JP2004241561A - Laser processing system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laser processing system with a construction and adjustment simple and easy for uniformizing one layer of an irradiated beam, and enabled to project the beam with stability and homogeneity, by preventing an interference between split beams due to superimposition. <P>SOLUTION: The laser processing system comprises at least one laser oscillator for generating a laser beam with its M2 value ≤100 which is the light harvesting index of the laser beam generated by the laser oscillator, a laser beam splitting means for splitting the laser beam from the laser oscillator into N split beams spatially in the beam cross section, a superimposing means for projecting the split beams roughly superimposed on each other on the beam receiving plane, and an optical path length/polarization direction control means for differentiating optical path lengths or polarization directions for neighboring beams in the N split beams. The M2 value satisfies a relation: M2≥N/2 at least in the beam splitting direction. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a laser processing apparatus that improves the homogeneity of an irradiation laser beam on an irradiation surface during laser processing of an object to be irradiated.
[0002]
[Prior art]
As an example of performing heat treatment by laser irradiation, in the case of manufacturing a polycrystalline silicon film, an amorphous silicon film is previously formed on a suitable substrate, for example, a glass substrate by a vapor phase forming method such as CVD. In addition, a method is known in which the amorphous silicon film is scanned with a laser beam to be polycrystallized.
[0003]
In the method of polycrystallizing a silicon film, for example, a laser beam from a laser light source is condensed on an amorphous silicon film by a lens and laser irradiation is performed. Some are crystallized during the process. The laser beam is usually an axially symmetric Gaussian distribution, with the axial intensity profile of the beam at the irradiation location depending on the profile of the laser source. The polycrystalline silicon film formed by irradiation with such a beam has extremely low crystallinity uniformity in the plane direction, and it has been difficult to use the polycrystalline silicon film as a semiconductor substrate in manufacturing a thin film transistor.
[0004]
Further, there is known a technique in which an excimer laser having a short wavelength is used to irradiate and heat a semiconductor film with a profile of an irradiation beam in a rectangular distribution. For example, there has been one in which a laser beam from an oscillator passes through two cylindrical lens arrays that cross each other in a plane perpendicular to the optical axis, passes through a converging lens, and converges on the surface of the semiconductor film. In this method, a laser beam having a Gaussian distribution is made uniform in two orthogonal directions by two cylindrical lens arrays, and an irradiation laser beam on the surface of the semiconductor film is orthogonal on the semiconductor surface. The width is different in two directions, and a polycrystalline band having a constant width is repeatedly formed on the semiconductor film by sweeping the irradiation laser beam (for example, see Patent Documents 1 and 2). .
[0005]
Recently, the maximum output of YAG lasers has been significantly improved. Since a YAG laser is a solid-state laser, it is easier to handle and easier to maintain than an excimer laser, which is a gas laser. Attention has been paid to a polycrystallizing method of a silicon film using a second harmonic of a YAG laser, which has this characteristic, because of its potential for higher mobility. However, the coherent length of an excimer laser is on the order of several microns to several tens of microns, and the optical interference when passing through an optical system that divides a laser beam into one is very weak. , And its second harmonic have a very long coherent length of about 1 cm. The effect of this interference cannot be ignored.
The interference generated in the superimposed beam on the irradiation surface is such that when a semiconductor film is heated and crystallized using a rectangular irradiation laser beam, the intensity profile in the direction of movement of the laser beam greatly affects crystal growth. However, it is not preferable to cause the crystal grains of the silicon film to grow large.
[0006]
There has been proposed a method for removing the non-uniformity of the irradiation laser intensity due to this interference.For example, a collimator converts a beam from a light source into a parallel light, irradiates the mirror with a step-like reflecting surface, and splits the beam by the mirror. An optical system configured to irradiate with a cylindrical lens array to be synthesized and a converging cylindrical lens is disclosed. This is to provide an optical path difference equal to or longer than the coherent length of a laser beam in each divided beam due to a step between respective reflection surfaces, thereby preventing interference between the divided beams on an irradiation surface (for example, Patent Document 3). reference).
[0007]
In addition, the laser beam from the light source is collimated by a beam collimator, irradiates a plurality of small reflecting mirrors, and the reflected light from each reflecting mirror is irradiated on the irradiation surface and superimposed. In some cases, interference is prevented by securing the optical path difference of the beam equal to or longer than the coherent length (for example, see Patent Document 4).
[0008]
[Patent Document 1]
JP-A-10-333077 (pages 2-5, FIGS. 1 and 2)
[Patent Document 2]
JP-A-6-69415 (pages 2-6, FIG. 1-15)
[Patent Document 3]
JP 2001-127003 A (Page 2-10, FIG. 6-10)
[Patent Document 4]
JP 2001-244213 A (Pages 2-20, FIG. 3-13)
[0009]
[Problems to be solved by the invention]
The above-mentioned beam uniformization technology prevents interference when splitting a laser beam from the same light source and superimposing them on the irradiation surface by providing an optical path difference using a reflector having multiple reflection surfaces. However, these optical systems required special reflecting mirrors. In particular, the optical system of Patent Document 4 requires an arrangement in which the optical axis of the optical system is bent by a reflecting mirror. Further, each reflecting mirror of the optical system accurately adjusts an irradiation surface in correspondence with a large number of split beams. However, there is a problem that the arrangement of the reflection mirror is complicated, and the degree of freedom of the optical system to be arranged as the heat treatment apparatus is reduced.
Moreover, if the optical path difference is provided for all the divided beams, the transfer conditions for each beam are greatly different, so that there is a problem that the divided beams cannot be overlapped on the irradiation surface in the same manner. For large laser sources, the device is large and complex, impractical, and difficult to optically adjust.
[0010]
The present invention provides a uniform intensity distribution on an irradiation surface by superimposing split beams obtained by splitting a laser beam having an M2 value (which is an index indicating the condensing property of a beam generated from a laser oscillator) of 100 or less. The purpose of the present invention is to prevent interference between divided beams due to superposition in a laser processing apparatus for forming an irradiated beam, thereby achieving a more uniform irradiation beam, and in particular, to prevent such interference. It is an object of the present invention to provide a laser processing apparatus which is simple and easy to make the configuration and adjustment for making the irradiation beam uniform, and enables stable and uniform irradiation.
[0011]
[Means for Solving the Problems]
A laser processing apparatus according to the present invention includes: at least one laser oscillator that generates a laser beam having an M2 value of 100 or less, which is an index indicating the condensing property of a beam generated by the laser oscillator; and a laser beam from the laser oscillator. A laser beam splitting means for spatially splitting the divided beams into N divided beams in a beam cross section, superimposing irradiation means for irradiating each of the divided beams substantially superimposed on an irradiation surface, and Optical path length or polarization direction control means for changing the optical path length or polarization direction of adjacent divided beams adjacent to each other, wherein the M2 value is M2 ≧ N / 2 at least in the beam division direction.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
1A and 1B are plan views showing a configuration of a laser processing apparatus according to a first embodiment of the present invention, in which FIG. 1A is a view as seen from a y direction, and FIG. 1B is a view as seen from an x direction.
In this embodiment mode, the laser processing apparatus shown in FIGS. 1A and 1B has a linear irradiation profile which spreads uniformly on the irradiation surface in the y direction and converges linearly in the x direction. Is shown.
[0013]
The laser processing apparatus includes a laser oscillator 100, a laser beam splitting unit 3, a superposition irradiation unit 6, and an optical delay unit 2. The laser beam splitting unit 3 uses a waveguide 4 to generate a laser beam. Is divided into a desired number of divided beams 16a to 16e, and the divided beams are imaged on the irradiation surface 90 of the irradiation object 9 by the overlapping irradiation means 6 as an irradiation beam 19 of a linear profile.
[0014]
In the present embodiment, the laser beam splitting means 3 includes an optical system for causing the laser beam 1 from the laser oscillator 100 to enter the waveguide 4, and includes a beam expanding lens 31 for converting the laser beam 1 into a parallel beam and a y-direction collimator. It includes a lens 32 and an x-direction collimating lens 33, and then includes a cylindrical lens condensing lens 34 that collects light in the y-direction and makes it enter the waveguide 4.
[0015]
The waveguide 4 has parallel main surfaces opposed to each other having reflection surfaces 41 and 42, and the reflection surfaces 41 and 42 are perpendicular to the y direction in this figure. An incident end face 43 and an outgoing end face 44 through which the laser beam 1 passes between the two reflecting surfaces are orthogonal to the optical axis of the laser beam. The incident laser beam 1 is a split beam of a component that passes between the reflection surfaces and radiates from the emission end, and a split beam (m = 1) of a component that is reflected once (m = 1) by one of the reflection surfaces 41 and 42. = + 1, m = -1) and two split beams (m = + 2, m = -2) of the component reflected twice (m = 2) on both reflecting surfaces, and three or more times Each pair of reflected split beams is split into components emitted from the emission end.
[0016]
The split beam from the waveguide 4 is superimposed and projected on the irradiation surface 90 by the superimposing irradiation unit 6. The superimposing irradiation unit 6 transfers the split beam onto the irradiation surface 90 in the y direction. It can be constituted by a transfer lens 61 (cylindrical lens) for the direction and a condenser lens 62 (cylindrical lens) for collecting light in the x direction. The y-direction transfer lens 61 extends to a specified length in the y-direction on the irradiation surface 90 through the x-direction condenser lens 62, and the x-direction condenser lens 62 converges linearly in the x direction. An irradiation beam 19 of a linear profile is obtained on the irradiation surface.
[0017]
The transfer lens 61 in the y-direction of the superposition irradiation means 6 is set so that each divided beam forms a real focus and projects onto the irradiation surface 19, and the divided beams are spatially separated from each other near the actual focus position. A light transmissive body 2 for delay is disposed at a position as an optical delay means, and the delay plate 2 is configured to divide one of the optical paths of divided beams existing in regions adjacent to each other before division. Is delayed with respect to the other optical path, and an optical path difference is provided optically to prevent interference between the two split beams when they are superimposed on the irradiation surface 19. In the example of FIG. 1, the delay plate 2 is arranged every other split beam at the actual focal position on the emission side of the transfer lens 61.
[0018]
More specifically, FIG. 2 shows the mode of splitting the laser beam from the laser oscillator 100 with respect to the waveguide of the laser beam splitting means. The laser beam from the laser oscillator 100 is applied to a condensing lens 34 of a cylindrical lens. Focus on F ₀ And enters the waveguide 4. In the waveguide, there is a split beam (the number of reflections m = 0) in which a part of the incident beam is transmitted without reflection on the reflection surface, and the split beam reflected only once on the reflection surface 41 or 42 opposed to each other. There are two types in the y direction (m = ± 1), and there are two types of split beams similarly reflected in the y direction in the y direction (m = ± 2). Radiated from Focus F perpendicular to optical axis ₀ The virtual image focus F of each split beam emitted from the exit surface 43 ₊₁ , F _-1 , F ₊₂ , F _-2 And each of the split beams has a virtual image focus F ₊₁ .. Appear to be radiated from the opening of the exit surface 43.
[0019]
Assuming that the laser beam spreads through the focal point by the condenser lens 34 assuming that there is no waveguide, the profile of the beam projected onto the surface at the position of the exit surface 44 is a circle 14. Can be decomposed into components of sections corresponding to each of the multiple split beams. When each component in the cross section of the laser beam 1 is divided in the order of m = −2, −1, 0, +1 and +2 in the y direction on the cross section, a component radiated from the emission surface 44 of the waveguide 4, that is, It should be noted that the split beams are arranged in the y direction in the order of the components of the number of reflections m = + 2, -1, 0, +1 and -2.
[0020]
FIG. 2 shows only the arrangement of the split beams of the components m = 0, +1 and +2 radiated from the exit surface 44 of the waveguide 4, and the split beams of m = + 1 and m = + 2 Radiated in opposite directions to the intermediate plane. On the other hand, the split beams of m = -1 and -2 are symmetrical with respect to the center plane of the reflection surface of m = + 1 and +2, but are omitted in the drawing.
[0021]
FIG. 3A shows a case where the laser beam is focused on a focal point F. ₀ FIG. 3 schematically illustrates the division width of the divided beam of the laser beam 14 projected on the corresponding plane of the emission surface 44 of the waveguide 4 without being reflected by the waveguide 4. This is an example in which a circular profile laser beam 14 is divided into seven by a waveguide.
[0022]
In the waveguide 4, split beams adjacent to each other are folded and superimposed on the emission surface 44 of the waveguide 4. Thus, the components adjacent to each other due to the division of the laser beam 1 have their boundary portions coincident with each other at the folded portion of the divided beam at the exit surface of the waveguide in FIG. For example, in FIG. 3A, the boundary III of the component of m = + 1 and the boundary iii of m = 0 that is in contact with the component are folded at the exit surface 44 of the waveguide as shown in FIG. 3B. And overlap.
[0023]
When such a folded split beam is projected onto the irradiation surface 90 by being superimposed on it via the y-direction transfer lens 61 and the x-direction condenser lens 62, the irradiation beam interferes on the irradiation surface. , A wavy distribution is formed in the intensity.
[0024]
Further, this embodiment includes an optical delay means for delaying one of adjacent split beams adjacent to each other among the split beams formed by the above-described waveguide with respect to the other longer than the temporal coherence distance. In.
This optical delay means is used for a hollow mirror or a solid translucent body, but it is necessary to prevent the split beams from adjacent areas from interfering with each other by providing an optical path difference between them. , To prevent interference.
[0025]
The temporal coherence length ΔL of the laser beam is
ΔL = cΔt ≒ λ ² / Δλ
Given by Here, c is the speed of light, Δt is the coherence time, Δλ is the wavelength width (spectrum width) of the laser, and the narrower the laser wavelength width, the longer the coherence distance.
For example, in the case of a YAG laser (Nd: YAG laser), the spectral width Δλ = 0.12 to 0.30 nm for a beam having a center wavelength λ = 1.06 μm, so that the temporal coherence length ΔL is ΔL = 3.8 to 9.4 mm. The value of ΔL is almost the same for the second harmonic laser (YAG2ω laser) of the YAG laser.
[0026]
In FIG. 1, at a position where a plurality of split beams are separated from each other, a translucent delay plate 2, that is, an optical glass plate 2 is inserted as an optical delay unit into any of the split beams that easily cause interference. Thus, an optical path difference is formed between adjacent split beams. In this example, the beam split by the waveguide 4 is transferred by the y-direction transfer lens 61, and the irradiation beam 19 is formed on the irradiation surface by the x-direction condenser lens 62. A focal point f is formed on each beam by the y-direction transfer lens 61 between the optical lens 62 and the glass plate as the delay plate 2 is inserted into any one of the adjacent beams before or after the focal position f. An optical path difference is provided. In this example, a glass plate is inserted every other five divided beams, and another divided beam passes through the space between the delay plates 2 and 2 adjacent to each other. With the delay plates 2 having such an arrangement, the irradiation beams superimposed on the irradiation surface do not cause interference between the divided beams adjacent to each other, so that a profile having a substantially uniform intensity distribution can be obtained. .
The optical path difference Δa due to the glass plate is represented by the thickness a of the glass plate and the refractive index n of the glass ₁ , The refractive index of air n ₀ From
Δa = a (n ₁ -N ₀ )
Given by
[0027]
Since the optical path difference Δa due to the glass plate is set to be equal to or greater than the temporal coherence distance ΔL (Δa ≧ ΔL), glass that gives an optical path difference equal to or greater than the temporal coherence distance ΔL between adjacent split beams from these equations. The thickness a is required. The thickness of the delay plate is preferably set so as to provide an optical path difference of twice or more, more preferably four times or more, the temporal coherence length ΔL by the delay plate. For example, in a YAG laser (Nd: YAG laser) or a YAG2ω laser, quartz (n ₁ = 1.46), the optical path difference Δa is 12 to 30 mm while the temporal interference distance ΔL is 3.8 to 9.4 mm.
[0028]
In the present embodiment, the laser oscillator 100 generates a second harmonic laser (YAG2ω laser) of YAG having a wavelength of 532 nm. Further, the value M2, which is an index indicating the light condensing property of the beam generated from the laser oscillator 100, is N / 2 or more when the number N of beam splits is at least in the beam split direction (y direction). The M2 value is an index indicating how many times the diameter of the focused beam is larger than that of a single mode (TEM00) beam when the same focusing optical system is used, that is, an index indicating the focusing property. Obviously, the larger the M2 value, the larger the focused beam diameter and the worse the beam quality.
[0029]
As described above, if every other delay plate 2 is inserted into the divided beams, any combination of two divided beams adjacent to each other (for example, the divided beams having the number of reflections m = + 1 and m = 0) However, interference between two beams other than adjacent beams (for example, between split beams with the number of reflections m = −2 and m = 0) cannot be prevented.
Therefore, in the present embodiment, as will be described in detail below, when the M2 value is the number of beam divisions N, by setting it to N / 2 or more, interference between all the divided beams can be prevented. ing.
[0030]
FIG. 4 shows that only two components of the split beam from the waveguide when the number of divisions N is approximately 7, for example, two components of the number of reflections m = + 1 and m = 0 are converted into the y-direction transfer lens 61 and x The figure shows the measurement results of the intensity distribution on the irradiation surface when the irradiation is performed while being superimposed on the irradiation surface 90 via the direction condensing lens 62 and the like. Here, the delay plate 2 that gives an optical path difference to adjacent divided beams is not inserted. FIG. 4A shows the result when M2 = 5.7, and FIG. 4B shows the result when M2 = 11.3. FIG. 4 shows that the spatial coherence length is clearly reduced by increasing M2 from 5.7 to 11.3.
[0031]
1 / e peak intensity at beam diameter ² FIG. 5 shows the spatial coherence distance with respect to the M2 value when the beam diameter is defined as 100% (where e is the base of natural logarithm). Here, the spatial coherence distance X is defined as the distance between two points that attenuates to 1 / e with respect to the intensity of interference generated when laser beams at the same position are superimposed, and is defined as a beam diameter. Distance. FIG. 5 shows a space in the case where the M2 value of each laser oscillator is changed using three laser oscillators A, B, and C having different power levels as the laser oscillator 100 in the laser processing apparatus having the configuration shown in FIG. It shows the measurement results of the typical coherence distance X. In each case, the number of divisions N is 7, and the coherence distance between two components of the number of reflections m = + 1 and m = 0 is shown. As is clear from the figure, it has been found that the spatial coherence distance X has a value of 1 / M2 or less. In the example shown in the figure, the measurement result of the coherence distance between two components of the number of reflections m = + 1 and m = 0 is shown. However, even when data between other adjacent components is used, the spatial interference is measured. The result is the same because it is a number defined by the interference distance.
[0032]
As described above, in the configuration of FIG. 1 including the delay plate 2, interference between adjacent beams can be suppressed by inserting the delay plate 2. Since the phase is temporally the same between m = 0 and m = ± 2, interference cannot be suppressed. In order to suppress the interference between the further divided beams, the spatial coherence distance is set to the distance between one or more divided components (between two adjacent components) (that is, 2 / N) The following may be set. If the delay plate 2 is inserted every other beam in the split beam, the necessary conditions for preventing the appearance of interference are as follows.
X = 1 / M2 ≦ 2 / N (N is a positive number)
Ie
M2 ≧ N / 2
It can be seen that it is.
[0033]
As described above, the present inventors, when using a laser oscillator that generates a laser beam having a relatively low M2 value of 100 or less at the maximum, divides the beam into N divided beams and separates each divided beam. In the case of overlapping irradiation on the irradiation surface, it has been found that there is a close relationship between the M2 value, which is an index indicating the light condensing property of the beam generated from the laser oscillator, and the spatial coherence length. It has been reached. Generally, the smaller the M2 value, the smaller the focused beam diameter and the better the beam quality. However, in the present invention, it has been found that there is an optimum M2 value according to the number of divided beams.
[0034]
As described above, according to the present embodiment, a laser beam from a laser oscillator is spatially divided into N divided beams in a beam cross section using reflecting surfaces facing each other, and the N divided beams are used. In contrast, when the delay plate 2 is inserted as an optical path length or polarization direction control means for every other beam and the divided beams are superimposed and irradiated on the irradiation surface, an index indicating the condensing property of the beam generated from the laser oscillator 100 If the M2 value is N / 2 or more when the number of beam splits is N, interference between all split beams due to superposition can be prevented. In particular, every other delay plate 2 is inserted for every N divided beams, and when the M2 value is the number of beam divisions N, it is only N / 2 or more. As described above, since there is no need to provide an optical path difference for all of the divided beams, the configuration and adjustment are simple and easy. In addition, when the M2 value is N / 2 or more when the number of beam divisions is N, the interference between two beams other than those adjacent to each other can be reliably suppressed, so that stable homogeneous irradiation is possible. It becomes.
The application of this technique in homogenization is typically the YAG2ω laser shown in the present embodiment, but other lasers are often used in the industrial field. Is required for a laser having a relatively high beam quality of 100 or less. In reality, the configuration according to the present patent is required for 50 or less lasers that require more condensing properties.
[0035]
Embodiment 2 FIG.
6A and 6B are plan views showing the configuration of a laser processing device according to a second embodiment of the present invention, wherein FIG. 6A is a diagram viewed from the y direction, and FIG. 6B is a diagram viewed from the x direction.
In this embodiment mode, the laser processing apparatus shown in FIGS. 6A and 6B spreads uniformly on the irradiation surface in the y direction and spreads in the x direction as in the first embodiment mode. An example of forming a linear irradiation profile converged linearly is shown.
[0036]
In the first embodiment, the case where the delay plate (optical delay means) 2 is used as the optical path length or polarization direction control means for changing the optical path length or polarization direction of the adjacent divided beams of the N divided beams. However, in the present embodiment, the optical rotation means 7 is used which makes one of the adjacent split beams of the N split beams substantially orthogonal to the polarization direction of the other split beam.
Other configurations are the same as those of the first embodiment, and therefore, the differences from the first embodiment will be mainly described below.
[0037]
The transfer lens 61 in the y-direction of the superposition irradiation means 6 is set so that each divided beam forms a real focus and projects onto the irradiation surface 19, and the divided beams are spatially separated from each other near the actual focus position. At the position, a half-wave plate for polarization rotation is arranged as the optical rotation means 7, and the optical rotation means 7 adjusts the polarization angle of any one of the divided beams in the regions adjacent to each other before the division with respect to the other. This is to prevent the interference between the two split beams when they are substantially orthogonal to each other and are superimposed on the irradiation surface 19. In the example of FIG. 6, the wave plate 7 is arranged at every actual split position at the actual focal position on the emission side of the transfer lens 61.
[0038]
The optical rotation means 7 rotates the polarization so that the polarization angles are substantially orthogonal to each other so that the two split beams do not substantially interfere with each other. Preferably, a half-wave plate made of quartz is used. . In FIG. 6, a focal point f is formed in front of the y-direction transfer lens 61 (cylindrical lens) in front of the waveguide 4, and the half-wave plate 7 is arranged at this focal position. The half-wave plate 7 is inserted only into the three divided beams of the number of reflections m = 0, m = + 2, and m = -2, and is not inserted in the other number of reflections m = + 1 and m = -1. In this configuration, a half-wave plate 7 is interposed every other split beam arranged in the y direction. Thereby, referring to FIG. 3 (A), half-wave plate 7 is inserted only into one of the two divided beams adjacent to each other, and the polarization angle is substantially changed with respect to the other divided beam. They are orthogonal. Thereby, even if two divided beams of any combination adjacent to each other are superimposed on the irradiation surface 90, no interference occurs. Thus, the substantially uniform superposition of the polarized beams improves the uniformity of the illumination beam.
[0039]
However, in this specification, the phrase that the polarization angle (polarization direction) is substantially orthogonal means that one split beam is shifted from the orthogonal state to a range of ± 30 ° with respect to the other split beam. And thereby substantially reduce interference between the split beams.
[0040]
As described above, when every other half-wave plate 7 is inserted into the split beams, any two adjacent split beams of any combination (for example, the split of the number of reflections m = + 1 and m = 0) Although interference can be prevented even between beams (beams), it is not possible to prevent interference between two beams other than those adjacent to each other (for example, between split beams with the number of reflections m = -2 and m = 0).
Therefore, also in the present embodiment, as described in the first embodiment, when the value of M2, which is an index indicating the condensing property of the beam generated from the laser oscillator 100, is N By setting it to / 2 or more, interference between all split beams is suppressed.
[0041]
Embodiment 3 FIG.
As described in the first embodiment, the laser beam from the laser oscillator is spatially divided into N divided beams in the beam cross section using the reflecting surfaces facing each other, and the N divided beams are divided by one. When the delay plate 2 is inserted every other beam and the divided beams are superimposed on the irradiation surface and irradiated, the M2 value, which is an index indicating the light condensing property of the beam generated from the laser oscillator 100, is determined by the number of beam splits N By setting N / 2 or more, it is possible to suppress interference between all the divided beams.
[0042]
The degree of interference suppression at this time largely depends on the optical path difference Δa between adjacent divided beams. When the optical path difference is large, the transfer is complete due to the interference suppression effect, but on the other hand, the transfer conditions for each split beam are shifted, and good transfer cannot be performed on the processing table. Therefore, it is desirable to make the spatial coherence distance shorter, and experimentally,
M2 ≧ N
It has been found that more favorable results can be obtained.
[0043]
Also, in the case where half-wave plates 7 are alternately inserted between adjacent beams to suppress interference, as described in the second embodiment, the half-wave plate 7 cannot be completely rotated by 90 degrees. Interference remains. Also in this case
M2 ≧ N
By shortening the spatial coherence distance under the condition (1), a more uniform beam can be obtained on the irradiation surface 90.
[0044]
Embodiment 4 FIG.
FIG. 7 is a plan view showing the configuration of a laser processing apparatus according to Embodiment 4 of the present invention, showing the arrangement of the optical system as viewed from the x direction. The optical path length or polarization direction control means (optical delay means 2) The arrangement is basically the same as that of the laser processing apparatus shown in FIGS. Hereinafter, points different from the first embodiment will be mainly described.
[0045]
In the present embodiment, in particular, the optical path length or polarization direction control means includes the shield 29, and the straight beam when the number of reflections is m = 0 is disposed at the focal position f after the y-direction transfer lens 61. The shielding is performed by the shield 29. Since the straight beam with m = 0 does not reach the irradiation surface, it does not contribute to interference. Therefore, as the optical delay means 2, only one of the group of split beams (m = + 1, -2) or (m = -1, +2) symmetrically arranged with respect to the straight beam (m = 0) , The other group does not have the optical delay means 2, so that the interference between the split beams on the irradiation surface is reduced, and the optical delay means 2 has one of the split beam groups ( It is possible to use a single glass plate or glass rod through which m = + 1, -2 can be transmitted at a time, which is advantageous in that the optical system can be simplified. As the shield 29, a solid that absorbs or reflects a laser beam, for example, graphite, ceramics, metal, or the like can be used.
[0046]
Embodiment 5 FIG.
FIG. 8 is a plan view showing the configuration of the laser processing apparatus according to the fifth embodiment of the present invention, showing the arrangement of the optical system as viewed from the x direction, and the arrangement of the optical path length or polarization direction control means (optical rotation means 7). Except for the difference, the laser processing apparatus is basically the same as the laser processing apparatus shown in FIGS. 6A and 6B. Hereinafter, points different from the second embodiment will be mainly described.
[0047]
In the second embodiment, as the optical path length or polarization direction control means for changing the optical path length or the polarization direction of the adjacent divided beams of the N divided beams, half of every other divided beam arranged in the y direction is used. Although the wave plate 7 is interposed, it is necessary to provide a gap between the half-wave plates 7 and 7 to transmit other split beams, and the structure of the half-wave plate is somewhat complicated.
In order to solve this, in the present embodiment, in particular, the optical path length or polarization direction control means includes a shield 29, and the straight beam when the number of reflections is m = 0 is transmitted to the rear of the y-direction transfer lens. This is blocked by a shield 29 arranged at the focal position f. Since the straight beam with m = 0 does not reach the irradiation surface, it does not contribute to interference. Therefore, as the optical rotation means 7, only one of the divided beam group (m = + 1, -2) or (m = -1, +2) symmetrically arranged with respect to the straight beam (m = 0) is inserted. Then, the other group does not have the optical rotation means 7, so that the interference between the divided beams on the irradiation surface is reduced, and the optical rotation means 7 allows the one of the divided beam groups (m = + 1, -2). ) Can be used, and there is an advantage that the optical system can be simplified by using a single half-wave plate. A solid that absorbs or reflects the laser beam, for example, graphite, ceramics, metal, or the like can be used for the shield 29, and can be disposed at the focal position f integrally with the optical rotation means 7.
[0048]
Embodiment 6 FIG.
FIG. 9 is a plan view showing the configuration of the laser processing apparatus according to Embodiment 6 of the present invention, showing the arrangement of the optical system as viewed from the x direction, except for differences in the arrangement of the optical path length or polarization direction control means. Basically, it is the same as the laser processing apparatus shown in FIGS. 6A and 6B. Hereinafter, points different from the second embodiment will be mainly described.
[0049]
In the present embodiment, a delay plate 2 made of a glass body is inserted as the optical path length compensating means into the other split beam in the second embodiment shown in FIG. As described above, the half-wave plate 7 is disposed as the optical rotation means for one of the split beams, but the interposition of the half-wave plate 7 extends the optical path length of the split beam. If the optical path lengths are different between the two types of split beams, the imaging positions on the irradiation surface are shifted from each other, and the profile becomes unclear. To correct this, the other split beam is provided with a delay plate 2 for extending the optical path length as optical path length compensating means. As the delay plate 2, one similar to that described in the first embodiment is used. For example, the thickness of the optical glass plate is set to a thickness that produces an optical path equal to the optical path length of the half-wave plate 7.
[0050]
Embodiment 7 FIG.
10A and 10B are plan views showing the configuration of a laser processing apparatus according to Embodiment 7 of the present invention, where FIG. 10A is a view as seen from the y direction, and FIG. 10B is a view as seen from the x direction.
In this embodiment mode, the laser processing apparatus shown in FIGS. 10A and 1B has a linear irradiation profile that spreads uniformly on the irradiation surface in the y direction and converges linearly in the x direction. Is shown.
[0051]
The laser processing apparatus includes a laser oscillator 100, a laser beam splitting unit, a superposition irradiation unit, and an optical delay unit 2. The laser beam splitting unit uses a cylindrical lens array 5 to generate a laser beam. The beam is divided into a number of divided beams 15a to 15e, and the divided beams are imaged as an irradiation beam 19 of a linear profile on the irradiation surface 90 of the irradiation object 9 by the superimposing irradiation means.
[0052]
In the present embodiment, the laser beam splitting means includes an optical system for causing the laser beam 1 from the laser oscillator 100 to enter the splitting cylindrical lens array 5, and includes a beam magnifying lens 31 and a y-axis for converting the laser beam 1 into a parallel beam. The collimating lens includes a directional collimating lens 32 and an x-directional collimating lens 33, and a parallel beam from the collimating lens 33 enters the cylindrical lens array 5.
[0053]
The dividing cylindrical lens array 5 refers to a lens in which column-shaped lenses in the x direction in the drawing are arranged and convex lenses having a cross-section convex toward the optical axis are stacked in the y direction. In the illustrated example, there are five stages of cylindrical lenses 5a to 5e. Thereby, the laser beam 1 from the laser oscillator 100 is one-dimensionally split into five split beams 15a to 15e in a beam cross section.
[0054]
The split beams from the splitting cylindrical lens array 5 are superimposed and projected onto the irradiation surface 90 by the superimposing irradiation means, and the superposition irradiation means applies the split beams from the splitting cylindrical lens array 5 to the irradiation surface 90. A transfer cylindrical lens array 51 (consisting of five stages of cylindrical lenses 51 a to 51 e) for transferring in the y direction on the 90, a condensing lens 62 for condensing light in the x direction, and a field lens 63 are included.
[0055]
The split beam in the y-direction from the splitting cylindrical lens array 5 is disposed in front of the splitting cylindrical lens array 5 and is incident on a separate transfer cylindrical lens array 51. The split beam from the transfer cylindrical lens array 51 has focal points fa to After passing through fe, the light is projected onto the irradiation surface 90 by a condenser lens 62 (cylindrical lens) that condenses in the x direction, and is converted into an irradiation beam 19 having a linear profile that is uniform in the y direction and narrowly converges in the x direction. It is to be molded. Further, a field lens 63 is disposed between the cylindrical lens array 51 for transfer and the condenser lens 62.
[0056]
A delay plate 2 is inserted as an optical delay unit into the split beams 15a to 15e split in the y direction from the splitting cylindrical lens array 5, and the delay plate 2 (delay plates 2a, 2c, 2e) It is inserted into every other split beam 15a, 15c, 15e, and not inserted into the other split beams 15b, 15d. Thereby, interference on the irradiation surface 90 between the divided beams adjacent to each other (for example, between the divided beams 15a and 15b or between the divided beams 15b and 15c) is suppressed, and interference of the overlapped irradiation beams is suppressed. The intensity distribution can be made uniform.
[0057]
Further, since the M2 value of the laser oscillator 100 is set to at least N / 2 or more with respect to the division number N, the spatial coherent length X is N / 2 or less as described in the first embodiment. In spite of the fact that there is no difference in the optical path length, the interference between one or more divided components is skipped, for example, between the split beams 15a and 15c, between the split beams 15a and 15d, and between the split beams 15a and 15d. Interference between the split beams 15b and 15d, between the split beams 15b and 15e, and between the split beams 15c and 15e is suppressed during 15e. As a result, a uniform top hat beam can be obtained.
[0058]
By the way, in the case of the division by the waveguide described in the first embodiment, the divided beams are overlapped so as to be folded at the boundary. As a result, light components at the same location spatially overlap each other at the boundary, and as shown in FIG. 4, strong interference is observed at the end. On the other hand, in the configuration according to the present embodiment shown in FIG. 10 using the cylindrical lens array 5, the split beams are superimposed in parallel. In other words, when superimposing on the irradiation surface 90, there is no turn-back, and they are simply superimposed. That is, light at the same spatial position is not superimposed, and if the beam diameter is 1, components separated by 1 / N or more are always superimposed. The interference suppression effect by this is large, and effectively,
M2 ≧ N / 2
It has been found that if the condition (1) is satisfied, the interference between one or more divided components (between two adjacent components) can be sufficiently suppressed.
[0059]
In the above description, the case where the lens array is used for the division of the laser beam and the overlapping irradiation of the divided beams on the irradiation surface has been described, but the present invention is not limited to this. For example, any optical system that superimposes divided beams and homogenizes them, such as an optical system using a prism, a diffraction grating, a hologram, etc. Optical delay means for delaying one of the adjacent split beams with respect to the other longer than the temporal coherence length of the laser beam, and
M2 ≧ N / 2
By doing so, it is possible to prevent interference between all the divided beams due to superposition.
Further, the delay plate 2 is inserted every other N beams, and the M2 value is merely set to N / 2 or more. As shown in Patent Documents 3 and 4, all the divided beams are used. Since there is no need to provide an optical path difference, the configuration and adjustment are simple and easy. In addition, by setting the M2 value to be equal to or more than N / 2, interference between two beams other than those adjacent to each other can be reliably suppressed, so that stable homogeneous irradiation can be performed.
[0060]
Embodiment 8 FIG.
FIGS. 11A and 11B are plan views showing the configuration of a laser processing apparatus according to Embodiment 8 of the present invention, wherein FIG. 11A is a view as seen from the y direction, and FIG. 11B is a view as seen from the x direction.
In this embodiment mode, the laser processing apparatus shown in FIGS. 11A and 11B spreads uniformly on the irradiation surface in the y-direction and spreads in the x-direction in the same manner as in the seventh embodiment. An example of forming a linear irradiation profile converged linearly is shown.
[0061]
In the seventh embodiment, the case where the delay plate (optical delay means) 2 is used as the optical path length or polarization direction control means for changing the optical path length or polarization direction of the adjacent divided beams of the N divided beams adjacent to each other. However, in the present embodiment, the optical rotation means 7 is used which makes one of the adjacent split beams of the N split beams substantially orthogonal to the polarization direction of the other split beam.
The other configuration is the same as that of the seventh embodiment, and therefore, the differences from the seventh embodiment will be mainly described below.
[0062]
Half-wave plates 7 are inserted as optical rotation means into the split beams 15a to 15e split in the y direction from the splitting cylindrical lens array 5, and the half-wave plate 7 is provided with every other split beam 15a, 15c, 15d, but not into the other split beams 15b, 15d. Thereby, the polarization angles are substantially orthogonal between the divided beams adjacent to each other (for example, between the divided beams 15a and 15b, between the divided beams 15b and 15c, or between other adjacent divided beams). The interference on the irradiation surface 90 is suppressed, and the intensity distribution due to the interference of the superposed irradiation beams 19 can be made uniform.
[0063]
As described above, when every other half-wave plate 7 is inserted into the split beams, interference is prevented between two split beams of any combination adjacent to each other (for example, between the split beams 15a and 15c). However, it is not possible to prevent interference between two beams other than those adjacent to each other (for example, between the split beams 15a and 15c).
Therefore, also in the present embodiment, as described in the seventh embodiment, by setting the M2 value, which is an index indicating the condensing property of the beam generated from the laser oscillator 100, to N / 2 or more, Interference between all split beams is suppressed.
[0064]
Embodiment 9 FIG.
FIG. 12 is a plan view showing the configuration of the laser processing apparatus according to Embodiment 9 of the present invention, showing the arrangement of the optical system as viewed from the x direction, except for differences in the arrangement of the optical path length or polarization direction control means. This is basically the same as the laser processing apparatus shown in FIGS. 11A and 11B. Hereinafter, points different from the eighth embodiment will be mainly described.
[0065]
In the present embodiment, in the eighth embodiment shown in FIG. 11, the other split beam (15b, 15d in this example) into which no optical rotation means is inserted is used as an optical path length compensating means as a glass for the delay plate 2 I am inserting my body. As described above, the half-wave plate 7 is disposed as the optical rotation means for one of the split beams, but the interposition of the half-wave plate 7 extends the optical path length of the split beam, and the two types of split beams are used. If the split beam has a different optical path length, the imaging positions on the irradiation surface are shifted from each other, and the profile becomes unclear. In order to correct this, a delay plate 72 for extending the optical path length is provided in the other split beam as a means for compensating the optical path length. As the delay plate 2, one similar to that described in the first embodiment is used. For example, the optical glass plate is set to a thickness that produces the same optical path length as that of the half-wave plate 7.
[0066]
In the cylindrical lens array 51 for y-direction transfer, different focal lengths are set for the minute cylindrical lens for the divided beam with the half-wave plate 7 inserted and the minute cylindrical lens for the divided beam without the half-wave plate 7 inserted. May be provided to compensate for the optical path length.
[0067]
Embodiment 10 FIG.
13A and 13B are diagrams showing a configuration of a laser processing apparatus according to a tenth embodiment of the present invention, wherein FIG. 13A is a plan view seen from the y direction, FIG. 13B is a plan view seen from the x direction, and FIG. It is sectional drawing of a delay plate.
In this embodiment mode, the laser processing apparatus shown in FIGS. 13A and 13B spreads uniformly on the irradiation surface in the y direction and spreads in the x direction as in the first embodiment mode. An example of forming a linear irradiation profile converged linearly is shown.
[0068]
The laser processing apparatus includes a laser oscillator 100, a laser beam splitting unit, an overlapping irradiation unit, and an optical delay unit. The laser beam splitting unit intersects the x-direction cylindrical lens array and the y-direction cylindrical lens array at right angles. To form split beams that are two-dimensionally split. As another laser beam splitting means, a two-dimensional lens array can also be used. In this case, a single two-dimensional lens array is used instead of the x-direction cylindrical lens array 5 and the y-direction cylindrical lens array 52. By arranging, split beams can be formed two-dimensionally in the xy directions. Further, a rectangular parallelepiped having four main reflecting surfaces around an axis connecting the incident surface and the emitting surface and the incident surface and the emitting surface. The laser beam introduced from the incident surface is reflected by the four reflecting surfaces. Alternatively, a two-dimensional waveguide that emits a split beam from the exit surface may be used.
[0069]
In the present embodiment, the x-direction cylindrical lens array 5 and the y-direction cylindrical lens array 52 are arranged orthogonally to form a large number of two-dimensionally separated split beams in parallel.
The laser beam splitting unit further includes a magnifying lens 51 and a collimating lens 32 for making the laser beam incident on the cylindrical lens array 5, and the enlarged parallel laser beam is incident on the cylindrical lens array 5.
[0070]
The superposition irradiation means superimposes a large number of divided beams on the irradiation surface 90 of the irradiation object 9 to form an irradiation beam. Here, the superposition irradiation means is a transfer cylindrical in the y direction. Light is condensed in the x direction by the cylindrical lens array 5 and the x direction condensing lens 62 (cylindrical lens) in the x direction so that it can be transferred over a predetermined length on the irradiation surface by the lens array 51. As a result, an image is formed on the irradiation surface as an irradiation beam having a linear profile.
[0071]
In this embodiment, the laser beam 1 is incident on the dividing cylindrical lens array 5 by the magnifying lens 31 and the collimating lens 32 as laser beam dividing means. In this example, the divided beam is divided into five in the x direction. Is formed, and further divided by the y-direction cylindrical lens array 52 in the y-direction. _x × N _y To obtain a splittable two-dimensional split beam. Division number N _x , N _y Is preferably an appropriate number of 5 or more in either one or both, and particularly preferably 7 or more. In this embodiment, the division number N _x × N _y Are two-dimensional split beams of 5 × 5 combinations.
[0072]
Each of the two-dimensional split beams has a rectangular cross section and is parallel to each other, and then passes through the delay plate 2 as an optical delay unit, enters the y-direction transfer cylindrical lens array 51, and The image is transferred onto the irradiation surface 90 to a predetermined length.
[0073]
As shown in FIG. 13C, the delay plate 2 is configured such that the delay elements 20 and the gaps 290 are alternately arranged. Layer. Specifically, the delay elements 20 and the gaps 290 are alternately arranged in the y direction on the delay plate, and also in the x direction, the delay elements 20 and the gaps 290 are alternately arranged.
[0074]
In the arrangement of the delay elements 20 in the delay plate 2, one of the split beams adjacent to each other passes through the delay element, the other passes through the air layer of the gap, and an optical path difference is provided between the two. I have. Originally, adjacent split beams interfere with each other when irradiated on an irradiation surface. However, the arrangement of the delay elements of the delay plate is determined by overlapping irradiation means including a transfer cylindrical lens array 51 in the y direction. Interference between the divided beams irradiated on the irradiation surface is reduced, and fluctuation of the combined irradiation beam is prevented.
[0075]
As described above, when every other delay element 20 is inserted into the split beams, interference is prevented between any two split beams of any combination adjacent to each other, but two other beams other than those adjacent to each other are used. Interference between two beams cannot be prevented.
Therefore, also in the present embodiment, as described in the seventh embodiment, the M2 value, which is an index indicating the condensing property of the beam generated from the laser oscillator 100, is set to N in each division direction. _x / 2 and N _y By setting the ratio to / 2 or more, interference between all split beams is suppressed.
[0076]
Note that the laser beam from the laser oscillator is two-dimensionally two-dimensionally _x × N _y When the beam is divided into a plurality of divided beams, the M2 value in each of the divided directions is set to N _x / 2 and N _y / 2 or more, more preferably N _x And N _y With the above, interference between all the divided beams can be suppressed.
[0077]
By arranging the optical delay means before and after the transfer cylindrical lens array 51 separately for the first delay plate and the second delay plate, the surface on which the split beam is transferred and the surface on which the split beam is transferred are conjugated. They can be arranged in a relational manner, which has the advantage that the effects of diffraction on the illuminated surface can be minimized. Further, a third delay plate is disposed as a delay means between the cylindrical lens array 53 and the x-direction condenser lens 62, and an optical path difference Δa is provided between divided beams adjacent in the x direction. Thus, mutual interference on the irradiation surface may be reduced.
[0078]
Embodiment 11 FIG.
FIGS. 14A and 14B are diagrams showing a configuration of a laser processing apparatus according to Embodiment 11 of the present invention, wherein FIG. 14A is a plan view seen from the y direction, FIG. 14B is a plan view seen from the x direction, and FIG. It is sectional drawing of a half-wave plate.
In the tenth embodiment, the case has been described where the optical delay means (delay plate 2) is used as the optical path length or polarization direction control means for changing the optical path length or polarization direction of adjacent divided beams adjacent to each other. May be used. In this case, the M2 value in each division direction is set to N. _x / 2 and N _y By setting the ratio to / 2 or more, it is possible to suppress interference between all the divided beams.
[0079]
As shown in FIG. 14 (C), the optical rotation plate 7 in which the optical rotation element 70 and the air gap 290 are alternately arranged in the x direction and the y direction as shown in FIG. The optical rotation plate 7 is disposed in front of the divisional cylindrical lens arrays 5 and 52 so that the divided beam passes through the optical rotation element 70 and the divided beam adjacent thereto passes through the gap 290, respectively. As a result, adjacent split beams have substantially orthogonal polarization planes. For the optical rotation element 70 of the optical rotation plate 7, a crystal single crystal is preferably used from an optical rotation material, and as an optical half-wave plate, as shown in FIG. They are arranged.
[0080]
The split beam into which the optical rotation element 70 of the optical rotation plate 7 is inserted rotates the optical rotation surface and increases the optical path length when compared with the split beam passing only through the air gap. Above, a shift of the imaging position occurs due to the difference in the optical path length from the split beam.
Therefore, the optical rotation element 70 and the optical path length compensation delay element may be alternately arranged instead of the air gap 290 in FIG. 14C with the optical path length compensation delay element. An optical glass plate is used for the optical path length compensating delay element, and the thickness a of the optical path length compensating delay element becomes an optical path length substantially equal to the optical path length generated by the crystal half-wave plate serving as the optical rotation element 70. It is decided as follows. Due to the compensation of the optical path length, there is no shift of the image forming position by the transfer cylindrical lens array between the divided beams adjacent to each other, whereby a clear image is obtained, and the irradiation beam on the irradiation surface is A more uniform intensity distribution is obtained.
In the cylindrical lens array 51 for y-direction transfer, a minute cylindrical lens that passes a split beam that passes through the optical rotation element 70 of the optical rotation plate 7 and a minute cylindrical lens that passes a split beam that passes through a gap 290 that is an air layer. Alternatively, the optical path length may be compensated by providing different focal lengths.
[0081]
Embodiment 12 FIG.
15A and 15B are diagrams showing a configuration of a laser processing apparatus according to Embodiment 12 of the present invention, wherein FIG. 15A is a plan view viewed from a y direction, FIG. 15B is a plan view viewed from an x direction, and FIG. FIG. 3D is a cross-sectional view of a half-wave plate, and FIG.
[0082]
Arranging the delay means and the optical rotation means for transmitting the split beams in front of the laser beam splitting means can prevent interference on the irradiation surface between the split beams adjacent to each other. In the example shown in FIGS. 7A and 7B, both the optical rotation plate 7 and the delay plate 2 are arranged in front of the splitting cylindrical lens arrays 5 and 52, and in front of them. , A cylindrical lens array 51 for transfer in the y direction, a field lens 63, a transfer cylindrical lens array 62 in the x direction, and a condensing lens 62 in the x direction are arranged to irradiate the irradiation surface 90 with the split beam passing therethrough. An irradiation beam 19 of the shape profile is obtained.
[0083]
In this example, the optical rotation plate 7 has the optical rotation elements 70 and the gaps 290 arranged alternately in the x direction and separately in the y direction. As a result, the split beams from the splitting cylindrical lens arrays 5 and 52 have their polarization angles orthogonal to each other in the x direction by the optical rotation plate 7 but do not change in the y direction. As a result, it is possible to rotate the polarization angle between a certain split beam and a split beam that is adjacent to the split beam in an oblique direction. Since the optical rotation element 70 of the optical rotation plate 7 does not change the polarization angle in the y direction, in order to compensate for this, the delay plate 2 disposed in front of the optical rotation plate 7 has the same configuration as that of the tenth embodiment. , The delay element 20 and the air gap 290 are alternately arranged in the x direction and the y direction, and the divided beam adjacent in the x direction and the y direction has an optical path difference Δa.
[0084]
Therefore, the arrangement of the optical rotation plate 7 and the delay plate 2 is such that, for the divided beams adjacent in the x direction and the y direction, the interference is reduced by the optical path difference by the delay plate 2 and for the divided beams adjacent in the oblique direction. In addition, the optical rotation by the optical rotation plate prevents the interference, so that a certain split beam and all adjacent split beams surrounding the split beam can reduce mutual interference.
[0085]
In each of the above embodiments, the solid-state laser having a long spatial coherence distance and its harmonic laser have been described as examples of the laser light source. ₂ The same effect can be obtained by applying the present invention to a laser, an Ar laser, other gas lasers, and semiconductor lasers. On the other hand, an excimer laser is currently applied to the polycrystallization method of silicon, but in this case, the laser light source is homogenized by simply dividing using a lens array and simply overlapping. Excimer lasers have an oscillation wavelength in the ultraviolet region, while the beam extraction cross section is structurally large, on the order of several centimeters, and the M2 value is well over at least 100 in a system to which a normal stable oscillator is applied. The size is large, on the order of over 1000, and the spatial coherence length is extremely short. Further, since the spectrum width is extremely wide, the temporal coherent length is short. In that sense, excimer lasers are an exceptional laser light source characterized by a long temporal and spatial coherence length, and most lasers other than excimer lasers have difficulty in emitting a homogeneous beam. The present invention can be applied.
[0086]
【The invention's effect】
As described above, according to the present invention, at least one laser oscillator that generates a laser beam having an M2 value of 100 or less, which is an index indicating the condensing property of a beam generated from the laser oscillator, A laser beam splitting means for spatially splitting a laser beam into N split beams in a beam cross section, a superposition irradiation means for irradiating each of the split beams substantially superimposed on an irradiation surface, and dividing the laser beam into the N pieces Light path length or polarization direction control means for changing the optical path length or polarization direction of adjacent split beams of beams adjacent to each other, wherein the M2 value is at least M2 ≧ N / 2 in the beam split direction. The structure and adjustment for further uniformizing the irradiation beam by preventing interference between split beams due to Laser processing apparatus is obtained which enables the quality illumination.
[Brief description of the drawings]
FIGS. 1A and 1B are plan views showing a configuration of a laser processing apparatus according to a first embodiment of the present invention, in which FIG. 1A is a view seen from a y direction, and FIG.
FIG. 2 is a cross-sectional view illustrating a mode of dividing a laser beam in a waveguide.
FIG. 3 is a diagram illustrating a manner of dividing a laser beam in a waveguide.
FIG. 4 is a diagram illustrating an intensity distribution of a combined irradiation beam when two adjacent divided beams separated by a waveguide are superimposed on an irradiation surface.
FIG. 5 is a diagram illustrating a relationship between an M2 value and a spatial coherence distance.
FIGS. 6A and 6B are plan views showing the configuration of a laser processing apparatus according to a second embodiment of the present invention, wherein FIG. 6A is a view seen from a y direction, and FIG.
FIGS. 7A and 7B are plan views showing a configuration of a laser processing apparatus according to a fourth embodiment of the present invention, wherein FIG. 7A is a view as seen from a y direction, and FIG.
8A and 8B are plan views illustrating a configuration of a laser processing apparatus according to a fifth embodiment of the present invention, wherein FIG. 8A is a view as viewed from a y direction, and FIG. 8B is a view as viewed from an x direction.
FIGS. 9A and 9B are plan views illustrating a configuration of a laser processing apparatus according to a sixth embodiment of the present invention, wherein FIG. 9A is a view as viewed from a y direction, and FIG. 9B is a view as viewed from an x direction.
FIGS. 10A and 10B are plan views showing a configuration of a laser processing apparatus according to a seventh embodiment of the present invention, wherein FIG. 10A is a view as seen from a y direction, and FIG. 10B is a view as seen from an x direction.
FIGS. 11A and 11B are plan views illustrating a configuration of a laser processing apparatus according to an eighth embodiment of the present invention, wherein FIG. 11A is a view as viewed from a y direction, and FIG.
FIGS. 12A and 12B are plan views illustrating a configuration of a laser processing apparatus according to a ninth embodiment of the present invention, in which FIG. 12A is a diagram viewed from a y direction, and FIG.
13A and 13B are diagrams illustrating a configuration of a laser processing apparatus according to a tenth embodiment of the present invention, wherein FIG. 13A is a plan view viewed from a y direction, FIG. 13B is a plan view viewed from an x direction, and FIG. FIG. 3 is a sectional view of a delay plate.
14A and 14B are diagrams illustrating a configuration of a laser processing apparatus according to an eleventh embodiment of the present invention, wherein FIG. 14A is a plan view viewed from a y direction, FIG. 14B is a plan view viewed from an x direction, and FIG. Is a cross-sectional view of a half-wave plate.
15A and 15B are diagrams showing a configuration of a laser processing apparatus according to a twelfth embodiment of the present invention, wherein FIG. 15A is a plan view as viewed from a y direction, FIG. 15B is a plan view as viewed from an x direction, and FIG. Is a cross-sectional view of a half-wave plate, and (D) is a cross-sectional view of a delay plate.
[Explanation of symbols]
REFERENCE SIGNS LIST 100 laser oscillator, 2 delay plate, 20 delay element, 29 shield, 290 gap, 31 beam magnifying lens, 32 y-direction collimating lens, 33 x-direction collimating lens, 34 focusing lens, 4 waveguide, 41 reflecting surface, 42 Reflective surface, 5 split cylindrical lens array, 51 transfer cylindrical lens array, 61 transfer lens, 62 condensing lens, 7 half-wave plate (optical rotation plate), 70 optical rotation element, 9 irradiated object, 90 irradiation surface.

Claims (7)

At least one laser oscillator that generates a laser beam having an M2 value of 100 or less, which is an index indicating the light condensing property of the beam generated from the laser oscillator, and N laser beams from the laser oscillator spatially in a beam cross section A laser beam splitting means for splitting the split beams into a plurality of split beams, a superimposing irradiation means for irradiating the split beams approximately on the irradiation surface, and an optical path length of the adjacent split beams of the N split beams. Or with an optical path length or polarization direction control means that changes the polarization direction,
When the M2 value is at least M2 ≧ N / 2 in the beam splitting direction.
A laser processing apparatus, characterized in that: 2. A laser processing apparatus according to claim 1, wherein said laser beam splitting means spatially splits a laser beam from a laser oscillator into N split beams in a beam cross section using reflecting surfaces facing each other. 2. The laser beam splitting means according to claim 1, wherein said laser beam splitting means splits a laser beam from a laser oscillator into N split beams one-dimensionally or two-dimensionally in a beam cross section by using reflecting surfaces facing each other. Laser processing equipment. When the M2 value is M2 ≧ N at least in the beam splitting direction.
3. The laser processing apparatus according to claim 2, wherein The optical path length or polarization direction control means includes an optical delay means for delaying one of adjacent split beams of the N split beams with respect to the other, longer than the temporal coherence length of the laser beam. The laser processing apparatus according to claim 1, further comprising: The optical path length or polarization direction control means includes optical rotation means for making one of adjacent divided beams of the N divided beams substantially orthogonal to the polarization direction with respect to the other. 2. The laser processing apparatus according to 1. 2. The laser processing apparatus according to claim 1, wherein the laser oscillator generates a fundamental wave or a harmonic of a solid-state laser or a semiconductor laser.

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