JP5800682B2 - Method for manufacturing photoelectric conversion element and method for manufacturing imaging element - Google Patents

Description

  The present invention relates to a photoelectric conversion element that has an organic layer (photoelectric conversion layer) that generates a charge in response to received light and converts a visible light image into an electrical signal, a manufacturing method thereof, an imaging element, and a manufacturing method thereof. In particular, the present invention relates to a photoelectric conversion element excellent in productivity and a manufacturing method thereof, and an imaging element and a manufacturing method thereof.

As an image sensor used for a digital still camera, a digital video camera, a mobile phone camera, an endoscope camera, etc., pixels including photodiodes are arranged on a semiconductor substrate such as a silicon (Si) chip, Solid-state imaging devices (so-called CCD sensors and CMOS sensors) that acquire signal charges corresponding to photoelectrons generated in a photodiode with a CCD type or CMOS type readout circuit are widely known.
In recent years, an imaging element using an organic material and having an organic photoelectric conversion layer that generates a charge in response to received light has been studied.

An image sensor having an organic photoelectric conversion layer is formed on a pixel electrode formed on a semiconductor substrate on which a signal readout circuit is formed, an organic photoelectric conversion layer formed on the pixel electrode, and an organic photoelectric conversion layer A transparent counter electrode (upper electrode), a protective film formed on the counter electrode and protecting the counter electrode, a color filter, and the like are included.
In a solid-state imaging device, by applying a bias voltage between the pixel electrode and the counter electrode, excitons generated in the organic photoelectric conversion layer dissociate into electrons and holes, and move to the pixel electrode according to the bias voltage. A signal corresponding to the charge of the electron or hole is acquired by a CCD or CMOS type signal readout circuit.

  In an imaging device having an organic photoelectric conversion layer, a protective film (for example, silicon oxide, silicon nitride, silicon oxynitride) is formed on a transparent upper electrode formed on the organic photoelectric conversion layer by low-temperature plasma CVD at about room temperature to 80 ° C. ) Is known (Patent Document 1). It is also known to provide a buffer layer (including silicon oxide) between the upper electrode and the plasma CVD protective film by a physical vapor deposition method such as a vacuum deposition method or a sputtering method (Patent Document 2).

Patent Document 3 includes an organic layer that generates a charge when irradiated with light between two electrodes, one of which is translucent, and a surface protective layer is laminated on the surface. An organic photoelectric conversion element is disclosed in which a layer is composed of an inorganic sealing layer formed by a vapor deposition method and a resin layer formed on the inorganic sealing layer. This inorganic sealing layer has an internal stress of −1 GPa to +1 GPa. In this case, a positive value indicates tensile stress and a negative value indicates compressive stress.
Moreover, in patent document 3, the sealing property with respect to an organic photoelectric converting laminated structure becomes high by setting the thickness of an inorganic sealing layer to be 1.0 μm or more, and the effect of blocking moisture and oxygen can be further enhanced. It is disclosed that it is possible. When forming an inorganic sealing layer, the glass transition temperature of each constituent organic material of the organic photoelectric conversion laminate structure in which an organic layer is laminated between two electrodes (the glass transition temperature of the organic material is generally 80 to 100 ° C.) or less It is disclosed that it is necessary to form a film at the substrate temperature.

  Furthermore, Patent Document 3 discloses that an inorganic sealing layer produced at a substrate temperature of 100 ° C. or lower has a lower film density and a film thickness of 1.0 μm compared to those produced at a substrate temperature of 100 ° C. or higher. It is disclosed that a pinhole penetrating the inorganic sealing layer is likely to remain if the ratio is less than 1, and the moisture permeability resistance and oxygen resistance resistance are inferior.

JP 2006-245045 A JP 2007-250890 A JP 2004-165512 A

Here, a silicon oxynitride film 154 (see FIG. 9B) formed by plasma CVD is formed as a protective film for the transparent upper electrode 152 formed on the organic layer 150 shown in FIG. 9A. This will be described as an example.
When the silicon oxynitride film 154 is formed, nitrogen gas (N ₂ gas) is used as an inert carrier gas, and silane gas (SiH ₄ gas) and nitrous oxide gas (N ₂ O gas) are used as reactive process gases. And the like, and ammonia gas (NH ₃ gas) are used. At this time, as shown in FIG. 9 (a), for example, when dust is attached to the upper electrode 152 on the organic layer 150 and there is a defect such as a pinhole 153 formed starting from this dust, From the pinhole 153, a reactive process gas (silane gas, flammable gas, ammonia gas) A enters the organic layer 150 and diffuses. The organic layer 150 is altered by the reactive process gas A, and an altered region 150a is generated in the organic layer 150 as shown in FIG. 9B. In addition, if the pinhole 153 is blocked with the silicon oxynitride film 154, the entry of the reactive process gas A into the organic layer 150 is suppressed.
The altered region 150 a due to the reactive process gas A has a lower photoelectric conversion sensitivity than other portions of the organic layer 150. Moreover, the altered region 150a has a predetermined range centered on the pinhole 153, as shown in FIG. 9C.

For example, if the image defect is only a local pinhole 153 region, it is possible to make a good product even if there is a defect such as the pinhole 153 by using pixel correction of an image sensor using normal peripheral pixels. it can.
However, as shown in FIG. 9C, when there is an altered region 150a in a predetermined range centered on the pinhole 153, it is difficult to use pixel correction using normal peripheral pixels. As described above, when the range in which the photoelectric conversion sensitivity is reduced is wide, it is not possible to obtain a non-defective product, and as a result, there is a problem in that the yield of the image sensor is reduced. A wide range in which the photoelectric conversion sensitivity that makes it difficult to use pixel correction using normal peripheral pixels is wide is called a black flaw.

  Such black scratches occur even in the case of a silicon oxide film that uses silane gas and nitrous oxide gas without using ammonia as a reactive process gas for plasma CVD. Further, it occurs even in the case of a silicon nitride film that uses a silane gas and an ammonia gas without using a flammable gas as the reactive process gas. When the protective film is formed of a silicon oxide film, a silicon oxynitride film, or a silicon nitride film by plasma CVD in this way, black scratches become a problem.

  Furthermore, regarding the protective film, it is required to shorten the film formation time, to reduce the internal stress, and to simplify the film formation facility. For this reason, it is desired to form a protective film including the buffer layer only by the plasma CVD method, which has a higher film forming speed than other film forming methods such as vapor deposition.

  An object of the present invention is to provide a photoelectric conversion element and a manufacturing method thereof, an imaging element and a manufacturing method thereof, which are free from the problems based on the above-described conventional techniques and have excellent productivity.

In order to achieve the above object, the present invention includes a substrate, a lower electrode formed on the substrate, an organic layer formed on the lower electrode and generating an electric charge when irradiated with light, and the organic A method for manufacturing a photoelectric conversion element, comprising: an upper electrode transparent to visible light formed on a layer; and an element protective layer formed on the upper electrode, wherein the element protective layer is formed Includes a step of supplying at least a carrier gas to generate plasma and a step of forming a silicon-containing protective film by supplying a reactive process gas containing at least SiH ₄ gas after the plasma is generated. The manufacturing method of the photoelectric conversion element characterized by these is provided.

The step of forming the element protective layer includes supplying a carrier gas and a combustion-supporting gas to generate plasma, and supplying a reactive process gas containing at least SiH ₄ gas after the plasma is generated. forming a buffer layer made of silicon oxide film, the carrier gas, the combustion-supporting gas, the SiH ₄ gas is supplied in a state in which plasma is generated, silicon oxynitride and further supplying the NH ₃ gas And a step of forming a protective film. The present invention provides a method for manufacturing a photoelectric conversion element.

When the carrier gas, the combustion-supporting gas, the SiH ₄ gas, and the NH ₃ gas are supplied and plasma is generated, the supply of the combustion-supporting gas is stopped, and the silicon nitride film is The present invention provides a method for manufacturing a photoelectric conversion element, which includes a step of forming a silicon oxynitride film.

When the carrier gas, the combustion-supporting gas, the silane gas, and the NH ₃ gas are supplied and plasma is generated, the supply of the combustion-supporting gas is stopped, and the silicon nitride film is oxidized and nitrided. It is preferable to have a step of forming on the silicon film.
The carrier gas is preferably N ₂ gas, and the combustion-supporting gas is preferably N ₂ O gas. For example, the substrate temperature at the time of forming the silicon oxynitride film is preferably 25 ° C. or more higher than the substrate temperature at the time of forming the silicon oxide film.

  Furthermore, it is a manufacturing method of the image pick-up element which has a photoelectric conversion element, Comprising: It has the process of manufacturing the said photoelectric conversion element with the manufacturing method of the photoelectric conversion element of the said invention, The manufacturing method of the image pick-up element characterized by the above-mentioned is provided. Is.

  Furthermore, a substrate, a lower electrode formed on the substrate, an organic layer that is formed on the lower electrode and generates a charge when irradiated with light, and visible light formed on the organic layer A transparent upper electrode and an element protective layer formed on the upper electrode, the element protective layer comprising a buffer layer made of a silicon oxide film formed on the upper electrode, and oxynitriding An intermediate layer made of a silicon oxynitride film having a nitrogen concentration decreased between the buffer layer and the silicon oxynitride film in a direction from the silicon oxynitride film toward the buffer layer. The intermediate layer has a thickness of 1 to 30 nm, and provides a photoelectric conversion element.

The element protective layer preferably has a silicon nitride film formed on the silicon oxynitride film.
The upper electrode preferably has a thickness of 5 to 30 nm.
The silicon oxide film preferably contains hydrogen and has a thickness of 1 to 100 nm.
The silicon oxide film is preferably formed by a chemical vapor deposition method.
Furthermore, the present invention provides an imaging device comprising the photoelectric conversion device of the present invention.

  According to the present invention, the occurrence of black scratches can be suppressed, the yield is high, and the photoelectric conversion element and the imaging element can be obtained with high productivity. In addition, this invention is applicable also to an organic electroluminescent film | membrane (organic EL) and an organic solar cell.

(A) is typical sectional drawing which shows the photoelectric conversion element of embodiment of this invention, (b) is a principal part enlarged view which shows the modification of the photoelectric conversion element of embodiment of this invention. It is a graph for demonstrating the structure of the protective film layer of the photoelectric conversion element of embodiment of this invention. It is a flowchart which shows the manufacturing method of the photoelectric conversion element of embodiment of this invention. It is a flowchart which shows the other manufacturing method of the photoelectric conversion element of embodiment of this invention. It is a flowchart which shows the manufacturing method of the modification of the photoelectric conversion element of embodiment of this invention. It is a typical sectional view showing an image sensor of an embodiment of the present invention. (A)-(c) is typical sectional drawing which shows the manufacturing method of the image pick-up element of embodiment of this invention in order of a process. (A)-(c) is typical sectional drawing which shows the manufacturing method of the image pick-up element of embodiment of this invention in order of a process, and shows the post process of FIG.7 (c). (A) And (b) is typical sectional drawing for demonstrating generation | occurrence | production of a black wound, (c) is a typical top view of FIG.9 (b).

  Hereinafter, based on preferred embodiments shown in the accompanying drawings, a photoelectric conversion element of the present invention and a manufacturing method thereof, an imaging element and a manufacturing method thereof will be described in detail. Fig.1 (a) is typical sectional drawing which shows the photoelectric conversion element of embodiment of this invention, (b) is a principal part enlarged view which shows the modification of the photoelectric conversion element of embodiment of this invention. .

  A photoelectric conversion element 100 shown in FIG. 1 converts incident light L into an electric signal. In the photoelectric conversion element 100, a lower electrode 104 is formed on a substrate 102, and an organic layer 106 is formed on the lower electrode 104. An upper electrode 108 is formed on the organic layer 106. An organic layer 106 is provided between the lower electrode 104 and the upper electrode 108. The organic layer 106 includes a photoelectric conversion layer 112 containing an organic substance and an electron blocking layer 114, and the electron blocking layer 114 is formed on the lower electrode 104. An element protective layer 115 is formed to cover the lower electrode 104, the organic layer 106, and the upper electrode 108.

The substrate 102 is composed of, for example, a silicon substrate or a glass substrate.
The lower electrode 104 is an electrode for collecting holes out of charges generated in the organic layer 106. Examples of the material of the lower electrode 104 include metals, metal oxides, metal nitrides, metal borides, organic conductive compounds, and mixtures thereof. Specific examples include tin oxide, zinc oxide, indium oxide, indium tin oxide (ITO), indium zinc oxide (IZO), indium tungsten oxide (IWO), conductive metal oxides such as titanium oxide, and titanium nitride (TiN). Metal nitrides such as gold (Au), platinum (Pt), silver (Ag), chromium (Cr), nickel (Ni), aluminum (Al), etc., and these metals and conductive metal oxides A mixture or laminate of the above, an organic conductive compound such as polyaniline, polythiophene, and polypyrrole, a laminate of these with ITO, and the like. The material of the lower electrode 104 is particularly preferably any of titanium nitride, molybdenum nitride, tantalum nitride, and tungsten nitride.

The organic layer 106 receives the incident light L and generates charges according to the amount of light. The organic layer 106 includes a photoelectric conversion layer 112 that includes a photoelectric conversion material. An organic compound can be used as the photoelectric conversion material. For example, the photoelectric conversion layer 112 is preferably a layer containing a p-type organic semiconductor material or an n-type organic semiconductor material. The photoelectric conversion layer is more preferably a bulk hetero layer in which an organic p-type compound and an organic n-type compound are mixed. More preferably, it is a bulk hetero layer in which an organic p-type compound and fullerene or a fullerene derivative are mixed. By using a bulk hetero layer as the photoelectric conversion layer 112, the disadvantage that the carrier diffusion length of the organic layer is short can be compensated and the photoelectric conversion efficiency can be improved. By producing a bulk hetero layer with an optimal mixing ratio, the electron mobility and hole mobility of the photoelectric conversion layer 112 can be increased, and the light response speed of the photoelectric conversion element can be sufficiently increased. . The proportion of fullerene or fullerene derivative in the bulk hetero layer is preferably 40% to 85% (volume ratio). The bulk hetero layer (bulk hetero junction structure) is described in detail in JP-A-2005-303266.
The photoelectric conversion layer 112 is altered by a reactive process gas (silane gas (SiH ₄ gas), combustion-supporting gas, ammonia gas), and the photoelectric conversion sensitivity is lowered.

  The thickness of the photoelectric conversion layer 112 is preferably 10 nm or more and 1000 nm or less, more preferably 50 nm or more and 800 nm or less, and particularly preferably 100 nm or more and 500 nm or less. By setting the thickness of the photoelectric conversion layer 112 to 10 nm or more, a suitable dark current suppressing effect can be obtained, and by setting the thickness of the photoelectric conversion layer 112 to 1000 nm or less, preferable photoelectric conversion efficiency can be obtained.

  The layer containing the above-described organic compound that constitutes the photoelectric conversion layer 112 is preferably formed by a vacuum evaporation method. It is preferable that all steps during the vapor deposition are performed in a vacuum, and basically the compound is not directly in contact with oxygen and moisture in the outside air. 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.

  The electron blocking layer 114 is a layer for suppressing injection of electrons from the lower electrode 104 to the organic layer 106. The electron blocking layer 114 includes an organic material, an inorganic material, or both.

The electron blocking layer 114 is a layer for preventing electrons from being injected into the organic layer 106 from the lower electrode 104, and is composed of a single layer or a plurality of layers. The electron blocking layer 114 may be composed of a single organic material film, or may be composed of a mixed film of a plurality of different organic materials. The electron blocking layer 114 is preferably made of a material having a high electron injection barrier from the adjacent lower electrode 104 and a high hole transporting property. As an electron injection barrier, the electron affinity of the electron blocking layer 114 is preferably 1 eV or less, more preferably 1.3 eV or more, and particularly preferably 1.5 eV or more than the work function of the adjacent electrode.
The electron blocking layer 114 is preferably 20 nm or more, more preferably in order to sufficiently suppress the contact between the lower electrode 104 and the photoelectric conversion layer 112 and to avoid the influence of defects and dust existing on the surface of the lower electrode 104. Is 40 nm or more, particularly preferably 60 nm or more.
If the electron blocking layer 114 is too thick, the problem of increasing the supply voltage necessary for applying an appropriate electric field strength to the photoelectric conversion layer 112 and the carrier transport process in the electron blocking layer 114 may be caused by photoelectric conversion. There arises a problem that adversely affects the performance of the element. The total thickness of the electron blocking layer 114 is preferably 300 nm or less, more preferably 200 nm or less, and still more preferably 100 nm or less.

  The upper electrode 108 is an electrode that collects electrons out of charges generated in the organic layer 106. The upper electrode 108 is sufficiently transparent to light having a wavelength with which the organic layer 106 has sensitivity, for example, visible light, so that light is incident on the organic layer 106. By applying a bias voltage between the upper electrode 108 and the lower electrode 104, among the charges generated in the organic layer 106, holes can be moved to the lower electrode 104 and electrons can be moved to the upper electrode 108.

The upper electrode 108 is for increasing the absolute amount of light incident on the photoelectric conversion layer and increasing the external quantum efficiency, and a transparent conductive oxide is used.
Preferred materials for the upper electrode 108 are ITO, IZO, SnO ₂ , ATO (antimony-doped tin oxide), ZnO, AZO (Al-doped zinc oxide), GZO (gallium-doped zinc oxide), TiO ₂ , FTO (fluorine-doped). Tin oxide).
The light transmittance of the upper electrode 108 is preferably 60% or more, more preferably 80% or more, more preferably 90% or more, and more preferably 95% or more in the visible light wavelength.
The upper electrode 108 preferably has a thickness of 5 to 30 nm. By making the upper electrode 108 a film thickness of 5 nm or more, the lower layer can be sufficiently covered, and uniform performance can be obtained. On the other hand, when the thickness of the upper electrode 108 exceeds 30 nm, the upper electrode 108 and the lower electrode 104 may be locally short-circuited, and the dark current may increase. By making the upper electrode 108 a film thickness of 30 nm or less, it is possible to suppress the occurrence of a local short circuit.

The element protective layer 115 includes a buffer layer 109, an intermediate layer 111, and a protective film 110 that are sequentially formed from the upper electrode 108 side. The buffer layer 109, the intermediate layer 111, and the protective film 110 are continuously formed.
The buffer layer 109 is for improving the heat resistance of the photoelectric conversion element 100. Specifically, the buffer layer 109 suppresses deterioration of the heat resistance of the organic layer 106 due to ammonia gas or ammonia radicals.
The buffer layer 109 is composed of a silicon oxide film (SiOx film) formed without using ammonia gas, and has a thickness of 1 to 100 nm, for example.
The buffer layer 109 is formed by, for example, a chemical vapor deposition method. This chemical vapor deposition method is preferably a plasma CVD method.
When a silicon oxide film (SiOx film) is formed as the buffer layer 109 by a plasma CVD method, silane gas (SiH ₄ gas) is used, and the silicon oxide film contains hydrogen. Therefore, the buffer layer 109 is a silicon oxide film containing hydrogen. When using the N _{2 O} gas to the combustion-supporting gas, in the case of using N ₂ gas is further carrier gas, sometimes also include slight nitrogen. Note that the buffer layer 109 is also transparent to the incident light L (visible light).
The SiOx film that is the buffer layer 109 is inferior in barrier properties of H ₂ O and O ₂ as a protective layer, and needs to be laminated with a silicon oxynitride film or a silicon nitride film. If the buffer layer 109 exceeds 100 nm, it is difficult to suppress the thickness of the entire protective film to about 100 nm, and it is difficult to suppress color mixing when the pixel size is less than 1 μm.

The protective film 110 is for preventing a factor that degrades an organic material such as water and oxygen from entering the organic layer 106 containing the organic material, and the organic layer 18 can be used for a long period of storage and long-term use. It is intended to prevent the deterioration. The protective film 110 is continuously formed on the intermediate layer 111 formed continuously from the buffer layer 109.
The protective film 110 contains hydrogen and silicon oxynitride (SiOxNy), and has a film thickness of, for example, 70 to 500 nm.
When the thickness of the protective film 110 is less than 70 nm, there is a possibility that the barrier property is lowered and the resistance of the color filter to the developer is lowered. On the other hand, if the thickness of the protective film 110 exceeds 500 nm, it is difficult to suppress color mixing when the pixel size is less than 1 μm.
The protective film 110 is preferably a nitrogen-rich SiOxNy film. This nitrogen-rich SiOxNy film has excellent barrier properties.

The protective film 110 is formed by, for example, a chemical vapor deposition method. This chemical vapor deposition method is, for example, a plasma CVD method. When the protective film 110 is formed by a chemical vapor deposition method, the internal stress can be reduced. For example, the internal stress of the protective film 110 can be set to 100 MPa or less in absolute value. That is, the protective film 110 can have an internal stress of 100 MPa or less in terms of tensile stress and 100 MPa or less in terms of compressive stress. The protective film 110 is also transparent to the incident light L (visible light).
When the internal stress of the protective film 110 exceeds ± 100 MPa, film peeling is likely to occur in the color filter development process.

The intermediate layer 111 is formed between the buffer layer 109 and the protective film 110 so as to be continuous with the buffer layer 109 and the protective film 110. The intermediate layer 111 has a thickness of 1 to 30 nm, for example.
As shown in FIG. 2, the intermediate layer 111 is made of a silicon oxynitride film in which the nitrogen concentration decreases and the oxygen concentration increases in the direction D from the protective film (SiON film) to the buffer layer (SiOx film). Is.
The intermediate layer 111 excludes a predetermined range β (for example, 10%) from the maximum nitrogen concentration and a predetermined range β (for example, 10%) from 0% when the nitrogen concentration of the protective film 110 is 100%. Further, it is assumed that the nitrogen concentration is in the range α of 10% to 90%.

In the photoelectric conversion element 100 configured as described above, the upper electrode 108 is used as a light incident side electrode. When incident light L is incident from above the upper electrode 108, this light is transmitted through the upper electrode 108 and the organic layer 106. The light enters the photoelectric conversion layer 112 and charges are generated in the photoelectric conversion layer 112. Holes in the generated charges move to the lower electrode 104. By converting the holes that have moved to the lower electrode 104 into a voltage signal corresponding to the amount of the holes and reading out the light, the light can be converted into a voltage signal and extracted.
Note that, in the photoelectric conversion element 100, the silicon oxide film (SiOx film) of the buffer layer 109 has excellent heat resistance, and the silicon oxynitride film (SiOxNy film) of the protective film 110 has excellent barrier properties. Excellent heat resistance.

  In the present embodiment, a silicon nitride film (SiNx film) 116 is further formed on the protective film 110 in the element protective layer 115 shown in FIG. 1A, like the element protective layer 115a shown in FIG. It may be a configured. Since the silicon nitride film (SiNx film) 116 has a high barrier property, the barrier property of the photoelectric conversion element can be further improved.

Next, a method for manufacturing the photoelectric conversion element 100 will be described.
First, as the lower electrode 104, for example, a TiN substrate in which a TiN electrode is formed on the substrate 102 is prepared.
In the TiN substrate, for example, TiN as a lower electrode material is formed on the substrate 102 by a sputtering method under a predetermined vacuum, and a TiN electrode is formed as the lower electrode 104.
Next, an electron blocking material, for example, a carbazole derivative, more preferably a bifluorene derivative, is formed on the lower electrode 104 under a predetermined vacuum using, for example, a vacuum deposition method to form the organic layer 106. An electron blocking layer 114 is formed.

Next, on the electron blocking layer 114, as a photoelectric conversion material, for example, a p-type organic semiconductor material and fullerene or a fullerene derivative are co-evaporated under a predetermined vacuum to form the photoelectric conversion layer 112 constituting the organic layer 106. Form.
Next, on the photoelectric conversion layer 112, for example, ITO is used as a transparent conductive oxide, and a film having a thickness of 5 to 30 nm is formed by a sputtering method. Thereby, for example, the upper electrode 108 made of ITO is formed on the photoelectric conversion layer 112.

Next, the element protective layer 115 is formed using a plasma CVD method so as to cover the lower electrode 104, the organic layer 106, and the upper electrode 108. Hereinafter, a method for forming the element protective layer 115 will be described with reference to FIG. In this case, the element protective layer 115 is a single protective film 110 (silicon-containing protective film).
In the present embodiment, a silicon oxynitride film (SiOxNy film) is formed to a thickness of, for example, 70 to 500 nm as the protective film 110 using the plasma CVD method. In this case, a reactive process gas is used. silane gas (SiH ₄ gas), ammonia gas (NH ₃ gas), _{N 2} O gas is used in the combustion supporting gas, _{N 2} gas is used as carrier gas. As the carrier gas, a gas inert to the photoelectric conversion film is used.
In this embodiment, first, before supplying the reactive process gas (silane gas (SiH ₄ gas), ammonia gas (NH ₃ gas), combustion-supporting gas (N ₂ O gas)), the carrier gas (N ₂ Gas) is supplied (step S10). Then, plasma is generated (step S12).

Next, with the plasma generated, a reactive process gas (silane gas (SiH ₄ gas), ammonia gas (NH ₃ gas), combustion-supporting gas (N ₂ O gas)) is then supplied (step S14). ). The supplied silane gas (SiH ₄ gas) is decomposed by plasma to form an initial silicon-containing film. Subsequently, a silicon oxynitride film having a preset composition is formed when the reactive process gas is stably decomposed by plasma. The initial silicon-containing film is a layer in which the contents of oxygen, nitrogen, and hydrogen are not constant, but since the film thickness is as thin as 1 to 30 nm, the performance of the protective film is not greatly affected. On the other hand, there is an advantage that the gas supply process is simplified.

Next, the element protective layer 115 is formed using a plasma CVD method so as to cover the lower electrode 104, the organic layer 106, and the upper electrode 108. Hereinafter, another method for forming the element protective layer 115 will be described with reference to FIGS.
In this embodiment, a silicon oxide film (SiOx film) is formed as the buffer layer 109 to a thickness of, for example, 1 to 100 nm using the plasma CVD method. In this case, silane gas (SiH ₄ gas) is used as a process gas. N ₂ gas is used as the carrier gas, and N ₂ O gas is used as the combustion-supporting gas.
As the protective film 110, a silicon oxynitride film (SiOxNy film) is formed to a thickness of, for example, 70 to 500 nm. In this case, a reactive process gas includes silane gas (SiH ₄ gas), ammonia gas (NH ₃ gas), A combustion-supporting gas (N ₂ O gas) is used, and N ₂ gas is used as a carrier gas inert to the photoelectric conversion layer 112 (photoelectric conversion film).
In the present embodiment, first, a carrier gas (N ₂ gas) is supplied before supplying a reactive process gas such as silane gas (SiH ₄ gas) (step S20). Then, plasma is generated (step S22).

Next, in a state where plasma is generated, after that, a combustion supporting gas (N ₂ O gas) which is a reactive process gas, and then a silane gas (SiH ₄ gas) are supplied (step S24). The supplied combustion-supporting gas (N ₂ O gas) and silane gas (SiH ₄ gas) are decomposed by plasma to form a silicon oxide film (SiOx film). When the flow rate of the combustion-supporting gas (N ₂ O gas) is as low as 100 sccm or less, the supply timing of the combustion-supporting gas may be simultaneously with the carrier gas (N ₂ gas) supply before plasma generation.
Subsequently, ammonia gas (NH ₃ gas) is further supplied in a state where the carrier gas, the combustion-supporting gas, and the silane gas are supplied and the plasma is generated (step S26). Immediately after the start of supply of ammonia gas (NH ₃ gas) is lower in an amount less concentration of ammonia gas (NH ₃ gas), a silicon oxynitride film to be formed, becomes low nitrogen concentration. As the supply amount of ammonia gas (NH ₃ gas) increases, the nitrogen concentration also increases, and finally, a silicon oxynitride film having a preset composition is formed. Thus, the nitrogen concentration increases in the deposition direction, that is, in the direction opposite to the direction D shown in FIG. 2 described above, so that silicon oxynitride is formed and a silicon oxynitride film is formed. A region where the nitrogen concentration changes between the silicon oxide film and the silicon oxynitride film is the intermediate layer 111. The intermediate layer 111 is also an inclined layer because the nitrogen concentration is inclined with respect to the deposition method.
The element protective layer 115 can be formed as described above, and the photoelectric conversion element 100 illustrated in FIG. 1 can be formed.

As the buffer layer 109, a silicon oxide film (SiOx film) is formed by a plasma CVD method using silane gas (SiH ₄ gas). For this reason, the buffer layer 109 is a SiOx film containing hydrogen. Note that the buffer layer 109 preferably has a deposition temperature of 125 ° C. to 150 ° C.
As the protective film 110, a silicon oxynitride film (SiOxNy film) is formed by a plasma CVD method using silane gas (SiH ₄ gas) and NH ₃ gas. For this reason, the protective film 110 is a silicon oxynitride film (SiOxNy film) containing hydrogen. Moreover, the internal stress can be reduced, for example, the absolute value can be 100 MPa or less. Note that the protective film 110 preferably has a film formation temperature of 150 ° C. to 230 ° C. In this case, the substrate temperature when the protective film 110 (silicon oxynitride film (SiOxNy film)) is formed is preferably 25 ° C. or more higher than the substrate temperature when the buffer layer 109 (silicon oxide film (SiOx film)) is formed.

In the present embodiment, the element protective layer 115a shown in FIG. 1B can be formed as follows.
In the step of forming the element protective layer 115a, steps S30 to S36 shown in FIG. 5 are the same as steps S20 to S26 which are the steps of forming the element protective layer 115 shown in FIG. Description is omitted. In the step of forming the element protection layer 115a, as shown in FIG. 5, after supplying NH ₃ gas (step S36) to form a silicon oxynitride film (SiOxNy film), a predetermined time elapses and oxidation is performed. After the silicon nitride film (SiOxNy film) is formed to a predetermined thickness, the supply of only the combustion-supporting gas (N ₂ O gas), which is a reactive process gas, is stopped while the plasma is being generated ( Step S38). In this case, the plasma is generated in a state where the reactive process gas of NH ₃ gas and SiH ₄ gas and N ₂ gas (carrier gas) are supplied, and the silicon oxynitride film is formed in such an atmosphere. A silicon nitride film (SiNx film) is formed on (SiOxNy film). In this way, the protective film 115a with better barrier properties can be formed.

In this embodiment, when forming a silicon-containing protective film as the element protective layers 115 and 115a, a reactive process gas (silane gas (SiH ₄ gas)) having high reactivity with the photoelectric conversion layer 112 (photoelectric conversion film). Before supplying ammonia gas (NH ₃ gas) and combustion-supporting gas), a carrier gas (N ₂ gas) having low reactivity with the photoelectric conversion layer 112 (photoelectric conversion film) is supplied to generate plasma. . After the plasma is generated, a reactive process gas (silane gas (SiH ₄ gas), ammonia gas (NH ₃ gas), combustion-supporting gas) is supplied. Reactive process gases (silane gas (SiH ₄ gas), ammonia gas (NH ₃ gas), and combustion-supporting gas) are decomposed by plasma when supplied. For this reason, for example, even if the upper electrode 108 has a defect such as a pinhole, the reactive process gas is prevented from entering the photoelectric conversion layer 112 of the organic layer 106 from the pinhole. This suppresses the occurrence of a decrease in sensitivity without altering the photoelectric conversion layer 112 of the organic layer 106. The occurrence of so-called black scratches can be suppressed. Therefore, the yield of the photoelectric conversion element 100 can be increased, and the productivity of the photoelectric conversion element 10 can be improved.

In the present embodiment, both of the element protective layers 115 and 115a are formed using the plasma CVD method, and can be formed in the same film formation chamber by changing the process gas. Therefore, the element protective layers 115 and 115a having the above-described configuration can be formed with one film forming apparatus, and the manufacturing equipment can be simplified. Thereby, the manufacturing cost of the photoelectric conversion element 100 can be reduced.
Furthermore, since the plasma CVD method has a higher film formation speed than other film formation methods such as vapor deposition, the productivity of the photoelectric conversion element 100 can be increased.
Note that since the silicon oxide film (SiOx film) of the buffer layer 109 has excellent heat resistance, and the silicon oxynitride film (SiOxNy film) of the protective film 110 has excellent barrier properties, the photoelectric conversion has excellent barrier properties and also excellent heat resistance. The element 100 can be manufactured.

Next, an image sensor using the photoelectric conversion element 100 will be described.
FIG. 6 is a schematic cross-sectional view showing the image sensor of the embodiment of the present invention.
The image sensor according to the embodiment of the present invention can be used in an imaging apparatus such as a digital camera or a digital video camera. Furthermore, it is used by being mounted on an imaging module such as an electronic endoscope and a cellular phone.

An image sensor 10 shown in FIG. 6 converts a visible light image into an electrical signal, and includes a substrate 12, an insulating layer 14, a pixel electrode (lower electrode) 16, an organic layer 18, and a counter electrode (upper electrode). ) 20, buffer layer 21, protective film (sealing layer) 22, color filter 26, partition wall 28, light shielding layer 29, and overcoat layer 30.
A reading circuit 40 and a counter electrode voltage supply unit 42 are formed on the substrate 12.
Note that the pixel electrode 16 corresponds to the lower electrode 104 of the photoelectric conversion element 100 described above, the counter electrode 20 corresponds to the upper electrode 108 of the photoelectric conversion element 100 described above, and the organic layer 18 corresponds to the photoelectric conversion element described above. 100 corresponding to the organic layer 106, and the element protective layer 25 corresponds to the element protective layer 115 of the photoelectric conversion element 100 described above.

As the substrate 12, for example, a glass substrate or a semiconductor substrate such as Si is used. An insulating layer 14 made of a known insulating material is formed on the substrate 12. A plurality of pixel electrodes 16 are formed on the surface of the insulating layer 14. The pixel electrodes 16 are arranged in a one-dimensional or two-dimensional manner, for example.
In addition, a first connection portion 44 that connects the pixel electrode 16 and the readout circuit 40 is formed in the insulating layer 14. Furthermore, a second connection portion 46 that connects the counter electrode 20 and the counter electrode voltage supply unit 42 is formed. The second connection portion 46 is formed at a position not connected to the pixel electrode 16 and the organic layer 18. The 1st connection part 44 and the 2nd connection part 46 are formed with the electroconductive material.

In addition, a wiring layer 48 made of a conductive material for connecting the readout circuit 40 and the counter electrode voltage supply unit 42 to, for example, the outside of the imaging device 10 is formed inside the insulating layer 14.
As described above, the circuit board 11 is formed by forming the pixel electrodes 16 connected to the first connection portions 44 on the surface 14 a of the insulating layer 14 on the substrate 12. The circuit board 11 is also referred to as a CMOS substrate.

The organic layer 18 is formed so as to cover the plurality of pixel electrodes 16 and to avoid the second connection portion 46. The organic layer 18 includes a photoelectric conversion layer 50 and an electron blocking layer 52.
In the organic layer 18, the electron blocking layer 52 is formed on the pixel electrode 16 side, and the photoelectric conversion layer 50 is formed on the electron blocking layer 52.
The electron blocking layer 52 is a layer for suppressing injection of electrons from the pixel electrode 16 to the photoelectric conversion layer 50.
The photoelectric conversion layer 50 generates electric charge according to the amount of received light such as incident light L (visible light), and includes an organic photoelectric conversion material. As long as the photoelectric conversion layer 50 and the electron blocking layer 52 have a constant film thickness on the pixel electrode 16, the film thickness may not be constant in other cases. The photoelectric conversion layer 50 will be described in detail later.

The counter electrode 20 is an electrode facing the pixel electrode 16 and is provided so as to cover the photoelectric conversion layer 50. A photoelectric conversion layer 50 is provided between the pixel electrode 16 and the counter electrode 20.
The counter electrode 20 is made of a conductive material that is transparent to the incident light L (visible light) in order to make light incident on the photoelectric conversion layer 50. The counter electrode 20 is electrically connected to the second connection portion 46 disposed outside the photoelectric conversion layer 50, and is connected to the counter electrode voltage supply portion 42 via the second connection portion 46. Yes.

The counter electrode 20 can use the same material as the upper electrode 108. For this reason, the detailed description about the material of the counter electrode 20 is abbreviate | omitted.
The light transmittance of the counter electrode 20 is preferably 60% or more, more preferably 80% or more, more preferably 90% or more, and more preferably 95% or more in the visible light wavelength.
The counter electrode 20 preferably has a thickness of 5 to 30 nm. By making the counter electrode 20 have a thickness of 5 nm or more, the lower layer can be sufficiently covered, and uniform performance can be obtained. On the other hand, if the counter electrode 20 has a film thickness exceeding 30 nm, the counter electrode 20 and the pixel electrode 16 may be locally short-circuited, resulting in an increase in dark current. By setting the counter electrode 20 to a film thickness of 30 nm or less, it is possible to suppress the occurrence of a local short circuit.

  The counter electrode voltage supply unit 42 applies a predetermined voltage to the counter electrode 20 via the second connection unit 46. When the voltage to be applied to the counter electrode 20 is higher than the power supply voltage of the image sensor 10, the power supply voltage is boosted by a booster circuit such as a charge pump to supply the predetermined voltage.

The pixel electrode 16 is an electrode for collecting charges for collecting charges generated in the photoelectric conversion layer 50 between the pixel electrode 16 and the counter electrode 20 facing the pixel electrode 16. The pixel electrode 16 is connected to the readout circuit 40 via the first connection portion 44. The readout circuit 40 is provided on the substrate 12 corresponding to each of the plurality of pixel electrodes 16, and reads out a signal corresponding to the charge collected by the corresponding pixel electrode 16.
The pixel electrode 16 can use the same material as the lower electrode 104. Therefore, a detailed description of the material of the pixel electrode 16 is omitted.

  A step corresponding to the film thickness of the pixel electrode 16 is steep at the end of the pixel electrode 16, there are significant irregularities on the surface of the pixel electrode 16, or minute dust (particles) adhere to the pixel electrode 16. As a result, a layer on the pixel electrode 16 becomes thinner than a desired film thickness or a crack occurs. When the counter electrode 20 is formed on the layer in such a state, a pixel defect such as an increase in dark current or a short circuit occurs due to contact or electric field concentration between the pixel electrode 16 and the counter electrode 20 in the defective portion. Further, the above-described defects may reduce the adhesion between the pixel electrode 16 and the layer above it and the heat resistance of the organic photoelectric conversion element 10.

  In order to prevent the above defects and improve the reliability of the element, the surface roughness Ra of the pixel electrode 16 is preferably 0.6 nm or less. The smaller the surface roughness Ra of the pixel electrode 16, the smaller the surface unevenness, and the better the surface flatness. In order to remove particles on the pixel electrode 16, it is particularly preferable to clean the pixel electrode 16 and the like using a general cleaning technique used in a semiconductor manufacturing process before forming the electron blocking layer 52. preferable.

The readout circuit 40 is constituted by, for example, a CCD, a MOS circuit, or a TFT circuit, and is shielded from light by a light shielding layer (not shown) provided in the insulating layer 14. The readout circuit 40 preferably employs a CCD or CMOS circuit for general image sensor applications, and preferably employs a CMOS circuit from the viewpoint of noise and high speed.
Although not shown, for example, a high-concentration n region surrounded by a p region is formed on the substrate 12, and a connection portion 44 is connected to the n region. A read circuit 40 is provided in the p region. The n region functions as a charge storage unit that stores the charge of the photoelectric conversion layer 50. The signal charge accumulated in the n region is converted into a signal corresponding to the amount of charge by the readout circuit 40 and output to the outside of the image sensor 10 via the wiring layer 48, for example.

The element protective layer 25 includes a buffer layer 21 formed without using ammonia gas (NH ₃ gas), an intermediate layer 23 with a composition gradient, and a protective film 22 formed in order from the counter electrode 20 side. . The buffer layer 21, the intermediate layer 23, and the protective film 22 are formed in succession.
The buffer layer 21 has the same configuration as the buffer layer 109 described above, and is for improving the heat resistance of the image sensor 10. Specifically, the buffer layer 21 suppresses deterioration of the heat resistance of the organic layer 18 when ammonia gas (NH ₃ gas) is used as the reactive process gas.
The buffer layer 21 is formed on the counter electrode 20. The buffer layer 21 is composed of a silicon oxide film (SiOx film), and has a thickness of 1 to 100 nm, for example.
The buffer layer 21 is formed by, for example, a vapor deposition method, and is preferably formed by a plasma CVD method.
When a silicon oxide film (SiOx film) is formed as the buffer layer 21 by a plasma CVD method, this silicon oxide film contains hydrogen. Therefore, the buffer layer 21 is a silicon oxide film containing hydrogen. Note that the buffer layer 21 is also transparent to the incident light L (visible light).

The protective film 22 has the same configuration as the protective film 110 described above. The protective film 22 protects the organic layer 18 including the photoelectric conversion layer 50 from deterioration factors such as water molecules and oxygen, and prevents deterioration of the organic layer 18 over long-term storage and long-term use. The protective film 22 is formed continuously on the intermediate layer 23 formed continuously from the buffer layer 21.
The protective film 22 contains hydrogen and silicon oxynitride (SiOxNy), and has a film thickness of, for example, 70 to 500 nm.
The protective film 22 is preferably a nitrogen-rich SiOxNy film containing hydrogen. This nitrogen-rich SiOxNy film has excellent barrier properties.

  The protective film 22 is formed by, for example, a vapor deposition method, and is preferably formed by a plasma CVD method. When the protective film 22 is formed by a vapor deposition method, the internal stress can be reduced. For this reason, for example, the internal stress of the protective film 22 can be made 100 MPa or less in absolute value, that is, 100 MPa or less in tensile stress and 100 MPa or less in compressive stress. The protective film 22 is also transparent to the incident light L (visible light).

The intermediate layer 23 is formed between the buffer layer 21 and the protective film 22 so as to be continuous with the buffer layer 21 and the protective film 22. The intermediate layer 23 has a thickness of 1 to 30 nm, for example.
As shown in FIG. 2, the intermediate layer 23 is a silicon oxynitride film in which the nitrogen concentration decreases and the oxygen concentration increases in the direction D from the protective film (SiON film) to the buffer layer (SiOx film). It consists of Since the configuration of the intermediate layer 23 is the same as that of the intermediate layer 111 of the photoelectric conversion element 100, detailed description thereof is omitted.
The intermediate layer 23 is formed when the buffer layer 21 and the protective film 22 are continuously formed.

  For example, in the image sensor 10 having a pixel dimension of less than 2 μm, particularly about 1 μm, if the distance between the color filter 28 and the photoelectric conversion layer 50, that is, the film thickness of the element protective layer 25 is large, the element protective layer 25 has a large thickness. Incident light L (visible light) may be diffracted or diverged to cause color mixing. For this reason, the element protective layer 25 is preferably thinner.

  The color filter 26 is formed on the protective film 22 of the element protective layer 25 at a position facing each pixel electrode 16. The partition wall 28 is provided between the color filters 26 on the protective film 22 of the element protective layer 25, and is for improving the light transmission efficiency of the color filter 26. The light shielding layer 29 is formed in a region other than the region (effective pixel region) where the color filter 26 and the partition wall 28 are provided on the protective film 22, and light is incident on the photoelectric conversion layer 50 formed outside the effective pixel region. Is to prevent. The color filter 26, the partition wall 28, and the light shielding layer 29 are formed to have substantially the same thickness, and are formed through, for example, a photolithography process and a resin baking process.

The overcoat layer 30 is for protecting the color filter 26 from subsequent processes and is formed so as to cover the color filter 26, the partition wall 28 and the light shielding layer 29.
In the image sensor 10, one pixel electrode 16 having the organic layer 18, the counter electrode 20, and the color filter 26 provided thereon is a unit pixel.

  For the overcoat layer 30, a polymer material such as an acrylic resin, a polysiloxane resin, a polystyrene resin, or a fluorine resin, or an inorganic material such as silicon oxide or silicon nitride can be used as appropriate. When a photosensitive resin such as polystyrene is used, the overcoat layer 30 can be patterned by a photolithography method, so that it is used as a photoresist when opening the peripheral light-shielding layer, sealing layer, insulating layer, etc. on the bonding pad. In addition, it is preferable because the overcoat layer 30 itself can be easily processed as a microlens. On the other hand, it is possible to use the overcoat layer 30 as an antireflection layer, and it is also preferable to form various low refractive index materials used as the partition walls of the color filter 26. In addition, in order to pursue a function as a protective layer and a function as an antireflection layer with respect to the post-process, the overcoat layer 30 can be configured to have two or more layers combining the above materials.

In the present embodiment, the pixel electrode 16 is configured on the surface of the insulating layer 14, but the configuration is not limited to this, and the pixel electrode 16 may be embedded in the surface portion of the insulating layer 14. Moreover, although the structure which provides the 2nd connection part 46 and the counter electrode voltage supply part 42 was made, it may be plural. For example, a voltage drop at the counter electrode 20 can be suppressed by supplying a voltage from both ends of the counter electrode 20 to the counter electrode 20. The number of sets of the second connection unit 46 and the counter electrode voltage supply unit 42 may be appropriately increased or decreased in consideration of the chip area of the element.
In the image sensor 10, the silicon oxide film (SiOx film) of the buffer layer 21 is excellent in heat resistance, and the silicon oxynitride film (SiOxNy film) of the protective film 22 is excellent in barrier properties. Excellent heat resistance.

Next, a manufacturing method of the image sensor 10 according to the embodiment of the present invention will be described.
In the method of manufacturing the image sensor 10 according to the embodiment of the present invention, first, as shown in FIG. 7A, the first circuit is formed on the substrate 12 on which the readout circuit 40 and the counter electrode voltage supply unit 42 are formed. The insulating layer 14 provided with the connecting portion 44, the second connecting portion 46, and the wiring layer 48 is formed, and the pixel electrode 16 connected to each first connecting portion 44 is further formed on the surface 14 a of the insulating layer 14. A formed circuit board 11 (CMOS substrate) is prepared. In this case, as described above, the first connection unit 44 and the readout circuit 40 are connected, and the second connection unit 46 and the counter electrode voltage supply unit 42 are connected. The pixel electrode 16 is made of, for example, TiN.

  Next, the film is transferred to a film forming chamber (not shown) for the electron blocking layer 52 through a predetermined transfer path, and as shown in FIG. The electron blocking material is formed into a film under a predetermined vacuum using, for example, a vapor deposition method so as to cover 16, thereby forming the electron blocking layer 52. As the electron blocking material, for example, a carbazole derivative, more preferably a bifluorene derivative is used.

  Next, the photoelectric conversion layer 50 is transferred to a film formation chamber (not shown) by a predetermined transfer path, and the photoelectric conversion layer 50 is formed on the surface 52a of the electron blocking layer 52 as shown in FIG. For example, it is formed under a predetermined vacuum using a vapor deposition method. As the photoelectric conversion material, for example, a p-type organic semiconductor material and fullerene or a fullerene derivative are used. Thereby, the photoelectric conversion layer 50 is formed and the organic layer 18 is formed.

  Next, after transporting to the film formation chamber (not shown) of the counter electrode 20 through a predetermined transport path, as shown in FIG. 8A, the photoelectric conversion layer 18 is covered and the second connection portion 46 is covered. The counter electrode 20 is formed in a predetermined vacuum using a sputtering method, for example, with a pattern formed in the above.

  Next, the element protective layer 25 is formed using a plasma CVD method so as to cover the counter electrode 20. Hereinafter, a method for forming the element protective layer 25 will be described. The method for forming the element protective layer 25 is the same as the method for forming the element protective layer 115 of the photoelectric conversion element 100 described above, and can be formed by the process shown in FIG. For this reason, the detailed description is abbreviate | omitted.

When a silicon oxide film (SiOx film) is formed as the buffer layer 21 using a plasma CVD method, for example, silane gas (SiH ₄ gas) or combustion-supporting gas (N ₂ O gas) is used as a reactive process gas. N ₂ gas is used as the carrier gas.
In the case where a silicon oxynitride film (SiOxNy film) is formed as the protective film 22 using the plasma CVD method, for example, silane gas (SiH ₄ gas), NH ₃ gas, and combustion-supporting gas (N ₂ O) are used as the reactive process gas. Gas) and N ₂ gas is used as the carrier gas.

Even in this case, the carrier gas (N ₂ gas) is first supplied before the reactive process gas is supplied (see step S20 in FIG. 4). Then, plasma is generated (see step S22 in FIG. 4).
Next, in a state where plasma is generated, a flammable gas which is a reactive process gas, silane gas (SiH ₄ gas) is then supplied (see step S24 in FIG. 4). Thereby, the combustion-supporting gas (N ₂ O gas) and the silane gas (SiH ₄ gas) are decomposed by plasma, and a silicon oxide film (SiOx film) is formed.

Subsequently, ammonia gas (NH ₃ gas) is further supplied in a state where the carrier gas, the combustion-supporting gas, and the silane gas are supplied and the plasma is generated (see step S26 in FIG. 4). NH ₃ immediately after the start of supply of gas has a low amount of small concentration of ammonia gas (NH ₃ gas), low silicon oxynitride film nitrogen concentration is formed, an increase in supply amount of ammonia gas (NH ₃ gas) Along with this, the nitrogen concentration increases, and finally, a silicon oxynitride film having a preset composition is formed. Thus, the nitrogen concentration increases in the deposition direction, that is, in the direction opposite to the direction D shown in FIG. 2 described above, so that silicon oxynitride is formed and a silicon oxynitride film is formed. A region where the nitrogen concentration changes between the silicon oxide film and the silicon oxynitride film becomes the intermediate layer 23. The intermediate layer 23 is also an inclined layer because the nitrogen concentration is inclined with respect to the deposition method. The element protective layer 25 can be formed as described above.

In forming the element protective layer 25, a silicon oxide film (SiOx film) is formed as the buffer layer 21 by a plasma CVD method using silane gas (SiH ₄ gas). For this reason, the buffer layer 21 is a SiOx film containing hydrogen. The buffer layer 21 preferably has a film formation temperature of 125 ° C. to 150 ° C.
As the protective film 22, a silicon oxynitride film (SiOxNy film) is formed by a plasma CVD method using silane gas (SiH ₄ gas), combustion-supporting gas (N ₂ O gas), and NH ₃ gas. Therefore, the protective film 22 is a silicon oxynitride film (SiOxNy film) containing hydrogen. Moreover, the internal stress can be reduced, for example, the absolute value can be 100 MPa or less. The protective film 22 preferably has a film forming temperature of 150 ° C. to 230 ° C. In this case, the substrate temperature when the protective film 22 (silicon oxynitride film (SiOxNy film)) is formed is preferably 25 ° C. or more higher than the substrate temperature when the buffer layer 21 (silicon oxide film (SiOx film)) is formed.

Next, the color filter 26, the partition wall 28, and the light shielding layer 29 are formed on the surface of the element protective layer 25, that is, the surface 22a of the protective film 22 by using, for example, a photolithography method. As the color filter 26, the partition wall 28, and the light shielding layer 29, known ones used for organic solid-state imaging devices are used. The formation process of the color filter 26, the partition wall 28, and the light shielding layer 29 may be performed under a predetermined vacuum or non-vacuum. The process of forming the color filter 26, the partition wall 28, and the light shielding layer 29 includes a resin baking process.
Next, the protective film 30 is formed using, for example, a coating method so as to cover the color filter 26, the partition wall 28, and the light shielding layer 29. Thereby, the image sensor 10 shown in FIG. 6 can be formed. As the protective film 30, a known film used for an organic solid-state imaging device is used. The formation process of the protective film 30 may be under a predetermined vacuum or non-vacuum.

When forming a silicon oxide film (SiOx film), before supplying a reactive process gas (silane gas (SiH ₄ gas), combustion-supporting gas (N ₂ O gas)), a carrier gas (N ₂ gas) is used. Supply and generate plasma. After the plasma is generated, a combustion-supporting gas (N ₂ O gas) and silane gas (SiH ₄ gas) are then supplied. Combustion gas (N ₂ O gas) and silane gas (SiH ₄ gas) are decomposed by plasma when supplied. Therefore, for example, even if the counter electrode 20 has a defect such as a pinhole, a combustion-supporting gas (N ₂ O gas) and a silane gas (SiH ₄ gas) enter the photoelectric conversion layer 50 of the organic layer 18 from the pinhole. Is suppressed. Thereby, generation | occurrence | production of a sensitivity fall is suppressed, without deteriorating the photoelectric converting layer 50 of the organic layer 18. FIG. The occurrence of so-called black scratches can be suppressed. Therefore, the yield of the image sensor 10 can be increased, and the productivity of the image sensor 10 can be improved.

Furthermore, the element protective layer 25 is formed using a plasma CVD method, and can be formed in the same film formation chamber by changing the process gas. For this reason, the element protective layer 25 having the above-described configuration can be formed with a single film forming apparatus, manufacturing equipment can be simplified, and manufacturing costs can be reduced. In addition, since the plasma CVD method is used, the deposition rate is higher than that of other deposition methods, so that productivity can be increased.
Further, the buffer layer 21 (SiOx film) is excellent in heat resistance. For example, even if a baking step is included in the formation process of the color filter 26, the photoelectric conversion characteristics of the organic layer 18 are deteriorated. Can be suppressed. Thereby, it is possible to manufacture the image sensor 10 having excellent barrier properties and excellent heat resistance.

Also in the present embodiment, the element protective layer 25 may have a configuration in which a silicon nitride film (SiNx film) is further formed on the silicon oxynitride film. Since this silicon nitride film (SiNx film) has a high barrier property, the barrier property of the image sensor 10 can be further enhanced.
The silicon nitride film (SiNx film) can be formed by the process shown in FIG. For example, in the step of forming the element protective layer 25 described above, after the silicon oxynitride film (SiOxNy film) is formed to a predetermined thickness, the plasma is generated and the combustion-supporting gas (N ₂ O The gas supply is stopped only (see step S38 in FIG. 5). In this case, plasma is generated in a state where NH ₃ gas, SiH ₄ gas, and N ₂ gas are supplied, and in this atmosphere, a silicon nitride film is formed on the silicon oxynitride film (SiOxNy film). (SiNx film) is formed.
Further, by forming the color filter 26, the partition wall 28, and the light shielding layer 29 on the silicon nitride film (SiNx film), an imaging device can be obtained.

Hereinafter, the photoelectric conversion layer 50 (photoelectric conversion layer 112) and the electron blocking layer 52 (electron blocking layer 114) constituting the organic layer 18 (organic layer 106) will be described in more detail.
The photoelectric conversion layer 50 has the same configuration as the photoelectric conversion layer 112 described above. The photoelectric conversion layer 50 includes a p-type organic semiconductor material and an n-type organic semiconductor material. Exciton dissociation efficiency can be increased by joining a p-type organic semiconductor material and an n-type organic semiconductor material to form a donor-acceptor interface. For this reason, the photoelectric conversion layer of the structure which joined the p-type organic-semiconductor material and the n-type organic-semiconductor material expresses high photoelectric conversion efficiency. In particular, a photoelectric conversion layer in which a p-type organic semiconductor material and an n-type organic semiconductor material are mixed is preferable because the junction interface is increased and the photoelectric conversion efficiency is improved.

  The p-type organic semiconductor material (compound) is a donor-type organic semiconductor material (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 the organic compound used as the n-type (acceptor) compound may be used as the donor organic semiconductor.

  The n-type organic semiconductor material (compound) is an acceptor organic semiconductor material, and is mainly represented by an electron-transporting organic compound and refers to an organic compound having a property of easily accepting electrons. More specifically, an n-type organic semiconductor refers to an organic compound having a larger 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, oxy Diazole, imidazopyridine, pyralidine, pyrrolopyridine, thiadiazolopyridine, dibenzazepine, tribenzazepine, etc.), polyarylene compounds, fluorene compounds, cyclopentadiene compounds, silyl compounds, nitrogen-containing heterocyclic compounds as ligands Etc. Not limited to this, as described above, any organic compound having an electron affinity higher than that of the organic compound used as the p-type (donor property) compound may be used as the acceptor organic semiconductor.

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

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

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

  When the photoelectric conversion layer contains fullerene or a fullerene derivative, electrons generated by photoelectric conversion can be quickly transported to the pixel electrode 16 or the counter electrode 20 via the fullerene molecule or fullerene derivative molecule. When fullerene molecules or fullerene derivative molecules are connected to form an electron path, the electron transport property is improved, and high-speed response of the photoelectric conversion element can be realized. For this purpose, the fullerene or fullerene derivative is preferably contained in the photoelectric conversion layer by 40% (volume ratio) or more. However, if there are too many fullerenes or fullerene derivatives, the p-type organic semiconductor is reduced, the junction interface becomes smaller, and the exciton dissociation efficiency decreases.

When the triarylamine compound described in Japanese Patent No. 4213832 is used as a p-type organic semiconductor material mixed with fullerene or a fullerene derivative in the photoelectric conversion layer 50, a high SN ratio of the photoelectric conversion element can be expressed. Is particularly preferred. If the ratio of fullerene or fullerene derivative in the photoelectric conversion layer is too large, the amount of triarylamine compounds decreases and the amount of incident light absorbed decreases. As a result, the photoelectric conversion efficiency is reduced. Therefore, the fullerene or fullerene derivative contained in the photoelectric conversion layer preferably has a composition of 85% (volume ratio) or less.
Note that the photoelectric conversion layer 50 (photoelectric conversion layer 112) is denatured by silane gas (SiH ₄ gas), and the sensitivity of photoelectric conversion decreases. Here, the higher the glass transition temperature, the smaller the degree of diffusion of the silane gas. For this reason, the one where the photoelectric conversion material which comprises the photoelectric converting layer 50 (photoelectric converting layer 112) has a higher glass transition temperature is preferable.

  The electron blocking layer 52 has the same configuration as the electron blocking layer 114 described above. An electron donating organic material can be used for the electron blocking layer 52. Specifically, in a low molecular material, N, N′-bis (3-methylphenyl)-(1,1′-biphenyl) -4,4′-diamine (TPD) or 4,4′-bis [N Aromatic diamine compounds such as-(naphthyl) -N-phenyl-amino] biphenyl (α-NPD), oxazole, oxadiazole, triazole, imidazole, imidazolone, stilbene derivative, pyrazoline derivative, tetrahydroimidazole, polyarylalkane, butadiene 4,4 ′, 4 ″ -tris (N- (3-methylphenyl) N-phenylamino) triphenylamine (m-MTDATA), porphine, tetraphenylporphine copper, phthalocyanine, copper phthalocyanine, titanium phthalocyanine oxide, etc. Polyphyrin compounds, triazole derivatives, oxa Zazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, annealing amine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives, hydrazone derivatives, silazane derivatives, carbazole derivatives, bifluorenes Derivatives can be used, and as the polymer material, polymers such as phenylene vinylene, fluorene, carbazole, indole, pyrene, pyrrole, picoline, thiophene, acetylene, diacetylene, and derivatives thereof can be used. Even if it is not an ionic compound, it can be used as long as it is a compound having sufficient hole transportability.

  As the electron blocking layer 52, an inorganic material can also be used. In general, since an inorganic material has a dielectric constant larger than that of an organic material, when it is used for the electron blocking layer 52, a large voltage is applied to the photoelectric conversion layer, and the photoelectric conversion efficiency can be increased. Materials that can be the electron blocking layer 52 include calcium oxide, chromium oxide, chromium oxide copper, manganese oxide, cobalt oxide, nickel oxide, copper oxide, gallium copper oxide, strontium copper oxide, niobium oxide, molybdenum oxide, indium copper oxide, Examples include indium silver oxide and iridium oxide.

In the electron blocking layer comprising a plurality of layers, the layer adjacent to the photoelectric conversion layer 50 among the plurality of layers is preferably a layer made of the same material as the p-type organic semiconductor contained in the photoelectric conversion layer 50. Thus, by using the same p-type organic semiconductor for the electron blocking layer 52, it is possible to suppress the formation of intermediate levels at the interface between the photoelectric conversion layer 50 and the adjacent layer, and to further suppress the dark current. Can do.
In the case where the electron blocking layer 52 is a single layer, the layer can be a layer made of an inorganic material, or in the case of a plurality of layers, one or more layers can be a layer made of an inorganic material. it can.

  The present invention is basically configured as described above. As described above, the photoelectric conversion element and the manufacturing method thereof, and the imaging element and the manufacturing method thereof have been described in detail. However, the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the gist of the present invention. Of course, improvements or changes may be made.

Hereinafter, the effects of the present invention will be specifically described.
In this example, samples of Examples 1 to 3 and Comparative Examples 1 to 3 were prepared and evaluated for black scratches. The results are shown in Table 1 below. In the evaluation of black scratches, the case where no black scratches occurred was evaluated as ◯, and the case where black scratches occurred was evaluated as x.
Hereinafter, a black scratch determination method will be described. In the method for determining black scratches, an imaging lens (single focus lens (aperture F = 5.6)) equipped with an IR cut filter and a 50% transmission ND filter is used and light is irradiated from a DC light source. An external electric field is applied to the photoelectric conversion layer, a DC output image is acquired, and the efficiency of a pixel having the highest sensitivity at the time of DC light source imaging is defined as 100%. Detected as.
As a criterion for determining black scratches, it is assumed that “1 pixel” in the sensitivity-degraded pixel area is good and “◎”, and that the sensitivity-degraded pixel area is “2 pixels” is the next best. A circle with “sensitivity-degraded pixel area” of “3 pixels or more” was marked as “x” because it was not good. Note that if the black scratch determination is “◎” or “○”, there is no problem in practical use of the image sensor.

As shown in Table 1, Examples 1 to 3 have no black scratches, high yields, and excellent productivity.
On the other hand, Comparative Examples 1 to 3 have black scratches.

DESCRIPTION OF SYMBOLS 10 Image pick-up element 12 Substrate 14 Insulating layer 16 Pixel electrode 18, 106 Organic layer 20 Counter electrode 21, 109 Buffer layer 22, 110 Protective film 23, 111 Intermediate layer 25, 115 Element protective layer 26 Color filter 30 Overcoat layer 40 Reading circuit 42 Counter electrode voltage supply unit 44 First connection unit 46 Second connection unit 50, 112 Photoelectric conversion layer 52, 114 Electron blocking layer 100 Photoelectric conversion element 104 Lower electrode 108 Upper electrode

Claims (6)

A substrate, a lower electrode formed on the substrate, an organic layer that is formed on the lower electrode and generates a charge when irradiated with light, and visible light formed on the organic layer A method for producing a photoelectric conversion element having a transparent upper electrode and an element protective layer formed on the upper electrode,
The step of forming the element protection layer includes supplying an inert carrier gas to the organic layer to generate plasma, and further supplying SiH ₄ gas in a state where the carrier gas is supplied and plasma is generated, And a process of forming a silicon oxynitride film by supplying a reactive process gas containing a combustion-supporting gas and an ammonia gas. A substrate, a lower electrode formed on the substrate, an organic layer that is formed on the lower electrode and generates a charge when irradiated with light, and visible light formed on the organic layer A method for producing a photoelectric conversion element having a transparent upper electrode and an element protective layer formed on the upper electrode,
The step of forming the element protective layer includes a step of supplying an inert carrier gas to the organic layer to generate plasma, and at least an SiH ₄ gas and a combustion-supporting gas after the plasma is generated. Supplying a reactive process gas to form a buffer layer made of a silicon oxide film;
Forming a silicon oxynitride film on the silicon oxide film by supplying NH ₃ gas in a state where plasma is generated by supplying the carrier gas, the combustion-supporting gas, and the SiH ₄ gas. A method for producing a photoelectric conversion element, comprising: When the carrier gas, the combustion-supporting gas, the SiH ₄ gas, and the NH ₃ gas are supplied and plasma is generated, the supply of the combustion-supporting gas is stopped, and the silicon nitride film is The manufacturing method of the photoelectric conversion element of Claim 1 or 2 which has the process of forming on a silicon oxynitride film | membrane. The method for manufacturing a photoelectric conversion element according to claim 1, wherein the carrier gas is N ₂ gas, and the combustion-supporting gas is N ₂ O gas.   5. The method of manufacturing a photoelectric conversion element according to claim 1, wherein a substrate temperature at the time of forming the silicon oxynitride film is 25 ° C. or more higher than a substrate temperature at the time of forming the silicon oxide film. A method of manufacturing an image sensor having a photoelectric conversion element,
It has a process of manufacturing the said photoelectric conversion element with the manufacturing method of the photoelectric conversion element of any one of Claims 1-5, The manufacturing method of the image pick-up element characterized by the above-mentioned.

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