JP5492939B2 - Manufacturing method of solid-state imaging device - Google Patents

Description

  The present invention relates to a method for manufacturing a photoelectric conversion element including a pair of electrodes and a photoelectric conversion layer sandwiched between the pair of electrodes, and a solid-state imaging device having a photoelectric conversion element manufactured by the manufacturing method.

  Conventionally, a photoelectric conversion element including a pair of electrodes and a photoelectric conversion layer sandwiched between the pair of electrodes is known (see Patent Document 1). In addition, a solid-state imaging device using this photoelectric conversion device has been proposed (see Patent Document 2).

JP-A-5-299682 JP 2003-332551 A

  In the photoelectric conversion element having the above-described configuration, the light transmittance of the light incident side electrode is higher in order to increase the absolute amount of light incident on the photoelectric conversion layer and increase the efficiency of carrier reading after photoelectric conversion. Things have been sought. In view of such high transmittance and low resistance value, it is generally considered that a transparent conductive oxide (TCO) thin film is preferable as the electrode on the light incident side. The TCO transparent electrode is generally formed by a sputtering method or the like. In that case, compared to a metal electrode formed by a thermal evaporation method such as an Al (aluminum) electrode, an increase in leakage current is likely to occur, and solid-state imaging is performed. When applied to an element, there are problems such as deterioration in S / N, performance variation, and in some cases, a DC short circuit occurs and the element does not drive. The reason for this will be described below.

  A case is considered in which a pair of electrodes included in the above-described photoelectric conversion element is an upper electrode and a lower electrode, and a lower electrode, a photoelectric conversion layer, and an upper electrode are stacked in this order on a substrate to produce a photoelectric conversion element. In this case, as a result of earnest analysis and examination when the leakage current becomes large, the main reason is that a crack occurs in the photoelectric conversion layer, the crack is generated by the upper electrode, and the upper electrode and the lower electrode are I found out that it was physically close. This phenomenon occurs particularly conspicuously in a film in which the upper electrode has a high coverage property, that is, in a dense TCO film formed by sputtering or the like, compared to a metal film formed by heating such as Al. Further, when the photoelectric conversion layer is formed by vapor deposition, this phenomenon is likely to occur, and the unevenness of the lower electrode and the unevenness caused by dust on the lower electrode are considered to cause cracks.

  As measures to prevent this crack, there is a contrivance such as making the bottom electrode as flat as possible or reducing dust as much as possible, and increasing the thickness of the photoelectric conversion layer itself so that the crack does not reach the bottom electrode And a method of inserting a thick layer to fill a crack between the photoelectric conversion layer and the upper electrode is also known (known document Appl. Phys. Lett. 85, 6269). However, when trying to smooth the lower electrode, it is possible to smooth the surface as much as possible, but when the lower electrode is patterned, the electrode edge becomes a step, and a new countermeasure for that part is added It may be necessary. Also, reducing dust can cause a leak even if it is a very small dust of a few hundreds of nanometers level, and thus a large burden is required in terms of cost and efficiency. Increasing the thickness of the photoelectric conversion layer itself or inserting a thick layer can degrade other performances of the device and limit the desired light absorption and interference design, so that the desired spectral characteristics and In some cases, driving at a low voltage may be hindered.

  The present invention has been made in view of the above circumstances, and a method for manufacturing a photoelectric conversion element capable of suppressing the occurrence of cracks in a photoelectric conversion layer, and a solid-state imaging having a photoelectric conversion element manufactured by the manufacturing method An object is to provide an element.

The method for producing a solid-state imaging device of the present invention is a method for producing a solid-state imaging device in which a large number of photoelectric conversion elements including a pair of electrodes and a photoelectric conversion layer sandwiched between the pair of electrodes are arranged in an array , The one electrode of each pixel of the solid-state imaging device is divided for each pixel, and a step of forming the one electrode, and an amorphous material is deposited on the one electrode by vapor deposition, thereby forming an amorphous property. A step of forming a single-layered uneven relief layer that is common to the plurality of pixels to relieve unevenness on the surface of the one electrode by heating a film of the material ; and the photoelectric conversion layer on the unevenness relief layer Forming the other electrode of the pair of electrodes on the photoelectric conversion layer.

  According to the present invention, in particular, when a transparent conductive oxide film is used for the upper electrode, it is possible to provide a method for manufacturing a photoelectric conversion element that suppresses increase in leakage current and increase in short circuit.

Sectional schematic diagram which shows schematic structure of the photoelectric conversion element for describing 1st embodiment of this invention Partial cross-sectional schematic diagram of a stacked solid-state imaging device for explaining a second embodiment of the present invention

  Embodiments of the present invention will be described below with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic cross-sectional view showing a schematic configuration of a photoelectric conversion element for explaining a first embodiment of the present invention.
A photoelectric conversion element 100 shown in FIG. 1 includes a lower electrode 2 formed on a substrate 1, an upper electrode 4 facing the lower electrode 2, and an intermediate layer between the lower electrode 2 and the upper electrode 4. The intermediate layer includes a photoelectric conversion layer 3, an uneven relief layer 5 formed between the photoelectric conversion layer 3 and the lower electrode 2, and a charge blocking layer formed between the photoelectric conversion layer 3 and the upper electrode 4. 6 is included. The intermediate layer only needs to include at least the photoelectric conversion layer 3 and the unevenness relief layer 5.

  In the example of FIG. 1, light is incident on the photoelectric conversion element 100 from the upper electrode 4 side, and charges corresponding to the light are generated in the photoelectric conversion layer 3. Then, by applying a voltage to the lower electrode 2 and the upper electrode 4, the charge generated in the photoelectric conversion layer 3 moves to the lower electrode 2 and the upper electrode 4, and moves to either the lower electrode 2 or the upper electrode 4. The signal corresponding to the generated charge can be extracted to the outside.

  The lower electrode 2 is an electrode for collecting charges (for example, electrons) generated in the photoelectric conversion layer 3. In the case where a stacked solid-state imaging device is realized by stacking at least one photoelectric conversion element 100 above the semiconductor substrate, the lower electrode 2 is preferably transparent. In this specification, the term “transparent” means that 80% or more of visible light having a wavelength in the range of about 420 nm to about 660 nm is transmitted.

  The upper electrode 4 is an electrode for collecting charges (for example, holes) generated in the photoelectric conversion layer 3. Since it is necessary to make light incident on the photoelectric conversion layer 3, the upper electrode 4 is preferably transparent. The present invention specifically considers that the upper electrode 4 is a transparent conductive film, and the effect is particularly remarkable in that case.

  The photoelectric conversion layer 3 absorbs light of a specific wavelength and generates a charge corresponding to the absorbed light. The photoelectric conversion layer may have a single layer structure or a multilayer structure. As a material constituting the photoelectric conversion layer, an inorganic material and an organic material can be used, but it is particularly preferable to use an organic material from the viewpoint of excellent spectral characteristics and sensitivity.

  The unevenness relief layer 5 is for relaxing unevenness on the surface of the lower electrode 2 on the photoelectric conversion layer 3 side (hereinafter simply referred to as the surface of the lower electrode 2). When the surface of the lower electrode 2 has irregularities, or when dust adheres to the surface of the lower electrode 2, for example, a low molecular organic material is deposited thereon to form the photoelectric conversion layer 3. Small cracks in the photoelectric conversion layer 3, that is, portions where the photoelectric conversion layer 3 is formed only thinly are easily formed. At this time, if the upper electrode 4 is further formed thereon, the crack portion is covered by the upper electrode 4 and the upper electrode 4 and the lower electrode 2 are close to each other, so that a DC short circuit and an increase in leakage current are likely to occur. In particular, when TCO is used as the upper electrode 4, the tendency is remarkable. For this reason, the unevenness | corrugation can be relieved by providing the uneven | corrugated relaxation layer 5 between the lower electrode 2 and the photoelectric converting layer 3 previously, and these can be suppressed.

  Furthermore, the present applicant has found that the occurrence of cracks can be effectively suppressed by satisfying the following conditions (A) to (C). By using the numerical values shown below, as described in Examples and Comparative Examples described later, it is possible to suppress the short circuit of the element and improve the yield.

(A) The average surface roughness Ra of the surface of the unevenness relief layer 5 on the photoelectric conversion layer 3 side (hereinafter simply referred to as the surface of the unevenness relief layer 5) is 1.0 nm or less, more preferably 0.5 nm or less, and still more preferably. 0.3 nm or less.
(B) The average surface roughness Ra of the surface of the unevenness relief layer 5 is 60% or less, more preferably 30% or less of the average surface roughness Ra of the surface of the lower electrode 2.
(C) Satisfy both (A) and (B).

  Methods for satisfying such conditions are listed below.

(A) An organic or inorganic amorphous material is used as the unevenness relief layer 5.
When an amorphous material is used, it is possible to form the unevenness relief layer 5 having a smooth surface. However, when the amorphous material is formed by vapor deposition, it is preferable to make the film thickness slightly thicker because the unevenness of the lower electrode 2 is strongly reflected. As a material capable of forming the unevenness relaxation layer 5 by vapor deposition, a material having a low crystallization temperature and a glass transition temperature such as m-MTDATA and TPD can be used.

(B) An organic or inorganic polymeric material is used as the unevenness relief layer 5.
By applying a polymeric material on the lower electrode 2 by a coating method (spin coating method or the like) to form the unevenness relief layer 5, the unevenness on the surface of the lower electrode 2 is leveled, and the unevenness relief layer 5 itself has smoothness. It can be increased. For this reason, the very big short-circuit prevention effect can be acquired. In the case of the coating method, unlike the above (a), the unevenness relief layer 5 does not have a shape reflecting the unevenness of the surface of the lower electrode 2, and the surface smoothness of the unevenness relief layer 5 is different from that of the substrate 1. This is to show smoothness due to wettability, material viscosity, coating conditions, heating temperature, and the like. As the polymeric material to be used, polymer materials such as polyaniline, polythiophene, polypyrrole, polycarbazole, PTPDES, and PTPDK are preferable.

(C) The unevenness relief layer 5 is formed on the lower electrode 2 and then heated.
After forming the unevenness relief layer 5 by vapor deposition or spin coating, the surface of the unevenness relief layer 5 can be smoothed by heating the unevenness relief layer 5. This is because the material molecules of the uneven relief layer 5 once formed are rearranged by heating. In addition, it is necessary to select heating temperature suitably according to the material (Amorphous material or polymeric material) to be used. In particular, when an organic material is used as the material of the unevenness-relieving layer 5, the device performance deteriorates due to the influence of oxygen and moisture. Therefore, it may be heated in an inert gas environment such as a nitrogen atmosphere or in a vacuum. desirable. In this heating step, it is desirable to heat in a vacuum when baking for removing the solvent for polymer coating is also required.

  The unevenness reducing layer 5 is desirably thick from the viewpoint of preventing short-circuiting, but it is desirable that the unevenness reducing layer 5 can be made thinner, that is, the degree of freedom in setting the layer thickness is higher in order not to deteriorate the device characteristics. By using the above methods (a) to (c), the thickness of the unevenness relief layer 5 can be set thin. The thickness is preferably 100 nm or less, and more preferably 50 nm or less. By setting it as such a numerical value, the short circuit of an element can be suppressed and the yield can be improved as described in Examples and Comparative Examples described later.

Here, the photoelectric conversion element 100 is one pixel, a large number of pixels are arranged in an array on a semiconductor substrate, and the lower electrode 2 included in the large number of pixels is divided for each pixel. Consider a solid-state imaging device that is connected to a charge storage portion formed on a substrate and can extract charges from each lower electrode 2.
In this case, when a highly conductive polymer such as PEDOTPS is used for the unevenness relief layer 5, it is preferable from the viewpoint of prevention of short circuit, but one problem occurs when the conductivity of the conductive polymer is too high. That is, when considering neighboring pixels, light is applied to one pixel and light is not applied to the other pixel. The potential of the lower electrode 2 connected to the electrode changes, but the lower electrode 2 that is not exposed to light remains at the original potential (normally reset potential, depending on the readout method). Occurs. In the case of a structure in which the photoelectric conversion layer 3 and the unevenness reducing layer 5 have a single structure common to each pixel, and the unevenness reducing layer 5 bridges adjacent pixels, there is no problem if the unevenness reducing layer 5 has low conductivity. In the case of high conductivity, charge transfer occurs between adjacent pixels. Since signal charges flow from pixels that are exposed to light to pixels that are not exposed, as a result, the image is blurred and device characteristics are deteriorated. In view of an efficient device fabrication process, it is desirable that only the lower electrode 2 be patterned and the layer thereon not patterned. Therefore, in consideration of such a structure, the conductivity of the uneven relief layer 5 is preferably 1 × 10 ¹⁵ Ω / □ or more in terms of sheet resistance, and more preferably 1 × 10 ¹⁶ Ω / □ or more. .

  The charge blocking layer 6 is provided to reduce dark current caused by injection of charges from the upper electrode 4, and suppresses injection of charges from the upper electrode 4 into the photoelectric conversion layer 3.

  Hereinafter, specific examples of the lower electrode 2, the intermediate layer, and the upper electrode 4 described above will be described.

(Middle layer)
The intermediate layer is formed by stacking or mixing a part that absorbs electromagnetic waves, a photoelectric conversion layer, an electron transport part, a hole transport part, an electron blocking part, a hole blocking part, a crystallization preventing part, and the like. The photoelectric conversion layer preferably contains an organic p-type compound or an organic n-type compound.

  The organic p-type semiconductor (compound) is a donor 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 compound, benzidine compound, pyrazoline compound, styrylamine compound, hydrazone compound, triphenylmethane compound, carbazole compound, polysilane compound, thiophene compound, phthalocyanine compound, cyanine compound, merocyanine compound, oxonol compound, polyamine compound, 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), 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 an organic compound used as an n-type (acceptor) compound may be used as a donor organic semiconductor.

  Organic n-type semiconductors (compounds) are acceptor organic semiconductors (compounds), and are mainly represented by electron-transporting organic compounds and refer to organic compounds that have a property of easily accepting electrons. More specifically, the organic compound having the higher electron affinity when two organic compounds are used in contact with each other. Therefore, any organic compound can be used as the acceptor organic compound 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 to this, 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. As the ligand contained in the metal complex, there are various known ligands. Examples include the ligands described in “Photochemistry and Photophysics of Coordination Compounds” by Yersin (Springer-Verlag, 1987), “Organic Metal Chemistry-Fundamentals and Applications” (Yukakabo, 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. Or a bidentate or higher ligand, preferably a bidentate ligand such as a pyridine ligand, a bipyridyl ligand, a quinolinol ligand, a hydroxyphenylazole ligand (hydroxyphenyl) Benzimidazole, hydroxyphenylbenzoxazole ligand, hydroxyphenylimidazole ligand)), alkoxy ligand (preferably 1-30 carbon atoms, more preferably 1-20 carbon atoms, particularly preferably carbon 1-10, for example, methoxy, ethoxy, butoxy, 2-ethylhexyloxy, etc.), aryloxy ligands Preferably it has 6 to 30 carbon atoms, more preferably 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as 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.), arylthio ligands (preferably having 6 to 30 carbon atoms, more preferred) Has 6 to 20 carbon atoms, particularly preferably 6 to 12 carbon atoms, such as phenylthio, etc.), a heterocyclic substituted thio ligand (preferably 1 to 30 carbon atoms, more preferably 1 to carbon atoms). 20, particularly preferably 1 to 12 carbon atoms, such as pyridylthio, 2-benzimidazolylthio, 2-benzoxazolylthio, 2-benzthiazolylthio and the like, or siloxy ligand (preferably Has 1 to 30 carbon atoms, more preferably 3 to 25 carbon atoms, particularly preferably 6 to 20 carbon atoms, and examples thereof include a triphenylsiloxy group, a triethoxysiloxy group, and a triisopropylsiloxy group. More preferably a nitrogen-containing heterocyclic ligand, an aryloxy ligand, a heteroaryloxy group, or a siloxy ligand, Preferably, a nitrogen-containing heterocyclic ligand, an aryloxy ligand, or a siloxy ligand is used.

  The photoelectric conversion layer has a p-type semiconductor layer and an n-type semiconductor layer between a lower electrode and an upper electrode, and at least one of the p-type semiconductor and the n-type semiconductor is an organic semiconductor, and those semiconductors It is preferable that a bulk heterojunction structure layer including the p-type semiconductor and the n-type semiconductor is provided as an intermediate layer between the layers. By including a bulk heterojunction structure, the disadvantage that the carrier diffusion length of the organic layer is short can be compensated, and the photoelectric conversion efficiency can be improved. The bulk heterojunction structure is described in detail in Japanese Patent Application No. 2004-080639.

  The photoelectric conversion layer may contain a structure having two or more repeating structures (tandem structures) of a pn junction layer formed of a p-type semiconductor layer and an n-type semiconductor layer between the lower electrode and the upper electrode. Preferably, more preferably, a thin layer of conductive material is inserted between the repetitive structures. The number of repeating structures (tandem structures) of the pn junction layer may be any number, but is preferably 2 to 50, more preferably 2 to 30, particularly preferably 2 or 10 in order to increase the photoelectric conversion efficiency. It is. Silver or gold is preferable as the conductive material, and silver is most preferable. The tandem structure is described in detail in Japanese Patent Application No. 2004-079930.

  In a photoelectric conversion layer having a p-type semiconductor layer, an n-type semiconductor layer (preferably a mixed / dispersed (bulk heterojunction structure) layer) between the lower electrode and the upper electrode, of the p-type semiconductor and the n-type semiconductor It is also preferable to include an organic compound whose orientation is controlled in at least one direction, and more preferably, it includes a (possible) organic compound whose orientation is controlled in both the p-type semiconductor and the n-type semiconductor. As the organic compound used for the photoelectric conversion site, those having π-conjugated electrons are preferably used, but this π-electron plane is not perpendicular to the substrate (electrode substrate) but is oriented at an angle close to parallel. The more preferable. The angle with respect to the substrate is preferably 0 ° or more and 80 ° or less, more preferably 0 ° or more and 60 ° or less, further preferably 0 ° or more and 40 ° or less, and further preferably 0 ° or more and 20 ° or less. Particularly preferably, it is 0 ° or more and 10 ° or less, and most preferably 0 ° (that is, parallel to the substrate). As described above, the organic compound layer whose orientation is controlled may be partially included in the entire organic layer, but preferably the proportion of the portion whose orientation is controlled with respect to the entire organic layer is 10% or more. More preferably, it is 30% or more, more preferably 50% or more, further preferably 70% or more, particularly preferably 90% or more, and most preferably 100%. Such a state compensates for the shortcoming of the short carrier diffusion length of the organic layer by controlling the orientation of the organic compound in the organic layer in the photoelectric conversion layer, and improves the photoelectric conversion efficiency.

  In the case where the orientation of the organic compound is controlled, it is more preferable that the heterojunction plane (for example, the pn junction plane) is not parallel to the substrate. It is more preferable that the heterojunction plane is oriented not at a parallel to the substrate (electrode substrate) but at an angle close to the vertical. The angle with respect to the substrate is preferably 10 ° or more and 90 ° or less, more preferably 30 ° or more and 90 ° or less, further preferably 50 ° or more and 90 ° or less, and further preferably 70 ° or more and 90 ° or less. Particularly preferably, it is 80 ° or more and 90 ° or less, and most preferably 90 ° (that is, perpendicular to the substrate). The organic compound layer whose heterojunction surface is controlled as described above may be partially included in the entire organic layer. Preferably, the proportion of the portion where the orientation is controlled with respect to the entire organic layer is 10% or more, more preferably 30% or more, more preferably 50% or more, further preferably 70% or more, and particularly preferably 90%. Above, most preferably 100%. In such a case, the area of the heterojunction surface in the organic layer is increased, the amount of carriers of electrons, holes, electron-hole pairs and the like generated at the interface is increased, and the photoelectric conversion efficiency can be improved. In the above-described photoelectric conversion film (photoelectric conversion film) in which the orientation of both the heterojunction plane and the π-electron plane of the organic compound is controlled, the photoelectric conversion efficiency can be particularly improved. These states are described in detail in Japanese Patent Application No. 2004-079931. In terms of light absorption, the thickness of the organic dye layer is preferably as large as possible, but considering the ratio that does not contribute to charge separation, the thickness of the organic dye layer is preferably 30 nm to 300 nm, more preferably 50 nm to 250 nm, Especially preferably, it is 80 nm or more and 200 nm or less.

(Formation method of organic layer)
The layer containing these organic compounds is formed by a dry film formation method or a wet film formation method. Specific examples of the dry film forming method include a physical vapor deposition method such as a vacuum evaporation method, a sputtering method, an ion plating method, a molecular beam epitaxy method, or a chemical vapor deposition method such as plasma polymerization. As the wet film forming method, a coating method, a spin coating method, a dipping method, an LB method, or the like is used.
In the case where a polymer compound is used as at least one of a p-type semiconductor (compound) or an n-type semiconductor (compound), it is preferable to form a film by a wet film formation method that is easy to create. When a dry film formation method such as vapor deposition is used, it is difficult to use a polymer because it may be decomposed, and the oligomer can be preferably used instead. On the other hand, when a low molecule is used, a dry film forming method is preferably used, and a vacuum deposition method is particularly preferably used. The vacuum deposition method is basically based on the method of heating compounds such as resistance heating deposition method and electron beam heating deposition method, shape of deposition source such as crucible and boat, degree of vacuum, deposition temperature, base temperature, deposition rate, etc. It is a parameter. In order to enable uniform deposition, it is preferable to perform deposition by rotating the substrate. The higher the degree of vacuum is, preferably 10 ⁻² Pa or less, preferably 10 ⁻⁴ Pa or less, particularly preferably 10 ⁻⁶ Pa or less. It is preferable that all steps during the vapor deposition be performed in the above-described vacuum, and basically the compound is not directly in contact with oxygen and moisture in the outside air. The above-described conditions of vacuum deposition affect the crystallinity, amorphousness, density, density, etc. of the organic film, and must be strictly controlled. It is preferable to use PI or PID control of the deposition rate using a film thickness monitor such as a quartz crystal resonator or an interferometer. When two or more kinds of compounds are vapor-deposited simultaneously, a co-evaporation method, a flash vapor deposition method, or the like can be preferably used.

(electrode)
The hole collecting electrode for collecting holes is preferably a hole transporting photoelectric conversion site or a hole transporting site, and is preferably a metal, an alloy, a metal oxide, an electrically conductive compound, or These are materials that can be used as a mixture. The electron collection electrode for collecting electrons preferably takes out electrons from the photoelectric conversion site, taking into consideration the adhesion with adjacent layers such as the photoelectric conversion site, electron affinity, ionization potential, stability, etc. To be elected. Specific examples of these include conductive metal oxides such as tin oxide, zinc oxide, indium oxide, indium zinc oxide (IZO), and indium tin oxide (ITO), or metals such as gold, silver, chromium, and nickel. Or conductive metal oxide mixtures or laminates, inorganic conductive materials such as copper iodide and copper sulfide, organic conductive materials such as polyaniline, polythiophene and polypyrrole, silicon compounds and laminates of these with ITO Preferred are conductive metal oxides, and ITO and IZO are particularly preferred in terms of productivity, high conductivity, transparency, and the like. The film thickness of the pixel electrode can be appropriately selected depending on the material, but is usually preferably in the range of 10 nm to 1 μm, more preferably 30 nm to 500 nm, and still more preferably 30 nm to 100 nm.

  In particular, when applied to a stacked solid-state imaging device in which photoelectric conversion elements are stacked, both the upper electrode and the lower electrode are preferably transparent. Furthermore, in order to suppress dark current, the electron collection electrode is composed of a conductive metal oxide thin film such as ITO and a metal ultrathin film with a small work function such as silver, indium and magnesium on the photoelectric conversion layer side. A laminated structure is more preferable. The structure of the electron collecting electrode is described in detail in Japanese Patent Application No. 2005-251745.

  Various methods are used for producing the electrode depending on the material. For example, in the case of ITO, such as electron beam heating vapor deposition, sputtering, resistance heating vapor deposition, chemical reaction method (sol-gel method, etc.), ITO dispersion coating, etc. A film is formed by the method. In the case of ITO, ultraviolet ozone treatment, plasma treatment, etc. can be performed.

  The transparent electrode film is preferably produced without plasma. By creating a transparent electrode film free from plasma, the influence of plasma on the substrate can be reduced, and the photoelectric conversion characteristics can be improved. Here, plasma free means that no plasma is generated during the formation of the transparent electrode film, or the distance from the plasma generation source to the substrate is 2 cm or more, preferably 10 cm or more, more preferably 20 cm or more. It means a state in which the plasma that reaches is reduced.

  Examples of apparatuses that do not generate plasma during the formation of the transparent electrode film include an electron beam heating vapor deposition apparatus (EB vapor deposition apparatus) and a pulse laser vapor deposition apparatus. Regarding the EB deposition system or pulse laser deposition system, the supervision of Yutaka Sawada “New development of transparent conductive film” (CMC, 1999), the supervision of Yutaka Sawada “New development of transparent conductive film II” (CMC, 2002), Devices as described in “Transparent conductive film technology” by the Japan Society for the Promotion of Science (Ohm Co., 1999) and references attached to them can be used. Hereinafter, a method of forming a transparent electrode film using an EB vapor deposition apparatus is referred to as an EB vapor deposition method, and a method of forming a transparent electrode film using a pulse laser vapor deposition apparatus is referred to as a pulse laser vapor deposition method. For an apparatus that can realize a state in which the distance from the plasma generation source to the substrate is 2 cm or more and the arrival of plasma to the substrate is reduced (hereinafter referred to as a plasma-free film forming apparatus), for example, an opposed target sputtering Equipment, arc plasma deposition, etc. are considered, and these are supervised by Yutaka Sawada “New development of transparent conductive film” (CMC, 1999), and supervised by Yutaka Sawada “New development of transparent conductive film II” (CMC, 2002). ), “Transparent conductive film technology” (Ohm Co., 1999) by the Japan Society for the Promotion of Science, and references and the like appended thereto can be used.

  The upper transparent electrode has been considered to have a lower resistance as a solid-state imaging device, but there is a range in which a higher resistance is better considering the dark current value that causes noise. The sheet resistance of the transparent conductive thin film is 100Ω / □ or more and 10,000Ω / □ or less, preferably 100Ω / □ or more and 3000Ω / □ or less, more preferably 500Ω / □ or more and 3000Ω / □ or less, and particularly preferably 500Ω / □ or more. 1000Ω / □ or less.

  In this way, when the sheet resistance can be set high, especially when a transparent conductive oxide film is used as the transparent conductive film, the conditions during the film formation can be less restricted.

  For charge transfer, it is preferable that the mobility of the electrode is large in order to increase the response speed. However, noise having a low carrier density is preferable. For this reason, the transparent conductive film preferably has a low carrier density and a high mobility. In order to reduce the carrier density, for example, in the case of a transparent conductive oxide film, the stoichiometric mismatch should be reduced. Is raised. By reducing the stoichiometric mismatch, a high transmittance can be obtained, and since defects in the crystal are reduced, the charge mobility can be increased. For this purpose, the amount of oxygen introduced at the time of film formation is made larger than the amount of oxygen introduced that minimizes the sheet resistance.

  Usually, in a transparent conductive oxide film, when it is desired to increase the mobility of an electrode, as described above, the film is formed so as to reduce crystal defects, that is, to reduce the stoichiometric mismatch (for example, film formation). A method of reducing oxygen defects in the film by introducing oxygen into the film). Conversely, when it is desired to increase the carrier density, make a stoichiometric mismatch (for example, introduce oxygen defects into the film by reducing the amount of oxygen introduced during film formation and introduce carriers). Method) is used. Therefore, high mobility and a large carrier density are required to obtain a lower resistance film, but the means for increasing the mobility (means for eliminating crystal defects) and the means for increasing the carrier density are contradictory. Therefore, for example, when the oxygen introduction amount is increased or decreased from the amount at which the lowest resistance value is obtained, the sheet resistance value is increased in both cases.

  Aside from the viewpoints of the mobility and carrier density of the transparent conductive film, the amount of oxygen introduced during film formation is less or less when considering the viewpoint of damage suppression, such as when considering an organic film as a photoelectric conversion layer. The condition which does not do is preferable. In this case, it is possible to realize the sheet resistance value within the range of the present invention by making the amount of oxygen introduced at the time of film formation smaller than the amount of oxygen introduced with the smallest sheet resistance.

In consideration of increasing the leakage current by covering the crack in the photoelectric conversion layer and covering the crack in the photoelectric conversion layer, the upper transparent electrode has a thin film thickness within a range that stably has an appropriate conductivity as an electrode. Is preferable.
The film thickness of the transparent conductive film of the present invention is preferably 5 to 100 nm, more preferably 5 to 50 nm, and particularly preferably 5 to 30 nm.

A stacked solid-state imaging device can be realized using the photoelectric conversion device 100 having the above configuration.
For example, as described in Patent Documents 1 and 2, at least one photoelectric conversion element 100 is stacked above a semiconductor substrate such as silicon, and a signal corresponding to the charge generated in the photoelectric conversion element 100 is output to a CCD, a CMOS circuit, or the like. By arranging a large number of pixels including a signal readout section to be read out in an array, a stacked solid-state imaging device can be realized. When one photoelectric conversion element 100 is stacked, a flat insulating layer may be formed on a semiconductor substrate instead of the substrate 1 shown in FIG. 1, and the photoelectric conversion element 100 may be formed on the flat surface of the insulating layer. . In the case where a plurality of photoelectric conversion elements 100 are stacked, an insulating layer may be formed over the already formed photoelectric conversion elements 100, and the photoelectric conversion elements 100 may be stacked thereon.

  When one photoelectric conversion element 100 is stacked above the semiconductor substrate, for example, by selecting a material that absorbs light in the G wavelength range as the material of the photoelectric conversion layer 3 of the photoelectric conversion element 100. Monochrome shooting can be performed. Further, when three photoelectric conversion elements 100 are stacked, as a material of each photoelectric conversion layer 3 of the three photoelectric conversion elements 100, a material that absorbs light in the G wavelength range and light in the R wavelength range. Color photography can be performed by selecting a material that absorbs light and a material that absorbs light in the B wavelength range.

  It is also possible to realize a solid-state imaging device in which a photodiode for detecting light transmitted through the stacked photoelectric conversion elements 100 is formed in a semiconductor substrate on which the photoelectric conversion elements 100 are stacked. In this case, one color is detected above the semiconductor substrate and two colors are detected within the semiconductor substrate to enable color photography, or two colors are detected above the semiconductor substrate and one color is detected within the semiconductor substrate. It is possible to realize a configuration that can detect color and perform color photography.

Hereinafter, a configuration example of the stacked solid-state imaging device will be described. Below, the part which performs the photoelectric conversion laminated | stacked on the semiconductor substrate is called an organic layer, the part which performs the photoelectric conversion formed in the semiconductor substrate is called an inorganic layer, and combines the organic layer and the inorganic layer into the photoelectric conversion part. That's it.
(Photoelectric converter)
The organic layer has a laminated structure of at least two layers capable of absorbing and photoelectrically converting at least blue light, green light, and red light. The blue light absorbing layer (B) can absorb at least light of 400 to 500 nm, and preferably the peak wavelength absorption in the wavelength region is 50% or more. The green light absorbing layer (G) can absorb at least light of 500 to 600 nm, and preferably has a peak wavelength absorption in the wavelength region of 50% or more. The red light absorption layer (R) 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. The order of these layers may be any order, and in the case of a three-layer stacked structure, the order of BGR, BRG, GBR, GRB, RBG, and RGB is possible from the upper layer. Preferably, the uppermost layer is G. In the case of a two-layer structure, when the upper layer is the R layer, the lower layer is the same BG layer, when the upper layer is the B layer, the lower layer is the same planar GR layer, and when the upper layer is the G layer, the lower layer is the same A BR layer is formed in a planar shape. Preferably, the upper layer is a G layer and the lower layer is a BR layer on the same plane. Thus, when two light absorption layers are provided in the same plane of the lower layer, it is preferable to provide, for example, a mosaic layer on the upper layer or a filter layer capable of color separation between the upper layer and the lower layer. In some cases, it is possible to provide a fourth layer or more as a new layer or in the same plane.

  In the photoelectric conversion part, the organic layer may form a B / G / R layer, or the inorganic layer may form a B / G / R layer. A mixture of an organic layer and an inorganic layer is preferred. In this case, basically, when the organic layer is one layer, the inorganic layer is one or two layers, and when the organic layer is two layers, the inorganic layer is one layer. In the case where the organic layer and the inorganic layer are one layer, a photoelectric conversion element that detects light of two or more colors in the same plane is formed. Preferably, the upper layer is an organic layer and is a G layer, and the lower layer is an inorganic layer and is an order of B layer and R layer from the top. In some cases, it is possible to provide a fourth layer or more as a new layer or in the same plane. In the case where the organic layer forms a B / G / R layer, a charge accumulation / transfer / readout portion is provided thereunder. When an inorganic layer is used as the photoelectric conversion unit, this inorganic layer also serves as a charge accumulation / transfer / readout part.

  The electrode used for the organic layer will be described in more detail. The organic photoelectric conversion layer is sandwiched between the pixel electrode film (lower electrode) and the counter electrode film (upper electrode). The pixel electrode film is an electrode film formed above the substrate on which the charge accumulation / transfer / read-out site is formed, and is usually divided for each pixel. This is to obtain an image by reading out the signal charges converted by the photoelectric conversion layer on a charge storage / transfer / signal readout circuit substrate for each pixel.

  The counter electrode film has a function of discharging a signal charge having a polarity opposite to that of the signal charge by sandwiching the photoelectric conversion layer together with the pixel electrode film. Since the discharge of the signal charge does not need to be divided between the pixels, the counter electrode film can be commonly used between the pixels. Therefore, it may be called a common electrode film (common electrode film). The photoelectric conversion layer is located between the pixel electrode film and the counter electrode film. The photoelectric conversion function functions by the photoelectric conversion layer, the pixel electrode film, and the counter electrode film.

  As an example of the configuration of the photoelectric conversion layer stack, first, when there is one organic layer stacked on the substrate, the pixel electrode film (basically a transparent electrode film), the photoelectric conversion layer, the counter electrode film (transparent electrode film) from the substrate ) In order, but is not limited thereto. Furthermore, when there are two organic layers stacked on the substrate, for example, from the substrate to the pixel electrode film (basically a transparent electrode film), a photoelectric conversion layer, a counter electrode film (transparent electrode film), an interlayer insulating film, a pixel electrode The structure which laminated | stacked the film | membrane (basically transparent electrode film), the photoelectric converting layer, and the counter electrode film (transparent electrode film) in order is mentioned.

  The material of the transparent electrode film sandwiching the photoelectric conversion layer is preferably one that can be formed by a plasma-free film forming apparatus, an EB vapor deposition apparatus, and a pulse laser vapor deposition apparatus. For example, a metal, an alloy, a metal oxide, a metal nitride, a metal boride, an organic conductive compound, a mixture thereof, and the like are preferably exemplified. Specific examples include tin oxide, zinc oxide, indium oxide, ITO, and IZO. , Conductive metal oxides such as indium tungsten oxide (IWO), metal nitrides such as titanium nitride, metals such as gold, platinum, silver, chromium, nickel, and aluminum, and these metals and conductive metal oxides Examples thereof include mixtures or laminates, inorganic conductive materials such as copper iodide and copper sulfide, organic conductive materials such as polyaniline, polythiophene and polypyrrole, and laminates of these with ITO. Also, supervised by Yutaka Sawada “New Development of Transparent Conductive Film” (CMC, 1999), supervised by Yutaka Sawada “New Development of Transparent Conductive Film II” (CMC, 2002), “Transparent Conductive Film” by Japan Society for the Promotion of Science. The technology described in detail in “Technology of” (Ohm, 1999) may be used.

  As the material for the transparent electrode film, ITO, IZO, tin oxide, antimony-doped tin oxide (ATO), fluorine-doped tin oxide (FTO), zinc oxide, aluminum-doped zinc oxide (AZO), gallium-doped zinc oxide ( GZO) or titanium oxide. The light transmittance of the transparent electrode film is preferably 60% or more, more preferably 80% or more, more preferably, in the photoelectric conversion light absorption peak wavelength of the photoelectric conversion film included in the photoelectric conversion element including the transparent electrode film. It is 90% or more, more preferably 95% or more. The preferred range of the surface resistance of the transparent electrode film varies depending on whether it is a pixel electrode or a counter electrode, and whether the charge storage / transfer / read-out site is a CCD structure or a CMOS structure. When it is used for the counter electrode and the charge storage / transfer / readout part has a CMOS structure, it is preferably 10000Ω / □ or less, more preferably 1000Ω / □ or less. When it is used for the counter electrode and the charge storage / transfer / readout part has a CCD structure, it is preferably 1000Ω / □ or less, more preferably 100Ω / □ or less. When used for a pixel electrode, it is preferably 1000000 Ω / □ or less, more preferably 100000 Ω / □ or less.

  The conditions at the time of forming the transparent electrode film will be mentioned. The substrate temperature at the time of forming the transparent electrode film is preferably 500 ° C. or lower, more preferably 300 ° C. or lower, further preferably 200 ° C. or lower, and further preferably 150 ° C. or lower. Further, a gas may be introduced during the formation of the transparent electrode film, and basically the gas species is not limited, but argon, helium, oxygen, nitrogen and the like can be used. Further, a mixed gas of these gases may be used. In particular, in the case of an oxide material, oxygen defects are often introduced, so that oxygen is preferably used.

When a voltage is applied to the photoelectric conversion layer, it is preferable in that the photoelectric conversion efficiency is improved. The applied voltage may be any voltage, but the necessary voltage varies depending on the thickness of the photoelectric conversion layer. That is, the photoelectric conversion efficiency improves as the electric field applied to the photoelectric conversion layer increases, but the applied electric field increases as the thickness of the photoelectric conversion layer decreases even at the same applied voltage. Therefore, when the photoelectric conversion layer is thin, the applied voltage may be relatively small. The electric field applied to the photoelectric conversion layer is preferably 10 V · m ⁻¹ or more, more preferably 1 × 10 ³ V · m ⁻¹ or more, more preferably 1 × 10 ⁵ V · m ⁻¹ or more, particularly preferably. 1 × 10 ⁶ V · m ⁻¹ or more, most preferably 1 × 10 ⁷ V · m ⁻¹ or more. There is no particular upper limit, but if an electric field is applied too much, an electric current flows even in a dark place, which is not preferable, and is preferably 1 × 10 ¹² V · m ⁻¹ or less, and more preferably 1 × 10 ⁹ V · m ⁻¹ or less.

(Inorganic layer)
The inorganic layer will be described. In this case, light passing through the upper organic layer is photoelectrically converted by the inorganic layer. As the inorganic layer, a pn junction or a pin junction of a compound semiconductor such as crystalline silicon, amorphous silicon, and gallium arsenide is generally used. The method disclosed in US Pat. No. 5,965,875 can be adopted as the laminated structure. In other words, a stacked light receiving portion is formed using the wavelength dependence of the absorption coefficient of silicon, and color separation is performed in the depth direction. In this case, since color separation is performed based on the light penetration depth of silicon, the spectral range detected by each stacked light receiving unit is broad. However, color separation is remarkably improved by using the above-described organic layer as an upper layer, that is, by detecting light transmitted through the organic layer in the depth direction of silicon. In particular, when the G layer is disposed in the organic layer, the light transmitted through the organic layer becomes blue light and red light, so that the separation of light in the depth direction in silicon is only blue / red light, and color separation is improved. Even when the organic layer is a B layer or an R layer, color separation is remarkably improved by appropriately selecting the photoelectric conversion site of silicon in the depth direction. When the organic layer has two layers, the function as a photoelectric conversion site in silicon may be basically one color, and preferable color separation can be achieved.

  The inorganic layer is preferably formed by stacking a plurality of photodiodes for each pixel in the depth direction in the semiconductor substrate, and a color signal corresponding to a signal charge generated in each photodiode by light absorbed by the plurality of photodiodes. It is a structure that reads out to the outside. Preferably, the plurality of photodiodes include at least one of a first photodiode provided at a depth that absorbs blue light and a second photodiode provided at a depth that absorbs red light, It is preferable to include a color signal readout circuit that reads out a color signal corresponding to the signal charge generated in each of the plurality of photodiodes. With this configuration, color separation can be performed without using a color filter. In some cases, light of a negative sensitivity component can also be detected, so that color imaging with good color reproducibility is possible. The junction of the first photodiode is formed to a depth of about 0.2 μm from the surface of the semiconductor substrate, and the junction of the second photodiode is about 2 μm from the surface of the semiconductor substrate. It is preferable to be formed to a depth.

  The inorganic layer will be described in more detail. Preferred configurations of the inorganic layer include a photoconductive type, a pn junction type, a Schottky junction type, a pin junction type, an MSM (metal-semiconductor-metal) type light receiving element, and a phototransistor type light receiving element. A plurality of first conductivity type regions and second conductivity type regions opposite to the first conductivity type are alternately stacked in a single semiconductor substrate, and the first conductivity type and the second conductivity type are stacked. It is preferable to use a light receiving element in which each joint surface of the conductive type region is formed to a depth suitable for mainly photoelectrically converting light in a plurality of different wavelength bands. As the single semiconductor substrate, single crystal silicon is preferable, and color separation can be performed using absorption wavelength characteristics depending on the depth direction of the silicon substrate.

As the inorganic semiconductor, an InGaN-based, InAlN-based, InAlP-based, or InGaAlP-based inorganic semiconductor can also be used. The InGaN-based inorganic semiconductor is adjusted so as to have a maximum absorption value in a blue wavelength range by appropriately changing the In-containing composition. That is, the composition is In _x Ga _1-x N (0 ≦ X <1). Such a compound semiconductor is manufactured using a metal organic chemical vapor deposition method (MOCVD method). A nitride semiconductor InAlN system using Al, which is the same group 13 raw material as Ga, can also be used as a short wavelength light receiving section in the same manner as the InGaN system. It is also possible to use InAlP or InGaAlP lattice-matched to the GaAs substrate.

  The inorganic semiconductor may have a buried structure. The embedded structure means a structure in which both ends of the short wavelength light receiving part are covered with a semiconductor different from the short wavelength light receiving part. The semiconductor covering both ends is preferably a semiconductor having a band gap wavelength shorter than or equivalent to the band gap wavelength of the short wavelength light receiving part. The organic layer and the inorganic layer may be combined in any form. In addition, it is preferable to provide an insulating layer between the organic layer and the inorganic layer in order to electrically insulate.

  The junction is preferably npn or pnpn from the light incident side. In particular, by providing a p-layer on the surface and increasing the surface potential, holes generated in the vicinity of the surface and dark current can be trapped and dark current can be reduced. preferable.

In such a photodiode, an n-type layer, a p-type layer, an n-type layer, and a p-type layer that are sequentially diffused from the surface of the p-type silicon substrate are formed deeply in this order, so that the pn junction diode has a silicon depth. Four layers of pnpn are formed in the direction. The light incident on the diode from the surface side penetrates deeper as the wavelength is longer, and the incident wavelength and attenuation coefficient show values specific to silicon, so that the depth of the pn junction surface satisfies each wavelength band of visible light. design. Similarly, an n-type layer, a p-type layer, and an n-type layer are formed in this order to obtain a npn three-layer junction diode. Here, an optical signal is taken out from the n-type layer, and the p-type layer is grounded.
Further, when an extraction electrode is provided in each region and a predetermined reset potential is applied, each region is depleted, and the capacitance of each junction becomes an extremely small value. Thereby, the capacity | capacitance produced in a joint surface can be made very small.

(Auxiliary layer)
Preferably, the uppermost layer of the photoelectric conversion layer has an ultraviolet absorption layer and / or an infrared absorption layer. The ultraviolet absorbing layer can absorb or reflect at least light of 400 nm or less, and preferably has an absorptance of 50% or more in a wavelength region of 400 nm or less. The infrared absorbing layer can absorb or reflect light of at least 700 nm or more, and preferably has an absorptance of 50% or more in a wavelength region of 700 nm or more.

  These ultraviolet absorbing layer and infrared absorbing layer can be formed by a conventionally known method. For example, a method of forming a colored layer by providing a mordant layer made of a hydrophilic polymer material such as gelatin, casein, mul or polyvinyl alcohol on a substrate and adding or dyeing a dye having a desired absorption wavelength to the mordant layer. Are known. Furthermore, a method using a colored resin in which a certain kind of coloring material is dispersed in a transparent resin is known. For example, JP-A-58-46325, JP-A-60-78401, JP-A-60-184202, JP-A-60-184203, JP-A-60-184204, JP As shown in Japanese Patent Application Laid-Open No. 60-184205 and the like, a colored resin film obtained by mixing a colorant with a polyamino resin can be used. A colorant using a polyimide resin having photosensitivity is also possible.

  Dispersing a coloring material in an aromatic polyamide resin having a photosensitivity group described in Japanese Patent Publication No. 7-113685 in a molecule and capable of obtaining a cured film at 200 ° C. or lower; It is also possible to use a dispersion colored resin with the content described in JP-A-69486. A dielectric multilayer film is preferably used. The dielectric multilayer film is preferably used because of its sharp wavelength dependency of light transmission.

  The plurality of stacked photoelectric conversion layers are preferably separated by an insulating layer. The insulating layer can be formed using a transparent insulating material such as glass, polyethylene, polyethylene terephthalate, polyethersulfone, and polypropylene. Silicon nitride, silicon oxide and the like are also preferably used. Silicon nitride formed by a plasma CVD method is preferably used because it has high density and good transparency. Furthermore, since the light collection efficiency can be improved by forming the microlens array on the light receiving element, such an embodiment is also preferable.

(Charge accumulation / transfer / readout part)
Regarding the charge transfer / readout site, reference can be made to JP-A-58-103166, JP-A-58-103165, JP-A-2003-332551, and the like. A configuration in which a MOS transistor is formed in each pixel unit on a semiconductor substrate or a configuration having a CCD as an element can be appropriately employed. For example, in the case of a stacked solid-state imaging device using a MOS transistor, charges are generated in the photoconductive film by incident light transmitted through the electrodes, and an electric field generated between the electrodes by applying a voltage to the electrodes. The charge travels through the photoelectric conversion layer to the electrode, and further moves to the charge storage portion of the MOS transistor, and the charge is stored in the charge storage portion. The charge accumulated in the charge accumulation unit moves to the charge readout unit by switching of the MOS transistor, and is further output as an electric signal. Thereby, a full color image signal is obtained. It is possible to inject a certain amount of bias charge into the storage diode (refresh mode) and store the constant charge (photoelectric conversion mode), and then read out the signal charge. The photoelectric conversion layer itself can be used as a storage diode, or a storage diode can be additionally provided.

  The signal readout will be described in more detail. An ordinary color readout circuit can be used for signal readout. The signal charge or signal current optically / electrically converted by the light receiving unit is stored in the light receiving unit itself or an attached capacitor. The stored charge is read out together with the selection of the pixel position by a technique of a MOS type image pickup device (so-called CMOS sensor) using an XY address method. In addition, as an address selection method, there is a method in which each pixel is sequentially selected by a multiplexer switch and a digital shift register and read as a signal voltage (or charge) to a common output line. An image sensor for XY address operation that is two-dimensionally arrayed is known as a CMOS sensor. This is because the switch provided in the pixel connected to the intersection of XY is connected to the vertical shift register, and when the switch is turned on by the voltage from the vertical scanning shift register, the pixel is read out from the pixel provided in the same row. The signal is read out to the output line in the column direction. This signal is sequentially read from the output through a switch driven by a horizontal scanning shift register.

  For reading out the output signal, a floating diffusion detector or a floating gate detector can be used. Further, the S / N can be improved by providing a signal amplification circuit in the pixel portion or a correlated double sampling technique.

  For signal processing, gamma correction by an ADC circuit, digitization by an AD converter, luminance signal processing, and color signal signal processing can be performed. Examples of the color signal processing include white balance processing, color separation processing, and color matrix processing. When used for NTSC signals, RGB signals can be converted to YIQ signals.

The charge transfer / readout site needs to have a charge mobility of 100 cm ² · V ⁻¹ · s ⁻¹ or more, and this mobility is based on the group IV, III-V and II-VI groups. It can be obtained by selecting from a semiconductor. Among these, a silicon semiconductor is preferable because of the progress in miniaturization technology and low cost. Many methods of charge transfer and charge reading have been proposed, but any method may be used. A particularly preferred method is a CMOS type or CCD type device. Further, the CMOS type is often preferable in terms of high-speed reading, pixel addition, partial reading, power consumption, and the like.

(Connection)
The electrodes sandwiching the photoelectric conversion layer and the plurality of contact parts that connect the charge transfer / readout part may be connected by any metal, but are preferably selected from copper, aluminum, silver, gold, chromium, and tungsten. In particular, copper is preferred. In accordance with a plurality of photoelectric conversion layers, it is necessary to install each contact part between the charge transfer / readout part. When a laminated structure of a plurality of photosensitive units of blue, green, and red light is employed, between the blue light extraction electrode and the charge transfer / readout portion, between the green light extraction electrode and the charge transfer / readout portion, and the red light extraction electrode And the charge transfer / readout part must be connected to each other.

(process)
The stacked solid-state imaging device can be manufactured according to a so-called microfabrication process used for manufacturing a known integrated circuit or the like. Basically, this method uses pattern exposure by active light or electron beam (mercury i, g emission line, excimer laser, X-ray, electron beam), pattern formation by development and / or burning, and element formation material By repeated operation of arrangement (coating, vapor deposition, sputtering, CV, etc.) and removal of non-patterned material (heat treatment, dissolution treatment, etc.).

(Use)
The chip size of the device can be selected from brownie size, 135 size, APS size, 1 / 1.8 inch, and even smaller size. The pixel size of the laminated photoelectric conversion element of the present invention is represented by a circle-equivalent diameter corresponding to the maximum area of a plurality of electromagnetic wave absorption / photoelectric conversion sites. Any pixel size may be used, but a pixel size of 2 to 20 microns is preferable. More preferably, it is 2 to 10 microns, but 3 to 8 microns is particularly preferable. When the pixel size exceeds 20 microns, the resolving power decreases, and even if the pixel size is smaller than 2 microns, the resolving power decreases due to radio wave interference between the sizes.

  The stacked solid-state imaging device can be used for a digital still camera. It is also preferable to use it for a television camera. Other applications include digital video cameras, surveillance cameras for the following applications (office buildings, parking lots, financial institutions and unmanned contractors, shopping centers, convenience stores, outlet malls, department stores, pachinko halls, karaoke boxes, game centers, Hospital), various other sensors (TV door phone, personal authentication sensor, factory automation sensor, home robot, industrial robot, piping inspection system), medical sensor (endoscope, fundus camera), video conference system, It can be used for applications such as videophones, camera-equipped mobile phones, car safety driving systems (back guide monitors, collision prediction, lane keeping systems), and video game sensors.

  Among these, the multilayer solid-state imaging device is suitable for TV camera applications. This is because a television camera can be reduced in size and weight because no color separation optical system is required. Further, since it has high sensitivity and high resolution, it is particularly preferable for a television camera for high-definition broadcasting. In this case, the high-definition broadcast television camera includes a digital high-definition broadcast camera. Further, the stacked solid-state imaging device is preferable in that an optical low-pass filter can be omitted, and higher sensitivity and higher resolution can be expected. Furthermore, since it is possible to reduce the thickness of the stacked solid-state imaging device and eliminate the need for a color separation optical system, “an environment with different brightness such as daytime and nighttime”, “still For shooting scenes that require different sensitivities, such as “subject and moving subject”, and other shooting scenes that require different spectral sensitivity and color reproducibility, one camera can be used by shooting with the stacked solid-state imaging device replaced. This camera can meet various demands for photography, and it is not necessary to carry multiple cameras at the same time. As the stacked solid-state imaging device to be exchanged, in addition to the above, an exchange photoelectric conversion device can be prepared for infrared light photography, monochrome photography, and dynamic range change.

  The TV camera can be referred to the description in Chapter 2 of “Design Technology for Television Cameras” edited by the Institute of Image Information and Television Engineers (Corona, 1999). For example, the color separation optical system shown in FIG. Further, the imaging device can be manufactured by replacing the part of the imaging device with the above-described stacked solid-state imaging device. The above-described photoelectric conversion elements can be used not only as an image pickup element by being arranged, but also as an optical sensor such as a biosensor or a chemical sensor or a color light receiving element as a single unit.

(Second embodiment)
In this embodiment, an example of a stacked solid-state imaging device using the photoelectric conversion element described in the first embodiment will be described.

FIG. 2 is a partial cross-sectional schematic view of a stacked solid-state imaging device for explaining a second embodiment of the present invention.
In FIG. 2, a cross section for two pixels in a pixel portion, which is a portion that detects light and accumulates charges, wiring connected to an electrode in the pixel portion, a bonding pad connected to the wiring, and the like are formed. The cross section with the peripheral circuit part which is a part to be performed is also shown.

  In the n-type silicon substrate 413 of the pixel portion, a p region 421 is formed on the surface portion, an n region 422 is formed on the surface portion of the p region 421, and a p region 423 is formed on the surface portion of the n region 422. N region 424 is formed on the surface of p region 423.

  The p region 421 accumulates red (R) component electrons photoelectrically converted by a pn junction with the n-type silicon substrate 413. A potential change in the p region 421 due to accumulation of R component electrons is read from the MOS transistor 426 formed in the n-type silicon substrate 413 to the signal read-out PAD 427 through the metal wiring 419 connected thereto.

  The p region 423 accumulates blue (B) component electrons photoelectrically converted by the pn junction with the n region 422. The potential change in the p region 423 due to the accumulation of the B component electrons is read from the MOS transistor 426 ′ formed in the n region 422 to the signal read PAD 427 through the metal wiring 419 connected thereto.

  In the n region 424, a hole accumulation region 425 including a p region for accumulating green (G) component holes generated in the photoelectric conversion layer 422 stacked above the n-type silicon substrate 413 is formed. The potential change in the hole accumulation region 425 due to the accumulation of the G component holes is caused by the signal readout PAD 427 from the MOS transistor 426 ″ formed in the n region 424 through the metal wiring 419 connected thereto. Is read out. Usually, the signal readout PAD 427 is provided separately for each transistor from which each color component is read out.

  Here, the n region, the p region, the transistor, the metal wiring, and the like are schematically shown. However, the structure and the like are not limited to this, and an optimal one is appropriately selected. Since the B light and R light are separated according to the depth of the silicon substrate, it is important to select the depth from the surface of the silicon substrate such as a pn junction and the doping concentration of each impurity.

  A transparent insulating layer 412 mainly composed of silicon oxide, silicon nitride, or the like is formed on the n-type silicon substrate 413, and a transparent insulating layer mainly composed of silicon oxide, silicon nitride, or the like is formed on the insulating layer 412. 411 is formed. The thinner the insulating layer 412 is, the more preferably 5 μm or less, preferably 3 μm or less, more preferably 2 μm or less, and further preferably 1 μm or less.

  In the insulating layers 411 and 412, a plug 415 mainly composed of, for example, tungsten is formed to electrically connect the lower electrode 414 and the p region 425 serving as a hole accumulation region. The plug 415 includes the insulating layer 411. And the insulating layer 412 are relay-connected by a pad 416. The pad 416 is preferably made mainly of aluminum. In the insulating layer 412, the above-described metal wiring 419, gate electrodes of the transistors 426, 426 ′, and 426 ″ are also formed. It is preferable that a barrier layer including a metal wiring is provided. The plug 415 is provided for each pixel.

  In the insulating layer 411, a light shielding film 417 is provided in order to prevent noise caused by the generation of electric charges due to the pn junction of the n region 424 and the p region 425. As the light shielding film 417, a film mainly composed of tungsten, aluminum, or the like is usually used. In the insulating layer 411, a bonding pad 420 (a pad for supplying power from the outside) and a signal readout pad 427 are formed.

  A transparent lower electrode 414 is formed on the plug 415 of each pixel in the insulating layer 411. The lower electrode 414 is divided for each pixel, and the light receiving area is determined by this size. An intermediate layer 42 is formed on the lower electrode 414, and an upper electrode 428 is formed thereon. A bias is applied to the upper electrode 428 through a wiring from the bonding pad 420.

  The intermediate layer 42 is configured by laminating an uneven relief layer 421, a photoelectric conversion layer 422, and a charge blocking layer 423 in this order on a lower electrode 414. The thickness of the intermediate layer 42 is 0.5 μm or less, more preferably 0.3 μm or less, and particularly preferably 0.2 μm or less. The thicknesses of the lower electrode 414 and the upper electrode 428 are each preferably 0.2 μm or less.

  In the configuration of FIG. 2, the photoelectric conversion layer 422 uses a material that absorbs green light and generates electrons and holes corresponding thereto. Since the intermediate layer 42 can be used in common for all pixels, it is not necessary to separate the pixels for each pixel.

  As the organic p-type semiconductor and organic n-type semiconductor constituting the photoelectric conversion layer 422, any of quinacridone derivatives, naphthalene derivatives, anthracene derivatives, phenanthrene derivatives, tetracene derivatives, pyrene derivatives, perylene derivatives, and fluoranthene derivatives are particularly preferably used. be able to.

  The stacked solid-state imaging device in FIG. 2 uses the upper electrode 428 as a light incident side electrode, electrons generated in the photoelectric conversion layer 422 move to the upper electrode 428, and holes generated in the photoelectric conversion layer 422 become lower electrode 414. A voltage is applied to the lower electrode 414 and the upper electrode 428 so as to move to.

  The charge blocking layer 423 is provided to reduce dark current caused by holes injected from the upper electrode 428 when a voltage is applied to the lower electrode 414 and the upper electrode 428. Is injected into the photoelectric conversion layer 422.

  Around the lower electrode 414, the intermediate layer 42, and the upper electrode 428, a protective layer 404 mainly composed of silicon nitride or silicon nitride oxide having a function of protecting them is formed. An opening is formed in the protective layer 404 at a position that does not overlap with the lower electrode 414 of the pixel portion, and an opening is formed in a part on the bonding pad 420 in the insulating layer 411 and the protective layer 404. A wiring 418 made of aluminum or the like for electrically connecting the upper electrode 428 exposed through the two openings and the bonding pad 420 and applying a potential to the upper electrode 428 is formed inside the opening and on the protective layer 404. Is formed. As a material of the wiring 418, an alloy containing aluminum such as Al—Si or Al—Cu alloy can be used.

  A protective layer 403 mainly composed of silicon nitride or the like for protecting the wiring 418 is formed on the wiring 418. An infrared blocking dielectric multilayer film 402 is formed on the protective layer 403, and the infrared blocking dielectric multilayer is formed. An antireflection layer 401 is formed on the film 402.

  The lower electrode 414 performs the same function as the lower electrode 2 shown in FIG. The photoelectric conversion layer 422 performs the same function as the photoelectric conversion layer 3 shown in FIG. The upper electrode 428 performs the same function as the upper electrode 4 shown in FIG. The unevenness relief layer 421 performs the same function as the unevenness relief layer 5 shown in FIG.

  With the above configuration, it is possible to perform color imaging by detecting light of BGR three colors with one pixel. In the configuration of FIG. 2, R and B are used as common values in two pixels and only the G value is used separately. However, since the sensitivity of G is important when generating an image, such a configuration is used. Even so, it is possible to generate a good color image.

Examples of the present invention will be described below.
In the following examples, the average surface roughness Ra was measured by measuring 10 ranges of 2 × 2 μm □ with an atomic force microscope (AFM) after the formation of the relief layer.

Example 1
A glass substrate on which a transparent electrode (thickness: 100 nm) made of ITO was formed was used as the lower electrode. The average surface roughness Ra of the surface of the transparent electrode was 1.6 nm. On the surface of this transparent electrode, m-MTDATA (thickness 100 nm) was heated and evaporated to form an unevenness relief layer. Next, quinacridone (thickness: 100 nm) was heated and deposited on the unevenness relaxation layer to form a photoelectric conversion layer. Next, on the photoelectric conversion layer, Alq ₃ (thickness 50 nm) was heated and deposited to form an electron blocking layer. Next, an ITO (thickness 10 nm) film was formed on the electron blocking layer by sputtering (distance between TSs, with offset) to form an upper electrode (hole collecting electrode). The average surface roughness Ra of the surface of the unevenness relief layer after the formation of the unevenness relief layer was 0.85 nm. The element thus manufactured is referred to as element A.

(Example 2)
In the manufacturing process of element A, an element was manufactured under the same conditions as in Example 1 except that m-MTDATA was deposited on ITO and then the element was heated at 150 ° C. for 1 hour in a nitrogen atmosphere. The element thus manufactured is referred to as element B.

(Example 3)
In device A, instead of depositing m-MTDATA on ITO, a dichloroethane solution of PTPDES was applied on ITO by spin coating, and after application, the film was heated at 100 ° C. for 2 hours under vacuum to have a thickness of 40 nm made of PTPDES. After that, an unevenness relief layer was formed, and thereafter, an element was fabricated under the same conditions as in Example 1. The average surface roughness Ra of the surface of the uneven relief layer was 0.4 nm. The element thus fabricated is referred to as element C.

(Comparative example)
An element was produced under the same conditions as in Example 1 except that the vapor deposition step of m-MTDATA was omitted in element A. The element thus manufactured is referred to as element D.

  The short ratio of the elements A to D manufactured as described above was obtained. The short-circuit rate is a ratio indicating how many of, for example, 10 elements are short-circuited. When the short rate of element D is 100, the short rate of element A is 65 or less, the short rate of element B is 30 or less, the short rate of element C is 16 or less, and the yield can be improved by providing an uneven relief layer. I understood.

  As described above, the following items are disclosed in this specification.

  The disclosed method for manufacturing a photoelectric conversion element is a method for manufacturing a photoelectric conversion element including a pair of electrodes and a photoelectric conversion layer sandwiched between the pair of electrodes, wherein one of the pair of electrodes is formed. And forming an amorphous material or a polymer material on the one electrode, and heating the amorphous material film or the polymer material film to alleviate unevenness on the surface of the one electrode. The method includes a step of forming an unevenness relief layer, a step of forming the photoelectric conversion layer on the unevenness relief layer, and a step of forming the other electrode of the pair of electrodes on the photoelectric conversion layer.

  In the disclosed method for producing a photoelectric conversion element, the film of the amorphous material or the film of the polymer material is heated in a vacuum in the step of forming the unevenness reducing layer.

  In the disclosed method for manufacturing a photoelectric conversion element, the amorphous material or the polymer material includes an organic material.

  In the disclosed method for producing a photoelectric conversion element, the other electrode is formed of a transparent conductive oxide.

In the disclosed method for manufacturing a photoelectric conversion element, the other electrode is formed using at least one of ITO, IZO, SnO ₂ , ZnO, and AZO.

  The disclosed solid-state imaging device is a solid-state imaging device having a large number of pixels arranged in an array, and each of the large number of pixels is manufactured by the manufacturing method in which at least one is stacked above a semiconductor substrate. And a signal reading unit that reads a signal corresponding to the electric charge generated in the photoelectric conversion element.

  In the disclosed solid-state imaging device, the one electrode is divided for each pixel, and the photoelectric conversion layer and the unevenness reducing layer have a single-sheet structure common to all the pixels.

DESCRIPTION OF SYMBOLS 1 Substrate 2 Lower electrode 3 Photoelectric conversion layer 4 Upper electrode 5 Concavity and convexity relaxation layer 6 Charge blocking layer 100 Photoelectric conversion element

Claims (4)

A method of manufacturing a solid-state imaging device in which a large number of photoelectric conversion elements including a pair of electrodes and a photoelectric conversion layer sandwiched between the pair of electrodes are arranged in an array ,
The one electrode of each pixel of the solid-state imaging device is divided for each pixel,
And forming the one electrode,
Wherein on one of the electrodes, the amorphous material is deposited by evaporation, by heating the film in an amorphous material, unevenness of the common single structure by the number of pixels to relax the unevenness of the surface of the one electrode Forming a relaxation layer;
Forming the photoelectric conversion layer on the uneven relief layer;
Method of manufacturing a solid-state imaging device comprising the step of forming the other electrode of the pair of electrodes in the photoelectric conversion layer. It is a manufacturing method of the solid-state image sensing device according to claim 1 ,
The amorphous material, Ri organic material der,
The manufacturing method of the solid-state image sensor whose sheet resistance of the said uneven | corrugated relief layer is 1 * 10 < ¹⁵ > (omega | ohm) / square or more . It is a manufacturing method of the solid-state image sensing device according to claim 1 or 2 ,
A method for producing a solid-state imaging device , wherein the other electrode is formed of a transparent conductive oxide. It is a manufacturing method of the solid-state image sensing device according to any one of claims 1 to 3 ,
A method for manufacturing a solid-state imaging device , wherein the other electrode is formed using at least one of ITO, IZO, SnO ₂ , ZnO, and AZO.

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