JP2009272528A - Photoelectric conversion element, method of manufacturing photoelectric conversion element, and solid-state image sensor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric conversion element capable of supressing dark current without reducing the efficiency of photoelectric conversion, to provide a method of manufacturing the photoelectric conversion element, and to provide a solid-state image sensor. <P>SOLUTION: The photoelectric conversion element includes a photoelectric conversion layer 102 arranged between a pair of electrodes 101 and 104, and an electric charge blocking layer 105 formed between the electrodes 101 and 104, and the photoelectric conversion layer 102, wherein an average surface roughness of the electric charge blocking layer 105 is 2.0 nm or less. In other words, a diffraction peak can not be observed in a X-ray diffraction spectrum of the electric charge blocking layer 105, or a half width of the highest diffraction peak therein is ≥5 degrees. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a photoelectric conversion element including a photoelectric conversion film between a pair of electrodes, and more particularly to a photoelectric conversion element including a charge blocking layer that serves as a barrier against charge injection from an electrode to a photoelectric conversion film.

  In general, an organic thin film solar cell is evaluated for performance without applying an external electric field because it aims to extract electric power. On the other hand, organic photoelectric conversion elements, such as image input elements and optical sensors, need to maximize photoelectric conversion efficiency, so voltage must be applied from the outside to improve photoelectric conversion efficiency and response speed. There are many. When an external voltage is applied to an organic photoelectric conversion element, dark current increases due to hole injection or electron injection from an electrode due to an external electric field, and an element having a large ratio of photocurrent to dark current can be obtained. There wasn't. Therefore, it can be said that the technique of suppressing the dark current without reducing the photocurrent is one of the important techniques of the photoelectric conversion element. Therefore, as a conventional organic photoelectric conversion element, there is a method of suppressing dark current by inserting a blocking layer serving as a Schottky barrier against carrier injection (dark current) from an electrode between the electrode and the photoelectric conversion layer. Are known. In this method, in order to suppress carrier injection from the electrode when an external electric field is applied, a material having a Schottky barrier with the electrode as large as possible is used as the blocking layer. In particular, organic materials and inorganic oxides are known as materials for the hole blocking layer that suppresses hole injection from the electrodes. As a photoelectric conversion element having a configuration including a blocking layer, for example, there are those shown in the following patent documents.

JP 2007-273945 A

  By the way, when an organic material is used, since a material having a deep electron affinity Ea is small and carriers generated by photoelectric conversion are also inhibited, a decrease in photoelectric conversion efficiency has been a problem. In addition, when an inorganic oxide is used, a material having a deep electron affinity can be selected, and the decrease in photoelectric conversion efficiency is small, but a sufficient dark current suppressing effect cannot be obtained, and a high S / N ratio cannot be realized. It was.

  The present invention has been made in view of the above circumstances, and an object thereof is to provide a photoelectric conversion element capable of suppressing dark current without reducing photoelectric conversion efficiency, a method for manufacturing the photoelectric conversion element, and a solid-state imaging element. It is to provide.

  The present inventor has found a method for suppressing dark current by forming an inorganic flat film from an inorganic oxide that tends to be a microcrystalline and uneven film. Specifically, a method of lowering crystallinity by mixing two or more kinds of inorganic oxides, a method of lowering crystallinity by cooling the substrate, or a method of combining them is effective. By using such an amorphous inorganic oxide layer as a hole blocking layer, it is possible to suppress dark current without lowering the photoelectric conversion efficiency compared to the case of using an uneven oxide-free layer. A higher S / N ratio can be realized.

The above object of the present invention is achieved by the following configurations.
(1) a pair of electrodes;
A photoelectric conversion layer disposed between the pair of electrodes;
A charge blocking layer that is formed between the one electrode and the photoelectric conversion layer, and suppresses injection of charge from one of the pair of electrodes to the photoelectric conversion layer when a voltage is applied to the pair of electrodes; A photoelectric conversion element comprising:
The photoelectric conversion element whose average roughness of the surface of the said charge blocking layer is 2.0 nm or less.
(2) a pair of electrodes;
A photoelectric conversion layer disposed between the pair of electrodes;
A charge blocking layer that is formed between the one electrode and the photoelectric conversion layer, and suppresses injection of charge from one of the pair of electrodes to the photoelectric conversion layer when a voltage is applied to the pair of electrodes; A photoelectric conversion element comprising:
A photoelectric conversion element in which a diffraction peak does not appear in an X-ray diffraction spectrum of the charge blocking layer, or a half-value width of a diffraction peak that is maximum therein is 5 ° or more.
(3) The photoelectric conversion element according to (1) or (2) above,
A photoelectric conversion element in which the charge blocking layer has an amorphous structure.
(4) The photoelectric conversion element according to any one of (1) to (3) above,
The photoelectric conversion element in which the said charge blocking layer contains 2 or more types of inorganic oxides.
(5) The photoelectric conversion element according to any one of (1) to (4) above,
The photoelectric conversion element in which the charge blocking layer is a mixture of two or more inorganic oxides.
(6) The photoelectric conversion element according to any one of (1) to (5) above,
A photoelectric conversion element using CeO ₂ as one of the inorganic oxides included in the charge blocking layer.
(7) The photoelectric conversion element according to any one of (1) to (69),
A photoelectric conversion element using SnO ₂ as one of the inorganic oxides included in the charge blocking layer.
(8) The photoelectric conversion element according to any one of (1) to (7) above,
A photoelectric conversion element using Ta ₂ O ₅ as one of the inorganic oxides included in the charge blocking layer.
(9) The photoelectric conversion element according to any one of (1) to (8) above,
A photoelectric conversion element using CeO ₂ and Ta ₂ O ₅ as an inorganic oxide contained in the charge blocking layer.
(10) The photoelectric conversion element according to any one of (1) to (9) above,
A photoelectric conversion element in which the charge blocking layer is further provided between the other of the pair of electrodes and the photoelectric conversion layer.
(11) The photoelectric conversion element according to any one of (1) to (10) above,
The photoelectric conversion element whose thickness of the said charge blocking layer is 10 nm-200 nm.
(12) The photoelectric conversion element according to any one of (1) to (11) above,
A photoelectric conversion element in which a value obtained by dividing a voltage applied from the outside to the pair of electrodes by a distance between the pair of electrodes is 1.0 × 10 ⁵ V / cm to 1.0 × 10 ⁷ V / cm.
(13) The photoelectric conversion element according to any one of (1) to (12) above,
A semiconductor substrate having at least one photoelectric conversion layer laminated thereon;
A charge storage unit formed in the semiconductor substrate for storing the charge generated in the photoelectric conversion layer;
A photoelectric conversion element provided with the electrode for taking out the said electric charge of the said pair of electrodes of the said photoelectric converting layer, and the connection part which electrically connects the said charge storage part.
(14) The photoelectric conversion element according to (13) above,
A photoelectric conversion element comprising an in-substrate photoelectric conversion unit that absorbs light transmitted through the photoelectric conversion layer in the semiconductor substrate, generates a charge corresponding to the light, and accumulates the charge.
(15) The photoelectric conversion element according to (14) above,
The photoelectric conversion element in which the photoelectric conversion part in the substrate is a plurality of photodiodes that absorb light of different colors stacked in the semiconductor substrate.
(16) The photoelectric conversion element according to (15) above,
A photoelectric conversion element in which the in-substrate photoelectric conversion unit is a plurality of photodiodes that absorb light of different colors arranged in a direction perpendicular to an incident direction of incident light in the semiconductor substrate.
(17) The photoelectric conversion element according to any one of (1) to (16) above,
The photoelectric conversion layer laminated on the semiconductor substrate is one,
The plurality of photodiodes are a blue photodiode having a pn junction surface formed at a position capable of absorbing blue light, and a red photodiode having a pn junction surface formed at a position capable of absorbing red light. Yes,
A photoelectric conversion element in which the photoelectric conversion layer absorbs green light.
(18) A solid-state imaging device in which a plurality of the photoelectric conversion devices according to any one of (1) to (17) are arranged in an array,
A solid-state imaging device including a signal reading unit that reads a signal corresponding to the charge accumulated in the charge accumulation unit of each of the plurality of photoelectric conversion elements.
(19) a pair of electrodes;
A photoelectric conversion layer disposed between the pair of electrodes;
A charge blocking layer that is formed between the one electrode and the photoelectric conversion layer, and suppresses injection of charge from one of the pair of electrodes to the photoelectric conversion layer when a voltage is applied to the pair of electrodes; A method for producing a photoelectric conversion element comprising:
A method for producing a photoelectric conversion element, wherein the substrate temperature is maintained at 0 ° C. or lower when the charge blocking layer is formed.

  ADVANTAGE OF THE INVENTION According to this invention, the photoelectric conversion element which can suppress a dark current, without reducing photoelectric conversion efficiency, the manufacturing method of a photoelectric conversion element, and a solid-state image sensor can be provided.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
(First embodiment)
Fig.1 (a) is a cross-sectional schematic diagram which shows the basic composition of the photoelectric conversion element which is 1st embodiment of this invention. Moreover, FIG.1 (b) is a cross-sectional schematic diagram which shows the modification of the photoelectric conversion element of 1st embodiment.
The photoelectric conversion element shown in FIG. 1A includes a substrate S, a lower electrode (pixel electrode) 101 formed on the substrate S, a photoelectric conversion layer 102 formed on the lower electrode 101, and a photoelectric conversion layer. A hole blocking layer 105 formed on the hole 102 and an upper electrode (counter electrode) 104 formed on the hole blocking layer 105 are provided. 1B includes a substrate S, a lower electrode (pixel electrode) 101 formed on the substrate S, an electron blocking layer 103 formed on the lower electrode 101, an electron A photoelectric conversion layer 102 formed on the blocking layer 103, a hole blocking layer 105 formed on the photoelectric conversion layer 102, and an upper electrode (counter electrode) 104 formed on the hole blocking layer 105 are provided. . In the following description, the hole blocking layer 105 and the electron blocking layer 103 are collectively referred to as a charge blocking layer.

  In the photoelectric conversion element shown in FIG. 1, light enters from above the upper electrode 104. Further, the photoelectric conversion element shown in FIG. 1 has a lower portion so that electrons out of charges (holes and electrons) generated in the photoelectric conversion layer 102 are moved to the upper electrode 104 and holes are moved to the lower electrode 101. A bias voltage is applied between the electrode 101 and the upper electrode 104. That is, the upper electrode 104 is an electron collecting electrode and the lower electrode 101 is a hole collecting electrode.

  The upper electrode 104 is made of a transparent conductive material because light needs to be incident on the photoelectric conversion layer 102. Here, the term “transparent” means that visible light having a wavelength in the range of about 420 nm to about 660 nm is transmitted by about 80% or more. ITO is preferably used as the transparent conductive material.

  The lower electrode 101 may be any conductive material and need not be transparent. However, although the photoelectric conversion element shown in FIG. 1 will be described later, since it may be necessary to transmit light also below the lower electrode 101, the lower electrode 101 may also be formed of a transparent conductive material. preferable. Like the upper electrode 104, the lower electrode 101 is also preferably made of ITO.

The photoelectric conversion layer 102 includes a material having a photoelectric conversion function. The photoelectric conversion function refers to a function capable of absorbing visible light, short-wavelength ultraviolet light, and X-rays from long-wavelength infrared rays, converting them into electricity, and extracting them to the outside. The photoelectric conversion layer can be made of a material that absorbs light having a wavelength such as X-rays other than visible and infrared, and the surface of the photoelectric conversion layer also exhibits crystallinity that causes unevenness (or shows The effect can be obtained in the same manner by providing the charge blocking layer of the present invention. The organic photoelectric conversion material that absorbs visible light will be described in detail below. The invention of this patent is based on CIGS (Cu-In-Ga-Se) for photoelectric conversion of infrared light and ZnO for photoelectric conversion of ultraviolet light. It is also possible to apply to wide gap oxides such as. It is also effective when using a photoelectric conversion material that photoelectrically converts X-rays. As a photoelectric conversion material, a-Se, Se-Te, Se-As-Te, doped with 10-200 ppm of a-Se, Cl, As ₂ Se ₃ , Bi ₁₂ MO ₂₀ (M: Ti, Si, Ge), Bi ₄ M ₃ O ₁₂ (M: Ti, Si, Ge), Bi ₂ O ₃ , BiMO ₄ (M: Nb, Ta, V) ), Bi ₂ WO ₆ , Bi ₂₄ B ₂ O ₃₉ , ZnO, ZnS, ZnSe, ZnTe, MNb0 ₃ (M: Li, Na, K), PbO, HgI ₂ , PbI ₂ , CdS, CdSe, CdTe, BiI ₃ Etc. can be used. Among these, those containing a-Se as a main component, which is excellent in that the quantum efficiency is relatively high with respect to radiation and the dark resistance is high, are preferable.
As the organic material suitable for the photoelectric conversion layer, various organic semiconductor materials such as those used in electrophotographic photosensitive materials can be used. Among them, the quinacridone skeleton is selected from the viewpoints of having high photoelectric conversion performance, excellent color separation at the time of spectroscopy, high durability against long-time light irradiation, and easy vacuum deposition. Particularly preferred are materials containing and organic materials containing a phthalocyanine skeleton.

  When quinacridone represented by the following formula is used as the photoelectric conversion layer 102, the photoelectric conversion layer 102 can absorb light in the green wavelength region and generate a charge corresponding to the light.

  When zinc phthalocyanine represented by the following formula is used as the photoelectric conversion layer 102, the photoelectric conversion layer 102 can absorb light in the red wavelength region and generate a charge corresponding to the light.

  Moreover, it is preferable that the organic material which comprises the photoelectric converting layer 102 contains at least one of an organic p-type semiconductor and an organic n-type semiconductor. As the organic p-type semiconductor and the organic n-type semiconductor, any of quinacridone derivatives, naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, and fluoranthene derivatives can be particularly preferably used.

  The organic p-type semiconductor (compound) is a donor-type organic semiconductor (compound), which is mainly represented by a hole-transporting organic compound and refers to an organic 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 compound as long as it is an electron-donating organic compound. For example, triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, triphenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds, phthalocyanine compounds, cyanine compounds, merocyanine compounds, oxonol compounds, polyamine compounds, indoles 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), nitrogen-containing heterocyclic compounds The metal complex etc. which it has as can be used. Not limited to this, as described above, any organic compound having an ionization potential smaller than that of the organic compound used as the n-type (acceptor property) compound may be used as the donor organic semiconductor.

  Organic n-type semiconductors (compounds) are acceptor organic semiconductors (compounds), which are mainly represented by electron-transporting organic compounds and refer to organic compounds that easily accept electrons. More specifically, the organic compound having the higher electron affinity when two organic compounds are used in contact with each other. Therefore, as the acceptor organic compound, any organic compound can be used as long as it is an electron-accepting organic compound. For example, condensed aromatic carbocyclic compounds (naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives), 5- to 7-membered heterocyclic compounds containing nitrogen atoms, oxygen atoms, and sulfur atoms (E.g., 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, triazolopyrimidine, tetrazaindene, o Metal complexes having ligands such as saziazole, imidazopyridine, pyralidine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, and nitrogen-containing heterocyclic compounds. Etc. Note that the present invention is not limited thereto, and as described above, any organic compound having an electron affinity higher than that of the organic compound used as the donor organic compound may be used as the acceptor organic semiconductor.

  Any p-type organic dye or n-type organic dye may be used, but preferably a cyanine dye, styryl dye, hemicyanine dye, merocyanine dye (including zero methine merocyanine (simple merocyanine)), three nucleus 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, triphenyl Methane dye, azo dye, azomethine dye, spiro compound, metallocene dye, fluorenone dye, fulgide dye, perylene dye, phenazine dye, phenothiazine dye, quinone dye, indigo Dye, diphenylmethane dye, polyene dye, acridine dye, acridinone dye, diphenylamine dye, quinacridone dye, quinophthalone dye, phenoxazine dye, phthaloperylene dye, porphyrin dye, chlorophyll dye, phthalocyanine dye, metal complex dye, condensed aromatic carbocyclic dye (Naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, fluoranthene derivatives).

  Next, the metal complex compound will be described. The metal complex compound is a metal complex having a ligand having at least one nitrogen atom or oxygen atom or sulfur atom coordinated to the metal, and the metal ion in the metal complex is not particularly limited, but preferably beryllium ion, magnesium Ion, aluminum ion, gallium ion, zinc ion, indium ion, or tin ion, more preferably beryllium ion, aluminum ion, gallium ion, or zinc ion, and still more preferably aluminum ion or zinc ion. There are various known ligands contained in the metal complex. For example, “Photochemistry and Photophysics of Coordination Compounds” published by Springer-Verlag H. Yersin in 1987, “Organometallic Chemistry— Examples of the ligands described in “Basics and Applications—” published by Akio Yamamoto, 1982, etc.

  The ligand is preferably a nitrogen-containing heterocyclic ligand (preferably having 1 to 30 carbon atoms, more preferably 2 to 20 carbon atoms, particularly preferably 3 to 15 carbon atoms, and a monodentate ligand. May also be a bidentate or higher ligand, preferably a bidentate ligand, such as a pyridine ligand, a bipyridyl ligand, a quinolinol ligand, a hydroxyphenylazole ligand (hydroxyphenylbenz). Imidazole, hydroxyphenylbenzoxazole ligand, hydroxyphenylimidazole ligand)), alkoxy ligand (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably carbon number). 1 to 10, for example, methoxy, ethoxy, butoxy, 2-ethylhexyloxy, etc.), aryloxy ligand (preferably Alternatively, it has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, and particularly preferably 6 to 12 carbon atoms. For example, phenyloxy, 1-naphthyloxy, 2-naphthyloxy, 2,4,6-trimethylphenyl Oxy, 4-biphenyloxy, etc.), heteroaryloxy ligands (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as pyridyl. Oxy, pyrazyloxy, pyrimidyloxy, quinolyloxy, etc.), alkylthio ligands (preferably having 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, particularly preferably 1 to 12 carbon atoms, such as methylthio, Ethylthio etc.), an arylthio ligand (preferably having 6 to 30 carbon atoms, more preferably A prime number of 6 to 20, particularly preferably 6 to 12 carbon atoms, such as phenylthio, and the like, a heterocyclic substituted thio ligand (preferably 1 to 30 carbon atoms, more preferably 1 to 20 carbon atoms, Particularly preferably, it has 1 to 12 carbon atoms, and examples thereof include pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio and the like, or siloxy ligand (preferably carbon 1-30, more preferably 3-25 carbon atoms, particularly preferably 6-20 carbon atoms, and examples thereof include triphenylsiloxy group, triethoxysiloxy group, triisopropylsiloxy group, and the like. Preferred are nitrogen-containing heterocyclic ligands, aryloxy ligands, heteroaryloxy groups, or siloxy ligands, and more preferred. Examples thereof include a nitrogen-containing heterocyclic ligand, an aryloxy ligand, and a siloxy ligand.

  In the present embodiment, in the photoelectric conversion element shown in FIG. 1A, the hole blocking layer 105 has an average surface roughness of 2.0 nm or less. Alternatively, the hole blocking layer 105 has a configuration in which a diffraction peak does not appear in the X-ray diffraction spectrum, or the half width of the maximum diffraction peak is 5 ° or more. Here, as an average roughness, an arithmetic average roughness defined by JIS standards can be used. The hole blocking layer 105 is formed between at least one of the counter electrode 104 and the pixel electrode 101 and the photoelectric conversion layer 102. Further, as shown in FIG. 1B, an electron blocking layer 103 is added, and a charge blocking layer is provided between both the counter electrode 104 and the photoelectric conversion layer 102 and between the pixel electrode 101 and the photoelectric conversion layer 102. It is good also as a provided structure. The hole blocking layer 105 and the electron blocking layer 103 may be interchanged depending on the direction in which the voltage is applied.

Next, candidate materials for the hole blocking layer 105 will be described.
The hole blocking layer 105 preferably has an amorphous structure. The hole blocking layer 105 preferably contains two or more kinds of inorganic oxides, and these inorganic oxides may be mixed. In the present embodiment, the hole blocking layer 105 preferably includes any one of cerium oxide (CeO ₂ ) and tantalum oxide (Ta ₂ O ₅ ), and more preferably includes both. The thickness of the hole blocking layer 105 is preferably in the range of 10 nm to 200 nm.
Other oxides that can be used for the hole blocking layer 105 are preferably materials that block holes and allow electrons to pass through, such as SiO, TiO ₂ , GaO, TiO, WO ₃ , In ₂ O ₃ , GeO ₂ , Ga ₂ O ₃ , ZnO, CaO, MoO _{3 and the} like can be used.

  When an inorganic oxide is used only for the electron blocking layer and an organic material is used for the hole blocking layer, 1,3-bis (4-tert-butylphenyl-1,3,4) is used as the organic electron transporting material. Oxadiazole derivatives such as oxadiazolyl) phenylene (OXD-7), anthraquinodimethane derivatives, diphenylquinone derivatives, bathocuproine, bathophenanthroline, and derivatives thereof, triazole compounds, tris (8-hydroxyquinolinato) aluminum complexes, Bis (4-methyl-8-quinolinato) aluminum complexes, distyrylarylene derivatives, silole compounds, and the like can be used. Further, porphyrin compounds, styryl compounds such as DCM (4-dicyanomethylene-2-methyl-6- (4- (dimethylaminostyryl))-4H pyran), 4H pyran compounds, and the like can also be used.

(Electronic blocking layer)
It is preferable to use a hole transporting material for the electron blocking layer, and it is preferable to transport an amorphous structure. The electron blocking layer 103 preferably contains two or more inorganic oxides, and these inorganic oxides may be mixed. In the present embodiment, the electron blocking layer 103 preferably includes any one of nickel oxide (NiO) and iridium oxide (IrO), and more preferably includes both. The thickness of the electron blocking layer 103 is preferably in the range of 10 nm to 200 nm.
Other oxides that can be used for the electron blocking layer 103 include CuAlO ₂ , CuGaO ₂ , CuScO ₂ , CuCrO ₂ , CuInO ₂ , CuYO ₂ , AgInO ₂ , SrCu ₂ O ₂ , CuO, CoO, MnO ₂ , Nb ₂ O ₅ , MoO _{3 and the} like.
In addition, when an inorganic oxide is used only for the hole blocking layer and an organic material is used for the electron blocking layer, triarylamine compounds, benzidine compounds, pyrazoline compounds, styrylamine compounds, hydrazone compounds, Phenylmethane compounds, carbazole compounds, polysilane compounds, thiophene compounds, phthalocyanine compounds, cyanine compounds, 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), and nitrogen-containing heterocyclic compounds as ligands It can be a metal complex.
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. Porphyrin compounds, triazole derivatives, oxazizazo Derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, annealing amine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, silazane derivatives, etc. As the polymer material, polymers such as phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, diacetylene, and derivatives thereof can be used.

A value obtained by dividing the voltage applied from the outside between the upper electrode 104 and the lower electrode 101 by the distance between the electrodes 101 and 104 is 1.0 × 10 ⁵ V / cm to 1.0 × 10 ⁷ V / cm. It is preferable that

If the film thickness of the charge blocking layer is too thin, sufficient blocking properties cannot be ensured. Conversely, if the film is too thick, the electric field applied to the photoelectric conversion layer is reduced, resulting in a decrease in efficiency. It is preferable that it is ˜15 μm. More preferably, it is 0.03-1 micrometer, More preferably, it is 0.05-0.2 micrometer.
Examples of the flattening of the charge blocking layer include methods such as substrate cooling at the time of forming the charge blocking layer and surface polishing after the film formation. In particular, the substrate cooling is highly effective when the temperature of the film formation surface is set to 0 ° C. or lower. As a substrate cooling method, a method of pressing a cooling block made of copper or the like from the back surface of the substrate is preferable because temperature control is easy. As the surface polishing method, a chemical-mechanical polishing (CMP) can be used. Chemical mechanical polishing technology uses chemical reactions provided by chemical auxiliaries and mechanical polishing that the charge blocking layer receives on the polishing table, removing uneven uneven surfaces of the unevenness on the surface of the charge blocking layer little by little. And flattening technology.

  According to the photoelectric conversion element of this embodiment, dark current can be suppressed by forming an amorphous flat film from an inorganic oxide that is generally microcrystalline and easily forms an uneven film. Such an inorganic oxide can be effectively formed by mixing two or more inorganic oxides to lower the crystallinity, reducing the crystallinity by cooling the substrate, or combining them. . In addition, in the structure of the photoelectric conversion element, the use of an amorphous inorganic oxide layer as a charge blocking layer suppresses dark current without lowering the photoelectric conversion efficiency compared to the case of using an uneven oxide-free layer. And a higher S / N ratio can be realized.

  In the following second to fifth embodiments, description will be given of configuration examples that can be cited as sensors having a configuration in which the photoelectric conversion elements as described above are stacked above a semiconductor substrate. In the embodiments described below, members having the same configuration / action as those already described are denoted by the same or corresponding reference numerals in the drawings, and description thereof is simplified or omitted.

(Second Embodiment)
FIG. 2 is a schematic cross-sectional view of one pixel of a solid-state image sensor for explaining the second embodiment of the present invention. In FIG. 2, the same components as those in FIG.
The solid-state imaging device 100 has a large number of one pixel shown in FIG. 2 arranged in an array on the same plane, and can generate one pixel data of image data by a signal obtained from the one pixel.

  2 includes a p-type silicon substrate 1, a transparent insulating film 7 formed on the p-type silicon substrate 1, a lower electrode 101 formed on the insulating film 7, and a lower electrode. A photoelectric conversion layer 102 formed on 101, an electron blocking layer 103 (not shown) formed on the photoelectric conversion layer 102, a hole blocking layer 105 (not shown) formed on the photoelectric conversion layer 102, And the photoelectric conversion element having the structure described in the first embodiment formed of the upper electrode 104 formed on the electron blocking layer 103, and a light shielding film 14 having an opening is provided on the photoelectric conversion element. Is formed. A transparent insulating film 15 is formed on the upper electrode 104.

  In the p-type silicon substrate 1, an n-type impurity region (hereinafter abbreviated as n region) 4, a p-type impurity region (hereinafter abbreviated as p region) 3, and an n region 2 are formed in this order from the shallowest side. Has been. A high-concentration n region (referred to as n + region) 6 is formed on the surface portion of the n region 4 that is shielded by the light shielding film 14, and the n + region 6 is surrounded by the p region 5.

  The depth of the pn junction surface between the n region 4 and the p region 3 from the surface of the p-type silicon substrate 1 is a depth that absorbs blue light (about 0.2 μm). Therefore, the n region 4 and the p region 3 form a photodiode (B photodiode) that absorbs blue light and accumulates a charge corresponding thereto. In the present embodiment, the B photodiode is formed in the semiconductor substrate and functions as a charge accumulation unit for accumulating charges generated in the photoelectric conversion layer of the photoelectric conversion unit 102. Electrons generated in the B photodiode are accumulated in the n region 4.

  The depth of the pn junction surface between the n region 2 and the p-type silicon substrate 1 from the surface of the p-type silicon substrate 1 is a depth that absorbs red light (about 2 μm). Therefore, the n region 2 and the p-type silicon substrate 1 form a photodiode (R photodiode) that absorbs red light and accumulates a charge corresponding thereto. The R photodiode is formed in the semiconductor substrate and functions as a charge accumulation unit for accumulating charges generated in the photoelectric conversion layer of the photoelectric conversion unit 102. Electrons generated in the R photodiode are accumulated in the n region 2.

  The n + region 6 is electrically connected to the lower electrode 101 through a connection portion 9 formed in an opening opened in the insulating film 7. The holes collected by the lower electrode 101 recombine with the electrons in the n + region 6, so that the electrons accumulated in the n + region 6 at the time of reset decrease according to the number of collected holes. The connection portion 9 is electrically insulated by the insulating film 8 except for the lower electrode 101 and the n + region 6.

  The electrons accumulated in the n region 2 are converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n channel MOS transistor formed in the p-type silicon substrate 1 and accumulated in the n region 4. The electrons are converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n-channel MOS transistor formed in the p region 3, and the electrons accumulated in the n + region 6 The signal is converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n-channel MOS transistor formed therein, and output to the outside of the solid-state imaging device 100. Each MOS circuit is connected to a signal readout pad (not shown) by wiring 10. If extraction electrodes are provided in the n region 2 and the n region 4 and a predetermined reset potential is applied, each region is depleted, and the capacitance of each pn junction becomes an extremely small value. Thereby, the capacity | capacitance produced in a joint surface can be made very small.

  With such a configuration, G light can be photoelectrically converted by the photoelectric conversion layer 102, and B light and R light can be photoelectrically converted by the B photodiode and the R photodiode in the p-type silicon substrate 1. In addition, since G light is first absorbed at the top, color separation between BG and between GR is excellent. This is a great advantage over a solid-state imaging device in which three PDs are stacked in a silicon substrate and all BGR light is separated in the silicon substrate.

  In the solid-state imaging device 100 of the present embodiment, the hole blocking layer 105 has an average surface roughness of 2.0 nm or less. Alternatively, the hole blocking layer 105 is configured such that a diffraction peak does not appear in the X-ray diffraction spectrum, or the half width of the maximum diffraction peak is 5 ° or more. Similar to the above embodiment, the hole blocking layer preferably has an amorphous structure, and preferably contains two or more kinds of inorganic oxides. By doing so, it becomes possible to suppress dark current without lowering the photoelectric conversion efficiency compared to the case of using an uneven oxide-free layer, and a higher S / N ratio can be realized.

(Third embodiment)
In the present embodiment, two photodiodes are not stacked in the silicon substrate 1 of FIG. 2, but two photodiodes are arranged in a direction perpendicular to the incident direction of incident light, and the p-type silicon substrate Thus, two colors of light are detected.

FIG. 3 is a schematic cross-sectional view of one pixel of a solid-state image sensor for explaining a third embodiment of the present invention. In FIG. 3, the same components as those in FIG.
3 includes a p-type silicon substrate 17, a lower electrode 101 formed above the p-type silicon substrate 17, a photoelectric conversion layer 102 formed on the lower electrode 101, and a photoelectric conversion layer. An electron blocking layer 103 (not shown) formed on the photoelectric conversion layer 102, a hole blocking layer 105 (not shown) formed below the photoelectric conversion layer 102, and an upper electrode 104 formed on the electron blocking layer 103. The photoelectric conversion element having the configuration described in the first embodiment is configured, and a light shielding film 34 having an opening is formed on the photoelectric conversion element. A transparent insulating film 33 is formed on the upper electrode 104.

  On the surface of the p-type silicon substrate 17 below the opening of the light shielding film 34, a photodiode composed of the p region 19 and the n region 18 and a photodiode composed of the p region 21 and the n region 20 are formed on the surface of the p-type silicon substrate 17. It is formed side by side. An arbitrary plane direction on the surface of the p-type silicon substrate 17 is a direction perpendicular to the incident direction of incident light.

  Above the photodiode composed of the p region 19 and the n region 18, a color filter 28 that transmits B light is formed through a transparent insulating film 24, and a lower electrode 101 is formed thereon. Above the photodiode composed of the p region 21 and the n region 20, a color filter 29 that transmits R light is formed through a transparent insulating film 24, and a lower electrode 101 is formed thereon. The periphery of the color filters 28 and 29 is covered with a transparent insulating film 25.

  The photodiode composed of the p region 19 and the n region 18 functions as an in-substrate photoelectric conversion unit that absorbs the B light transmitted through the color filter 28 and generates electrons corresponding thereto and accumulates the generated electrons in the n region 18. To do. The photodiode composed of the p region 21 and the n region 20 functions as an in-substrate photoelectric conversion unit that absorbs R light transmitted through the color filter 29 and generates electrons corresponding thereto and accumulates the generated electrons in the n region 20. To do.

  An n + region 23 is formed in a portion of the surface of the n-type silicon substrate 17 that is shielded by the light shielding film 34, and the n + region 23 is surrounded by the p region 22.

  The n + region 23 is electrically connected to the lower electrode 101 via a connection portion 27 formed in an opening opened in the insulating films 24 and 25. The holes collected by the lower electrode 101 recombine with the electrons in the n + region 23, so that the electrons accumulated in the n + region 23 at the time of resetting decrease according to the number of collected holes. The connecting portion 27 is electrically insulated by the insulating film 26 except for the lower electrode 101 and the n + region 23.

The electrons accumulated in the n region 18 are converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n channel MOS transistor formed in the p-type silicon substrate 17 and accumulated in the n region 20. The electrons are converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n-channel MOS transistor formed in the p-type silicon substrate 17, and the electrons accumulated in the n + region 23 are converted into p The signal is converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n-channel MOS transistor formed in the region 22 and output to the outside of the solid-state imaging device 200. Each MOS circuit is connected to a signal readout pad (not shown) by wiring 35.
The signal reading unit may be constituted by a CCD and an amplifier instead of the MOS circuit. That is, the electrons accumulated in the n region 18, the n region 20, and the n + region 23 are read out to a CCD formed in the p-type silicon substrate 17, and transferred to the amplifier by the CCD. It may be a signal reading unit that outputs a signal.

  As described above, the signal reading unit includes a CCD and a CMOS structure, but CMOS is preferable in terms of power consumption, high-speed reading, pixel addition, partial reading, and the like.

  In FIG. 3, the color filters 28 and 29 perform color separation of the R light and the B light. However, the color filters 28 and 29 are not provided, and the depths of the pn junction surfaces of the n region 20 and the p region 21 are as follows. The depths of the pn junction surfaces of the n region 18 and the p region 19 may be adjusted to absorb the R light and the B light with the respective photodiodes. In this case, the light transmitted through the photoelectric conversion layer 102 is absorbed between the p-type silicon substrate 17 and the lower electrode 101 (for example, between the insulating film 24 and the p-type silicon substrate 17), and according to the light. It is also possible to form an inorganic photoelectric conversion portion made of an inorganic material that generates and accumulates charges. In this case, a MOS circuit for reading a signal corresponding to the charge accumulated in the charge accumulation region of the inorganic photoelectric conversion unit is provided in the p-type silicon substrate 17, and the wiring 35 is also connected to the MOS circuit. That's fine.

  Alternatively, a single photodiode may be provided in the p-type silicon substrate 17 and a plurality of photoelectric conversion units may be stacked above the p-type silicon substrate 17. Further, a plurality of photodiodes provided in the p-type silicon substrate 17 may be provided, and a plurality of photoelectric conversion units may be stacked above the p-type silicon substrate 17. If there is no need to create a color image, a single photodiode provided in the p-type silicon substrate 17 and only one photoelectric conversion unit may be stacked.

  In the solid-state imaging device 200 of the present embodiment, the hole blocking layer 105 has an average surface roughness of 2.0 nm or less. Alternatively, the hole blocking layer 105 is configured such that a diffraction peak does not appear in the X-ray diffraction spectrum, or the half width of the maximum diffraction peak is 5 ° or more. Similar to the above embodiment, the hole blocking layer preferably has an amorphous structure, and preferably contains two or more kinds of inorganic oxides. By doing so, it becomes possible to suppress dark current without lowering the photoelectric conversion efficiency compared to the case of using an uneven oxide-free layer, and a higher S / N ratio can be realized.

(Fourth embodiment)
The solid-state imaging device of the present embodiment has a configuration in which a photodiode is not provided in the silicon substrate of FIG. 1 and a plurality (three in this case) of photoelectric conversion elements are stacked above the silicon substrate.
FIG. 4 is a schematic cross-sectional view of one pixel of a solid-state image sensor for explaining a fourth embodiment of the present invention.
4 includes a lower electrode 101r, a photoelectric conversion layer 102r stacked on the lower electrode 101r, and a hole blocking layer (not shown) formed on the photoelectric conversion layer 102r above the silicon substrate 41. An R photoelectric conversion element including an electron blocking layer (not shown) formed under the photoelectric conversion layer 102r and an upper electrode 104r stacked on the hole blocking layer, and the lower electrode 101b and the lower electrode 101b. The stacked photoelectric conversion layer 102b, the hole blocking layer (not shown) formed on the photoelectric conversion layer 102b, the electron blocking layer (not shown) formed below the photoelectric conversion layer 102r, and the hole blocking layer B photoelectric conversion element including upper electrode 104b laminated on top, lower electrode 101g, photoelectric conversion layer laminated on lower electrode 101g 02g, a hole blocking layer (not shown) formed on the photoelectric conversion layer 102g, an electron blocking layer (not shown) formed below the photoelectric conversion layer 102r, and an upper part laminated on the hole blocking layer The G photoelectric conversion element including the electrode 104g is stacked in this order with the lower electrode included in the G photoelectric conversion element facing the silicon substrate 41 side.

  A transparent insulating film 48 is formed on the silicon substrate 41, an R photoelectric conversion element is formed thereon, a transparent insulating film 59 is formed thereon, and a B photoelectric conversion element is formed thereon, A transparent insulating film 63 is formed thereon, a G photoelectric conversion element is formed thereon, a light shielding film 68 having an opening is formed thereon, and a transparent insulating film 67 is formed thereon. .

  The lower electrode 101g, the photoelectric conversion layer 102g, the hole blocking layer, the electron blocking layer, and the upper electrode 104g included in the G photoelectric conversion element are respectively the lower electrode 101, the photoelectric conversion layer 102, and the electron blocking layer 103 illustrated in FIG. The hole blocking layer 105 and the upper electrode 104 have the same configuration. However, the photoelectric conversion layer 102g uses an organic material that absorbs green light and generates electrons and holes according to the green light.

  The lower electrode 101b, the photoelectric conversion layer 102b, the hole blocking layer, the electron blocking layer, and the upper electrode 104b included in the B photoelectric conversion element are respectively the lower electrode 101, the photoelectric conversion layer 102, and the electron blocking layer 103 illustrated in FIG. The hole blocking layer 105 and the upper electrode 104 have the same configuration. However, the photoelectric conversion layer 102b uses an organic material that absorbs blue light and generates electrons and holes according to the blue light.

  The lower electrode 101r, the photoelectric conversion layer 102r, the hole blocking layer, the electron blocking layer, and the upper electrode 104r included in the R photoelectric conversion element are respectively the lower electrode 101, the photoelectric conversion layer 102, and the electron blocking layer 103 illustrated in FIG. The hole blocking layer 105 and the upper electrode 104 have the same configuration. However, the photoelectric conversion layer 102r uses an organic material that absorbs red light and generates electrons and holes corresponding to the red light.

  N + regions 43, 45, and 47 are formed in portions of the surface of the silicon substrate 41 that are shielded by the light-shielding film 68, and each is surrounded by p regions 42, 44, and 46.

  The n + region 43 is electrically connected to the lower electrode 101r through a connection portion 54 formed in an opening opened in the insulating film 48. The holes collected by the lower electrode 101r recombine with the electrons in the n + region 43. Therefore, the electrons accumulated in the n + region 43 at the time of resetting decrease according to the number of collected holes. The connecting portion 54 is electrically insulated by the insulating film 51 except for the lower electrode 101r and the n + region 43.

  The n + region 45 is electrically connected to the lower electrode 101b through a connection portion 53 formed in an opening formed in the insulating film 48, the R photoelectric conversion element, and the insulating film 59. The holes collected by the lower electrode 101b recombine with the electrons in the n + region 45, so that the electrons accumulated in the n + region 45 at the time of resetting decrease according to the number of collected holes. The connection portion 53 is electrically insulated by the insulating film 50 except for the lower electrode 101b and the n + region 45.

  The n + region 47 is electrically connected to the lower electrode 101g through the insulating film 48, the R photoelectric conversion element, the insulating film 59, the B photoelectric conversion element, and the connection portion 52 formed in the opening opened in the insulating film 63. Has been. The holes collected by the lower electrode 101g recombine with the electrons in the n + region 47, so that the electrons accumulated in the n + region 47 at the time of resetting decrease according to the number of collected holes. The connection portion 52 is electrically insulated by the insulating film 49 except for the lower electrode 101g and the n + region 47.

  The electrons accumulated in the n + region 43 are converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n-channel MOS transistor formed in the p region 42 and accumulated in the n + region 45. The electrons stored in the n + region 47 are converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n-channel MOS transistor formed in the p region 44. The signal is converted into a signal corresponding to the amount of charge by a MOS circuit (not shown) formed of an n-channel MOS transistor formed therein and output to the outside of the solid-state imaging device 300. Each MOS circuit is connected to a signal readout pad (not shown) by wiring 55. The signal reading unit may be constituted by a CCD and an amplifier instead of the MOS circuit. That is, the electrons accumulated in the n + regions 43, 45, and 47 are read out to a CCD formed in the silicon substrate 41, transferred to the amplifier by the CCD, and a signal corresponding to the hole is output from the amplifier. It may be a signal reading unit.

  In the above description, the photoelectric conversion layer that absorbs B light can absorb light of at least 400 to 500 nm, and preferably has a peak wavelength absorptance of 50% or more in that wavelength region. Means. The photoelectric conversion layer that absorbs G light means that it can absorb light of at least 500 to 600 nm, and preferably has a peak wavelength absorptance of 50% or more in that wavelength region. The photoelectric conversion layer that absorbs R light means that it can absorb light of at least 600 to 700 nm, and preferably has an absorption factor of a peak wavelength in the wavelength region of 50% or more.

  In the solid-state imaging device 300 of the present embodiment, the hole blocking layer 105 has an average surface roughness of 2.0 nm or less. Alternatively, the hole blocking layer 105 is configured such that a diffraction peak does not appear in the X-ray diffraction spectrum, or the half width of the maximum diffraction peak is 5 ° or more. Similar to the above embodiment, the hole blocking layer preferably has an amorphous structure, and preferably contains two or more kinds of inorganic oxides. By doing so, it becomes possible to suppress dark current without lowering the photoelectric conversion efficiency compared to the case of using an uneven oxide-free layer, and a higher S / N ratio can be realized.

(Fifth embodiment)
FIG. 5 is a schematic cross-sectional view of a solid-state imaging device for explaining a fifth embodiment of the present invention.
In the row direction on the same plane above the p-type silicon substrate 81 and the column direction perpendicular thereto, a color filter 93r that mainly transmits light in the R wavelength region and a color filter that mainly transmits light in the G wavelength region. A large number of three types of color filters, 93g and a color filter 93b that mainly transmits light in the B wavelength range, are arranged.

  A known material can be used for the color filter 93r, but such a material transmits a part of light in the infrared region in addition to the light in the R wavelength region. A known material can be used for the color filter 93g. However, such a material transmits part of light in the infrared region in addition to light in the G wavelength region. A known material can be used for the color filter 93b. However, such a material transmits part of light in the infrared region in addition to light in the B wavelength region.

  As the arrangement of the color filters 93r, 93g, 93b, a color filter arrangement (Bayer arrangement, vertical stripe, horizontal stripe, etc.) used in a known single-plate solid-state imaging device can be adopted.

  Below the color filter 93r, an n-type impurity region (hereinafter referred to as n region) 83r is formed corresponding to the color filter 93r, and the color filter 93r is formed by a pn junction between the n region 83r and the p-type silicon substrate 81. The R photoelectric conversion element corresponding to is configured.

  Below the color filter 93g, an n region 83g is formed corresponding to the color filter 93g, and a G photoelectric conversion element corresponding to the color filter 93g is configured by a pn junction between the n region 83g and the p-type silicon substrate 81. Has been.

  An n region 83b is formed below the color filter 93b so as to correspond to the color filter 93b, and a B photoelectric conversion element corresponding to the color filter 93b is configured by a pn junction between the n region 83b and the p-type silicon substrate 81. Has been.

  A lower electrode 87r (having the same function as the lower electrode 101 in FIG. 1) is formed above the n region 83r, and a lower electrode 87g (having the same function as the lower electrode 101 in FIG. 1) is formed above the n region 83g. A lower electrode 87b (having the same function as the lower electrode 101 in FIG. 1) is formed above the n region 83b. The lower electrodes 87r, 87g, 87b are divided corresponding to the color filters 93r, 93g, 93b, respectively. Each of the lower electrodes 87r, 87g, and 87b is made of a material that is transparent to visible light and infrared light. For example, ITO (Indium Tin Oxide), IZO (Indium Zico Oxide), or the like can be used. The transparent electrodes 87r, 87g, 87b are each embedded in the insulating layer.

  On each of the lower electrodes 87r, 87g, and 87b, light in the infrared region having a wavelength of 580 nm or more is mainly absorbed to generate a charge corresponding to the light, and a visible region other than the infrared region (wavelength of about 380 nm to about 580 nm). A photoelectric conversion layer 89 (having the same function as the photoelectric conversion layer 102 in FIG. 1) is formed, which is a single-sheet configuration common to each of the color filters 93r, 93g, and 93b. As a material constituting the photoelectric conversion layer 89, for example, a phthalocyanine-based organic material or a naphthalocyanine-based organic material is used.

  On the photoelectric conversion layer 89, an upper electrode 80 (having the same function as that of the upper electrode 104 in FIG. 1) is formed, which is a single-sheet configuration common to the color filters 93r, 93g, and 93b. The upper electrode 80 is made of a material transparent to visible light and infrared light, and for example, ITO or IZO can be used. Although not shown, an electron blocking layer having the same function as the electron blocking layer 103 in FIG. 1 is formed between the photoelectric conversion layer 89 and the upper electrode 80.

  A photoelectric conversion element corresponding to the color filter 93r is formed by the lower electrode 87r, the upper electrode 80 facing the lower electrode 87r, and a part of the photoelectric conversion layer 89 sandwiched therebetween. Hereinafter, since this photoelectric conversion element is formed on a semiconductor substrate, it is referred to as an R-substrate photoelectric conversion element.

  A photoelectric conversion element corresponding to the color filter 93g is formed by the lower electrode 87g, the upper electrode 80 facing the lower electrode 87g, and a part of the photoelectric conversion layer 89 sandwiched therebetween. Hereinafter, this photoelectric conversion element is referred to as a G-substrate photoelectric conversion element.

  A photoelectric conversion element corresponding to the color filter 93b is formed by the lower electrode 87b, the upper electrode 80 facing the lower electrode 87b, and a part of the photoelectric conversion layer 89 sandwiched therebetween. Hereinafter, this photoelectric conversion element is referred to as a B-substrate photoelectric conversion element.

  Next to the n region 83r, a high concentration n-type impurity region (hereinafter referred to as an n + region) 84r connected to the lower electrode 87r of the photoelectric conversion element on the R substrate is formed. In order to prevent light from entering the n + region 84r, it is preferable to provide a light shielding film on the n + region 84r.

  Next to the n region 83g, an n + region 84g connected to the lower electrode 87g of the photoelectric conversion element on the G substrate is formed. In order to prevent light from entering the n + region 84g, it is preferable to provide a light shielding film on the n + region 84g.

  Next to the n region 83b, an n + region 84b connected to the lower electrode 87b of the photoelectric conversion element on the B substrate is formed. In order to prevent light from entering the n + region 84b, it is preferable to provide a light shielding film on the n + region 84b.

  A contact portion 86r made of a metal such as tungsten or aluminum is formed on the n + region 84r, and a lower electrode 87r is formed on the contact portion 86r. The n + region 84r and the lower electrode 87r are electrically connected by the contact portion 86r. It is connected. The contact portion 86r is embedded in an insulating layer 85 that is transparent to visible light and infrared light.

  A contact portion 86g made of a metal such as tungsten or aluminum is formed on the n + region 84g, and a lower electrode 87g is formed on the contact portion 86g. The n + region 84g and the lower electrode 87g are electrically connected by the contact portion 86g. It is connected. The contact portion 86g is embedded in the insulating layer 85.

  A contact portion 86b made of a metal such as tungsten or aluminum is formed on the n + region 84b, and a lower electrode 87b is formed on the contact portion 86b. The n + region 84b and the lower electrode 87b are electrically connected by the contact portion 86b. It is connected. The contact part 86 b is embedded in the insulating layer 85.

  In the regions other than the n regions 83r, 83g, 83b and the n + regions 84r, 84g, 84b, n channels for reading out signals corresponding to electrons accumulated in the n region 83r and the n + region 84r, respectively. A signal reading unit 85r made of a MOS transistor, a signal reading unit 85g made of an n-channel MOS transistor for reading signals corresponding to electrons accumulated in the n region 83g and the n + region 84g, and an n region 83b and an n + region A signal reading unit 85b composed of an n-channel MOS transistor for reading signals corresponding to electrons stored in 84b is formed. Each of the signal reading units 85r, 85g, and 85b may be configured by a CCD. In order to prevent light from entering the signal readout portions 85r, 85g, and 85b, it is preferable to provide a light shielding film on the signal readout portions 85r, 85g, and 85b.

  According to such a configuration, an RGB color image and an infrared image can be obtained simultaneously with the same resolution. For this reason, this solid-state imaging device can be applied to an electronic endoscope or the like.

  In the solid-state imaging device 400 of this embodiment, the hole blocking layer 105 has an average surface roughness of 2.0 nm or less. Alternatively, the hole blocking layer 105 is configured such that a diffraction peak does not appear in the X-ray diffraction spectrum, or the half width of the maximum diffraction peak is 5 ° or more. Similar to the above embodiment, the hole blocking layer preferably has an amorphous structure, and preferably contains two or more kinds of inorganic oxides. By doing so, it becomes possible to suppress dark current without lowering the photoelectric conversion efficiency compared to the case of using an uneven oxide-free layer, and a higher S / N ratio can be realized.

  Any one of the photoelectric conversion materials in the photoelectric conversion part of the above embodiment can be an organic semiconductor having a maximum absorption spectrum peak in the near infrared region. At this time, the photoelectric conversion material is preferably transparent to visible light. Further, the photoelectric conversion material is preferably SnPc or silicon naphthalocyanines.

Next, examples according to the present invention will be described.
(Example 1)
A 25 mm square glass substrate with an ITO electrode was ultrasonically cleaned with acetone, semicoclean, and isopropyl alcohol (IPA) for 15 minutes. Finally, after IPA boiling cleaning, UV / O ₃ cleaning was performed.
After moving the substrate to the film forming chamber of the sputtering apparatus and evacuating to 1 × 10 ⁻⁴ Pa or less, argon gas and oxygen gas were allowed to flow while rotating the substrate holder, and in this atmosphere, the CeO ₂ target and Ta ₂ O ₅ targets were sputtered at the same time, and 500 hole-blocking layers were formed to have a volume ratio of 2: 1. At this time, sputtering was performed under the conditions of a degree of vacuum of 5 × 10 ⁻¹ Pa, a substrate temperature of 25 ° C., an input power of 100 W, and a film formation time of 15 minutes. This substrate holder was transferred to an organic film forming chamber in a vacuum, and 4-dicyanomethylene-2-methyl-6 was subjected to sufficient sublimation purification on the hole blocking layer in a vacuum of 1 × 10 ⁻⁴ Pa or less. While maintaining-(p-dimethylaminostyryl) -4H-pyran (DCM) at a deposition rate of 3.0 Å / sec, it was deposited to 1000 Å to form a photoelectric conversion layer.
Subsequently, EBM-1 represented by the following general formula subjected to sublimation purification was deposited as an electron blocking layer on this photoelectric conversion layer so as to be 1000 liters while maintaining a deposition rate of 3.0 liters / sec.

  This substrate holder was transferred to a sputtering chamber in a vacuum, and ITO was deposited as a counter electrode on the electron blocking layer to a thickness of 100 mm. The area of the photoelectric conversion region formed by the lowermost ITO electrode and the ITO counter electrode was 2 mm × 2 mm. Without exposing this board | substrate to air | atmosphere, it conveyed to the glove box which kept the water | moisture content and oxygen each 1 ppm or less, and sealed with the glass which put the moisture absorption agent using UV curable resin.

When an external electric field of 5.0 × 10 ⁵ V / cm ² is applied to the device manufactured in this way by using an optical constant energy quantum efficiency measuring device (source meter uses Keithley 6430). The external quantum efficiency was calculated by measuring the dark current value flowing when light was not irradiated and the photocurrent value flowing when light was irradiated. The area of the photoelectric conversion region was irradiated with light to a 1.5 mmφ region out of 2 mm × 2 mm. The amount of light irradiated was 50 μW / cm ² . The wavelength was measured at 480 nm which is the maximum absorption wavelength of the photoelectric conversion layer DCM. Moreover, the value which divided the external quantum efficiency obtained at the time of light irradiation by the dark current density obtained at the time of light non-irradiation was made into S / N ratio.

  In addition, in order to investigate the physical properties of the hole blocking layer containing an inorganic oxide, the film was formed up to the hole blocking layer separately from the above, and then taken out from the film forming apparatus and subjected to X-ray diffraction measurement and AFM measurement.

  X-ray diffraction was measured with Cu-Kα rays using a scientific Geiger flex. The average surface roughness was measured using an AFM (Atomic Force MicroScope). A range of 25 μm × 25 μm was scanned. The average surface roughness was determined within this range.

(Example 2)
In Example 1, the S / N ratio and the like were calculated in the same manner as in Example 1 except that the SnO ₂ target was used instead of the CeO ₂ target.

(Example 3)
In Example 1, the S / N ratio and the like were calculated in the same manner as in Example 1 except that an Al ₂ O ₃ target was used instead of the Ta ₂ O ₅ target.
Example 4
In Example 1, the S / N ratio and the like were calculated in the same manner as in Example 1 except that a NiO target and an IrO target were used instead of EBM-1 to form an electron blocking layer by sputtering.
The electron blocking layer is formed by sputtering a NiO target and an IrO target at the same time, under the conditions of a degree of vacuum of 5 × 10 ⁻¹ Pa, a substrate temperature of 25 ° C., an input power of 100 W, and a film formation time of 30 minutes. The volume ratio was 1: 1 and the film thickness was 1000 mm.
Further, in the same manner as in Example 1, X-ray diffraction measurement and AFM measurement were performed on a sample separately formed up to the electron blocking layer.

(Example 5)
A 25 mm square glass substrate with an ITO electrode was ultrasonically cleaned with acetone, semicoclean, and isopropyl alcohol (IPA) for 15 minutes. Finally, after IPA boiling cleaning, UV / O ₃ cleaning was performed. After moving the substrate to the organic film forming chamber of the vapor deposition apparatus and evacuating it to 1 × 10 ⁻⁴ Pa or less, while rotating the substrate holder, EBM-1 subjected to sublimation purification as an electron blocking layer was vapor deposition rate 3 While maintaining 0.0 kg / sec, vapor deposition was performed so as to be 1000 kg. Subsequently, 4-dicyanomethylene-2-methyl-6- (p-dimethylaminostyryl) -4H-pyran (DCM), which has been subjected to sufficient sublimation purification, was deposited to 1000 liters while maintaining a deposition rate of 3.0 liters / sec. Thus, a photoelectric conversion layer was formed.
Subsequently, the substrate holder is transferred to an inorganic film forming chamber in vacuum, a copper block is pressed against the upper surface of the substrate, and -40 ° C ethanol is circulated through the copper block to cool the substrate temperature to 0 ° C or lower. did. In this state, CeO ₂ having a purity of 99.99% (Furuuchi Chemical) was deposited as a hole blocking layer on the photoelectric conversion layer so as to be 500 Å while maintaining a deposition rate of 1.0 Å / sec. At this time, the deposition of the CeO ₂ because it requires a high temperature, was subjected to vapor deposition by heating directly tungsten filament to CeO ₂ in the crucible.
This substrate holder was transported to a sputtering chamber in a vacuum, and an ITO film having a thickness of 100 mm was formed as a counter electrode on the hole blocking layer. The area of the photoelectric conversion region formed by the lowermost ITO electrode and the ITO counter electrode was 2 mm × 2 mm. Without exposing this board | substrate to air | atmosphere, it conveyed to the glove box which kept the water | moisture content and oxygen each 1 ppm or less, and sealed with the glass which put the moisture absorption agent using UV curable resin. For the device thus fabricated, the S / N ratio and the like were calculated in the same manner as in Example 1.

(Comparative Example 1)
In Example 1, the S / N ratio and the like were calculated in the same manner as in Example 1 except that the hole blocking layer was formed only with the CeO ₂ target without using the Ta ₂ O ₅ target.

(Comparative Example 2)
In Example 1, the S / N ratio and the like were calculated in the same manner as in Example 1 except that the hole blocking layer was formed only with the Ta ₂ O ₅ target without using the CeO ₂ target.

(Comparative Example 3)
In Example 4, the S / N ratio and the like were calculated in the same manner as in Example 4 except that the electron blocking layer was formed only with the NiO target without using the IrO target.
(Comparative Example 4)
In Example 4, the S / N ratio and the like were calculated in the same manner as in Example 1 except that CeO ₂ was deposited at room temperature without cooling the substrate to form a hole blocking layer.

  The results of this measurement are shown in Table 1. In Examples 1 to 5, it was found that S / N was significantly improved as compared with Comparative Examples 1 to 4.

It is sectional drawing which shows the structure of 1st Embodiment of a photoelectric conversion element. It is sectional drawing which shows the structure of 2nd Embodiment of a photoelectric conversion element. It is sectional drawing which shows the structure of 3rd Embodiment of a photoelectric conversion element. It is sectional drawing which shows the structure of 4th Embodiment of a photoelectric conversion element. It is sectional drawing which shows the structure of 5th Embodiment of a photoelectric conversion element.

Explanation of symbols

100, 200, 300, 400 Photoelectric conversion element 101 Pixel electrode 102 Photoelectric conversion layer 103 Electron blocking layer (charge blocking layer)
104 Counter electrode 105 Hole blocking layer (charge blocking layer)

Claims (19)

A pair of electrodes;
A photoelectric conversion layer disposed between the pair of electrodes;
A charge blocking layer that is formed between the one electrode and the photoelectric conversion layer, and suppresses injection of charge from one of the pair of electrodes to the photoelectric conversion layer when a voltage is applied to the pair of electrodes; A photoelectric conversion element comprising:
The photoelectric conversion element whose average roughness of the surface of the said charge blocking layer is 2.0 nm or less. A pair of electrodes;
A photoelectric conversion layer disposed between the pair of electrodes;
A charge blocking layer that is formed between the one electrode and the photoelectric conversion layer, and suppresses injection of charge from one of the pair of electrodes to the photoelectric conversion layer when a voltage is applied to the pair of electrodes; A photoelectric conversion element comprising:
A photoelectric conversion element in which a diffraction peak does not appear in an X-ray diffraction spectrum of the charge blocking layer, or a half-value width of a diffraction peak that is maximum therein is 5 ° or more. The photoelectric conversion element according to claim 1 or 2,
A photoelectric conversion element in which the charge blocking layer has an amorphous structure. The photoelectric conversion element according to any one of claims 1 to 3, wherein
The photoelectric conversion element in which the said charge blocking layer contains 2 or more types of inorganic oxides. The photoelectric conversion device according to claim 1, wherein
The photoelectric conversion element in which the charge blocking layer is a mixture of two or more inorganic oxides. The photoelectric conversion element according to any one of claims 1 to 5,
A photoelectric conversion element using CeO ₂ as one of the inorganic oxides included in the charge blocking layer. The photoelectric conversion device according to claim 1, wherein
A photoelectric conversion element using SnO ₂ as one of the inorganic oxides included in the charge blocking layer. The photoelectric conversion element according to any one of claims 1 to 7,
A photoelectric conversion element using Ta ₂ O ₅ as one of the inorganic oxides included in the charge blocking layer. The photoelectric conversion element according to any one of claims 1 to 8,
A photoelectric conversion element using CeO ₂ and Ta ₂ O ₅ as an inorganic oxide contained in the charge blocking layer. The photoelectric conversion element according to claim 1, wherein
A photoelectric conversion element in which the charge blocking layer is further provided between the other of the pair of electrodes and the photoelectric conversion layer. It is a photoelectric conversion element given in any 1 paragraph of Claims 1-10,
The photoelectric conversion element whose thickness of the said charge blocking layer is 10 nm-200 nm. The photoelectric conversion element according to any one of claims 1 to 11,
A photoelectric conversion element in which a value obtained by dividing a voltage applied from the outside to the pair of electrodes by a distance between the pair of electrodes is 1.0 × 10 ⁵ V / cm to 1.0 × 10 ⁷ V / cm. The photoelectric conversion element according to any one of claims 1 to 12,
A semiconductor substrate having at least one photoelectric conversion layer laminated thereon;
A charge storage unit formed in the semiconductor substrate for storing the charge generated in the photoelectric conversion layer;
A photoelectric conversion element provided with the electrode for taking out the said electric charge of the said pair of electrodes of the said photoelectric converting layer, and the connection part which electrically connects the said charge storage part. The photoelectric conversion element according to claim 13,
A photoelectric conversion element comprising an in-substrate photoelectric conversion unit that absorbs light transmitted through the photoelectric conversion layer in the semiconductor substrate, generates a charge corresponding to the light, and accumulates the charge. The photoelectric conversion element according to claim 14,
The photoelectric conversion element in which the photoelectric conversion part in the substrate is a plurality of photodiodes that absorb light of different colors stacked in the semiconductor substrate. The photoelectric conversion device according to claim 15,
A photoelectric conversion element in which the in-substrate photoelectric conversion unit is a plurality of photodiodes that absorb light of different colors arranged in a direction perpendicular to an incident direction of incident light in the semiconductor substrate. The photoelectric conversion element according to any one of claims 1 to 16, wherein
The photoelectric conversion layer laminated on the semiconductor substrate is one,
The plurality of photodiodes are a blue photodiode having a pn junction surface formed at a position capable of absorbing blue light, and a red photodiode having a pn junction surface formed at a position capable of absorbing red light. Yes,
A photoelectric conversion element in which the photoelectric conversion layer absorbs green light. A solid-state imaging device in which a plurality of the photoelectric conversion devices according to claim 1 are arranged in an array,
A solid-state imaging device including a signal reading unit that reads a signal corresponding to the charge accumulated in the charge accumulation unit of each of the plurality of photoelectric conversion elements. A pair of electrodes;
A photoelectric conversion layer disposed between the pair of electrodes;
A charge blocking layer that is formed between the one electrode and the photoelectric conversion layer, and suppresses injection of charge from one of the pair of electrodes to the photoelectric conversion layer when a voltage is applied to the pair of electrodes; A method for producing a photoelectric conversion element comprising:
A method for producing a photoelectric conversion element, wherein the substrate temperature is maintained at 0 ° C. or lower when the charge blocking layer is formed.

Images