WO2007122061A1 - Apparatus for laser annealing of large substrates and method for laser annealing of large substrates - Google Patents

Apparatus for laser annealing of large substrates and method for laser annealing of large substrates Download PDF

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Publication number
WO2007122061A1
WO2007122061A1 PCT/EP2007/053030 EP2007053030W WO2007122061A1 WO 2007122061 A1 WO2007122061 A1 WO 2007122061A1 EP 2007053030 W EP2007053030 W EP 2007053030W WO 2007122061 A1 WO2007122061 A1 WO 2007122061A1
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WIPO (PCT)
Prior art keywords
expansion
substrate
illuminating line
line
illumination
Prior art date
Application number
PCT/EP2007/053030
Other languages
French (fr)
Inventor
Rafael Egger
Piotr Marczuk
Wolfgang Seifert
Thorsten Tritschler
Markus Zenzinger
Willi Anderl
Jörg Walther
Original Assignee
Carl Zeiss Laser Optics Gmbh
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Filing date
Publication date
Application filed by Carl Zeiss Laser Optics Gmbh filed Critical Carl Zeiss Laser Optics Gmbh
Priority to EP07727502A priority Critical patent/EP2010355A1/en
Priority to JP2009505824A priority patent/JP2009534820A/en
Publication of WO2007122061A1 publication Critical patent/WO2007122061A1/en

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Classifications

    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/09—Beam shaping, e.g. changing the cross-sectional area, not otherwise provided for
    • 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
    • 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
    • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • B23K26/0648—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising lenses
    • 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
    • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • B23K26/0652—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms comprising prisms
    • 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
    • B23K26/064—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms
    • B23K26/066—Shaping the laser beam, e.g. by masks or multi-focusing by means of optical elements, e.g. lenses, mirrors or prisms by using masks
    • 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
    • B23K26/073—Shaping the laser spot
    • B23K26/0738—Shaping the laser spot into a linear shape
    • 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
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/0823—Devices involving rotation of the workpiece
    • 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
    • B23K26/08—Devices involving relative movement between laser beam and workpiece
    • B23K26/083—Devices involving movement of the workpiece in at least one axial direction
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L27/00—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate
    • H01L27/02—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier
    • H01L27/12—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier the substrate being other than a semiconductor body, e.g. an insulating body
    • H01L27/1214—Devices consisting of a plurality of semiconductor or other solid-state components formed in or on a common substrate including semiconductor components specially adapted for rectifying, oscillating, amplifying or switching and having at least one potential-jump barrier or surface barrier; including integrated passive circuit elements with at least one potential-jump barrier or surface barrier the substrate being other than a semiconductor body, e.g. an insulating body comprising a plurality of TFTs formed on a non-semiconducting substrate, e.g. driving circuits for AMLCDs
    • H01L27/1259—Multistep manufacturing methods
    • H01L27/127—Multistep manufacturing methods with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement
    • H01L27/1274—Multistep manufacturing methods with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement using crystallisation of amorphous semiconductor or recrystallisation of crystalline semiconductor
    • H01L27/1285—Multistep manufacturing methods with a particular formation, treatment or patterning of the active layer specially adapted to the circuit arrangement using crystallisation of amorphous semiconductor or recrystallisation of crystalline semiconductor using control of the annealing or irradiation parameters, e.g. using different scanning direction or intensity for different transistors
    • 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
    • H01L21/02367—Substrates
    • H01L21/0237—Materials
    • H01L21/02422—Non-crystalline insulating materials, e.g. glass, polymers
    • 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

Definitions

  • the disclosure relates to an apparatus for laser annealing of large substrates.
  • the disclosure also relates to a method for laser annealing of large substrates.
  • the conversion of a-Si into p-Si may be employed by heat treatment at around 1000 0 C. Such a procedure may only be used for a-Si on heat resistant substrates such as quartz. Such materials are expensive compared to normal float glass for display purposes.
  • Light or in particular laser light induced crystallization of a-Si allows the formation of p-Si from a-Si without destroying the substrate by the thermal load during crystallization.
  • Amorphous Silicon may be deposited by a low cost process such as sputtering or chemical vapor deposition (CVD) on substrates such as glass, quartz or synthetics.
  • the subsequent laser induced crystallization procedures are well known as excimer laser crystallization (ELC), sequential lateral solidification (SLS) or thin beam crystallization procedure (TDXTM).
  • ELC excimer laser crystallization
  • SLS sequential lateral solidification
  • TDXTM thin beam crystallization procedure
  • Line beams with a typical size of e.g. 0.5 mm x 300 mm and a homogeneous intensity distribution are for example applied in silicon annealing on large substrates using excimer laser crystallization (ELC).
  • ELC excimer laser crystallization
  • State-of-the-art optical systems use refractive optical illumination systems containing crossed cylindrical lens arrays to create the desired intensity distribution. These arrays, the functionality of which is e.g. described in US
  • 2003/0202251 Al are examples of a more general group of homogenization schemes that divide the input beam into multiple beams using suitably shaped sub apertures.
  • the superposition of these multiple beams in the field plane averages out intensity variations and homogenizes the beam.
  • the line beam scans the substrate in short axis or width direction, i.e. in the direction with less expansion of the illuminating line.
  • the present invention relates to an apparatus for laser annealing of large substrates
  • an optical device for generating a narrow illuminating line on an illumination plane of said substrate and a scanning device.
  • Said illumination line is generated from a laser beam and has a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple.
  • Said scanning device is constructed for scanning a first section of said illumination plane of said substrate in said second direction with said illuminating line.
  • the apparatus further comprises a rotating device for rotating said substrate relative to said illuminating line by 180° about an axis of rotation being normal to said illumination plane after scanning said first section.
  • the apparatus for laser annealing further comprises an adjustment device for adjusting the expansion of said illuminating line in said first direction to a predetermined length.
  • Adjustment device in particular means a device that allows variably limiting the expansion of said illuminating line during processing or at least before or after a laser annealing or laser crystallization processing step. The advantage of such an adjustment device is the possibility to predefine the area to be processed in the annealing step.
  • Said adjustment device may e.g. comprise at least a blade for clipping said illuminating line at least on one side of said illuminating line in said first direction.
  • One blade may be sufficient if one edge of the processed area and the outer edge of the substrate to be processed are already well defined with respect to each other. This may e.g. be the case if these edges are factory-made pre-adjusted, or if one edge of the illuminating line and one edge of the substrate may be pre-positioned with respect to each other by means of e.g. a movable stage carrying the substrate or a movable optical device.
  • said adjustment device may comprise a zoom optic for reducing the expansion of said illuminating line in said first direction.
  • the advantage of the zoom optic is the possibility to reduce laser power and increase the lifetime of the whole system.
  • a preferred embodiment comprises as a rotating device a rotatable stage carrying the substrate.
  • the stage may be used for positioning said substrate with respect to the illuminating line as already indicated above in the first and second direction. Therefore, the stage may preferably be linearly movable. Furthermore, the stage may be rotatable movable in order to allow a meander shape scan of the illuminating line over the substrate.
  • the present invention relates to the respective method.
  • the respective method for laser annealing of large substrates according to the invention comprises the steps of:
  • the rotation of the stage by 180° is important if the profile of the beam in said second direction is different for the leading and trailing edges.
  • the scan direction should be the same for both subsequent processing steps.
  • the expansion of said illuminating line is adjusted in said first direction to a predetermined length before and/or while scanning said first section.
  • the area to be processed in the first annealing step is thus predefined.
  • the expansion of said illuminating line is adjusted in said first direction to a predetermined length after scanning said first section but before and/or while scanning said second section.
  • the area to be processed in the second annealing step is thus predefined.
  • the seam inherently resulting from the processing procedure comprising two subsequent processing steps, namely one for annealing of a first section of the substrate and another for annealing of a second section of the substrate, may be defined to a certain extent.
  • the present invention relates to an apparatus for laser annealing of large substrates comprising two optical devices for generating narrow illuminating lines on an illumination plane. Both illuminating lines are generated from respective laser beams or from one laser beam, only. Both illuminating lines have a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple.
  • the apparatus further comprises a scanning device which is constructed for scanning a first section of said illumination plane of said substrate in said second direction with one of said illuminating lines and for scanning a second section of said illumination plane of said substrate in said second direction with said other illuminating line. Said optical device and said other optical device according to the invention are arranged such that said narrow illuminating line and said other narrow illuminating line form a continuous illuminating line on said illumination plane of said substrate.
  • said optical device and said other optical device are arranged such that said continuous illuminating line is a straight line having uniform intensity along said first direction and an intensity profile along said second direction, which does not change with position along said first direction.
  • This arrangement allows annealing and crystallization of e.g. Silicon films on large substrates in one annealing step and without having a mal-crystallized seam occurring when using other stitching methods.
  • said optical device and/or said other optical device comprise a long axis expansion limiting device for limiting said expansion of said illuminating line and/or said other illuminating device in said first direction.
  • said limiting device may comprise one or more clipping blades.
  • said optical device and/or said other optical device may comprise an adjustment device for adjusting the expansion of said one illuminating line and/or said other illuminating line and/or said resulting illuminating line in said first direction.
  • Said adjusting device may e.g. comprise a movable clipping blade and/or a zoom optic.
  • the sum of the one and other illuminating lines results in a straight illuminating line with preferably uniform intensity and second- direction- intensity-pro file along the long axis.
  • the generation of well defined coinciding intensity ramps is possible if said optical device and/or said other optical device are arranged with respect to said illumination plane of said substrate such that said illuminating line forms a slightly defocused illuminating line and/or said other illuminating line forms a slightly defocused other illuminating line on said illuminating plane.
  • the present invention relates to a respective method for laser annealing of large substrates comprising the steps of:
  • said illuminating line and/or said other illuminating line may slightly be defocused on said illuminating plane.
  • the defocus is such that the intensity of said illuminating line and/or said other illuminating line have a constant slope at the respective edge(s) in said long axis direction.
  • a typical value for the distance between illuminating plane and the best focus position is 2-3 times ⁇ /NA , whereby NA refers to the long axis numerical aperture of the beam and ⁇ it is the wavelength.
  • the present invention relates to an apparatus for laser annealing of large substrates with an optical device for generating a narrow illuminating line on an illumination plane of said substrate, said illumination line being generated from a laser beam and having a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple, and a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line in said second direction.
  • said optical device comprises at least two optical elements with refractive power being integral parts of a projection/reduction optics for forming said illumination line on said illumination plane.
  • a second alternative embodiment comprises another optical device for generating another narrow illuminating line on said illumination plane of said substrate, said other illumination line being generated from a laser beam and having a cross-section with an expansion in said first direction and an expansion in said second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple.
  • Said optical device comprises at least one optical element with refractive power being integral part of a projection/reduction optics for forming said illumination line on said illumination plane.
  • Said other optical device comprises at least one other optical element with refractive power being integral part of another projection/reduction optics for forming said other illumination line on said illumination plane.
  • Said at least one optical element and said at least one other optical element being arranged adjacent to each other in said first direction.
  • Said optical elements and/or said optical element and said other optical element may be lenses or mirrors.
  • Said optical elements and/or said optical element and said other optical element preferably are the last optical elements with refractive power used for the projection/reduction optics.
  • a protection window between projection/reducing optics and substrate is not meant with the wording "optical element with refractive power" but only such optical elements which are involved in the projection/reduction act as such, only.
  • the present invention relates to another apparatus for laser annealing of large substrates
  • an optical device for generating a narrow illuminating line on an illumination plane of said substrate, said illumination line being generated from a laser beam and having a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple, and a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line in said second direction.
  • said optical device comprises one last optical element with refractive power which is integral part of a projection/reduction optics for forming said illumination line on said illumination plane.
  • the distance between said last optical element and said illumination plane of said substrate is chosen to be larger than 500 mm.
  • the distance between said last optical element and said illumination plane of said substrate may also be larger than 600 mm.
  • the distance is larger than 700 mm, more preferably larger than 800 mm, much more preferably larger than 900 mm and most preferably larger than 1000 mm.
  • said optical device may comprise a long axis beam expanding device for expanding said laser beam in said first direction to the expansion of said illuminating line in said first direction by an expansion angle, whereby said expansion angle is larger than 7°.
  • Said expansion angle may be larger than 15°.
  • Preferably said expansion angle is larger than 20°, more preferably larger than 25°, much more preferably larger than 30° and most preferably larger than 35°.
  • Figure 1 is a schematic illustration of an apparatus according to a first embodiment in top view showing the surface of a substrate and an illuminating line.
  • Figure 2 is a schematic illustration of the apparatus according to said first embodiment of Figure 1 in top view showing the surface of said substrate and said illuminating line after a first scanning step.
  • Figure 3 is a schematic illustration of the apparatus according to said first embodiment of Figures 1 and 2 in top view showing the surface of said substrate during rotation about an axis of rotation.
  • Figure 4 is a schematic illustration of the apparatus according to said first embodiment of Figures 1, 2 and 3 in top view showing the surface of said substrate after rotation about said axis of rotation by 180°.
  • Figure 5 is a schematic illustration of the apparatus according to said first embodiment of Figures 1 to 4 in top view showing the surface of said substrate after a second scanning step.
  • Figure 6 is a schematic illustration of an optical device according to the state of the art for generating a narrow illuminating line on an illumination plane of a substrate.
  • the optical device is drawn in the xz-plane of a Cartesian coordinate system.
  • Figure 7 is a schematic illustration of the optical device according to Figure 6 in the yz-plane of said Cartesian coordinate system.
  • Figure 8 is a schematic illustration of an optical device according to the invention for generating a narrow illuminating line on an illumination plane of a substrate.
  • the optical device is shown in the xz-plane of a Cartesian coordinate system.
  • Figure 9 are intensity profiles of the illuminating lines being generated in the illumination plane by the two optical devices forming the optical arrangement shown in Figure 8.
  • Figure 10 is the sum intensity profile resulting from a summation of the individual intensity profiles shown in Figure 9.
  • Figure 11 are other intensity profiles of the illuminating lines being generated in the illumination plane by the two optical devices forming the optical arrangement shown in Figure 8.
  • Figure 12 show intensity profiles of the illuminating lines when clipping beams forming the illuminating lines in the adjacent area.
  • Figure 13 is the sum intensity profile resulting from a summation of the individual intensity profiles shown in Figure 12.
  • Figure 14 is a schematic illustration of another embodiment of an optical device according to the invention for generating a narrow illuminating line on an illumination plane of a substrate.
  • the optical device is shown in the xz- plane of a Cartesian coordinate system.
  • Figure 15 shows the intensity profile of the illuminating line generated by the optical device according to Figure 14 and schematically the surface of the substrate being processed by means of said optical device according to Figure 14.
  • Figure 16 is a schematic illustration of an optical device according to the invention for generating a narrow illuminating line on an illumination plane of a substrate.
  • the optical device is drawn in the xz-plane of a Cartesian coordinate system
  • the long axis is the axis which is perpendicular to the scan direction.
  • the short axis is the axis which is parallel to the scan direction.
  • optical elements are lenses.
  • the optical element which focuses the beam in the short axis direction and the optical element which projects the field defining element onto the substrate are mirrors.
  • the so called bow tie error can be prevent if cylindrical mirrors are used instead of cylindrical lenses.
  • the apparatus for laser annealing of large substrates comprises an optical device for generating a narrow illuminating line of known type. Examples for such an optical device are e.g. disclosed in US 2006/0209310 Al. An alternative optical device is disclosed in US 5,721,416 A.
  • the apparatus further comprises a stage where the substrate may be positioned. The stage may be moved in a linear direction such that the illumination line scans the surface of said substrate. Furthermore, the stage may be rotated about an axis of rotation being normal to said surface of said substrate.
  • Figure 1 shows a schematic illustration of said apparatus in top view.
  • the drawing shows the surface 36 of said substrate 32 and said illuminating line 31 being generated by above mentioned optical device.
  • the substrate 32 is of rectangular shape and has a length 1 and a width w.
  • the lengthwise direction is in parallel to the y-direction of a Cartesian coordinate system, the widthwise direction is in parallel to the x-direction.
  • the substrate may e.g. be a conventional float glass covered by a thin amorphous Silicon layer of 50 nm in thickness.
  • the illuminating line 31 has also a mainly rectangular shape in the xy-plane with expansions in the perpendicular directions x and y of said Cartesian coordinate system.
  • the expansion in y-direction is indicated with the reference number A s
  • the expansion in x- direction is indicated with reference number A 1 .
  • the short axis expansion A s may for example be around 5-7 ⁇ m
  • the expansion in long axis direction Ai may e.g. be 730 mm. It is assumed that in long axis Ai direction x the illumination line 31 is homogeneous, i.e. the intensity is uniform as far as possible.
  • the intensity profile may also be uniform and the slope of the intensity at the edges may be as high as possible (top hat profile).
  • the illuminating line 31 may also have an intensity profile similar to that shown in Figure 36 of US 2006/0209310 Al, i.e. a profile with a less steep leading edge L as compared to the trailing edge T.
  • leading edge L and trailing edge T of the illuminating line 31 shown in Figure 1 are indicated with respective reference characters.
  • the reference characters used in Figure 1 of the present application coincide with the respective reference characters in Figure 36 of US 2006/0209310 Al.
  • the idea according to the present invention is to use a laser line 31 which is shorter than the width w of the substrate 32.
  • the substrate 32 has to be processed in two steps as shown in Figures 1 to 5.
  • the size of the thin laser beam 31 in lengthwise direction Ai is clipped by blades to the desired size.
  • a zoom optic can be used to adjust the size of the beam 31.
  • the advantage of the zoom optic is the possibility to reduce laser power and increase the lifetime of the whole system.
  • the substrate 32 is processed in a first step at only one side.
  • the stage is linearly moved in scanning direction 35 such that said illuminating line 31 scans a first section of the surface 36 of said substrate 32 resulting in a crystallization of the Silicon in said section.
  • Figure 2 shows the substrate 32 and said illuminating line 31 after said processing step.
  • the crystallized section of the substrate 32 is indicated with reference number 37 in Figure 2, the not crystallized section is indicated with reference number 36.
  • the size of the thin laser beam 33 has to be adjusted again, e.g. by means of blades or a zoom optic as already described above.
  • the substrate 32 is processed in a second step at the other side.
  • the stage is linearly moved in scanning direction 35 such that said illuminating line 33 scans a second section of the surface 36 of said substrate 32 adjacent to said first section resulting in a crystallization of the Silicon in said second section.
  • Figure 5 shows the substrate 32 and said illuminating line 33 after said processing step.
  • the crystallized sections of the substrate 32 are indicated with reference number 37.
  • At the edge of the laser beam 33 in long axis direction Ai adjoining the previously crystallized section 37 there will be a resulting seam 34. This is because of the drop in energy density at the edge of the beam 33.
  • the seam 34 can be very small if the beam clipping blade is close to the substrate 32 and the resulting ramp in the energy density has therefore a small size
  • the position of the seam can be moved according to the adjustment of the laser beam size in the long axis Ai direction x.
  • a rotating stage can be used in a very flexible way. For example rotating the stage by 90° will affect the orientation of the Si crystals and defines a preferred direction for further electronic components on the substrate.
  • a tilt of the stage of a few degrees can prevent the appearance of structures after processing.
  • An advantage of the first preferred embodiment of the present invention is that an existing system for a Gen4 size panel (730 mm x 920 mm) can be upgraded to a Gen5 size of 1100 mm x 1300 mm. Also the required transmission of the system will be the same.
  • Second preferred embodiment Stitching of lenses or/and mirrors
  • Another possibility to extend the length of the laser beam at the substrate is to stitch at least one of the lenses of mirrors of the optical device which generates said narrow illuminating line on the illumination plane of said substrate.
  • the lens (mirror) which is closest to the substrate must have a large extension in the long axis direction.
  • Figures 6 and 7 show the main principle of an optical device being capable of generating a narrow illuminating line.
  • Figure 6 is a plane view in the xz-plane of an optical device according to the prior art.
  • Figure 7 is a plane view in the yz-plane of the same optical device.
  • the optical device comprises two cylindrical lens arrays Ia, Ib forming a two- stage fly's eye homogenizer and a convex cylindrical condenser lens 3 which are optically active in x-direction.
  • the optical device further comprises a sliced cylindrical lens 2 consisting of a plurality (here three) cylinder lens segments 2a, 2b, 2c, a cylindrical lens 4 and a projection, namely a reducing optics, in particular in the example shown in Figures 6 and 7 a cylindrical lens 5 being optically active in y-direction.
  • a sliced cylindrical lens 2 consisting of a plurality (here three) cylinder lens segments 2a, 2b, 2c, a cylindrical lens 4 and a projection, namely a reducing optics, in particular in the example shown in Figures 6 and 7 a cylindrical lens 5 being optically active in y-direction.
  • the homogenizer for the long axis Ai direction x is built by said two cylindrical lens arrays Ia, Ib each comprising a plurality of cylindrical lenslets laa, lab, lac and lba, lbb, lbc, respectively, being arranged adjacent to each other and each having a focal length fi resulting in a focal length f arra y of said arrangement of arrays Ia, Ib and said condenser cylindrical lens 3 with a focal length f 3 .
  • An incoming laser beam 10 propagating in z- direction is split into a plurality of beamlets corresponding to the number of cylindrical lenslets laa, lab, lac of the first cylindrical lens array Ia.
  • Each beamlet is focused in the distance of the focal length f arra y and forms a diverging bundle of rays when hitting said condenser lens 3.
  • the condenser lens 3 transforms the angular distribution of the beamlets to a field distribution in the plane 6, where a substrate is to be located.
  • the size of the field depends on the focal length f 3 of the lens 3 and the maximum angle of the angular distribution of each beam let caused by the arrays Ia, Ib.
  • a possible homogenization scheme for the short axis A s is the sliced lens 2 concept already described in US 2006/0209310 Al.
  • the individual cylindrical lens lets 2a, 2b, 2c with curvatures in short axis A s direction y are shifted independently in direction y to the short axis A 8 .
  • the main beam 10a in short axis A s direction y is deflected depending on the amount of shift.
  • the size of the lenslets 2a, 2b, 2c in direction to the long axis Ai is equivalent to the size of one of the cylindrical lens elements laa, lab, lac of the lens array Ia.
  • the width of the beam depends on the divergence of the incoming beam in the short axis A s direction y. Because of overlapping several of these beamlets displaced by each other a homogenized beam profile in short axis A s direction y can be generated.
  • a field defining element 7 for example a field stop, can be placed at the position of the focused beam on the short axis A s direction y .
  • the projection optics 5 images the field defining element 7 onto the plane of the substrate 6.
  • the projection optics 5 in the present case is a cylindrical lens (an alternative may be a mirror) which does not affect the propagation of the beam in long axis Ai direction x.
  • the projection optics 5 may also reduce the expansion of the beam in short axis A s direction y.
  • the optical element 5 has a large extension in the long axis Ai direction x.
  • the following solutions are describing how larger field sizes can be achieved with limited size of the optical element 5 (in long axis Ai direction x).
  • Figure 8 shows two identical devices as shown in Figures 6 and 7 which are stitched together in long axis Ai direction x.
  • the cylindrical lenses 5 are arranged adjacent to each other in long axis Ai direction x.
  • the gap 5g between the two cylindrical lenses 5 is predefined such that at least the adjacent edge slopes of said illumination lines 6a, 6b being generated on the surface, namely the illumination plane 6, of said substrate at least partially overlap.
  • the two field distributions 11, 12 of the illuminating lines 6a, 6b intersect at the 50 % intensity value. If the two curves 11, 12 have an intensity distribution with the same linear slope at the edge the summation 13 of both curves 11, 12 which is shown in Figure 10 leads to a constant intensity all over the field. Small residual deviations from the linear slope as well as residual inhomogeneities in the intensity of the two field distributions 11, 12, may result in an overall intensity inhomogeneity.
  • a defined ramp can be achieved if the substrate plane 6 is not in the focal plane of the condenser lens 3 but slightly defocused.
  • the advantage of this scheme is that very large fields 13a can be produced.
  • Another possibility is to increase the overlap area 9, i.e. by increasing the distance of the imaging optics 5 to the substrate 6 or by increasing the angle of the beam in the long axis Ai direction x.
  • the initial field distributions 21, 22 of the two beams are shown in Figure 11.
  • the position of the intersection of illumination line 6a and illumination line 6b can be chosen over a wide range. This is indicated exemplarily by the different expansions of the beam profiles 21, 22 shown in Figure 12.
  • Figure 14 shows a plane view of an optical device in the xz-plane according to the invention.
  • the optical device comprises the same optical elements as compared to that disclosed in Figures 6 and 7.
  • the optical device comprises two cylindrical lens arrays Ia, Ib forming a two-stage fly's eye homogenizer and a convex cylindrical condenser lens 3 which are optically active in x-direction.
  • the optical device further comprises a sliced cylindrical lens 2 consisting of a plurality (here three) cylinder lens segments 2a, 2b, 2c, a cylindrical lens 4 and a projection optics, namely a reducing optics, in particular in the example referred to a cylindrical lens 5, being optically active in y- direction.
  • a field defining optical element e.g. a field stop 7
  • the illumination is modified in a way to increase the size Ai in long axis direction x of the field 6.
  • the upper part of Figure 15 shows the intensity profile 41 of the illuminating line 6 being generated by the optical device shown in Figure 14 and being the sum of the profiles 42, 43 of the beams 26c, 26d transmitting the lenses 5a, 5b being stitched together, respectively.
  • the total field size 46 is larger than the size 47 of the substrate 40 (see substrate 40 in the lower part of Figure 15). Therefore, the incoming laser beam 26 may be clipped on one or both sides by means of respective blades 8a, 8b.
  • blade 8a limits the expansion of the beam 26 resulting in an actual size 48 of the field shown on top of Figure 15.
  • the illumination line 6 with reduced expansion Ai in long axis direction x is scanned over the illumination plane of the substrate 40 by moving the substrate 40 in scanning direction 45. Due to the stitching lenses 5 a, 5b the intensity profile 41 of the illuminating line 6 has a discontinuity 49 in intensity. This discontinuity 49 results in a seam 44 after processing of the substrate 40. Depending on the allowed position of the seam 44 after processing the field size may be limited with the same degree on both sides resulting in a seam 44 being in the centre. Alternatively, the field may also be only limited at one side resulting in a seam 44 being off centred. The bottom of Figure 15 shows an off centred seam 44.
  • the stage carrying the substrate 40 may be moved in the long axis direction x as is indicated with reference number 45 a
  • the stage carrying the substrate 40 may be larger than the substrate 40.
  • the substrate 40 is adjusted with the use of limiters 8a, 8b to the actual field Third preferred embodiment: Modifying angular distribution and distances
  • Figure 16 shows a plane view in the xz-plane of an optical device of the present invention the functionality of which but not the particular layout is known from prior art.
  • the components of the optical device are those as already shown in Figures 6 and 7.
  • the optical device comprises two cylindrical lens arrays Ia, Ib forming a two-stage fly's eye homogenizer and a convex cylindrical condenser lens 3 which are optically active in x- direction.
  • the optical device further comprises a sliced cylindrical lens 2 consisting of a plurality (here three) cylinder lens segments 2a, 2b, 2c, a cylindrical lens 4 and a projection optics, namely a reducing optics, in particular a cylindrical lens 5, being optically active only in y-direction.
  • a laser beam 10 emitted from a high power laser source (not shown) is converted into a narrow illuminating line 6 on the surface of a substrate.
  • the extension of the field at the last lens 5 or mirror is significantly smaller than the size of the field 6 at the substrate.
  • the difference in field size is increased by the following actions:
  • the distance d between the last optical element 5 (Remark: The wording "last optical element” means here the last lens or mirror which is used for the projection optics. A protection window between projection optics and substrate does not count as an optical element here) and the substrate (position of the illuminating line 6) may be increased. This is possible if the aperture of the optical element 5 is increased in the short axis direction y or/and the numerical aperture NA in short axis direction y at the substrate is decreased.
  • the target for the distance d is a value larger than 500 mm. Favourable the distance is larger than 600mm.
  • the angle ⁇ of the edge beam 51 can be increased.
  • the energy density at the substrate is reduced at the edge by the cosine law.
  • additional aberrations will require a modified design of the homogenizer.
  • This design will require several lenses and possibly at least one aspheric cylindrical lens.
  • the maximum angle ⁇ in the long axis direction x should be larger then 7°.
  • the angle ⁇ should be larger than 15°. I.e. if the distance d between optical element 5 and substrate is 600 mm and the angle ⁇ is 15° a field Ai of 1100 mm can be produced with an optical element 5 with the size of 780 mm. For an angle ⁇ of 20° the size of the element 5 is reduced further to 660 mm.

Abstract

The invention relates to an apparatus for laser annealing of large substrates comprising an optical device for generating a narrow illuminating line (31) on an illumination plane (36) of said substrate (32), said illumination line (31) being generated from a laser beam and having a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple, and a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line in said second direction. According to the invention the apparatus comprises a rotating device for rotating (39) said substrate (32) relative to said illuminating line (31) by 180° about an axis (38) of rotation being normal to said illumination plane (36) after scanning said first section (37), whereby said scanning device is constructed for scanning a second section of said illumination plane (36) of said substrate (32) being adjacent to said first section of said illumination plane (36) of said substrate (32) with said illuminating line (31) in said second direction (y).

Description

APPARATUS FOR LASER ANNEALING OF LARGE SUBSTRATES AND METHOD FOR LASER ANNEALING OF LARGE SUBSTRATES
CROSS-REFERENCE TO RELATED APPLICATIONS
Under 35 U.S. C. 119(e)(l), this application claims priority to Provisional Application No. 60/745,333, filed on April 21, 2006.
TECHNICAL FIELD
The disclosure relates to an apparatus for laser annealing of large substrates. The disclosure also relates to a method for laser annealing of large substrates.
BACKGROUND
The conversion of a-Si into p-Si may be employed by heat treatment at around 1000 0C. Such a procedure may only be used for a-Si on heat resistant substrates such as quartz. Such materials are expensive compared to normal float glass for display purposes.
Light or in particular laser light induced crystallization of a-Si allows the formation of p-Si from a-Si without destroying the substrate by the thermal load during crystallization.
Amorphous Silicon may be deposited by a low cost process such as sputtering or chemical vapor deposition (CVD) on substrates such as glass, quartz or synthetics. The subsequent laser induced crystallization procedures are well known as excimer laser crystallization (ELC), sequential lateral solidification (SLS) or thin beam crystallization procedure (TDX™). An overview of these different fabrication procedures is e.g. given by D. S. Knowles et al. "Thin Beam Crystallization Method: A New Laser Annealing Tool with Lower Cost and Higher Yield for LTPS Panels" in SID 00 Digest, 1-3; Ji-Yong Park et al. "P-60: Thin Laser Beam Crystallization method for SOP and OLED application" in SID 05 Digest, 1-3 and in a brochure of the TCZ GmbH Company entitled "LCD Panel Manufacturing Moves to the next Level-Thin-Beam Directional X'tallization (TDX) Improves Yield, Quality and Throughput for Processing Poly-Silicon LCDs". Polycrystalline Silicon produced by one of these methods is called low temperature polycrystalline Si (LTPS).
Most of above mentioned laser crystallization procedures have in common that a focused laser beam is scanned over the substrate by moving a stage carrying the substrate and/or by moving the laser beam.
Line beams with a typical size of e.g. 0.5 mm x 300 mm and a homogeneous intensity distribution are for example applied in silicon annealing on large substrates using excimer laser crystallization (ELC). State-of-the-art optical systems use refractive optical illumination systems containing crossed cylindrical lens arrays to create the desired intensity distribution. These arrays, the functionality of which is e.g. described in US
2003/0202251 Al, are examples of a more general group of homogenization schemes that divide the input beam into multiple beams using suitably shaped sub apertures. The superposition of these multiple beams in the field plane averages out intensity variations and homogenizes the beam. The line beam scans the substrate in short axis or width direction, i.e. in the direction with less expansion of the illuminating line.
The future tendency is to reduce the width or short axis expansion as far as possible and to increase the length or long axis dimension of the line beam used for crystallization of the amorphous Silicon film. Therefore, US 2006/0209310 Al, which is herewith incorporated by reference, discloses for the crystallization process a long thin beam with the size of 5-15 μm x 700 mm or more (e.g. 5 μm x 730 mm) scanning the surface of the substrate in short axis direction. Such a thin and long illumination line with uniform or at least predetermined intensity distribution is produced from a beam being emitted from an Excimer laser by means of a specific homogenization scheme followed by a projection/reducing optics projecting/reducing said homogenized beam on the illumination plane. PROBLEM TO BE SOLVED
In order to increase the throughput the trend for the future is to use larger substrates. Especially for the "Thin beam Directional X'talization" (TDX™) process where a thin but long line beam is used the extension of the length leads to several problems:
• The large size requires large mirrors or lenses. The size is limited by machine lengths that are used for the production of lenses and mirrors and by coating technologies
• Increasing of the length requires higher effective transmission. The required transmission is proportional to the length of the line
SUMMARY
Therefore, it is an object of the present invention to provide an alternative solution for an apparatus and a method for processing larger substrates and in particular for substrates exceeding the dimensions used until now.
According to a first aspect, the present invention relates to an apparatus for laser annealing of large substrates comprising an optical device for generating a narrow illuminating line on an illumination plane of said substrate and a scanning device. Said illumination line is generated from a laser beam and has a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple. Said scanning device is constructed for scanning a first section of said illumination plane of said substrate in said second direction with said illuminating line. The main idea is that the apparatus further comprises a rotating device for rotating said substrate relative to said illuminating line by 180° about an axis of rotation being normal to said illumination plane after scanning said first section. Furthermore, said scanning device is constructed for scanning a second section of said illumination plane of said substrate being adjacent to said first section of said illumination plane of said substrate in said second direction with said illuminating line. Preferably, the apparatus for laser annealing further comprises an adjustment device for adjusting the expansion of said illuminating line in said first direction to a predetermined length. Adjustment device in particular means a device that allows variably limiting the expansion of said illuminating line during processing or at least before or after a laser annealing or laser crystallization processing step. The advantage of such an adjustment device is the possibility to predefine the area to be processed in the annealing step.
Said adjustment device may e.g. comprise at least a blade for clipping said illuminating line at least on one side of said illuminating line in said first direction. One blade may be sufficient if one edge of the processed area and the outer edge of the substrate to be processed are already well defined with respect to each other. This may e.g. be the case if these edges are factory-made pre-adjusted, or if one edge of the illuminating line and one edge of the substrate may be pre-positioned with respect to each other by means of e.g. a movable stage carrying the substrate or a movable optical device.
Instead of one or more blades or in addition said adjustment device may comprise a zoom optic for reducing the expansion of said illuminating line in said first direction. The advantage of the zoom optic is the possibility to reduce laser power and increase the lifetime of the whole system.
A preferred embodiment comprises as a rotating device a rotatable stage carrying the substrate. The stage may be used for positioning said substrate with respect to the illuminating line as already indicated above in the first and second direction. Therefore, the stage may preferably be linearly movable. Furthermore, the stage may be rotatable movable in order to allow a meander shape scan of the illuminating line over the substrate.
According to a second aspect, the present invention relates to the respective method. The respective method for laser annealing of large substrates according to the invention comprises the steps of:
• generating a narrow illuminating line on an illumination plane of said substrate from a laser beam, said illuminating line having a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple,
• scanning a first section of said illumination plane of said substrate with said illuminating line in said second direction, • rotating said substrate relative to said illuminating line by 180° about an axis of rotation being normal to said illumination plane,
• scanning a second section of said illumination plane of said substrate being adjacent to said first section of said illumination plane of said substrate with said illuminating line in said second direction.
The rotation of the stage by 180° is important if the profile of the beam in said second direction is different for the leading and trailing edges. In order to achieve similar annealing/crystallization quality results for both subsequently processed sections of the substrate the scan direction should be the same for both subsequent processing steps.
Preferably, the expansion of said illuminating line is adjusted in said first direction to a predetermined length before and/or while scanning said first section. The area to be processed in the first annealing step is thus predefined.
Furthermore, preferably the expansion of said illuminating line is adjusted in said first direction to a predetermined length after scanning said first section but before and/or while scanning said second section. The area to be processed in the second annealing step is thus predefined.
It is advantageous if the expansion of said illuminating line is adjusted such that the gap between said first and second sections or the overlap of said first and second sections has a predetermined value. The seam inherently resulting from the processing procedure comprising two subsequent processing steps, namely one for annealing of a first section of the substrate and another for annealing of a second section of the substrate, may be defined to a certain extent.
According to a third aspect, the present invention relates to an apparatus for laser annealing of large substrates comprising two optical devices for generating narrow illuminating lines on an illumination plane. Both illuminating lines are generated from respective laser beams or from one laser beam, only. Both illuminating lines have a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple. The apparatus further comprises a scanning device which is constructed for scanning a first section of said illumination plane of said substrate in said second direction with one of said illuminating lines and for scanning a second section of said illumination plane of said substrate in said second direction with said other illuminating line. Said optical device and said other optical device according to the invention are arranged such that said narrow illuminating line and said other narrow illuminating line form a continuous illuminating line on said illumination plane of said substrate.
In a preferred embodiment said optical device and said other optical device are arranged such that said continuous illuminating line is a straight line having uniform intensity along said first direction and an intensity profile along said second direction, which does not change with position along said first direction. This arrangement allows annealing and crystallization of e.g. Silicon films on large substrates in one annealing step and without having a mal-crystallized seam occurring when using other stitching methods.
In another preferred embodiment said optical device and/or said other optical device comprise a long axis expansion limiting device for limiting said expansion of said illuminating line and/or said other illuminating device in said first direction. This solution is advantageous for the generation of well defined one and other illuminating lines and in particular in order to produce a continuous illuminating line with pre-defined intensity profile in said first long axis direction.
Similar to the embodiments described with respect to the first aspect of the invention said limiting device may comprise one or more clipping blades.
It is favourable if the expansion of the illuminating line(s) in long axis direction is (are) not only factory-made pre-adjusted. Some applications may require an adjustment during processing or in particular between two processing steps. Therefore, said optical device and/or said other optical device may comprise an adjustment device for adjusting the expansion of said one illuminating line and/or said other illuminating line and/or said resulting illuminating line in said first direction.
Said adjusting device may e.g. comprise a movable clipping blade and/or a zoom optic.
As already mentioned above it is advantageous if the sum of the one and other illuminating lines results in a straight illuminating line with preferably uniform intensity and second- direction- intensity-pro file along the long axis. This requires that the edges of the illuminating lines being stitched together have well defined and pre-known intensity ramps. The generation of well defined coinciding intensity ramps is possible if said optical device and/or said other optical device are arranged with respect to said illumination plane of said substrate such that said illuminating line forms a slightly defocused illuminating line and/or said other illuminating line forms a slightly defocused other illuminating line on said illuminating plane.
According to a fourth aspect, the present invention relates to a respective method for laser annealing of large substrates comprising the steps of:
• generating a narrow illuminating line on an illumination plane of said substrate from a laser beam, said illuminating line having a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple,
• scanning a first section of said illumination plane of said substrate with said illuminating line in said second direction, • generating another narrow illuminating line on said illumination plane of said substrate, said other illumination line being generated from a laser beam and having a cross-section with an expansion in said first direction and an expansion in said second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple, • stitching said narrow illuminating line and said other narrow illuminating line for forming a continuous, preferably straight illuminating line on said illumination plane of said substrate and having preferably uniform intensity (and predetermined, in particular uniform second-direction-intensity-profile) along said first direction. In order to define the processed area as well as the long axis intensity profile during fabrication the expansion of said illuminating line and/or said other illuminating line may be limited or adjusted in said first direction.
In order to generate well defined intensity ramps in long axis direction said illuminating line and/or said other illuminating line may slightly be defocused on said illuminating plane. Preferably, the defocus is such that the intensity of said illuminating line and/or said other illuminating line have a constant slope at the respective edge(s) in said long axis direction. A typical value for the distance between illuminating plane and the best focus position is 2-3 times λ/NA , whereby NA refers to the long axis numerical aperture of the beam and λ it is the wavelength.
According to a fifth aspect, the present invention relates to an apparatus for laser annealing of large substrates with an optical device for generating a narrow illuminating line on an illumination plane of said substrate, said illumination line being generated from a laser beam and having a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple, and a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line in said second direction. In a first alternative embodiment said optical device comprises at least two optical elements with refractive power being integral parts of a projection/reduction optics for forming said illumination line on said illumination plane. Said at least two optical elements are arranged adjacent to each other in said first direction. A second alternative embodiment comprises another optical device for generating another narrow illuminating line on said illumination plane of said substrate, said other illumination line being generated from a laser beam and having a cross-section with an expansion in said first direction and an expansion in said second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple. Said optical device comprises at least one optical element with refractive power being integral part of a projection/reduction optics for forming said illumination line on said illumination plane. Said other optical device comprises at least one other optical element with refractive power being integral part of another projection/reduction optics for forming said other illumination line on said illumination plane. Said at least one optical element and said at least one other optical element being arranged adjacent to each other in said first direction.
Said optical elements and/or said optical element and said other optical element may be lenses or mirrors.
Said optical elements and/or said optical element and said other optical element preferably are the last optical elements with refractive power used for the projection/reduction optics. A protection window between projection/reducing optics and substrate is not meant with the wording "optical element with refractive power" but only such optical elements which are involved in the projection/reduction act as such, only.
According to a sixth aspect, the present invention relates to another apparatus for laser annealing of large substrates comprising an optical device for generating a narrow illuminating line on an illumination plane of said substrate, said illumination line being generated from a laser beam and having a cross-section with an expansion in a first direction and an expansion in a second direction, whereby said expansion in said first direction exceeds said expansion in said second direction by a multiple, and a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line in said second direction. According to the invention said optical device comprises one last optical element with refractive power which is integral part of a projection/reduction optics for forming said illumination line on said illumination plane. In order to increase the length dimension of the illuminating line produced by the optical device the distance between said last optical element and said illumination plane of said substrate is chosen to be larger than 500 mm.
The distance between said last optical element and said illumination plane of said substrate may also be larger than 600 mm. Preferably the distance is larger than 700 mm, more preferably larger than 800 mm, much more preferably larger than 900 mm and most preferably larger than 1000 mm.
Alternatively or additionally said optical device may comprise a long axis beam expanding device for expanding said laser beam in said first direction to the expansion of said illuminating line in said first direction by an expansion angle, whereby said expansion angle is larger than 7°.
Said expansion angle may be larger than 15°. Preferably said expansion angle is larger than 20°, more preferably larger than 25°, much more preferably larger than 30° and most preferably larger than 35°.
Most of the described solutions will lead to a resulting seam at the substrate. This seam is due to a discontinuity due to stitching of two mirrors or lenses or by a two step process technology. In general a seam is not problematic because the substrate will be cut anyway. But depending on the size of the desired panels the cut line can be in the center of the substrate or also off centered. Therefore all described solutions have the possibility to move the position of the seam.
BRIEF DESCRIPTION OF THE DRAWINGS
Embodiments are shown in the drawings and will be described hereinafter in more detail with reference to the drawings. Identical or functionally similar components are identified with the same reference numbers. In the drawings:
Figure 1 is a schematic illustration of an apparatus according to a first embodiment in top view showing the surface of a substrate and an illuminating line.
Figure 2 is a schematic illustration of the apparatus according to said first embodiment of Figure 1 in top view showing the surface of said substrate and said illuminating line after a first scanning step.
Figure 3 is a schematic illustration of the apparatus according to said first embodiment of Figures 1 and 2 in top view showing the surface of said substrate during rotation about an axis of rotation. Figure 4 is a schematic illustration of the apparatus according to said first embodiment of Figures 1, 2 and 3 in top view showing the surface of said substrate after rotation about said axis of rotation by 180°.
Figure 5 is a schematic illustration of the apparatus according to said first embodiment of Figures 1 to 4 in top view showing the surface of said substrate after a second scanning step.
Figure 6 is a schematic illustration of an optical device according to the state of the art for generating a narrow illuminating line on an illumination plane of a substrate. The optical device is drawn in the xz-plane of a Cartesian coordinate system.
Figure 7 is a schematic illustration of the optical device according to Figure 6 in the yz-plane of said Cartesian coordinate system.
Figure 8 is a schematic illustration of an optical device according to the invention for generating a narrow illuminating line on an illumination plane of a substrate. The optical device is shown in the xz-plane of a Cartesian coordinate system.
Figure 9 are intensity profiles of the illuminating lines being generated in the illumination plane by the two optical devices forming the optical arrangement shown in Figure 8.
Figure 10 is the sum intensity profile resulting from a summation of the individual intensity profiles shown in Figure 9.
Figure 11 are other intensity profiles of the illuminating lines being generated in the illumination plane by the two optical devices forming the optical arrangement shown in Figure 8. Figure 12 show intensity profiles of the illuminating lines when clipping beams forming the illuminating lines in the adjacent area.
Figure 13 is the sum intensity profile resulting from a summation of the individual intensity profiles shown in Figure 12.
Figure 14 is a schematic illustration of another embodiment of an optical device according to the invention for generating a narrow illuminating line on an illumination plane of a substrate. The optical device is shown in the xz- plane of a Cartesian coordinate system.
Figure 15 shows the intensity profile of the illuminating line generated by the optical device according to Figure 14 and schematically the surface of the substrate being processed by means of said optical device according to Figure 14.
Figure 16 is a schematic illustration of an optical device according to the invention for generating a narrow illuminating line on an illumination plane of a substrate. The optical device is drawn in the xz-plane of a Cartesian coordinate system
In the following description the long axis is the axis which is perpendicular to the scan direction. The short axis is the axis which is parallel to the scan direction.
For simplicity all shown optical elements are lenses. In general it is advantageous if the optical element which focuses the beam in the short axis direction and the optical element which projects the field defining element onto the substrate are mirrors. As explained in WO 2006/066687 Al the so called bow tie error can be prevent if cylindrical mirrors are used instead of cylindrical lenses.
First preferred embodiment: Rotation of a stage
A first preferred embodiment according to the invention is described referring to Figures 1 to 5. The apparatus for laser annealing of large substrates according to the first preferred embodiment comprises an optical device for generating a narrow illuminating line of known type. Examples for such an optical device are e.g. disclosed in US 2006/0209310 Al. An alternative optical device is disclosed in US 5,721,416 A. The apparatus further comprises a stage where the substrate may be positioned. The stage may be moved in a linear direction such that the illumination line scans the surface of said substrate. Furthermore, the stage may be rotated about an axis of rotation being normal to said surface of said substrate.
Figure 1 shows a schematic illustration of said apparatus in top view. The drawing shows the surface 36 of said substrate 32 and said illuminating line 31 being generated by above mentioned optical device. The substrate 32 is of rectangular shape and has a length 1 and a width w. The lengthwise direction is in parallel to the y-direction of a Cartesian coordinate system, the widthwise direction is in parallel to the x-direction. The substrate may e.g. be a conventional float glass covered by a thin amorphous Silicon layer of 50 nm in thickness.
The illuminating line 31 has also a mainly rectangular shape in the xy-plane with expansions in the perpendicular directions x and y of said Cartesian coordinate system. The expansion in y-direction is indicated with the reference number As, the expansion in x- direction is indicated with reference number A1. The short axis expansion As may for example be around 5-7 μm, the expansion in long axis direction Ai may e.g. be 730 mm. It is assumed that in long axis Ai direction x the illumination line 31 is homogeneous, i.e. the intensity is uniform as far as possible. In short axis As direction y the intensity profile may also be uniform and the slope of the intensity at the edges may be as high as possible (top hat profile). Instead of a uniform top hat profile in y-direction, the illuminating line 31 may also have an intensity profile similar to that shown in Figure 36 of US 2006/0209310 Al, i.e. a profile with a less steep leading edge L as compared to the trailing edge T. Both, leading edge L and trailing edge T of the illuminating line 31 shown in Figure 1 are indicated with respective reference characters. The reference characters used in Figure 1 of the present application coincide with the respective reference characters in Figure 36 of US 2006/0209310 Al. The idea according to the present invention is to use a laser line 31 which is shorter than the width w of the substrate 32. The substrate 32 has to be processed in two steps as shown in Figures 1 to 5.
• The size of the thin laser beam 31 in lengthwise direction Ai is clipped by blades to the desired size. Instead of using blades also a zoom optic can be used to adjust the size of the beam 31. The advantage of the zoom optic is the possibility to reduce laser power and increase the lifetime of the whole system.
• The substrate 32 is processed in a first step at only one side. For this purpose the stage is linearly moved in scanning direction 35 such that said illuminating line 31 scans a first section of the surface 36 of said substrate 32 resulting in a crystallization of the Silicon in said section. Figure 2 shows the substrate 32 and said illuminating line 31 after said processing step. The crystallized section of the substrate 32 is indicated with reference number 37 in Figure 2, the not crystallized section is indicated with reference number 36.
• The stage is then rotated by 180° about an axis 38 of rotation 39 (Figure 3) and moved back to the start position (Figure 4). This is important if the profile of the beam 31, 33 in the short axis direction As is different for the trailing edge T and the leading edge L as explained above. To achieve similar process results the scan direction for the process should be the same for both steps.
• The size of the thin laser beam 33 has to be adjusted again, e.g. by means of blades or a zoom optic as already described above. The substrate 32 is processed in a second step at the other side. For this purpose the stage is linearly moved in scanning direction 35 such that said illuminating line 33 scans a second section of the surface 36 of said substrate 32 adjacent to said first section resulting in a crystallization of the Silicon in said second section. Figure 5 shows the substrate 32 and said illuminating line 33 after said processing step. The crystallized sections of the substrate 32 are indicated with reference number 37. At the edge of the laser beam 33 in long axis direction Ai adjoining the previously crystallized section 37 there will be a resulting seam 34. This is because of the drop in energy density at the edge of the beam 33. The seam 34 can be very small if the beam clipping blade is close to the substrate 32 and the resulting ramp in the energy density has therefore a small size
As already mentioned there will be a seam at the border of the processed areas. The position of the seam can be moved according to the adjustment of the laser beam size in the long axis Ai direction x.
The disadvantage of this solution is the required two steps for processing and the implementation of a rotating stage. On the other hand a rotating stage can be used in a very flexible way. For example rotating the stage by 90° will affect the orientation of the Si crystals and defines a preferred direction for further electronic components on the substrate.
Because some of the substrates have structures in either the scan direction or orthogonal to the scan direction a tilt of the stage of a few degrees can prevent the appearance of structures after processing.
An advantage of the first preferred embodiment of the present invention is that an existing system for a Gen4 size panel (730 mm x 920 mm) can be upgraded to a Gen5 size of 1100 mm x 1300 mm. Also the required transmission of the system will be the same.
Second preferred embodiment: Stitching of lenses or/and mirrors
Another possibility to extend the length of the laser beam at the substrate is to stitch at least one of the lenses of mirrors of the optical device which generates said narrow illuminating line on the illumination plane of said substrate. Especially the lens (mirror) which is closest to the substrate must have a large extension in the long axis direction.
Figures 6 and 7 show the main principle of an optical device being capable of generating a narrow illuminating line. Figure 6 is a plane view in the xz-plane of an optical device according to the prior art. Figure 7 is a plane view in the yz-plane of the same optical device. The optical device comprises two cylindrical lens arrays Ia, Ib forming a two- stage fly's eye homogenizer and a convex cylindrical condenser lens 3 which are optically active in x-direction. The optical device further comprises a sliced cylindrical lens 2 consisting of a plurality (here three) cylinder lens segments 2a, 2b, 2c, a cylindrical lens 4 and a projection, namely a reducing optics, in particular in the example shown in Figures 6 and 7 a cylindrical lens 5 being optically active in y-direction.
The homogenizer for the long axis Ai direction x is built by said two cylindrical lens arrays Ia, Ib each comprising a plurality of cylindrical lenslets laa, lab, lac and lba, lbb, lbc, respectively, being arranged adjacent to each other and each having a focal length fi resulting in a focal length farray of said arrangement of arrays Ia, Ib and said condenser cylindrical lens 3 with a focal length f3. An incoming laser beam 10 propagating in z- direction is split into a plurality of beamlets corresponding to the number of cylindrical lenslets laa, lab, lac of the first cylindrical lens array Ia. Each beamlet is focused in the distance of the focal length farray and forms a diverging bundle of rays when hitting said condenser lens 3. The condenser lens 3 transforms the angular distribution of the beamlets to a field distribution in the plane 6, where a substrate is to be located. The size of the field depends on the focal length f3 of the lens 3 and the maximum angle of the angular distribution of each beam let caused by the arrays Ia, Ib.
A possible homogenization scheme for the short axis As is the sliced lens 2 concept already described in US 2006/0209310 Al. The individual cylindrical lens lets 2a, 2b, 2c with curvatures in short axis As direction y are shifted independently in direction y to the short axis A8. The main beam 10a in short axis As direction y is deflected depending on the amount of shift. The size of the lenslets 2a, 2b, 2c in direction to the long axis Ai is equivalent to the size of one of the cylindrical lens elements laa, lab, lac of the lens array Ia. In the focal plane of the cylindrical lens element 4, i.e. in the focal distance I4 to the cylindrical lens 4, the width of the beam depends on the divergence of the incoming beam in the short axis As direction y. Because of overlapping several of these beamlets displaced by each other a homogenized beam profile in short axis As direction y can be generated. At the position of the focused beam on the short axis As direction y a field defining element 7, for example a field stop, can be placed. The projection optics 5 images the field defining element 7 onto the plane of the substrate 6. The projection optics 5 in the present case is a cylindrical lens (an alternative may be a mirror) which does not affect the propagation of the beam in long axis Ai direction x. The projection optics 5 may also reduce the expansion of the beam in short axis As direction y.
As can be seen in Figure 6 the optical element 5 has a large extension in the long axis Ai direction x. The following solutions are describing how larger field sizes can be achieved with limited size of the optical element 5 (in long axis Ai direction x).
One possible solution to achieve a larger field size is to use two independent optical devices of the kind described above and stitch them together. Figure 8 shows two identical devices as shown in Figures 6 and 7 which are stitched together in long axis Ai direction x. In particular, the cylindrical lenses 5 are arranged adjacent to each other in long axis Ai direction x. The gap 5g between the two cylindrical lenses 5 is predefined such that at least the adjacent edge slopes of said illumination lines 6a, 6b being generated on the surface, namely the illumination plane 6, of said substrate at least partially overlap.
If the gap 5g between the two adjacent cylindrical lenses 5 is further reduced and in particular if the gap 5g is reduced essentially to zero there will be an overlapping area 9 of the illuminating lines 6a, 6b where the resulting intensity is higher. With the use of clipping blades 8a, 8b, 8c, 8d being arranged close to the illumination plane 6 the overlap can be adjusted as shown in Figure 9. The adjustment possibility of the clipping blades 8 is indicated in Figure 8 with respective arrows 28a, 28b, 28c, 28d.
In the present case the two field distributions 11, 12 of the illuminating lines 6a, 6b intersect at the 50 % intensity value. If the two curves 11, 12 have an intensity distribution with the same linear slope at the edge the summation 13 of both curves 11, 12 which is shown in Figure 10 leads to a constant intensity all over the field. Small residual deviations from the linear slope as well as residual inhomogeneities in the intensity of the two field distributions 11, 12, may result in an overall intensity inhomogeneity.
A defined ramp can be achieved if the substrate plane 6 is not in the focal plane of the condenser lens 3 but slightly defocused. The advantage of this scheme is that very large fields 13a can be produced. As an alternative it is also possible to use only one homogenizer on the two narrow line generating optical systems and to split the beam in the long axis Ai direction x with an axicon. This solution is not shown here.
Another possibility is to increase the overlap area 9, i.e. by increasing the distance of the imaging optics 5 to the substrate 6 or by increasing the angle of the beam in the long axis Ai direction x. The initial field distributions 21, 22 of the two beams are shown in Figure 11. By clipping of one or both of the beams 26a, 26b with blades 8a, 8b, 8c, 8d the position of the intersection of illumination line 6a and illumination line 6b can be chosen over a wide range. This is indicated exemplarily by the different expansions of the beam profiles 21, 22 shown in Figure 12.
In the intersection area 9 of the two illumination lines 6a, 6b there could be a small discontinuity 24 due to clipping of at least one of the beams 26a, 26b (here both beams 26a, 26b are clipped in the overlapping area 9). For clarity reasons this situation is shown in Figure 13 where the sum 23 of the intensity profiles 21, 22 in long axis direction x is drawn. This discontinuity 24 may lead to a seam at the substrate (not shown here, but in principle similar to the situation shown in Figure 5 resulting from a different silicon microstructure and surface morphology. The position of the seam can be moved over the whole area 9 of the intersection of the two beams 26a, 26b or illuminating lines 6a, 6b, respectively.
Another possibility to increase the size of the field is explained with reference to Figure 14. Figure 14 shows a plane view of an optical device in the xz-plane according to the invention. The optical device comprises the same optical elements as compared to that disclosed in Figures 6 and 7. In particular, the optical device comprises two cylindrical lens arrays Ia, Ib forming a two-stage fly's eye homogenizer and a convex cylindrical condenser lens 3 which are optically active in x-direction. The optical device further comprises a sliced cylindrical lens 2 consisting of a plurality (here three) cylinder lens segments 2a, 2b, 2c, a cylindrical lens 4 and a projection optics, namely a reducing optics, in particular in the example referred to a cylindrical lens 5, being optically active in y- direction. Furthermore, a field defining optical element, e.g. a field stop 7, is arranged in an intermediate conjugate field plane with respect to the short axis As direction y. The illumination is modified in a way to increase the size Ai in long axis direction x of the field 6. Deviating from the example according to the prior art shown in Figures 6 and 7 the last projection element 5 is split into two components 5 a and 5b which are stitched together at stitching position 5s. The upper part of Figure 15 shows the intensity profile 41 of the illuminating line 6 being generated by the optical device shown in Figure 14 and being the sum of the profiles 42, 43 of the beams 26c, 26d transmitting the lenses 5a, 5b being stitched together, respectively. In the example shown in Figure 15 the total field size 46 is larger than the size 47 of the substrate 40 (see substrate 40 in the lower part of Figure 15). Therefore, the incoming laser beam 26 may be clipped on one or both sides by means of respective blades 8a, 8b. Presently, blade 8a limits the expansion of the beam 26 resulting in an actual size 48 of the field shown on top of Figure 15.
The illumination line 6 with reduced expansion Ai in long axis direction x is scanned over the illumination plane of the substrate 40 by moving the substrate 40 in scanning direction 45. Due to the stitching lenses 5 a, 5b the intensity profile 41 of the illuminating line 6 has a discontinuity 49 in intensity. This discontinuity 49 results in a seam 44 after processing of the substrate 40. Depending on the allowed position of the seam 44 after processing the field size may be limited with the same degree on both sides resulting in a seam 44 being in the centre. Alternatively, the field may also be only limited at one side resulting in a seam 44 being off centred. The bottom of Figure 15 shows an off centred seam 44.
In order to adjust the substrate 40 to the field distribution 41 there are two possibilities:
• the stage carrying the substrate 40 may be moved in the long axis direction x as is indicated with reference number 45 a
• the stage carrying the substrate 40 may be larger than the substrate 40. The substrate 40 is adjusted with the use of limiters 8a, 8b to the actual field Third preferred embodiment: Modifying angular distribution and distances
With reference to Figure 16 a third solution to increase the size of the field at the substrate is explained. Figure 16 shows a plane view in the xz-plane of an optical device of the present invention the functionality of which but not the particular layout is known from prior art. The components of the optical device are those as already shown in Figures 6 and 7. The optical device comprises two cylindrical lens arrays Ia, Ib forming a two-stage fly's eye homogenizer and a convex cylindrical condenser lens 3 which are optically active in x- direction. The optical device further comprises a sliced cylindrical lens 2 consisting of a plurality (here three) cylinder lens segments 2a, 2b, 2c, a cylindrical lens 4 and a projection optics, namely a reducing optics, in particular a cylindrical lens 5, being optically active only in y-direction. A laser beam 10 emitted from a high power laser source (not shown) is converted into a narrow illuminating line 6 on the surface of a substrate.
According to the present invention the extension of the field at the last lens 5 or mirror is significantly smaller than the size of the field 6 at the substrate. The difference in field size is increased by the following actions:
• The distance d between the last optical element 5 (Remark: The wording "last optical element" means here the last lens or mirror which is used for the projection optics. A protection window between projection optics and substrate does not count as an optical element here) and the substrate (position of the illuminating line 6) may be increased. This is possible if the aperture of the optical element 5 is increased in the short axis direction y or/and the numerical aperture NA in short axis direction y at the substrate is decreased. The target for the distance d is a value larger than 500 mm. Favourable the distance is larger than 600mm.
• The angle α of the edge beam 51 can be increased. The energy density at the substrate is reduced at the edge by the cosine law. Also if the angle α is increased additional aberrations will require a modified design of the homogenizer. This design will require several lenses and possibly at least one aspheric cylindrical lens. The maximum angle α in the long axis direction x should be larger then 7°. Favourably, the angle α should be larger than 15°. I.e. if the distance d between optical element 5 and substrate is 600 mm and the angle α is 15° a field Ai of 1100 mm can be produced with an optical element 5 with the size of 780 mm. For an angle α of 20° the size of the element 5 is reduced further to 660 mm.

Claims

1. An apparatus for laser annealing of large substrates comprising:
- an optical device for generating a narrow illuminating line (31) on an illumination plane (36) of said substrate (32), said illumination line (31) being generated from a laser beam and having a cross-section with an expansion (Ai) in a first direction (x) and an expansion (A8) in a second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (As) in said second direction (y) by a multiple,
- a scanning device being constructed for scanning a first section (37) of said illumination plane (36) of said substrate (32) with said illuminating line (6) in said second direction (y,
35), characterized in
- a rotating device for rotating said substrate (32) relative to said illuminating line (6) by 180° about an axis (38) of rotation being normal to said illumination plane (6) after scanning said first section (37),
- said scanning device being constructed for scanning a second section of said illumination plane (36) of said substrate (32) being adjacent to said first section (37) of said illumination plane (36) of said substrate (32) with said illuminating line (31) in said second direction (y, 35).
2. The apparatus according to claim 1, characterized in an adjustment device for adjusting the expansion of said illuminating line (31) in said first direction (x) to a predetermined length.
3. The apparatus according to claim 2, characterized in that said adjustment device comprising at least a blade for clipping said illuminating line (31, 33) at least on one side of said illuminating line (31, 33) in said first direction (x).
4. The apparatus according to one of claims 2 or 3, characterized in that said adjustment device comprises a zoom optic for reducing the expansion of said illuminating line (31, 33) in said first direction (x).
5. The apparatus according to one of the preceding claims, characterized in that said rotating device comprising a stage for positioning said substrate (32) and being rotatable.
6. The apparatus according to claim 5, characterized in that said stage being linearly movable.
7. A method for laser annealing of large substrates (32) comprising the steps of:
- generating a narrow illuminating line (31) on an illumination plane (36) of said substrate (32) from a laser beam, said illuminating line (31) having a cross-section with an expansion (Ai) in a first direction (x) and an expansion (A8) in a second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A8) in said second direction (y) by a multiple,
- scanning a first section (37) of said illumination plane (36) of said substrate (32) with said illuminating line (31) in said second direction (y, 35), characterized in
- rotating (39) said substrate (32) relative to said illuminating line (31) by 180° about an axis (38) of rotation being normal to said illumination plane (36),
- scanning a second section of said illumination plane (36) of said substrate (32) being adjacent to said first section (37) of said illumination plane (36) of said substrate (32) with said illuminating line (31) in said second direction (y, 35).
8. The method according to claim 7, characterized in adjusting the expansion (Ai) of said illuminating line (31) in said first direction (x) to a predetermined length (Ai) before and/or while scanning said first section (37).
9. The method according to one of claims 7 or 8, characterized in adjusting the expansion (Ai) of said illuminating line (31) in said first direction (x) to a predetermined length (Ai) after scanning said first section (37) but before and/or while scanning said second section.
10. The method according to one of claims 7 to 9, characterized in adjusting the expansion (Ai) of said illuminating line (31) such that the gap between said first and second sections (37) or the overlap of said first and second sections (37) has a predetermined value.
11. An apparatus for laser annealing of large substrates comprising:
- an optical device for generating a narrow illuminating line (6a) on an illumination plane of said substrate, said illumination line (6a) being generated from a laser beam and having a cross-section with an expansion (Ai) in a first direction (x) and an expansion (A8) in a second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A8) in said second direction (y) by a multiple,
- a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line (6a) in said second direction (y), characterized in - another optical device for generating another narrow illuminating line (6b) on said illumination plane of said substrate, said other illumination line (6b) being generated from a laser beam and having a cross-section with an expansion (Ai) in said first direction (x) and an expansion (A8) in said second direction(y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A8) in said second direction (y) by a multiple, - said scanning device being constructed for scanning a second section of said illumination plane of said substrate with said other illuminating line (6b) in said second direction (y),
- said optical device and said other optical device being arranged such that said narrow illuminating line (6a) and said other narrow illuminating line (6b) form a continuous illuminating line (6) on said illumination plane of said substrate.
12. The apparatus according to claim 11, characterized in that said optical device and said other optical device being arranged such that said continuous illuminating line (6) being a straight line having uniform intensity along said first direction (x).
13. The apparatus according to one of claims 11 or 12, characterized in that said optical device and/or said other optical device comprising a long axis expansion (Ai) limiting device for limiting said expansion (Ai) of said illuminating line (6a) and/or said other illuminating line (6b) in said first direction (x).
14. The apparatus according to claim 13, characterized in that said limiting device comprising a clipping blade.
15. The apparatus according to one of claims 11 to 14, characterized in that said optical device and/or said other optical device comprising an adjustment device for adjusting the expansion (Ai) of said illuminating line (6a) and/or said other illuminating line (6b) in said first direction.
16. The apparatus according to claim 15, characterized in that said adjusting device comprising a movable clipping blade (8a, 8b, 8c, 8d).
17. The apparatus according to one of claims 11 to 16, characterized in that said optical device and/or said other optical device being arranged with respect to said illumination plane of said substrate such that said illuminating line and/or said other illuminating line forming a slightly defocused illuminating line (6a, 6b) on said illuminating plane.
18. A method for laser annealing of large substrates comprising the steps of: - generating a narrow illuminating line (6a) on an illumination plane of said substrate from a laser beam, said illuminating line having a cross-section with an expansion (Ai) in a first direction (x) and an expansion (A8) in a second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A8) in said second direction (y) by a multiple, - scanning a first section of said illumination plane of said substrate with said illuminating line (6a) in said second direction (y), characterized in
- generating another narrow illuminating line (6b) on said illumination plane of said substrate, said other illumination line (6b) being generated from a laser beam and having a cross-section with an expansion (Ai) in said first direction (x) and an expansion (A8) in said second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A1) in said second direction (y) by a multiple,
- stitching said narrow illuminating line (6a) and said other narrow illuminating line (6b) for forming a continuous illuminating line (6) on said illumination plane of said substrate.
19. The method according to claim 18, characterized in that said continuous illuminating line 86) being a straight line having uniform intensity along said first direction (x).
20. The method according to one of claims 18 or 19, characterized in limiting said expansion (Ai) of said illuminating line (6a) and/or said other illuminating line (6b) in said first direction (x).
21. The method according to one of claims 18 to 20, characterized in adjusting the expansion (Ai) of said illuminating line (6a) and/or said other illuminating line (6b) in said first direction (x).
22. The method according to one of claims 18 to 21, characterized in slightly defocusing said illuminating line (6a) and/or said other illuminating line (6b) on said illuminating plane such that the intensity of said illuminating line (6a) and/or said other illuminating line (6b) having a constant slope at the edge in said long axis direction (x).
23. An apparatus for laser annealing of large substrates comprising: - an optical device for generating a narrow illuminating line (6, 6a) on an illumination plane of said substrate, said illumination line (6, 6a) being generated from a laser beam (10) and having a cross-section with an expansion (Ai) in a first direction (x) and an expansion (A8) in a second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A8) in said second direction (y) by a multiple, - a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line (6, 6a) in said second direction (y), characterized in
- said optical device comprising at least two optical elements (5a, 5b) with refractive power being integral parts of a projection/reduction optics for forming said illumination line (6) on said illumination plane, whereby said at least two optical elements (5 a, 5b) being arranged adjacent to each other in said first direction (x) or
- another optical device for generating another narrow illuminating line (6b) on said illumination plane of said substrate, said other illumination line (6b) being generated from a laser beam and having a cross-section with an expansion (Ai) in said first direction (x) and an expansion (A8) in said second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A8) in said second direction (y) by a multiple, whereby said optical device comprising at least one optical element (5) with refractive power being integral part of a projection/reduction optics for forming said illumination line (6a) on said illumination plane, and whereby said other optical device comprising at least one other optical element (5) with refractive power being integral part of another projection/reduction optics for forming said other illumination line (6b) on said illumination plane, whereby said at least one optical element (5) and said at least one other optical element (5) being arranged adjacent to each other in said first direction (x).
24. The apparatus according to claim 23, characterized in that said optical elements (5 a, 5b) and/or said optical element (5) and said other optical element (5) being lenses or mirrors.
25. The apparatus according to claim 23 or 24, characterized in that said optical elements (5 a, 5b) and/or said optical element (5) and said other optical element (5) being the last optical elements (5, 5a, 5b) with refractive power used for the projection/reduction optics.
26. An apparatus for laser annealing of large substrates comprising:
- an optical device for generating a narrow illuminating line (6) on an illumination plane of said substrate, said illumination line (6) being generated from a laser beam (10) and having a cross-section with an expansion (Ai) in a first direction (x) and an expansion (A8) in a second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A8) in said second direction (y) by a multiple,
- a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line (6) in said second direction (y), characterized in
- said optical device comprising one last optical element (5) with refractive power being integral part of a projection/reduction optics for forming said illumination line (6) on said illumination plane, whereby a distance (d) between said last optical element (5) and said illumination plane of said substrate is larger than 500 mm.
27. The apparatus according to claim 26, characterized in that the distance (d) between said last optical element (5) and said illumination plane of said substrate is larger than 600 mm.
28. The apparatus according to claim 27, characterized in that the distance (d) between said last optical element (5) and said illumination plane of said substrate is larger than 700 mm.
29. The apparatus according to claim 28, characterized in that the distance (d) between said last optical element (5) and said illumination plane of said substrate is larger than 800 mm.
30. The apparatus according to claim 29, characterized in that the distance (d) between said last optical element (5) and said illumination plane of said substrate is larger than 900 mm.
31. The apparatus according to claim 30, characterized in that the distance (d) between said last optical element (5) and said illumination plane of said substrate is larger than 1000 mm.
32. The apparatus according to one of claims 26 to 31, characterized in that said optical device comprising a long axis beam expanding device (Ia, Ib, 3) for expanding said laser beam (10) in said first direction (x) to the expansion (Ai) of said illuminating line (6) in said first direction (x) by an expansion angle (α), whereby said expansion angle (α) is larger than 7°.
33. The apparatus according to claim 32, characterized in that said expansion angle (α) is larger than 15°.
34. The apparatus according to claim 33, characterized in that said expansion angle (α) is larger than 20°.
35. The apparatus according to claim 34, characterized in that said expansion angle (α) is larger than 25°.
36. The apparatus according to claim 35, characterized in that said expansion angle (α) is larger than 30°.
37. The apparatus according to claim 36, characterized in that said expansion angle (α) is larger than 35°.
38. An apparatus for laser annealing of large substrates comprising: - an optical device for generating a narrow illuminating line (6) on an illumination plane of said substrate, said illumination line (6) being generated from a laser beam (10) and having a cross-section with an expansion (Ai) in a first direction (x) and an expansion (A8) in a second direction (y), whereby said expansion (Ai) in said first direction (x) exceeds said expansion (A8) in said second direction (y) by a multiple,
- a scanning device being constructed for scanning a first section of said illumination plane of said substrate with said illuminating line (6) in said second direction, characterized in that said optical device comprising a long axis (Ai) beam expanding device (Ia, Ib, 3) for expanding said laser beam (10) in said first direction (x) to the expansion (Ai) of said illuminating line (6) in said first direction (x) by an expansion angle (α), whereby said expansion angle (α) is larger than 7°.
39. The apparatus according to claim 38, characterized in that said expansion angle (α) is larger than 15°.
40. The apparatus according to claim 39, characterized in that said expansion angle (α) is larger than 20°.
41. The apparatus according to claim 40, characterized in that said expansion angle (α) is larger than 25°.
42. The apparatus according to claim 41, characterized in that said expansion angle (α) is larger than 30°.
43. The apparatus according to claim 42, characterized in that said expansion angle (α) is larger than 35°.
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