WO2012117877A1 - Solar cell, and method for producing solar cell - Google Patents

Solar cell, and method for producing solar cell Download PDF

Info

Publication number
WO2012117877A1
WO2012117877A1 PCT/JP2012/053925 JP2012053925W WO2012117877A1 WO 2012117877 A1 WO2012117877 A1 WO 2012117877A1 JP 2012053925 W JP2012053925 W JP 2012053925W WO 2012117877 A1 WO2012117877 A1 WO 2012117877A1
Authority
WO
WIPO (PCT)
Prior art keywords
receiving surface
light
surface side
solar cell
film
Prior art date
Application number
PCT/JP2012/053925
Other languages
French (fr)
Japanese (ja)
Inventor
横沢　雄二
博之 赤田
伊坂　隆行
山崎　努
Original Assignee
シャープ株式会社
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by シャープ株式会社 filed Critical シャープ株式会社
Publication of WO2012117877A1 publication Critical patent/WO2012117877A1/en

Links

Images

Classifications

    • 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
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H01L31/02168—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells the coatings being antireflective or having enhancing optical properties for the solar cells
    • 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
    • H01L31/02—Details
    • H01L31/0236—Special surface textures
    • H01L31/02366—Special surface textures of the substrate or of a layer on the substrate, e.g. textured ITO/glass substrate or superstrate, textured polymer layer on glass substrate
    • 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
    • H01L31/04—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 adapted as photovoltaic [PV] conversion devices
    • H01L31/06—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068—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 adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • 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
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells

Definitions

  • the present invention relates to a solar cell and a method for manufacturing the solar cell, and more particularly to a structure on the light receiving surface side of the solar cell.
  • solar cells that directly convert solar energy into electrical energy have rapidly been expected as next-generation energy sources, particularly from the viewpoint of global environmental problems.
  • solar cells there are various types of solar cells such as a solar cell made of a compound semiconductor material or a solar cell made of an organic material.
  • the mainstream solar cell is a solar cell made of a silicon crystal material.
  • an antireflection film for suppressing reflection of incident light is formed on the light receiving surface located on the incident light side of the solar cell.
  • FIG. 9 is a schematic cross-sectional configuration diagram of an example of a conventional solar cell 100 disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 57-114291).
  • a diffusion layer 102 is formed on the light receiving surface side of the silicon wafer 101, and a titanium oxide film 103 and a surface side electrode 104 are formed on the upper surface of the diffusion layer 102.
  • the back electrode 105 is formed on the back side of the silicon wafer 101. That is, in the solar cell 100 shown in Patent Document 1, the side on which the surface side electrode 104 is provided is the light receiving surface.
  • Patent Document 1 a pn junction is formed by applying a mixed solution containing at least a dopant raw material, a titanate ester and an alcohol to a silicon substrate and heat-treating, and at the same time, a titanium oxide film which is an antireflection film is disclosed. It is described that it is formed.
  • Patent Document 1 describes oxides such as phosphorus pentoxide, boron oxide, and arsenic trioxide, or organic compounds such as phosphate esters and boron esters as dopant materials. And the Example of patent document 1 describes using phosphorus pentoxide as a dopant raw material and forming a titanium oxide film containing phosphorus as an impurity on a silicon substrate as an antireflection film.
  • the present invention has been made in view of the above problems, and an object thereof is to provide a solar cell having an antireflection film excellent in durability and weather resistance.
  • the solar cell of the present invention is formed on the light-receiving surface side diffusion layer formed on the light-receiving surface side of the silicon substrate, the light-receiving surface-side passivation film formed on the light-receiving surface-side diffusion layer, and the light-receiving surface-side passivation film. And an antireflection film including an impurity having the same conductivity type as that of the light receiving surface side diffusion layer.
  • the antireflection film is made of a titanium oxide containing titanium phosphate.
  • the sheet resistance value of the light-receiving surface side diffusion layer is preferably 100 ⁇ / ⁇ or more and less than 250 ⁇ / ⁇ .
  • the content of titanium phosphate contained in the antireflection film is preferably 15 wt% or more and 35 wt% or less as the phosphor oxide.
  • the method for manufacturing a solar cell of the present invention is a method for manufacturing a solar cell having a light receiving surface side diffusion layer on the light receiving surface side of a silicon substrate.
  • a light-receiving surface is coated with a solution containing at least an impurity-containing compound, titanium alkoxide, and alcohol to be contained in the light-receiving surface side diffusion layer, and then heat-treated in a nitrogen atmosphere.
  • the heat treatment in the step of forming the light-receiving surface side passivation film is performed in an oxygen atmosphere.
  • the heat treatment in the step of forming the light-receiving surface side passivation film is preferably performed at a temperature higher than 850 ° C.
  • the back-surface-side passivation film is formed on the back surface of the silicon substrate located on the side opposite to the light-receiving surface.
  • the step of forming the light receiving surface diffusion layer and the antireflection film and the step of forming the light receiving surface side passivation film are performed by a series of heat treatments.
  • the antireflection film contains titanium phosphate having excellent durability and weather resistance, the durability and weather resistance of the solar cell can be improved.
  • FIG.4 (j) is an enlarged view of the IVJ area
  • FIG.4 (j) is an enlarged view of the IVJ area
  • FIG.4 (g) is an enlarged view of the IVJ area
  • FIGS. 1 and 2 show an example of the configuration of the solar cell of the present invention in which electrodes are formed only on the back surface located on the side opposite to the light receiving surface.
  • FIG. 1 is a schematic plan view showing an example of the configuration of the back surface side of the solar cell 1 of the present invention.
  • FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the solar cell of the present invention, and is a cross-sectional view taken along the line II-II shown in FIG.
  • an uneven shape 5 having a texture structure is formed on the light receiving surface of the n-type silicon substrate 4 which is a single crystal silicon substrate (the surface serving as the light receiving surface of the solar cell 1). ing.
  • the height of the unevenness is not particularly limited, but is preferably on the order of several ⁇ m to several tens of ⁇ m.
  • an n + semiconductor layer that is the light receiving surface side diffusion layer 6 is formed as an FSF (Front Surface Field) layer, and on the light receiving surface side diffusion layer 6, the light receiving surface side passivation film is formed. 13 is formed.
  • An antireflection film 12 is formed on the light receiving surface side passivation film 13.
  • the structure of the light-receiving surface side diffusion layer 6 is not particularly limited, but the sheet resistance value of the light-receiving surface side diffusion layer 6 is preferably 100 ⁇ / ⁇ or more and less than 250 ⁇ / ⁇ , more preferably 100 ⁇ / ⁇ or more and 150 ⁇ / ⁇ or less. It is. Thereby, since the recombination current generated on the light receiving surface side of the solar cell 1 is reduced, the characteristics of the solar cell are improved. By adjusting the diffusion conditions and the impurity concentration, the sheet resistance value of the light-receiving surface side diffusion layer 6 can be made 100 ⁇ / ⁇ or more and less than 250 ⁇ / ⁇ .
  • the light-receiving surface side passivation film 13 is preferably a silicon oxide film, for example.
  • the film thickness of the light-receiving surface side passivation film 13 is preferably 5 nm to 200 nm, preferably 5 nm to 60 nm, or 100 nm to 200 nm.
  • the antireflection film 12 is made of a titanium oxide containing titanium phosphate.
  • titanium phosphate is more excellent in durability and weather resistance than phosphorus oxide. Therefore, the antireflection film 12 containing titanium phosphate is more excellent in durability and weather resistance than the antireflection film containing phosphorus oxide or the antireflection film not containing phosphorus oxide. Therefore, in the solar cell provided with such an antireflection film 12, durability and weather resistance are further improved.
  • the content of titanium phosphate contained in the antireflection film 12 is preferably 15 wt% or more and 35 wt% or less as the phosphor oxide, and is 30 wt% or more and 35 wt% or less. It is more preferable.
  • the content of titanium phosphate contained in the antireflection film 12 is 15 wt% or more and 35 wt% or less as the phosphor oxide” means that the mass of the titanium phosphate contained in the antireflection film 12 is the phosphor oxide. This means that the mass of phosphorus oxide contained in the antireflection film 12 is 15% or more and 35% or less with respect to the total mass of the antireflection film 12.
  • the content of the phosphor oxide in the antireflection film 12 is measured according to, for example, ICP (Inductively Coupled Plasma) emission spectroscopy or ICP mass spectrometry.
  • the film thickness of the antireflection film 12 is preferably 10 nm or more and 400 nm or less, for example.
  • a strip-shaped n-type electrode 2 and a strip-shaped p-type electrode 3 are formed on the back side of the n-type silicon substrate 4 located on the side opposite to the light receiving surface of the n-type silicon substrate 4. It is formed alternately. Specifically, n ++ regions 9 as n-type semiconductor regions and p + regions 10 as p-type semiconductor regions are alternately formed adjacent to each other on the back side of the n-type silicon substrate 4.
  • the n ++ region 9 is recessed closer to the n-type silicon substrate 4 side than the portion other than the n ++ region 9 on the back surface of the n-type silicon substrate 4, and the depth d (the bottom surface of the n ++ region 9 and p
  • the distance from the lower surface of the + region 10 is preferably on the order of several tens of nm. Since n ++ regions 9 and p + regions 10 are alternately formed adjacent to each other on the back side of n-type silicon substrate 4, the voltage is locally applied when reverse bias is applied to solar cell 1. Therefore, it is possible to prevent heat generation due to local occurrence of leakage current.
  • the n-type impurity concentration is preferably higher in the order of the n-type silicon substrate 4, the n + semiconductor layer that is the light-receiving surface side diffusion layer 6, and the n ++ region 9.
  • a back surface side passivation film 14 composed of a second back surface side passivation film 8 and a first back surface side passivation film 11 is formed.
  • the second back-side passivation film 8 and the first back-side passivation film 11 are preferably, for example, a silicon oxide film.
  • the thickness of the back-side passivation film 14 on the n ++ region 9 and the thickness of the back-side passivation film 14 on the p + region 10 are different from each other, and the thickness of the back-side passivation film 14 on the n ++ region 9 is different.
  • the film thickness is larger than the film thickness of the back-side passivation film 14 on the p + region 10.
  • the thickness of the second back-side passivation film 8 formed on the n ++ region 9 is preferably not less than 30 nm and not more than 100 nm, for example, and the second back-side passivation film 8 formed on the p + region 10 is formed.
  • the film thickness of the back surface side passivation film 8 is preferably not less than 10 nm and not more than 40 nm, for example.
  • n-type electrode 2 for example it is preferably made of silver
  • p-type electrode 3 is connected through the backside passivation film 14 on the p + region 10 to the p + region 10.
  • FIG. 3 is a schematic plan view showing an example of the configuration of the semiconductor region as viewed from the back side of the solar cell of the present invention. From the solar cell 1 to the n-type electrode 2, the p-type electrode 3, and the back side. This corresponds to a plan view of the solar cell after removing the passivation film 14 as seen from the back side.
  • a semiconductor region 71 (hereinafter referred to as “p + region 71”) to which neither the n-type electrode nor the p-type electrode is connected is formed on the periphery of the back surface of the n-type silicon substrate 4. .
  • p + region 71 A semiconductor region 71 (hereinafter referred to as “p + region 71”) to which neither the n-type electrode nor the p-type electrode is connected is formed on the periphery of the back surface of the n-type silicon substrate 4. .
  • the n ++ region 9 form different p + region 71 of the conductivity type around the n ++ region 9, even the semiconductor region is formed in an edge portion or the like of the solar cell 1,
  • the semiconductor region and the n ++ region 9 and the p + region 10 can be electrically separated.
  • a semiconductor region to which no electrode is connected exists at the periphery of the back surface of the n-type silicon substrate 4. Therefore, when a reverse bias is applied to the solar cell 1, it can be suppressed that a leak current is generated through the periphery of the n-type silicon substrate 4.
  • n ++ region 9 and p + region 10 are not limited to the configuration shown in FIG.
  • the n ++ regions 9 are all connected in FIG. 3 to form one semiconductor region, they are not necessarily connected.
  • the p + region 10 is separated into a plurality of regions in FIG. 3, but may be connected to each other to form one semiconductor region.
  • the solar cell can have a 180 ° rotation target structure. Therefore, when producing a solar cell module by arranging a plurality of solar cells, for example, the solar cells can be arranged upside down in FIG.
  • FIGS. 1 and 2 are schematic cross-sectional views showing an example of a method for manufacturing the solar cell of the present invention shown in FIGS. 1 and 2, and FIG. 4 (j) is a cross-sectional view of FIG. It is an enlarged view of IVJ area
  • a texture mask 21 made of a silicon nitride film or the like is formed on the back surface of an n-type silicon substrate 4 having a thickness of 100 ⁇ m, for example, by CVD or sputtering.
  • an uneven shape 5 having a texture structure is formed on the light receiving surface of the n-type silicon substrate 4 by etching.
  • Etching is preferably performed using, for example, a solution in which isopropyl alcohol is added to an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide and heated to 70 ° C. or higher and 80 ° C. or lower.
  • FIG. 4C after removing the texture mask 21 formed on the back surface of the n-type silicon substrate 4, a diffusion mask 22 made of a silicon oxide film or the like on the light-receiving surface of the n-type silicon substrate 4. Form. Thereafter, in addition to the location where the n ++ region 9 is to be formed on the back surface of the n-type silicon substrate 4, for example, a masking paste containing a solvent, a thickener and a silicon oxide precursor is applied by inkjet or screen printing, Heat treatment is performed.
  • a diffusion mask 23 is formed on the back surface of the n-type silicon substrate 4 in addition to the portion where the n ++ region 9 is to be formed.
  • phosphorus which is an n-type impurity, diffuses into a portion of the back surface of the n-type silicon substrate 4 exposed from the diffusion mask 23. As a result, an n ++ region 9 is formed.
  • thermal oxidation is performed by steam at 900 ° C.
  • the thickness of the silicon oxide film 24 formed on the region other than the n ++ region 9 becomes 70nm or 90nm or less, formed on the n ++ region 9
  • the film thickness of the silicon oxide film 24 is 250 nm or more and 350 nm or less.
  • the surface concentration of phosphorus in the n ++ region 9 before thermal oxidation with oxygen or water vapor is preferably 5 ⁇ 10 19 / cm 3 or more.
  • the treatment temperature for thermal oxidation with oxygen or water vapor is preferably 800 ° C. or higher and 1000 ° C. or lower for thermal oxidation with oxygen, and preferably 800 ° C. or higher and 950 ° C. or lower for thermal oxidation with water vapor.
  • the growth rate of the silicon oxide film by thermal oxidation is determined by the type of impurity diffused in the silicon substrate and the concentration of the impurity.
  • the n ++ region 9 has a higher n-type impurity concentration than the n-type silicon substrate 4. Therefore, the thickness of the silicon oxide film 24 formed on the n ++ region 9 is larger than the thickness of the silicon oxide film 24 formed on the n-type silicon substrate 4. Since the silicon oxide film 24 is formed by combining silicon and oxygen during thermal oxidation, the n ++ region 9 is recessed closer to the n-type silicon substrate 4 than the region where the n ++ region 9 is not formed. .
  • the film thickness of the silicon oxide film 24 formed on the n ++ region 9 and the n + The difference from the film thickness of the silicon oxide film 24 formed on the region other than the + region 9 is preferably 60 nm or more.
  • the silicon oxide film 24 formed on the light-receiving surface of the n-type silicon substrate 4 and the region other than the n ++ region 9 on the back surface of the n-type silicon substrate 4 are formed.
  • the silicon oxide film 24 thus formed is removed by etching.
  • the silicon oxide film 24 is formed thick on the n ++ region 9.
  • the etching rate is different between the silicon oxide film 24 formed on the formed areas other than the silicon oxide film 24 and the n ++ region 9 was on the n ++ region 9. Therefore, only the silicon oxide film 24 formed on the n ++ region 9 remains by etching.
  • the silicon oxide film 24 is formed by performing thermal oxidation with water vapor at 900 ° C. for 30 minutes, and the silicon oxide film 24 formed on the region other than the n ++ region 9 is removed by hydrofluoric acid treatment.
  • the silicon oxide film 24 having a thickness of about 120 nm remains on the n ++ region 9.
  • the difference between the thickness of the silicon oxide film 24 formed on the film thickness and n ++ region 9 other than the area of the silicon oxide film 24 formed on n ++ region 9 than 60nm the silicon oxide film 24 functions as a diffusion mask for the n ++ region 9 when the p + region 10 is formed. Therefore, the silicon oxide film 24 (having a film thickness of about 120 nm) remaining on the n ++ region 9 by the above method can function as a diffusion mask for the n ++ region 9 when the p + region 10 is formed.
  • a diffusion mask 25 made of a silicon oxide film or the like is formed on the light receiving surface of the n-type silicon substrate 4.
  • a solution obtained by dissolving a polymer obtained by reacting an organic polymer with a boron compound in an alcohol solvent is applied on the back surface of the n-type silicon substrate 4, and after drying, heat treatment is performed.
  • boron which is a p-type impurity, diffuses into a portion of the back surface of the n-type silicon substrate 4 exposed from the silicon oxide film 24, thereby forming a p + region 10 and a p + region 71.
  • the light receiving surface side of the n-type silicon substrate 4 is shown above.
  • the layer is removed, for example, by hydrofluoric acid treatment.
  • the first back surface side made of a silicon oxide film or the like on the back surface of the n-type silicon substrate 4 by CVD or by applying and baking SOG (spin-on-glass) on the back surface of the n-type silicon substrate 4.
  • a passivation film 11 is formed.
  • the first back-side passivation film 11 formed in this way has a film thickness of, for example, 50 nm to 100 nm and can also function as a diffusion mask.
  • an n + semiconductor layer and an antireflection film 12 which are the light-receiving surface side diffusion layers 6 are formed on the light-receiving surface of the n-type silicon substrate 4.
  • a liquid mixture containing at least a phosphorus compound, titanium alkoxide and alcohol is applied to the light receiving surface of the n-type silicon substrate 4 and dried.
  • phosphorus pentoxide or the like can be used as the phosphorus compound in the mixed solution
  • tetraisopropyl titanate or the like can be used as the titanium alkoxide
  • isopropyl alcohol or the like can be used as the alcohol.
  • heat treatment is performed.
  • the phosphorous diffusion is n-type impurity
  • Figure 4 n + semiconductor layer and the antireflection film 12 is a light receiving surface side diffusion layer 6 in the light-receiving surface the whole surface of the n-type silicon substrate 4, as shown in (j) Is formed.
  • This heat treatment is preferably performed in a nitrogen atmosphere, whereby the n-type impurity surface concentration of the light-receiving surface side diffusion layer 6 can be reduced.
  • the heat treatment temperature is preferably 850 ° C. or higher and 1000 ° C. or lower, and more preferably 880 ° C. or higher and 950 ° C. or lower.
  • a second back-side passivation film 8 that is a silicon oxide film is formed on the back surface of the n-type silicon substrate 4. Specifically, thermal oxidation is performed in an oxygen atmosphere. As a result, a silicon oxide film, which is the second back-side passivation film 8, is formed on the back surface of the n-type silicon substrate 4, and the entire light-receiving surface of the n-type silicon substrate 4 is formed as shown in FIG. A silicon oxide film is also formed. The silicon oxide film formed on the entire surface of the light receiving surface is formed between the light receiving surface side diffusion layer 6 and the antireflection film 12 and becomes the light receiving surface side passivation film 13. In addition, the antireflection film 12 becomes a titanium oxide film containing titanium phosphate.
  • the light receiving surface side passivation film 13 is formed between the light receiving surface side diffusion layer 6 and the antireflection film 12. .
  • the reason is as follows. In the concave portion of the concavo-convex shape 5 formed on the light receiving surface of the n-type silicon substrate 4, the antireflection film 12 is cracked because the antireflection film 12 is thick. Then, when oxygen enters from the location where the crack occurs, a silicon oxide film which is the light-receiving surface side passivation film 13 grows.
  • the film thickness of the antireflection film 12 is thin at the convex portion of the concavo-convex shape 5 formed on the light receiving surface of the n-type silicon substrate 4, oxygen can pass through the antireflection film 12. Then, when oxygen passes through the antireflection film 12, a silicon oxide film that is the light-receiving surface side passivation film 13 grows.
  • the second back surface passivation film 8 is formed between the back surface of the n-type silicon substrate 4 and the first back surface passivation film 11 by thermal oxidation in an oxygen atmosphere.
  • the reason is as follows. Since the first back surface passivation film 11 on the back surface of the n-type silicon substrate 4 is formed by a CVD method or the like, oxygen easily passes through the inside of the first back surface passivation film 11. Then, when oxygen passes through the first back surface side passivation film 11, a silicon oxide film as the second back surface side passivation film 8 is grown.
  • the antireflection film 12 can be a titanium oxide film containing titanium phosphate.
  • the reason is as follows. As described above, when the second back-side passivation film 8 is formed by thermal oxidation in an oxygen atmosphere, oxygen enters from cracks generated in the antireflection film 12 or oxygen passes through the antireflection film 12. A part of the oxygen that has entered the antireflection film 12 is combined with phosphorus and titanium in the antireflection film 12, thereby producing titanium phosphate.
  • the content of titanium phosphate contained in the antireflection film 12 is preferably 15 wt% or more and 35 wt% or less, and more preferably 30 wt% or more and 35 wt% or less as the phosphor oxide. When the content of the phosphorous oxide contained in the antireflection film 12 exceeds 35 wt%, the antireflection film 12 may turn white. If the content of phosphorous oxide contained in the antireflection film 12 is less than 15 wt%, the durability and weather resistance of the antireflection film 12 may not be sufficiently improved.
  • the heat treatment temperature in an oxygen atmosphere is not particularly limited, but is preferably higher than 850 ° C, more preferably 900 ° C or higher and 1000 ° C or lower.
  • oxygen easily diffuses, so that the light-receiving surface side passivation film 13 and the second back surface passivation film 8 are easily formed.
  • the antireflection film 12 can be a titanium oxide film containing titanium phosphate.
  • the recombination current generated on the light receiving surface side of the solar cell 1 can be reduced, the battery characteristics of the solar cell are further improved. Note that the recombination current generated on the light receiving surface side of the solar cell 1 can also be reduced by setting the sheet resistance value of the light receiving surface side diffusion layer 6 to 100 ⁇ / ⁇ or more and less than 250 ⁇ / ⁇ .
  • the film thickness of the light-receiving surface side passivation film 13 is preferably, for example, 5 nm to 200 nm, preferably 5 nm to 60 nm, or 100 nm to 200 nm.
  • the film thickness of the second back-side passivation film 8 formed on the n ++ region 9 is preferably, for example, 30 nm or more and 100 nm or less, and the p + region
  • the thickness of the second back-side passivation film 8 formed on 10 is preferably 10 nm or more and 40 nm or less, for example.
  • the formation of the second back surface side passivation film 8, the formation of the light receiving surface side passivation film 13, and the formation of the antireflection film 12 as a titanium oxide film containing titanium phosphate can be achieved by the light receiving surface side diffusion layer 6 and the reflection layer.
  • the heat treatment for forming the prevention film 12 it can be performed by switching the gas. That is, the heat treatment for forming the n + semiconductor layer and the antireflection film 12 that are the light-receiving surface side diffusion layer 6 and the heat treatment for forming the light-receiving surface side passivation film 13 can be performed by a series of heat treatments. Thereby, the manufacturing process number of a solar cell can be reduced.
  • electrodes are formed on each of the n ++ region 9 and the p + region 10 formed on the back surface side of the n-type silicon substrate 4.
  • patterning is performed on the back surface side passivation film 14 formed on the back surface of the n-type silicon substrate 4.
  • the patterning is performed by applying an etching paste on the backside passivation film 14 by screen printing or the like and then performing a heat treatment. Thereafter, the etching paste is ultrasonically cleaned and then removed by acid treatment.
  • the etching paste preferably contains at least one selected from the group consisting of phosphoric acid, hydrogen fluoride, ammonium fluoride, and ammonium hydrogen fluoride as an etching component, for example, water, an organic solvent, and a thickening agent. It is preferable to further contain an agent.
  • n-type electrode 2 is connected to n ++ region 9
  • p-type electrode 3 is connected to p + region 10. In this way, the solar cell 1 shown in FIGS. 1 and 2 is manufactured.
  • FIG. 5 is a cross-sectional view showing a configuration of a sample 81 produced for evaluating the performance of the antireflection film 12.
  • XRD X-Ray Diffraction
  • FIG. 5 is a cross-sectional view showing a configuration of a sample 81 produced for evaluating the performance of the antireflection film 12.
  • an n + semiconductor layer 83 corresponding to the light receiving surface side diffusion layer is formed on the light receiving surface side of the n-type silicon substrate 82, and the n + semiconductor layer 83 corresponds to the passivation film.
  • a silicon oxide film 84 and a film 85 corresponding to the antireflection film are sequentially formed.
  • FIG. 6 is a flowchart showing an example of a method for manufacturing the sample 81 shown in FIG.
  • a sample 81 shown in FIG. 5 was manufactured according to the following method.
  • step S1 the surface of the n-type silicon substrate 82 was flattened by etching or the like.
  • step S2 a mixed solution containing at least a phosphorus compound, titanium alkoxide, and alcohol was applied to the flat surface of the n-type silicon substrate 82 and dried.
  • phosphorus pentoxide was used as the phosphorus compound of the mixed solution
  • tetraisopropyl titanate was used as the titanium alkoxide
  • isopropyl alcohol was used as the alcohol.
  • step S3 phosphorus, which is an n-type impurity, was diffused by heat treatment, so that an n + semiconductor layer 83 and a film made of titanium oxide containing phosphorus (a film corresponding to an antireflection film) 85 were formed.
  • the heat treatment in step S3 was performed at 920 ° C. in a nitrogen atmosphere.
  • step S4 thermal oxidation was performed to form a silicon oxide film 84.
  • the heat treatment in step S4 was performed at 950 ° C.
  • step S4 is performed in an oxygen atmosphere and a water vapor atmosphere
  • the heat treatment in step S4 is performed in an oxygen atmosphere
  • the heat treatment in step S4 is performed in a water vapor atmosphere. It was set as Comparative Example 1.
  • FIG. 7A is a graph showing the measurement result of the X-ray diffraction of the antireflection film in Example 1.
  • FIG. 7B is an XRD pattern (JCPDS (Joint Committee for Powder Diffraction Standards) -ICDD (International Center for Diffraction Data) -PDF (Powder Diffraction Files)) of titanium phosphate (TiP 2 O 7 ).
  • FIG. 7C shows an XRD pattern (JCPDS-ICDD-PDF) of anatase type titanium oxide (TiO 2 ).
  • FIG. 8A is a graph showing the measurement result of the X-ray diffraction of the antireflection film in the comparative example.
  • FIG. 8B is an XRD pattern (JCPDS-ICDD-PDF) of anatase-type titanium oxide (TiO 2 ).
  • the heat treatment for producing the n + semiconductor layer that is the light-receiving surface side diffusion layer and the antireflection film is performed in a nitrogen atmosphere, and then the silicon oxide that is the light-receiving surface side passivation film
  • the antireflection film can be a titanium oxide film containing titanium phosphate. Therefore, since the antireflection film excellent in durability and weather resistance can be provided, a solar cell excellent in durability and weather resistance can be provided.
  • the n-type silicon substrate is described, but a p-type silicon substrate can also be used.
  • the light-receiving surface side diffusion layer becomes a p + semiconductor layer containing p-type impurities
  • the antireflection film becomes a film containing p-type impurities.
  • the solar cell structure other than the light-receiving surface side diffusion layer and the antireflection film is preferably the same as the solar cell structure provided with the n-type silicon substrate.
  • the total area of n ++ regions having a conductivity type different from that of the silicon substrate conductivity type and having electrodes formed thereon. Is preferably larger than the total area of the p + regions where the electrodes are formed.
  • n ++ region between the p + region is formed, p + regions may be separated in a direction perpendicular to the length direction, n ++ region length It may be separated in a direction perpendicular to the vertical direction, or an n ++ region may be formed between the p + regions.
  • the total area of n ++ regions is the total area of n ++ regions in a plane perpendicular to the growth direction
  • the total area of p + regions is a plane perpendicular to the growth direction. Is the sum of the areas of the p + regions at.
  • the concept of the solar cell of the present invention includes not only a solar cell in which both the p-type electrode and the n-type electrode are formed only on the back surface of the semiconductor substrate, but also the light-receiving surface of the semiconductor substrate and the semiconductor substrate.
  • a part of the electrode is disposed in a through hole provided in a semiconductor substrate in a solar cell in which electrodes are formed on each of the back surface of the substrate and an MWT (Metal Wrap Through) type solar cell (in the MWT type solar cell) ) Etc. are also included.
  • the phosphorus compound, titanium alkoxide, and alcohol contained in the mixed solution used when forming the light-receiving surface side diffusion layer 6 and the antireflection film 12 are merely examples, and are not limited to the above materials.
  • the material of the member which comprises solar cells other than the antireflection film 12, and the material of the mask used when manufacturing a solar cell are not limited to the said material.
  • the thickness of the member which comprises a solar cell is not limited to the said numerical value.
  • the constituent member of the solar cell includes an n-type impurity or a p-type impurity
  • the n-type impurity material, the p-type impurity material, the n-type impurity concentration, and the p-type impurity concentration in the constituent member are not particularly limited.
  • the substrate is a p-type silicon substrate
  • the p-type impurity concentration in p + region 10 is preferably higher than the p-type impurity concentration in the p-type silicon substrate.
  • the method for forming the n-type electrode 2 and the p-type electrode 3 is not particularly limited. Further, the heat treatment conditions for forming the n ++ region 9 and the p + region 10 are not particularly limited. Furthermore, the method for removing the texture mask or the diffusion mask is not particularly limited.

Landscapes

  • Engineering & Computer Science (AREA)
  • Microelectronics & Electronic Packaging (AREA)
  • Sustainable Development (AREA)
  • Physics & Mathematics (AREA)
  • Condensed Matter Physics & Semiconductors (AREA)
  • Electromagnetism (AREA)
  • General Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • Life Sciences & Earth Sciences (AREA)
  • Power Engineering (AREA)
  • Sustainable Energy (AREA)
  • Chemical & Material Sciences (AREA)
  • Crystallography & Structural Chemistry (AREA)
  • Photovoltaic Devices (AREA)

Abstract

A solar cell (1) is provided with a light-receiving surface diffusion layer (6) formed on the light-receiving surface of a silicon substrate (4), a light-receiving surface passivation film (13) formed on the light-receiving surface diffusion layer (6), and an anti-reflection film (12) formed on the light-receiving surface passivation film (13) and containing impurities having the same conductivity type as the conductivity type of the light-receiving surface diffusion layer (6). The anti-reflection film (12) comprises titanium oxides including titanium phosphate.

Description

太陽電池、および太陽電池の製造方法Solar cell and method for manufacturing solar cell
　本発明は、太陽電池、および太陽電池の製造方法に関し、特に、太陽電池の受光面側の構造に関する。 The present invention relates to a solar cell and a method for manufacturing the solar cell, and more particularly to a structure on the light receiving surface side of the solar cell.
　太陽光エネルギを電気エネルギに直接変換する太陽電池は、近年、特に地球環境問題の観点から、次世代のエネルギ源としての期待が急速に高まっている。太陽電池としては、化合物半導体材料からなる太陽電池または有機材料からなる太陽電池など種々の太陽電池があるが、現在、主流の太陽電池は、シリコン結晶材料からなる太陽電池である。太陽電池の入射光側に位置する受光面には、一般に、入射光の反射を抑えるための反射防止膜が形成されている。 In recent years, solar cells that directly convert solar energy into electrical energy have rapidly been expected as next-generation energy sources, particularly from the viewpoint of global environmental problems. As solar cells, there are various types of solar cells such as a solar cell made of a compound semiconductor material or a solar cell made of an organic material. Currently, the mainstream solar cell is a solar cell made of a silicon crystal material. In general, an antireflection film for suppressing reflection of incident light is formed on the light receiving surface located on the incident light side of the solar cell.
　図９は、特許文献１（特開昭５７－１１４２９１号公報）に示されている従来技術の太陽電池１００の一例の模式的な断面構成図である。特許文献１に示されている太陽電池１００では、シリコンウエハ１０１の受光面側には拡散層１０２が形成されており、拡散層１０２の上面上には酸化チタン膜１０３と表面側電極１０４とが形成されており、シリコンウエハ１０１の裏面側には裏面側電極１０５が形成されている。つまり、特許文献１に示されている太陽電池１００では、表面側電極１０４が設けられている側が受光面である。特許文献１には、ドーパント用原料、チタン酸エステルおよびアルコールを少なくとも含む混合液をシリコン基板に塗布して熱処理することにより、ｐ－ｎ接合が形成され、同時に反射防止膜である酸化チタン膜が形成されるということが記載されている。特許文献１には、ドーパント用原料としては、五酸化リン、酸化ホウ素、あるいは三酸化砒素等の酸化物、またはリン酸エステルあるいはボロンエステル等の有機化合物が記載されている。そして、特許文献１の実施例には、ドーパント用原料に五酸化リンを用い、リンを不純物として含む酸化チタン膜を反射防止膜としてシリコン基板に形成することが記載されている。 FIG. 9 is a schematic cross-sectional configuration diagram of an example of a conventional solar cell 100 disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 57-114291). In the solar cell 100 shown in Patent Document 1, a diffusion layer 102 is formed on the light receiving surface side of the silicon wafer 101, and a titanium oxide film 103 and a surface side electrode 104 are formed on the upper surface of the diffusion layer 102. The back electrode 105 is formed on the back side of the silicon wafer 101. That is, in the solar cell 100 shown in Patent Document 1, the side on which the surface side electrode 104 is provided is the light receiving surface. In Patent Document 1, a pn junction is formed by applying a mixed solution containing at least a dopant raw material, a titanate ester and an alcohol to a silicon substrate and heat-treating, and at the same time, a titanium oxide film which is an antireflection film is disclosed. It is described that it is formed. Patent Document 1 describes oxides such as phosphorus pentoxide, boron oxide, and arsenic trioxide, or organic compounds such as phosphate esters and boron esters as dopant materials. And the Example of patent document 1 describes using phosphorus pentoxide as a dopant raw material and forming a titanium oxide film containing phosphorus as an impurity on a silicon substrate as an antireflection film.
特開昭５７－１１４２９１号公報（昭和５７年７月１６日公開）JP 57-114291 A (published July 16, 1982)
　しかしながら、近年、太陽電池に設けられる反射防止膜として、特許文献１に記載のリンを不純物として含む酸化チタン膜よりも耐久性および耐候性にさらに優れた膜が切望されている。 However, in recent years, as an antireflection film provided in a solar cell, a film that is more excellent in durability and weather resistance than a titanium oxide film containing phosphorus as an impurity described in Patent Document 1 is desired.
　本発明は、上記の問題に鑑みてなされたものであり、その目的は、耐久性および耐候性に優れた反射防止膜を有する太陽電池を提供することにある。 The present invention has been made in view of the above problems, and an object thereof is to provide a solar cell having an antireflection film excellent in durability and weather resistance.
　本発明の太陽電池は、シリコン基板の受光面側に形成された受光面側拡散層と、受光面側拡散層上に形成された受光面側パッシベーション膜と、受光面側パッシベーション膜上に形成された、受光面側拡散層の導電型と同じ導電型の不純物を含む反射防止膜とを備える。反射防止膜は、リン酸チタンを含むチタン酸化物からなる。 The solar cell of the present invention is formed on the light-receiving surface side diffusion layer formed on the light-receiving surface side of the silicon substrate, the light-receiving surface-side passivation film formed on the light-receiving surface-side diffusion layer, and the light-receiving surface-side passivation film. And an antireflection film including an impurity having the same conductivity type as that of the light receiving surface side diffusion layer. The antireflection film is made of a titanium oxide containing titanium phosphate.
　受光面側拡散層のシート抵抗値が、１００Ω／□以上２５０Ω／□未満であることが好ましい。 The sheet resistance value of the light-receiving surface side diffusion layer is preferably 100Ω / □ or more and less than 250Ω / □.
　反射防止膜に含まれるリン酸チタンの含有量は、リン酸化物として１５ｗｔ％以上３５ｗｔ％以下であることが好ましい。 The content of titanium phosphate contained in the antireflection film is preferably 15 wt% or more and 35 wt% or less as the phosphor oxide.
　本発明の太陽電池の製造方法は、シリコン基板の受光面側に受光面側拡散層を有する太陽電池を製造する方法である。この製造方法は、受光面側拡散層に含まれることとなる不純物を含む化合物、チタンアルコキシドおよびアルコールを少なくとも含む溶液をシリコン基板の受光面に塗布してから窒素雰囲気下で熱処理することにより、受光面拡散層と反射防止膜とをシリコン基板の受光面上に形成する工程と、シリコン基板の受光面上に、熱処理により受光面側パッシベーション膜を形成する工程とを備える。受光面側パッシベーション膜を形成する工程の熱処理は、酸素雰囲気下で行われる。 The method for manufacturing a solar cell of the present invention is a method for manufacturing a solar cell having a light receiving surface side diffusion layer on the light receiving surface side of a silicon substrate. In this manufacturing method, a light-receiving surface is coated with a solution containing at least an impurity-containing compound, titanium alkoxide, and alcohol to be contained in the light-receiving surface side diffusion layer, and then heat-treated in a nitrogen atmosphere. Forming a surface diffusion layer and an antireflection film on the light receiving surface of the silicon substrate; and forming a light receiving surface side passivation film on the light receiving surface of the silicon substrate by heat treatment. The heat treatment in the step of forming the light-receiving surface side passivation film is performed in an oxygen atmosphere.
　受光面側パッシベーション膜を形成する工程の熱処理は、８５０℃よりも高い温度で行なわれることが好ましい。 The heat treatment in the step of forming the light-receiving surface side passivation film is preferably performed at a temperature higher than 850 ° C.
　受光面側パッシベーション膜を形成する工程において、受光面とは反対側に位置するシリコン基板の裏面上に裏面側パッシベーション膜が形成されることが好ましい。 In the step of forming the light-receiving surface-side passivation film, it is preferable that the back-surface-side passivation film is formed on the back surface of the silicon substrate located on the side opposite to the light-receiving surface.
　受光面拡散層および反射防止膜を形成する工程と受光面側パッシベーション膜を形成する工程とを一連の熱処理によって行うことが好ましい。 It is preferable that the step of forming the light receiving surface diffusion layer and the antireflection film and the step of forming the light receiving surface side passivation film are performed by a series of heat treatments.
　本発明によれば、反射防止膜が耐久性および耐候性に優れたリン酸チタンを含むので、太陽電池の耐久性および耐候性を向上させることができる。 According to the present invention, since the antireflection film contains titanium phosphate having excellent durability and weather resistance, the durability and weather resistance of the solar cell can be improved.
本発明の太陽電池の裏面側の構成の一例を示す模式的な平面図である。It is a typical top view which shows an example of the structure of the back surface side of the solar cell of this invention. 本発明の太陽電池の構成の一例を示す模式的な断面図である。It is typical sectional drawing which shows an example of a structure of the solar cell of this invention. 本発明の太陽電池の裏面側から見た半導体領域の構成の一例を示す模式的な平面図である。It is a typical top view which shows an example of a structure of the semiconductor region seen from the back surface side of the solar cell of this invention. 本発明の太陽電池の製造方法の一例を示す模式的な断面図であり、図４（ｊ）は、図４（ｇ）に示すＩＶＪ領域の拡大図である。It is typical sectional drawing which shows an example of the manufacturing method of the solar cell of this invention, FIG.4 (j) is an enlarged view of the IVJ area | region shown in FIG.4 (g). 本発明の効果を評価するためのサンプルの構成の一例を示す模式的な断面図である。It is typical sectional drawing which shows an example of the structure of the sample for evaluating the effect of this invention. 本発明の効果を評価するためのサンプルの製造方法の一例を示すフロー図である。It is a flowchart which shows an example of the manufacturing method of the sample for evaluating the effect of this invention. 実施例１における反射防止膜のＸ線回折の測定結果、および、当該測定結果を評価するためのリファレンスのＸ線回折スペクトルを示すグラフである。It is a graph which shows the X-ray-diffraction measurement result of the antireflection film in Example 1, and the X-ray diffraction spectrum of the reference for evaluating the measurement result. 比較例１における反射防止膜のＸ線回折の測定結果、および、当該測定結果を評価するためのリファレンスのＸ線回折スペクトルを示すグラフである。It is a graph which shows the X-ray-diffraction measurement result of the anti-reflective film in the comparative example 1, and the X-ray-diffraction spectrum of the reference for evaluating the said measurement result. 従来技術の太陽電池の構成の一例を示す模式的な断面図である。It is typical sectional drawing which shows an example of a structure of the solar cell of a prior art.
　以下、本発明の太陽電池およびその製造方法について図面を用いて説明する。なお、本発明の図面において、同一の参照符号は、同一部分または相当部分を表すものである。また、長さ、幅、厚さ、深さなどの寸法関係は図面の明瞭化と簡略化のために適宜変更されており、実際の寸法関係を表すものではない。 Hereinafter, the solar cell of the present invention and the manufacturing method thereof will be described with reference to the drawings. In the drawings of the present invention, the same reference numerals represent the same or corresponding parts. In addition, dimensional relationships such as length, width, thickness, and depth are changed as appropriate for clarity and simplification of the drawings, and do not represent actual dimensional relationships.
　図１～図２には、受光面とは反対側に位置する裏面にのみ電極が形成された本発明の太陽電池の構成の一例を示す。図１は、本発明の太陽電池１の裏面側の構成の一例を示す模式的な平面図である。図２は、本発明の太陽電池の構成の一例を示す模式的な断面図であり、図１に示すＩＩ－ＩＩ線における断面図である。 FIGS. 1 and 2 show an example of the configuration of the solar cell of the present invention in which electrodes are formed only on the back surface located on the side opposite to the light receiving surface. FIG. 1 is a schematic plan view showing an example of the configuration of the back surface side of the solar cell 1 of the present invention. FIG. 2 is a schematic cross-sectional view showing an example of the configuration of the solar cell of the present invention, and is a cross-sectional view taken along the line II-II shown in FIG.
　図１～図２に示す太陽電池１では、たとえば単結晶シリコン基板であるｎ型シリコン基板４の受光面（太陽電池１の受光面となる面）にはテクスチャ構造である凹凸形状５が形成されている。この凹凸の高さは特に限定されないが、数μｍ～数十μｍオーダーであることが好ましい。ｎ型シリコン基板４の受光面全面には、受光面側拡散層６であるｎ+半導体層がＦＳＦ（Front　Surface　Field）層として形成され、受光面側拡散層６上には受光面側パッシベーション膜１３が形成されている。受光面側パッシベーション膜１３上には反射防止膜１２が形成されている。 In the solar cell 1 shown in FIGS. 1 and 2, an uneven shape 5 having a texture structure is formed on the light receiving surface of the n-type silicon substrate 4 which is a single crystal silicon substrate (the surface serving as the light receiving surface of the solar cell 1). ing. The height of the unevenness is not particularly limited, but is preferably on the order of several μm to several tens of μm. On the entire light receiving surface of the n-type silicon substrate 4, an n + semiconductor layer that is the light receiving surface side diffusion layer 6 is formed as an FSF (Front Surface Field) layer, and on the light receiving surface side diffusion layer 6, the light receiving surface side passivation film is formed. 13 is formed. An antireflection film 12 is formed on the light receiving surface side passivation film 13.
　受光面側拡散層６の構成は特に限定されないが、受光面側拡散層６のシート抵抗値は１００Ω／□以上２５０Ω／□未満であることが好ましく、より好ましくは１００Ω／□以上１５０Ω／□以下である。これにより、太陽電池１の受光面側で発生する再結合電流が低減するので、太陽電池の特性が向上する。拡散条件および不純物濃度などを調整することにより、受光面側拡散層６のシート抵抗値を１００Ω／□以上２５０Ω／□未満とすることができる。 The structure of the light-receiving surface side diffusion layer 6 is not particularly limited, but the sheet resistance value of the light-receiving surface side diffusion layer 6 is preferably 100Ω / □ or more and less than 250Ω / □, more preferably 100Ω / □ or more and 150Ω / □ or less. It is. Thereby, since the recombination current generated on the light receiving surface side of the solar cell 1 is reduced, the characteristics of the solar cell are improved. By adjusting the diffusion conditions and the impurity concentration, the sheet resistance value of the light-receiving surface side diffusion layer 6 can be made 100Ω / □ or more and less than 250Ω / □.
　受光面側パッシベーション膜１３は、たとえば酸化シリコン膜であることが好ましい。受光面側パッシベーション膜１３の膜厚は、５ｎｍ以上２００ｎｍ以下であることが好ましく、５ｎｍ以上６０ｎｍ以下であっても良いし、１００ｎｍ以上２００ｎｍ以下であっても良い。 The light-receiving surface side passivation film 13 is preferably a silicon oxide film, for example. The film thickness of the light-receiving surface side passivation film 13 is preferably 5 nm to 200 nm, preferably 5 nm to 60 nm, or 100 nm to 200 nm.
　反射防止膜１２は、リン酸チタンを含むチタン酸化物からなる。ここで、リン酸チタンは、酸化リンよりも耐久性および耐候性に優れる。よって、リン酸チタンを含む反射防止膜１２は、酸化リンを含む反射防止膜または酸化リンを含まない反射防止膜に比べて、耐久性および耐候性に優れる。したがって、このような反射防止膜１２を備えた太陽電池では、耐久性および耐候性がさらに向上する。このような効果を有効に得るためには、反射防止膜１２に含まれるリン酸チタンの含有量はリン酸化物として１５ｗｔ％以上３５ｗｔ％以下であることが好ましく、３０ｗｔ％以上３５ｗｔ％以下であることがより好ましい。ここで、「反射防止膜１２に含まれるリン酸チタンの含有量がリン酸化物として１５ｗｔ％以上３５ｗｔ％以下である」とは、反射防止膜１２に含まれるリン酸チタンの質量をリン酸化物の質量として換算したときに、反射防止膜１２に含まれるリン酸化物の質量が反射防止膜１２の全質量に対して１５％以上３５％以下であることを意味する。反射防止膜１２中のリン酸化物の含有量はたとえばＩＣＰ（Inductively　Coupled　Plasma）発光分光分析法またはＩＣＰ質量分析法などにしたがって測定される。また、反射防止膜１２の膜厚は、たとえば１０ｎｍ以上４００ｎｍ以下であることが好ましい。 The antireflection film 12 is made of a titanium oxide containing titanium phosphate. Here, titanium phosphate is more excellent in durability and weather resistance than phosphorus oxide. Therefore, the antireflection film 12 containing titanium phosphate is more excellent in durability and weather resistance than the antireflection film containing phosphorus oxide or the antireflection film not containing phosphorus oxide. Therefore, in the solar cell provided with such an antireflection film 12, durability and weather resistance are further improved. In order to effectively obtain such an effect, the content of titanium phosphate contained in the antireflection film 12 is preferably 15 wt% or more and 35 wt% or less as the phosphor oxide, and is 30 wt% or more and 35 wt% or less. It is more preferable. Here, “the content of titanium phosphate contained in the antireflection film 12 is 15 wt% or more and 35 wt% or less as the phosphor oxide” means that the mass of the titanium phosphate contained in the antireflection film 12 is the phosphor oxide. This means that the mass of phosphorus oxide contained in the antireflection film 12 is 15% or more and 35% or less with respect to the total mass of the antireflection film 12. The content of the phosphor oxide in the antireflection film 12 is measured according to, for example, ICP (Inductively Coupled Plasma) emission spectroscopy or ICP mass spectrometry. The film thickness of the antireflection film 12 is preferably 10 nm or more and 400 nm or less, for example.
　ｎ型シリコン基板４の受光面とは反対側に位置するｎ型シリコン基板４の裏面側には、図１に示すように、帯状のｎ型用電極２と帯状のｐ型用電極３とが交互に形成されている。具体的には、ｎ型シリコン基板４の裏面側には、ｎ型半導体領域であるｎ++領域９とｐ型半導体領域であるｐ+領域１０とが交互に隣接して形成されている。ｎ++領域９はｎ型シリコン基板４の裏面のうちｎ++領域９以外の部分よりもｎ型シリコン基板４側に凹んでおり、その深さｄ（ｎ++領域９の下面とｐ+領域１０の下面との距離、図２参照）は数十ｎｍオーダーであることが好ましい。ｎ++領域９とｐ+領域１０とがｎ型シリコン基板４の裏面側において交互に隣接して形成されているので、太陽電池１に逆方向のバイアスがかかったときに、電圧が局所的にかかることを防止でき、よって、リーク電流が局所的に発生することに起因する発熱をさけることができる。なお、ｎ型不純物濃度は、ｎ型シリコン基板４、受光面側拡散層６であるｎ+半導体層、およびｎ++領域９の順に高くなることが好ましい。 As shown in FIG. 1, a strip-shaped n-type electrode 2 and a strip-shaped p-type electrode 3 are formed on the back side of the n-type silicon substrate 4 located on the side opposite to the light receiving surface of the n-type silicon substrate 4. It is formed alternately. Specifically, n ++ regions 9 as n-type semiconductor regions and p + regions 10 as p-type semiconductor regions are alternately formed adjacent to each other on the back side of the n-type silicon substrate 4. The n ++ region 9 is recessed closer to the n-type silicon substrate 4 side than the portion other than the n ++ region 9 on the back surface of the n-type silicon substrate 4, and the depth d (the bottom surface of the n ++ region 9 and p The distance from the lower surface of the + region 10 (see FIG. 2) is preferably on the order of several tens of nm. Since n ++ regions 9 and p + regions 10 are alternately formed adjacent to each other on the back side of n-type silicon substrate 4, the voltage is locally applied when reverse bias is applied to solar cell 1. Therefore, it is possible to prevent heat generation due to local occurrence of leakage current. The n-type impurity concentration is preferably higher in the order of the n-type silicon substrate 4, the n + semiconductor layer that is the light-receiving surface side diffusion layer 6, and the n ++ region 9.
　ｎ型シリコン基板４の裏面上には、第２の裏面側パッシベーション膜８と第１の裏面側パッシベーション膜１１とからなる裏面側パッシベーション膜１４が形成されている。第２の裏面側パッシベーション膜８および第１の裏面側パッシベーション膜１１は、たとえば酸化シリコン膜などであることが好ましい。ｎ++領域９上の裏面側パッシベーション膜１４の膜厚とｐ+領域１０上の裏面側パッシベーション膜１４の膜厚とは互いに異なっており、ｎ++領域９上の裏面側パッシベーション膜１４の膜厚はｐ+領域１０上の裏面側パッシベーション膜１４の膜厚よりも厚い。具体的には、ｎ++領域９上に形成された第２の裏面側パッシベーション膜８の膜厚はたとえば３０ｎｍ以上１００ｎｍ以下であることが好ましく、ｐ+領域１０上に形成された第２の裏面側パッシベーション膜８の膜厚はたとえば１０ｎｍ以上４０ｎｍ以下であることが好ましい。 On the back surface of the n-type silicon substrate 4, a back surface side passivation film 14 composed of a second back surface side passivation film 8 and a first back surface side passivation film 11 is formed. The second back-side passivation film 8 and the first back-side passivation film 11 are preferably, for example, a silicon oxide film. The thickness of the back-side passivation film 14 on the n ++ region 9 and the thickness of the back-side passivation film 14 on the p + region 10 are different from each other, and the thickness of the back-side passivation film 14 on the n ++ region 9 is different. The film thickness is larger than the film thickness of the back-side passivation film 14 on the p + region 10. Specifically, the thickness of the second back-side passivation film 8 formed on the n ++ region 9 is preferably not less than 30 nm and not more than 100 nm, for example, and the second back-side passivation film 8 formed on the p + region 10 is formed. The film thickness of the back surface side passivation film 8 is preferably not less than 10 nm and not more than 40 nm, for example.
　ｎ型用電極２は、たとえば銀からなることが好ましく、ｎ++領域９上の裏面側パッシベーション膜１４を貫通してｎ++領域９に接続されている。ｐ型用電極３は、たとえば銀からなることが好ましく、ｐ+領域１０上の裏面側パッシベーション膜１４を貫通してｐ+領域１０に接続されている。 n-type electrode 2, for example it is preferably made of silver, is connected to the n ++ region 9 through the backside passivation film 14 on the n ++ region 9. p-type electrode 3, for example, is preferably made of silver, is connected through the backside passivation film 14 on the p + region 10 to the p + region 10.
　図３は、本発明の太陽電池の裏面側から見た半導体領域の構成の一例を示す模式的な平面図であり、太陽電池１からｎ型用電極２、ｐ型用電極３、および裏面側パッシベーション膜１４を除去した後の太陽電池を裏面側から見た平面図に相当する。 FIG. 3 is a schematic plan view showing an example of the configuration of the semiconductor region as viewed from the back side of the solar cell of the present invention. From the solar cell 1 to the n-type electrode 2, the p-type electrode 3, and the back side. This corresponds to a plan view of the solar cell after removing the passivation film 14 as seen from the back side.
　ｎ型シリコン基板４の裏面の周縁には、ｎ型用電極およびｐ型用電極のどちらの電極も接続されていない半導体領域７１（以下では「ｐ+領域７１」と記す）が形成されている。このように、ｎ++領域９とは導電型の異なるｐ+領域７１をｎ++領域９の周囲に形成することにより、太陽電池１のエッジ部等に半導体領域が形成されたとしても、その半導体領域とｎ++領域９およびｐ+領域１０とを電気的に分離することが出来る。また、ｎ型シリコン基板４の裏面の周縁にｐ+領域７１を設けることにより、電極が接続されていない半導体領域がｎ型シリコン基板４の裏面の周縁に存在することとなる。よって、太陽電池１に逆方向のバイアスがかかったときには、リーク電流がｎ型シリコン基板４の周縁を通して発生することを抑制できる。 A semiconductor region 71 (hereinafter referred to as “p + region 71”) to which neither the n-type electrode nor the p-type electrode is connected is formed on the periphery of the back surface of the n-type silicon substrate 4. . Thus, by the n ++ region 9 form different p + region 71 of the conductivity type around the n ++ region 9, even the semiconductor region is formed in an edge portion or the like of the solar cell 1, The semiconductor region and the n ++ region 9 and the p + region 10 can be electrically separated. Further, by providing the p + region 71 at the periphery of the back surface of the n-type silicon substrate 4, a semiconductor region to which no electrode is connected exists at the periphery of the back surface of the n-type silicon substrate 4. Therefore, when a reverse bias is applied to the solar cell 1, it can be suppressed that a leak current is generated through the periphery of the n-type silicon substrate 4.
　なお、ｎ++領域９およびｐ+領域１０の各構成は図３に記載の構成に限定されない。たとえば、ｎ++領域９は、図３では全てがつながって１つの半導体領域を形成しているが、必ずしも全てがつながっていなくても良い。また、ｐ+領域１０は、図３では複数の領域に分離されているが、互いにつながって１つの半導体領域を形成していても良い。 Each configuration of n ++ region 9 and p + region 10 is not limited to the configuration shown in FIG. For example, although the n ++ regions 9 are all connected in FIG. 3 to form one semiconductor region, they are not necessarily connected. Further, the p + region 10 is separated into a plurality of regions in FIG. 3, but may be connected to each other to form one semiconductor region.
　また、図１に示すように、ｎ型シリコン基板４の裏面側では最も周縁に位置する電極の導電型が同じであるため、太陽電池を１８０°回転対象構造とすることが可能である。よって、太陽電池を複数並べて太陽電池モジュールを作製するときには、たとえば太陽電池を図１における上下逆にして配置することができる。 Further, as shown in FIG. 1, since the conductivity type of the electrode located at the outermost edge is the same on the back surface side of the n-type silicon substrate 4, the solar cell can have a 180 ° rotation target structure. Therefore, when producing a solar cell module by arranging a plurality of solar cells, for example, the solar cells can be arranged upside down in FIG.
　以下に、本発明の太陽電池の製造方法の一例を示す。
　図４（ａ）～（ｉ）は、図１および図２に示す本発明の太陽電池の製造方法の一例を示す模式的な断面図であり、図４（ｊ）は、図４（ｇ）に示すＩＶＪ領域の拡大図である。 Below, an example of the manufacturing method of the solar cell of this invention is shown.
4 (a) to 4 (i) are schematic cross-sectional views showing an example of a method for manufacturing the solar cell of the present invention shown in FIGS. 1 and 2, and FIG. 4 (j) is a cross-sectional view of FIG. It is an enlarged view of IVJ area | region shown in FIG.
　まず、図４（ａ）に示すように、たとえば１００μｍ厚のｎ型シリコン基板４の裏面上に、窒化シリコン膜等からなるテクスチャマスク２１をＣＶＤ法またはスパッタ法等により形成する。 First, as shown in FIG. 4A, a texture mask 21 made of a silicon nitride film or the like is formed on the back surface of an n-type silicon substrate 4 having a thickness of 100 μm, for example, by CVD or sputtering.
　次に、図４（ｂ）に示すように、ｎ型シリコン基板４の受光面にテクスチャ構造である凹凸形状５をエッチングにより形成する。エッチングは、たとえば水酸化ナトリウムまたは水酸化カリウムなどのアルカリ水溶液にイソプロピルアルコールを添加して７０℃以上８０℃以下に加熱した溶液を用いて、行われることが好ましい。 Next, as shown in FIG. 4 (b), an uneven shape 5 having a texture structure is formed on the light receiving surface of the n-type silicon substrate 4 by etching. Etching is preferably performed using, for example, a solution in which isopropyl alcohol is added to an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide and heated to 70 ° C. or higher and 80 ° C. or lower.
　次に、図４（ｃ）を用いて次工程を説明する。図４（ｃ）では、ｎ型シリコン基板４の裏面側を上に記している。図４（ｃ）に示すように、ｎ型シリコン基板４の裏面上に形成されたテクスチャマスク２１を除去してから、ｎ型シリコン基板４の受光面上に酸化シリコン膜等からなる拡散マスク２２を形成する。その後、ｎ型シリコン基板４の裏面においてｎ++領域９を形成しようとする箇所以外に、例えば、溶剤、増粘剤および酸化シリコン前駆体を含むマスキングペーストをインクジェットまたはスクリーン印刷等で塗布し、熱処理を行う。この熱処理により、ｎ型シリコン基板４の裏面においてｎ++領域９を形成しようとする箇所以外に、拡散マスク２３が形成される。ＰＯＣｌ3を用いた気相拡散によって、ｎ型シリコン基板４の裏面のうち拡散マスク２３から露出した箇所に、ｎ型不純物であるリンが拡散する。これにより、ｎ++領域９が形成される。 Next, the next step will be described with reference to FIG. In FIG.4 (c), the back side of the n-type silicon substrate 4 is described above. As shown in FIG. 4C, after removing the texture mask 21 formed on the back surface of the n-type silicon substrate 4, a diffusion mask 22 made of a silicon oxide film or the like on the light-receiving surface of the n-type silicon substrate 4. Form. Thereafter, in addition to the location where the n ++ region 9 is to be formed on the back surface of the n-type silicon substrate 4, for example, a masking paste containing a solvent, a thickener and a silicon oxide precursor is applied by inkjet or screen printing, Heat treatment is performed. By this heat treatment, a diffusion mask 23 is formed on the back surface of the n-type silicon substrate 4 in addition to the portion where the n ++ region 9 is to be formed. By vapor phase diffusion using POCl 3 , phosphorus, which is an n-type impurity, diffuses into a portion of the back surface of the n-type silicon substrate 4 exposed from the diffusion mask 23. As a result, an n ++ region 9 is formed.
　次に、図４（ｄ）に示すように、ｎ型シリコン基板４に形成された拡散マスク２２，２３と、拡散マスク２２，２３のそれぞれにリンが拡散することにより形成されたガラス層とを、たとえばフッ化水素酸処理により除去する。その後、酸素または水蒸気による熱酸化を行い、酸化シリコン膜２４を形成する。この際、図４（ｄ）に示すように、ｎ型シリコン基板４の裏面側に形成されたｎ++領域９上の酸化シリコン膜２４の膜厚が厚くなる。たとえば９００℃での水蒸気による熱酸化を行うと、ｎ++領域９以外の領域の上に形成された酸化シリコン膜２４の膜厚は７０ｎｍ以上９０ｎｍ以下となり、ｎ++領域９の上に形成された酸化シリコン膜２４の膜厚は２５０ｎｍ以上３５０ｎｍ以下となる。ここで、酸素または水蒸気による熱酸化前のｎ++領域９におけるリンの表面濃度は５×１０19／ｃｍ3以上であることが好ましい。また、酸素または水蒸気による熱酸化の処理温度としては、たとえば、酸素による熱酸化では８００℃以上１０００℃以下であることが好ましく、水蒸気による熱酸化では８００℃以上９５０℃以下であることが好ましい。 Next, as shown in FIG. 4D, diffusion masks 22 and 23 formed on the n-type silicon substrate 4 and glass layers formed by diffusion of phosphorus into the diffusion masks 22 and 23, respectively. For example, it is removed by hydrofluoric acid treatment. Thereafter, thermal oxidation with oxygen or water vapor is performed to form a silicon oxide film 24. At this time, as shown in FIG. 4D, the thickness of the silicon oxide film 24 on the n ++ region 9 formed on the back surface side of the n-type silicon substrate 4 is increased. For example, thermal oxidation is performed by steam at 900 ° C., the thickness of the silicon oxide film 24 formed on the region other than the n ++ region 9 becomes 70nm or 90nm or less, formed on the n ++ region 9 The film thickness of the silicon oxide film 24 is 250 nm or more and 350 nm or less. Here, the surface concentration of phosphorus in the n ++ region 9 before thermal oxidation with oxygen or water vapor is preferably 5 × 10 19 / cm 3 or more. The treatment temperature for thermal oxidation with oxygen or water vapor is preferably 800 ° C. or higher and 1000 ° C. or lower for thermal oxidation with oxygen, and preferably 800 ° C. or higher and 950 ° C. or lower for thermal oxidation with water vapor.
　熱酸化により形成された酸化シリコン膜の膜厚がｎ++領域９の上とｎ++領域９以外の領域の上とで異なる理由は次に示すとおりである。熱酸化による酸化シリコン膜の成長速度は、シリコン基板に拡散している不純物の種類とその不純物の濃度とによって決まる。特にシリコン基板におけるｎ型不純物濃度が高い場合には、熱酸化による酸化シリコン膜の成長速度は速くなる。ここで、ｎ++領域９の方が、ｎ型シリコン基板４よりも、ｎ型不純物濃度は高い。よって、ｎ++領域９上に形成された酸化シリコン膜２４の膜厚の方が、ｎ型シリコン基板４上に形成された酸化シリコン膜２４の膜厚よりも厚くなる。酸化シリコン膜２４は、熱酸化時にシリコンと酸素とが結びつくことにより形成されるので、ｎ++領域９は、ｎ++領域９が形成されていない領域よりもｎ型シリコン基板４側に凹む。 Why the film thickness of the silicon oxide film formed by thermal oxidation is different between on the upper and n ++ region 9 other than the area of the n ++ region 9 are as shown below. The growth rate of the silicon oxide film by thermal oxidation is determined by the type of impurity diffused in the silicon substrate and the concentration of the impurity. In particular, when the n-type impurity concentration in the silicon substrate is high, the growth rate of the silicon oxide film by thermal oxidation increases. Here, the n ++ region 9 has a higher n-type impurity concentration than the n-type silicon substrate 4. Therefore, the thickness of the silicon oxide film 24 formed on the n ++ region 9 is larger than the thickness of the silicon oxide film 24 formed on the n-type silicon substrate 4. Since the silicon oxide film 24 is formed by combining silicon and oxygen during thermal oxidation, the n ++ region 9 is recessed closer to the n-type silicon substrate 4 than the region where the n ++ region 9 is not formed. .
　なお、酸化シリコン膜２４をｐ+領域１０の形成時におけるｎ++領域９の拡散マスクとして使用する場合には、ｎ++領域９上に形成された酸化シリコン膜２４の膜厚とｎ++領域９以外の領域の上に形成された酸化シリコン膜２４の膜厚との差が６０ｎｍ以上であることが好ましい。 When the silicon oxide film 24 is used as a diffusion mask for the n ++ region 9 when the p + region 10 is formed, the film thickness of the silicon oxide film 24 formed on the n ++ region 9 and the n + The difference from the film thickness of the silicon oxide film 24 formed on the region other than the + region 9 is preferably 60 nm or more.
　次に、図４（ｅ）に示すように、ｎ型シリコン基板４の受光面に形成された酸化シリコン膜２４とｎ型シリコン基板４の裏面におけるｎ++領域９以外の領域の上に形成された酸化シリコン膜２４とをエッチングにより除去する。ｎ型シリコン基板４の裏面では、先述したように、酸化シリコン膜２４がｎ++領域９の上に厚く形成されている。それだけでなく、ｎ++領域９の上に形成された酸化シリコン膜２４とｎ++領域９以外の領域の上に形成された酸化シリコン膜２４とではエッチングレートが異なる。よって、エッチングにより、ｎ++領域９の上に形成された酸化シリコン膜２４のみが残るようになる。たとえば９００℃での水蒸気による熱酸化を３０分間行なうことにより酸化シリコン膜２４を形成し、フッ化水素酸処理によりｎ++領域９以外の領域の上に形成された酸化シリコン膜２４を除去した場合、ｎ++領域９の上には膜厚が１２０ｎｍ程度の酸化シリコン膜２４が残存する。先述したように、ｎ++領域９上に形成された酸化シリコン膜２４の膜厚とｎ++領域９以外の領域の上に形成された酸化シリコン膜２４の膜厚との差が６０ｎｍ以上であれば、酸化シリコン膜２４はｐ+領域１０の形成時におけるｎ++領域９の拡散マスクとして機能する。よって、上記方法によりｎ++領域９の上に残存した酸化シリコン膜２４（膜厚が１２０ｎｍ程度）は、ｐ+領域１０の形成時におけるｎ++領域９の拡散マスクとして機能しうる。 Next, as shown in FIG. 4E, the silicon oxide film 24 formed on the light-receiving surface of the n-type silicon substrate 4 and the region other than the n ++ region 9 on the back surface of the n-type silicon substrate 4 are formed. The silicon oxide film 24 thus formed is removed by etching. On the back surface of the n-type silicon substrate 4, as described above, the silicon oxide film 24 is formed thick on the n ++ region 9. Not only that, the etching rate is different between the silicon oxide film 24 formed on the formed areas other than the silicon oxide film 24 and the n ++ region 9 was on the n ++ region 9. Therefore, only the silicon oxide film 24 formed on the n ++ region 9 remains by etching. For example, the silicon oxide film 24 is formed by performing thermal oxidation with water vapor at 900 ° C. for 30 minutes, and the silicon oxide film 24 formed on the region other than the n ++ region 9 is removed by hydrofluoric acid treatment. In this case, the silicon oxide film 24 having a thickness of about 120 nm remains on the n ++ region 9. As previously described, the difference between the thickness of the silicon oxide film 24 formed on the film thickness and n ++ region 9 other than the area of the silicon oxide film 24 formed on n ++ region 9 than 60nm Then, the silicon oxide film 24 functions as a diffusion mask for the n ++ region 9 when the p + region 10 is formed. Therefore, the silicon oxide film 24 (having a film thickness of about 120 nm) remaining on the n ++ region 9 by the above method can function as a diffusion mask for the n ++ region 9 when the p + region 10 is formed.
　その後、ｎ型シリコン基板４の受光面上に酸化シリコン膜等からなる拡散マスク２５を形成する。続いて、ｎ型シリコン基板４の裏面上に、有機性高分子にホウ素化合物を反応させて得られたポリマーをアルコール系溶媒に溶解させることにより得られた溶液を塗布し、乾燥後、熱処理を行なう。これにより、ｎ型シリコン基板４の裏面のうち酸化シリコン膜２４から露出した箇所には、ｐ型不純物であるボロンが拡散し、よって、ｐ+領域１０とｐ+領域７１とが形成される。 Thereafter, a diffusion mask 25 made of a silicon oxide film or the like is formed on the light receiving surface of the n-type silicon substrate 4. Subsequently, a solution obtained by dissolving a polymer obtained by reacting an organic polymer with a boron compound in an alcohol solvent is applied on the back surface of the n-type silicon substrate 4, and after drying, heat treatment is performed. Do. As a result, boron, which is a p-type impurity, diffuses into a portion of the back surface of the n-type silicon substrate 4 exposed from the silicon oxide film 24, thereby forming a p + region 10 and a p + region 71.
　次に、図４（ｆ）を用いて次工程を説明する。図４（ｆ）では、ｎ型シリコン基板４の受光面側を上に記している。図４（ｆ）に示すように、ｎ型シリコン基板４に形成された酸化シリコン膜２４および拡散マスク２５と、酸化シリコン膜２４および拡散マスク２５のそれぞれにボロンが拡散することにより形成されたガラス層とを、たとえばフッ化水素酸処理により除去する。その後、ＣＶＤ法により、または、ｎ型シリコン基板４の裏面上にＳＯＧ（スピンオングラス）を塗布し焼成することにより、ｎ型シリコン基板４の裏面上に酸化シリコン膜等からなる第１の裏面側パッシベーション膜１１を形成する。このようにして形成された第１の裏面側パッシベーション膜１１は、たとえば５０ｎｍ以上１００ｎｍ以下の膜厚を有し、拡散マスクとしても機能しうる。 Next, the next process will be described with reference to FIG. In FIG. 4F, the light receiving surface side of the n-type silicon substrate 4 is shown above. As shown in FIG. 4 (f), the glass formed by diffusing boron into each of the silicon oxide film 24 and the diffusion mask 25 formed on the n-type silicon substrate 4 and the silicon oxide film 24 and the diffusion mask 25. The layer is removed, for example, by hydrofluoric acid treatment. Then, the first back surface side made of a silicon oxide film or the like on the back surface of the n-type silicon substrate 4 by CVD or by applying and baking SOG (spin-on-glass) on the back surface of the n-type silicon substrate 4. A passivation film 11 is formed. The first back-side passivation film 11 formed in this way has a film thickness of, for example, 50 nm to 100 nm and can also function as a diffusion mask.
　その後、図４（ｇ）および図４（ｊ）に示すように、ｎ型シリコン基板４の受光面上に、受光面側拡散層６であるｎ+半導体層および反射防止膜１２を形成する。具体的には、ｎ型シリコン基板４の受光面に、リン化合物、チタンアルコキシドおよびアルコールを少なくとも含む混合液を塗布して乾燥する。ここで、混合液のリン化合物としては、五酸化リンなどを用いることができ、チタンアルコキシドとしてはテトライソプロピルチタネートなどを用いることができ、アルコールとしてはイソプロピルアルコールなどを用いることができる。次に、熱処理を行なう。これにより、ｎ型不純物であるリンが拡散して、図４（ｊ）に示すようにｎ型シリコン基板４の受光面全面に受光面側拡散層６であるｎ+半導体層および反射防止膜１２が形成される。この熱処理は窒素雰囲気で行なわれることが好ましく、これにより、受光面側拡散層６のｎ型不純物表面濃度を低減することができる。この熱処理の処理温度はたとえば８５０℃以上１０００℃以下であることが好ましく、より好ましくは８８０℃以上９５０℃以下である。 Thereafter, as shown in FIGS. 4G and 4J, an n + semiconductor layer and an antireflection film 12 which are the light-receiving surface side diffusion layers 6 are formed on the light-receiving surface of the n-type silicon substrate 4. Specifically, a liquid mixture containing at least a phosphorus compound, titanium alkoxide and alcohol is applied to the light receiving surface of the n-type silicon substrate 4 and dried. Here, phosphorus pentoxide or the like can be used as the phosphorus compound in the mixed solution, tetraisopropyl titanate or the like can be used as the titanium alkoxide, and isopropyl alcohol or the like can be used as the alcohol. Next, heat treatment is performed. Thus, the phosphorous diffusion is n-type impurity, Figure 4 n + semiconductor layer and the antireflection film 12 is a light receiving surface side diffusion layer 6 in the light-receiving surface the whole surface of the n-type silicon substrate 4, as shown in (j) Is formed. This heat treatment is preferably performed in a nitrogen atmosphere, whereby the n-type impurity surface concentration of the light-receiving surface side diffusion layer 6 can be reduced. The heat treatment temperature is preferably 850 ° C. or higher and 1000 ° C. or lower, and more preferably 880 ° C. or higher and 950 ° C. or lower.
　その後、ｎ型シリコン基板４の裏面上に、酸化シリコン膜である第２の裏面側パッシベーション膜８を形成する。具体的には、酸素雰囲気下における熱酸化を行う。これにより、ｎ型シリコン基板４の裏面上に第２の裏面側パッシベーション膜８である酸化シリコン膜が形成されるとともに、図４（ｊ）に示すようにｎ型シリコン基板４の受光面全面にも酸化シリコン膜が形成される。この受光面全面に形成された酸化シリコン膜は、受光面側拡散層６と反射防止膜１２との間に形成され、受光面側パッシベーション膜１３となる。それだけでなく、反射防止膜１２がリン酸チタンを含むチタン酸化膜となる。 Thereafter, a second back-side passivation film 8 that is a silicon oxide film is formed on the back surface of the n-type silicon substrate 4. Specifically, thermal oxidation is performed in an oxygen atmosphere. As a result, a silicon oxide film, which is the second back-side passivation film 8, is formed on the back surface of the n-type silicon substrate 4, and the entire light-receiving surface of the n-type silicon substrate 4 is formed as shown in FIG. A silicon oxide film is also formed. The silicon oxide film formed on the entire surface of the light receiving surface is formed between the light receiving surface side diffusion layer 6 and the antireflection film 12 and becomes the light receiving surface side passivation film 13. In addition, the antireflection film 12 becomes a titanium oxide film containing titanium phosphate.
　このように、酸素雰囲気下における熱酸化により第２の裏面側パッシベーション膜８を形成する際に、受光面側拡散層６と反射防止膜１２との間に受光面側パッシベーション膜１３が形成される。その理由としては、次に示すことが挙げられる。ｎ型シリコン基板４の受光面に形成された凹凸形状５の凹部では、反射防止膜１２の膜厚が厚いため、反射防止膜１２にクラックが生じる。そして、クラックが生じた箇所から酸素が入り込むことにより、受光面側パッシベーション膜１３である酸化シリコン膜が成長する。また、ｎ型シリコン基板４の受光面に形成された凹凸形状５の凸部では、反射防止膜１２の膜厚が薄いため、酸素が反射防止膜１２を透過可能である。そして、酸素が反射防止膜１２を透過することにより、受光面側パッシベーション膜１３である酸化シリコン膜が成長する。 Thus, when forming the second back surface side passivation film 8 by thermal oxidation in an oxygen atmosphere, the light receiving surface side passivation film 13 is formed between the light receiving surface side diffusion layer 6 and the antireflection film 12. . The reason is as follows. In the concave portion of the concavo-convex shape 5 formed on the light receiving surface of the n-type silicon substrate 4, the antireflection film 12 is cracked because the antireflection film 12 is thick. Then, when oxygen enters from the location where the crack occurs, a silicon oxide film which is the light-receiving surface side passivation film 13 grows. Further, since the film thickness of the antireflection film 12 is thin at the convex portion of the concavo-convex shape 5 formed on the light receiving surface of the n-type silicon substrate 4, oxygen can pass through the antireflection film 12. Then, when oxygen passes through the antireflection film 12, a silicon oxide film that is the light-receiving surface side passivation film 13 grows.
　また、酸素雰囲気下における熱酸化により、第２の裏面側パッシベーション膜８はｎ型シリコン基板４の裏面と第１の裏面側パッシベーション膜１１との間に形成される。その理由としては、次に示すことが挙げられる。ｎ型シリコン基板４の裏面上の第１の裏面側パッシベーション膜１１はＣＶＤ法等により形成されるため、第１の裏面側パッシベーション膜１１の内部を酸素が透過しやすい。そして、酸素が第１の裏面側パッシベーション膜１１を透過することにより、第２の裏面側パッシベーション膜８である酸化シリコン膜が成長する。 In addition, the second back surface passivation film 8 is formed between the back surface of the n-type silicon substrate 4 and the first back surface passivation film 11 by thermal oxidation in an oxygen atmosphere. The reason is as follows. Since the first back surface passivation film 11 on the back surface of the n-type silicon substrate 4 is formed by a CVD method or the like, oxygen easily passes through the inside of the first back surface passivation film 11. Then, when oxygen passes through the first back surface side passivation film 11, a silicon oxide film as the second back surface side passivation film 8 is grown.
　それだけでなく、酸素雰囲気下における熱酸化により第２の裏面側パッシベーション膜８を形成すると、反射防止膜１２をリン酸チタンを含むチタン酸化膜とすることができる。その理由としては、次に示すことが挙げられる。上述のように、酸素雰囲気下における熱酸化により第２の裏面側パッシベーション膜８を形成すると、酸素が反射防止膜１２に生じたクラックから入り込む、または、酸素が反射防止膜１２を透過する。そして、反射防止膜１２内に入り込んだ酸素のうちの一部が反射防止膜１２内のリンおよびチタンと結合することにより、リン酸チタンが生じる。 In addition, when the second back surface passivation film 8 is formed by thermal oxidation in an oxygen atmosphere, the antireflection film 12 can be a titanium oxide film containing titanium phosphate. The reason is as follows. As described above, when the second back-side passivation film 8 is formed by thermal oxidation in an oxygen atmosphere, oxygen enters from cracks generated in the antireflection film 12 or oxygen passes through the antireflection film 12. A part of the oxygen that has entered the antireflection film 12 is combined with phosphorus and titanium in the antireflection film 12, thereby producing titanium phosphate.
　反射防止膜１２に含まれるリン酸チタンの含有量はリン酸化物として１５ｗｔ％以上３５ｗｔ％以下であることが好ましく、３０ｗｔ％以上３５ｗｔ％以下であることがより好ましい。反射防止膜１２に含まれるリン酸化物の含有量が３５ｗｔ％を超えると、反射防止膜１２は白く変色することがある。反射防止膜１２に含まれるリン酸化物の含有量が１５ｗｔ％未満であれば、反射防止膜１２の耐久性および耐候性が十分に向上しないことがある。 The content of titanium phosphate contained in the antireflection film 12 is preferably 15 wt% or more and 35 wt% or less, and more preferably 30 wt% or more and 35 wt% or less as the phosphor oxide. When the content of the phosphorous oxide contained in the antireflection film 12 exceeds 35 wt%, the antireflection film 12 may turn white. If the content of phosphorous oxide contained in the antireflection film 12 is less than 15 wt%, the durability and weather resistance of the antireflection film 12 may not be sufficiently improved.
　酸素雰囲気下における熱処理温度は、特に限定されないが、好ましくは８５０℃よりも高く、より好ましくは９００℃以上１０００℃以下である。これにより、酸素が拡散しやすくなるため、受光面側パッシベーション膜１３および第２の裏面側パッシベーション膜８が形成されやすくなる。また、反射防止膜１２を、リン酸チタンを含むチタン酸化膜とすることができる。それだけでなく、太陽電池１の受光面側で発生する再結合電流を低減することができるので、太陽電池の電池特性がさらに向上する。なお、受光面側拡散層６のシート抵抗値を１００Ω／□以上２５０Ω／□未満とすることによっても、太陽電池１の受光面側で発生する再結合電流を低減させることができる。 The heat treatment temperature in an oxygen atmosphere is not particularly limited, but is preferably higher than 850 ° C, more preferably 900 ° C or higher and 1000 ° C or lower. Thereby, oxygen easily diffuses, so that the light-receiving surface side passivation film 13 and the second back surface passivation film 8 are easily formed. Further, the antireflection film 12 can be a titanium oxide film containing titanium phosphate. In addition, since the recombination current generated on the light receiving surface side of the solar cell 1 can be reduced, the battery characteristics of the solar cell are further improved. Note that the recombination current generated on the light receiving surface side of the solar cell 1 can also be reduced by setting the sheet resistance value of the light receiving surface side diffusion layer 6 to 100 Ω / □ or more and less than 250 Ω / □.
　なお、受光面側パッシベーション膜１３の膜厚は、たとえば５ｎｍ以上２００ｎｍ以下であることが好ましく、５ｎｍ以上６０ｎｍ以下であっても良いし、１００ｎｍ以上２００ｎｍ以下であっても良い。第２の裏面側パッシベーション膜８の膜厚については、ｎ++領域９上に形成された第２の裏面側パッシベーション膜８の膜厚はたとえば３０ｎｍ以上１００ｎｍ以下であることが好ましく、ｐ+領域１０上に形成された第２の裏面側パッシベーション膜８の膜厚はたとえば１０ｎｍ以上４０ｎｍ以下であることが好ましい。 The film thickness of the light-receiving surface side passivation film 13 is preferably, for example, 5 nm to 200 nm, preferably 5 nm to 60 nm, or 100 nm to 200 nm. Regarding the film thickness of the second back-side passivation film 8, the film thickness of the second back-side passivation film 8 formed on the n ++ region 9 is preferably, for example, 30 nm or more and 100 nm or less, and the p + region The thickness of the second back-side passivation film 8 formed on 10 is preferably 10 nm or more and 40 nm or less, for example.
　また、第２の裏面側パッシベーション膜８の形成、受光面側パッシベーション膜１３の形成、および反射防止膜１２を、リン酸チタンを含むチタン酸化膜とすることは、受光面側拡散層６および反射防止膜１２を形成する熱処理に引き続き、ガスを切り替えることにより行なうことが可能である。すなわち、受光面側拡散層６であるｎ+半導体層および反射防止膜１２を形成するための熱処理と受光面側パッシベーション膜１３を形成するための熱処理とを一連の熱処理によって行なうことができる。これにより、太陽電池の製造工程数を減らすことができる。 Further, the formation of the second back surface side passivation film 8, the formation of the light receiving surface side passivation film 13, and the formation of the antireflection film 12 as a titanium oxide film containing titanium phosphate can be achieved by the light receiving surface side diffusion layer 6 and the reflection layer. Subsequent to the heat treatment for forming the prevention film 12, it can be performed by switching the gas. That is, the heat treatment for forming the n + semiconductor layer and the antireflection film 12 that are the light-receiving surface side diffusion layer 6 and the heat treatment for forming the light-receiving surface side passivation film 13 can be performed by a series of heat treatments. Thereby, the manufacturing process number of a solar cell can be reduced.
　次に、図４（ｈ）に示すように、ｎ型シリコン基板４の裏面側に形成されたｎ++領域９およびｐ+領域１０のそれぞれに電極を形成する。具体的には、ｎ型シリコン基板４の裏面上に形成された裏面側パッシベーション膜１４にパターニングを行う。パターニングは、エッチングペーストをスクリーン印刷法などで裏面側パッシベーション膜１４上に塗布してから加熱処理を行なうことにより、行なわれる。その後、エッチングペーストを超音波洗浄してから酸処理により除去する。ここで、エッチングペーストは、例えば、エッチング成分としてリン酸、フッ化水素、フッ化アンモニウムおよびフッ化水素アンモニウムからなる群から選択された少なくとも１種を含むことが好ましく、水、有機溶媒および増粘剤をさらに含むことが好ましい。 Next, as shown in FIG. 4H, electrodes are formed on each of the n ++ region 9 and the p + region 10 formed on the back surface side of the n-type silicon substrate 4. Specifically, patterning is performed on the back surface side passivation film 14 formed on the back surface of the n-type silicon substrate 4. The patterning is performed by applying an etching paste on the backside passivation film 14 by screen printing or the like and then performing a heat treatment. Thereafter, the etching paste is ultrasonically cleaned and then removed by acid treatment. Here, the etching paste preferably contains at least one selected from the group consisting of phosphoric acid, hydrogen fluoride, ammonium fluoride, and ammonium hydrogen fluoride as an etching component, for example, water, an organic solvent, and a thickening agent. It is preferable to further contain an agent.
　次に、図４（ｉ）に示すように、ｎ型シリコン基板４の裏面の所定の位置（裏面側パッシベーション膜１４に形成された貫通孔内）に、銀ペーストをたとえばスクリーン印刷法により塗布し、乾燥する。その後、焼成を行なう。これにより、ｎ++領域９にはｎ型用電極２が接続され、ｐ+領域１０にはｐ型用電極３が接続される。このようにして、図１～図２に示す太陽電池１が作製される。 Next, as shown in FIG. 4 (i), silver paste is applied to a predetermined position on the back surface of the n-type silicon substrate 4 (in the through-hole formed in the back surface side passivation film 14) by, for example, screen printing. ,dry. Thereafter, firing is performed. Thus, n-type electrode 2 is connected to n ++ region 9, and p-type electrode 3 is connected to p + region 10. In this way, the solar cell 1 shown in FIGS. 1 and 2 is manufactured.
　ここで、反射防止膜１２の性能を評価するためのサンプルを作製して、反射防止膜１２に対してＸ線回折（ＸＲＤ（X-Ray　Diffraction））測定を行った。図５は、反射防止膜１２の性能を評価するために作製したサンプル８１の構成を示す断面図である。図５に示すサンプル８１では、ｎ型シリコン基板８２の受光面側に受光面側拡散層に対応するｎ+半導体層８３が形成されており、ｎ+半導体層８３上にはパッシベーション膜に対応する酸化シリコン膜８４と反射防止膜に対応する膜８５とが順に形成されている。 Here, a sample for evaluating the performance of the antireflection film 12 was prepared, and X-ray diffraction (XRD (X-Ray Diffraction)) measurement was performed on the antireflection film 12. FIG. 5 is a cross-sectional view showing a configuration of a sample 81 produced for evaluating the performance of the antireflection film 12. In the sample 81 shown in FIG. 5, an n + semiconductor layer 83 corresponding to the light receiving surface side diffusion layer is formed on the light receiving surface side of the n-type silicon substrate 82, and the n + semiconductor layer 83 corresponds to the passivation film. A silicon oxide film 84 and a film 85 corresponding to the antireflection film are sequentially formed.
　図６は、図５に示すサンプル８１の製造方法の一例を示すフロー図である。図５に示すサンプル８１は次に示す方法にしたがって製造された。まず、工程Ｓ１では、ｎ型シリコン基板８２の表面をエッチング等でフラットにした。次に、工程Ｓ２では、フラットにされたｎ型シリコン基板８２の面に、リン化合物、チタンアルコキシドおよびアルコールを少なくとも含む混合液を塗布し、乾燥させた。ここで、混合液のリン化合物としては五酸化リンを用い、チタンアルコキシドとしてはテトライソプロピルチタネートを用い、アルコールとしてはイソプロピルアルコールを用いた。混合液中の五酸化リンの濃度は０．０２ｇ／ｃｍ3であった。続いて、工程Ｓ３では、熱処理によりｎ型不純物であるリンが拡散し、ｎ+半導体層８３およびリンを含有したチタン酸化物からなる膜（反射防止膜に対応する膜）８５が形成された。工程Ｓ３における熱処理を９２０℃、窒素雰囲気下で行った。続いて、工程Ｓ４では、熱酸化を行って酸化シリコン膜８４を形成した。工程Ｓ４における熱処理を９５０℃で行った。また、工程Ｓ４における熱処理を酸素雰囲気下および水蒸気雰囲気下のそれぞれで行い、工程Ｓ４における熱処理を酸素雰囲気下で行った場合を実施例１とし、工程Ｓ４における熱処理を水蒸気雰囲気下で行った場合を比較例１とした。 FIG. 6 is a flowchart showing an example of a method for manufacturing the sample 81 shown in FIG. A sample 81 shown in FIG. 5 was manufactured according to the following method. First, in step S1, the surface of the n-type silicon substrate 82 was flattened by etching or the like. Next, in step S2, a mixed solution containing at least a phosphorus compound, titanium alkoxide, and alcohol was applied to the flat surface of the n-type silicon substrate 82 and dried. Here, phosphorus pentoxide was used as the phosphorus compound of the mixed solution, tetraisopropyl titanate was used as the titanium alkoxide, and isopropyl alcohol was used as the alcohol. The concentration of phosphorus pentoxide in the mixture was 0.02 g / cm 3 . Subsequently, in step S3, phosphorus, which is an n-type impurity, was diffused by heat treatment, so that an n + semiconductor layer 83 and a film made of titanium oxide containing phosphorus (a film corresponding to an antireflection film) 85 were formed. The heat treatment in step S3 was performed at 920 ° C. in a nitrogen atmosphere. Subsequently, in step S4, thermal oxidation was performed to form a silicon oxide film 84. The heat treatment in step S4 was performed at 950 ° C. In addition, the heat treatment in step S4 is performed in an oxygen atmosphere and a water vapor atmosphere, the heat treatment in step S4 is performed in an oxygen atmosphere, and the heat treatment in step S4 is performed in a water vapor atmosphere. It was set as Comparative Example 1.
　図７（ａ）は、実施例１における反射防止膜のＸ線回折の測定結果を示すグラフである。図７（ｂ）は、リン酸チタン（ＴｉＰ2Ｏ7）のＸＲＤパターン（ＪＣＰＤＳ（Joint　Committee　for　Powder　Diffraction　Standards）－ＩＣＤＤ（International　Centre　for　Diffraction　Data）－ＰＤＦ（Powder　Diffraction　Files））である。図７（ｃ）は、アナタース型の酸化チタン（ＴｉＯ2）のＸＲＤパターン（ＪＣＰＤＳ－ＩＣＤＤ－ＰＤＦ）である。また、図８（ａ）は、比較例における反射防止膜のＸ線回折の測定結果を示すグラフである。図８（ｂ）は、アナタース型の酸化チタン（ＴｉＯ2）のＸＲＤパターン（ＪＣＰＤＳ－ＩＣＤＤ－ＰＤＦ）である。 FIG. 7A is a graph showing the measurement result of the X-ray diffraction of the antireflection film in Example 1. FIG. FIG. 7B is an XRD pattern (JCPDS (Joint Committee for Powder Diffraction Standards) -ICDD (International Center for Diffraction Data) -PDF (Powder Diffraction Files)) of titanium phosphate (TiP 2 O 7 ). FIG. 7C shows an XRD pattern (JCPDS-ICDD-PDF) of anatase type titanium oxide (TiO 2 ). FIG. 8A is a graph showing the measurement result of the X-ray diffraction of the antireflection film in the comparative example. FIG. 8B is an XRD pattern (JCPDS-ICDD-PDF) of anatase-type titanium oxide (TiO 2 ).
　図７（ａ）に示すグラフには、リン酸チタンに由来する強度の高いピークが観察され、また図７（ａ）において矢印で示した２θ＝４７度～４８度付近にリン酸チタンおよびアナタース型酸化チタンのそれぞれに特有なピークが並んで観察された。このことから、工程Ｓ３での熱処理を窒素雰囲気下で行い、次いで工程Ｓ４での熱酸化を酸素雰囲気下で行った場合には、反射防止膜に対応する膜８５は、微量のアナタース型酸化チタンを含むと考えられる。一方、図８（ａ）に示すグラフには、アナタース型酸化チタンに由来するピークのみが観察された。そのため、工程Ｓ４での熱酸化を水蒸気雰囲気下で行った場合には、反射防止膜に対応する膜は、アナタース型酸化チタンを含んだ膜であると考えられる。 In the graph shown in FIG. 7A, a high-intensity peak derived from titanium phosphate is observed, and titanium phosphate and anatase are in the vicinity of 2θ = 47 ° to 48 ° indicated by arrows in FIG. 7A. Peaks peculiar to each of the type titanium oxides were observed side by side. Therefore, when the heat treatment in step S3 is performed in a nitrogen atmosphere and then the thermal oxidation in step S4 is performed in an oxygen atmosphere, the film 85 corresponding to the antireflection film has a very small amount of anatase type titanium oxide. It is thought that it contains. On the other hand, only the peak derived from anatase type titanium oxide was observed in the graph shown in FIG. Therefore, when the thermal oxidation in step S4 is performed in a water vapor atmosphere, the film corresponding to the antireflection film is considered to be a film containing anatase-type titanium oxide.
　以上より、太陽電池の作製時において、受光面側拡散層であるｎ+半導体層と反射防止膜とを作製するときの熱処理を窒素雰囲気下で行い、その後、受光面側パッシベーション膜である酸化シリコン膜を酸素雰囲気下での熱酸化により形成することにより、反射防止膜をリン酸チタンを含むチタン酸化膜とすることができる。よって、耐久性および耐候性に優れた反射防止膜を提供できるため、耐久性および耐候性に優れた太陽電池を提供できる。 As described above, in the production of the solar cell, the heat treatment for producing the n + semiconductor layer that is the light-receiving surface side diffusion layer and the antireflection film is performed in a nitrogen atmosphere, and then the silicon oxide that is the light-receiving surface side passivation film By forming the film by thermal oxidation in an oxygen atmosphere, the antireflection film can be a titanium oxide film containing titanium phosphate. Therefore, since the antireflection film excellent in durability and weather resistance can be provided, a solar cell excellent in durability and weather resistance can be provided.
　なお、上記では、ｎ型シリコン基板について記載したが、ｐ型シリコン基板を用いることも可能である。その際、受光面側拡散層はｐ型不純物を含むｐ+半導体層となり、反射防止膜はｐ型不純物を含む膜となる。受光面側拡散層および反射防止膜以外の太陽電池の構造はｎ型シリコン基板を備えた太陽電池の構造と同一であることが好ましい。 In the above description, the n-type silicon substrate is described, but a p-type silicon substrate can also be used. At this time, the light-receiving surface side diffusion layer becomes a p + semiconductor layer containing p-type impurities, and the antireflection film becomes a film containing p-type impurities. The solar cell structure other than the light-receiving surface side diffusion layer and the antireflection film is preferably the same as the solar cell structure provided with the n-type silicon substrate.
　また、ｐ型シリコン基板を用いる場合、より高い短絡電流を得るためには、シリコン基板の導電型であるｐ型とは異なる導電型を有し且つ電極が形成されたｎ++領域の合計面積の方が、電極が形成されたｐ+領域の合計面積よりも大きいことが好ましい。この場合、ｐ+領域の間にｎ++領域が形成されていることが好ましく、ｐ+領域は長さ方向に対して垂直な方向に分離されていても良いし、ｎ++領域は長さ方向に対して垂直な方向に分離されていても良いし、ｐ+領域の間にｎ++領域が形成されていても良い。ここで、ｎ++領域の合計面積とは、成長方向に対して垂直な面におけるｎ++領域の面積の合計であり、ｐ+領域の合計面積とは、成長方向に対して垂直な面におけるｐ+領域の面積の合計である。 In addition, when a p-type silicon substrate is used, in order to obtain a higher short-circuit current, the total area of n ++ regions having a conductivity type different from that of the silicon substrate conductivity type and having electrodes formed thereon. Is preferably larger than the total area of the p + regions where the electrodes are formed. In this case, it is preferable that n ++ region between the p + region is formed, p + regions may be separated in a direction perpendicular to the length direction, n ++ region length It may be separated in a direction perpendicular to the vertical direction, or an n ++ region may be formed between the p + regions. Here, the total area of n ++ regions is the total area of n ++ regions in a plane perpendicular to the growth direction, and the total area of p + regions is a plane perpendicular to the growth direction. Is the sum of the areas of the p + regions at.
　また、本発明の太陽電池の概念には、半導体基板の裏面上にのみｐ型用電極およびｎ型用電極の双方が形成された構成の太陽電池だけでなく、半導体基板の受光面と半導体基板の裏面とのそれぞれに電極が形成された太陽電池、およびＭＷＴ（Metal　Wrap　Through）型太陽電池（ＭＷＴ型太陽電池では、半導体基板に設けられた貫通孔内に電極の一部が配置されている）なども含まれる。 Further, the concept of the solar cell of the present invention includes not only a solar cell in which both the p-type electrode and the n-type electrode are formed only on the back surface of the semiconductor substrate, but also the light-receiving surface of the semiconductor substrate and the semiconductor substrate. A part of the electrode is disposed in a through hole provided in a semiconductor substrate in a solar cell in which electrodes are formed on each of the back surface of the substrate and an MWT (Metal Wrap Through) type solar cell (in the MWT type solar cell) ) Etc. are also included.
　受光面側拡散層６および反射防止膜１２を形成するときに用いる混合液に含まれるリン化合物、チタンアルコキシドおよびアルコールについては、それぞれ、一例を記したに過ぎず、上記材料に限定されない。 The phosphorus compound, titanium alkoxide, and alcohol contained in the mixed solution used when forming the light-receiving surface side diffusion layer 6 and the antireflection film 12 are merely examples, and are not limited to the above materials.
　また、反射防止膜１２以外の太陽電池を構成する部材の材料および太陽電池を製造する際に用いるマスクの材料は、上記材料に限定されない。また、太陽電池を構成する部材の厚さは、上記数値に限定されない。また、太陽電池の構成部材がｎ型不純物またはｐ型不純物を含む場合、ｎ型不純物の材料、ｐ型不純物の材料、当該構成部材におけるｎ型不純物濃度およびｐ型不純物濃度は特に限定されない。また、基板がｐ型シリコン基板であるときには、ｐ+領域１０におけるｐ型不純物濃度はｐ型シリコン基板におけるｐ型不純物濃度よりも高いことが好ましい。 Moreover, the material of the member which comprises solar cells other than the antireflection film 12, and the material of the mask used when manufacturing a solar cell are not limited to the said material. Moreover, the thickness of the member which comprises a solar cell is not limited to the said numerical value. When the constituent member of the solar cell includes an n-type impurity or a p-type impurity, the n-type impurity material, the p-type impurity material, the n-type impurity concentration, and the p-type impurity concentration in the constituent member are not particularly limited. When the substrate is a p-type silicon substrate, the p-type impurity concentration in p + region 10 is preferably higher than the p-type impurity concentration in the p-type silicon substrate.
　ｎ型用電極２およびｐ型用電極３を形成する方法は特に限定されない。また、ｎ++領域９およびｐ+領域１０を形成するための熱処理の条件は特に限定されない。さらに、テクスチャマスクまたは拡散マスクを除去する方法は特に限定されない。 The method for forming the n-type electrode 2 and the p-type electrode 3 is not particularly limited. Further, the heat treatment conditions for forming the n ++ region 9 and the p + region 10 are not particularly limited. Furthermore, the method for removing the texture mask or the diffusion mask is not particularly limited.
　今回開示された実施の形態および実施例はすべての点で例示であって制限的なものではないと考えられるべきである。本発明の範囲は上記した説明ではなくて請求の範囲によって示され、請求の範囲と均等の意味および範囲内でのすべての変更が含まれることが意図される。 It should be considered that the embodiments and examples disclosed herein are illustrative and non-restrictive in every respect. The scope of the present invention is defined by the terms of the claims, rather than the description above, and is intended to include any modifications within the scope and meaning equivalent to the terms of the claims.
　１　太陽電池、２　ｎ型用電極、３　ｐ型用電極、４　ｎ型シリコン基板、５　凹凸形状、６　受光面側拡散層、８　第２の裏面側パッシベーション膜、９　ｎ++領域、１０　ｐ+領域、１１　第１の裏面側パッシベーション膜、１２　反射防止膜、１３　受光面側パッシベーション膜、１４　裏面側パッシベーション膜、２１　テクスチャマスク、２２　拡散マスク、２３　拡散マスク、２４　酸化シリコン膜、２５　拡散マスク、７１　ｐ+領域、８１　サンプル、８２　ｎ型シリコン基板、８３　ｎ+半導体層、８４　酸化シリコン膜、８５　反射防止膜となる膜、１００　太陽電池、１０１　シリコンウエハ、１０２　拡散層、１０３　酸化チタン膜、１０４　表面側電極、１０５　裏面側電極。 DESCRIPTION OF SYMBOLS 1 Solar cell, 2 n-type electrode, 3 p-type electrode, 4 n-type silicon substrate, 5 uneven | corrugated shape, 6 light-receiving surface side diffused layer, 8 2nd back surface side passivation film, 9 n ++ area | region, 10 p + Region, 11 first backside passivation film, 12 antireflection film, 13 light receiving side passivation film, 14 backside passivation film, 21 texture mask, 22 diffusion mask, 23 diffusion mask, 24 silicon oxide film, 25 diffusion mask , 71 p + region, 81 samples, 82 n-type silicon substrate, 83 n + semiconductor layer, 84 silicon oxide film, 85 film to be antireflection film, 100 solar cell, 101 silicon wafer, 102 diffusion layer, 103 titanium oxide film , 104 Front side electrode, 105 Back side electrode.

Claims (7)

  1. 　シリコン基板（４）の受光面側に形成された受光面側拡散層（６）と、
    　前記受光面側拡散層（６）上に形成された受光面側パッシベーション膜（１３）と、
    　前記受光面側パッシベーション膜（１３）上に形成された、前記受光面側拡散層（６）の導電型と同じ導電型の不純物を含む反射防止膜（１２）とを有し、
    　前記反射防止膜（１２）は、リン酸チタンを含むチタン酸化物からなる太陽電池（１）。     A light-receiving surface side diffusion layer (6) formed on the light-receiving surface side of the silicon substrate (4);
    A light-receiving surface side passivation film (13) formed on the light-receiving surface-side diffusion layer (6);
    An antireflection film (12) containing an impurity of the same conductivity type as the conductivity type of the light-receiving surface side diffusion layer (6) formed on the light-receiving surface side passivation film (13);
    The antireflection film (12) is a solar cell (1) made of a titanium oxide containing titanium phosphate.
  2. 　前記受光面側拡散層（６）のシート抵抗値が、１００Ω／□以上２５０Ω／□未満である請求項１に記載の太陽電池（１）。 The solar cell (1) according to claim 1, wherein a sheet resistance value of the light-receiving surface side diffusion layer (6) is 100Ω / □ or more and less than 250Ω / □.
  3. 　前記反射防止膜（１２）に含まれるリン酸チタンの含有量は、リン酸化物として１５ｗｔ％以上３５ｗｔ％以下である請求項１または２に記載の太陽電池（１）。 The solar cell (1) according to claim 1 or 2, wherein the content of titanium phosphate contained in the antireflection film (12) is 15 wt% or more and 35 wt% or less as a phosphorus oxide.
  4. 　シリコン基板（４）の受光面側に受光面側拡散層（６）を有する太陽電池（１）の製造方法であって、
    　前記受光面側拡散層（６）に含まれることとなる不純物を含む化合物、チタンアルコキシドおよびアルコールを少なくとも含む溶液を前記シリコン基板（４）の受光面に塗布してから窒素雰囲気下で熱処理することにより、前記受光面拡散層（６）と反射防止膜（１２）とを前記シリコン基板（４）の受光面上に形成する工程と、
    　前記シリコン基板（４）の受光面上に、熱処理により受光面側パッシベーション膜（１３）を形成する工程とを備え、
    　前記受光面側パッシベーション膜（１３）を形成する工程の熱処理は、酸素雰囲気下で行われる太陽電池（１）の製造方法。     A method for producing a solar cell (1) having a light-receiving surface side diffusion layer (6) on a light-receiving surface side of a silicon substrate (4),
    Applying a solution containing at least a compound containing impurities, titanium alkoxide, and alcohol to be included in the light-receiving surface side diffusion layer (6) to the light-receiving surface of the silicon substrate (4), and then performing heat treatment in a nitrogen atmosphere. Forming the light receiving surface diffusion layer (6) and the antireflection film (12) on the light receiving surface of the silicon substrate (4),
    Forming a light-receiving surface side passivation film (13) by heat treatment on the light-receiving surface of the silicon substrate (4),
    The method for manufacturing the solar cell (1), wherein the heat treatment in the step of forming the light-receiving surface side passivation film (13) is performed in an oxygen atmosphere.
  5. 　前記受光面側パッシベーション膜（１３）を形成する工程の熱処理は、８５０℃よりも高い温度で行なわれる請求項４に記載の太陽電池（１）の製造方法。 The method for manufacturing a solar cell (1) according to claim 4, wherein the heat treatment in the step of forming the light-receiving surface side passivation film (13) is performed at a temperature higher than 850 ° C.
  6. 　前記受光面側パッシベーション膜（１３）を形成する工程において、前記受光面とは反対側に位置するシリコン基板（４）の裏面上に裏面側パッシベーション膜（１４）が形成される請求項４または５に記載の太陽電池（１）の製造方法。 The back surface passivation film (14) is formed on the back surface of the silicon substrate (4) located on the opposite side of the light receiving surface in the step of forming the light receiving surface side passivation film (13). The manufacturing method of the solar cell (1) of description.
  7. 　前記受光面拡散層（６）および前記反射防止膜（１２）を形成する工程と前記受光面側パッシベーション膜（１３）を形成する工程とを一連の熱処理によって行う請求項４～６のいずれかに記載の太陽電池（１）の製造方法。 The process of forming the light receiving surface diffusion layer (6) and the antireflection film (12) and the step of forming the light receiving surface side passivation film (13) are performed by a series of heat treatments. The manufacturing method of the solar cell (1) of description.
PCT/JP2012/053925 2011-03-01 2012-02-20 Solar cell, and method for producing solar cell WO2012117877A1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
JP2011043690A JP2012182275A (en) 2011-03-01 2011-03-01 Solar cell and method for manufacturing solar cell
JP2011-043690 2011-03-01

Publications (1)

Publication Number Publication Date
WO2012117877A1 true WO2012117877A1 (en) 2012-09-07

Family

ID=46757816

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/JP2012/053925 WO2012117877A1 (en) 2011-03-01 2012-02-20 Solar cell, and method for producing solar cell

Country Status (2)

Country Link
JP (1) JP2012182275A (en)
WO (1) WO2012117877A1 (en)

Families Citing this family (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US9166417B2 (en) 2012-08-21 2015-10-20 Makita Corporation Charger
JP6090209B2 (en) * 2014-03-03 2017-03-08 三菱電機株式会社 Solar cell and method for manufacturing solar cell

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57114291A (en) * 1981-01-07 1982-07-16 Sharp Corp Manufacture of reflection preventive film
JPH0885874A (en) * 1994-07-21 1996-04-02 Sharp Corp Formation of phosphorus-containing titanium oxide film, production of solar cell and device therefor
JP2004193350A (en) * 2002-12-11 2004-07-08 Sharp Corp Solar battery cell and its manufacturing method
JP2008532311A (en) * 2005-03-03 2008-08-14 サンパワー コーポレイション Prevention of harmful polarization in solar cells

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JPS57114291A (en) * 1981-01-07 1982-07-16 Sharp Corp Manufacture of reflection preventive film
JPH0885874A (en) * 1994-07-21 1996-04-02 Sharp Corp Formation of phosphorus-containing titanium oxide film, production of solar cell and device therefor
JP2004193350A (en) * 2002-12-11 2004-07-08 Sharp Corp Solar battery cell and its manufacturing method
JP2008532311A (en) * 2005-03-03 2008-08-14 サンパワー コーポレイション Prevention of harmful polarization in solar cells

Also Published As

Publication number Publication date
JP2012182275A (en) 2012-09-20

Similar Documents

Publication Publication Date Title
JP5215330B2 (en) Manufacturing method of back electrode type solar cell, back electrode type solar cell and back electrode type solar cell module
WO2011136116A1 (en) Back contact solar cell and method for manufacturing back contact solar cell
KR101225978B1 (en) Sollar Cell And Fabrication Method Thereof
TWI597856B (en) Solar cell and manufacturing method thereof
US20120222734A1 (en) Solar battery cell and method of manufacturing the same
US20130032206A1 (en) Solar cell
WO2006117980A1 (en) Solar cell manufacturing method, solar cell, and semiconductor device manufacturing method
TWI550890B (en) Solar cell and method of manufacturing the same
JP5723143B2 (en) Manufacturing method of back electrode type solar cell and back electrode type solar cell
WO2012066918A1 (en) Back electrode type solar cell
WO2012176839A1 (en) Method for manufacturing rear face electrode type solar battery
WO2013100085A1 (en) Solar cell element, method for manufacturing solar cell element, and solar cell module
JP5323827B2 (en) Photovoltaic device and manufacturing method thereof
WO2012117877A1 (en) Solar cell, and method for producing solar cell
TWI649887B (en) High photoelectric conversion efficiency solar cell and high photoelectric conversion efficiency solar cell manufacturing method
CN103904168B (en) The manufacture method of solar battery cell
TWI584486B (en) Solar cell and manufacturing method thereof
JP5715509B2 (en) Solar cell and method for manufacturing solar cell
JP5994895B2 (en) Manufacturing method of solar cell
WO2013039101A1 (en) Method for producing solar cell, and solar cell
KR20120020824A (en) Method for texturing substrate for solar cell

Legal Events

Date Code Title Description
121 Ep: the epo has been informed by wipo that ep was designated in this application

Ref document number: 12752650

Country of ref document: EP

Kind code of ref document: A1

NENP Non-entry into the national phase

Ref country code: DE

122 Ep: pct application non-entry in european phase

Ref document number: 12752650

Country of ref document: EP

Kind code of ref document: A1