WO2011160819A2 - Method for fabrication of a back side contact solar cell - Google Patents

Method for fabrication of a back side contact solar cell Download PDF

Info

Publication number
WO2011160819A2
WO2011160819A2 PCT/EP2011/003066 EP2011003066W WO2011160819A2 WO 2011160819 A2 WO2011160819 A2 WO 2011160819A2 EP 2011003066 W EP2011003066 W EP 2011003066W WO 2011160819 A2 WO2011160819 A2 WO 2011160819A2
Authority
WO
WIPO (PCT)
Prior art keywords
diffusion region
silicon substrate
phosphorous
back side
phosphorous diffusion
Prior art date
Application number
PCT/EP2011/003066
Other languages
French (fr)
Other versions
WO2011160819A3 (en
Inventor
Valentin Dan Mihailetchi
Kristian Peter
Radovan Kopecek
Original Assignee
International Solar Energy Research Center Konstanz E.V.
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by International Solar Energy Research Center Konstanz E.V. filed Critical International Solar Energy Research Center Konstanz E.V.
Publication of WO2011160819A2 publication Critical patent/WO2011160819A2/en
Publication of WO2011160819A3 publication Critical patent/WO2011160819A3/en

Links

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/04—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
    • H01L31/0682—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 back-junction, i.e. rearside emitter, solar cells, e.g. interdigitated base-emitter regions back-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
    • H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/223—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a gaseous phase
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
    • H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
    • H01L21/2251—Diffusion into or out of group IV semiconductors
    • H01L21/2254—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides
    • H01L21/2255—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E10/00—Energy generation through renewable energy sources
    • Y02E10/50—Photovoltaic [PV] energy
    • Y02E10/547—Monocrystalline silicon PV cells
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
    • Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
    • Y02P70/50—Manufacturing or production processes characterised by the final manufactured product

Definitions

  • the invention relates to a method for fabrication of a back contact solar cell with the features of the preamble of claim 1 and a solar cell fabricated by application of said method.
  • Solar cells are well-known devices that convert light, i.e. electromagnetic radiation, to electrical energy.
  • the front side of a solar cell or of a substrate which is used to create a solar cell is the side that is facing the light when the solar cell is in use.
  • the back side (or rear side) of a solar cell or of a substrate which is used to create a solar cell is the side opposite to the front side.
  • a solar cell can be created by forming p-doped and n-doped regions in a semiconductor substrate, typically Silicon. Boron is frequently used as p-dopant and Phosphorous is frequently used as n-dopant. Light that impinges on the solar cell creates pairs of electrons and holes.
  • the thus created electrons and holes are typically moved into p-doped and n-doped regions by an electric field that is always generated when p-doped and n-doped regions are in contact with each other.
  • an electrical coupling the doped regions are coupled to contacts that are usually made from metal.
  • the n-doped regions at the front surface of the solar cell and at the back surface of the solar cell must match different conditions.
  • a high sheet resistance of the n-dopant Front Surface Field (FSF) will improve surface passivation.
  • FSF Front Surface Field
  • BSF Back Surface Field
  • the sheet resistance is largely determined by dopant concentration .
  • the method for fabrication of a back side contact solar cell comprises the steps of a) providing a crystalline silicon substrate with a front side and a back side and b) simultaneously diffusing a phosphorous dopant on at least part of said front side and at least part of said back side into said crystalline silicon substrate in such a way that a front phosphorous diffusion region with a first diffusion depth and a back phosphorous diffusion region with the same first diffusion depth are created and that during diffusion of said phosphorous dopant, a layer of phosphosili- cate glass is formed in situ on the front phosphorous diffusion region and a layer of phosphosilicate glass is formed in situ on the back phosphorous diffusion region.
  • step c) a dielectric coating film is formed on said phospho- silicate glass layer on at least part of the back side of the silicon substrate
  • step d) at least part of the phospho- silicate glass layer on the front side of the silicon substrate is removed
  • step e) the product obtained after performing the steps mentioned above is heated for a period of time at a temperature, wherein said period of time and that temperature are chosen in such a way that said front phospho- rous diffusion region and said back, phosphorous diffusion region expand further into the crystal up to a second diffusion depth that is different for the front phosphorous diffusion region and the back phosphorous diffusion region, respectively, after the heating.
  • Typical heating temperatures and times, respectively, are 850-1050°C and 10-300 minutes.
  • a source of dopant atoms is provided on the surface of the silicon substrate. Removal of at least part of said phosphosilicate glass layer on the front side of the substrate achieves that the amount of additional dopant atoms available from this source is different on the front side and on the back side. By heating, this difference of the amount of the additionally available dopant atoms leads to a difference of the diffusion profiles.
  • the method of this invention allows for a simultaneous formation phosphorous front surface field and phosphorous back surface field that removes the time- and cost- ineffective need to create these in two separate processing steps .
  • an n-type silicon substrate is provided in step a) because it provides higher lifetime.
  • the phosphosilicate layer is removed completely from the front surface in step d) before a second dielectric coating film is formed on the front side of the silicon substrate before step e)
  • a phosphosilicate glass layer of at least one nm thickness is present on the back surface of said silicon substrate.
  • Parameters that may be used to control the thickness are e.g. diffusion temperature, dif- fuseon time, 02 gas flow, N2 gas flow and the amount or flow of the used phosphorous diffusion source.
  • the process conditions for step d) are chosen in such a way that the front surface of the silicon substrate as ob- tained by performing step d) is hydrophobic.
  • the first dielectric coating film on at least part of the back side of the silicon substrate and/or said second dielectric coating film on the front side of the silicon substrate are used to provide a diffusion mask in a subseguent solar cell production process step. In this way, cross-contamination of dopants can be reliably avoided .
  • step c) and performing step e) at least the step of removing the dielectric coating film on the back side of said silicon substrate and removing the back phosphorous diffusion region in at least one area of the back side of said silicon substrate but not on the complete back side of said silicon substrate and the step of cleaning the areas, in which the dielectric coating film on the back side of said silicon substrate and the back phosphorous diffusion region have been removed, are performed because this is an easy and convenient way to define the regions in which boron doped material is to be provided.
  • step e) is performed in an atmosphere comprising 02, N2 and boron, so that a boron diffusion region is formed in those areas, in which the dielectric coating film on the back side of said silicon substrate and the back phosphorous diffusion region have been removed.
  • step e) is performed in an atmosphere comprising 02, N2 and boron, so that a boron diffusion region is formed in those areas, in which the dielectric coating film on the back side of said silicon substrate and the back phosphorous diffusion region have been removed.
  • the process conditions are chosen in such a way that after step e) the second diffusion depth for the front phosphorous diffusion region is smaller than second diffusion depth for the back phosphorous diffusion region .
  • step f) a third di- electric coating film (601) is deposited on the back side of the silicon substrate (101). In this way, boron diffusion from step f) may be passivated.
  • At least one of said di- electric coating films comprises one, several or all of the materials PECVD-deposited silicon nitride including hydrogen, silicon carbide including hydrogen, silicon oxinitride includ- ing hydrogen, amorphous silicon including hydrogen and silicon oxide. These materials can provide passivation of the surface and antireflection layers. They are also suited as diffusion barrier layers .
  • At least one back phosphorous diffusion region and at least one boron diffusion region are contacted and wherein said contacting is achieved by simultaneous metallization using the same metal paste or source in a single process step. This leads to further optimization of the production process.
  • Figure 1 a crystalline silicon substrate as provided in step a) of the method of this invention
  • Figure 2 the crystalline silicon substrate of Figure 1 after step b) has been performed
  • Figure 3 the crystalline silicon substrate of Figure 2 after steps c) and d) have been performed
  • Figure 4 the crystalline silicon substrate of Figure 3 after removal of parts of the dielectric coating film on the back side, forming a second dielectric coating film on the front side if the silicon substrate on the phosphorous diffusion re- gion and removal of parts of the back phosphorous diffusion region,
  • Figure 5 the crystalline silicon substrate of Figure 4 after performing step e) in an atmosphere containing boron
  • the crystalline silicon substrate of Figure 5 after deposition of a third dielectric coating film on the back side of the silicon substrate
  • Figure 7 the crystalline silicon substrate of Figure 6 after contacting the back phosphorous diffusion regions and the boron diffusion regions
  • Figure 8 experimental data showing the phosphorous diffu- sion profiles including the diffusion depth obtained by application of steps a) and b) of the method and after application of steps a) to e) of the method and formation of a second dielectric coating film.
  • Figures 1 through 7 relate to a single embodiment of the method, therefore identical reference numerals are used.
  • the relative thickness of layers and/or regions displayed in the Figures is partly represented in an exaggerated way in order to illustrate the effect of the application of respective steps of the method more clearly.
  • modified crystalline silicone substrate as used below relates to a silicon substrate whose properties have been changed including surface layers created thereon or added thereto, it does not only in- dicate changes in the silicon substrate body.
  • Figure 1 shows a crystalline silicon substrate 101 as provided in step a) of the method of this invention.
  • a phosphorous dopant is diffused into the crystalline silicon substrate 101 is simultaneously on the front side and the back side using known methods, for example in a tube furnace.
  • modified crystalline silicon substrate including a front phosphorous diffusion region 201 with a first diffusion depth and a back phosphorous diffusion region 203 with the same first diffusion depth are created.
  • the process conditions of the diffusion process specifically the phosphorous source, temperature, time, 02 gas flow and N2 gas flow are selected in such a way that during diffusion of said phosphorous dopant a layer of phosphosilicate glass 202 is formed in situ on the front phosphorous diffusion region 201 and a layer of phosphosilicate glass 204 is formed in situ on the back phosphorous diffusion region 203, as also displayed in Figure 2.
  • a first dielectric coating film 305 is formed on at least part of the back side of the modified crystalline silicon substrate 101 and a second dielectric coating film 306 is formed on the front side of the modified crystalline silicon substrate 101.
  • the second dielectric coating film serves as a barrier that protects the diffused phosphorous against a later diffusion of boron. Alternatively, such protection may be provided by loading the wafers in a front-to-front configuration for the boron diffusion step.
  • areas 401 with removed dielectric coating film 305, removed phosphosi licate glass layer 204 and removed phosphorous diffusion region 203 are created on the back side of the thus modified crystalline silicon substrate 101.
  • areas 401 all modifications the crystalline silicon substrate 101 that were located on the back side of the crystalline silicon substrate 101 have been removed.
  • no step towards creation of a back-contact solar cell would be made at all. Consequently, the use of the word "parts" in the above section is to be interpreted in a strict sense, ruling out the possibility of a complete removal on the entire back side.
  • the situation shown in Figure 5 is created by heating the thus modified crystalline silicon substrate 101 for a pe- riod of time, typically between 10 and 300 minutes, at an elevated temperature, typically 850-1050°C, in an atmosphere comprising 02, N2 and boron.
  • this leads to the diffusion of boron into the crystalline silicon substrate 101 and the formation of boron diffusion regions 501 in the areas 401.
  • Typical process parameters for creating suitable boron diffusion regions 501 are know in the art.
  • Figure 7 illustrates the phosphorous diffusion profiles including the diffusion depth obtained by application of steps a) and b)of the method and after application of steps a) to f) of the method, respectively using experimental diffusion data.
  • Triangles mark the initial P diffusion in both front and rear phosphorous diffusion region, circles the phosphorous diffusion after heating on the rear side and squares the phosphor- pus diffusion after heating on the front side.

Landscapes

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

Abstract

Method for fabrication of a back side contact solar cell comprising the steps of a)providing a crystalline silicon substrate (101) with a front side and a back side; b) simultaneously diffusing a phosphorous dopant on at least part of said front side and at least part of said back side into said crystalline silicon substrate (101), thus creating a front phosphorous diffusion region (201) with a first diffusion depth and a back phosphorous diffusion region (203) with the same first diffusion depth, wherein during diffusion of said phosphorous dopant a layer of phosphosilicate glass (202) is formed in situ on the front phosphorous diffusion region (201) and a layer of phosphosilicate glass (204) is formed in situ on the back phosphorous diffusion region ( 203 ); c) forming a first dielectric coating film (305) on at least part of the back side of the silicon substrate (101); d)removing at least part of the phosphosilicate glass layer (202) on the front side of the silicon substrate (101) and e)heating the product obtained after performing steps a) to d) as recited above for a period of time at a temperature, wherein said period of time and that temperature are chosen in such a way that said front phosphorous diffusion region (201) and said back phosphorous diffusion region (203) expand further into the crystal up to a second diffusion depth that is different for the front phosphorous diffusion region (203A) and the back phosphorous diffusion region (203B), respectively, after the heating.

Description

Method for fabrication of a back side contact solar cell
The invention relates to a method for fabrication of a back contact solar cell with the features of the preamble of claim 1 and a solar cell fabricated by application of said method.
Solar cells are well-known devices that convert light, i.e. electromagnetic radiation, to electrical energy. The front side of a solar cell or of a substrate which is used to create a solar cell is the side that is facing the light when the solar cell is in use. The back side (or rear side) of a solar cell or of a substrate which is used to create a solar cell is the side opposite to the front side. Generally, a solar cell can be created by forming p-doped and n-doped regions in a semiconductor substrate, typically Silicon. Boron is frequently used as p-dopant and Phosphorous is frequently used as n-dopant. Light that impinges on the solar cell creates pairs of electrons and holes. The thus created electrons and holes are typically moved into p-doped and n-doped regions by an electric field that is always generated when p-doped and n-doped regions are in contact with each other. In order to allow an ex- ternal electrical circuit to be powered by the solar cell, an electrical coupling, the doped regions are coupled to contacts that are usually made from metal.
In a back side contact solar cell, these contacts are provided on the back side of the solar cell. Variations of this type of solar cells and methods for their fabrication are known for example from US 6 998 288 Bl, US 7 135 350 Bl and WO
2009/074469 A2. In a back side contact solar cells, the n-doped regions at the front surface of the solar cell and at the back surface of the solar cell must match different conditions. At the front sur- face, a high sheet resistance of the n-dopant Front Surface Field (FSF) will improve surface passivation. At the back surface, a low sheet resistance of the n-dopant Back Surface Field (BSF) is preferable in order to reduce contact resis- tance. The sheet resistance is largely determined by dopant concentration .
For this reason, all known fabrication methods for back side contact solar cells use two separate process steps relating to the diffusion of n-dopant atoms into the substrate, one for forming the n-dopant Front Surface Field and the other for forming the n-dopant Back Surface Field. However, each of these process steps requires time and costs money. Therefore, it is the object of this invention to provide a more time-efficient and a more cost-efficient method for fabrication of a back side contact solar cell and a cheaper solar cell generated by this process. This problem is solved by a method for fabrication of a back side contact solar cell with the features of claim 1 and solar cell produced according to said method. Advantageous embodiments of the method are described in the dependent claims. The method for fabrication of a back side contact solar cell according to this invention comprises the steps of a) providing a crystalline silicon substrate with a front side and a back side and b) simultaneously diffusing a phosphorous dopant on at least part of said front side and at least part of said back side into said crystalline silicon substrate in such a way that a front phosphorous diffusion region with a first diffusion depth and a back phosphorous diffusion region with the same first diffusion depth are created and that during diffusion of said phosphorous dopant, a layer of phosphosili- cate glass is formed in situ on the front phosphorous diffusion region and a layer of phosphosilicate glass is formed in situ on the back phosphorous diffusion region. In further steps of the method according to the invention, as step c) a dielectric coating film is formed on said phospho- silicate glass layer on at least part of the back side of the silicon substrate , as step d) at least part of the phospho- silicate glass layer on the front side of the silicon substrate is removed, and as step e) the product obtained after performing the steps mentioned above is heated for a period of time at a temperature, wherein said period of time and that temperature are chosen in such a way that said front phospho- rous diffusion region and said back, phosphorous diffusion region expand further into the crystal up to a second diffusion depth that is different for the front phosphorous diffusion region and the back phosphorous diffusion region, respectively, after the heating. Typical heating temperatures and times, respectively, are 850-1050°C and 10-300 minutes.
The steps are preferredly executed in the same order as mentioned above and indicated by the order of the assigned letters in the alphabet.
By making sure that the first diffusion step leads to formation of a phosphosilicate glass layer, a source of dopant atoms is provided on the surface of the silicon substrate. Removal of at least part of said phosphosilicate glass layer on the front side of the substrate achieves that the amount of additional dopant atoms available from this source is different on the front side and on the back side. By heating, this difference of the amount of the additionally available dopant atoms leads to a difference of the diffusion profiles.
Consequently, the method of this invention allows for a simultaneous formation phosphorous front surface field and phosphorous back surface field that removes the time- and cost- ineffective need to create these in two separate processing steps . In an advantageous embodiment, an n-type silicon substrate is provided in step a) because it provides higher lifetime.
In another advantageous embodiment, the phosphosilicate layer is removed completely from the front surface in step d) before a second dielectric coating film is formed on the front side of the silicon substrate before step e)
In general, it is advantageous if a phosphosilicate glass layer of at least one nm thickness is present on the back surface of said silicon substrate. Parameters that may be used to control the thickness are e.g. diffusion temperature, dif- fuseon time, 02 gas flow, N2 gas flow and the amount or flow of the used phosphorous diffusion source.
In another advantageous embodiment, the process conditions for step d) , specifically etching time and concentration of the etching agent in the etching solution, are chosen in such a way that the front surface of the silicon substrate as ob- tained by performing step d) is hydrophobic.
In another advantageous embodiment, the first dielectric coating film on at least part of the back side of the silicon substrate and/or said second dielectric coating film on the front side of the silicon substrate are used to provide a diffusion mask in a subseguent solar cell production process step. In this way, cross-contamination of dopants can be reliably avoided . In another advantageous embodiment, between performing step c) and performing step e) at least the step of removing the dielectric coating film on the back side of said silicon substrate and removing the back phosphorous diffusion region in at least one area of the back side of said silicon substrate but not on the complete back side of said silicon substrate and the step of cleaning the areas, in which the dielectric coating film on the back side of said silicon substrate and the back phosphorous diffusion region have been removed, are performed because this is an easy and convenient way to define the regions in which boron doped material is to be provided. It is especially advantageous, if under these conditions step e) is performed in an atmosphere comprising 02, N2 and boron, so that a boron diffusion region is formed in those areas, in which the dielectric coating film on the back side of said silicon substrate and the back phosphorous diffusion region have been removed. This leads to a further optimization of the production process, specifically with respect to time, because the heating that is required in order to create the boron diffusion region, i.e. p-doped areas of the silicon substrate, can be simultaneously be used for obtaining the diffusion profiles that lead to the desired properties of the phosphorous front surface field and the phosphorous back surface field.
In another advantageous embodiment, the process conditions are chosen in such a way that after step e) the second diffusion depth for the front phosphorous diffusion region is smaller than second diffusion depth for the back phosphorous diffusion region .
In another advantageous embodiment, wherein the process conditions are chosen in such a way that after step e) the result- ing sheet resistance of the back phosphorous diffusion region is lower that the resulting sheet resistance for the front phosphorous diffusion region.
In another advantageous embodiment, after step f) a third di- electric coating film (601) is deposited on the back side of the silicon substrate (101). In this way, boron diffusion from step f) may be passivated.
In another advantageous embodiment, at least one of said di- electric coating films comprises one, several or all of the materials PECVD-deposited silicon nitride including hydrogen, silicon carbide including hydrogen, silicon oxinitride includ- ing hydrogen, amorphous silicon including hydrogen and silicon oxide. These materials can provide passivation of the surface and antireflection layers. They are also suited as diffusion barrier layers .
In another advantageous embodiment, at least one back phosphorous diffusion region and at least one boron diffusion region are contacted and wherein said contacting is achieved by simultaneous metallization using the same metal paste or source in a single process step. This leads to further optimization of the production process.
The invention is now explained further using the following figures that show:
Figure 1 : a crystalline silicon substrate as provided in step a) of the method of this invention,
Figure 2 : the crystalline silicon substrate of Figure 1 after step b) has been performed,
Figure 3 : the crystalline silicon substrate of Figure 2 after steps c) and d) have been performed,
Figure 4 : the crystalline silicon substrate of Figure 3 after removal of parts of the dielectric coating film on the back side, forming a second dielectric coating film on the front side if the silicon substrate on the phosphorous diffusion re- gion and removal of parts of the back phosphorous diffusion region,
Figure 5 : the crystalline silicon substrate of Figure 4 after performing step e) in an atmosphere containing boron, the crystalline silicon substrate of Figure 5 after deposition of a third dielectric coating film on the back side of the silicon substrate, Figure 7: the crystalline silicon substrate of Figure 6 after contacting the back phosphorous diffusion regions and the boron diffusion regions, and
Figure 8 : experimental data showing the phosphorous diffu- sion profiles including the diffusion depth obtained by application of steps a) and b) of the method and after application of steps a) to e) of the method and formation of a second dielectric coating film.
Figures 1 through 7 relate to a single embodiment of the method, therefore identical reference numerals are used. The relative thickness of layers and/or regions displayed in the Figures is partly represented in an exaggerated way in order to illustrate the effect of the application of respective steps of the method more clearly. The term "modified crystalline silicone substrate" as used below relates to a silicon substrate whose properties have been changed including surface layers created thereon or added thereto, it does not only in- dicate changes in the silicon substrate body.
Figure 1 shows a crystalline silicon substrate 101 as provided in step a) of the method of this invention. Next, a phosphorous dopant is diffused into the crystalline silicon substrate 101 is simultaneously on the front side and the back side using known methods, for example in a tube furnace.
As illustrated in Figure 2, during this process, modified crystalline silicon substrate including a front phosphorous diffusion region 201 with a first diffusion depth and a back phosphorous diffusion region 203 with the same first diffusion depth are created. In addition, the process conditions of the diffusion process, specifically the phosphorous source, temperature, time, 02 gas flow and N2 gas flow are selected in such a way that during diffusion of said phosphorous dopant a layer of phosphosilicate glass 202 is formed in situ on the front phosphorous diffusion region 201 and a layer of phosphosilicate glass 204 is formed in situ on the back phosphorous diffusion region 203, as also displayed in Figure 2.
As shown in Figure 3, next the phosphosilicate glass layer 202 on the front side of the modified crystalline silicon substrate 101 is removed, preferably in an etching process. Furthermore, a first dielectric coating film 305 is formed on at least part of the back side of the modified crystalline silicon substrate 101 and a second dielectric coating film 306 is formed on the front side of the modified crystalline silicon substrate 101. For this purpose, any of the methods known in the art for providing such a film for a solar cell can be used . The second dielectric coating film serves as a barrier that protects the diffused phosphorous against a later diffusion of boron. Alternatively, such protection may be provided by loading the wafers in a front-to-front configuration for the boron diffusion step.
After these steps it is still necessary to provide the modified crystalline silicon substrate 101 with p-doped regions. In order to achieve this, at first the situation shown in Figure 4 is created. Parts of the dielectric coating film 305 on the back side are removed in such a way that it does no longer cover the entire back surface of the device created during the previous processing steps, so that parts of the back side phosphosilicate glass layer 204 be accessed. The accessible parts are also removed, preferably by etching, so that parts of the back phosphorous diffusion region 203 may be accessed. Again, the then accessible parts are also removed. Methods for the removal parts of a dielectric coating film 305 and parts of a back side phosphorous diffusion layer are well known in the art. By these removals, areas 401 with removed dielectric coating film 305, removed phosphosi licate glass layer 204 and removed phosphorous diffusion region 203 are created on the back side of the thus modified crystalline silicon substrate 101. In other words, in the areas 401 all modifications the crystalline silicon substrate 101 that were located on the back side of the crystalline silicon substrate 101 have been removed. Naturally, if one would remove all modifications of the silicon substrate that have been performed up to this method step on the entire back side of the silicon substrate or on all but one side of the silicon substrate, no step towards creation of a back-contact solar cell would be made at all. Consequently, the use of the word "parts" in the above section is to be interpreted in a strict sense, ruling out the possibility of a complete removal on the entire back side.
Then, the situation shown in Figure 5 is created by heating the thus modified crystalline silicon substrate 101 for a pe- riod of time, typically between 10 and 300 minutes, at an elevated temperature, typically 850-1050°C, in an atmosphere comprising 02, N2 and boron. On the one hand, this leads to the diffusion of boron into the crystalline silicon substrate 101 and the formation of boron diffusion regions 501 in the areas 401. Typical process parameters for creating suitable boron diffusion regions 501 are know in the art. These parameters, specifically the respective time period and temperature, are also suited to make sure that the front phosphorous diffusion region 201 and the remaining parts of the back phosphorous diffusion region 203 expand further into the crystal up to a second diffusion depth that is different for the front phosphorous diffusion region 203A and the back phosphorous diffusion region 203B, respectively, after the heating. This difference is due to the different amount of phopshosilicate glass on the front side and the back side of the modified crystalline silicon substrate 101, which acts as a dopant source during diffusion. Next, the situation shown in Figure 6 is created by deposition of a third dielectric coating film on the back side of the thus modified crystalline silicon substrate 101 using known methods. Finally, contacting of the modified crystalline silicon substrate 101 of Figure 6, i.e. contacting the back phosphorous diffusion regions and the boron diffusion regions, leads to the situation shown in Figure 7, including metal contacts 701, 702 which may be created by any method known in the art. However, it is important to point out that for products obtained by the method according to this invention can be contacted by simultaneous metallization using the same metal paste or metal source in a single process step. Figure 8 illustrates the phosphorous diffusion profiles including the diffusion depth obtained by application of steps a) and b)of the method and after application of steps a) to f) of the method, respectively using experimental diffusion data. Triangles mark the initial P diffusion in both front and rear phosphorous diffusion region, circles the phosphorous diffusion after heating on the rear side and squares the phosphor- pus diffusion after heating on the front side. These data prove that the approach as presented above, based on a simultaneous diffusion of n-dopant into front and back side of the crystalline silicon substrate, does in fact provide significantly different diffusion profiles that according to state of the art methods always required two separate diffusion processes.
List of reference numerals
101 crystalline silicon substrate
201 front phosphorous diffusion region with first
diffusion depth
202 phosphosilicate glass layer
203 back phosphorous diffusion region with first
diffusion depth
204 phosphosilicate glass layer
305 first dielectric coating film
306 second dielectric coating film
401 area with removed dielectric coating film and removed phosphorous diffusion region
501 boron diffusion region
201A front phosphorous diffusion region after heating
203A back phosphorous diffusion region after heating
601 third dielectric coating film
701 contact to back phosphorousdiffusion region
702 contact to boron diffusion region

Claims

Claims
Method for fabrication of a back side contact solar cell comprising the steps of
a) providing a crystalline silicon substrate (101) with a front side and a back side;
b) simultaneously diffusing a phosphorous dopant on at least part of said front side and at least part of said back side into said crystalline silicon substrate ( 101 ) , thus creating a front phosphorous diffusion region (201) with a first diffusion depth and a back phosphorous diffusion region (203) with the same first diffusion depth, wherein during diffusion of said phosphorous dopant a layer of phosphosilicate glass (202) is formed in situ on the front phosphorous diffusion region (201) and a layer of phosphosilicate glass (204) is formed in situ on the back phosphorous diffusion region (203 ) ;
c) forming a first dielectric coating film (305) on at least part of the back side of the silicon substrate (101) ;
d) removing at least part of the phosphosilicate glass layer (202) on the front side of the silicon substrate (101) ;
e) heating the product obtained after performing steps a) to d) as recited above for a period of time at a temperature, wherein said period of time and that temperature are chosen in such a way that said front phosphorous diffusion region (201) and said back phosphorous diffusion region (203) expand further into the crystal up to a second diffusion depth that is different for the front phosphorous diffusion region (203A) and the back phosphorous diffusion region (203B) , respectively, after the heating.
Method according to claim 1, wherein in step a) n-type silicon substrate (101) is provided. Method according to claim 1 or 2, wherein the phospho- silicate layer is removed completely from the front side of the silicon substrate (101) in step d) and a second dielectric coating film (306) is formed on the front side of the silicon substrate (101) before step e)
Method according to one of claims 1 to 3, wherein the process conditions for step d) are chosen in such a way that the front surface of the silicon substrate (101) as obtained by performing step d) is hydrophobic.
Method according to one of claims 1 to 4, wherein said first dielectric coating film (305) on at least part of the back side of the silicon substrate and/or said second dielectric coating film (306) on the front side of the silicon substrate (101) are used to provide a diffusion mask in a subsequent solar cell production process step.
Method according to claim 1, wherein between performing step c)and performing step e) at least the steps of
-removing the dielectric coating film (305) on the back side of said silicon substrate and the back phosphorous diffusion region (203) are removed in at least one area of the back side of said silicon substrate (101), but not on the complete back side of said silicon substrate (101), and
-cleaning the areas (401), in which the dielectric coating film (305) on the back side of said silicon substrate (101) and the back phosphorous diffusion region (203) have been removed
are performed.
Method according to claim 6, wherein step e) is performed in an atmosphere comprising 02, N2 and boron, so that a boron diffusion region (501) is formed in those areas, in which the dielectric coating film (305) on the back side of said silicon substrate (101) and the back phosphorous diffusion region (203) have been removed.
Method according to one of claims 1 to 7, wherein the process conditions are chosen in such a way that after step e) the second diffusion depth for the front phosph rous diffusion region (201A) is smaller than second dif fusion depth for the back phosphorous diffusion region (203A) .
Method according to one of claims 1 to 8, wherein the process conditions are chosen in such a way that after step e) the resulting sheet resistance of the back phosphorous diffusion region (201A) is lower that the result ing sheet resistance for the front phosphorous diffusion region (203A) .
Method according to one of claims 1 to 9, wherein after step e) a third dielectric coating film (601) is deposited on the back side of the silicon substrate (101) .
Method according to one of claim 1 to 10, wherein at least one of said dielectric coating films (305,306,601) comprises one, several or all of the materials PECVD- deposited silicon nitride including hydrogen, silicon carbide including hydrogen, silicon oxinitride including hydrogen, amorphous silicon including hydrogen and silicon oxide .
Method according to one of claims 1 to 11, wherein at least one back phosphorous diffusion region (203A) and at least one boron diffusion region (501) are contacted and wherein said contacting is achieved by simultaneous metallization using the same metal paste or source in a single process step.
PCT/EP2011/003066 2010-06-23 2011-06-21 Method for fabrication of a back side contact solar cell WO2011160819A2 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102010024835A DE102010024835A1 (en) 2010-06-23 2010-06-23 Method for fabrication of a backside contact solar cell
DE102010024835.5 2010-06-23

Publications (2)

Publication Number Publication Date
WO2011160819A2 true WO2011160819A2 (en) 2011-12-29
WO2011160819A3 WO2011160819A3 (en) 2013-03-21

Family

ID=44629833

Family Applications (1)

Application Number Title Priority Date Filing Date
PCT/EP2011/003066 WO2011160819A2 (en) 2010-06-23 2011-06-21 Method for fabrication of a back side contact solar cell

Country Status (2)

Country Link
DE (1) DE102010024835A1 (en)
WO (1) WO2011160819A2 (en)

Cited By (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103606596A (en) * 2013-11-26 2014-02-26 英利集团有限公司 Phosphorus doping silicon wafer, manufacturing method of phosphorus doping silicon wafer, solar cell and manufacturing method of solar cell
CN107785456A (en) * 2017-09-27 2018-03-09 泰州中来光电科技有限公司 A kind of preparation method of back contact solar cell
CN113948611A (en) * 2021-10-15 2022-01-18 浙江爱旭太阳能科技有限公司 P-type IBC battery, preparation method and assembly thereof, and photovoltaic system

Families Citing this family (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE102013102573A1 (en) 2012-03-13 2013-09-19 centrotherm cell & module GmbH Method for manufacturing solar cell e.g. interdigitated-back contact solar cell, involves cleaning cell substrate, and diffusing boron from boron source layer and diffusing phosphorus into solar cell substrate in common diffusion step
DE102013102574A1 (en) 2012-03-13 2013-09-19 centrotherm cell & module GmbH Method for manufacturing back contact solar cell, involves diffusing second type dopant containing paste into solar cell substrate in common-emitter type impurity regions by sintering second type dopant containing paste
CN109809699B (en) * 2019-01-21 2021-05-28 西北大学 Phosphorus-doped glass powder, preparation method thereof and method for preparing front silver paste for solar cell by using phosphorus-doped glass powder

Citations (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6998288B1 (en) 2003-10-03 2006-02-14 Sunpower Corporation Use of doped silicon dioxide in the fabrication of solar cells
WO2009074469A2 (en) 2007-12-11 2009-06-18 Institut Für Solarenergieforschung Gmbh Rear-contact solar cell having large rear side emitter regions and method for producing the same

Family Cites Families (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US20090227095A1 (en) * 2008-03-05 2009-09-10 Nicholas Bateman Counterdoping for solar cells
DE102009015764A1 (en) * 2008-10-31 2010-06-17 Bosch Solar Energy Ag Process for producing monocrystalline n-silicon back contact solar cells
KR101002282B1 (en) * 2008-12-15 2010-12-20 엘지전자 주식회사 Solar cell and manufacturing method thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US6998288B1 (en) 2003-10-03 2006-02-14 Sunpower Corporation Use of doped silicon dioxide in the fabrication of solar cells
US7135350B1 (en) 2003-10-03 2006-11-14 Sunpower Corporation Use of doped silicon dioxide in the fabrication of solar cells
WO2009074469A2 (en) 2007-12-11 2009-06-18 Institut Für Solarenergieforschung Gmbh Rear-contact solar cell having large rear side emitter regions and method for producing the same

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN103606596A (en) * 2013-11-26 2014-02-26 英利集团有限公司 Phosphorus doping silicon wafer, manufacturing method of phosphorus doping silicon wafer, solar cell and manufacturing method of solar cell
CN107785456A (en) * 2017-09-27 2018-03-09 泰州中来光电科技有限公司 A kind of preparation method of back contact solar cell
CN113948611A (en) * 2021-10-15 2022-01-18 浙江爱旭太阳能科技有限公司 P-type IBC battery, preparation method and assembly thereof, and photovoltaic system
CN113948611B (en) * 2021-10-15 2023-12-01 浙江爱旭太阳能科技有限公司 P-type IBC battery, preparation method thereof, assembly and photovoltaic system

Also Published As

Publication number Publication date
DE102010024835A1 (en) 2011-12-29
WO2011160819A3 (en) 2013-03-21

Similar Documents

Publication Publication Date Title
NL2018356B1 (en) A method of manufacturing a passivated solar cell and resulting passivated solar cell
TWI655676B (en) Solar cell emitter region fabrication using ion implantation
JP6326661B2 (en) Method for manufacturing solar cell contacts
Röder et al. Add‐on laser tailored selective emitter solar cells
TWI549306B (en) Method for fabricating back-contact type solar cell
EP2210283B2 (en) Method of manufacturing crystalline silicon solar cells using co diffusion of boron and phosphorus
TWI542028B (en) Method for forming patterns of differently doped regions
WO2011160819A2 (en) Method for fabrication of a back side contact solar cell
KR20110020061A (en) Method of preparing selective emitter of solar cell and method of preparing solar cell
CN105637647B (en) Manufacture solar cell emitter region is injected and covered using autoregistration
CN111133589B (en) Dopant enhanced solar cell and method of manufacturing the same
JP2010161310A (en) Backside electrode type solar cell and method of manufacturing the same
TW201603296A (en) Solar cell with trench-free emitter regions
US20140166094A1 (en) Solar cell emitter region fabrication using etch resistant film
KR20170132224A (en) Polycrystalline Silicon for Blisterless Solar Cells
CN114914328B (en) Double-sided solar cell and preparation method thereof
NL2008755C2 (en) Method of manufacturing a solar cell and equipment therefore.
KR101162123B1 (en) Method for forming a selective emitter using doping mask with dopant and Method for manufacturing Solar cell thereof
NL2021449B1 (en) A method of manufacturing a passivated solar cell and resulting passivated solar cell
TW201637232A (en) Method for producing solar cell
CN110870082B (en) Method for producing PERT solar cells
TWI612682B (en) Solar cell with silicon oxynitride dielectric layer
TW201701491A (en) Photovoltaic cell manufacturing method
CN107002277A (en) Using the solar cell for simplifying depositing operation manufacture
TWI399863B (en) Rapid thermal annealing apparatus for selective heat treatment and method for selective emitter solar cell fabrication using the same

Legal Events

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

Ref document number: 11741095

Country of ref document: EP

Kind code of ref document: A2

122 Ep: pct application non-entry in european phase

Ref document number: 11741095

Country of ref document: EP

Kind code of ref document: A2