EP4022688A1 - Method for manufacturing a photovoltaic cell - Google Patents

Method for manufacturing a photovoltaic cell

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Publication number
EP4022688A1
EP4022688A1 EP20757928.5A EP20757928A EP4022688A1 EP 4022688 A1 EP4022688 A1 EP 4022688A1 EP 20757928 A EP20757928 A EP 20757928A EP 4022688 A1 EP4022688 A1 EP 4022688A1
Authority
EP
European Patent Office
Prior art keywords
substrate
dielectric layer
tunnel oxide
oxide film
layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20757928.5A
Other languages
German (de)
French (fr)
Inventor
Raphaël CABAL
Bernadette Grange
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
Original Assignee
Commissariat a lEnergie Atomique CEA
Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Publication of EP4022688A1 publication Critical patent/EP4022688A1/en
Pending legal-status Critical Current

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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
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
    • 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
    • H01L31/0248—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 characterised by their semiconductor bodies
    • H01L31/0256—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 characterised by their semiconductor bodies characterised by the material
    • H01L31/0264—Inorganic materials
    • H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
    • H01L31/0288—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table characterised by the doping material
    • 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
    • H01L31/0248—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 characterised by their semiconductor bodies
    • H01L31/036—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes
    • H01L31/0368—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including polycrystalline semiconductors
    • H01L31/03682—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 characterised by their semiconductor bodies characterised by their crystalline structure or particular orientation of the crystalline planes including polycrystalline semiconductors including only elements of Group IV of the Periodic Table
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/186—Particular post-treatment for the devices, e.g. annealing, impurity gettering, short-circuit elimination, recrystallisation
    • H01L31/1864—Annealing
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
    • H01L21/2251—Diffusion into or out of group IV semiconductors
    • H01L21/2254—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • 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
    • Y02E10/546—Polycrystalline silicon PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the invention relates to the technical field of photovoltaic cells.
  • the invention finds its application in particular in the manufacture of photo voltaic cells of the PERT ("PassivatedEmiter earTotall -diffused") type.
  • a method of manufacturing a photovoltaic cell known from the state of the art, in particular from document FR 3 035 740, comprises the steps: ao) providing a structure comprising:
  • a substrate based on crystalline silicon having a first surface and a second opposite surface
  • a first dielectric layer comprising boron atoms, and formed on the first surface of the substrate
  • step b) is carried out under an oxidizing atmosphere in order to increase the passivation of the structure and allow the conservation of the first and second dielectric layers.
  • passivation is meant the neutralization of electrically active defects at the first and second surfaces of the substrate.
  • the substrate based on crystalline silicon has a density of defects (eg pendant bonds, impurities, discontinuity of the crystal, etc.) which can lead to non-negligible losses linked to the surface recombination of the carriers in the case of an application. photovoltaic.
  • defects eg pendant bonds, impurities, discontinuity of the crystal, etc.
  • Such a method of the state of the art is not entirely satisfactory in terms of passivation of the structure.
  • Those skilled in the art seek to improve the performance of the photovoltaic cell with the highest possible open circuit voltage values V oc.
  • the invention aims to remedy all or part of the aforementioned drawbacks.
  • the invention relates to a method of manufacturing a photovoltaic cell, comprising the steps: a) providing a structure comprising:
  • a substrate based on crystalline silicon having a first surface and a second opposite surface
  • a first dielectric layer comprising boron atoms, and formed on the first surface of the substrate
  • the doped polysilicon layer being intended to be in contact with an electrode E.
  • such a method according to the invention makes it possible to increase the open circuit voltage values V oc with respect to the state of the art thanks to the presence of the tunnel oxide film and of the polysilicon layer which allow a excellent passivation of the second surface of the substrate.
  • the tunnel oxide film makes it possible to limit the diffusion of phosphorus and / or arsenic atoms from the polysilicon layer to the second surface of the substrate. In other words, the tunnel oxide film acts as a diffusion barrier to phosphorus / arsenic atoms towards the substrate.
  • the tunnel oxide film therefore makes it possible to sufficiently dope the polysilicon layer with phosphorus and / or arsenic during step b) in order to obtain an electrical contact, and this without requiring an increase in the thermal budget of step b).
  • An increase in the thermal budget during step b) would in fact not be desirable because it would also increase the depth of diffusion of the boron atoms under the first surface of the substrate, and would therefore degrade the value of the open circuit voltage V oc Electrical contact on the doped polysilicon layer can be carried out, for example, by screen printing.
  • the tunnel oxide film overcomes the difficulties associated with the different diffusion depths between the boron atoms and the phosphorus / arsenic atoms during their co-diffusion in step b), these difficulties being able to take place in the state of the art.
  • substrate is meant the mechanical support, self-supporting, intended for the manufacture of a photovoltaic cell.
  • crystalline is understood to mean the multicrystalline form or the monocrystalline form of silicon, therefore excluding amorphous silicon.
  • the term “based on” is understood to mean that the corresponding material is the main and majority material making up the substrate (or the layer).
  • dielectric is understood to mean that the layer has an electrical conductivity at 300 K of less than 1CT 8 S / cm.
  • tunnel oxide film an oxide thin enough to allow an electric current to flow within it by tunneling.
  • the method according to the invention may include one or more of the following characteristics.
  • step a) is performed so that the tunnel oxide film is a silicon oxide or an aluminum oxide.
  • silicon oxide is meant silicon oxide of formula S1O2 (silicon dioxide) or its non-stoichiometric SiO x derivatives.
  • aluminum oxide is understood to mean aluminum oxide of formula Al2O3 (alumina) or its non-stoichiometric A10 x derivatives.
  • step a) is carried out so that the tunnel oxide film is a silicon oxide formed on the second surface of the substrate by thermal means.
  • an advantage provided is to improve the density of silicon oxide over chemically formed silicon oxide, which improves the diffusion barrier properties to phosphorus / arsenic atoms.
  • step a) is performed so that the tunnel oxide film is an aluminum oxide formed on the second surface of the substrate by deposition of atomic layers.
  • the deposition of atomic layers is conventionally referred to by the acronym ALD for
  • step a) is carried out so that the tunnel oxide film has a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
  • step a) is carried out so that:
  • the tunnel oxide film is an aluminum oxide having a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm; the structure comprises an additional tunnel oxide film formed between the first surface of the substrate and the first dielectric layer, the additional tunnel oxide film being an aluminum oxide having a thickness less than or equal to 3 nm, preferably less or equal to 2 nm.
  • an advantage provided by the aluminum oxide, forming the additional tunnel oxide film is to weakly affect the diffusion of boron atoms within it, which makes it possible not to significantly degrade the lateral conductance of the first. doped semiconductor region, unlike silicon oxide.
  • a silicon oxide acts as a diffusion barrier to the boron atoms.
  • step a) is carried out so that the first dielectric layer is based on a silicon oxynitride SiO x N y verifying 0 £ y ⁇ x, preferably hydrogenated.
  • Such a first dielectric layer makes it possible to obtain satisfactory passivation of the first surface of the substrate, more precisely passivation of the interface between the first surface of the substrate and the first dielectric layer.
  • the hydrogenation of silicon oxynitride improves the passivation properties.
  • silicon oxynitride is silicon oxide.
  • step a) is carried out so that the second dielectric layer is based on a silicon oxynitride SiO x N y verifying 0 £ x ⁇ y, preferably hydrogenated.
  • silicon oxynitride is silicon nitride.
  • step b) is carried out by applying thermal annealing to the structure, the thermal annealing exhibiting:
  • an annealing temperature value between 850 ° C and 950 ° C, preferably between 900 ° C and 950 ° C,
  • an annealing time value of between 10 minutes and 1 hour, preferably between 30 minutes and 1 hour.
  • thermal annealing a heat treatment comprising:
  • the method comprises a step consisting in forming a layer based on a silicon oxynitride SiO x N y , verifying 0 £ x ⁇ y, preferably hydrogenated, on the first dielectric layer after the step b).
  • an advantage obtained is to improve both the passivation of the first surface of the substrate, and to form a so-called antireflection optical layer, with a suitable thickness.
  • This step is preferably carried out after step b) in order to easily enrich the first dielectric layer with oxygen when step b) is carried out under an oxidizing atmosphere.
  • G silicon oxynitride is silicon nitride.
  • the method comprises a step consisting in forming a layer based on a silicon oxynitride SiO x N y , verifying 0 £ x ⁇ y, preferably hydrogenated, on the second dielectric layer before the step b).
  • the silicon oxynitride is a silicon nitride.
  • an advantage provided is to prevent exo-diffusion of phosphorus / arsenic atoms from the second dielectric layer.
  • the first and second dielectric layers are retained after step b).
  • an advantage provided is a saving of operating time since it is not necessary to remove these layers and then to form dedicated passivation layers.
  • the subject of the invention is also a photo voltaic cell, comprising: - a substrate based on crystalline silicon, having a first surface and a second opposite surface;
  • a first doped semiconductor region extending below the first surface of the substrate, and comprising boron atoms
  • a first dielectric layer comprising boron atoms in a residual proportion, and formed on the first surface of the substrate;
  • a doped polysilicon layer formed on the tunnel oxide film, and comprising phosphorus and / or arsenic atoms;
  • a second dielectric layer comprising phosphorus and / or arsenic atoms in a residual proportion, and formed on the doped polysilicon layer.
  • Such a photovoltaic cell allows an increase in the value of the open circuit voltage V oc compared to the state of the art, thanks to the presence of the tunnel oxide film and of the polysilicon layer which allow excellent passivation. of the second surface of the substrate.
  • the photovoltaic cell comprises an additional tunnel oxide film formed between the first surface of the substrate and the first dielectric layer.
  • the presence of such an additional tunnel oxide film makes it possible to facilitate the manufacture of the photovoltaic cell by allowing the simultaneous formation of the tunnel oxide film and the additional tunnel oxide film on either side of the substrate, this which reduces operating time.
  • the tunnel oxide film and the additional tunnel oxide film are made of aluminum oxide and have a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
  • an advantage provided by the aluminum oxide, forming the additional tunnel oxide film is to weakly affect the diffusion of boron atoms within it, which makes it possible not to significantly degrade the lateral conductance of the first. doped semiconductor region, unlike silicon oxide.
  • a silicon oxide acts as a diffusion barrier to the boron atoms.
  • Figures 1a to 1c are schematic sectional views illustrating different steps of a first embodiment of a method according to the invention.
  • Figures 2a to 2c are schematic sectional views illustrating different steps of a second embodiment of a method according to the invention.
  • Figures 3a to 3d are schematic sectional views illustrating different steps of a third embodiment of a method according to the invention.
  • Figures 4a to 4d are schematic sectional views illustrating different steps of a fourth embodiment of a method according to the invention.
  • An object of the invention is a method of manufacturing a photovoltaic cell, comprising the steps: a) providing a structure comprising:
  • a substrate 1 based on crystalline silicon having a first surface 10 and an opposite second surface 11;
  • a first dielectric layer 2 comprising boron atoms, and formed on the first surface 10 of the substrate 1;
  • Step a) is illustrated in Figures la, 2a, 3a and 4a.
  • Step b) is illustrated in Figures lb, 2b, 3b and 4b.
  • the substrate 1 of the structure provided during step a) is advantageously n-type doped, and the first surface 10 of the substrate 1 is intended to be exposed to light radiation so as to form a standard emitter architecture.
  • the first doped semiconductor region 100 forms the emitter.
  • the substrate 1 is n-type doped.
  • the doped polysilicon layer 4, of the same type of doping as the substrate 1, is of the BSF (“Bach Surface Field”) type.
  • Step a) is advantageously carried out so that the first surface 10 of the substrate 1 is textured in order to reduce the reflection coefficient and the optical losses in the photovoltaic cell.
  • the first surface 10 of the substrate 1 preferably comprises inverted pyramid patterns arranged to create a surface roughness.
  • the texturing is preferably carried out by a chemical attack based on potassium hydroxide KOH.
  • the substrate 1 may have a thickness of the order of 150 ⁇ m.
  • Step a) is advantageously carried out so that the first and second surfaces 10, 11 of the substrate 1 are chemically cleaned beforehand.
  • Step a) is advantageously carried out so that the first dielectric layer 2 is based on a silicon oxynitride SiO x N y verifying 0 £ y ⁇ x, preferably hydrogenated.
  • the first dielectric layer 2 advantageously has a thickness between 3 nm and 50 nm, preferably between 20 nm and 50 nm.
  • the boron atoms advantageously have an atomic proportion in the first dielectric layer 2 of between 10% and 50%, preferably between 10% and 30% before step b).
  • the silicon oxynitride of the first dielectric layer 2 advantageously satisfies 0.2 £ x £ 0.5 and 0.05 £ y £ 0.15 before step b).
  • the method may include a step consisting in forming a layer 2 'based on a silicon oxynitride SiO x N y , verifying 0 £ x ⁇ y, preferably hydrogenated, on the first dielectric layer. 2 after step b).
  • these layers can be formed by chemical vapor deposition (PECVD for "Plasma-E nhanced Chemical Vapor Deposition” in English) from reactive gases comprising silane SiH 4 and nitrous oxide N2O or NH 3 .
  • PECVD chemical vapor deposition
  • reactive gases comprising silane SiH 4 and nitrous oxide N2O or NH 3 .
  • the boron atoms are advantageously incorporated into the hydrogenated silicon oxynitride by injection of diborane B 2 H 6 with the reactive gases.
  • the first dielectric layer 2 is kept after step b), as is layer 2 ’.
  • Step a) is advantageously carried out so that the tunnel oxide film 3 is a silicon oxide or an aluminum oxide.
  • Step a) is advantageously carried out so that the silicon oxide is formed on the second surface 11 of the substrate 1 by thermal means.
  • Step a) is advantageously carried out so that the aluminum oxide is formed on the second surface 11 of the substrate 1 by atomic layer deposition (ALD).
  • ALD atomic layer deposition
  • Step a) is advantageously carried out so that the tunnel oxide film 3 has a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
  • step a) is advantageously carried out so that: the tunnel oxide film 3 is an aluminum oxide having a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm;
  • the structure comprises an additional film 3 'of tunnel oxide formed between the first surface 10 of the substrate 1 and the first dielectric layer 2, the additional film 3' of tunnel oxide being an aluminum oxide having a thickness less than or equal at 3 nm, preferably less than or equal to 2 nm.
  • Step a) is advantageously carried out so that the polysilicon layer 4 has a thickness between 30 nm and 200 nm, preferably between 30 nm and 100 nm.
  • Step a) can be carried out so that the polysilicon layer 4 is formed on the tunnel oxide film 3 by depositing an amorphous silicon layer (eg by LPCVD “Eow Pressure Chemical Vapor Deposition” or by PECVD “Plasma-Enhanced Chemical Vapor Deposition”), followed by annealing to crystallize the amorphous silicon layer.
  • an amorphous silicon layer eg by LPCVD “Eow Pressure Chemical Vapor Deposition” or by PECVD “Plasma-Enhanced Chemical Vapor Deposition”
  • Step a) is advantageously carried out so that the second dielectric layer 5 is based on a silicon oxynitride SiO x N y verifying 0 £ x ⁇ y, preferably hydrogenated.
  • the second dielectric layer 5 advantageously has a thickness between 10 nm and 50 nm, preferably between 10 nm and 30 nm.
  • the phosphorus or arsenic atoms advantageously have a proportion by mass in the second dielectric layer 5 of greater than or equal to 4%, preferably between 10% and 30%.
  • the silicon oxynitride of the second dielectric layer 5 advantageously satisfies 0 £ x £ 0.05 and 0.30 £ y £ 0.55 before and after step b).
  • the method may include a step consisting in forming a layer 5 ′ based on a silicon oxynitride SiO x N y , verifying 0 £ x ⁇ y, preferably hydrogenated, on the second dielectric layer. 5 before step b), preferably with a thickness of less than 80 nm.
  • these layers can be formed by chemical vapor deposition (PECVD for "Plasma-E nhanced Chemical Vapor Deposition” in English) from reactive gases comprising silane SiH 4 and NH 3 .
  • PECVD chemical vapor deposition
  • the phosphorus atoms are advantageously incorporated into the hydrogenated silicon oxynitride by injection of phosphine PH 3 with the reactive gases.
  • the arsenic atoms are advantageously incorporated into the hydrogenated silicon oxynitride by injection of arsine AsH 3 with the reactive gases.
  • the second dielectric layer 5 is kept after step b), as is the layer 5 ’.
  • Step b) is advantageously carried out by applying thermal annealing to the structure, the thermal annealing exhibiting:
  • an annealing temperature value between 850 ° C and 950 ° C, preferably between 900 ° C and 950 ° C,
  • an annealing time value of between 10 minutes and 1 hour, preferably between 30 minutes and 1 hour.
  • the thermal annealing applied during step b) is an overall thermal annealing in the sense that it is applied to the whole of the structure provided during step a). It is therefore not a localized thermal annealing applied to a part of said assembly, for example using a laser.
  • Step b) is preferably carried out in an oven.
  • Thermal annealing can be applied in step b) under an oxidizing atmosphere.
  • an advantage provided by the oxidizing atmosphere is to improve the passivation of the first surface of the substrate (i.e. the interface between the first surface and the first dielectric layer) by enriching the first dielectric layer with oxygen.
  • the oxidizing atmosphere advantageously comprises a mixture of dioxygen and a neutral gas chosen from argon, nitrogen, or a mixture of argon and nitrogen.
  • the oxidizing atmosphere is advantageously constituted by a mixture of dioxygen and of a neutral gas chosen from argon, nitrogen, or a mixture of argon and nitrogen.
  • the oxidizing atmosphere is advantageously devoid of a doping agent such as phosphine.
  • thermal annealing can be applied during step b) under a neutral atmosphere, for example comprising N2.
  • the first doped semiconductor region 100 preferably has, at the first surface 10 of the substrate 1, a boron concentration greater than 10 19 at./cm 3 , more preferably between 10 19 at./ cm 3 and 3xl0 20 at./cm 3 , in order to form a good quality electrical contact zone.
  • the doped polysilicon layer 4 preferably has a phosphorus or arsenic concentration greater than 10 20 at./cm 3 , more preferably between 2xl0 20 at./cm 3 and 10 21 at./cm 3 , in order to form a good quality electrical contact zone.
  • the boron atoms advantageously have an atomic proportion in the first dielectric layer 2 of between 1% and 10%, preferably between 3% and 8% after step b).
  • the phosphorus or arsenic atoms advantageously have an atomic proportion in the second dielectric layer 5 of between 1% and 10%, preferably between 1% and 5% after step b).
  • the method may include a step c) consisting in bringing the first doped semiconductor region 100 and the doped polysilicon layer 4 into contact with an electrode E.
  • Step c) advantageously comprises a metallization step, preferably carried out by screen printing.
  • Each electrode E is preferably made of silver and / or aluminum.
  • the subject of the invention is also a photo voltaic cell, comprising:
  • a substrate 1 based on crystalline silicon having a first surface 10 and an opposite second surface 11;
  • first doped semiconductor region 100 extending under the first surface 10 of the substrate 1, and comprising boron atoms;
  • a first dielectric layer 2 comprising boron atoms in a residual proportion, and formed on the first surface 10 of the substrate 1;
  • a doped polysilicon layer 4 formed on the tunnel oxide film 3, and comprising phosphorus and / or arsenic atoms;
  • a second dielectric layer 5 comprising phosphorus and / or arsenic atoms in a residual proportion, and formed on the doped polysilicon layer 4.
  • the photovoltaic cell may include an additional tunnel oxide film 3 'formed between the first surface 10 of the substrate 1 and the first dielectric layer 2.
  • the tunnel oxide film 3 and the additional tunnel oxide film 3' are advantageously produced.
  • aluminum oxide and have a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
  • residual proportion is meant that: - the boron atoms have an atomic proportion in the first dielectric layer 2 of between 1% and 10%, preferably between 3% and 8%;
  • the phosphorus or arsenic atoms have an atomic proportion in the second dielectric layer 5 of between 1% and 10%, preferably between 1% and 5%.

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Abstract

Said method comprises the steps of: a) providing a structure comprising: - a crystalline silicon-based substrate (1); - a first dielectric layer (2) which comprises boron atoms and is formed on the first surface (10) of the substrate (1); - a tunnel oxide film (3) formed on the second surface (11) of the substrate; - a polysilicon layer (4) formed on the tunnel oxide film (3); - a second dielectric layer (5) which comprises phosphorus and/or arsenic atoms and is formed on the polysilicon layer (4); b) applying heat treatment to the structure so as to: - diffuse the boron atoms under the first surface (10) of the substrate (1) so as to form a first doped semiconductor region (100); - diffuse the phosphorus and/or arsenic atoms in the polysilicon layer (4) so as to dope the polysilicon layer (4).

Description

PROCEDE DE FABRICATION D’UNE CELLULE PHOTOVOLTAÏQUE Domaine technique PROCESS FOR MANUFACTURING A PHOTOVOLTAIC CELL Technical field
L’invention se rapporte au domaine technique des cellules photovoltaïques. L’invention trouve notamment son application dans la fabrication de cellules photo voltaïques de type PERT (« PassivatedEmiter earTotall -diffused » en langue anglaise). The invention relates to the technical field of photovoltaic cells. The invention finds its application in particular in the manufacture of photo voltaic cells of the PERT ("PassivatedEmiter earTotall -diffused") type.
État de l’art State of the art
Un procédé de fabrication d’une cellule photovoltaïque connu de l’état de la technique, notamment du document FR 3 035 740, comporte les étapes : ao) prévoir une structure comprenant : A method of manufacturing a photovoltaic cell known from the state of the art, in particular from document FR 3 035 740, comprises the steps: ao) providing a structure comprising:
- un substrat à base de silicium cristallin, présentant une première surface et une seconde surface opposée ; a substrate based on crystalline silicon, having a first surface and a second opposite surface;
- une première couche diélectrique, comprenant des atomes de bore, et formée sur la première surface du substrat ; - a first dielectric layer, comprising boron atoms, and formed on the first surface of the substrate;
- une deuxième couche diélectrique, comprenant des atomes de phosphore ou d’arsenic, et formée sur la seconde surface du substrat ; bo) appliquer un traitement thermique à la structure de manière à : - a second dielectric layer, comprising phosphorus or arsenic atoms, and formed on the second surface of the substrate; bo) apply a heat treatment to the structure so as to:
- diffuser les atomes de bore depuis la première couche diélectrique sous la première surface du substrat, de manière à former une première région semi-conductrice dopée destinée à être en contact avec une électrode ; - diffusing the boron atoms from the first dielectric layer under the first surface of the substrate, so as to form a first doped semiconductor region intended to be in contact with an electrode;
- diffuser les atomes de phosphore ou d’arsenic depuis la seconde couche diélectrique sous la seconde surface du substrat, de manière à former une seconde région semi- conductrice dopée destinée à être en contact avec une électrode. Un tel procédé de l’état de la technique permet de limiter le nombre d’étapes à exécuter grâce à la co-diffusion des atomes de bore et de phosphore/arsenic, et à la conservation des première et deuxième couches diélectriques après l’étape bo). A cet égard, l’étape bo) est exécutée sous une atmosphère oxydante afin d’augmenter la passivation de la structure et autoriser la conservation des première et deuxième couches diélectriques. Par « passivation », on entend la neutralisation de défauts électriquement actifs aux première et seconde surfaces du substrat. En effet, le substrat à base de silicium cristallin comporte une densité de défauts (e.g. liaisons pendantes, impuretés, discontinuité du cristal...) pouvant entraîner des pertes non négligeables liées à la recombinaison en surface des porteurs dans le cas d’une application photo voltaïque. Cependant, un tel procédé de l’état de la technique n’est pas entièrement satisfaisant en termes de passivation de la structure. L’homme du métier recherche à améliorer les performances de la cellule photovoltaïque avec des valeurs de tension de circuit ouvert Voc les plus élevées possible. - diffusing the phosphorus or arsenic atoms from the second dielectric layer under the second surface of the substrate, so as to form a second doped semiconductor region intended to be in contact with an electrode. Such a process of the state of the art makes it possible to limit the number of steps to be carried out thanks to the co-diffusion of the boron and phosphorus / arsenic atoms, and to the conservation of the first and second dielectric layers after the step. bo). In this regard, step b) is carried out under an oxidizing atmosphere in order to increase the passivation of the structure and allow the conservation of the first and second dielectric layers. By "passivation" is meant the neutralization of electrically active defects at the first and second surfaces of the substrate. In fact, the substrate based on crystalline silicon has a density of defects (eg pendant bonds, impurities, discontinuity of the crystal, etc.) which can lead to non-negligible losses linked to the surface recombination of the carriers in the case of an application. photovoltaic. However, such a method of the state of the art is not entirely satisfactory in terms of passivation of the structure. Those skilled in the art seek to improve the performance of the photovoltaic cell with the highest possible open circuit voltage values V oc.
Exposé de l’invention Disclosure of the invention
L’invention vise à remédier en tout ou partie aux inconvénients précités. A cet effet, l’invention a pour objet un procédé de fabrication d’une cellule photo voltaïque, comportant les étapes : a) prévoir une structure comprenant : The invention aims to remedy all or part of the aforementioned drawbacks. To this end, the invention relates to a method of manufacturing a photovoltaic cell, comprising the steps: a) providing a structure comprising:
- un substrat à base de silicium cristallin, présentant une première surface et une seconde surface opposée ; a substrate based on crystalline silicon, having a first surface and a second opposite surface;
- une première couche diélectrique, comprenant des atomes de bore, et formée sur la première surface du substrat ; - a first dielectric layer, comprising boron atoms, and formed on the first surface of the substrate;
- un film d’oxyde tunnel, formé sur la seconde surface du substrat ; - a tunnel oxide film, formed on the second surface of the substrate;
- une couche de polysilicium, formée sur le film d’oxyde tunnel ; - a layer of polysilicon, formed on the tunnel oxide film;
- une deuxième couche diélectrique, comprenant des atomes de phosphore et/ou d’arsenic, et formée sur la couche de polysilicium ; b) appliquer un traitement thermique à la structure de manière à : - a second dielectric layer, comprising phosphorus and / or arsenic atoms, and formed on the polysilicon layer; b) apply heat treatment to the structure so as to:
- diffuser les atomes de bore depuis la première couche diélectrique sous la première surface du substrat, de manière à former une première région semi-conductrice dopée destinée à être en contact avec une électrode ; - diffusing the boron atoms from the first dielectric layer under the first surface of the substrate, so as to form a first doped semiconductor region intended to be in contact with an electrode;
- diffuser les atomes de phosphore et/ou d’arsenic depuis la deuxième couche diélectrique dans la couche de polysilicium, de manière à doper la couche de polysilicium, la couche de polysilicium dopée étant destinée à être en contact avec une électrode E. - diffusing the phosphorus and / or arsenic atoms from the second dielectric layer into the polysilicon layer, so as to dope the polysilicon layer, the doped polysilicon layer being intended to be in contact with an electrode E.
Ainsi, un tel procédé selon l’invention permet d’augmenter les valeurs de tension de circuit ouvert Voc par rapport à l’état de la technique grâce à la présence du film d’oxyde tunnel et de la couche de polysilicium qui permettent une excellente passivation de la seconde surface du substrat. Le film d’oxyde tunnel permet de limiter la diffusion des atomes de phosphore et/ou d’arsenic depuis la couche de polysilicium vers la seconde surface du substrat. En d’autres termes, le film d’oxyde tunnel agit comme une barrière de diffusion aux atomes de phosphore/ arsenic vers le substrat. Le film d’oxyde tunnel permet donc de doper suffisamment la couche de polysilicium en phosphore et/ou en arsenic lors de l’étape b) afin d’obtenir un contact électrique, et ce sans nécessiter une augmentation du budget thermique de l’étape b). Une augmentation du budget thermique lors de l’étape b) ne serait en effet pas souhaitable car elle augmenterait également la profondeur de diffusion des atomes de bore sous la première surface du substrat, et dégraderait donc la valeur de tension de circuit ouvert Voc· La prise de contact électrique sur la couche de polysilicium dopée pourra s’effectuer par exemple par sérigraphie. Thus, such a method according to the invention makes it possible to increase the open circuit voltage values V oc with respect to the state of the art thanks to the presence of the tunnel oxide film and of the polysilicon layer which allow a excellent passivation of the second surface of the substrate. The tunnel oxide film makes it possible to limit the diffusion of phosphorus and / or arsenic atoms from the polysilicon layer to the second surface of the substrate. In other words, the tunnel oxide film acts as a diffusion barrier to phosphorus / arsenic atoms towards the substrate. The tunnel oxide film therefore makes it possible to sufficiently dope the polysilicon layer with phosphorus and / or arsenic during step b) in order to obtain an electrical contact, and this without requiring an increase in the thermal budget of step b). An increase in the thermal budget during step b) would in fact not be desirable because it would also increase the depth of diffusion of the boron atoms under the first surface of the substrate, and would therefore degrade the value of the open circuit voltage V oc Electrical contact on the doped polysilicon layer can be carried out, for example, by screen printing.
Par ailleurs, le film d’oxyde tunnel permet de s’affranchir de difficultés liées aux profondeurs de diffusion différentes entre les atomes de bore et les atomes de phosphore/arsenic lors de leur co-diffusion de l’étape b), ces difficultés pouvant avoir lieu dans l’état de la technique. Furthermore, the tunnel oxide film overcomes the difficulties associated with the different diffusion depths between the boron atoms and the phosphorus / arsenic atoms during their co-diffusion in step b), these difficulties being able to take place in the state of the art.
Définitions Definitions
- Par « substrat », on entend le support mécanique, autoporté, destiné à la fabrication d’une cellule photovoltaïque. - By "substrate" is meant the mechanical support, self-supporting, intended for the manufacture of a photovoltaic cell.
- Par « cristallin », on entend la forme multicristalline ou la forme monocristalline du silicium, excluant donc le silicium amorphe. The term “crystalline” is understood to mean the multicrystalline form or the monocrystalline form of silicon, therefore excluding amorphous silicon.
- Par « à base de », on entend que le matériau correspondant est le matériau principal et majoritaire composant le substrat (ou la couche). The term “based on” is understood to mean that the corresponding material is the main and majority material making up the substrate (or the layer).
- Par « diélectrique », on entend que la couche présente une conductivité électrique à 300 K inférieure à 1CT8 S/cm. The term “dielectric” is understood to mean that the layer has an electrical conductivity at 300 K of less than 1CT 8 S / cm.
- Par « film d’oxyde tunnel », on entend un oxyde suffisamment fin pour autoriser la circulation d’un courant électrique en son sein par effet tunnel. - By "tunnel oxide film" is meant an oxide thin enough to allow an electric current to flow within it by tunneling.
Le procédé selon l’invention peut comporter une ou plusieurs des caractéristiques suivantes. The method according to the invention may include one or more of the following characteristics.
Selon une caractéristique de l’invention, l’étape a) est exécutée de sorte que le film d’oxyde tunnel est un oxyde de silicium ou un oxyde d’aluminium. According to a feature of the invention, step a) is performed so that the tunnel oxide film is a silicon oxide or an aluminum oxide.
Par « oxyde de silicium », on entend l’oxyde de silicium de formule S1O2 (dioxyde de silicium) ou ses dérivés SiOx non-stœchiométriques. By “silicon oxide” is meant silicon oxide of formula S1O2 (silicon dioxide) or its non-stoichiometric SiO x derivatives.
Par « oxyde d’aluminium », on entend l’oxyde d’aluminium de formule AI2O3 (alumine) ou ses dérivés A10x non-stœchiométriques. The term “aluminum oxide” is understood to mean aluminum oxide of formula Al2O3 (alumina) or its non-stoichiometric A10 x derivatives.
Ainsi, un avantage procuré par de tels oxydes est leur propriété de barrière de diffusion aux atomes de phosphore/arsenic. Selon une caractéristique de l’invention, l’étape a) est exécutée de sorte que le film d’oxyde tunnel est un oxyde de silicium formé sur la seconde surface du substrat par voie thermique. Thus, an advantage provided by such oxides is their property of diffusion barrier to phosphorus / arsenic atoms. According to one characteristic of the invention, step a) is carried out so that the tunnel oxide film is a silicon oxide formed on the second surface of the substrate by thermal means.
Ainsi, un avantage procuré est d’améliorer la densité de l’oxyde de silicium par rapport à un oxyde de silicium formée par voie chimique, ce qui améliore les propriétés de barrière de diffusion aux atomes de phosphore/ arsenic. Thus, an advantage provided is to improve the density of silicon oxide over chemically formed silicon oxide, which improves the diffusion barrier properties to phosphorus / arsenic atoms.
Selon une caractéristique de l’invention, l’étape a) est exécutée de sorte que le film d’oxyde tunnel est un oxyde d’aluminium formé sur la seconde surface du substrat par un dépôt de couches atomiques. Le dépôt de couches atomiques est classiquement désigné par l’acronyme ALD pourAccording to a feature of the invention, step a) is performed so that the tunnel oxide film is an aluminum oxide formed on the second surface of the substrate by deposition of atomic layers. The deposition of atomic layers is conventionally referred to by the acronym ALD for
« Atomic l iyer Déposition » en langue anglaise. “Atomic l iyer Deposition” in English.
Selon une caractéristique de l’invention, l’étape a) est exécutée de sorte que le film d’oxyde tunnel présente une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. According to one characteristic of the invention, step a) is carried out so that the tunnel oxide film has a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
Selon une caractéristique de l’invention, l’étape a) est exécutée de sorte que : According to a characteristic of the invention, step a) is carried out so that:
- le film d’oxyde tunnel est un oxyde d’aluminium présentant une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm ; - la structure comprend un film additionnel d’oxyde tunnel formé entre la première surface du substrat et la première couche diélectrique, le film additionnel d’oxyde tunnel étant un oxyde d’aluminium présentant une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. - the tunnel oxide film is an aluminum oxide having a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm; the structure comprises an additional tunnel oxide film formed between the first surface of the substrate and the first dielectric layer, the additional tunnel oxide film being an aluminum oxide having a thickness less than or equal to 3 nm, preferably less or equal to 2 nm.
Ainsi, un avantage procuré par l’oxyde d’aluminium, formant le film additionnel d’oxyde tunnel, est de faiblement affecter la diffusion des atomes de bore en son sein, ce qui permet de ne pas dégrader significativement la conductance latérale de la première région semi- conductrice dopée, contrairement à un oxyde de silicium. En effet, un oxyde de silicium agit comme une barrière de diffusion aux atomes de bore. Thus, an advantage provided by the aluminum oxide, forming the additional tunnel oxide film, is to weakly affect the diffusion of boron atoms within it, which makes it possible not to significantly degrade the lateral conductance of the first. doped semiconductor region, unlike silicon oxide. In fact, a silicon oxide acts as a diffusion barrier to the boron atoms.
Par conséquent, l’utilisation d’un oxyde d’aluminium pour le film d’oxyde tunnel et pour le film additionnel d’oxyde tunnel permet de simplifier la mise en œuvre du procédé en autorisant leur formation simultanée de part et d’autre du substrat, ce qui réduit le temps d’opération. Selon une caractéristique de l’invention, l’étape a) est exécutée de sorte que la première couche diélectrique est à base d’un oxynitrure de silicium SiOxNy vérifiant 0£y<x, de préférence hydrogéné. Consequently, the use of an aluminum oxide for the tunnel oxide film and for the additional tunnel oxide film makes it possible to simplify the implementation of the method by allowing their simultaneous formation on either side of the substrate, which reduces operating time. According to one characteristic of the invention, step a) is carried out so that the first dielectric layer is based on a silicon oxynitride SiO x N y verifying 0 £ y <x, preferably hydrogenated.
Une telle première couche diélectrique permet d’obtenir une passivation satisfaisante de la première surface du substrat, plus précisément une passivation de l’interface entre la première surface du substrat et la première couche diélectrique. L’hydrogénation de l’oxynitrure de silicium permet d’améliorer les propriétés de passivation. Lorsque y=0, l’oxynitrure de silicium est un oxyde de silicium. Such a first dielectric layer makes it possible to obtain satisfactory passivation of the first surface of the substrate, more precisely passivation of the interface between the first surface of the substrate and the first dielectric layer. The hydrogenation of silicon oxynitride improves the passivation properties. When y = 0, silicon oxynitride is silicon oxide.
Selon une caractéristique de l’invention, l’étape a) est exécutée de sorte que la deuxième couche diélectrique est à base d’un oxynitrure de silicium SiOxNy vérifiant 0£x<y, de préférence hydrogéné. According to one characteristic of the invention, step a) is carried out so that the second dielectric layer is based on a silicon oxynitride SiO x N y verifying 0 £ x <y, preferably hydrogenated.
Lorsque x=0, l’oxynitrure de silicium est un nitrure de silicium. When x = 0, silicon oxynitride is silicon nitride.
Selon une caractéristique de l’invention, l’étape b) est exécutée en appliquant un recuit thermique à la structure, le recuit thermique présentant : According to a characteristic of the invention, step b) is carried out by applying thermal annealing to the structure, the thermal annealing exhibiting:
- une valeur de température de recuit comprise entre 850°C et 950°C, de préférence comprise entre 900°C et 950°C, - an annealing temperature value between 850 ° C and 950 ° C, preferably between 900 ° C and 950 ° C,
- une valeur de durée de recuit comprise entre 10 minutes et 1 heure, de préférence comprise entre 30 minutes et 1 heure. an annealing time value of between 10 minutes and 1 hour, preferably between 30 minutes and 1 hour.
Par « recuit thermique », on entend un traitement thermique comportant : By “thermal annealing” is meant a heat treatment comprising:
- une phase de montée graduelle en température (rampe de montée) jusqu’à atteindre une température dite température de recuit, - a gradual temperature rise phase (ramp up) until a temperature known as the annealing temperature is reached,
- une phase de maintien (plateau) à la température de recuit, pendant une durée dite durée de recuit, - a maintenance phase (plateau) at the annealing temperature, for a period known as the annealing time,
- une phase de refroidissement. - a cooling phase.
Selon une caractéristique de l’invention, le procédé comporte une étape consistant à former une couche à base d’un oxynitrure de silicium SiOxNy, vérifiant 0£x<y, de préférence hydrogéné, sur la première couche diélectrique après l’étape b). According to one characteristic of the invention, the method comprises a step consisting in forming a layer based on a silicon oxynitride SiO x N y , verifying 0 £ x <y, preferably hydrogenated, on the first dielectric layer after the step b).
Ainsi, un avantage procuré est d’améliorer à la fois la passivation de la première surface du substrat, et de former une couche optique dite antireflet, de par une épaisseur adaptée. Cette étape est préférentiellement exécutée après l’étape b) afin d’enrichir aisément en oxygène la première couche diélectrique lorsque l’étape b) est exécutée sous une atmosphère oxydante. Lorsque x=0, G oxynitrure de silicium est un nitrure de silicium. Selon une caractéristique de l’invention, le procédé comporte une étape consistant à former une couche à base d’un oxynitrure de silicium SiOxNy, vérifiant 0£x<y, de préférence hydrogéné, sur la deuxième couche diélectrique avant l’étape b). Lorsque x=0, l’ oxynitrure de silicium est un nitrure de silicium. Thus, an advantage obtained is to improve both the passivation of the first surface of the substrate, and to form a so-called antireflection optical layer, with a suitable thickness. This step is preferably carried out after step b) in order to easily enrich the first dielectric layer with oxygen when step b) is carried out under an oxidizing atmosphere. When x = 0, G silicon oxynitride is silicon nitride. According to one characteristic of the invention, the method comprises a step consisting in forming a layer based on a silicon oxynitride SiO x N y , verifying 0 £ x <y, preferably hydrogenated, on the second dielectric layer before the step b). When x = 0, the silicon oxynitride is a silicon nitride.
Ainsi, un avantage procuré est d’empêcher une exo-diffusion des atomes de phosphore/ arsenic depuis la deuxième couche diélectrique. Thus, an advantage provided is to prevent exo-diffusion of phosphorus / arsenic atoms from the second dielectric layer.
Selon une caractéristique de l’invention, les première et deuxième couches diélectriques sont conservées après l’étape b). According to a feature of the invention, the first and second dielectric layers are retained after step b).
Ainsi, un avantage procuré est un gain de temps d’opération puisqu’il n’est pas nécessaire de retirer ces couches puis de former des couches de passivation dédiées. Thus, an advantage provided is a saving of operating time since it is not necessary to remove these layers and then to form dedicated passivation layers.
L’invention a également pour objet une cellule photo voltaïque, comportant : - un substrat à base de silicium cristallin, présentant une première surface et une seconde surface opposée ; The subject of the invention is also a photo voltaic cell, comprising: - a substrate based on crystalline silicon, having a first surface and a second opposite surface;
- une première région semi-conductrice dopée, s’étendant sous la première surface du substrat, et comprenant des atomes de bore ; - a first doped semiconductor region, extending below the first surface of the substrate, and comprising boron atoms;
- une première couche diélectrique, comprenant des atomes de bore dans une proportion résiduelle, et formée sur la première surface du substrat ; a first dielectric layer, comprising boron atoms in a residual proportion, and formed on the first surface of the substrate;
- un film d’oxyde tunnel, formé sur la seconde surface du substrat ; - a tunnel oxide film, formed on the second surface of the substrate;
- une couche de polysilicium dopée, formée sur le film d’oxyde tunnel, et comprenant des atomes de phosphore et/ou d’arsenic ; - a doped polysilicon layer, formed on the tunnel oxide film, and comprising phosphorus and / or arsenic atoms;
- une deuxième couche diélectrique, comprenant des atomes de phosphore et/ou d’arsenic dans une proportion résiduelle, et formée sur la couche de polysilicium dopée. - a second dielectric layer, comprising phosphorus and / or arsenic atoms in a residual proportion, and formed on the doped polysilicon layer.
Ainsi, une telle cellule photovoltaïque autorise une augmentation de la valeur de tension de circuit ouvert Voc par rapport à l’état de la technique, grâce à la présence du film d’oxyde tunnel et de la couche de polysilicium qui permettent une excellente passivation de la seconde surface du substrat. Thus, such a photovoltaic cell allows an increase in the value of the open circuit voltage V oc compared to the state of the art, thanks to the presence of the tunnel oxide film and of the polysilicon layer which allow excellent passivation. of the second surface of the substrate.
Selon une caractéristique de l’invention, la cellule photovoltaïque comporte un film additionnel d’oxyde tunnel formé entre la première surface du substrat et la première couche diélectrique. La présence d’un tel film additionnel d’oxyde tunnel permet de faciliter la fabrication de la cellule photovoltaïque en autorisant la formation simultanée du film d’oxyde tunnel et du film additionnel d’oxyde tunnel de part et d’autre du substrat, ce qui réduit le temps d’opération. Selon une caractéristique de l’invention, le film d’oxyde tunnel et le film additionnel d’oxyde tunnel sont réalisés en oxyde d’aluminium et présentent une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. According to one characteristic of the invention, the photovoltaic cell comprises an additional tunnel oxide film formed between the first surface of the substrate and the first dielectric layer. The presence of such an additional tunnel oxide film makes it possible to facilitate the manufacture of the photovoltaic cell by allowing the simultaneous formation of the tunnel oxide film and the additional tunnel oxide film on either side of the substrate, this which reduces operating time. According to one characteristic of the invention, the tunnel oxide film and the additional tunnel oxide film are made of aluminum oxide and have a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
Ainsi, un avantage procuré par l’oxyde d’aluminium, formant le film additionnel d’oxyde tunnel, est de faiblement affecter la diffusion des atomes de bore en son sein, ce qui permet de ne pas dégrader significativement la conductance latérale de la première région semi- conductrice dopée, contrairement à un oxyde de silicium. En effet, un oxyde de silicium agit comme une barrière de diffusion aux atomes de bore. Thus, an advantage provided by the aluminum oxide, forming the additional tunnel oxide film, is to weakly affect the diffusion of boron atoms within it, which makes it possible not to significantly degrade the lateral conductance of the first. doped semiconductor region, unlike silicon oxide. In fact, a silicon oxide acts as a diffusion barrier to the boron atoms.
Brève description des dessins D’autres caractéristiques et avantages apparaîtront dans l’exposé détaillé de différents modes de réalisation de l’invention, l’exposé étant assorti d’exemples et de références aux dessins joints. Brief Description of the Drawings Other features and advantages will become apparent from the detailed disclosure of various embodiments of the invention, the disclosure being accompanied by examples and references to the accompanying drawings.
Figures la à le sont des vues schématiques en coupe illustrant différentes étapes d’un premier mode de mise en œuvre d’un procédé selon l’invention. Figures 2a à 2c sont des vues schématiques en coupe illustrant différentes étapes d’un deuxième mode de mise en œuvre d’un procédé selon l’invention. Figures 1a to 1c are schematic sectional views illustrating different steps of a first embodiment of a method according to the invention. Figures 2a to 2c are schematic sectional views illustrating different steps of a second embodiment of a method according to the invention.
Figures 3a à 3d sont des vues schématiques en coupe illustrant différentes étapes d’un troisième mode de mise en œuvre d’un procédé selon l’invention. Figures 3a to 3d are schematic sectional views illustrating different steps of a third embodiment of a method according to the invention.
Figures 4a à 4d sont des vues schématiques en coupe illustrant différentes étapes d’un quatrième mode de mise en œuvre d’un procédé selon l’invention. Figures 4a to 4d are schematic sectional views illustrating different steps of a fourth embodiment of a method according to the invention.
Il est à noter que les dessins décrits ci-avant sont schématiques et ne sont pas à l’échelle par souci de lisibilité et pour simplifier leur compréhension. Exposé détaillé des modes de réalisation It should be noted that the drawings described above are schematic and are not to scale for the sake of readability and to simplify their understanding. Detailed description of the embodiments
Les éléments identiques ou assurant la même fonction porteront les mêmes références pour les différents modes de réalisation, par souci de simplification. Un objet de l’invention est un procédé de fabrication d’une cellule photovoltaïque, comportant les étapes : a) prévoir une structure comprenant : The elements which are identical or perform the same function will bear the same references for the various embodiments, for the sake of simplicity. An object of the invention is a method of manufacturing a photovoltaic cell, comprising the steps: a) providing a structure comprising:
- un substrat 1 à base de silicium cristallin, présentant une première surface 10 et une seconde surface 11 opposée ; a substrate 1 based on crystalline silicon, having a first surface 10 and an opposite second surface 11;
- une première couche diélectrique 2, comprenant des atomes de bore, et formée sur la première surface 10 du substrat 1 ; a first dielectric layer 2, comprising boron atoms, and formed on the first surface 10 of the substrate 1;
- un film d’oxyde tunnel 3, formé sur la seconde surface 11 du substrat 1 ; - a tunnel oxide film 3, formed on the second surface 11 of the substrate 1;
- une couche de polysilicium 4, formée sur le film d’oxyde tunnel 3 ; - a polysilicon layer 4, formed on the tunnel oxide film 3;
- une deuxième couche diélectrique 5, comprenant des atomes de phosphore et/ou d’arsenic, et formée sur la couche de polysilicium 4 ; b) appliquer un traitement thermique à la structure de manière à : - a second dielectric layer 5, comprising phosphorus and / or arsenic atoms, and formed on the polysilicon layer 4; b) apply heat treatment to the structure so as to:
- diffuser les atomes de bore depuis la première couche diélectrique 2 sous la première surface 10 du substrat 1, de manière à former une première région semi-conductrice dopée 100 destinée à être en contact avec une électrode E ; - diffusing the boron atoms from the first dielectric layer 2 under the first surface 10 of the substrate 1, so as to form a first doped semiconductor region 100 intended to be in contact with an electrode E;
- diffuser les atomes de phosphore et/ou d’arsenic depuis la deuxième couche diélectrique 5 dans la couche de polysilicium 4, de manière à doper la couche de polysilicium 4, la couche de polysilicium 4 dopée étant destinée à être en contact avec une électrode E. - diffusing the phosphorus and / or arsenic atoms from the second dielectric layer 5 into the polysilicon layer 4, so as to dope the polysilicon layer 4, the doped polysilicon layer 4 being intended to be in contact with an electrode E.
L’étape a) est illustrée aux figures la, 2a, 3a et 4a. L’étape b) est illustrée aux figures lb, 2b, 3b et 4b. Step a) is illustrated in Figures la, 2a, 3a and 4a. Step b) is illustrated in Figures lb, 2b, 3b and 4b.
Substrat Substrate
Le substrat 1 de la structure prévue lors de l’étape a) est avantageusement dopé de type n, et la première surface 10 du substrat 1 est destinée à être exposée à un rayonnement lumineux de manière à former une architecture à émetteur standard. La première région semi- conductrice dopée 100 forme l’émetteur. Autrement dit, lorsque la première région semi- conductrice dopée 100 forme un émetteur standard, alors le substrat 1 est dopé de type n. La couche de polysilicium 4 dopée, du même type de dopage que le substrat 1, est de type BSF (« Bach Surface Field » en langue anglaise). The substrate 1 of the structure provided during step a) is advantageously n-type doped, and the first surface 10 of the substrate 1 is intended to be exposed to light radiation so as to form a standard emitter architecture. The first doped semiconductor region 100 forms the emitter. In other words, when the first doped semiconductor region 100 forms a standard emitter, then the substrate 1 is n-type doped. The doped polysilicon layer 4, of the same type of doping as the substrate 1, is of the BSF (“Bach Surface Field”) type.
L’étape a) est avantageusement exécutée de sorte que la première surface 10 du substrat 1 est texturée afin de réduire le coefficient de réflexion et les pertes optiques dans la cellule photo voltaïque. La première surface 10 du substrat 1 comporte préférentiellement des motifs en pyramide inversée agencés pour créer une rugosité de surface. La texturation est préférentiellement exécutée par une attaque chimique à base d’hydroxyde de potassium KOH. A titre d’exemple non limitatif, le substrat 1 peut présenter une épaisseur de l’ordre de 150 pm. Step a) is advantageously carried out so that the first surface 10 of the substrate 1 is textured in order to reduce the reflection coefficient and the optical losses in the photovoltaic cell. The first surface 10 of the substrate 1 preferably comprises inverted pyramid patterns arranged to create a surface roughness. The texturing is preferably carried out by a chemical attack based on potassium hydroxide KOH. By way of non-limiting example, the substrate 1 may have a thickness of the order of 150 μm.
L’étape a) est avantageusement exécutée de sorte que les première et seconde surfaces 10, 11 du substrat 1 sont préalablement nettoyées chimiquement. Step a) is advantageously carried out so that the first and second surfaces 10, 11 of the substrate 1 are chemically cleaned beforehand.
Première couche diélectrique First dielectric layer
L’étape a) est avantageusement exécutée de sorte que la première couche diélectrique 2 est à base d’un oxynitrure de silicium SiOxNy vérifiant 0£y<x, de préférence hydrogéné. La première couche diélectrique 2 présente avantageusement une épaisseur comprise entre 3 nm et 50 nm, de préférence comprise entre 20 nm et 50 nm. Les atomes de bore présentent avantageusement une proportion atomique dans la première couche diélectrique 2 comprise entre 10% et 50%, de préférence comprise entre 10% et 30% avant l’étape b). L’oxynitrure de silicium de la première couche diélectrique 2 vérifie avantageusement 0,2£x£0,5 et 0,05£y£0,15 avant l’étape b). Step a) is advantageously carried out so that the first dielectric layer 2 is based on a silicon oxynitride SiO x N y verifying 0 £ y <x, preferably hydrogenated. The first dielectric layer 2 advantageously has a thickness between 3 nm and 50 nm, preferably between 20 nm and 50 nm. The boron atoms advantageously have an atomic proportion in the first dielectric layer 2 of between 10% and 50%, preferably between 10% and 30% before step b). The silicon oxynitride of the first dielectric layer 2 advantageously satisfies 0.2 £ x £ 0.5 and 0.05 £ y £ 0.15 before step b).
Comme illustré aux figures 3c et 4c, le procédé peut comporter une étape consistant à former une couche 2’ à base d’un oxynitrure de silicium SiOxNy, vérifiant 0£x<y, de préférence hydrogéné, sur la première couche diélectrique 2 après l’étape b). As illustrated in FIGS. 3c and 4c, the method may include a step consisting in forming a layer 2 'based on a silicon oxynitride SiO x N y , verifying 0 £ x <y, preferably hydrogenated, on the first dielectric layer. 2 after step b).
Lorsque la première couche diélectrique 2 et la couche 2’ sont réalisées dans un matériau à base d'un oxynitrure de silicium hydrogéné, ces couches peuvent être formées par un dépôt chimique en phase vapeur (PECVD pour « Plasma-E nhanced Chemical Vapor Déposition » en langue anglaise) à partir de gaz réactifs comportant du silane SiH4 et du protoxyde d'azote N2O ou du NH3. Les atomes de bore sont avantageusement incorporés à l' oxynitrure de silicium hydrogéné par une injection de diborane B2H6 avec les gaz réactifs. When the first dielectric layer 2 and the layer 2 'are made of a material based on a hydrogenated silicon oxynitride, these layers can be formed by chemical vapor deposition (PECVD for "Plasma-E nhanced Chemical Vapor Deposition" in English) from reactive gases comprising silane SiH 4 and nitrous oxide N2O or NH 3 . The boron atoms are advantageously incorporated into the hydrogenated silicon oxynitride by injection of diborane B 2 H 6 with the reactive gases.
La première couche diélectrique 2 est conservée après l’étape b), de même que la couche 2’. The first dielectric layer 2 is kept after step b), as is layer 2 ’.
Film(s) d’oxyde tunnel Tunnel oxide film (s)
L’étape a) est avantageusement exécutée de sorte que le film d’oxyde tunnel 3 est un oxyde de silicium ou un oxyde d’aluminium. L’étape a) est avantageusement exécutée de sorte que l’oxyde de silicium est formé sur la seconde surface 11 du substrat 1 par voie thermique. L’étape a) est avantageusement exécutée de sorte que l’oxyde d’aluminium est formé sur la seconde surface 11 du substrat 1 par un dépôt de couches atomiques (ALD). Step a) is advantageously carried out so that the tunnel oxide film 3 is a silicon oxide or an aluminum oxide. Step a) is advantageously carried out so that the silicon oxide is formed on the second surface 11 of the substrate 1 by thermal means. Step a) is advantageously carried out so that the aluminum oxide is formed on the second surface 11 of the substrate 1 by atomic layer deposition (ALD).
L’étape a) est avantageusement exécutée de sorte que le film d’oxyde tunnel 3 présente une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. Step a) is advantageously carried out so that the tunnel oxide film 3 has a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
Comme illustré aux figures 2a et 4a, l’étape a) est avantageusement exécutée de sorte que : - le film d’oxyde tunnel 3 est un oxyde d’aluminium présentant une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm ; As illustrated in Figures 2a and 4a, step a) is advantageously carried out so that: the tunnel oxide film 3 is an aluminum oxide having a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm;
- la structure comprend un film additionnel 3’ d’oxyde tunnel formé entre la première surface 10 du substrat 1 et la première couche diélectrique 2, le film additionnel 3’ d’oxyde tunnel étant un oxyde d’aluminium présentant une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. - the structure comprises an additional film 3 'of tunnel oxide formed between the first surface 10 of the substrate 1 and the first dielectric layer 2, the additional film 3' of tunnel oxide being an aluminum oxide having a thickness less than or equal at 3 nm, preferably less than or equal to 2 nm.
Couche de polysilicium Polysilicon layer
L’étape a) est avantageusement exécutée de sorte que la couche de polysilicium 4 présente une épaisseur comprise entre 30 nm et 200 nm, de préférence comprise entre 30 nm et 100 nm. Step a) is advantageously carried out so that the polysilicon layer 4 has a thickness between 30 nm and 200 nm, preferably between 30 nm and 100 nm.
L’étape a) peut être exécutée de sorte que la couche de polysilicium 4 est formée sur le film d’oxyde tunnel 3 par un dépôt d’une couche de silicium amorphe (e.g. par LPCVD « Eow Pressure Chemical Vapor Déposition » ou par PECVD «Plasma-E nhanced Chemical Vapor Déposition »), suivi d’un recuit permettant de cristalliser la couche de silicium amorphe. Step a) can be carried out so that the polysilicon layer 4 is formed on the tunnel oxide film 3 by depositing an amorphous silicon layer (eg by LPCVD “Eow Pressure Chemical Vapor Deposition” or by PECVD “Plasma-Enhanced Chemical Vapor Deposition”), followed by annealing to crystallize the amorphous silicon layer.
Deuxième couche diélectrique Second dielectric layer
L’étape a) est avantageusement exécutée de sorte que la deuxième couche diélectrique 5 est à base d’un oxynitrure de silicium SiOxNy vérifiant 0£x<y, de préférence hydrogéné. La deuxième couche diélectrique 5 présente avantageusement une épaisseur comprise entre 10 nm et 50 nm, de préférence comprise entre 10 nm et 30 nm. Les atomes de phosphore ou d'arsenic présentent avantageusement une proportion massique dans la deuxième couche diélectrique 5 supérieure ou égale à 4%, de préférence comprise entre 10% et 30%. L’oxynitrure de silicium de la deuxième couche diélectrique 5 vérifie avantageusement 0£x£0,05 et 0,30£y£0,55 avant et après l’étape b). Step a) is advantageously carried out so that the second dielectric layer 5 is based on a silicon oxynitride SiO x N y verifying 0 £ x <y, preferably hydrogenated. The second dielectric layer 5 advantageously has a thickness between 10 nm and 50 nm, preferably between 10 nm and 30 nm. The phosphorus or arsenic atoms advantageously have a proportion by mass in the second dielectric layer 5 of greater than or equal to 4%, preferably between 10% and 30%. The silicon oxynitride of the second dielectric layer 5 advantageously satisfies 0 £ x £ 0.05 and 0.30 £ y £ 0.55 before and after step b).
Comme illustré aux figures 3a et 4a, le procédé peut comporter une étape consistant à former une couche 5’ à base d’un oxynitrure de silicium SiOxNy, vérifiant 0£x<y, de préférence hydrogéné, sur la deuxième couche diélectrique 5 avant l’étape b), de préférence avec une épaisseur inférieure à 80 nm. As illustrated in FIGS. 3a and 4a, the method may include a step consisting in forming a layer 5 ′ based on a silicon oxynitride SiO x N y , verifying 0 £ x <y, preferably hydrogenated, on the second dielectric layer. 5 before step b), preferably with a thickness of less than 80 nm.
Lorsque la deuxième couche diélectrique 5 et la couche 5’ sont réalisées dans un matériau à base d'un oxynitrure de silicium hydrogéné, ces couches peuvent être formées par un dépôt chimique en phase vapeur (PECVD pour « Plasma-E nhanced Chemical Vapor Déposition » en langue anglaise) à partir de gaz réactifs comportant du silane SiH4 et du NH3. Les atomes de phosphore sont avantageusement incorporés à l' oxynitrure de silicium hydrogéné par une injection de phosphine PH3 avec les gaz réactifs. Les atomes d’arsenic sont avantageusement incorporés à l'oxynitrure de silicium hydrogéné par une injection d’arsine AsH3 avec les gaz réactifs. When the second dielectric layer 5 and the layer 5 'are made of a material based on a hydrogenated silicon oxynitride, these layers can be formed by chemical vapor deposition (PECVD for "Plasma-E nhanced Chemical Vapor Deposition" in English) from reactive gases comprising silane SiH 4 and NH 3 . The phosphorus atoms are advantageously incorporated into the hydrogenated silicon oxynitride by injection of phosphine PH 3 with the reactive gases. The arsenic atoms are advantageously incorporated into the hydrogenated silicon oxynitride by injection of arsine AsH 3 with the reactive gases.
La deuxième couche diélectrique 5 est conservée après l’étape b), de même que la couche 5’. The second dielectric layer 5 is kept after step b), as is the layer 5 ’.
Traitement thermique Heat treatment
L’étape b) est avantageusement exécutée en appliquant un recuit thermique à la structure, le recuit thermique présentant : Step b) is advantageously carried out by applying thermal annealing to the structure, the thermal annealing exhibiting:
- une valeur de température de recuit comprise entre 850°C et 950°C, de préférence comprise entre 900°C et 950°C, - an annealing temperature value between 850 ° C and 950 ° C, preferably between 900 ° C and 950 ° C,
- une valeur de durée de recuit comprise entre 10 minutes et 1 heure, de préférence comprise entre 30 minutes et 1 heure. an annealing time value of between 10 minutes and 1 hour, preferably between 30 minutes and 1 hour.
Le recuit thermique appliqué lors de l'étape b) est un recuit thermique global au sens où il est appliqué à l'ensemble de la structure prévue lors de l'étape a). Il ne s'agit donc pas d'un recuit thermique localisé appliqué sur une partie dudit ensemble, par exemple à l'aide d'un laser. The thermal annealing applied during step b) is an overall thermal annealing in the sense that it is applied to the whole of the structure provided during step a). It is therefore not a localized thermal annealing applied to a part of said assembly, for example using a laser.
L'étape b) est préférentiellement exécutée dans un four. Step b) is preferably carried out in an oven.
Le recuit thermique peut être appliqué lors de l’étape b) sous une atmosphère oxydante. Ainsi, un avantage procuré par l’atmosphère oxydante est d’améliorer la passivation de la première surface du substrat (i.e. l’interface entre la première surface et la première couche diélectrique) en enrichissant en oxygène la première couche diélectrique. L'atmosphère oxydante comporte avantageusement un mélange de dioxygène et d'un gaz neutre choisi parmi l'argon, l'azote, ou un mélange d'argon et d'azote. L'atmosphère oxydante est avantageusement constituée par un mélange de dioxygène et d'un gaz neutre choisi parmi l'argon, l'azote, ou un mélange d'argon et d'azote. L'atmosphère oxydante est avantageusement dépourvue d'agent dopant tel que la phosphine. Selon une alternative, le recuit thermique peut être appliqué lors de l’étape b) sous une atmosphère neutre, comportant par exemple du N2. Thermal annealing can be applied in step b) under an oxidizing atmosphere. Thus, an advantage provided by the oxidizing atmosphere is to improve the passivation of the first surface of the substrate (i.e. the interface between the first surface and the first dielectric layer) by enriching the first dielectric layer with oxygen. The oxidizing atmosphere advantageously comprises a mixture of dioxygen and a neutral gas chosen from argon, nitrogen, or a mixture of argon and nitrogen. The oxidizing atmosphere is advantageously constituted by a mixture of dioxygen and of a neutral gas chosen from argon, nitrogen, or a mixture of argon and nitrogen. The oxidizing atmosphere is advantageously devoid of a doping agent such as phosphine. Alternatively, thermal annealing can be applied during step b) under a neutral atmosphere, for example comprising N2.
Après l'étape b), la première région semi-conductrice dopée 100 présente préférentiellement, à la première surface 10 du substrat 1, une concentration en bore supérieure à 1019 at./cm3, plus préférentiellement comprise entre 1019 at./cm3 et 3xl020 at./cm3, afin de former une zone de contact électrique de bonne qualité. After step b), the first doped semiconductor region 100 preferably has, at the first surface 10 of the substrate 1, a boron concentration greater than 10 19 at./cm 3 , more preferably between 10 19 at./ cm 3 and 3xl0 20 at./cm 3 , in order to form a good quality electrical contact zone.
Après l'étape b), la couche de polysilicium 4 dopée présente préférentiellement une concentration en phosphore ou arsenic supérieure à 1020 at./cm3, plus préférentiellement comprise entre 2xl020 at./cm3 et 1021 at./cm3, afin de former une zone de contact électrique de bonne qualité. After step b), the doped polysilicon layer 4 preferably has a phosphorus or arsenic concentration greater than 10 20 at./cm 3 , more preferably between 2xl0 20 at./cm 3 and 10 21 at./cm 3 , in order to form a good quality electrical contact zone.
Les atomes de bore présentent avantageusement une proportion atomique dans la première couche diélectrique 2 comprise entre 1% et 10%, de préférence comprise entre 3% et 8% après l’étape b). The boron atoms advantageously have an atomic proportion in the first dielectric layer 2 of between 1% and 10%, preferably between 3% and 8% after step b).
Les atomes de phosphore ou d’arsenic présentent avantageusement une proportion atomique dans la deuxième couche diélectrique 5 comprise entre 1% et 10%, de préférence comprise entre 1% et 5% après l’étape b). The phosphorus or arsenic atoms advantageously have an atomic proportion in the second dielectric layer 5 of between 1% and 10%, preferably between 1% and 5% after step b).
Cellule photovoltaïque Photovoltaic cell
Comme illustré aux figures le, 2c, 3d et 4d, le procédé peut comporter une étape c) consistant à mettre en contact la première région semi-conductrice dopée 100 et la couche de polysilicium dopée 4 avec une électrode E. L'étape c) comporte avantageusement une étape de métallisation, de préférence exécutée par sérigraphie. Chaque électrode E est préférentiellement réalisée en argent et/ou aluminium. As illustrated in FIGS. 1c, 2c, 3d and 4d, the method may include a step c) consisting in bringing the first doped semiconductor region 100 and the doped polysilicon layer 4 into contact with an electrode E. Step c) advantageously comprises a metallization step, preferably carried out by screen printing. Each electrode E is preferably made of silver and / or aluminum.
L’invention a également pour objet une cellule photo voltaïque, comportant : The subject of the invention is also a photo voltaic cell, comprising:
- un substrat 1 à base de silicium cristallin, présentant une première surface 10 et une seconde surface 11 opposée ; a substrate 1 based on crystalline silicon, having a first surface 10 and an opposite second surface 11;
- une première région semi-conductrice dopée 100, s’étendant sous la première surface 10 du substrat 1, et comprenant des atomes de bore ; - a first doped semiconductor region 100, extending under the first surface 10 of the substrate 1, and comprising boron atoms;
- une première couche diélectrique 2, comprenant des atomes de bore dans une proportion résiduelle, et formée sur la première surface 10 du substrat 1 ; a first dielectric layer 2, comprising boron atoms in a residual proportion, and formed on the first surface 10 of the substrate 1;
- un film d’oxyde tunnel 3, formé sur la seconde surface 11 du substrat 1 ; - a tunnel oxide film 3, formed on the second surface 11 of the substrate 1;
- une couche de polysilicium 4 dopée, formée sur le film d’oxyde tunnel 3, et comprenant des atomes de phosphore et/ou d’arsenic ; - a doped polysilicon layer 4, formed on the tunnel oxide film 3, and comprising phosphorus and / or arsenic atoms;
- une deuxième couche diélectrique 5, comprenant des atomes de phosphore et/ou d’arsenic dans une proportion résiduelle, et formée sur la couche de polysilicium 4 dopée. - a second dielectric layer 5, comprising phosphorus and / or arsenic atoms in a residual proportion, and formed on the doped polysilicon layer 4.
La cellule photovoltaïque peut comporter un film additionnel 3’ d’oxyde tunnel formé entre la première surface 10 du substrat 1 et la première couche diélectrique 2. Le film d’oxyde tunnel 3 et le film additionnel 3’ d’oxyde tunnel sont avantageusement réalisés en oxyde d’aluminium et présentent une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. The photovoltaic cell may include an additional tunnel oxide film 3 'formed between the first surface 10 of the substrate 1 and the first dielectric layer 2. The tunnel oxide film 3 and the additional tunnel oxide film 3' are advantageously produced. aluminum oxide and have a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
Par « proportion résiduelle », on entend que : - les atomes de bore présentent une proportion atomique dans la première couche diélectrique 2 comprise entre 1% et 10%, de préférence comprise entre 3% et 8% ; By "residual proportion" is meant that: - the boron atoms have an atomic proportion in the first dielectric layer 2 of between 1% and 10%, preferably between 3% and 8%;
- les atomes de phosphore ou d’arsenic présentent une proportion atomique dans la deuxième couche diélectrique 5 comprise entre 1% et 10%, de préférence comprise entre 1% et 5%. - the phosphorus or arsenic atoms have an atomic proportion in the second dielectric layer 5 of between 1% and 10%, preferably between 1% and 5%.
L’invention ne se limite pas aux modes de réalisation exposés. L’homme du métier est mis à même de considérer leurs combinaisons techniquement opérantes, et de leur substituer des équivalents. The invention is not limited to the embodiments disclosed. Those skilled in the art are able to consider their technically operative combinations, and to substitute equivalents for them.

Claims

REVENDICATIONS
1. Procédé de fabrication d’une cellule photo voltaïque, comportant les étapes : a) prévoir une structure comprenant : 1. A method of manufacturing a photo voltaic cell, comprising the steps: a) providing a structure comprising:
- un substrat (1) à base de silicium cristallin, présentant une première surface (10) et une seconde surface (11) opposée ; - a substrate (1) based on crystalline silicon, having a first surface (10) and an opposite second surface (11);
- une première couche diélectrique (2), comprenant des atomes de bore, et formée sur la première surface (10) du substrat (1) ; - a first dielectric layer (2), comprising boron atoms, and formed on the first surface (10) of the substrate (1);
- un film d’oxyde tunnel (3), formé sur la seconde surface (11) du substrat ; - a tunnel oxide film (3), formed on the second surface (11) of the substrate;
- une couche de polysilicium (4), formée sur le film d’oxyde tunnel (3) ; - a polysilicon layer (4), formed on the tunnel oxide film (3);
- une deuxième couche diélectrique (5), comprenant des atomes de phosphore et/ou d’arsenic, et formée sur la couche de polysilicium (4) ; b) appliquer un traitement thermique à la structure de manière à : - a second dielectric layer (5), comprising phosphorus and / or arsenic atoms, and formed on the polysilicon layer (4); b) apply heat treatment to the structure so as to:
- diffuser les atomes de bore depuis la première couche diélectrique (2) sous la première surface (10) du substrat (1), de manière à former une première région semi-conductrice dopée (100) destinée à être en contact avec une électrode (E) ; - diffusing the boron atoms from the first dielectric layer (2) under the first surface (10) of the substrate (1), so as to form a first doped semiconductor region (100) intended to be in contact with an electrode ( E);
- diffuser les atomes de phosphore et/ou d’arsenic depuis la deuxième couche diélectrique (5) dans la couche de polysilicium (4), de manière à doper la couche de polysilicium (4), la couche de polysilicium dopée étant destinée à être en contact avec une électrode (E). - diffusing the phosphorus and / or arsenic atoms from the second dielectric layer (5) in the polysilicon layer (4), so as to dope the polysilicon layer (4), the doped polysilicon layer being intended to be in contact with an electrode (E).
2. Procédé selon la revendication 1, dans lequel l’étape a) est exécutée de sorte que le film d’oxyde tunnel (3) est un oxyde de silicium ou un oxyde d’aluminium. 2. The method of claim 1, wherein step a) is performed such that the tunnel oxide film (3) is silicon oxide or aluminum oxide.
3. Procédé selon la revendication 2, dans lequel l’étape a) est exécutée de sorte que le film d’oxyde tunnel (3) est un oxyde de silicium formé sur la seconde surface (11) du substrat (1) par voie thermique. 3. The method of claim 2, wherein step a) is performed such that the tunnel oxide film (3) is a silicon oxide formed on the second surface (11) of the substrate (1) thermally. .
4. Procédé selon la revendication 2, dans lequel l’étape a) est exécutée de sorte que le film d’oxyde tunnel (3) est un oxyde d’aluminium formé sur la seconde surface (11) du substrat (1) par un dépôt de couches atomiques. The method according to claim 2, wherein step a) is performed such that the tunnel oxide film (3) is an aluminum oxide formed on the second surface (11) of the substrate (1) by a. deposition of atomic layers.
5. Procédé selon l’une des revendications 1 à 4, dans lequel l’étape a) est exécutée de sorte que le film d’oxyde tunnel (3) présente une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. 5. Method according to one of claims 1 to 4, wherein step a) is performed so that the tunnel oxide film (3) has a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
6. Procédé selon l’une des revendications 1 à 5, dans lequel l’étape a) est exécutée de sorte que : 6. Method according to one of claims 1 to 5, wherein step a) is carried out so that:
- le film d’oxyde tunnel (3) est un oxyde d’aluminium présentant une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm ; - the tunnel oxide film (3) is an aluminum oxide having a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm;
- la structure comprend un film additionnel (3’) d’oxyde tunnel formé entre la première surface (10) du substrat (1) et la première couche diélectrique (2), le film additionnel (3’) d’oxyde tunnel étant un oxyde d’aluminium présentant une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. - the structure comprises an additional film (3 ') of tunnel oxide formed between the first surface (10) of the substrate (1) and the first dielectric layer (2), the additional film (3') of tunnel oxide being a aluminum oxide having a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
7. Procédé selon l’une des revendications 1 à 6, dans lequel l’étape a) est exécutée de sorte que la première couche diélectrique (2) est à base d’un oxynitrure de silicium SiOxNy vérifiant 0£y<x, de préférence hydrogéné. 7. Method according to one of claims 1 to 6, wherein step a) is performed so that the first dielectric layer (2) is based on a silicon oxynitride SiO x N y verifying 0 £ y < x, preferably hydrogenated.
8. Procédé selon l’une des revendications 1 à 7, dans lequel l’étape a) est exécutée de sorte que la deuxième couche diélectrique (5) est à base d’un oxynitrure de silicium SiOxNy vérifiant 0£x<y, de préférence hydrogéné. 8. Method according to one of claims 1 to 7, wherein step a) is performed so that the second dielectric layer (5) is based on a silicon oxynitride SiO x N y verifying 0 £ x < y, preferably hydrogenated.
9. Procédé selon l’une des revendications 1 à 8, dans lequel l’étape b) est exécutée en appliquant un recuit thermique à la structure, le recuit thermique présentant : 9. Method according to one of claims 1 to 8, wherein step b) is performed by applying thermal annealing to the structure, the thermal annealing exhibiting:
- une valeur de température de recuit comprise entre 850°C et 950°C, de préférence comprise entre 900°C et 950°C, - an annealing temperature value between 850 ° C and 950 ° C, preferably between 900 ° C and 950 ° C,
- une valeur de durée de recuit comprise entre 10 minutes et 1 heure, de préférence comprise entre 30 minutes et 1 heure. an annealing time value of between 10 minutes and 1 hour, preferably between 30 minutes and 1 hour.
10. Procédé selon l’une des revendications 1 à 9, comportant une étape consistant à former une couche (2’) à base d’un oxynitrure de silicium SiOxNy, vérifiant 0£x<y, de préférence hydrogéné, sur la première couche diélectrique (2) après l’étape b). 10. Method according to one of claims 1 to 9, comprising a step consisting in forming a layer (2 ') based on a silicon oxynitride SiO x N y , verifying 0 £ x <y, preferably hydrogenated, on the first dielectric layer (2) after step b).
11. Procédé selon l’une des revendications 1 à 10, comportant une étape consistant à former une couche (5’) à base d’un oxynitrure de silicium SiOxNy, vérifiant 0£x<y, de préférence hydrogéné, sur la deuxième couche diélectrique (5) avant l’étape b). 11. Method according to one of claims 1 to 10, comprising a step of forming a layer (5 ') based on a silicon oxynitride SiO x N y , verifying 0 £ x <y, preferably hydrogenated, on the second dielectric layer (5) before step b).
12. Procédé selon l’une des revendications 1 à 11, dans lequel les première et deuxième couches diélectriques (2, 5) sont conservées après l’étape b). 12. Method according to one of claims 1 to 11, wherein the first and second dielectric layers (2, 5) are retained after step b).
13. Cellule photovoltaïque, comportant : 13. Photovoltaic cell, comprising:
- un substrat (1) à base de silicium cristallin, présentant une première surface (10) et une seconde surface (11) opposée ; - a substrate (1) based on crystalline silicon, having a first surface (10) and an opposite second surface (11);
- une première région semi-conductrice dopée (100), s’étendant sous la première surface (10) du substrat (10), et comprenant des atomes de bore ; - a first doped semiconductor region (100), extending under the first surface (10) of the substrate (10), and comprising boron atoms;
- une première couche diélectrique (2), comprenant des atomes de bore dans une proportion résiduelle selon une proportion atomique comprise entre 1% et 10%, et formée sur la première surface (10) du substrat (1) ; - a first dielectric layer (2), comprising boron atoms in a residual proportion in an atomic proportion of between 1% and 10%, and formed on the first surface (10) of the substrate (1);
- un film d’oxyde tunnel (3), formé sur la seconde surface (11) du substrat (1) ; - une couche de polysilicium (4) dopée, formée sur le film d’oxyde tunnel (3), et comprenant des atomes de phosphore et/ou d’arsenic ; - a tunnel oxide film (3), formed on the second surface (11) of the substrate (1); - a doped polysilicon layer (4), formed on the tunnel oxide film (3), and comprising phosphorus and / or arsenic atoms;
- une deuxième couche diélectrique (5), comprenant des atomes de phosphore et/ou d’arsenic dans une proportion résiduelle selon une proportion atomique comprise entre 1% et 10%, et formée sur la couche de polysilicium (4) dopée. - a second dielectric layer (5), comprising phosphorus and / or arsenic atoms in a residual proportion in an atomic proportion of between 1% and 10%, and formed on the doped polysilicon layer (4).
14. Cellule photovoltaïque selon la revendication 13, comportant un film additionnel (3’) d’oxyde tunnel formé entre la première surface (10) du substrat (1) et la première couche diélectrique (2). 14. Photovoltaic cell according to claim 13, comprising an additional film (3 ') of tunnel oxide formed between the first surface (10) of the substrate (1) and the first dielectric layer (2).
15. Cellule photovoltaïque selon la revendication 14, dans lequel le film d’oxyde tunnel (3) et le film additionnel (3’) d’oxyde tunnel sont réalisés en oxyde d’aluminium et présentent une épaisseur inférieure ou égale à 3 nm, de préférence inférieure ou égale à 2 nm. 15. Photovoltaic cell according to claim 14, in which the tunnel oxide film (3) and the additional tunnel oxide film (3 ') are made of aluminum oxide and have a thickness less than or equal to 3 nm, preferably less than or equal to 2 nm.
EP20757928.5A 2019-08-29 2020-08-25 Method for manufacturing a photovoltaic cell Pending EP4022688A1 (en)

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