EP1068646A1 - Method for doping one side of a semiconductor body - Google Patents

Method for doping one side of a semiconductor body

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Publication number
EP1068646A1
EP1068646A1 EP99914540A EP99914540A EP1068646A1 EP 1068646 A1 EP1068646 A1 EP 1068646A1 EP 99914540 A EP99914540 A EP 99914540A EP 99914540 A EP99914540 A EP 99914540A EP 1068646 A1 EP1068646 A1 EP 1068646A1
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EP
European Patent Office
Prior art keywords
doping
doped
substrate
layer
oxide layer
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Withdrawn
Application number
EP99914540A
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German (de)
French (fr)
Inventor
Steffen Sterk
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SolarWorld Industries Deutschland GmbH
Original Assignee
Siemens Solar GmbH
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Filing date
Publication date
Application filed by Siemens Solar GmbH filed Critical Siemens Solar GmbH
Publication of EP1068646A1 publication Critical patent/EP1068646A1/en
Withdrawn legal-status Critical Current

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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
    • H01L31/1804—Processes or apparatus specially adapted for the manufacture or treatment of these devices or of parts thereof comprising only elements of Group IV of the Periodic System
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L21/00—Processes or apparatus adapted for the manufacture or treatment of semiconductor or solid state devices or of parts thereof
    • H01L21/02—Manufacture or treatment of semiconductor devices or of parts thereof
    • H01L21/04—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer
    • H01L21/18—Manufacture or treatment of semiconductor devices or of parts thereof the devices having at least one potential-jump barrier or surface barrier, e.g. PN junction, depletion layer or carrier concentration layer the devices having semiconductor bodies comprising elements of Group IV of the Periodic System or AIIIBV compounds with or without impurities, e.g. doping materials
    • H01L21/22—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
    • H01L21/2256—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 through the applied layer
    • 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
    • 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
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S438/00—Semiconductor device manufacturing: process
    • Y10S438/914—Doping
    • Y10S438/923—Diffusion through a layer

Definitions

  • the present invention relates to a method for one-sided doping of a semiconductor body, in particular for one-sided doping of silicon wafers.
  • a targeted doping of the substrate or a semiconductor layer is necessary in order to set the desired conductivity properties.
  • a highly doped layer is applied to the back of the solar cell in order to create a field that counteracts the diffusion of minority charge carriers (back surface field).
  • a known method for one-sided doping is based on the fact that a protective layer (for example a protective lacquer) is first applied to the side of the semiconductor body which is not to be doped, or a thermal oxide is applied to both sides is woken up, which is then etched off on one side. The unprotected side of the semiconductor body can then be doped out of the gas phase, for example in a diffusion furnace.
  • a doping lacquer can also be applied to the side to be doped, which is not covered by a protection. The dopant contained in the dopant then diffuses in a temperature step. After the diffusion process, the protective layer is removed by etching.
  • One possibility to enable one-sided doping of a semiconductor body is to apply a protective layer on both sides, for example by thermally oxidizing the semiconductor body, and then detaching the protective film located on the side of the semiconductor body to be doped.
  • This side can then, as described above, be doped from the gas phase in a diffusion furnace or a doping layer (e.g. doping lacquer or doping paste) can be applied to the side of the semiconductor body to be doped and diffused in by a subsequent temperature treatment.
  • the protective layer is also removed by etching.
  • the present invention is therefore based on the object of providing a method for one-sided doping of a semiconductor body, in particular of silicon wafers, which enables reliable homogeneous doping of the desired side while at the same time reliably protecting the side which is not to be doped.
  • a central idea here is that the dopant contained in the doping layer passes through a conventional oxide layer during the diffusion process and diffuses into the side to be doped, the oxide layer on the non-doping side simultaneously serving as a protective layer and penetration of the dopant into this side prevented.
  • the doping lacquer By applying the doping lacquer to a previously applied oxide layer, a better lateral distribution of the dopant is achieved and "doping through" through the oxide layer supports homogeneous doping in a positive manner.
  • the method according to the invention has the advantage that in the case of an inhomogeneous dopant distribution Treatment or coating, in particular on rough surfaces (for example in the case of textured solar cells), also ensures homogeneous doping.
  • 1 to 3 show the individual method steps of the one-sided doping according to the invention, using cross-sectional layers of a semiconductor structure.
  • the semiconductor substrate (1) shown in FIG. 1 has a side (DS) to be doped and an opposite side (GS) not to be doped.
  • an oxide layer (2, 3) is applied to both sides of the substrate (1).
  • This oxide layer is preferably grown thermally.
  • the substrate (1) is heated in a furnace in an oxygen atmosphere to a temperature between 950 ° C and 1050 ° C, so that an oxide layer forms on the surfaces DS and GS of the substrate.
  • a doping layer (4) of high dopant concentration is then applied to the oxide layer (3), which is located on the side of the semiconductor substrate (1) to be doped, in a second method step. This is shown in Fig. 2.
  • the doping layer (4) is applied, for example, as a doping lacquer by spin-on or as a doping paste by printing. However, the doping layer can also be applied with a brush or by means of a one-sided CVD deposition of a doping oxide. Before the actual diffusion process, the liquid applied doping layer is dried. By applying the doping layer (4) to the oxide layer (3), the Diffusion achieves a very good homogeneous or uniform lateral distribution of the dopant, which is necessary for uniform doping.
  • the third process step, the actual diffusion process, is shown schematically in FIG. 3.
  • the doping layer (4) typically contains boron as a dopant.
  • the boron is driven in from the doping layer (4) in an oven at temperatures between 900 and 1200 ° C., preferably in a temperature range between 1000 and 1100 ° C.
  • the dopant first diffuses from the laterally homogeneously distributed doping layer (4) through the oxide layer (3) before it penetrates into the substrate (1).
  • the oxide layer (3) lying between the doping layer (4) and the substrate (1) does not act as a protective layer in the conventional sense, but as a layer that supports the diffusion process, quasi as a creeping oxide, which supports a uniform diffusion of the dopant.
  • volatile boron which may gas out into the atmosphere during heating and thus also reach the area of the substrate side (GS) that is not to be doped, is absorbed by the oxide layer (2) formed on this side.
  • the applied oxide layer (2) acts as a protective layer in the conventional sense and, with the low supply of dopants, provides adequate protection against unwanted doping.
  • the temperature of the diffusion process can be adapted in certain areas to the concentration of the dopant in the doping layer, for example if different dopants are to be diffused in.
  • An application example for this method is, for example, the generation of a so-called BSF (back surface field) on the back of solar cells by one-sided boron doping by means of a boron doping lacquer and subsequent diffusion, avoiding disadvantageous boron doping of the solar cells on the front.
  • the method according to the invention is not limited to the production of such solar cells, but can also be used for the coating of other semiconductor layers.
  • the method according to the invention is characterized here essentially by improved homogeneous doping with simultaneous reliable protection of the side not to be doped, which can be integrated in a simple manner into a conventional production method for solar cells.

Abstract

The invention relates to a method for doping one side of semiconductor bodies, especially of silicon wafers. To this end, a conventional oxide layer (2, 3) is firstly deposited on both the side (DS) of the substrate (1) to be doped and on the side (GS) of a substrate (1) which is not to be doped. Afterwards, a doping layer (4) containing the doping agent is deposited on the oxide layer (3) of the side (DS) which is to be doped. In a diffusion step, the doping agent firstly passes in a uniform manner through the oxide layer (3) located between the substrate (1) and the doped layer (4). The doping agent then penetrates the substrate (1), and produces a uniform doping.

Description

BESCHREIBUNG DESCRIPTION
VERFAHREN ZUR EINSEITIGEN DOTIERUNG EINES HALBLEITERKÖRPERSMETHOD FOR ONE-SIDED DOPING OF A SEMICONDUCTOR BODY
Die vorliegende Erfindung betrifft ein Verfahren zur einseitigen Dotierung eines Halbleiterkörpers, insbesondere zur einseitigen Dotierung von Silizium-Wafern.The present invention relates to a method for one-sided doping of a semiconductor body, in particular for one-sided doping of silicon wafers.
Bei der Herstellung von Halbleiterbauelementen ist eine gezielte Dotierung des Substrates bzw. einer Halbleiterschicht notwendig, um gewünschte Leitfähigkeitseigenschaften einzustellen. Für manche Anwendungen ist es vorteilhaft eine einseitige Dotierung durchzuführen, d.h. den Dotierstoff nur von einer Seite des zu dotierenden Körpers einzudiffundieren und dabei die Gegenseite vor einer ungewollten Dotierung zu schützen.In the production of semiconductor components, a targeted doping of the substrate or a semiconductor layer is necessary in order to set the desired conductivity properties. For some applications it is advantageous to carry out one-sided doping, i.e. to diffuse the dopant only from one side of the body to be doped and to protect the opposite side from unwanted doping.
Ein derartiges Vorgehen wird zum Beispiel bei der Herstellung von Solarzellen mit einem sogenannten Back-Surface-Field benötigt. Dazu wird eine hochdotierte Schicht auf der Rückseite der Solarzelle aufgetragen, um ein der Diffusion von Minoritätsladungsträgern entgegenwirkendes Feld (Back- Surface-Field) zu erzeugen. Ein bekanntes Verfahren zur einseitigen Dotierung, wie beispielsweise in der PCT-Anmeldung 096/28851 beschrieben, beruht darauf, daß auf die Seite des Halbleiterkörpers, die nicht dotiert werden soll, zunächst eine Schutzschicht (z.B. ein Schutzlack) aufgetragen wird oder beidseitig ein thermisches Oxid aufgewachen wird, das anschließend einseitig wieder abgeätzt wird. Danach kann die nicht geschützte Seite des Halbleiterkörpers z.B. in einem Diffusionsofen aus der Gasphase heraus dotiert werden. Auf die zu dotierende Seite, die nicht von einem Schutz bedeckt ist, kann auch ein Dotierlack aufgetragen werden. Der in dem Dotierlack enthaltene Dotierstoff diffundiert dann in einem Temperaturschritt ein. Nach dem Diffusionsprozeß wird die Schutzschicht durch Ätzen entfernt.Such a procedure is required, for example, in the production of solar cells with a so-called back surface field. For this purpose, a highly doped layer is applied to the back of the solar cell in order to create a field that counteracts the diffusion of minority charge carriers (back surface field). A known method for one-sided doping, as described for example in PCT application 096/28851, is based on the fact that a protective layer (for example a protective lacquer) is first applied to the side of the semiconductor body which is not to be doped, or a thermal oxide is applied to both sides is woken up, which is then etched off on one side. The unprotected side of the semiconductor body can then be doped out of the gas phase, for example in a diffusion furnace. A doping lacquer can also be applied to the side to be doped, which is not covered by a protection. The dopant contained in the dopant then diffuses in a temperature step. After the diffusion process, the protective layer is removed by etching.
Eine Möglichkeit eine einseitige Dotierung eines Halbleiterkörpers zu ermöglichen, ist das beidseitige Auftragen einer Schutzschicht, beispielsweise durch thermisches Oxidieren des Halbleiterkörpers, und anschließendes einseitiges Ablösen des sich auf der zu dotierenden Seite des Halbleiterkörpers befindenden Schutzfilmes. Diese Seite kann dann ebenfalls, wie oben beschrieben, in einem Diffusionsofen aus der Gasphase dotiert werden bzw. eine Dotierschicht (z.B. Dotierlack oder Dotierpaste) kann auf die zu dotierende Seite des Halbleiterkörpers aufgetragen werden und durch eine anschließende Temperaturbehandlung eindiffundiert werden. Nach dem Diffusionsschritt wird auch hier die Schutzschicht durch Ätzen entfernt.One possibility to enable one-sided doping of a semiconductor body is to apply a protective layer on both sides, for example by thermally oxidizing the semiconductor body, and then detaching the protective film located on the side of the semiconductor body to be doped. This side can then, as described above, be doped from the gas phase in a diffusion furnace or a doping layer (e.g. doping lacquer or doping paste) can be applied to the side of the semiconductor body to be doped and diffused in by a subsequent temperature treatment. After the diffusion step, the protective layer is also removed by etching.
Um gleichmäßige Eigenschaften und eine zuverlässige Funktion derartig hergestellter Halbleiterbauelemente zu erzielen ist eine gleichmäßige homogene Dotierung notwendig. Eine Rißbildung oder ein Abplatzen des aufgetragenen und getrockneten Dotierlackes bzw. jegliche Beschädigung des Dotierstoffes wirkt sich nachteilig auf die Funktionstüchtigkeit und Zuverlässigkeit der Bauelemente aus.In order to achieve uniform properties and a reliable function of semiconductor components manufactured in this way, uniform, homogeneous doping is necessary. A Cracking or flaking of the applied and dried dopant or any damage to the dopant has a disadvantageous effect on the functionality and reliability of the components.
Der vorliegenden Erfindung liegt daher die Aufgabe zugrunde, ein Verfahren zur einseitigen Dotierung eines Halbleiterkörpers, insbesondere von Silizium-Wafern, bereitzustellen, das eine zuverlässige homogene Dotierung der gewünschten Seite ermöglicht bei gleichzeitigem zuverlässigem Schutz der nicht zu dotierenden Seite.The present invention is therefore based on the object of providing a method for one-sided doping of a semiconductor body, in particular of silicon wafers, which enables reliable homogeneous doping of the desired side while at the same time reliably protecting the side which is not to be doped.
Diese Aufgabe wird erfindungsgemäß durch das in Patentanspruch 1 beschriebene Verfahren gelöst. Vorteilhafte Ausgestaltungen der Erfindung ergeben sich aus den Unteransprüchen.This object is achieved by the method described in claim 1. Advantageous refinements of the invention result from the subclaims.
Ein zentraler Gedanke ist hierbei, daß der in der Dotierschicht enthaltene Dotierstoff während des Diffusionsprozesses durch eine herkömmliche Oxidschicht hindurchtritt und in die zu dotierende Seite eindiffundiert, wobei die Oxidschicht auf der nicht zu dotierenden Seite gleichzeitig als Schutzschicht dient und ein Eindringen des Dotierstoffes in diese Seite verhindert.A central idea here is that the dopant contained in the doping layer passes through a conventional oxide layer during the diffusion process and diffuses into the side to be doped, the oxide layer on the non-doping side simultaneously serving as a protective layer and penetration of the dopant into this side prevented.
Durch ein Auftragen des Dotierlackes auf eine vorher aufgetragene Oxidschicht wird eine bessere laterale Verteilung des Dotierstoffes erzielt und ein "Hindurchdotieren" durch die Oxidschicht unterstützt eine homogene Dotierung in positiver Weise.By applying the doping lacquer to a previously applied oxide layer, a better lateral distribution of the dopant is achieved and "doping through" through the oxide layer supports homogeneous doping in a positive manner.
Zudem weist das erfindungsgemäße Verfahren den Vorteil auf, daß im Fall einer inhomogenen Dotierstoffverteilung nach Behandlung oder Beschichtung, insbesondere auf rauhen Oberflächen (z.B. bei texturierten Solarzellen), ebenfalls eine homogene Dotierung gewährleistet ist.In addition, the method according to the invention has the advantage that in the case of an inhomogeneous dopant distribution Treatment or coating, in particular on rough surfaces (for example in the case of textured solar cells), also ensures homogeneous doping.
Im folgenden wird die Erfindung anhand einzelner Verfahrensschritte und unter Bezugnahme auf die beigefügten Abbildungen beschrieben.In the following the invention is described on the basis of individual process steps and with reference to the attached figures.
Fig. 1 bis 3 zeigen die einzelnen Verfahrensschritte der erfindungsgemäßen einseitigen Dotierung, anhand von Querschnittsanschichten einer Halbleiterstruktur.1 to 3 show the individual method steps of the one-sided doping according to the invention, using cross-sectional layers of a semiconductor structure.
Das in Fig. 1 gezeigte Halbleitersubstrat (1) weist eine zu dotierende Seite (DS) und eine nicht zu dotierende gegenüberliegende Seite (GS) auf. Auf beide Seiten des Substrates (1) wird in einem ersten Verfahrensschritt eine Oxidschicht (2, 3) aufgetragen. Diese Oxidschicht wird vorzugsweise thermisch aufgewachsen. Hierzu wird das Substrat (1) in einem Ofen in einer Sauerstoffatmosphäre auf eine Temperatur zwischen 950°C und 1050°C erwärmt, so daß sich auf den Oberflächen DS und GS des Substrats eine Oxidschicht bildet. Anschließend wird in einem zweiten Verfahrensschritt auf die Oxidschicht (3) , die sich auf der zu dotierenden Seite des Halbleitersubstrats (1) befindet, eine Dotierschicht (4) hoher Dotierstoffkonzentration aufgetragen. Dies ist in Fig. 2 dargestellt. Die Dotierschicht (4) wird beispielsweise als Dotierlack durch Aufschleudern (Spin-On) oder als Dotierpaste durch Aufdrucken aufgetragen. Die Dotierschicht kann aber auch mit einem Pinsel oder mittels einer einseitigen CVD- Abscheidung eines Dotieroxids aufgetragen werden. Vor dem eigentlichen Diffusionsvorgang wird die flüssig aufgetragene Dotierschicht getrocknet. Durch das Auftragen der Dotierschicht (4) auf die Oxidschicht (3) wird bei der Diffusion eine sehr gute homogene bzw. gleichmäßige laterale Verteilung des Dotierstoffes erreicht was für eine gleichmäßige Dotierung notwendig ist.The semiconductor substrate (1) shown in FIG. 1 has a side (DS) to be doped and an opposite side (GS) not to be doped. In a first process step, an oxide layer (2, 3) is applied to both sides of the substrate (1). This oxide layer is preferably grown thermally. For this purpose, the substrate (1) is heated in a furnace in an oxygen atmosphere to a temperature between 950 ° C and 1050 ° C, so that an oxide layer forms on the surfaces DS and GS of the substrate. A doping layer (4) of high dopant concentration is then applied to the oxide layer (3), which is located on the side of the semiconductor substrate (1) to be doped, in a second method step. This is shown in Fig. 2. The doping layer (4) is applied, for example, as a doping lacquer by spin-on or as a doping paste by printing. However, the doping layer can also be applied with a brush or by means of a one-sided CVD deposition of a doping oxide. Before the actual diffusion process, the liquid applied doping layer is dried. By applying the doping layer (4) to the oxide layer (3), the Diffusion achieves a very good homogeneous or uniform lateral distribution of the dopant, which is necessary for uniform doping.
Der dritte Prozeßschritt, der eigentliche Diffusionsvorgang, ist in Fig. 3 schematisch dargestellt. Die Dotierschicht (4) enthält typischerweise Bor als Dotierstoff. Das Eintreiben des Bors aus der Dotierschicht (4) erfolgt in einem Ofen bei Temperaturen zwischen 900 und 1200°C, vorzugsweise in einem Temperaturbereich zwischen 1000 und 1100°C. Der Dotierstoff diffundiert zunächst aus der lateral homogen verteilten Dotierschicht (4) durch die Oxidschicht (3) hindurch, bevor er in das Substrat (1) eindringt. Hierbei wirkt die zwischen Dotierschicht (4) und Substrat (1) liegende Oxidschicht (3) nicht etwa als Schutzschicht im herkömmlichen Sinne, sondern als eine den Diffusionsvorgang unterstützende Schicht aus, quasi als Kriechoxid was ein gleichmäßiges Eindiffundieren des Dotierstoffes unterstützt. Andererseits wird flüchtiges Bor, das beim Erwärmen eventuell in die Atmosphäre ausgast und somit auch in den Bereich der nicht zu dotierenden Substratseite (GS) gelangt, durch die auf dieser Seite ausgebildete Oxidschicht (2) absorbiert. Auf der nicht zu dotierenden Seite (GS) wirkt die aufgetragene Oxidschicht (2) als eine Schutzschicht im herkömmlichen Sinne und gewährt bei dem geringen Dotierstoffangebot einen ausreichenden Schutz vor ungewollter Dotierung.The third process step, the actual diffusion process, is shown schematically in FIG. 3. The doping layer (4) typically contains boron as a dopant. The boron is driven in from the doping layer (4) in an oven at temperatures between 900 and 1200 ° C., preferably in a temperature range between 1000 and 1100 ° C. The dopant first diffuses from the laterally homogeneously distributed doping layer (4) through the oxide layer (3) before it penetrates into the substrate (1). Here, the oxide layer (3) lying between the doping layer (4) and the substrate (1) does not act as a protective layer in the conventional sense, but as a layer that supports the diffusion process, quasi as a creeping oxide, which supports a uniform diffusion of the dopant. On the other hand, volatile boron, which may gas out into the atmosphere during heating and thus also reach the area of the substrate side (GS) that is not to be doped, is absorbed by the oxide layer (2) formed on this side. On the side that is not to be doped (GS), the applied oxide layer (2) acts as a protective layer in the conventional sense and, with the low supply of dopants, provides adequate protection against unwanted doping.
Die Temperatur des Diffusionsvorganges kann hierbei in gewissen Bereichen an die Konzentration des sich in der Dotierschicht befindenden Dotierstoffes angepaßt werden, z.B. wenn unterschiedliche Dotierstoffe eindiffundiert werden sollen. Nach dem Diffusionsvorgang werden sowohl dieThe temperature of the diffusion process can be adapted in certain areas to the concentration of the dopant in the doping layer, for example if different dopants are to be diffused in. After the diffusion process, both the
Diffusionsschicht (4) als auch die Oxidschichten (2, 3) durch kurzes Eintauchen in HF-Säure entfernt.Diffusion layer (4) and the oxide layers (2, 3) removed by briefly immersing them in HF acid.
Ein Anwendungsbeispiel für dieses Verfahren ist beispielsweise die Erzeugung eines sogenannten BSF (Back- Surface-Field) auf der Rückseite von Solarzellen durch einseitige Bordotierung mittels eines Bor-Dotierlackes und anschließender Eindiffusion, wobei eine nachteilige Bordotierung der Solarzellen der Vorderseite vermieden wird. Das erfindungsgemäße Verfahren ist jedoch nicht auf die Herstellung von derartigen Solarzellen beschränkt, sondern kann auch für die Beschichtung anderer Halbleiterschichten verwendet werden. Das erfindungsgemäße Verfahren zeichnet sich hierbei im wesentlichen durch eine verbesserte homogene Dotierung aus bei gleichzeitigem zuverlässigem Schutz der nicht zu dotierenden Seite, das in einfacher Weise in ein herkömmliches Herstellungsverfahren für Solarzellen integriert werden kann. An application example for this method is, for example, the generation of a so-called BSF (back surface field) on the back of solar cells by one-sided boron doping by means of a boron doping lacquer and subsequent diffusion, avoiding disadvantageous boron doping of the solar cells on the front. However, the method according to the invention is not limited to the production of such solar cells, but can also be used for the coating of other semiconductor layers. The method according to the invention is characterized here essentially by improved homogeneous doping with simultaneous reliable protection of the side not to be doped, which can be integrated in a simple manner into a conventional production method for solar cells.

Claims

PATENTANSPRÜCHE PATENT CLAIMS
1. Verfahren zur einseitigen Dotierung eines Halbleiterkörpers, insbesondere von Silizium-Wafern, umfassend die Schritte:1. A method for one-sided doping of a semiconductor body, in particular of silicon wafers, comprising the steps:
Aufbringen einer Oxidschicht (2, 3) sowohl auf der zu dotierenden Seite (DS) als auch auf der nicht zu dotierenden Seite (GS) eines Substrates (1),Applying an oxide layer (2, 3) both on the side to be doped (DS) and on the side not to be doped (GS) of a substrate (1),
Aufbringen einer Dotierschicht (4) auf der Oxidschicht (3), die auf der zu dotierenden Seite (DS) des Substrates (1) aufgebracht ist, undApplying a doping layer (4) on the oxide layer (3), which is applied to the side to be doped (DS) of the substrate (1), and
Eindiffundieren des in der Dotierschicht (4) enthaltenen Dotierstoffes in das Substrat (1), wobei der Dotierstoff durch die zwischen Substrat (1) und Dotierschicht (3) liegende Oxidschicht (3) hindurchtritt.Diffusion of the dopant contained in the doping layer (4) into the substrate (1), the dopant passing through the oxide layer (3) lying between the substrate (1) and the doping layer (3).
2. Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t, daß die zu dotierende Seite (DS) des Substrates (1) eine rauhe Oberfläche aufweist.2. The method according to claim 1, characterized in that the side to be doped (DS) of the substrate (1) has a rough surface.
3. Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t, daß die Oxidschicht (2, 3) in einer sauerstoffhaltigen Atmosphäre bei einer Temperatur im Bereich von 600 bis 1200°C aufgebracht wird.3. The method according to claim 1, characterized in that the oxide layer (2, 3) in an oxygen-containing Atmosphere is applied at a temperature in the range of 600 to 1200 ° C.
Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t, daß dieA method according to claim 1, characterized in that the
Dotierschicht (4) aufgeschleudert, mit einem Pinsel aufgetragen bzw. mit einem CVD-Verfahren abgeschieden wird.The doping layer (4) is spun on, applied with a brush or deposited using a CVD process.
Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t, dasß der Diffusionsvorgang bei einer Temperatur zwischen 900 und 1200°C durchgeführt wird.A method according to claim 1, characterized in that the diffusion process is carried out at a temperature between 900 and 1200 ° C.
Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t, daß die Oxidschicht (2) auf der nicht zu dotierenden Seite (GS) des Substrates (1) ein Eindiffundieren des Dotierstoffes in die nicht zu dotierende Seite (GS) des Substrates verhindert.Method according to Claim 1, characterized in that the oxide layer (2) on the side (GS) of the substrate (1) which is not to be doped prevents the dopant from diffusing into the side (GS) of the substrate which is not to be doped.
Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t, daß dieA method according to claim 1, characterized in that the
Dotierschicht (4) Bor enthält.Doping layer (4) contains boron.
Verfahren nach Anspruch 1, dadurch g e k e n n z e i c h n e t, daß es zur Herstellung von Solarzellen, insbesondere vonMethod according to Claim 1, characterized in that it is used for the production of solar cells, in particular of
Solarzellen mit Back-Surface-Field verwendet wird. Solar cells with back surface field is used.
EP99914540A 1998-03-25 1999-03-25 Method for doping one side of a semiconductor body Withdrawn EP1068646A1 (en)

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DE19813188 1998-03-25
DE19813188A DE19813188A1 (en) 1998-03-25 1998-03-25 Method for one-sided doping of a semiconductor body
PCT/EP1999/002038 WO1999049521A1 (en) 1998-03-25 1999-03-25 Method for doping one side of a semiconductor body

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