Patent Publication Number: US-11049906-B2

Title: Imaging device, manufacturing device, and manufacturing method

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of U.S. patent application Ser. No. 16/126,756 filed on Sep. 10, 2018, which is a continuation of U.S. patent application Ser. No. 15/512,550, filed Mar. 18, 2017, now U.S. Pat. No. 10,074,696, which is a National Stage Entry of Patent Application No. PCT/JP2015/077011 filed Sep. 25, 2015, which claims priority benefit of Japanese Patent Application No. JP 2014-205442 filed in the Japan Patent Office Oct. 6, 2014. Each of the above-referenced applications is hereby incorporated herein by reference in its entirely. 
    
    
     TECHNICAL FIELD 
     The present technology relates to an imaging device, a manufacturing device, and a manufacturing method. Specifically, the present technology relates to an imaging device, a manufacturing device, and a manufacturing method preferably used to reduce an influence of hydrogen. 
     BACKGROUND ART 
     In recent years, in a charge coupled device (CCD) image sensor or a complementary metal oxide semiconductor (CMOS), a pixel size has been reduced. Therefore, sensitivity is lowered due to reduction in the number of photons incident on a unit pixel, and an S/N ratio is lowered. In addition, in a presently widely-used pixel array in which pixels of red, green, and blue are arranged on a plane, for example, in a Bayer array using a primary color filter, for example, in a red pixel, green and blue light does not pass through the color filter and is not used for photoelectric conversion, and therefore sensitivity is lost. In addition, when an interpolation process is performed between pixels, a false color may be generated due to generation of a color signal. 
     An image sensor to obtain three color photoelectric conversion signals with one pixel by stacking three photoelectric conversion layers in a vertical direction has been proposed. In Patent Document 1, as such a structure for stacking three color photoelectric conversion layers with one pixel, for example, a sensor in which a photoelectric conversion unit for detecting green light and generating a signal charge corresponding thereto is provided above a silicon substrate and blue light and red light are detected by two photodiodes stacked in the silicon substrate has been proposed. 
     In addition, Patent Document 2 has proposed a back surface irradiation type structure provided with a photoelectric conversion film  1  layer above a silicon substrate, having a two color photoelectric conversion unit in the silicon substrate, and having a circuit-forming surface formed on a side opposite to a light-receiving surface. When a back surface irradiation type organic photoelectric conversion layer is formed, a circuit, wiring, or the like is not formed between an inorganic photoelectric conversion unit and an organic photoelectric conversion unit. Therefore, a distance between the inorganic photoelectric conversion unit and the organic photoelectric conversion unit in the same pixel can be close to each other. Therefore, dependence of colors on an F value can be suppressed, and fluctuation in sensitivity between the colors can be suppressed. 
     CITATION LIST 
     Patent Document 
     Patent Document 1: Japanese Patent Application Laid-Open No. 2003-332551 
     Patent Document 2: Japanese Patent Application Laid-Open No. 2011-29337 
     Patent Document 3 Japanese Patent Application Laid-open No. 2008-252004 
     SUMMARY OF THE INVENTION 
     Problems to be Solved by the Invention 
     An organic photoelectric conversion film is generally susceptible to water or oxygen, and therefore it is necessary to form a sealing structure in an upper layer of an organic photoelectric conversion film. For example, Patent Document 3 has proposed formation of a sealing structure formed by stacking a SiN film formed by a sputtering method and an AlO film formed by an ALD method. 
     However, when such a sealing film is formed, the ALD method needs to use an organic metal such as trimethylaluminum (TMA) as a precursor, and hydrogen in the precursor may be diffused to upper and lower transparent electrodes. As a result of diffusion, not only the upper electrode but also the lower electrode is reduced, a work function becomes shallow, and an organic photoelectric conversion efficiency may be deteriorated. 
     The lower electrode preferably has a deep work function, and the upper electrode preferably has a shallow work function. This is because this can reduce a dark current by making an electron injection barrier from the lower electrode higher, and can improve a carrier extraction efficiency by increasing an internal electric field. 
     Therefore, as described above, it is desired to prevent diffusion of hydrogen in the precursor to the lower transparent electrode, reduction of the lower electrode, shallowing of the work function, and deterioration of an organic photoelectric conversion efficiency. 
     The present technology has been achieved in view of such a situation, and makes it possible to prevent conversion of the work function due to diffusion of hydrogen and deterioration in the organic photoelectric conversion efficiency. 
     Solutions to Problems 
     An imaging device in an aspect of the present technology includes an organic photoelectric conversion film, an upper electrode provided in an upper portion of the organic photoelectric conversion film, a lower electrode provided in a lower portion of the organic photoelectric conversion film, and a metal thin film provided between the organic photoelectric conversion film and the upper electrode or between the organic photoelectric conversion film and the lower electrode. 
     The metal thin film is provided between the organic photoelectric conversion film and the upper electrode. The upper electrode can be formed of an oxide semiconductor, a metal oxide, and the metal thin film. 
     The metal oxide is aluminum oxide (AlO). The metal thin film can be formed of aluminum (Al). 
     The metal thin film can be formed of any one of aluminum (Al), indium (In), silver (Ag), gold (Au), zinc (Zn), lithium (Li), tin (Sn), antimony (Sb), magnesium (Mg), cadmium (Cd), calcium (Ca), potassium (K), rubidium (Rb), cesium (Cs), strontium (Sr), barium (Ba), cerium (Ce), yttrium (Y), hafnium (Hf), nickel (Ni), gallium (Ga), and titanium (Ti). 
     Each of the upper electrode and the lower electrode can be formed of any one of ITO, tin oxide-based SnO2, zinc oxide-based materials aluminum zinc oxide, gallium zinc oxide, and indium zinc oxide, IGZO, CuI, InSbO4, ZnMgO, CuInO2, MgIn2O4, CdO, and ZnSnO3. 
     The organic photoelectric conversion film can be formed of any one of a quinacridone derivative, a naphthalene derivative, an anthracene derivative, a phenanthrene derivative, a tetracene derivative, a pyrene derivative, a perylene derivative, and a fluoranthene derivative. 
     The organic photoelectric conversion film can be formed of any one of a polymer of phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, or diacetylene, and a derivative thereof, a metal complex dye, a cyanine dye, a merocyanine dye, a phenylxanthene dye, a triphenylmethane dye, a rhodacyanine dye, a xanthene dye, a macrocyclic azaannulene dye, an azulene dye, naphthoquinone, an anthraquinone dye, a condensed polycyclic aromatic compound such as anthracene or pyrene, a chain compound obtained by condensing an aromatic ring or heterocyclic compound, a heterocyclic ring compound containing two nitrogen atoms and having a squarylium group and a croconic methine group as a bonding chain, such as quinoline, benzothiazole, or benzoxazole, and a cyanine-like dye bonded by a squarylium group and a croconic methine group. The metal complex dye can be any one of a dithiol metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye, and a ruthenium complex dye. 
     The metal thin film can have a thickness of 5 nm or less. 
     The metal thin film has a spherical shape or a predetermined shape, and can be scattered at equal intervals or at random. 
     A hole blocking layer can be provided between the metal thin film and the organic photoelectric conversion film. 
     An enthalpy control layer can be provided along with the metal thin film or in place of the metal thin film. 
     The enthalpy control layer can be provided between the organic photoelectric conversion film and the lower electrode. 
     The enthalpy control layer can be formed of any one of Ag2O, CoO, Co3O4, CdO, Cs2O, CuO, Cu2O, GeO(c), GeO2(c1), GeO2(c2), NiO(c), PbO(c), PbO2(c2), PbO2(c), PdO(c), Rb2O(c), Rb2O2(c), SeO2(c), SeO3(c), TeO2(C), Tl2O(c), and Tl2O3(c). 
     A manufacturing device in an aspect of the present technology forms an organic photoelectric conversion film, forms an upper electrode in an upper portion of the organic photoelectric conversion film, forms a lower electrode in a lower portion of the organic photoelectric conversion film, and forms a metal thin film between the organic photoelectric conversion film and the upper electrode or between the organic photoelectric conversion film and the lower electrode. 
     The metal thin film can be formed by vapor deposition. 
     The metal thin film can be formed between the organic photoelectric conversion film and the upper electrode. The upper electrode can be formed by stacking an oxide semiconductor, a metal oxide, and the metal thin film. The metal oxide can be formed by oxidization at the time of film formation of the oxide semiconductor. 
     The metal thin film can be formed into a spherical shape or a predetermined shape so as to be scattered at equal intervals or at random. 
     A hole blocking layer can be further formed between the metal thin film and the organic photoelectric conversion film. 
     An enthalpy control layer can be formed along with the metal thin film or in place of the metal thin film. 
     A manufacturing method in an aspect of the present technology includes steps of forming an organic photoelectric conversion film, forming an upper electrode in an upper portion of the organic photoelectric conversion film, forming a lower electrode in a lower portion of the organic photoelectric conversion film, and forming a metal thin film between the organic photoelectric conversion film and the upper electrode or between the organic photoelectric conversion film and the lower electrode. 
     An imaging device in an aspect of the present technology includes an organic photoelectric conversion film, an upper electrode provided in an upper portion of the organic photoelectric conversion film, a lower electrode provided in a lower portion of the organic photoelectric conversion film, and a metal thin film provided between the organic photoelectric conversion film and the upper electrode or between the organic photoelectric conversion film and the lower electrode. 
     A manufacturing device and a manufacturing method in an aspect of the present technology manufacture the imaging device. 
     Effects of the Invention 
     According to an aspect of the present technology, it is possible to prevent conversion of a work function due to diffusion of hydrogen and deterioration in an organic photoelectric conversion efficiency. 
     Note that effects of the present technology are not necessarily limited to the effects described herein, and may include any of the effects described in the present disclosure. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         FIG. 1  is a diagram for explaining a configuration of an imaging device. 
         FIG. 2  is a diagram for explaining a configuration of an imaging device. 
         FIG. 3  is a diagram for explaining a configuration of an imaging device according to a first embodiment. 
         FIG. 4  is a diagram for explaining another configuration of the imaging device according to the first embodiment. 
         FIG. 5  is a diagram for explaining another configuration of the imaging device according to the first embodiment. 
         FIG. 6  is a diagram for explaining manufacturing of an imaging device. 
         FIG. 7  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 8  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 9  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 10  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 11  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 12  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 13  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 14  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 15  is a diagram for explaining manufacturing of the imaging device. 
         FIG. 16  is a diagram for explaining a configuration of an imaging device according to a second embodiment. 
         FIG. 17  is a diagram for explaining the configuration of the imaging device according to the second embodiment. 
         FIG. 18  is a diagram for explaining the configuration of the imaging device according to the second embodiment. 
         FIG. 19  is a diagram for explaining a configuration of an imaging device according to a third embodiment. 
         FIG. 20  is a diagram for explaining a configuration of an imaging device according to a fourth embodiment. 
         FIG. 21  is a diagram for explaining a material forming an enthalpy control layer. 
         FIG. 22  is a diagram for explaining a configuration of an electronic apparatus. 
         FIG. 23  is a diagram for explaining a usage example of an imaging device. 
     
    
    
     MODES FOR CARRYING OUT THE INVENTION 
     Hereinafter, modes for carrying out the present technology (hereinafter, referred to as embodiments) will be described. Note that the description will be made in the following order. 
     1. Configuration of imaging device 
     2. Configuration of conventional imaging device 
     3. Configuration of first imaging device 
     4. Manufacturing of imaging device 
     5. Configuration of second imaging device 
     6. Configuration of third imaging device 
     7. Configuration of fourth imaging device 
     8. Configuration of electronic apparatus 
     9. Usage example of imaging device 
     &lt;Configuration of Imaging Device&gt; 
       FIG. 1  illustrates a schematic configuration of an example of a CMOS imaging device applied to the present embodiment. As illustrated in  FIG. 1 , an imaging device  1  of the present example includes a semiconductor substrate  11 , a pixel unit (so-called imaging region)  3  in which a plurality of pixels  2  each including a photoelectric conversion unit is two-dimensionally arranged with regularity on a silicon substrate, for example, and a peripheral circuit unit. Each of the pixels  2  includes a photoelectric conversion unit and a plurality of pixel transistors (so-called MOS transistors). 
     A plurality of pixel transistors can be formed, for example, by three transistors of a transfer transistor, a reset transistor, and an amplification transistor. In addition, by adding a selection transistor, the plurality of pixel transistors can be formed by four transistors. An equivalent circuit of a unit pixel is similar to a usual circuit, and therefore detailed description thereof will be omitted. In addition, a so-called pixel shared structure in which a plurality of photoelectric conversion units shares pixel transistors other than the transfer transistor and shares floating diffusion can be applied as a pixel. 
     The peripheral circuit unit includes a vertical driving circuit  4 , a column signal processing circuit  5 , a horizontal driving circuit  6 , an output circuit  7 , a control circuit  8 , and the like. 
     The control circuit  8  receives an input clock and data giving a command of an operation mode or the like, and outputs data of internal information or the like of an imaging device. That is, the control circuit  8  generates a clock signal and a control signal serving as references for operations of the vertical driving circuit  4 , the column signal processing circuit  5 , the horizontal driving circuit  6 , and the like on the basis of a vertical synchronization signal, a horizontal synchronization signal, and a master clock. Then, these signals are input to the vertical driving circuit  4 , the column signal processing circuit  5 , the horizontal driving circuit  6 , and the like. 
     The vertical driving circuit  4  is formed, for example, of a shift register, selects pixel driving wiring, supplies a pulse for driving a pixel to the selected pixel driving wiring, and drives the pixel in units of rows. That is, the vertical driving circuit  4  sequentially selects and scans each of the pixels  2  in the pixel region  3  in units of rows in a vertical direction, and supplies a pixel signal based on a signal charge generated in accordance with the amount of light received, for example, in a photodiode serving as a photoelectric conversion element of each of the pixels  2  to the column signal processing circuit  5  through a vertical signal line  9 . 
     The column signal processing circuit  5  is disposed, for example, for each of columns of the pixels  2 , and performs signal processing such as removal of a noise for a signal output from the pixels  2  in one row for each of the pixel columns. That is, the column signal processing circuit  5  performs signal processing such as CDS for removing a fixed pattern noise unique to the pixels  2 , signal amplification, or AD conversion. In an output stage of the column signal processing circuit  5 , a horizontal selection switch (not illustrated) is connected and provided between the column signal processing circuit  5  and a horizontal signal line  10 . 
     The horizontal driving circuit  6  is formed of a shift register, for example. The horizontal driving circuit  6  sequentially selects each of the column signal processing circuits  5  by sequentially outputting a horizontal scan pulse, and causes each of the column signal processing circuits  5  to output a pixel signal to the horizontal signal line  10 . 
     The output circuit  7  performs signal processing for a signal sequentially supplied from each of the column signal processing circuits  5  through the horizontal signal line  10 , and outputs the processed signal. For example, only buffering is performed, or black level adjustment, column variation correction, various types of digital signal processing, and the like are performed. An input and output terminal  12  exchanges a signal with the outside. 
     &lt;Configuration of Conventional Imaging Device&gt; 
     In order to clarify a difference between the imaging device to which the present technology is applied and a conventional imaging device, first, referring to  FIG. 2 , the conventional imaging device will be described.  FIG. 2  is a diagram illustrating a configuration of a conventional imaging device. The imaging device illustrated in  FIG. 2  is a CMOS imaging device.  FIG. 2  is a cross-sectional view of one pixel  20  in a pixel unit of the CMOS imaging device. 
     An imaging device  21  is formed by stacking one organic photoelectric conversion unit  41  and inorganic photoelectric conversion units PD  36  and the PD  37  having two pn junctions in the same pixel, that is, in one pixel in a depth direction. 
     More specifically, the imaging device  21  includes a semiconductor substrate (silicon substrate)  35  in which an inorganic photoelectric conversion unit is formed. A light-receiving surface on which light is incident is formed on a back surface side (upper side of the substrate  35  in  FIG. 2 ) of the substrate  35 . A circuit including a read circuit or the like is formed on a surface side of the substrate  35 . That is, the imaging device  21  includes the light-receiving surface on the back surface side of the substrate  35  and a circuit-forming surface formed on a substrate surface side opposite to the light-receiving surface. The semiconductor substrate  35  is formed of a first conductivity type, for example, an n-type semiconductor substrate. 
     In the semiconductor substrate  35 , an inorganic photoelectric conversion unit having two pn junctions, that is, a first photodiode PD  36  and a second photodiode PD  37  are formed so as to be stacked in a depth direction from the back surface side. In the semiconductor substrate  35 , the first photodiode PD  36  is formed, and the second photodiode PD  37  is formed from the back surface side toward a depth direction (downward direction in  FIG. 2 ). 
     In this example, the first photodiode PD  36  is for blue, and the second photodiode PD  37  is for red. 
     On the other hand, a first color organic photoelectric conversion unit  41  in which upper and lower surfaces of an organic photoelectric conversion film  32  are sandwiched by an upper electrode  31  and a lower electrode  33  is stacked on an upper layer of a back surface of a substrate in a region in which the first photodiode PD  36  and the second photodiode PD  37  are formed. In this example, the organic photoelectric conversion unit  36  is for green. The upper electrode  31  and the lower electrode  33  are formed, for example, of a transparent conductive film such as an indium tin oxide (ITO) film or an indium zinc oxide film. 
     Here, description will be made by assuming that the upper electrode  31  is formed of an oxide semiconductor (ITO)  51  and an aluminum oxide (AlO) thin film  52 . In addition, description will be made by assuming that the lower electrode  33  is formed of an oxide semiconductor (ITO). 
     Here, as a combination of colors, the organic photoelectric conversion unit  41  is green, the first photodiode PD  36  is blue, and the second photodiode PD  37  is red. However, another color combination can be used. For example, the organic photoelectric conversion unit  41  can be red or blue, and the first photodiode PD  36  and the second photodiode PD  37  can be set to other corresponding colors. In this case, positions of the first and second photodiodes PD  36  and PD  37  in the depth direction are set according to the color. 
     As an organic photoelectric conversion film for performing photoelectric conversion with green wavelength light, for example, an organic photoelectric conversion material containing a rhodamine dye, a meracyanine dye, or quinacridone can be used. As an organic photoelectric conversion film for performing photoelectric conversion with red wavelength light, an organic photoelectric conversion material containing a phthalocyanine dye can be used. As an organic photoelectric conversion film for performing photoelectric conversion with blue wavelength light, an organic photoelectric conversion material containing a coumarin dye, tris-8-hydryxyquinoline Al (Alq3), a meracyanine dye, or the like can be used. 
     In the organic photoelectric conversion unit  41 , the transparent lower electrode  33  is formed, and an insulating film  34  for insulating and separating the lower electrode  33  is formed. Then, the organic photoelectric conversion film  32  is formed on the lower electrode  33 , and the transparent upper electrode  31  is formed thereon. 
     In the semiconductor substrate  35  in one pixel  20 , a pair of wiring  39  and wiring  40  is formed. The lower electrode  33  in the organic photoelectric conversion unit  41  is connected to the wiring  39 , and the upper electrode  31  is connected to the wiring  40 . 
     For example, in order to suppress short-circuiting with Si, the wiring  39  and the wiring  40  can be formed of SiO2, a tungsten (W) plug having a SiN insulating layer in the periphery thereof, or a semiconductor layer by ion implantation. In this example, a signal charge is an electron. Therefore, the wiring  39  is an n-type semiconductor layer when being formed of a semiconductor layer by ion implantation. An upper electrode extracts a hole, and therefore can use a p-type. 
     In this example, an n-type region  38  for charge accumulation is formed on a surface side of the substrate  35 . This n-type region  38  functions as a floating diffusion portion of the organic photoelectric conversion unit  41 . 
     As the insulating film  34  on the back surface of the semiconductor substrate  35 , a film having a negative fixed charge can be used. Examples of the film having a negative fixed charge include a hafnium oxide film. That is, the insulating film  34  may be formed of a three-layer structure obtained by sequentially forming a silicon oxide film, a hafnium oxide film, and a silicon oxide film from the back surface. 
     On the circuit-forming surface on the surface side of the substrate  35 , a plurality of pixel transistors corresponding to the organic photoelectric conversion unit  36 , the first photodiode PD  36 , and the second photodiode PD  37  is formed. As the plurality of pixel transistors, the above four transistor configuration or the three transistor configuration can be used. A configuration sharing a pixel transistor can be also used. In  FIG. 2 , these transistors are not illustrated. 
     Note that in the surface side of the semiconductor substrate  35 , a pixel transistor of a pixel unit is formed, and a peripheral circuit such as a logic circuit is formed in the peripheral circuit unit, although not illustrated. A layer containing a peripheral circuit or the like is referred to as a multilayer wiring layer. The multilayer wiring layer is provided on the lower side of the substrate  35  in  FIG. 2 , although not illustrated. 
     A back surface side of the semiconductor substrate  35 , more specifically, a surface of the upper electrode  31  of the organic photoelectric conversion unit  41  is a light-receiving surface. In addition, an on-chip lens (not illustrated) is formed on the organic photoelectric conversion unit  41  through a flattened film (not illustrated). In this example, no color filter is formed. 
     An operation (driving method) of the imaging device  21  will be described. The imaging device  21  is formed as a so-called back surface irradiation type imaging device irradiated with light from the substrate back surface side. In this example, a fixed negative voltage VL (&lt;0 V) is applied to the lower electrode  33  of the organic photoelectric conversion unit  36  through necessary wiring of the multilayer wiring layer, and a voltage VU (&gt;VL) higher than the voltage VL of the lower electrode  33 , for example, a power supply voltage is applied to the upper electrode  31  at the time of charge accumulation. That is, the negative voltage VL is applied to the lower electrode  33  closer to the semiconductor substrate  35 . 
     At the time of charge accumulation, when light is incident on one pixel  20  without passing through a color filter, green wavelength light is photoelectrically converted in the organic photoelectric conversion film  32  having an absorption characteristic in the green wavelength light. Of an electron-hole pair generated by the photoelectric conversion, an electron serving as a signal charge is attracted by the upper electrode  31  of the high potential VU. 
     A photoelectrically converted hole is attracted by the lower electrode  33  of VL as a negative electrode. Blue wavelength light is absorbed by the first photodiode PD  36  formed in a shallow portion close to the back surface of the semiconductor substrate  35 , is photoelectrically converted, and a signal charge corresponding to blue is accumulated. The red wavelength light is absorbed by the second photodiode PD  37  formed in a deep portion from the back surface of the semiconductor substrate  35 , is photoelectrically converted, and a signal charge corresponding to red is accumulated. 
     When a charge is read, a transfer transistor (not illustrated) is turned on. Each transfer transistor is turned on, and the accumulated signal charges (electrons) of the organic photoelectric conversion unit  41 , the first photodiode PD  36 , and the second photodiode PD  37  are thereby transferred to floating diffusion portions (FD) corresponding thereto. Then, the red, green, and blue pixel signals are read by the vertical signal lines through the other pixel transistors, and are output. 
     By the way, the above vertical spectral type imaging device needs to use a transparent electrode along with the upper electrode  31  and the lower electrode  33 . However, a film formed at a low temperature such as an ALD method includes a large amount of hydrogen in the film, and reduces a work function of ITO due to hydrogen in the film when the ITO is used for the lower electrode  33 . 
     The ALD method reduces a precursor with O3, and therefore a film is formed by oxidization. O3 during film formation may denaturalize or deteriorate the organic photoelectric conversion film  32  and the lower electrode  33 . 
     On the other hand, in order to transport a hole from the organic photoelectric conversion film  32 , the lower electrode  33  needs to use a transparent electrode having a high work function, and the upper electrode  31  needs to use a transparent electrode having a low work function. When ITO is used for the lower electrode  33 , control is performed so as to obtain a film having a high work function by forming an O-rich film by an oxygen plasma treatment. 
     As described above, when the lower electrode  33  is denaturalized due to an influence of O3 during film formation, the work function may be reduced, hole transport may be inhibited, and sensitivity may be lowered. That is, when the lower electrode  33  is denaturalized due to an influence of hydrogen or the like, and the work function is reduced, sensitivity is lowered. Therefore, it is necessary to prevent such a situation. 
     &lt;Configuration of First Imaging Device&gt; 
     Therefore, as a first embodiment, an imaging device suppressing reduction of a lower electrode  33  by disposing a metal thin film between an upper electrode  31  and an organic photoelectric conversion film  32  will be described. 
       FIG. 3  is a diagram illustrating a configuration of an imaging device having a configuration for protecting the lower electrode  33  from a substance serving as a factor for reducing a work function of hydrogen or the like. The same reference signs are given to the same components as those of the imaging device  21  illustrated in  FIG. 2 , and description thereof will be omitted appropriately. 
     An imaging device  101  illustrated in  FIG. 3  includes a metal thin film  102  in the upper electrode  31 . More specifically, the metal thin film  102  is provided on a lower side of an oxide semiconductor  51  and an aluminum oxide (AlO) thin film  52  forming the upper electrode  31  between the AlO thin film  52  and an organic photoelectric conversion unit  41 . 
     As described above, in the first imaging device, the upper electrode  31  is formed of an oxide semiconductor film, a metal oxide film, and a metal film. 
     As the metal thin film  102 , for example, aluminum (Al) can be used. Aluminum has a low work function. In addition, a work function of the organic photoelectric conversion film  41  on the upper electrode  31  side is preferably set to a low value. Therefore, by providing a film formed of a material having a low work function such as aluminum on the upper electrode  31  side of the organic photoelectric conversion unit  41 , it is possible to maintain a low (shallow) work function, to maintain sensitivity, and to improve the sensitivity. 
     In addition, by providing the metal thin film  102  formed of aluminum or the like, the metal thin film  102  can prevent entrance of hydrogen or the like. That is, in this case, the metal thin film  102  can prevent a substance such as hydrogen from entering the organic photoelectric conversion film  32  from the upper electrode  31  side. Note that the metal thin film  102  is formed so as to have a thickness of 5 nm or less. With such a thickness, the metal thin film  102  can be provided without inhibiting light transmittance or causing sensitivity lowering or the like. 
     Therefore, it is possible to prevent a substance such as hydrogen from entering the organic photoelectric conversion film  32  or the lower electrode  33  provided on a lower side of the organic photoelectric conversion film  32 , and to prevent change of the organic photoelectric conversion film  32  or the lower electrode  33 , and reduction of the work function. 
     Note that the work function of the upper electrode  31  is preferably shallow. Therefore, even when the oxide semiconductor  51  forming the upper electrode  31  is changed due to a substance such as hydrogen, and the work function becomes shallow, sensitivity of the imaging device  101  is not lowered. Therefore, as illustrated in  FIG. 3 , the metal thin film  102  only needs to be provided not on an upper portion (oxide semiconductor  51 ) side of the upper electrode  31  but on a lower side (opposite to a light-receiving surface) thereof. 
     In addition, as illustrated in  FIG. 4 , the upper electrode  31  may be formed only of the metal thin film  112 . In the imaging device  111  illustrated in  FIG. 4 , the upper electrode  31  is formed of the metal thin film  112 . When the metal thin film  112  is formed of aluminum or the like, the metal thin film  112  can function as an electrode. Therefore, the metal thin film  112  may be used as the upper electrode  31 . 
     However, the upper electrode  31  is preferably transparent, and the metal thin film  112  is opaque. Therefore, it is necessary to configure the metal thin film  112  so as to be as thin as possible and to transmit light. 
     In addition, in order to prevent the work function of the lower electrode  33  from becoming shallow, as illustrated in  FIG. 5 , the metal thin film  102  may be provided on an upper side of the lower electrode  33 . In the imaging device  121  illustrated in  FIG. 5 , the metal thin film  122  is provided on the upper side of the lower electrode  33  between the lower electrode  33  and the organic photoelectric conversion film  32 . 
     In the imaging device  121 , the metal thin film  122  is provided in the upper portion of the lower electrode  33 , and therefore it is possible to prevent a substance such as hydrogen from entering the lower electrode  33  and to prevent the lower electrode  33  from being denaturalized. 
     Incidentally, in a case where the metal thin film  122  is provided on the lower electrode  33  side, when a material of the thin film used as the metal thin film  122  has a deep (high) work function, the work function of the lower electrode  33  is easily maintained in a deep state, and sensitivity of the imaging device  121  can be maintained. 
     In addition, similarly to the imaging device  111  illustrated in  FIG. 4 , the lower electrode  33  itself may be formed of the metal thin film  122 . Although not illustrated, the metal thin film  122  may be formed of a metal material having a high work function, and may be caused to function as the lower electrode  33 . 
     However, the lower electrode  33  is preferably transparent, and the metal thin film  122  is opaque. Therefore, it is necessary to configure the metal thin film  122  so as to be as thin as possible and to transmit light. 
     &lt;Manufacturing of Imaging Device&gt; 
     Manufacturing of the above imaging device will be described. Here, description will be made by exemplifying a case of manufacturing the imaging device  101  illustrated in  FIG. 3 . Note that the imaging device  111  illustrated in  FIG. 4  or the imaging device  121  illustrated in  FIG. 5  is basically manufactured through similar steps while the order of the manufacturing steps is changed, a step is added, or some of the steps are omitted. 
     First, as illustrated in  FIG. 6 , a so-called SOI substrate  203  in which a silicon layer  35  is formed on a silicon substrate  202  through a silicon oxide film  201  is prepared. Note that the silicon layer  35  corresponds to the above semiconductor substrate  35 . The silicon layer  35  is formed of an n-type silicon layer. 
     Subsequently, the first photodiode PD  36  for a second color and the second photodiode PD  37  for a third color are formed so as to be stacked on each other at different positions in the depth in the silicon layer  35 . In this example, the first photodiode PD  36  is formed as a photodiode absorbing blue wavelength light. The second photodiode PD  37  is formed as a photodiode absorbing red wavelength light. 
     The first photodiode PD  36  is formed by forming a p-type semiconductor region serving as a hole accumulation layer and an n-type semiconductor region serving as a charge accumulation layer on a back surface side of the silicon layer  35  by ion implantation so as to form a pn junction. 
     An n-type semiconductor region serving as a charge accumulation layer is formed on a surface side of the silicon layer  35  by ion implantation so as to form a pn junction, and the second photodiode PD  37  is formed of the n-type semiconductor region and a p-type semiconductor region in a lower layer. 
     Subsequently, as illustrated in  FIG. 8 , a multilayer wiring layer  211  disposed with a plurality of layers of wiring  212  through an interlayer insulating film  213  is formed on a surface of the silicon layer  35 . 
     In this example, as the first and second photodiodes PD 36  and PD 37 , photodiodes absorbing red and blue wavelength light have been exemplified. However, as described above, the combination is not necessarily limited to the two colors of blue and red. 
     Subsequently, as illustrated in  FIG. 8 , a supporting substrate  221  is attached onto the multilayer wiring layer  211 . Examples of the supporting substrate  221  include a silicon substrate. 
     Subsequently, as illustrated in  FIG. 9 , the silicon substrate  202  as the initial SOI substrate  203  and the silicon oxide film  201  are removed, and a back surface of the thin silicon layer  35  is exposed. 
     Subsequently, as illustrated in  FIG. 10 , the insulating film  34  is formed on the back surface of the silicon layer  35 . This insulating film  34  is provided in order to reduce an interface state between the insulating film  34  and the silicon layer  35  and to suppress generation of a dark current from an interface between the silicon layer  35  and the insulating film  34 . The interface state is preferably small. 
     As the insulating film  34 , for example, a stacked structure film formed of a hafnium oxide (HfO2) film formed by an ALD (atomic layer deposition) method and a silicon oxide (SiO2) film formed by a plasma CVD (chemical vapor deposition) method can be used. Note that other structures or other film formation methods can be used without being limited to the structure and film formation method described here. 
     Subsequently, as illustrated in  FIG. 11 , the wiring  39  also serving as a light-shielding film is formed on the silicon layer  35 . The wiring  39  is processed so as to leave a part to be light-shielded. The wiring  39  needs to be in contact with silicon (Si), and is used also as a light-shielding film, and therefore a stacked film formed of a barrier metal Ti and TiN, and tungsten (W) can be used therefor. However, the wiring  39  is not necessarily limited to the structure and the materials. 
     Subsequently, as illustrated in  FIG. 12 , the lower electrode  33  serving as a lower electrode of the organic photoelectric conversion unit  41  is formed. For example, the lower electrodes  33  are electrically insulated from each other by an insulating film such as a SiO2 film formed by a plasma CVD method, and flattening is performed by CMP or the like. 
     It is required for the lower electrode  33  to transmit light. Therefore, for example, a film of ITO is formed by a sputtering method, then patterning is performed by a photolithography technique, and processing is performed by dry etching or wet etching. 
     Note that a material of the lower electrode  33  is not limited to ITO. Examples thereof include tin oxide-based SnO2 (a dopant is added), zinc oxide-based materials aluminum zinc oxide (Al is added as a dopant to ZnO, for example, AZO), gallium zinc oxide (Ga is added as a dopant to ZnO, for example, GZO), and indium zinc oxide (In is added as a dopant to ZnO, for example, IZO), IGZO, CuI, InSbO4, ZnMgO, CuInO2, MgIn2O4, CdO, and ZnSnO3. 
     Note that the lower electrode  33  is electrically connected to a charge accumulation layer  38  through the wiring  39 . In addition, either of the wiring  39  and the lower electrode  33  may be patterned first. 
     Subsequently, as illustrated in  FIG. 13 , the organic photoelectric conversion film  32  is formed. For example, the organic photoelectric conversion film  32  can be formed of quinacridone by a vacuum vapor deposition method. This example also includes a case where the organic photoelectric conversion film  32  is formed by stacking an electron blocking and buffer film, a photoelectric conversion film, a hole blocking film, a hole blocking and buffer film, and a work function adjusting film on the lower electrode  33 . 
     In addition, the organic photoelectric conversion film  32  only needs to include at least one of an organic p-type semiconductor and an organic n-type semiconductor, but may have a pin bulk hetero structure including a p-type blocking layer, a co-vapor deposition layer of a p-type and an n-type, and an n-type blocking layer. 
     Examples of the organic p-type semiconductor and the organic n-type semiconductor include a quinacridone derivative, a naphthalene derivative, an anthracene derivative, a phenanthrene derivative, a tetracene derivative, a pyrene derivative, a perylene derivative, and a fluoranthene derivative. 
     In addition, a polymer of phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, diacetylene or the like, and a derivative thereof are used. In addition, for example, a metal complex dye, a cyanine dye, a merocyanine dye, a phenylxanthene dye, a triphenylmethane dye, a rhodacyanine dye, a xanthene dye, a macrocyclic azaanulene dye, an azulene dye, naphthoquinone, an anthraquinone dye, a condensed polycyclic aromatic compound such as anthracene or pyrene, a chain compound obtained by condensing an aromatic ring or heterocyclic compound, a heterocyclic ring compound containing two nitrogen atoms and having a squarylium group and a croconic methine group as a bonding chain, such as quinoline, benzothiazole, or benzoxazole, or a cyanine-like dye bonded by a squarylium group and a croconic methine group can be used. 
     In addition, examples of the metal complex dye include a dithiol metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye, and a ruthenium complex dye. Note that a dye not illustrated here may be used. 
     Note that the organic photoelectric conversion film  32  can be formed also by a coating method. 
     Subsequently, as illustrated in  FIGS. 14 and 15 , the upper electrode  31  is formed on the organic photoelectric conversion film  32 . Characteristics of the organic photoelectric conversion film  32  may fluctuate due to an influence of moisture, oxygen, hydrogen, or the like, as described above. Therefore, a film of the upper electrode  31  is formed consistently with the organic photoelectric conversion film  32  in vacuum. Here, as described with reference to  FIG. 3 , the upper electrode  31  is formed of the metal thin film  102 , the AlO thin film  52 , and the oxide semiconductor  51 . 
     For example, the metal thin film  102  can be an Al film made of aluminum (Al), and for example, can be formed by a vacuum vapor deposition method. Al has a shallow work function of about 4.3 eV, and is one of materials suitable for a material in contact with the organic photoelectric conversion film  32 . 
     In addition to Al, examples of a material which can be used as the metal thin film  102  include indium (In), silver (Ag), gold (Au), zinc (Zn), lithium (Li), tin (Sn), antimony (Sb), magnesium (Mg), cadmium (Cd), calcium (Ca), potassium (K), rubidium (Rb), cesium (Cs), strontium (Sr), barium (Ba), cerium (Ce), yttrium (Y), hafnium (Hf), nickel (Ni), gallium (Ga), and titanium (Ti). 
     Each of these materials may be used singly as the metal thin film  102 , these materials may form the metal thin film  102  as a plurality of compounds, or a compound formed of a material which has been listed here and a material which has not been listed here may be used as the metal thin film  102 . 
     Subsequently, the AlO film  52  is formed. For example, when the oxide semiconductor  51  is formed by a sputtering method after the metal thin film  102  is formed of Al, the metal thin film  102  is oxidized by energy of a sputtered particle, and the AlO thin film  52  can be formed easily so as to have a thickness of about several nm. For example, the AlO thin film  52  is formed so as to have a thickness of 20 nm or less. 
     Here, it has been described that the AlO thin film  52  is formed by oxidizing Al with energy of a sputtered particle. However, the AlO thin film  52  may be formed by an ALD method, a CVD method, or the like without being limited thereto. 
     Note that the AlO thin film  52  is an insulating film, but generally has a sufficiently wide photoelectric conversion area (area of the upper electrode  31 ) with respect to the thickness of the AlO film  52 , and therefore can take sufficient electrical conduction by a thermal diffusion component. It is known that an Al film or an AlO film formed in this manner has a high passivation property with respect to hydrogen. Hydrogen generated during a process can be shielded, and fluctuation of the work function of the lower electrode  33  can be suppressed. 
     In addition, when Al is used as the metal thin film  102 , for example, the remaining metal thin film  102  preferably has a thickness of 5 nm or less. This is because sufficient light transmittance can be ensured in a thin film region of 5 nm or less although Al has high a light-shielding property. 
     Subsequently, the oxide semiconductor  51  forming a part of the upper electrode  31  is formed. The oxide semiconductor  51  is also required to be transparent with respect to visible light. Here, the description has been made by exemplifying ITO, but the oxide semiconductor  51  is not limited to ITO. Examples thereof include tin oxide-based SnO2 (a dopant is added), zinc oxide-based materials aluminum zinc oxide (Al is added as a dopant to ZnO, for example, AZO), gallium zinc oxide (Ga is added as a dopant to ZnO, for example, GZO), and indium zinc oxide (In is added as a dopant to ZnO, for example, IZO), IGZO, CuI, InSbO4, ZnMgO, CuInO2, MgIn2O4, CdO, and ZnSnO3. 
     The upper electrode  31  is formed, and then for example, patterning is performed by a photolithography technique. Then, the upper electrode  31  and the organic photoelectric conversion film  32  are processed by dry etching. Thereafter, post-processing such as ashing or organic cleaning is performed, and a deposit and a residue are removed. 
     Note that description has been made by exemplifying a case where patterning is performed by photolithography and a dry etching method. However, patterning can be performed by using a shadow mask or the like. 
     Thereafter, the wiring  40  for electrical connection with a passivation film (not illustrated) or the upper electrode  31  is formed. When patterning is performed by a dry etching method, a sidewall of the organic photoelectric conversion film  32  is brought into direct contact with the passivation film. However, the lower electrode  33  is sufficiently separated from the passivation film, and therefore there is almost no influence. In addition, examples of the wiring  40  include tungsten (W), a barrier metal Ti, TiN, and aluminum (Al), but are not limited thereto. 
     For example, the wiring  40  is formed by performing patterning by a photolithography technique, performing processing by dry etching, performing post-processing such as ashing or organic cleaning, and removing a deposit and a residue. Thereafter, although not illustrated, a flattened film, an on-chip lens, or the like is formed. 
     The imaging device  101  is manufactured in this manner. Therefore, hydrogen during a manufacturing process can be shielded so as not to enter the lower electrode  33 , and fluctuation of the work function of the lower electrode  33  can be suppressed. 
     Note that this example has exemplified the structure obtained by stacking blue and red photoelectric conversion regions in silicon and stacking a green photoelectric conversion unit on an upper layer of the silicon. However, the scope of the present technology is not limited to such a structure. In addition, description has been made by exemplifying a back surface irradiation type CMOS imager structure. However, the scope of the present technology is not limited to such a structure. 
     &lt;Configuration of Second Imaging Device&gt; 
     Next, a configuration of an imaging device according to a second embodiment will be described.  FIG. 16  is a diagram illustrating the configuration of the imaging device according to the second embodiment. In an imaging device  301  illustrated in  FIG. 16 , similar reference signs are given to similar components to those of the imaging device  101  illustrated in  FIG. 3 , and description thereof will be omitted. 
     The metal thin film  102  of the imaging device  101  ( FIG. 3 ) according to the first embodiment is formed into a film shape. However, the imaging device  301  according to the second embodiment is different therefrom in that a film is not formed in the imaging device  301 . Here, a metal electrode  302  is described. As illustrated in  FIG. 16 , the metal electrode  302  is provided on a lower side of an AlO film  52  on an organic photoelectric conversion film  32  side, and is provided in a scattered manner. 
     In other words, the metal electrode  302  forming the upper electrode  31  can have a configuration remaining not in a shape of a film but at an atomic level. Also in the case of this configuration, AlO is present as the AlO film  52 , and therefore a passivation property is ensured. 
     When the imaging device  301  is viewed from above, as illustrated in  FIG. 17 , the metal electrode  302  is present. The metal electrode  302  may have a spherical shape, a quadrangle shape, or the like, and the shape thereof is not particularly limited. In addition, the metal electrode  302  may be disposed at regular intervals, or may be disposed at random intervals. 
     In addition, as illustrated in  FIG. 18 , the metal electrode  302  may be formed into a lattice shape. When the metal electrode  302  is formed into a lattice shape, the metal electrode  302  may be formed such that a first photodiode PD  36  is located in a lattice. In other words, the metal electrode  302  may be formed so as to be located between the photodiodes. 
     When the metal electrode  302  is formed into a lattice shape, the metal electrode  302  can have a light-shielding function. That is, by forming the metal electrode  302  into a lattice shape, forming the metal electrode  302  so as to have a width and a thickness capable of obtaining a light-shielding function, and forming the metal electrode  302  at a position at which the amount of light incident on a photodiode or the like is not reduced, the metal electrode  302  can be caused to function as a light-shielding film (light-shielding wall). 
     Note that when the metal electrode  302  is formed so as to have a predetermined shape such as a lattice shape, the metal electrode  302  can be formed by applying patterning, a shadow mask, or the like. 
     &lt;Configuration of Third Imaging Device&gt; 
     Next, a configuration of an imaging device according to a third embodiment will be described.  FIG. 19  is a diagram illustrating the configuration of the imaging device according to the third embodiment. In an imaging device  401  illustrated in  FIG. 19 , similar reference signs are given to similar components to those of the imaging device  101  illustrated in  FIG. 3 , and description thereof will be omitted. 
     The imaging device  401  according to the third embodiment includes a hole blocking layer. In the imaging device  401  illustrated in  FIG. 19 , a hole blocking layer  402  is provided as a part of an upper electrode  31 , and is provided on a lower side of a metal thin film  102  between the metal thin film  102  and an organic photoelectric conversion film  32 . 
     The hole blocking layer  402  is formed of a material such as lithium fluoride (LiF) or magnesium oxide (MgO). Even when the upper electrode  31  including the metal thin film  102  is stacked, a similar effect can be obtained, and a dark current can be reduced. 
     Note that here, the configuration in which the hole blocking layer  402  is provided in the imaging device  101  illustrated in  FIG. 3  has been described. However, the hole blocking layer  402  may be provided in the imaging device  111  illustrated in  FIG. 4 . Although not illustrated, when the hole blocking layer  402  is provided in the imaging device  111 , the hole blocking layer  402  is provided between the metal thin film  122  and the organic photoelectric conversion film  32 . 
     In addition, the hole blocking layer  402  may be provided in the imaging device  121  illustrated in  FIG. 5 . Although not illustrated, when the hole blocking layer  402  is provided in the imaging device  121 , the hole blocking layer  402  is provided between an AlO film  52  and the organic photoelectric conversion film  32 . 
     In addition, the hole blocking layer  402  may be provided in the imaging device  301  illustrated in  FIG. 16 . Although not illustrated, when the hole blocking layer  402  is provided in the imaging device  301 , the hole blocking layer  402  is provided between the AlO film  52  and the organic photoelectric conversion film  32 . In this case, a metal electrode  302  may be provided in the same layer as the hole blocking layer  402 , or the metal electrode  302  may be provided between the hole blocking layer  402  and the organic photoelectric conversion film  32 . 
     &lt;Configuration of Fourth Imaging Device&gt; 
     Next, a configuration of an imaging device according to a fourth embodiment will be described.  FIG. 20  is a diagram illustrating the configuration of the imaging device according to the fourth embodiment. In an imaging device  501  illustrated in  FIG. 20 , similar reference signs are given to similar components to those of the imaging device  101  illustrated in  FIG. 3 , and description thereof will be omitted. 
     The imaging device  501  according to the fourth embodiment includes an enthalpy control layer. In the imaging device  501  illustrated in  FIG. 20 , an enthalpy control layer  502  is provided on an upper side of a lower electrode  33  between an organic photoelectric conversion film  32  and the lower electrode  33 . 
     For example, the enthalpy control layer  502  is formed as an oxide film containing cadmium (Cd), copper (Cu), lead (Pb), palladium (Pd), or the like. In  FIG. 21 , materials which can be used as the enthalpy control layer  502  are listed. As illustrated in  FIG. 21 , the enthalpy control layer  502  can be formed of any one of Ag2O, CoO, Co3O4, CdO, Cs2O, CuO, Cu2O, GeO(c), GeO2(c1), GeO2(c2), NiO(c), PbO(c), PbO2(c2), PbO2(c), PdO(c), Rb2O(c), Rb2O2(c), SeO2(c), SeO3(c), TeO2 (C), Tl2O(c), and Tl2O3(c). 
     In  FIG. 21 , in the column of a transparent electrode, a material which can be used for the lower electrode  33  is described. In the column of a composition, the name of a substance (element symbol) for forming the material described in the column of the transparent electrode is described. In the column of a composition of an enthalpy control layer, the name of a substance (element symbol) forming a material which can be used as a material of the enthalpy control layer  502  is described. In addition, a numerical value described in association with each element symbol is a numerical value of a standard enthalpy of formation. 
     When the enthalpy control layer  502  is provided, like the imaging devices according to the first to third embodiments, it is possible to prevent the lower electrode  33  from being denaturalized, and to prevent a work function from becoming shallow, for example. 
     This indicates that in a case where the lower electrode  33  is formed of ITO, for example, when the enthalpy control layer  502  is formed of a film of copper oxide (CuO), the standard enthalpy of formation (−157.3 from  FIG. 21 ) of copper oxide is higher than the standard enthalpy of formation (−280.71 from  FIG. 21 ) of tin oxide (SnO) forming the ITO, and therefore the enthalpy control layer  502  is reduced selectively. 
     Therefore, hydrogen does not enter the lower electrode  33 , and fluctuation of a work function can be suppressed. Note that the enthalpy control layer  502  having a thickness of 5 nm is sufficient. 
     As described above, by providing the enthalpy control layer  502  in the lower electrode  33 , it is possible to prevent a substance such as hydrogen from entering the lower electrode  33 , and to prevent a work function of the lower electrode  33  from being changed. 
     Note that the enthalpy control layer  502  may be provided in any one of the above imaging devices according to the first to third embodiments. That is, the imaging device can be formed of a combination of any one of the metal thin film  102  ( FIG. 3 ), the metal thin film  112  ( FIG. 4 ), the metal thin film  122  ( FIG. 5 ), the metal electrode  302  ( FIG. 16 ), and the hole blocking layer  402  ( FIG. 19 ), and the enthalpy control layer  502 . 
     &lt;Configuration of Electronic Apparatus&gt; 
     The above imaging device can be applied to any electronic apparatus using a semiconductor device for an image capturing unit (photoelectric conversion unit), such as an imaging device including a digital still camera and a video camera, a mobile terminal device having an imaging function, including a portable telephone device, or a copying machine using an imaging device for an image reader. 
       FIG. 22  is a block diagram exemplifying a structure of an electronic apparatus according to the present technology, for example, an imaging device. As illustrated in  FIG. 22 , an imaging device  1000  according to the present technology includes an optical system including lenses  1001  or the like, an imaging element (imaging device)  1002 , a DSP circuit  1003 , a frame memory  1004 , a display device  1005 , a recording device  1006 , an operation system  1007 , a power supply system  1008 , and the like. In addition, the DSP circuit  1003 , the frame memory  1004 , the display device  1005 , the recording device  1006 , the operation system  1007 , and the power supply system  1008  are connected to one another through a bus line  1009 . 
     The lenses  1001  capture incident light (image light) from a subject to form an image on an imaging surface of the imaging element  1002 . The imaging element  1002  converts the amount of the incident light an image of which has been formed on the imaging surface by the lenses  1001  into an electrical signal in a pixel unit, and outputs the electrical signal as a pixel signal. 
     The display device  1005  is formed of a panel display device such as a liquid crystal display device or an organic electro luminescence (EL) display device, and displays a moving image or a still image formed by the imaging element  1002 . The recording device  1006  records the moving image or the still image formed by the imaging element  1002  in a recording medium such as a digital versatile disk (DVD) or a hard disk drive (HDD). 
     The operation system  1007  gives an operation command regarding various functions of the present imaging device under an operation of a user. The power supply system  1008  appropriately supplies various power sources serving as operation power sources for the DSP circuit  1003 , the frame memory  1004 , the display device  705 , the recording device  1006 , and the operation system  1007  to these supply targets. 
     The imaging device having the above configuration can used as an imaging device for a video camera, a digital still camera, a cameral module for a mobile apparatus, such as a portable telephone device, or the like. In addition, in the imaging device, the above imaging device can be used as the imaging element  1002 . 
     &lt;Usage Example of Imaging Device&gt; 
       FIG. 23  is a diagram illustrating a usage example using the above imaging device. 
     As described below, the above imaging device can be used in various cases of sensing light such as visible light, infrared light, ultraviolet light, or an X-ray.
         a device for taking an image used for appreciation, such as a digital camera or a portable apparatus with a camera function,   a device for transportation use, such as a vehicle-mounted sensor for imaging the front, the back, the surrounding, the inside, or the like of an automobile for safe driving such as automatic stop, for recognition of a driver&#39;s condition, and the like, a surveillance camera for monitoring a running vehicle and a road, or a measuring sensor for measuring a distance between vehicles or the like,   a device for home electronics use, such as a television set, a refrigerator, or an air conditioner for imaging a gesture of a user and operating an apparatus according to the gesture,   a device for medical care use and health care use, such as an endoscope or a device for receiving infrared light for angiography,   a device for security use, such as a surveillance camera for crime prevention or a camera for personal authentication,   a device for beauty care use, such as a skin measurement device for imaging a skin or a microscope for imaging a scalp,   a device for sports use, such as an action camera or a wearable camera for sports, and   a device for agricultural use, such as a camera for monitoring a condition of a field and a crop.       

     Note that the effects described here are merely examples, and the effects of the present technology are not limited thereto, and may include other effects. 
     Note that embodiments of the present technology are not limited to the above embodiments, and various modifications can be made to them without departing from the scope of the present technology. 
     Note that the present technology can have the following configurations. 
     (1) 
     An imaging device including: 
     an organic photoelectric conversion film; 
     an upper electrode provided in an upper portion of the organic photoelectric conversion film; 
     a lower electrode provided in a lower portion of the organic photoelectric conversion film; and 
     a metal thin film provided between the organic photoelectric conversion film and the upper electrode or between the organic photoelectric conversion film and the lower electrode. 
     (2) 
     The imaging device described in (1), in which 
     the metal thin film is provided between the organic photoelectric conversion film and the upper electrode, and 
     the upper electrode is formed of an oxide semiconductor, a metal oxide, and the metal thin film. 
     (3) 
     The imaging device described in (2), in which 
     the metal oxide is aluminum oxide (AlO), and the metal thin film is formed of aluminum (Al). 
     (4) 
     The imaging device described in any one of (1) to (3), in which the metal thin film is formed of any one of aluminum (Al), indium (In), silver (Ag), gold (Au), zinc (Zn), lithium (Li), tin (Sn), antimony (Sb), magnesium (Mg), cadmium (Cd), calcium (Ca), potassium (K), rubidium (Rb), cesium (Cs), strontium (Sr), barium (Ba), cerium (Ce), yttrium (Y), hafnium (Hf), nickel (Ni), gallium (Ga), and titanium (Ti). 
     (5) 
     The imaging device described in any one of (1) to (4), in which 
     each of the upper electrode and the lower electrode is formed of any one of ITO, tin oxide-based SnO2, zinc oxide-based materials aluminum zinc oxide, gallium zinc oxide, and indium zinc oxide, IGZO, CuI, InSbO4, ZnMgO, CuInO2, MgIn2O4, CdO, and ZnSnO3. 
     (6) 
     The imaging device described in any one of (1) to (5), in which 
     the organic photoelectric conversion film is formed of any one of a quinacridone derivative, a naphthalene derivative, an anthracene derivative, a phenanthrene derivative, a tetracene derivative, a pyrene derivative, a perylene derivative, and a fluoranthene derivative. 
     (7) 
     The imaging device described in any one of (1) to (6), in which the organic photoelectric conversion film is formed of any one of a polymer of phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, or diacetylene, and a derivative thereof, a metal complex dye, a cyanine dye, a merocyanine dye, a phenylxanthene dye, a triphenylmethane dye, a rhodacyanine dye, a xanthene dye, a macrocyclic azaannulene dye, an azulene dye, naphthoquinone, an anthraquinone dye, a condensed polycyclic aromatic compound such as anthracene or pyrene, a chain compound obtained by condensing an aromatic ring or heterocyclic compound, a heterocyclic ring compound containing two nitrogen atoms and having a squarylium group and a croconic methine group as a bonding chain, such as quinoline, benzothiazole, or benzoxazole, and a cyanine-like dye bonded by a squarylium group and a croconic methine group, and 
     the metal complex dye is any one of a dithiol metal complex dye, a metal phthalocyanine dye, a metal porphyrin dye, and a ruthenium complex dye. 
     (8) 
     The imaging device described in any one of (1) to (7), in which 
     the metal thin film has a thickness of 5 nm or less. 
     (9) 
     The imaging device described in any one of (1) to (8), in which the metal thin film is formed into a spherical shape or a predetermined shape, and is scattered at equal intervals or at random. 
     (10) 
     The imaging device described in any one of (1) to (9), further including a hole blocking layer between the metal thin film and the organic photoelectric conversion film. 
     (11) 
     The imaging device described in (1), including an enthalpy control layer along with the metal thin film or in place of the metal thin film. 
     (12) 
     The imaging device described in (11), in which the enthalpy control layer is provided between the organic photoelectric conversion film and the lower electrode. 
     (13) 
     The imaging device described in (11), in which the enthalpy control layer is formed of any one of Ag2O, CoO, Co3O4, CdO, Cs2O, CuO, Cu2O, GeO(c), GeO2(c1), GeO2(c2), NiO(c), PbO(c), PbO2(c2), PbO2(c), PdO(c), Rb2O(c), Rb2O2(c), SeO2(c), SeO3(c), TeO2 (C), Tl2O(c), and Tl2O3(c). 
     (14) 
     A manufacturing device for 
     forming an organic photoelectric conversion film, 
     forming an upper electrode in an upper portion of the organic photoelectric conversion film, 
     forming a lower electrode in a lower portion of the organic photoelectric conversion film, and 
     forming a metal thin film between the organic photoelectric conversion film and the upper electrode or between the organic photoelectric conversion film and the lower electrode. 
     (15) 
     The manufacturing device described in (14), in which the metal thin film is formed by vapor deposition. 
     (16) 
     The manufacturing device described in (14) or (15), in which 
     the metal thin film is formed between the organic photoelectric conversion film and the upper electrode, 
     the upper electrode is formed by stacking an oxide semiconductor, a metal oxide, and the metal thin film, and 
     the metal oxide is formed by oxidization at the time of film formation of the oxide semiconductor. 
     (17) 
     The manufacturing device described in any one of (14) to (16), in which the metal thin film is formed into a spherical shape or a predetermined shape so as to be scattered at equal intervals or at random. 
     (18) 
     The manufacturing device described in any one of (14) to (16), in which 
     a hole blocking layer is further formed between the metal thin film and the organic photoelectric conversion film. 
     (19) 
     The manufacturing device described in any one of (14) to (16), in which 
     an enthalpy control layer is formed along with the metal thin film or in place of the metal thin film. 
     (20) 
     A manufacturing device for 
     forming an organic photoelectric conversion film, 
     a step of forming an upper electrode in an upper portion of the organic photoelectric conversion film; 
     a step of forming a lower electrode in a lower portion of the organic photoelectric conversion film; and 
     a step of forming a metal thin film between the organic photoelectric conversion film and the upper electrode or between the organic photoelectric conversion film and the lower electrode. 
     REFERENCE SIGNS LIST 
     
         
           31  upper electrode 
           32  organic photoelectric conversion film 
           33  lower electrode 
           34  insulating film 
           35  substrate 
           36  first photodiode PD 
           37  second photodiode PD 
           102 ,  112 ,  122  metal thin film 
           302  metal electrode 
           402  hole blocking layer 
           502  enthalpy control layer