JP2013084789A - Organic image pick-up element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a residual image in an organic image pick-up element.SOLUTION: An organic image pick-up element 1 includes: plural pixel electrodes 40 having plural pixel parts 100 on a substrate 10, formed on a surface of the substrate 10 on a light incident side via an interlayer insulation layer 20, spaced from each other per pixel part 100, and electrically connected to a signal reading circuit 101; an optical functional layer 50 arranged on the plural pixel electrodes 40 in a continuous film manner; a counter electrode 60 arranged on the optical functional layer 50 and shared by the plural pixel parts 100; and at least one metallic wiring layer including plural metallic wiring portions 32 in the interlayer insulation layer 20. The optical functional layer 50 includes a photoelectric conversion layer including an organic material. A metallic wiring layer 32T nearest the pixel electrodes 40 has the metallic wiring portions 32 under the plural pixel electrodes 40, respectively. A gap 32w between the metallic wiring portions exists under a gap G between the pixel electrodes.

Description

  The present invention relates to an image pickup device, and more particularly to an image pickup device including an organic photoelectric conversion device having a photoelectric conversion layer containing an organic material in a pixel portion.

  Image sensors such as CCD sensors and CMOS sensors are widely known as image sensors used in digital still cameras, digital video cameras, mobile phone cameras, endoscope cameras, and the like.

  Currently, a plurality of pixel electrodes are arranged in a two-dimensional array on a substrate on which a readout circuit and the like are formed, and a photoelectric conversion layer containing at least an organic material and a counter electrode are sequentially provided thereon. Has been proposed (Patent Document 1).

  In the stacked imaging device described in Patent Document 1, the photoelectric conversion layer may be configured as a single sheet common to all the pixel portions, or may be divided for each pixel portion.

  On the other hand, in an image sensor having a configuration in which a photoelectric conversion layer is provided in a common film shape on a plurality of pixel electrodes, even when light is incident on the photoelectric conversion layer in the gap between adjacent pixel electrodes, Signal charges are generated in the same manner as when light enters the upper photoelectric conversion layer. These signal charges are collected by the pixel electrodes in the same manner as the signal charges generated on the pixel electrodes, and are read out as signal charges. As a result, although the pixel electrode size is smaller than the pixel size, the substantial aperture ratio is almost 100%, realizing high sensitivity.

JP 2008-263178 A

  However, in the image pickup device having the above configuration, after a lot of signal charges are generated due to particularly intense light irradiation, an afterimage may occur over a plurality of frames due to the residual charges in the photoelectric conversion layer. It is an upper problem.

  Such an afterimage is conspicuous particularly in the case of an organic CMOS image sensor using a CMOS transistor circuit composed of a plurality of metal wiring layers and transistors in a signal readout circuit below the pixel electrode, among organic image sensors.

  The present invention has been made in view of the above circumstances, and an object of the present invention is to provide an organic imaging device that suppresses the generation of residual charge that causes afterimage generation in an organic imaging device and has little afterimage.

The organic imaging device of the present invention is an organic imaging device having a plurality of pixel portions on a substrate on which a signal readout circuit is formed,
A plurality of pixel electrodes formed on the surface on the light incident side of the substrate via an interlayer insulating layer, formed separately for each pixel portion and electrically connected to the signal readout circuit;
An optical functional layer disposed on the plurality of pixel electrodes and between the pixel electrodes in a continuous film shape and shared by the plurality of pixel portions;
A counter electrode disposed on the optical functional layer and shared by the plurality of pixel portions;
In the interlayer insulating layer, including at least one metal wiring layer composed of a plurality of metal wiring portions,
The optical functional layer includes a photoelectric conversion layer containing an organic material,
The metal wiring layer closest to the pixel electrode is
Each of the metal wiring portions is provided under the plurality of pixel electrodes,
The gap between the adjacent metal wiring portions is formed so as to exist under the gap between the pixel electrodes corresponding to the metal wiring portions.

  In the organic imaging device of the present invention, the center line of the gap between the pixel electrodes and the center line of the gap between the metal wiring portions overlap in a cross-sectional view in the thickness direction in the direction connecting the pixel electrodes. Preferably, the metal wiring layer is formed to be substantially line symmetric with respect to the center line as an axis of symmetry, and the gap between the metal wiring portions is more than the gap between the pixel electrodes. Larger is preferred.

  The present inventor has found that the main cause of the afterimage generated in the image sensor having a configuration in which an organic photoelectric conversion layer is provided in a common film form on a plurality of pixel electrodes is a signal generated in the photoelectric conversion layer above the gap between the pixel electrodes. It has been found that a part of the electric charge is caused by taking time to be collected by the pixel electrode. As a result of intensive studies based on such knowledge, the present inventor has formed a metal wiring layer closest to the pixel electrode in the interlayer insulating layer with a gap under the gap between the pixel electrodes in the organic imaging device. With this configuration, in the optical functional layer above the gap between the pixel electrodes, the electric field strength in the direction toward the pixel electrodes is increased, and the time required for signal charges to be collected by the pixel electrodes is shortened. It has been found that the afterimage can be reduced.

  According to the present invention, in the organic imaging device, it is possible to suppress the generation of residual charges that cause afterimage generation, and thus it is possible to provide an organic imaging device with little afterimage.

1 is a schematic cross-sectional view showing a configuration of a main part of an image sensor according to an embodiment of the present invention. The top view which shows arrangement | positioning of a pixel electrode in the image pick-up element of FIG. 1A The figure which shows the relationship between the gap between pixel electrodes, and an afterimage (the 1) The figure which shows the relationship between the gap between pixel electrodes, and an afterimage (the 2) Cross-sectional schematic diagram showing electric field distribution in optical functional layer (Part 1) Cross-sectional schematic diagram showing electric field distribution in optical functional layer (Part 2) Diagram showing electric field strength distribution in the optical functional layer Diagram showing gap width dependency between pixel electrodes of electric field strength distribution in optical functional layer (thickness direction electric field strength) Diagram showing the gap width dependency between pixel electrodes in the electric field strength distribution in the optical functional layer (in-plane direction electric field strength) The figure which shows the gap width dependence between pixel electrodes of the area | region width | variety with weak electric field strength in FIG. The figure which shows the relationship between the area | region width with weak electric field strength in FIG. 6, and the number of afterimage electrons Schematic cross-sectional view of electric field strength examination model in the example (without electric wiring adjustment metal wiring layer gap) Cross-sectional schematic diagram of electric field strength examination model in Example (with electric wiring adjustment metal wiring layer gap) The figure which shows the gap width dependence of the metal wiring layer of the electric field strength distribution in the optical functional layer of the gap between pixel electrodes in an Example (in-plane direction electric field strength) Partial enlarged view of FIG. 10A The figure which shows the relationship between the gap | interval width | variety of a metal wiring layer in an Example, and the area | region width with a weak electric field strength

  An organic imaging device according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1A is a schematic cross-sectional view showing the configuration of the main part of the image sensor 1 of the present embodiment, and FIG. 1B is a plan view showing the arrangement of pixel electrodes in the image sensor 1 of FIG. 1A. In order to facilitate visual recognition, the scale of each part is appropriately changed and shown.

  The organic imaging device 1 of the present embodiment is an organic CMOS imaging device having a CMOS signal readout circuit that converts a signal charge accumulated in a signal readout circuit provided for each pixel into a voltage, as shown in FIG. The plurality of pixel portions 100 are provided on the substrate 10 on which the signal readout circuit 101 is formed, and are formed on the light incident side surface of the substrate 10 via the interlayer insulating layer 20 and separated for each pixel portion 100. And a plurality of pixel electrodes 40 electrically connected to the signal readout circuit 101 formed in this manner, and shared by the plurality of pixel portions 100 arranged in a continuous film shape on and between the pixel electrodes 40. An optical functional layer 50, a counter electrode 60 disposed on the optical functional layer 50 and shared by the plurality of pixel units 100, and a metal wiring including a plurality of metal wiring portions 32 in the interlayer insulating layer 20. Layer 32 The optical functional layer 50 includes a photoelectric conversion layer 52 including an organic material, and the metal wiring layer 32T closest to the pixel electrode 40 is provided under the plurality of pixel electrodes 40, respectively. And a gap (gap) 32w between adjacent metal wiring portions 32T is formed under a gap (gap) G between pixel electrodes 40 corresponding to the metal wiring portions. Yes.

  The plurality of pixel electrodes 40 are two-dimensionally arranged via the inter-pixel electrode gaps G as shown in FIG. 1B. The width 40 w of the pixel electrode 40 is smaller than that of the pixel unit 100.

In addition, a sealing layer 70 and a color filter 80 are sequentially stacked on the counter electrode 60.
"Mechanism of afterimage generation"

  First, the present inventor examined the main factors of afterimages in an organic imaging device. The number of afterimage electrons when the width of the pixel portion 100 was fixed to 3 μm and the gap G between the pixel electrodes was changed from 0.3 μm to 1.2 μm was examined up to 30 frames at a frame rate of 25 fps. The result is shown in FIG. 2A.

  As shown in FIG. 2A, it was confirmed that the larger the gap G between the pixel electrodes, the larger the number of afterimage electrons, that is, the afterimage is likely to occur. Further, it was confirmed that the afterimage was generated not only in the first frame but over a plurality of frames.

  In order to clarify the relationship between the afterimage and the gap G between the pixel electrodes, the relationship between the afterimage and the gap G between the pixel electrodes was examined for the third frame, the fourth frame, and the seventh frame after extinguishing. The result is shown in FIG. 2B.

  FIG. 2B shows that the number of afterimage electrons linearly decreases as the gap G decreases in any frame. 2A and 2B, it is clear that there is a deep relationship between the afterimage and the gap G, and the gap G is dominant over the afterimage.

  Next, the cause of the afterimage was examined. In the organic imaging device, an electric field is formed in the optical functional layer by applying a voltage to the counter electrode. When light is applied to the optical functional layer in a state where an electric field is formed, signal charges are generated in the photoelectric conversion layer of the optical functional layer, and the generated signal charges are transported to the pixel electrode 40. That is, the behavior of the signal charge in the optical functional layer is governed by the electric field. Therefore, the electric field strength distribution in the optical functional layer when a voltage was applied was examined.

  Usually, an organic imaging device has a connection portion (via plug) that connects a pixel electrode and a signal readout circuit. In addition, in the case of an organic CMOS image sensor, a plurality of metal wiring layers are provided inside an interlayer insulating layer below the pixel electrode in order to form a drive unit and a signal readout circuit.

  As described above, an afterimage becomes noticeable in the case of an organic CMOS image sensor using a CMOS circuit as a signal readout circuit among organic image sensors. Since the CMOS circuit is characterized by having a plurality of metal wiring layers inside the interlayer insulating layer under the pixel electrode, the electric field in the optical functional layer was examined with and without the metal wiring layer under the pixel electrode. .

  A preferred mode of the organic imaging device is that, like the organic imaging device 1 of the present embodiment, an electron blocking layer 51 and a photoelectric conversion layer are provided on a plurality of pixel electrodes and an optical functional layer 50 arranged in a continuous film shape on the gap between them. Since the layer 52 is included, the electric field in the optical functional layer 50 in consideration of the electron blocking layer and the photoelectric conversion layer was examined. The studied structures and results are shown in FIGS. 3A and 3B.

  FIG. 3A shows the case where there is no metal wiring layer, and FIG. 3B shows the case where there is a metal wiring layer. The pixel electrode 40, the optical functional layer 50, and the counter electrode 60 have the same configuration in FIGS. 3A and 3B. The thickness of the optical functional layer 50 is 500 nm, and the gap G between the pixel electrodes is 0.3 μm. The thickness of the insulating layer under the pixel electrode in FIG. 3A is 600 nm, and the metal wiring layer is disposed under the insulating layer so as to cover all the space G between the pixel electrodes. The voltage of each electrode is 10V for the counter voltage, 1V for the pixel electrode, and 0V for the metal wiring layer.

  When attention is paid to the electric field in the direction G of the pixel electrode 40 (horizontal direction in the drawing) in the optical function layer 50 in the gap G between the pixel electrodes, the electric field becomes stronger in the vicinity of the pixel electrodes 40 on both sides in both FIGS.

  On the other hand, regarding the electric field in the vertical direction in the drawing, in the aspect of FIG. 3A, the electric field is weaker toward the center of the gap G between the pixel electrodes. On the other hand, in the embodiment provided with the metal wiring layer 32 that is a continuous film shown in FIG. 3B, the electric field in the vertical direction in the inter-pixel electrode gap G is generally stronger than the embodiment in FIG. A stronger vertical electric field is observed on the part than in FIG. 3A.

  FIG. 4 shows the result of examining the distribution in the thickness direction of the electric field intensity on the pixel electrode 40 and in the central portion of the gap in FIGS. 3A and 3B. In the figure, the electric field intensity on the pixel electrode 40 is normalized as 1. As shown in the figure, on the pixel electrode 40, the electric field strength is substantially the same regardless of the presence or absence of the metal wiring layer 32, and is constant at any height (position in the thickness direction) in the optical functional layer. is there. On the other hand, in the central part of the gap, it is shown that the electric field strength is dramatically stronger in B having metal wiring than in A particularly at the height near the pixel electrode.

  From the above, it was shown that the organic CMOS image pickup device provided with the metal wiring layer in the interlayer insulating layer has higher electric field strength in the vertical direction at the central portion of the gap than that without the metal wiring layer. Further, the presence or absence of the metal wiring layer did not significantly affect the lateral electric field strength. Since the organic CMOS image sensor has a metal wiring layer that is a big difference from other organic image sensors, such a characteristic electric field strength distribution in the case where there is a metal wiring layer is This is considered to be the main cause of the remarkable afterimage. Then, next, the relationship between these electric field strength distributions and the afterimage in the organic CMOS image sensor shown in FIG. 2 was examined.

  In order to clarify the cause of the afterimage shown in FIG. 2, the electric field strength distribution was examined by changing the width of the gap G between the pixel electrodes 40 in the embodiment of FIG. 3B. The electric field strength distribution in the thickness direction on the pixel electrode 40 of the optical functional layer 50 and on the central portion of the gap between the pixel electrodes is represented by the electric field strength in the vertical direction (thickness direction) and the horizontal direction (direction toward the pixel electrode). Graphs divided into electric field strengths are shown in FIGS. 5 and 6 show only results when the gap G between the pixel electrodes is 0.3 μm, 0.6 μm, and 1.2 μm. Both FIG. 5 and FIG. 6 were normalized by assuming that the electric field intensity having the same magnitude as the vertical direction on the pixel electrode is 1.

  5 and 6, the electric field in the lateral direction is 0 on the pixel electrode. In addition, the vertical electric field was constant at all heights in the optical functional layer 50. On the other hand, on the gap G between the pixel electrodes, the electric field in the vertical direction was strong, and substantially the same electric field strength was obtained from the half on the pixel electrode. However, it was shown that the electric field in the lateral direction toward the pixel electrode direction is weak, and in particular, it is weaker near the center of the gap G between the pixel electrodes.

  5 and 6, it was found that when the gap is widened, the vertical electric field is slightly weakened, but the horizontal electric field is significantly weakened. That the electric field in the lateral direction is weak means that the force of the signal charges directed to the pixel electrode is weak, and there is a high possibility that the afterimage will be strongly affected. Therefore, FIG. 7 shows the gap width dependency between the pixel electrodes in a region where the horizontal electric field is weak (region which is 1/5 or less of the vertical electric field strength), and FIG. 7 shows the width of the region where the horizontal electric field strength is weak. FIG. 8 shows the results of examining the relationship between the number of afterimage electrons in the third, fourth, and seventh frames.

  From FIG. 7, it can be seen that the wider the gap width between the pixel electrodes, the wider the region where the lateral electric field strength is weaker. Further, it can be seen from FIG. 8 that the width of the region where the electric field in the lateral direction is weak and the number of afterimage electrons are linearly correlated. Therefore, it can be considered that the presence of a region having a weak lateral electric field is a dominant factor of the afterimage in the organic CMOS image sensor.

  Based on the examination results so far, the cause of the organic CMOS image sensor is considered as follows. First, in the optical functional layer on the pixel electrode, a signal charge is generated in the photoelectric conversion layer by a strong vertical electric field, and the signal charge generated by the strong vertical electric field is quickly transported to the pixel electrode. There is no causative residual charge. On the other hand, in the optical functional layer above the gap between the pixel electrodes, a signal charge is generated in the photoelectric conversion layer in the same manner as on the pixel electrode due to a strong vertical electric field. However, since the electric field in the lateral direction is weak, it takes a long time for signal charges to be transported to the pixel electrode, resulting in residual charges. As a result, it is considered that an afterimage is caused.

  As described above, the electric field in the lateral direction in the gap between the pixel electrodes is strengthened so that the signal charges generated in the photoelectric conversion layer near the center of the pixel electrode gap are transported to the pixel electrodes more quickly. It was found that the afterimage can be reduced by suppressing the image.

"Image sensor configuration"
Based on the above knowledge, the present inventor has developed a configuration in which the electric field in the lateral direction in the gap between the pixel electrodes is strengthened and the residual charge is suppressed, with respect to the metal wiring layer closest to the pixel electrode in the interlayer insulating layer. The present inventors have found a configuration having a gap in the vicinity of the center of the gap, and preferably having a gap larger than the gap between the pixel electrodes.

  In such a configuration, since the electric field strength in the lateral direction can be increased in the optical functional layer near the center of the gap between the pixel electrodes where the electric field in the vertical direction is strong, it occurred in the photoelectric conversion layer near the center of the gap between the pixel electrodes. The signal charge can be transported to the pixel electrode faster to suppress the residual charge, and as a result, the afterimage can be reduced.

  That is, the organic imaging device 1 of the present embodiment is a CMOS imaging device that converts signal charges accumulated in a signal readout circuit provided for each pixel into a voltage, and is formed on the substrate 10 on which the signal readout circuit 101 is formed. , Having a plurality of pixel portions 100, formed on the light incident side surface of the substrate 10 through the interlayer insulating layer 20, and electrically connected to the signal readout circuit 101 formed separately for each pixel portion 100. A plurality of pixel electrodes 40, and an optical functional layer 50 shared by the plurality of pixel portions 100 arranged in a continuous film shape on and between the pixel electrodes 40, and the optical functional layer 50 The counter electrode 60 that is shared by the plurality of pixel units 100 and the metal insulating layer 32 including a plurality of metal wiring portions 32 are included in the interlayer insulating layer 20. , Organic materials The metal wiring layer 32T closest to the pixel electrode 40 has a metal wiring part 32 under each of the plurality of pixel electrodes 40, and a gap 32w between the metal wiring parts is It is characterized by being formed so as to exist under the gap G between the pixel electrodes.

  The metal wiring layer 32T closest to the pixel electrode 40 is an electric field adjusting metal wiring layer 32T that strengthens the electric field in the lateral direction in the gap G between the pixel electrodes 40 and suppresses residual charges. The electric field adjusting metal wiring layer 32T has an electric field adjusting function, but may be a wiring layer having a function other than electric field adjusting as long as the electric field adjusting function is not impaired. Hereinafter, the metal wiring layer 32T closest to the pixel electrode 40 is represented as an electric field adjusting metal wiring layer 32T.

  The distance between the electric field adjusting metal wiring layer 32T and the pixel electrode 40 is determined by the design rule of the process for manufacturing the image sensor. Although the closer one is preferable, it is about 50 nm to 2000 nm.

  In the organic imaging device 1, in the cross-sectional view in the thickness direction in the direction connecting the pixel electrodes 40 (FIG. 1A), the center line of the gap between the pixel electrodes 40 and the center of the gap 32w between the adjacent electric field adjusting metal wiring layers 32T. Preferably, the electric field adjusting metal wiring layer 32T is formed substantially symmetrically with the center line as the axis of symmetry, and further, the electric field adjusting metal wiring layers 32T are arranged with each other. The gap 32w is preferably equal to or larger than the gap G between the pixel electrodes 40. Since the electric field adjusting metal wiring layer 32T is formed substantially symmetrically about the center line of the gap G between the pixel electrodes 40, the afterimage can be satisfactorily suppressed over the entire pixel.

  According to the organic imaging device 1, since it is possible to suppress the generation of residual charges that cause afterimages, a high-quality organic imaging device with few afterimages can be obtained.

  Below, the other layer structure of the organic photoelectric conversion element 1 is demonstrated.

<Substrate to interlayer insulation layer>
As the substrate 10, a silicon semiconductor substrate for a CMOS process is used. On the substrate 10, an interlayer insulating layer 20 made of a known insulating material such as SiO ₂ is formed. A plurality of pixel electrodes 40 are formed on the surface of the interlayer insulating layer 20. The pixel electrodes 40 are arranged in a one-dimensional or two-dimensional manner, for example. The pixel electrode will be described later.

  Further, a connection portion 31 (via plug) that connects the pixel electrode 40 and the signal readout circuit 101 is embedded in the interlayer insulating layer 20. The connection part 31 is made of a conductive material.

<< Signal readout circuit >>
The signal readout circuit 101 includes a CMOS transistor circuit (including a MOS transistor circuit) including a transistor formed in a substrate and a metal wiring layer 32 in an interlayer insulating layer.

  The signal readout circuit 101 includes, for example, a floating diffusion, a reset transistor, an output transistor, a selection transistor, etc., not shown. The reset transistor, the output transistor, and the selection transistor are each configured by an n-channel MOS transistor (hereinafter referred to as an nMOS transistor).

  Each transistor of the signal readout circuit 101 is shielded from light by a light shielding layer (not shown) provided in the interlayer insulating layer 20. The signal readout circuit 101 is connected to the pixel electrode 40 via the connection unit 31, accumulates signal charges generated in the optical functional layer, and outputs a signal voltage corresponding to the accumulated signal charge amount to the outside. Have

  The signal readout circuit 101, the interlayer insulating layer 20, the connection portion 31, the metal wiring layer 32, and the electric field adjusting metal wiring layer 32T are formed using a standard CMOS process.

<Optical functional layer>
An optical functional layer 50 having a photoelectric conversion layer 52 containing an organic material and an electron blocking layer 51 is formed so as to cover the plurality of pixel electrodes 40 and the interlayer insulating layer 20.

  In the optical functional layer 50, an electron blocking layer 51 is formed on the pixel electrode 40 side, and a photoelectric conversion layer 52 is formed on the electron blocking layer 51. The method for forming these optical functional layers 50 is not particularly limited, but vacuum vapor deposition is preferred. More specifically, resistance heating vapor deposition or electron beam heating vapor deposition is preferable.

<< Electron blocking layer >>
The electron blocking layer 51 is a layer for suppressing injection of electrons from the pixel electrode 40 to the photoelectric conversion layer 52 and has a function of suppressing dark current.

  The electron blocking layer 51 may be composed of a plurality of layers, for example, may be composed of a first blocking layer and a second blocking layer. Thus, by making the electron blocking layer 51 into a plurality of layers, an interface is formed between the first blocking layer and the second blocking layer, and discontinuity occurs in the intermediate level existing in each layer. It becomes difficult for the charge carriers to move through the intermediate level, and dark current can be suppressed. The electron blocking layer 51 may be a single layer.

  An electron-donating organic material can be used for the electron blocking layer 51. Specifically, in a low molecular material, N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD) or 4,4′-bis [N Aromatic diamine compounds such as-(naphthyl) -N-phenyl-amino] biphenyl (α-NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, pyrazoline derivative, tetrahydroimidazole, polyarylalkane, butadiene 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), porphine, tetraphenylporphine copper, phthalocyanine, copper phthalocyanine, titanium phthalocyanine oxide, etc. Polyphyrin compounds, triazole derivatives, oxa Zazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, annealed amine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, silazane derivatives, etc. In the polymer material, a polymer such as phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, diacetylene, or a derivative thereof can be used. Any compound having sufficient hole transportability can be used.

  An inorganic material can also be used for the electron blocking layer 51. In general, since an inorganic material has a dielectric constant larger than that of an organic material, when it is used for the electron blocking layer 51, a large voltage is applied to the photoelectric conversion layer, and the photoelectric conversion efficiency can be increased. Materials that can be used as the electron blocking layer 51 include calcium oxide, chromium oxide, chromium oxide copper, manganese oxide, cobalt oxide, nickel oxide, copper oxide, gallium copper oxide, strontium copper oxide, niobium oxide, molybdenum oxide, indium copper oxide, Examples include indium silver oxide and iridium oxide.

<< Photoelectric conversion layer >>
The photoelectric conversion layer 52 includes an organic material and generates a signal charge corresponding to the amount of received light. By including an organic material in the photoelectric conversion layer 52, desired spectral sensitivity can be easily obtained. The photoelectric conversion layer 52 includes a p-type organic semiconductor and an n-type organic semiconductor, among organic materials. Exciton dissociation efficiency can be increased by joining a p-type organic semiconductor and an n-type organic semiconductor to form a donor-acceptor interface. For this reason, the photoelectric conversion layer 52 having a configuration in which a p-type organic semiconductor and an n-type organic semiconductor are joined exhibits high photoelectric conversion efficiency. In particular, the photoelectric conversion layer 52 in which a p-type organic semiconductor and an n-type organic semiconductor are mixed is preferable because the junction interface is increased and the photoelectric conversion efficiency is improved.

  A p-type organic semiconductor (compound) is a donor organic semiconductor, and is mainly represented by a hole-transporting organic compound and refers to a compound having a property of easily donating electrons. More specifically, an organic compound having a smaller ionization potential when two organic materials are used in contact with each other. Therefore, any organic compound can be used as the donor organic semiconductor as long as it is an electron-donating organic compound.

  Although it does not specifically limit as a p-type semiconductor, For example, a triarylamine compound, a benzidine compound, a pyrazoline compound, a styrylamine compound, a hydrazone compound, a triphenylmethane compound, a carbazole compound, a polysilane compound, a thiophene compound, a phthalocyanine compound, a cyanine compound , Merocyanine compounds, oxonol compounds, polyamine compounds, indole compounds, pyrrole compounds, pyrazole compounds, polyarylene compounds, condensed aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives ), A metal complex having a nitrogen-containing heterocyclic compound as a ligand can be used. Not limited to this, as described above, any organic compound having an ionization potential smaller than that of an organic compound used as an n-type (acceptor) compound may be used as a donor organic semiconductor.

  An n-type organic semiconductor (compound) is an acceptor semiconductor, and is mainly represented by an electron-transporting compound and refers to a compound that easily accepts electrons. More specifically, an n-type semiconductor refers to a compound having a higher electron affinity when two compounds are used in contact with each other. Therefore, any compound can be used as the acceptor compound as long as it is an electron-accepting compound.

  The n-type semiconductor is not particularly limited. For example, a condensed aromatic carbocyclic compound (naphthalene derivative, anthracene derivative, phenanthrene derivative, tetracene derivative, pyrene derivative, perylene derivative, fluoranthene derivative), nitrogen atom, oxygen atom, sulfur atom 5- to 7-membered heterocyclic compounds (for example, pyridine, pyrazine, pyrimidine, pyridazine, triazine, quinoline, quinoxaline, quinazoline, phthalazine, cinnoline, isoquinoline, pteridine, acridine, phenazine, phenanthroline, tetrazole, pyrazole, imidazole, thiazole , Oxazole, indazole, benzimidazole, benzotriazole, benzoxazole, benzothiazole, carbazole, purine, triazolopyridazine, tria Ropyrimidine, tetrazaindene, oxadiazole, imidazopyridine, pyralidine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine, etc.), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, nitrogen-containing heterocyclic compounds And a metal complex having as a ligand. However, the present invention is not limited thereto, and as described above, any compound having an electron affinity higher than that of the compound used as the p-type (donor) compound may be used as the acceptor semiconductor.

  Any organic dye may be used as the p-type organic semiconductor or the n-type organic semiconductor, but preferably a cyanine dye, a styryl dye, a hemicyanine dye, a merocyanine dye (including zero methine merocyanine (simple merocyanine)), 3 Nuclear merocyanine dye, 4-nuclear merocyanine dye, rhodacyanine dye, complex cyanine dye, complex merocyanine dye, allopolar dye, oxonol dye, hemioxonol dye, squalium dye, croconium dye, azamethine dye, coumarin dye, arylidene dye, anthraquinone dye, tri Phenylmethane dye, azo dye, azomethine dye, spiro compound, metallocene dye, fluorenone dye, fulgide dye, perylene dye, perinone dye, phenazine dye, phenothiazine color , Quinone dye, diphenylmethane dye, polyene dye, acridine dye, acridinone dye, diphenylamine dye, quinacridone dye, quinophthalone dye, phenoxazine dye, phthaloperylene dye, diketopyrrolopyrrole dye, dioxane dye, porphyrin dye, chlorophyll dye, phthalocyanine dye, And metal complex dyes and condensed aromatic carbocyclic dyes (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives).

As the n-type organic semiconductor, it is particularly preferable to use fullerene or a fullerene derivative having excellent electron transport properties. Fullerene C ₆₀ , fullerene C ₇₀ , fullerene C ₇₆ , fullerene C ₇₈ , fullerene C ₈₀ , fullerene C ₈₂ , fullerene C ₈₄ , fullerene C ₉₀ , fullerene C ₉₆ , fullerene C ₂₄₀ , fullerene ₅₄₀ , mixed fullerene Represents a fullerene nanotube, and a fullerene derivative represents a compound having a substituent added thereto.

  The substituent for the fullerene derivative is preferably an alkyl group, an aryl group, or a heterocyclic group. More preferably, the alkyl group is an alkyl group having 1 to 12 carbon atoms, and the aryl group and the heterocyclic group are preferably a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, fluorene ring, triphenylene ring, naphthacene ring. , Biphenyl ring, pyrrole ring, furan ring, thiophene ring, imidazole ring, oxazole ring, thiazole ring, pyridine ring, pyrazine ring, pyrimidine ring, pyridazine ring, indolizine ring, indole ring, benzofuran ring, benzothiophene ring, isobenzofuran Ring, benzimidazole ring, imidazopyridine ring, quinolidine ring, quinoline ring, phthalazine ring, naphthyridine ring, quinoxaline ring, quinoxazoline ring, isoquinoline ring, carbazole ring, phenanthridine ring, acridine ring, phenanthroline , Thianthrene ring, chromene ring, xanthene ring, phenoxathiin ring, phenothiazine ring, or phenazine ring, more preferably a benzene ring, naphthalene ring, anthracene ring, phenanthrene ring, pyridine ring, imidazole ring, oxazole ring, or A thiazole ring, particularly preferably a benzene ring, a naphthalene ring, or a pyridine ring. These may further have a substituent, and the substituents may be bonded as much as possible to form a ring. In addition, you may have a some substituent and they may be the same or different. A plurality of substituents may be combined as much as possible to form a ring.

  When the photoelectric conversion layer 52 includes fullerene or a fullerene derivative, electrons generated by photoelectric conversion can be quickly transported to the pixel electrode 40 or the counter electrode 60 via the fullerene molecule or the fullerene derivative molecule. When fullerene molecules or fullerene derivative molecules are connected to form an electron path, the electron transport property is improved, and high-speed response of the photoelectric conversion element can be realized. For this purpose, it is preferable that 40% or more of fullerene or fullerene derivative is contained in the photoelectric conversion layer. However, when there are too many fullerenes or fullerene derivatives, the p-type organic semiconductor is reduced, the junction interface is reduced, and the exciton dissociation efficiency is lowered.

  When the triarylamine compound described in Japanese Patent No. 4213832 is used as a p-type organic semiconductor mixed with fullerene or a fullerene derivative in the photoelectric conversion layer 52, a high SN ratio of the photoelectric conversion element can be expressed. Particularly preferred. If the ratio of fullerene or fullerene derivative in the photoelectric conversion layer is too large, the amount of the triarylamine compound is reduced and the amount of incident light absorbed is reduced. As a result, the photoelectric conversion efficiency is reduced, so that the fullerene or fullerene derivative contained in the photoelectric conversion layer preferably has a composition of 85% or less.

<Counter electrode>
The counter electrode 60 is an electrode facing the pixel electrode 40 and is provided so as to cover the optical functional layer 50. An optical functional layer 50 including a photoelectric conversion layer 52 is provided between the pixel electrode 40 and the counter electrode 60.

  The counter electrode 60 is made of a conductive material that is transparent to incident light so that light enters the photoelectric conversion layer 52. The counter electrode 60 is connected to a counter electrode voltage supply unit (not illustrated) that applies a predetermined voltage to the counter electrode 60 via a connection unit (not illustrated) disposed outside the photoelectric conversion layer 52. .

  The counter electrode 60 is preferably composed of a transparent conductive film in order to allow light to enter the optical functional layer 50 including the photoelectric conversion layer 52, for example, a metal, a metal oxide, a metal nitride, a metal boride, an organic Examples thereof include conductive compounds and mixtures thereof. Specific examples include tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), indium tungsten oxide (IWO), conductive metal oxides such as titanium oxide, and metal nitrides such as TiN. Metal, gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni), aluminum (Al), etc., and a mixture or laminate of these metals and conductive metal oxides Products, organic conductive compounds such as polyaniline, polythiophene, and polypyrrole, and laminates of these with ITO. Particularly preferable materials for the transparent conductive film are ITO, IZO, tin oxide, antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), zinc oxide, antimony-doped zinc oxide (AZO), gallium-doped zinc oxide ( GZO).

  The surface resistance of the counter electrode 60 is preferably 10 kΩ / □ or less, more preferably 1 kΩ / □ or less when the signal readout circuit 101 is a CMOS type. When the signal readout circuit 101 is a CCD type, it is preferably 1 kΩ / □ or less, and more preferably 0.1 kΩ / □ or less.

  The light transmittance of the counter electrode 60 is preferably 60% or more, more preferably 80% or more, more preferably 90% or more, and more preferably 95% or more in the visible light wavelength.

  Of the signal charges generated in the photoelectric conversion layer 52, holes are collected at the pixel electrode 40 and electrons are collected at the counter electrode, so that a higher voltage than the pixel electrode is applied to the counter electrode 60. In order to achieve both high sensitivity and low dark current, the voltage applied to the counter electrode 60 is about 5V to 20V.

<Pixel electrode>
The pixel electrode 40 is an electrode for collecting charges for collecting charges generated in the photoelectric conversion layer 52 between the pixel electrode 40 and the counter electrode 60 facing the pixel electrode 40. The pixel electrode 40 is connected to the signal readout circuit 101 via the connection unit 31. The signal readout circuit 101 is provided on the substrate 10 corresponding to each of the plurality of pixel electrodes 40, and reads out a signal corresponding to the charge collected by the corresponding pixel electrode 40. The charges collected by each pixel electrode 40 become a signal in the signal readout circuit 101 of each corresponding pixel, and an image is synthesized from signals acquired from a plurality of pixels.

  The pixel electrode 40 is formed on the interlayer insulating film 20 by sputtering or the like and then etched through a mask to form a predetermined pattern. Before the optical functional layer 50 is formed, the pixel electrode 40 is formed. The interlayer insulating film is exposed between 40.

  The pixel electrode 40 is not particularly limited as long as it is a conductive material generally used as an electrode, and examples thereof include metals, metal oxides, metal nitrides, metal borides, organic conductive compounds, and mixtures thereof. Specific examples include tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), indium tungsten oxide (IWO), conductive metal oxides such as titanium oxide, and titanium oxynitride (TiNxOx). ), Metal nitrides such as titanium nitride (TiN), metals such as gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni), aluminum (Al), and these metals And conductive metal oxide mixtures or laminates, organic conductive compounds such as polyaniline, polythiophene, and polypyrrole, and laminates of these with ITO. Particularly preferred as the material of the pixel electrode 40 is any one of titanium oxynitride, titanium nitride, molybdenum nitride, tantalum nitride, and tungsten nitride.

  The size of the pixel electrode 40 is preferably 3 μm or less because the effect of the present invention is remarkable. More preferably, it is 2 μm or less. More preferably, it is 1.5 μm or less. The gap (pixel gap) G between the pixel electrodes 40 is preferably 0.3 μm or less, more preferably 0.25 μm or less, and still more preferably 0.2 μm or less.

  When the step corresponding to the film thickness of the pixel electrode 40 is steep at the end of the pixel electrode 40, there are significant irregularities on the surface of the pixel electrode 40, or minute dust adheres to the pixel electrode 40, A layer on the pixel electrode 40 becomes thinner than a desired film thickness or a crack occurs. When the counter electrode 60 is formed on the layer in such a state, a pixel defect such as an increase in dark current or a short circuit occurs due to contact or electric field concentration between the pixel electrode 40 and the counter electrode 60 in the defective portion. Further, the above-described defects may cause a decrease in manufacturing yield due to a decrease in the adhesion between the pixel electrode 40 and the layer above it.

  In order to prevent the above defects and improve the reliability of the element, it is preferable that the surface smoothness of the pixel electrode 40 is good. In order to remove particles on the pixel electrode 40, it is particularly preferable to clean the pixel electrode 40 and the like using a general cleaning technique used in a semiconductor manufacturing process before forming the electron blocking layer. .

<Sealing layer>
The sealing layer 70 protects the optical functional layer 50 from deterioration factors such as water molecules. The sealing layer 70 is formed so as to cover the counter electrode 20.

  As the sealing layer 70, the following conditions are required.

  First, it is possible to protect the photoelectric conversion layer by preventing intrusion of factors that degrade the organic photoelectric conversion material contained in the solution, plasma, and the like in each manufacturing process of the device.

  Secondly, after the device is manufactured, the intrusion of factors such as water molecules that degrade the organic photoelectric conversion material is prevented, and the organic photoelectric conversion layer is prevented from deteriorating over a long period of storage / use.

  Third, when the sealing layer 70 is formed, the already formed photoelectric conversion layer is not deteriorated.

  Fourth, since incident light reaches the photoelectric conversion layer through the sealing layer 70, the sealing layer 70 must be transparent to light having a wavelength detected by the photoelectric conversion layer.

  The sealing layer 70 can be composed of a thin film made of a single material. However, by providing a multi-layer structure and providing each layer with a different function, stress relaxation of the entire sealing layer 70 and generation of dust during the manufacturing process are possible. Such effects as the suppression of defects such as cracks and pinholes caused by the above, and the optimization of material development can be expected. The number of stacked sealing layers 70 is not particularly limited. For example, the sealing layer 70 has a two-layer structure of an alumina film formed by the ALCVD method and a silicon oxide film formed by the CVD method. .

The color filter 80 is formed at a position facing each pixel electrode 40 on the sealing layer 70. Although not shown, in practice, a partition for improving light utilization efficiency may be provided between the color filters 80 on the sealing layer 70.
As described above, the organic imaging element 1 is configured.

"Design changes"
The organic imaging device of the present invention has been described in detail above. In the above embodiment, the mode in which the pixel electrode gap is provided only in the uppermost layer of the metal wiring layer has been described. However, the metal wiring layer other than the uppermost layer may have a gap under the gap G between the pixel electrodes. . Other embodiments are not limited to the above-described embodiments, and can be appropriately changed without departing from the gist of the present invention.

  Examples of the present invention and comparative examples will be described.

  As an example, a mode (FIG. 9B) in which the electric field adjustment metal wiring layer 32T divided symmetrically about the center line of the gap G under the gap G between the pixel electrodes has a gap 32w (FIG. 9B), comparative example As for the embodiment (FIG. 9A) in which the electric field adjusting metal wiring layer 32T does not have a gap under the gap G between the pixel electrodes, an optical functional layer considering the photoelectric conversion layer and the electron blocking layer under the following conditions: The electric field strength distribution in 50 was examined.

  The numerical value described in the figure is a voltage value in each metal layer. The interlayer insulating film thickness is 0.6 μm, the pixel electrode thickness is 15 nm, the optical functional layer thickness is 0.5 μm, the gap G is 0.3 μm, and the relative dielectric constants of the interlayer insulating film 20 and the optical functional layer 50 are both 4. did. In this configuration, the electric field strength distribution in the optical functional layer 50 when the gap 32w of the electric field adjusting metal wiring layer 32T in FIG. 9B was changed from 0.2 μm to 0.6 μm was examined.

  The examination results are shown in FIG. 10A and FIG. 10B (enlarged view of the region circled in FIG. 10A). The numbers shown in the legend in FIGS. 10A and 10B represent the gap 32w of the electric field adjusting metal wiring layer 32T. 0 corresponds to the case of FIG. 9A. 10A and 10B are graphs plotting the electric field strength in the lateral direction at the interface between the photoelectric conversion film 50 and the interlayer insulating film 20 in the gap G between the pixel electrodes. 0 corresponds to the center of the gap G, and ± 0.15 μm corresponds to the pixel electrode end.

  As shown in FIG. 10B, it becomes clear that the lateral electric field in the optical functional layer 50 on the gap G of the pixel electrode 40 becomes stronger as the separation width 32w of the electric field adjusting metal wiring layer 32T becomes larger. It was.

  FIG. 11 shows the change in the width of the region where the electric field is weak (the electric field strength that is 1/5 or less of the electric field strength in the vertical direction) when the separation width 32w (space between control metals) is changed. As shown in FIG. 11, it was shown that by forming the separation width 32w wide, the width of the region having a low electric field strength in the lateral direction (direction toward the pixel electrode) can be reduced. As described above, since this region is the main cause of the afterimage, such a configuration can reduce the afterimage.

DESCRIPTION OF SYMBOLS 1 Image sensor 10 Board | substrate 20 Interlayer insulating layer 31 Connection part 32 Metal wiring part (metal wiring layer)
Metal wiring layer closest to the 32T pixel electrode (metal wiring layer for electric field adjustment)
40 pixel electrode 50 optical functional layer 60 counter electrode 70 sealing layer 80 color filter 100 pixel part 101 signal readout part G gap between pixel electrodes (gap between pixel electrodes)
32w gap between metal wiring parts

Claims (4)

An organic imaging device having a plurality of pixel portions on a substrate on which a signal readout circuit is formed,
A plurality of pixel electrodes formed on the light incident side surface of the substrate through an interlayer insulating film and formed separately for each pixel portion and electrically connected to the signal readout circuit;
An optical functional layer disposed on the plurality of pixel electrodes and between the pixel electrodes in a continuous film shape and shared by the plurality of pixel portions;
A counter electrode disposed on the optical functional layer and shared by the plurality of pixel portions;
In the interlayer insulating film, including at least one metal wiring layer composed of a plurality of metal wiring portions,
The optical functional layer includes a photoelectric conversion layer containing an organic material,
The metal wiring layer closest to the pixel electrode is
Each of the metal wiring portions is provided under the plurality of pixel electrodes,
An organic imaging device, wherein a gap between adjacent metal wiring portions is formed so as to exist under a gap between the pixel electrodes corresponding to the metal wiring portions.   2. The center line of the gap between the pixel electrodes and the center line of the gap between the metal wiring portions overlap in a cross-sectional view in the thickness direction in the direction connecting the pixel electrodes. Organic imaging device.   The organic imaging element according to claim 2, wherein the metal wiring layer is formed in substantially line symmetry with the center line as a symmetry axis.   The organic imaging element according to claim 1, wherein a gap between the metal wiring portions is larger than a gap between the pixel electrodes.