Solid-state image sensor

Abstract

To reduce the pupil correction amount of phase-difference detection pixels, thereby reducing the sensitivity difference between pixels adjacent to phase-difference detection pixels. [Solution] The pixel array 110 has a pixel unit 50 having a phase difference detection pixel 20 and a plurality of pixels 10 arranged around the phase difference detection pixel 20. The pixel unit 50 is divided into a plurality of pixel groups, each having a first pixel group 51 with one or more pixels 10 and a second pixel group 52 with one or more pixels 10 that are further from the phase difference detection pixel 20 than the first pixel group 51. The size of the first on-chip lens 11 of the pixels 10 arranged in the first pixel group 51 is larger than the size of the first on-chip lens 11 of the pixels 10 arranged in the second pixel group 52.

Description

Technical Field

[0001] The present invention relates to a solid-state imaging device.

Background Art

[0002] Conventionally, electronic devices having an imaging function such as digital still cameras and smartphones use solid-state imaging devices such as CMOS (Complementary Metal Oxide Semiconductor) image sensors.

[0003] As shown in, for example, Patent Document 1, a solid-state imaging device is known in which, separately from pixels that generate an electrical signal corresponding to incident light on a pixel array, phase difference detection pixels capable of detecting an image plane phase difference are arranged. In order to suppress a decrease in AF (Auto Focus) accuracy, in a plurality of predetermined phase difference detection pixels among the phase difference detection pixels of the solid-state imaging device of Patent Document 1, the on-chip lens is arranged with a deviation amount different from the exit pupil correction amount corresponding to the arrangement of the predetermined phase difference detection pixels.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] In a solid-state imaging device including phase difference detection pixels, the phase difference detection pixels have a different pixel size from the pixels arranged around them. The pixel size of the phase difference detection pixels is relatively larger than the pixel size of the surrounding pixels. Therefore, in the solid-state imaging device, the pupil correction amount of the phase difference detection pixels is different from the pupil correction amount of the pixels arranged around them. Also, in the solid-state imaging device, the difference between the pupil correction amounts of the phase difference detection pixels and the pixels increases as the image height at which they are arranged is higher.

[0006] As mentioned above, in solid-state image sensors, the pupil correction amount differs between pixels and phase-difference detection pixels. As a result, the on-chip lens of the phase-difference detection pixel, which is particularly located at a high image height, may overlap with the light transmission layer separation wall of an adjacent pixel. Therefore, solid-state image sensors have a problem in which color mixing and sensitivity reduction occur around the phase-difference detection pixel, especially at the boundary with the pixel adjacent to the phase-difference detection pixel, which significantly degrades image quality.

[0007] The present invention has been made in view of the above-mentioned problems, and specifically aims to provide a solid-state image sensor that can reduce the sensitivity difference between pixels surrounding a phase-difference pixel. [Means for solving the problem]

[0008] The above problem can be solved by any of the following means (1) to (13).

[0009] (1) A solid-state image sensor having a pixel array in which a plurality of pixels that generate an electrical signal in response to incident light and a plurality of phase difference detection pixels are arranged in a two-dimensional manner, wherein each pixel has a first photoelectric conversion unit, a first on-chip lens disposed on the incident side of the first photoelectric conversion unit for the incident light, and a first light transmission layer that transmits light of a specific wavelength in the incident light, and the phase difference detection pixels have a second photoelectric conversion unit, a second on-chip lens disposed on the incident side of the second photoelectric conversion unit for the incident light and having a larger diameter than the first on-chip lens, and a second light transmission layer that transmits light of a specific wavelength in the incident light A solid-state image sensor having a transparent layer, wherein the pixel array has a pixel unit having a phase-difference detection pixel and a plurality of pixels arranged around the phase-difference detection pixel, the pixel unit is divided into a plurality of pixel groups having a first pixel group having one or more of the pixels and a second pixel group having one or more of the pixels that are further away from the phase-difference detection pixel than the first pixel group, and the size of the first on-chip lens of the pixels arranged in the first pixel group is greater than the size of the first on-chip lens of the pixels arranged in the second pixel group.

[0010] (2) The solid-state image sensor according to (1) above, wherein the pixel group is further divided within the pixel unit according to the image height from the center of the pixel array.

[0011] (3) The pixel is a solid-state image sensor according to (1) or (2) above, wherein the size of the first on-chip lens is different from the diameter of the first on-chip lens in a plan view.

[0012] (4) The solid-state image sensor according to (3) above, wherein in the pixel unit, the diameter of the first on-chip lens of the pixel located on the side of the pixel array with a lower image height than the phase difference detection pixel is greater than the diameter of the first on-chip lens of the pixel located on the side of the pixel array with a higher image height than the phase difference detection pixel.

[0013] (5) The solid-state image sensor according to (3) or (4) above, wherein the diameter of the first on-chip lens of the pixel arranged in the first pixel group is greater than the diameter of the first on-chip lens of the pixel arranged in the second pixel group.

[0014] (6) The pixel is a solid-state image sensor as described in (1) or (2) above, wherein the size of the first on-chip lens is different from the height in the thickness direction of the first on-chip lens.

[0015] (7) The solid-state image sensor according to (6) above, wherein in the pixel unit, the height of the first on-chip lens of the pixel located on the side of the pixel array where the image height is lower than that of the phase-difference detection pixel is higher than the height of the first on-chip lens of the pixel located on the side of the pixel array where the image height is higher than that of the phase-difference detection pixel.

[0016] (8) The solid-state image sensor according to (6) or (7) above, wherein the height of the first on-chip lens of the pixel arranged in the first pixel group is greater than the height of the first on-chip lens of the pixel arranged in the second pixel group.

[0017] (9) The solid-state image sensor according to any one of (1) to (8) above, wherein the second light-transmitting layer of the phase-difference detection pixel is formed of a dielectric material that absorbs less light than the first light-transmitting layer.

[0018] (10) The solid-state image sensor according to any one of (1) to (9) above, wherein the pixel size of the phase difference detection pixel has a length of two pixels in the first direction and a length of two pixels in the second direction orthogonal to the first direction.

[0019] (11) The solid-state image sensor according to any one of (1) to (9) above, wherein the pixel size of the phase difference detection pixel has a length of one pixel in the first direction and a length of two pixels in the second direction orthogonal to the first direction.

[0020] (12) The solid-state image sensor according to any one of (1) to (9) above, wherein the pixel size of the phase difference detection pixel has a length of two pixels in the first direction and a length of one pixel in the second direction orthogonal to the first direction.

[0021] (13) A solid-state image sensor according to any one of (1) to (12) above, wherein in the pixel unit, the pupil correction amount of the first on-chip lens and the first light transmission layer of the pixel is determined according to the distance from the phase difference detection pixel and the image height from the center of the pixel array, and the pupil correction amount of the first on-chip lens and the first light transmission layer of the pixel arranged in the first pixel group is greater than the pupil correction amount of the first on-chip lens and the first light transmission layer of the pixel arranged in the second pixel group. [Effects of the Invention]

[0022] According to the present invention, the sensitivity difference between surrounding pixels of a phase difference detection pixel can be reduced. [Brief explanation of the drawing]

[0023] [Figure 1]It is a block diagram showing a solid-state imaging device according to an embodiment of the present invention. [Figure 2A] It is a partially enlarged plan view of a solid-state imaging device according to an embodiment of the present invention. [Figure 2B] It is a schematic cross-sectional view of a solid-state imaging device according to an embodiment of the present invention, which is partially cut. [Figure 3A] It is a schematic diagram showing the pixel size of a phase difference detection pixel. [Figure 3B] It is a schematic diagram showing the pixel size of a phase difference detection pixel. [Figure 3C] It is a schematic diagram showing the pixel size of a phase difference detection pixel. [Figure 4A] Sub-figure (a) is a schematic diagram showing a configuration example of a first on-chip lens and a second on-chip lens, sub-figure (b) is a schematic diagram showing a configuration example of a light transmission layer separation wall, and sub-figure (c) is a schematic diagram showing a configuration example of a pixel separation wall and a boundary separation wall. [Figure 4B] Sub-figure (a) is a schematic diagram showing another configuration example of a first on-chip lens and a second on-chip lens, sub-figure (b) is a schematic diagram showing another configuration example of a light transmission layer separation wall, and sub-figure (c) is a schematic diagram showing another configuration example of a pixel separation wall and a boundary separation wall. [Figure 5] It is a diagram showing an arrangement example of pixel units arranged in a pixel array. [Figure 6A] It is a diagram showing an example of dividing pixel groups according to the size of a first on-chip lens in a pixel unit arranged at the center of a pixel array. [Figure 6B] It is a diagram showing an example of dividing pixel groups according to the size of a first on-chip lens in a pixel unit arranged at the peripheral part of a pixel array. [Figure 7] It is a diagram showing an example of dividing pixel groups according to the pupil correction amount in a pixel unit arranged at the peripheral part of a pixel array. [Figure 8] It is a diagram showing the division of pixel groups in a pixel unit of a sample of an example. [Figure 9] It is a diagram showing the division of pixel groups in a pixel unit of a sample of a comparative example. [Figure 10] This graph shows the simulation results of the example. [Modes for carrying out the invention]

[0024] Embodiments of the present invention will be described in detail below with reference to the attached drawings. In the following drawings, the same reference numerals refer to the same components, and the size of each component in the drawings may be exaggerated for clarity and convenience of explanation. Furthermore, the embodiments described below are merely illustrative, and various modifications are possible from such embodiments.

[0025] In the following, "upper part" or "top" may include not only things that are directly above and in contact, but also things that are above but not in contact. Similarly, "lower part" or "bottom" may include not only things that are directly below and in contact, but also things that are below but not in contact.

[0026] A singular expression includes plural expressions unless the context clearly indicates that it is singular. Furthermore, when a part is said to "include," "possess," or "have" a component, it does not exclude other components, but rather may include other components unless otherwise specified.

[0027] Unless explicitly stated otherwise, the steps constituting the method shall be performed in the appropriate order. This order is not necessarily limited to the order in which the steps are described. All examples or illustrative terms are used solely to illustrate the technical idea and are not limited in scope to the claims.

[0028] In the following explanations, when ordinal numbers such as "1st" and "2nd" are used, they are for convenience only and do not prescribe any particular order unless otherwise specified.

[0029] The configuration of the solid-state image sensor 1 according to one embodiment of the present invention will be described.

[0030] For the sake of explanation, we set an XYZ Cartesian coordinate system for the solid-state image sensor 1. The direction parallel to the X-axis within a predetermined plane is defined as the X-axis direction. The direction parallel to the Y-axis perpendicular to the X-axis within the predetermined plane is defined as the Y-axis direction. The direction parallel to the Z-axis perpendicular to both the X-axis and the Y-axis is defined as the Z-axis direction. In this embodiment, the predetermined plane is the XY plane and parallel to the horizontal plane, and the Z-axis is perpendicular to the predetermined plane. Therefore, the Z-axis direction corresponds to the stacking direction (thickness direction) of each element constituting the solid-state image sensor 1, and the X-axis direction and Y-axis direction correspond to the planar direction perpendicular to the stacking direction.

[0031] As shown in Figure 1, the solid-state image sensor 1 comprises pixels 10, phase-difference detection pixels 20, and a chip substrate 100. The solid-state image sensor 1 can be configured as a CMOS image sensor.

[0032] As shown in Figure 1, the solid-state image sensor 1 has a pixel array 110 composed of a plurality of pixels 10 that output pixel signals on a chip substrate 100, and one or more phase difference detection pixels 20 capable of detecting image plane phase differences. The solid-state image sensor 1 includes a control circuit 120 that generates operation signals for operating each part, a vertical drive circuit 130 that can scan each pixel 10 in a vertical direction (Y-axis direction in the figure) which is a second direction orthogonal to the first direction and controls the output of a pixel signal according to the amount of light received by each pixel 10, a horizontal drive circuit 140 that outputs scanning pulses in the horizontal direction (X-axis direction in the figure) which is the first direction, a column signal processing circuit 150 that processes the pixel signals output from each pixel 10 and generates an image signal, a vertical signal line 160 that transmits the pixel signals generated by each pixel 10 to the column signal processing circuit 150, a horizontal signal line 170 that causes the column signal processing circuit 150 to output an image signal, and an output circuit 180 that processes the image signal received via the horizontal signal line 170 and outputs the processed signal. In Figure 1, the area enclosed by the thick line within the pixel array 110 represents the phase difference detection pixel 20.

[0033] The chip substrate 100 is made of silicon or the like, and pixels 10 and phase difference detection pixels 20 are formed on the substrate. The chip substrate 100 constitutes the first photoelectric conversion unit 13 and the second photoelectric conversion unit 23 (see diagram (c) in Figure 4A). On the side of the chip substrate 100 opposite to the incident surface of the light (hereinafter also referred to as "incident light L") incident on the solid-state image sensor 1, pixel transistors and wiring layers (not shown) are formed. The chip substrate 100 outputs pixel signals, which are electrical signals obtained by converting the incident light L received by the first photoelectric conversion unit 13 and the second photoelectric conversion unit 23, to the control circuit 120, etc.

[0034] Furthermore, the solid-state image sensor 1 can optionally and selectively employ components known in the field of solid-state image sensors, other than the pixels 10 and phase-difference detection pixels 20 formed in the pixel array 110. Therefore, in this specification, descriptions of components other than the pixels 10 and phase-difference detection pixels 20 will be omitted as appropriate.

[0035] Figure 2A shows a partially enlarged plan view of the solid-state image sensor 1 of this embodiment, cut horizontally (cut in the XY plane). Figure 2B shows a schematic cross-sectional view of the solid-state image sensor 1 (section AA in Figure 2A).

[0036] As shown in Figure 2A, pixel 10 is composed of a red pixel 10R, a green pixel 10G, and a blue pixel 10B. The pixels 10 are arranged in a two-dimensional manner (for example, in a matrix shape) on the chip substrate 100. The arrangement of pixels 10 can be appropriately set according to the specifications of the solid-state image sensor 1. In the solid-state image sensor 1 shown in Figure 2A, the red pixel group 10RG, the green pixel group 10GG, and the blue pixel group 10BG are arranged around the phase difference detection pixel 20, which has a pixel size of 2 pixels × 2 pixels and is enclosed by a dotted line. That is, in Figure 2A, each pixel group is configured in a Bayer array as a group unit. The red pixel group 10RG consists of 8 red pixels 10R. The green pixel group 10GG consists of 8 green pixels 10G. The blue pixel group 10BG consists of 8 blue pixels 10B.

[0037] As shown in Figure 2B, the pixel 10 is arranged in the following order from the incident light L side: a first on-chip lens 11, a first multilayer film layer 12, and a first photoelectric conversion unit 13. The pixel 10 is separated independently from adjacent pixels 10 and phase difference detection pixels 20 by light transmission layer separation walls 30 and pixel separation walls 40. The dotted line shown in Figure 2B indicates the boundary position between the first multilayer film layer 12 and the second multilayer film layer 22, which will be described later.

[0038] The first on-chip lens 11 is formed on the first planarization layer 12a of the first multilayer film layer 12. The first on-chip lenses 11 are arranged to correspond to each pixel 10. For example, the first on-chip lenses 11 are arranged two-dimensionally (for example, in a matrix shape) in a plane. The first on-chip lens 11 has a convex shape and a predetermined radius of curvature so that the incident light L is focused onto the first photoelectric conversion unit 13. The first on-chip lens 11 can be formed using an organic material such as a styrene resin, an acrylic resin, a styrene-acrylic copolymer resin, or a siloxane resin. As shown in Figure 2A, the first on-chip lenses 11 are positioned offset in a predetermined direction by an amount of pupil correction corresponding to the position of the pixels 10 in the pixel array 110.

[0039] The first multilayer film layer 12 comprises a first planarization layer 12a, a first light transmission layer 12b, and a first anti-reflective layer 12c. The first multilayer film layer 12 only needs to have a layer configuration that includes at least the first light transmission layer 12b and the first anti-reflective layer 12c, and may also be composed of other layers other than those described above.

[0040] The first planarization layer 12a is formed between the first on-chip lens 11 and the first light-transmitting layer 12b. The first planarization layer 12a has high transmittance to light incident on the first photoelectric conversion unit 13 and provides a flat forming surface with respect to the first on-chip lens 11. The first planarization layer 12a can be formed from, for example, an organic material such as resin.

[0041] The first light-transmitting layer 12b is formed between the first planarization layer 12a and the first photoelectric conversion unit 13, and is arranged two-dimensionally (for example, in a matrix shape) to correspond to each unit pixel. The first light-transmitting layer 12b has the function of transmitting light of a specific wavelength in the visible light region. Therefore, the first light-transmitting layer 12b can function as a variety of color filters for each unit pixel.

[0042] The first light-transmitting layer 12b can function as a red color filter, transmitting red light as light of a specific wavelength corresponding to the red pixel 10R and absorbing green and blue light. The first light-transmitting layer 12b can function as a green color filter, transmitting green light as light of a specific wavelength corresponding to the green pixel 10G and absorbing red and blue light. The first light-transmitting layer 12b can function as a blue color filter, transmitting blue light as light of a specific wavelength corresponding to the blue pixel 10B and absorbing red and green light. Furthermore, the first light-transmitting layer 12b can function as a so-called white filter, transmitting light across almost the entire visible light region as light of a specific wavelength.

[0043] The first light-transmitting layer 12b can be arranged in a Bayer pattern, including the first light-transmitting layer 12b corresponding to the red pixel 10R, green pixel 10G, and blue pixel 10B. However, this is illustrative, and the first light-transmitting layer 12b can also include a yellow filter, a magenta filter, and a cyan filter. The first light-transmitting layer 12b can be formed by including a pigment or dye of a desired color in a resin with low light absorption.

[0044] The first light-transmitting layer 12b has light-shielding light-transmitting layer separation walls 30 formed at the boundary with other adjacent first light-transmitting layers 12b and the second light-transmitting layer 22b of the phase-difference detection pixels 20. As a result, the first light-transmitting layer 12b is separated pixel by pixel from adjacent pixels 10 and phase-difference detection pixels 20.

[0045] The first anti-reflective layer 12c is formed between the first light-transmitting layer 12b and the first photoelectric conversion unit 13. The first anti-reflective layer 12c can be formed by laminating a layer of a high refractive index material (for example, silicon nitride (SiN), hydrofluoroolefin (HfO), tantalum oxide (TaO), titanium oxide (TiO), etc.) and a layer of a low refractive index material (silicon oxide (SiO2), etc.) in an appropriate combination.

[0046] The first photoelectric conversion unit 13 converts the transmitted light that reaches the first photoelectric conversion unit 13 from the incident light L incident on the solid-state image sensor 1 into an electrical signal. The first photoelectric conversion unit 13 is separated by pixel separation walls 40 so as to be separated from adjacent pixels 10 and phase difference detection pixels 20 on a pixel-by-pixel basis. The first photoelectric conversion unit 13 may include, but is not limited to, at least one of the following: a photodiode, a phototransistor, a photogate, a pinned photodiode, an organic photodiode, a quantum dot, and combinations thereof.

[0047] As shown in Figure 2B, the phase difference detection pixel 20 is arranged in the following order from the incident side of the incident light L: second on-chip lens 21, second multilayer film layer 22, and second photoelectric conversion unit 23. The phase difference detection pixel 20 is separated independently from each of the adjacent pixels 10 by light transmission layer separation walls 30 and pixel separation walls 40.

[0048] The phase difference detection pixel 20 has a structure in which the second photoelectric conversion unit 23 is divided into multiple sections by boundary separation walls 41. The phase difference detection pixel 20 detects the phase difference from the difference in pixel signals based on the charge amounts generated by the multiple second photoelectric conversion units 23, calculates the amount of focus shift, and achieves autofocus by moving the camera lens based on this calculation result. Therefore, an imaging device equipped with a solid-state image sensor 1 does not require a dedicated autofocus mechanism and can focus on the subject based on the phase difference of light incident on the phase difference detection pixel 20.

[0049] The second on-chip lens 21 is formed on the second planarization layer 22a of the second multilayer film layer 22. The second on-chip lenses 21 are arranged to correspond to each phase difference detection pixel 20. The second on-chip lenses 21 have a larger diameter than the first on-chip lens 11. The second on-chip lenses 21 are formed according to the shape and size of the phase difference detection pixel 20. Although the size of the second on-chip lens 21, such as the diameter and height in plan view, is different, the forming material and other components can be configured in the same way as the first on-chip lens 11. As shown in Figure 2A, the second on-chip lenses 21 are positioned offset in a predetermined direction by an amount of pupil correction corresponding to the placement position of the phase difference detection pixels 20 in the pixel array 110.

[0050] The second multilayer film layer 22 comprises a second planarization layer 22a, a second light transmission layer 22b, and a second anti-reflective layer 22c. The second multilayer film layer 22 only needs to have a layer structure that includes at least the second light transmission layer 22b and the second anti-reflective layer 22c, and may also be composed of other layers other than those described above.

[0051] The second planarization layer 22a is formed between the second on-chip lens 21 and the second light transmission layer 22b. The second planarization layer 22a has the same configuration as the first planarization layer 12a.

[0052] The second light-transmitting layer 22b is formed between the second planarization layer 22a and the second photoelectric conversion unit 23. The second light-transmitting layer 22b transmits light of a specific wavelength that is photoelectrically converted in the second photoelectric conversion unit 23. The second photoelectric conversion unit 23 can have the same configuration as the first photoelectric conversion unit 13 in terms of its forming material, etc.

[0053] The second light-transmitting layer 22b has a light-shielding light-transmitting layer separation wall 30 formed at the boundary with the first light-transmitting layer 12b of the adjacent pixel 10. As a result, the second light-transmitting layer 22b is separated from adjacent pixels 10 on a pixel-by-pixel basis.

[0054] The second anti-reflective layer 22c is formed between the second light-transmitting layer 22b and the second photoelectric conversion unit 23. The second anti-reflective layer 22c can have the same configuration as the first anti-reflective layer 12c in terms of its forming material, etc.

[0055] The second photoelectric conversion unit 23 converts the transmitted light that reaches the second photoelectric conversion unit 23 from the incident light L incident on the phase difference detection pixel 20 into an electrical signal. The second photoelectric conversion unit 23 is surrounded by a pixel separation wall 40 so as to be separated from adjacent pixels 10. The second photoelectric conversion unit 23 can be configured in the same way as the first photoelectric conversion unit 13 in terms of its forming material, etc.

[0056] The phase difference detection pixel 20 shown in Figure 3A has a larger element size than the pixel 10. The pixel size of the phase difference detection pixel 20 can be formed such that it has a length of two pixels of the pixel 10 in the first direction, the horizontal direction (X-axis direction), and a length of two pixels of the pixel 10 in the second direction, the vertical direction (Y-axis direction), as shown in Figure 3A.

[0057] The phase difference detection pixel 20 shown in Figure 3B has a larger element size than the pixel 10. The pixel size of the phase difference detection pixel 20 can be formed such that it has the length of one pixel of the pixel 10 in the first direction, the horizontal direction (X-axis direction), and the length of two pixels of the pixel 10 in the second direction, the vertical direction (Y-axis direction).

[0058] The phase difference detection pixel 20 shown in Figure 3C has a larger element size than the pixel 10. The pixel size of the phase difference detection pixel 20 can be formed such that it has the length of two pixels of the pixel 10 in the first direction, the horizontal direction (X-axis direction), and the length of one pixel of the pixel 10 in the second direction, the vertical direction (Y-axis direction).

[0059] Furthermore, the pixel size of the phase difference detection pixel 20 is not limited to the sizes shown in Figures 3A to 3C; it can be formed with a larger element size or with the same pixel size as the pixel 10.

[0060] Figures 4A and 4B show schematic diagrams illustrating examples of the shapes of the on-chip lenses, light transmission layer isolation walls, and pixel isolation walls that constitute each pixel of the solid-state image sensor 1. In Figure 4A, subdivision (a) shows an example configuration of the first on-chip lens 11 and the second on-chip lens 21 of the solid-state image sensor 1, subdivision (b) shows an example configuration of the light transmission layer isolation wall 30, and subdivision (c) shows an example configuration of the pixel isolation wall 40 and the boundary isolation wall 41. In Figure 4B, subdivision (a) shows another example configuration of the first on-chip lens 11 and the second on-chip lens 21 of the solid-state image sensor 1, subdivision (b) shows another example configuration of the light transmission layer isolation wall 30, and subdivision (c) shows another example configuration of the pixel isolation wall 40 and the boundary isolation wall 41.

[0061] The light-transmitting layer separation wall 30 is formed to surround the first light-transmitting layer 12b in the pixel 10 and the second light-transmitting layer 22b of the phase difference detection pixel 20. As shown in subdivision (b) of Figure 4A and subdivision (b) of Figure 4B, the light-transmitting layer separation wall 30 is arranged in a grid pattern in a plan view, forming boundaries between adjacent first light-transmitting layers 12b and second light-transmitting layers 22b, thereby partitioning and separating each layer to a predetermined size. The light-transmitting layer separation wall 30 has at least the function of preventing vignetting of incident light L incident on the pixel 10 and the function of blocking incoming light from adjacent pixels 10. Therefore, the light-transmitting layer separation wall 30 should be formed with a height and width that satisfy these functions. The light-transmitting layer separation wall 30 can be made of a dielectric material with low light absorption, such as silicon oxide (SiO2) or silicon nitride (SiN).

[0062] A light-shielding portion 31 can be formed between the light-transmitting layer separation wall 30 and the first anti-reflective layer 12c, and between the light-transmitting layer separation wall 30 and the second anti-reflective layer 22c. The light-shielding portion 31 can be formed to surround the first light-transmitting layer 12b and the second light-transmitting layer 22b. By providing the light-shielding portion 31 between adjacent pixels 10 and phase difference detection pixels 20, crosstalk between adjacent pixels can be suppressed, and the accuracy of phase difference detection can be further improved. The light-shielding portion 31 can be formed from a metallic material such as titanium nitride (TiN), titanium (Ti), tungsten (W), aluminum (Al), molybdenum (Mo), nickel (Ni), etc.

[0063] The pixel isolation wall 40 is formed using DTI (Deep Trench Isolation). As shown in subdivision (c) of Figure 4A and subdivision (c) of Figure 4B, the pixel isolation wall 40 is formed to surround the first photoelectric conversion unit 13 of the pixel 10 and the second photoelectric conversion unit 23 of the phase difference detection pixel 20. As a result, the first photoelectric conversion unit 13 of the pixel 10 and the second photoelectric conversion unit 23 of the phase difference detection pixel 20 are separated individually. The pixel isolation wall 40 may have boundary isolation walls 41 that divide the second photoelectric conversion unit 23 of the phase difference detection pixel 20 into multiple sections. The boundary isolation walls 41 divide the second photoelectric conversion unit 23 into a predetermined number of sections within the phase difference detection pixel 20 so that the image plane phase difference can be detected by the second photoelectric conversion unit 23.

[0064] As shown in subdivision (c) of Figure 4A, the pixel separation wall 40 can be formed so as not to enclose a portion of the entire circumference of the first photoelectric conversion unit 13 or the second photoelectric conversion unit 23. In other words, a configuration can be made using boundary separation walls 41 that do not have a separation wall in the center of the four pixels (four pixels 10, or four pixels constituting the phase difference detection pixels 20). This improves the noise reduction effect, although it may have some effect on the spectral characteristics.

[0065] The pixel separation wall 40 can be formed by dividing the first photoelectric conversion unit 13 and the second photoelectric conversion unit 23 into unit pixel sizes, as shown in subdivision (c) of Figure 4B. In the case of the shape shown in Figure 4B, the pixel separation wall 40 is divided independently according to the number of divisions of the second photoelectric conversion unit 23 of the phase difference detection pixel 20.

[0066] Furthermore, the shape of the pixel separation wall 40 is not limited to the shapes shown in Figures 4A and 4B, but can be a shape according to the specifications of the solid-state image sensor 1.

[0067] As shown in Figure 5, the solid-state image sensor 1 according to this embodiment has one or more pixel units 50 arranged within the pixel array 110, each having a phase-difference detection pixel 20 and a plurality of pixels 10 arranged around the phase-difference detection pixel 20. In the pixel unit 50 shown in Figure 5, the pixels 10 within the unit are not shown, but in reality, multiple pixels are arranged around the phase-difference detection pixel 20 so that, for example, there are 6 pixels × 6 pixels at the outermost edge of the unit. As shown in Figure 5, the pixel units 50 can be sparsely arranged with predetermined intervals from the center 110a of the pixel array 110 to the peripheral part 110b on the outer edge of the array. The arrangement position of the pixel units 50 within the pixel array 110 can be arbitrarily set according to the specifications of the solid-state image sensor 1, etc. Note that, as shown in Figure 5, the center 110a of the pixel array 110 includes a certain range (area enclosed by a dotted line) extending from the center of the pixel array 110 towards the outer edge. Furthermore, as shown in Figure 5, the peripheral portion 110b of the pixel array 110 includes a certain range (the area enclosed by the dashed line) extending from the outermost periphery of the pixel array 110 towards the center. The center of the pixel array 110 refers to the side of the symmetrical central line C (the dashed line in the figure) of the pixel array 110 shown in Figure 5.

[0068] In the pixel unit 50, the pixels 10 arranged within the unit are divided into multiple pixel groups. As shown in Figures 6A and 6B, the pixel unit 50 can be composed of a single phase-difference detection pixel 20 at its center, surrounded by a red pixel group 10RG, a green pixel group 10GG, and a blue pixel group 10BG. The red pixel group 10RG, the green pixel group 10GG, and the blue pixel group 10BG can be arranged in a Bayer array within the pixel unit 50 with the phase-difference detection pixel 20 at its center. Note that the pixel unit 50 is not limited to the configurations shown in Figures 6A and 6B, and the number of pixels 10 arranged within the unit and the number of phase-difference detection pixels 20 can be arbitrarily set.

[0069] As shown in Figures 6A and 6B, the pixel groups divide the pixels 10 into multiple groups according to their distance from the phase difference detection pixels 20 within the pixel unit 50 and / or their image height from the center of the pixel array 110. In Figures 6A and 6B, each pixel 10 in the pixel unit 50 is assigned a pixel group number (one of 1, 2, or 3).

[0070] When the pixel unit 50 is located in the central part 110a of the pixel array 110, the pixels 10 can be divided into multiple pixel groups (pixel group 1 to pixel group 3), as shown in Figure 6A. When the pixel unit 50 is located in the peripheral part 110b of the pixel array 110, the pixels 10 can be divided into multiple pixel groups (pixel group 1 to pixel group 3), as shown in Figure 6B. Comparing Figure 6A and Figure 6B, the group numbers assigned to the pixels 10 are different. The reason for the different group numbers is to set the appropriate size of the first on-chip lens 11 according to the distance from the phase-difference detection pixels 20 in the pixel unit 50 and / or the image height from the center of the pixel array 110. In other words, the sizes of the phase-difference detection pixels 20 and pixels 10, and the sizes of the second on-chip lens 21 and the first on-chip lens 11, are different, and the required pupil correction amount is different, which can result in a difference in sensitivity between the phase-difference detection pixels 20 and pixels 10. To mitigate this sensitivity gap, the size of the first on-chip lens 11 is appropriately set.

[0071] Pixel units 50 located near the center 110a of the pixel array 110 are less affected by the image height from the center of the pixel array 110, so pixels 10 can be separated solely by their distance from the phase-difference detection pixels 20. In other words, each pixel group can be arranged symmetrically around the phase-difference detection pixels 20. On the other hand, pixel units 50 located in the peripheral part 110b of the pixel array 110 are more susceptible to the image height from the center of the pixel array 110, so pixels 10 can be separated according to their distance from the phase-difference detection pixels 20 and their image height from the center of the pixel array 110. In other words, each pixel group can be arranged asymmetrically when viewed with respect to the phase-difference detection pixels 20.

[0072] The pixel unit 50 includes a first pixel group 51 having one or more pixels 10 within the unit, and a second pixel group 52 having one or more pixels 10 that are further from the phase difference detection pixels 20 than the first pixel group 51. The first pixel group 51 may consist of pixels 10 that are positioned relatively closer to the phase difference detection pixels 20 within the pixel unit 50 than the second pixel group 52. The second pixel group 52 may consist of pixels 10 that are positioned relatively further from the phase difference detection pixels 20 within the pixel unit 50 than the first pixel group 51. For example, as shown in Figures 6A and 6B, if the pixels 10 classified into pixel group 1 are considered the first pixel group 51, then the pixels 10 classified into pixel group 2 and pixel group 3 correspond to the second pixel group 52.

[0073] Within the pixel unit 50, the size of the first on-chip lens 11 of the pixel 10 located in the first pixel group 51 is larger than the size of the first on-chip lens 11 of the pixel 10 located in the second pixel group 52. The size of the first on-chip lens 11 is the lens diameter or lens height (thickness) in a planar view.

[0074] For example, if the diameter of the first on-chip lens 11 is based on the diameter of the first on-chip lens 11 of the pixel 10 corresponding to pixel group 1, the diameter of pixel group 2 can be reduced by 0.02 μm and the diameter of pixel group 3 can be reduced by 0.04 μm. Also, if the height of the first on-chip lens 11 is based on the height of the first on-chip lens 11 of the pixel 10 corresponding to pixel group 1, the height of pixel group 2 can be reduced by 0.02 μm and the height of pixel group 3 can be reduced by 0.04 μm.

[0075] In the pixel unit 50, it is preferable that the diameter of the first on-chip lens 11 of the pixel 10 located in the first pixel group 51 be larger than the diameter of the first on-chip lens 11 of the pixel 10 located in the second pixel group 52.

[0076] Furthermore, it is preferable that the diameter of the first on-chip lens 11 of a pixel 10 at a predetermined position in the pixel unit 50 located on the side of the pixel array 110 where the image height is lower than that of the phase-difference detection pixel 20 is larger than the diameter of the first on-chip lens 11 of a pixel 10 at the same predetermined position in the pixel unit 50 located on the side of the pixel array 110 where the image height is higher than that of the phase-difference detection pixel 20.

[0077] In the pixel unit 50, it is preferable that the height of the first on-chip lens 11 of the pixel 10 located in the first pixel group 51 be greater than the height of the first on-chip lens 11 of the pixel 10 located in the second pixel group 52.

[0078] Furthermore, it is preferable that the height of the first on-chip lens 11 of a pixel 10 at a predetermined position in the pixel unit 50 located on the side of the pixel array 110 where the image height is lower than that of the phase-difference detection pixel 20 is higher than the height of the first on-chip lens 11 of a pixel 10 at the same predetermined position in the pixel unit 50 located on the side of the pixel unit 50 where the image height is higher than that of the phase-difference detection pixel 20.

[0079] In the pixel unit 50, the diameter and height of the first on-chip lens 11 of the pixel 10 located in the first pixel group 51 may be larger in diameter and taller in height than the first on-chip lens 11 of the pixel 10 located in the second pixel group 52. Alternatively, in the pixel unit 50, the diameter and height of the first on-chip lens 11 of the pixel 10 located on the side of the pixel array 110 where the image height is lower than that of the phase-difference detection pixel 20 may be larger in diameter and taller in height than the first on-chip lens 11 of the pixel 10 located on the side of the pixel array 110 where the image height is higher than that of the phase-difference detection pixel 20.

[0080] As shown in Figure 7, the pixel unit 50 divides the pixels 10 within the unit into multiple pixel groups in order to determine pupil correction amounts according to the distance from the phase-difference detection pixels 20 and the image height from the center of the pixel array 110. The pupil correction amounts of the first on-chip lens 11 and the first light transmission layer 12b of the pixels 10 divided into each pixel group are determined for each group according to the distance from the phase-difference detection pixels 20 and the image height from the center of the pixel array 110.

[0081] When the pixel unit 50 is located in the peripheral portion 110b of the pixel array 110, the pixels 10 can be divided into multiple pixel groups (pixel group 1 to pixel group 3), as shown in Figure 7.

[0082] The pupil correction amount of the first on-chip lens 11 and first light transmission layer 12b of the pixel 10 located in the first pixel group 51 is greater than the pupil correction amount of the first on-chip lens 11 and first light transmission layer 12b of the pixel 10 located in the second pixel group 52.

[0083] For example, the pupil correction amount of the first on-chip lens 11 and first light transmission layer 12b of pixel 10 corresponding to pixel group 1 is set to 0.43 μm. In this case, the pupil correction amount of the first on-chip lens 11 and first light transmission layer 12b of pixel 10 corresponding to pixel group 2 can be set to 0.42 μm, and the pupil correction amount of the first on-chip lens 11 and first light transmission layer 12b of pixel 10 corresponding to pixel group 3 can be set to 0.41 μm. In each example, pixel group 1 corresponds to the first pixel group 51, and pixel group 2 and pixel group 3 correspond to the second pixel group 52.

[0084] Note that the group numbers for the pixel groups shown in Figures 6A, 6B, and 7 are merely examples and will be determined appropriately according to the specifications of the solid-state image sensor 1, such as the configuration of the pixel array 110.

[0085] In this embodiment, the solid-state image sensor 1 has a pixel unit 50 within the pixel array 110 that includes a phase-difference detection pixel 20 and a plurality of surrounding pixels 10, in order to appropriately correct the pupil of the first on-chip lens 11 and the second on-chip lens 21. The pixel unit 50 divides the pixels 10 into multiple pixel groups within the unit. The size of the first on-chip lens 11 for pixels 10 in the first pixel group 51, which is closer to the phase-difference detection pixel 20, is larger than the size of the first on-chip lens 11 for pixels 10 in the second pixel group 52, which is further from the phase-difference detection pixel 20 than the first pixel group 51. In this way, the solid-state image sensor 1 reduces the sensitivity difference between the phase-difference detection pixel 20 and the pixels 10, as well as the sensitivity difference between pixels 10, by appropriately changing the size of the first on-chip lens 11 and the amount of pupil correction according to the arrangement position of the pixels 10 relative to the phase-difference detection pixel 20 within the pixel unit 50.

[0086] As described above, the solid-state image sensor 1 according to the present invention has a pixel array 110 in which a plurality of pixels 10 that generate electrical signals in response to incident light L and a plurality of phase difference detection pixels 20 are arranged in two dimensions. Each pixel 10 has a first photoelectric conversion unit 13, a first on-chip lens 11 positioned on the incident side of the first photoelectric conversion unit 13 to the incident light L, and a first light transmission layer 12b that transmits light of a specific wavelength in the incident light L. Each phase difference detection pixel 20 has a second photoelectric conversion unit 23, a second on-chip lens 21 positioned on the incident side of the second photoelectric conversion unit 23 to the incident light L and having a larger diameter than the first on-chip lens 11, and a specific wavelength in the incident light L The pixel array 110 has a second light-transmitting layer 22b that transmits light, and the pixel array 110 has a pixel unit 50 having a phase-difference detection pixel 20 and a plurality of pixels 10 arranged around the phase-difference detection pixel 20, and the pixel unit 50 is divided into a plurality of pixel groups having a first pixel group 51 having one or more pixels 10 and a second pixel group 52 having one or more pixels 10 that are further away from the phase-difference detection pixel 20 than the first pixel group 51, and the size of the first on-chip lens 11 of the pixel 10 arranged in the first pixel group 51 is larger than the size of the first on-chip lens 11 of the pixel 10 arranged in the second pixel group 52.

[0087] With this configuration, the size of the first on-chip lens 11 is optimized according to the distance from the phase-difference detection pixel 20 of the solid-state image sensor 1, thereby reducing the sensitivity difference between pixels 10. [Examples]

[0088] Next, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0089] The following simulations were conducted to evaluate the sensitivity difference between multiple green pixels adjacent to the phase difference detection pixels of the solid-state image sensor of the present invention (Example) and a conventional solid-state image sensor (Comparative Example). The simulations were performed using Rsoft (Synopsys) to calculate the quantum efficiency within the photoelectric conversion section of multiple green pixels using the FDTD method (Finite-Difference Time-Domain method). The wavelength used for the calculations was 530 nm.

[0090] As shown in Figure 8, the sample of the embodiment consisted of a pixel unit in which a phase-difference detection pixel was placed in the center and pixels were arranged around it. Each pixel within the pixel unit was divided into three pixel groups according to its distance from the phase-difference detection pixel and its image height from the center of the pixel array. The height of the first on-chip lens of each pixel was set based on the height of the first on-chip lens of the pixels corresponding to pixel group 1, with the height of the first on-chip lens of pixels in pixel group 2 being 0.02 μm lower and the height of the first on-chip lens of pixels corresponding to pixel group 3 being 0.04 μm lower. Pixel group 1 corresponds to the first pixel group, and pixel groups 2 and 3 correspond to the second pixel group.

[0091] As shown in Figure 9, the comparative example sample configured a pixel unit with a phase-difference detection pixel at the center and other pixels arranged around it. Each pixel within the pixel unit belonged to only one pixel group, pixel group 1. In other words, in the comparative example's pixel unit, the height of the first on-chip lens of all pixels was the same.

[0092] Figure 10 shows a graph illustrating the simulation results of the same-color sensitivity difference between the example and the comparative example. The dotted line in the graph represents the same-color sensitivity difference in a solid-state image sensor without phase-difference detection pixels. As shown in Figure 10, comparing the example and the comparative example, it was confirmed that the pixel sensitivity difference was reduced in the example, approaching the sensitivity difference of a solid-state image sensor without phase-difference detection pixels.

[0093] The results above indicate that forming a pixel unit in a solid-state image sensor that includes a phase-difference detection pixel and multiple surrounding pixels, setting pixel groups within the pixel unit according to the distance from the phase-difference detection pixel and the image height from the center of the pixel array, and making the size (height) of the first on-chip lens of the pixels in the first pixel group (pixels in pixel group 1) greater than the size of the first on-chip lens of the pixels in the second pixel group (pixels in pixel group 2 and pixel group 3) is an effective factor in reducing the sensitivity difference between pixels adjacent to the phase-difference detection pixel. [Explanation of Symbols]

[0094] 1. Solid-state image sensor, 10 pixels, 10R red pixels, 10G green pixels, 10B blue pixels, 10RG red pixel group, 10GG green pixel group, 10BG blue pixel group, 11. First on-chip lens, 12 first multilayer film layer, 12a planarization layer, 12b light transmitting layer, 12c anti-reflection layer, 13 First photoelectric conversion unit, 20 phase-difference detection pixels, 21. Second on-chip lens, 22 second multilayer film layer, 22a second planarization layer, 22b second light transmitting layer, 22c second anti-reflection layer, 23 Second photoelectric conversion unit, 30 Light-transmitting layer separation wall, 40-pixel separation wall, 41 Boundary separation wall; 50 pixel unit, 51 First pixel group, 52 Second pixel group, 100 chip substrates, 110-pixel array, The center of the 110a pixel array, Peripheral part of the 110b pixel array, 120 control circuits, 130 Vertical drive circuit, 140 Horizontal drive circuit, 150-column signal processing circuit, 160 vertical signal lines, 170 horizontal signal lines, 180 output circuit, The central line of the C pixel array, L Incident light.

Claims

1. A solid-state image sensor having a pixel array in which a plurality of pixels that generate electrical signals in response to incident light and a plurality of phase difference detection pixels are arranged in a two-dimensional manner, The pixel comprises a first photoelectric conversion unit, a first on-chip lens positioned on the incident light side of the first photoelectric conversion unit, and a first light transmission layer that transmits light of a specific wavelength in the incident light. The phase difference detection pixel comprises a second photoelectric conversion unit, a second on-chip lens positioned on the incident side of the second photoelectric conversion unit and having a larger diameter than the first on-chip lens, and a second light transmission layer that transmits light of a specific wavelength in the incident light. The pixel array has a pixel unit having a phase difference detection pixel and a plurality of pixels arranged around the phase difference detection pixel, The pixel unit is divided into a plurality of pixel groups, each having a first pixel group having one or more pixels, and a second pixel group having one or more pixels that are further away from the phase difference detection pixels than the first pixel group. A solid-state image sensor in which the size of the first on-chip lens of the pixels arranged in the first pixel group is larger than the size of the first on-chip lens of the pixels arranged in the second pixel group.

2. The solid-state image sensor according to claim 1, wherein the pixel group is further divided within the pixel unit according to the image height from the center of the pixel array.

3. The solid-state image sensor according to claim 2, wherein the pixels are of different sizes from the first on-chip lens, with the diameter of the first on-chip lens in a plan view being different.

4. The solid-state image sensor according to claim 3, wherein in the pixel unit, the diameter of the first on-chip lens of the pixel located on the side of the pixel array with a lower image height than the phase-difference detection pixel is greater than the diameter of the first on-chip lens of the pixel located on the side of the pixel array with a higher image height than the phase-difference detection pixel.

5. The solid-state image sensor according to claim 3, wherein the diameter of the first on-chip lens of the pixels arranged in the first pixel group is greater than the diameter of the first on-chip lens of the pixels arranged in the second pixel group.

6. The solid-state image sensor according to claim 1, wherein the pixels have different heights in the thickness direction of the first on-chip lens as the size of the first on-chip lens.

7. The solid-state image sensor according to claim 6, wherein in the pixel unit, the height of the first on-chip lens of the pixel located on the side of the pixel array with a lower image height than the phase-difference detection pixel is higher than the height of the first on-chip lens of the pixel located on the side of the pixel array with a higher image height than the phase-difference detection pixel.

8. The solid-state image sensor according to claim 6, wherein the height of the first on-chip lens of the pixels arranged in the first pixel group is greater than the height of the first on-chip lens of the pixels arranged in the second pixel group.

9. The solid-state image sensor according to claim 1, wherein the second light-transmitting layer of the phase-difference detection pixel is formed of a dielectric material that absorbs less light than the first light-transmitting layer.

10. The solid-state image sensor according to claim 1, wherein the pixel size of the phase difference detection pixel has a length of two pixels in the first direction and a length of two pixels in the second direction orthogonal to the first direction.

11. The solid-state image sensor according to claim 1, wherein the pixel size of the phase difference detection pixel has a length of one pixel in the first direction and a length of two pixels in the second direction orthogonal to the first direction.

12. The solid-state image sensor according to claim 1, wherein the pixel size of the phase difference detection pixel has a length of two pixels in the first direction and a length of one pixel in the second direction orthogonal to the first direction.

13. In the pixel unit, the pupil correction amount of the first on-chip lens and the first light transmission layer of the pixel is determined according to the distance from the phase difference detection pixel and the image height from the center of the pixel array. The solid-state image sensor according to any one of claims 1 to 12, wherein the pupil correction amount of the first on-chip lens and first light transmission layer of the pixels arranged in the first pixel group is greater than the pupil correction amount of the first on-chip lens and first light transmission layer of the pixels arranged in the second pixel group.

Images