Solid-state image sensor

Abstract

A solid-state image sensor is configured to reduce the occurrence of stray light or color mixing by appropriately reflecting light from a wiring layer. The solid-state image sensor includes: a plurality of photoelectric conversion units arranged two-dimensionally; an on-chip lens formed on one side of the photoelectric conversion unit; a wiring layer formed on the other side of the photoelectric conversion unit; and a first periodic structure formed in a first wiring layer of the wiring layers, the first periodic structure having a periodicity in a two-dimensional direction perpendicular to the stacking direction. Among the wiring layers, a first wiring layer is closest to the photoelectric conversion unit. The first periodic structure includes a plurality of metal layers and a plurality of dielectric layers, the metal layers including a metal, and the dielectric layers including a dielectric material.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based on and claims the benefit of priority from Japanese Patent Application No. 2024-032694 filed in the Japan Patent Office on March 5, 2024, and Korean Patent Application No. 10-2024-0073182 filed in the Korean Intellectual Property Office on June 4, 2024, the disclosures of which are incorporated herein in their entirety by reference. Technical Field

[0002] The present disclosure relates to a solid-state image sensor. Background Art

[0003] Solid-state image sensors can be installed in various mobile devices, such as digital cameras or portable phones. Generally, a solid-state image sensor may include a plurality of photoelectric conversion units arranged two-dimensionally, an on-chip lens formed on the light-incident side of the photoelectric conversion unit, and a wiring layer formed on the other side of the photoelectric conversion unit, the other side being opposite to the light-incident side formed with the on-chip lens. Summary of the Invention

[0004] In some solid-state image sensors, some light not absorbed by the photoelectric conversion unit may be reflected by the wiring layer and returned to the unit. In this case, due to insufficient light reflection at the wiring layer, stray light or color mixing may occur. The present disclosure provides a solid-state image sensor that can reduce the occurrence of stray light and color mixing by appropriately reflecting light from the wiring layer.

[0005] In a first general aspect, a solid-state image sensor includes: a plurality of photoelectric conversion units arranged in two dimensions; an on-chip lens formed on one side of the photoelectric conversion unit; a wiring layer formed on the other side of the photoelectric conversion unit; and a first periodic structure formed in a first wiring layer among the wiring layers, the first periodic structure having periodicity in a two-dimensional direction perpendicular to the stacking direction, wherein, among the wiring layers, the first wiring layer is closest to the photoelectric conversion unit, wherein the first periodic structure includes a metal layer and a dielectric layer, the metal layer and the dielectric layer are each provided in plurality, the metal layer includes a metal, and the dielectric layer includes a dielectric material.

[0006] In a second general aspect, a solid-state image sensor includes: a plurality of photoelectric conversion units arranged in two dimensions; an on-chip lens formed on one side of the photoelectric conversion unit; a wiring layer formed on the other side of the photoelectric conversion unit; and a first periodic structure formed in an interlayer film between the photoelectric conversion unit and a first wiring layer in the wiring layers, the first periodic structure having periodicity in a two-dimensional direction perpendicular to the stacking direction, wherein, among the wiring layers, the first wiring layer is closest to the photoelectric conversion unit, wherein the first periodic structure includes a high refractive index layer and a low refractive index layer, the high refractive index layer and the low refractive index layer are each provided in plurality, and the refractive index of the high refractive index layer is higher than the refractive index of the low refractive index layer.

[0007] Implementations of the disclosed solid-state image sensors may include one or more of the following features.

[0008] In some embodiments, shapes of the metal layers of the first periodic structure include: an island shape, in which each metal layer is independently arranged; or a peninsula shape, a ring shape, or a line shape, in which the metal layers are connected to each other.

[0009] In some embodiments, the metal layer of the first periodic structure may include wirings for sensor operation and dummy wirings that do not contribute to the sensor operation.

[0010] In some embodiments, the width of the metal layer of the first periodic structure may be greater than the width of the dielectric layer.

[0011] In some embodiments, the period of the metal layer of the first periodic structure can vary according to the wavelength and incident angle of the light received by the photoelectric conversion unit and can be shorter than the wavelength, and the light irradiated to the first periodic structure can be configured to generate diffracted light in the first periodic structure.

[0012] In some embodiments, in each of the two-dimensionally arranged plurality of photoelectric conversion units, the period of the first periodic structure may be different in a pixel array central portion and a pixel array peripheral portion, wherein the pixel array peripheral portion may surround the pixel array central portion.

[0013] In some embodiments, when the wavelength of light received by the photoelectric conversion unit is 940 nm, the height of the first periodic structure may be in a range of about 100 nm to about 1500 nm.

[0014] In some embodiments, when the wavelength of light received by the photoelectric conversion unit is 940 nm, the height of the first periodic structure may satisfy a reflectivity of 70% or higher.

[0015] In some embodiments, the solid-state image sensor may further include a second periodic structure formed in an interlayer film located between the photoelectric conversion unit and the first wiring layer, the second periodic structure having periodicity in a two-dimensional direction perpendicular to the stacking direction, wherein the second periodic structure includes a high refractive index layer and a low refractive index layer, the high refractive index layer and the low refractive index layer are both arranged in plurality, and the refractive index of the high refractive index layer is higher than the refractive index of the low refractive index layer.

[0016] In some embodiments, shapes of the high refractive index layers of the second periodic structure may include an island shape in which each high refractive index layer is independently arranged, or a peninsula shape, a ring shape, or a line shape in which the high refractive index layers are connected to each other.

[0017] In some embodiments, the period of the second periodic structure may vary according to the wavelength and incident angle of light received by the photoelectric conversion unit and may be shorter than the wavelength, and the light irradiated to the second periodic structure is configured to generate diffracted light in the second periodic structure.

[0018] In some embodiments, in each of the two-dimensionally arranged plurality of photoelectric conversion units, the period of the second periodic structure may be different in a pixel array central portion and a pixel array peripheral portion, wherein the pixel array peripheral portion may surround the pixel array central portion.

[0019] In some embodiments, a distance from the bottom surface of the photoelectric conversion unit to the first periodic structure and a distance from the bottom surface of the photoelectric conversion unit to the second periodic structure may be an integer multiple of half a wavelength of incident light.

[0020] In some embodiments, the second periodic structure may have a concave-convex shape, and when the wavelength of light received by the photoelectric conversion unit is 940nm, the height of the convex portion of the concave-convex shape may be in the range of about 200nm to about 400nm, or in the range of about 1000nm to about 1200nm.

[0021] In some embodiments, the second periodic structure may have a concavo-convex shape, and a height of a convex portion of the concavo-convex shape may satisfy a reflectivity of 70% or higher when a wavelength of light received by the photoelectric conversion unit is 940 nm.

[0022] In some embodiments, shapes of the high refractive index layers of the first periodic structure may include an island shape in which each high refractive index layer is independently arranged, or a peninsula shape, a ring shape, or a line shape in which the high refractive index layers are connected to each other.

[0023] In some embodiments, the period of the first periodic structure may vary according to the wavelength and incident angle of light received by the photoelectric conversion unit and may be shorter than the wavelength, and the light irradiated to the first periodic structure may be configured to generate diffracted light in the first periodic structure.

[0024] In some embodiments, in each of the two-dimensionally arranged plurality of photoelectric conversion units, the period of the first periodic structure may be different in a pixel array central portion and a pixel array peripheral portion, wherein the pixel array peripheral portion may surround the pixel array central portion.

[0025] In some embodiments, the first periodic structure may be a concave-convex shape, and when the wavelength of light received by the photoelectric conversion unit is 940 nm, the height of the convex portion of the concave-convex shape is in the range of about 200 nm to about 400 nm, in the range of about 1000 nm to about 1200 nm, or satisfies a reflectivity of 70% or higher. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 is a front cross-sectional view of an example of a solid-state image sensor.

[0027] Figure 2 is a plan view of an example of a wiring layer of a solid-state image sensor.

[0028] Figure 3 is a plan view of another example of a wiring layer of a solid-state image sensor.

[0029] Figure 4 is a schematic front view of an example of a wiring layer of a solid-state image sensor when the pitch of the metal layer is relatively short.

[0030] Figure 5 is a plan view of an example of a pixel region including a plurality of pixels.

[0031] Figure 6 is a graph showing an example of the relationship between the pitch and reflectivity of the first periodic structure when the incident angle is changed to four types.

[0032] Figure 7 is a graph showing an example of the relationship between the height and reflectivity of the metal layer of the first periodic structure.

[0033] Figure 8 is a schematic front view of an example of a second periodic structure of a solid-state image sensor.

[0034] Figure 9 is a graph showing an example of the relationship between the pitch and reflectivity of the second periodic structure when the incident angle is changed to four types.

[0035] Figure 10 is a graph showing an example of the relationship between the height of the convex portion of the second periodic structure and the reflectivity.

[0036] Figure 11 is a schematic cross-sectional view illustrating an example in which incident light is reflected from the first periodic structure and the second periodic structure.

[0037] Figure 12 : is a graph showing an example of the relationship between the pitch and the reflectivity when the incident angle is changed to 4 types and the first periodic structure and the second periodic structure have the same pitch.

[0038] Figure 13 is a front cross-sectional view of a solid-state image sensor according to a comparative example.

[0039] Figure 14 is a plan view of a comparative example of a wiring layer of a solid-state image sensor according to a comparative example.

[0040] Figure 15 is a schematic cross-sectional view of an example of a second periodic structure of a solid-state image sensor.

[0041] Figure 16 is a plan view of an example of the first periodic structure.

[0042] Figure 17 is a plan view of another example of the first periodic structure.

[0043] Figure 18 is a plan view of another example of the first periodic structure.

[0044] Figure 19 is a plan view of another example of the first periodic structure.

[0045] Figure 20 is a plan view of another example of the first periodic structure.

[0046] Figure 21 is a plan view of an example of the second periodic structure.

[0047] Figure 22 is a plan view of another example of the second periodic structure.

[0048] Figure 23 is a plan view of another example of the second periodic structure.

[0049] The dimensional ratios in the drawings may be exaggerated for clarity and may be different from the actual proportions. DETAILED DESCRIPTION

[0050] Reference Figure 1The solid-state image sensor 1 may be a complementary metal oxide semiconductor (CMOS) solid-state image sensor. The solid-state image sensor 1 includes a plurality of photoelectric conversion units 10 arranged two-dimensionally, an on-chip lens 20 formed on the photoelectric conversion units 10, a first periodic structure 32, a wiring layer 30 formed below the photoelectric conversion units 10, and a second periodic structure 40 formed in an interlayer film 90 (e.g., an interlayer insulating film) between the photoelectric conversion units 10 and the wiring layer 30. The interlayer film 90 may include a dielectric material or an insulator.

[0051] The photoelectric conversion unit 10 may be formed in plural on a substrate 11. The substrate 11 may be, for example, a semiconductor substrate, such as a silicon (Si) substrate. Figure 1 In the embodiment, the lower surface of the substrate 11 may be the front surface of the substrate 11, and the upper surface of the substrate 11 may be the back surface of the substrate 11. Since the solid-state image sensor 1 in this example is a so-called back-illuminated type, the on-chip lens 20 may be formed on the back side of the substrate 11. The back side of the substrate 11 may be the light incident surface of the substrate 11. In addition, the wiring layer 30 may be formed on the surface side of the substrate 11. The substrate 11 may have a thickness of, for example, approximately 1 μm to approximately 6 μm.

[0052] The photoelectric conversion unit 10 can be formed for each pixel in the substrate 11. The photoelectric conversion unit 10 may include a p-type semiconductor region and an n-type semiconductor region. In the photoelectric conversion unit 10, a photodiode can be implemented by a pn junction between the p-type semiconductor region and the n-type semiconductor region, and converts light into charge. The photoelectric conversion unit 10 can receive light incident on the on-chip lens 20, generate signal charge based on the amount of received light, and accumulate the generated signal charge in the n-type semiconductor region.

[0053] like Figure 1 As shown, adjacent photoelectric conversion units 10 can be separated from each other by an insulating film 12. Therefore, it may be difficult for signal charge to flow from one pixel to an adjacent pixel. For this reason, when a signal charge exceeding the saturation charge amount is generated, the flow of signal charge from the photoelectric conversion unit 10 where the signal charge overflows to the photoelectric conversion unit 10 adjacent thereto can be reduced. Therefore, the occurrence of color mixing between pixels can be suppressed. The constituent material of the insulating film 12 may include a silicon oxide film, a silicon nitride film, a silicon oxynitride film, or a resin film. The insulating film 12 may include a film that has no positive fixed charge or has very little positive fixed charge.

[0054] Furthermore, a fixed charge film may be formed between adjacent photoelectric conversion units 10. The fixed charge film can reduce dark current and noise. The material constituting the fixed charge film may include, for example, 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 may include, for example, a chemical vapor deposition (CVD) process, a sputtering process, and an atomic layer deposition (ALD) process.

[0055] The on-chip lens 20 may be formed for each pixel. The on-chip lens 20 may condense incident light. The light condensed by the on-chip lens 20 may be incident on the photoelectric conversion unit 10.

[0056] Furthermore, a light shielding film and a planarization film may be formed between the on-chip lens 20 and the photoelectric conversion unit 10 .

[0057] like Figure 1 As shown, the wiring layer 30 may include a plurality of wiring layers along the stacking direction. Among the plurality of wiring layers 30 formed along the stacking direction, the first periodic structure 32 may be formed in the first wiring layer 31 closest to the photoelectric conversion unit 10.

[0058] like Figure 2 As shown, the first periodic structure 32 may have periodicity in a two-dimensional direction (plane direction) perpendicular to the stacking direction. Figure 2 and Figure 3 As shown, the first periodic structure 32 may include a metal layer 33 and a dielectric layer 34. The metal layer 33 and the dielectric layer 34 may be formed in plural.

[0059] like Figure 2 and Figure 3 As shown, each metal layer 33 may be independently arranged in an island shape, eg, not in contact with each other and separated by dielectric layer 34. Metal layers 33 may be arranged in a zigzag shape, eg, adjacent metal layers 33 are offset from each other in two horizontal directions.

[0060] The metal layer 33 may include wiring for sensor operation and dummy wiring that does not contribute to the sensor operation. Figure 2 In the embodiment, for example, the wirings 33A for sensor operation may be located at the center and both sides of the first periodic structure 32, and the dummy wirings 33B may be formed at the remaining positions, for example, between the wirings 33A. Figure 3For example, the wiring 33A for sensor operation may be located at the center and four corners of the first periodic structure 32, while the dummy wiring 33B may be formed at the remaining locations. When forming the wiring layer 30, it may be necessary to maintain the coverage of the metal layer 33 within a predetermined range to flatten the film thickness, and the dummy wiring may be formed so that the coverage of the metal layer 33 is maintained within the predetermined range.

[0061] like Figure 2 and Figure 3 As shown, the dielectric layer 34 may be linearly arranged along the outer periphery of the metal layer 33 having an island shape. The dielectric layer 34 may be linearly arranged to separate the metal layer 33.

[0062] like Figure 4 As shown, the width W1 of the metal layer 33 of the first periodic structure 32 can be greater than the width W2 of the dielectric layer 34. According to the above configuration, since the area occupied by the metal layer 33 that contributes to reflection is greater than the area occupied by the dielectric layer 34, the incident light can be properly reflected by the first periodic structure 32.

[0063] Assuming that the refractive index of the dielectric layer 34 is n1, the incident angle of the incident light is θ, the diffraction order m is a natural number, the wavelength of the incident light is λ, and the refractive index of the metal layer 33 is n2, the pitch P1 of the metal layer 33 in the horizontal plane direction can satisfy the following equation 1:

[0064] [Equation 1]

[0065]

[0066] When the periodic relationship defined by Equation 1 is satisfied, light incident on the first periodic structure 32 can be diffracted by the metal layer 33 in the first periodic structure 32 and can move in the lateral direction, thereby generating an evanescent wave. Therefore, due to surface plasmon resonance, the light intensity can be enhanced, thereby allowing the incident light to be more appropriately reflected by the first periodic structure 32.

[0067] In other words, the pitch P1 of the metal layer 33 of the first periodic structure 32 can be selected according to the wavelength λ and the incident angle θ of the light received by the photoelectric conversion unit 10. The pitch P1 can be shorter than the wavelength λ. In addition, the light irradiated to the first periodic structure 32 can generate diffracted light in the first periodic structure 32. As a result, the above-mentioned surface plasmon resonance effect can be obtained. In addition, by adjusting the pitch P1 of the metal layer 33 of the first periodic structure 32 to a size smaller than the wavelength λ, the reflectivity can be improved. Figure 6 As shown, when the wavelength λ of the incident light is 940 nm, the pitch P1 of the metal layer 33 may be in the range of about 200 nm to about 1000 nm, for example, in the range of about 400 nm to about 500 nm.

[0068] like Figure 6 As shown, when the pitch P1 of the first periodic structure 32 is constant, the reflectivity of the first periodic structure 32 may vary according to the incident angle θ. Figure 6 is a graph showing simulation results of the reflectivity of the first periodic structure 32 when the pitch P1 and the incident angle θ are appropriately changed.

[0069] Since the reflectivity of the first periodic structure 32 varies according to the incident angle θ, in order to improve the reflectivity, in each of the plurality of photoelectric conversion units 10 arranged two-dimensionally, the pitch P1 of the first periodic structure 32 may be at the center portion of the pixel array (see Figure 5 The pixel array central portion 10C in FIG) and the pixel array peripheral portion surrounding the pixel array central portion 10C (see FIG). Figure 5 The incident angle θ at the pixel array center 10C is different from the incident angle θ at the pixel array periphery 10E. This is likely due to the fact that the incident angle θ at the pixel array center 10C is different from the incident angle θ at the pixel array periphery 10E. With this configuration, the surface plasmon resonance effect can be appropriately exhibited in all pixels, and the reflectivity of the first periodic structure 32 can be improved.

[0070] Next, refer to Figure 7 Describe the height of the first periodic structure 32 (see Figure 4 H in ). Figure 7 : is a graph showing simulation results of the reflectivity of the first periodic structure 32 when the height H of the first periodic structure 32 is appropriately changed.

[0071] When the wavelength λ of light incident on the photoelectric conversion unit 10 is 940 nm, the height H of the first periodic structure 32 can be in the range of about 100 nm to about 1500 nm. According to the above numerical range, the reflectivity of the first periodic structure 32 can be improved. The height H of the first periodic structure 32 is not limited to the above numerical range and can be selected to satisfy a reflectivity of 70% or higher.

[0072] Next, refer to Figures 8 to 10 The configuration of the second periodic structure 40 is described below. Figure 1 As shown, the second periodic structure 40 may be formed in the interlayer film 90 between the photoelectric conversion unit 10 and the first wiring layer 31. The second periodic structure 40 may have periodicity in a two-dimensional direction perpendicular to the stacking direction.

[0073] like Figure 8 As shown, the second periodic structure 40 may include a high refractive index layer 41 and a low refractive index layer 42. The high refractive index layer 41 may have a higher refractive index than the low refractive index layer 42.

[0074] The high refractive index layer 41 may be formed of a silicon nitride film, and the low refractive index layer 42 may be formed of a silicon oxide film.

[0075] like Figure 8 As shown, high refractive index layer 41 (e.g., a diffraction grating) can include flat portions 43 and raised portions 44 (e.g., ridges of the diffraction grating). Each raised portion has a convex shape relative to flat portion 43, such that a line segment between any two different points on the boundary of raised portion 44 is above flat portion 43. Each raised portion 44 can be independently arranged in an island shape. As a result, the overall shape of high refractive index layer 41 is concave-convex, for example, alternating between raised portions and flat portions, resulting in alternating height variations in high refractive index layer 41.

[0076] like Figure 8 As shown, the flat portion 43 and the convex portion 44 of the high refractive index layer 41 may be inserted into the low refractive index layer 42 .

[0077] In the following, reference is made to Figure 8 The mechanism by which the second periodic structure 40 functions as a guided mode resonance grating is described.

[0078] When incident light enters the second periodic structure 40 configured as described above, the light may enter the high refractive index layer 41 from the low refractive index layer 42, and therefore, no phase difference may occur in the phase of the transmitted light. A phase difference π may occur in the phase Φ of the reflected light reflected by the high refractive index layer 41 and returned to the low refractive index layer 42. In addition, a phase difference π / 2 may occur in the phase Φ of the light diffracted by the second periodic structure 40.

[0079] Therefore, assuming that the phase Φ of the incident light A is 0, the phase Φ of the transmitted light B can be changed to 0, and the phase Φ of the reflected light C can be changed to π. In addition, the phase Φ of the light D diffracted by the convex portion 44 can be changed to π / 2. In addition, when the diffracted light D is guided within the convex portion 44 and enters the convex portion 44 again, a portion of the diffracted light D may be re-diffracted upward and downward in the convex portion 44. As a result, the phase Φ of the diffracted light D can be changed to π. In addition, the diffracted light D can be repeatedly guided within the convex portion 44 and diffracted upward and downward by the convex portion 44 again in the convex portion 44, and therefore, the phase Φ of the diffracted light D can be changed to π.

[0080] Therefore, the light emitted downward from the second periodic structure 40 includes a mixture of transmitted light B with a phase Φ of 0 and diffracted light D with a phase Φ of π. Therefore, the transmitted light B and the diffracted light D can destructively interfere with each other. In contrast, all the light emitted upward from the second periodic structure 40 can have a phase Φ of π and constructively interfere with each other.

[0081] When the light diffracted by the convex portion 44 satisfies the guided mode by satisfying the total reflection condition within the convex portion 44, the transmission of the incident light A with a wavelength λ can be suppressed (or blocked) in the second periodic structure 40, and most of the incident light A can be reflected.

[0082] Furthermore, when the wavelength of incident light, the period and height of the second periodic structure 40 , the width of the convex portion 44 , and the height of the flat portion 43 satisfy certain conditions, reflection of light may be achieved.

[0083] The pitch P2 of the convex portions 44 of the high refractive index layer 41 can vary depending on the wavelength λ and the incident angle θ of the light received by the photoelectric conversion unit 10, and can also be shorter than the wavelength λ. In addition, the light irradiated to the second periodic structure 40 can be selected to generate diffracted light in the second periodic structure 40. Because a lot of diffracted light is generated due to the above configuration, the incident light can be appropriately reflected by the second periodic structure 40. When the wavelength λ of the incident light is 940 nm, the pitch P2 of the convex portions 44 can be in the range of about 400 nm to about 800 nm.

[0084] like Figure 9 As shown, when the pitch P2 of the convex portions 44 of the second periodic structure 40 is constant, the reflectivity of the second periodic structure 40 may vary according to the incident angle θ. Figure 9 : is a graph showing simulation results of the reflectivity of the second periodic structure 40 when the pitch P2 and the incident angle θ are appropriately changed.

[0085] Since the reflectivity of the second periodic structure 40 varies depending on the incident angle θ and the pitch P2 of the second periodic structure 40, in order to improve the reflectivity, in each of the plurality of photoelectric conversion units 10 arranged two-dimensionally, the pitch P2 of the second periodic structure 40 may be different between the pixel array central portion 10C and the pixel array peripheral portion 10E surrounding the pixel array central portion 10C. This may be due to the fact that the incident angle θ of the pixel array central portion 10C is different from the incident angle θ of the pixel array peripheral portion 10E. According to the above configuration, the reflectivity of the second periodic structure 40 can be improved.

[0086] Next, refer to Figure 10 Describe the height of the convex portion 44 of the second periodic structure 40 (see Figure 8 H2 in ). Figure 10 : is a graph showing simulation results of the reflectivity of the second periodic structure 40 when the height H2 of the convex portion 44 of the second periodic structure 40 is appropriately changed.

[0087] When the wavelength λ of light incident on the photoelectric conversion unit 10 is 940 nm, the height H2 of the convex portion 44 of the second periodic structure 40 can be in the range of about 200 nm to about 400 nm or in the range of about 1000 nm to about 1200 nm. According to the above numerical range, the reflectivity of the second periodic structure 40 can be improved. The height H2 of the second periodic structure 40 is not limited to the above numerical range and can be set to meet a reflectivity of 70% or higher.

[0088] like Figure 11 As shown, the distance L1 from the bottom surface of the photoelectric conversion unit 10 to the center of the first periodic structure 32, and the distance L2 from the bottom surface of the photoelectric conversion unit 10 to the flat portion 43 of the second periodic structure 40 can be an integer multiple of half the wavelength of the incident light. According to the above configuration, the phases of the light reflected by the interface between the photoelectric conversion unit 10 and the low refractive index layer 42, the light reflected by the first periodic structure 32, and the light reflected by the second periodic structure 40 can be gathered and enhanced. Therefore, the light intensity in the photoelectric conversion unit 10 can be further improved.

[0089] Next, refer to Figure 11 The behavior of incident light when light is incident on this example of the solid-state image sensor 1 is described.

[0090] First, light can be emitted from the back side (or Figure 11 The upper part of the chip is illuminated and incident on the on-chip lens 20 ( Figure 11 (not shown). Light incident on the on-chip lens 20 can be focused by the on-chip lens 20 and enter the photoelectric conversion unit 10. The photoelectric conversion unit 10 can convert the incident light into electric charge through photoelectric conversion and generate signal charge. The signal charge can be output as a pixel signal through the wiring layer 30 formed on the surface of the substrate 11.

[0091] For example, Figure 13 and Figure 14 As shown, when the first periodic structure 32 and the second periodic structure 40 are replaced with a reflector M having a larger width located in the center (for example, of a solid-state image sensor), part of the light not absorbed by the photoelectric conversion unit may be reflected by the wiring layer and returned to the photoelectric conversion unit. However, due to insufficient light reflection at the wiring layer, stray light or color mixing may occur (see Figure 13 (arrow in the middle).

[0092] In contrast, in the solid-state image sensor 1 disclosed herein, for example, unlike the reflecting mirror M, by forming Figure 11As shown in the first periodic structure 32 and the second periodic structure 40 , incident light can be reflected by the first periodic structure 32 and the second periodic structure 40 and returned to the photoelectric conversion unit 10 , thereby reducing the occurrence of stray light or color mixing.

[0093] By arranging the first periodic structure 32 and the second periodic structure 40, as Figure 12 As shown, the influence of the incident angle θ can be reduced, thereby improving the reflectivity. Figure 12 : is a graph showing simulation results of the reflectivity of the first periodic structure 32 and the second periodic structure 40 when the pitch and the incident angle θ of the first periodic structure 32 and the second periodic structure 40 are appropriately changed.

[0094] Various modifications can be made to the foregoing examples without departing from the spirit of the present disclosure.

[0095] For example, in the above example, although the second periodic structure 40 includes the flat portion 43 and the convex portion 44, Figure 15 As shown, the second periodic structure 140 may include only the convex portion 44 without forming the flat portion 43 .

[0096] In the above example, the metal layer 33 may be arranged in a zigzag shape in the first periodic structure 32. However, as Figure 16 As shown, the metal layer 33 may have a square arrangement.

[0097] In the above example, the metal layer 33 may have an island shape. Figure 17 As shown near the center of , the metal layer 133 may have a ring shape.

[0098] In the above example, the metal layer 33 may have an island shape. Figures 18 to 20 As shown, the metal layers 233 may each have a peninsula shape and be connected to each other. Figure 18 Corresponding to Figure 2 Example of modification of the peninsula shape, Figure 19 Corresponding to Figure 16 A modified example of the peninsula shape, and Figure 20 Corresponding to Figure 17 Example of a modified peninsula shape.

[0099] In the above example, the metal layer 33 may have an island shape. However, the metal layer may have a line shape.

[0100] like Figure 15 As shown, when the second periodic structure 140 includes only the convex portions 44, the shape of the convex portions 44 may include an island shape, wherein each convex portion 44 is as shown in FIG. Figure 21 shown are arranged independently and can be Figure 21 The circle shown or Figure 22 In addition, as Figure 23 As shown, the low refractive index layer 42 may be configured in a circular shape, and thus, the convex portion 144 may be arranged to occupy the remaining position.

[0101] In the above-described example, the solid-state image sensor 1 may include both the first periodic structure 32 and the second periodic structure 40 . However, the solid-state image sensor 1 may not include either of the first periodic structure 32 and the second periodic structure 40 .

[0102] Although the present disclosure contains many specific implementation details, they should not be interpreted as limiting the scope of the claimed protection. Certain features described in the present disclosure in the context of separate embodiments may also be implemented in combination in a single embodiment. Conversely, various features described in the context of a single embodiment may also be implemented in multiple embodiments individually or in any suitable sub-combination. In addition, although the above features may be described as working in the form of certain combinations, in some cases, one or more features in a combination may be deleted from the combination, and a combination may refer to a sub-combination or a variant of a sub-combination.

[0103] While examples have 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 image sensor comprising: a plurality of photoelectric conversion units arranged two-dimensionally; an on-chip lens formed on a first side of each of the plurality of photoelectric conversion units; a wiring layer formed on a second side of each of the plurality of photoelectric conversion units; as well as a first periodic structure formed in a first wiring layer among the wiring layers, the first periodic structure having a two-dimensional periodicity in two directions perpendicular to a stacking direction, wherein, among the wiring layers, the first wiring layer is closest to each of the plurality of photoelectric conversion units, The first periodic structure includes a plurality of metal layers and a plurality of dielectric layers.

2. The solid-state image sensor according to claim 1, wherein The plurality of metal layers of the first periodic structure have: an island shape, wherein each of the plurality of metal layers is independently arranged; or a peninsula shape, a ring shape, or a line shape, wherein the plurality of metal layers are connected to each other.

3. The solid-state image sensor according to claim 1, wherein Each of the plurality of metal layers of the first periodic structure comprises: Wiring configured for sensor operation; and Dummy wiring.

4. The solid-state image sensor according to claim 1, wherein A width of each of the plurality of metal layers of the first periodic structure is greater than a width of each of the plurality of dielectric layers.

5. The solid-state image sensor according to claim 1, wherein The period of the metal layer of the first periodic structure varies according to the wavelength and incident angle of the light received by the multiple photoelectric conversion units, and the period of the metal layer is shorter than the wavelength, and the light irradiated to the first periodic structure is configured to generate diffracted light in the first periodic structure.

6. The solid-state image sensor according to claim 1, wherein In each of the plurality of photoelectric conversion units, a first period of the first periodic structure in a pixel array central portion is different from a second period in a pixel array peripheral portion surrounding the pixel array central portion.

7. The solid-state image sensor according to claim 1, wherein The wavelength of light received by the plurality of photoelectric conversion units is 940 nm, and the height of the first periodic structure is in the range of 100 nm to 1500 nm.

8. The solid-state image sensor according to claim 1, wherein The wavelength of light received by the plurality of photoelectric conversion units is 940 nm, and the height of the first periodic structure is set to satisfy a reflectivity of 70% or higher.

9. The solid-state image sensor according to claim 1 , further comprising: a second periodic structure formed in an interlayer film between each of the plurality of photoelectric conversion units and the first wiring layer, the second periodic structure having a two-dimensional periodicity in two directions perpendicular to the stacking direction; The second periodic structure includes a plurality of high refractive index layers and a plurality of low refractive index layers.

10. The solid-state image sensor according to claim 9, wherein The plurality of high refractive index layers of the second periodic structure have: an island shape, wherein each of the plurality of high refractive index layers is independently arranged; or a peninsula shape, a ring shape, or a line shape, wherein the plurality of high refractive index layers are connected to each other.

11. The solid-state image sensor according to claim 9, wherein The period of the second periodic structure is shorter than the wavelength of light received by the plurality of photoelectric conversion units, and The period of the second periodic structure, the wavelength of the light, and the incident angle of the light irradiated onto the second periodic structure are selected to generate diffracted light in the second periodic structure.

12. The solid-state image sensor according to claim 9, wherein In each of the plurality of photoelectric conversion units, a first period of the second periodic structure in a pixel array central portion is different from a second period in a pixel array peripheral portion surrounding the pixel array central portion.

13. The solid-state image sensor according to claim 9, wherein A first distance from the bottom surface of the plurality of photoelectric conversion units to the center of the first periodic structure and a second distance from the bottom surface of the plurality of photoelectric conversion units to the second periodic structure are both integer multiples of half a wavelength of incident light.

14. The solid-state image sensor according to claim 9, wherein The second periodic structure has a concavo-convex shape, and The wavelength of light received by the plurality of photoelectric conversion units is 940 nm, and the height of the convex portion of the concavo-convex shape is in the range of 200 nm to 400 nm or in the range of 1000 nm to 1200 nm.

15. The solid-state image sensor according to claim 9, wherein The second periodic structure has a concavo-convex shape, and The wavelength of light received by the plurality of photoelectric conversion units is 940 nm, and the height of the convex portion of the concavo-convex shape is set to satisfy a reflectivity of 70% or higher.

16. A solid-state image sensor comprising: a plurality of photoelectric conversion units arranged two-dimensionally; an on-chip lens formed on a first side of each of the plurality of photoelectric conversion units; a wiring layer formed on a second side of each of the plurality of photoelectric conversion units; as well as a first periodic structure formed in an interlayer film between each of the plurality of photoelectric conversion units and a first wiring layer among the wiring layers, the first periodic structure having two-dimensional periodicity in two directions perpendicular to a stacking direction, wherein, among the wiring layers, the first wiring layer is closest to each of the plurality of photoelectric conversion units, The first periodic structure includes a plurality of high refractive index layers and a plurality of low refractive index layers.

17. The solid-state image sensor according to claim 16, wherein The plurality of high refractive index layers of the first periodic structure have: an island shape, wherein each of the plurality of high refractive index layers is independently arranged; or a peninsula shape, a ring shape, or a line shape, wherein the plurality of high refractive index layers are connected to each other.

18. The solid-state image sensor according to claim 16, wherein The period of the first periodic structure is shorter than the wavelength of light received by the plurality of photoelectric conversion units, and The period of the first periodic structure, the wavelength of the light, and the incident angle of the light irradiated to the first periodic structure are selected to generate diffracted light in the first periodic structure.

19. The solid-state image sensor according to claim 16, wherein In each of the plurality of photoelectric conversion units, a first period of the first periodic structure in a pixel array central portion is different from a second period in a pixel array peripheral portion surrounding the pixel array central portion.

20. The solid-state image sensor according to claim 16, wherein The first periodic structure is a diffraction grating, and The wavelength of light received by the plurality of photoelectric conversion units is 940 nm, and the height of the convex portion of the diffraction grating is in the range of 200 nm to 400 nm, in the range of 1000 nm to 1200 nm, or is set to satisfy a reflectivity of 70% or higher.

Images