Solid-state image sensor

Abstract

To improve the separation ratio of incident light to phase difference detection pixels. [Solution] The solid-state image sensor 1 has a pixel array 110 in which a plurality of pixels 10 and one or more phase difference detection pixels 20 are arranged in two dimensions. The phase difference detection pixel 20 includes a photoelectric conversion unit 25, an on-chip lens 21 positioned on the incident side of the photoelectric conversion unit 25 to the incident light L, a light transmission layer 23 that transmits light of a specific wavelength in the incident light L, an anti-reflective layer 24 laminated on the photoelectric conversion unit 25, a pixel separation wall 40 positioned between the photoelectric conversion unit 25 and the photoelectric conversion unit 25 of other pixels 10 adjacent to the photoelectric conversion unit 25, and boundary separation walls 41 that divide the photoelectric conversion unit 25 surrounded by the pixel separation wall 40 into multiple parts. The anti-reflective layer 24 has a laminated structure in which a plurality of high refractive index layers 24a and low refractive index layers 24b are laminated, and the high refractive index layer 24a positioned closest to the photoelectric conversion unit 25 has a light separation slit 50 made of a low refractive index material formed within the layer.

Description

Technical Field

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[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 has an element structure in which phase difference detection pixels capable of detecting an image plane phase difference are arranged separately from pixels that generate an electrical signal corresponding to incident light on a pixel array.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] The phase difference detection pixels have a problem that the separation ratio, which is an index of AF performance, decreases due to the diffraction limit of incident light as the pixel array is miniaturized. In addition, the phase difference detection pixels have problems of increased color mixing and decreased sensitivity (decrease in QE (Quantum Efficiency)) due to the interaction between the pixel separation wall and the incident light on the incident surface of the incident light in the photoelectric conversion unit.

[0006] To solve these problems, the phase difference detection pixels are dealt with by forming a boundary separation wall that partitions the photoelectric conversion unit surrounded by the pixel separation wall. However, particularly when the pixel size is less than 1 μm, the separation ratio is likely to decrease and there is room for improvement.

[0007] <00,00034>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 improve the separation ratio of incident light to phase difference detection pixels. [Means for solving the problem]

[0008] The above problem can be solved by one of the following means (1) to (9).

[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 one or more phase difference detection pixels are arranged in a two-dimensional manner, wherein the phase difference detection pixels include a photoelectric conversion unit, an on-chip lens disposed on the incident side of the photoelectric conversion unit, a light transmission layer that transmits light of a specific wavelength in the incident light, an anti-reflective layer laminated on the photoelectric conversion unit, a pixel isolation wall disposed between the photoelectric conversion unit and the photoelectric conversion unit of other pixels adjacent to the photoelectric conversion unit, and boundary isolation walls that divide the photoelectric conversion unit surrounded by the pixel isolation wall into a plurality of parts, wherein the anti-reflective layer has a laminated structure in which a plurality of high refractive index layers and low refractive index layers are laminated, and the high refractive index layer disposed closest to the photoelectric conversion unit has a light isolation slit made of a low refractive index material formed in the layer.

[0010] (2) The solid-state image sensor according to (1), wherein the optical separation slit is arranged in the central part of the phase difference detection pixel in a planar direction perpendicular to the stacking direction of the phase difference detection pixel and parallel to the extending direction of the boundary separation wall.

[0011] (3) The solid-state image sensor according to (1) or (2) above, wherein the light separation slit has a cross-sectional shape of one of the following: rectangular, trapezoidal, or polygonal.

[0012] (4) The light separation slit has a shape in plan view that is one of the following: rectangular, rhombus, polygonal, circular, elliptical, or cross-shaped, as described in any one of (1) to (3) above, a solid-state image sensor.

[0013] (5) The solid-state image sensor according to any one of (1) to (4) above, wherein the material for forming the light separation slit is the same as the material for forming the low refractive index layer adjacent in the stacking direction to the high refractive index layer on which the light separation slit is formed.

[0014] (6) The solid-state image sensor according to any one of (1) to (5) above, wherein the light separation slit has a narrow portion with a width narrower than the wavelength size of the incident light.

[0015] (7) The solid-state image sensor according to any one of (1) to (6) above, wherein the height of the light separation slit in the stacking direction is lower than the wavelength size of the incident light.

[0016] (8) A solid-state image sensor according to any one of (1) to (7) above, wherein at least one of the width and center position of the light separation slit in a plan view differs depending on the image height from the center of the pixel array on which the phase difference detection pixels are arranged.

[0017] (9) The solid-state image sensor according to any one of (1) to (8) above, wherein the light separation slit is formed only on the phase difference detection pixels located in the peripheral part of the pixel array. [Effects of the Invention]

[0018] According to the present invention, the separation ratio of incident light to phase difference detection pixels can be improved. [Brief explanation of the drawing]

[0019] [Figure 1] This is a block diagram showing a solid-state imaging element according to an embodiment of the present invention. [Figure 2] A partially enlarged plan view of a solid-state image sensor according to an embodiment of the present invention. [Figure 3] This is a schematic cross-sectional view of a solid-state image sensor according to an embodiment of the present invention, partially cut. [Figure 4A] This is a schematic diagram of a solid-state image sensor according to an embodiment of the present invention when incident light is incident perpendicularly. [Figure 4B]It is a schematic diagram showing the light intensity distribution of incident light perpendicularly incident on the light separation slit in the solid-state imaging device according to an embodiment of the present invention. [Figure 4C] It is a schematic diagram showing the light intensity distribution of incident light perpendicularly incident on the photoelectric conversion unit in the solid-state imaging device according to an embodiment of the present invention. [Figure 5A] It is a schematic diagram of the solid-state imaging device according to an embodiment of the present invention when the incident light is obliquely incident. [Figure 5B] It is a schematic diagram showing the light intensity distribution of incident light obliquely incident on the light separation slit in the solid-state imaging device according to an embodiment of the present invention. [Figure 5C] It is a schematic diagram showing the light intensity distribution of incident light obliquely incident on the photoelectric conversion unit in the solid-state imaging device according to an embodiment of the present invention. [Figure 5D] It is a cross-sectional schematic diagram showing the refraction state of incident light obliquely incident on the solid-state imaging device according to an embodiment of the present invention. [Figure 5E] It is a cross-sectional schematic diagram showing the refraction state of incident light obliquely incident on a conventional solid-state imaging device without a light separation slit. [Figure 6A] [[ID=2,1]]It is a cross-sectional schematic diagram showing the light condensing state of a solid-state imaging device in which a condenser lens is arranged on an antireflection layer. [Figure 6B] It is a cross-sectional schematic diagram showing the light condensing state of the solid-state imaging device according to an embodiment of the present invention. [Figure 7A] It is a schematic diagram showing an example of the shape in plan view of the light separation slit when the photoelectric conversion unit is partitioned into two left and right parts in the horizontal direction. [Figure 7B] It is a schematic diagram showing another example of the shape in plan view of the light separation slit when the photoelectric conversion unit is partitioned into two left and right parts in the horizontal direction. [Figure 7C] It is a schematic diagram showing another example of the shape in plan view of the light separation slit when the photoelectric conversion unit is partitioned into two left and right parts in the horizontal direction. [Figure 7D] It is a schematic diagram showing another example of the shape in plan view of the light separation slit when the photoelectric conversion unit is partitioned into two left and right parts in the horizontal direction. [Figure 8A]This is a schematic diagram showing an example of the shape of the optical separation slit in a plan view when the photoelectric conversion unit is divided into two parts vertically, upper and lower. [Figure 8B] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into two parts vertically, upper and lower. [Figure 8C] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into two parts vertically, upper and lower. [Figure 9A] This is a schematic diagram showing an example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 9B] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 9C] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 9D] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 9E] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 9F] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 9G] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 9H] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 10A] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into two parts horizontally, left and right. [Figure 10B] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into two parts horizontally, left and right. [Figure 10C] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into two parts horizontally, left and right. [Figure 10D] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into two parts horizontally, left and right. [Figure 11A] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 11B] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 11C] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 11D] This schematic diagram shows another example of the shape of the optical separation slit in a plan view when the photoelectric conversion section is divided into four parts. [Figure 12A] This is a schematic cross-sectional diagram showing an example of the cross-sectional shape of an optical separation slit. [Figure 12B] This is a schematic cross-sectional diagram showing other examples of cross-sectional shapes of an optical separation slit. [Figure 12C] This is a schematic cross-sectional diagram showing other examples of cross-sectional shapes of an optical separation slit. [Figure 13A] This is a schematic diagram of the phase-difference detection pixels arranged on the low image height side in the solid-state image sensor of Modified Example 1. [Figure 13B] Figure 13A is a schematic cross-sectional view of the phase difference detection pixel shown, cut along line AA. [Figure 14A] This is a schematic diagram of the phase-difference detection pixels arranged on the high-image-height side in the solid-state image sensor of Modified Example 1. [Figure 14B] Figure 14A is a schematic cross-sectional view of the phase difference detection pixel shown, cut along the BB line. [Figure 15A] This is a schematic diagram of the phase-difference detection pixels arranged on the low image height side in the solid-state image sensor of Modified Example 2. [Figure 15B] Figure 15A is a schematic cross-sectional view of a phase difference detection pixel cut along the CC line. [Figure 16A] This is a schematic diagram of the phase-difference detection pixels positioned on the high-image-height side in the modified solid-state image sensor of example 2. [Figure 16B] Figure 16A is a schematic cross-sectional view of the phase difference detection pixel shown, cut along the DD line. [Figure 17A] This is a schematic cross-sectional diagram showing an example of the optical separation slit configuration in the solid-state image sensor of modification example 3. [Figure 17B] This is a schematic cross-sectional diagram showing another example of the optical separation slit in the solid-state image sensor of Modification Example 3. [Figure 17C] This is a schematic cross-sectional diagram showing another example of the optical separation slit in the solid-state image sensor of Modification Example 3. [Figure 18A] This is a schematic diagram of the solid-state image sensor in the embodiment. [Figure 18B] This is a schematic cross-sectional view of the high refractive index layer in which the optical separation slit is formed in the phase difference detection pixel of the embodiment. [Figure 19A] This is a schematic diagram of a comparative example solid-state image sensor. [Figure 19B] This is a schematic cross-sectional view of the high refractive index layer in the phase difference detection pixel of the comparative example. [Figure 20] This graph shows the simulation results of the example. [Modes for carrying out the invention]

[0020] 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.

[0021] 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.

[0022] 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.

[0023] 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.

[0024] 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.

[0025] The configuration of the solid-state image sensor 1 according to one embodiment of the present invention will be described.

[0026] 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.

[0027] 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.

[0028] 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 perpendicular 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.

[0029] Furthermore, as shown in Figure 1, the central part 110a of the pixel array 110 refers to a predetermined range extending from the center of the pixel array 110 toward the outer periphery, and the peripheral part 110b of the pixel array 110 refers to a predetermined range extending from the outermost periphery of the pixel array 110 toward the center.

[0030] The chip substrate 100 is made of silicon (Si) or the like, and pixels 10 and phase difference detection pixels 20 are formed on the substrate. The chip substrate 100 constitutes the photoelectric conversion unit of the pixel 10 and the photoelectric conversion unit 25 of the phase difference detection pixels 20. 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, wiring layers, etc. (not shown) are formed. The chip substrate 100 outputs the pixel signals, which are obtained by converting the incident light L received by the pixels 10 and the phase difference detection pixels 20 into electrical signals, to the control circuit 120, etc.

[0031] Furthermore, the solid-state image sensor 1 may optionally and selectively employ components known in the field of solid-state image sensors, other than the phase-difference detection pixels 20 formed in the pixel array 110. Therefore, in this specification, descriptions of components other than the phase-difference detection pixels 20 will be omitted as appropriate.

[0032] Figure 2 shows a partially enlarged plan view of the solid-state image sensor 1 of this embodiment, cut horizontally (cut in the XY plane). Figure 3 shows a schematic cross-sectional view of the solid-state image sensor 1, partially cut.

[0033] As shown in Figure 2, 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) on the chip substrate 100. The pixel array 110 can be arranged with pixels 10 and phase difference detection pixels 20 in a Bayer pattern. However, this is illustrative, and it may also include a yellow filter, a magenta filter, and a cyan filter. Furthermore, the arrangement positions of pixels 10 and phase difference detection pixels 20 in the pixel array 110, as well as the number of each pixel, can be arbitrarily set.

[0034] As shown in Figure 3, the phase difference detection pixel 20 is composed of an on-chip lens 21, a planarization layer 22, a light transmission layer 23, an anti-reflective layer 24, a photoelectric conversion unit 25, a light transmission layer separation wall 30, a pixel separation wall 40, and a light separation slit 50. The phase difference detection pixel 20 is partitioned by the light transmission layer separation wall 30 and the pixel separation wall 40, and is separated independently from each of the adjacent pixels 10 and phase difference detection pixels 20.

[0035] The phase-difference detection pixel 20 has a structure in which the photoelectric conversion unit 25 is divided into multiple parts by boundary separation walls 41. The phase-difference detection pixel 20 detects the phase difference from the difference in pixel signals based on the amount of charge generated by the multiple photoelectric conversion units 25, calculates the amount of focus shift, and achieves autofocus by moving the camera lens based on this calculation result. Therefore, the imaging device equipped with the solid-state image sensor 1 does not require a dedicated autofocus mechanism and can focus on the subject based on the phase difference of the light incident on the phase-difference detection pixel 20.

[0036] The on-chip lens 21 is formed on the planarization layer 22. The on-chip lens 21 is arranged corresponding to each phase difference detection pixel 20. For example, the on-chip lens 21 is arranged two-dimensionally (for example, in a matrix shape) in a plane. The on-chip lens 21 has a convex shape and a predetermined radius of curvature so that the incident light L is focused onto the photoelectric conversion unit 25. The on-chip lens 21 can be formed using an organic material such as a styrene resin, acrylic resin, styrene-acrylic copolymer resin, or siloxane resin.

[0037] The planarization layer 22 is formed between the on-chip lens 21 and the light transmission layer 23. The planarization layer 22 has high transmittance to incident light L into the photoelectric conversion unit 25 and provides a flat surface relative to the on-chip lens 21. The planarization layer 22 can be formed from, for example, an organic material such as resin.

[0038] The light-transmitting layer 23 is formed between the planarization layer 22 and the photoelectric conversion unit 25, and is arranged two-dimensionally (for example, in a matrix shape) to correspond to each unit pixel. The light-transmitting layer 23 can be formed by including a pigment or dye of a desired color in a resin with low light absorption. The refractive index of the light-transmitting layer 23 can be between 1.6 and 1.8.

[0039] The light-transmitting layer 23 has the function of transmitting light of a specific wavelength in the visible light region. The light-transmitting layer 23 can function as a color filter that transmits either red light, green light, or blue light as a specific wavelength, and absorbs other light. Alternatively, the light-transmitting layer 23 can function as a so-called white filter that transmits light of almost the entire visible light region as a specific wavelength.

[0040] The light-transmitting layer 23 has a light-shielding light-transmitting layer separation wall 30 formed at the boundary with other adjacent light-transmitting layers 23. As a result, the light-transmitting layer 23 is separated pixel by pixel from adjacent pixels 10 and phase difference detection pixels 20.

[0041] The anti-reflective layer 24 is formed between the light-transmitting layer 23 and the photoelectric conversion section 25. The anti-reflective layer 24 is formed by alternately stacking a high refractive index layer 24a made of a high refractive index material (for example, silicon nitride (SiN), hafnium oxide (HfO), tantalum oxide (TaO), titanium oxide (TiO), etc.) and a low refractive index layer 24b made of a low refractive index material (silicon oxide (SiO2), aluminum oxide (AlO), etc.).

[0042] As shown in Figure 3, the antireflection layer 24 can be formed by alternately stacking a low refractive index layer 24b and a high refractive index layer 24a from the incident side of the incident light L. The high refractive index layer 24a may be formed from the same material or different materials in each stacked layer. The low refractive index layer 24b may be formed from the same material or different materials in each stacked layer. The refractive index of the high refractive index layer 24a can be 1.9 or more and 2.6 or less. The refractive index of the low refractive index layer 24b can be 1.3 or more and 1.5 or less. The antireflection layer 24 shown in Figure 3 has a stacked structure formed from five layers in order from the incident side of the incident light L: low refractive index layer 24b, high refractive index layer 24a, low refractive index layer 24b, high refractive index layer 24a, and low refractive index layer 24b. There is no limit to the number of stacks of high refractive index layers 24a and low refractive index layers 24b in the antireflection layer 24, but it is preferable that at least the top and bottom layers be low refractive index layers 24b.

[0043] The photoelectric conversion unit 25 converts the transmitted light that has traveled through the incident light L to the photoelectric conversion unit 25 into an electrical signal. The photoelectric conversion unit 25 has a structure in which the photoelectric conversion unit 25 is divided into multiple parts by boundary separation walls 41. The photoelectric conversion unit 25 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, or a combination thereof.

[0044] The light-transmitting layer separation wall 30 is formed to surround the light-transmitting layer 23 within the phase-difference detection pixel 20. The light-transmitting layer separation wall 30 is arranged in a grid pattern in a plan view, forming boundaries between adjacent pixels 10 and dividing 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 phase-difference detection pixel 20 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 satisfies 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).

[0045] A light-shielding portion 31 can be formed between the light-transmitting layer separation wall 30 and the anti-reflective layer 24. The light-shielding portion 31 can be formed so as to surround the light-transmitting layer 23. By providing the light-shielding portion 31 between adjacent pixels 10 or 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.

[0046] The pixel isolation wall 40 is formed using DTI (Deep Trench Isolation). As shown in Figures 2 and 3, the pixel isolation wall 40 is formed to surround the photoelectric conversion unit 25 of the phase difference detection pixel 20. As a result, the photoelectric conversion unit 25 of the phase difference detection pixel 20 is individually separated for each pixel.

[0047] The pixel separation wall 40 may have boundary separation walls 41 that divide the photoelectric conversion unit 25 into multiple parts. The boundary separation walls 41 divide the photoelectric conversion unit 25 into a predetermined number of parts so that the image plane phase difference can be detected by the photoelectric conversion unit 25 within the phase difference detection pixel 20. Here, "divide" includes not only a structure in which a part of the photoelectric conversion unit 25 is divided and separated, as shown in Figure 4C, but also a structure in which the photoelectric conversion unit 25 is completely divided and separated by connecting boundary separation walls 41 as shown in Figure 4C so as to traverse the photoelectric conversion unit 25 longitudinally.

[0048] In this embodiment, as shown in Figure 3, the solid-state image sensor 1 has an optical separation slit 50 formed in the high refractive index layer 24a that constitutes the anti-reflective layer 24, which is located closest to the photoelectric conversion unit 25. The optical separation slit 50 is the region enclosed by the dotted line in Figure 3 (the region between the high refractive index layers 24a on the left and right).

[0049] As shown in Figure 3, the light separation slit 50 is formed in a part of the high refractive index layer 24a and has a slit structure that improves the separation ratio (separation characteristics) of incident light L. The light separation slit 50 shown in Figure 3 penetrates the high refractive index layer 24a and is formed continuously with the low refractive index layer 24b directly above it and the lowest low refractive index layer 24b. The light separation slit 50 may be formed from the same material as the low refractive index layer 24b, or from other low refractive index materials.

[0050] When the light separation slit 50 is placed in the center of the phase difference detection pixel 20 and surrounded by a high refractive index layer 24a, it exhibits the following effects depending on the incident angle of the incident light L.

[0051] As shown in Figure 4A, when incident light L is perpendicularly incident on the light separation slit 50, the slit structure becomes symmetrical with respect to the light intensity distribution, as shown in Figures 4B and 4C. The dot hatch gradient regions shown in Figures 4B, 4C, 5B, and 5C schematically represent the light intensity distribution of the incident light L. In each figure, the light intensity distribution shows that the light intensity increases from the region with coarser dots to the region with denser dots.

[0052] As shown in Figure 5A, when incident light L is obliquely incident on the light separation slit 50, the light intensity distribution is biased towards the high refractive index layer 24a side, as shown in Figures 5B and 5C. Because the light separation slit 50 is made of a low refractive index material, the incident light L (dotted line in the figure) passing through it continues straight without refraction, as shown in Figure 5D, while the light passing through the surrounding high refractive index layer 24a is refracted. Therefore, the incident light L is focused so that its width narrows towards the photoelectric conversion unit 25. On the other hand, Figure 5E shows the refraction state of incident light L (dotted line in the figure) obliquely incident on a conventional solid-state image sensor without a light separation slit. In a conventional solid-state image sensor, as shown in Figure 5E, because the light separation slit 50 is not formed, the entire light is refracted and not focused due to the action of the high refractive index layer 24a. Comparing the configuration in Figure 5D with the configuration in Figure 5E, it can be seen that the configuration with the light separation slit 50 shown in Figure 5D focuses the incident light L to one side of the element. Thus, by forming the light separation slit 50 in the center of the pixel as shown in Figure 5D, the incident light L can be focused to one side of the element (i.e., one side of the photoelectric conversion unit 25). Therefore, the phase difference detection pixel 20 equipped with the light separation slit 50 can improve the separation ratio by focusing the incident light L in such a way that the light intensity distribution to the photoelectric conversion unit 25 is biased.

[0053] If the phase-difference detection pixel 20 is to improve the separation ratio with a configuration other than the light separation slit 50, one possible configuration is to stack and arrange condensing lenses 200 on the anti-reflective layer 24, corresponding to each of the photoelectric conversion units 25, as shown in Figure 6A. However, in the phase-difference detection pixel 20 shown in Figure 6A, the pixel structure becomes taller due to the arrangement of the condensing lenses 200, and the curvature of the on-chip lens 21 must be reduced in order to concentrate light onto the photoelectric conversion unit 25. As a result, the diameter of the condensing spot of the phase-difference detection pixel 20 tends to increase. In contrast, the solid-state image sensor 1 of this embodiment, as shown in Figure 6B, eliminates the need for extra components such as the condensing lens 200 due to the slit structure of the light separation slit 50, thus allowing for a lower pixel structure. Therefore, as shown in Figure 6B, the solid-state image sensor 1 can arrange on-chip lenses 21 with a higher curvature than in Figure 6A, reducing the diameter of the condensing spot and effectively improving the separation ratio and sensitivity.

[0054] The light separation slit 50 can be formed in any shape that can exert a light-gathering effect within the high refractive index layer 24a, depending on the number and arrangement of the photoelectric conversion units 25. The light separation slit 50 can have a plan view shape as shown in Figures 7A to 7D, 8A to 8C, 9A to 9H, 10A to 10D, and 11A to 11D.

[0055] Figures 7A to 7D show examples of the shape of the optical separation slit 50 in plan view when the photoelectric conversion unit 25 is divided into two parts horizontally, left and right. As shown in Figures 7A to 7D, when the photoelectric conversion unit 25 is divided into two parts horizontally, left and right, the optical separation slit 50 can have a shape in plan view such as a rectangle as shown in Figure 7A, a straight line as shown in Figure 7B, a square as shown in Figure 7C, or an ellipse as shown in Figure 7D. The optical separation slit 50 shown in Figures 7A, 7B, and 7D is formed to extend vertically in accordance with the separation shape of the photoelectric conversion unit 25.

[0056] Figures 8A to 8C show examples of the shape of the optical separation slit 50 in plan view when the photoelectric conversion unit 25 is divided into two parts vertically. As shown in Figures 8A to 8D, when the photoelectric conversion unit 25 is divided into two parts vertically, the optical separation slit 50 can have a shape in plan view such as a rectangle as shown in Figure 8A, a straight line as shown in Figure 8B, or an ellipse as shown in Figure 8C. In addition, when the photoelectric conversion unit 25 is divided into two parts vertically, the optical separation slit 50 can also be a square as shown in Figure 7C. The optical separation slit 50 shown in Figures 8A, 8B, and 8C is formed to extend horizontally in accordance with the separation shape of the photoelectric conversion unit 25.

[0057] Figures 9A to 9H show examples of the plan view shapes of the optical separation slit 50 when the photoelectric conversion unit 25 is divided into four parts. As shown in Figures 9A to 9D, when the photoelectric conversion unit 25 is divided into four parts, the optical separation slit 50 can have the following shapes in plan view: a cross shape as shown in Figure 9A, two orthogonal lines as shown in Figure 9B, a vertically elongated cross shape as shown in Figure 9C, a rhombus as shown in Figure 9D, a shape combining a square and a cross as shown in Figure 9E, a shape combining a rhombus and a cross as shown in Figure 9F, a circle as shown in Figure 9G, and an elliptical cross as shown in Figure 9H. Note that the figures shown in Figures 9E, 9F, and 9H are shapes obtained by overlapping the center points of one figure and the other figure. For example, the "elliptical cross" shown in Figure 9H is a shape obtained by overlapping two ellipses that have the same in-plane shape and a common center point, such that the major axis of one ellipse is orthogonal to the major axis of the other.

[0058] Figures 10A to 10D show other examples of the shape of the optical separation slit in a plan view when the photoelectric conversion unit is divided into four parts. As shown in Figures 10A to 10D, as a modification of Figure 7, when the photoelectric conversion unit 25 is divided into two parts horizontally, the optical separation slit 50 can also be shaped such that the high refractive index layer 24a remains in the region that becomes the focusing area for the incident light L transmitted through the on-chip lens 21. Figure 10A shows a shape in which the focusing area of ​​a rectangle is made of the high refractive index layer 24a. Figure 10B shows a shape in which the focusing area of ​​a straight line is made of the high refractive index layer 24a. Figure 10C shows a shape in which the focusing area of ​​an ellipse is made of the high refractive index layer 24a. Figure 10D shows another shape in which the vertices in the major axis direction of the two divided ellipses are placed opposite each other and the focusing area is made of the high refractive index layer 24a.

[0059] Figures 11A to 11D show other examples of the shape of the optical separation slit in a plan view when the photoelectric conversion unit is divided into four parts. As shown in Figures 11A to 11D, as a modification of Figure 9, when the photoelectric conversion unit 25 is divided into four parts, the optical separation slit 50 can also be shaped in a plan view such that the high refractive index layer 24a is left in the region that becomes the light-gathering part of the on-chip lens 21. Figure 11A shows a shape in which the light-gathering region in a cross shape is made of the high refractive index layer 24a. Figure 11B shows a shape in which the light-gathering region in a shape combining a square and a cross shape is made of the high refractive index layer 24a. Figure 11C shows a shape in which the light-gathering region in a shape combining a rhombus and a cross shape is made of the high refractive index layer 24a. Figure 11D shows a shape in which the light-gathering region in an elliptical cross shape is made of the high refractive index layer 24a.

[0060] The light separation slit 50 can have any cross-sectional shape that can exert a light-gathering effect, as shown in Figures 12A to 12C. The cross-sectional shape of the light separation slit 50, when cut along the direction of alignment of the separated photoelectric conversion units 25, can be, for example, a rectangle as shown in Figure 12A, a trapezoid as shown in Figure 12B, or a polygon as shown in Figure 12C.

[0061] The light separation slit 50 has a narrow section 51 that is narrower than the wavelength of the incident light L. For example, if the light separation slit 50 is rectangular as shown in Figure 7A, elliptical as shown in Figure 7D, cross-shaped as shown in Figure 9A, or a combination of a square and a cross-shaped as shown in Figure 9E, the width of the arrow in the figure will be the narrow section 51 that is narrower than the wavelength of the incident light L.

[0062] The height of the optical separation slit 50 in the stacking direction is lower than the wavelength of the incident light L. For example, as shown in Figure 12A, the thickness of the optical separation slit 50 in the stacking direction (height indicated by the arrow in the figure) is lower than the wavelength of the incident light L.

[0063] As described above, the solid-state image sensor 1 has an optical separation slit 50 formed in the high refractive index layer 24a of the anti-reflective layer 24 located above the photoelectric conversion unit 25. The solid-state image sensor 1 can refract the incident light L with the slit structure of the optical separation slit 50, thereby biasing the light intensity distribution towards the high refractive index layer 24a side. As a result, the separation ratio of the solid-state image sensor 1 is improved.

[0064] Next, examples of modifications to the solid-state image sensor according to this embodiment will be described. The following modifications can be appropriately incorporated into the embodiments described above. Furthermore, the following modifications can be appropriately combined and adopted without departing from the spirit of the invention.

[0065] The solid-state image sensor 1A of Modified Example 1 in this embodiment will be described.

[0066] Figure 13A is a schematic diagram of the phase difference detection pixel 20 positioned on the low image height side in the solid-state image sensor 1A of Modified Example 1, and Figure 13B is a schematic cross-sectional view of the phase difference detection pixel 20 shown in Figure 13A cut along line AA. Figure 14A is a schematic diagram of the phase difference detection pixel 20 positioned on the high image height side in the solid-state image sensor 1A of Modified Example 1, and Figure 14B is a schematic cross-sectional view of the phase difference detection pixel 20 shown in Figure 14A cut along line BB.

[0067] As shown in Figures 13A, 13B, 14A, and 14B, the solid-state image sensor 1A of the modified example allows the width and / or center position of the optical separation slit 50 in a plan view to be set according to the image height from the center of the pixel array 110 of the phase difference detection pixels 20.

[0068] When the phase difference detection pixel 20 is located on the central side 110a of the pixel array 110, the incident light L is incident toward the central part of the phase difference detection pixel 20, as shown in Figures 13A and 13B. Therefore, as shown in Figures 13A and 13B, it is preferable to position the light separation slit 50 such that its central position C1 is located in the central part of the phase difference detection pixel 20.

[0069] When the phase difference detection pixels 20 are located on the peripheral 110b side of the pixel array 110, the incident light L is incident at an oblique angle, as shown in Figures 14A and 14B. Therefore, as shown in Figures 14A and 14B, it is preferable to position the light separation slit 50 so that its center position C1 is shifted in a predetermined direction from the center of the phase difference detection pixels 20 according to the direction of propagation of the incident light L. Furthermore, as shown in Figures 14A and 14B, when the phase difference detection pixels 20 are located at a high image height, it is preferable to form the light separation slit 50 with a wider width to accommodate the incident light L that is incident at an oblique angle.

[0070] Thus, in the modified example 1, the solid-state image sensor 1A can have the width and / or center position of the light separation slit 50 in a plan view arranged differently depending on the image height from the center of the pixel array 110 where the phase difference detection pixels 20 are located. As a result, the width and formation position of the light separation slit 50 of the solid-state image sensor 1A can be optimized for various incident angles of the incident light L, thereby more effectively improving the separation ratio.

[0071] The solid-state image sensor 1B of the modified example 2 in this embodiment will be described.

[0072] Figure 15A is a schematic diagram of the phase difference detection pixel 20 positioned on the low image height side in the solid-state image sensor 1B of Modified Example 2, and Figure 15B is a schematic cross-sectional view of the phase difference detection pixel 20 shown in Figure 15A cut along the CC line. Figure 16A is a schematic diagram of the phase difference detection pixel 20 positioned on the high image height side in the solid-state image sensor 1B of Modified Example 2, and Figure 16B is a schematic cross-sectional view of the phase difference detection pixel 20 shown in Figure 16A cut along the DD line.

[0073] In the modified example 2, as shown in Figures 15A, 15B, 16A, and 16B, the solid-state image sensor 1B has optical separation slits 50 formed only on phase-difference detection pixels 20 in positions where pupil correction is likely to be required and separation characteristics are likely to deteriorate, depending on the arrangement position of the phase-difference detection pixels 20 relative to the pixel array 110.

[0074] As shown in Figures 15A and 15B, when the phase-difference detection pixels 20 of the solid-state image sensor 1B are located in the central part 110a of the pixel array 110 (the central area of ​​the image height), sufficient separation characteristics can be obtained, and therefore the optical separation slit 50 can not be formed. As shown in Figures 16A and 16B, when the phase-difference detection pixels 20 of the solid-state image sensor 1B are located in the peripheral part 110b of the pixel array 110 (the high-image-height area), where separation characteristics tend to deteriorate, the optical separation slit 50 can be formed.

[0075] Thus, in the modified example 2, the solid-state image sensor 1B forms optical separation slits 50 only on phase-difference detection pixels 20 located in positions where separation characteristics are likely to deteriorate, depending on the arrangement position of the phase-difference detection pixels 20 relative to the pixel array 110. As a result, the solid-state image sensor 1B does not need to form optical separation slits 50 on phase-difference detection pixels 20 located on the central 110a side of the pixel array 110, which do not require pupil correction, thus simplifying the structure.

[0076] The solid-state image sensor 1C of Modified Example 3 in this embodiment will be described.

[0077] As shown in Figures 17A to 17C, the solid-state image sensor 1C of Modified Example 3 has a configuration in which the light separation slit 50 is formed without penetrating the high refractive index layer 24a in the stacking direction. The previously described solid-state image sensor 1 formed the light separation slit 50 by penetrating the high refractive index layer 24a so as to be continuous with the low refractive index layer 24b stacked on the high refractive index layer 24a, but the difference from the previous embodiment is that the slit is not penetrated.

[0078] As shown in Figure 17A, the solid-state image sensor 1C can be formed only at the bottom (lower surface) of the high refractive index layer 24a closest to the photoelectric conversion unit 25. In the configuration shown in Figure 17A, the light separation slit 50 and the lowest low refractive index layer 24b are formed adjacent to each other. Above the light separation slit 50, a thin high refractive index layer 24a is formed, as shown in Figure 17A.

[0079] Furthermore, as shown in Figure 17B, the solid-state image sensor 1C can be formed only on the ceiling (upper surface) of the high refractive index layer 24a closest to the photoelectric conversion unit 25. In the configuration shown in Figure 17B, the light separation slit 50 and the low refractive index layer 24b, which is the third layer from the bottom of the anti-reflective layer 24, are formed adjacent to each other. Also, a thin high refractive index layer 24a is formed below the light separation slit 50.

[0080] Furthermore, as shown in Figure 17C, the solid-state image sensor 1C can be formed in the middle portion of the high refractive index layer 24a in the thickness direction, which is closest to the photoelectric conversion unit 25. In the configuration shown in Figure 17C, the light separation slit 50 is formed surrounded by the high refractive index layer 24a in the vertical direction as well.

[0081] Thus, in the modified example 3, the solid-state image sensor 1C has a high refractive index layer 24a that is formed in the stacking direction of the light separation slit 50, or partially remains. Therefore, the solid-state image sensor 1C can enhance its anti-reflective function compared to the configuration in which the high refractive index layer 24a is formed through the layer as shown in Figure 3.

[0082] As described above, the solid-state image sensor 1 according to the present invention is an element having a pixel array 110 in which a plurality of pixels 10 that generate electrical signals in response to incident light L and one or more phase difference detection pixels 20 are arranged in a two-dimensional manner. The phase difference detection pixel 20 includes a photoelectric conversion unit 25, an on-chip lens 21 disposed on the incident light L side of the photoelectric conversion unit 25, a light transmission layer 23 that transmits light of a specific wavelength in the incident light L, an anti-reflective layer 24 laminated on the photoelectric conversion unit 25, a pixel separation wall 40 disposed between the photoelectric conversion unit 25 and the photoelectric conversion unit 25 of other pixels 10 adjacent to the photoelectric conversion unit 25, and boundary separation walls 41 that divide the photoelectric conversion unit 25 surrounded by the pixel separation wall 40 into a plurality of parts. The anti-reflective layer 24 has a laminated structure in which a plurality of high refractive index layers 24a and low refractive index layers 24b are laminated, and the high refractive index layer 24a disposed closest to the photoelectric conversion unit 25 has a light separation slit 50 made of a low refractive index material formed within the layer.

[0083] With this configuration, the solid-state image sensor 1 can effectively refract incident light L, especially light incident at an oblique angle, through the slit structure of the light separation slit 50, thereby biasing the light intensity distribution towards the high refractive index layer 24a. As a result, the solid-state image sensor 1 improves the separation ratio while reducing light scattering and color mixing caused by the pixel separation wall 40, etc. Furthermore, since the solid-state image sensor 1 does not require extra components such as a condensing lens 200 above the photoelectric conversion unit 25 to improve the separation ratio, the pixel structure can be made lower. Therefore, the solid-state image sensor 1 can accommodate an on-chip lens 21 with a high curvature, and the diameter of the condensing spot can be reduced, effectively improving the separation ratio and sensitivity. [Examples]

[0084] Next, embodiments of the present invention will be described, but the present invention is not limited to the following embodiments.

[0085] The following simulations were performed to evaluate the separation ratio of phase-difference detection pixels in the solid-state image sensor of the present invention (Example) and a conventional solid-state image sensor (Comparative Example). The simulation was performed using Rsoft (Synopsys) and the FDTD method (Finite-Difference Time-Domain method) to calculate the quantum efficiency within the photoelectric conversion section of the green pixel. The wavelength of the incident light was 530 nm, and it was incident at an incident angle of 10°.

[0086] Figure 18A shows a schematic diagram of the solid-state image sensor of the embodiment, and Figure 18B shows a schematic cross-sectional diagram of the high refractive index layer in which the optical separation slit is formed in the phase difference detection pixel of the embodiment. In the embodiment, as shown in Figure 18B, the optical separation slit 50 was formed in the high refractive index layer 24a on the photoelectric conversion section 25 side of the anti-reflective layer 24. In Figure 18A, the thickness T1 of the high refractive index layer 24a and the low refractive index layer 24b of the optical separation slit 50 was set to 100 nm. The width of the optical separation slit formed in the high refractive index layer was set to 100 nm. The optical separation slit 50 was positioned in the central part of the phase difference detection pixel 20, parallel to the boundary separation wall 41 in a planar direction perpendicular to the stacking direction.

[0087] Figure 19A shows a schematic diagram of the comparative solid-state image sensor, and Figure 19B shows a schematic cross-sectional diagram of the high refractive index layer in the phase difference detection pixel of the comparative example. The comparative example sample had a conventional structure without an optical separation slit 50, as shown in Figures 19A and 19B. In Figure 19A, the thickness T2 of the high refractive index layer 24a was set to 100 nm.

[0088] Figure 20 shows a graph illustrating the simulation results of the separation ratios for the example and the comparative example. As shown in Figure 20, it was confirmed that the example with the optical separation slit 50 had a higher separation ratio than the comparative example with a conventional structure that did not have the optical separation slit 50.

[0089] From the above results, it can be concluded that by forming an optical separation slit in the high-refractive-index layer located closest to the photoelectric conversion section among the high-refractive-index layers constituting the anti-reflective layer of the phase-difference detection pixel in a solid-state image sensor, the incident light L can be effectively refracted and the light intensity distribution can be biased toward the high-refractive-index layer. Therefore, the optical separation slit is effective in improving the separation ratio while reducing light scattering and color mixing in the phase-difference detection pixel. [Explanation of Symbols]

[0090] 1, 1A, 1B, 1C Solid-state image sensors, 10 pixels, 10R red pixels, 10G green pixels, 10B blue pixels, 20 phase-difference detection pixels, 21 on-chip lenses, 22 planarization layer, 23 light transmitting layer, 24 anti-reflection layer, 24a High refractive index layer, 24b Low refractive index layer, 25 Photoelectric conversion unit, 30 Light-transmitting layer separation wall, 31 Light-shielding part, 40-pixel separation wall, 41 Boundary separation wall; 50 light-separating slits, 51 Narrow section, 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 position of the C1 light separation slit in a plan view, L Incident light.

Claims

1. A solid-state image sensor having a pixel array in which multiple pixels that generate electrical signals in response to incident light and one or more phase-difference detection pixels are arranged in a two-dimensional manner, The aforementioned phase difference detection pixel is Photoelectric conversion unit, The photoelectric conversion unit includes an on-chip lens positioned on the incident side of the incident light, A light-transmitting layer that transmits light of a specific wavelength in the incident light, The anti-reflective layer laminated on the photoelectric conversion section, A pixel separation wall is disposed between the photoelectric conversion section of the photoelectric conversion section of an adjacent pixel and the photoelectric conversion section of another pixel. The photoelectric conversion unit surrounded by the pixel separation wall comprises boundary separation walls that divide the photoelectric conversion unit into multiple parts, The anti-reflective layer has a laminated structure in which multiple high-refractive-index layers and low-refractive-index layers are stacked. The high refractive index layer, positioned closest to the photoelectric conversion section, has a light-separating slit made of a low refractive index material formed within the layer, in a solid-state image sensor.

2. The solid-state image sensor according to claim 1, wherein the optical separation slit is arranged in the central part of the phase difference detection pixel in a planar direction perpendicular to the stacking direction of the phase difference detection pixel and parallel to the extending direction of the boundary separation wall.

3. The solid-state image sensor according to claim 1, wherein the light separation slit has a cross-sectional shape that is rectangular, trapezoidal, or polygonal.

4. The solid-state image sensor according to claim 1 or 2, wherein the light separation slit has a rectangular, rhombus, polygonal, circular, elliptical, or cross-shaped form when viewed from above.

5. The solid-state image sensor according to claim 1, wherein the material for forming the light separation slit is the same as the material for forming the low refractive index layer adjacent in the stacking direction to the high refractive index layer on which the light separation slit is formed.

6. The solid-state image sensor according to claim 1, wherein the light separation slit has a narrow portion with a width narrower than the wavelength size of the incident light.

7. The solid-state image sensor according to claim 1, wherein the height of the light separation slit in the stacking direction is lower than the wavelength size of the incident light.

8. The solid-state image sensor according to claim 1, wherein at least one of the width and center position of the light separation slit in a plan view differs depending on the image height from the center of the pixel array on which the phase difference detection pixels are arranged.

9. The solid-state image sensor according to claim 1, wherein the light separation slit is formed only on the phase difference detection pixels arranged in the peripheral portion of the pixel array.

Images