Solid-state imaging device

Abstract

Provided is a solid-state imaging device that makes it possible to reduce color mixing and improve the light absorptivity in a photoelectric conversion element. The pixel includes: a first periodic structure including a plurality of first layers and a plurality of second layers having a refractive index lower than that of the plurality of first layers and in at least one of the plurality of pixels, the plurality of first layers and the plurality of second layers of the first periodic structure are arranged such that a volume ratio of the plurality of first layers is greater than a volume ratio of the plurality of second layers in a pixel center portion in a horizontal direction. The volume ratio of the plurality of first layers decreases from the pixel center portion toward the pixel peripheral portion in the horizontal direction.

Description

[0001] This application claims the benefit of Japanese Patent Application No. 2024-032693 filed in the Japan Patent Office on March 5, 2024, the disclosure of which is incorporated herein by reference in its entirety. Technical Field

[0002] The inventive concept relates to a solid-state imaging device. Background Art

[0003] Solid-state imaging devices are installed in various mobile terminals such as digital cameras or mobile phones.

[0004] Referring to Japanese Patent Laid-Open No. 2022-108744, a solid-state imaging device includes a photoelectric conversion unit configured to generate and accumulate charge according to the amount of incident light, an on-chip lens installed on one side of the photoelectric conversion unit where light is incident, and a wiring layer installed on the other side of the photoelectric conversion unit.

[0005] In this solid-state imaging device, a concave-convex annular portion (zone plate) is positioned on one side of the photoelectric conversion unit. The annular portion comprises a first annular portion that includes a semiconductor region (a portion of a P-type semiconductor region), and a second annular portion that includes a fixed charge film and an insulating film arranged around the first annular portion. The concave-convex annular portion collects light incident through an on-chip lens onto the photoelectric conversion unit through a lens effect. Thus, the solid-state imaging device, including the concave-convex annular portion that exhibits a lens effect, can reduce the occurrence of color mixing between pixels. Summary of the Invention

[0006] One of the indicators for evaluating the performance of a solid-state imaging device is the light absorption rate in the photoelectric conversion unit. Since the photoelectric conversion unit has a higher light absorption rate, the solid-state imaging device exhibits high quantum efficiency (photoelectric conversion efficiency).

[0007] As described above, solid-state imaging devices can reduce color mixing by incorporating additional structures (such as a concave-convex annular portion) into the photoelectric conversion unit. However, the solid-state imaging device disclosed in Japanese Patent No. 2022-108744 does not specifically mention improving the quantum efficiency of the photoelectric conversion unit by focusing on research into the structure of the photoelectric conversion unit. Therefore, it can be seen that there is room for further improvement in the quantum efficiency of the photoelectric conversion unit in solid-state imaging devices.

[0008] The inventive concept has been made to solve the above problems, and is to provide a solid-state imaging device that enables color mixing to be reduced and improves light absorption efficiency in a photoelectric conversion unit.

[0009] According to one aspect of the inventive concept, a solid-state imaging device is provided, comprising: a pixel array comprising a plurality of pixels, wherein each of the plurality of pixels comprises: a photoelectric conversion unit configured to convert light into electric charge; an on-chip lens mounted on one side of the photoelectric conversion unit; a wiring layer mounted on the other side of the photoelectric conversion unit; and a first periodic structure mounted on the one side of the photoelectric conversion unit and having periodicity in a horizontal direction perpendicular to the stacking direction of the photoelectric conversion unit, the first periodic structure comprising a plurality of first layers and a plurality of second layers, the plurality of second layers having a refractive index lower than that of the plurality of first layers, and wherein, in at least one of the plurality of pixels, the plurality of first layers and the plurality of second layers of the first periodic structure are arranged so that a volume ratio of the plurality of first layers in a central portion of the pixel is greater than a volume ratio of the plurality of second layers in the central portion of the pixel, and the volume ratio of the plurality of first layers decreases in a horizontal direction from the central portion of the pixel toward a peripheral portion of the pixel.

[0010] In an embodiment, the widths of the plurality of second layers in the horizontal direction may be different from each other, and the first periodic structure may be configured such that a volume ratio of the plurality of first layers decreases from a pixel center portion toward a pixel peripheral portion.

[0011] In an embodiment, depths of the plurality of second layers in the stacking direction may be different from each other, and the first periodic structure may be configured such that a volume ratio of the plurality of first layers decreases from a pixel center portion toward a pixel peripheral portion.

[0012] In an embodiment, the period of the first periodic structure can be set to a specific value based on the wavelength and incident angle of light received by the photoelectric conversion unit, and can include a length smaller than the wavelength of the received light, and enable diffracted light to be generated in the photoelectric conversion unit.

[0013] In an embodiment, the depth of the multiple first layers in the stacking direction and the depth of the multiple second layers in the stacking direction may be equal to the wavelength of light received by the photoelectric conversion unit, and the thickness of the photoelectric conversion unit may be greater than the depth of the multiple first layers and the depth of the multiple second layers.

[0014] In an embodiment, the photoelectric conversion unit may be at least partially covered by a dielectric layer having a refractive index lower than that of the multiple first layers, and the period of the first periodic structure may include a length that enables the diffracted light generated in the photoelectric conversion unit to be completely reflected at the boundary between the photoelectric conversion unit and the dielectric layer.

[0015] In an embodiment, a wiring layer arranged at a position closest to the photoelectric conversion unit in the stacking direction may have a reflective structure that reflects light emitted by the photoelectric conversion unit.

[0016] In an embodiment, the pixel including the first periodic structure may further include: a second periodic structure, installed on the one side of the photoelectric conversion unit and having periodicity in the horizontal direction, and the second periodic structure may include a plurality of third layers and a plurality of fourth layers, the plurality of third layers having a refractive index equal to the refractive index of the plurality of first layers, and the plurality of fourth layers having a refractive index equal to the refractive index of the plurality of second layers.

[0017] In an embodiment, the second periodic structure has a periodicity identical to that of the first periodic structure.

[0018] In one embodiment, the distribution of volume proportions of the multiple first layers in the first periodic structure may be equivalent to the distribution of volume proportions of the multiple third layers in the second periodic structure, and the distribution of volume proportions of the multiple second layers in the first periodic structure may be equivalent to the distribution of volume proportions of the multiple fourth layers in the second periodic structure.

[0019] According to one aspect of the inventive concept, there is provided a solid-state imaging device, comprising: a pixel array comprising a plurality of pixels, wherein each of the plurality of pixels comprises: a photoelectric conversion unit configured to convert light into electric charge; an on-chip lens mounted on one side of the photoelectric conversion unit; a wiring layer mounted on the other side of the photoelectric conversion unit; and a first periodic structure mounted on the one side of the photoelectric conversion unit and having periodicity in a horizontal direction perpendicular to a stacking direction of the photoelectric conversion unit, wherein the first periodic structure comprises a plurality of first layers and a plurality of second layers, the plurality of second layers having a refractive index lower than that of the plurality of first layers, wherein, in at least one of the plurality of pixels, the first periodic structure The multiple first layers and the multiple second layers of the periodic structure are arranged so that the volume ratio of the multiple first layers in the central part of the pixel is greater than the volume ratio of the multiple second layers in the central part of the pixel, and the volume ratio of the multiple first layers decreases from the central part of the pixel toward the peripheral part of the pixel in the horizontal direction, wherein the pixel including the first periodic structure also includes: a second periodic structure, which is installed on the one side of the photoelectric conversion unit and has periodicity in the horizontal direction, and wherein the second periodic structure includes multiple third layers and multiple fourth layers, the multiple third layers have a refractive index equal to the refractive index of the multiple first layers, and the multiple fourth layers have a refractive index equal to the refractive index of the multiple second layers.

[0020] According to one aspect of the inventive concept, a solid-state imaging device is provided, comprising: a pixel array comprising a plurality of pixels, wherein each of the plurality of pixels comprises: a photoelectric conversion unit configured to convert light into electric charge; an on-chip lens mounted on one side of the photoelectric conversion unit; a wiring layer mounted on the other side of the photoelectric conversion unit; and a first periodic structure mounted on the one side of the photoelectric conversion unit and having periodicity in a horizontal direction perpendicular to a stacking direction of the photoelectric conversion unit, wherein the first periodic structure comprises a plurality of first layers and a plurality of second layers, the plurality of second layers having a refractive index lower than that of the plurality of first layers, and wherein, in at least one of the plurality of pixels, the depths of the plurality of second layers of the first periodic structure are equal to each other, and the widths of the plurality of second layers increase from a central portion of the pixel toward a peripheral portion of the pixel. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The embodiments will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings.

[0022] Figure 1 is a block diagram showing a solid-state imaging device according to the embodiment.

[0023] Figure 2 is a plan view showing a first periodic structure of a pixel according to the first embodiment.

[0024] Figure 3 is a cross-sectional view of a pixel according to the first embodiment, taken along the stacking direction.

[0025] Figure 4A is a cross-sectional view showing a first periodic structure of pixels arranged at the center portion of a pixel array according to the first embodiment.

[0026] Figure 4B is a cross-sectional view showing a first periodic structure of pixels arranged at a peripheral portion of a pixel array according to the first embodiment.

[0027] Figure 5 is a diagram for describing the functional effect of the first periodic structure of the pixel according to the first embodiment.

[0028] Figure 6 is a diagram for describing the functional effect of the first periodic structure of the pixel according to the first embodiment.

[0029] Figure 7 is a cross-sectional view for describing the functional effect of the first periodic structure of the pixel according to the first embodiment.

[0030] Figure 8 is a cross-sectional view illustrating a first periodic structure according to Modified Example 1.

[0031] Figure 9 is a cross-sectional view illustrating a first periodic structure according to Modified Example 2.

[0032] Figure 10 is a cross-sectional view illustrating a first periodic structure according to Modified Example 3.

[0033] Figure 11 is a plan view showing a first periodic structure according to Modified Example 4.

[0034] Figure 12 is a plan view showing a first periodic structure according to Modified Example 5.

[0035] Figure 13 is a plan view showing a first periodic structure according to Modified Example 6.

[0036] Figure 14 is a plan view showing a first periodic structure according to Modified Example 7.

[0037] Figure 15 is a plan view showing a first periodic structure according to Modified Example 8.

[0038] Figure 16 is a cross-sectional view of a pixel according to the second embodiment, taken along the stacking direction.

[0039] Figure 17 is a cross-sectional view for describing the functional effect of the first periodic structure of the pixel according to the second embodiment.

[0040] Figure 18 is a cross-sectional view of a pixel according to the third embodiment, taken along the stacking direction.

[0041] Figure 19 is a diagram for describing the functional effect of the first periodic structure of the pixel according to the third embodiment.

[0042] Figure 20 is a cross-sectional view of a pixel according to a fourth embodiment, taken along the stacking direction.

[0043] Figure 21 1 and 2 are diagrams for describing functional effects of the first periodic structure of pixels according to the fourth embodiment.

[0044] Figure 22 is a cross-sectional view of a pixel according to a fifth embodiment, taken along the stacking direction.

[0045] Figure 23 1 and 2 are diagrams for describing functional effects of a first periodic structure of a pixel according to a fifth embodiment. DETAILED DESCRIPTION

[0046] In the drawings, the sizes and relative sizes of layers and regions may be exaggerated for clarity. The same reference numerals represent the same elements throughout. Although different figures illustrate variations of exemplary embodiments, these figures are not necessarily intended to be mutually exclusive. On the contrary, as will be seen in the context of the detailed description below, when the figures and their description are considered as a whole, specific features depicted and described in different figures can be combined with other features from other figures to produce various embodiments.

[0047] <First embodiment>

[0048] In the following, reference will be made to Figures 1 to 7 The first embodiment is described. In addition, the dimensional ratios of the drawings may be exaggerated for convenience of description and may be different from the actual ratios.

[0049] Figure 1 : is a block diagram schematically showing the overall configuration of the solid-state imaging device 1 according to the present embodiment. Figure 2 is a plan view showing a single pixel 10 provided in the solid-state imaging device 1 . Figure 3 yes Figure 2 FIG. 4 is a cross-sectional view of a pixel 10 shown in FIG. 1 along the stacking direction. Figure 4A is a cross-sectional view schematically showing a portion of the first periodic structure 140 arranged in the central portion 21 of the pixel array (or pixel array central portion). Figure 4B 2 is a cross-sectional view schematically showing a portion of the first periodic structure 140 arranged in the peripheral portion (pixel array peripheral portion) 23 of the pixel array. Figures 5 to 7 140 is a diagram for describing the functional effect of the first periodic structure 140 .

[0050] The solid-state imaging device 1 according to the present embodiment is configured as a solid-state imaging device in the form of a complementary metal oxide semiconductor (CMOS) device.

[0051] like Figure 1 and Figure 2As shown in the figure, the solid-state imaging device 1 includes: a pixel array 20 composed of a plurality of pixels 10 configured to output pixel signals, a control circuit 30 configured to generate an operation signal for operating each unit pixel of the solid-state imaging device 1, a vertical driver circuit 40 configured to vertically scan each pixel 10 and control the output of the pixel signal according to the amount of light received by each pixel 10, a horizontal driver circuit 50 configured to output a horizontal scanning pulse, a column signal processing circuit 60 configured to process the pixel signal output from each pixel 10 to generate an image signal, a vertical signal line 70 configured to transmit the pixel signal generated from each pixel 10 to the column signal processing circuit 60, a horizontal signal line 80 configured to output the image signal from the column signal processing circuit 60, and an output circuit 90 configured to process the image signal received through the horizontal signal line 80 and output the processed signal.

[0052] Any known configuration in the technical field of solid-state imaging devices can be arbitrarily and selectively adopted for components other than the pixel 10 of the solid-state imaging device 1. Therefore, in this specification, descriptions of components other than the pixel 10 will be appropriately omitted.

[0053] like Figure 1 As shown in FIG, a plurality of pixels 10 are regularly arranged on a substrate 25. The pixel array 20 is formed by Figure 1 The image sensor is composed of a plurality of pixels 10 arranged in a two-dimensional array in a plan view. The substrate 25 on which the pixels 10 are arranged is a semiconductor substrate (such as a silicon (Si) substrate). As used herein, the term "pixel" or "unit pixel" refers to a sensor element of an image sensor and can refer to the smallest addressable photosensitive element of an image sensor.

[0054] like Figure 2 and Figure 3 As shown in , the solid-state imaging device 1 includes a photoelectric conversion unit 110 installed in each pixel 10. In addition, Figure 3 An example of two pixels 10 adjacent to each other in the horizontal direction is shown. In some embodiments, the pixel array 20 may include a plurality of photoelectric conversion units 110.

[0055] In this specification, the direction in which the on-chip lens 120 and the photoelectric conversion unit 110 are stacked (denoted by Figure 3 The direction indicated by the arrows Z1 and Z2 in the figure is called the "stacking direction". In addition, the direction perpendicular to the stacking direction (the direction perpendicular to the stacking direction) is called the "stacking direction". Figure 2 The direction parallel to each arrow X1, X2, Y1 and Y2 in FIG. 8 is called the “horizontal direction”.

[0056] like Figure 2 and Figure 3As shown in FIG, the pixel 10 includes a photoelectric conversion unit 110 configured to convert light into electric charges, an on-chip lens 120 mounted on one side of the photoelectric conversion unit 110 (the side indicated by arrow Z1, hereinafter also referred to as the "Z1 side"), wiring layers 131 and 132 mounted on the other side of the photoelectric conversion unit 110 (the side indicated by arrow Z2, hereinafter also referred to as the "Z2 side"), and a first periodic structure 140 mounted on the Z1 side of the photoelectric conversion unit 110 and having periodicity in the horizontal direction of the photoelectric conversion unit 110. As discussed further below, the first periodic structure 140 includes a plurality of first layers 141 and a plurality of second layers 142.

[0057] The solid-state imaging device 1 is configured as a so-called back-illuminated type. Therefore, the on-chip lens 120 is arranged on the back side of the pixel 10 (the same side as the Z1 side). Light F incident on the pixel 10 passes through the on-chip lens 120 and enters the photoelectric conversion unit 110 from the Z1 side.

[0058] In the drawings, for convenience of description, respective components of light F incident on the on-chip lens 120 are assigned different symbols F1, F2, and F3 according to their incident positions on the photoelectric conversion unit 110. In this specification, the entire incident light is simply referred to as "incident light F."

[0059] Photoelectric conversion unit 110 includes a p-type semiconductor region and an n-type semiconductor region. In photoelectric conversion unit 110, a photodiode is implemented by a pn junction between the p-type semiconductor region and the n-type semiconductor region, and the photodiode converts light into electric charge. Photoelectric conversion unit 110 receives light incident through on-chip lens 120, generates electric charge corresponding to the amount of received light, and accumulates the generated electric charge in the n-type semiconductor region.

[0060] like Figure 3 、 Figure 4A and Figure 4B As shown in , the first periodic structure 140 is provided in a specific range in the stacking direction of the photoelectric conversion unit 110. In this embodiment, as shown in Figure 4A and Figure 4B As shown in , the first periodic structure 140 corresponds to the range of the second layer 142 extending in the stacking direction of the photoelectric conversion unit 110 (the range between the end of the second layer 142 on the Z1 side and the other end of the second layer 142 on the Z2 side), and includes regions (portions) where the first layers 141 and the second layers 142 are alternately arranged in the horizontal direction. In some example embodiments, the first periodic structure 140 may have a thickness (or height) in the stacking direction that is equal to the thickness (or height) of the second layer 142 in the stacking direction.

[0061] like Figure 3 As shown in FIG, the photoelectric conversion units 110 adjacent to each other in the horizontal direction are separated from each other by the insulating film 170. In an exemplary embodiment, the lower surface of the insulating film 170 may be at the same level as the lower surface of the adjacent photoelectric conversion unit 110, and the upper surface of the insulating film 170 may be at a higher level than the upper surface of the adjacent photoelectric conversion unit 110. Since the pixel 10 includes the insulating film 170, when a signal charge exceeding a saturation charge amount occurs, the excess signal charge can be prevented from flowing out of the photoelectric conversion unit 110 to another photoelectric conversion unit 110 adjacent thereto in the horizontal direction. As a constituent material of the insulating film 170, for example, a silicon oxide film, a silicon nitride film, a silicon oxynitride film, a resin film, or the like can be used. In addition, as the insulating film 170, a film having no positive fixed charge or a film having a small amount of positive fixed charge can be used.

[0062] A fixed charge film can be installed between horizontally adjacent photoelectric conversion units 110. Since the fixed charge film is installed in the pixel 10, the pixel 10 can reduce noise by reducing the occurrence of dark current. The fixed charge film is formed of an oxide film or a nitride film containing at least one metal element selected from hafnium (Hf), aluminum (Al), zirconium (Zr), tantalum (Ta), and titanium (Ti). Methods for forming the fixed charge film include chemical vapor deposition (CVD), sputtering, atomic layer deposition (ALD), and the like.

[0063] The on-chip lens 120 collects incident light F entering from the Z1 side. The light collected by the on-chip lens 120 enters the photoelectric conversion unit 110 .

[0064] like Figure 2 As shown in FIG, a center portion 121 of the on-chip lens 120 in the horizontal direction is arranged to overlap with the pixel center portion 11 of the pixel 10 .

[0065] like Figure 3 As shown in , the solid-state imaging device 1 includes a plurality of wiring layers 131 and 132 arranged with spaces therebetween in the stacking direction. Hereinafter, the wiring layer 131 arranged closest to the photoelectric conversion unit 110 is referred to as a "first wiring layer," and the wiring layer 132 arranged farther from the photoelectric conversion unit 110 than the first wiring layer 131 is referred to as a "second wiring layer." Furthermore, there are no specific limitations on the number of wiring layers installed in one solid-state imaging device 1, the arrangement of the wiring layers in the horizontal direction, and the cross-sectional shape of the wiring layers in the stacking direction, and the wiring layers can be arbitrarily modified.

[0066] The first wiring layer 131 and the second wiring layer 132 extract the signal charge generated and accumulated by the photoelectric conversion unit 110 as a pixel signal. The first wiring layer 131 and the second wiring layer 132 output the extracted pixel signal through the vertical signal line 70.

[0067] like Figure 2 and Figure 3 As shown in , the first periodic structure 140 includes a plurality of first layers 141 and a plurality of second layers 142 having a lower refractive index than the first layers 141 .

[0068] The "refractive index difference" between the first layer 141 and the second layer 142 can be defined by, for example, the physical properties (e.g., dielectric constant) of the constituent materials of the respective layers 141 and 142. Furthermore, there is no particular limitation on the "refractive index difference" as long as the lens effect described below is exhibited, and diffracted light Fr described below is generated inside the photoelectric conversion unit 110.

[0069] As constituent materials of the respective layers 141 and 142 for achieving a desired refractive index difference, for example, a combination of the following materials can be selected.

[0070] As a constituent material of the first layer 141, for example, any one of silicon (Si), germanium (Ge), and indium gallium arsenide (InGaAs) can be used. For example, the first layer 141 may be formed of or include any one of silicon (Si), germanium (Ge), and indium gallium arsenide (InGaAs).

[0071] In the case where the first layer 141 is formed of any of the above materials, any one of silicon dioxide (SiO 2 ), silicon nitride (SiN), aluminum oxide (AlO), tantalum oxide (TaO), titanium nitride (TiN), and titanium oxide (TiO) can be used, for example, as a constituent material of the second layer 142. For example, the second layer 142 may be formed of any one of silicon dioxide (SiO 2 ), silicon nitride (SiN), aluminum oxide (AlO), tantalum oxide (TaO), titanium nitride (TiN), and titanium oxide (TiO), or may include any one of silicon dioxide (SiO 2 ), silicon nitride (SiN), aluminum oxide (AlO), tantalum oxide (TaO), titanium nitride (TiN), and titanium oxide (TiO).

[0072] As described above, the first periodic structure 140 is configured to have periodicity in the horizontal direction. Figure 2 、 Figure 4A and Figure 4BAs shown in , the expression “having periodicity in the horizontal direction” means that the arrangement interval of the second layer 142 in the horizontal direction (hereinafter, referred to as “period p”) is constant in the entire range in the horizontal direction or in any partial range in the horizontal direction.

[0073] like Figure 4A and Figure 4B As shown in FIG, in the pixel 10 of the present embodiment, the period p is constant over the entire range in the directions parallel to the horizontal arrows X1 and X2. Figure 1 The period p of the first periodic structure 140 may be configured differently in the central portion 21 of the pixel array (including any region at the center position in the plane direction of the pixel array 20) and the peripheral portion 23 of the pixel array (any region outside the central portion 21 of the pixel array in the plane view). Figure 4A The central portion 21 of the pixel array shown in FIG. Figure 1 ) may be smaller than the period p1 of the first periodic structure 140 arranged in Figure 4B The peripheral portion 23 of the pixel array shown in FIG. Figure 1 ) in the first periodic structure 140. When the central portion 21 of the pixel array (see Figure 1 ) and the peripheral portion 23 of the pixel array (see Figure 1 ) changes in the length of the period p, the incident light is incident on the center portion 21 of the pixel array (see Figure 1 ) and the peripheral portion 23 of the pixel array (see Figure 1 ) on the first periodic structure 140 at the surface of the first layer 141, the angles of diffraction of the light are equal to each other, the diffracted light is completely reflected at the boundary between the photoelectric conversion unit 110 and the insulating film 170 adjacent to each other in the horizontal direction, and the light is confined within the photoelectric conversion unit 110, so that the central portion 21 of the pixel array (see Figure 1 ) and the peripheral portion 23 of the pixel array (see Figure 1 ) can achieve high quantum efficiency. In addition, in the following description, the arrangement will be based on Figure 4A The central portion 21 of the pixel array shown in FIG. Figure 1 ) to describe the operational effect according to this embodiment.

[0074] Figure 4A Shows the horizontal direction from Figure 2 An example of four second layers 142a, 142b, 142c, and 142d arranged with a period p between the second layers 142 from the pixel center portion 11 of the pixel 10 toward the pixel peripheral portion 13 of the pixel 10. For example, Figure 4AThe four second layers 142a, 142b, 142c, and 142d are shown arranged in sequence in a direction parallel to the horizontal arrow X1, and the four second layers 142a, 142b, 142c, and 142d are shown arranged in sequence in a direction parallel to the horizontal arrow X2. However, there is no specific limitation on the number of second layers 142 provided in the pixel 10.

[0075] exist Figure 2 In a plan view, the first layer 141 is arranged in a quadrilateral pattern having a specific area.

[0076] exist Figure 2 In a plan view of , the second layers 142 are arranged in a line pattern extending to space apart the first layers 141 adjacent to each other in the horizontal direction.

[0077] exist Figure 3 and Figure 4A , a concavo-convex structure formed of the first layer 141 and the second layer 142 is mounted on the surface on the Z1 side of the photoelectric conversion unit 110. The concavo-convex structure is formed by the second layer 142 having a rectangular cross-sectional shape and extending from the Z1 side of the photoelectric conversion unit 110 to penetrate into the first layer 141.

[0078] Figure 4A The directions parallel to the arrows X1 and X2 are shown as horizontal directions used as references for the period p of the first periodic structure 140. However, the horizontal directions used as references for the periodicity of the first periodic structure 140 are not limited to the directions parallel to the arrows X1 and X2. For example, the first periodic structure 140 may be configured to pass through the pixel center portion 11 and be parallel to the first periodic structure 140. Figure 2 The pixel has a period p in at least one of the direction of arrow A1 orthogonal to arrows X1 and X2 in the plan view, the direction of arrow A2 passing through the pixel center 11 and orthogonal to arrows Y1 and Y2, and the directions of arrows A3 and A4 passing through the pixel center 11 and intersecting arrows A1 and A2 in the plan view at 45°.

[0079] like Figure 2 As shown in FIG, the first layer 141 is arranged in a central portion 145 in the horizontal direction of the first periodic structure 140. The central portion 145 in the horizontal direction of the first periodic structure 140 is arranged to overlap with the pixel central portion 11.

[0080] In the solid-state imaging device 1 , the first periodic structure 140 in at least one of the plurality of pixels 10 has the following configuration.

[0081] like Figure 2 、 Figure 3 as well as Figure 4A, in the first periodic structure 140, the first layer 141 and the second layer 142 are arranged such that the volume ratio of the first layer 141 is greater than the volume ratio of the second layer 142 in the pixel central portion 11 in the horizontal direction, and the volume ratio of the first layer 141 decreases in the horizontal direction from the pixel central portion 11 toward the pixel peripheral portion 13. In addition, the first layer 141 and the second layer 142 are arranged such that the volume ratio of the second layer 142 increases in the horizontal direction from the pixel central portion 11 toward the pixel peripheral portion 13. For example, when viewed in cross section, the width of the first layer 141 gradually narrows as the distance from the pixel central portion 11 increases, and the width of the second layer 142 gradually widens as the distance from the pixel central portion 11 increases.

[0082] Regarding the term “volume ratio”, for example, the volume ratio of the first layer 141 represents the ratio of the volume of the first layer 141 relative to the total volume of the photoelectric conversion unit 110, and the volume ratio of the second layer 142 represents the ratio of the volume of the second layer 142 relative to the total volume of the photoelectric conversion unit 110.

[0083] Will refer to Figure 5 The functional effect of the first periodic structure 140 (collecting incident light through a lens effect) is described.

[0084] Figure 5 (a) is a graph showing a relationship between the magnitude of the average refractive index of the lights F1 , F2 , and F3 incident on the photoelectric conversion unit 110 and the horizontal position in the photoelectric conversion unit 110 (first periodic structure 140 ). Figure 5 (b) is a color bar showing the magnitude relationship between the refractive indices of the incident lights F1 , F2 , and F3 indicated as corresponding to the horizontal positions in the graph. Figure 5 (c) schematically illustrates a principle in which each of the incident lights F1 , F2 , and F3 is collected by the first periodic structure 140 . Figure 5 The imaginary line H1 shown in (a) to (c) indicates the position where the refractive index is the maximum in the first periodic structure 140 (corresponding to Figure 2 The position of the pixel center 11 in the image and the position of the center 145 of the first periodic structure 140 are the same position).

[0085] In the first periodic structure 140, the volume ratio of the first layer 141 in the pixel center portion 11 is greater than the volume ratio of the second layer 142. In addition, the refractive index of the first layer 141 is greater than the refractive index of the second layer 142. Therefore, Figure 5 As shown in (a), the refractive index of the first periodic structure 140 in the horizontal direction is the largest in the pixel center portion 11 .

[0086] In the first periodic structure 140, the first layer 141 and the second layer 142 are arranged so that the volume ratio of the first layer 141 decreases from the pixel center portion 11 toward the pixel peripheral portion 13. Figure 5 As shown in FIG. 1( a ), the refractive index of the first periodic structure 140 in the horizontal direction gradually decreases from the pixel center portion 11 toward the pixel peripheral portion 13 .

[0087] Figure 5 The color bar of (b) indicates Figure 5 The magnitude relationship of the refractive index distribution in (a). In the color bar, the position with a higher refractive index is represented by a lighter color, and the position with a lower refractive index is represented by a darker color. Figure 5 As shown in (b), the location near the pixel center 11, where the volume ratio of the first layer 141 is greater than the volume ratio of the second layer 142, has a high refractive index. Therefore, in the color bar, the location near the pixel center 11 is represented by a color close to white. The location near the pixel periphery 13, where the volume ratio of the first layer 141 is smaller than the volume ratio of the first layer 141 at the pixel center 11, has a low refractive index. Therefore, in the color bar, the location near the pixel periphery 13 is represented by a color close to black.

[0088] like Figure 5 As shown in (c), the incident light F1 (actually, some components of the incident light) that has passed through the vicinity of the pixel center portion 11 (the center portion 145 of the first periodic structure 140) and then entered the photoelectric conversion unit 110 passes through the portion with a high refractive index of the first periodic structure 140. Therefore, the speed at which the incident light F1 propagates into the first periodic structure 140 is reduced.

[0089] like Figure 5 As shown in (c), the incident light F2 and F3 (actually, some components of the incident light) that have passed through the pixel peripheral portion 13 and then entered the photoelectric conversion unit 110 passes through the portion of the first periodic structure 140 having a refractive index smaller than that of the pixel central portion 11. Therefore, when the incident light F2 and F3 enters the photoelectric conversion unit 110 from the first periodic structure 140, the speed at which the incident light F2 and F3 propagates into the first periodic structure 140 increases.

[0090] As described above, the incident light F1 has different propagation speeds from the incident lights F2 and F3, and therefore, the incident lights F2 and F3 propagate while being refracted inside the first periodic structure 140. Figure 5In this manner, the first periodic structure 140 exhibits a lens effect of collecting incident light passing through the first periodic structure 140 onto the first wiring layer 131 arranged on the Z2 side.

[0091] In the pixel 10, the first periodic structure 140 can exhibit a lens effect to efficiently allow incident light that has passed through the photoelectric conversion unit 110 to reach the first wiring layer 131 arranged on the Z2 side of the photoelectric conversion unit 110. Therefore, the pixel 10 can prevent the incident light that has passed through the photoelectric conversion unit 110 from passing through the space between the first wiring layers 131 adjacent to each other in the horizontal direction ( Figure 3 ), thereby suppressing the occurrence of color mixing.

[0092] Will refer to Figure 6 The functional effect of the first periodic structure 140 (increase in quantum efficiency due to diffracted light) is described. Figure 6 is a schematic diagram used to describe the generation principle of diffracted light. Therefore, Figure 6 The arrangement or cross-sectional shape of the first layer 141 and the second layer 142 shown in FIG. Figure 3 The exemplary embodiments shown in do not necessarily have a strict correspondence.

[0093] The first layer 141 and the second layer 142 are regularly arranged so that the first periodic structure 140 has a period p in the horizontal direction. Figure 6 As shown in FIG, incident light F enters the first periodic structure 140 from the Z1 side of the photoelectric conversion unit 110. The first periodic structure 140 generates diffracted light Fr. The first periodic structure 140 has a constant period p in the horizontal direction. Therefore, the first periodic structure 140 can generate diffracted light Fr in each segment in the horizontal direction according to the period p.

[0094] like Figure 3 and Figure 6 As shown in , the diffracted light Fr generated by the first periodic structure 140 does not propagate along the shortest straight-line distance from the Z1 side to the Z2 side of the photoelectric conversion unit 110, but instead propagates along an oblique direction within the photoelectric conversion unit 110. Therefore, compared to a case where the diffracted light Fr does not occur, the pixel 10 can increase the optical path length of the light to be converted into charge by the photoelectric conversion unit 110. In the pixel 10, the amount of light absorbed in the photoelectric conversion unit 110 increases as the optical path length of the light to be converted into charge by the photoelectric conversion unit 110 increases. Due to this, the pixel 10 can exhibit high quantum efficiency in the photoelectric conversion unit 110.

[0095] The period p of the first periodic structure 140 has a specific size based on the wavelength (same meaning as the wavelength of the incident light) and the angle of incidence of the light received by the photoelectric conversion unit 110. Furthermore, the period p of the first periodic structure 140 may have a length that is shorter than the wavelength of the received light and is suitable for generating diffracted light Fr in the photoelectric conversion unit 110.

[0096] Figure 6 An example is shown of both first-order diffracted light Fr1 and second-order diffracted light Fr2 generated from light received by the first periodic structure 140. As the period p is set to an appropriate length according to the incident angle and wavelength of the incident light F, the pixel 10 can generate first-order diffracted light Fr1 and second-order diffracted light Fr2 inside the first periodic structure 140.

[0097] In the solid-state imaging device 1, for example, in the case where the incident angle of the incident light F is 0° and the wavelength of the incident light F is 940 nm, the length of the period p (in Figure 4A In the cross-sectional view of FIG, the straight-line distance between the centers of the second layers 142 adjacent to each other in the horizontal direction is preferably 400 nm to 600 nm, and more preferably 600 nm. When the period p is set in this manner, the diffraction angle θ1 between the incident light F1 and the first-order diffracted light Fr1 is, for example, 25.7°, and the diffraction angle θ2 between the incident light F1 and the second-order diffracted light Fr2 is, for example, 60.5°.

[0098] The length of period p is not particularly limited, as long as the photoelectric conversion unit 110 can generate diffracted light Fr, taking into account the incident angle and wavelength of the incident light F. For example, even when the incident angle of the incident light F is not 0° or the wavelength of the incident light F is not 940 nm, the length of period p can be changed to an appropriate length based on a known light diffraction equation (equation for emitted diffracted light). For example, when the incident angle of the incident light F is 30° and the wavelength is 940 nm, the length of period p can be set within the range of 500 nm to 700 nm.

[0099] like Figure 4A As shown in , because the widths w of the second layers 142 in the horizontal direction are different from each other, the first periodic structure 140 may be configured such that the volume ratio of the first layer 141 decreases from the pixel center portion 11 toward the pixel peripheral portion 13 .

[0100] exist Figure 4AIn the first periodic structure 140 shown in FIG, the second layers 142a, 142b, 142c, and 142d have the same depth d2. In addition, in the first periodic structure 140, the width w gradually increases from the second layer 142a arranged near the pixel center portion 11 toward the second layer 142d arranged in the pixel periphery 13. In the pixel 10, as described above, the width w of each of the second layers 142a, 142b, 142c, and 142d is different from each other, and therefore, the volume ratio of the first layer 141 can gradually decrease from the pixel center portion 11 toward the pixel periphery 13.

[0101] The depth d1 of the first layer 141 and the depth d2 of the second layer 142 in the stacking direction may be set to be equal to or less than the wavelength of light received by the photoelectric conversion unit 110. In addition, the thickness t ( Figure 3 ) may be set to be greater than a depth d1 of the first layer 141 and a depth d2 of the second layer 142 .

[0102] In the case where the wavelength of the incident light F is 940 nm as described above, the depth d1 of the first layer 141 and the depth d2 of the second layer 142 may be 940 nm, which is substantially the same as the wavelength of the incident light F. In addition, in the case where the depth d1 of the first layer 141 and the depth d2 of the second layer 142 are 940 nm, the thickness t of the photoelectric conversion unit 110 may be, for example, 7000 nm.

[0103] In addition, the depth d1 of the first layer 141 and the depth d2 of the second layer 142 are not limited to 940 nm. For example, when the incident angle of the incident light F is 0° or 30° and the wavelength is 940 nm, the depth d1 of the first layer 141 and the depth d2 of the second layer 142 can be set to any value within the range of 100 nm to 940 nm.

[0104] like Figure 3 and Figure 7 As shown in , the photoelectric conversion unit 110 is at least partially covered by a dielectric layer 146 having a lower refractive index than the first layer 141 . Figure 7 yes Figure 3 An enlarged view of a portion of the cross-sectional view.

[0105] The dielectric layer 146 may be arranged to cover the photoelectric conversion unit 110 at three locations (e.g., at left and right locations (X1 and X2 side locations) in the stacking direction, and at a Z2 side location). In some example embodiments, the dielectric layer 146 may contact the outer side surface and the bottom surface of the first layer 141. However, the location where the dielectric layer 146 is arranged is not particularly limited as long as the effect of completely reflecting diffracted light, which will be described below, can be exhibited.

[0106] For example, when the first layer 141 is formed of any of the above-described constituent materials, the constituent material of the dielectric layer 146 may be the same material as any of the above-described examples of the constituent material of the second layer 142. For example, the dielectric layer 146 may be formed of or include any of silicon dioxide (SiO2), silicon nitride (SiN), aluminum oxide (AlO), tantalum oxide (TaO), titanium nitride (TiN), and titanium oxide (TiO). However, as long as the dielectric layer 146 has a refractive index lower than that of the first layer 141, the constituent material of the dielectric layer 146 is not particularly limited.

[0107] The period p of the first periodic structure 140 may be set to a length such that the diffracted light Fr generated in the photoelectric conversion unit 110 is completely reflected between the photoelectric conversion unit 110 and the dielectric layer 146 . Figure 7 The state in which the diffracted light Fr is completely reflected by the dielectric layer 146 is shown.

[0108] The pixel 10 can increase the optical path length of the diffracted light Fr generated inside the photoelectric conversion unit 110 by completely reflecting the diffracted light Fr in the dielectric layer 146. Therefore, the pixel 10 can further increase the amount of light absorbed in the photoelectric conversion unit 110.

[0109] As described above, when the incident light F has an incident angle of 0° and a wavelength of 940 nm, the first periodic structure 140 has a period p of 600 nm, thereby generating first-order diffraction light Fr1 having a diffraction angle θ1 and second-order diffraction light Fr2 having a diffraction angle θ2 in the photoelectric conversion unit 110 (see FIG. Figure 6 ).like Figure 7 As shown in FIG, in the case where the period p has a length of 600 nm, the condition for the dielectric layer 146 to completely reflect each of the first-order diffracted light Fr1 and the second-order diffracted light Fr2 is that the incident angle θ3 (the incident angle θ3 of the dielectric layer 146) is ≥ 23.7°. This condition can be calculated by substituting the refractive index of the first layer 141 and the refractive index of the dielectric layer 146 into the known Snell's law.

[0110] The first periodic structure 140 can be configured such that the volume ratio of the first layer 141 and the volume ratio of the second layer 142 differ from each other based on the wavelength and incident angle of the light received by the photoelectric conversion unit 110. That is, the specific volume ratio of each layer 141 and 142 in each segment in the horizontal direction can be arbitrarily set according to the wavelength and incident angle of the incident light F. When the incident angle of the incident light F is 0° and the wavelength of the incident light F is 940 nm, the volume ratio of the first layer 141 near the pixel center 11 (the volume ratio of the first layer 141 relative to the total volume of the photoelectric conversion unit 110) can be, for example, 60% to 80%. Furthermore, the volume ratio of the second layer 142 near the pixel center 11 (the volume ratio of the second layer 142 relative to the total volume of the photoelectric conversion unit 110) can be, for example, 20% to 40%. In the case where the volume ratio of each of the layers 141 and 142 near the pixel center portion 11 is set as described above, the volume ratio of the first layer 141 near the pixel peripheral portion 13 can be, for example, 20% to 40%, and the volume ratio of the second layer 142 near the pixel peripheral portion 13 can be, for example, 60% to 80%. In addition, the volume ratios of the first layer 141 and the second layer 142, which can be set differently based on the wavelength and incident angle of the incident light F received by the photoelectric conversion unit 110, also apply to the volume ratios of the third layer 153 and the fourth layer 154 to be described below in the second embodiment.

[0111] The first wiring layer 131 arranged closest to the photoelectric conversion unit 110 in the stacking direction has a reflective structure that reflects light emitted by the photoelectric conversion unit 110 .

[0112] In the pixel 10, the first wiring layer 131 has a reflective structure, and therefore, at least a portion of the emitted light Ft that has passed through the photoelectric conversion unit 110 and reached the first wiring layer 131 can be reflected toward the photoelectric conversion unit 110. In the pixel 10, the light reflected from the reflective structure of the first wiring layer 131 enters the photoelectric conversion unit 110, and therefore, the optical path length of the light inside the photoelectric conversion unit 110 can be further increased. Therefore, the pixel 10 can further increase the amount of light absorbed in the photoelectric conversion unit 110.

[0113] The reflective structure installed in the first wiring layer 131 may be configured by, for example, a metal layer installed on at least a portion of the surface of the first wiring layer 131 arranged on one side of the photoelectric conversion unit 110. The metal layer may be formed of, for example, tungsten, aluminum, copper, or the like.

[0114] In the following, reference will be made to Figures 8 to 15 Modification examples regarding the horizontal arrangement of each of the layers 141 and 142 , or the cross-sectional shape of each of the layers 141 and 142 in the stacking direction are described. Figures 8 to 10 is with Figure 4Aand Figure 4B The sectional views correspond to the sectional views of the respective modified examples, and Figures 11 to 15 is with Figure 2 The plan views correspond to the plan views of the respective modified examples.

[0115] As will be described with respect to each of the following modified examples, as long as the above-mentioned lens effect and the effect of generating diffracted light can be achieved, the cross-sectional shape of each layer 141 and 142 of the first periodic structure 140 in the stacking direction and the arrangement of each layer 141 and 142 in the plan view can be changed arbitrarily.

[0116] like Figure 8 As shown in , because the depths d2 of the second layers 142 in the stacking direction are different from each other, the first periodic structure 140 of Modification Example 1 is configured so that the volume ratio of the first layer 141 decreases from the pixel center portion 11 toward the pixel peripheral portion 13.

[0117] exist Figure 8 In the first periodic structure 140 shown in FIG, the widths w of the second layers 142a, 142b, 142c, and 142d are equal to each other. In addition, in the first periodic structure 140, the depth d2 gradually increases from the second layer 142a arranged near the pixel center portion 11 to the second layer 142d arranged near the pixel periphery portion 13. In the pixel 10, the depths d2 of the second layers 142a, 142b, 142c, and 142d are different from each other, and therefore, the volume ratio of the first layer 141 can gradually decrease from the pixel center portion 11 toward the pixel periphery portion 13.

[0118] like Figure 9 As shown in , because the width w in the horizontal direction and the depth d2 in the stacking direction of the second layer 142 are different from each other, the first periodic structure 140 of the modified example 2 is configured so that the volume ratio of the first layer 141 decreases from the pixel center portion 11 toward the pixel peripheral portion 13.

[0119] exist Figure 9 In the first periodic structure 140 shown in FIG, the width w and the depth d2 gradually increase from the second layer 142a arranged near the pixel center portion 11 to the second layer 142d arranged near the pixel periphery portion 13. In the pixel 10, the second layers 142a, 142b, 142c, and 142d are different from each other in the width w and the depth d2, and therefore, the volume ratio of the first layer 141 can gradually decrease from the pixel center portion 11 toward the pixel periphery portion 13.

[0120] like Figure 10As shown in , in the first periodic structure 140 of Modification Example 3, the second layer 142 has a triangular cross-sectional shape with the base arranged on the Z1 side and the vertex arranged on the Z2 side.

[0121] As shown in the present modified example, the second layer 142 may be configured to have any cross-sectional shape as long as the size relationship between the volume ratios of the respective layers 141 and 142 in the horizontal direction can be adjusted.

[0122] In the first periodic structure 140 of Modification Example 3, since the width w in the horizontal direction and the depth d2 in the stacking direction of the second layer 142 are different from each other, the volume ratio of the first layer 141 decreases from the pixel center portion 11 toward the pixel peripheral portion 13. In addition, in the case where the cross-sectional shape of the second layer 142 is a triangular shape as shown in Modification Example 3, the width w can be defined as the length of the base of the triangle.

[0123] like Figure 11 As shown in , in the pixel 10 of Modification Example 4, the first layer 141 and the second layer 142 are arranged in a square frame shape in a plan view. For example, each of the first layer 141 and the second layer 142 may extend continuously to concentrically surround the pixel center portion 11. Each first layer 141 may become narrower as the distance from the pixel center portion 11 increases, and each second layer 142 may become wider as the distance from the pixel center portion 11 increases. When viewed in cross section, in the pixel 10 of Modification Example 4, the first layer 141 and the second layer 142 may respectively include Figures 8 to 10 The features of any one of Modification Example 1 to Modification Example 3.

[0124] like Figure 12 As shown in FIG, in the pixel 10 of the modification example 5, the second layer 142 is arranged in a rectangular shape having a specific length and width in a plan view. In addition, in the first periodic structure 140 of the modification example 5, the first layer 141 is arranged at a portion corresponding to the vertex of the square formed by the second layer 142 in a plan view. When viewed in cross section, in the pixel 10 of the modification example 5, the first layer 141 and the second layer 142 may respectively include Figures 8 to 10 The features of any one of Modification Example 1 to Modification Example 3.

[0125] like Figure 13As shown in FIG, in the pixel 10 of the modification example 6, the second layer 142 is arranged in a rectangular shape having a specific length and width in a plan view. The length of the second layer 142 in each direction of the arrows A1 and A2 is smaller than the length of the second layer 142 of the modification example 5. That is, the second layer 142 of the modification example 6 has a structure that subdivides the second layer 142 of the modification example 5 in a plan view. When viewed in cross section, in the pixel 10 of the modification example 6, the first layer 141 and the second layer 142 may respectively include Figures 8 to 10 The features of any one of Modification Example 1 to Modification Example 3.

[0126] like Figure 14 As shown in FIG, in the pixel 10 of the modification example 7, the second layer 142 is arranged in a rectangular shape having a specific length and width in a plan view. The second layer 142 of the modification example 7 is formed so that parts of the second layer 142 of the modification example 6 are connected to each other in a plan view. When viewed in cross section, in the pixel 10 of the modification example 7, the first layer 141 and the second layer 142 may respectively include Figures 8 to 10 The features of any one of Modification Example 1 to Modification Example 3.

[0127] like Figure 15 As shown in FIG, in the pixel 10 of the modification example 8, the second layer 142 is arranged to be connected to each other in the longitudinal direction and the lateral direction in the plan view like the squares of a checkerboard. When viewed in cross section, in the pixel 10 of the modification example 8, the first layer 141 and the second layer 142 may respectively include Figures 8 to 10 The features of any one of Modification Example 1 to Modification Example 3.

[0128] In addition, in addition to the arrangement of each layer 141 and 142 described above with respect to Modification Examples 4 to 8, the first periodic structure 140 can be arbitrarily changed as long as it has a certain period p across the entire region or a partial region in the horizontal direction. For example, each layer 141 and 142 can be arranged in a concentric pattern having its center arranged in the pixel center portion 11 in a plan view.

[0129] As described above, the solid-state imaging device 1 according to the first embodiment is a solid-state imaging device including a pixel array 20 composed of a plurality of pixels 10, wherein the pixel 10 includes: a photoelectric conversion unit 110 configured to convert light into electric charges, an on-chip lens 120 installed on the Z1 side of the photoelectric conversion unit 110, a first wiring layer 131 installed on the Z2 side of the photoelectric conversion unit 110, and a first periodic structure 140 installed on the Z1 side of the photoelectric conversion unit 110 and having periodicity in a horizontal direction perpendicular to the stacking direction of the photoelectric conversion unit 110, and the first periodic structure 140 includes a plurality of first layers 141 and a plurality of second layers 142 having a refractive index lower than that of the first layer 141. In at least one of the multiple pixels 10, the first periodic structure 140 can be configured in the horizontal direction so that the volume proportion of the first layer 141 in the pixel center portion 11 is greater than the volume proportion of the second layer 142 in the pixel center portion 11, and the first layer 141 and the second layer 142 can be arranged so that the volume proportion of the first layer 141 decreases in the horizontal direction from the pixel center portion 11 toward the pixel peripheral portion 13.

[0130] In the pixel 10 of the solid-state imaging device 1 of the present embodiment, the first periodic structure 140 mounted on the Z1 side of the photoelectric conversion unit 110 can exhibit a lens effect that collects the incident light F entering through the on-chip lens 120 onto the photoelectric conversion unit 110, and can generate a larger amount of diffracted light Fr inside the photoelectric conversion unit 110. Therefore, the solid-state imaging device 1 can reduce color mixing and improve light absorption in the photoelectric conversion unit 110.

[0131] Hereinafter, solid-state imaging devices according to the second to fifth embodiments will be described. In the descriptions of the second to fifth embodiments, the descriptions of the components, configurations, and the like provided above in the first embodiment will not be repeated. Furthermore, those not specifically described in the second to fifth embodiments may be the same as those in the first embodiment.

[0132] <Second embodiment>

[0133] Figure 16 is a cross-sectional view of a pixel 10A according to the second exemplary embodiment, taken along the stacking direction. Figure 17 is a cross-sectional view for describing the functional effects of the pixel 10A.

[0134] like Figure 16 As shown in , the pixel 10A according to the second embodiment includes a first periodic structure 140 and a second periodic structure 150 mounted on the Z2 side of the photoelectric conversion unit 110 and having periodicity in the horizontal direction perpendicular to the stacking direction.

[0135] The second periodic structure 150 includes a third layer 153 having the same refractive index as that of the first layer 141 and a fourth layer 154 having the same refractive index as that of the second layer 142 .

[0136] The third layer 153 can be formed of, for example, the same material as exemplified above as the constituent material of the first layer 141. The fourth layer 154 can be formed of, for example, the same material as exemplified above as the constituent material of the second layer 142. When the third layer 153 and the fourth layer 154 are configured as described above, the first layer 141 and the third layer 153 have the same optical properties (e.g., refractive index), and the second layer 142 and the fourth layer 154 also have the same optical properties (e.g., refractive index). Therefore, the refractive index difference between the third layer 153 and the fourth layer 154 is the same as the refractive index difference between the first layer 141 and the second layer 142.

[0137] Will refer to Figure 17 The functional effect of the second periodic structure 150 (the improvement of quantum efficiency caused by the reflection of diffracted light) is described. In addition, Figure 17 is a schematic diagram used to describe the reflection principle of diffracted light, and Figure 17 The arrangement or cross-sectional shape of the third layer 153 and the fourth layer 154 shown in FIG. Figure 16 The exemplary embodiments shown in do not necessarily have a strict correspondence.

[0138] In the pixel 10A, when light has reached the second periodic structure 150 arranged on the Z2 side of the photoelectric conversion element through the photoelectric conversion unit 110, diffracted light Fr is generated at the boundary between the photoelectric conversion unit 110 and the second periodic structure 150. In addition, Figure 17 The first-order diffracted light Fr1′ generated from the incident light F2 and F3 collected by the on-chip lens 120 and the first-order diffracted light Fr2′ generated from the incident light F2 and F3 collected by the on-chip lens 120 and the first-order diffracted light Fr3′ generated from the incident light F2 and F3 collected by the on-chip lens 120 Figure 7 ) An example of second-order diffracted light Fr2′ generated by the reflected first-order diffracted light Fr1 and second-order diffracted light Fr2.

[0139] In pixel 10A, when diffracted light Fr is generated in the second periodic structure 150, the light that has reached the second periodic structure 150 moves from the Z2 side toward the Z1 side of the photoelectric conversion element. Therefore, pixel 10A can further increase the optical path length of the light to be converted into charge by photoelectric conversion unit 110. Consequently, pixel 10A can further increase the amount of light absorbed in photoelectric conversion unit 110.

[0140] like Figure 16As shown in , the second periodic structure 150 can be configured to have the same periodicity as the first periodic structure 140. That is, the length of the period p of the first periodic structure 140 and the length of the period p of the second periodic structure 150 can be set to be substantially equal to each other. As described above, the length of the period p of the first periodic structure 140 can be set to 600 nm based on the incident angle (e.g., 0°) and wavelength (e.g., 940 nm) of the incident light F. Therefore, in this embodiment, the length of the period p of the second periodic structure 150 is set to 600 nm.

[0141] In pixel 10A, the length of period p of the first periodic structure 140 and the length of period p of the second periodic structure 150 are set to be approximately equal to each other. Therefore, the diffraction angles of diffracted light Fr generated on the Z1 side and the Z2 side of the photoelectric conversion unit 110 can be approximately equal to each other. In pixel 10A, the diffraction angles of diffracted light Fr generated on the Z1 side and the Z2 side of the photoelectric conversion unit 110 are fixed to be approximately equal to each other, making it easy to design an optical path that reflects all light within the photoelectric conversion unit 110. In addition, in pixel 10A, the length of period p of the second periodic structure 150 arranged on the Z2 side of the photoelectric conversion unit 110 is set to 600 nm, which is equal to the length of period p of the first periodic structure 140. Therefore, light that has reached the second periodic structure 150 can be fully reflected.

[0142] exist Figure 17 In the example shown in FIG, the diffraction angle θ4 of the first-order diffraction light Fr1′ generated in the second periodic structure 150 is approximately 26°, which is equal to the diffraction angle θ1 of the first-order diffraction light Fr1 generated in the first periodic structure 140 (see FIG. Figure 6 ). In addition, the diffraction angle θ5 of the second-order diffraction light Fr2' generated in the second periodic structure 150 is approximately 60°, which is equal to the diffraction angle θ2 of the second-order diffraction light Fr2 generated in the first periodic structure 140 (see Figure 6 ).

[0143] In the pixel 10A, the distribution of the volume ratio of the first layer 141 in the first periodic structure 140 is the same as the distribution of the volume ratio of the third layer 153 in the second periodic structure 150. In addition, the distribution of the volume ratio of the second layer 142 in the first periodic structure 140 is the same as the distribution of the volume ratio of the fourth layer 154 in the second periodic structure 150. In some embodiments, at least one of the first periodic structure 140 and the second periodic structure 150 is configured such that the volume ratio of the first layer 141 and the volume ratio of the second layer 142 are different from each other and / or the volume ratio of the third layer 153 and the volume ratio of the fourth layer 154 are different from each other based on the wavelength and incident angle of light received by the photoelectric conversion unit 110.

[0144] In the pixel 10A, as described above, the volume ratio distribution of the first layer 141 is the same as that of the third layer 153, and the volume ratio distribution of the second layer 142 is the same as that of the fourth layer 154. Therefore, the diffraction angles of the diffracted light Fr generated on the Z1 side and the Z2 side of the photoelectric conversion unit 110 are further fixed. Therefore, in the pixel 10A, the design of the optical path that reflects all light inside the photoelectric conversion unit 110 is further facilitated.

[0145] As Figure 4A and Figure 4B An example of the construction shown in Figure 16 The volume ratio of the first periodic structure 140 in the horizontal direction and the cross-sectional shape of each layer 141 and 142 are shown. Figure 16 In the embodiment of the present invention, the second periodic structure 150 is configured to have the same volume ratio and cross-sectional shape as those of the first periodic structure 140. However, when the pixel 10A is configured to have the first periodic structure 140 and the second periodic structure 150, there is no specific limitation on the horizontal volume ratio or cross-sectional shape of each of the first periodic structure 140 and the second periodic structure 150. For example, each of the first periodic structure 140 and the second periodic structure 150 can adopt any of the configurations described above in Modification Examples 1 to 8.

[0146] <Third embodiment>

[0147] Figure 18 is a cross-sectional view of a pixel 10B according to the third exemplary embodiment, taken along the stacking direction. Figure 19 A graph showing the relationship between the magnitude of the average refractive index of light F incident on the photoelectric conversion unit 110 and the horizontal position in the photoelectric conversion unit 110 is included, and a schematic cross-sectional view of the first periodic structure 140 taken along the stacking direction. In some embodiments, Figure 19Five second layers 142a, 142b, 142c, 142d, and 142e may be included.

[0148] like Figure 18 and Figure 19 As shown in , in the pixel 10B according to the third embodiment, the position where the first layer 141 of the first periodic structure 140 has the maximum volume ratio is arranged at a position corresponding to the position of the center portion 121 (the center portion in the horizontal direction) of the on-chip lens 120 .

[0149] The central portion 121 of the on-chip lens 120 may be arranged at a specific position between the pixel central portion 11 and the pixel peripheral portion 13 corresponding to the incident angle of light received by the photoelectric conversion unit 110 .

[0150] Figure 18 and Figure 19 The example shown in shows a state where light is incident from the left side in the drawing (left side in the horizontal direction) at a certain incident angle.

[0151] The center portion 121 of the on-chip lens 120 is arranged at a position shifted toward the side from which light comes. When light is incident on the on-chip lens 120 at a specific incident angle, in order to efficiently collect the incident light F3 onto the first wiring layer 131 arranged on the Z2 side of the photoelectric conversion unit 110, it is preferable that the incident light F3 (which comes from a position further to the right than the incident light F1 in the horizontal direction relative to the center portion 121) be further refracted toward the center by the first periodic structure 140. Therefore, in the pixel 10B, the position of the center portion 121 of the on-chip lens 120 is set to a position shifted to the left in the horizontal direction, and the position where the volume ratio of the first layer 141 of the first periodic structure 140 is the largest (given by Figure 19 The position indicated by the imaginary line H2 in FIG. 1 ) is arranged at a position corresponding to the center portion 121 of the on-chip lens 120.

[0152] in addition, Figure 19 The double-dashed line in the graph represents the refractive index distribution in the horizontal direction when the incident angle of the incident light F is 0° ( Figure 5 ). As described above in the first embodiment, Figure 19 The imaginary line H1 in the graph of φ indicates the position where the refractive index is maximum in the first periodic structure 140 (the same position as the pixel center portion 11 ).

[0153] In the pixel 10B of the third embodiment, the position where the volume ratio of the first layer 141 of the first periodic structure 140 is the largest is arranged at a position corresponding to the center portion 121 of the on-chip lens 120. Therefore, even when light F is incident on the first periodic structure 140 at a certain incident angle, the light can be efficiently collected onto the first wiring layer 131 arranged on the Z2 side of the photoelectric conversion unit 110.

[0154] <Fourth embodiment>

[0155] Figure 20 is a cross-sectional view of a pixel 10C taken along the stacking direction according to the fourth exemplary embodiment. Figure 21 Included are a graph showing the relationship between the magnitude of the average refractive index of light incident on the photoelectric conversion unit 110 and the horizontal position in the photoelectric conversion unit 110 , and a schematic cross-sectional view of the first periodic structure 140 taken along the stacking direction.

[0156] In at least one of the plurality of pixels 10 included in the solid-state imaging device 1, the first periodic structure 140 may be formed as follows. Figure 20 and Figure 21 , wherein the first layer 141 and the second layer 142 are arranged so that in the middle region 17 between the pixel central portion 11 and the pixel peripheral portion 13, the volume proportion of the first layer 141 is greater than the volume proportion of the second layer 142, and the volume proportion of the first layer 141 decreases from the middle region 17 toward the pixel central portion 11 and the pixel peripheral portion 13.

[0157] exist Figure 21 In the example shown in , one intermediate region 17 is provided between the pixel center portion 11 in the horizontal direction and the pixel peripheral portion 13 located on one side (left side) in the horizontal direction. Furthermore, in this example, one intermediate region 17 is provided between the pixel center portion 11 in the horizontal direction and the pixel peripheral portion 13 located on the other side (right side) in the horizontal direction.

[0158] As described above, in the first periodic structure 140, since the volume ratio of the first layer 141 in the middle region 17 is greater than the volume ratio of the second layer 142 in the middle region 17, and the volume ratio of the first layer 141 decreases from the middle region 17 toward the pixel center portion 11 and the pixel peripheral portion 13, Figure 21 As shown in the graph of , the average refractive index in the horizontal direction is maximum at the positions corresponding to the two middle regions 17 .

[0159] like Figure 20As shown in , in the pixel 10C including the first periodic structure 140 configured as described above, even in a case where, for example, the first wiring layer 131 arranged on the Z2 side of the photoelectric conversion unit 110 is arranged so as not to overlap with the central portion 121 of the on-chip lens 120 (in a case where the first wiring layer 131 is arranged at a position offset in the horizontal direction from the central portion 121 of the on-chip lens 120), the incident light F1 passing through the pixel central portion 11 (the central portion 121 of the first periodic structure 140) and the other incident light F2 and F3 can be collected from their positions in the two intermediate regions 17 onto each of the first wiring layers 131 arranged at specific intervals in the horizontal direction. Therefore, even in a case where the pixel 10C has a stacked structure in which the first wiring layer 131 is arranged so as not to overlap with the central portion 121 of the on-chip lens 120, the pixel 10C can effectively prevent the occurrence of color mixing.

[0160] In addition, in this embodiment, Figure 21 As shown in the figure, when two intermediate regions 17 with the largest refractive index of a first periodic structure 140 are installed, the width w of the second layer 142 can be set to increase from the intermediate region 17 toward the pixel center portion 11, and can also be set to increase from the intermediate region 17 toward the pixel peripheral portion 13.

[0161] <Fifth embodiment>

[0162] Figure 22 is a cross-sectional view of a pixel 10D according to a fifth exemplary embodiment, taken along the stacking direction. Figure 23 Included are a graph showing the relationship between the magnitude of the average refractive index of light incident on the photoelectric conversion unit 110 and the horizontal position in the photoelectric conversion unit 110 , and a schematic cross-sectional view of the first periodic structure 140 taken along the stacking direction.

[0163] In at least one of the plurality of pixels 10D included in the solid-state imaging device 1, the first periodic structure 140 may be formed as follows. Figure 22 and Figure 23 , in which the first layer 141 and the second layer 142 are arranged so that in the adjacent area 15 close to the pixel peripheral portion 13, the volume ratio of the first layer 141 is greater than the volume ratio of the second layer 142, and the volume ratio of the first layer 141 decreases from the pixel peripheral portion 13 toward the pixel center portion 11.

[0164] The first periodic structure 140 may be configured such that the volume ratio of the first layer 141 is greater than the volume ratio of the second layer 142 in the adjacent region 15 close to the pixel peripheral portion 13, and the volume ratio of the first layer 141 decreases from the pixel peripheral portion 13 toward the pixel central portion 11. Figure 23As shown in the graph of , in the first periodic structure 140, the average refractive index may be minimum at a position corresponding to the pixel center portion 11. Figure 23 An imaginary line H3 in the graph of φ indicates a position where the refractive index is minimum in the first periodic structure 140 (the same position as the pixel center portion 11 ).

[0165] like Figure 22 As shown in , in the pixel 10D including the first periodic structure 140 configured as described above, even in a case where, for example, the first wiring layer 131 arranged on the Z2 upper side of the photoelectric conversion unit 110 is arranged so as not to overlap with the central portion 121 of the on-chip lens 120, the incident light F1 passing through the pixel central portion 11 (the central portion 121 of the first periodic structure 140) and the other incident light F2 and F3 can be collected from their positions in the two adjacent regions 15 onto each of the first wiring layers 131 arranged at specific intervals in the horizontal direction. Therefore, even in a case where the pixel 10D has a stacked structure in which the first wiring layer 131 is arranged so as not to overlap with the central portion 121 of the on-chip lens 120, the pixel 10D can effectively prevent the occurrence of color mixing.

[0166] In addition, in this embodiment, Figure 23 , when the refractive index of the region corresponding to the pixel central portion 11 is the smallest and the refractive indexes of the two regions corresponding to the pixel peripheral portion 13 are the largest, the width w of the second layer 142 is set to decrease from the pixel central portion 11 toward the pixel peripheral portion 13. The period p can be set to have a specific length in the horizontal direction of the first periodic structure 140.

[0167] The solid-state imaging device according to the inventive concept has been described through the multiple embodiments and multiple modification examples, but the inventive concept is not limited to the description provided herein and can be modified appropriately.

[0168] For example, in the second to fifth embodiments, examples of pixels each including a first periodic structure and a second periodic structure are provided, but the pixel may be configured to include only the first periodic structure. In addition, the cross-sectional shape in the stacking direction or the arrangement in the plan view of each layer of the first periodic structure and / or each layer of the second periodic structure according to the first to fifth embodiments may be configured by arbitrarily adopting and combining those of Modification Examples 1 to 8.

[0169] While the inventive concept has been particularly shown and described with reference to embodiments thereof, it will be understood that various changes in form and details may be made therein without departing from the spirit and scope of the appended claims.

Claims

1. A solid-state imaging device comprising: A pixel array comprising a plurality of pixels, Wherein, each of the plurality of pixels comprises: a photoelectric conversion unit configured to convert light into electric charges; an on-chip lens mounted on one side of the photoelectric conversion unit; a wiring layer mounted on the other side of the photoelectric conversion unit; and a first periodic structure mounted on the one side of the photoelectric conversion unit and having periodicity in a horizontal direction perpendicular to the stacking direction of the photoelectric conversion unit, wherein the first periodic structure comprises a plurality of first layers and a plurality of second layers, the plurality of second layers having a refractive index lower than that of the plurality of first layers, and wherein, in at least one of the plurality of pixels, the plurality of first layers and the plurality of second layers of the first periodic structure are arranged so that a volume ratio of the plurality of first layers in the central portion of the pixel is greater than a volume ratio of the plurality of second layers in the central portion of the pixel, and the volume ratio of the plurality of first layers decreases in a horizontal direction from the central portion of the pixel toward the peripheral portion of the pixel.

2. The solid-state imaging device according to claim 1, wherein The widths of the plurality of second layers in the horizontal direction are different from each other, and The first periodic structure is configured such that a volume ratio of the plurality of first layers decreases from a central portion of the pixel toward a peripheral portion of the pixel.

3. The solid-state imaging device according to claim 1, wherein The depths of the plurality of second layers in the stacking direction are different from each other, and The first periodic structure is configured such that a volume ratio of the plurality of first layers decreases from a central portion of the pixel toward a peripheral portion of the pixel.

4. The solid-state imaging device according to claim 1, wherein The period of the first periodic structure is set to a specific value based on the wavelength and incident angle of light received by the photoelectric conversion unit, and includes a length smaller than the wavelength of the received light and enabling generation of diffracted light in the photoelectric conversion unit.

5. The solid-state imaging device according to claim 1, wherein The depth of the plurality of first layers in the stacking direction and the depth of the plurality of second layers in the stacking direction are equal to the wavelength of light received by the photoelectric conversion unit, and The thickness of the photoelectric conversion unit is greater than the depth of the plurality of first layers and the depth of the plurality of second layers.

6. The solid-state imaging device according to claim 1, wherein The photoelectric conversion unit is at least partially covered by a dielectric layer having a refractive index lower than that of the plurality of first layers, and The period of the first periodic structure includes a length that enables diffracted light generated in the photoelectric conversion unit to be completely reflected at a boundary between the photoelectric conversion unit and the dielectric layer.

7. The solid-state imaging device according to claim 1, wherein A wiring layer arranged at a position closest to the photoelectric conversion unit in the stacking direction among the wiring layers has a reflective structure that reflects light emitted by the photoelectric conversion unit.

8. The solid-state imaging device according to claim 1, wherein A position where the volume ratio of the first layer in the plurality of first layers of the first periodic structure is the largest is arranged at a position corresponding to a position of a center portion of the on-chip lens in the horizontal direction, and Here, the central portion of the on-chip lens is arranged at a specific position between the central portion of the pixel and the peripheral portion of the pixel corresponding to the incident angle of light received by the photoelectric conversion unit.

9. The solid-state imaging device according to claim 1, wherein In at least one of the multiple pixels, the multiple first layers and the multiple second layers of the first periodic structure are arranged so that in the middle area between the pixel center and the pixel periphery, the volume ratio of the multiple first layers is greater than the volume ratio of the multiple second layers, and the volume ratio of the multiple first layers decreases from the middle area toward the pixel center and the pixel periphery.

10. The solid-state imaging device according to claim 1, wherein In at least one of the multiple pixels, the multiple first layers and the multiple second layers of the first periodic structure are arranged so that in an adjacent area close to the peripheral portion of the pixel, the volume ratio of the multiple first layers is greater than the volume ratio of the multiple second layers, and the volume ratio of the multiple first layers decreases from the peripheral portion of the pixel toward the center portion of the pixel.

11. The solid-state imaging device according to claim 1, wherein The photoelectric conversion unit includes a plurality of photoelectric conversion units, The plurality of photoelectric conversion units are separated from each other by an insulating film.

12. The solid-state imaging device according to claim 1, wherein The photoelectric conversion unit includes a plurality of photoelectric conversion units, wherein the plurality of photoelectric conversion units are separated from each other by fixed charge films, and Here, the fixed charge film includes an oxide film or a nitride film containing at least one metal element among hafnium, aluminum, zirconium, tantalum, and titanium.

13. A solid-state imaging device comprising: A pixel array comprising a plurality of pixels, Each of the plurality of pixels comprises: a photoelectric conversion unit configured to convert light into electric charges; an on-chip lens mounted on one side of the photoelectric conversion unit; a wiring layer mounted on the other side of the photoelectric conversion unit; and a first periodic structure mounted on the one side of the photoelectric conversion unit and having periodicity in a horizontal direction perpendicular to the stacking direction of the photoelectric conversion unit, wherein the first periodic structure comprises a plurality of first layers and a plurality of second layers, the plurality of second layers having a refractive index lower than that of the plurality of first layers, wherein, in at least one of the plurality of pixels, the plurality of first layers and the plurality of second layers of the first periodic structure are arranged such that a volume ratio of the plurality of first layers in a central portion of the pixel is greater than a volume ratio of the plurality of second layers in the central portion of the pixel, and the volume ratio of the plurality of first layers decreases from the central portion of the pixel toward a peripheral portion of the pixel in a horizontal direction, The pixel including the first periodic structure further includes a second periodic structure installed on the other side of the photoelectric conversion unit and having periodicity in the horizontal direction, and The second periodic structure includes a plurality of third layers and a plurality of fourth layers, the plurality of third layers having a refractive index equal to that of the plurality of first layers, and the plurality of fourth layers having a refractive index equal to that of the plurality of second layers.

14. The solid-state imaging device according to claim 13, wherein The second periodic structure has a periodicity equivalent to that of the first periodic structure.

15. The solid-state imaging device according to claim 13, wherein The distribution of the volume proportions of the plurality of first layers in the first periodic structure is identical to the distribution of the volume proportions of the plurality of third layers in the second periodic structure, and The distribution of volume proportions of the plurality of second layers in the first periodic structure is identical to the distribution of volume proportions of the plurality of fourth layers in the second periodic structure.

16. The solid-state imaging device according to claim 13, wherein At least one of the first periodic structure and the second periodic structure is configured based on the wavelength and incident angle of the light received by the photoelectric conversion unit so that the volume ratio of the multiple first layers and the volume ratio of the multiple second layers are different from each other and / or the volume ratio of the multiple third layers and the volume ratio of the multiple fourth layers are different from each other.

17. The solid-state imaging device according to claim 13, wherein At least one of the periods of the first periodic structure in the central portion of the pixel array and the second periodic structure in the central portion of the pixel array is different from at least one of the periods of the first periodic structure in the peripheral portion of the pixel array and the second periodic structure in the peripheral portion of the pixel array.

18. A solid-state imaging device comprising: A pixel array comprising a plurality of pixels, Wherein, each of the plurality of pixels comprises: a photoelectric conversion unit configured to convert light into electric charges; an on-chip lens mounted on one side of the photoelectric conversion unit; a wiring layer mounted on the other side of the photoelectric conversion unit; and a first periodic structure mounted on the one side of the photoelectric conversion unit and having periodicity in a horizontal direction perpendicular to the stacking direction of the photoelectric conversion unit, wherein the first periodic structure comprises a plurality of first layers and a plurality of second layers, the plurality of second layers having a refractive index lower than that of the plurality of first layers, and In at least one of the plurality of pixels, depths of the plurality of second layers of the first periodic structure are equal to one another, and widths of the plurality of second layers increase from a central portion of the pixel toward a peripheral portion of the pixel.

19. The solid-state imaging device according to claim 18, wherein The plurality of first layers include any one of silicon, germanium, and indium gallium arsenide.

20. The solid-state imaging device according to claim 18, wherein The plurality of second layers include any one of silicon dioxide, silicon nitride, aluminum oxide, tantalum oxide, titanium nitride, and titanium oxide.

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