Imaging device and production method for imaging device

Abstract

An imaging device (10) comprises an imaging substrate (1) and an opposite substrate (2). The imaging substrate (1) includes a pixel region (13). The opposite substrate (2) is opposite the imaging substrate (1). A metasurface (MS) is provided at the imaging substrate (1) or the opposite substrate (2). The imaging substrate (1) is separated from the opposite substrate (2) by a spacer (3). The spacer (3) includes a plating layer (32a).

Description

Image pickup device and method for manufacturing the same

[0001] The present disclosure relates to an imaging device and a method for manufacturing an imaging device.

[0002] Conventionally, imaging devices capable of detecting infrared rays have been known (see, for example, JP 2022-542172 A). The imaging device includes an imaging substrate including a pixel region for detecting infrared rays and a counter substrate disposed opposite the imaging substrate. JP 2022-542172 A uses a metalens substrate provided with a metasurface as the counter substrate. The use of a metalens substrate can shorten the focal length of light.

[0003] Special Publication No. 2022-542172

[0004] However, since the focal length of light is shortened, it is difficult to position the imaging substrate in accordance with the focal length, and therefore there is room for improvement in adjusting the focal length of light.

[0005] The present disclosure has been made to solve the above-mentioned problems, and an object of the present disclosure is to provide an imaging device in which the focal length of light is easily adjusted, and a method for manufacturing the imaging device.

[0006] An imaging device according to the present disclosure includes an imaging substrate and a counter substrate. The imaging substrate includes a pixel region. The counter substrate faces the imaging substrate. A metasurface is provided on either the imaging substrate or the counter substrate. The imaging substrate is disposed so as to be spaced apart from the counter substrate by a spacer. The spacer includes a plating layer.

[0007] A method for manufacturing an imaging device according to the present disclosure includes the steps of preparing an imaging substrate and a counter substrate at a wafer level, bonding the imaging substrate and the counter substrate, and dicing the imaging substrate and the counter substrate after the bonding step is performed. In the preparing step, the imaging substrate includes a pixel region. A metasurface is provided on either the imaging substrate or the counter substrate. In the bonding step, the counter substrate and the imaging substrate are bonded together by a spacer including a plating layer.

[0008] Based on the above, it is possible to obtain an imaging device in which the focal length of light is easily adjusted.

[0009] 16 is a schematic cross-sectional view of an imaging device according to a first embodiment. FIG. 17 is a partially enlarged schematic cross-sectional view of a region II in FIG. 1. FIG. 18 is a schematic plan view of a counter substrate in the imaging device according to the first embodiment. FIG. 19 is a schematic cross-sectional view of a counter substrate taken along line IV-IV in FIG. 3. FIG. 19 is a schematic cross-sectional view of a modified example of a metasurface in the imaging device according to the first embodiment. FIG. 20 is a flowchart of a manufacturing method for the imaging device according to the first embodiment. FIG. 21 is a schematic cross-sectional view showing one step of a manufacturing method for the imaging device according to the first embodiment. FIG. 22 is a schematic cross-sectional view showing one step of a manufacturing method for the imaging device according to the first embodiment. FIG. 23 is a schematic cross-sectional view showing one step of a manufacturing method for the imaging device according to the first embodiment. FIG. 24 is a schematic cross-sectional view showing one step of a manufacturing method for the imaging device according to the first embodiment. FIG. 25 is a schematic cross-sectional view showing one step of a manufacturing method for the imaging device according to the first embodiment. 20. A partially enlarged schematic cross-sectional view of an area XX in Fig. 19. A schematic cross-sectional view of an imaging device according to embodiment 3. A schematic cross-sectional view of an imaging device according to embodiment 4. A schematic cross-sectional view of a modified example of the imaging device according to embodiment 4. A schematic cross-sectional view of an imaging device according to embodiment 5. A schematic cross-sectional view of an imaging device according to embodiment 6. A schematic cross-sectional view of an imaging device according to embodiment 7. A schematic plan view of a counter substrate in an imaging device according to embodiment 7. A schematic cross-sectional view of an imaging device according to embodiment 8. A schematic cross-sectional view of an imaging device according to embodiment 9. A schematic cross-sectional view showing one step of a manufacturing method for an imaging device according to embodiment 9. A schematic cross-sectional view showing one step of a manufacturing method for an imaging device according to embodiment 9. A schematic cross-sectional view showing one step of a manufacturing method for an imaging device according to embodiment 9. A schematic cross-sectional view showing one step of a manufacturing method for an imaging device according to embodiment 9.41. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to a ninth embodiment. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the ninth embodiment. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the ninth embodiment. A schematic cross-sectional view of an imaging device according to a tenth embodiment. A partially enlarged schematic cross-sectional view of an area XXXVII in FIG. 36. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the tenth embodiment. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the tenth embodiment. A schematic cross-sectional view of a first modified example of a metasurface in an imaging device according to the tenth embodiment. A schematic plan view of a second modified example of a metasurface in an imaging device according to the tenth embodiment. A schematic cross-sectional view of a metasurface taken along line XLII-XLII in FIG. 41. A schematic cross-sectional view of an imaging device according to an eleventh embodiment. A partially enlarged schematic cross-sectional view of an area XLIV in FIG. 43. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the eleventh embodiment. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the eleventh embodiment. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the eleventh embodiment. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the eleventh embodiment. A schematic cross-sectional view showing a step of a manufacturing method of an imaging device according to the eleventh embodiment. Fig. 22 is a schematic cross-sectional view showing one step of a manufacturing method for an imaging device according to embodiment 12. Fig. 23 is a schematic cross-sectional view showing one step of a manufacturing method for an imaging device according to embodiment 12. Fig. 24 is a schematic cross-sectional view showing one step of a manufacturing method for an imaging device according to embodiment 12. Fig. 25 is a schematic cross-sectional view showing one step of a manufacturing method for an imaging device according to embodiment 12.

[0010] Hereinafter, embodiments of the present disclosure will be described. Unless otherwise specified, the same or corresponding parts in the following drawings will be denoted by the same reference numerals, and the description thereof will not be repeated.

[0011] Embodiment 1. <Configuration of Imaging Device> Fig. 1 is a schematic cross-sectional view of an imaging device 10 according to embodiment 1. Fig. 2 is a partially enlarged schematic cross-sectional view of region II in Fig. 1. Fig. 3 is a schematic plan view of the counter substrate 2 in the imaging device 10 according to embodiment 1. Fig. 4 is a schematic cross-sectional view of the counter substrate 2 taken along line IV-IV in Fig. 3. The imaging device 10 shown in Figs. 1 to 4 is an imaging device 10 that detects electromagnetic waves such as infrared rays, and mainly comprises an imaging substrate 1, a counter substrate 2, and a spacer 3. The imaging device 10 is composed of a chip-level imaging substrate 1 and a counter substrate 2.

[0012] The imaging substrate 1 includes a pixel region 13 that detects electromagnetic waves (such as incident light IL, which will be described later). The electromagnetic waves may be long-wavelength infrared rays with wavelengths of 8 μm or more and 14 μm or less. The pixel region 13 may be a resistance change type bolometer or diode, or may include an infrared sensor such as a thermoelectric thermopile.

[0013] The pixel region 13 is configured to minimize the influence of heat received from the imaging substrate 1. Specifically, a hollow structure is provided in the pixel region 13. A recess may be provided in the surface of the imaging substrate 1 (such as the first main surface 11 described later). The infrared sensor may be held in the air in the region where the recess is formed so that the influence of heat received by the imaging substrate 1 on the infrared sensor is minimized. In this way, the pixel region 13 is disposed in a thermally insulated manner from the imaging substrate 1.

[0014] 1 , the imaging substrate 1 has a first main surface 11 and a second main surface 12. The first main surface 11 faces the counter substrate 2. The second main surface 12 is located opposite the first main surface 11. A pixel region 13 is provided on the first main surface 11.

[0015] In the imaging device 10 according to the first embodiment, the counter substrate 2 is, for example, a metalens substrate 2a. The material constituting the metalens substrate 2a may be silicon (Si), germanium (Ge), zinc sulfide (ZnS), or the like. The material constituting the metalens substrate 2a may be a semiconductor material that has high transmittance for the long-wavelength infrared light having a wavelength of 8 μm or more and 14 μm or less. The metalens substrate 2a may be formed from a thin-film substrate configured with mirrors on both sides.

[0016] 1, metalens substrate 2a (counter substrate 2) has a first surface 21 and a second surface 22. Second surface 22 is located opposite first surface 21.

[0017] 1, the first surface 21 faces the imaging substrate 1. The second surface 22 is a surface onto which incident light IL is incident. The incident light IL may be, for example, infrared light.

[0018] A metasurface MS is provided on the first surface 21. When viewed from the direction in which incident light IL is incident, the pixel region 13 is arranged to overlap the metasurface MS so that light transmitted through the metalens substrate 2 a (counter substrate 2) is imaged in the pixel region 13.

[0019] As shown in Fig. 2, the metasurface MS is formed from a plurality of meta-atoms MA. Specifically, the metasurface MS is formed by regularly arranging a plurality of meta-atoms MA. As shown in Fig. 3, the shape of the metasurface MS formed from a plurality of meta-atoms MA may be circular in a plan view of the first surface 21. The shape of the metasurface MS in a plan view of the first surface 21 may be elliptical or rectangular. As shown in Fig. 4, the shape of the meta-atoms MA may be concave.

[0020] Fig. 5 is a schematic cross-sectional view of a modified example of the metasurface MS in the imaging device 10 according to the first embodiment. Fig. 5 corresponds to Fig. 4. The counter substrate 2 shown in Fig. 5 basically has the same configuration as the counter substrate 2 shown in Figs. 1 to 4 and can achieve the same effects, but differs in that the shape of the meta-atoms MA is columnar. Thus, the shape of the meta-atoms MA may be concave (see Fig. 4) or columnar (see Fig. 5).

[0021] The height h of each of the multiple meta-atoms MA and the distance SP between the multiple meta-atoms MA may be close to the wavelength λ of the light to be detected (incident light IL). For example, the height h of each of the multiple meta-atoms MA and the distance SP between the multiple meta-atoms MA may be 15 μm or less, 10 μm or less, or 5 μm or less, depending on the wavelength λ of the light to be detected, such as long-wavelength infrared light. By arranging multiple microscale meta-atoms MA in this manner, a metasurface MS can be formed that is selectively endowed with any optical function, such as imaging, spectroscopy, or polarization.

[0022] The imaging substrate 1 and the metalens substrate 2a are connected via a spacer 3. As shown in FIG. 3 , in a plan view of the first surface 21, the spacer 3 extends to surround the metasurface MS. In a plan view of the first major surface 11, the spacer 3 extends to surround the pixel region 13. As shown in FIG. 1 , an internal space Q is formed by the imaging substrate 1, the counter substrate 2, and the spacer 3. From a different perspective, the pixel region 13 is vacuum-sealed by being surrounded by the first major surface 11 of the imaging substrate 1, the first surface 21 of the counter substrate 2 (metalens substrate 2a), and the spacer 3. In this way, the counter substrate 2 functions as a lid substrate.

[0023] The spacer 3 includes a solder layer 31 and plating layers 32a and 32b. The plating layer 32a is connected to the opposing substrate 2. The plating layer 32b is connected to the imaging substrate 1. As shown in Fig. 1, the solder layer 31 is sandwiched between the plating layers 32a and 32b. The solder layer 31 joins the plating layers 32a and 32b.

[0024] The solder layer 31 may be formed from a solder with a relatively low melting point. The material constituting the solder layer 31 may include any of tin (Sn), silver (Ag), and copper (Cu). The metalens substrate 2 a and the imaging substrate 1 are joined by heating the solder to its melting point using a vacuum chamber with a heater disposed therein.

[0025] 1 , the imaging substrate 1 is disposed so as to be spaced apart from the counter substrate 2 by the spacers 3. From a different perspective, the distance t between the imaging substrate 1 and the counter substrate 2 is determined by the height of the spacers 3. The distance t between the imaging substrate 1 and the counter substrate 2 is adjusted so that light is focused on the pixel region 13.

[0026] Here, a feature of the imaging device 10 according to the first embodiment is that, as shown in FIG. 1 , the distance t between the imaging substrate 1 and the counter substrate 2 is adjusted by the plating layers 32a and 32b. As shown in FIG. 1 , the distance t is the distance between the first surface 21 and the first main surface 11. The plating layers 32a and 32b are formed by plating. In this way, the thicknesses of the plating layers 32a and 32b are controlled on a microscale basis so that light transmitted through the metalens substrate 2a (counter substrate 2) is focused on the pixel region 13.

[0027] The imaging device 10 according to the first embodiment uses a lens provided with a metasurface MS. This results in a very short focal length of light. The focal length of light is 1 mm or less. The plating layers 32a and 32b allow the distance t between the imaging device 10 and the opposing substrate 2 to be adjusted on a microscale basis, so that the imaging device 10 according to the first embodiment, which has a short focal length of light, can focus light on the pixel region 13. In other words, the distance t between the imaging substrate 1 and the opposing substrate 2 can be reduced, resulting in a thinner imaging device 10.

[0028] The plating layers 32a and 32b may be made of a metal, such as copper (Cu), and each of the plating layers 32a and 32b may have a thickness of 10 μm or more.

[0029] <Method of Manufacturing Image Capturing Device> A method of manufacturing the image capturing device 10 according to the first embodiment will now be described. Fig. 6 is a flowchart of the method of manufacturing the image capturing device 10 according to the first embodiment. Figs. 7 to 14 are schematic cross-sectional views showing one step of the method of manufacturing the image capturing device 10 according to the first embodiment. Fig. 15 is a schematic plan view showing one step of the method of manufacturing the image capturing device 10 according to the first embodiment.

[0030] First, a step (S1) of preparing a wafer-level imaging substrate 1 and a counter substrate 2 is performed. The counter substrate 2 prepared in this step (S1) will be described. First, as shown in FIG. 7 , a thin substrate is prepared on which a metalens substrate 2a is formed as the counter substrate 2. The thin substrate may be, for example, a wafer-level silicon substrate. The thickness of the thin substrate may be, for example, 100 μm or more, or 200 μm or more. The thickness of the thin substrate may be, for example, 900 μm or less, or 800 μm or less. The front surface (first surface 21) of the thin-film substrate and the back surface (second surface 22) opposite the front surface may be polished.

[0031] The power supply layer 4 is provided on the entire surface (first surface 21) of the thin substrate. The material constituting the power supply layer 4 may be titanium (Ti) or copper (Cu). By providing the power supply layer 4 on the first surface 21, a plating layer 32a and a solder layer 31 are formed by electrolytic plating.

[0032] Next, a step of forming a first photoresist 51 is performed. In this step, as shown in FIG. 8 , the first photoresist 51 is formed on the power supply layer 4. The first photoresist 51 is a thick-film photoresist. By doing so, in the step of forming the plating layer 32a described below, it is possible to form the plating layer 32a and the solder layer 31 with a thickness of 10 μm or more. The first photoresist 51 may be formed by spin coating.

[0033] The first photoresist 51 is exposed to light using a mask aligner or a stepper, thereby patterning the first photoresist 51. Specifically, an opening 51h is provided in the first photoresist 51 so that a portion of the power supply layer 4 is exposed from the first photoresist 51. The power supply layer 4 is exposed from the first photoresist 51 in the region where the opening 51h is formed.

[0034] Next, the step of forming the plating layer 32a is carried out. In this step, as shown in FIG. 9 , the plating layer 32a is formed in the region where the opening 51h is formed. Specifically, the plating layer 32a is formed by plating on the power supply layer 4 exposed from the opening 51h of the first photoresist 51. The thickness of the plating layer 32a is adjusted on a microscale basis so that light transmitted through the metalens substrate 2a (counter substrate 2) is focused on the pixel region 13.

[0035] Thereafter, the solder layer 31 is formed. The solder layer 31 is formed from a solder having a relatively low melting point. The material constituting the solder layer 31 may include any of tin (Sn), silver (Ag), and copper (Cu).

[0036] Next, a step of removing the first photoresist 51 is performed. In this step, as shown in FIG. 10 , the first photoresist 51 is removed from the power supply layer 4. The first photoresist 51 is removed using an organic solvent. By removing the first photoresist 51, a portion of the power supply layer 4 is exposed. Thereafter, the exposed power supply layer 4 is etched using the plating layer 32 a and the solder layer 31 as a mask. In this way, the surface (first surface 21) of the thin substrate is exposed, as shown in FIG. 11 .

[0037] Next, a step of forming a second photoresist 52 is performed. In this step, as shown in Fig. 12, the second photoresist 52 is formed on the first surface 21 and on the solder layer 31. The first photoresist 51 may be formed by spin coating or spray coating.

[0038] The second photoresist 52 is exposed to light using a mask aligner or a stepper, thereby patterning the second photoresist 52. Specifically, an opening 52h is provided in the second photoresist 52 so that a portion of the first surface 21 is exposed from the second photoresist 52. The first surface 21 is exposed from the second photoresist 52 in the region where the opening 52h is formed.

[0039] Next, a step of forming a metasurface MS is performed. In this step, as shown in FIG. 13 , the metasurface MS is formed on the first surface 21. Specifically, a DRIE (Deep Reactive-Ion Etching) device is used to etch the first surface 21 exposed through the opening 52h of the second photoresist 52. In this way, meta-atoms MA with a relatively large aspect ratio (the height h of the meta-atoms MA in the direction perpendicular to the first surface 21 is relatively large) are formed.

[0040] Next, a step of removing the second photoresist 52 is performed. In this step, as shown in FIG. 14 , the second photoresist 52 is removed from the first surface 21 and the solder layer 31. The second photoresist 52 is made of oxygen (O ２ ) is removed by plasma ashing or the like. In this way, the opposing substrate 2 at the wafer level is prepared.

[0041] Next, the imaging substrate 1 prepared in this step (S1) will be described. The imaging substrate 1 prepared may be a wafer-level silicon substrate. The plating layer 32b and the solder layer 31 are formed using a process similar to the process for forming the plating layer 32a described above.

[0042] Next, a step of forming the pixel region 13 is carried out. In this step, the pixel region 13 having a hollow structure is formed on the first main surface 11. Specifically, a recess is provided on the surface (first main surface 11, etc.) of the imaging substrate 1. The infrared sensor is held in the air in the region where the recess is formed. In this way, the pixel region 13 is disposed in adiabatic relation to the imaging substrate 1.

[0043] A plurality of pixel regions 13 may be arranged in an array on the first main surface 11. The plating layer 32b and the solder layer 31 are arranged to surround the pixel regions 13. The pixel regions 13 may be infrared sensors such as PN junction diodes, resistive bolometers, and thermoelectric thermopiles. Because the hollow pixel regions 13 are fragile, the step of forming the pixel regions 13 may be performed immediately before the step (S2) of bonding the imaging substrate 1 and the counter substrate 2, which will be described later.

[0044] In this manner, the step (S1) of preparing the imaging substrate 1 and the opposing substrate 2 at the wafer level is carried out.

[0045] Next, a step (S2) of bonding the imaging substrate 1 and the counter substrate 2 at the wafer level is performed. In this step (S2), the imaging substrate 1 and the counter substrate 2 are heated using a vacuum chamber, thereby bonding the imaging substrate 1 and the counter substrate 2. Specifically, the solder layer 31 is heated to its melting point, thereby bonding the plating layers 32 a and 32 b. In this way, the imaging substrate 1 and the counter substrate 2 are bonded by the spacer 3 including the plating layers 32 a and 32 b.

[0046] By bonding the imaging substrate 1 and the counter substrate 2, an internal space Q is formed by the imaging substrate 1, the counter substrate 2, and the spacer 3. Within the internal space Q, the pixel region 13 is vacuum-sealed by being surrounded by the first main surface 11 of the imaging substrate 1, the first surface 21 of the counter substrate 2 (metalens substrate 2 a), and the spacer 3.

[0047] A getter may be disposed in the internal space Q. The getter adsorbs residual gas in the internal space Q. In this way, the degree of vacuum in the internal space Q can be maintained.

[0048] Next, a step (S3) of dicing the imaging substrate 1 and the counter substrate 2 is performed. Specifically, the bonded wafer-level imaging substrate 1 and counter substrate 2 are diced along dicing lines DL shown in Fig. 15. By dicing the bonded wafer-level imaging substrate 1 and counter substrate 2, the plurality of chip-level imaging devices 10 shown in Figs. 1 to 5 can be obtained.

[0049] The metasurface MS and the hollow pixel region 13 are arranged in the internal space Q. Therefore, as a wafer-level package, a step (S2) of bonding the imaging substrate 1 and the opposing substrate 2 at the wafer level may be performed, followed by a step (S3) of dicing the imaging substrate 1 and the opposing substrate 2.

[0050] Alternatively, after the step (S1) of preparing the imaging substrate 1 and the opposing substrate 2 at a wafer level, the step (S3) of dicing the imaging substrate 1 and the opposing substrate 2 may be performed. In this manner, after the imaging substrate 1 and the opposing substrate 2 at a chip level are prepared, the step (S2) of bonding the imaging substrate 1 and the opposing substrate 2 at the chip level may be performed.

[0051] <Effects> The imaging device 10 according to the present disclosure includes an imaging substrate 1 and a counter substrate 2. The imaging substrate 1 includes a pixel region 13. The counter substrate 2 faces the imaging substrate 1. A metasurface MS is provided on either the imaging substrate 1 or the counter substrate 2. The imaging substrate 1 is disposed so as to be spaced apart from the counter substrate 2 by a spacer 3. The spacer 3 includes a plating layer 32a.

[0052] In this way, in the imaging device 10 in which the focal length of light is significantly shortened by providing the metasurface MS, the distance t between the imaging substrate 1 and the metalens substrate 2a can be easily adjusted on a microscale basis, resulting in a thin imaging device 10.

[0053] According to the imaging device 10, the shape of the multiple meta-atoms MA that form the metasurface MS is columnar.

[0054] In this way, it is possible to form a metasurface MS that is selectively endowed with optical functions such as imaging, spectroscopy, and polarization.

[0055] According to the imaging device 10, the shape of the multiple meta-atoms MA that form the metasurface MS is concave.

[0056] In this way, it is possible to form a metasurface MS that is selectively endowed with optical functions such as imaging, spectroscopy, and polarization.

[0057] According to the imaging device 10, the pixel region 13 is surrounded by the imaging substrate 1, the counter substrate 2, and the spacer 3, and is thus vacuum-sealed.

[0058] In this way, the influence of heat from the outside on the pixel region 13 can be suppressed.

[0059] A manufacturing method for an imaging device 10 according to the present disclosure includes a step (S1) of preparing an imaging substrate 1 and a counter substrate 2 at wafer level, a step (S2) of bonding the imaging substrate 1 and the counter substrate 2 together, and a step (S3) of dicing the imaging substrate 1 and the counter substrate 2 after the bonding step (S2) is performed. In the preparation step (S1), the imaging substrate 1 includes a pixel region 13. A metasurface MS is provided on either the imaging substrate 1 or the counter substrate 2. In the bonding step (S2), the counter substrate 2 and the imaging substrate 1 are bonded together by a spacer 3 including plating layers 32a and 32b.

[0060] By dicing the wafer in which the opposing substrate 2 and the imaging substrate 1 are bonded together as a wafer-level package in this way, it is possible to obtain a chip-level imaging device 10 in which the pixel region 13 is vacuum-sealed.

[0061] Embodiment 2. <Configuration of Imaging Device> Fig. 16 is a schematic cross-sectional view of an imaging device 10 according to embodiment 2. Fig. 16 corresponds to Fig. 1. Fig. 17 is a partially enlarged schematic cross-sectional view of region XVII in Fig. 16. Fig. 18 is a partially enlarged schematic cross-sectional view of region XVIII in Fig. 16. Figs. 17 and 18 correspond to Fig. 2. The imaging device 10 shown in Figs. 16 to 18 basically has the same configuration as the imaging device 10 shown in Figs. 1 to 5 and can achieve the same effects, but differs in that the metasurface MS is divided into multiple regions.

[0062] 16, the metasurface MS includes a first metasurface section MS1 ​​and a second metasurface section MS2. Within the same internal space Q, the second metasurface section MS2 may be located at a different position from the first metasurface section MS1.

[0063] The first metasurface section MS1 ​​forms an image of light having a wavelength λ1 on the pixel region 13. The second metasurface section MS2 forms an image of light having a wavelength λ2 on the pixel region 13. In this way, the second metasurface section MS2 forms an image of light having a wavelength λ2 on the pixel region 13, which is different from the wavelength λ1 of the light formed on the pixel region 13 by the first metasurface section MS1.

[0064] In this case, the same image is formed on the pixel region 13 by each of the first metasurface section MS1 ​​and the second metasurface section MS2. Therefore, the same image is projected onto the pixel region 13 at wavelengths corresponding to each of the first metasurface section MS1 ​​and the second metasurface section MS2.

[0065] The height h1 of the meta-atom MA shown in Figure 17 may be different from the height h2 of the meta-atom MA shown in Figure 18. The width W1 of the meta-atom MA shown in Figure 17 may be different from the width W2 of the meta-atom MA shown in Figure 18. The distance SP1 between the multiple meta-atoms MA shown in Figure 17 may be different from the distance SP2 between the multiple meta-atoms MA shown in Figure 18. In this way, multiple types of meta-atoms MA may be arranged on first surface 21.

[0066] The imaging device 10 according to the second embodiment may be an optical system that allows easy wavelength selection as described above, or may be an optical system that images polarized light having different polarization states on the pixel region 13. Specifically, the second metasurface unit MS2 may image on the pixel region 13 light that has a polarization state different from the polarization state of the light that the first metasurface unit MS1 images on the pixel region 13.

[0067] In this way, one opposing substrate 2 may be given the optical functions of spectroscopic and imaging, or the optical functions of polarizing and imaging, or both optical functions.

[0068] Fig. 19 is a schematic cross-sectional view of a modified example of the imaging device 10 according to embodiment 2. Fig. 19 corresponds to Fig. 16. Fig. 20 is a partially enlarged schematic cross-sectional view of an area XX in Fig. 19. Fig. 20 corresponds to Figs. 17 and 18.

[0069] The imaging device 10 shown in Figures 19 and 20 basically has the same configuration as the imaging device 10 shown in Figures 16 to 18 and can achieve the same effects, but differs in that the area where light having wavelength λ1 is imaged in pixel area 13 and the area where light having wavelength λ2 is imaged in pixel area 13 are the same.

[0070] Specifically, as shown in Figure 20, the meta-atoms MA corresponding to wavelength λ1 and the meta-atoms MA corresponding to wavelength λ2 are arranged in the same region. In this way, the entire region where the metasurface MS is formed becomes the lens aperture, thereby increasing the aperture area of ​​the imaging device 10.

[0071] <Effects> According to the imaging device 10, the metasurface MS includes a first metasurface section MS1 ​​and a second metasurface section MS2. The second metasurface section MS2 forms an image on the pixel region 13 of light having a wavelength λ2 different from the wavelength λ1 of the light formed on the pixel region 13 by the first metasurface section MS1, or light having a polarization state different from the polarization state of the light formed on the pixel region 13 by the first metasurface section MS1.

[0072] In this way, one opposing substrate 2 may be given the optical functions of spectroscopic analysis and imaging, or the optical functions of polarizing light and imaging, or both optical functions.

[0073] Third Embodiment <Configuration of Imaging Device> Fig. 21 is a schematic cross-sectional view of an imaging device 10 according to a third embodiment. Fig. 21 corresponds to Fig. 1. The imaging device 10 shown in Fig. 21 basically has the same configuration as the imaging device 10 shown in Figs. 1 to 5 and can obtain the same effects, but differs in that the metasurface MS is provided on the second surface 22. That is, in the third embodiment, the metasurface MS is disposed outside the vacuum-sealed internal space Q, and incident light IL enters it.

[0074] In this way, the metasurface MS can be formed in an area larger than the area formed by the spacer 3. In other words, when viewed from a direction perpendicular to the first surface 21, the area where the spacer 3 is formed may be smaller than the area where the metasurface MS is formed.

[0075] Note that if a metasurface MS is formed on the second surface 22, there is a risk that the metasurface MS may be damaged by cutting water or the like when the opposing substrate 2 is diced. Therefore, the step (S3) of dicing the wafer-level imaging substrate 1 and the opposing substrate 2 may be performed to prepare the chip-level imaging substrate 1 and the opposing substrate 2, and then the step (S2) of bonding the chip-level imaging substrate 1 and the opposing substrate 2 may be performed. Furthermore, in the step (S3) of dicing the imaging substrate 1 and the opposing substrate 2 that have been bonded together, the imaging device 10 according to the third embodiment may be manufactured by stealth dicing using a laser.

[0076] <Effects> According to the imaging device 10, the opposing substrate 2 has a first surface 21 and a second surface 22. The first surface 21 faces the imaging substrate 1. The second surface 22 is located opposite the first surface. The metasurface MS is provided on the second surface 22.

[0077] In this way, the metasurface MS can be formed in an area larger than the area formed by the spacer 3. As a result, the aperture of the lens can be made larger.

[0078] Embodiment 4. <Configuration of imaging device> Fig. 22 is a schematic cross-sectional view of an imaging device 10 according to embodiment 4. Fig. 22 corresponds to Fig. 1. The imaging device 10 shown in Fig. 22 basically has the same configuration as the imaging device 10 shown in Figs. 1 to 5 and can obtain the same effects, but differs in that a metasurface MS is provided on a first surface 21 and a second surface 22.

[0079] 22 , the metasurface MS includes a first metasurface section MS1 ​​and a second metasurface section MS2. The first metasurface section MS1 ​​is provided on a first surface 21. The second metasurface section MS2 is provided on a second surface 22.

[0080] The optical function imparted to the second metasurface unit MS2 provided on the second surface 22 may be different from the optical function imparted to the first metasurface unit MS1 provided on the first surface 21. Specifically, the imaging device 10 shown in Figure 22 may be an optical system in which the first metasurface unit MS1 corrects the optical aberration caused by the second metasurface unit MS2. In this way, the accuracy of the image formed in the pixel region 13 is improved.

[0081] The second metasurface portion MS2 may function as a spectral filter that transmits infrared light having a specific wavelength.

[0082] Fig. 23 is a schematic cross-sectional view of a modified example of the imaging device 10 according to embodiment 4. Fig. 23 corresponds to Fig. 22. The imaging device 10 shown in Fig. 23 basically has the same configuration as the imaging device 10 shown in Fig. 22 and can obtain the same effects, but differs in that the metasurface MS includes a third metasurface portion MS3.

[0083] Specifically, the first metasurface section MS1 ​​is provided on the first surface, and the second metasurface section MS2 and the third metasurface section MS3 are provided on the second surface 22.

[0084] The second metasurface section MS2 focuses light having a wavelength λ2 onto the first metasurface section MS1. The third metasurface section MS3 focuses light having a wavelength λ3 onto the first metasurface section MS1. In this way, the third metasurface section MS3 may focus light having a wavelength λ3, which is different from the wavelength λ2 of the light focused by the second metasurface section MS2 onto the first metasurface section MS1, onto the first metasurface section MS1.

[0085] In this case, the same image is formed on the pixel region 13 by each of the second metasurface section MS2 and the third metasurface section MS3. Therefore, the same image is projected onto the pixel region 13 at wavelengths corresponding to each of the second metasurface section MS2 and the third metasurface section MS3.

[0086] Note that the imaging device 10 according to the fourth embodiment may be an optical system that allows easy wavelength selection as described above, or may be an optical system that images polarized light having different polarization states onto the pixel region 13. Specifically, the second metasurface unit MS2 may image onto the first metasurface unit MS1 light that has a polarization state different from the polarization state of the light that the third metasurface unit MS3 images onto the first metasurface unit MS1. In other words, the second metasurface unit MS2 and the third metasurface unit MS3 may function as polarizing filters that transmit specific polarized light.

[0087] It is difficult to simultaneously form the metasurface MS on both surfaces (first surface 21 and second surface 22) of the metalens substrate 2a. Therefore, after forming the metasurface MS on the first surface 21, a step (S2) of bonding the imaging substrate 1 and the opposing substrate 2 may be performed to form a vacuum-sealed internal space Q. After forming the internal space Q, the metasurface MS may be formed on the second surface 22. In this way, the imaging device 10 shown in Figures 22 and 23 can be obtained.

[0088] <Effects> According to the imaging device 10, the metasurface MS is provided on the first surface 21 and the second surface 22.

[0089] In this way, the imaging device 10 may be a two-stage metalens optical system. In this way, different optical functions can be imparted to the metasurfaces MS provided on the first surface 21 and the second surface 22. Specifically, the metasurface MS provided on the first surface 21 may function as an imaging lens, and the metasurface MS provided on the second surface 22 may function as a transmission filter.

[0090] Embodiment 5. <Configuration of imaging device> Fig. 24 is a schematic cross-sectional view of an imaging device 10 according to embodiment 5. Fig. 24 corresponds to Fig. 1. The imaging device 10 shown in Fig. 24 basically has the same configuration as the imaging device 10 shown in Figs. 1 to 5 and can obtain the same effects, but differs in that the metasurface MS is disposed between the first surface 21 and the second surface 22 as viewed from the imaging substrate 1.

[0091] Specifically, a recess 23 is formed in the first surface 21. The recess 23 is formed by wet etching. The recess 23 is formed by an inclined surface and a bottom surface. The inclined surface is continuous with the first surface 21 and the bottom surface. The inclined surface is a surface that is inclined with respect to the first surface 21. The bottom surface is continuous with the inclined surface. The bottom surface is the surface of the recess 23 that is farthest from the first surface 21.

[0092] The metasurface MS is disposed on the bottom surface of the recess 23. The depth of the recess 23 (the distance h2 from the first surface 21 to the bottom surface of the recess 23) is adjusted to match the focal length of the light. In addition, the transmittance of light passing through the metalens substrate 2a is improved.

[0093] <Effects> According to the imaging device 10, the opposing substrate 2 has a first surface 21 and a second surface 22. The first surface 21 faces the imaging substrate 1. The second surface 22 is located opposite the first surface 21. The metasurface MS is disposed between the first surface 21 and the second surface 22 when viewed from the imaging substrate 1.

[0094] In this way, the focal length of light can be adjusted by adjusting the depth of recess 23 (distance h2 from first surface 21 to the bottom surface of recess 23). In addition, the transmittance of light passing through metalens substrate 2a is improved.

[0095] Sixth Embodiment <Configuration of Imaging Device> Fig. 25 is a schematic cross-sectional view of an imaging device 10 according to a sixth embodiment. Fig. 25 corresponds to Fig. 1. The imaging device 10 shown in Fig. 25 basically has the same configuration as the imaging device 10 shown in Figs. 1 to 5 and can obtain the same effects, but differs in that a metasurface MS is provided on an imaging substrate 1.

[0096] Specifically, the metasurface MS is provided on the second main surface 12 of the imaging substrate 1. As shown in Figure 25, in the imaging device 10 according to the sixth embodiment, the second main surface 12 is the surface onto which the incident light IL is incident.

[0097] The opposing substrate 2 is not a metalens substrate 2a but a circuit substrate 2b electrically connected to the imaging substrate 1. In this way, the area of ​​the imaging device 10 can be reduced.

[0098] 25 , an internal space Q is formed by the imaging substrate 1, the counter substrate 2 (circuit substrate 2b), and the spacer 3. From a different perspective, the pixel region 13 is vacuum-sealed by being surrounded by the first main surface 11 of the imaging substrate 1, the first surface 21 of the counter substrate 2 (circuit substrate 2b), and the spacer 3. In this way, in the imaging device 10 according to the sixth embodiment, the circuit substrate 2b functions as a lid substrate.

[0099] Wiring pads 61 and 62 are formed on the surfaces of the imaging substrate 1 and the circuit substrate 2b, respectively. The wiring pads 61 and 62 are electrically connected to electrical signal lines arranged on the surface or inside the substrates.

[0100] The imaging device 10 includes metal wiring pillars 6. Wiring pads 61 are provided on the first main surface 11 of the imaging substrate 1. Wiring pads 62 are provided on the first surface 21 of the circuit board 2b. The wiring pads 61 and 62 are electrically connected by the metal wiring pillars 6. In this way, the metal wiring pillars 6 electrically connect the imaging substrate 1 and the counter substrate 2 (circuit board 2b).

[0101] The material constituting the metal wiring pillars 6 may be a material with low electrical resistance, and may be the same as the material constituting the solder layer 31 or the plating layers 32 a, 32 b. The material constituting the metal wiring pillars 6 may be gold (Au), copper (Cu), or indium (In).

[0102] It is difficult to simultaneously form the metasurface MS and the hollow pixel region 13 on the imaging substrate 1. Therefore, after forming the pixel region 13 on the first main surface 11, a step (S2) of bonding the imaging substrate 1 and the opposing substrate 2 (circuit substrate 2b) may be performed to form a vacuum-sealed internal space Q. After forming the internal space Q, the metasurface MS may be formed on the second main surface 12. In this way, the imaging device 10 shown in FIG. 25 can be obtained.

[0103] <Effects> The imaging device 10 includes metal wiring pillars 6. The metal wiring pillars 6 electrically connect the imaging substrate 1 and the counter substrate 2. The imaging substrate 1 has a first main surface 11 and a second main surface 12. The first main surface 11 faces the counter substrate 2. The second main surface 12 is located opposite the first main surface 11. The pixel region 13 is provided on the first main surface 11. The metasurface MS is provided on the second main surface 12.

[0104] By doing so, it is possible to reduce the area of ​​the imaging device 10. Seventh Embodiment <Configuration of Imaging Device> Fig. 26 is a schematic cross-sectional view of an imaging device 10 according to a seventh embodiment. Fig. 26 corresponds to Fig. 1. Fig. 27 is a schematic plan view of the opposing substrate 2 in the imaging device 10 according to the seventh embodiment. Fig. 27 corresponds to Fig. 3. The imaging device 10 shown in Figs. 26 and 27 basically has the same configuration as the imaging device 10 shown in Figs. 1 to 5 and can obtain the same effects, but differs in that a circuit portion 63 is formed on the first surface 21 of the metalens substrate 2a.

[0105] 27 , the circuit section 63 is connected to wiring pads 61 provided on the first surface 21 via wiring 64. The wiring pads 61 provided on the first surface 21 and the wiring pads 62 provided on the first main surface 11 are electrically connected by metal wiring pillars 6. In this way, the circuit section 63 is electrically connected to the imaging substrate 1.

[0106] 26 , the circuit unit 63 is disposed at a position different from the metasurface MS on the first surface 21. As shown in FIG. 26 , the circuit unit 63 does not have to be disposed within the internal space Q, but may be disposed within the internal space Q.

[0107] In this way, by providing the circuit section 63 on the metalens substrate 2a, the area of ​​the first surface 21 can be effectively utilized, and the imaging device 10 can be made smaller.

[0108] <Operation and Effect> According to the imaging device 10, the opposing substrate 2 (metalens substrate 2 a) has a first surface 21. The first surface 21 faces the imaging substrate 1. A circuit section 63 is formed on the first surface. The circuit section 63 is electrically connected to the imaging substrate 1.

[0109] In this way, by providing the circuit section 63 on the metalens substrate 2a, the area of ​​the first surface 21 can be effectively utilized, and the imaging device 10 can be made smaller.

[0110] Embodiment 8. <Configuration of Imaging Device> Fig. 28 is a schematic cross-sectional view of an imaging device 10 according to embodiment 8. Fig. 28 corresponds to Fig. 1. The imaging device 10 shown in Fig. 28 basically has the same configuration as the imaging device 10 shown in Figs. 1 to 5 and can obtain the same effects, but differs in that the plating layer 32a is directly connected to the imaging substrate 1 and the counter substrate 2.

[0111] Specifically, the spacer 3 may be configured only of the plating layer 32 a without including the solder layer 31. That is, in the imaging device 10 according to the eighth embodiment, the plating layer 32 a may be directly connected to the imaging substrate 1 or directly connected to the counter substrate 2.

[0112] The height of the plating layer 32a may be flattened on a nanoscale, so that the first main surface 11 of the substrate (particularly the imaging substrate 1 on which wiring is provided) that is the base of the plating layer 32a may be flattened.

[0113] The plating layer 32a may be directly bonded to the imaging substrate 1 and the opposing substrate 2 at low temperatures using a vacuum chamber, or the plating layer 32a may be directly bonded to the imaging substrate 1 and the opposing substrate 2 by a surface activated room temperature bonding method using an argon (Ar) beam or the like.

[0114] Since the imaging substrate 1 and the opposing substrate 2 are joined by the plating layer 32a, the focal length of light can be adjusted with high precision.

[0115] <Operation and Effect> According to the imaging device 10 , the plating layer 32 a is directly connected to the imaging substrate 1 and the counter substrate 2 .

[0116] In this way, the focal length of light can be adjusted with high precision. Ninth Embodiment <Configuration of Imaging Device> Figure 29 is a schematic cross-sectional view of an imaging device 10 according to a ninth embodiment. Figure 29 corresponds to Figure 1. The imaging device 10 shown in Figure 29 basically has the same configuration as the imaging device 10 shown in Figures 1 to 5 and can achieve the same effects, but differs in that it is made of a material that undergoes an electronic phase transition when a voltage is applied to the metasurface MS.

[0117] The material that undergoes an electronic phase transition when a voltage is applied may be, for example, a lanthanoid (LN) compound, such as vanadium dioxide (VO ２ ) or a Mott insulator. Materials that undergo an electronic phase transition when a voltage is applied change their dielectric constant when an external voltage is applied. This change in dielectric constant adjusts the focal length.

[0118] 29 , the metasurface MS is electrically connected to a wiring pad 61 via a wiring 64. The wiring 64 is disposed inside the metalens substrate 2a. The wiring pad 61 provided on the first surface 21 and the wiring pad 62 provided on the first main surface 11 are electrically connected by a metal wiring pillar 6. An external power source 65 is connected to the wiring pad 62. In this way, a voltage is applied to the metasurface MS from the outside.

[0119] In the imaging device 10 used as a thermal infrared imaging device, there is variation in the output of the pixel region 13. Therefore, the imaging device 10 requires a shutter to set the output when exposed to a blackbody surface with a uniform temperature as a reference.

[0120] In the imaging device 10 according to the ninth embodiment, applying a voltage to the metasurface MS can blur the focus of light. Furthermore, applying a voltage to the metasurface MS can impart the metasurface MS with the optical function of reflecting infrared light. In this way, the metalens substrate 2 a functions as a shutter, thereby providing an imaging device 10 that does not require a shutter.

[0121] <Method of Manufacturing Image Capturing Device> A method of manufacturing the image capturing device 10 according to the ninth embodiment will now be described. Figures 30 to 35 are schematic cross-sectional views showing steps of the method of manufacturing the image capturing device 10 according to the ninth embodiment.

[0122] First, a step (S1) is performed to prepare a wafer-level imaging substrate 1 and an opposing substrate 2. The opposing substrate 2 prepared in this step (S1) will be described. First, as shown in FIG. 30 , a thin substrate is prepared on which a metalens substrate 2a is formed as the opposing substrate 2.

[0123] A wiring layer 60 for applying a voltage to the metasurface MS (described later) is formed on the surface (first surface 21) of the thin substrate. Specifically, the wiring layer 60 is formed by depositing a film over the entire surface of the thin film substrate. Next, the deposited wiring layer 60 is patterned.

[0124] Next, a step of forming an electronic phase transition layer 70 is performed. In this step, as shown in FIG. 31 , the electronic phase transition layer 70 is formed in the region exposed on the first surface 21 from the wiring layer 60. An electronic phase transition material is deposited by sputtering or the like on the wiring layer 60, which has been formed and patterned, and on the first surface 21 exposed from the wiring layer 60. Next, the deposited electronic phase transition material is patterned to form the electronic phase transition layer 70 shown in FIG. 31 . The electronic phase transition layer 70 is disposed on a portion of the patterned wiring layer 60 and on the first surface 21 exposed from the wiring layer 60.

[0125] Next, the step of forming the insulating layer 80 is performed. In this step, as shown in FIG. 32 , the insulating layer 80 is formed on the patterned wiring layer 60. The insulating layer 80 is formed to electrically insulate the spacer 3 from either the wiring layer 60 or the electronic phase transition layer 70. By patterning the insulating layer 80, a portion of the wiring layer 60 is exposed from the insulating layer 80. In this manner, as shown in FIG. 32 , the portion of the wiring layer 60 exposed from the insulating layer 80 is formed as a wiring pad 61.

[0126] The material that constitutes the insulating layer 80 is silicon oxide (SiO ２ ) or silicon nitride (SiN).

[0127] In this manner, the counter substrate 2 is prepared. A patterned power supply layer 4 may be formed on the surface of the counter substrate 2 (the insulating layer 80, the electronic phase transition layer 70, and the surface of the wiring layer 60 exposed from the insulating layer 80).

[0128] Next, a plating layer 32a may be formed using a manufacturing method similar to that of the imaging device 10 according to embodiment 1. Specifically, the step of forming a first photoresist 51 in the manufacturing method of the imaging device 10 according to embodiment 1 is performed. Next, a step of forming a plating layer 32a is performed. In this step, the metal wiring pillar 6 may be formed simultaneously with the plating layer 32a and the solder layer 31. The plating layer 32a and the solder layer 31 are disposed on the insulating layer 80. The metal wiring pillar 6 is disposed on the wiring pad 61 (on the wiring layer 60 exposed from the insulating layer 80). Next, a step of removing the first photoresist 51 is performed. In this manner, the plating layer 32a, the solder layer 31, and the metal wiring pillar 6 are formed, as shown in FIG. 33 .

[0129] Next, the step of forming a second photoresist 52 is performed. In this step, the second photoresist 52 is formed on the insulating layer 80, the electronic phase transition layer 70, the metal wiring pillars 6, and the solder layer 31. As shown in FIG. 34 , openings 52h are formed in the second photoresist 52 so that portions of the electronic phase transition layer 70 are exposed from the second photoresist 52. The electronic phase transition layer 70 is exposed from the second photoresist 52 in the regions where the openings 52h are formed.

[0130] Next, a step of forming a metasurface MS is performed. In this step, the metasurface MS is formed on the electronic phase transition layer 70. Specifically, the electronic phase transition layer 70 exposed through the opening 52h in the second photoresist 52 is etched using a deep reactive-ion etching (DRIE) apparatus.

[0131] Next, a step of removing the second photoresist 52 is performed. In this manner, the counter substrate 2 provided with the metasurface MS formed of a material that undergoes an electronic phase transition when a voltage is applied is prepared, as shown in FIG.

[0132] Next, in the manufacturing method of the imaging device 10 according to embodiment 1, the process of bonding the imaging substrate 1 and the opposing substrate 2 at the wafer level (S2) and the process of dicing the imaging substrate 1 and the opposing substrate 2 (S3) are carried out sequentially.

[0133] <Effects> According to the imaging device 10, the metasurface MS is formed from a material that undergoes an electronic phase transition when a voltage is applied.

[0134] In this way, the metalens substrate 2a functions as a shutter, so that an imaging device 10 that does not require a shutter can be obtained.

[0135] Tenth Embodiment <Configuration of Imaging Device> Figure 36 is a schematic cross-sectional view of an imaging device 10 according to a tenth embodiment. Figure 36 corresponds to Figure 1. Figure 37 is a partially enlarged schematic cross-sectional view of region XXXVII in Figure 36. Figure 37 corresponds to Figure 2. The imaging device 10 shown in Figures 36 to 39 basically has the same configuration as the imaging device 10 shown in Figures 1 to 5 and can achieve the same effects, but differs in that the shape of the multiple meta-atoms MA that form the metasurface MS is three-dimensional. Specifically, the meta-atoms MA that form the metasurface MS may be meta-atoms MA with non-uniform widths. The metasurface MS may be formed by stacking meta-atoms MA with different widths.

[0136] 36, the metasurface MS includes a first metasurface section MS1 ​​and a second metasurface section MS2. In the imaging device 10 according to the tenth embodiment, the second metasurface section MS2 is formed on the first metasurface section MS1.

[0137] 37, the first metasurface portion MS1 ​​is formed by a plurality of first meta-atoms MA1. The second metasurface portion MS2 is formed by a plurality of second meta-atoms MA2. The second meta-atoms MA2 are disposed on the first meta-atoms MA1. The width W2 of the second meta-atoms MA2 is different from and smaller than the width W1 of the first meta-atoms MA1.

[0138] The central axis A2 of the second meta-atom MA2 in the width direction may be at the same position as the central axis A1 of the first meta-atom MA1, or may be at a different position as shown in FIG.

[0139] In this way, the metasurface MS is formed by two stages of metasurface sections. The metasurface MS may be formed by multiple stages of metasurface sections, or may be formed by three or more stages of metasurface sections.

[0140] The first metasurface section MS1 ​​forms an image of light having a wavelength λ1 on the pixel region 13. The second metasurface section MS2 forms an image of light having a wavelength λ2 on the pixel region 13. In this way, the second metasurface section MS2 forms an image of light having a wavelength λ2 on the pixel region 13, which is different from the wavelength λ1 of the light formed on the pixel region 13 by the first metasurface section MS1.

[0141] In this case, the same image is formed on the pixel region 13 by each of the first metasurface section MS1 ​​and the second metasurface section MS2. Therefore, the same image is projected onto the pixel region 13 at wavelengths corresponding to each of the first metasurface section MS1 ​​and the second metasurface section MS2.

[0142] The imaging device 10 according to the tenth embodiment may be an optical system that images polarized light having different polarization states on the pixel region 13. Specifically, the second metasurface unit MS2 may image light having a polarization state different from the polarization state of the light that the first metasurface unit MS1 images on the pixel region 13. In other words, the first metasurface unit MS1 and the second metasurface unit MS2 may function as polarizing filters that transmit specific polarized light.

[0143] In this way, a metasurface MS can be formed on one surface (first surface 21) of the metalens substrate 2a, to which one of the optical functions such as imaging, spectroscopy, or polarization is selectively imparted.

[0144] <Method of Manufacturing Image Capturing Device> A method of manufacturing the image capturing device 10 according to the tenth embodiment will now be described. Figures 38 and 39 are schematic cross-sectional views showing one step of the method of manufacturing the image capturing device according to the tenth embodiment. Figure 38 corresponds to Figure 12. Figure 39 corresponds to Figure 13.

[0145] First, in the step (S1) of preparing the imaging substrate 1 and the opposing substrate 2 at the wafer level, the same steps as those shown in FIGS. 7 to 11 are carried out.

[0146] Next, a step of forming a second photoresist 52 is performed. In this step, as shown in FIG. 38 , the second photoresist 52 is formed on the first surface 21 and on the solder layer 31. The shape of the second photoresist 52 disposed on the first surface 21 is three-dimensional. Specifically, an opening 52h is provided in the second photoresist 52 so that a portion of the first surface 21 is exposed from the second photoresist 52. The first surface 21 is exposed from the second photoresist 52 in the region where the opening 52h is formed.

[0147] The shape of the opening 52h is three-dimensional. Specifically, the width of the inner periphery of the opening 52h is not uniform to match the shape of the meta-atom MA. Such a three-dimensional second photoresist 52 can be formed using nanoimprinting, grayscale photoresist, an electron beam lithography system, or the like.

[0148] Next, a step of forming a metasurface MS is performed. In this step, as shown in FIG. 39 , a metasurface MS is formed on the first surface 21. The meta-atoms MA (first meta-atom MA1 and second meta-atom MA2) are formed to match the shape of the second photoresist 52. Therefore, the etching method may be selected based on the etching rate of the second photoresist 52 and the metalens substrate 2a. Specifically, a deep reactive-ion etching (DRIE) device or a reactive-ion etching (RIE) device is used to etch the second photoresist 52 and the metalens substrate 2a exposed through the openings 52h. In this manner, a metasurface MS formed by multiple three-dimensionally shaped meta-atoms can be formed, as shown in FIGS. 36 and 37 .

[0149] Next, a step similar to the step shown in Fig. 14 is carried out. Specifically, a step of removing the second photoresist 52 is carried out.

[0150] Next, the step (S2) of bonding the imaging substrate 1 and the opposing substrate 2 at the wafer level and the step (S3) of dicing the imaging substrate 1 and the opposing substrate 2 in the manufacturing method of the imaging device 10 according to the first embodiment are performed in this order. In this manner, the imaging device 10 shown in Figs. 36 and 37 is manufactured.

[0151] Figure 40 is a schematic cross-sectional view of a first modified example of the metasurface MS in the imaging device 10 according to the tenth embodiment. Figure 40 corresponds to Figure 37. If the shape of the meta-atom MA is three-dimensional, the shape of the meta-atom MA in the cross section of the meta-atom MA may be, for example, a trapezoid. Specifically, the meta-atom MA has an upper surface region 24 and a lower surface region 25.

[0152] In the meta-atom MA, the upper surface region 24 is, for example, the region farthest from the first surface 21. In the meta-atom MA, the lower surface region 25 is, for example, the region disposed on the first surface 21. The width W4 in the upper surface region 24 is smaller than the width W3 in the lower surface region 25. The side of the meta-atom MA is, for example, inclined with respect to the first surface 21, and the width of the meta-atom MA changes continuously from width W3 to width W4. In this way, the meta-atom MA may have a non-uniform width. A meta-atom MA as shown in FIG. 40 may be formed using the manufacturing method of the imaging device 10 of this embodiment 10.

[0153] FIG. 41 is a schematic plan view of a second modification of the metasurface MS in the imaging device 10 according to the tenth embodiment. FIG. 42 is a schematic cross-sectional view of the metasurface MS taken along line XLII-XLII in FIG. 41 . FIG. 42 corresponds to FIG. 40 . As shown in FIGS. 41 and 42 , a recess 26 may be formed in each of the multiple meta-atoms MA forming the metasurface MS. The recess 26 is formed in the upper surface region 24. The recess 26 may be formed in the center of the meta-atom MA. In this manner, the meta-atom MA is cylindrical. The meta-atom MA may be cylindrical as shown in FIG. 41 or rectangular. The depth of the recess 26 may be the same as the height h of the meta-atom MA, or may be smaller than the height h of the meta-atom MA as shown in FIG. 42 .

[0154] In this way, when the incident light IL is incident, resonance can occur in the metasurface MS, and as a result, the imaging device 10 can be used effectively for a wide range of wavelengths.

[0155] <Effects> According to the imaging device 10, the shape of the multiple meta-atoms MA that form the metasurface MS is three-dimensional.

[0156] In this way, one side of the opposing substrate 2 may be given the optical functions of spectroscopic and imaging, or the optical functions of polarizing and imaging, or both optical functions.

[0157] According to the imaging device 10, a recess 26 is formed in each of the multiple meta-atoms MA that form the metasurface MS.

[0158] This allows resonance to occur in the metasurface MS, making it possible to effectively use the imaging device 10 for a wide range of wavelengths.

[0159] Embodiment 11. <Configuration of Imaging Device> Fig. 43 is a schematic cross-sectional view of an imaging device 10 according to embodiment 11. Fig. 43 corresponds to Fig. 1. Fig. 44 is a partially enlarged schematic cross-sectional view of region XLIV in Fig. 43. Fig. 44 corresponds to Fig. 2. The imaging device 10 shown in Figs. 43 and 44 basically has the same configuration as the imaging device 10 shown in Figs. 1 to 5 and can obtain the same effects, but differs in that the opposing substrate 2 includes a thin film layer 27.

[0160] Thin film layer 27 is disposed inside metalens substrate 2a (counter substrate 2). The thickness of thin film layer 27 may be 10 nm or more and 900 nm or less, 100 nm or more and 800 nm or less, or 200 nm or more and 700 nm or less.

[0161] As described above, the material constituting the metalens substrate 2a (counter substrate 2) is, for example, silicon (Si). The material constituting the thin film layer 27 may be different from the material constituting the metalens substrate 2a (counter substrate 2), and may be, for example, silicon oxide (SiO ２ ) or silicon nitride (SiN).

[0162] The thin film layer 27 functions as an etching stop layer in the process of forming the metasurface MS. Therefore, the thin film layer 27 is positioned in contact with the multiple meta-atoms MA that form the metasurface MS. This improves the uniformity and reproducibility of the shape of the meta-atoms MA in the process of forming the metasurface MS.

[0163] <Method of Manufacturing Image Capturing Device> A method of manufacturing the image capturing device 10 according to the eleventh embodiment will now be described. Figures 45 to 49 are schematic cross-sectional views showing a step of the method of manufacturing the image capturing device according to the eleventh embodiment. Figure 49 corresponds to Figure 13 .

[0164] First, a step (S1) is carried out in which a wafer-level imaging substrate 1 and a counter substrate 2 are prepared. The counter substrate 2 prepared in this step (S1) will be described. First, as shown in FIG. 45 , a first thin substrate is prepared as a first layer 41. The first layer 41 forms a metalens substrate 2a as the counter substrate 2. The first layer 41 is a wafer-level silicon substrate.

[0165] 46, a thin film layer 27 is formed on the first thin substrate as the first layer 41. A material different from the material constituting the first layer 41 is deposited on the first layer 41 by thermal oxidation or CVD (Chemical Vapor Deposition), thereby forming the thin film layer 27. The material constituting the thin film layer 27 is, for example, silicon oxide (SiO ２ ), or silicon nitride (SiN).

[0166] 47, a second thin substrate forming a second layer 42 is bonded to the thin film layer 27. The material constituting the second layer 42 is different from the material constituting the thin film layer 27. The material constituting the second thin substrate as the second layer 42 may be the same as the material constituting the first thin substrate as the first layer 41, or may be different from the material constituting the first thin substrate.

[0167] As will be described later, a metasurface MS is formed on the second layer 42. Therefore, the material constituting the second thin substrate may be a semiconductor material with high transmittance for long-wavelength infrared light, and specifically, the material constituting the second thin substrate may be silicon (Si), germanium (Ge), zinc sulfide (ZnS), boron nitride (BN), etc. The boron nitride constituting the second thin substrate may be a hexagonal system (hexagonal boron nitride).

[0168] Next, as shown in FIG. 48 , the second thin substrate is thinned. By thinning the second thin substrate, a second layer 42 having a first surface 21 is formed. The second thin substrate may be thinned so that the thickness of the second layer 42 is equivalent to the height h of the meta-atom MA. That is, the second thin substrate may be thinned to match the wavelength λ of the light to be detected (incident light IL), such as long-wavelength infrared light, so that the thickness of the second layer 42 is close to the wavelength λ of the light to be detected. For example, the second thin substrate may be thinned using chemical mechanical polishing (CMP). In this manner, the opposing substrate 2 including the thin film layer 27 may be prepared.

[0169] Next, steps similar to those shown in Figures 7 to 12 are performed. Next, a step of forming a metasurface MS is performed. In this step, as shown in Figure 49, a metasurface MS is formed on the first surface 21. In this step (the step of forming the metasurface MS), the thin film layer 27 functions as an etching stop layer. Therefore, the second layer 42 is etched from the first surface 21 to the region where the thin film layer 27 is to be formed. In this way, multiple meta-atoms MA are formed with improved shape uniformity and reproducibility.

[0170] Next, a step similar to the step shown in Fig. 14 is carried out. Specifically, a step of removing the second photoresist 52 is carried out.

[0171] Next, the step (S2) of bonding the imaging substrate 1 and the opposing substrate 2 at the wafer level and the step (S3) of dicing the imaging substrate 1 and the opposing substrate 2 in the manufacturing method of the imaging device 10 according to the first embodiment are performed in this order. In this manner, the imaging device 10 shown in Figs. 43 and 44 is manufactured.

[0172] Embodiment 12. <Configuration of imaging device> Fig. 50 is a schematic cross-sectional view of an imaging device 10 according to embodiment 12. Fig. 50 corresponds to Fig. 43. The imaging device 10 shown in Fig. 50 basically has the same configuration as the imaging device 10 shown in Figs. 43 and 44 and can obtain the same effects, but differs in that a voltage can be applied to the thin film layer 27.

[0173] Specifically, the material constituting the thin film layer 27 may be a material that undergoes an electronic phase transition when a voltage is applied. Examples of the material that undergoes an electronic phase transition when a voltage is applied include a lanthanoid (LN) compound, and vanadium dioxide (VO ２ ) or may be a Mott insulator.

[0174] The material constituting the thin film layer 27 may be a material whose refractive index changes when a voltage is applied, and may be, for example, a two-dimensional material such as graphene, transition metal dichalcogenide (TMD), or black phosphorus.

[0175] The thin film layer 27 is electrically connected to a wiring pad 61. The thin film layer 27 may be directly connected to the wiring pad 61, or may be connected to the wiring pad 61 via a wiring 64 as shown in FIG. 50 . The wiring 64 is disposed inside the metalens substrate 2a. The wiring pad 61 provided on the first surface 21 and the wiring pad 62 provided on the first main surface 11 are electrically connected by a metal wiring pillar 6. An external power source 65 is connected to the wiring pad 62. In this manner, a voltage is applied to the thin film layer 27 from the outside.

[0176] In this way, by applying a voltage to the thin film layer 27, it is possible to impart the optical function of reflecting infrared rays to the thin film layer 27. Furthermore, by applying a voltage to the thin film layer 27, the refractive index of the thin film layer 27 changes. In this way, it is possible to adjust the position of the focal point of light.

[0177] In the eleventh and twelfth embodiments, the metasurface MS is provided on the opposing substrate 2, which is the metalens substrate 2a, and the thin film layer 27 is included in the opposing substrate 2. However, the metasurface MS may be provided on the imaging substrate 1, and the imaging substrate 1 may include the thin film layer 27. When the imaging substrate 1 includes the thin film layer 27, the material constituting the thin film layer 27 may be different from the material constituting the imaging substrate 1.

[0178] <Method of Manufacturing Image Capturing Device> A method of manufacturing the image capturing device 10 according to the twelfth embodiment will now be described. Figures 51 to 54 are schematic cross-sectional views showing a step in the method of manufacturing the image capturing device according to the twelfth embodiment.

[0179] First, a step (S1) is performed to prepare a wafer-level imaging substrate 1 and an opposing substrate 2. The opposing substrate 2 prepared in this step (S1) will be described. First, steps similar to those shown in Figs. 45 to 48 are performed.

[0180] The thin film layer 27, which is a two-dimensional material such as an electron transition material or graphene, is formed using sputtering or CVD. Specifically, when the material constituting the thin film layer 27 is a two-dimensional material such as graphene, graphene is grown on copper foil using thermal CVD, and then transferred onto the first layer 41, which is the target, by wet transfer. Note that graphene may also be grown directly on the first layer 41, which is the target. In this manner, the thin film layer 27 formed of graphene may be disposed on the first layer 41. Any method may be used to transfer the two-dimensional material. In this manner, the counter substrate 2 is prepared.

[0181] Next, a step of forming an insulating layer 80 is performed. In this step, as shown in FIG. 51 , the insulating layer 80 is formed on the second layer 42 of the opposing substrate 2. The insulating layer 80 is formed to electrically insulate the spacer 3 from the thin film layer 27. By patterning the insulating layer 80, a portion of the second layer 42 is exposed from the insulating layer 80.

[0182] The material that constitutes the insulating layer 80 is silicon oxide (SiO ２ ) or silicon nitride (SiN).

[0183] Next, a step of etching the portion of the second layer 42 exposed from the insulating layer 80 is performed. In this step, as shown in Fig. 53, the portion of the second layer 42 is etched to form an opening 42h in the second layer 42. In this way, the thin film layer 27 is exposed from the second layer 42 in the region where the opening 42h is formed.

[0184] In addition, in the second layer 42, a photoresist may be formed on the area where the metasurface MS is to be formed, so that the area exposed from the insulating layer 80 where the metasurface MS is to be formed is not etched.

[0185] In this way, the counter substrate 2 is prepared. A patterned power supply layer 4 may be formed on the surface of the counter substrate 2 (the insulating layer 80 and the surface of the thin film layer 27 exposed from the insulating layer 80).

[0186] Next, using a manufacturing method similar to that of the imaging device 10 according to the ninth embodiment, a plating layer 32a, a solder layer 31, a metal wiring pillar 6, and a second photoresist 52 are formed as shown in Fig. 54. The metal wiring pillar 6 is formed on the thin film layer 27 exposed from the second layer 42 in the region where the opening 42h is formed.

[0187] Next, a step of forming a metasurface MS is performed. In this step, as shown in FIG. 54, a metasurface MS is formed on the first surface 21. In this step (the step of forming the metasurface MS), the thin film layer 27 functions as an etching stop layer. Therefore, the second layer 42 is etched from the first surface 21 to the region where the thin film layer 27 is to be formed. In this way, multiple meta-atoms MA are formed with improved shape uniformity and reproducibility.

[0188] Next, a step similar to the step shown in Fig. 14 is carried out. Specifically, a step of removing the second photoresist 52 is carried out.

[0189] Next, the step (S2) of bonding the imaging substrate 1 and the opposing substrate 2 at the wafer level and the step (S3) of dicing the imaging substrate 1 and the opposing substrate 2 in the manufacturing method of the imaging device 10 according to the first embodiment are performed in this order. In this manner, the imaging device 10 shown in Fig. 50 is manufactured.

[0190] <Effects> According to the near-field thermal radiation power generation element 100, the metasurface MS is provided on the counter substrate 2. The counter substrate 2 includes a thin film layer 27. The material constituting the thin film layer 27 is different from the material constituting the counter substrate 2.

[0191] In this way, the thin film layer 27 functions as an etching stop layer, which improves the uniformity and reproducibility of the shape of the meta-atoms MA in the process of forming the metasurface MS.

[0192] According to the near-field thermal radiation power generation element 100, the metasurface MS is provided on the imaging substrate 1. The imaging substrate 1 includes a thin film layer 27. The material constituting the thin film layer 27 is different from the material constituting the imaging substrate 1.

[0193] In this way, the thin film layer 27 functions as an etching stop layer, which improves the uniformity and reproducibility of the shape of the meta-atoms MA in the process of forming the metasurface MS.

[0194] The embodiments disclosed herein should be considered to be illustrative in all respects and not restrictive. The basic scope of the present disclosure is defined by the claims, not the above description, and is intended to include all modifications within the meaning and scope of the claims.

[0195] 1 Imaging substrate, 2 Counter substrate, 2a Metalens substrate, 2b Circuit substrate, 3 Spacer, 4 Power supply layer, 6 Metal wiring pillar, 10 Imaging device, 11 First main surface, 12 Second main surface, 13 Pixel region, 21 First surface, 22 Second surface, 23, 26 Recess, 24 Upper surface region, 25 Lower surface region, 27 Thin film layer, 31 Solder layer, 32a, 32b Plating layer, 41 First layer, 42 Second layer, 51 First photoresist, 51h, 52h, 42h Opening, 52 Second photoresist, 60 Wiring layer, 61 Wiring pad, 62 Wiring pad, 63 Circuit portion, 64 Wiring, 65 External power supply, 70 Electronic phase transition layer, 80 Insulating layer, A1, A2 Central axis, DL Dicing line, h2 Distance, IL Incident light, MA Meta-atom, MA1 First meta-atom, MA2 second meta-atom, MS metasurface, MS1 first metasurface section, MS2 second metasurface section, MS3 third metasurface section, Q internal space, SP, SP1, SP2 distance, t distance, W1 width, W2 width, W3 width, W4 width, λ, λ1, λ2, λ3 wavelengths.

Claims

1. An imaging device comprising an imaging substrate including a pixel area and an opposing substrate facing the imaging substrate, wherein a metasurface is provided on either the imaging substrate or the opposing substrate, and the imaging substrate is spaced apart from the opposing substrate by a spacer including a plating layer.

2. The imaging device described in claim 1, wherein the shape of the multiple meta-atoms forming the metasurface is columnar.

3. An imaging device as described in claim 1 or claim 2, wherein the shape of the multiple meta-atoms forming the metasurface is concave.

4. An imaging device described in any one of claims 1 to 3, wherein the opposing substrate has a first surface facing the imaging substrate and a second surface positioned opposite the first surface, and the metasurface is provided on the second surface.

5. The imaging device described in claim 4, wherein the metasurface is provided on the first surface and the second surface.

6. An imaging device as described in any one of claims 1 to 5, wherein the metasurface includes a first metasurface section and a second metasurface section, and the second metasurface section images, onto the pixel area, light having a wavelength different from the wavelength of the light that the first metasurface section images onto the pixel area, or light having a polarization state different from the polarization state of the light that the first metasurface section images onto the pixel area.

7. An imaging device described in any one of claims 1 to 6, wherein the opposing substrate has a first surface facing the imaging substrate and a second surface positioned opposite the first surface, and the metasurface is arranged between the first surface and the second surface as viewed from the imaging substrate.

8. An imaging device as described in any one of claims 1 to 7, comprising metal wiring pillars that electrically connect the imaging substrate and the opposing substrate, the imaging substrate having a first main surface facing the opposing substrate and a second main surface positioned opposite the first main surface, the pixel region being provided on the first main surface, and the metasurface being provided on the second main surface.

9. An imaging device according to any one of claims 1 to 8, wherein the opposing substrate has a first surface facing the imaging substrate, and a circuit section electrically connected to the imaging substrate is formed on the first surface.

10. An imaging device described in any one of claims 1 to 9, wherein the metasurface is formed from a material that undergoes an electronic phase transition when a voltage is applied.

11. The imaging device according to any one of claims 1 to 10, wherein the plating layer is directly connected to the imaging substrate and the opposing substrate.

12. An imaging device according to any one of claims 1 to 11, wherein the pixel region is vacuum-sealed by being surrounded by the imaging substrate, the opposing substrate, and the spacer.

13. An imaging device described in any one of claims 1 to 12, wherein the shape of the multiple meta-atoms forming the metasurface is three-dimensional.

14. An imaging device described in any one of claims 1 to 13, wherein a recess is formed in each of the multiple meta-atoms forming the metasurface.

15. An imaging device described in any one of claims 1 to 14, wherein the metasurface is provided on the opposing substrate, the opposing substrate includes a thin film layer, and the material constituting the thin film layer is different from the material constituting the opposing substrate.

16. An imaging device described in any one of claims 1 to 15, wherein the metasurface is provided on the imaging substrate, the imaging substrate includes a thin film layer, and the material constituting the thin film layer is different from the material constituting the imaging substrate.

17. A method for manufacturing an imaging device, comprising: a step of preparing an imaging substrate and an opposing substrate at a wafer level; a step of bonding the imaging substrate and the opposing substrate; and a step of dicing the imaging substrate and the opposing substrate after the bonding step is performed; wherein in the preparing step, the imaging substrate includes a pixel region, and a metasurface is provided on either the imaging substrate or the opposing substrate, and in the bonding step, the opposing substrate and the imaging substrate are bonded by a spacer including a plating layer.

Images