Imaging device

Abstract

An imaging device pertaining to an embodiment of the present invention comprises a plurality of pixels. Each of the plurality of pixels includes a counter electrode through which incident light is transmitted, a pixel electrode facing the counter electrode, and a photoelectric conversion layer which is positioned between the counter electrode and the pixel electrode and which includes a plurality of carbon nanotubes. The plurality of pixels include first pixels and second pixels which are adjacent to the first pixels, and the pixel electrodes of the first pixels and the pixel electrodes of the second pixels are separated from each other. The plurality of carbon nanotubes included in the photoelectric conversion layers in at least one type of pixels selected from the group consisting of the first pixels and the second pixels include at least one of first carbon nanotubes satisfying the expression A < B, where A is the length of the carbon nanotubes along the direction in which the pixel electrodes of the first pixels and the pixel electrodes of the second pixels are arranged, and B is the interval between the pixel electrodes of the first pixels and the pixel electrodes of the second pixels.

Description

[Technical field]

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

[0002] In recent years, a stacked imaging device in which a photoelectric conversion element is provided on a semiconductor substrate has been realized. In the stacked imaging device, the photoelectric conversion layer of the photoelectric conversion element can be formed of a material different from that of the semiconductor substrate. Therefore, it is possible to form the photoelectric conversion layer with an inorganic material or an organic material different from conventional semiconductor materials such as silicon. This has resulted in the realization of an imaging device having physical properties or functions different from conventional imaging devices, such as sensitivity to a wavelength band different from that of conventional imaging devices. For example, Patent Document 1 discloses an imaging device having high light utilization efficiency by including two or more photoelectric conversion layers having sensitivity to different wavelength bands. Patent Document 2 discloses an imaging device including carbon nanotubes as a photoelectric conversion material of the photoelectric conversion layer. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2003-234460 A [Patent Document 2] Patent No. 6161018 Summary of the Invention [Problem to be solved by the invention]

[0004] There is a demand for high-image-quality imaging devices.

[0005] Therefore, the present disclosure provides an imaging device with high image quality. [Means for solving the problem]

[0006] An imaging device according to an aspect of the present disclosure includes a plurality of pixels. Each of the plurality of pixels includes a counter electrode through which incident light passes, a pixel electrode facing the counter electrode, and a photoelectric conversion layer located between the counter electrode and the pixel electrode and including a plurality of carbon nanotubes. The plurality of pixels includes a first pixel and a second pixel adjacent to the first pixel. The pixel electrodes of the first pixel and the second pixel are separated from each other. The photoelectric conversion layer is provided continuously between the first pixel and the second pixel. At least one of the plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel has a length of carbon nanotubes along the direction in which the pixel electrode of the first pixel and the pixel electrode of the second pixel are arranged. When the distance between the pixel electrode of the first pixel and the pixel electrode of the second pixel is B, it includes at least one first carbon nanotube that satisfies A < B.

[0007] Also, an imaging device according to an aspect of the present disclosure includes a plurality of pixels and a partition wall. Each of the plurality of pixels includes a counter electrode through which incident light passes, a pixel electrode facing the counter electrode, and a photoelectric conversion layer located between the counter electrode and the pixel electrode and including a plurality of carbon nanotubes. The pixel electrodes of each of the plurality of pixels are separated from each other. The partition wall is disposed in the photoelectric conversion layer and is located between the plurality of pixels so as to sandwich the pixel electrode in a plan view. The plurality of carbon nanotubes included in the photoelectric conversion layer in one of the plurality of pixels has a length of carbon nanotubes along the direction in which the pixel electrodes of each of the plurality of pixels are arranged. When the distance between the first portion of the partition wall and the second portion of the partition wall adjacent to the first portion with the pixel electrode therebetween is D, it includes at least one carbon nanotube that satisfies A < D.

Advantages of the Invention

[0008] According to an aspect of the present disclosure, a high-quality imaging device can be provided.

Brief Description of the Drawings

[0009] [Figure 1] FIG. 1 is a schematic cross-sectional view of a photoelectric conversion layer containing carbon nanotubes for illustrating the problem. [Diagram 2] FIG. 2 is a circuit diagram showing a circuit configuration of the imaging device according to the first embodiment. [Diagram 3] FIG. 3 is a schematic cross-sectional view showing the cross-sectional structure of two adjacent pixels of the imaging device according to the first embodiment. [Figure 4] FIG. 4 is a schematic cross-sectional view showing a cross-sectional structure of a photoelectric conversion unit of the imaging device according to the first embodiment. [Diagram 5] FIG. 5 is a schematic diagram for explaining the length of the carbon nanotube according to the first embodiment. [Figure 6A] FIG. 6A is a plan view showing a planar layout of pixel electrodes of the imaging device according to the first embodiment. [Figure 6B] FIG. 6B is a plan view showing an example of a planar layout of pixel electrodes for explaining the intervals between the pixel electrodes. [Figure 6C] FIG. 6C is a plan view showing another example of the planar layout of pixel electrodes for explaining the intervals between the pixel electrodes. [Figure 6D] FIG. 6D is a plan view showing another example of the planar layout of pixel electrodes for explaining the intervals between the pixel electrodes. [Figure 7] FIG. 7 is a schematic cross-sectional view showing a cross-sectional structure of a photoelectric conversion unit of an imaging device according to another example of the first embodiment. [Figure 8] FIG. 8 is a schematic cross-sectional view for explaining the flatness of the photoelectric conversion layer. [Figure 9] FIG. 9 is a schematic cross-sectional view showing a cross-sectional structure of a photoelectric conversion unit of an imaging device according to a comparative example. [Figure 10] FIG. 10 is a schematic cross-sectional view showing a cross-sectional structure of a photoelectric conversion unit of an imaging device according to the second embodiment. [Figure 11] FIG. 11 is a block diagram showing a structure of a camera system according to the third embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0010] (Findings that have led to one aspect of the present disclosure) An imaging device using carbon nanotubes as a photoelectric conversion material of a photoelectric conversion layer includes a photoelectric conversion layer 80 including carbon nanotubes 81 that are gently curved and long, as shown in the schematic cross-sectional view of FIG. 1. When a large amount of charge X that causes a leak current such as a dark current is generated in the photoelectric conversion layer 80 of the pixel 70b, the amount of charge collected in the pixel electrode 11 of the pixel 70b becomes very large, and the image quality becomes a white output that is an output similar to that of high-luminance light being incident. Hereinafter, this is called a white defect, and a pixel in which a white defect occurs is called a white defect pixel. When the photoelectric conversion layer 80 does not include the carbon nanotubes 81, only the pixel 70b becomes a white defect pixel. However, since the carbon nanotubes 81 are long and have high conductivity of charges as shown in FIG. 1, a problem is expected in which a leak current due to the charge generated in the pixel 70b is introduced to the adjacent pixel 70a via the carbon nanotubes, causing a white defect in the pixel 70a as well. In particular, unlike normal signal charges, the amount of charge that can cause white defects is large, and therefore even if the generated charge is collected in the pixel electrode 11 of pixel 70b by, for example, increasing the conductivity within pixel 70b, there is room for further improvement in order to prevent the introduction of leakage current to the adjacent pixel 70a.

[0011] When a white defect occurs, it is possible to detect the white defect and correct the white defect by interpolating based on the output of adjacent pixels. However, when carbon nanotubes 81 are contained in the photoelectric conversion layer 80 as described above, white defects also occur simultaneously in adjacent pixels, expanding the range of the white defect pixel and making correction difficult.

[0012] As described above, the inventors have found that in the case of an imaging device including a photoelectric conversion layer using carbon nanotubes as a photoelectric conversion material, the carbon nanotubes expand the range of white scratches, making correction difficult, which causes a deterioration in the image quality of the imaging device. Therefore, in the present disclosure, even in an imaging device including a photoelectric conversion layer using carbon nanotubes as a photoelectric conversion material above a silicon semiconductor substrate, an imaging device with few white scratch pixels and high image quality is provided.

[0013] The outline of one aspect of the present disclosure is as follows.

[0014] An imaging device according to one aspect of the present disclosure includes a plurality of pixels. Each of the plurality of pixels includes a counter electrode through which incident light passes, a pixel electrode facing the counter electrode, and a photoelectric conversion layer located between the counter electrode and the pixel electrode and including a plurality of carbon nanotubes. The plurality of pixels include a first pixel and a second pixel adjacent to the first pixel. The pixel electrodes of the first pixel and the second pixel are separated from each other. The plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel include first carbon nanotubes satisfying A < B, where A is the length of the carbon nanotubes along the direction in which the pixel electrode of the first pixel and the pixel electrode of the second pixel are arranged, and B is the distance between the pixel electrode of the first pixel and the pixel electrode of the second pixel.

[0015] As a result, in at least one of two adjacent pixels, the photoelectric conversion layer includes at least one carbon nanotube satisfying A < B. Therefore, the photoelectric conversion layer includes carbon nanotubes that are not arranged across the distance between the pixel electrodes of two adjacent pixels in plan view. Even if a large amount of signal charges that cause white spots due to pixel defects or the like are generated, the carbon nanotubes do not introduce a large amount of signal charges into adjacent pixels as leakage current. Thus, even when carbon nanotubes other than the carbon nanotubes introduce leakage current into adjacent pixels, the signal charges generated by the carbon nanotubes can be acquired from the difference in the amount of signal charges between bright and dark times. As a result, by correcting the signal charges acquired by the difference and using them as the signal charges for imaging, the spread of white spot pixels is suppressed. In addition, since the carbon nanotubes have a high charge conductivity, normal signal charges also move inside the carbon nanotubes. However, since one or more carbon nanotubes satisfying A < B are included, it becomes difficult for signal charges to be introduced from adjacent pixels. Therefore, color mixing between two adjacent pixels is suppressed. Thus, a high-quality imaging device is realized.

[0016] Further, for example, among the plurality of pixels, the number of pixels including the photoelectric conversion layer including at least one of the first carbon nanotubes may be 50% or more of the number of the plurality of pixels.

[0017] As a result, among the plurality of pixels, more than half of the pixels can use the signal charges acquired by the difference as the signal charges for imaging, and color mixing is also suppressed. Therefore, the MTF, which is an index representing the optical resolution of the imaging device, becomes 0.5 or more. When the MTF is 0.5 or more, it becomes possible to identify a straight line or the like by image processing or the like. Thus, a high-quality imaging device is realized.

[0018] Further, for example, among the plurality of pixels, the number of pixels including the photoelectric conversion layer including at least one of the first carbon nanotubes may be 80% or more of the number of the plurality of pixels.

[0019] As a result, among a plurality of pixels, signal charges obtained by 80% or more of the pixels by difference can be used as signal charges for imaging, and color mixing is also suppressed, so that the imaging device has an image quality that can be visually recognized as a focal plane array.

[0020] Further, for example, among the plurality of pixels, the number of pixels including the photoelectric conversion layer including at least one of the first carbon nanotubes may be 90% or more of the number of the plurality of pixels.

[0021] As a result, among a plurality of pixels, signal charges obtained by 90% or more of the pixels by difference can be used as signal charges for imaging, and color mixing is also suppressed, so that the MTF, which is an index representing the resolution feeling of the imaging device, becomes 0.9 or more. Therefore, high resolution is maintained without post-processing such as image processing, and a higher image quality imaging device is realized.

[0022] Further, for example, the content rate of the first carbon nanotubes in the plurality of carbon nanotubes included in all the photoelectric conversion layers included in the plurality of pixels may be 50% or more.

[0023] As a result, when substantially the same number of carbon nanotubes are included in each photoelectric conversion layer of a plurality of pixels, among the plurality of pixels, the number of pixels including a photoelectric conversion layer including at least one carbon nanotube satisfying A < B becomes 50% or more of the number of the plurality of pixels, and an imaging device that obtains the above-described effects can be easily realized.

[0024] Further, for example, the content rate of the first carbon nanotubes in the plurality of carbon nanotubes included in all the photoelectric conversion layers included in the plurality of pixels may be 80% or more.

[0025] As a result, when substantially the same number of carbon nanotubes are included in each photoelectric conversion layer of a plurality of pixels, among the plurality of pixels, the number of pixels including a photoelectric conversion layer including at least one carbon nanotube satisfying A < B becomes 80% or more of the number of the plurality of pixels, and an imaging device that obtains the above-described effects can be easily realized.

[0026] Further, for example, the content ratio of the first carbon nanotubes in the plurality of carbon nanotubes included in all the photoelectric conversion layers included in the plurality of pixels may be 90% or more.

[0027] Thereby, when substantially the same number of carbon nanotubes are included in each photoelectric conversion layer of a plurality of pixels, among the plurality of pixels, the number of pixels including a photoelectric conversion layer including at least one carbon nanotube satisfying A < B becomes 90% or more of the number of the plurality of pixels, and an imaging device capable of obtaining the above-described effects can be easily realized.

[0028] Further, for example, in the photoelectric conversion layer, the second portion located between the pixel electrode of the first pixel and the pixel electrode of the second pixel in plan view may contain more of the first carbon nanotubes than the first portion located on the pixel electrode of the first pixel in plan view.

[0029] Thereby, even in a photoelectric conversion layer having the same content ratio of carbon nanotubes satisfying A < B, carbon nanotubes having a length that cannot span the interval between adjacent pixel electrodes in plan view are likely to exist in the photoelectric conversion layer between adjacent pixel electrodes in plan view. Therefore, the spread to adjacent pixels of white scratch pixels and color mixing between adjacent pixels are more suppressed.

[0030] Further, for example, the plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel may include at least one second carbon nanotube satisfying A < (B / 2).

[0031] As a result, the photoelectric conversion layer of at least one pixel includes at least one carbon nanotube that satisfies A < (B / 2). Therefore, even when the range in which the pixel electrodes of adjacent pixels collect signal charges extends to the center of the interval between the pixel electrodes of adjacent pixels, the photoelectric conversion layer contains carbon nanotubes that do not introduce leakage current or the like from the range in which the pixel electrodes of adjacent pixels collect signal charges. Thus, the enlargement of white scratch pixels and color mixing between adjacent pixels are suppressed.

[0032] Also, for example, the plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel may include at least one third carbon nanotube that satisfies C < B when the linear distance between two spatially most distant points in one carbon nanotube is C.

[0033] As a result, no matter in what direction the carbon nanotubes in the photoelectric conversion layer are arranged, the photoelectric conversion layer contains at least one carbon nanotube that does not span between two adjacent pixels. Therefore, the enlargement of white scratch pixels to adjacent pixels and color mixing between adjacent pixels are suppressed. Thus, a high-image-quality imaging device can be easily realized.

[0034] Also, for example, the plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel may include at least one fourth carbon nanotube that satisfies C < (B / 2).

[0035] As a result, the photoelectric conversion layer of at least one pixel includes at least one carbon nanotube that satisfies C < (B / 2). Therefore, the range in which the pixel electrodes of adjacent pixels collect signal charges extends to the center of the interval between the pixel electrodes of adjacent pixels, and no matter in what direction the carbon nanotubes in the photoelectric conversion layer are arranged, the photoelectric conversion layer contains carbon nanotubes that do not introduce leakage current or the like from the range in which the pixel electrodes of adjacent pixels collect signal charges. As a result, the expansion of white spot pixels and color mixing between adjacent pixels are suppressed. Thus, a high-quality imaging device can be easily realized.

[0036] In addition, an imaging device according to one aspect of the present disclosure includes a plurality of pixels and partition walls. Each of the plurality of pixels includes a counter electrode through which incident light passes, a pixel electrode facing the counter electrode, and a photoelectric conversion layer located between the counter electrode and the pixel electrode and including a plurality of carbon nanotubes. The pixel electrodes of each of the plurality of pixels are separated from each other. The partition walls are arranged in the photoelectric conversion layer and are located between the plurality of pixels so as to sandwich the pixel electrodes in a plan view. The plurality of carbon nanotubes included in the photoelectric conversion layer in one of the plurality of pixels include at least one carbon nanotube that satisfies A < D, where A is the length of the carbon nanotubes along the direction in which the pixel electrodes of each of the plurality of pixels are arranged, and D is the distance between a first portion of the partition wall and a second portion of the partition wall adjacent to the first portion with the pixel electrode therebetween.

[0037] As a result, since partition walls are provided so as to sandwich the pixel electrodes in the photoelectric conversion layer, the movement of signal charges between adjacent pixels is suppressed, and color mixing between adjacent pixels is suppressed. Also, by making the length of the carbon nanotubes shorter than the interval between the partition walls, it becomes difficult for the carbon nanotubes to adhere to the partition walls, and it becomes easier to exhibit the effect of preventing color mixing by the partition walls. Also, it becomes difficult for the carbon nanotubes to cross over the partition walls, and the flatness on the partition walls is improved. Therefore, since the flatness of the counter electrode or the like formed on the partition walls is improved, uneven sensitivity is reduced. Thus, a high-quality imaging device is realized.

[0038] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Note that the present disclosure is not limited to the following embodiment. In addition, appropriate modifications are possible within the scope of the effects of the present disclosure. Furthermore, one embodiment can be combined with another embodiment. In the following description, the same or similar components are denoted by the same reference numerals. Also, duplicated descriptions may be omitted.

[0039] Furthermore, in this specification, terms indicating relationships between elements, such as "equal," terms indicating the shapes of elements, such as "square" or "circle," and numerical ranges are not expressions that only express a strict meaning, but are expressions that also include a substantially equivalent range, for example, a difference of about a few percent.

[0040] In this specification, the terms "upper" and "lower" do not refer to the upper direction (vertically upward) and lower direction (vertically downward) in absolute spatial recognition, but are used as terms defined by a relative positional relationship based on the stacking order in a stacked configuration. The terms "upper" and "lower" are applied not only to the case where two components are arranged with a gap between them and another component exists between the two components, but also to the case where two components are arranged closely together and are in contact with each other.

[0041] (Embodiment 1) [Circuit configuration of imaging device] First, the circuit configuration of the imaging device according to the present embodiment will be described with reference to FIG.

[0042] Fig. 2 is a schematic diagram showing an exemplary circuit configuration of an imaging device according to the present embodiment. The imaging device 100 shown in Fig. 2 has a pixel array PA including a plurality of pixels 10 arranged two-dimensionally. Fig. 2 shows a schematic example in which the pixels 10 are arranged in a matrix of two rows and two columns. The number and arrangement of the pixels 10 in the imaging device 100 are not limited to the example shown in Fig. 2. For example, the imaging device 100 may be a line sensor in which a plurality of pixels 10 are arranged in one column.

[0043] Each pixel 10 has a photoelectric conversion unit 13 and a signal detection circuit 14. As will be described later with reference to the drawings, the photoelectric conversion unit 13 has a photoelectric conversion layer sandwiched between two electrodes facing each other, and receives incident light to generate a signal. The photoelectric conversion unit 13 does not need to be an independent element for each pixel 10, and for example, a part of the photoelectric conversion unit 13 may span a plurality of pixels 10. The signal detection circuit 14 is a circuit that detects a signal generated by the photoelectric conversion unit 13. In this example, the signal detection circuit 14 includes a signal detection transistor 24 and an address transistor 26. The signal detection transistor 24 and the address transistor 26 are typically field effect transistors (FETs), and here, an N-channel MOSFET (Metal Oxide Semiconductor Field Effect Transistor) is exemplified as the signal detection transistor 24 and the address transistor 26. The signal detection transistor 24, the address transistor 26, and each transistor such as a reset transistor 28 described later have a control terminal, an input terminal, and an output terminal. The control terminal is, for example, a gate. The input terminal is one of the drain and the source, for example the drain, and the output terminal is the other of the drain and the source, for example the source.

[0044] As shown in FIG. 2, the control terminal of the signal detection transistor 24 has an electrical connection with the photoelectric conversion unit 13. The signal charge generated by the photoelectric conversion unit 13 is accumulated in a charge accumulation node 41 between the gate of the signal detection transistor 24 and the photoelectric conversion unit 13. Here, the signal charge is a hole or an electron. The charge accumulation node is an example of a charge accumulation unit and is also called a "floating diffusion node." In this specification, the charge accumulation node is called a charge accumulation region. The structure of the photoelectric conversion unit 13 will be described in detail later.

[0045] The photoelectric conversion unit 13 of each pixel 10 is further connected to a counter electrode 12. The counter electrode 12 is connected to a voltage supply circuit 32. The voltage supply circuit is also called a counter electrode supply circuit. The voltage supply circuit 32 is a circuit configured to be able to supply any variable voltage. When the imaging device 100 is in operation, the voltage supply circuit 32 supplies a predetermined voltage to the photoelectric conversion unit 13 via the counter electrode 12. The voltage supply circuit 32 is not limited to a specific power supply circuit, and may be a circuit that generates a predetermined voltage, or may be a circuit that converts a voltage supplied from another power supply into a predetermined voltage.

[0046] The voltage supplied from the voltage supply circuit 32 to the photoelectric conversion unit 13 is switched between a plurality of different voltages, thereby controlling the start and end of accumulation of signal charges from the photoelectric conversion unit 13 to the charge accumulation node 41. The above control can also be achieved by controlling the voltage on the charge accumulation node 41 side or the voltage of a pixel electrode, which will be described later. In other words, in this embodiment, an electronic shutter operation is performed by switching the voltage supplied from the voltage supply circuit 32 to the photoelectric conversion unit 13, or the initial voltage of the charge accumulation node 41 or the pixel electrode. An example of the operation of the imaging device 100 will be described later. In the configuration shown in FIG. 2, the charge accumulation node 41 and the pixel electrode are connected and have the same potential.

[0047] Each pixel 10 is connected to a power supply line 40 that supplies a power supply voltage VDD. As shown in the figure, an input terminal of a signal detection transistor 24 is connected to the power supply line 40. The power supply line 40 functions as a source follower power supply, so that the signal detection transistor 24 amplifies and outputs a signal generated by the photoelectric conversion unit 13.

[0048] An input terminal of the address transistor 26 is connected to an output terminal of the signal detection transistor 24. An output terminal of the address transistor 26 is connected to one of a plurality of vertical signal lines 47 arranged for each column of the pixel array PA. A control terminal of the address transistor 26 is connected to an address control line 46, and by controlling the potential of the address control line 46, the output of the signal detection transistor 24 can be selectively read out to the corresponding vertical signal line 47.

[0049] In the illustrated example, the address control line 46 is connected to the vertical scanning circuit 36. The vertical scanning circuit is also called a "row scanning circuit." The vertical scanning circuit 36 ​​applies a predetermined voltage to the address control line 46 to select a plurality of pixels 10 arranged in each row on a row-by-row basis. As a result, signals of the selected pixels 10 are read out and the charge storage nodes 41 are reset.

[0050] The vertical signal lines 47 are main signal lines that transmit pixel signals from the pixel array PA to peripheral circuits. Column signal processing circuits 37 are connected to the vertical signal lines 47. The column signal processing circuits are also called "row signal storage circuits." The column signal processing circuits 37 perform noise suppression signal processing, such as correlated double sampling, and analog-to-digital conversion (AD conversion). As shown in the figure, the column signal processing circuits 37 are provided corresponding to each column of pixels 10 in the pixel array PA. The column signal processing circuits 37 are connected to horizontal signal readout circuits 38. The horizontal signal readout circuits are also called "column scanning circuits." The horizontal signal readout circuits 38 sequentially read out signals from the multiple column signal processing circuits 37 to a horizontal common signal line 49.

[0051] The pixel 10 has a reset transistor 28. The reset transistor 28 is, for example, a field effect transistor, similar to the signal detection transistor 24 and the address transistor 26. In the following, unless otherwise specified, an example in which an N-channel MOSFET is applied as the reset transistor 28 will be described. As shown in the figure, the reset transistor 28 is connected between a reset voltage line 44 that supplies a reset voltage Vr and a charge storage node 41. A control terminal of the reset transistor 28 is connected to a reset control line 48, and the potential of the charge storage node 41 can be reset to the reset voltage Vr by controlling the potential of the reset control line 48. In this example, the reset control line 48 is connected to a vertical scanning circuit 36. Therefore, the vertical scanning circuit 36 ​​can apply a predetermined voltage to the reset control line 48 to reset a plurality of pixels 10 arranged in each row on a row-by-row basis.

[0052] In this example, a reset voltage line 44 that supplies a reset voltage Vr to the reset transistor 28 is connected to the reset voltage source 34. The reset voltage source is also called a "reset voltage supply circuit." The reset voltage source 34 is not limited to a specific power supply circuit as long as it has a configuration capable of supplying a predetermined reset voltage Vr to the reset voltage line 44 during operation of the imaging device 100, similar to the above-mentioned voltage supply circuit 32. Each of the voltage supply circuit 32 and the reset voltage source 34 may be a part of a single voltage supply circuit or may be an independent separate voltage supply circuit. Note that one or both of the voltage supply circuit 32 and the reset voltage source 34 may be a part of the vertical scanning circuit 36. Alternatively, the counter electrode voltage from the voltage supply circuit 32 and / or the reset voltage Vr from the reset voltage source 34 may be supplied to each pixel 10 via the vertical scanning circuit 36.

[0053] It is also possible to use the power supply voltage VDD of the signal detection circuit 14 as the reset voltage Vr. In this case, a voltage supply circuit (not shown in FIG. 2) that supplies a power supply voltage to each pixel 10 and the reset voltage source 34 can be made common. In addition, since the power supply line 40 and the reset voltage line 44 can be made common, the wiring in the pixel array PA can be simplified. However, using different voltages for the reset voltage Vr and the power supply voltage VDD of the signal detection circuit 14 allows for more flexible control of the imaging device 100.

[0054] [Cross-sectional structure of pixel] Next, the cross-sectional structure of a pixel of the imaging device 100 according to the present embodiment will be described with reference to FIG.

[0055] FIG. 3 is a schematic cross-sectional view showing the cross-sectional structure of two adjacent pixels 10 among the multiple pixels 10 shown in FIG. 2. The two adjacent pixels 10 shown in FIG. 3 have the same structure. One of the two adjacent pixels 10 will be described below. The two adjacent pixels 10 may have partially different structures. In the configuration illustrated in FIG. 3, the above-mentioned signal detection transistor 24, address transistor 26, and reset transistor 28 are formed on a semiconductor substrate 20. The semiconductor substrate 20 is not limited to a substrate whose entirety is a semiconductor. The semiconductor substrate 20 may be an insulating substrate having a semiconductor layer provided on the surface on which the photosensitive region is formed. Here, an example will be described in which a P-type silicon (Si) substrate is used as the semiconductor substrate 20.

[0056] The semiconductor substrate 20 has impurity regions 26s, 24s, 24d, 28d, and 28s, and an element isolation region 20t for electrical isolation between the pixels 10. Here, the impurity regions 26s, 24s, 24d, 28d, and 28s are N-type regions. The element isolation region 20t is also provided between the impurity region 24d and the impurity region 28d. The element isolation region 20t is formed, for example, by ion implantation of an acceptor under predetermined implantation conditions.

[0057] The impurity regions 26s, 24s, 24d, 28d, and 28s are, for example, impurity diffusion layers formed in the semiconductor substrate 20. As shown in FIG. 3, the signal detection transistor 24 includes the impurity regions 24s and 24d and a gate electrode 24g. The gate electrode 24g is formed using a conductive material. The conductive material is, for example, polysilicon doped with impurities to provide conductivity, but may also be a metal material. The impurity regions 24s and 24d function as, for example, a source region and a drain region of the signal detection transistor 24, respectively. A channel region of the signal detection transistor 24 is formed between the impurity regions 24s and 24d.

[0058] Similarly, the address transistor 26 includes impurity regions 26s and 24s and a gate electrode 26g connected to the address control line 46. The gate electrode 26g is formed using a conductive material. The conductive material is, for example, polysilicon doped with impurities to provide conductivity, but may be a metal material. In this example, the signal detection transistor 24 and the address transistor 26 are electrically connected to each other by sharing the impurity region 24s. The impurity region 24s functions as, for example, a drain region of the address transistor 26. The impurity region 26s functions as, for example, a source region of the address transistor 26. The impurity region 26s has a connection to a vertical signal line 47 not shown in FIG. 3. The impurity region 24s does not have to be shared by the signal detection transistor 24 and the address transistor 26. Specifically, the source region of the signal detection transistor 24 and the drain region of the address transistor 26 are separated in the semiconductor substrate 20, and may be electrically connected via a wiring layer provided in the interlayer insulating layer 50.

[0059] The reset transistor 28 includes impurity regions 28d and 28s, and a gate electrode 28g connected to a reset control line 48. The gate electrode 28g is formed using, for example, a conductive material. The conductive material is, for example, polysilicon that is doped with impurities to give it conductivity, but may also be a metal material. The impurity region 28s functions, for example, as a source region of the reset transistor 28. The impurity region 28s has a connection to a reset voltage line 44 not shown in FIG. 3. The impurity region 28d functions, for example, as a drain region of the reset transistor 28.

[0060] An interlayer insulating layer 50 is disposed on the semiconductor substrate 20 so as to cover the signal detection transistor 24, the address transistor 26, and the reset transistor 28. The interlayer insulating layer 50 is an example of a first insulating layer. The interlayer insulating layer 50 is formed of an insulating material such as silicon dioxide. As shown in the figure, a wiring layer 56 is disposed in the interlayer insulating layer 50. The wiring layer 56 is typically formed of a metal such as copper, and may include, for example, a signal line or a power line such as the above-mentioned vertical signal line 47 as a part thereof. The number of insulating layers in the interlayer insulating layer 50 and the number of layers included in the wiring layer 56 disposed in the interlayer insulating layer 50 can be set arbitrarily, and are not limited to the example shown in FIG. 3.

[0061] 3, a plug 52, a wiring 53, a contact plug 54, and a contact plug 55 are provided in the interlayer insulating layer 50. The wiring 53 may be a part of a wiring layer 56. The plug 52, the wiring 53, the contact plug 54, and the contact plug 55 are each formed using a conductive material. For example, the plug 52 and the wiring 53 are formed from a metal such as copper. The contact plugs 54 and 55 are formed from, for example, polysilicon doped with impurities to provide conductivity. The plug 52, the wiring 53, the contact plug 54, and the contact plug 55 may be formed from the same material as each other, or may be formed from different materials.

[0062] The plug 52, the wiring 53, and the contact plug 54 configure at least a part of the charge accumulation node 41 between the signal detection transistor 24 and the photoelectric conversion unit 13. In the configuration illustrated in FIG. 3, the gate electrode 24g of the signal detection transistor 24, the plug 52, the wiring 53, the contact plugs 54 and 55, and the impurity region 28d which is one of the source region and the drain region of the reset transistor 28 function as a charge accumulation region that accumulates signal charges collected by the pixel electrode 11 of the photoelectric conversion unit 13 located on the interlayer insulating layer 50.

[0063] Specifically, the pixel electrode 11 of the photoelectric conversion unit 13 is connected to the gate electrode 24g of the signal detection transistor 24 via the plug 52, the wiring 53, and the contact plug 54. In other words, the gate of the signal detection transistor 24 is electrically connected to the pixel electrode 11. The pixel electrode 11 is also connected to the impurity region 28d via the plug 52, the wiring 53, and the contact plug 55.

[0064] When the pixel electrode 11 collects the signal charge, a voltage corresponding to the amount of the signal charge accumulated in the charge accumulation region is applied to the gate of the signal detection transistor 24. The signal detection transistor 24 amplifies this voltage. The voltage amplified by the signal detection transistor 24 is selectively read out as a signal voltage via the address transistor 26.

[0065] The above-mentioned photoelectric conversion section 13 is disposed on the interlayer insulating layer 50. In other words, in this embodiment, a plurality of pixels 10 constituting the pixel array PA shown in FIG. 2 are formed in and on the semiconductor substrate 20. When the semiconductor substrate 20 is viewed in a plan view, the plurality of pixels 10 arranged two-dimensionally form a photosensitive region. The photosensitive region is also called a pixel region. The distance between two adjacent pixels 10 shown in FIG. 3, i.e., the pixel pitch, may be, for example, about 2 μm.

[0066] The color filter layer 19 provided on the counter electrode 12 in FIG. 3 may be a color filter that controls the transmittance corresponding to red, green, or blue visible light wavelengths as in a conventional imaging device, or a bandpass filter or longpass filter for ultraviolet light or near-infrared light.

[0067] [Photoelectric conversion section configuration] Hereinafter, a specific configuration of the photoelectric conversion section 13 located on the interlayer insulating layer 50 will be described.

[0068] The photoelectric conversion unit 13 includes a pixel electrode 11 and a photoelectric conversion layer 15 disposed between the pixel electrode 11 and the counter electrode 12. Furthermore, as shown in FIG. 3, between the counter electrode 12 and the pixel electrode 11 of the photoelectric conversion unit 13, an electron blocking layer 16, a photoelectric conversion layer 15, and an acceptor layer 17 are laminated in this order from the pixel electrode 11 side. In this example, the counter electrode 12, the photoelectric conversion layer 15, the electron blocking layer 16, and the acceptor layer 17 are formed across two adjacent pixels 10. The counter electrode 12, the photoelectric conversion layer 15, the electron blocking layer 16, and the acceptor layer 17 may be formed across other pixels 10 as well. The pixel electrode 11 is provided in each of the two adjacent pixels 10. The pixel electrodes 11 of the two adjacent pixels 10 are electrically separated by being spatially separated. 3, the pixel electrodes 11 are provided for each pixel 10. At least one of the counter electrode 12, the photoelectric conversion layer 15, the electron blocking layer 16, and the acceptor layer 17 may be provided separately for each pixel 10.

[0069] The pixel electrode 11 is an electrode for reading out a signal charge generated in the photoelectric conversion unit 13. At least one pixel electrode 11 exists for each pixel 10. The pixel electrode 11 is electrically connected to a gate electrode 24g of the signal detection transistor 24 and an impurity region 28d.

[0070] The pixel electrode 11 is formed using a conductive material, such as a metal such as aluminum or copper, a metal nitride, or polysilicon doped with impurities to be made conductive.

[0071] The counter electrode 12 is, for example, a transparent electrode made of a transparent conductive material. The counter electrode 12 is disposed on the side of the photoelectric conversion layer 15 on which light is incident. Therefore, light transmitted through the counter electrode 12 is incident on the photoelectric conversion layer 15. Note that the light detected by the imaging device 100 is not limited to light within the wavelength range of visible light. For example, the imaging device 100 may detect infrared light or ultraviolet light. Here, the wavelength range of visible light is, for example, 380 nm or more and 780 nm or less.

[0072] In this specification, "transparent" means that at least a part of the light in the wavelength range to be detected is transmitted, and it is not essential that the light is transmitted over the entire wavelength range of visible light. In this specification, electromagnetic waves in general, including infrared and ultraviolet rays, are referred to as "light" for convenience.

[0073] The counter electrode 12 is formed using a transparent conducting oxide (TCO) such as ITO, IZO, AZO, FTO, SnO2, TiO2, or ZnO2.

[0074] As described with reference to FIG. 2, the counter electrode 12 has a connection with the voltage supply circuit 32. Also, as shown in FIG. 3, the counter electrode 12 is formed across two adjacent pixels 10. Therefore, it is possible to collectively apply a counter electrode voltage of a desired magnitude from the voltage supply circuit 32 between two adjacent pixels 10 via the counter electrode 12. The counter electrode 12 may also be formed across a plurality of pixels 10 not shown in FIG. 3. Note that, as long as a counter electrode voltage of a desired magnitude can be applied from the voltage supply circuit 32, the counter electrode 12 may be provided separately for each of the two adjacent pixels 10 and each of the plurality of pixels 10 not shown.

[0075] The voltage supply circuit 32 controls the potential of the counter electrode 12 relative to the potential of the pixel electrode 11, so that either the holes or the electrons of the hole-electron pairs generated in the photoelectric conversion layer 15 by photoelectric conversion can be collected by the pixel electrode 11 as a signal charge. For example, when holes are used as signal charges, the pixel electrode 11 can selectively collect the holes by setting the potential of the counter electrode 12 higher than that of the pixel electrode 11. The following illustrates a case where holes are used as signal charges. It is also possible to use electrons as signal charges, and in this case, the potential of the counter electrode 12 can be set lower than that of the pixel electrode 11. The pixel electrode 11 facing the counter electrode 12 collects either the positive or negative charge generated by photoelectric conversion in the photoelectric conversion layer 15 by applying an appropriate bias voltage between the counter electrode 12 and the pixel electrode 11.

[0076] The photoelectric conversion layer 15 receives incident light and generates hole-electron pairs. The photoelectric conversion layer 15 includes a plurality of carbon nanotubes. The plurality of carbon nanotubes absorb a specific wavelength range of light incident on the photoelectric conversion layer 15 and generate hole-electron pairs. The chirality of the plurality of carbon nanotubes to provide wavelength selectivity may be different for each of the plurality of pixels 10, or may be the same for all of the pixels 10.

[0077] In a configuration in which photoelectric conversion layer 15 is stacked above a circuit board, as in imaging device 100 of this embodiment, unlike a CMOS (Complementary Metal Oxide Semiconductor) image sensor, a material other than Si, etc., that constitutes the circuit board can be selected to construct photoelectric conversion unit 13, thereby achieving the effect of realizing imaging that is not dependent on the wavelength characteristics of the circuit board.

[0078] The electron blocking layer 16 has a function of suppressing the movement of electrons, which are charges opposite to the signal charges, from the adjacent pixel electrode 11 to the photoelectric conversion layer 15, and transporting holes, which are signal charges generated in the photoelectric conversion layer 15, to the electrode. This suppresses the dark current of the imaging device. The material of the electron blocking layer 16 is, for example, a p-type semiconductor, and specifically, semiconductors made of inorganic materials such as nickel oxide, copper oxide, chromium oxide, cobalt oxide, titanium oxide, and zinc oxide are exemplified, but are not limited to these. The p-type semiconductor may be a p-type semiconductor made of an inorganic material in which impurities are doped into a metal oxide or a metal nitride, and specifically, for example, a film in which silicon oxide is doped with phosphorus, arsenic, antimony, or the like. The material of the electron blocking layer 16 may be a semiconductor made of an organic material such as a hole-transporting organic compound.

[0079] The acceptor layer 17 has a function of receiving electrons, which are charges opposite to the signal charges, from the photoelectric conversion layer 15, and transporting them to the counter electrode 12. The material of the acceptor layer 17 is, for example, fullerene or a fullerene derivative.

[0080] The photoelectric conversion layer 15 and the acceptor layer 17 form a planar hetero-type junction, and electrons are extracted at the interface between the photoelectric conversion layer 15 and the acceptor layer 17, and holes remaining in the photoelectric conversion layer 15 are collected on the pixel electrode 11 side due to the applied voltage.

[0081] In the present embodiment, a structure has been described in which an electron blocking layer 16 is provided to reduce dark current when holes are accumulated as signal charges from the photoelectric conversion layer 15 and read out. Conversely, when electrons are accumulated as signal charges and read out, a hole blocking layer may be used instead of the electron blocking layer 16, and a donor layer may be used instead of the acceptor layer 17. The hole blocking layer has a function of suppressing the movement of holes from the adjacent pixel electrode 11 to the photoelectric conversion layer 15, and transporting electrons generated in the photoelectric conversion layer 15 to the electrode. The donor layer has a function of receiving holes from the photoelectric conversion layer 15 and transporting them to the counter electrode 12.

[0082] The photoelectric conversion section 13 of this embodiment may not include the electron blocking layer 16 and the acceptor layer 17. When light incident on the photoelectric conversion layer 15 generates hole-electron pairs inside the carbon nanotube, and the generated signal charge moves in a direction perpendicular to the circumferential direction of the carbon nanotube, i.e., in the longitudinal direction of the carbon nanotube, before being collected by the pixel electrode 11 stacked directly below, there is a possibility that color mixing with adjacent pixels and a decrease in resolution will occur. When there is no acceptor layer 17 between the photoelectric conversion layer 15 and the pixel electrode 11, the influence may be noticeable. In this embodiment, as will be described in detail later, even if the signal charge generated in the carbon nanotube moves in the longitudinal direction of the carbon nanotube, it is possible to reduce color mixing with adjacent pixels and a decrease in resolution because the length of the carbon nanotube is limited.

[0083] In addition, in the example shown in Figure 3, the photoelectric conversion layer 15 has a planar heterostructure separated from the acceptor layer 17, but a photoelectric conversion layer with a bulk heterostructure in which the material of the photoelectric conversion layer 15 and the material of the acceptor layer 17 are mixed together may also be used.By using a bulk heterostructure, it is possible to increase the charge extraction efficiency and improve the sensitivity.

[0084] Furthermore, in FIG. 3, a hole blocking layer that limits the movement of holes, which are signal charges, may be laminated under the counter electrode 12 to reduce dark current due to hole injection from the counter electrode 12 side.

[0085] Next, the carbon nanotubes contained in the photoelectric conversion layer according to this embodiment will be described in detail.

[0086] FIG. 4 is a schematic cross-sectional view showing the cross-sectional structure of the photoelectric conversion unit 13a of the imaging device according to the present embodiment. Since FIG. 4 is a diagram for explaining carbon nanotubes, only the photoelectric conversion layer 15 is provided between the counter electrode 12 and the pixel electrodes 11a and 11b, and a donor layer or an acceptor layer for extracting charges from the photoelectric conversion layer 15, and an electron blocking layer or a hole blocking layer for reducing a dark current caused by injection of charges opposite to the signal charge from the pixel electrode 11 are omitted. FIG. 4 also shows a part of the interlayer insulating layer 50. In each of the schematic cross-sectional views showing the cross-sectional structure of the photoelectric conversion unit below, the configuration other than the photoelectric conversion unit and a part of the interlayer insulating layer is not shown, but the configuration other than the photoelectric conversion unit is the same as the configuration of the pixel 10 shown in FIG. 3.

[0087] Two adjacent pixels 10a and 10b are shown in Fig. 4. The pixel 10a is an example of a first pixel, and the pixel 10b is an example of a second pixel.

[0088] 4, each of two adjacent pixels 10a and 10b includes a counter electrode 12 that transmits incident light, pixel electrodes 11a and 11b that face the counter electrode 12, and a photoelectric conversion layer 15 that is sandwiched between the counter electrode 12 and the pixel electrodes 11a and 11b. Specifically, the counter electrode 12 and the photoelectric conversion layer 15 are formed across the two adjacent pixels 10a and 10b.

[0089] Further, each of the two adjacent pixels 10a and 10b includes an individual pixel electrode 11a and 11b. The interlayer insulating layer 50 is embedded between the two individual pixel electrodes 11a and 11b. That is, the pixel electrodes 11a and 11b of the two adjacent pixels 10a and 10b are separated from each other via the insulating material of the interlayer insulating layer 50. FIG. 4 shows a case where the pixel electrode 11a of the pixel 10a collects signal charges in the range of the collection region 10a1, and the pixel electrode 11b of the pixel 10b collects signal charges in the range of the collection region 10b1.

[0090] The photoelectric conversion layer 15 of the pixels 10a and 10b includes a plurality of carbon nanotubes. In Fig. 4, only one carbon nanotube 60a among the plurality of carbon nanotubes is illustrated, and the other carbon nanotubes are omitted. For example, carbon nanotubes may also be present in the photoelectric conversion layer 15 directly above the pixel electrodes 11a and 11b.

[0091] In the case where a pixel defect Y exists in the photoelectric conversion layer 15 in the pixel 10b, the pixel defect Y may be a source of charge such as room temperature thermally excited dark current, which may cause white defects. In order to prevent leakage current such as dark current caused by charge generated in the pixel defect Y from being introduced into the pixel 10a, the imaging device according to the present embodiment has a length A of at least one carbon nanotube 60a in the photoelectric conversion layer 15 that is shorter than the interval B between the pixel electrode 11a of the pixel 10a and the pixel electrode 11b of the pixel 10b in a planar view, as shown in FIG. 4. That is, the multiple carbon nanotubes included in the photoelectric conversion layer 15 in the pixel 10a include at least one carbon nanotube that satisfies the relationship of length A<interval B. The carbon nanotube that satisfies the relationship of length A<interval B has a short length A, and is therefore not disposed across the interval B between the pixel electrodes 11a and 11b in a planar view. Note that the carbon nanotube included in the photoelectric conversion layer 15 in the pixel 10a is a carbon nanotube that is at least partially included in the photoelectric conversion layer 15 in the pixel 10a.

[0092] The plurality of carbon nanotubes included in the photoelectric conversion layer 15 in the pixel 10b may also include at least one carbon nanotube that satisfies length A<spacing B.

[0093] Since white defects are caused by the generation of a large amount of electric charge, it is difficult to prevent the leakage current from being introduced into the adjacent pixel 10a by collecting the generated electric charge in the pixel electrode 11b or the like. However, in the pixel 10a according to the present embodiment, since the photoelectric conversion layer 15 contains at least one carbon nanotube that satisfies length A<spacing B among the multiple carbon nanotubes, even if the carbon nanotubes other than the carbon nanotube do not satisfy length A<spacing B and the leakage current that causes white defects is introduced from the adjacent pixel 10b, the signal charge generated by the carbon nanotube can be obtained from the difference in the signal charge amount between the light state and the dark state. Therefore, by using the signal charge obtained from the difference as the signal charge for imaging and performing correction, the expansion of the white defect pixel can be suppressed even if the adjacent pixel 10b is a white defect pixel. In other words, when the multiple carbon nanotubes contained in the photoelectric conversion layer 15 of at least one of the two adjacent pixels 10a and 10b include at least one carbon nanotube whose length A is less than the spacing B, the expansion of white defect pixels is suppressed, and a high-image-quality imaging device with fewer white defect pixels is realized.

[0094] In addition, because carbon nanotubes have high charge conductivity, normal signal charges also move inside the carbon nanotubes, but pixel 10a is less likely to introduce signal charges from adjacent pixel 10b because pixel 10a contains at least one carbon nanotube whose length A is smaller than the interval B among the multiple carbon nanotubes in photoelectric conversion layer 15. This makes it possible to suppress color mixing between adjacent pixels 10a and 10b.

[0095] As described above, in the imaging device of the present embodiment, the leakage current generated in the pixel 10b is transmitted to the adjacent pixel 10 a Since the signal charge generated in the pixel 10b is not introduced into the pixel 10a, the white defect can be prevented from spreading from the pixel 10b to the adjacent pixels such as the pixel 10a. In addition, the signal charge generated in the pixel 10b can be prevented from being introduced into the adjacent pixel 10a, etc. In other words, the deterioration of the resolution and the color mixing can be prevented.

[0096] Furthermore, the number of pixels including the photoelectric conversion layer 15 including at least one carbon nanotube that satisfies length A<spacing B may be 50% or more of the number of the pixels 10. This allows the signal charge obtained by the difference in more than half of the pixels 10 to be used as the signal charge for imaging, and color mixing is also suppressed, so that the MTF (Modular Transfer Function), which is an index representing the optical resolution of the imaging device, can be improved. ion The MTF is an index expressed between 0 and 1, with a higher value indicating a higher optical resolution. When the MTF is 0.5 or higher, it becomes possible to distinguish straight lines through image processing, etc., resulting in a high-image-quality imaging device.

[0097] Furthermore, among the multiple pixels 10, the number of pixels including the photoelectric conversion layer 15 including at least one carbon nanotube that satisfies length A<spacing B may be 80% or more of the multiple pixels 10. This allows 80% or more of the multiple pixels 10 to use the signal charge acquired by difference as the signal charge for imaging, and color mixing is also suppressed, resulting in image quality that can be viewed as a focal plane array by the imaging device.

[0098] Furthermore, the number of pixels including a photoelectric conversion layer 15 including at least one carbon nanotube that satisfies length A<spacing B among the plurality of pixels 10 may be 90% or more of the plurality of pixels 10. As a result, the signal charge acquired by difference in 90% or more of the plurality of pixels 10 can be used as the signal charge for imaging, and color mixing is also suppressed, so that the MTF, which is an index representing the resolution of the imaging device, becomes 0.9 or more. Therefore, a high resolution is maintained without post-processing such as image processing, and an imaging device with higher image quality is realized.

[0099] In addition, the content of carbon nanotubes that satisfy length A<interval B among the plurality of carbon nanotubes contained in all the photoelectric conversion layers 15 included in the plurality of pixels 10 may be 50% or more. The above content is the number of carbon nanotubes that satisfy length A<interval B relative to the number of all the plurality of carbon nanotubes. As a result, when the photoelectric conversion layers 15 of the plurality of pixels 10 contain approximately the same number of carbon nanotubes, the number of pixels that include photoelectric conversion layers 15 that include at least one carbon nanotube that satisfies length A<interval B among the plurality of pixels 10 is 50% or more of the number of the plurality of pixels 10, and an imaging device that can obtain the above-mentioned effects is easily realized. Furthermore, when the plurality of carbon nanotubes are uniformly dispersed in the photoelectric conversion layer 15, it is expected that the proportion of pixels that include at least one carbon nanotube that satisfies length A<interval B will be higher, and an imaging device with high image quality will be realized.

[0100] Furthermore, the content of carbon nanotubes that satisfy length A<spacing B among the multiple carbon nanotubes contained in all photoelectric conversion layers 15 included in the multiple pixels 10 may be 80% or more. As a result, when the photoelectric conversion layers 15 of the multiple pixels 10 each contain approximately the same number of carbon nanotubes, the number of pixels that include photoelectric conversion layers 15 that contain at least one carbon nanotube that satisfies length A<spacing B among the multiple pixels 10 is 80% or more of the number of the multiple pixels 10, and an imaging device that can obtain the above-mentioned effects is easily realized. Furthermore, when the multiple carbon nanotubes are uniformly dispersed in the photoelectric conversion layer 15, it is expected that the proportion of pixels that contain at least one carbon nanotube that satisfies length A<spacing B will be higher, and an imaging device with high image quality will be realized.

[0101] Furthermore, the content of carbon nanotubes that satisfy length A<spacing B among the multiple carbon nanotubes contained in all photoelectric conversion layers 15 included in the multiple pixels 10 may be 90% or more. As a result, when the photoelectric conversion layers 15 of the multiple pixels 10 each contain approximately the same number of carbon nanotubes, the number of pixels that contain photoelectric conversion layers 15 that contain at least one carbon nanotube that satisfies length A<spacing B among the multiple pixels 10 is 90% or more of the number of the multiple pixels 10, and an imaging device that can obtain the above-mentioned effects is easily realized. Furthermore, when the multiple carbon nanotubes are uniformly dispersed in the photoelectric conversion layer 15, it is expected that the proportion of pixels that contain at least one carbon nanotube that satisfies length A<spacing B will be higher, and an imaging device with high image quality will be realized.

[0102] In addition, the second portion of the photoelectric conversion layer 15 located between the pixel electrode 11a of the pixel 10a and the pixel electrode 11b of the pixel 10b in a planar view may contain more carbon nanotubes that satisfy the relationship of length A < interval B than the first portion located on the pixel electrode 11a of the pixel 10a in a planar view. As a result, even if the photoelectric conversion layer 15 has the same content rate of carbon nanotubes that satisfy the relationship of length A < interval B, carbon nanotubes of length A that cannot be arranged across the interval B are likely to be present in the photoelectric conversion layer between the pixel electrode 11a of the pixel 10a and the pixel electrode 11b of the pixel 10b in a planar view. Therefore, the spread of white defect pixels to adjacent pixels and color mixing between adjacent pixels are further suppressed. For example, by applying inks containing carbon nanotubes of different lengths to form photoelectric conversion layer 15, carbon nanotubes of different lengths can be arranged in the photoelectric conversion layer above pixel electrode 11a in a planar view and in the photoelectric conversion layer between pixel electrodes 11a and 11b in a planar view.

[0103] Here, the length of the carbon nanotube will be described. FIG. 5 is a schematic diagram for explaining the length of the carbon nanotube according to the present embodiment. The length A of the carbon nanotube 60 in this specification is not the effective length between both ends of the carbon nanotube itself, but the length of the carbon nanotube 60 along the arrangement direction in which the pixel electrodes 11c and 11d are arranged in a plan view, as shown in part (a) of FIG. 5. In the example shown in part (a) of FIG. 5, the arrangement direction of the pixel electrodes 11c and 11d is the same as the longitudinal direction of the carbon nanotube 60, and the linear distance between the ends of the carbon nanotube 60 is the same as the length A. In addition, as shown in part (b) of FIG. 5, when the longitudinal direction of the carbon nanotube 60 is inclined with respect to the arrangement direction of the pixel electrodes 11c and 11d, the length A becomes shorter than the linear distance between the ends of the carbon nanotube 60.

[0104] The photoelectric conversion layer 15 according to the present embodiment is manufactured, for example, by applying ink containing carbon nanotubes to the upper surface of the pixel electrodes 11, etc. The length A of the carbon nanotubes may be adjusted to the desired length A by adjusting the effective length of the carbon nanotubes themselves contained in the ink used to manufacture the photoelectric conversion layer 15, or, as shown in parts (a) and (b) of FIG. 5, the length A may be adjusted to the desired length A by controlling the longitudinal direction of the carbon nanotubes relative to the arrangement direction of the pixel electrodes in the photoelectric conversion layer 15, even if the carbon nanotubes have the same effective length. In parts (a) and (b) of FIG. 5, it has been described that the length A changes depending on the longitudinal direction of the carbon nanotubes in a plan view. However, in a cross-sectional view, the length A becomes shorter as the longitudinal direction of the carbon nanotubes is inclined relative to the arrangement direction of the pixel electrodes.

[0105] The inclination of the longitudinal direction of the carbon nanotubes relative to the arrangement direction of the pixel electrodes in the photoelectric conversion layer 15 can be controlled by various methods. For example, it can be easily controlled by the rotation speed or viscosity of the spin coater when applying the ink containing carbon nanotubes. Specifically, by increasing the rotation speed of the spin coater after dropping the ink containing carbon nanotubes on the upper surface of the pixel electrodes 11, etc., the longitudinal direction of the carbon nanotubes is likely to be oriented in a direction perpendicular to the stacking direction. Conversely, by increasing the viscosity of the ink containing carbon nanotubes or controlling the rotation speed of the spin coater to a low speed, the longitudinal direction of the carbon nanotubes is likely to be oriented in the stacking direction. The high or low rotation speed mentioned above is a relative speed with respect to a certain reference state, and is determined by the viscosity of the ink containing carbon nanotubes and the target film thickness.

[0106] As a method for adjusting the effective length of the carbon nanotube itself, a carbon nanotube of a desired length may be selected from available carbon nanotubes, or a carbon nanotube longer than the desired length may be obtained and cut by stirring or the like to adjust the length of the carbon nanotube. In addition, since a typical carbon nanotube is a mixture of carbon nanotubes of various lengths, a carbon nanotube of a desired length may be separated by filtration or the like. In addition, a carbon nanotube of a desired length may be synthesized by a known method such as a microplasma CVD (Chemical Vapor Deposition) method, a carbon infiltration method, or a SiC surface decomposition method.

[0107] In addition, in the imaging device according to the present embodiment, instead of the length A of the carbon nanotube 60, as shown in part (c) of FIG. 5, the linear distance C between the two spatially most distant points in one carbon nanotube 60 may be shorter than the interval B shown in FIG. 4. That is, the multiple carbon nanotubes included in the photoelectric conversion layer 15 in the pixel 10a shown in FIG. 4 may include at least one carbon nanotube that satisfies linear distance C<interval B. In this way, no matter what direction the carbon nanotubes in the photoelectric conversion layer 15 are arranged in, the photoelectric conversion layer 15 includes at least one carbon nanotube that is not arranged across two adjacent pixels. Therefore, the spread of a white defect pixel to an adjacent pixel and color mixing between adjacent pixels are suppressed. Therefore, an imaging device with high image quality can be easily realized.

[0108] In the example shown in part (c) of Fig. 5, the linear distance between the ends of carbon nanotubes 60 is the same as the linear distance C between the two spatially most distant points. On the other hand, as shown in part (d) of Fig. 5, when carbon nanotubes 61 are curved so that the two ends approach each other, the linear distance C between the two spatially most distant points becomes longer than the distance between the ends of carbon nanotubes 61.

[0109] Next, the interval B between two adjacent pixels will be described. FIG. 6A is a plan view showing the planar layout of pixel electrodes of an imaging device according to the present embodiment. As shown in FIG. 6A, a plurality of pixel electrodes 11e1, 11e2, 11e3, 11e4, 11e5, 11e6, 11e7, 11e8, and 11e9 are arranged in a matrix. When a plurality of pixel electrodes are arranged in a matrix, the interval B1 between the pixel electrodes of two pixels adjacent in the horizontal or vertical direction, such as the pixel electrodes 11e5 and 11e6 of two adjacent pixels, is the shortest. In addition, the interval B2 between the pixel electrodes of two pixels adjacent in a 45-degree diagonal direction, such as the pixel electrodes 11e4 and 11e8 of two adjacent pixels, is longer than the interval B1. Note that, in the case of the pixel electrodes 11e4 and 11e8 of two pixels adjacent in a 45-degree diagonal direction, the interval in the case of a pixel electrode arrangement in which the interval varies depending on the position is the interval between the closest parts of the two adjacent pixel electrodes.

[0110] With regard to the spacing B shown in FIG. 4, which affects the reduction of color mixing, etc., depending on where the carbon nanotubes are arranged, the arrangement direction shown in FIG. 6A may be horizontal and a spacing B1 may be used between pixel electrodes 11e5 and 11e6, or the arrangement direction may be diagonal at 45 degrees and a spacing B2 may be used between pixel electrodes 11e4 and 11e8.

[0111] Furthermore, if optical filters such as color filters, bandpass filters, or longpass filters are provided on the upper layers of the pixel electrodes 11e5 and 11e6, and the optical characteristics of the optical filters arranged on the pixel electrodes 11e5 and 11e6 are the same, the degree of color mixing is reduced compared to between adjacent pixels in which optical filters with different optical characteristics are arranged, even if the length A of the carbon nanotube is longer than the interval B1 between the pixel electrodes 11e5 and 11e6. On the other hand, when optical filters with different optical characteristics are arranged on a plurality of pixel electrodes, it is preferable to set the length A of the carbon nanotube according to the interval between the pixel electrodes of the pixels in which the optical filters with different optical characteristics are provided. For example, when optical filters with different optical characteristics are arranged on the upper layers of the pixel electrodes 11e4 and 11e8, it is preferable to determine the length A of the carbon nanotube with respect to the interval B2 adjacent to each other in the diagonal direction.

[0112] The shape of the pixel electrode in plan view is not particularly limited. For example, the pixel electrode may be a circle, or a regular polygon such as a regular hexagon or a regular octagon. The arrangement of the pixel electrodes is also not particularly limited, and the pixel electrodes may be arranged in a diagonal direction, for example.

[0113] 6B, 6C, and 6D are plan views showing examples of the planar layout of pixel electrodes to explain the intervals between the pixel electrodes. For example, as shown in FIG. 6B, when pixel electrodes 111a each having a regular octagonal shape in plan view are arranged in a matrix, the interval B4 between adjacent pixel electrodes 111a in a 45-degree diagonal direction is longer than the interval B3 between adjacent pixel electrodes 111a in the horizontal direction. Also, as shown in FIG. 6C, when pixel electrodes 111b each having a regular octagonal shape in plan view are arranged in a row in a 45-degree diagonal direction, the interval B6 between adjacent pixel electrodes 111b in the horizontal direction is longer than the interval B5 between adjacent pixel electrodes 111b in the 45-degree diagonal direction. Also, for example, as shown in FIG. 6D, when the planar shape is a regular octagon and larger pixel electrodes 111L and smaller pixel electrodes 111S are arranged alternately in a matrix, the distance B8 between adjacent pixel electrodes 111L in a 45 degree diagonal direction is longer than the distance B7 between adjacent pixel electrodes 111L and 111S in the horizontal direction.

[0114] 6A to 6D, the pixel electrodes may be spaced apart from each other by any of the distances B1 to B8 in the direction in which the pixel electrodes are arranged, depending on the location of the carbon nanotubes.

[0115] Next, an imaging device according to another example of the present embodiment will be described. FIG. 7 is a schematic cross-sectional view showing a cross-sectional structure of a photoelectric conversion unit of an imaging device according to another example of the present embodiment. In part (a) of FIG. 7, a photoelectric conversion unit 13b formed in two adjacent pixels 10c and 10d is shown, and in part (b) of FIG. 7, a photoelectric conversion unit 13c formed in two adjacent pixels 10e and 10f is shown. In addition, in parts (a) and (b) of FIG. 7, a part of an interlayer insulating layer 50 is also shown. The photoelectric conversion units 13b and 13c shown in parts (a) and (b) of FIG. 7 are different from the photoelectric conversion unit 13a shown in FIG. 4 in that a collection region, which is a range in which a pixel electrode collects signal charges, is larger. The pixels 10c and 10e are examples of a first pixel, and the pixels 10d and 10f are examples of a second pixel. In part (a) and part (b) of FIG. 7, only one carbon nanotube 60b or 60c out of the multiple carbon nanotubes is illustrated, and the other carbon nanotubes are omitted.

[0116] The range in which the signal charges generated in the photoelectric conversion layer are collected by the pixel electrodes can be adjusted to some extent by the electric field generated by the voltage applied between the counter electrode and the pixel electrode. In the case of the pixels 10c and 10d shown in part (a) of FIG. 7, the pixel electrode 11f of the pixel 10c collects the signal charges in the range of the collection region 10c1, and the pixel electrode 11g of the pixel 10d collects the signal charges in the range of the collection region 10d1. In the photoelectric conversion unit 13b, the boundary between the collection region 10c1 and the collection region 10d1 is the center of the interval B between the pixel electrodes 11f and 11g. At this time, it is assumed that the reset voltages, which are the initial potentials of the pixel electrodes 11f and 11g, are equal.

[0117] Therefore, in order to prevent leakage current due to charge generated in pixel defect Y on pixel electrode 11g of pixel 10d from being introduced to adjacent pixel 10c, as shown in part (a) of FIG. 7, the plurality of carbon nanotubes included in photoelectric conversion layer 15 of pixel 10c may include at least one carbon nanotube 60b having a length A shorter than half B / 2 of the interval B between pixel electrodes 11f and 11g. This allows the photoelectric conversion layer 15 of pixel 10c to include carbon nanotubes 60b that do not introduce leakage current or the like from the photoelectric conversion layer 15 on pixel electrode 11g of adjacent pixel 10d, thereby suppressing the expansion of white defect pixels and color mixing between adjacent pixels. In addition, the plurality of carbon nanotubes included in photoelectric conversion layer 15 of pixel 10c may include at least one carbon nanotube having a linear distance C shorter than half B / 2 of the interval between pixel electrodes 11f and 11g.

[0118] In order to increase the allowable length A of the carbon nanotube, the size of the pixel electrodes 11h and 11i is changed to the pixel electrode 11 shown in part (a) of FIG. 7 as shown in part (b) of FIG. f and 11 g It is preferable to make the size of the pixel electrode smaller than the size of the pixel electrode. Generally, reducing the size of the pixel electrode of a stacked imaging device narrows the capture range of the signal charge, which leads to a decrease in sensitivity. However, in a stacked imaging device in which the carbon nanotube is included in the photoelectric conversion layer, the capture range of the signal charge can be made wider than the size of the pixel electrode because the carbon nanotube itself is long. Therefore, as shown in part (b) of FIG. 7, the length A of the carbon nanotube 60c may be longer than the width of the pixel electrodes 11h and 11i. Also, the length A of the carbon nanotube 60c may be shorter than half the distance B / 2 between the pixel electrodes 11h and 11i. Also, the width of the pixel electrodes 11h and 11i may be shorter than the distance B between the pixel electrodes 11h and 11i, or shorter than half the distance B / 2 between the pixel electrodes 11h and 11i.

[0119] Next, another effect of the length of the carbon nanotubes will be described. FIG. 8 is a schematic cross-sectional view for explaining the flatness of the photoelectric conversion layer. Part (a) of FIG. 8 shows an example in which the length of the carbon nanotubes 81a contained in the photoelectric conversion layer 80a is relatively long, and part (b) of FIG. 8 shows an example in which the length of the carbon nanotubes 60d contained in the photoelectric conversion layer 15 is relatively short. When manufacturing an imaging device including a photoelectric conversion layer containing carbon nanotubes, in order to improve sensitivity, ink containing carbon nanotubes may be applied multiple times or multiple layers to increase the concentration of carbon nanotubes in the photoelectric conversion layer. At that time, since the carbon nanotubes dispersed in the solvent have the characteristic of being rigid and long, as shown in part (a) of FIG. 8, in the case of a photoelectric conversion layer 80a including carbon nanotubes 81a that are long relative to the size and interval of the pixel electrodes 11, that is, length A>interval B, the surface shape of the photoelectric conversion layer 80a after the drying process becomes a shape with large undulations. The undulations of the photoelectric conversion layer 80a have a period larger than the pixel pitch, which causes sensitivity unevenness observed as different sensitivities for each pixel. In contrast, as shown in part (b) of FIG. 8, the photoelectric conversion layer 15 contains carbon nanotubes 60d whose length A is shorter than the interval B between adjacent pixel electrodes 11, thereby reducing the period of the undulations of the photoelectric conversion layer 15 to less than the pixel pitch. This provides the effect of reducing sensitivity unevenness for each pixel. Furthermore, when the linear distance C between the two spatially most distant points of the carbon nanotubes 60d is shorter than the interval B between the adjacent pixel electrodes 11, the magnitude of the undulations in the surface shape of the photoelectric conversion layer 15 is also reduced, making it easier to stack the counter electrodes and the like on the photoelectric conversion layer 15 flatly.

[0120] (Embodiment 2) Next, a description will be given of embodiment 2. Embodiment 2 differs from embodiment 1 in that a partition wall is provided in the photoelectric conversion layer. In the following, the differences from embodiment 1 will be mainly described, and descriptions of commonalities will be omitted or simplified.

[0121] First, an imaging device according to Comparative Example 1 for explaining the second embodiment will be described. Fig. 9 is a schematic cross-sectional view showing a cross-sectional structure of a photoelectric conversion unit 90 of the imaging device according to the comparative example. Two pixels 70c and 70d adjacent to each other are shown in Fig. 9. Note that Fig. 9 shows a state in which the photoelectric conversion layer 80b and the counter electrode 12 are separated from each other.

[0122] 9, each of the pixels 70c and 70d includes a counter electrode 12 that transmits incident light, pixel electrodes 11j and 11k that face the counter electrode 12, and a photoelectric conversion layer 80b sandwiched between the counter electrode 12 and the pixel electrodes 11j and 11k. Each of the pixels 70c and 70d also includes individual pixel electrodes 11j and 11k.

[0123] Photoelectric conversion layer 80b includes a plurality of carbon nanotubes. In Fig. 9, only one carbon nanotube 81b among the plurality of carbon nanotubes is illustrated, and the other carbon nanotubes are omitted.

[0124] In the photoelectric conversion layer 80b between the pixels 70c and 70d and between the other pixels not shown in the drawing, partition walls 18 are provided so as to sandwich the pixel electrodes 11j and 11k, respectively. The length A of the carbon nanotube 81b is longer than the distance D between a first portion of the partition wall 18 located on the left side of the pixel electrode 11j and a second portion of the partition wall 18 located on the right side of the pixel electrode 11j.

[0125] In this way, when a partition 18 is provided for each pixel to optically or electrically prevent color mixing, and the length A of the carbon nanotube 81b is longer than the distance D between the first portion of the partition 18 located to the left of the pixel electrode 11j and the second portion of the partition 18 located to the right of the pixel electrode 11j in a plan view, as shown in Fig. 9, there is a problem that the carbon nanotube 81b climbs over the partition 18, compromising the flatness of the partition 18. In addition, there is a problem that the carbon nanotube 81b adheres to the partition 18 and connects with adjacent pixels, reducing the effect of the partition 18 in preventing color mixing.

[0126] Next, an imaging device according to the present embodiment will be described with reference to Fig. 10. Fig. 10 is a schematic cross-sectional view showing a cross-sectional structure of a photoelectric conversion unit 13d of the imaging device according to the present embodiment. Fig. 10 also shows a part of an interlayer insulating layer 50. Fig. 10 shows two pixels 10g and 10h adjacent to each other.

[0127] 10, each of the pixels 10g and 10h includes a counter electrode 12 that transmits incident light, pixel electrodes 11m and 11n that face the counter electrode 12, and a photoelectric conversion layer 15a that is sandwiched between the counter electrode 12 and the pixel electrodes 11m and 11n. The counter electrode 12 and the photoelectric conversion layer 15a are formed across two adjacent pixels 10g and 10h.

[0128] In addition, each of the pixels 10g and 10h includes an individual pixel electrode 11m and 11n. The interlayer insulating layer 50 is embedded between the two individual pixel electrodes 11m and 11n. That is, the pixel electrodes 11m and 11n of the two adjacent pixels 10g and 10h are separated from each other by the insulating material of the interlayer insulating layer 50.

[0129] The photoelectric conversion layers 15a of the pixels 10g and 10h include a plurality of carbon nanotubes. In Fig. 10, only one carbon nanotube 60e among the plurality of carbon nanotubes is illustrated, and the other carbon nanotubes are omitted.

[0130] In the photoelectric conversion layer 15a between the pixels 10g and 10h in plan view and between the other pixels not shown, partition walls 18 are provided so as to sandwich the pixel electrodes 11m and 11n corresponding to the pixels in plan view. The length A of the carbon nanotube 60e included in the photoelectric conversion layer 15a in the pixel 10g is shorter than the interval D between the first portion of the partition wall 18 located to the left of the pixel electrode 11m and the second portion of the partition wall 18 located to the right of the pixel electrode 11m along the arrangement direction of the pixel electrodes 11m and 11n. That is, the carbon nanotubes included in the photoelectric conversion layer 15a in the pixel 10g include the carbon nanotubes 60e that satisfy the relationship of length A<interval D. The carbon nanotubes included in the photoelectric conversion layer 15a in the pixel 10h may also include the carbon nanotubes 60e that satisfy the relationship of length A<interval D.

[0131] The partition 18 is formed of a material having a higher electrical resistance and a lower conductivity of charge than the photoelectric conversion layer 15a. This suppresses the movement of signal charges between the adjacent pixels 10g and 10h, thereby suppressing color mixing between the adjacent pixels 10g and 10h. The material of the partition 18 may be a material having a higher resistivity than the photoelectric conversion layer 15a containing carbon nanotubes. The material of the partition 18 may be an insulating material such as SiO2, AlO, or SiN. The material of the partition 18 is not limited to an insulating material, and may be any material having a higher electrical resistance than the photoelectric conversion layer 15a, and may be selected from a wide range of materials depending on the required physical properties. For example, when a planarization process such as CMP (Chemical Mechanical Polishing) is performed after the formation of the partition 18 and the photoelectric conversion layer 15a, the hardness of the partition 18 and the photoelectric conversion layer 15a affects the flatness, so that a material having an appropriate hardness may be used for the partition 18.

[0132] In this way, the partition wall 18 is provided for each pixel to optically or electrically suppress color mixing, and the length A of the carbon nanotube 60e is made shorter than the distance D between the first portion of the partition wall 18 located on the left side of the pixel electrode 11m and the second portion of the partition wall 18 located on the right side of the pixel electrode 11m, so that the carbon nanotube 60e is less likely to adhere to the partition wall 18, and the color mixing prevention effect of the partition wall 18 is easily realized. In addition, the carbon nanotube 60e is less likely to overcome the partition wall 18, and the flatness on the partition wall 18 is improved. As a result, the flatness and thickness uniformity are improved in the film formation of the layer located on the upper side of the photoelectric conversion layer 15a, for example, in the film formation of the counter electrode 12. By improving the flatness of the counter electrode 12, the film thickness of the photoelectric conversion unit 13d at the portion where the voltage is applied from the counter electrode 12 to the pixel electrodes 11m and 11n for each pixel becomes uniform, and the sensitivity unevenness is reduced. In addition, if the thickness of the counter electrode 12 differs from pixel to pixel, the resistance value of the counter electrode 12 varies. Making the film thickness of the counter electrode 12 uniform provides the following effects: reduction in time constant variations when the potential of the counter electrode is changed in accordance with the operation of the imaging device; reduction in variations between imaging devices; and improvement in yield.

[0133] In FIG. 10, the photoelectric conversion layer 15a is also disposed on the partition wall 18, but the photoelectric conversion layer 15a may not be present on the partition wall 18, and the counter electrode 12 may be formed thereon. In FIG. 10, the distance D between the first portion of the partition wall 18 located on the left side of the pixel electrode 11m and the second portion of the partition wall 18 located on the right side of the pixel electrode 11m is the same as the width of the pixel electrode 11m, but the distance D may be different from the width of the pixel electrode 11m. For example, by making the distance D larger than the width of the pixel electrode 11m, the area functioning in the photoelectric conversion layer 15a can be enlarged to improve the sensitivity, and the allowable length A of the carbon nanotube 60e is also increased. In FIG. 10, the length A of the carbon nanotube 60e is longer than the distance between the pixel electrodes 11m and 11n, but the length A of the carbon nanotube 60e may be shorter than the distance between the pixel electrodes 11m and 11n.

[0134] Furthermore, as in embodiment 1, the number of pixels including a photoelectric conversion layer containing at least one carbon nanotube satisfying length A<spacing D among the multiple pixels may be 50% or more of the number of the multiple pixels, 80% or more, or 90% or more.

[0135] Furthermore, the content of carbon nanotubes that satisfy length A<spacing D among the multiple carbon nanotubes contained in all photoelectric conversion layers 15a included in the multiple pixels may be 50% or more, 80% or more, or 90% or more.

[0136] (Embodiment 3) Next, a third embodiment will be described.

[0137] 11 is a block diagram showing the structure of a camera system 600 according to this embodiment. The camera system 600 includes a lens optical system 601, an imaging device 602, a system controller 603, and a camera signal processing unit 604.

[0138] The lens optical system 601 includes, for example, an autofocus lens, a zoom lens, and an aperture. The lens optical system 601 focuses light on an imaging surface of the imaging device 602. Light passing through the lens optical system 601 enters the photoelectric conversion unit 13, where it is photoelectrically converted to generate a signal charge. The signal charge is read out by the readout circuit 30, which outputs an imaging signal. The imaging device according to the first or second embodiment is used as the imaging device 602. The readout circuit 30 is composed of, for example, the circuits shown in FIG. 2.

[0139] The system controller 603 controls the entire camera system 600. The system controller 603 can be realized by, for example, a microcomputer.

[0140] The camera signal processing unit 604 functions as a signal processing circuit that processes an output signal from the imaging device 602. The camera signal processing unit 604 performs processes such as gamma correction, color interpolation processing, spatial interpolation processing, auto white balance, distance measurement calculation, wavelength information separation, etc. The camera signal processing unit 604 can be realized by, for example, a DSP (Digital Signal Processor).

[0141] According to camera system 600 of this embodiment, by using the imaging device according to the first or second embodiment, it is possible to provide high-quality imaging.

[0142] (Other embodiments) Although the imaging device according to one or more aspects has been described based on the embodiments, the present disclosure is not limited to these embodiments. As long as it does not deviate from the gist of the present disclosure, various modifications conceived by a person skilled in the art to the present embodiment and forms constructed by combining components of different embodiments are also included within the scope of the present disclosure.

[0143] For example, the imaging device may be an imaging device that has pixels including a photoelectric conversion layer that does not contain multiple carbon nanotubes, and in which pixels including a photoelectric conversion layer that includes multiple carbon nanotubes and pixels including a photoelectric conversion layer that does not contain multiple carbon nanotubes are arranged.

[0144] Furthermore, for example, the photoelectric conversion layer may contain, in addition to carbon nanotubes, other photoelectric conversion materials such as organic semiconductors, and semiconducting polymers for improving the dispersibility of carbon nanotubes. [Industrial Applicability]

[0145] The imaging device according to the present disclosure can be applied to various camera systems and sensor systems, such as medical cameras, surveillance cameras, vehicle-mounted cameras, distance measuring cameras, microscope cameras, drone cameras, and robot cameras. [Explanation of symbols]

[0146] 10, 10a, 10b, 10c, 10d, 10e, 10f, 10g, 10h, 70a, 70b, 70c, 70d pixels 10a1, 10b1, 10c1, 10d1 Collection area 11, 11a, 11b, 11c, 11d, 11e1, 11e2, 11e3, 11e4, 11e5, 11e6, 11e7, 11e8, 11e9, 11f, 11g, 11h, 11i, 11j, 11k, 11m, 11n, 111a, 111b, 111L, 111S pixel electrodes 12 Counter electrode 13, 13a, 13b, 13c, 13d, 90 Photoelectric conversion unit 14 Signal detection circuit 15, 15a, 80, 80a, 80b Photoelectric conversion layer 16 Electron Blocking Layer 17 Acceptor Layer 18 Bulkhead 19 Color filter layer 20 Semiconductor substrate 20t Element isolation area 24 Signal detection transistor 24d, 24s, 26s, 28d, 28s impurity region 24g, 26g, 28g Gate electrode 26 Address transistor 28 Reset transistor 30 Readout circuit 32 Voltage supply circuit 34 Reset voltage source 36 Vertical scanning circuit 37 Column signal processing circuit 38 Horizontal signal readout circuit 40 Power line 41 Charge storage node 44 Reset voltage line 46 Address Control Line 47 Vertical signal line 48 Reset control line 49 Horizontal common signal line 50, 51 Interlayer insulation layer 52 Plug 53 Wiring 54, 55 Contact plug 56 wiring layer 60, 60a, 60b, 60c, 60d, 60e, 61, 81, 81a Carbon nanotubes 100, 602 Imaging device 600 Camera System 601 Lens Optical System 603 System Controller 604 Camera signal processing unit

Claims

1. A plurality of pixels are provided, Each of the plurality of pixels is a counter electrode through which incident light passes; a pixel electrode facing the counter electrode; a photoelectric conversion layer located between the counter electrode and the pixel electrode, the photoelectric conversion layer including a plurality of carbon nanotubes that absorb the incident light and generate hole-electron pairs; the plurality of pixels includes a first pixel and a second pixel adjacent to the first pixel, the pixel electrode of the first pixel and the pixel electrode of the second pixel are separated from each other; the photoelectric conversion layer is provided continuously between the first pixel and the second pixel, The plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel are When the length of the carbon nanotube along the direction in which the pixel electrode of the first pixel and the pixel electrode of the second pixel are arranged is A and the distance between the pixel electrode of the first pixel and the pixel electrode of the second pixel is B, At least one first carbon nanotube that satisfies A<B; In the photoelectric conversion layer, at least a part of the first carbon nanotube is located between the pixel electrode of the first pixel and the pixel electrode of the second pixel in a plan view. Imaging device.

2. Among the plurality of pixels, the number of pixels including at least one of the first carbon nanotubes is 50% or more of the number of the plurality of pixels. The imaging device according to claim 1 .

3. Among the plurality of pixels, the number of pixels including at least one of the first carbon nanotubes is 80% or more of the number of the plurality of pixels. The imaging device according to claim 1 .

4. Among the plurality of pixels, the number of pixels including at least one of the first carbon nanotubes is 90% or more of the number of the plurality of pixels. The imaging device according to claim 1 .

5. a content rate of the first carbon nanotube in the plurality of carbon nanotubes contained in all of the photoelectric conversion layers included in the plurality of pixels is 50% or more; The imaging device according to claim 1 .

6. a content rate of the first carbon nanotube in the plurality of carbon nanotubes contained in all of the photoelectric conversion layers included in the plurality of pixels is 80% or more; The imaging device according to claim 1 .

7. a content rate of the first carbon nanotube in the plurality of carbon nanotubes contained in all of the photoelectric conversion layers included in the plurality of pixels is 90% or more; The imaging device according to claim 1 .

8. a second portion of the photoelectric conversion layer located between the pixel electrode of the first pixel and the pixel electrode of the second pixel in a planar view contains more of the first carbon nanotubes than a first portion of the photoelectric conversion layer located on the pixel electrode of the first pixel in a planar view; The imaging device according to claim 1 .

9. The plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel are At least one second carbon nanotube satisfying A<(B / 2); The imaging device according to claim 1 .

10. The plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel are When the linear distance between the two most distant points in a single carbon nanotube is C, At least one third carbon nanotube satisfying C<B; The imaging device according to claim 1 .

11. The plurality of carbon nanotubes included in the photoelectric conversion layer in at least one selected from the group consisting of the first pixel and the second pixel are At least one fourth carbon nanotube satisfying C<(B / 2); The imaging device according to claim 10.

Images