Imaging device

Abstract

An imaging device according to one aspect of the present disclosure comprises a photoelectric conversion unit and a microlens. The microlens is provided above the photoelectric conversion unit. In a cross-section, the upper surface of the microlens forms a contour line at which an upwardly convex first curve and a downwardly convex second curve are connected at a first deflection point. In the cross section, the radius of curvature of the second curve at the lower end is greater than the distance from the upper end of the first curve to the first deflection point in the thickness direction of the microlens.

Description

[Technical Field]

[0001] The present disclosure relates to an imaging device. [Background technology]

[0002] Solid-state imaging devices are widely used in digital still cameras, digital video cameras, etc. Known types of solid-state imaging devices include amplified solid-state imaging devices and charge-transfer solid-state imaging devices. A typical example of the amplified solid-state imaging device is a MOS image sensor such as a CMOS (Complementary Metal Oxide Semiconductor). A typical example of the charge-transfer solid-state imaging device is a CCD (Charge Coupled Device) image sensor. In recent years, CMOS image sensors with low power supply voltages have been widely used as solid-state imaging devices mounted on mobile devices such as camera-equipped mobile phones and smartphones, from the viewpoint of power consumption, etc. For example, Patent Document 1 discloses a solid-state imaging device having a microlens. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2018-110147 Summary of the Invention [Problem to be solved by the invention]

[0004] In the field of imaging devices, there is a demand for techniques suitable for suppressing flare. [Means for solving the problem]

[0005] An imaging device according to one aspect of the present disclosure includes: a photoelectric conversion unit; a microlens provided above the photoelectric conversion unit; Equipped with. In cross section, the top surface of the microlens forms a contour line in which a first curved line that is convex upward and a second curved line that is convex downward are connected via a first inflection point; The radius of curvature at the lower end of the second curve is greater than the distance in the thickness direction of the microlens from the upper end of the first curve to the first inflection point. [Effects of the Invention]

[0006] The technology according to the present disclosure is suitable for suppressing flare. [Brief explanation of the drawings]

[0007] [Figure 1] FIG. 1 is a schematic diagram showing an imaging system according to a reference embodiment. [Figure 2A] FIG. 2A is a cross-sectional view showing an example of an imaging device according to a reference embodiment. [Figure 2B] FIG. 2B is a cross-sectional view showing another example of an imaging device according to a reference embodiment. [Figure 3] FIG. 3 is a top view of the imaging device. [Figure 4A] FIG. 4A is a perspective view showing a lens portion of a microlens according to a reference embodiment. [Figure 4B] FIG. 4B is a cross-sectional view showing a microlens according to a reference embodiment. [Figure 4C] FIG. 4C is another cross-sectional view showing a microlens according to the reference embodiment. [Figure 5] FIG. 5 is an explanatory diagram of a flare. [Figure 6A] FIG. 6A is an explanatory diagram of a flare. [Figure 6B] FIG. 6B is an explanatory diagram of a flare. [Figure 6C] FIG. 6C is an explanatory diagram of a flare. [Figure 7] FIG. 7 is a cross-sectional view of the imaging device according to the embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view of the imaging device according to the embodiment. [Figure 9A] FIG. 9A is a perspective view showing the top surface of a microlens according to an embodiment. [Figure 9B] FIG. 9B is a cross-sectional view showing a microlens according to the embodiment. [Figure 9C] FIG. 9C is an explanatory diagram of a microlens according to an embodiment. [Figure 9D] FIG. 9D is an explanatory diagram of a microlens according to an embodiment. [Figure 10] FIG. 10 is a schematic diagram showing an imaging system according to an embodiment. [Figure 11] FIG. 11 is a conceptual diagram of the simulation space. [Figure 12A] FIG. 12A is a diagram showing the light intensity distribution calculated in the optical simulation 1. FIG. [Figure 12B] FIG. 12B is a diagram showing the light intensity distribution calculated in optical simulation 2. [Figure 13] FIG. 13 is a diagram showing an example of the relationship between incident light and the sensitivity of each color. DETAILED DESCRIPTION OF THE INVENTION

[0008] (Findings that formed the basis of this disclosure) 1 shows an imaging system 500 according to a reference embodiment. The imaging system 500 includes a transparent substrate 501, a resin layer 502, a package 503, an imaging device 550, wiring 507a, and bonding wires 506.

[0009] The package 503 and the transparent substrate 501 cooperate to form a housing. The housing houses an imaging device 550. Specifically, in the housing, the package 503 and the transparent substrate 501 are bonded together by a resin layer 502.

[0010] The imaging device 550 includes a semiconductor substrate 504, a photoelectric conversion unit 505, and wiring 507b. Although not shown in Fig. 1, the imaging device 550 also includes other elements such as a microlens and a color filter (see Figs. 2A and 2B).

[0011] Similar to the wiring 507a, the semiconductor substrate 504 is disposed on the bottom surface within the package 503. A photoelectric conversion unit 505 is disposed within the semiconductor substrate 504 or above the semiconductor substrate 504.

[0012] The imaging device 550 is connected to the wiring 507a by a bonding wire 506. Specifically, the bonding wire 506 connects the wiring 507a and the wiring 507b. In FIG. 1, the wiring 507b is a schematic representation of the wiring present in the upper portion of the imaging device 550. In FIGS. 2A and 2B, the wiring 507b is not shown.

[0013] The imaging device 550 may be a CMOS image sensor or a CCD image sensor, or may be a stacked sensor.

[0014] Examples of materials for the package 503 include ceramic and plastic. Examples of materials for the transparent substrate 501 include glass. Specifically, the transparent substrate 501 may be a glass plate. Examples of materials for the resin layer 502 include organic resins such as acrylic, polyimide, and epoxy resin. Examples of materials for the semiconductor substrate 504 include silicon.

[0015] In this reference example, the material of the bonding wire 506 is a metal. Examples of the material of the bonding wire 506 include aluminum, copper, silver, and gold. The material of the bonding wire 506 may contain at least two metals selected from these. The same applies to the materials of the wiring 507a and the wiring 507b. In one specific example, the material of the bonding wire 506 is gold, and the material of the wiring 507a and the wiring 507b is copper.

[0016] 2A shows an imaging device 550a, which is an example of the imaging device 550. FIG 2B shows an imaging device 550b, which is another example of the imaging device 550.

[0017] The imaging device 550a shown in FIG. 2A includes a semiconductor substrate 504, a photodiode 552, an interlayer insulating layer 554, wiring 531, a color filter layer 558, and a microlens 560.

[0018] A photodiode 552 is disposed in the semiconductor substrate 504. The photodiode 552 constitutes a photoelectric conversion unit 505.

[0019] An interlayer insulating layer 554 is disposed on a semiconductor substrate 504. Wiring 531 is buried in the interlayer insulating layer 554. Examples of materials for the wiring 531 include metal and semiconductor. In the example of FIG. 2A, the interlayer insulating layer 554 has a film shape.

[0020] A color filter layer 558 is disposed on the interlayer insulating layer 554. The color filter layer 558 includes a green color filter 558a, a blue color filter 558b, and a red color filter 558c.

[0021] A microlens 560 is disposed on the color filter layer 558. The microlens 560 includes a lens portion 561 and a flat portion 562. The lens portion 561 collects light onto the photodiode 552. The flat portion 562 is interposed between the lens portion 561 and the color filter layer 558. In the example of FIG. 2A , the flat portion 562 has a film shape. Therefore, the flat portion 562 may also be referred to as a planarization film.

[0022] 2B includes a semiconductor substrate 504, an interlayer insulating layer 554, wiring 531, a shield electrode 553, a pixel electrode 555, a photoelectric conversion layer 556, a counter electrode 557, an insulating layer 559, a color filter layer 558, and a microlens 560. The imaging device 550b constitutes a stacked sensor.

[0023] The combination of the pixel electrode 555, the photoelectric conversion layer 556, and the counter electrode 557 constitutes the photoelectric conversion unit 505. The photoelectric conversion layer 556 performs photoelectric conversion. The pixel electrode 555 collects the charges obtained by the photoelectric conversion. The sensitivity of the photoelectric conversion layer 556 to light is adjusted by adjusting the voltage of the counter electrode 557.

[0024] 2B, the photoelectric conversion layer 556 has a film shape. Specifically, the photoelectric conversion layer 556 is an organic film. The counter electrode 557 is a transparent electrode.

[0025] The insulating layer 559 is disposed on the counter electrode 557. The insulating layer 559 is a protective layer that protects the photoelectric conversion unit 505. The insulating layer 559 has a film shape. A color filter layer 558 is disposed on the insulating layer 559, and a microlens 560 is disposed on the color filter layer 558.

[0026] 2A and 2B. As shown in FIG. 3, one lens portion 561 is arranged corresponding to one of green color filter 558a, blue color filter 568b, and red color filter 568c. Note that flat portion 562 is not shown in FIG. 3.

[0027] Fig. 4A is a perspective view of a lens portion 561 of a microlens 560. Fig. 4B is a cross-sectional view of the microlens 560 of the imaging device 550b taken along line 4B-4B in Fig. 3. Fig. 4C is a cross-sectional view of the microlens 560 taken along line 4C-4C in Fig. 3. Figs. 4B and 4C also show a shield electrode 553, a pixel electrode 555, a photoelectric conversion layer 556, a counter electrode 557, an insulating layer 559, and a color filter layer 558.

[0028] However, when strong light such as sunlight is directed toward a microlens, flare can occur. The flare occurs when light is reflected from the microlens and leaks into dark areas. The flare can depend on the optical characteristics of the microlens.

[0029] Flare is further explained with reference to Figures 5 through 6C.

[0030] FIG. 5 shows a schematic diagram of a situation in which high-intensity light is irradiated onto the imaging device 550.

[0031] 4B and 5 to 6C, arrows 570 schematically represent the traveling direction of light. Light can be reflected in various directions by microlens 560. As shown in FIG. 5, the reflected light generated by microlens 560 is further reflected by transparent substrate 501. The reflected light generated by transparent substrate 501 approaches photoelectric conversion unit 505 again. Stray light can be generated when light is reflected by microlens 560 and transparent substrate 501. The stray light can then cause flare.

[0032] It should be noted that stray light and flare may also be generated by reflections other than those on the transparent substrate 501. For example, reflections on the camera housing may also cause stray light and flare.

[0033] According to the inventors' investigations, in the configurations of FIGS. 4A to 4C, light is likely to be reflected at a high angle (see the results of the optical simulations described below). Here, light being reflected at a high angle means that the angle θ2 shown in FIG. 4B becomes large. When light is reflected at a high angle, the light reflected by the lens portion 561 travels in a direction close to horizontal. As a result, flare may occur.

[0034] There is a demand for improving the quality of images formed by imaging devices. Suppressing flare is an effective way to improve image quality. Therefore, the present inventors have investigated techniques suitable for suppressing flare.

[0035] (Summary of one aspect of the present disclosure) An imaging device according to a first aspect of the present disclosure includes: a photoelectric conversion unit; a microlens provided above the photoelectric conversion unit; Equipped with. In cross section, the top surface of the microlens forms a contour line in which a first curved line that is convex upward and a second curved line that is convex downward are connected via a first inflection point; The radius of curvature at the lower end of the second curve is greater than the distance in the thickness direction of the microlens from the upper end of the first curve to the first inflection point.

[0036] The technique according to the first aspect is suitable for suppressing flare.

[0037] In a second aspect of the present disclosure, for example, in the imaging device according to the first aspect, In the cross section, the radius of curvature at the lower end of the second curve may be greater than the distance from the upper end to the lower end in the thickness direction.

[0038] The technique according to the second aspect is suitable for suppressing flare.

[0039] In a third aspect of the present disclosure, for example, in the imaging device according to the first or second aspect, In the cross section, the radius of curvature at the lower end of the second curve may be greater than the distance in the thickness direction from the upper end to the lower surface of the microlens.

[0040] The technique according to the third aspect is suitable for suppressing flare.

[0041] In a fourth aspect of the present disclosure, for example, the imaging device according to any one of the first to third aspects may further include an amplifying transistor including a gate electrode, In the cross section, a focus of the first curve may be located below the gate electrode.

[0042] The focal position of the fourth aspect is a specific example of the focal position.

[0043] In a fifth aspect of the present disclosure, for example, the imaging device according to any one of the first to fourth aspects may further include an amplifying transistor including a gate electrode, In a plan view, a focus of the first curve may be spaced apart from the gate electrode.

[0044] According to the fifth aspect, light incident on the first curved line is less likely to affect the amplifying transistor, which is advantageous from the viewpoint of reducing noise.

[0045] In a sixth aspect of the present disclosure, for example, in the imaging device according to the fourth or fifth aspect, The photoelectric conversion unit may include a photoelectric conversion layer that converts light into electric charges and a pixel electrode that collects the electric charges, In the cross section, a first line segment connecting a first end of the first curve and the focal point, and a second line segment connecting a second end of the first curve and the focal point may intersect with the pixel electrode.

[0046] According to the sixth aspect, the pixel electrode can suppress the influence of light incident on the first curved line on elements located below the pixel electrode, which is advantageous from the viewpoint of reducing noise.

[0047] In a seventh aspect of the present disclosure, for example, in the imaging device according to the sixth aspect, The pixel electrode may contain at least one selected from the group consisting of a metal and a metal compound.

[0048] According to the seventh aspect, the pixel electrode having the above noise reduction effect can be configured.

[0049] In an eighth aspect of the present disclosure, for example, in the imaging device according to any one of the first to seventh aspects, The photoelectric conversion unit may include a photoelectric conversion layer that converts light into electric charges and a pixel electrode that collects the electric charges, The imaging device may further include a shield electrode spaced apart from the pixel electrode and configured to collect the electric charges. In the cross section, a reference line passing through the upper end and extending along the thickness direction may pass through the pixel electrode; The shield electrode may be located outside the outer edge of the pixel electrode when viewed from the reference line.

[0050] According to the eighth aspect, crosstalk can be suppressed by the shield electrode, and the first curve can prevent the shield electrode from collecting excessive electric charge.

[0051] In a ninth aspect of the present disclosure, for example, in the imaging device according to any one of the first to eighth aspects, In the cross section, the radius of curvature at the lower end of the second curved line may be smaller than the radius of curvature at the upper end of the first curved line.

[0052] The configuration of the ninth aspect is a specific example of the configuration of the imaging device.

[0053] In a tenth aspect of the present disclosure, for example, in the imaging device according to any one of the first to ninth aspects, In the cross section, the radius of curvature at the lower end of the second curve may be greater than 50 nm.

[0054] The technique according to the tenth aspect is suitable for suppressing flare.

[0055] In an eleventh aspect of the present disclosure, for example, in the imaging device according to any one of the first to tenth aspects, In the cross section, a direction in which a tangent to the contour line at the first inflection point extends may deviate from a horizontal direction perpendicular to the thickness direction by an angle greater than 0 degrees and equal to or smaller than 35 degrees.

[0056] The technique according to the eleventh aspect is suitable for suppressing flare.

[0057] In a twelfth aspect of the present disclosure, for example, in the imaging device according to any one of the first to eleventh aspects, the microlens includes a lens portion including the upper surface and a flat portion connected to the lens portion; In the cross section, the dimension of the flat portion in the thickness direction may be greater than the distance from the upper end to the lower end in the thickness direction.

[0058] The microlens of the twelfth aspect is easy to manufacture, and therefore, according to the twelfth aspect, it is easy to ensure the reliability of the imaging device.

[0059] In a thirteenth aspect of the present disclosure, for example, in the imaging device according to any one of the first to twelfth aspects, The photoelectric conversion unit may include a photoelectric conversion layer that converts light into electric charges, In the cross section, the contour line may be such that the first curved line, the second curved line, and an upwardly convex third curved line are connected in this order, In a plan view, the first curve, the second curve, and the third curve may overlap with the photoelectric conversion layer.

[0060] According to the thirteenth aspect, it is easy to efficiently perform photoelectric conversion on light incident on the imaging device.

[0061] In a fourteenth aspect of the present disclosure, for example, in the imaging device according to any one of the first to thirteenth aspects, The upper surface may include a plurality of first curved surfaces, each of which is upwardly convex, and a plurality of second curved surfaces, each of which is downwardly convex, The direction in which the plurality of first curved surfaces are arranged and the direction in which the plurality of second curved surfaces are arranged may each include a vertical direction, a horizontal direction, and an oblique direction, When the cross section is referred to as a specific cross section, at least one selected from the group consisting of a longitudinal cross section extending in the thickness direction and the vertical direction, a transverse cross section extending in the thickness direction and the horizontal direction, and an oblique cross section extending in the thickness direction and the diagonal direction may correspond to the specific cross section.

[0062] The configuration of the fourteenth aspect is a specific example of the configuration of the imaging device.

[0063] In a fifteenth aspect of the present disclosure, for example, in the imaging device according to the fourteenth aspect, The oblique cross section may correspond to the specific cross section. In a sixteenth aspect of the present disclosure, for example, in the imaging device according to the fourteenth aspect, The longitudinal section and / or the transverse section and the oblique section may correspond to the specific section, The lower end in the oblique cross section may be located lower than the lower end in the longitudinal cross section and / or the transverse cross section.

[0064] The configurations of the fifteenth and sixteenth aspects are specific examples of the configuration of the imaging device.

[0065] An imaging device according to a seventeenth aspect of the present disclosure includes: a photoelectric conversion layer that converts light into electric charges; a microlens provided above the photoelectric conversion layer; Equipped with. In a cross section, the top surface of the microlens defines a contour line in which a first curved line that is convex upward, a second curved line that is convex downward, and a third curved line that is convex upward are connected in this order; In a plan view, the first curve, the second curve, and the third curve overlap with the photoelectric conversion layer.

[0066] The technique according to the seventeenth aspect is suitable for efficiently photoelectrically converting light incident on an imaging device while suppressing flare.

[0067] An imaging device according to an eighteenth aspect of the present disclosure includes: Photoelectric conversion unit and a microlens provided above the photoelectric conversion unit; Equipped with. In cross section, an upper surface of the microlens defines a contour line formed by connecting a first curved line that is convex upward and a second curved line that is convex downward; The radius of curvature at the lower end of the second curve is greater than half the distance from the lower end of the second curve to the upper end of the first curve in the thickness direction of the microlens.

[0068] The technique according to the eighteenth aspect is suitable for suppressing flare.

[0069] An imaging device according to a 19th aspect of the present disclosure includes: a photoelectric conversion unit; a microlens provided above the photoelectric conversion unit; Equipped with. In cross section, the top surface of the microlens forms a contour line in which a first curved line that is convex upward and a second curved line that is convex downward are connected via a first inflection point; The direction in which a tangent to the contour line at the first inflection point extends deviates from a horizontal direction perpendicular to the thickness direction of the microlens by an angle greater than 0 degrees and equal to or smaller than 35 degrees.

[0070] The technique according to the nineteenth aspect is suitable for suppressing flare.

[0071] An imaging device according to a twentieth aspect of the present disclosure includes: a photoelectric conversion unit; a microlens provided above the photoelectric conversion unit; Equipped with. In cross section, an upper surface of the microlens defines a contour line formed by connecting a first curved line that is convex upward and a second curved line that is convex downward; The radius of curvature at the lower end of the second curve is greater than the radius of curvature at the upper end of the first curve.

[0072] The technique according to the twentieth aspect is suitable for suppressing flare.

[0073] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings.

[0074] The present disclosure is not limited to the following embodiments. Appropriate modifications are possible without departing from the scope of the effects of the present disclosure. Furthermore, one embodiment can be combined with another embodiment. In the following description, identical or similar components are designated by the same reference numerals. Further, duplicated descriptions may be omitted.

[0075] In this specification, terms such as "upper," "lower," "upper surface," and "lower surface" are used solely to specify the relative positions of components, and are not intended to limit the position of the imaging device when in use.

[0076] In this specification, ordinal numbers such as 1st, 2nd, 3rd, etc. may be used. When an element is assigned an ordinal number, it is not necessary that there is an element of the same type with a lower number. The number of ordinal numbers can be changed as needed.

[0077] In this specification, the concept of flare includes ghosting.

[0078] In this specification, the term "metal" is a concept that encompasses both a simple metal made of one type of metal element and an alloy made of two or more types of metal elements.

[0079] The thickness, length, etc. of each element in the drawings may differ from the actual shape due to the drawing process. In addition, the number of conductor patterns on the main surface of the optical element may also differ from the actual number, and may be shown in a number that is easy to illustrate.

[0080] (Embodiment) 7 is a cross-sectional view of an imaging device 200 according to this embodiment. The imaging device 200 constitutes a stacked sensor.

[0081] The imaging device 200 according to this embodiment includes a semiconductor substrate 210 and a plurality of pixels 211. The plurality of pixels 211 are located on the semiconductor substrate 210. Each of the plurality of pixels 211 includes a photoelectric conversion unit 212 and a microlens 220. The microlens 220 is located above the photoelectric conversion unit 212.

[0082] The photoelectric conversion unit 212 has a counter electrode 204, a pixel electrode 202, and a photoelectric conversion layer 203. The pixel electrode 202 is located below the counter electrode 204. The photoelectric conversion layer 203 is located between the counter electrode 204 and the pixel electrode 202. The counter electrode 204 is configured to transmit light. The photoelectric conversion layer 203 converts light into electric charges. The pixel electrode 202 collects the electric charges generated by photoelectric conversion in the photoelectric conversion layer 203. In a typical example, the photoelectric conversion layer 203 has a film shape. The electric charges collected by the pixel electrode 202 can be used to form an image.

[0083] In this embodiment, the pixel electrode 202 contains at least one of a metal and a metal compound. Examples of metals contained in the pixel electrode 202 include titanium (Ti) and tantalum (Ta). Examples of metal compounds contained in the pixel electrode 202 include metal nitrides. Specifically, examples of metal compounds contained in the pixel electrode 202 include titanium nitride (TiN) and tantalum nitride (TaN). Titanium (Ti), tantalum (Ta), titanium nitride (TiN), and tantalum nitride (TaN) are opaque. However, the pixel electrode 202 may contain a transparent material such as ITO (indium tin oxide). In this embodiment, the counter electrode 204 contains a transparent material such as ITO.

[0084] Furthermore, the imaging device 200 includes an insulating layer 205 formed on the counter electrode 204 of the photoelectric conversion section 212 , and a color filter layer 206 formed on the insulating layer 205 .

[0085] The insulating layer 205 functions as a protective layer that protects the photoelectric conversion unit 212. In this embodiment, the insulating layer 205 has a film shape. Examples of materials contained in the insulating layer 205 include silicon oxide and metal oxide. Examples of metal oxides contained in the insulating layer 205 include aluminum oxide (Al2O3) and silicon oxynitride (SiON). The insulating layer 205 may be a stacked body including a silicon oxynitride layer and a metal oxide layer.

[0086] In this embodiment, the color filter layer 206 is a three-primary color filter layer consisting of three colors: red (R), green (G), and blue (B). Specifically, the color filter layer 206 includes a green color filter 206a, a blue color filter 206b, and a red color filter 206c. The green color filter 206a transmits light in the green wavelength range. The blue color filter 206b transmits light in the blue wavelength range. The red color filter 206c transmits light in the red wavelength range. The color filters of each color are arranged in a Bayer array corresponding to the pixels 211.

[0087] However, it is also possible to adopt other forms of color filter layer 206. In a modified example, color filter layer 206 is a color filter layer of a complementary color system consisting of cyan (C), magenta (M), and yellow (Y).

[0088] The imaging device 200 also includes an interlayer insulating layer 201 and a semiconductor substrate 210. The interlayer insulating layer 201 is located below the photoelectric conversion layer 203. The semiconductor substrate 210 is located below the interlayer insulating layer 201.

[0089] A charge accumulation region FD (see FIG. 8) is formed on the semiconductor substrate 210. The charge accumulation region FD is a diffusion region. The charge accumulation region FD is connected to the pixel electrode 202. The charge accumulation region FD accumulates charges sent from the pixel electrode 202. Note that the charge accumulation region FD is not shown in FIG. 7.

[0090] Furthermore, a signal detection unit 209 is formed on the semiconductor substrate 210. The signal detection unit 209 outputs a signal corresponding to the charge obtained by the photoelectric conversion unit 212. The signal detection unit 209 is formed by combining a plurality of transistors such as CMOS transistors, for example.

[0091] In this embodiment, the signal detection unit 209 includes an amplifier transistor 218 (see FIG. 8). The amplifier transistor 218 generates a signal by utilizing the charge. Specifically, a gate electrode 218g of the amplifier transistor 218 is connected to a charge accumulation region FD. The amplifier transistor 218 outputs a signal corresponding to the charge accumulated in the charge accumulation region FD.

[0092] In this embodiment, the signal detection unit 209 includes a reset transistor. The reset transistor resets the charge accumulation region FD. Specifically, in this embodiment, the source or drain of the reset transistor configures the charge accumulation region FD.

[0093] In this embodiment, as schematically shown in FIG. 8 , the pixel electrode 202, the charge storage region FD, and the gate electrode 218g of the amplification transistor 218 are connected via an electrical path 219. The electrical path 219 includes at least one plug 216. The electrical path 219 also includes at least one wiring 217. Examples of materials for the plug 216 include metals and semiconductors. The same applies to the material for the wiring 217. In a typical example, the amplification transistor 218 is a MOSFET (Metal Oxide Semiconductor Field Effect Transistor). Note that in the amplification transistor 218 in FIG. 8 , reference numeral 218a denotes one of the source and drain. Reference numeral 218b denotes the other of the source and drain. Note that the reset transistor is not shown in FIG. 8 .

[0094] The imaging device 200 also includes a shield electrode 215. The shield electrode 215 is spaced apart from the pixel electrodes 202. The shield electrode 215 collects charges generated by photoelectric conversion in the photoelectric conversion layer 203. In this way, the shield electrode 215 can suppress noise from entering the charge accumulation region FD.

[0095] Specifically, the shield electrode 215 is located below the photoelectric conversion layer 203. In other words, the shield electrode 215 is located on the same side as the pixel electrode 202 when viewed from the photoelectric conversion layer 203. The shield electrode 215 is also located between adjacent pixel electrodes 202. Specifically, the shield electrode 215 extends so as to straddle the boundary between adjacent pixels 211. The charges collected by the shield electrode 215 are discharged through an electrical path electrically separated from the electrical path 219 connecting the pixel electrode 202 and the charge accumulation region FD. Such an arrangement of the shield electrode 215 is suitable for suppressing crosstalk between adjacent pixels 211. This suppresses color mixing between adjacent pixels 211 in the color imaging device 200.

[0096] In this embodiment, the photoelectric conversion layer 203 contains an organic material, and specifically is made of an organic material. In the photoelectric conversion layer 203, an n-type organic semiconductor and a p-type organic semiconductor may be joined together.

[0097] However, the photoelectric conversion layer 203 may contain or be made of an inorganic material, such as amorphous silicon or quantum dots.

[0098] The microlens 220 is provided above the photoelectric conversion unit 212. Specifically, the microlens 220 is provided above the photoelectric conversion layer 203. More specifically, the microlens 220 is provided above the color filter layer 206.

[0099] The microlens 220 has a lens portion 208 and a flat portion 207. The lens portion 208 and the flat portion 207 are connected to each other. The lens portion 208 includes an upper surface 220x of the microlens 220. The flat portion 207 includes a lower surface 220y of the microlens 220.

[0100] In this embodiment, one lens portion 208 is disposed corresponding to one of the green color filter 206a, the blue color filter 206b, and the red color filter 206c.

[0101] In this embodiment, the lens portion 208 and the flat portion 207 are made of the same material. However, the lens portion 208 and the flat portion 207 may be made of different materials.

[0102] Examples of materials for the microlenses 220 include acrylic resin, resin containing cyclohexane, etc. The same applies to the materials for the lens portions 208 and the flat portion 207.

[0103] The refractive index of the lens portion 208 is, for example, about 1.2 to 1.7.

[0104] In this embodiment, the flat portion 207 has a film shape, and therefore may also be referred to as a planarizing film.

[0105] 9A is a perspective view of the upper surface 220x of the microlens 220. FIG. 9B is a cross-sectional view of the microlens 220. FIG. 9C is an explanatory diagram of the cross-section of the microlens 220. FIG. 9D is a partially enlarged view of FIG. 9C. FIGS. 9B and 9C also show the color filter layer 206 and the like. In FIG. 9B, θ1 indicates the angle between the incident direction and the reflected direction of light.

[0106] 9A to 9D, a cross section of the imaging device 200 will be described. For convenience of explanation, the term "specific cross section" may be used below. Specifically, the specific cross section extends in the up-down direction 290, which corresponds to the thickness direction of the microlens 220.

[0107] 9C shows a specific cross section. The imaging device 200 may have at least one specific cross section. In FIGS. 9A to 9D, an arrow indicating an upward direction 291, an arrow indicating a downward direction 292, and an arrow indicating a horizontal direction 293 are shown. The horizontal direction 293 is a direction perpendicular to the upward / downward direction 290.

[0108] In this embodiment, as shown in FIG. 9C , in a specific cross section, the top surface 220x of the microlens 220 forms a contour line 220h. In the contour line 220h, the downwardly convex 0th curve 220o is connected to the upwardly convex first curve 220a. This connection is made via the 0th inflection point 220l. In other words, the 0th inflection point 220l is an inflection point between the 0th curve 220o and the first curve 220a. In the contour line 220h, the upwardly convex first curve 220a is connected to the downwardly convex second curve 220b. This connection is made via the first inflection point 220m. In other words, the first inflection point 220m is an inflection point between the first curve 220a and the second curve 220b. In addition, in the contour line 220h, the downwardly convex second curve 220b is connected to the upwardly convex third curve 220c. This connection is made via the second inflection point 220n. In other words, the second inflection point 220n is the inflection point between the second curve 220b and the third curve 220c. In this way, on the contour 220h, the zeroth curve 220o, the first curve 220a, the second curve 220b, and the third curve 220c are connected in this order.

[0109] Here, the term "inflection point" in this specification will be explained. In the example of Fig. 9C, an "inflection point" is a point where a curve changes from an upwardly convex state to a downwardly convex state, or a point where a curve changes from a downwardly convex state to an upwardly convex state. Specifically, the zeroth inflection point 220l, the first inflection point 220m, and the second inflection point 220n are such points.

[0110] However, in this specification, the concept of "inflection point" encompasses a connection point between a curve and a line segment. Therefore, in an example in which a first curve 220a, a first line segment, and a second curve 220b are connected in this order, the connection point between the first curve 220a and the first line segment may be an inflection point. Also, the connection point between the first line segment and the second curve 220b may be an inflection point.

[0111] The expression "a contour line 220h in which an upwardly convex first curve 220a and a downwardly convex second curve 220b are connected via a first inflection point 220m" will now be explained. This expression includes a case in which the first curve 220a and the second curve 220b are directly connected at one point. In this case, this point is the first inflection point 220m. The above expression also includes a case in which the first curve 220a is directly connected to one end of a line segment and the second curve 220b is directly connected to the other end of the line segment. In this case, the connection point between the first curve 220a and the line segment (i.e., the one end of the line segment) is the first inflection point 220m. In this case, the tangent line at the first inflection point 220m of the contour line 220h in the specific cross section may be a straight line including the line segment.

[0112] Similarly, the expression "the first curve 220a and the second curve 220b are connected" is a concept that encompasses both a configuration in which the first curve 220a and the second curve 220b are directly connected and a configuration in which the first curve 220a and the second curve 220b are connected via a line segment. The expression "the first curve 220a, the second curve 220b, and the third curve 220c are connected in this order" is a concept that encompasses both a configuration in which the curves are directly connected and a configuration in which the curves are connected via a line segment. The same applies to other similar expressions.

[0113] In the cross section shown in FIG. 4B, contour line 560h formed by upper surface 560x of microlens 560 is bent sharply into a V shape at lower end 560b. In the cross section shown in FIG. 4C, contour line 560h is connected to upwardly convex curve 560a and straight flat portion 560f. The cross section shown in FIG. 9C is different from the cross sections of FIGS. 4B and 4C.

[0114] In this embodiment, the zeroth curve 220o, the first curve 220a, the second curve 220b, and the third curve 220c have a sinusoidal shape. The sinusoidal shape can prevent light from being reflected at high angles. However, these curves may have other shapes, such as an arc shape.

[0115] 9C, in the specific cross section, the radius of curvature R at the lower end 220k of the second curve 220b is greater than the distance h1 in the vertical direction 290 from the upper end 220j of the first curve 220a to the first inflection point 220m. This configuration is suitable for suppressing flare. As described above, the specific cross section is specifically a cross section that extends in the vertical direction 290.

[0116] With a configuration in which the radius of curvature R is relatively large, when light traveling in the downward direction 292 is reflected by the microlens 220, the light is unlikely to be reflected at a high angle. In other words, the reflected light is unlikely to travel in a direction close to the horizontal direction 293 (see the results of the optical simulation described below). Therefore, even if the light reflected by the microlens 220 is further reflected by an object located above the microlens 220, the light is unlikely to propagate far in the horizontal direction 293 from the position where it first entered the microlens 220. In other words, even if the light that first entered the microlens 220 is reflected by the microlens 220 and becomes stray light, the stray light is unlikely to propagate far. Therefore, flare can be suppressed. The object may be a transparent substrate such as glass. The object may also be a camera housing.

[0117] Specifically, compared to an upward convex curve, a downward convex curve is less likely to lose light-gathering ability even if the radius of curvature is increased. Therefore, a configuration with a relatively large radius of curvature R makes it easier to ensure the lens's light-gathering ability while suppressing flare.

[0118] 9C, in the specific cross section, the radius of curvature R at the lower end 220k of the second curve 220b is greater than the distance h2 in the vertical direction 290 from the upper end 220j of the first curve 220a to the lower end 220k of the second curve 220b. Such a configuration is suitable for suppressing flare.

[0119] 9C, in the specific cross section, the radius of curvature R at the lower end 220k of the second curve 220b is greater than the distance h3 in the vertical direction 290 from the upper end 220j of the first curve 220a to the lower surface 220y of the microlens 220. Such a configuration is suitable for suppressing flare.

[0120] 9C , in the specific cross section, the radius of curvature R at the lower end 220k of the second curve 220b is greater than half the distance h2 in the vertical direction 290 from the lower end 220k of the second curve 220b to the upper end 220j of the first curve 220a. This configuration is suitable for suppressing flare. This configuration can also be said to be a configuration in which the center of curvature at the lower end 220k of the second curve 220b is located above the midpoint between the lower end 220k and the upper end 220j in the vertical direction 290.

[0121] 9C , in the specific cross section, the radius of curvature R at the lower end 220k of the second curve 220b is greater than the distance h2 in the vertical direction 290 from the lower end 220k of the second curve 220b to the upper end 220j of the first curve 220a. This configuration is suitable for suppressing flare. This configuration can also be said to be a configuration in which the center of curvature at the lower end 220k of the second curve 220b is located higher in the vertical direction 290 than the upper end 220j.

[0122] In this embodiment, in the specific cross section, the radius of curvature R at the lower end 220k of the second curve 220b is smaller than the radius of curvature at the upper end 220j of the first curve 220a.

[0123] However, in the specific cross section, the radius of curvature R at the lower end 220k of the second curve 220b and the radius of curvature at the upper end 220j of the first curve 220a may be the same. In the specific cross section, the radius of curvature R at the lower end 220k of the second curve 220b may be larger than the radius of curvature at the upper end 220j of the first curve 220a.

[0124] The ratio of the radius of curvature R at the lower end 220k of the second curve 220b to the radius of curvature R at the upper end 220j of the first curve 220a is, for example, 0.7 or more and 1.3 or less, or may be 0.8 or more and 1.2 or less, or 0.9 or more and 1.1 or less.

[0125] In this embodiment, the radius of curvature R at the bottom end 220k of the second curve 220b in the specific cross section is greater than 50 nm. Such a configuration is suitable for suppressing flare.

[0126] The radius of curvature R may be greater than 300 nm. The radius of curvature R may be greater than or equal to 500 nm. The radius of curvature R may be, for example, less than 10,000 nm. The radius of curvature R may be less than 5,000 nm. The radius of curvature R may be less than 1,200 nm. The radius of curvature R may be, for example, greater than 50 nm and less than 10,000 nm. The radius of curvature R may be greater than 300 nm and less than 5,000 nm. The radius of curvature R may be greater than 500 nm and less than 1,200 nm.

[0127] In this embodiment, as shown in FIG. 9D , in the specific cross section, the deviation angle θ3 of the direction of extension of tangent 280 at first inflection point 220m of contour line 220h from horizontal direction 293 is greater than 0 degrees and not greater than 35 degrees. If deviation angle θ3 is this small, it is easy to make the curvature of upper surface 220x of microlens 220 gentle overall. Therefore, even if light initially incident on microlens 220 is reflected and becomes stray light, the stray light is unlikely to propagate far. Therefore, this configuration is suitable for suppressing flare.

[0128] The deviation angle θ3 may be 30 degrees or less, or may be 10 degrees or less. The deviation angle θ3 may be 1 degree or more, or may be 3 degrees or more.

[0129] In this embodiment, as shown in FIG. 9C , in a specific cross section, the dimension of the flat portion 207 in the up-down direction 290 is greater than the distance h2 from the upper end 220j to the lower end 220k in the up-down direction 290. A microlens having such characteristics is easy to manufacture. Therefore, according to this embodiment, it is easy to ensure the reliability of the imaging device. The dimension of the flat portion 207 in the up-down direction 290 is a thickness t1.

[0130] However, in the specific cross section, the dimension of the flat portion 207 in the vertical direction 290 may be the same as the distance h2 from the upper end 220j to the lower end 220k in the vertical direction 290. Furthermore, in the specific cross section, the dimension of the flat portion 207 in the vertical direction 290 may be smaller than the distance h2 from the upper end 220j to the lower end 220k in the vertical direction 290.

[0131] 9C , in the specific cross section, the first curve 220a, the second curve 220b, and the third curve 220c are connected in this order along the contour line 220h. When viewed from above in the specific cross section, the first curve 220a, the second curve 220b, and the third curve 220c overlap with the photoelectric conversion layer 203. This configuration is suitable for efficiently photoelectrically converting light incident on the imaging device 200 while suppressing flare.

[0132] The reason why such a configuration is suitable for efficiently converting incident light into electricity while suppressing flare can be explained as follows.

[0133] That is, in the example of FIG. 4B, in the cross section of FIG. 4B, contour line 560h formed by upper surface 560x of microlens 560 is bent sharply into a V-shape at its lower end 560b. In contrast, in the example of FIG. 9C, second curve 220b is present. As can be understood from the above explanation, with the configuration including second curve 220b, when light traveling in downward direction 292 is reflected by microlens 220, reflection of the light at a high angle can be suppressed. Therefore, even if light initially incident on microlens 220 is reflected by microlens 220 and becomes stray light, the stray light is unlikely to propagate far. Therefore, flare can be suppressed.

[0134] However, when the lens portions 561-208 of the microlenses 560-220 have the same height in the vertical direction 290, the configuration of FIG. 9C may be less advantageous than the configuration of FIG. 4B in terms of ensuring the light-condensing function of the lens portions. Specifically, the contour line 560h in FIG. 4B is bent sharply into a V shape at its lower end 560b. In this case, the angle of deviation from the horizontal direction of the direction in which the tangent to the upwardly convex curve 560a extends tends to increase from the upper end of the curve 560a to the lower end 560b (note that in the example of FIG. 4B, the lower end 560b is the lower end of the lens portion 561). A large deviation angle is advantageous in terms of ensuring the light-condensing function of the first curve 220a and the third curve 220c. In contrast, in the example of FIG. 9C, the downwardly convex second curve 220b is connected to the upwardly convex first curve 220a. In this case, the deviation angle from horizontal direction 293 of the direction to which the tangent of first curve 220a extends is unlikely to become large from upper end 220j of first curve 220a to first inflection point 220m (note that in the example of FIG. 9C, first inflection point 220m is located above the lower end of lens unit 208). Keeping the deviation angle within a small range is disadvantageous from the perspective of ensuring the light-collecting function of first curve 220a and third curve 220c. However, this embodiment employs a configuration that enables efficient photoelectric conversion of light incident on imaging device 200. This point will be described below.

[0135] Suppose a small first photoelectric conversion layer is placed below the first curve 220a and a small second photoelectric conversion layer is placed below the third curve 220c. The first curve 220a refracts light to focus on the first photoelectric conversion layer, and the third curve 220c refracts light to focus on the second photoelectric conversion layer. The first and second photoelectric conversion layers are spaced apart. In this case, if the light-focusing function is poor, some light may be guided into the gaps between the photoelectric conversion layers rather than into the photoelectric conversion layers, potentially resulting in inefficient photoelectric conversion of light incident on the imaging device. In contrast, in the example of FIG. 9C, when viewed from above in a specific cross section, the first curve 220a, the second curve 220b, and the third curve 220c all overlap with one photoelectric conversion layer 203. With this configuration, even if the light-collecting function of the first curve 220a and the third curve 220c is low, light can reach the photoelectric conversion layer 203. Therefore, light incident on the imaging device 200 can be efficiently photoelectrically converted.

[0136] To be precise, in this embodiment, in a specific cross section, when viewed from above, the entire first curve 220a, the entire second curve 220b, and the entire third curve 220c overlap with the photoelectric conversion layer 203.

[0137] In this embodiment, it can also be said that the first curve 220a, the second curve 220b, and the third curve 220c are contained within both ends of the photoelectric conversion layer 203 in the horizontal direction 293 in the specific cross section. As long as the first curve 220a, the second curve 220b, and the third curve 220c are contained within both ends of one photoelectric conversion layer 203, even if the light-collecting functions of the first curve 220a and the third curve 220c are low, light can reach the photoelectric conversion layer 203. Strictly speaking, in this embodiment, the entire first curve 220a, the entire second curve 220b, and the entire third curve 220c are contained within both ends of the photoelectric conversion layer 203 in the horizontal direction 293 in the specific cross section.

[0138] In this embodiment, FIGS. 7 and 8 also show specific cross sections.

[0139] In this embodiment, as shown in FIG. 8, the focal point 220p of the first curve 220a is located below the gate electrode 218g of the amplifying transistor 218 in the specific cross section.

[0140] In this embodiment, in the specific cross section, a first line segment 221 connecting a first inflection point 220m corresponding to one end of the first curve 220a and the focal point 220p, and a second line segment 222 connecting a zeroth inflection point 220l corresponding to the other end of the first curve 220a and the focal point 220p, intersect with the pixel electrode 202. With this configuration, the pixel electrode 202 can suppress the influence of light incident on the first curve 220a on elements located below the pixel electrode 202. This is advantageous from the viewpoint of reducing noise.

[0141] In this embodiment, as described above, the focal point 220p of the first curve 220a is located below the gate electrode 218g of the amplifier transistor 218. When the focal point 220p is located at this position, there is a possibility that light that converges and travels downward will reach the amplifier transistor 218. The light that reaches the amplifier transistor 218 in this manner may affect the amplifier transistor 218 and cause noise. However, when the first line segment 221 and the second line segment 222 intersect with the pixel electrode 202, the intensity of the light that reaches the amplifier transistor 218 may be weakened. In this way, when the focal point 220p is located below the gate electrode 218g, the above-mentioned noise reduction effect may be achieved.

[0142] In this embodiment, the pixel electrode 202 contains at least one of a metal and a metal compound, thereby enabling the pixel electrode 202 to have the above-described noise reduction effect.

[0143] In this embodiment, the pixel electrode 202 contains a metal, which makes it easy to configure the pixel electrode 202 with the above-described noise reduction effect.

[0144] In this embodiment, the pixel electrode 202 contains a material that has lower optical transparency than the interlayer insulating layer 201 and / or lower optical transparency than ITO (Indium Tin Oxide). This characteristic can also be advantageous in ensuring the above-mentioned noise reduction effect.

[0145] In this embodiment, the focal length f of the lens portion 208 of the microlens 220 is expressed by the following formula (1). f={n1 / (n1-n0)}r (1) Here, r is the radius of curvature of lens portion 208, n1 is the refractive index of the material of lens portion 208, and n0 is the refractive index of the medium in contact with the light incident side of the lens portion. In other words, equation (1) represents the focal length f of lens portion 208 when light is incident from a medium (e.g., an air layer) with a refractive index n0 onto lens portion 208 having a refractive index n1 and a curvature radius r.

[0146] As described above, in this embodiment, the expression "focal length of first curve 220a" is used. The focal length of first curve 220a means the focal length given based on equation (1). As can be understood from equation (1), the focal length of first curve 220a takes into consideration not only the shape of first curve 220a but also the material of lens portion 208, etc.

[0147] In this embodiment, when viewed from above in a specific cross section, the focal point 220p of the first curve 220a is spaced apart from the gate electrode 218g of the amplifier transistor 218. In other words, when viewed from above in a specific cross section, the focal point 220p of the first curve 220a does not overlap with the gate electrode 218g of the amplifier transistor 218. With this configuration, light incident on the first curve 220a is less likely to affect the amplifier transistor 218. This is advantageous from the perspective of reducing noise. Note that "when viewed from above" can be replaced with "in a plan view." "Plan view" refers to a view along the thickness direction of the semiconductor substrate 210.

[0148] In this embodiment, in the specific cross section, the gate electrode 218g of the amplifier transistor 218 is outside the region between the first line segment 221 and the second line segment 222. With this configuration, light incident on the first curve 220a is less likely to affect the amplifier transistor 218. This is advantageous from the viewpoint of reducing noise.

[0149] In this embodiment, as shown in FIG. 8 , in the specific cross section, the reference line 223 passes through the pixel electrode 202. In the specific cross section, the reference line 223 is a line that passes through the upper end 220j of the first curve 220a and extends in the up-down direction 290. In the specific cross section, the shield electrode 215 is located outward of the outer end 202e of the pixel electrode 202 as viewed from the reference line 223. With this configuration, the shield electrode 215 can suppress crosstalk. Furthermore, the first curve 220a can prevent the shield electrode 215 from excessively collecting charge.

[0150] In this embodiment, as shown in FIG. 9A , the upper surface 220x of the microlens 220 has a plurality of upwardly convex first curved surfaces 230 and a plurality of downwardly convex second curved surfaces 240. The directions in which the plurality of upwardly convex first curved surfaces 230 are arranged and the directions in which the plurality of downwardly convex second curved surfaces 240 are arranged are a vertical direction 295, a horizontal direction 296, and a diagonal direction 297, respectively. Here, a cross section extending in the vertical direction 290 and the vertical direction 295 is defined as a vertical cross section. A cross section extending in the vertical direction 290 and the horizontal direction 296 is defined as a horizontal cross section. A cross section extending in the vertical direction 290 and the diagonal direction 297 is defined as a diagonal cross section. In this case, at least one of the vertical cross section, the horizontal cross section, and the diagonal cross section corresponds to the specific cross section.

[0151] 9A , in this embodiment, vertical direction 295, horizontal direction 296, and diagonal direction 297 belong to horizontal direction 293. Vertical direction 295, horizontal direction 296, and diagonal direction 297 are different directions from one another. In a typical example, vertical direction 295 and horizontal direction 296 are perpendicular to one another, and diagonal direction 297 is a direction shifted by 45 degrees from each of vertical direction 295 and horizontal direction 296.

[0152] In this embodiment, the upward convex first curve 220a belongs to one of the multiple upward convex first curved surfaces 230. The upward convex third curve 220c belongs to one of the multiple upward convex first curved surfaces 230. The downward convex second curve 220b belongs to one of the multiple downward convex second curved surfaces 240.

[0153] In this embodiment, as shown in Fig. 9A, the longitudinal section and / or the transverse section and the oblique section correspond to the specific section. The lower end 220k in the oblique section is located lower than the lower end 220k in the longitudinal section and / or the transverse section.

[0154] 9A, the portion that may correspond to the lower end 220k in the longitudinal section and the lower end 220k in the transverse section is indicated by the reference symbol k1, and the portion that may correspond to the lower end 220k in the oblique section is indicated by the reference symbol k2.

[0155] In this embodiment, the at least one specific cross section can be said to include at least one of a longitudinal cross section, a transverse cross section, and an oblique cross section. Alternatively, the at least one specific cross section can be said to include a longitudinal cross section and / or a transverse cross section, and an oblique cross section.

[0156] In this embodiment, a plurality of pixel electrodes 202 are arranged in row and column directions to form an array. The row direction may correspond to one of the vertical direction 295 and the horizontal direction 296. The column direction may correspond to the other of the vertical direction 295 and the horizontal direction 296. A cross section extending in the up-down direction 290 and the row direction is defined as a first cross section. A cross section extending in the up-down direction 290 and the column direction is defined as a second cross section. In this case, the first cross section may correspond to a specific cross section. The second cross section may correspond to a specific cross section.

[0157] The photoelectric conversion unit may be a photodiode. The photodiode is formed, for example, in a semiconductor substrate. Even when the photoelectric conversion unit is a photodiode, the imaging device can be configured in the same manner as when the photoelectric conversion unit has a counter electrode 204, a pixel electrode 202, and a photoelectric conversion layer 203.

[0158] A specific example in which the photoelectric conversion unit is a photodiode will be described. In this specific example, a plurality of photodiodes are arranged in row and column directions to form an array. The row direction may correspond to one of the vertical direction 295 and the horizontal direction 296. The column direction may correspond to the other of the vertical direction 295 and the horizontal direction 296. A cross section extending in the up-down direction 290 and the row direction is defined as a third cross section. A cross section extending in the up-down direction 290 and the column direction is defined as a fourth cross section. In this case, the third cross section may correspond to the specific cross section. The fourth cross section may correspond to the specific cross section.

[0159] 10 shows an imaging system 300 according to this embodiment. The imaging system 300 includes a transparent substrate 501, a resin layer 502, a package 503, the imaging device 200, wiring 507a, and bonding wires 506.

[0160] The transparent substrate 501, the resin layer 502, and the package 503 are the same as those described with reference to Fig. 1. The imaging device 200 is the same as those described with reference to Figs. 7 to 9D. Note that some elements are not shown in Fig. 10.

[0161] The imaging device 200 is connected to the wiring 507a by a bonding wire 506. Specifically, the bonding wire 506 connects the wiring 507a to the wiring 507b of the imaging device 200. In Fig. 10, the wiring 507b is a schematic representation of the wiring present in the upper portion of the imaging device 200. In Fig. 7, the wiring 507b is omitted from the illustration.

[0162] An optical simulation performed to verify the relationship between the shape of the microlens and the degree of flare will now be described.

[0163] (Optical Simulation 1) Fig. 11 shows a conceptual diagram of the simulation space of optical simulation 1. In optical simulation 1, an X-axis, a Y-axis, and a Z-axis that are orthogonal to each other are set. Fig. 11 conceptually shows an XZ plane that passes through the center of the Y-axis direction of the simulation space. The YZ plane that passes through the center of the X-axis direction of the simulation space also has substantially the same configuration as Fig. 11. In Fig. 11, an arrow 470 indicates the traveling direction of light.

[0164] The dimension of the simulation space in the X-axis direction is 200 μm. The dimension of the simulation space in the Y-axis direction is 200 μm. The dimension of the simulation space in the Z-axis direction is 40 μm. The boundary condition of the simulation space is an open boundary.

[0165] In the simulation space, a light source 400 and an optical element 410 were simulated.

[0166] The light source 400 was simulated by setting a circular planar area with a radius of 15 μm that radiates uniform light with a wavelength of 530 nm in the XY plane passing through one end of the simulation space in the Z-axis direction. The light with a wavelength of 530 nm corresponds to green light. Hereinafter, the XY plane passing through one end of the simulation space in the Z-axis direction may be referred to as the plane including the light source 400.

[0167] The optical element 410 is arranged along the XY plane passing through the other end in the Z-axis direction in the simulation space. In the optical element 410, an organic film, an ITO layer, an Al2O3 layer, a SiON layer, a color filter layer 402, and a microlens 401 are stacked in this order. The organic film corresponds to the photoelectric conversion layer. The ITO layer corresponds to the counter electrode. The combination of the Al2O3 layer and the SiON layer corresponds to the protective layer. The color filter layer 402 includes a green color filter 402a, a blue color filter 402b, and a red color filter 402c.

[0168] Specifically, the optical element 410 is positioned so that the microlens 401 faces the light source 400. The distance between the plane including the light source 400 and the closest position on the top surface of the microlens 401 to the plane is 40 μm. The cell size is 3 μm. Here, a cell size of 3 μm means that the pixel has a dimension of 3 μm in the X direction and a dimension of 3 μm in the Y direction. The green color filter 402a, the blue color filter 402b, and the red color filter 402c each have a dimension equivalent to the cell size.

[0169] The microlens 401 in optical simulation 1 corresponds to the microlens 560 of the reference embodiment described with reference to FIGS. 4A to 4C. Therefore, optical simulation 1 allows evaluation of the optical characteristics of the microlens 560 of the reference embodiment. Specifically, in optical simulation 1, the light intensity distribution in a plane including the light source 400 was calculated by wave analysis. The calculation results are shown in FIG. 12A.

[0170] (Optical Simulation 2) In Optical Simulation 2, the microlens 401 corresponds to the microlens 220 of the embodiment described with reference to FIGS. 9A to 9D , rather than the microlens 560 of the reference embodiment. Otherwise, Optical Simulation 2 was performed in the same manner as Optical Simulation 1. Specifically, in Optical Simulation 2, the radius of curvature R at the lower end 220k of the second curve 220b was set to 1200 nm. The distance h1 in the vertical direction 290 from the upper end 220j of the first curve 220a to the first inflection point 220m was set to 200 nm. The distance h2 in the vertical direction 290 from the upper end 220j of the first curve 220a to the lower end 220k of the second curve 220b was set to 400 nm. The distance h3 in the vertical direction 290 from the upper end 220j of the first curve 220a to the lower surface 220y of the microlens 220 was set to 750 nm. The radius of curvature at the upper end 220j of the first curve 220a was set to 1200 nm. The angle θ3 of deviation from the horizontal direction 293 of the direction in which tangent 280 at first inflection point 220m of contour line 220h extends was set to 22.7 degrees. In optical simulation 2, the light intensity distribution in a plane including light source 400 was also calculated by wave analysis. The calculation results are shown in FIG. 12B.

[0171] 12A and 12B are color maps. In FIGS. 12A and 12B, darker areas indicate areas with stronger light intensity. In FIGS. 12A and 12B, a dotted circle 450 is indicated. In FIGS. 12A and 12B, a dark circular area is located in the center of the dotted circle 450. In the peripheral area surrounding the center of the dotted circle 450, there are fewer dark areas in FIG. 12B compared to FIG. 12A.

[0172] When configuring an imaging system as shown in FIGS. 1 and 10, in reality, light reflected by a microlens may be further reflected by the transparent substrate 501 or the like and travel back toward the microlens. This can cause flare. However, as can be seen from FIGS. 12B and 12A, in the embodiment, light is less likely to be reflected at a high angle by the microlens 220 than in the reference embodiment. Therefore, light is less likely to propagate far from the position where it first enters the microlens. Therefore, the microlens 220 of the embodiment can suppress flare.

[0173] As mentioned above, in FIG. 12B , there is a dark circular area in the center of the dotted circle 450. However, this does not necessarily mean that flare will occur even when the microlens 220 of the embodiment described with reference to FIGS. 9A to 9D is used. In a typical example, the size of a real light source in the horizontal direction 293 is larger than that of the light source 400 used in the simulation, and light reflected directly above the microlens 220 is absorbed by the light source. Therefore, light reflected directly above the microlens 220 is unlikely to cause flare. More specifically, in reality, light reflected directly above the microlens may be further reflected by the transparent substrate 501 or the like and travel back toward the microlens. Therefore, due to this repeated reflection, the light may propagate to a position some distance away from the position where it first entered the microlens. However, in an imaging system including an optical system corresponding to optical simulation 2, the range of propagation is limited. Therefore, it is believed that a light source of a typical size can sufficiently absorb the propagating light, and therefore problematic flare will not occur.

[0174] On the other hand, the fact that there are many dark areas in the periphery of the dotted circle 450 in Figure 12A corresponds to a situation in which the intensity of light reflected at a high angle by the microlens is strong. In other words, this corresponds to a situation in which the angle θ2 shown in Figure 4B is large, and the intensity of light reflected by the microlens and traveling in a direction close to horizontal is strong. In this situation, light propagates far from the position where it first entered the microlens, resulting in the appearance of flare.

[0175] As described above, when the angle θ2 shown in FIG. 4B is large, the light propagates far from the position where it first enters the microlens, causing flare. Furthermore, in this case, the light may enter the color filter layer and the photoelectric conversion unit at a high angle (i.e., a large angle of incidence) at that distant position. This may result in red or blue colored flare rather than white flare. However, the microlens 220 of the embodiment can also suppress colored flare. This will be described in detail below with reference to FIG. 13.

[0176] FIG. 13 shows an example of the relationship between the angle of incidence of green light incident on the color filter layer and the photoelectric conversion unit and the sensitivity of green, red, and blue light. In FIG. 13, the horizontal axis represents the angle of incidence (unit: degrees), and the vertical axis represents sensitivity. Here, the angle of incidence is 0 degrees when light is perpendicular to the main surfaces of the color filter layer and the photoelectric conversion unit. The sensitivity shown in FIG. 13 is a normalized sensitivity obtained by normalizing the sensitivity of each color by setting the green sensitivity at an incident angle of 0 degrees to 100%. In the example of FIG. 13, when the angle of incidence is greater than approximately 55 degrees, the sensitivity of red and blue light is greater than when the angle of incidence is 0 degrees. This means that when the angle of incidence is greater than approximately 55 degrees, a magenta color appears. However, the microlens 220 of the embodiment can attenuate the intensity of light reflected at a high angle by the microlens 220, thereby attenuating the intensity of light approaching the color filter layer and the photoelectric conversion unit at a high angle. Therefore, colored flare can be suppressed.

[0177] (others) 7 has a color filter layer 206 between the photoelectric conversion unit 212 and the microlens 220. However, the color filter layer 206 is not essential.

[0178] 7 has only one photoelectric conversion unit 212 between the semiconductor substrate 210 and the microlens 220. However, a plurality of photoelectric conversion units may be provided between the semiconductor substrate 210 and the microlens 220.

[0179] 7 constitutes a front-illuminated sensor, but the imaging device may also constitute a back-illuminated sensor. [Industrial Applicability]

[0180] The imaging device of the present disclosure can be used in cameras such as digital cameras and vehicle-mounted cameras, for example. [Explanation of symbols]

[0181] 200, 550, 550a, 550b Imaging device 201,554 Interlayer insulating layer 202,555 pixel electrodes 202e outer end 203,556 Photoelectric conversion layer 204,557 Counter electrode 205,559 Insulating layer 206,402,558 Color filter layer 206a, 402a, 558a Green color filter 206b, 402b, 558b Blue color filter 206c, 402c, 558c red color filter 207,562 flat area 208,561 Lens section 209 Signal detection unit 210,504 Semiconductor substrate 211 pixels 212,505 Photoelectric conversion unit 215,553 Shield electrode 216 Plug 217,507a,507b,531 Wiring 218 Amplifying Transistor 218a One of the source and drain 218b The other of the source and drain 218g gate electrode 219 Electrical Path 220,401,560 Microlenses 220a First curve, upward convex 220b Second curve convex downwards 220c Third curve, upward convex 220h,560h Contour 220j top end 220k,k1,k2 lower end 220l 0th inflection point 220m 1st inflection point 220n Second inflection point 220o 0th curve 220p focus 220x,560x top 220y bottom surface 221 First Line 222 Second line segment 223 Reference Line 230 First surface with upward convexity 240 Downward convex second surface 280 tangent 290 Up and Down 291 upward direction 292 downward direction 293 horizontal direction 295 vertical 296 Horizontal 297 Diagonal 300,500 Imaging System 400 light sources 410 Optical Elements 450 dotted circle 470,570 Direction of light 501 Transparent substrate 502 Resin layer 503 packages 506 Bonding Wire 552 Photodiode 560a Convex curve 560b bottom end 560f flat section FD charge accumulation region

Claims

1. a photoelectric conversion unit; a microlens provided above the photoelectric conversion unit; An imaging device comprising: In cross section, the upper surface of the microlens forms a contour line in which a first curved line that is convex upward and a second curved line that is convex downward are connected via a first inflection point; an imaging device, wherein a radius of curvature at a lower end of the second curve is greater than a distance in a thickness direction of the microlens from an upper end of the first curve to the first inflection point.

2. In the cross section, the radius of curvature at the lower end of the second curve is greater than the distance from the upper end to the lower end in the thickness direction. The imaging device according to claim 1 .

3. In the cross section, the radius of curvature at the lower end of the second curve is greater than the distance in the thickness direction from the upper end to the lower surface of the microlens.

3. The imaging device according to claim 1.

4. further comprising an amplifying transistor including a gate electrode; In the cross section, a focus of the first curve is located below the gate electrode. The imaging device according to claim 1 .

5. further comprising an amplifying transistor including a gate electrode; In a plan view, a focus of the first curve is away from the gate electrode. The imaging device according to claim 1 .

6. the photoelectric conversion unit includes a photoelectric conversion layer that converts light into electric charges and a pixel electrode that collects the electric charges; In the cross section, a first line segment connecting a first end of the first curve and the focal point and a second line segment connecting a second end of the first curve and the focal point intersect with the pixel electrode.

6. The imaging device according to claim 4.

7. the pixel electrode includes at least one selected from the group consisting of a metal and a metal compound; The imaging device according to claim 6 .

8. the photoelectric conversion unit includes a photoelectric conversion layer that converts light into electric charges and a pixel electrode that collects the electric charges; the imaging device further includes a shield electrode spaced apart from the pixel electrode and configured to collect the charges; In the cross section, a reference line passing through the upper end and extending along the thickness direction passes through the pixel electrode; the shield electrode is located outside the outer edge of the pixel electrode when viewed from the reference line; The imaging device according to claim 1 .

9. In the cross section, the radius of curvature at the lower end of the second curve is smaller than the radius of curvature at the upper end of the first curve. The imaging device according to claim 1 .

10. In the cross section, the radius of curvature at the lower end of the second curve is greater than 50 nm. The imaging device according to claim 1 .

11. In the cross section, a deviation angle of a direction in which a tangent line at the first inflection point of the contour line extends from a horizontal direction perpendicular to the thickness direction is greater than 0 degrees and is equal to or smaller than 35 degrees. The imaging device according to claim 1 .

12. the microlens includes a lens portion including the upper surface and a flat portion connected to the lens portion; In the cross section, the dimension of the flat portion in the thickness direction is greater than the distance from the upper end to the lower end in the thickness direction. The imaging device according to claim 1 .

13. the photoelectric conversion unit includes a photoelectric conversion layer that converts light into electric charges, In the cross section, the contour line is connected in this order to the first curved line, the second curved line, and a third curved line that is convex upward; In a plan view, the first curve, the second curve, and the third curve overlap with the photoelectric conversion layer. The imaging device according to claim 1 .

14. the upper surface includes a plurality of first curved surfaces, each of which is upwardly convex, and a plurality of second curved surfaces, each of which is downwardly convex; a direction in which the plurality of first curved surfaces are arranged and a direction in which the plurality of second curved surfaces are arranged include a vertical direction, a horizontal direction, and an oblique direction, When the cross section is referred to as a specific cross section, at least one selected from the group consisting of a longitudinal cross section extending in the thickness direction and the vertical direction, a transverse cross section extending in the thickness direction and the horizontal direction, and an oblique cross section extending in the thickness direction and the oblique direction corresponds to the specific cross section. The imaging device according to claim 1 .

15. The oblique cross section corresponds to the specific cross section. The imaging device according to claim 14.

16. The longitudinal section and / or the transverse section and the oblique section correspond to the specific section, The lower end in the oblique cross section is located lower than the lower end in the longitudinal cross section and / or the transverse cross section. The imaging device according to claim 14.

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