WO2012097914A1 - Method for producing a silicon solar cell - Google Patents
Method for producing a silicon solar cell Download PDFInfo
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- WO2012097914A1 WO2012097914A1 PCT/EP2011/071891 EP2011071891W WO2012097914A1 WO 2012097914 A1 WO2012097914 A1 WO 2012097914A1 EP 2011071891 W EP2011071891 W EP 2011071891W WO 2012097914 A1 WO2012097914 A1 WO 2012097914A1
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- emitter
- dopant
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- oxide
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- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 title claims abstract description 8
- 229910052710 silicon Inorganic materials 0.000 title claims abstract description 8
- 239000010703 silicon Substances 0.000 title claims abstract description 8
- 238000004519 manufacturing process Methods 0.000 title claims abstract description 7
- 239000002019 doping agent Substances 0.000 claims abstract description 24
- 239000000463 material Substances 0.000 claims abstract description 9
- 239000002184 metal Substances 0.000 claims abstract description 9
- 150000004767 nitrides Chemical class 0.000 claims abstract description 7
- 239000000758 substrate Substances 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 35
- 238000002161 passivation Methods 0.000 claims description 14
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 10
- 239000012298 atmosphere Substances 0.000 claims description 9
- 239000011521 glass Substances 0.000 claims description 8
- 238000005530 etching Methods 0.000 claims description 7
- KRHYYFGTRYWZRS-UHFFFAOYSA-N Fluorane Chemical compound F KRHYYFGTRYWZRS-UHFFFAOYSA-N 0.000 claims description 5
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 5
- 239000001301 oxygen Substances 0.000 claims description 5
- 229910052760 oxygen Inorganic materials 0.000 claims description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims description 5
- 239000011574 phosphorus Substances 0.000 claims description 5
- 238000000623 plasma-assisted chemical vapour deposition Methods 0.000 claims description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 229940110728 nitrogen / oxygen Drugs 0.000 claims 1
- 230000008569 process Effects 0.000 description 15
- 210000004027 cell Anatomy 0.000 description 10
- 229910052581 Si3N4 Inorganic materials 0.000 description 4
- 238000010586 diagram Methods 0.000 description 4
- HQVNEWCFYHHQES-UHFFFAOYSA-N silicon nitride Chemical compound N12[Si]34N5[Si]62N3[Si]51N64 HQVNEWCFYHHQES-UHFFFAOYSA-N 0.000 description 4
- 229910000040 hydrogen fluoride Inorganic materials 0.000 description 3
- 230000003287 optical effect Effects 0.000 description 3
- 230000009467 reduction Effects 0.000 description 3
- VYPSYNLAJGMNEJ-UHFFFAOYSA-N Silicium dioxide Chemical compound O=[Si]=O VYPSYNLAJGMNEJ-UHFFFAOYSA-N 0.000 description 2
- 230000009471 action Effects 0.000 description 2
- 230000000873 masking effect Effects 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 238000007639 printing Methods 0.000 description 2
- 238000004886 process control Methods 0.000 description 2
- 238000007650 screen-printing Methods 0.000 description 2
- 229910052814 silicon oxide Inorganic materials 0.000 description 2
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- 229910007991 Si-N Inorganic materials 0.000 description 1
- 229910006294 Si—N Inorganic materials 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000002596 correlated effect Effects 0.000 description 1
- 229910021419 crystalline silicon Inorganic materials 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000000151 deposition Methods 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000005669 field effect Effects 0.000 description 1
- 238000010304 firing Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000007641 inkjet printing Methods 0.000 description 1
- 238000001465 metallisation Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 239000005360 phosphosilicate glass Substances 0.000 description 1
- 239000004065 semiconductor Substances 0.000 description 1
- 230000035945 sensitivity Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
Classifications
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L31/18—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof
- H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic Table
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
- H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
- H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer
- H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having potential barriers, e.g. a PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic Table or AIIIBV compounds with or without impurities, e.g. doping materials
- H01L21/22—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities
- H01L21/225—Diffusion of impurity materials, e.g. doping materials, electrode materials, into or out of a semiconductor body, or between semiconductor regions; Interactions between two or more impurities; Redistribution of impurities using diffusion into or out of a solid from or into a solid phase, e.g. a doped oxide layer
- H01L21/2251—Diffusion into or out of group IV semiconductors
- H01L21/2254—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides
- H01L21/2255—Diffusion into or out of group IV semiconductors from or through or into an applied layer, e.g. photoresist, nitrides the applied layer comprising oxides only, e.g. P2O5, PSG, H3BO3, doped oxides
-
- 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
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/547—Monocrystalline silicon PV cells
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02P—CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS
- Y02P70/00—Climate change mitigation technologies in the production process for final industrial or consumer products
- Y02P70/50—Manufacturing or production processes characterised by the final manufactured product
Definitions
- the invention relates to a method for producing a silicon solar cell having emitters produced by doping in a surface of a silicon substrate and metal contact regions provided locally on the emitter, wherein a dopant source material is stacked flat on the substrate surface and a first dopant driving step is carried out the layer of the dopant source material is structured in accordance with the intended metal contact areas, and in the structured state a second dopant driving step is carried out.
- a dopant source material is stacked flat on the substrate surface and a first dopant driving step is carried out the layer of the dopant source material is structured in accordance with the intended metal contact areas, and in the structured state a second dopant driving step is carried out.
- Fig. 1 shows schematically essential process steps a) to e) of this method.
- a first step a) first an Si wafer 10 is coated with phosphor glass 11 and a first dopant driving step is carried out to produce a full-surface P doping in the wafer surface occupied by the phosphor glass.
- a second step b) serving as dopant source material phosphorus glass 11 is masked and wet-structured by standing in those areas where later (not shown) metal contact areas or "fingers" are applied, stops and in the intermediate areas ("Zwischenfinger meansen”) is removed.
- a second dopant driving-in step takes place in an oxygen atmosphere, through which the P-doping in the intermediate finding regions is driven deep and in this case the surface concentration is lowered.
- a slightly phosphorus-containing oxide plain 13 is removed, and in step e), an Si-N passivation layer 14 is deposited on the wafer.
- this type of emitter can achieve very good blue sensitivity.
- Another problem of the process flow described is difficulty in aligning the metallization with the heavily doped finger regions. Since the heavily doped area is not visible after deposition of the SiN passivation, the orientation of the screen can only be based on other marks or the edges.
- Silicon nitride thickened Since here a relatively thick oxide layer with high
- DE 697 31 485 T2 also describes a method for producing a semiconductor device (in particular a photovoltaic cell) with selectively diffused regions.
- a semiconductor device in particular a photovoltaic cell
- this document also mentions the provision of a passivation oxide layer and a silicon nitride layer serving as an antireflection coating.
- WO 2010/012062 A1 describes a crystalline silicon solar cell with selective emitter which is produced with high precision using a low-temperature etching and passivation process. The method described therein may include passivation with an electrochemically formed silicon oxide layer.
- a method according to the invention comprises the features of claim 1. Advantageous embodiments of this method are the subject of the dependent claims.
- an oxide formed during the driving step of the selective emitter in combination with a nitride layer is used for the passivation.
- this oxide is etched back to a thickness of about 5 nm to 20 nm by an etch-back step (for example wet-chemically in dilute HF).
- an etch-back step for example wet-chemically in dilute HF.
- the driving step takes place in a sequence in FIG.
- Nitrogen and oxygen atmosphere whereby specifically an oxide layer can be grown with a layer thickness between 5 nm and 20 nm. This modification eliminates the re-etching step which results in a reduction in process complexity over the original sequence.
- the application of the nitride layer is carried out by means of PECVD.
- the thickness of the nitride layer is set in particular to a value in the range from 25 nm to 100 nm, preferably 40 nm to 90 nm.
- Fig. 1 is a schematic representation of a process flow after the
- FIG. 2 shows a schematic representation of a process flow according to a first embodiment of the invention
- Fig. 3 is a schematic representation of a process flow according to a second embodiment of the invention
- Fig. 4 is a further schematic representation of the second embodiment of the invention.
- FIG. 2 The schematic representation of a method sequence according to the invention in FIG. 2 is based on the representation in FIG. 1, and the steps a) to c) are the same. It should be noted that the masking by means of ink jet printing or screen printing of a suitable resist and the masked etching of the phosphorus glass (POCI 3 ) by means of HF (hydrogen fluoride) can take place.
- HF hydrogen fluoride
- a silicon nitride layer is deposited in a step e) by means of plasma-assisted chemical vapor deposition (PECVD). With the thin SiN layer 16, the desired optical properties of the cell surface are restored. In a manner known per se, this is followed by the steps (not shown) of printing and firing the metal contact regions (fingers).
- FIG. 3 shows an alternative process control, in which again the first
- Steps correspond to the already practiced in the applicant method of FIG. 1 largely.
- the second dopant driving-in step ie step c
- the second dopant driving-in step is carried out in a modified atmosphere in which only a thinner oxide layer 17 grows, which does not have to be etched back.
- the dopant residual layer 12 of the phosphor glass in the region of the intended metal contact fingers remains in this process procedure, and in step d) -as in the above-described process control according to FIG. 2 -a SiN layer 16 is deposited by means of PECVD.
- the upper part of the figure is schematically a temperature-time diagram A and in the lower part a correlated thereto with respect to the time axis gas flow-time diagram B for the second dopant driving step.
- Diagram A shows the driving according to the Applicant's practiced method in oxygen atmosphere (with application of a nitrogen atmosphere only in the initial phase of the temperature rise and the final phase of lowering the temperature), while the diagram B shows the change from an N 2 atmosphere into a 0 2 atmosphere during the phase of high temperature holding (Eintreibtemperatur) shows.
- the duration of the action of the N 2 or O 2 atmosphere By suitable positioning of the duration of the action of the N 2 or O 2 atmosphere, the growth of a thin oxide layer can be controlled sufficiently precisely.
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- Engineering & Computer Science (AREA)
- Manufacturing & Machinery (AREA)
- Physics & Mathematics (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Electromagnetism (AREA)
- Photovoltaic Devices (AREA)
Abstract
Method for producing a silicon solar cell comprising an emitter produced in a surface of a silicon substrate by doping, and comprising metal contact regions locally provided on the emitter, wherein a dopant source material is stacked areally onto the substrate surface and a first dopant drive-in step is performed and then the layer of the dopant source material is structured in accordance with the metal contact regions provided and a second dopant drive-in step is performed in the structured state, wherein, for passivating the emitter, an oxide layer formed in the second dopant drive-in step is left at least with part of its thickness on the emitter and a nitride layer is applied to the residual oxide.
Description
Beschreibung Titel Description title
Verfahren zur Herstellung einer Silizium-Solarzelle Process for producing a silicon solar cell
Die Erfindung betrifft ein Verfahren zur Herstellung einer Silizium-Solarzelle mit in einer Oberfläche eines Silizium-Substrats durch Dotierung erzeugtem Emitter und auf dem Emitter lokal vorgesehenen Metallkontaktbereichen, wobei ein Dotierstoff-Quellmaterial flächig auf die Substratoberfläche aufgeschichtet und ein erster Dotierstoff-Eintreibschritt ausgeführt und danach die Schicht des Dotierstoff-Quellmaterials gemäß den vorgesehenen Metallkontaktbereichen strukturiert und im strukturierten Zustand ein zweiter Dotierstoff-Eintreibschritt ausgeführt wird. Stand der Technik The invention relates to a method for producing a silicon solar cell having emitters produced by doping in a surface of a silicon substrate and metal contact regions provided locally on the emitter, wherein a dopant source material is stacked flat on the substrate surface and a first dopant driving step is carried out the layer of the dopant source material is structured in accordance with the intended metal contact areas, and in the structured state a second dopant driving step is carried out. State of the art
Ein derartiges Verfahren wurde bei der Anmelderin entwickelt und in der DE 102009015307.5 beschrieben. Fig. 1 zeigt schematisch wesentliche Verfahrensschritte a) bis e) dieses Verfahrens. In diesem Prozessfluss wird in einem ersten Schritt a) zunächst ein Si-Wafer 10 mit Phosphorglas 11 belegt und ein erster Dotierstoff-Eintreibschritt zur Erzeugung einer ganzflächigen P-Dotierung in der mit dem Phosphorglas belegten Wafer-Oberfläche ausgeführt. Anschließend wird in einem zweiten Schritt b) das als Dotierstoff-Quellmaterial dienende Phosphorglas 11 maskiert und nasschemisch strukturiert, indem es in den- jenigen Bereichen, in denen später (nicht dargestellte) Metallkontaktbereiche bzw.„Finger" aufgebracht werden sollen, stehen bleibt und in den dazwischen liegenden Bereichen („Zwischenfingergebieten") entfernt wird. Such a method was developed by the applicant and described in DE 102009015307.5. Fig. 1 shows schematically essential process steps a) to e) of this method. In this process flow, in a first step a) first an Si wafer 10 is coated with phosphor glass 11 and a first dopant driving step is carried out to produce a full-surface P doping in the wafer surface occupied by the phosphor glass. Subsequently, in a second step b) serving as dopant source material phosphorus glass 11 is masked and wet-structured by standing in those areas where later (not shown) metal contact areas or "fingers" are applied, stops and in the intermediate areas ("Zwischenfingergebieten") is removed.
Nach Entfernen der Maskierung findet in einer Sauerstoffatmosphäre ein zwei- ter Dotierstoff-Eintreibschritt statt, durch den die P-Dotierung in den Zwischenfindergebieten tief eingetrieben und hierbei die Oberflächenkonzentration abgesenkt wird. Dabei wächst sowohl in den Zwischenfingergebieten als auch unterhalb der Phosphorglas-Restschicht 12 eine leicht phosphorhaltige Oxid-
schlicht 13, wie in Fig. lc) dargestellt. Im Schritt d) werden die Phosphorglas- Restschicht und die erwähnte Oxidschicht entfernt, und im Schritt e) wird eine Si-N-Passivierschicht 14 auf den Wafer abgeschieden. After removal of the masking, a second dopant driving-in step takes place in an oxygen atmosphere, through which the P-doping in the intermediate finding regions is driven deep and in this case the surface concentration is lowered. In this case, both in the intermediate finger areas and below the phosphor glass residual layer 12, a slightly phosphorus-containing oxide plain 13, as shown in Fig. Lc). In step d), the phosphor glass residue layer and the aforementioned oxide layer are removed, and in step e), an Si-N passivation layer 14 is deposited on the wafer.
Durch die geringe Oberflächenkonzentration lässt sich mit dieser Art von Emit- tern eine sehr gute Blauempfindlichkeit erreichen. Wegen eines geringeren Feldeffekts an der Waferoberfläche ist es aber notwendig, eine gegenüber dem in der Standardzelle verwendeten Siliziumnitrid verbesserte Passivierung einzusetzen. Ein weiteres Problem des beschriebenen Prozessflusses besteht in Schwierigkeiten beim Ausrichten der Metallisierung auf die hochdotierten Fingerberei- che. Da der hochdotierte Bereich nach der Abscheidung der SiN-Passivierung nicht sichtbar ist, kann die Ausrichtung des Siebes nur anhand weiterer Marken oder der Kanten erfolgen. Due to the low surface concentration, this type of emitter can achieve very good blue sensitivity. However, because of a lower field effect on the wafer surface, it is necessary to use improved passivation over the silicon nitride used in the standard cell. Another problem of the process flow described is difficulty in aligning the metallization with the heavily doped finger regions. Since the heavily doped area is not visible after deposition of the SiN passivation, the orientation of the screen can only be based on other marks or the edges.
In der Forschung wird zur hochwertigen Passivierung üblicherweise ein Stapel aus thermisch gewachsenem Siliziumoxid (Si02) und einer Schicht mit hohem Brechungsindex eingesetzt. Diese Art der Passivierung erfordert jedoch einen zusätzlichen Hochtemperaturschritt und ist daher in der Massenfertigung zu teuer. In R.E. Schlosser, K.A. Münzer, A. Froitzheim, R. Tolle, M.G. Winstel,„Manufac- turing of transparent selective emitter and boron back-surface-field solar cells using screen printing technique" 21st EU-PVSEC, 2006, Dresden, Germany wird ein Prozessfluss beschrieben, bei welchem eine dicke Oxidschicht (>40 nm), die zur Maskierung der Diffusion der hochdotierten Fingergebiete genutzt wird, gleichzeitig als Oxidpassivierung dient. Um eine gute Verspiegelung der Zelle zu erreichen, wird die Oxidschicht durch einen nasschemischen Schritt zurück geätzt (vermutlich auf 10 nm bis 15 nm) und anschließend mit höher brechendem In research, a stack of thermally grown silicon oxide (Si0 2 ) and a layer with a high refractive index is usually used for high-quality passivation. However, this type of passivation requires an additional high-temperature step and is therefore too expensive in mass production. In RE Schlosser, KA Münzer, A. Froitzheim, R. Tolle, MG Winstel, "Manufacturing of transparent selective emitter and boron back-surface-field solar cells using screen printing technique" 21 st EU-PVSEC, 2006, Dresden, Germany describes a process flow in which a thick oxide layer (> 40 nm), which is used to mask the diffusion of the heavily doped finger areas, simultaneously serves as oxide passivation.To achieve good mirroring of the cell, the oxide layer is replaced by a wet chemical step etched (presumably at 10 nm to 15 nm) and then with higher refractive index
Siliziumnitrid aufgedickt. Da hier eine relativ dicke Oxidschicht mit hoher Silicon nitride thickened. Since here a relatively thick oxide layer with high
Genauigkeit zurück geätzt werden muss, wird diese Variante als relativ instabil ausgewiesen.
Aus der DE 10 2007 035 068 AI ist ein ähnliches Verfahren bekannt, bei dem optional auch das Erzeugen einer Dielektrikumschicht als Antireflex- und/oder Passivierungsschicht vorgesehen ist. Accuracy must be etched back, this variant is reported as relatively unstable. From DE 10 2007 035 068 AI a similar method is known in which optionally also the generation of a dielectric layer is provided as an antireflection and / or passivation layer.
Auch die DE 697 31 485 T2 beschreibt ein Verfahren zur Herstellung einer Halbleitervorrichtung (insbesondere einer photovoltaischen Zelle) mit selektiv diffundierten Bereichen. Neben dem Einsatz gasförmiger Dotierstoffe wird in dieser Druckschrift auch das Vorsehen einer Passivierungs-Oxidschicht sowie einer als Antireflexbeschichtung dienenden Siliziumnitridschicht erwähnt. Die WO 2010/012062 AI beschreibt eine kristalline Silizium-Solarzelle mit selektivem Emitter, welche unter Einsatz eines Niedertemperatur-Ätz- und Passivierungsprozesses mit hoher Präzision erzeugt wird. Das dort beschriebene Verfahren kann eine Passivierung mit einer elektrochemisch gebildeten Silizium -Oxid Schicht einschließen. DE 697 31 485 T2 also describes a method for producing a semiconductor device (in particular a photovoltaic cell) with selectively diffused regions. In addition to the use of gaseous dopants, this document also mentions the provision of a passivation oxide layer and a silicon nitride layer serving as an antireflection coating. WO 2010/012062 A1 describes a crystalline silicon solar cell with selective emitter which is produced with high precision using a low-temperature etching and passivation process. The method described therein may include passivation with an electrochemically formed silicon oxide layer.
Offenbarung der Erfindung Disclosure of the invention
Ein Verfahren gemäß der Erfindung weist die Merkmale des Anspruches 1 auf. Zweckmäßige Ausgestaltungen dieses Verfahrens sind Gegenstand der abhängi- gen Ansprüche. A method according to the invention comprises the features of claim 1. Advantageous embodiments of this method are the subject of the dependent claims.
Erfindungsgemäß wird ein beim Eintreibschritt des selektiven Emitters entstehendes Oxid in Kombination mit einer Nitridschicht zur Passivierung verwendet. Dazu wird in einer Ausführung der Erfindung dieses Oxid durch einen Rückätz- schritt (z. B. nasschemisch in verdünnter HF) auf eine Dicke von ca. 5 nm bis 20nm zurück geätzt. Gegenüber dem Stand der Technik kann so eine erhebliche Reduktion des Emittersättigungsstroms erreicht werden, welche direkt in eine höhere Solarzelleneffizienz umgesetzt werden kann. In diesem Prozessfluss wächst nur ein relativ dünnes Oxid, wodurch der Rückätzprozess gegenüber dem Prozessfluss in Schlosser et al. besser zu kontrollieren ist. According to the invention, an oxide formed during the driving step of the selective emitter in combination with a nitride layer is used for the passivation. For this purpose, in one embodiment of the invention, this oxide is etched back to a thickness of about 5 nm to 20 nm by an etch-back step (for example wet-chemically in dilute HF). Compared to the prior art, such a significant reduction of the emitter saturation current can be achieved, which can be converted directly into a higher solar cell efficiency. In this process flow grows only a relatively thin oxide, whereby the etching back process compared to the process flow in Schlosser et al. is better to control.
Da sich im Fingerbereich vor dem Eintreiben eine Restschicht von Dotierstoff- Quellmaterial (speziell etwa Phosphorsilikatglas) befand, ist die Oxidschicht in
diesem Bereich auch nach Eintreiben und Rückätzen etwas dicker. Dieses hat zur Folge dass der Fingerbereich optisch hervorgehoben wird, was ein optisches Ausrichten der Siebdruckmetallisierung auf die hochdotierten Fingerbereiche ermöglicht. In einer alternativen Variante erfolgt der Eintreibschritt in einer Sequenz inSince there was a residual layer of dopant source material in the finger area (especially about phosphosilicate glass) prior to driving, the oxide layer is in This area also after driving and etching back a little thicker. This has the consequence that the finger area is highlighted, which allows an optical alignment of Siebdruckmetallisierung on the highly doped finger areas. In an alternative variant, the driving step takes place in a sequence in FIG
Stickstoff- und Sauerstoffatmosphäre, wodurch gezielt eine Oxidschicht mit einer Schichtdicke zwischen 5 nm und 20 nm gewachsen werden kann. Durch diese Modifikation kann der Rückätzschritt entfallen, welches zu einer Reduktion der Prozesskomplexität gegenüber der ursprünglichen Sequenz führt. Nitrogen and oxygen atmosphere, whereby specifically an oxide layer can be grown with a layer thickness between 5 nm and 20 nm. This modification eliminates the re-etching step which results in a reduction in process complexity over the original sequence.
In einer Ausgestaltung wird das Aufbringen der Nitridschicht mittels PECVD ausgeführt. Hierbei wird die Dicke der Nitridschicht insbesondere auf einen Wert im Bereich von 25 nm bis 100 nm, bevorzugt 40 nm bis 90 nm, eingestellt. Als Vorteile der Erfindung bzw. vorteilhafte Ausgestaltungen derselben sind insbesondere zu nennen: In one embodiment, the application of the nitride layer is carried out by means of PECVD. In this case, the thickness of the nitride layer is set in particular to a value in the range from 25 nm to 100 nm, preferably 40 nm to 90 nm. As advantages of the invention or advantageous embodiments thereof are to be mentioned in particular:
- eine Verbesserung der Emitterpassivierung, und damit Solarzelleneffizienz; an improvement in emitter passivation, and hence solar cell efficiency;
- eine Reduktion der Prozesskomplexität gegenüber dem ursprünglichen - a reduction in process complexity compared to the original one
Prozessfluss (Variante C); Process flow (variant C);
- eine Vereinfachung der Optischen Ausrichtung des Drucksiebes auf die a simplification of the optical alignment of the printing screen on the
hochdotierten Fingerbereiche. highly doped finger areas.
Zeichnungen drawings
Vorteile und Zweckmäßigkeiten der Erfindung ergeben sich aus der Beschreibung von Ausführungsbeispielen anhand der Figuren. Von diesen zeigen: Advantages and advantages of the invention will become apparent from the description of embodiments with reference to FIGS. From these show:
Fig. 1 eine schematische Darstellung eines Prozessflusses nach dem Fig. 1 is a schematic representation of a process flow after the
Stand der Technik, State of the art,
Fig. 2 eine schematische Darstellung eines Prozessflusses gemäß einer ersten Ausführung der Erfindung,
Fig. 3 eine schematische Darstellung eines Prozessflusses gemäß einer zweiten Ausführung der Erfindung und 2 shows a schematic representation of a process flow according to a first embodiment of the invention, Fig. 3 is a schematic representation of a process flow according to a second embodiment of the invention and
Fig. 4 eine weitere schematische Darstellung zur zweiten Ausführungsform der Erfindung. Fig. 4 is a further schematic representation of the second embodiment of the invention.
Die schematische Darstellung eines erfindungsgemäßen Verfahrensablaufs in Fig. 2 ist an die Darstellung in Fig. 1 angelehnt, und die Schritte a) bis c) sind die gleichen. Angemerkt sei, dass die Maskierung mittels Tintenstrahldruck oder Siebdruck eines geeigneten Resists und das maskierte Ätzen des Phos- phorglases (POCI3) mittels HF (Fluorwasserstoff) erfolgen können. The schematic representation of a method sequence according to the invention in FIG. 2 is based on the representation in FIG. 1, and the steps a) to c) are the same. It should be noted that the masking by means of ink jet printing or screen printing of a suitable resist and the masked etching of the phosphorus glass (POCI 3 ) by means of HF (hydrogen fluoride) can take place.
Nach dem zweiten Dotiermittel-Eintreibschritt gemäß Fig. 2c) in Sauerstoffatmosphäre wird ein lediglich partielles Rückätzen der beim Eintreiben entstandenen Oxidschicht 13 ausgeführt, welches eine erste Passivierungs-Teilschicht 15 auf der Emitteroberfläche zurücklässt; vgl. Fig. 2d). Auf diese Schicht wird in einem Schritt e) mittels plasmagestützter chemischer Gasphasenabscheidung (PECVD) eine Siliziumnitrid-Schicht abgeschieden. Mit der dünnen SiN-Schicht 16 werden die gewünschten optischen Eigenschaften der Zellenoberfläche wieder hergestellt. In an sich bekannter Weise folgen darauf die (nicht gezeigten) Schritte des Druckens und Feuerns der Metallkontaktbereiche (Finger). After the second dopant driving-in step according to FIG. 2c) in an oxygen atmosphere, only a partial etching back of the oxide layer 13 formed during driving is carried out, which leaves a first passivation partial layer 15 on the emitter surface; see. Fig. 2d). In this step, a silicon nitride layer is deposited in a step e) by means of plasma-assisted chemical vapor deposition (PECVD). With the thin SiN layer 16, the desired optical properties of the cell surface are restored. In a manner known per se, this is followed by the steps (not shown) of printing and firing the metal contact regions (fingers).
Fig. 3 zeigt eine alternative Prozessführung, bei der abermals die ersten FIG. 3 shows an alternative process control, in which again the first
Schritten dem bei der Anmelderin bereits praktizierten Verfahren gemäß Fig. 1 weitgehend entsprechen. Jedoch wird hier der zweite Dotierstoff-Eintreib- schritt, also Schritt c), in einer modifizierten Atmosphäre ausgeführt, in der nur eine dünnere Oxidschicht 17 wächst, welche nicht zurückgeätzt werden muss. Die Dotierstoff-Restschicht 12 des Phosphorglases im Bereich der vorgesehenen Metallkontaktfinger bleibt bei dieser Verfahrensführung stehen, und im Schritt d) wird - wie bei der vorbeschriebenen Verfahrensführung gemäß Fig. 2 - eine SiN-Schicht 16 mittels PECVD abgeschieden.
Fig. 4 dient der weiteren Verdeutlichung der Verfahrensführung im Schritt c) gemäß Fig. 3. Im oberen Bereich der Figur ist schematisch ein Temperatur- Zeit-Diagramm A und im unteren Teil ein hierzu bezüglich der Zeitachse korreliertes Gasfluss-Zeit-Diagramm B für den zweiten Dotierstoff-Eintreibschritt gezeigt. Diagramm A zeigt hierbei das Eintreiben gemäß dem praktizierten Ver- fahren der Anmelderin in Sauerstoffatmosphäre (mit Anwendung einer Stickstoffatmosphäre lediglich in der Anfangsphase des Temperaturanstieges und der Endphase des Absenkens der Temperatur), während das Diagramm B den Wechsel von einer N2-Atmosphäre in eine 02-Atmosphäre während der Phase des Haltens hoher Temperatur (Eintreibtemperatur) zeigt. Durch geeignete Ei n- Stellung der Dauer der Einwirkung der N2- bzw.02-Atmosphäre lässt sich das Aufwachsen einer dünnen Oxidschicht hinreichend präzise steuern. Steps correspond to the already practiced in the applicant method of FIG. 1 largely. However, here the second dopant driving-in step, ie step c), is carried out in a modified atmosphere in which only a thinner oxide layer 17 grows, which does not have to be etched back. The dopant residual layer 12 of the phosphor glass in the region of the intended metal contact fingers remains in this process procedure, and in step d) -as in the above-described process control according to FIG. 2 -a SiN layer 16 is deposited by means of PECVD. In the upper part of the figure is schematically a temperature-time diagram A and in the lower part a correlated thereto with respect to the time axis gas flow-time diagram B for the second dopant driving step. Diagram A shows the driving according to the Applicant's practiced method in oxygen atmosphere (with application of a nitrogen atmosphere only in the initial phase of the temperature rise and the final phase of lowering the temperature), while the diagram B shows the change from an N 2 atmosphere into a 0 2 atmosphere during the phase of high temperature holding (Eintreibtemperatur) shows. By suitable positioning of the duration of the action of the N 2 or O 2 atmosphere, the growth of a thin oxide layer can be controlled sufficiently precisely.
Im Rahmen fachmännischen Handelns ergeben sich weitere Ausgestaltungen und Ausführungsformen des hier nur beispielhaft beschriebenen Verfahrens und der Vorrichtung.
Within the scope of expert action, further refinements and embodiments of the method and apparatus described here by way of example only arise.
Claims
Ansprüche claims
Verfahren zur Herstellung einer Silizium-Solarzelle mit in einer Oberfläche eines Silizium-Substrats (10) durch Dotierung erzeugtem Emitter und auf dem Emitter lokal vorgesehenen Metallkontaktbereichen, wobei ein Dotierstoff-Quellmaterial (11) flächig auf die Substratoberfläche aufgeschichtet und ein erster Dotierstoff-Eintreibschritt ausgeführt und danach die Schicht des Dotierstoff-Quellmaterials gemäß den vorgesehenen Metallkontaktbereichen strukturiert und im strukturierten Zustand (12) ein zweiter Dotierstoff-Eintreibschritt ausgeführt wird, A method for producing a silicon solar cell with an emitter produced in a surface of a silicon substrate (10) by doping and metal contact regions provided locally on the emitter, wherein a dopant source material (11) is coated flat on the substrate surface and a first dopant driving step is carried out and then the layer of the dopant source material is patterned according to the intended metal contact areas and in the structured state (12) a second dopant driving step is carried out,
wobei zur Passivierung des Emitters eine im zweiten Dotierstoff-Eintreibschritt ausgebildete Oxidschicht (13; 17) mindestens mit einem Teil ihrer Dicke auf dem Emitter belassen und auf das verbliebene Oxid eine Nitridschicht (14;16) aufgebracht wird. wherein, for passivation of the emitter, an oxide layer (13; 17) formed in the second dopant driving step leaves at least a portion of its thickness on the emitter and a nitride layer (14; 16) is deposited on the remaining oxide.
Verfahren nach Anspruch 1, Method according to claim 1,
wobei ein Teil der Dicke des gebildeten Oxids (13) rückgeätzt wird. Verfahren nach Anspruch 2, wherein a part of the thickness of the formed oxide (13) is etched back. Method according to claim 2,
wobei das Rückätzten nasschemisch, insbesondere mittels verdünnter Flusssäure, ausgeführt wird. wherein the etching back is carried out wet-chemically, in particular by means of dilute hydrofluoric acid.
Verfahren nach einem der vorangehenden Ansprüche, Method according to one of the preceding claims,
wobei die Oxidschicht (17) in einer vorbestimmten Dicke von 40 nm oder weniger, insbesondere 30 nm oder weniger, durch eine Schrittfolge des Eintreibens in wechselnder Stickstoff- und Sauerstoff-Atmosphäre oder in Stickstoff-/Sauerstoff-Mischatmosphäre ausgebildet wird. wherein the oxide layer (17) is formed in a predetermined thickness of 40 nm or less, more preferably 30 nm or less, by a step sequence of driving in alternating nitrogen and oxygen atmosphere or in nitrogen / oxygen mixed atmosphere.
5. Verfahren nach einem der vorangehenden Ansprüche, 5. The method according to any one of the preceding claims,
wobei die Dicke der Oxidschicht (13; 17) auf einen Wert im Bereich zwischen 5 nm und 30 nm eingestellt wird.
wherein the thickness of the oxide layer (13; 17) is set to a value in the range between 5 nm and 30 nm.
6. Verfahren nach einem der vorangehenden Ansprüche, 6. The method according to any one of the preceding claims,
wobei das Aufbringen der Nitridschicht (14;16) mittels PECVD ausgeführt wird. wherein the application of the nitride layer (14; 16) is carried out by means of PECVD.
7. Verfahren nach einem der vorangehenden Ansprüche, 7. The method according to any one of the preceding claims,
wobei die Dicke der Nitridschicht (14;16) im Bereich zwischen 25 nm bis 100 nm, bevorzugt 40 nm bis 90 nm, eingestellt wird. wherein the thickness of the nitride layer (14; 16) is set in the range between 25 nm to 100 nm, preferably 40 nm to 90 nm.
8. Verfahren nach einem der vorangehenden Ansprüche, 8. The method according to any one of the preceding claims,
wobei die Dotierung eine Phosphor-Dotierung ist und das Dotierstoff- Quellmaterial Phosphorglas (11) aufweist.
wherein the doping is a phosphorus doping and the dopant source material comprises phosphorus glass (11).
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CN110265293A (en) * | 2019-05-24 | 2019-09-20 | 江苏润阳悦达光伏科技有限公司 | The P-N junction manufacture craft of solar battery |
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DE102018114873B4 (en) | 2018-06-20 | 2022-02-03 | JMS AG Jet Maintenance & Service | Tow bar with electrical movement device for the tow bar undercarriage |
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