US20150194563A1 - Method for selective under-etching of porous silicon - Google Patents
Method for selective under-etching of porous silicon Download PDFInfo
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- US20150194563A1 US20150194563A1 US14/667,157 US201514667157A US2015194563A1 US 20150194563 A1 US20150194563 A1 US 20150194563A1 US 201514667157 A US201514667157 A US 201514667157A US 2015194563 A1 US2015194563 A1 US 2015194563A1
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- United States
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- surfactant
- silicon
- porous silicon
- aqueous etchant
- silicon layer
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- 238000000034 method Methods 0.000 title claims abstract description 40
- 229910021426 porous silicon Inorganic materials 0.000 title claims abstract description 40
- 238000005530 etching Methods 0.000 title claims description 14
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- 229910052710 silicon Inorganic materials 0.000 claims abstract description 45
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- 229910021421 monocrystalline silicon Inorganic materials 0.000 claims abstract description 17
- -1 poly(ethylene oxide) Polymers 0.000 claims description 20
- 239000004094 surface-active agent Substances 0.000 claims description 16
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- 239000011521 glass Substances 0.000 claims description 8
- 229910021419 crystalline silicon Inorganic materials 0.000 claims description 7
- 229920003171 Poly (ethylene oxide) Polymers 0.000 claims description 6
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims description 5
- YFSUTJLHUFNCNZ-UHFFFAOYSA-M 1,1,2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-heptadecafluorooctane-1-sulfonate Chemical compound [O-]S(=O)(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F YFSUTJLHUFNCNZ-UHFFFAOYSA-M 0.000 claims description 4
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- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 4
- 229960000686 benzalkonium chloride Drugs 0.000 claims description 4
- 229960001950 benzethonium chloride Drugs 0.000 claims description 4
- UREZNYTWGJKWBI-UHFFFAOYSA-M benzethonium chloride Chemical compound [Cl-].C1=CC(C(C)(C)CC(C)(C)C)=CC=C1OCCOCC[N+](C)(C)CC1=CC=CC=C1 UREZNYTWGJKWBI-UHFFFAOYSA-M 0.000 claims description 4
- CADWTSSKOVRVJC-UHFFFAOYSA-N benzyl(dimethyl)azanium;chloride Chemical compound [Cl-].C[NH+](C)CC1=CC=CC=C1 CADWTSSKOVRVJC-UHFFFAOYSA-N 0.000 claims description 4
- 229960001927 cetylpyridinium chloride Drugs 0.000 claims description 4
- YMKDRGPMQRFJGP-UHFFFAOYSA-M cetylpyridinium chloride Chemical compound [Cl-].CCCCCCCCCCCCCCCC[N+]1=CC=CC=C1 YMKDRGPMQRFJGP-UHFFFAOYSA-M 0.000 claims description 4
- BXWNKGSJHAJOGX-UHFFFAOYSA-N hexadecan-1-ol Chemical compound CCCCCCCCCCCCCCCCO BXWNKGSJHAJOGX-UHFFFAOYSA-N 0.000 claims description 4
- 229910000040 hydrogen fluoride Inorganic materials 0.000 claims description 4
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- ALSTYHKOOCGGFT-KTKRTIGZSA-N (9Z)-octadecen-1-ol Chemical compound CCCCCCCC\C=C/CCCCCCCCO ALSTYHKOOCGGFT-KTKRTIGZSA-N 0.000 claims description 2
- SNGREZUHAYWORS-UHFFFAOYSA-M 2,2,3,3,4,4,5,5,6,6,7,7,8,8,8-pentadecafluorooctanoate Chemical compound [O-]C(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F SNGREZUHAYWORS-UHFFFAOYSA-M 0.000 claims description 2
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- BTBJBAZGXNKLQC-UHFFFAOYSA-N ammonium lauryl sulfate Chemical compound [NH4+].CCCCCCCCCCCCOS([O-])(=O)=O BTBJBAZGXNKLQC-UHFFFAOYSA-N 0.000 claims description 2
- 229940063953 ammonium lauryl sulfate Drugs 0.000 claims description 2
- 229940077388 benzenesulfonate Drugs 0.000 claims description 2
- 229960000541 cetyl alcohol Drugs 0.000 claims description 2
- MRUAUOIMASANKQ-UHFFFAOYSA-N cocamidopropyl betaine Chemical compound CCCCCCCCCCCC(=O)NCCC[N+](C)(C)CC([O-])=O MRUAUOIMASANKQ-UHFFFAOYSA-N 0.000 claims description 2
- 229940073507 cocamidopropyl betaine Drugs 0.000 claims description 2
- WOQQAWHSKSSAGF-WXFJLFHKSA-N decyl beta-D-maltopyranoside Chemical compound O[C@@H]1[C@@H](O)[C@H](OCCCCCCCCCC)O[C@H](CO)[C@H]1O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 WOQQAWHSKSSAGF-WXFJLFHKSA-N 0.000 claims description 2
- SYELZBGXAIXKHU-UHFFFAOYSA-N dodecyldimethylamine N-oxide Chemical compound CCCCCCCCCCCC[N+](C)(C)[O-] SYELZBGXAIXKHU-UHFFFAOYSA-N 0.000 claims description 2
- 150000002191 fatty alcohols Chemical class 0.000 claims description 2
- 239000000463 material Substances 0.000 claims description 2
- DVEKCXOJTLDBFE-UHFFFAOYSA-N n-dodecyl-n,n-dimethylglycinate Chemical compound CCCCCCCCCCCC[N+](C)(C)CC([O-])=O DVEKCXOJTLDBFE-UHFFFAOYSA-N 0.000 claims description 2
- HEGSGKPQLMEBJL-RKQHYHRCSA-N octyl beta-D-glucopyranoside Chemical compound CCCCCCCCO[C@@H]1O[C@H](CO)[C@@H](O)[C@H](O)[C@H]1O HEGSGKPQLMEBJL-RKQHYHRCSA-N 0.000 claims description 2
- 229940055577 oleyl alcohol Drugs 0.000 claims description 2
- XMLQWXUVTXCDDL-UHFFFAOYSA-N oleyl alcohol Natural products CCCCCCC=CCCCCCCCCCCO XMLQWXUVTXCDDL-UHFFFAOYSA-N 0.000 claims description 2
- SNGREZUHAYWORS-UHFFFAOYSA-N perfluorooctanoic acid Chemical compound OC(=O)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)C(F)(F)F SNGREZUHAYWORS-UHFFFAOYSA-N 0.000 claims description 2
- 229920001451 polypropylene glycol Polymers 0.000 claims description 2
- 229920000136 polysorbate Polymers 0.000 claims description 2
- 229940068965 polysorbates Drugs 0.000 claims description 2
- 239000000344 soap Substances 0.000 claims description 2
- 229940057950 sodium laureth sulfate Drugs 0.000 claims description 2
- SXHLENDCVBIJFO-UHFFFAOYSA-M sodium;2-[2-(2-dodecoxyethoxy)ethoxy]ethyl sulfate Chemical compound [Na+].CCCCCCCCCCCCOCCOCCOCCOS([O-])(=O)=O SXHLENDCVBIJFO-UHFFFAOYSA-M 0.000 claims description 2
- 239000003760 tallow Substances 0.000 claims description 2
- 239000002888 zwitterionic surfactant Substances 0.000 claims 2
- 150000004665 fatty acids Chemical class 0.000 claims 1
- 239000000758 substrate Substances 0.000 abstract description 12
- 235000012431 wafers Nutrition 0.000 description 45
- 229910021420 polycrystalline silicon Inorganic materials 0.000 description 6
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- 239000013078 crystal Substances 0.000 description 4
- 238000000151 deposition Methods 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- 239000002019 doping agent Substances 0.000 description 4
- 238000004146 energy storage Methods 0.000 description 4
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- 238000000576 coating method Methods 0.000 description 3
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- 229910052751 metal Inorganic materials 0.000 description 3
- 239000002184 metal Substances 0.000 description 3
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000006117 anti-reflective coating Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000005468 ion implantation Methods 0.000 description 2
- 239000002210 silicon-based material Substances 0.000 description 2
- 238000002207 thermal evaporation Methods 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229910052581 Si3N4 Inorganic materials 0.000 description 1
- BQCADISMDOOEFD-UHFFFAOYSA-N Silver Chemical compound [Ag] BQCADISMDOOEFD-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
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- 238000007650 screen-printing Methods 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 1
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Images
Classifications
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- 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 at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System 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
- H01L21/302—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to change their surface-physical characteristics or shape, e.g. etching, polishing, cutting
- H01L21/306—Chemical or electrical treatment, e.g. electrolytic etching
- H01L21/30604—Chemical etching
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/0248—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 System
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/04—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices
- H01L31/06—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier
- H01L31/068—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof adapted as photovoltaic [PV] conversion devices characterised by at least one potential-jump barrier or surface barrier the potential barriers being only of the PN homojunction type, e.g. bulk silicon PN homojunction solar cells or thin film polycrystalline silicon PN homojunction solar cells
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1892—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof methods involving the use of temporary, removable substrates
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- 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 at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System 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
- H01L21/31—Treatment of semiconductor bodies using processes or apparatus not provided for in groups H01L21/20 - H01L21/26 to form insulating layers thereon, e.g. for masking or by using photolithographic techniques; After treatment of these layers; Selection of materials for these layers
- H01L21/3105—After-treatment
- H01L21/311—Etching the insulating layers by chemical or physical means
- H01L21/31105—Etching inorganic layers
- H01L21/31111—Etching inorganic layers by chemical means
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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
- This invention relates to a method for making solar cells. More particularly, the present invention relates to selective etching of a porous silicon layer to under-cut and release a silicon-based device layer that is then used for making solar cells.
- Solar cells are semiconductor devices that are usually manufactured from silicon-based material. Some solar cells are made from screen printed poly-crystalline silicon. Single crystalline wafers can be used to make very efficient solar cells. However, high manufacturing costs for making single crystalline materials makes the large scale production of solar cells from these materials impractical.
- Poly-crystalline silicon wafers used to manufacture solar cells are made by cutting 180 to 350 micrometer thick wafers from block-cast silicon ingots.
- the wafers are usually lightly p-type doped.
- a surface diffusion of n-type dopants is performed on the front side of the wafer. This forms a p-n junction a few hundred nanometers below the surface.
- Solar cells usually also include anti-reflective coatings, such as silicon nitride or titanium dioxide and/or have textured surfaces increase efficiency of light absorption. This method is disadvantageous in that the crystal takes an exceptionally long time to grow on the silicon ingot.
- Metal contacts are formed on the back and front surfaces of poly-crystalline silicon wafers by screen-printing metal pastes, such as silver paste or aluminum paste. After the metal contacts are formed, the solar cells are assembled into panels and are sandwiched between glass and polymer resins.
- metal pastes such as silver paste or aluminum paste.
- solar cells and solar panels that are formed from single crystal silicon are preferred because of the efficiency of the solar cells and panels made from single crystal silicon.
- the present invention is direct to a method of making a solar cell.
- a silicon-based device layer is formed on a base wafer.
- the base wafer includes a single crystal silicon wafer and a sacrificial porous silicon layer that is deposited thereon.
- the sacrificial porous silicon layer is formed using thermal deposition or any other suitable coating or deposition technique.
- the porous silicon layer has a porosity of 30 percent or more.
- the sacrificial porous silicon layer comprises, for example, carbon doped oxide, spin-on-glass (SOG), fluoridated silicon glass (FSG) or a combination thereof.
- the thickness of the porous silicon layer is preferably in a range of several nanometers to several microns.
- the silicon-based device layer is preferably crystalline or semi-crystalline, as opposed to being amorphous, and is epitaxially grown on top of the sacrificial porous silicon layer.
- the silicon-based device layer is preferably a p-doped silicon-based device layer that has a thickness of several microns to several hundred microns.
- the silicon-based device layer is formed using any suitable growth or deposition technique, such as chemical vapor deposition.
- a working wafer that includes the single crystal silicon wafer, the silicon-based device layer and the sacrificial porous silicon layer sandwiched between the single crystal silicon wafer and the silicon-based device layer is referred to herein as a composited wafer.
- the sacrificial layer is selectively etched thereby releasing the silicon-based device layer, or a portion thereof and the single crystal wafer, or a portion thereof.
- the released silicon-based device layer, or the portion thereof is then provided with the appropriate electrical contacts and anti-reflective coatings and is coupled to one or more substrates to form a solar cell.
- the released single crystal wafer, or the portion thereof is then used to make additional composite wafers and additional solar cells, such as described above.
- the etch rate of the porous silicon layer needs to be significantly faster than the etch rates of either the single crystal wafer or of the silicon-based device layer.
- Selective etching of the sacrificial porous silicon layer has been observed by treating the composite wafer to an aqueous etchant that is maintained at temperatures in a range of 0 to 10 degrees Celsius.
- the aqueous etchant preferably includes one or more etchants such as potassium hydroxide, sodium hydroxide and hydrogen fluoride in a concentration of 5% or less by weight.
- the aqueous etchant includes an alcohol, such as isopropyl alcohol, in a concentration of 10% or less by weight.
- the etchant includes a surfactant in a concentration of 1% or less by weight. Also, to further control etch rates during the selective etching step, the composite wafer and the aqueous etchant are treated with ultrasonic energy.
- FIG. 1A shows a composite wafer used to make a silicon-based device layer for solar cells, in accordance with the embodiments of the invention.
- FIG. 1B illustrates releasing a silicon-based device layer from the composite wafer, in accordance with the embodiments of the invention.
- FIG. 1C shows a released silicon-based device layer coupled to a substrate to form a solar cell, in accordance with the embodiments of the invention.
- FIG. 2A shows a block-flow diagram outlining steps for making a solar cell, in accordance with the method of the invention.
- FIG. 2B shows a block-flow diagram outlining steps for making a composite wafer, in accordance with the method of the invention.
- FIG. 2C shows a block-flow diagram outlining steps for releasing a device layer from the composite wafer, in accordance with the method of the invention.
- FIG. 3 shows a schematic representation of a solar panel with multiple solar cells on a common substrate, in accordance with the embodiments of the invention.
- FIG. 4 shows a schematic representation of a system that utilizes a solar cell or panel, in accordance with the embodiments of the invention.
- FIG. 1 shows a composite wafer 100 used to make a silicon-based device layer used in solar cells.
- the composite wafer 100 includes a single crystal silicon wafer 101 and a sacrificial porous silicon layer 103 that is deposited thereon, which is referred to herein as a base wafer.
- the composite wafer 100 also includes a silicon-based device layer 105 that is preferably crystalline or semi-crystalline and is epitaxially grown on top of the sacrificial porous silicon layer 103 .
- the sacrificial porous silicon layer 103 preferably has a porosity of 30 percent or more and is several nanometers to several microns thick.
- the sacrificial porous silicon layer 103 is formed from any suitable porous silicon material including, but not limited to carbon doped oxide, spin-on-glass (SOG), fluoridated silicon glass (FSG) or a combination thereof.
- the silicon-based device layer 105 is preferably a p-doped silicon-based device layer that has a thickness of several microns to several hundred microns.
- the sacrificial porous silicon layer 103 and the silicon-based device layer 105 are formed using any suitable coating, growth and/or deposition techniques including, but not limited to, thermal deposition and chemical vapor deposition.
- FIG. 1B illustrates a schematic representation 120 of a released silicon-based device layer 105 ′ and a released single crystal silicon wafer 101 ′ which are formed by selectively etching the sacrificial porous silicon layer 103 , as indicated by the arrow 109 .
- Selective etching of the sacrificial porous silicon layer 103 is preferably accomplished by steps outlined and described below with reference to FIGS. 2A-C
- FIG. 1C shows the released silicon-based device layer 105 ′ coupled to a new substrate 101 ′′ to form a solar cell 130 .
- the released silicon-based device layer 105 ′ and/or substrate 101 ′′ are preferably provided with the appropriate electrical contacts and anti-reflecting coatings to form a working solar cell 130 .
- the released single crystal silicon wafer 101 ′ is reused preferably from 0-50 times, and more preferably from 20-30 times to make additional composite wafers and solar cells.
- FIG. 2A shows a block flow diagram 200 outlining steps for making a solar cell.
- a composite wafer 100 is formed, such as described with reference to FIG. 1A .
- the sacrificial porous silicon layer 103 is controllably or selectively etched to form a released silicon-based device layer 105 ′ and a released single crystal silicon wafer 101 ′, such as shown in FIG. 1B .
- the composite wafer 100 is formed using any number of techniques or combination of techniques.
- the sacrificial porous silicon layer 103 is deposited in the step 202 by spin coating poly-silicon on the substrate 101 , which is preferably a single crystal silicon wafer.
- the poly-silicon is then dried or cured to remove solvent and form the sacrificial porous silicon layer 103 .
- the sacrificial porous silicon layer 103 has a porosity of 30% or more, which is believed to increase the selectivity of the etch rate for the sacrificial porous silicon layer 103 .
- the device layer 105 is formed over the sacrificial porous silicon layer 103 .
- the device layer 105 is preferably formed using any suitable technique, but is preferably formed by epitaxially growing a crystalline or semi-crystalline silicon device layer using vapor deposition techniques.
- the device layer 105 that is formed in the step 204 is preferably a p-doped device layer.
- the device layer 105 is formed, for example, by vapour depositing silicon-based precursors that includes a p-dopant or p-dopants, herein referred to as p-doped silicon-based precursors.
- Suitable p-doped silicon-based precursors include trivalent atoms typically from group IIIA of the periodic table, such as boron or aluminum.
- the device layer 105 may be doped after its formation using ion implantation techniques.
- the sacrificial porous silicon layer 103 is controllably or selectively etched to form a released silicon-based device layer 105 ′ and a released single crystal silicon wafer 101 ′.
- the sacrificial porous silicon layer 103 is controllably or selectively etched by first patterning the device layer 105 with access groove or holes in the step 206 . After the device layer 105 is patterned with access grooves or holes in the step 206 , the composite wafer 100 is treated with an etchant, such as described above and below.
- Patterning the device layer 105 with access grooves or holes prior to treating the composite wafer 100 with an etchant can result in faster etch rates by allowing a greater surface area of the sacrificial poly-silicon layer 103 to be initially exposed to the etchant.
- the device layer 105 is patterned with access groves or holes in the step 206 by using photo-resist masking and etching techniques. It will be clear to one skilled in the art that while patterning the device layer 105 with access groves or holes, such as described above, can be beneficial, it is not necessary to implement the present invention. Regardless of whether the step 206 of patterning the device layer 105 with access groves or holes is performed, in the step 208 the composite wafer 100 is treated with an etchant to form a released silicon-based device layer 105 ′ and a release single crystal silicon wafer 101 ′, such as shown in FIG. 1B .
- the composite wafer 100 is treated with an aqueous etchant comprising one or more of potassium hydroxide, sodium hydroxide and hydrogen fluoride in concentrations of 5% or less by weight.
- the aqueous etchant is maintained at temperatures in a range of 0 to 10 degrees Celsius during the step 208 . This temperature range results in better selectivity during the etching process.
- the aqueous etchant includes an alcohol, such as isopropyl alcohol, in a concentration of 10% or less by weight.
- the etchant includes a surfactant in a concentration of 1% or less by weight. Suitable surfactants include, but are not limited to:
- Anionic Surfactants such as, for example, Perfluorooctanoate (PFOA or PFO), Perfluorooctanesulfonate (PFOS), Sodium dodecyl sulfate (SDS), ammonium lauryl sulfate, Sodium laureth sulfate and Alkyl benzene sulfonate; 2) Soap or fatty acid salt surfactants; 3) Cationic Surfactants, such as, for example, Cetyl trimethylammonium bromide (CTAB), a.k.a.
- CTAB Cetyl trimethylammonium bromide
- hexadecyl trimethyl ammonium bromide Cetylpyridinium chloride (CPC), Polyethoxylated tallow amine (POEA), Benzalkonium chloride (BAC) and Benzethonium chloride (BZT); 4) Zwitterionic (amphoteric) Surfactants, such as, for example Dodecyl betaine, Cocamidopropyl betaine, Coco ampho glycinate; and 5) Nonionic Surfactants, such as, for example Alkyl poly(ethylene oxide), Alkylphenol poly(ethylene oxide) Copolymers of poly(ethylene oxide) and poly(propylene oxide), Octyl glucoside, Decyl maltoside, Fatty alcohols, Cetyl alcohol, Oleyl alcohol, Cocamide MEA, cocamide DEA, Polysorbates and Dodecyl dimethylamine oxide.
- CPC Cetylpyridinium chloride
- POEA Polyethoxylated tallow amine
- the composite wafer 100 and the aqueous etchant are treated with ultrasonic energy.
- silicon-based device layer 105 ′ is formed in the step 203 .
- the released silicon-based device layer 105 ′ is attached to a suitable substrate 101 ′′, such as, for example, a glass substrate, and provided with all the appropriate inter-connects to form a solar cell.
- a solar panel 300 is formed by attaching multiple solar cells 130 , 130 ′ and 130 ′′, such as the solar cell described above, to a common substrate 301 .
- the solar cells 130 , 130 ′ and 130 ′′ are provided with all of the appropriate inter-connects 302 , 302 ′ and 302 ′′ to each other and/or the substrate 301 to allow the solar panel 300 to collect solar energy and provide power to a device 401 such as described below.
- a system 400 includes a solar panel 300 , such as described above with reference to FIG. 3 .
- the solar panel 300 is electrically coupled to a battery or energy storage device 403 through an electrical connection 413 .
- the solar panel 300 and the battery or energy storage device 403 are electrically coupled to a device 401 through electrical connections 411 and 415 , respectively.
- the device 401 is configured with the appropriate circuitry, such that the solar panel 300 and the battery or energy storage device is capable of powering the device 401 .
- the device 401 may be computer, a hand-held communication device or any other electronic device now known or later developed.
- the solar panel 300 and battery energy storage device 403 are built into the device 401 and the device 401 includes a display unit, screen or user interface 405 .
Abstract
A method for making a solar cell is disclosed. In accordance with the method of the present invention a composite wafer is formed. The composite layer includes a single crystal silicon wafer, a silicon-based device layer and sacrificial porous silicon sandwiched therebetween. The composite wafer is treated to an aqueous etchant maintained below ambient temperatures to selectively etch the sacrificial porous silicon and release or undercut the silicon-based layer from the single crystal silicon wafer. The released silicon device layer is attached to a substrate to make a solar cell and the released single crystal silicon wafer is reused to make additional silicon device layer.
Description
- The present application is a continuation of U.S. patent application Ser. No. 12/716,785, filed Mar. 3, 2010, which claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/157,195, filed on Mar. 3, 2009, and titled “METHOD FOR SELECTIVE UNDER-ETCHING OF POROUS SILICON,” the entirety of which is hereby incorporated by reference.
- This invention relates to a method for making solar cells. More particularly, the present invention relates to selective etching of a porous silicon layer to under-cut and release a silicon-based device layer that is then used for making solar cells.
- Solar cells are semiconductor devices that are usually manufactured from silicon-based material. Some solar cells are made from screen printed poly-crystalline silicon. Single crystalline wafers can be used to make very efficient solar cells. However, high manufacturing costs for making single crystalline materials makes the large scale production of solar cells from these materials impractical.
- Poly-crystalline silicon wafers used to manufacture solar cells are made by cutting 180 to 350 micrometer thick wafers from block-cast silicon ingots. The wafers are usually lightly p-type doped. To make a solar cell from the wafer, a surface diffusion of n-type dopants is performed on the front side of the wafer. This forms a p-n junction a few hundred nanometers below the surface. Solar cells usually also include anti-reflective coatings, such as silicon nitride or titanium dioxide and/or have textured surfaces increase efficiency of light absorption. This method is disadvantageous in that the crystal takes an exceptionally long time to grow on the silicon ingot.
- Metal contacts are formed on the back and front surfaces of poly-crystalline silicon wafers by screen-printing metal pastes, such as silver paste or aluminum paste. After the metal contacts are formed, the solar cells are assembled into panels and are sandwiched between glass and polymer resins.
- As mentioned above, solar cells and solar panels that are formed from single crystal silicon are preferred because of the efficiency of the solar cells and panels made from single crystal silicon.
- The present invention is direct to a method of making a solar cell. In accordance with the method of the present invention, a silicon-based device layer is formed on a base wafer. The base wafer includes a single crystal silicon wafer and a sacrificial porous silicon layer that is deposited thereon. The sacrificial porous silicon layer is formed using thermal deposition or any other suitable coating or deposition technique. Preferably, the porous silicon layer has a porosity of 30 percent or more. The sacrificial porous silicon layer comprises, for example, carbon doped oxide, spin-on-glass (SOG), fluoridated silicon glass (FSG) or a combination thereof. The thickness of the porous silicon layer is preferably in a range of several nanometers to several microns.
- The silicon-based device layer is preferably crystalline or semi-crystalline, as opposed to being amorphous, and is epitaxially grown on top of the sacrificial porous silicon layer. The silicon-based device layer is preferably a p-doped silicon-based device layer that has a thickness of several microns to several hundred microns. The silicon-based device layer is formed using any suitable growth or deposition technique, such as chemical vapor deposition. A working wafer that includes the single crystal silicon wafer, the silicon-based device layer and the sacrificial porous silicon layer sandwiched between the single crystal silicon wafer and the silicon-based device layer is referred to herein as a composited wafer.
- In accordance with the embodiments of the invention, after the composite wafer is formed the sacrificial layer is selectively etched thereby releasing the silicon-based device layer, or a portion thereof and the single crystal wafer, or a portion thereof. The released silicon-based device layer, or the portion thereof, is then provided with the appropriate electrical contacts and anti-reflective coatings and is coupled to one or more substrates to form a solar cell. The released single crystal wafer, or the portion thereof, is then used to make additional composite wafers and additional solar cells, such as described above.
- In order to accomplish release of the silicon-based device layer, or the portion thereof, the etch rate of the porous silicon layer needs to be significantly faster than the etch rates of either the single crystal wafer or of the silicon-based device layer. Selective etching of the sacrificial porous silicon layer has been observed by treating the composite wafer to an aqueous etchant that is maintained at temperatures in a range of 0 to 10 degrees Celsius. The aqueous etchant preferably includes one or more etchants such as potassium hydroxide, sodium hydroxide and hydrogen fluoride in a concentration of 5% or less by weight. In further embodiments of the invention the aqueous etchant includes an alcohol, such as isopropyl alcohol, in a concentration of 10% or less by weight. In still further embodiments of the invention the etchant includes a surfactant in a concentration of 1% or less by weight. Also, to further control etch rates during the selective etching step, the composite wafer and the aqueous etchant are treated with ultrasonic energy.
-
FIG. 1A shows a composite wafer used to make a silicon-based device layer for solar cells, in accordance with the embodiments of the invention. -
FIG. 1B illustrates releasing a silicon-based device layer from the composite wafer, in accordance with the embodiments of the invention. -
FIG. 1C shows a released silicon-based device layer coupled to a substrate to form a solar cell, in accordance with the embodiments of the invention. -
FIG. 2A shows a block-flow diagram outlining steps for making a solar cell, in accordance with the method of the invention. -
FIG. 2B shows a block-flow diagram outlining steps for making a composite wafer, in accordance with the method of the invention. -
FIG. 2C shows a block-flow diagram outlining steps for releasing a device layer from the composite wafer, in accordance with the method of the invention. -
FIG. 3 shows a schematic representation of a solar panel with multiple solar cells on a common substrate, in accordance with the embodiments of the invention. -
FIG. 4 shows a schematic representation of a system that utilizes a solar cell or panel, in accordance with the embodiments of the invention. -
FIG. 1 shows acomposite wafer 100 used to make a silicon-based device layer used in solar cells. Thecomposite wafer 100 includes a singlecrystal silicon wafer 101 and a sacrificialporous silicon layer 103 that is deposited thereon, which is referred to herein as a base wafer. Thecomposite wafer 100 also includes a silicon-baseddevice layer 105 that is preferably crystalline or semi-crystalline and is epitaxially grown on top of the sacrificialporous silicon layer 103. - As described above, the sacrificial
porous silicon layer 103 preferably has a porosity of 30 percent or more and is several nanometers to several microns thick. The sacrificialporous silicon layer 103 is formed from any suitable porous silicon material including, but not limited to carbon doped oxide, spin-on-glass (SOG), fluoridated silicon glass (FSG) or a combination thereof. - The silicon-based
device layer 105 is preferably a p-doped silicon-based device layer that has a thickness of several microns to several hundred microns. The sacrificialporous silicon layer 103 and the silicon-baseddevice layer 105 are formed using any suitable coating, growth and/or deposition techniques including, but not limited to, thermal deposition and chemical vapor deposition. -
FIG. 1B illustrates aschematic representation 120 of a released silicon-baseddevice layer 105′ and a released singlecrystal silicon wafer 101′ which are formed by selectively etching the sacrificialporous silicon layer 103, as indicated by the arrow 109. Selective etching of the sacrificialporous silicon layer 103 is preferably accomplished by steps outlined and described below with reference toFIGS. 2A-C -
FIG. 1C shows the released silicon-baseddevice layer 105′ coupled to anew substrate 101″ to form asolar cell 130. Prior to coupling the released silicon-baseddevice layer 105′ to thenew substrate 101″, the released silicon-baseddevice layer 105′ and/orsubstrate 101″ are preferably provided with the appropriate electrical contacts and anti-reflecting coatings to form a workingsolar cell 130. The released singlecrystal silicon wafer 101′ is reused preferably from 0-50 times, and more preferably from 20-30 times to make additional composite wafers and solar cells. -
FIG. 2A shows a block flow diagram 200 outlining steps for making a solar cell. In the step 201 acomposite wafer 100 is formed, such as described with reference toFIG. 1A . After thecomposite wafer 100 is formed in thestep 201, in thestep 203 the sacrificialporous silicon layer 103 is controllably or selectively etched to form a released silicon-baseddevice layer 105′ and a released singlecrystal silicon wafer 101′, such as shown inFIG. 1B . - Referring to
FIG. 2B , thecomposite wafer 100 is formed using any number of techniques or combination of techniques. For example, the sacrificialporous silicon layer 103 is deposited in thestep 202 by spin coating poly-silicon on thesubstrate 101, which is preferably a single crystal silicon wafer. The poly-silicon is then dried or cured to remove solvent and form the sacrificialporous silicon layer 103. As described above, the sacrificialporous silicon layer 103 has a porosity of 30% or more, which is believed to increase the selectivity of the etch rate for the sacrificialporous silicon layer 103. - After the sacrificial
porous silicon layer 103 is formed in thestep 202, in thestep 204 thedevice layer 105 is formed over the sacrificialporous silicon layer 103. Thedevice layer 105 is preferably formed using any suitable technique, but is preferably formed by epitaxially growing a crystalline or semi-crystalline silicon device layer using vapor deposition techniques. Thedevice layer 105 that is formed in thestep 204 is preferably a p-doped device layer. Thedevice layer 105 is formed, for example, by vapour depositing silicon-based precursors that includes a p-dopant or p-dopants, herein referred to as p-doped silicon-based precursors. Suitable p-doped silicon-based precursors include trivalent atoms typically from group IIIA of the periodic table, such as boron or aluminum. Alternatively to using p-doped silicon-based precursors to form thedevice layer 105, thedevice layer 105 may be doped after its formation using ion implantation techniques. In some cases, it can be useful to form thedevice layer 105 by using p-doped silicon-based precursors, such as described above, and further doping thedevice layer 105 with the same or different dopants using ion implantation techniques. - Now referring to
FIG. 2C , instep 203 the sacrificialporous silicon layer 103 is controllably or selectively etched to form a released silicon-baseddevice layer 105′ and a released singlecrystal silicon wafer 101′. In accordance with the embodiments of the invention, the sacrificialporous silicon layer 103 is controllably or selectively etched by first patterning thedevice layer 105 with access groove or holes in thestep 206. After thedevice layer 105 is patterned with access grooves or holes in thestep 206, thecomposite wafer 100 is treated with an etchant, such as described above and below. Patterning thedevice layer 105 with access grooves or holes prior to treating thecomposite wafer 100 with an etchant can result in faster etch rates by allowing a greater surface area of the sacrificial poly-silicon layer 103 to be initially exposed to the etchant. - In accordance with the embodiments of the invention, the
device layer 105 is patterned with access groves or holes in thestep 206 by using photo-resist masking and etching techniques. It will be clear to one skilled in the art that while patterning thedevice layer 105 with access groves or holes, such as described above, can be beneficial, it is not necessary to implement the present invention. Regardless of whether thestep 206 of patterning thedevice layer 105 with access groves or holes is performed, in thestep 208 thecomposite wafer 100 is treated with an etchant to form a released silicon-baseddevice layer 105′ and a release singlecrystal silicon wafer 101′, such as shown inFIG. 1B . - Still referring to
FIG. 2C , in thestep 208 thecomposite wafer 100 is treated with an aqueous etchant comprising one or more of potassium hydroxide, sodium hydroxide and hydrogen fluoride in concentrations of 5% or less by weight. Preferably, the aqueous etchant is maintained at temperatures in a range of 0 to 10 degrees Celsius during thestep 208. This temperature range results in better selectivity during the etching process. In further embodiments of the invention the aqueous etchant includes an alcohol, such as isopropyl alcohol, in a concentration of 10% or less by weight. In still further embodiments of the invention, the etchant includes a surfactant in a concentration of 1% or less by weight. Suitable surfactants include, but are not limited to: - 1) Anionic Surfactants, such as, for example, Perfluorooctanoate (PFOA or PFO), Perfluorooctanesulfonate (PFOS), Sodium dodecyl sulfate (SDS), ammonium lauryl sulfate, Sodium laureth sulfate and Alkyl benzene sulfonate;
2) Soap or fatty acid salt surfactants;
3) Cationic Surfactants, such as, for example, Cetyl trimethylammonium bromide (CTAB), a.k.a. hexadecyl trimethyl ammonium bromide, Cetylpyridinium chloride (CPC), Polyethoxylated tallow amine (POEA), Benzalkonium chloride (BAC) and Benzethonium chloride (BZT);
4) Zwitterionic (amphoteric) Surfactants, such as, for example Dodecyl betaine, Cocamidopropyl betaine, Coco ampho glycinate; and
5) Nonionic Surfactants, such as, for example Alkyl poly(ethylene oxide), Alkylphenol poly(ethylene oxide) Copolymers of poly(ethylene oxide) and poly(propylene oxide), Octyl glucoside, Decyl maltoside, Fatty alcohols, Cetyl alcohol, Oleyl alcohol, Cocamide MEA, cocamide DEA, Polysorbates and Dodecyl dimethylamine oxide. - In still further embodiments of the invention, during the
selective etching step 208 thecomposite wafer 100 and the aqueous etchant are treated with ultrasonic energy. After the release, silicon-baseddevice layer 105′ is formed in thestep 203. In thestep 205 the released silicon-baseddevice layer 105′ is attached to asuitable substrate 101″, such as, for example, a glass substrate, and provided with all the appropriate inter-connects to form a solar cell. - Referring now to
FIG. 3 , in further embodiments of the invention, asolar panel 300 is formed by attaching multiplesolar cells common substrate 301. Thesolar cells appropriate inter-connects substrate 301 to allow thesolar panel 300 to collect solar energy and provide power to adevice 401 such as described below. - With reference to
FIG. 4 , asystem 400 includes asolar panel 300, such as described above with reference toFIG. 3 . Thesolar panel 300 is electrically coupled to a battery orenergy storage device 403 through anelectrical connection 413. Thesolar panel 300 and the battery orenergy storage device 403 are electrically coupled to adevice 401 throughelectrical connections device 401 is configured with the appropriate circuitry, such that thesolar panel 300 and the battery or energy storage device is capable of powering thedevice 401. Thedevice 401 may be computer, a hand-held communication device or any other electronic device now known or later developed. In accordance with the embodiments of the invention, thesolar panel 300 and batteryenergy storage device 403 are built into thedevice 401 and thedevice 401 includes a display unit, screen oruser interface 405. - The present invention has been described in terms of specific embodiments incorporating details to facilitate the understanding of the principles of construction and operation of the invention. As such, references herein to specific embodiments and details thereof are not intended to limit the scope of the claims appended hereto. It will be apparent to those skilled in the art that modifications can be made in the embodiments chosen for illustration without departing from the spirit and scope of the invention.
Claims (20)
1. A method of selectively etching a silicon wafer, the method comprising:
a) providing a sacrificial porous silicon layer on a single crystal silicon wafer; and
b) selectively etching the sacrificial porous silicon layer with an aqueous etchant;
wherein the aqueous etchant is maintained at a temperature in a range of 0° C. to 10° C. during step b) and the aqueous etchant comprises one or more of potassium hydroxide, sodium hydroxide and hydrogen fluoride.
2. The method of claim 1 , wherein the aqueous etchant includes one or more of the potassium hydroxide, sodium hydroxide and hydrogen fluoride in a concentration of 5% or less by weight.
3. The method of claim 1 , wherein the aqueous etchant further comprises a surfactant.
4. The method of claim 3 , wherein the surfactant is selected from the group consisting of anionic surfactants, fatty acid surfactants, cationic surfactants, zwitterionic surfactants, and non-ionic surfactants.
5. The method of claim 1 , wherein the aqueous etchant comprises 1% or less by weight of the surfactant.
6. The method of claim 1 , wherein the aqueous etchant further comprises an alcohol.
7. The method of claim 6 , wherein the alcohol is isopropyl alcohol.
8. The method of claim 1 further comprising subsequent to step a) and prior to step b), forming a crystalline silicon device layer on the sacrificial porous silicon layer.
9. The method of claim 9 , wherein the crystalline silicon device layer is patterned with access grooves or holes sacrificial porous silicon layer.
10. The method of claim 10 , wherein the aqueous etchant contacts the sacrificial porous silicon layer via the access grooves or holes in the crystalline silicon device layer.
11. The method of claim 1 , wherein the sacrificial porous silicon layer comprises a material selected from the group consisting of a carbon doped oxide, a spin-on-glass (SOG) and fluoridated silicon glass (FSG).
12. The method of claim 8 , wherein the crystalline silicon layer is a p-doped crystalline silicon layer.
13. A method of selectively etching a silicon wafer, the method comprising:
a) providing a sacrificial porous silicon layer on a single crystal silicon wafer;
b) forming a p-doped crystalline silicon device layer on the sacrificial porous silicon layer, thereby forming a composite wafer; and
c) selectively etching the sacrificial porous silicon layer with an aqueous etchant;
wherein the aqueous etchant is maintained at a temperature in a range of 0° C. to 10° C. during step c) and the aqueous etchant comprises a surfactant.
15. The method of claim 13 , wherein the aqueous etchant comprises the surfactant in a concentration of 1% by weight or less.
15. The method of claim 13 , wherein the surfactant is an anionic surfactant selected from the group consisting of Perfluorooctanoate (PFOA or PFO), Perfluorooctanesulfonate (PFOS), Sodium dodecyl sulfate (SDS), ammonium lauryl sulfate, Sodium laureth sulfate, and Alkyl benzene sulfonate.
16. The method of claim 13 , wherein the surfactant is a cationic surfactant selected from the group consisting of Cetyltrimethylammonium bromide (CTAB), Cetylpyridinium chloride (CPC), Polyethoxylated tallow amine (POEA), Benzalkonium chloride (BAC) and Benzethonium chloride (BZT).
17. The method of claim 13 , wherein the surfactant is a zwitterionic surfactant selected from the group consisting of Dodecyl betaine, Cocamidopropyl betaine, and Coco ampho glycinate.
18. The method of claim 13 , wherein the surfactant is a non-ionic surfactant selected from the group consisting of Alkyl poly(ethylene oxide), Alkylphenol poly(ethylene oxide) Copolymers of poly(ethylene oxide) and poly(propylene oxide), Octyl glucoside, Decyl maltoside, Fatty alcohols, Cetyl alcohol, Oleyl alcohol, Cocamide MEA, cocamide DEA, Polysorbates and Dodecyl dimethylamine oxide.
19. The method of claim 13 , wherein the surfactant is a soap or a fatty acid salt.
20. The method of claim 13 further comprising during step c) treating the composite wafer and aqueous etchant to ultrasonic energy.
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US10181405B2 (en) | 2019-01-15 |
WO2010102013A3 (en) | 2010-12-16 |
US20160358785A1 (en) | 2016-12-08 |
US20100227432A1 (en) | 2010-09-09 |
WO2010102013A2 (en) | 2010-09-10 |
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