WO2015082828A1 - Mesa semiconductor device and production method - Google Patents

Mesa semiconductor device and production method Download PDF

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Publication number
WO2015082828A1
WO2015082828A1 PCT/FR2014/053127 FR2014053127W WO2015082828A1 WO 2015082828 A1 WO2015082828 A1 WO 2015082828A1 FR 2014053127 W FR2014053127 W FR 2014053127W WO 2015082828 A1 WO2015082828 A1 WO 2015082828A1
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semiconductor
semiconductor device
substrate
junction
stack
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PCT/FR2014/053127
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French (fr)
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Vincent Mevellec
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Alchimer
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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
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/072—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type
    • H01L31/0735—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN heterojunction type comprising only AIIIBV compound semiconductors, e.g. GaAs/AlGaAs or InP/GaInAs solar cells
    • C—CHEMISTRY; METALLURGY
    • C09—DYES; PAINTS; POLISHES; NATURAL RESINS; ADHESIVES; COMPOSITIONS NOT OTHERWISE PROVIDED FOR; APPLICATIONS OF MATERIALS NOT OTHERWISE PROVIDED FOR
    • C09D—COATING COMPOSITIONS, e.g. PAINTS, VARNISHES OR LACQUERS; FILLING PASTES; CHEMICAL PAINT OR INK REMOVERS; INKS; CORRECTING FLUIDS; WOODSTAINS; PASTES OR SOLIDS FOR COLOURING OR PRINTING; USE OF MATERIALS THEREFOR
    • C09D5/00—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes
    • C09D5/44—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications
    • C09D5/4476—Coating compositions, e.g. paints, varnishes or lacquers, characterised by their physical nature or the effects produced; Filling pastes for electrophoretic applications comprising polymerisation in situ
    • C—CHEMISTRY; METALLURGY
    • C25—ELECTROLYTIC OR ELECTROPHORETIC PROCESSES; APPARATUS THEREFOR
    • C25D—PROCESSES FOR THE ELECTROLYTIC OR ELECTROPHORETIC PRODUCTION OF COATINGS; ELECTROFORMING; APPARATUS THEREFOR
    • C25D9/00—Electrolytic coating other than with metals
    • C25D9/02—Electrolytic coating other than with metals with organic materials
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/02—Details
    • H01L31/0216—Coatings
    • H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
    • H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
    • H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • H01L31/0687—Multiple junction or tandem solar cells
    • H01L31/06875—Multiple junction or tandem solar cells inverted grown metamorphic [IMM] multiple junction solar cells, e.g. III-V compounds inverted metamorphic multi-junction 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 potential barriers
    • H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
    • 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 potential barriers the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells 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
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02109—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates
    • H01L21/02112—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer
    • H01L21/02118—Forming insulating materials on a substrate characterised by the type of layer, e.g. type of material, porous/non-porous, pre-cursors, mixtures or laminates characterised by the material of the layer carbon based polymeric organic or inorganic material, e.g. polyimides, poly cyclobutene or PVC
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/02104—Forming layers
    • H01L21/02107—Forming insulating materials on a substrate
    • H01L21/02225—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer
    • H01L21/0226—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process
    • H01L21/02282—Forming insulating materials on a substrate characterised by the process for the formation of the insulating layer formation by a deposition process liquid deposition, e.g. spin-coating, sol-gel techniques, spray coating
    • 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
    • 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 semiconductor devices having a vertical multi-junction structure, particularly voltaic cells, having an improved electrical efficiency.
  • the invention also relates to a method of manufacturing these devices.
  • the efficiency of the mesa-type semiconductor devices can be improved by preventing electron recombination phenomena at the interfaces that leave several different semiconductor materials flush. It has been proposed in the prior art to cover the silicon dioxide interfaces, or to treat the wafers of passivating flush semiconductor materials, the passivation resulting in transforming the surface of the material into oxide or nitride.
  • passivation processes have the disadvantage of being carried out in the vapor phase (Chemical Vapor Deposition) or by thermal oxidation, which requires the use of expensive equipment at high temperatures, typically between 200 and 450 ° C.
  • the present invention therefore proposes a method of manufacturing a device and a device that overcomes these disadvantages.
  • the process of the invention can be carried out at much lower temperatures and wet, so that the semiconductor devices obtained have good or even better energy efficiency while being produced at lower cost.
  • the mechanical properties of the device of the invention are also improved, particularly as regards the adhesion and the cohesion of the insulating film.
  • a first object of the invention is a semiconductor device of mesa structure comprising a first semiconductor material and a second semiconductor material different from the first, which are in contact with one another and deposited on a substrate in a manner that to create at least one pn junction, said device comprising trenches of which at least one surface is flush with the two materials and optionally the substrate,
  • said surface of the trench is covalently bonded to an insulating organic polymer film, whereby said film can suppress electronic recombinations likely to occur at the pn junction (s) during the operation of said illuminated device or turned on.
  • the devices of the invention comprise a stack of several semiconductor materials in which the electronic recombination phenomena are limited or even eliminated.
  • the reduction of electronic recombinations in a photovoltaic cell of the invention can be evaluated by measuring the open-circuit potential of the device (E oc ).
  • the organic polymer film allows a gain of the value E oc of between 0.5 and 1% relative to the same device without an insulating film in the case of photovoltaic cells having a surface area of between 400 and 700 pm 2 , preferably between 500 and 600 pm 2 '.
  • the open-circuit potential E oc of the device of the invention can be between 2,700 and 2,800 V, preferably between 2,750 and 2,760 V.
  • the mesas of the photovoltaic cells of the invention may have a square side shape of between 20 and 40 microns.
  • the height of the mesas is for example of the order of 50 to 150 microns.
  • the present invention makes it possible to limit the recombination phenomena by covering the walls of the trenches with the aid of an organic polymer that insulates electricity.
  • the polymer film is deposited on the surface of the trench preferably by electrografting. Electrografting makes it possible to obtain a solidly grafted layer, in a single step, selectively (ie by covering the semiconductor materials that cover the other elements of the device that are exposed to the polymer or monomer solution). other current passivation method can not achieve.
  • the organic polymer used in the context of the invention comprises free functional groups capable of engaging bonds with the semiconductor materials and the substrate selectively.
  • the polyimide polymers suggested in the prior art as an insulator do not include such functional groups.
  • the bonds between the polymer film and the semiconductor materials may be covalent bonds or non-covalent bonds, for example ionic, hydrogen or van der Waals.
  • the organic polymer can be obtained from a vinyl monomer comprising one or more non-polymerizable functional groups capable of binding by covalent bonds to the surface of the trenches surrounding the mesa.
  • the polymer may be chosen from polymers comprising one or more functional groups chosen from the primary amine, secondary amine, enamine, alcohol, thiol, carboxylic acid, non-aromatic heterocyclic and aromatic heterocyclic groups, in particular nitrogenous aromatic heterocycles such as pyridine, pyrrole or thiophene.
  • the polymer is for example obtained from at least one polymerizable carbonaceous monomer comprising at least one functional group as described above.
  • Radically polymerizable chain monomers such as vinyl monomers
  • the monomers will advantageously be chosen from water-soluble vinyl monomers comprising at least one functional group capable of initiating a non-covalent bond with a metal ion.
  • Such monomers will advantageously be chosen from polyvinylamines, in particular chosen from vinyl derivatives of amines such as:
  • primary aliphatic amines in particular ethylamine, cyclohexylamine, cyclohexanediamine;
  • tertiary aliphatic amines in particular hydroxyethyldiethylamine, tetraethylenepentamine
  • aromatic amines in particular 1,2-diaminobenzene, 3,5-dimethylaniline;
  • nitrogen heterocycles in particular pyridine, 2,2'-bipyridine, 8-hydroxyquinoline sulphonate, 1,10-phenanthroline, 3,5-dimethylpyridine, 2,2'-bipyrimidine;
  • oximes in particular dimethylglyoxime.
  • the polymers of a vinyl nitrogen aromatic heterocycle in particular the polymers of a vinyl nitrogen aromatic heterocycle.
  • the nitrogen atoms are not bonded to the vinyl group, so that the nitrogen atom remains available to bind to the metal ions.
  • the monomers are, for example, chosen from unsaturated nitrogen-containing carbon monomers and their thio-analogues, of which:
  • vinylpyridines such as 2-vinylpyridine or 4-vinylpyridine; and N-lower alkyl (C1-C8) vinylpyridines such as 2-methyl-5-vinylpyridine, 2-ethyl-5-vinylpyridine, 3-methyl-5-vinylpyridine, 2,3 5-dimethyl-5-vinylpyridine and 2-methyl-3-ethyl-5-vinylpyridine;
  • vinylquinolines and vinylpyrrolidones vinylimidazoles, vinylcarbazoles and vinylsuccinimide.
  • the monomer is 4-vinylpyridine or 2-vinylpyridine.
  • the monomers may also be chosen from:
  • monomers comprising a carbon-carbon double bond bound to a carboxylic group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and their sodium, potassium or ammonia salts, or 'amine,
  • monomers comprising a carbon-carbon double bond linked to an ester group of the abovementioned carboxylic acids, such as 2-hydroxyethyl methacrylate, glycidyl methacrylate, dimethyl or diethylamino (ethyl or propyl) (meth) acrylate and their salts; as well as the quaternized derivatives of these cationic esters such as, for example, acryloxyethyltrimethylammonium chloride, 2-acrylamido-2-methylpropanesulphonic acid (AMPS), vinylsulfonic acid, vinylphosphoric acid, acid vinyllactic and their salts, acrylonitrile, N-vinylpyrrolidone, vinyl acetate, N-vinylimidazoline and its derivatives, N-vinylimidazole and diallylammonium derivatives such as dimethyldiallylammonium chloride, dimethyldiallylammonium bromide, diethyldiallylammonium chloride.
  • the thickness of organic polymer film may be between 50 and 1000 nm, preferably between 80 and 300 nm.
  • the walls of the mesa structures of the device of the invention are covered with a poly-4-vinyl film having a thickness of between 100 and 400 nanometers.
  • the polymer is preferably deposited on the substrate by an electrografting or spin-coating process.
  • Electrografting is a wet deposition technique based on initiation and then polymerization, by electro-induced chain propagation, of electroactive monomers on a surface to be coated.
  • electrografting requires:
  • the polymer is preferably deposited on a substrate according to one of the electrografting methods described in application FR 2 933 425.
  • One of the methods according to the invention comprises:
  • a protic solvent preferably water
  • a diazonium salt preferably a 4-nitrobenzene diazonium salt
  • the polymerizable monomer described above and soluble in said protic solvent preferably a vinylpyridine;
  • At least one acid in an amount sufficient to stabilize said diazonium salt by adjusting the pH of said solution to a value of less than 7, preferably less than 2.5;
  • the polarization of the surface to be covered by the film is carried out according to a pulsed mode of which each cycle is characterized by:
  • a polarization time T is between 0.01 and 1s, during which a potential difference or a current is applied to the substrate surface; and a rest period at potential or zero current with a duration of between 0.01 and 1 s.
  • the walls of the trench may be perpendicular to a plane parallel to the surface of the substrate or may form an angle greater than 90 ° with it.
  • the two walls of the trench form an angle greater than 90 ° with the surface of the substrate so that the section of the trench perpendicular to a plane parallel to the surface of the substrate is smaller at the bottom of the trench. 'at the opening of the trench.
  • the average diameter of the bottom of the trench is for example between 10 and 1000 microns, especially between 50 and 500 microns.
  • the substrate of the device may be chosen from the group consisting of Ge,
  • GaAs, and Si GaAs, and Si.
  • the first semiconductor material comprises for example an alloy selected from the group consisting of GaAs, GalnP, GaInAs, GaAsSb and GaInAsN
  • the second semiconductor material comprises for example an alloy selected from the group consisting of GaAs, Gain, GaInAs , GaAsSb and GaInAsN.
  • the semiconductor device comprises three the stack of three semiconductor materials: a first InGaAs semiconductor material, a second InGaAIAs semiconductor material, and a third InGaP semiconductor material.
  • the semiconductor device may comprise metal contacts, which are deposited on the surface of the second semiconductor material or an additional semiconductor material. These contacts generally comprise at least one element selected from the group consisting of Ti, Pd, Au and Ag.
  • the device of the invention may be a photovoltaic cell or a diode.
  • the device is said to have a multiple function, when it comprises at least two, preferably at least three, p-n junctions.
  • the device of the invention is a triple junction photovoltaic cell of the mesa type.
  • the solar cells of the invention may include a first electrical contact on the front side of the cell (the side exposed to solar radiation) and a second electrical contact placed on the back side of the cell (on the non-sun-exposed side).
  • the solar cells may be rear contact solar cells (i.e. having two electrical contacts located at the rear of the cell).
  • a second object of the invention is a method of manufacturing a semiconductor device comprising the following succession of steps:
  • the method of the invention is a method of manufacturing a solar cell by providing a substrate; depositing on the substrate the stack of at least two layers of different semiconductor materials; deposition of metallic contact lines on the surface of the stack; depositing a photosensitive resin to cover the metal contact lines and the surface of the stack not covered with metal contact lines; etching of hollows until the outcropping of semiconductor materials; and electrografting an organic polymer as described above on the surface of semiconductor materials flush with the walls of the recesses.
  • the deposition of a photosensitive resin is carried out by a photolithography technique known to those skilled in the art.
  • Figure 1A shows a cross-sectional view of a semiconductor device with a mesa structure of the prior art.
  • Figure 1B shows a cross-sectional view of a semiconductor device with a mesa structure according to the present invention.
  • the device of the invention differs from that of the prior art by the presence of an organic polymer film deposited on the wall of the recesses defining the mesas.
  • the device of the prior art and the device of the invention comprise a substrate (1) covered by the stack of three semiconductor materials (2) defining three pn junctions.
  • the semiconductor stack (2) is covered with conductive metal lines (3) themselves completely covered with a resin film photosensitive (4).
  • the two devices shown in the Figures each comprise two mesas separated by a trench (5) which has been cut to flush the three semiconductor materials and the substrate (1).
  • the surface of the trench is covalently bonded to an insulating organic polymer film (6), so that the film suppresses electronic recombinations that may occur at the pn junctions during operation. said device.
  • the substrate used in this example was a 4 cm (4 x 4 cm) and 750 ⁇ m thick coupon comprising triple-junction mesa-type photovoltaic cells.
  • the surface of the sample was covered with a photolithography resin except in the 100 ⁇ m wide trenches present on the sample. Solution:
  • the electrografting solution used in this example was an aqueous solution prepared by introducing 5 ml of 4-vinylpyridine (4-VP, 4.5 ⁇ 10 -2 mol) in 95 ml of 1M HCl and then adding to the mixture consisting of 236 mg of 4-nitrobenzene diazonium tetrafluoroborate (DN0 2 , 1.10 3 mol).
  • the lamp was placed for this at a distance of about 10 cm from the surface of the sample. The sample was illuminated for the duration of the experiment.
  • Electrografting of P4VP occurred locally on the walls and bottom of the trenches of 100 ⁇ m in width. Electrografting of P4VP was created by imposing the substrate, previously rotated at a speed of 40 to 100 r 1 (60 tr.min in Example 1), an electrochemical protocol "potentiokinetic pulsed" for a predetermined duration of the order of 10 to 30 minutes (15 minutes in the example), with:
  • a polarization time T is between 0.01 and 1 second (0.02 second in the example) during which a potential difference of 0.1 V to 10 V is imposed on the surface of the substrate (cathodic potential of -0.5 V in the example);
  • T off a zero potential rest period noted T off of a duration of between 0.01 and 1 second (0.200 seconds in the example).
  • This electrografting step dependsed, as understood, on the desired thickness of the polymer insulating layer. This time can be easily determined by those skilled in the art, the growth of the layer being a function of the applied potential difference.
  • a scanning electron microscopy (SEM) analysis made it possible to visualize the presence of a homogeneous polymer film on the surface of the sample consisting of mesa-type photovoltaic cells having a triple pn junction.
  • the electrografted film was present only on the walls and the bottom of the trenches of the made of the presence of the photolithography resin on the upper part of the sample thus protecting the gold contacts on the surface of the photovoltaic cell.
  • Electrical tests were carried out in order to highlight the beneficial effect of a layer of electrografted polymer on the walls of the trenches present in the photovoltaic cells, this insulating layer making it possible to limit the phenomena of recombination of the electrons at this interface.
  • Open circuit potential measurements showed an improvement in E oc from 2.731 V to 2.751 V for photovoltaic cells with a surface area of 567 pm 2 .

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Abstract

The invention relates to semiconductor devices, especially voltaic cells with a vertical multi-junction structure, having an improved electrical performance. The invention also relates to a method for producing said devices. The efficiency of said small mesa-type photovoltaic cells is improved by preventing the phenomena of recombinations of the electrons at the interfaces as a result of electrografting a polymer at the surface of the junctions.

Description

Dispositif semi-conducteur mésa et procédé de fabrication  Mesa semiconductor device and method of manufacture
La présente invention concerne des dispositifs semi-conducteurs à structure multi-jonction verticale, notamment des cellules voltaïques, présentant un rendement électrique amélioré. L'invention concerne également un procédé de fabrication de ces dispositifs. The present invention relates to semiconductor devices having a vertical multi-junction structure, particularly voltaic cells, having an improved electrical efficiency. The invention also relates to a method of manufacturing these devices.
L'efficacité des dispositifs semi-conducteurs de type mésa, et plus particulièrement ceux de petite taille, peut être améliorée en empêchant les phénomènes de recombinaisons des électrons au niveau des interfaces qui laissent affleurer plusieurs matériaux semi-conducteurs différents. Il a été proposé dans l'art antérieur de recouvrir les interfaces de dioxyde de silicium, ou de traiter les tranches de matériaux semi-conducteurs affleurant par passivation, la passivation ayant pour résultat de transformer la surface du matériau en oxyde ou en nitrure.  The efficiency of the mesa-type semiconductor devices, and more particularly those of small size, can be improved by preventing electron recombination phenomena at the interfaces that leave several different semiconductor materials flush. It has been proposed in the prior art to cover the silicon dioxide interfaces, or to treat the wafers of passivating flush semiconductor materials, the passivation resulting in transforming the surface of the material into oxide or nitride.
Les procédés de passivation présentent cependant l'inconvénient d'être réalisés en phase vapeur (Chemical Vapor Déposition) ou par oxydation thermique, ce qui nécessite l'utilisation d'équipements coûteux à des températures élevées, typiquement entre 200 et 450 °C.  However, passivation processes have the disadvantage of being carried out in the vapor phase (Chemical Vapor Deposition) or by thermal oxidation, which requires the use of expensive equipment at high temperatures, typically between 200 and 450 ° C.
L'utilisation de polymères tels que les polyimides pour isoler la surface des semi-conducteurs a également été suggérée. Cependant, ces polymères ne permettent pas d'engager des liaisons chimiques avec les constituants des matériaux semiconducteurs, si bien que les phénomènes de recombinaisons électroniques ne peuvent pas être totalement exclus, que des fissures peuvent se créer plus facilemenFclëns le film isolant, et que l'adhésion du film sur les matériaux semi-conducteurs est médiocre.  The use of polymers such as polyimides to isolate the surface of semiconductors has also been suggested. However, these polymers do not make it possible to initiate chemical bonds with the constituents of the semiconductor materials, so that the phenomena of electronic recombinations can not be totally excluded, that cracks can be created more easily in the insulating film, and that the Film adhesion to semiconductor materials is poor.
La présente invention propose donc un procédé de fabrication d'un dispositif et un dispositif qui remédient à ces inconvénients. Le procédé de l'invention peut être mis en œuvre à des températures bien inférieures et par voie humide, si bien que les dispositifs semi-conducteurs obtenus ont une bonne, voire une meilleure rentabilité énergétique tout en étant produit à moindre coût. Les propriétés mécaniques du dispositif de l'invention sont également améliorées, en ce qui concerne notamment l'adhésion et la cohésion du film isolant.  The present invention therefore proposes a method of manufacturing a device and a device that overcomes these disadvantages. The process of the invention can be carried out at much lower temperatures and wet, so that the semiconductor devices obtained have good or even better energy efficiency while being produced at lower cost. The mechanical properties of the device of the invention are also improved, particularly as regards the adhesion and the cohesion of the insulating film.
Un premier objet de l'invention est un dispositif semi-conducteur de structure mésa comprenant un premier matériau semi-conducteur et un deuxième matériau semiconducteur différent du premier, qui sont en contact l'un avec l'autre et déposés sur un substrat de manière à créer aux moins une jonction p-n, ledit dispositif comportant des tranchées dont au moins une surface laisse affleurer les deux matériaux et éventuellement le substrat, A first object of the invention is a semiconductor device of mesa structure comprising a first semiconductor material and a second semiconductor material different from the first, which are in contact with one another and deposited on a substrate in a manner that to create at least one pn junction, said device comprising trenches of which at least one surface is flush with the two materials and optionally the substrate,
caractérisé en ce que ladite surface de la tranchée est liée par liaisons covalentes à un film de polymère organique isolant, si bien que ledit film peut supprimer les recombinaisons électroniques susceptibles de se produire au niveau de la ou des jonctions p-n pendant le fonctionnellement dudit dispositif éclairé ou mis sous tension.  characterized in that said surface of the trench is covalently bonded to an insulating organic polymer film, whereby said film can suppress electronic recombinations likely to occur at the pn junction (s) during the operation of said illuminated device or turned on.
Les dispositifs de l'invention comprennent un empilement de plusieurs matériaux semi-conducteurs dans lequel les phénomènes de recombinaison électronique sont limités voire supprimés.  The devices of the invention comprise a stack of several semiconductor materials in which the electronic recombination phenomena are limited or even eliminated.
La diminution des recombinaisons électroniques dans une cellule photovoltaïque de l'invention peut être évaluée en mesurant le potentiel à circuit ouvert du dispositif (Eoc). Selon un mode de réalisation de l'invention, le film de polymère organique permet un gain de la valeur Eoc compris entre 0,5 et 1% par rapport au même dispositif dépourvu de film isolant dans le cas de cellules photovoltaïques ayant une surface comprise entre 400 et 700 pm2, de préférence entre 500 et 600 pm2'. Le potentiel à circuit ouvert Eoc du dispositif de l'invention peut être compris entre 2,700 et 2,800 V, de préférence entre 2,750 et 2,760 V. The reduction of electronic recombinations in a photovoltaic cell of the invention can be evaluated by measuring the open-circuit potential of the device (E oc ). According to one embodiment of the invention, the organic polymer film allows a gain of the value E oc of between 0.5 and 1% relative to the same device without an insulating film in the case of photovoltaic cells having a surface area of between 400 and 700 pm 2 , preferably between 500 and 600 pm 2 '. The open-circuit potential E oc of the device of the invention can be between 2,700 and 2,800 V, preferably between 2,750 and 2,760 V.
Les mésas des cellules photovoltaïques de l'invention peuvent avoir une forme carrée de côté compris entre 20 et 40 microns. La hauteur des mésas est par exemple de l'ordre de 50 à 150 microns.  The mesas of the photovoltaic cells of the invention may have a square side shape of between 20 and 40 microns. The height of the mesas is for example of the order of 50 to 150 microns.
La présente invention permet de limiter les phénomènes de recombinaisons en recouvrant les murs des tranchées à l'aide d'un polymère organique isolant de l'électricité. Le film de polymère est déposé sur la surface de la tranchée de préférence par électrogreffage. L'électrogreffage permet d'obtenir une couche solidement greffée, en une seule étape, de façon sélective (i.e. en recouvrant les matériaux semiconducteurs snas recouvrir les autres éléments du dispositif qui sont exposés à la solution de polymère ou de monomères) ce qu'aucune autre méthode de passivation actuelle ne peut réaliser.  The present invention makes it possible to limit the recombination phenomena by covering the walls of the trenches with the aid of an organic polymer that insulates electricity. The polymer film is deposited on the surface of the trench preferably by electrografting. Electrografting makes it possible to obtain a solidly grafted layer, in a single step, selectively (ie by covering the semiconductor materials that cover the other elements of the device that are exposed to the polymer or monomer solution). other current passivation method can not achieve.
Le polymère organique utilisé dans le cadre de l'invention comprend des groupes fonctionnels libres capables d'engager des liaisons avec les matériaux semiconducteurs et le substrat de façon sélective. Au contraire, les polymères polyimides suggérés dans l'art antérieur comme isolant ne comprennent pas de tels groupements fonctionnels. Les liaisons entre le film de polymère et les matériaux semi-conducteurs peuvent être des liaisons covalentes ou des liaisons non covalentes, par exemple de nature ionique, hydrogène ou de Van der Waals. The organic polymer used in the context of the invention comprises free functional groups capable of engaging bonds with the semiconductor materials and the substrate selectively. In contrast, the polyimide polymers suggested in the prior art as an insulator do not include such functional groups. The bonds between the polymer film and the semiconductor materials may be covalent bonds or non-covalent bonds, for example ionic, hydrogen or van der Waals.
Le polymère organique peut être obtenu à partir d'un monomère vinylique comportant un ou plusieurs groupements fonctionnels non polymérisables susceptibles de se lier par liaisons covalentes à la surface des tranchées encadrant le mésa.  The organic polymer can be obtained from a vinyl monomer comprising one or more non-polymerizable functional groups capable of binding by covalent bonds to the surface of the trenches surrounding the mesa.
Le polymère peut être choisi parmi les polymères comportant un ou plusieurs groupements fonctionnels choisis parmi les groupements aminé primaire, aminé secondaire, énamine, alcool, thiol, acide carboxylique, hétérocyclique non aromatique et hétérocyclique aromatique, notamment hétérocycle aromatique azoté tel que pyridine, pyrrole ou thiophène.  The polymer may be chosen from polymers comprising one or more functional groups chosen from the primary amine, secondary amine, enamine, alcohol, thiol, carboxylic acid, non-aromatic heterocyclic and aromatic heterocyclic groups, in particular nitrogenous aromatic heterocycles such as pyridine, pyrrole or thiophene.
Le polymère est par exemple obtenu à partir d'au moins un monomère carboné polymérisable comprenant au moins un groupement fonctionnel tel que décrit précédemment.  The polymer is for example obtained from at least one polymerizable carbonaceous monomer comprising at least one functional group as described above.
On préfère des monomères polymérisables en chaîne par voie radicalaire, comme les monomères vinyliques par exemple. Aussi, les monomères seront avantageusement choisis parmi les monomères vinyliques solubles dans l'eau comprenant au moins un groupement fonctionnel susceptible d'engager une liaison non covalente avec un ion métallique.  Radically polymerizable chain monomers, such as vinyl monomers, are preferred. Also, the monomers will advantageously be chosen from water-soluble vinyl monomers comprising at least one functional group capable of initiating a non-covalent bond with a metal ion.
De tels monomères seront avantageusement choisis parmi les poly(vinyl- amine)s, en particulier choisis parmi les dérivés vinyliques des aminés telles que :  Such monomers will advantageously be chosen from polyvinylamines, in particular chosen from vinyl derivatives of amines such as:
- les aminés aliphatiques primaires, en particulier éthylamine, cyclohexylamine, cyclohexanediamine ;  primary aliphatic amines, in particular ethylamine, cyclohexylamine, cyclohexanediamine;
- les aminés aliphatiques secondaires, en particulier pyrrolidine ;  secondary aliphatic amines, in particular pyrrolidine;
- les aminés aliphatiques tertiaires, en particulier hydroxyéthyldiéthylamine, tétraéthylènepentamine ;  tertiary aliphatic amines, in particular hydroxyethyldiethylamine, tetraethylenepentamine;
- les aminés aromatiques, en particulier 1,2- diaminobenzène, 3,5- diméthylaniline ;  aromatic amines, in particular 1,2-diaminobenzene, 3,5-dimethylaniline;
- les hétérocycles azotés, en particulier pyridine, 2,2'-bipyridine, 8- hydroxyquinoléine sulfonate, 1,10-phénanthroline, 3,5- diméthylpyridine, 2,2'- bipyrimidine ;  nitrogen heterocycles, in particular pyridine, 2,2'-bipyridine, 8-hydroxyquinoline sulphonate, 1,10-phenanthroline, 3,5-dimethylpyridine, 2,2'-bipyrimidine;
- les oximes, en particulier diméthylglyoxime.  oximes, in particular dimethylglyoxime.
en particulier les polymères d'un hétérocycle aromatique azoté vinylique. Dans les poly(vinyl-amine)s utilisées dans le cadre de l'invention, les atomes d'azote ne sont pas liés au groupement vinyl, de telle sorte que l'atome d'azote reste disponible pour se lier aux ions métalliques. in particular the polymers of a vinyl nitrogen aromatic heterocycle. In the poly (vinyl amines) used in the context of the invention, the nitrogen atoms are not bonded to the vinyl group, so that the nitrogen atom remains available to bind to the metal ions.
Les monomères sont par exemple choisis parmi les monomères carbonés insaturés azotés et de leurs thio-analogues, dont :  The monomers are, for example, chosen from unsaturated nitrogen-containing carbon monomers and their thio-analogues, of which:
- les vinylpyridines telles que la 2-vinylpyridine ou la 4-vinylpyridine; et les vinylpyridines N-substituées par un alkyle inférieur (C1-C8) telles que la 2-méthyl-5- vinyl-pyridine, la 2-éthyl-5-vinylpyridine, la 3-méthyl-5-vinylpyridine, la 2,3-diméthyl-5- vinyl-pyridine, et la 2-méthyl-3-éthyl -5-vinylpyridine;  vinylpyridines such as 2-vinylpyridine or 4-vinylpyridine; and N-lower alkyl (C1-C8) vinylpyridines such as 2-methyl-5-vinylpyridine, 2-ethyl-5-vinylpyridine, 3-methyl-5-vinylpyridine, 2,3 5-dimethyl-5-vinylpyridine and 2-methyl-3-ethyl-5-vinylpyridine;
- les vinylquinoléines, les vinylpyrrolidones; les vinylimidazoles, les vinylcarbazoles et les vinyl-succinimide.  vinylquinolines and vinylpyrrolidones; vinylimidazoles, vinylcarbazoles and vinylsuccinimide.
Dans un mode de réalisation, le monomère est la 4-vinylpyridine ou la 2- vinylpyridine.  In one embodiment, the monomer is 4-vinylpyridine or 2-vinylpyridine.
Les monomères peuvent être également choisis parmi :  The monomers may also be chosen from:
- les monomères comportant une double liaison carbone-carbone liée à un groupement carboxylique comme l'acide acrylique, l'acide méthacrylique, l'acide itaconique, l'acide maléique, l'acide fumarique et leurs sels sodiques, potassiques, ammoniacaux ou d'amine,  monomers comprising a carbon-carbon double bond bound to a carboxylic group such as acrylic acid, methacrylic acid, itaconic acid, maleic acid, fumaric acid and their sodium, potassium or ammonia salts, or 'amine,
- les monomères comportant une double liaison carbone-carbone liée à un groupement amide des acides carboxyliques précités, et en particulier, l'acrylamide et le méthacrylamide ainsi que leurs dérivés N-substitués,  monomers comprising a carbon-carbon double bond linked to an amide group of the abovementioned carboxylic acids, and in particular acrylamide and methacrylamide and their N-substituted derivatives,
- les monomères comportant une double liaison carbone-carbone liée à un groupement ester des acides carboxyliques précités tels que le 2-hydroxyéthyl méthacrylate, le méthacrylate de glycidyle, le diméthyl ou le diéthyl amino (éthyl ou propyl) (méth) acrylate et leurs sels, ainsi que les dérivés quaternisés de ces esters cationiques comme, par exemple, le chlorure d'acryloxyéthyl triméthylammonium, l'acide 2-acrylamido-2- méthylpropane sulfonique (AMPS), l'acide vinylsulfonique, l'acide vinylphosphorique, l'acide vinyllactique et leurs sels, l'acrylonitrile, la N-vinylpyrrolidone, l'acétate de vinyle, le N-vinylimidazoline et ses dérivés, le N- vinylimidazole et les dérivés du type diallylammonium comme le chlorure de diméthyldiallylammonium, le bromure de diméthyldiallylammonium, le chlorure de diéthyldiallylammonium.  monomers comprising a carbon-carbon double bond linked to an ester group of the abovementioned carboxylic acids, such as 2-hydroxyethyl methacrylate, glycidyl methacrylate, dimethyl or diethylamino (ethyl or propyl) (meth) acrylate and their salts; as well as the quaternized derivatives of these cationic esters such as, for example, acryloxyethyltrimethylammonium chloride, 2-acrylamido-2-methylpropanesulphonic acid (AMPS), vinylsulfonic acid, vinylphosphoric acid, acid vinyllactic and their salts, acrylonitrile, N-vinylpyrrolidone, vinyl acetate, N-vinylimidazoline and its derivatives, N-vinylimidazole and diallylammonium derivatives such as dimethyldiallylammonium chloride, dimethyldiallylammonium bromide, diethyldiallylammonium chloride.
L'épaisseur de film de polymère organique peut être comprise entre 50 et 1000 nm, de préférence entre 80 et 300 nm. Selon un mode de réalisation particulier, les parois des structures mésas du dispositif de l'invention sont recouvertes d'un film de poly-4-vi ny I py ri d i ne d'une épaisseur comprise entre 100 et 400 nanomètres. The thickness of organic polymer film may be between 50 and 1000 nm, preferably between 80 and 300 nm. According to a particular embodiment, the walls of the mesa structures of the device of the invention are covered with a poly-4-vinyl film having a thickness of between 100 and 400 nanometers.
Le polymère est de préférence déposé sur le substrat par un procédé d'électrogreffage ou d'enduction centrifuge (spin-coating).  The polymer is preferably deposited on the substrate by an electrografting or spin-coating process.
L'électrogreffage est une technique de dépôt par voie humide basée sur l'initiation puis la polymérisation, par propagation en chaîne électro-induite, de monomères électro-actifs sur une surface à recouvrir.  Electrografting is a wet deposition technique based on initiation and then polymerization, by electro-induced chain propagation, of electroactive monomers on a surface to be coated.
D'une façon générale, l'électrogreffage requiert :  In general, electrografting requires:
- d'une part, l'utilisation d'une solution liquide contenant un composé initiateur et du monomère décrit précédemment; et  on the one hand, the use of a liquid solution containing an initiator compound and the monomer described above; and
- d'autre part, un protocole électrochimique permettant la réaction de polymérisation et la formation d'un film de polymère à la surface du substrat à revêtir.  - On the other hand, an electrochemical protocol for the polymerization reaction and the formation of a polymer film on the surface of the substrate to be coated.
Le polymère est de préférence déposé sur un substrat selon un des procédés d'électrogreffage décrits dans la demande FR 2 933 425. Un des procédés conforme à l'invention comprend :  The polymer is preferably deposited on a substrate according to one of the electrografting methods described in application FR 2 933 425. One of the methods according to the invention comprises:
a) la mise en contact de ladite surface avec une solution liquide comprenant :  a) bringing said surface into contact with a liquid solution comprising:
- un solvant protique, de préférence l'eau ;  a protic solvent, preferably water;
- un sel de diazonium, de préférence un sel de 4-nitrobenzène diazonium;  a diazonium salt, preferably a 4-nitrobenzene diazonium salt;
- le monomère polymérisable décrit précédemment et soluble dans ledit solvant protique, de préférence une vinyl-pyridine;  the polymerizable monomer described above and soluble in said protic solvent, preferably a vinylpyridine;
- au moins un acide en une quantité suffisante pour stabiliser ledit sel de diazonium par ajustement du pH de ladite solution à une valeur inférieure à 7, de préférence inférieure à 2,5 ;  at least one acid in an amount sufficient to stabilize said diazonium salt by adjusting the pH of said solution to a value of less than 7, preferably less than 2.5;
b) la polarisation de ladite surface selon un mode potentio- ou galvano- pulsé.  b) polarizing said surface in a potentio- or galvano-pulsed mode.
D'une façon générale, la polarisation de la surface à recouvrir par le film est réalisée selon un mode puisé dont chaque cycle est caractérisé par :  In general, the polarization of the surface to be covered by the film is carried out according to a pulsed mode of which each cycle is characterized by:
- une période totale P comprise entre 10 ms et 2 s;  a total period P of between 10 ms and 2 s;
- un temps de polarisation Ton compris entre 0,01 et 1 s, durant lequel une différence de potentiel ou un courant est imposé à la surface du substrat ; et - un temps de repos à potentiel ou courant nul d'une durée comprise entre 0,01 et 1 s. - a polarization time T is between 0.01 and 1s, during which a potential difference or a current is applied to the substrate surface; and a rest period at potential or zero current with a duration of between 0.01 and 1 s.
Les parois de la tranchée peuvent être perpendiculaires à un plan parallèle à la surface du substrat ou former un angle supérieur à 90° avec celui-ci. Sur la Figure 1B, les deux parois de la tranchée forment un angle supérieur à 90° avec la surface du substrat si bien que la section de la tranchée perpendiculaire à un plan parallèle à la surface du substrat est plus petite au fond de la tranchée qu'à l'ouverture de la tranchée. Le diamètre moyen du fond de la tranchée est par exemple compris entre 10 et 1000 microns, notamment entre 50 et 500 microns.  The walls of the trench may be perpendicular to a plane parallel to the surface of the substrate or may form an angle greater than 90 ° with it. In FIG. 1B, the two walls of the trench form an angle greater than 90 ° with the surface of the substrate so that the section of the trench perpendicular to a plane parallel to the surface of the substrate is smaller at the bottom of the trench. 'at the opening of the trench. The average diameter of the bottom of the trench is for example between 10 and 1000 microns, especially between 50 and 500 microns.
Le substrat du dispositif peut être choisi dans le groupe constitué par le Ge, The substrate of the device may be chosen from the group consisting of Ge,
GaAs, et Si. GaAs, and Si.
Le premier matériau semi-conducteur comprend par exemple un alliage choisi dans le groupe constitué par GaAs, GalnP, GaInAs, GaAsSb et GaInAsN, et le deuxième matériau semi-conducteur comprend par exemple un alliage choisi dans le groupe constitué par GaAs, Gain, GaInAs, GaAsSb et GaInAsN.  The first semiconductor material comprises for example an alloy selected from the group consisting of GaAs, GalnP, GaInAs, GaAsSb and GaInAsN, and the second semiconductor material comprises for example an alloy selected from the group consisting of GaAs, Gain, GaInAs , GaAsSb and GaInAsN.
Dans un mode de réalisation particulier, le dispositif semi-conducteur comprend trois l'empilement de trois matériaux semi-conducteurs : un premier matériau semiconducteur InGaAs, un deuxième matériau semi-conducteur InGaAIAs, et un troisième matériau semi-conducteur InGaP.  In a particular embodiment, the semiconductor device comprises three the stack of three semiconductor materials: a first InGaAs semiconductor material, a second InGaAIAs semiconductor material, and a third InGaP semiconductor material.
Le dispositif semi-conducteur peut comprendre des contacts métalliques, qui sont déposés à la surface du deuxième matériau semi-conducteur ou d'un matériau semi-conducteur additionnel. Ces contacts comprennent généralement au moins un élément choisi dans le groupe constitué par Ti, Pd, Au et Ag.  The semiconductor device may comprise metal contacts, which are deposited on the surface of the second semiconductor material or an additional semiconductor material. These contacts generally comprise at least one element selected from the group consisting of Ti, Pd, Au and Ag.
Le dispositif de l'invention peut être une cellule photovoltaïque ou une diode. Le dispositif est dit à fonction multiple, lorsqu'il comprend au moins deux, de préférence au moins trois jonctions p-n. Dans un mode de réalisation particulier, le dispositif de l'invention est une cellule photovoltaïque à triple jonction de type mésa.  The device of the invention may be a photovoltaic cell or a diode. The device is said to have a multiple function, when it comprises at least two, preferably at least three, p-n junctions. In a particular embodiment, the device of the invention is a triple junction photovoltaic cell of the mesa type.
Les cellules solaires de l'invention peuvent comporter un premier contact électrique sur la face avant de la cellule (le côté exposé au rayonnement solaire) et un deuxième contact électrique placé sur le côté arrière de la cellule (du côté non exposé au soleil). Alternativement, les cellules solaires peuvent être des cellules solaires à contact arrière (i.e. ayant deux contacts électriques situés à l'arrière de la cellule).  The solar cells of the invention may include a first electrical contact on the front side of the cell (the side exposed to solar radiation) and a second electrical contact placed on the back side of the cell (on the non-sun-exposed side). Alternatively, the solar cells may be rear contact solar cells (i.e. having two electrical contacts located at the rear of the cell).
Les dispositifs de l'invention peuvent être disposés selon un quadrillage pour fabriquer des modules, par exemple des modules photovoltaïques ou des panneaux solaire. Un deuxième objet de l'invention est un procédé de fabrication d'un dispositif semi-conducteur comprenant la succession d'étapes suivante : The devices of the invention may be arranged according to a grid to produce modules, for example photovoltaic modules or solar panels. A second object of the invention is a method of manufacturing a semiconductor device comprising the following succession of steps:
- l'empilement d'au moins deux matériaux semi-conducteurs différents sur un substrat semi-conducteur de manière à créer au moins une jonction p-n,  stacking at least two different semiconductor materials on a semiconductor substrate so as to create at least one p-n junction,
- le dépôt de lignes de métal conducteur à la surface de l'empilement,  depositing conductive metal lines on the surface of the stack,
- le dépôt d'une couche de résine photosensible par photolithographie à la surface de l'empilement pour recouvrir les lignes de métal conducteur,  depositing a layer of photosensitive resin by photolithography on the surface of the stack to cover the conductive metal lines,
- la gravure de tranchées dans un sens vertical à un plan parallèle à la surface de l'empilement de manière à laisser affleurer les matériaux semi-conducteurs et éventuellement le substrat,  the etching of trenches in a vertical direction at a plane parallel to the surface of the stack so as to leave the semiconductor materials and possibly the substrate flush,
- le dépôt sélectif d'un polymère par électrogreffage sur la surface des matériaux semi-conducteurs affleurant sur les parois des tranchées gravées.  the selective deposition of a polymer by electrografting on the surface of semiconductor materials flush with the walls of the etched trenches.
Selon un mode de réalisation particulier le procédé de l'invention est un procédé de fabrication d'une cellule solaire par fourniture d'un substrat; dépôt sur le substrat de l'empilement d'au moins deux couches de matériaux semi-conducteurs différents ; dépôt de lignes de contact métallique à la surface de l'empilement; dépôt d'une résine photosensible pour recouvrir les lignes de contact métallique et la surface de l'empilement non recouvert de lignes de contact métallique ; gravure de creux jusqu'à affleurement des matériaux semi-conducteurs ; et électrogreffage d'un polymère organique tel que décrit précédemment sur la surface des matériaux semi-conducteurs affleurant sur les parois des creux.  According to a particular embodiment, the method of the invention is a method of manufacturing a solar cell by providing a substrate; depositing on the substrate the stack of at least two layers of different semiconductor materials; deposition of metallic contact lines on the surface of the stack; depositing a photosensitive resin to cover the metal contact lines and the surface of the stack not covered with metal contact lines; etching of hollows until the outcropping of semiconductor materials; and electrografting an organic polymer as described above on the surface of semiconductor materials flush with the walls of the recesses.
Le dépôt d'une résine photosensible est effectué par une technique de photolithographie connue de l'homme du métier.  The deposition of a photosensitive resin is carried out by a photolithography technique known to those skilled in the art.
Les caractéristiques qui ont été décrites en rapport avec le premier objet de l'invention s'appliquent au deuxième objet de l'invention.  The features which have been described in connection with the first subject of the invention apply to the second subject of the invention.
La Figure 1A représente une vue en coupe transversale d'un dispositif semiconducteur doté d'une structure mésa de l'art antérieur.  Figure 1A shows a cross-sectional view of a semiconductor device with a mesa structure of the prior art.
La Figure 1B représente une vue en coupe transversale d'un dispositif semiconducteur doté d'une structure mésa selon la présente invention.  Figure 1B shows a cross-sectional view of a semiconductor device with a mesa structure according to the present invention.
Le dispositif de l'invention diffère de celui de l'art antérieur par la présence d'un film de polymère organique déposé sur la paroi des creux définissant les mésas.  The device of the invention differs from that of the prior art by the presence of an organic polymer film deposited on the wall of the recesses defining the mesas.
Le dispositif de l'art antérieur et le dispositif de l'invention comprennent un substrat (1) recouvert par l'empilement de trois matériaux semi-conducteurs (2) définissant trois jonctions p-n. L'empilement de semi-conducteurs (2) est recouvert de lignes de métal conducteur (3) elles-mêmes entièrement recouvertes d'un film de résine photosensible (4). Les deux dispositifs représentés sur les Figures comprennent chacun deux mésas séparées par une tranchée (5) qui a été creusée pour faire affleurer les trois matériaux semi-conducteurs et le substrat (1). Dans le dispositif de l'invention, la surface de la tranchée est liée par liaisons covalentes à un film de polymère organique isolant (6), si bien que le film supprime les recombinaisons électroniques susceptibles de se produire au niveau des jonctions p-n pendant le fonctionnement dudit dispositif. The device of the prior art and the device of the invention comprise a substrate (1) covered by the stack of three semiconductor materials (2) defining three pn junctions. The semiconductor stack (2) is covered with conductive metal lines (3) themselves completely covered with a resin film photosensitive (4). The two devices shown in the Figures each comprise two mesas separated by a trench (5) which has been cut to flush the three semiconductor materials and the substrate (1). In the device of the invention, the surface of the trench is covalently bonded to an insulating organic polymer film (6), so that the film suppresses electronic recombinations that may occur at the pn junctions during operation. said device.
La demande est illustrée par les exemples suivants. Exemple - Fabrication d'une cellule photovoltaïque de type mésa comprenant un film de polymère The request is illustrated by the following examples. Example - Manufacture of a mesa-type photovoltaic cell comprising a polymer film
Préparation d'un film de poly-4-vinylpyridine (P4VP) sur le substrat : Preparation of a poly-4-vinylpyridine (P4VP) film on the substrate:
Le substrat utilisé dans cet exemple était un coupon de 4 cm de côté (4 x 4 cm) et de 750 pm d'épaisseur comprenant des cellules photovoltaïques de type mésa à triple jonction p-n. La surface de l'échantillon était recouverte d'une résine de photolithographie exceptée dans les tranchées de 100 pm de largeur présentes sur l'échantillon. Solution :  The substrate used in this example was a 4 cm (4 x 4 cm) and 750 μm thick coupon comprising triple-junction mesa-type photovoltaic cells. The surface of the sample was covered with a photolithography resin except in the 100 μm wide trenches present on the sample. Solution:
La solution d'électrogreffage mise en œuvre dans cet exemple était une solution aqueuse préparée en introduisant 5 ml de 4-vinylpyridine (4-VP; 4,5.10"2 mol) dans 95 ml d'HCI 1M, puis en ajoutant au mélange ainsi constitué 236 mg de 4-nitrobenzène diazonium tétrafluoroborate (DN02 ; 1.103 mol). The electrografting solution used in this example was an aqueous solution prepared by introducing 5 ml of 4-vinylpyridine (4-VP, 4.5 × 10 -2 mol) in 95 ml of 1M HCl and then adding to the mixture consisting of 236 mg of 4-nitrobenzene diazonium tetrafluoroborate (DN0 2 , 1.10 3 mol).
Protocole : Protocol:
Pour réaliser l'électrogreffage sur le substrat on a utilisé un système composé : To carry out the electrografting on the substrate, a compound system was used:
- d'un porte échantillon équipé de moyens de mise en rotation à vitesse prédéterminée et conformé pour supporter le substrat, l'ensemble ainsi constitué étant destiné à servir d'électrode de travail ; - A sample holder equipped with rotating means at a predetermined speed and shaped to support the substrate, the assembly thus formed being intended to serve as a working electrode;
- d'une feuille de carbone destinée à servir de contre électrode ;  a carbon sheet intended to serve as a counter electrode;
- d'une alimentation électrique stabilisée et d'un dispositif de mise en contact électrique - éventuellement d'une source lumineuse (lampe halogène, 150 W) placée devant l'échantillon de silicium dopé P, de façon à obtenir le maximum d'intensité lumineuse sur la surface de l'échantillon. La lampe a été placée pour cela à une distance d'environ 10 cm de la surface de l'échantillon. L'échantillon a été éclairé pendant toute la durée de l'expérience. - a stabilized power supply and an electrical contact device - possibly a light source (halogen lamp, 150 W) placed in front of the P-doped silicon sample, so as to obtain the maximum light intensity on the surface of the sample. The lamp was placed for this at a distance of about 10 cm from the surface of the sample. The sample was illuminated for the duration of the experiment.
Du fait de la présence de la résine en surface, l'électrogreffage de la P4VP s'est produit de façon localisée sur les parois et le fond des tranchées de 100 pm de largeur. L'électrogreffage de la P4VP a été réalisé en imposant au substrat, préalablement mis en rotation à une vitesse de 40 à 100 tr.min 1 (60 tr.min 1 dans l'exemple), un protocole électrochimique "potentio-pulsé" pendant une durée prédéterminée de l'ordre de 10 à 30 minutes (15 minutes dans l'exemple), avec : Due to the presence of the resin at the surface, electrografting of P4VP occurred locally on the walls and bottom of the trenches of 100 μm in width. Electrografting of P4VP was created by imposing the substrate, previously rotated at a speed of 40 to 100 r 1 (60 tr.min in Example 1), an electrochemical protocol "potentiokinetic pulsed" for a predetermined duration of the order of 10 to 30 minutes (15 minutes in the example), with:
- une période totale P comprise entre 0,01 et 2 secondes (0,220 seconde dans l'exemple);  a total period P of between 0.01 and 2 seconds (0.220 seconds in the example);
- un temps de polarisation Ton compris entre 0,01 et 1 seconde (0,02 seconde dans l'exemple) durant lequel une différence de potentiel de 0,1 V à 10 V est imposée à la surface du substrat (potentiel cathodique de -0,5 V dans l'exemple) ; et a polarization time T is between 0.01 and 1 second (0.02 second in the example) during which a potential difference of 0.1 V to 10 V is imposed on the surface of the substrate (cathodic potential of -0.5 V in the example); and
- un temps de repos à potentiel nul noté Toff d'une durée comprise entre 0,01 et 1 seconde (0,200 seconde dans l'exemple). a zero potential rest period noted T off of a duration of between 0.01 and 1 second (0.200 seconds in the example).
La durée de cette étape d'électrogreffage dépendait, comme on le comprend, de l'épaisseur souhaitée de la couche isolante de polymère. Cette durée peut être facilement déterminée par l'homme du métier, la croissance de la couche étant fonction de la différence de potentiel appliquée.  The duration of this electrografting step depended, as understood, on the desired thickness of the polymer insulating layer. This time can be easily determined by those skilled in the art, the growth of the layer being a function of the applied potential difference.
Dans les conditions précitées, on a obtenu une couche de polymère (P4VP) présentant une épaisseur de 200 nanomètres et localisée uniquement sur les parois et le fond des tranchées de 100 pm de largeur.  Under the above conditions, there was obtained a polymer layer (P4VP) having a thickness of 200 nanometers and located only on the walls and the bottom of the trenches of 100 μm in width.
Une fois l'électrogreffage terminé, l'échantillon a été rincé plusieurs fois à l'eau avant d'être séché sous courant d'argon puis à l'étuve sous atmosphère inerte pendant 10 min (250°C). Caractérisations :  Once the electrografting was completed, the sample was rinsed several times with water before being dried under a stream of argon and then in an oven under an inert atmosphere for 10 min (250 ° C). Characterizations:
Une analyse en microscopie électronique à balayage (MEB) a permis de visualiser la présence d'un film homogène de polymère sur la surface de l'échantillon constituée de cellules photovoltaïques de type mésa présentant une triple jonction p-n. Le film électrogreffé était présent uniquement sur les parois et le fond des tranchées du fait de la présence de la résine de photolithographie sur la partie supérieur de l'échantillon protégeant ainsi les contacts en or sur la surface de la cellule photovoltaïque. Des tests électriques ont été effectués afin de mettre en avant l'effet bénéfique d'une couche de polymère électrogreffé sur les parois des tranchées présentes dans les cellules photovoltaïques, cette couche isolante permettant de limiter les phénomènes de recombinaison des électrons à cette interface. A scanning electron microscopy (SEM) analysis made it possible to visualize the presence of a homogeneous polymer film on the surface of the sample consisting of mesa-type photovoltaic cells having a triple pn junction. The electrografted film was present only on the walls and the bottom of the trenches of the made of the presence of the photolithography resin on the upper part of the sample thus protecting the gold contacts on the surface of the photovoltaic cell. Electrical tests were carried out in order to highlight the beneficial effect of a layer of electrografted polymer on the walls of the trenches present in the photovoltaic cells, this insulating layer making it possible to limit the phenomena of recombination of the electrons at this interface.
Les mesures de potentiel à circuit ouvert ont montré une amélioration du Eoc passant de 2,731 V à 2,751 V pour des cellules photovoltaïques ayant une surface de 567 pm2. Open circuit potential measurements showed an improvement in E oc from 2.731 V to 2.751 V for photovoltaic cells with a surface area of 567 pm 2 .

Claims

REVENDICATIONS
1. Dispositif semi-conducteur de structure mésa comprenant un premier matériau semi-conducteur et un deuxième matériau semi-conducteur différent du premier, qui sont en contact l'un avec l'autre et déposés sur un substrat de manière à créer aux moins une jonction p-n, ledit dispositif comportant des tranchées dont au moins une surface laisse affleurer les deux matériaux et le substrat, A semiconductor device of mesa structure comprising a first semiconductor material and a second semiconductor material different from the first, which are in contact with each other and deposited on a substrate so as to create at least one pn junction, said device comprising trenches of which at least one surface allows to be flush with the two materials and the substrate,
caractérisé en ce que ladite surface de la tranchée est liée par liaisons covalentes à un film de polymère organique isolant, si bien que ledit film supprime les recombinaisons électroniques susceptibles de se produire au niveau de la ou des jonctions pendant le fonctionnellement dudit dispositif.  characterized in that said surface of the trench is covalently bonded to an insulating organic polymer film, whereby said film suppresses electronic recombinations likely to occur at the junction (s) during the operation of said device.
2. Dispositif semi-conducteur selon la revendication 1, caractérisé en ce que le film de polymère est obtenu par un procédé d'électrogreffage.  2. Semiconductor device according to claim 1, characterized in that the polymer film is obtained by an electrografting process.
3. Dispositif semi-conducteur selon la revendication 1 ou 2, caractérisé en ce que le polymère est la poly-4-vinylpyridine.  3. Semiconductor device according to claim 1 or 2, characterized in that the polymer is poly-4-vinylpyridine.
4. Dispositif semi-conducteur selon l'une des revendications précédentes, caractérisé en ce que les matériaux semi-conducteurs sont des semi-conducteurs III-V, et que le dispositif est une cellule photovoltaïque à jonction multiple.  4. Semiconductor device according to one of the preceding claims, characterized in that the semiconductor materials are III-V semiconductors, and that the device is a multi-junction photovoltaic cell.
5. Dispositif semi-conducteur selon la revendication précédente, caractérisé en ce le premier matériau semi-conducteur comprend un alliage choisi dans le groupe constitué par GaAs, GalnP, GalnAs, GaAsSb et GalnAsN, et en ce que le deuxième matériau semi-conducteur comprend un alliage choisi dans le groupe constitué par GaAs, Gain, GalnAs, GaAsSb et GalnAsN.  5. Semiconductor device according to the preceding claim, characterized in that the first semiconductor material comprises an alloy selected from the group consisting of GaAs, GalnP, GalnAs, GaAsSb and GalnAsN, and in that the second semiconductor material comprises an alloy selected from the group consisting of GaAs, Gain, GalnAs, GaAsSb and GalnAsN.
6. Dispositif semi-conducteur selon l'une des revendications précédentes, caractérisé en ce que le polymère organique est obtenu à partir d'un monomère vinylique comportant un ou plusieurs groupements fonctionnels non polymérisables susceptibles de se lier par liaisons covalentes à la surface de la tranchée.  6. semiconductor device according to one of the preceding claims, characterized in that the organic polymer is obtained from a vinyl monomer comprising one or more non-polymerizable functional groups capable of binding by covalent bonds to the surface of the trench.
7. Procédé de fabrication d'un dispositif semi-conducteur comprenant la succession d'étapes suivante :  7. A method of manufacturing a semiconductor device comprising the following succession of steps:
- l'empilement d'au moins deux matériaux semi-conducteurs différents sur un substrat semi-conducteur de manière à créer au moins une jonction p-n,  stacking at least two different semiconductor materials on a semiconductor substrate so as to create at least one p-n junction,
- le dépôt de lignes de métal conducteur à la surface de l'empilement,  depositing conductive metal lines on the surface of the stack,
- le dépôt d'une couche de résine photosensible par photolithographie à la surface de l'empilement pour recouvrir les lignes de métal conducteur, - la gravure de tranchées dans un sens vertical à un plan parallèle à la surface de l'empilement de manière à laisser affleurer les matériaux semi-conducteurs et éventuellement le substrat, depositing a layer of photosensitive resin by photolithography on the surface of the stack to cover the conductive metal lines, the etching of trenches in a vertical direction at a plane parallel to the surface of the stack so as to leave the semiconductor materials and possibly the substrate flush,
- le dépôt sélectif d'un polymère par électrogreffage sur la surface des matériaux semi-conducteurs affleurant sur les parois des tranchées gravées.  the selective deposition of a polymer by electrografting on the surface of semiconductor materials flush with the walls of the etched trenches.
PCT/FR2014/053127 2013-12-02 2014-12-02 Mesa semiconductor device and production method WO2015082828A1 (en)

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