Solid-state imaging element

Abstract

A solid-state imaging element (1) is a solid-state imaging element including a QPD structure in which one microlens (ML) is disposed for every four pixels. In each microlens, a central part (CP) including an optical axis (AX) is formed with a first curvature radius (r1), and a peripheral part (PP) around the central part is formed with a second curvature radius (r2) smaller than the first curvature radius.

Description

solid-state imaging device

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

[0002] Solid-state imaging devices with a configuration for improving sensitivity are known. For example, Patent Documents 1 and 2 describe a configuration in which a microlens is formed in a special shape to increase the amount of light received by each pixel in order to improve sensitivity.

[0003] Phase difference detection is known as a method for performing high-speed autofocus in imaging devices. In phase difference detection, phase differences are detected using some of the pixels. The pixels used for phase difference detection cannot be used for imaging. As a result, phase difference detection has the disadvantage of degrading image quality.

[0004] A solid-state imaging device with a QPD (Quad Phase Detection) structure can eliminate the disadvantage of image quality degradation in the phase difference detection method. In a solid-state imaging device with a QPD structure, one microlens is arranged over four pixels. These four pixels are used to perform autofocus using the phase difference detection method and capture an image at the same time. Since a solid-state imaging device with a QPD structure does not have pixels dedicated to phase difference detection, image quality degradation is suppressed.

[0005] JP 2015-153975 A JP 2022-88944 A

[0006] A solid-state imaging device with a QPD structure is required to have sensitivity characteristics that improve autofocus accuracy. However, with the configurations described in Patent Documents 1 and 2, it is difficult to achieve sensitivity characteristics that improve autofocus accuracy for obliquely incident light.

[0007] In view of the above circumstances, an object of an embodiment of the present disclosure is to provide a solid-state imaging device with a QPD structure that can improve autofocus accuracy.

[0008] A solid-state imaging device according to an embodiment of the present disclosure is a solid-state imaging device including a QPD structure in which one microlens is arranged for every four pixels, wherein the microlens has a central portion including an optical axis formed with a first radius of curvature and a peripheral portion surrounding the central portion formed with a second radius of curvature smaller than the first radius of curvature.

[0009] According to an embodiment of the present disclosure, a solid-state imaging device with a QPD structure capable of improving autofocus accuracy is provided.

[0010] FIG. 1 is a cross-sectional schematic diagram of a solid-state imaging element according to an embodiment of the present disclosure. FIG. 2 is a schematic diagram showing a pixel array of a solid-state imaging element according to an embodiment of the present disclosure. FIG. 3 is a diagram illustrating a configuration of a microlens according to an embodiment of the present disclosure. FIG. 4 is a diagram illustrating a microlens according to an embodiment of the present disclosure. FIG. 5 is a diagram illustrating a microlens according to an embodiment of the present disclosure. FIG. 6 is a graph showing a difference in left-right sensitivity in each example of the present disclosure. FIG. 7 is a graph showing sensitivity variations in each example of the present disclosure. FIG. 8 is a schematic diagram illustrating, by way of example, a method for manufacturing a microlens array according to an embodiment of the present disclosure. FIG. 9 is a schematic diagram illustrating, by way of example, another method for manufacturing a microlens array according to an embodiment of the present disclosure.

[0011] The following description relates to a solid-state imaging device according to an embodiment of the present disclosure. Common or corresponding elements are denoted by the same or similar reference numerals, and redundant descriptions are appropriately simplified or omitted. Note that in this specification, the notation "to" includes the lower limit and upper limit. For example, values ​​N1 to N2 indicate a range in which the lower limit is value N1 and the upper limit is value N2.

[0012] 1 and 2 are diagrams showing the configuration of a solid-state imaging element 1 according to an embodiment of the present disclosure. Fig. 1 is a schematic cross-sectional view of the solid-state imaging element 1. Fig. 2 is a schematic diagram showing a pixel array of the solid-state imaging element 1. For convenience, only a portion of the solid-state imaging element 1 is shown in both Fig. 1 and Fig. 2.

[0013] In the following description, two mutually orthogonal directions are referred to as the X direction and the Y direction. The direction orthogonal to both the X direction and the Y direction is referred to as the Z direction. That is, the X, Y, and Z directions are orthogonal to each other. The three-axis coordinate system of XYZ is a left-handed system. For convenience, the axes extending in the X direction, Y direction, and Z direction may be referred to as the X axis, Y axis, and Z axis, respectively. The X direction may also be referred to as the horizontal direction or the left-right direction. The Y direction may also be referred to as the vertical direction or the up-down direction. The Z direction may also be referred to as the height direction or the front-back direction. Note that the names of directions are used for convenience to explain the relative positional relationships of components and do not indicate absolute directions. For example, depending on the orientation of the device, the X direction may not necessarily be the left-right direction but may be the up-down direction.

[0014] The solid-state imaging device 1 is, for example, a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS) image sensor, and is mounted in imaging devices such as video cameras, digital cameras, and smartphones.

[0015] 1, the solid-state imaging device 1 includes a semiconductor substrate 10. A plurality of photoelectric conversion elements 12 are arranged on the semiconductor substrate 10. The photoelectric conversion elements 12 are arranged in a matrix on the semiconductor substrate 10.

[0016] A partition wall 14 is formed on the semiconductor substrate 10. The partition wall 14 is formed in a wall shape and separates the photoelectric conversion elements 12. The partition wall 14 is formed so as to surround the outer periphery of each photoelectric conversion element 12 in a plan view.

[0017] The space defined by the partition wall 14 is filled with a sealing resin 16. The sealing resin 16 is a transparent resin that has a high transmittance at least in the visible light region. Examples of the material for the sealing resin 16 include acrylic resin, polyurethane resin, polyester resin, polyolefin resin, polycarbonate resin, polyethyleneimine resin, epoxy resin, and thioether resin.

[0018] The solid-state imaging device 1 includes a color filter 20. The color filter 20 is, for example, an on-chip color filter in a Bayer array in which red filters 20R, green filters 20G, and blue filters 20B are arranged in a mosaic pattern. The color filter 20 may be another filter, such as a complementary color filter. In FIG. 2 , reference numeral 20W denotes a partition wall between the red filters 20R, green filters 20G, and blue filters 20B.

[0019] The microlens array MLA is disposed on the color filter 20. The microlens array MLA is formed of, for example, an organic material such as acrylic resin, epoxy resin, or silicon resin, or an inorganic material such as SiN or SiO 2 .

[0020] The microlens array MLA includes a plurality of microlenses ML, which are arranged in a matrix.

[0021] The solid-state imaging device 1 has a QPD structure, whereby one microlens ML and one filter (either a red filter 20R, a green filter 20G, or a blue filter 20B) are arranged for every four pixels arranged in two rows and two columns.

[0022] Of the four pixels arranged in two rows and two columns, for convenience, the two pixels in the left column (an example of the first column) are denoted by the symbols PX1 and PX2, and the two pixels in the right column (an example of the second column) are denoted by the symbols PX3 and PX4. Each pixel is separated by a partition wall 14 and includes one photoelectric conversion element 12.

[0023] In the solid-state imaging device 1, not all pixels need to have a QPD structure. That is, a configuration including four pixels with a QPD structure and at least one microlens ML falls within the scope of the present invention. For example, the green filter 20G is configured as a QPD structure, and the red filter 20R and the green filter 20G are configured as a normal structure having one hemispherical microlens per pixel.

[0024] A plurality of flat optical elements, such as a seal glass 32, an optical low-pass filter 34, and an IR cut filter 36, are arranged on the microlens array MLA.

[0025] Light from an imaging lens (not shown) passes through the IR cut filter 36, the optical low-pass filter 34, and the seal glass 32 in this order, and is then incident on the microlens ML. The light incident on the microlens ML is collected by the microlens ML, passes through a filter (one of the red filter 20R, the green filter 20G, and the blue filter 20B), and is received by the photoelectric conversion element 12. The photoelectric conversion element 12 accumulates the received optical image as an electric charge according to the amount of light, and outputs an image signal.

[0026] As described above, the solid-state imaging device 1 having the QPD structure is required to have sensitivity characteristics that improve autofocus accuracy with respect to obliquely incident light. In this embodiment, the sensitivity characteristics that affect the autofocus accuracy include "sensitivity variation" and "left-right sensitivity difference."

[0027] In this embodiment, the sensitivity of a pixel is represented by the magnitude of the image signal output from the photoelectric conversion element 12 in response to light incident on the microlens ML.

[0028] In the phase difference detection method, the distance to the subject is measured based on the phase, and the optimal focus state is calculated from the measured distance. The greater the difference in sensitivity between the four pixels PX1 to PX4, the lower the accuracy of distance measurement. As a result, the accuracy of phase difference detection also decreases. Sensitivity variation indicates the deviation in sensitivity of the four pixels PX1 to PX4 to obliquely incident light. The smaller the value of the sensitivity variation, the smaller the difference in sensitivity between the four pixels PX1 to PX4, and therefore the higher the accuracy of phase difference detection. The larger the value of the sensitivity variation, the larger the difference in sensitivity between the four pixels PX1 to PX4, and therefore the lower the accuracy of phase difference detection. Sensitivity variation is expressed by the following equation:

[0029] Sensitivity variation=(highest sensitivity among pixels PX1 to PX4) / (lowest sensitivity among pixels PX1 to PX4)

[0030] The left-right sensitivity difference indicates the ratio of the sensitivities of left and right pixels to obliquely incident light. The larger the value of the left-right sensitivity difference, the greater the difference in sensitivity between left and right pixels. The greater the difference in sensitivity between left and right pixels, the less likely the accuracy of phase difference detection to decrease even in dark places. Therefore, the larger the value of the left-right sensitivity difference, the more accurate the phase difference detection. The smaller the value of the left-right sensitivity difference, the smaller the difference in sensitivity between left and right pixels, and the more accurate the phase difference detection decreases. The left-right sensitivity difference is expressed by the following equation. As mentioned above, the positional relationship between the "left and right" changes depending on the orientation of the device, so the "left-right sensitivity difference" is merely a convenient expression. In other words, the left-right sensitivity difference is the difference in sensitivity between the first pixel pair arranged in the first column and the second pixel pair arranged in the second column. Therefore, depending on the orientation of the device, it can also mean the difference in sensitivity between front and rear pixels, the difference in sensitivity between top and bottom pixels, etc.

[0031] Left-right sensitivity difference=(sum of sensitivity of pixel PX3 and sensitivity of pixel PX4) / (sum of sensitivity of pixel PX1 and sensitivity of pixel PX2)

[0032] If the value of the sensitivity variation is reduced, the difference in sensitivity between pixels will be reduced, resulting in a deterioration in the left-right sensitivity difference. Conversely, if the value of the left-right sensitivity difference is increased, the difference in sensitivity between pixels will be increased, resulting in a deterioration in the sensitivity variation.

[0033] In other words, there is a trade-off between the sensitivity variation and the left-right sensitivity difference. Therefore, in a conventional solid-state imaging device with a QPD structure, it has been difficult to improve autofocus accuracy by achieving both the sensitivity variation and the left-right sensitivity difference for obliquely incident light. In this embodiment, by forming the microlenses ML as described below, the sensitivity variation and the left-right sensitivity difference are achieved in the solid-state imaging device 1 with a QPD structure.

[0034] FIG. 3 is a diagram illustrating a microlens ML according to this embodiment. The microlens L1 shown in FIG. 3 is an ellipsoidal microlens formed with a general curvature in a solid-state imaging device with a QPD structure. The microlens L2 shown in FIG. 3 is an ellipsoidal microlens with a larger curvature than the microlens L1. In FIG. 3, the entire area indicated by the solid line and the dashed-dotted line is an ellipsoidal hemisphere. That is, in the schematic diagram of FIG. 3, the microlenses L1 and L2 have a shape in which a portion of an ellipsoidal hemisphere has been cut out.

[0035] As shown in Figure 3, when obliquely incident light is incident on the microlens L1, a large spot is formed due to the small incident angle and small refraction of light. As the spot size increases, the difference in the amount of light incident on each of the four pixels PX1 to PX4 tends to decrease. Therefore, the difference in sensitivity between the four pixels PX1 to PX4 decreases, and the sensitivity variation improves. In other words, the shape of the microlens L1 is advantageous for reducing sensitivity variation.

[0036] As shown in Figure 3, when obliquely incident light is incident on the microlens L2, the angle of incidence is large and the light is refracted greatly, resulting in the formation of a small spot. The smaller the spot size, the greater the difference in the amount of light incident on the left and right pixels tends to be. This increases the difference in sensitivity between the left and right pixels, improving the left-right sensitivity difference. In other words, the shape of the microlens L2 is advantageous for reducing the left-right sensitivity difference.

[0037] The microlens ML according to this embodiment has a shape that combines microlenses L1 and L2 in order to achieve both sensitivity variation and a difference in sensitivity between the left and right.

[0038] It should be noted that the microlenses L1 and L2 (in other words, the central portion CP and peripheral portion PP) that form the basis of the microlens ML are not limited to a shape obtained by cutting out a portion of an elliptical hemisphere. For example, the microlens L1 may be formed as an elliptical hemisphere. The microlenses L1 and L2 may also have a shape obtained by cutting out a portion of a hemisphere. The microlenses L1 may also be formed as a hemisphere. The microlenses L1 and L2 may be designed so that a virtual curved surface obtained by virtually extending the central portion CP intersects with the edge of the second surface (exit surface) of the microlens ML. In other words, the microlenses L1 and L2 that form the basis of the microlens ML can have various shapes, allowing for design freedom.

[0039] 4 is a diagram showing a microlens ML according to this embodiment. The microlens ML has a central portion CP including the optical axis AX, and a peripheral portion PP surrounding the central portion CP. The central portion CP and the peripheral portion PP are formed rotationally symmetrically with respect to the optical axis AX. For convenience, the intersection between the entrance surface (first surface) of the microlens ML and the optical axis AX is referred to as the "first intersection point P1." The intersection between the exit surface (second surface) of the microlens ML and the optical axis AX is referred to as the "second intersection point P2."

[0040] The central portion CP and the peripheral portion PP have a shape obtained by cutting out a portion of an elliptical hemisphere. The central portion CP is formed with a radius of curvature r1 (an example of a first radius of curvature). The peripheral portion PP is formed with a radius of curvature r2 (an example of a second radius of curvature) that is smaller than the radius of curvature r1. The central portion CP and the peripheral portion PP may be formed in a shape different from the shape obtained by cutting out a portion of an elliptical hemisphere. For example, in the examples of Equation 3 and Equation 4 described below, the peripheral portion PP is formed in a shape different from the shape obtained by cutting out a portion of an elliptical hemisphere.

[0041] It should be noted that any reference to an element using a designation such as "first," "second," etc., used in this disclosure does not generally limit the quantity or order of those elements. These designations are used for convenience to distinguish between two or more elements. Thus, reference to a first and a second element does not imply, for example, that only two elements are employed, that the first element must precede the second element, etc.

[0042] The radius of curvature r1 is the radius of curvature of the central portion CP on the optical axis AX. The radius of curvature r2 is the radius of curvature of the peripheral portion PP. More specifically, the radius of curvature r2 is the radius of curvature of a circle C2 (see FIG. 4) that approximates the curved shape of the peripheral portion PP.

[0043] 4, by forming the microlens ML into a two-stage shape with a central portion CP and a peripheral portion PP, it is possible to achieve both sensitivity variation and a difference in sensitivity between the left and right sides. Therefore, by achieving both of these characteristics, autofocus accuracy is improved.

[0044] The radius of curvature r1 is larger than the radius of curvature r2, and is, for example, 1.92 μm or less. By setting the radius of curvature r1 to 1.92 μm or less, the microlens ML can be formed to a size suitable for the solid-state imaging device 1 with a QPD structure, and the sensitivity variation and the left-right sensitivity difference can be simultaneously achieved, and in particular, the left-right sensitivity difference can be improved.

[0045] More preferably, the radius of curvature r1 may be set to 1.86 μm or less. By setting the radius of curvature r1 to 1.86 μm or less, the difference in sensitivity between the left and right lenses can be further improved.

[0046] The radius of curvature r2 is, for example, 0.2 μm to 0.9 μm. By setting the radius of curvature r2 to a value within this range, it is possible to achieve both a reduction in sensitivity variation and a reduction in the difference in sensitivity between the left and right sides.

[0047] To achieve a better balance between the sensitivity variation and the left-right sensitivity difference, the curvature radius r2 may be set to 0.28 μm to 0.66 μm. To achieve an even better balance between the sensitivity variation and the left-right sensitivity difference, the curvature radius r2 may be set to 0.4 μm to 0.5 μm.

[0048] The distance between the first intersection point P1 and the second intersection point P2 is referred to as a "first distance D1." An optical axis-orthogonal plane including the boundary line between the central portion CP and the peripheral portion PP is referred to as an "optical axis-orthogonal plane PL." The distance between the optical axis-orthogonal plane PL and the second intersection point P2 is referred to as a "second distance D2." The microlens ML is formed, for example, so that the ratio RT1 (= D2 / D1) of the second distance D2 to the first distance D1 is 0.2 to 0.7.

[0049] By setting the ratio RT1 to a value within this range, it is possible to achieve both the sensitivity variation and the left-right sensitivity difference.

[0050] The microlenses ML may be formed so that the ratio RT1 is 0.2 to 0.66. By setting the ratio RT1 to a value within this range, it is possible to achieve a better balance between the sensitivity variation and the left-right sensitivity difference.

[0051] More preferably, the microlenses ML may be formed so that the ratio RT1 is 0.44 to 0.66. By setting the ratio RT1 to a value within this range, it is possible to achieve a better balance between the sensitivity variation and the left-right sensitivity difference.

[0052] More preferably, the microlenses ML may be formed so that the ratio RT1 is 0.44 to 0.53. By setting the ratio RT1 to a value within this range, it is possible to achieve an even greater balance between the sensitivity variation and the left-right sensitivity difference.

[0053] The radius of the central portion CP is referred to as a "first radius Rd1." The radius of the microlens ML consisting of the central portion CP and the peripheral portion PP is referred to as a "second radius Rd2." The microlens ML is formed, for example, so that the ratio RT2 (=Rd1 / Rd2) of the first radius Rd1 to the second radius Rd2 is 0.6 to 0.9.

[0054] By setting the ratio RT2 to a value within this range, it is possible to achieve both sensitivity variation and a right-left sensitivity difference.

[0055] More preferably, the microlenses ML may be formed so that the ratio RT2 is 0.70 to 0.77. By setting the ratio RT2 to a value within this range, it is possible to achieve a better balance between the sensitivity variation and the left-right sensitivity difference.

[0056] Next, the microlenses of each example (Comparative Examples 1 to 3 and Examples 1 to 8) will be described. Comparative Examples 1 to 3 are simple elliptical hemispherical microlenses. Examples 1 to 8 are microlenses ML having a central portion CP and a peripheral portion PP. As an example, FIGS. 5 to 9 show the microlenses ML of Examples 1 to 5. FIGS. 5 to 9 are cross-sectional views of the microlenses ML in the diagonal direction (the direction of line A1-A2 in FIG. 2). That is, in each of FIGS. 5 to 9, the horizontal axis indicates the diagonal direction parallel to the XY plane. The vertical axis indicates the height direction (Z direction).

[0057] Equations 1 to 5 are functions that represent the shape of the microlens ML in Examples 1 to 5, respectively. These functions are modified functions of an elliptical hemisphere with a circular base and an elliptical side cross section. In each of Equations 1 to 5, the upper equation represents the shape of the central portion CP. The lower equation represents the shape of the peripheral portion PP. In the upper equations, the value of the denominator of the fraction with x and y as numerators represents the radius of the base when the central portion CP is an elliptical hemisphere. In the lower equations, the value of the denominator of the fraction with x and y as numerators represents the radius of the base when the peripheral portion PP is an elliptical hemisphere. However, in the examples of Equations 3 and 4, the peripheral portion PP has a shape that cannot be expressed by a simple elliptical hemisphere. Therefore, in the lower equations of Equations 3 and 4, the value of the denominator of the fraction with x and y as numerators does not represent the radius of the base.

[0058] (Formula 1)

[0059] (Formula 2)

[0060] (Formula 3)

[0061] (Formula 4)

[0062] (Formula 5)

[0063] Fig. 10 is a graph showing the difference in left-right sensitivity in each example. In Fig. 10, the vertical axis represents the difference in left-right sensitivity, and the horizontal axis represents the angle of incidence (unit: degrees). Fig. 11 is a graph showing the variation in sensitivity in each example. In Fig. 11, the vertical axis represents the variation in sensitivity, and the horizontal axis represents the angle of incidence (unit: degrees). The angle of incidence may also be referred to as the angle of obliquely incident light.

[0064] The graphs in Figures 10 and 11 were created under the following conditions. The "pixel set" below indicates four pixels PX1 to PX4. The sensitivity of each pixel was calculated from the intensity of light incident on the photoelectric conversion element 12 surrounded by the partition 14. The optical simulation performed to create the graphs used the FDTD (Finite Difference Time Domain) method as the wave analysis method. TOCCATA-FDTD from Link Research, Inc. was used as the optical simulator.

[0065] <<Partition between pixels>> 0.2 μm <<Partition between RGB filters>> 0.2 μm <<Pitch between pixel sets>> 2.394 μm <<Sensitivity calculation area>> Area including G pixels, slightly larger than the G pixels (with a 10 nm margin all around) <<Fill factor: Occupancy rate of microlens ML in pixel>> 99% <<Wavelength of incident light>> 530 nm <<Angle of incidence>> 0 degrees to 40 degrees

[0066] 10 and 11 , the larger the angle of oblique incident light, the less the sensitivity variation and the left-right sensitivity difference can be achieved in Comparative Examples 1 to 3. In contrast, even when the angle of oblique incident light is large, Examples 1 to 8 can achieve both the sensitivity variation and the left-right sensitivity difference. In particular, when the angle of oblique incident light is 28 degrees or more, a significant difference is observed between Comparative Examples 1 to 3 and Examples 1 to 8 in terms of achieving both the sensitivity variation and the left-right sensitivity difference.

[0067] Table 1 shows various values ​​of the microlenses in each example. Specifically, Table 1 shows the left-right sensitivity difference, sensitivity variation, ratio RT1, ratio RT2, radius of curvature r1, radius of curvature r2, and device characteristics. The device characteristics indicate whether the sensitivity variation and the left-right sensitivity difference are compatible with each other using four levels: "x", "o", "xxx", and "xxx". The more "xxx" there are in the device characteristics, the more the sensitivity variation and the left-right sensitivity difference are compatible with each other.

[0068] The left-right sensitivity difference and sensitivity variation in Table 1 are values ​​when the angle of oblique incident light is 28 degrees.

[0069] (Table 1)

[0070] As shown in Table 1, in Comparative Examples 1 to 3, it is not possible to achieve a suitable value for either the left-right sensitivity difference or the sensitivity variation, which may result in insufficient autofocus accuracy.

[0071] In contrast, both the left-right sensitivity difference and the sensitivity variation are preferably achieved in Examples 1 to 8. Specifically, the left-right sensitivity difference falls within the range of 3.3 to 4.3, and the sensitivity variation falls within the range of 7.3 to 12.2.

[0072] Furthermore, in Examples 2 to 7, the left-right sensitivity difference falls within the range of 3.5 to 3.9, and at the same time, the sensitivity variation falls within the range of 9.8 to 11.1. In Examples 2 to 7, both the left-right sensitivity difference and the sensitivity variation are more suitably achieved.

[0073] Furthermore, in Examples 4 and 5, the left-right sensitivity difference falls within the range of 3.8 to 3.9, and at the same time, the sensitivity variation falls within the range of 10.2 to 10.3. In Examples 4 and 5, both the left-right sensitivity difference and the sensitivity variation are more suitably achieved.

[0074] FIG. 12 is a schematic view illustrating an example of a method for manufacturing a microlens array MLA according to an embodiment of the present disclosure.

[0075] In the example of FIG. 12 , a base layer 40 that forms the basis of the microlens array MLA is formed on the color filter 20. Furthermore, a sacrificial layer (not shown) made of a photosensitive resin is formed on the base layer 40. When the sacrificial layer is exposed and developed with a pattern (referred to as a "first pattern" for convenience) that corresponds to the position of each pixel set (a set of pixels PX1 to PX4), sacrificial patterns 50A are formed on the base layer 40, as shown in step S101. Next, heat flow is used to flow each of the sacrificial patterns 50A corresponding to each pixel set, and as shown in step S102, the sacrificial patterns 50A are deformed into rounded shapes. The deformed sacrificial patterns 50A are referred to as sacrificial patterns 50a.

[0076] A sacrificial layer (not shown) is formed on the sacrificial pattern 50a. When the sacrificial layer is exposed and developed with a pattern (referred to as a "second pattern" for convenience) corresponding to the position of the center portion CP of each microlens ML, a sacrificial pattern 50B is formed on the sacrificial pattern 50a, as shown in step S103. Next, the sacrificial patterns 50a and 50B corresponding to each pixel set are individually flowed by heat flow. By heat flowing under appropriate conditions, the sacrificial patterns 50a and 50B can be deformed into a shape similar to the microlens array MLA, as shown in step S104. The deformed pattern is referred to as a sacrificial pattern 50C.

[0077] Dry etching is performed on the base material layer 40 and the sacrificial pattern 50C (see step S105). As a result, as shown in step S106, the sacrificial pattern 50C disappears and is transferred to the base material layer 40, thereby forming a microlens array MLA on the color filter 20.

[0078] FIG. 13 is a schematic view illustrating another method for manufacturing a microlens array MLA according to an embodiment of the present disclosure.

[0079] In the example of FIG. 13 , a base layer 40 is formed on the color filter 20. Furthermore, a sacrificial layer is formed on the base layer 40. The sacrificial layer is exposed and developed with a first pattern. As a result, a sacrificial pattern 50A is formed on the base layer 40, as shown in step S201. Next, a sacrificial layer is formed on the sacrificial pattern 50A. This sacrificial layer is exposed and developed with a second pattern. As a result, a sacrificial pattern 50B is formed on the sacrificial pattern 50A, as shown in step S202. When the two-layer sacrificial patterns 50A and 50B are thermally flowed, a sacrificial pattern 50C similar to the microlens array MLA is formed on the base layer 40, as shown in step S203. Dry etching is performed on the base layer 40 and the sacrificial pattern 50C (see step S204). As a result, the sacrificial pattern 50C disappears and is transferred to the base layer 40, forming the microlens array MLA on the color filter 20, as shown in step S205.

[0080] The microlens array MLA may be manufactured using a method using a gray-tone mask. The gray-tone mask is a quartz substrate on which a light-shielding film with variable light transmittance is formed to correspond to the lens elements to be manufactured. The gray-tone mask is configured, for example, so that the light transmittance is lower in the region corresponding to the center portion CP of each microlens ML than in the region corresponding to the peripheral portion PP of each microlens ML. The microlens array MLA can also be manufactured using such a gray-tone mask.

[0081] The above is a description of exemplary embodiments of the present disclosure. The embodiments of the present disclosure are not limited to those described above, and various modifications are possible within the scope of the technical idea of ​​the present disclosure. For example, the embodiments of the present application also include appropriate combinations of embodiments explicitly shown in the specification or obvious embodiments.

[0082] This application is based on Japanese Patent Application No. 2024-107825, filed on July 4, 2024, the contents of which are incorporated herein in their entirety.

Claims

1. A solid-state imaging device including a QPD (Quad Phase Detection) structure in which one microlens is arranged for every four pixels, wherein the microlens has a central portion including the optical axis formed with a first radius of curvature, and a peripheral portion around the central portion formed with a second radius of curvature smaller than the first radius of curvature.

2. The solid-state imaging device according to claim 1, wherein when a first distance is defined as a distance between a first intersection point of a first surface of the microlens and the optical axis and a second intersection point of a second surface of the microlens and the optical axis, and a second distance is defined as a distance between a plane perpendicular to the optical axis that includes the boundary line between the central portion and the peripheral portion and the second intersection point, the microlens is formed so that the ratio of the second distance to the first distance is 0.2 or more and 0.7 or less.

3. The solid-state imaging device according to claim 2, wherein the microlens is formed so that the ratio of the second distance to the first distance is 0.2 or more and 0.66 or less.

4. The solid-state imaging device according to claim 2, wherein the microlens is formed so that the ratio of the second distance to the first distance is 0.44 or more and 0.53 or less.

5. The solid-state imaging device according to claim 1, wherein when the radius of the central portion is defined as a first radius and the radius of the microlens consisting of the central portion and the peripheral portion is defined as a second radius, the microlens is formed so that the ratio of the first radius to the second radius is 0.6 or more and 0.9 or less.

6. The solid-state imaging device according to claim 5, wherein the ratio of the first radius to the second radius is 0.70 or more and 0.77 or less.

7. The solid-state imaging device according to claim 1, wherein the first radius of curvature is 1.92 μm or less.

8. The solid-state imaging device according to claim 7, wherein the first radius of curvature is 1.86 μm or less.

9. The solid-state imaging device according to claim 1, wherein the second radius of curvature is 0.2 μm or more and 0.9 μm or less.

10. The solid-state imaging device according to claim 9, wherein the second radius of curvature is 0.28 μm or more and 0.66 μm or less.

11. The solid-state imaging device according to claim 10, wherein the second radius of curvature is 0.4 μm or more and 0.5 μm or less.

12. The solid-state imaging device of claim 1, wherein the four pixels are arranged in two rows and two columns, the sensitivity ratio of the two pixels in the second column to the two pixels in the first column is 3.3 or more and 4.3 or less, and the ratio of the highest sensitivity of the four pixels to the lowest sensitivity of the four pixels is 7.3 or more and 12.2 or less.

Images