WO2010097064A2 - Laser crystallisation by irradiation - Google Patents

Laser crystallisation by irradiation Download PDF

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Publication number
WO2010097064A2
WO2010097064A2 PCT/DE2009/050072 DE2009050072W WO2010097064A2 WO 2010097064 A2 WO2010097064 A2 WO 2010097064A2 DE 2009050072 W DE2009050072 W DE 2009050072W WO 2010097064 A2 WO2010097064 A2 WO 2010097064A2
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Prior art keywords
laser
semiconductor layer
lasers
lines
substrate
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PCT/DE2009/050072
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German (de)
French (fr)
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WO2010097064A3 (en
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Hans-Ulrich Zühlke
Gabriele Eberhardt
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Jenoptik Automatisierungstechnik Gmbh
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Priority to EP09807437A priority Critical patent/EP2401773A2/en
Publication of WO2010097064A2 publication Critical patent/WO2010097064A2/en
Publication of WO2010097064A3 publication Critical patent/WO2010097064A3/en

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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
    • H01L31/186—Particular post-treatment for the devices, e.g. annealing, impurity gettering, short-circuit elimination, recrystallisation
    • H01L31/1872—Recrystallisation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/0006—Working by laser beam, e.g. welding, cutting or boring taking account of the properties of the material involved
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K26/00—Working by laser beam, e.g. welding, cutting or boring
    • B23K26/02—Positioning or observing the workpiece, e.g. with respect to the point of impact; Aligning, aiming or focusing the laser beam
    • B23K26/06—Shaping the laser beam, e.g. by masks or multi-focusing
    • B23K26/0604—Shaping the laser beam, e.g. by masks or multi-focusing by a combination of beams
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B1/00—Single-crystal growth directly from the solid state
    • C30B1/02—Single-crystal growth directly from the solid state by thermal treatment, e.g. strain annealing
    • C30B1/023—Single-crystal growth directly from the solid state by thermal treatment, e.g. strain annealing from solids with amorphous structure
    • C—CHEMISTRY; METALLURGY
    • C30—CRYSTAL GROWTH
    • C30B—SINGLE-CRYSTAL GROWTH; UNIDIRECTIONAL SOLIDIFICATION OF EUTECTIC MATERIAL OR UNIDIRECTIONAL DEMIXING OF EUTECTOID MATERIAL; REFINING BY ZONE-MELTING OF MATERIAL; PRODUCTION OF A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; SINGLE CRYSTALS OR HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; AFTER-TREATMENT OF SINGLE CRYSTALS OR A HOMOGENEOUS POLYCRYSTALLINE MATERIAL WITH DEFINED STRUCTURE; APPARATUS THEREFOR
    • C30B29/00—Single crystals or homogeneous polycrystalline material with defined structure characterised by the material or by their shape
    • C30B29/02—Elements
    • C30B29/06—Silicon
    • 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
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02518—Deposited layers
    • H01L21/02521—Materials
    • H01L21/02524—Group 14 semiconducting materials
    • H01L21/02532—Silicon, silicon germanium, germanium
    • 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
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02656—Special treatments
    • H01L21/02664—Aftertreatments
    • H01L21/02667—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
    • H01L21/02675—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth using laser beams
    • H01L21/02678—Beam shaping, e.g. using a mask
    • 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
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02656—Special treatments
    • H01L21/02664—Aftertreatments
    • H01L21/02667—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
    • H01L21/02675—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth using laser beams
    • H01L21/02686—Pulsed laser beam
    • 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
    • H01L21/02104—Forming layers
    • H01L21/02365—Forming inorganic semiconducting materials on a substrate
    • H01L21/02656—Special treatments
    • H01L21/02664—Aftertreatments
    • H01L21/02667—Crystallisation or recrystallisation of non-monocrystalline semiconductor materials, e.g. regrowth
    • H01L21/02691—Scanning of a beam
    • 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
    • H01L21/26—Bombardment with radiation
    • H01L21/263—Bombardment with radiation with high-energy radiation
    • H01L21/268—Bombardment with radiation with high-energy radiation using electromagnetic radiation, e.g. laser radiation
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B23—MACHINE TOOLS; METAL-WORKING NOT OTHERWISE PROVIDED FOR
    • B23K—SOLDERING OR UNSOLDERING; WELDING; CLADDING OR PLATING BY SOLDERING OR WELDING; CUTTING BY APPLYING HEAT LOCALLY, e.g. FLAME CUTTING; WORKING BY LASER BEAM
    • B23K2103/00—Materials to be soldered, welded or cut
    • B23K2103/50—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26
    • B23K2103/56—Inorganic material, e.g. metals, not provided for in B23K2103/02 – B23K2103/26 semiconducting
    • 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 process for the crystallization or recrystallization of a semiconductor layer, in particular an amorphous silicon layer for a solar cell, according to claim 1, and a laser system for carrying out the method according to claim 11.
  • the semiconductor layers form the seed and absorber layer of a solar cell with a glass-containing substrate.
  • the seed layer is an amorphous silicon layer deposited on the substrate. It is irradiated in tracks and while overlapping with a laser, such as a diode laser. The overlapping takes place in such a way that a part of the coarse-grained regions of the preceding track are remelted, whereby an improved crystallization is achieved and the solar cell has an increased energy efficiency.
  • the seed layer is doped by diffusion with boron or phosphate. Subsequently, the absorber layer is applied to the seed layer.
  • the absorber layer consists of additionally deposited amorphous silicon. After reaching a certain layer thickness, the additional silicon is irradiated in tracks with a pulsed excimer laser. In this case, the excimer laser is guided over the coated substrate in such a way that the irradiation surfaces adjoin one another and thus form linear boundary regions.
  • a disadvantage of this type of laser crystallization is that the substrate is irradiated in tracks one after the other or scanned, whereby the treatment of large-area substrates is correspondingly time-consuming. Furthermore, it is disadvantageous that the entire realizable focal width of the laser is used, whereby not only the guidance of the laser across the substrate for forming the overlap or boundary regions must be very accurate, but also the laser has to have a very accurate energy distribution profile ,
  • a method of laser crystallization of a semiconductor layer having a plurality of lasers arranged side by side along a line is described in US 6,780,692 B2.
  • the lasers are arranged downstream of means for homogenizing the radiation intensity so that a laser line with a homogeneous radiation intensity is imaged on the irradiated surface of a substrate.
  • a method for the production of solar cells is described in EP 1 738 402 B1, in which a laser beam is imaged in a line focus on a solid (substrate), the length of the line focus being between 100 ⁇ m and 10 mm, and the Width is less than 10 microns.
  • the substrate should be mounted on an X-Y linear displacement table and the laser beam stationary remain fixed in space.
  • the substrate remains stationary and the optical system, which directs the laser beam onto the substrate, scans the laser beam over the substrate.
  • the substrate is sequentially scanned into strips equal to the length of the line focus.
  • the strips are in principle subjected to homogeneous laser radiation.
  • the boundary areas between the adjacent strips are problematic, since on the one hand the intensity at the ends of the laser line can not be abruptly zero, which would correspond to an edge in the intensity distribution curve of 90 °, and on the other hand the strips are practically not ideal and can be irradiated side by side without overlapping.
  • boundary area As the boundary area to be referred to below the area in which two adjacent laser lines have a drop in intensity, d. H. it is the area defined by the length of the flanks of the intensity distribution curves plus a possible distance or minus any overlap area.
  • the ends of the laser lines overlap in this boundary region, whereby advantageously the border region is minimized in its width.
  • the width of the overlap region and thus also the width of the boundary region vary depending on the stability of the laser line and the accuracy of the scanning movement of the adjacent laser lines, the boundary region is undefined with its electrical properties, because the energy input in the border areas differs from the otherwise least almost constant energy input into the scanned surface areas undefined. As a result, the crystallization of the semiconductor layer takes place at a deviating and undefined extent in the boundary regions.
  • the object of the present invention is to provide a method and a laser system for
  • a laser system is provided with a plurality of lasers, each with an associated beam shaping optics, each focusing a laser beam in a laser line and longitudinally adjacent to the semiconductor layer, wherein each adjacent laser lines form a boundary region, preferably with an overlap region.
  • a relative movement, preferably perpendicular to the laser lines is generated between the laser system and the substrate, so that the semiconductor layer is scanned by the individual laser lines in each case along a strip in the working direction over a large area.
  • the boundary regions with the overlapping regions on the semiconductor layer are each guided over a passive region, in which after a subsequent processing step, at least in sections, no absorption of light photons takes place.
  • the length of the laser lines which is equal to the focal length in the case of direct focusing on the semiconductor layer, is matched to the center distance of these passive regions.
  • the semiconductor layer can also be scanned in strips successively with one or preferably with a few laser lines. Accordingly, the laser system would require only a laser beam shaping optics for this purpose. The lower demand for lasers is offset by the greater amount of time required.
  • the invention does not use the entire realizable focus length of the laser lines for restructuring, but it is the end portions of the laser lines, which are displayed on the passive areas and lead due to the intensity drop and the eventual overlap to a different energy input, quasi hidden whereby the active regions lying between the passive regions, which serve for photon absorption, are exposed to laser radiation of a homogeneous intensity distribution, so that the efficiency of the semiconductor layer can be accurately predetermined.
  • the width of the border regions is equal to or smaller than the width of the passive regions.
  • the semiconductor layer is removed at least in sections in the passive regions.
  • the passive regions are formed by isolation trenches formed, for example, in a P2 patterning.
  • the structure width of the isolation trenches is preferably 10 ⁇ m to 100 ⁇ m.
  • the passive regions extend in the direction of the relative movement (working direction) substantially over the entire length of the semiconductor layer.
  • the center distances of two adjacent passive regions are each defined by two parallel imaginary lines on the semiconductor layer, which preferably have a distance of 6 mm to 8 mm from each other.
  • the relative movement between the laser system and the substrate can take place via a movement of the laser lines or via a movement of the substrate.
  • the substrate material such as substrate wafers or the like, is generally uneven under production conditions.
  • focus width which is preferably very narrow in the working direction, only a very small depth of field is conventionally available in the technical realization.
  • a laser line can be individually and locally focused on this area. In this way, the unevenness or waviness of the substrate can be taken into account in a differentiated manner.
  • a laser system has a plurality of juxtaposed lasers, each with a beam shaping optics, which each focus a laser beam emitted by a laser beam in a laser line and in the longitudinal direction side by side on the semiconductor layer.
  • adjacent laser lines on the semiconductor layer each form a boundary region, which is formed in each case on a passive region of the semiconductor layer.
  • the lasers are pulsed diode lasers having a wavelength range of about 532 nm.
  • the diode lasers may be operated in combination with NIR lasers in the cw range.
  • the laser system can have an advancing device.
  • FIG. 1 shows a plan view of a semiconductor layer subjected to a multiplicity of laser lines
  • FIG. 2 shows a profile of the irradiation energy distribution along the laser lines
  • FIG. 3 shows a schematic diagram of a perspective structure of a laser system according to the invention.
  • FIG. 1 shows a top view of a semiconductor layer 2, which is covered by a multiplicity of Laser lines 6 of a laser system 6 shown in Figure 3 is scanned strip by strip.
  • the semiconductor layer 2 is, as a silicon-based seed or absorber layer of a thin-film solar cell, applied to a glass substrate.
  • the application of the semiconductor layer 2 to the substrate was carried out by known methods, such as plasma enhanced chemical vapor deposition (PECVD).
  • PECVD plasma enhanced chemical vapor deposition
  • the scanning of the semiconductor layer 2 by the laser lines 8, 10, 12 serves to crystallize the amorphous semiconductor layer 2.
  • the juxtaposition of the laser lines 8, 10, 12 extends in the y-direction over the entire width of the semiconductor layer 2 and is perpendicular thereto Scanned in the x direction (working direction) over the length of the semiconductor layer 2.
  • the laser lines 8, 10, 12 each form with their adjacent laser lines 8, 10, 12 in their end portions boundary regions 15, 17 preferably with overlap regions 14, 16 on the semiconductor layer. 2
  • the laser lines 8, 10, 12 are generated by lasers 18, 20, 22 of the laser system 6 shown in FIG.
  • the boundary regions 15, 17 are guided on the semiconductor layer 2 via passive regions 23, 25 which are delimited by two parallel imaginary lines 24, 26 and 28, 30, respectively.
  • the lines 24, 26 and 28, 30 extend in the x direction over the entire length of the semiconductor layer 2 and subdivide the surface of the semiconductor layer into passive and active regions.
  • the passive regions are formed by isolation trenches, which form in a subsequent P2 structuring by, for example, mechanical removal or ablation by means of lasers of the semiconductor layer 2.
  • the isolation trenches have a structure width of 10 ⁇ m to 100 ⁇ m.
  • the overlapping end sections 14, 16 of the laser lines 8, 10, 12, advantageously the entire boundary regions 15, 17, are imaged along the subsequently formed isolation trenches, which have no significance with regard to the energy efficiency of the solar cell, since there is no absorption in the isolation trenches of light photons occurs.
  • FIG. 2 shows a profile of an irradiation energy distribution 32 over the length of the juxtaposed laser lines.
  • the irradiation energy distribution 32 is composed of individual energy areas 34, 36, 38 of the laser lines.
  • the individual energy regions 34, 36, 38 form boundary regions 15, 17 with internal overlapping regions 14, 16.
  • the expansion of the overlap regions 14, 16 in the y-direction can be achieved by a displacement of the laser system 6 in the z-direction or by a modified fanning of the Energy ranges 34, 36, 38, ie changed focus lengths vary.
  • FIG. 3 shows an example of a laser system 6 according to the invention.
  • the laser system 6 has a multiplicity of lasers 18, 20, 22 arranged side by side in the y-direction on.
  • the lasers 18, 20, 22 are pulsed diode lasers with a wavelength range of about 532 nm. They emit laser beams 40, 42, 44 which are each focused via a downstream beam-shaping optical system 46, 48, 50 into a line focus which is as homogeneous as possible Has intensity distribution over its focal length and as narrow as possible over its focus width.
  • the relative movement between the laser lines and the substrate can be realized by scanner mirrors, not shown, which are arranged downstream of the beam-forming optics or even via a feed device, not shown, of the laser system 6.
  • the laser beams 40, 42, 44 which are emitted by the lasers 18, 20, 22, respectively pass through their associated beam shaping optics 46, 48, 50 and impinge on the semiconductor layer 2. They form the laser lines 8, 10, 12 and the boundary regions 15, 17 with internal overlapping regions 14, 16 between the adjacent laser lines 8, 10, 12.
  • Example of an amorphous Si-based seed or absorber layer on a glass substrate is also suitable for other systems, such as CIS (chalcopyrite, CuInSe 2 ), CIGS (calkopyrite with addition of gallium, Cu (In, Ga), (S, Se) 2 ) or CdTe (cadmium Telluride), provided thermal processes with scanned energy input are used for production.
  • CIS chalcopyrite, CuInSe 2
  • CIGS calkopyrite with addition of gallium, Cu (In, Ga), (S, Se) 2
  • CdTe cadmium Telluride

Abstract

The invention relates to a method for restructuring a semiconductor layer (2) with a multiplicity of lasers (18, 20, 22) which are arranged next to one another and, by means of respectively assigned beam shaping optics (46, 48, 50), project on the semiconductor layer (2) laser lines (8, 10, 12) arranged next to one another, with marginal regions (15, 17) and inner overlapping regions (14, 16), wherein at least the overlapping regions (14, 16) are projected completely and on passive regions (14, 16) of the semiconductor layer (2) in which the semiconductor layer is removed in a following processing step, and relates to a laser system for carrying out the method.

Description

Beschreibung Laserkristallisation durch Bestrahlung Description Laser crystallization by irradiation
[0001] Die Erfindung betrifft ein Verfahren zur Kristallisation bzw. Rekristallisation einer Halbleiterschicht, insbesondere einer amorphen Siliziumschicht für eine Solarzelle, gemäß Anspruch 1, sowie ein Lasersystem zur Durchführung des Verfahrens nach Anspruch 11.The invention relates to a process for the crystallization or recrystallization of a semiconductor layer, in particular an amorphous silicon layer for a solar cell, according to claim 1, and a laser system for carrying out the method according to claim 11.
[0002] Ein bekanntes Verfahren zur Umstrukturierung von Halbleiterschichten ist in der WO 02/19437 A2 offenbart. Die Halbleiterschichten bilden die Saat- und Absorberschicht einer Solarzelle mit einem glashaltigen Substrat. Die Saatschicht ist eine amorphe Siliziumsschicht, die auf das Substrat abgeschieden wird. Sie wird spurweise und dabei überlappend mit einem Laser, beispielsweise einem Diodenlaser bestrahlt. Die Überlappung erfolgt derart, dass ein Teil der grobkörnigen Bereiche der vorhergehenden Spur wieder aufgeschmolzen werden, wodurch eine verbesserte Kristallisation erreicht wird und die Solarzelle eine erhöhte Energieeffizienz aufweist. Während der Bestrahlung mit dem Laser wird die Saatschicht durch Diffusion mit Bor oder Phospat dotiert. Anschließend wird die Absorberschicht auf die Saatschicht aufgebracht. Die Absorberschicht besteht aus zusätzlich abgeschiedenem amorphen Silizium. Nach dem Erreichen einer bestimmten Schichtdicke wird das zusätzliche Silizium spurweise mit einem gepulsten Excimerlaser bestrahlt. Dabei wird der Exci- merlaser derart über das beschichtete Substrat geführt, dass die Bestrahlungsflächen aneinander anschließen und somit linienförmige Grenzbereiche bilden.A known method for the restructuring of semiconductor layers is disclosed in WO 02/19437 A2. The semiconductor layers form the seed and absorber layer of a solar cell with a glass-containing substrate. The seed layer is an amorphous silicon layer deposited on the substrate. It is irradiated in tracks and while overlapping with a laser, such as a diode laser. The overlapping takes place in such a way that a part of the coarse-grained regions of the preceding track are remelted, whereby an improved crystallization is achieved and the solar cell has an increased energy efficiency. During irradiation with the laser, the seed layer is doped by diffusion with boron or phosphate. Subsequently, the absorber layer is applied to the seed layer. The absorber layer consists of additionally deposited amorphous silicon. After reaching a certain layer thickness, the additional silicon is irradiated in tracks with a pulsed excimer laser. In this case, the excimer laser is guided over the coated substrate in such a way that the irradiation surfaces adjoin one another and thus form linear boundary regions.
[0003] Nachteilig an dieser Art der Laserkristallisation ist, dass das Substrat spurweise nacheinander bestrahlt bzw. gescannt wird, wodurch die Behandlung großflächiger Substrate entsprechend zeitintensiv ist. Des Weiteren ist nachteilig, dass die gesamte realisierbare Fokusbreite des Lasers verwendet wird, wodurch nicht nur die Führung des Lasers über das Substrat zur Bildung der Überlapp- bzw. Grenzbereiche sehr genau sein muss, sondern auch der Laser ein sehr genaues Energie- Verteilungsprofil aufzuweisen hat.A disadvantage of this type of laser crystallization is that the substrate is irradiated in tracks one after the other or scanned, whereby the treatment of large-area substrates is correspondingly time-consuming. Furthermore, it is disadvantageous that the entire realizable focal width of the laser is used, whereby not only the guidance of the laser across the substrate for forming the overlap or boundary regions must be very accurate, but also the laser has to have a very accurate energy distribution profile ,
[0004] Ein Verfahren zur Laserkristallisation einer Halbleiterschicht mit einer Vielzahl von nebeneinander entlang einer Linie angeordneten Lasern ist in der US 6,780,692 B2 beschrieben. Den Lasern sind Mittel zur Homogenisierung der Strahlungsintensität nachgeordnet, sodass auf der bestrahlten Oberfläche eines Substrates eine Laserlinie mit einer homogenen Strahlungsintensität abgebildet wird.A method of laser crystallization of a semiconductor layer having a plurality of lasers arranged side by side along a line is described in US 6,780,692 B2. The lasers are arranged downstream of means for homogenizing the radiation intensity so that a laser line with a homogeneous radiation intensity is imaged on the irradiated surface of a substrate.
[0005] Durch eine relative Bewegung zwischen der abgebildeten Laserlinie und dem Substrat senkrecht zur Richtung der Laserlinie wird die gesamte Oberfläche des Substrats bestrahlt.By relative movement between the imaged laser line and the substrate perpendicular to the direction of the laser line, the entire surface of the substrate is irradiated.
[0006] Nachteilig an einer solchen Lösung ist die Notwendigkeit von Mitteln zur Homoge- nisierung und der durch sie unvermeidliche Intensitätsverlust.A disadvantage of such a solution is the need for homoge- and the inevitable loss of intensity.
[0007] Aus der EP 1 738 402 B 1 ist ein Verfahren zur Herstellung von Solarzellen beschrieben, bei dem ein Laserstrahl in einem Linienfokus auf einem Festkörper (Substrat) abgebildet wird, wobei die Länge des Linienfokus zwischen 100 um und 10 mm liegt und die Breite kleiner 10 μm ist.A method for the production of solar cells is described in EP 1 738 402 B1, in which a laser beam is imaged in a line focus on a solid (substrate), the length of the line focus being between 100 μm and 10 mm, and the Width is less than 10 microns.
[0008] Vorzugsweise soll das Substrat auf einem X- Y-Linear- Verschiebetisch montiert sein und der Laserstrahl stationär fest im Raum bleiben. Es könnte jedoch auch vorgesehen sein, dass das Substrat stationär bleibt und das optische System, welches den Laserstrahl auf das Substrat richtet, den Laserstrahl scannend über das Substrat führt.Preferably, the substrate should be mounted on an X-Y linear displacement table and the laser beam stationary remain fixed in space. However, it could also be provided that the substrate remains stationary and the optical system, which directs the laser beam onto the substrate, scans the laser beam over the substrate.
[0009] In beiden Fällen wird das Substrat nacheinander in Streifen gleich der Länge des Linienfokus abgescannt.In both cases, the substrate is sequentially scanned into strips equal to the length of the line focus.
[0010] Mit einem Linienfokus, der über seine Länge eine homogene Intensitäts Verteilung aufweist, werden die Streifen grundsätzlich homogen mit Laserstrahlung beaufschlagt.With a line focus, which has a homogeneous intensity distribution over its length, the strips are in principle subjected to homogeneous laser radiation.
[0011] Problematisch sind jedoch die Grenzbereiche zwischen den benachbarten Streifen, da zum einen die Intensität an den Enden der Laserlinie nicht schlagartig Null sein kann, was einer Flanke in der Intensitätsverteilungskurve von 90° entspräche, und zum anderen die Streifen praktisch auch nicht ideal lückenlos und ohne Überlappung nebeneinander bestrahlt werden können.However, the boundary areas between the adjacent strips are problematic, since on the one hand the intensity at the ends of the laser line can not be abruptly zero, which would correspond to an edge in the intensity distribution curve of 90 °, and on the other hand the strips are practically not ideal and can be irradiated side by side without overlapping.
[0012] Als Grenzbereich soll nachfolgend der Bereich bezeichnet werden, in dem zwei benachbart abgebildete Laserlinien einen Intensitätsabfall aufweisen, d. h. es ist der Bereich, der durch die Länge der Flanken der Intensitätsverteilungskurven zuzüglich eines eventuellen Abstandes bzw. abzüglich eines eventuellen Überlappungsbereiches definiert wird.As the boundary area to be referred to below the area in which two adjacent laser lines have a drop in intensity, d. H. it is the area defined by the length of the flanks of the intensity distribution curves plus a possible distance or minus any overlap area.
[0013] Üblicherweise überlappen sich die Enden der Laserlinien in diesem Grenzbereich, wodurch vorteilhaft der Grenzbereich in seiner Breite minimiert wird. Da jedoch die Breite des Überlappungsbereiches und damit auch die Breite des Grenzbereiches in Abhängigkeit von der Stabilität der Laserlinie und der Genauigkeit der Scanbewegung der benachbarten Laserlinien schwanken, ist der Grenzbereich mit seinen elektrischen Eigenschaften Undefiniert, denn der Energieeintrag in den Grenzbereichen weicht von dem ansonsten wenigsten nahezu konstanten Energieeintrag in die abgescannten Oberflächenbereiche Undefiniert ab. Das hat zur Folge, dass in den Grenzbereichen die Kristallisation der Halbleiterschicht in einem abweichenden und Undefinierten Maße erfolgt.Usually, the ends of the laser lines overlap in this boundary region, whereby advantageously the border region is minimized in its width. However, since the width of the overlap region and thus also the width of the boundary region vary depending on the stability of the laser line and the accuracy of the scanning movement of the adjacent laser lines, the boundary region is undefined with its electrical properties, because the energy input in the border areas differs from the otherwise least almost constant energy input into the scanned surface areas undefined. As a result, the crystallization of the semiconductor layer takes place at a deviating and undefined extent in the boundary regions.
[0014] Aufgabe der vorliegenden Erfindung ist es, ein Verfahren und ein Lasersystem zurThe object of the present invention is to provide a method and a laser system for
Umstrukturierung von Halbleiterschichten zu schaffen, die die vorgenannten Nachteile beseitigen.To provide restructuring of semiconductor layers, which eliminate the aforementioned disadvantages.
[0015] Diese Aufgabe wird gelöst durch ein Verfahren mit den Merkmalen nach Anspruch 1 und durch einem Lasersystem mit den Merkmalen nach Anspruch 9. [0016] Bei einem erfindungsgemäßen Verfahren zur Umstrukturierung von Halbleiterschichten, insbesondere von amorphen Siliziumschichten für Solarzellen, wird eine Halbleiterschicht auf ein Substrat aufgebracht.This object is achieved by a method having the features of claim 1 and by a laser system having the features of claim 9. In a method according to the invention for the restructuring of semiconductor layers, in particular of amorphous silicon layers for solar cells, a semiconductor layer is applied to a substrate.
[0017] Dann wird ein Lasersystem mit einer Vielzahl von Lasern mit jeweils einer zugeordneten Strahlformungsoptik bereitgestellt, die jeweils einen Laserstrahl in eine Laserlinie fokussieren und in Längsrichtung nebeneinander liegend auf die Halbleiterschicht abbilden, wobei jeweils benachbarte Laserlinien einen Grenzbereich, bevorzugt mit einem Überlappbereich bilden.Then, a laser system is provided with a plurality of lasers, each with an associated beam shaping optics, each focusing a laser beam in a laser line and longitudinally adjacent to the semiconductor layer, wherein each adjacent laser lines form a boundary region, preferably with an overlap region.
[0018] Anschließend wird zwischen dem Lasersystem und dem Substrat eine Relativbewegung, vorzugsweise senkrecht zu den Laserlinien erzeugt, so dass die Halbleiterschicht von den einzelnen Laserlinien jeweils entlang eines Streifens in Arbeitsrichtung großflächig abgescannt wird. Dabei werden die Grenzbereiche mit den Überlappungsbereichen auf der Halbleiterschicht jeweils über einen passiven Bereich geführt, in dem nach einem folgenden Bearbeitungsschritt zumindest abschnittsweise keine Absorption von Lichtphotonen stattfindet. Zu diesem Zweck ist die Länge der Laserlinien, die bei einer unmittelbaren Fokussierung auf der Halbleiterschicht gleich der Fokuslänge ist, auf den Mittenabstand dieser passiven Bereiche zueinander abgestimmt.Subsequently, a relative movement, preferably perpendicular to the laser lines is generated between the laser system and the substrate, so that the semiconductor layer is scanned by the individual laser lines in each case along a strip in the working direction over a large area. In this case, the boundary regions with the overlapping regions on the semiconductor layer are each guided over a passive region, in which after a subsequent processing step, at least in sections, no absorption of light photons takes place. For this purpose, the length of the laser lines, which is equal to the focal length in the case of direct focusing on the semiconductor layer, is matched to the center distance of these passive regions.
[0019] Anstelle des gleichzeitigen Abscannens mit mehreren Laserlinien, kann die Halbleiterschicht auch streifenweise nacheinander mit einer oder bevorzugt mit einigen wenigen Laserlinien abgescannt werden. Entsprechend würde das Lasersystem hierfür nur einen Laser mit Strahlformungsoptik benötigen. Dem geringeren Bedarf an Lasern steht der höhere Zeitaufwand entgegen.Instead of the simultaneous Abscannens with multiple laser lines, the semiconductor layer can also be scanned in strips successively with one or preferably with a few laser lines. Accordingly, the laser system would require only a laser beam shaping optics for this purpose. The lower demand for lasers is offset by the greater amount of time required.
[0020] In beiden Ausführungsvarianten wird erfindungsgemäß nicht die gesamte realisierbare Fokuslänge der Laserlinien zur Umstrukturierung verwendet, sondern es werden die Endabschnitte der Laserlinien, die auf den passiven Bereichen abgebildet werden und aufgrund des Intensitätsabfalls und der eventuellen Überlappung zu einem abweichenden Energieeintrag führen, quasi ausgeblendet, wodurch die zwischen den passiven Bereichen liegenden aktiven Bereiche, die der Photonenabsorption dienen, mit Laserstrahlung einer homogenen Intensitätsverteilung beaufschlagt werden, so dass der Wirkungsgrad der Halbleiterschicht genau vorbestimmt werden kann. Idealerweise entspricht die Breite der Grenzbereiche der Breite der passiven Bereiche oder ist kleiner als diese.In both embodiments, the invention does not use the entire realizable focus length of the laser lines for restructuring, but it is the end portions of the laser lines, which are displayed on the passive areas and lead due to the intensity drop and the eventual overlap to a different energy input, quasi hidden whereby the active regions lying between the passive regions, which serve for photon absorption, are exposed to laser radiation of a homogeneous intensity distribution, so that the efficiency of the semiconductor layer can be accurately predetermined. Ideally, the width of the border regions is equal to or smaller than the width of the passive regions.
[0021] Bei einem folgenden B earbeitungs schritt wird die Halbleiterschicht in den passiven Bereichen zumindest abschnittsweise abgetragen.In a subsequent processing step, the semiconductor layer is removed at least in sections in the passive regions.
[0022] Bei einem bevorzugten Ausführungsbeispiel werden die passiven Bereiche durch Isolationsgräben, die zum Beispiel bei einer P2- Strukturierung ausgebildet werden, gebildet. Die Strukturbreite der Isolationsgräben beträgt vorzugsweise 10 μm bis 100 μm.In a preferred embodiment, the passive regions are formed by isolation trenches formed, for example, in a P2 patterning. The structure width of the isolation trenches is preferably 10 μm to 100 μm.
[0023] Aus fertigungstechnischer Sicht ist es vorteilhaft, wenn sich die passiven Bereiche in Richtung der Relativbewegung (Arbeitsrichtung) im Wesentlichen über die gesamte Länge der Halbleiterschicht erstrecken.From a manufacturing point of view, it is advantageous if the passive regions extend in the direction of the relative movement (working direction) substantially over the entire length of the semiconductor layer.
[0024] Bei einem Ausführungsbeispiel werden die Mittenabstände zweier benachbarter passiver Bereiche jeweils durch zwei parallele gedachte Linien auf der Halbleiterschicht definiert, die vorzugsweise einen Abstand von 6 mm bis 8 mm voneinander haben.In one embodiment, the center distances of two adjacent passive regions are each defined by two parallel imaginary lines on the semiconductor layer, which preferably have a distance of 6 mm to 8 mm from each other.
[0025] Die Relativbewegung zwischen dem Lasersystem und dem Substrat kann über eine Bewegung der Laserlinien oder über eine Bewegung des Substrates erfolgen.The relative movement between the laser system and the substrate can take place via a movement of the laser lines or via a movement of the substrate.
[0026] Das Substratmaterial, beispielsweise Substratscheiben oder dergleichen, ist unter Produktionsbedingungen in der Regel uneben. Für einen präzisen, in Arbeitsrichtung vorzugsweise sehr schmalen Laserfokus (Fokusbreite), ist bei der technischen Realisierung herkömmlicherweise nur eine sehr geringe Tiefenschärfe verfügbar. Indem eine Laserlinie jeweils nur einen aktiven Bereich abscannt, kann diese individuell und lokal auf diesen Bereich fokussiert werden. Damit kann der Unebenheit bzw. Welligkeit des Substrates differenziert Rechnung getragen werden.The substrate material, such as substrate wafers or the like, is generally uneven under production conditions. For a precise laser focus (focus width) which is preferably very narrow in the working direction, only a very small depth of field is conventionally available in the technical realization. By scanning only one active area at a time, a laser line can be individually and locally focused on this area. In this way, the unevenness or waviness of the substrate can be taken into account in a differentiated manner.
[0027] Ein erfindungsgemäßes Lasersystem hat eine Vielzahl von nebeneinander angeordneter Lasern mit jeweils einer Strahlformungsoptik, die jeweils einen von einem Laser emittierten Laserstrahl in eine Laserlinie fokussieren und in Längsrichtung nebeneinander liegend auf der Halbleiterschicht abbilden. Erfindungsgemäß bilden benachbarte Laserlinien auf der Halbleiterschicht jeweils einen Grenzbereich, der jeweils auf einem passiven Bereich der Halbleiterschicht gebildet wird.A laser system according to the invention has a plurality of juxtaposed lasers, each with a beam shaping optics, which each focus a laser beam emitted by a laser beam in a laser line and in the longitudinal direction side by side on the semiconductor layer. According to the invention, adjacent laser lines on the semiconductor layer each form a boundary region, which is formed in each case on a passive region of the semiconductor layer.
[0028] Bei einem Ausführungsbeispiel sind die Laser gepulste Diodenlaser mit einem Wellenlängenbereich von etwa 532 nm. Optional oder alternativ können die Diodenlaser in Kombination mit NIR-Lasern im cw-Bereich betrieben werden.In one embodiment, the lasers are pulsed diode lasers having a wavelength range of about 532 nm. Optionally or alternatively, the diode lasers may be operated in combination with NIR lasers in the cw range.
[0029] Zur Erzeugung einer Relativbewegung zwischen dem Lasersystem und dem Substrat kann das Lasersystem eine Vorschubeinrichtung aufweisen.To generate a relative movement between the laser system and the substrate, the laser system can have an advancing device.
[0030] Sonstige vorteilhafte Ausführungsbeispiele sind Gegenstand weiterer Unteransprüche.Other advantageous embodiments are the subject of further subclaims.
[0031] Im Folgenden wird ein bevorzugtes Ausführungsbeispiel der Erfindung anhand sche- matischer Darstellungen näher erläutert. Es zeigenIn the following, a preferred embodiment of the invention will be explained in more detail with reference to schematic representations. Show it
[0032] Figur 1 eine Draufsicht auf eine Halbleiterschicht beaufschlagt mit einer Vielzahl von Laserlinien,FIG. 1 shows a plan view of a semiconductor layer subjected to a multiplicity of laser lines,
[0033] Figur 2 ein Profil der Bestrahlungsenergieverteilung entlang der LaserlinienFIG. 2 shows a profile of the irradiation energy distribution along the laser lines
[0034] Figur 3 eine Prinzipskizze eines perspektivischen Aufbaus eines erfindungsgemäßen Lasersystems.3 shows a schematic diagram of a perspective structure of a laser system according to the invention.
[0035] Figur 1 zeigt eine Draufsicht auf eine Halbleiterschicht 2, die von einer Vielzahl von Laserlinien eines in Figur 3 dargestellten Lasersystems 6 streifenweise gescannt wird. Die Halbleiterschicht 2 ist, als siliziumbasierte Saat- bzw. Absorberschicht einer Dünnschicht-Solarzelle, auf ein Glas-Substrat aufgebracht. Die Aufbringung der Halbleiterschicht 2 auf das Substrat erfolgte durch bekannte Verfahren, wie beispielsweise Plasma Enhanced Chemical Vapor Deposition (PECVD).FIG. 1 shows a top view of a semiconductor layer 2, which is covered by a multiplicity of Laser lines 6 of a laser system 6 shown in Figure 3 is scanned strip by strip. The semiconductor layer 2 is, as a silicon-based seed or absorber layer of a thin-film solar cell, applied to a glass substrate. The application of the semiconductor layer 2 to the substrate was carried out by known methods, such as plasma enhanced chemical vapor deposition (PECVD).
[0036] Das Abscannen der Halbleiterschicht 2 durch die Laserlinien 8, 10, 12 dient der Kristallisation der amorphen Halbleiterschicht 2. Die Aneinanderreihung der Laserlinien 8, 10, 12 erstreckt sich in y-Richtung über die gesamte Breite der Halbleiterschicht 2 und wird hierzu senkrecht in x-Richtung (Arbeitsrichtung) über die Länge der Halbleiterschicht 2 gescannt.The scanning of the semiconductor layer 2 by the laser lines 8, 10, 12 serves to crystallize the amorphous semiconductor layer 2. The juxtaposition of the laser lines 8, 10, 12 extends in the y-direction over the entire width of the semiconductor layer 2 and is perpendicular thereto Scanned in the x direction (working direction) over the length of the semiconductor layer 2.
[0037] Die Laserlinien 8, 10, 12 bilden jeweils mit ihren benachbarten Laserlinien 8, 10, 12 in ihren Endabschnitten Grenzbereiche 15, 17 bevorzugt mit Überlappungsbereichen 14, 16 auf der Halbleiterschicht 2.The laser lines 8, 10, 12 each form with their adjacent laser lines 8, 10, 12 in their end portions boundary regions 15, 17 preferably with overlap regions 14, 16 on the semiconductor layer. 2
[0038] Die Laserlinien 8, 10, 12 werden von in Figur 3 dargestellten Lasern 18, 20, 22 des Lasersystems 6 erzeugt.The laser lines 8, 10, 12 are generated by lasers 18, 20, 22 of the laser system 6 shown in FIG.
[0039] Die Grenzbereiche 15, 17 werden auf der Halbleiterschicht 2 über passive Bereiche 23, 25 geführt, die jeweils von zwei parallelen gedachten Linien 24, 26 bzw. 28, 30 begrenzt werden. Die Linien 24, 26 bzw. 28, 30 erstrecken sich in x-Richtung über die gesamte Länge der Halbleiterschicht 2 und unterteilen die Oberfläche der Halbleiterschicht in passive und aktive Bereiche. Die passiven Bereiche werden durch Isolationsgräben gebildet, die sich bei einer folgenden P2-Strukturierung durch beispielsweise ein mechanisches Abtragen oder Abtragen mittels Laser der Halbleiterschicht 2 ausbilden. Die Isolationsgräben haben eine Strukturbreite von 10 μm bis 100 μm. Erfindungsgemäß werden somit wenigstens die sich überlappenden Endabschnitte 14, 16 der Laserlinien 8, 10, 12, vorteilhaft die gesamten Grenzbereiche 15, 17, entlang der nachfolgend ausgebildeten Isolationsgräben abgebildet, denen keine Bedeutung hinsichtlich der Energieeffizienz der Solarzelle zukommt, da in den Isolationsgräben keine Absorption von Lichtphotonen erfolgt.The boundary regions 15, 17 are guided on the semiconductor layer 2 via passive regions 23, 25 which are delimited by two parallel imaginary lines 24, 26 and 28, 30, respectively. The lines 24, 26 and 28, 30 extend in the x direction over the entire length of the semiconductor layer 2 and subdivide the surface of the semiconductor layer into passive and active regions. The passive regions are formed by isolation trenches, which form in a subsequent P2 structuring by, for example, mechanical removal or ablation by means of lasers of the semiconductor layer 2. The isolation trenches have a structure width of 10 μm to 100 μm. According to the invention, at least the overlapping end sections 14, 16 of the laser lines 8, 10, 12, advantageously the entire boundary regions 15, 17, are imaged along the subsequently formed isolation trenches, which have no significance with regard to the energy efficiency of the solar cell, since there is no absorption in the isolation trenches of light photons occurs.
[0040] Figur 2 zeigt ein Profil einer Bestrahlungsenergie Verteilung 32 über die Länge der aneinandergereihten Laserlinien. Die Bestrahlungsenergieverteilung 32 setzt sich aus einzelnen Energiebereichen 34, 36, 38 der Laserlinien zusammen. Die einzelnen Energiebereiche 34, 36, 38 bilden Grenzbereiche 15, 17 mit innenliegenden Überlappungsbereichen 14, 16. Die Ausdehnung der Überlappungsbereiche 14, 16 in y-Richtung lässt sich durch eine Verschiebung des Lasersystems 6 in z-Richtung bzw. durch eine veränderte Auffächerung der Energiebereiche 34, 36, 38, d.h. veränderte Fokuslängen variieren.FIG. 2 shows a profile of an irradiation energy distribution 32 over the length of the juxtaposed laser lines. The irradiation energy distribution 32 is composed of individual energy areas 34, 36, 38 of the laser lines. The individual energy regions 34, 36, 38 form boundary regions 15, 17 with internal overlapping regions 14, 16. The expansion of the overlap regions 14, 16 in the y-direction can be achieved by a displacement of the laser system 6 in the z-direction or by a modified fanning of the Energy ranges 34, 36, 38, ie changed focus lengths vary.
[0041] Figur 3 zeigt ein Beispiel eines erfindungsgemäßen Lasersystems 6. Das Lasersystem 6 weist eine Vielzahl von in y-Richtung nebeneinander angeordneten Lasern 18, 20, 22 auf. Die Laser 18, 20, 22 sind gepulste Diodenlaser mit einem Wellenlängenbereich von etwa 532 nm. Sie emittieren Laserstrahlen 40, 42, 44, die jeweils über eine nach- geordnete Strahlformungsoptik 46, 48, 50 in einen Linienfokus fokussiert werden, der eine möglichst homogene Intensitätsverteilung über seine Fokuslänge aufweist und über seine Fokusbreite möglichst schmal ist.FIG. 3 shows an example of a laser system 6 according to the invention. The laser system 6 has a multiplicity of lasers 18, 20, 22 arranged side by side in the y-direction on. The lasers 18, 20, 22 are pulsed diode lasers with a wavelength range of about 532 nm. They emit laser beams 40, 42, 44 which are each focused via a downstream beam-shaping optical system 46, 48, 50 into a line focus which is as homogeneous as possible Has intensity distribution over its focal length and as narrow as possible over its focus width.
[0042] Die Relativbewegung zwischen den Laserlinien und dem Substrat kann durch nicht dargestellte Scannerspiegel realisiert werden, die den Strahlformungsoptiken nachgeordnet sind oder auch über eine nicht dargestellte Vorschubeinrichtung des Lasersystems 6 erfolgen.The relative movement between the laser lines and the substrate can be realized by scanner mirrors, not shown, which are arranged downstream of the beam-forming optics or even via a feed device, not shown, of the laser system 6.
[0043] Die Laserstrahlen 40, 42, 44, die von den Lasern 18, 20, 22 emittiert werden, durchlaufen jeweils die ihnen zugeordnete Strahlformungsoptik 46, 48, 50 und treffen auf die Halbleiterschicht 2 auf. Dabei bilden sie die Laserlinien 8, 10, 12 und die Grenzbereiche 15,17 mit innenliegenden Überlappungsbereichen 14, 16 zwischen den benachbarten Laserlinien 8, 10, 12.The laser beams 40, 42, 44, which are emitted by the lasers 18, 20, 22, respectively pass through their associated beam shaping optics 46, 48, 50 and impinge on the semiconductor layer 2. They form the laser lines 8, 10, 12 and the boundary regions 15, 17 with internal overlapping regions 14, 16 between the adjacent laser lines 8, 10, 12.
[0044] Die obenstehende Erläuterung des erfindungsgemäßen Verfahrens erfolgt amThe above explanation of the method according to the invention takes place on
Beispiel einer amorphen Si-basierten Saat- bzw. Absorberschicht auf einem Substrat aus Glas. Das erfindungsgemäße Verfahren bzw. Lasersystem ist jedoch auch für andere Systeme, wie zum Beispiel CIS (Chalkopyrit, CuInSe2), CIGS (Calkopyrit mit Zugabe von Gallium, Cu (In, Ga), (S, Se)2) oder CdTe (Cadmium Tellurid) geeignet, sofern thermische Prozesse mit gescannter Energiezufuhr zur Herstellung verwendet werden.Example of an amorphous Si-based seed or absorber layer on a glass substrate. However, the method or laser system according to the invention is also suitable for other systems, such as CIS (chalcopyrite, CuInSe 2 ), CIGS (calkopyrite with addition of gallium, Cu (In, Ga), (S, Se) 2 ) or CdTe (cadmium Telluride), provided thermal processes with scanned energy input are used for production.
[0045] Ebenso ist es möglich, dass erfindungsgemäße Verfahren bzw. Lasersystem bei Zellen mit mehreren funktionalen Schichten wie zum Beispiel Tandem-Zellen zu verwenden.It is likewise possible to use the method or laser system according to the invention in cells having a plurality of functional layers, for example tandem cells.
[0046] Des Weiteren ist es vorstellbar, ein erfindungsgemäßes Verfahren bzw. Lasersystem zur Rekristallisation einer Halbleiterschicht 2 zu verwenden.Furthermore, it is conceivable to use a method or laser system according to the invention for the recrystallization of a semiconductor layer 2.
[0047] Offenbart ist ein Verfahren zur Umstrukturierung einer Halbleiterschicht mit einer Vielzahl von nebeneinander angeordneten Lasern, deren Laserlinien auf der Halbleiterschicht Überlappungsbereiche bilden, in denen nach einem folgenden Behandlungsschritt keine Absorption von Lichtphotonen erfolgt sowie ein Lasersystem mit einer Vielzahl von Lasern, deren Laserlinien auf einer Halbleiterschicht Grenzbereiche bilden.Disclosed is a method for restructuring a semiconductor layer having a plurality of juxtaposed lasers whose laser lines form overlap areas on the semiconductor layer, in which after a subsequent treatment step no absorption of light photons, and a laser system with a plurality of lasers whose laser lines on form a boundary layer of a semiconductor layer.
[0048] Bezugszeichenliste[0048] List of Reference Numerals
[0049] 2 Halbleiterschicht2 semiconductor layer
[0050] 6 Lasersystem6 laser system
[0051] 8 Laserlinie8 laser line
[0052] 10 Laserlinie10 laser line
[0053] 12 Laserlinie [0054] 14 Überlappungsbereich12 laser line [0054] 14 overlap area
[0055] 15 Grenzbereich[0055] 15 Boundary range
[0056] 16 Überlappungsbereich16 overlap area
[0057] 17 Grenzbereich17 border area
[0058] 18 Laser18 lasers
[0059] 20 Laser20 lasers
[0060] 22 Laser22 lasers
[0061] 23 passiver Bereich23 passive area
[0062] 24 Linie24 line
[0063] 25 passiver Bereich25 passive area
[0064] 26 Linie[0064] 26 line
[0065] 28 Linie28 line
[0066] 30 Linie30 line
[0067] 32 Bestrahlungsenergie[0067] 32 irradiation energy
[0068] 34 Energiebereich[0068] 34 energy range
[0069] 36 Energiebereich[0069] 36 energy range
[0070] 38 Energiebereich[0070] 38 energy range
[0071] 40 Laserstrahl40 laser beam
[0072] 42 Laserstrahl42 laser beam
[0073] 44 Laserstrahl44 laser beam
[0074] 46 Strahlformungsoptik[0074] 46 beam shaping optics
[0075] 48 Strahlformungsoptik[0075] 48 beam shaping optics
[0076] 50 Strahlformungsoptik [0076] 50 beam shaping optics

Claims

Ansprücheclaims
[0001] 1. Verfahren zur Umstrukturierung einer Halbleiterschicht (2), insbesondere einer amorphen Siliziumschicht für Solarzellen, mit den Schritten:1. A method for restructuring a semiconductor layer (2), in particular an amorphous silicon layer for solar cells, comprising the steps:
- Aufbringen der Halbleiterschicht (2) auf ein Substrat,Applying the semiconductor layer (2) to a substrate,
- Bereitstellen eines Lasersystems (6) mit einer Vielzahl von Lasern (18, 20, 22) mit jeweils einer zugeordneten Strahlformungsoptik (46, 48, 50), die jeweils einen Laserstrahl in eine Laserlinie (8, 10, 12) fokussieren und in Längsrichtung nebeneinander liegend auf der Halbleiterschicht (2) abbilden, wobei jeweils benachbarte Laserlinien (8, 10, 12) einen Grenzbereich (15,17) mit einem innenliegenden Überlappungsbereich (14, 16) bilden,- Providing a laser system (6) having a plurality of lasers (18, 20, 22), each with an associated beam shaping optics (46, 48, 50), each of which focus a laser beam in a laser line (8, 10, 12) and in the longitudinal direction lying adjacent to each other on the semiconductor layer (2), wherein in each case adjacent laser lines (8, 10, 12) form a border region (15, 17) with an inner overlapping region (14, 16),
- Abscannen der Halbleiterschicht durch die Laserlinien (8, 10, 12), wobei wenigstens die Überlappungsbereiche (14, 16) vollständig auf der Halbleiterschicht jeweils in einem passiven Bereich (23, 25) abgebildet werden, in dem in einem nachfolgenden Bearbeitungsschritt die Halbleiterschicht abgetragen wird.- Scanning of the semiconductor layer by the laser lines (8, 10, 12), wherein at least the overlapping regions (14, 16) are completely imaged on the semiconductor layer in each case in a passive region (23, 25), in which removed in a subsequent processing step, the semiconductor layer becomes.
[0002] 2. Verfahren nach Anspruch 1, wobei mit dem Abtragen Isolationsgräben gebildet werden, die bei einer P2-Strukturierung, im Bereich der Überlappungsbereiche (14, 16) ausgebildet werden.2. The method of claim 1, wherein with the removal isolation trenches are formed, which are formed in a P2 structuring, in the region of the overlap regions (14, 16).
[0003] 3. Verfahren nach Anspruch 2, wobei Isolationsgräben eine Strukturbreite von3. The method of claim 2, wherein isolation trenches have a feature width of
10 μm bis 100 μm haben.10 μm to 100 μm.
[0004] 4. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Relativbewegung durch eine Bewegung der Laserlinien (8, 10, 12) über die Halbleiterschicht (2) erzeugt wird.4. The method according to any one of the preceding claims, wherein the relative movement is generated by a movement of the laser lines (8, 10, 12) via the semiconductor layer (2).
[0005] 5. Verfahren nach einem der Ansprüche 1 bis 3, wobei die Relativbewegung durch eine Bewegung der Halbleiterschicht (2) erzeugt wird.5. The method according to any one of claims 1 to 3, wherein the relative movement is generated by a movement of the semiconductor layer (2).
[0006] 6. Verfahren nach einem der vorhergehenden Ansprüche, wobei die Laserlinien6. The method according to any one of the preceding claims, wherein the laser lines
(8, 10, 12) individuell auf die Halbleiterschicht (2) fokussiert werden.(8, 10, 12) are individually focused on the semiconductor layer (2).
[0007] 7. Verfahren nach einem der vorhergehenden Ansprüche, wobei auch die Grenzbereiche (15, 17) vollständig auf den passiven Bereichen (23, 25) abgebildet werden.7. The method according to any one of the preceding claims, wherein the boundary areas (15, 17) completely on the passive areas (23, 25) are mapped.
[0008] 8. Lasersystem zur Durchführung des Verfahrens nach einem der vorhergehenden Ansprüche, mit einer Vielzahl von nebeneinander angeordneten Lasern (18, 20, 22) mit jeweils einer zugeordneten Strahlformungsoptik (46, 48, 50) zur Abbildung von nebeneinander angeordneten Laserlinien (8, 10, 12) auf einer Halbleitschicht (2) auf einem Substrat, wobei benachbarte Laserlinien (8, 10, 12) auf der Halbleiterschicht (2) jeweils einen Grenzbereich (15, 17) mit einem innenliegenden Überlappungsbereich (14, 16) bilden.8. Laser system for carrying out the method according to one of the preceding claims, with a plurality of juxtaposed lasers (18, 20, 22) each having an associated beam-shaping optical system (46, 48, 50) for imaging of juxtaposed laser lines (8 , 10, 12) on a semiconductor layer (2) on a substrate, wherein adjacent laser lines (8, 10, 12) on the semiconductor layer (2) each form a border region (15, 17) with an inner overlap region (14, 16).
[0009] 9. Lasersystem nach Anspruch 8, wobei die Laser (18, 20, 22) gepulste Di- odenlaser mit einem Wellenlängenbereich von etwa 532 nm sind.9. A laser system according to claim 8, wherein the lasers (18, 20, 22) have pulsed di- odenlaser with a wavelength range of about 532 nm.
[0010] 10. Lasersystem nach Anspruch 9, wobei die gepulsten Laser (18, 20, 22) mit10. A laser system according to claim 9, wherein the pulsed laser (18, 20, 22) with
NIR-Lasern im cw-Betrieb kombiniert sind.NIR lasers are combined in cw operation.
[0011] 11. Lasersystem nach einem der Ansprüche 8 bis 9, wobei jeweils eine Strahlformungsoptik (46, 48, 50) zur Formung der Laserlinien (18, 20, 22) vorgesehen ist.11. Laser system according to one of claims 8 to 9, wherein in each case a beam-shaping optical system (46, 48, 50) for forming the laser lines (18, 20, 22) is provided.
[0012] 12. Lasersystem nach einem der Ansprüche 8 bis 11, wobei eine Vorschubeinrichtung zur Erzeugung einer Relativbewegung zwischen dem Lasersystem (6) und dem Substrat vorgesehen ist. 12. Laser system according to one of claims 8 to 11, wherein a feed device for generating a relative movement between the laser system (6) and the substrate is provided.
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EP1738402B1 (en) 2004-07-26 2008-09-17 Jürgen H. Werner Laser doping of solid bodies using a linear-focussed laser beam and production of solar-cell emitters based on said method

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