EP2979306A1 - Process for manufacturing a multi-junction structure for a photovoltaic cell - Google Patents

Process for manufacturing a multi-junction structure for a photovoltaic cell

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Publication number
EP2979306A1
EP2979306A1 EP14718665.4A EP14718665A EP2979306A1 EP 2979306 A1 EP2979306 A1 EP 2979306A1 EP 14718665 A EP14718665 A EP 14718665A EP 2979306 A1 EP2979306 A1 EP 2979306A1
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EP
European Patent Office
Prior art keywords
layer
support substrate
junction
seed layer
substrate
Prior art date
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Application number
EP14718665.4A
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German (de)
French (fr)
Inventor
Emmanuelle Lagoutte
Thomas Signamarcheix
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Commissariat a lEnergie Atomique et aux Energies Alternatives CEA
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Publication of EP2979306A1 publication Critical patent/EP2979306A1/en
Withdrawn legal-status Critical Current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
    • H01L31/1892—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates
    • 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 at least one potential-jump barrier or surface barrier
    • 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 at least one potential-jump barrier or surface barrier 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
    • H01L31/0687—Multiple junction or tandem solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—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 at least one potential-jump barrier or surface barrier
    • 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 at least one potential-jump barrier or surface barrier 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
    • H01L31/0693—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 at least one potential-jump barrier or surface barrier 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 the devices including, apart from doping material or other impurities, only AIIIBV compounds, e.g. GaAs or InP 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
    • H01L31/1804—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 System
    • 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
    • H01L31/184—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof the active layers comprising only AIIIBV compounds, e.g. GaAs, InP
    • 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
    • H01L31/1892—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates
    • H01L31/1896—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates for thin-film semiconductors
    • 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
    • H01L21/70—Manufacture or treatment of devices consisting of a plurality of solid state components formed in or on a common substrate or of parts thereof; Manufacture of integrated circuit devices or of parts thereof
    • H01L21/71—Manufacture of specific parts of devices defined in group H01L21/70
    • H01L21/76—Making of isolation regions between components
    • H01L21/762—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers
    • H01L21/7624—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology
    • H01L21/76251—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques
    • H01L21/76254—Dielectric regions, e.g. EPIC dielectric isolation, LOCOS; Trench refilling techniques, SOI technology, use of channel stoppers using semiconductor on insulator [SOI] technology using bonding techniques with separation/delamination along an ion implanted layer, e.g. Smart-cut, Unibond
    • 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
    • Y02E10/544—Solar cells from Group III-V materials
    • 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 present invention relates to a method of manufacturing a multijunction structure for a photovoltaic cell, the multijunction structure comprising at least a first junction and at least a second junction interconnected by a bonding interface. It also relates to a multijunction structure for a photovoltaic cell.
  • multijunctions comprising 4 to 6 junctions each for absorbing a wavelength range of the solar spectrum.
  • these solar cells can be made by making junctions on each other by epitaxy of materials formed of alloys based on, inter alia, In, P, As, and Ga.
  • the exact composition of the alloys forming each of the junctions is extremely important.
  • compositions of materials corresponds to a crystal lattice parameter of the junction.
  • the epitaxial growth junction stack relies on a compromise between the composition of the junctions concerned, and the matching of the mesh parameter between each of these junctions, which limits the possibilities of stacking a large number of junctions from different materials.
  • a composition junction "a” can not necessarily be made on a junction "b” if the mesh parameters of the different materials considered are too far apart and homo-epitaxial growth of very good quality can not be ensured. .
  • a promising alternative to this method of manufacture is to superpose separately produced junctions by implementing direct bonding technology also known as molecular bonding technology.
  • This technology must respect two important criteria: the optical transparency of the assembly of the junctions so that the solar radiation can cross the stack and be collected by each of the junctions superimposed, and electrical conduction between the junctions to allow the collection of the current generated in each of the junctions with a minimum of resistance, and therefore losses.
  • the quality of the bonding interface between two junctions is critical to obtain a direct bonding assembly that is of good quality.
  • the topology of the surfaces to be assembled must in particular have a very high flatness with a long wavelength and a very low roughness with a short wavelength.
  • the more the number of epitaxial layers increase the more the defectivity at the surface increases in terms of constraints (adaptation of the mesh parameters), epitaxial growth defects , roughness etc.
  • more than ten layers of different composition must be made to obtain a final thickness of about one micrometer.
  • this bonding layer does not disturb the proper functioning of the junctions, but it can however degrade the operation of the stack of junctions if it generates a pronounced optical absorption, blocking the transmission of photons in the lower junctions. It is then appropriate for the bonding layer to have as thin a thickness as possible, which is extremely difficult to control during a polishing thinning step, especially when it is desired to obtain a thickness of bonding layer of thickness typically less than 100 nanometers with very good uniformity over the entire substrate.
  • the bonding layer in order to avoid a negative electrical impact, it is necessary for the bonding layer to have a low electrical resistivity.
  • the implementation of direct bonding technology is accompanied by a sealing heat treatment to reduce the resistivity of the contact.
  • heat treatment temperatures of the order of 500 ° C or 600 ° C, which can cause deterioration of the assembled junctions. Indeed, when the junctions are obtained under thermal epitaxial conditions of the order of 500 ° C to 600 ° C, they do not tolerate or little heat such a high budget.
  • One of the aims of the invention is to overcome at least one of these disadvantages.
  • the invention proposes a method for manufacturing a multijunction structure for a photovoltaic cell, the multijunction structure comprising at least a first junction and at least one second junction connected together by a bonding interface, the method comprising the steps of
  • this method makes it possible to form a junction after direct bonding, also known as molecular bonding, so as to overcome the constraints associated with bonding. It is then possible to insert a sealing heat treatment step increasing the electrical conductivity of the bonding interface, before the epitaxy of the junction is made.
  • difference in nature of material is meant in the present application a material whose chemical composition is different. This excludes differences obtained by doping.
  • an AI2O3 sapphire support substrate has a material nature different from that of a second InP or GaAs layer.
  • the respective surface topologies of the first seed layer and the second layer are adapted to allow direct bonding (or molecular bonding) between the two surfaces.
  • the surfaces intended to be brought into contact for direct bonding are planar and have, for example, an arrow of less than 50 ⁇ for a substrate with a diameter of 100 mm. They also have a roughness typically less than 1 nanometer RMS.
  • the first support substrate comprises a first detachment region allowing removal of the first support substrate so as to expose the first seed layer.
  • the method comprises, before step a), a step j) consisting in implanting ionic species in the first donor substrate so as to form a weakening plane, forming the first detachment region and defining the other the first support substrate and the first seed layer, and the step d) of removing the first support substrate is performed by detaching the first support substrate at the weakening plane.
  • a step j) consisting in implanting ionic species in the first donor substrate so as to form a weakening plane, forming the first detachment region and defining the other the first support substrate and the first seed layer
  • the step d) of removing the first support substrate is performed by detaching the first support substrate at the weakening plane.
  • the method comprises, before step a), a step k) consisting of carrying out, for example according to Smart Cut TM technology, the first seed layer on a first support substrate via a layer forming the first detachment region comprising a buried detachment layer.
  • Step d) of removing the first support substrate is furthermore carried out by laser irradiation carried out at the absorption wavelength of the buried detachment layer.
  • the support substrate is advantageously sapphire, the layer forming the first silicon oxide detachment region and the buried silicon nitride detachment layer so that the sapphire is transparent to the wavelength used during laser irradiation.
  • step d) the first support substrate removed in step d) is recycled for reuse according to step j) or k) of the method.
  • the first seed layer comprises an etching stop layer epitaxially grown on the surface of the first donor substrate and the process comprises, before step e) a step I) of thinning at least a portion of the first seed layer until to respectively reach the etch stop layer.
  • the thinning step I) can be carried out by any type of material removal, for example carried out by chemical etching, polishing or plasma etching.
  • the etch stop layer is particularly useful for limiting etching to at least a portion of the first seed layer transferred by removal of the first support substrate by Smart Cut TM.
  • the epitaxy takes place on the remainder of the first seed layer formed by the etch stop layer.
  • the etch stop layer may also make it possible to complete the removal of the first support substrate by plasma etching, polishing and / or chemical etching, or else by laser irradiation while allowing to obtain a thin and uniform layer thickness. on the entire surface.
  • the process comprises, after step c), a step of applying a heat treatment, preferably carried out at a temperature of between 200 ° C. and 800 ° C., and more preferably carried out at a temperature between 300 ° C and 600 ° C, for example with treatment times between a few seconds and several hours, typically 3 hours.
  • a heat treatment makes it possible to reinforce the direct bonding of the first layer with the second layer and to reduce the electrical resistivity of the bonding without damaging the first bond.
  • the method comprises after step e) a step o) comprising the manufacture of the second junction in contact with the second layer.
  • the second donor substrate comprises at least one second junction interposed between the second support substrate and the second layer.
  • the multijunction structure is quickly obtained.
  • This embodiment is particularly advantageous when the second junction is made of a material that is not very sensitive to the heat treatment of sealing the direct bonding or when the reinforcement of the direct bonding does not require the application of a very large thermal budget and also when the second layer is optically highly transparent so that its thickness has little effect on the absorption of the solar spectrum of the multijunction.
  • the process comprises after step e) of epitaxy,
  • the second support substrate comprises a second detachment region allowing the removal of the second support substrate so as to expose the second layer.
  • the second layer comprises an etching stop layer epitaxially grown on the surface of the second donor substrate and prior to epitaxial step ee) of at least one second junction, the method comprises thinning at least a portion of the second layer until reaching the etch stop layer. It is thus possible to thin in a simple and reproducible way the second layer so as to reduce the optical absorption of the layers at the bonding interface.
  • the etch stop layer may also complete the removal of the first support substrate by polishing, plasma etching and / or chemical etching, or by laser irradiation while allowing to obtain a thin and uniform layer thickness on the substrate. entire surface.
  • the epitaxy in this case takes place on the remainder of the second layer formed by the etch stop layer.
  • the process comprises, before step b), a step jj) consisting in implanting ionic species in the second donor substrate so as to form a weakening plane, forming the second detachment region and delimiting on both sides other the second support substrate and the second layer and the dd) removal step of the second support substrate comprises a detachment at the weakening plane delimiting the second layer and the second support substrate.
  • the method comprises, before step b), a step kk) consisting in bonding the second layer to a second support substrate, for example made of sapphire, by means of a layer, for example made of silicon oxide, forming the second detachment region, comprising a buried detachment layer, for example silicon nitride, and the dd) removal step of the second support substrate comprises a laser irradiation step of the buried silicon nitride detachment layer.
  • the second support substrate can be easily removed and recycled for further use.
  • the etch stop layer may also complete the removal of the second support substrate after laser irradiation, as after mechanical, plasma and / or chemical etching of the second support substrate, while allowing to obtain a thin layer thickness and uniform over the entire surface.
  • the first seed layer and the second layer each consist of a monocrystalline semiconductor material selected from Ge and alloys based on at least one of In, P, As and Ga.
  • these layers serve as seed for the epitaxy of at least one of the layers of a junction (they are then called seed layers), they consist of a material having a mesh parameter compatible with the epitaxial growth of the desired material for forming at least one of the layers of the junction.
  • the nature of the material of the first seed layer and the second layer are chosen so that their mesh parameter is close to that of the at least one first junction and the at least one second junction, respectively.
  • the mesh parameter of the first seed layer is close to that of the first junction so as to grow a monocrystalline material of very good quality.
  • the process comprises, before step a) a step i) of epitaxial growth of the first seed layer on the first support substrate and / or of the second layer on the second support substrate.
  • the first support substrate comprises on the surface a monocrystalline material whose mesh parameter is close to that of the first seed layer, it can then have a good quality (few dislocations, rough surface) and be monocrystalline for the epitaxy of the first junction.
  • the invention proposes a method of manufacturing a photovoltaic cell comprising a multijunction structure manufactured as previously described.
  • the invention proposes a method of manufacturing a photovoltaic system comprising a photovoltaic cell manufactured as previously described.
  • the invention proposes a multijunction structure comprising at least one first junction and at least one second junction connected by a bonding interface having a thickness of less than 200 nanometers, an electrical resistivity of less than 50 mohm.cm 2, and a conversion efficiency greater than 40%.
  • FIGS. 6 to 10 illustrate a variant of the embodiment previously illustrated.
  • FIG. 1 1 to 18 illustrate a second embodiment of the method according to the invention.
  • FIG. 1 illustrates a step j) of the process consisting in implanting ionic species, for example with a dose of between 10 E 16 and 10 E 17 at / cm 2 of hydrogen-based ions, in a first donor substrate 1 of Ge, GaAs or InP, so as to form an embrittlement plane 2, forming the first detachment region and delimiting a first support substrate 3 and a first seed layer 4.
  • the implantation conditions allow to create a weakening plane 2 at a shallow depth of up to 1 nm in the donor substrate 1 so that the first seed layer 4 is very thin.
  • the first donor substrate 1 provided for direct bonding according to step a) of the method.
  • FIG. 2 illustrates a step b) of the method of providing a second donor substrate 5 comprising a second support substrate 6, a second layer 7 and a second junction 8 interposed between the second support substrate 6 and the second layer 7.
  • the topologies of the surface of the first seed layer 4 and the second layer 7 have been prepared beforehand so as to have a roughness of less than 1 nanometer RMS and a flatness adapted to direct bonding of the order of 50 ⁇ for a 100 mm substrate between the two layers 4.7.
  • FIG. 3 illustrates step c) of the method consisting in bringing the first seed layer 4 and the second layer 7 into contact to form a bonding interface 9 and obtaining direct bonding.
  • FIG. 4 illustrates the removal of the first support substrate 3 by detachment at the embrittlement plane 2.
  • the first seed layer of small thickness is thus exposed so as to produce an epitaxy of a first junction January 1 on its surface (FIG. ).
  • a multijunction structure 12 is thus obtained by direct bonding comprising at least a first seed layer 4 also serving as a thin bonding.
  • a heat sealing treatment of the direct bonding at 300 ° C. for a typical duration ranging from a few seconds to 120 min for example is applied to the structure before the epitaxy is made so as to reduce the electrical resistivity. (typically less than 50 mohm.cm 2 of the contact obtained without damaging the second junction 8.
  • step d) of removing the first support substrate 3 is carried out by applying a heat treatment typically at a temperature of 100-350 ° C and for a duration of between 30 min and 120 min allowing both the development of the cavities at the weakening plane leading to the detachment of the first support substrate 3 and also the strengthening of the seal decreasing the electrical resistivity of the bonding.
  • step d) of removing the first support substrate 3 is obtained by applying a mechanical stress at the level of the weakening plane 2 so as not to damage the second junction 8.
  • a heat treatment can be applied in addition to the mechanical stress to obtain the detachment of the first support substrate 3, this heat treatment then participates in the sealing favoring the reduction of the resistivity of the bonding interface 9.
  • Figures 6 to 10 illustrate a manufacturing method which differs from that illustrated in Figures 1 to 5 in that the first seed layer 4 comprises an etching stop layer 13 at the surface of the first donor substrate 1 ( Figure 6).
  • This etching stop layer 13 is formed beforehand by epitaxialization of a material having a reactivity different from the other part of the first seed layer 4 facing etching (chemical, mechanical or plasma).
  • This etch stop layer 13 obtained by epitaxy is monocrystalline has a small uniform thickness and can be used as seed for the epitaxy of the first junction 11.
  • the first donor substrate 1 is a solid InP substrate comprising at the surface an etching stop layer 13 of InGaAs at the mesh parameter adapted to the subsequent growth of at least one junction.
  • Ion implantation based on hydrogen, helium or other gaseous species forms a weakening plane 2 in the InP substrate 1 which delimits the first InP support substrate 3 and a first InP seed layer 4 comprising at the surface of the etching stop layer 13 of InGaAs.
  • After the detachment of the first support substrate 3 and at least a part of the first seed layer 4 is removed for example by etching, polishing or plasma, until reaching the etching stop layer 13.
  • an epitaxy of a first InGaAs junction 1 1 is followed by the epitaxy of an additional InGaAsP junction to obtain a multi-junction structure 12.
  • FIGS 12 to 18 illustrate an alternative embodiment of the method according to the invention.
  • FIG. 11 illustrates a first donor substrate 1 comprising a first GaAs seed layer 4 bonded to a first support substrate 3 made of sapphire material (step k) via a silicon oxide layer 14 forming the first detachment region, comprising a silicon nitride layer (not shown).
  • This prior gluing step may have been performed by Smart Cut TM technology to obtain a first seed layer 4 with a controlled thickness of about 50 nanometers.
  • FIG. 12 illustrates a second donor substrate 5 comprising a second seed layer 7 made of InP having a thickness of approximately 50 nanometers bonded to a second support substrate 6, for example made of sapphire material, by means of bonding layers ( silicon oxide, silicon nitride, etc.) 14 forming the second region of detachment comprising at least one buried layer of detachment of silicon nitride (not shown) (step kk).
  • bonding layers silicon oxide, silicon nitride, etc.
  • FIG. 13 illustrates the bringing into contact of the first seed layer 4 and of the second layer 7, the surfaces of which have been prepared beforehand in order to obtain surface topologies suitable for direct bonding (step c). Then a heat sealing treatment of the direct bonding is applied at 600 ° C for a few seconds to 2 hours to improve the electrical conductivity of the bonding interface 9 to less than 50 mohm.cm 2 .
  • Figure 14 illustrates step d) of removing the first sapphire support substrate 3 by laser irradiation therethrough at the absorption wavelength of the silicon nitride. This absorption generates the degradation of the silicon nitride layer, which allows the detachment of the support substrate 3. It can advantageously be recycled for a new use in a subsequent process.
  • FIG. 15 illustrates the step e) of producing an epitaxy of at least a first junction 1 1 made of AIGaAs or GaAs material on the first exposed GaAs seed layer 4 after cleaning the residues of the silicon oxide layer 14 .
  • the first junction 1 1 is secured to a host substrate 15 such as a semiconductor substrate (Si, Ge, etc.), metal (Mo, Cu, etc.) or insulator (glass, Sapphire, etc.) (FIG. 16 step m) so as to be able to remove the second support substrate 6 (step dd).
  • a host substrate 15 such as a semiconductor substrate (Si, Ge, etc.), metal (Mo, Cu, etc.) or insulator (glass, Sapphire, etc.)
  • This shrinkage is in particular carried out by laser irradiation as previously described (FIG. 17).
  • an epitaxy of at least one second junction 8 is produced so as to obtain a multi-function structure 12 having a thickness at the bonding interface 9 less than 200 nanometers and an electrical resistivity lower than 50 mohm.cm 2 (step ee).
  • the second donor substrate 5 comprises two junctions 8.8 'interposed between the second support substrate 6 and the second layer 7.
  • Step d) of the process comprises the epitaxy of two junctions 11, 11 'or even an epitx of three junctions.
  • the second donor substrate 5 comprising a second junction 8 is previously bonded with a second second donor substrate 5 comprising another junction 8 '.
  • step c) of the process three junctions 11, 11 'and 11''are epitaxially grown on the first seed layer 4 according to step d) of the method.
  • the present invention thus makes it possible to envisage all the possible combinations of bonding of several junctions and of epitaxies of several junctions making it possible to obtain multi-function structures comprising 4, 5 or even 6 junctions having weakly optically absorbing bonding interfaces 9 and presenting a very good electrical conductivity.
  • the present invention proposes the manufacture of a multijunction structure 12 comprising at least a first and at least a second junction 8.1 1 connected by a bonding interface 9 simple to implement, preserving the integrity of the layers of junctions 8.1 1 and which provides a bonding interface 9 weakly optically absorbing and very good electrical conductivity.

Abstract

Process for manufacturing a multi-junction structure for a photovoltaic cell. The process comprises steps consisting in: a) providing a first donor substrate (1) comprising a first carrier substrate (3) and a first seed layer (4) comprising a first material; b) providing a second donor substrate (5) comprising a second carrier substrate (6) and a second layer (7) comprising a second material different from the first material; c) bringing the first seed layer (4) and the second layer (7) into contact so as to obtain a direct bond between the first seed layer (4) and the second layer (7) with a view to forming the bonding interface (9); d) removing the first carrier substrate (3) so as to expose the first seed layer (4); and e) epitaxially growing at least one first junction (11) on the first seed layer (4).

Description

Procédé de fabrication d'une structure à multijonctions pour cellule photovoltaïque  Method of manufacturing a multijunction structure for a photovoltaic cell
La présente invention concerne un procédé de fabrication d'une structure à multijonctions pour cellule photovoltaïque, la structure à multijonctions comprenant au moins une première jonction et au moins une deuxième jonction reliées entre elles par une interface de collage. Elle concerne également une structure à multijonctions pour cellule photovoltaïque. The present invention relates to a method of manufacturing a multijunction structure for a photovoltaic cell, the multijunction structure comprising at least a first junction and at least a second junction interconnected by a bonding interface. It also relates to a multijunction structure for a photovoltaic cell.
Afin d'améliorer la rentabilité de l'utilisation de cellules solaires, il est intéressant d'accroître leur rendement de conversion. Dans le domaine du photovoltaïque à concentration, l'amélioration de ce rendement repose sur un empilement astucieux de jonctions permettant d'optimiser l'absorption du spectre solaire. A cet effet, il est nécessaire de fabriquer des cellules solaires dites « multijonctions » comprenant 4 à 6 jonctions permettant chacune d'absorber une plage de longueur d'onde du spectre solaire. A ce jour, ces cellules solaires peuvent être réalisées par fabrication de jonctions les unes sur les autres par épitaxie de matériaux formés d'alliages à base, entre autre, d'In, P, As, et Ga. Pour pouvoir collecter le spectre solaire dans une certaine gamme spectrale, l'exacte composition des alliages formant chacune des jonctions est extrêmement importante. A chacune de ces compositions de matériaux correspond alors un paramètre de maille cristalline de la jonction. De fait, l'empilement de jonction par croissance épitaxiale repose sur un compromis entre la composition des jonctions visées, et l'accordance du paramètre de maille entre chacune de ces jonctions ce qui limite les possibilités de fabrication d'empilement d'un grand nombre de jonctions à partir de différents matériaux. Ainsi, une jonction de composition « a » ne peut pas forcément être réalisée sur une jonction « b » si les paramètres de maille des différents matériaux considérés sont trop éloignés et qu'une croissance par homo-épitaxie de très bonne qualité ne peut être assurée.  In order to improve the profitability of the use of solar cells, it is interesting to increase their conversion efficiency. In the field of concentrated photovoltaics, the improvement of this performance is based on a clever stack of junctions to optimize the absorption of the solar spectrum. For this purpose, it is necessary to manufacture solar cells called "multijunctions" comprising 4 to 6 junctions each for absorbing a wavelength range of the solar spectrum. To date, these solar cells can be made by making junctions on each other by epitaxy of materials formed of alloys based on, inter alia, In, P, As, and Ga. In order to be able to collect the solar spectrum in a certain spectral range, the exact composition of the alloys forming each of the junctions is extremely important. Each of these compositions of materials then corresponds to a crystal lattice parameter of the junction. In fact, the epitaxial growth junction stack relies on a compromise between the composition of the junctions concerned, and the matching of the mesh parameter between each of these junctions, which limits the possibilities of stacking a large number of junctions from different materials. Thus, a composition junction "a" can not necessarily be made on a junction "b" if the mesh parameters of the different materials considered are too far apart and homo-epitaxial growth of very good quality can not be ensured. .
Une alternative prometteuse à cette méthode de fabrication consiste à superposer des jonctions produites séparément en mettant en œuvre la technologie de collage direct également connue sous le nom de technologie de collage par adhésion moléculaire.  A promising alternative to this method of manufacture is to superpose separately produced junctions by implementing direct bonding technology also known as molecular bonding technology.
Cette technologie doit respecter deux critères importants : la transparence optique de l'assemblage des jonctions afin que le rayonnement solaire puisse traverser l'empilement et être collecté par chacune des jonctions superposées, et la conduction électrique entre les jonctions afin de permettre la collection du courant généré dans chacune des jonctions avec un minimum de résistance, et donc de pertes. This technology must respect two important criteria: the optical transparency of the assembly of the junctions so that the solar radiation can cross the stack and be collected by each of the junctions superimposed, and electrical conduction between the junctions to allow the collection of the current generated in each of the junctions with a minimum of resistance, and therefore losses.
Ainsi, la qualité de l'interface de collage entre deux jonctions est critique pour obtenir un assemblage par collage direct qui soit de bonne qualité. A cet effet, la topologie des surfaces à assembler doit notamment présenter une très grande planéité à grande longueur d'onde et une très faible rugosité à faible longueur d'onde. Or, lors de l'épitaxie de jonctions, il est connu que plus le nombre de couches épitaxiées augmentent, plus la défectivité au niveau de la surface augmente en termes de contraintes (adaptation des paramètres de maille), de défauts de croissances d'épitaxies, de rugosité etc. Dans le cas de la croissance de jonctions, plus d'une dizaine de couches de composition différentes doivent être réalisées pour obtenir une épaisseur finale de l'ordre du micromètre.  Thus, the quality of the bonding interface between two junctions is critical to obtain a direct bonding assembly that is of good quality. For this purpose, the topology of the surfaces to be assembled must in particular have a very high flatness with a long wavelength and a very low roughness with a short wavelength. However, during the epitaxial junctions, it is known that the more the number of epitaxial layers increase, the more the defectivity at the surface increases in terms of constraints (adaptation of the mesh parameters), epitaxial growth defects , roughness etc. In the case of the growth of junctions, more than ten layers of different composition must be made to obtain a final thickness of about one micrometer.
II convient donc de traiter la surface en vue de son aplanissement par exemple par une étape de polissage mécano-chimique pour réduire ces défauts et atteindre les pré-requis (rugosité, planéité) du collage direct. Cette étape de préparation génère alors un enlèvement de matière conséquent qui ne peut être réalisé directement sur la jonction solaire car l'épaisseur des diverses couches dites de jonctions est critique pour son fonctionnement. Une solution possible consiste alors à recouvrir cette jonction par une couche de collage d'un matériau n'impactant pas le fonctionnement de la jonction, pouvant être travaillée par polissage mécano-chimique sans craindre de perdre une quantité de matière trop importante.  It is therefore appropriate to treat the surface with a view to its flattening, for example by a chemical-mechanical polishing step to reduce these defects and to meet the prerequisites (roughness, flatness) of the direct bonding. This preparation step then generates a consequent removal of material which can not be carried out directly on the solar junction because the thickness of the various so-called junction layers is critical for its operation. A possible solution is then to cover this junction by a bonding layer of a material that does not affect the operation of the junction, which can be worked by chemical mechanical polishing without fear of losing too much material.
La présence de cette couche de collage ne perturbe pas le fonctionnement propre des jonctions, mais elle peut toutefois dégrader le fonctionnement de l'empilement des jonctions si celle-ci génère une absorption optique prononcée, bloquant alors la transmission des photons dans les jonctions inférieures. Il convient alors que la couche de collage présente une épaisseur la plus fine possible, ce qui est extrêmement difficile à contrôler lors d'une étape d'amincissement par polissage notamment lorsque l'on souhaite obtenir une épaisseur de couche de collage d'épaisseur typiquement inférieure à 100 nanomètres présentant une très bonne uniformité sur tout le substrat.  The presence of this bonding layer does not disturb the proper functioning of the junctions, but it can however degrade the operation of the stack of junctions if it generates a pronounced optical absorption, blocking the transmission of photons in the lower junctions. It is then appropriate for the bonding layer to have as thin a thickness as possible, which is extremely difficult to control during a polishing thinning step, especially when it is desired to obtain a thickness of bonding layer of thickness typically less than 100 nanometers with very good uniformity over the entire substrate.
Par ailleurs, afin d'éviter un impact électrique négatif, il est nécessaire que la couche assurant le collage présente une faible résistivité électrique. A cet effet, la mise en œuvre de la technologie de collage direct est accompagnée d'un traitement thermique de scellement pour diminuer la résistivité du contact. Dans le cas de matériaux comme ΙηΡ et le GaAs, il convient typiquement d'appliquer des températures de traitement thermique de l'ordre de 500°C ou 600°C, ce qui peut engendrer une détérioration des jonctions assemblées. En effet, lorsque les jonctions sont obtenues dans des conditions thermiques d'épitaxie de l'ordre de 500°C à 600°C, elles ne tolèrent pas ou peu un budget thermique aussi élevé. Moreover, in order to avoid a negative electrical impact, it is necessary for the bonding layer to have a low electrical resistivity. For this purpose, the implementation of direct bonding technology is accompanied by a sealing heat treatment to reduce the resistivity of the contact. In the case of materials such as ΙηΡ and GaAs, it is typically necessary to apply heat treatment temperatures of the order of 500 ° C or 600 ° C, which can cause deterioration of the assembled junctions. Indeed, when the junctions are obtained under thermal epitaxial conditions of the order of 500 ° C to 600 ° C, they do not tolerate or little heat such a high budget.
Un des buts de l'invention consiste à pallier l'un au moins de ces inconvénients.  One of the aims of the invention is to overcome at least one of these disadvantages.
A cet effet, l'invention propose un procédé de fabrication d'une structure à multijonctions pour cellule photovoltaïque, la structure à multijonctions comprenant au moins une première jonction et au moins une deuxième jonction reliées entre elles par une interface de collage, le procédé comprenant les étapes consistant à  For this purpose, the invention proposes a method for manufacturing a multijunction structure for a photovoltaic cell, the multijunction structure comprising at least a first junction and at least one second junction connected together by a bonding interface, the method comprising the steps of
- a) Fournir un premier substrat donneur comprenant un premier substrat support et une première couche germe comportant un premier matériau  a) Providing a first donor substrate comprising a first support substrate and a first seed layer comprising a first material
- b) Fournir un deuxième substrat donneur comprenant un deuxième substrat support et une deuxième couche comportant un deuxième matériau différent du premier matériau, la nature du deuxième matériau étant différente de celle du matériau constituant le deuxième substrat support,  b) providing a second donor substrate comprising a second support substrate and a second layer comprising a second material different from the first material, the nature of the second material being different from that of the material constituting the second support substrate,
- c) Mettre en contact la première couche germe et la deuxième couche de sorte à obtenir un collage direct entre la première couche germe et la deuxième couche en vue de constituer l'interface de collage,  c) bringing the first seed layer and the second layer into contact so as to obtain a direct bonding between the first seed layer and the second layer in order to constitute the bonding interface,
- d) Retirer le premier substrat support de sorte à exposer la première couche germe, et  d) removing the first support substrate so as to expose the first seed layer, and
- e) Réaliser une épitaxie d'au moins une première jonction sur la première couche germe.  e) Producing an epitaxy of at least a first junction on the first seed layer.
Ainsi, ce procédé permet de réaliser une jonction après le collage direct également connu sous le nom de collage par adhérence moléculaire, de sorte de s'affranchir des contraintes liés au collage. Il est alors possible d'intercaler une étape de traitement thermique de scellement augmentant la conductivité électrique de l'interface de collage, avant la réalisation de l'épitaxie de la jonction. Par différence de nature de matériau, on entend dans la présente demande un matériau dont la composition chimique est différente. Ceci exclue des différences obtenues par dopage. Par exemple, un substrat support de saphir AI2O3 présente une nature de matériau différente de celle d'une deuxième couche en InP ou en GaAs. Thus, this method makes it possible to form a junction after direct bonding, also known as molecular bonding, so as to overcome the constraints associated with bonding. It is then possible to insert a sealing heat treatment step increasing the electrical conductivity of the bonding interface, before the epitaxy of the junction is made. By difference in nature of material, is meant in the present application a material whose chemical composition is different. This excludes differences obtained by doping. For example, an AI2O3 sapphire support substrate has a material nature different from that of a second InP or GaAs layer.
En particulier, les topologies de surface respectives de la première couche de germe et de la seconde couche sont adaptées pour permettre un collage direct (ou collage par adhésion moléculaire) entre les deux surfaces. Plus particulièrement dans le présent document, les surfaces destinées à être mises en contact pour assurer le collage direct sont planes et présentent par exemple une flèche inférieure à 50 μιτι pour un substrat de diamètre 100 mm. Elles présentent de plus une rugosité typiquement inférieure à 1 nanomètre RMS.  In particular, the respective surface topologies of the first seed layer and the second layer are adapted to allow direct bonding (or molecular bonding) between the two surfaces. More particularly in the present document, the surfaces intended to be brought into contact for direct bonding are planar and have, for example, an arrow of less than 50 μιτι for a substrate with a diameter of 100 mm. They also have a roughness typically less than 1 nanometer RMS.
Selon une possibilité, le premier substrat support comprend une première région de détachement permettant le retrait du premier substrat support de sorte à exposer la première couche germe.  According to one possibility, the first support substrate comprises a first detachment region allowing removal of the first support substrate so as to expose the first seed layer.
Selon une disposition particulière, le procédé comprend avant l'étape a) une étape j) consistant à implanter des espèces ioniques dans le premier substrat donneur de sorte à former un plan de fragilisation, formant la première région de détachement et délimitant de part et d'autre le premier substrat support et la première couche germe, et l'étape d) de retrait du premier substrat support est réalisée par détachement du premier substrat support au niveau du plan de fragilisation. L'utilisation de la technologie Smart Cut™ pour le retrait du substrat support rend ainsi possible l'obtention d'une première couche germe d'une épaisseur uniforme très fine (d'une finesse allant jusqu'à 1 nanomètre) engendrant une faible absorption optique. De plus, la première couche germe obtenue par cette technique présente une bonne planéité et une faible rugosité.  According to one particular arrangement, the method comprises, before step a), a step j) consisting in implanting ionic species in the first donor substrate so as to form a weakening plane, forming the first detachment region and defining the other the first support substrate and the first seed layer, and the step d) of removing the first support substrate is performed by detaching the first support substrate at the weakening plane. The use of Smart Cut ™ technology for the removal of the support substrate thus makes it possible to obtain a first seed layer with a very fine uniform thickness (with a fineness of up to 1 nanometer) giving low absorption optical. In addition, the first seed layer obtained by this technique has good flatness and low roughness.
Selon une variante de réalisation, le procédé comprend avant l'étape a) une étape k) consistant à reporter, par exemple selon la technologie Smart Cut™, la première couche germe sur un premier substrat support par l'intermédiaire d'une couche formant la première région de détachement comprenant une couche enterrée de détachement. L'étape d) de retrait du premier substrat support est de plus réalisée par irradiation laser effectuée à la longueur d'onde d'absorption de la couche enterrée de détachement. Dans cette variante, le substrat support est avantageusement en saphir, la couche formant la première région de détachement en oxyde de silicium et la couche enterrée de détachement de nitrure de silicium de sorte que le saphir est transparent à la longueur d'onde utilisée lors de l'irradiation laser. According to an alternative embodiment, the method comprises, before step a), a step k) consisting of carrying out, for example according to Smart Cut ™ technology, the first seed layer on a first support substrate via a layer forming the first detachment region comprising a buried detachment layer. Step d) of removing the first support substrate is furthermore carried out by laser irradiation carried out at the absorption wavelength of the buried detachment layer. In this variant, the support substrate is advantageously sapphire, the layer forming the first silicon oxide detachment region and the buried silicon nitride detachment layer so that the sapphire is transparent to the wavelength used during laser irradiation.
Il est ainsi facile d'obtenir une première couche germe d'une épaisseur uniforme et facile à contrôler du fait que la gravure du premier substrat support n'est plus indispensable selon ce procédé.  It is thus easy to obtain a first seed layer of a uniform thickness that is easy to control because the etching of the first support substrate is no longer indispensable according to this method.
En parallèle, le premier substrat support retiré à l'étape d) est recyclé pour une réutilisation selon l'étape j) ou k) du procédé.  In parallel, the first support substrate removed in step d) is recycled for reuse according to step j) or k) of the method.
Avantageusement, la première couche germe comprend une couche d'arrêt de gravure épitaxiée en surface du premier substrat donneur et le procédé comprend avant l'étape e) une étape I) d'amincissement d'au moins une partie de la première couche germe jusqu'à atteindre respectivement la couche d'arrêt de gravure. Ainsi, il est possible d'amincir encore la première couche germe de façon contrôlée. L'étape I) d'amincissement peut être effectuée par tout type de retrait de matière, par exemple réalisé par gravure chimique, polissage ou gravure au plasma. La couche d'arrêt de gravure est particulièrement utile pour limiter la gravure à au moins une partie de la première couche germe transférée par retrait du premier substrat support par Smart Cut™. Il est ainsi possible de facilement compléter l'amincissement de la première couche germe si nécessaire ou de retirer la zone pouvant être endommagée par l'implantation ionique au niveau du plan de fragilisation. Il est entendu que dans ce cas, l'épitaxie a lieu sur le restant de la première couche germe formée par la couche d'arrêt de gravure.  Advantageously, the first seed layer comprises an etching stop layer epitaxially grown on the surface of the first donor substrate and the process comprises, before step e) a step I) of thinning at least a portion of the first seed layer until to respectively reach the etch stop layer. Thus, it is possible to further thin the first seed layer in a controlled manner. The thinning step I) can be carried out by any type of material removal, for example carried out by chemical etching, polishing or plasma etching. The etch stop layer is particularly useful for limiting etching to at least a portion of the first seed layer transferred by removal of the first support substrate by Smart Cut ™. It is thus possible to easily complete the thinning of the first seed layer if necessary or to remove the zone that may be damaged by the ion implantation at the weakening plane. It is understood that in this case, the epitaxy takes place on the remainder of the first seed layer formed by the etch stop layer.
La couche d'arrêt de gravure peut également permettre de compléter le retrait du premier substrat support par gravure au plasma, polissage et/ou gravure chimique, ou bien par irradiation laser tout en permettant l'obtention d'une épaisseur de couche fine et uniforme sur l'ensemble de la surface.  The etch stop layer may also make it possible to complete the removal of the first support substrate by plasma etching, polishing and / or chemical etching, or else by laser irradiation while allowing to obtain a thin and uniform layer thickness. on the entire surface.
Par ailleurs, la couche d'arrêt de gravure étant très fine, typiquement d'épaisseur inférieure à 200nm, celle-ci présente la même topologie de surface que celle sur laquelle elle a été épitaxiée, sa présence n'engendre donc pas d'étape de préparation de surface supplémentaire pour le collage direct. Selon une possibilité, le procédé comprend après l'étape c) une étape d'application d'un traitement thermique, de préférence réalisé à une température comprise entre 200°C et 800°C, et de préférence encore réalisé à une température comprise entre 300°C et 600°C, par exemple avec des durées de traitement comprises entre quelques secondes et plusieurs heures, typiquement 3 heures. Ce traitement thermique permet de renforcer le collage direct de la première couche avec la deuxième couche et de diminuer la résistivité électrique du collage sans détériorer la première jonction. Furthermore, since the etch stop layer is very thin, typically less than 200 nm thick, it has the same surface topology as that on which it was epitaxially grown, so its presence does not generate a step. extra surface preparation for direct bonding. According to one possibility, the process comprises, after step c), a step of applying a heat treatment, preferably carried out at a temperature of between 200 ° C. and 800 ° C., and more preferably carried out at a temperature between 300 ° C and 600 ° C, for example with treatment times between a few seconds and several hours, typically 3 hours. This heat treatment makes it possible to reinforce the direct bonding of the first layer with the second layer and to reduce the electrical resistivity of the bonding without damaging the first bond.
Selon une possibilité, le procédé comprend après l'étape e) une étape o) comprenant la fabrication de la deuxième jonction au contact de la deuxième couche.  According to one possibility, the method comprises after step e) a step o) comprising the manufacture of the second junction in contact with the second layer.
Selon un mode de réalisation, le deuxième substrat donneur comprend au moins une deuxième jonction intercalée entre le deuxième substrat support et la deuxième couche. Ainsi, la structure à multijonctions est rapidement obtenue. Ce mode de réalisation est notamment intéressant lorsque la deuxième jonction est réalisée dans un matériau peu sensible au traitement thermique de scellement du collage direct ou lorsque le renforcement du collage direct ne nécessite pas l'application d'un budget thermique très important et également lorsque la deuxième couche est optiquement fortement transparente de sorte que son épaisseur a peu d'incidence sur l'absorption du spectre solaire de la multijonction.  According to one embodiment, the second donor substrate comprises at least one second junction interposed between the second support substrate and the second layer. Thus, the multijunction structure is quickly obtained. This embodiment is particularly advantageous when the second junction is made of a material that is not very sensitive to the heat treatment of sealing the direct bonding or when the reinforcement of the direct bonding does not require the application of a very large thermal budget and also when the second layer is optically highly transparent so that its thickness has little effect on the absorption of the solar spectrum of the multijunction.
Selon un autre mode de réalisation, le procédé comprend après l'étape e) d'épitaxie,  According to another embodiment, the process comprises after step e) of epitaxy,
- une étape de collage m) d'au moins la première jonction à un substrat hôte,  a step of bonding m) of at least the first junction to a host substrate,
- une étape de retrait dd) du deuxième substrat support de sorte à exposer la deuxième couche, et  a step of removing dd) from the second support substrate so as to expose the second layer, and
- une étape d'épitaxie ee) d'au moins une deuxième jonction sur la dite deuxième couche.  an epitaxial step ee) of at least one second junction on said second layer.
II est ainsi possible de former au moins une deuxième jonction après le collage direct et le traitement thermique de scellement. It is thus possible to form at least a second junction after the direct bonding and the sealing heat treatment.
Selon une disposition, le deuxième substrat support comprend une deuxième région de détachement permettant le retrait du deuxième substrat support de sorte à exposer la deuxième couche.  According to one arrangement, the second support substrate comprises a second detachment region allowing the removal of the second support substrate so as to expose the second layer.
Selon une autre disposition, la deuxième couche comprend une couche d'arrêt de gravure épitaxiée en surface du deuxième substrat donneur et avant l'étape d'épitaxie ee) d'au moins une deuxième jonction, le procédé comprend un amincissement d'au moins une partie de la deuxième couche jusqu'à atteindre la couche d'arrêt de gravure. Il est ainsi possible d'amincir de façon simple et reproductible la deuxième couche de sorte à réduire l'absorption optique des couches à l'interface de collage. La couche d'arrêt de gravure peut également compléter le retrait du premier substrat support par polissage, gravure au plasma et/ou gravure chimique, ou bien par irradiation laser tout en permettant l'obtention d'une épaisseur de couche fine et uniforme sur l'ensemble de la surface. According to another arrangement, the second layer comprises an etching stop layer epitaxially grown on the surface of the second donor substrate and prior to epitaxial step ee) of at least one second junction, the method comprises thinning at least a portion of the second layer until reaching the etch stop layer. It is thus possible to thin in a simple and reproducible way the second layer so as to reduce the optical absorption of the layers at the bonding interface. The etch stop layer may also complete the removal of the first support substrate by polishing, plasma etching and / or chemical etching, or by laser irradiation while allowing to obtain a thin and uniform layer thickness on the substrate. entire surface.
II est entendu que l'épitaxie dans ce cas a lieu sur le restant de la deuxième couche formée par la couche d'arrêt de gravure.  It is understood that the epitaxy in this case takes place on the remainder of the second layer formed by the etch stop layer.
Selon une possibilité, le procédé comprend avant l'étape b) une étape jj) consistant à implanter des espèces ioniques dans le deuxième substrat donneur de sorte à former un plan de fragilisation, formant la deuxième région de détachement et délimitant de part et d'autre le deuxième substrat support et la deuxième couche et l'étape de retrait dd) du deuxième substrat support comprend un détachement au niveau du plan de fragilisation délimitant la deuxième couche et le deuxième substrat support. Il est ainsi possible d'obtenir une deuxième couche qui soit mince, et puisse avoir la fonction de couche germe pour une épitaxie d'une au moins deuxième jonction. La couche d'arrêt de gravure peut également compléter le retrait du deuxième substrat support après détachement par Smart Cut™ tout en permettant l'obtention d'une épaisseur de couche fine et uniforme sur l'ensemble de la surface.  According to one possibility, the process comprises, before step b), a step jj) consisting in implanting ionic species in the second donor substrate so as to form a weakening plane, forming the second detachment region and delimiting on both sides other the second support substrate and the second layer and the dd) removal step of the second support substrate comprises a detachment at the weakening plane delimiting the second layer and the second support substrate. It is thus possible to obtain a second layer which is thin, and can have the function of seed layer for epitaxy of at least one second junction. The etch stop layer can also complete the removal of the second support substrate after detachment by Smart Cut ™ while allowing a thin and uniform layer thickness to be obtained over the entire surface.
Selon une alternative, le procédé comprend avant l'étape b) une étape kk) consistant à coller la deuxième couche sur un deuxième substrat support par exemple en saphir par l'intermédiaire d'une couche, par exemple en oxyde de silicium, formant la deuxième région de détachement, comprenant une couche enterrée de détachement, par exemple de nitrure de silicium, et l'étape de retrait dd) du deuxième substrat support comprend une étape d'irradiation laser de la couche enterrée de détachement de nitrure de silicium. Ainsi le deuxième substrat support peut être facilement retiré puis recyclé pour une nouvelle utilisation.  According to an alternative, the method comprises, before step b), a step kk) consisting in bonding the second layer to a second support substrate, for example made of sapphire, by means of a layer, for example made of silicon oxide, forming the second detachment region, comprising a buried detachment layer, for example silicon nitride, and the dd) removal step of the second support substrate comprises a laser irradiation step of the buried silicon nitride detachment layer. Thus the second support substrate can be easily removed and recycled for further use.
La couche d'arrêt de gravure peut également compléter le retrait du deuxième substrat support après irradiation laser, comme après gravure mécanique, plasma et/ou chimique du deuxième substrat support, tout en permettant l'obtention d'une épaisseur de couche fine et uniforme sur l'ensemble de la surface. The etch stop layer may also complete the removal of the second support substrate after laser irradiation, as after mechanical, plasma and / or chemical etching of the second support substrate, while allowing to obtain a thin layer thickness and uniform over the entire surface.
De préférence, la première couche germe et la deuxième couche sont constituées chacune d'un matériau semi-conducteur monocristallin choisi parmi le Ge et les alliages à base d'au moins un des éléments choisi parmi In, P, As et Ga.  Preferably, the first seed layer and the second layer each consist of a monocrystalline semiconductor material selected from Ge and alloys based on at least one of In, P, As and Ga.
Ainsi, lorsque ces couches servent de germe pour l'épitaxie d'au moins une des couches d'une jonction (elles sont alors appelées couches germes), elles sont constituées par un matériau présentant un paramètre de maille compatible avec la croissance par épitaxie du matériau désiré pour former au moins une des couches de la jonction.  Thus, when these layers serve as seed for the epitaxy of at least one of the layers of a junction (they are then called seed layers), they consist of a material having a mesh parameter compatible with the epitaxial growth of the desired material for forming at least one of the layers of the junction.
De préférence, la nature du matériau de la première couche germe et de la deuxième couche sont choisies pour que leur paramètre de maille soit proche respectivement de celui de la au moins une première jonction et de la au moins une deuxième jonction.  Preferably, the nature of the material of the first seed layer and the second layer are chosen so that their mesh parameter is close to that of the at least one first junction and the at least one second junction, respectively.
Avantageusement, le paramètre de maille de la première couche germe est proche de celui de la première jonction de sorte à faire croître un matériau monocristallin de très bonne qualité.  Advantageously, the mesh parameter of the first seed layer is close to that of the first junction so as to grow a monocrystalline material of very good quality.
Selon une possibilité, le procédé comprend avant l'étape a) une étape i) d'épitaxie de la première couche germe sur le premier substrat support et/ou de la deuxième couche sur le deuxième substrat support. Lorsque le premier substrat support comprend en surface un matériau monocristallin dont le paramètre de maille est voisin de celui de la première couche germe, celle-ci peut alors présenter une bonne qualité (peu de dislocations, surface peu rugueuse) et être monocristalline pour l'épitaxie de la première jonction.  According to one possibility, the process comprises, before step a) a step i) of epitaxial growth of the first seed layer on the first support substrate and / or of the second layer on the second support substrate. When the first support substrate comprises on the surface a monocrystalline material whose mesh parameter is close to that of the first seed layer, it can then have a good quality (few dislocations, rough surface) and be monocrystalline for the epitaxy of the first junction.
Selon un deuxième aspect, l'invention propose un procédé de fabrication d'une cellule photovoltaïque comprenant une structure à multijonctions fabriquée tel que précédemment décrit.  According to a second aspect, the invention proposes a method of manufacturing a photovoltaic cell comprising a multijunction structure manufactured as previously described.
Selon un troisième aspect, l'invention propose un procédé de fabrication d'un système photovoltaïque comprenant une cellule photovoltaïque fabriquée tel que précédemment décrit.  According to a third aspect, the invention proposes a method of manufacturing a photovoltaic system comprising a photovoltaic cell manufactured as previously described.
Selon un quatrième aspect, l'invention propose une structure à multijonctions comprenant au moins une première jonction et au moins une deuxième jonction reliée par une interface de collage présentant une épaisseur inférieure à 200 nanomètres, une résistivité électrique inférieure à 50 mohm.cm2 et un rendement de conversion supérieur à 40%. D'autres aspects, buts et avantages de la présente invention apparaîtront mieux à la lecture de la description suivante de deux modes de réalisation de celle-ci, donnée à titre d'exemples non limitatifs et fait en référence aux dessins annexés. Les figures ne respectent pas nécessairement l'échelle de tous les éléments représentés de sorte à améliorer leur lisibilité. Les traits pointillés illustrent un plan de fragilisation formé par implantation d'espèces ioniques. Les traits continus et gras illustrent l'interface de collage direct. Dans la suite de la description, par souci de simplification, des éléments identiques, similaires ou équivalents des différentes formes de réalisation portent les mêmes références numériques. According to a fourth aspect, the invention proposes a multijunction structure comprising at least one first junction and at least one second junction connected by a bonding interface having a thickness of less than 200 nanometers, an electrical resistivity of less than 50 mohm.cm 2, and a conversion efficiency greater than 40%. Other aspects, objects and advantages of the present invention will appear better on reading the following description of two embodiments thereof, given by way of non-limiting examples and with reference to the accompanying drawings. The figures do not necessarily respect the scale of all the elements represented so as to improve their readability. The dashed lines illustrate a weakening plane formed by implantation of ionic species. Continuous and bold lines illustrate the direct bonding interface. In the remainder of the description, for the sake of simplification, identical, similar or equivalent elements of the various embodiments bear the same numerical references.
- Les figures 1 à 5 illustrent un mode de réalisation du procédé selon l'invention.  - Figures 1 to 5 illustrate an embodiment of the method according to the invention.
- Les figures 6 à 10 illustrent une variante du mode de réalisation précédemment illustré.  FIGS. 6 to 10 illustrate a variant of the embodiment previously illustrated.
- Les figures 1 1 à 18 illustrent un deuxième mode de réalisation du procédé selon l'invention.  - Figures 1 1 to 18 illustrate a second embodiment of the method according to the invention.
La figure 1 illustre une étape j) du procédé consistant à implanter des espèces ioniques, par exemple avec une dose comprise entre 10E16 et 10E17 at/cm2 d'ions à base d'hydrogène, dans un premier substrat donneur 1 de Ge, GaAs ou InP, de sorte à former un plan de fragilisation 2, formant la première région de détachement et délimitant un premier substrat support 3 et une première couche germe 4. Les conditions de l'implantation permettent de créer un plan de fragilisation 2 à une faible profondeur allant jusqu'à 1 nm dans le substrat donneur 1 de sorte que la première couche germe 4 est très fine. A l'issue de cette étape j) est formé le premier substrat donneur 1 fourni pour un collage direct selon l'étape a) du procédé. FIG. 1 illustrates a step j) of the process consisting in implanting ionic species, for example with a dose of between 10 E 16 and 10 E 17 at / cm 2 of hydrogen-based ions, in a first donor substrate 1 of Ge, GaAs or InP, so as to form an embrittlement plane 2, forming the first detachment region and delimiting a first support substrate 3 and a first seed layer 4. The implantation conditions allow to create a weakening plane 2 at a shallow depth of up to 1 nm in the donor substrate 1 so that the first seed layer 4 is very thin. At the end of this step j) is formed the first donor substrate 1 provided for direct bonding according to step a) of the method.
La figure 2 illustre une étape b) du procédé consistant à fournir un deuxième substrat donneur 5 comprenant un deuxième substrat support 6, une deuxième couche 7 et une deuxième jonction 8 intercalée entre le deuxième substrat support 6 et la deuxième couche 7.  FIG. 2 illustrates a step b) of the method of providing a second donor substrate 5 comprising a second support substrate 6, a second layer 7 and a second junction 8 interposed between the second support substrate 6 and the second layer 7.
Selon une possibilité, les topologies de la surface de la première couche germe 4 et de la deuxième couche 7 ont été préparées au préalable de sorte à présenter une rugosité inférieure à 1 nanomètre RMS et une planéité adaptée au collage direct de l'ordre de 50μηη pour un substrat de 100 mm entre les deux couches 4,7. La figure 3 illustre l'étape c) du procédé consistant à mettre en contact la première couche germe 4 et de la deuxième couche 7 pour constituer une interface de collage 9 et l'obtention d'un collage direct. According to one possibility, the topologies of the surface of the first seed layer 4 and the second layer 7 have been prepared beforehand so as to have a roughness of less than 1 nanometer RMS and a flatness adapted to direct bonding of the order of 50μηη for a 100 mm substrate between the two layers 4.7. FIG. 3 illustrates step c) of the method consisting in bringing the first seed layer 4 and the second layer 7 into contact to form a bonding interface 9 and obtaining direct bonding.
La figure 4 illustre le retrait du premier substrat support 3 par détachement au niveau du plan de fragilisation 2. La première couche germe de faible épaisseur est ainsi exposée de sorte à réaliser une épitaxie d'une première jonction 1 1 à sa surface (figure 5). Une structure à multijonctions 12 est ainsi obtenue par collage direct comprenant au moins une première couche germe 4 servant également de collage de faible épaisseur.  FIG. 4 illustrates the removal of the first support substrate 3 by detachment at the embrittlement plane 2. The first seed layer of small thickness is thus exposed so as to produce an epitaxy of a first junction January 1 on its surface (FIG. ). A multijunction structure 12 is thus obtained by direct bonding comprising at least a first seed layer 4 also serving as a thin bonding.
Selon une disposition non illustrée, un traitement thermique de scellement du collage direct à 300°C pour une durée typique allant de quelques secondes à 120 min par exemple est appliqué à la structure avant la réalisation de l'épitaxie de sorte à réduire la résistivité éléctrique (typiquement inférieure à 50 mohm.cm2 du contact obtenu sans détériorer la deuxième jonction 8. According to a provision not illustrated, a heat sealing treatment of the direct bonding at 300 ° C. for a typical duration ranging from a few seconds to 120 min for example is applied to the structure before the epitaxy is made so as to reduce the electrical resistivity. (typically less than 50 mohm.cm 2 of the contact obtained without damaging the second junction 8.
Selon une possibilité non illustrée, l'étape d) de retrait du premier substrat support 3 est réalisée par application d'un traitement thermique typiquement à une température de 100-350°C et pour une durée comprise entre 30 min et 120 min permettant à la fois le développement des cavités au niveau du plan de fragilistion conduisant au détachement du premier substrat support 3 et également le renforcement du scellement diminuant la résistivité électrique du collage.  According to a possibility not illustrated, step d) of removing the first support substrate 3 is carried out by applying a heat treatment typically at a temperature of 100-350 ° C and for a duration of between 30 min and 120 min allowing both the development of the cavities at the weakening plane leading to the detachment of the first support substrate 3 and also the strengthening of the seal decreasing the electrical resistivity of the bonding.
Selon une variante, l'étape d) de retrait du premier substrat support 3 est obtenu par application d'une contrainte mécanique au niveau du plan de fragilisation 2 de sorte à ne pas endommager la deuxième jonction 8.  According to one variant, step d) of removing the first support substrate 3 is obtained by applying a mechanical stress at the level of the weakening plane 2 so as not to damage the second junction 8.
Par ailleus, un traitement thermique peut être appliqué en complément de la contrainte mécanique pour obtenir le détachement du premier substrat support 3, ce traitement thermique participe alors au scellement favorisant la diminution de la résistivité de l'interface de collage 9.  By ailleus, a heat treatment can be applied in addition to the mechanical stress to obtain the detachment of the first support substrate 3, this heat treatment then participates in the sealing favoring the reduction of the resistivity of the bonding interface 9.
Les figures 6 à 10 illustrent un procédé de fabrication qui diffère de celui illustré aux figures 1 à 5 en ce que la première couche germe 4 comprend une couche d'arrêt de gravure 13 en surface du premier substrat donneur 1 (figure 6). Cette couche d'arrêt de gravure 13 est formée au préalable par épitaxite d'un matériau présentant une réactivité différente de l'autre partie de la première couche germe 4 face à la gravure (chimique, mécanique ou plasma). Une fois le collage direct (figure 8) effectué avec le deuxième substrat donneur 5 (figure 7) et le premier substrat support 3 est détaché par application d'un traitement thermique participant au scellement du collage, complété par application d'une contrainte mécanique latéralement au plan de fragilisation 2 (figure 9). Puis la première couche germe 4 exposée est amincie au moins en partie jusqu'à atteindre la couche d'arrêt de gravure 13 (étape I) figure 10). Cette couche d'arrêt de gravure 13 obtenue par épitaxie est monocristalline présente une faible épaisseur uniforme et peut être utilisée comme germe pour l'épitaxie de la première jonction 1 1 . Figures 6 to 10 illustrate a manufacturing method which differs from that illustrated in Figures 1 to 5 in that the first seed layer 4 comprises an etching stop layer 13 at the surface of the first donor substrate 1 (Figure 6). This etching stop layer 13 is formed beforehand by epitaxialization of a material having a reactivity different from the other part of the first seed layer 4 facing etching (chemical, mechanical or plasma). Once the direct bonding (FIG. 8) carried out with the second substrate donor 5 (FIG. 7) and the first support substrate 3 is detached by application of a heat treatment participating in the sealing of the bonding, completed by applying a mechanical stress laterally to the embrittlement plane 2 (FIG. 9). Then the exposed first seed layer 4 is thinned at least in part until reaching the etch stop layer 13 (step I) FIG. 10). This etch stop layer 13 obtained by epitaxy is monocrystalline has a small uniform thickness and can be used as seed for the epitaxy of the first junction 11.
Selon une possibilité non illustrée, le premier substrat donneur 1 est un substrat massif d'InP comprenant en surface une couche d'arrêt de gravure 13 en InGaAs au paramètre de maille adapté à la croissance ultérieure d'au moins une jonction. L'implantation ionique à base d'hydrogène, d'helium ou autre espèces gazeuses, forme un plan de fragilisation 2 dans le substrat 1 d'InP qui délilmite le premier substrat support 3 en InP et une première couche germe 4 d'InP comprenant en surface la couche d'arrêt de gravure 13 d'InGaAs. Après le détachement du premier substrat support 3 et d'au moins une partie de la première couche germe 4 est retirée par exemple par gravure, polissage ou plasma, jusqu'à atteindre la couche d'arrêt de gravure 13. Puis une épitaxie d'une première jonction 1 1 en InGaAs est suivie de l'épitaxie d'une jonction d'InGaAsP supplémentaire pour l'obtention d'une structure à multijonctions 12.  According to a possibility not illustrated, the first donor substrate 1 is a solid InP substrate comprising at the surface an etching stop layer 13 of InGaAs at the mesh parameter adapted to the subsequent growth of at least one junction. Ion implantation based on hydrogen, helium or other gaseous species forms a weakening plane 2 in the InP substrate 1 which delimits the first InP support substrate 3 and a first InP seed layer 4 comprising at the surface of the etching stop layer 13 of InGaAs. After the detachment of the first support substrate 3 and at least a part of the first seed layer 4 is removed for example by etching, polishing or plasma, until reaching the etching stop layer 13. Then an epitaxy of a first InGaAs junction 1 1 is followed by the epitaxy of an additional InGaAsP junction to obtain a multi-junction structure 12.
Les figures 12 à 18 illustrent une alternative de réalisation du procédé selon l'invention.  Figures 12 to 18 illustrate an alternative embodiment of the method according to the invention.
La figure 1 1 illustre un premier substrat donneur 1 comprenant une première couche germe 4 en GaAs collée sur un premier substrat support 3 en matériau de saphir (étape k) par l'intermédiaire d'une couche d'oxyde de silicium 14 formant la première région de détachement, comprenant une couche de nitrure de silicium (non illustrée). Cette étape de collage préalable peut avoir été réalisée par la technologie Smart Cut™ permettant l'obtention d'une première couche germe 4 d'une épaisseur contrôlée d'environ 50 nanomètres.  FIG. 11 illustrates a first donor substrate 1 comprising a first GaAs seed layer 4 bonded to a first support substrate 3 made of sapphire material (step k) via a silicon oxide layer 14 forming the first detachment region, comprising a silicon nitride layer (not shown). This prior gluing step may have been performed by Smart Cut ™ technology to obtain a first seed layer 4 with a controlled thickness of about 50 nanometers.
La figure 12 illustre un deuxième substrat donneur 5 comprenant une deuxième couche germe 7 en InP d'une épaisseur d'environ 50 nanomètres collée sur un deuxième substrat support 6, par exemple en matériau de saphir, par l'intermédiaire de couches de collage (oxyde de silicium, nitrure de silicium, etc.) 14 formant la deuxième région de détachement comprenant au moins une couche enterrée de détachement de nitrure de silicium (non illustrée) (étape kk). FIG. 12 illustrates a second donor substrate 5 comprising a second seed layer 7 made of InP having a thickness of approximately 50 nanometers bonded to a second support substrate 6, for example made of sapphire material, by means of bonding layers ( silicon oxide, silicon nitride, etc.) 14 forming the second region of detachment comprising at least one buried layer of detachment of silicon nitride (not shown) (step kk).
La figure 13 illustre la mise en contact de la première couche germe 4 et de la deuxième couche 7 dont les surfaces ont été préparées au préalable pour l'obtention de topologies de surface adaptées au collage direct (étape c). Puis un traitement thermique de scellement du collage direct est appliqué à 600°C de quelques secondes à 2 heures permettant d'améliorer la conductivité électrique de l'interface de collage 9 à moins de 50 mohm.cm2. FIG. 13 illustrates the bringing into contact of the first seed layer 4 and of the second layer 7, the surfaces of which have been prepared beforehand in order to obtain surface topologies suitable for direct bonding (step c). Then a heat sealing treatment of the direct bonding is applied at 600 ° C for a few seconds to 2 hours to improve the electrical conductivity of the bonding interface 9 to less than 50 mohm.cm 2 .
La figure 14 illustre l'étape d) du retrait du premier substrat support 3 de saphir par irradiation laser à travers ce dernier à la longueur d'onde d'absorption du nitrure de silicium. Cette absorption génère la dégradation de la couche de nitrure de silicium, ce qui de permet le détachement du substrat support 3. Celui ci peut être avantageusement recyclé pour une nouvelle utilisation dans un procédé ultérieur.  Figure 14 illustrates step d) of removing the first sapphire support substrate 3 by laser irradiation therethrough at the absorption wavelength of the silicon nitride. This absorption generates the degradation of the silicon nitride layer, which allows the detachment of the support substrate 3. It can advantageously be recycled for a new use in a subsequent process.
La figure 15 illustre l'étape e) consistant à réaliser une épitaxie d'au moins une première jonction 1 1 en matériau AIGaAs ou GaAs sur la première couche germe 4 exposée en GaAs après nettoyage des résidus de la couche d'oxyde de silicium 14.  FIG. 15 illustrates the step e) of producing an epitaxy of at least a first junction 1 1 made of AIGaAs or GaAs material on the first exposed GaAs seed layer 4 after cleaning the residues of the silicon oxide layer 14 .
Puis la première jonction 1 1 est solidarisée avec un substrat hôte 15 comme par exemple un substrat semiconducteur (Si, Ge, etc.), métallique (Mo, Cu, etc.) ou isolant (verre, Sapphire, etc.) (figure 16 - étape m) de sorte à pouvoir effectuer le retrait du deuxième substrat support 6 (étape dd). Ce retrait est notamment effectué par irradiation laser comme précédemment décrit (figure 17).  Then the first junction 1 1 is secured to a host substrate 15 such as a semiconductor substrate (Si, Ge, etc.), metal (Mo, Cu, etc.) or insulator (glass, Sapphire, etc.) (FIG. 16 step m) so as to be able to remove the second support substrate 6 (step dd). This shrinkage is in particular carried out by laser irradiation as previously described (FIG. 17).
Enfin, la deuxième couche 7 d'InP du deuxième substrat donneur 5 étant exposée, une épitaxie d'une au moins deuxième jonction 8 est réalisée de sorte à obtenir une structure à multijonctions 12 présentant une épaisseur à l'interface de collage 9 inférieure à 200 nanomètres et une résistivité électrique inférieure à 50 mohm.cm2 (étape ee). Finally, the second InP layer 7 of the second donor substrate 5 being exposed, an epitaxy of at least one second junction 8 is produced so as to obtain a multi-function structure 12 having a thickness at the bonding interface 9 less than 200 nanometers and an electrical resistivity lower than 50 mohm.cm 2 (step ee).
Selon une possibilité non illustrée, le deuxième substrat donneur 5 comprend deux jonctions 8,8' intercalées entre le deuxième substrat support 6 et la deuxième couche 7. Une fois le collage direct réalisé avec la première couche germe 4 selon l'étape c) l'étape d) du procédé comprend l'épitaxie de deux jonctions 1 1 , 1 1 ' voire une épitxie de trois jonctions.  According to a possibility not illustrated, the second donor substrate 5 comprises two junctions 8.8 'interposed between the second support substrate 6 and the second layer 7. Once the direct bonding has been achieved with the first seed layer 4 according to step c) Step d) of the process comprises the epitaxy of two junctions 11, 11 'or even an epitx of three junctions.
Selon une autre variante non illustrée, le deuxième substrat donneur 5 comprenant une deuxième jonction 8 est collé au préalable avec un second deuxième substrat donneur 5 comprenant une autre jonction 8'. Après l'étape c) du procédé, trois jonctions 1 1 , 1 1 ' et 1 1 "' sont épitaxiées sur la première couche germe 4 selon l'étape d) du procédé. According to another variant not illustrated, the second donor substrate 5 comprising a second junction 8 is previously bonded with a second second donor substrate 5 comprising another junction 8 '. After step c) of the process, three junctions 11, 11 'and 11''are epitaxially grown on the first seed layer 4 according to step d) of the method.
La présente invention permet ainsi d'envisager toutes les combinaisons possibles de collage de plusiuers jonctions et d'épitaxie de plusieurs jonctions permettant d'obtenir des structrures multijonctions comprenant 4, 5 voire 6 jonctions présentant des interfaces de collages 9 faiblement optiquement absorbante et présentant une très bonne conductivité électrique.  The present invention thus makes it possible to envisage all the possible combinations of bonding of several junctions and of epitaxies of several junctions making it possible to obtain multi-function structures comprising 4, 5 or even 6 junctions having weakly optically absorbing bonding interfaces 9 and presenting a very good electrical conductivity.
Ainsi, la présente invention propose la fabrication d'une structure à multijonctions 12 comprenant au moins un première et au moins une deuxième jonction 8,1 1 reliées par une interface de collage 9 simple à mettre en œuvre, préservant l'intégrité des couches de jonctions 8,1 1 et qui permette d'obtenir une interface de collage 9 faiblement optiquement absorbante et d'une très bonne conductivité électrique.  Thus, the present invention proposes the manufacture of a multijunction structure 12 comprising at least a first and at least a second junction 8.1 1 connected by a bonding interface 9 simple to implement, preserving the integrity of the layers of junctions 8.1 1 and which provides a bonding interface 9 weakly optically absorbing and very good electrical conductivity.
Il va de soi que l'invention n'est pas limitée aux variantes de réalisation décrites ci-dessus à titre d'exemples mais qu'elle comprend tous les équivalents techniques et les variantes des moyens décrits ainsi que leurs combinaisons.  It goes without saying that the invention is not limited to the embodiments described above as examples but that it includes all the technical equivalents and variants of the means described and their combinations.

Claims

REVENDICATIONS
1 . Procédé de fabrication d'une structure à multijonctions (12) pour cellule photovoltaïque, la structure à multijonctions (12) comprenant au moins une première jonction (1 1 ) et au moins une deuxième jonction (8) reliées entre elles par une interface de collage (9), le procédé comprenant les étapes consistant à 1. A method of manufacturing a multijunction structure (12) for a photovoltaic cell, the multijunction structure (12) comprising at least a first junction (1 1) and at least one second junction (8) interconnected by a bonding interface (9), the method comprising the steps of
- a) Fournir un premier substrat donneur (1 ) comprenant un premier substrat support (3) et une première couche germe (4) comportant un premier matériau,  a) providing a first donor substrate (1) comprising a first support substrate (3) and a first seed layer (4) comprising a first material,
- b) Fournir un deuxième substrat donneur (5) comprenant un deuxième substrat support (6) et une deuxième couche (7) comportant un deuxième matériau différent du premier matériau, la nature du deuxième matériau étant différente de celle du matériau constituant le deuxième substrat support (6), b) providing a second donor substrate (5) comprising a second support substrate (6) and a second layer (7) comprising a second material different from the first material, the nature of the second material being different from that of the material constituting the second substrate; support (6),
- c) Mettre en contact la première couche germe (4) et la deuxième couche (7) de sorte à obtenir un collage direct entre la première couche germe (4) et la deuxième couche (7) en vue de constituer l'interface de collage (9), - c) contacting the first seed layer (4) and the second layer (7) so as to obtain a direct bonding between the first seed layer (4) and the second layer (7) in order to constitute the interface of collage (9),
- d) Retirer le premier substrat support (3) de sorte à exposer la première couche germe (4), et  - d) removing the first support substrate (3) so as to expose the first seed layer (4), and
- e) Réaliser une épitaxie d'au moins une première jonction (1 1 ) sur la première couche germe (4).  e) Producing an epitaxy of at least a first junction (1 1) on the first seed layer (4).
2. Procédé selon la revendication 1 , caractérisé en ce que la première couche germe (4) comprend une couche d'arrêt de gravure (13) épitaxiée en surface respectivement du premier substrat donneur (1 ) et en ce que le procédé comprend avant l'étape e) une étape I) d'amincissement d'au moins une partie de la première couche germe (4) jusqu'à atteindre respectivement la couche d'arrêt de gravure (13). 2. Method according to claim 1, characterized in that the first seed layer (4) comprises an etching stop layer (13) epitaxially surface respectively of the first donor substrate (1) and in that the method comprises before the step e) a step I) of thinning at least a portion of the first seed layer (4) until reaching respectively the etch stop layer (13).
3. Procédé selon l'une des revendications 1 à 2, caractérisé en ce que le premier substrat support (3) comprend une première région de détachement (2, 14) permettant le retrait du premier substrat support (3) de sorte à exposer la première couche germe (4). 3. Method according to one of claims 1 to 2, characterized in that the first support substrate (3) comprises a first detachment region (2, 14) for the removal of the first support substrate (3) so as to expose the first seed layer (4).
4. Procédé selon la revendication 3, caractérisé en ce que le procédé comprend avant l'étape a) une étape j) consistant à implanter des espèces ioniques dans le premier substrat donneur (1 ) de sorte à former un plan de fragilisation (2) formant la première région de détachement et délimitant de part et d'autre le premier substrat support (3) et la première couche germe (4) et en ce que l'étape d) de retrait du premier substrat support (3) est réalisée par détachement du premier substrat support (3) au niveau du plan de fragilisation (2). 4. Method according to claim 3, characterized in that the process comprises before step a) a step j) of implanting ionic species in the first donor substrate (1) so as to form an embrittlement plane (2) forming the first detachment region and delimiting on either side the first support substrate (3) and the first seed layer (4) and in that step d) of removing the first support substrate (3) is carried out by detachment of the first support substrate (3) at the weakening plane (2).
5. Procédé selon la revendication 3, caractérisé en ce que le procédé comprend avant l'étape a) une étape k) consistant à reporter la première couche germe (4) sur un premier substrat support (3) par l'intermédiaire d'une couche (14) formant la première région de détachement, comprenant une couche enterrée de détachement et en ce que l'étape d) de retrait du premier substrat support (3) est réalisée par irradiation laser effectuée à la longueur d'onde d'absorption de la couche enterrée de détachement. 5. Method according to claim 3, characterized in that the method comprises, before step a) a step k) consisting of transferring the first seed layer (4) to a first support substrate (3) via a layer (14) forming the first detachment region, comprising a buried detachment layer and in that step d) of removing the first support substrate (3) is performed by laser irradiation carried out at the absorption wavelength the buried layer of detachment.
6. Procédé selon l'une des revendications 1 à 5, caractérisé en ce que le procédé comprend après l'étape c) une étape d'application d'un traitement thermique, de préférence réalisé à une température comprise entre 200°C et 800°C, et de préférence encore réalisé à une température comprise entre 300°C et 600°C. 6. Method according to one of claims 1 to 5, characterized in that the method comprises after step c) a step of applying a heat treatment, preferably carried out at a temperature between 200 ° C and 800 ° C, and more preferably carried out at a temperature between 300 ° C and 600 ° C.
7. Procédé selon l'une des revendications 1 à 6, caractérisé en ce que le deuxième substrat donneur (5) comprend au moins la deuxième jonction (8) intercalée entre le deuxième substrat support (6) et la deuxième couche (7). 7. Method according to one of claims 1 to 6, characterized in that the second donor substrate (5) comprises at least the second junction (8) interposed between the second support substrate (6) and the second layer (7).
8. Procédé selon l'une des revendications 1 à 6, caractérisé en ce que le procédé comprend après l'étape e) d'épitaxie, 8. Method according to one of claims 1 to 6, characterized in that the method comprises after step e) of epitaxy,
- une étape de collage m) d'au moins la première jonction (1 1 ) à un substrat hôte (15),  a step of bonding m) of at least the first junction (1 1) to a host substrate (15),
- une étape dd) de retrait du deuxième substrat support (6) de sorte à exposer la deuxième couche (7), et  a step dd) of removing the second support substrate (6) so as to expose the second layer (7), and
- une étape d'épitaxie ee) d'au moins la deuxième jonction (8) sur ladite deuxième couche (7). an epitaxial step ee) of at least the second junction (8) on said second layer (7).
9. Procédé selon la revendication 8, caractérisé en ce que la deuxième couche (7) comprend une couche d'arrêt de gravure (13) épitaxiée en surface du deuxième substrat donneur (5) et en ce que avant l'étape d'épitaxie ee) d'au moins la deuxième jonction (8), le procédé comprend un amincissement d'au moins une partie de la deuxième couche (7) jusqu'à atteindre la couche d'arrêt de gravure (13). 9. Method according to claim 8, characterized in that the second layer (7) comprises an etching stop layer (13) epitaxially grown on the surface of the second donor substrate (5) and in that before the epitaxial step ee) at least the second junction (8), the method comprises thinning at least a portion of the second layer (7) until reaching the etch stop layer (13).
10. Procédé selon l'une des revendications 8 à 9, caractérisé en ce que le deuxième substrat support (6) comprend une deuxième région de détachement (2, 14) permettant le retrait du deuxième substrat support (6) de sorte à exposer la deuxième couche (7). 10. Method according to one of claims 8 to 9, characterized in that the second support substrate (6) comprises a second detachment region (2, 14) for the removal of the second support substrate (6) so as to expose the second layer (7).
1 1 . Procédé selon la revendication 10, caractérisé en ce que le procédé comprend avant l'étape b) une étape jj) consistant à implanter des espèces ioniques dans le deuxième substrat donneur (5) de sorte à former un plan de fragilisation (2) formant la deuxième région de détachement et délimitant de part et d'autre le deuxième substrat support (6) et la deuxième couche (7) et en ce que l'étape de retrait dd) du deuxième substrat support (6) comprend un détachement au niveau du plan de fragilisation (2) délimitant la deuxième couche (7) et le deuxième substrat support (6). 1 1. Process according to Claim 10, characterized in that the process comprises, before step b), a step jj) of implanting ionic species in the second donor substrate (5) so as to form an embrittlement plane (2) forming the second detachment region and delimiting on either side the second support substrate (6) and the second layer (7) and in that the removal step dd) of the second support substrate (6) comprises a detachment at the level of embrittlement plane (2) delimiting the second layer (7) and the second support substrate (6).
12. Procédé selon la revendication 10, caractérisé en ce que le procédé comprend avant l'étape b) une étape kk) consistant à coller la deuxième couche (7) sur un deuxième substrat support (6) par exemple en saphir par l'intermédiaire d'une couche (14) par exemple en oxyde de silicium formant la deuxième région de détachement, comprenant au moins une couche enterrée de détachement, par exemple en nitrure de silicium et en ce que l'étape de retrait dd) du deuxième substrat support (6) comprend une étape d'irradiation laser de la couche enterrée de détachement. 12. The method of claim 10, characterized in that the method comprises before step b) a step kk) of bonding the second layer (7) on a second support substrate (6) for example sapphire via a layer (14) for example made of silicon oxide forming the second detachment region, comprising at least one buried detachment layer, for example made of silicon nitride and in that the step of removing dd) from the second support substrate (6) comprises a laser irradiation step of the buried detachment layer.
13. Procédé selon l'une des revendications 1 à 12, caractérisé en ce que la première couche germe (4) et la deuxième couche (7) sont constituées chacune d'un matériau semi-conducteur monocristallin choisi parmi le Ge et les alliages à base d'au moins un des éléments choisis parmi In, P, As et Ga. 13. Method according to one of claims 1 to 12, characterized in that the first seed layer (4) and the second layer (7) each consist of a monocrystalline semiconductor material selected from Ge and alloys to base of at least one of the elements selected from In, P, As and Ga.
14. Procédé de fabrication d'une cellule photovoltaïque caractérisée en ce qu'elle comprend une structure à multijonctions (12) fabriquée selon l'une des revendications 1 à 13. 14. A method of manufacturing a photovoltaic cell characterized in that it comprises a multijunction structure (12) manufactured according to one of claims 1 to 13.
15. Procédé de fabrication d'un système photovoltaïque comprenant une cellule photovoltaïque fabriquée selon la revendication 14. 15. A method of manufacturing a photovoltaic system comprising a photovoltaic cell manufactured according to claim 14.
EP14718665.4A 2013-03-25 2014-03-24 Process for manufacturing a multi-junction structure for a photovoltaic cell Withdrawn EP2979306A1 (en)

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FR1352627A FR3003692B1 (en) 2013-03-25 2013-03-25 METHOD FOR MANUFACTURING A MULTIJUNCTION STRUCTURE FOR A PHOTOVOLTAIC CELL
PCT/FR2014/050689 WO2014154993A1 (en) 2013-03-25 2014-03-24 Process for manufacturing a multi-junction structure for a photovoltaic cell

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FR3079346B1 (en) * 2018-03-26 2020-05-29 Soitec METHOD FOR MANUFACTURING A DONOR SUBSTRATE FOR TRANSFERRING A PIEZOELECTRIC LAYER, AND METHOD FOR TRANSFERRING SUCH A PIEZOELECTRIC LAYER
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