Imaging Element and Imaging Device

Abstract

An imaging element according to an embodiment of the present disclosure is provided with: a first electrode; a second electrode disposed opposite to the first electrode; an organic layer disposed between the first electrode and the second electrode and including at least a photoelectric conversion layer; a first semiconductor layer disposed between the second electrode and the organic layer and containing at least one of a carbon-containing compound and an inorganic compound, the electron affinity of the carbon-containing compound being greater than the work function of the first electrode, and the work function of the inorganic compound being greater than the work function of the first electrode; and a second semiconductor layer disposed between the second electrode and the first semiconductor layer, and the absolute value B of the difference between the highest occupied molecular orbital (HOMO) energy level and the Fermi energy level of the second electrode is greater than or equal to the absolute value A of the difference between the first lowest unoccupied molecular orbital (LUMO) energy level calculated from the optical band gap and the Fermi energy level, or has an energy level within a band gap where the density of states is 1 / 10000 or more relative to the HOMO energy level near the Fermi energy level.

Description

Technical Field

[0001] The present disclosure relates to an imaging element using, for example, an organic material and an imaging device including the imaging element. Background Art

[0002] In recent years, a so-called vertical spectroscopic imaging element having a vertical multilayer structure has been proposed, in which an organic photoelectric conversion section is disposed above a semiconductor substrate. In the vertical spectroscopic imaging element, light in the red and blue wavelength ranges is subjected to photoelectric conversion by respective photoelectric conversion sections (photo diodes PD1 and PD2) formed in the semiconductor substrate, and light in the green wavelength range is subjected to photoelectric conversion by an organic photoelectric conversion film provided in the organic photoelectric conversion section.

[0003] In such an imaging element, charges generated by photoelectric conversion by the photo diodes PD1 and PD2 are temporarily accumulated in the photo diodes PD1 and PD2 and then transferred to respective floating diffusion layers. This allows the photo diodes PD1 and PD2 to be completely depleted. On the other hand, charges generated by the organic photoelectric conversion section are directly accumulated in the floating diffusion layer. This makes it difficult to completely deplete the organic photoelectric conversion section, thereby increasing kTC noise and degrading random noise. This results in a reduction in image quality during imaging.

[0004] In contrast, for example, Patent Document 1 discloses an imaging element provided with a charge accumulation electrode in a photoelectric conversion section, thereby suppressing a reduction in image quality during imaging, where the photoelectric conversion section is provided on a semiconductor substrate and includes a stacked first electrode, a photoelectric conversion layer, and a second electrode. The charge accumulation electrode is disposed separately from the first electrode and faces the photoelectric conversion layer with an insulating layer therebetween.

[0005] Citation List

[0006] Patent Document

[0007] Patent Document 1: Japanese Unexamined Patent Application Publication No. 2017-157816 Summary of the Invention

[0008] Incidentally, higher light responsiveness is required for the imaging element.

[0009] There is a desire to provide an imaging element and an imaging device capable of improving light responsiveness.

[0010] An imaging element according to an embodiment of the present disclosure includes: a first electrode, a second electrode, an organic layer, a first semiconductor layer, and a second semiconductor layer. The second electrode is disposed opposite to the first electrode. The organic layer is provided between the first electrode and the second electrode and includes at least a photoelectric conversion layer. The first semiconductor layer is provided between the second electrode and the organic layer and contains at least one of a carbon-containing compound and an inorganic compound. The electron affinity of the carbon-containing compound is greater than the work function of the first electrode, and the work function of the inorganic compound is greater than the work function of the first electrode. The second semiconductor layer is provided between the second electrode and the first semiconductor layer, and the absolute value B of the difference between the HOMO (highest occupied molecular orbital) energy level and the Fermi energy level of the second electrode is greater than or equal to the absolute value A of the difference between the first LUMO (lowest unoccupied molecular orbital) energy level calculated from the optical band gap and the Fermi energy level, or has an energy level within the band gap with a density of states relative to the HOMO energy level of 1 / 10,000 or more near the Fermi energy level.

[0011] An imaging device according to an embodiment of the present disclosure includes one or more of the above-described imaging elements according to an embodiment of the present disclosure for each of a plurality of pixels.

[0012] In both the imaging element according to an embodiment of the present disclosure and the imaging device according to the embodiment, a first semiconductor layer is provided between the second electrode and the organic layer. The second electrode is configured to be opposite to the first electrode with the organic layer therebetween. The organic layer includes at least a photoelectric conversion layer. The first semiconductor layer contains at least one of a carbon-containing compound and an inorganic compound. The electron affinity of the carbon-containing compound is greater than the work function of the first electrode, and the work function of the inorganic compound is greater than the work function of the first electrode. Further, in both the imaging element according to an embodiment of the present disclosure and the imaging device according to the embodiment, a second semiconductor layer is provided between the second electrode and the first semiconductor layer. The absolute value B of the difference between the HOMO energy level of the second semiconductor layer and the Fermi energy level of the second electrode is greater than or equal to the absolute value A of the difference between the first LUMO energy level calculated from the optical band gap and the Fermi energy level, or has an energy level within the band gap with a density of states relative to the HOMO energy level of 1 / 10,000 or more near the Fermi energy level. This promotes the injection of electrons from the second electrode into the first semiconductor layer. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 is a cross-sectional schematic view showing an example of a schematic configuration of an imaging element according to an embodiment of the present disclosure.

[0014] Figure 2 is Figure 1 the equivalent circuit diagram of the imaging element shown.

[0015] Figure 3 is a schematic diagram showing Figure 1 the arrangement of the lower electrode of the organic optoelectronic conversion section and the transistor included in the control section shown.

[0016] Figure 4A is a schematic diagram showing Figure 1 an example of the energy levels of the organic optoelectronic conversion section shown.

[0017] Figure 4B is a schematic diagram showing Figure 1 another example of the energy levels of the organic optoelectronic conversion section shown.

[0018] Figure 5 is a graph showing the measurement results of the respective energy levels of NBphen.

[0019] Figure 6 is a graph showing the measurement results of the respective energy levels of NDI35.

[0020] Figure 7 is a cross-sectional view for explaining Figure 1 the manufacturing method of the imaging element shown.

[0021] Figure 8 is Figure 7 a cross-sectional view of the steps after.

[0022] Figure 9 is Figure 8 a cross-sectional view of the steps after.

[0023] Figure 10 is Figure 9 a cross-sectional view of the steps after.

[0024] Figure 11 is Figure 10 a cross-sectional view of the steps after.

[0025] Figure 12 is Figure 11 a cross-sectional view of the steps after.

[0026] Figure 13 is Figure 12 a cross-sectional view of the steps after.

[0027] Figure 14 is a timing chart showing Figure 1 an operation example of the imaging element shown.

[0028] Figure 15 is a block diagram showing Figure 1 the configuration of an imaging device using the imaging element shown as a pixel.

[0029] Figure 16 is a schematic diagram showing the use of Figure 15Functional block diagram of an example of an electronic device (camera) of the imaging device shown.

[0030] Figure 17 It is a block diagram showing an example of a schematic configuration of an in-vivo information acquisition system.

[0031] Figure 18 It is a diagram showing an example of a schematic configuration of an endoscopic surgery system.

[0032] Figure 19 It is a block diagram showing an example of a functional configuration of a camera and a camera control unit (CCU).

[0033] Figure 20 It is a block diagram showing an example of a schematic configuration of a vehicle control system.

[0034] Figure 21 It is a diagram for assisting in explaining the installation positions of an out-of-vehicle information detection unit and an imaging unit.

[0035] Figure 22 It is a cross-sectional schematic diagram of a device structure as an evaluation sample. Detailed Description of the Invention

[0036] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. The following description is a specific example of the present disclosure, but the present disclosure is not limited to the following modes. In addition, the present disclosure is not limited to the arrangement, dimensions, dimensional ratios, etc. of the respective components shown in the respective drawings. Note that the description will be made in the following order.

[0037] 1. Embodiment (Example of providing an electron injection promoting layer having a predetermined energy level between a work function adjusting layer and an upper electrode)

[0038] 1-1. Configuration of the imaging element

[0039] 1-2. Manufacturing method of the imaging element

[0040] 1-3. Actions and effects

[0041] 2. Application examples

[0042] 3. Usage examples

[0043] 4. Examples

[0044] <1. Embodiment>

[0045] Figure 1 Shows a cross-sectional configuration of an imaging element (imaging element 10) according to an embodiment of the present disclosure. Figure 2 Is Figure 1 The equivalent circuit diagram of the imaging element 10 shown. Figure 3 Schematically shows Figure 1The arrangement of the lower electrode 21 of the imaging element 10 shown and the transistors included in the control unit. The imaging element 10 is included, for example, in one pixel (unit pixel P) of an imaging device (imaging device 1; see Figure 15 ). The imaging device is, for example, a CMOS (complementary metal oxide semiconductor) image sensor for an electronic device such as a digital camera or a video camera. The imaging element 10 according to the present embodiment is provided in the organic photoelectric conversion unit 20 provided on the semiconductor substrate 30 with a work function adjustment layer 25 (first semiconductor layer) located between the photoelectric conversion layer 24 and the upper electrode 27 (second electrode), and an electron injection promotion layer 26 (second semiconductor layer) located between the upper electrode 27 and the work function adjustment layer 25. The work function adjustment layer 25 (first semiconductor layer) has a predetermined work function or electron affinity. The electron injection promotion layer 26 (second semiconductor layer) has a predetermined energy level.

[0046] (1-1. Configuration of Imaging Element)

[0047] The imaging element 10 is a so-called longitudinal spectroscopic imaging element in which one organic photoelectric conversion unit 20 and two inorganic photoelectric conversion units 32B and 32R are stacked along the longitudinal direction. The organic photoelectric conversion unit 20 is provided on the first surface (back surface) 30A side of the semiconductor substrate 30. The inorganic photoelectric conversion units 32B and 32R are formed to be buried in the semiconductor substrate 30 and stacked along the thickness direction of the semiconductor substrate 30. The organic photoelectric conversion unit 20 includes a photoelectric conversion layer 24 between the lower electrode 21 (first electrode) and the upper electrode 27 which are arranged opposite to each other. The photoelectric conversion layer 24 is formed by using an organic material. The photoelectric conversion layer 24 contains a p-type semiconductor and an n-type semiconductor and has a bulk heterojunction structure in the layer. The bulk heterojunction structure is a p / n junction surface formed by mixing a p-type semiconductor and an n-type semiconductor.

[0048] The organic photoelectric conversion unit 20 and the inorganic photoelectric conversion units 32B and 32R perform photoelectric conversion by selectively detecting light in different wavelength ranges. Specifically, the organic photoelectric conversion unit 20 acquires a color signal of, for example, green (G). The inorganic photoelectric conversion units 32B and 32R acquire a color signal of, for example, blue (B) and a color signal of red (R) respectively by using the difference in absorption coefficients. This enables the imaging element 10 to acquire multiple color signals in one pixel without using any color filters.

[0049] Note that in the present embodiment, the case where among the electron-hole pairs (excitons) generated by photoelectric conversion, electrons are read out as signal charges is described. In other words, the case where the n-type semiconductor region is used as the photoelectric conversion layer is described. Further, in the drawings, the “+” added to “p” and “n” indicates a high p-type or n-type impurity concentration.

[0050] On the second surface (front surface) 30B of the semiconductor substrate 30, for example, a floating diffusion portion (floating diffusion layer) FD1 (region 36B within the semiconductor substrate 30), FD2 (region 37C within the semiconductor substrate 30), and FD3 (region 38C within the semiconductor substrate 30), transfer transistors Tr2 and Tr3, an amplifying transistor (modulating element) AMP, a reset transistor RST, a selection transistor SEL, and a multilayer wiring layer 40 are provided. The multilayer wiring layer 40 has a configuration in which wiring layers 41, 42, and 43 are laminated within an insulating layer 44, for example.

[0051] Note that in the figure, the first surface 30A side of the semiconductor substrate 30 is shown as the light incident side S1 and its second surface 30B side is shown as the wiring layer side S2.

[0052] The organic photoelectric conversion portion 20 has a configuration in which a lower electrode 21, a charge accumulation layer 23, a photoelectric conversion layer 24, a work function adjustment layer 25, an electron injection promotion layer 26, and an upper electrode 27 are sequentially laminated from the first surface 30A side of the semiconductor substrate 30. In addition, an insulating layer 22 is provided between the lower electrode 21 and the charge accumulation layer 23. For example, the lower electrode 21 is formed for each imaging element 10. Although described in detail below, the lower electrode 21 includes a readout electrode 21A and an accumulation electrode 21B that are separated from each other with the insulating layer 22 therebetween. The readout electrode 21A of the lower electrode 21 is electrically connected to the photoelectric conversion layer 24 via an opening 22H provided in the insulating layer 22. Figure 1 An example in which the charge accumulation layer 23, the photoelectric conversion layer 24, the work function adjustment layer 25, and the upper electrode 27 are respectively formed for each imaging element 10 is shown. However, for example, the charge accumulation layer 23, the photoelectric conversion layer 24, the work function adjustment layer 25, and the upper electrode 27 may be formed as continuous layers shared by a plurality of imaging elements 10.

[0053] For example, an insulating layer 28 and an interlayer insulating layer 29 are provided between the first surface 30A of the semiconductor substrate 30 and the lower electrode 21. The insulating layer 28 includes a layer having fixed charges (fixed charge layer) 28A and a dielectric layer 28B having insulating properties. A protective layer 51 is provided on the upper electrode 27. For example, a light shielding film 52 is provided within the protective layer 51 above the readout electrode 21A. It is sufficient that the light shielding film 52 is provided so as to cover at least the region of the readout electrode 21A that is in direct contact with the photoelectric conversion layer 24, and at least not cover the accumulation electrode 21B. Optical components such as a planarization layer (not shown) and an on-chip lens 53 are provided above the protective layer 51.

[0054] A through electrode 34 is provided between the first surface 30A and the second surface 30B of the semiconductor substrate 30. The organic optoelectronic conversion unit 20 is connected via the through electrode 34 to the gate Gamp of the amplification transistor AMP provided on the second surface 30B side of the semiconductor substrate 30 and to one source / drain region 36B of the reset transistor RST (reset transistor Tr1rst) that also serves as the floating diffusion portion FD1. This allows the imaging element 10 to advantageously transfer the charge (here, electrons) generated by the organic optoelectronic conversion unit 20 on the first surface 30A side of the semiconductor substrate 30 to the second surface 30B side of the semiconductor substrate 30 via the through electrode 34 and improve the characteristics.

[0055] The lower end of the through electrode 34 is connected to the connection portion 41A in the wiring layer 41, and the connection portion 41A and the gate Gamp of the amplification transistor AMP are connected via the lower first contact 45. The connection portion 41A and the floating diffusion portion FD1 (region 36B) are connected via the lower second contact 46, for example. The upper end of the through electrode 34 is connected to the readout electrode 21A via the pad portion 39A and the upper first contact 39C, for example.

[0056] The through electrode 34 is provided, for example, for each organic optoelectronic conversion unit 20 in each imaging element 10. The through electrode 34 functions as a connector between the organic optoelectronic conversion unit 20 and the gate Gamp of the amplification transistor AMP and the floating diffusion portion FD1, and also serves as a transmission path for the charge generated by the organic optoelectronic conversion unit 20.

[0057] The reset gate Grst of the reset transistor RST is arranged adjacent to the floating diffusion portion FD1 (one source / drain region 36B of the reset transistor RST). This allows the reset transistor RST to reset the charge accumulated in the floating diffusion portion FD1.

[0058] In the imaging element 10 according to the present embodiment, the light incident on the organic optoelectronic conversion unit 20 from the upper electrode 27 side is absorbed by the photoelectric conversion layer 24. The excitons generated thereby move to the interface between the electron donor and the electron acceptor contained in the photoelectric conversion layer 24, and exciton separation occurs. In other words, the excitons are dissociated into electrons and holes. The charge (electrons and holes) generated here is transferred to different electrodes due to diffusion caused by the carrier concentration difference and the internal electric field caused by the work function difference between the anode (here, the upper electrode 27) and the cathode (here, the lower electrode 21). The transferred charge is detected as a photocurrent. In addition, by applying a potential between the lower electrode 21 and the upper electrode 27, the transfer directions of electrons and holes can be controlled.

[0059] The configuration, materials, etc. of each part will be described below.

[0060] The organic optoelectronic conversion unit 20 is an organic optoelectronic conversion element that absorbs green light corresponding to a selected wavelength range (including, for example, part or all of the wavelength range of 450 nm or more and 650 nm or less) and generates excitons.

[0061] As described above, the lower electrode 21 includes a separately formed readout electrode 21A and an accumulation electrode 21B. The readout electrode 21A is used to transfer the charges (here, electrons) generated in the organic optoelectronic conversion layer 24 to the floating diffusion section FD1. The readout electrode 21A is connected to the floating diffusion section FD1, for example, via the upper first contact 39C, the pad section 39A, the through electrode 34, the connection section 41A, and the lower second contact 46. The accumulation electrode 21B is used to accumulate electrons among the charges generated in the optoelectronic conversion layer 24 as signal charges in the charge accumulation layer 23. The accumulation electrode 21B is provided in a region that faces the light-receiving surfaces of the inorganic optoelectronic conversion sections 32B and 32R formed in the semiconductor substrate 30 and covers the light-receiving surfaces. Preferably, the accumulation electrode 21B is larger than the readout electrode 21A. This can accumulate more charges.

[0062] The lower electrode 21 includes a conductive film having translucency. The lower electrode 21 contains, for example, ITO (indium tin oxide). However, in addition to ITO, a tin oxide (SnO2)-based material doped with a dopant or a zinc oxide-based material obtained by adding a dopant to zinc oxide (ZnO) can also be used as the material included in the lower electrode 21. Examples of the zinc oxide-based material include aluminum-doped zinc oxide (AZO) with aluminum (Al) added as a dopant, gallium-doped zinc oxide (GZO) with gallium (Ga) added, and indium-doped zinc oxide (IZO) with indium (In) added. In addition, in addition to these, CuI, InSbO4, ZnMgO, CuInO2, MgIn2O4, CdO, ZnSnO3, etc. can also be used.

[0063] The charge accumulation layer 23 is provided under the photoelectric conversion layer 24. Specifically, the charge accumulation layer 23 is provided between the insulating layer 22 and the photoelectric conversion layer 24. The charge accumulation layer 23 is used to accumulate the signal charges generated in the photoelectric conversion layer 24. In the present embodiment, electrons are used as the signal charges. Therefore, preferably, the charge accumulation layer 23 is formed by using an n-type semiconductor material. For example, a material having an energy level shallower than the work function of the lower electrode 21 at the lowest edge of the conduction band is preferably used. Examples of such n-type semiconductor materials include IGZO (In-Ga-Zn-O-based oxide semiconductor), ZTO (Zn-Sn-O-based oxide semiconductor), IGZTO (In-Ga-Zn-Sn-O-based oxide semiconductor), GTO (Ga-Sn-O-based oxide semiconductor), IGO (In-Ga-O-based oxide semiconductor), etc. At least one of the above oxide semiconductor materials is preferably used for the charge accumulation layer 23. Among them, IGZO is preferably used. The thickness of the charge accumulation layer 23 is, for example, 30 nm or more and 200 nm or less. The thickness of the charge accumulation layer 23 is preferably 60 nm or more and 150 nm or less. By providing the charge accumulation layer 23 containing the above materials under the photoelectric conversion layer 24, charge recombination during charge accumulation can be prevented and the transfer efficiency can be improved.

[0064] The photoelectric conversion layer 24 is used to convert light energy into electrical energy. The photoelectric conversion layer 24 contains, for example, two or more organic semiconductor materials (p-type semiconductor material or n-type semiconductor material) respectively serving as a p-type semiconductor or an n-type semiconductor. The photoelectric conversion layer 24 has a junction surface (p / n junction surface) between these p-type semiconductor materials and n-type semiconductor materials in the layer. The p-type semiconductor serves as an electron donor relatively, and the n-type semiconductor serves as an electron acceptor relatively. The photoelectric conversion layer 24 provides a place where excitons generated when absorbing light are separated into electrons and holes there. Specifically, the excitons are separated into electrons and holes at the interface (p / n junction surface) between the electron donor and the electron acceptor.

[0065] In addition to the p-type semiconductor material and the n-type semiconductor material, the photoelectric conversion layer 24 may also contain an organic material or a so-called dye material. The organic material or the dye material performs photoelectric conversion on light in a predetermined wavelength range and transmits light in other wavelength ranges. When the photoelectric conversion layer 24 is formed by using these three organic materials, namely, the p-type semiconductor material, the n-type semiconductor material, and the dye material, the p-type semiconductor material and the n-type semiconductor material are preferably materials having light transmittance in the visible light region (for example, 450 nm or more and 800 nm or less). The photoelectric conversion layer 24 has a thickness of, for example, 50 nm or more and 500 nm or less.

[0066] Preferably, the photoelectric conversion layer 24 according to the present embodiment contains an organic material and has absorption between visible light and near-infrared light. Examples of the organic material contained in the photoelectric conversion layer 24 include quinacridone, boron subphthalocyanine chloride, pentacene, benzothienobenzothiophene, fullerenes and their derivatives. The photoelectric conversion layer 24 contains a combination of two or more of the above-mentioned organic materials. The above-mentioned organic materials act as p-type semiconductors or n-type semiconductors according to the combination.

[0067] Note that the organic material contained in the photoelectric conversion layer 24 is not particularly limited. For example, in addition to the above-mentioned organic materials, it is also preferable to use any one of naphthalene, anthracene, phenanthrene, tetracene, pyrene, perylene, fluoranthene or their derivatives. Alternatively, polymers or their derivatives such as phenyleneethyne, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene or diacetylene can be used. In addition, metal complex dyes, cyanine dyes, merocyanine dyes, phenylxanthene dyes, triphenylmethane dyes, rhodacyanine dyes, xanthene dyes, macrocyclic azacyanine dyes, azulene dyes, naphthoquinones, anthraquinone dyes, chain compounds in which fused polycyclic aryl groups such as anthracene and pyrene are fused with aromatic rings or heterocyclic compounds, or cyanine dyes in which two nitrogen-containing heterocycles such as quinoline, benzothiazole and benzoxazole are bonded through a squarylium group and a croconium group or through a squarylium group and a croconium group can be preferably used. Note that as the above-mentioned metal complex dyes, dithiol metal complex dyes, metal phthalocyanine dyes, metal porphyrin dyes or ruthenium complex dyes are preferable, but not limited thereto.

[0068] The work function adjustment layer 25 is provided on the upper layer of the photoelectric conversion layer 24. The work function adjustment layer 25 is used to change the internal electric field in the photoelectric conversion layer 24, so as to quickly transfer the signal charges generated in the photoelectric conversion layer 24 to the charge accumulation layer 23 and accumulate therein. The work function adjustment layer 25 has light transmittance. Preferably, the work function adjustment layer 25 has a light absorption rate of 10% or less for visible light, for example. In addition, a carbon-containing compound having an electron affinity greater than the work function of the charge accumulation layer 23 can be used to form the work function adjustment layer 25. Note that the electron affinity corresponds to the difference between the LUMO energy level (LUMO2) calculated from the following optical band gap and the vacuum energy level.

[0069] Examples of the material included in the work function adjustment layer 25 include tetracyanoquinodimethane derivatives such as 2,3,5,6-tetrafluoro-tetracyanoquinodimethane (F4-TCNQ), 2,3,5-trifluoro-tetracyanoquinodimethane (F3-TCNQ), 2,5-difluoro-tetracyanoquinodimethane (F2-TCNQ), 2-fluoro-tetracyanoquinodimethane (F1-TCNQ), 2-trifluoromethyl-tetracyanoquinodimethane (CF3-TCNQ), and 1,3,4,5,7,8-hexafluoro-tetracyano-naphthoquinodimethane (F6-TCNQ); hexaazatriphenylene derivatives such as 1,4,5,8,9,12-hexaazatriphenylene-2,3,6,7,10,11-hexacarbonitrile (HATCN); hexaazatrinaphthylene derivatives such as 2,3,8,9,14,15-hexachloro-5,6,11,12,17,18-hexaazatrinaphthalene (HATNA-Cl6) and 2,3,8,9,14,15-hexafluoro-5,6,11,12,17,18-hexaazatrinaphthalene (HATNA-F6); phthalocyanine derivatives such as 1,2,3,4,8,9,10,11,15,16,17,18,22,23,24,25-hexafluorocopper phthalocyanine (F16-CuPc); fluorinated fullerenes such as C 60 F 36 and C 60 F 48 and so on. Optionally, an inorganic compound having a work function greater than that of the lower electrode 21 (especially the accumulation electrode 21B) can be used to form the work function adjustment layer 25. Examples of such materials include transition metal oxides such as molybdenum oxide (MoO3), tungsten oxide (WO3), vanadium oxide (V2O5), and rhenium oxide (ReO3), and salts such as copper iodide (CuI), antimony pentachloride (SbCl5), iron(III) chloride (FeCl3), and sodium chloride (NaCl). The work function adjustment layer 25 can be formed as a single-layer film using only the above carbon-containing compound or inorganic compound, or can be formed as a laminated film including a layer of a carbon compound and a layer of an inorganic compound. In this case, considering the damage caused by the annealing treatment during the film formation of the upper electrode 27, it is preferable to sequentially stack the carbon-containing compound film and the inorganic compound film. The work function adjustment layer 25 has a thickness of, for example, 0.5 nm or more and 30 nm or less.

[0070] The electron injection promoting layer 26 is provided between the work function adjusting layer 25 and the upper electrode 27 and promotes the injection of electrons from the upper electrode 27. As in the present embodiment, in the imaging element 10 that reads out electrons as signal charges from the readout electrode 21A, holes generated by the photoelectric conversion layer 24 and electrons injected from the upper electrode 27 recombine at the interface between the work function adjusting layer 25 and the organic layer including the photoelectric conversion layer 24 adjacent to the work function adjusting layer 25. This recombination enables the effective readout of electrons (signal charges) from the readout electrode 21A. The recombination of holes and electrons at the interface between the work function adjusting layer 25 and the organic layer including the photoelectric conversion layer 24 adjacent to the work function adjusting layer 25 depends on the charge densities of the holes and electrons. The injection of electrons from the upper electrode 27 into the work function adjusting layer 25 is promoted by the electron injection promoting layer 26 having energy levels such as Figure 4A or Figure 4B shown.

[0071] For example, for the electron injection promoting layer 26, preferably, the absolute value B of the difference between the HOMO (highest occupied molecular orbital) energy level and the Fermi energy level of the upper electrode 27 is greater than or equal to the absolute value A (1) of the difference between the LUMO (lowest unoccupied molecular orbital) energy level (corresponding to LUMO2 or the first LUMO energy level) calculated from the optical band gap and the Fermi energy level of the upper electrode 27. Specifically, for example, preferably, the absolute value B of the difference between the HOMO energy level and the Fermi energy level of the upper electrode 27 is 1.5 times or more the absolute value A of the difference between LUMO2 and the Fermi energy level of the upper electrode 27. Further, for the electron injection promoting layer 26, preferably, the absolute value B of the difference between the HOMO energy level and the Fermi energy level of the upper electrode 27 is greater than the absolute value A' (2) of the difference between the LUMO energy level (LUMO1) and the Fermi energy level of the upper electrode 27.

[0072] Alternatively, preferably, the electron injection promoting layer 26 has an in-gap energy level (3) with a density of states relative to the HOMO energy level of 1 / 10000 or more near the Fermi energy level of the upper electrode 27. More specifically, for example, preferably, the absolute value b of the difference between the HOMO energy level and the in-gap energy level of the electron injection promoting layer 26 is 2 times or more the absolute value a of the difference between the LUMO energy level (LUMO2) calculated from the optical band gap and the in-gap energy level (4). Alternatively, preferably, the absolute value b of the difference between the HOMO energy level and the in-gap energy level of the electron injection promoting layer 26 is 1.5 times or more the absolute value a' of the difference between the LUMO energy level (LUMO1) and the in-gap energy level (5).

[0073] Note that the above-mentioned HOMO energy level and LUMO energy level (LUMO2) are obtained by using ultraviolet photoelectron spectroscopy (UPS) and ultraviolet-visible spectroscopy, respectively. The LUMO energy level (LUMO1) is obtained by using low-energy inverse photoelectron spectroscopy (LEIPS). The difference between LUMO1 and LUMO2 corresponds to the exciton binding energy.

[0074] Examples of the materials included in the electron injection layer promoter 26 include [2,9-bis(naphthalen-2-yl)-4,7-diphenyl-1,10-phenanthroline] (NBphen), naphthalenediimide-based molecules (e.g., NDI35), and lithium fluoride (LiF). Figure 5 The respective energy levels of NBphen are analyzed by high-sensitivity ultraviolet photoelectron spectroscopy (HS-UPS). NBphen satisfies the above (1), (3), and (4). In addition, even when considering the exciton binding energy, it satisfies the above (1), (2), and (5). Figure 6 The respective energy levels of NDI35 are analyzed by UPS and low-energy inverse photoelectron spectroscopy (LEIPS). NDI35 satisfies all of the above (1) to (5). The thickness of the electron injection promoting layer 26 is, for example, 0.5 nm or more and 10 nm or less.

[0075] Other organic layers may be provided between the photoelectric conversion layer 24 and the lower electrode 21 (e.g., between the charge accumulation layer 23 and the photoelectric conversion layer 24) and between the photoelectric conversion layer 24 and the upper electrode 27 (e.g., between the photoelectric conversion layer 24 and the work function adjustment layer 25). Specifically, for example, the charge accumulation layer 23, the hole blocking layer, the photoelectric conversion layer 24, the electron blocking layer, the work function adjustment layer 25, the electron injection promoting layer 26, etc. may be sequentially stacked from the lower electrode 21 side. In addition, a bottom layer and a hole transport layer may be provided between the lower electrode 21 and the photoelectric conversion layer 24, and a buffer layer, etc. may be provided between the photoelectric conversion layer 24 and the upper electrode 27. Note that when a buffer layer adjacent to the electron injection promoting layer 26, for example, is provided between the photoelectric conversion layer 24 and the upper electrode 27, the buffer layer preferably has an energy level shallower than the work function of the work function adjustment layer 25. In addition, the buffer layer is preferably formed of an organic material having a glass transition point higher than, for example, 100°C.

[0076] Like the lower electrode 21, the upper electrode 27 includes a conductive film having translucency. In the imaging device 1 in which the imaging element 10 is used as one pixel, the upper electrode 27 may be separated for each pixel, or the upper electrode 27 may be formed as an electrode shared by each pixel. For example, the work function of the upper electrode 27 is smaller than the work function of the work function adjustment layer 25. The thickness of the upper electrode 27 is, for example, 10 nm to 200 nm.

[0077] The fixed charge layer 28A can be a film with positive fixed charges or a film with negative fixed charges. As materials for the film with negative fixed charges, it includes hafnium oxide, aluminum oxide, zirconium oxide, tantalum oxide, titanium oxide, etc. In addition, as materials other than the above, it also includes lanthanum oxide, praseodymium oxide, cerium oxide, neodymium oxide, promethium oxide, samarium oxide, europium oxide, gadolinium oxide, terbium oxide, dysprosium oxide, holmium oxide, thulium oxide, ytterbium oxide, lutetium oxide, yttrium oxide, aluminum nitride film, hafnium oxynitride film, aluminum oxynitride film, etc.

[0078] The fixed charge layer 28A can also have a structure in which two or more types of film layers are stacked. In the case of a film with negative fixed charges, for example, this can further enhance the function as a hole accumulation layer.

[0079] Although the material of the dielectric layer 28B is not particularly limited, the dielectric layer 28B is formed by using, for example, a silicon oxide film, TEOS, a silicon nitride film, a silicon oxynitride film, etc.

[0080] The interlayer insulating layer 29 includes, for example, a single-layer film containing one of silicon oxide, silicon nitride, silicon oxynitride (SiON), etc., or a stacked film containing two or more of them.

[0081] The insulating layer 22 is used to electrically isolate the accumulation electrode 21B and the charge accumulation layer 23. The insulating layer 22 is disposed, for example, above the interlayer insulating layer 29 to cover the lower electrode 21. As described above, the insulating layer 22 has an opening 22H above the readout electrode 21A, and the readout electrode 21A and the charge accumulation layer 23 are electrically connected via the opening 22H. The insulating layer 22 can be formed by using, for example, a material similar to that of the interlayer insulating layer 29. The insulating layer 22 includes, for example, a single-layer film containing one of silicon oxide, silicon nitride, silicon oxynitride (SiON), or a stacked film containing two or more of them. The insulating layer 22 has a thickness of, for example, 20 nm to 500 nm.

[0082] The semiconductor substrate 30 includes, for example, an n-type silicon (Si) substrate and includes a p-well 31 in a predetermined region. The above-mentioned transfer transistors Tr2 and Tr3, amplifier transistor AMP, reset transistor RST, selection transistor SEL, etc. are disposed on the second surface 30B of the p-well 31. In addition, a peripheral circuit portion 130 including a logic circuit, etc. (for example, see Figure 15 ) is provided in the peripheral portion of the semiconductor substrate 30.

[0083] The reset transistor RST (reset transistor Tr1rst) resets the charge transferred from the organic photoelectric conversion unit 20 to the floating diffusion unit FD1, and includes, for example, a MOS transistor. Specifically, the reset transistor Tr1rst includes a reset gate Grst, a channel formation region 36A, and source / drain regions 36B and 36C. The reset gate Grst is connected to the reset line RST1. One of the source / drain regions 36B of the reset transistor Tr1rst also serves as the floating diffusion unit FD1. The other source / drain region 36C included in the reset transistor Tr1rst is connected to the power supply line VDD.

[0084] The amplification transistor AMP is a modulation element that modulates the amount of charge generated by the organic photoelectric conversion unit 20 into a voltage, and includes, for example, a MOS transistor. Specifically, the amplification transistor AMP includes a gate Gamp, a channel formation region 35A, and source / drain regions 35B and 35C. The gate Gamp is connected to the readout electrode 21A and one of the source / drain regions 36B (floating diffusion unit FD1) of the reset transistor Tr1rst via the lower first contact 45, the connection portion 41A, the lower second contact 46, the through electrode 34, etc. In addition, one of the source / drain regions 35B shares a region with the other source / drain region 36C included in the reset transistor Tr1rst and is connected to the power supply line VDD.

[0085] The selection transistor SEL (selection transistor TR1sel) includes a gate Gsel, a channel formation region 34A, and source / drain regions 34B and 34C. The gate Gsel is connected to the selection line SEL1. In addition, one of the source / drain regions 34B shares a region with the other source / drain region 35C included in the amplification transistor AMP, and the other source / drain region 34C is connected to the signal line (data output line) VSL1.

[0086] Each of the inorganic photoelectric conversion units 32B and 32R has a pn junction in a predetermined region of the semiconductor substrate 30. Each of the inorganic photoelectric conversion units 32B and 32R allows light to be spectroscopically analyzed in the longitudinal direction because the light to be absorbed has wavelengths that vary according to the depth of light incidence in the silicon substrate. The inorganic photoelectric conversion unit 32B selectively detects, for example, blue light to accumulate signal charges corresponding to blue. The inorganic photoelectric conversion unit 32B is installed at a depth that allows efficient photoelectric conversion of blue light. The inorganic photoelectric conversion unit 32R selectively detects, for example, red light to accumulate signal charges corresponding to red. The inorganic photoelectric conversion unit 32R is installed at a depth that allows efficient photoelectric conversion of red light. Note that blue (B) is a color corresponding to a wavelength range of, for example, 450 nm to 495 nm, and red (R) is a color corresponding to a wavelength range of, for example, 620 nm to 750 nm. It is sufficient that each of the inorganic photoelectric conversion units 32B and 32R is configured to detect light in part or all of each wavelength range.

[0087] The inorganic photoelectric conversion unit 32B includes, for example, a p+ region serving as a hole accumulation layer and an n region serving as an electron accumulation layer. The inorganic photoelectric conversion unit 32R includes, for example, a p+ region serving as a hole accumulation layer and an n region (having a p-n-p stack structure) serving as an electron accumulation layer. The n region of the inorganic photoelectric conversion unit 32B is connected to the vertical transfer transistor Tr2. The p+ region of the inorganic photoelectric conversion unit 32B bends along the transfer transistor Tr2 and leads to the p+ region of the inorganic photoelectric conversion unit 32R.

[0088] The transfer transistor Tr2 (transfer transistor TR2trs) is used to transfer the signal charges (here, electrons) corresponding to blue, which are generated and accumulated in the inorganic photoelectric conversion unit 32B, to the floating diffusion section FD2. Since the inorganic photoelectric conversion unit 32B is formed at a position deeper from the second surface 30B of the semiconductor substrate 30, preferably, the transfer transistor TR2trs of the inorganic photoelectric conversion unit 32B includes a vertical transistor. In addition, the transfer transistor TR2trs is connected to the transfer gate line TG2. In addition, the floating diffusion section FD2 is provided in a region 37C near the gate Gtrs2 of the transfer transistor TR2trs. The charges accumulated in the inorganic photoelectric conversion unit 32B are read out to the floating diffusion section FD2 via a transfer channel formed along the gate Gtrs2.

[0089] The transfer transistor Tr3 (transfer transistor TR3trs) transfers the signal charge (here, electrons) corresponding to red, which is generated and accumulated in the inorganic photoelectric conversion section 32R, to the floating diffusion section FD3. The transfer transistor Tr3 (transfer transistor TR3trs) includes, for example, a MOS transistor. In addition, the transfer transistor TR3trs is connected to the transfer gate line TG3. Further, the floating diffusion section FD3 is provided in the region 38C near the gate Gtrs3 of the transfer transistor TR3trs. The charge accumulated in the inorganic photoelectric conversion section 32R is read out to the floating diffusion section FD3 via the transfer channel formed along the gate Gtrs3.

[0090] On the second surface 30B side of the semiconductor substrate 30, a reset transistor TR2rst, an amplification transistor TR2amp, and a selection transistor TR2sel, which are included in the control section of the inorganic photoelectric conversion section 32B, are also provided. In addition, a reset transistor TR3rst, an amplification transistor TR3amp, and a selection transistor TR3sel, which are included in the control section of the inorganic photoelectric conversion section 32R, are provided.

[0091] The reset transistor TR2rst includes a gate, a channel formation region, and source / drain regions. The gate of the reset transistor TR2rst is connected to the reset line RST2, and one source / drain region of the reset transistor TR2rst is connected to the power supply line VDD. The other source / drain region of the reset transistor TR2rst also serves as the floating diffusion section FD2.

[0092] The amplification transistor TR2amp includes a gate, a channel formation region, and source / drain regions. The gate is connected to the other source / drain region (floating diffusion section FD2) of the reset transistor TR2rst. In addition, one source / drain region included in the amplification transistor TR2amp shares a region with one source / drain region included in the reset transistor TR2rst and is connected to the power supply line VDD.

[0093] The selection transistor TR2sel includes a gate, a channel formation region, and source / drain regions. The gate is connected to the selection line SEL2. In addition, one source / drain region included in the selection transistor TR2sel shares a region with the other source / drain region included in the amplification transistor TR2amp. The other source / drain region included in the selection transistor TR2sel is connected to the signal line (data output line) VSL2.

[0094] The reset transistor TR3rst includes a gate, a channel formation region, and a source / drain region. The gate of the reset transistor TR3rst is connected to the reset line RST3, and one of the source / drain regions included in the reset transistor TR3rst is connected to the power supply line VDD. The other source / drain region included in the reset transistor TR3rst also serves as the floating diffusion region FD3.

[0095] The amplification transistor TR3amp includes a gate, a channel formation region, and a source / drain region. The gate is connected to the other source / drain region (floating diffusion portion FD3) included in the reset transistor TR3rst. In addition, one of the source / drain regions included in the amplification transistor TR3amp shares a region with one of the source / drain regions included in the reset transistor TR3rst and is connected to the power supply line VDD.

[0096] The selection transistor TR3sel includes a gate, a channel formation region, and a source / drain region. The gate is connected to the selection line SEL3. In addition, one of the source / drain regions included in the selection transistor TR3sel shares a region with the other source / drain region included in the amplification transistor TR3amp. The other source / drain region included in the selection transistor TR3sel is connected to the signal line (data output line) VSL3.

[0097] The reset lines RST1, RST2, and RST3, the selection lines SEL1, SEL2, and SEL3, and the transfer gate lines TG2 and TG3 are all connected to the vertical drive circuit 112 included in the drive circuit. The signal lines (data output lines) VSL1, VSL2, and VSL3 are connected to the column signal processing circuit 113 included in the drive circuit.

[0098] For example, the lower first contact 45, the lower second contact 46, the upper first contact 39C, and the upper second contact 39D all contain doped silicon materials such as PDAS (phosphorus-doped amorphous silicon) or metal materials such as aluminum (Al), tungsten (W), titanium (Ti), cobalt (Co), hafnium (Hf), or tantalum (Ta).

[0099] The protective layer 51 is provided above the organic optoelectronic conversion unit 20 and contains a material having light transmissibility. Specifically, the protective layer 51 includes, for example, a single-layer film containing any one of silicon oxide, silicon nitride, silicon oxynitride, etc., or a laminated film containing two or more of them. The protective layer 51 has a thickness of, for example, 100 nm to 30000 nm.

[0100] The light-shielding film 52 is disposed, for example, within the protective layer 51 so as to cover the readout electrode 21A. Examples of the material of the light-shielding film 52 include tungsten (W), titanium (Ti), titanium nitride (TiN), or aluminum (Al). The light-shielding film 52 is configured, for example, as a stacked film of W / TiN / Ti or a single-layer film of W. The thickness of the light-shielding film 52 is, for example, 50 nm or more and 400 nm or less.

[0101] On the protective layer 51, the pixel portion 1a is provided with an on-chip lens 53, for example, for each unit pixel P. The on-chip lens 53 converges incident light onto the light-receiving surfaces of the organic photoelectric conversion portion 20, the inorganic photoelectric conversion portion 32B, and the inorganic photoelectric conversion portion 32R, respectively.

[0102] (1-2. Method of manufacturing the imaging element)

[0103] For example, the imaging element 10 according to the present embodiment can be manufactured as follows.

[0104] Figures 7 to 13 The method of manufacturing the imaging element 10 is shown in sequential steps. First, as Figure 7 shown, for example, a p-well 31 as a well of the first conductivity type is formed within the semiconductor substrate 30. The inorganic photoelectric conversion portions 32B and 32R of the second conductivity type (e.g., n-type) are formed within the p-well 31. A p+ region is formed near the first surface 30A of the semiconductor substrate 30.

[0105] Similarly, as Figure 7 shown, for example, n+ regions serving as the floating diffusion portions FD1 to FD3 are formed on the second surface 30B of the semiconductor substrate 30, and then a gate insulating layer 33 and a gate wiring layer 47 are formed. The gate wiring layer 47 includes the gates of the transfer transistors Tr2, Tr3, the selection transistor SEL, the amplification transistor AMP, and the reset transistor RST. Thus, the transfer transistors Tr2, Tr3, the selection transistor SEL, the amplification transistor AMP, and the reset transistor RST are formed. In addition, a multilayer wiring layer 40 is formed on the second surface 30B of the semiconductor substrate 30. The multilayer wiring layer 40 includes wiring layers 41 to 43 and an insulating layer 44. The wiring layers 41 to 43 include a lower first contact 45, a lower second contact 46, and a connection portion 41A.

[0106] As the substrate of the semiconductor substrate 30, for example, an SOI (silicon-on-insulator) substrate is used, in which a semiconductor substrate 30, a buried oxide film (not shown), and a holding substrate (not shown) are stacked. Although not shown in Figure 7 , the buried oxide film and the holding substrate are bonded to the first surface 30A of the semiconductor substrate 30. After ion implantation, an annealing process is performed.

[0107] Next, a support substrate (not shown), another semiconductor substrate, etc. are bonded to the second surface 30B side (the multi-layer wiring layer 40 side) of the semiconductor substrate 30, and then the substrate is turned upside down. Subsequently, the semiconductor substrate 30 is separated from the buried oxide film of the SOI substrate and the holding substrate to expose the first surface 30A of the semiconductor substrate 30. The above steps can be performed using techniques employed in ordinary CMOS processes such as ion implantation and CVD (Chemical Vapor Deposition).

[0108] Next, as Figure 8 shown, the semiconductor substrate 30 is processed from the first surface 30A side, for example, by dry etching to form, for example, an annular opening 34H. As Figure 8 shown, the depth of the opening 34H extends from the first surface 30A of the semiconductor substrate 30 to the second surface 30B and reaches, for example, the connection portion 41A.

[0109] Subsequently, for example, a negative fixed charge layer 28A is formed on the first surface 30A of the semiconductor substrate 30 and the side surfaces of the opening 34H. Two or more types of films can be stacked as the negative fixed charge layer 28A. This can further enhance the function as a hole accumulation layer. After forming the negative fixed charge layer 28A, a dielectric layer 28B is formed. Next, pad portions 39A and 39B are formed at predetermined positions on the dielectric layer 28B. Thereafter, an interlayer insulating layer 29 is formed on the dielectric layer 28B and the pad portions 39A and 39B, and the surface of the interlayer insulating layer 29 is planarized using the CMP (Chemical Mechanical Polishing) method.

[0110] Subsequently, as Figure 9 shown, openings 29H1 and 29H2 are respectively formed above the pad portions 39A and 39B. Then, these openings 29H1 and 29H2 are filled with a conductive material such as Al, for example, to form an upper first contact 39C and an upper second contact 39D.

[0111] Next, as Figure 10 shown, a conductive film 21x is formed on the interlayer insulating layer 29. Thereafter, a photoresist PR is formed at a predetermined position on the conductive film 21x. Subsequently, by etching and removing the photoresist PR, as Figure 11 shown, the readout electrode 21A and the accumulation electrode 21B are patterned.

[0112] Subsequently, as Figure 12 shown, an insulating layer 22 is formed on the interlayer insulating layer 29, the readout electrode 21A, and the accumulation electrode 21B. Thereafter, an opening 22H is provided above the readout electrode 21A.

[0113] Next, as Figure 13As shown, a charge accumulation layer 23, a photoelectric conversion layer 24, a work function adjustment layer 25, an electron injection promotion layer 26, and an upper electrode 27 are formed on an insulating layer 22. Note that when the charge accumulation layer 23, the work function adjustment layer 25, and the electron injection promotion layer 26 are formed of an organic material, it is desirable to continuously form the charge accumulation layer 23, the photoelectric conversion layer 24, and the work function adjustment layer 25 in a vacuum process (in-situ vacuum process). In addition, the method of forming the photoelectric conversion layer 24 does not have to be limited to the technique using a vacuum evaporation method. Other methods, such as a spin coating technique or a printing technique, can be used. Finally, a protective layer 51 including a light-shielding film 52 and an on-chip lens 53 are formed above the organic photoelectric conversion unit 20. Thus, the Figure 1 imaging element 10 shown is completed.

[0114] In the imaging element 10, when light enters the organic photoelectric conversion unit 20 via the on-chip lens 53, the light sequentially passes through the organic photoelectric conversion unit 20 and the inorganic photoelectric conversion units 32B and 32R. When the light passes through the organic photoelectric conversion unit 20 and the inorganic photoelectric conversion units 32B and 32R, photoelectric conversion is performed for each of green light, blue light, and red light. The operation of obtaining signals of various colors will be described below.

[0115] (Obtaining a green signal through the organic photoelectric conversion unit 20)

[0116] First, among the light entering the imaging element 10, green light is selectively detected (absorbed) and photoelectrically converted by the organic photoelectric conversion unit 20.

[0117] The organic photoelectric conversion unit 20 is connected to the gate Gamp of the amplification transistor AMP and the floating diffusion portion FD1 via the through electrode 34. Therefore, among the electron-hole pairs generated by the organic photoelectric conversion unit 20, electrons are taken out from the lower electrode 21 side, transmitted to the second surface 30B side of the semiconductor substrate 30 via the through electrode 34, and accumulated in the floating diffusion portion FD1. At the same time, the amplification transistor AMP modulates the amount of charge generated by the organic photoelectric conversion unit 20 into a voltage.

[0118] In addition, the reset gate Grst of the reset transistor RST is arranged adjacent to the floating diffusion portion FD1. This causes the reset transistor RST to reset the charge accumulated in the floating diffusion portion FD1.

[0119] Here, the organic photoelectric conversion unit 20 is connected not only to the amplification transistor AMP via the through electrode 34 but also to the floating diffusion portion FD1, allowing the reset transistor RST to easily reset the charge accumulated in the floating diffusion portion FD1.

[0120] In contrast, when the through electrode 34 and the floating diffusion section FD1 are not connected, it is difficult to reset the charge accumulated in the floating diffusion section FD1. A large voltage must be applied to pull the charge to the upper electrode 27 side. As a result, the photoelectric conversion layer 24 may be damaged. In addition, a structure that allows resetting in a short time causes an increase in dark-time noise, which is a trade-off, and such a structure is difficult to achieve.

[0121] Figure 14 An operation example of the imaging element 10 is shown. (A) shows the potential at the accumulation electrode 21B, (B) shows the potential at the floating diffusion section FD1 (readout electrode 21A), and (C) shows the potential at the gate (Gsel) of the reset transistor TR1rst. In the imaging element 10, voltages are applied to the readout electrode 21A and the accumulation electrode 21B, respectively.

[0122] In the imaging element 10, during the accumulation period, the drive circuit applies a potential V1 to the readout electrode 21A and a potential V2 to the accumulation electrode 21B. Here, it is assumed that the potentials V1 and V2 satisfy V2 > V1. This causes the charge (here, electrons) generated by photoelectric conversion to be attracted to the accumulation electrode 21B and accumulated in the region of the charge accumulation layer 23 opposite to the accumulation electrode 21B (during the accumulation period). In addition, as the photoelectric conversion time progresses, the potential value in the region of the charge accumulation layer 23 opposite to the accumulation electrode 21B becomes more negative. Note that holes are transferred from the upper electrode 27 to the drive circuit.

[0123] In the imaging element 10, a reset operation is performed in the latter stage of the accumulation period. Specifically, at time t1, the scanning section changes the voltage of the reset signal RST from low level to high level. This turns on the reset transistor TR1rst in the unit pixel P, and as a result, the voltage of the floating diffusion section FD1 is set to the power supply line VDD, and the voltage of the floating diffusion section FD1 is reset (during the reset period).

[0124] After the reset operation is completed, the charge is read out. Specifically, at time t2, the drive circuit applies a potential V3 to the readout electrode 21A and a potential V4 to the accumulation electrode 21B. Here, it is assumed that the potentials V3 and V4 satisfy V3 < V4. This causes the charge (here, electrons) accumulated in the region corresponding to the accumulation electrode 21B to be read out from the readout electrode 21A to the floating diffusion section FD1. In other words, the charge accumulated in the charge accumulation layer 23 is read out to the control section (during the transfer period).

[0125] After the readout operation is completed, the drive circuit applies the potential V1 to the readout electrode 21A again, and applies the potential V2 to the accumulation electrode 21B. This causes the charges (here, electrons) generated by photoelectric conversion to be attracted to the accumulation electrode 21B and accumulate in the region of the photoelectric conversion layer 24 opposite to the accumulation electrode 21B (during the accumulation period).

[0126] (Obtaining blue and red signals through the inorganic photoelectric conversion units 32B and 32R)

[0127] Subsequently, among the light passing through the organic photoelectric conversion unit 20, blue light and red light are sequentially absorbed and photoelectrically converted by the inorganic photoelectric conversion unit 32B and the inorganic photoelectric conversion unit 32R, respectively. In the inorganic photoelectric conversion unit 32B, electrons corresponding to the incident blue light are accumulated in the n-region of the inorganic photoelectric conversion unit 32B, and the accumulated electrons are transferred to the floating diffusion unit FD2 by the transfer transistor Tr2. Similarly, in the inorganic photoelectric conversion unit 32R, electrons corresponding to the incident red light are accumulated in the n-region of the inorganic photoelectric conversion unit 32R, and the accumulated electrons are transferred to the floating diffusion unit FD3 by the transfer transistor Tr3.

[0128] (1-3. Functions and effects)

[0129] In the imaging element 10 according to the present embodiment, the work function adjustment layer 25 and the electron injection promotion layer 26 having a predetermined energy level are sequentially stacked from the side of the photoelectric conversion layer 24 between the photoelectric conversion layer 24 and the upper electrode 27. The work function adjustment layer 25 contains at least one of a carbon-containing compound having an electron affinity greater than the work function of the lower electrode 21 and an inorganic compound having a work function greater than the work function of the lower electrode 21. The electron injection promotion layer 26 has an energy level such that the absolute value B of the difference between the HOMO energy level and the Fermi energy level of the upper electrode 27 is greater than or equal to the absolute value A of the difference between the LUMO energy level (LUMO2) calculated from the optical band gap and the Fermi energy level. Alternatively, the electron injection promotion layer 26 has an in-band energy level near the Fermi energy level of the upper electrode 27 with a density of states relative to the HOMO energy level of 1 / 10000 or more. This promotes the injection of electrons from the upper electrode 27 into the work function adjustment layer 25. This will be described below.

[0130] In an imaging device that separately extracts B / G / R signals from one pixel, as described above, charges generated in the semiconductor substrate are temporarily accumulated in respective photoelectric conversion sections (photoelectric diodes PD1 and PD2) formed in the semiconductor substrate, and then transferred to corresponding floating diffusion sections FD. This enables complete depletion of each photoelectric conversion section. In contrast, charges generated by photoelectric conversion performed by an organic photoelectric conversion section disposed, for example, above the semiconductor substrate are directly accumulated in the floating diffusion section FD provided in the semiconductor substrate via a vertical transfer path provided in the semiconductor substrate. This makes it difficult to completely deplete the photoelectric conversion layer, thereby increasing kTC noise and degrading random noise. This results in a reduction in image quality during imaging.

[0131] As a method for solving this problem, an imaging element provided with a charge accumulation electrode is designed. The charge accumulation electrode is configured to be separated from one of a pair of electrodes (for example, a lower electrode) that are disposed opposite each other with the photoelectric conversion layer interposed therebetween. In addition, the charge accumulation electrode faces the photoelectric conversion layer with an insulating layer interposed therebetween. In this imaging element, charges generated in the photoelectric conversion layer are accumulated in a region of the photoelectric conversion layer that faces the charge accumulation electrode. The accumulated charges are appropriately transferred and read out to the charge readout electrode side. This enables complete depletion of the charge accumulation section at the start of exposure, thereby suppressing kTC noise and improving image quality during imaging. Further, such an imaging element is provided with a semiconductor layer using a metal oxide (for example, which is an n-type semiconductor such as IGZO) below the photoelectric conversion layer. This can prevent recombination of charges during charge accumulation and further improve the efficiency of transferring the accumulated charges to the charge readout electrode.

[0132] However, when a metal oxide as an n-type semiconductor is used for the semiconductor layer, there is a problem that electrons generated in the photoelectric conversion layer by light irradiation are rapidly transferred to and accumulated in the semiconductor layer. This problem can be solved by improving the light responsiveness of the photoelectric conversion layer.

[0133] In contrast, in the present embodiment, the electron injection promoting layer 26 is disposed between the work function adjusting layer 25 provided above the photoelectric conversion layer 24 and the upper electrode 27. The electron injection promoting layer 26 has the following values as energy levels after being joined to the upper electrode 27. When the electron injection promoting layer 26 is joined to the upper electrode 27, the HOMO energy level and the LUMO energy level migrate in the deep direction according to the Fermi energy level of the upper electrode 27. The Fermi energy level of the upper electrode 27 and the LUMO energy level of the electron injection promoting layer 26 are close to each other in energy. Specifically, in the present embodiment, the electron injection promoting layer 26 is provided such that the absolute value B of the difference between the HOMO energy level and the Fermi energy level of the upper electrode 27 is greater than or equal to the absolute value A of the difference between the LUMO energy level (LUMO2) calculated from the optical band gap and the Fermi energy level, or has an in-gap energy level with a density of states relative to the HOMO energy level of 1 / 10,000 or more near the Fermi energy level. In other words, at the interface between the work function adjusting layer 25 and the organic layer including the photoelectric conversion layer 24 adjacent to the work function adjusting layer 25, the carrier density of electrons increases.

[0134] Therefore, in the imaging element 10 according to the present embodiment, the recombination of holes and electrons at the interface between the work function adjusting layer 25 and the organic layer including the photoelectric conversion layer 24 adjacent to the work function adjusting layer 25 is promoted. This can improve the light responsiveness of the photoelectric conversion layer 24.

[0135] <2. Application Examples>

[0136] (Application Example 1)

[0137] Figure 15 The overall configuration of an imaging device (imaging device 1) in which the imaging element 10 described in the above embodiment is used for each pixel is shown. The imaging device 1 is a CMOS image sensor. The imaging device 1 includes a pixel portion 1a as an imaging region on a semiconductor substrate 30 and a peripheral circuit portion 130 in a peripheral region of the pixel portion 1a. The peripheral circuit portion 130 includes, for example, a row scanning portion 131, a horizontal selection portion 133, a column scanning portion 134, and a system control portion 132.

[0138] The pixel portion 1a includes, for example, a plurality of unit pixels P (each corresponding to the imaging element 10) two-dimensionally arranged in a matrix. These unit pixels P are provided with, for example, pixel drive lines Lread (specifically, row selection lines and reset control lines) for each pixel row, and vertical signal lines Lsig for each pixel column. The pixel drive lines Lread transmit drive signals for reading signals from the pixels. One end of the pixel drive lines Lread is connected to the output ends corresponding to the respective rows of the row scanning portion 131.

[0139] The line scanning unit 131 is a pixel driving unit that includes a shift register, an address decoder, etc., and drives each unit pixel P of the pixel unit 1a line by line, for example. Signals output from each unit pixel P in the pixel row selectively scanned by the line scanning unit 131 are supplied to the horizontal selection unit 133 through respective vertical signal lines Lsig. The horizontal selection unit 133 includes amplifiers, horizontal selection switches, etc. provided for each vertical signal line Lsig.

[0140] The column scanning unit 134 includes a shift register, an address decoder, etc. The column scanning unit 134 drives sequentially while scanning each horizontal selection switch of the horizontal selection unit 133. Through the selective scanning of the column scanning unit 134, signals of each pixel transmitted through respective vertical signal lines Lsig are sequentially output to the horizontal signal line 135, and the signals are transmitted to the outside of the semiconductor substrate 30 through the horizontal signal line 135.

[0141] The circuit portion including the line scanning unit 131, the horizontal selection unit 133, the column scanning unit 134, and the horizontal signal line 135 can be formed directly on the semiconductor substrate 30, or can be provided on an external control IC. In addition, the circuit portion can be formed in another substrate connected by a cable or the like.

[0142] The system control unit 132 receives a clock, data for an instruction regarding an operation mode, etc. supplied from the outside of the semiconductor substrate 30, and outputs data such as internal information of the imaging device 1. The system control unit 132 also includes a timing generator that generates various timing signals, and controls the driving of peripheral circuits such as the line scanning unit 131, the horizontal selection unit 133, and the column scanning unit 134 based on the various timing signals generated by the timing generator.

[0143] (Application Example 2)

[0144] The above imaging device 1 is applicable to any type of electronic device having an imaging function, including camera systems such as digital cameras, video cameras, etc., mobile phones having an imaging function, and the like. Figure 16 The schematic configuration of an electronic device 2 (camera) is shown as an example thereof. The electronic device 2 is, for example, a video camera capable of shooting still images or moving images. The electronic device 2 includes an imaging device 1, an optical system (optical lens) 210, a shutter device 211, a driving unit 213 that drives the imaging device 1 and the shutter device 211, and a signal processing unit 212.

[0145] The optical system 210 guides the image light (incident light) from the subject to the pixel section 1a of the imaging device 1. The optical system 210 may include a plurality of optical lenses. The shutter device 211 controls the light irradiation period and the light shielding period of the imaging device 1. The drive unit 213 controls the transfer operation of the imaging device 1 and the shutter operation of the shutter device 211. The signal processing unit 212 performs various signal processes on the signal output from the imaging device 1. The image signal Dout that has undergone signal processing is stored in a storage medium such as a memory or output to a monitor or the like.

[0146] In addition, the above-described imaging device 1 is also applicable to the following electronic devices (the capsule endoscope 10100 and a moving body such as a vehicle).

[0147] <3. Application Example>

[0148] [Application Example of In-Vivo Information Acquisition System]

[0149] Furthermore, the technology according to the present disclosure (this technology) is applicable to various products. For example, the technology according to the present disclosure can be applied to an endoscopic surgical system.

[0150] Figure 17 is a block diagram showing an example of a schematic configuration of an in-vivo information acquisition system for a patient using a capsule endoscope to which the technology (this technology) according to an embodiment of the present disclosure can be applied.

[0151] The in-vivo information acquisition system 10001 includes a capsule endoscope 10100 and an external control device 10200.

[0152] The capsule endoscope 10100 is swallowed by the patient during an examination. The capsule endoscope 10100 has an image pickup function and a wireless communication function, and sequentially captures internal images (hereinafter referred to as in-vivo images) of organs at predetermined intervals while moving through organs such as the stomach or intestine by peristaltic movement until it is naturally discharged from the patient. Then, the capsule endoscope 10100 sequentially transmits information on the in-vivo images to the external control device 10200 outside the body by wireless transmission.

[0153] The external control device 10200 comprehensively controls the operation of the in-vivo information acquisition system 10001. In addition, the external control device 10200 receives the information on the in-vivo images sent from the capsule endoscope 10100, and generates image data for displaying the in-vivo images on a display device (not shown) based on the received information on the in-vivo images.

[0154] In the in-vivo information acquisition system 10001, in-vivo images of the state of the patient's body can be captured at any time during the period from when the capsule endoscope 10100 is swallowed until it is discharged.

[0155] The configurations and functions of the capsule endoscope 10100 and the external control device 10200 will be described in more detail below.

[0156] The capsule endoscope 10100 includes a capsule-shaped housing 10101, which houses a light source unit 10111, an image pickup unit 10112, an image processing unit 10113, a wireless communication unit 10114, a power supply unit 10115, a power source unit 10116, and a control unit 10117.

[0157] The light source unit 10111 includes, for example, a light source such as a light-emitting diode (LED), and irradiates light onto the imaging field of view of the image pickup unit 10112.

[0158] The image pickup unit 10112 includes an image pickup element and an optical system, and the optical system includes a plurality of lenses provided in front of the image pickup element. The reflected light of the light irradiated on the body tissue as the observation object (hereinafter referred to as observation light) is converged by the optical system and incident on the image pickup element. In the image pickup unit 10112, the incident observation light is photoelectrically converted by the image pickup element, thereby generating an image signal corresponding to the observation light. The image signal generated by the image pickup unit 10112 is supplied to the image processing unit 10113.

[0159] The image processing unit 10113 includes a processor such as a central processing unit (CPU) or a graphics processing unit (GPU), and performs various signal processes on the image signal generated by the image pickup unit 10112. The image processing unit 10113 supplies the image signal on which the signal process has been performed as RAW data to the wireless communication unit 10114.

[0160] The wireless communication unit 10114 performs predetermined processes such as modulation processing on the image signal that has been signal-processed by the image processing unit 10113, and transmits it to the external control device 10200 via the antenna 10114A. In addition, the wireless communication unit 10114 receives a control signal related to the drive control of the capsule endoscope 10100 from the external control device 10200 via the antenna 10114A. The wireless communication unit 10114 supplies the control signal received from the external control device 10200 to the control unit 10117.

[0161] The power supply unit 10115 includes an antenna coil for receiving power, a power regeneration circuit for regenerating power from the current generated in the antenna coil, a booster circuit, etc. The power supply unit 10115 generates power using the principle of non-contact charging.

[0162] The power source unit 10116 includes a secondary battery and stores the power generated by the power supply unit 10115. Figure 17In order to avoid complex illustrations, arrow marks indicating the supply destinations of the power from the power supply unit 10116 are omitted. However, the power stored in the power supply unit 10116 is supplied to the light source unit 10111, the image pickup unit 10112, the image processing unit 10113, the wireless communication unit 10114, and the control unit 10117 and can be used for driving.

[0163] The control unit 10117 includes a processor such as a CPU and appropriately controls the driving of the light source unit 10111, the image pickup unit 10112, the image processing unit 10113, the wireless communication unit 10114, and the power supply unit 10115 according to the control signals transmitted thereto from the external control device 10200.

[0164] The external control device 10200 includes a processor such as a CPU or a GPU or a microcomputer, a control board, etc. in which a processor and a storage element such as a memory are mixedly installed. The external control device 10200 transmits a control signal to the control unit 10117 of the capsule endoscope 10100 through the antenna 10200A to control the operation of the capsule endoscope 10100. In the capsule endoscope 10100, for example, the light irradiation conditions on the observation object of the light source unit 10111 can be changed according to the control signal from the external control device 10200. In addition, the image pickup conditions (e.g., the frame rate, the exposure value, etc. of the image pickup unit 10112) can be changed according to the control signal from the external control device 10200. In addition, the processing content of the image processing unit 10113 or the conditions for transmitting the image signal from the wireless communication unit 10114 (e.g., the transmission interval, the number of transmitted images, etc.) can be changed according to the control signal from the external control device 10200.

[0165] In addition, the external control device 10200 performs various image processes on the image signal transmitted from the capsule endoscope 10100 to generate image data for displaying the captured in-vivo image on the display device. As the image process, various signal processes can be performed, such as imaging process (demosaicing process), image quality improvement process (bandwidth enhancement process, super-resolution process, noise reduction (NR) process, and / or image stabilization process), and / or magnification process (electronic zoom process). The external control device 10200 controls the driving of the display device based on the generated image data to cause the display device to display the captured in-vivo image. Alternatively, the external control device 10200 can also control a recording device (not shown) to record the generated image data or control a printing device (not shown) to print and output the generated image data.

[0166] Examples of in-vivo information acquisition systems to which the technology according to the present disclosure can be applied have been described above. For example, the technology according to the present disclosure can be applied to the image pickup unit 10112 among the above configurations. This improves the detection accuracy.

[0167] (Application Example of Endoscopic Surgery System)

[0168] The technology according to the present disclosure (this technology) is applicable to a variety of products. For example, the technology according to the present disclosure can be applied to an endoscopic surgery system.

[0169] Figure 18 FIG. is an example showing a schematic configuration of an endoscopic surgery system to which the technology (this technology) according to an embodiment of the present disclosure can be applied.

[0170] Figure 18 FIG. shows a state in which a surgeon (doctor) 11131 is performing surgery on a patient 11132 on a hospital bed 11133 using an endoscopic surgery system 11000. As shown, the endoscopic surgery system 11000 includes an endoscope 11100, other surgical instruments 11110 such as a pneumoperitoneum tube 11111 and an energy device 11112, a support arm device 11120 for supporting the endoscope 11100, and a cart 11200 on which various devices for endoscopic surgery are mounted.

[0171] The endoscope 11100 includes a lens barrel 11101 in which a region of a predetermined length from the distal end is inserted into the body cavity of the patient 11132 and a camera 11102 connected to the proximal end of the lens barrel 11101. In the example shown, a rigid endoscope 11100 having a rigid lens barrel 11101 is shown. However, the endoscope 11100 may alternatively be a flexible endoscope having a flexible lens barrel 11101.

[0172] The lens barrel 11101 has an opening for mounting an objective lens at its distal end. A light source device 11203 is connected to the endoscope 11100 such that light generated by the light source device 11203 is guided through an optical fiber extending inside the lens barrel 11101 to the distal end of the lens barrel 11101 and emitted toward an observation object in the body cavity of the patient 11132 via the objective lens. Note that the endoscope 11100 may be a direct-view endoscope, an oblique-view endoscope, or a side-view endoscope.

[0173] An optical system and an image pickup element are provided inside the camera 11102 such that reflected light (observation light) from the observation object is converged on the image pickup element through the optical system. The observation light is subjected to photoelectric conversion by the image pickup element to generate an electrical signal corresponding to the observation light, that is, an image signal corresponding to the observation image. The image signal is transmitted to the CCU 11201 as RAW data.

[0174] The CCU 11201 includes a central processing unit (CPU), a graphics processing unit (GPU), etc., and comprehensively controls the operations of the endoscope 11100 and the display device 11202. In addition, the CCU 11201 receives an image signal from the camera 11102, and performs various image processing operations such as imaging processing (demosaicing processing) on the image signal for displaying an image based on the image signal.

[0175] The display device 11202 displays an image based on the image signal that has been subjected to image processing by the CCU 11201 under the control of the CCU 11201.

[0176] The light source device 11203 includes a light source such as a light-emitting diode (LED), etc., and supplies irradiation light to the endoscope 11100 when imaging the surgical area.

[0177] The input device 11204 is an input interface for the endoscopic surgery system 11000. The user can input various information and instructions into the endoscopic surgery system 11000 via the input device 11204. For example, the user inputs instructions, etc. through the use of the endoscope 11100 to change the image pickup conditions (type of irradiation light, magnification, focal length, etc.).

[0178] The treatment instrument control device 11205 controls the drive of the energy device 11112 for cauterizing and incising tissues, sealing blood vessels, etc. The pneumoperitoneum device 11206 injects gas into the body cavity of the patient 11132 via the pneumoperitoneum tube 11111 to expand the body cavity of the patient 11132, for ensuring the field of view of the endoscope 11100 and ensuring the working space for the surgeon. The recorder 11207 is a device capable of recording various information related to the surgery. The printer 11208 is a device capable of printing various information related to the surgery in various forms such as text, image, graph, etc.

[0179] Note that the light source device 11203 that supplies irradiation light to the endoscope 11100 when the endoscope 11100 captures the surgical site may, for example, be equipped with a white light source that is a combination of an LED, a laser light source, or a combination thereof. In the case where the white light source includes a combination of red, green, and blue (RGB) laser light sources, since the output intensity and output timing of various colors (each wavelength) can be controlled with high precision, the white balance adjustment of the captured image can be performed in the light source device 11203. In addition, in this case, if the laser light from each RGB laser light source is irradiated onto the observation object in a time-division manner and the drive of the image pickup element of the camera 11102 is controlled in synchronization with the irradiation timing. After that, images corresponding to R, G, and B can also be picked up in a time-division manner. According to this method, a color image can be obtained without a color filter being provided in the image pickup element.

[0180] In addition, the driving of the light source device 11203 can be controlled so as to change the intensity of the light to be output at every predetermined time. By controlling the driving of the image pickup element of the camera 11102 in synchronization with the timing of the change in the light intensity to acquire images in a time-division manner and synthesize the images, a high-dynamic-range image that does not have underexposed shadows and overexposed highlights can be generated.

[0181] In addition, the light source device 11203 can be configured to supply light in a predetermined wavelength band corresponding to special light observation. In special light observation, for example, so-called narrow-band light observation (narrow-band imaging) is performed, in which, by using the wavelength dependence of light absorption in body tissues, a predetermined tissue such as blood vessels in the mucosal surface layer is imaged with high contrast by irradiating light in a narrower wavelength band than the irradiation light (i.e., white light) during normal observation. Alternatively, in special light observation, fluorescence observation for obtaining an image by irradiating excitation light can be performed. In fluorescence observation, for example, body tissues can be irradiated with excitation light to observe fluorescence from the body tissues (autofluorescence observation), or a reagent such as indocyanine green (ICG) can be locally injected into the body tissues and the body tissues can be irradiated with excitation light corresponding to the fluorescence wavelength of the reagent to obtain a fluorescence image. The light source device 11203 can be configured to supply narrow-band light and / or excitation light corresponding to such special light observation.

[0182] Figure 19 is a diagram showing Figure 18 an example of the functional configuration of the camera 11102 and the CCU 11201 shown.

[0183] The camera 11102 includes a lens unit 11401, an image pickup unit 11402, a driving unit 11403, a communication unit 11404, and a camera control unit 11405. The CCU 11201 includes a communication unit 11411, an image processing unit 11412, and a control unit 11413. The camera 11102 and the CCU 11201 are communicably connected to each other via a transmission cable 11400.

[0184] The lens unit 11401 is an optical system provided at the connection portion with the lens barrel 11101. Observation light received from the distal end of the lens barrel 11101 is guided to the camera 11102 and incident on the lens unit 11401. The lens unit 11401 includes a combination of a plurality of lenses (including a zoom lens and a focusing lens).

[0185] The number of imaging elements included in the imaging unit 11402 may be one (single-board type) or multiple (multi-board type). When the imaging unit 11402 is configured as a multi-board type, for example, image signals corresponding to R, G, and B respectively can be generated by the imaging elements, and a color image can be obtained by combining the image signals. The imaging unit 11402 can also be configured to have a pair of imaging elements for obtaining respective image signals for the right eye and the left eye to prepare for three-dimensional (3D) display. If 3D display is performed, the surgeon 11131 can more accurately grasp the depth of the body tissue in the surgical site. Note that when the imaging unit 11402 is configured as a multi-board type, a plurality of systems of lens units 11401 are provided corresponding to the respective imaging elements.

[0186] In addition, the imaging unit 11402 does not have to be provided on the camera 11102. For example, the imaging unit 11402 can be provided directly behind the objective lens inside the lens barrel 11101.

[0187] The drive unit 11403 includes an actuator and moves the zoom lens and the focus lens of the lens unit 11401 along the optical axis by a predetermined distance under the control of the camera control unit 11405. Therefore, the magnification and focus of the image captured by the imaging unit 11402 can be appropriately adjusted.

[0188] The communication unit 11404 includes a communication device for transmitting and receiving various information to and from the CCU 11201. The communication unit 11404 transmits the image signal obtained from the imaging unit 11402 as RAW data to the CCU 11201 via the transmission cable 11400.

[0189] In addition, the communication unit 11404 receives a control signal for controlling the drive of the camera 11102 from the CCU 11201, and supplies the control signal to the camera control unit 11405. The control signal includes, for example, information related to imaging conditions, such as information specifying the frame rate of the captured image, information specifying the exposure value at the time of imaging, and / or information specifying the magnification and focus of the captured image, etc.

[0190] Note that imaging conditions such as the frame rate, exposure value, magnification, and focus can be specified by the user or can be automatically set by the control unit 11413 of the CCU 11201 based on the captured image signal. In the latter case, an automatic exposure (AE) function, an automatic focus (AF) function, and an automatic white balance (AWB) function are installed in the endoscope 11100.

[0191] The camera control unit 11405 controls the driving of the camera 11102 based on the control signal received from the CCU 11201 via the communication unit 11404.

[0192] The communication unit 11411 includes communication devices for transmitting and receiving various information to and from the camera 11102. The communication unit 11411 receives the image signal transmitted from the camera 11102 via the transmission cable 11400.

[0193] In addition, the communication unit 11411 transmits the control signal for controlling the driving of the camera 11102 to the camera 11102. The image signal and the control signal can be transmitted by electrical communication, optical communication, etc.

[0194] The image processing unit 11412 performs various image processing operations on the image signal that is RAW data transmitted from the camera 11102.

[0195] The control unit 11413 performs various controls related to the image pickup of the surgical site, etc. using the endoscope 11100 and the display of the captured image obtained by imaging the surgical site, etc. For example, the control unit 11413 generates a control signal for controlling the driving of the camera 11102.

[0196] In addition, the control unit 11413 causes the display device 11202 to display the captured image of the surgical site, etc. based on the image signal processed by the image processing unit 11412. At this time, the control unit 11413 can identify various objects in the captured image by using various image recognition techniques. For example, the control unit 11413 can identify surgical instruments such as forceps, specific living body parts, bleeding, fog when using the energy device 11112, etc. by detecting the edge shape, color, etc. of the objects included in the captured image. When the captured image is displayed on the display device 11202, by using the recognition result, the control unit 11413 can superimpose and display various surgical support information related to the image of the surgical site. When the surgical support information is displayed in a superimposed manner and presented to the surgeon 11131, the burden on the surgeon 11131 can be reduced, and the surgeon 11131 can perform the surgery reliably.

[0197] The transmission cable 11400 that interconnects the camera 11102 and the CCU 11201 is an electrical signal cable for electrical signal communication, an optical fiber for optical communication, or a composite cable for electro-optical communication.

[0198] Here, in the illustrated example, communication is performed wired by using the transmission cable 11400, but communication between the camera 11102 and the CCU 11201 can be performed wirelessly.

[0199] The example of the endoscopic surgical system to which the technology according to the present disclosure can be applied has been described above. The technology according to the present disclosure can be applied to the image pickup unit 11402 among the above configurations. By applying the technology according to the present disclosure to the image pickup unit 11402, the detection accuracy can be improved.

[0200] Note that the endoscopic surgical system has been described as an example here, but the technology according to the present disclosure can be applied to, for example, a microsurgical system.

[0201] (Application example of a moving body)

[0202] The technology according to the present disclosure (this technology) can be applied to various products. For example, the technology according to the present disclosure can be implemented as a device installed on any type of moving body such as an automobile, an electric vehicle, a hybrid electric vehicle, a motorcycle, a bicycle, a personal mobility device, an aircraft, an unmanned aerial vehicle, a ship, a robot, a construction machine, or an agricultural machine (tractor).

[0203] Figure 20 FIG. is a block diagram showing a schematic configuration example of a vehicle control system, which is an example of a moving body control system to which the technology according to the present disclosure can be applied.

[0204] The vehicle control system 12000 includes a plurality of electronic control units connected to each other via a communication network 12001. In Figure 20 the example shown, the vehicle control system 12000 includes a drive system control unit 12010, a body system control unit 12020, an outside vehicle information detection unit 12030, an inside vehicle information detection unit 12040, and an integrated control unit 12050. In addition, as a functional configuration of the integrated control unit 12050, a microcomputer 12051, an audio / image output unit 12052, and a vehicle-mounted network interface (I / F) 12053 are shown.

[0205] The drive system control unit 12010 controls the operation of devices related to the drive system of the vehicle according to various programs. For example, the drive system control unit 12010 serves as a control device for a driving force generation device such as an internal combustion engine or a drive motor for generating the driving force of the vehicle, a driving force transmission mechanism for transmitting the driving force to the wheels, a steering mechanism for adjusting the steering angle of the vehicle, and a braking device for generating the braking force of the vehicle.

[0206] The main body system control unit 12020 controls the operations of various devices installed in the vehicle body according to various programs. For example, the main body system control unit 12020 serves as a control device for a keyless entry system, a smart key system, an electric window device, or various lights such as headlights, taillights, brake lights, turn signal lights, or fog lights. In this case, radio waves transmitted from a portable device or signals from various switches used in place of a button can be input to the main body system control unit 12020. The main body system control unit 12020 receives the input of the radio waves or signals and controls the vehicle door lock device, the electric window device, the lights, etc.

[0207] The vehicle exterior information detection unit 12030 detects information on the exterior of the vehicle including the vehicle control system 12000. For example, the imaging unit 12031 is connected to the vehicle exterior information detection unit 12030. The vehicle exterior information detection unit 12030 causes the imaging unit 12031 to capture an image of the vehicle exterior and receives the captured image. The vehicle exterior information detection unit 12030 can perform object detection processing such as for a person, a car, an obstacle, a sign, words on the road, etc. or distance detection processing based on the received image.

[0208] The imaging unit 12031 is an optical sensor that receives light and outputs an electrical signal corresponding to the amount of received light. The imaging unit 12031 can output the electrical signal as an image, or can output the electrical signal as ranging information. In addition, the light received by the imaging unit 12031 can be visible light or invisible light such as infrared light.

[0209] The vehicle interior information detection unit 12040 detects information inside the vehicle. For example, the driver state detection unit 12041 that detects the state of the driver is connected to the vehicle interior information detection unit 12040. The driver state detection unit 12041 includes, for example, a camera that images the driver. Based on the detection information input from the driver state detection unit 12041, the vehicle interior information detection unit 12040 can calculate the driver's fatigue or concentration, or can determine whether the driver is drowsy.

[0210] The microcomputer 12051 can calculate control target values for a driving force generation device, a steering mechanism, or a braking device based on information on the interior and exterior of the vehicle obtained by the vehicle exterior information detection unit 12030 or the vehicle interior information detection unit 12040, and can output a control instruction to the drive system control unit 12010. For example, the microcomputer 12051 can perform coordinated control to implement functions of an advanced driver assistance system (ADAS) including vehicle collision avoidance or collision mitigation, following driving based on the distance between vehicles, vehicle speed holding driving, vehicle collision warning, and vehicle lane departure warning.

[0211] In addition, the microcomputer 12051 can perform coordinated control by controlling a driving force generation device, a steering mechanism, a braking device, etc. based on information about the surroundings of the vehicle obtained by the out-vehicle information detection unit 12030 or the in-vehicle information detection unit 12040, so as to achieve autonomous driving of the vehicle without relying on the driver's operation, such as autonomous driving.

[0212] In addition, the microcomputer 12051 can output a control command to the main system control unit 12020 based on information outside the vehicle obtained by the out-vehicle information detection unit 12030. For example, the microcomputer 12051 can perform coordinated control by controlling the headlamp according to the position of the vehicle ahead or the oncoming vehicle detected by the out-vehicle information detection unit 12030, so as to prevent glare, such as switching the high beam to the low beam.

[0213] The audio / image output unit 12052 transmits an output signal of at least one of audio and image to an output device capable of notifying information to vehicle occupants or outside the vehicle visually or auditorily. In Figure 20 the example, as the output device, an audio speaker 12061, a display unit 12062, and a dashboard 12063 are shown. For example, the display unit 12062 may include at least one of an in-vehicle display and a head-up display.

[0214] Figure 21 is a diagram showing an example of the installation position of the imaging unit 12031.

[0215] In Figure 21 , the imaging unit 12031 includes imaging units 12101, 12102, 12103, 12104, and 12105.

[0216] The imaging units 12101, 12102, 12103, 12104, and 12105 are provided at positions such as the front of the vehicle 12100, side mirrors, rear bumpers, rear doors, and the upper part of the windshield inside the vehicle, for example. The imaging unit 12101 provided at the front of the vehicle and the imaging unit 12105 provided at the upper part of the windshield inside the vehicle mainly obtain images in front of the vehicle 12100. The imaging units 12102 and 12103 provided at the side mirrors mainly obtain images on the sides of the vehicle 12100. The imaging unit 12104 provided at the rear bumper or rear door mainly obtains images behind the vehicle 12100. The imaging unit 12105 provided at the upper part of the windshield inside the vehicle is mainly used to detect vehicles ahead, pedestrians, obstacles, traffic signals, traffic signs, lanes, etc.

[0217] In addition, Figure 21An example of the imaging ranges of imaging units 12101 to 12104 is shown. Imaging range 12111 represents the imaging range of imaging unit 12101 provided at the front of the vehicle. Imaging ranges 12112 and 12113 represent the imaging ranges of imaging units 12102 and 12103 provided at the side mirrors, respectively. Imaging range 12114 represents the imaging range of imaging unit 12104 provided at the rear bumper or rear door. For example, a bird's-eye view image of vehicle 12100 as seen from above is obtained by superimposing the image data captured by imaging units 12101 to 12104.

[0218] At least one of imaging units 12101 to 12104 may have a function of acquiring distance information. For example, at least one of imaging units 12101 to 12104 may be a stereo camera including a plurality of imaging elements, or may be an imaging element having pixels for phase difference detection.

[0219] For example, based on the distance information obtained from imaging units 12101 to 12104, by obtaining the distance to each solid object within imaging ranges 12111 to 12114 and the temporal change of the distance (relative speed with respect to vehicle 12100), the microcomputer 12051 extracts a solid object that is particularly the closest and traveling in a direction substantially the same as that of vehicle 12100 at a predetermined speed (e.g., 0 km / h or more) on the driving route of vehicle 12100 as a preceding vehicle. In addition, the microcomputer 12051 can set a pre-guaranteed inter-vehicle distance for the preceding vehicle and can perform automatic braking control (including follow-up driving stop control), automatic acceleration control (including follow-up driving start control), etc. Thus, coordinated control for autonomous driving and the like in which the vehicle travels autonomously without relying on the driver's operation can be performed.

[0220] For example, based on the distance information obtained from imaging units 12101 to 12104, the microcomputer 12051 can classify solid object data on solid objects into two-wheeled vehicles, ordinary vehicles, large vehicles, pedestrians, utility poles, and other solid objects, extract the solid object data, and automatically avoid obstacles using the solid object data. For example, the microcomputer 12051 identifies obstacles around vehicle 12100 as obstacles that can be visually recognized by the driver of vehicle 12100 and obstacles that are difficult to visually recognize. Then, the microcomputer 12051 determines a collision risk indicating the degree of danger of collision with each obstacle. When the collision risk is equal to or higher than a set value and there is a possibility of collision, a warning can be output to the driver via the audio speaker 12061 and the display unit 12062, and forced deceleration or avoidance steering can be performed via the drive system control unit 12010. The microcomputer 12051 can thus assist driving to avoid collisions.

[0221] At least one of the imaging units 12101 to 12104 may be an infrared camera that detects infrared rays. For example, the microcomputer 12051 may identify a pedestrian by determining whether a pedestrian exists in the images captured by the imaging units 12101 to 12104. For example, pedestrian identification is performed by a step of extracting feature points in the images captured by the imaging units 12101 to 12104 that are infrared cameras and a step of performing pattern matching processing on a series of feature points indicating the outline of an object to determine whether the object is a pedestrian. When the microcomputer 12051 determines that a pedestrian exists in the images captured by the imaging units 12101 to 12104 and identifies the pedestrian, the audio / image output unit 12052 causes the display unit 12062 to superimpose and display a quadrilateral contour line for emphasis on the identified pedestrian. In addition, the audio / image output unit 12052 may also control the display unit 12062 to display an icon indicating a pedestrian or the like at a desired position.

[0222] <4. Embodiment>

[0223] Next, embodiments of the present disclosure will be described in detail. An imaging element having the Figure 22 shown cross-sectional configuration is fabricated as a device sample, and the device characteristics are evaluated.

[0224] (Experimental Example 1)

[0225] Using a sputtering apparatus, an ITO film having a thickness of 100 nm is formed on a quartz substrate. The ITO film is patterned by photolithography and etching to form an ITO electrode (lower electrode 21). Subsequently, the quartz substrate provided with the ITO electrode is cleaned by UV / ozone treatment. Thereafter, the quartz substrate is transferred into a vacuum evaporator, and while rotating the substrate holder, each organic layer is sequentially laminated on the quartz substrate under a reduced pressure state of 1×10 -5 Pa or less. First, using NDI35 represented by the following formula (1), a hole blocking layer 24A having a thickness of 10 nm is formed on the lower electrode 21 at a substrate temperature of 0°C. Next, at a substrate temperature of 40°C and film formation rates of / second, / second and / second, F6-OPh-26F2 represented by the following formula (2), BP-rBDT represented by the following formula (3), and fullerene C 60A film is used to provide a thickness of 230 nm as a hybrid layer, and a photoactive layer 24 is formed. Subsequently, a film of PC-ID represented by the following formula (4) is formed at a substrate temperature of 0 °C to have a thickness of 10 nm, and an electron blocking layer 24B is formed. Thereafter, a film of HATCN represented by the following formula (5) is formed to have a thickness of 10 nm, and a work function adjustment layer 25 is formed. Next, a film of NDI35 represented by the following formula (1) is formed to have a thickness of 2 nm, and an electron injection promoting layer 26 is formed. Finally, the quartz substrate is moved to a sputtering apparatus. An ITO film with a thickness of 50 nm is formed on the electron injection promoting layer 26, and an upper electrode 27 is formed. In the above manufacturing method, a sample with a photoactive area of 1 mm × 1 mm is fabricated (Experimental Example 1). The fabricated device sample is annealed at 150 °C for 210 minutes in a nitrogen (N2) atmosphere.

[0226] [Chemical formula 1]

[0227]

[0228] (Experimental Example 2)

[0229] In Experimental Example 2, a device sample is fabricated using the same method as Experimental Example 1, except that the electron injection promoting layer 26 is not formed (Experimental Example 2).

[0230] (Experimental Example 3)

[0231] In Experimental Example 3, except that a film is formed at a substrate temperature of 40 °C and film formation rates of 60 / second and / second respectively using BP-rBDT and fullerene C represented by the above formula (3) to provide a thickness of 230 nm as a hybrid layer to form the photoactive layer 24, a device sample is fabricated using the same method as Experimental Example 1 (Experimental Example 3). / second to form a film to provide a thickness of 230 nm as a hybrid layer to form the photoactive layer 24, a device sample is fabricated using the same method as Experimental Example 1 (Experimental Example 3).

[0232] (Experimental Example 4)

[0233] In Experimental Example 4, a device sample is fabricated using the same method as Experimental Example 3, except that the electron injection promoting layer 26 is not formed (Experimental Example 4).

[0234] (Experimental Example 5)

[0235] In the experimental example, except that an electron injection promoting layer 26 is formed by using CzBDF represented by the following formula (6) to have a thickness of 2 nm, a device sample is fabricated using the same method as Experimental Example 1 (Experimental Example 5).

[0236] [Chemical formula 2]

[0237]

[0238] (Experimental Example 6)

[0239] In Experimental Example 6, a device sample (Experimental Example 6) was fabricated in the same manner as in Experimental Example 1, except that the electron injection promoting layer 26 was formed by forming NBphen represented by the following formula (7) to have a thickness of 2 nm.

[0240] [Chemical Formula 3]

[0241]

[0242] (Experimental Example 7)

[0243] In Experimental Example 7, a device sample (Experimental Example 7) was fabricated in the same manner as in Experimental Example 1, except that the electron injection promoting layer 26 was formed by forming BCP represented by the following formula (8) to have a thickness of 2 nm.

[0244] [Chemical Formula 4]

[0245]

[0246] (Experimental Example 8)

[0247] In Experimental Example 8, a device sample (Experimental Example 8) was fabricated in the same manner as in Experimental Example 1, except that the electron injection promoting layer 26 was formed by forming LiF to have a thickness of 2 nm.

[0248] The energy levels of the electron injection promoting layer 26 formed in the above Experimental Examples 1 to 8 were analyzed using the following evaluation method. In addition, the dark current, external quantum efficiency (EQE), and photosensitivity of each device sample in Experimental Examples 1 to 6 were evaluated. These are listed in Table 1.

[0249] (Evaluation of Energy Levels)

[0250] Samples were formed in which an ITO film and a single film of each material to be measured were formed on a quartz substrate, and their respective energy levels were obtained using UPS and LEIPS.

[0251] (Evaluation of Dark Current)

[0252] As an evaluation of the dark current, the current value obtained was measured in the dark state by using a semiconductor parameter analyzer to control the bias voltage applied between the electrodes of the photoelectric conversion element and setting the voltage applied to the lower electrode 21 to -2.6 V with respect to the upper electrode 27.

[0253] (Evaluation of External Photoelectric Conversion Efficiency)

[0254] As an evaluation of the external photoelectric conversion efficiency, the number of effective carriers is obtained by subtracting the dark current value from the bright current value, where the device sample is irradiated with light having a wavelength of 560 nm from a light source via a filter at a light amount of 1.62 μW / cm 2 and the bright current value is obtained under the condition that the bias voltage applied between the electrodes of the device sample is controlled by using a semiconductor parameter analyzer and the voltage applied to the lower electrode 21 is set to 2.6 V with respect to the upper electrode 27. The external photoelectric conversion efficiency is calculated by dividing it by the number of incident photons. The characteristic values in Experimental Example 2 are normalized to 1 for relative comparison.

[0255] (Evaluation of Photoresponsivity)

[0256] As an evaluation of the photoresponsivity, the decrease in the current value after light irradiation is measured under the condition that the bias voltage applied between the electrodes of the device sample is controlled by using a semiconductor parameter analyzer and the voltage applied to the lower electrode 21 is set to 2.6 V with respect to the upper electrode 27. After light irradiation, the current values from 1 ms to 110 ms after the light is blocked are integrated and evaluated as relative values. The smaller the value, the better the photoresponsivity.

[0257]

[0258] As can be seen from Table 1, in the case of having an in-gap energy level with a density of states of 1 / 10000 or more relative to the HOMO energy level, the photoresponsivity tends to improve. In addition, the larger the value of B / A, B / A', a / b, or a / b', the more the photoresponsivity tends to improve.

[0259] Although the description has been given with reference to the embodiments, examples, application examples, and usage examples, the content of the present disclosure is not limited to the above embodiments and the like. Various modifications can be made. For example, in the above embodiment, the imaging element has a configuration in which the organic photoelectric conversion unit 20 that detects green light and the inorganic photoelectric conversion units 32B and 32R that detect blue light and red light, respectively, are stacked. However, the content of the present disclosure is not limited to such a structure. In other words, the organic photoelectric conversion unit can detect red light or blue light, or the inorganic photoelectric conversion unit can detect green light.

[0260] In addition, the number or the ratio of these organic photoelectric conversion units and inorganic photoelectric conversion units is not limited. Two or more organic photoelectric conversion units can be provided, or color signals of multiple colors can be obtained only by using the organic photoelectric conversion units.

[0261] In addition, in the above-described embodiments, an example has been described in which two electrodes, i.e., a readout electrode 21A and an accumulation electrode 21B, are provided as a plurality of electrodes included in the lower electrode 21. However, three or more electrodes, such as a transfer electrode or a discharge electrode, may be additionally provided.

[0262] In addition, in the above-described embodiments, an example has been described in which the lower electrode 21 is formed using a plurality of electrodes. However, the present technology even allows an imaging element including a lower electrode having a single electrode to achieve a similar effect.

[0263] Note that the effects described herein are merely examples and not restrictive. In addition, there may be other effects.

[0264] Note that the present disclosure may have the following configuration. In the present technology having the following configuration, a first semiconductor layer is provided between the second electrode and the organic layer. The second electrode is disposed opposite to the first electrode with the organic layer therebetween. The organic layer includes at least a photoelectric conversion layer. The first semiconductor layer contains at least one of a carbon-containing compound and an inorganic compound, the electron affinity of the carbon-containing compound being greater than the work function of the first electrode, and the work function of the inorganic compound being greater than the work function of the first electrode. In addition, in the present technology having the following configuration, a second semiconductor layer is provided between the second electrode and the first semiconductor layer. The absolute value B of the difference between the HOMO energy level of the second semiconductor layer and the Fermi energy level of the second electrode is greater than or equal to the absolute value A of the difference between the first LUMO energy level calculated from the optical band gap and the Fermi energy level, or has an in-gap energy level having a density of states of 1 / 10000 or more relative to the HOMO energy level near the Fermi energy level. This promotes the injection of electrons from the second electrode into the first semiconductor layer and can improve the photoresponsiveness.

[0265] (1) An imaging element, comprising:

[0266] A first electrode;

[0267] A second electrode disposed opposite to the first electrode;

[0268] An organic layer disposed between the first electrode and the second electrode and including at least a photoelectric conversion layer;

[0269] A first semiconductor layer disposed between the second electrode and the organic layer and containing at least one of a carbon-containing compound and an inorganic compound, the electron affinity of the carbon-containing compound being greater than the work function of the first electrode, and the work function of the inorganic compound being greater than the work function of the first electrode; and

[0270] a second semiconductor layer disposed between the second electrode and the first semiconductor layer, and an absolute value B of a difference between a HOMO (highest occupied molecular orbital) energy level and a Fermi energy level of the second electrode is greater than or equal to an absolute value A of a difference between a first LUMO (lowest unoccupied molecular orbital) energy level calculated from an optical band gap and the Fermi energy level, or has an in-gap energy level having a density of states of 1 / 10,000 or more relative to the HOMO energy level near the Fermi energy level.

[0271] (2) The imaging element according to (1), wherein an absolute value B of a difference between the HOMO energy level and the Fermi energy level of the second semiconductor layer is greater than an absolute value A' of a difference between a second LUMO energy level and the Fermi energy level.

[0272] (3) The imaging element according to (1) or (2), wherein an absolute value b of a difference between the HOMO energy level and the in-gap energy level of the second semiconductor layer is 2 times or more an absolute value a of a difference between the first LUMO energy level and the in-gap energy level.

[0273] (4) The imaging element according to any one of (1) to (3), wherein an absolute value b of a difference between the HOMO energy level and the in-gap energy level of the second semiconductor layer is 1.5 times or more an absolute value a' of a difference between a second LUMO energy level and the in-gap energy level.

[0274] (5) The imaging element according to any one of (1) to (4), wherein a work function of the second electrode is smaller than a work function of the first semiconductor layer.

[0275] (6) The imaging element according to any one of (1) to (5), wherein

[0276] the organic layer adjacent to the first semiconductor layer contains an organic material, and

[0277] the HOMO energy level of the organic material has a shallower energy level than the work function of the first semiconductor layer.

[0278] (7) The imaging element according to any one of (1) to (6), wherein

[0279] the organic layer adjacent to the first semiconductor layer contains an organic material, and

[0280] the glass transition point of the organic material is higher than 100 °C.

[0281] (8) The imaging element according to any one of (1) to (7), wherein the first semiconductor layer has a light absorption rate of 10% or less for visible light.

[0282] (9) The imaging element according to any one of (1) to (8) further includes a third semiconductor layer located between the first electrode and the organic layer and containing an oxide semiconductor material, wherein

[0283] the lowest edge of the conduction band of the oxide semiconductor material has an energy level shallower than the work function of the first electrode.

[0284] (10) The imaging element according to any one of (1) to (9), wherein the first electrode includes a plurality of electrodes independent of each other.

[0285] (11) The imaging element according to (10), wherein the first electrode includes a charge readout electrode and a charge accumulation electrode as the plurality of electrodes.

[0286] (12) The imaging element according to (11), wherein each of the plurality of electrodes is individually applied with a voltage.

[0287] (13) The imaging element according to (11) or (12) further includes:

[0288] a third semiconductor layer, which is located between the first electrode and the organic layer and contains an oxide semiconductor material; and

[0289] an insulating layer, which is located between the first electrode and the third semiconductor layer, wherein

[0290] the charge readout electrode is electrically connected to the third semiconductor layer via an opening provided in the insulating layer.

[0291] (14) The imaging element according to any one of (1) to (13), wherein the first electrode is disposed on a side opposite to the light incident surface with respect to the organic layer.

[0292] (15) The imaging element according to any one of (1) to (14), wherein an organic photoelectric conversion unit having one or more organic layers and one or more inorganic photoelectric conversion units are stacked, and the one or more inorganic photoelectric conversion units perform photoelectric conversion in a wavelength range different from that of the organic photoelectric conversion unit.

[0293] (16) The imaging element according to (15), wherein

[0294] the inorganic photoelectric conversion unit is formed to be buried in a semiconductor substrate, and

[0295] the organic photoelectric conversion unit is formed on the first surface side of the semiconductor substrate.

[0296] (17) The imaging element according to (16), wherein a multilayer wiring layer is formed on the second surface side of the semiconductor substrate.

[0297] (18) The imaging element according to (16) or (17), wherein

[0298] the organic photoelectric conversion unit performs photoelectric conversion on green light, and

[0299] an inorganic photoelectric conversion unit that performs photoelectric conversion on blue light and an inorganic photoelectric conversion unit that performs photoelectric conversion on red light are stacked inside the semiconductor substrate.

[0300] (19) An imaging device, comprising

[0301] a plurality of pixels, each pixel being provided with one or more imaging elements, wherein

[0302] each of the imaging elements includes

[0303] a first electrode,

[0304] a second electrode, the second electrode being disposed opposite to the first electrode;

[0305] an organic layer, the organic layer being disposed between the first electrode and the second electrode and including at least a photoelectric conversion layer;

[0306] a first semiconductor layer, the first semiconductor layer being disposed between the second electrode and the organic layer and containing at least one of a carbon-containing compound and an inorganic compound, the electron affinity of the carbon-containing compound being greater than the work function of the first electrode, and the work function of the inorganic compound being greater than the work function of the first electrode; and

[0307] a second semiconductor layer, the second semiconductor layer being disposed between the second electrode and the first semiconductor layer, and the absolute value B of the difference between the HOMO (highest occupied molecular orbital) energy level and the Fermi energy level of the second electrode being greater than or equal to the absolute value A of the difference between the first LUMO (lowest unoccupied molecular orbital) energy level calculated from the optical band gap and the Fermi energy level, or having an energy level within the band gap where the density of states is 1 / 10000 or more relative to the HOMO energy level near the Fermi energy level.

[0308] (20) The imaging device according to (19), wherein the first electrode is formed for each pixel and has a plurality of electrodes within the pixel.

[0309] This application claims the benefit of Japanese Patent Application No. 2020-012779, filed with the Japan Patent Office on January 29, 2020, the entire contents of which are incorporated herein by reference.

[0310] Those skilled in the art should understand that various modifications, combinations, sub - combinations and alterations can be made in accordance with the design requirements and other factors, as long as they are within the scope of the appended claims or their equivalents.

Claims

1. An imaging element, comprising: First electrode; Second electrode, the second electrode being disposed opposite to the first electrode; Organic layer, the organic layer being disposed between the first electrode and the second electrode and including at least a photoelectric conversion layer; First semiconductor layer, the first semiconductor layer being disposed between the second electrode and the organic layer and including at least one of a carbon-containing compound and an inorganic compound, the electron affinity of the carbon-containing compound being greater than the work function of the first electrode, and the work function of the inorganic compound being greater than the work function of the first electrode; and Second semiconductor layer, the second semiconductor layer being disposed between the second electrode and the first semiconductor layer, and the absolute value B of the difference between the HOMO energy level of the second semiconductor layer and the Fermi energy level of the second electrode being greater than or equal to the absolute value A of the difference between the first LUMO energy level calculated from the optical band gap and the Fermi energy level, or having an in-band energy level with a density of states relative to the HOMO energy level of 1 / 10000 or more near the Fermi energy level.

2. The imaging element according to claim 1, wherein, The absolute value B of the difference between the HOMO energy level of the second semiconductor layer and the Fermi energy level is greater than the absolute value A' of the difference between the second LUMO energy level and the Fermi energy level.

3. The imaging element according to claim 1 or 2, wherein, The absolute value b of the difference between the HOMO energy level of the second semiconductor layer and the in-band energy level is 2 times or more the absolute value a of the difference between the first LUMO energy level and the in-band energy level.

4. The imaging element according to claim 1 or 2, wherein, The absolute value b of the difference between the HOMO energy level of the second semiconductor layer and the in-band energy level is 1.5 times or more the absolute value a' of the difference between the second LUMO energy level and the in-band energy level.

5. The imaging element according to claim 1 or 2, wherein, The work function of the second electrode is less than the work function of the first semiconductor layer.

6. The imaging element according to claim 1 or 2, wherein, The organic layer adjacent to the first semiconductor layer includes an organic material, and The HOMO energy level of the organic material has a shallower energy level than the work function of the first semiconductor layer.

7. The imaging element according to claim 1 or 2, wherein, The organic layer adjacent to the first semiconductor layer includes an organic material, and The glass transition point of the organic material is higher than 100 °C.

8. The imaging element according to claim 1 or 2, wherein, The first semiconductor layer has a light absorption rate of 10% or less for visible light.

9. The imaging element according to claim 1 or 2, further comprising a third semiconductor layer located between the first electrode and the organic layer and comprising an oxide semiconductor material, wherein, The lowest edge of the conduction band of the oxide semiconductor material has a shallower energy level than the work function of the first electrode.

10. The imaging element according to claim 1 or 2, wherein, The first electrode includes a plurality of electrodes independent of each other.

11. The imaging element according to claim 10, wherein, The first electrode includes a charge readout electrode and a charge accumulation electrode as the plurality of electrodes.

12. The imaging element according to claim 11, wherein, Each of the plurality of electrodes is individually applied with a voltage.

13. The imaging element according to claim 11, further comprising: Third semiconductor layer, the third semiconductor layer being located between the first electrode and the organic layer and including an oxide semiconductor material; and Insulating layer, the insulating layer being located between the first electrode and the third semiconductor layer, wherein The charge readout electrode is electrically connected to the third semiconductor layer via an opening provided in the insulating layer.

14. The imaging element according to claim 1 or 2, wherein, The first electrode is disposed on the side opposite to the light incident surface with respect to the organic layer.

15. The imaging element according to claim 1 or 2, wherein, An organic photoelectric conversion unit having one or more of the organic layers and one or more inorganic photoelectric conversion units are stacked, and the one or more inorganic photoelectric conversion units perform photoelectric conversion in a wavelength range different from the wavelength range of the organic photoelectric conversion unit.

16. The imaging element according to claim 15, wherein, The inorganic photoelectric conversion portion is formed to be embedded in the semiconductor substrate, and the organic photoelectric conversion portion is formed on the first surface side of the semiconductor substrate.

17. The imaging element according to claim 16, wherein, The multilayer wiring layer is formed on the second surface side of the semiconductor substrate.

18. The imaging element according to claim 16, wherein, The organic photoelectric conversion portion performs photoelectric conversion on green light, and the inorganic photoelectric conversion portion that performs photoelectric conversion on blue light and the inorganic photoelectric conversion portion that performs photoelectric conversion on red light are stacked inside the semiconductor substrate.

19. An imaging device, comprising a plurality of pixels, each pixel being provided with one or more imaging elements, wherein, Each of the imaging elements includes a first electrode, a second electrode, the second electrode being disposed opposite to the first electrode; an organic layer, the organic layer being disposed between the first electrode and the second electrode and including at least a photoelectric conversion layer; a first semiconductor layer, the first semiconductor layer being disposed between the second electrode and the organic layer and containing at least one of a carbon-containing compound and an inorganic compound, the electron affinity of the carbon-containing compound being greater than the work function of the first electrode, and the work function of the inorganic compound being greater than the work function of the first electrode; and a second semiconductor layer, the second semiconductor layer being disposed between the second electrode and the first semiconductor layer, and the absolute value B of the difference between the HOMO energy level and the Fermi energy level of the second electrode being greater than or equal to the absolute value A of the difference between the first LUMO energy level calculated from the optical band gap and the Fermi energy level, or having an energy level within a band gap where the density of states is 1 / 10000 or more relative to the HOMO energy level near the Fermi energy level.

20. The imaging device according to claim 19, wherein, The first electrode is formed for each pixel and has a plurality of electrodes within the pixel.

Images