WO2019134924A1

WO2019134924A1 - Optical system for producing an illumination line

Info

Publication number: WO2019134924A1
Application number: PCT/EP2019/050063
Authority: WO
Inventors: Berthold Burghardt; Hans-Juergen Kahlert; Johannes Richter
Original assignee: Innovavent Gmbh
Priority date: 2018-01-04
Filing date: 2019-01-03
Publication date: 2019-07-11
Also published as: CN111465889B; JP2021508857A; CN111465889A; DE102018200078A1; KR20200101987A; JP6813719B1; KR102459299B1; DE102018200078B4

Abstract

The invention relates to an optical system for producing an illumination line. The optical system comprises a laser beam source for producing a laser beam along an optical axis. The optical system also comprises a beam-forming device, which is designed to form the laser beam in such a way that a beam profile of the laser beam has a long axis and a short axis, and an imaging device, which is arranged downstream of the beam-forming device in the beam path of the laser beam and which is designed to image the laser beam thus formed as an illumination line. The beam-forming device comprises at least one telescope assembly, which comprises a first lens group and a second lens group. The first lens group and the second lens group have an optical power at least with respect to the short axis. The optical system comprises a first movement device for moving at least one of the first and second lens groups along the optical axis. The optical system also comprises a control unit, which is designed to control the first movement device in such a way that the at least one of the first and second lens groups is moved while the laser beam source produces the laser beam. The invention further relates to a method for producing an illumination line.

Description

Optical system for generating a lighting line

The invention relates to an optical system for generating a lighting line, in particular for example for so-called laser lift-off applications or for a system for processing thin-film layers, and to a method for generating a lighting line, in particular for laser lift-off applications or for processing thin-film layers.

The technique presented below can be used, for example, in connection with laser lift-off applications. Laser Lift Off applications dissolve plastic substrates from a glass substrate. A laser line (ie an illumination line) is focused through a transparent glass onto a plastic substrate. The bond is dissolved with the laser beam and the plastic substrate is thus separated contactlessly from the glass substrate. For example, flexible OLED displays are fabricated on PI films adhered to glass plates for production. After the production, the z. For example, by incorporating vapor deposition and photolithography processes, the display substrate is detached from the glass slide using a laser lift-off (LLO) process. For these processes are pulsed Festkör ^¬ perlaser that emit, for example, 343 nm and 355 nm laser light and will be readily absorbed by the polyimide layer and an adhesive layer, are almost transparent but for the glass, are used.

One possible application of an LLO process is, for example, the detachment of flexible OLED display substrates from a glass slide. Here are on a flat glass plate of z. B. 0.5 mm thick polyimide films of several 10-100 pm pasted, on which OLED display structures are built. After completion of the display film, it must be removed from the glass slide. For this purpose, a laser line is focused by the 343 nm or 355 nm transparent glass on the Kunst ^¬ fabric film. At typical energy densities of 100-500 mJ / cm ² , the bonding is achieved by moving a 20-50 pm wide line over it at a speed of 50-300 mm / s. The plastic substrate remains unbe ^¬ damaged and the flexible OLED display substrate can be used for further processing z. B. be used in smartphones.

Another application of the technique presented concerns the processing of thin film layers. For the crystallization of thin-film layers, for example for the production of thin-film transistors (in short: TFT) are laser used. As the semiconductor to be processed in particular silicon (in short: Si), more precisely a-Si is used. The thickness of the semiconductor layer is z. 50 nm, which is typically on a substrate (eg glass substrate) or other substrate.

The layer is illuminated with the light of the laser, for example a pulsed solid-state laser. In this case, the light with a wavelength of z. B. of 532 nm or 515 nm to a line of illumination, see, for. B. DE 10 2012 007 601 Al or WO 2013/156384 Al. For some years, lasers with wavelengths of 343 nm and 355 nm have also been used for these processes. By means of a beam shaping device, the laser beam can be shaped such that a beam profile of the laser beam has a long axis and a short axis. Subsequently, the laser beam thus formed can be imaged as the illumination line on the basis of an imaging device arranged in the beam path of the laser beam of the beam shaping device in order to generate the illumination line from the light of the laser beam. A corresponding optical system is described for example in DE 10 2015 002 537.

In detail, the beam-shaping device may, for example, comprise an anamorphic optical system and have different imaging properties with respect to a first and a second imaging axis. In particular, the beam shaping device can be set up to produce a laser beam whose laser beam profile has a long axis and a short axis at a location directly in front of the imaging ^device , the beam profile having a (largely) homogenized (or in the Substantially homogeneous) intensity distribution. The imaging device then focused (insbesonde- re exclusively) the short axis of the beam profile produced by the beam shaping means directly in front of the imaging device to generate the short axis of BL LEVEL ^¬ processing line. However, the imaging device has (in particular) no focusing properties, in particular with respect to the long axis, so that the long axis of the beam profile generated by the beam shaping device directly in front of the imaging device can pass virtually unchanged through the imaging device and thus correspond to the long axis of the illumination line.

The illumination line has therefore as the previously shaped beam profile of the laser beam ^¬ also a short axis and a long axis, where - for the purpose of Clarification - in particular the short axis of the beam profile of the laser beam before imaging by the imaging device corresponds to the short axis of the illumination line and the long axis of the beam profile corresponds to the (homogenized) long axis of the illumination line. The intensity distribution of the illumination line along the long axis is ideally rectangular and has, for example, a length (or full width at half maximum, in short: FWHM) of several 100 mm, eg. B. 750 mm to 1000 mm or longer, on. The intensity distribution along the short axis is typically Gaussian and has a FWHM of about 5 pm to 100 pm. The short and the long axis thus form a relatively high aspect ratio.

The illumination line is guided over the semiconductor layer at a feed of approximately 1 mm / s to 50 mm / s, preferably 10 mm / s to 20 mm / s in the direction of the short axis. The intensity (in the case of continuous wave lasers) or the pulse energy (in the case of pulsed lasers) of the light beam is adjusted such that the half ^¬ conductor layer for a short time (ie, on a time scale of about 50 ns to 100 ps) on ^¬ melts and when solidified crystalline layer with improved electrical properties. In addition to the above-described fields of application in connection with LLO and the manufacture of thin film transistors, a row, there are other fields of application in which the generation of a line of illumination having a high aspect behaves ^¬ nis for illuminating a substrate is required. The quality of the generated illumination line depends, in particular, on the spatial intensity distribution integrated along the short and / or the long axis and influences the material of the substrate to be processed with the illumination line. Thus, even small inhomogeneities of the intensity distribution along a long axis, that is, for example, local deviations or modulations of the absolute intensity of an (ideal) homogeneous intensity distribution in the low single digits Prozentbe ^¬ rich effect in the crystallization of amorphous silicon layers (z. B. about 2%) , in the advance of the illumination line in turn spatial inhomogeneities in the crystal structure (eg., By local variation of the grain size), which have an influence on the quality of the thin film layer and thus on the quality of the thin film transistor. This results in the following relationship: the more homogenous (ie more uniform) the intensity distribution of the illumination line, the more homogeneous (more uniform) is the crystal structure of the thin-film layer and the more homogeneous (uniform) are the properties of a final sample formed therefrom. such as the TFTs of a screen area in a display device (eg, monitor, monitor, etc.).

In addition to the above-described spatial homogeneity of the intensity of the illumination line, the temporal homogeneity of the intensity (which means the temporal change of the intensity during the scanning) is of comparatively great importance. Temporal intensity variations of the illumination line cause areas of the illuminated material over which the illumination line is guided to be illuminated with different (i.e., inhomogeneous) intensity, which may lead to undesirable nonuniform properties of the final product formed.

Against this background, it is desirable to keep the optical properties of the generated illumination line as constant as possible over time. In particular, it is desirable to keep an intensity (in particular an entire intensity distribution or at least a maximum intensity) of the illumination line and a half-width (FWHM) of the illumination line along the short axis as constant as possible over time.

An object of the invention is therefore to provide an improved optical system for generating a lighting line, in particular for a plant for processing thin-film layers, which enables the generation of a high-quality and temporally constant illumination line.

This object is achieved by means of an optical system according to claim 1 and by means of a method according to claim 12.

According to a first aspect, an optical system for generating a BL LEVEL ^¬ processing line is provided (especially for an installation for the processing of thin film layers). The optical system includes a laser beam source for generating a laser beam along an optical axis. Furthermore, the optical system comprises a beam shaping device that is configured to shape the laser beam in such a way that a beam profile of the laser beam has a long axis and a short axis (in particular perpendicular to the long axis) and one downstream of the beam shaping device in the beam path of the laser beam (in particular ^¬ sondere cylindrical) imaging device, which is adapted to the ^so-¬ shaped laser beam (in particular, the short axis of the thus formed laser beam) depict than (or on) a line of illumination. The beam shaping device comprises at least one telescope arrangement, which comprises a first lens group and a second lens group, wherein the first lens group and the second lens group at least with respect to the short axis have an optical power. The optical system comprises a first movement device for moving at least one of the first and second lens groups along the optical axis. The optical system further includes a control unit configured to drive the first movement means to move the at least one of the first and second lens groups while the laser beam source generates the laser beam.

In particular, a beam profile of the laser beam (in particular directly) in front of the imaging device is understood as the beam profile of the laser beam. The telescope arrangement can also be referred to as a telescope arrangement and describes the optical arrangement of the lens groups or lenses of this arrangement and their optical properties. In particular, the telescope arrangement may be a Kepler telescope or a Galileo telescope, as described in detail below. The telescope arrangement comprises at least a first and a second lens group. The term "lens group" is to be understood in this case as meaning that it can each be a single lens (for example a converging lens or a diverging lens) or a group of lenses composed of a plurality of (for example cemented) lenses. In the simplest case, therefore, the telescope arrangement can consist of two individual lenses which each form a separate lens group as a single lens. The telescope arrangement can be designed such that a focal point of the first lens group spatially coincides with a focal point of the second lens group. The first lens group may for example consist of a single cylindrical lens or composed of several ren cylindrical lenses. The same applies regardless of the arrangement of the first lens group for the second lens group. The optical axis extends along a z-axis in accordance with the convention used herein. The first movement device is thus adapted to move the first lens group, the second lens group or both lens groups along the z-axis. For this purpose, the first movement device may comprise, for example, a linear servomotor or a piezo element.

The terms "first" and "second", as used for example in connection with the "first movement device" and the later-described "second movement device", are for the sole purpose of distinctness and trans- port no further sense content. Alternatively, for example, the "first movement device" could be referred to as "movement device" and the "second movement device" as "further movement device". The control unit may comprise, for example, at least one processor and at least one memory. In the memory, instructions may be stored which cause the control unit to control the first movement device according to a predefined sequence. Furthermore, the control unit can also be used for controlling further elements of the optical system, such as the laser beam source and the two shutter elements, which are described below.

The technique described above has the effect and the advantage that optical changes of the optical system which result during the generation of the laser beam can be compensated by a movement or adjustment of the telescope arrangement. In particular, a thermal lens effect, which is caused by heating of an optical component of the optical system, caused by the laser beam, can be compensated or at least reduced by the movement of the first movement device.

The laser beam source may include a laser resonator, a laser resonator in the beam path downstream Strah ^¬ frequenzvervielfachende crystal arrangement and arranged in the beam path between the laser resonator Strah ^¬ and the crystal assembly first shutter member. Furthermore, the control unit may be configured to control the first movement device in dependence on an opening state of the first shutter element (in particular based on control data which are stored in a memory of the control unit).

The laser resonator can be, for example, a solid-state laser which emits laser radiation, in particular in the infrared range. The laser resonator ^¬ tor example, a Nd: YAG laser include. The frequency-multiplying crystal arrangement can comprise, for example, a crystal for frequency doubling (also: SHG crystal) and / or a crystal for frequency tripling (also: THG crystal). In addition to the control of the first movement device, the control unit can be set up to control the first shutter element. The first shutter element may, for example, comprise a mechanical shutter. The shutter element can be controlled to either block the laser beam so that the laser beam source is in a state in which it is does not generate a laser beam or makes it pass the laser beam (for example, by moving a mechanical shutter out of the beam path) so that the laser beam source is in a state of producing a laser beam. In other words, the first shutter element can be regarded as an on / off switch of the laser beam source for the frequency-multiplied laser radiation, and by driving the first shutter element, the laser beam source can be made to generate a laser beam or stop generation of a laser beam. Thus, by means of the shutter element, a period of time in which the frequency-multiplying crystal array is exposed to the laser beam can be reduced to times in which the laser beam is actually used for illuminating a substrate (for example, a thin-film layer).

A control in dependence on an opening state of the first shutter element can mean that a time sequence of the movement of the first and / or the second lens group is dependent (in particular triggered) on a closing or opening of the first shutter element. Expressed differently, a triggering of an opening of the shutter element can occur in a predefined temporal relationship with an activation of the first movement device. In particular, an activation of the first movement device can be triggered by an opening (or an open command) of the shutter element.

The control unit may be configured to control the first movement device so that (in particular immediately) after opening the first shutter element, the telescopic arrangement is moved continuously from a first position to a second position to a voltage by heating the Kristallanord (in particular in the laser) caused thermal lensing effect to compensate at least partially.

The control unit can take over the control of the first shutter element and the first movement device, wherein control data are stored in a memory of the control unit, which cause the control unit, immediately after opening the first shutter element, the telescope arrangement from the first position to drive the second position.

The thermal lensing effect may result in a displacement of a beam waist of the laser beam, the z. B. generated in the laser, lead along the optical axis. These Displacement in an optical system for generating a lighting line causes the focus width at the substrate and the focus position and thus the intensity to change. The control unit may be configured to compensate for this displacement so that a width of the illumination line (in particular along the short axis) and / or an intensity of the illumination line is kept substantially constant.

In a memory of the control unit control data may be stored, which are based for example on simulated data or calibration data describing a temporal dependence of the thermal lensing effect. The control data for controlling the first movement unit can be designed so that they compensate for this thermal lensing effect as best as possible.

The at least one telescope arrangement may be, for example, a Kepler telescope or a Galileo telescope. The telescope assembly may be configured to allow a substantially collimated incident laser beam to exit as a substantially collimated laser beam. The telescope arrangement in the case of a Kepler telescope can consist of two lens groups with positive refractive power and in particular of two individual converging lenses. In this case, an image-side focal point of the first lens group (which is arranged in the beam path in front of the second lens group) substantially coincide with an object-side focal point of the second lens group (in at least one possible position of the telescope arrangement). The telescope arrangement in the case of a Galileo telescope can consist of a first lens group (which is arranged in the beam path in front of the second lens group) with negative refractive power and a second lens group with positive refractive power. In this case, an object-side focal point of the first lens group may substantially coincide with an object-side focal point of the second lens group (in at least one possible position of the telescope arrangement). The Galileo telescope can thus represent a beam expander (for example, a 1: 5 beam expander or a 1: 5 telescope).

The telescope arrangement may be a Kepler telescope, wherein the first lens group and the second lens group have the same focal length. Alternatively, the second lens group may have a larger focal length than the first lens group, wherein the second lens group is arranged in the beam path behind the Ers th lens group, so that an incoming laser beam in the telescope arrangement exits as an expanded laser beam. In addition to the telescope tion can be located in the beam path in front of or behind the telescope arrangement another telescope arrangement. For example, the further telescope arrangement can be provided in the beam path behind the telescope arrangement, wherein the telescope arrangement is a telescope arrangement whose first and second lens group have the same focal length and wherein the further telescope arrangement is a beam-expanding telescope arrangement (for example, a 1: 5-telescopic).

The second lens group can be arranged in the beam path behind the first lens group, wherein the first movement device is arranged to move the first lens group, and wherein the second lens group (in particular with respect to other elements of the beam shaping device, with respect to the laser beam ^¬ source and / or with respect to the imaging device) is rigidly mounted. Thus, the first lens group may be moved by the moving means while the second lens group remains in place along with other (optical) elements of the beam shaping means. It has been found that the thermal lens effect can be compensated for particularly effectively by displacing the first lens group of the telescope arrangement.

The control unit may be configured to move the first lens group along the optical axis in the direction of the beam ^path after opening the first shutter element. The optical system may further comprise second moving means for moving the imaging means along the optical axis. With the Abbil ^¬ dung means a cylindrical focusing lens or a cylindrical lens can be meant, for example, immediately before the substrate. The control unit may be adapted to control the second moving means so that the imaging device is moved simultaneously with the at least one of the first and two ^¬ th lens group.

The movement of the imaging device may serve to compensate for a shift of the focus position (with respect to the short axis) along the optical axis, which is caused by the thermal lensing effect and / or by the movement of the first movement device. It can be stored in a memory of the control unit corresponding control data which a temporal and spatial sequence of the movement of the first and / or the second movement Define generating device. This control data may have been obtained based on a previous calibration or a previous simulation.

The control unit may be configured to control the second movement device such that (in particular immediately) the imaging device is moved continuously from a first position to a second position after opening the first shutter element.

The imaging device is in particular moved from the first position to the second position in order to compensate for a shift of a focus position of the short axis of the illumination line in the direction of the optical axis (in particular to the substrate). This shift of the focus position can be caused, for example, by the thermal lensing effect and / or the movement of the first movement device. The movement of the second movement device can ensure that a focus position in the direction of the optical axis and thus a width (FWHM) and an intensity of the illumination line in the imaging plane (the plane of the illuminated substrate) are kept constant.

The optical system may further comprise a second shutter element which is arranged in the beam path behind the crystal arrangement. The control unit may be configured to drive the first shutter element and the second shutter element so that first the first shutter element is opened while the second shutter element is closed, and after a predetermined period of time the second shutter element is opened.

Thus, in addition to the correction made by the first movement means, it can be ensured that a change in the optical properties of the optical system immediately after opening the first shutter element has no influence on the illumination line, since the second shutter element is still closed at this time , Only when the thermal lens effect has einigerma ^¬ SEN "leveled" or stabilized, the second shutter member is opened, and minor changes in the thermal lens effect can be compensated in the open state of the second shutter member by the first moving means or the change is small enough so that this is insignificant for the process.

According to a second aspect, a method for generating an illumination ^¬ line is provided. The method includes generating a laser beam along a optical axis, shaping the laser beam so that a beam profile of the laser beam has a long axis and a short axis, imaging the thus formed laser beam as a line of illumination, and moving at least a first lens group or a second lens group of a telescope assembly along the optical axis and the laser beam is generated, wherein the first lens group and the second lens group have an optical refractive power at least with respect to the short axis.

The embodiments made above with regard to the optical system of the first aspect also apply correspondingly to the method of the second aspect. In particular, the method of the second aspect can be carried out with the optical system of the first aspect, wherein all the details of the first aspect can also apply to the second aspect, as far as possible. A laser beam source which generates the laser beam may comprise a laser resonator, a frequency-multiplying crystal arrangement arranged downstream of the laser resonator in the beam path, and a first shutter element arranged in the beam path between the laser resonator and the crystal arrangement. The first lens group or the second lens group can be moved in response to an opening state of the first shutter element.

After opening the first shutter member, the telescopic arrangement may be continu ously ^¬ moved from a first position to a second position to a neffekt caused by heating of the crystal array thermal lentil to compensate at least partially.

The thermal lens effect can lead to a displacement of a beam waist of the laser beam ^¬ along the optical axis. The movement may result in compensating for this shift so that a width of the illumination line and / or an intensity (in particular the entire intensity distribution or at least a maximum intensity) of the illumination line is kept substantially constant.

The invention will be further explained with reference to the accompanying drawings, of which

1a, 1b show a schematic overview of an optical system for a system for processing thin-film layers from different viewing directions, Fig. 2 shows details of the laser beam source of the optical system of Fig. 1a, 1b and a displacement of the beam waist in the laser caused by the thermal lensing effect,

Fig. 3 is a schematic illustration of the displacement of the beam waist in the optical system of Figs. 1a, 1b and an associated change in the illumination of the cylindrical imaging lens,

Fig. 4 shows the effect of the effect of the thermal lens on the intensity and

Shows the width of the illumination line in the substrate plane,

Fig. 5 shows the effect of the effect of the thermal lens on the intensity and

Width of the illumination line with repeated switching on and off of the frequency-multiplied laser beam,

6 shows a schematic representation of the beam path (Gaussian beam propagation) in an optical system according to the invention,

Fig. 7 for the arrangement of FIG. 6, the effect of a shift of

Lens group no. 1 and the imaging device no. 5 on the width of the illumination line in the plane no. 6 shows,

Fig. 8 for the arrangement of Fig. 6 shows the time course of the displacement of the waist position of the laser beam in conjunction with a suitable shift of the lens group no. 1 and the imaging device no. 5, and

9 shows a chronological sequence of an activation of a first and a second shutter element.

An optical system for a system for processing thin-film layers is shown in FIG. 1a, 1b and designated generally by reference numeral 10. Although in the following ei ^¬ nem optical system 10 for a system for processing thin-film layers is mentioned, the described optical system 10 can be used for any other appli ^¬ tion, for which a lighting line is needed. The optical system 10 comprises a beam-shaping device 12, which is set up to form a laser beam 14 such that a beam profile 16 of the laser beam 14 has a long axis and a short axis, as well as a downstream in the beam path of the laser beam 14 of the beam shaping device 12 imaging device 18 which is adapted to the so-formed laser beam 14 as an illumination line 22. The imaging device 18 thus generates the short axis of the illumination line 22 from the short axis of the laser beam 14 formed by the beam shaping device 12.

By convention, in the figures, the short axis parallel to the x-axis, the long axis parallel to the y-axis and the optical axis of the optical system 10 parallel to the z-axis. In FIG. 1a, the optical system 10 is shown, for example, as seen from above (viewing direction along the x-direction), and in FIG. 1b, for example, seen from one side (viewing direction along the y-direction). The beam shaping device 12 may represent or comprise, for example, the anamorphic optics 42 shown in FIGS. 4 to 6 of DE 10 2012 007 601 A1.

In particular, the beam shaping device 12 may comprise one or more of the components 20, 54, 56, 58, 62, 66, 68, 74 shown in FIGS. 4 to 6 of DE 10 2012 007 601 A1.

In other words, the beam forming apparatus 12, a can by a (the x-axis of the coordinate system parallel) first imaging axis x (parallel to the y axis of the coordinate system) to the first imaging axis x perpendicular second Abbil ^¬ dung axis y, and a second to the first and Image axis x, y vertical (parallel to the z-axis of the coordinate system) optical axis z described ^¬ who. The beam shaping device 12 (for example as anamorphic optical system) has different Ab ^¬ education ^properties with respect to the first and the second imaging axis x, y. The beam-shaping device 12 may be configured to generate a laser beam 14 at the location "16" in front of the imaging device 18 (see, for example, FIGS. 1 a, 1 b) from laser light whose beam profile 16 has a long axis (y) and a short axis (x), wherein the beam profile in the long axis (y) has a largely homogenized (or substantially homogeneous) intensity ^¬ distribution. In detail: The beam shaping device 12 may comprise (in particular as anamorphic optical system) (see FIGS. 1a, 1b):

A first telescopic arrangement 20, which is optically active with respect to the short axis x, ie has a refractive power with respect to the short axis x. The first telescope arrangement 20 is composed of a first cylindrical lens 23 as a first lens group and a second cylindrical lens 24 as a second lens group. The first cylindrical lens 23 receives the laser beam 14 from a laser beam source 26 and focuses it with respect to the short axis x on a first intermediate image 28. The second cylindrical lens 24 is disposed in the beam path behind the first cylindrical lens 23 and collimates the light beams of the first intermediate image 28. As in 1 b, the first telescope arrangement 20 is a 1: 1 telescope, which is designed as a Kepler telescope. Here, the first cylindrical lens 23 and the second cylindrical lens 24 are each a converging lens having substantially the same focal length. The image-side focal point of the first cylindrical lens 23 substantially coincides with the object-side focal point of the second cylindrical lens.

A cylindrical lens 30 arranged in the beam path behind the first telescope arrangement 20 and having a refractive power with respect to the long axis y. The cylindrical lens 30 receives the laser beam 14, which was not influenced by the first telescope arrangement 20 with respect to the long axis y, from the laser beam source 26 and focuses it onto an intermediate image 32.

A cylindrical lens 34 arranged in the beam path behind the cylindrical lens 30 and having a refractive power with respect to the long axis y. The cylindrical lens 34 collimates the light beams of the intermediate image 32. As shown in FIG. 1a, the cylindrical lens 30 and the cylindrical lens 34 form a Kepler telescope which serves to widen the laser beam 14 with respect to the long axis y.

A arranged in the beam path behind the cylindrical lens 34 second Telesko ^¬ panordnung 36, which is optically effective with respect to the short axis x, ie, with respect to the short axis x has a refractive power. The second telescopic arrangement 36 is composed of a first cylindrical lens 38 as a first lens group and a second cylindrical lens 40 arranged in the beam path behind the first cylindrical lens 38 as a second lens group. The first cylindrical lens 38 expands the laser beam 14 with respect to the short axis x and the second cylindrical lens 40 collimates this expanded laser beam again. As shown in FIGURE 1b, the second telescope assembly 36 is a beam-expanding telescope (eg, a 1: 5 telescope) configured as a Galileo telescope. Here, the first cylindrical lens is a diverging lens 38 and the second cylindrical lens 40, a collecting ^¬ lens, wherein the focal points of the first cylindrical lens 38 and the second cylindrical lens 40 substantially coincide or are superimposed. The result is a virtual second intermediate image in the beam path in front of the first cylindrical lens 38 (not shown). Anamorphotic homogenizing optics 42 arranged in the beam path behind the second telescope arrangement 36 for (largely) homogenizing the laser beam 14 with respect to the long axis y.

An arranged in the beam path behind the anamorphic homogenization optics 42 and with respect to the long axis y refractive power having condensor cylinder lens 44 for superposition of the homogenized laser beams on the illumination line 22nd

In the beam path behind the condenser cylinder lens 44 is the imaging device 18. The imaging device 18 may comprise or represent, for example, the component 66 shown in FIGS. 4 to 6 of DE 10 2012 007 601 A1. In the latter case, the imaging device 18 thus represents, for example, a Fokussierzylinderlinsenoptik 66, which is arranged in the beam path behind the condenser cylinder lens 44 and serves to focus the laser beam 14 with respect to the axis x on the illumination line 22.

The beam forming device 12 downstream imaging device 18 thus attacks the beam profile 16 in front of the imaging device 18 and images the laser ^¬ beam 14 as the illumination line 22, wherein only (more precisely: exclusively) the short axis x of the beam profile 16, but not the homogenized long Axis y of the beam profile 16 is focused. The imaging device 18 is typically non from diffraction limited, but may in some embodiments also be diffraction limited ^¬ mapping. The illumination line generated by the optical system 10 22 may for crystallization of thin film layers, for example for the production of Dünnfilmtran ^¬ sistoren (in English: Thin film transistor; short TFT) are used. In this case, a semiconductor layer to be processed is acted upon by the illumination line 22 and guided over the semiconductor layer, wherein the intensity of the illumination line 22 is adjusted such that the semiconductor layer melts for a short time and solidifies again as a crystalline layer with improved electrical properties.

As described above, anamorphic optical arrangements are used to generate a laser line beam geometry. This z. B. in the one (long) beam axis y of the laser beam emitted from the laser beam source 26 14 homogenized by means of cylindrical lens arrays. The other (short) axis x is optically processed as Gauss beam and the beam waist of the laser beam source 26 in the Transfer level of homogenization. A typical arrangement is shown in Figs. 1a, 1b and has been discussed in detail above.

In the axis y to be homogenized, the laser beam 14 is widened cylindrically (typically 2 to 4 times) and guided on two successive lens arrays. The focal length of the condenser cylinder lens 44 produces the homogenized long beam axis y. The beam waist of the laser beam 14 formed in the laser beam source 26 is recollimated with a cylindrical 1: 1 telescope 20 and expanded with another telescope 36 to produce a Gaussian small beam axis x of the desired width with the focusing lens 18.

Fig. 2 shows details of the laser beam source 26 of the optical system 10 of Fig. 1a, 1b. The laser beam source 26 comprises a laser resonator 46 for generating the laser beam 14, which may be, for example, an infrared solid-state laser and in particular a Nd: YAG laser. Furthermore, the laser beam source 26 comprises in the beam path behind the laser resonator 46 a first shutter element 48, which is, for example, an electronically controllable mechanical shutter which is set up to block or pass the laser beam 14 entwe ^¬ der. The laser beam source 26 further comprises in the beam path behind the first shutter element 48, a converging lens 50 for focusing ^¬ the laser beam 14 in a frequency-multiplying crystal array 52, which is arranged in the beam path behind the converging lens 50. The frequency multiplying crystal array 52 includes an SHG crystal for doubling a frequency (or halving a wavelength, respectively) of the laser beam 14 and / or a THG crystal for tripling the frequency of the laser beam 14.

The laser beam source 26 further comprises a condenser lens as a recollimation lens 54. The recollimation lens 54 is suitable for substantially collimating the laser beam 14.

One possible mode of operation for operating the laser beam source 26 is to leave the laser resonator 46 permanently switched on (or at least for a longer period of time, which comprises a plurality of illumination processes), so that it generates a continuous infrared laser beam 14 that is very constant in time. However, the delicate crystal array 10 does not unnecessarily permanently suspend 52 (life limited by the generation of UV laser light) and optionally other components of the optical system of the (possibly interfering or GUESS ^¬-damaging) the laser radiation, the first shutter device 48 is only then opened when the illumination line 22 is really needed to illuminate a substrate. In other words, the laser beam 14 can be switched off by closing the first shutter element 48 when it is not needed, for example because a substrate to be illuminated is exchanged. In this way, a period of time in which the crystal array 52 is exposed to the laser beam 14 can be minimized and the effective life can be increased.

The above-described mode of operation of the laser beam source 26, in which the first shutter element 48 is opened when required, is also referred to below as burst mode. If, in the following, it is said that the laser beam source 26 emits / does not emit the laser beam 14 or the laser beam source 26 is switched on / off, this means that the first shutter element 48 is opened / closed at these times.

For the use of lighting lines z. As in lift-off applications (illumination of glued films on glass through the glass) but also in thin-film silicon crystallization application, it is important that the laser beam 14 a constant (ie constant time) width (FWHM) and peak intensity having.

The use of the burst mode can be important to reduce and optimize laser operating times and thus operating costs. In a typical lift-off process for large glass substrates, for example, the cycle time is in the range of 60-100 s, but the laser beam itself is only needed for about 20-30 s for the detachment of a plastic substrate from a glass carrier disk. In contrast to the burst mode, in continuous operation of the laser beam source 26, a process shutter (see the second shutter element 66 described below) would be closed and opened, and the laser beam source 26 would operate permanently and permanently illuminate the crystal array 52.

In burst mode operation the UV laser operation can be reduced from 60-100 to 20-30 s s and offers the potential, the operating costs to reduzie ^¬ ren by a factor of 2-4. When the above-described external (outside the laser resonator 46) frequenzver ^¬ multiple laser beam source 26 is operated in burst mode, is formed in Vervielfa ^¬ tion crystal (SHG and TFIG) 52 with the start of a pulse sequence (ie immediately after opening the first shutter element 48), a thermal lens (radial Tempe- temperature profile causes refractive index change) in the first 10-20 s, which then remains essentially stable until the pulse sequence is terminated. This thermal lens causes a laser beam waist, the laser beam 14th

characterized (beam quality, position, waist diameter and divergence angle) is generated optically at another location in the laser. The beam position can thereby change by several cm up to a half meter or even more, depending on how the focusing of the IR laser beam 14 into the frequency-multiplying crystal arrangement 52 is designed. In Fig. 2 it is shown how the position of the beam waist from the position 56 immediately after starting the pulse sequence (t = 0, when opening the first shutter element 48) to the position 58 after about t = 10-20 s is. In position 58, the optical system 10 and in particular the formed thermal lens is in thermal equilibrium and the position of the beam waist does not change significantly with the first shutter element 48 still open.

The virtual origin (waist) of the emitted laser beam 14 is passed through the thermal lens (in particular in the z-direction along the optical axis).

The jet waist position change has essentially no effect on the long line beam axis y to be homogenized.

The generation of the small beam axis x of the line beam, however, uses the Gaussian beam propagation, and thus it follows that the waist position in the laser beam source 26 has an influence on the beam waist in the focus of the objective lens 18.

Typically as that of FIG line in beam arrays. La, lb a line width (along the short axis x) between 10-100 pm FWHM (Full Width at Half ^¬ Maxi mum) generated. For this purpose, the laser beam is optically transported in the 1: 1 telescope (first telescope ^arrangement 20) and then expanded in the further telescope (second telescope arrangement 36) 1: 1 to 1: 5. The cylindrical lens 18 focuses the laser beam 14 into the homogenized plane (see FIG. 3, which shows the arrangement according to FIG. 1b).

The arrangement is designed so that beam waist position changes to the position of the focus behind the focusing lens 18 in the context of the set Schärfentie ^¬ fe practically have no effect. Basically, however, the position of the focus shifts (along the optical axis z). The changes in the position of the radiation elements in the laser beam source 26, however, have significant effects on the illumination of the cylindrical focusing lens 18 (imaging device 18). For the Gaussian beam propagation, the focus diameter follows the equation: d (l / e ² ) = 4 f AM ² / (n D (l / e ² ))

Here d is the diameter in focus and D is the diameter (1 / e ² ) of the laser beam 14 on the imaging device 18 with the focal length f, M ² is the beam quality number of the laser beam 14, l is the wavelength.

If, due to the displacement of the beam waist (see FIGS. 2 and 3) of the diameter D at the focusing lens 18, the focus diameter d becomes larger.

As a result, the peak intensity of the Gaussian distribution in the plane of the illumination line 22 drops.

This behavior has been observed in the optical ^¬ rule system according to Fig. La, lb with the laser beam 14, the laser beam source 26. With the switching on of a pulse sequence (opening of the first shutter element 48), a focus is observed which increases within typically 10-20 s to a ~ 10% greater width d. Thereafter, the width and intensity of the focus stabilizes.

This behavior, which is a result of the thermal lens produced in the crystal assembly 52, is shown in FIG. At time t = 720 s, the first shutter element 48 is opened and the laser beam source 26 generates the laser beam 14. As can be seen from the upper curve of FIG. 4 (intensity, left scale), the initial intensity of the illumination line 22 decreases from one Maximum value within the first approx. 10 s to a value which remains largely constant in the course of the further illumination (the first shutter element 48 remains open). Analogously, the width along the short axis x of the illumination line 22 (lower curve, FWHM, right scale) immediately at the switching on of the laser beam 14 to an initial value and then increases within the first about 10 s to a value which in the course of remains largely constant.

As shown in FIG. 5, the behavior of the BL LEVEL ^¬ tung line 22 described above is reproducible and also occurs with repeated switching on and off the laser beam source 26, that is on repeated opening and closing of the first shutter member 48 (in the recurring burst mode) , on. The crystal array 52 in the laser beam source 26 is actively stabilized to a target temperature to efficiently adjust the frequency conversion (refractive indices matching). For different burst mode sequences, a slightly different balance may occur.

According to the invention, the optical system 10 comprises a first movement device 60 (see, for example, FIGS. 1a, 1b), which is suitable for reducing and at best completely compensating for the above-described effect of varying the intensity and width (FWHM) of the illumination line 22.

In other words, according to the present invention, the 1: 1 telescope (the first telescope assembly 20) and / or the 1: 1 ... 5 telescope (the second telescope assembly 36) are specifically detuned to thereby accommodate the beam waist location change described above compensate for the fact that peak intensity and beam width at the substrate (ie in the plane of the illumination line 22) do not change or only slightly (for example <1%).

In the examined versions, it has been shown that the first telescope arrangement 20 (the 1: 1 telescope) is particularly suitable for this purpose. An adjustment of 0.1-0.2 mm is sufficient in certain arrangements. Since the temporal behavior of the

Radiation waist position change for defined burst mode sequences is reproducible, a fixed set time-dependent adjustment of the first lens group 23 (ie in the arrangement of Figures la, lb the closer to the laser beam source 26 positioned converging lens 23 of the first telescope assembly 20) with the start of the pulse sequence (ie with the opening of the first shutter element 48) can be used. As a first movement means 60 are linear actuators or, for example, piezo drives.

The shift of the focus with respect to the short axis x behind the focusing objective 18 is typically 20-100 pm along the optical axis z, a fraction of the usual depth of field. However, in principle it is possible, at the same time the imaging device 18 to proceed ^¬ using a second BEWE ^¬ restriction device 62 (the focus lens 18) also. In FIG. 6, the Gaussian beam propagation is provides ^¬ Darge in a real optical path. Using the beam propagation can beam diameter and focal position be true ^¬ are for the respective waist position in the laser beam source 26th The adjustment of the first cylindrical lens 38 is shown as an example for a compensation of the beam waist change in Fig. 7, at the same time the associated adjustment of the imaging device 18 for the configuration shown in Fig. 6. The simultaneous displacement of the imaging device 18 may be necessary if the depth of field is not significantly greater than the adjustment. The depth of field is determined by the beam quality of the laser beam 14 (measure M ² ) or by a possible treatment / reduction of the beam quality with a beam transformation optics. 7 shows a suitable change of a position of the first cylindrical lens 23 of the first telescope arrangement 20 ("telescope lens shift", right-hand scale) .A further suitable change of a position of the imaging apparatus 18 is shown ("focusing lens shift", right-hand scale). The resulting half-width ("FWHM") of the illumination line 22 with respect to the short axis x is also shown in FIG. 7, it being understood that it remains substantially constant and thus the effect of the thermal lens can be almost completely compensated.

FIG. 8 shows the same change of the first telescopic arrangement 20 and of the imaging device 18 as in FIG. 7 and additionally the change of the position of the beam waist ("waist position in the laser", left scale).

According to the invention, it is thus provided that at least one of the cylindrical lenses 23, 24, 38 and 40 is moved along the optical axis z by an associated first movement device 60 as soon as the laser beam source 26 is switched on, ie as soon as (or immediately after) the first shutter Element 48 of the laser ^¬ beam source 26 is opened. In this case, a displacement of the first cylindrical lens 23 of the first telescopic arrangement 20 has proven to be advantageous, wherein instead of or in addition, one of the cylindrical lenses 24, 38 and / or 40 can be moved in a similar manner.

Further, in the above Examples 7 and 8, a displacement of the Abbil ^¬-making device 18 using a second movement device 62 is the Fig. Described, which is however optional.

For controlling the movement of the first movement device 60 and possibly the second movement device 62, a control unit 64 is provided (see FIG. 1a, 1b). In addition to controlling the movement of the respective movement Supply device 60, 62, the control unit 64 for driving the laser beam source 26 is responsible. More specifically, the control unit 64 controls a timing of turning on and off the laser beam source 26 and the opening and closing of the first shutter member 48, respectively. The optional second shutter member 66 described later may also be controlled by the control unit 64.

The control unit 64 comprises a memory in which control data are stored, on the basis of which the first movement device 60 (and optionally the second movement device 62) perform a movement of the first cylindrical lens 23 (and optionally the imaging device 18). In particular, data may be stored which define a chronological sequence of a movement of the respective movement device 60, 62. Thus, the data stored in the memory of the controller 64 may be representative of that shown in FIGS. 7 and 8

be represented curve which describes the location of the first cylindrical lens 23 as a function of time. The same applies to the curve which describes the location of the imaging device 18 as a function of time.

The control data may have been obtained based on a previous calibration or may have been obtained by calculation and / or simulation, as described in connection with FIG.

In particular, the control unit 64 may be configured to move the first cylindrical lens 23 (in particular immediately after opening the first shutter element 48) in accordance with a predetermined position-time relationship. Optionally, the control unit 64 may be configured to proceed the imaging device 18 (particularly, immediately after opening of the first shutter member 48) in accordance with an agreed vorbe ^¬ space-time relationship.

The control unit 64 can also control other functions and / or elements of the optical system 10 or a system comprising the optical system 10, take over.

In addition to the above-described technique of moving a lens of the telescopic assemblies 20, 36, the optical system 10 according to an exporting ^¬ approximate shape optional second shutter member 66 comprise (see Fig. La, lb). The second shutter element 66 is located in the beam path at any point behind the crystal arrangement, for example, directly behind the laser beam source 26. The second shutter element 66 is driven by the control unit 64.

More specifically, the control unit 64 is adapted to drive the first shutter element 48 and the second shutter element 66 so that first the first shutter element is opened while the second shutter element 66 is closed and after one predetermined period of time (for example in the range of 10-20 s), the second shutter element 66 is opened. This sequence can ensure that a large change in the waist position immediately after switching on the laser beam source 26 (ie directly after the opening of the first shutter element 48) does not lead to a sharp change in the beam intensity or beam width of the illumination line 22 At this time of the strong initial change (for example in the first 10 s after opening the first shutter element 48), the second shutter element 66 still remains closed and no illumination line 22 is generated at this time. Only after the effect of the thermal lens has stabilized to some extent is the second shutter element 66 opened and a line of illumination 22 is generated whose intensity and width remain largely constant. Minor changes, which may still occur after this predetermined time in the position of the beam waist, are compensated by a movement of the first movement device 60 and possibly the second movement device 62, as described above.

The above-described technique of using a second shutter element 66 is shown in FIG. In the figure, the intensity of the illumination line 22 is plotted over time. For better illustration, FIG. 9 also shows the intensity of the illumination line 22 at times when the second shutter element 66 is closed and thus no illumination line 22 is generated at all. The intensity shown in these times is an intensity which the illumination line 22 would have when the second shutter element 66 was opened.

In Fig. 9, a period 68 is shown, in which the laser beam source 26 is turned on, that is, in which the first shutter element 48 is opened. During this period, the intensity would initially be at a maximum and would fall sharply within the first 10-20 s until a largely stable state is reached, see also Figs. 4 and 5. As indicated by the period 70, at the beginning, however, still closed, the second shutter member 66 (for a predetermined period of time 72 after opening the first shutter member 48) and no BL LEVEL ^¬ tung line 22 generates. Only after the period 72 in the period 74, the second Shutter element 66 (process shutter) is opened and a lighting line 22 is generated. Fluctuations in the intensity and / or width (FWHM) of the illumination line 22 are - as described in detail above - compensated by moving at least one lens group 23, 24, 38, 40 of at least one telescope arrangement 20, 36.

However, it is also possible in an example not to provide a first movement device 60 and a second movement device 62 and to compensate for the effect of the thermal lens only by controlling the second shutter element 66, as described in connection with FIG.

The above-described technique provides a way, compensate an effect of ther ^¬ mix lens and in particular an associated displacement of the beam waist of the laser beam 14 reliably and in a simple and reproducible manner to com-. In this way, a substrate with constant intensity and constant beam width can be illuminated, which leads to stable material properties and thus to an improved material quality.

The figures or their parts are not necessarily to be considered as true to scale. In this respect, for example, in Fig. Lb, the short axis x of the beam profile 16 appear to be longer than the long axis y in Fig. La.

Unless expressly stated otherwise, identical reference numerals in the figures stand for identical or identically acting elements. In addition, any combination of the features shown in the figures is conceivable.

Claims

Claims 1. An optical system (10) for generating a lighting line (22), comprising:

a laser beam source (26) for generating a laser beam (14) along an optical axis (z);

a beam shaping device (12) adapted to shape the laser beam (14) such that a beam profile (16) of the laser beam (14) has a long axis (y) and a short axis (x); and

an imaging device (18) arranged downstream of the beam shaping device (12) in the beam path of the laser beam (14) and configured to image the laser beam (14) thus formed as an illumination line (22),

wherein the beam-shaping device (12) has at least one telescope arrangement

(20) comprising a first lens group (23) and a second lens group (24), the first lens group (23) and the second lens group (24) having an optical power at least with respect to the short axis (x),

wherein the optical system (10) comprises a first moving means (60) for moving at least one of the first and second lens groups along the optical ^¬ rule axis (z), and

wherein the optical system (10) further comprises a control unit (64) adapted to drive the first movement means (62) to move the at least one of the first and second lens groups while the laser beam source (26) is moving the laser beam generated.

2. An optical system (10) according to claim 1,

wherein the laser beam source (26) comprises a laser resonator (46), a frequency multiplying crystal arrangement (52) arranged downstream of the laser resonator (46) in the beam path and a first shutter arranged in the beam path between the laser resonator (46) and the crystal arrangement (52). Includes element (48), and

wherein the control unit (64) is ^adapted to the first Bewegungsseinrich ^¬ device (60) in response to an opening state of the first shutter element (48) to control.

3. An optical system (10) according to claim 2,

wherein the control unit (64) is arranged to control the first movement device (60) in such a way that after opening the first shutter element (48) the telescope assembly (20) is driven continuously from a first position to a second position to at least partially compensate for a thermal lensing effect caused by heating of the crystal array (52). 4. An optical system (10) according to claim 3,

wherein the thermal lensing effect results in a displacement of a beam waist of the laser beam (14) along the optical axis (z), and wherein the control unit (64) is adapted to compensate for this displacement such that a width of the illumination line (22) and / or a maximum intensity of the illumination line (22) is kept substantially constant.

5. Optical system (10) according to one of claims 2 to 4,

wherein the at least one telescope arrangement (20) is a Kepler telescope or a Galileo telescope, and

said telescopic assembly (20) is arranged to a substantially collimated for exiting collimated laser beam ^¬ incoming laser beam as a substantially.

6. Optical system (10) according to claim 5,

wherein the telescope assembly (20) is a Kepler telescope and wherein the first lens group (23) and the second lens group (24) have the same focal length, or

wherein the second lens group (40) is arranged in the beam path behind the first lens group (38) and wherein the second lens group (40) has a greater focal length than the first group of sensors (38), so that a laser beam entering the telescope arrangement (36) is expanded Laser beam emerges.

7. An optical system (10) according to any one of claims 2 to 6,

wherein the second lens group (24) is arranged in the beam path behind the first lens group (23),

wherein said first moving means (60) for moving the first lens group ^¬ (23) is arranged, and

wherein the second lens group (24) is rigidly mounted. 8. An optical system (10) according to claim 7,

wherein the control unit (64) is adapted to move the first lens group (23) along the optical axis (z) in the direction of the beam path after opening the first shutter element (48).

The optical system (10) of any of claims 2 to 8, further comprising: second movement means (62) for moving the imaging means (18) along the optical axis (z),

wherein the control unit (64) is arranged to control the second movement device (62) such that the imaging device (18) is moved simultaneously with the at least one of the first and second lens groups.

10. An optical system (10) according to claim 9,

wherein the control unit (64) is arranged to control the second movement device (62) so that after opening the first shutter element (48) the imaging device (18) is moved continuously from a first position to a second position. 11. The optical system according to claim 2, further comprising: a second shutter element arranged in the beam path behind the crystal arrangement,

wherein the control unit (64) is arranged to control the first shutter element (48) and the second shutter element (66) in such a way that first the first shutter element (48) is opened while the second shutter element (48) 66) is closed, and after a predetermined period of time, the second shutter element (66) is opened.

12. A method of generating a lighting line, comprising:

- generating a laser beam (14) along an optical axis (z);

Forming the laser beam (14) such that a beam profile (16) of the laser beam (14) has a long axis (y) and a short axis (x);

Imaging the thus-formed laser beam (14) as a line of illumination (22); and

Moving at least a first lens group (23) or a second lens group (24) of a telescope arrangement (20) along the optical axis (z) and while the laser beam (14) is generated, the first lens group (23) and the second lens group (24) 24) have an opti ^¬ cal refractive power at least with respect to the short axis (x).

13. The method according to claim 12,

wherein a laser beam source (26), which generates the laser beam (14), a laser resonator (46), a laser resonator (46) in the beam path downstream comprising a frequency multiplying crystal arrangement (52) and a first shutter element (48) arranged in the beam path between the laser resonator (46) and the crystal arrangement (52), and

wherein the first lens group (23) or the second lens group (24) is moved in response to an opening state of the first shutter member (48).

14. The method according to claim 13,

wherein after opening of the first shutter element (48) the telescopic arrangement (20) is moved continuously from a first position to a second position in order to at least partially compensate for a thermal lensing effect caused by heating of the crystal arrangement (52).

15. The method according to claim 14,

wherein the thermal lensing effect results in a displacement of a beam waist of the laser beam (14) along the optical axis (z), and wherein the movement results in compensating for this displacement such that a width of the illumination line (22) and / or a maximum intensity of the Lighting line (22) is kept substantially constant.