Laser processing device and laser processing method

Abstract

To provide a laser beam machining apparatus which can be downsized and in which contamination of a quarter plate can be suppressed.SOLUTION: A laser beam machining apparatus 1A comprises: a laser source 2; a stage 3; an fθ lens 4; a galvanometer scanner 5 which scans a to-be-machined surface 100a of a workpiece 100 with a laser beam L1 by operating a dielectric mirror thereby adjusting an incidence angle of the laser beam L1 with respect to the fθ lens 4; a polarization beam splitter 6 disposed between the laser source 2 and the galvanometer scanner 5 on an optical path of the laser beam L1; a quarter-wave plate 7 disposed between the polarization beam splitter 6 and the galvanometer scanner 5 on the optical path; and a light detection unit 8A that detects a return beam L2 of the laser beam L1 from the to-be-machined 100a irradiated with the laser beam L1, that is, the return beam L2 passing through the fθ lens 4, the galvanometer scanner 5, the quarter-wave plate 7, and the polarization beam splitter 6 in this order.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present disclosure relates to a laser processing apparatus and a laser processing method. [Background technology]

[0002] Patent Document 1 discloses a configuration in which, in a laser processing apparatus that uses a galvanometer scanner to scan the surface of a workpiece with laser light, a quarter-wave plate is placed between an fθ lens and the workpiece in order to suitably detect reflected light from the workpiece with a light detection unit. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2007-29964 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the configuration disclosed in the above-mentioned Patent Document 1, since the quarter-wave plate is located after the laser light scanning unit (i.e., closer to the workpiece than the laser light scanning unit), it is necessary to use a quarter-wave plate large enough to cover the entire processing surface of the workpiece (i.e., the area to be scanned). Therefore, the size of the quarter-wave plate needs to be large according to the size of the processing surface. As a result, there is a risk that the size of the entire device will become large. In addition, there is a risk that the quarter-wave plate will be contaminated by splashes generated from the workpiece during laser processing.

[0005] In view of the above, an object of one aspect of the present disclosure is to provide a laser processing apparatus and a laser processing method that can reduce the size of the apparatus and suppress contamination of the quarter-wave plate. [Means for solving the problem]

[0006] A laser processing apparatus according to one aspect of the present disclosure includes a laser light source that outputs laser light, a support stage that supports a workpiece, an fθ lens that focuses the laser light on a processing surface of the workpiece, an optical scanning unit that scans the laser light on the processing surface by operating a dielectric mirror to adjust the angle of incidence of the laser light with respect to the fθ lens, a polarizing beam splitter that is arranged between the laser light source and the optical scanning unit on the optical path of the laser light, a quarter-wave plate that is arranged between the polarizing beam splitter and the optical scanning unit on the optical path, and an optical detection unit that detects return light of the laser light from the processing surface of the workpiece irradiated with the laser light, which passes through the fθ lens, the optical scanning unit, the quarter-wave plate, and the polarizing beam splitter in this order.

[0007] In the above laser processing device, by using the polarizing beam splitter and the quarter-wave plate, the detection efficiency of the return light from the processing surface of the workpiece can be improved compared to when the polarizing beam splitter and the quarter-wave plate are not used. Furthermore, by disposing the quarter-wave plate between the polarizing beam splitter and the optical scanning unit, the size of the quarter-wave plate can be reduced compared to when the quarter-wave plate is disposed between the fθ lens and the workpiece. As a result, the entire laser processing device can be reduced in size. In addition, by not disposing the quarter-wave plate at a position facing the workpiece, it is possible to prevent the quarter-wave plate from being contaminated by splashes generated from the workpiece during laser processing.

[0008] The laser processing device may further include a control unit that monitors the processing state of the workpiece based on the return light detected by the light detection unit. According to the above configuration, the processing state of the workpiece can be easily monitored based on the return light detected during laser processing.

[0009] The light detection unit may detect a signal strength of the return light, and the control unit may detect an abnormality in the processing state of the workpiece based on the signal strength detected by the light detection unit. With the above configuration, it is possible to appropriately detect an abnormality in the processing state based on the signal strength of the return light and appropriately deal with it.

[0010] The control unit may correct the signal intensity based on the scanning position of the laser light, and may detect an abnormality in the processing state of the workpiece based on the corrected signal intensity. The laser light output from the laser light source becomes linearly polarized by passing through a polarizing beam splitter, and is further converted into circularly polarized light by passing through a quarter-wave plate. Here, when an optical scanning unit including a dielectric mirror is used, the phase difference between the orthogonal polarized light of the laser light changes when the laser light is reflected by the dielectric mirror. Due to this, the return light near the center of the scanning range maintains a circularly polarized state, whereas the return light in the peripheral portion away from the center of the scanning range becomes elliptically polarized. As a result, a difference occurs between the signal intensity detected for the return light in the center of the scanning range and the signal intensity detected for the return light in the peripheral portion of the scanning range. Specifically, the signal intensity of the detected return light tends to decrease as the irradiation position (scanning position) of the laser light moves away from the center of the scanning range. According to the above configuration, the signal intensity is corrected based on such a tendency, so that the magnitude of the signal intensity of the return light detected at each position of the scanning range can be made uniform. This makes it possible to determine whether or not laser processing is being performed normally for each scanning position based on a uniform standard.

[0011] The control unit may determine whether the laser processing of the scanning position has been performed normally based on the signal intensity detected at the scanning position each time the laser light is irradiated to the scanning position, and may detect an abnormality in the processing state of the workpiece in response to determining that the laser processing of the scanning position has not been performed normally. According to the above configuration, an abnormality in the processing state can be detected appropriately and immediately during the processing process.

[0012] The control unit may determine whether the signal strength is an appropriate value based on the relationship between the irradiation energy and signal strength of the laser light output from the laser light source and the diameter of the machining mark formed on the machining surface, and the target value of the diameter of the machining mark, and may detect an abnormality in the machining state of the object to be machined in response to the signal strength being determined to be not an appropriate value. According to the above configuration, during the machining process, an abnormality in the machining state can be appropriately detected based on the relationship between the irradiation energy of the laser light, the signal strength of the return light, and the diameter of the machining mark.

[0013] The control unit may integrate the signal strength detected at each scanning position in the entire predetermined scanning range, and may detect an abnormality in the processing state of the workpiece based on the integration result. According to the above configuration, by using the integration result of the signal strength detected in the entire scanning range, it is possible to absorb the difference in signal strength due to the difference in scanning position and perform abnormality detection for each scanning range. In addition, since it is not necessary to correct the signal strength of the return light detected at each scanning position, the amount of calculation can be reduced accordingly.

[0014] The light detection unit may detect a two-dimensional image of the return light, and the control unit may adjust the distance between the fθ lens and the processing surface based on the two-dimensional image detected by the light detection unit. According to the above configuration, the distance between the fθ lens and the processing surface can be adjusted based on the two-dimensional image (i.e., the beam profile) of the return light from the processing object so that the beam profile at the processing position (irradiation position) has an appropriate shape. This can improve the processing quality.

[0015] The control unit may adjust the distance between the fθ lens and the processing surface based on the relationship between the two-dimensional image and the shape of the processing mark formed on the processing surface and the target shape of the processing mark so that the two-dimensional image corresponding to the target shape is detected by the light detection unit. According to the above configuration, the distance between the fθ lens and the processing surface can be appropriately adjusted based on the relationship between the two-dimensional image and the shape of the processing mark grasped in advance.

[0016] A laser processing method according to another aspect of the present disclosure is a laser processing method for processing an object by concentrating a laser beam on a processing surface of the object supported by a support with an fθ lens, the method including the steps of: directing a laser beam output from a laser light source to an optical scanning unit via a polarizing beam splitter and a quarter-wave plate in this order, and scanning the laser beam on the processing surface by operating a dielectric mirror in the optical scanning unit to change the incident angle of the laser beam on the fθ lens; and detecting, by an optical detection unit, the return beam of the laser beam from the processing surface of the object irradiated with the laser beam, which returns via the fθ lens, the optical scanning unit, the quarter-wave plate, and the polarizing beam splitter in this order. According to the laser processing method, the same effect as that of the above-mentioned laser processing device is achieved.

[0017] The laser processing method may further include a step of monitoring a processing state of the workpiece based on the return light detected by the light detection unit. According to the above configuration, the processing state of the workpiece can be easily monitored based on the return light detected during laser processing.

[0018] In the detecting step, the signal strength of the return light may be detected, and in the monitoring step, an abnormality in the processing state of the workpiece may be detected based on the detected signal strength. According to the above configuration, it is possible to appropriately detect an abnormality in the processing state based on the signal strength of the return light and to appropriately deal with it.

[0019] The monitoring step may include a process of correcting the signal intensity based on the scanning position of the laser light, and a process of detecting an abnormality in the processing state of the workpiece based on the corrected signal intensity. According to the above configuration, it is possible to make the magnitude of the signal intensity of the return light detected at each position in the scanning range uniform and to determine whether the laser processing is being performed normally or not for each scanning position based on a uniform criterion.

[0020] The monitoring step may include a process of determining whether the laser processing of the scanning position has been performed normally based on the signal intensity detected at the scanning position each time the laser light is irradiated to the scanning position, and a process of detecting an abnormality in the processing state of the workpiece in response to the determination that the laser processing of the scanning position has not been performed normally. According to the above configuration, an abnormality in the processing state can be detected appropriately and immediately during the processing process.

[0021] The monitoring step may include a process of determining whether the signal strength is an appropriate value based on the relationship between the irradiation energy of the laser light output from the laser light source, the signal strength, and the diameter of the machining mark formed on the machining surface, and a target value for the diameter of the machining mark, and a process of detecting an abnormality in the machining state of the object to be machined in response to the determination that the signal strength is not an appropriate value. According to the above configuration, during the machining process, an abnormality in the machining state can be appropriately detected based on the relationship between the irradiation energy of the laser light, the signal strength of the return light, and the diameter of the machining mark.

[0022] The monitoring step may include a process of integrating the signal strength detected at each scanning position in the entire predetermined scanning range, and a process of detecting an abnormality in the processing state of the workpiece based on the integration result. According to the above configuration, by using the integration result of the signal strength detected in the entire scanning range, it is possible to absorb the difference in signal strength due to the difference in scanning position and perform abnormality detection in units of scanning range. In addition, since it is not necessary to correct the signal strength of the return light detected at each scanning position, the amount of calculation can be reduced accordingly.

[0023] In the detecting step, a two-dimensional image of the return light may be detected, and in the monitoring step, the distance between the fθ lens and the processing surface may be adjusted based on the detected two-dimensional image. According to the above configuration, the distance between the fθ lens and the processing surface can be adjusted based on the two-dimensional image (i.e., the beam profile) of the return light from the processing object so that the beam profile at the processing position (irradiation position) has an appropriate shape. This can improve the processing quality.

[0024] In the monitoring step, the distance between the fθ lens and the processing surface may be adjusted based on the relationship between the two-dimensional image and the shape of the processing mark formed on the processing surface and the target shape of the processing mark so that the two-dimensional image corresponding to the target shape is detected by the light detection unit. According to the above configuration, the distance between the fθ lens and the processing surface can be appropriately adjusted based on the relationship between the two-dimensional image and the shape of the processing mark grasped in advance. Effect of the Invention

[0025] According to one aspect of the present disclosure, it is possible to provide a laser processing apparatus and a laser processing method that can reduce the size of the apparatus and suppress contamination of the quarter-wave plate. [Brief description of the drawings]

[0026] [Figure 1] FIG. 1 is a configuration diagram of a laser processing apparatus according to the first embodiment. [Diagram 2] FIG. 2 is a diagram showing an example of an object to be processed, the signal intensity of return light detected by a light detection unit, and processing marks formed on a processing surface. [Diagram 3] FIG. 3 is a diagram illustrating an example of a correction process for the signal intensity of the returned light. [Figure 4] FIG. 4 is a diagram showing an example of the relationship between the irradiation energy of the laser light, the signal intensity of the return light, and the diameter of the processed mark. [Diagram 5] FIG. 5 is a diagram showing a first operation example of the laser processing apparatus according to the first embodiment. [Figure 6] FIG. 6 is a diagram showing a second operation example of the laser processing apparatus according to the first embodiment. [Figure 7] FIG. 7 is a configuration diagram of a laser processing apparatus according to the second embodiment. [Figure 8] FIG. 8 is a diagram showing an example of the relationship between a two-dimensional image of return light detected by the laser processing device of the second embodiment and processing marks. [Figure 9] FIG. 9 is a diagram showing an example of the operation of the laser processing apparatus according to the second embodiment. [Figure 10]FIG. 10 is a diagram showing an example of the relationship between the irradiation energy and the diameter of the processed mark measured by the laser processing device of the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0027] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are designated by the same reference numerals, and duplicated description will be omitted.

[0028] [First embodiment] 1 is an apparatus for processing an object 100 by irradiating a processing surface 100a of the object 100 with a laser beam L1. The laser processing apparatus 1A includes a laser light source 2, a stage 3 (support unit), an fθ lens 4, a galvano scanner 5 (light scanning unit), a polarizing beam splitter 6, a quarter-wave plate 7, a light detection unit 8A, and a control unit 9.

[0029] The laser light source 2 is a device that outputs laser light L1 to be irradiated onto the workpiece 100. The laser light L1 output from the laser light source 2 may be continuous light or pulsed light. In this embodiment, the laser light L1 is pulsed light. The wavelength of the laser light L1 output from the laser light source 2 is appropriately selected depending on the material of the workpiece 100 (e.g., metal, resin, etc.). The wavelength of the laser light L1 is, for example, 1030 nm.

[0030] The stage 3 is a device that supports the workpiece 100. For example, the workpiece 100 is placed on a mounting surface (upper surface) of the stage 3. The stage 3 is, for example, an XYZ stage that is movable in X-axis and Y-axis directions that are parallel to the mounting surface of the stage 3 and perpendicular to each other, and in a Z-axis direction that is perpendicular to the mounting surface of the stage 3.

[0031] The fθ lens 4 is a lens that focuses the laser light L1 on the processing surface 100a of the workpiece 100 placed on the stage 3. The fθ lens 4 is composed of a plurality of lenses. By using the fθ lens 4 as an objective lens for the workpiece 100, it is possible to perform a constant speed scan on the processing surface 100a.

[0032] The galvano scanner 5 is composed of a galvano mirror 5a (dielectric mirror). The galvano scanner 5 scans the laser light L1 on the processing surface 100a by operating the galvano mirror 5a to adjust the incident angle of the laser light L1 with respect to the fθ lens 4. The galvano scanner 5 may be configured to scan the processing surface 100a one-dimensionally, or may be configured to scan the processing surface 100a two-dimensionally. In the latter case, the galvano scanner 5 is configured to include, for example, a first galvano mirror for scanning the laser light L1 in the X-axis direction on the processing surface 100a, and a second galvano mirror for scanning the laser light L1 in the Y-axis direction on the processing surface 100a.

[0033] The polarizing beam splitter 6 is disposed between the laser light source 2 and the galvano scanner 5 on the optical path of the laser light L1. Specifically, the polarizing beam splitter 6 is disposed between the laser light source 2 and the quarter-wave plate 7. The polarizing beam splitter 6 is disposed at an inclination of 45 degrees with respect to the optical path of the laser light L1 so that the angle of incidence of the laser light L1 on the polarizing beam splitter 6 is 45 degrees. The polarizing beam splitter 6 has a property of transmitting a first polarized component (e.g., p-polarized component) of the laser light L1 and reflecting a second polarized component (e.g., s-polarized component) of the laser light L1 that is orthogonal to the first polarized component. Therefore, the laser light L1 that has passed through the polarizing beam splitter 6 becomes linearly polarized light L11 that contains only the first polarized component.

[0034] The quarter-wave plate 7 is disposed between the polarizing beam splitter 6 and the galvano scanner 5 on the optical path of the laser light L1. The quarter-wave plate 7 converts linearly polarized light and circularly polarized light into each other. That is, linearly polarized light transmitted through the quarter-wave plate 7 is converted into circularly polarized light, and circularly polarized light transmitted through the quarter-wave plate 7 is converted into linearly polarized light. Therefore, the laser light L1 (linearly polarized light L11) that has passed through the polarizing beam splitter 6 becomes circularly polarized light L12 when it passes through the quarter-wave plate 7.

[0035] The light detection unit 8A detects return light L2 of the laser light L1 from the processing surface 100a of the workpiece 100 irradiated with the laser light L1. In this embodiment, the light detection unit 8A detects the signal intensity of the return light L2. The light detection unit 8A is, for example, a photodiode. After being reflected by the processing surface 100a, the return light L2 passes through the fθ lens 4, the galvano scanner 5, the ¼ wavelength plate 7, and the polarizing beam splitter 6 in this order, and reaches the light detection unit 8A.

[0036] In the laser processing apparatus 1A having the above configuration, the laser light L1 output from the laser light source 2 passes through the polarizing beam splitter 6, the quarter-wave plate 7, the galvano scanner 5, and the fθ lens 4 in this order, and is irradiated onto the processing surface 100a of the workpiece 100 placed on the stage 3. The laser light L1 becomes linearly polarized light L11 containing only the first polarization component by passing through the polarizing beam splitter 6. Thereafter, the laser light L1 (linearly polarized light L11) passes through the quarter-wave plate 7, and becomes circularly polarized light L12 corresponding to the first polarization component. The laser light L1 in the state of circularly polarized light L12 passes through the galvano scanner 5 and the fθ lens 4, and is irradiated onto the processing surface 100a of the workpiece 100 on the stage 3.

[0037] A part of the laser light L1 is reflected by the processing surface 100a, and thus a return light L2 is generated. The return light L2 immediately after being reflected by the processing surface 100a becomes circularly polarized light L21, which has a rotation direction opposite to that of the laser light L1 (circularly polarized light L12) incident on the processing surface 100a. This return light L2 (circularly polarized light L21) passes through the ¼ wavelength plate 7 via the fθ lens 4 and the galvano scanner 5. At this time, the return light L2 (circularly polarized light L21) is converted into linearly polarized light L22 by the ¼ wavelength plate 7. Here, the rotation direction of the return light L2 (circularly polarized light L21) incident on the ¼ wavelength plate 7 is opposite to that of the laser light L1 (circularly polarized light L12) after passing through the ¼ wavelength plate 7. Therefore, the return light L2 (linearly polarized light L22) that has passed through the quarter-wave plate 7 becomes linearly polarized light containing only a second polarization component whose polarization direction is 90 degrees different from that of the laser light L1 (linearly polarized light L11) before passing through the quarter-wave plate 7. Therefore, the return light L2 (linearly polarized light L22) does not pass through the polarizing beam splitter 6, but is reflected by the polarizing beam splitter 6. The light detection unit 8A is disposed on the optical path of the return light L2 (linearly polarized light L22) reflected in this manner. In this manner, by using the polarizing beam splitter 6 and the quarter-wave plate 7, the return light L2 can be detected by the light detection unit 8A while performing laser processing on the workpiece 100 using the laser light L1.

[0038] The control unit 9 monitors the processing state of the workpiece 100 based on the return light L2 detected by the light detection unit 8A. The processing state is, for example, the state (e.g., shape, diameter, depth, etc.) of the processing mark formed at the irradiation position (scanning position) of the laser light L1. In this embodiment, the control unit 9 detects an abnormality in the processing state of the workpiece 100 based on the signal intensity of the return light L2 detected by the light detection unit 8A.

[0039] The control unit 9 may be configured by a computer device having, for example, a processor such as a CPU (Central Processing Unit), a memory such as a RAM (Random Access Memory) or a ROM (Read Only Memory), an auxiliary storage device such as a HDD (Hard Disk Drive) or an SSD (Solid State Drive), etc. The control unit 9 is communicatively connected to each part of the laser processing apparatus 1A (in this embodiment, the laser light source 2, the stage 3, the galvano scanner 5, and the light detection unit 8A) and controls the operation of each part.

[0040] 2 is a diagram showing an example of the object 100, the signal intensity of the return light L2 detected by the light detection unit 8A, and a processing mark formed on the processing surface 100a. As shown in the upper part of FIG. 2, in this embodiment, as an example, the object 100 has a silicon substrate (silicon wafer) 101 and a metal layer 102 formed on the silicon substrate 101. As an example, the metal layer 102 is made of gold (Au) with a thickness of 100 nm. In this example, the processing surface 100a is the surface of the metal layer 102 opposite to the silicon substrate 101 side.

[0041] The lower left part of Fig. 2 shows an example of a signal waveform of return light L2 (detection light) detected by the light detection unit 8A when one shot of pulsed laser light L1 is irradiated to a certain scanning position on the processing surface 100a of the workpiece 100. As shown in Fig. 2, when the laser light L1 is a pulsed light, the signal waveform of the obtained return light L2 is also pulsed. The light detection unit 8A acquires, for example, the detection peak value (mV) of such pulsed return light L2 as the signal intensity of the return light L2.

[0042] 2 shows an example of an observation image of a processing mark formed at a certain scanning position on the processing surface 100a of the workpiece 100 after irradiating the scanning position with one shot of pulsed laser light L1. Such an observation image can be obtained by observation using a microscope or the like.

[0043] As described above, the laser light L1 output from the laser light source 2 becomes linearly polarized light L11 by passing through the polarizing beam splitter 6, and is further converted into circularly polarized light L12 by passing through the ¼ wavelength plate 7. Here, when the galvanometer scanner 5 including the galvanometer mirror 5a (dielectric mirror) is used as the optical scanning unit as in this embodiment, the phase difference between the orthogonal polarized lights of the laser light L1 changes when the laser light L1 is reflected by the galvanometer mirror 5a. Due to this, the return light L2 near the center of the scanning range of the processing surface 100a (i.e., the range that can be scanned by the galvanometer scanner 5) remains close to circularly polarized light (perfect circle), whereas the return light L2 at the periphery away from the center of the scanning range becomes elliptically polarized light. More specifically, when the galvano scanner 5 is adjusted so that the return light L2 obtained when the laser light L1 is irradiated to the center of the range that can be scanned by the galvano scanner 5 on the processing surface 100a (for example, a line segment area in the case of one-dimensional scanning, or a rectangular area in the case of two-dimensional scanning) is circularly polarized, the polarization state of the return light L2 becomes an ellipse with a higher flatness as the scanning position of the laser light L1 moves away from the center. As a result, a difference occurs between the signal intensity of the return light L2 from the center of the scanning range and the signal intensity of the return light L2 from the periphery of the scanning range. Specifically, the signal intensity of the return light L2 detected by the light detection unit 8A tends to decrease as the scanning position of the laser light L1 moves away from the center of the scanning range. Note that such a relationship between the scanning range and the signal intensity (optical characteristics) is uniquely determined by the galvano scanner 5 used. That is, the relationship between the scanning range and the signal intensity does not change over time or due to differences in the processing target 100.

[0044] Therefore, the control unit 9 may correct the signal intensity of the return light L2 obtained by the light detection unit 8A based on the scanning position of the laser light L1. An example of the correction process by the control unit 9 will be described with reference to Fig. 3. Here, the case where the laser light L1 is scanned one-dimensionally (i.e., the scanning range is a one-dimensional line segment area) will be described as an example.

[0045] The left part of Fig. 3 shows an example of signal intensity data indicating the signal intensity (mV) of the return light L2 at each scanning position acquired by the light detection unit 8A. As shown in the left part of Fig. 3, the signal intensity (detection peak value) of the return light L2 detected by the light detection unit 8A is maximum at the center of the scanning range, and decreases as it moves away from the center of the scanning range. That is, as shown in the left part of Fig. 3, when the horizontal axis represents the scanning position and the vertical axis represents the signal intensity, the contour of the graph representing the signal intensity of the return light L2 at each scanning position has a mountain-shaped shape. The control unit 9 derives a fitting function by performing curve fitting on such signal intensity data.

[0046] The center of Fig. 3 shows an example of a fitting function obtained from the signal intensity data in the left part of Fig. 3. Next, the control unit 9 calculates a correction coefficient (offset amount) based on the fitting function to make the signal intensity of the return light L2 at each scanning position equal to the signal intensity of the return light L2 at the center of the scanning range. For example, if the signal intensity of the return light L2 at the center of the scanning range is represented as Imax, the signal intensity of the return light L2 at an arbitrary scanning position p other than the center is represented as Ip, and the correction coefficient for the scanning position p is represented as r, the control unit 9 calculates the correction coefficient r for each scanning position p such that "Imax ≈ Ip + r".

[0047] The right part of FIG. 3 shows an example of the correction coefficient for each scanning position obtained in this way. The control unit 9 can obtain a signal intensity for each scanning position equivalent to the signal intensity obtained at the center of the scanning range by adding a correction coefficient according to the scanning position to the signal intensity of the return light L2 detected by the light detection unit 8A. As a result, it becomes possible to perform processing based on the signal intensity of the return light L2 on a uniform basis regardless of the scanning position (for example, detection of abnormality in the processing state, adjustment of the irradiation energy of the laser light L1, etc.). In addition, in the case of two-dimensional scanning of the laser light L1, the control unit 9 can calculate a correction coefficient for each scanning position based on the same idea as in the case of one-dimensional scanning of the laser light L1. In addition, the correction coefficient is not limited to the above example. For example, a correction coefficient r such that "Imax ≒ Ip × r" may be used.

[0048] FIG. 4 is a diagram showing an example of the relationship between the irradiation energy of the laser light L1, the signal intensity of the return light L2, and the diameter of the processing mark. In FIG. 4, the horizontal axis represents the irradiation energy (%) when the maximum value of the irradiation energy (μJ) of the laser light L1 (maximum output of the laser light source 2) is set to 100%. The vertical axis represents the ratio of the signal intensity (mV) of the return light L2 to the irradiation energy (μJ) of the laser light L1 (i.e., "the detection peak value (mV) of the return light L2 detected by the light detection unit 8A ÷ the irradiation energy (μJ) of the laser light L1") and the diameter (μm) of the processing mark (see the lower right of FIG. 2) formed on the processing surface 100a. The graph G1 shown in FIG. 4 shows the relationship between the irradiation energy of the laser light L1 and the signal intensity of the return light L. The graph G2 shows the relationship between the irradiation energy of the laser light L1 and the diameter of the processing mark formed on the processing surface 100a.

[0049] The graph G1 is obtained, for example, as follows. As described above, the laser processing apparatus 1A can detect the signal intensity of the return light L2 in the light detection unit 8A while performing laser processing (irradiation of the laser light L1) on the workpiece 100. The control unit 9 can obtain the graph G1 by performing arithmetic processing based on the irradiation energy of the laser light L1 and the signal intensity of the return light L2 detected in the light detection unit 8A. Here, as described above, the control unit 9 can correct the signal intensity of the return light L2 based on the scanning position of the laser light L1. More specifically, the control unit 9 can obtain the signal intensity at any scanning position based on the signal intensity obtained at the center of the scanning range by adding a correction coefficient according to the scanning position to the signal intensity of the return light L2 detected by the light detection unit 8A. Therefore, for example, on the processing surface 100a of the same workpiece 100, the signal intensity of the return light L2 can be detected while changing the irradiation energy of the laser light L1 for each scanning position, the detected signal intensity is corrected according to the scanning position, and the corrected signal intensity is used to easily generate graph G1.

[0050] The graph G2 is obtained, for example, as follows: That is, an observation image of the processing mark formed at each scanning position after laser processing of the processing object 100 is obtained, and the obtained observation image is analyzed to obtain the diameter of the processing mark. Then, the obtained diameter is related to the irradiation energy of the laser light L1 irradiated to each scanning position, whereby the graph G2 can be obtained.

[0051] As shown in FIG. 4, in this example, from graphs G1 and G2 and the observation image acquired when creating graph G2, three classifications (areas R1, R2, and R3) of the processing state according to the irradiation energy of the laser light L1 were grasped.

[0052] Region R1, where the irradiation energy of the laser light L1 is 5% to 15% of the maximum output, is a region where only a small part of the irradiation energy of the laser light L1 irradiated to the workpiece 100 is converted into processing energy for processing the processing surface 100a. In region R1, the return light L2 is detected with a relatively high reflectance (i.e., the ratio of the signal intensity of the return light L2 to the irradiation energy of the laser light L1). Also, in region R1, a part of the metal layer 102 on the silicon substrate 101 is processed, and the rate of change in the diameter of the processing mark with respect to the irradiation energy of the laser light L1 becomes relatively large.

[0053] Region R2, where the irradiation energy of the laser light L1 is 15% to 90% of the maximum output, is a region where a part (a higher proportion than in region R1) of the irradiation energy of the laser light L1 irradiated to the workpiece 100 is converted into processing energy. In region R2, the reflectance of the return light L2 is lower than in region R1. Also, in region R2, a part of the metal layer 102 on the silicon substrate 101 is removed, and the size of the removed region (diameter of the processing mark) changes depending on the irradiation energy of the laser light L1. In region R2, as the irradiation energy increases, the reflectance with respect to the irradiation energy decreases almost linearly, and the diameter of the processing mark increases almost linearly.

[0054] In region R3 where the irradiation energy of the laser light L1 is 90% to 100% of the maximum output, the diameter of the processed mark is approximately the maximum diameter determined by the optical system of the laser processing apparatus 1A, and both the reflectance and the diameter of the processed mark are saturated.

[0055] 4, it was confirmed that there is a correlation between the ratio of the return light L2 to the irradiation energy of the laser light L1 (the reflectance of the return light L2) and the diameter of the processing mark. By utilizing such a correlation, the control unit 9 can determine whether or not the diameter of the processing mark formed on the processing surface 100a matches a predetermined target value (or target range) based on the signal intensity of the return light L2 detected by the light detection unit 8A (in this embodiment, a correction value obtained by adding a correction coefficient according to the scanning position; the same applies below) while performing laser processing (irradiation of the laser light L1) on the processing object 100.

[0056] For example, in the example of Fig. 4, it is assumed that the target value of the diameter of the processing mark is set to 75 µm. In this case, the control unit 9 can specify the irradiation energy of the laser light L1 for making the diameter of the processing mark 75 µm from the graph G2 of Fig. 4. In the example of Fig. 4, "50%" is specified as the above-mentioned irradiation energy. As a result, the control unit 9 can control the output of the laser light source 2 so that the irradiation energy of the laser light L1 is 50%.

[0057] Furthermore, the control unit 9 can specify the ratio of the signal intensity of the return light L2 to the irradiation energy of the laser light L1 when the irradiation energy of the laser light L1 is set to 50% from the graph G1 in FIG. 4 (i.e., the normal value obtained when the laser processing is performed normally). In the example of FIG. 4, "2.8" is specified as the above ratio. Therefore, the control unit 9 can monitor the signal intensity of the return light L2 obtained by irradiating the processing surface 100a with the laser light L1, and determine whether the signal intensity of the return light L2 during the laser processing is an appropriate value based on whether the ratio of the signal intensity of the return light L2 to the irradiation energy of the laser light L1 coincides with "2.8" (or whether the difference from "2.8" is equal to or less than a predetermined threshold). That is, the control unit 9 can determine whether the laser processing of the processing object 100 is performed normally based on whether the ratio of the signal intensity of the return light L2 to the irradiation energy of the laser light L1 is a predetermined normal value (in this example, a value within a predetermined threshold value from "2.8"). In other words, the control unit 9 can detect an abnormality in the processing state of the workpiece 100 (e.g., the diameter of the processing mark, etc.) when the signal intensity of the return light L2 is not an appropriate value (i.e., when the above ratio is not a predetermined normal value).

[0058] (First operation example) A first operation example of the laser processing apparatus 1A will be described with reference to FIG. 5. In step S101, the workpiece 100 is placed on the stage 3. In step S102, the control unit 9 drives the stage 3 to adjust (align) the position of the workpiece 100. In step S103, laser processing (scanning) is started. More specifically, the laser light L1 output from the laser light source 2 is guided to the galvanometer scanner 5 via the polarizing beam splitter 6 and the ¼ wavelength plate 7 in this order, and the galvanometer scanner 5 operates the galvanometer mirror 5a to change the incident angle of the laser light L1 with respect to the fθ lens 4, thereby scanning the laser light L1 on the processing surface 100a.

[0059] In step S104, the light detection unit 8A detects the return light L2 of the laser light L1. More specifically, the light detection unit 8A detects the return light L2 of the laser light L1 from the processing surface 100a of the workpiece 100 irradiated with the laser light L1, which passes through the fθ lens 4, the galvano scanner 5, the ¼ wavelength plate 7, and the polarizing beam splitter 6 in this order. In this embodiment, the light detection unit 8A detects the signal intensity (detection peak value) of the return light L2 for each scanning position.

[0060] In step S105, the control unit 9 corrects the signal intensity detected by the light detection unit 8A based on the scanning position of the laser light L1. As an example, the control unit 9 obtains the corrected signal intensity by adding the correction coefficient for each scanning position calculated by the above-mentioned method to the signal intensity detected by the light detection unit 8A.

[0061] In step S106, the control unit 9 detects an abnormality in the processing state of the workpiece 100 based on the corrected signal intensity. For example, the control unit 9 judges whether the signal intensity of the return light L2 acquired during laser processing is an appropriate value (a value such that the ratio of the signal intensity of the return light L2 to the irradiation energy of the laser light L1 falls within a predetermined threshold value from "2.8" in the example of FIG. 4) based on the graphs G1 and G2 in FIG. 4 (i.e., information showing the relationship between the irradiation energy of the laser light L1 output from the laser light source 2, the signal intensity of the return light L2, and the diameter of the processing mark formed on the processing surface 100a) and a target value of the diameter of the processing mark (e.g., 75 μm).

[0062] When it is determined that the signal intensity of the return light L2 is not an appropriate value (step S106: NO), the control unit 9 detects an abnormality in the processing state of the workpiece 100 (step S107). Then, the control unit 9 executes a predetermined abnormality processing. For example, the control unit 9 may control the operation of the laser light source 2 and the galvano scanner 5 so as to perform additional processing (re-irradiation of the laser light L1) on the scanning position where the abnormality was detected. The control unit 9 may also adjust the irradiation energy (output power) of the laser light L1 by controlling the operation of the laser light source 2. The control unit 9 may also stop the operation of the laser light source 2 and the galvano scanner 5 at the time when the abnormality is detected, and interrupt the laser processing. The control unit 9 may also output display information indicating the occurrence of an error to a display unit such as a display provided in the control unit 9, or may output an alert sound indicating the occurrence of an error from a speaker or the like provided in the control unit 9.

[0063] The processes of steps S103 to S106 are executed for each scanning position. That is, the processes of steps S103 to S106 are executed for each scanning position until scanning of all scanning positions within a predetermined scanning range is completed (step S108: NO). When it is determined that the signal intensity of the return light L2 is an appropriate value at each scanning position (step S106: YES) and scanning of all scanning positions is completed (step S108: YES), the laser processing of the workpiece 100 by the laser processing apparatus 1A is normally completed.

[0064] In the first operation example described above, the control unit 9 determines whether or not the laser processing of the scanning position has been performed normally (i.e., whether or not the signal intensity is an appropriate value) based on the signal intensity detected at the scanning position (in this embodiment, the signal intensity after correction of the return light L2) each time the laser light L1 is irradiated to the scanning position. Then, in response to determining that the laser processing of the scanning position has not been performed normally (step S106: NO), the control unit 9 detects an abnormality in the processing state of the workpiece 100.

[0065] (Second operation example) In the second operation example, after the laser processing (scanning) of the entire predetermined scanning range is completed, the control unit 9 integrates the signal intensity of the return light L2 detected by the light detection unit 8A for each scanning position of the entire scanning range, and detects an abnormality in the processing state of the workpiece 100 based on the integration result. This is based on the following idea. That is, as described above, there is a difference in the signal intensity of the return light L2 obtained at the center and the periphery of the scanning range. Such a difference in the magnitude of the signal intensity due to the scanning position becomes a problem when monitoring the processing state for each scanning position. For this reason, in the first operation example in which the processing state is monitored for each scanning position, the control unit 9 performs a correction process of the signal intensity using a correction coefficient according to the scanning position so that there is no variation in the signal intensity of the return light L2 obtained for each scanning position. On the other hand, if it is sufficient to monitor whether the laser processing has been performed normally for each scanning range (for example, for each workpiece 100), such a correction process can be omitted. For example, first, laser processing is performed on the entire scanning range of a certain object 100, and an integrated value of the signal intensity of the return light L2 detected at each scanning position in the entire scanning range is obtained. Then, it is confirmed afterwards by a predetermined inspection such as visual inspection that the laser processing of the object 100 has been performed normally. This makes it possible to grasp the integrated value (i.e., the normal value of the integrated value) obtained when the laser processing of the entire scanning range (in this example, one object 100) is performed normally. Therefore, when performing similar laser processing on multiple objects 100 of the same type, the control unit 9 calculates the integrated value of the signal intensity of the return light L2 detected at each scanning position in the entire scanning range each time the laser processing of the entire scanning range of one object 100 is completed, and determines whether the calculated integrated value is within a predetermined threshold value from a previously determined normal value, thereby making it possible to determine whether the laser processing of the object 100 has been performed normally.

[0066] A second operation example of the laser processing apparatus 1A will be described with reference to FIG. 6. The processes of steps S201 to S204 are the same as those of steps S101 to S104. In the second operation example, the processes of steps S203 and S204 are executed until scanning within a predetermined scanning range is completed (step S205: NO). When scanning within the scanning range (i.e., irradiation of all scanning positions within the scanning range with the laser light L1) is completed (step S205: YES), the control unit 9 acquires an integrated value of the signal intensity of the return light L2 detected at each scanning position within the entire scanning range (step S206).

[0067] In step S207, the control unit 9 judges whether the integrated value obtained in step S206 is an appropriate value. For example, the control unit 9 judges whether the integrated value is within a predetermined threshold from a previously grasped normal value. If the difference between the integrated value and the normal value exceeds the threshold (step S207: NO), the control unit 9 detects an abnormality in the processing state of the workpiece 100 (step S208). Then, the control unit 9 executes a predetermined abnormality processing. For example, the control unit 9 may output display information indicating the occurrence of an error to a display unit such as a display provided in the control unit 9, or may output an alert sound or the like indicating the occurrence of an error from a speaker or the like provided in the control unit 9. On the other hand, if it is judged that the integrated value is an appropriate value (i.e., the difference between the integrated value and the normal value is within the threshold) (step S208: NO), the abnormality processing is not executed, and the laser processing of the workpiece 100 by the laser processing device 1A is normally completed.

[0068] In the laser processing apparatus 1A described above, by using the polarizing beam splitter 6 and the quarter-wave plate 7, the detection efficiency of the return light L2 from the processing surface 100a of the processing object 100 can be improved compared to the case where the polarizing beam splitter 6 and the quarter-wave plate 7 are not used. More specifically, all of the return light L2 (linearly polarized light L22) can be reflected by the polarizing beam splitter 6 and guided to the light detection unit 8A. Furthermore, by disposing the quarter-wave plate 7 between the polarizing beam splitter 6 and the galvano scanner 5, the size of the quarter-wave plate 7 can be made smaller than the case where the quarter-wave plate 7 is disposed between the fθ lens 4 and the processing object 100 (stage 3). In other words, it is not necessary to increase the size of the quarter-wave plate 7 according to the size of the processing object 100 so as to cover the entire processing object 100 (processing surface 100a). As a result, the entire laser processing apparatus 1A can be made smaller. Furthermore, by not locating the quarter-wave plate 7 in a position facing the workpiece 100, it is possible to prevent the quarter-wave plate 7 from being contaminated by droplets and the like generated from the workpiece 100 during laser processing.

[0069] As in the above embodiment, the control unit 9 may monitor the processing state of the workpiece 100 based on the return light L2 detected by the light detection unit 8A (in this embodiment, the signal intensity of the return light L2). According to the above configuration, the processing state of the workpiece 100 can be easily monitored based on the return light L2 detected during laser processing. More specifically, since the return light L2 for monitoring the processing state can be detected by the light detection unit 8A at the same time as the laser light L1 is irradiated onto the workpiece 100, the processing state can be easily monitored during the processing process.

[0070] As in the above embodiment, the light detection unit 8A may detect the signal intensity of the return light L2, and the control unit 9 may detect an abnormality in the processing state of the work-piece 100 based on the signal intensity detected by the light detection unit 8A. According to the above configuration, it is possible to appropriately detect an abnormality in the processing state based on the signal intensity of the return light L2 and take appropriate measures.

[0071] As in the above embodiment (first operation example), the control unit 9 may correct the signal intensity of the return light L2 based on the scanning position of the laser light L1, and may detect an abnormality in the processing state of the workpiece 100 based on the corrected signal intensity. According to the above configuration, the signal intensity of the return light L2 detected at each position in the scanning range can be made uniform by correcting the signal intensity based on the tendency that the signal intensity of the return light L2 detected decreases as the irradiation position (scanning position) of the laser light L1 moves away from the center of the scanning range. This makes it possible to determine whether the laser processing is being performed normally (i.e., whether the signal intensity (correction value) is an appropriate value) for each scanning position based on a uniform standard.

[0072] As in the above embodiment (first operation example), the control unit 9 may determine whether or not the laser processing of the scanning position has been performed normally based on the signal intensity detected at the scanning position each time the laser light L1 is irradiated to the scanning position, and may detect an abnormality in the processing state of the workpiece 100 in response to determining that the laser processing of the scanning position has not been performed normally. According to the above configuration, an abnormality in the processing state can be detected appropriately and immediately during the processing process.

[0073] As in the above embodiment (first operation example), the control unit 9 may determine whether the signal intensity of the return light L2 (in this embodiment, the corrected value) is an appropriate value based on the relationship between the irradiation energy of the laser light L1 output from the laser light source 2, the signal intensity of the return light L2, and the diameter of the machining mark formed on the machining surface 100a, and the target value of the diameter of the machining mark, and may detect an abnormality in the machining state of the workpiece 100 in response to the determination that the signal intensity is not an appropriate value. According to the above configuration, during the machining process, an abnormality in the machining state can be appropriately detected based on the relationship between the irradiation energy of the laser light L1, the signal intensity of the return light L2, and the diameter of the machining mark.

[0074] As in the above embodiment (second operation example), the control unit 9 may integrate the signal intensity of the return light L2 detected at each scanning position in the entire predetermined scanning range, and may detect an abnormality in the processing state of the workpiece 100 based on the integration result. According to the above configuration, by using the integration result of the signal intensity of the return light L2 detected in the entire scanning range, it is possible to absorb the difference in signal intensity due to the difference in scanning position and perform abnormality detection for each scanning range. In addition, since it is not necessary to correct the signal intensity of the return light L2 detected at each scanning position, the amount of calculation (i.e., the processing load of the control unit 9) can be reduced accordingly.

[0075] The laser processing method performed by the laser processing apparatus 1A is a method of processing the object 100 by focusing laser light L1 on a processing surface 100a of the object 100 placed (supported) on a stage 3 using an fθ lens 4. This laser processing method includes the steps of guiding the laser light L1 output from the laser light source 2 to the galvanometer scanner 5 via the polarizing beam splitter 6 and the 1 / 4 wavelength plate 7 in this order, and scanning the laser light L1 on the processing surface 100a by operating the galvanometer mirror 5a in the galvanometer scanner 5 to change the incident angle of the laser light L1 with respect to the fθ lens 4 (for example, step S103 in FIG. 5, step S203 in FIG. 6, etc.), and detecting the return light L2 of the laser light L1 from the processing surface 100a of the workpiece 100 irradiated with the laser light L1, which passes through the fθ lens 4, the galvanometer scanner 5, the 1 / 4 wavelength plate 7, and the polarizing beam splitter 6 in this order, by the light detection unit 8A (for example, step S104 in FIG. 5, step S204 in FIG. 6, etc.). According to the above laser processing method, the same effect as that of the above-mentioned laser processing apparatus 1A is achieved.

[0076] The above-described laser processing method may further include a step of monitoring the processing state of the workpiece 100 based on the return light L2 detected by the light detection unit 8A (for example, steps S105 to S107 in FIG. 5, steps S206 to S208 in FIG. 6, etc.). According to the above-described configuration, the processing state of the workpiece 100 can be easily monitored based on the return light L2 detected during laser processing.

[0077] In the above laser processing method, the detecting step may detect the signal intensity of the return light L2, and the monitoring step may detect an abnormality in the processing state of the workpiece 100 based on the detected signal intensity. According to the above configuration, it is possible to appropriately detect an abnormality in the processing state based on the signal intensity of the return light L2 and appropriately deal with it.

[0078] In the above laser processing method, the monitoring step may include a process of correcting the signal intensity based on the scanning position of the laser light L1 (e.g., step S105 in FIG. 5), and a process of detecting an abnormality in the processing state of the workpiece 100 based on the corrected signal intensity (e.g., steps S106 and S107 in FIG. 5). According to the above configuration, it is possible to make the magnitude of the signal intensity of the return light L2 detected at each position in the scanning range uniform, and to determine whether the laser processing is being performed normally for each scanning position based on a uniform criterion.

[0079] In the above laser processing method, the monitoring step may include a process of determining whether or not the laser processing of the scanning position has been performed normally based on the signal intensity detected at the scanning position each time the laser light L1 is irradiated to the scanning position (e.g., step S106 in FIG. 5), and a process of detecting an abnormality in the processing state of the workpiece 100 in response to determining that the laser processing of the scanning position has not been performed normally (e.g., step S107 in FIG. 5). According to the above configuration, an abnormality in the processing state can be detected appropriately and immediately during the processing process.

[0080] In the above laser processing method, the monitoring step may include a process of determining whether or not the signal intensity is an appropriate value based on the relationship between the irradiation energy of the laser light L1 output from the laser light source 2, the signal intensity of the return light L2, and the diameter of the processing mark formed on the processing surface 100a, and a target value of the diameter of the processing mark (e.g., step S106 in FIG. 5), and a process of detecting an abnormality in the processing state of the processing object 100 in response to the determination that the signal intensity is not an appropriate value (e.g., steps S106 and S107 in FIG. 5). According to the above configuration, during the processing process, an abnormality in the processing state can be appropriately detected based on the relationship between the irradiation energy of the laser light L1, the signal intensity of the return light L2, and the diameter of the processing mark.

[0081] In the above laser processing method, the monitoring step may include a process of integrating the signal intensity of the return light L2 detected at each scanning position in the entire predetermined scanning range (e.g., step S206 in FIG. 6), and a process of detecting an abnormality in the processing state of the workpiece 100 based on the integration result (e.g., steps S207 and S208 in FIG. 6). According to the above configuration, by using the integration result of the signal intensity detected in the entire scanning range, it is possible to absorb the difference in signal intensity due to the difference in scanning position and perform abnormality detection for each scanning range. In addition, since it is not necessary to correct the signal intensity of the return light L2 detected at each scanning position, the amount of calculation can be reduced accordingly.

[0082] [Second embodiment] 7 differs from the laser processing apparatus 1A in that the laser processing apparatus 1B of the second embodiment further includes a beam shaping unit 10. The laser processing apparatus 1B also differs from the laser processing apparatus 1A in that the laser processing apparatus 1B includes a light detection unit 8B instead of the light detection unit 8A.

[0083] The beam shaping unit 10 is a beam shaping element that performs beam shaping of the laser light L1. The beam shaping unit 10 is, for example, a beam homogenizer. When performing beam shaping by such a beam shaping unit 10, the beam profile (beam shape) on the processing surface 100a changes depending on the distance between the processing lens (fθ lens 4) and the processing surface 100a of the processing object 100 (i.e., the distance between the fθ lens 4 and the stage 3). Therefore, in the second embodiment, in order to observe the beam profile during laser processing, the light detection unit 8B is configured to be able to detect a two-dimensional image of the return light L2. For example, the light detection unit 8B is configured by a camera.

[0084] 8A and 8B show examples of a two-dimensional image (upper side) of the return light L2 detected (imaged) by the light detection unit 8B when the laser light L1 is irradiated onto the processing surface 100a, and an observation image (lower side) of the processing mark actually formed on the processing surface 100a. FIG. 8A shows a two-dimensional image (upper side) and an observation image (lower side) when the distance between the fθ lens 4 and the processing surface 100a is appropriate and a processing mark having an appropriate shape close to a predetermined target shape is obtained. FIG. 8B shows a two-dimensional image (upper side) and an observation image (lower side) when the distance between the fθ lens 4 and the processing surface 100a is not appropriate and a processing mark having an inappropriate shape different from the target shape is obtained.

[0085] From the results shown in FIG. 8, it was confirmed that there is a correlation between the two-dimensional image of the return light L2 captured by the light detection unit 8B when the laser light L1 is irradiated onto the processing surface 100a and the shape of the processing mark formed on the processing surface 100a. In other words, it was confirmed that it is possible to estimate the approximate shape of the processing mark formed on the processing surface 100a from the two-dimensional image of the return light L2. Therefore, it is possible to perform laser processing appropriately by adjusting the distance between the fθ lens 4 and the processing surface 100a so that a two-dimensional image corresponding to a processing mark having an appropriate shape close to the target shape is obtained as shown in FIG. 8(A). Therefore, the control unit 9 adjusts the distance between the fθ lens 4 and the processing surface 100a so that a two-dimensional image corresponding to the target shape is detected by the light detection unit 8B, for example, based on the relationship between the two-dimensional image captured by the light detection unit 8B and the shape of the processing mark formed on the processing surface 100a, and the target shape of the processing mark. Here, the relationship between the two-dimensional image and the shape of the processing marks is information that associates several observation images of the processing marks with the two-dimensional images at that time, as shown in FIG.

[0086] An example of the operation of the laser processing apparatus 1B will be described with reference to Fig. 9. Steps S301 and S302 are similar to steps S101 and S102.

[0087] In step S303, the laser processing apparatus 1B irradiates a predetermined position on the processing surface 100a with the laser light L1.

[0088] In step S304, the light detection unit 8B detects a two-dimensional image (see the upper side of FIG. 8(A) or (B)) of the return light L2 of the laser light L1.

[0089] In step S305, the control unit 9 adjusts the distance between the fθ lens 4 and the stage 3 (i.e., the distance between the fθ lens 4 and the processing surface 100a) based on the two-dimensional image detected by the light detection unit 8B. For example, based on the relationship between the two-dimensional image detected by the light detection unit 8B and the shape of the processing mark formed on the processing surface 100a and the target shape of the processing mark, the control unit 9 adjusts the distance between the fθ lens 4 and the stage 3 so that the two-dimensional image corresponding to the target shape is detected by the light detection unit 8B. For example, the control unit 9 adjusts the distance between the fθ lens 4 and the stage 3 by driving the stage 3 and adjusting the position (height position) of the stage 3 in the Z-axis direction.

[0090] For example, the laser processing apparatus 1B can first grasp the appropriate distance between the fθ lens 4 and the stage 3 suitable for the workpiece 100 by executing the process shown in Fig. 9 using an adjustment sample (workpiece 100) prepared for adjusting the distance between the fθ lens 4 and the stage 3. Thereafter, when performing laser processing on the same type of workpiece 100 as the adjustment sample, the laser processing apparatus 1B (control unit 9) sets the distance between the fθ lens 4 and the stage 3 to the appropriate distance and then starts laser processing on the processing surface 100a, thereby improving the laser processing accuracy of the processing surface 100a.

[0091] In addition, according to the laser processing device 1B, the relationship between the irradiation energy (%) of the laser light L1 and the diameter (μm) of the processing mark as shown in FIG. 10 can be easily grasped. For example, consider the case where the beam shaping unit 10 shapes the beam of the laser light L1 so that the beam profile of the laser light L1 follows a Gaussian distribution. In such a case, a circular two-dimensional image is obtained by the light detection unit 8B. In addition, as described above, there is a correlation between the two-dimensional image obtained by the light detection unit 8B and the shape of the processing mark actually formed on the processing surface 100a. Therefore, by grasping the correlation between the two-dimensional image and the shape (diameter) of the processing mark in advance, it becomes possible to calculate (estimate) the diameter of the processing mark from the two-dimensional image. For example, the control unit 9 can easily obtain information as shown in FIG. 10 by executing a process of correlating the irradiation energy of the laser light L1 output from the laser light source 2 with the two-dimensional image of the return light L2 of the laser light L1 and the diameter of the processing mark calculated from the above correlation while changing the scanning position and the irradiation energy of the laser light L1.

[0092] In the laser processing apparatus 1B, the light detection unit 8B detects a two-dimensional image of the return light L2, and the control unit 9 adjusts the distance between the fθ lens 4 and the stage 3 (i.e., the distance between the fθ lens 4 and the processing surface 100a) based on the two-dimensional image detected by the light detection unit 8B. That is, in the laser processing method performed by the laser processing apparatus 1B, a two-dimensional image of the return light L2 is detected in a detection step (e.g., step S304 in FIG. 9), and the distance between the fθ lens 4 and the stage 3 is adjusted based on the detected two-dimensional image in a monitoring step (e.g., step S305 in FIG. 9). According to the above configuration, the distance between the fθ lens 4 and the stage 3 can be adjusted based on the two-dimensional image (i.e., the beam profile) of the return light L2 from the processing target 100 so that the beam profile at the processing position (irradiation position) on the processing surface 100a has an appropriate shape. This can improve the processing quality.

[0093] In the above embodiment, the control unit 9 may adjust the distance between the fθ lens 4 and the stage 3 (i.e., the distance between the fθ lens 4 and the processing surface 100a) based on the relationship between the two-dimensional image and the shape (e.g., diameter, etc.) of the processing mark formed on the processing surface 100a and the target shape of the processing mark so that the two-dimensional image corresponding to the target shape is detected by the light detection unit 8B. That is, in the laser processing method performed by the laser processing apparatus 1B, in the monitoring step (e.g., step S305 in FIG. 9), the distance between the fθ lens 4 and the stage 3 may be adjusted based on the relationship between the two-dimensional image and the diameter of the processing mark formed on the processing surface 100a and the target shape of the processing mark so that the two-dimensional image corresponding to the target shape is detected by the light detection unit 8B. According to the above configuration, the distance between the fθ lens 4 and the stage 3 can be appropriately adjusted based on the relationship between the two-dimensional image and the shape of the processing mark grasped in advance.

[0094] [Variations] Although one embodiment of the present disclosure has been described above, the present disclosure is not limited to the above embodiment. The materials and shapes of each component are not limited to the above-mentioned materials and shapes, and various materials and shapes can be adopted.

[0095] For example, in the above embodiment, the laser light L1 is transmitted through the polarizing beam splitter 6, and the return light L2 is reflected by the polarizing beam splitter 6. However, the laser light L1 may be reflected by the polarizing beam splitter 6, and the return light L2 may be transmitted through the polarizing beam splitter 6. More specifically, in the above embodiment, the first polarized component (linearly polarized light L11) of the laser light L1 that has transmitted through the polarizing beam splitter 6 is guided to the workpiece 100, but the linearly polarized light (component traveling upward in FIG. 1) having only the second polarized component of the laser light L1 reflected by the polarizing beam splitter 6 may be guided to the workpiece 100 via the quarter-wave plate 7, the galvano scanner 5, and the fθ lens 4. In this case, the return light L2 that returns to the polarizing beam splitter 6 by following a path opposite to that of the linearly polarized light having only the second polarized component of the laser light L1 is linearly polarized light having only the first polarized component, and is therefore configured to transmit through the polarizing beam splitter 6 and reach the light detection unit 8A.

[0096] Furthermore, in the first operation example of the first embodiment described above, whether or not the laser processing has been performed normally is determined based on whether or not the ratio of the signal intensity of the return light L2 to the irradiation energy of the laser light L1 is a normal value. However, more simply, whether or not the laser processing has been performed normally may be determined based on whether or not the signal intensity of the return light L2 is a predetermined normal value.

[0097] In addition, in the first operation example of the first embodiment, the correction process of the signal intensity of the return light L2 may be omitted. For example, if a normal value of the signal intensity of the return light L2 is acquired in advance for each scanning position, it is possible to determine whether the signal intensity of the return light L2 is an appropriate value (i.e., whether the laser processing has been performed normally) by comparing the signal intensity of the return light L2 before correction with the normal value prepared for each scanning position. However, by performing the correction process, it is possible to eliminate the need to prepare a normal value to be compared for each scanning position.

[0098] In the above embodiment, the outer surface of the workpiece 100 (for example, the surface of the metal layer 102 opposite to the silicon substrate 101 side) is the processing surface 100a, but the processing surface to be laser processed is not limited to the outer surface of the workpiece. For example, in the above embodiment, the interface between the silicon substrate 101 and the metal layer 102 (i.e., the surface located inside the workpiece) may be the processing surface. In this case, for example, in FIG. 2, the workpiece 100 may be arranged so that the silicon substrate 101 is on the upper side (the fθ lens 4 side) and the metal layer 102 is on the lower side (the stage 3 side). Then, the laser light L1 having a wavelength that transmits through the silicon substrate 101 may be irradiated from the silicon substrate 101 side, and the laser light L1 may be focused on the surface of the metal layer 102 on the silicon substrate 101 side (i.e., the interface between the silicon substrate 101 and the metal layer 102), thereby performing laser processing on the interface (processing surface). In this case, the return light L2 generated at the interface passes through the silicon substrate 101 and travels toward the fθ lens 4.

[0099] Furthermore, the support part that supports the object 100 is not limited to the stage 3. For example, instead of the stage 3, an arm member or the like configured to hold (clamp) the side surface of the object 100 may be used as the support part.

[0100] Furthermore, a portion of the configuration in one of the above-described embodiments or modifications can be arbitrarily applied to configurations in other embodiments or modifications. [Explanation of symbols]

[0101] Reference Signs List 1A, 1B... laser processing device, 2... laser light source, 3... stage, 4... fθ lens, 5... galvanometer scanner (light scanning unit), 5a... galvanometer mirror (dielectric mirror), 6... polarizing beam splitter, 7... 1 / 4 wavelength plate, 8A, 8B... light detection unit, 9... control unit, 100... object to be processed, 100a... processing surface, L1... laser light, L2... return light.

Claims

1. a laser light source that outputs laser light; A support portion that supports the workpiece; an fθ lens that focuses the laser light on a processing surface of the object; an optical scanning unit that scans the laser light on the processing surface by adjusting an incident angle of the laser light with respect to the fθ lens by operating a dielectric mirror; a polarizing beam splitter disposed between the laser light source and the optical scanning unit on an optical path of the laser light; a quarter-wave plate disposed on the optical path between the polarizing beam splitter and the optical scanning unit; a light detection unit that detects return light of the laser light from the processing surface of the object irradiated with the laser light, the return light passing through the fθ lens, the light scanning unit, the quarter wavelength plate, and the polarizing beam splitter in this order; a control unit that monitors a processing state of the object based on the return light detected by the light detection unit, The light detection unit detects a two-dimensional image of the return light, The control unit adjusts the distance between the fθ lens and the processing surface based on the two-dimensional image detected by the light detection unit.

2. The control unit adjusts the distance between the fθ lens and the processing surface based on a relationship between the two-dimensional image and a shape of a processing mark formed on the processing surface and a target shape of the processing mark so that the two-dimensional image corresponding to the target shape is detected by the light detection unit.

2. The laser processing apparatus according to claim 1.

3. A laser light source that outputs laser light; A support portion that supports the workpiece; an fθ lens that focuses the laser light on a processing surface of the object; an optical scanning unit that scans the laser light on the processing surface by adjusting an incident angle of the laser light with respect to the fθ lens by operating a dielectric mirror; a polarizing beam splitter disposed between the laser light source and the optical scanning unit on an optical path of the laser light; a quarter-wave plate disposed on the optical path between the polarizing beam splitter and the optical scanning unit; a light detection unit that detects return light of the laser light from the processing surface of the object irradiated with the laser light, the return light passing through the fθ lens, the light scanning unit, the quarter wavelength plate, and the polarizing beam splitter in this order; a control unit that monitors a processing state of the object based on the return light detected by the light detection unit, The light detection unit detects a signal intensity of the return light, The control unit determines whether or not the signal strength detected by the light detection unit is an appropriate value based on the relationship between the irradiation energy of the laser light output from the laser light source, the signal strength, and the diameter of the processing mark formed on the processing surface, and a target value for the diameter of the processing mark, and detects an abnormality in the processing state of the object to be processed if it is determined that the signal strength is not an appropriate value.

4. The control unit corrects the signal intensity based on a scanning position of the laser light, and detects an abnormality in the processing state of the object based on the corrected signal intensity. The laser processing apparatus according to claim 3.

5. the control unit determines whether or not the laser processing of the scanning position has been performed normally based on the signal intensity detected at the scanning position each time the laser light is irradiated to the scanning position, and detects an abnormality in the processing state of the workpiece when it is determined that the laser processing of the scanning position has not been performed normally.

5. The laser processing apparatus according to claim 3 or 4.

6. A laser light source that outputs laser light; A support portion that supports the workpiece; an fθ lens that focuses the laser light on a processing surface of the object; an optical scanning unit that scans the laser light on the processing surface by adjusting an incident angle of the laser light with respect to the fθ lens by operating a dielectric mirror; a polarizing beam splitter disposed between the laser light source and the optical scanning unit on an optical path of the laser light; a quarter-wave plate disposed on the optical path between the polarizing beam splitter and the optical scanning unit; a light detection unit that detects return light of the laser light from the processing surface of the object irradiated with the laser light, the return light passing through the fθ lens, the light scanning unit, the quarter wavelength plate, and the polarizing beam splitter in this order; a control unit that monitors a processing state of the object based on the return light detected by the light detection unit, The light detection unit detects a signal intensity of the return light, The control unit integrates the signal strength detected at each scanning position over a predetermined entire scanning range, and detects an abnormality in the processing state of the workpiece based on the integration result.

7. A laser processing method for processing an object by focusing laser light on a processing surface of the object supported by a support portion using an fθ lens, comprising: a step of directing the laser light output from a laser light source to an optical scanning unit via a polarizing beam splitter and a quarter-wave plate in this order, and scanning the laser light on the processing surface by changing an incident angle of the laser light with respect to the fθ lens by operating a dielectric mirror in the optical scanning unit; a step of detecting, by a light detection unit, return light of the laser light from the processing surface of the object irradiated with the laser light, the return light passing through the fθ lens, the light scanning unit, the ¼ wavelength plate, and the polarizing beam splitter in this order; monitoring a processing state of the object based on the return light detected by the light detection unit; In the detecting step, a two-dimensional image of the return light is detected; In the monitoring step, a distance between the fθ lens and the processing surface is adjusted based on the detected two-dimensional image.

8. In the monitoring step, a distance between the fθ lens and the machining surface is adjusted based on a relationship between the two-dimensional image and a shape of the machining mark formed on the machining surface and a target shape of the machining mark so that the two-dimensional image corresponding to the target shape is detected by the optical detection unit. The laser processing method according to claim 7.

9. A laser processing method for processing an object supported by a support by focusing laser light on a processing surface of the object using an fθ lens, comprising: a step of directing the laser light output from a laser light source to an optical scanning unit via a polarizing beam splitter and a quarter-wave plate in this order, and scanning the laser light on the processing surface by changing an incident angle of the laser light with respect to the fθ lens by operating a dielectric mirror in the optical scanning unit; a step of detecting, by a light detection unit, return light of the laser light from the processing surface of the object irradiated with the laser light, the return light passing through the fθ lens, the light scanning unit, the ¼ wavelength plate, and the polarizing beam splitter in this order; monitoring a processing state of the object based on the return light detected by the light detection unit; In the detecting step, a signal intensity of the return light is detected; The monitoring step includes: a process of determining whether the signal intensity detected in the monitoring step is an appropriate value or not based on a relationship between the irradiation energy of the laser light output from the laser light source, the signal intensity, and a diameter of a processing mark formed on the processing surface, and a target value of the diameter of the processing mark; and detecting an abnormality in the processing state of the workpiece in response to a determination that the signal intensity is not an appropriate value.

10. The monitoring step includes: A process of correcting the signal intensity based on a scanning position of the laser light; and detecting an abnormality in a processing state of the object based on the corrected signal intensity. The laser processing method according to claim 9.

11. The monitoring step includes: a process of determining whether or not laser processing of a scanning position has been normally performed based on the signal intensity detected at the scanning position every time the laser light is irradiated to the scanning position; and detecting an abnormality in a processing state of the object to be processed in response to a determination that the laser processing at the scanning position is not performed normally. The laser processing method according to claim 9 or 10.

12. A laser processing method for processing an object by focusing laser light by an fθ lens onto a processing surface of the object supported by a support, comprising: a step of directing the laser light output from a laser light source to an optical scanning unit via a polarizing beam splitter and a quarter-wave plate in this order, and scanning the laser light on the processing surface by changing an incident angle of the laser light with respect to the fθ lens by operating a dielectric mirror in the optical scanning unit; a step of detecting, by a light detection unit, return light of the laser light from the processing surface of the object irradiated with the laser light, the return light passing through the fθ lens, the light scanning unit, the ¼ wavelength plate, and the polarizing beam splitter in this order; monitoring a processing state of the object based on the return light detected by the light detection unit; In the detecting step, a signal intensity of the return light is detected; The monitoring step includes: A process of integrating the signal strength detected at each scanning position over a predetermined entire scanning range; and detecting an abnormality in the processing state of the workpiece based on an integration result.

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