JP2006253571A - Laser emission apparatus and method therefor, and laser anneal apparatus and method therefor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser emission apparatus and method that can emit a laser beam with arranged polarization directions even when laser beams emitted from a plurality of laser oscillators are composed so as to thereby obtain isotropic crystal grains, in the case of applying this method to laser anneal of an amorphous semiconductor, and can enhance the processing efficiency and improve the productivity; and to provide a laser anneal apparatus and method. <P>SOLUTION: The laser emission apparatus disclosed herein includes a plurality of the laser oscillators 2A, 2B for emitting pulse laser beams; a pulse control unit 4 for outputting a control signal to the laser oscillators 2A, 2B to deviate pulse timings of a plurality of the laser oscillators 2A, 2B; a polarization beam splitter 6 for composing a plurality of the laser beams onto a coaxial optical path; and a polarization adjustment means 12 arranged on the optical path for the composed laser beam, selectively rotating the polarization direction different from that to be arranged in polarization components orthogonal to each other in incident laser beams, so as to arrange the polarization directions of the laser beams emitted to an object 1 to be emitted. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a laser irradiation apparatus and method suitable for crystallizing an amorphous semiconductor using pulsed laser light, and a laser annealing apparatus and method.

In the manufacturing process of a liquid crystal display, laser annealing is performed in which an amorphous silicon film formed on a glass substrate is irradiated with pulsed laser light to be modified into polycrystalline silicon, and a laser annealing apparatus is used as this means. According to such laser annealing, a high-performance, high-quality polysilicon TFT liquid crystal panel can be manufactured, and the market is expanding to monitors for digital cameras, mobile phones, PDAs (personal digital assistants), notebook computers, and the like. . Conventionally, an excimer laser is mainly used as a laser oscillator of a laser annealing apparatus, but in recent years, solid-state lasers such as YAG, YLF, and YVO ₄ have been attracting attention.

  Here, FIG. 6 is a diagram showing a configuration of a “laser processing apparatus” disclosed in Patent Document 1 below. As shown in the figure, the apparatus of Patent Document 1 includes two laser oscillators 51A and 51B, control means 52 for controlling the emission timing of laser light from each of the two laser oscillators, and two lasers. And a polarization beam splitter 53 for synthesizing laser beams from the respective oscillators on a coaxial optical path. Reference numeral 55 denotes a reflecting mirror, and reference numeral 56 denotes a condenser lens. In this apparatus, the processing speed is doubled compared to the case of one laser oscillator by combining two laser beams irradiated at different emission timings and irradiating the workpiece 54 with the combined laser beams.

JP-A-4-135083 (FIG. 1)

  In order to improve the throughput of the laser annealing apparatus, it is conceivable to apply the technique of Patent Document 1 as described above to configure the laser irradiation apparatus shown in FIG. In this laser irradiation apparatus, the pulse laser beam L1 irradiated from the laser oscillator 2A is rotated by 90 ° in the polarization direction by the half-wave plate 32, reflected by the reflection mirror 34, and reflected from the laser beam L1 and the laser oscillator 2B. The laser beam L2 is synthesized on the coaxial optical path by the polarization beam splitter 6, condensed by the condenser lens 36, and irradiated to the irradiation object 1 (for example, an amorphous silicon substrate). When two laser beams are combined by the polarization beam splitter 6, as shown in this figure, it is necessary to make the laser beams whose polarization directions are orthogonal to each other, so that the combined laser beams Lc are components whose polarization directions are orthogonal to each other. (P-polarized light and S-polarized light) are mixed. For this reason, the irradiated object 1 is irradiated with laser beams whose polarization directions are alternately orthogonal. However, this causes a problem that the energy distribution produced by linearly polarized light changes every shot (one pulse), and isotropic crystal grains cannot be obtained, resulting in non-uniform transistor characteristics.

  Therefore, in order to solve such a problem of the prior art, the present invention can irradiate laser beams having the same polarization direction even if the laser beams emitted from a plurality of laser oscillators are combined. Laser irradiation apparatus and method, laser annealing apparatus and method capable of obtaining isotropic crystal grains and improving processing efficiency and productivity when applied to laser annealing of crystalline semiconductors The purpose is to provide.

  In order to solve the above-described problems, the present invention is a laser irradiation apparatus that irradiates an object to be irradiated with pulsed laser light, and a plurality of laser oscillators that emit pulsed laser light and pulse timings of the plurality of laser oscillators are shifted. A pulse control unit for outputting a control signal to each of them, a polarization beam splitter for synthesizing a plurality of laser beams on a coaxial optical path, and polarization components orthogonal to each other in the incident laser beam arranged on the optical path of the synthesized laser beam Polarization adjusting means for selectively rotating the polarization direction that is different from the polarization direction to be aligned, and aligning the polarization direction of the laser light irradiated to the irradiation object (Claim 1). .

  In the laser irradiation apparatus of the present invention, preferably, the polarization adjusting unit includes a half-wave plate disposed on the optical path of the synthesized laser beam, and the half-wave plate is combined with the light of the synthesized laser beam. A drive unit that rotates about an axis, and the drive unit is a half-wave plate so that the polarization directions of the laser beams that have passed through the half-wave plate are aligned based on the pulse timing of the plurality of laser oscillators Is rotated (claim 2).

  In the laser irradiation apparatus of the present invention, preferably, the drive unit is configured such that when the polarization direction of the laser light incident on the half-wave plate coincides with the polarization direction to be aligned, the polarization direction of the laser light. And the optical axis of the half-wave plate is 0 ° or 90 °, and when the polarization direction of the laser light incident on the half-wave plate is orthogonal to the polarization direction to be aligned, The half-wave plate is rotated so that the angle formed by the polarization direction and the optical axis of the half-wave plate is 45 °.

  In the laser irradiation apparatus of the present invention, preferably, the polarization adjusting unit is arranged on an optical path of the synthesized laser beam and rotates the polarization direction of the laser beam at a right angle when a predetermined operating condition is satisfied. And an optical element actuating means for actuating the optical element, and the optical element actuating means is a polarized light whose polarization direction of laser light incident on the optical element is to be aligned based on the pulse timing of the plurality of laser oscillators. The optical element is operated so as to rotate the polarization direction at a right angle only when orthogonal to the direction.

  In the laser irradiation apparatus of the present invention, preferably, the optical element is an electro-optical element, and the optical element operating means is a power source for applying a voltage to the electro-optical element.

  In the laser irradiation apparatus of the present invention, preferably, the optical element is a magneto-optical element, and the optical element actuating means is a magnetic field generator that applies a magnetic field to the magneto-optical element.

  Further, the laser irradiation method of the present invention emits a pulse laser beam from a plurality of laser oscillators so that each pulse timing is shifted, and combines the plurality of laser beams by a polarization beam splitter that synthesizes them on a coaxial optical path. Rotate the polarization direction of the laser beam that is different from the polarization direction to be aligned among the polarized components orthogonal to each other in the laser beam to align the polarization direction of the laser beam that irradiates the irradiation object, and irradiate the irradiation object with this. (Claim 7).

  In the laser irradiation method of the present invention, preferably, a half-wave plate is disposed on the optical path of the synthesized laser beam, and passes through the half-wave plate based on the pulse timing of the plurality of laser oscillators. The half-wave plate is rotationally driven around the optical axis of the synthesized laser light so that the polarization directions of the laser light are aligned.

  In the laser irradiation method of the present invention, preferably, when the polarization direction of the laser light incident on the half-wave plate coincides with the polarization direction to be aligned, the polarization direction of the laser light and the half wavelength. When the angle between the optical axis of the plate is 0 ° or 90 ° and the polarization direction of the laser light incident on the half-wave plate is orthogonal to the polarization direction to be aligned, the polarization direction of the laser light is 1 / The half-wave plate is rotated so that the angle formed by the optical axis of the two-wave plate is 45 ° (claim 9).

  In the laser irradiation method of the present invention, preferably, an optical element that rotates the polarization direction of the combined laser beam at a right angle when a predetermined operating condition is satisfied is disposed on the optical path of the combined laser beam, Based on the pulse timing of the laser oscillator, the optical element is operated so as to rotate the polarization direction at a right angle only when the polarization direction of the laser light incident on the optical element is orthogonal to the polarization direction to be aligned (claim 10). .

  In the laser irradiation method of the present invention, preferably, an electro-optical element or a magneto-optical element is used as the optical element.

  A laser annealing apparatus of the present invention includes the laser irradiation apparatus according to any one of claims 1 to 6, and applies laser light to an irradiation object having an amorphous semiconductor film formed on a substrate by the laser irradiation apparatus. Irradiation (claim 12).

  In addition, the laser annealing method of the present invention is characterized by irradiating an irradiated object having an amorphous semiconductor film formed on a substrate with a laser beam by the laser irradiation method according to any one of claims 7 to 11. (Claim 13).

  According to the apparatus and method of the present invention, a laser beam emitted from a plurality of laser oscillators is synthesized by a polarization beam splitter that synthesizes the light beams on a coaxial optical path and irradiates the irradiated object. The pulse frequency of light can be set to a frequency obtained by adding the pulse frequencies emitted from the laser oscillators. Therefore, the processing speed for the irradiated object can be increased.

  Further, according to the present invention, a pulse laser beam is emitted from a plurality of laser oscillators so that each pulse timing is shifted, and a polarization direction different from the polarization direction to be aligned among the mutually orthogonal polarization components in the synthesized laser beam. Is selectively rotated to align the polarization direction of the laser beam irradiated to the irradiated object and to irradiate the irradiated object, so that the energy distribution of the laser beam irradiated to the irradiated object is shot ( It does not change every 1 pulse). Therefore, isotropic crystal grains can be obtained when applied to laser annealing of an amorphous semiconductor.

  In other words, according to the present invention, it is possible to irradiate laser beams having the same polarization direction even if laser beams emitted from a plurality of laser oscillators are combined, and this is applied to laser annealing of amorphous semiconductors. In this case, an isotropic crystal grain can be obtained, and an excellent effect can be obtained that the processing efficiency can be increased and the productivity can be improved.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings. In each figure, the same portions are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a diagram showing a configuration of a laser irradiation apparatus according to the first embodiment of the present invention. This laser irradiation apparatus is an apparatus that irradiates an object to be irradiated with pulsed laser light. In this embodiment, the object to be irradiated on which an amorphous semiconductor film is formed on a substrate is irradiated with laser light to be polycrystallized. It is applied to the laser annealing equipment. As shown in this figure, the laser irradiation apparatus includes a plurality of laser oscillators 2A and 2B, a pulse control unit 4, a polarization beam splitter 6, and a polarization adjustment unit 12. Hereinafter, each component will be described.

In this example, the laser oscillators 2A and 2B use a YAG laser and emit a pulse laser having a pulse frequency of 1 kHz. In the laser irradiation apparatus according to the present embodiment, there are two laser oscillators, and the pulse laser beams L1 and L2 having the same pulse period and the same pulse time width are oscillated. The laser oscillator of the present invention is not limited to a YAG laser, and may be another solid-state laser (YLF, YVO ₄ or the like) or an excimer laser.

  Further, in this figure, a bidirectional arrow and a double circle (a figure in which a black circle is arranged in a white circle) shown on the optical path of each laser beam are a single laser pulse emitted from each laser oscillator 2A, 2B. (That is, a single shot), the double-headed arrow indicates a pulse (shot) having a polarization component (P-polarized light) whose polarization plane is parallel to the paper surface, and a double circle indicates a polarization whose polarization surface is perpendicular to the paper surface A pulse (shot) having a component (S-polarized light) is shown.

  A half-wave plate 32 and a reflection mirror 34 are disposed on the optical path of the laser light L1 emitted from the laser oscillator 2A. The half-wave plate 32 has a function of rotating the polarization plane of linearly polarized light, and the linearly polarized light enters the half-wave plate 32, and the incident polarization plane and the optical axis of the half-wave plate are When the angle formed is θ, the emitted light is linearly polarized light rotated by 2θ with respect to the incident polarization plane. Therefore, if the half-wave plate 32 is arranged so that the angle formed by the optical axis and the polarization direction of the laser light L1 is 45 °, the laser light L1 that has passed through the half-wave plate 32 as shown in FIG. Can be rotated at right angles. That is, the polarization direction of the laser light L1 emitted from the laser oscillator 2A can be rotated from P-polarized light to S-polarized light. The reflection mirror 34 reflects the laser beam L 1 that has passed through the half-wave plate 32 at a right angle and guides it to the polarization beam splitter 6.

  As another means for rotating the polarization direction of the laser light L1 emitted from the laser oscillator 2A at a right angle, a 90 ° rotator or a dove prism having a function of rotating the polarization direction of the incident light by 90 ° and emitting it is used. Alternatively, the polarization direction may be rotated by 90 ° by a combination of mirrors. In order to rotate the polarization direction by a combination of mirrors, for example, a configuration example shown in FIG. 2 can be considered. As shown in FIG. 2, mirrors M1 to M4 are arranged, and laser light L1 is incident on the mirror M1 in a direction perpendicular to the surface from the surface of the paper, and this is reflected in a right angle direction parallel to the paper. Reflected sequentially by mirrors M2 to M4. As a result, the incident laser beam L1 is emitted with its polarization direction rotated by 90 °. Further, if the laser oscillator 2A itself is rotated by 90 ° about the optical axis from the state shown in FIG. 1 so that the polarization direction of the emitted laser light becomes S-polarized light from the beginning, these rotating means can be used. Can be omitted.

  The pulse controller 4 outputs a pulse signal as a control signal to each so that the pulse timings (shot timings) of the two laser oscillators 2A and 2B are shifted in time. In the present embodiment, the pulse timing is shifted so that the laser pulses of the combined laser beam are arranged at regular intervals in time.

  The polarization beam splitter 6 reflects the laser light L1 from the laser oscillator 2A in the right-angle direction and transmits the laser light L2 from the laser oscillator 2B, thereby allowing the laser light from the two laser oscillators 2A and 2B to be on the coaxial optical path. To synthesize. Hereinafter, this synthesized laser beam is referred to as a synthesized laser beam Lc. As a result, as shown in FIG. 1, the laser pulses of the synthesized laser beam Lc are arranged at equal intervals in time, and the pulse frequency is the sum of the pulse frequencies from the original laser oscillators 2A and 2B, that is, twice the pulse frequency. It becomes frequency. Further, as shown in this figure, the pulse of the combined laser beam Lc immediately after passing through the polarization beam splitter 6 is composed of mutually orthogonal polarization components.

  The polarization adjusting unit 12 is disposed on the optical path of the combined laser beam Lc, and selectively rotates the polarization direction of the orthogonally polarized components in the laser beam incident thereon different from the change direction to be aligned. The laser beam irradiates the irradiated object 1 with the function of aligning the polarization direction of the laser beam. In the present embodiment, the polarization adjusting unit 12 rotates the half-wave plate 14 disposed on the optical path of the combined laser beam Lc and the half-wave plate 13 around the optical axis of the combined laser beam Lc. And a drive unit 16. In this example, the drive unit 16 includes a motor 18 that can rotate at a high speed and a control unit 20 that controls the rotation of the motor. With this configuration, the polarization adjusting unit 12 can control the rotation of the half-wave plate 14 so that the polarization directions of the laser light L3 that has passed through the half-wave plate 14 are aligned based on the pulse timing of the laser oscillator. it can.

  The laser beam La that has passed through the polarization adjusting unit 12 is condensed by the condenser lens 36 and irradiated onto the irradiation object 1. The irradiated object 1 in this embodiment is formed by forming an amorphous semiconductor film (for example, amorphous silicon) on a glass substrate, and the irradiated film portion is melted and solidified by laser light irradiation to be polycrystallized. Is done.

  FIG. 3 is a diagram for specifically explaining a method of aligning the polarization direction of the combined laser light Lc by the polarization adjusting unit 12 of the present embodiment. Here, a case where the polarization direction to be aligned is P-polarized light will be described. As shown in this figure, the combined laser beam Lc is incident on the half-wave plate 14, but in this laser beam, polarized components (P-polarized light and S-polarized light) orthogonal to each other are arranged at equal intervals in time. . (A)-(D) in the figure is the figure which arranged a mode that synthetic laser beam Lc progressed in order from the top. As described above, the half-wave plate 14 has a function of rotating the polarization plane of linearly polarized light. The linearly polarized light enters the half-wave plate, and the incident polarization plane and the half-wave plate When the angle formed with the optical axis is θ, the emitted light is linearly polarized light rotated by 2θ with respect to the incident polarization plane. The present invention utilizes the property of this half-wave plate.

  That is, when the polarization direction of the laser light incident on the half-wave plate 14 matches the polarization direction to be aligned (P-polarized light in this example) as shown in FIG. If the angle θ formed with the optical axis a of the two-wavelength plate is 0 °, the polarization direction of the laser light after passing does not rotate. Therefore, the polarization direction of the laser light after passing is still P-polarized light, and the laser light is oriented in the polarization direction to be aligned.

  On the other hand, when the half-wave plate is rotated 45 ° from the position (A) as shown in (B) and the polarization direction of the laser light incident on the half-wave plate 14 is orthogonal to the polarization direction to be aligned. If the angle θ formed by the polarization direction of the laser light and the optical axis a of the half-wave plate is 45 °, the polarization direction of the laser light after passing is rotated by 2θ, that is, 90 °. Therefore, the polarization direction of the laser light after passing is P-polarized light, and the laser light faces the polarization direction to be aligned.

  Subsequently, as shown in (C), the laser beam advances and the half-wave plate is rotated 45 ° from the position (B), so that the polarization direction of the laser beam incident on the half-wave plate 14 is aligned. If the angle θ formed by the polarization direction of the laser beam and the optical axis a of the half-wave plate 14 is 90 ° when it coincides with the power polarization direction, the polarization direction of the laser beam after passing is 2θ, that is, Rotate 180 °. However, when viewed as the polarization direction of linearly polarized light, it is almost the same as not rotating as a result. Therefore, the polarization direction of the laser light after passing is still P-polarized light, and the laser light faces the polarization direction to be aligned. Yes.

  Subsequently, as shown in (D), the laser beam advances and the half-wave plate is rotated 45 ° from the position (C), so that the polarization direction of the laser beam incident on the half-wave plate 14 is aligned. If the angle θ formed between the polarization direction of the laser beam and the optical axis a of the half-wave plate is 45 ° when orthogonal to the power polarization direction, the polarization direction of the laser beam after passing is 2θ, that is, 90 Rotate. Therefore, the polarization direction of the laser light after passing is P-polarized light, and the laser light faces the polarization direction to be aligned.

  As described above, the half-wave plate 14 is rotated by rotating the half-wave plate 14 so that the optical axis a becomes a predetermined angle in accordance with the polarization direction of the laser beam incident on the half-wave plate 14. The polarization direction can be made uniform. Therefore, when the polarization direction of the laser light incident on the half-wave plate coincides with the polarization direction to be aligned, the drive unit 16 of the polarization adjusting unit 12 and the polarization direction of the laser light and the half-wave plate When the angle between the optical axis is 0 ° or 90 ° and the polarization direction of the laser light incident on the half-wave plate is orthogonal to the polarization direction to be aligned, the polarization direction of the laser light and the half wavelength The half-wave plate 14 is rotated so that the angle formed by the optical axis of the plate is 45 °. That is, in the case where laser beams having orthogonal polarization directions are alternately incident, the half-wave plate 14 may be controlled to rotate by 45 ° between pulses (shots). For example, when a laser oscillator having a pulse frequency of 1 kHz is used as in this example, the pulse interval (shot interval) of the combined laser beam Lc is 500 μsec. Therefore, if the half-wave plate 14 is rotated once in 4 msec, the polarization direction of the synthetic laser light Lc can be made uniform.

  According to the first embodiment of the present invention, since the laser beams L1 and L2 emitted from the two laser oscillators 2A and 2B are combined by the polarization beam splitter 6 that combines on the coaxial optical path, the irradiated object 1 is irradiated. The pulse frequency of the laser beam La irradiated to the irradiation object 1 can be made twice the pulse frequency emitted from each of the laser oscillators 2A and 2B. Therefore, the processing speed with respect to the irradiated object 1 can be increased.

  Further, according to the present embodiment, the pulse laser beams L1 and L2 are emitted from the two laser oscillators 2A and 2B so that the respective pulse timings are shifted, and are aligned among the mutually orthogonal polarization components in the combined laser beam Lc. Since the polarization direction of the laser beam La that is irradiated to the irradiation object 1 is aligned by selectively rotating the polarization direction that is different from the power polarization direction, the irradiation object 1 is irradiated with this. The energy distribution of the laser light applied to the laser beam does not change every shot (one pulse). Therefore, isotropic crystal grains can be obtained when applied to laser annealing of an amorphous semiconductor.

  In other words, according to the present invention, it is possible to irradiate laser beams having the same polarization direction even if laser beams emitted from a plurality of laser oscillators are combined, and this is applied to laser annealing of amorphous semiconductors. In this case, an isotropic crystal grain can be obtained, and an excellent effect can be obtained that the processing efficiency can be increased and the productivity can be improved.

  Next, a second embodiment of the present invention will be described. FIG. 4 is a diagram showing a configuration of a laser irradiation apparatus according to the second embodiment of the present invention. The difference of the second embodiment from the first embodiment is that the polarization adjusting means 12 has a different configuration. However, in this embodiment, the pulse timing is shifted so that the laser pulses of the synthesized laser light Lc are aligned at regular intervals in time, but it is not always necessary to have regular intervals. Other configurations are the same as those of the first embodiment.

  In the second embodiment, the polarization adjusting means 12 is arranged on the optical path of the combined laser beam Lc and rotates the polarization direction of the laser beam at a right angle when a predetermined operating condition is satisfied, and the optical element 22 And an optical element actuating means 24 for actuating. Based on the pulse timing of the laser oscillators 2A and 2B, the optical element operating unit 24 rotates the polarization direction at a right angle only when the polarization direction of the laser light incident on the optical element 22 is orthogonal to the polarization direction to be aligned. Has a function of operating the optical element 22.

  In the present embodiment, the optical element 22 is an electro-optical element, and the optical element actuating means 24 is a power source that applies a voltage to the electro-optical element. The electro-optic element 22 uses a DKDP crystal that is a birefringent crystal (a crystal having a different refractive index depending on the polarization direction). This DKDP crystal is cut into a cube at 45 ° Zcut, and the Y ′ direction of the crystal and the traveling direction of the laser beam coincide with each other, and the polarization direction of the laser beam and the Z direction of the DKDP crystal form an angle of 45 °. Has been. The DKDP crystal is a birefringent material, and the laser light incident on the crystal propagates with the polarization direction separated into two, the X ′ direction and the Z direction. The DKDP crystal is provided with electrodes on the Z plane so that a voltage can be applied in the Z direction, and the refractive index for polarized light in the Z direction can be changed by applying a voltage in the Z direction. In this case, since the amount of change in the refractive index in the Z direction is proportional to the applied voltage (Pockels effect), an arbitrary phase difference can be given to the polarized light in the X ′ direction and the Z direction at the time of crystal emission by the applied voltage. When the phase difference between the polarized light in the X ′ direction and the Z direction is exactly λ / 2, the direction of the polarized light in which the X ′ direction and the Z direction polarized light are combined after exiting the crystal is orthogonal to the polarization direction at the time of crystal incidence. become. In this case, the voltage applied to the crystal is referred to as λ / 2 voltage.

  In this embodiment, the power source as the optical element actuating means 24 is based on the pulse timing of the laser oscillators 2A and 2B, and the polarization direction of the laser light incident on the electro-optical element 22 should be aligned (in this example, P-polarized light). The λ / 2 voltage is applied to the electro-optic element 22 only when it is orthogonal to (). That is, when the half-wave plate 14 in FIG. 3 is replaced with the electro-optic element 22, in (A) and (C), no voltage is applied to the electro-optic element 22, and (B) and (D). Only at this time, the λ / 2 voltage is applied to the electro-optic element 22. As a result, only the polarization component of the S-polarized light in the combined laser light Lc is rotated by 90 ° by the electro-optic element 22, so that the polarization direction of the laser light La that has passed therethrough is aligned with the P-polarized light.

  Thus, also by the second embodiment of the present invention, the same effect as that of the first embodiment described above can be obtained.

  Next, a third embodiment of the present invention will be described. FIG. 5 is a diagram showing a configuration of a laser irradiation apparatus according to the third embodiment of the present invention. As shown in this figure, the laser irradiation apparatus according to the third embodiment includes three laser oscillators 2A, 2B, and 2C, a pulse control unit 4, first and second polarizing beam splitters 6A and 6B, And second polarization adjusting means 12A and 12B. The three laser oscillators 2A, 2B, 2C and the first and second polarization beam splitters 6A, 6B have the same configuration as in the first and second embodiments. The first and second polarization adjusting units 12A and 12B each have the same electro-optic element 22 and power source 24 as those in the second embodiment.

  The pulse controller 4 outputs a pulse signal to each of the three laser oscillators 2A, 2B, and 2C so that the pulse timings (shot timings) of the laser oscillators 2A, 2B, and 2C are shifted in time. In this embodiment, the pulse timing is shifted so that the laser pulses of the synthesized laser light are aligned at regular intervals in time, but it is not always necessary to have regular intervals.

  The first polarization beam splitter 6A combines the laser beams L1 and L2 emitted from the laser oscillator 2A and the laser oscillator 2B on the coaxial optical axis to generate a first combined laser beam Lc1. The first polarization adjusting unit 12A aligns the polarization direction of the first combined laser beam Lc1 in the same manner as described in the second embodiment.

  The second polarization beam splitter 6B is disposed on the optical path of the first combined laser beam Lc1 that has passed through the first polarization adjusting unit 12A, and the first combined laser beam Lc1 and the laser emitted from the laser oscillator 2C. The light L3 is combined on the coaxial optical path to generate a second combined laser light Lc2. Then, as shown in this figure, since the S-polarized laser beam L3 from the laser oscillator 2C is synthesized with the second synthesized laser beam Lc2, P-polarized light and S-polarized light are mixed, and the polarization directions are orthogonal to each other. The polarization component to be included is included. In the second polarization adjusting unit 12B, the optical element operating unit (power source) 24 should align the polarization direction of the laser light incident on the electro-optical element 22 based on the pulse timings of the three laser oscillators 2A, 2B, and 2C. A voltage (λ / 2 voltage) is applied to the electro-optic element 22 so that the polarization direction is rotated by 90 ° only when orthogonal to the polarization direction (P-polarized light in this example). As a result, only the polarization component of the S-polarized light in the second synthetic laser beam Lc2 is rotated by 90 ° by the electro-optic element 22, so the polarization direction of the second synthetic laser beam Lc2 that has passed through this is P Aligned with polarized light.

  According to the third embodiment of the present invention, the laser beams emitted from the three laser oscillators are synthesized on the coaxial optical path and irradiated onto the irradiated object. Therefore, the pulse frequency of the laser light irradiated onto the irradiated object is set to , And 3 times the pulse frequency emitted from each laser oscillator. Therefore, the processing speed for the irradiated object can be further increased than in the first embodiment. For this reason, the outstanding effect that processing efficiency can further be raised and productivity can be improved more is acquired.

  In the first to third embodiments described above, the polarization direction of the laser beam is aligned by rotating the S-polarized component in the combined laser beam. Conversely, the P-polarized component is rotated. Thus, the polarization directions may be aligned.

  Further, in the second and third embodiments described above, the number of laser beams to be combined is two and three, respectively, but the present invention is not limited to this. May be. In this case, the polarization beam splitter 6 and the polarization adjusting unit 12 may be arranged by increasing by an appropriate number as in the example of the third embodiment.

  In the second and third embodiments of the present invention described above, as the optical element for rotating the polarization direction by 90 °, an electro-optical element using the Pockels effect is used. The optical element is not limited to this, and the same effect can be obtained even if the Kerr effect in which the birefringence is proportional to the square of the applied voltage is used.

  Even if a magneto-optical element using the Faraday effect, which is one of the magneto-optical effects, is used to rotate the polarization direction, the polarization direction can be rotated by 90 °, and the above-described electro-optical element is used. The same effect as the case can be obtained. In this case, the optical element actuating means is a magnetic field generator that applies a magnetic field to the magneto-optical element.

  In addition, the technical scope of the present invention is not limited to the above-described embodiment, and various modifications can be made without departing from the scope of the present invention.

It is a figure explaining 1st Embodiment of this invention. It is a figure which shows the structural example for rotating a polarization direction with the combination of a mirror. It is a figure explaining the polarization | polarized-light of the laser beam by the polarization adjusting means of 1st Embodiment of this invention. It is a figure explaining 2nd Embodiment of this invention. It is a figure explaining 3rd Embodiment of this invention. It is a figure explaining a prior art. It is a figure explaining a prior art.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Irradiated object 2A, 2B, 2C Laser oscillator 4 Pulse control part 6 Polarization beam splitter 6A First polarization beam splitter 6B Second polarization beam splitter 12 Polarization adjustment means 12A First polarization adjustment means 12B Second polarization adjustment Means 14 Half-wave plate 16 Drive unit 18 Motor 20 Control unit 22 Optical element (electro-optical element)
24 Optical element operation means (power supply)
32 half-wave plate 34 reflecting mirror 36 condensing lens a optical axis M1 to M4 reflecting mirror

Claims (13)

A laser irradiation apparatus for irradiating an irradiated object with pulsed laser light,
A plurality of laser oscillators emitting pulsed laser light;
A pulse control unit that outputs a control signal to each of the pulse timings of a plurality of laser oscillators, and
A polarization beam splitter that combines a plurality of laser beams on a coaxial optical path;
Polarization of laser light that irradiates the irradiated object by selectively rotating the polarization direction that is different from the polarization direction that should be aligned among the orthogonal polarization components in the incident laser light that is placed on the optical path of the synthesized laser light Polarization adjusting means for aligning the direction,
The laser irradiation apparatus characterized by the above-mentioned. The polarization adjusting means includes a half-wave plate disposed on the optical path of the synthesized laser beam, and a drive unit that rotates the half-wave plate about the optical axis of the synthesized laser beam,
2. The drive unit according to claim 1, wherein the drive unit rotates the half-wave plate so that the polarization directions of the laser beams that have passed through the half-wave plate are aligned based on pulse timings of the plurality of laser oscillators. The laser irradiation apparatus as described. The drive unit is
When the polarization direction of the laser light incident on the half-wave plate coincides with the polarization direction to be aligned, the angle formed by the polarization direction of the laser light and the optical axis of the half-wave plate is 0 ° or 90 °. And
When the polarization direction of the laser beam incident on the half-wave plate is orthogonal to the polarization direction to be aligned, the angle formed by the polarization direction of the laser beam and the optical axis of the half-wave plate is 45 ° The laser irradiation apparatus according to claim 2, wherein the half-wave plate is rotated. The polarization adjusting means is disposed on the optical path of the combined laser light, and rotates an optical element that rotates the polarization direction of the laser light at a right angle when a predetermined operating condition is satisfied, and an optical element operating means that operates the optical element. Have
The optical element actuating means rotates the polarization direction at right angles only when the polarization direction of the laser light incident on the optical element is orthogonal to the polarization direction to be aligned, based on the pulse timing from the plurality of laser oscillators. The laser irradiation apparatus according to claim 1, wherein the optical element is operated.   The laser irradiation apparatus according to claim 4, wherein the optical element is an electro-optical element, and the optical element operating unit is a power source that applies a voltage to the electro-optical element.   The laser irradiation apparatus according to claim 4, wherein the optical element is a magneto-optical element, and the optical element actuating means is a magnetic field generator that applies a magnetic field to the magneto-optical element.   Pulse laser beams are emitted from a plurality of laser oscillators so that their pulse timings are shifted, and the plurality of laser beams are synthesized by a polarization beam splitter that synthesizes them on a coaxial optical path. A laser irradiation method characterized by selectively rotating a polarization direction that is different from a polarization direction to be aligned, aligning a polarization direction of laser light to be irradiated on the irradiated object, and irradiating the irradiated object with this .   A half-wave plate is arranged on the optical path of the synthesized laser beam, and the synthesized laser beam is aligned so that the polarization directions of the laser beams that have passed through the half-wave plate are aligned based on the pulse timing of the plurality of laser oscillators. The laser irradiation method according to claim 7, wherein the half-wave plate is driven to rotate about the optical axis of the laser beam.   When the polarization direction of the laser light incident on the half-wave plate coincides with the polarization direction to be aligned, the angle formed by the polarization direction of the laser light and the optical axis of the half-wave plate is 0 ° or 90 °. When the polarization direction of the laser light incident on the half-wave plate is orthogonal to the polarization direction to be aligned, the angle formed by the polarization direction of the laser light and the optical axis of the half-wave plate is 45 °. The laser irradiation method according to claim 8, wherein the half-wave plate is rotated as follows.   An optical element that rotates the polarization direction of the synthesized laser beam at a right angle when a predetermined operating condition is satisfied is disposed on the optical path of the synthesized laser beam, and is incident on the optical element based on the pulse timing of the plurality of laser oscillators. 8. The laser irradiation method according to claim 7, wherein the optical element is operated so as to rotate the polarization direction at a right angle only when the polarization direction of the laser light is orthogonal to the polarization direction to be aligned.   The laser irradiation method according to claim 10, wherein an electro-optical element or a magneto-optical element is used as the optical element.   A laser annealing comprising the laser irradiation apparatus according to claim 1, wherein the laser irradiation is performed to irradiate an object having an amorphous semiconductor film formed on a substrate by the laser irradiation apparatus. apparatus.   12. A laser annealing method, comprising: irradiating an irradiation object having an amorphous semiconductor film formed on a substrate with a laser beam by the laser irradiation method according to claim 7.

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