JP2004200497A - Light emitting device and laser annealing device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting device capable of irradiating an irradiation range with uniform irradiation intensity. <P>SOLUTION: A laser anneal device 10 is provided with a light splitting portion 14 for splitting one laser beam into four laser beams. The light splitting portion 14 is provided with first and second beam splitters 21 and 22 and a reflecting mirror 23 arranged in parallel. A laser beam emitted from a laser light source is made incident to the first beam splitter 21. Light transmitted the first beam splitter 21 and the laser beam of the first beam splitter 21 reflected by the reflecting mirror 23 are made incident to the second beam splitter 22. Two beams of transmitted light are emitted to the outside by the second beam splitter 22, and the reflected light of the second beam splitter 22 are further reflected by the reflecting mirror 23, and emitted to the outside. Furthermore, the laser annealing device 10 is provided with a polarizing portion 18 for polarizing the four laser beams split by the light splitting portion 14 so that the polarizing directions can be made orthogonal between adjacent beams. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laser annealing apparatus used for manufacturing a thin film transistor using polysilicon as a channel layer, and a light irradiation apparatus applied to a laser annealing apparatus and the like.
[0002]
[Prior art]
In recent years, in a thin film transistor used for a liquid crystal display or the like, a polysilicon film having high carrier mobility is used for a channel layer. Generally, a polysilicon film of a thin film transistor is manufactured by forming amorphous silicon on a glass substrate and annealing the amorphous silicon by irradiating the amorphous silicon with laser light. A device that irradiates a substance with laser light to anneal the substance is called a laser annealing apparatus.
[0003]
2. Description of the Related Art In a laser annealing apparatus used for manufacturing a thin film transistor, an excimer laser capable of irradiating high-power ultraviolet laser light has been conventionally used as a light source. FIG. 17 shows a configuration of a conventional laser annealing apparatus employing an excimer laser as a light source.
[0004]
As shown in FIG. 17, a conventional laser annealing apparatus 200 includes a stage 202 on which a substrate 201 to be annealed is placed, a laser light source 203 for emitting laser light, and a laser light emitted from the laser light source 203. A telescope 204 having a parallel light beam having a predetermined diameter; a first fly-eye lens 205 and a second fly-eye lens which divide the laser beam passing through the telescope 204 into a plurality of light beams and collect the laser beams to form a group of point light sources; A lens 206 and a condenser lens 207 for combining and irradiating each laser beam passing through the second fly-eye lens 206 to a predetermined irradiation area on the substrate 201 are provided.
[0005]
In the conventional laser annealing apparatus 200 as described above, a single light beam is divided by the first and second fly-eye lenses 205 and 206 to generate a plurality of secondary light sources, and a plurality of secondary light sources generated from the secondary light sources are generated. Are irradiated on predetermined irradiation areas on the substrate 201, respectively. For this reason, in the conventional laser annealing apparatus 200, when a single light beam is irradiated as it is, the intensity distribution becomes Gaussian distribution and it is impossible to give uniform energy to the substrate 201. The laser light is divided using the fly-eye lenses 205 and 206 and then combined for irradiation. Therefore, the intensity distribution of the laser light applied to the substrate 201 can be made uniform.
[0006]
When laser annealing is performed with laser light having such a uniform intensity distribution, uniform energy is applied to the entire surface of the substrate 201, and a polysilicon film having a uniform grain size can be manufactured.
[0007]
[Problems to be solved by the invention]
By the way, an excimer laser used as a light source of a conventional laser annealing apparatus lacks output stability and is a very difficult device to handle. Therefore, from the viewpoint of output stability, it is considered preferable to use a solid-state laser or semiconductor laser in the ultraviolet light region, which has a stable laser beam energy and a long life, as a light source of the laser annealing apparatus.
[0008]
However, the laser light emitted from the solid-state laser and the semiconductor laser has higher coherence than the laser light emitted from the excimer laser. Therefore, when a solid-state laser or a semiconductor laser is employed as the laser light source 203, the laser beams split into a plurality of secondary light sources by the first fly-eye lens 205 and the second fly-eye lens 206 are combined and irradiated. In this case, they interfere with each other, and when irradiating the substrate 201, an interference pattern as shown in FIG. 18 occurs. Therefore, even if the light source of the conventional laser annealing apparatus 200 is replaced with a semiconductor laser or a solid-state laser having high coherence as it is, the intensity distribution of the laser beam to be irradiated cannot be made uniform, and the particle size may be reduced. It is not possible to manufacture a uniform polysilicon film.
[0009]
The present invention has been proposed in view of the conventional circumstances described above, and has as its object to provide a light irradiation device capable of irradiating an irradiation range with a uniform irradiation intensity. Another object of the present invention is to provide a laser annealing apparatus capable of annealing an irradiation target with uniform energy.
[0010]
[Means for Solving the Problems]
In order to achieve the above-described object, a light irradiation device and a laser annealing device according to the present invention include a laser light source that emits a laser beam, and a light splitting device that divides a laser beam emitted from the laser light source into a plurality of laser beams. Means, a polarizing means for controlling the polarization direction of the laser beam split by the light splitting means, and an irradiating means for irradiating the irradiation object with the plurality of laser beams.
[0011]
The light splitting means of the light irradiation device and the laser annealing device has a light separating surface for reflecting and transmitting an incident laser beam and separating the laser beam into two laser beams of reflected light and transmitted light. K (where k is a natural number of 1 or more) beam splitters arranged in parallel, a light reflecting surface is made parallel to a light splitting surface of the beam splitter, and reflected light from all the beam splitters is incident. A laser beam emitted from the laser light source is incident on the first beam splitter from the laser light source side, and is applied to the (m + 1) th (where m is a natural number) beam splitter. Are transmitted by the m-th beam splitter and the laser beam reflected by the reflecting mirror after being reflected by the m-th beam splitter are incident on the k-th beam splitter. Splitter, 2 ^(K-1) The transmitted light is output to the outside, and the reflecting mirror receives the light transmitted from the k-th beam splitter. ^(K-1) The reflected light of the book is reflected and output to the outside.
[0012]
The light splitting means and the polarizing means of the laser annealing device polarize the plurality of laser beams split by the light splitting means such that adjacent beams have polarization directions orthogonal to each other.
[0013]
BEST MODE FOR CARRYING OUT THE INVENTION
(1) First embodiment
A first embodiment of the present invention will be described. The laser annealing apparatus according to the first embodiment of the present invention, for example, irradiates a laser beam to a TFT substrate after an amorphous silicon film is formed, and heat-treats the amorphous silicon film to form the amorphous silicon film. This is a device for converting to a polysilicon film.
[0014]
FIG. 1 shows a configuration of a laser annealing apparatus 10 according to the first embodiment.
[0015]
The laser annealing apparatus 10 includes a stage 11 on which the substrate 1 to be annealed is mounted, a laser light source 12 for emitting laser light, a collimator 13 provided on an optical path of the laser light emitted from the laser light source 12, and A light splitting unit 14 for splitting one laser beam emitted from the collimator 13 into four laser beams, a lens array 15 composed of four convex lenses, and four lasers emitted from the lens array 15 The apparatus includes a condenser lens 16 that guides light to a predetermined area of the substrate 1, a control unit 17 that controls the position of the stage 11, and the like, and a polarizing unit 18.
[0016]
The stage 11 has a flat main surface on which the flat substrate 1 is mounted. The substrate 1 mounted on the stage 11 is, for example, a TFT substrate after an amorphous silicon film is formed. The stage 11 moves in a direction parallel to the main surface (the X and Y directions in FIG. 1) while holding the substrate 1 placed on the main surface. In the laser annealing apparatus 10, the irradiation position of the laser beam on the substrate 1 can be moved by moving the stage 11. That is, the position on the substrate 1 where the annealing is performed can be controlled by moving the stage 11. The movement of the stage 11 is controlled by the control unit 17.
[0017]
The laser light source 12 is a device that outputs a pulsed laser beam. The laser annealing apparatus 10 employs a solid-state laser as the laser light source 12. A solid-state laser is a device that uses a transparent substance such as crystal or glass other than a semiconductor as a base material, and excites a solid-state laser material in which a base material is doped with rare earth ions, transition metal ions, and the like, and emits laser light. It is. An example of a solid-state laser is Nd using glass as a base material. ³⁺ Glass laser doped with ³⁺ -Doped ruby laser, yttrium aluminum garnet (YAG) with Nd ³⁺ Doped YAG lasers, and lasers whose wavelengths have been converted using nonlinear optical crystals. Further, as the laser light source 12, a semiconductor laser or the like may be used instead of the fixed laser.
[0018]
Laser light emitted from the laser light source 12 enters the collimator 13.
[0019]
The collimator 13 converts the incident laser light into a parallel light having a predetermined beam diameter. The laser light emitted from the collimator 13 enters the light splitting unit 14. Note that the beam diameter of the laser light that has passed through the collimator 13 may be expanded by a beam expander or the like.
[0020]
Hereinafter, the laser light incident on the light splitting unit 14 from the collimator 13 is referred to as a laser light L1.
[0021]
The light splitting unit 14 splits the laser light L1 and emits four laser lights arranged in parallel at equal intervals. The four laser beams emitted from the light splitting unit 14 are arranged, for example, in the X direction in FIG.
A specific configuration example of the light splitting unit 14 will be described later in detail.
[0022]
The four laser beams emitted from the light splitting unit 14 pass through the polarizing unit 18 and then enter the lens array 15.
[0023]
The polarization unit 18 changes the polarization directions of the four laser beams emitted from the light splitting unit 14 to be orthogonal to each other between adjacent beams. For example, the polarization unit 18 polarizes the four incident laser beams so that P-polarized light and S-polarized light are alternately arranged. In order to arrange the P-polarized laser light and the S-polarized laser light alternately in this manner, for example, the S-polarized or P-polarized laser light is emitted from the laser light source 12, and the polarizing unit 18 is moved to the position shown in FIG. As shown, the first half-wave plate 18a and the second half-wave plate 18c are configured, and the first half-wave plate 18a and the second half-wave plate 18c are arranged in a line. It is sufficient to dispose every other laser light arranged in a row. By using such a polarizing section 18, adjacent laser beams do not interfere with each other. In the present embodiment, a P-polarized or S-polarized laser beam is emitted from the laser light source 12, and a first half-wave plate 18a is provided in front of a first convex lens 15a described below. It is assumed that a second half-wave plate 18c is provided in front of the third convex lens 5c.
[0024]
Further, the polarizing section 18 is provided between the light splitting section 14 and the lens array 15, but may be provided between the lens array 15 and the condenser lens 16 as shown by a dotted line in FIG.
[0025]
The lens array 15 includes four convex lenses 15a to 15d arranged in a line at equal intervals in a direction in which the four laser beams emitted from the light splitting unit 14 are arranged (for example, the X direction in FIG. 1). Have been. The arrangement interval of the convex lenses 15a to 15d is the same as the interval between the four laser beams emitted from the light splitting unit 14, and each convex lens 15a to 15d is provided on the optical axis of each laser beam. The lens array 15 condenses each of the four incident laser beams to generate four secondary light sources. The four laser beams emitted from the lens array 15 are once condensed to become a secondary light source, and then enter the condenser lens 16.
[0026]
The condenser lens 16 receives the four laser beams condensed by the lens array 15 and irradiates the incident four laser beams onto the substrate 1.
[0027]
The control unit 17 controls the irradiation position of the laser beam on the substrate 1 by controlling the movement of the stage 11 in the X direction and the Y direction in FIG.
[0028]
In the laser annealing apparatus 10 configured as described above, the substrate 1 is placed on the stage 11, and thereafter, the laser annealing process is started. When the laser annealing process is started, the laser annealing apparatus 10 emits a pulse laser from the laser light source 12.
[0029]
The laser light emitted from the laser light source 12 passes through the light splitting section 14 and the polarizing section 18, so that adjacent beams are converted into four parallel light beams having the same intensity and having no interference with each other.
[0030]
The four laser beams are converted into four secondary light sources by the lens array 15. The four laser beams emitted from the secondary light source are applied to a predetermined area on the substrate 1 via the condenser lens 16.
[0031]
Then, in the laser annealing apparatus 10, the stage 11 is moved in parallel to move the flat substrate 1 in a direction parallel to the main surface (the XY direction in FIG. 1). An annealing process is performed by irradiating a laser beam.
[0032]
Next, the configuration of the light splitting unit 14 will be described in more detail. FIG. 2 shows the configuration of the light splitting unit 14. The direction of the optical axis of the laser beam L1 incident on the light splitting unit 14 is defined as a Z direction. The directions of the optical axes of the four laser beams emitted from the light splitting unit 14 are also the Z direction. Here, the Z direction is a direction orthogonal to the main surface of the stage 11. The four laser beams emitted from the light splitting section 14 are emitted side by side in parallel to a predetermined direction, and the arrangement direction of the laser beams is defined as the X direction. Here, the X direction is a direction parallel to the main surface of the stage 11. The Y direction is a direction orthogonal to the X direction and the Z direction.
[0033]
As shown in FIG. 2, the light splitting unit 14 includes a first beam splitter (BS) 21 and a second BS 22 in which planar light separation surfaces are arranged in the Z direction. The first BS 21 and the second BS 22 are elements that transmit and reflect the laser light incident on the light separation surface and separate the laser light into two laser lights. The separation ratio between transmission and reflection is 1: 1 in design.
[0034]
The light splitting unit 14 includes a mirror 23 whose light reflecting surface is parallel to the light separating surfaces of the first BS 21 and the second BS 22 and which is arranged alongside the first BS 21 and the second BS 22 in the Z direction. ing. The mirror 23 is an element that reflects the laser light incident on the planar light reflecting surface. The mirror 23 is arranged on the laser beam L1 incident side with respect to the first BS 21.
[0035]
The light separating surfaces of the first BS 21 and the second BS 22 and the light reflecting surface of the mirror 23 are arranged perpendicularly to a plane formed by the XZ axis, and serve to detect the incident laser light L1. They are arranged at a predetermined angle (90 ° −θ) (0 ° <θ <90 °) with respect to the incident direction (that is, the Z direction). That is, the laser beam L1 is incident on the light separation surfaces of the first BS 21 and the second BS 22 at an incident angle θ.
[0036]
The first BS 21 is arranged on the optical axis of the laser light L1. Further, the second BS 22 is also arranged on the optical axis of the laser beam L1. Further, the first BS 21 is arranged and sized so that only the laser beam L1 is incident and other light is not incident. The second BS 22 is arranged and sized so that the transmitted light of the first BS 21 and the reflected light of the first BS 21 after being reflected by the mirror 23 are incident, and other light is not incident. . The mirror 23 is arranged and sized so that the reflected light of the first BS 21 and the two reflected lights of the second BS 22 enter and do not block the laser light L1.
[0037]
Specifically, it is assumed that the four laser lights emitted from the light splitting unit 14 are a first laser light L1-1, a second laser light L1-2, a third laser light L1_3, and a fourth laser light L1_4. The above-described first to fourth laser beams L1_1 to L1_4 are generated through the following route. That is, the first laser light L1_1 is generated in a path that transmits through the first BS 21, transmits through the second BS 22, and emits outside. The second laser light L1_2 is generated in a path that reflects the first BS 21, reflects the mirror 23, transmits through the second BS 22, and emits outside. The third laser light L1_3 is generated on a path that transmits through the first BS 21, reflects on the second BS 22, reflects on the mirror 23, and emits outside. The fourth laser light L1_4 is generated on a path that reflects the first BS 21, reflects the second BS 22, reflects the mirror 23, and emits the light to the outside.
[0038]
With the above configuration, the light splitting unit 14 can emit four laser beams mutually aligned in the X direction.
[0039]
Further, the light splitting unit 14 may be configured so that all of the four laser lights emitted from the polarizing unit 18 are incoherent light having no interference with each other.
[0040]
In this case, the distance t0 between the first BS 21 and the mirror 23 is set to {L / (2 cos θ)} / 2 or more, where L is the coherent distance set by the laser light source 12. The distance t1 between the first BS 21 and the second BS 22 is also set to {L / (2 cos θ)} / 2 or more, where L is the coherent distance set by the laser light source 12.
[0041]
The laser annealing apparatus 10 according to the first embodiment includes the light splitting unit 14 that can split one laser beam into four laser beams with a simple configuration as described above. Further, in the laser annealing apparatus 10 of the first embodiment, the polarization section 18 that polarizes the four laser beams emitted from the light splitting section 14 so that the polarization directions of the adjacent beams are orthogonal to each other. Have.
[0042]
Therefore, in the laser annealing apparatus 10 of the first embodiment, since adjacent laser beams are polarized orthogonal to each other, when forming one irradiation region with a plurality of laser beams, adjacent laser beams Can be irradiated while overlapping. Therefore, a large irradiation area without unevenness in intensity can be formed, and as shown in FIG. 3, it becomes possible to irradiate the substrate 1 with uniform energy. That is, in the laser annealing apparatus 10, it becomes possible to irradiate the substrate 1 with a uniform laser beam, and therefore, it is possible to apply uniform energy to the substrate 1 and to obtain polysilicon having a uniform particle size. A film can be produced.
[0043]
Further, in the laser annealing apparatus 10 of the first embodiment, when the coherence distance set by the laser light source 12 is L, the distance t0 between the first BS 21 of the light splitting unit 14 and the mirror 23 is set. Is not more than {L / (2 cos θ)} / 2, and the distance t1 between the first BS 21 and the second BS 22 is also not less than {L / (2 cos θ)} / 2 so that they are not adjacent to each other. The difference in the optical path length between the laser beams is greater than the coherence length L. That is, an optical path length difference of the coherent distance L or more can be provided between laser beams having the same polarization. More specifically, the laser light incident on the first convex lens 15a and the laser light incident on the third convex lens 15c are mutually incoherent light, and the laser light incident on the second convex lens 15b and The laser light incident on the fourth convex lens 15d can be mutually incoherent light.
[0044]
As a result, the laser beams that have passed through the polarizing unit 18 are all laser beams that do not interfere with each other. Therefore, as shown in FIG. 4, it is possible to combine the laser beams condensed by the lens array 15 with the condenser lens 19 and irradiate the same irradiation area on the substrate 1.
[0045]
Also, as shown in FIG. 5, a light transmitting member 24 such as glass, which transmits laser light, is provided in the light splitting unit 14, and the first BS 21 and the second BS 22 are attached to the light transmitting member 24. The first BS 21, the second BS 22, and the light transmitting member 24 may be integrally configured. This facilitates the position adjustment of the first BS 21, the second BS 22, and the mirror 23.
[0046]
In this case, refraction occurs when laser light is incident on the light transmitting member 24 and when laser light is emitted from the light transmitting member 24. Therefore, when the coherent distance set by the laser light source 12 is L, the refractive index of the light transmitting member 24 is n, and the refractive index of air is 1, the distance between the first BS 21 and the second BS 22 Let the distance t1 be ｛L / (2 (n ² −sin ² θ) ^1/2 By setting｝ / 2 or more, the four laser beams L1_1 to L1_4 emitted from the polarization unit 18 can be lights having no interference with each other.
[0047]
(2) Second embodiment
A second embodiment of the present invention will be described. As in the first embodiment, the laser annealing apparatus according to the second embodiment of the present invention irradiates a laser beam to a TFT substrate after an amorphous silicon film is formed, for example. Is a device that converts an amorphous silicon film to a polysilicon film by heat-treating the amorphous silicon film.
[0048]
In describing the laser annealing apparatus according to the second embodiment, the same components as those in the laser annealing apparatus 10 according to the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof will be given. Omitted. The X, Y, and Z directions used in the description of the second embodiment are also the same as those in the first embodiment.
[0049]
FIG. 6 shows a configuration of a laser annealing apparatus 30 according to the second embodiment.
[0050]
The laser annealing apparatus 30 includes a stage 11 on which the substrate 1 to be annealed is mounted, a laser light source 12 for emitting laser light, a collimator 13 provided on an optical path of the laser light emitted from the laser light source 12, and A light splitting unit 14 that splits one laser beam emitted from the collimator 13 into four laser beams (hereinafter, in the second embodiment, the light splitting unit 14 is referred to as a first light splitting unit 14). ), A second light splitting unit 31 that splits each of the four laser beams emitted from the first light splitting unit 14 into four laser beams and emits 16 laser beams, and 16 , A condenser lens 16 that guides 16 laser beams emitted from the lens array 32 to a predetermined area of the substrate 1, and a control unit 17 that controls the position of the stage 11. And a polarizing unit 37.
[0051]
The first light splitting section 14 splits the laser light L1 and emits four laser lights arranged in parallel at equal intervals. The four laser beams emitted from the first light splitting unit 14 are arranged in the X direction. The four laser beams emitted from the first light splitting unit 14 enter the second light splitting unit 31.
[0052]
The second light splitting unit 31 splits the four laser beams arranged in parallel in the X direction into four laser beams arranged in the Y direction and outputs the laser beams. Therefore, a total of 16 laser beams are emitted from the second light splitting unit 31. The optical axes of the 16 laser beams emitted from the second light splitting unit 31 are arranged in a matrix of four rows in the X direction and four rows in the Y direction. The configuration of the second light splitting unit 31 will be described later in detail.
[0053]
The 16 laser beams emitted from the second light splitting unit 31 enter the lens array 32 via the polarizing unit 37.
[0054]
The polarization unit 37 changes the polarization direction of the 16 laser beams emitted from the second light splitting unit 31 into mutually orthogonal polarizations between adjacent beams. For example, the polarization unit 37 polarizes the incident 16 laser beams so that P-polarized light and S-polarized light are alternately arranged. In order to arrange the P-polarized laser light and the S-polarized laser light alternately in this way, for example, the S-polarized or P-polarized laser light is emitted from the laser light source 12, and the polarizing unit 37 is turned on as shown in FIG. As shown in a), a first half-wave plate 37a, a second half-wave plate 37c, a third half-wave plate 37f, a fourth half-wave plate 37h, , A fifth half-wave plate 37i, a sixth half-wave plate 37k, a seventh half-wave plate 37m, and an eighth half-wave plate 37p. And these may be arranged every other laser light arranged in a matrix. By using such a polarization unit 37, adjacent laser beams do not interfere with each other.
[0055]
In the present embodiment, a P-polarized or S-polarized laser beam is emitted from the laser light source 12, and a first half-wave plate 37a is provided in front of a first convex lens 33a described below. A second half-wave plate 37c is provided in front of the third convex lens 33c, a third half-wave plate 37f is provided in front of the sixth convex lens 33f, and a second half-wave plate 37f is provided in front of the eighth convex lens 33h. A half-wave plate 37h is provided before the ninth convex lens 33i, a fifth half-wave plate 37i is provided before the ninth convex lens 33i, and a sixth half-wave plate 37k is provided before the eleventh convex lens 33k. Is provided, a seventh half-wave plate 37m is provided before the fourteenth convex lens 33m, and an eighth half-wave plate 37p is provided before the sixteenth convex lens 33p. .
[0056]
The polarizing section 37 is provided between the second light splitting section 31 and the lens array 33, but may be provided between the lens array 33 and the condenser lens 16.
[0057]
As shown in FIG. 7B, the lens array 32 includes sixteen convex lenses 32a to 32p arranged in a matrix of four in each of the X and Y directions. The arrangement interval of the convex lenses 32a to 32p is the same as the interval between the 16 laser beams emitted from the second light splitting unit 31, and each of the convex lenses 32a to 32p is provided on the optical axis of each laser beam. The lens array 32 condenses the incident 16 laser beams, respectively, to generate 16 secondary light sources. The 16 laser beams emitted from the lens array 32 are once condensed to become a secondary light source, and then enter the condenser lens 16.
[0058]
The condenser lens 16 irradiates the substrate 1 with 16 laser beams collected by the lens array 32.
[0059]
In the laser annealing apparatus 30 configured as described above, the substrate 1 is placed on the stage 11, and thereafter, a laser annealing process is started. When the laser annealing process is started, the laser annealing device 30 emits a pulse laser from the laser light source 12.
[0060]
The laser light emitted from the laser light source 12 passes through the first light splitting section 14, the second light splitting section 31, and the polarizing section 37, so that adjacent laser lights have no interference with each other. Of parallel light beams.
[0061]
The 16 laser beams are converted into 16 secondary light sources by the lens array 32. The 16 laser beams emitted from the secondary light source are applied to a predetermined area on the substrate 1 via the condenser lens 16.
[0062]
Then, in the laser annealing apparatus 30, the stage 11 is moved in parallel to move the flat substrate 1 in a direction parallel to the main surface (the XY direction in FIG. 6). An annealing process is performed by irradiating a laser beam.
[0063]
Next, the configuration of the second light splitting unit 31 will be described in more detail. FIG. 8 shows a configuration of the first light splitting unit 14 and the second light splitting unit 31. FIG. 8 is a diagram of the first light splitting unit 14 and the second light splitting unit 31 viewed from the X direction.
[0064]
The second light splitting unit 31 can be realized by rotating the first light splitting unit 14 by 90 degrees around an axis parallel to the Z direction. However, since four laser beams arranged in the X direction are incident on the second light splitting unit 31, the width in the X direction is sufficiently long so that these four laser beams are incident. A long length is required.
[0065]
Hereinafter, the configuration of the second light splitting unit 31 will be specifically described.
[0066]
As shown in FIG. 8, the second light splitting unit 31 includes a first BS 34 and a second BS 35 in which planar light separation surfaces are arranged in the Z direction. The first BS 34 and the second BS 35 are elements that transmit and reflect the laser light incident on the light separation surface and separate the laser light into two laser lights. The separation ratio between transmission and reflection is 1: 1 in design.
[0067]
The second light splitting section 31 has a mirror whose light reflecting surface is parallel to the light separating surfaces of the first BS 34 and the second BS 35, and which is arranged alongside the first BS 34 and the second BS 35 in the Z direction. 36. The mirror 36 is an element that reflects the laser light incident on the planar light reflecting surface. The mirror 36 is arranged on the laser beam L1 incident side with respect to the first BS 34.
[0068]
The light separating surfaces of the first BS 34 and the second BS 35 and the light reflecting surface of the mirror 36 are arranged perpendicular to a plane formed by the YZ axes, and the incident laser beams L1_1 to L1_1. They are arranged at a predetermined angle (90 ° −θ ′) (0 ° <θ ′ <90 °) with respect to the incident direction of L1_4 (that is, the Z direction). That is, the laser beams L1_1 to L1_4 are incident on the light separation surfaces of the first BS 34 and the second BS 35 at an incident angle θ ′.
[0069]
The first BS 34 is arranged on the optical axis of the laser beams L1_1 to L1_4. Further, the second BS 35 is also arranged on the optical axis of the laser beams L1_1 to L1_4. Further, the first BS 34 is arranged and sized such that only the laser beams L1-1_1 to L1_4 are incident and other beams are not incident. The second BS 35 is arranged and sized such that the transmitted light of the first BS 34 and the reflected light of the first BS 34 after being reflected by the mirror 36 are incident and other light is not incident. . The mirror 36 is arranged and sized so that the reflected light of the first BS 34 and the two reflected lights of the second BS 35 are incident thereon and do not block the incident laser beams L1_1 to L1_4.
[0070]
Further, the first light splitting unit 14 and the second light splitting unit 31 are configured so that all of the 16 laser beams emitted from the polarization unit 37 are incoherent light having no interference with each other. You may.
[0071]
In this case, assuming that the coherence distance set by the laser light source 12 is L, the distance t0 between the first BS 21 of the first light splitting unit 14 and the mirror 23 is {L / (2 cos θ)}. / 2 or more, and the distance t1 between the first BS 21 and the second BS 22 is also {L / (2 cos θ)} / 2 or more.
[0072]
The distance t′0 between the first BS 34 and the mirror 36 of the second light splitting unit 31 and the distance t′1 between the first BS 34 and the second BS 35 are expressed by the following equations. Adjustment is performed as shown in (1) and equation (2).
t′0 ≧ {(Lmax−Lmin) + L} / (2cosθ ′)｝ / 2 (1)
t′1 ≧ {(Lmax−Lmin) + L} / (2cosθ ′)｝ / 2 (2)
Lmin and Lmax used in the above equations (1) and (2) are values determined from the configuration of the first light splitting unit 14 in the preceding stage. Lmin is the optical path length of the laser light having the shortest optical path length among the plurality of laser lights obtained from the first light splitting unit 14. Lmax is the optical path length of the laser light having the longest optical path length among the plurality of laser lights obtained from the first light splitting unit 14.
[0073]
The laser annealing apparatus 30 according to the second embodiment includes a first light splitting unit 14 and a second light splitting unit 31 that can split one laser beam into one laser beam with the simple configuration as described above. It has. Further, the laser annealing apparatus 30 of the second embodiment includes a polarization section 37 that polarizes the divided 16 laser beams so that the polarization directions of the adjacent laser beams are orthogonal to each other.
[0074]
Therefore, in the laser annealing apparatus 30 according to the second embodiment, since adjacent laser beams are polarized orthogonally to each other, when forming one irradiation region with a plurality of laser beams, adjacent laser beams Can be irradiated while overlapping. Therefore, a large irradiation area without unevenness in intensity can be formed, and the substrate 1 can be irradiated with uniform energy.
[0075]
Further, in the laser annealing apparatus 30 of the second embodiment, when the coherence distance set by the laser light source 12 is L, the distance between the first BS 21 of the first light splitting unit 14 and the mirror 23 is set. Is set to {L / (2 cos θ)} / 2 or more, the distance t1 between the first BS 21 and the second BS 22 is also set to {L / (2 cos θ)} / 2 or more, and By setting the light splitting section 31 as shown in the above equations (1) and (2), a difference of the coherence length L or more can be given to the optical path length of the laser beams that are not adjacent to each other. . That is, an optical path length difference of the coherent distance L or more can be provided between laser beams having the same polarization.
[0076]
As a result, the laser beams that have passed through the polarization unit 37 are all laser beams that do not interfere with each other. Therefore, each laser beam condensed by the lens array 32 can be irradiated to the same irradiation area on the substrate 1 by the condenser lens.
[0077]
In the laser annealing apparatus 30 of the second embodiment, the laser annealing apparatus 10 of the first embodiment irradiates four laser beams in a line, whereas the laser annealing apparatus 10 of the second embodiment emits two laser beams. It is divided into a dimensional matrix. For this reason, when the irradiation is performed by the laser annealing apparatus 10 of the first embodiment, the irradiation area U1 has a so-called linear shape as shown in FIG. As shown in FIG. 9B, the irradiation area U2 has a rectangular shape, and the irradiation area can be expanded.
[0078]
Also, in the laser annealing apparatus 30 of the second embodiment, similarly to the first embodiment, a light transmitting member such as glass, which transmits laser light, is provided in the second light splitting unit 31. The first BS 34 and the second BS 35 may be attached to the light transmitting member, and the first BS 34, the second BS 35, and the light transmitting member may be integrally formed. This facilitates position adjustment of the first BS 34, the second BS 35, and the mirror 36.
[0079]
In this case, by setting the distance t′1 between the first BS 34 and the second BS 35 as shown in the following equation (3), all the 16 laser beams emitted from the polarization unit 37 are set. Can be incoherent with each other. Here, n is the refractive index of the light transmitting member.
t′1 ≧ {(Lmax−Lmin) + L} / (2 (n ² −sin ² θ ') ^1/2 ｝ / 2… (3)
[0080]
(3) Third embodiment
A third embodiment of the present invention will be described. As in the first embodiment, the laser annealing apparatus according to the third embodiment of the present invention irradiates a laser beam to a TFT substrate after an amorphous silicon film is formed, for example. Is a device that converts an amorphous silicon film to a polysilicon film by heat-treating the amorphous silicon film.
[0081]
In describing the laser annealing apparatus according to the third embodiment, the same components as those of the laser annealing apparatus 10 according to the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof will be given. Omitted. The X, Y, and Z directions used in the description of the third embodiment are also the same as those in the first embodiment.
[0082]
FIG. 10 shows a configuration of a laser annealing apparatus 40 according to the third embodiment.
[0083]
The laser annealing apparatus 40 includes a stage 11 on which the substrate 1 to be annealed is mounted, a laser light source 12 for emitting laser light, a collimator 13 provided on an optical path of the laser light emitted from the laser light source 12, A light splitting unit 41 that splits one laser beam emitted from the collimator 13 into eight laser beams, a lens array 42 composed of eight convex lenses, and eight lasers emitted from the lens array 42 It includes a condenser lens 43 that guides light to a predetermined region of the substrate 1, a control unit 17 that controls the position of the stage 11, and the like, and a polarizing unit 48.
[0084]
The light splitting unit 41 splits the laser light L1 and emits eight laser lights arranged in parallel at equal intervals. The eight laser beams emitted from the light splitting unit 41 are arranged in the X direction. The specific configuration example of the light splitting unit 41 will be described later in detail.
[0085]
The eight laser beams emitted from the light splitting unit 41 enter the lens array 42 via the polarizing unit 48.
[0086]
The polarization unit 48 changes the polarization directions of the eight laser beams emitted from the light splitting unit 41 into mutually orthogonal polarizations between adjacent beams. For example, the polarization unit 38 polarizes the incident 16 laser beams so that P-polarized light and S-polarized light are alternately arranged. In order to arrange the P-polarized laser light and the S-polarized laser light alternately in this manner, for example, the S-polarized or P-polarized laser light is emitted from the laser light source 12, and the polarizing unit 48 is changed to the state shown in FIG. As shown in a), a first half-wave plate 48a, a second half-wave plate 48c, a third half-wave plate 48e, a fourth half-wave plate 48g, It is sufficient to constitute the four wavelength plates, and to arrange them every other for eight laser beams. By using such a polarizing section 48, adjacent laser beams do not interfere with each other.
[0087]
In the present embodiment, a P-polarized or S-polarized laser beam is emitted from the laser light source 12, and a first half-wave plate 48a is provided in front of the first convex lens 42a described below. A second half-wave plate 37c is provided in front of the third convex lens 42c, a third half-wave plate 48e is provided in front of the fifth convex lens 42e, and a second half-wave plate 48e is provided in front of the seventh convex lens 42g. It is assumed that a 4 1/2 wavelength plate 48g is provided.
[0088]
Further, the polarizing section 48 is provided between the light splitting section 41 and the lens array 42, but may be provided between the lens array 42 and the condenser lens 43.
[0089]
As shown in FIG. 11B, the lens array 42 includes eight convex lenses 42a to 42h arranged in a line at equal intervals in a direction in which the eight laser beams emitted from the light splitting unit 41 are arranged. It is composed of The arrangement interval of the convex lenses 42a to 42h is the same as the interval between the eight laser beams emitted from the light splitting unit 41, and each of the convex lenses 42a to 42h is provided on the optical axis of each laser beam. The lens array 42 collects the eight incident laser beams to generate eight secondary light sources. The eight laser beams emitted from the lens array 42 are once condensed to become a secondary light source, and then enter the condenser lens 43.
[0090]
The condenser lens 43 irradiates the substrate 1 with eight laser beams collected by the lens array 42.
[0091]
In the laser annealing apparatus 40 having the above-described configuration, the substrate 1 is placed on the stage 11, and thereafter, a laser annealing process is started. When the laser annealing process is started, the laser annealing device 40 emits a pulse laser from the laser light source 12.
[0092]
The laser light emitted from the laser light source 12 passes through the light splitting section 41 and the polarizing section 48, so that the adjacent laser lights are converted into eight parallel light beams having the same intensity and having no interference with each other.
[0093]
The eight laser beams are converted into eight secondary light sources by the lens array 42. Eight laser beams emitted from the secondary light source are applied to a predetermined area on the substrate 1 via the condenser lens 43.
[0094]
In the laser annealing apparatus 40, the stage 11 is moved in parallel to move the flat substrate 1 in a direction parallel to the main surface (the XY direction in FIG. 10). An annealing process is performed by irradiating a laser beam.
[0095]
Next, the configuration of the light splitting unit 41 will be described in more detail. FIG. 12 shows the configuration of the light splitting unit 41. FIG. 12 is a diagram of the light splitting unit 41 as viewed from the Y direction.
[0096]
As shown in FIG. 12, the light splitting unit 41 includes a first BS 44, a second BS 45, and a third BS 46 in which planar light separating surfaces are arranged in the Z direction. . The first BS 44, the second BS 45, and the third BS 46 are elements that transmit and reflect the laser light incident on the light separating surface and separate the laser light into two laser lights. The separation ratio between transmission and reflection is 1: 1 in design.
[0097]
The light splitting unit 41 is configured such that the light separating surface of the first BS 44, the second BS 45, and the third BS 46 and the light reflecting surface are parallel, and the first BS 44, the second BS 45, the third BS 46, and the Z It has a mirror 47 arranged side by side in the direction. The mirror 47 is an element that reflects the laser light incident on the planar light reflecting surface. The mirror 47 is arranged on the laser beam L1 incident side of the first BS 44.
[0098]
The light separating surfaces of the first BS 44, the second BS 45, and the third BS 46, and the light reflecting surface of the mirror 47 are arranged perpendicularly to a plane formed by the XZ axis and are incident. The laser light L1 is disposed at a predetermined angle (90 ° −θ) (0 ° <θ <90 °) with respect to the incident direction (that is, the Z direction) of the laser beam L1. That is, the laser beam L1 is incident on the light separation plane of the first BS 44, the second BS 45, and the third BS 46 at an incident angle θ.
[0099]
The first BS 44 is arranged on the optical axis of the laser light L1. Further, the second BS 45 and the third BS 46 are also arranged on the optical axis of the laser beam L1. The first BS 44 is arranged and sized so that only the laser beam L1 is incident and no other light is incident. The second BS 45 is arranged and sized such that the transmitted light of the first BS 44 and the reflected light of the first BS 44 after being reflected by the mirror 47 are incident, and other light is not incident. . The third BS 46 receives the two transmitted lights of the second BS 45 and the two reflected lights of the second BS 45 after being reflected by the mirror 47, and prevents other light from entering. Arrangement and size. The mirror 47 receives one reflected light of the first BS 44, two reflected lights of the second BS 45, and four reflected lights of the third BS 46 so as not to block the laser light L1. Arrangement and size.
[0100]
Specifically, the eight laser beams emitted from the light splitting unit 41 are divided into a first laser beam L1-1, a second laser beam L1-2, a third laser beam L1_3, a fourth laser beam L1_4, and a first laser beam L1_4. Laser light L1_1, second laser light L1-2, third laser light L1_3, fourth laser light L1_4, fifth laser light L1_5, sixth laser light L1_6, seventh laser light L1_7, and eighth laser Assuming that the light is L1_8, the above-described first to eighth laser lights L1_1 to L1_8 are generated through the following route.
[0101]
That is, the first laser light L1_1 is generated in a path of the first BS 44 (transmission) → the second BS 45 (transmission) → the third BS 46 (transmission) → emission. The second laser beam L1_2 is generated in a path of the first BS 44 (reflection) → the mirror 47 → the second BS 45 (transmission) → the third BS 46 (transmission) → emission. The third laser beam L1_3 is generated in a path of the first BS 44 (transmission) → the second BS 45 (reflection) → the mirror 47 → the third BS 46 (transmission) → emission. The fourth laser light L1_4 is generated in a path of the first BS 44 (reflection) → the mirror 47 → the second BS 45 (reflection) → the mirror 47 → the third BS 46 (transmission) → emission. The fifth laser light L1_5 is generated in a path of the first BS 44 (transmission) → the second BS 45 (transmission) → the third BS 46 (reflection) → the mirror 47 → the emission. The sixth laser light L1_6 is generated in a path of the first BS 44 (reflection) → the mirror 47 → the second BS 45 (transmission) → the third BS 46 (reflection) → the mirror 47 → the emission. The seventh laser beam L1_7 is generated in a path of the first BS 44 (transmission) → the second BS 45 (reflection) → the mirror 47 → the third BS 46 (reflection) → the mirror 47 → the emission. The eighth laser light L1_8 is generated in a path of the first BS 44 (reflection) → the mirror 47 → the second BS 45 (reflection) → the mirror 47 → the third BS 46 (reflection) → the mirror 47 → the emission.
[0102]
With the above configuration, the light splitting unit 41 can emit eight laser lights arranged in parallel in the X direction.
[0103]
Furthermore, the light splitting unit 41 may be configured so that all eight laser beams emitted from the polarizing unit 48 are incoherent light having no interference with each other.
[0104]
In this case, when the coherence distance set by the laser light source 12 is L, the distance t0 between the first BS 44 and the mirror 47 is set to {L / (2 cos θ)} / 2 or more, and the first BS 44 The distance t1 between the second BS 45 and the second BS 45 is set to {L / (2 cos θ)} / 2 or more, and the distance t 2 between the second BS 45 and the third BS 46 is set to {(2 × L) / (2 cos θ). )｝ / 2 or more.
[0105]
The laser annealing apparatus 40 according to the third embodiment includes the light splitting unit 41 that can split one laser beam into eight laser beams with a simple configuration as described above. Further, the laser annealing apparatus 40 of the third embodiment converts the eight laser beams emitted from the light splitting section 41 into polarizing sections 48 so that the polarizing directions of adjacent beams are orthogonal to each other. It has.
[0106]
Therefore, in the laser annealing apparatus 40 according to the third embodiment, since adjacent laser beams are polarized orthogonally to each other, when forming one irradiation region with a plurality of laser beams, adjacent laser beams Can be irradiated while overlapping. Therefore, a large irradiation area without unevenness in intensity can be formed, and the substrate 1 can be irradiated with uniform energy.
[0107]
Further, in the laser annealing apparatus 40 according to the third embodiment, when the coherence distance set by the laser light source 12 is L, the distance t0 between the first BS 44 and the mirror 47 is ｛L / ( 2 cos θ)｝ / 2 or more, the distance t1 between the first BS 44 and the second BS 45 is set to {L / (2 cos θ)} / 2 or more, and the distance between the second BS 45 and the third BS 46 By setting t2 to be equal to or more than {(2 × L) / (2cos θ)} / 2, it is possible to make a difference equal to or more than the coherence distance L to the optical path length between the laser beams that are not adjacent to each other. That is, an optical path length difference of the coherent distance L or more can be provided between laser beams having the same polarization.
[0108]
As a result, the eight laser beams that have passed through the polarization unit 48 are all laser beams that do not interfere with each other. Therefore, each laser beam condensed by the lens array 42 can be irradiated to the same irradiation area on the substrate 1 by the condenser lens.
[0109]
Further, in the laser annealing apparatus 40 according to the third embodiment, by providing the light splitting section 41, the number of split laser beams is increased as compared with the laser annealing apparatus 10 according to the first embodiment. , More uniform irradiation can be performed.
[0110]
In the laser annealing apparatus 40 according to the third embodiment, the laser annealing apparatus 10 according to the first embodiment irradiates four laser beams in a line, whereas eight laser beams are emitted. Irradiate in a line. Therefore, when the irradiation is performed by the laser annealing apparatus 10 according to the first embodiment, the irradiation area U1 becomes as shown in FIG. 13A. However, when the irradiation is performed by the laser annealing apparatus 40 according to the third embodiment, FIG. As shown in FIG. 13B, the length of the irradiation area U3 is approximately doubled, and the irradiation area can be expanded.
[0111]
In the third embodiment, the number of laser beams split by the light splitting unit 41 is eight. However, in the present invention, the laser beams are arranged in parallel based on the following equations (4) to (7). By increasing the number of beam splitters, the number of divisions of the laser beam can be further increased.
[0112]
First, the number of laser beams split by the light splitting unit is j, the number of beam splitters provided in the light splitting unit is k, and the m-th beam arranged from the collimator 13 side (mirror side in the light splitting unit). BS splitter _m And Here, m is a natural number, and its maximum value is j.
[0113]
First, the relationship between j and k is as shown in the following equation (4).
j = 2 ^k ... (4)
[0114]
If the transmittance T and the reflectance R of each beam splitter are all 50%, the light amount P of one laser beam after splitting is obtained. ₂ Is the light amount of the laser beam before the division ₁ Then, the following equation (5) is obtained.
P ₂ = P ₁ /J...(5)
[0115]
Further, in order to make the j laser beams output from the polarization unit into incoherent light which does not interfere with each other, it is necessary to arrange the beam splitters and the reflecting mirrors as follows. Note that the incident angle of the laser light incident on each beam splitter is θ, and the coherence length of the laser light is L.
[0116]
1st beam splitter BS ₁ The distance t0 between the mirror and the reflecting mirror is set as shown in the following equation (6).
t0 ≧ {L / (2 cos θ)} / 2 (6)
[0117]
Also, the m-th beam splitter BS _m And the (m + 1) th beam splitter BS _{(M + 1)} Distance t between _m Is set as shown in the following equation (7).
t _m ≧ ｛(2 ^(M-1) × L) / (2cosθ)｝ / 2 (7)
[0118]
By arranging the beam splitters in this way, j parallel laser beams that are mutually incoherent and have the same intensity can be emitted from the polarization unit.
[0119]
(4) Fourth embodiment
A fourth embodiment of the present invention will be described. As in the first embodiment, the laser annealing apparatus according to the fourth embodiment of the present invention irradiates a laser beam to a TFT substrate after an amorphous silicon film is formed, for example. Is a device that converts an amorphous silicon film to a polysilicon film by heat-treating the amorphous silicon film.
[0120]
The laser annealing apparatus according to the fourth embodiment uses two laser light sources, divides the laser light emitted from these two laser light sources, respectively, and places each of the divided laser lights in the same region on the substrate. Irradiation.
[0121]
In describing the laser annealing apparatus according to the fourth embodiment, the same components as those of the laser annealing apparatus 10 according to the above-described first embodiment are denoted by the same reference numerals, and detailed description thereof will be given. Omitted. The X, Y, and Z directions used in the description of the fourth embodiment are also the same as those in the first embodiment.
[0122]
FIG. 14 shows a configuration of a laser annealing apparatus 50 according to the fourth embodiment.
[0123]
As shown in FIG. 14, a laser annealing apparatus 50 according to the fourth embodiment has a stage 11 on which a substrate 1 to be annealed is mounted, a laser light source 12 that emits laser light, and a laser light source 12 that emits laser light. A collimator 13 provided on the optical path of the laser light, a light dividing unit 14 for dividing one laser light emitted from the collimator 13 into four laser lights, and a lens array including four convex lenses 15, a condenser lens 16 for guiding four laser beams emitted from the lens array 15 to a predetermined area of the substrate 1, a control unit 17 for controlling the position of the stage 11 and the like, and a polarizing unit 18. .
[0124]
The configuration and positional relationship of the stage 11, the first laser light source 12, the first collimator 13, the first light splitting unit 14, the lens array 15, the condenser lens 16, and the polarizing unit 18 are the same as those in the first embodiment. This is the same as the embodiment. Hereinafter, in the description of the fourth embodiment, the laser light source 12 will be referred to as the first laser light source 12, the collimator 13 will be referred to as the first collimator 13, and the light splitting unit 14 will be referred to as the first laser light source. It is referred to as the light splitting unit 14. The laser light emitted from the first collimator 13 to the first light splitting unit 14 is hereinafter referred to as a first laser light L1.
[0125]
Further, the laser annealing apparatus 50 according to the fourth embodiment includes a second laser light source 51 for emitting laser light, and a second laser light source 51 provided on an optical path of the laser light emitted from the second laser light source 51. A collimator 52, a light guide mirror 53 that reflects the laser light emitted from the second collimator 52, and a second light that divides one laser light reflected from the light guide mirror 53 into two laser lights. A splitting section 54 and an emission control section 55 for controlling the emission of laser light from the first and second laser light sources 12 and 51 are provided.
[0126]
The second laser light source 51 is a device having the same function as the laser light source 12 used in the laser annealing device 10 of the first embodiment. The laser light emitted from the second laser light source 51 enters the second collimator 52.
[0127]
The second collimator 52 converts the laser light incident from the second laser light source 51 into a parallel light beam having a predetermined beam diameter. The laser light emitted from the second collimator 52 is reflected by the light guide mirror 53 and then enters the second light splitting section 54. Note that the laser light emitted from the second collimator 52 to the second light splitting unit 54 is hereinafter referred to as a second laser light L2.
[0128]
The second light splitting unit splits the second laser light L2 and emits two laser lights arranged in parallel at equal intervals. The specific configuration of the second light splitting unit 54 will be described later in detail.
[0129]
The two laser beams emitted from the second light splitting unit 54 enter the first light splitting unit 14.
[0130]
Here, the first light splitting section 14 receives two laser lights from the second light splitting section 54, and splits the two laser lights into four laser lights and emits them. That is, the first light splitting unit 14 splits the first laser light L1 into four and emits four laser lights, and splits the second laser light L2 into four and emits four laser lights. are doing. Then, the first light splitting unit 14 coaxially combines the four laser lights obtained by dividing the first laser light L1 and the four laser lights obtained by dividing the second laser light L2. Out.
[0131]
Details of the laser light emitted from the first light splitting section 14 will be described later.
[0132]
The emission control unit 55 controls the emission timing of the pulse light emitted from the first and second laser light sources 12 and 51. The control example of the emission control unit 55 will be described later in detail.
[0133]
In the laser annealing apparatus 50 having the above-described configuration, the substrate 1 is placed on the stage 11, and thereafter, a laser annealing process is started. When the laser annealing process is started, the laser annealing device 50 emits a pulse laser from the first and second laser light sources 12 and 51.
[0134]
The laser beams emitted from the first laser light source 12 and the second laser light source 51 pass through the first light splitting unit 14 and the polarizing unit 18 so that adjacent beams have the same interference and no coherence. Four parallel light beams of high intensity are obtained.
[0135]
The four laser beams are converted into four secondary light sources by the lens array 15. The four laser beams emitted from the secondary light source are combined via the condenser lens 16 and irradiated to a predetermined area on the substrate 1.
[0136]
Then, in the laser annealing apparatus 50, the stage 11 is moved in parallel to move the flat substrate 1 in a direction parallel to the main surface (the XY direction in FIG. 14). An annealing process is performed by irradiating a laser beam.
[0137]
Next, the first light splitting unit 14 and the second light splitting unit 54 will be described in more detail. FIG. 15 shows a configuration of the first light splitting unit 14 and the second light splitting unit 54.
[0138]
As shown in FIG. 15, the second light splitting section 54 includes a BS 57 in which planar light splitting surfaces are arranged in the Z direction. The BS 57 is an element that transmits and reflects the laser light incident on the light separating surface and separates the laser light into two laser lights. The separation ratio between transmission and reflection is 1: 1 in design.
[0139]
The second light splitting unit 54 includes a mirror 58 having a light splitting surface of the BS 57 and a light reflecting surface parallel to each other, and being arranged alongside the BS 57 in the Z direction. The mirror 58 is an element that reflects the laser light incident on the planar light reflecting surface. The mirror 58 is disposed closer to the laser beam L2 incidence side than the BS 57.
[0140]
The light separating surface of the BS 57 and the light reflecting surface of the mirror 58 are arranged perpendicular to a plane formed by the XZ axis, and have a predetermined angle (90 °) with respect to the incident direction of the laser beam L2. −θ ″) (0 ° <θ ″ <90 °). That is, the laser light L2 is incident on the light separation surface of the BS 57 at an incident angle θ ″.
[0141]
The BS 57 is arranged on the optical axis of the laser light L2. Further, the BS 57 is arranged and sized so that only the laser beam L2 is incident and no other light is incident. The mirror 58 is arranged and sized so that one reflected beam of the BS 57 is incident thereon and does not block the laser beam L2.
[0142]
Next, the generation path of the laser light incident on the first light splitting unit 14 and the laser light emitted from the first light splitting unit 14 will be described.
[0143]
Note that the light that passes through the first BS 21 of the first light splitting unit 14 and enters the second BS 22 is defined as a first intermediate light a1, and is reflected by the first BS 21 of the first light splitting unit 14. The light that subsequently enters the second BS 22 via the mirror 23 is referred to as second intermediate light a2. Further, two laser beams are emitted from the second light splitting unit 54, and the two laser beams are incident on the second BS 22 of the first light splitting unit 14. The light that has passed through the first beam BS57 of the second light splitting unit 54 and is emitted therefrom is used as the third intermediate light a3, and after reflecting the first beam BS57 of the second light splitting unit 54, the mirror 23 is moved. The light reflected and emitted is referred to as a fourth intermediate light a4.
[0144]
First, the first intermediate light a1 and the second intermediate light a2 are incident from one surface (hereinafter, referred to as a surface) of the second BS 22. The first intermediate light a1 is split into two laser lights by the second BS 22, the transmitted light is emitted to the outside as laser light L1-1, and the reflected light is reflected by the mirror 23, and then as laser light L1_3. It is emitted outside. The second intermediate light a2 is split into two laser lights by the second BS 22, the transmitted light is emitted to the outside as laser light L1_2, and the reflected light is reflected by the mirror 23 and then becomes the laser light L1_4. It is emitted outside.
[0145]
On the other hand, the third intermediate light a3 and the fourth intermediate light a4 are the second from the surface opposite to the surface on which the first intermediate light a1 and the second intermediate light a2 are incident (hereinafter, referred to as the back surface). To the BS22. The third intermediate light a3 is split into two laser lights by the second BS 22, the reflected light is emitted to the outside as laser light L2_1, and the transmitted light is reflected by the mirror 23 and then becomes the laser light L2_3. It is emitted outside. The fourth intermediate light a4 is split into two laser lights by the second BS 22, the reflected light is emitted to the outside as laser light L2_2, and the transmitted light is reflected by the mirror 23 and then becomes the laser light L2_4. It is emitted outside.
[0146]
Further, the first to fourth intermediate lights a1 to a4 are all incident on the second BS 22 along a plane (that is, an XZ plane) orthogonal to the light dividing plane of the second BS 22. The first to fourth intermediate lights a1 to a4 are incident on the light separation surface of the second BS 22 at a predetermined angle θ (0 ° <θ <90 °).
[0147]
Furthermore, the first intermediate light a1 and the third intermediate light a3 are incident on the same position on the light separation surface of the second BS 22 (although there is a difference between the front surface and the back surface), and Light is incident so that the optical axes do not coincide. Further, the second intermediate light a2 and the fourth intermediate light a4 are incident on the same position (although there is a difference between the front surface and the back surface) on the light separation surface of the second BS 22, and Light is incident so that the optical axes do not coincide.
[0148]
Therefore, the laser light L1_1 that is the transmitted light of the first intermediate light a1 and the laser light L2_1 that is the reflected light of the third intermediate light a3 are coaxially combined and emitted. The laser light L1_3, which is the reflected light of the first intermediate light a1, and the laser light L2_3, which is the transmitted light of the third intermediate light a3, are coaxially combined and emitted. The laser light L1_2, which is the transmitted light of the second intermediate light a2, and the laser light L2_2, which is the reflected light of the fourth intermediate light a4, are coaxially combined and emitted. The laser light L1_4, which is the reflected light of the second intermediate light a2, and the laser light L2_4, which is the transmitted light of the fourth intermediate light a4, are coaxially combined and emitted.
[0149]
Therefore, the first light splitting unit 14 and the second light splitting unit 54 split the laser light emitted from the two laser light sources into four laser lights, respectively, and coaxially separate the four laser lights one by one. The light can be combined and emitted.
[0150]
Further, the first light splitting unit 14 and the second light splitting unit 54 are configured so that all of the four laser lights emitted from the polarizing unit 18 are incoherent light having no interference with each other. You may.
[0151]
In this case, when the longer one of the coherence distance set by the laser light source 12 and the coherence distance set by the second laser light source 51 is L, the first light The distance t0 between the first BS 21 and the mirror 23 of the splitting unit 14 is set to {L / (2 cos θ)} / 2 or more, and the distance t1 between the first BS 21 and the second BS 22 is also L / (2 cos θ) or more.
[0152]
Further, assuming that the coherence distance set by the second laser light source 51 is L ″, the distance t ″ 0 between the BS 57 of the second light splitting unit 54 and the mirror 58 is L ″ / (2 cos θ). ″) Or more.
[0153]
Next, the emission timing of the pulse light from the first laser light source 12 and the second laser light source 51 will be described.
[0154]
The emission control unit 55 controls the timing at which the first laser light source 12 emits pulsed light and the timing at which the second laser light source 51 emits pulsed light. The emission control unit 55 shifts the light emission timing of the pulse light emitted from the first laser light source 12 and the light emission timing of the pulse light emitted from the second laser light source 51 by a predetermined time (Δt), and adjusts the light emission period of the pulse light. Are partially overlapped.
[0155]
Specifically, as shown in FIG. 16, for example, as shown in FIG. 16, immediately after the intensity of the laser light L1 emitted from the first laser light source 12 on the substrate 1 reaches a peak, The timing at which the first laser light source 12 emits the laser light L1 and the timing at which the second laser light source 51 emits the laser light L2 so that the intensity of the laser light L2 emitted from the laser light source 51 increase. Control. In FIG. 16, Δt indicates a time lag between the time when the first laser light source 12 emits the laser light L1 and the time when the second laser light source 51 emits the laser light L2. As described above, the time when the laser light emitted from the first laser light source 12 irradiates the substrate 1 and the time when the laser light emitted from the second laser light source 51 irradiates the substrate 1 are partly set. By overlapping, the effective pulse width of the laser light irradiated onto the substrate 1 can be increased. That is, it is possible to lengthen the time for irradiating the substrate 1 with the laser light. In addition, as shown in FIG. 16, the cooling rate of the substrate 1 can be reduced by making the peak intensity of the subsequent pulse light weaker than the peak intensity of the preceding pulse light. When the cooling rate of the substrate 1 is reduced, it is possible to increase the size of the crystal grain size of the generated polysilicon.
[0156]
The laser annealing apparatus 50 according to the fourth embodiment has a first light splitting device that splits two laser lights emitted from two laser light sources into four laser lights, respectively, with the simple configuration as described above. And a second light splitting unit 54. Furthermore, the laser annealing apparatus 50 of the fourth embodiment converts the laser beams emitted from the first light splitting section 41 and the second light splitting section 54 such that the polarization directions of the adjacent beams are orthogonal to each other. And a polarizing section 18 that is polarized in the direction shown in FIG.
[0157]
Therefore, in the laser annealing apparatus 50 according to the fourth embodiment, since adjacent laser beams are polarized perpendicular to each other, when forming one irradiation region with a plurality of laser beams, adjacent laser beams Can be irradiated while overlapping. Therefore, a large irradiation area without unevenness in intensity can be formed, and the substrate 1 can be irradiated with uniform energy.
[0158]
Further, in the laser annealing apparatus 50 of the fourth embodiment, since the laser beams emitted from the two laser light sources are combined, the intensity of the laser beam to be irradiated can be increased, or the pulse width of the pulse light can be increased. Can be lengthened.
[0159]
Further, in the laser annealing apparatus 50 of the fourth embodiment, the longer one of the coherent distance set by the laser light source 12 and the coherent distance set by the second laser light source 51 is used. When the interference distance is L, the distance t0 between the first BS 21 and the mirror 23 of the first light splitting unit 14 is set to {L / (2 cos θ)} / 2 or more, and the first BS 21 and the second BS 21 Is set to L / (2 cos θ) or more, and if the coherence distance set by the second laser light source 51 is L ″, the second light splitting unit 54 By setting the distance t ″ 0 between the BS 57 and the mirror 58 to be L ″ / (2 cos θ ″) or more, all four laser beams that have passed through the polarization unit 18 do not interfere with each other. Laser light can be used. With this setting, it becomes possible to irradiate the same irradiation area on the substrate 1 with each condenser light condensed by the lens array 15 by the condenser lens.
[0160]
【The invention's effect】
In the light irradiation device according to the present invention, the plurality of split laser beams are polarized so that the polarization directions of the adjacent beams are orthogonal to each other, so that the irradiation target can be irradiated with uniform intensity.
In the laser annealing apparatus according to the present invention, the object to be annealed can be annealed with uniform energy.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a laser annealing apparatus according to a first embodiment.
FIG. 2 is a diagram illustrating a configuration of a light splitting unit of the laser annealing apparatus according to the first embodiment.
FIG. 3 is a diagram showing an intensity distribution of laser light emitted from the first laser annealing apparatus.
FIG. 4 is a diagram showing a modification of the first embodiment.
FIG. 5 is a view showing a modification of the light splitting unit of the laser annealing apparatus according to the first embodiment.
FIG. 6 is a diagram illustrating a configuration of a laser annealing apparatus according to a second embodiment.
FIG. 7 is a diagram illustrating a polarizing unit and a lens array of the laser annealing apparatus according to the second embodiment.
FIG. 8 is a diagram illustrating a configuration of a first light splitting unit and a second light splitting unit of the laser annealing apparatus according to the second embodiment.
FIG. 9 is a diagram showing an irradiation area by the laser annealing apparatus according to the first embodiment, and a view showing an irradiation area by the laser annealing apparatus according to the second embodiment.
FIG. 10 is a diagram illustrating a configuration of a laser annealing apparatus according to a third embodiment.
FIG. 11 is a diagram illustrating a polarizing unit and a lens array of the laser annealing apparatus according to the third embodiment.
FIG. 12 is a diagram illustrating a configuration of a light splitting unit of the laser annealing apparatus according to the third embodiment.
FIG. 13 is a diagram illustrating an irradiation region by the laser annealing apparatus according to the first embodiment, and FIG. 14B is a diagram illustrating an irradiation region by the laser annealing device according to the third embodiment.
FIG. 14 is a diagram illustrating a configuration of a laser annealing apparatus according to a fourth embodiment.
FIG. 15 is a diagram showing a configuration of a first light splitting unit and a second light splitting unit of the laser annealing apparatus according to the fourth embodiment.
FIG. 16 is a diagram showing emission timing of laser light emitted from the laser annealing apparatus according to the fourth embodiment.
FIG. 17 is a diagram showing a configuration of a conventional laser annealing apparatus.
FIG. 18 is a diagram showing interference fringes generated when a solid-state laser is applied to a light source of a conventional laser annealing apparatus.
[Explanation of symbols]
1 substrate, 10, 30, 40, 50 laser annealing apparatus, 11 stage, 12, 51 laser light source, 13, 52 collimator, 14, 31, 41, 54 light splitting section, 18, 37, 48 polarizing section, 15, 32 , 42 Lens array, 16, 19, 43 Condenser lens, 17 Control unit

Claims (26)

A laser light source for emitting a laser beam,
Light splitting means for splitting a laser beam emitted from the laser light source into a plurality of laser beams,
Polarizing means for controlling the polarization direction of the laser beam split by the light splitting means,
Irradiating means for irradiating the irradiation object with the plurality of laser beams,
The light splitting means,
A light separating surface for reflecting and transmitting an incident laser beam and separating the laser beam into two laser beams of reflected light and transmitted light; and k arranged such that the light separating surfaces are parallel to each other (where k is one or more). A natural number.) Beam splitters,
A light reflecting surface is parallel to the light separating surface of the beam splitter, and includes a reflecting mirror on which reflected light from all the beam splitters is incident.
A laser beam emitted from the laser light source is incident on a first beam splitter from the laser light source side,
The transmitted light from the m-th beam splitter and the laser beam reflected by the reflecting mirror after being reflected by the m-th beam splitter are transmitted to the (m + 1) th (where m is a natural number) beam splitter. Incident
The k-th beam splitter outputs 2 ^(k-1) transmitted lights to the outside,
The reflecting mirror reflects 2 ^(k-1) reflected lights incident from the ^k-th beam splitter and outputs the reflected light to the outside,
The light irradiating apparatus, wherein the polarizing means polarizes the plurality of laser beams split by the light splitting means so that adjacent polarizing beams have orthogonal polarization directions. The light splitting means,
The distance between the light separation surface of the m-th beam splitter and the light separation surface of the (m + 1) -th beam splitter is as follows: θ is the incident angle of the laser beam incident on each beam splitter, and the laser beam is emitted from the laser light source. When the coherence length of the laser beam to be performed is L, it is set to {(2 ^(m-1) × L) / (2 cos θ)} / 2 or more,
The distance between the light splitting surface of the first beam splitter and the light reflecting surface of the reflecting mirror is set such that the incident angle of the laser beam incident on each beam splitter is θ, and the distance of the laser beam emitted from the laser light source is 2. The light irradiation apparatus according to claim 1, wherein when the interference distance is L, the distance is {L / (2 cos θ)} / 2} / 2 or more. 3. The light irradiation device according to claim 2, wherein the irradiation unit irradiates the irradiation target with a plurality of laser beams polarized by the polarization unit, overlapping the same irradiation position. 4. The light irradiation apparatus according to claim 3, wherein the reflected light and the transmitted light separated by the light separating surface of the beam splitter have a light intensity ratio of 1: 1. The light irradiation device according to claim 3, wherein a plurality of beam splitters are integrated by arranging a light transmitting member between the beam splitters. The light irradiation device according to claim 3, wherein a plurality of beam splitters are integrated by disposing a light transmitting member between the beam splitter and the reflecting mirror. The light irradiation device according to claim 1, wherein the laser light source is a solid-state laser. The light irradiation device according to claim 1, wherein the laser light source is a semiconductor laser. The light irradiation device according to claim 1, wherein the laser light source performs pulse oscillation. A laser beam emitted from the laser light source is provided with a parallelizing unit that converts the laser beam into a parallel light beam,
2. The light irradiation apparatus according to claim 1, wherein the irradiation means includes one or more lenses on which a plurality of laser beams output from the light splitting means are incident. A plurality of condenser lenses for condensing each laser beam output from the light splitting means,
The light irradiation apparatus according to claim 1, wherein each laser beam is incident on the irradiation means via the plurality of condenser lenses. The light irradiation device according to claim 1, wherein the laser light source emits a laser beam having a predetermined polarization. The light splitting unit splits a laser beam emitted from the laser light source into a plurality of laser beams arranged in a line or in a matrix,
The irradiating means has a plurality of condensing lenses arranged in a row or in a matrix corresponding to a plurality of laser beams emitted from the light dividing means,
The polarizing means is disposed before or after the plurality of condenser lenses in the emission direction of the laser beam, and is disposed every other one of the plurality of condenser lenses arranged in a line or in a matrix. The light irradiation device according to claim 1, further comprising a plurality of polarization 90-degree rotation elements formed. A stage for placing an object to be annealed,
A laser light source for emitting a laser beam,
Light splitting means for splitting a laser beam emitted from the laser light source into a plurality of laser beams,
Polarizing means for controlling the polarization direction of the laser beam split by the light splitting means,
Irradiating means for irradiating the irradiation object with the plurality of laser beams,
The light splitting means,
A light separating surface for reflecting and transmitting an incident laser beam and separating the laser beam into two laser beams of reflected light and transmitted light; and k arranged such that the light separating surfaces are parallel to each other (where k is one or more). A natural number.) Beam splitters,
A light reflecting surface is parallel to the light separating surface of the beam splitter, and includes a reflecting mirror on which reflected light from all the beam splitters is incident.
A laser beam emitted from the laser light source is incident on a first beam splitter from the laser light source side,
The transmitted light from the m-th beam splitter and the laser beam reflected by the reflecting mirror after being reflected by the m-th beam splitter are transmitted to the (m + 1) th (where m is a natural number) beam splitter. Incident
The k-th beam splitter outputs 2 ^(k-1) transmitted lights to the outside,
The reflecting mirror reflects 2 ^(k-1) reflected lights incident from the ^k-th beam splitter and outputs the reflected light to the outside,
A laser annealing apparatus, wherein the polarizing means polarizes the plurality of laser beams split by the light splitting means so that adjacent beams have polarization directions orthogonal to each other. The light splitting means,
The distance between the light separation surface of the m-th beam splitter and the light separation surface of the (m + 1) -th beam splitter is as follows: θ is the incident angle of the laser beam incident on each beam splitter, and the laser beam is emitted from the laser light source. When the coherence length of the laser beam to be performed is L, it is set to {(2 ^(m-1) × L) / (2 cos θ)} / 2 or more,
The distance between the light splitting surface of the first beam splitter and the light reflecting surface of the reflecting mirror is set such that the incident angle of the laser beam incident on each beam splitter is θ, and the distance of the laser beam emitted from the laser light source is 14. The laser annealing apparatus according to claim 13, wherein when the interference distance is L, the distance is {L / (2 cos θ)} / 2} / 2 or more. 16. The laser annealing apparatus according to claim 15, wherein the irradiating unit irradiates the object to be irradiated with a plurality of laser beams polarized by the polarizing unit so as to overlap the same irradiation position. 17. The laser annealing apparatus according to claim 16, wherein the reflected light and the transmitted light separated by the light separating surface of the beam splitter have a light intensity ratio of 1: 1. 17. The laser annealing apparatus according to claim 16, wherein a plurality of beam splitters are integrated by disposing a light transmitting member between the respective beam splitters. 17. The laser annealing apparatus according to claim 16, wherein a plurality of beam splitters are integrated by disposing a light transmitting member between the beam splitter and the reflecting mirror. The laser annealing apparatus according to claim 14, wherein the laser light source is a solid-state laser. The laser annealing apparatus according to claim 14, wherein the laser light source is a semiconductor laser. 15. The laser annealing apparatus according to claim 14, wherein the laser light source performs pulse oscillation. A laser beam emitted from the laser light source is provided with a parallelizing unit that converts the laser beam into a parallel light beam,
15. The laser annealing apparatus according to claim 14, wherein said irradiating means comprises one or more lenses on which a plurality of laser beams output from said light splitting means are incident. A plurality of condenser lenses for condensing each laser beam output from the light splitting means,
15. The laser annealing apparatus according to claim 14, wherein each of the laser beams is incident on the irradiation unit through the plurality of condenser lenses. The laser annealing apparatus according to claim 14, wherein the laser light source emits a laser beam having a predetermined polarization. The light splitting unit splits a laser beam emitted from the laser light source into a plurality of laser beams arranged in a line or in a matrix,
The irradiating means has a plurality of condensing lenses arranged in a row or in a matrix corresponding to a plurality of laser beams emitted from the light dividing means,
The polarizing means is disposed before or after the plurality of condenser lenses in the emission direction of the laser beam, and is disposed every other one of the plurality of condenser lenses arranged in a line or in a matrix. 15. The laser annealing apparatus according to claim 14, comprising a plurality of 90-degree polarization rotating elements.

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