Laser processing equipment

Abstract

To provide a laser processing device capable of processing a processed material in a desired shape without reducing an energy of a laser beam contributed to processing.SOLUTION: A laser beam irradiation unit 20 of a laser processing device, includes: a laser oscillator 21; an image forming element 23 that forms an image of a laser beam 201 ejected from the laser oscillator 21 on a processed material 100; and a phase modulation unit 22 that generates a phase difference in the laser beam 201 so as to be distributed between the laser oscillator 21 and the image forming element 23 and so that a laser beam 203 forms an intensity distribution along a Gauss distribution in an X-shaft direction parallel to a division scheduled line set on the processed material 100 and the laser beam 203 forms the intensity distribution along a top hat shape at an image forming point in a Y-shaft direction being a width direction of the division scheduled line set on the processed material 100.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a laser processing apparatus. [Background Art]

[0002] As a means for singulating a workpiece such as a semiconductor wafer, blade dicing, in which a thin disk-shaped blade rotated at high speed is caused to cut into the workpiece, is generally used. On the other hand, in recent years, laser dicing, in which a workpiece is diced by irradiating a laser beam along lines to divide, has also been developed and put into practical use. For this laser dicing, a technique has been proposed in which the imaging shape of a laser beam on a workpiece is deformed into a desired shape using a mask to adjust a processing line (see, for example, Patent Document 1). [Prior Art Literature] [Patent Literature]

[0003] [Patent Document 1] Japanese Unexamined Patent Application Publication No. 2010-089094 [Summary of Invention] [Problem to be Solved by the Invention]

[0004] When the method of Patent Document 1 is used, a workpiece can be processed into a desired shape; however, since most of the laser beam is blocked by the mask, there has been a problem that less energy can be contributed to processing.

[0005] The present invention has been made in view of such problems, and an object thereof is to provide a laser processing apparatus capable of processing a workpiece into a desired shape without reducing the energy of a laser beam that contributes to processing. [Means for Solving the Problem]

[0008] aboveTo solve the problems described above and achieve the objective, the present invention provides a laser processing apparatus that processes a workpiece having a plurality of intersecting division lines by irradiating a laser beam along the division lines, comprising: a holding table for holding the workpiece; a laser beam irradiation unit for irradiating a laser beam onto the workpiece held on the holding table; an X-axis movement unit for relative processing feed of the workpiece and the imaging point of the laser beam in the X-axis direction; and a Y-axis movement unit for relative indexing feed of the workpiece and the imaging point of the laser beam in the Y-axis direction perpendicular to the X-axis direction, wherein the laser beam irradiation unit comprises a laser oscillator and the laser The device comprises an imaging element that images a laser beam emitted from a laser oscillator, and a first phase plate and a second phase plate disposed between the laser oscillator and the imaging element, which create a phase difference in the laser beam such that the laser beam forms an intensity distribution along a Gaussian distribution in the X-axis direction parallel to the division line set on the workpiece, and the laser beam forms an intensity distribution along a top-hat shape at the imaging point in the Y-axis direction which is the width direction of the division line set on the workpiece, wherein the first phase plate and the second phase plate are configured to be relatively movable, and the amount of movement is adjusted based on the beam diameter of the laser beam incident on the first phase plate and the second phase plate.

[0009] The first phase plate and the second phase plate are configured to have a thicker region and a thinner region, the thicker region of the first phase plate facing the thinner region of the second phase plate, and the width of the top hat shape may be adjusted by adjusting the width of the overlap between the thin region of the first phase plate and the thin region of the second phase plate. [Effects of the Invention]

[0010] This invention achieves a top-hat shape by changing the intensity distribution of the laser beam from a Gaussian distribution to an Airy disk pattern using a phase modulation unit, without using a mask that reduces the energy of the laser beam by 60% to 70% as in conventional methods, and then imaging the beam. Therefore, it is possible to laser process a workpiece into a desired shape without reducing the energy of the laser beam that contributes to the laser processing. [Brief explanation of the drawing]

[0011] [Figure 1] Figure 1 is a perspective view showing an example of the configuration of a laser processing apparatus according to Embodiment 1. [Figure 2] Figure 2 is a cross-sectional view showing an example of the configuration of the laser beam irradiation unit in Figure 1. [Figure 3] Figure 3 is a graph illustrating an example of the intensity distribution of the laser beam emitted by the laser oscillator shown in Figure 2. [Figure 4] Figure 4 is a perspective view showing the phase modulation unit in Figure 2. [Figure 5] Figure 5 is a top view showing the phase modulation unit in Figure 2. [Figure 6] Figure 6 is a graph illustrating an example of the intensity distribution of the laser beam formed by the laser beam irradiation unit shown in Figure 2. [Figure 7] Figure 7 is a graph illustrating an example of the intensity distribution of the laser beam formed by the laser beam irradiation unit shown in Figure 2. [Figure 8] Figure 8 is a top view illustrating an example of the intensity profile of the laser beam formed by the laser beam irradiation unit shown in Figure 2. [Figure 9] Figure 9 is a top view illustrating an example of an imaging point of the laser beam formed by the laser beam irradiation unit shown in Figure 2. [Figure 10] Figure 10 is a cross-sectional view showing an example of the configuration of the laser beam irradiation unit of a laser processing apparatus according to Embodiment 2. [Figure 11] Figure 11 is a perspective view showing the phase modulation unit in Figure 10. [Figure 12] Figure 12 shows the bottom and top views of the phase modulation unit shown in Figure 10. [Figure 13] Figure 13 is a graph illustrating an example of the intensity distribution of the laser beam formed by the laser beam irradiation unit of a modified laser processing apparatus. [Figure 14] Figure 14 is a graph illustrating an example of the intensity profile of the laser beam formed by the laser beam irradiation unit of a modified laser processing apparatus. [Figure 15] Figure 15 is a graph illustrating another example of the intensity distribution of the laser beam formed by the laser beam irradiation unit of a modified laser processing apparatus. [Figure 16] Figure 16 is a graph illustrating another example of the intensity profile of the laser beam formed by the laser beam irradiation unit of a modified laser processing apparatus. [Modes for carrying out the invention]

[0012] Embodiments for carrying out the present invention will be described in detail with reference to the drawings. The present invention is not limited to the contents described in the following embodiments. Furthermore, the components described below include those that can be easily imagined by those skilled in the art, and those that are substantially the same. In addition, the configurations described below can be combined as appropriate. Furthermore, various omissions, substitutions, or modifications of the configurations can be made without departing from the spirit of the present invention.

[0013] [Embodiment 1] A laser processing apparatus 1 according to Embodiment 1 of the present invention will be described based on the drawings. Figure 1 is a perspective view showing an example of the configuration of the laser processing apparatus 1 according to Embodiment 1. As shown in Figure 1, the laser processing apparatus 1 according to Embodiment 1 comprises a holding table 10, a laser beam irradiation unit 20, an imaging unit 30, an X-axis movement unit 41, a Y-axis movement unit 42, a Z-axis movement unit 43, a display unit 50, an input unit 60, and a control unit 70.

[0014] As shown in FIG. 1, the workpiece 100 to be processed by the laser processing apparatus 1 according to Embodiment 1 is, for example, a disk-shaped semiconductor wafer or an optical device wafer using silicon, sapphire, silicon carbide (SiC), gallium arsenide, glass or the like as a base material. As shown in FIG. 1, in the workpiece 100, chip-sized devices 103 are formed in regions partitioned by a plurality of planned dividing lines 102 formed (set) in a grid pattern on the flat surface 101. In Embodiment 1, as shown in FIG. 1, an adhesive tape 105 is attached to the back surface 104 opposite the front surface 101 of the workpiece 100, and an annular frame 106 is attached to the outer edge of the adhesive tape 105, but the present invention is not limited thereto. In addition, in the present invention, the workpiece 100 may also be a rectangular package substrate having a plurality of resin-sealed devices, a ceramic plate, a glass plate, or the like.

[0015] The holding table 10 includes a disk-shaped frame body with a recess formed therein, and a disk-shaped suction part fitted into the recess. The suction part of the holding table 10 is formed of porous ceramic or the like having a large number of porous holes, and is connected to a vacuum suction source (not shown) via a vacuum suction path (not shown). As shown in FIG. 1, the upper surface of the suction part of the holding table 10 is a holding surface 11 on which the workpiece 100 is placed, and which sucks and holds the placed workpiece 100 by negative pressure introduced from the vacuum suction source. In Embodiment 1, the workpiece 100 is placed on the holding surface 11 with the surface 101 facing upward, and the holding surface 11 sucks and holds the placed workpiece 100 from the back surface 104 side via the adhesive tape 105. The holding surface 11 and the upper surface of the frame body of the holding table 10 are arranged on the same plane, and are formed parallel to the horizontal XY plane.

[0016] The holding table 10 is provided to move freely in the X-axis direction parallel to the horizontal direction by the X-axis movement unit 41, and is provided to move freely in the Y-axis direction parallel to the horizontal direction and perpendicular to the X-axis direction by the Y-axis movement unit 42. By moving the holding table 10 along the X-axis direction and Y-axis direction by the X-axis movement unit 41 and the Y-axis movement unit 42, respectively, the workpiece 100 held on the holding table 10 is moved in the X-axis direction and Y-axis direction relative to the imaging point 330 (see Figure 2) of the laser beam 203 (see Figure 2) formed by the laser beam irradiation unit 20 and the imaging unit 30, respectively. The holding table 10 is provided to move freely around the Z-axis parallel to the vertical direction and perpendicular to the XY plane by a rotation drive source (not shown). The holding table 10 is rotated appropriately by the rotation drive source so that the orientation around the Z-axis is adjusted so that the division line 102 in any one direction of the workpiece 100 held on the holding surface 11 is parallel to the X-axis direction.

[0017] Figure 2 is a cross-sectional view showing an example configuration of the laser beam irradiation unit 20 in Figure 1. Figure 3 is a graph illustrating an example of the intensity distribution of the laser beam 201 emitted from the laser oscillator 21 in Figure 2. Figures 4 and 5 are perspective and top views, respectively, of the phase modulation unit 22 in Figure 2. Figures 6 and 7 are graphs illustrating an example of the intensity distribution of the laser beams 202 and 203 formed by the laser beam irradiation unit 20 in Figure 2. Figure 8 is a top view illustrating an example of the intensity profile of the laser beam 203 formed by the laser beam irradiation unit 20 in Figure 2. Figure 9 is a top view illustrating an example of the imaging point 330 of the laser beam 203 formed by the laser beam irradiation unit 20 in Figure 2. Note that in the graphs shown in Figures 3, 6, and 7, the horizontal axis represents the position in the Y-axis direction, which is the width direction of the planned division line 102 with the optical axis as the origin, and the vertical axis represents the intensity of the laser beams 201, 202, and 203, respectively. Furthermore, Figure 8 shows that within the frame, the horizontal direction of the paper represents the position in the X-axis direction parallel to the planned division line 102, the vertical direction of the paper represents the position in the Y-axis direction, and the color density represents the intensity of the laser beam 203. The higher the color density, the higher the intensity of the laser beam 203.

[0018] As shown in Figure 2, the laser beam irradiation unit 20 includes a laser oscillator 21, a phase modulation unit 22, and an imaging element 23. The laser oscillator 21 emits a laser beam 201 with a wavelength absorbed by the workpiece 100 towards the workpiece 100 held on the holding table 10 along the Z-axis. The laser beam 201 forms an intensity distribution 301 along a Gaussian distribution both in the X-axis direction and in the Y-axis direction, as shown in Figure 3, with respect to the optical axis. In Embodiment 1, the laser beam 201 is, for example, pulsed with a beam diameter of 5 mm and a wavelength of 355 nm, but the present invention is not limited to this.

[0019] As shown in Figure 2, the phase modulation unit 22 is positioned on the optical path of the laser beam 201 emitted from the laser oscillator 21, between the laser oscillator 21 and the imaging element 23. As shown in Figures 2, 4, and 5, the phase modulation unit 22 is a phase plate that can adjust the phase of light, formed in the shape of a plate sufficiently larger than the beam diameter of the laser beam 201 in both the X-axis and Y-axis directions, and having a pair of first and second surfaces 25 and 26 that are parallel to the XY plane and perpendicular to the optical axis of the laser beam 201 emitted from the laser oscillator 21. For example, the phase modulation unit 22 is made of synthetic quartz with a refractive index of 1.449 formed in the shape of a plate with a thickness of 6 mm. The first surface 25 is oriented upward in the Z-axis direction, and the second surface 26 is oriented downward in the Z-axis direction.

[0020] The phase modulation unit 22 has a recess 27 formed on its first surface 25 such that it forms an intensity distribution 302 along an Airy disk pattern as shown in Figure 6 in the Y-axis direction. Specifically, the recess 27 is a groove that extends sufficiently longer than the beam diameter of the laser beam 201 in the X-axis direction, is symmetrical with respect to a plane parallel to the X-axis that contains the optical axis of the laser beam 201, and has a rectangular cross-sectional shape along the YZ plane. The width 28 of the recess 27 in the Y-axis direction is a predetermined length that allows the laser beam 201 to straddle the recess 27 in the width direction, i.e., narrower than the beam diameter of the laser beam 201. The width 28 of the recess 27 is determined based on the beam diameter of the laser beam 201 and a desired value of the top-hat shape width 310 (see Figure 7) of the intensity distribution 303 (see Figure 7) of the laser beam 203 that irradiates the workpiece 100, which will be described later.

[0021] The depth 29 of the recess 27 in the Z-axis direction is a predetermined length that allows a predetermined phase difference (e.g., a phase difference of π / 2) to be generated with respect to the laser beam 201 passing through the phase modulation unit 22, due to the difference in thickness of the laser beam 201 in the optical axis direction being equivalent to the depth 29 formed by the recess 27. The depth 29 of the recess 27 is determined according to the refractive index of the substrate of the phase modulation unit 22; for example, if the substrate of the phase modulation unit 22 is synthetic quartz, it is approximately 395 nm.

[0022] Since the phase modulation unit 22 has a recess 27 of this shape, with respect to the laser beam 201 incident from the first surface 25, the laser beam 201 does not cross the step created by the recess 27 in the X-axis direction in which the recess 27 extends, so no phase modulation occurs. However, in the Y-axis direction in which the step is formed by the recess 27, the laser beam 201 crosses the step created by the recess 27, so a phase difference is created by the step in the recess 27, causing phase modulation and forming an intensity distribution 302 along the Airy disk pattern. As a result, the phase modulation unit 22 can create a phase difference in the laser beam 201 incident from the first surface 25 so that in the X-axis direction, an intensity distribution 301 along a Gaussian distribution similar to that of the laser beam 201 is formed, and in the Y-axis direction, an intensity distribution 302 along the Airy disk pattern is formed.

[0023] When the laser beam 201 is incident on the first surface 25 of the phase modulation unit 22, the laser beam 202 is emitted from the second surface 26, forming an intensity distribution 301 along a Gaussian distribution in the X-axis direction and an intensity distribution 302 along an Airy disk pattern in the Y-axis direction. The intensity distribution 302 along the Airy disk pattern is then imaged by the imaging element 23, as will be described later, to form an intensity distribution 303 along a top-hat shape at the imaging point 330, as shown in Figure 7.

[0024] In Embodiment 1, the phase modulation unit 22 has a recess 27 formed on the first surface 25, but the present invention is not limited to this, and a convex portion may be formed on the first surface 25. In this case, the convex portion extends along the X-axis direction, has a rectangular cross-sectional shape along the YZ plane, has a width the same as the width 28 of the recess 27, and has a height the same as the depth 29 of the recess 27. Even when a convex portion is formed instead of a recess 27 in this way, the phase modulation unit 22 causes the same phase modulation as when a recess 27 is formed. Therefore, when a laser beam 201 is incident on the first surface 25, the laser beam 202 is emitted from the second surface 26, forming an intensity distribution 301 along a Gaussian distribution in the X-axis direction and an intensity distribution 302 along an Airy disk pattern in the Y-axis direction. Furthermore, the phase modulation unit 22 is not limited to these in the present invention, and the recesses 27 and protrusions may be formed on the second surface 26 instead of the first surface 25, or they may be formed on both the first surface 25 and the second surface 26.

[0025] Furthermore, the phase modulation unit 22 may have a recess 27 with a depth 29 equal to the plate thickness of the phase modulation unit 22. That is, the phase modulation unit 22 may have a gap formed in the optical axis direction of the laser beam 201 with a width similar to the width 28 in the Y axis direction, and the laser beam 201 may pass through the phase plate only on the outer circumference in the Y axis direction.

[0026] The imaging element 23 images the laser beam 202 emitted from the laser oscillator 21 and whose phase has been modulated by the phase modulation unit 22, and images it onto the workpiece 100 held on the holding table 10 to form an imaging point 330. In this way, the imaging element 23 images the laser beam 202, which forms an intensity distribution 301 along a Gaussian distribution in the X-axis direction and an intensity distribution 302 along an Airy disk pattern in the Y-axis direction, thereby forming a laser beam 203 that forms an intensity distribution 301 along a Gaussian distribution in the X-axis direction and an intensity distribution 303 along a top-hat shape in the Y-axis direction, as shown in Figure 7.

[0027] The width 310 of the top hat shape of the strength distribution 303 is formed to a desired value equivalent to the groove width of the machined groove formed along the planned division line 102, by appropriately setting the width 28 of the recess 27.

[0028] As shown in Figure 8, the laser beam 203 formed via the imaging element 23 forms an intensity profile 320 with a width 310 equivalent to the width of the intensity distribution 303 in the Y-axis direction. When irradiated onto the planned division line 102 of the workpiece 100, it forms an imaging point 330 with a shape equivalent to the intensity profile 320, as shown in Figure 9.

[0029] The laser beam irradiation unit 20 emits a laser beam 201 from the laser oscillator 21 that forms an intensity distribution 301 along a Gaussian distribution. Through the phase modulation unit 22 and imaging element 23, it forms a laser beam 203 that forms an intensity distribution 301 along a Gaussian distribution in the X-axis direction and an intensity distribution 303 along a top-hat shape in the Y-axis direction. The laser beam 203 is then irradiated onto the workpiece 100 held on the holding table 10, forming an image point 330 on the workpiece 100.

[0030] The imaging element 23 included in the laser beam irradiation unit 20 is provided so as to be movable in the Z-axis direction by the Z-axis direction movement unit 43. By moving along the Z-axis direction by the Z-axis direction movement unit 43, the imaging element 23 included in the laser beam irradiation unit 20 moves the imaging point 330 of the laser beam 203 formed by the laser beam irradiation unit 20 and the imaging unit 30 relative to the workpiece 100 held on the holding table 10 in the Z-axis direction.

[0031] The imaging unit 30 is equipped with an image sensor that images the surface 101 of the workpiece 100 held on the holding table 10, the division line 102, the processing groove formed on the surface 101, etc. The image sensor is, for example, a CCD (Charge-Coupled Device) image sensor or a CMOS (Complementary MOS) image sensor. In Embodiment 1, the imaging unit 30 is positioned adjacent to the laser beam irradiation unit 20 so as to move integrally with the imaging element 23 included in the laser beam irradiation unit 20.

[0032] The imaging unit 30 takes a picture of the workpiece 100 held on the holding table 10 before laser processing, and obtains an image for performing alignment, such as aligning the workpiece 100 with the laser beam irradiation unit 20 (image point 330), and outputs the obtained image to the control unit 70. The imaging unit 30 also takes a picture of the workpiece 100 held on the holding table 10 after laser processing, and obtains an image for performing a so-called kerf check, such as automatically checking whether the processed groove is within the planned division line 102 and whether any large chips have occurred, and outputs the obtained image to the control unit 70.

[0033] The X-axis movement unit 41 feeds the workpiece 100 held on the holding table 10 and the imaging point 330 of the laser beam 203 irradiated by the laser beam irradiation unit 20 relatively in the X-axis direction. The Y-axis movement unit 42 indexes and feeds the workpiece 100 held on the holding table 10 and the imaging point 330 of the laser beam 203 irradiated by the laser beam irradiation unit 20 relatively in the Y-axis direction. The Z-axis movement unit 43 moves the workpiece 100 held on the holding table 10 and the imaging point 330 of the laser beam 203 irradiated by the laser beam irradiation unit 20 relatively in the Z-axis direction. The X-axis movement unit 41, the Y-axis movement unit 42, and the Z-axis movement unit 43 detect the relative positions of the holding table 10 and the laser beam irradiation unit 20 in the X-axis, Y-axis, and Z-axis directions, and output the detected relative positions to the control unit 70.

[0034] The display unit 50 is mounted on a cover (not shown) of the laser processing apparatus 1, with its display surface facing outwards. It displays, for the operator's viewing convenience, screens showing settings such as the irradiation conditions of the laser beam 203 of the laser processing apparatus 1, as well as screens showing the results of processing including alignment, autofocus, automatic light intensity adjustment, and kerf check. The display unit 50 is composed of a liquid crystal display device or the like. The display unit 50 is equipped with an input unit 60 used by the operator to input command information such as various operations of the laser processing apparatus 1, laser beam irradiation conditions, and image display. The input unit 60 provided on the display unit 50 is composed of at least one of a touch panel provided on the display unit 50 and a keyboard or the like.

[0035] The control unit 70 controls the operation of each component of the laser processing apparatus 1 to irradiate the workpiece 100 with a laser beam 203 and perform laser processing, etc. In Embodiment 1, the control unit 70 includes a computer system. The computer system included in the control unit 70 has an arithmetic processing unit having a microprocessor such as a CPU (Central Processing Unit), a storage device having memory such as ROM (Read Only Memory) or RAM (Random Access Memory), and an input / output interface device. The arithmetic processing unit of the control unit 70 performs arithmetic processing according to the computer program stored in the storage device of the control unit 70 and outputs control signals for controlling the laser processing apparatus 1 to each component of the laser processing apparatus 1 via the input / output interface device of the control unit 70.

[0036] An example of the operation process of the laser processing apparatus 1 according to Embodiment 1 will be described. First, the laser processing apparatus 1 holds the workpiece 100 on the holding surface 11 with the holding table 10, rotates the holding table 10 with the rotation drive source to adjust the planned division line 102 in one direction of the workpiece 100 on the holding table 10 so that it is parallel to the X-axis direction, and performs alignment by taking an image of the workpiece 100 on the holding table 10 with the imaging unit 30 to align the workpiece 100 with the laser beam irradiation unit 20 (imaging point 330).

[0037] Next, the laser processing apparatus 1 irradiates the workpiece 100, which is held on the holding table 10, with a laser beam 203 that forms an intensity distribution 301 along a Gaussian distribution in the X-axis direction and an intensity distribution 303 along a top-hat shape in the Y-axis direction using a laser beam irradiation unit 20, and feeds the workpiece 100, which is held on the holding table 10, along the planned division line 102 relative to the imaging point 330 of the laser beam 203 using an X-axis movement unit 41, thereby laser processing the workpiece 100 along the planned division line 102 with the laser beam 203 (so-called ablation processing).

[0038] The laser processing apparatus 1 according to Embodiment 1, having the above configuration, does not use a mask that reduces the energy of the laser beam by 60% to 70% as in the conventional method. Instead, it uses a phase modulation unit 22 (phase plate) to change the intensity distribution of the laser beam from a Gaussian distribution to an Airy disk pattern, and then forms an image to achieve a top-hat shape at the imaging point 330. This provides the advantage of being able to laser process the workpiece 100 in a desired shape without reducing the energy of the laser beam that contributes to the laser processing.

[0039] Furthermore, the laser processing apparatus 1 according to Embodiment 1 suppresses damage to the device 103 and uneven wear of the cutting blade during subsequent blade dicing processes by making the intensity distribution in the width direction (Y-axis direction) of the division line 102 formed on the workpiece 100 a top-hat shape, while efficiently removing evaluation elements such as TEGs (Test Element Groups) present on the division line 102 by making the intensity distribution in the processing feed direction (X-axis direction) along the division line 102 a Gaussian distribution.

[0040] Furthermore, in the laser processing apparatus 1 according to Embodiment 1, the phase modulation unit 22 has recesses 27 or protrusions formed so as to form an Airy disk pattern in the Y-axis direction. Therefore, it is possible to suitably realize irradiation of a laser beam 203 in which the intensity distribution in the X-axis direction is formed as a Gaussian distribution and the intensity distribution in the Y-axis direction is formed as a top-hat shape.

[0041] [Embodiment 2] A laser processing apparatus 1-2 according to Embodiment 2 of the present invention will be described based on the drawings. Figure 10 is a cross-sectional view showing an example of the configuration of the laser beam irradiation unit 20-2 of the laser processing apparatus 1-2 according to Embodiment 2. Figure 11 is a perspective view showing the phase modulation unit 22-2 of Figure 10. Figure 12 is a bottom view and a top view showing the phase modulation unit 22-2 of Figure 10. In Figure 12, the upper side of the paper shows a bottom view of the first phase plate 81, and the lower side of the paper shows a top view of the second phase plate 82. Figures 10 to 12 use the same reference numerals as Embodiment 1, and their descriptions are omitted.

[0042] The laser processing apparatus 1-2 according to Embodiment 2 is the same as that of Embodiment 1, but with the laser beam irradiation unit 20 replaced by a laser beam irradiation unit 20-2. The laser beam irradiation unit 20-2 is the same as that of Embodiment 1, but with the phase modulation unit 22 replaced by a phase modulation unit 22-2. The laser processing apparatus 1-2 according to Embodiment 2 is the same as that of Embodiment 1 described above in other respects.

[0043] Similar to the phase modulation unit 22, the phase modulation unit 22-2 emits a laser beam 202 from the second surface 89 that, when a laser beam 201 is incident from the first surface 86, forms an intensity distribution 301 along a Gaussian distribution in the X-axis direction and an intensity distribution 302 along an Airy disk pattern in the Y-axis direction.

[0044] As shown in Figure 10, the phase modulation unit 22-2 includes a first phase plate 81, a second phase plate 82, and a moving part 83. As shown in Figures 10, 11, and 12, the first phase plate 81 is formed in a plate shape and has a thicker region 84 and a thinner region 85. The first phase plate 81 has a first surface 86 parallel to the XY plane, and on the surface opposite to the first surface 86, a step with a depth of 92 in the Z-axis direction is formed at the boundary between region 84 and region 85. As shown in Figures 10, 11, and 12, the second phase plate 82 is formed in a plate shape and has a thicker region 87 and a thinner region 88. The second phase plate 82 has a second surface 89 parallel to the XY plane, and on the surface opposite to the second surface 89, a step with a depth of 93 in the Z-axis direction is formed at the boundary between region 87 and region 88. Regions 85 and 88 have a wider width in the Y-axis direction than regions 84 and 87. The first phase plate 81 and the second phase plate 82 are both made of the same material as the phase modulation unit 22 in Embodiment 1, for example, and are formed into plates of roughly the same size and thickness. Depths 92 and 93 are set to be the same in Embodiment 2, for example, about half the depth 29 of Embodiment 1.

[0045] As shown in Figures 10, 11, and 12, the first phase plate 81 and the second phase plate 82 are arranged such that the region 84 of the first phase plate 81 faces the region 88 of the second phase plate 82, the region 87 of the second phase plate 82 faces the region 85 of the first phase plate 81, and the region 85 of the first phase plate 81 and the region 88 of the second phase plate 82 overlap in the Z-axis direction. The first phase plate 81 is positioned above the second phase plate 82 such that its first surface 86 faces upward in the Z-axis direction, and the stepped surface opposite to the first surface 86 faces the stepped surface opposite to the second surface 89 of the second phase plate 82 in the Z-axis direction. The second phase plate 82 is positioned below the first phase plate 81 such that its second surface 89 is oriented downward in the Z-axis direction, and its stepped surface opposite to the second surface 89 faces the stepped surface of the first phase plate 81 opposite to the first surface 86 in the Z-axis direction.

[0046] The moving unit 83 supports the first phase plate 81 and the second phase plate 82 so that they can move relative to each other in the Y-axis direction. The moving unit 83 moves the first phase plate 81 and the second phase plate 82 relative to each other in the Y-axis direction so that the boundary (step) between region 84 and region 85 and the boundary (step) between region 87 and region 88 are symmetric with respect to a plane that includes the optical axis of the laser beam 201 and is parallel to the X-axis, that is, so that the region where region 85 of the first phase plate 81 and region 88 of the second phase plate 82 overlap in the Z-axis direction is symmetric with respect to a plane that includes the optical axis of the laser beam 201 and is parallel to the X-axis. For example, when the moving unit 83 moves the first phase plate 81 in a direction approaching the optical axis of the laser beam 201, it also moves the second phase plate 82 in a direction approaching the optical axis of the laser beam 201. Furthermore, when the moving unit 83 moves the first phase plate 81 in a direction away from the optical axis of the laser beam 201, it also moves the second phase plate 82 in a direction away from the optical axis of the laser beam 201. The moving unit 83 is controlled by the control unit 70.

[0047] In the phase modulation unit 22-2, based on the beam diameter of the laser beam 201 incident on the first phase plate 81 and the second phase plate 82, and a desired value for the width 310 of the top-hat shape of the intensity distribution 303 of the laser beam 203 irradiating the workpiece 100, the width 91 in the Y-axis direction of the region where the region 85 of the first phase plate 81 and the region 88 of the second phase plate 82 overlap in the Z-axis direction is determined, and based on this width 91, the amount of movement of the first phase plate 81 and the second phase plate 82 by the movement amount 83 is determined. By adjusting the amount of movement of the first phase plate 81 and the second phase plate 82 by the movement amount 83, the phase modulation unit 22-2 can adjust the width 91 to adjust the width 310 of the top-hat shape of the intensity distribution 303 of the laser beam 203 irradiating the workpiece 100 to a desired value. In Embodiment 2, the width 91 is adjusted to, for example, the same extent as the width 28 of the recess 27 in Embodiment 1.

[0048] Furthermore, the phase modulation unit 22-2 may have the thickness of the thin region 85 of the first phase plate 81 set to 0, and the thickness of the thin region 88 of the second phase plate 82 set to 0. That is, the phase modulation unit 22-2 may be configured such that the first phase plate 81 consists only of the thick region 84, and the second phase plate 82 consists only of the thick region 87, so that the laser beam 201 passes through the phase plates (regions 84, 87) only on the outer periphery in the Y-axis direction.

[0049] The laser processing apparatus 1-2 according to this second embodiment is a modified version of the first embodiment in which the phase modulation unit 22 is replaced with a phase modulation unit 22-2. Similar to the second embodiment, when a laser beam 201 is incident on the first surface 86 of the second embodiment, the phase modulation unit 22-2 emits a laser beam 202 from the second surface 89 that forms an intensity distribution 301 along a Gaussian distribution in the X-axis direction and an intensity distribution 302 along an Airy disk pattern in the Y-axis direction. Therefore, the laser processing apparatus 1-2 according to the second embodiment achieves the same effects as the first embodiment.

[0050] The laser processing apparatus 1-2 according to Embodiment 2 further has a phase modulation unit 22-2 which has a first phase plate 81 and a second phase plate 82 that are relatively movable in the Y-axis direction. By adjusting the amount of movement of these plates, the width 91 in the Y-axis direction of the region where the thin-thickness region 85 of the first phase plate 81 and the thin-thickness region 88 of the second phase plate 82 overlap in the Z-axis direction can be adjusted to accommodate various beam diameters of the laser beam 201 emitted by the laser oscillator 21. This allows for laser processing with a changed beam diameter and can also compensate for deterioration of the laser oscillator 21 and machine differences in the apparatus.

[0051] [Variation] A modified example of the present invention, a laser processing apparatus 1,1-2, will be described based on the drawings. Figures 13 and 14 are graphs illustrating examples of the intensity distribution and intensity profile of the laser beam 203 formed by the laser beam irradiation units 20,20-2 of the modified laser processing apparatus 1,1-2, respectively. The horizontal and vertical axes in Figures 13 and 15 are the same as those in Figures 3, 6, and 7. The horizontal, vertical, and brightness directions of the paper in Figures 14 and 16 are the same as those in Figure 8. Figures 13 to 16 use the same reference numerals as embodiments 1 and 2, and their descriptions are omitted.

[0052] When the beam diameter of the laser beam 201 is targeted to 0.9 mm, and various widths and depths of the phase modulation units 22 and 22-2 of the laser beam irradiation units 20 and 20-2 are set so that a laser beam 203 with intensity distribution 303 and intensity profile 320 is formed, if the beam diameter of the laser beam 201 is increased to 1.4 mm, which is larger than the target, then for the laser beam 203, an intensity distribution 304 and intensity profile 324 are obtained in which the peak is separated into two in the Y-axis direction, as shown in Figures 13 and 14. Furthermore, if the beam diameter of the laser beam 201 is increased to 1.0 mm, which is slightly larger than the target, then for the laser beam 203, an intensity distribution 305 and intensity profile 325 are obtained in which the peak is spread out in a smaller area in the Y-axis direction, as shown in Figures 15 and 16. In the modified laser processing apparatus 1 and 1-2, the workpiece 100 may be laser processed using the laser beam 203 that forms such intensity distributions 304, 305 and intensity profiles 324, 325.

[0053] It should be noted that the present invention is not limited to the embodiments described above. That is, it can be implemented with various modifications without departing from the core principles of the present invention. For example, in embodiments 1 and 2, the phase modulation units 22 and 22-2 are said to consist of one or two phase plates, but the present invention is not limited to this, and may also be a spatial light modulator, a so-called LCOS-SLM (Liquid Crystal on Silicon-Spatial Light Modulator), which adjusts the optical characteristics of the laser beam 201 emitted from the laser oscillator 21. [Explanation of Symbols]

[0054] 1,1-2 Laser processing equipment 10 Retention Table 20,20-2 Laser beam irradiation unit 21. Laser Oscillator 22,22-2 Phase Modulation Unit 23 Imaging element 27 recess 41 X-axis movement unit 42 Y-axis movement unit 81 First Phase Plate 82 Second Phase Plate 84,85,87,88 area 91,310 width 100 Workpiece 102 planned division lines 201, 202, 203 Laser beams 301,302,303,304,305 intensity distribution 330 imaging points

Claims

1. A laser processing apparatus that processes a workpiece having multiple intersecting division lines by irradiating it with a laser beam along the division lines, A holding table for holding the workpiece, A laser beam irradiation unit that irradiates a workpiece held on the holding table with a laser beam, An X-axis movement unit that moves the workpiece and the imaging point of the laser beam relative to each other in the X-axis direction, The system includes a Y-axis movement unit that relatively indexes and feeds the workpiece and the imaging point of the laser beam in the Y-axis direction perpendicular to the X-axis direction, The laser beam irradiation unit is Laser oscillator and, An imaging element that forms an image of the laser beam emitted from the laser oscillator, Displaced between the laser oscillator and the imaging element, the laser beam has a first phase plate and a second phase plate that create a phase difference in the laser beam such that, in the X-axis direction parallel to the planned division line set on the workpiece, the laser beam forms an intensity distribution along a Gaussian distribution, and in the Y-axis direction, which is the width direction of the planned division line set on the workpiece, the laser beam forms an intensity distribution along a top-hat shape at the imaging point. The first phase plate and the second phase plate are configured to be relatively movable, A laser processing apparatus characterized in that the amount of movement is adjusted based on the beam diameter of the laser beam incident on the first phase plate and the second phase plate.

2. The first phase plate and the second phase plate are It is configured to have a region with a thicker thickness and a region with a thinner thickness. The region of the first phase plate that is thicker faces the region of the second phase plate that is thinner, and the region of the first phase plate that is thinner faces the region of the second phase plate that is thicker. The laser processing apparatus according to claim 1, characterized in that the width of the top hat shape is adjusted by adjusting the width of the overlap between the region where the thickness of the first phase plate is thin and the region where the thickness of the second phase plate is thin.

Images