Imaging device and camera system

Abstract

To provide an imaging device or the like that can increase sensitivity. [Solution] The imaging device 1 comprises a semiconductor substrate 20, a wiring layer 30 located on the semiconductor substrate 20 and including a plurality of wirings 31B, a pixel electrode 40 located on the wiring layer 30, a counter electrode 50 located above the pixel electrode 40, a photoelectric conversion layer 60 located between the pixel electrode 40 and the counter electrode 50 and absorbing light of a first wavelength to generate a signal charge, and a charge storage unit electrically connected to the pixel electrode 40 and accumulating the signal charge. The wiring layer 30 further includes a reflective layer 35 that covers at least a portion of the area outside the pixel electrode 40 in a plan view. A plurality of layers, including the photoelectric conversion layer 60 and the counter electrode 50, are arranged in a continuous manner directly above the reflective layer 35. The optical path length of each of the plurality of layers is shorter than twice the first wavelength.

Description

Technical Field

[0001] The present disclosure relates to an imaging device and a camera system.

Background Art

[0002] Patent Document 1 discloses an imaging device including a photoelectric conversion element having spectral sensitivity in the near-infrared region. The imaging device disclosed in Patent Document 1 includes a pixel electrode, a counter electrode, and a photoelectric conversion layer provided between the pixel electrode and the counter electrode. In the photoelectric conversion layer, light passing through the transparent counter electrode is photoelectrically converted to generate charges, and the generated charges are collected by the pixel electrode.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, the above conventional imaging device has a problem of low sensitivity.

[0005] Therefore, the present disclosure provides an imaging device capable of enhancing sensitivity and a camera system including the imaging device.

Means for Solving the Problems

[0006] An imaging apparatus according to one aspect of the present disclosure comprises a semiconductor substrate, a wiring layer located on the semiconductor substrate and including a plurality of wirings, a first electrode located on the wiring layer, a third electrode located on the first electrode, a photoelectric conversion layer located between the first electrode and the second electrode and absorbing light of a first wavelength to generate a signal charge, and a charge storage unit electrically connected to the first electrode and accumulating the signal charge, wherein the wiring layer further includes a reflective layer that covers at least a portion of the area outside the first electrode in a plan view, and a plurality of layers including the photoelectric conversion layer and the second electrode are arranged in a continuous manner directly above the reflective layer, and the optical path length of each of the plurality of layers is shorter than twice the first wavelength.

[0007] A camera system according to one aspect of the present disclosure comprises an imaging device according to the above-described aspect and an optical system for injecting the light into the imaging device. [Effects of the Invention]

[0008] According to this disclosure, it is possible to provide an imaging device capable of increasing sensitivity, and a camera system equipped with the imaging device. [Brief explanation of the drawing]

[0009] [Figure 1] Figure 1 is a diagram showing the configuration of the imaging device according to Embodiment 1. [Figure 2] Figure 2 is a cross-sectional view of a pixel in the imaging device according to Embodiment 1. [Figure 3] Figure 3 is a plan view of the pixels of the imaging device according to Embodiment 1. [Figure 4] Figure 4 is a cross-sectional view of an imaging device according to a modified example 1 of Embodiment 1. [Figure 5] Figure 5 is a cross-sectional view of an imaging device according to a modified example 2 of Embodiment 1. [Figure 6] Figure 6 is a cross-sectional view of an imaging device according to a modified example 3 of Embodiment 1. [Figure 7] Figure 7 shows the dependence of the light absorption rate in the pixels of the imaging apparatus according to the comparative example and the example on the thickness of the active layer. [Figure 8] Figure 8 shows the dependence of the light absorption rate in the pixels of the imaging device according to the embodiment on the film thickness of ITO. [Figure 9] Figure 9 shows the light absorption rates at the pixels of the imaging apparatus according to the comparative example and the example. [Figure 10] Figure 10 shows the light absorption rates at the pixels of the imaging apparatus according to the comparative example and the example. [Figure 11] Figure 11 is a diagram showing the configuration of the camera system according to Embodiment 2. [Modes for carrying out the invention]

[0010] (Knowledge that forms the basis of this disclosure) The inventors have found that the following problems arise with the conventional imaging device described in the "Background Art" section.

[0011] Imaging devices are required to have high sensitivity to light. In recent years, photoelectric conversion films that are sensitive to the near-infrared light band have been formed using organic materials as photoelectric conversion films for imaging devices that are sensitive to the near-infrared light band.

[0012] However, imaging devices equipped with photoelectric conversion films sensitive to the near-infrared light band tend to have lower light absorption rates and lower photoelectric conversion efficiency (specifically, external quantum efficiency (EQE)) compared to imaging devices equipped with photoelectric conversion films sensitive to the visible light band. Typically, photoelectric conversion films sensitive to the near-infrared light band have a narrow band gap. Therefore, increasing the thickness of the photoelectric conversion film tends to increase the dark current due to thermal excitation, making it difficult to increase the amount of light absorbed by increasing the film thickness. Consequently, in imaging devices equipped with photoelectric conversion films sensitive to the near-infrared light band, light that is not fully absorbed by the photoelectric conversion film and is transmitted downwards, as well as light reflected by the pixel electrodes that is not reabsorbed by the photoelectric conversion film and is emitted outside the imaging device, constitutes a loss.

[0013] An imaging device including a photoelectric conversion film formed using an organic material or quantum dots includes a multilayer thin film including the photoelectric conversion film, unlike a Si photodiode formed as a single layer having a depth of about several μm. When light is incident on the multilayer thin film, multiple interference of light occurs, causing the light to reinforce and cancel each other out. Therefore, by effectively utilizing the interference, it is possible to increase the amount of light absorption in the photoelectric conversion film and potentially enhance the sensitivity of the imaging device.

[0014] Based on the above considerations, through intensive studies by the inventors, a configuration of an imaging device capable of enhancing sensitivity has been found.

[0015] The imaging device according to the first aspect of the present disclosure includes a semiconductor substrate, a wiring layer located on the semiconductor substrate and including a plurality of wirings, a first electrode located on the wiring layer, a second electrode located above the first electrode, a photoelectric conversion layer located between the first electrode and the second electrode and generating signal charges by absorbing light of a first wavelength, and a charge storage unit electrically connected to the first electrode and accumulating the signal charges. The wiring layer further includes a reflective layer covering at least a part of the region outside the first electrode in plan view. A plurality of layers including the photoelectric conversion layer and the second electrode are continuously arranged in the direction directly above the reflective layer, and the optical path length of each of the plurality of layers is shorter than twice the first wavelength.

[0016] As a result, the light that passes through the photoelectric conversion layer without being absorbed by the photoelectric conversion layer is reflected by the reflective layer. Therefore, the amount of light absorption in the photoelectric conversion layer can be increased, and the sensitivity of the imaging device can be enhanced. At this time, since the light reflected by the reflective layer can interfere with the plurality of layers located in the direction directly above the reflective layer, when the light intensity in the photoelectric conversion layer is increased, the sensitivity of the imaging device can be further enhanced. Thus, according to the imaging device according to this aspect, the sensitivity can be enhanced.

[0017] Furthermore, imaging devices may sometimes require even lower noise in the dark. However, imaging devices equipped with photoelectric conversion films sensitive to the near-infrared light band have a larger current flowing through the elements in the dark (called dark current) compared to imaging devices equipped with photoelectric conversion films sensitive to the visible light band. Dark current tends to increase as the area of ​​the electrodes that collect the signal charge generated in the photoelectric conversion film (called pixel electrodes) increases. In other words, if the area of ​​the pixel electrodes can be reduced, it may be possible to reduce the dark current.

[0018] In contrast, an imaging apparatus according to a second aspect of the present disclosure is an imaging apparatus according to a first aspect, further comprising a third electrode located on the wiring layer and adjacent to the first electrode, the second electrode further located above the third electrode, the photoelectric conversion layer located between the third electrode and the second electrode, and the wiring layer covering at least a portion of the space between the first electrode and the third electrode in a plan view.

[0019] As a result, since a third electrode is provided next to the first electrode, the signal charge generated in the photoelectric conversion layer can be efficiently collected by the first electrode by adjusting the potential applied to the third electrode. Therefore, the area of ​​the first electrode can be reduced, and thus the dark current can be reduced. Thus, the imaging device according to this embodiment can reduce the dark current and increase sensitivity.

[0020] An imaging device according to a third aspect of the present disclosure is an imaging device according to the first or second aspect, wherein the reflective layer is insulated from any of the plurality of wirings.

[0021] This makes it possible to suppress parasitic capacitance that occurs between the reflective layer and other wiring.

[0022] An imaging apparatus according to a fourth aspect of the present disclosure is an imaging apparatus according to any one of the first to third aspects, wherein the distance between the reflective layer and the photoelectric conversion layer is shorter than the distance between the reflective layer and the semiconductor substrate.

[0023] This allows light that has passed through the photoelectric conversion layer to be reflected at a position close to the photoelectric conversion layer. Since the photoelectric conversion efficiency can be increased, the sensitivity of the imaging device can be further enhanced.

[0024] An imaging device according to a fifth aspect of the present disclosure is an imaging device according to any one of the first to fourth aspects, further comprising a first layer located above the photoelectric conversion layer and absorbing or reflecting visible light.

[0025] This makes it possible to suppress the incidence of visible light, which can be a source of noise, on the photoelectric conversion layer and semiconductor substrate.

[0026] An imaging apparatus according to a sixth aspect of the present disclosure is an imaging apparatus according to any one of the second to fifth aspects, wherein the third electrode is arranged to surround the first electrode in a plan view, and the area of ​​the first electrode is smaller than the area of ​​the gap between the first electrode and the third electrode in a plan view.

[0027] This allows the area of ​​the first electrode to be reduced, thereby reducing the dark current.

[0028] An imaging apparatus according to the seventh aspect of this disclosure is an imaging apparatus according to any one of the first to sixth aspects, wherein the distance between the reflective layer and the semiconductor substrate is the same as the distance between the first electrode and the semiconductor substrate.

[0029] This allows the first electrode and the reflective layer to be formed in the same process.

[0030] An imaging apparatus according to the eighth aspect of the present disclosure is an imaging apparatus according to any one of the first to seventh aspects, wherein the absorption rate for light of the first wavelength in the portion of the photoelectric conversion layer located directly above the reflective layer is higher than the absorption rate for light of the first wavelength in the portion of the photoelectric conversion layer located directly above the reflective layer, assuming that a second layer having an optical path length longer than twice the first wavelength is arranged between the reflective layer and the photoelectric conversion layer.

[0031] This allows the light reflected by the reflective layer to interfere with multiple layers located directly above it, thereby increasing the light intensity within the photoelectric conversion layer. As a result, the sensitivity of the imaging device can be further enhanced.

[0032] An imaging apparatus according to the ninth aspect of the present disclosure is an imaging apparatus according to any one of the first to eighth aspects, wherein the optical path length of each of the plurality of layers is less than half of the first wavelength.

[0033] This makes light interference more likely, allowing for a further increase in the sensitivity of the imaging device.

[0034] An imaging device according to the tenth aspect of this disclosure is an imaging device according to any one of the first to ninth aspects, wherein the first wavelength is 750 nm or more and 2500 nm or less.

[0035] This allows for increased sensitivity to infrared light.

[0036] An imaging apparatus according to the eleventh aspect of this disclosure is an imaging apparatus according to any one of the first to tenth aspects, wherein the potential difference between the third electrode and the second electrode is smaller than the potential difference between the first electrode and the second electrode.

[0037] This allows signal charges generated within the photoelectric conversion layer to be efficiently collected on the first electrode. As a result, the area of ​​the first electrode can be reduced, thereby reducing dark current.

[0038] A camera system according to a twelfth aspect of this disclosure comprises an imaging device according to any one of the first to eleventh aspects, and an optical system for injecting the light into the imaging device.

[0039] This allows for a reduction in dark current and an increase in sensitivity.

[0040] The embodiments will be described in detail below with reference to the drawings.

[0041] The embodiments described below are all comprehensive or specific examples. The numerical values, shapes, materials, components, arrangement and connection configurations of components, steps, and the order of steps shown in the following embodiments are examples only and are not intended to limit this disclosure. Furthermore, any components in the following embodiments that are not described in an independent claim will be described as optional components.

[0042] Furthermore, each figure is a schematic diagram and not necessarily a strictly accurate representation. Therefore, for example, the scale may not necessarily match in each figure. Also, in each figure, substantially identical components are given the same reference numerals, and redundant explanations are omitted or simplified.

[0043] Furthermore, in this specification, terms indicating relationships between elements such as parallel and perpendicular, terms indicating the shapes of elements such as circles and rectangles, and numerical ranges do not represent only strict meanings, but also include substantially equivalent ranges, such as differences of a few percent.

[0044] Furthermore, in this specification, the terms "upper" and "lower" do not refer to the upward (vertically upward) and downward (vertically downward) directions in absolute spatial perception, but rather to terms defined by the relative positional relationship based on the stacking order in a stacked structure. Moreover, the terms "upper" and "lower" apply not only when two components are spaced apart and another component exists between them, but also when two components are placed in close contact with each other and touch. In the description of the cross-sectional configuration of pixels in this specification, unless otherwise specified, "upper" means the direction in which the photoelectric conversion layer is provided relative to the substrate, and "lower" means the opposite direction.

[0045] Furthermore, in this specification, unless otherwise specified, "plan view" means a view taken from a direction perpendicular to the main surface of the substrate of the imaging device, that is, a view of the main surface of the substrate from the front.

[0046] Furthermore, in this specification, "A and B overlap in a plan view" means that at least a part of A and at least a part of B overlap. That is, this includes cases where a part of A and a part of B overlap, where all of A overlaps with B, where all of B overlaps with A, where A and B completely overlap each other, and so on.

[0047] Furthermore, in this specification, "main component" means the component with the highest content among all components constituting the member. For example, a component with a content of 50% or more is the main component. Components include materials, elements, or compounds. Also, "member A is composed of component B" means that member A substantially contains only component B. However, member A may contain impurities other than component B that are unavoidable to include during manufacturing.

[0048] Furthermore, in this specification, ordinal numbers such as "first," "second," etc., do not indicate the number or order of components unless otherwise specified, but are used to avoid confusion and to distinguish similar components.

[0049] (Embodiment 1) First, the imaging device according to Embodiment 1 will be described.

[0050] Figure 1 shows the configuration of the imaging device 1 according to this embodiment. As shown in Figure 1, the imaging device 1 comprises a pixel array 2, a vertical scanning circuit 3, a horizontal signal readout circuit 4, a plurality of signal lines 5 and 6, and a horizontal signal common line 7. Although not shown, the imaging device 1 also includes a control circuit that controls the vertical scanning circuit 3 and the horizontal signal readout circuit 4, etc.

[0051] The pixel array 2 contains multiple pixels 10 arranged in a matrix. The number of pixels 10 arranged in the row direction (also called the horizontal direction) and the number of pixels 10 arranged in the column direction (also called the vertical direction) may be the same or different. Furthermore, all pixels 10 included in the pixel array 2 may be arranged in one row (or one column), and the imaging device 1 may be implemented as a so-called line sensor. Alternatively, the imaging device 1 may be a single-pixel sensor having only one pixel 10.

[0052] Pixel 10 is sensitive to the wavelength of the light detected by the imaging device 1. The wavelength of the light to be detected is an example of a first wavelength, for example, 750 nm to 2500 nm. In other words, pixel 10 is sensitive to the infrared light band between 750 nm and 2500 nm. Alternatively, pixel 10 may be sensitive to the near-infrared light band between 800 nm and 1600 nm. Note that the wavelength of the light to be detected may be included in the visible light band between 400 nm and 750 nm, or the infrared light band above 2500 nm, and pixel 10 may be sensitive to the visible light band or the infrared light band. In this case, pixel 10 does not need to be sensitive to the near-infrared light band.

[0053] In this embodiment, multiple pixels 10 have the same configuration as each other. The specific configuration of the pixels 10 will be described later.

[0054] The vertical scanning circuit 3, also called the row scanning circuit, is connected to each of the multiple pixels 10 via signal lines 5, which are provided corresponding to each row of the multiple pixels 10. The vertical scanning circuit 3 drives the multiple pixels 10 in row units. Specifically, the vertical scanning circuit 3 supplies signals necessary for driving the pixels 10, such as row selection signals and reset signals, to the multiple signal lines 5.

[0055] For example, the multiple signal lines 5 include an address signal line that supplies a row selection signal for selecting a row. The multiple signal lines 5 also include a reset signal line that supplies a reset signal for resetting the charge accumulated in the pixel 10.

[0056] The horizontal signal readout circuit 4, also called the column scanning circuit, is connected to each of the multiple pixels 10 via signal lines 6, which are provided corresponding to each column of the pixels 10. The signal lines 6, also called vertical signal lines, are signal lines for reading out the signal charge generated by photoelectric conversion at each pixel 10. Although not shown in Figure 1, the signal lines 6 are provided with column signal processing circuits that perform noise suppression signal processing, such as correlated double sampling, and analog-to-digital conversion. The horizontal signal readout circuit 4 sequentially reads signals from the column signal processing circuits to the horizontal signal common line 7.

[0057] Next, the specific cross-sectional configuration of the pixel 10 will be explained using Figure 2. Figure 2 is a cross-sectional view of the pixel 10 of the imaging device 1 according to this embodiment.

[0058] As shown in Figure 2, the imaging device 1 comprises a semiconductor substrate 20, a wiring layer 30, a pixel electrode 40, a shield electrode 45, a counter electrode 50, a photoelectric conversion layer 60, an insulating layer 70, a visible light cut filter 80, and a microlens 90. In this embodiment, the semiconductor substrate 20, wiring layer 30, counter electrode 50, photoelectric conversion layer 60, insulating layer 70, and visible light cut filter 80 are provided across multiple pixels 10. The pixel electrode 40, shield electrode 45, and microlens 90 are provided for each pixel 10. The shield electrode 45 may be provided between adjacent pixels 10. The microlens 90 may also be provided across multiple pixels 10.

[0059] The semiconductor substrate 20 is a support substrate that supports the wiring layer 30 and the photoelectric conversion layer 60, etc. The semiconductor substrate 20 is, for example, a p-type silicon (Si) substrate. As shown in Figure 2, the semiconductor substrate 20 is provided with one or more impurity regions (also called diffusion regions) including an impurity region 21. The semiconductor substrate 20 may be a glass substrate, a semiconductor substrate, a plastic substrate, etc.

[0060] The impurity region 21 is a region formed by the addition of n-type impurities such as phosphorus (P) by means of ion implantation, for example. The impurity region 21 is an example of a charge storage area that stores signal charges generated in the photoelectric conversion layer 60. The impurity region 21 is electrically connected to the pixel electrode 40 via via 32A, wiring 31A, and contact plug 33A. The via 32A, wiring 31A, and contact plug 33A are part of the charge storage area.

[0061] Although not shown in Figure 2, the semiconductor substrate 20 is provided with a signal readout circuit for reading out the signal charge generated in the photoelectric conversion layer 60. The signal readout circuit includes a charge storage unit electrically connected to the pixel electrode 40, and one or more transistors such as an amplification transistor, a selection transistor, and a reset transistor. The transistors are, for example, field-effect transistors, and include a plurality of impurity regions provided on the semiconductor substrate 20 as sources and drains, and include a gate insulating film and a gate electrode. The gate insulating film has a single-layer or multi-layer structure of an insulating film such as a silicon oxide film or a silicon nitride film, and is provided so as to cover the surface of the semiconductor substrate 20. The gate insulating film can be considered as the bottom layer of the interlayer insulating film 34 included in the wiring layer 30. The gate electrode mainly consists of a conductive material such as conductive polysilicon or a metal such as copper, and is provided on the gate insulating film. The gate electrode can be considered as one of a plurality of wirings included in the wiring layer 30.

[0062] The wiring layer 30 is located on the semiconductor substrate 20 and includes a plurality of wirings 31A and 31B. Specifically, as shown in Figure 2, the wiring layer 30 further includes a plurality of vias 32A and 32B, a contact plug 33A, an interlayer insulating film 34, and a reflective layer 35.

[0063] The wiring 31A, via 32A, and contact plug 33A are all conductive and are part of the charge storage section. Specifically, the wiring 31A is electrically connected to the pixel electrode 40 via via 32A. Via 32A is in contact with the lower surface of the pixel electrode 40 and the upper surface of the wiring 31A. The wiring 31A is also electrically connected to the impurity region 21 via contact plug 33A. Contact plug 33A is in contact with the lower surface of the wiring 31A and the upper surface of the impurity region 21. The signal charge collected at the pixel electrode 40 is transferred to the impurity region 21 via via 32A, wiring 31A, and contact plug 33A, and read out via an amplification transistor (not shown) or the like.

[0064] Both wiring 31B and via 32B are conductive. Wiring 31B and via 32B are part of the power supply wiring for supplying a predetermined potential (called the shield potential) to the shield electrode 45. Wiring 31B is electrically connected to the shield electrode 45 via via 32B. Via 32B is in contact with the lower surface of the shield electrode 45 and the upper surface of wiring 31B. Wiring 31B is also connected to a power supply circuit (not shown). Alternatively, if the shield potential is fixed at 0V, the shield potential may be connected to a ground wire (not shown). Wiring 31B may also be electrically connected to an impurity region provided on the semiconductor substrate 20 via a contact plug.

[0065] Wirings 31A and 31B, vias 32A and 32B, and contact plug 33A all contain conductive material as their main component. For example, wirings 31A and 31B, vias 32A and 32B, and contact plug 33A contain metals such as copper (Cu), aluminum (Al), and gold (Au), conductive metal nitrides or metal oxides, or conductive polysilicon as their main component.

[0066] Furthermore, the wiring layer 30 may include multiple wirings that are not electrically connected to either the pixel electrode 40 or the shield electrode 45. For example, the multiple wirings may include signal wiring and power wiring electrically connected to one or more transistors included in the signal readout circuit, wiring for supplying a predetermined potential to the counter electrode 50, ground wiring to which ground potential (0V) is supplied, and wiring that functions as part of the electrodes of a capacitive element.

[0067] The interlayer insulating film 34 is a laminate of multiple insulating films provided between the semiconductor substrate 20 and the photoelectric conversion layer 60. The multiple insulating films are, for example, silicon oxide films, silicon nitride films, silicon oxynitride films, aluminum oxide films, or TEOS films (also called TEOS oxide films) formed using TEOS (Tetra Ethoxy Silane).

[0068] In a plan view, the reflective layer 35 covers at least a portion of the area outside the pixel electrode 40. Specifically, in a plan view, the reflective layer 35 covers at least a portion of the area between the pixel electrode 40 and the shield electrode 45. The specific plan view shape of the reflective layer 35 will be described later.

[0069] The reflective layer 35 can reflect light of the first wavelength, which is the target of detection by the imaging device 1. For example, the reflectivity of the reflective layer 35 for light of the first wavelength is higher than the reflectivity of the counter electrode 50 for light of the first wavelength. The reflective layer 35 mainly contains a material that is reflective to light of the first wavelength. For example, the reflective layer 35 may contain the same main components as the wiring contained in the wiring layer 30. Since the reflective layer 35 and the wiring can be formed in the same process, the manufacturing process can be simplified. This can suppress the occurrence of manufacturing errors and improve the reliability of the imaging device 1.

[0070] The reflectance of the reflective layer 35 with respect to the light to be detected by the imaging device 1 is, for example, 50% or more. However, this reflectance may be 60% or more, 70% or more, 80% or more, or 90% or more. As will be described in detail later, the higher the reflectance of the reflective layer 35 with respect to the light to be detected by the imaging device 1, the higher the sensitivity of the imaging device 1 can be increased. Note that the reflective layer 35 only needs to be able to reflect the light to be detected by the imaging device 1 and does not necessarily need to have a high reflectance.

[0071] For example, the reflective layer 35 mainly contains metals with high reflectivity such as aluminum (Al), tungsten (W), silver (Ag), copper (Cu), gold (Au), magnesium (Mg), and cobalt (Co). Alternatively, the reflective layer 35 may mainly contain metal nitrides that have conductivity and light reflectivity, such as titanium nitride (TiN) or tantalum nitride (TaN). Furthermore, the reflective layer 35 may mainly contain transparent conductive oxides that have conductivity, such as indium tin oxide (ITO).

[0072] In this embodiment, the reflective layer 35 is located below the pixel electrode 40 and the shield electrode 45. As shown in Figure 2, the distance D1 between the reflective layer 35 and the photoelectric conversion layer 60 is shorter than the distance D2 between the reflective layer 35 and the semiconductor substrate 20. This allows light that has passed through the photoelectric conversion layer 60 to be reflected at a position close to the photoelectric conversion layer 60. This increases the photoelectric conversion efficiency, and thus further increases the sensitivity of the imaging device 1.

[0073] Distances D1 and D2 are both lengths along the stacking direction and correspond to the shortest distances between them. For example, the upper and lower surfaces of the reflective layer 35, the lower surface of the photoelectric conversion layer 60, and the upper surface of the semiconductor substrate 20 are parallel to each other. Therefore, distance D1 is the distance between the upper surface of the reflective layer 35 and the lower surface of the photoelectric conversion layer 60, and distance D2 is the distance between the lower surface of the reflective layer 35 and the upper surface of the semiconductor substrate 20.

[0074] The pixel electrode 40 is an example of a first electrode and is located on the wiring layer 30. In this embodiment, the pixel electrode 40 is provided so as to be embedded in the uppermost layer of the interlayer insulating film 34 of the wiring layer 30. By making the upper surface of the pixel electrode 40 and the upper surface of the interlayer insulating film 34 flush, the flatness of the photoelectric conversion layer 60 can be improved and the film quality can be enhanced.

[0075] The pixel electrode 40 is electrically connected to the photoelectric conversion layer 60 and collects the signal charge generated in the photoelectric conversion layer 60. The pixel electrode 40 collects the charge of one of the electron-hole pairs generated in the photoelectric conversion layer 60 as a signal charge and outputs the signal charge to a signal readout circuit provided on the semiconductor substrate 20 via a conductive via 32A, wiring 31A, and contact plug 33A. One pixel electrode 40 is provided for each pixel 10.

[0076] The pixel electrode 40 may mainly contain a conductive material that can reflect the light of the target to be detected by the imaging device 1. For example, the reflectance of the pixel electrode 40 to the light of the target to be detected by the imaging device 1 is equal to or greater than that of the counter electrode 50. For example, the reflectance of the pixel electrode 40 to the light of the target to be detected by the imaging device 1 is 50% or more. This reflectance may be 60% or more, 70% or more, 80% or more, or 90% or more. As will be described in detail later, the higher the reflectance of the pixel electrode 40 to the light of the target to be detected by the imaging device 1, the higher the sensitivity of the imaging device 1 can be increased. The pixel electrode 40 does not necessarily need to have a high reflectance as long as it can reflect the light of the target to be detected by the imaging device 1. For example, the reflectance of the pixel electrode 40 to the light of the target to be detected may be lower than the reflectance of the counter electrode 50 to the light of the target to be detected.

[0077] Furthermore, when adjusting for compatibility with the photoelectric conversion layer 60, it may not be possible to use a material with sufficiently high reflectivity as the pixel electrode 40. In such cases, a light-reflecting layer may be formed on the lower surface of the pixel electrode 40. That is, the pixel electrode 40 can be configured to improve reflectivity by being a laminated electrode including an electrode layer and a light-reflecting layer.

[0078] The pixel electrode 40 mainly comprises a metal nitride having conductivity and light reflectivity, such as TiN or TaN. Alternatively, the pixel electrode 40 may mainly comprise a highly reflective metal such as Al, W, Ag, Cu, Au, Mg, or Co. Alternatively, the pixel electrode 40 may mainly comprise a transparent conductive oxide having conductivity, such as ITO.

[0079] The shield electrode 45 is an example of a third electrode, located on the wiring layer 30 and adjacent to the pixel electrode 40. A gap 43 is provided between the shield electrode 45 and the pixel electrode 40, so they are not in contact with each other. In this embodiment, the shield electrode 45 is provided so as to be embedded in the uppermost layer of the interlayer insulating film 34 of the wiring layer 30. By making the upper surface of the shield electrode 45 and the upper surface of the interlayer insulating film 34 flush, the flatness of the photoelectric conversion layer 60 can be improved and the film quality can be enhanced.

[0080] The shield electrode 45 is supplied with a different potential than the pixel electrode 40. Specifically, by supplying a predetermined shielding potential to the shield electrode 45 via the wiring 31B and via 32B, it is possible to suppress the leakage of signal charge generated in the photoelectric conversion layer 60 to the adjacent pixel 10. In other words, the mixing of signal charge between pixels 10 can be suppressed, and the deterioration of image quality can be suppressed. Specifically, the shielding potential is such that the potential difference between the shield electrode 45 and the counter electrode 50 is smaller than the potential difference between the pixel electrode 40 and the counter electrode 50.

[0081] For example, when the pixel electrode 40 collects holes as signal charges, a voltage lower than the bias voltage applied between the pixel electrode 40 and the counter electrode 50 is applied between the shield electrode 45 and the counter electrode 50. For example, the potentials are set to increase in the order of pixel electrode 40, shield electrode 45, and counter electrode 50. This makes it easier for holes, which are signal charges, to be collected by the pixel electrode 40. When the pixel electrode 40 collects electrons as signal charges, the potentials should be set to decrease in the order of pixel electrode 40, shield electrode 45, and counter electrode 50.

[0082] In this way, by applying a predetermined potential difference between the pixel electrode 40 and the counter electrode 50, signal charges generated in the region directly above the pixel electrode 40 of the photoelectric conversion layer 60 can be efficiently collected on the pixel electrode 40. Furthermore, by applying a predetermined potential difference between the shield electrode 45 and the counter electrode 50, charges generated near the boundary of the pixel 10 in the photoelectric conversion layer 60 can be collected on the shield electrode 45, thereby suppressing the leakage of charge to the adjacent pixel 10. At this time, by making the potential difference between the shield electrode 45 and the counter electrode 50 smaller than the potential difference between the pixel electrode 40 and the counter electrode 50, a predetermined potential difference can also be applied between the counter electrode 50 and the pixel electrode 40. As a result, charges generated in the region directly above the gap 43 of the photoelectric conversion layer 60 can be collected on the pixel electrode 40. Since light reflected by the reflective layer 35 is easily incident on the region directly above the gap 43, the charges generated by the photoelectric conversion of the light reflected by the reflective layer 35 can be collected on the pixel electrode 40 as signal charges. This makes it possible to increase the sensitivity of the imaging device 1.

[0083] Furthermore, the shield electrode 45 may also have light reflectivity, similar to the pixel electrode 40. This allows the shield electrode 45 to be used for light reflection, increasing the number of reflections and further enhancing the sensitivity of the pixel 10.

[0084] The shield electrode 45 mainly contains the same material as the pixel electrode 40, for example. This allows the shield electrode 45 and the pixel electrode 40 to be formed in the same process. For example, the shield electrode 45 mainly contains a metal nitride having conductivity and light reflectivity, such as TiN or TaN. Alternatively, the shield electrode 45 may mainly contain a highly reflective metal such as Al, W, Ag, Cu, Au, Mg, or Co. The shield electrode 45 may also be light-transmitting and may mainly contain the same material as the counter electrode 50. The shield electrode 45 may mainly contain a transparent conductive oxide such as ITO, IZO, AZO, FTO, SnO2, TiO2, or ZnO2.

[0085] Furthermore, the shield electrode 45 may contain a different material as its main component than the pixel electrode 40. For example, the material that can be used for the pixel electrode 40 may be limited in order to meet the requirements for compatibility with the photoelectric conversion layer 60, in addition to reflectivity. In contrast, the shield electrode 45 has fewer restrictions than the pixel electrode 40, so for example, a material with a higher reflectivity than the pixel electrode 40 can be used.

[0086] The counter electrode 50 is an example of a second electrode and is provided above the pixel electrode 40 and the shield electrode 45. Specifically, the counter electrode 50 faces the pixel electrode 40 and the shield electrode 45, respectively, via the photoelectric conversion layer 60. The counter electrode 50 can transmit the light to be detected by the imaging device 1. For example, the transmittance of the counter electrode 50 to the light to be detected by the imaging device 1 is 50% or more. This transmittance may be 60% or more, 70% or more, 80% or more, or 90% or more. The higher the transmittance, the higher the sensitivity of the imaging device 1 can be. The counter electrode 50 collects the charge of the other electron-hole pair generated in the photoelectric conversion layer 60.

[0087] In this embodiment, the counter electrode 50 is provided across multiple pixels 10. Specifically, the counter electrode 50 is not separated for each pixel 10, but is configured as a single electrode film. However, the counter electrode 50 may be separated for each row or column of the pixel array 2, or for each block containing multiple pixels 10, or for each pixel 10. The counter electrode 50 is formed with a substantially uniform film thickness.

[0088] The counter electrode 50 mainly contains a transparent conductive oxide (TCO) which has high transmittance and low resistance to the light detected by the imaging device 1. Alternatively, the counter electrode 50 may be a thin metal film such as Au. However, if a transmittance of 90% or more in the near-infrared light band is to be obtained, the resistance may increase drastically compared to when a thin metal film made of Au is formed as the counter electrode 50 to obtain a transmittance of 60% to 80%. Therefore, TCO has higher transparency to near-infrared light and a lower resistance than metal materials such as Au, allowing for the creation of a transparent electrode. The TCO is not particularly limited, but examples include ITO, IZO (Indium Zinc Oxide), AZO (Aluminum-doped Zinc Oxide), FTO (Florine-doped Tin Oxide), SnO2, TiO2, ZnO2, etc. The counter electrode 50 may be formed by combining TCO and metal materials individually or in combination as appropriate, depending on the desired transmittance.

[0089] Various methods can be used to form the counter electrode 50, depending on the material used. For example, when forming an ITO film, chemical reaction methods such as electron beam method, sputtering method, resistance heating deposition method, sol-gel method, or coating of indium tin oxide dispersion may be used. In this case, after forming the ITO film, further treatments such as UV-ozone treatment or plasma treatment may be performed.

[0090] The photoelectric conversion layer 60 absorbs light of a first wavelength and generates a signal charge. Specifically, the photoelectric conversion layer 60 generates a hole-electron pair by photoelectric conversion of the incident light of the first wavelength. One of the hole and electron in the hole-electron pair is the signal charge. For example, depending on the polarity of the bias voltage applied between the pixel electrode 40 and the counter electrode 50, one of the hole and the electron can be collected as a signal charge by the pixel electrode 40. For example, by applying a bias voltage such that the potential of the pixel electrode 40 is lower than the potential of the counter electrode 50, the pixel electrode 40 collects the hole as a signal charge, and the collected hole can be read out by the signal readout circuit. Alternatively, by applying a bias voltage such that the potential of the pixel electrode 40 is higher than the potential of the counter electrode 50, the pixel electrode 40 collects the electron as a signal charge, and the collected electron can be read out by the signal readout circuit. Thus, in the imaging device 1, either the hole or the electron may be read out as the signal charge.

[0091] The bias voltage is calculated based on the electric field generated in the photoelectric conversion layer 60, which is 1.0 × 10⁻⁶. 3 V / cm or more 1.0×10 7 It may be applied so as to be within the range of V / cm or less, 1.0 × 10 4 V / cm or more 1.0×10 6 The value may be within the range of V / cm or less. By adjusting the magnitude of the bias voltage in this way, it becomes possible to efficiently transfer signal charge to the pixel electrode 40 and extract a signal corresponding to the signal charge to the outside.

[0092] The photoelectric conversion layer 60 is located between the pixel electrode 40 and the counter electrode 50. Specifically, the photoelectric conversion layer 60 is located between the pixel electrode 40 and the shield electrode 45 and the counter electrode 50. In this embodiment, the photoelectric conversion layer 60 is provided across multiple pixels 10. Specifically, the photoelectric conversion layer 60 is not separated for each pixel 10, but is configured as a single photoelectric conversion film. The photoelectric conversion layer 60 continuously covers the multiple pixel electrodes 40, the multiple shield electrodes 45, and the interlayer insulating film 34 located as the uppermost layer of the wiring layer 30 between the pixel electrode 40 and the shield electrode 45. The photoelectric conversion layer 60 may be separated for each row or column of the pixel array 2, or for each block containing multiple pixels 10, or for each pixel 10.

[0093] The photoelectric conversion layer 60 mainly contains a photoelectric conversion material that is sensitive to the wavelength of light to be detected by the imaging device 1. For example, the photoelectric conversion material is sensitive to the near-infrared light band. The photoelectric conversion material may also be sensitive to the visible light band or the infrared light band. In this case, the photoelectric conversion material does not need to be sensitive to the near-infrared light band. As the photoelectric conversion material, organic semiconductors, carbon nanotubes, quantum dots, inorganic materials, etc., can be used.

[0094] The insulating layer 70 is provided above the counter electrode 50. Specifically, the insulating layer 70 functions as a planarizing film that covers and flattens the upper surface of the counter electrode 50. The upper surface of the insulating layer 70 is a flat surface. The insulating layer 70 has light transmittance similar to that of the counter electrode 50. The insulating layer 70 is, for example, a TEOS film, but may have a single-layer or multi-layer structure such as an SiO2 film, a SiN film, or a SiON film. Note that the insulating layer 70 may not be provided at all.

[0095] The visible light cut filter 80 is located above the photoelectric conversion layer 60 and is an example of a first layer that absorbs or reflects visible light. For example, the photoelectric conversion layer 60 may be sensitive to visible light bands other than the wavelength of the light detected by the imaging device 1. In this case, the visible light cut filter 80 can reduce the visible light incident on the photoelectric conversion layer 60 by absorbing or reflecting visible light in the wavelength band to which the photoelectric conversion layer 60 is sensitive. This can suppress the generation of unwanted charges within the photoelectric conversion layer 60.

[0096] Furthermore, even if the photoelectric conversion layer 60 is not sensitive to the visible light band, the visible light incident on the semiconductor substrate 20 can be reduced by providing the visible light cut filter 80. If visible light is incident on the semiconductor substrate 20, there is a risk that unnecessary current will flow in the transistor, potentially causing noise or malfunction. By providing the visible light cut filter 80, the occurrence of noise and malfunction can be suppressed. In addition, for the purpose of suppressing the incident of visible light on the semiconductor substrate 20, the visible light cut filter 80 may be provided between the photoelectric conversion layer 60 and the semiconductor substrate 20. For example, the visible light cut filter 80 may be provided both above the photoelectric conversion layer 60 and between the photoelectric conversion layer 60 and the semiconductor substrate 20.

[0097] The visible light cut filter 80 is not required. Alternatively, instead of the visible light cut filter 80, the imaging device 1 may be equipped with a filter that absorbs or reflects light of a second wavelength other than the first wavelength of the light to be detected. For example, the filter may be a bandpass filter that includes a predetermined wavelength band including the first wavelength as a passband and wavelength bands other than the passband as a cutoff band.

[0098] The microlens 90 focuses light near the pixel electrode 40. The microlens 90 is formed using a light-transmitting resin or the like. The microlens 90 is formed integrally with the microlens 90 of the adjacent pixel 10 to form a microlens array. Alternatively, the microlens 90 may be provided separately for each pixel 10.

[0099] The provision of the microlens 90 suppresses reflection from the surface of the imaging device 1, thereby increasing the efficiency of light incidence. Furthermore, by focusing the light with the microlens 90 and suppressing light incident at an oblique angle, crosstalk can be suppressed. Note that the microlens 90 is not required.

[0100] Next, the positional relationship and shape of the pixel electrode 40, shield electrode 45, and reflective layer 35 of the pixel 10 of the imaging device 1 according to this embodiment will be explained in plan view using Figure 3. Figure 3 is a plan view of the pixel 10 of the imaging device 1 according to this embodiment. In Figure 3, only the pixel electrode 40, shield electrode 45, reflective layer 35, and via 32B of the pixel 10 are shown. The reflective layer 35 and via 32B are each covered with a dotted pattern.

[0101] As shown in Figure 3, a shield electrode 45 is provided so as to surround a pixel electrode 40 that has a square shape in plan view. The shield electrode 45 is located between two adjacent pixel electrodes 40. For example, for a plurality of pixel electrodes 40 arranged in a matrix, the shield electrode 45 is formed in a grid pattern so as to separate each pixel electrode 40.

[0102] For example, focusing on a single pixel 10, the shield electrode 45 is formed in a rectangular ring shape so as to surround the pixel electrode 40. Furthermore, a rectangular ring gap 43 exists between the pixel electrode 40 and the shield electrode 45, and a rectangular ring reflective layer 35 is provided to cover this gap 43. In this embodiment, the reflective layer 35 is provided to cover the entire gap 43 between the pixel electrode 40 and the shield electrode 45. This increases the reflectivity of the light that has passed through the photoelectric conversion layer 60 at the reflective layer 35.

[0103] Furthermore, a portion of the reflective layer 35 overlaps with the pixel electrode 40, and another portion of the reflective layer 35 overlaps with the shield electrode 45. In each overlapping portion, light traveling obliquely to the stacking direction can be reflected, thus further increasing the reflectivity of the reflective layer 35. By increasing the reflectivity, the amount of light absorbed by the photoelectric conversion layer 60 can be increased, thereby increasing the sensitivity of the imaging device 1.

[0104] The reflective layer 35 is insulated from any of the multiple wirings included in the wiring layer 30. This suppresses parasitic capacitance between the reflective layer 35 and other wirings 31A and 31B, etc. For example, as shown in Figure 3, a gap is provided between the reflective layer 35 and via 32B so that they do not come into contact with each other. The reflective layer 35 is electrically floating. If the effect of parasitic capacitance is small, a predetermined potential such as 0V may be supplied to the reflective layer 35.

[0105] Via 32B may also reflect light of the first wavelength. For example, via 32B may be formed using the same reflective material as the reflective layer 35. This allows light reflected by the reflective layer 35 to be reflected by via 32B, suppressing light leakage to adjacent pixels. Therefore, the amount of light absorbed in the photoelectric conversion layer 60 can be increased, thereby increasing the sensitivity of the imaging device 1.

[0106] As shown in Figure 3, vias 32B are arranged in a rectangular ring shape so as to completely surround the pixel electrode 40 and the reflective layer 35 in a plan view. By completely surrounding the reflective layer 35 with vias 32B, light leakage can be further suppressed. Therefore, the amount of light absorbed by the photoelectric conversion layer 60 can be further increased, and the sensitivity of the imaging device 1 can be further enhanced.

[0107] Furthermore, gaps may be provided in the rectangular annular via 32B. For example, via 32B may be provided in multiple parts separated in a dotted or dashed line pattern in a plan view. Also, via 32B may transmit light of the first wavelength without reflecting it. Similarly, the shield electrode 45 does not need to completely surround the pixel electrode 40, and gaps may be provided. For example, the shield electrode 45 may be provided in multiple parts separated so that the grid lines are dashed or dotted.

[0108] The plan view shapes of the pixel electrode 40, the reflective layer 35, and the shield electrode 45 are not limited to the example shown in Figure 3. For example, the pixel electrode 40 may be circular, rectangular, or an octagon. The plan view shape of the reflective layer 35 may be annular, or it may follow the contour of the plan view shape of the pixel electrode 40. Furthermore, the reflective layer 35 may cover only a portion of the gap 43 between the pixel electrode 40 and the shield electrode 45.

[0109] As described above, in the imaging device 1 according to this embodiment, light that passes through the photoelectric conversion layer 60 without being absorbed by the photoelectric conversion layer 60 is reflected by the reflective layer 35. When the light reflected by the reflective layer 35 passes through the photoelectric conversion layer 60, it is absorbed by the photoelectric conversion layer 60. Therefore, the amount of light absorbed by the photoelectric conversion layer 60 can be increased, and thus the sensitivity of the imaging device 1 can be increased. In addition, since a shield electrode 45 is provided next to the pixel electrode 40, by adjusting the potential applied to the shield electrode 45, signal charges generated in the photoelectric conversion layer 60 can be efficiently collected on the pixel electrode 40. For example, light reflected by the reflective layer 35 is easily photoelectrically converted in the region directly above the gap 43 of the photoelectric conversion layer 60. By applying a predetermined potential difference between the shield electrode 45 and the pixel electrode 40, the charge generated in the region directly above the gap 43 can be efficiently collected on the pixel electrode 40 as a signal charge. Therefore, the area of ​​the pixel electrode 40 can be reduced, and thus the dark current can be reduced. Thus, according to the imaging device 1 of this embodiment, dark current can be reduced and sensitivity can be increased.

[0110] Furthermore, in the imaging device 1 according to this embodiment, a plurality of layers, including a photoelectric conversion layer 60 and a counter electrode 50, are arranged in a continuous manner directly above the reflective layer 35. The optical path length of each of these plurality of layers is shorter than twice the wavelength of the first wavelength, which is the wavelength of the light to be detected by the imaging device 1. The optical path length of each layer is expressed as the product of the layer thickness and the refractive index.

[0111] Furthermore, in multiple layers continuously arranged directly above the reflective layer 35, the refractive index differs between two layers that are in contact in the stacking direction. For example, the interlayer insulating film 34 may have a structure in which multiple insulating films having the same refractive index are stacked in succession. In this case, multiple insulating films having the same refractive index are considered as a single layer.

[0112] Thus, because the optical path length of each of the multiple layers is shorter than twice the first wavelength, the light reflected by the reflective layer 35 can interfere with the multiple layers located directly above the reflective layer 35. Therefore, if the light intensity is increased within the photoelectric conversion layer 60, the sensitivity of the imaging device 1 can be further increased. The conditions under which the light intensity increases within the photoelectric conversion layer 60 due to interference will be explained later.

[0113] (modified version) Next, a modified version of the imaging device 1 according to Embodiment 1 will be described. In the following, the differences from Embodiment 1 will be the main focus of the explanation, and the explanation of the common points will be omitted or simplified.

[0114] [Example 1] First, the pixel 100 of the imaging device according to Modification 1 will be explained using Figure 4. Figure 4 is a cross-sectional view of the pixel 100 of the imaging device according to Modification 1. The pixel 100 shown in Figure 4 differs from the pixel 10 shown in Figure 2 in that it has a photoelectric conversion layer 160 instead of a photoelectric conversion layer 60.

[0115] The photoelectric conversion layer 160 has a laminated structure of multiple functional layers. Specifically, as shown in Figure 4, it includes an active layer 161, an electron blocking layer 162, and a hole blocking layer 163.

[0116] The active layer 161 is an example of a functional layer that primarily performs photoelectric conversion. The active layer 161 is substantially the same as the photoelectric conversion layer 60 shown in Figure 2, and it absorbs light of the first wavelength to generate a signal charge.

[0117] The electron blocking layer 162 is an example of a functional layer that blocks holes and allows electrons to pass through. In this modified example, the electron blocking layer 162 is provided between the active layer 161 and the pixel electrode 40. The electron blocking layer 162 is provided between the active layer 161 and the pixel electrode 40 and the shield electrode 45.

[0118] The hole-blocking layer 163 is an example of a functional layer that blocks electrons and allows holes to pass through. In this modified example, the hole-blocking layer 163 is provided between the active layer 161 and the counter electrode 50.

[0119] In this way, by including functional layers other than the active layer 161 in the photoelectric conversion layer 160, the efficiency of collecting signal charges can be increased. Therefore, the photoelectric conversion efficiency of each pixel 100 can be increased, and the sensitivity can be improved. In addition, since the injection of charge from the pixel electrode 40 or the counter electrode 50 into the active layer 161 can be suppressed, dark current can be suppressed.

[0120] Furthermore, the photoelectric conversion layer 160 according to this modified example is applicable when holes are used as signal charges. When electrons are used as signal charges, the electron blocking layer 162 and the hole blocking layer 163 can be arranged in reverse. That is, the electron blocking layer 162 can be placed between the active layer 161 and the counter electrode 50, and the hole blocking layer 163 can be placed between the active layer 161 and the pixel electrode 40.

[0121] Furthermore, the photoelectric conversion layer 160 does not necessarily have to include either the electron blocking layer 162 or the hole blocking layer 163. The photoelectric conversion layer 160 may also include other functional layers, such as an electron transport layer to assist electron movement and a hole transport layer to assist hole movement.

[0122] Furthermore, the active layer 161, the electron blocking layer 162, the hole blocking layer 163, and at least one of the other functional layers may be provided for each pixel 100, for each block composed of multiple pixels 100, or for each row or column of the pixel array 2.

[0123] Furthermore, as in this modified example, when the photoelectric conversion layer 160 has a stacked structure of multiple functional layers with different refractive indices between adjacent layers, each of the multiple functional layers corresponds to one of the multiple layers continuously arranged directly above the reflective layer 35. Specifically, the active layer 161, the electron blocking layer 162, and the hole blocking layer 163 each correspond to one of the multiple layers continuously arranged directly above the reflective layer 35. That is, the optical path length of each of the active layer 161, the electron blocking layer 162, and the hole blocking layer 163 is shorter than twice the first wavelength. As a result, when the light reflected by the reflective layer 35 interferes and the intensity of light in the active layer 161 is increased, the sensitivity of the pixel 100 can be further increased. The conditions under which the intensity of light in the active layer 161 increases due to interference will be explained later.

[0124] [Differentiation 2] Next, the pixel 200 of the imaging device according to the modified example 2 will be explained using Figure 5. Figure 5 is a cross-sectional view of the pixel 200 of the imaging device according to this modified example. In the pixel 200 shown in Figure 5, the size of the pixel electrode 40 and the reflective layer 35 differs from that of the pixel 10 shown in Figure 2.

[0125] In this modified example, in a plan view, the area of ​​the pixel electrode 40 is smaller than the area of ​​the gap 43 between the pixel electrode 40 and the shield electrode 45. In a plan view, the reflective layer 35 covers at least a portion of the gap 43. Specifically, similar to the example shown in Figure 3, the reflective layer 35 covers the entire gap 43 between the pixel electrode 40 and the shield electrode 45. Therefore, the area of ​​the pixel electrode 40 is smaller than the area of ​​the reflective layer 35. By reducing the area of ​​the pixel electrode 40, the imaging device can be miniaturized and the dark current can be reduced.

[0126] When the area of ​​the pixel electrode 40 is reduced, the area of ​​the gap 43 increases, and the amount of light that passes through the photoelectric conversion layer 60 and through the gap 43 increases. In the pixel 200 according to this modified example, the light passing through the gap 43 can be reflected by the reflective layer 35 and returned to the photoelectric conversion layer 60. Therefore, even if the area of ​​the pixel electrode 40 is reduced, it is possible to suppress the reduction in the amount of light that is photoelectrically converted in the photoelectric conversion layer 60. Thus, it is possible to suppress the decrease in EQE and reduce the dark current at the same time.

[0127] In addition, the pixel 200 in this modified example may include the photoelectric conversion layer 160 shown in Figure 4 instead of the photoelectric conversion layer 60.

[0128] [Difference 3] Next, the pixel 300 of the imaging device according to Modification 3 will be explained using Figure 6. Figure 6 is a cross-sectional view of the pixel 300 of the imaging device according to this modification. In the pixel 300 shown in Figure 6, the position of the reflective layer 35 is different from that of the pixel 10 shown in Figure 2. Specifically, the reflective layer 35 is located at the same height as the pixel electrode 40. Hereinafter, height is expressed as the distance from the semiconductor substrate 20. The distance D2 between the reflective layer 35 and the semiconductor substrate 20 is the same as the distance D3 between the pixel electrode 40 and the semiconductor substrate 20.

[0129] Furthermore, the reflective layer 35 is provided so as to be embedded in the uppermost layer of the interlayer insulating film 34 of the wiring layer 30. By making the upper surface of the reflective layer 35 and the upper surface of the interlayer insulating film 34 flush, the flatness of the photoelectric conversion layer 60 can be improved and the film quality can be enhanced.

[0130] The reflective layer 35 can be manufactured using the same process as the pixel electrode 40 or the shield electrode 45. By suppressing the complexity of the manufacturing method for the pixel 300, the occurrence of manufacturing errors can be suppressed, and highly reliable pixels 300 can be manufactured.

[0131] In this modified example, the multiple layers arranged continuously directly above the reflective layer 35 include the photoelectric conversion layer 60 and the counter electrode 50, but do not include the interlayer insulating film 34. The multiple layers arranged continuously directly above the reflective layer 35 may also include an insulating layer 70.

[0132] In addition, the pixel 300 in this modified example may be equipped with a photoelectric conversion layer 160 as shown in Figure 4 instead of the photoelectric conversion layer 60. Furthermore, in the pixel 300, as shown in the pixel 200 in Figure 5, the area of ​​the pixel electrode 40 may be smaller than the area of ​​the gap 43 in a plan view.

[0133] [Conditions for interference] Next, based on simulation results, we will explain the conditions under which the light intensity increases within the photoelectric conversion layer 60 or the active layer 161 due to interference of light reflected by the reflective layer 35.

[0134] The simulation used analysis software capable of numerically calculating the multiple interference of light incident on or emitting from a multilayer thin film using an equation based on Fresnel's formula. By providing parameters such as the film thickness, refractive index, and extinction coefficient of each layer constituting the multilayer thin film, the transmittance and reflectance of the multilayer thin film, as well as the light absorption rate of each layer, can be obtained.

[0135] Table 1 below shows the optical constants of each layer used in the simulation.

[0136] [Table 1]

[0137] In Table 1, n is the refractive index and k is the extinction coefficient. Both the refractive index and the extinction coefficient are values ​​for light with a wavelength of 1300 nm. In Table 1, Air corresponds to the air layer and Al corresponds to the reflective layer 35. Each layer between Air and Al is a plurality of layers arranged continuously directly above the reflective layer 35.

[0138] The first SiO2 and Al2O3 correspond to the insulating layer 70. The HBL (Hole Blocking Layer), active layer, and EBL (Electron Blocking Layer) correspond to the hole blocking layer 163, active layer 161, and electron blocking layer 162, respectively. If the HBL and EBL are not provided, the active layer 161 corresponds to the photoelectric conversion layer 60. The second SiO2 corresponds to the portion of the interlayer insulating film 34 provided directly above the reflective layer 35. The two non-interfering layers are layers provided in conventional imaging devices, and thick layers that do not cause interference were assumed. Note that the microlens 90 and visible light cut filter 80 were excluded from the simulation.

[0139] First, we will describe the simplest configuration, where multiple layers are arranged continuously directly above the reflective layer 35, and each layer consists of a photoelectric conversion layer 60, which is an active layer, and a counter electrode 50. In the following, a configuration without the reflective layer 35 will be referred to as the comparative example, and configurations with the reflective layer 35 will be referred to as Examples A and B. In the comparative example and Example A, two non-interfering layers are provided. Both non-interfering layers are examples of second layers having an optical path length longer than twice the wavelength of the light detected by the imaging device (i.e., the first wavelength). By providing two such thick non-interfering layers, interference of light between the two non-interfering layers is suppressed. On the other hand, in Example B, neither of the two non-interfering layers is provided. Therefore, in Example B, light interference can occur, and a distribution of light intensity is formed in the thickness direction. The distribution of light intensity depends on the thickness of each layer.

[0140] The film thicknesses of each layer in the comparative example and the layer configurations of Examples A and B are shown in Table 2 below. The unit of film thickness in Table 2 is nm.

[0141] [Table 2]

[0142] The film thickness of the counter electrode 50 (ITO in this case) was fixed at 20 nm, and the film thickness of the photoelectric conversion layer 60 (active layer in this case) was varied within the range of 20 nm to 2000 nm. The light absorption rate in the photoelectric conversion layer 60 was then calculated by simulation. The results are shown in Figure 7.

[0143] Figure 7 shows the dependence of the light absorption rate at the pixels of the imaging apparatus according to the comparative example and the example on the thickness of the active layer. In Figure 7, the horizontal axis represents the thickness of the active layer (unit: nm), and the vertical axis represents the light absorption rate in the active layer.

[0144] As shown in Figure 7, in both the comparative example and Examples A and B, a tendency was observed for the light absorption rate to increase as the thickness of the active layer increased. In this case, compared to the comparative example, in which the reflective layer 35 was not provided and no interference occurred, in Example A, in which the reflective layer 35 was provided, an improvement in light absorption rate was confirmed in the entire range of film thickness from 20 nm to 2000 nm. In other words, it can be seen that providing the reflective layer 35 increases the light absorption rate in the active layer and contributes to improving the sensitivity of the imaging device.

[0145] On the other hand, in Example B, where interference occurs, the light absorption rate varies depending on the thickness of the active layer. This is presumed to be because incident light, reflected light, and transmitted light interfere at numerous interfaces within the multilayer thin film, and the light absorption rate increases when the thickness of the active layer satisfies the conditions for light strengthening due to interference, and decreases when the conditions for light weakening are met. The light absorption rate of Example A is located near the center of the variation in the light absorption rate of Example B. In other words, it can be seen that in Example B, depending on the thickness of the active layer, it is possible to achieve a higher light absorption rate than in Example A. Therefore, by setting the thickness of the active layer within an appropriate range, it is possible to increase the light absorption rate compared to Example A, which has a reflective layer 35 without utilizing interference. For example, when the thickness of the active layer is 700 nm, the light absorption rate of Example B is at its maximum, achieving a higher light absorption rate than that of Example A. On the other hand, when the thickness of the active layer is 820 nm, the light absorption rate of Example B is at its minimum, achieving a light absorption rate similar to that of the comparative example.

[0146] The condition for causing interference of light of the first wavelength by multiple layers continuously arranged directly above the reflective layer 35 is that the optical path length of these multiple layers is shorter than twice the first wavelength. By adjusting the optical path length of each of the multiple layers while satisfying this condition, the light absorption rate can be further increased. Specifically, the light absorption rate for light of the first wavelength in the portion of the photoelectric conversion layer 60 or active layer 161 located directly above the reflective layer 35 is higher than the absorption rate for light of the first wavelength in the portion of the photoelectric conversion layer 60 or active layer 161 located directly above the reflective layer 35, assuming that a non-interfering layer is placed between the reflective layer 35 and the photoelectric conversion layer 60. As a result, the light reflected by the reflective layer 35 can be interfered with by the multiple layers located directly above the reflective layer 35, increasing the intensity of light within the photoelectric conversion layer 60 or active layer 161. Therefore, the sensitivity of the imaging device 1 can be further increased.

[0147] In the following, we specifically examined the appropriate optical path length by fixing the optical constants of each layer and varying the film thickness, but this is not the only approach. The optical constants may also be changed by changing the material of each layer.

[0148] The following describes the simulation results for determining appropriate film thickness values ​​for multiple layers (hereinafter simply referred to as "multiple layers") arranged directly above the reflective layer 35, so as to increase light absorption by utilizing interference. The simulation started with two layers, and based on the appropriate conditions for film thickness with a small number of layers, the number of layers was increased, and examples of appropriate film thicknesses were calculated in the range of two to seven layers. In the simulation described below, the film thickness of the air layer (Air) is 1 × 10⁻⁶. 6 The nm value was fixed, and the film thickness of the reflective layer 35 (Al) was fixed at 100 nm. In addition, the film thickness of the active layer 161 or the photoelectric conversion layer 60 (active layer) was fixed at 200 nm.

[0149] A 200 nm active layer thickness corresponds to the thickness at which the first peak of the graph for Example B, shown in Figure 7, intersects with the graph for Example A. When the active layer thickness is large, dark current due to thermal excitation is more likely to occur between the donor and acceptor. Therefore, reducing the thickness can suppress the generation of dark current. For example, the active layer thickness can be selected to be in a range where the light absorption rate is higher than that of the graph for Example A at the first peak shown in Figure 7. Specifically, the light absorption rate can be increased by setting the active layer thickness to between 80 nm and 200 nm. Note that the active layer thickness is not limited to this range; a range where the light absorption rate is higher than that of the graph for Example A from the second peak onward may also be selected.

[0150] [Examples 1-1, 1-2, 1-3: Two-layer structure] First, Examples 1-1, 1-2, and 1-3, which consist of two layers, will be described. In the case of two layers, the layers include a counter electrode 50 (ITO) and an active layer 161. In the simulation, the film thickness of the active layer was fixed at 200 nm, and the light absorption rate was calculated by varying the film thickness of the ITO within a predetermined range. The film thickness of each layer (in nm) is shown in Table 3 below. Table 3 also shows the calculated light absorption rate (in %).

[0151] [Table 3]

[0152] Example 1-1 has a configuration in which a non-interference layer is provided, similar to Example A in Figure 7. Examples 1-2 and 1-3 have a configuration in which a non-interference layer is not provided, similar to Example B in Figure 7. The ITO film thickness in Example 1-1 is the film thickness at which the light absorption rate is maximized when a non-interference layer is provided. The ITO film thickness in Example 1-2 is the film thickness at which the light absorption rate reaches the largest of several local minimums when a non-interference layer is not provided. The ITO film thickness in Example 1-3 is the film thickness at which the light absorption rate reaches the largest of several local maximums when a non-interference layer is not provided.

[0153] Figure 8 shows the dependence of the light absorption rate at the pixels of the imaging device according to the embodiment on the film thickness of ITO. The results of calculating the light absorption rate by varying the film thickness of ITO in the range of 20 nm to 1000 nm for both cases where a non-interference layer is provided and where a non-interference layer is not provided are shown. In Figure 8, a dotted line is drawn at the maximum light absorption rate of 34.8% when a non-interference layer is provided. In the graph for the case without a non-interference layer, the range in which the light absorption rate is higher than the dotted line is the range in which the light absorption rate can be increased by interference. Specifically, the ITO film thickness is 140 nm to 410 nm and 620 nm to 810 nm. As shown in Example 1-3, the light absorption rate is maximum at an ITO film thickness of 280 nm. As shown in Example 1-2, the light absorption rate is minimum at an ITO film thickness of 80 nm.

[0154] Furthermore, the ITO film thickness may be between 20 nm and 140 nm. In this case, the light absorption rate is lower than when no non-interference layer is provided. However, because the ITO film thickness is small, the manufacturing process can be simplified. It is also possible to make pixels thinner. Additionally, the ITO film thickness may be 500 nm or less. For example, in the range of ITO film thickness between 120 nm and 500 nm, the light absorption rate is higher when no non-interference layer is provided (solid line graph) than when a non-interference layer is provided (dashed line graph). In other words, by utilizing interference without providing a non-interference layer, the light absorption rate can be increased.

[0155] [Examples 2-1, 2-2, 2-3: 3-layer structure] Next, Examples 2-1, 2-2, and 2-3, which have a three-layer configuration, will be described. In the case of a three-layer configuration, the multiple layers include a first SiO2 layer of insulating layer 70 in addition to the two-layer configuration. In the simulation, the film thickness of the active layer was fixed at 200 nm, and the film thickness of the ITO and the first SiO2 were varied within predetermined ranges to calculate the light absorption rate. The fixed values ​​used were those obtained when the light absorption rate was maximized in the simulation of the two-layer configuration. The film thickness of each layer (in nm) is shown in Table 4 below. Table 4 also shows the calculated light absorption rate (in %).

[0156] [Table 4]

[0157] Example 2-1 has a configuration in which a non-interference layer is provided, similar to Example A in Figure 7. Examples 2-2 and 2-3 have a configuration in which a non-interference layer is not provided, similar to Example B in Figure 7. The film thickness of ITO and the film thickness of the first SiO2 in Example 2-1 are the film thicknesses at which the light absorption rate is maximized when a non-interference layer is provided. The film thickness of ITO and the film thickness of the first SiO2 in Example 2-2 are the film thicknesses at which the light absorption rate reaches the largest of several minimum values ​​when a non-interference layer is not provided. The film thickness of ITO and the film thickness of the first SiO2 in Example 2-3 are the film thicknesses at which the light absorption rate reaches the largest of several maximum values ​​when a non-interference layer is not provided.

[0158] As shown in Example 2-3, the light absorption rate is maximized when the film thickness of the first SiO2 is 280 nm and the film thickness of the ITO is 20 nm. As shown in Example 2-2, the light absorption rate is minimized when the film thickness of the first SiO2 is 460 nm and the film thickness of the ITO is 500 nm. Simulation results show that, for example, the light absorption rate can be increased by setting the sum of the film thicknesses of the first SiO2 and the ITO to a range of 200 nm to 400 nm.

[0159] [Examples 3-1, 3-2, 3-3: 4-layer structure] Next, Examples 3-1, 3-2, and 3-3, which have a four-layer structure, will be described. In the case of a four-layer structure, the multiple layers include a second SiO2 layer of interlayer insulating film 34 in addition to the three-layer structure. In the simulation, the film thickness of the active layer was fixed at 200 nm, the film thickness of the ITO was fixed at 20 nm, and the film thickness of the first SiO2 and the second SiO2 were varied within predetermined ranges to calculate the light absorption rate. Each fixed value is the value at which the light absorption rate was maximized in the simulation of the three-layer structure. The film thickness of each layer (in nm) is shown in Table 5 below. Table 5 also shows the calculated light absorption rate (in %).

[0160] [Table 5]

[0161] Example 3-1 has a configuration in which a non-interference layer is provided, similar to Example A in Figure 7. Examples 3-2 and 3-3 have a configuration in which a non-interference layer is not provided, similar to Example B in Figure 7. The film thickness of the first SiO2 and the film thickness of the second SiO2 in Example 3-1 are the film thicknesses at which the light absorption rate is maximized when a non-interference layer is provided. The film thickness of the first SiO2 and the film thickness of the second SiO2 in Example 3-2 are the film thicknesses at which the light absorption rate is largest among multiple local minimums when a non-interference layer is not provided. The film thickness of the first SiO2 and the film thickness of the second SiO2 in Example 3-3 are the film thicknesses at which the light absorption rate is largest among multiple local maximums when a non-interference layer is not provided.

[0162] As shown in Example 3-3, the light absorption rate is maximized when the film thickness of the first SiO2 is 360 nm and the film thickness of the second SiO2 is 400 nm. As shown in Example 3-2, the light absorption rate is minimized when the film thickness of the first SiO2 is 360 nm and the film thickness of the second SiO2 is 220 nm.

[0163] [Examples 4-1, 4-2, 4-3: 5-layer structure] Next, Examples 4-1, 4-2, and 4-3, which have a five-layer configuration, will be described. In the case of a five-layer configuration, the multiple layers include an Al2O3 layer of insulating layer 70 in addition to the four-layer configuration. In the simulation, the film thickness of the active layer was fixed at 200 nm, the film thickness of the ITO was fixed at 20 nm, the film thickness of the second SiO2 was fixed at 400 nm, and the film thickness of the first SiO2 and Al2O3 were varied within predetermined ranges to calculate the light absorption rate. In the configuration of Example 4-1, which has a non-interference layer, the film thickness of the second SiO2 was fixed at 500 nm. Each fixed value is the value at which the light absorption rate was maximized in the simulation of the four-layer configuration. The film thickness of each layer (unit: nm) is shown in Table 6 below. Table 6 also shows the calculated light absorption rate (unit: %).

[0164] [Table 6]

[0165] Example 4-1 has a configuration in which a non-interference layer is provided, similar to Example A in Figure 7. Examples 4-2 and 4-3 have a configuration in which a non-interference layer is not provided, similar to Example B in Figure 7. The film thickness of the first SiO2 and the film thickness of Al2O3 in Example 4-1 are the film thicknesses at which the light absorption rate is maximized when a non-interference layer is provided. The film thickness of the first SiO2 and the film thickness of Al2O3 in Example 4-2 are the film thicknesses at which the light absorption rate is largest among multiple minimum values ​​when a non-interference layer is not provided. The film thickness of the first SiO2 and the film thickness of Al2O3 in Example 4-3 are the film thicknesses at which the light absorption rate is largest among multiple maximum values ​​when a non-interference layer is not provided.

[0166] As shown in Example 4-3, the light absorption rate is maximized when the film thickness of the first SiO2 is 440 nm and the film thickness of the Al2O3 is 320 nm. As shown in Example 4-2, the light absorption rate is minimized when the film thickness of the first SiO2 is 460 nm and the film thickness of the Al2O3 is 120 nm. Simulation results show that, for example, the light absorption rate can be increased by setting the sum of the film thicknesses of the first SiO2 and the Al2O3 to a range of 260 nm to 440 nm, or 680 nm to 900 nm.

[0167] [Examples 5-1, 5-2, 5-3: 6-layer structure] Next, Examples 5-1, 5-2, and 5-3, which have a six-layer configuration, will be described. In the case of a six-layer configuration, the multiple layers include an electron blocking layer 162 (EBL) in addition to the five-layer configuration. In the simulation, the film thickness of the active layer was fixed at 200 nm, the film thickness of the ITO was fixed at 20 nm, the film thickness of the first SiO2 was fixed at 440 nm, the film thickness of the Al2O3 was fixed at 320 nm, and the film thickness of the EBL and the second SiO2 were varied within predetermined ranges to calculate the light absorption rate. In the configuration of Example 5-1, which includes a non-interference layer, the film thickness of the first SiO2 was fixed at 240 nm and the film thickness of the Al2O3 was fixed at 160 nm. Each fixed value is the value at which the light absorption rate was maximized in the simulation of the five-layer configuration. The film thickness of each layer (unit: nm) is shown in Table 7 below. Table 7 also shows the calculated light absorption rate (unit: %).

[0168] [Table 7]

[0169] Example 5-1 has a configuration in which a non-interference layer is provided, similar to Example A in Figure 7. Examples 5-2 and 5-3 have a configuration in which a non-interference layer is not provided, similar to Example B in Figure 7. The film thickness of the EBL and the film thickness of the second SiO2 in Example 5-1 are the film thicknesses at which the light absorption rate is maximized when a non-interference layer is provided. The film thickness of the EBL and the film thickness of the second SiO2 in Example 5-2 are the film thicknesses at which the light absorption rate reaches the largest of several minimum values ​​when a non-interference layer is not provided. The film thickness of the EBL and the film thickness of the second SiO2 in Example 5-3 are the film thicknesses at which the light absorption rate reaches the largest of several maximum values ​​when a non-interference layer is not provided.

[0170] As shown in Example 5-3, the light absorption rate is maximized when the EBL film thickness is 160 nm and the secondary SiO2 film thickness is 220 nm. As shown in Example 5-2, the light absorption rate is minimized when the EBL film thickness is 200 nm and the secondary SiO2 film thickness is 440 nm. Simulation results show that, for example, the light absorption rate can be increased by setting the sum of the EBL film thickness and the secondary SiO2 film thickness to a range of 320 nm to 460 nm.

[0171] [Examples 6-1, 6-2, 6-3: 7-layer structure] Next, Examples 6-1, 6-2, and 6-3, which have a 7-layer configuration, will be described. In the case of a 7-layer configuration, the layers include a hole block layer 163 (HBL) in addition to the 6-layer configuration. In the simulation, the film thickness of the active layer was fixed at 200 nm, the film thickness of the ITO was fixed at 20 nm, the film thickness of the second SiO2 was fixed at 220 nm, the film thickness of the Al2O3 was fixed at 320 nm, and the film thickness of the EBL was fixed at 160 nm. The light absorption rate was calculated by varying the film thickness of the first SiO2 and the HBL within predetermined ranges. In the configuration of Example 6-1, which includes a non-interfering layer, the film thickness of the Al2O3 was fixed at 160 nm and the film thickness of the EBL was fixed at 280 nm. Each fixed value is the value at which the light absorption rate was maximized in the simulation of the 6-layer configuration. The film thickness of each layer (unit: nm) is shown in Table 8 below. Table 8 also shows the calculated light absorption rates (in %).

[0172] [Table 8]

[0173] Example 6-1 has a configuration in which a non-interference layer is provided, similar to Example A in Figure 7. Examples 6-2 and 6-3 have a configuration in which a non-interference layer is not provided, similar to Example B in Figure 7. The film thickness of the first SiO2 and the HBL in Example 6-1 are the film thicknesses at which the light absorption rate is maximized when a non-interference layer is provided. The film thickness of the first SiO2 and the HBL in Example 6-2 are the film thicknesses at which the light absorption rate reaches the largest of several minimum values ​​when a non-interference layer is not provided. The film thickness of the first SiO2 and the HBL in Example 6-3 are the film thicknesses at which the light absorption rate reaches the largest of several maximum values ​​when a non-interference layer is not provided.

[0174] As shown in Example 6-3, the light absorption rate is maximized when the film thickness of the first SiO2 is 900 nm and the film thickness of the HBL is 300 nm. As shown in Example 6-2, the light absorption rate is minimized when the film thickness of the first SiO2 is 460 nm and the film thickness of the HBL is 140 nm.

[0175] As described above, the conditions for the film thickness of each layer that can increase the light absorption rate can be determined by simulation, depending on the number of layers placed directly above the reflective layer 35. In the above simulation, the order in which the layers are added is just one example, and the material (i.e., optical constant) of each layer can also be changed as appropriate.

[0176] Figure 9 shows the light absorption rates at the pixels of the imaging devices according to the comparative examples and examples. Specifically, Figure 9 shows the improvement effect of the light absorption rate for Examples 1-1, 1-3, 2-3, 3-3, 4-3, 5-3, and 6-3 compared to the comparative examples. The improvement effect is the ratio of the light absorption rate of each example to the light absorption rate of the comparative examples. In all examples, an improvement effect of about 1.5 to 3 times was obtained.

[0177] Furthermore, each of the above-described embodiments can be further improved based on process factors and / or electrical factors. Table 9 below shows the film thickness (in nm) and calculated light absorption rate (in %) of each layer after improvements based on process factors and / or electrical factors. Note that in each embodiment shown in Table 9, a non-interference layer is not provided, so the description of the non-interference layer has been omitted.

[0178] [Table 9]

[0179] Examples 7 to 10 correspond to configurations with 4 to 7 layers, respectively, of multiple layers arranged directly above the reflective layer 35. For example, increasing the thickness of the ITO layer can lower the sheet resistance of the ITO. Also, decreasing the thickness of the Al2O3 layer can shorten the time required for film formation. Furthermore, reducing the thickness of the HBL and EBL layers can achieve lower resistance.

[0180] Figure 10 shows the light absorption rates at the pixels of the imaging devices according to the comparative example and the example. Specifically, Figure 10 shows the improvement effect of the light absorption rate for Example 1-1 and Examples 7 to 10 compared to the comparative example. The improvement effect is the ratio of the light absorption rate of each example to the light absorption rate of the comparative example. An improvement effect of approximately 2.7 to 3 times was obtained in all of Examples 7 to 10.

[0181] As described above, in the imaging device according to this embodiment, the optical path length of each of the multiple layers arranged continuously directly above the reflective layer 35 is shorter than twice the first wavelength. Furthermore, the absorption rate for light of the first wavelength in the portion of the photoelectric conversion layer 60 or active layer 161 located directly above the reflective layer 35 can be made higher than the absorption rate for light of the first wavelength in the portion of the photoelectric conversion layer 60 or active layer 161 located directly above the reflective layer 35, assuming that a non-interfering layer having an optical path length longer than twice the first wavelength is arranged between the reflective layer 35 and the photoelectric conversion layer 60 or active layer 161. As a result, the light reflected by the reflective layer 35 can be interfered with by the multiple layers located directly above the reflective layer 35, increasing the intensity of light within the photoelectric conversion layer 60 or active layer 161. Therefore, the sensitivity of the imaging device 1 can be further increased.

[0182] (Embodiment 2) Next, Embodiment 2 will be described. Specifically, a camera system equipped with an imaging device according to each of the embodiments or modified examples described above will be described. In the following, the differences from Embodiment 1 will be the main focus of the explanation, and the explanation of the common points will be omitted or simplified.

[0183] Figure 11 shows an example of a camera system 400 equipped with an imaging device according to this embodiment. Here, we will describe a camera system 400 equipped with an imaging device 1 according to Embodiment 1.

[0184] As shown in Figure 11, the camera system 400 comprises a lens optical system 401, an imaging device 1, a system controller 402, and a camera signal processing circuit 403.

[0185] The lens optical system 401 includes, for example, an autofocus lens, a zoom lens, and an aperture. The lens optical system 401 focuses light onto the imaging surface of the imaging device 1. Light that has passed through the lens optical system 401 is incident on the photoelectric conversion layer 60, and a portion of it is absorbed by the photoelectric conversion layer 60 and converted into a signal charge. Light that is not absorbed by the photoelectric conversion layer 60 is reflected by the reflective layer 35. This makes it possible to increase the sensitivity of the imaging device 1.

[0186] The system controller 402 controls the imaging device 1 and the camera signal processing circuit 403. The system controller 402 may be, for example, a microcomputer.

[0187] The camera signal processing circuit 403 functions as a signal processing circuit that processes the signals generated by the imaging device 1 and outputs them as images or data. For example, the camera signal processing circuit 403 generates an NIR image or a SWIR image based on signals from multiple pixels 10. The camera signal processing circuit 403 performs processing such as gamma correction, color interpolation, spatial interpolation, and white balance. The camera signal processing circuit 403 may be, for example, a DSP (Digital Signal Processor). The camera signal processing circuit 403 may perform distance measurement based on the NIR image or SWIR image.

[0188] (Other embodiments) Although one or more embodiments of an imaging device have been described above based on these embodiments, this disclosure is not limited to these embodiments. Without departing from the spirit of this disclosure, various modifications to these embodiments that a person skilled in the art could conceive, as well as configurations constructed by combining components from different embodiments, are also included within the scope of this disclosure.

[0189] Furthermore, each of the above embodiments can be modified, replaced, added, or omitted in various ways within the scope of the claims or their equivalents. [Industrial applicability]

[0190] This disclosure can be used, for example, in cameras, distance measuring devices, inspection devices, etc. [Explanation of symbols]

[0191] 1. Imaging device 2-pixel array 3. Vertical scanning circuit 4. Horizontal signal readout circuit 5, 6 signal lines 7 Horizontal signal common line 10, 100, 200, 300 pixels 20 Semiconductor substrates 21 Impurity region 30 wiring layer 31A, 31B wiring 32A, 32B vias 33A Contact Plug 34 Interlayer insulating film 35 Reflective layer 40 Pixel Electrodes 43 Gap 45 Shielding electrodes 50 Counterelectrode 60, 160 Photoelectric conversion layer 70 Insulating layer 80 Visible Light Cut Filter 90 Microlenses 161 Active layer 162 Electron Block Layer 163 Hole Block Layer 400 Camera System 401 Lens Optics 402 System Controller 403 Camera signal processing circuit

Claims

1. Semiconductor substrate and A wiring layer located on the aforementioned semiconductor substrate and including multiple wirings, A first electrode located on the aforementioned wiring layer, A second electrode located above the first electrode, A photoelectric conversion layer located between the first electrode and the second electrode, which absorbs light of a first wavelength and generates a signal charge, The device comprises a charge storage unit electrically connected to the first electrode and storing the signal charge, The wiring layer further includes a reflective layer that, in a plan view, covers at least a portion of the area outside the first electrode. Multiple layers, including the photoelectric conversion layer and the second electrode, are arranged in a continuous manner directly above the reflective layer. The optical path length of each of the aforementioned layers is shorter than twice the first wavelength. Imaging device.

2. The wiring layer further comprises a third electrode located adjacent to the first electrode, The aforementioned second electrode is further located above the aforementioned third electrode, The photoelectric conversion layer is located between the third electrode and the second electrode, The wiring layer, in a plan view, covers at least a portion of the space between the first electrode and the third electrode. The imaging apparatus according to claim 1.

3. The reflective layer is insulated from any of the plurality of wirings. The imaging apparatus according to claim 1.

4. The distance between the reflective layer and the photoelectric conversion layer is shorter than the distance between the reflective layer and the semiconductor substrate. The imaging apparatus according to claim 1.

5. The system further comprises a first layer located above the photoelectric conversion layer, which absorbs or reflects visible light. The imaging apparatus according to claim 1.

6. The third electrode is arranged so as to surround the first electrode in a plan view. In a plan view, the area of ​​the first electrode is smaller than the area of ​​the gap between the first electrode and the third electrode. The imaging apparatus according to claim 2.

7. The distance between the reflective layer and the semiconductor substrate is the same as the distance between the first electrode and the semiconductor substrate. The imaging apparatus according to claim 1.

8. The absorption rate for light of the first wavelength in the portion of the photoelectric conversion layer located directly above the reflective layer is higher than the absorption rate for light of the first wavelength in the portion of the photoelectric conversion layer located directly above the reflective layer, assuming that a second layer having an optical path length longer than twice the first wavelength is placed between the reflective layer and the photoelectric conversion layer. The imaging apparatus according to claim 1.

9. The optical path length of each of the aforementioned layers is less than half of the first wavelength. The imaging apparatus according to claim 8.

10. The first wavelength is between 750 nm and 2500 nm. The imaging apparatus according to claim 1.

11. The potential difference between the third electrode and the second electrode is smaller than the potential difference between the first electrode and the second electrode. The imaging apparatus according to claim 2.

12. An imaging device according to any one of claims 1 to 11, The imaging device comprises an optical system for injecting the light, Camera system.

Images