TW202220776A - Apparatus and method for generating a defined laser line on a working plane - Google Patents

Abstract

An apparatus for generating a defined laser line (12) on a working plane (14) includes a laser light source (22) configured to generate a laser raw beam (24). It further includes an optical arrangement (26) that receives the laser raw beam (24) and transforms it along an optical axis (40) into an illumination beam (28). The illumination beam (28) defines a beam direction (29) that intersects the working plane (14) and has, in the region of the working plane (14), a beam profile (50) that has, perpendicular to the beam direction (29), a long axis (52) with a long axis beam width and a short axis (54) with a short axis beam width. The optical arrangement (26) is movable relative to the working plane (14) along a direction of movement (20) in order to process a workpiece (16) by means of the illumination beam (28). The beam profile (50) has a defined intensity characteristic (62) along the short-axis beam width, which intensity characteristic (62) has a leading edge (56) in the direction of movement (20), a trailing edge (58) in the direction of movement (20) and a plateau (60) lying between the leading edge (56) and the trailing edge (58). The plateau (60) has a higher intensity level in the region of the leading edge (56) than in the region of the trailing edge (58). The optical arrangement (26) is adjusted in such a way that the plateau (60) has a continuously decreasing mean (64) intensity level.

Description

Apparatus and method for generating defined laser rays on a work plane

The present invention relates to an apparatus for generating a defined laser beam on a working plane, comprising a laser light source arranged to generate a laser raw beam, and comprising a method of receiving the laser raw beam and converting it into an illumination beam along the optical axis Optical configuration, wherein the illumination beam defines a beam direction intersecting the work plane, wherein the illumination beam has a beam profile in a region of the work plane, the beam profile perpendicular to the beam direction having a major axis having a major axis beam width and having a minor axis the short axis of the beam width, wherein the optical configuration is movable relative to the work plane in the direction of movement in order to process a workpiece with the illumination beam, and wherein the beam profile has an intensity characteristic defined along the short axis of the beam width, the intensity characteristic in the direction of movement has a leading edge, a trailing edge in the direction of movement, and a platform located between the leading edge and the trailing edge, wherein the platform has a higher strength level in the leading edge region than in the trailing edge region.

The present invention further relates to a method for generating a defined laser beam on a work plane, comprising the steps of: – Provides a laser light source that produces the original laser beam, – Provide an optical configuration that receives the laser raw beam and converts it along an optical axis into an illumination beam defining a beam direction intersecting the work plane, the optical configuration having a plurality of optical elements and being movable relative to the laser beam in the direction of movement the work plane is moved so that the workpiece is processed by this illumination beam, and – put the laser light source into operation, wherein the illumination beam obtains a beam profile in the region of the working plane, the beam profile perpendicular to the beam direction having a long axis with a long axis beam width and a short axis with a short axis beam width, wherein the beam profile is along the short axis beam width has a defined strength characteristic that obtains a leading edge in the direction of travel, a trailing edge in the direction of travel, and a platform located between the leading edge and the trailing edge, and wherein the platform has a ratio in the leading edge region Higher intensity levels in the trailing edge region.

Such a device and a corresponding method are known from US 2014/0027417 A1.

Known devices produce linear laser illumination on a work plane for processing workpieces. In particular, the workpiece may be amorphous silicon on a carrier. Amorphous silicon is melted row by row by laser light and converted to polysilicon by cooling. This application is commonly referred to in practice as solid state laser annealing (SLA) or excimer laser annealing (ELA).

This application requires the laser beam on the work plane to be as long as possible in one direction to cover the widest possible work area, and very short in the other direction to provide the energy density required for the corresponding treatment. Therefore, elongated laser rays parallel to the working plane are required. Generally, the direction in which the laser light travels is called the long axis, and the thickness of the line is called the short axis of the so-called beam profile. In general, laser rays should have intensity properties defined along two axes. In particular, it is desirable for the ray-like rays on the long axis to have as rectangular as possible or possibly trapezoidal intensity characteristics, the latter being advantageous if several such laser rays are connected together to form a longer overall line. On the short axis, SLA applications typically require ideal rectangular strength characteristics (the so-called top hat profile) with a leading edge in the direction of travel, a trailing edge in the direction of travel, and a flat between the leading and trailing edges platform.

However, US 2014/0027417 A1 discloses an improved, in a sense two-stage top hat profile, which is advantageous for SLA or ELA processing, since the polysilicon is formed in several parts as the laser beam moves relative to the workpiece Successive steps are performed, and as the movement progresses, the optimal energy density of the molten material decreases. The laser light is generated in pulses as it moves relative to the workpiece, and each part of the workpiece is illuminated by approximately 20 laser pulses as it moves. Here it is revealed that laser pulses melt silicon multiple times and change its properties. To this end, US 2014/0027417 A1 proposes to use two laser original beams that overlap in the area of the working plane to generate a beam profile of the laser rays. The optical configuration includes separate beam paths for each of the two laser raw beams. Each of the two beam paths produces a roughly top hat-shaped beam profile along the minor axis. The two top hat beam profiles are offset from each other in the direction of the minor axis on the work plane, resulting in an overall beam profile with a defined step separating the two mostly flat platform segments.

One disadvantage of this solution is the expense of providing two laser original beams and two parallel beam paths. In view of this, it is an object of the present invention to provide an apparatus and method of the type described above, which allows, in an alternative manner, to provide the best possible energy density during the SLA processing of workpieces.

According to one aspect of the present invention, there is provided an apparatus of the type described above, wherein the optical configuration is adjusted such that the stage has a continuously decreasing average intensity level. Still further, a method of the type described above is provided wherein the optical elements are adjusted in such a way that the stage achieves a continuously decreasing average intensity level.

As in the apparatus and method described above, the illumination beam is preferably generated in pulses, in particular by a laser light source that emits the laser raw beam in pulses. Irrespective of this, the intensity characteristic of the beam profile along the short axis here falls in a mostly linear fashion opposite to the direction of movement, from a higher first order in the leading edge region to a lower second order in the trailing edge region. Therefore, the strength properties of the new device and the corresponding method are similar to those of a mono-pitched roof. In buildings, a monopitch roof is a roof shape with only one sloping roof surface. Therefore, the beam profile has mono-pitched roof-shaped intensity characteristics along the short axis. Preferably, the platform has no steps. It is clear to those skilled in the art that the strength characteristics of the apparatus and method are not ideally flat in reality, but rather that there may be small waves and ripples in plateaus inclined opposite to the direction of movement. Small waves and ripples are unavoidable due to diffraction effects and manufacturing tolerances. However, compared to the height of the plateau, the waves and ripples are small and negligible in the idealized schema. In some embodiments, the waves and ripples may be less than 10%, preferably less than 5%, relative to the strength level of the platform. Therefore, if viewed from the opposite direction of the movement, the platform of the new device and method has an average continuous decline, especially when considering the regression line that crosses waves and ripples.

New equipment and methods enable more uniform workpiece machining due to the continued reduction in strength levels. Still further, it generally allows simpler and cheaper implementation using only one laser beam. As a result, new devices and methods can be implemented with older, already existing devices by readjusting the optics in the beam path for short-axis profiles in the manner shown. It is conceivable to install additional optics later, but is usually not necessary. It turns out that, in many cases, monoclinic intensity properties can already be achieved with improved fine-tuning of the optics. The above-mentioned objects are thus achieved in a simple and cost-effective manner.

In a preferred refinement of the invention, the optical arrangement is arranged to generate the platform with a single laser tube bundle. Therefore, in the preferred embodiment, the platform is produced with a single laser raw beam.

In this refinement, the new device and method benefit from the advantageous possibilities already pointed out above. Homogeneous SLA processing of workpieces is possible in a particularly economical way.

In a further refinement, the optical configuration includes a plurality of optical elements forming a beam path relative to the minor axis of the beam profile, wherein one of the plurality of optical elements is an objective lens located at the end of the beam path, and wherein the beam path Illuminate off-center objectives.

In a preferred exemplary embodiment, the objective lens focuses the illumination beam onto the working plane. Preferably, the objective has dominant power with respect to the short axis of the beam profile and has no effect on the long axis of the beam profile. The short-axis beam path places the laser beam asymmetrically on the objective with respect to the optical axis of the short-axis beam path. Asymmetric or off-center illumination can cause the spherical aberration effect of the objective to reshape the laser beam more on one side of the optical axis than on the other. This advantageously results in a tilted plateau in the intensity characteristic of the short-axis beam profile. It turns out that specific adjustments of optics in the short-axis beam path can advantageously facilitate off-center illumination of the objective to achieve a monoclinic stage-like stage in the intensity characteristics of the short-axis beam profile in a simple and cost-effective manner.

In a further refinement, the plurality of optical elements includes a telescoping lens in the beam path, the telescoping lens being off-center with respect to the optical axis.

This improvement is a very cost-effective way of building a monoclinic stage, since a telescoping configuration is usually required in the (short-axis) beam path of the optical configuration anyway. Advantageously, the telescoping lens has the dominant power for the short axis of the beam profile and has no effect on the long axis of the beam profile. An off-center-adjusted telescoping lens can conveniently and inexpensively assist in placing the laser beam off-center on the aforementioned objective to form a tilted stage.

In a further refinement, the plurality of optical elements includes a telescoping lens in the beam path, the telescoping lens being inclined with respect to the optical axis.

This improvement is also a very cost-effective way to build a monoclinic stage, since a telescoping configuration is usually required in the (short-axis) beam path of the optical configuration anyway. Advantageously, the telescoping lens has the dominant power for the short axis of the beam profile and has no effect on the long axis of the beam profile. In a preferred exemplary embodiment, a tilted telescoping lens can be achieved by rotating the telescoping lens about its long axis when adjusting the optical arrangement. Again, this provides a simple and inexpensive way to place the laser beam off-centre on the aforementioned objective. In some preferred exemplary embodiments, the telescoping lens can be positioned off-center relative to the optical axis of the short-axis beam path, and can also be tilted or rotated about the long-axis relative to the optical axis of the short-axis beam path. In these exemplary embodiments, the tilt of the platform can be optimized in a simple and cost-effective manner.

In a further refinement, the plurality of optical elements includes a plurality of mirrors that fold the beam path, wherein at least one mirror of the plurality of mirrors is arranged to illuminate the objective off-center.

The folding of the beam path, especially with respect to the short axis, allows for a compact design of the new device. Tilting of the platform can be achieved in a very simple and cost-effective manner by new adjustments to one or more mirrors of this configuration. Still further, with this improvement, high beam quality can be achieved by tuning the lenses of this optical configuration primarily for high beam quality, while the tilting of the platform is achieved by one or more folding mirrors. Alternatively or additionally, the tilting of the platform can be achieved by adjusting the lens as described above and by adjusting one or more mirrors, which allows flexibility to optimize new equipment.

It goes without saying that the features mentioned above and those yet to be explained below can be used not only in combination in each case, but also in other combinations or alone without departing from the scope of the present invention.

In FIG. 1 , an exemplary embodiment of the new device is generally designated by reference numeral 10 . The device 10 generates the laser beam 12 in the region of the working plane 14 in order to process the workpiece 16 , which is here placed in the region of the working plane 14 . Here, the laser beam 12 extends in the direction of the x-axis ( FIG. 2 ), and the line width is observed here in the direction of the y-axis. Therefore, the x-axis hereinafter represents the long axis of the beam profile formed on the working plane 14 (FIG. 2), and the y-axis represents the short axis.

In a preferred exemplary embodiment, workpiece 16 may include a layer of amorphous silicon that is melted and converted to polysilicon using laser light 12 . FIG. 1 shows apparatus 10 in a simplified and schematic diagram of a short-axis beam path 18 that forms the short-axis of a laser ray. Therefore, in the "side view" of Figure 1 (along the x-axis), the laser ray can only be seen as a point. To process workpiece 16 , laser beam 12 may be moved relative to workpiece 16 in the direction of arrow 20 .

The device 10 has a laser light source 22, which may be, for example, a solid state laser that generates laser light in the infrared range or the ultraviolet range. For example, laser light source 22 may comprise an Nd:YAG laser having a wavelength in the 1030 nm range. In further examples, the laser light source 22 may comprise a diode laser, an excimer laser, or a solid state laser, each of which can produce wavelengths between 150 nm and 360 nm, 500 nm and 530 nm, or 900 nm Lasers between 1070 nm.

For example, laser light source 22 emits a laser raw beam 24, which may be coupled to optical arrangement 26 via an optical fiber. The laser raw beam 24 is converted by an optical arrangement 26 into an illumination beam 28 defining a beam direction 29 . The beam direction 29 intersects the working plane 14 .

The optical configuration 26 includes a beam transformer 30 that expands the laser original beam 24 in the x-direction (corresponding to the long axis). In some demonstrative embodiments, beam transformer 30 may be implemented as a beam transformer as described in detail in WO 2018/019374 A1. Accordingly, WO 2018/019374 A1 is incorporated herein by reference for additional details regarding beam converters and optical configurations, such as in particular long-axis beam shaping.

According to WO 2018/019374 A1, the beam converter 30 may comprise a transparent, monolithic, plate-like member having front and rear sides substantially parallel to each other. The plate-like elements may be arranged at an acute angle with respect to the original laser beam 24 . The front and rear sides may each include a reflective coating such that the laser raw beam 24 coupled obliquely into the plate-like element on the front side undergoes multiple reflections in the plate-like element before it spreads out at the rear side of the plate-like element.

The optical arrangement 26 includes long-axis optics (not shown here) that shape the transformed laser beam 24 on the long axis. In particular, the long-axis optics may include one or more microlens arrays (not shown here) and one or more lenses having positive power predominantly on the long axis. The microlens array and one or more lenses may include barrel lenses extending in the y-direction and specifically form an imaging homogenizer that homogenizes the laser raw beam 24 in the long axis to provide a benefit in the long axis The top hat strength properties.

The optical arrangement 26 further includes a plurality of optical elements 32, 34, 36, 38 that shape and focus the expanded laser beam on the short axis onto the working plane. The optical elements 32 , 34 , 36 , 38 are arranged along the optical axis 40 and here include a first lens 32 and a second lens 34 which together form a telescope arrangement 42 . Reference numeral 38 designates a mirror arrangement comprising a plurality of mirrors 44, 46, 48 (see FIG. 2) that fold the beam path 18 along the minor axis. Here, the optical element 38 is the objective lens that focuses the illumination beam 28 onto the working plane 14 .

The optical configuration 26 is arranged to generate an illumination beam 28 having a defined beam profile 50 in the area of the working plane 14 . FIG. 3 shows such a beam profile 50 in an idealized diagram. The beam profile 50 describes the laser radiation intensity I on the working plane 14 as a function of corresponding positions along the x- and y-axes. As shown, the beam profile 50 has a major axis 52 having a major axis beam width in the x-direction and a minor axis having a minor axis beam width in the y-direction, and a minor axis 54 . The short-axis beam width 54 may be defined, for example, as the full width at half maximum (FWHM) or the width between 90% intensity values (90% full width maximum, FW@90%). Here, the beam profile 50 has a top hat profile on the short axis with a first edge 56 , a second edge 58 and a platform 60 descending continuously from the first edge 56 to the second edge 58 . Preferably, the platform 60 descends substantially linearly from the first edge 56 to the second edge 58 , as shown in simplified form in FIG. 3 .

As shown in FIGS. 1 and 2 , the beam profile 50 is moved relative to the work plane 14 parallel to the y-axis to process the workpiece 16 . In some preferred exemplary embodiments, the workpiece 16 is disposed on a table that is movable in the y-direction. Thus, the first edge 56 advances in the direction of movement 20 and the second edge 58 retreats in the direction of movement 20 (FIG. 2). The platform 60 is inclined in a direction opposite to the direction of movement and has a monoclinic shape in a view parallel to the x-axis. For good order, it should be noted that the short-axis beam profile with edges 56, 58 and plateau 60 is greatly exaggerated in Figures 1 and 2 for illustration. In a preferred exemplary embodiment, the short-axis beam width FWHM is in the range between 50 μm and 150 μm. Long-axis beam widths can range between 20 mm and 1200 mm.

FIG. 4 shows an exemplary intensity characteristic 62 on the short axis of the beam profile 50 according to an exemplary embodiment of the new device 10 . As can be seen here, the real short-axis beam profile 62 has many ripples and waves, especially in the region of the platform 60 . The edges 56, 58 have finite slopes, but ideally vertical edges are required in each case. Reference numeral 64 denotes an average line, which may be, for example, a regression line through ripples and waves 66 . As can be seen from the mean line 64 , the plateau 60 of the beam profile 62 here slopes from the leading edge 56 to the trailing edge 58 . In the illustrated exemplary embodiment, the slope is about 3%. Preferably, the inclination of the platform 60 is between 0.5% and 5%, inclusive.

In a preferred exemplary embodiment of the new method, the inclination of the platform 60 is achieved by selective adjustment of the optical elements 32, 34, 36, 38. In particular, as shown in FIGS. 1 and 2 , telescoping lens 34 and/or mirrors 44 , 46 , 48 may be used to adjust short-axis beam path 18 such that the illumination of objective 38 is off-center relative to optical axis 40 . In particular, the telescoping lens 34 can be moved along the optical axis, ie, in the z-direction, as indicated by arrow 68 , and/or it can be pivoted about its long axis (parallel to the x-axis) as indicated by arrow 70 . Additionally, off-center illumination of the objective 38 and/or other lenses of the short-axis beam path 18 may be moved in the y-direction, as indicated by arrow 72 . Finally, one or more mirrors 44, 46, 48 of the mirror arrangement can be pivoted. In the exemplary embodiment according to FIG. 4 , the telescopic lens 32 is moved by 100 μm in the y-direction. In addition, the telescopic lens 34 is further displaced -40 mm in the z-direction. As an alternative to the telescoping lens 32 being displaced in the y-direction, the telescoping lens 34 is here pivotable by an angle 74 of 0.5°.

10: Equipment 12: Laser light 14: Work plane 16: Workpiece 18: Beam Path 20, 68, 70, 72: Arrow 22: Laser light source 24: Laser original beam 26: Optical configuration 28: Lighting Beam 29: Beam direction 30: Beam changer 32, 34, 36, 38: Optical Components 40: Optical axis 42: Telescope Configuration 44, 46, 48: Reflector 50: Define beam profile 52: long axis 54: Short axis 56: First Edge 58: Second Edge 60: Platform 62: Strength properties 64: Average Line 66: Ripple and Waves 74: Angle

Exemplary embodiments of the present invention are illustrated in the accompanying drawings and are explained in greater detail in the following description. These are displayed in:

1 is a simplified schematic diagram of the short-axis beam path of a first exemplary embodiment of the new device;

Figure 2 is a simplified diagram of mirror folding to explain another exemplary embodiment of the new device;

3 is a simplified diagram of a beam profile according to an exemplary embodiment of the new apparatus;

4 is a simplified diagram of a short-axis beam profile according to an exemplary embodiment of the new apparatus.

10: Equipment

12: Laser light

14: Work plane

16: Workpiece

18: Beam Path

20, 68, 70, 72: Arrow

22: Laser light source

24: Laser original beam

26: Optical configuration

28: Lighting Beam

29: Beam direction

30: Beam changer

32, 34, 36, 38: Optical Components

40: Optical axis

42: Telescope Configuration

60: Platform

74: Angle

Claims (7)

A device for generating a defined laser beam (12) on a working plane (14), comprising a laser light source (22) arranged to generate a laser raw beam (24), and comprising receiving the laser raw beam (24) Optical configuration (26) of light beam (24) and converting it into an illumination beam (28) along an optical axis (40), wherein the illumination beam (28) defines a beam direction ( 29), wherein the illumination beam (28) in the region of the working plane (14) has a beam profile (50) perpendicular to the beam direction (29) having a long beam width with a long axis an axis (52) and a short axis (54) having a short axis beam width, wherein the optical arrangement (26) is movable relative to the working plane (14) in a direction of movement (20) in order to pass the illumination beam (28) Processing a workpiece (16) and wherein the beam profile (50) has a defined intensity characteristic (62) defined along the short-axis beam width, the intensity characteristic (62) having a leading edge in the direction of travel (20) (56), a trailing edge (58) in the direction of movement (20) and a platform (60) located between the leading edge (56) and the trailing edge (58), wherein the platform (60) is The leading edge ( 56 ) has a higher intensity level in the region of the trailing edge ( 58 ), characterized in that the optical configuration ( 26 ) is adjusted in such a way that the platform ( 60 ) has a continuous Reduced average (64) intensity level. The apparatus of claim 1, characterized in that the optical arrangement (26) is arranged to generate the platform (60) with a single laser raw beam (24). Apparatus according to claim 1 or 2, characterized in that the optical arrangement (26) comprises a plurality of optical elements (32, 34, 36, 38) forming a beam path (18) with respect to the minor axis of the beam profile (50) ), wherein one of the optical elements is an objective (38) at the end of the beam path, and wherein the beam path (18) illuminates the objective (38) off-center. Apparatus as claimed in claim 3, characterized in that the plurality of optical elements (32, 34, 36, 38) comprise a telescopic lens (34) in the beam path (18), the telescopic lens (34) opposing off-center from the optical axis (40). Apparatus as claimed in claim 3 or 4, characterized in that the plurality of optical elements (32, 34, 36, 38) comprise a telescopic lens (34) in the beam path (18), the telescopic lens (34) ) arranged to be inclined relative to the optical axis (40). Apparatus according to any of claims 3 to 5, characterized in that the plurality of optical elements (32, 34, 36, 38) comprise a plurality of mirrors (44, 46, 48) that fold the beam path (18) ), wherein at least one of the plurality of mirrors (44, 46, 48) is arranged to illuminate the objective (38) off-centre. A method for generating a defined laser ray (12) on a working plane (14), comprising the steps of: – providing a laser light source (22) generating a laser original beam (24), – providing an optical arrangement (26) that receives the laser raw beam (24) and converts it along an optical axis (40) into an illumination beam defining a beam direction (29) intersecting the working plane (14) (28), the optical arrangement (26) having a plurality of optical elements (32, 34, 36, 38) and movable relative to the working plane (14) in a direction of movement (20) in order to pass the illumination beam (28) ) process a workpiece (16), and – put the laser light source (22) into operation, wherein the illumination beam ( 28 ) acquires a beam profile ( 50 ) in the region of the working plane ( 14 ), the beam profile having a long axis ( 52 ) with a long axis beam width perpendicular to the beam direction ( 29 ) and A short axis (54) having a short axis beam width, wherein the beam profile (50) has a defined intensity characteristic (62) along the short axis beam width, the intensity characteristic (62) obtained in the direction of movement (20) A leading edge (56) of the moving direction (20), a trailing edge (58) in the moving direction (20), and a platform (60) between the leading edge (56) and the trailing edge (58), and wherein the platform (60) having a higher intensity level in the region of the leading edge (56) than in the region of the trailing edge (58), characterized in that the optical elements (32, 34, 36, 38) are in this way Adjusted so that the platform (60) achieves a continuously decreasing average (64) intensity level.

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