Optical element, manufacturing method, and electronic device

Abstract

The present disclosure relates to an optical element, a manufacturing method, and an electronic device that make it possible to manufacture a metasurface in a more suitable manner. The metasurface includes: a fine structure having fine projections arranged in a prescribed pattern; a support substrate for supporting the fine structure; and an adhesive film for bonding the fine structure to the support substrate. The fine structure is laminated onto the support substrate via the adhesive film. This technology can be applied, for example, to a metasurface that is an optical element that makes it possible to control the optical characteristics of a substance.

Description

Optical element, manufacturing method, and electronic device

[0001] The present disclosure relates to an optical element, a manufacturing method thereof, and an electronic device, and more particularly to an optical element, a manufacturing method thereof, and an electronic device that can be manufactured more efficiently.

[0002] In recent years, there has been progress in the development of metasurfaces, which are optical elements that enable the control of the optical properties of materials by arranging microstructures, for example, microstructures with sizes smaller than the wavelength of light, periodically on a plane. Conventionally, metasurfaces have been fabricated using a manufacturing process to form microstructures using resin materials with high refractive indexes that can be fabricated using photolithography, etching, or imprinting processes.

[0003] For example, Patent Literature 1 discloses a method for manufacturing a microstructure, which generates a microstructure by subjecting a multilayer structure having at least two or more metal layers and inorganic oxide layers formed on a substrate made of an inorganic material or a polymer material to a reactive ion etching process. Patent Literature 2 also discloses a method for manufacturing a metasurface, which involves performing atomic layer deposition to deposit a conformal thin film and removing the upper part of the conformal thin film to expose the upper surface of a metasurface unit within an opening in a pattern layer.

[0004] International Publication No. 2004 / 103893 Special Publication No. 2018-536204

[0005] Conventionally, resin materials with a refractive index of approximately 1.6 to 1.7 have been used to form microstructures. However, resin materials with such a refractive index have a significantly lower refractive index than common high-refractive-index materials. Therefore, when using such resin materials, it is necessary to form microstructures with a large aspect ratio. While the refractive index can be increased by incorporating inorganic nanoparticles into the resin, this method presents concerns about poor application and shape stability. Alternatively, the refractive index can be increased by coating the resin with a high-refractive-index ceramic material. However, this method requires conformal deposition, which complicates the manufacturing process. Furthermore, it is difficult to obtain a sufficiently high refractive index because low-refractive-index resin remains inside the resin.

[0006] On the other hand, metasurfaces that do not use resin materials generally use oxides such as titanium oxide, hafnium oxide, and niobium pentoxide as high-refractive-index materials. However, these oxides are difficult to etch, making it difficult to achieve a high aspect ratio. There are also concerns about pattern collapse due to side etching and other factors. Furthermore, because the patterns are small (less than a few hundred nanometers), a lithography process using electron beam writing is required, which raises concerns about the extremely long writing time required for this writing process.

[0007] Therefore, there was a need for a manufacturing method that could produce metasurfaces with high aspect ratios and high refractive indexes using a simpler manufacturing process.

[0008] The present disclosure has been made in light of this situation and aims to enable better manufacturing of metasurfaces.

[0009] An optical element according to one aspect of the present disclosure comprises a microstructure having minute protrusions arranged in a predetermined pattern, a support substrate that supports the microstructure, and an adhesive film that bonds the microstructure and the support substrate, with the microstructure laminated on the support substrate via the adhesive film.

[0010] A manufacturing method according to one aspect of the present disclosure includes the steps of forming a microstructure having minute protrusions arranged in a predetermined pattern, forming an adhesive film on a support substrate that supports the microstructure, and bonding the microstructure to the support substrate via the adhesive film.

[0011] An electronic device according to one aspect of the present disclosure comprises an optical element having a microstructure having minute protrusions arranged in a predetermined pattern, a support substrate that supports the microstructure, and an adhesive film that bonds the microstructure and the support substrate, in which the microstructure is laminated on the support substrate via the adhesive film.

[0012] In one aspect of the present disclosure, a microstructure having minute protrusions arranged in a predetermined pattern and a support substrate supporting the microstructure are bonded together by an adhesive film, and the microstructure is laminated on the support substrate via the adhesive film.

[0013] Fig. 1 is a diagram showing a configuration example of an embodiment of a metasurface to which the present technology is applied; Fig. 2 is a diagram explaining a manufacturing process of the metasurface; Fig. 3 is a diagram explaining a manufacturing process of the metasurface; Fig. 4 is a diagram showing a modified example of the metasurface; Fig. 5 is a diagram showing a modified example of the microstructure; Fig. 6 is a diagram showing an application example of the metasurface to a display device; Fig. 7 is a diagram showing an application example of the metasurface to an imaging device; Fig. 8 is a diagram showing a use example using an image sensor.

[0014] Hereinafter, specific embodiments to which the present technology is applied will be described in detail with reference to the drawings.

[0015] <Configuration Example of Metasurface> FIG. 1 is a diagram showing a cross-sectional configuration example of one embodiment of a metasurface, which is an optical element to which the present technology is applied.

[0016] As shown in FIG. 1, the metasurface 11 is constructed by stacking a microstructure 14 on a support substrate 12 via an adhesive film 13 .

[0017] The support substrate 12 is a substrate for supporting the microstructure 14 via the adhesive film 13, and can be made of either an inorganic material or an organic material.

[0018] The adhesive film 13 is an adhesion layer (adhesion layer) made of an inorganic material and provided between the support substrate 12 and the microstructure 14 to bond the support substrate 12 and the microstructure 14. For example, the adhesive film 13 can be made of silicon dioxide or titanium oxide, and has a thickness of 10 nm or less, and more preferably 5 nm or less.

[0019] The microstructure 14 is configured by nano-level minute protrusions (structures) of any shape made of a high refractive index material and arranged in a predetermined pattern. For example, the microstructure 14 is configured by a base 21 having a flat bonding surface with the support substrate 12, and a micropattern 22 having a plurality of protrusions on the sub-micron level (e.g., with a height of 2 μm or less). By forming the plurality of protrusions of the microstructure 14 to have a certain periodic structure, it is possible to control the desired optical properties.

[0020] The metasurface 11 configured in this manner can prevent the micropattern 22 of the microstructure 14 from collapsing, thereby improving quality, by stacking the microstructure 14 on the support substrate 12 via the adhesive film 13. Furthermore, in the metasurface 11, by thinning the adhesive film 13, the effects of light scattering and absorption can be suppressed, resulting in excellent optical properties.

[0021] <Metasurface Manufacturing Process> The manufacturing process for manufacturing the metasurface 11 will be described with reference to FIGS. 2 and 3 .

[0022] 2, a master 31 having a shape that is an inverse of the micropattern 22 of the microstructure 14 is fabricated using lithography and etching techniques. The master 31 is made of a material such as silicon, quartz, or resin, and has a plurality of recesses 32 formed therein that are recessed in accordance with the plurality of protrusions of the micropattern 22.

[0023] In the second step, as shown in the second row of Fig. 2, a stamper 33 is produced using the original plate 31. A plurality of protrusions 34 are formed on the stamper 33, which are inverse patterns to the plurality of recesses 32 on the original plate 31. For example, when a metal material such as nickel, copper, or chromium is used, the stamper 33 is produced by electroless or electrolytic plating on the original plate 31 using an electroforming process. When a resin material such as acrylic or polyimide is used, the stamper 33 is produced by pressing the original plate 31 against the resin material using an imprinting technique.

[0024] 2, in the third step, a resin layer 35 is formed by injection molding a soluble polymer onto the stamper 33. A plurality of recesses 36 are formed in the resin layer 35, which are inverse patterns to the plurality of protrusions 34 of the stamper 33. For example, the resin layer 35 may be made of a resin material such as polycarbonate, PVA (polyvinyl alcohol), or acrylic.

[0025] In the fourth step, as shown in the fourth row of FIG. 2 , a high-refractive index material is filled into multiple recesses 36 in the resin layer 35 to form the micropattern 22, and a base 21 is formed by layering it on the surface of the resin layer 35. For example, the micropattern 22 and base 21 can be formed by applying or depositing a material with a refractive index that matches the design of the metasurface 11. For example, the base 21 and micropattern 22 can be formed using inorganic materials such as titanium oxide, hafnium oxide, silicon nitride, and niobium pentoxide by techniques such as sputtering, chemical vapor deposition (CVD), pulsed laser deposition (PLD), atomic layer deposition (ALD), and liquid phase deposition (LPD). The base 21 and micropattern 22 are preferably made of inorganic materials, but may also contain polymers. For example, the inorganic material content of the base 21 and micropattern 22 may be 95% or more, more preferably 99% or more.

[0026] 3, the bonding surface of the base 21 is subjected to a planarization process by chemical mechanical polishing (CMP), thereby forming the microstructure 14. Note that if the planarization of the bonding surface of the base 21 is ensured when the high refractive index material is embedded in the fourth step, the fifth step may be omitted.

[0027] 3, an adhesive film 13 is formed on the surface of the support substrate 12. For example, the adhesive film 13 can be formed by sputtering, ALD, PLD, CVD, or other techniques using inorganic materials such as silicon dioxide, titanium oxide, titanium, or gold.

[0028] In the seventh step, as shown in the third row of FIG. 3, the bonding surface of the base 21 of the microstructure 14 is bonded to the adhesive film 13 by atomic diffusion bonding, thereby bonding the microstructure 14 to the support substrate 12.

[0029] In the eighth step, as shown in the fourth row of Fig. 3, the resin layer 35 is dissolved and removed using, for example, water or an organic solvent such as methyl ethyl ketone, thereby producing the metasurface 11. Depending on the application of the metasurface 11, the resin layer 35 may remain in place without performing the eighth step.

[0030] By using the manufacturing process described above, it is possible to more effectively manufacture a metasurface 11 having a structure in which a microstructure 14 is stacked on a support substrate 12 via an adhesive film 13.

[0031] For example, in this manufacturing process, either a glass substrate or a resin substrate can be used as the support substrate 12. Furthermore, in this manufacturing process, the master 31 only needs to be produced once, the material can be selected, and difficult processing methods such as dry etching can be omitted.

[0032] Furthermore, by providing the adhesive film 13 between the support substrate 12 and the microstructure 14, it is possible to improve the resistance of the multiple protrusions of the micropattern 22 to collapse, and as a result, it is possible to stably form the shape of the protrusions. Furthermore, by providing the adhesive film 13 between the support substrate 12 and the microstructure 14, atomic diffusion bonding becomes possible, and as a result, the adhesion between the support substrate 12 and the microstructure 14 can be improved.

[0033] In conventional manufacturing processes, after the imprinting process of a curable material containing inorganic nanoparticles, annealing for increasing the refractive index can cause problems such as deformation, insufficient structural height, and melting of the resin substrate. In contrast, in a manufacturing process using the present technology, a microstructure 14 is formed by embedding a high-purity, high-refractive-index inorganic material into a pattern of recesses 36 formed in a resin layer 35 made of a soluble polymer, and the microstructure 14 is then bonded to a support substrate 12 via an adhesive film 13. This process then involves dissolving the resin layer 35, thereby producing a microstructure 14 that ensures a high refractive index and making it difficult for the shape of the microstructure 14 to change.

[0034] Furthermore, the manufacturing process using this technology allows for the use of a wide range of materials, even those that are difficult or impossible to process, expanding the range of materials to match the refractive index. Furthermore, if the deposition area can be limited, it is possible to create microstructures 14 with different patterns in each deposition area, easily manufacturing metasurfaces 11 that function as lenses or other devices with their own optical properties. Furthermore, high performance metasurfaces 11 can be achieved through a simple manufacturing process that does not require special gases or complex processing.

[0035] <Modified Examples of Metasurface> Modified examples of the metasurface 11 will be described with reference to Fig. 4. Note that in the metasurfaces 11A and 11B shown in Fig. 4, components common to the metasurface 11 in Fig. 1 are denoted by the same reference numerals, and detailed descriptions thereof will be omitted.

[0036] 4A shows a cross-sectional configuration example of a metasurface 11A as a first modified example. As shown in the figure, the metasurface 11A is configured by stacking a microstructure 14A on a support substrate 12 via an adhesive film 13.

[0037] The microstructure 14A does not have the base 21 that the microstructure 14 in Figure 1 has, and is composed only of a plurality of fine protrusions, and each protrusion is bonded to the support substrate 12 via an adhesive film 13.

[0038] FIG. 4B shows an example of the cross-sectional configuration of a metasurface 11B, which is a second modified example.

[0039] As shown in FIG. 4B, the metasurface 11B is constructed by stacking a microstructure 14B on a support substrate 12 via an adhesive film 13.

[0040] The microstructure 14B is configured by forming the protrusions of the micropattern 22B using two types of inorganic materials 41 a and 41 b. In the illustrated example, the tip side of the micropattern 22B is formed using the inorganic material 41 b, and the base side of the micropattern 22B and the base 21 are formed using the inorganic material 41 a.

[0041] <Modifications of Microstructure> Modifications of the microstructure 14 will be described with reference to Fig. 5. In the microstructures 14C to 14E shown in Fig. 5, the same components as those of the microstructure 14 in Fig. 1 are denoted by the same reference numerals, and detailed description thereof will be omitted.

[0042] FIG. 5A shows a cross-sectional configuration example of a microstructure 14C as a first modified example.

[0043] 5A, the microstructure 14C has a micropattern 22C formed of three different inorganic materials 41a to 41c, and the heights of the protrusions of the micropattern 22C are approximately the same. In the illustrated example, the microstructure 14C is configured such that the tip side of the micropattern 22C is formed of the inorganic material 41c, the middle part of the micropattern 22C is formed of the inorganic material 41b, and the base side of the micropattern 22C and the base 21 are formed of the inorganic material 41a.

[0044] FIG. 5B shows a cross-sectional configuration example of a microstructure 14D as a second modified example.

[0045] 5B, the microstructure 14D is configured such that the micropattern 22D is formed of three different inorganic materials 41a to 41c, and the protrusions of the micropattern 22D have two different heights. In the illustrated example, the microstructure 14D is configured such that the tip side of the micropattern 22D is formed of the inorganic material 41c, the middle part of the micropattern 22D is formed of the inorganic material 41b, and the base side of the micropattern 22D and the base 21 are formed of the inorganic material 41a. Furthermore, in the microstructure 14D, the micropattern 22D is formed in a pattern in which two protrusions of a first length and one protrusion of a second length (<the first length) are arranged in order.

[0046] FIG. 5C shows a cross-sectional configuration example of a microstructure 14E as a third modified example.

[0047] As shown in FIG. 5C , the microstructure 14E has a micropattern 22E formed of three different inorganic materials 41a to 41c, and the protrusions of the micropattern 22E are configured to have three different heights. In the illustrated example, for the protrusions of the first height and the protrusions of the second height (<first length), the tip side of the micropattern 22E is formed of the inorganic material 41c, the middle part of the micropattern 22E is formed of the inorganic material 41b, and the base side of the micropattern 22E is formed of the inorganic material 41a. For the protrusions of the third height (<second length), the tip side of the micropattern 22E is formed of the inorganic material 41c, and the base side of the micropattern 22E is formed of the inorganic material 41b. Furthermore, in the microstructure 14E, the micropattern 22E is formed in a pattern in which protrusions of the first length, protrusions of the second length, and protrusions of the third length are arranged in order.

[0048] <Application Examples of Metasurface> Application examples of the metasurface 11 will be described with reference to Figures 6 and 7 .

[0049] Figure 6 shows an example of applying the metasurface 11 to a display device.

[0050] The display device 51 shown in FIG. 6 is incorporated into a wearable device for providing users with, for example, virtual reality (VR) or augmented reality (AR). The display device 51 includes an image forming unit 52 having a light source, a projection lens 53 as an optical system, a light guide plate 54 for bending light in a certain direction, and two metasurfaces 11-1 and 11-2. For example, the metasurfaces 11-1 and 11-2 are provided with protrusions of microstructures 14-1 and 14-2 so as to have optical properties that result in a transmission type diffraction grating, and are disposed near both ends of one side of the light guide plate 54.

[0051] In the illustrated configuration example, a light guide plate 54 is used as the support substrate 12, and a microstructure 14-1 is bonded to one end thereof and a microstructure 14-2 is bonded to the other end thereof via an adhesive film 13 that is continuously provided over the entire surface of one side of the light guide plate 54. With this configuration, it is possible to employ a process in which the microstructures 14-1 and 14-2 are fabricated together and simultaneously bonded to the support substrate 12 via the adhesive film 13, thereby avoiding the occurrence of misalignment that may be a concern when, for example, a process in which they are bonded individually is employed.

[0052] In the display device 51, the light of the image created in the image forming unit 52 is collected by the projection lens 53, bent at an angle toward the light guide angle direction through the metasurface 11-1, and enters the light guide plate 54, and is bent at an angle toward the user's eyeball through the metasurface 11-2 and exits the light guide plate 54. In this way, the light of the image enters the user's eyeball, allowing the user to see the image.

[0053] The display device 51 configured in this manner can be made even smaller by using the metasurfaces 11-1 and 11-2.

[0054] Figure 7 shows an example of applying the metasurface 11 to an imaging device.

[0055] As shown in Figure 7, the imaging device 61 is composed of a group of bulk lenses 62 that focus light on a convex or concave curved surface, an image sensor 63 that captures an image, and a metasurface 11.

[0056] The metasurface 11 is disposed between the bulk lens group 62 and the image sensor 63 with the microstructure 14 facing the image sensor 63. The protrusions of the microstructure 14 are formed so that the metasurface 11, together with the bulk lens group 62, has optical properties that allow it to function as a lens that focuses light from a subject on the imaging surface of the image sensor 63.

[0057] In the imaging device 61, the subject imaged by the bulk lens group 62 and the metasurface 11 can be captured by the image sensor 63.

[0058] The imaging device 61 configured in this manner can be made significantly thinner by using a metasurface 11 in which protrusions on the microstructure 14 are formed so that the refractive index is higher than that of lenses using convex and concave curved surfaces, for example.

[0059] <Example of use of imaging device> Figure 8 is a diagram showing an example of use of an imaging device to which the metasurface 11 described above is applied.

[0060] The imaging device can be used in various cases to sense light such as visible light, infrared light, ultraviolet light, and X-rays, for example, as follows.

[0061] ・Devices for taking images for viewing purposes, such as digital cameras and mobile devices with camera functions. ・Devices for traffic purposes, such as in-vehicle sensors that take images of the front, rear, surroundings, and interior of a car for safe driving such as automatic stopping, and for recognizing the driver's state, surveillance cameras that monitor moving vehicles and roads, and distance measuring sensors that measure distances between vehicles. ・Devices for home appliances such as TVs, refrigerators, and air conditioners that take images of user gestures and operate the device according to those gestures. ・Devices for medical and healthcare purposes, such as endoscopes and devices that take images of blood vessels by receiving infrared light. ・Devices for security purposes, such as surveillance cameras for crime prevention and cameras for person authentication. ・Devices for beauty purposes, such as skin measuring devices that take images of the skin and microscopes that take images of the scalp. ・Devices for sports purposes, such as action cameras and wearable cameras for sports, etc. ・Devices for agricultural purposes, such as cameras to monitor the condition of fields and crops.

[0062] <Examples of Combinations of Configurations> The present technology can also be configured as follows. (1) An optical element comprising: a microstructure having minute protrusions arranged in a predetermined pattern; a support substrate supporting the microstructure; and an adhesive film bonding the microstructure and the support substrate, wherein the microstructure is laminated on the support substrate via the adhesive film. (2) The optical element according to (1) above, wherein the support substrate is a resin substrate, and the adhesive film is made of an inorganic material. (3) The optical element according to (2) above, wherein the microstructure is composed of the protrusions made of at least two or more types of inorganic material. (4) The optical element according to (3) above, wherein the plurality of protrusions of the microstructure are composed of at least two or more different heights. (5) The optical element according to any one of (1) to (4) above, wherein the height of the protrusions is 2 μm or less. (6) The optical element according to any one of (1) to (5) above, wherein the inorganic material content of the microstructure is 95% or more. (7) The optical element according to any one of (2) to (6), wherein the adhesive film is formed of silicon dioxide or titanium oxide. (8) The optical element according to (7), wherein the adhesive film has a film thickness of 10 nm or less. (9) The optical element according to any one of (1) to (8), wherein the microstructure is configured such that the protrusions are arranged in a certain periodic structure. (10) A method for manufacturing an optical element, comprising: forming a microstructure having fine protrusions arranged in a predetermined pattern; depositing an adhesive film on a support substrate that supports the microstructure; and bonding the microstructure to the support substrate via the adhesive film. (11) An electronic device comprising an optical element, comprising: a microstructure having fine protrusions arranged in a predetermined pattern; a support substrate that supports the microstructure; and an adhesive film that bonds the microstructure and the support substrate, wherein the microstructure is stacked on the support substrate via the adhesive film.

[0063] It should be noted that the present embodiment is not limited to the above-described embodiment, and various modifications are possible within the scope of the gist of the present disclosure. Furthermore, the effects described in this specification are merely examples and are not intended to be limiting, and other effects may also be obtained.

[0064] REFERENCE SIGNS LIST 11 metasurface, 12 support substrate, 13 adhesive film, 14 microstructure, 21 base, 22 micropattern, 31 master, 32 recess, 33 stamper, 34 protrusion, 35 resin layer, 36 recess, 41 inorganic material, 51 display device, 52 image forming unit, 53 projection lens, 54 light guide plate, 61 imaging device, 62 bulk lens group, 63 image sensor

Claims

1. An optical element comprising: a microstructure having minute protrusions arranged in a predetermined pattern; a support substrate supporting the microstructure; and an adhesive film bonding the microstructure and the support substrate, wherein the microstructure is laminated on the support substrate via the adhesive film.

2. The optical element according to claim 1, wherein the supporting substrate is a resin substrate, and the adhesive film is made of an inorganic material.

3. The optical element according to claim 2, wherein the microstructure is composed of protrusions made of at least two types of inorganic materials.

4. The optical element according to claim 3, wherein the plurality of protrusions of the microstructure are configured with at least two or more different heights.

5. The optical element according to claim 1, wherein the height of the protrusion is 2 μm or less.

6. The optical element according to claim 1, wherein the content of inorganic material in the microstructure is 95% or more.

7. The optical element according to claim 2, wherein the adhesive film is formed of silicon dioxide or titanium oxide.

8. The optical element according to claim 7, wherein the adhesive film has a thickness of 10 nm or less.

9. The optical element according to claim 1, wherein the microstructure is configured by arranging the protrusions in a constant periodic structure.

10. A method for manufacturing an optical element, comprising the steps of: forming a microstructure having minute protrusions arranged in a predetermined pattern; depositing an adhesive film on a supporting substrate that supports the microstructure; and bonding the microstructure to the supporting substrate via the adhesive film.

11. An electronic device comprising an optical element comprising: a microstructure having minute protrusions arranged in a predetermined pattern; a support substrate supporting the microstructure; and an adhesive film bonding the microstructure and the support substrate, wherein the microstructure is laminated on the support substrate via the adhesive film.