JP3781091B2 - Beam shaping device - Google Patents

Description

[0001]
[Field of the Invention]
The present invention relates to a beam shaping apparatus and method for making irradiation light incident on a target surface in a predetermined beam shape, and in particular, a beam applicable to a processing apparatus such as an annealing apparatus or a surface modification apparatus using a laser. The present invention relates to a shaping apparatus and method.
[0002]
[Prior art]
For example, a laser annealing apparatus for polycrystallizing an amorphous Si film includes an optical system called a homogenizer as a beam shaping apparatus for irradiating annealing light onto a substrate on which an amorphous Si film is formed. In particular, when the laser annealing apparatus is of a scan type that irradiates a linear laser beam on the substrate in a single axis direction in the short axis direction, a linear beam homogenizer that forms a linear beam from a rectangular beam is used.
[0003]
In the laser annealing apparatus as described above, the annealing process results differ depending on the beam cross-sectional shape in the short axis direction (particularly the slope and peak energy density of the edge portion) formed by the linear beam homogenizer. It is important to keep the beam cross-sectional shape constant during irradiation.
[0004]
Moreover, if the beam cross-sectional shape can be intentionally changed and irradiation can be performed, conditions for the annealing process can be easily determined. In particular, if irradiation can be performed while changing the slope of the short side edge portion in various ways, there is a possibility that the state of the silicon layer that is polycrystallized on the substrate can be freely controlled.
[0005]
[Problems to be solved by the invention]
However, in the conventional apparatus, when the annealing laser is continuously irradiated, the phenomenon that the divergence angle of the emitted beam gradually changes due to some reason inside the laser light source occurs, and the substrate is irradiated through the homogenizer. The beam cross-sectional shape (particularly the beam slope) also changes.
[0006]
This point will be briefly explained. A laser beam having a divergence angle θ can be focused only on a spot of fθ using an ideal lens (focal length f). That is, when the divergence angle of the annealing laser changes during the irradiation, there arises a problem that the slope of the edge of the laser beam becomes gentler in proportion to the divergence angle θ. In addition, there is a problem that the peak energy density is lowered due to the beam component of the central top flat portion entering the beam slope portion that has become gentle. Such a phenomenon means that irradiation states are different when a series of annealing processes are compared, and it is difficult to obtain stable quality.
[0007]
Further, in the conventional beam shaping apparatus, there is no simple method for actively controlling the beam cross-sectional shape, and it is not easy to determine process conditions. Here, the following methods can be considered to adjust the beam cross-sectional shape.
(A) Move the homogenizer on the optical axis to defocus (b) Replace with another homogenizer that forms another beam shape (c) Method of (a) above, replacing part of the constituent lenses of the homogenizer However, there is a problem that not only the short side edge slope but also the entire beam is deformed to an unexpected shape due to defocusing. Regarding the methods (b) and (c), the optical design is complicated, and the replacement mechanism and operation are also complicated, which is not practical.
[0008]
Therefore, an object of the present invention is to provide a beam shaping apparatus and method that can easily control the beam shape and the like.
[0009]
[Means for Solving the Problems]
In order to solve the above problems, a beam shaping device according to the present invention is disposed between a homogenizer that makes irradiation light from a light source incident on a predetermined surface with a predetermined cross-sectional shape and intensity, and between the light source and the homogenizer. An afocal zoom optical system that adjusts a divergence angle of the irradiation light incident on the homogenizer.
[0010]
In the beam shaping device of the present invention , an afocal zoom optical system is arranged between the light source and the homogenizer and adjusts the spread angle of the irradiation light incident on the homogenizer, so that the setting of the homogenizer itself is changed. In addition, it is possible to easily adjust the cross-sectional shape and the like of the irradiation light emitted from the homogenizer and incident on the predetermined surface. That is, even if the divergence angle of the irradiation light emitted from the light source gradually changes, the sectional shape of the illumination light incident on the predetermined surface can be kept constant only by adjusting the afocal zoom optical system. Further, the beam cross-sectional shape can be positively controlled by appropriately adjusting the divergence angle of the irradiation light by an afocal zoom optical system. Note that when the afocal zoom optical system cancels the phenomenon in which the divergence angle of the light emitted from the light source changes gradually as in the former case, the adjustment of the divergence angle by the afocal zoom optical system must be continuous. is there.
[0012]
Further, since the beam shaping apparatus of the present invention uses an afocal zoom optical system , when the irradiation light incident on the homogenizer is a substantially parallel light beam, the angular magnification of the afocal zoom optical system is only changed as appropriate. Thus, the spread angle of the irradiation light can be easily adjusted.
[0013]
In a preferred aspect of the above apparatus, the apparatus further comprises detection means for detecting the divergence angle of the irradiation light and control means for controlling the angular magnification of the afocal zoom optical system based on the detection value of the detection means.
[0014]
In this case, since the control means controls the angular magnification of the afocal zoom optical system based on the detection value of the detection means, the change in the divergence angle of the irradiation light can be easily and quickly compensated for stable cross-sectional shape and intensity. Irradiation light can be incident on a predetermined surface.
[0015]
The beam shaping method according to the present invention is a beam shaping method in which irradiation light from a light source is incident on a predetermined surface with a predetermined cross-sectional shape and intensity distribution by a homogenizer, and spreads the irradiation light incident on the homogenizer. Adjust the angle with the afocal zoom optical system .
[0016]
In the beam shaping method, by adjusting the divergence angle of the irradiation light incident on the homogenizer with an afocal zoom optical system, the beam is emitted from the homogenizer and incident on a predetermined surface without changing the setting of the homogenizer itself. Not only can the cross-sectional shape of the irradiated light be easily adjusted, but if the irradiated light incident on the homogenizer is a substantially parallel light beam, it can be easily changed by simply changing the angular magnification of the afocal zoom optical system. The spread angle of the irradiation light can be adjusted.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
[First Embodiment]
FIG. 1 is a diagram for explaining the structure of an irradiation optical system incorporating the beam shaping apparatus according to the first embodiment of the present invention.
[0018]
The irradiation optical system includes a laser light source 10 that generates a light beam as irradiation light, a homogenizer 20 that causes the light beam from the laser light source 10 to be incident on a predetermined irradiated surface IS with a predetermined cross-sectional shape and intensity, An afocal zoom optical system 30 that is an angle adjusting optical system that is disposed between the laser light source 10 and the homogenizer 20 and adjusts the spread angle of the light beam incident on the homogenizer 20 is provided. Here, the homogenizer 20 and the afocal zoom optical system 30 constitute a beam shaping device. A beam delivery (mirror or the like) for guiding a light beam from the laser light source 10 to the afocal zoom optical system 30 and the homogenizer 20 is not shown. Further, on the irradiated surface IS, for example, an amorphous Si film deposited on a glass substrate is disposed.
[0019]
In the afocal zoom optical system 30, when the height from the optical axis before and after the incidence of the light beam passing therethrough is h0 and h ′, and the intersecting angles with the optical axis before and after the incidence are u0 and u ′, the angular magnification γ is
γ = h0 / h ′ = u ′ / u0 = γ0 to γ ′
Is given and variable. That is, by passing through the afocal zoom optical system 30, the divergence angle of the light beam incident on the homogenizer 20 can be easily adjusted within a certain range.
[0020]
The overall operation will be described. First, a substantially parallel light beam of emitted light is emitted from the laser light source 10 and is incident on the afocal zoom optical system 30 with variable angular magnification before entering the homogenizer 20. The light beam that has passed through the afocal zoom optical system 30 is incident on the homogenizer 20. By controlling the angular magnification by the afocal zoom optical system 30, the spread angle of the light beam incident on the homogenizer 20 can be adjusted. it can. Thereby, the light beam that has passed through the homogenizer 20 can be incident on the irradiated surface IS with a desired cross-sectional shape and intensity distribution as a linear beam.
[0021]
When an amorphous Si film is disposed on the irradiated surface IS, the surface of the amorphous Si film is scanned with a linear beam having a desired cross-sectional shape as described above. An annealed polysilicon film is formed.
[0022]
FIG. 2 is a diagram illustrating the structure of the homogenizer. 2A is a diagram relating to the long axis direction of the filament beam, FIG. 2B is a diagram relating to the minor axis direction of the filament beam, and FIG. 2C is a component of the homogenizer. It is a perspective view explaining the structure of a certain cylindrical lens array.
[0023]
The homogenizer 20 includes first to fourth cylindrical lens arrays CA1 to CA4 and a condenser lens 21 which is a convex lens. Here, the first and third cylindrical lens arrays CA1 and CA3 have a curvature in the short-axis cross section, and the second and fourth cylindrical lens arrays CA2 and CA4 have a curvature in the long-axis cross section.
[0024]
The light beam incident on the homogenizer 20 forms a secondary light source divided by the first to fourth cylindrical lens arrays CA1 to CA4 into the number of segments constituting the cylindrical lens in both the short axis and long axis directions. The divided light beam from the secondary light source is determined by the combined focal length faw of the first and third arrays CA1, CA3, the combined focal length fal of the second and fourth arrays CA2, CA4, and the segment width d. Are incident on the condenser lens 21 with different output NAs. The light beams from the respective secondary light sources incident on the condenser lens 21 are superposed on the irradiated surface IS arranged at the back focus position of the condenser lens 21 to form a uniform filament beam. Note that the line width W and length L of the filament beam projected onto the irradiated surface IS can be adjusted to desired values by appropriately setting the composite focal lengths faw and fal.
[0025]
FIG. 3 is a diagram illustrating an example of the configuration of the afocal zoom optical system 30, and FIGS. 3A to 3C are diagrams illustrating changes in the angular magnification γ.
[0026]
As is apparent from the figure, this afocal zoom optical system 30 is composed of a three-group system composed of three convex lenses 31, 32, 33, and the arrangement of the lenses 32, 33 on the optical axis is relatively By changing, the light beams incident at the same angle can be emitted at different angles.
[0027]
In FIGS. 3A, 3B, and 3C, details of the lens data are omitted, but the light beam is incident on the afocal zoom optical system 30 at the same angle u, respectively. exits at different angles of u1 ', u2', u3 '
u1 '<u2'<u3'
There is a relationship. That is, the angular magnification γ of the afocal zoom optical system 30 is
γ1 <γ2 <γ3
It has become. At this time, the curvature and arrangement of the lens can be adjusted as appropriate to set, for example, the conditions of γ1 <1, γ2 = 1, 1 <γ3, and the variable range γ1 to γ3 can be designed to some extent according to the purpose. can do.
[0028]
Here, if the divergence angle of the laser light emitted from the laser light source 10 is θ, the divergence angle of the light beam after passing through the afocal zoom optical system is γ · θ. Since the angular magnification γ is variable from γ1 to γ3 as described above, the divergence angle of the light beam incident on the homogenizer 20 can be controlled in the γ1 · θ to γ3 · θ range. The laser divergence angle γ · θ after passing through the afocal zoom optical system is
γ1 ・ θ <γ2 ・ θ <γ3 ・ θ
Therefore, the slope width of the linear beam image formed on the irradiated surface IS by the homogenizer 20 is narrow, that is, steep in the order of γ 1 · θ, γ 2 · θ, and γ 3 · θ.
[0029]
FIG. 4 is a graph showing the slope width of the line beam image projected on the irradiated surface IS by the homogenizer 20. FIG. 4A shows a profile at a relatively large spread angle γ3 · θ, and FIG. 4B shows a profile at a relatively small spread angle γ1 · θ. In the graph, the horizontal axis indicates the distance in the minor axis direction, and the vertical axis indicates the power of the light beam. The slope width SW of the line beam image can be continuously changed between the two states shown in each graph by setting the afocal zoom optical system 30 to an appropriate angular magnification γ. The zoom operation of the afocal zoom optical system 30 may be performed manually, but is usually performed by changing the lens arrangement using a motor.
[0030]
As is clear from the above description, in the beam shaping device of the first embodiment, the divergence angle of the light beam incident on the homogenizer 20 can be adjusted by the afocal zoom optical system 30, so that the beam cross section such as the slope width can be adjusted. The shape can be positively controlled. More specifically, the beam shaping device of the first embodiment can be used for determining the conditions of a laser processing process. In general, the optimum beam slope width differs depending on the process to be employed, and it is necessary to find out this. However, if this beam shaping device is used, the beam will pass through the homogenizer 20 and be projected onto the irradiated surface IS, which is the processing surface. Since the slope of the projected image can be continuously changed within a predetermined variable range, the optimum conditions in the process can be easily found.
[0031]
Note that the afocal zoom optical system 30 has the above-described characteristics regarding the conversion of the divergence angle, but care must be taken regarding the conversion of the beam size by the afocal zoom optical system 30. That is, before and after the afocal zoom optical system 30, the beam size becomes 1 / γ according to the angular magnification. Therefore, the beam aperture of the homogenizer 20 is increased in accordance with the angular magnification γ1 at which the beam size is the largest. It is necessary to keep.
[Second Embodiment]
FIG. 5 is a diagram for explaining the structure of an irradiation optical system incorporating the beam shaping device of the second embodiment. This irradiation optical system is an irradiation optical system in which a portion of the beam shaping device shown in FIG. 1 is deformed, and a laser light source 10 that generates a light beam, and a predetermined irradiated surface IS with a predetermined cross-sectional shape and intensity. The homogenizer 20 that is incident on the top, the afocal zoom optical system 30 that adjusts the spread angle of the light beam incident on the homogenizer 20, and the light beam from the laser light source 10 are guided to the afocal zoom optical system 30 and the homogenizer 20. Beam delivery 40. In the apparatus of the second embodiment, the time-dependent change in the divergence angle of the light beam from the laser light source 10 is corrected to keep the divergence angle of the light beam incident on the homogenizer 20 constant. For this reason, a beam splitter 51 that is arranged between the homogenizer 20 and the afocal zoom optical system 30 and partially branches the light beam, a spread angle detector 52 that detects the spread angle of the branched light from the beam splitter 51, A zoom controller 55 that drives the afocal zoom optical system 30 based on the detection result of the divergence angle detector 52 is further provided.
[0032]
The light beam emitted from the laser light source 10 enters the afocal zoom optical system 20 through the beam delivery 40. The light beam incident on the afocal zoom optical system 30 is converted into a divergence angle from θ to γθ and is incident on the homogenizer 20. The beam splitter 51 branches about 1% of the light beam immediately before entering the homogenizer 20 and supplies it to the spread angle detector 52. The divergence angle detector 52 is composed of, for example, a lens having a focal length f and a CCD camera, and detects the width of the beam at the condensing point narrowed by this lens with the CCD camera. Since the beam width cd detected by the CCD camera is given by cd = fθ, the divergence angle can be obtained as θ = cd / f. If the angular magnification of the afocal zoom optical system 30 is controlled by the zoom controller 55 based on the detection value of the divergence angle obtained in this way, the divergence angle of the light beam incident on the homogenizer 20 is always a constant value. Control becomes possible. If the divergence angle is controlled to a constant value, the beam shape of the light beam emitted from the homogenizer 20 and projected onto the irradiated surface IS is stabilized, so that the product obtained as a result of the process does not vary in quality. It will be good.
[0033]
With respect to the detection position of the divergence angle, if the divergence angle at the exit of the laser light source 10 corresponds to the angular magnification of the afocal zoom optical system 30 and the divergence angle after zooming, the divergence is performed at the exit of the laser light source 10. A corner may be detected. In this case, the value of the divergence angle at the exit of the laser light source 10 is used to indirectly control the divergence angle of the light beam incident on the homogenizer 20. Specifically, as shown in FIG. 5, a beam splitter 151 is disposed between the laser light source 10 and the beam delivery 40 instead of the beam splitter 51. The branched light from the beam splitter 151 is detected by the divergence angle detector 152. The zoom controller 55 drives the afocal zoom optical system 30 based on the detection result of the divergence angle detector 152, and finally makes the divergence angle of the light beam emitted from the afocal zoom optical system 30 constant.
[Third Embodiment]
FIG. 6 is a view for explaining the structure of a laser annealing apparatus incorporating a beam shaping apparatus similar to that of the second embodiment.
[0034]
This laser annealing apparatus has a stage 70 on which a workpiece WO, which is a glass plate on which a semiconductor thin film of amorphous Si or the like is formed, can be moved smoothly in three dimensions, and a semiconductor thin film on the workpiece WO. A laser light source 110 for generating an excimer laser or other laser beam LB for heating, an irradiation optical system 80 for causing the laser beam LB to be incident on the workpiece WO at a predetermined illuminance, and the workpiece WO are mounted. A stage driving device 90 that is a driving means for moving the stage 70 relative to the irradiation optical system 80 or the like by a necessary amount, and a main control device 100 that comprehensively controls the operation of each part of the entire laser annealing apparatus. .
[0035]
The irradiation optical system 80 adjusts the homogenizer 20 that makes the laser beam LB incident on the workpiece WO as a linear beam image having a predetermined cross-sectional shape and intensity extending in the Y-axis direction, and the spread angle of the laser beam LB incident on the homogenizer 20. An afocal zoom optical system 30. The partially transmitted light of the mirror 251 disposed between the laser light source 110 and the irradiation optical system 80 is detected by the spread angle detector 152. Main controller 100 drives zoom driver 155 based on the detection result of spread angle detector 152 to adjust the angular magnification of afocal zoom optical system 30.
[0036]
Hereinafter, the operation of the apparatus of FIG. 6 will be described. First, the workpiece WO is transported and placed on the stage 70 of the laser annealing apparatus. Next, while moving the stage 70 in the X-axis direction with respect to the irradiation optical system 80, the laser beam LB from the irradiation optical system 80 is incident on the workpiece WO as a linear beam image extending in the Y direction. As a result, the entire surface of the workpiece WO is scanned with the laser beam LB.
[0037]
When scanning with the laser beam LB, the diverging light from the mirror 251 is detected by the divergence angle detector 152. The main controller 100 drives the afocal zoom optical system 30 via the zoom driver 155 based on the detection result of the divergence angle detector 152, and makes the divergence angle of the light beam emitted from the afocal zoom optical system 30 constant. To do. Thereby, the time-dependent change of the divergence angle of the light beam from the laser light source 10 is corrected, and the divergence angle of the light beam projected on the workpiece WO is kept constant.
[0038]
The main controller 100 can also intentionally change the divergence angle of the light beam incident on the homogenizer 20 by appropriately driving the afocal zoom optical system 30 via the zoom driver 155. As a result, it is possible to determine the conditions for the polishing process of a semiconductor thin film such as amorphous Si. For example, it has been reported that, in the process of polymorphizing amorphous Si, when the slope is wider and gentler, the temperature gradient at the time of melting and solidification is smaller and stress is not generated, so that the surface roughness can be suppressed and high quality can be obtained. Conversely, if the slope width is made extremely wide and gentle, the beam of the flat portion goes around the slope portion and the energy density of the top flat region does not increase. Through an experiment for determining conditions while changing the angular magnification of the afocal zoom optical system 30, it is possible to find an optimum beam slope while considering both conditions. In the process of polymorphizing amorphous Si, crystallinity using a Raman spectrometer, crystal grain size using TEM, and the like are used as process evaluation means.
[0039]
As described above, the present invention has been described according to the embodiment, but the present invention is not limited to the above embodiment. For example, in the above-described embodiment, the angular magnification of the afocal zoom optical system 30 is continuously changed. However, when the process condition is determined, the angular magnification is discontinuous and changes in multiple steps. Can do. Further, the range in which the angular magnification is changed can be appropriately changed according to the purpose and application such as condition setting. Further, the lens configuration of the afocal zoom optical system 30 is not limited to the three-group configuration with convex and concave portions, and various modifications such as the concave and convex portions and the four-group configuration or more are possible.
[0040]
【The invention's effect】
According to the beam shaping device of the present invention, the afocal zoom optical system is arranged between the light source and the homogenizer and adjusts the spread angle of the irradiation light incident on the homogenizer, so that it is emitted from the homogenizer and incident on a predetermined surface. The cross-sectional shape and the like of the irradiated light can be adjusted. That is, even if the divergence angle of the irradiation light emitted from the light source gradually changes, the cross-sectional shape of the illumination light incident on the predetermined surface through the homogenizer can be kept constant without changing the setting of the homogenizer. Further, the beam cross-sectional shape can be positively controlled by adjusting the divergence angle of the irradiation light by an afocal zoom optical system.
[0041]
Further, according to the beam shaping method of the present invention, by adjusting the divergence angle of the irradiation light incident on the homogenizer, the cross-sectional shape of the irradiation light emitted from the homogenizer and incident on the predetermined surface can be easily adjusted. can do.
[Brief description of the drawings]
FIG. 1 is a diagram showing a structure of an irradiation optical system incorporating a beam shaping device according to a first embodiment.
FIG. 2 is a diagram for explaining the structure of a homogenizer, (a) is a diagram related to the long axis direction of the filament beam, (b) is a diagram related to the minor axis direction of the filament beam, (c ) Is a perspective view for explaining the structure of a cylindrical lens array constituting a part of the homogenizer.
FIGS. 3A and 3B are diagrams illustrating an example of a configuration of an afocal zoom optical system, and FIGS. 3A to 3C are diagrams illustrating changes in angular magnification γ. FIGS.
FIG. 4 is a graph showing a slope width of a linear beam image formed by a homogenizer. (A) shows a relatively large divergence profile, and (b) shows a relatively small divergence profile.
FIG. 5 is a diagram for explaining the structure of an irradiation optical system incorporating a beam shaping device according to a second embodiment.
FIG. 6 is a view for explaining the structure of a laser annealing apparatus incorporating the beam shaping apparatus of the second embodiment.
[Explanation of symbols]
10 laser light source 20 afocal zoom optical system 20 homogenizer 30 afocal zoom optical system 31, 32, 33 lens 51 beam splitter 52 divergence angle detector 55 zoom controller

Claims (3)

A homogenizer that makes irradiation light from a light source incident on a predetermined surface with a predetermined cross-sectional shape and intensity;
An afocal zoom optical system that is disposed between the light source and the homogenizer and adjusts a spread angle of the irradiation light incident on the homogenizer ;
A beam shaping device comprising: 2. The apparatus according to claim 1, further comprising: a detection unit that detects a spread angle of the irradiation light; and a control unit that controls an angular magnification of the afocal zoom optical system based on a detection value of the detection unit. Beam shaping device. A beam shaping method in which irradiation light from a light source is incident on a predetermined surface with a predetermined cross-sectional shape and intensity distribution by a homogenizer,
A beam shaping method, wherein an divergence angle of the irradiation light incident on the homogenizer is adjusted by an afocal zoom optical system .

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