removing the exposed portion of the hard mask 410, the pattern of the resist layer 412 is transferred to the underlying hard mask layer 410, and then a portion of the high refractive index layer 408 is exposed. The portion of the hard mask 410 may be removed using a wet etching process or a dry etching process that does not remove the high refractive index layer or removes only a minimal amount. In some embodiments, preferably, the exposed portion of the hard mask 410 is removed using anisotropic etching so as not to undercut the patterned resist features.

[0035] As shown in Figure 4F, the remaining portion of the patterned resist layer 414 is removed, leaving the patterned mask layer 416 on the high refractive index layer 408. The patterned resist layer 412 may also be removed using a wet etching process or a dry etching process that does not remove or removes only minimally the exposed portion of the underlying high refractive index layer 408.

[0036] As shown in Figure 4G, by using a thin hard mask 410, portions of the exposed high refractive index layer 408 are removed, while portions of the high refractive index layer 408 beneath the hard mask 410 are not removed and remain on the curved surface. In some embodiments, the thin hard mask 410 may have a thickness of 5 to 20 nanometers. The portions of the high refractive index layer 408 may be removed using directional etching techniques such as reactive ion etching, inductively coupled plasma etching, or deep reactive ion etching. In some embodiments, other suitable directional etching techniques may also be used. In some cases, as shown in Figure 4H, a thick hard mask 410 is used, and directional etching of the high refractive index material 408 may result in a shadowing effect where the exposure of some areas is reduced or completely shadowed. In some embodiments, the thick hard mask 410 may have a thickness of 20 to 200 nanometers.

[0037] As shown in Figure 4I, the remaining portion of the hard mask 410 is removed by etching. In some cases, the portion of the hard mask 410 may be removed using wet etching. In other cases, the portion of the hard mask 410 may be removed using dry etching. In some embodiments, other suitable etching techniques may be used. Once the portion of the hard mask 410 is removed by etching, the pattern layer 414 is formed on the curved surface 406 and may include a plurality of meta-optical structures 416. Each of the plurality of meta-structures 416 has a cross-sectional width of 30 to 500 nanometers. In some examples, if the plurality of meta-structures are formed in a circular or cylindrical shape, the diameter of each structure is 30 to 500 nanometers. In some embodiments, the diameter of the plurality of meta-structures may be up to 1000 nanometers. The pattern layer 414 may be formed in a pattern complementary to the mold used to pattern the resist layer 412. In some embodiments, as shown in Figure 4I, after the hard mask 410 is removed, the resulting structure may be the final apparatus or may be further processed.

[0038] Next, as shown in Figure 4J, one or more metastructures formed on the curved surface 406 are sealed by forming an arbitrary sealing material 418 on the pattern layer 416. In some cases, the sealing material 418 is a spin-on glass material or a polymer. In some cases, the polymer includes a photoresist material that is spin-on coated and then cured, and can function as a sealing material. The sealing material 418 can function as a protective layer that helps protect the metastructure from physical, chemical, and / or environmental degradation. In some cases, the thickness of the sealing material 418 is the same as or greater than the thickness of the structure formed on the pattern layer 416. In some cases, the thickness of the sealing material 418 is at least twice the wavelength of light in the application in which the metastructure is used. In some cases, the sealing material 418 has a refractive index of 1.2 to 2.1. In some embodiments, after forming the sealing material 418 on the pattern layer 416 as shown in Figure 4J, the resulting structure may be a final apparatus or may be further processed.

[0039] Next, as shown in Figure 4K, an optional reflective or anti-reflective coating 420 is formed. The reflective or anti-reflective coating 420 may be formed on the surface of the sealing material 418, or on the surface of one or more metastructures of the pattern layer 416 if no sealing material is present. The coating 420 may be formed using physical deposition techniques such as thermal deposition, electron beam deposition, or sputtering. In some embodiments, the coating 420 may be formed using ALD. In some embodiments, the coating 420 may be formed on the back surface of the substrate 402.

[0040] While several embodiments of the present invention have been described, it will be understood that various modifications are possible without departing from the spirit and scope of the invention. Therefore, other embodiments are also included in the claims.

Claims

1. It is a method, The steps include: preparing a substrate with a curved surface, The steps include forming a resist layer on the curved surface, The steps include forming a patterned resist layer by patterning the resist layer on the curved surface using imprint lithography, The steps include removing residual resist material from the patterned resist layer, The steps include forming a first layer on the patterned resist layer using atomic layer deposition, A method comprising the step of forming a first patterned layer on the curved surface by removing the patterned resist layer.

2. The method according to claim 1, wherein the first pattern layer on the curved surface includes a metastructure.

3. The metastructure includes one or more structures formed perpendicular to the curved surface, The method according to claim 2, wherein the height of each of the one or more metastructures is perpendicular to the curved surface.

4. The method according to claim 3, wherein each of the one or more structures formed perpendicular to the curved surface has a diameter of 30 to 500 nanometers.

5. The method according to claim 1, further comprising the step of sealing the first pattern layer with a sealing material.

6. The method according to claim 5, wherein the sealing material comprises spin-on glass or a polymer.

7. The method according to claim 1, further comprising the step of exposing at least a portion of the patterned resist layer by removing a portion of the first layer.

8. The method according to claim 7, wherein the step of exposing at least a portion of the patterned resist layer by removing the portion of the first layer includes etching the first layer.

9. The method according to any one of the preceding claims, wherein the substrate is a substrate that is transparent to visible light, infrared light, near-infrared light, or short-wavelength infrared light.

10. The step of patterning the resist layer is: Physically bringing a mold having a pattern into contact with the resist layer, Pressing the mold and the substrate together, The resist is cured, The method according to any one of the preceding claims, comprising forming the patterned resist layer by separating the mold from the resist layer.

11. The method according to claim 10, wherein the mold includes a flexible material.

12. The method according to any one of the preceding claims, wherein the curved surface includes a surface that is convex with respect to the substrate.

13. The method according to any one of claims 1 to 9, wherein the curved surface includes a surface that is concave with respect to the substrate.

14. The method according to any one of claims 1 to 9, wherein the curved surface includes a combination of a plurality of surfaces that are convex with respect to the substrate.

15. The method according to any one of claims 1 to 9, wherein the curved surface includes a combination of a plurality of surfaces that are concave with respect to the substrate.

16. The method according to any one of claims 1 to 9, wherein the curved surface includes a surface that is concave with respect to the substrate and a surface that is convex with respect to the substrate.

17. The method according to claim 1, wherein the resist is a thermosetting resist or a UV-curable resist.

18. The method according to claim 1, wherein the step of removing the residual resist material includes using a dry etching technique.

19. The method according to claim 1, wherein the first layer comprises amorphous silicon, niobium oxide, titanium oxide, aluminum oxide, hafnium oxide, silicon oxide, titanium strontium oxide, tantalum oxide, gadolinium oxide, zirconium oxide, gallium oxide, or vanadium oxide.

20. It is a device, A substrate having a curved surface, An apparatus comprising one or more metastructures on the curved surface.

21. The apparatus according to claim 20, wherein one or more metastructures of the curved surface have a diameter of up to 1,000 nanometers.

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