Laser processing device and laser processing method

Abstract

To accurately process a work piece in accordance with a trajectory scanned by a laser beam.SOLUTION: A laser processing device 100 includes a first laser beam output part 1, a first galvano-mirror 2 and a second galvano-mirror 3. The first laser beam output part 1 outputs a first laser beam L1 having axisymmetric polarization of which multiple polarization directions are distributed axisymmetrically. The first galvano-mirror 2 and / or the second galvano-mirror 3 scan over a work piece G with the first laser beam L1 along a processing line ML of the work piece G.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a laser processing apparatus and a laser processing method that perform processing by scanning a laser beam along a processing line on a workpiece. [Background technology]

[0002] An apparatus and method are known for processing a workpiece, such as a glass substrate, by scanning and irradiating a laser beam along a processing line on the workpiece to cut out small pieces inside the processing line (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2013-226591 A Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional laser processing, generally, circularly polarized laser light is used, and the laser light is scanned on the workpiece using a galvanometer mirror. In conventional laser processing methods, the workpiece was sometimes not processed according to the scanning trajectory of the laser light. Specifically, the processed shape of the surface of the workpiece directly irradiated with the laser light (front surface) was sometimes different from the processed shape of the opposite surface (back surface). The following two points are considered to be the causes of this phenomenon.

[0005] The first reason is thought to be that p-polarized light (polarized light in which the electric field oscillates perpendicular to the machining surface) is more easily absorbed by the workpiece than s-polarized light (polarized light in which the electric field oscillates parallel to the machining surface). In other words, this is thought to be because the machining speed of the workpiece using p-polarized light is faster than the machining speed using s-polarized light. The "machined surface" referred to here means, for example, the wall surface of a through hole. Since circularly polarized light has p-polarized and s-polarized components of equal intensity, when processing is performed using circularly polarized light, processing progresses more in the direction parallel to the p-polarized light.

[0006] The second reason is that by scanning a circularly polarized laser beam using a galvanometer mirror, the laser beam cannot maintain its circular polarization on the workpiece and becomes polarized closer to an ellipse. In other words, the irradiation intensity of the laser beam on the surface of the workpiece is directional, which is thought to be the cause of the directional dependency of the processing speed of the workpiece.

[0007] An object of the present invention is to process a workpiece precisely in accordance with the scanning locus of the laser light in a laser processing apparatus and method for irradiating the workpiece with laser light to process the workpiece. [Means for solving the problem]

[0008] In the following, several aspects will be described as means for solving the problems. These aspects can be arbitrarily combined as necessary. A laser processing apparatus according to one aspect of the present invention is an apparatus for processing a workpiece by irradiating the workpiece with a laser beam. The laser processing apparatus includes a first laser beam output unit and a galvanometer mirror. The first laser beam output unit outputs a first laser beam having axially symmetric polarization in which a plurality of polarization directions are distributed axially symmetrically. The galvanometer mirror scans the first laser beam along a processing line on the workpiece. In the above-mentioned laser processing device, the first laser light having axially symmetric polarization is scanned along the processing line on the workpiece by the galvanometer mirror. The polarization direction of the first laser light having axially symmetric polarization is aligned axially symmetrically, and unlike circularly polarized light, the polarization state is not changed by the galvanometer mirror, so that the processing speed of the workpiece does not become directional dependent. This makes it possible to keep the processing speed of the workpiece constant at each position of the processing line, so that the workpiece can be processed accurately along the processing line.

[0009] The first laser beam output unit may have a polarization conversion element that polarizes the laser beam axially symmetrically to generate the first laser beam. This makes it possible to easily generate the first laser beam having axially symmetric polarization without using a special laser beam output device.

[0010] The first laser beam may have radial polarization. The first laser beam having radial polarization, which is axially symmetric polarized light, can process the workpiece with high precision.

[0011] The first laser beam may have azimuthally polarized light. The first laser beam having azimuthally polarized light, which is axially symmetric polarized light, can process the workpiece with high precision.

[0012] The first laser light output section may include a randomly polarized laser light output device that outputs, as the first laser light, a laser light having random polarization in which the polarization directions are randomly distributed. Since the first laser light whose polarization direction is arranged substantially axially symmetrically by randomly distributing the polarization direction is used for processing the workpiece, the workpiece can be processed precisely along the processing line without causing directional dependency in the processing speed of the workpiece.

[0013] A laser processing apparatus according to another aspect of the present invention includes a second laser light output unit, a galvanometer mirror, and a polarization adjustment unit. The second laser light output unit outputs a second laser light having a linear polarization. The galvanometer mirror scans the second laser light along a processing line on the workpiece. The polarization adjustment unit adjusts the polarization direction of the second laser light so that it is perpendicular to the processing line. In the above laser processing device, the polarization direction of the linearly polarized second laser light is adjusted to be perpendicular to the processing line of the workpiece. This allows the processing speed of the workpiece to be constant in the direction perpendicular to the processing line, so that the workpiece can be processed accurately along the processing line.

[0014] A laser processing apparatus according to yet another aspect of the present invention includes a third laser beam output section, a galvanometer mirror, and an intensity adjustment section. The third laser light output unit outputs the third laser light. The galvanometer mirror scans the third laser light along a processing line on the workpiece. The intensity adjustment unit adjusts the intensity of the third laser light so that the processing speed of the workpiece is the same at each position on the processing line. In the above laser processing device, the intensity of the third laser light is adjusted so that the processing speed at each position on the processing line of the workpiece is the same. This makes it possible to make the processing speed of the workpiece constant at each position on the processing line, so that the workpiece can be processed accurately along the processing line.

[0015] The workpiece may be a member made of a material selected from the group consisting of polycrystalline diamond, single crystal diamond, ceramics, glass, metal, and resin. This allows the workpiece, which is a member made of any material, to be processed.

[0016] A laser processing method according to still another aspect of the present invention is a method for processing a workpiece by irradiating the workpiece with laser light. The laser processing method includes the following steps. A step of outputting a first laser light having axially symmetric polarization in which a plurality of polarization directions are distributed axially symmetrically. Scanning a first laser beam along a processing line on the workpiece. In the above laser processing method, the first laser light having axially symmetric polarization is scanned along the processing line on the workpiece. The first laser light having axially symmetric polarization includes p-polarized light or s-polarized light axially symmetrically, and the polarization state does not change due to the scanning of the first laser light, so that the processing speed of the workpiece does not become directional dependent. This makes it possible to keep the processing speed of the workpiece constant at each position on the processing line, so that the workpiece can be processed accurately along the processing line.

[0017] A laser processing method according to yet another aspect of the present invention includes the following steps. Outputting a second laser light having linear polarization. Scanning a second laser beam along a processing line on the workpiece. Adjusting the polarization direction of the second laser light so that it is perpendicular to the processing line. In the above laser processing method, the polarization direction of the linearly polarized second laser light is adjusted to be perpendicular to the processing line of the workpiece, so that the processing speed of the workpiece can be made constant in the direction perpendicular to the processing line, and the workpiece can be processed accurately along the processing line.

[0018] A laser processing method according to yet another aspect of the present invention includes the following steps. Outputting a third laser light. Scanning a third laser beam along a processing line on the workpiece. A step of adjusting the intensity of the third laser light so that the processing speed of the workpiece at each position on the processing line is the same. In the above laser processing method, the intensity of the third laser light is adjusted so that the processing speed at each position on the processing line of the workpiece is the same. This makes it possible to make the processing speed of the workpiece constant at each position on the processing line, so that the workpiece can be processed accurately along the processing line. Effect of the Invention

[0019] When a laser beam is irradiated along a processing line to process a workpiece, the processing speed of the workpiece can be made constant at each position on the processing line by using a laser beam having the above characteristics. As a result, the workpiece can be processed along the processing line with high precision. [Brief description of the drawings]

[0020] [Figure 1] 1 is a diagram showing the configuration of a laser processing apparatus according to a first embodiment. [Diagram 2] 4 is a flowchart showing a laser processing operation of a workpiece. [Diagram 3] 4A to 4C are diagrams showing an example of a processed state when irradiated with a first laser beam having radial polarization. [Figure 4] 4A to 4C are diagrams showing an example of a processed state when irradiating with a first laser beam having azimuthally polarized light. [Diagram 5]1A and 1B are diagrams showing an example of a processed state when irradiated with linearly polarized laser light. [Figure 6] 1A and 1B are diagrams showing an example of a processed state when irradiated with circularly polarized laser light. [Figure 7A] FIG. 4 is a diagram showing an example of a processed state of a cylinder formed by irradiating a first laser beam having radial polarization. [Figure 7B] 4 is an enlarged view of the rear surface of a cylinder formed by irradiating it with a first laser beam having radial polarization. [Figure 8A] FIG. 4 is a diagram showing an example of a processed state of a cylinder formed by irradiating a first laser beam having azimuthally polarized light. [Figure 8B] 4 is an enlarged view of the rear surface of a cylinder formed by irradiating a first laser beam having azimuthally polarized light. [Figure 9A] FIG. 13 is a diagram showing an example of a processed state of a cylinder formed by irradiating linearly polarized laser light. [Figure 9B] FIG. 13 is an enlarged view of the rear surface of a cylinder formed by irradiating it with linearly polarized laser light. [Figure 10A] FIG. 13 is a diagram showing an example of a processed state of a cylinder formed by irradiating a circularly polarized laser beam. [Figure 10B] FIG. 13 is an enlarged view of the rear surface of a cylinder formed by irradiating it with circularly polarized laser light. [Figure 11] 6A and 6B are diagrams showing an example of the circularity of a through hole formed by irradiation with a first laser beam having radial polarization. [Figure 12] FIG. 4 is a diagram showing an example of the circularity of a through hole formed by irradiation with a first laser beam having circular polarization. [Figure 13] FIG. 4 is a diagram showing an example of a three-dimensional structure of a through-hole formed by irradiation with a first laser beam having radial polarization. [Figure 14] FIG. 4 is a diagram showing an example of a three-dimensional structure of a through-hole formed by irradiation with a first laser beam having circular polarization. [Figure 15] FIG. 13 is a diagram showing the configuration of a laser processing apparatus according to a second embodiment. [Figure 16] FIG. 13 is a diagram showing the configuration of a laser processing apparatus according to a third embodiment. [Figure 17] FIG. 13 is a diagram showing the configuration of a laser processing apparatus according to a fourth embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] 1. First embodiment (1) Configuration of laser processing equipment The configuration of a laser processing apparatus 100 according to the first embodiment will be described with reference to Fig. 1. Fig. 1 is a diagram showing the configuration of the laser processing apparatus according to the first embodiment. The laser processing apparatus 100 is an apparatus for irradiating a workpiece G with a laser beam (first laser beam L1) to perform processing such as drilling a hole. The workpiece G is a member (e.g., a substrate) made of, for example, polycrystalline diamond (Poly Crystalline Diamond, PCD), single crystal diamond, ceramics, glass, metal, resin, or the like. The laser processing apparatus 100 mainly includes a first laser light output unit 1, a first galvanometer mirror 2, a second galvanometer mirror 3, and a control unit 4.

[0022] Here, as shown in Fig. 1, in a plane along the top surface of the flat workpiece G, mutually orthogonal axes are defined as the X-axis and Y-axis, and the vertical axis orthogonal to these axes is defined as the Z-axis. In addition, both directions (+ direction and - direction) along the X-axis are defined as the X-axis directions, both directions along the Y-axis are defined as the Y-axis directions, and both directions along the Z-axis are defined as the Z-axis directions.

[0023] The first laser light output unit 1 outputs a first laser light L1 having axially symmetric polarization. Axially symmetric polarization is polarization in which a plurality of polarization directions are distributed symmetrically with respect to the optical axis (Z axis). Specifically, the first laser light output unit 1 has a laser light output device 11, a beam expander 13, and a polarization conversion element 15. The laser light output device 11 is a device that outputs laser light L. The laser light L output from the laser light output device 11 of this embodiment is, for example, a pulsed laser light having a wavelength of 355 nm, a pulse width of 15 picoseconds (ps), and a repetition frequency of 1000 kHz. The laser light L output from the laser light output device 11 has linear polarization.

[0024] The beam expander 13 is disposed on the optical path of the laser light L, and expands the laser light L into a parallel beam with a certain magnification.

[0025] The polarization conversion element 15 is disposed on the optical path of the laser light L that has passed through the beam expander 13, and polarizes the linearly polarized laser light L axially symmetrically to generate a first laser light L1. The polarization conversion element 15 is, for example, a photonic crystal polarization optical element that converts the linearly polarized laser light L into the first laser light L1 having radial polarization or azimuth polarization. Radial polarization refers to polarization in which multiple linearly polarized light beams are arranged radially and axially symmetrically. On the other hand, azimuth polarization refers to polarization in which multiple linearly polarized light beams are arranged axially symmetrically along a circumference. Whether the polarization conversion element 15 outputs a laser beam having radial polarization or an azimuthally polarized beam can be determined by the angle formed between the reference direction of the polarization conversion element 15 and the linearly polarized beam of the laser beam L.

[0026] Since the first laser light output section 1 has the polarization conversion element 15, it can easily generate the first laser light L1 having axially symmetric polarization (radial polarization, azimuth polarization) without using a special laser light output device.

[0027] The first galvanometer mirror 2 is a mirror that can rotate around the Z axis, and scans the focal point of the first laser light L1 on the workpiece G in the X axis direction. The second galvanometer mirror 3 is a mirror that can rotate around the X-axis, and scans the focal point of the first laser light L1 on the workpiece G in the Y-axis direction.

[0028] By driving the first galvanometer mirror 2 and / or the second galvanometer mirror 3, the focal point of the first laser light L1 can be scanned in any direction on the workpiece G along the processing line ML of the workpiece G. For example, the focal point of the first laser light L1 can be scanned on the workpiece G in any shape, such as a straight line, a circle, a polygon, or a star, to process the workpiece G into any shape.

[0029] The control unit 4 is a computer system having a CPU, a storage device (RAM, ROM, hard disk, SSD, etc.), and various interfaces, and controls each component of the laser processing apparatus 100. A part or all of the control of the laser processing apparatus 100 may be realized by a program stored in a storage device of a computer system constituting the control unit 4. Alternatively, a part or all of the control of the laser processing apparatus 100 may be realized by hardware constituting the control unit 4.

[0030] The laser processing apparatus 100 includes an fθ lens 5. The fθ lens 5 is a lens disposed between the second galvanometer mirror 3 and the workpiece G so as to be movable in the Z-axis direction. The fθ lens 5 focuses the first laser light L1 at an arbitrary position in the Z-axis direction on or in the workpiece G. It is also possible to focus the first laser light L1 at an arbitrary position in the Z-axis direction on or in the workpiece G by moving the entire system consisting of the first galvanometer mirror 2, the second galvanometer mirror 3, and the fθ lens 5 in the Z-axis direction.

[0031] The laser processing apparatus 100 includes a work table 6. The work table 6 is a table on which a workpiece G is placed as a work. A table moving mechanism (not shown) for moving the work table 6 in the X-axis direction and the Y-axis direction may be provided below the work table 6.

[0032] Although not shown, the laser processing apparatus 100 may be provided with other optical elements, such as a path conversion element (e.g., a mirror) for converting the optical path of the laser light L emitted from the laser light output device 11 and / or the first laser light L1 axially symmetrically polarized by the polarization conversion element 15, as necessary.

[0033] (2) Laser processing of a workpiece in a laser processing device A laser processing operation of a workpiece with the first laser light L1 using the above-mentioned laser processing apparatus 100 will be described with reference to Fig. 2. Fig. 2 is a flow chart showing the laser processing operation of a workpiece. First, the workpiece G to be processed is placed on the work table 6, and the laser processing apparatus 100 (work table 6, etc.) is adjusted so that the focal point of the first laser beam L1 is located at the start position of the planned processing line ML.

[0034] After the laser processing apparatus 100 is adjusted so that the focal point of the first laser beam L1 is located at the start position of the processing line ML, the first laser beam L1 is output toward the workpiece G in step S1. Specifically, the control unit 4 commands the laser light output device 11 to emit laser light L. The laser light L emitted from the laser light output device 11 has its light beam expanded by the beam expander 13 and is guided to the polarization conversion element 15. The laser light L guided to the polarization conversion element 15 is converted by the polarization conversion element 15 into a first laser light L1 having axially symmetric polarization.

[0035] The first laser light L1 is focused by a first galvanometer mirror 2, a second galvanometer mirror 3, and an fθ lens 5 at a start position of a processing line ML on the workpiece G to form a focusing point. Thereafter, in step S2, the control unit 4 controls the rotation angle of the first galvanometer mirror 2 and / or the second galvanometer mirror 3 to cause the focal point of the first laser light L1 to scan along the processing line ML (circular in FIG. 1).

[0036] In addition, when processing a thick workpiece G by irradiating the first laser light L1, the control unit 4 controls the height of the fθ lens 5 relative to the workpiece G to move the focal point of the first laser light L1 in the thickness direction of the workpiece G (the Z-axis direction in Figure 1). In addition, for example, if the processing line ML extends over a wide area of ​​the workpiece G and the first galvanometer mirror 2 and the second galvanometer mirror 3 alone cannot irradiate the focal point of the first laser light L1 to all of the processing line ML, the work table 6 is moved in the X-axis direction and / or Y-axis direction to change the position of the focal point of the first laser light L1 relative to the workpiece G.

[0037] (3) Examples An example in which the workpiece G was actually processed using the laser processing device 100 according to the first embodiment in accordance with the flow chart shown in FIG. 2 will be described below. In the example described below, an alumina ceramic substrate having a thickness of 0.635 mm was used as the workpiece G, and an attempt was made to form a circular through-hole in this workpiece G. In addition, as the laser light L output from the laser light output device 11, a pulsed laser light having a wavelength of 355 nm, a pulse width of 15 picoseconds, and a repetition frequency of 1000 kHz was used.

[0038] FIG. 3 is a diagram showing an example of a processing state when a first laser light having radial polarization is irradiated, and FIG. 4 is a diagram showing an example of a processing state when a first laser light having azimuth polarization is irradiated. As a comparative example, an example of the processed state when irradiating a linearly polarized laser beam is shown in Fig. 5, and an example of the processed state when irradiating a circularly polarized laser beam is shown in Fig. 6. Figs. 3 to 6 show the processed shape on the back surface (the surface opposite to the surface irradiated with the laser beam) of the workpiece G. In Figs. 3 to 6, the arrows drawn in the upper right corner represent the polarization state of the laser beam irradiated to the workpiece G, and the dashed circle represents a perfect circle (guideline).

[0039] As shown in Figures 3 to 6, the machining shape of the back surface when using a radially polarized or azimuthally polarized laser beam was closer to a perfect circle than when using a circularly polarized or linearly polarized laser beam. The machining shape of the front surface of the workpiece G showed almost no difference depending on the polarization, and was almost a perfect circle for both polarizations. When processing is performed with a circularly polarized or linearly polarized laser beam, processing progresses more in a specific direction, and the processed shape of the back surface becomes elliptical. For example, when a linearly polarized laser beam is used, processing progresses more in a direction parallel to the polarization direction.

[0040] Next, an example will be described in which a cylinder is formed from a workpiece G using the laser processing apparatus 100 according to the first embodiment. In the example described below, an alumina ceramic substrate having a thickness of 0.635 mm is used as the workpiece G. In addition, as the laser light L output from the laser light output device 11, a pulsed laser light having a wavelength of 355 nm, a pulse width of 15 picoseconds, and a repetition frequency of 1000 kHz is used.

[0041] Fig. 7A is a diagram showing an example of a processed state of a cylinder formed by irradiating a first laser beam having radial polarization, Fig. 7B is an enlarged view of the back surface of the cylinder, and Fig. 8A is a diagram showing an example of a processed state of a cylinder formed by irradiating a first laser beam having azimuth polarization, and Fig. 8B is an enlarged view of the back surface of the cylinder. As a comparative example, Fig. 9A shows an example of a machined state of a cylinder formed by irradiating a linearly polarized laser beam, and Fig. 9B shows an enlarged view of the back surface of the cylinder. Fig. 10A shows an example of a machined state of a cylinder formed by irradiating a circularly polarized laser beam, and Fig. 10B shows an enlarged view of the back surface of the cylinder. In Figs. 7 to 10, the arrows drawn in the upper right corner represent the polarization state of the laser beam irradiated to the workpiece G, and the dashed circle represents a perfect circle (guideline).

[0042] As shown in these figures, the machining shape of the back surface when radially or azimuthally polarized laser light was used was closer to a perfect circle than when circularly or linearly polarized laser light was used. There was almost no difference in the machining shape on the front surface of the workpiece G, and it was almost a perfect circle. Also, the cylinder formed by machining the workpiece G has a tapered shape (the shape of the back surface is larger than the front surface, and the side is not perpendicular to the front and back surfaces but is an oblique side) because as the focusing position of the first laser light L1 is shifted toward the back surface, part of the beam is blocked by the edge of the hole on the front surface side.

[0043] As in the case of through holes, when a cylinder is machined with a circularly polarized or linearly polarized laser beam, machining progresses in a specific direction, and the machined shape on the back side becomes an ellipse. Note that, because the cylinder falls freely during machining, the cylinders in Figures 9 and 10 were observed by positioning the major axis of the ellipse in the vertical direction of the figure for convenience.

[0044] Next, a beam rotator was added to the optical path (between the first laser light output unit 1 and the first galvanometer mirror 2) of the laser processing apparatus 100 according to the first embodiment to attempt to form a circular through-hole in the workpiece G. The beam rotator rotates the first laser light L1 in synchronization with the scanning on the processing line ML so that the first laser light L1 is not blocked by the edge of the hole formed on the front surface side of the workpiece G. This makes it possible to prevent the through-hole formed in the workpiece G from having a tapered shape as much as possible.

[0045] In the example described below, a PCD substrate having a thickness of 0.75 mm was used as the workpiece G. In addition, as the laser light L output from the laser light output device 11, a pulsed laser light having a wavelength of 355 nm, a pulse width of 15 picoseconds, and a repetition frequency of 500 kHz was used.

[0046] The through holes formed in the workpiece G under the above conditions were evaluated using "roundness". Roundness refers to the degree of deviation of a circular shape from a geometrically correct circle (perfect circle), and is defined as the difference between the radius of the circumscribing circle and the radius of the inscribing circle of the processed shape. Therefore, the smaller the roundness, the closer the processed shape is to a perfect circle. Specifically, the shape of the through hole is measured at multiple points in the depth direction from the surface of the workpiece G, the measured shapes of the through holes are aligned and overlaid, the smallest circumscribing circle and the largest inscribing circle are calculated for the overlaid shapes of the through holes, and the difference between the radius of the circumscribing circle and the radius of the inscribing circle is measured as the circularity.

[0047] Fig. 11 is a diagram showing an example of the circularity of a through hole formed by irradiating a first laser beam having radial polarization. Fig. 12 is a diagram showing an example of the circularity of a through hole formed by irradiating a first laser beam having circular polarization. Figs. 11 and 12 show the maximum circumscribed circle and the minimum inscribed circle of the shape of the through hole measured at 11 positions of depths of 0.07, 0.12, 0.17, 0.22, 0.27, 0.32, 0.37, 0.42, 0.47, 0.52, and 0.57 mm from the surface of the workpiece G.

[0048] As shown in Figs. 11 and 12, the circularity was about 0.8 μm to 2.4 μm when a radially polarized laser beam was used, whereas the circularity was about 1.3 μm to 4.0 μm when a circularly polarized laser beam was used. In addition, the shape of the through hole formed using the radially polarized laser beam has almost the same error from a perfect circle, whereas the shape of the through hole formed using the circularly polarized laser beam has a large error from a perfect circle in a specific direction. In other words, when the radially polarized laser beam is used, the shape of the front side of the workpiece G is almost maintained to the back side, whereas when the circularly polarized laser beam is used, the shape of the front side of the workpiece G cannot be maintained to the back side. This means that irradiation with the first laser beam L1 having axially symmetric polarization can process a shape closer to a perfect circle than irradiation with the circularly polarized laser beam.

[0049] Furthermore, the shape of the through-hole formed in the workpiece G was evaluated using "cylindricity." Cylindricity refers to the degree of deviation of a cylindrical body from a geometrically correct cylinder, and is defined as the difference between the radius of the smallest inscribed circle and the radius of the largest circumscribed circle of multiple circular shapes defined in the height direction of the cylindrical shape. Therefore, the smaller the cylindricity, the closer the formed through-hole is to a correct cylinder. Fig. 13 is a diagram showing an example of the three-dimensional structure of a through-hole formed by irradiating a first laser beam having radial polarization, and Fig. 14 is a diagram showing an example of the three-dimensional structure of a through-hole formed by irradiating a first laser beam having circular polarization. Figs. 13 and 14 show the results of measuring the shape of a through-hole at 11 positions at depths of 0.07, 0.12, 0.17, 0.22, 0.27, 0.32, 0.37, 0.42, 0.47, 0.52, and 0.57 mm from the surface, and the error from a perfect circle, arranged three-dimensionally.

[0050] 13 and 14, the cylindricity was about 2.7 μm when a radially polarized laser beam was used, whereas the cylindricity was about 5.6 μm when a circularly polarized laser beam was used. The through-hole formed using a radially polarized laser beam was hardly tapered, whereas the through-hole formed using a circularly polarized laser beam was tapered, with the size of the shape of each depth varying from the front surface to the back surface of the workpiece G. That is, irradiation with the first laser beam L1 having axially symmetric polarization can form a through-hole closer to a cylinder than irradiation with a circularly polarized laser beam.

[0051] As described above, in the laser processing apparatus 100 according to the first embodiment, the first laser light L1 having axially symmetric polarization is scanned along the processing line ML of the workpiece G by the first galvanometer mirror 2 and / or the second galvanometer mirror 3. The polarization directions of the first laser light L1 having axially symmetric polarization are aligned axially symmetrically, and unlike circularly polarized light, the polarization state is not changed by the galvanometer mirror, so that no directional dependency is caused in the processing speed of the workpiece G. This makes it possible to keep the processing speed of the workpiece G constant at each position on the processing line ML, so that the workpiece G can be processed accurately along the processing line ML.

[0052] 2. Second embodiment In the first embodiment described above, the linearly polarized laser light L is converted by the polarization conversion element 15 into the first laser light L1 having axially symmetric polarization (radially polarized light, azimuthally polarized light). The method of generating the first laser light L1 having axially symmetric polarization is not limited to the above, and the first laser light output section 1' of the laser processing apparatus 200 of the second embodiment outputs laser light having random polarization in which the polarization directions are randomly distributed as the first laser light L1'.

[0053] As shown in Fig. 15, a first laser beam output section 1' according to the second embodiment has a randomly polarized laser beam output device 11' that outputs a laser beam having random polarization as a first laser beam L1'. Fig. 15 is a diagram showing the configuration of a laser processing apparatus according to the second embodiment. The randomly polarized laser light output device 11' is, for example, a laser oscillation device having a cylindrical member that confines a laser medium and a pair of resonator mirrors arranged to sandwich the cylindrical member. The laser light output device 11 according to the first embodiment has a Brewster window between the cylindrical member and the resonator mirror, and is capable of extracting only the laser light L having linear polarization.

[0054] In the laser processing apparatus 200 of the second embodiment, the first laser light L1', whose polarization direction is arranged substantially axially symmetrically by randomly distributing the polarization direction, is used to process the workpiece G, so that the workpiece can be processed precisely along the processing line ML without causing directional dependency in the processing speed of the workpiece G. Furthermore, as shown in FIG. 15, by using a randomly polarized laser light output device 11', it is possible to generate laser light having axially symmetric polarization without using the polarization conversion element 15 of the first embodiment.

[0055] The laser processing apparatus 200 according to the second embodiment differs from the first laser light output unit 1 according to the first embodiment only in the configuration of the first laser light output unit 1', and other configurations are the same as those of the laser processing apparatus 100 according to the first embodiment. Therefore, here, explanations of configurations other than the first laser light output unit 1' will be omitted.

[0056] 3. Third embodiment The laser light used to process the workpiece G is not limited to the laser light having axially symmetric polarization. The second laser light output unit 1'' of the laser processing apparatus 300 according to the third embodiment outputs the second laser light L2 having linear polarization, and further adjusts the polarization direction of the second laser light L2 to be perpendicular to the processing line ML. As shown in Fig. 16, a second laser beam output section 1'' of a laser processing apparatus 300 according to the third embodiment has a laser beam output device 11, a beam expander 13, and a polarization adjuster 15'. Fig. 16 is a diagram showing the configuration of the laser processing apparatus according to the third embodiment. Incidentally, the laser light output device 11 and the beam expander 13 are respectively the same as the laser light output device 11 and the beam expander 13 of the first laser light output section 1 according to the first embodiment, and therefore a description thereof will be omitted here.

[0057] The polarization adjustment unit 15' generates the second laser light L2 having linear polarization, and, under the control of the control unit 4, orients the polarization direction of the second laser light L2 perpendicular to the processing line ML. The polarization adjustment unit 15' has, for example, a polarization rotation element (e.g., a 1 / 2 wavelength plate) that rotates the polarization direction of the linearly polarized laser light L around the optical axis, and a mechanism that rotates the polarization rotation element itself around the optical axis of the second laser light L2 under the control of the control unit 4.

[0058] In the laser processing apparatus 300 according to the third embodiment, a second laser light L2 having linear polarization is output from the second laser light output unit 1'', and the second laser light L2 is scanned along the processing line ML on the workpiece G by the first galvanometer mirror 2 and / or the second galvanometer mirror 3, while the polarization adjustment unit 15' is controlled by the control unit 4 to adjust the polarization direction of the second laser light L2 so that it is perpendicular to the processing line ML, thereby processing the workpiece G.

[0059] In the laser processing apparatus 300 according to the third embodiment, the polarization direction of the linearly polarized second laser light L2 is adjusted to be perpendicular to the processing line ML of the workpiece G. In other words, the p-polarized component of the second laser light L2 is always perpendicular to the processing line ML. This allows the processing speed of the workpiece G to be constant in the direction perpendicular to the processing line ML, so that the workpiece G can be processed accurately along the processing line ML.

[0060] The laser processing apparatus 300 according to the third embodiment differs from the first laser light output unit 1 according to the first embodiment and the first laser light output unit 1' according to the second embodiment only in that the second laser light output unit 1'' has a different configuration from that of the first laser light output unit 1 according to the first embodiment, and the other configurations are the same as those of the laser processing apparatus 100 according to the first embodiment. Therefore, here, a description of the configurations other than that of the second laser light output unit 1'' will be omitted.

[0061] 4. Fourth embodiment The laser light used to process the workpiece G is not limited to laser light having axially symmetric polarization, or laser light having linear polarization adjusted so that the polarization direction is perpendicular to the processing line ML. The third laser light output unit 1''' of the laser processing apparatus 400 according to the fourth embodiment adjusts the intensity of the circularly polarized third laser light L3 so that the processing speed of the workpiece G at each position on the processing line ML is the same. As shown in FIG. 17, a third laser beam output section 1''' of a laser processing apparatus 400 according to the fourth embodiment has a laser beam output device 11'', a beam expander 13, and a polarization conversion section 15''. FIG. 17 is a diagram showing the configuration of the laser processing apparatus according to the fourth embodiment.

[0062] The laser light output device 11'' outputs a laser light L' whose intensity has been adjusted under the control of a control unit 4 (an example of an intensity adjusting unit). The polarization conversion unit 15'' is, for example, a quarter-wave plate that converts the laser light L' output from the laser light output device 11'' into a third laser light L3 having circular polarization. Incidentally, the beam expander 13 is the same as the beam expander 13 of the first laser light output section 1 according to the first embodiment, and therefore a description thereof will be omitted here.

[0063] In the laser processing apparatus 400 according to the fourth embodiment, the laser light L' output from the laser light output device 11'' is converted into circularly polarized light by the polarization conversion unit 15'' to generate a third laser light L3, and the third laser light L3 is scanned along the processing line ML on the workpiece G by the first galvanometer mirror 2 and / or the second galvanometer mirror 3, while the laser light output device 11'' is controlled by the control unit 4 to adjust the intensity of the third laser light L3 so that the processing speed of the workpiece G at each position on the processing line ML is the same, thereby processing the workpiece G. Specifically, at each position of the processing line ML where the processing speed is slow when circularly polarized laser light is used, the intensity of the third laser light L3 is increased, while at a position where the processing speed is fast when circularly polarized laser light is used, the intensity of the third laser light L3 is decreased.

[0064] In the laser processing apparatus 400 according to the fourth embodiment, the intensity of the third laser beam L3 is adjusted so that the processing speed at each position on the processing line ML of the workpiece G is the same. As a result, even when a circularly polarized laser beam is used to process the workpiece G, the processing speed of the workpiece G can be made constant at each position on the processing line ML, so that the workpiece can be processed accurately along the processing line ML.

[0065] The laser processing apparatus 400 according to the fourth embodiment differs from the laser beam output units according to the first to third embodiments only in the configuration of the third laser beam output unit 1''', and other configurations are the same as those of the laser processing apparatuses according to the first to third embodiments. Therefore, here, description of configurations other than that of the third laser beam output unit 1''' will be omitted.

[0066] 4. Other embodiments Although several embodiments of the present invention have been described above, the present invention is not limited to the above-mentioned embodiments, and various modifications are possible without departing from the gist of the invention. In particular, several embodiments and modifications described in this specification can be arbitrarily combined as necessary. (A) In the above first to fourth embodiments, the fθ lens 5 is used as a focusing means for the laser light, but this is not limited to this, and any lens that can focus the laser light may be used, and is not limited to an fθ lens. [Industrial Applicability]

[0067] INDUSTRIAL APPLICABILITY The present invention can be widely applied to laser processing apparatuses and laser processing methods that perform processing by scanning a laser beam along a processing line on a workpiece. [Explanation of symbols]

[0068] 100~400 laser processing equipment 1, 1' First laser light output section 1'' Second laser light output section 1'' Third laser light output section 11, 11'' laser light output device 11' Randomly polarized laser light output device 13 Beam Expander 15 Polarization conversion element 15' Polarization adjustment section 15'' Polarization conversion unit 2. First Galvanometer Mirror 3. Second Galvanometer Mirror 4. Control section 5 fθ lens 6 Work Table G Workpiece ML processing line L, L' laser light L1, L1' First laser beam L2 Second laser beam L3 Third laser beam

Claims

1. A laser processing device that irradiates a workpiece with laser light to form a hole or a pillar of a predetermined shape in the workpiece, a first laser light output unit that outputs a first laser light having axially symmetric polarized light in which a plurality of polarization directions are distributed axially symmetrically; a galvanometer mirror that scans the first laser light along a processing line on the workpiece for forming a hole or a pillar in the workpiece while outputting the first laser light; A laser processing apparatus comprising:

2. 2. The laser processing apparatus according to claim 1, wherein the first laser light output section has a polarization conversion element that axially symmetrically polarizes the laser light to generate the first laser light.

3. The laser processing apparatus according to claim 1 , wherein the first laser light has radial polarization.

4. The laser processing apparatus according to claim 1 , wherein the first laser light has azimuthally polarized light.

5. The laser processing apparatus according to any one of claims 1 to 4, wherein the workpiece is a member made of a material selected from the group consisting of polycrystalline diamond, single crystal diamond, ceramics, glass, metal, and resin.

6. A laser processing method for forming a hole or a pillar of a predetermined shape in a workpiece by irradiating the workpiece with laser light, comprising: outputting a first laser beam having axially symmetric polarization in which a plurality of polarization directions are distributed axially symmetrically; a step of scanning the first laser light along a processing line on the workpiece for forming a hole or a pillar in the workpiece while outputting the first laser light; A laser processing method comprising:

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