WO2015010167A1 - High concentration doping in silicon - Google Patents
High concentration doping in silicon Download PDFInfo
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- WO2015010167A1 WO2015010167A1 PCT/AU2014/050146 AU2014050146W WO2015010167A1 WO 2015010167 A1 WO2015010167 A1 WO 2015010167A1 AU 2014050146 W AU2014050146 W AU 2014050146W WO 2015010167 A1 WO2015010167 A1 WO 2015010167A1
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- WO
- WIPO (PCT)
- Prior art keywords
- crystalline silicon
- dopant
- hydrogen
- region
- doped
- Prior art date
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- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 102
- 239000010703 silicon Substances 0.000 title claims abstract description 102
- 229910052739 hydrogen Inorganic materials 0.000 claims abstract description 145
- 239000001257 hydrogen Substances 0.000 claims abstract description 144
- 239000002019 doping agent Substances 0.000 claims abstract description 138
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 claims abstract description 132
- 229910021419 crystalline silicon Inorganic materials 0.000 claims abstract description 132
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 101
- 238000010438 heat treatment Methods 0.000 claims abstract description 70
- 125000004429 atom Chemical group 0.000 claims abstract description 65
- 125000004435 hydrogen atom Chemical group [H]* 0.000 claims abstract description 54
- 230000007935 neutral effect Effects 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims description 84
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 claims description 72
- 229910052796 boron Inorganic materials 0.000 claims description 64
- 238000005984 hydrogenation reaction Methods 0.000 claims description 60
- 238000005286 illumination Methods 0.000 claims description 37
- 229910052698 phosphorus Inorganic materials 0.000 claims description 35
- 230000009849 deactivation Effects 0.000 claims description 33
- 230000008569 process Effects 0.000 claims description 33
- 238000001816 cooling Methods 0.000 claims description 31
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 29
- 239000011574 phosphorus Substances 0.000 claims description 29
- 230000007420 reactivation Effects 0.000 claims description 16
- 238000012545 processing Methods 0.000 claims description 13
- 230000007547 defect Effects 0.000 claims description 10
- 239000000969 carrier Substances 0.000 claims description 9
- 230000001186 cumulative effect Effects 0.000 claims description 8
- PNEYBMLMFCGWSK-UHFFFAOYSA-N aluminium oxide Inorganic materials [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 claims description 6
- 239000004065 semiconductor Substances 0.000 claims description 6
- 229910052581 Si3N4 Inorganic materials 0.000 claims description 4
- 239000004411 aluminium Substances 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 4
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 claims description 4
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052733 gallium Inorganic materials 0.000 claims description 3
- 229910021417 amorphous silicon Inorganic materials 0.000 claims 1
- 239000002674 ointment Substances 0.000 claims 1
- 235000012431 wafers Nutrition 0.000 description 43
- 239000010410 layer Substances 0.000 description 30
- 229910052751 metal Inorganic materials 0.000 description 25
- 239000002184 metal Substances 0.000 description 25
- 238000001465 metallisation Methods 0.000 description 17
- YZCKVEUIGOORGS-UHFFFAOYSA-N Hydrogen atom Chemical compound [H] YZCKVEUIGOORGS-UHFFFAOYSA-N 0.000 description 16
- 239000000463 material Substances 0.000 description 14
- 238000000059 patterning Methods 0.000 description 13
- 238000007650 screen-printing Methods 0.000 description 12
- 230000015572 biosynthetic process Effects 0.000 description 9
- 125000004437 phosphorous atom Chemical group 0.000 description 9
- 238000004519 manufacturing process Methods 0.000 description 7
- 238000007747 plating Methods 0.000 description 7
- 239000013078 crystal Substances 0.000 description 6
- 238000002161 passivation Methods 0.000 description 6
- 230000003247 decreasing effect Effects 0.000 description 5
- 150000002500 ions Chemical class 0.000 description 5
- 230000008901 benefit Effects 0.000 description 4
- 238000009792 diffusion process Methods 0.000 description 4
- 150000002431 hydrogen Chemical class 0.000 description 4
- GPRLSGONYQIRFK-UHFFFAOYSA-N hydron Chemical compound [H+] GPRLSGONYQIRFK-UHFFFAOYSA-N 0.000 description 3
- 238000005215 recombination Methods 0.000 description 3
- 230000006798 recombination Effects 0.000 description 3
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000000356 contaminant Substances 0.000 description 2
- -1 dielectric layers Chemical compound 0.000 description 2
- 239000003989 dielectric material Substances 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000035876 healing Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 230000007246 mechanism Effects 0.000 description 2
- 230000008542 thermal sensitivity Effects 0.000 description 2
- 241000282320 Panthera leo Species 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 238000003491 array Methods 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- 239000000919 ceramic Substances 0.000 description 1
- 239000002800 charge carrier Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- ZPUCINDJVBIVPJ-LJISPDSOSA-N cocaine Chemical compound O([C@H]1C[C@@H]2CC[C@@H](N2C)[C@H]1C(=O)OC)C(=O)C1=CC=CC=C1 ZPUCINDJVBIVPJ-LJISPDSOSA-N 0.000 description 1
- 238000011109 contamination Methods 0.000 description 1
- CVSVTCORWBXHQV-UHFFFAOYSA-N creatine Chemical compound NC(=[NH2+])N(C)CC([O-])=O CVSVTCORWBXHQV-UHFFFAOYSA-N 0.000 description 1
- 238000010494 dissociation reaction Methods 0.000 description 1
- 230000005593 dissociations Effects 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 238000002955 isolation Methods 0.000 description 1
- 238000004377 microelectronic Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 238000006386 neutralization reaction Methods 0.000 description 1
- 238000013021 overheating Methods 0.000 description 1
- MCYTYTUNNNZWOK-LCLOTLQISA-N penetratin Chemical compound C([C@H](NC(=O)[C@H](CC=1C2=CC=CC=C2NC=1)NC(=O)[C@H]([C@@H](C)CC)NC(=O)[C@H](CCCCN)NC(=O)[C@@H](NC(=O)[C@H](CCC(N)=O)NC(=O)[C@@H](N)CCCNC(N)=N)[C@@H](C)CC)C(=O)N[C@@H](CCC(N)=O)C(=O)N[C@@H](CC(N)=O)C(=O)N[C@@H](CCCNC(N)=N)C(=O)N[C@@H](CCCNC(N)=N)C(=O)N[C@@H](CCSC)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CC=1C2=CC=CC=C2NC=1)C(=O)N[C@@H](CCCCN)C(=O)N[C@@H](CCCCN)C(N)=O)C1=CC=CC=C1 MCYTYTUNNNZWOK-LCLOTLQISA-N 0.000 description 1
- 108010043655 penetratin Proteins 0.000 description 1
- 230000000149 penetrating effect Effects 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 230000001681 protective effect Effects 0.000 description 1
- 230000008439 repair process Effects 0.000 description 1
- 230000001846 repelling effect Effects 0.000 description 1
- 239000002210 silicon-based material Substances 0.000 description 1
- 239000004071 soot Substances 0.000 description 1
- 239000002344 surface layer Substances 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
Classifications
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- H—ELECTRICITY
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- 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
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- 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
- H01L21/2225—Diffusion sources
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- 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
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- 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
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/3003—Hydrogenation or deuterisation, e.g. using atomic hydrogen from a plasma
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- 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
- H01L21/30—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26
- H01L21/324—Thermal treatment for modifying the properties of semiconductor bodies, e.g. annealing, sintering
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- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0256—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by the material
- H01L31/0264—Inorganic materials
- H01L31/028—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table
- H01L31/0288—Inorganic materials including, apart from doping material or other impurities, only elements of Group IV of the Periodic Table characterised by the doping material
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- H01L31/0248—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies
- H01L31/0352—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions
- H01L31/035272—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by their semiconductor bodies characterised by their shape or by the shapes, relative sizes or disposition of the semiconductor regions characterised by at least one potential jump barrier or surface barrier
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- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
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- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/186—Particular post-treatment for the devices, e.g. annealing, impurity gettering, short-circuit elimination, recrystallisation
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- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/186—Particular post-treatment for the devices, e.g. annealing, impurity gettering, short-circuit elimination, recrystallisation
- H01L31/1864—Annealing
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- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1876—Particular processes or apparatus for batch treatment of the devices
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- 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
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- 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 methods of manufacturing solar ceils and in particular the invention provides new method of hydrogenation of silicon material.
- Hydrogenation of crystalline silicon involves the bonding of hydrogen atoms to crystallographic defects or contamination within, the silicon lattice in a way that prevents that defect o contaminant from acting as a recombination site for minority charge carriers. This is known as passivation of the particular recombination site. This is important for semiconductor devices that require long minority carrier Lifetimes such as solar ceils and particularly where cheap silicon is used that often has poor crystallographic quality and/or purity and therefore needs passivation to bring the quality to acceptable levels for high efficiency solar cells.
- Low cost silicon in general has much higher densities of silicon crystallographic defects and/or unwanted impurities. These lower the minority carrier lifetime of the silicon and therefore reduce the efficiencies of solar cells made from suc material. Passivation of such defects and contaminants to improve minority carrier lifetimes is therefore an important part of being able to fabricate high efficiency solar cells when using lower quality silicon than that routinely used by the microelectronics industry such as with floatzone (FZ) wafers formed from semiconductor grade silicon.
- FZ floatzone
- ⁇ can interact with ionised boron atoms ( ⁇ ) to form neutral boron- hydrogen (B-H) complexes.
- H * can interact with ionised phosphorus atoms (P ' ) to form neutral phosphorus-hydrogen (P-H) complexes.
- RO AU Boron (B) is a valency 3 element which can be used to dope silicon to produce p-type material, when taking on substitutional sites within the silicon lattice. Each such boron atom therefore produces a free "hole", leaving the boron atom with a. fixed negative charge. If atomic hydrogen is directed into such a p-type region and if the hydrogen take on the positive charge state (H+), strong electrostatic forces exist between the B " and H* atoms. leading to a high probability that the two will react to form a B-H bond, therefore trapping the hydrogen atom at that location but while simultaneously deactivating the boron atom such that electronically it acts as if it were no longer there.
- H+ positive charge state
- phosphorus (P) is a valency 5 element which can be used to dope silicon to produce n-type material when taking on substitutional sites within the silicon lattice. Each such phosphorus atom therefore produces a free "electron", leaving the phosphorus atom with a fixed positive charge. If atomic hydrogen is directed into such an n-type region and if the hydrogen takes on the negative charge state (H-), strong electrostatic forces exist between the P+ and H- atoms, leading to a high probability that the two will react to form a P-H bond, therefore trapping the hydrogen atom at tha location but while simultaneously deactivating the phosphorus atom such that: electronically it acts as if i were no longer there.
- H- negative charge state
- a method for the processing of a crystalline silicon device, havin a plurality of crystalline silicon regions.
- the crystalline silicon device may have at least one crystalline silicon region being a doped crystalline silicon region (e.g. valency 3 dopant such as boron, aluminium gallium - or a valency 5 dopant such as phosphorus) in whic some dopant atoms are deactivated by combining (coulombicly) with a hydrogen atom.
- the method may comprise reactivating some of the deactivated dopant .atoms by heating and illuminating die doped crystalline silicon region to break at least some of the dopant - hydrogen bonds. Conditions may be simultaneously maintained to create a relatively high concentration of hydrogen atoms having a. neutral charge state and/or
- the illumination may be maintained as the doped crystalline silicon region is subsequently cooled to maintain the increased concentration of hydrogen atoms having a neutral charge state and/ r hydrogen atoms charged with the same charge polarity as the dopant atoms.
- a method for the processing of a crystalline silicon device.
- the method may comprise doping a crystalline silicon region of the device with dopant atoms of a first, dopant polarity (e.g. p-type or n-type) to create a. doped crystalline silicon region with a dopant atom concentration greater than a required final active dopant atom concentration .of the doped crystalline silicon region.
- dopant atoms in the doped crystalline silicon region may be deactivated by introducing hydrogen atoms into die doped crystalline silicon region. Consequently the some of the hydrogen atoms may (eoulombicly) bond with some or all of the dopant atoms of the first, dopant type to deactivate the respective dopant atoms,
- the doped crystalline silicon region may be a surface region of the crystalline silicon device.
- a crystalline silicon device comprises a. silicon region doped with a first, dopant and at least some of the dopant deactivated b being bonded with hydrogen.
- the doped crystalline silicon region after deactivation may have a sheet resistivity which is at least 25% higher than the sheet, resistivity prior to deactivation.
- a crystalline silicon device comprises a crystalline silicon region simultaneously doped with a first dopant of a first dopant polarity and a second dopant of an opposite dopant polarity.
- the relative concentration of the dopant of the first polarity may be greater than the dopant of die second polarity.
- At least some of the dopant of the first polarity may be deactivated by being bonded with hydrogen atoms such that the region after deactivation has a. net active doping of the second dopant, type exceeding that of the first dopant type therefore leading to the region adopting a polarity as determined by the second dopant type.
- a crystalline silicon device comprises a crystalline silicon region simultaneously doped with a first dopant of a first dopant polarity and a second dopant of an opposite dopant, polarity.
- the relative concentration of the dopant of the first polarit may be equaL to the dopant of the second polarity.
- At least some of the dopant of the first. polarity may be deactivated by being bound with hydrogen such that the doped crystalline silicon region after deactivation has a net doping polarity of the second dopant polarity.
- Some or all of the deactivated dopant atoms may subsequently be reactivated by subjecting the doped crysialline silicon region to heat in the presence of illumination whereby electron hole pairs are generated to increase the proportion of minority carriers in the doped crystalline silicon regio to allow at least some of the released hydrogen atoms to take on a charge state that allows it to escape from the coulombic attraction of the dopant atom to which it was previously bonded. Subsequent cooling of the doped crystalline silicon region while preferably maintaining illumination, minimises the likelihood of the dopant atom being reactivated by hydrogen atoms.
- Seme or all of the deactivated dopant atoms in a selected crystalline silicon region may al so he subsequently reactivated by subjecting, the dopant atoms in the selected crystalline silicon region, to heat and illuminating a crystalline silicon region adjacent to the selected region whereby electron hole pairs are generated to increase the proportion of minority carriers in the crystalline silicon region adjacent to the selected crystalline silicon region such that the minority carriers generated in the crystalline si licon region adjacent to the selected crystalline silicon region will diffuse to the selected crystalline silicon region and therefore allow reactivation of toe dopants i the selected crystalline silicon region.
- the heatin and/or illumination of the dopant atom and /or the selected crystalline silicon region and the crystalline silicon region adjacent to the selected crystalline silicon region may be performed with a laser.
- the laser ma be scanned over a plurality of crysialline silicon regions to process a larger area or an entire cell.
- Hydrogen atoms may be introduced into the crystalline silicon device by forming a dielectric which contains hydrogen, such as silicon nitride, silicon oxynitride. aluminium oxides- etc. on a surface of the crystalline silicon device and subsequently heating the crystalline silicon device to migrate the hydrogen atoms into the silicon.
- dielectric hydrogen sources will be formed (at least temporarily) on each of the front and rear surfaces of the crystalline silicon device.
- the hydrogen atoms may be introduced into the crystalline silicon device from the hydrogen source by heating the crystalline silicon device in the absence of illumination or i lo illumination conditions (e.g. only unavoidable light- emitting from the light source),
- the method will be more effective when silicon surface n-type diffused layers through which hydrogen must diffuse have peak, net active doping concentrations (i.e. dopant atoms that have not been deactivated) of 1 10' atoms/em or less. Similarly, the method will be more effective when an silicon surface diffused p-type layers through which hydrogen must diffuse have peak net active doping concentrations of lxl 0 i? atoms/cm 3 or less.
- the heating of the crystalline silicon device may comprise heating at least a region of the device to at least 40 C C while simultaneously illuminating at least some of the crystalline silicon device with at least one light source whereby the cumulative power of all the incident photons with sufficient energy to generate electron hole pairs within silicon (in other words photons wit energy levels above the bandgap of silicon of 1.12eV) is at. least 20mW/cm 2 .
- the illumination from the at least one light sources may be provided at levels whereby the cumulative power of all the incident photons with sufficient energy to generate electron hole pairs within silicon is at least 50 mW/cm 2 , or 60 ffi /cm or 70 mW/cm 2 , or 80 mW/cm 2 , or 90 mW/cm 3 , or 100 mW/cm 2 , or 150 mW/em 2 , 200 raW/cm or
- the heating of the crystalline silicon device may comprise heating at least a region of the device to at least 100°C.
- the heating may be followed by cooling of the crystalline silicon device while simultaneousl illuminating at least some of the device with at least, one .light source whereby the cumulative power of all the incident photons with sufficient energy to generate electron hole pairs within silicon is at. least 20mW/em 2 .
- the heating of the crystalline silicon device may comprise heating the device to at least 140T.
- the heating of the .crystalline silicon device may comprise heating the device to at least I SOT, or 200 T or 400 °C depending on the conditions required and the thermal sensitivity of existing structures in the device.
- temperatures may be employed such as to at least 500 , or to at least 600°C, or to at least TOOT; or to at. least 8Q0T, or to at. least 900 , or to at least ⁇ , ⁇ , or to at least L20G or to a temperature at. which crystalline silicon begins to melt.
- the lowe the temperature the higher the corresponding light intensity will need to be for optimal hydrogenation.
- Minority carrier concentrations may be controlled, through the use of light and heat, during; a cool-dow period after heating, and any post hydrogenation thermal proces es, to maintain hydrogen charge states during cool-down to minimise reactivation of delects, or reacti vation of dopants, to which hydrogen atoms have previously bound.
- the intensity of illumination applied to the crystalline silicon device may be varied durin the thermal processing and cooling.
- the intensity of illumination applied to the crystalline silicon device may be increased, or decreased, during a cooling stage after the hydrogenalion or other thermal processes.
- the intensity o.f illumination applied to the crystalline silicon device may be increased, or decreased, with decreasing temperature of the device.
- the source- of illumination applied to the crystalline silicon device may be an array of LEDs.
- the source of illumination applied to the crystalline silico device may also be one or more infrared lamps.
- the illuminatio applied to the device may be pul sed.
- the intensity of illumination applied to the crystalline silicon device may be controlled to maintain the Fermi level at a value of 0.10 to 0.22ev above mid-gap,
- the method may be used to process silico for use in the fabrication of a photovoltaic device having at least one rectifying junction.
- the dopant introduced in excess of requirements may be a p-type (valency 3) dopant such as boron, aluminium or gallium or an n-type (valency 5) dopant such as phosphorus.
- valency 3 dopant
- valency 5 dopant
- the method is particularl effective when boron is used as a dopant in silicon.
- the doped region may al so be doped with boron and phosphorus .
- Such .surface layer can even include the deliberate additio of two opposite polarity dopants, such as boron and phosphorus, whereby the layer i s p-type prior to boron deactivation, n-fype after deactivation by hydrogen and then with localised p-type and n-type regions after localised reactivation of boron atoms takes place.
- the boron dopants are locally reacti vated to allow such regions to return from n-type to being p-type.
- Such p-type regions can penetrate from one surface of the wafer through to the opposite surface for various purposes such as to form conductive vias or else to create isolating regions of p-type that electricall isolate adjacent n-type regions on either side of the p-type region such as for series interconnecting adjacent devices: on the same wafer, and can include points, dashes, lines or any other geometry based on the pattem used in the application of the light and heat to locally reactivate the boron dopants.
- Figure 1 diagrammatically represents a -p-type silicon crystal lattice structure (boron doped);
- Figure 2 diagrammatically represents t e p-type silicon crystal lattice structure of Figure 1 after hydrogenation
- Figure 3 diagrammatically represents an n-type silicon crystal lattice structure (phosphorus doped);
- Figure 4 diagrammatically represents the n-type silicon crystal lattice structure of Figure 3 after hydrogenation
- Figure 5 diagrammatically represents the p-type silicon crystal lattice structure of
- Figure 6 diagrammatically represents the n-type silicon crystal lattice structure of Figure 4 showing the reactivation of the phosphorus dopant with the application of heat and light;
- Figure 7 diagrammatically illustrates a textured n-type wafer in which an
- Figure 8 diagrammatically illustrates the wafer of Figure 7 after initial doping of the front and rear surfaces
- Figure 9 diagrammatically illustrates the wafer of Figure 8 after dielectric layers are added
- Figure 10 diagrammatically illustrates the wafer of Figure 8 after patterning of the top surface dielectric
- FIG 11 diagrammatically illustrates the wafer of Figure 10 after hydrogenation of the emitter region:
- Figure 12 diagrammatically illustrates the wafer of Figure 11 after emitter metallisation is applied
- Figure 13 diagrammatically illustrates the wafer of Figure 12 after patterning of the rear surface dielectric
- Figure 14 diagraminatieally illustrates the wafer of Figure 13 after hydrogenation of the rear doped region:
- Figure 15 diagrammalica ' Uy illustrates the wafer of Figure 14 after rear surface- metallisation is applied
- Figure 16 diagrammatically illustrates a textured p-type wafer in whic a embodiment of the invention may be formed
- Figure 17 diagrammatically illustrates the wafer of Figure 16 after initial doping of the front and rear surfaces
- Figure 18 diagrammaticail illustrates the wafer of Figure 17 after dielectric layers are added
- Figure 19 diagrammatically illustrates the wafer of Figure 18 after patterning of the top surface dielectric
- Figure 20 diagrammatically illustrates the wafer of Figure 19 after hydrogenation o the emitter region:
- Figure 21 diagrammatically illustrates the wafer of Figure 20 after emitter metallisation is applied
- Figure 22 diagrammatically illustrates the wafer of Figure 21 after patterning of the rear surface dielectric
- Figure 23 diagrammaticaliy illustrates the water of Figure 22 after liydrogenation of thereat doped region:
- Figure 24 diagrammatically illustrates the wafer of Figure 23 after rear surface metallisation is applied
- FIGS. 25 to 27 diagrammatically illustrate an alternative sequence for the
- Figures 28 to 30 diagrammatically illustrate a further alternative sequence for the patterning, metallisation and hydrogenation of the wafer to that shown in Figures 10, 11 and ! "> ⁇
- Figures 31 to 35 diagrammatically illustrate, yet a further alternative sequence for the patterning, metallisation and hydrogenation of the wafer to that shown in Figures 10, 11 and 12;
- Figures 36 & 37 diagrammatically il lustrate two examples of belt furnaces modified to provide illumination in the heatin and cooling zones;
- Figures 38 illustrates and example of localised hydrogenation.
- Processes described herein provide & method for altering the active dopant densit through simple hydrogenation processes, by either deactivating or reactivating dopants, while also facilitating storing or releasing hydrogen as a source internal to the silicon respectively.
- This uniquely provides the opportunity for creating a hydrogen source internally within the silicon that can be exploited later for hydrogenation purposes by releasing the atomic hydrogen through the process of reactivating dopant atoms.
- Such strateg can also be used on a localised scale to reactivate localised doped regions so as to create a selective emitter structure. This provides a very simple mechanism for forming selective emitters - using only heat and light to manipulate the charge state of hydrogen in such a way as to facilitate deactivation or reactivation of dopants in localised areas as and where required.
- boron (B) is a valency 3 element which eait be used to dope silicon to produce p-type material when taking on substitutional sites within the silicon lattice, as illustrated in Figure 1, Each such, boron atom therefore produces a free "hol e" 1 1 , lea ving the boron atom with a fixed negative charge. Additional holes 12, 13 are seen in Figure 1, which will have moved away from the doping sights where they were created .
- the hydrogen may take on the positive charge state (H + ), by giving up two electrons which may subsequentl combine with a holes 13 as the hydrogen passes through the silicon lattice.
- phosphorus (P) is a. valency 5 element which can be used to dope silicon to produce n-type material when taking on substitutional sites within the silicon lattice, as illustrated in Figure 3, Each such phosphorus atom therefore produces a free "electron" 31, leaving the phosphorus atom with fixed positive charge.
- H 4" The dominant charge state for hydrogen i p-type silicon is H 4" and thus it is relatively simple to deactivate boron dopant atoms close to a silicon surface, however the H + will not have high mobility and will not travel far before being captured, hi the simple ease the charge state may be altered by healing which can allow H + to penetrate further into a doped region and with removal of the heat source will lock the hydrogen in when it has bonded with a dopant. H wever heating alone is less effective when trying to release hydrogen that is bonded to dopant atoms, to reactivate the dopant atoms, as the hydrogen will re-bond, particularly during cooling.
- H * is the dominant charge state and while heating will help in increasing the size of the region of deactivation of n-type dopant atoms, it will not be particularly effective in reactivation.
- the minority carrier concentrations can be increased sufficiently to allow large increase in the concentration of hydrogen atom that have a single electron attached to the hydrogen atom nucleus, therefore giving neutral charge state. It is also possible to significantly increase in the concentration of hydrogen atoms that have two electrons attached to the hydrogen atom nucleus, therefore giving a negative charge state.
- the neutral hydrogen atoms (and negative Hydrogen ions) are also more effective at bonding to many types of recombination sites due to the presence of the electron with the hydrogen atom.
- the coulombie forces holding hydrogen and boron atom together may be disrupted by thermal energy 5.1, releasing H + ions, while photons 52, 53 striking the silicon lattice may release electrons to form electron-hole pairs.
- active dopant concentration ' may be controlled by deactivation and reactivation of dopants as required;
- the above (1) can take place in localised areas so as to create localised regions of varying active doping concentration and even varying polarity such as may be useful for selective emitter or isolation regions;
- Boron can be intentionall added to the silicon.
- B manipulatin tire charge state of hydrogen in some or all areas of the device and providing, sufficient, thermal energy (typically 150° - SOOT) to increase the amount and mobility of the hydrogen, the boron can be de-activated (or re-activated as desired) - by enabling boron & hydrogen to bond together (or break and separate if boron reactivation is desired).
- This has many important implementations such as profiling resistivity in an emitter to for a selective Emitter, which can be done in a number of ways including but not limited to: (i) Example 1 - local deactivation :
- an n-type wafer 70 is textured 71; 2) A boron diffusion of the top surface to notionally achieve a p + region with a sheet resistance of 45-55 ⁇ / ⁇ (but which could be anywhere within a range of 1-80 ⁇ / ⁇ ) creates an em tter layer 82 seen in Figure 8;
- a phosphorus diffusion 93 may also be added to the rear surface to again notionally achieve an n* region with a sheet resistance of 45-55 ⁇ ⁇ (but which could be anywhere within a range of 1-80 ⁇ / ⁇ ) as also seen in Figure 8;
- a front surface dielectric layer 93 and a rear surface dielectric layer 94 are then deposited as seen in Figure 9.
- the dielectric layers 93 & 94 act as hydrogen sources and may be selected from hydrogen containing dielectric material such as silicon nitride, silicon oxynitride, aluminium oxides etc.;
- the front surface dielectric laye 93 is patterned as seen in Figure 10, to create openings 105 for emitter metallisation. This can be done by a laser 101, by screen printing or Inkjet patterning or other suitable known processes;
- hydiOgenation of the emitter i performed, in areas of silicon 112 where the dielectric 93 has not been removed (i.e. where hydrogen source is present), such as by heating the device to 400 " in darkness or in low light.
- This proces manipulates the charge state in suc a way that boron is deactivated wherever hydrogen is present. Boron is deactivated by hydrogen which bonds with the negative boron atoms that are active in the silicon lattice.
- Metal contacts .128 may then be applied to the exposed p + regions 82, such as by plating or aligned screen printing, as seen in Figure 12.
- the rear surface dielectric laye 94 is patterned as. seen in Figure 13, to create opening 1 for rea metallisation. This can be done by a laser 132, by screen printing or .inkjet. patternin or other suitable known processes;
- Hydrogenatian performed in a manner which maximises the amount of W present will enable (he H " to bond with the P + thereby de-activating the phosphorus and creating higher sheet resistivity materia] in these regions, while leavin lower sheet resistivity regions 83 where the dielectric hydrogen source 94 has been removed to form, openings 136 for the subsequent formation of metal contacts.
- the percentage of atomic hydrogen in the negative charge state is maximised by keeping the hole concentration low such as by minimising the light generated by the heating sources which have photons with energy levels above the bandgap of silicon (1.12eV) and by avoiding temperatures significantly above the 30Q-5GG°C range that is desirable for reasonable hydrogen mobility and the release of hydrogen from the dielectric hydrogen sources 94.
- Metal contacts 156 may then be applied to the exposed n + regions 83, such as by plating or aligned screen printing, a seen in Figure 15.
- Example 2 - local deactivation 1) Referring to Figure 16, a p-type wafer 160 is textured 161;
- a boron diffusion 173 may also be added to the rear surface to again notionally achieve an " region with a sheet, resistance of 45-55 ⁇ / ⁇ (but which could be anywhere within a range of 1-80 ⁇ / ⁇ ) as also seen in Figure 17;
- a front surface dielectric layer 183 and rear surface dielectric layer 184 are then deposited as seen in Figure 18.
- the dielectric layers 183 & 184 act as hydrogen sources and may be selected from hydrogen containing dielectric materials such as silicon nitride, silicon oxynitride, aluminium oxides etc.;
- the front surface dielectric layer 183 s patterned as seen in Figure 19, to create openings 195 for emitter metallisation. This can be done by a laser 191, by screen printin or ittkjet patterning or other suitable known processes; 6) Referring to Figure 20, hydrogenation of the emitter is performed, in areas of silicon 202 where the dielectric 183 has not been removed (i.e. where hydrogen source is present), such as by heating the device to 400°C in darkness or low light. This process manipulates the charge state in such a way that phosphorus is deactivated wherever hydrogen is present. Phosphorus is deactivated by hydrogen (H " ) which bonds with the positive phosphorus atoms that, are active in the silicon lattice.
- H " hydrogen
- Metal contact 218 may then be applied to the exposed n + regions 172, such as by plating or aligned screen printing, as seen in Figure 21.
- the rear surface dielectric layer 184 is patterned as seen in Figure 22, to create openings 226 for rear metallisation. This can be done by a laser 222, by screen printing or Inkjet patterning or other suitable known processes;
- the percentage of atomic hydrogen in the positive charge state is maximised by keeping the electron concentration low such as by minimising the light generation of carriers whic is in turn minimised by minimising the light incident on the wafer which necessitates the use of heaters that radiate minimal light which has photons with energy levels above the bandgap of silicon (.1.12eV) and by avoiding temperatures above about 30Q-500°C that are desirable for reasonable hydrogen mobility and the release of hydrogen fro the dielectric hydrogen sources 184.
- the identical conditions have been described for phosphorus and boron deactivation s as to facilitate simultaneous deactivation of both the phosphorus at the front and boron at the rear.
- different hydrogen tion (deactivation) processing conditions may be beneficial for the phosphorus and boron suc that the two processes should therefore be carried out separately.
- Metal contacts. 246 may then be applied to the exposed, p + regions 83, such as by plating or aligned screen printing, as seen in Figure 24,
- the percentage of atomic hydrogen in the positive charge state is maximised b keeping the electron concentration low such as by minimising any light having photons with energy levels above the bandgap of silicon ( 1.12eV) such as light generated by the heat sources and b avoiding temperatures above about 300-500°C that are desirable for reasonable hydrogen mobility and the release of hydrogen from the .dielectric .hydrogen sources 93.
- the front surface dielectric layer 93 is the patterned as seen in Figure 26, to create openings 265 for emitter metallisation. This can be done by a laser 101, by screen printing or inkjet patternin or other suitable known processes. If a laser is used to open the front suiface dielectric layer 93, the boron in the underlying p-type silicon may be simultaneously re-activated to create a p+ region 272, seen in Figure 27, by controlling the light and heat applied to the silicon during the opening step.
- the laser light not only ablates the dielectric locally, but also generates heat and electron-hole pairs within the surface of the silicon so as to raise the electron concentration, therefore allowing more of the bonded H (bonded to the boron atoms as previously discussed) in the localised .area to be released and take on the neutral or even H- charge state and therefore escape from the B- atom. This therefore reactivates the boron atom.
- the opening 265 is formed by other means a subsequent ste of heating with localised illumination may be used to reactivate the boron in the area 272 under the opening 165.
- Metal contacts 1.28 may then, be applied to the exposed p + regions 272, in th same manner that the metal contacts 128 are applied to the exposed p + regions 82 in Figure 12, such as by plating or aligned screen printing, as seen in Figure 12,
- steps 1) - 3) above may also be applied to modify the hydrogenation of die rear surface n + region 83, the opening of the rear surface dielectric 94, the deactivation of the phosphorus in the rear surface n + region 141 and the formation of the rear surface contact 156, described with reference to Figures 13-15, however this may need different hydrogenation processing conditions for optimal charge state manipulation.
- the method described in steps 1) -3) above may also be applied to modify the processes described for the formation of devices formed in the p-type wafer illustrated in Figures 16-24.
- This approach relies on deactivation of the boron (or phosphorus) dopants after the dielectric hydrogen source has already been patterned, whereby the regions without dielectric coating do not receive significant levels of hydrogen (i.e. no hydrogen source) and therefore locally prevents its deactivation.
- the first steps of this process are the same as for a device created in an n-type wafer 70 with surface dielectric layers 93, 94 and low sheet resistivit n + emitter 82 (1-100 ⁇ / ⁇ ), as previously described above with reference to Figures 7 & 8.
- the front surface dielectric layer 93 is patterned as seen in Figure 28 (as for the step described with reference to Figure 9), to create openings 105 for emitter metallisation. This can be done by a laser 101, by screen printing or Inkjet patterning or othe suitable known processes;
- the hydrogenation process can be performed locally to deactivate dopants wherever the hydrogen source is still present or alternatively, metal contacts 298 may first be applied to the exposed p + regions 82, such as by plating or aligned screen, printing, as seen in Figure 29 (similar to the step described with reference to Figure 12), however in this latter case the emitter 82 has not yet.
- a hydrogenation process is performed to deactivate most of the boron in the emitter 82 to produce a higher resistance p-type emitter 302 with a sheet resistance >100 ⁇ ⁇ , (typically 120-200: ⁇ / ⁇ ), while leaving the p + region 82 in the regions without the dielectric source and/or under the metal contact 298.
- This requires manipulating the charge state of hydrogen to enable high concentrations of H + to bond with and deacti vate the B in the parts of the emitter 302 directly exposed to the dielectric hydrogen source layer 93.
- a similar sequence modification may also be applied to modify the hydrogenation of the rear surface n + region 83, the opening of the rear surface dielectric 94, the deactivation of the phosphorus in the rear surface n + region 141 and the formation of the rear surface contacts 156. described with reference to Figures 13-15, however this may need different
- Another variation of the proces e described above is to deactivate all the boron to >100 ⁇ / ⁇ prior to metallisation to produce a structure which after metallisation still has higher resistance p-type material (i.e. > ⁇ / ⁇ ) under the metal contacts, and subsequently processing the material under the metal contacts to reactivate the dopant.
- This process manipulates the hydrogen charge state in such a way that boron i deactivated wherever hydrogen is present. Boron is deactivated by hydrogen which bonds with the negati e boron atoms that are active in the silicon lattice. Hydrogenation performed in a manne which maximises the amount of H* present will enable the H + to bond with the B " thereby deactivating the boron and creating higher sheet resistivit material in these regions.
- the percentage of atomic hydrogen in the positive charge state is maximised by keeping the electron concentration low such as by minimising any light from the heaters which has photons with energy levels above the band gap of silicon (l, 12eV) and by avoiding significantly above the typical range of 300-5O0°C thai is necessary for reasonable hydrogen mobility and the release of hydrogen from the dielectric hydrogen sources 93.
- the front surface dielectric layer 93 is patterned as seen in Figure 32, to create openings 325 for emitter metallisation. This can be done by a laser 321, by screen printing or Inkjet patterning or other suitable known processes;
- Metal contacts 338 may then be applied to the exposed p + regions 312. such as by plating or aligned screen printing, as seen in Figure 33.
- a laser can then be used locally in the vicinity of the
- the local reactivation of the dopants through the use of the laser requires some of the laser light to be absorbed within the silicon (to generate the electron-hole pairs to control the hydrogen charge-state) and therefore the laser 341 needs to be incident- locally on the silicon just adjacent to the metal contacts, whereby electron-hole pairs generated adjacent to the metal contacts 338 (i.e. just outside the shadow of the metal contacts) are able to diffuse underneath the metal contacts 338 and therefore locall raise the electron concentration to facilitate the necessary control of the hydrogen charge and so facilitate reactivation of the dopants.
- cooling is sufficiently rapid when the laser is removed relative to the lifetime of the hydrogen charge states and/or lifetime of the electron-hole pairs such that little opporturtity is provided for the hydrogenation process to reverse.
- a laser 351. may be applied to the rear surface as seen in Figure 35 to generate the p+ region 352. Creating an internal hydrogen source
- the hydrogenation process as described above can be performed in such a way as to manipulate the charge states of the hydrogen so that it can facilitate either increased or decreased formation of the B-H bonds (deactivation of the boron atoms) and therefore also either increased or decreased breaking of the B-H. bonds (with corresponding reactivation of the boron atoms).
- Extra dopant atoms such as boron can be diffused, grown, implanted etc. into the silicon, and then in the presence of a hydrogen source such as from a. dielectric, the extra dopant can be deactivated by a process that manipulates the charge state of hydrogen to enable high concentrations of H + to bond with and deactivate the B " .
- a hydrogen source such as from a. dielectric
- this can be done by performing hydrogenation at a temperature in the range 20Q-5GO°C in the dark or with low illumination.
- Each boron atom that is deactivated is therefore bound to a hydrogen atom, so that hydrogen atoms can be located all throughout the silicon wafer in the areas that were deactivated by the hydrogenation process, essentially creating internal store of hydrogen throughout the wafer.
- Belt furnaces are commonly used for heat processin of semiconductor devices, By modifying a belt furnace to incorporate- illumination source in the heating and cooling stages, such that heating and cooling may be performed under illumination, belt furnaces may be used to perform hydrogenation or to redistribute hydrogen in the device being processed, Such a modified belt furnace may also be used in a "dark" mode with some or all of the illumination disabled for dark processing.
- a first modified belt furnace 3601 is illustrated.
- the urnace of Figure 3 has a heat resistant belt 3602 (e.g. a ceramic rolle or metal link style belt which passes through the furnace and extends from each end for loading and unloading.
- the furnace has a heating zone 3605 and a cooling zone 3606. Through which the belt passes.
- the heating zone has heating lamps 3603 which direct heat at the belt 3602 and anything carried on the belt, such as a wafer 3611 undergoing hydrogenation in the process to make a solar cell.
- the heating lamps 3603 typically produce radiant heat, and may be high powered lights which produce large amounts of radiant heat such as infra-Rid lamps.
- the heaters may be high powered lights w ich are chosen (or driven differently) to also provide high levels of light.
- supplementary lightin 3609 may optionally also be provided.
- light levels from 0.1. sun up to 100 suns might be provided in the heating zone 3605, Jn the cooling zone of a conventional belt furnace, cooling is performed in the dark.
- lamps 3604 are provided in the cooling zone 3606 such that solar cells processed in the belt furnace may be illuminated during cool-down.
- the lamps 3604 in the cooling zone may advantageousl provide less heating than the lamps in the heating zone. This may be achieved by usin cooler or more efficient (e.g.
- the lamps 3604 in the cooling zone 3606 may be pulsed (taking advantage of the lifetime of the light induced charge states and/or the lifetime of the generated electro -hole pairs) to reduce their average heat output.
- the cooling zone 3606 may optionally be cooled by ⁇ passing cooling air throug the cooling zone usin inlet fans 3607 and exhaust fans 3608 to counteract any heating effects of the lamps 3604, to more rapidly bring the target device below a temperature at which the hydrogen passivated defects in the device will become stable.
- the cooling air may be chilled.
- other gasses may be introduced at low temperature to assist cooling.
- a second modified belt furnace 3601 is illustrated.
- the furnace of Figure 37 has a heat resistant belt 3602 (e.g. a metal link style belt which passes through the furnace and extends from each end for loading and unloading).
- the furnace has a heating zone 3605 and a cooling zone 3606, through which the belt passes.
- the heating zone in this case has plate heaters 3610 which direct heat from beneath the belt 3602 to heat anything carried on the belt, such a a wafer 3611 undergoing hydrogenation in the process to make a solar cell.
- supplementar lighting 360 is provided in the heating zone 3605, as there would be no lighting in the heating zone of a conventional belt furnace which used plate or resistive heaters. Again, ideally light levels of up to 100 suns might be provided in the heating zone 3605. In the cooling zone of a conventional belt furnace, cooling is performed in the dark. However in the present, modified belt furnace 3601, as with the previous example, lamps 3604 are provided in the cooling zone 3606 such that solar cells proces sed in the belt furnace may be illuminated during cool -down.
- the cooling zone 360 of Figure 37 may be identical to that of Figure 36.
- a finished cell including protective encapsulatin layers 3840 over both surfaces.
- Localised hydrogenation processing or redistribution of hydrogen may be performed at any time during the manufacture of a cell and after the cell is completed as shown in Figure 38. Localised processing involve performing hydrogenation on a small area of the cell to avoid damaging parts of the cell structure that may be damaged either by excessive heat or for which hydrogenation is not appropriate. If larger areas require hydrogenalion then this .may be achieved incrementally by scanning the heating and lighting source over the areas of the device to be processed at a rate that for example avoids excessive heating of the entire device.
- heating m ay be achieved by a laser 3842 which heats and illuminates a small zone 3841 of the device.
- the laser may be defoeused to heat a larger area and to avoid over heating as the laser is scanned slowly over the surface of the device.
- the laser may also be pulsed to allow further control of temperature and lightin conditions. As the laser moves to a ne zone (e.g. by scanning to an adjacent zone), the previous zone will cool quickly as heat i conducted away through the bulk of the device.
- the localised heat and light source may also be another type of light source rather than a laser.
- the source migh be an infra-red light source which is focused and shielded to illuminate only selected area of the device at any gi ven time.
- the light source may also be pulsed to control the temperature and illumination levels applied to the zone being hydrogenated.
- This technique has the advantage that, provided adequate hydrogen source material was incorporated i the cell at manufacture, it may be used on installed solar ceil arrays, amongst other uses, to repair or rejuvenate cells that have degraded in the field. It ca also be used during manufacture to avoid damaging cells that progre sed to a point in the manufacturing process where excessive heating of the entire device will damage the cell. For example it is possible to treat areas away from the metallisation, while avoiding heating the metallised areas, which if heated excessively could result in the metal penetrating an underlying junction.
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CN110323130A (en) * | 2019-07-12 | 2019-10-11 | 吉林大学 | A kind of chromium doped black silicon material and preparation method thereof |
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WO2018094462A1 (en) * | 2016-11-22 | 2018-05-31 | Newsouth Innovations Pty Limited | Advanced hydrogen passivation that mitigates hydrogen-induced recombination (hir) and surface passivation deterioration in pv devices |
US11031520B2 (en) | 2016-11-22 | 2021-06-08 | Newsouth Innovations Pty Limited | Advanced hydrogen passivation that mitigates hydrogen-induced recombination (HIR) and surface passivation deterioration in PV devices |
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AU2014295816A1 (en) | 2016-02-11 |
SG11201600282SA (en) | 2016-02-26 |
TWI625769B (en) | 2018-06-01 |
US9947821B2 (en) | 2018-04-17 |
TW201519289A (en) | 2015-05-16 |
EP3025367A4 (en) | 2017-04-26 |
KR102289901B1 (en) | 2021-08-18 |
CN105474364B (en) | 2018-11-16 |
AU2014295816B2 (en) | 2018-09-13 |
CN105474364A (en) | 2016-04-06 |
EP3025367A1 (en) | 2016-06-01 |
US20160225930A1 (en) | 2016-08-04 |
KR20160039635A (en) | 2016-04-11 |
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