WO2010150358A1 - Photoelectromotive device, and method for manufacturing the same - Google Patents

Photoelectromotive device, and method for manufacturing the same Download PDF

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Publication number
WO2010150358A1
WO2010150358A1 PCT/JP2009/061425 JP2009061425W WO2010150358A1 WO 2010150358 A1 WO2010150358 A1 WO 2010150358A1 JP 2009061425 W JP2009061425 W JP 2009061425W WO 2010150358 A1 WO2010150358 A1 WO 2010150358A1
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Prior art keywords
film
back surface
semiconductor substrate
insulating film
photovoltaic device
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PCT/JP2009/061425
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French (fr)
Japanese (ja)
Inventor
濱本　哲
隆 石原
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三菱電機株式会社
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Priority to PCT/JP2009/061425 priority Critical patent/WO2010150358A1/en
Priority to PCT/JP2010/058646 priority patent/WO2010150606A1/en
Priority to TW099117549A priority patent/TW201104898A/en
Publication of WO2010150358A1 publication Critical patent/WO2010150358A1/en

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    • 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
    • H01L31/0224—Electrodes
    • H01L31/022408—Electrodes for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/022425—Electrodes for devices characterised by at least one potential jump barrier or surface barrier for 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
    • H01L31/04—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
    • H01L31/054—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means
    • H01L31/056—Optical elements directly associated or integrated with the PV cell, e.g. light-reflecting means or light-concentrating means the light-reflecting means being of the back surface reflector [BSR] type
    • 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
    • Y02E10/52—PV systems with concentrators

Definitions

  • the present invention relates to a photovoltaic device and a manufacturing method thereof.
  • the wavelength that has not been fully utilized before can be achieved by confining light in the photovoltaic device and suppressing the recombination speed of carriers on the front and back surfaces. It is important to realize structures and manufacturing methods that contribute to the generation of light in the region. Therefore, it is very important to improve the back surface structure of the substrate that plays the role.
  • Patent Document 1 a film that suppresses the recombination rate is formed after the back electrode is printed and baked. In this case, especially during firing, the attachment and fixation of contaminants proceeds on the back surface of the substrate, and therefore it is extremely difficult to keep the carrier recombination rate on the back surface of the substrate low as intended. There is.
  • an electrode paste is printed so as to cover almost the entire surface of the film that suppresses the recombination speed to form a back electrode that also functions as a light reflection function. This contact is partially made.
  • the back electrode is made of, for example, a paste containing aluminum (Al), which is a typical material, the light reflectivity on the back surface cannot be increased, and sufficient photovoltaic power can be introduced into the photovoltaic device. There is a problem that the optical confinement effect cannot be obtained.
  • the back electrode is made of, for example, a paste containing silver (Ag), which is a typical material
  • a film that suppresses the recombination rate even in a region other than the original contact portion during the electrode firing process Is eroded by fire-through, and there is a problem that a sufficient effect of suppressing the recombination rate of carriers cannot be obtained.
  • the present invention has been made in view of the above, and an object of the present invention is to obtain a photovoltaic device having a low recombination speed and a high back surface reflectance and excellent photoelectric conversion efficiency and a method for manufacturing the photovoltaic device.
  • a photovoltaic device includes a first conductivity type semiconductor substrate having an impurity diffusion layer in which a second conductivity type impurity element is diffused on one side.
  • a back surface structure having both a low recombination speed and a high back surface reflectance can be realized, and a solar cell having excellent long wavelength sensitivity and high photoelectric conversion efficiency can be obtained. There is an effect that it is possible.
  • FIG. 1-1 is a cross-sectional view of relevant parts for explaining the cross-sectional structure of the solar battery cell according to the first embodiment of the present invention.
  • FIG. 1-2 is a top view of the solar cell according to the first embodiment of the present invention as viewed from the light receiving surface side.
  • FIG. 1-3 is a bottom view of the solar battery cell according to the first embodiment of the present invention as viewed from the back surface side.
  • FIG. 2 is a characteristic diagram showing the reflectance on the back surface of the semiconductor substrate in three types of samples having different back surface structures.
  • FIG. 3 is a characteristic diagram showing the relationship between the area ratio of the back electrode and the open circuit voltage (Voc) in the sample manufactured by simulating the solar battery cell according to the first embodiment.
  • FIGS. 5-1 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-2 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-3 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-4 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-5 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-6 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-7 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-8 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-9 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIG. FIG. 5-6 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention.
  • FIGS. FIGS. 5-7 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1
  • FIG. 6-1 is a plan view showing an example of a printed region of the back surface side electrode material paste on the back surface insulating film of the solar battery cell according to the first embodiment of the present invention.
  • FIG. 6-2 is a plan view showing an example of a printed region of the back surface side electrode material paste on the back surface insulating film of the solar battery cell according to the first embodiment of the present invention.
  • FIG. 7 is principal part sectional drawing for demonstrating the cross-section of the photovoltaic cell concerning Embodiment 2 of this invention.
  • FIG. FIGS. 1-1 to 1-3 are diagrams showing a configuration of a solar battery cell that is a photovoltaic device according to the present embodiment, and FIG. 1-1 is for explaining a cross-sectional structure of the solar battery cell.
  • FIG. 1-2 is a top view of the solar cell viewed from the light receiving surface side
  • FIG. 1-3 is a bottom view of the solar cell viewed from the side opposite to the light receiving surface (back side).
  • FIG. 1-1 is a cross-sectional view of an essential part taken along line AA in FIG. 1-2.
  • the solar cell according to the present embodiment includes a solar cell substrate having a photoelectric conversion function and having a pn junction, An antireflection film 4 made of a silicon nitride film (SiN film) which is an insulating film formed on the light receiving surface side (surface) and prevents reflection of incident light on the light receiving surface, and a light receiving surface side of the semiconductor substrate 1 On the surface (front surface), the light receiving surface side electrode 5 that is the first electrode formed surrounded by the antireflection film 4 and the silicon nitride film (back surface) opposite to the light receiving surface of the semiconductor substrate 1 (back surface)
  • Back surface reflection film 1 provided to cover back surface side electrode 9 And, equipped with a.
  • the semiconductor substrate 1 includes a p-type polycrystalline silicon substrate 2 which is a first conductivity type layer, and an impurity diffusion layer (n-type impurity diffusion) which is a second conductivity type layer formed by phosphorous diffusion on the light receiving surface side of the semiconductor substrate 1.
  • the layer) 3 constitutes a pn junction.
  • the n-type impurity diffusion layer 3 has a surface sheet resistance of 30 to 100 ⁇ / ⁇ .
  • the light-receiving surface side electrode 5 includes a grid electrode 6 and a bus electrode 7 of the solar battery cell, and is electrically connected to the n-type impurity diffusion layer 3.
  • the grid electrode 6 is locally provided on the light receiving surface to collect electricity generated by the semiconductor substrate 1.
  • the bus electrode 7 is provided substantially orthogonal to the grid electrode 6 in order to take out the electricity collected by the grid electrode 6.
  • the back surface side electrode 9 is embedded in the back surface insulating film 8 provided over the entire back surface of the semiconductor substrate 1. That is, the back insulating film 8 is provided with a substantially circular dot-shaped opening 8 a that reaches the back surface of the semiconductor substrate 1.
  • a back-side electrode 9 made of an electrode material containing aluminum, glass, or the like is provided so as to fill the opening 8a and to have an outer shape wider than the diameter of the opening 8a in the in-plane direction of the back insulating film 8. Yes.
  • the back insulating film 8 is made of a silicon nitride film (SiN film), and is formed on almost the entire back surface of the semiconductor substrate 1 by a plasma CVD (Chemical Vapor Deposition) method.
  • SiN film silicon nitride film formed by the plasma CVD method
  • the back surface reflection film 10 is provided on the back surface of the semiconductor substrate 1 so as to cover the back surface side electrode 9 and the back surface insulating film 8.
  • the back surface reflecting film 10 covering the back surface insulating film 8
  • the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained. it can.
  • the back surface reflecting film 10 is comprised by the silver (Ag) film
  • the solar battery cell according to the present embodiment can obtain an excellent light confinement effect by including the back surface reflection film 10 formed of a silver sputtering film.
  • the material of the back surface reflection film 10 for example, it is preferable to use a metal material having a reflectance of 90% or more, preferably 95% or more with respect to light having a wavelength near 1100 nm.
  • a solar cell having high long wavelength sensitivity and excellent light confinement effect for light in the long wavelength region can be realized. That is, although depending on the thickness of the semiconductor substrate 1, light having a long wavelength of 900 nm or more, particularly about 1000 nm to 1100 nm, can be efficiently taken into the semiconductor substrate 1 and a high generated current (Jsc) can be realized. Characteristics can be improved.
  • a material for example, aluminum (Al) can be used in addition to silver (Ag).
  • the fine back surface side electrode 9 is formed on the back surface of the semiconductor substrate 1, and the back surface reflection film 10 is formed thereon.
  • the back surface reflecting film 10 shown in FIG. 1C actually has fine unevenness due to the back side electrode 9, the description of the fine unevenness is omitted in FIG. ing.
  • an aluminum-silicon (Al—Si) alloy portion 11 is formed in a region on the back surface side of the semiconductor substrate 1 and in the vicinity of the region in contact with the back electrode 9. Further, on the outer periphery thereof, the BSF (Back Surface Filed layer) 12 is formed.
  • the solar cell configured as described above, sunlight is applied from the light receiving surface side of the solar cell to the pn junction surface of the semiconductor substrate 1 (the junction surface between the p-type polycrystalline silicon substrate 2 and the n-type impurity diffusion layer 3).
  • the generated electrons move toward the n-type impurity diffusion layer 3, and the holes move toward the p-type polycrystalline silicon substrate 2.
  • the number of electrons in the n-type impurity diffusion layer 3 becomes excessive, and the number of holes in the p-type polycrystalline silicon substrate 2 becomes excessive.
  • a photovoltaic force is generated.
  • This photovoltaic power is generated in the direction of biasing the pn junction in the forward direction, the light receiving surface side electrode 5 connected to the n-type impurity diffusion layer 3 becomes a negative electrode, and the back surface side electrode 9 connected to the p-type polycrystalline silicon substrate 2. Becomes a positive pole, and current flows in an external circuit (not shown).
  • FIG. 2 is a characteristic diagram showing the reflectance on the back surface of the semiconductor substrate in three types of samples having different back surface structures.
  • FIG. 2 shows the relationship between the wavelength of light incident on the sample and the reflectance.
  • Each sample is produced by imitating a solar battery cell, and the basic structure other than the back surface structure is the same as that of the solar battery cell according to this embodiment.
  • the details of the back surface structure of each sample are as follows.
  • Example A An aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is provided over the entire back surface of the semiconductor substrate (corresponding to a conventional general structure).
  • Sample B A back insulating film made of a silicon nitride film (SiN) is formed over the entire back surface of the semiconductor substrate, and an aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is provided over the entire back insulating film (preceding) Technology (equivalent to Patent Document 2)).
  • a back insulating film made of a silicon nitride film (SiN) is formed over the entire back surface of the semiconductor substrate, and an aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is locally provided on the back surface of the semiconductor substrate. Further, a high reflection film made of a silver sputtering film is provided on the entire surface of the back insulating film (corresponding to the solar battery cell according to the present embodiment).
  • the sample B corresponding to the prior art has a slight improvement in reflectance as compared with the sample A corresponding to the conventional general structure, but the effect of improving the reflectance is sufficient. It can not be said.
  • Sample C corresponding to the solar battery cell according to the present embodiment has a higher reflectance than Sample A and Sample B, and a high reflectance between “silicon (semiconductor substrate) and back surface structure” is recognized. Thus, it can be seen that it is suitable for high efficiency based on the light confinement action on the back surface.
  • FIG. 3 shows the area ratio of the back electrode (ratio occupied by the back electrode on the back surface of the semiconductor substrate) and the open-circuit voltage (Voc) in the sample manufactured by simulating the solar battery cell according to the present embodiment in the same manner as the sample C described above.
  • FIG. 4 shows the area ratio of the back electrode (ratio occupied by the back electrode on the back surface of the semiconductor substrate) and the short-circuit current in the sample manufactured by imitating the solar battery cell according to the present embodiment in the same manner as the sample C described above. It is the characteristic view which showed the relationship with (Jsc).
  • the open circuit voltage (Voc) increases as the area ratio of the aluminum (Al) paste electrode as the back electrode decreases, that is, as the area ratio of the highly reflective film according to the present embodiment increases.
  • the short-circuit current (Jsc) are improved, and it is recognized that a good effect of suppressing the recombination rate of carriers is obtained on the back surface of the semiconductor substrate.
  • the solar cell according to the first embodiment configured as described above by providing a silicon nitride film (SiN film) formed by plasma CVD on the back surface of the semiconductor substrate 1 as the back surface insulating film 8, A good effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained. Thereby, in the photovoltaic cell concerning this Embodiment, the improvement of an output characteristic is achieved and the high photoelectric conversion efficiency is implement
  • SiN film silicon nitride film
  • the back surface reflection film 10 made of a silver sputtering film is provided so as to cover the back surface insulating film 8, thereby making it more than a silver (Ag) film formed by a conventional printing method.
  • High light reflection can be realized, and more light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, in the solar cell according to the present embodiment, an excellent light confinement effect can be obtained, the output characteristics can be improved, and high photoelectric conversion efficiency is realized.
  • the solar cell according to the first embodiment by having the structure of the back surface having both the low recombination speed and the high back surface reflectance, the long-wavelength sensitivity is excellent and the photoelectric conversion efficiency is improved.
  • the obtained solar battery cell is realized.
  • FIGS. 5-1 to 5-9 are cross-sectional views for explaining the manufacturing process of the solar battery cell according to the present embodiment.
  • a p-type polycrystalline silicon substrate that is most frequently used for consumer solar cells is prepared (hereinafter referred to as a p-type polycrystalline silicon substrate 1a) (FIG. 5-1).
  • a p-type polycrystalline silicon substrate 1a for example, a polycrystalline silicon substrate having an electrical resistance of about 0.5 to 3 ⁇ cm containing a group III element such as boron (B) is used.
  • the p-type polycrystalline silicon substrate 1a is manufactured by slicing an ingot formed by cooling and solidifying molten silicon with a wire saw, damage at the time of slicing remains on the surface. Therefore, the p-type polycrystalline silicon substrate 1a is first removed by immersing the surface of the p-type polycrystalline silicon substrate 1a in an acid or a heated alkaline solution, for example, in an aqueous solution of sodium hydroxide so as to remove the damaged layer. Thus, the damaged region existing near the surface of the p-type polycrystalline silicon substrate 1a is removed.
  • the thickness of the p-type polycrystalline silicon substrate 1a after the damage removal is, for example, 200 ⁇ m, and the dimension is, for example, 150 mm ⁇ 150 mm.
  • fine irregularities may be formed as a texture structure on the surface of the p-type polycrystalline silicon substrate 1a on the light receiving surface side.
  • this invention is invention concerning the back surface structure of a photovoltaic apparatus, it does not restrict
  • an alkaline aqueous solution containing isopropyl alcohol, a method using acid etching mainly composed of a mixed solution of hydrofluoric acid and nitric acid, or a mask material partially provided with an opening is formed on the surface of the p-type polycrystalline silicon substrate 1a.
  • RIE reactive gas etching
  • this p-type polycrystalline silicon substrate 1a is put into a thermal oxidation furnace and heated in an atmosphere of phosphorus (P) which is an n-type impurity.
  • phosphorus (P) is diffused on the surface of the p-type polycrystalline silicon substrate 1a to form an n-type impurity diffusion layer 3 to form a semiconductor pn junction (FIG. 5-2).
  • the n-type impurity diffusion layer 3 is formed by heating the p-type polycrystalline silicon substrate 1a in a phosphorus oxychloride (POCl 3 ) gas atmosphere at a temperature of, for example, 800 ° C. to 850 ° C.
  • the heat treatment is controlled so that the surface sheet resistance of the n-type impurity diffusion layer 3 is, for example, 30 to 80 ⁇ / ⁇ , preferably 40 to 60 ⁇ / ⁇ .
  • a phosphorus glass layer mainly composed of glass is formed on the surface immediately after the formation of the n-type impurity diffusion layer 3, it is removed using a hydrofluoric acid solution or the like.
  • a silicon nitride film (SiN film) is formed as the antireflection film 4 on the light receiving surface side of the p-type polycrystalline silicon substrate 1a on which the n-type impurity diffusion layer 3 is formed in order to improve the photoelectric conversion efficiency (FIG. 5-3).
  • a plasma CVD method is used, and a silicon nitride film is formed as the antireflection film 4 using a mixed gas of silane and ammonia.
  • the film thickness and refractive index of the antireflection film 4 are set to values that most suppress light reflection. Note that two or more films having different refractive indexes may be laminated as the antireflection film 4. Further, a different film forming method such as a sputtering method may be used for forming the antireflection film 4. Further, a silicon oxide film may be formed as the antireflection film 4.
  • the n-type impurity diffusion layer 3 formed on the back surface of the p-type polycrystalline silicon substrate 1a is removed by diffusion of phosphorus (P).
  • P phosphorus
  • the semiconductor substrate 1 having a pn junction is obtained (FIG. 5-4).
  • the removal of the n-type impurity diffusion layer 3 formed on the back surface of the p-type polycrystalline silicon substrate 1a is performed using, for example, a single-sided etching apparatus.
  • a method of using the antireflection film 4 as a mask material and immersing the entire p-type polycrystalline silicon substrate 1a in an etching solution may be used.
  • an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide heated to room temperature to 95 ° C., preferably 50 ° C. to 70 ° C. is used.
  • a mixed aqueous solution of nitric acid and hydrofluoric acid may be used as the etching solution.
  • the silicon surface exposed on the back surface of the semiconductor substrate 1 is washed in order to keep the recombination rate low in film formation described later.
  • the cleaning is performed using, for example, RCA cleaning or a 1% to 20% hydrofluoric acid aqueous solution.
  • a back surface insulating film 8 made of a silicon nitride film (SiN film) is formed on the back surface side of the semiconductor substrate 1 (FIG. 5-5).
  • a back insulating film 8 made of a silicon nitride film (SiN film) having a refractive index of 1.9 to 2.2 and a thickness of 60 nm to 300 nm is formed on the silicon surface exposed on the back side of the semiconductor substrate 1 by plasma CVD. Film.
  • plasma CVD plasma CVD, the back surface insulating film 8 made of a silicon nitride film can be reliably formed on the back surface side of the semiconductor substrate 1.
  • the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be suppressed, and silicon (Si) and silicon nitride film (SiN film) on the back surface of the semiconductor substrate 1 can be suppressed. ), A recombination velocity of 100 cm / sec or less is obtained. Thereby, it is possible to realize a sufficient back surface interface for high output.
  • the refractive index of the back surface insulating film 8 deviates from 1.9 to 2.2, it is difficult to stabilize the deposition environment of the silicon nitride film (SiN film), and the film quality of the silicon nitride film (SiN film) deteriorates. As a result, the recombination rate at the interface with silicon (Si) also deteriorates.
  • the thickness of the back insulating film 8 is smaller than 60 nm, the interface with silicon (Si) is not stable, and the carrier recombination rate is deteriorated.
  • the thickness of the back insulating film 8 is larger than 300 nm, there is no functional inconvenience, but it takes time to form a film and increases costs, which is not preferable from the viewpoint of productivity.
  • the back insulating film 8 may have a two-layer structure in which a silicon oxide film (silicon thermal oxide film: SiO 2 film) formed by thermal oxidation and a silicon nitride film (SiN film) are stacked, for example.
  • the silicon oxide film (SiO 2 film) here is not a natural oxide film formed on the back side of the semiconductor substrate 1 during the process, but a silicon oxide film (SiO 2 film) intentionally formed by thermal oxidation, for example. To do.
  • SiO 2 film silicon oxide film
  • the effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained more stably than the silicon nitride film (SiN film).
  • the thickness of the silicon oxide film (SiO 2 film) intentionally formed by thermal oxidation is preferably about 10 nm to 50 nm.
  • the thickness of the silicon oxide film (SiO 2 film) formed by thermal oxidation is less than 10 nm, the interface with silicon (Si) is not stable, and the recombination rate of carriers deteriorates.
  • the thickness of the silicon oxide film (SiO 2 film) formed by thermal oxidation is larger than 50 nm, there is no functional inconvenience, but the film formation takes time and the cost increases. It is not preferable from the viewpoint.
  • the film formation process is performed at a high temperature in order to shorten the time, the quality of the crystalline silicon itself is lowered, leading to a reduction in lifetime.
  • dot-shaped openings 8a having a predetermined interval are formed on a part or the entire surface of the back insulating film 8 (FIGS. 5-6).
  • the opening 8a is formed by performing direct patterning, for example, by laser irradiation on the back surface insulating film 8.
  • the cross-sectional area of the opening 8 a in the in-plane direction of the back insulating film 8 is increased, and the opening of the opening 8 a in the plane of the back insulating film 8. It is preferable to increase the density.
  • the cross-sectional area of the opening 8a is small and the opening density of the opening 8a is low. Therefore, it is preferable that the shape and density of the opening 8a be kept to a minimum level necessary for realizing a good contact.
  • the shape of the opening 8a has a diameter or width of 20 ⁇ m to 200 ⁇ m, and a substantially circular dot shape or a substantially rectangular shape with an interval between adjacent opening portions 8a of 0.5 mm to 2 mm. Is mentioned.
  • a stripe shape having a width of 20 ⁇ m to 200 ⁇ m and a distance between adjacent openings 8a of 0.5 mm to 3 mm can be cited.
  • dot-shaped openings 8 a are formed by laser irradiation on the back surface insulating film 8.
  • a back-side electrode material paste 9a containing aluminum, glass, or the like which is an electrode material for the back-side electrode 9, fills the opening 8a and is slightly larger than the diameter of the opening 8a in the in-plane direction of the back-side insulating film 8. It is applied in a limited manner by screen printing so as not to come into contact with the back-side electrode material paste 9a covering a wide area and filling the adjacent opening 8a (FIGS. 5-7).
  • the application shape, application amount, and the like of the back-side electrode material paste 9a can be changed according to various conditions such as the diffusion concentration of aluminum in the Al—Si alloy part 11 and the BSF 12 in the firing step described later.
  • the light reflectance (back surface reflectance) by the back surface side electrode 9 in the region where the back surface insulating film 8 (silicon nitride film) and the back surface side electrode 9 are laminated on the back surface of the semiconductor substrate 1 is not sufficient.
  • the formation area of the back surface side electrode 9 on the back surface insulating film 8 becomes wide, the light confinement effect in the photovoltaic device is lowered. Therefore, the area where the back side electrode material paste 9a is printed is limited to the minimum necessary after balancing the formation conditions of the Al—Si alloy part 11 and the BSF 12 and the light confinement effect in the photovoltaic device. There is a need.
  • FIGS. 6A and 6B are plan views showing an example of the printing region of the back surface side electrode material paste 9a on the back surface insulating film 8.
  • FIGS. FIG. 6A shows an example in which the opening 8a has a substantially circular dot shape
  • FIG. 6B shows an example in which the opening 8a has a substantially rectangular shape.
  • Overlap amount is, 1000 .mu.m 2 from 200 [mu] m 2 in sectional area from the end of the opening 8a, preferably it is desirable to control in the range of 400 [mu] m 2 of 1000 .mu.m 2.
  • the paste thickness of the back side electrode material paste 9a containing aluminum (Al) is 20 ⁇ m, in terms of the width of the overlap, 10 ⁇ m to 50 ⁇ m, preferably 20 ⁇ m from the end of the opening 8a. It corresponds to the range of 50 ⁇ m.
  • the overlap width is less than 10 ⁇ m, the effect of preventing the peeling of the back surface insulating film 8 will not be exhibited, but the supply of aluminum (Al) will not be successful at the time of firing, that is, when the alloy is formed, and the BSF structure will not be formed well. Part occurs.
  • the overlap width is larger than 50 ⁇ m, the area ratio occupied by the paste printing portion increases, that is, the area ratio of the high reflection film decreases, and the deviation from the intention of the present invention becomes large.
  • the outer periphery of the opening 8a on the back insulating film 8 includes a ring-shaped overlap region 9b having a width of 20 ⁇ m.
  • the opening 8a has a substantially rectangular shape as shown in FIG. 6B
  • a frame-shaped overlap region 9b having a width of 20 ⁇ m is provided on the outer periphery of the opening 8a on the back surface insulating film 8
  • the back surface side electrode material paste 9a is limitedly applied on the back surface insulating film 8 by screen printing.
  • the width w of the opening 8a is 100 ⁇ m
  • a light receiving surface electrode material paste 5 a which is an electrode material of the light receiving surface side electrode 5 and contains silver (Ag), glass or the like is formed into the shape of the light receiving surface side electrode 5.
  • the light-receiving surface electrode material paste 5a is, for example, a pattern of elongated grid electrodes 6 having a width of 80 ⁇ m to 150 ⁇ m and a spacing of 2 mm to 3 mm, and a strip shape having a width of 1 mm to 3 mm and a spacing of 5 mm to 10 mm in a direction substantially perpendicular to the pattern.
  • the pattern of the bus electrode 7 is printed.
  • the shape of the light receiving surface side electrode 5 is not directly related to the present invention, it may be freely set while balancing between the electrode resistance and the printing light shielding rate.
  • firing is performed at a peak temperature of 760 ° C. to 900 ° C. using, for example, an infrared furnace heater.
  • the light receiving surface side electrode 5 and the back surface side electrode 9 are formed, and the Al—Si alloy portion 11 is formed in the region on the back surface side of the semiconductor substrate 1 and in contact with the back surface side electrode 9 and its vicinity. Is done.
  • a BSF 12 that is a p + region in which aluminum is diffused in a high concentration from the back surface side electrode 9 is formed on the outer periphery of the Al—Si alloy portion 11, and the BSF layer 12 and the back surface side electrode 9 are electrically connected to each other. Connection ( Figure 5-8).
  • the recombination speed at the interface deteriorates at this connection point, but the BSF layer 12 can negate this effect. Further, the silver in the light receiving surface side electrode 5 penetrates the antireflection film 4, and the n-type impurity diffusion layer 3 and the light receiving surface side electrode 5 are electrically connected.
  • the semiconductor substrate 1 since the region where the back surface side electrode material paste 9a is not applied on the back surface of the semiconductor substrate 1 is protected by the back surface insulating film 8 made of a silicon nitride film (SiN film), the semiconductor substrate 1 is also subjected to heating by baking. The adherence and fixation of contaminants do not proceed with respect to the back surface, and a good state is maintained without degrading the recombination speed.
  • SiN film silicon nitride film
  • a highly reflective structure is formed on the back side of the semiconductor substrate 1. That is, a silver (Ag) film (silver sputtering film) is formed on the entire back surface of the semiconductor substrate 1 by a sputtering method so as to cover the back electrode 9 and the back insulating film 8 (FIG. 5-9). ).
  • a silver (Ag) film silver sputtering film
  • a dense back surface reflection film 10 can be formed, and the back surface reflection film 10 that realizes higher light reflection than a silver (Ag) film formed by a printing method is formed. can do.
  • the back surface reflection film 10 may be formed so as to cover at least the back surface insulating film 8 on the back surface side of the semiconductor substrate 1. .
  • the solar battery cell according to Embodiment 1 shown in FIGS. 1-1 to 1-3 is manufactured.
  • the order of application of the paste as the electrode material may be switched between the light receiving surface side and the back surface side.
  • the back surface side electrode material paste 9a is applied and fired. Therefore, the region where the back surface side electrode material paste 9a is not applied is protected by the back surface insulating film 8. Thereby, even in the heating by baking, adherence and fixation of the contaminant do not proceed to the back surface of the semiconductor substrate 1, and a good state is maintained without deteriorating the recombination speed, and the photoelectric conversion efficiency is improved.
  • the back surface reflecting film 10 is formed on the back surface of the semiconductor substrate 1 so as to cover at least the back surface insulating film 8.
  • the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected by the back surface reflective film 10 and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained.
  • high photoelectric conversion efficiency can be realized.
  • the back surface reflecting film 10 is formed by a sputtering method.
  • a dense back surface reflecting film 10 can be formed by forming the back surface reflecting film 10 by a sputtering film, not by a printing method using an electrode paste, and realizes higher light reflection than a film formed by the printing method.
  • the back reflective film 10 can be formed, and an excellent light confinement effect can be obtained.
  • the manufacturing method of the solar cell according to the first embodiment it is possible to obtain a back surface structure having both a low recombination speed and a high back surface reflectance, an excellent long wavelength sensitivity, and a photoelectric conversion efficiency.
  • Solar cells with high efficiency can be manufactured.
  • the photoelectric conversion efficiency of the solar battery cell can be increased, the semiconductor substrate 1 can be thinned, the manufacturing cost can be reduced, and the high-quality solar battery cell excellent in battery cell characteristics can be achieved. Can be manufactured at low cost.
  • FIG. Embodiment 2 demonstrates the case where the back surface reflecting film 10 is comprised with metal foil as another form of the back surface reflecting film 10.
  • FIG. 7 is a main part sectional view for explaining a sectional structure of the solar battery cell according to the present embodiment, and corresponds to FIG. 1-1.
  • the difference between the solar battery cell according to the second embodiment and the solar battery cell according to the first embodiment is that the back surface reflection film is formed of an aluminum foil (aluminum foil) instead of a silver sputtering film. Since the structure of those other than this is the same as that of the photovoltaic cell concerning Embodiment 1, detailed description is abbreviate
  • the back surface reflecting film 22 made of aluminum foil is formed by the conductive adhesive 21 disposed on the back surface side electrode 9 on the back surface of the semiconductor substrate 1.
  • the backside electrode 9 and the backside insulating film 8 are attached so as to be covered, and are electrically connected to the backside electrode 9 through the conductive adhesive 21. Even in such a configuration, the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1 as in the case of the first embodiment, and good light confinement can be achieved with an inexpensive configuration. An effect can be obtained.
  • the back surface reflecting film 22 is comprised with the aluminum foil which is a metal stay. Since the back surface reflection film 22 is not a film formed by a printing method using an electrode paste, but is made of a metal stay, it can realize a higher light reflection than a metal film formed by a printing method, More light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, the solar battery cell according to the present embodiment can obtain an excellent light confinement effect as in the case of the first embodiment by including the back surface reflection film 22 composed of the aluminum foil that is a metal stay. it can.
  • the material of the back surface reflection film 22 a metal material that can be processed into a foil can be used.
  • the reflectance with respect to light having a wavelength near 1100 nm is 90% or more, preferably 95%. It is preferable to use the above metal materials.
  • a solar cell having high long wavelength sensitivity and excellent light confinement effect for light in the long wavelength region can be realized. That is, although depending on the thickness of the semiconductor substrate 1, light having a long wavelength of 900 nm or more, particularly about 1000 nm to 1100 nm, can be efficiently taken into the semiconductor substrate 1 and a high generated current (Jsc) can be realized. Characteristics can be improved.
  • silver (Ag) can be used in addition to aluminum (Al).
  • the solar battery cell according to the present embodiment configured as described above has a conductive adhesive on the back-side electrode 9 after the steps described in Embodiment 1 with reference to FIGS. 5-1 to 5-8. 21 is applied, and the back surface side electrode 9 and the back surface insulating film 8 are covered with the conductive adhesive 21 and the back surface reflecting film 22 is attached.
  • the back surface reflection film 22 may be formed so as to cover at least the back surface insulating film 8 on the back surface side of the semiconductor substrate 1.
  • the solar cell according to the second embodiment configured as described above, by providing a silicon nitride film (SiN film) formed by plasma CVD on the back surface of the semiconductor substrate 1 as the back surface insulating film 8, A good effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained. Thereby, in the photovoltaic cell concerning this Embodiment, the improvement of an output characteristic is achieved and the high photoelectric conversion efficiency is implement
  • SiN film silicon nitride film
  • the back surface insulating film 8 is provided so as to cover the back surface insulating film 8 and include a back surface reflecting film 22 made of aluminum foil that is a metal stay. High light reflection can be realized, and more light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, in the solar cell according to the present embodiment, an excellent light confinement effect can be obtained, the output characteristics can be improved, and high photoelectric conversion efficiency is realized.
  • the solar cell according to the second embodiment by having the structure of the back surface having both the low recombination speed and the high back surface reflectivity, the long wavelength sensitivity is excellent, and the photoelectric conversion efficiency is improved.
  • the obtained solar battery cell is realized.
  • the back side electrode material paste 9a is applied and fired.
  • the region where the back side electrode material paste 9a is not applied is protected by the back side insulating film 8.
  • the back surface reflection film 22 is formed on the back surface of the semiconductor substrate 1 so as to cover at least the back surface insulating film 8.
  • the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected by the back surface reflective film 22 and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained.
  • high photoelectric conversion efficiency can be realized.
  • the back surface reflecting film 22 is formed by attaching an aluminum foil that is a metal stay on the back surface side electrode 9.
  • a dense back surface reflection film 22 can be formed by forming the back surface reflection film 22 using an aluminum foil as a back surface reflection film 22 instead of a printing method using an electrode paste.
  • the back surface reflection film 22 that realizes light reflection higher than that of the formed film can be formed, and an excellent light confinement effect can be obtained.
  • the method for manufacturing a solar battery cell according to the second embodiment it is possible to obtain a back surface structure having both a low recombination speed and a high back surface reflectance, an excellent long wavelength sensitivity, and a photoelectric conversion efficiency. Solar cells with high efficiency can be manufactured. Further, since the photoelectric conversion efficiency of the solar battery cell can be increased, the semiconductor substrate 1 can be thinned, the manufacturing cost can be reduced, and the high-quality solar battery cell excellent in battery cell characteristics can be achieved. Can be manufactured at low cost.
  • the case where a p-type silicon substrate is used as the semiconductor substrate has been described.
  • a reverse conductivity type solar cell in which a p-type diffusion layer is formed using an n-type silicon substrate.
  • a polycrystalline silicon substrate is used as the semiconductor substrate, a single crystal silicon substrate may be used.
  • the substrate thickness of the semiconductor substrate is 200 ⁇ m.
  • a semiconductor substrate that can be self-held, for example, thinned to about 50 ⁇ m, can be used.
  • the size of the semiconductor substrate is 150 mm ⁇ 150 mm, but the size of the semiconductor substrate is not limited to this.
  • the photovoltaic device according to the present invention is useful for realizing a highly efficient photovoltaic device with a low recombination speed and a high back surface reflectance.
  • SYMBOLS 1 Semiconductor substrate 1a p-type polycrystalline silicon substrate 2 p-type polycrystalline silicon substrate 3 n-type impurity diffusion layer 4 Antireflection film 5 Light-receiving surface side electrode 5a Light-receiving surface electrode material paste 6 Grid electrode 7 Bus electrode 8 Back surface insulating film 8a Opening Part 9 Back side electrode 9a Back side electrode material paste 9b Overlapping region 10 Back side reflection film 11 Aluminum-silicon (Al-Si) alloy part 12 BSF layer 21 Conductive adhesive 22 Back side reflection film

Abstract

Disclosed is a photoelectromotive device comprising a semiconductor substrate (1) of a first conduction type having such an impurity-diffused layer (3) on one face side as has an impurity element of a second conduction type diffused, a reflection preventing film (4) formed over the impurity-diffused layer, first electrodes (5) connected electrically with the impurity-diffused layer (3) through the reflection preventing film (4), a back insulating film (8) so formed on the other face side of the semiconductor substrate (1) as has a plurality of openings (8a) to reach the other face side of the semiconductor substrate (1), second electrodes (9) buried in at least the openings (8a) and connected electrically with the other face side of the semiconductor substrate (1), and a back reflecting film (10) either made of a metal film formed by a vapor-phase growth method or constituted to include a metal foil, and formed to cover at least the back insulating film (8).

Description

光起電力装置およびその製造方法Photovoltaic device and manufacturing method thereof
　本発明は、光起電力装置およびその製造方法に関するものである。 The present invention relates to a photovoltaic device and a manufacturing method thereof.
　近年の光起電力装置においては、高出力化を目指して、素材や製造プロセスの改善が進んでいる。このため、より一層の高出力化を図るためには、光起電力装置内への光閉じ込めや、表面・裏面におけるキャリアの再結合速度の抑制により、従前は十分な活用ができていなかった波長域の光を発電に寄与させる構造や製法を実現することが重要になっている。したがって、その一翼を担う基板の裏面構造の改善は、非常に重要である。 In recent photovoltaic devices, materials and manufacturing processes have been improved for higher output. For this reason, in order to further increase the output, the wavelength that has not been fully utilized before can be achieved by confining light in the photovoltaic device and suppressing the recombination speed of carriers on the front and back surfaces. It is important to realize structures and manufacturing methods that contribute to the generation of light in the region. Therefore, it is very important to improve the back surface structure of the substrate that plays the role.
　そこで、基板の裏面側での反射や基板の裏面での再結合速度の抑制を目指して、例えば裏面電極を局所的に印刷・焼成した後に再結合速度を抑制する膜の成膜を行う技術が提唱されている（例えば、特許文献１参照）。その他にも、例えば基板の裏面に再結合速度を抑制する膜の成膜を行った後に、その一部に開口部を設け、さらに裏面電極ペーストを全面に印刷・焼成する技術が提唱されている（例えば、特許文献２参照）。 Therefore, with the aim of suppressing reflection on the back side of the substrate and recombination rate on the back side of the substrate, for example, there is a technique for forming a film that suppresses the recombination rate after locally printing and baking the back electrode. Has been proposed (see, for example, Patent Document 1). In addition, for example, after forming a film that suppresses the recombination rate on the back surface of the substrate, a technique is proposed in which an opening is provided in a part of the substrate, and a back electrode paste is printed and fired on the entire surface. (For example, refer to Patent Document 2).
特開平６－１６９０９６号公報JP-A-6-169096 特開２００２－２４６６２５号公報JP 2002-246625 A
　しかしながら、上記特許文献１の方法では、裏面電極の印刷・焼成した後に、再結合速度を抑制する膜の成膜を行う。この場合は、特に焼成の際に、基板の裏面に対して汚染物質の付着や固定が進むため、基板の裏面でのキャリアの再結合速度を意図するように低く抑えることが極めて難しい、という問題がある。 However, in the method of Patent Document 1, a film that suppresses the recombination rate is formed after the back electrode is printed and baked. In this case, especially during firing, the attachment and fixation of contaminants proceeds on the back surface of the substrate, and therefore it is extremely difficult to keep the carrier recombination rate on the back surface of the substrate low as intended. There is.
　また、上記特許文献２の方法では、再結合速度を抑制する膜のほぼ全面を覆う形で電極ペーストが印刷されて光反射機能を兼ねた裏面電極が形成され、該裏面電極と基板の裏面とのコンタクトは部分的になされている。しかし、裏面電極を、例えば代表的な材料であるアルミニウム（Ａｌ）を含むペーストから構成した場合には、裏面での光反射率を高くすることができず、十分な光起電力装置内への光閉じ込め効果を得ることができない、という問題がある。また、裏面電極を、例えば代表的な材料である銀（Ａｇ）を含むペーストから構成した場合には、電極の焼成処理の際に、本来のコンタクト部分以外の領域でも再結合速度を抑制する膜がファイヤースルーにより浸食され、十分なキャリアの再結合速度の抑制効果を得ることができない、という問題がある。 Further, in the method of Patent Document 2, an electrode paste is printed so as to cover almost the entire surface of the film that suppresses the recombination speed to form a back electrode that also functions as a light reflection function. This contact is partially made. However, when the back electrode is made of, for example, a paste containing aluminum (Al), which is a typical material, the light reflectivity on the back surface cannot be increased, and sufficient photovoltaic power can be introduced into the photovoltaic device. There is a problem that the optical confinement effect cannot be obtained. Further, when the back electrode is made of, for example, a paste containing silver (Ag), which is a typical material, a film that suppresses the recombination rate even in a region other than the original contact portion during the electrode firing process. Is eroded by fire-through, and there is a problem that a sufficient effect of suppressing the recombination rate of carriers cannot be obtained.
　本発明は、上記に鑑みてなされたものであって、低い再結合速度と高い裏面反射率とを備え、光電変換効率に優れた光起電力装置およびその製造方法を得ることを目的とする。 The present invention has been made in view of the above, and an object of the present invention is to obtain a photovoltaic device having a low recombination speed and a high back surface reflectance and excellent photoelectric conversion efficiency and a method for manufacturing the photovoltaic device.
　上述した課題を解決し、目的を達成するために、本発明にかかる光起電力装置は、一面側に第２導電型の不純物元素が拡散された不純物拡散層を有する第１導電型の半導体基板と、前記不純物拡散層上に形成された反射防止膜と、前記反射防止膜を貫通して前記不純物拡散層に電気的に接続する第１電極と、前記半導体基板の他面側に達する複数の開口部を有して前記半導体基板の他面側に形成された裏面絶縁膜と、少なくとも前記開口部に埋め込まれて前記半導体基板の他面側に電気的に接続する第２電極と、気相成長法によって形成される金属膜からなり、または金属箔を含んで構成され、少なくとも前記裏面絶縁膜上を覆って形成された裏面反射膜と、を備えることを特徴とする。 In order to solve the above-described problems and achieve the object, a photovoltaic device according to the present invention includes a first conductivity type semiconductor substrate having an impurity diffusion layer in which a second conductivity type impurity element is diffused on one side. An antireflection film formed on the impurity diffusion layer, a first electrode that penetrates the antireflection film and is electrically connected to the impurity diffusion layer, and a plurality of layers reaching the other surface side of the semiconductor substrate A back surface insulating film formed on the other surface side of the semiconductor substrate with an opening; a second electrode embedded in at least the opening and electrically connected to the other surface side of the semiconductor substrate; It comprises a metal film formed by a growth method or includes a metal foil, and includes a back surface reflection film formed to cover at least the back surface insulating film.
　本発明によれば、低い再結合速度と高い裏面反射率の双方を有する裏面の構造を実現し、長波長感度に優れ、光電変換効率の高効率化が図られた太陽電池セルを得ることができる、という効果を奏する。 According to the present invention, a back surface structure having both a low recombination speed and a high back surface reflectance can be realized, and a solar cell having excellent long wavelength sensitivity and high photoelectric conversion efficiency can be obtained. There is an effect that it is possible.
図１－１は、本発明の実施の形態１にかかる太陽電池セルの断面構造を説明するための要部断面図である。FIG. 1-1 is a cross-sectional view of relevant parts for explaining the cross-sectional structure of the solar battery cell according to the first embodiment of the present invention. 図１－２は、本発明の実施の形態１にかかる太陽電池セルを受光面側からみた上面図である。FIG. 1-2 is a top view of the solar cell according to the first embodiment of the present invention as viewed from the light receiving surface side. 図１－３は、本発明の実施の形態１にかかる太陽電池セルを裏面側からみた下面図である。FIG. 1-3 is a bottom view of the solar battery cell according to the first embodiment of the present invention as viewed from the back surface side. 図２は、異なる裏面構造を有する３種類の試料における半導体基板の裏面での反射率を示す特性図である。FIG. 2 is a characteristic diagram showing the reflectance on the back surface of the semiconductor substrate in three types of samples having different back surface structures. 図３は、実施の形態１にかかる太陽電池セルを模して作製した試料における裏面電極の面積率と開放電圧（Ｖｏｃ）との関係を示した特性図である。FIG. 3 is a characteristic diagram showing the relationship between the area ratio of the back electrode and the open circuit voltage (Voc) in the sample manufactured by simulating the solar battery cell according to the first embodiment. 図４は、実施の形態１にかかる太陽電池セルを模して作製した試料における裏面電極の面積率と短絡電流（Ｊｓｃ）との関係を示した特性図である。FIG. 4 is a characteristic diagram showing the relationship between the area ratio of the back electrode and the short-circuit current (Jsc) in the sample manufactured by simulating the solar battery cell according to the first embodiment. 図５－１は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-1 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図５－２は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-2 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図５－３は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-3 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図５－４は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-4 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図５－５は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-5 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図５－６は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-6 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図５－７は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-7 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図５－８は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-8 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図５－９は、本発明の実施の形態１にかかる太陽電池セルの製造工程を説明するための断面図である。FIGS. 5-9 is sectional drawing for demonstrating the manufacturing process of the photovoltaic cell concerning Embodiment 1 of this invention. FIGS. 図６－１は、本発明の実施の形態１にかかる太陽電池セルの裏面絶縁膜上における裏面側電極材料ペーストの印刷領域の例を示す平面図である。FIG. 6-1 is a plan view showing an example of a printed region of the back surface side electrode material paste on the back surface insulating film of the solar battery cell according to the first embodiment of the present invention. 図６－２は、本発明の実施の形態１にかかる太陽電池セルの裏面絶縁膜上における裏面側電極材料ペーストの印刷領域の例を示す平面図である。FIG. 6-2 is a plan view showing an example of a printed region of the back surface side electrode material paste on the back surface insulating film of the solar battery cell according to the first embodiment of the present invention. 図７は、本発明の実施の形態２にかかる太陽電池セルの断面構造を説明するための要部断面図である。FIG. 7: is principal part sectional drawing for demonstrating the cross-section of the photovoltaic cell concerning Embodiment 2 of this invention.
　以下に、本発明にかかる光起電力装置およびその製造方法の実施例を図面に基づいて詳細に説明する。なお、本発明は以下の記述により限定されるものではなく、本発明の要旨を逸脱しない範囲において適宜変更可能である。また、以下に示す図面においては、理解の容易のため、各部材の縮尺が実際とは異なる場合がある。各図面間においても同様である。 Hereinafter, embodiments of the photovoltaic device and the manufacturing method thereof according to the present invention will be described in detail with reference to the drawings. In addition, this invention is not limited by the following description, In the range which does not deviate from the summary of this invention, it can change suitably. In the drawings shown below, the scale of each member may be different from the actual scale for easy understanding. The same applies between the drawings.
実施の形態１．
　図１－１～図１－３は、本実施の形態にかかる光起電力装置である太陽電池セルの構成を示す図であり、図１－１は、太陽電池セルの断面構造を説明するための要部断面図、図１－２は、受光面側からみた太陽電池セルの上面図、図１－３は、受光面と反対側（裏面側）からみた太陽電池セルの下面図である。図１－１は、図１－２の線分Ａ－Ａにおける要部断面図である。 Embodiment 1 FIG.
FIGS. 1-1 to 1-3 are diagrams showing a configuration of a solar battery cell that is a photovoltaic device according to the present embodiment, and FIG. 1-1 is for explaining a cross-sectional structure of the solar battery cell. FIG. 1-2 is a top view of the solar cell viewed from the light receiving surface side, and FIG. 1-3 is a bottom view of the solar cell viewed from the side opposite to the light receiving surface (back side). FIG. 1-1 is a cross-sectional view of an essential part taken along line AA in FIG. 1-2.
　本実施の形態にかかる太陽電池セルは、図１－１～図１－３に示されるように、光電変換機能を有する太陽電池基板であってｐｎ接合を有する半導体基板１と、半導体基板１の受光面側の面（表面）に形成されて受光面での入射光の反射を防止する絶縁膜であるシリコン窒化膜（ＳｉＮ膜）からなる反射防止膜４と、半導体基板１の受光面側の面（表面）において反射防止膜４に囲まれて形成された第１電極である受光面側電極５と、半導体基板１の受光面と反対側の面（裏面）に形成されたシリコン窒化膜（ＳｉＮ膜）からなる裏面絶縁膜８と、半導体基板１の裏面において裏面絶縁膜８に囲まれて形成された第２電極である裏面側電極９と、半導体基板１の裏面において裏面絶縁膜８と裏面側電極９とを覆って設けられた裏面反射膜１０と、を備える。 As shown in FIGS. 1-1 to 1-3, the solar cell according to the present embodiment includes a solar cell substrate having a photoelectric conversion function and having a pn junction, An antireflection film 4 made of a silicon nitride film (SiN film) which is an insulating film formed on the light receiving surface side (surface) and prevents reflection of incident light on the light receiving surface, and a light receiving surface side of the semiconductor substrate 1 On the surface (front surface), the light receiving surface side electrode 5 that is the first electrode formed surrounded by the antireflection film 4 and the silicon nitride film (back surface) opposite to the light receiving surface of the semiconductor substrate 1 (back surface) A back insulating film 8 made of SiN film, a back electrode 9 as a second electrode formed on the back surface of the semiconductor substrate 1 and surrounded by the back insulating film 8, and a back insulating film 8 on the back surface of the semiconductor substrate 1. Back surface reflection film 1 provided to cover back surface side electrode 9 And, equipped with a.
　半導体基板１は、第１導電型層であるｐ型多結晶シリコン基板２と、半導体基板１の受光面側にリン拡散によって形成された第２導電型層である不純物拡散層（ｎ型不純物拡散層）３と、によりｐｎ接合が構成されている。ｎ型不純物拡散層３は、表面シート抵抗が３０～１００Ω／□とされている。 The semiconductor substrate 1 includes a p-type polycrystalline silicon substrate 2 which is a first conductivity type layer, and an impurity diffusion layer (n-type impurity diffusion) which is a second conductivity type layer formed by phosphorous diffusion on the light receiving surface side of the semiconductor substrate 1. The layer) 3 constitutes a pn junction. The n-type impurity diffusion layer 3 has a surface sheet resistance of 30 to 100Ω / □.
　受光面側電極５は、太陽電池セルのグリッド電極６およびバス電極７を含み、ｎ型不純物拡散層３に電気的に接続されている。グリッド電極６は、半導体基板１で発電された電気を集電するために受光面に局所的に設けられている。バス電極７は、グリッド電極６で集電された電気を取り出すためにグリッド電極６にほぼ直交して設けられている。 The light-receiving surface side electrode 5 includes a grid electrode 6 and a bus electrode 7 of the solar battery cell, and is electrically connected to the n-type impurity diffusion layer 3. The grid electrode 6 is locally provided on the light receiving surface to collect electricity generated by the semiconductor substrate 1. The bus electrode 7 is provided substantially orthogonal to the grid electrode 6 in order to take out the electricity collected by the grid electrode 6.
　一方、裏面側電極９は、半導体基板１の裏面に全体にわたって設けられた裏面絶縁膜８に一部が埋設されている。すなわち、裏面絶縁膜８には、半導体基板１の裏面に達する略円形のドット状の開口部８ａが設けられている。そして、該開口部８ａを埋めるとともに裏面絶縁膜８の面内方向において開口部８ａの径よりも広い外形を有するように、アルミニウム、ガラス等を含む電極材料からなる裏面側電極９が設けられている。 On the other hand, a part of the back surface side electrode 9 is embedded in the back surface insulating film 8 provided over the entire back surface of the semiconductor substrate 1. That is, the back insulating film 8 is provided with a substantially circular dot-shaped opening 8 a that reaches the back surface of the semiconductor substrate 1. A back-side electrode 9 made of an electrode material containing aluminum, glass, or the like is provided so as to fill the opening 8a and to have an outer shape wider than the diameter of the opening 8a in the in-plane direction of the back insulating film 8. Yes.
　裏面絶縁膜８は、シリコン窒化膜（ＳｉＮ膜）からなり、半導体基板１の裏面のほぼ全面にプラズマＣＶＤ（Chemical　Vapor　Deposition）法により形成されている。裏面絶縁膜８として、プラズマＣＶＤ法により形成されたシリコン窒化膜（ＳｉＮ膜）を用いることにより、半導体基板１の裏面において良好なキャリアの再結合速度の抑制効果を得ることができる。 The back insulating film 8 is made of a silicon nitride film (SiN film), and is formed on almost the entire back surface of the semiconductor substrate 1 by a plasma CVD (Chemical Vapor Deposition) method. By using a silicon nitride film (SiN film) formed by the plasma CVD method as the back surface insulating film 8, it is possible to obtain a favorable carrier recombination rate suppressing effect on the back surface of the semiconductor substrate 1.
　裏面反射膜１０は、半導体基板１の裏面において裏面側電極９および裏面絶縁膜８を覆って設けられている。裏面絶縁膜８を覆う裏面反射膜１０を備えることにより、半導体基板１および裏面絶縁膜８を透過してきた光を反射して半導体基板１に戻すことができ、良好な光閉じ込め効果を得ることができる。そして、本実施の形態では、裏面反射膜１０は気相成長法によって形成される金属膜であるスパッタリング法により形成された銀（Ａｇ）膜（銀スパッタリング膜）により構成されている。裏面反射膜１０は、電極ペーストを用いた印刷法により形成された膜ではなく、スパッタリング膜により構成されているため、印刷法により形成された銀（Ａｇ）膜よりも高い光反射を実現することができ、半導体基板１および裏面絶縁膜８を透過してきた光をより多く反射して半導体基板１に戻すことができる。したがって、本実施の形態にかかる太陽電池セルは、銀スパッタリング膜により構成された裏面反射膜１０を備えることにより、優れた光閉じ込め効果を得ることができる。 The back surface reflection film 10 is provided on the back surface of the semiconductor substrate 1 so as to cover the back surface side electrode 9 and the back surface insulating film 8. By providing the back surface reflecting film 10 covering the back surface insulating film 8, the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained. it can. And in this Embodiment, the back surface reflecting film 10 is comprised by the silver (Ag) film | membrane (silver sputtering film) formed by the sputtering method which is a metal film formed by a vapor phase growth method. Since the back surface reflecting film 10 is not a film formed by a printing method using an electrode paste but is formed by a sputtering film, it realizes higher light reflection than a silver (Ag) film formed by the printing method. Thus, more light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, the solar battery cell according to the present embodiment can obtain an excellent light confinement effect by including the back surface reflection film 10 formed of a silver sputtering film.
　裏面反射膜１０の材料としては、例えば波長が１１００ｎｍ近傍の光に対する反射率が９０％以上、好ましくは９５％以上の金属材料を用いることが好ましい。これにより、高い長波長感度を有し、長波長領域の光に対する光閉じこめ効果に優れた太陽電池セルを実現できる。すなわち、半導体基板１の厚みにもよるが、波長が９００ｎｍ以上、特に１０００ｎｍ～１１００ｎｍ程度の長波長の光を半導体基板１に効率良く取り込み、高い発生電流（Ｊｓｃ）を実現することができ、出力特性を向上させることができる。このような材料としては、銀（Ａｇ）の他に例えばアルミニウム（Ａｌ）を用いることができる。 As the material of the back surface reflection film 10, for example, it is preferable to use a metal material having a reflectance of 90% or more, preferably 95% or more with respect to light having a wavelength near 1100 nm. Thereby, a solar cell having high long wavelength sensitivity and excellent light confinement effect for light in the long wavelength region can be realized. That is, although depending on the thickness of the semiconductor substrate 1, light having a long wavelength of 900 nm or more, particularly about 1000 nm to 1100 nm, can be efficiently taken into the semiconductor substrate 1 and a high generated current (Jsc) can be realized. Characteristics can be improved. As such a material, for example, aluminum (Al) can be used in addition to silver (Ag).
　なお、本実施の形態にかかる太陽電池セルでは、上述したように半導体基板１の裏面に微細な裏面側電極９が形成され、その上に裏面反射膜１０が形成されている。このため、図１－３に示した裏面反射膜１０には実際には裏面側電極９に起因した微細な凹凸が形成されているが、図１－３ではこの微細な凹凸の記載を省略している。 In the solar battery cell according to the present embodiment, as described above, the fine back surface side electrode 9 is formed on the back surface of the semiconductor substrate 1, and the back surface reflection film 10 is formed thereon. For this reason, although the back surface reflecting film 10 shown in FIG. 1C actually has fine unevenness due to the back side electrode 9, the description of the fine unevenness is omitted in FIG. ing.
　また、半導体基板１の裏面側の領域であって裏面側電極９に接する領域およびその近傍にはアルミニウム－シリコン（Ａｌ－Ｓｉ）合金部１１が形成されている。さらにその外周部には、該アルミニウム－シリコン（Ａｌ－Ｓｉ）合金部１１を囲って、ｐ型多結晶シリコン基板２と等しい導電型の高濃度拡散層であるＢＳＦ（Back
Surface Filed層）１２が形成されている。 In addition, an aluminum-silicon (Al—Si) alloy portion 11 is formed in a region on the back surface side of the semiconductor substrate 1 and in the vicinity of the region in contact with the back electrode 9. Further, on the outer periphery thereof, the BSF (Back
Surface Filed layer) 12 is formed.
　このように構成された太陽電池セルでは、太陽光が太陽電池セルの受光面側から半導体基板１のｐｎ接合面（ｐ型多結晶シリコン基板２とｎ型不純物拡散層３との接合面）に照射されると、ホールと電子が生成する。ｐｎ接合部の電界によって、生成した電子はｎ型不純物拡散層３に向かって移動し、ホールはｐ型多結晶シリコン基板２に向かって移動する。これにより、ｎ型不純物拡散層３に電子が過剰となり、ｐ型多結晶シリコン基板２にホールが過剰となる結果、光起電力が発生する。この光起電力はｐｎ接合を順方向にバイアスする向きに生じ、ｎ型不純物拡散層３に接続した受光面側電極５がマイナス極となり、ｐ型多結晶シリコン基板２に接続した裏面側電極９がプラス極となって、図示しない外部回路に電流が流れる。 In the solar cell configured as described above, sunlight is applied from the light receiving surface side of the solar cell to the pn junction surface of the semiconductor substrate 1 (the junction surface between the p-type polycrystalline silicon substrate 2 and the n-type impurity diffusion layer 3). When irradiated, holes and electrons are generated. Due to the electric field at the pn junction, the generated electrons move toward the n-type impurity diffusion layer 3, and the holes move toward the p-type polycrystalline silicon substrate 2. As a result, the number of electrons in the n-type impurity diffusion layer 3 becomes excessive, and the number of holes in the p-type polycrystalline silicon substrate 2 becomes excessive. As a result, a photovoltaic force is generated. This photovoltaic power is generated in the direction of biasing the pn junction in the forward direction, the light receiving surface side electrode 5 connected to the n-type impurity diffusion layer 3 becomes a negative electrode, and the back surface side electrode 9 connected to the p-type polycrystalline silicon substrate 2. Becomes a positive pole, and current flows in an external circuit (not shown).
　図２は、異なる裏面構造を有する３種類の試料における半導体基板の裏面での反射率を示す特性図である。図２では、試料に入射した光の波長と反射率との関係を示している。なお、各試料は太陽電池セルを模して作製し、裏面構造以外の基本的な構造は本実施の形態にかかる太陽電池セルと同様である。各試料の裏面構造の詳細は、以下の通りである。 FIG. 2 is a characteristic diagram showing the reflectance on the back surface of the semiconductor substrate in three types of samples having different back surface structures. FIG. 2 shows the relationship between the wavelength of light incident on the sample and the reflectance. Each sample is produced by imitating a solar battery cell, and the basic structure other than the back surface structure is the same as that of the solar battery cell according to this embodiment. The details of the back surface structure of each sample are as follows.
（試料Ａ）
　半導体基板の裏面全面にわたってアルミニウム（Ａｌ）を含む電極ペーストから形成したアルミニウム（Ａｌ）ペースト電極を備える（従来の一般的な構造に相当）。
（試料Ｂ）
　半導体基板の裏面全面にわたってシリコン窒化膜（ＳｉＮ）からなる裏面絶縁膜を形成し、該裏面絶縁膜上の全面にアルミニウム（Ａｌ）を含む電極ペーストから形成したアルミニウム（Ａｌ）ペースト電極を備える（先行技術（特許文献２）に相当）。
（試料Ｃ）
　半導体基板の裏面全面にわたってシリコン窒化膜（ＳｉＮ）からなる裏面絶縁膜を形成し、且つアルミニウム（Ａｌ）を含む電極ペーストから形成したアルミニウム（Ａｌ）ペースト電極を半導体基板の裏面の局所的に有し、さらに該裏面絶縁膜上の全面に銀スパッタリング膜からなる高反射膜を備える（本実施の形態にかかる太陽電池セルに相当）。 (Sample A)
An aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is provided over the entire back surface of the semiconductor substrate (corresponding to a conventional general structure).
(Sample B)
A back insulating film made of a silicon nitride film (SiN) is formed over the entire back surface of the semiconductor substrate, and an aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is provided over the entire back insulating film (preceding) Technology (equivalent to Patent Document 2)).
(Sample C)
A back insulating film made of a silicon nitride film (SiN) is formed over the entire back surface of the semiconductor substrate, and an aluminum (Al) paste electrode formed from an electrode paste containing aluminum (Al) is locally provided on the back surface of the semiconductor substrate. Further, a high reflection film made of a silver sputtering film is provided on the entire surface of the back insulating film (corresponding to the solar battery cell according to the present embodiment).
　各試料は裏面構造が異なるだけで、その他の構造は同一であるため、図２から「シリコン（半導体基板）－裏面構造」間の反射率の違いを確認することができる。裏面反射の状態を見るには、シリコンへの吸収がほとんど無い波長１２００ｎｍ近辺を比較するとよい。１１００ｎｍ以下の波長ではシリコンへの吸収があり既に発電に寄与しているため、裏面反射の比較には適さないためである。なお、図２において示している反射率は、厳密には裏面での多重反射の結果、再び半導体基板の表面に漏れて来る成分である。 Since each sample is different only in the back surface structure and the other structure is the same, the difference in reflectance between “silicon (semiconductor substrate) -back surface structure” can be confirmed from FIG. In order to see the state of back surface reflection, it is preferable to compare the vicinity of a wavelength of 1200 nm where there is almost no absorption in silicon. This is because the wavelength of 1100 nm or less is absorbed in silicon and has already contributed to power generation, and is not suitable for comparison of back surface reflection. Note that the reflectance shown in FIG. 2 is a component that leaks to the surface of the semiconductor substrate again as a result of multiple reflection on the back surface.
　図２から分かるように、先行技術（特許文献２）に相当する試料Ｂは、従来の一般的な構造に相当する試料Ａに比べて多少の反射率改善があるが、反射率改善効果は十分とは言えない。一方、本実施の形態にかかる太陽電池セルに相当する試料Ｃは、試料Ａおよび試料Ｂに比べて反射率が大きく、「シリコン（半導体基板）－裏面構造」間の反射率の高さが認められ、裏面における光閉じこめ作用に基づく高効率化に適していることが分かる。 As can be seen from FIG. 2, the sample B corresponding to the prior art (Patent Document 2) has a slight improvement in reflectance as compared with the sample A corresponding to the conventional general structure, but the effect of improving the reflectance is sufficient. It can not be said. On the other hand, Sample C corresponding to the solar battery cell according to the present embodiment has a higher reflectance than Sample A and Sample B, and a high reflectance between “silicon (semiconductor substrate) and back surface structure” is recognized. Thus, it can be seen that it is suitable for high efficiency based on the light confinement action on the back surface.
　図３は、上述した試料Ｃと同様に本実施の形態にかかる太陽電池セルを模して作製した試料における裏面電極の面積率（半導体基板の裏面において裏面電極が占める比率）と開放電圧（Ｖｏｃ）との関係を示した特性図である。また、図４は、上述した試料Ｃと同様に本実施の形態にかかる太陽電池セルを模して作製した試料における裏面電極の面積率（半導体基板の裏面において裏面電極が占める比率）と短絡電流（Ｊｓｃ）との関係を示した特性図である。 FIG. 3 shows the area ratio of the back electrode (ratio occupied by the back electrode on the back surface of the semiconductor substrate) and the open-circuit voltage (Voc) in the sample manufactured by simulating the solar battery cell according to the present embodiment in the same manner as the sample C described above. FIG. Further, FIG. 4 shows the area ratio of the back electrode (ratio occupied by the back electrode on the back surface of the semiconductor substrate) and the short-circuit current in the sample manufactured by imitating the solar battery cell according to the present embodiment in the same manner as the sample C described above. It is the characteristic view which showed the relationship with (Jsc).
　図３および図４から分かるように、裏面電極であるアルミニウム（Ａｌ）ペースト電極の面積率の減少に伴い、すなわち本実施の形態にかかる高反射膜の面積率の増加に伴い、開放電圧（Ｖｏｃ）、短絡電流（Ｊｓｃ）ともに向上しており、半導体基板の裏面において良好なキャリアの再結合速度の抑制効果が得られていることが認められる。これにより、本実施の形態にかかる太陽電池セルの構造により、裏面反射改善と半導体基板の裏面におけるキャリアの再結合速度の抑制とを両立できること、および本実施の形態にかかる高反射膜の面積率を高めるほど、上記の効果をより顕著に得られることが分かる。 As can be seen from FIGS. 3 and 4, the open circuit voltage (Voc) increases as the area ratio of the aluminum (Al) paste electrode as the back electrode decreases, that is, as the area ratio of the highly reflective film according to the present embodiment increases. ) And the short-circuit current (Jsc) are improved, and it is recognized that a good effect of suppressing the recombination rate of carriers is obtained on the back surface of the semiconductor substrate. Thereby, by the structure of the solar cell according to the present embodiment, it is possible to achieve both the back surface reflection improvement and the suppression of the carrier recombination rate on the back surface of the semiconductor substrate, and the area ratio of the highly reflective film according to the present embodiment. It can be seen that the above effect can be obtained more remarkably as the value is increased.
　以上のように構成された実施の形態１にかかる太陽電池セルにおいては、裏面絶縁膜８として、半導体基板１の裏面にプラズマＣＶＤ法により形成されたシリコン窒化膜（ＳｉＮ膜）を備えることにより、半導体基板１の裏面において良好なキャリアの再結合速度の抑制効果を得ることができる。これにより、本実施の形態にかかる太陽電池セルにおいては、出力特性の向上が図られ、高い光電変換効率が実現されている。 In the solar cell according to the first embodiment configured as described above, by providing a silicon nitride film (SiN film) formed by plasma CVD on the back surface of the semiconductor substrate 1 as the back surface insulating film 8, A good effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained. Thereby, in the photovoltaic cell concerning this Embodiment, the improvement of an output characteristic is achieved and the high photoelectric conversion efficiency is implement | achieved.
　また、実施の形態１にかかる太陽電池セルにおいては、裏面絶縁膜８を覆って銀スパッタリング膜からなる裏面反射膜１０を備えることにより、従来の印刷法により形成された銀（Ａｇ）膜よりも高い光反射を実現することができ、半導体基板１および裏面絶縁膜８を透過してきた光をより多く反射して半導体基板１に戻すことができる。したがって、本実施の形態にかかる太陽電池セルにおいては、優れた光閉じ込め効果を得ることができ、出力特性の向上が図られ、高い光電変換効率が実現されている。 In the solar cell according to the first embodiment, the back surface reflection film 10 made of a silver sputtering film is provided so as to cover the back surface insulating film 8, thereby making it more than a silver (Ag) film formed by a conventional printing method. High light reflection can be realized, and more light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, in the solar cell according to the present embodiment, an excellent light confinement effect can be obtained, the output characteristics can be improved, and high photoelectric conversion efficiency is realized.
　したがって、実施の形態１にかかる太陽電池セルにおいては、低い再結合速度と高い裏面反射率の双方を有する裏面の構造を有することにより、長波長感度に優れ、光電変換効率の高効率化が図られた太陽電池セルが実現されている。 Therefore, in the solar cell according to the first embodiment, by having the structure of the back surface having both the low recombination speed and the high back surface reflectance, the long-wavelength sensitivity is excellent and the photoelectric conversion efficiency is improved. The obtained solar battery cell is realized.
　つぎに、このような太陽電池セルの製造方法の一例について図５－１～図５－９を参照して説明する。図５－１～図５－９は、本実施の形態にかかる太陽電池セルの製造工程を説明するための断面図である。 Next, an example of a method for manufacturing such a solar battery cell will be described with reference to FIGS. 5-1 to 5-9. FIGS. 5-1 to 5-9 are cross-sectional views for explaining the manufacturing process of the solar battery cell according to the present embodiment.
　まず、半導体基板１として、例えば民生用太陽電池向けとして最も多く使用されているｐ型多結晶シリコン基板を用意する（以下、ｐ型多結晶シリコン基板１ａと呼ぶ）（図５－１）。ｐ型多結晶シリコン基板１ａとしては、例えばホウ素（Ｂ）等のIII族元素を含有した電気抵抗が０．５～３Ωｃｍ程度の多結晶シリコン基板を用いる。 First, as the semiconductor substrate 1, for example, a p-type polycrystalline silicon substrate that is most frequently used for consumer solar cells is prepared (hereinafter referred to as a p-type polycrystalline silicon substrate 1a) (FIG. 5-1). As the p-type polycrystalline silicon substrate 1a, for example, a polycrystalline silicon substrate having an electrical resistance of about 0.5 to 3 Ωcm containing a group III element such as boron (B) is used.
　ｐ型多結晶シリコン基板１ａは、溶融したシリコンを冷却固化してできたインゴットをワイヤーソーでスライスして製造するため、表面にスライス時のダメージが残っている。そこで、まずはこのダメージ層の除去も兼ねて、ｐ型多結晶シリコン基板１ａを酸または加熱したアルカリ溶液中、例えば水酸化ナトリウム水溶液に浸漬して表面をエッチングすることにより、シリコン基板の切り出し時に発生してｐ型多結晶シリコン基板１ａの表面近くに存在するダメージ領域を取り除く。ダメージ除去後のｐ型多結晶シリコン基板１ａの厚みは、例えば２００μｍ、寸法は例えば１５０ｍｍ×１５０ｍｍである。 Since the p-type polycrystalline silicon substrate 1a is manufactured by slicing an ingot formed by cooling and solidifying molten silicon with a wire saw, damage at the time of slicing remains on the surface. Therefore, the p-type polycrystalline silicon substrate 1a is first removed by immersing the surface of the p-type polycrystalline silicon substrate 1a in an acid or a heated alkaline solution, for example, in an aqueous solution of sodium hydroxide so as to remove the damaged layer. Thus, the damaged region existing near the surface of the p-type polycrystalline silicon substrate 1a is removed. The thickness of the p-type polycrystalline silicon substrate 1a after the damage removal is, for example, 200 μm, and the dimension is, for example, 150 mm × 150 mm.
　また、ダメージ除去と同時に、またはダメージ除去に続いて、ｐ型多結晶シリコン基板１ａの受光面側の表面にテクスチャー構造として微小凹凸を形成してもよい。このようなテクスチャー構造を半導体基板１の受光面側に形成することで、太陽電池セルの表面で光の多重反射を生じさせ、太陽電池セルに入射する光を効率的にｐ型多結晶シリコン基板１ａの内部に吸収させることができ、実効的に反射率を低減し変換効率を向上させることができる。 Also, at the same time as the removal of damage or subsequent to the removal of damage, fine irregularities may be formed as a texture structure on the surface of the p-type polycrystalline silicon substrate 1a on the light receiving surface side. By forming such a texture structure on the light receiving surface side of the semiconductor substrate 1, multiple reflection of light is caused on the surface of the solar battery cell, and light incident on the solar battery cell is efficiently transmitted to the p-type polycrystalline silicon substrate. 1a can be absorbed, and the reflectance can be effectively reduced and the conversion efficiency can be improved.
　なお、本発明は光起電力装置の裏面構造にかかる発明であるので、テクスチャー構造の形成方法や形状については、特に制限するものではない。例えば、イソプロピルアルコールを含有させたアルカリ水溶液や主にフッ酸、硝酸の混合液からなる酸エッチングを用いる方法、部分的に開口を設けたマスク材をｐ型多結晶シリコン基板１ａの表面に形成して該マスク材を介したエッチングによりｐ型多結晶シリコン基板１ａの表面にハニカム構造や逆ピラミッド構造を得る方法、或いは反応性ガスエッチング（ＲＩＥ：Reactive
Ion Etching）を用いた手法など、何れの手法を用いても差し支えない。 In addition, since this invention is invention concerning the back surface structure of a photovoltaic apparatus, it does not restrict | limit in particular about the formation method and shape of a texture structure. For example, an alkaline aqueous solution containing isopropyl alcohol, a method using acid etching mainly composed of a mixed solution of hydrofluoric acid and nitric acid, or a mask material partially provided with an opening is formed on the surface of the p-type polycrystalline silicon substrate 1a. A method of obtaining a honeycomb structure or an inverted pyramid structure on the surface of the p-type polycrystalline silicon substrate 1a by etching through the mask material, or reactive gas etching (RIE)
Any method such as a method using Ion Etching may be used.
　つぎに、このｐ型多結晶シリコン基板１ａを熱酸化炉へ投入し、ｎ型の不純物であるリン（Ｐ）の雰囲気下で加熱する。この工程によりｐ型多結晶シリコン基板１ａの表面にリン（Ｐ）を拡散させて、ｎ型不純物拡散層３を形成して半導体ｐｎ接合を形成する（図５－２）。本実施の形態では、ｐ型多結晶シリコン基板１ａをオキシ塩化リン（ＰＯＣｌ３）ガス雰囲気中において、例えば８００℃～８５０℃の温度で加熱することにより、ｎ型不純物拡散層３を形成する。ここで、ｎ型不純物拡散層３の表面シート抵抗が例えば３０～８０Ω／□、好ましくは４０～６０Ω／□となるように加熱処理を制御する。 Next, this p-type polycrystalline silicon substrate 1a is put into a thermal oxidation furnace and heated in an atmosphere of phosphorus (P) which is an n-type impurity. Through this step, phosphorus (P) is diffused on the surface of the p-type polycrystalline silicon substrate 1a to form an n-type impurity diffusion layer 3 to form a semiconductor pn junction (FIG. 5-2). In the present embodiment, the n-type impurity diffusion layer 3 is formed by heating the p-type polycrystalline silicon substrate 1a in a phosphorus oxychloride (POCl 3 ) gas atmosphere at a temperature of, for example, 800 ° C. to 850 ° C. Here, the heat treatment is controlled so that the surface sheet resistance of the n-type impurity diffusion layer 3 is, for example, 30 to 80Ω / □, preferably 40 to 60Ω / □.
　ここで、ｎ型不純物拡散層３の形成直後の表面にはガラスを主成分とするリンガラス層が形成されているため、フッ酸溶液等を用いて除去する。 Here, since a phosphorus glass layer mainly composed of glass is formed on the surface immediately after the formation of the n-type impurity diffusion layer 3, it is removed using a hydrofluoric acid solution or the like.
　つぎに、ｎ型不純物拡散層３を形成したｐ型多結晶シリコン基板１ａの受光面側に、光電変換効率改善のために、反射防止膜４としてシリコン窒化膜（ＳｉＮ膜）を形成する（図５－３）。反射防止膜４の形成には、例えばプラズマＣＶＤ法を使用し、シランとアンモニアの混合ガスを用いて反射防止膜４としてシリコン窒化膜を形成する。反射防止膜４の膜厚および屈折率は、光反射を最も抑制する値に設定する。なお、反射防止膜４として、屈折率の異なる２層以上の膜を積層してもよい。また、反射防止膜４の形成には、スパッタリング法などの異なる成膜方法を用いてもよい。また、反射防止膜４としてシリコン酸化膜を形成してもよい。 Next, a silicon nitride film (SiN film) is formed as the antireflection film 4 on the light receiving surface side of the p-type polycrystalline silicon substrate 1a on which the n-type impurity diffusion layer 3 is formed in order to improve the photoelectric conversion efficiency (FIG. 5-3). For the formation of the antireflection film 4, for example, a plasma CVD method is used, and a silicon nitride film is formed as the antireflection film 4 using a mixed gas of silane and ammonia. The film thickness and refractive index of the antireflection film 4 are set to values that most suppress light reflection. Note that two or more films having different refractive indexes may be laminated as the antireflection film 4. Further, a different film forming method such as a sputtering method may be used for forming the antireflection film 4. Further, a silicon oxide film may be formed as the antireflection film 4.
　つぎに、リン（Ｐ）の拡散によりｐ型多結晶シリコン基板１ａの裏面に形成されたｎ型不純物拡散層３を除去する。これにより、第１導電型層であるｐ型多結晶シリコン基板２と、半導体基板１の受光面側に形成された第２導電型層である不純物拡散層（ｎ型不純物拡散層）３と、によりｐｎ接合が構成された半導体基板１が得られる（図５－４）。 Next, the n-type impurity diffusion layer 3 formed on the back surface of the p-type polycrystalline silicon substrate 1a is removed by diffusion of phosphorus (P). Thus, the p-type polycrystalline silicon substrate 2 as the first conductivity type layer, the impurity diffusion layer (n-type impurity diffusion layer) 3 as the second conductivity type layer formed on the light receiving surface side of the semiconductor substrate 1, Thus, the semiconductor substrate 1 having a pn junction is obtained (FIG. 5-4).
　ｐ型多結晶シリコン基板１ａの裏面に形成されたｎ型不純物拡散層３の除去は、例えば片面エッチング装置を用いて行う。または、反射防止膜４をマスク材として活用し、エッチング液にｐ型多結晶シリコン基板１ａの全体を浸漬させる方法を用いてもよい。エッチング液は、水酸化ナトリウム、水酸化カリウムなどのアルカリ水溶液を、室温～９５℃、好ましくは５０℃～７０℃に加熱したものを用いる。また、エッチング液として、硝酸とフッ酸との混合水溶液を用いてもよい。 The removal of the n-type impurity diffusion layer 3 formed on the back surface of the p-type polycrystalline silicon substrate 1a is performed using, for example, a single-sided etching apparatus. Alternatively, a method of using the antireflection film 4 as a mask material and immersing the entire p-type polycrystalline silicon substrate 1a in an etching solution may be used. As the etching solution, an alkaline aqueous solution such as sodium hydroxide or potassium hydroxide heated to room temperature to 95 ° C., preferably 50 ° C. to 70 ° C. is used. Alternatively, a mixed aqueous solution of nitric acid and hydrofluoric acid may be used as the etching solution.
　ｎ型不純物拡散層３の除去のエッチングの後、後述する成膜で再結合速度を低く保つために、半導体基板１の裏面に露出したシリコン面を洗浄する。洗浄は、例えばＲＣＡ洗浄、または１％～２０％程度のフッ酸水溶液を用いて行う。 After the etching for removing the n-type impurity diffusion layer 3, the silicon surface exposed on the back surface of the semiconductor substrate 1 is washed in order to keep the recombination rate low in film formation described later. The cleaning is performed using, for example, RCA cleaning or a 1% to 20% hydrofluoric acid aqueous solution.
　ついで、半導体基板１の裏面側に、シリコン窒化膜（ＳｉＮ膜）からなる裏面絶縁膜８を形成する（図５－５）。半導体基板１の裏面側に露出させたシリコン面に対して、プラズマＣＶＤにより屈折率１．９～２．２、厚さ６０ｎｍ～３００ｎｍのシリコン窒化膜（ＳｉＮ膜）からなる裏面絶縁膜８を成膜する。プラズマＣＶＤを用いることにより、半導体基板１の裏面側に、シリコン窒化膜からなる裏面絶縁膜８を確実に形成することができる。そして、このような裏面絶縁膜８を形成することにより、半導体基板１の裏面におけるキャリアの再結合速度を抑制することができ、半導体基板１の裏面のシリコン（Ｓｉ）とシリコン窒化膜（ＳｉＮ膜）との界面では、１００ｃｍ／秒以下の再結合速度が得られる。これにより、高出力化の為に十分な裏面界面を実現することができる。 Next, a back surface insulating film 8 made of a silicon nitride film (SiN film) is formed on the back surface side of the semiconductor substrate 1 (FIG. 5-5). A back insulating film 8 made of a silicon nitride film (SiN film) having a refractive index of 1.9 to 2.2 and a thickness of 60 nm to 300 nm is formed on the silicon surface exposed on the back side of the semiconductor substrate 1 by plasma CVD. Film. By using plasma CVD, the back surface insulating film 8 made of a silicon nitride film can be reliably formed on the back surface side of the semiconductor substrate 1. By forming such a back surface insulating film 8, the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be suppressed, and silicon (Si) and silicon nitride film (SiN film) on the back surface of the semiconductor substrate 1 can be suppressed. ), A recombination velocity of 100 cm / sec or less is obtained. Thereby, it is possible to realize a sufficient back surface interface for high output.
　裏面絶縁膜８の屈折率が１．９～２．２を外れると、シリコン窒化膜（ＳｉＮ膜）の成膜環境の安定が難しく、またシリコン窒化膜（ＳｉＮ膜）の膜質が悪化し、その結果、シリコン（Ｓｉ）との界面の再結合速度も悪化する。また、裏面絶縁膜８の厚さが６０ｎｍより小である場合は、シリコン（Ｓｉ）との界面が安定せず、キャリアの再結合速度が悪化する。裏面絶縁膜８の厚さが３００ｎｍより大である場合は、機能的な不都合はないが成膜に時間を要し、コストが増加するため生産性の観点から好ましくない。 If the refractive index of the back surface insulating film 8 deviates from 1.9 to 2.2, it is difficult to stabilize the deposition environment of the silicon nitride film (SiN film), and the film quality of the silicon nitride film (SiN film) deteriorates. As a result, the recombination rate at the interface with silicon (Si) also deteriorates. On the other hand, when the thickness of the back insulating film 8 is smaller than 60 nm, the interface with silicon (Si) is not stable, and the carrier recombination rate is deteriorated. When the thickness of the back insulating film 8 is larger than 300 nm, there is no functional inconvenience, but it takes time to form a film and increases costs, which is not preferable from the viewpoint of productivity.
　また、裏面絶縁膜８は、例えば熱酸化により形成されたシリコン酸化膜（シリコン熱酸化膜：ＳｉＯ２膜）とシリコン窒化膜（ＳｉＮ膜）とが積層された２層の積層構造としてもよい。ここでのシリコン酸化膜（ＳｉＯ２膜）は、工程中において半導体基板１の裏面側に形成された自然酸化膜ではなく、例えば熱酸化により意図的に形成したシリコン酸化膜（ＳｉＯ２膜）とする。このようなシリコン酸化膜（ＳｉＯ２膜）を用いることにより、シリコン窒化膜（ＳｉＮ膜）よりも安定して半導体基板１の裏面におけるキャリアの再結合速度の抑制効果を得ることができる。 The back insulating film 8 may have a two-layer structure in which a silicon oxide film (silicon thermal oxide film: SiO 2 film) formed by thermal oxidation and a silicon nitride film (SiN film) are stacked, for example. The silicon oxide film (SiO 2 film) here is not a natural oxide film formed on the back side of the semiconductor substrate 1 during the process, but a silicon oxide film (SiO 2 film) intentionally formed by thermal oxidation, for example. To do. By using such a silicon oxide film (SiO 2 film), the effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained more stably than the silicon nitride film (SiN film).
　また、熱酸化により意図的に形成したシリコン酸化膜（ＳｉＯ２膜）の厚さは１０ｎｍ～５０ｎｍ程度とすることが好ましい。熱酸化により形成されたシリコン酸化膜（ＳｉＯ２膜）の厚さが１０ｎｍより小である場合は、シリコン（Ｓｉ）との界面が安定せず、キャリアの再結合速度が悪化する。熱酸化により形成されたシリコン酸化膜（ＳｉＯ２膜）の厚さが５０ｎｍより大である場合は、機能的な不都合はないが成膜に時間を要し、コストが増加するため、生産性の観点から好ましくない。また、時間短縮のために高温で成膜処理を行うと、結晶シリコン自体の品質が低下し、ライフタイム低下に繋がる。 The thickness of the silicon oxide film (SiO 2 film) intentionally formed by thermal oxidation is preferably about 10 nm to 50 nm. When the thickness of the silicon oxide film (SiO 2 film) formed by thermal oxidation is less than 10 nm, the interface with silicon (Si) is not stable, and the recombination rate of carriers deteriorates. When the thickness of the silicon oxide film (SiO 2 film) formed by thermal oxidation is larger than 50 nm, there is no functional inconvenience, but the film formation takes time and the cost increases. It is not preferable from the viewpoint. In addition, when the film formation process is performed at a high temperature in order to shorten the time, the quality of the crystalline silicon itself is lowered, leading to a reduction in lifetime.
　その後、半導体基板１の裏面側とのコンタクトを取るために、裏面絶縁膜８の一部または全面に、所定の間隔を有するドット状の開口部８ａを形成する（図５－６）。開口部８ａは、例えば裏面絶縁膜８に対するレーザ照射により直接パターニングを行って形成する。 Thereafter, in order to make contact with the back surface side of the semiconductor substrate 1, dot-shaped openings 8a having a predetermined interval are formed on a part or the entire surface of the back insulating film 8 (FIGS. 5-6). The opening 8a is formed by performing direct patterning, for example, by laser irradiation on the back surface insulating film 8.
　半導体基板１の裏面側との良好なコンタクトを形成するためには、裏面絶縁膜８の面内方向における開口部８ａの断面積を大きくし、裏面絶縁膜８の面内における開口部８ａの開口密度を高くすることが好ましい。しかし、半導体基板１の裏面側において高い光反射率（裏面反射率）を得るためには、逆に開口部８ａの断面積が小さく、開口部８ａの開口密度が低いことが好ましい。したがって、開口部８ａの形状および密度は、良好なコンタクトを実現するための必要最小限のレベルにとどめることが好ましい。 In order to form a good contact with the back side of the semiconductor substrate 1, the cross-sectional area of the opening 8 a in the in-plane direction of the back insulating film 8 is increased, and the opening of the opening 8 a in the plane of the back insulating film 8. It is preferable to increase the density. However, in order to obtain a high light reflectance (back surface reflectance) on the back surface side of the semiconductor substrate 1, it is preferable that the cross-sectional area of the opening 8a is small and the opening density of the opening 8a is low. Therefore, it is preferable that the shape and density of the opening 8a be kept to a minimum level necessary for realizing a good contact.
　具体的には、開口部８ａの形状としては、径または幅が２０μｍ～２００μｍの大きさであり、隣接する開口部８ａ間の間隔が０．５ｍｍ～２ｍｍの略円形のドット状または略矩形形状が挙げられる。また、その他の開口部８ａの形状としては、幅が２０μｍ～２００μｍ、隣接する開口部８ａ間の間隔が０．５ｍｍ～３ｍｍのストライプ状の形状が挙げられる。本実施の形態では、裏面絶縁膜８に対するレーザ照射によりドット状の開口部８ａを形成する。 Specifically, the shape of the opening 8a has a diameter or width of 20 μm to 200 μm, and a substantially circular dot shape or a substantially rectangular shape with an interval between adjacent opening portions 8a of 0.5 mm to 2 mm. Is mentioned. As other shapes of the opening 8a, a stripe shape having a width of 20 μm to 200 μm and a distance between adjacent openings 8a of 0.5 mm to 3 mm can be cited. In the present embodiment, dot-shaped openings 8 a are formed by laser irradiation on the back surface insulating film 8.
　つぎに、裏面側電極９の電極材料であってアルミニウム、ガラス等を含む裏面側電極材料ペースト９ａを、開口部８ａを埋めるとともに裏面絶縁膜８の面内方向において開口部８ａの径よりも多少広い領域を覆い、且つ隣接する開口部８ａを埋める裏面側電極材料ペースト９ａと接触しないように、スクリーン印刷法により限定的に塗布し、乾燥させる（図５－７）。裏面側電極材料ペースト９ａの塗布形状・塗布量等は、後述の焼成工程でＡｌ－Ｓｉ合金部１１とＢＳＦ１２とにおけるアルミニウムの拡散濃度等の諸条件により変更可能である。 Next, a back-side electrode material paste 9a containing aluminum, glass, or the like, which is an electrode material for the back-side electrode 9, fills the opening 8a and is slightly larger than the diameter of the opening 8a in the in-plane direction of the back-side insulating film 8. It is applied in a limited manner by screen printing so as not to come into contact with the back-side electrode material paste 9a covering a wide area and filling the adjacent opening 8a (FIGS. 5-7). The application shape, application amount, and the like of the back-side electrode material paste 9a can be changed according to various conditions such as the diffusion concentration of aluminum in the Al—Si alloy part 11 and the BSF 12 in the firing step described later.
　開口部８ａにおいては十分なペースト量を確保し、焼成工程においてＡｌ－Ｓｉ合金部１１とＢＳＦ層１２を確実に形成する必要がある。一方、半導体基板１の裏面上に裏面絶縁膜８（シリコン窒化膜）と裏面側電極９とが積層された領域における裏面側電極９による光反射率（裏面反射率）は十分とは言えない。このため、裏面絶縁膜８上における裏面側電極９の形成領域が広くなると、光起電力装置内への光閉じ込め効果が低下する。したがって、裏面側電極材料ペースト９ａを印刷する領域は、Ａｌ－Ｓｉ合金部１１およびＢＳＦ１２の形成条件と光起電力装置内への光閉じ込め効果とのバランスを取った上で、必要最小限に絞る必要がある。 It is necessary to secure a sufficient amount of paste in the opening 8a and to surely form the Al—Si alloy part 11 and the BSF layer 12 in the firing step. On the other hand, the light reflectance (back surface reflectance) by the back surface side electrode 9 in the region where the back surface insulating film 8 (silicon nitride film) and the back surface side electrode 9 are laminated on the back surface of the semiconductor substrate 1 is not sufficient. For this reason, when the formation area of the back surface side electrode 9 on the back surface insulating film 8 becomes wide, the light confinement effect in the photovoltaic device is lowered. Therefore, the area where the back side electrode material paste 9a is printed is limited to the minimum necessary after balancing the formation conditions of the Al—Si alloy part 11 and the BSF 12 and the light confinement effect in the photovoltaic device. There is a need.
　本実施の形態では、アルミニウム（Ａｌ）含有の裏面側電極材料ペースト９ａを、開口部８ａの端から各々２０μｍの幅だけ裏面絶縁膜８上にオーバーラップさせる形で厚さ２０μｍで印刷を行う。この場合、裏面絶縁膜８上にオーバーラップさせることにより、形成される裏面電極９が裏面絶縁膜８の開口部８ａ部での剥離を防ぐ効果がある。図６－１および図６－２は、裏面絶縁膜８上における裏面側電極材料ペースト９ａの印刷領域の例を示す平面図である。図６－１は、開口部８ａを略円形のドット状とした例を示しており、図６－２は、開口部８ａを略矩形形状とした例を示している。 In this embodiment, printing is performed with a thickness of 20 μm in such a manner that aluminum (Al) -containing back-side electrode material paste 9a is overlapped on the back-side insulating film 8 by a width of 20 μm from the end of the opening 8a. In this case, by overlapping the back surface insulating film 8, there is an effect that the back surface electrode 9 to be formed is prevented from peeling off at the opening 8 a portion of the back surface insulating film 8. FIGS. 6A and 6B are plan views showing an example of the printing region of the back surface side electrode material paste 9a on the back surface insulating film 8. FIGS. FIG. 6A shows an example in which the opening 8a has a substantially circular dot shape, and FIG. 6B shows an example in which the opening 8a has a substantially rectangular shape.
　オーバーラップ量は、開口部８ａの端から断面積で２００μｍ２から１０００μｍ２、好ましくは４００μｍ２から１０００μｍ２の範囲で制御することが望ましい。本実施の形態では、アルミニウム（Ａｌ）含有の裏面側電極材料ペースト９ａのペースト厚が２０μｍなので、オーバーラップの幅という表現で言えば、開口部８ａの端から各々１０μｍから５０μｍ、好ましくは２０μｍから５０μｍの範囲に相当する。オーバーラップの幅が１０μｍ未満では、裏面絶縁膜８の剥離を防ぐ効果を発揮しないだけでなく、焼成時すなわち合金形成時に、アルミニウム（Ａｌ）の供給がうまくいかず、ＢＳＦ構造が良好に形成されない部分が発生する。一方、オーバーラップの幅が５０μｍより大きいと、ペースト印刷の部分が占める面積比率が増加、すなわち高反射膜の面積率が減少し、本発明の意図からの逸脱が大きくなってしまう。 Overlap amount is, 1000 .mu.m 2 from 200 [mu] m 2 in sectional area from the end of the opening 8a, preferably it is desirable to control in the range of 400 [mu] m 2 of 1000 .mu.m 2. In the present embodiment, since the paste thickness of the back side electrode material paste 9a containing aluminum (Al) is 20 μm, in terms of the width of the overlap, 10 μm to 50 μm, preferably 20 μm from the end of the opening 8a. It corresponds to the range of 50 μm. If the overlap width is less than 10 μm, the effect of preventing the peeling of the back surface insulating film 8 will not be exhibited, but the supply of aluminum (Al) will not be successful at the time of firing, that is, when the alloy is formed, and the BSF structure will not be formed well. Part occurs. On the other hand, if the overlap width is larger than 50 μm, the area ratio occupied by the paste printing portion increases, that is, the area ratio of the high reflection film decreases, and the deviation from the intention of the present invention becomes large.
　図６－１に示すように開口部８ａが略円形のドット状である場合は、裏面絶縁膜８上における開口部８ａの外周部に幅が２０μｍのリング状のオーバーラップ領域９ｂを含んだ略円形状に裏面側電極材料ペースト９ａをスクリーン印刷法により裏面絶縁膜８上に限定的に塗布する。例えば開口部８ａの直径ｄが２００μｍである場合は、裏面側電極材料ペースト９ａは、「２００μｍ＋２０μｍ＋２０μｍ＝２４０μｍ」の直径を有する略円形状に印刷される。 As shown in FIG. 6A, when the opening 8a has a substantially circular dot shape, the outer periphery of the opening 8a on the back insulating film 8 includes a ring-shaped overlap region 9b having a width of 20 μm. The back electrode material paste 9a is applied in a circular shape on the back insulating film 8 in a limited manner by screen printing. For example, when the diameter d of the opening 8a is 200 μm, the back surface side electrode material paste 9a is printed in a substantially circular shape having a diameter of “200 μm + 20 μm + 20 μm = 240 μm”.
　また、図６－２に示すように開口部８ａが略矩形形状である場合は、裏面絶縁膜８上における開口部８ａの外周部に幅が２０μｍの枠状のオーバーラップ領域９ｂを設けて、裏面側電極材料ペースト９ａをスクリーン印刷法により裏面絶縁膜８上に限定的に塗布する。例えば開口部８ａの幅ｗが１００μｍである場合は、裏面側電極材料ペースト９ａは、「１００μｍ＋２０μｍ＋２０μｍ＝１４０μｍ」の幅を有する略矩形形状に印刷される。 Further, when the opening 8a has a substantially rectangular shape as shown in FIG. 6B, a frame-shaped overlap region 9b having a width of 20 μm is provided on the outer periphery of the opening 8a on the back surface insulating film 8, The back surface side electrode material paste 9a is limitedly applied on the back surface insulating film 8 by screen printing. For example, when the width w of the opening 8a is 100 μm, the back surface side electrode material paste 9a is printed in a substantially rectangular shape having a width of “100 μm + 20 μm + 20 μm = 140 μm”.
　つぎに、半導体基板１の反射防止膜４上に、受光面側電極５の電極材料であって銀（Ａｇ）、ガラス等を含む受光面電極材料ペースト５ａを、受光面側電極５の形状に選択的にスクリーン印刷法により塗布し、乾燥する（図５－７）。受光面電極材料ペースト５ａは、例えば、８０μｍ～１５０μｍ幅、２ｍｍ～３ｍｍ間隔の長尺状のグリッド電極６のパターンと、このパターンに略直交する方向に１ｍｍ～３ｍｍ幅、５ｍｍ～１０ｍｍ間隔の帯状のバス電極７のパターンと、を印刷する。ただし、受光面側電極５の形状については、本発明と直接の関係はないので、電極抵抗と印刷遮光率の間でバランスを取りながら、自由に設定してよい。 Next, on the antireflection film 4 of the semiconductor substrate 1, a light receiving surface electrode material paste 5 a which is an electrode material of the light receiving surface side electrode 5 and contains silver (Ag), glass or the like is formed into the shape of the light receiving surface side electrode 5. Selectively apply by screen printing and dry (Figure 5-7). The light-receiving surface electrode material paste 5a is, for example, a pattern of elongated grid electrodes 6 having a width of 80 μm to 150 μm and a spacing of 2 mm to 3 mm, and a strip shape having a width of 1 mm to 3 mm and a spacing of 5 mm to 10 mm in a direction substantially perpendicular to the pattern. The pattern of the bus electrode 7 is printed. However, since the shape of the light receiving surface side electrode 5 is not directly related to the present invention, it may be freely set while balancing between the electrode resistance and the printing light shielding rate.
　その後、例えば赤外炉ヒータを用いてピーク温度７６０℃～９００℃で焼成を行う。これにより、受光面側電極５および裏面側電極９が形成されるとともに、半導体基板１の裏面側の領域であって裏面側電極９に接する領域およびその近傍にはＡｌ－Ｓｉ合金部１１が形成される。さらにその外周部には、該Ａｌ－Ｓｉ合金部１１を囲って、裏面側電極９からアルミニウムが高濃度に拡散したｐ＋領域であるＢＳＦ１２が形成され該ＢＳＦ層１２と裏面側電極９とが電気的に接続する（図５－８）。なお、この接続個所では界面の再結合速度が悪化するが、ＢＳＦ層１２がこの影響を無効化できる。また、受光面側電極５中の銀が反射防止膜４を貫通して、ｎ型不純物拡散層３と受光面側電極５とが電気的に接続する。 Thereafter, firing is performed at a peak temperature of 760 ° C. to 900 ° C. using, for example, an infrared furnace heater. Thus, the light receiving surface side electrode 5 and the back surface side electrode 9 are formed, and the Al—Si alloy portion 11 is formed in the region on the back surface side of the semiconductor substrate 1 and in contact with the back surface side electrode 9 and its vicinity. Is done. Further, a BSF 12 that is a p + region in which aluminum is diffused in a high concentration from the back surface side electrode 9 is formed on the outer periphery of the Al—Si alloy portion 11, and the BSF layer 12 and the back surface side electrode 9 are electrically connected to each other. Connection (Figure 5-8). Note that the recombination speed at the interface deteriorates at this connection point, but the BSF layer 12 can negate this effect. Further, the silver in the light receiving surface side electrode 5 penetrates the antireflection film 4, and the n-type impurity diffusion layer 3 and the light receiving surface side electrode 5 are electrically connected.
　この際、半導体基板１の裏面において裏面側電極材料ペースト９ａが塗布されていない領域はシリコン窒化膜（ＳｉＮ膜）からなる裏面絶縁膜８により保護されているため、焼成による加熱においても半導体基板１の裏面に対して汚染物質の付着や固定が進まず、再結合速度を劣化させることなく、良好な状態が維持される。 At this time, since the region where the back surface side electrode material paste 9a is not applied on the back surface of the semiconductor substrate 1 is protected by the back surface insulating film 8 made of a silicon nitride film (SiN film), the semiconductor substrate 1 is also subjected to heating by baking. The adherence and fixation of contaminants do not proceed with respect to the back surface, and a good state is maintained without degrading the recombination speed.
　つぎに、半導体基板１の裏面側に高反射構造を形成する。すなわち、裏面側電極９および裏面絶縁膜８を覆うように、裏面反射膜１０として銀（Ａｇ）膜（銀スパッタリング膜）を半導体基板１の裏面の全面にスパッタリング法により形成する（図５－９）。裏面反射膜１０をスパッタリング法により形成することにより緻密な裏面反射膜１０を形成することができ、印刷法により形成された銀（Ａｇ）膜よりも高い光反射を実現する裏面反射膜１０を形成することができる。なお、裏面反射膜１０は、蒸着法により形成してもよい。また、ここでは、半導体基板１の裏面の全面に裏面反射膜１０を形成しているが、裏面反射膜１０は少なくとも半導体基板１の裏面側における裏面絶縁膜８を覆うように形成されればよい。 Next, a highly reflective structure is formed on the back side of the semiconductor substrate 1. That is, a silver (Ag) film (silver sputtering film) is formed on the entire back surface of the semiconductor substrate 1 by a sputtering method so as to cover the back electrode 9 and the back insulating film 8 (FIG. 5-9). ). By forming the back surface reflection film 10 by a sputtering method, a dense back surface reflection film 10 can be formed, and the back surface reflection film 10 that realizes higher light reflection than a silver (Ag) film formed by a printing method is formed. can do. In addition, you may form the back surface reflecting film 10 by a vapor deposition method. Here, although the back surface reflection film 10 is formed on the entire back surface of the semiconductor substrate 1, the back surface reflection film 10 may be formed so as to cover at least the back surface insulating film 8 on the back surface side of the semiconductor substrate 1. .
　以上により、図１－１～図１－３に示す実施の形態１にかかる太陽電池セルが作製される。なお、電極材料であるペーストの塗布の順番を、受光面側と裏面側とで入れ替えてもよい。 Thus, the solar battery cell according to Embodiment 1 shown in FIGS. 1-1 to 1-3 is manufactured. Note that the order of application of the paste as the electrode material may be switched between the light receiving surface side and the back surface side.
　上述したように、実施の形態１にかかる太陽電池セルの製造方法においては、開口部８ａを有する裏面絶縁膜８を半導体基板１の裏面に形成した後に裏面側電極材料ペースト９ａを塗布し、焼成を行うため、裏面側電極材料ペースト９ａが塗布されていない領域は裏面絶縁膜８により保護される。これにより、焼成による加熱においても半導体基板１の裏面に対して汚染物質の付着や固定が進まず、再結合速度を劣化させることなく、良好な状態が維持され、光電変換効率が向上する。 As described above, in the method for manufacturing the solar cell according to the first embodiment, after forming the back surface insulating film 8 having the opening 8a on the back surface of the semiconductor substrate 1, the back surface side electrode material paste 9a is applied and fired. Therefore, the region where the back surface side electrode material paste 9a is not applied is protected by the back surface insulating film 8. Thereby, even in the heating by baking, adherence and fixation of the contaminant do not proceed to the back surface of the semiconductor substrate 1, and a good state is maintained without deteriorating the recombination speed, and the photoelectric conversion efficiency is improved.
　また、実施の形態１にかかる太陽電池セルの製造方法においては、少なくとも裏面絶縁膜８を覆うように裏面反射膜１０を半導体基板１の裏面に形成する。これにより、半導体基板１および裏面絶縁膜８を透過してきた光を裏面反射膜１０において反射して半導体基板１に戻すことができ、良好な光閉じ込め効果を得ることができるため、出力特性の向上を図って、高い光電変換効率を実現することができる。 Further, in the method for manufacturing the solar cell according to the first embodiment, the back surface reflecting film 10 is formed on the back surface of the semiconductor substrate 1 so as to cover at least the back surface insulating film 8. Thereby, the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected by the back surface reflective film 10 and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained. Thus, high photoelectric conversion efficiency can be realized.
　また、実施の形態１にかかる太陽電池セルの製造方法においては、裏面反射膜１０をスパッタリング法により形成する。電極ペーストを用いた印刷法ではなく、スパッタリング膜により裏面反射膜１０を形成することにより緻密な裏面反射膜１０を形成することができ、印刷法により形成された膜よりも高い光反射を実現する裏面反射膜１０を形成することができ、優れた光閉じ込め効果を得ることができる。 Further, in the method for manufacturing the solar battery cell according to the first embodiment, the back surface reflecting film 10 is formed by a sputtering method. A dense back surface reflecting film 10 can be formed by forming the back surface reflecting film 10 by a sputtering film, not by a printing method using an electrode paste, and realizes higher light reflection than a film formed by the printing method. The back reflective film 10 can be formed, and an excellent light confinement effect can be obtained.
　したがって、実施の形態１にかかる太陽電池セルの製造方法によれば、低い再結合速度と高い裏面反射率の双方を有する裏面の構造を得ることができ、長波長感度に優れ、光電変換効率の高効率化が図られた太陽電池セルを作製することができる。さらに、太陽電池セルの光電変換効率の高効率化が図れるため、半導体基板１の薄板化が可能であり、製造コストの低下を図ることができ、電池セル特性に優れた高品質な太陽電池セルを安価に作製することができる。 Therefore, according to the manufacturing method of the solar cell according to the first embodiment, it is possible to obtain a back surface structure having both a low recombination speed and a high back surface reflectance, an excellent long wavelength sensitivity, and a photoelectric conversion efficiency. Solar cells with high efficiency can be manufactured. Further, since the photoelectric conversion efficiency of the solar battery cell can be increased, the semiconductor substrate 1 can be thinned, the manufacturing cost can be reduced, and the high-quality solar battery cell excellent in battery cell characteristics can be achieved. Can be manufactured at low cost.
実施の形態２．
　実施の形態２では、裏面反射膜１０の他の形態として、裏面反射膜１０を金属箔により構成する場合について説明する。図７は、本実施の形態にかかる太陽電池セルの断面構造を説明するための要部断面図であり、図１－１に対応する図である。実施の形態２にかかる太陽電池セルが実施の形態１にかかる太陽電池セルと異なる点は、裏面反射膜が銀スパッタリング膜ではなく、アルミニウム箔（アルミニウムホイル）により構成されている点である。これ以外の構成は、実施の形態１にかかる太陽電池セルと同様であるため、詳細な説明は省略する。 Embodiment 2. FIG.
Embodiment 2 demonstrates the case where the back surface reflecting film 10 is comprised with metal foil as another form of the back surface reflecting film 10. FIG. FIG. 7 is a main part sectional view for explaining a sectional structure of the solar battery cell according to the present embodiment, and corresponds to FIG. 1-1. The difference between the solar battery cell according to the second embodiment and the solar battery cell according to the first embodiment is that the back surface reflection film is formed of an aluminum foil (aluminum foil) instead of a silver sputtering film. Since the structure of those other than this is the same as that of the photovoltaic cell concerning Embodiment 1, detailed description is abbreviate | omitted.
　図７に示すように、本実施の形態にかかる太陽電池セルにおいては、アルミホイルからなる裏面反射膜２２が、半導体基板１の裏面において裏面側電極９上に配置された導電性接着剤２１により裏面側電極９および裏面絶縁膜８を覆って着設されるとともに、該導電性接着剤２１を介して裏面側電極９に電気的に接続されている。このような構成においても、実施の形態１の場合と同様に半導体基板１および裏面絶縁膜８を透過してきた光を反射して半導体基板１に戻すことができ、安価な構成で良好な光閉じ込め効果を得ることができる。 As shown in FIG. 7, in the solar battery cell according to the present embodiment, the back surface reflecting film 22 made of aluminum foil is formed by the conductive adhesive 21 disposed on the back surface side electrode 9 on the back surface of the semiconductor substrate 1. The backside electrode 9 and the backside insulating film 8 are attached so as to be covered, and are electrically connected to the backside electrode 9 through the conductive adhesive 21. Even in such a configuration, the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1 as in the case of the first embodiment, and good light confinement can be achieved with an inexpensive configuration. An effect can be obtained.
　そして、本実施の形態では、裏面反射膜２２は金属泊であるアルミホイルにより構成されている。裏面反射膜２２は、電極ペーストを用いた印刷法により形成された膜ではなく、金属泊により構成されているため、印刷法により形成された金属膜よりも高い光反射を実現することができ、半導体基板１および裏面絶縁膜８を透過してきた光をより多く反射して半導体基板１に戻すことができる。したがって、本実施の形態にかかる太陽電池セルは、金属泊であるアルミホイルにより構成された裏面反射膜２２を備えることにより、実施の形態１の場合と同様に優れた光閉じ込め効果を得ることができる。 And in this Embodiment, the back surface reflecting film 22 is comprised with the aluminum foil which is a metal stay. Since the back surface reflection film 22 is not a film formed by a printing method using an electrode paste, but is made of a metal stay, it can realize a higher light reflection than a metal film formed by a printing method, More light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, the solar battery cell according to the present embodiment can obtain an excellent light confinement effect as in the case of the first embodiment by including the back surface reflection film 22 composed of the aluminum foil that is a metal stay. it can.
　裏面反射膜２２の材料としては、箔に加工できる金属材料を用いることができ、裏面反射膜１０の場合と同様に、例えば波長が１１００ｎｍ近傍の光に対する反射率が９０％以上、好ましくは９５％以上の金属材料を用いることが好ましい。これにより、高い長波長感度を有し、長波長領域の光に対する光閉じこめ効果に優れた太陽電池セルを実現できる。すなわち、半導体基板１の厚みにもよるが、波長が９００ｎｍ以上、特に１０００ｎｍ～１１００ｎｍ程度の長波長の光を半導体基板１に効率良く取り込み、高い発生電流（Ｊｓｃ）を実現することができ、出力特性を向上させることができる。このような材料としては、アルミニウム（Ａｌ）の他に例えば銀（Ａｇ）を用いることができる。 As the material of the back surface reflection film 22, a metal material that can be processed into a foil can be used. As in the case of the back surface reflection film 10, for example, the reflectance with respect to light having a wavelength near 1100 nm is 90% or more, preferably 95%. It is preferable to use the above metal materials. Thereby, a solar cell having high long wavelength sensitivity and excellent light confinement effect for light in the long wavelength region can be realized. That is, although depending on the thickness of the semiconductor substrate 1, light having a long wavelength of 900 nm or more, particularly about 1000 nm to 1100 nm, can be efficiently taken into the semiconductor substrate 1 and a high generated current (Jsc) can be realized. Characteristics can be improved. As such a material, for example, silver (Ag) can be used in addition to aluminum (Al).
　このように構成された本実施の形態にかかる太陽電池セルは、実施の形態１において図５－１～図５－８を用いて説明した工程の後、裏面側電極９上に導電性接着剤２１を塗布し、該導電性接着剤２１により裏面側電極９および裏面絶縁膜８を覆って裏面反射膜２２を着設することにより作製することができる。なお、この場合も、裏面反射膜２２は少なくとも半導体基板１の裏面側における裏面絶縁膜８を覆うように形成されればよい。 The solar battery cell according to the present embodiment configured as described above has a conductive adhesive on the back-side electrode 9 after the steps described in Embodiment 1 with reference to FIGS. 5-1 to 5-8. 21 is applied, and the back surface side electrode 9 and the back surface insulating film 8 are covered with the conductive adhesive 21 and the back surface reflecting film 22 is attached. In this case as well, the back surface reflection film 22 may be formed so as to cover at least the back surface insulating film 8 on the back surface side of the semiconductor substrate 1.
　以上のように構成された実施の形態２にかかる太陽電池セルにおいては、裏面絶縁膜８として、半導体基板１の裏面にプラズマＣＶＤ法により形成されたシリコン窒化膜（ＳｉＮ膜）を備えることにより、半導体基板１の裏面において良好なキャリアの再結合速度の抑制効果を得ることができる。これにより、本実施の形態にかかる太陽電池セルにおいては、出力特性の向上が図られ、高い光電変換効率が実現されている。 In the solar cell according to the second embodiment configured as described above, by providing a silicon nitride film (SiN film) formed by plasma CVD on the back surface of the semiconductor substrate 1 as the back surface insulating film 8, A good effect of suppressing the recombination rate of carriers on the back surface of the semiconductor substrate 1 can be obtained. Thereby, in the photovoltaic cell concerning this Embodiment, the improvement of an output characteristic is achieved and the high photoelectric conversion efficiency is implement | achieved.
　また、実施の形態２にかかる太陽電池セルにおいては、裏面絶縁膜８を覆って金属泊であるアルミホイルからなる裏面反射膜２２を備えることにより、従来の印刷法により形成された金属膜よりも高い光反射を実現することができ、半導体基板１および裏面絶縁膜８を透過してきた光をより多く反射して半導体基板１に戻すことができる。したがって、本実施の形態にかかる太陽電池セルにおいては、優れた光閉じ込め効果を得ることができ、出力特性の向上が図られ、高い光電変換効率が実現されている。 Further, in the solar cell according to the second embodiment, the back surface insulating film 8 is provided so as to cover the back surface insulating film 8 and include a back surface reflecting film 22 made of aluminum foil that is a metal stay. High light reflection can be realized, and more light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected back to the semiconductor substrate 1. Therefore, in the solar cell according to the present embodiment, an excellent light confinement effect can be obtained, the output characteristics can be improved, and high photoelectric conversion efficiency is realized.
　したがって、実施の形態２にかかる太陽電池セルにおいては、低い再結合速度と高い裏面反射率の双方を有する裏面の構造を有することにより、長波長感度に優れ、光電変換効率の高効率化が図られた太陽電池セルが実現されている。 Therefore, in the solar cell according to the second embodiment, by having the structure of the back surface having both the low recombination speed and the high back surface reflectivity, the long wavelength sensitivity is excellent, and the photoelectric conversion efficiency is improved. The obtained solar battery cell is realized.
　また、実施の形態２にかかる太陽電池セルの製造方法においては、開口部８ａを有する裏面絶縁膜８を半導体基板１の裏面に形成した後に裏面側電極材料ペースト９ａを塗布し、焼成を行うため、裏面側電極材料ペースト９ａが塗布されていない領域は裏面絶縁膜８により保護される。これにより。焼成による加熱においても半導体基板１の裏面に対して汚染物質の付着や固定が進まず、再結合速度を劣化させることなく、良好な状態が維持され、光電変換効率が向上する。 Moreover, in the method for manufacturing a solar battery cell according to the second embodiment, after the back surface insulating film 8 having the opening 8a is formed on the back surface of the semiconductor substrate 1, the back side electrode material paste 9a is applied and fired. The region where the back side electrode material paste 9a is not applied is protected by the back side insulating film 8. By this. Even in the heating by firing, the adherence and fixation of contaminants do not proceed to the back surface of the semiconductor substrate 1, and a good state is maintained without degrading the recombination speed, and the photoelectric conversion efficiency is improved.
　また、実施の形態２にかかる太陽電池セルの製造方法においては、少なくとも裏面絶縁膜８を覆うように裏面反射膜２２を半導体基板１の裏面に形成する。これにより、半導体基板１および裏面絶縁膜８を透過してきた光を裏面反射膜２２において反射して半導体基板１に戻すことができ、良好な光閉じ込め効果を得ることができるため、出力特性の向上を図って、高い光電変換効率を実現することができる。 In the method for manufacturing a solar battery cell according to the second embodiment, the back surface reflection film 22 is formed on the back surface of the semiconductor substrate 1 so as to cover at least the back surface insulating film 8. As a result, the light transmitted through the semiconductor substrate 1 and the back surface insulating film 8 can be reflected by the back surface reflective film 22 and returned to the semiconductor substrate 1, and a good light confinement effect can be obtained. Thus, high photoelectric conversion efficiency can be realized.
　また、実施の形態２にかかる太陽電池セルの製造方法においては、金属泊であるアルミホイルを裏面側電極９上に着設することにより裏面反射膜２２を形成する。電極ペーストを用いた印刷法ではなく、裏面反射膜２２として金属泊であるアルミホイルを用いて裏面反射膜２２を形成することにより緻密な裏面反射膜２２を形成することができ、印刷法により形成された膜よりも高い光反射を実現する裏面反射膜２２を形成することができ、優れた光閉じ込め効果を得ることができる。 Further, in the method for manufacturing a solar battery cell according to the second embodiment, the back surface reflecting film 22 is formed by attaching an aluminum foil that is a metal stay on the back surface side electrode 9. A dense back surface reflection film 22 can be formed by forming the back surface reflection film 22 using an aluminum foil as a back surface reflection film 22 instead of a printing method using an electrode paste. The back surface reflection film 22 that realizes light reflection higher than that of the formed film can be formed, and an excellent light confinement effect can be obtained.
　したがって、実施の形態２にかかる太陽電池セルの製造方法によれば、低い再結合速度と高い裏面反射率の双方を有する裏面の構造を得ることができ、長波長感度に優れ、光電変換効率の高効率化が図られた太陽電池セルを作製することができる。さらに、太陽電池セルの光電変換効率の高効率化が図れるため、半導体基板１の薄板化が可能であり、製造コストの低下を図ることができ、電池セル特性に優れた高品質な太陽電池セルを安価に作製することができる。 Therefore, according to the method for manufacturing a solar battery cell according to the second embodiment, it is possible to obtain a back surface structure having both a low recombination speed and a high back surface reflectance, an excellent long wavelength sensitivity, and a photoelectric conversion efficiency. Solar cells with high efficiency can be manufactured. Further, since the photoelectric conversion efficiency of the solar battery cell can be increased, the semiconductor substrate 1 can be thinned, the manufacturing cost can be reduced, and the high-quality solar battery cell excellent in battery cell characteristics can be achieved. Can be manufactured at low cost.
　なお、上記の実施の形態においては、半導体基板としてｐ型のシリコン基板を使用する場合について説明したが、ｎ型のシリコン基板を用いてｐ型拡散層を形成する逆導電型の太陽電池セルとしてもよい。また、半導体基板として多結晶シリコン基板を用いたが、単結晶シリコン基板を用いてもよい。また、上記においては半導体基板の基板厚を２００μｍとしたが、自己保持が可能な程度の基板厚、例えば５０μｍ程度まで薄型化した半導体基板を用いることもできる。さらに、上記においては半導体基板の寸法を１５０ｍｍ×１５０ｍｍとしたが、半導体基板の寸法はこれに限定されるものではない。 In the above embodiment, the case where a p-type silicon substrate is used as the semiconductor substrate has been described. However, as a reverse conductivity type solar cell in which a p-type diffusion layer is formed using an n-type silicon substrate. Also good. Further, although a polycrystalline silicon substrate is used as the semiconductor substrate, a single crystal silicon substrate may be used. In the above description, the substrate thickness of the semiconductor substrate is 200 μm. However, a semiconductor substrate that can be self-held, for example, thinned to about 50 μm, can be used. Furthermore, in the above description, the size of the semiconductor substrate is 150 mm × 150 mm, but the size of the semiconductor substrate is not limited to this.
　以上のように、本発明にかかる光起電力装置は、低い再結合速度と高い裏面反射率とにより高効率の光起電力装置を実現する場合に有用である。 As described above, the photovoltaic device according to the present invention is useful for realizing a highly efficient photovoltaic device with a low recombination speed and a high back surface reflectance.
　１　半導体基板
　１ａ　ｐ型多結晶シリコン基板
　２　ｐ型多結晶シリコン基板
　３　ｎ型不純物拡散層
　４　反射防止膜
　５　受光面側電極
　５ａ　受光面電極材料ペースト
　６　グリッド電極
　７　バス電極
　８　裏面絶縁膜
　８ａ　開口部
　９　裏面側電極
　９ａ　裏面側電極材料ペースト
　９ｂ　オーバーラップ領域
　１０　裏面反射膜
　１１　アルミニウム－シリコン（Ａｌ－Ｓｉ）合金部
　１２　ＢＳＦ層
　２１　導電性接着剤
　２２　裏面反射膜 DESCRIPTION OF SYMBOLS 1 Semiconductor substrate 1a p-type polycrystalline silicon substrate 2 p-type polycrystalline silicon substrate 3 n-type impurity diffusion layer 4 Antireflection film 5 Light-receiving surface side electrode 5a Light-receiving surface electrode material paste 6 Grid electrode 7 Bus electrode 8 Back surface insulating film 8a Opening Part 9 Back side electrode 9a Back side electrode material paste 9b Overlapping region 10 Back side reflection film 11 Aluminum-silicon (Al-Si) alloy part 12 BSF layer 21 Conductive adhesive 22 Back side reflection film

Claims (18)

  1. 　一面側に第２導電型の不純物元素が拡散された不純物拡散層を有する第１導電型の半導体基板と、
    　前記不純物拡散層上に形成された反射防止膜と、
    　前記反射防止膜を貫通して前記不純物拡散層に電気的に接続する第１電極と、
    　前記半導体基板の他面側に達する複数の開口部を有して前記半導体基板の他面側に形成された裏面絶縁膜と、
    　少なくとも前記開口部に埋め込まれて前記半導体基板の他面側に電気的に接続する第２電極と、
    　気相成長法によって形成される金属膜からなり、または金属箔を含んで構成され、少なくとも前記裏面絶縁膜上を覆って形成された裏面反射膜と、
    　を備えることを特徴とする光起電力装置。     A first conductivity type semiconductor substrate having an impurity diffusion layer in which an impurity element of the second conductivity type is diffused on one side;
    An antireflection film formed on the impurity diffusion layer;
    A first electrode penetrating the antireflection film and electrically connected to the impurity diffusion layer;
    A back surface insulating film formed on the other surface side of the semiconductor substrate with a plurality of openings reaching the other surface side of the semiconductor substrate;
    A second electrode embedded in at least the opening and electrically connected to the other side of the semiconductor substrate;
    A back surface reflecting film formed of a metal film formed by a vapor deposition method or including a metal foil, and formed to cover at least the back surface insulating film;
    A photovoltaic device comprising:
  2. 　前記裏面絶縁膜が、プラズマＣＶＤ法により形成されたシリコン窒化膜であること、
    　を特徴とする請求項１に記載の光起電力装置。     The back insulating film is a silicon nitride film formed by a plasma CVD method;
    The photovoltaic device according to claim 1.
  3. 　前記裏面絶縁膜が、熱酸化により形成されたシリコン酸化膜とプラズマＣＶＤ法により形成されたシリコン窒化膜とが前記半導体基板の他面側から積層された積層膜であること、
    　を特徴とする請求項１に記載の光起電力装置。     The back insulating film is a laminated film in which a silicon oxide film formed by thermal oxidation and a silicon nitride film formed by a plasma CVD method are laminated from the other surface side of the semiconductor substrate;
    The photovoltaic device according to claim 1.
  4. 　前記シリコン酸化膜は、厚さが１０ｎｍ以上５０ｎｍ以下であること、
    　を特徴とする請求項３に記載の光起電力装置。     The silicon oxide film has a thickness of 10 nm to 50 nm,
    The photovoltaic device according to claim 3.
  5. 　前記シリコン窒化膜は、屈折率が１．９以上２．２以下であり、厚さが６０ｎｍ以上３００ｎｍ以下であること、
    　を特徴とする請求項２または３に記載の光起電力装置。     The silicon nitride film has a refractive index of 1.9 to 2.2 and a thickness of 60 nm to 300 nm.
    The photovoltaic device according to claim 2, wherein:
  6. 　前記開口部は、径または幅が２０μｍ～２００μｍの大きさであり、隣接する前記開口部間の間隔が０．５ｍｍ～２ｍｍの略円形のドット状または略矩形形状であること、
    　を特徴とする請求項１に記載の光起電力装置。     The opening has a diameter or width of 20 μm to 200 μm, and has a substantially circular dot shape or a substantially rectangular shape with an interval between adjacent opening portions of 0.5 mm to 2 mm.
    The photovoltaic device according to claim 1.
  7. 　前記開口部は、幅が２０μｍ～２００μｍであり、隣接する前記開口部間の間隔が０．５ｍｍ～３ｍｍのストライプ状であること、
    　を特徴とする請求項１に記載の光起電力装置。     The opening has a stripe shape with a width of 20 μm to 200 μm, and an interval between adjacent openings of 0.5 mm to 3 mm.
    The photovoltaic device according to claim 1.
  8. 　前記第２電極は、前記開口部に埋め込まれるとともに前記裏面絶縁膜上にオーバーラップして形成されていることを特徴とする請求項６または７に記載の光起電力装置。 The photovoltaic device according to claim 6 or 7, wherein the second electrode is embedded in the opening and formed to overlap the back insulating film.
  9. 　前記第２電極は、前記開口部の端部から１０μｍ～５０μｍの幅で前記裏面絶縁膜上にオーバーラップして形成されていること、
    　を特徴とする請求項８に記載の光起電力装置。     The second electrode has a width of 10 μm to 50 μm from the end of the opening, and is formed to overlap the back insulating film;
    The photovoltaic device according to claim 8.
  10. 　前記金属箔は、アルミニウム箔であること、
    　を特徴とする請求項１に記載の光起電力装置。     The metal foil is an aluminum foil;
    The photovoltaic device according to claim 1.
  11. 　前記金属箔は、導電性接着剤により前記第２電極に着設されるとともに前記導電性接着剤を介して前記第２電極に電気的に接続されていること、
    　を特徴とする請求項１に記載の光起電力装置。     The metal foil is attached to the second electrode by a conductive adhesive and is electrically connected to the second electrode via the conductive adhesive;
    The photovoltaic device according to claim 1.
  12. 　前記気相成長法によって形成される金属膜は、金属のスパッタリング膜もしくは蒸着膜であること、
    　を特徴とする請求項１に記載の光起電力装置。     The metal film formed by the vapor deposition method is a metal sputtering film or a vapor deposition film,
    The photovoltaic device according to claim 1.
  13. 　第１導電型の半導体基板の一面側に、第２導電型の不純物元素が拡散された不純物拡散層を形成する第１工程と、
    　前記不純物拡散層上に反射防止膜を形成する第２工程と、
    　前記半導体基板の他面側に裏面絶縁膜を形成する第３工程と、
    　前記裏面絶縁膜の少なくとも一部に前記半導体基板の他面側に達する複数の開口部を形成する第４工程と、
    　前記反射防止膜上に第１電極材料を塗布する第５工程と、
    　少なくとも前記複数の開口部を埋めるように第２電極材料を塗布する第６工程と、
    　前記第１電極材料および前記第２電極材料を焼成して、前記反射防止膜を貫通して前記不純物拡散層に電気的に接続する第１電極と、前記半導体基板の他面側に電気的に接続する第２電極と、を形成する第７工程と、
    　気相成長法によって形成される金属膜からなり、または金属箔を含んで構成された裏面反射膜を、少なくとも前記裏面絶縁膜上を覆って形成する第８工程と、
    　を含むことを特徴とする光起電力装置の製造方法。     A first step of forming an impurity diffusion layer in which an impurity element of the second conductivity type is diffused on one surface side of the first conductivity type semiconductor substrate;
    A second step of forming an antireflection film on the impurity diffusion layer;
    A third step of forming a back surface insulating film on the other surface side of the semiconductor substrate;
    A fourth step of forming a plurality of openings reaching the other surface side of the semiconductor substrate in at least a part of the back surface insulating film;
    A fifth step of applying a first electrode material on the antireflection film;
    A sixth step of applying a second electrode material so as to fill at least the plurality of openings;
    The first electrode material and the second electrode material are baked, and the first electrode that penetrates the antireflection film and is electrically connected to the impurity diffusion layer is electrically connected to the other surface side of the semiconductor substrate. A seventh step of forming a second electrode to be connected;
    An eighth step of forming a back reflecting film made of a metal film formed by vapor deposition or including a metal foil so as to cover at least the back insulating film;
    A method for manufacturing a photovoltaic device, comprising:
  14. 　前記第３工程では、前記裏面絶縁膜としてプラズマＣＶＤ法によりシリコン窒化膜を形成すること、
    　を特徴とする請求項１３に記載の光起電力装置の製造方法。     In the third step, a silicon nitride film is formed by plasma CVD as the back surface insulating film,
    The method for manufacturing a photovoltaic device according to claim 13.
  15. 　前記第３工程では、前記裏面絶縁膜として前記半導体基板の他面側に熱酸化によりシリコン酸化膜を形成し、さらに前記シリコン酸化膜上にプラズマＣＶＤ法によりシリコン窒化膜を形成すること、
    　を特徴とする請求項１３に記載の光起電力装置の製造方法。     In the third step, a silicon oxide film is formed by thermal oxidation on the other surface side of the semiconductor substrate as the back surface insulating film, and a silicon nitride film is further formed on the silicon oxide film by a plasma CVD method,
    The method for manufacturing a photovoltaic device according to claim 13.
  16. 　前記第６工程では、前記開口部を埋めるとともに前記開口部の端部から１０μｍ～５０μｍの幅で前記裏面絶縁膜上にオーバーラップさせて前記第２電極材料を塗布すること、
    　を特徴とする請求項１３に記載の光起電力装置の製造方法。     In the sixth step, the second electrode material is applied to fill the opening and overlap the back insulating film with a width of 10 μm to 50 μm from the end of the opening;
    The method for manufacturing a photovoltaic device according to claim 13.
  17. 　前記金属箔は、アルミニウム箔であること、
    　を特徴とする請求項１３に記載の光起電力装置の製造方法。     The metal foil is an aluminum foil;
    The method for manufacturing a photovoltaic device according to claim 13.
  18. 　前記気相成長法によって形成される金属膜は、金属のスパッタリング膜もしくは蒸着膜であること、
    　を特徴とする請求項１３に記載の光起電力装置の製造方法。     The metal film formed by the vapor deposition method is a metal sputtering film or a vapor deposition film,
    The method for manufacturing a photovoltaic device according to claim 13.
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