JP2021508857A - Optical system for generating irradiation lines - Google Patents

Abstract

An optical system for generating an irradiation line is provided. The optics include a laser beam source for generating a laser beam along the optical axis. Further, the optical system forms an image of a beam shaping device configured to shape the laser beam so that the beam shape of the laser beam has a long axis and a short axis, and a laser beam shaped so as an irradiation line. It is provided with an imaging device which is configured as described above and is arranged after the beam shaping device in the beam path of the laser beam. The beam shaping device includes at least one telescope configuration including a first lens group and a second lens group, and the first lens group and the second lens group exert optical refractive power at least with respect to the short axis. Have. The optical system includes a first moving device for moving at least one of the first lens group and the second lens group along the optical axis. The optics are further controlled to control the first moving device such that at least one of the first lens group and the second lens group moves while the laser beam source generates the laser beam. Equipped with a unit. Further provided are methods for generating irradiation lines.
[Selection diagram] FIG. 1b

Description

The present invention is used to generate an optical system for generating an irradiation line for so-called laser lift-off applications or equipment for processing a thin film layer, and particularly for generating an irradiation line for laser lift-off applications or processing a thin film layer. Regarding the method.

The techniques presented below can be used, for example, in connection with laser lift-off applications. For laser lift-off applications, the plastic substrate is peeled off from the glass carrier. In this case, the laser line (ie, the irradiation line) is focused on the plastic substrate through clear glass. The bond is melted with a laser beam and the plastic substrate is non-contactly separated from the glass substrate. For example, flexible OLED displays are made on PI foil glued to a glass plate for manufacturing. After manufacturing, including a vapor deposition process and a photolithography process, the display substrate is stripped from the glass carrier using a laser lift-off (LLO) process. In this process, for example, a pulsed solid-state laser is used that emits laser beams of 343 nm and 355 nm and is well absorbed by the polyimide layer or the adhesive layer, but is nearly transparent to the glass.

Possible uses of the LLO process are, for example, stripping flexible OLED display substrates from glass carriers. In this case, for example, a polyimide film having a thickness of 0.5 mm and a thickness of several to 100 μm is adhered onto a flat glass plate, and an OLED display structure is formed on the polyimide film. Once the display film is complete, it must be removed from the glass carrier. For this purpose, a laser line is focused on a plastic film through a glass that is permeable to 343 nm or 355 nm. At a typical energy density of 100-500 mJ / cm ^2, the bond is melted by moving a line 20-50 μm wide over it at a rate of 50-300 mm / s. At this time, the plastic substrate is not damaged, and the flexible OLED display substrate can be used for secondary processing in, for example, a smartphone.

Another use of the presented technique relates to the processing of thin film layers. For example, a laser is used to crystallize a thin film transistor in order to manufacture a thin film transistor (abbreviation: TFT). As the semiconductor to be processed, in particular silicon (abbreviation: Si), more accurately a-Si is used. The thickness of the semiconductor layer is, for example, 50 nm, which is usually on a substrate (eg, a glass carrier) or other carrier.

The layer is irradiated with light from a laser, such as a pulsed solid-state laser. In this case, for example, light having a wavelength of 532 nm or 515 nm is shaped into an irradiation line. For this, refer to, for example, German patent application DE1020122003701Al or international patent application WO2013 / 156384Al. Lasers with wavelengths of 343 nm and 355 nm have also been used in these processes for several years. A beam shaping device can be used to shape the laser beam so that the beam shape of the laser beam has a major axis and a minor axis. Subsequently, in order to generate an irradiation line from the light of the laser beam, the laser beam shaped in this way is imaged as an irradiation line by an imaging device arranged after the beam shaping device in the optical path of the laser beam. .. Corresponding optics are described, for example, in German patent application DE102015002537.

Specifically, the beam shaping apparatus can include, for example, an anamorphic optical system and can have different imaging characteristics with respect to the first imaging axis and the second imaging axis. In particular, the beam shaping apparatus can be configured to generate a laser beam having a long axis and a short axis in the beam shape from the laser beam at a position immediately before the imaging apparatus. This beam shape has a (nearly) homogenized (or substantially homogeneous) intensity distribution on the long axis. Next, the imaging apparatus focuses the short axis (particularly only the minor axis) of the beam shape generated immediately before the imaging apparatus by the beam shaping apparatus to generate the minor axis of the irradiation line. However, since the imaging device does not have (substantially) focusing characteristics with respect to the (especially) long axis, the long axis of the beam shape generated by the beam shaping device immediately before the imaging device can be substantially changed. It can pass through the imaging device without it, and therefore can correspond to the long axis of the irradiation line.

Accordingly, the irradiation line has a short axis and a long axis similar to the previously shaped beam shape of the laser beam, and for clarification, especially the beam shape of the laser beam before being imaged by the imaging device. The minor axis of the beam corresponds to the minor axis of the irradiation line, and the major axis of the beam shape corresponds to the (homogenized) major axis of the irradiation line. The intensity distribution of the irradiation line along the long axis is ideally rectangular, for example, the length (or half width, English: Full Width at Half Maximum, abbreviation: FWHM) is 100 mm, for example 750 mm to 1000 mm or more. is there. The intensity distribution along the short axis is usually a Uth distribution, with a FWHM of about 5 μm to 100 μm. Therefore, the minor axis and the major axis form a relatively high aspect ratio.

The irradiation line is guided on the semiconductor layer in the direction of the minor axis at a feed rate of about 1 mm / s to 50 mm / s, preferably 10 mm / s to 20 mm / sec. The intensity of the light beam (in the case of a continuous wave laser) or pulse energy (in the case of a pulsed laser) is such that the semiconductor layer melts for a short time (that is, on a time scale of about 50 ns to 100 μs), and again as a crystal layer with improved electrical characteristics. Adjusted to solidify.

Alongside the application fields described above in connection with the manufacture of LLOs and thin film transistors, there is a series of other application fields that require the generation of high aspect ratio irradiation lines to irradiate the substrate.

The quality of the generated irradiation line depends in particular on the spatial intensity distribution integrated along the minor and / or major axes and affects the material of the substrate processed in the irradiation line. During the crystallization of the amorphous silicon layer, the slight inhomogeneity of the intensity distribution along the major axis, eg, from the (ideal) homogeneous intensity distribution in the low percentage range of an order of magnitude (eg about 2%). Local deviations or modulations of absolute intensity also cause spatial inhomogeneity within the crystal structure (eg, due to local variations in particle size) when sending the irradiation line, which affects the quality of the thin film transistor. As a result, it also affects the quality of the thin film transistor. From here, the following relationship arises. The more homogeneous (ie, uniform) the intensity distribution of the irradiation line, the more homogeneous (more uniform) the crystal structure of the thin film transistor, and the more homogeneous (more uniform) the crystal structure of the thin film transistor is The properties of the TFT in the region are more homogeneous (more uniform).

Along with the spatial homogeneity of the intensity of the irradiation line described above, the temporal homogeneity of the intensity (meaning the temporal change in intensity during scanning) is relatively important. Due to temporary fluctuations in the intensity of the irradiation line, the area in which the irradiation line is guided differs (ie, heterogeneous or non-uniform) in the material to be irradiated, resulting in an undesired non-uniformity of the final product. It may lead to various characteristics.

Against this background, it is desirable to keep the optical characteristics of the generated irradiation line as constant as possible in time. In particular, it is desirable to keep the intensity of the irradiation line (particularly the overall intensity distribution or at least the maximum intensity) and the full width at half maximum (FWHM) of the irradiation line along the minor axis as constant as possible in terms of time.

An object of the present invention is therefore to provide an improved optical system that allows the generation of high quality, time-consistent irradiation lines, especially for the generation of equipment for processing thin film layers. Is.

The above problems are solved based on the optical system according to claim 1 and based on the method according to claim 12.

According to the first aspect, an optical system for generating an irradiation line (especially for equipment for processing a thin film layer) is provided. The optics include a laser beam source for generating a laser beam along the optical axis. Further, the optical system includes a beam shaping device configured to shape the laser beam so that the beam shape of the laser beam has a long axis and a short axis (particularly oriented perpendicular to the long axis). A laser beam shaped like this (particularly the short axis of the laser beam shaped in this way) is configured to form an image as (or above) an irradiation line of the beam shaping device within the beam path of the laser beam. It is provided with a (particularly cylindrical) imaging device arranged in the subsequent stage. The beam shaping device includes at least one telescope configuration including a first lens group and a second lens group, and the first lens group and the second lens group exert optical refractive power at least with respect to the short axis. Have. The optical system has a first moving device for moving at least one of a first lens group and a second lens group along an optical axis. The optics are further controlled to control the first moving device such that at least one of the first lens group and the second lens group moves while the laser beam source generates the laser beam. Equipped with a unit.

The beam shape of the laser beam is understood as the beam shape of the laser beam, especially in front of (especially immediately before) the imaging device. The telescope configuration is also called a telescope configuration, and represents the lens group or the optical configuration of the lens of this configuration and their optical characteristics. In particular, the telescope configuration can be a Kepler telescope or a Galileo telescope, as described in detail below. The telescope configuration includes at least a first lens group and a second lens group. It should be understood that the term "lens group" may here be a lens group composed of a single lens (eg, a focusing lens or a diffuser lens) or a plurality of (eg, joined) lenses, respectively. Thus, in the simplest case, the telescope configuration can consist of two individual lenses, each forming a unique lens group as a single lens. The telescope configuration can be configured such that the focal point of the first lens group spatially coincides with the focal point of the second lens group. The first lens group may consist of, for example, a single cylinder lens or may consist of a plurality of cylinder lenses. The same applies regardless of the arrangement of the first lens group with respect to the second lens group.

The optical axis extends along the z-axis according to the conventions used herein. Therefore, the first moving device is configured to move the first lens group, the second lens group, or both lens groups along the z-axis. For this purpose, the first moving device can include, for example, a linear servomotor or a piezo element.

For example, the terms "first" and "second" used in connection with the "first mobile device" and the "second mobile device" described below are used solely to distinguish them. It does not have the above meaning. Alternatively, for example, the "first mobile device" may be referred to as a "mobile device" and the "second mobile device" may be referred to as an "another mobile device".

The control unit can include, for example, at least one processor and at least one memory. The memory can store instructions for causing the control unit to control the first mobile device according to a predetermined sequence. Further, the control unit can also be used to control other elements of the optical system, such as a laser beam source and both shutter elements described below.

The techniques described above have the effect and advantage of being able to compensate for the optical changes in the optical system that occur during the generation of the laser beam by moving or adjusting the telescope configuration. The thermal lens effect due to the heating of the optical components of the optics, in particular caused by the laser beam, can be compensated or at least reduced by the movement of the first moving device.

The laser beam source includes a laser cavity, a frequency-multiplied crystal configuration located after the laser cavity in the beam path, and a first shutter element located between the laser cavity and the crystal structure in the beam path. Can include. Further, the control unit can be configured to control the first mobile device (particularly based on the control data stored in the memory of the control unit) according to the open state of the first shutter element.

The laser cavity can be, for example, a solid-state laser that emits a laser beam, especially in the infrared range. The laser cavity can include, for example, an Nd: YAG laser. The frequency multiplying crystal structure may include, for example, a crystal for frequency doubling (also referred to as SHG crystal) and / or a crystal for frequency doubling (also referred to as THG crystal). Along with the control of the first mobile device, the control unit can be configured to control the first shutter element. The first shutter element can include, for example, a mechanical shutter. The shutter element either blocks the laser beam so that the laser beam source does not generate a laser beam or passes the laser beam (eg, by moving the mechanical shutter out of the beam path), so that the laser beam source Can be controlled to generate a laser beam. In other words, the first shutter element can be thought of as an on / off switch for the laser beam source for a frequency-multiplied laser beam, and by controlling the first shutter element, the laser can be applied to the laser beam source. The beam can be generated or the laser beam can be stopped. Therefore, the time that the frequency-multiplied crystal structure is exposed to the laser beam by using the shutter element can be shortened to the time that the laser beam is actually used for irradiating the substrate (for example, the thin film layer).

The control according to the open state of the first shutter element means that the temporal sequence of movement of the first and / or second lens group depends on the closing or opening of the first shutter element (particularly triggered). Means that. In other words, the control of opening the shutter element can be in a predetermined temporal relationship with the control of the first mobile device. In particular, the control of the first moving device can be triggered by the release (or release command) of the shutter element.

The control unit has a first telescope configuration (especially immediately after) after the first shutter element is opened to at least partially compensate for the thermal lens effect caused by heating the crystalline configuration (especially in the lens). The first moving device can be configured to control the first moving device so as to continuously move from the position of.

The control unit can take control of the first shutter element and the first moving device, and the telescope configuration is moved from the first position to the second position immediately after the first shutter element is opened in the control unit. The control data to be moved is stored in the memory of the control unit.

Due to the thermal lens effect, for example, the beam waist of a laser beam generated in a laser may be displaced along the optical axis. This displacement leads to changes in the focal width and position, and thus the intensity, on the substrate in the optical system for generating the irradiation line. The control unit can be configured to compensate for this displacement so that the width of the irradiation line (especially along the minor axis) and / or the intensity of the irradiation line remains substantially constant.

The memory of the control unit can store, for example, simulated data or control data based on calibration data that describes the time dependence of the thermal lens effect. The control data for controlling the first moving unit can be designed to compensate for this thermal lens effect in the best possible way.

The at least one telescope configuration may be, for example, a Kepler telescope or a Galileo telescope. The telescope configuration can be configured to emit a substantially collimated incident laser beam as a substantially collimated laser beam. In the case of the Kepler telescope, the telescope configuration can consist of two groups of lenses with positive power, in particular two individual focusing lenses. Here, the image-side focus of the first lens group (located in front of the second lens group in the beam path) is that of the second lens group (at at least one possible position in the telescope configuration). It can substantially coincide with the focal point on the object side. For the Galileo telescope, the telescope configuration consists of a first lens group with negative power (located in front of the second lens group in the beam path) and a second lens with positive power. Can consist of groups. Here, the object-side focus of the first lens group can substantially coincide with the object-side focus of the second lens group (at at least one possible position in the telescope configuration). Thus, the Galileo telescope can represent a beam expander (eg, a 1: 5 beam expander or a 1: 5 telescope).

The telescope configuration can be a Kepler telescope in which the first lens group and the second lens group have the same focal length. Alternatively, the second lens group can have a larger focal length than the first lens group, since the second lens group is located behind the first lens group in the beam path. , The laser beam incident on the telescope configuration is emitted as a magnified laser beam. In addition to this telescope configuration, another telescope configuration can be placed in front of or behind the telescope configuration in the beam path. For example, another telescope configuration is provided after the telescope configuration in the beam path, and the telescope configuration is a telescope configuration in which the first lens group and the second lens group have the same focal length, and another telescope configuration is provided. The scope configuration can be a telescope configuration that expands the beam (eg, a 1: 5 telescope).

The second lens group can be placed behind the first lens group in the beam path, the first moving device is configured to move the first lens group, and the second lens group (particularly). It is statically supported (with respect to the laser beam source and / or the imaging device) with respect to other elements of the beam shaping device.

Thus, while the first lens group can be moved by the moving device, the second lens group stays in their place along with the other (optical) elements of the beam shaping device. It was found that the thermal lens effect can be compensated particularly effectively by displacing the first lens group of the telescope configuration.

The control unit can be configured to displace the first lens group along the optical axis in the direction of the beam path after the first shutter element is opened.

The optical system can further include a second moving device for moving the imaging device along the optical axis. The imaging device can mean, for example, a cylindrical focusing lens or a cylindrical objective lens immediately in front of the substrate. The control unit can be configured to control the second moving device so that the imaging device moves at the same time as at least one of the first lens group and the second lens group.

The movement of the imaging device can serve to compensate for the displacement of the focal position along the optical axis (with respect to the minor axis) caused by the thermal lens effect and / or the movement of the first moving device. The memory of the control unit can store appropriate control data that defines the temporal and spatial sequence of movement of the first and / or second mobile device. These control data can be obtained based on previous calibration or previous simulation.

The control unit can be configured to control the second moving device so that the imaging device continuously moves from the first position to the second position after the first shutter element is opened.

The imaging apparatus moves from a first position to a second position in particular to compensate for the short axis focal position of the irradiation line being displaced in the direction of the optical axis (particularly towards the substrate). This displacement of the focal position is caused, for example, by the thermal lens effect and / or the movement of the first moving device. The movement of the second moving device can ensure that the focal position in the direction of the optical axis, and thus the width (FWHM) and intensity of the irradiation line in the imaging plane (the plane of the irradiated substrate) is kept constant.

The optics can further include a second shutter element located behind the crystal structure in the beam path. The control unit can be configured to control so that the first shutter element opens first while the second shutter element is closed, and the second shutter element opens after a predetermined time has elapsed.

Therefore, in addition to the correction performed by the first moving device, immediately after the first shutter element is opened, the second shutter element is still closed at this point, so that the change in the optical characteristics of the optical system is irradiated. It can be guaranteed that it does not affect the line. The second shutter element opens only when the thermal lens effect is "calm" or stable to some extent, and slight changes in the thermal lens effect can be compensated by the first moving device with the second shutter element open. Or this change is small enough that it is not important to the process.

According to the second aspect, a method for generating an irradiation line is provided. In this method, a laser beam is generated along the optical axis, the laser beam is shaped so that the beam shape of the laser beam has a long axis and a short axis, and the laser beam thus shaped is used as an irradiation line. The first lens group and the second lens group include the imaging and the movement of at least one of the first lens group or the second lens group of the telescope configuration along the optical axis while generating the laser beam. The lens group has an optical refractive force at least with respect to the minor axis.

The description given above for the optical system of the first aspect also applies to the method of the second aspect. In particular, the method of the second aspect can be carried out using the optical system of the first aspect, and all the details of the first aspect can be applied to the second aspect as much as possible.

The laser beam source that generates the laser beam is arranged between the laser cavity, the frequency-multiplied crystal configuration placed after the laser cavity in the beam path, and between the laser cavity and the crystal structure in the beam path. It can include a first shutter element. The first lens group or the second lens group can move according to the open state of the first shutter element.

The telescope configuration can be continuously moved from the first position to the second position after the first shutter element is opened to at least partially compensate for the thermal lens effect caused by heating the crystalline configuration.

The thermal lens effect can displace the beam waist of the laser beam along the optical axis. The movement can ensure that the width of the irradiation line and / or the intensity of the irradiation line (especially the overall intensity distribution or at least the maximum intensity) remains substantially constant.

The present invention will be described below with reference to the accompanying drawings.

It is a figure which shows the outline from the different observation directions of the optical system for the equipment for processing a thin film layer. It is a figure which shows the outline from the different observation directions of the optical system for the equipment for processing a thin film layer. It is a figure which shows the detail of the laser beam source of the optical system shown in FIGS. 1a and 1b, and the displacement of the beam waist in a laser caused by the thermal lens effect. It is a figure which shows the outline of the displacement of the beam waist in the optical system of FIGS. 1a and 1b, and the change of the irradiation of a cylindrical imaging lens accompanying it. FIG. 4 shows the effect of the thermal lens effect on the intensity and the width of the irradiation line on the substrate plane. FIG. 5 shows the effect of the thermal lens effect on the intensity and the width of the irradiation line when the frequency-multiplied laser beam is repeatedly turned on / off. It is a figure which shows the outline of the beam transition (Gaussian beam propagation) in the optical system by this invention. Regarding the configuration shown in FIG. 6, the lens group No. 1 and the imaging device No. 5 is the plane No. It is a figure which shows the influence on the width of the irradiation line in 6. Regarding the configuration shown in FIG. 6, the transition of the waist position of the laser beam with time and the lens group No. 1 and imaging device No. It is a figure which shows the relationship with the appropriate displacement of 5. It is a figure which shows the temporal sequence of control of the 1st and 2nd shutter elements.

The optical system for the equipment for processing the thin film layer is shown in FIGS. 1a and 1b, and is generally represented by 10. Although the optical system 10 for equipment for processing a thin film layer will be described below, the described optical system 10 can be used for any other application in which an irradiation line is required. The optical system 10 includes a beam shaping device 12 configured to shape the laser beam 14 so that the beam shape 16 of the laser beam 14 has a long axis and a short axis, and a beam shaping device within the beam path of the laser beam 14. It is provided with an imaging device 18 which is arranged after the 12 and is configured to image the laser beam 14 thus shaped as an irradiation line 22. Therefore, the imaging device 18 generates the short axis of the irradiation line 22 from the short axis of the laser beam 14 formed by the beam shaping device 12.

By convention, the short axis is parallel to the x-axis, the long axis is parallel to the y-axis, and the optical axis of the optical system 10 extends parallel to the z-axis in the figure. FIG. 1a shows, for example, the optical system 10 viewed from above (the line-of-sight direction along the x direction), and FIG. 1b shows, for example, the optical system 10 viewed from above (the line-of-sight direction along the y direction). It is shown.

The beam shaping apparatus 12 can form or include, for example, the anamorphic optical system 42 shown in FIGS. 4 to 6 of German patent application DE1020123007031A1. In particular, the beam shaping apparatus 12 can include one or more of the components 20, 54, 56, 58, 62, 66, 68, 74 shown in FIGS. 4 to 6 of German patent application DE10201200760A1.

In other words, the beam shaping device 12 has a first imaging axis x (parallel to the x-axis of the coordinate system), a second imaging axis y perpendicular to the first imaging axis x, and a first connection. It can be represented by an optical axis z (parallel to the z-axis of the coordinate system) perpendicular to the image axis x and the second imaging axis y. The beam shaping apparatus 12 (for example, as an anamorphic optical system) has different imaging characteristics with respect to the first imaging axis x and the second imaging axis y. The beam shaping device 12 is a laser beam 14 having a beam shape 16 having a major axis (y) and a minor axis (x) from the laser beam at a position “16” (see, for example, FIGS. 1a and 1b) in front of the imaging device 18. The beam shape has a nearly homogenized (or substantially homogeneous) intensity distribution along the long axis (y).

In detail, the beam shaping device 12 (particularly the anamorphic optics) can include: (see FIGS. 1a and 1b).
-A first telescope configuration 20 that acts optically with respect to the minor axis x, i.e. has a refractive power with respect to the minor axis x. The first telescope configuration 20 is composed of a first cylinder lens 23 which is a first lens group and a second cylinder lens 24 which is a second lens group. The first cylinder lens 23 receives the laser beam 14 from the laser beam source 26 and focuses it on the first intermediate image 28 with respect to the minor axis x. The second cylinder lens 24 is located behind the first cylinder lens 23 in the beam path and collimates the light rays of the first intermediate image 28. As shown in FIG. 1b, the first telescope configuration 20 is a 1: 1 telescope designed as a Kepler telescope. Here, the first cylinder lens 23 and the second cylinder lens 24 are condenser lenses having substantially the same focal length. The image-side focus of the first cylinder lens 23 substantially coincides with the object-side focus of the second cylinder lens.
-Cylinder lens 30 located behind the first telescope configuration 20 in the beam path and having a refractive power with respect to the major axis y. The cylinder lens 30 receives from the laser beam source 26 the laser beam 14 unaffected by the first telescope configuration 20 with respect to the major axis y and focuses on the intermediate image 32.
-Cylinder lens 34 located behind the cylinder lens 30 in the beam path and having a refractive power with respect to the major axis y. The cylinder lens 34 collimates the light rays of the intermediate image 32. As shown in FIG. 1a, the cylinder lens 30 and the cylinder lens 34 form a Kepler telescope that acts to magnify the laser beam 14 with respect to the major axis y.
-A second telescope configuration 36 that is located behind the cylinder lens 34 in the beam path and acts optically with respect to the short axis x, i.e. has a refractive power with respect to the short axis x. The second telescope configuration 36 includes a first cylinder lens 38, which is a first lens group, and a second lens group, which is a second lens group arranged behind the first cylinder lens 38 in the beam path. It is composed of a cylinder lens 40. The first cylinder lens 38 magnifies the laser beam 14 with respect to the minor axis x, and the second cylinder lens 40 collimates the magnified laser beam again. As shown in FIG. 1b, the second telescope configuration 36 is a beam-expanding telescope (eg, a 1: 5 telescope) designed as a Galileo telescope. Here, the first cylinder lens 38 is a diffusion lens, the second cylinder lens 40 is a focusing lens, and the focal points of the first cylinder lens 38 and the second cylinder lens 40 are substantially aligned or up and down. It overlaps with. A virtual second intermediate image (not shown) occurs in front of the first cylinder lens 38 in the beam path.
-Anamorphic homogenizing optics 42 placed behind the second telescope configuration 36 in the beam path to (mostly) homogenize the laser beam 14 with respect to the major axis y.
-A condensing cylinder lens 44 that is located behind the anamorphic homogenizing optics 42 in the beam path and has refractive power with respect to the major axis y to superimpose on the homogenized laser beam on the irradiation line 22.

There is an imaging device 18 in the beam path behind the condensing cylinder lens 44. The imaging apparatus 18 includes, for example, the component 66 shown in FIGS. 4 to 6 of the German patent application DE102012007601A1, or can form the component 66. In the latter case, the imaging apparatus 18 forms, for example, a focusing cylinder lens optical system 66 that is arranged in the beam path behind the focusing cylinder lens 44 and functions to focus the laser beam 14 on the irradiation line 22 with respect to the axis x. ..

Therefore, the imaging device 18 arranged after the beam shaping device 12 picks up the beam shape 16 in front of the imaging device 18, shapes the laser beam 14 as the irradiation line 22, and at that time, the beam shape 16 is homogeneous. Instead of focusing on the modified major axis y, it is simply (more precisely) focused on the minor axis x of the beam shape 16. The imaging device 18 typically forms an image without limited diffraction, but in some embodiments the diffraction can also be limited to form an image.

The irradiation line 22 generated by the optical system 10 can be used for crystallization of a thin film layer, for example, for manufacturing a thin film transistor (abbreviation: TFT). In this case, the irradiation line 22 is irradiated on the semiconductor layer to be processed and guided on the semiconductor layer 21. At that time, the intensity of the irradiation line 22 is adjusted so that the semiconductor layer melts for a short time and solidifies again as a crystal layer having improved electrical characteristics.

As mentioned above, an anamorphic optical configuration is used to generate the laser line beam shape. Here, for example, the laser beam 14 emitted from the laser beam source 26 is homogenized using a cylinder lens array in one (long) beam axis y. The other (short) axis x is optically treated as a Gaussian beam and the beam waist of the laser beam source 26 is transferred to a homogenized plane. Typical configurations are shown in FIGS. 1a and 1b and have been described in detail above.

On the homogenized axis y, the laser beam 14 is expanded cylindrically (typically 2-4 times) and guided onto two consecutive lens arrays. A homogenized long beam axis y is generated at the focal length of the condensing cylinder lens 44. The beam waist of the laser beam 14 formed by the laser beam source 26 is recollimated with a cylindrical 1: 1 telescope 20, magnified by another telescope 36, and a Gaussian small beam of the desired width by the focusing lens 18. Generate an axis.

FIG. 2 shows the details of the laser beam source 26 of the optical system 10 of FIGS. 1a and 1b. The laser beam source 26 includes a laser cavity 46 for generating the laser beam 14, which may be, for example, an infrared solid-state laser, particularly an Nd: YAG laser. Further, the laser beam source 26 includes, for example, a first shutter element 48 in the beam path behind the laser cavity 46, which is an electronically controllable machine configured to block or pass the laser beam 14. It is a typical shutter. The laser beam source 26 further includes a focusing lens 50 that focuses the laser beam 14 on a frequency multiplying crystal structure 52 arranged in the beam path behind the focusing lens 50 behind the first shutter element 48 in the beam path. .. The frequency-multiplied crystal configuration 52 includes an SHG crystal for doubling (or halving) the frequency of the laser beam 14 and / or a THG crystal for trebling the frequency of the laser beam 14.

The laser beam source 26 further includes a focusing lens as the recollaboration lens 54. The recollaboration lens 54 is suitable for largely collimating the laser beam 14.

A possible mode of operation for operating the laser beam source 26 is very constant in time, leaving the laser cavity 46 permanently (or for an extended period of time including at least multiple irradiation processes) on. Is to generate the continuous infrared laser beam 14 of the above. However, in order not to expose the sensitive crystal structure 52 (lifetime limitation due to the generation of UV laser light) and, in some cases, another component of the optical system 10 unnecessarily long (possibly damaging or damaging) the laser beam. The first shutter element 48 opens only when the irradiation line 22 is actually required to irradiate the substrate. In other words, if the laser beam 14 is not needed, for example when the substrate to be irradiated is just replaced, the laser beam 14 can be switched off by closing the first shutter element 48. In this way, the time that the crystal structure 52 is exposed to the laser beam 14 can be minimized, and the effective service life can be extended.

The operation mode of the laser beam source 26 in which the first shutter element 48 opens as needed is also hereinafter referred to as a burst mode. In the following, when it is stated that the laser beam source 26 emits / does not emit the laser beam 14, or the laser beam source 26 is switched on / off, it means that the first shutter element 48 is open for that time. / Means that it is closed.

The width of the laser beam 14 is constant (that is, does not change over time), for example, for use in lift-off applications (irradiating a film adhered on glass through glass), and also in thin film silicon crystallization applications. It is important to have (FWHM) and peak intensity.

The use of burst mode is important for optimizing laser operating time, thus reducing and operating costs. In a typical lift-off process for large glass carriers, for example, the cycle time is in the range of 60-100 seconds, but the laser beam itself only takes about 20-30 seconds to detach the plastic substrate from the glass carrier substrate. .. Contrary to the burst mode, in the continuous operation of the laser beam source 26, the process shutter (see the second shutter element 66 described further below) is opened and closed, the laser beam source 26 operates permanently, and the crystal structure 52 is permanently operated. Will be irradiated.

In burst mode operation, the UV laser operation can be shortened from 60 to 100 seconds to 20 to 30 seconds, providing the possibility of reducing the operating cost by 2 to 4 times.

When the external frequency-multiplying laser beam source 26 described above (outside the laser cavity 46) is operated in burst mode, the multiplying crystal (SHG) occurs at the start of the pulse sequence (ie, immediately after the first shutter element 48 opens). And TFIG) 52, a thermal lens is formed in the first 10-20 seconds (the radial temperature profile causes a change in the index of refraction) and is then substantially stable until the end of the pulse sequence. This thermal lens features a laser beam (beam quality, position, waist diameter, diffusion angle) that optically generates a laser beam waist elsewhere in the laser. In this case, the beam position can vary from a few centimeters to 0.5 meters or more, depending on how the focus of the IR laser beam 14 onto the frequency multiplying crystal structure 52 is designed. In FIG. 2, the position of the beam waist has moved from the position 56 immediately after the start of the pulse sequence (t = 0, when the first shutter element 48 is opened) to the position 58 after about t = 10 to 20 seconds. It is shown. At position 58, the optical system 10, particularly 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 open.

The virtual origin (waist) of the emitted laser beam 14 is displaced by the thermal lens (particularly in the z direction along the optical axis).

Changes in beam waist position have virtually no effect on the homogenized long line beam axis y.

However, the generation of the short beam axis x of the line beam utilizes Gaussian beam propagation, so that the waist position at the laser beam source 26 affects the beam waist at the focal point of the objective lens 18.

In the line beam configuration as shown in FIGS. 1 and 2, a line width of 10 to 100 μm FWHM (full width at half maximum) is typically generated (along the short axis x). For this purpose, the laser beam is optically transported within a 1: 1 telescope (first telescope configuration 20) and subsequently 1: 1 within another telescope (second telescope configuration 36). Is expanded from 1: 5. The laser beam 14 is focused on a plane homogenized by the cylinder lens 18 (see FIG. 3 showing the configuration according to FIG. 1b).

This configuration is designed so that changes in beam waist position do not substantially affect the position of the focal point behind the focusing lens 18 within the adjusted depth of field. However, the position of the focal point is basically displaced (along the optical axis z). However, the change in the position of the beam waist at the laser beam source 26 has a significant effect on the irradiation of the cylindrical focusing lens 18 (imaging device 18). For Gaussian beam propagation, the focal diameter follows the following equation.
d (l / e ² ) = 4fλM ² / (nD (l / e ² ))

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

When the diameter D of the focusing lens 18 becomes smaller due to the displacement of the beam waist (see FIGS. 2 and 3), the focal diameter d becomes larger. As a result, the peak intensity of the Gaussian distribution decreases in the plane of the irradiation line 22.

This behavior was observed with the laser beam 14 from the laser beam source 26 in the optical system according to FIGS. 1a and 1b. When the pulse sequence is switched on (when the first shutter element 48 is opened), it is usually observed that the focal width d increases by about 10% within 10 to 20 seconds. After that, the width and intensity of the focal point stabilize.

This behavior, which is the result of the thermal lens produced in the crystal structure 52, is shown in FIG. At the time point t = 720 seconds, the first shutter element 48 opens, and the laser beam source 26 generates the laser beam 14. As can be seen from the upper curve (intensity, left scale) of FIG. 4, the initial intensity of the irradiation line 22 starts from the maximum value within about 10 seconds at the beginning, and in the subsequent irradiation process (the first shutter element 48 opens). (Stay) It drops to a value that remains almost constant. Similarly, the width of the irradiation line 22 along the short axis x (lower curve, FWHM, right scale) becomes the initial value as soon as the laser beam 14 is turned on, and then within the first approximately 10 seconds thereafter. In the process of irradiation, the value rises to a value that remains almost constant.

As shown in FIG. 5, the behavior of the irradiation line 22 described above can be reproduced, and even if the laser beam source 26 is repeatedly turned on / off, that is, the first shutter element 48 is repeated (in the repeated burst mode). It occurs even if it is opened and closed.

In order to efficiently adjust the frequency conversion (refractive index matching), the crystal structure 52 in the laser beam source 26 is actively stabilized to the target temperature. Slightly different equilibrium states can occur for different burst mode sequences.

According to the present invention, the optical system 10 is a first moving device suitable for reducing the above-mentioned effects of changes in the intensity and width (FWHM) of the irradiation line 22 and, in the best case, fully compensating for it. Includes 60 (see, eg, FIGS. 1a and 1b).

In other words, according to the present invention, the 1: 1 telescope (first telescope configuration 20) and / or the 1: 1 ... 5 telescope (second telescope configuration 36) are deliberately detuned, which Can compensate for the above-mentioned changes in beam waist position such that the peak intensity and beam width on the substrate (ie, in the plane of the irradiation line 22) do not change or change only slightly (eg, less than 1%).

The designs investigated have shown that the first telescope configuration 20 (1: 1 telescope) is particularly suitable for this. Adjustments of 0.1 to 0.2 mm are sufficient for certain configurations. Since the temporal behavior of the change in beam waist position with respect to the defined burst mode sequence is reproducible, the first lens group 23 (ie, FIGS. 1a and 1b) at the start of the pulse sequence (ie, with the opening of the first shutter element 48). The condensing lens 23 of the first telescope configuration 20 positioned in the vicinity of the laser beam source 26) can be used. A linear drive, for example a piezo drive, is suitable as the first mobile device 60.

The amount of focal displacement with respect to the minor axis x behind the focusing lens 18 is typically 20-100 μm along the optical axis z, which is a small portion of the normal depth of field. However, basically, it is also possible to move the imaging device 18 (focusing lens 18) at the same time by using the second moving device 62.

FIG. 6 shows Gaussian beam propagation within the actual beam path. Beam propagation can be used to determine the beam diameter and focal position for each waist start position in the laser beam source 26.

FIG. 7 illustrates an adjustment of the first cylinder lens 38 to compensate for beam waist variation and at the same time a related adjustment of the imaging device 18 for the configuration shown in FIG. Simultaneous displacement of the imaging device 18 may be necessary if the depth of field is not significantly greater than the adjustment. The range of depth of field is determined by the beam quality of the laser beam 14 (coefficient M ² ) or, in some cases, the increase / decrease of the beam quality by the beam conversion optical system.

FIG. 7 shows in detail an appropriate change in the position of the first cylinder lens 23 of the first telescope configuration 20 (“displacement of the telescope lens”, right scale). Further, an appropriate change in the position of the imaging device 18 (“displacement of the focusing lens”, right scale) is shown. The full width at half maximum (“FWHM”) of the irradiation line 22 with respect to the resulting short axis x is also shown in FIG. 7, from which the full width at half maximum remains substantially constant, thus almost perfecting the effect of the thermal lens. It can be seen that it can be compensated.

FIG. 8 shows the same changes in the first telescope configuration 20 and the imaging device 18 as in FIG. 7, and further changes in the beam waist position (“waist position in the laser”, left scale).

Therefore, according to the present invention, as soon as the laser beam source 26 is switched on, that is, as soon as (or immediately after) the first shutter element 48 of the laser beam source 26 is opened, the cylinder lenses 23, 24, 38 And at least one of 40 is moved along the optical axis z by the associated first moving device 60. It has been found here that it is advantageous for the first cylinder lens 23 of the first telescope configuration 20 to be displaced, and instead or additionally move one of the cylinder lenses 24, 38 and / or 40. be able to.

Further, in the above example of FIGS. 7 and 8, the displacement of the imaging device 18 using the second moving device 62 is described, which is optional.

A control unit 64 is provided to control the movement of the first moving device 60 and, in some cases, the second moving device 62 (see FIGS. 1a and 1b). Along with controlling the movement of the moving devices 60 and 62, the control unit 64 is in charge of controlling the laser beam source 26. More precisely, the control unit 64 controls the on / off switching of the laser beam source 26 or the temporal order of opening and closing of the first shutter element 48. The optional second shutter element 66 described below can also be controlled by the control unit 64.

The control unit 64 includes a memory in which control data is stored, and based on the control data, the first moving device 60 (and in some cases, the second moving device 62) makes a first cylinder lens 23 (and in some cases, a second moving device 62). And, in some cases, the movement of the imaging device 18) is performed. In particular, data that defines the temporal order of movement of the moving devices 60 and 62 can be stored. Therefore, the data stored in the memory of the control unit 64 is represented by a curve showing the relationship between the position and time of the first cylinder lens 23 in FIGS. 7 and 8. The same applies to the curve showing the relationship between the position and time of the imaging device 18.

Control data can be obtained based on previous calibration or by calculation and / or simulation, as described in connection with FIG.

In particular, the control unit 64 can be configured to move the first cylinder lens 23 (especially immediately after the first shutter element 48 is opened) according to a predetermined position-time relationship. Optionally, the control unit 64 can be configured to move the imaging device 18 (especially immediately after the first shutter element 48 is opened) according to a predetermined position-time relationship.

The control unit 64 can further control the optical system 10 or other functions and / or elements of the equipment including the optical system 10.

In addition to the technique of displacing one of the lenses of the telescope configurations 20 and 36 described above, the optical system 10 according to one embodiment may optionally include a second shutter element 66 (see FIGS. 1a and 1b). .. The second shutter element 66 can be at any position in the crystal structure within the beam path, eg, just behind the laser beam source 26. The second shutter element 66 is controlled by the control unit 64.

More precisely, the control unit 64 first opens the first shutter element while the second shutter element is closed, and after a predetermined time (for example, in the range of 10 to 20 seconds) elapses, the second shutter element is used. It is configured to control the first shutter element 48 and the second shutter element 66 so that the shutter element 66 opens. A strong change in the waist position immediately after the laser beam source 26 is turned on (that is, immediately after the first shutter element 48 is opened) in this order does not cause a strong change in the beam intensity or the beam width of the irradiation line 22. Can be guaranteed. This is because at the time of this strong initial change (for example, the first 10 seconds after the first shutter element 48 is opened), the second shutter element 66 remains closed, at which point the irradiation line 22 is not generated. .. Only after the effect of the thermal lens has stabilized to some extent does the second shutter element 66 open to generate the irradiation line 22, the intensity and width of which remain substantially constant. The slight changes that may occur at the beam waist position even after this predetermined time are compensated for by the movement of the first mobile device 60 and, in some cases, the second mobile device 62 as described above.

A technique using the second shutter element 66 described above is shown in FIG. In this figure, the intensity of the irradiation line 22 is plotted against time. For clarity, FIG. 9 also shows the intensity of the irradiation line 22 at a time when the second shutter element 66 is closed and therefore no irradiation line 22 is generated. The intensities shown at these time points are the intensities that the irradiation line 22 would have if the second shutter element 66 were open.

FIG. 9 shows the time 68 when the laser beam source 26 is switched on, that is, the first shutter element 48 is open. During this time, the intensity will initially be at its maximum and will drop sharply within the first 10-20 seconds to reach a near stable state (see also FIGS. 4 and 5). However, as indicated by time 70, first (during a predetermined time 72 after the first shutter element 48 was opened), the second shutter element 66 was still closed and the irradiation line 22 was generated. Not done. The second shutter element 66 (process shutter) opens at time 74 for the first time after time 72, and the irradiation line 22 is generated. Fluctuations in intensity and / or width (FWHM) of irradiation line 22 move at least one lens group 23, 24, 38, 40 of at least one telescope configuration 20, 36, as described in detail above. Compensated by.

However, in one example, as described in connection with FIG. 9, neither the first moving device 60 nor the second moving device 62 is provided, and the influence of the thermal lens is compensated only by controlling the second shutter element 66. It is also possible.

The techniques described above provide the effect of thermal lenses, and in particular the possibility of compensating for the associated displacement of the beam waist of the laser beam 14 reliably, easily and reproducibly. In this way the substrate can be irradiated with constant intensity and constant beamwidth, which leads to stable material properties and thus improved material quality.

The figure or part of the figure should not necessarily be considered to scale. Therefore, for example, in FIG. 1b, the short axis x of the beam shape 16 may appear longer than the long axis y in FIG. 1a.

Unless otherwise stated, the same reference symbols in the figures represent elements that are the same or act the same. In addition, any combination of features shown in the figure is also conceivable.

Claims (15)

The optical system (10) for generating the irradiation line (22) is
A laser beam source (26) for generating a laser beam (14) along the optical axis (z), and
A beam shaping device (12) configured to shape the laser beam (14) so that the beam shape (16) of the laser beam (14) has a major axis (y) and a minor axis (x).
The laser beam (14) shaped in this way is configured to form an image as an irradiation line (22), and is arranged after the beam shaping device (12) in the beam path of the laser beam (14). It is equipped with an imaging device (18).
The beam shaping device (12) includes at least one telescope configuration (20) including a first lens group (23) and a second lens group (24), and the first lens group (23). And the second lens group (24) have an optical power of refraction at least with respect to the minor axis (x).
The optical system (10) includes a first moving device (60) for moving at least one of the first lens group and the second lens group along the optical axis (z).
The optical system (10) further comprises a first moving device (62) such that at least one of the first lens group and the second lens group moves while the laser beam source (26) generates the laser beam. An optical system (10) for generating an irradiation line (22), comprising a control unit (64) configured to control). The laser beam source (26) includes a laser cavity (46), a frequency-multiplied crystal structure (52) arranged after the laser cavity (46) in the beam path, and a laser cavity (52) in the beam path. It includes a first shutter element (48) disposed between the crystal structure (52) and 46).
The optical system according to claim 1, wherein the control unit (64) is configured to control the first moving device (60) according to an open state of the first shutter element (48). 10). In order to at least partially compensate for the thermal lens effect caused by the heating of the crystal configuration (52), the control unit (64) may have a telescope configuration (20) after the first shutter element (48) has been opened. The optical system (10) according to claim 2, wherein the optical system (10) is configured to control the first moving device (60) so that the lens continuously moves from the first position to the second position. The thermal lens effect displaces the beam waist of the laser beam (14) along the optical axis (z) so that the control unit (64) has the width of the irradiation line (22) and / or the maximum intensity of the irradiation line (22). The optical system (10) according to claim 3, wherein the optical system (10) is configured to compensate for this displacement so that the lens is kept substantially constant. At least one telescope configuration (20) is a Kepler telescope or a Galileo telescope.
The optics according to any one of claims 2 to 4, wherein the telescope configuration (20) is configured to emit a substantially collimated incident laser beam as a substantially collimated laser beam. System (10). The telescope configuration (20) is a Kepler telescope, the first lens group (23) and the second lens group (24) have the same focal length, or the second lens group (40) has a beam. Since it is located behind the first lens group (38) in the path and the second lens group (40) has a larger focal length than the first lens group (38), the telescope configuration (36) The optical system (10) according to claim 5, wherein the laser beam incident on the lens is emitted as an enlarged laser beam. The second lens group (24) is located behind the first lens group (23) in the beam path.
The first moving device (60) is configured to move the first lens group (23).
The optical system (10) according to any one of claims 2 to 6, wherein the second lens group (24) is supported so as not to move. The control unit (64) is configured to displace the first lens group (23) along the optical axis (z) in the direction of the beam path after the first shutter element (48) is opened. The optical system (10) according to claim 7. It also includes a second moving device (62) for moving the imaging device (18) along the optical axis (z).
The control unit (64) controls the second moving device (62) so that the imaging device (18) moves at the same time as at least one of the first lens group and the second lens group. The optical system (10) according to any one of claims 2 to 8, which is configured in the above. The control unit (64) has a second movement so that the imaging device (18) continuously moves from the first position to the second position after the first shutter element (48) is opened. The optical system (10) according to claim 9, which is configured to control the device (62). It also includes a second shutter element (66) located behind the crystal structure (52) in the beam path.
In the control unit (64), the first shutter element (48) is first opened while the second shutter element (66) is closed, and after a predetermined time elapses, the second shutter element (66) is opened. The optical system (10) according to any one of claims 2 to 10, which is configured to control a first shutter element (48) and a second shutter element (66) so as to open. A method for generating irradiation lines,
Generating a laser beam (14) along the optical axis (z),
Shaping the laser beam (14) so that the beam shape (16) of the laser beam (14) has a major axis (y) and a minor axis (x).
The laser beam (14) shaped in this way is imaged as an irradiation line (22), and the first lens group (23) or the second lens of the telescope configuration (20) is generated while the laser beam is generated. The first lens group (23) and the second lens group (24) include optical power of refraction with respect to at least the minor axis (x), including moving at least one of the groups (24) along the optical axis (z). A method for producing an irradiation line having. The laser beam source (26) that generates the laser beam includes the laser cavity (46), the frequency-multiplied crystal structure (52) arranged after the laser cavity (46) in the beam path, and the beam path. It includes a first shutter element (48) disposed between the laser cavity (46) and the crystal structure (52).
The method according to claim 12, wherein the first lens group (23) or the second lens group (24) moves according to the open state of the first shutter element (48). After the first shutter element (48) is opened, the telescope configuration (20) is second from the first position in order to at least partially compensate for the thermal lens effect caused by the heating of the crystal configuration (52). 13. The method of claim 13, wherein the method continuously moves to the position of. The thermal lens effect displaces the beam waist of the laser beam (14) along the optical axis (z), and the movement causes the width of the irradiation line (22) and / or the maximum intensity of the irradiation line (22) to be substantially constant. 14. The method of claim 14, which compensates for this displacement so as to be maintained in.

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