Metalens, method for manufacturing metalens, and light-emitting device

Abstract

The objective is to provide a metal lens having a pattern of a desired height, a method for manufacturing a metal lens, and a light-emitting device. [Solution] A method for manufacturing a metalens, comprising: preparing a laminate on a substrate in which a metalens material having a thickness of 2 μm or more and a refractive index of 1.5 or less, a first mask which is a mask for the metalens material, a second mask which is a mask for the first mask, and a third mask having a first pattern with intervals of a predetermined wavelength or less are sequentially laminated; etching the second mask through the third mask to form a second pattern; etching the first mask through the second mask to form a third pattern; and etching the metalens material through the first mask.

Description

[Technical Field]

[0001] This disclosure relates to a metalens, a method for manufacturing the same, and a light-emitting device. [Background technology]

[0002] In recent years, there has been a surge in the application of microfabrication techniques to materials with dimensions smaller than the wavelength, resulting in the development of various properties. In particular, metalenses, formed by arranging patterns processed to sizes smaller than the wavelength, can reproduce the properties of optical elements such as convex and concave lenses without forming a lens shape.

[0003] Materials for forming a metalens are disclosed, for example, in Patent Document 1. In Patent Document 1, fine Si pillars or TiO2 pillars are sometimes used. These materials have relatively high refractive indices, and predetermined optical properties can be obtained even if the pillar height is relatively low. An example in which the pillar height is 1000 nm or less is disclosed.

[0004] An example of narrow-pitch patterning is disclosed, for example, in Patent Document 2. In Patent Document 2, a CrN (chromium nitride) layer is formed on a synthetic quartz substrate, and WO is applied on the CrN layer. x (Tungsten oxide) layer is formed, WO x An example is disclosed in which a resist is formed on a layer, and these are etched to form an imprint mold (photomask blank) on a quartz substrate with a pattern. [Prior art documents] [Patent Documents]

[0005] [Patent Document 1] Special Publication No. 2020-537193 [Patent Document 2] Japanese Patent Publication No. 2011-211083 [Overview of the Initiative] [Problems that the invention aims to solve]

[0006] When forming a metalens on a material with a relatively low refractive index, the desired optical properties can be obtained by forming a deep pattern on the material that will become the metalens. However, in conventional examples, it is difficult to form a metalens with a pattern of the desired height due to the relationship between the etching rate ratio of the mask and the material being processed.

[0007] One embodiment of this disclosure aims to provide a metalens having a pattern of a desired height, a method for manufacturing the same, and a light-emitting device. [Means for solving the problem]

[0008] One embodiment of the present disclosure is a method for manufacturing a metalens, comprising: preparing a laminate on a substrate in which a metalens material having a thickness of 2 μm or more and a refractive index of 1.5 or less is sequentially laminated a first mask which is a mask for the metalens material, a second mask which is a mask for the first mask, and a third mask having a first pattern with intervals of a predetermined wavelength or less; etching the second mask through the third mask to form a second pattern; etching the first mask through the second mask to form a third pattern; and etching the metalens material through the first mask.

[0009] One embodiment of the present disclosure is a metalens comprising a substrate and a metalens portion disposed on the substrate, wherein the metalens portion has a plurality of convex portions or a plurality of recesses adjacent to each other with a center distance of less than or equal to a predetermined wavelength, the plurality of convex portions or the plurality of recesses consists of a single layer of a material having a refractive index of less than 1.5 at the predetermined wavelength, and the height of the plurality of convex portions or the plurality of recesses is 2 μm or more. [Effects of the Invention]

[0010] According to one embodiment of the present disclosure, a metalens having a pattern of a desired height, a method for manufacturing the same, and a light-emitting device can be provided.

Brief Description of the Drawings

[0011] [Figure 1] It is a diagram showing the process of preparing a laminate. [Figure 2] It is a diagram showing the process of preparing a laminate. [Figure 3] It is a diagram showing the process of forming a second pattern. [Figure 4] It is a diagram showing the process of forming a third pattern. [Figure 5] It is a diagram showing the process of etching a metalens material. [Figure 6] It is a diagram showing the process of etching a metalens material. [Figure 7] It is a diagram showing another example of the process of etching a metalens material. [Figure 8] It is a top view of a metalens. [Figure 9] It is a cross-sectional view taken along the line IX - IX of FIG. 8. [Figure 10] It is a top view showing a part of the metalens portion. [Figure 11] It is a cross-sectional view taken along the line XI - XI of FIG. 10. [Figure 12] It is a top view showing a part of the metalens portion of Modification 1. [Figure 13] It is a cross-sectional view taken along the line XIII - XIII of FIG. 10. [Figure 14] It is a cross-sectional view showing the light-emitting device of Application Example 1. [Figure 15] It is a cross-sectional view showing the light-emitting device of Application Example 2. [Figure 16] It is a SEM image showing a part of the metalens of Example 1. [Figure 17] It is a SEM image showing another part of the metalens of Example 1.

Modes for Carrying Out the Invention

[0012] In this specification, the term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes, as long as their intended purpose is achieved. Furthermore, the upper and lower limits of the numerical ranges described herein can be arbitrarily selected and combined from the numerical values ​​exemplified as numerical ranges. Embodiments of the present invention will now be described in detail. However, the embodiments shown below are illustrative examples of metalens and methods for manufacturing the same to embody the technical concept of the present invention, and the present invention is not limited to the metalens and methods for manufacturing the same shown below.

[0013] <Method for manufacturing Metalens 100> A method for manufacturing a metallens according to the present disclosure will be described. The method for manufacturing a metallens 100 according to the present disclosure includes preparing a laminate on a substrate 10 in which a metallens material 20 having a thickness of 2 μm or more and a refractive index of 1.5 or less is sequentially laminated, a first mask 30 which is a mask for the metallens material 20, a second mask 40 which is a mask for the first mask 30, and a third mask 50 having a first pattern 52 with a spacing of less than or equal to a predetermined wavelength is sequentially laminated, etching the second mask 40 through the third mask 50 to form a second pattern 42, etching the first mask 30 through the second mask 40 to form a third pattern 32, and etching the metallens material 20 through the first mask 30.

[0014] By positioning the second mask 40, which is a mask for the first mask 30, between the first mask 30 and the third mask 50, the thickness of the first mask 30 can be set to any desired thickness. Therefore, the metalens material 20 can be processed to the desired height regardless of the etching rate. Each configuration is described below.

[0015] (Process for preparing the laminate) First, a laminate is prepared by stacking multiple materials. The laminate consists of a substrate 10 on which a metalens material 20 with a thickness of 2 μm or more and a refractive index of 1.5 or less, a first mask 30 which is a mask for the metalens material 20, a second mask 40 which is a mask for the first mask 30, and a third mask 50 which has a first pattern 52 with spacing less than or equal to a predetermined wavelength is stacked in order. Figure 1 is a schematic diagram showing the laminate before the first pattern 52 is formed.

[0016] (Circuit board 10) The substrate 10 is a component that supports the metalens material 20. The substrate 10 may be a light-transmitting substrate 10 or a reflective substrate 10. A light-transmitting substrate 10 is preferred if it is used in an application where light is transmitted through the substrate 10. A reflective substrate 10 is preferred if it is used in an application where light is reflected. The material of the substrate 10 may be, for example, quartz, sapphire, gallium nitride, gallium arsenide, or silicon.

[0017] (Metalens material 20) The metalens material 20 is etched at intervals of a predetermined wavelength or less by an etching process described later, forming a plurality of protrusions 22 or a plurality of recesses 24. The refractive index of the metalens material 20 is 1.5 or less, which is relatively small. Therefore, in order to enhance the function as a metalens 100, it is preferable to increase the height of the plurality of protrusions 22 or a plurality of recesses 24 so that the distance that light travels through the plurality of protrusions 22 or a plurality of recesses 24 is increased. The thickness of the metalens material 20 is 2 μm or more. This allows the height of the metalens portion 20A to be increased when the metalens material 20 is etched to form the metalens portion 20A. Alternatively, the thickness of the metalens material 20 may be 4 μm or less. This allows the aspect ratio of the metalens portion 20A to be set to a desired value when the metalens material 20 is etched to form the metalens portion 20A. The metalens material 20 may be, for example, silicon oxide.

[0018] (First mask 30) The first mask 30 is a mask for the metalens material 20. The first mask 30 is preferably made of a material that has a high etching selectivity ratio for the metalens material 20. The material of the first mask 30 is, for example, Cr (chromium), Ni (nickel), or CrO x It may be chromium oxide, preferably Cr or Ni. This allows the metalens material 20 to be easily etched. The first mask 30 may also contain Cr, and is particularly preferably metallic Cr. Metallic Cr can be CrN or CrO x Compared to other materials, this is preferable because it allows for a higher selectivity ratio for etching with the metal lens material 20. Also, metallic Cr is preferable to Ni because it is easier to remove. Even if metallic Cr and Ni form a passivation film, the passivation film formed by metallic Cr is easier to remove. When the material of the metal lens material 20 is silicon oxide, the first mask 30 is preferably made of metallic Cr alone. The thickness of the first mask 30 may be 0.2 μm or more and 0.6 μm or less, preferably 0.2 μm or more and 0.4 μm or less. This allows for easy etching of the metal lens material 20.

[0019] (2nd mask 40) The second mask 40 is a mask for the first mask 30. The second mask 40 is preferably made of a material that has a high etching selectivity ratio compared to the first mask 30. The material of the second mask 40 may be, for example, silicon oxide, titanium oxide, or aluminum oxide, and preferably silicon oxide. This allows the first mask 30 to be easily etched. In particular, when the first mask 30 is metallic Cr, silicon oxide is preferred for the second mask 40. This allows the thickness of the first mask to be increased compared to when the third mask 50 is directly formed on the first mask 30, so that the metalens material 20 can be etched to a desired depth and a metalens of a desired height can be formed.

[0020] The thickness of the second mask 40 may be between 0.05 μm and 0.2 μm. This allows for easy etching of the first mask 30. The thickness of the second mask 40 may be between 0.5 and 1 times the thickness of the first mask 30. Also, the thickness of the second mask 40 may be between 0.015 and 0.08 times the thickness of the metalens material 20.

[0021] (3rd Mask 50) The third mask 50 is a mask for the second mask 40. The third mask 50 is preferably made of a material with a higher etching selectivity than the second mask 40. The third mask 50 may be a resist. The thickness of the third mask 50 may be between 0.1 μm and 0.5 μm. Furthermore, the thickness of the third mask 50 may be between 1 and 3 times the thickness of the second mask 40.

[0022] (Step to form the first pattern 52) Figure 2 is a schematic diagram showing the step of forming a first pattern 52 on a third mask 50, which is part of the process of preparing the laminate. The first pattern 52 is formed such that the spacing is less than or equal to the length of a predetermined wavelength. The first pattern 52 is formed by patterning the third mask 50 using electron beam lithography or nanoimprint. This allows for efficient pattern formation even for dimensions less than or equal to the wavelength of light on which the metalens 100 acts. In the process of preparing the laminate, a laminate with the first pattern 52 formed on it is prepared. The spacing of the first pattern 52 may be, for example, 500 nm or less, 400 nm or less, or 300 nm or less.

[0023] (Step to form the second pattern 42) Next, a second pattern 42 is formed. Figure 3 is a schematic diagram illustrating the process of forming the second pattern 42. In this process, the second mask 40 is etched through the third mask 50 having the first pattern 52 to form the second pattern 42. The second pattern 42 is obtained by dry etching the second mask 40. Dry etching may be reactive ion etching (RIE).

[0024] The second mask 40 is made of a material resistant to the etching conditions of the first mask 30. The material of the second mask 40 is, for example, silicon oxide. When the third mask 50 is formed directly on top of the first mask 30, the thickness of the first mask 30 needs to be changed according to the etching depth of the metalens material 20 required to form the metalens 100. If the etching depth of the metalens material 20 is increased, the thickness of the first mask 30 needs to be increased, and in that case, the thickness of the third mask 50 also needs to be increased accordingly. In other words, the conditions of the third mask 50 need to be changed each time according to the etching depth of the metalens material 20. In this embodiment, since the second mask 40, which is resistant to the etching conditions of the first mask 30, is formed on top of the first mask 30, there is no need to change the thickness of the third mask 50 according to the etching depth of the metalens material 20. The manufacturing conditions are relaxed.

[0025] Furthermore, increasing the thickness of the third mask 50 may lead to the following problems. Specifically, if the thickness of the third mask 50 is large, the amount of electron beam irradiation required when patterning and developing the third mask 50 using electron beam lithography increases. At this time, the metalens material 20 becomes charged, and the hardening reaction of the third mask 50 proceeds from the bottom of the third mask 50 that is in contact with the first mask 30. If the hardening reaction of the third mask 50 progresses, it becomes difficult to see the substrate (i.e., the metalens material 20) even after development, which may induce development defects. Therefore, even if the etching depth of the metalens material 20 increases, it is desirable to form the third mask 50 with a predetermined thickness and not change the conditions for forming the first pattern 52. In this embodiment, by forming the second mask 40 on top of the first mask 30, the thickness of the third mask 50 can be maintained at a predetermined thickness.

[0026] (Step to form the third pattern 32) Next, a third pattern 32 is formed. Figure 4 is a schematic diagram showing the process of forming the third pattern 32. In this process, the first mask 30 is etched through a second mask 40 having the second pattern 42 to form the third pattern 32. The third pattern 32 is obtained by dry etching the first mask 30. Dry etching may be RIE.

[0027] The first mask 30 is made of a material resistant to the etching conditions of the metalens material 20. The material of the first mask 30 is, for example, chromium. In this embodiment, the metalens material 20 is etched to a thickness of 2 μm or more. Therefore, the first mask 30 needs to have a thickness sufficient to allow this etching. As described above, since the first mask 30 is protected by the second mask 40, the first mask 30 can form the third pattern 32 while leaving a predetermined thickness.

[0028] The step of forming the third pattern 32 includes removing the third mask 50 that remained after forming the second pattern 42. This reduces the number of steps.

[0029] (Process of etching the metalens material 20) Next, the metalens portion 20A is formed. Figure 5 is a schematic diagram showing the process of etching the metalens material 20. In this process, the metalens material 20 is etched through a first mask 30 having a third pattern 32. The metalens portion 20A is obtained by dry etching the metalens material 20. Dry etching may be RIE.

[0030] In this process, the metalens material 20 is etched to a depth of 2 μm or more. To do this, the first mask 30 must be formed to a predetermined thickness. In this embodiment, since a second mask 40 that is resistant to the etching conditions of the first mask 30 is formed, the thickness of the first mask 30 can be set to any thickness. Therefore, it becomes possible to etch the metalens material 20 to a depth of 2 μm or more.

[0031] The step of etching the metalens material 20 includes removing the second mask 40 that remains after forming the third pattern 32. This reduces the number of steps. It is preferable that the metalens material 20 and the second mask 40 are made of the same material. This allows the second mask 40, which masks the first mask 30, to be removed simultaneously when etching the metalens material 20. It is preferable that silicon oxide is used for both the metalens material 20 and the second mask 40.

[0032] Next, the first mask 30 is removed. Figure 6 is a schematic diagram illustrating the process of removing the first mask 30. By etching the first mask 30, the metalens portion 20A obtained by etching the metalens material 20 remains on the substrate 10. Through the above process, the metalens 100 can be formed.

[0033] Instead of the etching process for the metalens material 20 described in Figures 5 and 6, the metalens material 20 can also be etched using the method shown in Figure 7. That is, in the etching process for the metalens material 20, the etching may be terminated before the surface to be etched reaches the surface of the substrate 10. This shortens the etching time for the metalens material 20, thereby improving the lead time. Furthermore, since etching can be terminated at a predetermined time according to the etching rate, it becomes unnecessary to determine whether the etching has reached the substrate 10, thus simplifying the process.

[0034] <Metalens 100> Next, the metal lens 100 of this embodiment will be described. However, parts of the description of the manufacturing method of the metal lens 100 that overlap with the description of the individual components may be omitted.

[0035] The metalens 100 of this embodiment comprises a substrate 10 and a metalens portion 20A disposed on the substrate 10. The metalens portion 20A has a plurality of convex portions 22 or a plurality of recesses 24 adjacent to each other with a center distance of less than or equal to a predetermined wavelength. The plurality of convex portions 22 or a plurality of recesses 24 consists of a single layer of a material having a refractive index of less than 1.5 at a predetermined wavelength. The height of the plurality of convex portions 22 or a plurality of recesses 24 is 2 μm or more.

[0036] Even if the refractive index of the metalens portion 20A is relatively small, by making the heights of the multiple protrusions 22 or the multiple recesses 24 relatively high, the distance over which light of a predetermined wavelength acts can be increased, thereby providing a metalens 100 with desired optical properties.

[0037] Figure 8 shows a top view of the metal lens 100. The metal lens 100 has, for example, multiple convex portions 22 or multiple concave portions 24 arranged concentrically. Figure 9 shows a cross-sectional view along the line VI-VI in Figure 8. Figure 9 shows an example in which multiple convex portions 22 are provided. In the cross-sectional view shown in Figure 9, there are a very large number of convex portions 22, and the omitted parts are represented by "...".

[0038] The multiple protrusions 22 are made of a single layer of material having a refractive index of less than 1.5 at a predetermined wavelength. The predetermined wavelength is the wavelength at which the metalens 100 acts, and may be, for example, 360 nm to 700 nm, or 360 nm to 550 nm. The multiple protrusions 22 are made of, for example, silicon oxide.

[0039] The distance p between the centers of the multiple protrusions 22 is less than or equal to a predetermined wavelength. The distance p between the centers may be, for example, 500 nm or less, 400 nm or less, or 300 nm or less.

[0040] The height h of the multiple protrusions 22 is 2 μm or more. This allows the metalens 100 to act effectively on light of a predetermined wavelength even if the refractive index of the multiple protrusions 22 is relatively small. Alternatively, the height of the multiple protrusions 22 may be 4 μm or less. This allows for a sufficiently large aspect ratio of the protrusions 22.

[0041] The width d of the multiple protrusions 22 is smaller than the distance p between the centers of the multiple protrusions 22. The width d may be, for example, 5 nm to 500 nm, or 60 nm to 300 nm. If the protrusion 22 is circular when viewed from above, the width d represents the diameter, and if it is polygonal, it represents the length of the diagonal passing through the center of the polygon.

[0042] The aspect ratio (h / d) of the multiple protrusions 22 may be, for example, 1.5 or more and 10 or less, preferably 2 or more and 8 or less. This makes it possible to obtain the desired phase difference.

[0043] Next, the principle of the metalens 100 will be briefly explained using Figure 10. The metalens 100 is made of a dielectric material and has multiple columns or holes with dimensions smaller than a predetermined wavelength. When light passes through the metalens 100, the light is given a phase difference corresponding to the width and height of the columns or holes at the point of passage. If the phase distribution due to this phase difference is the same as that of a lens, the metalens 100 can be given the same properties as a lens.

[0044] Let's consider an example of reproducing a lens with the Metalens 100. For example, if we define an origin O and coordinates (x,y) on the substrate 10 in a top view, and let f be the focal length of the lens we want to reproduce, then the phase distribution can be obtained based on the phase distribution function φ(x,y) defined by the following equation (1). φ(x,y)=-(2π / λ)×{(x 2 +y 2 +f 2 ) -1 / 2 -f}···(1)

[0045] Equation (1) can also be expressed in polar coordinates as shown in equation (2). φ(r) = -(2π / λ) × {(r2 +f 2 ) -1 / 2 -f} ··· (2) In the formula, r represents the distance from the center O of the metalens 100, that is, the radial distance.

[0046] If a plurality of pillars or a plurality of holes are arranged so as to satisfy formula (1) or formula (2), the metalens 100 functions as a lens with a focal length f.

[0047] The metalens 100 repeats, with one unit being up to where a phase difference of 2π occurs in the radial direction between a plurality of convex portions 22 or concave portions 24. In FIG. 10, the i-th unit Ui from the center O of the metalens 100 is shown. One unit Ui has a plurality of unit cells with a side length of p. The length p of the unit cell is the same as the center-to-center distance p of the plurality of convex portions 22. A plurality of convex portions 22 with widths d1i to dnii are formed in the unit cell. d1i > d2i > d3i > ··· > dnii. In FIG. 10, the phase difference between the light passing through the convex portion 22 with width d1i and the light passing through the convex portion 22 with width dnii is 2π.

[0048] FIG. 11 is a cross-sectional view along the line XI-XI of FIG. 10. In the example of FIG. 11, the width dnii of the convex portion 22 is smaller than the length p of the unit cell, and the width gradually decreases from d1i to dnii. By having a plurality of units Ui of the metalens 100 having a plurality of convex portions 22 whose widths gradually decrease in this way, a phase distribution similar to the phase distribution of a predetermined lens shape can be obtained.

[0049] In FIG. 11, the widths of the plurality of convex portions 22 decrease in the radial direction from the center O side of the metalens 100. In this example, for example, an effect similar to that of a convex lens can be obtained. Instead of this, the widths of the plurality of convex portions 22 may be increased in the radial direction from the center O side of the metalens 100. Thereby, an effect similar to that of a concave lens can be obtained.

[0050] The multiple protrusions 22 are adjacent to a medium with a refractive index smaller than that of the material forming the metalens portion 20A. This allows the effective refractive index of the unit cell to be adjusted to a predetermined value within the unit cell. The multiple protrusions 22 may be adjacent to air. It is preferable that the multiple protrusions 22 are in contact with a medium with a refractive index smaller than that of the material forming the metalens portion 20A. This allows the effective refractive index of the unit cell to be adjusted using only the refractive index of the material forming the metalens portion 20A and the refractive index of the medium, thus making it easy to control the effective refractive index of the unit cell.

[0051] (Variation 1) Figure 12 is another example of a top view showing a part of the metalens portion 20A. The metalens 100 of Modification 1 differs from the metalens 100 of the embodiment in the following respect: the metalens portion 20A is formed by a plurality of recesses 24. The plurality of recesses 24 are surrounded all around by the metalens material 20. In Figure 12, the phase difference between light passing through a recess 24 of width d1i and light passing through a recess 24 of width dnii is 2π.

[0052] Figure 13 is a cross-sectional view of Modification 1 along the line XIII-XIII. As shown in Figure 13, multiple recesses 24 are arranged in the radial direction from the center O side of the metalens 100 such that the width d1i>d2i>d3i>···>dnii, that is, the width of the recesses 24 decreases. In the example shown in Figure 13, the metalens 100 can obtain an effect similar to that of a concave lens. In the metalens 100 of Modification 1, instead, the width of the multiple recesses 24 may be increased in the radial direction from the center O side of the metalens 100. This can obtain an effect similar to that of a convex lens.

[0053] The metalens 100 of Embodiment and Modification 1 may be given the effect of optical elements other than convex or concave lenses. In this case, the metalens 100 may be called a metasurface. The optical elements reproduced by the metasurface may be, for example, a prism, a diffraction grating or waveplate, or an antenna.

[0054] <Application Examples> The metalens 100 can be combined with a light-emitting element to form a light-emitting device. The light-emitting device includes a light-emitting element and a metalens 100 positioned in the optical path of the light emitted from the light-emitting element. This allows the metalens 100, which has predetermined optical properties, to act on the light emitted from the light-emitting element.

[0055] (Application Example 1) Figure 14 is a schematic diagram showing the light-emitting device 200 of Application Example 1. In Application Example 1, the light-emitting element 60A is a light-emitting diode.

[0056] The light-emitting element 60A has an n-side semiconductor layer, a p-side semiconductor layer, and an active layer disposed between the n-side and p-side semiconductor layers. The light-emitting element 60A emits light with a peak wavelength of, for example, 360 nm to 700 nm. An electrode 60n is disposed in the n-side semiconductor layer, and an electrode 60p is disposed in the p-side semiconductor layer. A wavelength conversion member 70 is disposed on the upper surface of the light-emitting element 60A, and the wavelength conversion member 70 is connected to the light-emitting element 60A via a light-transmitting adhesive 75. The wavelength conversion member 70 may be, for example, a sintered phosphor. Light of a desired color is obtained by mixing the light from the light-emitting element 60A with the light whose wavelength has been converted by the wavelength conversion member 70. For example, white light with a color temperature (or correlated color temperature) in the range of 2000 K to 10000 K can be obtained.

[0057] The light-emitting element 60A is connected to the wiring board 90. The wiring board 90 has wiring 90n and wiring 90p. Wiring 90n is connected to electrode 60n, and wiring 90p is connected to electrode 60p. In Figure 14, electrodes 60n and 60p are located on the same side, and the light-emitting element 60A is flip-chip mounted.

[0058] The metalens 100 is positioned on top of the light-emitting element 60A. The metalens 100 is positioned in the optical path of the light emitted from the light-emitting element 60A. The light is extracted from the back surface of the substrate 10. The back surface of the substrate 10 is roughened. The roughened surface forms a prism surface, which can narrow the light distribution. The metalens portion 20A also has multiple convex or concave portions arranged to narrow the light distribution. The metalens portion 20A and the roughened surface of the substrate 10 can narrow the light distribution of the light emitted from the light-emitting element 60A.

[0059] The metalens 100 is supported by the third light-reflecting member 83. There is a gap G between the metalens 100 and the wavelength-converting member 70. The distance of the gap G, that is, the distance between the wavelength-converting member 70 and the metalens 100, is greater than the length of the wavelength emitted by the light-emitting element. The gap G is filled with air and is also called an air gap. The light emitted from the light-emitting element 60A passes through this air gap before passing through the metalens 100, which allows for further narrowing of the light distribution.

[0060] The metalens portion 20A is in contact with the gap G. As a result, the multiple protrusions 22 or multiple recesses 24 formed on the metalens portion 20A are not exposed from the light-emitting device 200, and the multiple protrusions 22 or multiple recesses 24 can be protected.

[0061] The full width at half maximum of the beam angle of the light emitted from the light-emitting device 200 may be, for example, 70° or more and 120° or less, preferably 70° or more and 100° or less, and more preferably 70° or more and 90° or less.

[0062] The top surface of the wiring board 90, the sides of the electrodes 60n and 60p, the sides and bottom surface of the light-emitting element 60A, the sides of the adhesive 75, the sides of the wavelength conversion member 70, and the sides of the metalens 100 are covered by the light-reflecting member 80. The light-reflecting member 80 includes a first light-reflecting member 81 that covers from the wiring board 90 to the wavelength conversion member 70, a second light-reflecting member 82 that covers the metalens 100, and a third light-reflecting member 83 that is positioned between the first light-reflecting member 81 and the second light-reflecting member 82 and supports the metalens 100. The first light-reflecting member 81, the second light-reflecting member 82, and the third light-reflecting member 83 may be a single integrated member, or the third light-reflecting member 83 may be an integrated member with either the first light-reflecting member 81 or the second light-reflecting member 82. The light-reflecting member 80 may be a resin containing a light-reflecting filler, or it may be a ceramic.

[0063] (Application Example 2) Figure 15 is a schematic diagram showing the light-emitting device 300 in Application Example 2. In Application Example 2, the light-emitting element 60B is a semiconductor laser element.

[0064] The light-emitting device 300 includes a wiring board 90, a submount 65 positioned on the wiring board 90, and a light-emitting element 60B positioned on the submount 65. A metalens 100 and a collimating lens 150 are further positioned on the wiring board 90, with the metalens 100 and collimating lens 150 located on the optical axis of the light-emitting element 60B.

[0065] This allows for efficient collimation of the laser beam. The metalens 100 and the collimating lens 150 may act on either the fast-axis or slow-axis component of the laser beam.

[0066] In the light-emitting device 300, the metalens 100 and the collimating lens 150 may act in different directions, such as the fast axis direction and the slow axis direction of the laser light. It is preferable that the collimating lens is not placed on the wiring board 90, and that the metalens 100 alone collimates the laser light in both the fast axis direction and the slow axis direction. Since the metalens 100 is lighter than the collimating lens 150, the light-emitting device 300 can be made lighter. [Examples]

[0067] The present invention will be described in detail below with reference to examples, but the present invention is not limited to these examples.

[0068] <Example 1> A metalens according to the embodiment was fabricated. In Example 1, a metalens was first formed on a synthetic quartz substrate by sequentially forming silicon oxide, a 2400 nm metalens material, Cr, a 230 nm first mask, silicon oxide, a 200 nm second mask, and a 300 nm third mask, a resist. Next, a first pattern was patterned onto the third mask by electron beam lithography to obtain a laminate. Next, the second mask was dry-etched through the third mask having the first pattern to form a second pattern. Next, the first mask was dry-etched through the second mask having the second pattern to obtain a third pattern. At this time, the third mask remaining after forming the second pattern was removed. Next, the metalens material was dry-etched through the first mask having the third pattern to obtain a metalens portion. At this time, the second mask remaining after forming the third pattern was removed. Finally, the first mask remaining on the metalens portion was removed to obtain a metalens.

[0069] Figure 16 shows a scanning electron microscope (SEM) image of a portion of the fabricated metalens. The scan was performed under conditions of an acceleration voltage of 5kV and a field of view of 6.40μm × 4.80μm. The observation angle was tilted 30° relative to the normal to the top surface of the substrate. From the SEM image, it was found that the height of the fabricated metalens is approximately 2.2μm.

[0070] Figure 17 is an SEM image showing another part of the fabricated metalens. The field of view was changed to a range of 12.8 μm × 9.6 μm. From Figure 17, it can be seen that in the area indicated by the dashed line, the thickness of multiple convex parts gradually decreases from the upper left to the lower right of the SEM image. Outside this area, the thickness of the convex parts becomes abruptly thinner or abruptly thicker. This indicates that the area indicated by the dashed line is the unit Ui which transforms the phase by 2π. Furthermore, from this SEM image, it was confirmed that a metalens of the predetermined height could be formed using the method of the example.

[0071] The above disclosure includes the following forms: (Section 1) A laminate is prepared by sequentially stacking a metalens material having a thickness of 2 μm or more and a refractive index of 1.5 or less on a substrate, a first mask which is a mask for the metalens material, a second mask which is a mask for the first mask, and a third mask having a first pattern with spacing less than or equal to a predetermined wavelength. Etching the second mask through the third mask to form a second pattern, Etching the first mask through the second mask to form a third pattern, Etching the metalens material through the first mask, A method for manufacturing metalens containing metalens. (Section 2) The first pattern is formed by the third mask being formed by electron beam lithography or nanoimprint. A method for manufacturing a metal lens as described in item 1. (Section 3) The process of forming the third pattern includes removing the third mask that remained when forming the second pattern, A method for manufacturing a metalens as described in item 1 or 2. (Section 4) The process of etching the metalens material includes removing the second mask that remains when forming the third pattern, A method for manufacturing a metalens as described in any one of items 1 to 3. (Section 5) The thickness of the first mask is 0.2 μm or more and 0.6 μm or less. A method for manufacturing a metalens as described in any one of items 1 to 4. (Section 6) The first mask contains Cr, A method for manufacturing a metal lens as described in any one of items 1 to 5. (Section 7) The second mask contains silicon oxide, A method for manufacturing a metalens as described in any one of items 1 to 6. (Section 8) The aforementioned metalens material is silicon oxide. A method for manufacturing a metalens as described in any one of items 1 to 7. (Section 9) The thickness of the metalens material is 4 μm or less. A method for manufacturing a metalens as described in any one of items 1 to 8. (Section 10) circuit board and A metalens portion disposed on the substrate, Equipped with, The aforementioned metalens portion is It has a plurality of convex or concave portions where the distance between the centers of adjacent portions is less than or equal to a predetermined wavelength, The plurality of protrusions or the plurality of recesses consist of a single layer of a material having a refractive index of less than 1.5 at the predetermined wavelength. The height of the plurality of protrusions or the plurality of recesses is 2 μm or more. Metalens. (Section 11) The plurality of protrusions or the plurality of recesses are adjacent to a medium having a refractive index smaller than that of the material forming the metalens portion. The metal lens described in item 10. (Section 12) The plurality of protrusions or the plurality of recesses are made of silicon oxide. A metalens as described in item 10 or item 11. (Section 13) Light-emitting element and The metalens included is arranged in the optical path of the light emitted from the light-emitting element, according to any one of claims 10 to 12. Light-emitting device. [Explanation of symbols]

[0072] 10 circuit boards 20 Metalens Materials 20A Metalens section 22 Convex part 24 recesses 30 First Mask 32. Third Pattern 40. Second Mask 42. Second pattern 50 Third Mask 52 Pattern 1 60A, 60B light-emitting element 60n, 60p electrode 65 Submount 70 Wavelength conversion component 75 Adhesives 80 Light-reflecting member 81 First light reflecting member 82 Second light reflecting member 83 Third light-reflecting member 90 Wiring board 90n, 90p wiring 100 Metalens 150 Collimating Lens 200, 300 light-emitting devices

Claims

1. A laminate is prepared by sequentially stacking a metalens material having a thickness of 2 μm or more and a refractive index of 1.5 or less on a substrate, a first mask which is a mask for the metalens material, a second mask which is a mask for the first mask, and a third mask having a first pattern with intervals of a predetermined wavelength or less. Etching the second mask through the third mask to form a second pattern, Etching the first mask through the second mask to form a third pattern, Etching the metalens material through the first mask, A method for manufacturing metalens containing metalens.

2. The first pattern is formed by the third mask being formed by electron beam lithography or nanoimprint. A method for manufacturing a metal lens according to claim 1.

3. The process of forming the third pattern includes removing the third mask that remained when forming the second pattern, A method for manufacturing a metal lens according to claim 1.

4. The process of etching the metalens material includes removing the second mask that remains after forming the third pattern, A method for manufacturing a metal lens according to claim 1.

5. The thickness of the first mask is 0.2 μm or more and 0.6 μm or less. A method for manufacturing a metalens according to any one of claims 1 to 4.

6. The first mask contains Cr, A method for manufacturing a metalens according to any one of claims 1 to 4.

7. The second mask contains silicon oxide, A method for manufacturing a metalens according to any one of claims 1 to 4.

8. The aforementioned metalens material is silicon oxide. A method for manufacturing a metalens according to any one of claims 1 to 4.

9. The thickness of the metallens material is 4 μm or less. A method for manufacturing a metalens according to any one of claims 1 to 4.

10. circuit board and A metalens portion disposed on the substrate, Equipped with, The aforementioned metalens portion is It has a plurality of convex or concave portions where the distance between the centers of adjacent portions is less than or equal to a predetermined wavelength, The plurality of protrusions or the plurality of recesses are made of a single layer of a material having a refractive index of less than 1.5 at the predetermined wavelength. The height of the plurality of protrusions or the plurality of recesses is 2 μm or more. Metalens.

11. The plurality of protrusions or the plurality of recesses are adjacent to a medium having a refractive index smaller than that of the material forming the metalens portion. The metal lens according to claim 10.

12. The plurality of protrusions or the plurality of recesses are made of silicon oxide. The metal lens according to claim 10.

13. Light-emitting element and The metalens described in claim 10 is arranged in the optical path of the light emitted from the light-emitting element, Light-emitting device.

Images