WO2012164163A1 - A method and a structure for protecting a passivating layer - Google Patents
A method and a structure for protecting a passivating layer Download PDFInfo
- Publication number
- WO2012164163A1 WO2012164163A1 PCT/FI2012/050514 FI2012050514W WO2012164163A1 WO 2012164163 A1 WO2012164163 A1 WO 2012164163A1 FI 2012050514 W FI2012050514 W FI 2012050514W WO 2012164163 A1 WO2012164163 A1 WO 2012164163A1
- Authority
- WO
- WIPO (PCT)
- Prior art keywords
- layer
- passivating
- barrier layer
- passivating layer
- oxygen
- Prior art date
Links
- 238000000034 method Methods 0.000 title claims abstract description 80
- 230000004888 barrier function Effects 0.000 claims abstract description 98
- 239000000758 substrate Substances 0.000 claims abstract description 48
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 claims abstract description 46
- 229910052710 silicon Inorganic materials 0.000 claims abstract description 46
- 239000010703 silicon Substances 0.000 claims abstract description 46
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims abstract description 35
- 239000000126 substance Substances 0.000 claims abstract description 29
- 230000003993 interaction Effects 0.000 claims abstract description 14
- 230000000694 effects Effects 0.000 claims abstract description 13
- 239000002243 precursor Substances 0.000 claims description 65
- 238000006243 chemical reaction Methods 0.000 claims description 54
- 238000000151 deposition Methods 0.000 claims description 48
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 39
- 229910052760 oxygen Inorganic materials 0.000 claims description 39
- 239000001301 oxygen Substances 0.000 claims description 39
- 230000008569 process Effects 0.000 claims description 39
- 238000000231 atomic layer deposition Methods 0.000 claims description 32
- 229910052782 aluminium Inorganic materials 0.000 claims description 26
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 26
- 239000010936 titanium Substances 0.000 claims description 12
- 229910052715 tantalum Inorganic materials 0.000 claims description 10
- GUVRBAGPIYLISA-UHFFFAOYSA-N tantalum atom Chemical compound [Ta] GUVRBAGPIYLISA-UHFFFAOYSA-N 0.000 claims description 10
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 9
- 229910052719 titanium Inorganic materials 0.000 claims description 9
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims description 7
- 238000006557 surface reaction Methods 0.000 claims description 7
- 229910052726 zirconium Inorganic materials 0.000 claims description 7
- 229910052735 hafnium Inorganic materials 0.000 claims description 6
- VBJZVLUMGGDVMO-UHFFFAOYSA-N hafnium atom Chemical compound [Hf] VBJZVLUMGGDVMO-UHFFFAOYSA-N 0.000 claims description 6
- 229940024548 aluminum oxide Drugs 0.000 description 30
- 230000008021 deposition Effects 0.000 description 22
- 235000010210 aluminium Nutrition 0.000 description 21
- 239000000463 material Substances 0.000 description 20
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 15
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 13
- 238000010926 purge Methods 0.000 description 12
- 238000002161 passivation Methods 0.000 description 10
- 230000008901 benefit Effects 0.000 description 9
- BPUBBGLMJRNUCC-UHFFFAOYSA-N oxygen(2-);tantalum(5+) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Ta+5].[Ta+5] BPUBBGLMJRNUCC-UHFFFAOYSA-N 0.000 description 9
- 229910001936 tantalum oxide Inorganic materials 0.000 description 9
- 239000010408 film Substances 0.000 description 8
- 239000012159 carrier gas Substances 0.000 description 7
- 239000007789 gas Substances 0.000 description 7
- 229910000449 hafnium oxide Inorganic materials 0.000 description 7
- WIHZLLGSGQNAGK-UHFFFAOYSA-N hafnium(4+);oxygen(2-) Chemical compound [O-2].[O-2].[Hf+4] WIHZLLGSGQNAGK-UHFFFAOYSA-N 0.000 description 7
- RVTZCBVAJQQJTK-UHFFFAOYSA-N oxygen(2-);zirconium(4+) Chemical compound [O-2].[O-2].[Zr+4] RVTZCBVAJQQJTK-UHFFFAOYSA-N 0.000 description 7
- 229910001928 zirconium oxide Inorganic materials 0.000 description 7
- 238000004519 manufacturing process Methods 0.000 description 6
- 239000004065 semiconductor Substances 0.000 description 6
- XJDNKRIXUMDJCW-UHFFFAOYSA-J titanium tetrachloride Chemical compound Cl[Ti](Cl)(Cl)Cl XJDNKRIXUMDJCW-UHFFFAOYSA-J 0.000 description 6
- 239000002800 charge carrier Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 230000006798 recombination Effects 0.000 description 5
- 238000005215 recombination Methods 0.000 description 5
- 230000000875 corresponding effect Effects 0.000 description 4
- 230000007246 mechanism Effects 0.000 description 4
- PNEYBMLMFCGWSK-UHFFFAOYSA-N Alumina Chemical compound [O-2].[O-2].[O-2].[Al+3].[Al+3] PNEYBMLMFCGWSK-UHFFFAOYSA-N 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 3
- 239000006227 byproduct Substances 0.000 description 3
- 239000000306 component Substances 0.000 description 3
- 230000003750 conditioning effect Effects 0.000 description 3
- 238000005137 deposition process Methods 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- UOACKFBJUYNSLK-XRKIENNPSA-N Estradiol Cypionate Chemical compound O([C@H]1CC[C@H]2[C@H]3[C@@H](C4=CC=C(O)C=C4CC3)CC[C@@]21C)C(=O)CCC1CCCC1 UOACKFBJUYNSLK-XRKIENNPSA-N 0.000 description 2
- 238000000277 atomic layer chemical vapour deposition Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 229910021419 crystalline silicon Inorganic materials 0.000 description 2
- 238000005516 engineering process Methods 0.000 description 2
- 238000005530 etching Methods 0.000 description 2
- 238000011066 ex-situ storage Methods 0.000 description 2
- 230000014509 gene expression Effects 0.000 description 2
- 238000010438 heat treatment Methods 0.000 description 2
- 230000000670 limiting effect Effects 0.000 description 2
- 229910052751 metal Inorganic materials 0.000 description 2
- 239000002184 metal Substances 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000036961 partial effect Effects 0.000 description 2
- 238000005240 physical vapour deposition Methods 0.000 description 2
- 238000000678 plasma activation Methods 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 125000004213 tert-butoxy group Chemical group [H]C([H])([H])C(O*)(C([H])([H])[H])C([H])([H])[H] 0.000 description 2
- 239000010409 thin film Substances 0.000 description 2
- VXUYXOFXAQZZMF-UHFFFAOYSA-N titanium(IV) isopropoxide Chemical compound CC(C)O[Ti](OC(C)C)(OC(C)C)OC(C)C VXUYXOFXAQZZMF-UHFFFAOYSA-N 0.000 description 2
- VOITXYVAKOUIBA-UHFFFAOYSA-N triethylaluminium Chemical compound CC[Al](CC)CC VOITXYVAKOUIBA-UHFFFAOYSA-N 0.000 description 2
- NSMXQKNUPPXBRG-SECBINFHSA-N (R)-lisofylline Chemical compound O=C1N(CCCC[C@H](O)C)C(=O)N(C)C2=C1N(C)C=N2 NSMXQKNUPPXBRG-SECBINFHSA-N 0.000 description 1
- 241000905957 Channa melasoma Species 0.000 description 1
- 206010013710 Drug interaction Diseases 0.000 description 1
- 229910003865 HfCl4 Inorganic materials 0.000 description 1
- 241000257303 Hymenoptera Species 0.000 description 1
- 241000183024 Populus tremula Species 0.000 description 1
- 229910007926 ZrCl Inorganic materials 0.000 description 1
- 229910007928 ZrCl2 Inorganic materials 0.000 description 1
- 238000010521 absorption reaction Methods 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- PQLAYKMGZDUDLQ-UHFFFAOYSA-K aluminium bromide Chemical compound Br[Al](Br)Br PQLAYKMGZDUDLQ-UHFFFAOYSA-K 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 229940000425 combination drug Drugs 0.000 description 1
- 230000001143 conditioned effect Effects 0.000 description 1
- 238000010276 construction Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000006731 degradation reaction Methods 0.000 description 1
- UZBQIPPOMKBLAS-UHFFFAOYSA-N diethylazanide Chemical compound CC[N-]CC UZBQIPPOMKBLAS-UHFFFAOYSA-N 0.000 description 1
- 125000002147 dimethylamino group Chemical group [H]C([H])([H])N(*)C([H])([H])[H] 0.000 description 1
- DWCMDRNGBIZOQL-UHFFFAOYSA-N dimethylazanide;zirconium(4+) Chemical compound [Zr+4].C[N-]C.C[N-]C.C[N-]C.C[N-]C DWCMDRNGBIZOQL-UHFFFAOYSA-N 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000010574 gas phase reaction Methods 0.000 description 1
- PDPJQWYGJJBYLF-UHFFFAOYSA-J hafnium tetrachloride Chemical compound Cl[Hf](Cl)(Cl)Cl PDPJQWYGJJBYLF-UHFFFAOYSA-J 0.000 description 1
- 230000009931 harmful effect Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000011068 loading method Methods 0.000 description 1
- 230000000116 mitigating effect Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 230000001590 oxidative effect Effects 0.000 description 1
- 238000005289 physical deposition Methods 0.000 description 1
- 229920000136 polysorbate Polymers 0.000 description 1
- 238000007639 printing Methods 0.000 description 1
- 238000005086 pumping Methods 0.000 description 1
- 238000000746 purification Methods 0.000 description 1
- 230000036647 reaction Effects 0.000 description 1
- 230000002829 reductive effect Effects 0.000 description 1
- 238000007650 screen-printing Methods 0.000 description 1
- MISXNQITXACHNJ-UHFFFAOYSA-I tantalum(5+);pentaiodide Chemical compound [I-].[I-].[I-].[I-].[I-].[Ta+5] MISXNQITXACHNJ-UHFFFAOYSA-I 0.000 description 1
- OEIMLTQPLAGXMX-UHFFFAOYSA-I tantalum(v) chloride Chemical compound Cl[Ta](Cl)(Cl)(Cl)Cl OEIMLTQPLAGXMX-UHFFFAOYSA-I 0.000 description 1
- HSXKFDGTKKAEHL-UHFFFAOYSA-N tantalum(v) ethoxide Chemical compound [Ta+5].CC[O-].CC[O-].CC[O-].CC[O-].CC[O-] HSXKFDGTKKAEHL-UHFFFAOYSA-N 0.000 description 1
- JMXKSZRRTHPKDL-UHFFFAOYSA-N titanium ethoxide Chemical compound [Ti+4].CC[O-].CC[O-].CC[O-].CC[O-] JMXKSZRRTHPKDL-UHFFFAOYSA-N 0.000 description 1
- NLLZTRMHNHVXJJ-UHFFFAOYSA-J titanium tetraiodide Chemical compound I[Ti](I)(I)I NLLZTRMHNHVXJJ-UHFFFAOYSA-J 0.000 description 1
- JLTRXTDYQLMHGR-UHFFFAOYSA-N trimethylaluminium Chemical compound C[Al](C)C JLTRXTDYQLMHGR-UHFFFAOYSA-N 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—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
- H01L31/1868—Passivation
-
- C—CHEMISTRY; METALLURGY
- C23—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; CHEMICAL SURFACE TREATMENT; DIFFUSION TREATMENT OF METALLIC MATERIAL; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL; INHIBITING CORROSION OF METALLIC MATERIAL OR INCRUSTATION IN GENERAL
- C23C—COATING METALLIC MATERIAL; COATING MATERIAL WITH METALLIC MATERIAL; SURFACE TREATMENT OF METALLIC MATERIAL BY DIFFUSION INTO THE SURFACE, BY CHEMICAL CONVERSION OR SUBSTITUTION; COATING BY VACUUM EVAPORATION, BY SPUTTERING, BY ION IMPLANTATION OR BY CHEMICAL VAPOUR DEPOSITION, IN GENERAL
- C23C16/00—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes
- C23C16/22—Chemical coating by decomposition of gaseous compounds, without leaving reaction products of surface material in the coating, i.e. chemical vapour deposition [CVD] processes characterised by the deposition of inorganic material, other than metallic material
- C23C16/30—Deposition of compounds, mixtures or solid solutions, e.g. borides, carbides, nitrides
- C23C16/40—Oxides
- C23C16/405—Oxides of refractory metals or yttrium
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/02—Details
- H01L31/0216—Coatings
- H01L31/02161—Coatings for devices characterised by at least one potential jump barrier or surface barrier
- H01L31/02167—Coatings for devices characterised by at least one potential jump barrier or surface barrier for solar cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the present invention relates to a method for protecting a passivating layer and to a structure comprising a barrier layer configured to protect the pas ⁇ sivating layer and to the use thereof.
- Photovoltaic cells are gradually becoming an important means of generating electrical energy. Espe ⁇ cially solar cells, photovoltaic cells designed to convert sunlight into electrical energy, are consid- ered as one of the most promising candidates for re ⁇ newable energy production.
- a promising material candidate for passivating a silicon surface is aluminum oxide.
- ALD-grown (Atomic Layer Deposition) aluminum oxide has shown to present good passivation on rear surface of p-type silicon solar cells.
- the back electrode on the alumi- num oxide passivating layer can be made of screen printed aluminum, i.e. aluminum paste.
- a problem is the relatively weak chemical resistance of amorphous aluminum oxide in the circumstances used in this kind of manufacturing process.
- This manufacturing method of the back electrode contains a firing step, which is done at an elevated temperature of about 700 - 800 °C .
- the aluminum paste contains chemicals which etch the passivating layer comprising aluminum oxide and thus causes at least partial removal of aluminum oxide, whereby the surface passivation is weakened or destroyed .
- the inventors have identified a need for an efficient technique of protecting the passivating lay ⁇ er from chemical interactions between the passivation layer and the electrode comprising aluminum.
- a purpose of the present invention is to pro ⁇ vide a new method and a structure for protecting a passivating layer comprising aluminum oxide and being formed on a surface of a silicon substrate from ef ⁇ fects caused by chemical interaction between the pas- sivating layer and a conducting electrode. Further, the purpose of the present invention is to provide a new use of the structure.
- the present invention relates to a method for protecting a passivating layer comprising aluminum oxide and being formed on a surface of a silicon sub ⁇ strate from effects caused by chemical interaction be ⁇ tween the passivating layer and a conducting electrode by fabricating a barrier layer between the passivating layer and the conducting electrode, wherein the method comprises depositing a barrier layer comprising titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafnium and oxygen, or a combination of any of these, or a combination of any of these with aluminum and oxygen, on the passivating layer by exposing the passivating layer in a reaction space to alternately repeated surface reactions of two or more different precursors, wherein at least one of the precursors is a precursor for oxygen; and forming the conducting electrode on the barrier layer deposited on the pas ⁇ sivating layer by making a layer comprising aluminum paste on the barrier layer.
- the present invention relates further to a structure comprising a barrier layer between a passivating layer and a conducting electrode, wherein the barrier layer is configured to protect the passivating layer comprising aluminum oxide and being formed on a surface of a silicon substrate from effects caused by chemical interaction between the passivating layer and the conducting electrode, wherein the barrier layer comprises titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafnium and oxygen, or a combination of any of these, or a combination of any of these with aluminum and oxygen, and the conducting electrode comprises a layer comprising aluminum paste.
- the barrier layer is deposited on the passivating layer by exposing the passivating layer in a reaction space to alternately repeated surface reactions of two or more different precursors, wherein at least one of the precursors is a precursor for oxygen; and the con ⁇ ducting electrode is formed on the barrier layer de ⁇ posited on the passivating layer by making a layer comprising aluminum paste on the barrier layer.
- the aluminum paste used in the present inven- tion can be any aluminum paste usually used for the production of a photovoltaic cell.
- the method and the structure of the present invention provide an efficient way of protecting the passivating layer from effects caused by chemical in- teraction between the passivating layer and the conducting electrode.
- the barrier layer formed by exposing the passivating layer in a reaction space to alternately repeated surface reactions of two or more different precursors effi- ciently protected the passivating layer by inhibiting chemical reactions from occurring between the passivating layer and the conducting electrode.
- passivating should be understood as the passivation of a surface for reducing surface recombi ⁇ nation, i.e. for reducing the recombination of charge carriers on or in immediate proximity to the passivat- ed surface.
- the pas ⁇ sivating layer comprises aluminum oxide.
- the passivating layer comprises a mixture comprising aluminum oxide.
- the barrier layer is deposited on the passivating layer in a reaction space by an atomic layer deposition (ALD) type process.
- ALD atomic layer deposition
- Atomic Layer Deposition is a method for depositing uniform and confor- mal films, e.g. thin-films, over substrates of various shapes, even over complex 3D (three dimensional) structures.
- ALD-type methods the deposit is grown by alternately repeating, essentially self-limiting, surface reactions between a precursor and a surface to be coated. Therefore the growth mechanism in an ALD- type process is commonly not as sensitive as in other coating methods to e.g.
- a re- action chamber which may be a source for non- uniformity, especially in coating methods relying on gas-phase reactions or in physical deposition methods, such as metal-organic chemical vapor deposition (MOCVD) or physical vapor deposition (PVD) .
- MOCVD metal-organic chemical vapor deposition
- PVD physical vapor deposition
- two or more different chemicals can be introduced to a reaction space in a sequential, alternating manner and the pre- cursors adsorb on desired surfaces inside the reaction space.
- the sequential, alternating, introduction of precursors is commonly called pulsing (of precursors) .
- pulsing of precursors
- a purging period during which a flow of gas which does not react with the precursors used in the process is introduced through the reaction space.
- This gas often called the carrier gas is therefore inert towards the precursors used in the process and purges the reaction space from e.g. surplus precursor and by-products re ⁇ sulting from the adsorption reactions of the previous precursor pulse.
- This purging can be arranged also by other means .
- the essential feature of the ALD-type methods is to sequentially expose the deposition surface to precursors and to growth reactions of precursors es ⁇ sentially on the deposition surface.
- the alternate or sequential exposure of the deposition surface to dif ⁇ ferent precursors can be carried out in different man- ners .
- the substrate to be deposited is placed in a reaction space, into which precursor and purge gases are being introduced in a predetermined cycle.
- constant gas flow zones separated in space and a mov- ing substrate are used in order to obtain the time se ⁇ quential exposure.
- a continuous coating process is achieved enabling roll-to-roll coating of a substrate.
- the cycle time depends on the speed of movement of the substrate between the gas flow zones in the reaction space .
- the thickness of the deposit, coating or lay- er produced by the ALD-type process can be increased by repeating several times a pulsing sequence compris ⁇ ing the aforementioned pulses containing the precursor material, and the purging periods.
- the number of how many times this sequence, called the "ALD cycle" is repeated depends on the targeted thickness of the lay ⁇ er .
- ALD atomic layer deposition
- Other names besides ALD have also been employed for these types of processes, where the alternate introduction of two or more different precursors lead to the growth of the layer, often through essentially self-limiting surface reactions.
- These other names or process vari ⁇ ants include atomic layer epotaxy (ALE) , atomic layer chemical vapour deposition (ALCVD) , and corresponding plasma enhanced variants. Unless otherwise stated, these processes will be collectively addressed as ALD- type processes in this specification.
- depositing the barrier layer comprises de- positing a layer comprising titanium and oxygen, or a layer comprising tantalum and oxygen.
- the barrier layer comprises titanium and oxygen, or tantalum and oxygen.
- depositing the barrier layer comprises depositing a layer comprising an oxide.
- the barrier layer comprises an oxide.
- depositing the barrier layer comprises de- positing a layer comprising titanium oxide, or tantalum oxide.
- the barrier layer comprises titanium oxide, or tantalum oxide.
- depositing the barrier layer com- prises depositing a layer comprising a combination of any of the above described materials.
- the barrier layer comprises a combination of any of the above described materials .
- depositing the barrier layer comprises de- positing a layer comprising titanium oxide, tantalum oxide, zirconium oxide, hafnium oxide, or a combina ⁇ tion of any of these, or a combination of any of these with aluminum oxide.
- the barrier layer comprises ti- tanium oxide, tantalum oxide, zirconium oxide, hafnium oxide, or a combination of any of these, or a combina ⁇ tion of any of these with aluminum oxide.
- depositing the barrier layer comprises de- positing a layer comprising a nanolaminate structure.
- the barrier layer comprises a nanolaminate structure.
- the nanolaminate structure comprises alter- nating layers of different oxide materials.
- depositing the barrier layer comprises depositing a layer comprising a nanolaminate structure of aluminum oxide and an inert material.
- the barrier layer comprises a nanolaminate structure of aluminum oxide and an inert material.
- the inert material is selected from a group consisting of titanium oxide, tantalum oxide, zirconium oxide, and hafnium oxide.
- depositing the barrier layer comprises depositing a layer comprising a nanolaminate structure of aluminum oxide and titanium oxide, tantalum oxide, zirconium oxide, or hafnium oxide.
- the barrier layer comprises a nanolaminate structure of aluminum oxide and titanium oxide, tantalum oxide, zirconium oxide, or hafnium oxide.
- the nanolaminate structure is formed with an ALD-type method using an ALD cycle ratio of 2 - 50 cy ⁇ cles for depositing aluminum oxide to 1 - 10 cycles for depositing inert material.
- the inert material is selected from a group consisting of titanium oxide, tantalum oxide, zirconium oxide, and hafnium oxide.
- the surprising barrier effect achieved with the present invention was attributed to the compati ⁇ bility of the barrier layer between the passivating layer and the conducting electrode. Without limiting the invention to any specific mechanism of why the aforementioned advantage of effective protection was achieved, it is assumed that the barrier layer, com ⁇ prising titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafnium and oxygen, or a combina- tion of any of these, or a combination of any of these with aluminum and oxygen, being a stable material, e.g. chemically inert, is able to protect the passiv ⁇ ating layer comprising aluminum oxide e.g. during the firing step of the manufacturing method of e.g. photo- voltaic cells.
- the ALD-type method used for forming the barrier layer between the passivating layer and the conducting electrode provided advantageous proper ⁇ ties to the formed barrier layer enabling effective protection of the passivating layer.
- the barrier layer is fabricated on the passivating layer by an ALD-type process excellent conformity and uniformity is achieved for the barrier layer.
- excellent conformity and uniformity is achieved for the passivating layer.
- the passivating layer is fabricated on the surface of the silicon substrate by an ALD-type process excellent conformity and uniformity is achieved for the passivating layer.
- the conducting electrode comprises metal. According to one embodiment of the present invention the conducting electrode comprises aluminum.
- depositing the barrier layer is terminated before the barrier layer reaches a thickness of 100 nanometers.
- the barrier layer has a thickness of below 100 nanometers.
- the barrier layer has a thickness of 2 - 50 nanometers, and preferably 1 - 10 nanometers.
- the passivating layer has a thickness of 2 - 50 nanometers, and preferably 5 - 10 nanometers.
- the passivating layer is formed on the surface of the silicon substrate by depositing the pas ⁇ sivating layer on the surface of the silicon substrate in a reaction space by an atomic layer deposition (ALD) type process.
- ALD atomic layer deposition
- the thickness of the barrier layer can be in ⁇ creased in some embodiments of the present invention by repeatedly exposing the deposition surface to the precursors in the reactions space such that a portion of them adsorbs onto the exposed surfaces in the reac- tion space i.e. onto the deposition surfaces. In this way the protection of the passivating layer may be enhanced in some embodiments of the present invention. In a similar manner also the thickness of the passiv ⁇ ating layer can be increased during the ALD-type pro- cess.
- the silicon substrate is in the form of an electrically conducting layer to an arrangement for a photovoltaic cell.
- the growth of the passivating layer and/or the barrier layer in the ALD-type process is essen ⁇ tially thermally activated.
- the passivation ef ⁇ fect is enhanced when the ALD-type process is essen ⁇ tially thermally activated i.e. no plasma activation is employed.
- the precursors for the deposition process of the barrier layer and/or the passivating layer can be selected from a large group of chemicals.
- the precursor for titanium is selected from the group of titanium tetrachloride (TiCl 4 ) , titanium isopropoxide
- Ti (OCH (CH 3 ) 2 ) 4 titanium ethoxide (Ti (OCH 2 CH 3 ) 4 ) , ti ⁇ tanium tetramethoxide (Ti(OCH 3 ) 4 ) and titanium iodide (Til 4 ) .
- the precursor for tantalum is selected from the group of tantalum pentachloride (TaCl 5 ) , tantalum pentaiodide (Tal 5 ) , tantalum pentaethoxide (Ta(OEt) 5 ), pentakis (dimethylamido) tantalum (Ta(NMe 2 )s), and tanta ⁇ lum (V) diethylamide TA(NEt 2 ) 5-
- the precursor for zirco- nium is selected from the group of ZrCl , ZrCl 2 [N (SiMe 3 ) 2] 2, Zrl 4 , Zr(OtBu) 4 , Zr (OtBu) 2 (mmp) 2 , Zr(mmp) 4 , Zr(ONEt 2 ) 4 , Zr(NMe 2 ) 4 , Zr(NEt 2 ) 4
- the precursor for hafnium is selected from the group of HfCl 4 , HfCl 2 [N (SiMe 3 ) 2 ] 2, Hfl 4 , Hf(OtBu) 4 , Hf (OtBu) 2 (mmp) 2, Hf(mmp) 4 , Hf(ONEt 2 ) , Hf(NMe 2 ) , Hf (NEt 2 ) , and Hf (NEtMe ) .
- the precursor for aluminum is selected from the group of TMA ( trimethylaluminum) , TEA (triethyl- aluminum) , A1C1 3 , AlBr 3 , AlMe 2 Cl AlMe 2 OiPr, A10nPr 3 and AlOnPr.
- the precursor for oxygen is selected from the group of H 2 0, 0 2 , 0 3 , ROHd, A10Et 3 , A10iOr 3 , H 2 0 2 , N 2 0 and N 2 0 4 . Selecting the other process parameters to de ⁇ posit the barrier layer and the passivating layer with the selected precursors will be obvious to the skilled person in light of this specification.
- the silicon substrate has a thickness of be ⁇ low 200 micrometers.
- the method comprises protecting the passivating layer from effects caused by chemical interac ⁇ tion between the passivating layer and the conducting electrode in a photovoltaic cell.
- the barrier layer is configured to protect the passivating layer from ef ⁇ fects caused by chemical interaction between the pas ⁇ sivating layer and the conducting electrode in a photovoltaic cell.
- the present invention further relates to the use of the structure according to the present inven ⁇ tion for protecting a passivating layer comprising aluminum oxide and being formed on a surface of a sil ⁇ icon substrate from effects caused by chemical inter- action between the passivating layer and a conducting electrode in a photovoltaic cell.
- An advantage of the present invention is that it enables the protection of the passivating layer from being affected by chemicals contained in the back electrode, i.e. the layer comprising aluminum paste, which chemicals would cause etching of the passivation layer.
- the barrier layer according to the present invention prevents etching of the passivating layer, which would lead to at least partial removal of the aluminum oxide and would thus weaken or destroy the surface passivation.
- An advantage of the present invention is that the barrier layer fabricated in an ALD-type process and comprising e.g. titanium oxide is stable and has the ability to protect the passivating layer compris- ing aluminum oxide during the firing step of the manu ⁇ facturing method of the back electrode.
- An advantage of the present invention is that both the passivating layer comprising aluminum oxide and the barrier layer can be fabricated in the same ALD-process and apparatus thus removing the need of using any additional deposition equipment.
- barrier layer comprising a combination of e.g. two different oxide materials, e.g. a nanolaminate structure, is that a more compact structure can be formed compared to using separate layers or films.
- the barrier layer comprising a nanolaminate structure is able to provide effective protection of the passivating layer
- the barrier layer having a nanolaminate structure is able to reduce the presence of grain boundaries in the depth direction of the film or layer.
- the space between grains can be a potential route for traversing the barrier layer.
- the second material will fill the grain boundaries of the material firstly de ⁇ posited thus hindering unwanted materials from trav ⁇ ersing the barrier film.
- Fig. 1 is a flow-chart illustration of a method according to one embodiment of the present in- vention.
- Fig. 2 is a schematic illustration of a structure according to one embodiment of the present invention .
- Atomic Layer Deposition is a method for depos ⁇ iting uniform and conformal films or layers over sub- strates of various shapes. Further, as presented above in ALD-type processes the deposit is grown by alter ⁇ nately repeating, essentially self-limiting, surface reactions between a precursor and a surface to be coated.
- the prior art discloses a wide range of mate- rials that can be synthesized and deposited on a sub ⁇ strate by alternately exposing the surface of the sub ⁇ strate to different precursors, in an ALD-type pro ⁇ cess. Also many different apparatuses suitable for carrying out an ALD-type process are disclosed in the prior art. For example US patent 6824816 discloses processes for depositing metal thin-films by ALD, and US patent 6174377 describes deposition tools for ALD.
- the tool can be e.g. a con ⁇ ventional ALD tool suitable for handling the process chemicals.
- ALD tools i.e. reactors
- Al so, many other known operations or features are not described here in detail nor mentioned, in order to emphasize relevant aspects of the various embodiments of the invention.
- the method of Fig. 1 and the structure of Fig. 2 illustrate, respectively, a method and the cor- responding resulting structure according to one embodiment of the invention.
- the method of Fig. 1 presents how to carry out the method for passivating the sili ⁇ con substrate 1 with a passivating layer 2 comprising aluminium oxide, and for protecting the passivating layer 2 with a barrier layer 3 against chemical interaction of the passivating layer 2 with the conducting electrode 4 deposited on the other side of the barrier layer 3.
- the silicon substrate 1 can be prepared by e.g. depositing a film of silicon on a substrate in its microcrystalline, nanocrystalline or polycrystal- line phase.
- the embodiment of Fig. 1 begins by bring ⁇ ing the silicon substrate 1 into the reaction space (step 1)) of a typical reactor tool, e.g. a tool suit ⁇ able for carrying out an ALD-type process.
- the reaction space is subsequently pumped down to a pressure suitable for forming the passivat- ing layer 2 comprising aluminum oxide.
- the reaction space can be pumped down to the suitable pressure us ⁇ ing e.g. a mechanical vacuum pump or, in the case of atmospheric pressure ALD systems and/or processes, gas flows can be set to protect the deposition zone from the atmosphere.
- the silicon substrate 1 is also heated to a temperature suitable for forming the passivating layer 2 by the used method.
- the silicon substrate 1 can be introduced to the reaction space through e.g. an airtight load-lock system or simply through a loading hatch.
- the silicon substrate 1 can be heated by e.g. resistive heating elements which also heat the entire reaction space.
- the silicon surface can be conditioned such that the passivating deposit may be essentially directly deposited on the silicon surface.
- This conditioning of the silicon surface on which the passivating layer 2 is to be deposited can include chemical purification of the surface of the silicon film from impurities and/or oxidation. Especially removal of oxide is beneficial when the silicon surface has been imported into the reaction space via an oxidizing environment, e.g. when trans ⁇ porting the exposed silicon surface from one deposi- tion tool to another.
- the details of the process for removing impurities and/or oxide from the surface of the silicon film will be obvious to the skilled person in view of this specification.
- the conditioning can be done ex-situ, i.e. outside the tool suitable for ALD-type processes.
- An example of an ex-situ conditioning process is etch ⁇ ing for 1 min in a 1 % HF solution followed by rinsing in Dl-water.
- Step a) in Fig. 1 After the silicon substrate 1 has been condi ⁇ tioned, an alternate exposure of the deposition sur ⁇ face to different precursor chemicals is started, to form the passivating layer 2 comprising aluminum oxide directly on the silicon substrate 1 (Step a) in Fig. 1) .
- Each exposure of the deposition surface to a pre ⁇ cursor results in the formation of additional deposit on the deposition surface, as a result of adsorption reactions of the corresponding precursor with the deposition surface.
- a typical reactor suitable for ALD-type depo ⁇ sition comprises a system for introducing carrier gas, such as nitrogen or argon into the reaction space such that the reaction space can be purged from surplus chemical and reaction by-products before introducing the next precursor chemical into the reaction space.
- carrier gas such as nitrogen or argon
- This feature together with the controlled dosing of vaporized precursors enables alternately exposing the substrate surface to precursors without significant intermixing of different precursors in the reaction space or in other parts of the reactor.
- the flow of carrier gas is commonly continuous through the reaction space throughout the deposition process and only the various precursors are alternately intro ⁇ quizd to the reaction space with the carrier gas.
- Thickness of the passivating layer 2 on the silicon substrate 1 can be controlled by the number of exposures of the deposition surface to the different precursors.
- the thickness of the passivating layer 2 is increased until a targeted thickness is reached, after which the barrier layer 3 is deposited on the passivating layer 2 (Step b) in Fig. 1) .
- Deposition of the barrier layer 3, in one embodiment of the invention, is carried out in an ALD- type process in the same deposition tool directly af ⁇ ter the deposition of the passivating layer 2 has ended.
- deposition of the barrier layer 3 can begin simply by changing the precursor chemicals from those used for the deposition of the passivating layer 2 to those suitable for the deposition of the barrier layer 3.
- Ti0 2 titanium oxide
- a barrier layer 3 was formed on a passivating layer 2 of aluminum oxide (A1 2 0 3 ) deposited on a sur ⁇ face of a silicon substrate 1; step b) of the embodi ⁇ ment of the invention shown in Fig. 1.
- the barrier layer 3 was deposited inside the reaction space of a P400 ALD batch tool (available from Beneq OY, Finland) directly after the passivating layer 2 was deposited on the silicon substrate 1 as discussed above.
- the silicon substrate 1 was a photovoltaic cell structure. This structure was positioned inside the reaction space such that the passivating layer 2 was exposed to the reaction environment.
- the pressure and temperature during the depo ⁇ sition of the barrier layer 3 was about 1 mbar (1 hPa) and about 300 °C inside the reaction space, respec- tively.
- the carrier gas discussed above, and responsible for purging the reaction space was nitrogen (N 2 ) .
- the processing temperature was suf- ficient to result in a thermally activated ALD-type growth and no plasma activation was employed in this example .
- the precursors were changed to start the deposition of titanium oxide as the barrier layer 3 on the passivating layer 2.
- Titanium tetrachloride TiCl 4
- TiCl 4 Titanium tetrachloride
- the carrier gas purge the reaction space from surplus first precursor and reaction byproducts
- the resulting surface of the substrate was similarly ex ⁇ posed to the second precursor, the precursor for oxy ⁇ gen, here water (H 2 0) . After this, the reaction space was purged again.
- exposure of the surface of the substrate to a specific precursor was carried out by switching on the pulsing valve of the P400 ALD tool controlling the flow of the precursor chemicals into the reaction space.
- Purging of the reaction space was carried out by closing the valves controlling the flow of precursors into the reaction space, and thereby letting only the continuous flow of carrier gas flow through the reaction space.
- the pulsing sequence in this example was in detail as follows: 0.6 s exposure to titanium tetrachloride, 1.5 s purge, 0.4 s exposure to water, 2.0 s purge.
- An exposure time and a purge time in this sequence signify a time a specific puls- ing valve for a specific precursor was kept open and a time all the pulsing valves for precursors were kept closed, respectively.
- the first precursor is titanium tetrachloride and the second precursor is wa ⁇ ter, but other precursors can also be used depending on the desired barrier material and composition.
- the invention is not limited to using the aforementioned precursors in particular and the advantages of the in ⁇ vention can be obtained by the skilled person in light of this specification also with other precursors.
- the aluminum electrode is fabricated on the barrier layer 3 to finalize the structure of Fig. 2.
- the aluminum electrode 4 is then fabricated on the barrier layer 3 by a screen printing method comprising e.g. printing the aluminum paste on the barrier layer, drying and curing the paste at high temperature using method steps, which will be obvious to the person skilled in the art.
- the barrier layer 3 efficiently protects the underlying passivating lay ⁇ er 2 of aluminum oxide which passivates the surface of the silicon substrate 1 an thereby minimizes surface recombination on the interface between the silicon substrate 1 and the passivating layer 2.
- the barrier layer com prises titanium oxide
- the barrier layer could al ⁇ so comprise other materials such as tantalum oxide, zirconium oxide, hafnium oxide, or a combination of any of these, or a combination of any of these with aluminum oxide, as will be obvious to a skilled person in light of this specification.
- the invention is not limited to using the aforementioned barrier layer in particular and the advantages of the invention can be readily obtained by the skilled person in light of this specification also with the other materials mentioned above.
Abstract
The present invention relates to a method for protecting a passivating layer (2) comprising aluminum oxide and being formed on a surface of a silicon substrate (1) from effects caused by chemical interaction between the passivating layer (2) and a conducting electrode (4) by fabricating a barrier layer (3) between the passivating layer (2) and the conducting electrode (4). Further, the present invention relates to a corresponding structure and its use.
Description
A METHOD AND A STRUCTURE FOR PROTECTING A PASSIVATING LAYER
FIELD OF THE INVENTION
The present invention relates to a method for protecting a passivating layer and to a structure comprising a barrier layer configured to protect the pas¬ sivating layer and to the use thereof. BACKGROUND OF THE INVENTION
Photovoltaic cells are gradually becoming an important means of generating electrical energy. Espe¬ cially solar cells, photovoltaic cells designed to convert sunlight into electrical energy, are consid- ered as one of the most promising candidates for re¬ newable energy production.
An important issue slowing down the utiliza¬ tion and mitigating the commercial potential of solar cells is their low efficiency relative to their cost, i.e. the cost per one watt of installed solar power is high. To reduce the fabrication cost and to improve the efficiency of solar cells, new technologies and new solar cell structures have been developed. One of the improvements in crystalline silicon (c-Si) solar cells has been the introduction of rear surface pas¬ sivation to reduce the charge carrier recombination on the back side of silicon wafer.
Surface recombination in semiconductors is a result of possibly many different mechanisms leading to trapping of charge carriers in specific energy states at or close to the surface of a semiconductor. These energy states, or surface states as they are of¬ ten called, may originate from different sources, such as impurities at the surface or the inevitable disrup- tion of periodicity of a semiconductor crystal at the surface. In a photovoltaic cell the quantum efficien-
cy, and therefore the overall efficiency, decreases as charge carriers generated by the absorption of photons in the semiconductor recombine with the surface states and therefore cannot be collected in the cell elec- trodes to contribute to the cell current.
To reduce surface recombination of charge carriers, several ways of passivating a surface of a semiconductor (or conducting doped semiconductor) have been developed. A promising material candidate for passivating a silicon surface is aluminum oxide. Especially ALD-grown (Atomic Layer Deposition) aluminum oxide has shown to present good passivation on rear surface of p-type silicon solar cells. In the manufac¬ turing of solar cells the back electrode on the alumi- num oxide passivating layer can be made of screen printed aluminum, i.e. aluminum paste. However, a problem is the relatively weak chemical resistance of amorphous aluminum oxide in the circumstances used in this kind of manufacturing process. This manufacturing method of the back electrode contains a firing step, which is done at an elevated temperature of about 700 - 800 °C . The aluminum paste contains chemicals which etch the passivating layer comprising aluminum oxide and thus causes at least partial removal of aluminum oxide, whereby the surface passivation is weakened or destroyed .
The inventors have identified a need for an efficient technique of protecting the passivating lay¬ er from chemical interactions between the passivation layer and the electrode comprising aluminum.
PURPOSE OF THE INVENTION
A purpose of the present invention is to pro¬ vide a new method and a structure for protecting a passivating layer comprising aluminum oxide and being formed on a surface of a silicon substrate from ef¬ fects caused by chemical interaction between the pas-
sivating layer and a conducting electrode. Further, the purpose of the present invention is to provide a new use of the structure. SUMMARY OF THE INVENTION
The method according to the present invention is characterized by what is presented in independent claim 1.
The structure according to the present inven- tion is characterized by what is presented in inde¬ pendent claim 8.
The use according to the present invention is characterized by what is presented in independent claim 16.
The present invention relates to a method for protecting a passivating layer comprising aluminum oxide and being formed on a surface of a silicon sub¬ strate from effects caused by chemical interaction be¬ tween the passivating layer and a conducting electrode by fabricating a barrier layer between the passivating layer and the conducting electrode, wherein the method comprises depositing a barrier layer comprising titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafnium and oxygen, or a combination of any of these, or a combination of any of these with aluminum and oxygen, on the passivating layer by exposing the passivating layer in a reaction space to alternately repeated surface reactions of two or more different precursors, wherein at least one of the precursors is a precursor for oxygen; and forming the conducting electrode on the barrier layer deposited on the pas¬ sivating layer by making a layer comprising aluminum paste on the barrier layer.
The present invention relates further to a structure comprising a barrier layer between a passivating layer and a conducting electrode, wherein the barrier layer is configured to protect the passivating
layer comprising aluminum oxide and being formed on a surface of a silicon substrate from effects caused by chemical interaction between the passivating layer and the conducting electrode, wherein the barrier layer comprises titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafnium and oxygen, or a combination of any of these, or a combination of any of these with aluminum and oxygen, and the conducting electrode comprises a layer comprising aluminum paste. According to one embodiment of the present invention the barrier layer is deposited on the passivating layer by exposing the passivating layer in a reaction space to alternately repeated surface reactions of two or more different precursors, wherein at least one of the precursors is a precursor for oxygen; and the con¬ ducting electrode is formed on the barrier layer de¬ posited on the passivating layer by making a layer comprising aluminum paste on the barrier layer.
The aluminum paste used in the present inven- tion can be any aluminum paste usually used for the production of a photovoltaic cell.
The method and the structure of the present invention provide an efficient way of protecting the passivating layer from effects caused by chemical in- teraction between the passivating layer and the conducting electrode. Surprisingly it was noted that the barrier layer formed by exposing the passivating layer in a reaction space to alternately repeated surface reactions of two or more different precursors effi- ciently protected the passivating layer by inhibiting chemical reactions from occurring between the passivating layer and the conducting electrode. It was noted that when a barrier layer comprising titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafni- urn and oxygen, or a combination of any of these, or a combination of any of these with aluminum and oxygen, was fabricated between the passivating layer and the
conducting electrode the harmful effects reducing the passivation property of the passivating layer were significantly reduced compared to an otherwise identi¬ cal structure without the barrier layer.
In this specification the expression "passivating", "passivation", "surface passivation" or other corresponding expressions should be understood as the passivation of a surface for reducing surface recombi¬ nation, i.e. for reducing the recombination of charge carriers on or in immediate proximity to the passivat- ed surface.
According to the present invention the pas¬ sivating layer comprises aluminum oxide. According to one embodiment of the present the passivating layer comprises a mixture comprising aluminum oxide.
According to one embodiment of the present invention the barrier layer is deposited on the passivating layer in a reaction space by an atomic layer deposition (ALD) type process.
Atomic Layer Deposition (ALD) , or an ALD-type method, is a method for depositing uniform and confor- mal films, e.g. thin-films, over substrates of various shapes, even over complex 3D (three dimensional) structures. In ALD-type methods the deposit is grown by alternately repeating, essentially self-limiting, surface reactions between a precursor and a surface to be coated. Therefore the growth mechanism in an ALD- type process is commonly not as sensitive as in other coating methods to e.g. the flow dynamics inside a re- action chamber which may be a source for non- uniformity, especially in coating methods relying on gas-phase reactions or in physical deposition methods, such as metal-organic chemical vapor deposition (MOCVD) or physical vapor deposition (PVD) .
In an ALD-type process two or more different chemicals (precursors) can be introduced to a reaction space in a sequential, alternating manner and the pre-
cursors adsorb on desired surfaces inside the reaction space. The sequential, alternating, introduction of precursors is commonly called pulsing (of precursors) . In between each precursor pulse there is commonly a purging period during which a flow of gas which does not react with the precursors used in the process is introduced through the reaction space. This gas, often called the carrier gas is therefore inert towards the precursors used in the process and purges the reaction space from e.g. surplus precursor and by-products re¬ sulting from the adsorption reactions of the previous precursor pulse. This purging can be arranged also by other means .
The essential feature of the ALD-type methods is to sequentially expose the deposition surface to precursors and to growth reactions of precursors es¬ sentially on the deposition surface. The alternate or sequential exposure of the deposition surface to dif¬ ferent precursors can be carried out in different man- ners . In a batch type ALD process the substrate to be deposited is placed in a reaction space, into which precursor and purge gases are being introduced in a predetermined cycle. In a continuous ALD-type process constant gas flow zones separated in space and a mov- ing substrate are used in order to obtain the time se¬ quential exposure. By moving the substrate through stationary zones, providing precursor exposure and purging areas, in the reaction space, a continuous coating process is achieved enabling roll-to-roll coating of a substrate. In continuous ALD-type process the cycle time depends on the speed of movement of the substrate between the gas flow zones in the reaction space .
The thickness of the deposit, coating or lay- er produced by the ALD-type process can be increased by repeating several times a pulsing sequence compris¬ ing the aforementioned pulses containing the precursor
material, and the purging periods. The number of how many times this sequence, called the "ALD cycle", is repeated depends on the targeted thickness of the lay¬ er .
The alternate introduction of precursors is characteristic to this deposition process, which is often called atomic layer deposition (ALD) . Other names besides ALD have also been employed for these types of processes, where the alternate introduction of two or more different precursors lead to the growth of the layer, often through essentially self-limiting surface reactions. These other names or process vari¬ ants include atomic layer epotaxy (ALE) , atomic layer chemical vapour deposition (ALCVD) , and corresponding plasma enhanced variants. Unless otherwise stated, these processes will be collectively addressed as ALD- type processes in this specification.
According to one embodiment of the present invention depositing the barrier layer comprises de- positing a layer comprising titanium and oxygen, or a layer comprising tantalum and oxygen. According to one embodiment of the present invention the barrier layer comprises titanium and oxygen, or tantalum and oxygen. According to one embodiment of the present invention depositing the barrier layer comprises depositing a layer comprising an oxide. According to one embodiment of the present invention the barrier layer comprises an oxide. According to one embodiment of the present invention depositing the barrier layer comprises de- positing a layer comprising titanium oxide, or tantalum oxide. According to one embodiment of the present invention the barrier layer comprises titanium oxide, or tantalum oxide. According to one embodiment of the present invention depositing the barrier layer com- prises depositing a layer comprising a combination of any of the above described materials. According to one embodiment of the present invention the barrier layer
comprises a combination of any of the above described materials .
According to one embodiment of the present invention depositing the barrier layer comprises de- positing a layer comprising titanium oxide, tantalum oxide, zirconium oxide, hafnium oxide, or a combina¬ tion of any of these, or a combination of any of these with aluminum oxide. According to one embodiment of the present invention the barrier layer comprises ti- tanium oxide, tantalum oxide, zirconium oxide, hafnium oxide, or a combination of any of these, or a combina¬ tion of any of these with aluminum oxide.
According to one embodiment of the present invention depositing the barrier layer comprises de- positing a layer comprising a nanolaminate structure. According to one embodiment of the present invention the barrier layer comprises a nanolaminate structure.
According to one embodiment of the present invention the nanolaminate structure comprises alter- nating layers of different oxide materials.
According to one embodiment of the present invention depositing the barrier layer comprises depositing a layer comprising a nanolaminate structure of aluminum oxide and an inert material. According to one embodiment of the present invention the barrier layer comprises a nanolaminate structure of aluminum oxide and an inert material. According to one embodi¬ ment of the present invention the inert material is selected from a group consisting of titanium oxide, tantalum oxide, zirconium oxide, and hafnium oxide.
According to one embodiment of the present invention depositing the barrier layer comprises depositing a layer comprising a nanolaminate structure of aluminum oxide and titanium oxide, tantalum oxide, zirconium oxide, or hafnium oxide. According to one embodiment of the present invention the barrier layer comprises a nanolaminate structure of aluminum oxide
and titanium oxide, tantalum oxide, zirconium oxide, or hafnium oxide.
According to one embodiment of the present invention the nanolaminate structure is formed with an ALD-type method using an ALD cycle ratio of 2 - 50 cy¬ cles for depositing aluminum oxide to 1 - 10 cycles for depositing inert material. According to one embod¬ iment of the present invention the inert material is selected from a group consisting of titanium oxide, tantalum oxide, zirconium oxide, and hafnium oxide.
The surprising barrier effect achieved with the present invention was attributed to the compati¬ bility of the barrier layer between the passivating layer and the conducting electrode. Without limiting the invention to any specific mechanism of why the aforementioned advantage of effective protection was achieved, it is assumed that the barrier layer, com¬ prising titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafnium and oxygen, or a combina- tion of any of these, or a combination of any of these with aluminum and oxygen, being a stable material, e.g. chemically inert, is able to protect the passiv¬ ating layer comprising aluminum oxide e.g. during the firing step of the manufacturing method of e.g. photo- voltaic cells. The ALD-type method used for forming the barrier layer between the passivating layer and the conducting electrode provided advantageous proper¬ ties to the formed barrier layer enabling effective protection of the passivating layer. When the barrier layer is fabricated on the passivating layer by an ALD-type process excellent conformity and uniformity is achieved for the barrier layer. In a similar manner when the passivating layer is fabricated on the surface of the silicon substrate by an ALD-type process excellent conformity and uniformity is achieved for the passivating layer. These advantages of the present
invention come in addition to the advantageous protec¬ tion property of the barrier layer discussed above.
According to one embodiment of the present invention the conducting electrode comprises metal. According to one embodiment of the present invention the conducting electrode comprises aluminum.
According to one embodiment of the present invention depositing the barrier layer is terminated before the barrier layer reaches a thickness of 100 nanometers. According to one embodiment of the present invention the barrier layer has a thickness of below 100 nanometers.
According to one embodiment of the present invention the barrier layer has a thickness of 2 - 50 nanometers, and preferably 1 - 10 nanometers.
According to one embodiment of the present invention the passivating layer has a thickness of 2 - 50 nanometers, and preferably 5 - 10 nanometers.
According to one embodiment of the present invention the passivating layer is formed on the surface of the silicon substrate by depositing the pas¬ sivating layer on the surface of the silicon substrate in a reaction space by an atomic layer deposition (ALD) type process.
The thickness of the barrier layer can be in¬ creased in some embodiments of the present invention by repeatedly exposing the deposition surface to the precursors in the reactions space such that a portion of them adsorbs onto the exposed surfaces in the reac- tion space i.e. onto the deposition surfaces. In this way the protection of the passivating layer may be enhanced in some embodiments of the present invention. In a similar manner also the thickness of the passiv¬ ating layer can be increased during the ALD-type pro- cess.
According to one embodiment of the present invention the silicon substrate is in the form of an
electrically conducting layer to an arrangement for a photovoltaic cell.
According to one embodiment of the present invention the growth of the passivating layer and/or the barrier layer in the ALD-type process is essen¬ tially thermally activated. E.g. the passivation ef¬ fect is enhanced when the ALD-type process is essen¬ tially thermally activated i.e. no plasma activation is employed.
The precursors for the deposition process of the barrier layer and/or the passivating layer can be selected from a large group of chemicals. According to one embodiment of the present invention the precursor for titanium is selected from the group of titanium tetrachloride (TiCl4) , titanium isopropoxide
(Ti (OCH (CH3) 2) 4) , titanium ethoxide (Ti (OCH2CH3) 4) , ti¬ tanium tetramethoxide (Ti(OCH3)4) and titanium iodide (Til4) . According to one embodiment of the present in¬ vention the precursor for tantalum is selected from the group of tantalum pentachloride (TaCl5) , tantalum pentaiodide (Tal5) , tantalum pentaethoxide (Ta(OEt)5), pentakis (dimethylamido) tantalum (Ta(NMe2)s), and tanta¬ lum (V) diethylamide TA(NEt2) 5- According to one embodi¬ ment of the present invention the precursor for zirco- nium is selected from the group of ZrCl , ZrCl2 [N (SiMe3) 2] 2, Zrl4, Zr(OtBu)4, Zr (OtBu) 2 (mmp) 2, Zr(mmp)4, Zr(ONEt2)4, Zr(NMe2)4, Zr(NEt2)4, and
Zr(NEtMe) . According to one embodiment of the present invention the precursor for hafnium is selected from the group of HfCl4, HfCl2 [N (SiMe3) 2] 2, Hfl4, Hf(OtBu)4, Hf (OtBu) 2 (mmp) 2, Hf(mmp)4, Hf(ONEt2) , Hf(NMe2) , Hf (NEt2) , and Hf (NEtMe ) .
According to one embodiment of the present invention the precursor for aluminum is selected from the group of TMA ( trimethylaluminum) , TEA (triethyl- aluminum) , A1C13, AlBr3 , AlMe2Cl AlMe2OiPr, A10nPr3 and AlOnPr. According to one embodiment of the present in-
vention the precursor for oxygen is selected from the group of H20, 02, 03, ROHd, A10Et3, A10iOr3, H202, N20 and N204. Selecting the other process parameters to de¬ posit the barrier layer and the passivating layer with the selected precursors will be obvious to the skilled person in light of this specification.
According to one embodiment of the present invention the silicon substrate has a thickness of be¬ low 200 micrometers.
According to one embodiment of the present invention the method comprises protecting the passivating layer from effects caused by chemical interac¬ tion between the passivating layer and the conducting electrode in a photovoltaic cell. According to one em- bodiment of the present invention the barrier layer is configured to protect the passivating layer from ef¬ fects caused by chemical interaction between the pas¬ sivating layer and the conducting electrode in a photovoltaic cell.
The present invention further relates to the use of the structure according to the present inven¬ tion for protecting a passivating layer comprising aluminum oxide and being formed on a surface of a sil¬ icon substrate from effects caused by chemical inter- action between the passivating layer and a conducting electrode in a photovoltaic cell.
An advantage of the present invention is that it enables the protection of the passivating layer from being affected by chemicals contained in the back electrode, i.e. the layer comprising aluminum paste, which chemicals would cause etching of the passivation layer. The barrier layer according to the present invention prevents etching of the passivating layer, which would lead to at least partial removal of the aluminum oxide and would thus weaken or destroy the surface passivation.
An advantage of the present invention is that the barrier layer fabricated in an ALD-type process and comprising e.g. titanium oxide is stable and has the ability to protect the passivating layer compris- ing aluminum oxide during the firing step of the manu¬ facturing method of the back electrode.
An advantage of the present invention is that both the passivating layer comprising aluminum oxide and the barrier layer can be fabricated in the same ALD-process and apparatus thus removing the need of using any additional deposition equipment.
An advantage of a barrier layer comprising a combination of e.g. two different oxide materials, e.g. a nanolaminate structure, is that a more compact structure can be formed compared to using separate layers or films.
Without limiting the invention to any specific mechanism of why the barrier layer comprising a nanolaminate structure is able to provide effective protection of the passivating layer, it is assumed that the barrier layer having a nanolaminate structure is able to reduce the presence of grain boundaries in the depth direction of the film or layer. The space between grains can be a potential route for traversing the barrier layer. In the nanolaminate structure of two or more oxide materials, the second material will fill the grain boundaries of the material firstly de¬ posited thus hindering unwanted materials from trav¬ ersing the barrier film.
The embodiments of the invention described hereinbefore may be used in any combination with each other. Several of the embodiments may be combined to¬ gether to form a further embodiment of the invention. A method, a structure or a use, to which the invention is related, may comprise at least one of the embodi¬ ments of the invention described hereinbefore.
BRIEF DESCRIPTION OF THE DRAWINGS
The accompanying drawings, which are included to provide a further understanding of the invention and constitute a part of this specification, illus- trate embodiments of the invention and together with the description help to explain the principles of the invention. In the drawings:
Fig. 1 is a flow-chart illustration of a method according to one embodiment of the present in- vention, and
Fig. 2 is a schematic illustration of a structure according to one embodiment of the present invention . DETAILED DESCRIPTION OF THE INVENTION
Reference will now be made in detail to the embodiments of the present invention, examples of which are illustrated in the accompanying drawings.
For reasons of simplicity, item numbers will be maintained in the following exemplary embodiments in the case of repeating components.
As presented above Atomic Layer Deposition (ALD) , or an ALD-type process, is a method for depos¬ iting uniform and conformal films or layers over sub- strates of various shapes. Further, as presented above in ALD-type processes the deposit is grown by alter¬ nately repeating, essentially self-limiting, surface reactions between a precursor and a surface to be coated. The prior art discloses a wide range of mate- rials that can be synthesized and deposited on a sub¬ strate by alternately exposing the surface of the sub¬ strate to different precursors, in an ALD-type pro¬ cess. Also many different apparatuses suitable for carrying out an ALD-type process are disclosed in the prior art. For example US patent 6824816 discloses
processes for depositing metal thin-films by ALD, and US patent 6174377 describes deposition tools for ALD.
The construction of a processing tool suitable for carrying out the methods in the following em- bodiments will be obvious to the skilled person in light of this disclosure. The tool can be e.g. a con¬ ventional ALD tool suitable for handling the process chemicals. ALD tools (i.e. reactors) are disclosed in e.g. US patent 4389973 and US patent 4413022 which are included herein as references. Many of the steps re¬ lated to handling such tools, such as delivering a substrate into the reaction space, pumping the reac¬ tion space down to a low pressure, or adjusting gas flows in the tool if the process is done at atmospher- ic pressure, heating the substrates and the reaction space etc., will be obvious to the skilled person. Al¬ so, many other known operations or features are not described here in detail nor mentioned, in order to emphasize relevant aspects of the various embodiments of the invention.
The detailed description below discloses some embodiments of the invention in such a detail that a person skilled in the art is able to utilize the in¬ vention based on the disclosure. Not all steps or com- ponents of the embodiments are discussed in detail, as many of the steps or components will be obvious to the person skilled in the art based on this specification.
The method of Fig. 1 and the structure of Fig. 2 illustrate, respectively, a method and the cor- responding resulting structure according to one embodiment of the invention. The method of Fig. 1 presents how to carry out the method for passivating the sili¬ con substrate 1 with a passivating layer 2 comprising aluminium oxide, and for protecting the passivating layer 2 with a barrier layer 3 against chemical interaction of the passivating layer 2 with the conducting
electrode 4 deposited on the other side of the barrier layer 3.
The silicon substrate 1 can be prepared by e.g. depositing a film of silicon on a substrate in its microcrystalline, nanocrystalline or polycrystal- line phase. The embodiment of Fig. 1 begins by bring¬ ing the silicon substrate 1 into the reaction space (step 1)) of a typical reactor tool, e.g. a tool suit¬ able for carrying out an ALD-type process.
The reaction space is subsequently pumped down to a pressure suitable for forming the passivat- ing layer 2 comprising aluminum oxide. The reaction space can be pumped down to the suitable pressure us¬ ing e.g. a mechanical vacuum pump or, in the case of atmospheric pressure ALD systems and/or processes, gas flows can be set to protect the deposition zone from the atmosphere. The silicon substrate 1 is also heated to a temperature suitable for forming the passivating layer 2 by the used method. The silicon substrate 1 can be introduced to the reaction space through e.g. an airtight load-lock system or simply through a loading hatch. The silicon substrate 1 can be heated by e.g. resistive heating elements which also heat the entire reaction space.
After the silicon substrate 1 and the reac¬ tion space have reached the targeted temperature and other conditions suitable for deposition, the silicon surface can be conditioned such that the passivating deposit may be essentially directly deposited on the silicon surface. This conditioning of the silicon surface on which the passivating layer 2 is to be deposited can include chemical purification of the surface of the silicon film from impurities and/or oxidation. Especially removal of oxide is beneficial when the silicon surface has been imported into the reaction space via an oxidizing environment, e.g. when trans¬ porting the exposed silicon surface from one deposi-
tion tool to another. The details of the process for removing impurities and/or oxide from the surface of the silicon film will be obvious to the skilled person in view of this specification. In some embodiments of the invention the conditioning can be done ex-situ, i.e. outside the tool suitable for ALD-type processes. An example of an ex-situ conditioning process is etch¬ ing for 1 min in a 1 % HF solution followed by rinsing in Dl-water.
After the silicon substrate 1 has been condi¬ tioned, an alternate exposure of the deposition sur¬ face to different precursor chemicals is started, to form the passivating layer 2 comprising aluminum oxide directly on the silicon substrate 1 (Step a) in Fig. 1) . Each exposure of the deposition surface to a pre¬ cursor results in the formation of additional deposit on the deposition surface, as a result of adsorption reactions of the corresponding precursor with the deposition surface.
A typical reactor suitable for ALD-type depo¬ sition comprises a system for introducing carrier gas, such as nitrogen or argon into the reaction space such that the reaction space can be purged from surplus chemical and reaction by-products before introducing the next precursor chemical into the reaction space. This feature together with the controlled dosing of vaporized precursors enables alternately exposing the substrate surface to precursors without significant intermixing of different precursors in the reaction space or in other parts of the reactor. In practice the flow of carrier gas is commonly continuous through the reaction space throughout the deposition process and only the various precursors are alternately intro¬ duced to the reaction space with the carrier gas.
Thickness of the passivating layer 2 on the silicon substrate 1 can be controlled by the number of exposures of the deposition surface to the different
precursors. The thickness of the passivating layer 2 is increased until a targeted thickness is reached, after which the barrier layer 3 is deposited on the passivating layer 2 (Step b) in Fig. 1) .
Deposition of the barrier layer 3, in one embodiment of the invention, is carried out in an ALD- type process in the same deposition tool directly af¬ ter the deposition of the passivating layer 2 has ended. In this case deposition of the barrier layer 3 can begin simply by changing the precursor chemicals from those used for the deposition of the passivating layer 2 to those suitable for the deposition of the barrier layer 3.
The following example describes in detail how a barrier layer 3 of titanium oxide (Ti02) can be de¬ posited on the passivating layer 2 residing on the silicon substrate 1.
EXAMPLE
A barrier layer 3 was formed on a passivating layer 2 of aluminum oxide (A1203) deposited on a sur¬ face of a silicon substrate 1; step b) of the embodi¬ ment of the invention shown in Fig. 1. The barrier layer 3 was deposited inside the reaction space of a P400 ALD batch tool (available from Beneq OY, Finland) directly after the passivating layer 2 was deposited on the silicon substrate 1 as discussed above. The silicon substrate 1 was a photovoltaic cell structure. This structure was positioned inside the reaction space such that the passivating layer 2 was exposed to the reaction environment.
The pressure and temperature during the depo¬ sition of the barrier layer 3 was about 1 mbar (1 hPa) and about 300 °C inside the reaction space, respec- tively. In this example the carrier gas discussed above, and responsible for purging the reaction space, was nitrogen (N2) . The processing temperature was suf-
ficient to result in a thermally activated ALD-type growth and no plasma activation was employed in this example .
After the passivating layer 2 of aluminum ox- ide was deposited the precursors were changed to start the deposition of titanium oxide as the barrier layer 3 on the passivating layer 2. Titanium tetrachloride (TiCl4) was introduced to the reaction space to expose the passivating layer 2 to this first precursor. After letting the carrier gas purge the reaction space from surplus first precursor and reaction byproducts, the resulting surface of the substrate was similarly ex¬ posed to the second precursor, the precursor for oxy¬ gen, here water (H20) . After this, the reaction space was purged again. This pulsing sequence was carried out once and then repeated 299 times before the pro¬ cess was ended and the substrates were ejected from the reaction space and from the ALD tool. These 300 "ALD cycles" resulted in a barrier layer 3 of titanium oxide with a thickness of approximately 25 nm on the passivating aluminum oxide layer 2.
More specifically, exposure of the surface of the substrate to a specific precursor was carried out by switching on the pulsing valve of the P400 ALD tool controlling the flow of the precursor chemicals into the reaction space. Purging of the reaction space was carried out by closing the valves controlling the flow of precursors into the reaction space, and thereby letting only the continuous flow of carrier gas flow through the reaction space. The pulsing sequence in this example was in detail as follows: 0.6 s exposure to titanium tetrachloride, 1.5 s purge, 0.4 s exposure to water, 2.0 s purge. An exposure time and a purge time in this sequence signify a time a specific puls- ing valve for a specific precursor was kept open and a time all the pulsing valves for precursors were kept closed, respectively.
In the example above the first precursor is titanium tetrachloride and the second precursor is wa¬ ter, but other precursors can also be used depending on the desired barrier material and composition. The invention is not limited to using the aforementioned precursors in particular and the advantages of the in¬ vention can be obtained by the skilled person in light of this specification also with other precursors. After the passivating layer 2 and the barrier layer 3 on the passivating layer 2 have been deposited in a single process as described above, the conducting electrode 4, e.g. aluminum electrode, is fabricated on the barrier layer 3 to finalize the structure of Fig. 2. The aluminum electrode 4 is then fabricated on the barrier layer 3 by a screen printing method comprising e.g. printing the aluminum paste on the barrier layer, drying and curing the paste at high temperature using method steps, which will be obvious to the person skilled in the art.
In the structure of Fig. 2 the barrier layer 3 efficiently protects the underlying passivating lay¬ er 2 of aluminum oxide which passivates the surface of the silicon substrate 1 an thereby minimizes surface recombination on the interface between the silicon substrate 1 and the passivating layer 2.
Test results have shown that in the structure of Fig. 2, fabricated with the method of Fig. 1 as de¬ scribed above, the titanium oxide barrier layer 3 pro- tects the aluminum oxide passivating layer 2 especially from chemical interactions with the aluminum elec¬ trode 4. This surprisingly enables the passivating layer 2 to retain the passivating effect on the surface of the silicon substrate 1 without significant degradation over time even under challenging environmental conditions such as high temperature. An addi¬ tional benefit of the method according to the embodi-
ment of Fig. 1 is that, as presented above, the pas- sivating layer 2 and the barrier layer 3 can be fabricated in a single ALD-type process on the silicon sub¬ strate 1. The layered structure of Fig. 2 is commonly used in, for example, solar cells and other photovol¬ taic devices.
In the example above the barrier layer com¬ prises titanium oxide, but the barrier layer could al¬ so comprise other materials such as tantalum oxide, zirconium oxide, hafnium oxide, or a combination of any of these, or a combination of any of these with aluminum oxide, as will be obvious to a skilled person in light of this specification. Thus, the invention is not limited to using the aforementioned barrier layer in particular and the advantages of the invention can be readily obtained by the skilled person in light of this specification also with the other materials mentioned above.
It is obvious to a person skilled in the art that with the advancement of technology, the basic idea of the invention may be implemented in various ways. The invention and its embodiments are thus not limited to the examples described above; instead they may vary within the scope of the claims.
Claims
1. A method for protecting a passivating layer (2) comprising aluminum oxide and being formed on a surface of a silicon substrate (1) from effects caused by chemical interaction between the passivating layer and a conducting electrode (4) by fabricating a barrier layer (3) between the passivating layer and the conducting electrode, c h a r a c t e r i z e d in that the method comprises
- depositing a barrier layer (3) comprising titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafnium and oxygen, or a combination of any of these, or a combination of any of these with aluminum and oxygen, on the passivating layer (2) by exposing the passivating layer in a reaction space to alternately repeated surface reactions of two or more different precursors, wherein at least one of the pre¬ cursors is a precursor for oxygen; and
- forming the conducting electrode (4) on the barrier layer (3) deposited on the passivating layer by making a layer comprising aluminum paste on the barrier layer.
2. The method of claim 1, c h a r a c t e r i z e d in that the barrier layer (3) is deposited on the passivating layer (2) in a reaction space by an atomic layer deposition (ALD) type process.
3. The method of any one of claims 1 - 2, c h a r a c t e r i z e d in that depositing the barrier layer (3) comprises depositing a layer comprising a nanolaminate structure.
4. The method of any one of claims 1 - 3, c h a r a c t e r i z e d in that depositing the barrier layer (3) is terminated before the barrier layer reaches a thickness of 100 nanometers.
5. The method of any one of claims 1 - 4, c h a r a c t e r i z e d in that the passivating layer (2) is formed on the surface of the silicon substrate (1) by depositing the passivating layer on the surface of the silicon substrate in a reaction space by an atomic layer deposition (ALD) type process.
6. The method of any one of claims 1 - 5, c h a r a c t e r i z e d in that the silicon substrate
(1) is in the form of an electrically conducting layer to an arrangement for a photovoltaic cell.
7. The method of any one of claims 1 - 6, c h a r a c t e r i z e d in that the method comprises protecting the passivating layer (2) from effects caused by chemical interaction between the passivating layer and the conducting electrode (4) in a photovol¬ taic cell.
8. A structure comprising a barrier layer (3) between a passivating layer (2) and a conducting electrode (4), wherein the barrier layer is configured to protect the passivating layer comprising aluminum oxide and being formed on a surface of a silicon sub¬ strate (1) from effects caused by chemical interaction between the passivating layer and the conducting electrode, c h a r a c t e r i z e d in that the barrier lay¬ er (3) comprises titanium and oxygen, tantalum and oxygen, zirconium and oxygen, hafnium and oxygen, or a combination of any of these, or a combination of any of these with aluminum and oxygen, and the conducting electrode (4) comprises a layer comprising aluminum paste .
9. A structure of claim 8, c h a r a c t e r i z e d in that the barrier layer (3) is deposited on the passivating layer (2) by exposing the passivating layer in a reaction space to alternately repeated sur¬ face reactions of two or more different precursors, wherein at least one of the precursors is a precursor for oxygen; and the conducting electrode (4) is formed on the barrier layer deposited on the passivating layer by making a layer comprising aluminum paste on the barrier layer.
10. The structure of any one of claims 8 - 9, c h a r a c t e r i z e d in that the barrier layer (3) is deposited on the passivating layer (2) in a reaction space by an atomic layer deposition (ALD) type process.
11. The structure of any one of claims 8 - 10, c h a r a c t e r i z e d in that the barrier layer (3) comprises a nanolaminate structure.
12. The structure of any one of claims 8 - 11, c h a r a c t e r i z e d in that the barrier layer
(3) has a thickness of below 100 nanometers.
13. The structure of any one of claims 8 -
12, c h a r a c t e r i z e d in that the passivating layer (2) is formed on the surface of the silicon sub- strate (1) by depositing the passivating layer on the surface of the silicon substrate in a reaction space by an atomic layer deposition (ALD) type process.
14. The structure of any one of claims 8 -
13, c h a r a c t e r i z e d in that the silicon sub- strate (1) is in the form of an electrically conduct¬ ing layer to an arrangement for a photovoltaic cell.
15. The structure of any one of claims 8 -
14, c h a r a c t e r i z e d in that the barrier layer (3) is configured to protect the passivating layer (2) from effects caused by chemical interaction between the passivating layer and the conducting electrode (4) in a photovoltaic cell.
16. The use of a structure of any one of claims 8 - 15 for protecting a passivating layer (2) comprising aluminum oxide and being formed on a surface of a silicon substrate (1) from effects caused by chemical interaction between the passivating layer (2) and a conducting electrode (4) in a photovoltaic cell.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| FI20115534 | 2011-05-30 | ||
| FI20115534A FI20115534A0 (en) | 2011-05-30 | 2011-05-30 | Method and structure for protecting a passivating layer |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| WO2012164163A1 true WO2012164163A1 (en) | 2012-12-06 |
Family
ID=44071658
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| PCT/FI2012/050514 WO2012164163A1 (en) | 2011-05-30 | 2012-05-28 | A method and a structure for protecting a passivating layer |
Country Status (3)
| Country | Link |
|---|---|
| FI (1) | FI20115534A0 (en) |
| TW (1) | TW201308633A (en) |
| WO (1) | WO2012164163A1 (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109148643A (en) * | 2018-08-06 | 2019-01-04 | 横店集团东磁股份有限公司 | A method of the PERC battery solving ALD mode is reduced in electrical pumping or light injection behind efficiency |
Families Citing this family (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104471720A (en) | 2012-07-19 | 2015-03-25 | 日立化成株式会社 | Passivation-layer-forming composition, semiconductor substrate having passivation layer, method for manufacturing semiconductor substrate having passivation layer, solar-cell element, method for manufacturing solar-cell element, and solar cell |
| TW201511300A (en) * | 2013-09-11 | 2015-03-16 | Inst Nuclear Energy Res Atomic Energy Council | Preparation method of aluminum metal electrode having doped silicon or boron atoms |
| CN110047950A (en) * | 2019-05-22 | 2019-07-23 | 通威太阳能（安徽）有限公司 | A kind of solar cell and preparation method thereof with passivation layer structure |
Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6420279B1 (en) * | 2001-06-28 | 2002-07-16 | Sharp Laboratories Of America, Inc. | Methods of using atomic layer deposition to deposit a high dielectric constant material on a substrate |
| EP1635398A2 (en) * | 2004-09-10 | 2006-03-15 | North Carolina State University | Semiconductor devices having an interfacial dielectric layer and related methods |
| US20100263725A1 (en) * | 2007-11-14 | 2010-10-21 | Institut Für Solarenergieforschung Gmbh | Method for manufacturing a solar cell with a surface-passivating dielectric double layer, and corresponding solar cell |
| EP2312650A2 (en) * | 2009-10-13 | 2011-04-20 | IPS Ltd | Solar Cell and Method of Fabricating the Same |
-
2011
- 2011-05-30 FI FI20115534A patent/FI20115534A0/en not_active Application Discontinuation
-
2012
- 2012-05-28 WO PCT/FI2012/050514 patent/WO2012164163A1/en active Application Filing
- 2012-05-30 TW TW101119282A patent/TW201308633A/en unknown
Patent Citations (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US6420279B1 (en) * | 2001-06-28 | 2002-07-16 | Sharp Laboratories Of America, Inc. | Methods of using atomic layer deposition to deposit a high dielectric constant material on a substrate |
| EP1635398A2 (en) * | 2004-09-10 | 2006-03-15 | North Carolina State University | Semiconductor devices having an interfacial dielectric layer and related methods |
| US20100263725A1 (en) * | 2007-11-14 | 2010-10-21 | Institut Für Solarenergieforschung Gmbh | Method for manufacturing a solar cell with a surface-passivating dielectric double layer, and corresponding solar cell |
| EP2312650A2 (en) * | 2009-10-13 | 2011-04-20 | IPS Ltd | Solar Cell and Method of Fabricating the Same |
Non-Patent Citations (4)
| Title |
|---|
| DINGEMANS, G. ET AL.: "Recent Progress in the Development and Understanding of Silicon Surface Passivation by Aluminum Oxide for Photovoltaics", EU PVSEC PROCEEDINGS, 25TH EUROPEAN PHOTOVOLTAIC SOLAR ENERGY CONFERENCE AND EXHIBITION / 5TH WORLD CONFERENCE ON PHOTOVOLTAIC ENERGY CONVERSION, 6 September 2010 (2010-09-06) - 10 September 2010 (2010-09-10), VALENCIA, SPAIN, pages 1083 - 1090 * |
| SAINT-CAST, P. ET AL.: "High-Efficiency c-Si Solar Cells Passivated With ALD and PECVD Aluminum Oxide", IEEE ELECTR. LETT., vol. 31, no. 7, July 2010 (2010-07-01), pages 695 - 697 * |
| SCHMIDT, J. ET AL.: "Silicon surface passivation by ultrathin Al2O3 films and Al2O3/SiNx stacks", CONFERENCE PROCEEDINGS, 35TH IEEE PHOTOVOLTAIC SPECIALISTS CONFERENCE (PVSC), 20 June 2010 (2010-06-20) - 25 June 2010 (2010-06-25), HONOLULU, USA, pages 885 - 890 * |
| SCHMIDT, J. ET AL.: "Surface passivation of high-efficiency silicon solar cells by atomic-layer-deposited Al2O3", PROG. PHOTOVOLT: RES. APPL., vol. 16, no. 6, September 2008 (2008-09-01), pages 461 - 466 * |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109148643A (en) * | 2018-08-06 | 2019-01-04 | 横店集团东磁股份有限公司 | A method of the PERC battery solving ALD mode is reduced in electrical pumping or light injection behind efficiency |
| CN109148643B (en) * | 2018-08-06 | 2021-02-09 | 横店集团东磁股份有限公司 | Method for solving problem of efficiency reduction of PERC battery in ALD mode after electric injection or light injection |
Also Published As
| Publication number | Publication date |
|---|---|
| TW201308633A (en) | 2013-02-16 |
| FI20115534A0 (en) | 2011-05-30 |
Similar Documents
| Publication | Publication Date | Title |
|---|---|---|
| KR102481449B1 (en) | Method for forming a photonic device on a substrate | |
| US11658030B2 (en) | Method for forming doped metal oxide films on a substrate by cyclical deposition and related semiconductor device structures | |
| Kääriäinen et al. | Atomic layer deposition: principles, characteristics, and nanotechnology applications | |
| JP6367658B2 (en) | Method of generating oxide film by plasma assist process | |
| KR101664504B1 (en) | Solar cell, and method of manufacturing the same | |
| US7608539B2 (en) | ALD method and apparatus | |
| KR102013927B1 (en) | Deposition of smooth metal nitride films | |
| JP6576362B2 (en) | Fluorine-containing conductive film | |
| TWI488290B (en) | Semiconductor device including carbon-containing electrode and method for fabricating the same | |
| US20130069207A1 (en) | Method for producing a deposit and a deposit on a surface of a silicon substrate | |
| WO2012164163A1 (en) | A method and a structure for protecting a passivating layer | |
| WO2012031192A1 (en) | Deposition system | |
| WO2012109523A2 (en) | Deposition of thin films on energy sensitive surfaces | |
| WO2014083241A1 (en) | Method for fabricating a passivation film on a crystalline silicon surface | |
| WO2013079800A1 (en) | An n-type silicon photovoltaic cell structure | |
| KR101521800B1 (en) | A preparation method of nickel sulfide film | |
| WO2011009681A1 (en) | Plasma enhanced deposition method, semiconductor device, and deposition device | |
| WO2014083240A1 (en) | A method for fabricating a structure comprising a passivation layer on a surface of a substrate | |
| WO2014080080A1 (en) | Method for fabricating a passivation film on a crystalline silicon surface | |
| JPH0532473B2 (en) |
Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| 121 | Ep: the epo has been informed by wipo that ep was designated in this application |
Ref document number: 12792662 Country of ref document: EP Kind code of ref document: A1 |
|
| NENP | Non-entry into the national phase |
Ref country code: DE |
|
| 122 | Ep: pct application non-entry in european phase |
Ref document number: 12792662 Country of ref document: EP Kind code of ref document: A1 |