JP2010129579A - Method of manufacturing photoelectric conversion device, and method of manufacturing electronic instrument - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manufacture a photoelectric conversion device, with ease at a low cost, having good characteristics by using liquid material. <P>SOLUTION: The method of manufacturing the photoelectric conversion device includes a first step in which a coating film is formed above a substrate (1) by applying a liquid silicon compound material, a second step in which after first heating is performed with the coating film in an inactive atmosphere at ≥250°C and ≤350°C, second heating is performed in the oxidizing atmosphere at ≥350°C to form a silicon oxide film containing much silicon (SiOa, a<2), and a third step in which a thermal treatment is applied to the silicon oxide film containing much silicon in the inactive atmosphere so that nano crystal grain (d) of silicon is precipitated in the silicon oxide film. Thus, using liquid silicon compound material, a silicon oxide film containing much silicon is formed. Then, by making an excessive silicon in the film to be precipitated as nano crystal grain of silicon, the nano crystal grain is confined in the silicon oxide film. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a method for manufacturing a photoelectric conversion device and the like.

  BACKGROUND ART Solar cells (photoelectric conversion devices) are actively developed as energy sources that are energy-saving and resource-saving and clean. A solar cell is a power device that uses the photovoltaic effect to directly convert light energy into electric power. Various structures such as organic thin-film solar cells, dye-sensitized solar cells, and multi-junction structure solar cells have been studied for the configuration. Among them, a solar cell using quantum dots (nanocrystal grains) has attracted attention as a next-generation solar cell that theoretically enables conversion efficiency of 60% or more.

For example, Patent Document 1 below discloses a solar cell having a plurality of crystalline semiconductor material quantum dots separated by a thin dielectric material layer.
Special Table 2007-535806

  However, in the above-mentioned Patent Document 1, since a silicon oxide film and a silicon-rich silicon oxide film are alternately stacked by a sputtering method and heat treatment is performed, silicon is deposited as quantum dots. A membrane device is required.

  Therefore, a specific aspect of the present invention aims to easily and inexpensively manufacture a photoelectric conversion device having good characteristics by using a liquid material.

  The manufacturing method of the photoelectric conversion device according to the present invention includes a first step of forming a coating film by applying a liquid silicon compound material above a substrate, and 250 ° C. or higher in an inert atmosphere with respect to the coating film. A second step of forming a silicon-rich silicon oxide film (SiOa, a <2) by performing a second heating at 350 ° C. or higher in an oxidizing atmosphere after performing a first heating at 350 ° C. or lower; And a third step of subjecting the silicon-rich silicon oxide film to a heat treatment in an inert atmosphere to deposit a plurality of silicon nanocrystal grains in the silicon-rich silicon oxide film.

  According to this method, a silicon-rich silicon oxide film can be formed using a liquid silicon compound material. Furthermore, by depositing excess silicon in the film as silicon nanocrystal grains (quantum dots), the silicon nanocrystal grains can be confined in the silicon oxide film by a simple method.

  The method for manufacturing a photoelectric conversion device according to the present invention includes a first step of forming a laminated film above a substrate, and a second step of depositing nanocrystal grains in the laminated film, Step 1 is a third step of applying a liquid silicon compound material to form a first coating film, and a first heating of 250 to 350 ° C. in an inert atmosphere with respect to the first coating film. And a second step of forming a silicon-rich first silicon oxide film (SiOa, a <2) by performing second heating at 350 ° C. or higher in an oxidizing atmosphere, and the first silicon oxide A fifth step of applying the liquid silicon compound material on the film to form a second coating film; and performing a third heating at 350 ° C. or higher in an oxidizing atmosphere on the second coating film. , Second silicon oxide film (SiOb, b> a) And in the first step, the first oxidation is performed by repeating the third step, the fourth step, the fifth step, and the sixth step in the first step. A first laminated film in which a plurality of layers made of a silicon film and the second silicon film are laminated is formed above the substrate, and in the second step, the first laminated film is formed in an inert atmosphere. Heat treatment is performed to deposit a plurality of nanocrystal grains of silicon in the plurality of first silicon oxide films.

  According to this method, the first silicon oxide film containing nanocrystal grains and the second silicon oxide film not containing nanocrystal grains can be alternately stacked, and the arrangement of nanocrystal grains in the silicon oxide film has periodicity. Can be made. Thereby, a device with high photoelectric conversion efficiency can be formed.

  For example, the heat treatment is performed in an atmosphere of 1000 ° C. or higher. Silicon nanocrystal grains can be deposited by such high-temperature treatment.

  For example, the liquid silicon compound material is an organic solvent liquid of polysilane. Thus, an organic solvent liquid of polysilane may be used as the liquid silicon compound material.

  In the method for manufacturing a photoelectric conversion device according to the present invention, a first semiconductor layer forming step of forming a first conductivity type semiconductor layer above a substrate, and a liquid silicon compound material is applied on the first conductivity type semiconductor layer. And a first step of forming a coating film by the first heating of 250 ° C. to 350 ° C. in an inert atmosphere, and then a second heating of 350 ° C. or more in an oxidizing atmosphere. By performing the second step of forming a silicon-rich first silicon oxide film (SiOa, a <2) and applying heat treatment to the first silicon oxide film in an inert atmosphere, the first step is performed. A third step of changing the silicon oxide film into a second silicon oxide film having a plurality of silicon nanocrystal grains, and a second semiconductor layer for forming a second conductivity type semiconductor layer on the second silicon oxide film Molding worker And, with a.

  According to this method, it is possible to form a photoelectric conversion device in which a silicon oxide film on which silicon nanocrystal grains are deposited is disposed between the first conductive semiconductor layer and the second conductive semiconductor layer.

  The method for manufacturing a photoelectric conversion device according to the present invention includes a first semiconductor layer forming step of forming a first conductive type semiconductor layer above a substrate, and a first step of forming a laminated film above the first conductive type semiconductor layer. A step, a second step of depositing nanocrystal grains in the laminated film, and a second semiconductor layer forming step of forming a second conductivity type semiconductor layer on the laminated film on which the nanocrystal grains are deposited. The first step includes applying a liquid silicon compound material to form a first coating film, and a first step of 250 ° C. to 350 ° C. in an inert atmosphere with respect to the first coating film. After the heating, a fourth step of forming a silicon-rich first silicon oxide film (SiOa, a <2) by performing a second heating at 350 ° C. or higher in an oxidizing atmosphere, and the first oxidation The liquid silicon compound material is applied onto the silicon film. Then, a second silicon oxide film (SiOb, b> a) is formed by performing a fifth step of forming the second coating film and performing third heating at 350 ° C. or higher in an oxidizing atmosphere on the second coating film. And a sixth step of forming the first silicon oxide film and the sixth step by repeating the third step, the fourth step, the fifth step, and the sixth step in the first step. A first laminated film in which a plurality of layers made of a second silicon oxide film are laminated is formed above the first conductive type semiconductor layer, and in the second step, the first laminated film is subjected to heat treatment in an inert atmosphere. Forming a second stacked film in which the nanocrystal grains of silicon are precipitated in the plurality of first silicon oxide films, and in the second semiconductor layer forming step, the second stacked film is formed on the second stacked film. Forming the second conductive type semiconductor layer; The features. For example, the second conductivity type semiconductor layer has a conductivity type opposite to that of the first conductivity type semiconductor layer.

  According to this method, a stacked body in which the first silicon oxide film containing nanocrystal grains and the second silicon oxide film not containing the nanocrystal grains are alternately stacked is formed between the first conductive semiconductor layer and the second conductive semiconductor layer. A pin-type photoelectric conversion device arranged between them can be formed.

  For example, the first-conductivity-type semiconductor layer is a first-conductivity-type-container-containing layer and is formed by heat treatment of a solution of a compound in which a part of the H bond of polysilane is replaced with a first-conductivity-type impurity element. The second conductive type semiconductor layer is a second conductive type semiconductor-containing layer, and is formed by heat treatment of a solution of a compound in which a part of the H bond of polysilane is replaced with a second conductive type impurity element. According to this method, an impurity-containing silicon-rich silicon oxide film can be formed. In this way, nanocrystal grains made of a semiconductor doped with impurities (first and second conductivity types) may be deposited in the film to form first and second conductivity type semiconductor layers.

  The manufacturing method of the electronic device which concerns on this invention has the manufacturing method of the said photoelectric conversion apparatus. According to such a configuration, a high-performance electronic device can be manufactured by a simple method.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, the same or related code | symbol is attached | subjected to what has the same function, and the repeated description is abbreviate | omitted.

<Structure of photoelectric conversion device>
FIG. 1 is a cross-sectional view illustrating a configuration of a quantum dot photoelectric conversion device (photoelectric conversion element, solar cell) of the present embodiment.

  The photoelectric conversion device shown in FIG. 1 includes a multilayer film 8 formed on the substrate 1, an upper electrode 11 formed on the multilayer film 8, and a lower electrode 3 formed on the back surface (lower part) of the substrate 1. Have

  The multilayer film 8 is composed of a plurality of thin films (8A, 8B), and includes a silicon oxide film 8A containing quantum dots (QD, nanocrystal grains) d made of silicon and a silicon oxide film 8B not containing quantum dots d. It is laminated repeatedly.

  Here, “quantum dots (nanocrystal grains)” mean fine crystal particles made of a semiconductor (including a compound semiconductor), and are a collection of hundreds to tens of thousands of atoms. The particle diameter is about the de Broglie wavelength of electrons (several tens to several nanometers). In particular, in this specification, a particle having a particle size of 1 nm or more and 20 nm or less is referred to as a “quantum dot”, and the crystal includes a single crystal and a polycrystalline state.

  As the substrate 1, for example, a p-type single crystal silicon substrate is used. As the substrate to be used, a substrate having high heat resistance that can withstand heat treatment (1000 ° C. or higher) described later is preferable.

  As a material of the lower electrode 3 and the upper electrode 11, for example, Al (aluminum) is used. Other metals such as nickel (Ni), cobalt (Co), platinum (Pt), silver (Ag), gold (Au), copper (Cu), molybdenum (Mo), titanium (Ti), and tantalum (Ta) Materials can be used. Moreover, you may use these alloys.

  Thus, in this Embodiment, since the quantum dot d is contained in the multilayer film 8, an improvement in photoelectric conversion efficiency can be aimed at. The reason why the photoelectric conversion efficiency is improved is considered to be due to (1) quantum size effect, (2) multiple exciton generation effect, and (3) miniband formation effect. Hereinafter, these will be described in detail with reference to FIGS. FIG. 2 is an energy band diagram for explaining the quantum size effect. FIG. 3 is an energy band diagram for explaining the effect of multiple exciton generation in the case of bulk and the case of quantum dots. FIG. 4 is a cross-sectional perspective view schematically showing a superlattice structure, FIGS. 5 and 6 are energy band diagrams when a miniband is formed, and FIG. 7 is a case where a miniband is not formed. FIG. In the band diagram, black circles indicate electrons (e) and white circles indicate holes (h). FIG. 8 is a cross-sectional view showing another configuration of the quantum dot photoelectric conversion device (photoelectric conversion element, solar cell) of this embodiment.

(1) Quantum size effect As shown in Fig. 2, HOMO (Highest Occupied Molecular Orbital) and LUMO (Lowest Unoccupied Molecular Orbital) for one semiconductor atom are molecules, clusters. As the number of aggregates of nanocrystal grains, bulk, and atoms increases, in the bulk, each orbital continues and becomes a conduction band and a valence band. Conversely, when a bulk semiconductor mass is reduced to the atomic level through the particle level, the band gap (Band gap, forbidden band) Eg increases. In FIG. 2, the vertical axis represents energy, and the relationship between “particle size (nm) and number of atoms” of atoms, molecules, clusters, nanocrystal grains, and bulk is, for example, “0.1 nm or less and 1 atom number”, respectively. ", 0.2 nm or less, 2 atoms", "less than 1 nm, 10 atoms or less", "1 nm or more and 20 nm or less, 10 ² or more atoms and 10 ⁴ or less", "1000 nm or more, 10 atoms. More than ²³ ".

  Here, in photoelectric conversion, electrons (carriers) that have absorbed light energy transit between the valence band and the conduction band across the band gap Eg, and are extracted as electric energy (electric power).

  Therefore, the band gap can be adjusted by changing the grain size of the nanocrystal grains, and thus, for example, in the solar spectrum, the ultraviolet light region, the visible light region, the infrared light region, etc. having a large energy can be specified. The band gap can be adjusted according to the wavelength (for example, 400 nm to 800 nm). As a result, light can be efficiently converted into electrical energy. In addition, by stacking photoelectric conversion units having different band gaps, it is possible to efficiently convert light of various wavelengths in the solar spectrum into electric energy, not limited to the visible light region and the infrared light region.

(2) Multiple Exciton Generation (MEG)
As shown in FIG. 3A, in a bulk semiconductor, carriers (electrons) are light energy (E = hν = hc / λ, h: Planck constant, ν: frequency, c: speed of light, λ: wavelength), transitions to the valence band, and is extracted as electrical energy. Here, when the optical energy hν is more than twice as large as the band gap Eg (hν> 2Eg), the carrier transitions to the upper part of the valence band, but the excess energy exceeding Eg quickly moves to the lattice system as heat. Then, it moves to the lower part of the more stable valence band. That is, energy exceeding Eg is lost as heat. Therefore, only one carrier can be generated by one photon. Since holes remain for the excited electrons, these pairs are called excitons.

  On the other hand, as shown in FIG. 3B, when the quantum dot d is used, the band gap Eg of the quantum dot d and the surrounding layer (hereinafter, this layer may be referred to as “matrix layer”). ) With the band gap Egs (Egs> Eg), a quantum well is formed.

  This quantum well restricts the direction of electron movement three-dimensionally. Also, the electron orbit formed in this quantum well is not continuous. Therefore, when the light energy hν is more than twice as large as the band gap Eg (hν> 2Eg), when the electrons excited to the upper orbit fall to the upper end of the band gap, energy is given to the lattice system as heat. The process of relaxation is very slow. As a result, the probability of impact ionization that excites other electrons in the same quantum well to Eg or higher is increased, and when the light energy hν is larger than 2 Eg, further electrons (exciton) are generated. Therefore, a plurality of carriers (for example, electrons) can be generated from one photon. Therefore, photoelectric conversion efficiency can be improved by taking out these as currents.

(3) Miniband formation effect For example, as shown in FIG. 4, quantum dots (quantum wells) are formed by regularly arranging quantum dots d through a thin film (having a three-dimensional periodicity). ) To form a miniband. That is, as shown in FIG. 5, a miniband is generated between the quantum wells by the tunnel effect, and excited carriers can be taken out to the outside at high speed through the miniband. Therefore, loss due to carrier recombination can be reduced and photoelectric conversion efficiency can be improved. In the band diagram, the multilayer film 8 is sandwiched between the n layer and the p layer. Further, as shown in FIG. 6, transition electrons generated by the above-described multiple exciton generation effect, transition electrons between minibands, and the like can be efficiently extracted via the minibands. As shown in FIG. 6, not only electrons but also holes remaining in the lower quantum well can be taken out. A structure in which quantum dots are given a three-dimensional periodicity in this way is called a superlattice (SL) or multi-quantum well (MQW) structure.

  In addition, when the quantum dots d are dispersed three-dimensionally at random, as shown in FIG. 8, there are places where the tunnel effect between the quantum wells hardly occurs. In this case, no miniband is formed between the quantum wells. However, in this case as well, as shown in the figure, the excited electrons can pass through the quantum well by thermal excitation or the like and escape out of the quantum well. Therefore, even if it is not a superlattice, although the probability is low, electrons can be taken out of the quantum well. Further, as shown in FIG. 4, a structure in which quantum dots d are regularly arranged vertically and horizontally and vertically is ideal, but it is not easy to arrange quantum dots d in this way. Therefore, in FIG. 1, in each film (8A), the quantum dots d are arranged randomly in a plane and alternately arranged with the film (8B) not including the quantum dots d, thereby providing the periodicity of the arrangement. It is Such a configuration can also improve the formation rate of the miniband and improve the photoelectric conversion efficiency. In FIG. 1, the quantum dots d are arranged one atom at a time in the film 8A. However, in the atomic arrangement in the film, about two or three atoms may be arranged in the vertical direction. . In short, it is important to provide periodicity of the arrangement by alternately laminating thin films (8A, 8B).

  Further, as described above, in FIG. 1, the thin films (8A, 8B) are alternately laminated to provide the periodicity of the arrangement. However, as shown in FIG. The quantum dots d may be randomly dispersed three-dimensionally. Also in this case, as described with reference to FIG. 7, electrons can be taken out of the quantum well.

  As described in detail through (1) to (3) above, the photoelectric conversion efficiency can be improved by including the quantum dots d.

<Method for Manufacturing Photoelectric Conversion Device>
Next, a method for manufacturing the photoelectric conversion device illustrated in FIG. 1 will be described. 9 and 10 are cross-sectional views illustrating manufacturing steps of the photoelectric conversion device of this embodiment. FIG. 11 is a cross-sectional view illustrating another configuration and manufacturing process of the photoelectric conversion device of the present embodiment.

As shown in FIG. 9A, for example, a p-type single crystal silicon substrate is prepared as the substrate 1, and a liquid silicon compound material L8A is applied on the substrate 1 in an inert atmosphere such as nitrogen or Ar (argon). Coating is performed by a spin coating method or the like to form a coating film (FIG. 9A). As the liquid silicon compound material L8A, for example, a liquid in which cyclopentasilane (Si ₅ H ₁₀ ) is dispersed in an organic solvent is used and polymerized by irradiating with ultraviolet rays to form a polysilane solution. In addition to the spin coating method, other discharge methods such as a spray method and an ink jet method may be used.

Next, heat treatment is performed to make the coating film (L8A) a silicon-rich silicon oxide film (SiOa, a <2) D8A (FIG. 9B). Here, “silicon rich” means stoichiometry (stoichiometric composition), a silicon oxide film (SiO ₂ ), that is, a film having a higher Si ratio than when Si: O is 1: 2. Say. When the film is SiOa, a <2.

  Specifically, the heat treatment is performed at 250 ° C. to 350 ° C. for about 15 minutes to 1 hour in an inert atmosphere such as nitrogen or Ar (argon) as the first step (first heating). Next, as a second step (second heating), treatment is performed at 350 ° C. to 450 ° C. for about 10 minutes to 1 hour in an oxidizing atmosphere.

  The reason why the silicon-rich silicon oxide film is thereby formed will be described below. Regarding the baking (heat treatment) of the liquid silicon compound material, it becomes a silicon film when heat-treated in an inert atmosphere, and becomes a silicon oxide film when heat-treated in an oxidizing atmosphere.

  Therefore, in the first step, partial or incomplete siliconization of the coating film occurs. However, since the temperature is lower or shorter than the temperature (for example, 350 ° C. or more) and the processing time (for example, 0.5 hour or more) in the case of complete siliconization, complete siliconization is not possible. It is not considered. For example, it is considered that Si—H bonds are partially broken, and intermediate reactions to Si formation occur in various parts of the film. Thereafter, in the second step, when heat treatment is performed in an oxidizing atmosphere, Si is formed, and the oxidation reaction is insufficient at the site where Si conversion is advanced, and a silicon-rich silicon oxide film (SiOa, a < 2) is considered to be formed.

  Next, as shown in FIG. 9C, the above-mentioned polysilane solution is used as a liquid silicon compound material L8B in an inert atmosphere such as nitrogen or Ar (argon) as a silicon-rich silicon oxide film (SiOa, a <2) D8A. A coating film is formed by applying a spin coating method or the like thereon. In addition to the spin coating method, other discharge methods such as a spray method and an ink jet method may be used.

  Next, heat treatment is performed to make the coating film (L8B) a silicon oxide film (SiOb, b> a) D8B. Here, heat treatment is performed so that the silicon oxide film is closer to stoichiometry (stoichiometric composition), that is, b is larger than a and preferably close to 2. Specifically, as a first step (first heating), treatment is performed at 150 ° C. to 250 ° C. for about 15 minutes to 1 hour in an inert atmosphere such as nitrogen or Ar (argon). Next, as a second step (second heating), treatment is performed at 350 ° C. to 450 ° C. for about 10 minutes to 1 hour in an oxidizing atmosphere. In this step, the first step may be omitted.

  In this manner, these stacked films are formed by repeating the process of forming the silicon-rich silicon oxide film D8A and the more stoichiometric silicon oxide film D8B (FIG. 9D). In the above, the silicon-rich silicon oxide film D8A is the bottom layer, but the more stoichiometric silicon oxide film D8B may be the bottom layer, and the number of layers may be even or odd.

  Next, as shown in FIG. 10A, the laminated film (D8A, D8B) is subjected to heat treatment at 1000 ° C. or higher for about 15 minutes to 1 hour in an inert atmosphere such as nitrogen or Ar (argon). Do. For the heat treatment, a furnace or the like may be used, or lamp annealing or laser annealing may be used. By this heat treatment, silicon is deposited in the silicon-rich silicon oxide film D8A to form quantum dots d. Thereby, the multilayer film 8 in which the silicon oxide films 8A containing the quantum dots d made of silicon and the silicon oxide films 8B not containing the quantum dots d made of silicon are alternately laminated is formed.

  Next, as shown in FIG. 10B, a metal such as Al is formed on the multilayer film 8 by sputtering and patterned into a desired shape to form the upper electrode 11. Further, a metal such as Al is formed on the back surface of the substrate 1 by sputtering to form the lower electrode 3.

  FIG. 10 schematically shows a state in which d quantum dots are randomly arranged in a plane in the thin film 8A. However, the present invention is not limited to this, and a plurality of atoms are stacked in the vertical direction in the thin film 8A. It is good also as a film thickness of the grade to do. That is, as described above, it is important to increase the number of locations where the minibands are formed by alternately laminating thin films so as to provide the periodicity of the arrangement of quantum dots d.

  As described above, according to this embodiment, the silicon-rich silicon oxide film can be easily formed with good controllability by devising the heat treatment condition of the liquid silicon compound material. Thereafter, by depositing quantum dots in a silicon-rich silicon oxide film, a photoelectric conversion device with high conversion efficiency can be formed. In addition, it is possible to produce the device at low cost.

  Here, in FIG. 10, the multilayer film 8 is formed on the substrate 1, but as shown in FIG. 11, n-type and p-type semiconductor films (impurity layers, 5N, 7N, 7P,. 5P) layer may be formed, and an n-type silicon film 9 may be formed on the multilayer film 8.

  For example, a p-type single crystal silicon substrate is prepared as the substrate 1, and an n-type silicon film 5N is formed on the substrate 1. Specifically, for example, an n-type impurity-containing polysilane solution in which a liquid silicon compound material (for example, cyclopentasilane) is dispersed in an organic solvent and an n-type impurity compound such as phosphorus is added and polymerized is added. Used, spin-coated on the substrate 1 and then fired. Next, a highly doped n-type silicon film 7N is formed on the n-type silicon film 5N. The film is formed, for example, by applying and baking the polysilane solution having a high concentration of impurities to be added.

  Next, a highly doped p-type silicon film 5P is formed on the highly doped n-type silicon film 7N. Specifically, for example, a liquid silicon compound material (for example, cyclopentasilane) is dispersed in an organic solvent, and a p-type impurity compound such as boron (boron) is added at a high concentration and polymerized. A polysilane solution containing a concentration p-type impurity is spin-coated and then baked. Next, a p-type silicon film 5P is formed on the highly doped p-type silicon film 7P. The film is also formed by, for example, applying and baking a polysilane solution to which a p-type impurity compound such as boron is added.

  In addition, you may form each impurity layer (5N, 7N, 7P, 5P) by laminating | stacking the said coating film, drying and baking at once.

  Of the impurity layers, the highly doped impurity layers (7N, 7P) serve to prevent recombination of the generated carriers.

  Thereafter, the multilayer film 8 is formed on the p-type silicon film 5P. The lower impurity layer becomes amorphous due to the thermal load during the formation of the multilayer film 8.

  Next, an n-type silicon film 9 is formed on the multilayer film 8 in the same manner as the n-type silicon film 5N. Note that, before the multilayer film 8 is fired, an n-type impurity-containing polysilane solution may be applied and fired at once. In this case, the n-type silicon film 9 is also made amorphous.

Next, a transparent electrode 10 is formed on the n-type silicon film 9, and an upper electrode 11 is formed thereon. The transparent electrode 10 is formed, for example, by depositing an indium tin oxide (ITO) film by sputtering. In addition to the ITO film, other conductive metal oxides such as fluorine-doped tin oxide (FTO), indium oxide (IO), and tin oxide (SnO ₂ ) may be used. The upper electrode 11 is formed by forming a metal such as Al by sputtering and patterning it into a desired shape. Further, a metal such as Al is formed on the back surface of the substrate 1 by sputtering to form the lower electrode 3.

  Note that a silicon oxide film containing p-type quantum dots and n-type quantum dots may be used as an alternative film for the impurity layers (5N, 5P, 7N, 7P).

  Specifically, a compound in which part of the H bond of polysilane is substituted with an impurity element (for example, B (boron) in the case of p-type, P (phosphorus) in the case of n-type) or the like (hereinafter, “ n-type polysilane ”or“ p-type polysilane ”).

  That is, the p-type polysilane solution is applied by spin coating or the like to form a coating film. Next, as a first step (first heating), treatment is performed at 150 ° C. to 250 ° C. for about 15 minutes to 1 hour in an inert atmosphere such as nitrogen or Ar (argon). Next, as a second step (second heating), treatment is performed at 350 ° C. to 450 ° C. for about 10 minutes to 1 hour in an oxidizing atmosphere.

  According to this treatment, as described above, a silicon-rich silicon oxide film (SiOa, a <2) is formed, but the film also contains p-type impurities. The film after the treatment is referred to as a p-type impurity-containing silicon-rich silicon oxide film. By high-temperature treatment of this film at 1000 ° C. or higher, silicon containing p-type impurities is precipitated, and a silicon oxide film containing p-type quantum dots dp is formed. This may be used as a substitute film for the impurity layer (5P or 7P). Further, the film and the multilayer film 8 may be baked together.

  Further, the n-type polysilane solution is applied by spin coating or the like to form a coating film. Next, as a first step (first heating), treatment is performed at 150 ° C. to 250 ° C. for about 15 minutes to 1 hour in an inert atmosphere such as nitrogen or Ar (argon). Next, as a second step (second heating), treatment is performed at 350 ° C. to 450 ° C. for about 10 minutes to 1 hour in an oxidizing atmosphere.

According to such treatment, as described above, a silicon-rich silicon oxide film (SiOa, a <2) is formed, but the film also contains n-type impurities. The film after the treatment is referred to as an n-type impurity-containing silicon rich silicon oxide film. By high-temperature treatment of this film at 1000 ° C. or higher, silicon containing n-type impurities is deposited, and a silicon oxide film containing n-type quantum dots dn is formed. This may be used as a substitute film for the impurity layer (5N or 7N). Further, the film and the multilayer film 8 may be baked together.
(Example)
Next, the present embodiment will be described more specifically with reference to examples.

(1) Formation of a substantially stoichiometric silicon oxide film (SiO ₂ ) On a quartz (SiO ₂ ) substrate, as a liquid silicon compound material, in a nitrogen atmosphere, cyclopentasilane (Si ₅ H ₁₀ ) is used as an organic solvent. A polysilane solution that is dispersed and polymerized by irradiation with ultraviolet rays is applied to form a coating film (polysilane thin film).

Next, as a first step (first heating), treatment was performed at 220 ° C. for 1 hour (60 minutes) in a nitrogen atmosphere (in N ₂ ). Next, as a second step (second heating), a treatment at 410 ° C. for 30 minutes was performed in the air (in air). The treated membrane is designated as Sample 1.

(2) Formation of silicon-rich silicon oxide film (SiOa, a <2) (2-1) Cyclopentasilane (Si ₅ H) as a liquid silicon compound material on a quartz (SiO ₂ ) substrate under a nitrogen atmosphere ₁₀ ) is dispersed in an organic solvent, and a polysilane solution polymerized by irradiating ultraviolet rays is applied to form a coating film (polysilane thin film).

  Next, as a first step (first heating), treatment was performed at 270 ° C. for 1 hour in a nitrogen atmosphere. Next, as a second step (second heating), treatment was performed at 410 ° C. for 30 minutes in the air. The treated membrane is designated as Sample 2. The film thickness was 2 to 10 nm. By controlling the film thickness, the particle size of the quantum dots d can be controlled.

(2-2) Cyclopentasilane (Si ₅ H ₁₀ ) is dispersed in an organic solvent as a liquid silicon compound material in an inert atmosphere such as nitrogen or Ar (argon) on a quartz (SiO ₂ ) substrate, A polysilane solution polymerized by irradiation with ultraviolet rays is applied to form a coating film.

  Next, as a first step (first heating), treatment was performed at 315 ° C. for 1 hour in a nitrogen atmosphere. Next, as a second step (second heating), treatment was performed at 410 ° C. for 30 minutes in the air. The treated membrane is designated as sample 3.

In Samples 1 to 3, Sample 1 showed colorless transparency unique to SiO ₂ , whereas Sample 2 was confirmed to be light reddish (light auburn). Furthermore, in sample 3, redness was darker than sample 2 (auburn). Since the Si film having the same thickness exhibits a dark brown color, Samples 2 and 3 are silicon-rich silicon oxide films, and the content of silicon is higher in Sample 3 than in Sample 2. It is expected that.

  The processing steps of Samples 1 to 3 and the film color are summarized in FIG.

  Next, composition analysis of the films of Samples 1 to 3 was performed using X-ray photoelectron spectroscopy. Each analysis result is shown in FIGS. In each figure, the vertical axis represents the atomic ratio (Atomic Ratio [%]), and the horizontal axis represents the film depth (Depth [nm]). In the horizontal axis, the portion after about 170 nm is a substrate.

  As shown in FIG. 13, in sample 1, it can be seen that the ratio of silicon (Si) to oxygen (O) is a stoichiometric one-to-two ratio.

  On the other hand, as shown in FIG. 14, in the sample 2, the ratio of Si increases and the ratio of O decreases. In particular, at a depth of 100 to 150 nm, Si: O is about 45:55.

  Further, as shown in FIG. 15, in the sample 3, the Si ratio is further increased, and the O ratio is further decreased. In particular, at a depth of 75 to 125 nm, Si: O is approximately 1: 1.

  Thus, Samples 2 and 3 were silicon-rich silicon oxide films, and it was confirmed that the content of silicon was higher in Sample 3 than in Sample 2.

  By further applying high temperature treatment to the films of Samples 2 and 3, excessive silicon in the film is precipitated, and nanocrystal grains (quantum dots) are formed. Thus, quantum dots can be confined in the silicon oxide film.

In this embodiment, cyclopentasilane (Si ₅ H ₁₀ ) is polymerized as the liquid silicon compound material. However, other silicon compounds may be polymerized and used. As the silicon compound, a silicon compound represented by Si _n X _m can be used. Specific examples of the compound in which m = 2n + 2 include hydrogenated silanes such as trisilane, tetrasilane, pentasilane, hexasilane, and heptasilane, and those obtained by substituting some or all of these hydrogen atoms with halogen atoms. Specific examples of m = 2n include one ring system such as cyclotrisilane, cyclotetrasilane, the above-mentioned cyclopentasilane, silylcyclopentasilane, cyclohexasilane, silylcyclohexasilane, and cycloheptasilane. Silicon hydride compounds and hexachlorocyclotrisilane, trichlorocyclotrisilane, octachlorocyclotetrasilane, tetrachlorocyclotetrasilane, decachlorocyclopentasilane, pentane in which some or all of these hydrogen atoms are substituted with halogen atoms Chlorocyclopentasilane, dodecachlorocyclohexasilane, hexachlorocyclohexasilane, tetradecachlorocycloheptasilane, heptachlorocycloheptasilane, hexabromocyclotrisilane, tribromocyclotrisilane, Interbromocyclotrisilane, tetrabromocyclotrisilane, octabromocyclotetrasilane, tetrabromocyclotetrasilane, decabromocyclopentasilane, pentabromocyclopentasilane, dodecabromocyclohexasilane, hexabromocyclohexasilane, tetradeca Examples thereof include halogenated cyclic silicon compounds such as bromocycloheptasilane and heptabromocycloheptasilane. Specific examples of the compound in which m = 2n-2 include 1,1′-biscyclobutasilane, 1,1′-biscyclopentasilane, 1,1′-biscyclohexasilane, 1,1′-bis. Cycloheptasilane, 1,1′-cyclobutasilylcyclopentasilane, 1,1′-cyclobutasilylcyclohexasilane, 1,1′-cyclobutasilylcycloheptasilane, 1,1′-cyclopentasilylcyclohexasilane Lan, 1,1′-cyclopentasilylcycloheptasilane, 1,1′-cyclohexasilylcycloheptasilane, spiro [2,2] pentasilane, spiro [3,3] heptatasilane, spiro [4,4] nonasilane, Spiro [4,5] decasilane, spiro [4,6] undecasilane, spiro [5,5] undecasilane, spiro [5,6] dodecasilane, spiro [6 6] Silicon hydride compounds having two ring systems such as tridecasilane, and silicon compounds in which some or all of these hydrogen atoms are substituted with SiH ₃ groups or halogen atoms. Further, a compound in which m = n, a silicon compound in which some or all of these hydrogen atoms are partially substituted with SiH ₃ groups or halogen atoms, or a silicon compound represented by the general formula SiaXbYc may be used. . These compounds can be used in combination of two or more. In the polymerization, in addition to the ultraviolet rays, heat or other energy rays may be used.

  The solvent used in the liquid silicon compound material is not particularly limited as long as it dissolves the silicon compound and does not react with the solvent. Specific examples include n-hexane, n-heptane, n-octane, n- In addition to hydrocarbon solvents such as decane, dicyclopentane, benzene, toluene, xylene, durene, indene, tetrahydronaphthalene, decahydronaphthalene, squalane, dipropyl ether, ethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol methyl ethyl Ether, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol methyl ethyl ether, tetrahydrofuran, tetrahydropyran, 1,2-dimethoxyethane, bis (2 Methoxyethyl) ether, soluble, propylene carbonate, such as p- dioxane, .gamma.-butyrolactone, N- methyl-2-pyrrolidone, dimethyl formamide, acetonitrile, dimethyl sulfoxide, can be mentioned polar solvents such as chloroform. Of these, hydrocarbon solvents and ether solvents are preferable in view of solubility in silicon compounds and modified silicon compounds and stability of the solution, and more preferable solvents include hydrocarbon solvents. These solvents can be used singly or as a mixture of two or more. In particular, the hydrocarbon-based solvent is suitable from the viewpoint of improving the solubility of the silicon compound and suppressing the residual of the silicon compound during heat treatment or light treatment described later.

<Electronic equipment>
The photoelectric conversion device can be incorporated into various electronic devices. There is no limitation on applicable electronic devices, but an example thereof will be described.

  16 is a plan view showing a calculator to which the solar cell (photoelectric conversion device) of the present invention is applied, and FIG. 17 is a perspective view showing a mobile phone (including PHS) to which the solar cell (photoelectric conversion device) of the present invention is applied. FIG.

  A calculator 100 illustrated in FIG. 16 includes a main body 101, a display unit 102 provided on the upper surface (front surface) of the main body 101, a plurality of operation buttons 103, and a photoelectric conversion element installation unit 104.

  In the configuration illustrated in FIG. 16, five photoelectric conversion elements 1 d are arranged and connected in series in the photoelectric conversion element installation unit 104. The photoelectric conversion device can be incorporated as the photoelectric conversion element 1d.

  A cellular phone 200 illustrated in FIG. 17 includes a main body portion 201, a display portion 202 provided on the front surface of the main body portion 201, a plurality of operation buttons 203, an earpiece 204, a mouthpiece 205, and a photoelectric conversion element installation portion 206. I have.

  In the configuration illustrated in FIG. 17, the photoelectric conversion element installation unit 206 is provided so as to surround the display unit 202, and a plurality of photoelectric conversion elements 1 d are arranged in series. The photoelectric conversion device can be incorporated as the photoelectric conversion element 1d.

  In addition to the calculator shown in FIG. 16 and the mobile phone shown in FIG. 17, the electronic device of the present invention can be applied to, for example, an optical sensor, an optical switch, an electronic notebook, an electronic dictionary, a wristwatch, a clock, and the like.

  FIG. 18 is a perspective view illustrating a wrist watch that is an example of an electronic apparatus. The wristwatch 1100 includes a display unit 1101. For example, the photoelectric conversion device can be incorporated in the outer periphery of the display unit 1101.

  The photoelectric conversion device is suitable for cost reduction and mass production, and is also suitable for use in a solar power generation system for home use or business use.

  It should be noted that the examples and application examples described through the above embodiment can be used in appropriate combination according to the application, or can be used with modifications or improvements, and the present invention is limited to the description of the above embodiment. Is not to be done.

It is sectional drawing which shows the structure of the quantum dot type photoelectric conversion apparatus (a photoelectric conversion element, a solar cell) of this Embodiment. It is an energy band figure for demonstrating a quantum size effect. It is an energy band figure for demonstrating the multiple exciton production | generation effect in the case of a bulk and the case of a quantum dot. It is the cross-sectional perspective view which showed the superlattice structure typically. It is an energy band figure in case a miniband is formed. It is an energy band figure in case a miniband is formed. It is an energy band figure in case a miniband is not formed. It is sectional drawing which shows the other structure of the quantum dot type photoelectric conversion apparatus (a photoelectric conversion element, a solar cell) of this Embodiment. It is sectional drawing which shows the manufacturing process of the photoelectric conversion apparatus of this Embodiment. It is sectional drawing which shows the manufacturing process of the photoelectric conversion apparatus of this Embodiment. It is sectional drawing which shows the other manufacturing process of the photoelectric conversion apparatus of this Embodiment. It is the figure put together about the processing process and film color (Film color) of samples 1-3. It is a figure which shows the composition-analysis result by the X ray photoelectron spectroscopy of the sample 1. It is a figure which shows the composition analysis result by the X ray photoelectron spectroscopy of the sample 2. It is a figure which shows the compositional analysis result by the X ray photoelectron spectroscopy of the sample 3. It is a top view which shows the calculator to which the solar cell (photoelectric conversion apparatus) is applied. It is a perspective view which shows the mobile telephone to which the solar cell (photoelectric conversion apparatus) is applied. It is a perspective view which shows the wristwatch which is an example of an electronic device.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 1d ... Photoelectric conversion element, 3 ... Upper electrode, 5N ... N-type silicon film, 5P ... P-type silicon film, 7N ... Highly doped n-type silicon film, 7P ... Highly doped p-type silicon film, 8 ... Multilayer film, DESCRIPTION OF SYMBOLS 9 ... Transparent electrode, 10 ... Transparent electrode, 11 ... Upper electrode, 8A ... Silicon oxide film containing quantum dot d, 8B ... Silicon oxide film not containing quantum dot d, 100 ... Calculator, 101 ... Main-body part, 102 ... Display unit 103 ... Operation button 104 ... Photoelectric conversion element installation unit 200 ... Mobile phone 201 201 Main body unit 202 ... Display unit 203 ... Operation button 204 ... Earpiece 205 ... Mouthpiece 206 ... Photoelectric Conversion element installation unit, 1100 ... wristwatch, 1101 ... display unit, d ... quantum dot, D8A ... silicon-rich silicon oxide film (SiOa, a <2), D8B ... more stoichiometry Silicon oxide film, L8A, L8B ... liquid silicon compound material

Claims (10)

A first step of forming a coating film by applying a liquid silicon compound material over the substrate;
The coating film is subjected to first heating at 250 ° C. or higher and 350 ° C. or lower in an inert atmosphere, and then second heating at 350 ° C. or higher in an oxidizing atmosphere, whereby a silicon-rich silicon oxide film ( A second step of forming SiOa, a <2);
Applying a heat treatment to the silicon-rich silicon oxide film in an inert atmosphere to deposit a plurality of silicon nanocrystal grains in the silicon-rich silicon oxide film;
A process for producing a photoelectric conversion device, comprising: A first step of forming a laminated film above the substrate;
A second step of depositing nanocrystal grains in the laminated film;
Have
The first step includes
Applying a liquid silicon compound material to form a first coating film;
The first coating film is subjected to a first heating at 250 ° C. or higher and 350 ° C. or lower in an inert atmosphere, and then a second heating at 350 ° C. or higher in an oxidizing atmosphere. A fourth step of forming a silicon oxide film (SiOa, a <2);
A fifth step of applying the liquid silicon compound material on the first silicon oxide film to form a second coating film;
A sixth step of forming a second silicon oxide film (SiOb, b> a) by performing third heating at 350 ° C. or higher in an oxidizing atmosphere on the second coating film;
Including
In the first step, by repeating the third step, the fourth step, the fifth step, and the sixth step, a layer composed of the first silicon oxide film and the second silicon film A first laminated film in which a plurality of layers are laminated above the substrate,
In the second step,
A method for manufacturing a photoelectric conversion device, wherein the first laminated film is subjected to a heat treatment in an inert atmosphere to deposit a plurality of silicon nanocrystal grains in the plurality of first silicon oxide films. .   The method for manufacturing a photoelectric conversion device according to claim 1, wherein the heat treatment is performed in an atmosphere of 1000 ° C. or higher.   The method for producing a photoelectric conversion device according to any one of claims 1 to 3, wherein the liquid silicon compound material is an organic solvent liquid of polysilane. A first semiconductor layer forming step of forming a first conductivity type semiconductor layer above the substrate;
A first step of forming a coating film by applying a liquid silicon compound material on the first conductivity type semiconductor layer;
The coating film is subjected to first heating at 250 ° C. or higher and 350 ° C. or lower in an inert atmosphere, and then second heating at 350 ° C. or higher in an oxidizing atmosphere, whereby silicon-rich first oxidation is performed. A second step of forming a silicon film (SiOa, a <2);
A third step of changing the first silicon oxide film to a second silicon oxide film having a plurality of silicon nanocrystal grains by performing a heat treatment on the first silicon oxide film in an inert atmosphere;
A second semiconductor layer forming step of forming a second conductivity type semiconductor layer on the second silicon oxide film;
A process for producing a photoelectric conversion device, comprising: A first semiconductor layer forming step of forming a first conductivity type semiconductor layer above the substrate;
A first step of forming a laminated film above the first conductive semiconductor layer;
A second step of depositing nanocrystal grains in the laminated film;
A second semiconductor layer forming step of forming a second conductivity type semiconductor layer on the laminated film on which the nanocrystal grains are deposited;
Have
The first step includes
Applying a liquid silicon compound material to form a first coating film;
The first coating film is subjected to a first heating at 250 ° C. or higher and 350 ° C. or lower in an inert atmosphere, and then a second heating at 350 ° C. or higher in an oxidizing atmosphere. A fourth step of forming a silicon oxide film (SiOa, a <2);
Applying a liquid silicon compound material on the first silicon oxide film to form a second coating film;
A sixth step of forming a second silicon oxide film (SiOb, b> a) by performing third heating at 350 ° C. or higher in an oxidizing atmosphere on the second coating film;
Including
In the first step, by repeating the third step, the fourth step, the fifth step, and the sixth step, a plurality of layers composed of the first silicon oxide film and the second silicon oxide film are stacked. Forming a first laminated film above the first conductive semiconductor layer;
In the second step,
By performing a heat treatment in an inert atmosphere on the first laminated film, a second laminated film in which a plurality of nanocrystal grains of silicon are precipitated in a plurality of the first silicon oxide films is formed,
Forming the second conductive semiconductor layer on the second stacked film in the second semiconductor layer forming step;
A method for manufacturing a photoelectric conversion device.   The method for manufacturing a photoelectric conversion device according to claim 5, wherein the second conductivity type semiconductor layer has a conductivity type opposite to that of the first conductivity type semiconductor layer.   The first conductive type semiconductor layer is a layer containing a first conductive type semiconductor, and is formed by heat treatment of a solution of a compound in which part of the H bond of polysilane is replaced with an impurity element of the first conductive type. The manufacturing method of the photoelectric conversion apparatus in any one of Claim 5 thru | or 7.   The second conductive type semiconductor layer is a layer containing a second conductive type semiconductor, and is formed by heat treatment of a solution of a compound in which part of the H bond of polysilane is replaced with an impurity element of the second conductive type. The manufacturing method of the photoelectric conversion apparatus as described in any one of 5 thru | or 8.   A method for manufacturing an electronic apparatus, comprising the method for manufacturing a photoelectric conversion device according to claim 1.

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