WO2023079957A1 - P-type impurity-diffused composition and method for producing solar cell using same - Google Patents

P-type impurity-diffused composition and method for producing solar cell using same Download PDF

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WO2023079957A1
WO2023079957A1 PCT/JP2022/038911 JP2022038911W WO2023079957A1 WO 2023079957 A1 WO2023079957 A1 WO 2023079957A1 JP 2022038911 W JP2022038911 W JP 2022038911W WO 2023079957 A1 WO2023079957 A1 WO 2023079957A1
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impurity diffusion
type impurity
diffusion composition
group
film
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PCT/JP2022/038911
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French (fr)
Japanese (ja)
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田邉脩平
北田剛
弓場智之
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東レ株式会社
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the present invention relates to a p-type impurity diffusion composition and a method for manufacturing a solar cell using the same.
  • a method of forming a diffusion source on the substrate and diffusing the impurity into the semiconductor substrate by thermal diffusion is used. being taken.
  • the diffusion source is formed by a CVD method or a solution coating method of a liquid impurity diffusion composition.
  • a thermal oxide film is first formed on the surface of a semiconductor substrate, and then a resist having a predetermined pattern is laminated on the thermal oxide film by photolithography.
  • n-type or p-type diffusion composition is applied to adhere the diffusion composition to the openings of the mask.
  • the impurity component in the composition is thermally diffused into the semiconductor substrate at 600 to 1250° C. to form an n-type or p-type impurity diffusion layer.
  • the present invention has been made based on the circumstances as described above, and an object of the present invention is to provide a p-type impurity diffusion composition that achieves thinning of the pattern.
  • the p-type impurity diffusion composition of the present invention has the following constitution.
  • a p-type impurity diffusion composition containing (A) a Group 13 element compound, (B) a hydroxyl group-containing polymer, and (C) an organic filler comprising a crosslinked polymer.
  • the (C) organic filler made of a crosslinked polymer has an oxyethylene group or an oxypropylene group.
  • the (C) organic filler made of a crosslinked polymer, (C-1) a compound having at least one selected from an acryloyl group and a methacryloyl group and (C-2) a compound having an acryloyl group or a methacryloyl group attached to both ends of a structure having an oxyethylene group or an oxypropylene group.
  • the p-type impurity diffusion composition according to any one of [1] to [3], wherein (B) the hydroxyl group-containing polymer is polyvinyl alcohol.
  • a method for manufacturing a solar cell including a step of forming an impurity diffusion layer with two or more levels of different impurity concentrations, At least one level or more of impurity diffusion layer is formed by applying the p-type impurity diffusion composition according to any one of [1] to [6] to a semiconductor substrate to partially form an impurity diffusion composition film (a).
  • the method for producing a solar cell according to [8], wherein the step of diffusing impurities in the portion where the impurity diffusion composition film (a) is not formed is a step of heating in an atmosphere containing an impurity diffusion component.
  • the p-type impurity diffusion composition of the present invention contains (A) a Group 13 element compound, (B) a hydroxyl group-containing polymer, and (C) an organic filler consisting of a crosslinked polymer.
  • the p-type impurity diffusion composition of the present invention can form a p-type impurity diffusion layer in a semiconductor substrate by containing a group 13 element compound as an impurity diffusion component.
  • a boron compound is preferable as the Group 13 element compound.
  • boron compounds include boric acid, diboron trioxide, methylboronic acid, phenylboronic acid, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, trioctyl borate, and triphenyl borate.
  • boric acid and diboron trioxide are preferable from the viewpoint of doping properties.
  • the content of (A) the group 13 element compound contained in the p-type impurity diffusion composition can be arbitrarily determined depending on the resistance value required for the semiconductor substrate, but it is 0.1 in 100% by mass of the entire composition. It is preferably up to 10% by mass, more preferably 0.5 to 5% by mass.
  • (B) hydroxyl group-containing polymer In the p-type impurity diffusion composition of the present invention, (B) the hydroxyl group-containing polymer forms a complex with (A) the group 13 element compound, particularly preferably the boron compound, to form a uniform coating during coating. is an ingredient.
  • the (B) hydroxyl group-containing polymer examples include polyvinyl alcohol resins such as polyvinyl alcohol and modified polyvinyl alcohol; vinyl alcohol derivatives such as polyvinyl acetal and polyvinyl butyral; polyalkylene oxides such as polyethylene oxide and polypropylene oxide; Polyhydroxyacrylates such as ethyl cellulose, polyhydroxymethyl acrylate, polyhydroxyethyl acrylate, polyhydroxypropyl acrylate may be mentioned.
  • polyvinyl alcohol is preferable from the viewpoint of the ability to form a complex with (A) a group 13 element compound, particularly preferably a boron compound, the stability of the formed complex, and the storage stability of the p-type impurity diffusion composition.
  • the degree of saponification of polyvinyl alcohol is preferably 20 mol% or more and less than 70 mol%.
  • the degree of saponification is preferably 20 mol% or more and less than 70 mol%.
  • the degree of saponification of polyvinyl alcohol is more preferably 30 mol % or more and less than 50 mol %.
  • the average degree of polymerization of polyvinyl alcohol is most preferably 150 to 1000 in terms of solubility and complex stability.
  • both the average degree of polymerization and the degree of saponification are values measured according to JIS K 6726 (1994).
  • the degree of saponification is a value measured by the back titration method among the methods described in the JIS.
  • the content of (B) the hydroxyl group-containing polymer is preferably 1 to 20% by mass based on 100% by mass of the entire composition. Preferably, it is 5 to 15% by mass.
  • the mass ratio (A):(B) of (A) the Group 13 element compound and (B) the hydroxyl group-containing polymer is preferably 1:20 to 1:1, and 1: 15 to 1:3 is more preferred.
  • the p-type impurity diffusion composition of the present invention contains (C) an organic filler comprising a crosslinked polymer in order to impart thixotropic properties and improve printing characteristics.
  • thixotropy means increasing the ratio ( ⁇ 1 / ⁇ 2 ) of the viscosity ( ⁇ 1 ) at low shear stress and the viscosity ( ⁇ 2 ) at high shear stress. By increasing the thixotropy, it is possible to improve the pattern accuracy of screen printing. This is for the following reasons.
  • the p-type impurity diffusion composition with high thixotropy has low viscosity at high shear stress, clogging of the screen hardly occurs during screen printing, and high viscosity at low shear stress causes bleeding immediately after printing and reduction of pattern line width. It becomes difficult to get fat.
  • the thixotropy can be determined from the ratio of viscosities at different rotational speeds obtained by the viscosity measurement method described above.
  • the thixotropy is defined as the ratio ( ⁇ 2 / ⁇ 20 ) of the viscosity ( ⁇ 20 ) at a rotation speed of 20 rpm and the viscosity ( ⁇ 2 ) at a rotation speed of 2 rpm.
  • the thixotropy is preferably 2 or more, more preferably 3 or more.
  • the (C) organic filler composed of a crosslinked polymer stabilizes the complex of (A) the group 13 element compound and (B) the hydroxyl group-containing polymer, and improves the dispersibility in these complexes. This contributes to the thinning of the pattern, improves the uniformity of the resistance value after diffusion, reduces the resistance value, and has the effect of improving the carrier life.
  • crosslinked polymers include, but are not limited to, polymers of acryloyl compounds, methacryloyl compounds, vinyl compounds, epoxy compounds, and phenol compounds.
  • the organic filler composed of a crosslinked polymer contains oxyethylene groups. Alternatively, it preferably has an oxypropylene group.
  • the oxyethylene group or oxypropylene group may be contained in the network of the network structure of the crosslinked polymer, or may be contained at the end of the network structure.
  • the organic filler composed of a crosslinked polymer is more preferably (C-1) a compound having at least one selected from acryloyl groups and methacryloyl groups and (C-2) an oxyethylene group or an oxypropylene group. It is a crosslinked product obtained by copolymerizing a compound in which an acryloyl group or a methacryloyl group is bonded to both ends of the structure having the structure. Thereby, in addition to the oxyethylene group or oxypropylene group of (C-2), the carbonyl group in the acryloyl group or methacryloyl group of (C-1) is combined with (A) a Group 13 element compound and (B) a hydroxyl group. It contributes to further stabilization of the complex with the contained polymer. As a result, a finer pattern, a lower resistance value, an improved uniformity of the resistance value, and a further improvement in the carrier life can be expected.
  • (C-1) Specific examples of the compound having at least one selected from an acryloyl group and a methacryloyl group include acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, methacrylic acid- Examples include, but are not limited to, 2-hydroxyethyl, glycidyl acrylate, glycidyl methacrylate, and the like.
  • Specific examples of compounds in which acrylic groups or methacrylic groups are bonded to both ends of a structure having an oxyethylene group or oxypropylene group include polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethylene glycol diacrylate, and ethylene. Examples include, but are not limited to, glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, and the like.
  • (C-2) is 0.5 to 20 mol per 100 mol% of (C-1). %, more preferably 1 to 10 mol %.
  • (C) an organic filler composed of a crosslinked polymer can be obtained.
  • it can be obtained by suspension polymerization at 60 to 100° C. in a poor solvent and isolating the resulting fine particles, but is not limited to these methods.
  • the p-type impurity diffusion composition of the present invention preferably contains 100 to 1000% by mass of (C) an organic filler composed of a crosslinked polymer when (B) the hydroxyl group-containing polymer is 100% by mass. It is preferably 200 to 700% by mass.
  • the p-type impurity diffusion composition of the present invention preferably further contains a solvent.
  • the solvent refers to a solvent that is liquid at normal pressure and 23° C. and capable of dissolving (B) the hydroxyl group-containing polymer and dispersing (C) the organic filler composed of the crosslinked polymer.
  • the solvent content is preferably 10 to 90% by mass, more preferably 20 to 70% by mass, based on 100% by mass of the entire composition.
  • the solvent can be used without any particular limitation, but from the viewpoint of further improving the printability when using a screen printing method, a spin coat printing method, or the like, a solvent with a boiling point of 100°C or higher is preferable. If the boiling point is 100° C. or higher, for example, when the p-type impurity diffusion composition is printed on a printing plate used in screen printing, the p-type impurity diffusion composition is prevented from drying and sticking on the printing plate. can. It is preferably 160° C. or higher, more preferably 180° C. or higher.
  • the content of the solvent with a boiling point of 100°C or higher is preferably 20% by weight or more with respect to the total amount of the solvent.
  • solvents having a boiling point of 100°C or higher include ethyl lactate (boiling point 155°C), diacetone alcohol (boiling point 169°C), propylene glycol monomethyl ether acetate (boiling point 145°C), propylene glycol monomethyl ether (boiling point 120°C), and 3-methoxy.
  • the solvent more preferably contains 1,3-propanediol. Containing 1,3-propanediol further improves the stability of the complex of (A) the Group 13 element compound and (B) the hydroxyl group-containing polymer.
  • the phenomenon in which (A) the group 13 element compound and (B) the hydroxyl group-containing polymer that have already formed a complex further react to form a three-dimensional complex is easily suppressed, and the p-type impurity diffusion composition It becomes easy to suppress the increase in the viscosity of the substance over time and the generation of gel-like foreign matter due to the increase in viscosity.
  • the uniformity of the resistance value is not impaired and it can be used stably. .
  • the p-type impurity diffusion composition of the present invention does not impair the thinning of the pattern from the viewpoint of improving printability and is within a range that is not affected by the residual inorganic component (C)
  • the organic filler made of a crosslinked polymer may contain a thixotropic agent.
  • Fine particles of silicon oxide are preferred from the viewpoint of compatibility with other components in the composition and reduction of residue.
  • the viscosity of the p-type impurity diffusion composition of the present invention is not limited, and can be appropriately changed according to the printing method and film thickness.
  • the viscosity of the diffusion composition is preferably 5,000 mPa ⁇ s or more. This is because it is possible to suppress bleeding of the printed pattern and obtain a good pattern.
  • a more preferable viscosity is 10,000 mPa ⁇ s or more. Although there is no particular upper limit, it is preferably 100,000 mPa ⁇ s or less from the viewpoint of storage stability and handleability.
  • the viscosity is less than 1,000 mPa s, it is a value measured at a rotation speed of 20 rpm using an E-type digital viscometer based on JIS Z 8803 (1991) "Solution viscosity-measurement method", In the case of 1,000 mPa ⁇ s or more, it is a value measured at a rotational speed of 20 rpm using a B-type digital viscometer based on JIS Z 8803 (1991) "Solution viscosity-measurement method".
  • the p-type impurity diffusion composition of the present invention may contain a surfactant. By containing a surfactant, coating unevenness is improved, and a more uniform coating film can be obtained.
  • a surfactant fluorine-based surfactants and silicone-based surfactants are preferably used.
  • the content of the surfactant, if included, is preferably 0.0001 to 1% by weight in the p-type impurity diffusion composition.
  • the solid content concentration of the p-type impurity diffusion composition of the present invention is not particularly limited, but is preferably in the range of 1% by mass or more and 90% by mass or less. If the concentration is lower than this range, the coating film thickness becomes too thin, and it may be difficult to obtain the desired doping properties and masking properties. Moreover, if the concentration is higher than this range, the storage stability may be lowered.
  • the p-type impurity diffusion composition of the present invention is used in photovoltaic elements such as solar cells, and semiconductor devices in which impurity diffusion regions are patterned on the semiconductor surface, such as transistor arrays, diode arrays, photodiode arrays, and transducers. can also be expanded.
  • a solar cell manufacturing method of the present invention includes a step of forming an impurity diffusion layer with two or more levels of different impurity concentrations, Formation of at least one or more levels of impurity diffusion layer is a step of applying the p-type impurity diffusion composition of the present invention to a semiconductor substrate to partially form an impurity diffusion composition film (a); heating the obtained impurity-diffused composition film (a) to diffuse impurities into the semiconductor substrate to form an impurity-diffused layer (b).
  • different impurity concentrations means that the difference in impurity concentration is 1 ⁇ 10 17 atoms/cm 3 or more, and the difference in sheet resistance of the portion of the substrate surface where the impurity diffusion layer is formed is 10 ⁇ / ⁇ or more. Point. The present embodiment will be described in detail below.
  • a semiconductor substrate 1 is partially coated with the p-type impurity diffusion composition of the present invention to form a pattern 2 of the p-type impurity diffusion composition film (a). .
  • semiconductor substrates include n-type single-crystal silicon, polycrystalline silicon, and crystalline silicon substrates mixed with other elements such as germanium and carbon, each having an impurity concentration of 10 15 to 10 16 atoms/cm 3 . mentioned. It is also possible to use p-type single crystal silicon or a semiconductor other than silicon.
  • the semiconductor substrate has a thickness of 50 to 300 ⁇ m and an outline of a substantially square shape with a side of 100 to 250 mm.
  • the surface of the semiconductor substrate is formed with a large number of uneven texture shapes having a typical width of about 40 to 100 ⁇ m and a depth of about 3 to 4 ⁇ m.
  • the step of forming impurity diffusion layers with different impurity concentrations of two or more levels at least one level or more of impurity diffusion layers are formed by applying the p-type impurity diffusion composition of the present invention to a semiconductor substrate and partially removing p-type impurities. It includes a step of forming a diffusion composition film (a) and a step of heating it to diffuse impurities into a semiconductor substrate to form an impurity diffusion layer (b).
  • Examples of methods for applying the p-type impurity diffusion composition include spin coating, screen printing, inkjet printing, slit coating, spray coating, letterpress printing, and intaglio printing.
  • the semiconductor substrate 1 coated with the p-type impurity diffusion composition is dried with a hot plate, an oven, or the like at a temperature in the range of 50 to 300° C. for 30 seconds to 30 minutes. to form a pattern 2 of the p-type impurity diffusion composition film (a).
  • the thickness of the p-type impurity diffusion composition film (a) after drying is preferably 100 nm or more from the viewpoint of impurity diffusion, and preferably 7 ⁇ m or less from the viewpoint of residue after etching.
  • the impurity diffusion composition film (a) is heated and diffused into the semiconductor substrate 1 to form an impurity diffusion layer (b).
  • a known thermal diffusion method can be used, and for example, methods such as electric heating, infrared heating, laser heating, and microwave heating can be used.
  • the time and temperature of thermal diffusion can be appropriately set so as to obtain desired diffusion characteristics such as impurity concentration and diffusion depth.
  • a diffusion layer having a surface impurity concentration of 10 19 to 10 21 atoms/cm 3 can be formed by thermally diffusing at 800° C. or higher and 1200° C. or lower for 1 to 120 minutes.
  • the diffusion atmosphere is not particularly limited, and may be carried out in the air, or an inert gas such as nitrogen or argon may be used to appropriately control the amount of oxygen in the atmosphere. From the viewpoint of shortening the diffusion time, it is preferable to set the oxygen concentration in the atmosphere to 3% or less. If necessary, the p-type impurity diffusion composition film (a) may be baked at a temperature of 200° C. to 850° C. before diffusion to decompose and remove organic matter.
  • an impurity diffusion composition film (a) is formed using the impurity diffusion composition film (a) as a mask. It is preferable to include a step of diffusing impurities into the unformed portion. Specifically, as shown in FIG. 1(iii), the pattern 2 of the impurity diffusion composition film (a) is used as a mask, and the non-patterned portion has the same conductivity as the impurity diffusion layer (b), and An impurity diffusion layer (c) having a different impurity concentration is formed.
  • the step of diffusing impurities into a portion where the impurity diffusion composition film (a) is not formed using the impurity diffusion composition film (a) as a mask includes: is heated to diffuse impurities into the semiconductor substrate 1 to form an impurity diffusion layer (b).
  • ions containing impurity diffusion components are implanted into the semiconductor substrate 1 with the pattern 2 of the impurity diffusion composition film (a) and then annealed.
  • a method of heating the semiconductor substrate 1 with the pattern 2 of the impurity diffusion composition film (a) in an atmosphere containing an impurity diffusion component Another impurity diffusion composition having a different impurity concentration and having a different impurity concentration is applied to the portion where the impurity diffusion composition film (a) is not formed to form an impurity diffusion composition film, followed by electric heating, infrared heating, laser A method of heating, microwave heating, and the like can be mentioned.
  • the step of diffusing the impurity into the portion where the impurity diffusion composition film (a) is not formed is preferably the step of heating in an atmosphere containing the impurity diffusion component.
  • the impurity diffusion layer (c) can be formed by heating the semiconductor substrate 1 with the pattern 2 of the impurity diffusion composition film (a) at 800 to 1000° C. in an atmosphere containing an impurity diffusion component.
  • the impurity concentration of the impurity diffusion layer (c) can be set higher or lower than the impurity concentration of the impurity diffusion layer (b) by adjusting the gas pressure and heating conditions.
  • the substrate is put into the heating furnace of FIG. They may be formed at the same time.
  • an impurity diffusion layer (c) having an impurity concentration different from that of the impurity diffusion layer (b) is formed in one batch by additionally introducing a gas containing the component and heating under conditions different from the heating conditions for only the inert gas.
  • oxidation of the surface of the semiconductor substrate in the portion where the impurity diffusion composition film (a) is not formed causes boron silicate glass when the impurity is p-type, and phosphor silicate glass when the impurity is n-type.
  • a layer (d) comprising silicon oxide, such as glass, is formed.
  • the pattern 2 of the impurity diffusion composition film (a) and the layer (d) containing silicon oxide can be removed by a known etching method.
  • the material used for etching is not particularly limited, but includes, for example, at least one of hydrogen fluoride, ammonium, phosphoric acid, sulfuric acid, and nitric acid as an etching component, and water, an organic solvent, etc. as other components. preferable.
  • the method for manufacturing a solar cell of the present invention may include a back surface forming step.
  • a back surface forming step For example, when forming a p-type impurity diffusion layer with two or more levels of different impurity concentrations on the substrate surface and forming an n-type impurity diffusion layer on the back surface, the surface is covered with a SiO 2 film so as to prevent n-type impurities from entering the surface. etc. to protect.
  • a preferable film thickness for obtaining a protective effect is 100 to 1000 nm, and in order to suppress the influence on the p-type diffusion layer on the substrate surface, it is preferably formed by plasma CVD with a high deposition rate at a low temperature. More specifically, the mixed gas flow rate ratio SiH 4 /N 2 O is 0.01 to 5.0, the pressure in the reaction chamber is 0.1 to 4 Torr, and the temperature during film formation is 300° C. to 550° C. formed by
  • the semiconductor substrate is heated at 800 to 900° C. in an atmosphere containing impurity diffusion components by bubbling phosphorus oxychloride (POCl 3 ) to the rear surface and flowing N 2 .
  • an n-type impurity diffusion layer is formed on the back surface of the substrate, and at the same time, a layer containing silicon oxide, such as a phosphosilicate glass layer, is formed on the outermost portion of the back surface by oxidation.
  • the inorganic film on the substrate surface and the layer containing silicon oxide on the back surface are removed by etching.
  • Specific examples of preferred etching are the same as those for forming impurity diffusion layers with two or more levels of different impurity concentrations.
  • passivation films for suppressing surface recombination and preventing light reflection may be provided on the front and back surfaces of the semiconductor substrate after the etching step, if there is a back surface forming step.
  • a passivation film for the p-type diffusion layer SiO 2 obtained by heat treatment in a high-temperature oxygen atmosphere at 700° C. or higher and a silicon nitride film for protecting this film may be provided.
  • SiNx film may be formed. In this case, it can be formed by a plasma CVD method using a mixed gas of SiH 4 and NH 3 as a raw material.
  • hydrogen diffuses into the crystal, and orbitals that do not contribute to the bonding of silicon atoms, ie, dangling bonds, bond with hydrogen to deactivate defects (hydrogen passivation). More specifically, under the conditions that the mixed gas flow rate ratio NH 3 /SiH 4 is 0.05 to 5.0, the pressure in the reaction chamber is 0.1 to 4 Torr, and the temperature during film formation is 300° C. to 550° C. It is formed.
  • a metal paste is printed by a screen printing method so as to be on the high-concentration impurity diffusion layer among the two levels of impurity diffusion layers, and dried to form an electrode.
  • the metal paste for electrodes contains metal particles and glass particles as essential components, and if necessary, a resin binder, other additives, and the like. Ag and Al are preferably used as the metal particles used at this time.
  • Electrode baking process The electrodes are then heat treated (fired) to complete the solar cell.
  • heat-treated (fired) in the range of 600° C. to 900° C. for several seconds to several minutes, the glass particles contained in the electrode metal paste melt the antireflection film, which is an insulating film, on the light-receiving surface side, and the silicon surface is also partially melted.
  • metal particles (for example, silver particles) in the paste form contact portions with the semiconductor substrate and solidify. As a result, the formed light-receiving surface electrode and the semiconductor substrate are electrically connected. This is called fire-through.
  • the light-receiving surface electrodes are generally composed of busbar electrodes and finger electrodes intersecting the busbar electrodes.
  • Such a light-receiving surface electrode can be formed by means such as screen printing of the metal paste described above, plating of an electrode material, vapor deposition of an electrode material by electron beam heating in a high vacuum, or the like.
  • the busbar electrodes and finger electrodes can be formed by a known method.
  • the method for manufacturing a solar cell of the present invention is not limited to the above-described embodiments, and modifications such as various design changes can be made based on the knowledge of those skilled in the art. Such embodiments are also included in the scope of the present invention.
  • a substrate As a substrate, a semiconductor substrate (silicon wafer) made of n-type single crystal silicon with a side of 156 mm was prepared, and alkali etching was performed on both surfaces in order to remove slice damage and natural oxide. At this time, countless irregularities (textures) typically having a width of 40 to 100 ⁇ m and a depth of 3 to 4 ⁇ m were formed on both surfaces of the semiconductor substrate, and this was used as a coated substrate.
  • silicon wafer silicon wafer
  • alkali etching was performed on both surfaces in order to remove slice damage and natural oxide.
  • countless irregularities (textures) typically having a width of 40 to 100 ⁇ m and a depth of 3 to 4 ⁇ m were formed on both surfaces of the semiconductor substrate, and this was used as a coated substrate.
  • the substrate was heated at 200° C. for 10 minutes in air to form an impurity diffusion composition film having a thickness of about 3.5 ⁇ m.
  • each substrate was immersed in a 5% by weight hydrofluoric acid aqueous solution at 23° C. for 1 minute to remove the impurity diffusion composition film. After the removal, the substrate was immersed in pure water and washed, and the presence or absence of residue was visually observed on the surface. After immersion for 1 minute, surface deposits can be visually confirmed, but can be removed by rubbing with a waste cloth. When the surface deposits could not be visually confirmed, it was rated as A, and B or higher was rated as acceptable.
  • the substrate after impurity diffusion used for residue evaluation is p/n judged using a p / n judgment machine, and the surface resistance is measured by a four-probe type surface resistance measurement device RT-70V (Napson (manufactured by Co., Ltd.). This measurement was performed on a total of 13 points of data at intervals of 20 mm in the vertical and horizontal directions from the center of the square substrate, and the average value was evaluated as the sheet resistance value, and the variation in the values was evaluated as the uniformity of the resistance value.
  • the sheet resistance value is an index of impurity diffusibility, and a smaller value means a larger amount of impurity diffusion. The smaller the variation in the value indicating the uniformity of the resistance value, the better, and the value within 20% above and below the average value was considered acceptable.
  • the same screen printer as used for residue evaluation was used, and the screen mask had an opening with a width of 70 ⁇ m and a length of 13.5 cm on the center line of the substrate (parallel to the side of the substrate).
  • Seven striped parallel patterns were formed by using 3 strips (400 mesh, wire diameter 23 ⁇ m, manufactured by SUS Co., Ltd.), 3 strips on each side of the strip, which were sandwiched in parallel with each other at intervals of 1 cm.
  • the substrate was heated at 200° C. for 10 minutes in air to form a pattern with a thickness of about 3.5 ⁇ m.
  • the width of the pattern printed with the 70 ⁇ m mask was actually measured using a microscope (MX61L manufactured by Olympus Corporation), and how much the pattern spread with respect to the 70 ⁇ m mask was evaluated.
  • a curing liquid prepared by dissolving 0.6 equivalent of piperazine in 8 cc of water was added to the uncured epoxy emulsion, and the mixture was gently stirred to homogenize. This liquid was allowed to stand at 25° C. for 3 days to cure into a spherical filler having an average particle size of about 6 ⁇ m.
  • the filler collected by filtration was placed in an eggplant-shaped flask, and 400 g of acetonitrile (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added to re-disperse. A condenser was attached to this, and extraction was performed for 8 hours in a water bath at 50° C. while heating and stirring to refine the filler. After cooling, the organic filler B was obtained by suction filtration and drying under reduced pressure at 50° C. for 8 hours.
  • Example 1 1.5 g of boric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 5.0 g of polyvinyl alcohol (manufactured by Nippon Acetate & Poval Co., Ltd.) with a degree of saponification of 80% (hereinafter referred to as PVA (80)) Then, 40.0 g of organic filler A, 34.0 g of 3-methoxy-3-methyl-1-butanol (manufactured by Tokyo Kasei Co., Ltd.) (hereinafter referred to as MMB), and 20.0 g of water are mixed and uniform. A p-type impurity diffused composition 1 was obtained by sufficiently stirring as above.
  • Example 2 A p-type impurity diffusion composition 2 was obtained in the same manner as in Example 1 except that the organic filler B was used instead of the organic filler A.
  • Example 3 A p-type impurity diffusion composition 3 was obtained in the same manner as in Example 1 except that the organic filler C was used instead of the organic filler A.
  • Example 1 A p-type impurity diffusion composition 4 was obtained in the same manner as in Example 1 except that the organic filler D was used instead of the organic filler A.
  • Example 2 A p-type impurity diffusion composition 5 was obtained in the same manner as in Example 1 except that a silica filler (SO-E2: manufactured by Admatechs Co., Ltd.) was used instead of the organic filler A.
  • a silica filler SO-E2: manufactured by Admatechs Co., Ltd.
  • Example 4 Instead of 5.0 g of PVA (80), 12.5 g of polyvinyl alcohol having a degree of saponification of 10% (manufactured by Nippon Vinyl Poval Co., Ltd.) (hereinafter referred to as PVA (10)), 34.0 g of MMB and 20.0 g of water.
  • P-type impurity diffusion composition 7 was prepared in the same manner as in Example 1, except that 27.0 g of terpineol (manufactured by Tokyo Kasei Co., Ltd.) (hereinafter referred to as TP), 11.0 g of MMB, and 10.0 g of water were used instead of 0 g. got
  • Example 5 Example 4 except that instead of 12.5 g of PVA (10), 10.0 g of polyvinyl alcohol (manufactured by Nippon Acetate & Poval Co., Ltd.) having a degree of saponification of 49% (hereinafter referred to as PVA (49)) was used.
  • PVA (49) polyvinyl alcohol having a degree of saponification of 49%
  • Example 6 10.0 g of PVA (49) in place of 5.0 g of PVA (80), 27.0 g of TP in place of 34.0 g of MMB and 20.0 g of water, and 1,3-propanediol (hereinafter referred to as 1,3-PD) 11
  • 1,3-PD 1,3-propanediol
  • Example 7 A p-type impurity diffusion composition 10 was prepared in the same manner as in Example 1 except that polyethylene glycol 400 (manufactured by Tokyo Kasei Co., Ltd.) was used instead of PVA (80) and organic filler B was used instead of organic filler A. Obtained.
  • Evaluations (1) to (5) were performed on the obtained p-type impurity diffusion compositions of Examples 1 to 7 and Comparative Examples 1 to 3. Table 2 shows the evaluation results.

Abstract

Provided is a p-type impurity-diffused composition with which a pattern can be thinned. The p-type impurity-diffused composition contains (A) a group 13 element compound, (B) a hydroxyl group-containing high molecule, and (C) an organic filler composed of a cross-linked polymer.

Description

ｐ型不純物拡散組成物、それを用いた太陽電池の製造方法P-type impurity diffusion composition and method for producing solar cell using the same
　本発明は、ｐ型不純物拡散組成物、それを用いた太陽電池の製造方法に関する。 The present invention relates to a p-type impurity diffusion composition and a method for manufacturing a solar cell using the same.
　現在、太陽電池の製造において、半導体基板中にｎ型またはｐ型の不純物拡散層を形成する場合には、基板上に拡散源を形成して熱拡散により半導体基板中に不純物を拡散させる方法が採られている。拡散源はＣＶＤ法や液状の不純物拡散組成物の溶液塗布法により形成される。例えば、液状の不純物拡散組成物を使用する場合、まず半導体基板表面に熱酸化膜を形成し、続いてフォトリソグラフィー法により所定のパターンを有するレジストを熱酸化膜上に積層する。そして当該レジストをマスクとして酸またはアルカリによりレジストでマスクされていない熱酸化膜部分をエッチングし、レジストを剥離して熱酸化膜によるマスクを形成する。続いてｎ型またはｐ型の拡散組成物を塗布してマスクが開口している部分に拡散組成物を付着させる。その後、組成物中の不純物成分を６００～１２５０℃で半導体基板中に熱拡散させてｎ型またはｐ型の不純物拡散層を形成している。 At present, when forming an n-type or p-type impurity diffusion layer in a semiconductor substrate in the manufacture of a solar cell, a method of forming a diffusion source on the substrate and diffusing the impurity into the semiconductor substrate by thermal diffusion is used. being taken. The diffusion source is formed by a CVD method or a solution coating method of a liquid impurity diffusion composition. For example, when a liquid impurity diffusion composition is used, a thermal oxide film is first formed on the surface of a semiconductor substrate, and then a resist having a predetermined pattern is laminated on the thermal oxide film by photolithography. Then, using the resist as a mask, portions of the thermal oxide film not masked by the resist are etched with acid or alkali, and the resist is removed to form a mask of the thermal oxide film. Subsequently, an n-type or p-type diffusion composition is applied to adhere the diffusion composition to the openings of the mask. After that, the impurity component in the composition is thermally diffused into the semiconductor substrate at 600 to 1250° C. to form an n-type or p-type impurity diffusion layer.
　このような太陽電池の製造に関して、近年では従来のフォトリソグラフィー技術を用いず、簡易的に印刷方式などで不純物拡散層領域の微細なパターニング形成を行い、低コストで太陽電池を製造することが検討されている（例えば、特許文献１参照）。印刷方式ではマスクを使用せずに直接ドーピング層形成領域に拡散剤を選択的に吐出してパターニングするため、従来のフォトリソグラフィー法と比較して複雑な工程を必要とせず、使用液量も低減することができる。 In recent years, it has been considered to manufacture solar cells at low cost by forming fine patterning of the impurity diffusion layer region by a simple printing method, etc., without using the conventional photolithography technology. (See Patent Document 1, for example). In the printing method, the diffusing agent is selectively ejected directly onto the doping layer formation area without using a mask, and patterning is performed. can do.
　印刷方式に適したｎ型、ｐ型の不純物拡散組成物の構成成分としては、ポリシロキサンを使用することが知られている（例えば、特許文献２～５参照）。 It is known to use polysiloxane as a constituent component of n-type and p-type impurity diffusion compositions suitable for printing methods (see Patent Documents 2 to 5, for example).
特表２００３－１６８８１０号公報Japanese translation of PCT publication No. 2003-168810 特表２００２－５３９６１５号公報Japanese Patent Publication No. 2002-539615 特開２０１２－１１４２９８号公報JP 2012-114298 A 特許第６３６１５０５号公報Japanese Patent No. 6361505 特表２０１９－５３３０２６号公報Japanese Patent Publication No. 2019-533026
　しかしながら、これら不純物拡散組成物については印刷して乾燥する際、パターンが広がってしまい、細線パターンを形成するのが困難である。通常はフィラーの添加等でチクソ性を付与し改善を図るが、ｐ型不純物拡散組成物の場合は不純物拡散組成物中のフィラーの分散不良等で十分な細線化に至らないとされてきた。 However, when these impurity diffusion compositions are printed and dried, the pattern spreads, making it difficult to form a fine line pattern. Although thixotropy is usually improved by adding a filler or the like, in the case of a p-type impurity diffusion composition, it has been believed that sufficient thinning cannot be achieved due to poor dispersion of the filler in the impurity diffusion composition.
　本発明は、上述のような事情に基づいてなされたものであり、パターンの細線化を達成するｐ型不純物拡散組成物を提供することを目的とする。 The present invention has been made based on the circumstances as described above, and an object of the present invention is to provide a p-type impurity diffusion composition that achieves thinning of the pattern.
　上記課題を解決するため、本発明のｐ型不純物拡散組成物は以下の構成を有する。
[１]（Ａ）第１３族元素化合物、（Ｂ）水酸基含有高分子および（Ｃ）架橋された重合体からなる有機フィラーを含有するｐ型不純物拡散組成物。
[２]前記（Ｃ）架橋された重合体からなる有機フィラーがオキシエチレン基またはオキシプロピレン基を有する[１]に記載のｐ型不純物拡散組成物。
[３]前記（Ｃ）架橋された重合体からなる有機フィラーが、
（Ｃ－１）アクリロイル基、メタクリロイル基から選ばれる少なくとも１つを有する化合物および
（Ｃ－２）オキシエチレン基またはオキシプロピレン基を有する構造の両末端にアクリロイル基またはメタクリロイル基が結合した化合物
を共重合した架橋体である[２]に記載のｐ型不純物拡散組成物。
[４]前記（Ｂ）水酸基含有高分子がポリビニルアルコールである［１］～［３］のいずれかに記載のｐ型不純物拡散組成物。
[５]前記ポリビニルアルコールのケン化度が２０モル％以上７０モル％未満である[４]に記載のｐ型不純物拡散組成物。
[６]溶媒として１，３－プロパンジオールを含有する[１]～[５]のいずれかに記載のｐ型不純物拡散組成物。
[７]２水準以上の異なる不純物濃度で不純物拡散層を形成する工程を含む太陽電池の製造方法であって、
少なくとも１水準以上の不純物拡散層形成は［１］～［６］のいずれかに記載のｐ型不純物拡散組成物を半導体基板に塗布して部分的に不純物拡散組成物膜（ａ）を形成する工程と、
得られた不純物拡散組成物膜（ａ）を加熱して不純物を半導体基板に拡散させて不純物拡散層（ｂ）を形成する工程とを含む太陽電池の製造方法。
［８］不純物拡散組成物膜（ａ）をマスクとして不純物拡散組成物膜（ａ）未形成部分に不純物を拡散させる工程を含む［７］に記載の太陽電池の製造方法。
［９］不純物拡散組成物膜（ａ）未形成部分に不純物を拡散させる工程が、不純物拡散成分を含む雰囲気中で加熱する工程である［８］に記載の太陽電池の製造方法。 In order to solve the above problems, the p-type impurity diffusion composition of the present invention has the following constitution.
[1] A p-type impurity diffusion composition containing (A) a Group 13 element compound, (B) a hydroxyl group-containing polymer, and (C) an organic filler comprising a crosslinked polymer.
[2] The p-type impurity diffusion composition according to [1], wherein the (C) organic filler made of a crosslinked polymer has an oxyethylene group or an oxypropylene group.
[3] The (C) organic filler made of a crosslinked polymer,
(C-1) a compound having at least one selected from an acryloyl group and a methacryloyl group and (C-2) a compound having an acryloyl group or a methacryloyl group attached to both ends of a structure having an oxyethylene group or an oxypropylene group. The p-type impurity diffusion composition according to [2], which is a polymerized crosslinked product.
[4] The p-type impurity diffusion composition according to any one of [1] to [3], wherein (B) the hydroxyl group-containing polymer is polyvinyl alcohol.
[5] The p-type impurity diffusion composition according to [4], wherein the degree of saponification of the polyvinyl alcohol is 20 mol% or more and less than 70 mol%.
[6] The p-type impurity diffusion composition according to any one of [1] to [5], containing 1,3-propanediol as a solvent.
[7] A method for manufacturing a solar cell including a step of forming an impurity diffusion layer with two or more levels of different impurity concentrations,
At least one level or more of impurity diffusion layer is formed by applying the p-type impurity diffusion composition according to any one of [1] to [6] to a semiconductor substrate to partially form an impurity diffusion composition film (a). process and
and a step of heating the obtained impurity-diffused composition film (a) to diffuse impurities into the semiconductor substrate to form an impurity-diffused layer (b).
[8] The method for producing a solar cell according to [7], including the step of diffusing impurities into the portion where the impurity diffusion composition film (a) is not formed, using the impurity diffusion composition film (a) as a mask.
[9] The method for producing a solar cell according to [8], wherein the step of diffusing impurities in the portion where the impurity diffusion composition film (a) is not formed is a step of heating in an atmosphere containing an impurity diffusion component.
　本発明によれば、パターンの細線化を達成するｐ型不純物拡散組成物を提供することができる。 According to the present invention, it is possible to provide a p-type impurity diffusion composition that achieves thinning of patterns.
本発明のｐ型不純物拡散組成物を用いた太陽電池の製造方法の一例を示す工程断面図である。It is process sectional drawing which shows an example of the manufacturing method of the solar cell using the p-type impurity diffusion composition of this invention.
　以下、本発明に係るｐ型不純物拡散組成物およびこれを用いた半導体素子の製造方法の好適な実施形態を、必要に応じて図面を参照しながら詳細に説明する。なお、本発明は、これらの実施形態により限定されるものではない。 Hereinafter, preferred embodiments of the p-type impurity diffusion composition according to the present invention and the method of manufacturing a semiconductor device using the same will be described in detail with reference to the drawings as necessary. In addition, this invention is not limited by these embodiments.
　本発明のｐ型不純物拡散組成物は、（Ａ）第１３族元素化合物、（Ｂ）水酸基含有高分子および（Ｃ）架橋された重合体からなる有機フィラーを含有する。 The p-type impurity diffusion composition of the present invention contains (A) a Group 13 element compound, (B) a hydroxyl group-containing polymer, and (C) an organic filler consisting of a crosslinked polymer.
　（（Ａ）第１３族元素化合物）
　本発明のｐ型不純物拡散組成物は、不純物拡散成分として第１３族元素化合物を含むことにより、半導体基板中にｐ型の不純物拡散層を形成することができる。第１３族元素化合物としてはホウ素化合物であることが好ましい。 ((A) Group 13 element compound)
The p-type impurity diffusion composition of the present invention can form a p-type impurity diffusion layer in a semiconductor substrate by containing a group 13 element compound as an impurity diffusion component. A boron compound is preferable as the Group 13 element compound.
　ホウ素化合物としては、ホウ酸、三酸化二ホウ素、メチルボロン酸、フェニルボロン酸、ホウ酸トリメチル、ホウ酸トリエチル、ホウ酸トリプロピル、ホウ酸トリブチル、ホウ酸トリオクチル、ホウ酸トリフェニル等を挙げることができる。なかでもドーピング性の点から、ホウ酸、三酸化二ホウ素であることが好ましい。 Examples of boron compounds include boric acid, diboron trioxide, methylboronic acid, phenylboronic acid, trimethyl borate, triethyl borate, tripropyl borate, tributyl borate, trioctyl borate, and triphenyl borate. can. Among them, boric acid and diboron trioxide are preferable from the viewpoint of doping properties.
　ｐ型不純物拡散組成物中に含まれる（Ａ）第１３族元素化合物の含有量は、半導体基板に求められる抵抗値により任意に決めることができるが、組成物全体１００質量％中に０．１～１０質量％であることが好ましく、０．５～５質量％であることがより好ましい。 The content of (A) the group 13 element compound contained in the p-type impurity diffusion composition can be arbitrarily determined depending on the resistance value required for the semiconductor substrate, but it is 0.1 in 100% by mass of the entire composition. It is preferably up to 10% by mass, more preferably 0.5 to 5% by mass.
　（（Ｂ）水酸基含有高分子）
　本発明のｐ型不純物拡散組成物において、（Ｂ）水酸基含有高分子は、（Ａ）第１３族元素化合物、特に好ましくはホウ素化合物と錯体を形成し、塗布時に均一な被膜を形成するための成分である。 ((B) hydroxyl group-containing polymer)
In the p-type impurity diffusion composition of the present invention, (B) the hydroxyl group-containing polymer forms a complex with (A) the group 13 element compound, particularly preferably the boron compound, to form a uniform coating during coating. is an ingredient.
　（Ｂ）水酸基含有高分子としては、具体的には、ポリビニルアルコール、変性ポリビニルアルコールなどのポリビニルアルコール樹脂、ポリビニルアセタール、ポリビニルブチラールなどのビニルアルコール誘導体、ポリエチレンオキサイド、ポリプロピレンオキサイドなどのポリアルキレンオキサイド、ヒドロキシエチルセルロース、ポリヒドロキシメチルアクリレート、ポリヒドロキシエチルアクリレート、ポリヒドロキシプロピルアクリレートなどのポリヒドロキシアクリレート類を挙げることができる。中でも（Ａ）第１３族元素化合物、特に好ましくはホウ素化合物との錯体の形成性および形成した錯体の安定性及びｐ型不純物拡散組成物の保存安定性の面からポリビニルアルコールが好ましい。 Specific examples of the (B) hydroxyl group-containing polymer include polyvinyl alcohol resins such as polyvinyl alcohol and modified polyvinyl alcohol; vinyl alcohol derivatives such as polyvinyl acetal and polyvinyl butyral; polyalkylene oxides such as polyethylene oxide and polypropylene oxide; Polyhydroxyacrylates such as ethyl cellulose, polyhydroxymethyl acrylate, polyhydroxyethyl acrylate, polyhydroxypropyl acrylate may be mentioned. Among them, polyvinyl alcohol is preferable from the viewpoint of the ability to form a complex with (A) a group 13 element compound, particularly preferably a boron compound, the stability of the formed complex, and the storage stability of the p-type impurity diffusion composition.
　錯体安定性の観点からポリビニルアルコールのケン化度は２０モル％以上７０モル％未満であることが好ましい。ケン化度を２０％以上とすることで、（Ａ）不純物拡散成分との錯体安定性が高まり、低抵抗値化と抵抗値の均一性向上、キャリア寿命の向上が見込める。また、ケン化度を７０％未満とすることで、（Ｃ）架橋された重合体からなる有機フィラーの分散性が向上し、低抵抗値化と抵抗均一性の向上、キャリア寿命の向上が見込める。保存安定性向上の観点から、ポリビニルアルコールのケン化度は３０モル％以上５０モル％未満であることがさらに好ましい。ポリビニルアルコールの平均重合度は、溶解度と錯体安定性の点で１５０～１０００が最も好ましい。本発明において、平均重合度およびケン化度は、いずれもＪＩＳ　Ｋ　６７２６（１９９４）に従って測定した値である。ケン化度は当該ＪＩＳに記載の方法のうち逆滴定法によって測定した値である。 From the viewpoint of complex stability, the degree of saponification of polyvinyl alcohol is preferably 20 mol% or more and less than 70 mol%. By setting the degree of saponification to 20% or more, the stability of the complex with (A) the impurity diffusion component is enhanced, and it is expected that the resistance value will be reduced, the uniformity of the resistance value will be improved, and the carrier life will be improved. In addition, by setting the degree of saponification to less than 70%, the dispersibility of the (C) organic filler made of a crosslinked polymer is improved, and it is expected that the resistance value will be reduced, the resistance uniformity will be improved, and the carrier life will be improved. . From the viewpoint of improving storage stability, the degree of saponification of polyvinyl alcohol is more preferably 30 mol % or more and less than 50 mol %. The average degree of polymerization of polyvinyl alcohol is most preferably 150 to 1000 in terms of solubility and complex stability. In the present invention, both the average degree of polymerization and the degree of saponification are values measured according to JIS K 6726 (1994). The degree of saponification is a value measured by the back titration method among the methods described in the JIS.
　良好な熱拡散と、組成物除去後の基板上の有機残渣抑制の点で、（Ｂ）水酸基含有高分子の含有量は、組成物全体１００質量％中に１～２０質量％であることが好ましく、５～１５質量％であることがより好ましい。 In terms of good thermal diffusion and suppression of organic residue on the substrate after removal of the composition, the content of (B) the hydroxyl group-containing polymer is preferably 1 to 20% by mass based on 100% by mass of the entire composition. Preferably, it is 5 to 15% by mass.
　また、拡散均一性の観点から、（Ａ）第１３族元素化合物と（Ｂ）水酸基含有高分子の質量比（Ａ）：（Ｂ）としては、１：２０～１：１が好ましく、１：１５～１：３がより好ましい。 Further, from the viewpoint of diffusion uniformity, the mass ratio (A):(B) of (A) the Group 13 element compound and (B) the hydroxyl group-containing polymer is preferably 1:20 to 1:1, and 1: 15 to 1:3 is more preferred.
　（（Ｃ）架橋された重合体からなる有機フィラー）
　本発明のｐ型不純物拡散組成物は、チクソ性を付与して印刷特性の向上を図るべく、（Ｃ）架橋された重合体からなる有機フィラーを含有することが重要である。チクソ性を付与するとは、低せん断応力時の粘度（η１）と高せん断応力時の粘度（η２）の比（η１／η２）を大きくすることである。チクソ性が大きくなることで、スクリーン印刷のパターン精度を高めることができる。それは以下のような理由による。チクソ性が高いｐ型不純物拡散組成物は、高せん断応力時には粘度が低いため、スクリーン印刷時にスクリーンの目詰まりが起こりにくく、低せん断応力時には粘度が高いため、印刷直後の滲みやパターン線幅の太りが起きにくくなる。 ((C) Organic filler made of crosslinked polymer)
It is important that the p-type impurity diffusion composition of the present invention contains (C) an organic filler comprising a crosslinked polymer in order to impart thixotropic properties and improve printing characteristics. Giving thixotropy means increasing the ratio (η 1 /η 2 ) of the viscosity (η 1 ) at low shear stress and the viscosity (η 2 ) at high shear stress. By increasing the thixotropy, it is possible to improve the pattern accuracy of screen printing. This is for the following reasons. Since the p-type impurity diffusion composition with high thixotropy has low viscosity at high shear stress, clogging of the screen hardly occurs during screen printing, and high viscosity at low shear stress causes bleeding immediately after printing and reduction of pattern line width. It becomes difficult to get fat.
　チクソ性は、上記粘度測定方法で得られた異なる回転数における粘度の比から求めることができる。本発明においては、回転数２０ｒｐｍでの粘度（η２０）と回転数２ｒｐｍでの粘度（η２）の比（η２／η２０）をチクソ性と定義する。スクリーン印刷で精度の良いパターン形成するためには、チクソ性が２以上であることが好ましく、３以上がさらに好ましい。 The thixotropy can be determined from the ratio of viscosities at different rotational speeds obtained by the viscosity measurement method described above. In the present invention, the thixotropy is defined as the ratio (η 2 /η 20 ) of the viscosity (η 20 ) at a rotation speed of 20 rpm and the viscosity (η 2 ) at a rotation speed of 2 rpm. In order to form a pattern with good accuracy by screen printing, the thixotropy is preferably 2 or more, more preferably 3 or more.
　また、（Ｃ）架橋された重合体からなる有機フィラーは、（Ａ）第１３族元素化合物と（Ｂ）水酸基含有高分子との錯体を安定化させ、これら錯体中での分散性を向上させることで、パターンの細線化に寄与し、さらには拡散後の抵抗値の均一性を向上させ、抵抗値を低減させるとともに、キャリア寿命を向上させる効果もある。 In addition, the (C) organic filler composed of a crosslinked polymer stabilizes the complex of (A) the group 13 element compound and (B) the hydroxyl group-containing polymer, and improves the dispersibility in these complexes. This contributes to the thinning of the pattern, improves the uniformity of the resistance value after diffusion, reduces the resistance value, and has the effect of improving the carrier life.
　架橋された重合体の具体例としては、アクリロイル化合物、メタクリロイル化合物、ビニル化合物、エポキシ化合物、フェノール化合物の重合体などが挙げられるがこれらに限定されない。 Specific examples of crosslinked polymers include, but are not limited to, polymers of acryloyl compounds, methacryloyl compounds, vinyl compounds, epoxy compounds, and phenol compounds.
　錯体をさらに安定化させて拡散後の抵抗値の均一性を向上させる観点、組成物膜の除去後の残渣低減の観点より、（Ｃ）架橋された重合体からなる有機フィラーは、オキシエチレン基またはオキシプロピレン基を有することが好ましい。オキシエチレン基またはオキシプロピレン基は架橋された重合体の網目構造の網目中に含まれていてもよいし、網目構造の末端に含まれていてもよい。 From the viewpoint of further stabilizing the complex to improve the uniformity of the resistance value after diffusion and from the viewpoint of reducing the residue after removal of the composition film, (C) the organic filler composed of a crosslinked polymer contains oxyethylene groups. Alternatively, it preferably has an oxypropylene group. The oxyethylene group or oxypropylene group may be contained in the network of the network structure of the crosslinked polymer, or may be contained at the end of the network structure.
　（Ｃ）架橋された重合体からなる有機フィラーは、より好ましくは（Ｃ－１）アクリロイル基、メタクリロイル基から選ばれる少なくとも１つを有する化合物および（Ｃ－２）オキシエチレン基またはオキシプロピレン基を有する構造の両末端にアクリロイル基またはメタクリロイル基が結合した化合物を共重合した架橋体である。これにより、（Ｃ－２）のオキシエチレン基またはオキシプロピレン基に加えて、（Ｃ－１）のアクリロイル基またはメタクリロイル基中のカルボニル基が、（Ａ）第１３族元素化合物と（Ｂ）水酸基含有高分子との錯体のさらなる安定化に寄与する。結果、パターンの細線化、低抵抗値化、抵抗値の均一性の向上、キャリア寿命の更なる向上が見込める。 (C) the organic filler composed of a crosslinked polymer is more preferably (C-1) a compound having at least one selected from acryloyl groups and methacryloyl groups and (C-2) an oxyethylene group or an oxypropylene group. It is a crosslinked product obtained by copolymerizing a compound in which an acryloyl group or a methacryloyl group is bonded to both ends of the structure having the structure. Thereby, in addition to the oxyethylene group or oxypropylene group of (C-2), the carbonyl group in the acryloyl group or methacryloyl group of (C-1) is combined with (A) a Group 13 element compound and (B) a hydroxyl group. It contributes to further stabilization of the complex with the contained polymer. As a result, a finer pattern, a lower resistance value, an improved uniformity of the resistance value, and a further improvement in the carrier life can be expected.
　（Ｃ－１）アクリロイル基、メタクリロイル基から選ばれる少なくとも１つを有する化合物の具体例としては、アクリル酸、メタクリル酸、アクリル酸メチル、メタクリル酸メチル、アクリル酸－２－ヒドロキシエチル、メタクリル酸－２－ヒドロキシエチル、アクリル酸グリシジル、メタクリル酸グリシジルなどが挙げられるがこれらに限定されない。 (C-1) Specific examples of the compound having at least one selected from an acryloyl group and a methacryloyl group include acrylic acid, methacrylic acid, methyl acrylate, methyl methacrylate, 2-hydroxyethyl acrylate, methacrylic acid- Examples include, but are not limited to, 2-hydroxyethyl, glycidyl acrylate, glycidyl methacrylate, and the like.
　（Ｃ－２）オキシエチレン基またはオキシプロピレン基を有する構造の両末端にアクリル基またはメタクリル基が結合した化合物の具体例としては、ポリエチレングリコールジアクリレート、ポリエチレングリコールジメタクリレート、エチレングリコールジアクリレート、エチレングリコールジメタクリレート、ジエチレングリコールジアクリレート、ジエチレングリコールジメタクリレート、ジプロピレングリコールジアクリレート、ジプロピレングリコールジメタクリレート、ポリプロピレングリコールジアクリレート、ポリプロピレングリコールジメタクリレートなどが挙げられるがこれらに限定されない。 (C-2) Specific examples of compounds in which acrylic groups or methacrylic groups are bonded to both ends of a structure having an oxyethylene group or oxypropylene group include polyethylene glycol diacrylate, polyethylene glycol dimethacrylate, ethylene glycol diacrylate, and ethylene. Examples include, but are not limited to, glycol dimethacrylate, diethylene glycol diacrylate, diethylene glycol dimethacrylate, dipropylene glycol diacrylate, dipropylene glycol dimethacrylate, polypropylene glycol diacrylate, polypropylene glycol dimethacrylate, and the like.
　（Ａ）第１３族元素化合物と（Ｂ）水酸基含有高分子との錯体のさらなる安定化の観点から、（Ｃ－２）は（Ｃ－１）１００モル％に対し、０．５～２０モル％であることが好ましく、１～１０モル％であることがより好ましい。 From the viewpoint of further stabilization of the complex of (A) Group 13 element compound and (B) hydroxyl group-containing polymer, (C-2) is 0.5 to 20 mol per 100 mol% of (C-1). %, more preferably 1 to 10 mol %.
　これらについて、アゾビスイソブチロニトリルなどのラジカル重合開始剤を用いて良溶媒中で６０～１００℃で重合し、得られた架橋体を濾過などの手法で単離して粉砕して微粒子化することで、（Ｃ）架橋された重合体からなる有機フィラーを得ることができる。あるいは貧溶媒中で６０～１００℃で懸濁重合し、得られた微粒子を単離するなどして得られるが、これら方法に限定されない。 These are polymerized at 60 to 100° C. in a good solvent using a radical polymerization initiator such as azobisisobutyronitrile, and the resulting crosslinked product is isolated by a method such as filtration and pulverized into fine particles. Thus, (C) an organic filler composed of a crosslinked polymer can be obtained. Alternatively, it can be obtained by suspension polymerization at 60 to 100° C. in a poor solvent and isolating the resulting fine particles, but is not limited to these methods.
　本発明のｐ型不純物拡散組成物は、（Ｂ）水酸基含有高分子を１００質量％としたときに、（Ｃ）架橋された重合体からなる有機フィラーを１００～１０００質量％含むことが好ましい。好ましくは２００～７００質量％である。 The p-type impurity diffusion composition of the present invention preferably contains 100 to 1000% by mass of (C) an organic filler composed of a crosslinked polymer when (B) the hydroxyl group-containing polymer is 100% by mass. It is preferably 200 to 700% by mass.
　（溶媒）
　本発明のｐ型不純物拡散組成物は、さらに溶媒を含むことが好ましい。ここで、溶媒とは常圧、２３℃において液体で（Ｂ）水酸基含有高分子を溶解し、（Ｃ）架橋された重合体からなる有機フィラーを分散することが可能なものを指す。溶媒の含有量は、組成物全体１００質量％中に１０～９０質量％であることが好ましく、２０～７０質量％であることがより好ましい。 (solvent)
The p-type impurity diffusion composition of the present invention preferably further contains a solvent. Here, the solvent refers to a solvent that is liquid at normal pressure and 23° C. and capable of dissolving (B) the hydroxyl group-containing polymer and dispersing (C) the organic filler composed of the crosslinked polymer. The solvent content is preferably 10 to 90% by mass, more preferably 20 to 70% by mass, based on 100% by mass of the entire composition.
　溶媒は特に制限なく用いることができるが、スクリーン印刷法やスピンコート印刷法などを利用する場合の印刷性をより向上させる観点から、沸点が１００℃以上の溶媒であることが好ましい。沸点が１００℃以上であると、例えば、スクリーン印刷法で用いられる印刷版にｐ型不純物拡散組成物を印刷した際に、ｐ型不純物拡散組成物が印刷版上で乾燥し固着することを抑制できる。好ましくは１６０℃以上、より好ましくは１８０℃以上である。 The solvent can be used without any particular limitation, but from the viewpoint of further improving the printability when using a screen printing method, a spin coat printing method, or the like, a solvent with a boiling point of 100°C or higher is preferable. If the boiling point is 100° C. or higher, for example, when the p-type impurity diffusion composition is printed on a printing plate used in screen printing, the p-type impurity diffusion composition is prevented from drying and sticking on the printing plate. can. It is preferably 160° C. or higher, more preferably 180° C. or higher.
　沸点が１００℃以上の溶媒の含有量は、溶媒の全量に対して２０重量％以上であることが好ましい。沸点１００℃以上の溶媒としては、乳酸エチル（沸点１５５℃）、ジアセトンアルコール（沸点１６９℃）、プロピレングリコールモノメチルエーテルアセテート（沸点１４５℃）、プロピレングリコールモノメチルエーテル（沸点１２０℃）、３－メトキシ－３－メチル－１－ブタノール（沸点１７４℃）、γ－ブチロラクトン（沸点２０４℃）、Ｎ－メチル－２－ピロリドン（沸点２０４℃）、Ｎ、Ｎ－ジメチルイミダゾリジノン（沸点２２６℃）、テルピネオール（沸点２１９℃）、１，３－プロパンジオール（２１４℃）を例示することができる。 The content of the solvent with a boiling point of 100°C or higher is preferably 20% by weight or more with respect to the total amount of the solvent. Examples of solvents having a boiling point of 100°C or higher include ethyl lactate (boiling point 155°C), diacetone alcohol (boiling point 169°C), propylene glycol monomethyl ether acetate (boiling point 145°C), propylene glycol monomethyl ether (boiling point 120°C), and 3-methoxy. -3-methyl-1-butanol (boiling point 174°C), γ-butyrolactone (boiling point 204°C), N-methyl-2-pyrrolidone (boiling point 204°C), N,N-dimethylimidazolidinone (boiling point 226°C), Examples include terpineol (boiling point 219°C) and 1,3-propanediol (214°C).
　また、溶媒は１，３－プロパンジオールを含有することがより好ましい。１，３－プロパンジオールが含まれることで、（Ａ）第１３族元素化合物と（Ｂ）水酸基含有高分子の錯体の安定性がより向上する。その結果、既に錯体を形成した（Ａ）第１３族元素化合物と（Ｂ）水酸基含有高分子がさらに反応して３次元的な錯体を形成するといった事象が抑制されやすくなり、ｐ型不純物拡散組成物の経時的な増粘や、増粘に起因するゲル状異物の発生が抑制されやすくなる。これにより、抵抗値の均一性向上、パターンの細線化に加え、室温でｐ型不純物拡散組成物を放置しても抵抗値の均一性が損なわれることがなく、安定して使用することができる。 Further, the solvent more preferably contains 1,3-propanediol. Containing 1,3-propanediol further improves the stability of the complex of (A) the Group 13 element compound and (B) the hydroxyl group-containing polymer. As a result, the phenomenon in which (A) the group 13 element compound and (B) the hydroxyl group-containing polymer that have already formed a complex further react to form a three-dimensional complex is easily suppressed, and the p-type impurity diffusion composition It becomes easy to suppress the increase in the viscosity of the substance over time and the generation of gel-like foreign matter due to the increase in viscosity. As a result, in addition to improving the uniformity of the resistance value and thinning the pattern, even if the p-type impurity diffusion composition is left at room temperature, the uniformity of the resistance value is not impaired and it can be used stably. .
　（チクソ剤）
　本発明のｐ型不純物拡散組成物は、印刷性向上の点からパターンの細線化を損なわず、残留無機成分の影響がない範囲で（Ｃ）架橋された重合体からなる有機フィラーに加えて、さらにチクソ剤を含有してもよい。 (thixotropic agent)
The p-type impurity diffusion composition of the present invention does not impair the thinning of the pattern from the viewpoint of improving printability and is within a range that is not affected by the residual inorganic component (C) In addition to the organic filler made of a crosslinked polymer, Furthermore, it may contain a thixotropic agent.
　具体的にはセルロース誘導体、アルギン酸ナトリウム、多糖類、ベントナイト、モンモリロン石、酸化ケイ素の微粒子（微粒子酸化ケイ素）、コロイダルアルミナ、炭酸カルシウムなどを例示できる。組成物中の他成分との相溶性や残渣低減の点から、酸化ケイ素の微粒子が好ましい。 Specific examples include cellulose derivatives, sodium alginate, polysaccharides, bentonite, montmorillonite, fine particles of silicon oxide (fine particles of silicon oxide), colloidal alumina, and calcium carbonate. Fine particles of silicon oxide are preferred from the viewpoint of compatibility with other components in the composition and reduction of residue.
　本発明のｐ型不純物拡散組成物の粘度に制限はなく、印刷法、膜厚に応じて適宜変更することができる。ここで例えば好ましい印刷形態の一つであるスクリーン印刷方式の場合、拡散組成物の粘度は５，０００ｍＰａ・ｓ以上であることが好ましい。印刷パターンのにじみを抑制し良好なパターンを得ることができるからである。さらに好ましい粘度は１０，０００ｍＰａ・ｓ以上である。上限は特にないが保存安定性や取り扱い性の観点から１００，０００ｍＰａ・ｓ以下が好ましい。 The viscosity of the p-type impurity diffusion composition of the present invention is not limited, and can be appropriately changed according to the printing method and film thickness. Here, for example, in the case of screen printing, which is one of the preferred printing modes, the viscosity of the diffusion composition is preferably 5,000 mPa·s or more. This is because it is possible to suppress bleeding of the printed pattern and obtain a good pattern. A more preferable viscosity is 10,000 mPa·s or more. Although there is no particular upper limit, it is preferably 100,000 mPa·s or less from the viewpoint of storage stability and handleability.
　ここで、粘度は、１，０００ｍＰａ・ｓ未満の場合は、ＪＩＳ　Ｚ　８８０３（１９９１）「溶液粘度－測定方法」に基づきＥ型デジタル粘度計を用いて回転数２０ｒｐｍで測定された値であり、１，０００ｍＰａ・ｓ以上の場合は、ＪＩＳ　Ｚ　８８０３（１９９１）「溶液粘度－測定方法」に基づきＢ型デジタル粘度計を用いて回転数２０ｒｐｍで測定された値である。 Here, when the viscosity is less than 1,000 mPa s, it is a value measured at a rotation speed of 20 rpm using an E-type digital viscometer based on JIS Z 8803 (1991) "Solution viscosity-measurement method", In the case of 1,000 mPa·s or more, it is a value measured at a rotational speed of 20 rpm using a B-type digital viscometer based on JIS Z 8803 (1991) "Solution viscosity-measurement method".
　（界面活性剤）
　本発明のｐ型不純物拡散組成物は、界面活性剤を含有してもよい。界面活性剤を含有することで、塗布ムラが改善し、より均一な塗布膜が得られる。界面活性剤としてはフッ素系界面活性剤や、シリコーン系界面活性剤が好ましく用いられる。界面活性剤の含有量は、含有する場合、ｐ型不純物拡散組成物中０．０００１～１重量％とするのが好ましい。 (Surfactant)
The p-type impurity diffusion composition of the present invention may contain a surfactant. By containing a surfactant, coating unevenness is improved, and a more uniform coating film can be obtained. As the surfactant, fluorine-based surfactants and silicone-based surfactants are preferably used. The content of the surfactant, if included, is preferably 0.0001 to 1% by weight in the p-type impurity diffusion composition.
　（固形分濃度）
　本発明のｐ型不純物拡散組成物は、固形分濃度としては特に制限はないが、１質量％以上９０質量％以下が好ましい範囲である。本濃度範囲よりも低いと塗布膜厚が薄くなりすぎ所望のドーピング性、マスク性を得にくい場合がある。また、本濃度範囲よりも高いと保存安定性が低下する場合がある。 (Solid content concentration)
The solid content concentration of the p-type impurity diffusion composition of the present invention is not particularly limited, but is preferably in the range of 1% by mass or more and 90% by mass or less. If the concentration is lower than this range, the coating film thickness becomes too thin, and it may be difficult to obtain the desired doping properties and masking properties. Moreover, if the concentration is higher than this range, the storage stability may be lowered.
　本発明のｐ型不純物拡散組成物は、太陽電池などの光起電力素子や、半導体表面に不純物拡散領域をパターン形成する半導体デバイス、例えば、トランジスターアレイやダイオードアレイ、フォトダイオードアレイ、トランスデューサーなどにも展開することができる。 The p-type impurity diffusion composition of the present invention is used in photovoltaic elements such as solar cells, and semiconductor devices in which impurity diffusion regions are patterned on the semiconductor surface, such as transistor arrays, diode arrays, photodiode arrays, and transducers. can also be expanded.
　＜太陽電池の製造方法＞
　本発明の太陽電池の製造方法は、２水準以上の異なる不純物濃度で不純物拡散層を形成する工程を含む太陽電池の製造方法であって、
少なくとも１水準以上の不純物拡散層形成は本発明のｐ型不純物拡散組成物を半導体基板に塗布して部分的に不純物拡散組成物膜（ａ）を形成する工程と、
得られた不純物拡散組成物膜（ａ）を加熱して不純物を半導体基板に拡散させて不純物拡散層（ｂ）を形成する工程とを含む。ここでいう異なる不純物濃度とは、不純物濃度差で１×１０１７ａｔｏｍｓ／ｃｍ３以上であり、不純物拡散層を形成した部分の基板表面のシート抵抗値の差が１０Ω／□以上であることを指す。以下、本実施形態について詳述する。 <Method for manufacturing solar cell>
A solar cell manufacturing method of the present invention includes a step of forming an impurity diffusion layer with two or more levels of different impurity concentrations,
Formation of at least one or more levels of impurity diffusion layer is a step of applying the p-type impurity diffusion composition of the present invention to a semiconductor substrate to partially form an impurity diffusion composition film (a);
heating the obtained impurity-diffused composition film (a) to diffuse impurities into the semiconductor substrate to form an impurity-diffused layer (b). The term "different impurity concentrations" as used herein means that the difference in impurity concentration is 1×10 17 atoms/cm 3 or more, and the difference in sheet resistance of the portion of the substrate surface where the impurity diffusion layer is formed is 10Ω/□ or more. Point. The present embodiment will be described in detail below.
　まず、図１（ｉ）に示すように、半導体基板１の上に本発明のｐ型不純物拡散組成物を部分的に塗布し、ｐ型不純物拡散組成物膜（ａ）のパターン２を形成する。 First, as shown in FIG. 1(i), a semiconductor substrate 1 is partially coated with the p-type impurity diffusion composition of the present invention to form a pattern 2 of the p-type impurity diffusion composition film (a). .
　半導体基板としては、例えば不純物濃度が１０１５～１０１６ａｔｏｍｓ／ｃｍ３であるｎ型単結晶シリコン、多結晶シリコン、およびゲルマニウム、炭素などのような他の元素が混合されている結晶シリコン基板が挙げられる。ｐ型単結晶シリコンやシリコン以外の半導体を用いることも可能である。 Examples of semiconductor substrates include n-type single-crystal silicon, polycrystalline silicon, and crystalline silicon substrates mixed with other elements such as germanium and carbon, each having an impurity concentration of 10 15 to 10 16 atoms/cm 3 . mentioned. It is also possible to use p-type single crystal silicon or a semiconductor other than silicon.
　半導体基板は、厚さが５０～３００μｍ、外形が一辺１００～２５０ｍｍの概略四角形であることが好ましい。また、スライスダメージや自然酸化膜を除去するために、フッ酸溶液やアルカリ溶液などで半導体基板表面をエッチングしておくことが好ましい。この際、半導体基板の表面には典型的な幅が４０～１００μｍ、深さ３～４μｍ程度の無数の凹凸テクスチャー形状が形成される。 It is preferable that the semiconductor substrate has a thickness of 50 to 300 μm and an outline of a substantially square shape with a side of 100 to 250 mm. In order to remove slice damage and natural oxide films, it is preferable to etch the surface of the semiconductor substrate with a hydrofluoric acid solution, an alkaline solution, or the like. At this time, the surface of the semiconductor substrate is formed with a large number of uneven texture shapes having a typical width of about 40 to 100 μm and a depth of about 3 to 4 μm.
　２水準以上の異なる不純物濃度で不純物拡散層を形成する工程については、少なくとも１水準以上の不純物拡散層形成が本発明のｐ型不純物拡散組成物を半導体基板に塗布して部分的にｐ型不純物拡散組成物膜（ａ）を形成する工程とそれを加熱して不純物を半導体基板に拡散させて不純物拡散層（ｂ）を形成する工程を含む。 In the step of forming impurity diffusion layers with different impurity concentrations of two or more levels, at least one level or more of impurity diffusion layers are formed by applying the p-type impurity diffusion composition of the present invention to a semiconductor substrate and partially removing p-type impurities. It includes a step of forming a diffusion composition film (a) and a step of heating it to diffuse impurities into a semiconductor substrate to form an impurity diffusion layer (b).
　ｐ型不純物拡散組成物の塗布方法としては、例えばスピンコート法、スクリーン印刷法、インクジェット印刷法、スリット塗布法、スプレー塗布法、凸版印刷法、凹版印刷法などが挙げられる。 Examples of methods for applying the p-type impurity diffusion composition include spin coating, screen printing, inkjet printing, slit coating, spray coating, letterpress printing, and intaglio printing.
　これらの方法でｐ型不純物拡散組成物を塗布後、ｐ型不純物拡散組成物が塗布された半導体基板１をホットプレート、オーブンなどで、５０～３００℃の範囲で３０秒～３０分間乾燥することで脱溶媒し、ｐ型不純物拡散組成物膜（ａ）のパターン２を形成することが好ましい。 After applying the p-type impurity diffusion composition by these methods, the semiconductor substrate 1 coated with the p-type impurity diffusion composition is dried with a hot plate, an oven, or the like at a temperature in the range of 50 to 300° C. for 30 seconds to 30 minutes. to form a pattern 2 of the p-type impurity diffusion composition film (a).
　乾燥後のｐ型不純物拡散組成物膜（ａ）の膜厚は、不純物の拡散性の観点から１００ｎｍ以上が好ましく、エッチング後の残渣の観点から７μｍ以下が好ましい。 The thickness of the p-type impurity diffusion composition film (a) after drying is preferably 100 nm or more from the viewpoint of impurity diffusion, and preferably 7 μm or less from the viewpoint of residue after etching.
　次に、図１（ｉｉ）に示すように、不純物拡散組成物膜（ａ）を加熱して半導体基板１に拡散させ、不純物拡散層（ｂ）を形成する。不純物の拡散方法は、公知の熱拡散方法が利用でき、例えば、電気加熱、赤外加熱、レーザー加熱、マイクロ波加熱などの方法を用いることができる。 Next, as shown in FIG. 1(ii), the impurity diffusion composition film (a) is heated and diffused into the semiconductor substrate 1 to form an impurity diffusion layer (b). As a method for diffusing impurities, a known thermal diffusion method can be used, and for example, methods such as electric heating, infrared heating, laser heating, and microwave heating can be used.
　熱拡散の時間および温度は、不純物濃度、拡散深さなど所望の拡散特性が得られるように適宜設定することができる。例えば、８００℃以上１２００℃以下で１～１２０分間加熱拡散することで、表面不純物濃度が１０１９～１０２１ａｔｏｍｓ／ｃｍ３の拡散層を形成できる。 The time and temperature of thermal diffusion can be appropriately set so as to obtain desired diffusion characteristics such as impurity concentration and diffusion depth. For example, a diffusion layer having a surface impurity concentration of 10 19 to 10 21 atoms/cm 3 can be formed by thermally diffusing at 800° C. or higher and 1200° C. or lower for 1 to 120 minutes.
　拡散雰囲気は、特に限定されず、大気中で行ってもよいし、窒素、アルゴンなどの不活性ガスを用いて雰囲気中の酸素量等を適宜コントロールしてもよい。拡散時間短縮の観点から雰囲気中の酸素濃度を３％以下にすることが好ましい。また、必要に応じて拡散前に２００℃～８５０℃の範囲で焼成し、ｐ型不純物拡散組成物膜（ａ）中の有機物の分解除去を行ってもよい。 The diffusion atmosphere is not particularly limited, and may be carried out in the air, or an inert gas such as nitrogen or argon may be used to appropriately control the amount of oxygen in the atmosphere. From the viewpoint of shortening the diffusion time, it is preferable to set the oxygen concentration in the atmosphere to 3% or less. If necessary, the p-type impurity diffusion composition film (a) may be baked at a temperature of 200° C. to 850° C. before diffusion to decompose and remove organic matter.
　本発明のｐ型不純物拡散組成物を用いた、２水準以上の異なる不純物濃度で不純物拡散層を形成する工程としては、不純物拡散組成物膜（ａ）をマスクとして不純物拡散組成物膜（ａ）未形成部分に不純物を拡散させる工程を含むことが好ましい。具体的には、図１（ｉｉｉ）に示すように、不純物拡散組成物膜（ａ）のパターン２をマスクとしてパターン未形成部分に不純物拡散層（ｂ）と同じ型の導電性で、かつ、不純物濃度の異なる不純物拡散層（ｃ）を形成する。 As a step of forming an impurity diffusion layer with two or more levels of different impurity concentrations using the p-type impurity diffusion composition of the present invention, an impurity diffusion composition film (a) is formed using the impurity diffusion composition film (a) as a mask. It is preferable to include a step of diffusing impurities into the unformed portion. Specifically, as shown in FIG. 1(iii), the pattern 2 of the impurity diffusion composition film (a) is used as a mask, and the non-patterned portion has the same conductivity as the impurity diffusion layer (b), and An impurity diffusion layer (c) having a different impurity concentration is formed.
　不純物拡散組成物膜（ａ）をマスクとして不純物拡散組成物膜（ａ）未形成部分に不純物を拡散させる工程（不純物拡散層（ｃ）を形成する工程）は、不純物拡散組成物膜（ａ）を加熱して不純物を前記半導体基板１に拡散させて不純物拡散層（ｂ）を形成した後に行うことができる。 The step of diffusing impurities into a portion where the impurity diffusion composition film (a) is not formed using the impurity diffusion composition film (a) as a mask (the step of forming the impurity diffusion layer (c)) includes: is heated to diffuse impurities into the semiconductor substrate 1 to form an impurity diffusion layer (b).
　不純物拡散組成物膜（ａ）未形成部分に不純物を拡散させる方法の具体例としては、不純物拡散組成物膜（ａ）のパターン２付き半導体基板１に不純物拡散成分を含むイオンを注入後アニーリングする方法、不純物拡散組成物膜（ａ）のパターン２付き半導体基板１を不純物拡散成分を含む雰囲気中で加熱する方法、不純物拡散組成物膜（ａ）のパターン２付き半導体基板１に同じ型の導電性で、かつ、不純物濃度の異なる別の不純物拡散組成物を不純物拡散組成物膜（ａ）未形成部分に塗布し、不純物拡散組成物膜を形成させた後、電気加熱、赤外加熱、レーザー加熱、マイクロ波加熱を行う方法等が挙げられる。 As a specific example of the method of diffusing impurities into the portion where the impurity diffusion composition film (a) is not formed, ions containing impurity diffusion components are implanted into the semiconductor substrate 1 with the pattern 2 of the impurity diffusion composition film (a) and then annealed. a method of heating the semiconductor substrate 1 with the pattern 2 of the impurity diffusion composition film (a) in an atmosphere containing an impurity diffusion component; Another impurity diffusion composition having a different impurity concentration and having a different impurity concentration is applied to the portion where the impurity diffusion composition film (a) is not formed to form an impurity diffusion composition film, followed by electric heating, infrared heating, laser A method of heating, microwave heating, and the like can be mentioned.
　このうち、好ましくは不純物拡散組成物膜（ａ）未形成部分に不純物を拡散させる工程が、不純物拡散成分を含む雰囲気中で加熱する工程である。 Among these, the step of diffusing the impurity into the portion where the impurity diffusion composition film (a) is not formed is preferably the step of heating in an atmosphere containing the impurity diffusion component.
　不純物拡散成分を含む雰囲気中で加熱する場合は、例えばｐ型の場合は臭化ホウ素（ＢＢｒ３）、ｎ型の場合はオキシ塩化リン（ＰＯＣｌ３）をバブリングして、Ｎ２で流すことによって不純物拡散成分を含む雰囲気とした中で不純物拡散組成物膜（ａ）のパターン２付き半導体基板１を８００～１０００℃で加熱し、不純物拡散層（ｃ）を形成することができる。ガス圧、加熱条件設定により、不純物拡散層（ｃ）の不純物濃度を不純物拡散層（ｂ）の不純物濃度よりも高く設定することも、低く設定することも可能となる。 When heating in an atmosphere containing an impurity diffusion component, for example, boron bromide (BBr 3 ) for p-type and phosphorus oxychloride (POCl 3 ) for n-type are bubbled and N 2 is flowed. The impurity diffusion layer (c) can be formed by heating the semiconductor substrate 1 with the pattern 2 of the impurity diffusion composition film (a) at 800 to 1000° C. in an atmosphere containing an impurity diffusion component. The impurity concentration of the impurity diffusion layer (c) can be set higher or lower than the impurity concentration of the impurity diffusion layer (b) by adjusting the gas pressure and heating conditions.
　また、図１（ｉ）に示すように、半導体基板１の上に本発明のｐ型不純物拡散組成物を部分的に塗布し、不純物拡散組成物膜（ａ）のパターン２を形成した後、図１（ｉｉ）の拡散工程を行わずに、図１（ｉｉｉ）の加熱炉に投入し、不純物拡散成分を含む雰囲気中での加熱で不純物拡散層（ｂ）、不純物拡散層（ｃ）を同時に形成してもよい。 Further, as shown in FIG. 1(i), after partially applying the p-type impurity diffusion composition of the present invention on a semiconductor substrate 1 to form a pattern 2 of the impurity diffusion composition film (a), Without performing the diffusion step of FIG. 1(ii), the substrate is put into the heating furnace of FIG. They may be formed at the same time.
　また、図１（ｉ）に示すように、半導体基板１の上に本発明のｐ型不純物拡散組成物を部分的に塗布し、不純物拡散組成物膜（ａ）のパターン２を形成した後、図１（ｉｉ）の拡散工程を行わずに、図１（ｉｉｉ）の加熱炉に投入し、まずは不活性ガスのみで加熱して不純物拡散層（ｂ）を形成し、そのまま炉内に不純物拡散成分を含むガスを追加導入して、不活性ガスのみの加熱条件とは異なる条件で加熱することにより不純物拡散層（ｂ）とは不純物濃度の異なる不純物拡散層（ｃ）を１バッチで形成してもよい。 Further, as shown in FIG. 1(i), after partially applying the p-type impurity diffusion composition of the present invention on a semiconductor substrate 1 to form a pattern 2 of the impurity diffusion composition film (a), Without performing the diffusion step of FIG. 1(ii), it is put into the heating furnace of FIG. An impurity diffusion layer (c) having an impurity concentration different from that of the impurity diffusion layer (b) is formed in one batch by additionally introducing a gas containing the component and heating under conditions different from the heating conditions for only the inert gas. may
　また、図１（ｉｉｉ）の工程においては不純物拡散組成物膜（ａ）未形成部分の半導体基板表面の酸化によって、不純物がｐ型の場合はボロンシリケートガラス、不純物がｎ型の場合はリンシリケートガラスといった、酸化シリコンを含む層（ｄ）が形成される。 In the step of FIG. 1(iii), oxidation of the surface of the semiconductor substrate in the portion where the impurity diffusion composition film (a) is not formed causes boron silicate glass when the impurity is p-type, and phosphor silicate glass when the impurity is n-type. A layer (d) comprising silicon oxide, such as glass, is formed.
　＜エッチング工程＞
　こうして２水準以上の異なる不純物濃度で不純物拡散層を形成する工程後は図１（ｉｖ）、に示すように、不純物拡散組成物膜（ａ）のパターン２や表面に形成された酸化シリコンを含む層（ｄ）を除去することが好ましい。 <Etching process>
After the step of forming impurity diffusion layers with different impurity concentrations of two or more levels in this way, as shown in FIG. It is preferred to remove layer (d).
　不純物拡散組成物膜（ａ）のパターン２、および、酸化シリコンを含む層（ｄ）の除去については公知のエッチング法により除去することができる。エッチングに用いる材料としては、特に限定されないが、例えばエッチング成分としてフッ化水素、アンモニウム、リン酸、硫酸、硝酸のうち少なくとも１種類を含み、それ以外の成分として水や有機溶剤などを含むものが好ましい。 The pattern 2 of the impurity diffusion composition film (a) and the layer (d) containing silicon oxide can be removed by a known etching method. The material used for etching is not particularly limited, but includes, for example, at least one of hydrogen fluoride, ammonium, phosphoric acid, sulfuric acid, and nitric acid as an etching component, and water, an organic solvent, etc. as other components. preferable.
　＜裏面形成工程＞
　本発明の太陽電池の製造方法は、裏面形成工程を含んでいてもよい。
例えば、基板表面に２水準以上の異なる不純物濃度でｐ型不純物拡散層を形成して裏面にｎ型不純物拡散層を形成する場合、表面にｎ型の不純物が回り込まないよう、表面をＳｉＯ２膜などで保護する。保護効果を得るための好ましい膜厚については１００～１０００ｎｍであり、基盤表面のｐ型拡散層への影響を抑えるため、低温で成膜速度の速いプラズマＣＶＤで形成するのが好ましい。より具体的には、混合ガス流量比ＳｉＨ４／Ｎ２Ｏが０．０１～５．０、反応室の圧力が０．１～４Ｔｏｒｒ、成膜時の温度が３００℃～５５０℃の条件下で形成される。 <Back surface forming process>
The method for manufacturing a solar cell of the present invention may include a back surface forming step.
For example, when forming a p-type impurity diffusion layer with two or more levels of different impurity concentrations on the substrate surface and forming an n-type impurity diffusion layer on the back surface, the surface is covered with a SiO 2 film so as to prevent n-type impurities from entering the surface. etc. to protect. A preferable film thickness for obtaining a protective effect is 100 to 1000 nm, and in order to suppress the influence on the p-type diffusion layer on the substrate surface, it is preferably formed by plasma CVD with a high deposition rate at a low temperature. More specifically, the mixed gas flow rate ratio SiH 4 /N 2 O is 0.01 to 5.0, the pressure in the reaction chamber is 0.1 to 4 Torr, and the temperature during film formation is 300° C. to 550° C. formed by
　その後、裏面にオキシ塩化リン（ＰＯＣｌ３）をバブリングして、Ｎ２で流すことによって不純物拡散成分を含む雰囲気とした中で半導体基板を８００～９００℃で加熱する。この時、基板裏面にｎ型の不純物拡散層が形成され、同時に酸化によってリンシリケートガラス層といった、酸化シリコンを含む層が裏面の最外部に形成される。 Then, the semiconductor substrate is heated at 800 to 900° C. in an atmosphere containing impurity diffusion components by bubbling phosphorus oxychloride (POCl 3 ) to the rear surface and flowing N 2 . At this time, an n-type impurity diffusion layer is formed on the back surface of the substrate, and at the same time, a layer containing silicon oxide, such as a phosphosilicate glass layer, is formed on the outermost portion of the back surface by oxidation.
　さらに、基板表面の無機膜、裏面の酸化シリコンを含む層をエッチングによって除去する。好ましいエッチングの具体例については２水準以上の異なる不純物濃度で不純物拡散層を形成する際の具体例と同じである。 Furthermore, the inorganic film on the substrate surface and the layer containing silicon oxide on the back surface are removed by etching. Specific examples of preferred etching are the same as those for forming impurity diffusion layers with two or more levels of different impurity concentrations.
　＜パッシベーション工程＞
　本発明の太陽電池の製造方法は、エッチング工程後、裏面形成工程がある場合はその後に、表面再結合を抑制し光反射を防止するためのパッシベーション膜を半導体基板の表面と裏面に設けることが好ましい。例えば、ｐ型拡散層のパッシベーション膜としては７００℃以上の高温酸素雰囲気での熱処理で得られるＳｉＯ２と、この膜を保護するために、シリコン窒化膜を設けてもよい。またＳｉＮｘ膜だけ形成してもよい。この場合、ＳｉＨ４とＮＨ３との混合ガスを原料とするプラズマＣＶＤ法により形成することができる。このとき、水素が結晶中に拡散し、ケイ素原子の結合に寄与しない軌道、即ちダングリングボンドと水素とが結合し、欠陥を不活性化（水素パッシベーション）する。より具体的には、混合ガス流量比ＮＨ３／ＳｉＨ４が０．０５～５．０、反応室の圧力が０．１～４Ｔｏｒｒ、成膜時の温度が３００℃～５５０℃の条件下で形成される。 <Passivation process>
In the method for manufacturing a solar cell of the present invention, passivation films for suppressing surface recombination and preventing light reflection may be provided on the front and back surfaces of the semiconductor substrate after the etching step, if there is a back surface forming step. preferable. For example, as a passivation film for the p-type diffusion layer, SiO 2 obtained by heat treatment in a high-temperature oxygen atmosphere at 700° C. or higher and a silicon nitride film for protecting this film may be provided. Alternatively, only the SiNx film may be formed. In this case, it can be formed by a plasma CVD method using a mixed gas of SiH 4 and NH 3 as a raw material. At this time, hydrogen diffuses into the crystal, and orbitals that do not contribute to the bonding of silicon atoms, ie, dangling bonds, bond with hydrogen to deactivate defects (hydrogen passivation). More specifically, under the conditions that the mixed gas flow rate ratio NH 3 /SiH 4 is 0.05 to 5.0, the pressure in the reaction chamber is 0.1 to 4 Torr, and the temperature during film formation is 300° C. to 550° C. It is formed.
　＜電極形成工程＞
　ついでパッシベーション膜の上から２水準の不純物拡散層のうち、高濃度の不純物拡散層上にくるよう金属ペーストをスクリーン印刷法で印刷し、乾燥させ、電極を形成する。電極用金属ペーストは、金属粒子とガラス粒子とを必須成分とし、必要に応じて樹脂バインダ、その他の添加剤等を含む。このとき使用する金属粒子についてはＡｇ、Ａｌが好ましく用いられる。 <Electrode formation process>
Next, from above the passivation film, a metal paste is printed by a screen printing method so as to be on the high-concentration impurity diffusion layer among the two levels of impurity diffusion layers, and dried to form an electrode. The metal paste for electrodes contains metal particles and glass particles as essential components, and if necessary, a resin binder, other additives, and the like. Ag and Al are preferably used as the metal particles used at this time.
　＜電極焼成工程＞
　ついで電極を熱処理（焼成）して、太陽電池を完成させる。６００℃～９００℃の範囲で数秒～数分間熱処理（焼成）すると、受光面側では電極用金属ペーストに含まれるガラス粒子によって絶縁膜である反射防止膜が溶融し、更にシリコン表面も一部溶融して、ペースト中の金属粒子（例えば銀粒子）が半導体基板と接触部を形成し凝固する。これにより、形成した受光面電極と半導体基板とが導通される。これはファイヤースルーと称されている。 <Electrode baking process>
The electrodes are then heat treated (fired) to complete the solar cell. When heat-treated (fired) in the range of 600° C. to 900° C. for several seconds to several minutes, the glass particles contained in the electrode metal paste melt the antireflection film, which is an insulating film, on the light-receiving surface side, and the silicon surface is also partially melted. Then, metal particles (for example, silver particles) in the paste form contact portions with the semiconductor substrate and solidify. As a result, the formed light-receiving surface electrode and the semiconductor substrate are electrically connected. This is called fire-through.
　受光面電極は、一般に、バスバー電極、及び該バスバー電極と交差しているフィンガ電極で構成される。このような受光面電極は、上述の金属ペーストのスクリーン印刷、又は電極材料のメッキ、高真空中における電子ビーム加熱による電極材料の蒸着等の手段により形成することができる。バスバー電極及びフィンガ電極は、公知の方法により形成することができる。 The light-receiving surface electrodes are generally composed of busbar electrodes and finger electrodes intersecting the busbar electrodes. Such a light-receiving surface electrode can be formed by means such as screen printing of the metal paste described above, plating of an electrode material, vapor deposition of an electrode material by electron beam heating in a high vacuum, or the like. The busbar electrodes and finger electrodes can be formed by a known method.
　本発明の太陽電池の製造方法は、上述の実施形態に限定されるものではなく、当業者の知識に基づいて各種の設計変更などの変形を加えることも可能であり、そのような変形が加えられた実施形態も本発明の範囲に含まれるものである。 The method for manufacturing a solar cell of the present invention is not limited to the above-described embodiments, and modifications such as various design changes can be made based on the knowledge of those skilled in the art. Such embodiments are also included in the scope of the present invention.
　以下、実施例を挙げて、本発明をさらに具体的に説明するが、本発明はこれら実施例に限定されない。 The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.
　（１）基板の残渣評価
　基板としては、一辺１５６ｍｍのｎ型単結晶シリコンからなる半導体基板（シリコンウェハー）を用意し、スライスダメージや自然酸化物を除去するために、両表面をアルカリエッチングした。この際、半導体基板の両面には典型的な幅が４０～１００μｍ、深さ３～４μｍ程度の無数の凹凸（テクスチャー）が形成され、これを塗布基板とした。 (1) Substrate Residue Evaluation As a substrate, a semiconductor substrate (silicon wafer) made of n-type single crystal silicon with a side of 156 mm was prepared, and alkali etching was performed on both surfaces in order to remove slice damage and natural oxide. At this time, countless irregularities (textures) typically having a width of 40 to 100 μm and a depth of 3 to 4 μm were formed on both surfaces of the semiconductor substrate, and this was used as a coated substrate.
　スクリーン印刷機（マイクロテック（株）ＴＭ－７５０型）を用い、スクリーンマスクとしては基板と同じ大きさの開口部を形成したもの（ＳＵＳ（株）製、４００メッシュ、線径２３μｍ）を用い、基板全面にスクリーン印刷を行った。 Using a screen printer (Microtech Co., Ltd. TM-750 type), using a screen mask with openings of the same size as the substrate (manufactured by SUS Co., Ltd., 400 mesh, wire diameter 23 μm), Screen printing was performed on the entire surface of the substrate.
　ｐ型不純物拡散組成物１～９をスクリーン印刷後、空気中にて基板を２００℃で１０分間加熱することで、厚さ約３．５μｍの不純物拡散組成物膜を形成した。 After screen-printing the p-type impurity diffusion compositions 1 to 9, the substrate was heated at 200° C. for 10 minutes in air to form an impurity diffusion composition film having a thickness of about 3.5 μm.
　続いて各基板を電気炉内に配置し、窒素：酸素＝９９：１（体積比）の雰囲気下、９５０℃で６０分間維持して不純物を熱拡散させた。 Subsequently, each substrate was placed in an electric furnace and maintained at 950° C. for 60 minutes in an atmosphere of nitrogen:oxygen=99:1 (volume ratio) to thermally diffuse impurities.
　熱拡散後の各基板を、５重量％のフッ酸水溶液に２３℃で１分間浸浸させて、不純物拡散組成物膜を除去した。除去後、基板を純水に浸漬させて洗浄し、表面の目視により残渣の有無を観察した。１分浸漬後目視で表面付着物が確認できるがウエスでこすることで除去できるものをＣ、３０秒を上回り１分以内で表面付着物が目視確認できなくなったものをＢ、３０秒以内で表面付着物が目視確認できなくなったものをＡとし、Ｂ以上を合格とした。 After thermal diffusion, each substrate was immersed in a 5% by weight hydrofluoric acid aqueous solution at 23° C. for 1 minute to remove the impurity diffusion composition film. After the removal, the substrate was immersed in pure water and washed, and the presence or absence of residue was visually observed on the surface. After immersion for 1 minute, surface deposits can be visually confirmed, but can be removed by rubbing with a waste cloth. When the surface deposits could not be visually confirmed, it was rated as A, and B or higher was rated as acceptable.
　（２）抵抗値評価
　残渣評価に用いた不純物拡散後の基板に対して、ｐ／ｎ判定機を用いてｐ／ｎ判定し、表面抵抗を四探針式表面抵抗測定装置ＲＴ－７０Ｖ　（ナプソン（株）製）を用いて測定した。この測定は正方形の基板の中心から、縦・横に２０ｍｍ間隔で合計１３点のデータについて行い、平均値をシート抵抗値、値のバラツキを抵抗値の均一性として評価した。シート抵抗値は不純物拡散性の指標となるものであり、値が小さいほど不純物拡散量が大きいことを意味する。抵抗値均一性を示す値のバラツキは値が小さいほど良く、平均値に対して上下２０％以内を合格とした。 (2) Resistance value evaluation The substrate after impurity diffusion used for residue evaluation is p/n judged using a p / n judgment machine, and the surface resistance is measured by a four-probe type surface resistance measurement device RT-70V (Napson (manufactured by Co., Ltd.). This measurement was performed on a total of 13 points of data at intervals of 20 mm in the vertical and horizontal directions from the center of the square substrate, and the average value was evaluated as the sheet resistance value, and the variation in the values was evaluated as the uniformity of the resistance value. The sheet resistance value is an index of impurity diffusibility, and a smaller value means a larger amount of impurity diffusion. The smaller the variation in the value indicating the uniformity of the resistance value, the better, and the value within 20% above and below the average value was considered acceptable.
　（３）スクリーン印刷性（最小パターン評価）
　スクリーン印刷により各実施例及び比較例のｐ型不純物拡散組成物をストライプ状にパターニングし、そのストライプ幅精度を確認した。 (3) Screen printability (minimum pattern evaluation)
The p-type impurity diffusion composition of each example and comparative example was patterned into stripes by screen printing, and the stripe width precision was confirmed.
　塗布基板は、残渣評価に用いたものと同じものを用いた。 The same coated substrate as used for residue evaluation was used.
　スクリーン印刷機は残渣評価に用いたものと同じものを用い、スクリーンマスクとしては幅７０μｍ、長さ１３．５ｃｍの開口部が基板の中心線（基板の辺と平行）上に１本、それを挟むようにして平行に１ｃｍ間隔で両外側に３本ずつ、計７本形成したもの（ＳＵＳ（株）製、４００メッシュ、線径２３μｍ）を用い、ストライプ状の平行パターンを７本形成した。 The same screen printer as used for residue evaluation was used, and the screen mask had an opening with a width of 70 μm and a length of 13.5 cm on the center line of the substrate (parallel to the side of the substrate). Seven striped parallel patterns were formed by using 3 strips (400 mesh, wire diameter 23 μm, manufactured by SUS Co., Ltd.), 3 strips on each side of the strip, which were sandwiched in parallel with each other at intervals of 1 cm.
　ｐ型不純物拡散組成物１～９をスクリーン印刷後、空気中にて基板を２００℃で１０分間加熱することで、厚さ約３．５μｍのパターンを形成した。 After screen-printing the p-type impurity diffusion compositions 1 to 9, the substrate was heated at 200° C. for 10 minutes in air to form a pattern with a thickness of about 3.5 μm.
　このとき７０μｍのマスクで印刷されたパターンの幅を顕微鏡（ＭＸ６１Ｌ　オリンパス株式会社製）を用いて実測し、７０μｍのマスクに対してどれくらいパターンが広がったか評価し、１５０μｍ以下を合格とした。 At this time, the width of the pattern printed with the 70 μm mask was actually measured using a microscope (MX61L manufactured by Olympus Corporation), and how much the pattern spread with respect to the 70 μm mask was evaluated.
　（４）キャリア寿命測定
　抵抗値の均一性評価に用いた基板をPhotoconductance Lifetime Tester（WCT-120 SINTON CONSULTING INC.製）に設置し、開放電圧Voc（Voltage Open Circuit）を測定した。Vocが高い程、キャリア寿命が長い特性良好な太陽電池セルと言える。 (4) Carrier Lifetime Measurement The substrate used for evaluating the uniformity of the resistance value was placed in a Photoconductance Lifetime Tester (WCT-120 manufactured by SINTON CONSULTING INC.), and the open circuit voltage Voc (Voltage Open Circuit) was measured. It can be said that the higher the Voc, the longer the carrier life and the better the characteristics of the solar battery cell.
　（５）経時安定性評価
　ｐ型不純物拡散組成物１～９を２５℃で１４日間放置し、放置後に（２）抵抗値の均一性評価を行った。このときも抵抗値の均一性を示す値のバラツキが平均値に対して上下２０％以内を合格とした。 (5) Evaluation of stability over time The p-type impurity diffusion compositions 1 to 9 were left at 25° C. for 14 days, and (2) the uniformity of the resistance value was evaluated after the standing. Also in this case, the variation of the value indicating the uniformity of the resistance value was judged to be within 20% above and below the average value.
　（合成例１）
　＜（Ｃ）架橋された重合体からなる有機フィラーＡの合成＞
　アクリル酸２－ヒドロキシエチル（東京化成工業（株）製）２１．３ｇ、ポリエチレングリコールジアクリレート（Ａ－４００、新中村化学工業（株）製）０．１ｇ、純水５９．１ｇを２５０ｍｌポリプロピレン製容器に仕込んだ。次いで、マグネチックスターラーで撹拌を開始し、１００ｍｌ／分で３０分間窒素置換を行った。次いで、撹拌を継続しながら５０℃まで昇温した。液温を５０℃に安定させた後、開始剤として２，２‘－アゾビス（２－メチルプロピオンアミジン）ジヒドロクロライド（東京化成工業（株）製）の１０質量％水溶液を０．６ｇ添加し重合を開始した。重合反応が進み、ゲルが生成した後、９０℃で３０分間熟成を行い、重合を終了した。得られたゲルを解砕し、１２０℃で２時間乾燥を行うことにより、平均粒子径約３μｍの有機フィラーＡを得た。 (Synthesis example 1)
<(C) Synthesis of organic filler A composed of crosslinked polymer>
21.3 g of 2-hydroxyethyl acrylate (manufactured by Tokyo Chemical Industry Co., Ltd.), 0.1 g of polyethylene glycol diacrylate (A-400, manufactured by Shin-Nakamura Chemical Co., Ltd.), and 59.1 g of pure water in 250 ml of polypropylene packed in a container. Then, stirring was started with a magnetic stirrer, and nitrogen substitution was performed at 100 ml/min for 30 minutes. Then, the temperature was raised to 50°C while stirring was continued. After the liquid temperature was stabilized at 50° C., 0.6 g of a 10% by mass aqueous solution of 2,2′-azobis(2-methylpropionamidine) dihydrochloride (manufactured by Tokyo Chemical Industry Co., Ltd.) was added as an initiator to polymerize. started. After the polymerization reaction proceeded and gel was formed, aging was performed at 90° C. for 30 minutes to complete the polymerization. The obtained gel was pulverized and dried at 120° C. for 2 hours to obtain an organic filler A having an average particle size of about 3 μm.
　（合成例２）
　＜（Ｃ）架橋された重合体からなる有機フィラーＢの合成＞
　市販のビスフェノールＡジグリシジルエーテルタイプのエポキシ樹脂（ｊＥＲ８２８：ジャパンエポキシレジン（株）製、エポキシ当量１８６）１０．０ｇを１００ｃｃ３つ口フラスコにとり、これに界面活性剤（ノイゲンＥＡ－１３７：第一工業製薬（株）製）を０．８ｇ加え、１分間混練した。続いて注射器に入れた６ｃｃの水を１．５ｃｃずつ１分間隔で、攪拌をしながら順次加えた。フラスコ内には乳白色のエマルジョンが得られた。　　　 (Synthesis example 2)
<(C) Synthesis of organic filler B composed of crosslinked polymer>
Take 10.0 g of a commercially available bisphenol A diglycidyl ether type epoxy resin (jER828: manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent 186) in a 100 cc three-necked flask, add a surfactant (Noigen EA-137: Daiichi Kogyo Pharmaceutical Co., Ltd.) was added and kneaded for 1 minute. Subsequently, 1.5 cc of water in a syringe was sequentially added at intervals of 1 minute while stirring. A milky white emulsion was obtained in the flask.
 
　この未硬化エポキシエマルジョンに、０．６当量のピペラジンを８ｃｃの水に溶解した硬化液を加え、ゆるやかに攪拌して均一化した。この液を２５℃で３日間静置放置して、平均粒子径約６μｍの球状フィラーに硬化させた。 
A curing liquid prepared by dissolving 0.6 equivalent of piperazine in 8 cc of water was added to the uncured epoxy emulsion, and the mixture was gently stirred to homogenize. This liquid was allowed to stand at 25° C. for 3 days to cure into a spherical filler having an average particle size of about 6 μm.
　上記濾取したフィラーをナス型フラスコに入れ、アセトニトリル（東京化成工業（株）製）４００ｇを加えて再分散させた。これにコンデンサーを付け５０℃のウォーターバス中で加熱攪拌下、８時間抽出を行うことによりフィラーを精製した。冷却後、吸引濾過し、５０℃で８時間減圧乾燥し有機フィラーＢを得た。 The filler collected by filtration was placed in an eggplant-shaped flask, and 400 g of acetonitrile (manufactured by Tokyo Kasei Kogyo Co., Ltd.) was added to re-disperse. A condenser was attached to this, and extraction was performed for 8 hours in a water bath at 50° C. while heating and stirring to refine the filler. After cooling, the organic filler B was obtained by suction filtration and drying under reduced pressure at 50° C. for 8 hours.
　（合成例３）
　＜（Ｃ）架橋された重合体からなる有機フィラーＣの合成＞
　ビスフェノールＡジグリシジルエーテルタイプのエポキシ樹脂（ｊＥＲ８２８：ジャパンエポキシレジン（株）製、エポキシ当量１８６）１０．０ｇのかわりに、ｊＥＲ８２８　８．０ｇ、ジエチレングリコールジグリシジルエーテル（エポライト１００E：共栄社化学（株）製）２．０ｇを加えた以外は合成例２と同様にして有機フィラーＣを得た。 (Synthesis Example 3)
<(C) Synthesis of organic filler C composed of crosslinked polymer>
Instead of 10.0 g of bisphenol A diglycidyl ether type epoxy resin (jER828: manufactured by Japan Epoxy Resin Co., Ltd., epoxy equivalent 186), 8.0 g of jER828, diethylene glycol diglycidyl ether (Epolite 100E: manufactured by Kyoeisha Chemical Co., Ltd. ) to obtain an organic filler C in the same manner as in Synthesis Example 2, except that 2.0 g was added.
　（合成例４）
　＜架橋されていない重合体からなる有機フィラーＤの合成＞
　セパラブルフラスコの中に、ポリフッ化ビニリデン（シグマ－アルドリッチ（株）製）１．５ｇ、ヒドロキシプロピルセルロース（東京化成工業（株）製）７．５ｇ、アセトン（東京化成工業（株）製）４１．０ｇを加え、５０℃で攪拌を行った。内部が白濁化し、エマルションが形成されていた。引き続き、水１００ｇを０．４１ｇ／分のスピードで加え、全量の水を入れ終わった後に、攪拌したまま室温まで降温させ、得られた懸濁液を、ろ過し、イオン交換水１００ｇで洗浄し、濾別したものを、８０℃で１０時間真空乾燥を行い、粒子径約６μｍの球状有機フィラーＤを得た。 (Synthesis Example 4)
<Synthesis of Organic Filler D Composed of Non-Crosslinked Polymer>
In a separable flask, polyvinylidene fluoride (manufactured by Sigma-Aldrich Co., Ltd.) 1.5 g, hydroxypropyl cellulose (manufactured by Tokyo Chemical Industry Co., Ltd.) 7.5 g, acetone (manufactured by Tokyo Chemical Industry Co., Ltd.) 41 0 g was added and stirring was carried out at 50°C. The inside became cloudy and an emulsion was formed. Subsequently, 100 g of water was added at a rate of 0.41 g/min, and after the total amount of water was added, the temperature was lowered to room temperature while stirring, and the resulting suspension was filtered and washed with 100 g of ion-exchanged water. , and vacuum-dried at 80° C. for 10 hours to obtain a spherical organic filler D having a particle size of about 6 μm.
　（実施例１）
　ホウ酸（富士フイルム和光純薬（株）製）１．５ｇと、ケン化度が８０％のポリビニルアルコール（日本酢ビ・ポバール（株）製）（以下ＰＶＡ（８０）と表す）５．０ｇと、有機フィラーＡ４０．０ｇと、３－メトキシ－３－メチル－１－ブタノール（東京化成（株）製）（以下ＭＭＢと表す）３４．０ｇと、水２０．０ｇを混合し、均一になるように十分撹拌し、ｐ型不純物拡散組成物１を得た。 (Example 1)
1.5 g of boric acid (manufactured by Fujifilm Wako Pure Chemical Industries, Ltd.) and 5.0 g of polyvinyl alcohol (manufactured by Nippon Acetate & Poval Co., Ltd.) with a degree of saponification of 80% (hereinafter referred to as PVA (80)) Then, 40.0 g of organic filler A, 34.0 g of 3-methoxy-3-methyl-1-butanol (manufactured by Tokyo Kasei Co., Ltd.) (hereinafter referred to as MMB), and 20.0 g of water are mixed and uniform. A p-type impurity diffused composition 1 was obtained by sufficiently stirring as above.
　（実施例２）
　有機フィラーＡのかわりに有機フィラーＢを用いた以外は実施例１と同様にしてｐ型不純物拡散組成物２を得た。 (Example 2)
A p-type impurity diffusion composition 2 was obtained in the same manner as in Example 1 except that the organic filler B was used instead of the organic filler A.
　（実施例３）
　有機フィラーＡのかわりに有機フィラーＣを用いた以外は実施例１と同様にしてｐ型不純物拡散組成物３を得た。 (Example 3)
A p-type impurity diffusion composition 3 was obtained in the same manner as in Example 1 except that the organic filler C was used instead of the organic filler A.
　（比較例１）
　有機フィラーＡのかわりに有機フィラーＤを用いた以外は実施例１と同様にしてｐ型不純物拡散組成物４を得た。 (Comparative example 1)
A p-type impurity diffusion composition 4 was obtained in the same manner as in Example 1 except that the organic filler D was used instead of the organic filler A.
　（比較例２）
　有機フィラーＡのかわりにシリカフィラー（ＳＯ－Ｅ２：アドマテックス（株）製）を用いた以外は実施例１と同様にしてｐ型不純物拡散組成物５を得た。 (Comparative example 2)
A p-type impurity diffusion composition 5 was obtained in the same manner as in Example 1 except that a silica filler (SO-E2: manufactured by Admatechs Co., Ltd.) was used instead of the organic filler A.
　（比較例３）
　有機フィラーＡを用いない以外は実施例１と同様にしてｐ型不純物拡散組成物６を得た。 (Comparative Example 3)
A p-type impurity diffusion composition 6 was obtained in the same manner as in Example 1, except that the organic filler A was not used.
　（実施例４）
　ＰＶＡ（８０）５．０ｇのかわりにケン化度が１０％のポリビニルアルコール（日本酢ビ・ポバール（株）製）（以下ＰＶＡ（１０）と表す）１２．５ｇ、ＭＭＢ３４．０ｇと水２０．０ｇのかわりにテルピネオール（東京化成（株）製）（以下ＴＰと表す）２７．０ｇとＭＭＢ１１．０ｇと水１０．０ｇを用いた以外は実施例１と同様にしてｐ型不純物拡散組成物７を得た。 (Example 4)
Instead of 5.0 g of PVA (80), 12.5 g of polyvinyl alcohol having a degree of saponification of 10% (manufactured by Nippon Vinyl Poval Co., Ltd.) (hereinafter referred to as PVA (10)), 34.0 g of MMB and 20.0 g of water. P-type impurity diffusion composition 7 was prepared in the same manner as in Example 1, except that 27.0 g of terpineol (manufactured by Tokyo Kasei Co., Ltd.) (hereinafter referred to as TP), 11.0 g of MMB, and 10.0 g of water were used instead of 0 g. got
　（実施例５）
　ＰＶＡ（１０）１２．５ｇのかわりにケン化度が４９％のポリビニルアルコール（日本酢ビ・ポバール（株）製）（以下ＰＶＡ（４９）と表す）１０．０ｇを用いた以外は実施例４と同様にしてｐ型不純物拡散組成物８を得た。 (Example 5)
Example 4 except that instead of 12.5 g of PVA (10), 10.0 g of polyvinyl alcohol (manufactured by Nippon Acetate & Poval Co., Ltd.) having a degree of saponification of 49% (hereinafter referred to as PVA (49)) was used. A p-type impurity diffusion composition 8 was obtained in the same manner as above.
　（実施例６）
　ＰＶＡ（８０）５．０ｇのかわりにＰＶＡ（４９）１０．０ｇ、ＭＭＢ３４．０ｇと水２０．０ｇのかわりにＴＰ２７．０ｇと１，３－プロパンジオール（以下１，３－ＰＤと表す）１１．０ｇと水１０．０ｇを用いた以外は実施例１と同様にしてｐ型不純物拡散組成物９を得た。 (Example 6)
10.0 g of PVA (49) in place of 5.0 g of PVA (80), 27.0 g of TP in place of 34.0 g of MMB and 20.0 g of water, and 1,3-propanediol (hereinafter referred to as 1,3-PD) 11 A p-type impurity diffusion composition 9 was obtained in the same manner as in Example 1, except that 10.0 g of water and 0.0 g of water were used.
　（実施例７）
　ＰＶＡ（８０）のかわりにポリエチレングリコール４００（東京化成(株)製）を用い、有機フィラーＡのかわりに有機フィラーＢを用いた以外は実施例１と同様にしてｐ型不純物拡散組成物１０を得た。 (Example 7)
A p-type impurity diffusion composition 10 was prepared in the same manner as in Example 1 except that polyethylene glycol 400 (manufactured by Tokyo Kasei Co., Ltd.) was used instead of PVA (80) and organic filler B was used instead of organic filler A. Obtained.
　得られた実施例１～７、比較例１～３のｐ型不純物拡散組成物について、（１）～（５）の評価を行った。評価結果を表２に示す。 Evaluations (1) to (5) were performed on the obtained p-type impurity diffusion compositions of Examples 1 to 7 and Comparative Examples 1 to 3. Table 2 shows the evaluation results.
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000001
Figure JPOXMLDOC01-appb-T000002
Figure JPOXMLDOC01-appb-T000002
１　半導体基板
２　不純物拡散組成物膜（ａ）のパターン
３　不純物拡散成分含有ガス
（ｂ）、（ｃ）不純物拡散層
（ｄ）酸化シリコンを含む層 1 semiconductor substrate 2 impurity diffusion composition film (a) pattern 3 impurity diffusion component containing gas (b), (c) impurity diffusion layer (d) layer containing silicon oxide

Claims (9)

  1. （Ａ）第１３族元素化合物、（Ｂ）水酸基含有高分子および（Ｃ）架橋された重合体からなる有機フィラーを含有するｐ型不純物拡散組成物。 A p-type impurity diffusion composition containing (A) a Group 13 element compound, (B) a hydroxyl group-containing polymer and (C) an organic filler comprising a crosslinked polymer.
  2. 前記（Ｃ）架橋された重合体からなる有機フィラーがオキシエチレン基またはオキシプロピレン基を有する請求項１に記載のｐ型不純物拡散組成物。 2. The p-type impurity diffusion composition according to claim 1, wherein the (C) organic filler comprising a crosslinked polymer has an oxyethylene group or an oxypropylene group.
  3. 前記（Ｃ）架橋された重合体からなる有機フィラーが、
    （Ｃ－１）アクリロイル基、メタクリロイル基から選ばれる少なくとも１つを有する化合物および
    （Ｃ－２）オキシエチレン基またはオキシプロピレン基を有する構造の両末端にアクリロイル基またはメタクリロイル基が結合した化合物
    を共重合した架橋体である請求項２に記載のｐ型不純物拡散組成物。     (C) the organic filler made of a crosslinked polymer,
    (C-1) a compound having at least one selected from an acryloyl group and a methacryloyl group and (C-2) a compound having an acryloyl group or a methacryloyl group attached to both ends of a structure having an oxyethylene group or an oxypropylene group. 3. The p-type impurity diffusion composition according to claim 2, which is a polymerized crosslinked product.
  4. 前記（Ｂ）水酸基含有高分子がポリビニルアルコールである請求項１～３のいずれかに記載のｐ型不純物拡散組成物。 4. The p-type impurity diffusion composition according to any one of claims 1 to 3, wherein the (B) hydroxyl group-containing polymer is polyvinyl alcohol.
  5. 前記ポリビニルアルコールのケン化度が２０モル％以上７０モル％未満である請求項４に記載のｐ型不純物拡散組成物。 The p-type impurity diffusion composition according to claim 4, wherein the polyvinyl alcohol has a saponification degree of 20 mol% or more and less than 70 mol%.
  6. 溶媒として１，３－プロパンジオールを含有する請求項１～３のいずれかに記載のｐ型不純物拡散組成物。 4. The p-type impurity diffusion composition according to any one of claims 1 to 3, containing 1,3-propanediol as a solvent.
  7. ２水準以上の異なる不純物濃度で不純物拡散層を形成する工程を含む太陽電池の製造方法であって、
    少なくとも１水準以上の不純物拡散層形成は請求項１～３のいずれかに記載のｐ型不純物拡散組成物を半導体基板に塗布して部分的に不純物拡散組成物膜（ａ）を形成する工程と、
    得られた不純物拡散組成物膜（ａ）を加熱して不純物を半導体基板に拡散させて不純物拡散層（ｂ）を形成する工程とを含む太陽電池の製造方法。     A method for manufacturing a solar cell, including a step of forming an impurity diffusion layer with two or more levels of different impurity concentrations,
    The step of forming at least one level or more of an impurity diffusion layer is the step of applying the p-type impurity diffusion composition according to any one of claims 1 to 3 to a semiconductor substrate to partially form an impurity diffusion composition film (a). ,
    and a step of heating the obtained impurity-diffused composition film (a) to diffuse impurities into the semiconductor substrate to form an impurity-diffused layer (b).
  8. 不純物拡散組成物膜（ａ）をマスクとして不純物拡散組成物膜（ａ）未形成部分に不純物を拡散させる工程を含む請求項７に記載の太陽電池の製造方法。 8. The method for manufacturing a solar cell according to claim 7, further comprising the step of diffusing impurities into the portion where the impurity diffusion composition film (a) is not formed using the impurity diffusion composition film (a) as a mask.
  9. 不純物拡散組成物膜（ａ）未形成部分に不純物を拡散させる工程が、不純物拡散成分を含む雰囲気中で加熱する工程である請求項８に記載の太陽電池の製造方法。 9. The method of manufacturing a solar cell according to claim 8, wherein the step of diffusing impurities in the portion where the impurity diffusion composition film (a) is not formed is a step of heating in an atmosphere containing an impurity diffusion component.
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