KR101529344B1 - Method and arrangement for producing a laser beam with a linear beam cross section - Google Patents

Abstract

The present invention relates to a method and apparatus for producing a laser beam having a linear cross section, the cross section having a long beam cross section axis and a short beam cross section axis, having a length of at least 200 mm in the long axis and a length of no more than 800 탆 in the short axis, A laser beam emitted from a laser beam source is separately equalized with respect to a short axis and a short axis so that the laser beam is focused on each of a plurality of partial beams formed by division of the beam cross- And the plurality of partial beams are then guided together to form a laser beam which is subsequently uniformized in the beam cross-section, and the laser beam is telecentrically imaged with respect to at least the tangential axis, that is, A laser beam is guided by a condensing optical system (LACL), a beam path assignable to the imaged laser beam, A set of parallel light in the vertical direction with respect to the direction of propagation direction is imaged part to the animation beam path consisting of beams. The present invention relates to a process comprising the following steps:
- imaging of a beam cross section that is uniformly converged in a short axis by a first condensing optical system (SACL1) to form a uniform image field (HFSA1), and a focal plane The step of forming the first pupil P1 by the first field lens optical system (SAFL1)
Imaging the uniform image field HFSA1 with a second image field SAFL2 by a second condensing optical system SACL2 and imaging the second image field HFSA2 with a second pupil P2 by a second field lens optical system SAFL2. Wherein the second pupil (P2) comprises an imaging surface in which a laser beam homogenized with respect to the axis is imaged by the condensing optical system (LACL), the telecentricity of the laser beam Corresponds to the entrance pupil of the imaging optical system (p-lens SA) for imaging.

Description

FIELD OF THE INVENTION [0001] The present invention relates to a method and apparatus for generating a laser beam having a linear cross-

The present invention relates to a method and apparatus for producing a laser beam having a linear cross section, the cross section having a long beam cross section and a short beam cross section, having a length of at least 200 mm in the long axis and a length of less than 800 μm in the short axis , The laser beam from the laser beam source is separately equalized with respect to the long axis and the short axis so that the laser beam is focused on the long axis and the short axis by a plurality of partial beams focused by the division of the beam cross section of the laser beam And the plurality of partial beams are then guided together to form a laser beam which is then uniformized in the beam cross-section. The laser beam is telecentrically imaged at least about the long axis. That is, the laser beam that is homogenized with respect to the long axis is imaged by the condensing optical system into a beam path that can be assigned to the imaged laser beam, that is, a beam path consisting of partial beams of parallel light that is vertically oriented with respect to the propagation direction. do.

Such methods and devices have long been used in the industrial manufacture of flat panel displays based on thin film transistor (TFT) technology. One of the measures for this is the provision of a polycrystalline silicon layer as large as possible, on which a plurality of thin film transistors arranged in an array are processed. For the production of the polycrystalline silicon layer, the substrate is coated with amorphous silicon and the silicon is converted during the short-time melting process to polycrystalline silicon by controlled, local, photo-induced heating during the laser using exposure process. In an exposure method known in these publications, an excimer laser such as an XeCl-laser is used in a known manner, and since the laser can emit light in the ultraviolet spectrum range which is almost completely absorbed by silicon, Resulting in thermal heating and concomitant recrystallization of the amorphous silicon with polycrystalline silicon. In this connection, it is often referred to the ELA method (E xcimer L aser A nnealing) . In order to provide the energy density required for the melting process by the laser beam to the surface of the substrate coated with amorphous silicon for a short time while at the same time meeting the demands of industrial manufacturing, the laser beam emitted from the excimer laser is irradiated with a laser beam having a line length of, It has been found desirable to convert the laser beam into a laser beam having a linear cross-sectional shape with a line width of 400 mu m, and the laser beam of the above type is irradiated onto the substrate surface coated with amorphous silicon for a local, short-time melting of the amorphous silicon layer in a controlled manner Scanned or rasterized throughout.

Particularly preferably, this is necessary for the uniform recrystallization of a suitably formed laser beam with excellent uniformity in the distribution of the light intensity along the long and short axes of the rectangular cross-section of the beam. It is also desirable to form the beam profile with respect to the light intensity distribution along the short axis to have a large edge slope on both sides so that the light intensity is as close as possible to the rectangular profile considered as ideal for the short beam cross section axis. That is, the beam intensity plateau value reaches to the side edge and dives from the edge.

An example of this prior art is US 2005/0035103 A1. Here, a notable configuration for the prior art relating to the ELA method is shown, and in particular with respect to FIG. 1, a beam guiding optic arranged rearward in the beam path for producing a laser beam with a linear beam cross- An excimer laser device having a beam forming optical device is presented. The telephoto lens device assists in matching the rectangular beam cross-section emitted from the excimer laser beam to the incidence aperture of a subsequent uniformizer in the beam path, the latter having a cross-section of a rectilinear laser beam separately taken from its short beam cross- Can be uniformized with respect to the light intensity distribution with respect to the transverse axis. In this case, the laser beam first passes through a so-called long axis equalizer. Wherein said long axis equalizer comprises a first device of cylinder lenses oriented parallel to each other and a second device of cylinder lenses arranged in parallel behind each other arranged in the beam path behind said first device, The focal points or focal lines of the cylinder lenses lie between the first and second devices of the cylinder lens device. In the beam path, a condenser lens disposed behind the cylinder lens arrangement is provided for imaging a beam cross section formed in a rectangular shape in the long axis. Subsequently, a short axis homogenizer is arranged, said short axis homogenizing means comprising a first device of cylinder lenses arranged parallel to each other and a second device of cylinder lenses arranged in parallel with each other following said first device in the beam path do. The axes of the cylinder lenses of the short axis homogenizer are arranged perpendicular to the cylinder lens axes of the long axis homogenizer. Like the long axis homogenizer, the focus or focal line of the first device of the cylinder lenses, respectively, also lie between the two cylinder lens devices in short axis homogenizers. For subsequent imaging of the beam cross-section homogenized in the short axis, a condenser lens and a field lens are subsequently provided, which image the beam cross-section homogenized in the short axis to the area of the gap lens. Finally, the optical magnifying device shrinks the beam cross-sectional shape in a short axis, and the laser beam, which is linearly formed in the beam cross-section, is imaged onto the substrate surface coated with amorphous silicon. Other details of this are disclosed in the above-mentioned US 2005/0035103 Al. In addition, additionally, publications US 2006/0209310 A1 and US 2007/0091978 A1 are mentioned, in which there is also shown an embodiment in which the laser beam is homogenized and subsequently transformed into a laser beam with a linear cross section, 2005/0035103 A1, the improvement is not disclosed.

Efforts to enlarge the linear shape of the beam cross section along the long axis of the beam and eventually to coat the substrate surface of the largest possible area coated with amorphous silicon economically by the ELA method increase the problem of image field warping. The image field curvature causes unclear imaging along the laser line due to the different depth of focus and the uncertainty increases with increasing distance between the image center and the image edge area. This imaging error also becomes even greater when the focal depth of the imaging system is approximately equal to or smaller than the focal position shift relative to the focal position at the image center, particularly at the image edge area caused by image field curvature. If the laser beam is imaged, telecentricly imaged along its long axis, that is, the partial beams assignable to the laser beam are oriented parallel to each other after passing through the condensing optical system arranged behind the long axis homogenizer, , Imaging errors that are unfavorable due to image field curvature can be minimized. However, such an optical structure for implementing a long designed laser line, typically having a line length of 450 mm or more, requires a large gap between a long axis equalizer and a long axis condensing optical system for the implementation of a telecentric imaging optical system. However, this means that when imaging the laser beam along its short axis, it has a light intensity distribution as close as possible to an ideal rectangular profile along a short axis over the entire line length of the laser beam, preferably with a defined line 1/2 width and a distinct edge slope Problems in implementing the profile.

A method for producing a laser beam having a linear cross section, the cross section having a long beam cross section axis and a short beam cross section axis and having a length of at least 200 mm, preferably at least 400 mm, The laser beam having a length of less than or equal to 탆, preferably less than or equal to 400 탆, the laser beam coming out of the laser beam source being separately made uniform with respect to the long axis and the short axis, And the plurality of partial beams are subsequently guided together to form a uniformized laser beam in the beam cross-section, and the laser beam is guided along at least a long axis The laser beam that is telecentrically imaged with respect to the long axis, i.e., the laser beam that is uniformized with respect to the long axis, is condensed by the condensing optical system, 11. A method of generating a laser beam having a linear cross section, wherein a beam path is assigned to a low beam, said beam path consisting of partial beams of parallel light oriented in the longitudinal direction with respect to the propagation direction, The profile is imaged on the imaging surface with a rectangular profile that is as clear as possible, despite a large imaging gap, that is, a sharp edge slope as clearly as possible and a defined line 1/2 width. In particular, optical measures must be taken that cause unique variations of the beam profile with respect to the short axis in relation to the edge slope and line 1/2 width along the entire length of the linear laser beam cross-section. In addition, a laser beam generating apparatus that meets the above-mentioned requirement must be provided.

The above problem is solved by claim 1. The above-mentioned problem related to the apparatus is solved by claim 6. Preferred embodiments of the invention are set forth in the dependent claims and particularly in the following description with reference to examples.

According to the invention, a method of generating a laser beam with a linear cross-section according to the preamble of claim 1 is characterized in that a two-stage optical imaging is made in the beam path for beam forming and beam imaging of the laser beam cross- The optical imaging allows spatial bridging of a long distance between the short axis homogenizer due to the telecentric beam guide on the one hand and the imaging plane on which the substrate with the amorphous Si layer is arranged, Are characterized by independent adjustability of the edge tilt and line 1/2 width.

The two-stage imaging is carried out by two optical imaging branches which are successively arranged in turn in the beam path according to the invention, the first one of the two optical imaging branches being the cylinder lens device of the short axis homogenizer, Followed by a short axis condensing optical system and a short axis field lens optical system following the beam path. In this case, the individual optical units, on the one hand, form a uniform image field on the short axis condensing optical system and on the other hand the subsequent field lens optical system is clearly imaged between the two cylinder devices of the short axis homogenizer The focal plane is imaged with the first pupil plane, and the partial beams divided with respect to the short axis are imaged onto the focal plane in the form of a lens array.

A second imaging branch disposed behind the first imaging branch in the beam path is configured to image a uniform image field formed in the first uniform branching category by a second condensing optical system to a second uniform image field, The focal plane of the short axis homogenizer imaged in the pupil is imaged by the second field lens optical system to the second pupil and the second pupil is imaged onto the imaging plane of the imaging pupil of the imaging optical system for telecentric imaging of the laser beam And a laser beam which is simultaneously homogenized with respect to the axis of the imaging plane is imaged by the long axis condensing optical system. Thus, the second imaging branch consists only of a short axis condensing optical system and a short axis field lens optical system.

The assumptions for separately changing or intentionally optimizing the beam profile of the short axis with respect to the edge slope and line 1/2 width, by imaging separated in two optical branches, each comprising a condensing optical system and a field lens optical system It is known that conditions are formed. This can be achieved by axial movement of the individual condensing optical system and / or the field lens optical system belonging to the optical imaging branch as shown in other embodiments. Also, the rotation of the optical system included along the imaging branch adjusts at least the line 1/2 width.

The concept according to the present invention and the specific arrangement of the optical elements arranged along the imaging beam path are described below with reference to the embodiments.

With the present invention, the beam profile along the short axis is imaged onto the imaging surface with a rectangular profile, preferably as pronounced edge slope and defined line 1/2 width, as clearly as possible despite the large imaging gap.

The present invention will now be described, by way of example only, with reference to the accompanying drawings, but it is not limited thereto.
BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 shows a beam path with optical elements for imaging of a laser beam cross-section for a short axis,
Figure 2 shows a beam path with optical elements for imaging of a laser beam with respect to a long axis,
Figs. 3A and 3B are diagrams for illustrating separate adjustability of edge slope and line 1/2 width for a short axis. Fig.

1 shows a cross-sectional view of a short-axis < RTI ID = 0.0 > axis < / RTI > to form a linear beam cross-section having a line length greater than 200 mm, preferably greater than 450 mm, A beam path for indicating the formation and imaging of a laser beam for the laser beam is shown. Figure 2, which shows a view rotated 90 degrees with respect to the beam path according to Figure 1, shows beam formation along a long axis. Hereinafter, two drawings can be referred to at the same time.

The laser beam L emitted from the excimer laser is focused by an appropriate imaging optical system such as a telephoto lens to the incidence aperture of a homogenizer H consisting of a long axis homogenizer (LAH) and a short axis homogenizer (SAH) It is assumed.

The beam path shown in Figs. 1 and 2 has a cylinder lens apparatus (LAH1, LAH2) belonging to a so-called long axis homogenizer in the beam direction from left to right. The cylinder lens devices together with a long axial condenser lens (LACL) form a non-focal optical system and form a telecentric imaging optical system. The telecentric imaging optical system longitudinally collimates the laser beam after passing through a long axial condenser lens (LACL) in the long beam cross-sectional axis with respect to the optical axis, Thereby forming an image field uniform in the long axis on the placed imaging plane HFLA. Also, telecentric imaging along the long axis can at least very strongly suppress imaging errors caused by image field curvature. The long axis condenser lens (LACL) is arranged at intervals such that for each cylinder lens device consisting of LAH2 and LAH1, each partial beam separated by said long axis equalizer forms a partial beam parallel to the back of the condenser lens, One partial beams are superimposed on the imaging plane HFLA.

Due to the chosen optical focal length of the optical element for long axis formation, the distance d is usually at least 3 meters long, which is a relatively large distance that must be covered to image the beam cross section to be homogenized in the short axis onto the image plane HFLA to be. To this end, a so-called short axis homogenizer (SAH) composed of a first cylinder lens device (SAH1) and a second cylinder lens device (SAH2) is disposed behind the long axis homogenizer (LAH) in the beam path. As with the long axis homogenizer, a focal plane lying between the two cylinder lens devices (SAH1, SAH2) is provided. A short beam cross section divided into partial beams by the first cylinder lens device SAH1 is focused on the focal plane in the form of a point or line array.

A short axis condenser lens SACL1 is disposed behind the short axis homogenizer and an image field HFSA1 is formed uniformly along the short beam cross section axis by the condenser lens. The homogenized image field HFSA1 has a nearly rectangular beam profile in the short axis, and the profile is imaged with the imaging plane HFLA. In the beam path, a short axial field lens (SAFL1) is provided in front of the homogenized image field (HFSA1), a pupil (P1) is defined by the field lens, and two cylindrical lens devices (SAH1, SAH2 are clearly imaged into the pupil P1. The optical elements form a so-called first imaging branch (I) in connection with the imaging of a laser beam profile which is uniformized in the short axis, i.e. SAH1, SAH2, SACL1 and SAFL1, and the first imaging branch is a homogenized image field (HFSA1 ). ≪ / RTI >

The second optical imaging branch II subsequent to the beam path includes only the second short axis condenser lens SACL2 and the second short axis field lens SAFL2 subsequent to the beam path. In this case, the second short axis condenser lens SACL2 is arranged for imaging of the first uniform image field HFSA1, and preferably on the spatial plane along the beam path in which the slit-shaped diaphragm device is installed, (HFSA2). The slit size is largely set larger than the actual beam cross-section of the uniform image field (HFSA2). The second short axis field lens SAFL2 images the pupil P1 into the pupil P2. The pupil P2 corresponds to the incident angle of the imaging optical system p-lens SA at the same time. Typically, the imaging optical system consists of a reduced optical system in which the short axis of the laser beam cross-section is reduced, for example 5 times, by telecentric imaging on the imaging plane HFLA.

It is very important to provide one condenser lens and one field lens in each of the two optical imaging branches I and II. With this provision, it is possible to form a nearly rectangular beam profile in a short axis within the uniform image fields (HFSA1 or HFSA2), and to adjust the edge tilt and line 1/2 width of the beam profile separately . By shifting the position of the field lens in the second imaging branch, particularly the short axis field lens SAFL2, along its optical axis in the axial direction, the line 1/2 width can be varied if the edge slope does not change or does not change substantially. This is shown in the diagram shown in Fig. 3A, where the ordinate of the diagram shows the light intensity value and its abscissa shows the deflection distance (mm). The three graphs shown in the diagram show the light profile when moving the axial field lens SAFL2, which is as short as 20 mm to the right (see graph 2) and 20 mm to the left (see graph 3 for normal position) from the normal position 1 . At three positions in total, the edge slope of the beam profile remains substantially the same despite variations in line 1/2 width.

In contrast, by the axial movement of the short axis condenser lens SACL2, the edge slope can be varied while the line 1/2 width remains constant. This is shown in the diagram according to FIG. 3b, and its axis design is the same as according to the diagram of FIG. Here again, the three different beam profiles differ by the different axial positions of the short axis condenser lens 2. [

LAH Tightening Uniformizer
The first cylinder lens device of the LAH1 tightening uniformizer
The second cylinder lens device of the LAH2 tightening uniformizer
SAH short axis uniformizer
The first cylinder lens device of SAH1 short axis uniformizer
The second cylinder lens device of the SHA2 short axis uniformizer
SACL1 short axis condenser lens
SAFL1 Short Axis Field Lens
First uniform image field for HFSA1 short axis
P1 First joint
LACL shrink condenser lens
SACL2 second short axis condenser lens
SAFL1 second short axis field lens
Second uniform image field for HFSA2 short axis
P2 second joint
p-Lens SA reduction lens
HFLA Imaging Face
H uniformizer

Claims (11)

A method of generating a laser beam having a linear cross section, the cross section having a long beam cross section axis and a short beam cross section axis, having a length of at least 200 mm in the short axis and a length of no more than 800 탆 in the short axis, Is uniformized with respect to the short axis and the short axis so that the laser beam is uniformized with respect to the short axis and the short axis while forming the respective focal planes in which the plurality of partial beams formed by the division of the beam cross section of the laser beam are focused, The plurality of partial beams are then guided together to form a uniformed laser beam in the beam cross section, which laser beam is uniformly telescoped by the shrink condenser lens (LACL) It is made up of partial beams of parallel light oriented in the longitudinal direction with respect to the propagation direction, In the method for generating a laser beam having a linear cross section formed by a laser beam which is imaged by each possible beam path,
Imaging of a beam cross section that is uniformly converged in the short axis by a short axis condenser lens (SACL1) to form a uniform image field (HFSA1), and imaging of the beam plane in which the partial beams divided for the short axis are focused, A step of forming the first pupil P1 by the short axis field lens SAFL1,
- imaging the uniform image field (HFSA1) with a second short axis condenser lens (SACL2) into a second uniform image field (HFSA2), imaging the first pupil (HFSA2) with a second short axis field lens P1) into a second pupil (P2), wherein the second pupil (P2) comprises an imaging surface on which a laser beam homogenized with respect to the axis is imaged by the tractive condenser lens (LACL) Characterized in that it corresponds to the entrance pupil of an imaging optical system (p-lens SA) for telecentric imaging.
2. The method according to claim 1, characterized in that, by the axial movement of the short axis condenser lens (SACL1) along the beam direction, the edge slope assignable to the short axis does not affect the line 1/2 width that can be assigned to the short axis Wherein the laser beam has a linear cross-section. 3. The method according to claim 1 or 2, characterized in that, due to axial movement of the short axis field lens (SAFL1) along the beam direction, the line 1/2 width that can be assigned to the short axis affects the edge tilt Wherein the first and second laser beams are incident on the first laser beam and the second laser beam, respectively. 3. A method according to claim 1 or 2, characterized in that a laser beam having a linear beam cross-section with a length of 450 mm or more in the axis of the short axis and a length of 800 mu m or less in the short axis is produced Way.
3. A method according to claim 1 or 2, characterized in that the second uniform image field (HFSA2) is imaged in the region of the slit-type diaphragm device. CLAIMS What is claimed is: 1. An apparatus for generating a laser beam having a long beam cross-section axis and a short beam cross-section axis comprising a laser emitting a laser beam and having a linear cross-section with a length of at least 200 mm in the short axis and a length of no more than 800 탆 in the short axis, The following elements affecting the laser beam along the direction of the beam
A telephoto lens for matching the beam cross-section width of the laser beam to the incidence aperture of a subsequent homogenizer in the beam path, wherein the homogenization of the light intensity distribution of the laser beam is performed separately along a short axis and a short axis of the beam cross-
A first telecentric imaging optical system for telecentric imaging the laser beam homogenized along the constriction to the imaging plane and
- a second imaging optical system for imaging a laser beam homogenized along a short axis to said imaging plane
An apparatus for generating a laser beam having a linear cross section,
The second imaging optical system comprises two or more optical system pairs, each of which is comprised of a condensing optical system and a field lens optical system, which are sequentially arranged in the beam direction,
The first optical system pair in the beam direction includes a short axis condenser lens SACL1 for forming a uniform image field HFSA1 and a short axis field lens SAFL1 for forming a first pupil P1,
A second optical system pair disposed behind the first optical system pair in the beam direction comprises a second short axis condenser lens for imaging the uniform image field HFSA1 into a second uniform image field HFSA2 And a second short axis field lens (SAFL2) for imaging the first pupil (P1) into a second pupil (P2), wherein the second pupil is telecentric imaging Characterized in that it corresponds to the entrance pupil of the imaging optical system (p-lens (SA)) for the laser beam. 7. The apparatus according to claim 6, wherein the short axis condenser lens (SACL1) or the short axis field lens (SAFL1) is controlled in a beam direction and arranged to be movable. 8. A method as claimed in claim 6 or 7, characterized in that the short axis condenser lens (SACL1) or the short axis field lens (SAFL1) is rotatably arranged to be controlled about an axis disposed perpendicular to the beam direction A device for generating a laser beam having a cross section. 8. The apparatus according to claim 6 or 7, wherein the short axis condenser lens (SACL1) and the second short axis condenser lens (SACL2) are each formed as a condenser lens, and the short axis field lens (SAFL1) (SAFL2) are each formed as a field lens. 8. A telecentric imaging optical system for telecentric imaging of a laser beam homogenized along said axis to an imaging plane comprises a homogenizer (LAH1, LAH2) provided with respect to said axis of < RTI ID = 0.0 > (LACL). ≪ RTI ID = 0.0 > 11. < / RTI > The apparatus of claim 6 or 7, wherein a slit-shaped diaphragm device is provided in front of the imaging surface in the beam direction.

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