KR20240141609A - Meta lens, electronic device including the same, and method of manufacturing meta lens - Google Patents

Abstract

The disclosed meta-lens comprises a substrate; a plurality of nanostructures provided on the substrate; and a high-refractive-index atomic layer formed along a surface of the plurality of nanostructures and including a material having a higher refractive index than the plurality of nanostructures.

Description

Meta lens, electronic device including the same, and method of manufacturing meta lens

The disclosed embodiments relate to a metalens and a method of manufacturing the same.

A meta-lens is a planar diffractive element that utilizes a meta-structure. It can exhibit various optical effects that conventional refractive elements cannot achieve and can implement thin optical systems, so it is receiving increasing attention in many fields.

Meta-structures include nanostructures whose shape, period, etc. are applied with a value smaller than the wavelength of incident light. A phase profile suitable for the desired optical performance can be implemented by controlling the arrangement and shape of the nanostructures, and it is necessary that these design specifications are well implemented through the process.

Recently, research has been conducted on manufacturing methods that can mass-produce meta-lenses. For example, mass production processes that can well implement the desired nanostructure shape are being attempted using i-line stepper lithography, KrF stepper lithography, etc. However, due to low patterning resolution and limitations in available materials, it is difficult to produce meta-lenses that can be utilized in the entire visible light range.

A metalens and a method for manufacturing the same are provided.

According to an embodiment, a metalens is provided, including: a substrate; a plurality of nanostructures provided on the substrate; and a high-refractive-index atomic layer formed along a surface of the plurality of nanostructures and including a material having a higher refractive index than the plurality of nanostructures.

The above high refractive atomic layer may include TiO ₂ .

The thickness of the above high refractive atomic layer may be 20 nm or more and 30 nm or less.

The thickness of the high-refractive-index atomic layer can be determined so that the polarization conversion efficiency of green light by the nanostructure coated with the high-refractive-index atomic layer is 70% or more.

The above high refractive atomic layer may include ZrO ₂ .

The plurality of nanostructures may include an ultraviolet curable resin.

A flat layer including the same material as the plurality of nanostructures may be further provided between the substrate and the plurality of nanostructures.

According to an embodiment, an electronic device is provided, including: a lens assembly including one of the above-described meta lenses; an image sensor for converting an optical image of a subject formed by the lens assembly into an electrical signal; and a processor for processing a signal from the image sensor.

According to an embodiment, an electronic device is provided, comprising: a display element providing image light; a metalens according to any one of claims 1 to 8 for focusing light provided from the display element into a user's field of view; and a processor for controlling the display element.

The electronic device may further include a beam splitter arranged in a path through which the image light is directed toward the user's field of view; and the processor may control the display element to output an additional image suitable for the environment viewed by the user.

According to an embodiment, a method for manufacturing a meta-lens is provided, comprising: a step of manufacturing a master stamp having a first pattern formed identical to a plurality of nanostructure arrays to be provided in the meta-lens; a step of manufacturing a replica mold by replicating the master stamp; a step of forming a nanostructure layer including the plurality of nanostructures by imprinting the replica mold into an ultraviolet-curable resin; and a step of conformally forming a high-refractive-index atomic layer on the surfaces of the plurality of nanostructures.

The step of preparing a reticle to be used in manufacturing the above master stamp may further be included.

The step of manufacturing the above master stamp may include a step of forming a hard mask layer on a substrate; a step of forming a photoresist layer on the hard mask layer; a step of patterning the photoresist layer to have the first pattern; a step of etching the hard mask layer using the photoresist layer patterned with the first pattern as an etching mask; and a step of etching the substrate using the patterned photoresist layer and the etched hard mask layer as etching masks.

In the above patterning step, a step and scan exposure process using only some of the light incident near the optical axis of the lens optical system can be used.

The above substrate may be a silicon substrate having a diameter of 4 inches or more.

The above hard mask layer may include an amorphous carbon layer.

The above high refractive atomic layer may include TiO ₂ .

The thickness of the above high refractive atomic layer may be 20 nm or more and 30 nm or less.

The above-described meta-lens can operate with high efficiency for light in the visible light wavelength band.

According to the above-described method for manufacturing a meta-lens, mass production of a meta-lens is possible, and the process yield can also be improved.

According to the above-described method for manufacturing a metalens, there is a high degree of freedom in selecting a variety of ultraviolet-curable resins for the imprint process.

Fig. 1 is a cross-sectional view showing a schematic structure of a metalens according to an embodiment.
FIG. 2 is a partial cutaway perspective view showing an exemplary shape of a nanostructure provided in a metalens according to an embodiment.
FIG. 3 is a simulation diagram showing the conversion efficiency according to the height of the nanostructure provided in the meta lens according to the embodiment and the thickness of the high-refractive atomic layer coated on the nanostructure.
Figure 4 is a simulation diagram showing the conversion efficiency according to the width and length of the cross-section of the nanostructure provided in the meta lens according to the embodiment.
FIG. 5 is a simulation diagram showing the conversion efficiency according to the thickness of a high-refractive atomic layer coated on a nanostructure provided in a meta-lens according to an embodiment for light of R, G, and B wavelengths.
Figure 6 is a simulation diagram showing the electric field distribution by the nanostructures provided in the meta lens according to the embodiment.
Figure 7 is a simulation diagram showing the change in refractive index according to the thickness of a high-refractive atomic layer coated on a nanostructure provided in a meta lens according to an embodiment.
Figure 8 is a simulation diagram showing the electric field distribution by the nanostructures provided in the meta lens according to a comparative example.
Figure 9 is a flow chart schematically illustrating a method for manufacturing a metalens according to an embodiment.
FIGS. 10A to 10E are drawings showing exemplary processes for manufacturing a reticle used in producing a master stamp.
Figures 11a to 11i are drawings showing exemplary processes for manufacturing a master stamp.
Figures 12a and 12b are drawings explaining details of the exposure process.
FIGS. 13a to 13e are drawings showing an exemplary process of forming a replica mold by replicating a master stamp and using the same to manufacture a metalens.
Figure 14 shows a microscope photograph of a wafer on which meta-lenses are formed according to a method for manufacturing a meta-lens according to an embodiment.
FIG. 15 shows enlarged microscopic photographs of a portion of a meta-lens manufactured according to a method for manufacturing a meta-lens according to an embodiment.
Figures 16a to 17c are drawings showing the performance of a metalens according to an embodiment.
Fig. 18 is a graph showing the MTF by a metalens according to an embodiment.
Figure 19 is a drawing showing the resolution performance by a metalens according to an embodiment.
Fig. 20 shows a schematic structure of an electronic device according to an embodiment.
Figure 21 is a photograph showing experimentally that a meta-lens according to an embodiment can be applied to a virtual reality device.
Fig. 22 shows a schematic structure of an electronic device according to another embodiment.
Fig. 23 shows a schematic structure of an electronic device according to another embodiment.

Hereinafter, embodiments will be described in detail with reference to the attached drawings. The described embodiments are merely exemplary, and various modifications are possible from these embodiments. In the drawings below, the same reference numerals refer to the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of explanation.

Hereinafter, the terms “upper” or “upper” may include not only things that are directly above in contact, but also things that are above in a non-contact manner.

The terms first, second, etc. may be used to describe various components, but are used only to distinguish one component from another. These terms do not limit the material or structure of the components.

Singular expressions include plural expressions unless the context clearly indicates otherwise. Also, when a part is said to "include" a certain component, this does not mean that it excludes other components, but rather that it may include other components, unless the contrary is specifically stated.

Additionally, terms such as “unit”, “module”, etc., described in the specification mean a unit that processes at least one function or operation, which may be implemented by hardware or software, or a combination of hardware and software.

The use of the term “above” and similar referential terms may refer to both the singular and the plural.

The steps of a method may be performed in any order, unless there is an explicit statement that they must be performed in the order described. Also, the use of any exemplary terms (e.g., etc.) is intended merely to elaborate the technical idea and does not limit the scope of the rights by such terms, unless otherwise defined by the claims.

Fig. 1 is a cross-sectional view showing a schematic structure of a metalens according to an embodiment.

A meta-lens (100) is a diffractive element that utilizes nanostructures (NS) having sub-wavelength shape dimensions. Here, the sub-wavelength means a value smaller than the wavelength of incident light that is a modulation target, or a value smaller than the center wavelength of the wavelength band of the incident light. The shape and arrangement of the nanostructures (NS) provided in the meta-optical element can be set so that a desired lens performance, for example, a desired focal length, F number, etc., is implemented for the incident light. The sub-wavelength nanostructure may also be called (meta-atom), and an array in which nanostructures are arranged may also be called a meta-surface.

A meta lens (100) includes a substrate (110), a plurality of nanostructures (NS) provided on the substrate (110), and a high-refractive atomic layer (135) formed along the surfaces of the plurality of nanostructures (NS).

A flat layer (132) may be positioned between the nanostructure (NS) and the substrate (110). The flat layer (132) includes the same material as the nanostructure (NS) and may be formed according to the manufacturing process described below. The flat layer (132) may be very thin or may be almost nonexistent. A plurality of nanostructures (NS) and the flat layer (132) will be collectively referred to as a nanostructure layer (130).

The substrate (110) may be made of any one of materials among glass (fused silica, BK7, etc.), Quartz, polymer (PMMA, SU-8, etc.), and plastic, and may also be a semiconductor substrate. The substrate (110) may be made of a material having a lower refractive index than that of the nanostructure (NS). However, the present invention is not limited thereto.

Nanostructures (NS) are materials having a different refractive index than the surrounding material, for example, they may be made of materials having a higher refractive index than the surrounding material. For example, nanostructures (NS) may include c-Si, p-Si, a-Si, and III-V compound semiconductors (GaP, GaN, GaAs, etc.), SiC, TiO2, SiN, and/or combinations thereof.

The nanostructure (NS) may include a UV-curable resin. The UV-curable resin forming the nanostructure (NS) may be selected by considering properties such as refractive index, surface energy, and shrinkage. For example, a resin having low surface energy, small shrinkage, high refractive index in the visible light wavelength band, and being UV-curable may be used.

The shrinkage of the UV-curable resin can be, for example, less than 5%. The UV-curable resin can exhibit a refractive index of approximately 1.5 to 1.6 in the visible wavelength band.

When the surface energy of the ultraviolet-curable resin is low, when manufacturing a meta lens (100) using an imprint method, it is easy to separate the replica mold from the nanostructures (NS) after imprinting, which is also advantageous for the manufacturing yield.

For example, if the surface energy of the UV-curable resin is high, a separate surface treatment process may be required for the replica mold to properly separate the replica mold from the nanostructure (NS).

The conventional metalens process using nanoimprinting has been conducted in the direction of improving the performance of the metalens by mixing particles with a high refractive index in the visible range into the resin. However, the metalens manufactured in this way have an efficiency of only about 50%. In the embodiment, the process of mixing such particles into the resin can be eliminated, so that the degree of freedom of the resin that can be used can be increased. In addition, a resin material having the characteristics of low surface energy and low shirinkage (<5%) that can be used for a post-process without a separate surface treatment can be used. For example, a commercial MINS-311RM resin can be used as an ultraviolet-curable resin.

The high-refractive-index atomic layer (135) includes a material having a higher refractive index than the refractive index of the nanostructure (NS). For example, when the material of the nanostructure (NS) is an ultraviolet-curable resin, the high-refractive-index atomic layer (135) may be formed of a material having a higher refractive index than the ultraviolet-curable resin. The high-refractive-index atomic layer (135) may include, for example, TiO ₂ . TiO 2 may exhibit a refractive index of approximately 2.5 in a visible light wavelength band. The material of the high-refractive-index atomic layer (135) is not limited to TiO 2, and various materials exhibiting a higher refractive index than the ultraviolet-curable resin in the visible light wavelength band may be used. Alternatively, the material of the high-refractive-index atomic layer (135) may be a material suitable for a wavelength band other than the visible light wavelength band, depending on the purpose of the metalens (100). For example, ZrO 2 suitable for an ultraviolet wavelength band may be used.

The high-refractive atomic layer (135) is proposed in consideration of the fact that it may be difficult to implement the desired lens performance in the visible light wavelength band with the refractive index exhibited by the material of the nanostructures (NS). The material of the nanostructures (NS) may be determined according to the convenience of manufacturing, but the material of the nanostructures (NS) may be limited depending on the manufacturing method described below using the imprint method, and it may be difficult to match the desired refractive index. Therefore, a structure is adopted in which the surface of the nanostructures (NS) is conformally coated with a material having a refractive index higher than the refractive index of the nanostructures (NS).

The thickness of the high-refractive-index atomic layer (135) can be determined by considering the light modulation efficiency of the metalens (100), that is, the light modulation efficiency by the coated nanostructures (NS) of the high-refractive-index atomic layer (135). The light modulation efficiency can be expressed as the polarization conversion efficiency. For example, the arrangement angles of a plurality of nanostructures (NS) included in the metalens (100) are determined differently depending on the position, and therefore, the polarization conversion of incident light by the nanostructures (NS) is controlled depending on the position, so that a desired phase profile can be implemented. In this case, the higher the polarization conversion efficiency, the better the desired phase profile can be implemented. However, the arrangement form of the nanostructures (NS) is not limited thereto. For example, a desired phase profile can also be implemented by a method of arranging nanostructures (NS) of different sizes depending on the position.

The thickness of the high-refractive-index atomic layer (135) may be approximately 20 nm to 30 nm, or 20 nm to 25 nm. However, the present invention is not limited thereto, and may be determined in consideration of the polarization conversion efficiency according to the detailed shape and dimensions of the nanostructure (NS). For example, the thickness of the high-refractive-index atomic layer (135) may be determined so that the polarization conversion efficiency of light in the entire visible wavelength band by the nanostructure (NS) coated with the high-refractive-index atomic layer (135) is 60% or more, or 65% or more, or, for example, the polarization conversion efficiency of green light is 60% or more, 65% or more, 70% or more, 80% or more, or 85% or more.

FIG. 2 is a partial cutaway perspective view showing an exemplary shape of a nanostructure provided in a metalens according to an embodiment.

The nanostructure (NS) may have a rectangular parallelepiped shape with defined height, width, and length. Along the surface shape of the nanostructure (NS), a high-refractive atomic layer (135) may be formed with a predetermined thickness.

The simulation results for determining the details of these shape dimensions are examined with reference to Figs. 3 to 7.

FIG. 3 is a drawing showing the results of a simulation for conversion efficiency according to the height of a nanostructure equipped in a meta-lens according to an embodiment and the thickness of a high-refractive atomic layer coated on the nanostructure, and FIG. 4 is a drawing showing the results of a simulation for conversion efficiency according to the width and length of a cross-section of a nanostructure equipped in a meta-lens according to an embodiment.

In the simulation, the wavelength of the incident light was 532 nm, the length, width, and height of the nanostructures (NS) were in the ranges of 260 nm to 400 nm, 70 nm to 200 nm, and 500 nm to 900 nm, respectively, and the array pitch of the nanostructures (NS) was 450 nm. In addition, the thickness range of the high-refractive atomic layer (135) was set to 0 nm to 40 nm. The material of the nanostructure (NS) was UV-curable resin, the material of the high-refractive atomic layer (135) was TiO2, and the material of the substrate (110) was _SiO2 .

The simulation drawing of Fig. 4 is for the case where the height of the nanostructure (NS) is 900 nm and the thickness of the high-refractive atomic layer (135) is 23 nm.

Through these simulations, the width, length, height, and thickness of the high-refractive-index atomic layer (135) of the nanostructure (NS) can be appropriately set.

FIG. 5 is a simulation diagram showing the conversion efficiency according to the thickness of a high-refractive atomic layer (135) coated on a nanostructure (NS) provided in a meta lens according to an embodiment for light of R, G, and B wavelengths.

In the entire visible light wavelength band, the thickness of the high-refractive atomic layer (135) that can exhibit high polarization conversion efficiency, for example, an efficiency of more than 60%, can be seen to be in the range of approximately 20 nm to 25 nm.

Figure 5 shows the measured results by fabricating a high refractive atomic layer (135) with a thickness of 23 nm, and it can be seen that the results are similar to the simulation results.

Figure 6 is a simulation diagram showing the electric field distribution by the nanostructures provided in the meta lens according to the embodiment.

The simulation results show two main modes excited by circularly polarized incident light in the cross-section perpendicular to the height direction of the nanostructure (NS). The quasi-TE (quasi transverse electric) mode and the quasi-TM (quasi transverse magnetic) mode are excited by the x-direction polarization component and the y-direction polarization component, respectively. The birefringence of the nanostructure (NS) can be expressed by the refractive index difference (Δn) between the two modes, and a larger Δn indicates a higher polarization conversion efficiency.

Figure 7 is a simulation diagram showing the change in refractive index according to the thickness of a high-refractive atomic layer coated on a nanostructure provided in a meta lens according to an embodiment.

Referring to Fig. 7, it can be seen that Δn increases and then saturates depending on the thickness of the high-refractive-index atomic layer (135). Similar to what was examined in the graph of Fig. 5, it can be seen that the thickness of the high-refractive-index atomic layer (135) can be set to approximately 20 nm to 25 nm.

Figure 8 is a simulation diagram showing the electric field distribution by the nanostructures provided in the meta lens according to a comparative example.

The meta-lens of the comparative example is a structure in which the nanostructure (NS) includes a UV-curable resin and does not include a high-refractive-index atomic layer like the example.

Referring to Fig. 8, the quasi-TE (quasi transverse electric) mode and the quasi-TM (quasi transverse magnetic) mode are excited by circularly polarized light, that is, by the x-direction polarization component and the y-direction polarization component. When Fig. 8 is compared with Fig. 6, which is the result according to the embodiment, it can be analyzed that the comparative example exhibits a lower Δn than the embodiment, and therefore, exhibits lower polarization conversion efficiency.

In addition, as in the embodiment, the meta-lens (100) having a structure in which the high-refractive-index atomic layer (135) is conformally formed on the surface of the nanostructure (NS) can exhibit a performance that is strong even against external impact, compared to the meta-lens of the comparative example, i.e., the case in which the high-refractive-index atomic layer is not provided. As a result of simulating the bending stiffness, the bending stiffness of the structure in which the high-refractive-index atomic layer (135) is coated on the surface of the nanostructure (NS) as in the embodiment was calculated to be 35.621 N/m, which is approximately 770 times higher than the nanostructure of the comparative example in which the bending stiffness was calculated to be 0.046 N/m.

Figure 9 is a flow chart schematically illustrating a method for manufacturing a metalens according to an embodiment.

A method for manufacturing a meta lens according to an embodiment may include a step of manufacturing a master stamp (S300), a step of forming a replica mold by duplicating the master stamp (S400), a step of forming a nanostructure layer by imprinting the replica mold into an ultraviolet-curable resin (S450), and a step of forming a high-refractive-index atomic layer on a surface of the nanostructure layer (S500). In addition, before manufacturing the master stamp, a step of preparing a reticle to be used in an exposure process during manufacturing the master stamp (S200) may be further performed.

FIGS. 10A to 10E are drawings showing exemplary processes for manufacturing a reticle used in producing a master stamp.

Referring to Fig. 10a, a photoresist layer (220) is formed on a transparent substrate (210).

Referring to Fig. 10b, an exposure area (221) is formed in a set pattern on a photoresist layer (220). This process can be performed using an electron beam lithography method.

Next, when the exposure area (221) is removed by the development process, the photoresist layer (220) is patterned as shown in Fig. 10c. The pattern formed in the photoresist layer (220) corresponds to the reverse pattern of the master stamp to be manufactured.

Referring to FIG. 10d, a metal layer (230) is formed over a patterned photoresist layer (220). The metal layer (230) may include various metals capable of blocking light. The metal layer (230) may include, for example, Al, but is not limited thereto.

A lift-off process is performed on the structure of Fig. 10d to remove the patterned photoresist layer (220). At this time, a portion of the metal layer (230) formed on the photoresist layer (220) is removed together with the photoresist layer (220).

Referring to FIG. 10e, a reticle (200) is provided in which a patterned metal layer (230) is formed on a transparent substrate (210).

Figures 11a to 11i are drawings showing exemplary processes for manufacturing a master stamp.

A master stamp can be manufactured through an exposure process using a reticle (200) prepared through the process of FIGS. 10a to 10e.

First, referring to 11a, a hard mask layer (320) may be formed on a substrate (310). The substrate (310) may be, for example, a silicon substrate. The substrate (310) may have various sizes. The substrate (310) may have a diameter of 4 inches or more, for example, 4 inches, 6 inches, 8 inches, or 12 inches, but is not limited to the exemplified sizes. The hard mask layer (320) may be, for example, an amorphous carbon layer. The material of the hard mask layer (320) is a material having a lower etching selectivity than a photoresist material to be formed over the hard mask layer (320), and is not limited to an amorphous carbon material.

Referring to FIG. 11b, a photoresist layer (330) is formed on a hard mask layer (320).

The hard mask layer (320) and the photoresist layer (330) are used as an etching mask for etching the substrate (310) into a predetermined pattern. When only the photoresist layer (330) is used as an etching mask, the photoresist layer (330) has a very high etching selectivity, making it difficult to make the depth of the pattern formed on the substrate (310) deep. In other words, the photoresist layer (330) may be etched first before the substrate (310) is etched to a desired depth, making it difficult to manufacture a master stamp capable of manufacturing a high aspect ratio structure. By further forming a hard mask layer (320) with a low etching selectivity between the substrate (310) and the photoresist layer (330), it may be advantageous to manufacture a master stamp suitable for manufacturing a high aspect ratio structure.

Referring to FIG. 11c, the photoresist layer (330) is patterned by an exposure process. The reticle (200) prepared by the process of FIGS. 10a to 10e acts as an exposure mask for light provided by an exposure device (250). The light provided by the exposure device (250) transmits only the portion of the reticle (200) where the metal layer (230) is not formed, thereby forming exposure areas (331). When the exposure areas (331) are removed by a development process, a patterned photoresist layer (330) is formed, as shown in FIG. 11d. This exposure process can be performed, for example, by utilizing an ArF Immersion Scanner.

Referring to FIG. 11e, the hard mask layer (320) can be etched using the patterned photoresist layer (330) as an etching mask.

Referring to FIG. 11F, the substrate (310) is etched using the photoresist layer (330) and the hard mask layer (320) as etching masks. As described above, when the substrate (310) is etched using only the photoresist layer (330) as an etching mask, the photoresist layer (330) having a high etching selectivity can be etched away before the substrate (310) is etched to a desired depth. As in the embodiment, when the hard mask layer (320) is further provided between the substrate (310) and the photoresist layer (330), even when the photoresist layer (330) is not completely etched away, the hard mask layer (320) having a low etching selectivity can serve as an etching mask. Therefore, it becomes possible to etch the substrate (310) to a desired depth. Next, when the photoresist layer (330) and the hard mask layer (320) are removed, a master stamp (300) having a pattern (300a) is completed, as shown in FIG. 11g.

Figures 12a and 12b are drawings explaining details of the exposure process described in Figure 11c.

The exposure device (250) described in FIG. 11c may include a light source (251), an aperture (253), one or more lenses (255, 256, 257), and may also include a driving stage (not shown) for moving the reticle (200) and the wafer (WA). The lens (255) is a collimating lens that parallels incident light, and the lenses (256, 257) are relay lenses (259) that adjust the beam width. The shape of the lens optical system is exemplary and may be changed to another shape.

Light from a light source (251) is not directed to the periphery of the lens (255) by the aperture (253), but only to the center near the optical axis, and a predetermined area on the wafer (WA) is exposed in a predetermined pattern by this light. In addition, the reticle (200) and the wafer (WA) are precisely moved simultaneously, so that the entire wafer (WA) can be exposed.

As illustrated in FIG. 12b, an area of a photoresist layer (330) formed on a substrate (310) can be scanned, stepped, and exposed, as indicated by arrows.

This method exposes the wafer (WA) using only light that does not cause lens distortion, unlike a general stepper that uses all light transmitted through the lens, so the accuracy of the edge process can be improved and it is advantageous for producing a large-area master stamp.

FIGS. 13a to 13e are drawings showing an exemplary process of forming a replica mold by replicating a master stamp and using the same to manufacture a metalens.

Referring to FIG. 13a, a replica mold (400) is formed by replicating a pattern (300a) formed on a master stamp (300). The pattern (300a) formed in a positive or negative manner on the master stamp (300) has a shape corresponding to the shape and arrangement of nanostructures forming a meta lens to be manufactured. A mold material may be pressed onto the master stamp (300) to form a replica mold (400) in which the pattern (300a) of the master stamp (300) is replicated. The replica mold (400) may include a first layer (420) and a second layer (430). The second layer (430) in direct contact with the pattern (300a) of the master stamp (300) may be made of a material having lower viscosity and higher mechanical strength than the first layer (420). For example, the first layer (420) may be made of hard polydimethylsiloxane (PDMS), and the second layer (430) may be made of hard polydimethylsiloxane (h-PDMS). However, this is exemplary, and the replica mold (400) may be formed as a single layer using a flexible material.

Referring to Fig. 13b, a UV curable resin (533) is applied on a replica mold (400). The UV curable resin (533) fills the inside of the engraved area formed in the replica mold (400) in an uncured liquid form.

Referring to FIG. 13c, after a substrate (510) is placed on a structure such as FIG. 13b, pressure may be applied and ultraviolet (UV) light may be irradiated. In this process, a UV-curable resin (533) is cured. The cured UV-curable resin (533) forms a nanostructure layer (530) having a plurality of nanostructures (NS), as illustrated in FIG. 13d. The nanostructure layer (530) may have a shape that further includes a flat layer (532). The flat layer (532) may have a very thin thickness or almost none.

Referring to FIG. 13d, the replica mold (400) is separated from the nanostructure layer (532). As described above, the ultraviolet-curable resin used as the material of the nanostructure layer (532) can be selected as a material having low surface energy and low shrinkage, and therefore, this separation process can be easily performed without causing damage to the replica mold (400) or the nanostructure (NS).

Referring to Fig. 13e, when a high-refractive atomic layer (535) is formed on the surface of a nanostructure (NS), a wafer-level meta-lens (500) is completed.

The high-refractive-index atomic layer (535) can be conformally deposited along the surface of the nanostructure (NS). Various deposition methods can be used to form the high-refractive-index atomic layer (535), and sputtering or an ALD (atomic layer deposition) method can be used. The high-refractive-index atomic layer (535) can be made of a material having a refractive index higher than the refractive index of the nanostructure (NS). The thickness of the high-refractive-index atomic layer (535) can be approximately 20 nm to 30 nm or 20 nm to 25 nm, but is not limited thereto, and can be appropriately determined in consideration of polarization conversion efficiency for incident light.

A wafer-level meta-lens (500) may include a very large number of meta-lenses proportional to the diameter of the substrate (510). The substrate (510) may have a diameter of, for example, approximately 30 cm.

The above-described manufacturing method is advantageous for mass production of meta-lenses because it can be used repeatedly and utilizes a large-area replica mold (400). For example, the yield of implementing detailed shapes of nanostructures provided in a meta-lens is low using a general photolithography process, and furthermore, manufacturing a meta-lens using electron beam lithography takes a long time to manufacture even one meta-lens and is also expensive, which is very disadvantageous for mass production.

The manufacturing method according to the embodiment includes a process of making a reticle (200) using electron beam lithography, manufacturing a large-area master stamp (300) through a scan and step exposure process using the reticle (200), and then replicating the pattern formed on the master stamp (300) onto a replica mold (400). At this time, the replica mold (400) can be reused multiple times, and if the replica mold (400) becomes difficult to reuse, the replica mold (400) can be manufactured again using the master stamp (300).

FIG. 14 shows a microscope photograph of a wafer having meta-lenses formed thereon, manufactured according to a method for manufacturing a meta-lens according to an embodiment.

As shown in the microscopic image, it is confirmed that structures with a critical dimension (CD) of approximately 40 nm are well-produced.

According to this manufacturing method, it was experimentally confirmed that 68 meta-lenses can be mass-produced on a 4-inch wafer, 153 on a 6-inch wafer, 272 on an 8-inch wafer, and 669 on a 12-inch wafer. In addition, as a result of a defect test on the 68 meta-lenses formed on a 4-inch wafer, it was confirmed that no defects were detected in 65 of them, i.e., a yield of approximately 95% was achieved.

FIG. 15 shows enlarged microscopic photographs of a portion of a meta-lens manufactured according to a method for manufacturing a meta-lens according to an embodiment.

In the illustrated SEM images, images labeled a and d show structures obtained using replica molds that were used 5 times, images labeled b and e, and images labeled c and f show structures obtained using replica molds that were used 10 and 20 times, respectively.

These experimental results demonstrate that a high-efficiency metalens can be mass-produced at a high yield using the manufacturing method of the present embodiment. This result is a result that has not been reported in existing metalens structures or existing metalens manufacturing methods.

For example, it has been reported that the existing method of manufacturing a metalens using an imprint process exhibits an optical efficiency of less than 50% except for a specific wavelength, which is the designed target wavelength, due to limitations in the materials that can be used in the large-area process.

In order to improve the performance of a metalens in the visible wavelength band, a method of manufacturing a metalens by mixing nanoparticles with a high refractive index into a resin has been attempted, but the yield of the metalens manufactured in this way is only about 50%. This can be seen as a limitation in selecting a resin material suitable for mixing nanoparticles.

Since the manufacturing method of the embodiment does not involve a process of mixing nanoparticles into the resin, the degree of freedom in the resin that can be used is increased, and for example, a resin with low surface energy and low shirinkage characteristics that allows a post-process to be performed without a separate surface treatment can be used.

Figures 16a to 17c are drawings showing the performance of a metalens according to an embodiment.

Figures 16a, 16b, and 16c are light intensity distributions showing focusing performance for light having wavelengths of 450 nm, 522 nm, and 635 nm, respectively.

Figures 17a, 17b, and 17c are graphs expressing the focusing performance for light with wavelengths of 450 nm, 522 nm, and 635 nm, respectively, in terms of Strehl ratio (SR).

It can be seen that the metalens manufactured according to the manufacturing method of the embodiment exhibits good focusing performance for light in the entire visible light wavelength band.

Fig. 18 is a graph showing the MTF (modulation transfer function) by a metalens according to an embodiment.

It can be seen that the measured MTF is very close to the MTF of the ideal case (ideal metalens).

Figure 19 is a drawing showing the resolution performance by a metalens according to an embodiment.

The resolution test of the meta-lens used the 1951 USAF negative resolution target, and it was confirmed that sizes less than 3㎛ could be resolved.

Fig. 20 shows a schematic structure of an electronic device according to an embodiment.

An electronic device (1000) includes a display element (600) and a metalens (100). The electronic device (100) may further include a processor (640) that controls the display element (600).

The display element (600) provides image light and may include various known display elements, for example, an LCoS (liquid crystal on silicon) element, an LCD (liquid crystal display) element, an OLED (organic light emitting diode) display element, a DMD (digital micromirror device), and further, may include next-generation display elements such as a Micro LED and a QD (quantum dot) LED.

The image light provided from the display device (600) may be a two-dimensional image or a three-dimensional image. The three-dimensional image may be, for example, a stereo image, a hologram image, a light field image, or an IP (integral photography) image, and may also include an image in a multi-view or super multi-view manner.

The meta-lens (100) can focus image light provided from the display element (600) on the user's field of vision. The user can perceive the image provided from the display element (600) as an enlarged image (600a) floated on a virtual image plane (VP) at a predetermined location. The location of the virtual plane (VP) or the magnification of the image is determined by the focal length of the meta-lens (100), the distance (d _e ) between the user's eye and the meta-lens (100), the distance between the meta-lens (100) and the display element (600), etc. The field of view (FOV) can be determined by the distance (d _e ) between the user's eye and the meta-lens (100) and the effective diameter ( _al ) of the meta-lens (100).

The electronic device (100) can be utilized as a virtual reality device and can be implemented in an eye-wearable form.

Figure 21 is a photograph showing experimentally that a meta-lens according to an embodiment can be applied to a virtual reality device.

The photographs shown in Fig. 21 were taken with a mobile phone after focusing the screen displayed on the micro display through a meta lens.

Fig. 22 shows a schematic structure of an electronic device according to another embodiment.

The electronic device (2000) includes a display element (600) that provides image light (IL) and a metalens (100) that focuses the image light (IL) on a user's field of view. The electronic device (2000) may further include a beam splitter (700) arranged in a path through which the image light (IL) faces the user's field of view and a processor (650) that controls the display element (600).

The beam splitter (700) can change the path of the image light (IL) toward the user's field of view. The beam splitter (700) can also transmit the ambient light (EL) from the user's surrounding environment (ENV) toward the user's field of view. The beam splitter (700) can be a half mirror or a polarizing beam splitter. Depending on the type of the beam splitter (700), additional optical elements may be provided in the path of the image light (IL) or the path of the ambient light (EL).

The processor (650) can control the display element (600) to output additional images suitable for the environment viewed by the user, for example.

The user perceives the image light (IL) provided from the display element (600) as an enlarged image projected on a virtual plane (VP) located at a predetermined distance in front of the user, and can also perceive the ambient light (IL).

These electronic devices (2000) can be utilized as augmented reality devices.

Fig. 23 shows a schematic structure of an electronic device according to another embodiment.

An electronic device (3000) includes a lens assembly (800) including a meta lens (100), an image sensor (900) that converts an optical image of an object (OBJ) formed by the lens assembly (800) into an electrical signal, and a processor (image signal processor, ISP) (900) that processes a signal from the image sensor (900).

The lens assembly (800) may further include an additional lens unit (850) in addition to the meta lens (100). The lens unit (850) may include one or more lenses, and one or more of the lenses may be general refractive lenses or meta lenses.

The position of the meta lens (100) is not limited to the illustrated position, and may be changed to any appropriate position within the lens assembly (800) or any appropriate position within the lens unit (850).

Although the above-described meta-lens, the method for manufacturing the meta-lens, and the electronic device including the meta-lens have been described with reference to the embodiments illustrated in the drawings, these are merely exemplary, and those skilled in the art will understand that various modifications and equivalent other embodiments are possible from this. Therefore, the disclosed embodiments should be considered in an illustrative rather than a restrictive sense. The scope of the present disclosure is indicated by the claims rather than the foregoing description, and all differences within a scope equivalent thereto should be construed as being included.

100, 500: Meta Lens
135: High-index atomic layer
110, 510: Substrate
NS: Nanostructures
200: Reticle
300: Master Stamp
400: Replica Mold
1000, 2000, 3000: Electronic Devices

Claims (18)

substrate;
A plurality of nanostructures provided on the substrate; and
A metalens comprising a high-refractive atomic layer formed along the surface of the plurality of nanostructures and including a material having a higher refractive index than the plurality of nanostructures. In the first paragraph,
A metalens, wherein the high refractive atomic layer comprises TiO ₂ . In the first paragraph,
A meta-lens, wherein the thickness of the high-refractive-index atomic layer is 20 nm or more and 30 nm or less. In the first paragraph,
The thickness of the above high refractive atomic layer is
A meta-lens, wherein the polarization conversion efficiency of green light by the nanostructure coated with the high refractive atomic layer is determined to be 70% or more. In the first paragraph,
A metalens, wherein the high-refractive atomic layer comprises ZrO ₂ . In the first paragraph,
The above plurality of nanostructures are metalens comprising an ultraviolet-curable resin. In the first paragraph,
A metalens further comprising a flat layer formed between the substrate and the plurality of nanostructures and including the same material as the plurality of nanostructures. A lens assembly comprising a metalens according to any one of claims 1 to 7;
An image sensor that converts an optical image of a subject formed by the lens assembly into an electrical signal; and
An electronic device, comprising a processor for processing a signal from the image sensor. A display element that provides video light;
A metalens according to any one of claims 1 to 7, which focuses light provided from the display element into the user's field of view; and
An electronic device comprising a processor controlling the display element. In Article 9,
further comprising a beam splitter arranged in a path through which the above image light is directed toward the user's field of view;
An electronic device in which the processor controls the display element to output additional images suitable for the environment viewed by the user. In the manufacturing method of a metalens,
A step of manufacturing a master stamp having a first pattern formed identical to a plurality of nanostructure arrays to be provided on the above meta lens;
A step of manufacturing a replica mold by duplicating the above master stamp;
A step of forming a nanostructure layer including a plurality of nanostructures by imprinting a replica mold on a first material; and
A method for manufacturing a metalens, comprising: a step of conformally forming a high refractive atomic layer on the surface of the plurality of nanostructures. In Article 11,
A method for manufacturing a metalens, further comprising: a step of preparing a reticle to be used in manufacturing the master stamp. In Article 11,
The steps for manufacturing the above master stamp are:
A step of forming a hard mask layer on a substrate;
A step of forming a photoresist layer on the hard mask layer;
A step of patterning the photoresist layer to have the first pattern;
A step of etching the hard mask layer using the photoresist layer patterned with the first pattern as an etching mask;
A method for manufacturing a metalens, comprising: a step of etching the substrate using the patterned photoresist layer and the etched hard mask layer as an etching mask. In Article 13,
In the above patterning step
A method for manufacturing a metalens using a scanning and step exposure process that uses only a portion of light incident near the optical axis of the lens optical system. In Article 13,
A method for manufacturing a metalens, wherein the substrate is a silicon substrate having a diameter of 4 inches or more. In Article 13,
A method for manufacturing a metalens, wherein the hard mask layer includes an amorphous carbon layer. In Article 11,
A method for manufacturing a metalens, wherein the high refractive atomic layer comprises TiO ₂ . In Article 11,
A method for manufacturing a metalens, wherein the thickness of the high refractive atomic layer is 20 nm or more and 30 nm or less.

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